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1

Metamaterial-based efficient electrically small antennas  

Microsoft Academic Search

A metamaterial paradigm for achieving an efficient, electrically small antenna is introduced. Spherical shells of homogenous, isotropic negative permittivity (ENG) material are designed to create electrically small resonant systems for several antennas: an infinitesimal electric dipole, a very short center-fed cylindrical electric dipole, and a very short coaxially-fed electric monopole over an infinite ground plane. Analytical and numerical models demonstrate

Richard W. Ziolkowski; Aycan Erentok

2006-01-01

2

Metamaterial-Inspired Efficient Electrically Small Antennas  

Microsoft Academic Search

Planar two-dimensional (2D) and volumetric three-dimensional (3D) metamaterial-inspired efficient electrically-small antennas that are easy to design; are easy and inexpensive to build; and are easy to test; are reported, i.e., the EZ antenna systems. The proposed 2D and 3D electrical- and magnetic-based EZ antennas are shown to be naturally matched to a 50 source, i.e., without the introduction of a

Aycan Erentok; Richard W. Ziolkowski

2008-01-01

3

Electrically Small Folded Slot Antenna Utilizing Capacitive Loaded Slot Lines  

NASA Technical Reports Server (NTRS)

This paper presents an electrically small, coplanar waveguide fed, folded slot antenna that uses capacitive loading. Several antennas are fabricated with and without capacitive loading to demonstrate the ability of this design approach to reduce the resonant frequency of the antenna, which is analogous to reducing the antenna size. The antennas are fabricated on Cu-clad Rogers Duriod(TM) 6006 with multilayer chip capacitors to load the antennas. Simulated and measured results show close agreement, thus, validating the approach. The electrically small antennas have a measured return loss greater than 15 dB and a gain of 5.4, 5.6, and 2.7 dBi at 4.3, 3.95, and 3.65 GHz, respectively.

Scardelletti, Maximilian C.; Ponchak, George E.; Merritt, Shane; Minor, John S.; Zorman, Christian A.

2007-01-01

4

Design Methodology for Wideband Electrically Small Antennas (ESA) Based on the Theory of Characteristic Modes (CM).  

E-print Network

??Emerging broadband applications with market pressures for miniaturized communication devices have encouraged the use of electrically small antennas (ESA) and highly integrated RF circuitry for… (more)

Obeidat, Khaled Ahmad

2010-01-01

5

Achieving wide bandwidth electrically small antennas using internal non-foster elements  

NASA Astrophysics Data System (ADS)

Electromagnetic equations pertaining to electrically small dipole antennas and electrically small monopole antennas with small circular ground planes are reviewed. Two electrically small antenna designs are analyzed numerically and the results are compared. The first is a frequency agile version of the two-dimensional (2D) planar Egyptian axe dipole (EAD) antenna. The second is its three-dimensional (3D) counterpart. The frequency agile performance characteristics of both the 2D and 3D EAD designs are studied and compared. The potential for non-Foster augmentation to achieve large instantaneous fractional impedance bandwidths is detailed for each antenna. In addition, details are given on how to run frequency agile simulations in both ANSYS HFSS and Agilent's ADS. Details are also provided on how to generate an antenna's non-Foster |S11| and radiation efficiency curves using HFSS, and how to generate an antenna's non-Foster |S11| curve using ADS.

Cutshall, Ryan T.

6

Low-Q, Electrically Small, Efficient Near-Field Resonant Parasitic Antennas  

Microsoft Academic Search

Metamaterial-inspired electrically small Z, stub and canopy antennas are reported. They are near-field, resonant parasitic designs. Different Z and stub antenna configurations and the effect on their Q values are studied. Their behavior led to the canopy antenna design. At the size of ka ~ 0.046, the canopy antenna is an electric-based antenna with high overall efficiency (over 90%) and

Peng Jin; Richard W. Ziolkowski

2009-01-01

7

Thin magnetic conductor substrate for placement-immune, electrically-small antennas.  

SciTech Connect

An antenna is considered to be placement-immune when the antenna operates effectively regardless of where it is placed. By building antennas on magnetic conductor materials, the radiated fields will be positively reinforced in the desired radiation direction instead of being negatively affected by the environment. Although this idea has been discussed thoroughly in theoretical research, the difficulty in building thin magnetic conductor materials necessary for in-phase field reflections prevents this technology from becoming more widespread. This project's purpose is to build and measure an electrically-small antenna on a new type of non-metallic, thin magnetic conductor. This problem has not been previously addressed because non-metallic, thin magnetic conductor materials have not yet been discovered. This work proposed the creation of an artificial magnetic conductor (AMC) with in-phase field reflections without using internal electric conductors, the placement of an electrically-small antenna on this magnetic conductor, and the development of a transmit-receive system that utilizes the substrate and electrically-small antenna. By not using internal electric conductors to create the AMC, the substrate thickness can be minimized. The electrically-small antenna will demonstrate the substrate's ability to make an antenna placement immune, and the transmit-receive system combines both the antenna and the substrate while adding a third layer of system complexity to demonstrate the complete idea.

Eubanks, Travis Wayne; McDonald, Jacob J.; Loui, Hung

2011-09-01

8

Electrically small antennas: developments in the early decades of the 20th century  

Microsoft Academic Search

Today, it is well known that the performance of an electrically small antenna is a function of how well it is impedance matched to the transmitter and receiver and how well its radiation efficiency is maximized. Recently, much attention has also focused on optimizing the bandwidth or quality factor (Q) of small antennas as a function of their electrical size.

Steven R. Best

2012-01-01

9

Aircraft antennas/conformal antennas missile antennas  

NASA Astrophysics Data System (ADS)

Three major areas of airborne microwave antennas are examined. The basic system environment for missile telemetry/telecommand and fuze functions is sketched and the basic antenna design together with practical examples are discussed. The principle requirements of modern nose radar flat plate antennas are shown to result from missile/aircraft system requirements. Basic principles of slotted waveguide antenna arrays are sketched and practical antenna designs are discussed. The present early warning system designs are sketched to point out requirements and performance of practical radar warning and jamming antennas (broadband spiral antennas and horn radiators). With respect to newer developments in the ECM scenario, some demonstrated and proposed antenna systems (lens fed arrays, phased array, active array) are discussed.

