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Sample records for printed high-frequency phased-array

  1. Fully Printed High-Frequency Phased-Array Antenna on Flexible Substrate

    NASA Technical Reports Server (NTRS)

    Chen, Yihong; Lu, Xuejun

    2010-01-01

    To address the issues of flexible electronics needed for surface-to-surface, surface-to-orbit, and back-to-Earth communications necessary for manned exploration of the Moon, Mars, and beyond, a room-temperature printing process has been developed to create active, phased-array antennas (PAAs) on a flexible Kapton substrate. Field effect transistors (FETs) based on carbon nanotubes (CNTs), with many unique physical properties, were successfully proven feasible for phased-array antenna systems. The carrier mobility of an individual CNT is estimated to be at least 100,000 sq cm/V(dot)s. The CNT network in solution has carrier mobility as high as 46,770 sq cm/V(dot)s, and has a large current-density carrying capacity of approx. 1,000 mA/sq cm , which corresponds to a high carrying power of over 2,000 mW/ sq cm. Such high carrier mobility, and large current carrying capacity, allows the achievement of high-speed (>100 GHz), high-power, flexible electronic circuits that can be monolithically integrated on NASA s active phasedarray antennas for various applications, such as pressurized rovers, pressurized habitats, and spacesuits, as well as for locating beacon towers for lunar surface navigation, which will likely be performed at S-band and attached to a mobile astronaut. A fully printed 2-bit 2-element phasedarray antenna (PAA) working at 5.6 GHz, incorporating the CNT FETs as phase shifters, is demonstrated. The PAA is printed out at room temperature on 100-mm thick Kapton substrate. Four CNT FETs are printed together with microstrip time delay lines to function as a 2-bit phase shifter. The FET switch exhibits a switching speed of 0.2 ns, and works well for a 5.6-GHz RF signal. The operating frequency is measured to be 5.6 GHz, versus the state-of-the-art flexible FET operating frequency of 52 MHz. The source-drain current density is measured to be over 1,000 mA/sq cm, while the conventional organic FETs, and single carbon nanotube-based FETs, are typically in the m

  2. Acoustic trapping with a high frequency linear phased array

    NASA Astrophysics Data System (ADS)

    Zheng, Fan; Li, Ying; Hsu, Hsiu-Sheng; Liu, Changgeng; Tat Chiu, Chi; Lee, Changyang; Ham Kim, Hyung; Shung, K. Kirk

    2012-11-01

    A high frequency ultrasonic phased array is shown to be capable of trapping and translating microparticles precisely and efficiently, made possible due to the fact that the acoustic beam produced by a phased array can be both focused and steered. Acoustic manipulation of microparticles by a phased array is advantageous over a single element transducer since there is no mechanical movement required for the array. Experimental results show that 45 μm diameter polystyrene microspheres can be easily and accurately trapped and moved to desired positions by a 64-element 26 MHz phased array.

  3. Acoustic trapping with a high frequency linear phased array.

    PubMed

    Zheng, Fan; Li, Ying; Hsu, Hsiu-Sheng; Liu, Changgeng; Tat Chiu, Chi; Lee, Changyang; Ham Kim, Hyung; Shung, K Kirk

    2012-11-19

    A high frequency ultrasonic phased array is shown to be capable of trapping and translating microparticles precisely and efficiently, made possible due to the fact that the acoustic beam produced by a phased array can be both focused and steered. Acoustic manipulation of microparticles by a phased array is advantageous over a single element transducer since there is no mechanical movement required for the array. Experimental results show that 45 μm diameter polystyrene microspheres can be easily and accurately trapped and moved to desired positions by a 64-element 26 MHz phased array.

  4. Fully Printed, Flexible, Phased Array Antenna for Lunar Surface Communication

    NASA Technical Reports Server (NTRS)

    Subbaraman, Harish; Hen, Ray T.; Lu, Xuejun; Chen, Maggie Yihong

    2013-01-01

    NASAs future exploration missions focus on the manned exploration of the Moon, Mars, and beyond, which will rely heavily on the development of a reliable communications infrastructure from planetary surface-to-surface, surface-to-orbit, and back to Earth. Flexible antennas are highly desired in many scenarios. Active phased array antennas (active PAAs) with distributed control and processing electronics at the surface of an antenna aperture offer numerous advantages for radar communications. Large-area active PAAs on flexible substrates are of particular interest in NASA s space radars due to their efficient inflatable package that can be rolled up during transportation and deployed in space. Such an inflatable package significantly reduces stowage volume and mass. Because of these performance and packaging advantages, large-area inflatable active PAAs are highly desired in NASA s surface-to-orbit and surface-to-relay communications. To address the issues of flexible electronics, a room-temperature printing process of active phased-array antennas on a flexible Kapton substrate was developed. Field effect transistors (FETs) based on carbon nanotubes (CNTs), with many unique physical properties, were successfully proved feasible for the PAA system. This innovation is a new type of fully inkjet-printable, two-dimensional, high-frequency PAA on a flexible substrate at room temperature. The designed electronic circuit components, such as the FET switches in the phase shifter, metal interconnection lines, microstrip transmission lines, etc., are all printed using a special inkjet printer. Using the developed technology, entire 1x4, 2x2, and 4x4 PAA systems were developed, packaged, and demonstrated at 5.3 GHz. Several key solutions are addressed in this work to solve the fabrication issues. The source/drain contact is developed using droplets of silver ink printed on the source/drain areas prior to applying CNT thin-film. The wet silver ink droplets allow the silver to

  5. Design and development of high frequency matrix phased-array ultrasonic probes

    NASA Astrophysics Data System (ADS)

    Na, Jeong K.; Spencer, Roger L.

    2012-05-01

    High frequency matrix phased-array (MPA) probes have been designed and developed for more accurate and repeatable assessment of weld conditions of thin sheet metals commonly used in the auto industry. Unlike the line focused ultrasonic beam generated by a linear phased-array (LPA) probe, a MPA probe can form a circular shaped focused beam in addition to the typical beam steering capabilities of phased-array probes. A CIVA based modeling and simulation method has been used to design the probes in terms of various probe parameters such as number of elements, element size, overall dimensions, frequency etc. Challenges associated with the thicknesses of thin sheet metals have been resolved by optimizing these probe design parameters. A further improvement made on the design of the MPA probe proved that a three-dimensionally shaped matrix element can provide a better performing probe at a much lower probe manufacturing cost by reducing the total number of elements and lowering the operational frequency. This three dimensional probe naturally matches to the indentation shape of the weld on the thin sheet metals and hence a wider inspection area with the same level of spatial resolution obtained by a twodimensional flat MPA probe operating at a higher frequency. The two aspects, a wider inspection area and a lower probe manufacturing cost, make this three-dimensional MPA sensor more attractive to auto manufacturers demanding a quantitative nondestructive inspection method.

  6. PMN-PT Single-Crystal High-Frequency Kerfless Phased Array

    PubMed Central

    Chen, Ruimin; Cabrera-Munoz, Nestor E.; Lam, Kwok Ho; Hsu, Hsiu-sheng; Zheng, Fan; Zhou, Qifa; Shung, K. Kirk

    2015-01-01

    This paper reports the design, fabrication, and characterization of a miniature high-frequency kerfless phased array prepared from a PMN-PT single crystal for forward-looking intravascular or endoscopic imaging applications. After lapping down to around 40 μm, the PMN-PT material was utilized to fabricate 32-element kerfless phased arrays using micromachining techniques. The aperture size of the active area was only 1.0 × 1.0 mm. The measured results showed that the array had a center frequency of 40 MHz, a bandwidth of 34% at −6 dB with a polymer matching layer, and an insertion loss of 20 dB at the center frequency. Phantom images were acquired and compared with simulated images. The results suggest that the feasibility of developing a phased array mounted at the tip of a forward-looking intravascular catheter or endoscope. The fabricated array exhibits much higher sensitivity than PZT ceramic-based arrays and demonstrates that PMN-PT is well suited for this application. PMID:24859667

  7. PMN-PT single-crystal high-frequency kerfless phased array.

    PubMed

    Chen, Ruimin; Cabrera-Munoz, Nestor E; Lam, Kwok Ho; Hsu, Hsiu-sheng; Zheng, Fan; Zhou, Qifa; Shung, K Kirk

    2014-06-01

    This paper reports the design, fabrication, and characterization of a miniature high-frequency kerfless phased array prepared from a PMN-PT single crystal for forward-looking intravascular or endoscopic imaging applications. After lapping down to around 40 μm, the PMN-PT material was utilized to fabricate 32-element kerfless phased arrays using micromachining techniques. The aperture size of the active area was only 1.0 × 1.0 mm. The measured results showed that the array had a center frequency of 40 MHz, a bandwidth of 34% at -6 dB with a polymer matching layer, and an insertion loss of 20 dB at the center frequency. Phantom images were acquired and compared with simulated images. The results suggest that the feasibility of developing a phased array mounted at the tip of a forward-looking intravascular catheter or endoscope. The fabricated array exhibits much higher sensitivity than PZT ceramic-based arrays and demonstrates that PMN-PT is well suited for this application.

  8. PMN-PT single-crystal high-frequency kerfless phased array.

    PubMed

    Chen, Ruimin; Cabrera-Munoz, Nestor E; Lam, Kwok Ho; Hsu, Hsiu-sheng; Zheng, Fan; Zhou, Qifa; Shung, K Kirk

    2014-06-01

    This paper reports the design, fabrication, and characterization of a miniature high-frequency kerfless phased array prepared from a PMN-PT single crystal for forward-looking intravascular or endoscopic imaging applications. After lapping down to around 40 μm, the PMN-PT material was utilized to fabricate 32-element kerfless phased arrays using micromachining techniques. The aperture size of the active area was only 1.0 × 1.0 mm. The measured results showed that the array had a center frequency of 40 MHz, a bandwidth of 34% at -6 dB with a polymer matching layer, and an insertion loss of 20 dB at the center frequency. Phantom images were acquired and compared with simulated images. The results suggest that the feasibility of developing a phased array mounted at the tip of a forward-looking intravascular catheter or endoscope. The fabricated array exhibits much higher sensitivity than PZT ceramic-based arrays and demonstrates that PMN-PT is well suited for this application. PMID:24859667

  9. Scan blindness in infinite phased arrays of printed dipoles

    NASA Technical Reports Server (NTRS)

    Pozar, D. M.; Schaubert, D. H.

    1984-01-01

    A comprehensive study of infinite phased arrays of printed dipole antennas is presented, with emphasis on the scan blindness phenomenon. A rigorous and efficient moment method procedure is used to calculate the array impedance versus scan angle. Data are presented for the input reflection coefficient for various element spacings and substrate parameters. A simple theory, based on coupling from Floquet modes to surface wave modes on the substrate, is shown to predict the occurrence of scan blindness. Measurements from a waveguide simulator of a blindness condition confirm the theory.

  10. High frequency GaAlAs modulator and photodetector for phased array antenna applications

    NASA Technical Reports Server (NTRS)

    Claspy, P. C.; Chorey, C. M.; Hill, S. M.; Bhasin, K. B.

    1988-01-01

    A waveguide Mach-Zehnder electro-optic modulator and an interdigitated photoconductive detector designed to operate at 820 nm, fabricated on different GaAlAs/GaAs heterostructure materials, are being investigated for use in optical interconnects in phased array antenna systems. Measured optical attenuation effects in the modulator are discussed and the observed modulation performance up to 1 GHz is presented. Measurements of detector frequency response are described and results presented.

  11. Fabrication and performance of a miniaturized 64-element high-frequency endoscopic phased array.

    PubMed

    Bezanson, Andre; Adamson, Rob; Brown, Jeremy

    2014-01-01

    We have developed a 40-MHz, 64-element phased-array transducer packaged in a 2.5 x 3.1 mm endoscopic form factor. The array is a forward-looking semi-kerfed design based on a 0.68Pb(Mg(1/3)Nb(2/3))O(3) - 0.32PbTiO3 (PMN-32%PT) single-crystal wafer with an element-to-element pitch of 38 µm. To achieve a miniaturized form factor, a novel technique of wire bonding the array elements to a polyimide flexible circuit board oriented parallel to the forward looking ultrasound beam and perpendicular to the array was developed. A technique of partially dicing into the back of the array was also implemented to improve the directivity of the array elements. The array was fabricated with a single-layer P(VDF-TrFE)-copolymer matching layer and a polymethylpentene (TPX) lens for passive elevation focusing to a depth of 7 mm. The two-way -6-dB pulse bandwidth was measured to be 55% and the average electromechanical coupling (k(eff)) for the individual elements was measured to be 0.62. The one-way -6-dB directivities from several array elements were measured to be ±20°, which was shown to be an improvement over an identical kerfless array. The -3-dB elevation focus resulting from the TPX lens was measured to be 152 µm at the focal depth, and the focused lateral resolution was measured to be 80 µm at a steering angle of 0°. To generate beam profiles and images, the probe was connected to a commercial ultrasound imaging platform which was reprogrammed to allow for phased array transmit beamforming and receive data collection. The collected RF data were then processed offline using a numerical computing script to generate sector images. The radiation pattern for the beamformed transmit pulse was collected along with images of wire phantoms in water and tissue-equivalent medium with a dynamic range of 60 dB. Finally, ex vivo tissue images were generated of porcine brain tissue.

  12. X-band printed phased array antennas using high-performance CNT/ion gel/Ag transistors

    NASA Astrophysics Data System (ADS)

    Grubb, Peter M.; Bidoky, Fazel; Mahajan, Ankit; Subbaraman, Harish; Li, Wentao; Frisbie, Daniel; Chen, Ray T.

    2016-05-01

    This paper reports a fully printed phased array antenna developed on a 125 micron thick flexible Kapton substrate. Switching for the phase delay lines is accomplished using printed carbon nanotube transistors with ion gel dielectric layers. Design of each element of the phased array antenna is reported, including a low loss constant impedance power divider, a phase shifter network, and patch antenna design. Steering of an X-band PAA operating at 10GHz from 0 degrees to 22.15 degrees is experimentally demonstrated. In order to completely package the array with electrical interconnects, a single substrate interconnect scheme is also investigated.

  13. Cobalt Nanoparticle Inks for Printed High Frequency Applications on Polycarbonate

    NASA Astrophysics Data System (ADS)

    Nelo, Mikko; Myllymäki, Sami; Juuti, Jari; Uusimäki, Antti; Jantunen, Heli

    2015-12-01

    In this work the high frequency properties of low curing temperature cobalt nanoparticle inks printed on polycarbonate substrates were investigated. The inks consisted of 30-70 vol.% metallic cobalt nanoparticles and poly (methylene methacrylate) polymer, having excellent adhesion on polycarbonate and a curing temperature of 110°C. The influence of binder material content on the electromagnetic properties of the ink was investigated using the shorted microstrip transmission-line perturbation method. Changes in mechanical properties were evaluated with adhesion tests using the pull-out strength test and the ASTM D 3359-B cross-hatch tape peel test. The microstructure of the printed patterns was investigated with field emission scanning electron microscopy (FESEM). The inks remained mechanically durable with metal contents up to 60 vol.%, achieving pull-off strength of up to 5.2 MPa and the highest marks in adhesion of the tape peel test. The inks obtained a relative permeability of 1.5-3 in the 45 MHz-10 GHz band with a magnetic loss tangent of 0.01-0.06. The developed inks can be utilized in various printed electronics applications such as antenna miniaturization, antenna substrates and magnetic sensors or sensing.

  14. Printed silver nanowire antennas with low signal loss at high-frequency radio.

    PubMed

    Komoda, Natsuki; Nogi, Masaya; Suganuma, Katsuaki; Kohno, Kazuo; Akiyama, Yutaka; Otsuka, Kanji

    2012-05-21

    Silver nanowires are printable and conductive, and are believed to be promising materials in the field of printed electronics. However, the resistivity of silver nanowire printed lines is higher than that of metallic particles or flakes even when sintered at high temperatures of 100-400 °C. Therefore, their applications have been limited to the replacement of transparent electrodes made from high-resistivity materials, such as doped metallic oxides, conductive polymers, carbon nanotubes, or graphenes. Here we report that using printed silver nanowire lines, signal losses obtained in the high-frequency radio were lower than those obtained using etched copper foil antennas, because their surfaces were much smoother than those of etched copper foil antennas. This was the case even though the resistivity of silver nanowire lines was 43-71 μΩ cm, which is much higher than that of etched copper foil (2 μΩ cm). When printed silver nanowire antennas were heated at 100 °C, they achieved signal losses that were much lower than those of silver paste antennas comprising microparticles, nanoparticles, and flakes. Furthermore, using a low temperature process, we succeeded in remotely controlling a commercialized radio-controlled car by transmitting a 2.45 GHz signal via a silver nanowire antenna printed on a polyethylene terephthalate film.

  15. Printed silver nanowire antennas with low signal loss at high-frequency radio.

    PubMed

    Komoda, Natsuki; Nogi, Masaya; Suganuma, Katsuaki; Kohno, Kazuo; Akiyama, Yutaka; Otsuka, Kanji

    2012-05-21

    Silver nanowires are printable and conductive, and are believed to be promising materials in the field of printed electronics. However, the resistivity of silver nanowire printed lines is higher than that of metallic particles or flakes even when sintered at high temperatures of 100-400 °C. Therefore, their applications have been limited to the replacement of transparent electrodes made from high-resistivity materials, such as doped metallic oxides, conductive polymers, carbon nanotubes, or graphenes. Here we report that using printed silver nanowire lines, signal losses obtained in the high-frequency radio were lower than those obtained using etched copper foil antennas, because their surfaces were much smoother than those of etched copper foil antennas. This was the case even though the resistivity of silver nanowire lines was 43-71 μΩ cm, which is much higher than that of etched copper foil (2 μΩ cm). When printed silver nanowire antennas were heated at 100 °C, they achieved signal losses that were much lower than those of silver paste antennas comprising microparticles, nanoparticles, and flakes. Furthermore, using a low temperature process, we succeeded in remotely controlling a commercialized radio-controlled car by transmitting a 2.45 GHz signal via a silver nanowire antenna printed on a polyethylene terephthalate film. PMID:22522460

  16. Printed silver nanowire antennas with low signal loss at high-frequency radio

    NASA Astrophysics Data System (ADS)

    Komoda, Natsuki; Nogi, Masaya; Suganuma, Katsuaki; Kohno, Kazuo; Akiyama, Yutaka; Otsuka, Kanji

    2012-05-01

    Silver nanowires are printable and conductive, and are believed to be promising materials in the field of printed electronics. However, the resistivity of silver nanowire printed lines is higher than that of metallic particles or flakes even when sintered at high temperatures of 100-400 °C. Therefore, their applications have been limited to the replacement of transparent electrodes made from high-resistivity materials, such as doped metallic oxides, conductive polymers, carbon nanotubes, or graphenes. Here we report that using printed silver nanowire lines, signal losses obtained in the high-frequency radio were lower than those obtained using etched copper foil antennas, because their surfaces were much smoother than those of etched copper foil antennas. This was the case even though the resistivity of silver nanowire lines was 43-71 μΩ cm, which is much higher than that of etched copper foil (2 μΩ cm). When printed silver nanowire antennas were heated at 100 °C, they achieved signal losses that were much lower than those of silver paste antennas comprising microparticles, nanoparticles, and flakes. Furthermore, using a low temperature process, we succeeded in remotely controlling a commercialized radio-controlled car by transmitting a 2.45 GHz signal via a silver nanowire antenna printed on a polyethylene terephthalate film.Silver nanowires are printable and conductive, and are believed to be promising materials in the field of printed electronics. However, the resistivity of silver nanowire printed lines is higher than that of metallic particles or flakes even when sintered at high temperatures of 100-400 °C. Therefore, their applications have been limited to the replacement of transparent electrodes made from high-resistivity materials, such as doped metallic oxides, conductive polymers, carbon nanotubes, or graphenes. Here we report that using printed silver nanowire lines, signal losses obtained in the high-frequency radio were lower than those

  17. Phased-array radars

    NASA Astrophysics Data System (ADS)

    Brookner, E.

    1985-02-01

    The operating principles, technology, and applications of phased-array radars are reviewed and illustrated with diagrams and photographs. Consideration is given to the antenna elements, circuitry for time delays, phase shifters, pulse coding and compression, and hybrid radars combining phased arrays with lenses to alter the beam characteristics. The capabilities and typical hardware of phased arrays are shown using the US military systems COBRA DANE and PAVE PAWS as examples.

  18. Non-Planar Pad-Printed Thick-Film Focused High-Frequency Ultrasonic Transducers for Imaging and Therapeutic Applications

    PubMed Central

    Lethiecq, Marc; Lou-Moeller, Rasmus; Ketterling, Jeffrey A.; Levassort, Franck; Tran-Huu-Hue, Louis Pascal; Filoux, Erwan; Silverman, Ronald H.; Wolny, Wanda W.

    2013-01-01

    Pad-printed thick-film transducers have been shown to be an interesting alternative to lapped bulk piezoceramics, because the film is deposited with the required thickness, size, and geometry, thus avoiding any subsequent machining to achieve geometrical focusing. Their electromechanical properties are close to those of bulk ceramics with similar composition despite having a higher porosity. In this paper, pad-printed high-frequency transducers based on a low-loss piezoceramic composition are designed and fabricated. High-porosity ceramic cylinders with a spherical top surface are used as the backing substrate. The transducers are characterized in view of imaging applications and their imaging capabilities are evaluated with phantoms containing spherical inclusions and in different biological tissues. In addition, the transducers are evaluated for their capability to produce high-acoustic intensities at frequencies around 20 MHz. High-intensity measurements, obtained with a calibrated hydrophone, show that transducer performance is promising for applications that would require the same device to be used for imaging and for therapy. Nevertheless, the transducer design can be improved, and simulation studies are performed to find a better compromise between low-power and high-power performance. The size, geometry, and constitutive materials of optimized configurations are proposed and their feasibility is discussed. PMID:23007770

  19. The NMR phased array.

    PubMed

    Roemer, P B; Edelstein, W A; Hayes, C E; Souza, S P; Mueller, O M

    1990-11-01

    We describe methods for simultaneously acquiring and subsequently combining data from a multitude of closely positioned NMR receiving coils. The approach is conceptually similar to phased array radar and ultrasound and hence we call our techniques the "NMR phased array." The NMR phased array offers the signal-to-noise ratio (SNR) and resolution of a small surface coil over fields-of-view (FOV) normally associated with body imaging with no increase in imaging time. The NMR phased array can be applied to both imaging and spectroscopy for all pulse sequences. The problematic interactions among nearby surface coils is eliminated (a) by overlapping adjacent coils to give zero mutual inductance, hence zero interaction, and (b) by attaching low input impedance preamplifiers to all coils, thus eliminating interference among next nearest and more distant neighbors. We derive an algorithm for combining the data from the phased array elements to yield an image with optimum SNR. Other techniques which are easier to implement at the cost of lower SNR are explored. Phased array imaging is demonstrated with high resolution (512 x 512, 48-cm FOV, and 32-cm FOV) spin-echo images of the thoracic and lumbar spine. Data were acquired from four-element linear spine arrays, the first made of 12-cm square coils and the second made of 8-cm square coils. When compared with images from a single 15 x 30-cm rectangular coil and identical imaging parameters, the phased array yields a 2X and 3X higher SNR at the depth of the spine (approximately 7 cm). PMID:2266841

  20. Large phased-array radars

    SciTech Connect

    Brookner, D.E.

    1988-12-15

    Large phased-array radars can play a very important part in arms control. They can be used to determine the number of RVs being deployed, the type of targeting of the RVs (the same or different targets), the shape of the deployed objects, and possibly the weight and yields of the deployed RVs. They can provide this information at night as well as during the day and during rain and cloud covered conditions. The radar can be on the ground, on a ship, in an airplane, or space-borne. Airborne and space-borne radars can provide high resolution map images of the ground for reconnaissance, of anti-ballistic missile (ABM) ground radar installations, missile launch sites, and tactical targets such as trucks and tanks. The large ground based radars can have microwave carrier frequencies or be at HF (high frequency). For a ground-based HF radar the signal is reflected off the ionosphere so as to provide over-the-horizon (OTH) viewing of targets. OTH radars can potentially be used to monitor stealth targets and missile traffic.

  1. Multibeam Phased Array Antennas

    NASA Technical Reports Server (NTRS)

    Popovic, Zoya; Romisch, Stefania; Rondineau, Sebastien

    2004-01-01

    In this study, a new architecture for Ka-band multi-beam arrays was developed and demonstrated experimentally. The goal of the investigation was to demonstrate a new architecture that has the potential of reducing the cost as compared to standard expensive phased array technology. The goals of this specific part of the project, as stated in the yearly statement of work in the original proposal are: 1. Investigate bounds on performance of multi-beam lens arrays in terms of beamwidths, volume (size), isolation between beams, number of simultaneous beams, etc. 2. Design a small-scale array to demonstrate the principle. The array will be designed for operation around 3OGHz (Ka-band), with two 10-degree beamwidth beams. 3. Investigate most appropriate way to accomplish fine-tuning of the beam pointing within 5 degrees around the main beam pointing angle.

  2. UAVSAR Phased Array Aperture

    NASA Technical Reports Server (NTRS)

    Chamberlain, Neil; Zawadzki, Mark; Sadowy, Greg; Oakes, Eric; Brown, Kyle; Hodges, Richard

    2009-01-01

    This paper describes the development of a patch antenna array for an L-band repeat-pass interferometric synthetic aperture radar (InSAR) instrument that is to be flown on an unmanned aerial vehicle (UAV). The antenna operates at a center frequency of 1.2575 GHz and with a bandwidth of 80 MHz, consistent with a number of radar instruments that JPL has previously flown. The antenna is designed to radiate orthogonal linear polarizations in order to facilitate fully-polarimetric measurements. Beam-pointing requirements for repeat-pass SAR interferometry necessitate electronic scanning in azimuth over a range of -20degrees in order to compensate for aircraft yaw. Beam-steering is accomplished by transmit/receive (T/R) modules and a beamforming network implemented in a stripline circuit board. This paper, while providing an overview of phased array architecture, focuses on the electromagnetic design of the antenna tiles and associated interconnects. An important aspect of the design of this antenna is that it has an amplitude taper of 10dB in the elevation direction. This is to reduce multipath reflections from the wing that would otherwise be detrimental to interferometric radar measurements. This taper is provided by coupling networks in the interconnect circuits as opposed to attenuating the output of the T/R modules. Details are given of material choices and fabrication techniques that meet the demanding environmental conditions that the antenna must operate in. Predicted array performance is reported in terms of co-polarized and crosspolarized far-field antenna patterns, and also in terms of active reflection coefficient.

  3. Grounded Coplanar Waveguide Feeds Phased-Array Antenna

    NASA Technical Reports Server (NTRS)

    Ponchak, G.E.; Lee, R. Q.; Simons, R. N.; Fernandez, N.S.

    1993-01-01

    Prototype electronically steerable K-band end-fire antenna includes phased array of four printed-circuit linear dipole elements fed by grounded coplanar waveguide (GCPW). Distribution-and-phasing network of antenna fed through single entering antenna split equally by three GCPW T junctions onto four GCPW transmission lines.

  4. Modeling of phased array transducers.

    PubMed

    Ahmad, Rais; Kundu, Tribikram; Placko, Dominique

    2005-04-01

    Phased array transducers are multi-element transducers, where different elements are activated with different time delays. The advantage of these transducers is that no mechanical movement of the transducer is needed to scan an object. Focusing and beam steering is obtained simply by adjusting the time delay. In this paper the DPSM (distributed point source method) is used to model the ultrasonic field generated by a phased array transducer and to study the interaction effect when two phased array transducers are placed in a homogeneous fluid. Earlier investigations modeled the acoustic field for conventional transducers where all transducer points are excited simultaneously. In this research, combining the concepts of delayed firing and the DPSM, the phased array transducers are modeled semi-analytically. In addition to the single transducer modeling the ultrasonic fields from two phased array transducers placed face to face in a fluid medium is also modeled to study the interaction effect. The importance of considering the interaction effect in multiple transducer modeling is discussed, pointing out that neighboring transducers not only act as ultrasonic wave generators but also as scatterers.

  5. Active membrane phased array radar

    NASA Technical Reports Server (NTRS)

    Moussessian, Alina; Del Castillo, Linda; Huang, John; Sadowy, Greg; Hoffman, James; Smith, Phil; Hatake, Toshiro; Derksen, Chuck; Lopez, Bernardo; Caro, Ed

    2005-01-01

    We have developed the first membrane-based active phased array in L-band (1.26GHz). The array uses membrane compatible Transmit/Receive (T/R) modules (membrane T/R) for each antenna element. We use phase shifters within each T/R module for electronic beam steering. We will discuss the T/R module design and integration with the membrane, We will also present transmit and receive beam-steering results for the array.

  6. Distributed phased array architecture study

    NASA Technical Reports Server (NTRS)

    Bourgeois, Brian

    1987-01-01

    Variations in amplifiers and phase shifters can cause degraded antenna performance, depending also on the environmental conditions and antenna array architecture. The implementation of distributed phased array hardware was studied with the aid of the DISTAR computer program as a simulation tool. This simulation provides guidance in hardware simulation. Both hard and soft failures of the amplifiers in the T/R modules are modeled. Hard failures are catastrophic: no power is transmitted to the antenna elements. Noncatastrophic or soft failures are modeled as a modified Gaussian distribution. The resulting amplitude characteristics then determine the array excitation coefficients. The phase characteristics take on a uniform distribution. Pattern characteristics such as antenna gain, half power beamwidth, mainbeam phase errors, sidelobe levels, and beam pointing errors were studied as functions of amplifier and phase shifter variations. General specifications for amplifier and phase shifter tolerances in various architecture configurations for C band and S band were determined.

  7. Optical phased-array ladar.

    PubMed

    Montoya, Juan; Sanchez-Rubio, Antonio; Hatch, Robert; Payson, Harold

    2014-11-01

    We demonstrate a ladar with 0.5 m class range resolution obtained by integrating a continuous-wave optical phased-array transmitter with a Geiger-mode avalanche photodiode receiver array. In contrast with conventional ladar systems, an array of continuous-wave sources is used to effectively pulse illuminate a target by electro-optically steering far-field fringes. From the reference frame of a point in the far field, a steered fringe appears as a pulse. Range information is thus obtained by measuring the arrival time of a pulse return from a target to a receiver pixel. This ladar system offers a number of benefits, including broad spectral coverage, high efficiency, small size, power scalability, and versatility.

  8. Proceedings: EPRI Second Phased Array Inspection Seminar

    SciTech Connect

    2001-11-01

    The Second EPRI Phased Array Inspection Seminar focused on industrial applications of phased array technology that have been achieved to date or are planned for the near future. Presentations were made by developers of inspection techniques, inspection services vendors, and utility personnel who have performed inspections using arrays.

  9. Delamination Detection Using Guided Wave Phased Arrays

    NASA Technical Reports Server (NTRS)

    Tian, Zhenhua; Yu, Lingyu; Leckey, Cara

    2016-01-01

    This paper presents a method for detecting multiple delaminations in composite laminates using non-contact phased arrays. The phased arrays are implemented with a non-contact scanning laser Doppler vibrometer (SLDV). The array imaging algorithm is performed in the frequency domain where both the guided wave dispersion effect and direction dependent wave properties are considered. By using the non-contact SLDV array with a frequency domain imaging algorithm, an intensity image of the composite plate can be generated for delamination detection. For the proof of concept, a laboratory test is performed using a non-contact phased array to detect two delaminations (created through quasi-static impact test) at different locations in a composite plate. Using the non-contact phased array and frequency domain imaging, the two impact-induced delaminations are successfully detected. This study shows that the non-contact phased array method is a potentially effective method for rapid delamination inspection in large composite structures.

  10. Phased Array Ultrasonic Inspection of Titanium Forgings

    SciTech Connect

    Howard, P.; Klaassen, R.; Kurkcu, N.; Barshinger, J.; Chalek, C.; Nieters, E.; Sun, Zongqi; Fromont, F. de

    2007-03-21

    Aerospace forging inspections typically use multiple, subsurface-focused sound beams in combination with digital C-scan image acquisition and display. Traditionally, forging inspections have been implemented using multiple single element, fixed focused transducers. Recent advances in phased array technology have made it possible to perform an equivalent inspection using a single phased array transducer. General Electric has developed a system to perform titanium forging inspection based on medical phased array technology and advanced image processing techniques. The components of that system and system performance for titanium inspection will be discussed.

  11. Phased Array Ultrasonic Inspection of Titanium Forgings

    NASA Astrophysics Data System (ADS)

    Howard, P.; Klaassen, R.; Kurkcu, N.; Barshinger, J.; Chalek, C.; Nieters, E.; Sun, Zongqi; deFromont, F.

    2007-03-01

    Aerospace forging inspections typically use multiple, subsurface-focused sound beams in combination with digital C-scan image acquisition and display. Traditionally, forging inspections have been implemented using multiple single element, fixed focused transducers. Recent advances in phased array technology have made it possible to perform an equivalent inspection using a single phased array transducer. General Electric has developed a system to perform titanium forging inspection based on medical phased array technology and advanced image processing techniques. The components of that system and system performance for titanium inspection will be discussed.

  12. Analysis of phased-array diode lasers

    SciTech Connect

    Hardy, A.; Streifer, W.

    1985-07-01

    An improved, more accurate analysis of phased-array diode lasers is presented, which yields results that differ both qualitatively and quantitatively from those previously employed. A numerical example indicating decreased splitting in array mode gains is included.

  13. A phased array tracking antenna for vehicles

    NASA Technical Reports Server (NTRS)

    Ohmori, Shingo; Mano, Kazukiko; Tanaka, Kenji; Matsunaga, Makoto; Tsuchiya, Makio

    1990-01-01

    An antenna system including antenna elements and a satellite tracking method is considered a key technology in implementing land mobile satellite communications. In the early stage of land mobile satellite communications, a mechanical tracking antenna system is considered the best candidate for vehicles, however, a phased array antenna will replace it in the near future, because it has many attractive advantages such as a low and compact profile, high speed tracking, and potential low cost. Communications Research Laboratory is now developing a new phased array antenna system for land vehicles based on research experiences of the airborne phased array antenna, which was developed and evaluated in satellite communication experiments using the ETS-V satellite. The basic characteristics of the phased array antenna for land vehicles are described.

  14. Large-scale nanophotonic phased array.

    PubMed

    Sun, Jie; Timurdogan, Erman; Yaacobi, Ami; Hosseini, Ehsan Shah; Watts, Michael R

    2013-01-10

    Electromagnetic phased arrays at radio frequencies are well known and have enabled applications ranging from communications to radar, broadcasting and astronomy. The ability to generate arbitrary radiation patterns with large-scale phased arrays has long been pursued. Although it is extremely expensive and cumbersome to deploy large-scale radiofrequency phased arrays, optical phased arrays have a unique advantage in that the much shorter optical wavelength holds promise for large-scale integration. However, the short optical wavelength also imposes stringent requirements on fabrication. As a consequence, although optical phased arrays have been studied with various platforms and recently with chip-scale nanophotonics, all of the demonstrations so far are restricted to one-dimensional or small-scale two-dimensional arrays. Here we report the demonstration of a large-scale two-dimensional nanophotonic phased array (NPA), in which 64 × 64 (4,096) optical nanoantennas are densely integrated on a silicon chip within a footprint of 576 μm × 576 μm with all of the nanoantennas precisely balanced in power and aligned in phase to generate a designed, sophisticated radiation pattern in the far field. We also show that active phase tunability can be realized in the proposed NPA by demonstrating dynamic beam steering and shaping with an 8 × 8 array. This work demonstrates that a robust design, together with state-of-the-art complementary metal-oxide-semiconductor technology, allows large-scale NPAs to be implemented on compact and inexpensive nanophotonic chips. In turn, this enables arbitrary radiation pattern generation using NPAs and therefore extends the functionalities of phased arrays beyond conventional beam focusing and steering, opening up possibilities for large-scale deployment in applications such as communication, laser detection and ranging, three-dimensional holography and biomedical sciences, to name just a few.

  15. Intracavitary ultrasound phased arrays for thermal therapies

    NASA Astrophysics Data System (ADS)

    Hutchinson, Erin

    Currently, the success of hyperthermia and thermal surgery treatments is limited by the technology used in the design and fabrication of clinical heating devices and the completeness of the thermometry systems used for guidance. For both hyperthermia and thermal surgery, electrically focused ultrasound generated by phased arrays provides a means of controlling localized energy deposition in body tissues. Intracavitary applicators can be used to bring the energy source close to a target volume, such as the prostate, thereby minimizing normal tissue damage. The work performed in this study was aimed at improving noninvasive prostate thermal therapies and utilized three research approaches: (1) Acoustic, thermal and optimization simulations, (2) Design and fabrication of multiple phased arrays, (3) Ex vivo and in vivo experimental testing of the heating capabilities of the phased arrays. As part of this study, a novel aperiodic phased array design was developed which resulted in a 30- 45% reduction in grating lobe levels when compared to conventional phased arrays. Measured acoustic fields generated by the constructed aperiodic arrays agreed closely with the fields predicted by the theoretical simulations and covered anatomically appropriate ranges. The power capabilities of these arrays were demonstrated to be sufficient for the purposes of hyperthermia and thermal surgery. The advantage of using phased arrays in place of fixed focus transducers was shown by demonstrating the ability of electronic scanning to increase the size of the necrosed tissue volume while providing a more uniform thermal dose, which can ultimately reduce patient treatment times. A theoretical study on the feasibility of MRI (magnetic resonance imaging) thermometry for noninvasive temperature feedback control was investigated as a means to improve transient and steady state temperature distributions achieved in hyperthermia treatments. MRI guided ex vivo and in vivo experiments demonstrated

  16. Improved Phased Array Imaging of a Model Jet

    NASA Technical Reports Server (NTRS)

    Dougherty, Robert P.; Podboy, Gary G.

    2010-01-01

    An advanced phased array system, OptiNav Array 48, and a new deconvolution algorithm, TIDY, have been used to make octave band images of supersonic and subsonic jet noise produced by the NASA Glenn Small Hot Jet Acoustic Rig (SHJAR). The results are much more detailed than previous jet noise images. Shock cell structures and the production of screech in an underexpanded supersonic jet are observed directly. Some trends are similar to observations using spherical and elliptic mirrors that partially informed the two-source model of jet noise, but the radial distribution of high frequency noise near the nozzle appears to differ from expectations of this model. The beamforming approach has been validated by agreement between the integrated image results and the conventional microphone data.

  17. An experimental X band phased array

    NASA Astrophysics Data System (ADS)

    Rao, N. P. R.; Limaye, K. U.; Ramalingam, R. P.; Gangadharan, T. S.; Bhandopadhyay, G.; Deshpande, P. A.

    1983-10-01

    The details of an X band experimental 11 x 11 element Phased Array Antenna of phased lens configuration with a monopulse space feed developed at LRDE are presented. The studies carried and the results obtained on collimation, beam steering, pattern variation with scan, array operation in two-dimensional search, dedicated track and track while scan (TWS) are also given.

  18. Control of phased-array antennas

    NASA Astrophysics Data System (ADS)

    Samoilenko, V. I.; Shishov, Iu. A.

    Principles and algorithms for the control of phased arrays are described. Particular consideration is given to algorithms for the control of phase distribution, adaptive arrays, beam-steerable arrays, the design of phase shifters, the compensation of beam-pointing errors, and the calibration of high-gain antenna pointing.

  19. Multi-beam Phased Array Antennas

    NASA Technical Reports Server (NTRS)

    Lee, R. Q.; Romisch, S.; Popovic, Z.

    2002-01-01

    Many of NASA's future missions require multiple accesses to work together as a single system. To accomplish these missions, multi-beam phased array antennas are required to communicate between satellites flying in fixed formation. In this paper, a comparison of different multi-beam systems will be given followed by detailed discussions of the lens array architecture and test results.

  20. Print.

    ERIC Educational Resources Information Center

    Hurlburt, Carol J.

    2000-01-01

    Provides descriptions of jobs related to the printing industry. Includes information on salaries, labor market outlook, and education/training needed. Describes careers in commercial printing and graphic communications. (JOW)

  1. MSAT-X electronically steered phased array antenna system

    NASA Technical Reports Server (NTRS)

    Chung, H. H.; Foy, W.; Schaffner, G.; Pagels, W.; Vayner, M.; Nelson, J.; Peng, S. Y.

    1988-01-01

    A low profile electronically steered phased array was successfully developed for the Mobile Satellite Experiment Program (MSAT-X). The newly invented cavity-backed printed crossed-slot was used as the radiating element. The choice of this element was based on its low elevation angle gain coverage and low profile. A nineteen-way radial type unequal power divider and eighteen three-bit diode phase shifters constitute the beamformer module which is used to scan the beams electronically. A complete hybrid mode pointing system was also developed. The major features of the antenna system are broad coverage, low profile, and fast acquisition and tracking performance, even under fading conditions. Excellent intersatellite isolation (better than 26 dB) was realized, which will provide good quality mobile satellite communication in the future.

  2. Phased Array Inspection of Irregular Surfaces

    NASA Astrophysics Data System (ADS)

    Long, R.; Cawley, P.

    2007-03-01

    The purpose of this project is to research and develop new conformable phased arrays that allow reliable ultrasonic inspection of components with an irregular surface. Two alternative approaches have been considered: flexible contact arrays in which the array itself conforms to the surface and a membrane device in which a standard array is coupled to the surface via a fluid-filled membrane. A linear flexible contact phased array was purchased from CEA France and a conformable membrane device was designed and manufactured at Imperial College. Initial investigations were conducted to evaluate both approaches when coupling to test pieces with machined surfaces representative of typical welded pipes without removal of the weld caps. The research incorporated beam modelling using the CEA CIVA software and comparisons with experimental measurements. It is shown that the conformable membrane approach using a standard array transducer is competitive with the bespoke flexible array.

  3. Ka-Band Phased Array System Characterization

    NASA Technical Reports Server (NTRS)

    Acosta, R.; Johnson, S.; Sands, O.; Lambert, K.

    2001-01-01

    Phased Array Antennas (PAAs) using patch-radiating elements are projected to transmit data at rates several orders of magnitude higher than currently offered with reflector-based systems. However, there are a number of potential sources of degradation in the Bit Error Rate (BER) performance of the communications link that are unique to PAA-based links. Short spacing of radiating elements can induce mutual coupling between radiating elements, long spacing can induce grating lobes, modulo 2 pi phase errors can add to Inter Symbol Interference (ISI), phase shifters and power divider network introduce losses into the system. This paper describes efforts underway to test and evaluate the effects of the performance degrading features of phased-array antennas when used in a high data rate modulation link. The tests and evaluations described here uncover the interaction between the electrical characteristics of a PAA and the BER performance of a communication link.

  4. Photorefractive processing for large adaptive phased arrays.

    PubMed

    Weverka, R T; Wagner, K; Sarto, A

    1996-03-10

    An adaptive null-steering phased-array optical processor that utilizes a photorefractive crystal to time integrate the adaptive weights and null out correlated jammers is described. This is a beam-steering processor in which the temporal waveform of the desired signal is known but the look direction is not. The processor computes the angle(s) of arrival of the desired signal and steers the array to look in that direction while rotating the nulls of the antenna pattern toward any narrow-band jammers that may be present. We have experimentally demonstrated a simplified version of this adaptive phased-array-radar processor that nulls out the narrow-band jammers by using feedback-correlation detection. In this processor it is assumed that we know a priori only that the signal is broadband and the jammers are narrow band. These are examples of a class of optical processors that use the angular selectivity of volume holograms to form the nulls and look directions in an adaptive phased-array-radar pattern and thereby to harness the computational abilities of three-dimensional parallelism in the volume of photorefractive crystals. The development of this processing in volume holographic system has led to a new algorithm for phased-array-radar processing that uses fewer tapped-delay lines than does the classic time-domain beam former. The optical implementation of the new algorithm has the further advantage of utilization of a single photorefractive crystal to implement as many as a million adaptive weights, allowing the radar system to scale to large size with no increase in processing hardware.

  5. A MRI rotary phased array head coil.

    PubMed

    Li, Bing Keong; Weber, Ewald; Crozier, Stuart

    2013-08-01

    A new rotary phased array (RPA) head coil that can provide homogenous brain images comparable to volumetric radiofrequency coils is proposed for magnetic resonance brain imaging applications. The design of the RPA head coil is a departure from conventional circumferential array design method, as coil elements of the RPA head coil have a "paddle-like" structure consisting of a pair of main conductors located on opposite sides, inserted equi-angularly around and over the head. A prototype 2T receive-only 4-element RPA head coil was constructed and experimentally tested against a conventional receive-only 4-element phased array head coil and a commercial receive-only quadrature birdcage head coil. Homogenous phantom images acquired by the RPA head coil show that signal intensity deep at the center of the phantom was improved as compared to the conventional phased array head coil and this improvement allow the RPA head coil to acquire homogenous brain images similar to brain images acquired with the birdcage head coil. In addition, partial parallel imaging was used in conjunction with the RPA head coil to enable rapid imaging.

  6. Proceedings of the Third EPRI Phased Array Ultrasound Seminar

    SciTech Connect

    2003-12-01

    Phased array technology for ultrasonic examination is providing innovative solutions for nuclear in-service examination applications. EPRI has been a prime mover in the development and deployment of phased array ultrasound applications in the domestic nuclear market over the past decade. As part of this strategic effort, EPRI has hosted a series of seminars on phased array technology and its applications.

  7. Phased array antenna matching: Simulation and optimization of a planar phased array of circular waveguide elements

    NASA Technical Reports Server (NTRS)

    Dudgeon, J. E.

    1972-01-01

    A computerized simulation of a planar phased array of circular waveguide elements is reported using mutual coupling and wide angle impedance matching in phased arrays. Special emphasis is given to circular polarization. The aforementioned computer program has as variable inputs: frequency, polarization, grid geometry, element size, dielectric waveguide fill, dielectric plugs in the waveguide for impedance matching, and dielectric sheets covering the array surface for the purpose of wide angle impedance matching. Parameter combinations are found which produce reflection peaks interior to grating lobes, while dielectric cover sheets are successfully employed to extend the usable scan range of a phased array. The most exciting results came from the application of computer aided optimization techniques to the design of this type of array.

  8. Design of a K-Band Transmit Phased Array For Low Earth Orbit Satellite Communications

    NASA Technical Reports Server (NTRS)

    Watson, Thomas; Miller, Stephen; Kershner, Dennis; Anzic, Godfrey

    2000-01-01

    The design of a light weight, low cost phased array antenna is presented. Multilayer printed wiring board (PWB) technology is utilized for Radio Frequencies (RF) and DC/Logic manifold distribution. Transmit modules are soldered on one side and patch antenna elements are on the other, allowing the use of automated assembly processes. The 19 GHz antenna has two independently steerable beams, each capable of transferring data at 622 Mbps. A passive, self-contained phase change thermal management system is also presented.

  9. Solid-state phased array (SSPA) performance

    NASA Astrophysics Data System (ADS)

    Kley, Robert C., Jr.; Hull, W. Porter, Jr.; Lamb, Franklin D.

    The solid-state phased-array (SSPA) is an active electronically scanned array (AESA) designed and built for airborne radar applications using transmit/receive module hybrid technology. Details of its subassemblies and results of testing the array and its subassemblies are presented. The SSPA T/R (transmit/receive) modules used a hybrid construction that is labor-intensive and leads to parameter variations. The next generation of modules uses monolithic microwave integrated circuit (MMIC) devices, which will result in more uniform parameters and lower manufacturing cost.

  10. Wide Angle Liquid Crystal Optical Phased Array

    NASA Technical Reports Server (NTRS)

    Wang, Xing-Hua; Wang, Bin; Bos, Philip J.; Anderson, James E.; Pouch, John J.; Miranda, Felix A.; McManamon, Paul F.

    2004-01-01

    Accurate modeling of a high resolution, liquid crystal (LC) based, optical phased array (OPA) is shown. The simulation shows excellent agreement with a test 2-D LC OPA. The modeling method is extendable to cases where the array element size is close to the wavelength of light. The fringing fields of such a device are first studied, and subsequently reduced. This results in a device that demonstrates plus or minus 7.4 degrees of continuous beam steering at a wavelength of 1550 nm, and a diffraction efficiency (DE) higher than 72%.

  11. Phased array performance evaluation with photoelastic visualization

    SciTech Connect

    Ginzel, Robert; Dao, Gavin

    2014-02-18

    New instrumentation and a widening range of phased array transducer options are affording the industry a greater potential. Visualization of the complex wave components using the photoelastic system can greatly enhance understanding of the generated signals. Diffraction, mode conversion and wave front interaction, together with beam forming for linear, sectorial and matrix arrays, will be viewed using the photoelastic system. Beam focus and steering performance will be shown with a range of embedded and surface targets within glass samples. This paper will present principles and sound field images using this visualization system.

  12. [High frequency ultrasound].

    PubMed

    Sattler, E

    2015-07-01

    Diagnostic ultrasound has become a standard procedure in clinical dermatology. Devices with intermediate high frequencies of 7.5-15 MHz are used in dermato-oncology for the staging and postoperative care of skin tumor patients and in angiology for improved vessel diagnostics. In contrast, the high frequency ultrasound systems with 20-100 MHz probes offer a much higher resolution, yet with a lower penetration depth of about 1 cm. The main indications are the preoperative measurements of tumor thickness in malignant melanoma and other skin tumors and the assessment of inflammatory and soft tissue diseases, offering information on the course of these dermatoses and allowing therapy monitoring. This article gives an overview on technical principles, devices, mode of examination, influencing factors, interpretation of the images, indications but also limitations of this technique. PMID:25636803

  13. High frequency reference electrode

    DOEpatents

    Kronberg, James W.

    1994-01-01

    A high frequency reference electrode for electrochemical experiments comprises a mercury-calomel or silver-silver chloride reference electrode with a layer of platinum around it and a layer of a chemically and electrically resistant material such as TEFLON around the platinum covering all but a small ring or "halo" at the tip of the reference electrode, adjacent to the active portion of the reference electrode. The voltage output of the platinum layer, which serves as a redox electrode, and that of the reference electrode are coupled by a capacitor or a set of capacitors and the coupled output transmitted to a standard laboratory potentiostat. The platinum may be applied by thermal decomposition to the surface of the reference electrode. The electrode provides superior high-frequency response over conventional electrodes.

  14. High frequency reference electrode

    DOEpatents

    Kronberg, J.W.

    1994-05-31

    A high frequency reference electrode for electrochemical experiments comprises a mercury-calomel or silver-silver chloride reference electrode with a layer of platinum around it and a layer of a chemically and electrically resistant material such as TEFLON around the platinum covering all but a small ring or halo' at the tip of the reference electrode, adjacent to the active portion of the reference electrode. The voltage output of the platinum layer, which serves as a redox electrode, and that of the reference electrode are coupled by a capacitor or a set of capacitors and the coupled output transmitted to a standard laboratory potentiostat. The platinum may be applied by thermal decomposition to the surface of the reference electrode. The electrode provides superior high-frequency response over conventional electrodes. 4 figs.

  15. [High frequency ultrasound].

    PubMed

    Sattler, E

    2015-07-01

    Diagnostic ultrasound has become a standard procedure in clinical dermatology. Devices with intermediate high frequencies of 7.5-15 MHz are used in dermato-oncology for the staging and postoperative care of skin tumor patients and in angiology for improved vessel diagnostics. In contrast, the high frequency ultrasound systems with 20-100 MHz probes offer a much higher resolution, yet with a lower penetration depth of about 1 cm. The main indications are the preoperative measurements of tumor thickness in malignant melanoma and other skin tumors and the assessment of inflammatory and soft tissue diseases, offering information on the course of these dermatoses and allowing therapy monitoring. This article gives an overview on technical principles, devices, mode of examination, influencing factors, interpretation of the images, indications but also limitations of this technique.

  16. Optimizing an ELF/VLF Phased Array at HAARP

    NASA Astrophysics Data System (ADS)

    Fujimaru, S.; Moore, R. C.

    2013-12-01

    The goal of this study is to maximize the amplitude of 1-5 kHz ELF/VLF waves generated by ionospheric HF heating and measured at a ground-based ELF/VLF receiver. The optimization makes use of experimental observations performed during ELF/VLF wave generation experiments at the High-frequency Active Auroral Research Program (HAARP) Observatory in Gakona, Alaska. During these experiments, the amplitude, phase, and propagation delay of the ELF/VLF waves were carefully measured. The HF beam was aimed at 15 degrees zenith angle in 8 different azimuthal directions, equally spaced in a circle, while broadcasting a 3.25 MHz (X-mode) signal that was amplitude modulated (square wave) with a linear frequency-time chirp between 1 and 5 kHz. The experimental observations are used to provide reference amplitudes, phases, and propagation delays for ELF/VLF waves generated at these specific locations. The presented optimization accounts for the trade-off between duty cycle, heated area, and the distributed nature of the source region in order to construct a "most efficient" phased array. The amplitudes and phases generated by modulated heating at each location are combined in post-processing to find an optimal combination of duty cycle, heating location, and heating order.

  17. Quantitative flaw characterization with ultrasonic phased arrays

    NASA Astrophysics Data System (ADS)

    Engle, Brady John

    Ultrasonic nondestructive evaluation (NDE) is a critical diagnostic tool in many industries. It is used to characterize potentially dangerous flaws in critical components for aerospace, automotive, and energy applications. The use of phased array transducers allows for the extension of traditional techniques and the introduction of new methods for quantitative flaw characterization. An equivalent flaw sizing technique for use in time-of-flight diffraction setups is presented that provides an estimate of the size and orientation of isolated cracks, surface-breaking cracks, and volumetric flaws such as voids and inclusions. Experimental validation is provided for the isolated crack case. A quantitative imaging algorithm is developed that corrects for system effects and wave propagation, making the images formed directly related to the properties of the scatterer present. Simulated data is used to form images of cylindrical and spherical inclusions. The contributions of different signals to the image formation process are discussed and examples of the quantitative nature of the images are shown.

  18. Multiband Photonic Phased-Array Antenna

    NASA Technical Reports Server (NTRS)

    Tang, Suning

    2015-01-01

    A multiband phased-array antenna (PAA) can reduce the number of antennas on shipboard platforms while offering significantly improved performance. Crystal Research, Inc., has developed a multiband photonic antenna that is based on a high-speed, optical, true-time-delay beamformer. It is capable of simultaneously steering multiple independent radio frequency (RF) beams in less than 1,000 nanoseconds. This high steering speed is 3 orders of magnitude faster than any existing optical beamformer. Unlike other approaches, this technology uses a single controlling device per operation band, eliminating the need for massive optical switches, laser diodes, and fiber Bragg gratings. More importantly, only one beamformer is needed for all antenna elements.

  19. PHASED ARRAY FEED CALIBRATION, BEAMFORMING, AND IMAGING

    SciTech Connect

    Landon, Jonathan; Elmer, Michael; Waldron, Jacob; Jones, David; Stemmons, Alan; Jeffs, Brian D.; Warnick, Karl F.; Richard Fisher, J.; Norrod, Roger D.

    2010-03-15

    Phased array feeds (PAFs) for reflector antennas offer the potential for increased reflector field of view and faster survey speeds. To address some of the development challenges that remain for scientifically useful PAFs, including calibration and beamforming algorithms, sensitivity optimization, and demonstration of wide field of view imaging, we report experimental results from a 19 element room temperature L-band PAF mounted on the Green Bank 20 Meter Telescope. Formed beams achieved an aperture efficiency of 69% and a system noise temperature of 66 K. Radio camera images of several sky regions are presented. We investigate the noise performance and sensitivity of the system as a function of elevation angle with statistically optimal beamforming and demonstrate cancelation of radio frequency interference sources with adaptive spatial filtering.

  20. A Phased Array Approach to Rock Blasting

    SciTech Connect

    Leslie Gertsch; Jason Baird

    2006-07-01

    A series of laboratory-scale simultaneous two-hole shots was performed in a rock simulant (mortar) to record the shock wave interference patterns produced in the material. The purpose of the project as a whole was to evaluate the usefulness of phased array techniques of blast design, using new high-precision delay technology. Despite high-speed photography, however, we were unable to detect the passage of the shock waves through the samples to determine how well they matched the expected interaction geometry. The follow-up mine-scale tests were therefore not conducted. Nevertheless, pattern analysis of the vectors that would be formed by positive interference of the shockwaves from multiple charges in an ideal continuous, homogeneous, isotropic medium indicate the potential for powerful control of blast design, given precise characterization of the target rock mass.

  1. MMIC Phased Array Demonstrations with ACTS

    NASA Technical Reports Server (NTRS)

    Raquet, Charles A. (Compiler); Martzaklis, Konstantinos (Compiler); Zakrajsek, Robert J. (Compiler); Andro, Monty (Compiler); Turtle, John P.

    1996-01-01

    Over a one year period from May 1994 to May 1995, a number of demonstrations were conducted by the NASA Lewis Research Center (LeRC) in which voice, data, and/or video links were established via NASA's advanced communications technology satellite (ACTS) between the ACTS link evaluation terminal (LET) in Cleveland, OH, and aeronautical and mobile or fixed Earth terminals having monolithic microwave integrated circuit (MMIC) phased array antenna systems. This paper describes four of these. In one, a duplex voice link between an aeronautical terminal on the LeRC Learjet and the ACTS was achieved. Two others demonstrated duplex voice (and in one case video as well) links between the ACTS and an Army vehicle. The fourth demonstrated a high data rate downlink from ACTS to a fixed terminal. Array antenna systems used in these demonstrations were developed by LeRC and featured LeRC and Air Force experimental arrays using gallium arsenide MMIC devices at each radiating element for electronic beam steering and distributed power amplification. The single 30 GHz transmit array was developed by NASA/LeRC and Texas Instruments. The three 20 GHz receive arrays were developed in a cooperative effort with the Air Force Rome Laboratory, taking advantage of existing Air Force array development contracts with Boeing and Lockheed Martin. The paper describes the four proof-of-concept arrays and the array control system. The system configured for each of the demonstrations is described, and results are discussed.

  2. Phased-Array Study of Dual-Flow Jet Noise: Effect of Nozzles and Mixers

    NASA Technical Reports Server (NTRS)

    Soo Lee, Sang; Bridges, James

    2006-01-01

    A 16-microphone linear phased-array installed parallel to the jet axis and a 32-microphone azimuthal phased-array installed in the nozzle exit plane have been applied to identify the noise source distributions of nozzle exhaust systems with various internal mixers (lobed and axisymmetric) and nozzles (three different lengths). Measurements of velocity were also obtained using cross-stream stereo particle image velocimetry (PIV). Among the three nozzle lengths tested, the medium length nozzle was the quietest for all mixers at high frequency on the highest speed flow condition. Large differences in source strength distributions between nozzles and mixers occurred at or near the nozzle exit for this flow condition. The beamforming analyses from the azimuthal array for the 12-lobed mixer on the highest flow condition showed that the core flow and the lobe area were strong noise sources for the long and short nozzles. The 12 noisy spots associated with the lobe locations of the 12-lobed mixer with the long nozzle were very well detected for the frequencies 5 KHz and higher. Meanwhile, maps of the source strength of the axisymmetric splitter show that the outer shear layer was the most important noise source at most flow conditions. In general, there was a good correlation between the high turbulence regions from the PIV tests and the high noise source regions from the phased-array measurements.

  3. High-frequency ECG

    NASA Technical Reports Server (NTRS)

    Tragardh, Elin; Schlegel, Todd T.

    2006-01-01

    The standard ECG is by convention limited to 0.05-150 Hz, but higher frequencies are also present in the ECG signal. With high-resolution technology, it is possible to record and analyze these higher frequencies. The highest amplitudes of the high-frequency components are found within the QRS complex. In past years, the term "high frequency", "high fidelity", and "wideband electrocardiography" have been used by several investigators to refer to the process of recording ECGs with an extended bandwidth of up to 1000 Hz. Several investigators have tried to analyze HF-QRS with the hope that additional features seen in the QRS complex would provide information enhancing the diagnostic value of the ECG. The development of computerized ECG-recording devices that made it possible to record ECG signals with high resolution in both time and amplitude, as well as better possibilities to store and process the signals digitally, offered new methods for analysis. Different techniques to extract the HF-QRS have been described. Several bandwidths and filter types have been applied for the extraction as well as different signal-averaging techniques for noise reduction. There is no standard method for acquiring and quantifying HF-QRS. The physiological mechanisms underlying HF-QRS are still not fully understood. One theory is that HF-QRS are related to the conduction velocity and the fragmentation of the depolarization wave in the myocardium. In a three-dimensional model of the ventricles with a fractal conduction system it was shown that high numbers of splitting branches are associated with HF-QRS. In this experiment, it was also shown that the changes seen in HF-QRS in patients with myocardial ischemia might be due to the slowing of the conduction velocity in the region of ischemia. This mechanism has been tested by Watanabe et al by infusing sodium channel blockers into the left anterior descending artery in dogs. In their study, 60 unipolar ECGs were recorded from the entire

  4. Simulation of Temperature Field Induced by 8-Element Phased Array HIFU Transducer with Concave Spherical Surface

    NASA Astrophysics Data System (ADS)

    Sun, Wujun; Zhang, Ping; Zhang, Xiaojing; Jian, Xiqi; Li, Zhihua

    2011-09-01

    Multi-element High Intensity Focused Ultrasound (HIFU) transducers can change their focal lengths and form multi-foci. In this paper the Westervelt formula and Pennes bio-heat transfer equation have been used along, with the Finite Difference Time Domain (FDTD) method, to study the temperature distribution induced by an 8-element phased array HIFU transducer inside the human body. We evaluated the effects of the gap in the arc between two rings, the frequency of excitation function and pre-focal length on the temperature field. For HIFU therapy, skin burns were caused by high frequency, small pre-focal length, or a big gap between two rings. The focal region may be no longer an ellipsoid due to high frequency. In addition, the actual focal length is slightly different from the pre-focal length.