Solbach, Klaus

1987-04-01

10

Electrically small antennas and the low-frequency aircraft antenna problem  

Microsoft Academic Search

This paper is concerned with the properties of antennas which are small relative to their operating wavelength. A brief analysis based upon quasi-static principles is presented, and two experimental procedures suggested by the nature of the analytical results are described. The application of these experimental procedures is illustrated with examples of measurements made in connection with the design of low-frequency

J. Bolljahn; R. Reese

1953-01-01

11

The Study and Implementation of Electrically Small Printed Antennas for an Integrated Transceiver Design  

SciTech Connect

This work focuses on the design and evaluation of the inverted-F, meandering-monopole, and loop antenna geometries. These printed antennas are studied with the goal of identifying which is suitable for use in a miniaturized transceiver design and which has the ability to provide superior performance using minimal Printed Circuit Board (PCB) space. As a result, the main objective is to characterize tradeoffs and identify which antenna provides the best compromise among volume, bandwidth and efficiency. For experimentation purposes, three types of meandering-monopole antenna are examined resulting in five total antennas for the study. The performance of each antenna under study is evaluated based upon return loss, operational bandwidth, and radiation pattern characteristics. For our purposes, return loss is measured using the S11-port reflection coefficient which helps to characterize how well the small antenna is able to be efficiently fed. Operational bandwidth is measured as the frequency range over which the antenna maintains 2:1 Voltage Standing Wave Ratio (VSWR) or equivalently has 10-dB return loss. Ansoft High Frequency Structure Simulator (HFSS) is used to simulate expected resonant frequency, bandwidth, VSWR, and radiation pattern characteristics. Ansoft HFSS simulation is used to provide a good starting point for antenna design before actual prototype are built using an LPKF automated router. Simulated results are compared with actual measurements to highlight any differences and help demonstrate the effects of antenna miniaturization. Radiation characteristics are measured illustrating how each antenna is affected by the influence of a non-ideal ground plane. The antenna with outstanding performance is further evaluated to determine its maximum range of communication. Each designs range performance is evaluated using a pair of transceivers to demonstrate round-trip communication. This research is intended to provide a knowledge base which will help decrease the number of design iterations needed for future implementation of products requiring integration of small printed antennas. In the past, several design iterations have been needed to fine tune antenna dimensions and achieve acceptable levels of performance. This process consumes a large amount of time and material resources leading to costly development of transceiver designs. Typically, this occurs because matching components and antenna geometries are almost never correct on the first design. This work hopes to determine the limitations associated with antenna miniaturization and provide well known antenna examples that can be easily used in future work.

Speer, Pete

2009-04-15

12

Electrically small, near-field resonant parasitic (NFRP) antennas augmented with passive and active circuit elements to enhance their functionality  

NASA Astrophysics Data System (ADS)

Metamaterials have drawn considerable attention because they can exhibit epsilon-negative (ENG) and/or mu-negative (MNG) properties, which in turn can lead to exotic physical effects that can enable interesting, practical applications. For instance, ENG and MNG properties can be engineered to yield double negative (DNG) properties, such as a negative index of refraction, which leads to flat lenses. Similarly, their extreme versions enable cloaking effects. Inspired by such metamaterial properties, a promising methodology has been developed to design electrically small antennas (ESAs). These ESAs use unit cells of metamaterials as their near-field resonant parasitic (NFRP) elements. This new metamaterial-inspired antenna miniaturization method is extended in this dissertation by augmenting the antenna designs with circuits. A rectifying circuit augmentation is used to achieve electrically small, high efficiency rectenna systems. Rectennas are the enabling components of power harvesting and wireless power transmission systems. Electrically small, integrated rectennas have become popular and in demand for several wireless applications including sensor networks and bio-implanted devices. Four global positioning system (GPS) L1 frequency (1.5754 GHz) rectenna systems were designed, fabricated and measured: three resistor-loaded and one supercapacitor-loaded. The simulated and measured results will be described; good agreement between them was obtained. The NFRP ESAs are also augmented with active, non-Foster elements in order to overcome the physical limits of the impedance bandwidth of passive ESA systems. Unlike conventional active external matching network approaches, the non-Foster components are incorporated directly into the NFRP element of the ESA. Three 300 MHz non-Foster circuit-augmented broadband, ESA systems were demonstrated: an Egyptian axe monopole (EAM) antenna, an Egyptian axe dipole (EAD) antenna, and a protractor antenna. The simulated and measured results will be described; reasonable agreement between them was obtained. Moreover, a deeper practical engineering understanding of how lumped components with tighter tolerances, more accurate transistor models, and integrated circuit-based implementations will lead to more satisfactory performance characteristics of the non-Foster circuit-augmented ESAs was accomplished and is also reported.

Zhu, Ning

13

The Study and Implementation of Electrically Small Printed Antennas for an Integrated Transceiver Design  

E-print Network

the antenna maintains 2:1 Voltage Standing Wave Ratio (VSWR) or equivalently has 10-dB return loss. Ansoft High Frequency Structure Simulator (HFSS) is used to simulate expected resonant frequency, bandwidth, VSWR, and radiation pattern characteristics. Ansoft...

Speer, Peter Clark

2009-01-01

14

New results for minimum Q, maximum gain, and polarization properties of electrically small arbitrary antennas  

Microsoft Academic Search

This paper will review previous and recent work on the maximum gain and minimum Q of arbitrary lossless antennas, with the goal of trying to eliminate some of the confusion, incompleteness, and erroneous statements that sometimes occur in the literature. Our attention will primarily focus on the effects of polarization and the presence of TM, TE, or TM and TE

David M. Pozar

2009-01-01

15

Conformal Fractal Loop Antennas for RFID Tag Applications  

Microsoft Academic Search

This paper presents the design of novel conformal fractal loop antennas proposed for the rapidly developing RF identification (RFID) wireless technology. Two antennas, based on Koch and Hilbert fractal geometries, are designed and optimized for 0.953 GHz RFID band. Key design requirement has been maximizing the antenna gain and directivity that results in increasing the read range of RFID system.

Andrey S. Andrenko

2005-01-01

16

Conformal, Transparent Printed Antenna Developed for Communication and Navigation Systems  

NASA Technical Reports Server (NTRS)

Conformal, transparent printed antennas have advantages over conventional antennas in terms of space reuse and aesthetics. Because of their compactness and thin profile, these antennas can be mounted on video displays for efficient integration in communication systems such as palmtop computers, digital telephones, and flat-panel television displays. As an array of multiple elements, the antenna subsystem may save weight by reusing space (via vertical stacking) on photovoltaic arrays or on Earth-facing sensors. Also, the antenna could go unnoticed on automobile windshields or building windows, enabling satellite uplinks and downlinks or other emerging high-frequency communications.

Lee, Richard Q.; Simons, Rainee N.

1999-01-01

17

Thin conformal antenna array for microwave power conversions  

NASA Technical Reports Server (NTRS)

A structure of a circularly polarized, thin conformal, antenna array which may be mounted integrally with the skin of an aircraft employs microstrip elliptical elements and interconnecting feed lines spaced from a circuit ground plane by a thin dielectric layer. The feed lines are impedance matched to the elliptical antenna elements by selecting a proper feedpoint inside the periphery of the elliptical antenna elements. Diodes connected between the feed lines and the ground plane rectify the microwave power, and microstrip filters (low pass) connected in series with the feed lines provide dc current to a microstrip bus. Low impedance matching strips are included between the elliptical elements and the rectifying and filtering elements.