  5. Extremely high frequency RF effects on electronics.

    SciTech Connect

    Loubriel, Guillermo Manuel; Vigliano, David; Coleman, Phillip Dale; Williams, Jeffery Thomas; Wouters, Gregg A.; Bacon, Larry Donald; Mar, Alan

    2012-01-01

    The objective of this work was to understand the fundamental physics of extremely high frequency RF effects on electronics. To accomplish this objective, we produced models, conducted simulations, and performed measurements to identify the mechanisms of effects as frequency increases into the millimeter-wave regime. Our purpose was to answer the questions, 'What are the tradeoffs between coupling, transmission losses, and device responses as frequency increases?', and, 'How high in frequency do effects on electronic systems continue to occur?' Using full wave electromagnetics codes and a transmission-line/circuit code, we investigated how extremely high-frequency RF propagates on wires and printed circuit board traces. We investigated both field-to-wire coupling and direct illumination of printed circuit boards to determine the significant mechanisms for inducing currents at device terminals. We measured coupling to wires and attenuation along wires for comparison to the simulations, looking at plane-wave coupling as it launches modes onto single and multiconductor structures. We simulated the response of discrete and integrated circuit semiconductor devices to those high-frequency currents and voltages, using SGFramework, the open-source General-purpose Semiconductor Simulator (gss), and Sandia's Charon semiconductor device physics codes. This report documents our findings.

  6. S-band antenna phased array communications system

    NASA Technical Reports Server (NTRS)

    Delzer, D. R.; Chapman, J. E.; Griffin, R. A.

    1975-01-01

    The development of an S-band antenna phased array for spacecraft to spacecraft communication is discussed. The system requirements, antenna array subsystem design, and hardware implementation are examined. It is stated that the phased array approach offers the greatest simplicity and lowest cost. The objectives of the development contract are defined as: (1) design of a medium gain active phased array S-band communications antenna, (2) development and test of a model of a seven element planar array of radiating elements mounted in the appropriate cavity matrix, and (3) development and test of a breadboard transmit/receive microelectronics module.

  7. High Rate User Ka-Band Phased Array Antenna Test Results

    NASA Technical Reports Server (NTRS)

    Caroglanian, Armen; Perko, Kenneth; Seufert, Steve; Dod, Tom; Warshowsky, Jay; Day, John H. (Technical Monitor)

    2001-01-01

    The High Rate User Phased Array Antenna (HRUPAA) is a Ka-Band planar phased array designed by the Harris Corporation for the NASA Goddard Space Flight Center. The HRUPAA permits a satellite to downlink data either to a ground station or through the Tracking and Data Relay Satellite System (TDRSS). The HRUPAA is scanned electronically by ground station / user satellite command over a 120 degree cone angle. The phased array has the advantage of not imparting attitude disturbances to the user spacecraft. The 288-element transmit-only array has distributed RF amplifiers integrated behind each of the printed patch antenna elements. The array has 33 dBW EIRP and is left-hand circularly polarized. An engineering model of a partially populated array has been developed and delivered to NASA Goddard Space Flight Center. This report deals with the testing of the engineering model at the Goddard Antenna Range near-field and compact range facilities. The antenna specifications are described first, followed by the test plan and test results.

  8. Phased-array sources based on nonlinear metamaterial nanocavities.

    PubMed

    Wolf, Omri; Campione, Salvatore; Benz, Alexander; Ravikumar, Arvind P; Liu, Sheng; Luk, Ting S; Kadlec, Emil A; Shaner, Eric A; Klem, John F; Sinclair, Michael B; Brener, Igal

    2015-07-01

    Coherent superposition of light from subwavelength sources is an attractive prospect for the manipulation of the direction, shape and polarization of optical beams. This phenomenon constitutes the basis of phased arrays, commonly used at microwave and radio frequencies. Here we propose a new concept for phased-array sources at infrared frequencies based on metamaterial nanocavities coupled to a highly nonlinear semiconductor heterostructure. Optical pumping of the nanocavity induces a localized, phase-locked, nonlinear resonant polarization that acts as a source feed for a higher-order resonance of the nanocavity. Varying the nanocavity design enables the production of beams with arbitrary shape and polarization. As an example, we demonstrate two second harmonic phased-array sources that perform two optical functions at the second harmonic wavelength (∼5 μm): a beam splitter and a polarizing beam splitter. Proper design of the nanocavity and nonlinear heterostructure will enable such phased arrays to span most of the infrared spectrum.

  9. Phased-array sources based on nonlinear metamaterial nanocavities

    NASA Astrophysics Data System (ADS)

    Wolf, Omri; Campione, Salvatore; Benz, Alexander; Ravikumar, Arvind P.; Liu, Sheng; Luk, Ting S.; Kadlec, Emil A.; Shaner, Eric A.; Klem, John F.; Sinclair, Michael B.; Brener, Igal

    2015-07-01

    Coherent superposition of light from subwavelength sources is an attractive prospect for the manipulation of the direction, shape and polarization of optical beams. This phenomenon constitutes the basis of phased arrays, commonly used at microwave and radio frequencies. Here we propose a new concept for phased-array sources at infrared frequencies based on metamaterial nanocavities coupled to a highly nonlinear semiconductor heterostructure. Optical pumping of the nanocavity induces a localized, phase-locked, nonlinear resonant polarization that acts as a source feed for a higher-order resonance of the nanocavity. Varying the nanocavity design enables the production of beams with arbitrary shape and polarization. As an example, we demonstrate two second harmonic phased-array sources that perform two optical functions at the second harmonic wavelength (~5 μm): a beam splitter and a polarizing beam splitter. Proper design of the nanocavity and nonlinear heterostructure will enable such phased arrays to span most of the infrared spectrum.

  10. Phase Noise in Photonic Phased-Array Antenna Systems

    NASA Technical Reports Server (NTRS)

    Logan, Ronald T., Jr.; Maleki, Lute

    1998-01-01

    The total noise of a phased-array antenna system employing a photonic feed network is analyzed using a model for the individual component noise including both additive and multiplicative equivalent noise generators.

  11. Phased-array sources based on nonlinear metamaterial nanocavities

    SciTech Connect

    Wolf, Omri; Campione, Salvatore; Benz, Alexander; Ravikumar, Arvind P.; Liu, Sheng; Luk, Ting S.; Kadlec, Emil Andrew; Shaner, Eric A.; Klem, John Frederick; Sinclair, Michael B.; Brener, Igal

    2015-07-01

    Coherent superposition of light from subwavelength sources is an attractive prospect for the manipulation of the direction, shape and polarization of optical beams. This phenomenon constitutes the basis of phased arrays, commonly used at microwave and radio frequencies. Here we propose a new concept for phased-array sources at infrared frequencies based on metamaterial nanocavities coupled to a highly nonlinear semiconductor heterostructure. Optical pumping of the nanocavity induces a localized, phase-locked, nonlinear resonant polarization that acts as a source feed for a higher-order resonance of the nanocavity. Varying the nanocavity design enables the production of beams with arbitrary shape and polarization. As an example, we demonstrate two second harmonic phased-array sources that perform two optical functions at the second harmonic wavelength (~5 μm): a beam splitter and a polarizing beam splitter. As a result, proper design of the nanocavity and nonlinear heterostructure will enable such phased arrays to span most of the infrared spectrum.

  12. Laser-scanning photoacoustic microscopy with ultrasonic phased array transducer.

    PubMed

    Zheng, Fan; Zhang, Xiangyang; Chiu, Chi Tat; Zhou, Bill L; Shung, K Kirk; Zhang, Hao F; Jiao, Shuliang

    2012-11-01

    In this paper, we report our latest progress on proving the concept that ultrasonic phased array can improve the detection sensitivity and field of view (FOV) in laser-scanning photoacoustic microscopy (LS-PAM). A LS-PAM system with a one-dimensional (1D) ultrasonic phased array was built for the experiments. The 1D phased array transducer consists of 64 active elements with an overall active dimension of 3.2 mm × 2 mm. The system was tested on imaging phantom and mouse ear in vivo. Experiments showed a 15 dB increase of the signal-to-noise ratio (SNR) when beamforming was employed compared to the images acquired with each single element. The experimental results demonstrated that ultrasonic phased array can be a better candidate for LS-PAM in high sensitivity applications like ophthalmic imaging.

  13. [Modeling and simulation of responses from ultrasonic linear phased array].

    PubMed

    He, Wenjing; Zhu, Yuanzhong; Wang, Yufeng; He, Lingli; Lai, Siyu

    2012-10-01

    Phased array transducers are very attractive because the beam generated by the arrays can be electronically focused and steered. The present work characterizes far-field 2D properties of phased array system by functions that are deduced from rectangle source, rectangle line array and phased array based on point source. Results are presented for the distribution of ultrasound intensity on plane xoz and on x-axis by simulation using numerical calculation. It is shown that the shape of response of rectangle line array is modulated by the single array element. It is also demonstrated that the delay time of phased array is the key to steer the beam, sacrificing the value of main lobe and increasing the number of side lobes.

  14. Coherent optical monolithic phased-array antenna steering system

    DOEpatents

    Hietala, Vincent M.; Kravitz, Stanley H.; Vawter, Gregory A.

    1994-01-01

    An optical-based RF beam steering system for phased-array antennas comprising a photonic integrated circuit (PIC). The system is based on optical heterodyning employed to produce microwave phase shifting by a monolithic PIC constructed entirely of passive components. Microwave power and control signal distribution to the antenna is accomplished by optical fiber, permitting physical separation of the PIC and its control functions from the antenna. The system reduces size, weight, complexity, and cost of phased-array antenna systems.

  15. MSAT mobile electronically steered phased array antenna development

    NASA Technical Reports Server (NTRS)

    Schmidt, Fred

    1988-01-01

    The Mobile Satellite Experiment (MSAT-X) breadboard antenna design demonstrates the feasibility of using a phased array in a mobile satellite application. An electronically steerable phased array capable of tracking geosynchronous satellites from anywhere in the Continental United States has been developed. The design is reviewed along with the test data. Cost analysis are presented which indicate that this design can be produced at a cost of $1620 per antenna.

  16. Optimizing Satellite Communications With Adaptive and Phased Array Antennas

    NASA Technical Reports Server (NTRS)

    Ingram, Mary Ann; Romanofsky, Robert; Lee, Richard Q.; Miranda, Felix; Popovic, Zoya; Langley, John; Barott, William C.; Ahmed, M. Usman; Mandl, Dan

    2004-01-01

    A new adaptive antenna array architecture for low-earth-orbiting satellite ground stations is being investigated. These ground stations are intended to have no moving parts and could potentially be operated in populated areas, where terrestrial interference is likely. The architecture includes multiple, moderately directive phased arrays. The phased arrays, each steered in the approximate direction of the satellite, are adaptively combined to enhance the Signal-to-Noise and Interference-Ratio (SNIR) of the desired satellite. The size of each phased array is to be traded-off with the number of phased arrays, to optimize cost, while meeting a bit-error-rate threshold. Also, two phased array architectures are being prototyped: a spacefed lens array and a reflect-array. If two co-channel satellites are in the field of view of the phased arrays, then multi-user detection techniques may enable simultaneous demodulation of the satellite signals, also known as Space Division Multiple Access (SDMA). We report on Phase I of the project, in which fixed directional elements are adaptively combined in a prototype to demodulate the S-band downlink of the EO-1 satellite, which is part of the New Millennium Program at NASA.

  17. An inkjet vision measurement technique for high-frequency jetting

    SciTech Connect

    Kwon, Kye-Si Jang, Min-Hyuck; Park, Ha Yeong; Ko, Hyun-Seok

    2014-06-15

    Inkjet technology has been used as manufacturing a tool for printed electronics. To increase the productivity, the jetting frequency needs to be increased. When using high-frequency jetting, the printed pattern quality could be non-uniform since the jetting performance characteristics including the jetting speed and droplet volume could vary significantly with increases in jet frequency. Therefore, high-frequency jetting behavior must be evaluated properly for improvement. However, it is difficult to measure high-frequency jetting behavior using previous vision analysis methods, because subsequent droplets are close or even merged. In this paper, we present vision measurement techniques to evaluate the drop formation of high-frequency jetting. The proposed method is based on tracking target droplets such that subsequent droplets can be excluded in the image analysis by focusing on the target droplet. Finally, a frequency sweeping method for jetting speed and droplet volume is presented to understand the overall jetting frequency effects on jetting performance.

  18. Remoting alternatives for a multiple phased-array antenna network

    NASA Astrophysics Data System (ADS)

    Shi, Zan; Foshee, James J.

    2001-10-01

    Significant improvements in technology have made phased array antennas an attractive alternative to the traditional dish antenna for use on wide body airplanes. These improvements have resulted in reduced size, reduced cost, reduced losses in the transmit and receive channels (simplifying the design), a significant extension in the bandwidth capability, and an increase in the functional capability. Flush mounting (thus reduced drag) and rapid beam switching are among the evolving desirable features of phased array antennas. Beam scanning of phased array antennas is limited to +/-45 degrees at best and therefore multiple phased array antennas would need to be used to insure instantaneous communications with any ground station (stations located at different geographical locations on the ground) and with other airborne stations. The exact number of phased array antennas and the specific installation location of each antenna on the wide body airplane would need to be determined by the specific communication requirements, but it is conceivable as many as five phased array antennas may need to be used to provide the required coverage. Control and switching of these antennas would need to be accomplished at a centralized location on the airplane and since these antennas would be at different locations on the airplane an efficient scheme of remoting would need to be used. To save in cost and keep the phased array antennas as small as possible the design of the phased array antennas would need to be kept simple. A dish antenna and a blade antenna (small size) could also be used to augment the system. Generating the RF signals at the central location and then using RF cables or waveguide to get the signal to any given antenna could result in significant RF losses. This paper will evaluate a number of remoting alternatives to keep the system design simple, reduce system cost, and utilize the functional capability of networking multiple phased array antennas on a wide body

  19. Phased Array Radiometer Calibration Using a Radiated Noise Source

    NASA Technical Reports Server (NTRS)

    Srinivasan, Karthik; Limaye, Ashutoch S.; Laymon, Charles A.; Meyer, Paul J.

    2010-01-01

    Electronic beam steering capability of phased array antenna systems offer significant advantages when used in real aperture imaging radiometers. The sensitivity of such systems is limited by the ability to accurately calibrate variations in the antenna circuit characteristics. Passive antenna systems, which require mechanical rotation to scan the beam, have stable characteristics and the noise figure of the antenna can be characterized with knowledge of its physical temperature [1],[2]. Phased array antenna systems provide the ability to electronically steer the beam in any desired direction. Such antennas make use of active components (amplifiers, phase shifters) to provide electronic scanning capability while maintaining a low antenna noise figure. The gain fluctuations in the active components can be significant, resulting in substantial calibration difficulties [3]. In this paper, we introduce two novel calibration techniques that provide an end-to-end calibration of a real-aperture, phased array radiometer system. Empirical data will be shown to illustrate the performance of both methods.

  20. Optical phased arrays with evanescently-coupled antennas

    DOEpatents

    Sun, Jie; Watts, Michael R; Yaacobi, Ami; Timurdogan, Erman

    2015-03-24

    An optical phased array formed of a large number of nanophotonic antenna elements can be used to project complex images into the far field. These nanophotonic phased arrays, including the nanophotonic antenna elements and waveguides, can be formed on a single chip of silicon using complementary metal-oxide-semiconductor (CMOS) processes. Directional couplers evanescently couple light from the waveguides to the nanophotonic antenna elements, which emit the light as beams with phases and amplitudes selected so that the emitted beams interfere in the far field to produce the desired pattern. In some cases, each antenna in the phased array may be optically coupled to a corresponding variable delay line, such as a thermo-optically tuned waveguide or a liquid-filled cell, which can be used to vary the phase of the antenna's output (and the resulting far-field interference pattern).

  1. Phased arrays for satellites and the TDRSS antennas

    NASA Astrophysics Data System (ADS)

    Imbriale, W. A.

    The design and performance of satellite phased-array systems are examined by considering several specific antennas built for spacecraft use. Particular consideration is given to: (1) the JARED (Jammer Reduction Antenna System) antenna, and adaptive phased array which can be used to null jammer signals while providing coverage to specific user areas; (2) the algorithm used in the JARED antenna; and (3) a technique that can be used to detect and locate jammers. The antennas used by the Tracking and Data Relay Satellite System (TDRSS) are then described. A significant aspect of the TDRSS is the multiple access antenna which is a 30-element phased array, providing a single steered beam on transmit and the ability to receive data from 20 simultaneous users. Also included on the TDRSS is a mesh deployable reflector and a C-band and K-band communications system.

  2. Phased arrays for satellites and the TDRSS antennas

    NASA Technical Reports Server (NTRS)

    Imbriale, W. A.

    1983-01-01

    The design and performance of satellite phased-array systems are examined by considering several specific antennas built for spacecraft use. Particular consideration is given to: (1) the JARED (Jammer Reduction Antenna System) antenna, and adaptive phased array which can be used to null jammer signals while providing coverage to specific user areas; (2) the algorithm used in the JARED antenna; and (3) a technique that can be used to detect and locate jammers. The antennas used by the Tracking and Data Relay Satellite System (TDRSS) are then described. A significant aspect of the TDRSS is the multiple access antenna which is a 30-element phased array, providing a single steered beam on transmit and the ability to receive data from 20 simultaneous users. Also included on the TDRSS is a mesh deployable reflector and a C-band and K-band communications system.

  3. Ka-Band Multibeam Aperture Phased Array Being Developed

    NASA Technical Reports Server (NTRS)

    Reinhart, Richard C.; Kacpura, Thomas J.

    2004-01-01

    Phased-array antenna systems offer many advantages to low-Earth-orbiting satellite systems. Their large scan angles and multibeam capabilities allow for vibration-free, rapid beam scanning and graceful degradation operation for high rate downlink of data to users on the ground. Technology advancements continue to reduce the power, weight, and cost of these systems to make phased arrays a competitive alternative in comparison to the gimbled reflector system commonly used in science missions. One effort to reduce the cost of phased arrays is the development of a Ka-band multibeam aperture (MBA) phased array by Boeing Corporation under a contract jointly by the NASA Glenn Research Center and the Office of Naval Research. The objective is to develop and demonstrate a space-qualifiable dual-beam Ka-band (26.5-GHz) phased-array antenna. The goals are to advance the state of the art in Ka-band active phased-array antennas and to develop and demonstrate multibeam transmission technology compatible with spacecraft in low Earth orbit to reduce the cost of future missions by retiring certain development risks. The frequency chosen is suitable for space-to-space and space-to-ground communication links. The phased-array antenna has a radiation pattern designed by combining a set of individual radiating elements, optimized with the type of radiating elements used, their positions in space, and the amplitude and phase of the currents feeding the elements. This arrangement produces a directional radiation pattern that is proportional to the number of individual radiating elements. The arrays of interest here can scan the main beam electronically with a computerized algorithm. The antenna is constructed using electronic components with no mechanical parts, and the steering is performed electronically, without any resulting vibration. The speed of the scanning is limited primarily by the control electronics. The radiation performance degrades gracefully if a portion of the elements

  4. Ultrasonic Phased-Array Characterization for NDE Applications

    NASA Technical Reports Server (NTRS)

    Hanley, John J.; Tennis, Richard F.; Pickens, Keith S.

    1995-01-01

    Southwest Research Institute (SwRI) recently fabricated and delivered the 100-channel Ultrasonic Phased-Array Testbed System (UPATS) for NASA's Langley Research Center. NASA prepared the specifications and provided the funding to develop UPATS in order to provide a tool for the improvement of ultrasonic nondestructive evaluation (NDE) and characterization of materials. UPATS incorporates state-of-the-art phased-array concepts such as beam steering, focusing, apodization, and phase-sensitive detection which make it possible to develop more sophisticated testing methodologies. It also can be used to investigate fundamental ultrasonic propagation and detection phenomena such as refraction, diffraction, scattering, and beam broadening.

  5. Microwave power transmitting phased array antenna research project

    NASA Technical Reports Server (NTRS)

    Dickinson, R. M.

    1978-01-01

    An initial design study and the development results of an S band RF power transmitting phased array antenna experiment system are presented. The array was to be designed, constructed and instrumented to permit wireless power transmission technology evaluation measurements. The planned measurements were to provide data relative to the achievable performance in the state of the art of flexible surface, retrodirective arrays, as a step in technically evaluating the satellite power system concept for importing to earth, via microwave beams, the nearly continuous solar power available in geosynchronous orbit. Details of the microwave power transmitting phased array design, instrumentation approaches, system block diagrams, and measured component and breadboard characteristics achieved are presented.

  6. Reconfigurable Wave Velocity Transmission Lines for Phased Arrays

    NASA Technical Reports Server (NTRS)

    Host, Nick; Chen, Chi-Chih; Volakis, John L.; Miranda, Felix

    2013-01-01

    Phased array antennas showcase many advantages over mechanically steered systems. However, they are also more complex, heavy and most importantly costly. This presentation paper presents a concept which overcomes these detrimental attributes by eliminating all of the phase array backend (including phase shifters). Instead, a wave velocity reconfigurable transmission line is used in a series fed array arrangement to allow phase shifting with one small (100mil) mechanical motion. Different configurations of the reconfigurable wave velocity transmission line are discussed and simulated and experimental results are presented.

  7. The Potential of Phased Arrays for Planetary Exploration

    NASA Astrophysics Data System (ADS)

    Pogorzelski, Ronald J.

    2000-01-01

    Phased array antennas provide a set of operational capabilities which are very attractive for certain mission applications and not very attractive for others. Such antennas are by no means a panacea for telecommunications. In this paper the features of phased arrays are reviewed and their implications for space missions are considered in terms of benefits and costs. The primary capability provided by a phased array is electronic beam agility. The beam direction may be controlled at electronic speeds (vs. mechanical actuation) permitting time division multiplexing of multiple "users." Moreover, the beam direction can be varied over a full hemisphere (for a planar array). On the other hand, such antennas are typically much more complicated than the more commonly used reflectors and horns and this implies higher cost. In some applications, this increased cost must be accepted if the mission is to be carried out at all. The SIR-C radar is an example of such a case albeit not for deep space. Assuming for the sake of argument that the complexity and cost of a phased array can be significantly reduced, where can such antennas be of value in the future of planetary exploration? Potential applications to be discussed are planetary rovers, landers, and orbiters including both the areosynchronous and low orbit varieties. In addition, consideration is given to links from deep space to earth. As may be fairly obvious, the deep space link to earth would not benefit from the wide angle steering capability provided by a phase array whereas a rover could gain advantage from the capability to steer a beam anywhere in the sky. In the rover case, however, physical size of the aperture becomes a significant factor which, of course, has implications regarding the choice of frequency band. Recent research work concerning phased arrays has suggested that future phased arrays might be made less complex and, therefore, less costly. Successful realization of such phased arrays would enable

  8. Phased-array sources based on nonlinear metamaterial nanocavities

    PubMed Central

    Wolf, Omri; Campione, Salvatore; Benz, Alexander; Ravikumar, Arvind P.; Liu, Sheng; Luk, Ting S.; Kadlec, Emil A.; Shaner, Eric A.; Klem, John F.; Sinclair, Michael B.; Brener, Igal

    2015-01-01

    Coherent superposition of light from subwavelength sources is an attractive prospect for the manipulation of the direction, shape and polarization of optical beams. This phenomenon constitutes the basis of phased arrays, commonly used at microwave and radio frequencies. Here we propose a new concept for phased-array sources at infrared frequencies based on metamaterial nanocavities coupled to a highly nonlinear semiconductor heterostructure. Optical pumping of the nanocavity induces a localized, phase-locked, nonlinear resonant polarization that acts as a source feed for a higher-order resonance of the nanocavity. Varying the nanocavity design enables the production of beams with arbitrary shape and polarization. As an example, we demonstrate two second harmonic phased-array sources that perform two optical functions at the second harmonic wavelength (∼5 μm): a beam splitter and a polarizing beam splitter. Proper design of the nanocavity and nonlinear heterostructure will enable such phased arrays to span most of the infrared spectrum. PMID:26126879

  9. Code-modulated interferometric imaging system using phased arrays

    NASA Astrophysics Data System (ADS)

    Chauhan, Vikas; Greene, Kevin; Floyd, Brian

    2016-05-01

    Millimeter-wave (mm-wave) imaging provides compelling capabilities for security screening, navigation, and bio- medical applications. Traditional scanned or focal-plane mm-wave imagers are bulky and costly. In contrast, phased-array hardware developed for mass-market wireless communications and automotive radar promise to be extremely low cost. In this work, we present techniques which can allow low-cost phased-array receivers to be reconfigured or re-purposed as interferometric imagers, removing the need for custom hardware and thereby reducing cost. Since traditional phased arrays power combine incoming signals prior to digitization, orthogonal code-modulation is applied to each incoming signal using phase shifters within each front-end and two-bit codes. These code-modulated signals can then be combined and processed coherently through a shared hardware path. Once digitized, visibility functions can be recovered through squaring and code-demultiplexing operations. Pro- vided that codes are selected such that the product of two orthogonal codes is a third unique and orthogonal code, it is possible to demultiplex complex visibility functions directly. As such, the proposed system modulates incoming signals but demodulates desired correlations. In this work, we present the operation of the system, a validation of its operation using behavioral models of a traditional phased array, and a benchmarking of the code-modulated interferometer against traditional interferometer and focal-plane arrays.

  10. Phased-array sources based on nonlinear metamaterial nanocavities

    DOE PAGESBeta

    Wolf, Omri; Campione, Salvatore; Benz, Alexander; Ravikumar, Arvind P.; Liu, Sheng; Luk, Ting S.; Kadlec, Emil Andrew; Shaner, Eric A.; Klem, John Frederick; Sinclair, Michael B.; et al

    2015-07-01

    Coherent superposition of light from subwavelength sources is an attractive prospect for the manipulation of the direction, shape and polarization of optical beams. This phenomenon constitutes the basis of phased arrays, commonly used at microwave and radio frequencies. Here we propose a new concept for phased-array sources at infrared frequencies based on metamaterial nanocavities coupled to a highly nonlinear semiconductor heterostructure. Optical pumping of the nanocavity induces a localized, phase-locked, nonlinear resonant polarization that acts as a source feed for a higher-order resonance of the nanocavity. Varying the nanocavity design enables the production of beams with arbitrary shape and polarization.more » As an example, we demonstrate two second harmonic phased-array sources that perform two optical functions at the second harmonic wavelength (~5 μm): a beam splitter and a polarizing beam splitter. As a result, proper design of the nanocavity and nonlinear heterostructure will enable such phased arrays to span most of the infrared spectrum.« less

  11. Beam-pointing errors of planar-phased arrays.

    NASA Technical Reports Server (NTRS)

    Carver, K. R.; Cooper, W. K.; Stutzman, W. L.

    1973-01-01

    Using both analytical and Monte Carlo techniques, beam-pointing errors of planar-phased arrays are analyzed. The obtained simple formulas for rms pointing errors are applicable to uniform planar arrays with both uniform and Gaussian uncorrelated phase-error distributions and for any arbitrary scan angle.

  12. NASA Adaptive Multibeam Phased Array (AMPA): An application study

    NASA Technical Reports Server (NTRS)

    Mittra, R.; Lee, S. W.; Gee, W.

    1982-01-01

    The proposed orbital geometry for the adaptive multibeam phased array (AMPA) communication system is reviewed and some of the system's capabilities and preliminary specifications are highlighted. Typical AMPA user link models and calculations are presented, the principal AMPA features are described, and the implementation of the system is demonstrated. System tradeoffs and requirements are discussed. Recommendations are included.

  13. Guided wave phased array beamforming and imaging in composite plates.

    PubMed

    Yu, Lingyu; Tian, Zhenhua

    2016-05-01

    This paper describes phased array beamforming using guided waves in anisotropic composite plates. A generic phased array algorithm is presented, in which direction dependent guided wave parameters and the energy skew effect are considered. This beamforming at an angular direction is achieved based on the classic delay-and-sum principle by applying phase delays to signals received at array elements and adding up the delayed signals. The phase delays are determined with the goal to maximize the array output at the desired direction and minimize it otherwise. For array characterization, the beam pattern of rectangular grid arrays in composite plates is derived. In addition to the beam pattern, the beamforming factor in terms of wavenumber distribution is defined to provide intrinsic explanations for phased array beamforming. The beamforming and damage detection in a composite plate are demonstrated using rectangular grid arrays made by a non-contact scanning laser Doppler vibrometer. Detection images of the composite plate with multiple surface defects at various directions are obtained. The results show that the guided wave phased array method is a potential effective method for rapid inspection of large composite structures.

  14. Looking Below the Surface with Ultrasonic Phased Array

    SciTech Connect

    Cinson, Anthony D.; Crawford, Susan L.

    2010-10-01

    This article is a brief tutorial on the benefits of volumetric ultrasonic phased array line scanning. The article describes the need, the approach, and the methods/practices used to analyze the data for flaw detection and characterization in the nuclear power plant component arena.

  15. Phased arrays. Citations from the NTIS data base

    NASA Astrophysics Data System (ADS)

    Reed, W. E.

    1980-04-01

    The design, performance, radiation patterns, and applications of phased arrays are presented in these Federally-sponsored research reports. Applications include communications, radar, optical, spacecraft, and navigational aids. This updated bibliography contains 244 abstracts, 44 of which are new entries to the previous edition.

  16. High frequency integrated MOS filters

    NASA Technical Reports Server (NTRS)

    Peterson, C.

    1990-01-01

    Several techniques exist for implementing integrated MOS filters. These techniques fit into the general categories of sampled and tuned continuous-time filters. Advantages and limitations of each approach are discussed. This paper focuses primarily on the high frequency capabilities of MOS integrated filters.

  17. Large Phased Array Radar Using Networked Small Parabolic Reflectors

    NASA Technical Reports Server (NTRS)

    Amoozegar, Farid

    2006-01-01

    Multifunction phased array systems with radar, telecom, and imaging applications have already been established for flat plate phased arrays of dipoles, or waveguides. In this paper the design trades and candidate options for combining the radar and telecom functions of the Deep Space Network (DSN) into a single large transmit array of small parabolic reflectors will be discussed. In particular the effect of combing the radar and telecom functions on the sizes of individual antenna apertures and the corresponding spacing between the antenna elements of the array will be analyzed. A heterogeneous architecture for the DSN large transmit array is proposed to meet the radar and telecom requirements while considering the budget, scheduling, and strategic planning constrains.

  18. A novel serrated columnar phased array ultrasonic transducer

    NASA Astrophysics Data System (ADS)

    Zou, Cheng; Sun, Zhenguo; Cai, Dong; Song, Hongwei; Chen, Qiang

    2016-02-01

    Traditionally, wedges are required to generate transverse waves in a solid specimen and mechanical rotation device is needed for interrogation of a specimen with a hollow bore, such as high speed railway locomotive axles, turbine rotors, etc. In order to eliminate the mechanical rotation process, a novel array pattern of phased array ultrasonic transducers named as serrated columnar phased array ultrasonic transducer (SCPAUT) is designed. The elementary transducers are planar rectangular, located on the outside surface of a cylinder. This layout is aimed to generate electrically rotating transverse waveforms so as to inspect the longitudinal cracks on the outside surface of a specimen which has a hollow bore at the center, such as the high speed railway locomotive axles. The general geometry of the SCPAUT and the inspection system are illustrated. A FEM model and mockup experiment has been carried out. The experiment results are in good agreement with the FEM simulation results.

  19. A design concept for an MMIC microstrip phased array

    NASA Technical Reports Server (NTRS)

    Lee, R. Q.; Smetana, J.; Acosta, R.

    1986-01-01

    A conceptual design for a microstrip phased array with monolithic microwave integrated circuit (MMIC) amplitude and phase controls is described. The MMIC devices used are 20 GHz variable power amplifiers and variable phase shifters recently developed by NASA contractors for applications in future Ka band advanced satellite communication antenna systems. The proposed design concept is for a general NxN element array of rectangular lattice geometry. Subarray excitation is incorporated in the MMIC phased array design to reduce the complexity of the beam forming network and the number of MMIC components required. The proposed design concept takes into consideration the RF characteristics and actual phyical dimensions of the MMIC devices. Also, solutions to spatial constraints and interconnections associated with currently available packaging designs are discussed. Finally, the design of the microstrip radiating elements and their radiation characteristics are examined.

  20. Phase control circuits using frequency multiplications for phased array antennas

    NASA Technical Reports Server (NTRS)

    Mailloux, R. J.; Caron, P. R. (Inventor)

    1973-01-01

    A phase control coupling circuit for use with a phased array antenna is described. The coupling circuit includes a combining circuit which is coupled to a transmission line, a frequency multiplier circuit which is coupled to the combining circuit, and a recombining circuit which is coupled between the frequency multiplier circuit and phased array antenna elements. In a doubler embodiment, the frequency multiplier circuit comprises frequency doublers and the combining and recombining circuits comprise four-port hybrid power dividers. In a generalized embodiment, the multiplier circuit comprises frequency multiplier elements which multiply to the Nth power, the combining circuit comprises four-part hybrid power dividers, and the recombinding circuit comprises summing circuits.

  1. Ultrasonic Phased Array Simulations of Welded Components at NASA

    NASA Technical Reports Server (NTRS)

    Roth, D. J.; Tokars, R. P.; Martin, R. E.; Rauser, R. W.; Aldrin, J. C.

    2009-01-01

    Comprehensive and accurate inspections of welded components have become of increasing importance as NASA develops new hardware such as Ares rocket segments for future exploration missions. Simulation and modeling will play an increasing role in the future for nondestructive evaluation in order to better understand the physics of the inspection process, to prove or disprove the feasibility for an inspection method or inspection scenario, for inspection optimization, for better understanding of experimental results, and for assessment of probability of detection. This study presents simulation and experimental results for an ultrasonic phased array inspection of a critical welded structure important for NASA future exploration vehicles. Keywords: nondestructive evaluation, computational simulation, ultrasonics, weld, modeling, phased array

  2. Removing Background Noise with Phased Array Signal Processing

    NASA Technical Reports Server (NTRS)

    Podboy, Gary; Stephens, David

    2015-01-01

    Preliminary results are presented from a test conducted to determine how well microphone phased array processing software could pull an acoustic signal out of background noise. The array consisted of 24 microphones in an aerodynamic fairing designed to be mounted in-flow. The processing was conducted using Functional Beam forming software developed by Optinav combined with cross spectral matrix subtraction. The test was conducted in the free-jet of the Nozzle Acoustic Test Rig at NASA GRC. The background noise was produced by the interaction of the free-jet flow with the solid surfaces in the flow. The acoustic signals were produced by acoustic drivers. The results show that the phased array processing was able to pull the acoustic signal out of the background noise provided the signal was no more than 20 dB below the background noise level measured using a conventional single microphone equipped with an aerodynamic forebody.

  3. An Overview of Recent Phased Array Measurements at NASA Glenn

    NASA Technical Reports Server (NTRS)

    Podboy, Gary G.

    2008-01-01

    A review of measurements made at the NASA Glenn Research Center using an OptiNAV Array 48 phased array system is provided. Data were acquired on a series of round convergent and convergent-divergent nozzles using the Small Hot Jet Acoustic Rig. Tests were conducted over a range of jet operating conditions, including subsonic and supersonic and cold and hot jets. Phased array measurements were also acquired on a Williams International FJ44 engine. These measurements show how the noise generated by the engine is split between the inlet-radiated and exhaust-radiated components. The data also show inlet noise being reflected off of the inflow control device used during the test.

  4. MSAT-X phased array antenna adaptions to airborne applications

    NASA Technical Reports Server (NTRS)

    Sparks, C.; Chung, H. H.; Peng, S. Y.

    1988-01-01

    The Mobile Satellite Experiment (MSAT-X) phased array antenna is being modified to meet future requirements. The proposed system consists of two high gain antennas mounted on each side of a fuselage, and a low gain antenna mounted on top of the fuselage. Each antenna is an electronically steered phased array based on the design of the MSAT-X antenna. A beamforming network is connected to the array elements via coaxial cables. It is essential that the proposed antenna system be able to provide an adequate communication link over the required space coverage, which is 360 degrees in azimuth and from 20 degrees below the horizon to the zenith in elevation. Alternative design concepts are suggested. Both open loop and closed loop backup capabilities are discussed. Typical antenna performance data are also included.

  5. Robotic inspection of fiber reinforced composites using phased array UT

    NASA Astrophysics Data System (ADS)

    Stetson, Jeffrey T.; De Odorico, Walter

    2014-02-01

    Ultrasound is the current NDE method of choice to inspect large fiber reinforced airframe structures. Over the last 15 years Cartesian based scanning machines using conventional ultrasound techniques have been employed by all airframe OEMs and their top tier suppliers to perform these inspections. Technical advances in both computing power and commercially available, multi-axis robots now facilitate a new generation of scanning machines. These machines use multiple end effector tools taking full advantage of phased array ultrasound technologies yielding substantial improvements in inspection quality and productivity. This paper outlines the general architecture for these new robotic scanning systems as well as details the variety of ultrasonic techniques available for use with them including advances such as wide area phased array scanning and sound field adaptation for non-flat, non-parallel surfaces.

  6. Control of Complex Components with Smart Flexible Phased Arrays

    NASA Astrophysics Data System (ADS)

    Casula, O.; Poidevin, C.; Cattiaux, G.; Dumas, Ph.

    2006-03-01

    The inspection of piping in nuclear plants is mainly performed in contact with ultrasonic wedge transducers. During the scanning, the fixed shape of wedges cannot fit the irregular surfaces and complex geometries of components (butt weld, nozzle, elbow). The variable thickness of the coupling layer, between the wedge and the local surface, leads to beam distortions and losses of sensitivity. Previous studies have shown that these two phenomena contribute to reduce the inspection performances leading to shadow area, split beam. To improve such controls, a new concept of contact "Smart Flexible Phased Array" has been developed with the support of the French "Institut de Radioprotection et de Sûreté Nucléaire". The phased array is flexible to fit the complex profile and to minimize the thickness of the coupling layer. The independent piezoelectric elements composing the radiating surface are mechanically assembled in order to build an articulated structure. A profilometer, embedded in the transducer, measures the local surface distortion allowing to compute in real-time the optimized delay laws and compensating the distortions of 2D or 3D profiles. Those delay laws are transferred to the real-time UT acquisition system, which applies them to the piezoelectric elements. This self-adaptive process preserves, during the scanning, the features of the focused beam (orientation and focal depth) in the specimen. To validate the concept of the Smart Flexible Phased Array Transducer, two prototypes have been integrated to detect flaws machined in mock-ups with realistic irregular 2D and 3D shapes. Inspections have been carried out on samples showing the enhancement performances of the "Smart Flexible Phased Array" and validating the mechanical and acoustical behaviours of these probes.

  7. Optical beam forming techniques for phased array antennas

    NASA Technical Reports Server (NTRS)

    Wu, Te-Kao; Chandler, C.

    1993-01-01

    Conventional phased array antennas using waveguide or coax for signal distribution are impractical for large scale implementation on satellites or spacecraft because they exhibit prohibitively large system size, heavy weight, high attenuation loss, limited bandwidth, sensitivity to electromagnetic interference (EMI) temperature drifts and phase instability. However, optical beam forming systems are smaller, lighter, and more flexible. Three optical beam forming techniques are identified as applicable to large spaceborne phased array antennas. They are (1) the optical fiber replacement of conventional RF phased array distribution and control components, (2) spatial beam forming, and (3) optical beam splitting with integrated quasi-optical components. The optical fiber replacement and the spatial beam forming approaches were pursued by many organizations. Two new optical beam forming architectures are presented. Both architectures involve monolithic integration of the antenna radiating elements with quasi-optical grid detector arrays. The advantages of the grid detector array in the optical process are the higher power handling capability and the dynamic range. One architecture involves a modified version of the original spatial beam forming approach. The basic difference is the spatial light modulator (SLM) device for controlling the aperture field distribution. The original liquid crystal light valve SLM is replaced by an optical shuffling SLM, which was demonstrated for the 'smart pixel' technology. The advantages are the capability of generating the agile beams of a phased array antenna and to provide simultaneous transmit and receive functions. The second architecture considered is the optical beam splitting approach. This architecture involves an alternative amplitude control for each antenna element with an optical beam power divider comprised of mirrors and beam splitters. It also implements the quasi-optical grid phase shifter for phase control and grid

  8. Adaptive multibeam phased array design for a Spacelab experiment

    NASA Technical Reports Server (NTRS)

    Noji, T. T.; Fass, S.; Fuoco, A. M.; Wang, C. D.

    1977-01-01

    The parametric tradeoff analyses and design for an Adaptive Multibeam Phased Array (AMPA) for a Spacelab experiment are described. This AMPA Experiment System was designed with particular emphasis to maximize channel capacity and minimize implementation and cost impacts for future austere maritime and aeronautical users, operating with a low gain hemispherical coverage antenna element, low effective radiated power, and low antenna gain-to-system noise temperature ratio.

  9. Phased-array design for MST and ST radars

    NASA Technical Reports Server (NTRS)

    Ecklund, W. L.

    1986-01-01

    All of the existing radar systems fully dedicated to clear-air radar studies use some type of phased-array antennas. The effects of beam-steering techniques including feed networks and phase shifters; sidelobe control; ground-clutter suppression; low altitude coverage; arrays with integrated radiating elements and feed networks; analysis of coaxial-collinear antennas; use of arrays with multiple beams; and array testing and measure on structural design of the antenna are discussed.

  10. Reconstructions of phase contrast, phased array multicoil data.

    PubMed

    Bernstein, M A; Grgic, M; Brosnan, T J; Pelc, N J

    1994-09-01

    We present a reconstruction method for phased array multicoil data that is compatible with phase contrast MR angiography. The proposed algorithm can produce either complex difference or phase difference angiograms. Directional flow and quantitative information are preserved with the phase difference reconstruction. The proposed method is computationally efficient and avoids intercoil cancellation errors near the velocity aliasing boundary. Feasibility of the method is demonstrated on human scans.

  11. A 32-GHz phased array transmit feed for spacecraft telecommunications

    NASA Technical Reports Server (NTRS)

    Lee, K. A.; Rascoe, D. L.; Crist, R. A.; Huang, J.; Wamhof, P. D.; Lansing, F. S.

    1992-01-01

    A 21-element phased array transmit feed was demonstrated as part of an effort to develop and evaluate state-of-the-art transmitter and receiver components at 32 and 34 GHz for future deep-space missions. Antenna pattern measurements demonstrating electronic beam steering of the two-dimensional array are reported and compared with predictions based on measured performance of MMIC-based phase shifter and amplifier modules and Vivaldi slotline radiating elements.

  12. Control of complex components with Smart Flexible Phased Arrays.

    PubMed

    Casula, O; Poidevin, C; Cattiaux, G; Dumas, Ph

    2006-12-22

    The inspection is mainly performed in contact with ultrasonic wedge transducers; However, the shape cannot fit the changing geometries of components (butt weld, nozzle, elbow). The variable thickness of the coupling layer, between the wedge and the local surface, leads to beam distortions and losses of sensitivity. Previous studies have shown that these two phenomena contribute to reduce the inspection performances leading to shadow area, split beam.... Flexible phased arrays have been developed to fit the complex profile and improve such controls. The radiating surface is composed with independent piezoelectric elements mechanically assembled and a profilometer, embedded in the transducer, measures the local distortion. The computed shape is used by an algorithm to compute in real-time the adapted delay laws compensating the distortions of 2D or 3D profiles. Those delay laws are transferred to the real-time UT acquisition system, which applies them to the piezoelectric elements. This self-adaptive process preserves, during the scanning, the features of the focused beam (orientation and focal depth) in the specimen. To validate the concept of the Smart Flexible Phased Array Transducer, prototypes have been integrated to detect flaws machined in mock-ups with realistic irregular 2D and 3D shapes. Inspections have been carried out on samples showing the enhancement performances of the "Smart Flexible Phased Array" and validating the mechanical and acoustical behaviors of these probes.

  13. Phased-Array Satcom Antennas Developed for Aeronautical Applications

    NASA Technical Reports Server (NTRS)

    Kerczewski, Robert J.

    2001-01-01

    The Advanced Communications (AC) for Aeronautics research at the NASA Glenn Research Center integrates both aeronautics and space communications technologies to achieve the national objective of upgrading the present National Airspace System infrastructure by responding to the agency's aviation capacity and safety goals. One concept for future air traffic management, free flight, presents a significantly increased demand for communications systems capacity and performance in comparison to current air traffic management practices. Current aeronautical communications systems are incapable of supporting the anticipated demands, and the new digital data communications links that are being developed, or are in the early stages of implementation, are not primarily designed to carry the data-intensive free flight air traffic management (ATM) communications loads. Emerging satellite communications technologies are the best potential long-term solution to provide the capacity and performance necessary to enable a mature free flight concept to be deployed. NASA AC/ATM funded the development of a Boeing-designed Ku-band transmit phased-array antenna, a combined in-house and contract effort. Glenn designed and integrated an Aeronautical Mobile Satellite Communications terminal based on the transmit phased-array antenna and a companion receive phased-array antenna previously developed by Boeing.

  14. Ultrasonic Phased Array Inspection of Seeded Titanium Billet

    NASA Astrophysics Data System (ADS)

    Friedl, J. H.; Gray, T. A.; Khandelwal, P.; Dunhill, T.

    2004-02-01

    As part of efforts by Rolls-Royce to evaluate the use of ultrasonic phased arrays for inspection of titanium billets, a series of ultrasonic phased array inspections were performed at the Center for Nondestructive Evaluation (CNDE). The inspections were performed using a sectorial-annular array designed especially for titanium billets by R/D Tech and supplied to Rolls-Royce. The billet test piece is seeded with thirteen yttria disks, each located at successive depths below the outer diameter surface to just past the billet centerline. The phased array inspections employed both fixed-focus and dynamic-depth-focus (DDF) focal laws in conjunction with several depth gating schemes. Aperture and focal parameters were changed as a function of depth when using fixed-focus focal laws. Results include characterization of transducer performance and delay-time correction of imperfections, signal-to-noise measurements for the yttria disks in the billet test piece, and effects of probe misalignment on flaw sensitivity.

  15. Phased-array-fed antenna configuration study. Volume 1: Technology assessment

    NASA Technical Reports Server (NTRS)

    Sorbello, R. M.; Zaghloul, A. I.; Lee, B. S.; Siddiqi, S.; Geller, B. D.; Gerson, H. I.; Srinivas, D. N.

    1983-01-01

    The status of the technologies for phased-array-fed dual reflector systems is reviewed. The different aspects of these technologies, including optical performances, phased array systems, problems encountered in phased array design, beamforming networks, MMIC design and its incorporation into waveguide systems, reflector antenna structures, and reflector deployment mechanisms are addressed.

  16. Phased-array vector velocity estimation using transverse oscillations.

    PubMed

    Pihl, Michael J; Marcher, Jonne; Jensen, Jorgen A

    2012-12-01

    A method for estimating the 2-D vector velocity of blood using a phased-array transducer is presented. The approach is based on the transverse oscillation (TO) method. The purposes of this work are to expand the TO method to a phased-array geometry and to broaden the potential clinical applicability of the method. A phased-array transducer has a smaller footprint and a larger field of view than a linear array, and is therefore more suited for, e.g., cardiac imaging. The method relies on suitable TO fields, and a beamforming strategy employing diverging TO beams is proposed. The implementation of the TO method using a phased-array transducer for vector velocity estimation is evaluated through simulation and flow-rig measurements are acquired using an experimental scanner. The vast number of calculations needed to perform flow simulations makes the optimization of the TO fields a cumbersome process. Therefore, three performance metrics are proposed. They are calculated based on the complex TO spectrum of the combined TO fields. It is hypothesized that the performance metrics are related to the performance of the velocity estimates. The simulations show that the squared correlation values range from 0.79 to 0.92, indicating a correlation between the performance metrics of the TO spectrum and the velocity estimates. Because these performance metrics are much more readily computed, the TO fields can be optimized faster for improved velocity estimation of both simulations and measurements. For simulations of a parabolic flow at a depth of 10 cm, a relative (to the peak velocity) bias and standard deviation of 4% and 8%, respectively, are obtained. Overall, the simulations show that the TO method implemented on a phased-array transducer is robust with relative standard deviations around 10% in most cases. The flow-rig measurements show similar results. At a depth of 9.5 cm using 32 emissions per estimate, the relative standard deviation is 9% and the relative bias is -9

  17. Distortion generated in angle-modulation systems by phased arrays

    NASA Technical Reports Server (NTRS)

    Rogers, J. D.; Lagrone, A. H.; Fowler, J.

    1973-01-01

    The magnitude and characteristics of distortion produced in demodulated signals by corporate-fed phased arrays are reviewed. Graphs depicting distortion, plotted as a function of signal characteristics and array geometry, display the effects of large arrays on broadband signals. These curves show that distortion in angle-modulation systems is more a function of modulation index than of bandwidth. The data presented provide a basis for predicting distortion levels in practical array systems and for extending analyses to other signal-array configurations.

  18. Optoelectronic Infrastructure for Radio Frequency and Optical Phased Arrays

    NASA Technical Reports Server (NTRS)

    Cai, Jianhong

    2015-01-01

    Optoelectronic integrated circuits offer radiation-hardened solutions for satellite systems in addition to improved size, weight, power, and bandwidth characteristics. ODIS, Inc., has developed optoelectronic integrated circuit technology for sensing and data transfer in phased arrays. The technology applies integrated components (lasers, amplifiers, modulators, detectors, and optical waveguide switches) to a radio frequency (RF) array with true time delay for beamsteering. Optical beamsteering is achieved by controlling the current in a two-dimensional (2D) array. In this project, ODIS integrated key components to produce common RF-optical aperture operation.

  19. Jet Noise Source Localization Using Linear Phased Array

    NASA Technical Reports Server (NTRS)

    Agboola, Ferni A.; Bridges, James

    2004-01-01

    A study was conducted to further clarify the interpretation and application of linear phased array microphone results, for localizing aeroacoustics sources in aircraft exhaust jet. Two model engine nozzles were tested at varying power cycles with the array setup parallel to the jet axis. The array position was varied as well to determine best location for the array. The results showed that it is possible to resolve jet noise sources with bypass and other components separation. The results also showed that a focused near field image provides more realistic noise source localization at low to mid frequencies.

  20. SAR processing with stepped chirps and phased array antennas.

    SciTech Connect

    Doerry, Armin Walter

    2006-09-01

    Wideband radar signals are problematic for phased array antennas. Wideband radar signals can be generated from series or groups of narrow-band signals centered at different frequencies. An equivalent wideband LFM chirp can be assembled from lesser-bandwidth chirp segments in the data processing. The chirp segments can be transmitted as separate narrow-band pulses, each with their own steering phase operation. This overcomes the problematic dilemma of steering wideband chirps with phase shifters alone, that is, without true time-delay elements.

  1. 2-D scalable optical controlled phased-array antenna system

    NASA Astrophysics Data System (ADS)

    Chen, Maggie Yihong; Howley, Brie; Wang, Xiaolong; Basile, Panoutsopoulos; Chen, Ray T.

    2006-02-01

    A novel optoelectronically-controlled wideband 2-D phased-array antenna system is demonstrated. The inclusion of WDM devices makes a highly scalable system structure. Only (M+N) delay lines are required to control a M×N array. The optical true-time delay lines are combination of polymer waveguides and optical switches, using a single polymeric platform and are monolithically integrated on a single substrate. The 16 time delays generated by the device are measured to range from 0 to 175 ps in 11.6 ps. Far-field patterns at different steering angles in X-band are measured.

  2. Reconfigurable Wave Velocity Transmission Lines for Phased Arrays

    NASA Technical Reports Server (NTRS)

    Host, Nicholas Keith; Chen, Chi-Chih; Volakis, John L.

    2012-01-01

    This presentation discussed a novel phased array with an emphasis to simplify the array feed. Specifically, we will demonstrate a simple, low cost feeding approach by mechanically controlling the substrate thickness. The array feed lines are constructed from parallel plate transmission lines whose thickness are adjusted to control their effective dielectric constant (Epsilon_eff). As a result the phase delay/excitation at each array element will be adjusted per desired beam direction. The proposed antenna elements will be overlapping dipoles operating over a 2:1 bandwidth in the Ku-Band spectrum. Preliminary simulation and experimental demonstration of such an array will be presented.

  3. Ultrasonic Phased Array Inspection Simulations of Welded Components at NASA

    NASA Technical Reports Server (NTRS)

    Roth, D. J.; Tokars, R. P.; Martin, R. E.; Rauser, R. W.; Aldrin, J. C.; Schumacher, E. J.

    2009-01-01

    Comprehensive and accurate inspections of welded components have become of increasing importance as NASA develops new hardware such as Ares rocket segments for future exploration missions. Simulation and modeling will play an increased role in the future for nondestructive evaluation in order to better understand the physics of the inspection process and help explain the experimental results. It will also help to prove or disprove the feasibility for an inspection method or inspection scenario, help optimize inspections, and allow to a first approximation limits of detectability. This study presents simulation and experimental results for an ultrasonic phased array inspection of a critical welded structure important for NASA future exploration vehicles.

  4. Optical phased array radiating optical vortex with manipulated topological charges.

    PubMed

    Ma, Xiaoliang; Pu, Mingbo; Li, Xiong; Huang, Cheng; Pan, Wenbo; Zhao, Bo; Cui, Jianhua; Luo, Xiangang

    2015-02-23

    Optical antennas are key elements in quantum optics emitting and sensing, and behave wide range applications in optical domain. However, integration of optical antenna radiating orbital angular momentum is still a challenge in nano-scale. We theoretically demonstrate a sub-wavelength phased optical antenna array, which manipulates the distribution of the orbital angular momentum in the near field. Orbital angular momentum with topological charge of 4 can be obtained by controlling the phase distribution of the fundamental mode orbital angular momentum in each antenna element. Our results indicate this phased array may be utilized in high integrated optical communication systems.

  5. Phased Array Ultrasonic Evaluation of Space Shuttle Main Engine (SSME) Nozzle Weld

    NASA Technical Reports Server (NTRS)

    James, Steve; Engel, J.; Kimbrough, D.; Suits, M.; Hopson, George (Technical Monitor)

    2001-01-01

    This viewgraph presentation gives an overview of the phased array ultrasonic evaluation of the Space Shuttle Main Engine (SSME) nozzle weld. Details are given on the nondestructive testing evaluation approach, conventional shear wave and phased array techniques, and an x-ray versus phased array risk analysis. The field set-up was duplicated to the greatest extent possible in the laboratory and the phased array ultrasonic technique was developed and validated prior to weld evaluation. Results are shown for the phased array ultrasonic evaluation and conventional ultrasonic evaluation results.

  6. High frequency power distribution system

    NASA Technical Reports Server (NTRS)

    Patel, Mikund R.

    1986-01-01

    The objective of this project was to provide the technology of high frequency, high power transmission lines to the 100 kW power range at 20 kHz frequency. In addition to the necessary design studies, a 150 m long, 600 V, 60 A transmission line was built, tested and delivered for full vacuum tests. The configuration analysis on five alternative configurations resulted in the final selection of the three parallel Litz straps configuration, which gave a virtually concentric design in the electromagnetic sense. Low inductance, low EMI and flexibility in handling are the key features of this configuration. The final design was made after a parametric study to minimize the losses, weight and inductance. The construction of the cable was completed with no major difficulties. The R,L,C parameters measured on the cable agreed well with the calculated values. The corona tests on insulation samples showed a safety factor of 3.

  7. Manipulating Liquids With Acoustic Radiation Pressure Phased Arrays

    NASA Technical Reports Server (NTRS)

    Oeftering, Richard C.

    1999-01-01

    High-intensity ultrasound waves can produce the effects of "Acoustic Radiation Pressure" (ARP) and "acoustic streaming." These effects can be used to propel liquid flows and to apply forces that can be used to move or manipulate floating objects or liquid surfaces. NASA's interest in ARP includes the remote-control agitation of liquids and the manipulation of bubbles and drops in liquid experiments and propellant systems. A high level of flexibility is attained by using a high-power acoustic phased array to generate, steer, and focus a beam of acoustic waves. This is called an Acoustic Radiation Pressure Phased Array, or ARPPA. In this approach, many acoustic transducer elements emit wavelets that converge into a single beam of sound waves. Electronically coordinating the timing, or "phase shift," of the acoustic waves makes it possible to form a beam with a predefined direction and focus. Therefore, a user can direct the ARP force at almost any desired point within a liquid volume. ARPPA lets experimenters manipulate objects anywhere in a test volume. This flexibility allow it to be used for multiple purposes, such as to agitate liquids, deploy and manipulate drops or bubbles, and even suppress sloshing in spacecraft propellant tanks.

  8. Simulation and Data Processing for Ultrasonic Phased-Arrays Applications

    NASA Astrophysics Data System (ADS)

    Chaffaï-Gargouri, S.; Chatillon, S.; Mahaut, S.; Le Ber, L.

    2007-03-01

    The use of phased-arrays techniques has considerably contributed to extend the domain of applications and the performances of ultrasonic methods on complex configurations. Their adaptability offers a great freedom for conceiving the inspection leading to a wide range of functionalities gathering electronic commutation, applications of different delay laws and so on. This advantage allows to circumvent the difficulties encountered with more classical techniques especially when the inspection is assisted by simulation at the different stages : probe design (optimization of the number and characteristics of the elements), evaluation of the performances in terms of flaw detection (zone coverage) and characterization, driving the array (computation of adapted delay laws) and finally analyzing the results (versatile model-based imaging tools allowing in particular to locate the data in the real space). The CEA is strongly involved in the development of efficient simulation-based tools adapted to these needs. In this communication we present the recent advances done at CEA in this field and show several examples of complex NDT phased arrays applications. On these cases we show the interest and the performances of simulation-helped array design, array-driving and data analysis.

  9. A 220 GHz reflection-type phased array concept study

    NASA Astrophysics Data System (ADS)

    Hedden, Abigail S.; Dietlein, Charles R.; Wikner, David A.

    2011-05-01

    The goal of this project is to enable light-weight, durable, and portable systems capable of performing standoff detection of person-borne improvised explosive devices (PB-IEDs) through the development of millimeter-wave reflection-type phased arrays. Electronic beam steering eliminates the need for complex mechanical scanners that are commonly implemented with millimeter-wave imaging systems and would reduce overall system size and weight. We present a concept study of a 220 GHz reflection-type phased array for the purpose of performing beam scanning of a confocal reflector system. Requirements for effective imaging of the desired target region are established, including spatial resolution, total scan angle, and number of image pixels achievable. We examine the effects of array architecture on beam characteristics as it is scanned off broadside, including Gaussicity and encircled energy. Benchmark requirements are determined and compared with the capabilities of several potential phase shifter technologies, including MEMS-based variable capacitor phase shifters, switches, and varactor diode-based phase shifters.

  10. Application of Phased-array Vibrator System in shallow oil shale exploration

    NASA Astrophysics Data System (ADS)

    Jiang, T.; Lin, J.; Xu, X.

    2011-12-01

    Due to the huge oil and gas demands in China, exploration of unconventional oil shale at shallow depths becomes more critical. 52.83% of the identified reserves in China are from Jilin province and Nong'an is one of the main areas of oil shale in Jilin. The average buried depth of oil shale in Nong'an is between 300m and 800m. Since explosive sources are not allowed to operate in civil area and the inconvenience of vibroseis, Phased-array Vibrator System (PAVS) is applied in the exploration of oil shale in Nong'an. We have developed a series electromagnetic Portable High-frequency Vibrator System (PHVS), including single, combination, and phased-array modes. Single mode is the simplest mode, with output force less than 500N, and thus is only suitable for engineering seismic prospecting. Combination mode is a source array, which uses a controller to synchronize all vibrator units and let them work consistently with each other. Thus, it can increase output force than single case. The field test indicates that it can improve signal-to-noise ratio (SNR) of reflected waves in deep layer significantly. However, it contributes little for signals from shallow layers and sometimes it can even deteriorate shallow reflected signals than single source. This is because for signals reflected from shallow depths, the assumption in combination mode that seismic waves propagate along vertical rays is no longer valid. Therefore, they are not stacked constructively. Phased-array mode belongs to a new source array, whose key part is so-called delay/phase controller. By coordinating the signal of each unit using the controller, the seismic waves can be beamed into any interested direction, based on the underground structure and the depth of interested reflected layer. In this case, SNR of the concerned reflected wave can be improved apparently. PHVS in phased-array mode is called PAVS. We made two field tests to evaluate the performance of PAVS. In the first test, we compare PAVS with

  11. Special Aspects in Designing High - Frequency Betatron

    NASA Astrophysics Data System (ADS)

    Filimonov, A. A.; Kasyanov, S. V.; Kasyanov, V. A.

    2016-01-01

    The article is devoted to designing the high - frequency betatron. In high - frequency betatron most important problem is overheating of the elements of the body radiator unit. In an article some directions of solving this problem are shown.

  12. Receiver Would Control Phasing of a Phased-Array Antenna

    NASA Technical Reports Server (NTRS)

    Dunn, Charles E.; Young, Lawrence E.

    2006-01-01

    In a proposed digital signal-processing technique, a radio receiver would control the phasing of a phased-array antenna to aim the peaks of the antenna radiation pattern toward desired signal sources while aiming the nulls of the pattern toward interfering signal sources. The technique was conceived for use in a Global Positioning System (GPS) receiver, for which the desired signal sources would be GPS satellites and typical interference sources would be terrestrial objects that cause multipath propagation. The technique could also be used to optimize reception in spread-spectrum cellular-telephone and military communication systems. During reception of radio signals in a conventional phased-array antenna system, received signals at their original carrier frequencies are phase-shifted, then combined by analog circuitry. The combination signal is then subjected to down-conversion and demodulation. In a system according to the proposed technique (see figure), the signal received by each antenna would be subjected to down-conversion, spread-spectrum demodulation, and correlation; this processing would be performed separately from, and simultaneously with, similar processing of signals received by the other antenna elements. Following analog down-conversion to baseband, the signals would be digitized, and all subsequent processing would be digital. In the digital process, residual carriers would be removed and each signal would be correlated with a locally generated model pseudorandum-noise code, all following normal GPS procedure. As part of this procedure, accumulated values would be added in software and the resulting signals would be phase-shifted in software by the amounts necessary to synthesize the desired antenna directional gain pattern of peaks and nulls. The principal advantage of this technique over the conventional radio-frequency-combining technique is that the parallel digital baseband processing of the signals from the various antenna elements would be

  13. Large-Aperture Membrane Active Phased-Array Antennas

    NASA Technical Reports Server (NTRS)

    Karasik, Boris; McGrath, William; Leduc, Henry

    2009-01-01

    Large-aperture phased-array microwave antennas supported by membranes are being developed for use in spaceborne interferometric synthetic aperture radar systems. There may also be terrestrial uses for such antennas supported on stationary membranes, large balloons, and blimps. These antennas are expected to have areal mass densities of about 2 kg/sq m, satisfying a need for lightweight alternatives to conventional rigid phased-array antennas, which have typical areal mass densities between 8 and 15 kg/sq m. The differences in areal mass densities translate to substantial differences in total mass in contemplated applications involving aperture areas as large as 400 sq m. A membrane phased-array antenna includes patch antenna elements in a repeating pattern. All previously reported membrane antennas were passive antennas; this is the first active membrane antenna that includes transmitting/receiving (T/R) electronic circuits as integral parts. Other integral parts of the antenna include a network of radio-frequency (RF) feed lines (more specifically, a corporate feed network) and of bias and control lines, all in the form of flexible copper strip conductors on flexible polymeric membranes. Each unit cell of a prototype antenna (see Figure 1) contains a patch antenna element and a compact T/R module that is compatible with flexible membrane circuitry. There are two membrane layers separated by a 12.7-mm air gap. Each membrane layer is made from a commercially available flexible circuit material that, as supplied, comprises a 127-micron-thick polyimide dielectric layer clad on both sides with 17.5-micron-thick copper layers. The copper layers are patterned into RF, bias, and control conductors. The T/R module is located on the back side of the ground plane and is RF-coupled to the patch element via a slot. The T/R module is a hybrid multilayer module assembled and packaged independently and attached to the membrane array. At the time of reporting the information for

  14. High frequency-heated air turbojet

    NASA Technical Reports Server (NTRS)

    Miron, J. H. D.

    1986-01-01

    A description is given of a method to heat air coming from a turbojet compressor to a temperature necessary to produce required expansion without requiring fuel. This is done by high frequency heating, which heats the walls corresponding to the combustion chamber in existing jets, by mounting high frequency coils in them. The current transformer and high frequency generator to be used are discussed.

  15. Time-delayed directional beam phased array antenna

    DOEpatents

    Fund, Douglas Eugene; Cable, John William; Cecil, Tony Myron

    2004-10-19

    An antenna comprising a phased array of quadrifilar helix or other multifilar antenna elements and a time-delaying feed network adapted to feed the elements. The feed network can employ a plurality of coaxial cables that physically bridge a microstrip feed circuitry to feed power signals to the elements. The cables provide an incremental time delay which is related to their physical lengths, such that replacing cables having a first set of lengths with cables having a second set of lengths functions to change the time delay and shift or steer the antenna's main beam. Alternatively, the coaxial cables may be replaced with a programmable signal processor unit adapted to introduce the time delay using signal processing techniques applied to the power signals.

  16. Phased-array-fed antenna configuration study, volume 2

    NASA Technical Reports Server (NTRS)

    Sorbello, R. M.; Zaghloul, A. I.; Lee, B. S.; Siddiqi, S.; Geller, B. D.

    1983-01-01

    Increased capacity in future satellite systems can be achieved through antenna systems which provide multiplicity of frequency reuses at K sub a band. A number of antenna configurations which can provide multiple fixed spot beams and multiple independent spot scanning beams at 20 GHz are addressed. Each design incorporates a phased array with distributed MMIC amplifiers and phasesifters feeding a two reflector optical system. The tradeoffs required for the design of these systems and the corresponding performances are presented. Five final designs are studied. In so doing, a type of MMIC/waveguide transition is described, and measured results of the breadboard model are presented. Other hardware components developed are described. This includes a square orthomode transducer, a subarray fed with a beamforming network to measure scanning performance, and another subarray used to study mutual coupling considerations. Discussions of the advantages and disadvantages of the final design are included.

  17. Hyperthermia and inhomogeneous tissue effects using an Annular Phased Array

    SciTech Connect

    Turner, P.F.

    1984-08-01

    A regional hyperthermia Annular Phased Array (APA) applicator is described, and examples of its various heating patterns, obtained by scanning the electric fields with a small E-field sensor, are illustrated. Also shown are the effects of different frequencies of an elliptical phantom cylinder having a 1-cm-thick artificial fat wall and the general dimensions of the human trunk. These studies show the APA's ability to achieve uniform heating at lower frequencies (below 70 MHz) or to focus central heating at moderately higher frequencies (above 70 MHz). The influence of human anatomical contours in altering heating patterns is discussed using results obtained with a female mannequin having a thin latex shell filled with tissue-equivalent phantom. Field perturbations caused by internally embedded low-dielectric structures are presented, showing the localized effects of small objects whose surfaces are perpendicular to the electric field.

  18. The frequency response of phased-array antennas

    NASA Astrophysics Data System (ADS)

    Brock, B. C.

    1989-02-01

    The phased-array antenna will be examined from the point of view of effects caused by changes in frequency. Both simple linear arrays and the more complex conformal array are examined. For the conformal array, a comparison between a corporate-feed structure and a row series-feed structure is included. There are two primary effects which will be discussed: beam-pointing errors and distortion of large bandwidth signals. A formula for estimating the operating or tunable array bandwidth for narrow-bandwidth signals is derived. An expression for the wide-bandwidth-signal transfer function is also obtained and examined. It will be shown that the transfer function depends both on the array scan angle and the position within the mainbeam.

  19. The frequency response of phased-array antennas

    SciTech Connect

    Brock, B.C.

    1989-02-01

    The phased-array antenna will be examined from the point of view of effects caused by changes in frequency. Both simple linear arrays and the more complex conformal array are examined. For the conformal array, a comparison between a corporate-feed structure and a row series-feed structure is included. There are two primary effects which will be discussed: beam-pointing errors and distortion of large bandwidth signals. A formula for estimating the operating or tunable array bandwidth for narrow-bandwidth signals is derived. An expression for the wide-bandwidth-signal transfer function is also obtained and examined. It will be shown that the transfer function depends both on the array scan angle and the position within the mainbeam. 25 figs.

  20. Cylindrical Antenna With Partly Adaptive Phased-Array Feed

    NASA Technical Reports Server (NTRS)

    Hussein, Ziad; Hilland, Jeff

    2003-01-01

    A proposed design for a phased-array fed cylindrical-reflector microwave antenna would enable enhancement of the radiation pattern through partially adaptive amplitude and phase control of its edge radiating feed elements. Antennas based on this design concept would be attractive for use in radar (especially synthetic-aperture radar) and other systems that could exploit electronic directional scanning and in which there are requirements for specially shaped radiation patterns, including ones with low side lobes. One notable advantage of this design concept is that the transmitter/ receiver modules feeding all the elements except the edge ones could be identical and, as a result, the antenna would cost less than in the cases of prior design concepts in which these elements may not be identical.

  1. Phased-Array Measurements of Single Flow Hot Jets

    NASA Technical Reports Server (NTRS)

    Bridges, James; Lee, Sang Soo

    2005-01-01

    A 16 microphone phased-array system has been successfully applied to measure jet noise source distributions. In this study, a round convergent nozzle was tested at various hot and cold flow conditions: acoustic Mach numbers are between 0.35 and 1.6 and static temperature ratios are varied from cold to 2.7. The classical beamforming method was applied on narrowband frequencies. From the measured source distributions locations of peak strength were tracked and found to be very consistent between adjacent narrowband frequencies. In low speed heated and unheated jets, the peak source locations vary smoothly from the nozzle exit to downstream as the frequency is decreased. When the static temperature ratio was kept constant, the peak source position moved downstream with increasing acoustic Mach number for the Strouhal numbers smaller than about 1.5. It was also noted that the peak source locations of low frequencies occur farther downstream than the end of potential core.

  2. Integrated phased array for wide-angle beam steering.

    PubMed

    Yaacobi, Ami; Sun, Jie; Moresco, Michele; Leake, Gerald; Coolbaugh, Douglas; Watts, Michael R

    2014-08-01

    We demonstrate an on-chip optical phased array fabricated in a CMOS compatible process with continuous, fast (100 kHz), wide-angle (51°) beam-steering suitable for applications such as low-cost LIDAR systems. The device demonstrates the largest (51°) beam-steering and beam-spacing to date while providing the ability to steer continuously over the entire range. Continuous steering is enabled by a cascaded phase shifting architecture utilizing, low power and small footprint, thermo-optic phase shifters. We demonstrate these results in the telecom C-band, but the same design can easily be adjusted for any wavelength between 1.2 and 3.5 μm.

  3. Complex direct comb spectroscopy with a virtually imaged phased array.

    PubMed

    Scholten, Sarah K; Anstie, James D; Hébert, Nicolas Bourbeau; White, Richard T; Genest, Jérôme; Luiten, Andre N

    2016-03-15

    We demonstrate a simple interferometric technique to directly measure the complex optical transmittance over a large spectral range using a frequency-comb spectrometer based on a virtually imaged phased array. A Michelson interferometer encodes the phase deviations induced by a sample contained in one of its arms into an interferogram image. When combined with an additional image taken from each arm separately, along with a frequency-calibration image, this allows full reconstruction of the sample's optical transfer function. We demonstrate the technique with a vapor cell containing H13C14N, producing transmittance and phase spectra spanning 2.9 THz (∼23  nm) with ∼1 GHz resolution.

  4. Phased array antenna investigation for CubeSat size satellites

    NASA Astrophysics Data System (ADS)

    Dang, Kien

    Increasing bandwidth of the communication link has been a challenge for CubeSat class satellite. Traditional satellites usually utilizes high gain antennas for this purpose, but these antenna are rarely seen in CubeSat because of its power, volume and weight constraints. To solve these issues, this dissertation presents a phased array antenna system prototyped at 2.45 GHz with 17.7 dBi gain at broadside, 14.2 dBi at +/-40°, 50 MHz bandwidth, and fits on a side of a 3U CubeSat. The gain can be increased by adding more antenna elements into the array as needed. Testing for electronic beam steering has been completed and detailed results will be presented.

  5. Fabrication and characterization of a hybrid SOI 1×4 silicon-slot optical modulator array incorporating EO polymers for optical phased-array antenna applications

    NASA Astrophysics Data System (ADS)

    Kim, Richard S.; Szep, Attila; Usechak, Nicholas G.; Chen, Antao; Sun, Haishan; Shi, Shouyuan; Abeysinghe, Don; You, Young-Hwan; Dalton, Larry R.

    2012-03-01

    Optical phased arrays are promising candidates for both RF signal processing and optical beam forming and steering. These platforms not only enable accurate electrically controlled beam steering at high frequencies but also have the potential to significantly improve the performance of future free-space optical communications systems. In this work we exploit recent advancements in both nano-scale hybrid silicon-slot waveguides and electro-optic (EO) polymers to demonstrate an integrated optical phased-array antenna. Specifically, we create a hybrid integrated "photonic circuit" that connects an array of optical phase modulators, fed by a common optical signal and a 1x4 splitter, to a compact optical waveguide diffraction array for optical beam steering applications. The fundamental characteristics of the resulting integrated optical beam former, including the optical insertion loss, driving voltage, and phase control from the waveguide aperture are summarized in this letter.

  6. 4 T actively detunable transmit/receive transverse electromagnetic coil and 4-channel receive-only phased array for (1)H human brain studies.

    PubMed

    Avdievich, Nikolai I; Hetherington, Hoby P

    2004-12-01

    The design and construction of a 4 T transverse electromagnetic (TEM) transmit/receive head coil and a four-channel phased array receive-only RF system are described. To enable both high-resolution imaging of the entire brain and high-resolution spectroscopic imaging, active PIN diode decoupling was used in both the TEM resonator and each surface coil in the array. This configuration allows for both transmission and reception from the volume coil as well as reception from the phased array. The surface coils were decoupled by overlapping the coils and using preamplifier decoupling. Since at high frequencies construction of a lumped element matching quarter wavelength transformer, an important component of the preamplifier decoupling, becomes difficult, a transmission line approach was used. The system was tested and compared to a TEM volume transmit/receive head coil. A four- to sixfold improvement in signal-to-noise ratio from the sensitive volume of the array was achieved.

  7. 4 T actively detunable transmit/receive transverse electromagnetic coil and 4-channel receive-only phased array for (1)H human brain studies.

    PubMed

    Avdievich, Nikolai I; Hetherington, Hoby P

    2004-12-01

    The design and construction of a 4 T transverse electromagnetic (TEM) transmit/receive head coil and a four-channel phased array receive-only RF system are described. To enable both high-resolution imaging of the entire brain and high-resolution spectroscopic imaging, active PIN diode decoupling was used in both the TEM resonator and each surface coil in the array. This configuration allows for both transmission and reception from the volume coil as well as reception from the phased array. The surface coils were decoupled by overlapping the coils and using preamplifier decoupling. Since at high frequencies construction of a lumped element matching quarter wavelength transformer, an important component of the preamplifier decoupling, becomes difficult, a transmission line approach was used. The system was tested and compared to a TEM volume transmit/receive head coil. A four- to sixfold improvement in signal-to-noise ratio from the sensitive volume of the array was achieved. PMID:15562466

  8. Feasibility of Using Lateral Mode Coupling Method for a Large Scale Ultrasound Phased Array for Noninvasive Transcranial Therapy

    PubMed Central

    Song, Junho; Hynynen, Kullervo

    2009-01-01

    A hemispherical-focused, ultrasound phased array was designed and fabricated using 1372 cylindrical piezoelectric transducers that utilize lateral coupling for noninvasive transcranial therapy. The cylindrical transducers allowed the electrical impedance to be reduced by at least an order of magnitude, such that effective operation could be achieved without electronic matching circuits. In addition, the transducer elements generated the maximum acoustic average surface intensity of 27 W/cm2. The array, driven at the low (306 kHz) or high frequency (840 kHz), achieved excellent focusing through an ex vivo human skull and an adequate beam steering range for clinical brain treatments. It could electronically steer the ultrasound beam over cylindrical volumes of 100 mm in diameter and 60 mm in height at 306 kHz, and 30-mm in diameter and 30-mm in height at 840 kHz. A scanning laser vibrometer was used to investigate the radial and length mode vibrations of the element. The maximum pressure amplitudes through the skull at the geometric focus were predicted to be 5.5 MPa at 306 kHz and 3.7 MPa at 840 kHz for RF power of 1 W on each element. This is the first study demonstrating the feasibility of using cylindrical transducer elements and lateral coupling in construction of ultrasound phased arrays. PMID:19695987

  9. Through Weld Inspection of Wrought Stainless Steel Piping Using Phased Arrays

    SciTech Connect

    Anderson, Michael T.; Cumblidge, Stephen E.; Doctor, Steven R.

    2004-12-31

    Outline: Discuss far-side weld problem and phased array techniques applied. Describe laboratory work on flawed piping specimens using L- and S-wave arrays and provide synopsis of results. Discuss conclusions ofr capability of phased array as applied to austenitic welds. Research Approach: Evaluate phased arrays on unifornly-welded piping specimens. Apply best methods to non-uniform welds. Correlate acoustic responses as function of weld microstructures.

  10. High Frequency Chandler Wobble Excitation

    NASA Astrophysics Data System (ADS)

    Seitz, F.; Stuck, J.; Thomas, M.

    2003-04-01

    and OMCT forcing fields give no hint for increased excitation power in the Chandler band. Thus it is assumed, that continuous high frequency excitation due to stochastic weather phenomena is responsible for the perpetuation of the Chandler wobble.

  11. The application of ultrasonic phased array technology to offshore platform structures inspection

    NASA Astrophysics Data System (ADS)

    Baohua, Shan; Hua, Wang; Zhongdong, Duan; Jinping, Ou

    2007-04-01

    Aimed at the practical requirement of tubular joints weld inspection of offshore platform structures of Shengli oil field, the ultrasonic phased array inspection arithmetic for offshore platform structures is proposed. The integrated design of ultrasonic phased array inspection imaging system for offshore platform structures is completed, the ultrasonic phased array inspection imaging system for offshore platform structure is integrated on the basis of the each module and the exploitation of subsystem, which is made up of computer, ultrasonic circuit system, scanning device and phased array transducer. The ultrasonic phased array inspection experiment of T shape tubular joint model is performed with the ultrasonic phased array inspection imaging system for offshore platform structures, the flaws characteristic could be exactly estimated and the flaws size could be measured. Experiment results indicate that the ultrasonic phased array inspection arithmetic for offshore platform structures is practical, the ultrasonic phased array inspection imaging system could inspect artificial defects in tubular joint model, such as slag inclusion, crack, gas porosity, etc., the whole development trend of flaws is factually imaging by the ultrasonic phased array inspection technology of offshore platform structures.

  12. Cantilever RF-MEMS for monolithic integration with phased array antennas on a PCB

    NASA Astrophysics Data System (ADS)

    Aguilar-Armenta, C. J.; Porter, S. J.

    2015-12-01

    This article presents the development and operation of a novel electrostatic metal-to-metal contact cantilever radio-frequency microelectromechanical system (RF-MEMS) switch for monolithic integration with microstrip phased array antennas (PAAs) on a printed circuit board. The switch is fabricated using simple photolithography techniques on a Rogers 4003c substrate, with a footprint of 200 µm × 100 µm, based on a 1 µm-thick copper cantilever. An alternative wet-etching technique for effectively releasing the cantilever is described. Electrostatic and electromagnetic measurements show that the RF-MEMS presents an actuation voltage of 90 V for metal-to-metal contact, an isolation of -8.7 dB, insertion loss of -2.5 dB and a return loss of -15 dB on a 50 Ω microstrip line at 12.5 GHz. For proof-of-concept, a beam-steering 2 × 2 microstrip PAA, based on two 1-bit phase shifters suitable for the monolithic integration of the RF-MEMS, has been designed and measured at 12.5 GHz. Measurements show that the beam-steering system presents effective radiation characteristics with scanning capabilities from broadside towards 29° in the H-plane.

  13. 75 FR 81284 - Nationwide Use of High Frequency and Ultra High Frequency Active SONAR Technology; Draft...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-12-27

    ... SECURITY Coast Guard Nationwide Use of High Frequency and Ultra High Frequency Active SONAR Technology... of High Frequency (HF) and Ultra High Frequency (UHF) Sound Navigation and Ranging (SONAR) Technology... in the January 17, 2008, issue of the Federal Register (73 FR 3316). Background and Purpose...

  14. High-frequency synthetic ultrasound array incorporating an actuator

    NASA Astrophysics Data System (ADS)

    Ritter, Timothy A.; Shrout, Thomas R.; Shung, K. Kirk

    2001-05-01

    Ultrasound imaging at frequencies above 20 MHz relies almost exclusively on single-element transducers. IN order to apply array technology at these frequencies, several practical problems must be solved, including spatial scale and fabrication limitations, low device capacitance, and lack of a hardware beamformer. One method of circumventing these problems is to combine an array, an actuator, and a synthetic aperture software beamformer. The array can use relatively wide elements spaced on a coarse pitch. The actuator is used to move the array in short steps (less than the element pitch), and pulse-echo data is acquired at intermediate sample positions. The synthetic aperture beamformer reconstructs the image from the pulse-echo data. A 50 MHz example is analyzed in detail. Estimates of signal-to-noise reveal performance comparable to a standard phased array; furthermore, the actuated array requires half the number of elements, the elements are 8x wider, and only one channel is required. Simulated three-dimensional point spread functions demonstrate side lobe levels approaching - 40dB and main beam widths of 50 to 100 microns. A 50 MHz piezo-composite array design has been tested which displays experimental bandwidth of 70% while maintaining high sensitivity. Individual composite sub-elements are 18 microns wide. Once this array is integrated with a suitable actuator, it is anticipated that a tractable method of imaging with high frequency arrays will result.

  15. Tunable elastomer-based virtually imaged phased array.

    PubMed

    Metz, Philipp; Block, Hendrik; Behnke, Christopher; Krantz, Matthias; Gerken, Martina; Adam, Jost

    2013-02-11

    Virtually imaged phased arrays (VIPAs) offer a high potential for wafer-level integration and superior optical properties compared to conventional gratings. We introduce an elastomer-based tunable VIPA enabling fine tuning of the dispersion characteristics. It consists of a poly-dimethylsiloxane (PDMS) layer sandwiched between silver bottom and top coatings, which form the VIPA's high reflective and semi-transparent mirror, respectively. The latter also acts as an electrode for Joule heating, such that the optical PDMS resonator cavity tuning is carried out via a combination of thermal expansion and the thermo-optic effect. Analogous to the free spectral range (FSR), based on a VIPA specific dispersion law, we introduce a new characteristic VIPA performance measure, namely the free angular range (FAR). We report a tuning span of one FAR achieved by a 7.2K temperature increase of a 170μm PDMS VIPA. Both resonance quality and tunability are analyzed in numerical simulations and experiments. PMID:23481792

  16. Evolutionary Design of a Phased Array Antenna Element

    NASA Technical Reports Server (NTRS)

    Globus, Al; Linden, Derek; Lohn, Jason

    2006-01-01

    We present an evolved S-band phased array antenna element design that meets the requirements of NASA's TDRS-C communications satellite scheduled for launch early next decade. The original specification called for two types of elements, one for receive only and one for transmit/receive. We were able to evolve a single element design that meets both specifications thereby simplifying the antenna and reducing testing and integration costs. The highest performance antenna found using a genetic algorithm and stochastic hill-climbing has been fabricated and tested. Laboratory results are largely consistent with simulation. Researchers have been investigating evolutionary antenna design and optimization since the early 1990s, and the field has grown in recent years its computer speed has increased and electromagnetic simulators have improved. Many antenna types have been investigated, including wire antennas, antenna arrays and quadrifilar helical antennas. In particular, our laboratory evolved a wire antenna design for NASA's Space Technology 5 (ST5) spacecraft. This antenna has been fabricated, tested, and is scheduled for launch on the three spacecraft in 2006.

  17. PARAS program: Phased array radio astronomy from space

    NASA Technical Reports Server (NTRS)

    Jakubowski, Antoni K.; Haynes, David A.; Nuss, Ken; Hoffmann, Chris; Madden, Michael; Dungan, Michael

    1992-01-01

    An orbiting radio telescope is proposed which, when operated in a Very Long Baseline Interferometry (VLBLI) scheme, would allow higher (than currently available) angular resolution and dynamic range in the maps, and the ability of observing rapidly changing astronomical sources. Using a passive phases array technology, the proposed design consists of 656 hexagonal modules forming a 150 meter diameter dish. Each observatory module is largely autonomous, having its own photovoltaic power supply and low-noise receiver and processor for phase shifting. The signals received by the modules are channeled via fiber optics to the central control computer in the central bus module. After processing and multiplexing, the data is transmitted to telemetry stations on the ground. The truss frame supporting each observatory pane is a hybrid structure consisting of a bottom graphite/epoxy tubular triangle and rigidized inflatable Kevlar tubes connecting the top observatory panel and bottom triangle. Attitude control and stationkeeping functions are performed by a system of momentum wheels in the bus and four propulsion modules located at the compass points on the periphery of the observatory dish. Each propulsion module has four monopropellant thrusters and six hydrazine arcjets, the latter supported by a nuclear reactor. The total mass of the spacecraft is 22,060 kg.

  18. High power compatible internally sensed optical phased array.

    PubMed

    Roberts, Lyle E; Ward, Robert L; Francis, Samuel P; Sibley, Paul G; Fleddermann, Roland; Sutton, Andrew J; Smith, Craig; McClelland, David E; Shaddock, Daniel A

    2016-06-13

    The technical embodiment of the Huygens-Fresnel principle, an optical phased array (OPA) is an arrangement of optical emitters with relative phases controlled to create a desired beam profile after propagation. One important application of an OPA is coherent beam combining (CBC), which can be used to create beams of higher power than is possible with a single laser source, especially for narrow linewidth sources. Here we present an all-fiber architecture that stabilizes the relative output phase by inferring the relative path length differences between lasers using the small fraction of light that is back-reflected into the fiber at the OPA's glass-air interface, without the need for any external sampling optics. This architecture is compatible with high power continuous wave laser sources (e.g., fiber amplifiers) up to 100 W per channel. The high-power compatible internally sensed OPA was implemented experimentally using commercial 15 W fiber amplifiers, demonstrating an output RMS phase stability of λ/194, and the ability to steer the beam at up to 10 kHz. PMID:27410363

  19. Project PARAS: Phased array radio astronomy from space

    NASA Technical Reports Server (NTRS)

    Nuss, Kenneth; Hoffmann, Christopher; Dungan, Michael; Madden, Michael; Bendakhlia, Monia

    1992-01-01

    An orbiting radio telescope is proposed which, when operated in a very long baseline interferometry (VLBI) scheme, would allow higher than currently available angular resolution and dynamic range in the maps and the ability to observe rapidly changing astronomical sources. Using passive phased array technology, the proposed design consists of 656 hexagonal modules forming a 150-m diameter antenna dish. Each observatory module is largely autonomous, having its own photovoltaic power supply and low-noise receiver and processor for phase shifting. The signals received by the modules are channeled via fiber optics to the central control computer in the central bus module. After processing and multiplexing, the data are transmitted to telemetry stations on the ground. The truss frame supporting each observatory panel is a novel hybrid structure consisting of a bottom graphite/epoxy tubular triangle and rigidized inflatable Kevlar tubes connecting the top observatory panel and the bottom triangle. Attitude control and station keeping functions will be performed by a system of momentum wheels in the bus and four propulsion modules located at the compass points on the periphery of the observatory dish. Each propulsion module has four monopropellant thrusters and four hydrazine arcjets, the latter supported by either a photovoltaic array or a radioisotope thermoelectric generator. The total mass of the spacecraft is about 20,500 kg.

  20. Thermal dispersion method for an ultrasonic phased-array transducer

    NASA Astrophysics Data System (ADS)

    Choi, Euna; Lee, Wonseok; Roh, Yongrae

    2016-07-01

    When the driving voltage of an ultrasonic transducer is increased to improve the quality of ultrasound images, heat is generated inside the transducer, which can burn the patient’s skin and degrade transducer performance. In this study, the method to disperse the heat inside an ultrasonic phased-array transducer has been examined. The mechanism of temperature rise due to heat generation inside the transducer was investigated by numerical analysis and the effects of the thermal properties of the components of the transducer such as specific heat and thermal conductivity on the temperature rise were analyzed. On the basis of the results, a heat-dispersive structure was devised to reduce the temperature at the surface of the acoustic lens of the transducer. Prototype transducers were fabricated to check the efficacy of the heat-dispersive structure. By experiments, we have confirmed that the new heat-dispersive structure can reduce the internal temperature by as much as 50% in comparison with the conventional structure, which confirms the validity of the thermal dispersion mechanism developed in this work.

  1. Matrix phased array (MPA) imaging technology for resistance spot welds

    SciTech Connect

    Na, Jeong K.; Gleeson, Sean T.

    2014-02-18

    A three-dimensional MPA probe has been incorporated with a high speed phased array electronic board to visualize nugget images of resistance spot welds. The primary application area of this battery operated portable MPA ultrasonic imaging system is in the automotive industry which a conventional destructive testing process is commonly adopted to check the quality of resistance spot welds in auto bodies. Considering an average of five-thousand spot welds in a medium size passenger vehicle, the amount of time and effort given to popping the welds and measuring nugget size are immeasurable in addition to the millions of dollars' worth of scrap metals recycled per plant per year. This wasteful labor intensive destructive testing process has become less reliable as auto body sheet metal has transitioned from thick and heavy mild steels to thin and light high strength steels. Consequently, the necessity of developing a non-destructive inspection methodology has become inevitable. In this paper, the fundamental aspects of the current 3-D probe design, data acquisition algorithms, and weld nugget imaging process are discussed.

  2. Matrix phased array (MPA) imaging technology for resistance spot welds

    NASA Astrophysics Data System (ADS)

    Na, Jeong K.; Gleeson, Sean T.

    2014-02-01

    A three-dimensional MPA probe has been incorporated with a high speed phased array electronic board to visualize nugget images of resistance spot welds. The primary application area of this battery operated portable MPA ultrasonic imaging system is in the automotive industry which a conventional destructive testing process is commonly adopted to check the quality of resistance spot welds in auto bodies. Considering an average of five-thousand spot welds in a medium size passenger vehicle, the amount of time and effort given to popping the welds and measuring nugget size are immeasurable in addition to the millions of dollars' worth of scrap metals recycled per plant per year. This wasteful labor intensive destructive testing process has become less reliable as auto body sheet metal has transitioned from thick and heavy mild steels to thin and light high strength steels. Consequently, the necessity of developing a non-destructive inspection methodology has become inevitable. In this paper, the fundamental aspects of the current 3-D probe design, data acquisition algorithms, and weld nugget imaging process are discussed.

  3. Performance limits of planar phased array with dome lens

    NASA Astrophysics Data System (ADS)

    Geren, W. P.; Taylor, Michael

    1998-10-01

    Communication systems based on low-earth-orbit (LEO) satellites have generated a requirement for high-performance phased array antennas with exceptional gain, sidelobe levels, and axial ratio over broad scan angles and 360 degree azimuth coverage. One approach to mitigating the effects of scan dependence is to cover the planar array with a hemispherical lens, or dome, which implements passive or active phase correction of the scanned beam. The phase correction over the dome surface may be represented as the function (Delta) (Phi) ((theta) , (phi) ), with (theta) and (phi) the polar and azimuth angles in a coordinate system having z-axis normal to the array. The purpose of this study was to determine the performance improvement achievable with such an ideal lens. Three cases were considered: a conventional lens with fixed optimum phase correction, an active lens with scan-dependent phase correction a function of polar angle only, and an active lens with phase correction a function of polar and azimuthal angles. In all cases, the planar array distribution had a fixed radial Taylor amplitude distribution and a phase taper consisting of a linear beam-pointing term and a non-linear focusing term.

  4. Matrix phased arrays for the inspection of CFRP-components

    SciTech Connect

    Kreutzbruck, M.; Brackrock, D.; Brekow, G.; Montag, H.-J.; Boehm, R.; Illerhaus, B.

    2014-02-18

    Lightweight components are increasingly used in different industrial sectors such as transportation, energy generation and automotive. This growing field includes different types of CFRP-structures, hybrid materials and glued components showing - compared to their pure metallic counterparts- a significant more complicated structure in terms of internal interfaces and anisotropy of material parameters. In this work we present the use of matrix phased array to increase the amount of obtained information to enhance the inspection quality. We used different types of carbon materials such as 6 mm thick uni- and bidirectional prepreg specimens containing impact damages. The latter were introduced with different energy levels ranging from 1.3 to 7.2 J. By scanning a 2.25 MHz matrix array with 6 × 10 elements above the prepreg surface and using different angels of incidence a complete 3D-image was generated which allows the detection of defects as small as 1mm in a depth of 4 mm. A comparison with conventional approaches show that the signal-to-noise ratio can be highly increased. This enables us to visualize the region of damage within the impact zone, clearly showing the cone-like damage distribution along increasing material depth. The detection quality allows the estimation of the opening angles of the cone shaped damage, which can be used for further evaluation and quantitation of energy dependent impact damages.

  5. Evolutionary Adaptive Discovery of Phased Array Sensor Signal Identification

    SciTech Connect

    Timothy R. McJunkin; Milos Manic

    2011-05-01

    Tomography, used to create images of the internal properties and features of an object, from phased array ultasonics is improved through many sophisiticated methonds of post processing of data. One approach used to improve tomographic results is to prescribe the collection of more data, from different points of few so that data fusion might have a richer data set to work from. This approach can lead to rapid increase in the data needed to be stored and processed. It also does not necessarily lead to have the needed data. This article describes a novel approach to utilizing the data aquired as a basis for adapting the sensors focusing parameters to locate more precisely the features in the material: specifically, two evolutionary methods of autofocusing on a returned signal are coupled with the derivations of the forumulas for spatially locating the feature are given. Test results of the two novel methods of evolutionary based focusing (EBF) illustrate the improved signal strength and correction of the position of feature using the optimized focal timing parameters, called Focused Delay Identification (FoDI).

  6. Ultrasound cylindrical phased array for transoesophageal thermal therapy: initial studies

    NASA Astrophysics Data System (ADS)

    Melodelima, David; Lafon, Cyril; Prat, Frederic; Birer, Alain; Cathignol, Dominique

    2002-12-01

    This work was undertaken to investigate the feasibility of constructing a cylindrical phased array composed of 64 elements spread around the periphery (OD 10.6 mm) for transoesophageal ultrasound thermotherapy. The underlying operating principle of this applicator is to rotate a plane ultrasound beam electronically. For this purpose, eight adjacent transducers were successively excited with appropriate delay times so as to generate a plane wave. The exposure direction was changed by exciting a different set of eight elements. For these feasibility studies, we used a cylindrical prototype (OD 10.6 mm) composed of 16 elementary transducers distributed over a quarter of the cylinder, all operating at 4.55 MHz. The active part was mechanically reinforced by a rigid damper structure behind the transducers. It was shown that an ultrasound field similar to that emitted by a plane transducer could be generated. Ex vivo experiments on pig's liver demonstrated that the ultrasound beam could be accurately rotated to generate sector-based lesions to a suitable depth (up to 19 mm). Throughout these experiments, exposures lasting 20 s were delivered at an acoustic intensity of 17 W cm-2. By varying the power from exposure to exposure, the depth of the lesion at different angles could be controlled.

  7. High power compatible internally sensed optical phased array.

    PubMed

    Roberts, Lyle E; Ward, Robert L; Francis, Samuel P; Sibley, Paul G; Fleddermann, Roland; Sutton, Andrew J; Smith, Craig; McClelland, David E; Shaddock, Daniel A

    2016-06-13

    The technical embodiment of the Huygens-Fresnel principle, an optical phased array (OPA) is an arrangement of optical emitters with relative phases controlled to create a desired beam profile after propagation. One important application of an OPA is coherent beam combining (CBC), which can be used to create beams of higher power than is possible with a single laser source, especially for narrow linewidth sources. Here we present an all-fiber architecture that stabilizes the relative output phase by inferring the relative path length differences between lasers using the small fraction of light that is back-reflected into the fiber at the OPA's glass-air interface, without the need for any external sampling optics. This architecture is compatible with high power continuous wave laser sources (e.g., fiber amplifiers) up to 100 W per channel. The high-power compatible internally sensed OPA was implemented experimentally using commercial 15 W fiber amplifiers, demonstrating an output RMS phase stability of λ/194, and the ability to steer the beam at up to 10 kHz.

  8. KPAF (K-band phased array feed) instrument concept

    NASA Astrophysics Data System (ADS)

    Locke, Lisa; Claude, Stéphane; Bornemann, Jens; Henke, Doug; Di Francesco, James; Jiang, Frank; Garcia, Dominic; Wevers, Ivan; Niranjanan, Pat

    2014-07-01

    Astronomical surveys are demanding more throughput from telescope receivers. Currently, microwave/millimeter telescopes with mature cryogenic single pixel receivers are upgrading to multi-pixel receivers by replacing the conventional feed horns with phased array feeds (PAFs) to increase the field of view and, thus, imaging speeds. This step in astronomy instrumentation has been taken by only a few research laboratories world-wide and primarily in Lband (0.7-1.5 GHz). We present a K-band (18-26 GHz) 5x5 modular PAF to demonstrate the feasibility of higher frequency receiving arrays. The KPAF system includes a tapered slot antenna array, a cryogenic commercial GaAs MMIC amplifier block, and a mixing stage to down-convert to L band for an existing beamformer. The noise temperature and power budget are outlined. Full antenna S-parameters and far-field beam patterns are simulated and measured using both planar near-field and far-field techniques. Cryogenic and room temperature amplifier noise measurements with varying bias levels are presented.

  9. Matrix phased arrays for the inspection of CFRP-components

    NASA Astrophysics Data System (ADS)

    Kreutzbruck, M.; Brackrock, D.; Brekow, G.; Montag, H.-J.; Boehm, R.; Illerhaus, B.

    2014-02-01

    Lightweight components are increasingly used in different industrial sectors such as transportation, energy generation and automotive. This growing field includes different types of CFRP-structures, hybrid materials and glued components showing - compared to their pure metallic counterparts- a significant more complicated structure in terms of internal interfaces and anisotropy of material parameters. In this work we present the use of matrix phased array to increase the amount of obtained information to enhance the inspection quality. We used different types of carbon materials such as 6 mm thick uni- and bidirectional prepreg specimens containing impact damages. The latter were introduced with different energy levels ranging from 1.3 to 7.2 J. By scanning a 2.25 MHz matrix array with 6 × 10 elements above the prepreg surface and using different angels of incidence a complete 3D-image was generated which allows the detection of defects as small as 1mm in a depth of 4 mm. A comparison with conventional approaches show that the signal-to-noise ratio can be highly increased. This enables us to visualize the region of damage within the impact zone, clearly showing the cone-like damage distribution along increasing material depth. The detection quality allows the estimation of the opening angles of the cone shaped damage, which can be used for further evaluation and quantitation of energy dependent impact damages.

  10. Phased Array Beamforming and Imaging in Composite Laminates Using Guided Waves

    NASA Technical Reports Server (NTRS)

    Tian, Zhenhua; Leckey, Cara A. C.; Yu, Lingyu

    2016-01-01

    This paper presents the phased array beamforming and imaging using guided waves in anisotropic composite laminates. A generic phased array beamforming formula is presented, based on the classic delay-and-sum principle. The generic formula considers direction-dependent guided wave properties induced by the anisotropic material properties of composites. Moreover, the array beamforming and imaging are performed in frequency domain where the guided wave dispersion effect has been considered. The presented phased array method is implemented with a non-contact scanning laser Doppler vibrometer (SLDV) to detect multiple defects at different locations in an anisotropic composite plate. The array is constructed of scan points in a small area rapidly scanned by the SLDV. Using the phased array method, multiple defects at different locations are successfully detected. Our study shows that the guided wave phased array method is a potential effective method for rapid inspection of large composite structures.

  11. Monolithic optical phased-array transceiver in a standard SOI CMOS process.

    PubMed

    Abediasl, Hooman; Hashemi, Hossein

    2015-03-01

    Monolithic microwave phased arrays are turning mainstream in automotive radars and high-speed wireless communications fulfilling Gordon Moores 1965 prophecy to this effect. Optical phased arrays enable imaging, lidar, display, sensing, and holography. Advancements in fabrication technology has led to monolithic nanophotonic phased arrays, albeit without independent phase and amplitude control ability, integration with electronic circuitry, or including receive and transmit functions. We report the first monolithic optical phased array transceiver with independent control of amplitude and phase for each element using electronic circuitry that is tightly integrated with the nanophotonic components on one substrate using a commercial foundry CMOS SOI process. The 8 × 8 phased array chip includes thermo-optical tunable phase shifters and attenuators, nano-photonic antennas, and dedicated control electronics realized using CMOS transistors. The complex chip includes over 300 distinct optical components and over 74,000 distinct electrical components achieving the highest level of integration for any electronic-photonic system.

  12. Monolithic optical phased-array transceiver in a standard SOI CMOS process.

    PubMed

    Abediasl, Hooman; Hashemi, Hossein

    2015-03-01

    Monolithic microwave phased arrays are turning mainstream in automotive radars and high-speed wireless communications fulfilling Gordon Moores 1965 prophecy to this effect. Optical phased arrays enable imaging, lidar, display, sensing, and holography. Advancements in fabrication technology has led to monolithic nanophotonic phased arrays, albeit without independent phase and amplitude control ability, integration with electronic circuitry, or including receive and transmit functions. We report the first monolithic optical phased array transceiver with independent control of amplitude and phase for each element using electronic circuitry that is tightly integrated with the nanophotonic components on one substrate using a commercial foundry CMOS SOI process. The 8 × 8 phased array chip includes thermo-optical tunable phase shifters and attenuators, nano-photonic antennas, and dedicated control electronics realized using CMOS transistors. The complex chip includes over 300 distinct optical components and over 74,000 distinct electrical components achieving the highest level of integration for any electronic-photonic system. PMID:25836869

  13. Phased array beamforming and imaging in composite laminates using guided waves

    NASA Astrophysics Data System (ADS)

    Tian, Zhenhua; Leckey, Cara A. C.; Yu, Lingyu

    2016-04-01

    This paper presents the phased array beamforming and imaging using guided waves in anisotropic composite laminates. A generic phased array beamforming formula is presented, based on the classic delay-and-sum principle. The generic formula considers direction-dependent guided wave properties induced by the anisotropic material properties of composites. Moreover, the array beamforming and imaging are performed in frequency domain where the guided wave dispersion effect has been considered. The presented phased array method is implemented with a non-contact scanning laser Doppler vibrometer (SLDV) to detect multiple simulated defects at different locations in an anisotropic composite plate. The array is constructed of scan points in a small area rapidly scanned by the SLDV. Using the phased array method, multiple simulated defects at different locations are successfully detected. Our study shows that the guided wave phased array method is a potential effective method for rapid inspection of large composite structures.

  14. Lightning protection devices for high frequencies equipments

    SciTech Connect

    Pierre, J.

    1983-01-01

    Contents: Mechanism of a Lightning Stroke from Antenna to Ground; Principles of Protection Devices for Feeders; Electrical Characteristics of H.F. Protection Devices; Calculation of H.F. Protection Devices; Catalogue Devices for High Frequency Protection; Some Measurement Results for Tees; Measurement Results for Decoupling Line Devices; Installation of High Frequency Devices.

  15. Monolithic Microwave Integrated Circuit (MMIC) Phased Array Demonstrated With ACTS

    NASA Technical Reports Server (NTRS)

    1996-01-01

    Monolithic Microwave Integrated Circuit (MMIC) arrays developed by the NASA Lewis Research Center and the Air Force Rome Laboratory were demonstrated in aeronautical terminals and in mobile or fixed Earth terminals linked with NASA's Advanced Communications Technology Satellite (ACTS). Four K/Ka-band experimental arrays were demonstrated between May 1994 and May 1995. Each array had GaAs MMIC devices at each radiating element for electronic beam steering and distributed power amplification. The 30-GHz transmit array used in uplinks to ACTS was developed by Lewis and Texas Instruments. The three 20-GHz receive arrays used in downlinks from ACTS were developed in cooperation with the Air Force Rome Laboratory, taking advantage of existing Air Force integrated-circuit, active-phased-array development contracts with the Boeing Company and Lockheed Martin Corporation. Four demonstrations, each related to an application of high interest to both commercial and Department of Defense organizations, were conducted. The location, type of link, and the data rate achieved for each of the applications is shown. In one demonstration-- an aeronautical terminal experiment called AERO-X--a duplex voice link between an aeronautical terminal on the Lewis Learjet and ACTS was achieved. Two others demonstrated duplex voice links (and in one case, interactive video links as well) between ACTS and an Army high-mobility, multipurpose wheeled vehicle (HMMWV, or "humvee"). In the fourth demonstration, the array was on a fixed mount and was electronically steered toward ACTS. Lewis served as project manager for all demonstrations and as overall system integrator. Lewis engineers developed the array system including a controller for open-loop tracking of ACTS during flight and HMMWV motion, as well as a laptop data display and recording system used in all demonstrations. The Jet Propulsion Laboratory supported the AERO-X program, providing elements of the ACTS Mobile Terminal. The successful

  16. Airborne ultrasonic phased arrays using ferroelectrets: a new fabrication approach.

    PubMed

    Ealo, Joao L; Camacho, Jorge J; Fritsch, Carlos

    2009-04-01

    In this work, a novel procedure that considerably simplifies the fabrication process of ferroelectret-based multielement array transducers is proposed and evaluated. Also, the potential of ferroelectrets being used as active material for air-coupled ultrasonic transducer design is demonstrated. The new construction method of multi-element transducers introduces 2 distinctive improvements. First, active ferroelectret material is not discretized into elements, and second, the need of structuring upper and/or lower electrodes in advance of the permanent polarization of the film is removed. The aperture discretization and the mechanical connection are achieved in one step using a through-thickness conductive tape. To validate the procedure, 2 linear array prototypes of 32 elements, with a pitch of 3.43 mm and a wide usable frequency range from 30 to 300 kHz, were built and evaluated using a commercial phased-array system. A low crosstalk among elements, below -30 dB, was measured by interferometry. Likewise, a homogeneous response of the array elements, with a maximum deviation of +/-1.8 dB, was obtained. Acoustic beam steering measurements were accomplished at different deflection angles using a calibrated microphone. The ultrasonic beam parameters, namely, lateral resolution, side lobe level, grating lobes, and focus depth, were congruent with theory. Acoustic images of a single reflector were obtained using one of the array elements as the receiver. Resulting images are also in accordance with numerical simulation, demonstrating the feasibility of using these arrays in pulse-echo mode. The proposed procedure simplifies the manufacturing of multidimensional arrays with arbitrary shape elements and not uniformly distributed. Furthermore, this concept can be extended to nonflat arrays as long as the transducer substrate conforms to a developable surface. PMID:19406714

  17. Optimization of pelvic heating rate distributions with electromagnetic phased arrays.

    PubMed

    Paulsen, K D; Geimer, S; Tang, J; Boyse, W E

    1999-01-01

    Deep heating of pelvic tumours with electromagnetic phased arrays has recently been reported to improve local tumour control when combined with radiotherapy in a randomized clinical trial despite the fact that rather modest elevations in tumour temperatures were achieved. It is reasonable to surmise that improvements in temperature elevation could lead to even better tumour response rates, motivating studies which attempt to explore the parameter space associated with heating rate delivery in the pelvis. Computational models which are based on detailed three-dimensional patient anatomy are readily available and lend themselves to this type of investigation. In this paper, volume average SAR is optimized in a predefined target volume subject to a maximum allowable volume average SAR outside this zone. Variables under study include the position of the target zone, the number and distribution of radiators and the applicator operating frequency. The results show a clear preference for increasing frequency beyond 100 MHz, which is typically applied clinically, especially as the number of antennae increases. Increasing both the number of antennae per circumferential distance around the patient, as well as the number of independently functioning antenna bands along the patient length, is important in this regard, although improvements were found to be more significant with increasing circumferential antenna density. However, there is considerable site specific variation and cases occur where lower numbers of antennae spread out over multiple longitudinal bands are more advantageous. The results presented here have been normalized relative to an optimized set of antenna array amplitudes and phases operating at 100 MHz which is a common clinical configuration. The intent is to provide some indications of avenues for improving the heating rate distributions achievable with current technology.

  18. Phased-array ultrasonic surface contour mapping system. Technical note

    SciTech Connect

    Fasching, G.E.; Loudin, W.J.; Paton, D.E.; Smith, N.S. Jr.

    1992-11-01

    The development of reliable mechanistic models for prediction of conventional and fluidized-bed combustor and gasifier operation and solids flow behavior in silos or other solids handling and storage components requires knowledge of the contained solids flow characteristics. This knowledge is gained from dynamic experimental measurements of bed top surface contours in addition to measurements of bulk bed properties. The surface contour mapping system (SCMS) provides a means of generating surface contour maps in real time with a unique, automatically focused, density-compensated, digital phased-array scanning, ultrasonic-range measurement system. The system is designed to operate in environments having gas temperatures up to 1,600 {degree}F and pressures to 1,000 psig. Computer simulation of several SCMS candidates and acoustic carrier modulation techniques indicates that a surface measurement resolution of {plus_minus}2 inches over a range of 5 to 20 feet distance between the transmit/receive (T/R) transducers and the bed surface can be expected. The simulation of a particular design, a 9-T/R, 25-pixel bed surface, in which the level of each pixel was randomly set between 5 and 7 feet below the plane of the T/R transducers, then measured using two different modulation techniques, produced excellent results. The simulation of this surface contour mapping system determined the value of the level of each of the 25 pixels to within {plus_minus}1 inch for over 95 percent of more than 100 test cases for one of the modulation techniques, and for over 99 percent of about 100 test cases for a second modulation technique. A hardware implementation of the design simulated but using only a two-T/R, three-pixel SCMS produced results very closely approximating those obtained during the simulation.

  19. 78 FR 70567 - Nationwide Use of High Frequency and Ultra High Frequency Active SONAR Technology; Final...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-11-26

    ... SECURITY Coast Guard Nationwide Use of High Frequency and Ultra High Frequency Active SONAR Technology...) and Ultra High Frequency (UHF) Sound Navigation and Ranging (SONAR) Technology and Finding of No... less than two weeks; however, for environmental disasters such as the Deepwater Horizon oil...

  20. Propagation of high frequencies in Scandinavia

    SciTech Connect

    Bame, D.

    1989-04-01

    To determine if seismic signals at frequencies up to 50 Hz are useful for detecting events and discriminating between earthquakes and explosions, approximately 180 events from the three-component high-frequency seismic element (HFSE) installed at the center of the Norwegian Regional Seismic Array (NRSA) have been analyzed. The attenuation of high-frequency signals in Scandinavia varies with distance, azimuth, magnitude, and source effects. Most of the events were detected with HFSE, although detections were better on the NRSA where signal processing techniques were used. Based on a preliminary analysis, high-frequency data do not appear to be a useful discriminant in Scandinavia. 21 refs., 29 figs., 3 tabs.

  1. Design and fabrication of a large airborne phased-array antenna

    NASA Astrophysics Data System (ADS)

    Cooke, William P.; Harris, Joseph M.; Jameson, Calvin R.

    1989-01-01

    A large phased-array antenna has been developed and mounted for missile test range trials on the Dash 8 aircraft, with a view to eventual installation on the E-9A Airborne Platform. The antenna is a one-dimensional scan, multiple-channel phased array of 30-ft length and 30-in height. This polarization-insensitive antenna operates in the 2.2-2.4 range, and uses modular parts to improve reliability and reduce maintenance time; being electronically steerable, the phased-array antenna is able to simultaneously receive five independent telemetry signals within its field-of-view.

  2. Impact: a low cost, reconfigurable, digital beamforming common module building block for next generation phased arrays

    NASA Astrophysics Data System (ADS)

    Paulsen, Lee; Hoffmann, Ted; Fulton, Caleb; Yeary, Mark; Saunders, Austin; Thompson, Dan; Chen, Bill; Guo, Alex; Murmann, Boris

    2015-05-01

    Phased array systems offer numerous advantages to the modern warfighter in multiple application spaces, including Radar, Electronic Warfare, Signals Intelligence, and Communications. However, a lack of commonality in the underlying technology base for DoD Phased Arrays has led to static systems with long development cycles, slow technology refreshes in response to emerging threats, and expensive, application-specific sub-components. The IMPACT module (Integrated Multi-use Phased Array Common Tile) is a multi-channel, reconfigurable, cost-effective beamformer that provides a common building block for multiple, disparate array applications.

  3. Pulse-Echo Phased Array Ultrasonic Inspection of Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS)

    NASA Technical Reports Server (NTRS)

    Johnston, Pat H.

    2010-01-01

    A PRSEUS test article was subjected to controlled impact on the skin face followed by static and cyclic axial compressions. Phased array ultrasonic inspection was conducted before impact, and after each of the test conditions. A linear phased array probe with a manual X-Y scanner was used for interrogation. Ultrasound showed a delamination between the skin and stringer flange adjacent to the impact. As designed, the stitching in the flange arrested the lateral flaw formation. Subsequent ultrasonic data showed no delamination growth due to continued loading. Keywords: Phased Array, Ultrasonics, Composites, Out-of-Autoclave

  4. A portable ultrasonic phased array device for tabular joint weld inspection of offshore platform structures

    NASA Astrophysics Data System (ADS)

    Shan, Baohua; Li, Jingan; Duan, Zhongdong; Ou, Jinping; Shen, Wei

    2012-05-01

    To meet the inspection need for complex tabular joints weld of offshore platform structures, a portable ultrasonic phased array inspection device is developed. The integrated device is small and portable. As designed, the device can implement different algorithm of the ultrasonic phased array inspection technology. With proposed inspection plan, the experiment of Y tubular joint model was performed in lab. Experiment results indicate that the possible ultrasonic phased array inspection device can detect and visualize the flaws on Y tubular joint weld, which are nearly consistent with the actual condition.

  5. Electronically controlled optical beam-steering by an active phased array of metallic nanoantennas.

    PubMed

    DeRose, C T; Kekatpure, R D; Trotter, D C; Starbuck, A; Wendt, J R; Yaacobi, A; Watts, M R; Chettiar, U; Engheta, N; Davids, P S

    2013-02-25

    An optical phased array of nanoantenna fabricated in a CMOS compatible silicon photonics process is presented. The optical phased array is fed by low loss silicon waveguides with integrated ohmic thermo-optic phase shifters capable of 2π phase shift with ∼ 15 mW of applied electrical power. By controlling the electrical power to the individual integrated phase shifters fixed wavelength steering of the beam emitted normal to the surface of the wafer of 8° is demonstrated for 1 × 8 phased arrays with periods of both 6 and 9 μm. PMID:23482053

  6. Phased Array Inspection of Titanium Disk Forgings Targeting no. 1/2 FBH Sensitivity

    SciTech Connect

    Roberts, R.A.; Friedl, J.

    2005-04-09

    The phased array implementation of a focused zoned ultrasonic inspection to achieve a >3dB signal-to-noise for no. 1/2 flat bottom holes (FBH) in titanium is reported. Previous work established the ultrasound focusing required to achieve the targeted sensitivity. This work reports on the design of a phased array transducer capable of maintaining the needed focus to the depths required in the forging inspection. The performance of the phased array inspection is verified by examining signal-to-noise of no. 1/2 FBHs contained in coupons cut from actual forgings.

  7. An optically controlled phased array antenna based on single sideband polarization modulation.

    PubMed

    Zhang, Yamei; Wu, Huan; Zhu, Dan; Pan, Shilong

    2014-02-24

    A novel optically controlled phased array antenna consisting a simple optical beamforming network and an N element linear patch antenna array is proposed and demonstrated. The optical beamforming network is realized by N independent phase shifters using a shared optical single sideband (OSSB) polarization modulator together with N polarization controllers (PCs), N polarization beam splitters (PBSs) and N photodetectors (PDs). An experiment is carried out. A 4-element linear patch antenna array operating at 14 GHz and a 1 × 4 optical beamforming network (OBFN) is employed to realize the phased array antenna. The radiation patterns of the phased array antenna at -30°, 0° and 30° are achieved.

  8. Neural coding of high-frequency tones

    NASA Technical Reports Server (NTRS)

    Howes, W. L.

    1976-01-01

    Available evidence was presented indicating that neural discharges in the auditory nerve display characteristic periodicities in response to any tonal stimulus including high-frequency stimuli, and that this periodicity corresponds to the subjective pitch.

  9. Overview of the Advanced High Frequency Branch

    NASA Technical Reports Server (NTRS)

    Miranda, Felix A.

    2015-01-01

    This presentation provides an overview of the competencies, selected areas of research and technology development activities, and current external collaborative efforts of the NASA Glenn Research Center's Advanced High Frequency Branch.

  10. High power, high frequency component test facility

    NASA Technical Reports Server (NTRS)

    Roth, Mary Ellen; Krawczonek, Walter

    1990-01-01

    The NASA Lewis Research Center has available a high frequency, high power laboratory facility for testing various components of aerospace and/or terrestrial power systems. This facility is described here. All of its capabilities and potential applications are detailed.

  11. Real-time, high frequency QRS electrocardiograph

    NASA Technical Reports Server (NTRS)

    Schlegel, Todd T. (Inventor); DePalma, Jude L. (Inventor); Moradi, Saeed (Inventor)

    2006-01-01

    Real time cardiac electrical data are received from a patient, manipulated to determine various useful aspects of the ECG signal, and displayed in real time in a useful form on a computer screen or monitor. The monitor displays the high frequency data from the QRS complex in units of microvolts, juxtaposed with a display of conventional ECG data in units of millivolts or microvolts. The high frequency data are analyzed for their root mean square (RMS) voltage values and the discrete RMS values and related parameters are displayed in real time. The high frequency data from the QRS complex are analyzed with imbedded algorithms to determine the presence or absence of reduced amplitude zones, referred to herein as RAZs. RAZs are displayed as go, no-go signals on the computer monitor. The RMS and related values of the high frequency components are displayed as time varying signals, and the presence or absence of RAZs may be similarly displayed over time.

  12. Beale Air Force Base, Perimeter Acquisition Vehicle Entry PhasedArray Warning ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Beale Air Force Base, Perimeter Acquisition Vehicle Entry Phased-Array Warning System, Satellite Communications Terminal, End of Spencer Paul Road, north of Warren Shingle Road (14th Street), Marysville, Yuba County, CA

  13. Beale Air Force Base, Perimeter Acquisition Vehicle Entry PhasedArray Warning ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Beale Air Force Base, Perimeter Acquisition Vehicle Entry Phased-Array Warning System, Civil Engineering Storage Building, End of Spencer Paul Road, north of Warren Shingle Road (14th Street), Marysville, Yuba County, CA

  14. Beale Air Force Base, Perimeter Acquisition Vehicle Entry PhasedArray Warning ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Beale Air Force Base, Perimeter Acquisition Vehicle Entry Phased-Array Warning System, Microwave Equipment Building, End of Spencer Paul Road, north of Warren Shingle Road (14th Street), Marysville, Yuba County, CA

  15. Beale Air Force Base, Perimeter Acquisition Vehicle Entry PhasedArray Warning ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Beale Air Force Base, Perimeter Acquisition Vehicle Entry Phased-Array Warning System, Clean Lubrication Oil Storage Tank & Enclosure, End of Spencer Paul Road, north of Warren Shingle Road (14th Street), Marysville, Yuba County, CA

  16. Development of components for an S-band phased array antenna subsystem

    NASA Technical Reports Server (NTRS)

    1975-01-01

    The system requirements, module test data, and S-band phased array subsystem test data are discussed. Of the two approaches to achieving antenna gain (mechanically steered reflector or electronically steered phased array), the phased array approach offers the greatest simplicity and lowest cost (size, weight, power, and dollars) for this medium gain. A competitive system design is described as well as hardware evaluation which will lead to timely availability of this technology for implementing such a system. The objectives of the study were: to fabricate and test six engineering model transmit/receive microelectronics modules; to design, fabricate, and test one dc and logic multilayer manifold; and to integrate and test an S-band phased array antenna subsystem composed of antenna elements, seven T/R modules, RF manifolds and dc manifold.

  17. Phased Array Ultrasonic Sound Field Mapping in Cast Austenitic Stainless Steel

    SciTech Connect

    Crawford, Susan L.; Prowant, Matthew S.; Cinson, Anthony D.; Larche, Michael R.; Diaz, Aaron A.; Anderson, Michael T.

    2014-05-31

    This study maps the phased array-generated acoustic sound fields through three types of CASS microstructure in four specimens to quantitatively assess the beam formation effectiveness in these materials.

  18. New customizable phased array UT instrument opens door for furthering research and better industrial implementation

    NASA Astrophysics Data System (ADS)

    Dao, Gavin; Ginzel, Robert

    2014-02-01

    Phased array UT as an inspection technique in itself continues to gain wide acceptance. However, there is much room for improvement in terms of implementation of Phased Array (PA) technology for every unique NDT application across several industries (e.g. oil and petroleum, nuclear and power generation, steel manufacturing, etc.). Having full control of the phased array instrument and customizing a software solution is necessary for more seamless and efficient inspections, from setting the PA parameters, collecting data and reporting, to the final analysis. NDT researchers and academics also need a flexible and open platform to be able to control various aspects of the phased array process. A high performance instrument with advanced PA features, faster data rates, a smaller form factor, and capability to adapt to specific applications, will be discussed.

  19. Monolithic optical integrated control circuitry for GaAs MMIC-based phased arrays

    NASA Technical Reports Server (NTRS)

    Bhasin, K. B.; Ponchak, G. E.; Kascak, T. J.

    1985-01-01

    Gallium arsenide (GaAs) monolithic microwave integrated circuits (MMIC's) show promise in phased-array antenna applications for future space communications systems. Their efficient usage will depend on the control of amplitude and phase signals for each MMIC element in the phased array and in the low-loss radiofrequency feed. For a phased array contining several MMIC elements a complex system is required to control and feed each element. The characteristics of GaAs MMIC's for 20/30-GHz phased-array systems are discussed. The optical/MMIC interface and the desired characteristics of optical integrated circuits (OIC's) for such an interface are described. Anticipated fabrication considerations for eventual full monolithic integration of optical integrated circuits with MMIC's on a GaAs substrate are presented.

  20. Beale Air Force Base, Perimeter Acquisition Vehicle Entry PhasedArray Warning ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Beale Air Force Base, Perimeter Acquisition Vehicle Entry Phased-Array Warning System, Techinical Equipment Building, End of Spencer Paul Road, north of Warren Shingle Road (14th Street), Marysville, Yuba County, CA

  1. Beale Air Force Base, Perimeter Acquisition Vehicle Entry PhasedArray ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    - Beale Air Force Base, Perimeter Acquisition Vehicle Entry Phased-Array Warning System, Techinical Equipment Building, End of Spencer Paul Road, north of Warren Shingle Road (14th Street), Marysville, Yuba County, CA

  2. Beale Air Force Base, Perimeter Acquisition Vehicle Entry PhasedArray Warning ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Beale Air Force Base, Perimeter Acquisition Vehicle Entry Phased-Array Warning System, Supply Warehouse, End of Spencer Paul Road, north of Warren Shingle Road (14th Street), Marysville, Yuba County, CA

  3. Beale Air Force Base, Perimeter Acquisition Vehicle Entry PhasedArray Warning ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Beale Air Force Base, Perimeter Acquisition Vehicle Entry Phased-Array Warning System, Electric Substation, End of Spencer Paul Road, north of Warren Shingle Road (14th Street), Marysville, Yuba County, CA

  4. Beale Air Force Base, Perimeter Acquisition Vehicle Entry PhasedArray Warning ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Beale Air Force Base, Perimeter Acquisition Vehicle Entry Phased-Array Warning System, Emergency Generator Enclosure, End of Spencer Paul Road, north of Warren Shingle Road (14th Street), Marysville, Yuba County, CA

  5. Phased Array Antenna Testbed Development at the NASA Glenn Research Center

    NASA Technical Reports Server (NTRS)

    Lambert, Kevin M.; Kubat, Gregory; Johnson, Sandra K.; Anzic, Godfrey

    2003-01-01

    Ideal phased array antennas offer advantages for communication systems, such as wide-angle scanning and multibeam operation, which can be utilized in certain NASA applications. However, physically realizable, electronically steered, phased array antennas introduce additional system performance parameters, which must be included in the evaluation of the system. The NASA Glenn Research Center (GRC) is currently conducting research to identify these parameters and to develop the tools necessary to measure them. One of these tools is a testbed where phased array antennas may be operated in an environment that simulates their use. This paper describes the development of the testbed and its use in characterizing a particular K-Band, phased array antenna.

  6. On the (Frequency) Modulation of Coupled Oscillator Arrays in Phased Array Beam Control

    NASA Technical Reports Server (NTRS)

    Pogorzelski, R.; Acorn, J.; Zawadzki, M.