Dickinson, R. M. (inventor)

1978-01-01

18

Thermal analysis of a conformal phased array antenna  

Microsoft Academic Search

Development of an advanced re-entry vehicle instrumentation system required the thermal\\/structural analysis of a conformal phased array antenna subjected to hypersonic re-entry velocities. Thermal, structural, and electrical considerations mandated that three-dimensional temperature fields in a charring, ablating medium be developed. The approach taken to solve the problem was to develop boundary conditions via multiple 1-D charring ablation analyses and impose

K. Campion; L. R. Paradis; F. A. Shukis

1984-01-01

19

A finite element-boundary integral method for conformal antenna arrays on a circular cylinder  

NASA Technical Reports Server (NTRS)

Conformal antenna arrays offer many cost and weight advantages over conventional antenna systems. In the past, antenna designers have had to resort to expensive measurements in order to develop a conformal array design. This was due to the lack of rigorous mathematical models for conformal antenna arrays. As a result, the design of conformal arrays was primarily based on planar antenna design concepts. Recently, we have found the finite element-boundary integral method to be very successful in modeling large planar arrays of arbitrary composition in a metallic plane. We are extending this formulation to conformal arrays on large metallic cylinders. In doing so, we will develop a mathematical formulation. In particular, we discuss the finite element equations, the shape elements, and the boundary integral evaluation. It is shown how this formulation can be applied with minimal computation and memory requirements.

Kempel, Leo C.; Volakis, John L.

1992-01-01

20

A finite element-boundary integral method for conformal antenna arrays on a circular cylinder  

NASA Technical Reports Server (NTRS)

Conformal antenna arrays offer many cost and weight advantages over conventional antenna systems. In the past, antenna designers have had to resort to expensive measurements in order to develop a conformal array design. This is due to the lack of rigorous mathematical models for conformal antenna arrays, and as a result the design of conformal arrays is primarily based on planar antenna design concepts. Recently, we have found the finite element-boundary integral method to be very successful in modeling large planar arrays of arbitrary composition in a metallic plane. Herewith we shall extend this formulation for conformal arrays on large metallic cylinders. In this we develop the mathematical formulation. In particular we discuss the finite element equations, the shape elements, and the boundary integral evaluation, and it is shown how this formulation can be applied with minimal computation and memory requirements. The implementation shall be discussed in a later report.

Kempel, Leo C.; Volakis, John L.; Woo, Alex C.; Yu, C. Long

1992-01-01

21

Thermal analysis of a conformal phased array antenna  

NASA Astrophysics Data System (ADS)

Development of an advanced re-entry vehicle instrumentation system required the thermal/structural analysis of a conformal phased array antenna subjected to hypersonic re-entry velocities. Thermal, structural, and electrical considerations mandated that three-dimensional temperature fields in a charring, ablating medium be developed. The approach taken to solve the problem was to develop boundary conditions via multiple 1-D charring ablation analyses and impose these on a 3D ADINA-T model using the GIFTS preprocessing routine. A time-temperature boundary condition was imposed on the 3-D model at a depth below the pre-flight external surface. ADINA-T developed the in-depth temperature fields, which were than used together with other structural analysis routines to estimate material stress levels during flight.

Campion, K.; Paradis, L. R.; Shukis, F. A.

1984-06-01

22

Rapid Prototyping of Conformal Antenna Structures , R.C.Y.Auyeung1  

E-print Network

compatible with conformal antenna designs. 2. TECHNICAL APPROACH A spherical fiberglass dome was chosen range of orientations. The fiberglass domes were coated with a ~100 µm thick conductive silver epoxy of the fiberglass dome affecte

Arnold, Craig B.

23

Characteristics of a Linearly Tapered Slot Antenna (LTSA) Conformed Longitudinally Around a Cylinder  

NASA Technical Reports Server (NTRS)

The family of tapered slot antennas (TSA s) is suitable for numerous applications. Their ease of fabrication, wide bandwidth, and high gain make them desirable for military and commercial systems. Fabrication on thin, flexible substrates allows the TSA to be conformed over a given body, such as an aircraft wing or a piece of clothing for wearable networks. Previously, a Double Exponentially Tapered Slot Antenna (DETSA) was conformed around an exponential curvature, which showed that the main beam skewed towards the direction of curvature. This paper presents a Linearly Tapered Slot Antenna (LTSA) conformed longitudinally around a cylinder. Measured and simulated radiation patterns and the direction of maximum H co-polarization (Hco) as a function of the cylinder radius are presented.

Jordan, Jennifer L.; Ponchak, George E.; Tavassolian, Negar; Tentzeris, Manos M.

2007-01-01

24

Designing of a small wearable conformal phased array antenna for wireless communications  

NASA Astrophysics Data System (ADS)

In this thesis, a unique design of a self-adapting conformal phased-array antenna system for wireless communications is presented. The antenna system is comprised of one microstrip antenna array and a sensor circuit. A 1x4 printed microstrip patch antenna array was designed on a flexible substrate with a resonant frequency of 2.47 GHz. However, the performance of the antenna starts to degrade as the curvature of the surface of the substrate changes. To recover the performance of the system, a flexible sensor circuitry was designed. This sensor circuitry uses analog phase shifters, a flexible resistor and operational-amplifier circuitry to compensate the phase of each array element of the antenna. The proposed analytical method for phase compensation has been first verified by designing an RF test platform consisting of a microstrip antenna array, commercially available analog phase shifters, analog voltage attenuators, 4-port power dividers and amplifiers. The platform can be operated through a LabVIEW GUI interface using a 12-bit digital-to-analog converter. This test board was used to design and calibrate the sensor circuitry by observing the behavior of the antenna array system on surfaces with different curvatures. In particular, this phased array antenna system was designed to be used on the surface of a spacesuit or any other flexible prototype. This work was supported in part by the Defense Miroelectronics Activity (DMEA), NASA ND EPSCoR and DARPA/MTO.

Roy, Sayan

25

Design of antenna conformal to V-shaped tail of UAV based on the method of Characteristic Modes  

Microsoft Academic Search

The method of characteristic modes is used to design a vertically polarized communications antenna conformal to the V-shaped tail of a small UAV. The antenna must operate in the band from 50 to 90 MHz and must be omni-directional. This antenna has a vertical dimension of lambda\\/17 at 50 MHz.

Khaled Obeidat; Roberto G. Rojas; Bryan Raines

2009-01-01

26

Fast Characterization of Radiation Patterns of Conformal Array Antennas  

E-print Network

of such large arrays for a range of beam steering and observation directions poses a non- trivial computational of the radiation patterns of beam steered conformal arrays is presented. The algorithm can be used to obtain errors. The computational scheme is based on a hierarchical decomposition of the array into smaller sub

Paris-Sud XI, Université de

27

An investigation of conformable antennas for the astronaut backpack communication system  

NASA Technical Reports Server (NTRS)

During periods of extravehicular activity it is obviously important that communication and telemetry systems continue to function independently of the astronaut. A system of antennas must therefore be designed that will provide the necessary isotropic coverage using circular polarization over both the transmit and receive frequency bands. To avoid the inherent physical limitations to motion that would be incurred with any sort of protruding antenna, it is necessary that the radiator be essentially flush-mounted or conformable to the structure on which it is attached. Several individual antenna elements are needed for the desired coverage. Both the particular elements chosen and their location determine the ultimate radiation pattern of the overall system. For these reasons a two-fold research plan was undertaken. First, individual elements were investigated and designed. Then various mounting locations were considered and the radiation patterns were predicted taking into account the effects of the astronaut's backpack.

Long, Stuart A.; Jackson, David R.; Williams, Jeffery T.; Wilton, Donald R.

1988-01-01

28

An investigation of conformable antennas for the astronaut backpack communication system  

NASA Astrophysics Data System (ADS)

During periods of extravehicular activity it is obviously important that communication and telemetry systems continue to function independently of the astronaut. A system of antennas must therefore be designed that will provide the necessary isotropic coverage using circular polarization over both the transmit and receive frequency bands. To avoid the inherent physical limitations to motion that would be incurred with any sort of protruding antenna, it is necessary that the radiator be essentially flush-mounted or conformable to the structure on which it is attached. Several individual antenna elements are needed for the desired coverage. Both the particular elements chosen and their location determine the ultimate radiation pattern of the overall system. For these reasons a two-fold research plan was undertaken. First, individual elements were investigated and designed. Then various mounting locations were considered and the radiation patterns were predicted taking into account the effects of the astronaut's backpack.

Long, Stuart A.; Jackson, David R.; Williams, Jeffery T.; Wilton, Donald R.

1988-06-01

29

Conformal doping of topographic silicon structures using a radial line slot antenna plasma source  

NASA Astrophysics Data System (ADS)

Fin extension doping for 10 nm front end of line technology requires ultra-shallow high dose conformal doping. In this paper, we demonstrate a new radial line slot antenna plasma source based doping process that meets these requirements. Critical to reaching true conformality while maintaining fin integrity is that the ion energy be low and controllable, while the dose absorption is self-limited. The saturated dopant later is rendered conformal by concurrent amorphization and dopant containing capping layer deposition followed by stabilization anneal. Dopant segregation assists in driving dopants from the capping layer into the sub silicon surface. Very high resolution transmission electron microscopy-Energy Dispersive X-ray spectroscopy, used to prove true conformality, was achieved. We demonstrate these results using an n-type arsenic based plasma doping process on 10 to 40 nm high aspect ratio fins structures. The results are discussed in terms of the different types of clusters that form during the plasma doping process.

Ueda, Hirokazu; Ventzek, Peter L. G.; Oka, Masahiro; Horigome, Masahiro; Kobayashi, Yuuki; Sugimoto, Yasuhiro; Nozawa, Toshihisa; Kawakami, Satoru

2014-06-01

30

High-Strength, Metalized Fibers for Conformal Load Bearing Antenna Applications  

Microsoft Academic Search

we propose the use of high strength, metal-coated Kevlar yarns to weave flexible, conformal, and load-bearing antennas for an emerging class of applications emphasizing multiple functionality. In particular, here we present a unified, quantitative analysis of multiple properties of conductors as load-bearing materials in stress-, weight-, and shape-critical applications (e.g., in aerial vehicles), suggesting advantageous electrical conductor configurations to be

Steven E. Morris; Yakup Bayram; Lanlin Zhang; Zheyu Wang; Max Shtein; John L. Volakis

2011-01-01

31

Characteristics of Double Exponentially Tapered Slot Antenna (DETSA) Conformed in the Longitudinal Direction Around a Cylindrical Structure  

NASA Technical Reports Server (NTRS)

The characteristics of a double exponentially tapered slot antenna (DETSA) as a function of the radius that the DETSA is conformed to in the longitudinal direction is presented. It is shown through measurements and simulations that the radiation pattern of the conformed antenna rotates in the direction through which the antenna is curved, and that diffraction affects the radiation pattern if the radius of curvature is too small or the frequency too high. The gain of the antenna degrades by only 1 dB if the radius of curvature is large and more than 2 dB for smaller radii. The main effect due to curving the antenna is an increased cross-polarization in the E-plane.

Ponchak, George E.; Jordan, Jennifer L.; Chevalier, Christine T.

2006-01-01

32

Shaping and resizing of multifed slot radiators used in conformal microwave antenna arrays for hyperthermia treatment of large superficial diseases  

PubMed Central

It has been recently shown that chestwall recurrence of breast cancer and many other superficial diseases can be successfully treated with the combination of radiation, chemotherapy and hyperthermia. Conformal microwave antenna array for hyperthermia treatment of large area superficial diseases can significantly increase patient comfort while at the same time facilitate treatment of larger and more irregularly shaped disease. A large number of small efficient antennas is preferable for improved control of heating, as the disease can be more accurately contoured and the lower power requirement correlates with system reliability, linearity and reduced cost. Thus, starting from the initially proposed square slot antennas, we investigated new designs for multi-fed slot antennas of several shapes that maximize slot perimeter while reducing radiating area, thus increasing antenna efficiency. Simulations were performed with commercial electromagnetic simulation software packages (Ansoft HFSS) to demonstrate that the antenna size reduction method is effective for several dual concentric conductor (DCC) aperture shapes and operating frequencies. The theoretical simulations allowed the development of a set of design rules for multi-fed DCC slot antennas that facilitate conformal heat treatments of irregular size and shape disease with large multi-element arrays. Independently on the shape, it is shown that the perimeter of 10cm at 915 MHz delivers optimal radiation pattern and efficiency. While the maximum radiation is obtained for a circular pattern the rectangular shape is the one that feels more efficiently the array space. PMID:24352575

Maccarini, Paolo F.; Arunachalam, Kavitha; Juang, Titania; De Luca, Valeria; Rangarao, Sneha; Neumann, Daniel; Martins, Carlos Daniel; Craciunescu, Oana; Stauffer, Paul R.

2013-01-01

33

Energy flow in the cryptophyte PE545 antenna is directed by bilin pigment conformation.  

PubMed

Structure-based calculations are combined with quantitative modeling of spectra and energy transfer dynamics to detemine the energy transfer scheme of the PE545 principal light-harvesting antenna of the cryptomonad Rhodomonas CS24. We use a recently developed quantum-mechanics/molecular mechanics (QM/MM) method that allows us to account for pigment-protein interactions at atomic detail in site energies, transition dipole moments, and electronic couplings. In addition, conformational flexibility of the pigment-protein complex is accounted for through molecular dynamics (MD) simulations. We find that conformational disorder largely smoothes the large energetic differences predicted from the crystal structure between the pseudosymmetric pairs PEB50/61C-PEB50/61D and PEB82C-PEB82D. Moreover, we find that, in contrast to chlorophyll-based photosynthetic complexes, pigment composition and conformation play a major role in defining the energy ladder in the PE545 complex, rather than specific pigment-protein interactions. This is explained by the remarkable conformational flexibility of the eight bilin pigments in PE545, characterized by a quasi-linear arrangement of four pyrrole units. The MD-QM/MM site energies allow us to reproduce the main features of the spectra, and minor adjustments of the energies of the three red-most pigments DBV19A, DBV19B, and PEB82D allow us to model the spectra of PE545 with a similar quality compared to our original model (model E from Novoderezhkin et al. Biophys. J.2010, 99, 344), which was extracted from the spectral and kinetic fit. Moreover, the fit of the transient absorption kinetics is even better in the new structure-based model. The largest difference between our previous and present results is that the MD-QM/MM calculations predict a much smaller gap between the PEB50/61C and PEB50/61D sites, in better accord with chemical intuition. We conclude that the current adjusted MD-QM/MM energies are more reliable in order to explore the spectral properties and energy transfer dynamics in the PE545 complex. PMID:22992117