    2000-01-01

    It has been shown that arrays of voltage controlled oscillators coupled to nearest neighbors can be used to produce useful aperture phase distributions for phased array antennas. However, placing information of the transmitted signal requires that the oscillations be modulated.

  7. Manipulation of Liquids Using Phased Array Generation of Acoustic Radiation Pressure

    NASA Technical Reports Server (NTRS)

    Oeftering, Richard C. (Inventor)

    2000-01-01

    A phased array of piezoelectric transducers is used to control and manipulate contained as well as uncontained fluids in space and earth applications. The transducers in the phased array are individually activated while being commonly controlled to produce acoustic radiation pressure and acoustic streaming. The phased array is activated to produce a single pulse, a pulse burst or a continuous pulse to agitate, segregate or manipulate liquids and gases. The phased array generated acoustic radiation pressure is also useful in manipulating a drop, a bubble or other object immersed in a liquid. The transducers can be arranged in any number of layouts including linear single or multi- dimensional, space curved and annular arrays. The individual transducers in the array are activated by a controller, preferably driven by a computer.

  8. New customizable phased array UT instrument opens door for furthering research and better industrial implementation

    SciTech Connect

    Dao, Gavin; Ginzel, Robert

    2014-02-18

    Phased array UT as an inspection technique in itself continues to gain wide acceptance. However, there is much room for improvement in terms of implementation of Phased Array (PA) technology for every unique NDT application across several industries (e.g. oil and petroleum, nuclear and power generation, steel manufacturing, etc.). Having full control of the phased array instrument and customizing a software solution is necessary for more seamless and efficient inspections, from setting the PA parameters, collecting data and reporting, to the final analysis. NDT researchers and academics also need a flexible and open platform to be able to control various aspects of the phased array process. A high performance instrument with advanced PA features, faster data rates, a smaller form factor, and capability to adapt to specific applications, will be discussed.

  9. An Update on Phased Array Results Obtained on the GE Counter-Rotating Open Rotor Model

    NASA Technical Reports Server (NTRS)

    Podboy, Gary; Horvath, Csaba; Envia, Edmane

    2013-01-01

    Beamform maps have been generated from 1) simulated data generated by the LINPROP code and 2) actual experimental phased array data obtained on the GE Counter-rotating open rotor model. The beamform maps show that many of the tones in the experimental data come from their corresponding Mach radius. If the phased array points to the Mach radius associated with a tone then it is likely that the tone is a result of the loading and thickness noise on the blades. In this case, the phased array correctly points to where the noise is coming from and indicates the axial location of the loudest source in the image but not necessarily the correct vertical location. If the phased array does not point to the Mach radius associated with a tone then some mechanism other than loading and thickness noise may control the amplitude of the tone. In this case, the phased array may or may not point to the actual source. If the source is not rotating it is likely that the phased array points to the source. If the source is rotating it is likely that the phased array indicates the axial location of the loudest source but not necessarily the correct vertical location. These results indicate that you have to be careful in how you interpret phased array data obtained on an open rotor since they may show the tones coming from a location other than the source location. With a subsonic tip speed open rotor the tones can come form locations outboard of the blade tips. This has implications regarding noise shielding.

  10. Phased Array Ultrasonic Examination of Space Shuttle Main Engine Nozzle Weld

    NASA Technical Reports Server (NTRS)

    James, S.; Engel, J.; Kimbrough, D.; Suits, M.; McCool, Alex (Technical Monitor)

    2001-01-01

    This paper describes a Phased Array Ultrasonic Examination that was developed for the examination of a limited access circumferential Inconel 718 fusion weld of a Space Shuttle Main Engine Nozzle - Cone. The paper discusses the selection and formation criteria used for the phased array focal laws, the reference standard that simulated hardware conditions, the examination concept, and results. Several unique constraints present during this examination included limited probe movement to a single axis and one-sided access to the weld.

  11. A study program on large aperture electronic scanning phased array antennas for the shuttle imaging microwave system

    NASA Technical Reports Server (NTRS)

    1974-01-01

    Fundamental phased array theory and performance parameters are discussed in terms of their application to microwave radiometry, and four scanning phased arrays representing current examples of state-of-the-art phased array technology are evaluated for potential use as components of the multispectral antenna system for the space shuttle imaging microwave system (SIMS). A discussion of problem areas, both in performance and fabrication is included, with extrapolations of performance characteristics for phased array antennas of increased sizes up to 20 m by 20 m. The possibility of interlacing two or more phased arrays to achieve a multifrequency aperture is considered, and, finally, a specific antenna system is recommended for use with SIMS.

  12. Low-Cost Phased Array Antenna for Sounding Rockets, Missiles, and Expendable Launch Vehicles

    NASA Technical Reports Server (NTRS)

    Mullinix, Daniel; Hall, Kenneth; Smith, Bruce; Corbin, Brian

    2012-01-01

    A low-cost beamformer phased array antenna has been developed for expendable launch vehicles, rockets, and missiles. It utilizes a conformal array antenna of ring or individual radiators (design varies depending on application) that is designed to be fed by the recently developed hybrid electrical/mechanical (vendor-supplied) phased array beamformer. The combination of these new array antennas and the hybrid beamformer results in a conformal phased array antenna that has significantly higher gain than traditional omni antennas, and costs an order of magnitude or more less than traditional phased array designs. Existing omnidirectional antennas for sounding rockets, missiles, and expendable launch vehicles (ELVs) do not have sufficient gain to support the required communication data rates via the space network. Missiles and smaller ELVs are often stabilized in flight by a fast (i.e. 4 Hz) roll rate. This fast roll rate, combined with vehicle attitude changes, greatly increases the complexity of the high-gain antenna beam-tracking problem. Phased arrays for larger ELVs with roll control are prohibitively expensive. Prior techniques involved a traditional fully electronic phased array solution, combined with highly complex and very fast inertial measurement unit phased array beamformers. The functional operation of this phased array is substantially different from traditional phased arrays in that it uses a hybrid electrical/mechanical beamformer that creates the relative time delays for steering the antenna beam via a small physical movement of variable delay lines. This movement is controlled via an innovative antenna control unit that accesses an internal measurement unit for vehicle attitude information, computes a beam-pointing angle to the target, then points the beam via a stepper motor controller. The stepper motor on the beamformer controls the beamformer variable delay lines that apply the appropriate time delays to the individual array elements to properly

  13. Metrology For High-Frequency Nanoelectronics

    SciTech Connect

    Wallis, T. Mitch; Imtiaz, Atif; Nembach, Hans T.; Rice, Paul; Kabos, Pavel

    2007-09-26

    Two metrological tools for high-frequency measurements of nanoscale systems are described: (i) two/N-port analysis of nanoscale devices as well as (ii) near-field scanning microwave microscopy (NSMM) for materials characterization. Calibrated two/N-port measurements were made on multiwalled carbon nanotubes (MWNT) welded to a coplanar waveguide. Significant changes in the extracted high-frequency electrical response of the welded MWNT were measured when the contacts to the MWNT were modified. Additionally, NSMM was used to characterize films of nanotube soot deposited on copper and sapphire substrates. The material properties of the films showed a strong dependence on the substrate material.

  14. High frequency III–V nanowire MOSFETs

    NASA Astrophysics Data System (ADS)

    Lind, Erik

    2016-09-01

    III–V nanowire transistors are promising candidates for very high frequency electronics applications. The improved electrostatics originating from the gate-all-around geometry allow for more aggressive scaling as compared with planar field-effect transistors, and this can lead to device operation at very high frequencies. The very high mobility possible with In-rich devices can allow very high device performance at low operating voltages. GaN nanowires can take advantage of the large band gap for high voltage operation. In this paper, we review the basic physics and device performance of nanowire field- effect transistors relevant for high frequency performance. First, the geometry of lateral and vertical nanowire field-effect transistors is introduced, with special emphasis on the parasitic capacitances important for nanowire geometries. The basic important high frequency transistor metrics are introduced. Secondly, the scaling properties of gate-all-around nanowire transistors are introduced, based on geometric length scales, demonstrating the scaling possibilities of nanowire transistors. Thirdly, to model nanowire transistor performance, a two-band non-parabolic ballistic transistor model is used to efficiently calculate the current and transconductance as a function of band gap and nanowire size. The intrinsic RF metrics are also estimated. Finally, experimental state-of-the-art nanowire field-effect transistors are reviewed and benchmarked, lateral and vertical transistor geometries are explored, and different fabrication routes are highlighted. Lateral devices have demonstrated operation up to 350 GHz, and vertical devices up to 155 GHz.

  15. Psychophysical tuning curves at very high frequencies

    NASA Astrophysics Data System (ADS)

    Yasin, Ifat; Plack, Christopher J.

    2005-10-01

    For most normal-hearing listeners, absolute thresholds increase rapidly above about 16 kHz. One hypothesis is that the high-frequency limit of the hearing-threshold curve is imposed by the transmission characteristics of the middle ear, which attenuates the sound input [Masterton et al., J. Acoust. Soc. Am. 45, 966-985 (1969)]. An alternative hypothesis is that the high-frequency limit of hearing is imposed by the tonotopicity of the cochlea [Ruggero and Temchin, Proc. Nat. Acad. Sci. U.S.A. 99, 13206-13210 (2002)]. The aim of this study was to test these hypotheses. Forward-masked psychophysical tuning curves (PTCs) were derived for signal frequencies of 12-17.5 kHz. For the highest signal frequencies, the high-frequency slopes of some PTCs were steeper than the slope of the hearing-threshold curve. The results also show that the human auditory system displays frequency selectivity for characteristic frequencies (CFs) as high as 17 kHz, above the frequency at which absolute thresholds begin to increase rapidly. The findings suggest that, for CFs up to 17 kHz, the high-frequency limitation in humans is imposed in part by the middle-ear attenuation, and not by the tonotopicity of the cochlea.

  16. Transponder System for High-Frequency Ranging

    NASA Technical Reports Server (NTRS)

    Lichtenberg, C. L.; Shores, P. W.; Kobayashi, H. S.

    1986-01-01

    Transponder system uses phase difference between transmitted and reflected high-frequency radio waves to measure distance to target. To suppress spurious measurements of reflections from objects near target at transmitted frequency and its harmonics, transponder at target generates return signal at half transmitted frequency. System useful in such applications as surveying, docking of ships, and short-range navigation.

  17. High frequency pressure oscillator for microcryocoolers

    NASA Astrophysics Data System (ADS)

    Vanapalli, S.; ter Brake, H. J. M.; Jansen, H. V.; Zhao, Y.; Holland, H. J.; Burger, J. F.; Elwenspoek, M. C.

    2008-04-01

    Microminiature pulse tube cryocoolers should operate at a frequency of an order higher than the conventional macro ones because the pulse tube cryocooler operating frequency scales inversely with the square of the pulse tube diameter. In this paper, the design and experiments of a high frequency pressure oscillator is presented with the aim to power a micropulse tube cryocooler operating between 300 and 80K, delivering a cooling power of 10mW. Piezoelectric actuators operate efficiently at high frequencies and have high power density making them good candidates as drivers for high frequency pressure oscillator. The pressure oscillator described in this work consists of a membrane driven by a piezoelectric actuator. A pressure ratio of about 1.11 was achieved with a filling pressure of 2.5MPa and compression volume of about 22.6mm3 when operating the actuator with a peak-to-peak sinusoidal voltage of 100V at a frequency of 1kHz. The electrical power input was 2.73W. The high pressure ratio and low electrical input power at high frequencies would herald development of microminiature cryocoolers.

  18. High frequency pressure oscillator for microcryocoolers.

    PubMed

    Vanapalli, S; ter Brake, H J M; Jansen, H V; Zhao, Y; Holland, H J; Burger, J F; Elwenspoek, M C

    2008-04-01

    Microminiature pulse tube cryocoolers should operate at a frequency of an order higher than the conventional macro ones because the pulse tube cryocooler operating frequency scales inversely with the square of the pulse tube diameter. In this paper, the design and experiments of a high frequency pressure oscillator is presented with the aim to power a micropulse tube cryocooler operating between 300 and 80 K, delivering a cooling power of 10 mW. Piezoelectric actuators operate efficiently at high frequencies and have high power density making them good candidates as drivers for high frequency pressure oscillator. The pressure oscillator described in this work consists of a membrane driven by a piezoelectric actuator. A pressure ratio of about 1.11 was achieved with a filling pressure of 2.5 MPa and compression volume of about 22.6 mm(3) when operating the actuator with a peak-to-peak sinusoidal voltage of 100 V at a frequency of 1 kHz. The electrical power input was 2.73 W. The high pressure ratio and low electrical input power at high frequencies would herald development of microminiature cryocoolers.

  19. High frequency III-V nanowire MOSFETs

    NASA Astrophysics Data System (ADS)

    Lind, Erik

    2016-09-01

    III-V nanowire transistors are promising candidates for very high frequency electronics applications. The improved electrostatics originating from the gate-all-around geometry allow for more aggressive scaling as compared with planar field-effect transistors, and this can lead to device operation at very high frequencies. The very high mobility possible with In-rich devices can allow very high device performance at low operating voltages. GaN nanowires can take advantage of the large band gap for high voltage operation. In this paper, we review the basic physics and device performance of nanowire field- effect transistors relevant for high frequency performance. First, the geometry of lateral and vertical nanowire field-effect transistors is introduced, with special emphasis on the parasitic capacitances important for nanowire geometries. The basic important high frequency transistor metrics are introduced. Secondly, the scaling properties of gate-all-around nanowire transistors are introduced, based on geometric length scales, demonstrating the scaling possibilities of nanowire transistors. Thirdly, to model nanowire transistor performance, a two-band non-parabolic ballistic transistor model is used to efficiently calculate the current and transconductance as a function of band gap and nanowire size. The intrinsic RF metrics are also estimated. Finally, experimental state-of-the-art nanowire field-effect transistors are reviewed and benchmarked, lateral and vertical transistor geometries are explored, and different fabrication routes are highlighted. Lateral devices have demonstrated operation up to 350 GHz, and vertical devices up to 155 GHz.

  20. Navy Applications of High-Frequency Acoustics

    NASA Astrophysics Data System (ADS)

    Cox, Henry

    2004-11-01

    Although the emphasis in underwater acoustics for the last few decades has been in low-frequency acoustics, motivated by long range detection of submarines, there has been a continuing use of high-frequency acoustics in traditional specialized applications such as bottom mapping, mine hunting, torpedo homing and under ice navigation. The attractive characteristics of high-frequency sonar, high spatial resolution, wide bandwidth, small size and relatively low cost must be balanced against the severe range limitation imposed by attenuation that increases approximately as frequency-squared. Many commercial applications of acoustics are ideally served by high-frequency active systems. The small size and low cost, coupled with the revolution in small powerful signal processing hardware has led to the consideration of more sophisticated systems. Driven by commercial applications, there are currently available several commercial-off-the-shelf products including acoustic modems for underwater communication, multi-beam fathometers, side scan sonars for bottom mapping, and even synthetic aperture side scan sonar. Much of the work in high frequency sonar today continues to be focused on specialized applications in which the application is emphasized over the underlying acoustics. Today's vision for the Navy of the future involves Autonomous Undersea Vehicles (AUVs) and off-board ASW sensors. High-frequency acoustics will play a central role in the fulfillment of this vision as a means of communication and as a sensor. The acoustic communication problems for moving AUVs and deep sensors are discussed. Explicit relationships are derived between the communication theoretic description of channel parameters in terms of time and Doppler spreads and ocean acoustic parameters, group velocities, phase velocities and horizontal wavenumbers. Finally the application of synthetic aperture sonar to the mine hunting problems is described.

  1. A Study of Phased Array Antennas for NASA's Deep Space Network

    NASA Technical Reports Server (NTRS)

    Jamnejad, Vahraz; Huang, John; Cesarone, Robert J.

    2001-01-01

    In this paper we briefly discuss various options but focus on the feasibility of the phased arrays as a viable option for this application. Of particular concern and consideration will be the cost, reliability, and performance compared to the present 70-meter antenna system, particularly the gain/noise temperature levels in the receive mode. Many alternative phased arrays including planar horizontal arrays, hybrid mechanically/electronically steered arrays, phased array of mechanically steered reflectors, multi-faceted planar arrays, phased array-fed lens antennas, and planar reflect-arrays are compared and their viability is assessed. Although they have many advantages including higher reliability, near-instantaneous beam switching or steering capability, the cost of such arrays is presently prohibitive and it is concluded that the only viable array options at the present are the arrays of a few or many small reflectors. The active planar phased arrays, however, may become feasible options in the next decade and can be considered for deployment in smaller configurations as supplementary options.

  2. High-Resolution Ultrasonic Imaging of Dento-Periodontal Tissues Using a Multi-Element Phased Array System.

    PubMed

    Nguyen, Kim-Cuong T; Le, Lawrence H; Kaipatur, Neelambar R; Zheng, Rui; Lou, Edmond H; Major, Paul W

    2016-10-01

    Intraoral ultrasonography uses high-frequency mechanical waves to study dento-periodontium. Besides the advantages of portability and cost-effectiveness, ultrasound technique has no ionizing radiation. Previous studies employed a single transducer or an array of transducer elements, and focused on enamel thickness and distance measurement. This study used a phased array system with a 128-element array transducer to image dento-periodontal tissues. We studied two porcine lower incisors from a 6-month-old piglet using 20-MHz ultrasound. The high-resolution ultrasonographs clearly showed the cross-sectional morphological images of the hard and soft tissues. The investigation used an integration of waveform analysis, travel-time calculation, and wavefield simulation to reveal the nature of the ultrasound data, which makes the study novel. With the assistance of time-distance radio-frequency records, we robustly justified the enamel-dentin interface, dentin-pulp interface, and the cemento-enamel junction. The alveolar crest level, the location of cemento-enamel junction, and the thickness of alveolar crest were measured from the images and compared favorably with those from the cone beam computed tomography with less than 10% difference. This preliminary and fundamental study has reinforced the conclusions from previous studies, that ultrasonography has great potential to become a non-invasive diagnostic imaging tool for quantitative assessment of periodontal structures and better delivery of oral care.

  3. Free space optical communication link using a silicon photonic optical phased array

    NASA Astrophysics Data System (ADS)

    Rabinovich, William S.; Goetz, Peter G.; Pruessner, Marcel; Mahon, Rita; Ferraro, Mike S.; Park, Doe; Fleet, Erin; DePrenger, Michael J.

    2015-03-01

    Many components for free space optical communication systems have shrunken in size over the last decade. However, the steering systems have remained large and power hungry. Non-mechanical beam steering offers a path to reducing the size of these systems. Optical phased arrays can allow integrated beam steering elements. One of the most important aspects of an optical phased array technology is its scalability to a large number of elements. Silicon photonics can potentially offer this scalability using CMOS foundry techniques. In this paper a small-scale silicon photonic optical phased array is demonstrated for both the transmitter and receiver functions in a free space optical link. The device using an array of thermo-optically controlled waveguide phase shifters and demonstrates one-dimensional steering with a single control electrode. Transmission of a digitized video data stream over the link is shown.

  4. Design of an inflatable, optically controlled and fed, phased array antenna

    NASA Astrophysics Data System (ADS)

    Kunath, Richard R.; Sharp, G. R.

    1991-09-01

    Initial studies on the antenna requirements of the Space Exploration Initiative (SEI) system architecture have indicated the need for large, lightweight antennas. This paper discusses the design of a modular, inflatable, optically controlled and fed phased array antenna suitable for SEI aplications. When high gain antennas are required for space applications, large aperture mesh or collapsible solid antenna reflectors are considered. However, these designs are generally not lightweight, and have complicated deployment mechanisms. Alternatively, the modular, inflatable antenna design discussed here is a lightweight, modular design that incorporates a simple deployment scheme, and after deployment, can be rigidized to enhance its structural integrity. Further, the design features the fiberoptic distribution of both RF and control signals to individual microwave integrated circuit/reflector modules in each of the inflatable, phased array antenna cells. The result of combining these two technologies is a modular, phased array antenna design that is both mechanically and electrically agile and robust.

  5. Nonparaxial multi-Gaussian beam models and measurement models for phased array transducers.

    PubMed

    Zhao, Xinyu; Gang, Tie

    2009-01-01

    A nonparaxial multi-Gaussian beam model is proposed in order to overcome the limitation that paraxial Gaussian beam models lose accuracy in simulating the beam steering behavior of phased array transducers. Using this nonparaxial multi-Gaussian beam model, the focusing and steering sound fields generated by an ultrasonic linear phased array transducer are calculated and compared with the corresponding results obtained by paraxial multi-Gaussian beam model and more exact Rayleigh-Sommerfeld integral model. In addition, with help of this novel nonparaxial method, an ultrasonic measurement model is provided to investigate the sensitivity of linear phased array transducers versus steering angles. Also the comparisons of model predictions with experimental results are presented to certify the accuracy of this provided measurement model.

  6. Phased array compaction cell for measurement of the transversely isotropic elastic properties of compacting sediments

    SciTech Connect

    Nihei, K.T.; Nakagawa, S.; Reverdy, F.; Meyer, L.R.; Duranti, L.; Ball, G.

    2010-12-15

    Sediments undergoing compaction typically exhibit transversely isotropic (TI) elastic properties. We present a new experimental apparatus, the phased array compaction cell, for measuring the TI elastic properties of clay-rich sediments during compaction. This apparatus uses matched sets of P- and S-wave ultrasonic transducers located along the sides of the sample and an ultrasonic P-wave phased array source, together with a miniature P-wave receiver on the top and bottom ends of the sample. The phased array measurements are used to form plane P-waves that provide estimates of the phase velocities over a range of angles. From these measurements, the five TI elastic constants can be recovered as the sediment is compacted, without the need for sample unloading, recoring, or reorienting. This paper provides descriptions of the apparatus, the data processing, and an application demonstrating recovery of the evolving TI properties of a compacting marine sediment sample.

  7. High-current, high-frequency capacitors

    NASA Technical Reports Server (NTRS)

    Renz, D. D.

    1983-01-01

    The NASA Lewis high-current, high-frequency capacitor development program was conducted under a contract with Maxwell Laboratories, Inc., San Diego, California. The program was started to develop power components for space power systems. One of the components lacking was a high-power, high-frequency capacitor. Some of the technology developed in this program may be directly usable in an all-electric airplane. The materials used in the capacitor included the following: the film is polypropylene, the impregnant is monoisopropyl biphenyl, the conductive epoxy is Emerson and Cuming Stycast 2850 KT, the foil is aluminum, the case is stainless steel (304), and the electrode is a modified copper-ceramic.

  8. Apparatus for measuring high frequency currents

    NASA Technical Reports Server (NTRS)

    Hagmann, Mark J. (Inventor); Sutton, John F. (Inventor)

    2003-01-01

    An apparatus for measuring high frequency currents includes a non-ferrous core current probe that is coupled to a wide-band transimpedance amplifier. The current probe has a secondary winding with a winding resistance that is substantially smaller than the reactance of the winding. The sensitivity of the current probe is substantially flat over a wide band of frequencies. The apparatus is particularly useful for measuring exposure of humans to radio frequency currents.

  9. Radome structures for high frequency applications

    NASA Astrophysics Data System (ADS)

    Hager, W.

    The optimization of radome structures for high-frequency applications is examined for the cases of thin-walled radomes, thick-walled radomes, sandwich radomes, and multilayer radomes. Examples of applications are briefly described, including radomes in an ECM-pod of a Tornado aircraft, a radome for a mobile two-dimensional radar installation, and a radome for a millimeter wave search radar.

  10. Ionospheric modifications in high frequency heating experiments

    SciTech Connect

    Kuo, Spencer P.

    2015-01-15

    Featured observations in high-frequency (HF) heating experiments conducted at Arecibo, EISCAT, and high frequency active auroral research program are discussed. These phenomena appearing in the F region of the ionosphere include high-frequency heater enhanced plasma lines, airglow enhancement, energetic electron flux, artificial ionization layers, artificial spread-F, ionization enhancement, artificial cusp, wideband absorption, short-scale (meters) density irregularities, and stimulated electromagnetic emissions, which were observed when the O-mode HF heater waves with frequencies below foF2 were applied. The implication and associated physical mechanism of each observation are discussed and explained. It is shown that these phenomena caused by the HF heating are all ascribed directly or indirectly to the excitation of parametric instabilities which instigate anomalous heating. Formulation and analysis of parametric instabilities are presented. The results show that oscillating two stream instability and parametric decay instability can be excited by the O-mode HF heater waves, transmitted from all three heating facilities, in the regions near the HF reflection height and near the upper hybrid resonance layer. The excited Langmuir waves, upper hybrid waves, ion acoustic waves, lower hybrid waves, and field-aligned density irregularities set off subsequent wave-wave and wave-electron interactions, giving rise to the observed phenomena.

  11. A design concept for an MMIC (Monolithic Microwave Integrated Circuit) microstrip phased array

    NASA Technical Reports Server (NTRS)

    Lee, Richard Q.; Smetana, Jerry; Acosta, Roberto

    1987-01-01

    A conceptual design for a microstrip phased array with monolithic microwave integrated circuit (MMIC) amplitude and phase controls is described. The MMIC devices used are 20 GHz variable power amplifiers and variable phase shifters recently developed by NASA contractors for applications in future Ka proposed design, which concept is for a general NxN element array of rectangular lattice geometry. Subarray excitation is incorporated in the MMIC phased array design to reduce the complexity of the beam forming network and the number of MMIC components required.

  12. Ultrasonic Phased Array Inspection for an Isogrid Structural Element with Cracks

    NASA Technical Reports Server (NTRS)

    Roth, D. J.; Tokars, R. P.; Martin, R. E.; Rauser, R. W.; Aldrin, J. C.; Schumacher, E. J.

    2010-01-01

    In this investigation, a T-shaped aluminum alloy isogrid stiffener element used in aerospace applications was inspected with ultrasonic phased array methods. The isogrid stiffener element had various crack configurations emanating from bolt holes. Computational simulation methods were used to mimic the experiments in order to help understand experimental results. The results of this study indicate that it is at least partly feasible to interrogate this type of geometry with the given flaw configurations using phased array ultrasonics. The simulation methods were critical in helping explain the experimental results and, with some limitation, can be used to predict inspection results.

  13. Inspection of Spot Welds Using a Portable Ultrasonic Phased-Array System

    SciTech Connect

    Reverdy, F.; Hopkins, D.

    2005-04-09

    Results were presented last year to demonstrate the feasibility of using an ultrasonic phased array to inspect spot welds. Analysis of the signals in the Fourier domain allows identification of satisfactory, undersized and defective welds. Signal- and image-processing techniques have been implemented with the goal of extracting the dimensions of the weld nugget. The results presented here were obtained using a portable phased-array controller. Toward developing a fully portable system, a housing for the probe is under development with an integrated mechanical scanning system.

  14. High speed optical phased array using high contrast grating all-pass filters.

    PubMed

    Yang, Weijian; Sun, Tianbo; Rao, Yi; Megens, Mischa; Chan, Trevor; Yoo, Byung-Wook; Horsley, David A; Wu, Ming C; Chang-Hasnain, Connie J

    2014-08-25

    We report a high speed 8x8 optical phased array using tunable 1550 nm all-pass filters with ultrathin high contrast gratings (HCGs) as the microelectromechanical-actuated top reflectors. The all-pass filter design enables a highly efficient phase tuning (1.7 π) with a small actuation voltage (10 V) and actuation displacement of the HCG (50 nm). The microelectromechanical HCG structure facilitates a high phase tuning speed >0.5 MHz. Beam steering is experimentally demonstrated with the optical phased array.

  15. Pulse-echo phased array ultrasonic inspection of pultruded rod stitched efficient unitized structure (PRSEUS)

    SciTech Connect

    Johnston, P. H.

    2011-06-23

    A PRSEUS test article was subjected to controlled impact on the skin face followed by static and cyclic axial compressions. Phased array ultrasonic inspection was conducted before impact, and after each of the test conditions. A linear phased array probe with a manual X-Y scanner was used for interrogation. Ultrasound showed a delamination between the skin and stringer flange adjacent to the impact. As designed, the stitching in the flange arrested the lateral flaw formation. Subsequent ultrasonic data showed no delamination growth due to continued loading.

  16. Multiple-access phased array antenna simulator for a digital beam forming system investigation

    NASA Technical Reports Server (NTRS)

    Kerczewski, Robert J.; Yu, John; Walton, Joanne C.; Perl, Thomas D.; Andro, Monty; Alexovich, Robert E.

    1992-01-01

    Future versions of data relay satellite systems are currently being planned by NASA. Being given consideration for implementation are on-board digital beamforming techniques which will allow multiple users to simultaneously access a single S-band phased array antenna system. To investigate the potential performance of such a system, a laboratory simulator has been developed at NASA's Lewis Research Center. This paper describes the system simulator, and in particular, the requirements, design, and performance of a key subsystem, the phased array antenna simulator, which provides realistic inputs to the digital processor including multiple signals, noise, and nonlinearities.

  17. Ultrasonic Phased Array Inspection Experiments and Simulations for AN Isogrid Structural Element with Cracks

    NASA Astrophysics Data System (ADS)

    Roth, D. J.; Tokars, R. P.; Martin, R. E.; Rauser, R. W.; Aldrin, J. C.; Schumacher, E. J.

    2010-02-01

    In this investigation, a T-shaped aluminum alloy isogrid stiffener element used in aerospace applications was inspected with ultrasonic phased array methods. The isogrid stiffener element had various crack configurations emanating from bolt holes. Computational simulation methods were used to mimic the experiments in order to help understand experimental results. The results of this study indicate that it is at least partly feasible to interrogate this type of geometry with the given flaw configurations using phased array ultrasonics. The simulation methods were critical in helping explain the experimental results and, with some limitation, can be used to predict inspection results.

  18. High-frequency Rayleigh-wave method

    USGS Publications Warehouse

    Xia, J.; Miller, R.D.; Xu, Y.; Luo, Y.; Chen, C.; Liu, J.; Ivanov, J.; Zeng, C.

    2009-01-01

    High-frequency (???2 Hz) Rayleigh-wave data acquired with a multichannel recording system have been utilized to determine shear (S)-wave velocities in near-surface geophysics since the early 1980s. This overview article discusses the main research results of high-frequency surface-wave techniques achieved by research groups at the Kansas Geological Survey and China University of Geosciences in the last 15 years. The multichannel analysis of surface wave (MASW) method is a non-invasive acoustic approach to estimate near-surface S-wave velocity. The differences between MASW results and direct borehole measurements are approximately 15% or less and random. Studies show that simultaneous inversion with higher modes and the fundamental mode can increase model resolution and an investigation depth. The other important seismic property, quality factor (Q), can also be estimated with the MASW method by inverting attenuation coefficients of Rayleigh waves. An inverted model (S-wave velocity or Q) obtained using a damped least-squares method can be assessed by an optimal damping vector in a vicinity of the inverted model determined by an objective function, which is the trace of a weighted sum of model-resolution and model-covariance matrices. Current developments include modeling high-frequency Rayleigh-waves in near-surface media, which builds a foundation for shallow seismic or Rayleigh-wave inversion in the time-offset domain; imaging dispersive energy with high resolution in the frequency-velocity domain and possibly with data in an arbitrary acquisition geometry, which opens a door for 3D surface-wave techniques; and successfully separating surface-wave modes, which provides a valuable tool to perform S-wave velocity profiling with high-horizontal resolution. ?? China University of Geosciences (Wuhan) and Springer-Verlag GmbH 2009.

  19. The LASI high-frequency ellipticity system

    SciTech Connect

    Sternberg, B.K.; Poulton, M.M.

    1995-10-01

    A high-frequency, high-resolution, electromagnetic (EM) imaging system has been developed for environmental geophysics surveys. Some key features of this system include: (1) rapid surveying to allow dense spatial sampling over a large area, (2) high-accuracy measurements which are used to produce a high-resolution image of the subsurface, (3) measurements which have excellent signal-to-noise ratio over a wide bandwidth (31 kHz to 32 MHz), (4) large-scale physical modeling to produce accurate theoretical responses over targets of interest in environmental geophysics surveys, (5) rapid neural network interpretation at the field site, and (6) visualization of complex structures during the survey.

  20. The LASI high-frequency ellipticity system

    SciTech Connect

    Sternberg, B.K.; Poulton, M.M.

    1995-12-31

    A high-frequency, high-resolution, electromagnetic (EM) imaging system has been developed for environmental geophysics surveys. Some key features of this system include: (1) rapid surveying to allow dense spatial sampling over a large area, (2) high-accuracy measurements which are used to produce a high-resolution image of the subsurface, (3) measurements which have excellent signal-to-noise ratio over a wide bandwidth (31 kHz to 32 MHz), (4) large-scale physical modeling to produce accurate theoretical responses over targets of interest in environmental geophysics surveys, (5) rapid neural network interpretation at the field site, and (6) visualization of complex structures during the survey.

  1. Progress and prospects of silicon-based design for optical phased array

    NASA Astrophysics Data System (ADS)

    Hu, Weiwei; Peng, Chao; Chang-Hasnain, Connie

    2016-03-01

    The high-speed, high-efficient, compact phase modulator array is indispensable in the Optical-phased array (OPA) which has been considered as a promising technology for realizing flexible and efficient beam steering. In our research, two methods are presented to utilize high-contrast grating (HCG) as high-efficient phase modulator. One is that HCG possesses high-Q resonances that origins from the cancellation of leaky waves. As a result, sharp resonance peaks appear on the reflection spectrum thus HCGs can be utilized as efficient phase shifters. Another is that low-Q mode HCG is utilized as ultra-lightweight mirror. With MEMS technology, small HCG displacement (~50 nm) leads to large phase change (~1.7π). Effective beam steering is achieved in Connie Chang-Hasnian's group. On the other hand, we theoretically and experimentally investigate the system design for silicon-based optical phased array, including the star coupler, phased array, emission elements and far-field patterns. Further, the non-uniform optical phased array is presented.

  2. Two dimensional thermo-optic beam steering using a silicon photonic optical phased array

    NASA Astrophysics Data System (ADS)

    Mahon, Rita; Preussner, Marcel W.; Rabinovich, William S.; Goetz, Peter G.; Kozak, Dmitry A.; Ferraro, Mike S.; Murphy, James L.

    2016-03-01

    Components for free space optical communication terminals such as lasers, amplifiers, and receivers have all seen substantial reduction in both size and power consumption over the past several decades. However, pointing systems, such as fast steering mirrors and gimbals, have remained large, slow and power-hungry. Optical phased arrays provide a possible solution for non-mechanical beam steering devices that can be compact and lower in power. Silicon photonics is a promising technology for phased arrays because it has the potential to scale to many elements and may be compatible with CMOS technology thereby enabling batch fabrication. For most free space optical communication applications, two-dimensional beam steering is needed. To date, silicon photonic phased arrays have achieved two-dimensional steering by combining thermo-optic steering, in-plane, with wavelength tuning by means of an output grating to give angular tuning, out-of-plane. While this architecture might work for certain static communication links, it would be difficult to implement for moving platforms. Other approaches have required N2 controls for an NxN element phased array, which leads to complexity. Hence, in this work we demonstrate steering using the thermo-optic effect for both dimensions with a simplified steering mechanism requiring only two control signals, one for each steering dimension.

  3. Through Weld Inspection of Wrought Stainless Steel Piping Using Phased-Array Ultrasonic Probes.

    SciTech Connect

    Anderson, Michael T.; Cumblidge, Stephen E.; Doctor, Steven R.

    2004-08-05

    A study was conducted to assess the ability of phased-array ultrasonic techniques to detect and accurately determine the size of flaws from the far-side of wrought austenitic piping welds. Far-side inspections of these welds are currently performed on a “best effort” basis and do not conform to ASME Code Section XI Appendix VIII performance demonstration requirements. For this study, four circumferential welds in 610mm diameter, 36mm thick ASTM A-358, Grade 304 vintage austenitic stainless steel pipe were examined. The welds were fabricated with varied welding parameters; both horizontal and vertical pipe orientations were used, with air and water backing, to simulate field welding conditions. A series of saw cuts, electro-discharge machined (EDM) notches, and implanted fatigue cracks were placed into the heat affected zones of the welds. The saw cuts and notches range in depth from 7.5% to 28.4% through-wall. The implanted cracks ranged in depth from 5% through wall to 64% through wall. The welds were examined with two phased-array probes, a 2.0 MHz transmit-receive longitudinal wave array and a 2.0 MHz transmit-receive shear wave array. These examinations showed that both phased-array transducers were able to detect and accurately length-size, but not depth size, all of the notches and flaws through the welds. The phased-array results were not strongly affected by the different welding techniques used in each weld.

  4. A prototype high-speed optically-steered X-band phased array antenna.

    PubMed

    Wu, Pengfei; Tang, Suning; Raible, Daniel E

    2013-12-30

    We develop a prototype of optically-steered X-band phased array antenna with capabilities of multi-band and multi-beam operations. It exploits high-speed wavelength tunable lasers for optical true-time delays over a dispersive optical fiber link, enabling agile, broadband and vibration-free RF beam steering with large angle.

  5. High frequency inductive lamp and power oscillator

    DOEpatents

    MacLennan, Donald A.; Turner, Brian P.; Dolan, James T.; Kirkpatrick, Douglas A.; Leng, Yongzhang

    2000-01-01

    A high frequency inductively coupled electrodeless lamp includes an excitation coil with an effective electrical length which is less than one half wavelength of a driving frequency applied thereto, preferably much less. The driving frequency may be greater than 100 MHz and is preferably as high as 915 MHz. Preferably, the excitation coil is configured as a non-helical, semi-cylindrical conductive surface having less than one turn, in the general shape of a wedding ring. At high frequencies, the current in the coil forms two loops which are spaced apart and parallel to each other. Configured appropriately, the coil approximates a Helmholtz configuration. The lamp preferably utilizes an bulb encased in a reflective ceramic cup with a pre-formed aperture defined therethrough. The ceramic cup may include structural features to aid in alignment and/or a flanged face to aid in thermal management. The lamp head is preferably an integrated lamp head comprising a metal matrix composite surrounding an insulating ceramic with the excitation integrally formed on the ceramic. A novel solid-state oscillator preferably provides RF power to the lamp. The oscillator is a single active element device capable of providing over 70 watts of power at over 70% efficiency. Various control circuits may be employed to match the driving frequency of the oscillator to a plurality of tuning states of the lamp.

  6. High frequency inductive lamp and power oscillator

    DOEpatents

    MacLennan, Donald A.; Dymond, Jr., Lauren E.; Gitsevich, Aleksandr; Grimm, William G.; Kipling, Kent; Kirkpatrick, Douglas A.; Ola, Samuel A.; Simpson, James E.; Trimble, William C.; Tsai, Peter; Turner, Brian P.

    2001-01-01

    A high frequency inductively coupled electrodeless lamp includes an excitation coil with an effective electrical length which is less than one half wavelength of a driving frequency applied thereto, preferably much less. The driving frequency may be greater than 100 MHz and is preferably as high as 915 MHz. Preferably, the excitation coil is configured as a non-helical, semi-cylindrical conductive surface having less than one turn, in the general shape of a wedding ring. At high frequencies, the current in the coil forms two loops which are spaced apart and parallel to each other. Configured appropriately, the coil approximates a Helmholtz configuration. The lamp preferably utilizes an bulb encased in a reflective ceramic cup with a pre-formed aperture defined therethrough. The ceramic cup may include structural features to aid in alignment and I or a flanged face to aid in thermal management. The lamp head is preferably an integrated lamp head comprising a metal matrix composite surrounding an insulating ceramic with the excitation integrally formed on the ceramic. A novel solid-state oscillator preferably provides RF power to the lamp. The oscillator is a single active element device capable of providing over 70 watts of power at over 70% efficiency. Various control circuits may be employed to adjust the driving frequency of the oscillator.

  7. High Frequency Plasma Generators for Ion Thrusters

    NASA Technical Reports Server (NTRS)

    Divergilio, W. F.; Goede, H.; Fosnight, V. V.

    1981-01-01

    The results of a one year program to experimentally adapt two new types of high frequency plasma generators to Argon ion thrusters and to analytically study a third high frequency source concept are presented. Conventional 30 cm two grid ion extraction was utilized or proposed for all three sources. The two plasma generating methods selected for experimental study were a radio frequency induction (RFI) source, operating at about 1 MHz, and an electron cyclotron heated (ECH) plasma source operating at about 5 GHz. Both sources utilize multi-linecusp permanent magnet configurations for plasma confinement. The plasma characteristics, plasma loading of the rf antenna, and the rf frequency dependence of source efficiency and antenna circuit efficiency are described for the RFI Multi-cusp source. In a series of tests of this source at Lewis Research Center, minimum discharge losses of 220+/-10 eV/ion were obtained with propellant utilization of .45 at a beam current of 3 amperes. Possible improvement modifications are discussed.

  8. Optical generation of narrowband high frequency ultrasound

    NASA Astrophysics Data System (ADS)

    Hung, Shi-Yao; Hsieh, Bao-Yu; Li, Pai-Chi

    2014-03-01

    We propose a multilayer film structure to generate high frequency and narrowband ultrasound. It consists of three light-absorbing layers and two light-transmittance layers. The amplitude is tunable by adjusting the optical absorption coefficient of light-absorbing layers. The delay can be adjusted by changing thicknesses of light-transmittance layers. In one example, the generated high frequency narrowband ultrasound signal has a center frequency of 18.4MHz and 32.6% fractional bandwidth using the proposed multilayer structure. Compared with this result, the single layer structure produces a center frequency of 20.2MHz and 125.7% fractional bandwidth. In addition, a single laser pulse was employed to generate US on the multilayer film as an US source and PA signals of the high optical absorption region of the phantom at the same time. Because the spectral characteristics of the ultrasound signals generated by the multi-layer film are tunable, it can be designed such that the US echo and PA echo are spectrally separable, thus enabling simultaneous US/PA imaging using only a single laser pulse. Feasibility of this proposed method was demonstrated by imaging of a cyst-like phantom.

  9. Investigating Sonothrombolysis with High Frequency Ultrasound

    NASA Astrophysics Data System (ADS)

    Wright, Cameron; Hynynen, Kullervo; Goertz, David

    2009-04-01

    Despite a significant body of work establishing the feasibility of ultrasound mediated thrombolysis in vitro, in vivo, and in clinical settings, there remains considerable uncertainty about the specific mechanisms involved in this process. This motivates further work to elucidate these mechanisms, which will be central to optimizing safe and effective operating conditions, and to guide the development of novel approaches and instrumentation. In this study, we investigate the use of high frequency ultrasound as a means of gaining mechanistic insight into sonothrombolysis. A high frequency ultrasound (20-50 MHz) instrument is employed which provides the ability to conduct volumetric clot imaging as well as pulsed-wave Doppler to monitor hemodynamics within vessels and clots. With modifications, it is enabled to perform the acquisition of RF data to assess the displacement of clots and vessel walls subjected to therapeutic pulses. Additional modifications were made to perform nonlinear imaging of micron to submicron sized bubbles, which are of interest in enhancing clot lysis. Experiments were performed on in vitro clots, and in vivo using a rabbit femoral artery clot model initiated by the injection of thrombin. Therapeutic pulses are provided by a single element spherically focused air backed transducer with transmit frequencies of 1.68 MHz. Clear visualization of the clots, displacements, and presence or absence of flow within these vessels is shown to be feasible, indicating the potential of this approach as a tool for providing insight into sonothrombolysis.

  10. Noise temperature in graphene at high frequencies

    NASA Astrophysics Data System (ADS)

    Rengel, Raúl; Iglesias, José M.; Pascual, Elena; Martín, María J.

    2016-07-01

    A numerical method for obtaining the frequency-dependent noise temperature in monolayer graphene is presented. From the mobility and diffusion coefficient values provided by Monte Carlo simulation, the noise temperature in graphene is studied up to the THz range, considering also the influence of different substrate types. The influence of the applied electric field is investigated: the noise temperature is found to increase with the applied field, dropping down at high frequencies (in the sub-THz range). The results show that the low-frequency value of the noise temperature in graphene on a substrate tends to be reduced as compared to the case of suspended graphene due to the important effect of remote polar phonon interactions, thus indicating a reduced emitted noise power; however, at very high frequencies the influence of the substrate tends to be significantly reduced, and the differences between the suspended and on-substrate cases tend to be minimized. The values obtained are comparable to those observed in GaAs and semiconductor nitrides.

  11. High frequency ultrasonic scattering by biological tissues

    NASA Astrophysics Data System (ADS)

    Shung, K. Kirk; Maruvada, Subha

    2002-05-01

    High frequency (HF) diagnostic ultrasonic imaging devices at frequencies higher than 20 MHz have found applications in ophthalmology, dermatology, and vascular surgery. To be able to interpret these images and to further the development of these devices, a better understanding of ultrasonic scattering in biological tissues such as blood, liver, myocardium in the high frequency range is crucial. This work has previously been hampered by the lack of suitable transducers. With the availability of HF transducers going to 90 MHz, HF attenuation and backscatter experiments have been made on porcine red blood cell (RBC) suspensions, for which much data on attenuation and backscatter can be found in the literature in the lower frequency range for frequencies, from 30 to 90 MHz and on bovine tissues for frequencies from 10 to 30 MHz using a modified substitution method that allow the utilization of focused transducers. These results will be reviewed in this talk along with relevant theoretical models that could be applied to interpreting them. The relevance of the parameter that has been frequently used in the biomedical ultrasound literature to describe backscattering, the backscattering coefficient, will be critically examined.

  12. High-Frequency Fluctuations During Magnetic Reconnection

    NASA Astrophysics Data System (ADS)

    Jara-Almonte, J.; Ji, H.; Daughton, W. S.; Roytershteyn, V.; Yamada, M.; Yoo, J.; Fox, W. R., II

    2014-12-01

    During collisionless reconnection, the decoupling of the field from the plasma is known to occur only within the localized ion and electron diffusion regions, however predictions from fully kinetic simulations do not agree with experimental observations on the size of the electron diffusion region, implying differing reconnection mechanisms. Previous experiments, along with 2D and 3D simulations, have conclusively shown that this discrepancy cannot be explained by either classical collisions or Lower-Hybrid Drift Instability (Roytershtyn 2010, 2013). Due to computational limitations, however, previous simulations were constrained to have minimal scale separation between the electron skin depth and the Debye length (de/λD ~ 10), much smaller than in experiments (de/λD ~ 300). This lack of scale-separation can drastically modify the electrostatic microphysics within the diffusion layer. Using 3D, fully explicit kinetic simulations with a realistic and unprecedentedly large separation between the Debye length and the electron skin depth, de/λD = 64, we show that high frequency electrostatic waves (ω >> ωLH) can exist within the electron diffusion region. These waves generate small-scale turbulence within the electron diffusion region which acts to broaden the layer. Anomalous resistivity is also generated by the turbulence and significantly modifies the force balance. In addition to simulation results, initial experimental measurements of high frequency fluctuations (electrostatic and electromagnetic, f ≤ 1 GHz) in the Magnetic Reconnection Experiment (MRX) will be presented.

  13. Printed-Circuit Cross-Slot Antenna

    NASA Technical Reports Server (NTRS)

    Foy, Wong; Chung, Hsien-Hsien; Peng, Sheng Y.

    1990-01-01

    Coupling between perpendicular slots suppressed. Balanced feed configuration minimizes coupling between slots of printed-circuit cross-slot antenna unit. Unit and array have conventional cavity-backed-printed-circuit, crossed-slot antenna design. Strip-line feeders behind planar conductive antenna element deliver power to horizontal slot in opposite phase. As result, little or no power propagates into vertical slot. Similar considerations apply to strip lines that feed vertical slot. Units of this type elements of phased-array antennas for radar, mobile/satellite communications, and other applications requiring flush mounting and/or rapid steering of beams with circular polarization.

  14. An adaptive microwave phased array for targeted heating of deep tumours in intact breast: animal study results.

    PubMed

    Fenn, A J; Wolf, G L; Fogle, R M

    1999-01-01

    It has previously been reported in phantoms, that an adaptive radiofrequency phased array can generate deep focused heating distributions without overheating the skin and superficial healthy tissues. The present study involves adaptive microwave phased array hyperthermia tests in animals (rabbits) with and without tumours. The design of the adaptive phased array as applied to the treatment of tumours in intact breast, is described. The adaptive phased array concept uses breast compression and dual-opposing 915 MHz air-cooled waveguide applicators with electronic phase shifters and electric-field feedback, to focus automatically by computer control the microwave radiation in deep tissue. Temperature measurements for a clinical adaptive phased array hyperthermia system demonstrate tissue heating at depth with reduced skin heating.

  15. Parametric nanomechanical amplification at very high frequency.

    PubMed

    Karabalin, R B; Feng, X L; Roukes, M L

    2009-09-01

    Parametric resonance and amplification are important in both fundamental physics and technological applications. Here we report very high frequency (VHF) parametric resonators and mechanical-domain amplifiers based on nanoelectromechanical systems (NEMS). Compound mechanical nanostructures patterned by multilayer, top-down nanofabrication are read out by a novel scheme that parametrically modulates longitudinal stress in doubly clamped beam NEMS resonators. Parametric pumping and signal amplification are demonstrated for VHF resonators up to approximately 130 MHz and provide useful enhancement of both resonance signal amplitude and quality factor. We find that Joule heating and reduced thermal conductance in these nanostructures ultimately impose an upper limit to device performance. We develop a theoretical model to account for both the parametric response and nonequilibrium thermal transport in these composite nanostructures. The results closely conform to our experimental observations, elucidate the frequency and threshold-voltage scaling in parametric VHF NEMS resonators and sensors, and establish the ultimate sensitivity limits of this approach. PMID:19736969

  16. High-frequency ultrasonic wire bonding systems

    PubMed

    Tsujino; Yoshihara; Sano; Ihara

    2000-03-01

    The vibration characteristics of longitudinal-complex transverse vibration systems with multiple resonance frequencies of 350-980 kHz for ultrasonic wire bonding of IC, LSI or electronic devices were studied. The complex vibration systems can be applied for direct welding of semiconductor tips (face-down bonding, flip-chip bonding) and packaging of electronic devices. A longitudinal-complex transverse vibration bonding system consists of a complex transverse vibration rod, two driving longitudinal transducers 7.0 mm in diameter and a transverse vibration welding tip. The vibration distributions along ceramic and stainless-steel welding tips were measured at up to 980 kHz. A high-frequency vibration system with a height of 20.7 mm and a weight of less than 15 g was obtained.

  17. High-frequency micromechanical columnar resonators

    NASA Astrophysics Data System (ADS)

    Kehrbusch, Jenny; Ilin, Elena A.; Bozek, Peter; Radzio, Bernhard; Oesterschulze, Egbert

    2009-06-01

    High-frequency silicon columnar microresonators are fabricated using a simple but effective technological scheme. An optimized fabrication scheme was invented to obtain mechanically protected microcolumns with lateral dimensions controlled on a scale of at least 1 μm. In this paper, we investigate the influence of the environmental conditions on the mechanical resonator properties. At ambient conditions, we observed a frequency stability δf/f of less than 10-6 during 5 h of operation at almost constant temperature. However, varying the temperature shifts the frequency by approximately -173 Hz °C- 1. In accordance with a viscous damping model of the ambient gas, we perceived that the quality factor of the first flexural mode decreased with the inverse of the square root of pressure. However, in the low-pressure regime, a linear dependence was observed. We also investigated the influence of the type of the immersing gas on the resonant frequency.

  18. High-frequency resonant-tunneling oscillators

    NASA Technical Reports Server (NTRS)

    Brown, E. R.; Parker, C. D.; Calawa, A. R.; Manfra, M. J.; Chen, C. L.

    1991-01-01

    Advances in high-frequency resonant-tunneling-diode (RTD) oscillators are described. Oscillations up to a frequency of 420 GHz have been achieved in the GaAs/AlAs system. Recent results obtained with In0.53Ga0.47As/AlAs and InAs/AlSb RTDs show a greatly increased power density and indicate the potential for fundamental oscillations up to about 1 THz. These results are consistent with a lumped-element equivalent circuit model of the RTD. The model shows that the maximum oscillation frequency of the GaAs/AlAs RTDs is limited primarily by series resistance, and that the power density is limited by low peak-to-valley current ratio.

  19. Parametric nanomechanical amplification at very high frequency.

    PubMed

    Karabalin, R B; Feng, X L; Roukes, M L

    2009-09-01

    Parametric resonance and amplification are important in both fundamental physics and technological applications. Here we report very high frequency (VHF) parametric resonators and mechanical-domain amplifiers based on nanoelectromechanical systems (NEMS). Compound mechanical nanostructures patterned by multilayer, top-down nanofabrication are read out by a novel scheme that parametrically modulates longitudinal stress in doubly clamped beam NEMS resonators. Parametric pumping and signal amplification are demonstrated for VHF resonators up to approximately 130 MHz and provide useful enhancement of both resonance signal amplitude and quality factor. We find that Joule heating and reduced thermal conductance in these nanostructures ultimately impose an upper limit to device performance. We develop a theoretical model to account for both the parametric response and nonequilibrium thermal transport in these composite nanostructures. The results closely conform to our experimental observations, elucidate the frequency and threshold-voltage scaling in parametric VHF NEMS resonators and sensors, and establish the ultimate sensitivity limits of this approach.

  20. Fundamentals of bipolar high-frequency surgery.

    PubMed

    Reidenbach, H D

    1993-04-01

    In endoscopic surgery a very precise surgical dissection technique and an efficient hemostasis are of decisive importance. The bipolar technique may be regarded as a method which satisfies both requirements, especially regarding a high safety standard in application. In this context the biophysical and technical fundamentals of this method, which have been known in principle for a long time, are described with regard to the special demands of a newly developed field of modern surgery. After classification of this method into a general and a quasi-bipolar mode, various technological solutions of specific bipolar probes, in a strict and in a generalized sense, are characterized in terms of indication. Experimental results obtained with different bipolar instruments and probes are given. The application of modern microprocessor-controlled high-frequency surgery equipment and, wherever necessary, the integration of additional ancillary technology into the specialized bipolar instruments may result in most useful and efficient tools of a key technology in endoscopic surgery.

  1. Leaf Printing.

    ERIC Educational Resources Information Center

    Mitchell, Charles W.

    1985-01-01

    Using many different media, students can turn leaves into images which can be used for study, bulletin boards, collections, and identification. The simple techniques described include pastel printing, smoke prints, ink or tempura printing, bleach printing on t-shirts, ditto machine printing using carbon paper, and making cutouts. (DH)

  2. Software for Displaying High-Frequency Test Data

    NASA Technical Reports Server (NTRS)

    Elmore, Jason L.

    2003-01-01

    An easy-to-use, intuitive computer program was written to satisfy a need of test operators and data requestors to quickly view and manipulate high-frequency test data recorded at the East and West Test Areas at Marshall Space Flight Center. By enabling rapid analysis, this program makes it possible to reduce times between test runs, thereby potentially reducing the overall cost of test operations. The program can be used to perform quick frequency analysis, using multiple fast- Fourier-transform windowing and amplitude options. The program can generate amplitude-versus-time plots with full zoom capabilities, frequency-component plots at specified time intervals, and waterfall plots (plots of spectral intensity versus frequency at successive small time intervals, showing the changing frequency components over time). There are options for printing of the plots and saving plot data as text files that can be imported into other application programs. The program can perform all of the aforementioned plotting and plot-data-handling functions on a relatively inexpensive computer; other software that performs the same functions requires computers with large amounts of power and memory.

  3. High frequency characterization of conductive inks embedded within a structural composite

    NASA Astrophysics Data System (ADS)

    Pa, Peter; McCauley, Raymond; Larimore, Zachary; Mills, Matthew; Yarlaggada, Shridhar; Mirotznik, Mark S.

    2015-06-01

    Woven fabric composites provide an attractive platform for integrating electromagnetic functionality—such as conformal load-bearing antennas and frequency selective surfaces—into a structural platform. One practical fabrication method for integrating conductive elements within a woven fabric composite system involves using additive manufacturing systems such as screen printing. While screen printing is an inherently scalable, flexible and cost effective method, little is known about the high frequency electrical properties of its conductive inks when they are embedded within the woven fabric composite. Thus, we have completed numerical and experimental studies to determine the electrical conductivity of screen printable conductive inks that are embedded within this composite. We have also performed mechanical studies to evaluate how printing affects the structural performance of the composite.

  4. Grating lobes analysis based on blazed grating theory for liquid crystal optical-phased array

    NASA Astrophysics Data System (ADS)

    Chen, Jian; Cui, Guolong; Kong, Lingjiang; Xiao, Feng; Liu, Xin; Zhang, Xiaoguang

    2013-09-01

    The grating lobes of the liquid crystal optical-phased array (LCOPA) based on blazed grating theory is studied. Using the Fraunhofer propagation principle, the analytical expressions of the far-field intensity distribution are derived. Subsequently, we can obtain both the locations and the intensities of the grating lobes. The derived analytical functions that provide an insight into single-slit diffraction and multislit interference effect on the grating lobes are discussed. Utilizing the conventional microwave-phased array technique, the intensities of the grating lobes and the main lobe are almost the same. Different from this, the derived analytical functions demonstrate that the intensities of the grating lobes are less than that of the main lobe. The computer simulations and experiments show that the proposed method can correctly estimate the locations and the intensities of the grating lobes for a LCOPA simultaneously.

  5. Optical techniques to feed and control GaAs MMIC modules for phased array antenna applications

    NASA Technical Reports Server (NTRS)

    Bhasin, K. B.; Anzic, G.; Kunath, R. R.; Connolly, D. J.

    1986-01-01

    A complex signal distribution system is required to feed and control GaAs monolithic microwave integrated circuits (MMICs) for phased array antenna applications above 20 GHz. Each MMIC module will require one or more RF lines, one or more bias voltage lines, and digital lines to provide a minimum of 10 bits of combined phase and gain control information. In a closely spaced array, the routing of these multiple lines presents difficult topology problems as well as a high probability of signal interference. To overcome GaAs MMIC phased array signal distribution problems optical fibers interconnected to monolithically integrated optical components with GaAs MMIC array elements are proposed as a solution. System architecture considerations using optical fibers are described. The analog and digital optical links to respectively feed and control MMIC elements are analyzed. It is concluded that a fiber optic network will reduce weight and complexity, and increase reliability and performance, but higher power will be required.

  6. Application of Ultrasonic Phased Array Technology to the Detection of Defect in Composite Stiffened-structures

    NASA Astrophysics Data System (ADS)

    Zhou, Yuan-Qi; Zhan, Li-Hua

    2016-05-01

    Composite stiffened-structure consists of the skin and stringer has been widely used in aircraft fuselage and wings. The main purpose of the article is to detect the composite material reinforced structure accurately and explore the relationship between defect formation and structural elements or curing process. Based on ultrasonic phased array inspection technology, the regularity of defects in the manufacture of composite materials are obtained, the correlation model between actual defects and nondestructive testing are established. The article find that the forming quality of deltoid area in T-stiffened structure is obviously improved by pre-curing, the defects of hat-stiffened structure are affected by the mandrel. The results show that the ultrasonic phased array inspection technology can be an effectively way for the detection of composite stiffened-structures, which become an important means to control the defects of composite and improve the quality of the product.

  7. Abdominal and obstetric applications of a dynamically focused phased array real time ultrasound system.

    PubMed

    Morgan, C L; Trought, W S; von Ramm, O T; Thurstone, F L

    1980-05-01

    Abdominal and obstetric applications of a dynamically focused phased array real time ultrasonic system are described. This work was performed utilising both the Thaumascan (two-dimensional, high resolution, actual time, ultrasound, multi-element array scanner) and the first commercial unit based on this system, the Grumman RT-400. Examples of normal and pathological anatomy are presented from over 300 examinations performed to date, including a series of 28 abdominal aortic aneurysms studied with the RT-400. Following electronic alterations in the Thaumascan with resultant improvement in the grey scale, prospective analyses in 86 obstetric and 23 abdominal examinations were undertaken. These studies indicate that fetal, intra-uterine, and abdominal structures can be rapidly and consistently imaged. The value of real time ultrasonic scanning in obstetric and abdominal examinations is illustrated. The principles of dynamically focused phased arrays are described, and the merits and limitations of these systems are discussed.

  8. Improved light extraction from white organic light-emitting devices using a binary random phase array

    SciTech Connect

    Inada, Yasuhisa Nishiwaki, Seiji; Hirasawa, Taku; Nakamura, Yoshitaka; Hashiya, Akira; Wakabayashi, Shin-ichi; Suzuki, Masa-aki; Matsuzaki, Jumpei

    2014-02-10

    We have developed a binary random phase array (BRPA) to improve the light extraction performance of white organic light-emitting devices (WOLEDs). We demonstrated that the scattering of incoming light can be controlled by employing diffraction optics to modify the structural parameters of the BRPA. Applying a BRPA to the substrate of the WOLED leads to enhanced extraction efficiency and suppression of angle-dependent color changes. Our systematic study clarifies the effect of scattering on the light extraction of WOLEDs.

  9. Microwave monolithic integrated circuit development for future spaceborne phased array antennas

    NASA Technical Reports Server (NTRS)

    Anzic, G.; Kascak, T. J.; Downey, A. N.; Liu, D. C.; Connolly, D. J.

    1983-01-01

    The development of fully monolithic gallium arsenide (GaAs) receive and transmit modules suitable for phased array antenna applications in the 30/20 gigahertz bands is presented. Specifications and various design approaches to achieve the design goals are described. Initial design and performance of submodules and associated active and passive components are presented. A tradeoff study summary is presented highlighting the advantages of distributed amplifier approach compared to the conventional single power source designs.

  10. Phased Array Ultrasound: Initial Development of PAUT Inspection of Self-Reacting Friction Stir Welds

    NASA Technical Reports Server (NTRS)

    Rairigh, Ryan

    2008-01-01

    This slide presentation reviews the development of Phased Array Ultrasound (PAUT) as a non-destructive examination method for Self Reacting Friction Stir Welds (SR-FSW). PAUT is the only NDE method which has been shown to detect detrimental levels of Residual Oxide Defect (ROD), which can result in significant decrease in weld strength. The presentation reviews the PAUT process, and shows the results in comparison with x-ray radiography.

  11. Comparison of steering angle and bandwidth for various phased array antenna concepts

    NASA Astrophysics Data System (ADS)

    Bonjour, Romain; Singleton, Matthew; Leuchtmann, Pascal; Leuthold, Juerg

    2016-08-01

    In this paper we compare different integratable ultra-fast tunable true-time delay concepts with respect to their performances in a phased array system. The performances of the schemes are assessed with respect to the supported range, i.e. the range within which beam steering for a given fractional bandwidth can be achieved with a gain flatness better than 3 dB. We also compare the array gain as of function of steering angle and fractional bandwidth.

  12. Acoustic Field Calculation of Ultrasonic Linear Phased Array Transducers with Curve Surface

    NASA Astrophysics Data System (ADS)

    Xu, Chunguang; Wang, Lijiu; Xiao, Dingguo; Zhou, Shiyuan

    2011-06-01

    The focus law and acoustic field computation method about circular arc linear phased array have been discussed in the paper. Acoustic field of transducers is given by the use of the coordinate transformation and an approximation with rectangle element instead of circular arc element, and was validated using Rayleigh-Sommerfeld Integral and nonparallel multiple Gaussian beam model respectively. The results of two methods match well.

  13. Image-guided ultrasound phased arrays are a disruptive technology for non-invasive therapy.

    PubMed

    Hynynen, Kullervo; Jones, Ryan M

    2016-09-01

    Focused ultrasound offers a non-invasive way of depositing acoustic energy deep into the body, which can be harnessed for a broad spectrum of therapeutic purposes, including tissue ablation, the targeting of therapeutic agents, and stem cell delivery. Phased array transducers enable electronic control over the beam geometry and direction, and can be tailored to provide optimal energy deposition patterns for a given therapeutic application. Their use in combination with modern medical imaging for therapy guidance allows precise targeting, online monitoring, and post-treatment evaluation of the ultrasound-mediated bioeffects. In the past there have been some technical obstacles hindering the construction of large aperture, high-power, densely-populated phased arrays and, as a result, they have not been fully exploited for therapy delivery to date. However, recent research has made the construction of such arrays feasible, and it is expected that their continued development will both greatly improve the safety and efficacy of existing ultrasound therapies as well as enable treatments that are not currently possible with existing technology. This review will summarize the basic principles, current statures, and future potential of image-guided ultrasound phased arrays for therapy. PMID:27494561

  14. K-Band Phased Array Developed for Low- Earth-Orbit Satellite Communications

    NASA Technical Reports Server (NTRS)

    Anzic, Godfrey

    1999-01-01

    Future rapid deployment of low- and medium-Earth-orbit satellite constellations that will offer various narrow- to wide-band wireless communications services will require phased-array antennas that feature wide-angle and superagile electronic steering of one or more antenna beams. Antennas, which employ monolithic microwave integrated circuits (MMIC), are perfectly suited for this application. Under a cooperative agreement, an MMIC-based, K-band phased-array antenna is being developed with 50/50 cost sharing by the NASA Lewis Research Center and Raytheon Systems Company. The transmitting array, which will operate at 19 gigahertz (GHz), is a state-of-the-art design that features dual, independent, electronically steerable beam operation ( 42 ), a stand-alone thermal management, and a high-density tile architecture. This array can transmit 622 megabits per second (Mbps) in each beam from Earth orbit to small Earth terminals. The weight of the total array package is expected to be less than 8 lb. The tile integration technology (flip chip MMIC tile) chosen for this project represents a major advancement in phased-array engineering and holds much promise for reducing manufacturing costs.

  15. Image-guided ultrasound phased arrays are a disruptive technology for non-invasive therapy

    NASA Astrophysics Data System (ADS)

    Hynynen, Kullervo; Jones, Ryan M.

    2016-09-01

    Focused ultrasound offers a non-invasive way of depositing acoustic energy deep into the body, which can be harnessed for a broad spectrum of therapeutic purposes, including tissue ablation, the targeting of therapeutic agents, and stem cell delivery. Phased array transducers enable electronic control over the beam geometry and direction, and can be tailored to provide optimal energy deposition patterns for a given therapeutic application. Their use in combination with modern medical imaging for therapy guidance allows precise targeting, online monitoring, and post-treatment evaluation of the ultrasound-mediated bioeffects. In the past there have been some technical obstacles hindering the construction of large aperture, high-power, densely-populated phased arrays and, as a result, they have not been fully exploited for therapy delivery to date. However, recent research has made the construction of such arrays feasible, and it is expected that their continued development will both greatly improve the safety and efficacy of existing ultrasound therapies as well as enable treatments that are not currently possible with existing technology. This review will summarize the basic principles, current statures, and future potential of image-guided ultrasound phased arrays for therapy.

  16. Simulation and Application of Dynamic Inspection Modes Using Ultrasonic Phased Arrays

    NASA Astrophysics Data System (ADS)

    Mahaut, Steve; Chatillon, Sylvain; Raillon-Picot, Raphaële; Calmon, Pierre

    2004-02-01

    NDT techniques using phased arrays are more and more applied in different industrial contexts. Their main advantage is the adaptability to the testing configuration : ability to steer and to focus the beam inside the inspected component taking account the geometry and the constitutive materials, high acquisition rates without raster scanning pattern of the probe using electronic commutation, sectorial scanning inspection to fully insonify the specimen, etc. Optimal use of phased arrays requires simulation tools accounting for the actual testing configuration. For several years, such tools have been developed at the French Atomic Energy Commission. Delay laws, beam forming and echo formation (interaction of the beam with defects or specimen boundaries) models are used to design the arrays, to conceive and to evaluate the performances of methods in realistic and complex configurations. Recently, works have been made to extend the simulation skills to advanced inspection modes : electronic commutation with separate Transmission/Reception patterns, non-symmetric Transmit/Receive delay laws, sectorial scanning inspections. This paper presents some examples of simulation and application of such inspections carried out over complex specimen. These examples demonstrate the interest for simulation tools in terms of prediction, optimization and interpretation of phased arrays techniques.

  17. System-Level Integrated Circuit (SLIC) Technology Development for Phased Array Antenna Applications

    NASA Technical Reports Server (NTRS)

    Windyka, John A.; Zablocki, Ed G.

    1997-01-01

    This report documents the efforts and progress in developing a 'system-level' integrated circuit, or SLIC, for application in advanced phased array antenna systems. The SLIC combines radio-frequency (RF) microelectronics, digital and analog support circuitry, and photonic interfaces into a single micro-hybrid assembly. Together, these technologies provide not only the amplitude and phase control necessary for electronic beam steering in the phased array, but also add thermally-compensated automatic gain control, health and status feedback, bias regulation, and reduced interconnect complexity. All circuitry is integrated into a compact, multilayer structure configured for use as a two-by-four element phased array module, operating at 20 Gigahertz, using a Microwave High-Density Interconnect (MHDI) process. The resultant hardware is constructed without conventional wirebonds, maintains tight inter-element spacing, and leads toward low-cost mass production. The measured performances and development issues associated with both the two-by-four element module and the constituent elements are presented. Additionally, a section of the report describes alternative architectures and applications supported by the SLIC electronics. Test results show excellent yield and performance of RF circuitry and full automatic gain control for multiple, independent channels. Digital control function, while suffering from lower manufacturing yield, also proved successful.

  18. Computer modeling of hyperthermia temperature distributions produced by hybrid RF/US phased arrays

    NASA Astrophysics Data System (ADS)

    Wu, Liyong; Zeng, Xiaozheng; Chen, Duo; McGough, Robert J.

    2006-05-01

    Simulation studies of hyperthermia as an adjuvant treatment for locally advanced breast cancer (LABC) show that temperature distributions are significantly improved with hybrid devices that combine ultrasound (US) and radio-frequency (RF) electromagnetic phased arrays. Ultrasound phased arrays, which generate relatively small focal spots in deep targets, are limited by intervening tissue heating in 60-minute hyperthermia treatments of large LABC tumors. In contrast RF phased arrays are regional heating devices with limited penetration depths. This combination offsets the drawbacks of each modality while offering multiple opportunities for optimization in LABC tumors. One optimization strategy partitions the tumor into two regions that are targeted individually by each modality. This approach targets the portion of the tumor proximal to the RF applicator and/or the skin surface with the RF component, and the US component delivers heat to the tumor in regions that the RF fails to reach. This heating strategy includes US contributions from focal points and intervening tissue heating within the tumor target. The resulting temperature distribution achieves higher, more uniform temperatures within the tumor target than either modality applied individually.

  19. Development of a twin crystal membrane coupled conformable phased array for the inspection of austenitic welds

    SciTech Connect

    Russell, J.; Long, R.; Cawley, P.

    2011-06-23

    The inspection of welded austenitic stainless steel components can be challenging. Austenitic welds contain an anisotropic, inhomogeneous grain structure which causes attenuation, scattering and beam bending. The inspection of components where the weld cap has not been removed is even more difficult due to the irregularity of the surface geometry. A twin crystal membrane coupled device has now been produced containing two linear phased arrays positioned adjacent to one another within the same housing. The arrays are angled relative to one another so that the transducer provides a pseudo-focusing effect at a depth corresponding to the beam crossing point. This type of design is used to improve the signal to noise ratio of the defect response in comparison to simple linear phased array transducer designs and to remove an internal noise signal found in linear phased array devices. Experimental results obtained from the through weld inspection of an austenitic stainless steel component with an undressed weld cap using the twin crystal membrane device are presented. These results demonstrate that small lack of side wall fusion defects can be reliably detected in large complex structures.

  20. Image-guided ultrasound phased arrays are a disruptive technology for non-invasive therapy.

    PubMed

    Hynynen, Kullervo; Jones, Ryan M

    2016-09-01

    Focused ultrasound offers a non-invasive way of depositing acoustic energy deep into the body, which can be harnessed for a broad spectrum of therapeutic purposes, including tissue ablation, the targeting of therapeutic agents, and stem cell delivery. Phased array transducers enable electronic control over the beam geometry and direction, and can be tailored to provide optimal energy deposition patterns for a given therapeutic application. Their use in combination with modern medical imaging for therapy guidance allows precise targeting, online monitoring, and post-treatment evaluation of the ultrasound-mediated bioeffects. In the past there have been some technical obstacles hindering the construction of large aperture, high-power, densely-populated phased arrays and, as a result, they have not been fully exploited for therapy delivery to date. However, recent research has made the construction of such arrays feasible, and it is expected that their continued development will both greatly improve the safety and efficacy of existing ultrasound therapies as well as enable treatments that are not currently possible with existing technology. This review will summarize the basic principles, current statures, and future potential of image-guided ultrasound phased arrays for therapy.

  1. High frequency, high power capacitor development

    NASA Technical Reports Server (NTRS)

    White, C. W.; Hoffman, P. S.

    1983-01-01

    A program to develop a special high energy density, high power transfer capacitor to operate at frequency of 40 kHz, 600 V rms at 125 A rms plus 600 V dc bias for space operation. The program included material evaluation and selection, a capacitor design was prepared, a thermal analysis performed on the design. Fifty capacitors were manufactured for testing at 10 kHz and 40 kHz for 50 hours at Industrial Electric Heating Co. of Columbus, Ohio. The vacuum endurance test used on environmental chamber and temperature plate furnished by Maxwell. The capacitors were energized with a special power conditioning apparatus developed by Industrial Electric Heating Co. Temperature conditions of the capacitors were monitored by IEHCo test equipment. Successful completion of the vacuum endurance test series confirmed achievement of the main goal of producing a capacitor or reliable operation at high frequency in an environment normally not hospitable to electrical and electronic components. The capacitor developed compared to a typical commercial capacitor at the 40 kHz level represents a decrease in size and weight by a factor of seven.

  2. High-frequency plasma-heating apparatus

    DOEpatents

    Brambilla, Marco; Lallia, Pascal

    1978-01-01

    An array of adjacent wave guides feed high-frequency energy into a vacuum chamber in which a toroidal plasma is confined by a magnetic field, the wave guide array being located between two toroidal current windings. Waves are excited in the wave guide at a frequency substantially equal to the lower frequency hybrid wave of the plasma and a substantially equal phase shift is provided from one guide to the next between the waves therein. For plasmas of low peripheral density gradient, the guides are excited in the TE.sub.01 mode and the output electric field is parallel to the direction of the toroidal magnetic field. For exciting waves in plasmas of high peripheral density gradient, the guides are excited in the TM.sub.01 mode and the magnetic field at the wave guide outlets is parallel to the direction of the toroidal magnetic field. The wave excited at the outlet of the wave guide array is a progressive wave propagating in the direction opposite to that of the toroidal current and is, therefore, not absorbed by so-called "runaway" electrons.

  3. High frequency, high power capacitor development

    NASA Astrophysics Data System (ADS)

    White, C. W.; Hoffman, P. S.

    1983-03-01

    A program to develop a special high energy density, high power transfer capacitor to operate at frequency of 40 kHz, 600 V rms at 125 A rms plus 600 V dc bias for space operation. The program included material evaluation and selection, a capacitor design was prepared, a thermal analysis performed on the design. Fifty capacitors were manufactured for testing at 10 kHz and 40 kHz for 50 hours at Industrial Electric Heating Co. of Columbus, Ohio. The vacuum endurance test used on environmental chamber and temperature plate furnished by Maxwell. The capacitors were energized with a special power conditioning apparatus developed by Industrial Electric Heating Co. Temperature conditions of the capacitors were monitored by IEHCo test equipment. Successful completion of the vacuum endurance test series confirmed achievement of the main goal of producing a capacitor or reliable operation at high frequency in an environment normally not hospitable to electrical and electronic components. The capacitor developed compared to a typical commercial capacitor at the 40 kHz level represents a decrease in size and weight by a factor of seven.

  4. Radio spectra of High Frequency Peakers

    NASA Astrophysics Data System (ADS)

    Dallacasa, D.; Orienti, M.

    2016-02-01

    New radio spectra of High Frequency Peakers (HFP) obtained from the Jansky Very Large Array (JVLA) show that variability is common among this class of sources. A subsample of sources have been observed with a nearly continuous spectral sampling between 1 and 10 GHz. The observed HFP sources were previously classified as F (flat), H (HFP profile with little or no flux density variability) and V (variable, but preserving a peaked spectrum). In general, sources classified as V and H show a decrease of the flux density measured in the optically thin part of the spectrum, while there is a moderate increment in the optically thick region, resulting into a progressive shift of the spectral peak to lower frequencies. This is consistent with the idea of an expanding bubble of radio plasma. The sources with an F classification instead show substantial variability, both in spectral shape and in time evolution. In these HFP sources an irregular production of energy is best observed since the radio emission is dominated by recently generated relativistic plasma, and the contribution of mini lobes, in which old plasma accumulates, is marginal if not absent at all, given the short radiative life of electrons in strong magnetic fields (tens of mG) found in these objects.

  5. A High Frequency Model of Cascade Noise

    NASA Technical Reports Server (NTRS)

    Envia, Edmane

    1998-01-01

    Closed form asymptotic expressions for computing high frequency noise generated by an annular cascade in an infinite duct containing a uniform flow are presented. There are two new elements in this work. First, the annular duct mode representation does not rely on the often-used Bessel function expansion resulting in simpler expressions for both the radial eigenvalues and eigenfunctions of the duct. In particular, the new representation provides an explicit approximate formula for the radial eigenvalues obviating the need for solutions of the transcendental annular duct eigenvalue equation. Also, the radial eigenfunctions are represented in terms of exponentials eliminating the numerical problems associated with generating the Bessel functions on a computer. The second new element is the construction of an unsteady response model for an annular cascade. The new construction satisfies the boundary conditions on both the cascade and duct walls simultaneously adding a new level of realism to the noise calculations. Preliminary results which demonstrate the effectiveness of the new elements are presented. A discussion of the utility of the asymptotic formulas for calculating cascade discrete tone as well as broadband noise is also included.

  6. Plant Responses to High Frequency Electromagnetic Fields

    PubMed Central

    Vian, Alain; Davies, Eric; Gendraud, Michel; Bonnet, Pierre

    2016-01-01

    High frequency nonionizing electromagnetic fields (HF-EMF) that are increasingly present in the environment constitute a genuine environmental stimulus able to evoke specific responses in plants that share many similarities with those observed after a stressful treatment. Plants constitute an outstanding model to study such interactions since their architecture (high surface area to volume ratio) optimizes their interaction with the environment. In the present review, after identifying the main exposure devices (transverse and gigahertz electromagnetic cells, wave guide, and mode stirred reverberating chamber) and general physics laws that govern EMF interactions with plants, we illustrate some of the observed responses after exposure to HF-EMF at the cellular, molecular, and whole plant scale. Indeed, numerous metabolic activities (reactive oxygen species metabolism, α- and β-amylase, Krebs cycle, pentose phosphate pathway, chlorophyll content, terpene emission, etc.) are modified, gene expression altered (calmodulin, calcium-dependent protein kinase, and proteinase inhibitor), and growth reduced (stem elongation and dry weight) after low power (i.e., nonthermal) HF-EMF exposure. These changes occur not only in the tissues directly exposed but also systemically in distant tissues. While the long-term impact of these metabolic changes remains largely unknown, we propose to consider nonionizing HF-EMF radiation as a noninjurious, genuine environmental factor that readily evokes changes in plant metabolism. PMID:26981524

  7. Aerodynamics of high frequency flapping wings

    NASA Astrophysics Data System (ADS)

    Hu, Zheng; Roll, Jesse; Cheng, Bo; Deng, Xinyan

    2010-11-01

    We investigated the aerodynamic performance of high frequency flapping wings using a 2.5 gram robotic insect mechanism developed in our lab. The mechanism flaps up to 65Hz with a pair of man-made wing mounted with 10cm wingtip-to-wingtip span. The mean aerodynamic lift force was measured by a lever platform, and the flow velocity and vorticity were measured using a stereo DPIV system in the frontal, parasagittal, and horizontal planes. Both near field (leading edge vortex) and far field flow (induced flow) were measured with instantaneous and phase-averaged results. Systematic experiments were performed on the man-made wings, cicada and hawk moth wings due to their similar size, frequency and Reynolds number. For insect wings, we used both dry and freshly-cut wings. The aerodynamic force increase with flapping frequency and the man-made wing generates more than 4 grams of lift at 35Hz with 3 volt input. Here we present the experimental results and the major differences in their aerodynamic performances.

  8. Plant Responses to High Frequency Electromagnetic Fields.

    PubMed

    Vian, Alain; Davies, Eric; Gendraud, Michel; Bonnet, Pierre

    2016-01-01

    High frequency nonionizing electromagnetic fields (HF-EMF) that are increasingly present in the environment constitute a genuine environmental stimulus able to evoke specific responses in plants that share many similarities with those observed after a stressful treatment. Plants constitute an outstanding model to study such interactions since their architecture (high surface area to volume ratio) optimizes their interaction with the environment. In the present review, after identifying the main exposure devices (transverse and gigahertz electromagnetic cells, wave guide, and mode stirred reverberating chamber) and general physics laws that govern EMF interactions with plants, we illustrate some of the observed responses after exposure to HF-EMF at the cellular, molecular, and whole plant scale. Indeed, numerous metabolic activities (reactive oxygen species metabolism, α- and β-amylase, Krebs cycle, pentose phosphate pathway, chlorophyll content, terpene emission, etc.) are modified, gene expression altered (calmodulin, calcium-dependent protein kinase, and proteinase inhibitor), and growth reduced (stem elongation and dry weight) after low power (i.e., nonthermal) HF-EMF exposure. These changes occur not only in the tissues directly exposed but also systemically in distant tissues. While the long-term impact of these metabolic changes remains largely unknown, we propose to consider nonionizing HF-EMF radiation as a noninjurious, genuine environmental factor that readily evokes changes in plant metabolism. PMID:26981524

  9. A high frequency electromagnetic impedance imaging system

    SciTech Connect

    Tseng, Hung-Wen; Lee, Ki Ha; Becker, Alex

    2003-01-15

    Non-invasive, high resolution geophysical mapping of the shallow subsurface is necessary for delineation of buried hazardous wastes, detecting unexploded ordinance, verifying and monitoring of containment or moisture contents, and other environmental applications. Electromagnetic (EM) techniques can be used for this purpose since electrical conductivity and dielectric permittivity are representative of the subsurface media. Measurements in the EM frequency band between 1 and 100 MHz are very important for such applications, because the induction number of many targets is small and the ability to determine the subsurface distribution of both electrical properties is required. Earlier workers were successful in developing systems for detecting anomalous areas, but quantitative interpretation of the data was difficult. Accurate measurements are necessary, but difficult to achieve for high-resolution imaging of the subsurface. We are developing a broadband non-invasive method for accurately mapping the electrical conductivity and dielectric permittivity of the shallow subsurface using an EM impedance approach similar to the MT exploration technique. Electric and magnetic sensors were tested to ensure that stray EM scattering is minimized and the quality of the data collected with the high-frequency impedance (HFI) system is good enough to allow high-resolution, multi-dimensional imaging of hidden targets. Additional efforts are being made to modify and further develop existing sensors and transmitters to improve the imaging capability and data acquisition efficiency.

  10. Using Silver Nano-Particle Ink in Electrode Fabrication of High Frequency Copolymer Ultrasonic Transducers: Modeling and Experimental Investigation

    PubMed Central

    Decharat, Adit; Wagle, Sanat; Jacobsen, Svein; Melandsø, Frank

    2015-01-01

    High frequency polymer-based ultrasonic transducers are produced with electrodes thicknesses typical for printed electrodes obtained from silver (Ag) nano-particle inks. An analytical three-port network is used to study the acoustic effects imposed by a thick electrode in a typical layered transducer configuration. Results from the network model are compared to experimental findings for the implemented transducer configuration, to obtain a better understanding of acoustical effects caused by the additional printed mass loading. The proposed investigation might be supportive of identification of suitable electrode-depositing methods. It is also believed to be useful as a feasibility study for printed Ag-based electrodes in high frequency transducers, which may reduce both the cost and production complexity of these devices. PMID:25903552

  11. Performance of annular high frequency thermoacoustic engines

    NASA Astrophysics Data System (ADS)

    Rodriguez, Ivan A.

    This thesis presents studies of the behavior of miniature annular thermoacoustic prime movers and the imaging of the complex sound fields using PIV inside the small acoustic wave guides when driven by a temperature gradient. Thermoacoustic engines operating in the standing wave mode are limited in their acoustic efficiency by a high degree of irreversibility that is inherent in how they work. Better performance can be achieved by using traveling waves in the thermoacoustic devices. This has led to the development of an annular high frequency thermoacoustic prime mover consisting of a regenerator, which is a random stack in-between a hot and cold heat exchanger, inside an annular waveguide. Miniature devices were developed and studied with operating frequencies in the range of 2-4 kHz. This corresponds to an average ring circumference of 11 cm for the 3 kHz device, the resonator bore being 6 mm. A similar device of 11 mm bore, length of 18 cm was also investigated; its resonant frequency was 2 kHz. Sound intensities as high as 166.8 dB were generated with limited heat input. Sound power was extracted from the annular structure by an impedance-matching side arm. The nature of the acoustic wave generated by heat was investigated using a high speed PIV instrument. Although the acoustic device appears symmetric, its performance is characterized by a broken symmetry and by perturbations that exist in its structure. Effects of these are observed in the PIV imaging; images show axial and radial components. Moreover, PIV studies show effects of streaming and instabilities which affect the devices' acoustic efficiency. The acoustic efficiency is high, being of 40% of Carnot. This type of device shows much promise as a high efficiency energy converter; it can be reduced in size for microcircuit applications.

  12. High frequency stimulation can block axonal conduction.

    PubMed

    Jensen, Alicia L; Durand, Dominique M

    2009-11-01

    High frequency stimulation (HFS) is used to control abnormal neuronal activity associated with movement, seizure, and psychiatric disorders. Yet, the mechanisms of its therapeutic action are not known. Although experimental results have shown that HFS suppresses somatic activity, other data has suggested that HFS could generate excitation of axons. Moreover it is unclear what effect the stimulation has on tissue surrounding the stimulation electrode. Electrophysiological and computational modeling literature suggests that HFS can drive axons at the stimulus frequency. Therefore, we tested the hypothesis that unlike cell bodies, axons are driven by pulse train HFS. This hypothesis was tested in fibers of the hippocampus both in-vivo and in-vitro. Our results indicate that although electrical stimulation could activate and drive axons at low frequencies (0.5-25 Hz), as the stimulus frequency increased, electrical stimulation failed to continuously excite axonal activity. Fiber tracts were unable to follow extracellular pulse trains above 50 Hz in-vitro and above 125 Hz in-vivo. The number of cycles required for failure was frequency dependent but independent of stimulus amplitude. A novel in-vitro preparation was developed, in which, the alveus was isolated from the remainder of the hippocampus slice. The isolated fiber tract was unable to follow pulse trains above 75 Hz. Reversible conduction block occurred at much higher stimulus amplitudes, with pulse train HFS (>150 Hz) preventing propagation through the site of stimulation. This study shows that pulse train HFS affects axonal activity by: (1) disrupting HFS evoked excitation leading to partial conduction block of activity through the site of HFS; and (2) generating complete conduction block of secondary evoked activity, as HFS amplitude is increased. These results are relevant for the interpretation of the effects of HFS for the control of abnormal neural activity such as epilepsy and Parkinson's disease. PMID

  13. High-frequency furnace. Final technical report

    SciTech Connect

    Zumbrunnen, A.D.

    1985-04-30

    An experimental furnace has been built for the purpose of evaluating a new technique for the high purity melting of certain metals and semiconductors. The melt is contained in a solidified skull of the same material being melted, thus avoiding crucible reactions that are a problem in conventional processing. A number of commercial applications of the invention are discussed, assuming that feasibility can be etablished. These include the melting and crystal growth of silicon, where the avoidance of crucible contamination would improve the energy conversion efficiency of solar cells; and the consolidation of titanium sponge and scrap, where energy savings and other process advantages would be realized. The production of ferrous and non-ferrous, specialty alloys is also discussed. Heating power is derived from the electrical, proximity effect which is used to concentrate a high-frequency (9.6 kHz) current in the melt zone. The power source is a conventional, 50 kW, solid-state inverter of the type used in induction heating practice. All heats were conducted on a cast iron workpiece in argon at atmospheric pressure. The melt temperature of the casting (2100/sup 0/F) was not achieved in any test run; however, the ability of proximity effect to generate localized heating was clearly demonstrated. A maximum temperature of about 1600/sup 0/F was reached at an inverter power output of approximately seventy-five percent. Full power was not obtained because of a poor impedance match between the furnace and power supply. Temperature was further limited because of the absence of heat shielding and other factors which resulted in excessive heat loss from the workpiece. These results are considered to be only preliminary since no attempt has been made to optimize either the electrical or thermal characteristics of the system.

  14. High Frequency QRS ECG Accurately Detects Cardiomyopathy

    NASA Technical Reports Server (NTRS)

    Schlegel, Todd T.; Arenare, Brian; Poulin, Gregory; Moser, Daniel R.; Delgado, Reynolds

    2005-01-01

    High frequency (HF, 150-250 Hz) analysis over the entire QRS interval of the ECG is more sensitive than conventional ECG for detecting myocardial ischemia. However, the accuracy of HF QRS ECG for detecting cardiomyopathy is unknown. We obtained simultaneous resting conventional and HF QRS 12-lead ECGs in 66 patients with cardiomyopathy (EF = 23.2 plus or minus 6.l%, mean plus or minus SD) and in 66 age- and gender-matched healthy controls using PC-based ECG software recently developed at NASA. The single most accurate ECG parameter for detecting cardiomyopathy was an HF QRS morphological score that takes into consideration the total number and severity of reduced amplitude zones (RAZs) present plus the clustering of RAZs together in contiguous leads. This RAZ score had an area under the receiver operator curve (ROC) of 0.91, and was 88% sensitive, 82% specific and 85% accurate for identifying cardiomyopathy at optimum score cut-off of 140 points. Although conventional ECG parameters such as the QRS and QTc intervals were also significantly longer in patients than controls (P less than 0.001, BBBs excluded), these conventional parameters were less accurate (area under the ROC = 0.77 and 0.77, respectively) than HF QRS morphological parameters for identifying underlying cardiomyopathy. The total amplitude of the HF QRS complexes, as measured by summed root mean square voltages (RMSVs), also differed between patients and controls (33.8 plus or minus 11.5 vs. 41.5 plus or minus 13.6 mV, respectively, P less than 0.003), but this parameter was even less accurate in distinguishing the two groups (area under ROC = 0.67) than the HF QRS morphologic and conventional ECG parameters. Diagnostic accuracy was optimal (86%) when the RAZ score from the HF QRS ECG and the QTc interval from the conventional ECG were used simultaneously with cut-offs of greater than or equal to 40 points and greater than or equal to 445 ms, respectively. In conclusion 12-lead HF QRS ECG employing

  15. Design and calibration of high-frequency magnetic probes for the SUNIST spherical tokamak.

    PubMed

    Liu, Yangqing; Tan, Yi; Pan, Ou; Ke, Rui; Wang, Wenhao; Gao, Zhe

    2014-11-01

    A new high-frequency magnetic diagnostic system is designed, installed, and calibrated in the Sino-United Spherical Tokamak (SUNIST) to investigate Alfvén waves (AWs). The system consists of a fixed toroidal array and a movable radial array of high-frequency magnetic probes (HFMPs) with 21 and 60 probes, respectively. Based on the method of vacuum enameled wire wound on ceramic bobbins, the fixed toroidal array is located as near as possible to the plasma and carefully shielded to reduce the attenuation of high-frequency magnetic field. Meanwhile, by using the technology of commercial chip inductors mounted on printed circuit boards, the movable radial array is inserted into a thin quartz tube that allows positioning along radial direction. A Helmholtz coil is utilized to calibrate the effective areas as well as the frequency response of each HFMP. The calibration results are consistent with the calculated results of an equivalent probe-and-cable circuit model. High-frequency magnetic signals related to AW are detected with these HFMPs. These HFMPs are expected to play a key role in analyzing Alfvén eigenmodes excited by AW antenna in the SUNIST.

  16. Design and calibration of high-frequency magnetic probes for the SUNIST spherical tokamak.

    PubMed

    Liu, Yangqing; Tan, Yi; Pan, Ou; Ke, Rui; Wang, Wenhao; Gao, Zhe

    2014-11-01

    A new high-frequency magnetic diagnostic system is designed, installed, and calibrated in the Sino-United Spherical Tokamak (SUNIST) to investigate Alfvén waves (AWs). The system consists of a fixed toroidal array and a movable radial array of high-frequency magnetic probes (HFMPs) with 21 and 60 probes, respectively. Based on the method of vacuum enameled wire wound on ceramic bobbins, the fixed toroidal array is located as near as possible to the plasma and carefully shielded to reduce the attenuation of high-frequency magnetic field. Meanwhile, by using the technology of commercial chip inductors mounted on printed circuit boards, the movable radial array is inserted into a thin quartz tube that allows positioning along radial direction. A Helmholtz coil is utilized to calibrate the effective areas as well as the frequency response of each HFMP. The calibration results are consistent with the calculated results of an equivalent probe-and-cable circuit model. High-frequency magnetic signals related to AW are detected with these HFMPs. These HFMPs are expected to play a key role in analyzing Alfvén eigenmodes excited by AW antenna in the SUNIST. PMID:25430367

  17. Phased-array cancellation of nonlinear FWM in coherent OFDM dispersive multi-span links.

    PubMed

    Nazarathy, Moshe; Khurgin, Jacob; Weidenfeld, Rakefet; Meiman, Yehuda; Cho, Pak; Noe, Reinhold; Shpantzer, Isaac; Karagodsky, Vadim

    2008-09-29

    We develop an analytic model of Coherent Optical Orthogonal Frequency Division Multiplexing (OFDM) propagation and detection over multi-span long-haul fiber links, comprehensively and rigorously analyzing the impairments due the combined effects of FWM, Dispersion and ASE noise. Consistent with prior work of Innoe and Schadt in the WDM context, our new closed-form expressions for the total FWM received power fluctuations in the wake of dispersive phase mismatch in OFDM transmission, indicate that the FWM contributions of the multitude of spans build-up on a phased-array basis. For particular ultra-long haul link designs, the effectiveness of dispersion in reducing FWM is far greater than previously assumed in OFDM system analysis. The key is having the dominant FWM intermodulation products due to the multiple spans, destructively interfere, mutually cancelling their FWM intermodulation products, analogous to operating at the null of a phased-array antenna system. By applying the new analysis tools, this mode of effectively mitigating the FWM impairment, is shown under specific dispersion and spectral management conditions, to substantially suppress the FWM power fluctuations. Accounting for the phased-array concept and applying the compact OFDM design formulas developed here, we analyzed system performance of a 40 Gbps coherent OFDM system, over standard G.652 fiber, with cyclic prefix based electronic dispersion compensation but no optical compensation along the link. The transmission range for 10-3 target BER is almost tripled from 2560 km to 6960 km, relative to a reference system performing optical dispersion compensation in every span (ideally accounting for FWM and ASE noise and the cyclic prefix overhead, but excluding additional impairments). PMID:18825217

  18. Development of a pseudo phased array technique using EMATs for DM weld testing

    NASA Astrophysics Data System (ADS)

    Cobb, Adam C.; Fisher, Jay L.; Shiokawa, Nobuyuki; Hamano, Toshiaki; Horikoshi, Ryoichi; Ido, Nobukazu

    2015-03-01

    Ultrasonic inspection of dissimilar metal (DM) welds in piping with cast austenitic stainless steel (CASS) has been an area ongoing research for many years given its prevalence in the petrochemical and nuclear industries. A typical inspection strategy for pipe welds is to use an ultrasonic phased array system to scan the weld from a sensor located on the outer surface of the pipe. These inspection systems generally refract either longitudinal or shear vertical (SV) waves at varying angles to inspect the weld radially. In DM welds, however, the welding process can produce a columnar grain structure in the CASS material in a specific orientation. This columnar grain structure can skew ultrasonic waves away from their intended path, especially for SV and longitudinal wave modes. Studies have shown that inspection using the shear horizontal (SH) wave mode significantly reduces the effect of skewing. Electromagnetic acoustic transducers (EMATs) are known to be effective for producing SH waves in field settings. This paper presents an inspection strategy that seeks to reproduce the scanning and imaging capabilities of a commercial phase array system using EMATs. A custom-built EMAT was used to collect data at multiple propagation angles, and a processing strategy known as the synthetic aperture focusing technique (SAFT) was used to combine the data to produce an image. Results are shown using this pseudo phased array technique to inspect samples with a DM weld and artificial defects, demonstrating the potential of this approach in a laboratory setting. Recommendations for future work to transition the technique to the field are also provided.

  19. Jet-Surface Interaction Test: Phased Array Noise Source Localization Results

    NASA Technical Reports Server (NTRS)

    Podboy, Gary G.

    2012-01-01

    An experiment was conducted to investigate the effect that a planar surface located near a jet flow has on the noise radiated to the far-field. Two different configurations were tested: 1) a shielding configuration in which the surface was located between the jet and the far-field microphones, and 2) a reflecting configuration in which the surface was mounted on the opposite side of the jet, and thus the jet noise was free to reflect off the surface toward the microphones. Both conventional far-field microphone and phased array noise source localization measurements were obtained. This paper discusses phased array results, while a companion paper discusses far-field results. The phased array data show that the axial distribution of noise sources in a jet can vary greatly depending on the jet operating condition and suggests that it would first be necessary to know or be able to predict this distribution in order to be able to predict the amount of noise reduction to expect from a given shielding configuration. The data obtained on both subsonic and supersonic jets show that the noise sources associated with a given frequency of noise tend to move downstream, and therefore, would become more difficult to shield, as jet Mach number increases. The noise source localization data obtained on cold, shock-containing jets suggests that the constructive interference of sound waves that produces noise at a given frequency within a broadband shock noise hump comes primarily from a small number of shocks, rather than from all the shocks at the same time. The reflecting configuration data illustrates that the law of reflection must be satisfied in order for jet noise to reflect off of a surface to an observer, and depending on the relative locations of the jet, the surface, and the observer, only some of the jet noise sources may satisfy this requirement.

  20. Development of a pseudo phased array technique using EMATs for DM weld testing

    SciTech Connect

    Cobb, Adam C. Fisher, Jay L.; Shiokawa, Nobuyuki; Hamano, Toshiaki; Horikoshi, Ryoichi; Ido, Nobukazu

    2015-03-31

    Ultrasonic inspection of dissimilar metal (DM) welds in piping with cast austenitic stainless steel (CASS) has been an area ongoing research for many years given its prevalence in the petrochemical and nuclear industries. A typical inspection strategy for pipe welds is to use an ultrasonic phased array system to scan the weld from a sensor located on the outer surface of the pipe. These inspection systems generally refract either longitudinal or shear vertical (SV) waves at varying angles to inspect the weld radially. In DM welds, however, the welding process can produce a columnar grain structure in the CASS material in a specific orientation. This columnar grain structure can skew ultrasonic waves away from their intended path, especially for SV and longitudinal wave modes. Studies have shown that inspection using the shear horizontal (SH) wave mode significantly reduces the effect of skewing. Electromagnetic acoustic transducers (EMATs) are known to be effective for producing SH waves in field settings. This paper presents an inspection strategy that seeks to reproduce the scanning and imaging capabilities of a commercial phase array system using EMATs. A custom-built EMAT was used to collect data at multiple propagation angles, and a processing strategy known as the synthetic aperture focusing technique (SAFT) was used to combine the data to produce an image. Results are shown using this pseudo phased array technique to inspect samples with a DM weld and artificial defects, demonstrating the potential of this approach in a laboratory setting. Recommendations for future work to transition the technique to the field are also provided.

  1. Control algorithms of liquid crystal phased arrays used as adaptive optic correctors

    NASA Astrophysics Data System (ADS)

    Dayton, David; Gonglewski, John; Browne, Stephen

    2006-08-01

    Multi-segment liquid crystal phased arrays have been demonstrated as adaptive optics elements for correction of atmospheric turbulence. High speed dual-frequency nematic liquid crystal has sufficient bandwidth to keep up with moderate atmospheric Greenwood frequencies. However the segmented piston correction only spatial nature of the devices requires novel approaches to control algorithms especially when used with Shack-Hartmann wave front sensors. In this presentation we explore approaches and their effects on closed loop Strehl ratios. A Zernike modal based approach has produced the best results. The presentation will contain results from experiments with a Meadowlark optics liquid crystal device.

  2. Assessment of Microphone Phased Array for Measuring Launch Vehicle Lift-off Acoustics

    NASA Technical Reports Server (NTRS)

    Garcia, Roberto

    2012-01-01

    The specific purpose of the present work was to demonstrate the suitability of a microphone phased array for launch acoustics applications via participation in selected firings of the Ares I Scale Model Acoustics Test. The Ares I Scale Model Acoustics Test is a part of the discontinued Constellation Program Ares I Project, but the basic understanding gained from this test is expected to help development of the Space Launch System vehicles. Correct identification of sources not only improves the predictive ability, but provides guidance for a quieter design of the launch pad and optimization of the water suppression system. This document contains the results of the NASA Engineering and Safety Center assessment.

  3. A 19 element cryogenic phased array feed for the Green Bank Telescope

    NASA Astrophysics Data System (ADS)

    Roshi, D. Anish; Warnick, Karl F.; Brandt, Joe; Fisher, J. Richard; Ford, Pam; Jeffs, Brian D.; Marganian, Paul; McLeod, Morgan; Mello, Melinda; Morgan, Matthew; Norrod, Roger; Shillue, William; Simon, Robert; White, Steven

    2015-10-01

    A low-noise cryogenic phased array feed (PAF) is in development for the Green Bank Telescope (GBT). The feed consists of electrically small elements tuned to operate near 1.4 GHz and optimized for active impedance matching to cooled front end low noise amplifiers (LNAs). A prototype cryogenic PAF with analog fiber link, down-converters and streaming data acquisition system was recently tested on the GBT. Preliminary results are presented. These efforts form an important step towards the development of a new receiver system, the focal L-band array for the GBT (FLAG).

  4. Microwave monolithic integrated circuit development for future spaceborne phased array antennas

    NASA Technical Reports Server (NTRS)

    Anzic, G.; Kascak, T. J.; Downey, A. N.; Liu, D. C.; Connolly, D. J.

    1984-01-01

    The development of fully monolithic gallium arsenide (GaAs) receive and transmit modules suitable for phased array antenna applications in the 30/20 gigahertz bands is presented. Specifications and various design approaches to achieve the design goals are described. Initial design and performance of submodules and associated active and passive components are presented. A tradeoff study summary is presented, highlighting the advantages of a distributed amplifier approach compared to the conventional single power source designs. Previously announced in STAR as N84-13399

  5. Fundamental study of molten pool depth measurement method using an ultrasonic phased array system

    NASA Astrophysics Data System (ADS)

    Mizota, Hirohisa; Nagashima, Yoshiaki; Obana, Takeshi

    2015-07-01

    The molten pool depth measurement method using an ultrasonic phased array system has been developed. The molten pool depth distribution is evaluated by comparing the times taken by the ultrasonic wave to propagate through a molten pool and a solid-phase and through only the solid-phase near the molten pool. Maximum molten pool depths on a flat type-304 stainless-steel plate, formed with a gas tungsten arc welding machine for different welding currents from 70 to 150 A, were derived within an error of ±0.5 mm.

  6. Assessment of weld quality of aerospace grade metals by using ultrasonic matrix phased array technology

    NASA Astrophysics Data System (ADS)

    Na, Jeong K.; Gleeson, Sean T.

    2014-03-01

    Advantages of two dimensional electronic ultrasonic beam focusing, steering and scanning with the matrix phased array (MPA) technology has been used to visualize the conditions of resistance spot welds in auto vehicle grade advanced high strength steel carbon steels nondestructively. Two of the commonly used joining techniques, resistance spot welding and resistance seam welding, for thin aerospace grade plates made of aluminum, titanium, and stainless steels have also been inspected with the same MPA NDE system. In this study, a detailed discussions of the current MPA based ultrasonic real time imaging methodology has been made followed by some of the NDT results obtained with various welded test coupons.

  7. An Evaluation of Signal Processing Tools for Improving Phased Array Ultrasonic Weld Inspection

    SciTech Connect

    Ramuhalli, Pradeep; Cinson, Anthony D.; Crawford, Susan L.; Harris, Robert V.; Diaz, Aaron A.; Anderson, Michael T.

    2011-03-24

    Cast austenitic stainless steel (CASS) commonly used in U.S. nuclear power plants is a coarse-grained, elastically anisotropic material. The coarse-grained nature of CASS makes ultrasonic inspection of in-service components difficult. Recently, low-frequency phased array ultrasound has emerged as a candidate for the CASS piping weld inspection. However, issues such as low signal-to-noise ratio and difficulty in discriminating between flaw and non-flaw signals remain. This paper discusses the evaluation of a number of signal processing algorithms for improving flaw detection in CASS materials. The full paper provides details of the algorithms being evaluated, along with preliminary results.

  8. Spectral dispersion modeling of virtually imaged phased array by using angular spectrum of plane waves.

    PubMed

    Hu, Xinrong; Sun, Qiang; Li, Jing; Li, Chun; Liu, Ying; Zhang, Jianzhong

    2015-01-12

    We present an analytical treatment for the relatively new spectral disperser termed virtually imaged phased array (VIPA). Angular spectrum representation of the input Gaussian beam helps us obtain an exact analytic dispersion model and a dispersion law for a general VIPA by using the principle of multiple-beam interference. The consideration of the optical aberrations caused by refractions makes our model more accurate and practical than previous models. The validity of the proposed dispersion law has been validated theoretically by comparing with previous results. Some considerations of using a VIPA are also provided.

  9. Laser induced ultrasonic phased array using full matrix capture data acquisition and total focusing method.

    PubMed

    Stratoudaki, Theodosia; Clark, Matt; Wilcox, Paul D

    2016-09-19

    Laser ultrasonics is a technique where lasers are employed to generate and detect ultrasound. A data collection method (full matrix capture) and a post processing imaging algorithm, the total focusing method, both developed for ultrasonic arrays, are modified and used in order to enhance the capabilities of laser ultrasonics for nondestructive testing by improving defect detectability and increasing spatial resolution. In this way, a laser induced ultrasonic phased array is synthesized. A model is developed and compared with experimental results from aluminum samples with side drilled holes and slots at depths of 5 - 20 mm from the surface.

  10. Image reconstruction from phased-array data based on multichannel blind deconvolution.

    PubMed

    She, Huajun; Chen, Rong-Rong; Liang, Dong; Chang, Yuchou; Ying, Leslie

    2015-11-01

    In this paper we consider image reconstruction from fully sampled multichannel phased array MRI data without knowledge of the coil sensitivities. To overcome the non-uniformity of the conventional sum-of-square reconstruction, a new framework based on multichannel blind deconvolution (MBD) is developed for joint estimation of the image function and the sensitivity functions in image domain. The proposed approach addresses the non-uniqueness of the MBD problem by exploiting the smoothness of both functions in the image domain through regularization. Results using simulation, phantom and in vivo experiments demonstrate that the reconstructions by the proposed algorithm are more uniform than those by the existing methods.

  11. Continuous Beam Steering From A Segmented Liquid Crystal Optical Phased Array

    NASA Technical Reports Server (NTRS)

    Pouch, John; Nguyen, Hung; Miranda, Felix; Titus, Charles M.; Bos, Philip J.

    2002-01-01

    Optical communications to and from deep space probes will require beams possessing divergence on the order of a microradian, and must be steered with sub-microradian precision. Segmented liquid crystal spatial phase modulators, a type of optical phased array, are considered for this ultra-high resolution beam steering. It is shown here that in an ideal device of this type, there are ultimately no restrictions on the angular resolution. Computer simulations are used to obtain that result, and to analyze the influence of beam truncation and substrate flatness on the performance of this type of device.

  12. Extending the scanning angle of a phased array antenna by using a null-space medium.

    PubMed

    Sun, Fei; He, Sailing

    2014-01-01

    By introducing a columnar null-space region as the reference space, we design a radome that can extend the scanning angle of a phased array antenna (PAA) by a predetermined relationship (e.g. a linear relationship between the incident angle and steered output angle can be achieved). After some approximation, we only need two homogeneous materials to construct the proposed radome layer by layer. This kind of medium is called a null-space medium, which has been studied and fabricated for realizing hyper-lenses and some other devices. Numerical simulations verify the performance of our radome.

  13. Continuous Beam Steering From a Segmented Liquid Crystal Optical Phased Array

    NASA Technical Reports Server (NTRS)

    Titus, Charles M.; Pouch, John; Nguyen, Hung; Miranda, Felix; Bos, Philip J.

    2002-01-01

    Optical communications to and from deep space probes will require beams possessing divergence on the order of a microradian, and must be steered with sub-microradian precision. Segmented liquid crystal spatial phase modulators, a type of optical phased array, are considered for this ultra-high resolution beam steering. It is shown here that in an ideal device of this type, there are ultimately no restrictions on the angular resolution. Computer simulations are used to obtain that result, and to analyze the influence of beam truncation and substrate flatness on the performance of this type of device.

  14. Novel Phased Array Scanning Employing A Single Feed Without Using Individual Phase Shifters

    NASA Technical Reports Server (NTRS)

    Host, Nicholas K.; Chen, Chi-Chih; Volakis, John L.; Miranda, Felix A.

    2012-01-01

    Phased arrays afford many advantages over mechanically steered systems. However, they are also more complex, heavy, and most of all costly. The high cost mainly originates from the complex feeding structure. This paper proposes a novel feeding scheme to eliminate all phase shifters and achieve scanning via one-dimensional motion. Beam scanning is achieved via a series fed array incorporating feeding transmission lines whose wave velocity can be mechanically adjusted. Along with the line design, ideal element impedances to be used in conjunction with the line are derived. Practical designs are shown which achieve scanning to +/-30deg from boresight. Finally, a prototype is fabricated and measured, demonstrating the concept.

  15. Extending the scanning angle of a phased array antenna by using a null-space medium.

    PubMed

    Sun, Fei; He, Sailing

    2014-01-01

    By introducing a columnar null-space region as the reference space, we design a radome that can extend the scanning angle of a phased array antenna (PAA) by a predetermined relationship (e.g. a linear relationship between the incident angle and steered output angle can be achieved). After some approximation, we only need two homogeneous materials to construct the proposed radome layer by layer. This kind of medium is called a null-space medium, which has been studied and fabricated for realizing hyper-lenses and some other devices. Numerical simulations verify the performance of our radome. PMID:25355198

  16. Extending the scanning angle of a phased array antenna by using a null-space medium

    NASA Astrophysics Data System (ADS)

    Sun, Fei; He, Sailing

    2014-10-01

    By introducing a columnar null-space region as the reference space, we design a radome that can extend the scanning angle of a phased array antenna (PAA) by a predetermined relationship (e.g. a linear relationship between the incident angle and steered output angle can be achieved). After some approximation, we only need two homogeneous materials to construct the proposed radome layer by layer. This kind of medium is called a null-space medium, which has been studied and fabricated for realizing hyper-lenses and some other devices. Numerical simulations verify the performance of our radome.

  17. Extending the scanning angle of a phased array antenna by using a null-space medium

    PubMed Central

    Sun, Fei; He, Sailing

    2014-01-01

    By introducing a columnar null-space region as the reference space, we design a radome that can extend the scanning angle of a phased array antenna (PAA) by a predetermined relationship (e.g. a linear relationship between the incident angle and steered output angle can be achieved). After some approximation, we only need two homogeneous materials to construct the proposed radome layer by layer. This kind of medium is called a null-space medium, which has been studied and fabricated for realizing hyper-lenses and some other devices. Numerical simulations verify the performance of our radome. PMID:25355198

  18. Laser induced ultrasonic phased array using full matrix capture data acquisition and total focusing method.

    PubMed

    Stratoudaki, Theodosia; Clark, Matt; Wilcox, Paul D

    2016-09-19

    Laser ultrasonics is a technique where lasers are employed to generate and detect ultrasound. A data collection method (full matrix capture) and a post processing imaging algorithm, the total focusing method, both developed for ultrasonic arrays, are modified and used in order to enhance the capabilities of laser ultrasonics for nondestructive testing by improving defect detectability and increasing spatial resolution. In this way, a laser induced ultrasonic phased array is synthesized. A model is developed and compared with experimental results from aluminum samples with side drilled holes and slots at depths of 5 - 20 mm from the surface. PMID:27661927

  19. Effects of interelectrode gap on high frequency and very high frequency capacitively coupled plasmas

    SciTech Connect

    Bera, Kallol; Rauf, Shahid; Ramaswamy, Kartik; Collins, Ken

    2009-07-15

    Capacitively coupled plasma (CCP) discharges using high frequency (HF) and very high frequency (VHF) sources are widely used for dielectric etching in the semiconductor industry. A two-dimensional fluid plasma model is used to investigate the effects of interelectrode gap on plasma spatial characteristics of both HF and VHF CCPs. The plasma model includes the full set of Maxwell's equations in their potential formulation. The peak in plasma density is close to the electrode edge at 13.5 MHz for a small interelectrode gap. This is due to electric field enhancement at the electrode edge. As the gap is increased, the plasma produced at the electrode edge diffuses to the chamber center and the plasma becomes more uniform. At 180 MHz, where electromagnetic standing wave effects are strong, the plasma density peaks at the chamber center at large interelectrode gap. As the interelectrode gap is decreased, the electron density increases near the electrode edge due to inductive heating and electrostatic electron heating, which makes the plasma more uniform in the interelectrode region.

  20. On-clip high frequency reliability and failure test structures

    DOEpatents

    Snyder, Eric S.; Campbell, David V.

    1997-01-01

    Self-stressing test structures for realistic high frequency reliability characterizations. An on-chip high frequency oscillator, controlled by DC signals from off-chip, provides a range of high frequency pulses to test structures. The test structures provide information with regard to a variety of reliability failure mechanisms, including hot-carriers, electromigration, and oxide breakdown. The system is normally integrated at the wafer level to predict the failure mechanisms of the production integrated circuits on the same wafer.

  1. On-clip high frequency reliability and failure test structures

    DOEpatents

    Snyder, E.S.; Campbell, D.V.

    1997-04-29

    Self-stressing test structures for realistic high frequency reliability characterizations. An on-chip high frequency oscillator, controlled by DC signals from off-chip, provides a range of high frequency pulses to test structures. The test structures provide information with regard to a variety of reliability failure mechanisms, including hot-carriers, electromigration, and oxide breakdown. The system is normally integrated at the wafer level to predict the failure mechanisms of the production integrated circuits on the same wafer. 22 figs.

  2. Photonic generation of high frequency millimeter-wave and transmission over optical fiber.

    PubMed

    Kumar, Amitesh; Priye, Vishnu

    2016-08-01

    A novel technique of photonic generation of millimeter-waves beyond the presently reported 120 GHz and with a wider tunability (∼240  GHz) is proposed and demonstrated through a simulation experiment. The scheme consists of generating 24 times the frequency of a conventional low frequency microwave source using a combination of a LiNbO3 Mach-Zehnder modulator and four-wave mixing in a semiconductor optical amplifier. The filtering of a high frequency sideband and the suppression of a carrier are achieved by incorporating an optical band pass and fiber Bragg grating filters, respectively. Next, the spectral purity of the generated millimeter-wave parameters is evaluated after propagation through a conventional fiber of different lengths by digitally modulating it at 2.5 Gbps and generating an eye diagram. The constraints on the selection of the frequency of the millimeter-wave and length of fiber are discussed. The present method of millimeter-wave generation and distribution will find applications in photonic up/down conversion, phase-array antennas, photonic sensors, radars, and terahertz applications.

  3. Photonic generation of high frequency millimeter-wave and transmission over optical fiber.

    PubMed

    Kumar, Amitesh; Priye, Vishnu

    2016-08-01

    A novel technique of photonic generation of millimeter-waves beyond the presently reported 120 GHz and with a wider tunability (∼240  GHz) is proposed and demonstrated through a simulation experiment. The scheme consists of generating 24 times the frequency of a conventional low frequency microwave source using a combination of a LiNbO3 Mach-Zehnder modulator and four-wave mixing in a semiconductor optical amplifier. The filtering of a high frequency sideband and the suppression of a carrier are achieved by incorporating an optical band pass and fiber Bragg grating filters, respectively. Next, the spectral purity of the generated millimeter-wave parameters is evaluated after propagation through a conventional fiber of different lengths by digitally modulating it at 2.5 Gbps and generating an eye diagram. The constraints on the selection of the frequency of the millimeter-wave and length of fiber are discussed. The present method of millimeter-wave generation and distribution will find applications in photonic up/down conversion, phase-array antennas, photonic sensors, radars, and terahertz applications. PMID:27505360

  4. Optimization of a phased-array transducer for multiple harmonic imaging in medical applications: frequency and topology.

    PubMed

    Matte, Guillaume M; Van Neer, Paul L M J; Danilouchkine, Mike G; Huijssen, Jacob; Verweij, Martin D; de Jong, Nico

    2011-03-01

    Second-harmonic imaging is currently one of the standards in commercial echographic systems for diagnosis, because of its high spatial resolution and low sensitivity to clutter and near-field artifacts. The use of nonlinear phenomena mirrors is a great set of solutions to improve echographic image resolution. To further enhance the resolution and image quality, the combination of the 3rd to 5th harmonics--dubbed the superharmonics--could be used. However, this requires a bandwidth exceeding that of conventional transducers. A promising solution features a phased-array design with interleaved low- and high-frequency elements for transmission and reception, respectively. Because the amplitude of the backscattered higher harmonics at the transducer surface is relatively low, it is highly desirable to increase the sensitivity in reception. Therefore, we investigated the optimization of the number of elements in the receiving aperture as well as their arrangement (topology). A variety of configurations was considered, including one transmit element for each receive element (1/2) up to one transmit for 7 receive elements (1/8). The topologies are assessed based on the ratio of the harmonic peak pressures in the main and grating lobes. Further, the higher harmonic level is maximized by optimization of the center frequency of the transmitted pulse. The achievable SNR for a specific application is a compromise between the frequency-dependent attenuation and nonlinearity at a required penetration depth. To calculate the SNR of the complete imaging chain, we use an approach analogous to the sonar equation used in underwater acoustics. The generated harmonic pressure fields caused by nonlinear wave propagation were modeled with the iterative nonlinear contrast source (INCS) method, the KZK, or the Burger's equation. The optimal topology for superharmonic imaging was an interleaved design with 1 transmit element per 6 receive elements. It improves the SNR by ~5 dB compared with

  5. Wavenumber-frequency deconvolution of aeroacoustic microphone phased array data of arbitrary coherence

    NASA Astrophysics Data System (ADS)

    Bahr, Christopher J.; Cattafesta, Louis N.

    2016-11-01

    Deconvolution of aeroacoustic data acquired with microphone phased arrays is a computationally challenging task for distributed sources with arbitrary coherence. A new technique for performing such deconvolution is proposed. This technique relies on analysis of the array data in the wavenumber-frequency domain, allowing for fast convolution and reduced storage requirements when compared to traditional coherent deconvolution. A positive semidefinite constraint for the iterative deconvolution procedure is implemented and shows improved behavior in terms of quantifiable convergence metrics when compared to a standalone covariance inequality constraint. A series of simulations validates the method's ability to resolve coherence and phase angle relationships between partially coherent sources, as well as determines convergence criteria for deconvolution analysis. Simulations for point sources near the microphone phased array show potential for handling such data in the wavenumber-frequency domain. In particular, a physics-based integration boundary calculation is described, and can successfully isolate sources and track the appropriate integration bounds with and without the presence of flow. Magnitude and phase relationships between multiple sources are successfully extracted. Limitations of the deconvolution technique are determined from the simulations, particularly in the context of a simulated acoustic field in a closed test section wind tunnel with strong boundary layer contamination. A final application to a trailing edge noise experiment conducted in an open-jet wind tunnel matches best estimates of acoustic levels from traditional calculation methods and qualitatively assesses the coherence characteristics of the trailing edge noise source.

  6. Saft-reconstruction in ultrasonic immersion technique using phased array transducers

    NASA Astrophysics Data System (ADS)

    Kitze, J.; Prager, J.; Boehm, R.; Völz, U.; Montag, H.-J.

    2012-05-01

    The two main preconditions for the application of the Synthetic Aperture Focusing Technique (SAFT) are: (i) a large divergence of the sound beam of the transducer and (ii) an exact knowledge about the sound propagation path. These requirements are easily fulfilled for point sources directly mounted on the surface of the specimen. In many cases, however, the transducer is wedge mounted and/or coupled using a water delay line, e.g. in immersion technique. These delay lines change the beam index and the propagation path has to be evaluated for each pixel separately considering Fermat's principle. Using phased array transducers, a sector scan can improve the divergence of the sound beam. The introduced method combines the advantages of using a phased array transducer in immersion technique to improve SAFT reconstruction. An algorithm is presented accounting the influence of the delay line on the reconstruction method. The applicability of the algorithm is shown by validation with simulated echo responses and with experimental results collected from a specimen with artificial flaws.

  7. Three-Dimensional Mid-Air Acoustic Manipulation by Ultrasonic Phased Arrays

    PubMed Central

    Ochiai, Yoichi; Hoshi, Takayuki; Rekimoto, Jun

    2014-01-01

    The essence of levitation technology is the countervailing of gravity. It is known that an ultrasound standing wave is capable of suspending small particles at its sound pressure nodes. The acoustic axis of the ultrasound beam in conventional studies was parallel to the gravitational force, and the levitated objects were manipulated along the fixed axis (i.e. one-dimensionally) by controlling the phases or frequencies of bolted Langevin-type transducers. In the present study, we considered extended acoustic manipulation whereby millimetre-sized particles were levitated and moved three-dimensionally by localised ultrasonic standing waves, which were generated by ultrasonic phased arrays. Our manipulation system has two original features. One is the direction of the ultrasound beam, which is arbitrary because the force acting toward its centre is also utilised. The other is the manipulation principle by which a localised standing wave is generated at an arbitrary position and moved three-dimensionally by opposed and ultrasonic phased arrays. We experimentally confirmed that expanded-polystyrene particles of 0.6 mm, 1 mm, and 2 mm in diameter could be manipulated by our proposed method. PMID:24849371

  8. Considerations for Using Phased Array Ultrasonics in a Fully Automated Inspection System

    NASA Astrophysics Data System (ADS)

    Kramb, V. A.; Olding, R. B.; Sebastian, J. R.; Hoppe, W. C.; Petricola, D. L.; Hoeffel, J. D.; Gasper, D. A.; Stubbs, D. A.

    2004-02-01

    The University of Dayton Research Institute (UDRI) under contract by the US Air Force has designed and constructed a fully automated ultrasonic inspection system for the detection of embedded defects in rotating gas turbine engine components. The system performs automated inspections using the "scan plan" concept developed for the Air Force sponsored "Retirement For Cause" (RFC) automated eddy current system. Execution of the scan plan results in a fully automated inspection process producing engine component accept/reject decisions based on probability of detection (POD) information. Use of the phased-array ultrasonic instrument and probes allows for optimization of both the sensitivity and resolution for each inspection through electronic beamforming, scanning, and focusing processes. However, issues such as alignment of the array probe, calibration of individual elements and overall beam response prior to the inspection have not been addressed for an automated system. This paper will discuss current progress in the development of an automated alignment and calibration procedure for various phased array apertures and specimen geometries.

  9. Capabilities of Ultrasonic Phased Arrays for Far-Side Examinations of Austenitic Stainless Steel Piping Welds

    SciTech Connect

    Anderson, Michael T.; Cumblidge, Stephen E.; Doctor, Steven R.

    2006-10-01

    A study was conducted to assess the ability of advanced ultrasonic techniques to detect and accurately determine the size of flaws from the far-side of wrought austenitic piping welds. Far-side inspections of nuclear system austenitic piping welds are currently performed on a “best effort” basis and do not conform to ASME Code Section XI Appendix VIII performance demonstration requirements for near side inspection. For this study, four circumferential welds in 610mm (24inch) diameter, 36mm (1.42inch) thick ASTM A-358, Grade 304 vintage austenitic stainless steel pipe were examined. The welds were fabricated with varied welding parameters; both horizontal and vertical pipe orientations were used, with air and water backing, to simulate field welding conditions. A series of saw cuts, electro-discharge machined (EDM) notches, and implanted fatigue cracks were placed into the heat affected zones of the welds. The saw cuts and notches ranged in depth from 7.5% to 28.4% through-wall. The implanted cracks ranged in depth from 5% through-wall to 64% through-wall. The welds were examined with phased array technology at 2.0 MHz, and compared to conventional ultrasonic techniques as a baseline. The examinations showed that phased-array methods were able to detect and accurately length-size, but not depth size, the notches and flaws through the welds. The ultrasonic results were insensitive to the different welding techniques used in each weld.

  10. Development of Phased Array Probes for Austenitic Weld Inspections Using Multi-Gaussian Beam Modeling

    NASA Astrophysics Data System (ADS)

    Kono, N.; Baba, A.