Curutchet, Carles; Novoderezhkin, Vladimir I; Kongsted, Jacob; Muñoz-Losa, Aurora; van Grondelle, Rienk; Scholes, Gregory D; Mennucci, Benedetta

2013-04-25

34

Size reduction and radiation pattern shaping of multi-fed DCC slot antennas used in conformal microwave array hyperthermia applicators  

PubMed Central

The use of conformal antenna array in the treatment of superficial diseases can significantly increase patient comfort while enhancing the local control of large treatment area with irregular shapes. Originally a regular square multi-fed slot antenna (Dual Concentric Conductor - DCC) was proposed as basic unit cell of the array. The square DCC works well when the outline of the treatment area is rectangular such as in the main chest or back area but is not suitable to outline diseases spreading along the armpit and neck area. In addition as the area of the patch increases, the overall power density decreases affecting the efficiency and thus the ability to deliver the necessary thermal dose with medium power amplifier (<50W). A large number of small efficient antennas is preferable as the disease is more accurately contoured and the lower power requirement for the amplifiers correlates with system reliability, durability, linearity and overall reduced cost. For such reason we developed a set of design rules for multi-fed slot antennas with irregular contours and we implemented a design that reduce the area while increasing the perimeter of the slot, thus increasing the antenna efficiency and the power density. The simulation performed with several commercial packages (Ansoft HFSS, Imst Empire, SemcadX and CST Microwave Studio) show that the size reducing method can be applied to several shapes and for different frequencies. The SAR measurements of several DCCs are performed using an in-house high resolution scanning system with tumor equivalent liquid phantom both at 915 MHz for superficial hyperthermia systems in US) and 433 MHz (Europe). The experimental results are compared with the expected theoretical predictions and both simulated and measured patterns of single antennas of various size and shapes are then summed in various combinations using Matlab to show possible treatment irregular contours of complex diseases. The local control is expected to significantly improve while maintaining the patient comfort. PMID:24224073

Maccarini, Paolo F.; Arunachalam, Kavitha; Martins, Carlos D.; Stauffer, Paul R.

2013-01-01

35

Size reduction and radiation pattern shaping of multi-fed DCC slot antennas used in conformal microwave array hyperthermia applicators  

NASA Astrophysics Data System (ADS)

The use of conformal antenna array in the treatment of superficial diseases can significantly increase patient comfort while enhancing the local control of large treatment area with irregular shapes. Originally a regular square multi-fed slot antenna (Dual Concentric Conductor - DCC) was proposed as basic unit cell of the array. The square DCC works well when the outline of the treatment area is rectangular such as in the main chest or back area but is not suitable to outline diseases spreading along the armpit and neck area. In addition as the area of the patch increases, the overall power density decreases affecting the efficiency and thus the ability to deliver the necessary thermal dose with medium power amplifier (<50W). A large number of small efficient antennas is preferable as the disease is more accurately contoured and the lower power requirement for the amplifiers correlates with system reliability, durability, linearity and overall reduced cost. For such reason we developed a set of design rules for multi-fed slot antennas with irregular contours and we implemented a design that reduce the area while increasing the perimeter of the slot, thus increasing the antenna efficiency and the power density. The simulation performed with several commercial packages (Ansoft HFSS, Imst Empire, SemcadX and CST Microwave Studio) show that the size reducing method can be applied to several shapes and for different frequencies. The SAR measurements of several DCCs are performed using an in-house high resolution scanning system with tumor equivalent liquid phantom both at 915 MHz for superficial hyperthermia systems in US) and 433 MHz (Europe). The experimental results are compared with the expected theoretical predictions and both simulated and measured patterns of single antennas of various size and shapes are then summed in various combinations using Matlab to show possible treatment irregular contours of complex diseases. The local control is expected to significantly improve while maintaining the patient comfort.

Maccarini, Paolo F.; Arunachalam, Kavitha; Martins, Carlos D.; Stauffer, Paul R.

2009-02-01

36

Impact Behavior and Radiation Performance of a Structurally Integrated Antenna Array Conformed Around Cylindrical Bodies  

E-print Network

significantly and nonlinearly as the curvature increases due to the reduced density of curved honeycomb structurally integrated antenna array, termed composite antenna is proposed. A composite sandwich structure consisting of glass/epoxy facesheet and honeycomb core is used as a basic mechanical topology, in which

Tentzeris, Manos

37

Antenna Technologies for NASA Applications  

NASA Technical Reports Server (NTRS)

This presentation addresses the efforts being performed at GRC to develop antenna technology in support of NASA s Exploration Vision. In particular, the presentation discusses the communications architecture asset-specific data services, as well as wide area coverage, high gain, low mass deployable antennas. Phased array antennas as well as electrically small, lightweight, low power, multifunctional antennas will be also discussed.

Miranda, Felix

2007-01-01

38

The zeaxanthin-independent and zeaxanthin-dependent qE components of nonphotochemical quenching involve common conformational changes within the photosystem II antenna in Arabidopsis.  

PubMed

The light-harvesting antenna of higher plant photosystem II (LHCII) has the intrinsic capacity to dissipate excess light energy as heat in a process termed nonphotochemical quenching (NPQ). Recent studies suggest that zeaxanthin and lutein both contribute to the rapidly relaxing component of NPQ, qE, possibly acting in the minor monomeric antenna complexes and the major trimeric LHCII, respectively. To distinguish whether zeaxanthin and lutein act independently as quenchers at separate sites, or alternatively whether zeaxanthin fulfills an allosteric role regulating lutein-mediated quenching, the kinetics of qE and the qE-related conformational changes (DeltaA535) were compared in Arabidopsis (Arabidopsis thaliana) mutant/antisense plants with altered contents of minor antenna (kolhcb6, aslhcb4), trimeric LHCII (aslhcb2), lutein (lut2, lut2npq1, lut2npq2), and zeaxanthin (npq1, npq2). The kinetics of the two components of NPQ induction arising from zeaxanthin-independent and zeaxanthin-dependent qE were both sensitive to changes in the protein composition of the photosystem II antenna. The replacement of lutein by zeaxanthin or violaxanthin in the internal Lhcb protein-binding sites affected the kinetics and relative amplitude of each component as well as the absolute chlorophyll fluorescence lifetime. Both components of qE were characterized by a conformational change leading to nearly identical absorption changes in the Soret region that indicated the involvement of the LHCII lutein 1 domain. Based on these observations, we suggest that both components of qE arise from a common quenching mechanism based upon a conformational change within the photosystem II antenna, optimized by Lhcb subunit-subunit interactions and tuned by the synergistic effects of external and internally bound xanthophylls. PMID:19011000

Johnson, Matthew P; Pérez-Bueno, María L; Zia, Ahmad; Horton, Peter; Ruban, Alexander V

2009-02-01

39

Analysis of cylindrical wrap-around and doubly conformal patch antennas by way of the finite element-artificial absorber method  

NASA Technical Reports Server (NTRS)

The goal of this project was to develop analysis codes for computing the scattering and radiation of antennas on cylindrically and doubly conformal platforms. The finite element-boundary integral (FE-BI) method has been shown to accurately model the scattering and radiation of cavity-backed patch antennas. Unfortunately extension of this rigorous technique to coated or doubly curved platforms is cumbersome and inefficient. An alternative approximate approach is to employ an absorbing boundary condition (ABC) for terminating the finite element mesh thus avoiding use of a Green's function. A FE-ABC method is used to calculate the radar cross section (RCS) and radiation pattern of a cavity-backed patch antenna which is recessed within a metallic surface. It is shown that this approach is accurate for RCS and antenna pattern calculations with an ABC surface displaced as little as 0.3 lambda from the cavity aperture. These patch antennas may have a dielectric overlay which may also be modeled with this technique.