    2008-02-01

    Phased array ultrasonic testing techniques have been applied to sizing of cracks in welds, especially stainless steels and nickel based alloys welds. Ultrasonic phased array probes are capable of providing high SN ratio and high resolution by means of focal beams with various depths, positions, and angles. In this study, a simple design method using numerical analysis is proposed to optimize parameters on array probes. Acoustical fields of array probes are calculated approximately based on a multi-Gaussian beam modeling for single transducers. Calculation results are compared with experimental data with a laser interferometer. Validity of the modeling for the acoustical fields of the array probes is confirmed by good agreement between simulations and experiments. In order to design array probes that satisfy inspection requirements, e.g. range and resolution, an index of focusing (focusing factor) is important in addition to the parameters of array probes. Specifications of array probes are discussed for two kinds of requirements, wide range and high resolution.

  11. Pelvic imaging with phased-array coils: quantitative assessment of signal-to-noise ratio improvement.

    PubMed

    Hayes, C E; Dietz, M J; King, B F; Ehman, R L

    1992-01-01

    The signal-to-noise ratios (S/Ns) of two different pelvic magnetic resonance (MR) imaging phased arrays were compared with that of the body coil. Each array consisted of two coils placed anteriorly and two posteriorly, oriented transversely in one array and longitudinally in the other. S/N measurements were obtained in an adjustable water-filled phantom that stimulated the shape and radio-frequency loading effects of various-size patients. Depending on the simulated anterior-posterior thickness of the patient, the S/N produced by the longitudinal array ranged from 2.3 to 3.1 times higher than that of the body coil. The S/N of the transverse array was 3.1 to 3.4 times higher. The increased coil sensitivity permits imaging with shorter acquisition times, smaller fields of view, finer resolution, and/or thinner sections. Two examples in patients demonstrate the enhanced imaging capability of the phased arrays.

  12. Phased Array Noise Source Localization Measurements Made on a Williams International FJ44 Engine

    NASA Technical Reports Server (NTRS)

    Podboy, Gary G.; Horvath, Csaba

    2010-01-01

    A 48-microphone planar phased array system was used to acquire noise source localization data on a full-scale Williams International FJ44 turbofan engine. Data were acquired with the array at three different locations relative to the engine, two on the side and one in front of the engine. At the two side locations the planar microphone array was parallel to the engine centerline; at the front location the array was perpendicular to the engine centerline. At each of the three locations, data were acquired at eleven different engine operating conditions ranging from engine idle to maximum (take off) speed. Data obtained with the array off to the side of the engine were spatially filtered to separate the inlet and nozzle noise. Tones occurring in the inlet and nozzle spectra were traced to the low and high speed spools within the engine. The phased array data indicate that the Inflow Control Device (ICD) used during this test was not acoustically transparent; instead, some of the noise emanating from the inlet reflected off of the inlet lip of the ICD. This reflection is a source of error for far field noise measurements made during the test. The data also indicate that a total temperature rake in the inlet of the engine is a source of fan noise.

  13. Phased Array Technology with Phase and Amplitude Controlled Magnetron for Microwave Power Transmission

    NASA Astrophysics Data System (ADS)

    Shinohara, N.; Matsumoto, H.

    2004-12-01

    We need a microwave power transmitter with light weight and high DC-RF conversion efficiency for an economical SSPS (Space Solar Power System). We need a several g/W for a microwave power transmission (MPT) system with a phased array with 0.0001 degree of beam control accuracy (=tan-1 (100m/36,000km)) and over 80 % of DC-RF conversion efficiency when the weight of the 1GW-class SPS is below a several thousand ton - a several tens of thousand ton. We focus a microwave tube, especially magnetron by economical reason and by the amount of mass-production because it is commonly used for microwave oven in the world. At first, we have developed a phase controlled magnetron (PCM) with different technologies from what Dr. Brown developed. Next we have developed a phase and amplitude controlled magnetron (PACM). For the PACM, we add a feedback to magnetic field of the PCM with an external coil to control and stabilize amplitude of the microwave. We succeed to develop the PACM with below 10-6 of frequency stability and within 1 degree of an error in phase and within 1% of amplitude. We can control a phase and amplitude of the PACM and we have developed a phased array the PCMs. With the PCM technology, we have developed a small light weight MPT transmitter COMET (Compact Microwave Energy Transmitter) with consideration of heat radiation for space use and with consideration of mobility to space.

  14. Ultrasonic Phased Array Evaluation of Control Rod Drive Mechanism (CRDM) Nozzle Interference Fit and Weld Region

    SciTech Connect

    Cinson, Anthony D.; Crawford, Susan L.; MacFarlan, Paul J.; Mathews, Royce; Hanson, Brady D.; Diaz, Aaron A.

    2011-07-31

    Ultrasonic phased array data were collected on a removed-from-service CRDM nozzle specimen to assess a previously reported leak path. First a mock-up CRDM specimen was evaluated that contained two 0.076-mm (3.0-mil) interference fit regions formed from an actual Inconel CRDM tube and two 152.4-mm (6.0-in.) thick carbon steel blocks. One interference fit region has a series of precision crafted electric discharge machining (EDM) notches at various lengths, widths, depths, and spatial separations for establishing probe sensitivity, resolution and calibration. The other interference fit has zones of boric acid (crystal form) spaced periodically between the tube and block to represent an actively leaking CRDM nozzle assembly in the field. Ultrasonic phased-array evaluations were conducted using an immersion 8-element annular 5.0-MHz probe from the tube inner diameter (ID). A variety of focal laws were employed to evaluate the interference fit regions and J grove weld, where applicable. Responses from the mock-up specimen were evaluated to determine detection limits and characterization ability as well as contrast the ultrasonic response differences with the presence of boric acid in the fit region. Nozzle 63, from the North Anna Unit-2 nuclear power plant, was evaluated to assess leakage path(s) and was destructively dismantled to allow a visual verification of the leak path(s).

  15. LOW-FREQUENCY PHASED-ARRAY METHODS FOR CRACK DETECTION IN CAST AUSTENITIC PIPING COMPONENTS

    SciTech Connect

    Anderson, Michael T.; Crawford, Susan L.; Cumblidge, Stephen E.; Diaz, Aaron A.; Doctor, Steven R.

    2008-01-01

    Studies at the Pacific Northwest National Laboratory (PNNL) in Richland, Washington, are being conducted to evaluate nondestructive examination (NDE) approaches for inspecting coarse-grained, austenitic stainless steel reactor components. The work provides information to the United States Nuclear Regulatory Commission (NRC) on the utility, effectiveness, limitations, and reliability of advanced inspection techniques for application on safety-related components in commercial nuclear power plants. This paper describes results from recent assessments using a low-frequency phased-array methodology for detecting cracks in cast austenitic piping welds. Piping specimens that contain thermal and mechanical fatigue cracks located adjacent to welds were examined. The specimens have surface geometrical conditions and weld features that simulate portions of primary piping systems in many U.S. pressurized water reactors (PWRs). In addition, segments of vintage centrifugally cast piping were examined to assess inherent acoustic noise and scattering due to grain structures and determine consistency of ultrasonic (UT) responses from varied circumferential locations. The phased-array UT methods were applied from the outside surface of the specimens using automated scanning devices and water coupling, and employed a modified instrument operating between 500 kHz and 1.0 MHz. Composite volumetric images of the specimens were generated. Results from laboratory studies for assessing crack detection and sizing effectiveness are discussed, including acoustic parameters observed in centrifugally cast piping base materials.

  16. Low Frequency Phased Array Application for Crack Detection in Cast Austenitic Piping

    SciTech Connect

    Anderson, Michael T.; Cumblidge, Stephen E.; Doctor, Steven R.

    2006-10-01

    As part of a multi-year program funded by the United States Nuclear Regulatory Commission (US NRC) to address nondestructive examination (NDE) reliability of inservice inspection (ISI) programs, studies conducted at the Pacific N¬orthwest National Laboratory (PNNL) in Richland, Washington, have focused on assessing novel NDE approaches for the inspection of coarse-grained, cast stainless steel reactor components. The primary objective of this work is to provide information to the US NRC on the utility, effec¬tiveness and reliability of ultrasonic testing (UT) as related to the ISI of primary piping components in US commercial nuclear power plants. This paper describes progress, recent developments and results from an assessment of a portion of the work relating to the ultrasonic low frequency phased array inspection technique. Westinghouse Owner’s Group (WOG) cast stainless steel pipe segments with thermal and mechanical fatigue cracks, PNNL samples containing thermal fatigue cracks and several blank vintage specimens having very coarse grains that are representative of early centrifugally cast piping installed in PWRs, were used for assessing the inspection method. The phased array approach was implemented using an R/D Tech Tomoscan III system operating at 1.0 MHz and 500 kHz, providing composite volumetric images of the samples. Several dual, transmit-receive, custom designed low-frequency arrays were employed in laboratory trials. Results from laboratory studies for assessing detection, localization and length sizing effectiveness are discussed.

  17. Jet-Surface Interaction Test: Phased Array Noise Source Localization Results

    NASA Technical Reports Server (NTRS)

    Podboy, Gary

    2012-01-01

    Subsonic jets are relatively simple. The peak noise source location gradually moves upstream toward the nozzle as frequency increases. 2) Supersonic jets are more complicated. The peak noise source location moves downstream as frequency increases through a BBSN hump. 3) In both subsonic and supersonic jets the peak noise source location corresponding to a given frequency of noise moves downstream as jet Mach number increases. 4) The noise generated at a given frequency in a BBSN hump is generated by a small number of shocks, not from all the shocks at the same time. 5) Single microphone spectrum levels decrease when the noise source locations measured with the phased array are blocked by a shielding surface. This consistency validates the phased array data and the stationary monopole source model used to process it. 6) Reflecting surface data illustrate that the law of reflection must be satisfied for noise to reflect off a surface toward an observer. Depending on the relative locations of the jet, the surface and the observer only some of the jet noise sources may satisfy this requirement. 7) The low frequency noise created when a jet flow impinges on a surface comes primarily from the trailing edge regardless of the axial extent impacted by the flow.

  18. Limitations of Phased Array Beamforming in Open Rotor Noise Source Imaging

    NASA Technical Reports Server (NTRS)

    Horvath, Csaba; Envia, Edmane; Podboy, Gary G.

    2013-01-01

    Phased array beamforming results of the F31/A31 historical baseline counter-rotating open rotor blade set were investigated for measurement data taken on the NASA Counter-Rotating Open Rotor Propulsion Rig in the 9- by 15-Foot Low-Speed Wind Tunnel of NASA Glenn Research Center as well as data produced using the LINPROP open rotor tone noise code. The planar microphone array was positioned broadside and parallel to the axis of the open rotor, roughly 2.3 rotor diameters away. The results provide insight as to why the apparent noise sources of the blade passing frequency tones and interaction tones appear at their nominal Mach radii instead of at the actual noise sources, even if those locations are not on the blades. Contour maps corresponding to the sound fields produced by the radiating sound waves, taken from the simulations, are used to illustrate how the interaction patterns of circumferential spinning modes of rotating coherent noise sources interact with the phased array, often giving misleading results, as the apparent sources do not always show where the actual noise sources are located. This suggests that a more sophisticated source model would be required to accurately locate the sources of each tone. The results of this study also have implications with regard to the shielding of open rotor sources by airframe empennages.

  19. Recent Enhancements of the Phased Array Mirror Extendible Large Aperture (PAMELA) Telescope Testbed at MSFC

    NASA Technical Reports Server (NTRS)

    Rakoczy, John; Burdine, Robert (Technical Monitor)

    2001-01-01

    Recent incremental upgrades to the Phased Array Mirror Extendible Large Aperture (PAMELA) telescope testbed have enabled the demonstration of phasing (with a monochromatic source) of clusters of primary mirror segments down to the diffraction limit. PAMELA upgrades include in improved Shack-Hartmann wavefront sensor, passive viscoelastic damping treatments for the voice-coil actuators, mechanical improvement of mirror surface figures, and optical bench baffling. This report summarizes the recent PAMELA upgrades, discusses the lessons learned, and presents a status of this unique testbed for wavefront sensing and control. The Marshall Space Flight Center acquired the Phased Array Mirror Extendible Large Aperture (PAMELA) telescope in 1993 after Kaman Aerospace was unable to complete integration and testing under the limited SDIO and DARPA funding. The PAMELA is a 36-segment, half-meter aperture, adaptive telescope which utilizes a Shack-Hartmann wavefront sensor, inductive coil edge sensors, voice coil actuators, imaging CCD cameras and interferometry for figure alignment, wavefront sensing and control. MSFC originally obtained the PAMELA to supplement its research in the interactions of control systems with flexible structures. In August 1994, complete tip, tilt and piston control was successfully demonstrated using the Shack-Hartmann wavefront sensor and the inductive edge sensors.

  20. Low Frequency Phased Array Techniques for Crack Detection in Cast Austenitic Piping Welds: A Feasibility Study

    SciTech Connect

    Anderson, Michael T.; Cumblidge, Stephen E.; Doctor, Steven R.

    2007-01-01

    Studies conducted at the Pacific Northwest National Laboratory (PNNL) in Richland, Washington have focused on developing and evaluating the reliability of nondestructive testing (NDT) approaches for coarse-grained stainless steel reactor components. The objective of this work is to provide information to the United States Nuclear Regulatory Commission (NRC) on the utility, effectiveness and limitation of NDT techniques as related to inservice testing of primary system piping components in pressurized water reactors. We examined cast stainless steel pipe specimens containing thermal and mechanical fatigue cracks located close to the weld roots and having inner and outer diameter surface geometrical conditions that simulate several water reactor primary piping configurations. In addition, segments of vintage centrifugally cast piping were examined to characterize the inherent acoustic noise and scattering caused by grain structures and to determine the consistency of ultrasonic responses when propagating through differing microstructures. Advanced ultrasonic phased array techniques were applied from the outside surface of these specimens using automated scanning devices and water coupling. The phased array approach was implemented with a modified instrument operating at low frequencies, and composite volumetric images of the specimens were generated. Results from laboratory studies for assessing crack detection effectiveness in cast stainless steel as a function of frequency are discussed in this paper.

  1. Microstrip patch antenna panel for large aperture L-band phased array

    NASA Technical Reports Server (NTRS)

    Chamberlain, Neil; Amaro, Luis; Oakes, Eric; Hodges, Richard; Spitz, Suzanne; Rosen, Paul A.

    2004-01-01

    This paper describes the design and development of a large, lightweight antenna panel for an active phased array operating at L-band. The panel was developed under a JPL program of technology development for space based radar. It utilizes dual-stacked patch elements that are interconnected with corporate feed manifold of striplines. This paper focuses on the electromagnetic design and performance of the radiating elements, with emphasis on scan performance, and also addresses mechanical and thermal aspects of the panel. The element in the array environment has a bandwidth of more than 80MHz centered at 1260MHz and is fed so that it can radiate orthogonal linear polarizations. The envisioned phased array, with a nominal aperture of 50m x 2m, is designed to scan +/-45 degrees in azimuth and +/-20 degrees in elevation. The panel of radiating elements has a mass density of 3.9 kg/m2, which represents approximately 50% of the target 8kg/m2 total panel mass density that includes T/R modules and feed manifolds.

  2. Three-dimensional mid-air acoustic manipulation by ultrasonic phased arrays.

    PubMed

    Ochiai, Yoichi; Hoshi, Takayuki; Rekimoto, Jun

    2014-01-01

    The essence of levitation technology is the countervailing of gravity. It is known that an ultrasound standing wave is capable of suspending small particles at its sound pressure nodes. The acoustic axis of the ultrasound beam in conventional studies was parallel to the gravitational force, and the levitated objects were manipulated along the fixed axis (i.e. one-dimensionally) by controlling the phases or frequencies of bolted Langevin-type transducers. In the present study, we considered extended acoustic manipulation whereby millimetre-sized particles were levitated and moved three-dimensionally by localised ultrasonic standing waves, which were generated by ultrasonic phased arrays. Our manipulation system has two original features. One is the direction of the ultrasound beam, which is arbitrary because the force acting toward its centre is also utilised. The other is the manipulation principle by which a localised standing wave is generated at an arbitrary position and moved three-dimensionally by opposed and ultrasonic phased arrays. We experimentally confirmed that expanded-polystyrene particles of 0.6 mm, 1 mm, and 2 mm in diameter could be manipulated by our proposed method.

  3. Three-dimensional mid-air acoustic manipulation by ultrasonic phased arrays.

    PubMed

    Ochiai, Yoichi; Hoshi, Takayuki; Rekimoto, Jun

    2014-01-01

    The essence of levitation technology is the countervailing of gravity. It is known that an ultrasound standing wave is capable of suspending small particles at its sound pressure nodes. The acoustic axis of the ultrasound beam in conventional studies was parallel to the gravitational force, and the levitated objects were manipulated along the fixed axis (i.e. one-dimensionally) by controlling the phases or frequencies of bolted Langevin-type transducers. In the present study, we considered extended acoustic manipulation whereby millimetre-sized particles were levitated and moved three-dimensionally by localised ultrasonic standing waves, which were generated by ultrasonic phased arrays. Our manipulation system has two original features. One is the direction of the ultrasound beam, which is arbitrary because the force acting toward its centre is also utilised. The other is the manipulation principle by which a localised standing wave is generated at an arbitrary position and moved three-dimensionally by opposed and ultrasonic phased arrays. We experimentally confirmed that expanded-polystyrene particles of 0.6 mm, 1 mm, and 2 mm in diameter could be manipulated by our proposed method. PMID:24849371

  4. Phased array focusing with guided waves in a viscoelastic coated hollow cylinder.

    PubMed

    Luo, Wei; Rose, Joseph L

    2007-04-01

    Guided wave phased array focusing has shown many advantages in long-range pipeline inspection, such as, longer inspection distance, greater wave penetration power and higher detection resolution. Viscoelastic coatings applied to a large percentage of pipes for protection purposes created some challenges in terms of focusing feasibility and inspection ability. Previous studies were all based on bare pipe models. In this work, guided wave phased array focusing in viscoelastic coated pipes is studied for the first time. Work was carried out with both numerical and experimental methods. A three-dimensional finite element model was developed for quantitatively and systematically modeling guided waves in pipes with different viscoelastic materials. A method of transforming measured coating properties to finite element method inputs was created in order to create a physically based model of guided waves in coated pipes. Guided wave focusing possibilities in viscoelastic coated pipes and the effects from coatings were comprehensively studied afterwards. A comparison of focusing and nonfocusing inspections was also studied quantitatively in coated pipe showing that focusing increased the wave energy and consequently the inspection ability tremendously. This study provides an important base line and guidance for guided wave propagation and focusing in a real field pipeline under various coating and environmental conditions.

  5. Circumferential phased array of shear-horizontal wave magnetostrictive patch transducers for pipe inspection.

    PubMed

    Kim, Hoe Woong; Lee, Joo Kyung; Kim, Yoon Young

    2013-02-01

    Several investigations report effective uses of magnetostrictive patch transducers to generate and measure longitudinal and torsional guided waves in a pipe. They can be used to form a phased array for the circumferential inspection of pipes. Although there are circumferential phased arrays employing piezoelectric transducers or EMAT's, no magnetostrictive patch transducer based array system has been attempted. In this investigation, we aim to develop a circumferential phased magnetostrictive patch transducer (PMPT) array that can focus shear-horizontal waves at any target point on a cylindrical surface of a pipe. For the development, a specific configuration of a PMPT array employing six magnetostrictive patch transducers is proposed. A wave simulation model is also developed to determine time delays and amplitudes of signals generated by the transducers of the array. This model should be able to predict accurately the angular profiles of shear-horizontal waves generated by the transducers. For wave focusing, the time reversal idea will be utilized. The wave focusing ability of the developed PMPT array is tested with multiple-crack detection experiments. Imaging of localized surface inspection regions is also attempted by using wave signals measured by the developed PMPT array system.

  6. Effects of high frequency current in welding aluminum alloy 6061

    NASA Technical Reports Server (NTRS)

    Fish, R. E.

    1968-01-01

    Uncontrolled high frequency current causes cracking in the heat-affected zone of aluminum alloy 6061 weldments during tungsten inert gas ac welding. Cracking developed when an improperly adjusted superimposed high frequency current was agitating the semimolten metal in the areas of grain boundary.

  7. Monitoring method and apparatus using high-frequency carrier

    DOEpatents

    Haynes, Howard D.

    1996-01-01

    A method and apparatus for monitoring an electrical-motor-driven device by injecting a high frequency carrier signal onto the power line current. The method is accomplished by injecting a high frequency carrier signal onto an AC power line current. The AC power line current supplies the electrical-motor-driven device with electrical energy. As a result, electrical and mechanical characteristics of the electrical-motor-driven device modulate the high frequency carrier signal and the AC power line current. The high frequency carrier signal is then monitored, conditioned and demodulated. Finally, the modulated high frequency carrier signal is analyzed to ascertain the operating condition of the electrical-motor-driven device.

  8. Monitoring method and apparatus using high-frequency carrier

    DOEpatents

    Haynes, H.D.

    1996-04-30

    A method and apparatus for monitoring an electrical-motor-driven device by injecting a high frequency carrier signal onto the power line current. The method is accomplished by injecting a high frequency carrier signal onto an AC power line current. The AC power line current supplies the electrical-motor-driven device with electrical energy. As a result, electrical and mechanical characteristics of the electrical-motor-driven device modulate the high frequency carrier signal and the AC power line current. The high frequency carrier signal is then monitored, conditioned and demodulated. Finally, the modulated high frequency carrier signal is analyzed to ascertain the operating condition of the electrical-motor-driven device. 6 figs.

  9. Haemodynamic changes during high frequency oscillation for respiratory distress syndrome.

    PubMed Central

    Laubscher, B.; van Melle, G.; Fawer, C. L.; Sekarski, N.; Calame, A.

    1996-01-01

    In a crossover trial left ventricular output (LVO), cerebral blood flow velocity (CBFV), and resistance index (RI) of the anterior cerebral artery were compared using Doppler ultrasonography, in eight preterm infants with respiratory distress syndrome (RDS) during conventional mechanical ventilation and high frequency oscillation. LVO was 14% to 18% lower with high frequency oscillation. There were no significant changes in CBFV. On the first day of life there was a trend towards lower RI on high frequency oscillation; the fall in LVO on high frequency oscillation was not related to lung hyperinflation. Changes in ventilation type (from conventional mechanical ventilation to high frequency oscillation, or vice versa) can induce significant LVO changes in preterm infants with RDS. PMID:8777679

  10. Jet-Surface Interaction Test: Phased Array Noise Source Localization Results

    NASA Technical Reports Server (NTRS)

    Podboy, Gary G.

    2013-01-01

    An experiment was conducted to investigate the effect that a planar surface located near a jet flow has on the noise radiated to the far-field. Two different configurations were tested: 1) a shielding configuration in which the surface was located between the jet and the far-field microphones, and 2) a reflecting configuration in which the surface was mounted on the opposite side of the jet, and thus the jet noise was free to reflect off the surface toward the microphones. Both conventional far-field microphone and phased array noise source localization measurements were obtained. This paper discusses phased array results, while a companion paper (Brown, C.A., "Jet-Surface Interaction Test: Far-Field Noise Results," ASME paper GT2012-69639, June 2012.) discusses far-field results. The phased array data show that the axial distribution of noise sources in a jet can vary greatly depending on the jet operating condition and suggests that it would first be necessary to know or be able to predict this distribution in order to be able to predict the amount of noise reduction to expect from a given shielding configuration. The data obtained on both subsonic and supersonic jets show that the noise sources associated with a given frequency of noise tend to move downstream, and therefore, would become more difficult to shield, as jet Mach number increases. The noise source localization data obtained on cold, shock-containing jets suggests that the constructive interference of sound waves that produces noise at a given frequency within a broadband shock noise hump comes primarily from a small number of shocks, rather than from all the shocks at the same time. The reflecting configuration data illustrates that the law of reflection must be satisfied in order for jet noise to reflect off of a surface to an observer, and depending on the relative locations of the jet, the surface, and the observer, only some of the jet noise sources may satisfy this requirement.

  11. Development of a Microphone Phased Array Capability for the Langley 14- by 22-Foot Subsonic Tunnel

    NASA Technical Reports Server (NTRS)

    Humphreys, William M.; Brooks, Thomas F.; Bahr, Christopher J.; Spalt, Taylor B.; Bartram, Scott M.; Culliton, William G.; Becker, Lawrence E.

    2014-01-01

    A new aeroacoustic measurement capability has been developed for use in open-jet testing in the NASA Langley 14- by 22-Foot Subsonic Tunnel (14x22 tunnel). A suite of instruments has been developed to characterize noise source strengths, locations, and directivity for both semi-span and full-span test articles in the facility. The primary instrument of the suite is a fully traversable microphone phased array for identification of noise source locations and strengths on models. The array can be mounted in the ceiling or on either side of the facility test section to accommodate various test article configurations. Complementing the phased array is an ensemble of streamwise traversing microphones that can be placed around the test section at defined locations to conduct noise source directivity studies along both flyover and sideline axes. A customized data acquisition system has been developed for the instrumentation suite that allows for command and control of all aspects of the array and microphone hardware, and is coupled with a comprehensive data reduction system to generate information in near real time. This information includes such items as time histories and spectral data for individual microphones and groups of microphones, contour presentations of noise source locations and strengths, and hemispherical directivity data. The data acquisition system integrates with the 14x22 tunnel data system to allow real time capture of facility parameters during acquisition of microphone data. The design of the phased array system has been vetted via a theoretical performance analysis based on conventional monopole beamforming and DAMAS deconvolution. The performance analysis provides the ability to compute figures of merit for the array as well as characterize factors such as beamwidths, sidelobe levels, and source discrimination for the types of noise sources anticipated in the 14x22 tunnel. The full paper will summarize in detail the design of the instrumentation

  12. Non-destructive visualization of linear explosive-induced Pyroshock using phase arrayed laser-induced shock in a space launcher composite

    NASA Astrophysics Data System (ADS)

    kyeong Jang, Jae; Ryul Lee, Jung

    2015-07-01

    Separation mechanism of Space launch vehicles are used in various separation systems and pyrotechnic devices. The operation of these pyrotechnic devices generates Pyroshock that can cause failures in electronic components. The prediction of high frequency structural response, especially the shock response spectrum (SRS), is important. This paper presents a non-destructive visualization and simulation of linear explosive-induced Pyroshock using phase arrayed Laser-induced shock. The proposed method includes a laser shock test based on laser beam and filtering zone conditioning to predict the SRS of Pyroshock. A ballistic test based on linear explosive and non-contact Laser Doppler Vibrometers and a nondestructive Laser shock measurement using laser excitation and several PZT sensors, are performed using a carbon composite sandwich panel. The similarity of the SRS of the conditioned laser shock to that of the real explosive Pyroshock is evaluated with the Mean Acceleration Difference. The average of MADs over the two training points was 33.64%. And, MAD at verification point was improved to 31.99%. After that, experimentally found optimal conditions are applied to any arbitrary points in laser scanning area. Finally, it is shown that linear explosive-induced real Pyroshock wave propagation can be visualized with high similarity based on the proposed laser technology.

  13. V-band pseudomorphic HEMT MMIC phased array components for space communications

    NASA Technical Reports Server (NTRS)

    Lan, G. L.; Pao, C. K.; Wu, C. S.; Hu, M.; Downey, Alan N.

    1992-01-01

    Recent advances in pseudomorphic high-electron-mobility transistor (PMHEMT) monolithic microwave integrated circuit (MMIC) technology have made it the preferred candidate for high performance millimeter-wave components for phased array applications. The development of V-band PMHEMT/MMIC components including power amplifiers and phase shifters is described. For the single-stage MMIC power amplifier employing a 200 micron PMHEMT, we achieved 151.4 mW output power (757.0 mW/mm) with 1.8 dB associated gain and 26.4 percent power-added efficiency at 60 GHz. A two-stage MMIC amplifier utilizing the same devices demonstrated small-signal gain as high as 15 dB at 58 GHz. And, for the phase shifter, a four-bit phase shifter with less than 8 dB insertion loss from 61 to 63 GHz was measured.

  14. AlGaAs laser diode FM spectrum: Phased array antenna application

    NASA Astrophysics Data System (ADS)

    Chamberland, Martin; Tetu, Michel

    Preliminary results are presented on the use of an AlGaAs laser diode to generate microwave signals suitable for application with phased array antennas. The relative intensity noise (RIN) was measured under various operating conditions to give an indication of the frequency response limitation of the laser diode. The frequency response to intensity modulation was also measured directly at microwave frequencies. Finally, the FM spectrum was observed using a heterodyne technique and compared with an empirical model. The spectrum of intensity fluctuations shows a peak near the relaxation oscillation frequency. This is a good indication of the cutoff frequency for direct current modulation of the laser diode. The behavior of the modulated laser diode is well characterized by the simultaneous intensity and frequency modulation taking into account a phase difference between the two.

  15. A double-stage injection-locked oscillator for optically fed phased array antennas

    NASA Technical Reports Server (NTRS)

    Berceli, Tibor; Jemison, William D.; Herczfeld, Peter R.; Daryoush, Afshin S.; Paolella, Arthur

    1991-01-01

    In an optically fed phased array antenna system, the microwave carrier signal is transmitted via a modulated lightwave to each active T/R (transmit/receive) module, where it must be converted back to the microwave domain. Currently, efficient optical-to-microwave conversion is extremely difficult, as the detected microwave signal is weak and noisy. A novel circuit, containing a high-gain/low-noise microwave injection-locked oscillator, has been developed to improve the interface between the optical and microwave components. The circuit utilizes two FETs and a dielectric resonator, which serves as a frequency-dependent feedback element. The circuit, designed to operate at about 8 GHz, provides significant amplitude and phase noise suppression. In addition, the circuit realization is compatible with MMIC technology.

  16. Influence of phase delay profile on diffraction efficiency of liquid crystal optical phased array

    NASA Astrophysics Data System (ADS)

    Xu, Lin; Zhang, Jian; Wu, Li Ying

    2009-06-01

    The hardware structure and driving voltage of liquid crystal optical phased array (LCOPA) devices determine the produced phase delay characteristics. The phase delay profile influences directly the device's diffraction efficiency. In this paper, a sawtooth-shaped phase delay model of LCOPA was proposed to analyze quantitatively the influence factors of diffraction efficiency employing Fourier optics theory. Analysis results show that flyback region size is the main factor that affects diffraction efficiency. The influence extent varies with different maximum-phase-delays and grating periods. There exists an optimized curve between maximum-phase-delay and flyback region, and between maximum-phase-delay and grating period, individually. The smaller the grating period is or the larger the flyback region is, the more evident the optimization effect becomes, and the maximum increase ratio is up to 16%. Some feasible experiments were done to test theoretical analysis, and the experimental results agreed with the analysis results.

  17. Using Phased Array Ultrasonic Testing in Lieu of Radiography for Acceptance of Carbon Steel Piping Welds

    SciTech Connect

    Moran, Traci L.; Anderson, Michael T.; Cinson, Anthony D.; Crawford, Susan L.; Nove, Carol A.

    2014-08-01

    The Pacific Northwest National Laboratory (PNNL) is conducting studies for the U.S. Nuclear Regulatory Commission (NRC) to assess the capability, effectiveness, and reliability of ultrasonic testing (UT) as a replacement method for radiographic testing (RT) for volumetric examination of nuclear power plant (NPP) components. This particular study focused on evaluating the use of UT on carbon steel plate welds. Welding fabrication flaws included a combination of planar and volumetric types, e.g., incomplete fusion, lack of penetration, cracks, porosity, and slag inclusions. The examinations were conducted using phased-array (PA) UT techniques applied primarily for detection and flaw type characterization. This paper will discuss the results of using UT in lieu of RT for detection and classification of fabrication flaws in carbon steel plate welds.

  18. Acousto-optic liquid-crystal analog beam former for phased-array antennas.

    PubMed

    Riza, N A

    1994-06-10

    A compact phased-array antenna acousto-optic beam former with element-level analog phase (0-2π) and amplitude control using nematic-liquid-crystal display-type technology is experimentally demonstrated. Measurements indicate > 6-bit phase control and 52.6 dB of amplitude-attenuation control. High-quality error calibration and antenna sidelobe-level control is possible with this low-control-power analog beam former. Optical system options using rf Bragg cells or wideband Bragg cells are discussed, with the rf design being the current preferred approach. Transmit-receive beam forming based on frequency upconversion-downconversion by electronic mixing is introduced for the rf Bragg-cell beam former, and comparisons with digital beam forming are highlighted. A millimeter-wave signal generation and control optical architecture is described.

  19. Beam-Switch Transient Effects in the RF Path of the ICAPA Receive Phased Array Antenna

    NASA Technical Reports Server (NTRS)

    Sands, O. Scott

    2003-01-01

    When the beam of a Phased Array Antenna (PAA) is switched from one pointing direction to another, transient effects in the RF path of the antenna are observed. Testing described in the report has revealed implementation-specific transient effects in the RF channel that are associated with digital clocking pulses that occur with transfer of data from the Beam Steering Controller (BSC) to the digital electronics of the PAA under test. The testing described here provides an initial assessment of the beam-switch phenomena by digitally acquiring time series of the RF communications channel, under CW excitation, during the period of time that the beam switch transient occurs. Effects are analyzed using time-frequency distributions and instantaneous frequency estimation techniques. The results of tests conducted with CW excitation supports further Bit-Error-Rate (BER) testing of the PAA communication channel.

  20. Thermal imaging of plasma with a phased array antenna in QUEST

    SciTech Connect

    Mishra, Kishore Nagata, K.; Akimoto, R.; Banerjee, S.; Idei, H.; Zushi, H.; Hanada, K.; Hasegawa, M.; Nakamura, K.; Fujisawa, A.; Nagashima, Y.; Onchi, T.; Kuzmin, A.; Yamamoto, M. K.

    2014-11-15

    A thermal imaging system to measure plasma Electron Bernstein Emission (EBE) emanating from the mode conversion region in overdense plasma is discussed. Unlike conventional ECE/EBE imaging, this diagnostics does not employ any active mechanical scanning mirrors or focusing optics to scan for the emission cones in plasma. Instead, a standard 3 × 3 waveguide array antenna is used as a passive receiver to collect emission from plasma and imaging reconstruction is done by accurate measurements of phase and intensity of these signals by heterodyne detection technique. A broadband noise source simulating the EBE, is installed near the expected mode conversion region and its position is successfully reconstructed using phase array technique which is done in post processing.

  1. RF MEMS Phase Shifters and their Application in Phase Array Antennas

    NASA Technical Reports Server (NTRS)

    Scardelletti, Maximilian; Ponchak, George E.; Zaman, Afroz J.; Lee, Richard Q.

    2005-01-01

    Electronically scanned arrays are required for space based radars that are capable of tracking multiple robots, rovers, or other assets simultaneously and for beam-hopping communication systems between the various assets. ^Traditionally, these phased array antennas used GaAs Monolithic Microwave Integrated Circuit (MMIC) phase shifters, power amplifiers, and low noise amplifiers to amplify and steer the beam, but the development of RF MEMS switches over the past ten years has enabled system designers to consider replacing the GaAs MMIC phase shifters with RF Micro-Electro Mechanical System (MEMS) phase shifters. In this paper, the implication of replacing the relatively high loss GaAs MMICs with low loss MEMS phase shifters is investigated.

  2. Insonation of fixed porcine kidney by a prototype sector-vortex-phased array applicator.

    PubMed

    Umemura, S I; Holmes, K R; Frizzell, L A; Cain, C A

    1992-01-01

    The sector-vortex applicator, an ultrasound phased array with a geometric focus having multiple sectors and tracks, can directly synthesize, without scanning, diffuse focal patterns useful for hyperthermia. A perfused tissue phantom, consisting of an alcohol-fixed porcine kidney with thermocouples placed in the cortex, is insonated by a prototype sector-vortex applicator with 16 sectors and two tracks at an ultrasound frequency of 750 kHz. Steady-state temperature distributions are measured for a wide range of perfusion rates. Results demonstrate that the radius of the heated region can be controlled effectively by choosing the focal mode of the applicator as it is predicted by theoretical analysis. PMID:1479208

  3. Experimental validation of an 8 element EMAT phased array probe for longitudinal wave generation

    NASA Astrophysics Data System (ADS)

    Le Bourdais, Florian; Marchand, Benoit

    2015-03-01

    Sodium cooled Fast Reactors (SFR) use liquid sodium as a coolant. Liquid sodium being opaque, optical techniques cannot be applied to reactor vessel inspection. This makes it necessary to develop alternative ways of assessing the state of the structures immersed in the medium. Ultrasonic pressure waves are well suited for inspection tasks in this environment, especially using pulsed electromagnetic acoustic transducers (EMAT) that generate the ultrasound directly in the liquid sodium. The work carried out at CEA LIST is aimed at developing phased array EMAT probes conditioned for reactor use. The present work focuses on the experimental validation of a newly manufactured 8 element probe which was designed for beam forming imaging in a liquid sodium environment. A parametric study is carried out to determine the optimal setup of the magnetic assembly used in this probe. First laboratory tests on an aluminium block show that the probe has the required beam steering capabilities.

  4. System-level integrated circuit (SLIC) development for phased array antenna applications

    NASA Technical Reports Server (NTRS)

    Shalkhauser, K. A.; Raquet, C. A.

    1991-01-01

    A microwave/millimeter wave system-level integrated circuit (SLIC) being developed for use in phased array antenna applications is described. The program goal is to design, fabricate, test, and deliver an advanced integrated circuit that merges radio frequency (RF) monolithic microwave integrated circuit (MMIC) technologies with digital, photonic, and analog circuitry that provide control, support, and interface functions. As a whole, the SLIC will offer improvements in RF device performance, uniformity, and stability while enabling accurate, rapid, repeatable control of the RF signal. Furthermore, the SLIC program addresses issues relating to insertion of solid state devices into antenna systems, such as the reduction in number of bias, control, and signal lines. Program goals, approach, and status are discussed.

  5. System-Level Integrated Circuit (SLIC) development for phased array antenna applications

    NASA Technical Reports Server (NTRS)

    Shalkhauser, K. A.; Raquet, C. A.

    1991-01-01

    A microwave/millimeter wave system-level integrated circuit (SLIC) being developed for use in phased array antenna applications is described. The program goal is to design, fabricate, test, and deliver an advanced integrated circuit that merges radio frequency (RF) monolithic microwave integrated circuit (MMIC) technologies with digital, photonic, and analog circuitry that provide control, support, and interface functions. As a whole, the SLIC will offer improvements in RF device performance, uniformity, and stability while enabling accurate, rapid, repeatable control of the RF signal. Furthermore, the SLIC program addresses issues relating to insertion of solid state devices into antenna systems, such as the reduction in number of bias, control, and signal lines. Program goals, approach, and status are discussed.

  6. Phased array ultrasonic testing of dissimilar metal welds using geometric based referencing delay law technique

    NASA Astrophysics Data System (ADS)

    Han, Taeyoung; Schubert, Frank; Hillmann, Susanne; Meyendorf, Norbert

    2015-03-01

    Phased array ultrasonic testing (PAUT) techniques are widely used for the non-destructive testing (NDT) of austenitic welds to find defects like cracks. However, the propagation of ultrasound waves through the austenitic material is intricate due to its inhomogeneous and anisotropic nature. Such a characteristic leads beam path distorted which causes the signal to be misinterpreted. By employing a reference block which is cutout from the mockup of which the structure is a dissimilar metal weld (DMW), a new method of PAUT named as Referencing Delay Law Technique (RDLT) is introduced. With the RDLT, full matrix capture (FMC) was used for data acquisition. To reconstruct the images, total focusing method (TFM) was used. After the focal laws were calculated, PAUT was then performed. As a result, the flaws are more precisely positioned with significantly increased signal-to-noise ratio (SNR).

  7. Ultrasonic Phased Array Implementation of the Inside Diameter Creeping Wave Sizing Method

    SciTech Connect

    Timothy R. McJunkin; J. Mark Davis; Dennis C. Kunerth; Arthur D. Watkins

    2006-05-01

    This paper describes a technique for implementing the ultrasonic inside diameter (ID) creeping wave technique for detection and sizing ID connected defects using a phased array ultrasonic system. The technique uses multiple focal laws to produce the examination modes. The first focal law is designed to create a shear wave nominally at the critical angle for mode conversion to a longitudinal wave at the ID of a part, thus creating a creeping wave. This focal law is focused at the ID to improve sensitivity. The rest of the laws are designed to create tandem sound paths that progress up a vertical surface directly above the focal point of the creeping wave generation point. When a defect on the inner surface is detected with the creeping wave, the height of the defect can be measured from the response of a set of tandem laws without readjusting the position of the probe. Results from standard one-inch long notches of varying depths are presented.

  8. Experimental validation of an 8 element EMAT phased array probe for longitudinal wave generation

    SciTech Connect

    Le Bourdais, Florian Marchand, Benoit

    2015-03-31

    Sodium cooled Fast Reactors (SFR) use liquid sodium as a coolant. Liquid sodium being opaque, optical techniques cannot be applied to reactor vessel inspection. This makes it necessary to develop alternative ways of assessing the state of the structures immersed in the medium. Ultrasonic pressure waves are well suited for inspection tasks in this environment, especially using pulsed electromagnetic acoustic transducers (EMAT) that generate the ultrasound directly in the liquid sodium. The work carried out at CEA LIST is aimed at developing phased array EMAT probes conditioned for reactor use. The present work focuses on the experimental validation of a newly manufactured 8 element probe which was designed for beam forming imaging in a liquid sodium environment. A parametric study is carried out to determine the optimal setup of the magnetic assembly used in this probe. First laboratory tests on an aluminium block show that the probe has the required beam steering capabilities.

  9. Ultrasonic Phased Array Evaluation of Control Rod Drive Mechanism (CRDM) Nozzle Interference Fit and Weld Region

    SciTech Connect

    Cinson, Anthony D.; Crawford, Susan L.; MacFarlan, Paul J.; Mathews, Royce; Hanson, Brady D.; Diaz, Aaron A.

    2011-10-01

    In this investigation, non-destructive and destructive testing were used to evaluate potential boric acid leakage paths around an Alloy 600 CRDM penetration (Nozzle 63) from the North Anna Unit 2 reactor pressure vessel head that was removed from service in 2003. For this investigation, Nozzle 63 was examined using phased array ultrasonic testing. Prior to examining Nozzle 63, a CRDM penetration mockup with known notches and boric acid deposits was used to assess probe sensitivity, resolution and calibration. Following the non-destructive testing of Nozzle 63, the nozzle was destructively examined to visually assess the leak paths. These destructive and nondestructive results are compared and results are presented. The results of this investigation may be used by NRC to evaluate licensees’ volumetric leak path assessment methodologies and to support regulatory inspection requirements.

  10. Experimental instrumentation system for the Phased Array Mirror Extendible Large Aperture (PAMELA) test program

    NASA Technical Reports Server (NTRS)

    Boykin, William H., Jr.

    1993-01-01

    Adaptive optics are used in telescopes for both viewing objects with minimum distortion and for transmitting laser beams with minimum beam divergence and dance. In order to test concepts on a smaller scale, NASA MSFC is in the process of setting up an adaptive optics test facility with precision (fraction of wavelengths) measurement equipment. The initial system under test is the adaptive optical telescope called PAMELA (Phased Array Mirror Extendible Large Aperture). Goals of this test are: assessment of test hardware specifications for PAMELA application and the determination of the sensitivities of instruments for measuring PAMELA (and other adaptive optical telescopes) imperfections; evaluation of the PAMELA system integration effort and test progress and recommended actions to enhance these activities; and development of concepts and prototypes of experimental apparatuses for PAMELA.

  11. Theoretical analysis of H-Horn annular phased array system for heating deep-seated tumors.

    PubMed

    Tianquan, D; Zheng, L; Wei, R

    1991-01-01

    This paper discusses a type of annular phased array system--H-Horn APA. The phase and amplitude control of power deposition patterns for this system are theoretically analyzed at a frequency of 200 MHz. The formulas for calculating E-field and SAR for this APA system are derived, and can be applied to other type APA systems. Models of computerized tomography (CT) scans from liver and lung regions have been used, respectively, for predicting optimization of E-field and SAR patterns in the case of the relative phase and amplitude changes. It is shown that the techniques of the phase and amplitude control of SAR patterns result in more selectively and effectively heating of tumors situated eccentrically and deeply within bodies of patients. The APA hyperthermia described in this paper shows great promise, and it looks very useful for developing clinical applications.

  12. Ultra-sharp plasmonic resonances from monopole optical nanoantenna phased arrays

    SciTech Connect

    Li, Shi-Qiang; Bruce Buchholz, D.; Zhou, Wei; Ketterson, John B.; Ocola, Leonidas E.; Sakoda, Kazuaki; Chang, Robert P. H.

    2014-06-09

    Diffractively coupled plasmonic resonances possess both ultra-sharp linewidths and giant electric field enhancement around plasmonic nanostructures. They can be applied to create a new generation of sensors, detectors, and nano-optical devices. However, all current designs require stringent index-matching at the resonance condition that limits their applicability. Here, we propose and demonstrate that it is possible to relieve the index-matching requirement and to induce ultra-sharp plasmon resonances in an ordered vertically aligned optical nano-antenna phased array by transforming a dipole resonance to a monopole resonance with a mirror plane. Due to the mirror image effect, the monopole resonance not only retained the dipole features but also enhanced them. The engineered resonances strongly suppressed the radiative decay channel, resulting in a four-order of magnitude enhancement in local electric field and a Q-factor greater than 200.

  13. Rigorous investigation of the array-tilt aberration for hexagonal, optical phased arrays.

    PubMed

    Hyde, Milo W; Wyman, Jason E; Tyler, Glenn A

    2014-04-10

    An investigation of the array-tilt aberration for hexagonal, optical phased arrays is presented. The investigation begins with theoretical derivations of the far-zone radiated field, the array factor, and the far-field radiated power for the seven-element hexagonal array with array tilt present. Physical insights gained from this analysis are discussed. An analytical treatment of correlation-based array-tilt estimators is also undertaken. Two novel array-tilt estimation techniques are developed from the analysis. The new techniques are shown to be significantly more efficient computationally than the traditional estimation approach. Simulation and experimental results are presented to validate the new array-tilt estimation methods.

  14. AN ULTRASONIC PHASED ARRAY EVALUATION OF CAST AUSTENITIC STAINLESS STEEL PRESSURIZER SURGE LINE PIPING WELDS

    SciTech Connect

    Diaz, Aaron A.; Cinson, Anthony D.; Crawford, Susan L.; Moran, Traci L.; Anderson, Michael T.

    2010-07-22

    A set of circumferentially oriented thermal fatigue cracks (TFCs) were implanted into three cast austenitic stainless steel (CASS) pressurizer (PZR) surge-line specimens (pipe-to-elbow welds) that were fabricated using vintage CASS materials formed in the 1970s, and flaw responses from these cracks were used to evaluate detection and sizing performance of the phased-array (PA) ultrasonic testing (UT) methods applied. Four different custom-made PA probes were employed in this study, operating nominally at 800 kHz, 1.0 MHz, 1.5 MHz, and 2.0 MHz center frequencies. The CASS PZR surge-line specimens were polished and chemically etched to bring out the microstructures of both pipe and elbow segments. Additional studies were conducted and documented to address baseline CASS material noise and observe possible ultrasonic beam redirection phenomena.

  15. On-chip silicon optical phased array for two-dimensional beam steering.

    PubMed

    Kwong, David; Hosseini, Amir; Covey, John; Zhang, Yang; Xu, Xiaochuan; Subbaraman, Harish; Chen, Ray T

    2014-02-15

    A 16-element optical phased array integrated on chip is presented for achieving two-dimensional (2D) optical beam steering. The device is fabricated on the silicon-on-insulator platform with a 250 nm silicon device layer. Steering is achieved via a combination of wavelength tuning and thermo-optic phase shifting with a switching power of P(π)=20  mW per channel. Using a silicon waveguide grating with a polycrystalline silicon overlay enables narrow far field beam widths while mitigating the precise etching needed for conventional shallow etch gratings. Using this system, 2D steering across a 20°×15° field of view is achieved with a sidelobe level better than 10 dB and with beam widths of 1.2°×0.5°.

  16. Thermal imaging of plasma with a phased array antenna in QUEST.

    PubMed

    Mishra, Kishore; Idei, H; Zushi, H; Nagata, K; Akimoto, R; Yamamoto, M K; Hanada, K; Hasegawa, M; Nakamura, K; Fujisawa, A; Nagashima, Y; Banerjee, S; Onchi, T; Kuzmin, A

    2014-11-01

    A thermal imaging system to measure plasma Electron Bernstein Emission (EBE) emanating from the mode conversion region in overdense plasma is discussed. Unlike conventional ECE/EBE imaging, this diagnostics does not employ any active mechanical scanning mirrors or focusing optics to scan for the emission cones in plasma. Instead, a standard 3 × 3 waveguide array antenna is used as a passive receiver to collect emission from plasma and imaging reconstruction is done by accurate measurements of phase and intensity of these signals by heterodyne detection technique. A broadband noise source simulating the EBE, is installed near the expected mode conversion region and its position is successfully reconstructed using phase array technique which is done in post processing.

  17. LONG-TERM CALIBRATION STABILITY OF A RADIO ASTRONOMICAL PHASED ARRAY FEED

    SciTech Connect

    Elmer, Michael; Jeffs, Brian D.; Warnick, Karl F.

    2013-01-01

    There are many challenges associated with the implementation of a phased array feed for radio astronomy applications. Among these is the need to have an adequate set of calibration measurements so that reliable beamformers can be computed. Changes in the operating environment and temporal gain drift in the electronics contribute to calibration drift, which affects the beamformer performance. We will show that calibration measurements are relatively stable over a 5 day period and may remain so for up to 70 days or longer. We have incorporated the use of a calibration update system that has the potential to refresh a set of old calibrators, specifically correcting for electronic gain drift. However, the long-term variations that are present with fresh, current calibrators are greater than the degradation due to using an old calibration set, suggesting that, at this time, there is not a need for sophisticated calibration update systems or algorithms.

  18. Electron Cyclotron / Bernstein Wave Heating and Current Drive Experiments using Phased-array Antenna in QUEST

    SciTech Connect

    Idei, H.; Zushi, H.; Hanada, K.; Nakamura, K.; Fujisawa, A.; Hasegawa, M.; Yoshida, N.; Watanebe, H.; Tokunaga, K.; Nagashima, Y.; Kawasaki, S.; Nakashima, H.; Higashijima, A.; Sakamoto, M.; Ejiri, A.; Takase, Y.; Sakaguchi, M.; Kalinnikova, E.; Ishiguro, M.; Tashima, S.

    2011-12-23

    The phased-array antenna system for Electron Cyclotron/Bernstein Wave Heating and Current Drive experiments has been developed in the QUEST. The antenna was designed to excite a pure O-mode wave in the oblique injection for the O-X-B mode conversion experiments, and its good performances were confirmed at a low power level. The plasma current (<{approx}15 kA) with an aspect ratio of 1.5 was started up and sustained by only RF injection in the low-density operations. The long pulse discharge of 10 kA was also attained for 37 s. The new density window to sustain the plasma current was observed in the high-density plasmas. The single-null divertor configuration with the high plasma current (<{approx}25 kA) was attained in the 17 s plasma sustainment.

  19. Through-Weld Ultrasonic Phased Array Inspection Using Full Matrix Capture

    NASA Astrophysics Data System (ADS)

    Long, R.; Russell, J.; Cawley, P.

    2010-02-01

    Rolls-Royce and Imperial College are developing phased array inspections for welded stainless steel piping with an undressed weld cap. An inspection that proves particularly challenging requires ultrasonic waves to propagate across the irregular weld-cap profile, and through the structurally complex weld material. Simulations of ultrasonic wave propagation through the weld region were obtained using the CIVA software to predict the effect on inspection performance. Simulated and experimental data was collected as Full Matrix Capture (FMC) which was then processed using our own software with results then displayed in a Beta version of CIVA. An investigation was conducted to confirm the principle of updating delay laws for variations in material properties.

  20. Experimental analysis of beam pointing system based on liquid crystal optical phase array

    NASA Astrophysics Data System (ADS)

    Shi, Yubin; Zhang, Jianmin; Zhang, Zhen

    2016-06-01

    In this paper, we propose and demonstrate an elementary non-mechanical beam aiming and steering system with a single liquid crystal optical phase array (LC-OPA) and charge-coupled device (CCD). With the conventional method of beam steering control, the LC-OPA device can realize one dimensional beam steering continuously. An improved beam steering strategy is applied to realize two dimensional beam steering with a single LC-OPA. The whole beam aiming and steering system, including an LC-OPA and a retroreflective target, is controlled by the monitor. We test the feasibility of beam steering strategy both in one dimension and in two dimension at first, then the whole system is build up based on the improved strategy. The experimental results show that the max experimental pointing error is 56 µrad, and the average pointing error of the system is 19 µrad.

  1. Full-matrix capture and USB3.0 for open platform phased array instruments

    NASA Astrophysics Data System (ADS)

    Dao, Gavin; Lallement, Rémi; Carcreff, Ewen; Braconnier, Dominique

    2016-02-01

    Nondestructive evaluation (NDE) using ultrasonic waves is an efficient technique to assess industrial component integrity. The use of array probes enables inspection flexibility and advanced imaging techniques such as the total focusing method (TFM). In particular, the TFM imaging approach tremendously increases the quantity of data compared to conventional ultrasonic testing. Data transfer rates from the ultrasonic equipment to the computer are therefore continuously increasing due to large quantities of data and high speed inspections. In this work, we propose to use a USB 3.0 communication protocol for high speed throughput in a phased array device. To our knowledge, such protocol has not be proposed before for such an equipment. In this paper, we show that this protocol offers high transfer rates and is suitably adapted to ultrasonic inspection with array probes.

  2. High-extinction virtually imaged phased array-based Brillouin spectroscopy of turbid biological media

    NASA Astrophysics Data System (ADS)

    Fiore, Antonio; Zhang, Jitao; Shao, Peng; Yun, Seok Hyun; Scarcelli, Giuliano

    2016-05-01

    Brillouin microscopy has recently emerged as a powerful technique to characterize the mechanical properties of biological tissue, cell, and biomaterials. However, the potential of Brillouin microscopy is currently limited to transparent samples, because Brillouin spectrometers do not have sufficient spectral extinction to reject the predominant non-Brillouin scattered light of turbid media. To overcome this issue, we combined a multi-pass Fabry-Perot interferometer with a two-stage virtually imaged phased array spectrometer. The Fabry-Perot etalon acts as an ultra-narrow band-pass filter for Brillouin light with high spectral extinction and low loss. We report background-free Brillouin spectra from Intralipid solutions and up to 100 μm deep within chicken muscle tissue.

  3. The application of taylor weighting, digital phase shifters, and digital attenuators to phased-array antennas.

    SciTech Connect

    Brock, Billy C.

    2008-03-01

    Application of Taylor weighting (taper) to an antenna aperture can achieve low peak sidelobes, but combining the Taylor weighting with quantized attenuators and phase shifters at each radiating element will impact the performance of a phased-array antenna. An examination of array performance is undertaken from the simple point of view of the characteristics of the array factor. Design rules and guidelines for determining the Taylor-weighting parameters, the number of bits required for the digital phase shifter, and the dynamic range and number of bits required for the digital attenuator are developed. For a radar application, when each element is fed directly from a transmit/receive module, the total power radiated by the array will be reduced as a result of the taper. Consequently, the issue of whether to apply the taper on both transmit and receive configurations, or only on the receive configuration is examined with respect to two-way sidelobe performance.

  4. The Implications of Encoder/Modulator/ Phased Array Designs for Future Broadband LEO Communications

    NASA Technical Reports Server (NTRS)

    Vanderaar, Mark; Jensen, Chris A.; Terry, John D.

    1997-01-01

    In this paper we summarize the effects of modulation and channel coding on the design of wide angle scan, broadband, phased army antennas. In the paper we perform several trade studies. First, we investigate the amplifier back-off requirement as a function of variability of modulation envelope. Specifically, we contrast constant and non-constant envelope modulations, as well as single and multiple carrier schemes. Additionally, we address the issues an(f concerns of using pulse shaping filters with the above modulation types. Second, we quantify the effects of beam steering on the quality of data, recovery using selected modulation techniques. In particular, we show that the frequency response of the array introduces intersymbol interference for broadband signals and that the mode of operation for the beam steering controller may introduce additional burst or random errors. Finally, we show that the encoder/modulator design must be performed in conjunction with the phased array antenna design.

  5. MRI-compatible ultrasound heating system with ring-shaped phased arrays for breast tumor thermal therapy.

    PubMed

    Chen, Hung-Nien; Chen, Guan-Ming; Lin, Bo-Sian; Lien, Pi-Hsien; Chen, Yung-Yaw; Chen, Gin-Shin; Lin, Win-Li

    2013-01-01

    Therapeutic ultrasound transducers can carry out precise and efficient power deposition for tumor thermal therapy under the guidance of magnetic resonance imaging. For a better heating, organ-specific ultrasound transducers with precision location control system should be developed for tumors located at various organs. It is feasible to perform a better heating for breast tumor thermal therapy with a ring-shaped ultrasound phased-array transducer. In this study, we developed ring-shaped phased-array ultrasound transducers with 1.0 and 2.5 MHz and a precision location control system to drive the transducers to the desired location to sonicate the designated region. Both thermo-sensitive hydrogel phantom and ex vivo fresh pork were used to evaluate the heating performance of the transducers. The results showed that the ring-shaped phased array ultrasound transducers were very promising for breast tumor heating with the variation of heating patterns and without overheating the ribs.

  6. Acoustic investigation of wall jet over a backward-facing step using a microphone phased array

    NASA Astrophysics Data System (ADS)

    Perschke, Raimund F.; Ramachandran, Rakesh C.; Raman, Ganesh

    2015-02-01

    The acoustic properties of a wall jet over a hard-walled backward-facing step of aspect ratios 6, 3, 2, and 1.5 are studied using a 24-channel microphone phased array at Mach numbers up to M=0.6. The Reynolds number based on inflow velocity and step height assumes values from Reh = 3.0 ×104 to 7.2 ×105. Flow without and with side walls is considered. The experimental setup is open in the wall-normal direction and the expansion ratio is effectively 1. In case of flow through a duct, symmetry of the flow in the spanwise direction is lost downstream of separation at all but the largest aspect ratio as revealed by oil paint flow visualization. Hydrodynamic scattering of turbulence from the trailing edge of the step contributes significantly to the radiated sound. Reflection of acoustic waves from the bottom plate results in a modulation of power spectral densities. Acoustic source localization has been conducted using a 24-channel microphone phased array. Convective mean-flow effects on the apparent source origin have been assessed by placing a loudspeaker underneath a perforated flat plate and evaluating the displacement of the beamforming peak with inflow Mach number. Two source mechanisms are found near the step. One is due to interaction of the turbulent wall jet with the convex edge of the step. Free-stream turbulence sound is found to be peaked downstream of the step. Presence of the side walls increases free-stream sound. Results of the flow visualization are correlated with acoustic source maps. Trailing-edge sound and free-stream turbulence sound can be discriminated using source localization.

  7. Ultrasonic Inspection System for Automated Round-Bar Based on Phased Array Technique

    NASA Astrophysics Data System (ADS)

    Schenk, Gottfried; Brackrock, Daniel; Brekow, Gerhard; Kreutzbruck, Marc; Deutsch, W. A. K.; Joswig, M.; Maxam, K.; Schuster, V.

    2010-02-01

    Within a know-how transfer project funded by the government conventional ultrasonic technique was replaced by phased array technique for automated round-bar testing. Instead of applying a great number of conventional probes to achieve acceptable volume coverage we used curved linear arrays. The benefits of phased array technique such as programmable skew angles, beamforming and beam positions, led not only to a significant decrease in inspection time, but also the number of probes could be substantially reduced . Finally, the testing parameters for a large range of bar-diameters could be adapted by software control instead of time-consuming mechanical replacement. The probe-design was carried out by a proprietary modelling program. Both the theoretical calculations as well as the latter experimental verifications revealed significant advantages of curved arrays versus the planar types. A radial oriented probe offers perfect adaption to the cylindrical shape of the specimen allowing wide variations of the sound field. Thus beam direction, beam size and beam position could be optimized with respect to a minimum of inspection cycles, as inspections have to be executed in-line during the production. A number of laboratory tests were carried out on special test components. In order to achieve an optimal performance of the reference rod we implemented three different types of reference reflectors: (i) flat-bottom-holes with diameters of 0.8 mm and 1.2 mm, (ii) side-drilled-holes with a diameter of 0.7 mm for the detection of volumetric flaws, and (iii) notches with a depth of 0.2 mm and 0.5 mm for the detection of surface-oriented defects. All laboratory tests were carried out with the COMPAS-XXL inspection system, a proprietary development of BAM.

  8. Passive monitoring using a combination of focused and phased array radiometry: a simulation study.

    PubMed

    Farantatos, Panagiotis; Karanasiou, Irene S; Uzunoglu, Nikolaos

    2011-01-01

    Aim of this simulation study is to use the focusing properties of a conductive ellipsoidal reflector in conjunction with directive phased microwave antenna configurations in order to achieve brain passive monitoring with microwave radiometry. One of the main modules of the proposed setup which ensures the necessary beamforming and focusing on the body and brain areas of interest is a symmetrical axis ellipsoidal conductive wall cavity. The proposed system operates in an entirely non-invasive contactless manner providing temperature and/or conductivity variations monitoring and is designed to also provide hyperthermia treatment. In the present paper, the effect of the use of patch antennas as receiving antennas on the system's focusing properties and specifically the use of phased array setups to achieve scanning of the areas under measurement is investigated. Extensive simulations to compute the electric field distributions inside the whole ellipsoidal reflector and inside two types of human head models were carried out using single and two element microstrip patch antennas. The results show that clear focusing (creation of "hot spots") inside the head models is achieved at 1.53GHz. In the case of the two element antennas, the "hot spot" performs a linear scan around the brain area of interest while the phase difference of the two microstrip patch antennas significantly affects the way the scanning inside the head model is achieved. In the near future, phased array antennas with multiband and more elements will be used in order to enhance the system scanning properties toward the acquisition of tomography images without the need of subject movement.

  9. Using Low-Frequency Phased Arrays to Detect Cracks in Cast Austenitic Piping Components

    SciTech Connect

    Anderson, Michael T.; Cumblidge, Stephen E.; Doctor, Steven R.

    2005-12-30

    As part of a multi-year program funded by the United States Nuclear Regulatory Commission (US NRC) to address NDE reliability of inservice inspection (ISI) programs, recent studies conducted at the Pacific N¬orthwest National Laboratory (PNNL) in Richland, Washington, have focused on assessing novel NDE approaches for the inspection of coarse-grained, cast stainless steel reactor components. The primary objective of this work is to provide information to the US NRC on the utility, effec¬tiveness and reliability of ultrasonic testing (UT) and eddy current testing (ET) inspection techniques as related to the ISI of primary piping components in pressurized water reactors (PWRs). This paper describes progress, recent developments and early results from an assessment of a portion of this work relating to the ultrasonic low frequency phased array inspection technique. Westinghouse Owner’s Group (WOG) cast stainless steel pipe segments with thermal and mechanical fatigue cracks, PNNL samples containing thermal fatigue cracks and several blank vintage specimens having very coarse grains that are representative of early centrifugally cast piping installed in PWRs, are being used for assessing the inspection method. The phased array approach was implemented using an R/D Tech Tomoscan III system operating at 1.0 MHz and 500 kHz, providing composite volumetric images of the samples. Several dual, transmit-receive, custom designed low-frequency arrays are employed in laboratory trials. Results from laboratory studies for assessing detection of thermal and mechanical fatigue cracks in cast stainless steel piping welds are discussed. This work was sponsored by the U.S. Nuclear Regulatory Commission under Contract DE-AC06-76RLO 1830; NRC JCN Y6604; Mr. Wallace Norris, Program Monitor.

  10. Phased Array-Fed Reflector (PAFR) Antenna Architectures for Space-Based Sensors

    NASA Technical Reports Server (NTRS)

    Cooley, Michael E.

    2014-01-01

    Communication link and target ranges for satellite communications (SATCOM) and space-based sensors (e.g. radars) vary from approximately 1000 km (for LEO satellites) to 35,800 km (for GEO satellites). At these long ranges, large antenna gains are required and legacy payloads have usually employed large reflectors with single beams that are either fixed or mechanically steered. For many applications, there are inherent limitations that are associated with the use of these legacy antennas/payloads. Hybrid antenna designs using Phased Array Fed Reflectors (PAFRs) provide a compromise between reflectors and Direct Radiating phased Arrays (DRAs). PAFRs provide many of the performance benefits of DRAs while utilizing much smaller, lower cost (feed) arrays. The primary limitation associated with hybrid PAFR architectures is electronic scan range; approximately +/-5 to +/- 10 degrees is typical, but this range depends on many factors. For LEO applications, the earth FOV is approximately +/-55 degrees which is well beyond the range of electronic scanning for PAFRs. However, for some LEO missions, limited scanning is sufficient or the CONOPS and space vehicle designs can be developed to incorporate a combination mechanical slewing and electronic scanning. In this paper, we review, compare and contrast various PAFR architectures with a focus on their general applicability to space missions. We compare the RF performance of various PAFR architectures and describe key hardware design and implementation trades. Space-based PAFR designs are highly multi-disciplinary and we briefly address key hardware engineering design areas. Finally, we briefly describe two PAFR antenna architectures that have been developed at Northrop Grumman.

  11. An Automated Dosing Method for a HIFU Device Containing Multiple Phased Arrays

    NASA Astrophysics Data System (ADS)

    Zeng, Xiaozheng Jenny; Barnes, Steve; Sekins, K. Michael

    2010-03-01

    A device containing multiple 2D therapeutic and imaging ultrasound phased arrays is proposed for acoustic hemostasis applications. An automated dosing algorithm selects the optimal combination of therapeutic phased arrays and calculates the acoustic power required of each array. Simulations demonstrate that therapeutic temperatures (70° C

  12. Passive monitoring using a combination of focused and phased array radiometry: a simulation study.

    PubMed

    Farantatos, Panagiotis; Karanasiou, Irene S; Uzunoglu, Nikolaos

    2011-01-01

    Aim of this simulation study is to use the focusing properties of a conductive ellipsoidal reflector in conjunction with directive phased microwave antenna configurations in order to achieve brain passive monitoring with microwave radiometry. One of the main modules of the proposed setup which ensures the necessary beamforming and focusing on the body and brain areas of interest is a symmetrical axis ellipsoidal conductive wall cavity. The proposed system operates in an entirely non-invasive contactless manner providing temperature and/or conductivity variations monitoring and is designed to also provide hyperthermia treatment. In the present paper, the effect of the use of patch antennas as receiving antennas on the system's focusing properties and specifically the use of phased array setups to achieve scanning of the areas under measurement is investigated. Extensive simulations to compute the electric field distributions inside the whole ellipsoidal reflector and inside two types of human head models were carried out using single and two element microstrip patch antennas. The results show that clear focusing (creation of "hot spots") inside the head models is achieved at 1.53GHz. In the case of the two element antennas, the "hot spot" performs a linear scan around the brain area of interest while the phase difference of the two microstrip patch antennas significantly affects the way the scanning inside the head model is achieved. In the near future, phased array antennas with multiband and more elements will be used in order to enhance the system scanning properties toward the acquisition of tomography images without the need of subject movement. PMID:22254358

  13. High-frequency energy in singing and speech

    NASA Astrophysics Data System (ADS)

    Monson, Brian Bruce

    While human speech and the human voice generate acoustical energy up to (and beyond) 20 kHz, the energy above approximately 5 kHz has been largely neglected. Evidence is accruing that this high-frequency energy contains perceptual information relevant to speech and voice, including percepts of quality, localization, and intelligibility. The present research was an initial step in the long-range goal of characterizing high-frequency energy in singing voice and speech, with particular regard for its perceptual role and its potential for modification during voice and speech production. In this study, a database of high-fidelity recordings of talkers was created and used for a broad acoustical analysis and general characterization of high-frequency energy, as well as specific characterization of phoneme category, voice and speech intensity level, and mode of production (speech versus singing) by high-frequency energy content. Directionality of radiation of high-frequency energy from the mouth was also examined. The recordings were used for perceptual experiments wherein listeners were asked to discriminate between speech and voice samples that differed only in high-frequency energy content. Listeners were also subjected to gender discrimination tasks, mode-of-production discrimination tasks, and transcription tasks with samples of speech and singing that contained only high-frequency content. The combination of these experiments has revealed that (1) human listeners are able to detect very subtle level changes in high-frequency energy, and (2) human listeners are able to extract significant perceptual information from high-frequency energy.

  14. Thermal therapy for breast tumors by using a cylindrical ultrasound phased array with multifocus pattern scanning: a preliminary numerical study

    NASA Astrophysics Data System (ADS)

    Ho, Cheng-Shiao; Ju, Kuen-Cheng; Cheng, Tze-Yuan; Chen, Yung-Yaw; Lin, Win-Li

    2007-08-01

    The purpose of this study is to investigate the feasibility of using a 1 MHz cylindrical ultrasound phased array with multifocus pattern scanning to produce uniform heating for breast tumor thermal therapy. The breast was submerged in water and surrounded by the cylindrical ultrasound phased array. A multifocus pattern was generated and electrically scanned by the phased array to enlarge the treatment lesion in single heating. To prevent overheating normal tissues, a large planning target volume (PTV) would be divided into several planes with several subunits on each plane and sequentially treated with a cooling phase between two successive heatings of the subunit. Heating results for different target temperatures (Ttgt), blood perfusion rates and sizes of the PTV have been studied. Furthermore, a superficial breast tumor with different water temperatures was also studied. Results indicated that a higher target temperature would produce a slightly larger thermal lesion, and a higher blood perfusion rate would not affect the heating lesion size but increase the heating time significantly. The acoustic power deposition and temperature elevations in ribs can be minimized by orienting the acoustic beam from the ultrasound phased array approximately parallel to the ribs. In addition, a large acoustic window on the convex-shaped breast surface for the proposed ultrasound phased array and the cooling effect of water would prevent the skin overheating for the production of a lesion at any desired location. This study demonstrated that the proposed cylindrical ultrasound phased array can provide effective heating for breast tumor thermal therapy without overheating the skin and ribs within a reasonable treatment time.

  15. Phased-array ultrasound technology enhances accuracy of dual frequency ultrasound measurements - towards improved ultrasound bone diagnostics.

    PubMed

    Linder, Hans; Malo, Markus K H; Liukkonen, Jukka; Jurvelin, Jukka S; Töyräs, Juha

    2016-08-01

    Overlying soft tissues attenuate ultrasound backscattered from bone, complicating diagnostics of osteoporosis at the most important fracture sites. Dual-frequency ultrasound technique (DFUS) has been proposed to solve this problem through determination of thickness and composition of overlying soft tissue. This study applies DFUS technique for the first time with a phased-array transducer to investigate if the thickness of two interfering layers (oil and water) can be accurately determined in a variety of configurations. Results indicate that DFUS may be used with phased-array ultrasound systems, making them a suitable combination to consider in future development of clinical in vivo ultrasound methodologies. PMID:27187271

  16. Phased-array ultrasound technology enhances accuracy of dual frequency ultrasound measurements - towards improved ultrasound bone diagnostics.

    PubMed

    Linder, Hans; Malo, Markus K H; Liukkonen, Jukka; Jurvelin, Jukka S; Töyräs, Juha

    2016-08-01

    Overlying soft tissues attenuate ultrasound backscattered from bone, complicating diagnostics of osteoporosis at the most important fracture sites. Dual-frequency ultrasound technique (DFUS) has been proposed to solve this problem through determination of thickness and composition of overlying soft tissue. This study applies DFUS technique for the first time with a phased-array transducer to investigate if the thickness of two interfering layers (oil and water) can be accurately determined in a variety of configurations. Results indicate that DFUS may be used with phased-array ultrasound systems, making them a suitable combination to consider in future development of clinical in vivo ultrasound methodologies.

  17. Quantum inductance and high frequency oscillators in graphene nanoribbons.

    PubMed

    Begliarbekov, Milan; Strauf, Stefan; Search, Christopher P

    2011-04-22

    Here we investigate high frequency AC transport through narrow graphene nanoribbons with top-gate potentials that form a localized quantum dot. We show that as a consequence of the finite dwell time of an electron inside the quantum dot (QD), the QD behaves like a classical inductor at sufficiently high frequencies ω ≥ GHz. When the geometric capacitance of the top-gate and the quantum capacitance of the nanoribbon are accounted for, the admittance of the device behaves like a classical serial RLC circuit with resonant frequencies ω ∼ 100-900 GHz and Q-factors greater than 10(6). These results indicate that graphene nanoribbons can serve as all-electronic ultra-high frequency oscillators and filters, thereby extending the reach of high frequency electronics into new domains.

  18. High-frequency matrix converter with square wave input

    DOEpatents

    Carr, Joseph Alexander; Balda, Juan Carlos

    2015-03-31

    A device for producing an alternating current output voltage from a high-frequency, square-wave input voltage comprising, high-frequency, square-wave input a matrix converter and a control system. The matrix converter comprises a plurality of electrical switches. The high-frequency input and the matrix converter are electrically connected to each other. The control system is connected to each switch of the matrix converter. The control system is electrically connected to the input of the matrix converter. The control system is configured to operate each electrical switch of the matrix converter converting a high-frequency, square-wave input voltage across the first input port of the matrix converter and the second input port of the matrix converter to an alternating current output voltage at the output of the matrix converter.

  19. High frequency ultrasound with color Doppler in dermatology*

    PubMed Central

    Barcaui, Elisa de Oliveira; Carvalho, Antonio Carlos Pires; Lopes, Flavia Paiva Proença Lobo; Piñeiro-Maceira, Juan; Barcaui, Carlos Baptista

    2016-01-01

    Ultrasonography is a method of imaging that classically is used in dermatology to study changes in the hypoderma, as nodules and infectious and inflammatory processes. The introduction of high frequency and resolution equipments enabled the observation of superficial structures, allowing differentiation between skin layers and providing details for the analysis of the skin and its appendages. This paper aims to review the basic principles of high frequency ultrasound and its applications in different areas of dermatology. PMID:27438191

  20. High frequency single mode traveling wave structure for particle acceleration

    NASA Astrophysics Data System (ADS)

    Ivanyan, M. I.; Danielyan, V. A.; Grigoryan, B. A.; Grigoryan, A. H.; Tsakanian, A. V.; Tsakanov, V. M.; Vardanyan, A. S.; Zakaryan, S. V.

    2016-09-01

    The development of the new high frequency slow traveling wave structures is one of the promising directions in accomplishment of charged particles high acceleration gradient. The disc and dielectric loaded structures are the most known structures with slowly propagating modes. In this paper a large aperture high frequency metallic two-layer accelerating structure is studied. The electrodynamical properties of the slowly propagating TM01 mode in a metallic tube with internally coated low conductive thin layer are examined.

  1. High frequency, small signal MH loops of ferromagnetic thin films

    NASA Technical Reports Server (NTRS)

    Grimes, C. A.; Ong, K. G.

    2000-01-01

    A method is presented for transforming the high frequency bias susceptibility measurements of ferromagnetic thin films into the form of a MH loop with, depending upon the measurement geometry, the y-axis zero crossing giving a measure of the coercive force or anisotropy field. The loops provide a measure of the quantitative and qualitative high frequency switching properties of ferromagnetic thin films. c2000 American Institute of Physics.

  2. Development of Radar Control system for Multi-mode Active Phased Array Radar for atmospheric probing

    NASA Astrophysics Data System (ADS)

    Yasodha, Polisetti; Jayaraman, Achuthan; Thriveni, A.

    2016-07-01

    Modern multi-mode active phased array radars require highly efficient radar control system for hassle free real time radar operation. The requirement comes due to the distributed architecture of the active phased array radar, where each antenna element in the array is connected to a dedicated Transmit-Receive (TR) module. Controlling the TR modules, which are generally few hundreds in number, and functioning them in synchronisation, is a huge task during real time radar operation and should be handled with utmost care. Indian MST Radar, located at NARL, Gadanki, which is established during early 90's, as an outcome of the middle atmospheric program, is a remote sensing instrument for probing the atmosphere. This radar has a semi-active array, consisting of 1024 antenna elements, with limited beam steering, possible only along the principle planes. To overcome the limitations and difficulties, the radar is being augmented into fully active phased array, to accomplish beam agility and multi-mode operations. Each antenna element is excited with a dedicated 1 kW TR module, located in the field and enables to position the radar beam within 20° conical volume. A multi-channel receiver makes the radar to operate in various modes like Doppler Beam Swinging (DBS), Spaced Antenna (SA), Frequency Domain Interferometry (FDI) etc. Present work describes the real-time radar control (RC) system for the above described active phased array radar. The radar control system consists of a Spartan 6 FPGA based Timing and Control Signal Generator (TCSG), and a computer containing the software for controlling all the subsystems of the radar during real-time radar operation and also for calibrating the radar. The main function of the TCSG is to generate the control and timing waveforms required for various subsystems of the radar. Important components of the RC system software are (i) TR module configuring software which does programming, controlling and health parameter monitoring of the

  3. Development of Radar Control system for Multi-mode Active Phased Array Radar for atmospheric probing

    NASA Astrophysics Data System (ADS)

    Yasodha, Polisetti; Jayaraman, Achuthan; Thriveni, A.

    2016-07-01

    Modern multi-mode active phased array radars require highly efficient radar control system for hassle free real time radar operation. The requirement comes due to the distributed architecture of the active phased array radar, where each antenna element in the array is connected to a dedicated Transmit-Receive (TR) module. Controlling the TR modules, which are generally few hundreds in number, and functioning them in synchronisation, is a huge task during real time radar operation and should be handled with utmost care. Indian MST Radar, located at NARL, Gadanki, which is established during early 90's, as an outcome of the middle atmospheric program, is a remote sensing instrument for probing the atmosphere. This radar has a semi-active array, consisting of 1024 antenna elements, with limited beam steering, possible only along the principle planes. To overcome the limitations and difficulties, the radar is being augmented into fully active phased array, to accomplish beam agility and multi-mode operations. Each antenna element is excited with a dedicated 1 kW TR module, located in the field and enables to position the radar beam within 20° conical volume. A multi-channel receiver makes the radar to operate in various modes like Doppler Beam Swinging (DBS), Spaced Antenna (SA), Frequency Domain Interferometry (FDI) etc. Present work describes the real-time radar control (RC) system for the above described active phased array radar. The radar control system consists of a Spartan 6 FPGA based Timing and Control Signal Generator (TCSG), and a computer containing the software for controlling all the subsystems of the radar during real-time radar operation and also for calibrating the radar. The main function of the TCSG is to generate the control and timing waveforms required for various subsystems of the radar. Important components of the RC system software are (i) TR module configuring software which does programming, controlling and health parameter monitoring of the

  4. SweepSAR: Beam-forming on Receive Using a Reflector-Phased Array Feed Combination for Spaceborne SAR

    NASA Technical Reports Server (NTRS)

    Freeman, A.; Krieger, G.; Rosen, P.; Younis, M.; Johnson, W. T. K.; Huber, S.; Jordan, R.; Moreira, A.

    2012-01-01

    In this paper, an alternative approach is described that is suited for longer wavelength SARs in particular, employing a large, deployable reflector antenna and a much simpler phased array feed. To illuminate a wide swath, a substantial fraction of the phased array feed is excited on transmit to sub-illuminate the reflector. Shorter transmit pulses are required than for conventional SAR. On receive, a much smaller portion of the phased array feed is used to collect the return echo, so that a greater portion of the reflector antenna area is used. The locus of the portion of the phased array used on receive is adjusted using an analog beam steering network, to 'sweep' the receive beam(s) across the illuminated swath, tracking the return echo. This is similar in some respects to the whiskbroom approach to optical sensors, hence the name: SweepSAR.SweepSAR has advantages over conventional SAR in that it requires less transmit power, and if the receive beam is narrow enough, it is relatively immune to range ambiguities. Compared to direct radiating arrays with digital beam- forming, it is much simpler to implement, uses currently available technologies, is better suited for longer wavelength systems, and does not require extremely high data rates or onboard processing.

  5. Recirculating photonic filter: a wavelength-selective time delay for optically controlled phased-array antenna

    NASA Astrophysics Data System (ADS)

    Yegnanarayanan, Siva; Trinh, Paul D.; Jalali, Bahram

    1996-11-01

    A wavelength-selective photonic time delay filter is proposed and demonstrated. The device consists of an optical phased-array waveguide grating in a recirculating feedback configuration. It can function as a true-time-delay generator for squint-free beam steering in optically- controlled phased-array antennas. As the photonic filter uses the optical carrier wavelength to select the desired time delay, a one-to-one map is established between the optical carrier wavelength and the desired antenna direction, thus eliminating complex switching networks required to select the appropriate delay line. The proposed device can also function as the encoder/decoder in wavelength-CDMA. The concept uses a waveguide prism in a symmetric feedback (recirculating) configuration. The modulated optical carrier is steered by the waveguide prism to the appropriate integrated delay line depending on the carrier wavelength. The signal is delayed and is fed back into the symmetric input port. The prism then focuses the delayed beam into the common output port. Thus three sequential operations are performed: (1) wavelength demultiplexing, (2) time delay, and (3) wavelength multiplexing. It is important to note that the recirculating photonic filter has no 1/N loss; all the power at a given wavelength is diffracted into the output port. Furthermore, high resolution (6 - 8 bits) can be obtained in a compact integrated device. A prototype regular recirculating photonic filter true-time delay device was realized using a 8-channel arrayed-waveguide grating demultiplexer and external (off-chip) fiber delay lines. The grating was fabricated in the silica waveguide technology with 0.8 nm channel spacing (FSR equals 6.4 nm) and operating in the 1.5 micrometers wavelength range. Light from an external cavity tunable laser was rf modulated at 10 - 40 MHz and was coupled into the arrayed waveguide grating chip and time/phase measurements were performed sing a digital oscilloscope. Feedback delay

  6. Development and Observation of the Phase Array Radar at X band

    NASA Astrophysics Data System (ADS)

    Ushio, T.; Shimamura, S.; Wu, T.; Kikuchi, H.; Yoshida, S.; Kawasaki, Z.; Mizutani, F.; Wada, M.; Satoh, S.; Iguchi, T.

    2013-12-01

    A new Phased Array Radar (PAR) system for thunderstorm observation has been developed by Toshiba Corporation and Osaka University under a grant of NICT, and installed in Osaka University, Japan last year. It is now well known that rapidly evolving severe weather phenomena (e.g., microbursts, severe thunderstorms, tornadoes) are a threat to our lives particularly in a densely populated area and is closely related to the production of lightning discharges. Over the past decade, mechanically rotating radar systems at the C-band or S-band have been proved to be effective for weather surveillance especially in a wide area more than 100 km in range. However, severe thunderstorm sometimes develops rapidly on the temporal and spatial scales comparable to the resolution limit (-10 min. and -500m) of typical S-band or C-band radar systems, and cannot be fully resolved with these radar systems. In order to understand the fundamental process and dynamics of such fast changing weather phenomena like lightning and tornado producing thunderstorm, volumetric observations with both high temporal and spatial resolution are required. The phased array radar system developed has the unique capability of scanning the whole sky with 100m and 10 to 30 second resolution up to 60 km. The system adopts the digital beam forming technique for elevation scanning and mechanically rotates the array antenna in azimuth direction within 10 to 30 seconds. The radar transmits a broad beam of several degrees with 24 antenna elements and receives the back scattered signal with 128 elements digitizing at each elements. Then by digitally forming the beam in the signal processor, the fast scanning is realized. After the installation of the PAR system in Osaka University, the initial observation campaign was conducted in Osaka urban area with Ku-band Broad Band Radar (BBR) network, C-band weather radar, and lightning location system. The initial comparison with C band radar system shows that the developed

  7. Digital printing

    NASA Astrophysics Data System (ADS)

    Sobotka, Werner K.

    1997-02-01

    Digital printing is described as a tool to replace conventional printing machines completely. Still this goal was not reached until now with any of the digital printing technologies to be described in the paper. Productivity and costs are still the main parameters and are not really solved until now. Quality in digital printing is no problem anymore. Definition of digital printing is to transfer digital datas directly on the paper surface. This step can be carried out directly or with the use of an intermediate image carrier. Keywords in digital printing are: computer- to-press; erasable image carrier; image carrier with memory. Digital printing is also the logical development of the new digital area as it is pointed out in Nicholas Negropotes book 'Being Digital' and also the answer to networking and Internet technologies. Creating images text and color in one country and publishing the datas in another country or continent is the main advantage. Printing on demand another big advantage and last but not least personalization the last big advantage. Costs and being able to coop with this new world of prepress technology is the biggest disadvantage. Therefore the very optimistic growth rates for the next few years are really nonexistent. The development of complete new markets is too slow and the replacing of old markets is too small.

  8. Printed electronics

    NASA Technical Reports Server (NTRS)

    Crain, John M. (Inventor); Lettow, John S. (Inventor); Aksay, Ilhan A. (Inventor); Korkut, Sibel A. (Inventor); Chiang, Katherine S. (Inventor); Chen, Chuan-hua (Inventor); Prud'Homme, Robert K. (Inventor)

    2012-01-01

    Printed electronic device comprising a substrate onto at least one surface of which has been applied a layer of an electrically conductive ink comprising functionalized graphene sheets and at least one binder. A method of preparing printed electronic devices is further disclosed.

  9. Printed Electronics

    NASA Technical Reports Server (NTRS)

    Crain, John M. (Inventor); Lettow, John S. (Inventor); Aksay, Ilhan A. (Inventor); Korkut, Sibel A. (Inventor); Chiang, Katherine S. (Inventor); Chen, Chuan-Hua (Inventor); Prud'Homme, Robert K. (Inventor)

    2014-01-01

    Printed electronic device comprising a substrate onto at least one surface of which has been applied a layer of an electrically conductive ink comprising functionalized graphene sheets and at least one binder. A method of preparing printed electronic devices is further disclosed.

  10. Printed Electronics

    NASA Technical Reports Server (NTRS)

    Crain, John M. (Inventor); Lettow, John S. (Inventor); Aksay, Ilhan A. (Inventor); Korkut, Sibel (Inventor); Chiang, Katherine S. (Inventor); Chen, Chuan-Hua (Inventor); Prud'Homme, Robert K. (Inventor)

    2015-01-01

    Printed electronic device comprising a substrate onto at least one surface of which has been applied a layer of an electrically conductive ink comprising functionalized graphene sheets and at least one binder. A method of preparing printed electronic devices is further disclosed.

  11. Control of the external photoluminescent quantum yield of emitters coupled to nanoantenna phased arrays

    SciTech Connect

    Guo, Ke; Verschuuren, Marc A.; Lozano, Gabriel

    2015-08-21

    Optical losses in metals represent the largest limitation to the external quantum yield of emitters coupled to plasmonic antennas. These losses can be at the emission wavelength, but they can be more important at shorter wavelengths, i.e., at the excitation wavelength of the emitters, where the conductivity of metals is usually lower. We present accurate measurements of the absolute external photoluminescent quantum yield of a thin layer of emitting material deposited over a periodic nanoantenna phased array. Emission and absorptance measurements of the sample are performed using a custom-made setup including an integrating sphere and variable angle excitation. The measurements reveal a strong dependence of the external quantum yield on the angle at which the optical field excites the sample. Such behavior is attributed to the coupling between far-field illumination and near-field excitation mediated by the collective resonances supported by the array. Numerical simulations confirm that the inherent losses associated with the metal can be greatly reduced by selecting an optimum angle of illumination, which boosts the light conversion efficiency in the emitting layer. This combined experimental and numerical characterization of the emission from plasmonic arrays reveals the need to carefully design the illumination to achieve the maximum external quantum yield.

  12. Extension of DAMAS Phased Array Processing for Spatial Coherence Determination (DAMAS-C)

    NASA Technical Reports Server (NTRS)

    Brooks, Thomas F.; Humphreys, William M., Jr.

    2006-01-01

    The present study reports a new development of the DAMAS microphone phased array processing methodology that allows the determination and separation of coherent and incoherent noise source distributions. In 2004, a Deconvolution Approach for the Mapping of Acoustic Sources (DAMAS) was developed which decoupled the array design and processing influence from the noise being measured, using a simple and robust algorithm. In 2005, three-dimensional applications of DAMAS were examined. DAMAS has been shown to render an unambiguous quantitative determination of acoustic source position and strength. However, an underlying premise of DAMAS, as well as that of classical array beamforming methodology, is that the noise regions under study are distributions of statistically independent sources. The present development, called DAMAS-C, extends the basic approach to include coherence definition between noise sources. The solutions incorporate cross-beamforming array measurements over the survey region. While the resulting inverse problem can be large and the iteration solution computationally demanding, it solves problems no other technique can approach. DAMAS-C is validated using noise source simulations and is applied to airframe flap noise test results.

  13. MIMO based optical phased array technology with electronic beam steering for laser radar applications

    NASA Astrophysics Data System (ADS)

    Sharma, Neha; Zmuda, Henry

    2010-04-01

    This paper will address the analysis and design of an electronically scanned phased array laser radar (ladar) system utilizing the techniques of multi-input multi-output (MIMO) array design. MIMO radar is has attracted much attention recently from both researchers and practitioners alike due to its significant potential for advancing the state-of-the-art RF radar technology. The laser radar architecture presented stands to gain significant inroads on the ability to apply RF array processing methods to laser radar systems in several ways. Specifically, using MIMO array design concepts, it is shown that the resolution of the ladar array can substantially exceed the diffraction limited resolution of a conventional array. Additionally, the use of array methods provides the capability to electronically steer the aperture, thus avoiding the mechanical beam scanning methods generally encountered in laser radar systems. Finally, by using an array of radiators, an increase in total radiated power is achieved, relieving the power burden on a single laser. The problems traditionally encountered in applying conventional array techniques to laser/detector arrays, for example, the inability to achieve half-wavelength spacing or the surfacing of source coherence issues, actually work to one's advantage when viewed in the MIMO paradigm. It is anticipated that the successful implementation of this system will significantly advance the state-of-the-art of laser radar capabilities for high speed imaging, target detection, tracking, and signature analysis.

  14. Optical phase-locked loop signal sources for phased-array communications antennas

    NASA Astrophysics Data System (ADS)

    Langley, Lloyd N.; Edge, Colin; Wale, Michael J.; Gliese, Ulrik B.; Seeds, Alwyn J.; Walton, Channing; Wright, James G.; Coryell, Louis A.

    1997-10-01

    A coherent, optical heterodyne approach to signal generation and beamforming is particularly advantageous in multi-beam mobile phased arrays. Use of optical technology allows an optimum distribution of weight and power to be achieved between the antenna face and central electronics, together with an efficient implementation of the beamforming function and a modular design approach in which the basic building blocks are frequency-independent. Systems of this type employ a pair of optical carriers with a difference frequency equal to the required microwave signal. Phased- locking is necessary in order to achieve sufficiently low phase noise in the radio communication link. Optical phase locked loops (OPLLs) have been shown to be potential candidates for this application, yet work still needs to be done to bring them from the laboratory to field demonstrations. This paper describes the construction of a laser-diode OPLL subsystem for evaluation in a proof-of- concept beamforming system. This involves optimization of the loop design, development of single-frequency laser diodes with the correct linewidth, modulation and tuning characteristics and integration into a micro-optic assembly with custom wideband electronics.

  15. Closed-crack imaging and scattering behavior analysis using confocal subharmonic phased array

    NASA Astrophysics Data System (ADS)

    Sugawara, Azusa; Jinno, Kentaro; Ohara, Yoshikazu; Yamanaka, Kazushi

    2015-07-01

    To solve the underestimation of closed-crack depth, we have developed an imaging method, subharmonic phased array for crack evaluation (SPACE). However, a single-array SPACE can image only the vicinity of a transmission focal point (TFP) when the TFP is fixed. In this study, we have developed a confocal SPACE that defines multiple TFPs for imaging closed cracks over a wide area. We demonstrated its usefulness by measuring a stress corrosion crack (SCC). Moreover, we proposed a radarlike display that shows single-focus images with a line indicating the incident direction. By applying it to the SCC specimen, a moving crack response (MCR) was observed with varying incident angles. To analyze this behavior, we performed a simulation using a finite-difference time-domain (FDTD) method with a damped double node (DDN) model. Furthermore, we examined the ratio of the subharmonic to fundamental responses depending on the stress ratio between input wave stress and crack closure stress (σc).

  16. A novel encoded excitation scheme in a phased array for the improving data acquisition rate.

    PubMed

    Gutiérrez-Fernández, César; Jiménez, Ana; Martín-Arguedas, Carlos Julián; Ureña, Jesús; Hernández, Álvaro

    2013-12-31

    One of the challenges of phased array (PA) ultrasonic imaging systems is their limited capability to deal with real-time applications, such as echocardiography and obstetrics. In its most basic outline, these systems require emitting and receiving with the entire array for each image line to be acquired; therefore, with many image lines, a higher acquisition time and a lower frame rate. This constraint requires one to find alternatives to reduce the total number of emissions needed to obtain the whole image. In this work, we propose a new PA scheme based on the Code Division Multiple Access (CDMA) technique, where a different code is assigned to each steering direction, allowing the array to emit in several directions simultaneously. However, the use of encoding techniques produces a reduction of the image contrast because of the interferences between codes. To solve this, a new scheme based on merging several images is proposed, allowing the system to get close to the theoretical maximum frame rate, as well as to limit the loss of contrast, intrinsic to the technique.

  17. Inspection design using 2D phased array, TFM and cueMAP software

    SciTech Connect

    McGilp, Ailidh; Dziewierz, Jerzy; Lardner, Tim; Mackersie, John; Gachagan, Anthony

    2014-02-18

    A simulation suite, cueMAP, has been developed to facilitate the design of inspection processes and sparse 2D array configurations. At the core of cueMAP is a Total Focusing Method (TFM) imaging algorithm that enables computer assisted design of ultrasonic inspection scenarios, including the design of bespoke array configurations to match the inspection criteria. This in-house developed TFM code allows for interactive evaluation of image quality indicators of ultrasonic imaging performance when utilizing a 2D phased array working in FMC/TFM mode. The cueMAP software uses a series of TFM images to build a map of resolution, contrast and sensitivity of imaging performance of a simulated reflector, swept across the inspection volume. The software takes into account probe properties, wedge or water standoff, and effects of specimen curvature. In the validation process of this new software package, two 2D arrays have been evaluated on 304n stainless steel samples, typical of the primary circuit in nuclear plants. Thick section samples have been inspected using a 1MHz 2D matrix array. Due to the processing efficiency of the software, the data collected from these array configurations has been used to investigate the influence sub-aperture operation on inspection performance.

  18. Lab on a chip phased-array MR multi-platform analysis system.

    PubMed

    Gruschke, Oliver G; Baxan, Nicoleta; Clad, Lars; Kratt, Kai; von Elverfeldt, Dominik; Peter, Andreas; Hennig, Jürgen; Badilita, Vlad; Wallrabe, Ulrike; Korvink, Jan G

    2012-02-01

    We present a lab on a chip (LOC) compatible modular platform for magnetic resonance (MR)-based investigation of sub-millimetre samples. The platform combines the advantages offered respectively by microcoils (high resolution at the microscale) and macroscopic surface coils (large field of view) as MR-detectors and consists of a phased array of microcoils (PAMs) providing a flat MR-sensitive area of 18.3 mm(2) with a B(0)-field uniformity better than 0.25 ppm in the sensor centre area. We demonstrate both high-resolution magnetic resonance imaging (MRI) and NMR spectroscopy using this platform. To demonstrate the application for biological samples, we report MR imaging of fish oocytes with an in-plane resolution of 30 × 30 μm(2) and a contrast to noise ratio of 10 for a scan time of only 13 min 39 s. We have also demonstrated high-resolution spectroscopy of a water phantom achieving 11 ppb (4.5 Hz at 400 MHz) linewidth and an SNR of 28 for only 12 s scan time. State of the art automatic wire bonding technology in conjunction with MEMS techniques has been employed to manufacture the platform with potential applications in MR-investigation of planar samples. PMID:22200053

  19. Analysis and design of a high power laser adaptive phased array transmitter

    NASA Technical Reports Server (NTRS)

    Mevers, G. E.; Soohoo, J. F.; Winocur, J.; Massie, N. A.; Southwell, W. H.; Brandewie, R. A.; Hayes, C. L.

    1977-01-01

    The feasibility of delivering substantial quantities of optical power to a satellite in low earth orbit from a ground based high energy laser (HEL) coupled to an adaptive antenna was investigated. Diffraction effects, atmospheric transmission efficiency, adaptive compensation for atmospheric turbulence effects, including the servo bandwidth requirements for this correction, and the adaptive compensation for thermal blooming were examined. To evaluate possible HEL sources, atmospheric investigations were performed for the CO2, (C-12)(O-18)2 isotope, CO and DF wavelengths using output antenna locations of both sea level and mountain top. Results indicate that both excellent atmospheric and adaption efficiency can be obtained for mountain top operation with a micron isotope laser operating at 9.1 um, or a CO laser operating single line (P10) at about 5.0 (C-12)(O-18)2um, which was a close second in the evaluation. Four adaptive power transmitter system concepts were generated and evaluated, based on overall system efficiency, reliability, size and weight, advanced technology requirements and potential cost. A multiple source phased array was selected for detailed conceptual design. The system uses a unique adaption technique of phase locking independent laser oscillators which allows it to be both relatively inexpensive and most reliable with a predicted overall power transfer efficiency of 53%.

  20. Finite Element Analysis of Ultrasonic Phased Array Inspections on Anisotropic Welds

    NASA Astrophysics Data System (ADS)

    Harvey, G.; Tweedie, A.; Carpentier, C.; Reynolds, P.

    2011-06-01

    This paper describes a theoretical investigation into the behaviour of anisotropic welds under phased array inspection procedures using a 128 element linear array. Two advanced inspection techniques are simulated, and their suitability compared. A finite element (FE) model, configured in PZFlex, is used to represent both the variations in crystal orientation found in a typical anisotropic weld, and also the linear array configuration. Firstly, through transmission spectra of the weld are used to determine the optimum operating frequency and configuration of the array in order to detect a 3 mm SDH in the weld. Next, the Full Matrix Capture (FMC) technique is simulated, and an image of the weld constructed using the Total Focussing Method (TFM). This is accomplished by transmitting on each element sequentially, while receiving on the remaining 127 elements. This approach provides spatial averaging over the weld area, reducing the distortion caused by the anisotropic media. Finally, Time Reversal Acoustic (TRA) methods were employed to coherently focus the array at the defect and compensate for the elemental timing variations caused by the complex medium. Results illustrate the potential for inspecting anisotropic welds when using correctly designed arrays and implementing novel inspection procedures.

  1. A Novel Encoded Excitation Scheme in a Phased Array for The Improving Data Acquisition Rate

    PubMed Central

    Gutiérrez-Fernández, César; Jiménez, Ana; Martín-Arguedas, Carlos Julián; Ureña, Jesús; Hernández, Álvaro

    2014-01-01

    One of the challenges of phased array (PA) ultrasonic imaging systems is their limited capability to deal with real-time applications, such as echocardiography and obstetrics. In its most basic outline, these systems require emitting and receiving with the entire array for each image line to be acquired; therefore, with many image lines, a higher acquisition time and a lower frame rate. This constraint requires one to find alternatives to reduce the total number of emissions needed to obtain the whole image. In this work, we propose a new PA scheme based on the Code Division Multiple Access (CDMA) technique, where a different code is assigned to each steering direction, allowing the array to emit in several directions simultaneously. However, the use of encoding techniques produces a reduction of the image contrast because of the interferences between codes. To solve this, a new scheme based on merging several images is proposed, allowing the system to get close to the theoretical maximum frame rate, as well as to limit the loss of contrast, intrinsic to the technique. PMID:24385031

  2. Coherent beam combining using a 2D internally sensed optical phased array.

    PubMed

    Roberts, Lyle E; Ward, Robert L; Sutton, Andrew J; Fleddermann, Roland; de Vine, Glenn; Malikides, Emmanuel A; Wuchenich, Danielle M R; McClelland, David E; Shaddock, Daniel A

    2014-08-01

    Coherent combination of multiple lasers using an optical phased array (OPA) is an effective way to scale optical intensity in the far field beyond the capabilities of single fiber lasers. Using an actively phase locked, internally sensed, 2D OPA we demonstrate over 95% fringe visibility of the interfered beam, λ/120 RMS output phase stability over a 5 Hz bandwidth, and quadratic scaling of intensity in the far field using three emitters. This paper presents a new internally sensed OPA architecture that employs a modified version of digitally enhanced heterodyne interferometry (DEHI) based on code division multiplexing to measure and control the phase of each emitter. This internally sensed architecture can be implemented with no freespace components, offering improved robustness to shock and vibration exhibited by all-fiber devices. To demonstrate the concept, a single laser is split into three channels/emitters, each independently controlled using separate electro-optic modulators. The output phase of each channel is measured using DEHI to sense the small fraction of light that is reflected back into the fiber at the OPA's glass-air interface. The relative phase between emitters is used to derive the control signals needed to stabilize their relative path lengths and maintain coherent combination in the far field.

  3. On the Fringe Field of Wide Angle LC Optical Phased Array

    NASA Technical Reports Server (NTRS)

    Wang, Xighua; Wang, Bin; Bos, Philip J.; Anderson, James E.; Pouch, John; Miranda, Felix; McManamon, Paul F.

    2004-01-01

    For free space laser communication, light weighted large deployable optics is a critical component for the transmitter. However, such an optical element will introduce large aberrations due to the fact that the surface figure of the large optics is susceptable to deformation in the space environment. We propose to use a high-resolution liquid crystal spatial light modulator to correct for wavefront aberrations introduced by the primary optical element, and to achieve very fine beam steering and shaping at the same time. A 2-D optical phased array (OPA) antenna based on a Liquid Crystal on Silicon (LCOS) spatial light modulator is described. This device offers a combination of low cost, high resolution, high accuracy, high diffraction efficiency at video speed. To quantitatively understand the influence factor of the different design parameters, a computer simulation of the device is given by the 2-D director simulation and the Finite Difference Time domain (FDTD) simulation. For the 1-D OPA, we define the maximum steering angle to have a grating period of 8 pixel/reset scheme; as for larger steering angles than this criterion, the diffraction efficiency drops dramatically. In this case, the diffraction efficiency of 0.86 and the Strehl ratio of 0.9 are obtained in the simulation. The performance of the device in achieving high resolution wavefront correction and beam steering is also characterized experimentally.

  4. DAMAS Processing for a Phased Array Study in the NASA Langley Jet Noise Laboratory

    NASA Technical Reports Server (NTRS)

    Brooks, Thomas F.; Humphreys, William M.; Plassman, Gerald e.

    2010-01-01

    A jet noise measurement study was conducted using a phased microphone array system for a range of jet nozzle configurations and flow conditions. The test effort included convergent and convergent/divergent single flow nozzles, as well as conventional and chevron dual-flow core and fan configurations. Cold jets were tested with and without wind tunnel co-flow, whereas, hot jets were tested only with co-flow. The intent of the measurement effort was to allow evaluation of new phased array technologies for their ability to separate and quantify distributions of jet noise sources. In the present paper, the array post-processing method focused upon is DAMAS (Deconvolution Approach for the Mapping of Acoustic Sources) for the quantitative determination of spatial distributions of noise sources. Jet noise is highly complex with stationary and convecting noise sources, convecting flows that are the sources themselves, and shock-related and screech noise for supersonic flow. The analysis presented in this paper addresses some processing details with DAMAS, for the array positioned at 90 (normal) to the jet. The paper demonstrates the applicability of DAMAS and how it indicates when strong coherence is present. Also, a new approach to calibrating the array focus and position is introduced and demonstrated.

  5. T/R module development for large aperture L-band phased array

    NASA Technical Reports Server (NTRS)

    Chamberlain, Neil; Andricos, Constantine; Kumley, Kendra; Berkun, Andrew; Hodges, Richard; Spitz, Suzanne

    2004-01-01

    This paper describes a transmit / receive (T/R) module for a large L-band space based radar active phased array being developed at JPL. Electrical performance and construction techniques are described, with emphasis on the former. The T/R modules have a bandwidth of more than 80 MHz centered at 1260MHz and support dual, switched polarizations. Phase and amplitude are controlled by a 6-bit phase shifter and a 6-bit attenuator, respectively. The transmitter power amplifier generates 2.4 W into a nominal 50 ohm load with 36% overall efficiency. The receiver noise figure is 4.4 dB including all front-end losses. The module weighs 32 g and has a footprint of 8 cm x 4.5 cm. Fourteen of these T/R modules were fabricated at the JPL Pick-and-Place Facility and were tested using a computer-controlled measurement facility developed at JPL. Calibrated performance of this set of T/R modules is presented and shows good agreement with design predictions.

  6. Measurement of the Earth-Observer-1 Satellite X-Band Phased Array

    NASA Technical Reports Server (NTRS)

    Perko, Kenneth; Dod, Louis; Demas, John

    2003-01-01

    The recent launch and successful orbiting of the EO-1 Satellite has provided an opportunity to validate the performance of a newly developed X-Band transmit-only phased array aboard the satellite. This paper will compare results of planar near-field testing before and after spacecraft installation as well as on-orbit pattern characterization. The transmit-only array is used as a high data rate antenna for relaying scientific data from the satellite to earth stations. The antenna contains distributed solid-state amplifiers behind each antenna element that cannot be monitored except for radiation pattern measurements. A unique portable planar near-field scanner allows both radiation pattern measurements and also diagnostics of array aperture distribution before and after environmental testing over the ground-integration and prelaunch testing of the satellite. The antenna beam scanning software was confirmed from actual pattern measurements of the scanned beam positions during the spacecraft assembly testing. The scanned radiation patterns on-orbit were compared to the near-field patterns made before launch to confirm the antenna performance. The near-field measurement scanner has provided a versatile testing method for satellite high gain data-link antennas.

  7. Ultrabroadband phased-array radio frequency (RF) receivers based on optical techniques

    NASA Astrophysics Data System (ADS)

    Overmiller, Brock M.; Schuetz, Christopher A.; Schneider, Garrett; Murakowski, Janusz; Prather, Dennis W.

    2014-03-01

    Military operations require the ability to locate and identify electronic emissions in the battlefield environment. However, recent developments in radio detection and ranging (RADAR) and communications technology are making it harder to effectively identify such emissions. Phased array systems aid in discriminating emitters in the scene by virtue of their relatively high-gain beam steering and nulling capabilities. For the purpose of locating emitters, we present an approach realize a broadband receiver based on optical processing techniques applied to the response of detectors in conformal antenna arrays. This approach utilizes photonic techniques that enable us to capture, route, and process the incoming signals. Optical modulators convert the incoming signals up to and exceeding 110 GHz with appreciable conversion efficiency and route these signals via fiber optics to a central processing location. This central processor consists of a closed loop phase control system which compensates for phase fluctuations induced on the fibers due to thermal or acoustic vibrations as well as an optical heterodyne approach for signal conversion down to baseband. Our optical heterodyne approach uses injection-locked paired optical sources to perform heterodyne downconversion/frequency identification of the detected emission. Preliminary geolocation and frequency identification testing of electronic emissions has been performed demonstrating the capabilities of our RF receiver.

  8. An advanced Ka band phased array communication system at commercial frequencies

    NASA Astrophysics Data System (ADS)

    Wald, Lawrence; Kacpura, Thomas; Kershner, Dennis

    2000-01-01

    The Glenn Research Center (GRC) Direct Data Distribution (D3) project will demonstrate an advanced, high-performance communication system that transmits information from a technology payload carried by the Space Shuttle in low-Earth orbit (LEO) to a small receiving terminal on the Earth. The Shuttle-based communications package will utilize a solid-state, Ka-band phased array antenna that electronically steers the 19.05 Ghz RF signal toward a low-cost, tracking ground terminal, thereby providing agile, vibration-free, electronic steering at reduced size and weight with increased reliability. The project will also demonstrate new digital modulation and processing technology that will allow transmission of user/platform data at rates up to 1200 Mbits per second. This capability will enable the management of the substantially increased amounts of data to be collected from the International Space Station (ISS) or other LEO platforms directly to NASA field centers, principal investigators, or into the commercial terrestrial communications network. .

  9. A Ku band 5 bit MEMS phase shifter for active electronically steerable phased array applications

    NASA Astrophysics Data System (ADS)

    Sharma, Anesh K.; Gautam, Ashu K.; Farinelli, Paola; Dutta, Asudeb; Singh, S. G.

    2015-03-01

    The design, fabrication and measurement of a 5 bit Ku band MEMS phase shifter in different configurations, i.e. a coplanar waveguide and microstrip, are presented in this work. The development architecture is based on the hybrid approach of switched and loaded line topologies. All the switches are monolithically manufactured on a 200 µm high resistivity silicon substrate using 4 inch diameter wafers. The first three bits (180°, 90° and 45°) are realized using switched microstrip lines and series ohmic MEMS switches whereas the fourth and fifth bits (22.5° and 11.25°) consist of microstrip line sections loaded by shunt ohmic MEMS devices. Individual bits are fabricated and evaluated for performance and the monolithic device is a 5 bit Ku band (16-18 GHz) phase shifter with very low average insertion loss of the order of 3.3 dB and a return loss better than 15 dB over the 32 states with a chip area of 44 mm2. A total phase shift of 348.75° with phase accuracy within 3° is achieved over all of the states. The performance of individual bits has been optimized in order to achieve an integrated performance so that they can be implemented into active electronically steerable antennas for phased array applications.

  10. Phased-array ultrasonic surface contour mapping system and method for solids hoppers and the like

    DOEpatents

    Fasching, George E.; Smith, Jr., Nelson S.

    1994-01-01

    A real time ultrasonic surface contour mapping system is provided including a digitally controlled phased-array of transmitter/receiver (T/R) elements located in a fixed position above the surface to be mapped. The surface is divided into a predetermined number of pixels which are separately scanned by an arrangement of T/R elements by applying phase delayed signals thereto that produce ultrasonic tone bursts from each T/R that arrive at a point X in phase and at the same time relative to the leading edge of the tone burst pulse so that the acoustic energies from each T/R combine in a reinforcing manner at point X. The signals produced by the reception of the echo signals reflected from point X back to the T/Rs are also delayed appropriately so that they add in phase at the input of a signal combiner. This combined signal is then processed to determine the range to the point X using density-corrected sound velocity values. An autofocusing signal is developed from the computed average range for a complete scan of the surface pixels. A surface contour map is generated in real time form the range signals on a video monitor.

  11. Guided wave phased array sensor tuning for improved defect detection and characterization

    NASA Astrophysics Data System (ADS)

    Philtron, Jason H.; Rose, Joseph L.

    2014-03-01

    Ultrasonic guided waves are finding increased use in a variety of Nondestructive Evaluation and Structural Health Monitoring applications due to their efficiency in defect detection using a sensor at a single location to inspect a large area of a structure and an ability to inspect hidden and coated areas for example. With a thorough understanding of guided wave mechanics, researchers can predict which guided wave modes will have a high probability of success in a particular nondestructive evaluation application. For example, in a sample problem presented here to access bond integrity, researchers may choose to use a guided wave mode which has high in-plane displacement, stress, or other feature at the interface. However, since material properties used for modeling work may not be precise for the development of dispersion curves, in many cases guided wave mode and frequency selection should be adjusted for increased inspection efficiency in the field. In this work, a phased array comb transducer is used to sweep over phase velocity - frequency space to tune mode excitation for improved defect characterization performance. A thin polycarbonate layer bonded to a thick metal plate is considered with a contaminated surface prior to bonding. Physicallybased features are used to correlate wave signals with defect detection. Features assessed include arrival time and the frequency of maximum amplitude. A pseudo C-scan plot is presented which can be used to simplify data analysis. Excellent results are obtained.

  12. A novel strategy to increase heating efficiency in a split-focus ultrasound phased array.

    PubMed

    Liu, Hao-Li; Shih, Tzu-Ching; Chen, Wen-Shiang; Ju, Kuen-Cheng

    2007-07-01

    Focus splitting using sector-based phased arrays increases the necrosed volume in a single sonication and reduces the total treatment time in the treatment of large tumors. However, split-focus sonication results in a lower energy density and worse focal-beam distortion, which limits its usefulness in practical treatments. Here, we propose a new heating strategy involving consecutive strongly focused and split-focus sonications to improve the heating efficiency. Theoretical predictions including linear and thermal-dose-dependent attenuation change were employed to investigate potential factors of this strategy, and ex vivo tissue experiments were conducted to confirm its effectiveness. Results showed that the thermal lesions produced by the proposed strategy could be increased when comparing with the previous reported strategies. The proposed heating strategy also induces a thermal lesion more rapidly, and exhibits higher robustness to various blood perfusion conditions, higher robustness to various power/heating time combinations, and superiority to generate deep-seated lesions through tissues with complex interfaces. Possible mechanisms include the optimization of the thermal conduction created by the strongly focused sonication and the temperature buildup gained from thermally induced tissue attenuation change based on the theoretical analysis. This may represent a useful technique for increasing the applicability of split-focus and multiple-focus sonication techniques, and solve the obstacles encountered when attempting to use these methods to shorten the total clinical treatment time.

  13. Solution of high frequency variations of ERP from VLBI observations

    NASA Astrophysics Data System (ADS)

    Zhang, B.; Li, J. L.; Wang, G. L.; Zhao, M.

    2005-01-01

    In the astrometric and geodetic VLBI data analysis software CALC/SOLVE, the high frequency variations of the Earth Rotation Parameters (ERP) are determined by a constrained continuous piecewise linear model. The ERP rate within two epoch nodes is constrained to be smaller than a limitation setting, and the ERP is forced to be continuous at epoch nodes. Observation analysis shows that when the data points are not very dense the constraint and the continuation requirement are helpful to the improvement in the stability of the solution, but degrade the independence of ERP solutions at epoch nodes as well. By using the Userpartial entry of CALC/SOLVE a direct solution module of the high frequency variations of ERP is realized without any constraint on the rate nor the requirement of continuation at nodes. It is shown from real observation reduction that the direct solution mode is feasible. In the solution of high frequency variations of ERP from VLBI observations with long period coverage, the model errors of the precession and nutation (celestial pole offset) should be taken into consideration. A corresponding module is realized and global solutions of the high frequency variation of ERP are successfully performed on the VLBI observations from 1979 to 2003. Comparison of the solutions shows that with the consideration of the pole offsets the precision of parameters could be improved obviously. In the solution of high frequency variation of ERP from VLBI observations, the direct solution mode with the consideration of the pole offsets is accordingly recommended.

  14. A digital multigate Doppler method for high frequency ultrasound.

    PubMed

    Qiu, Weibao; Ye, Zongying; Yu, Yanyan; Chen, Yan; Chi, Liyang; Mu, Peitian; Li, Guofeng; Wang, Congzhi; Xiao, Yang; Dai, Jiyan; Sun, Lei; Zheng, Hairong

    2014-01-01

    Noninvasive visualization of blood flow with high frequency Doppler ultrasound has been extensively used to assess the morphology and hemodynamics of the microcirculation. A completely digital implementation of multigate pulsed-wave (PW) Doppler method was proposed in this paper for high frequency ultrasound applications. Analog mixer was eliminated by a digital demodulator and the same data acquisition path was shared with traditional B-mode imaging which made the design compact and flexible. Hilbert transform based quadrature demodulation scheme was employed to achieve the multigate Doppler acquisition. A programmable high frequency ultrasound platform was also proposed to facilitate the multigate flow visualization. Experimental results showed good performance of the proposed method. Parabolic velocity gradient inside the vessel and velocity profile with different time slots were acquired to demonstrate the functionality of the multigate Doppler. Slow wall motion was also recorded by the proposed method.

  15. Switch over to the high frequency rf systems near transition

    SciTech Connect

    Brennan, J.M.; Wei, J.

    1988-01-01

    The purpose of this note is to point out that since bunch narrowing naturally occurs in the acceleration process in the vicinity of transition, it should be possible to switch over to the high frequency system close to transition when the bunch has narrowed enough to fit directly into the high frequency bucket. The advantage of this approach is the simplicity, no extra components or gymnastics are required of the low frequency system. The disadvantage, of course, is for protons which do not go through transition. But on the other hand, there is no shortage of intensity for protons and so it should be possible to keep the phase space area low for protons, and then matching to the high frequency bucket should be easily accomplished by adiabatic compression. 3 refs., 7 figs.

  16. High Frequency Haplotypes are Expected Events, not Historical Figures.

    PubMed

    Guillot, Elsa G; Cox, Murray P

    2015-01-01

    Cultural transmission of reproductive success states that successful men have more children and pass this raised fecundity to their offspring. Balaresque and colleagues found high frequency haplotypes in a Central Asian Y chromosome dataset, which they attribute to cultural transmission of reproductive success by prominent historical men, including Genghis Khan. Using coalescent simulation, we show that these high frequency haplotypes are consistent with a neutral model, where they commonly appear simply by chance. Hence, explanations invoking cultural transmission of reproductive success are statistically unnecessary.

  17. High Frequency Haplotypes are Expected Events, not Historical Figures

    PubMed Central

    Guillot, Elsa G.; Cox, Murray P.

    2016-01-01

    Cultural transmission of reproductive success states that successful men have more children and pass this raised fecundity to their offspring. Balaresque and colleagues found high frequency haplotypes in a Central Asian Y chromosome dataset, which they attribute to cultural transmission of reproductive success by prominent historical men, including Genghis Khan. Using coalescent simulation, we show that these high frequency haplotypes are consistent with a neutral model, where they commonly appear simply by chance. Hence, explanations invoking cultural transmission of reproductive success are statistically unnecessary. PMID:26834987

  18. Real-Time, High-Frequency QRS Electrocardiograph

    NASA Technical Reports Server (NTRS)

    Schlegel, Todd T.; DePalma, Jude L.; Moradi, Saeed

    2003-01-01

    An electronic system that performs real-time analysis of the low-amplitude, high-frequency, ordinarily invisible components of the QRS portion of an electrocardiographic signal in real time has been developed. Whereas the signals readily visible on a conventional electrocardiogram (ECG) have amplitudes of the order of a millivolt and are characterized by frequencies <100 Hz, the ordinarily invisible components have amplitudes in the microvolt range and are characterized by frequencies from about 150 to about 250 Hz. Deviations of these high-frequency components from a normal pattern can be indicative of myocardial ischemia or myocardial infarction

  19. A MEMS-based high frequency x-ray chopper.

    PubMed

    Siria, A; Dhez, O; Schwartz, W; Torricelli, G; Comin, F; Chevrier, J

    2009-04-29

    Time-resolved x-ray experiments require intensity modulation at high frequencies (advanced rotating choppers have nowadays reached the kHz range). We here demonstrate that a silicon microlever oscillating at 13 kHz with nanometric amplitude can be used as a high frequency x-ray chopper. We claim that using micro-and nanoelectromechanical systems (MEMS and NEMS), it will be possible to achieve higher frequencies in excess of hundreds of megahertz. Working at such a frequency can open a wealth of possibilities in chemistry, biology and physics time-resolved experiments.

  20. Induced and Form Birefringence in High-Frequency Polarization Gratings

    NASA Astrophysics Data System (ADS)

    Martinez-Ponce, Geminiano; Solano, Cristina

    2001-08-01

    High-frequency phase polarization gratings are fabricated holographically in dichromated gelatin dyed with malachite green. It is observed that the intensity of the -1 diffracted beam is a sinusoidal function of the incident polarization angle. In addition, we analyze the dependence of the diffracted order polarization on grating frequency. It is evident from our results that form birefringence becomes significant when the grating period is smaller than the illumination wavelength, thus modifying the optically induced birefringence. Then, in polarization hologram reconstruction, it is not possible to obtain the polarization distribution at the recording step for high-frequency objects.

  1. Guided Lamb wave based 2-D spiral phased array for structural health monitoring of thin panel structures

    NASA Astrophysics Data System (ADS)

    Yoo, Byungseok

    2011-12-01

    In almost all industries of mechanical, aerospace, and civil engineering fields, structural health monitoring (SHM) technology is essentially required for providing the reliable information of structural integrity of safety-critical structures, which can help reduce the risk of unexpected and sometimes catastrophic failures, and also offer cost-effective inspection and maintenance of the structures. State of the art SHM research on structural damage diagnosis is focused on developing global and real-time technologies to identify the existence, location, extent, and type of damage. In order to detect and monitor the structural damage in plate-like structures, SHM technology based on guided Lamb wave (GLW) interrogation is becoming more attractive due to its potential benefits such as large inspection area coverage in short time, simple inspection mechanism, and sensitivity to small damage. However, the GLW method has a few critical issues such as dispersion nature, mode conversion and separation, and multiple-mode existence. Phased array technique widely used in all aspects of civil, military, science, and medical industry fields may be employed to resolve the drawbacks of the GLW method. The GLW-based phased array approach is able to effectively examine and analyze complicated structural vibration responses in thin plate structures. Because the phased sensor array operates as a spatial filter for the GLW signals, the array signal processing method can enhance a desired signal component at a specific direction while eliminating other signal components from other directions. This dissertation presents the development, the experimental validation, and the damage detection applications of an innovative signal processing algorithm based on two-dimensional (2-D) spiral phased array in conjunction with the GLW interrogation technique. It starts with general backgrounds of SHM and the associated technology including the GLW interrogation method. Then, it is focused on the

  2. Co/Ti-substituted M-type hexagonal ferrites for high-frequency multilayer inductors

    NASA Astrophysics Data System (ADS)

    Bierlich, S.; Reimann, T.; Bartsch, H.; Töpfer, J.

    2015-06-01

    The sintering behavior, microstructure and permeability of Co/Ti-substituted M-type hexagonal ferrites BaCoxTixFe12-2xO19 (1.0≤x≤1.4) was studied for applications as multilayer inductors in the high-frequency range up to 2 GHz. Single-phase M-type ferrites were obtained after calcination at 1000 °C. The saturation magnetization and coercivity decrease with x and hysteresis measurements illustrate a gradual transition of the anisotropy from uniaxial to planar. Addition of 5 wt% of a BBSZ glass allows densification at 900 °C through liquid-phase sintering. The permeability of samples sintered at 900 °C increases with the Co/Ti substitution and reaches its maximum of μ‧=16 at 1 MHz at x=1.3 with a resonance frequency fr≥1 GHz. Monolithic ferrite multilayer inductors were fabricated with printed Ag coil patterns by co-firing at 900 °C. It is shown that Co/Ti-substituted hexagonal M-type ferrite is an excellent material for the high-frequency multilayer inductors.

  3. Compact 4 cm aperture transmissive liquid crystal optical phased array for free-space optical communications

    NASA Astrophysics Data System (ADS)

    Lin, Yu-Hua; Mahajan, Milind; Taber, Donald; Wen, Bing; Winker, Bruce

    2005-08-01

    There is a critical need for high bandwidth, high availability free-space optical communication links between the battlefield and the global information grid. Compact large aperture transceivers with low size, weight and power (SWaP) are needed to initiate and maintain communication links involving airborne platforms. The transceiver optical beam director typically contains fine and coarse steering stages. Existing beam director technology is based on electro-mechanical gimbaled mirrors with large SWaP that hinders deployment on many airborne platforms. To address the need for compact beam directors, we designed, fabricated, and tested an optical phased array (OPA) based on electro-optic dual frequency liquid crystal technology. This OPA has a transmissive architecture that enables a lower system SWaP, as compared to conventional reflective OPA. It has an 8 μm pixel pitch and steers over a 2.5° field of regard in one dimension at 1.55 μm. Two such OPAs can be stacked to steer in two dimensions. It has four independently addressable 1 cm x 4 cm regions arranged in a linear array to produce a continuous 4 cm x 4 cm aperture. The device incorporates novel addressing schemes to reduce the number of control channels by over an order of magnitude compared to conventional OPA addressing methods. It also utilizes proprietary low-loss transparent conductive TransconTM film for low optical absorption in the infrared. The OPA uses a custom multi-channel controller circuit operating at a 500 Hz frame rate. We present results on OPA design, fabrication, and optical performance on steering.