Volakis, J. L.; Kempel, L. C.; Sliva, R.; Wang, H. T. G.; Woo, A. G.

1994-01-01

40

Low-Profile Vertically Polarized Omnidirectional Antennas for Ground Sensor Networks.  

National Technical Information Service (NTIS)

This paper presents for the first time low-profile, electrically small antenna with omnidirectional vertically polarized radiation similar to a short monopole antenna. Planar antennas capable of producing vertical polarization have long been sought for ma...

K. Sarabandi, W. Hong

2008-01-01

41

47 CFR 78.105 - Antenna systems.  

Code of Federal Regulations, 2010 CFR

...TELEVISION RELAY SERVICE Technical Regulations § 78.105 Antenna systems. (a) For fixed...may approve antenna systems not conforming to the technical standards where a persuasive...detail why an antenna system complying with...

2010-10-01

42

Design and Development of Compact Conformal RFID Antennas Utilizing Novel Flexible Magnetic Composite Materials for Wearable RF and  

E-print Network

are wearable RFIDs and bio-monitoring wireless probes. The successful implementation of the flexible magnetic and the same antenna was redesigned for 480 MHz by reducing its size, thus proving the miniaturization concept substrate is the first flexible magnetic composite tested and proven for the 480 MHz bandwidth

Tentzeris, Manos

43

Design methodology for multiport antennas  

NASA Astrophysics Data System (ADS)

Multiport antennas offer greater design flexibility than traditional one-port designs. An antenna array is a special case of a multiport antenna. If the antenna's inter-element spacing is electrically small, the antenna is capable of achieving superdirectivity. Superdirective antenna arrays are known to be narrow band and have low radiation resistance which leads to low radiation efficiency and high VSWR. However, by increasing the self-impedance of the antenna elements, the radiation resistance is increased but the bandwidth remains narrow. A design methodology is developed using the ability to superimpose electric fields and multi-objective optimization to design antenna feed networks. While the emphasis in this dissertation is on antenna arrays and superdirectivity, the design methodology is general and can be applied to other multiport antennas. The design methodology is used to design a multiport impedance-matching network and optimize both the input impedance and radiation pattern of a two-port superdirective antenna array. It is shown that the multiport impedance-matching network is capable of improving the input impedance of the antenna array while maintaining high directionality. The antenna design is critical for the methodology to improve the bandwidth and radiation characteristics of the array. To double the bandwidth of the two-port impedance matched superdirective antenna array, a three-port Yagi-Uda antenna design is demonstrated. The addition of the extra antenna element does not increase the footprint of the antenna array. The design methodology is then used to design a symmetrical antenna array capable of steering its main beam in two directions.

Arceo, Diana

44

Design and analysis of a helical spherical antenna using the theory of characteristic modes  

Microsoft Academic Search

Electrically small dipole antennas with ka less than 0.5 exhibit low radiation resistance, high capacitive reactance and high Q factor which is inversely proportional to antenna bandwidth. Here, the k is the free space wave number and a is the radius of an imaginary sphere which circumscribes the whole antenna. Spherical dipole antennas potently have higher effective volume if compared

Khaled A. Obeidat; Bryan D. Raines; Roberto G. Rojas

2008-01-01

45

IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 55, NO. 3, MARCH 2007 731 A Hybrid Optimization Method to Analyze  

E-print Network

--Electrically small antennas, genetic algorithm (GA), metamaterials, optimization methods. I. INTRODUCTION ANTENNAS in part by DARPA under Contract HR0011-05-C-0068. The authors are with the Department of Electrical

Ziolkowski, Richard W.

46

X-Antenna: A graphical interface for antenna analysis codes  

NASA Technical Reports Server (NTRS)

This report serves as the user's manual for the X-Antenna code. X-Antenna is intended to simplify the analysis of antennas by giving the user graphical interfaces in which to enter all relevant antenna and analysis code data. Essentially, X-Antenna creates a Motif interface to the user's antenna analysis codes. A command-file allows new antennas and codes to be added to the application. The menu system and graphical interface screens are created dynamically to conform to the data in the command-file. Antenna data can be saved and retrieved from disk. X-Antenna checks all antenna and code values to ensure they are of the correct type, writes an output file, and runs the appropriate antenna analysis code. Volumetric pattern data may be viewed in 3D space with an external viewer run directly from the application. Currently, X-Antenna includes analysis codes for thin wire antennas (dipoles, loops, and helices), rectangular microstrip antennas, and thin slot antennas.

Goldstein, B. L.; Newman, E. H.; Shamansky, H. T.

1995-01-01

47

Space antennas  

NASA Astrophysics Data System (ADS)

The design and operation of ground based space communication antennas are generally reviewed. Antenna components, phased arrays, atmospheric attenuation, and characteristic radition patterns are addressed.

Andreyev, V.; Shagov, V.

1982-08-01

48

Development of an Electrically Small Vivaldi Antenna: The CReSIS Aerial Vivaldi (CAV-A)  

E-print Network

– Revision 3 and 4 SMA connectors; left – Pasternack 4190 [38], right – Amphenol 132134 [4]......................................................................................... 75 8 LIST OF TABLES Table 1.1 – Aircraft specifications... of Ice Sheets (CReSIS) airborne science missions employ manned aircraft such as the Orion P-3 and Twin Otter DHC-6. However, manned missions over polar regions are dangerous for pilots and crews given the low altitude, indistinct horizon...

Panzer, Benjamin Garrett

2007-12-12

49

Microstrip antennas  

Microsoft Academic Search

Microstrip antennas have been one of the most innovative topics in antenna theory and design in recent years, and are increasingly finding application in a wide range of modern microwave systems. This paper begins with a brief overview of the basic characteristics of microstrip antennas, and then concentrates on the most significant developments in microstrip antenna technology that have been

DAVID M. POZAR

1992-01-01

50

Temperature induced conformational changes in hybrid complexes formed from CdSe/ZnS nanocrystals and the phycobiliprotein antenna of Acaryochloris marina  

NASA Astrophysics Data System (ADS)

In hybrid systems which are self-assembled in solution from surface treated CdSe/ZnS quantum dots (QDs) and isolated phycobiliprotein (PBP) complexes from the cyanobacterium Acaryochloris marina, excitation energy transfer (EET) from the QDs to the PBP complexes was observed. The EET from the QDs to attached PBPs was analyzed with time integrated fluorescence spectroscopy and time-correlated single photon counting (TCSPC) at different temperatures. This functional connection between QDs and PBPs via EET is interrupted at temperatures below 273 K (0 °C) (Schmitt et al 2010 Photon. Nanostruct. submitted). The evaluation of the temperature-dependent fluorescence spectra of the QDs showed that the change of the excitation energy transfer efficiency at temperatures below 273 K cannot be explained by the change of the spectral overlap integral alone. Therefore the value of ?2/R126 must change at 273 K. We assume that micro crystals of water, formed in between the QDs and the PBP antenna structures, lead to a structural change of the hybrid complex. Our results show that TCSPC is suitable to distinguish strongly coupled and weakly coupled QD-PBP complexes at different temperatures.

Schmitt, Franz-Josef

2010-08-01

51

Land vehicle antennas for satellite mobile communications  

NASA Technical Reports Server (NTRS)

Antenna designs applicable to future satellite mobile vehicle communications are examined. Microstrip disk, quadrifilar helix, cylindrical microstrip, and inverted V and U crossed-dipole low gain antennas (3-5 dBic) that provide omnidirectional coverage are described. Diagrams of medium gain antenna (9-12 dBic) concepts are presented; the antennas are classified into three types: (1) electronically steered with digital phase shifters; (2) electronically switched with switchable power divider/combiner; and (3) mechanically steered with motor. The operating characteristics of a conformal antenna with electronic beam steering and a nonconformal design with mechanical steering are evaluated with respect to isolation levels in a multiple satellite system. Vehicle antenna pointing systems and antenna system costs are investigated.

Haddad, H. A.; Paschen, D.; Pieper, B. V.

1985-01-01

52

The antennas  

Microsoft Academic Search

As part of the Australia Telescope construction project CSIRO, in conjunction with Macdonald Wagner and Priddle (now Connell Wagner), produced two new designs for 22-m diameter antennas (one mounted on bogies, the other fixed), to operate at frequencies up to 116 GHz. In the evolution from currently operating antennas, special attention was given to transportability, azimuth transfer, control systems, thermal

Dennis N. Cooper; Graeme L. James; Barry F. Parsons; Don E. Yabsley

1992-01-01

53

Land vehicle antennas for satellite mobile communications  

NASA Technical Reports Server (NTRS)

The RF performance, size, pointing system, and cost were investigated concepts are: for a mechanically steered 1 x 4 tilted microstrip array, a mechanically steered fixed-beam conformal array, and an electronically steered conformal phased array. Emphasis is on the RF performance of the tilted 1 x 4 antenna array and methods for pointing the various antennas studied to a geosynchronous satellite. An updated version of satellite isolations in a two-satellite system is presented. Cost estimates for the antennas in quantities of 10,000 and 100,000 unites are summarized.

Haddad, H. A.; Pieper, B. V.; Mckenna, D. B.

1985-01-01

54

Adjoint sensitivity analysis of an ultrawideband antenna  

SciTech Connect

The frequency domain finite element method using H(curl)-conforming finite elements is a robust technique for full-wave analysis of antennas. As computers become more powerful, it is becoming feasible to not only predict antenna performance, but also to compute sensitivity of antenna performance with respect to multiple parameters. This sensitivity information can then be used for optimization of the design or specification of manufacturing tolerances. In this paper we review the Adjoint Method for sensitivity calculation, and apply it to the problem of optimizing a Ultrawideband antenna.

Stephanson, M B; White, D A

2011-07-28

55

Antenna Controller  

NASA Technical Reports Server (NTRS)

A NASA-developed computer program has effected substantial savings in inclined orbit trackings for Research Concepts, Inc. Artificial Satellite Analysis Program (ASAP) allowed the company to avoid duplicating research and shortened the time needed to develop an R2000B antenna controller. The device controls a dish antenna for tracking a communications satellite and represents a significant advance because it provides an accurate, cost-effective way to track satellites in inclined orbits. These have been difficult and expensive to track.

1994-01-01

56

Antenna Technologies for Future NASA Exploration Missions  

NASA Technical Reports Server (NTRS)

NASA s plans for the manned exploration of the moon and Mars will rely heavily on the development of a reliable communications infrastructure on the surface and back to Earth. Future missions will thus focus not only on gathering scientific data, but also on the formation of the communications network. In either case, unique requirements become imposed on the antenna technologies necessary to accomplish these tasks. For example, surface activity applications such as robotic rovers, human extravehicular activities (EVA), and probes will require small size, lightweight, low power, multi-functionality, and robustness for the antenna elements being considered. Trunk-line communications to a centralized habitat on the surface and back to Earth (e.g., surface relays, satellites, landers) will necessitate wide-area coverage, high gain, low mass, deployable antennas. Likewise, the plethora of low to high data rate services desired to guarantee the safety and quality of mission data for robotic and human exploration will place additional demands on the technology. Over the past year, NASA Glenn Research Center has been heavily involved in the development of candidate antenna technologies with the potential for meeting these strict requirements. This technology ranges from electrically small antennas to phased array and large inflatable structures. A summary of this overall effort is provided, with particular attention being paid to small antenna designs and applications. A discussion of the Agency-wide activities of the Exploration Systems Mission Directorate (ESMD) in forthcoming NASA missions, as they pertain to the communications architecture for the lunar and Martian networks is performed, with an emphasis on the desirable qualities of potential antenna element designs for envisioned communications assets. Identified frequency allocations for the lunar and Martian surfaces, as well as asset-specific data services will be described to develop a foundation for viable antenna technologies which might address these requirements and help guide future technology development decisions.

Miranda, Felix A.

2006-01-01

57

Parallel/Series-Fed Microstrip Array Antenna  

NASA Technical Reports Server (NTRS)

Characteristics include low cross-polarization and high efficiency. Microstrip array antenna fabricated on two rectangular dielectric substrates. Produces fan-shaped beam polarized parallel to its short axis. Mounted conformally on outside surface of aircraft for use in synthetic-aperture radar. Other antennas of similar design mounted on roofs or sides of buildings, ships, or land vehicles for use in radar or communications.

Huang, John

1994-01-01

58

Structurally Integrated Antenna Concepts for HALE UAVs  

NASA Technical Reports Server (NTRS)

This technical memorandum describes work done in support of the Multifunctional Structures and Materials Team under the Vehicle Systems Program's ITAS (Integrated Tailored Aero Structures) Project during FY 2005. The Electromagnetics and Sensors Branch (ESB) developed three ultra lightweight antenna concepts compatible with HALE UAVs (High Altitude Long Endurance Unmanned Aerial Vehicles). ESB also developed antenna elements that minimize the interaction between elements and the vehicle to minimize the impact of wing flexure on the EM (electromagnetic) performance of the integrated array. In addition, computer models were developed to perform phase correction for antenna arrays whose elements are moving relative to each other due to wing deformations expected in HALE vehicle concepts. Development of lightweight, conformal or structurally integrated antenna elements and compensating for the impact of a lightweight, flexible structure on a large antenna array are important steps in the realization of HALE UAVs for microwave applications such as passive remote sensing and communications.