  4. Optical BEAMTAP beam-forming and jammer-nulling system for broadband phased-array antennas.

    PubMed

    Kriehn, G; Kiruluta, A; Silveira, P E; Weaver, S; Kraut, S; Wagner, K; Weverka, R T; Griffiths, L

    2000-01-10

    We present an approach to receive-mode broadband beam forming and jammer nulling for large adaptive antenna arrays as well as its efficient and compact optical implementation. This broadband efficient adaptive method for true-time-delay array processing (BEAMTAP) algorithm decreases the number of tapped delay lines required for processing an N-element phased-array antenna from N to only 2, producing an enormous savings in delay-line hardware (especially for large broadband arrays) while still providing the full NM degrees of freedom of a conventional N-element time-delay-and-sum beam former that requires N tapped delay lines with M taps each. This allows the system to adapt fully and optimally to an arbitrarily complex spatiotemporal signal environment that can contain broadband signals of interest, as well as interference sources and narrow-band and broadband jammers--all of which can arrive from arbitrary angles onto an arbitrarily shaped array--thus enabling a variety of applications in radar, sonar, and communication. This algorithm is an excellent match with the capabilities of radio frequency (rf) photonic systems, as it uses a coherent optically modulated fiber-optic feed network, gratings in a photorefractive crystal as adaptive weights, a traveling-wave detector for generating time delay, and an acousto-optic device to control weight adaptation. Because the number of available adaptive coefficients in a photorefractive crystal is as large as 10(9), these photonic systems can adaptively control arbitrarily large one- or two-dimensional antenna arrays that are well beyond the capabilities of conventional rf and real-time digital signal processing techniques or alternative photonic techniques.

  5. A 1372-element Large Scale Hemispherical Ultrasound Phased Array Transducer for Noninvasive Transcranial Therapy

    SciTech Connect

    Song, Junho; Hynynen, Kullervo

    2009-04-14

    Noninvasive transcranial therapy using high intensity focused ultrasound transducers has attracted high interest as a promising new modality for the treatments of brain related diseases. We describe the development of a 1372 element large scale hemispherical ultrasound phased array transducer operating at a resonant frequency of 306 kHz. The hemispherical array has a diameter of 31 cm and a 15.5 cm radius of curvature. It is constructed with piezoelectric (PZT-4) tube elements of a 10 mm in diameter, 6 mm in length and 1.4 mm wall thickness. Each element is quasi-air backed by attaching a cork-rubber membrane on the back of the element. The acoustic efficiency of the element is determined to be approximately 50%. The large number of the elements delivers high power ultrasound and offers better beam steering and focusing capability. Comparisons of sound pressure-squared field measurements with theoretical calculations in water show that the array provides good beam steering and tight focusing capability over an efficient volume of approximately 100x100x80 mm{sup 3} with nominal focal spot size of approximately 2.3 mm in diameter at -6 dB. We also present its beam steering and focusing capability through an ex vivo human skull by measuring pressure-squared amplitude after phase corrections. These measurements show the same efficient volume range and focal spot sizes at -6 dB as the ones in water without the skull present. These results indicate that the array is sufficient for use in noninvasive transcranial ultrasound therapy.

  6. The effect of variation in phased array element performance for Non-Destructive Evaluation (NDE).

    PubMed

    Duxbury, David; Russell, Jonathan; Lowe, Michael

    2013-08-01

    This paper reports the results of an investigation into the effects of phased array element performance on ultrasonic beam integrity. This investigation has been performed using an array beam model based on Huygens' principle to independently investigate the effects of element sensitivity and phase, and non-functioning elements via Monte Carlo simulation. The purpose of this work is to allow a new method of array calibration for Non-Destructive Evaluation (NDE) to be adopted that focuses on probe integrity rather than beam integrity. This approach is better suited to component inspections that utilise Full Matrix Capture (FMC) to record data as the calibration routine is uncoupled from the beams that the array is required to produce. For this approach to be adopted specifications must be placed on element performance that guarantee beam quality without carrying out any beam forming. The principal result of this investigation is that the dominant outcome following variations in array element performance is the introduction of beam artefacts such as main beam broadening, raising of the noise floor of the ultrasonic field, and the enlargement or creation of side lobes. Specifications for practical allowable limits of element sensitivity, element phase, and the number of non-functioning elements have been suggested based on a minimum amplitude difference between beam artefacts and the main beam peak of 8 dB. Simulation at a number of centre frequencies has led to a recommendation that the product of transducer bandwidth and maximum phase error should be kept below 0.051 and 0.035 for focused and plane beams respectively. Element sensitivity should be within 50% of mean value of the aperture, and no more than 9% of the elements should be non-functioning.

  7. Comparison of 3-D synthetic aperture phased-array ultrasound imaging and parallel beamforming.

    PubMed

    Rasmussen, Morten Fischer; Jensen, Jørgen Arendt

    2014-10-01

    This paper demonstrates that synthetic aperture imaging (SAI) can be used to achieve real-time 3-D ultrasound phased-array imaging. It investigates whether SAI increases the image quality compared with the parallel beamforming (PB) technique for real-time 3-D imaging. Data are obtained using both simulations and measurements with an ultrasound research scanner and a commercially available 3.5- MHz 1024-element 2-D transducer array. To limit the probe cable thickness, 256 active elements are used in transmit and receive for both techniques. The two imaging techniques were designed for cardiac imaging, which requires sequences designed for imaging down to 15 cm of depth and a frame rate of at least 20 Hz. The imaging quality of the two techniques is investigated through simulations as a function of depth and angle. SAI improved the full-width at half-maximum (FWHM) at low steering angles by 35%, and the 20-dB cystic resolution by up to 62%. The FWHM of the measured line spread function (LSF) at 80 mm depth showed a difference of 20% in favor of SAI. SAI reduced the cyst radius at 60 mm depth by 39% in measurements. SAI improved the contrast-to-noise ratio measured on anechoic cysts embedded in a tissue-mimicking material by 29% at 70 mm depth. The estimated penetration depth on the same tissue-mimicking phantom shows that SAI increased the penetration by 24% compared with PB. Neither SAI nor PB achieved the design goal of 15 cm penetration depth. This is likely due to the limited transducer surface area and a low SNR of the experimental scanner used.

  8. A novel, flat, electronically-steered phased array transducer for tissue ablation: preliminary results.

    PubMed

    Ellens, Nicholas P K; Lucht, Benjamin B C; Gunaseelan, Samuel T; Hudson, John M; Hynynen, Kullervo H

    2015-03-21

    Flat, λ/2-spaced phased arrays for therapeutic ultrasound were examined in silico and in vitro. All arrays were made by combining modules made of 64 square elements with 1.5 mm inter-element spacing along both major axes. The arrays were designed to accommodate integrated, co-aligned diagnostic transducers for targeting and monitoring. Six arrays of 1024 elements (16 modules) and four arrays of 6144 elements (96 modules) were modelled and compared according to metrics such as peak pressure amplitude, focal size, ability to be electronically-steered far off-axis and grating lobe amplitude. Two 1024 element prototypes were built and measured in vitro, producing over 100 W of acoustic power. In both cases, the simulation model of the pressure amplitude field was in good agreement with values measured by hydrophone. Using one of the arrays, it was shown that the peak pressure amplitude dropped by only 24% and 25% of the on-axis peak pressure amplitude when steered to the edge of the array (40 mm) at depths of 30 mm and 50 mm. For the 6144 element arrays studied in in silico only, similarly high steerability was found: even when steered 100 mm off-axis, the pressure amplitude decrease at the focus was less than 20%, while the maximum pressure grating lobe was only 20%. Thermal simulations indicate that the modules produce more than enough acoustic power to perform rapid ablations at physiologically relevant depths and steering angles. Arrays such as proposed and tested in this study have enormous potential: their high electronic steerability suggests that they will be able to perform ablations of large volumes without the need for any mechanical translation.

  9. The effect of variation in phased array element performance for Non-Destructive Evaluation (NDE).

    PubMed

    Duxbury, David; Russell, Jonathan; Lowe, Michael

    2013-08-01

    This paper reports the results of an investigation into the effects of phased array element performance on ultrasonic beam integrity. This investigation has been performed using an array beam model based on Huygens' principle to independently investigate the effects of element sensitivity and phase, and non-functioning elements via Monte Carlo simulation. The purpose of this work is to allow a new method of array calibration for Non-Destructive Evaluation (NDE) to be adopted that focuses on probe integrity rather than beam integrity. This approach is better suited to component inspections that utilise Full Matrix Capture (FMC) to record data as the calibration routine is uncoupled from the beams that the array is required to produce. For this approach to be adopted specifications must be placed on element performance that guarantee beam quality without carrying out any beam forming. The principal result of this investigation is that the dominant outcome following variations in array element performance is the introduction of beam artefacts such as main beam broadening, raising of the noise floor of the ultrasonic field, and the enlargement or creation of side lobes. Specifications for practical allowable limits of element sensitivity, element phase, and the number of non-functioning elements have been suggested based on a minimum amplitude difference between beam artefacts and the main beam peak of 8 dB. Simulation at a number of centre frequencies has led to a recommendation that the product of transducer bandwidth and maximum phase error should be kept below 0.051 and 0.035 for focused and plane beams respectively. Element sensitivity should be within 50% of mean value of the aperture, and no more than 9% of the elements should be non-functioning. PMID:23337826

  10. Focusing of high intensity ultrasound through the rib cage using a therapeutic random phased array

    PubMed Central

    Bobkova, Svetlana; Gavrilov, Leonid; Khokhlova, Vera; Shaw, Adam; Hand, Jeffrey; #, ||

    2010-01-01

    A method for focusing high intensity ultrasound through a rib cage that aims to minimize heating of the ribs whilst maintaining high intensities at the focus (or foci) is proposed and tested theoretically and experimentally. Two approaches, one based on geometric acoustics and the other accounting for diffraction effects associated with propagation through the rib cage, are investigated theoretically for idealized source conditions. It is shown that for an idealized radiator the diffraction approach provides a 23% gain in peak intensity and results in significantly less power losses on the ribs (1% versus 7.5% of the irradiated power) compared with the geometric one. A 2D 1-MHz phased array with 254 randomly distributed elements, tissue mimicking phantoms, and samples of porcine rib cages are used in experiments; the geometric approach is used to configure how the array is driven. Intensity distributions are measured in the plane of the ribs and in the focal plane using an infra-red camera. Theoretical and experimental results show that it is possible to provide adequate focusing through the ribs without overheating them for a single focus and several foci, including steering at ± 10–15 mm off and ± 20 mm along the array axis. Focus splitting due to the periodic spatial structure of ribs is demonstrated both in simulations and experiments; the parameters of splitting are quantified. The ability to produce thermal lesions with a split focal pattern in ex vivo porcine tissue placed beyond the rib phantom is also demonstrated. The results suggest that the method is potentially useful for clinical applications of HIFU for which the rib cage lies between the transducer(s) and the targeted tissue. PMID:20510186

  11. Optical BEAMTAP Beam-Forming and Jammer-Nulling System for Broadband Phased-Array Antennas

    NASA Astrophysics Data System (ADS)

    Kriehn, Gregory; Kiruluta, Andrew; Silveira, Paulo E. X.; Weaver, Sam; Kraut, Shawn; Wagner, Kelvin; Weverka, R. Ted; Griffiths, Lloyd

    2000-01-01

    We present an approach to receive-mode broadband beam forming and jammer nulling for large adaptive antenna arrays as well as its efficient and compact optical implementation. This broadband efficient adaptive method for true-time-delay array processing (BEAMTAP) algorithm decreases the number of tapped delay lines required for processing an N -element phased-array antenna from N to only 2, producing an enormous savings in delay-line hardware (especially for large broadband arrays) while still providing the full NM degrees of freedom of a conventional N -element time-delay-and-sum beam former that requires N tapped delay lines with M taps each. This allows the system to adapt fully and optimally to an arbitrarily complex spatiotemporal signal environment that can contain broadband signals of interest, as well as interference sources and narrow-band and broadband jammers all of which can arrive from arbitrary angles onto an arbitrarily shaped array thus enabling a variety of applications in radar, sonar, and communication. This algorithm is an excellent match with the capabilities of radio frequency (rf) photonic systems, as it uses a coherent optically modulated fiber-optic feed network, gratings in a photorefractive crystal as adaptive weights, a traveling-wave detector for generating time delay, and an acousto-optic device to control weight adaptation. Because the number of available adaptive coefficients in a photorefractive crystal is as large as 10 9 , these photonic systems can adaptively control arbitrarily large one- or two-dimensional antenna arrays that are well beyond the capabilities of conventional rf and real-time digital signal processing techniques or alternative photonic techniques.

  12. High-frequency hearing in seals and sea lions.

    PubMed

    Cunningham, Kane A; Reichmuth, Colleen

    2016-01-01

    Existing evidence suggests that some pinnipeds (seals, sea lions, and walruses) can detect underwater sound at frequencies well above the traditional high-frequency hearing limits for their species. This phenomenon, however, is not well studied: Sensitivity patterns at frequencies beyond traditional high-frequency limits are poorly resolved, and the nature of the auditory mechanism mediating hearing at these frequencies is unknown. In the first portion of this study, auditory sensitivity patterns in the 50-180 kHz range were measured for one California sea lion (Zalophus californianus), one harbor seal (Phoca vitulina), and one spotted seal (Phoca largha). Results show the presence of two distinct slope-regions at the high-frequency ends of the audiograms of all three subjects. The first region is characterized by a rapid decrease in sensitivity with increasing frequency-i.e. a steep slope-followed by a region of much less rapid sensitivity decrease-i.e. a shallower slope. In the second portion of this study, a masking experiment was conducted to investigate how the basilar membrane of a harbor seal subject responded to acoustic energy from a narrowband masking noise centered at 140 kHz. The measured masking pattern suggests that the initial, rapid decrease in sensitivity on the high-frequency end of the subject's audiogram is not due to cochlear constraints, as has been previously hypothesized, but rather to constraints on the conductive mechanism. PMID:26519092

  13. Piezoelectric films for high frequency ultrasonic transducers in biomedical applications.

    PubMed

    Zhou, Qifa; Lau, Sienting; Wu, Dawei; Shung, K Kirk

    2011-02-01

    Piezoelectric films have recently attracted considerable attention in the development of various sensor and actuator devices such as nonvolatile memories, tunable microwave circuits and ultrasound transducers. In this paper, an overview of the state of art in piezoelectric films for high frequency transducer applications is presented. Firstly, the basic principles of piezoelectric materials and design considerations for ultrasound transducers will be introduced. Following the review, the current status of the piezoelectric films and recent progress in the development of high frequency ultrasonic transducers will be discussed. Then details for preparation and structure of the materials derived from piezoelectric thick film technologies will be described. Both chemical and physical methods are included in the discussion, namely, the sol-gel approach, aerosol technology and hydrothermal method. The electric and piezoelectric properties of the piezoelectric films, which are very important for transducer applications, such as permittivity and electromechanical coupling factor, are also addressed. Finally, the recent developments in the high frequency transducers and arrays with piezoelectric ZnO and PZT thick film using MEMS technology are presented. In addition, current problems and further direction of the piezoelectric films for very high frequency ultrasound application (up to GHz) are also discussed.

  14. Factors Affecting the Benefits of High-Frequency Amplification

    ERIC Educational Resources Information Center

    Horwitz, Amy R.; Ahlstrom, Jayne B.; Dubno, Judy R.

    2008-01-01

    Purpose: This study was designed to determine the extent to which high-frequency amplification helped or hindered speech recognition as a function of hearing loss, gain-frequency response, and background noise. Method: Speech recognition was measured monaurally under headphones for nonsense syllables low-pass filtered in one-third-octave steps…

  15. Disappearance of high frequency modes in polymer dilute solution viscoelasticity

    NASA Astrophysics Data System (ADS)

    Larson, Ronald; Jain, Semant

    2009-03-01

    We address the problem of the ``missing modes'' in the high frequency rheology of dilute polymer solutions. According to the Rouse-Zimm theory, the slow viscoelastic response of dilute polymers is dominated by the collective motion of the chain, as described by a bead-spring model. However, one expects this description to break down at high frequencies at which chain motion on scales too small to be represented by beads and springs should be evident; this motion should be controlled by rotations of individual backbone bonds of the polymer. The viscoelastic response produced by these ``local modes'' is observable in polymer melts; however, for dilute polymer solutions, the ``local modes'' are absent from viscoelastic spectra, as shown by Schrag and coworkers (Peterson, et al., J. Polym. Sci. B, 39:2860 (2001)). Here we address this problem by directly simulating single polymer chains using Brownian dynamics simulations, with realistic bending and torsional potentials. We show using these simulations that the ``missing modes'' result from barriers to bond rotation that make the chain ``dynamically rigid'' at high frequencies. As a result, the ``dynamical Kuhn length'' of the chain exceeds the static one, and the chain at high frequencies is not able to explore local conformations as fast as would be needed for their relaxation to contribute to the mechanical relaxation spectrum.

  16. Pulsating fireballs with high-frequency sheath-plasma instabilities

    NASA Astrophysics Data System (ADS)

    Stenzel, R. L.; Gruenwald, J.; Ionita, C.; Schrittwieser, R.

    2011-08-01

    High-frequency instabilities are observed in connection with unstable fireballs. Fireballs are discharge phenomena near positively biased electrodes in discharge plasmas. They are bounded by a double layer whose potential is of order of the ionization potential. Fireballs become unstable when plasma losses and plasma production are not in balance, resulting in periodic fireball pulses. High-frequency instabilities in the range of the electron plasma frequency have been observed. These occur between fireball pulses, hence are not due to electron beam-plasma instabilities since there are no beams without double layers. The instability has been identified as a sheath-plasma instability. Electron inertia creates a phase shift between high-frequency current and electric fields which destabilizes the sheath-plasma resonance. High-frequency signals are observed in the current to the electrode and on probes near the sheath of the electrode. Waveforms and spectra are presented, showing bursty emissions, phase shifts, frequency jumps, beat phenomena between two sheaths, and nonlinear effects such as amplitude clipping. These reveal many interesting properties of sheaths with periodic ionization phenomena.

  17. Collocations of High Frequency Noun Keywords in Prescribed Science Textbooks

    ERIC Educational Resources Information Center

    Menon, Sujatha; Mukundan, Jayakaran

    2012-01-01

    This paper analyses the discourse of science through the study of collocational patterns of high frequency noun keywords in science textbooks used by upper secondary students in Malaysia. Research has shown that one of the areas of difficulty in science discourse concerns lexis, especially that of collocations. This paper describes a corpus-based…

  18. High frequency excitation of Earth rotation parameters (ERP) from atmosphere.

    NASA Astrophysics Data System (ADS)

    Xie, Boquan; Zheng, Dawei

    1996-06-01

    The data sets of Earth rotation parameters measured by space geodetic techniques and atmospheric angular momentum reduced by the global meteorological data from 1983 through 1992 are used to analyze and study the high frequency excitations of Earth rotation parameters for the length of day and polar motion up to the monthly time scale from the atmosphere. The main results are given.

  19. High-frequency hearing in seals and sea lions.

    PubMed

    Cunningham, Kane A; Reichmuth, Colleen

    2016-01-01

    Existing evidence suggests that some pinnipeds (seals, sea lions, and walruses) can detect underwater sound at frequencies well above the traditional high-frequency hearing limits for their species. This phenomenon, however, is not well studied: Sensitivity patterns at frequencies beyond traditional high-frequency limits are poorly resolved, and the nature of the auditory mechanism mediating hearing at these frequencies is unknown. In the first portion of this study, auditory sensitivity patterns in the 50-180 kHz range were measured for one California sea lion (Zalophus californianus), one harbor seal (Phoca vitulina), and one spotted seal (Phoca largha). Results show the presence of two distinct slope-regions at the high-frequency ends of the audiograms of all three subjects. The first region is characterized by a rapid decrease in sensitivity with increasing frequency-i.e. a steep slope-followed by a region of much less rapid sensitivity decrease-i.e. a shallower slope. In the second portion of this study, a masking experiment was conducted to investigate how the basilar membrane of a harbor seal subject responded to acoustic energy from a narrowband masking noise centered at 140 kHz. The measured masking pattern suggests that the initial, rapid decrease in sensitivity on the high-frequency end of the subject's audiogram is not due to cochlear constraints, as has been previously hypothesized, but rather to constraints on the conductive mechanism.

  20. Piezoelectric films for high frequency ultrasonic transducers in biomedical applications

    PubMed Central

    Zhou, Qifa; Lau, Sienting; Wu, Dawei; Shung, K. Kirk

    2011-01-01

    Piezoelectric films have recently attracted considerable attention in the development of various sensor and actuator devices such as nonvolatile memories, tunable microwave circuits and ultrasound transducers. In this paper, an overview of the state of art in piezoelectric films for high frequency transducer applications is presented. Firstly, the basic principles of piezoelectric materials and design considerations for ultrasound transducers will be introduced. Following the review, the current status of the piezoelectric films and recent progress in the development of high frequency ultrasonic transducers will be discussed. Then details for preparation and structure of the materials derived from piezoelectric thick film technologies will be described. Both chemical and physical methods are included in the discussion, namely, the sol–gel approach, aerosol technology and hydrothermal method. The electric and piezoelectric properties of the piezoelectric films, which are very important for transducer applications, such as permittivity and electromechanical coupling factor, are also addressed. Finally, the recent developments in the high frequency transducers and arrays with piezoelectric ZnO and PZT thick film using MEMS technology are presented. In addition, current problems and further direction of the piezoelectric films for very high frequency ultrasound application (up to GHz) are also discussed. PMID:21720451

  1. High-Frequency Oscillations and Seizure Generation in Neocortical Epilepsy

    ERIC Educational Resources Information Center

    Worrell, Greg A.; Parish, Landi; Cranstoun, Stephen D.; Jonas, Rachel; Baltuch, Gordon; Litt, Brian

    2004-01-01

    Neocortical seizures are often poorly localized, explosive and widespread at onset, making them poorly amenable to epilepsy surgery in the absence of associated focal brain lesions. We describe, for the first time in an unselected group of patients with neocortical epilepsy, the finding that high-frequency (60--100 Hz) epileptiform oscillations…

  2. Printed photodetectors

    NASA Astrophysics Data System (ADS)

    Pace, Giuseppina; Grimoldi, Andrea; Sampietro, Marco; Natali, Dario; Caironi, Mario

    2015-10-01

    Photodetectors convert light pulses into electrical signals and are fundamental building blocks for any opto-electronic system adopting light as a probe or information carrier. They have widespread technological applications, from telecommunications to sensors in industrial, medical and civil environments. Further opportunities are plastic short-range communications systems, interactive large-area surfaces and light-weight, flexible, digital imagers. These applications would greatly benefit from the cost-effective fabrication processes enabled by printing technology. While organic semiconductors are the most investigated materials for printed photodetectors, and are the main focus of the present review, there are notable examples of other inorganic or hybrid printable semiconductors for opto-electronic systems, such as quantum-dots and nanowires. Here we propose an overview on printed photodetectors, including three-terminal phototransistors. We first give a brief account of the working mechanism of these light sensitive devices, and then we review the recent progress achieved with scalable printing techniques such as screen-printing, inkjet and other non-contact technologies in the development of all-printed or hybrid systems.

  3. Experimental demonstration of a multi-target detection technique using an X-band optically steered phased array radar.

    PubMed

    Shi, Nuannuan; Li, Ming; Deng, Ye; Zhang, Lihong; Sun, Shuqian; Tang, Jian; Li, Wei; Zhu, Ninghua

    2016-06-27

    An X-band optically-steered phased array radar is developed to demonstrate high resolution multi-target detection. The beam forming is implemented based on wavelength-swept true time delay (TTD) technique. The beam forming system has a wide direction tuning range of ± 54 degree, low magnitude ripple of ± 0.5 dB and small delay error of 0.13 ps/nm. To further verify performance of the proposed optically-steered phased array radar, three experiments are then carried out to implement the single and multiple target detection. A linearly chirped X-band microwave signal is used as radar signal which is finally compressed at the receiver to improve the detection accuracy. The ranging resolution for multi-target detection is up to 2 cm within the measuring distance over 4 m and the azimuth angle error is less than 4 degree.

  4. Experimental demonstration of a multi-target detection technique using an X-band optically steered phased array radar.

    PubMed

    Shi, Nuannuan; Li, Ming; Deng, Ye; Zhang, Lihong; Sun, Shuqian; Tang, Jian; Li, Wei; Zhu, Ninghua

    2016-06-27

    An X-band optically-steered phased array radar is developed to demonstrate high resolution multi-target detection. The beam forming is implemented based on wavelength-swept true time delay (TTD) technique. The beam forming system has a wide direction tuning range of ± 54 degree, low magnitude ripple of ± 0.5 dB and small delay error of 0.13 ps/nm. To further verify performance of the proposed optically-steered phased array radar, three experiments are then carried out to implement the single and multiple target detection. A linearly chirped X-band microwave signal is used as radar signal which is finally compressed at the receiver to improve the detection accuracy. The ranging resolution for multi-target detection is up to 2 cm within the measuring distance over 4 m and the azimuth angle error is less than 4 degree. PMID:27410597

  5. An Implementation of real-time phased array radar fundamental functions on DSP-focused, high performance embedded computing platform

    NASA Astrophysics Data System (ADS)

    Yu, Xining; Zhang, Yan; Patel, Ankit; Zahrai, Allen; Weber, Mark

    2016-05-01

    This paper investigates the feasibility of real-time, multiple channel processing of a digital phased array system backend design, with focus on high-performance embedded computing (HPEC) platforms constructed based on general purpose digital signal processor (DSP). Serial RapidIO (SRIO) is used as inter-chip connection backend protocol to support the inter-core communications and parallelisms. Performance benchmark was obtained based on a SRIO system chassis and emulated configuration similar to a field scale demonstrator of Multi-functional Phased Array Radar (MPAR). An interesting aspect of this work is comparison between "raw and low-level" DSP processing and emerging tools that systematically take advantages of the parallelism and multi-core capability, such as OpenCL and OpenMP. Comparisons with other backend HPEC solutions, such as FPGA and GPU, are also provided through analysis and experiments.

  6. Ultrasonic Phased Array Sound Field Mapping Through Large-Bore Coarse Grained Cast Austenitic Stainless Steel (CASS) Piping Materials

    SciTech Connect

    Cinson, Anthony D.; Crawford, Susan L.; Prowant, Matthew S.; Diaz, Aaron A.; Hathaway, John E.; Anderson, Michael T.

    2012-04-16

    A sound field beam mapping exercise was conducted to further understand the effects of coarse grained microstructures found in CASS materials on phased array ultrasonic wave propagation. Laboratory measurements were made on three CASS specimens with different microstructures; the specimens were polished and etched to reveal measurable grain sizes, shapes and orientations. Three longitudinal, phased array probes were fixed on a specimen's outside diameter with the sound field directed toward one end (face) of the pipe segment over a fixed range of angles. A point receiver was raster scanned over the surface of the specimen face generating a sound field image. A slice of CASS material was then removed from the specimen end and the beam mapping exercise repeated. The sound fields acquired were analyzed for spot size, coherency, and beam redirection. Analyses were conducted between the resulting sound fields and the microstructural characteristics of each specimen.

  7. Ku- and Ka-Band Phased Array Antenna for the Space-Based Telemetry and Range Safety Project

    NASA Technical Reports Server (NTRS)

    Whiteman, Donald E.; Valencia, Lisa M.; Birr, Richard B.

    2005-01-01

    The National Aeronautics and Space Administration Space-Based Telemetry and Range Safety study is a multiphase project to increase data rates and flexibility and decrease costs by using space-based communications assets for telemetry during launches and landings. Phase 1 used standard S-band antennas with the Tracking and Data Relay Satellite System to obtain a baseline performance. The selection process and available resources for Phase 2 resulted in a Ku-band phased array antenna system. Several development efforts are under way for a Ka-band phased array antenna system for Phase 3. Each phase includes test flights to demonstrate performance and capabilities. Successful completion of this project will result in a set of communications requirements for the next generation of launch vehicles.

  8. Space-Based Telemetry and Range Safety Project Ku-Band and Ka-Band Phased Array Antenna

    NASA Technical Reports Server (NTRS)

    Whiteman, Donald E.; Valencia, Lisa M.; Birr, Richard B.

    2005-01-01

    The National Aeronautics and Space Administration Space-Based Telemetry and Range Safety study is a multiphase project to increase data rates and flexibility and decrease costs by using space-based communications assets for telemetry during launches and landings. Phase 1 used standard S-band antennas with the Tracking and Data Relay Satellite System to obtain a baseline performance. The selection process and available resources for Phase 2 resulted in a Ku-band phased array antenna system. Several development efforts are under way for a Ka-band phased array antenna system for Phase 3. Each phase includes test flights to demonstrate performance and capabilities. Successful completion of this project will result in a set of communications requirements for the next generation of launch vehicles.

  9. Development of Phased-array Antenna System and Its Application to EBWH/CD Experiments in QUEST

    NASA Astrophysics Data System (ADS)

    Idei, H.; Sakaguchi, M.; Kalinnikova, E. I.; Nagata, K.; Zushi, H.; Hanada, K.; Tashima, S.; Ishiguro, M.; Liu, H. Q.; Igami, H.; Kubo, S.; Nakamura, K.; Fujisawa, A.; Sakamoto, M.; Hassegawa, M.; Higashizono, Y.; Ogata, R.; Ryokai, T.; Sharma, S. K.; Kawasaki, S.; Nakashima, H.; Higashijima, A.; Takase, Y.; Maekawa, T.; Mitarai, O.; Kishimoto, Y.

    2011-02-01

    The prototype phased-array antenna system has been developed to control the incident angle and polarization to conduct the Electron Bernstein Wave Heating and Current Drive (EBWH/CD) experiments on the QUEST. The two orthogonal fields measured at the low power level were in excellent agreement with those evaluated by a developed Kirchhoff code. The elliptical polarization in two orthogonal fields can be controlled to excite pure O-mode in the oblique injection. The non-inductive plasma current of 10 kA was ramped up and sustained for 0.7 s. The phased-array antenna system for the reflectometry and the EBW radiometry has been also develoloped concerning the EBWH/CD experiments, and was confirmed to work well in the low power tests.

  10. Feed system design and experimental results in the uhf model study for the proposed Urbana phased array

    NASA Technical Reports Server (NTRS)

    Loane, J. T.; Bowhill, S. A.; Mayes, P. E.

    1982-01-01

    The effects of atmospheric turbulence and the basis for the coherent scatter radar techniques are discussed. The reasons are given for upgrading the Radar system to a larger steerable array. Phase array theory pertinent to the system design is reviewed, along with approximations for maximum directive gain and blind angles due to mutual coupling. The methods and construction techniques employed in the UHF model study are explained. The antenna range is described, with a block diagram for the mode of operation used.

  11. LDEF (Prelaunch), AO133 : Effect of Space Environment on Space-Based Radar Phased-Array Antenna, Tra

    NASA Technical Reports Server (NTRS)

    1984-01-01

    LDEF (Prelaunch), AO133 : Effect of Space Environment on Space-Based Radar Phased-Array Antenna, Tray H07 The prelaunch photograph was taken in SAEF II at KSC prior to installation of the integrated tray on the LDEF. The Space-Based Radar (SBR) Phased-Array Antenna Experiment occupies a six (6) inch deep LDEF end corner tray located on the space end of the LDEF. The SBR Phased-Array Antenna experiment consists of both passive and active parts. The passive part , shown in the left half of the experiment tray, investigates the dimensional stability of Kapton when exposed to induced stresses in the space environment. Continuous and spliced specimen of both plain Kapton (127 um thick) and glass reinforced Kapton (196 um thick) will be exposed for the entire mission. The Kapton specimen array contains eight 2.54-cm-wide specimen and sixteen (16) 1.27-cm-wide specimen. The specimen are stretched over an aluminum roller assembly and utilize a spring loaded mechanism to provide preselected stresses. An aluminum support structure houses two (2) identical set of specimen, one exposed to the total environment and one shadowed. The fasteners are non-magnetic stainless steel and the black surface is a thermal control coating, 3M-Nextel 401-610 (Black Velvet). The active part of the experiment, located in the right half of the tray, investigates the interaction between high voltage and low-Earth-orbit plasma. A fourteen (14) inch wide by twenty eight (28) inch long section of the Grumman SBR Phased-Array antenna consisting of two Kapton antenna planes and a perforated aluminum ground plane mounted on an aluminum support structure. Cop- per dipole elements deposited on the Kapton antenna plane provide the high voltage electrodes. The fasteners are non-magnetic stainless steel and the black surface is a thermal control coating, 3M-Nextel 401-610 (Black Velvet).

  12. Reconfigurable Transmission Line for a Series-Fed Ku-Band Phased Array Using a Single Feed

    NASA Technical Reports Server (NTRS)

    Host, Nicholas K.; Chen, Chi-Chih; Volakis, John L.; Miranda. Felix, A.

    2013-01-01

    The paper presents a novel approach to realize a lowcost phased array using a simple feeding mechanism. Specifically, a single coplanar stripline (CPS) transmission line is used to feed the antenna array elements. By controlling the CPS's dielectric properties using a movable dielectric plunger, scanning is achieved. Due to its simplicity, single feed, and no phase shifters, this approach leads to a dramatic reduction in cost which does not scale for larger arrays.

  13. Applying Ultrasonic Phased Array Technology to Examine Austenitic Coarse-Grained Structures for Light Water Reactor Piping

    SciTech Connect

    Anderson, Michael T.; Cumblidge, Stephen E.; Doctor, Steven R.

    2003-12-18

    Pacific Northwest Laboratory is evaluating the capabilities and limitations of phased array (PA) technology to detect service-type flaws in coarse-grained austenitic piping structures. The work is being sponsored by the U.S. Nuclear Regulatory Commission, Office of Research. This paper presents initial work involving the use of PA technology to determine the effectiveness of detecting and accurately characterizing flaws on the far-side of austenitic piping welds.

  14. Application of Piezocomposite Twin, Side by Side, Phased Array UT Probes for the Inspection of Stainless Steel

    SciTech Connect

    Delaide, M.; Dumas, Ph

    2005-04-09

    UT probes to be used for the examination of coarse-grain structure must allow to detect and size cracks, with a high reliability level. The combination of TRL probes, with phased array and piezocomposite technologies allows to improve probes performances and inspection speed. Single element crystals are replaced by matrix arrays, allowing to deflect and skew the beams, to change the inspection depth. This paper describes the designing, the manufacturing and the characterisation of several probes.

  15. Design and Characterization of Dual-Curvature 1.5-Dimensional High-Intensity Focused Ultrasound Phased-Array Transducer

    PubMed Central

    Chen, Gin-Shin; Lin, Che-Yu; Jeong, Jong Seob; Cannata, Jonathan M.; Lin, Win-Li; Chang, Hsu; Shung, K. Kirk

    2013-01-01

    A dual-curvature focused ultrasound phased-array transducer with a symmetric control has been developed for noninvasive ablative treatment of tumors. The 1.5-D array was constructed in-house and the electro-acoustic conversion efficiency was measured to be approximately 65%. In vitro experiments demonstrated that the array uses 256 independent elements to achieve 2-D wide-range high-intensity electronic focusing. PMID:22293745

  16. Graphene-based fine-tunable optical delay line for optical beamforming in phased-array antennas.

    PubMed

    Tatoli, Teresa; Conteduca, Donato; Dell'Olio, Francesco; Ciminelli, Caterina; Armenise, Mario N

    2016-06-01

    The design of an integrated graphene-based fine-tunable optical delay line on silicon nitride for optical beamforming in phased-array antennas is reported. A high value of the optical delay time (τg=920  ps) together with a compact footprint (4.15  mm2) and optical loss <27  dB make this device particularly suitable for highly efficient steering in active phased-array antennas. The delay line includes two graphene-based Mach-Zehnder interferometer switches and two vertically stacked microring resonators between which a graphene capacitor is placed. The tuning range is obtained by varying the value of the voltage applied to the graphene electrodes, which controls the optical path of the light propagation and therefore the delay time. The graphene provides a faster reconfigurable time and low values of energy dissipation. Such significant advantages, together with a negligible beam-squint effect, allow us to overcome the limitations of conventional RF beamformers. A highly efficient fine-tunable optical delay line for the beamsteering of 20 radiating elements up to ±20° in the azimuth direction of a tile in a phased-array antenna of an X-band synthetic aperture radar has been designed. PMID:27411185

  17. LDEF (Postflight), AO133 : Effect of Space Environment on Space-Based Radar Phased-Array Antenna, Tr

    NASA Technical Reports Server (NTRS)

    1990-01-01

    LDEF (Postflight), AO133 : Effect of Space Environment on Space-Based Radar Phased-Array Antenna, Tray H07 The postflight photograph was taken in the KSC SAEF II facility after the experiment was removed from the LDEF. The Space-Based Radar (SBR) Phased-Array Antenna occupies a six (6) inch deep LDEF end corner tray located on the space end of the LDEF. A light tan discoloration is visible on the left and lower flanges of the experiment tray and also on the unpainted aluminum filler to the left of the passive part of the experiment. A darker stain has discolored the lower corners of the tray structure. The SBR Phased-Array Antenna experiment, consisting of an active part in the upper half of the tray and a passive part located in the lower half of the experiment tray, appears to be intact with no apparent physical damage. The black thermal coating on the active part of the experiment appears to have changed from a flat black to a dark gray while the coating on the passive part of the experiment appears less degraded. The exposed Kapton specimen surfaces in both the active and passive parts of the experiment appear to have changed from specular to diffuse from exposure to the space environment.

  18. Graphene-based fine-tunable optical delay line for optical beamforming in phased-array antennas.

    PubMed

    Tatoli, Teresa; Conteduca, Donato; Dell'Olio, Francesco; Ciminelli, Caterina; Armenise, Mario N

    2016-06-01

    The design of an integrated graphene-based fine-tunable optical delay line on silicon nitride for optical beamforming in phased-array antennas is reported. A high value of the optical delay time (τg=920  ps) together with a compact footprint (4.15  mm2) and optical loss <27  dB make this device particularly suitable for highly efficient steering in active phased-array antennas. The delay line includes two graphene-based Mach-Zehnder interferometer switches and two vertically stacked microring resonators between which a graphene capacitor is placed. The tuning range is obtained by varying the value of the voltage applied to the graphene electrodes, which controls the optical path of the light propagation and therefore the delay time. The graphene provides a faster reconfigurable time and low values of energy dissipation. Such significant advantages, together with a negligible beam-squint effect, allow us to overcome the limitations of conventional RF beamformers. A highly efficient fine-tunable optical delay line for the beamsteering of 20 radiating elements up to ±20° in the azimuth direction of a tile in a phased-array antenna of an X-band synthetic aperture radar has been designed.

  19. A phased array antenna with a broadly steerable beam based on a low-loss metasurface lens

    NASA Astrophysics Data System (ADS)

    Liu, Yahong; Jin, Xueyu; Zhou, Xin; Luo, Yang; Song, Kun; Huang, Lvhongzi; Zhao, Xiaopeng

    2016-10-01

    A new concept for a gradient phase discontinuity metasurface lens integrated with a phased array antenna possessing a broadly steerable beam is presented in this paper. The metasurface lens is composed of a metallic H-shaped pattern and the metallic square split ring can achieve complete 360° transmission phase coverage at 30° phase intervals. The metasurface can refract an incident plane wave to an angle at will by varying the lattice constant. We demonstrate that the beam steering range of the phased array antenna is between 12° and 85° when the metasurface lens with a refracting electromagnetic wave is employed at 45°. Interestingly, the proposed array antenna has a much higher gain than a conventional phased array antenna at low elevation angles. It is expected that the proposed array antenna will have potential applications in wireless and satellite communications. Furthermore, the proposed array antenna is fabricated easily and is also low in cost due to its microstrip technology.

  20. Use of a Microphone Phased Array to Determine Noise Sources in a Rocket Plume

    NASA Technical Reports Server (NTRS)

    Panda, J.; Mosher, R.

    2010-01-01

    A 70-element microphone phased array was used to identify noise sources in the plume of a solid rocket motor. An environment chamber was built and other precautions were taken to protect the sensitive condenser microphones from rain, thunderstorms and other environmental elements during prolonged stay in the outdoor test stand. A camera mounted at the center of the array was used to photograph the plume. In the first phase of the study the array was placed in an anechoic chamber for calibration, and validation of the indigenous Matlab(R) based beamform software. It was found that the "advanced" beamform methods, such as CLEAN-SC was partially successful in identifying speaker sources placed closer than the Rayleigh criteria. To participate in the field test all equipments were shipped to NASA Marshal Space Flight Center, where the elements of the array hardware were rebuilt around the test stand. The sensitive amplifiers and the data acquisition hardware were placed in a safe basement, and 100m long cables were used to connect the microphones, Kulites and the camera. The array chamber and the microphones were found to withstand the environmental elements as well as the shaking from the rocket plume generated noise. The beamform map was superimposed on a photo of the rocket plume to readily identify the source distribution. It was found that the plume made an exceptionally long, >30 diameter, noise source over a large frequency range. The shock pattern created spatial modulation of the noise source. Interestingly, the concrete pad of the horizontal test stand was found to be a good acoustic reflector: the beamform map showed two distinct source distributions- the plume and its reflection on the pad. The array was found to be most effective in the frequency range of 2kHz to 10kHz. As expected, the classical beamform method excessively smeared the noise sources at lower frequencies and produced excessive side-lobes at higher frequencies. The "advanced" beamform

  1. Development of an Experimental Phased Array Feed System and Algorithms for Radio Astronomy

    NASA Astrophysics Data System (ADS)

    Landon, Jonathan C.

    Phased array feeds (PAFs) are a promising new technology for astronomical radio telescopes. While PAFs have been used in other fields, the demanding sensitivity and calibration requirements in astronomy present unique new challenges. This dissertation presents some of the first astronomical PAF results demonstrating the lowest noise temperature and highest sensitivity at the time (66 Kelvin and 3.3 m^2/K, respectively), obtained using a narrowband (425 kHz bandwidth)prototype array of 19 linear co-polarized L-band dipoles mounted at the focus of the Green Bank 20 Meter Telescope at the National Radio Astronomy Observatory (NRAO) in Green Bank, West Virginia. Results include spectral line detection of hydroxyl (OH) sources W49N and W3OH, and some of the first radio camera images made using a PAF, including an image of the Cygnus X region. A novel array Y-factor technique for measuring the isotropic noise response of the array is shown along with experimental measurements for this PAF. Statistically optimal beamformers (Maximum SNR and MVDR) are used throughout the work. Radio-frequency interference (RFI) mitigation is demonstrated experimentally using spatial cancelation with the PAF. Improved RFI mitigation is achieved in the challenging cases of low interference-to-noise ratio (INR) and moving interference by combining subspace projection (SP) beamforming with a polynomial model to track a rank 1 subspace. Limiting factors in SP are investigated including sample estimation error, subspace smearing, noise bias, and spectral scooping; each of these factors is overcome with the polynomial model and prewhitening. Numerical optimization leads to the polynomial subspace projection (PSP) method, and least-squares fitting to the series of dominant eigenvectors over a series of short term integrations (STIs) leads to the eigenvector polynomial subspace projection (EPSP) method. Expressions for the gradient, Hessian, and Jacobian are given for use in numerical optimization

  2. True-time-delay photonic beamformer for an L-band phased array radar

    NASA Astrophysics Data System (ADS)

    Zmuda, Henry; Toughlian, Edward N.; Payson, Paul M.; Malowicki, John E.

    1995-10-01

    The problem of obtaining a true-time-delay photonic beamformer has recently been a topic of great interest. Many interesting and novel approaches to this problem have been studied. This paper examines the design, construction, and testing of a dynamic optical processor for the control of a 20-element phased array antenna operating at L-band (1.2-1.4 GHz). The approach taken here has several distinct advantages. The actual optical control is accomplished with a class of spatial light modulator known as a segmented mirror device (SMD). This allows for the possibility of controlling an extremely large number (tens of thousands) of antenna elements using integrated circuit technology. The SMD technology is driven by the HDTV and laser printer markets so ultimate cost reduction as well as technological improvements are expected. Optical splitting is efficiently accomplished using a diffractive optical element. This again has the potential for use in antenna array systems with a large number of radiating elements. The actual time delay is achieved using a single acousto-optic device for all the array elements. Acousto-optic device technologies offer sufficient delay as needed for a time steered array. The topological configuration is an optical heterodyne system, hence high, potentially millimeter wave center frequencies are possible by mixing two lasers of slightly differing frequencies. Finally, the entire system is spatially integrated into a 3D glass substrate. The integrated system provides the ruggedness needed in most applications and essentially eliminates the drift problems associated with free space optical systems. Though the system is presently being configured as a beamformer, it has the ability to operate as a general photonic signal processing element in an adaptive (reconfigurable) transversal frequency filter configuration. Such systems are widely applicable in jammer/noise canceling systems, broadband ISDN, and for spread spectrum secure communications

  3. How High Frequency Trading Affects a Market Index

    PubMed Central

    Kenett, Dror Y.; Ben-Jacob, Eshel; Stanley, H. Eugene; gur-Gershgoren, Gitit

    2013-01-01

    The relationship between a market index and its constituent stocks is complicated. While an index is a weighted average of its constituent stocks, when the investigated time scale is one day or longer the index has been found to have a stronger effect on the stocks than vice versa. We explore how this interaction changes in short time scales using high frequency data. Using a correlation-based analysis approach, we find that in short time scales stocks have a stronger influence on the index. These findings have implications for high frequency trading and suggest that the price of an index should be published on shorter time scales, as close as possible to those of the actual transaction time scale. PMID:23817553

  4. Transformation ray method: controlling high frequency elastic waves (L).

    PubMed

    Chang, Zheng; Liu, Xiaoning; Hu, Gengkai; Hu, Jin

    2012-10-01

    Elastic ray theory is a high frequency asymptotic approximation of solution of elastodynamic equation, and is widely used in seismology. In this paper, the form invariance under a general spatial mapping and high frequency wave control have been examined by transformation method. It is showed that with the constraint of major and minor symmetry of the transformed elastic tensor, the eikonal equation keeps its form under a general mapping, however, the transport equation loses its form except for conformal mapping. Therefore, the elastic ray path can be controlled in an exact manner by a transformation method, whereas energy distribution along the ray is only approximately controlled. An elastic rotator based on ray tracing method is also provided to illustrate the method and to access the approximation. PMID:23039561

  5. Clustered Desynchronization from High-Frequency Deep Brain Stimulation.

    PubMed

    Wilson, Dan; Moehlis, Jeff

    2015-12-01

    While high-frequency deep brain stimulation is a well established treatment for Parkinson's disease, its underlying mechanisms remain elusive. Here, we show that two competing hypotheses, desynchronization and entrainment in a population of model neurons, may not be mutually exclusive. We find that in a noisy group of phase oscillators, high frequency perturbations can separate the population into multiple clusters, each with a nearly identical proportion of the overall population. This phenomenon can be understood by studying maps of the underlying deterministic system and is guaranteed to be observed for small noise strengths. When we apply this framework to populations of Type I and Type II neurons, we observe clustered desynchronization at many pulsing frequencies. PMID:26713619

  6. High-frequency oscillations and the neurobiology of schizophrenia.

    PubMed

    Uhlhaas, Peter J; Singer, Wolf

    2013-09-01

    Neural oscillations at low- and high-frequency ranges are a fundamental feature of large-scale networks. Recent evidence has indicated that schizophrenia is associated with abnormal amplitude and synchrony of oscillatory activity, in particular, at high (beta/gamma) frequencies. These abnormalities are observed during task-related and spontaneous neuronal activity which may be important for understanding the pathophysiology of the syndrome. In this paper, we shall review the current evidence for impaired beta/gamma-band oscillations and their involvement in cognitive functions and certain symptoms of the disorder. In the first part, we will provide an update on neural oscillations during normal brain functions and discuss underlying mechanisms. This will be followed by a review of studies that have examined high-frequency oscillatory activity in schizophrenia and discuss evidence that relates abnormalities of oscillatory activity to disturbed excitatory/inhibitory (E/I) balance. Finally, we shall identify critical issues for future research in this area.

  7. High-Frequency Power Gain in the Mammalian Cochlea

    NASA Astrophysics Data System (ADS)

    Maoiléidigh, Dáibhid Ó.; Hudspeth, A. J.

    2011-11-01

    Amplification in the mammalian inner ear is thought to result from a nonlinear active process known as the cochlear amplifier. Although there is much evidence that outer hair cells (OHCs) play a central role in the cochlear amplifier, the mechanism of amplification remains uncertain. In non-mammalian ears hair bundles can perform mechanical work and account for the active process in vitro, yet in the mammalian cochlea membrane-based electromotility is required for amplification in vivo. A key issue is how OHCs conduct mechanical power amplification at high frequencies. We present a physical model of a segment of the mammalian cochlea that can amplify the power of external signals. In this representation both electromotility and active hair-bundle motility are required for mechanical power gain at high frequencies. We demonstrate how the endocochlear potential, the OHC resting potential, Ca2+ gradients, and ATP-fueled myosin motors serve as the energy sources underlying mechanical power gain in the cochlear amplifier.

  8. High Frequency Amplitude Detector for GMI Magnetic Sensors

    PubMed Central

    Asfour, Aktham; Zidi, Manel; Yonnet, Jean-Paul

    2014-01-01

    A new concept of a high-frequency amplitude detector and demodulator for Giant-Magneto-Impedance (GMI) sensors is presented. This concept combines a half wave rectifier, with outstanding capabilities and high speed, and a feedback approach that ensures the amplitude detection with easily adjustable gain. The developed detector is capable of measuring high-frequency and very low amplitude signals without the use of diode-based active rectifiers or analog multipliers. The performances of this detector are addressed throughout the paper. The full circuitry of the design is given, together with a comprehensive theoretical study of the concept and experimental validation. The detector has been used for the amplitude measurement of both single frequency and pulsed signals and for the demodulation of amplitude-modulated signals. It has also been successfully integrated in a GMI sensor prototype. Magnetic field and electrical current measurements in open- and closed-loop of this sensor have also been conducted. PMID:25536003

  9. Imaging Observations of a Very High Frequency Type II Burst

    NASA Astrophysics Data System (ADS)

    White, S. M.; Mercier, C.; Bradley, R.; Bastian, T.; Kerdraon, A.; Pick, M.

    2006-05-01

    A remarkable Type II burst was detected by the high-frequency system of the Green Bank Solar Radio Burst Spectrometer on 2005 November 14. The harmonic branch of the Type II extended up to 800 MHz, making it one of the highest frequency Type II bursts ever detected, but it failed to propagate to heights corresponding to frequencies below 100 MHz. At such high frequencies, it implies the formation of a shock relatively low in the corona. No coronal mass ejection was evident in the LASCO data for this east limb event. It is one of the few Type II bursts to be observable at every frequency of observation of the Nancay Radio Heliograph (164-432 MHz). Here we present analysis of images of the event, including simultaneous imaging of the fundamental and harmonic branches.

  10. Clustered Desynchronization from High-Frequency Deep Brain Stimulation

    PubMed Central

    Wilson, Dan; Moehlis, Jeff

    2015-01-01

    While high-frequency deep brain stimulation is a well established treatment for Parkinson’s disease, its underlying mechanisms remain elusive. Here, we show that two competing hypotheses, desynchronization and entrainment in a population of model neurons, may not be mutually exclusive. We find that in a noisy group of phase oscillators, high frequency perturbations can separate the population into multiple clusters, each with a nearly identical proportion of the overall population. This phenomenon can be understood by studying maps of the underlying deterministic system and is guaranteed to be observed for small noise strengths. When we apply this framework to populations of Type I and Type II neurons, we observe clustered desynchronization at many pulsing frequencies. PMID:26713619

  11. Parametric Study of High Frequency Pulse Detonation Tubes

    NASA Technical Reports Server (NTRS)

    Cutler, Anderw D.

    2008-01-01

    This paper describes development of high frequency pulse detonation tubes similar to a small pulse detonation engine (PDE). A high-speed valve injects a charge of a mixture of fuel and air at rates of up to 1000 Hz into a constant area tube closed at one end. The reactants detonate in the tube and the products exit as a pulsed jet. High frequency pressure transducers are used to monitor the pressure fluctuations in the device and thrust is measured with a balance. The effects of injection frequency, fuel and air flow rates, tube length, and injection location are considered. Both H2 and C2H4 fuels are considered. Optimum (maximum specific thrust) fuel-air compositions and resonant frequencies are identified. Results are compared to PDE calculations. Design rules are postulated and applications to aerodynamic flow control and propulsion are discussed.

  12. High frequency vibration analysis by the complex envelope vectorization.

    PubMed

    Giannini, O; Carcaterra, A; Sestieri, A

    2007-06-01

    The complex envelope displacement analysis (CEDA) is a procedure to solve high frequency vibration and vibro-acoustic problems, providing the envelope of the physical solution. CEDA is based on a variable transformation mapping the high frequency oscillations into signals of low frequency content and has been successfully applied to one-dimensional systems. However, the extension to plates and vibro-acoustic fields met serious difficulties so that a general revision of the theory was carried out, leading finally to a new method, the complex envelope vectorization (CEV). In this paper the CEV method is described, underlying merits and limits of the procedure, and a set of applications to vibration and vibro-acoustic problems of increasing complexity are presented.

  13. Microstrip antenna modeling and measurement at high frequencies

    SciTech Connect

    Bevensee, R.M.

    1986-04-30

    This report addresses the task C(i) of the Proposal for Microstrip Antenna Modeling and Measurement at High Frequencies by the writer, July 1985. The task is: Assess the advantages and disadvantages of the three computational approaches outlined in the Proposal, including any difficulties to be resolved and an estimate of the time required to implement each approach. The three approaches are (1) Finite Difference, (2) Sommerfeld-GTD-MOM, and (3) Surface Intergral Equations - MOM. These are discussed in turn.

  14. High-frequency audibility: benefits for hearing-impaired listeners.

    PubMed

    Hogan, C A; Turner, C W

    1998-07-01

    The present study was a systematic investigation of the benefit of providing hearing-impaired listeners with audible high-frequency speech information. Five normal-hearing and nine high-frequency hearing-impaired listeners identified nonsense syllables that were low-pass filtered at a number of cutoff frequencies. As a means of quantifying audibility for each condition, Articulation Index (AI) was calculated for each condition for each listener. Most hearing-impaired listeners demonstrated an improvement in speech recognition as additional audible high-frequency information was provided. In some cases for more severely impaired listeners, increasing the audibility of high-frequency speech information resulted in no further improvement in speech recognition, or even decreases in speech recognition. A new measure of how well hearing-impaired listeners used information within specific frequency bands called "efficiency" was devised. This measure compared the benefit of providing a given increase in speech audibility to a hearing-impaired listener to the benefit observed in normal-hearing listeners for the same increase in speech audibility. Efficiencies were calculated using the old AI method and the new AI method (which takes into account the effects of high speech presentation levels). There was a clear pattern in the results suggesting that as the degree of hearing loss at a given frequency increased beyond 55 dB HL, the efficacy of providing additional audibility to that frequency region was diminished, especially when this degree of hearing loss was present at frequencies of 4000 Hz and above. A comparison of analyses from the "old" and "new" AI procedures suggests that some, but not all, of the deficiencies of speech recognition in these listeners was due to high presentation levels.

  15. High frequency resolution terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Sangala, Bagvanth Reddy

    2013-12-01

    A new method for the high frequency resolution terahertz time-domain spectroscopy is developed based on the characteristic matrix method. This method is useful for studying planar samples or stack of planar samples. The terahertz radiation was generated by optical rectification in a ZnTe crystal and detected by another ZnTe crystal via electro-optic sampling method. In this new characteristic matrix based method, the spectra of the sample and reference waveforms will be modeled by using characteristic matrices. We applied this new method to measure the optical constants of air. The terahertz transmission through the layered systems air-Teflon-air-Quartz-air and Nitrogen gas-Teflon-Nitrogen gas-Quartz-Nitrogen gas was modeled by the characteristic matrix method. A transmission coefficient is derived from these models which was optimized to fit the experimental transmission coefficient to extract the optical constants of air. The optimization of an error function involving the experimental complex transmission coefficient and the theoretical transmission coefficient was performed using patternsearch algorithm of MATLAB. Since this method takes account of the echo waveforms due to reflections in the layered samples, this method allows analysis of longer time-domain waveforms giving rise to very high frequency resolution in the frequency-domain. We have presented the high frequency resolution terahertz time-domain spectroscopy of air and compared the results with the literature values. We have also fitted the complex susceptibility of air to the Lorentzian and Gaussian functions to extract the linewidths.

  16. Nonlocal theory for heat transport at high frequencies

    NASA Astrophysics Data System (ADS)

    Koh, Yee Kan; Cahill, David G.; Sun, Bo

    2014-11-01

    We develop a nonlocal theory for heat conduction under high-frequency temperature fields and apply the theory to explain reductions of the apparent thermal conductivity observed in recent experiments. Our nonlocal theory is an analytical solution of the Boltzmann transport equation for phonons in a semi-infinite solid, similar to a prior nonlocal theory for heat conduction under a high-temperature gradient but subjected to periodic heating at the surface. The boundary condition of periodic heating, as opposed to prior calculations of heating by a single laser pulse, better mimics time-domain thermoreflectance (TDTR) and broadband frequency-domain thermoreflectance (BB-FDTR) measurements. We find that, except for pure crystals at high frequencies, the effective thermal conductivity derived using the nonlocal theory compares well with calculations of a modified Callaway model that includes an upper limit on the phonon mean-free path at twice the thermal penetration depth. For pure crystals, however, the effective thermal conductivity derived from the out-of-phase calculations are independent of frequency, in agreement with prior TDTR measurements, due to the countereffect of reduced heat flux and diminished relative phase between the heat flux and temperature oscillations at high frequencies. Our results suggest that empirical interpretation of ballistic phonons not contributing to heat conduction is not general and can only be applied to measurements on alloys and not pure crystals, even when a large laser spot size is used in the experiments and the interfacial thermal resistance is negligible.

  17. The Origin of High-Frequency Hearing in Whales.

    PubMed

    Churchill, Morgan; Martinez-Caceres, Manuel; de Muizon, Christian; Mnieckowski, Jessica; Geisler, Jonathan H

    2016-08-22

    Odontocetes (toothed whales) rely upon echoes of their own vocalizations to navigate and find prey underwater [1]. This sensory adaptation, known as echolocation, operates most effectively when using high frequencies, and odontocetes are rivaled only by bats in their ability to perceive ultrasonic sound greater than 100 kHz [2]. Although features indicative of ultrasonic hearing are present in the oldest known odontocetes [3], the significance of this finding is limited by the methods employed and taxa sampled. In this report, we describe a new xenorophid whale (Echovenator sandersi, gen. et sp. nov.) from the Oligocene of South Carolina that, as a member of the most basal clade of odontocetes, sheds considerable light on the evolution of ultrasonic hearing. By placing high-resolution CT data from Echovenator sandersi, 2 hippos, and 23 fossil and extant whales in a phylogenetic context, we conclude that ultrasonic hearing, albeit in a less specialized form, evolved at the base of the odontocete radiation. Contrary to the hypothesis that odontocetes evolved from low-frequency specialists [4], we find evidence that stem cetaceans, the archaeocetes, were more sensitive to high-frequency sound than their terrestrial ancestors. This indicates that selection for high-frequency hearing predates the emergence of Odontoceti and the evolution of echolocation. PMID:27498568

  18. High-frequency hearing loss among mobile phone users.

    PubMed

    Velayutham, P; Govindasamy, Gopala Krishnan; Raman, R; Prepageran, N; Ng, K H

    2014-01-01

    The objective of this study is to assess high frequency hearing (above 8 kHz) loss among prolonged mobile phone users is a tertiary Referral Center. Prospective single blinded study. This is the first study that used high-frequency audiometry. The wide usage of mobile phone is so profound that we were unable to find enough non-users as a control group. Therefore we compared the non-dominant ear to the dominant ear using audiometric measurements. The study was a blinded study wherein the audiologist did not know which was the dominant ear. A total of 100 subjects were studied. Of the subjects studied 53% were males and 47% females. Mean age was 27. The left ear was dominant in 63%, 22% were dominant in the right ear and 15% did not have a preference. This study showed that there is significant loss in the dominant ear compared to the non-dominant ear (P < 0.05). Chronic usage mobile phone revealed high frequency hearing loss in the dominant ear (mobile phone used) compared to the non dominant ear.

  19. Source of high-frequency oscillations in oblique saccade trajectory.

    PubMed

    Ghasia, Fatema F; Shaikh, Aasef G

    2014-04-01

    Most common eye movements, oblique saccades, feature rapid velocity, precise amplitude, but curved trajectory that is variable from trial-to-trial. In addition to curvature and inter-trial variability, the oblique saccade trajectory also features high-frequency oscillations. A number of studies proposed the physiological basis of the curvature and inter-trial variability of the oblique saccade trajectory, but kinematic characteristics of high-frequency oscillations are yet to be examined. We measured such oscillations and compared their properties with orthogonal pure horizontal and pure vertical oscillations generated during pure vertical and pure horizontal saccades, respectively. We found that the frequency of oscillations during oblique saccades ranged between 15 and 40 Hz, consistent with the frequency of orthogonal saccadic oscillations during pure horizontal or pure vertical saccades. We also found that the amplitude of oblique saccade oscillations was larger than pure horizontal and pure vertical saccadic oscillations. These results suggest that the superimposed high-frequency sinusoidal oscillations upon the oblique saccade trajectory represent reverberations of disinhibited circuit of reciprocally innervated horizontal and vertical burst generators.

  20. Neuronal morphology generates high-frequency firing resonance.

    PubMed

    Ostojic, Srdjan; Szapiro, Germán; Schwartz, Eric; Barbour, Boris; Brunel, Nicolas; Hakim, Vincent

    2015-05-01

    The attenuation of neuronal voltage responses to high-frequency current inputs by the membrane capacitance is believed to limit single-cell bandwidth. However, neuronal populations subject to stochastic fluctuations can follow inputs beyond this limit. We investigated this apparent paradox theoretically and experimentally using Purkinje cells in the cerebellum, a motor structure that benefits from rapid information transfer. We analyzed the modulation of firing in response to the somatic injection of sinusoidal currents. Computational modeling suggested that, instead of decreasing with frequency, modulation amplitude can increase up to high frequencies because of cellular morphology. Electrophysiological measurements in adult rat slices confirmed this prediction and displayed a marked resonance at 200 Hz. We elucidated the underlying mechanism, showing that the two-compartment morphology of the Purkinje cell, interacting with a simple spiking mechanism and dendritic fluctuations, is sufficient to create high-frequency signal amplification. This mechanism, which we term morphology-induced resonance, is selective for somatic inputs, which in the Purkinje cell are exclusively inhibitory. The resonance sensitizes Purkinje cells in the frequency range of population oscillations observed in vivo. PMID:25948257