Cravey, Robin L.; Vedeler, Erik; Goins, Larry; Young, W. Robert; Lawrence, Roland W.

2006-01-01

59

A novel multiband antenna: fractal antenna  

Microsoft Academic Search

Fractal-shaped antennas have already been proved to have some unique characteristics that are linked to the geometrical properties of the fractals. The purpose of this article is to introduce the concept of the fractal, review the progress in fractal antenna study and implementation, compare different types of fractal antenna elements and arrays and discuss the challenge and future of this

Tian Tiehong; Zhou Zheng

2003-01-01

60

Transparent Flexible Conductive Polymer Antennas Nicholas A. Vacirca, Nicholas J. Kirsch, Elizabeth E. Plowman, Adam K. Fontecchio, Kapil R. Dandekar, Timothy P. Kurzweg  

E-print Network

Transparent Flexible Conductive Polymer Antennas Nicholas A. Vacirca, Nicholas J. Kirsch, Elizabeth-printable conductive polymer antennas. These antennas have an extremely small profile, are flexible and can conform and Computer Engineering, Drexel University Antenna Testing & Results . PEDOT:PSS Conductive Polymer Printing

Kurzweg, Timothy P.

61

Computer controlled antenna system  

NASA Technical Reports Server (NTRS)

The application of small computers using digital techniques for operating the servo and control system of large antennas is discussed. The advantages of the system are described. The techniques were evaluated with a forty foot antenna and the Sigma V computer. Programs have been completed which drive the antenna directly without the need for a servo amplifier, antenna position programmer or a scan generator.

Raumann, N. A.

1972-01-01

62

Antenna deployment mechanism  

NASA Technical Reports Server (NTRS)

All-mechanical antenna deployment system operates by single cable tensioned by electrically driven drum. Device is comprised of set of pulleys fixed to telescoping antenna mast, ratchet which prevents premature antenna retraction, and special latch which holds antenna in retracted position.

Griffin, C. R.; Leavy, W. A.

1979-01-01

63

FRACTAL ANTENNAS Philip Felber  

E-print Network

FRACTAL ANTENNAS by Philip Felber A literature study as a project for ECE 576 Illinois Institute of Technology December 12, 2000 (Revised: January 16, 2001) #12;2 Felber: "Fractal Antennas" Abstract 3 Introduction 3 Chronology 3 Background 4 Fractals 5 Antennas 6 Fractal Antennas 7 Applications 9 Classic

64

Modeling the electromagnetic radiation from electrically small table-top products  

Microsoft Academic Search

A bstruct-Often, the most difficult radiated electromagnetic interfer- ence (EMI) problems with table-top products occur at frequencies where the maximum dimensions of the product are much smaller than a wave- length. Electrically small table-top products tend to be much more effi- cient radiation sources than dipole source models would predict and the radiation is generally much more difficult to contain

T. H. Hubing; J. F. Kauffman

1989-01-01

65

A Review of Antenna Technologies for Future NASA Exploration Missions  

NASA Technical Reports Server (NTRS)

NASA's plans for the manned exploration of the Moon and Mars will rely heavily on the development of a reliable communications infrastructure from planetary surface-to-surface, surface-to-orbit and back to Earth. Future missions will thus focus not only on gathering scientific data, but also on the formation of the communications network. In either case, unique requirements become imposed on the antenna technologies necessary to accomplish these tasks. For example, proximity (i.e., short distance) surface activity applications such as robotic rovers, human extravehicular activities (EVA), and probes will require small size, lightweight, low power, multi-functionality, and robustness for the antenna elements being considered. In contrast, trunk-line communications to a centralized habitat on the surface and back to Earth (e.g., relays, satellites, and landers) will necessitate high gain, low mass antennas such as novel inflatable/deployable antennas. Likewise, the plethora of low to high data rate services desired to guarantee the safety and quality of mission data for robotic and human exploration will place additional demands on the technology. Over the last few years, NASA Glenn Research Center has been heavily involved in the development and evaluation of candidate antenna technologies with the potential for meeting the aforementioned requirements. These technologies range from electrically small antennas to phased arrays and large inflatable antenna structures. A summary of these efforts will be discussed in this paper. NASA planned activities under the Exploration Vision as they pertain to the communications architecture for the Lunar and Martian scenarios will be discussed, with emphasis on the desirable qualities of potential antenna element designs for envisioned communications assets. Identified frequency allocations for the Lunar and Martian surfaces, as well as asset-specific data services will be described to develop a foundation for viable antenna technologies which might address these requirements and help guide future technology development decisions.

Miranda, Felix A.; Nessel, James A.; Romanofsky, Robert R.; Acosta, J.

2007-01-01

66

Mutual Elements and Substrate Effect Analysis on Patch Antenna Arrays  

NASA Astrophysics Data System (ADS)

There have been many different technology advancements with the invention of solid state electronics, leading to the digital era which has changed the way users employ electronic circuits. Antennas are no different; however, they are still analog devices. With the advancements in technology, antennas are being fabricated on much higher frequencies and with greater bandwidths, all while trying to keep size and weight to a minimum. Centimeter and millimeter wave technologies have evolved for many different radio frequency (RF) applications. Microstrip patch antennas have been developed, as wire and tubular antenna elements are difficult to fabricate with the tolerances required at micro-wavelengths. Microstrip patch antennas are continuously being improved. These types of antennas are great for embedded or conformal applications where size and weight are of the essence and the ease of manufacturing elements to tight tolerances is important. One of the greatest benefits of patch antennas is the ease in creating an array. Many simulation programs have been created to assist in the design of patch antennas and arrays. However, there are still discrepancies between simulated results and actual measurements. This research will focus on these differences. It begins with a literature research of patch antenna design, followed by an assessment of simulation programs used for patch antenna design. The resulting antenna design was realized by the fabrication of an antenna from the Genesys software. Laboratory measurements of the real-world antenna are then compared to the theoretical antenna characteristics. This process is used to illustrate deficiencies in the software models and likely improvements that need to be made.

Wallace, Matthew J.

67

Wideband active antenna cancellation  

E-print Network

There exists a simultaneous transmit and receive antenna system where the transmitted signal is creating wideband interference of the receiver. To resolve this interference problem, the isolation between the transmit antenna ...

Adaniya, Hana L

2008-01-01

68

Atacama compact array antennas  

NASA Astrophysics Data System (ADS)

The ACA (Atacama Compact Array) system is an important element of ALMA and consists of four ACA 12-m antennas and twelve ACA 7-m antennas. The ACA system aims to acquire the total power data with four 12-m antennas and the short baseline interferometer data with 7-m antennas. The ACA system also increases reliability of the interferometer maps of astronomical sources larger than the field view of the 12-m antenna. The science performance of these antennas has been extensively verified at OSF (operation support facility) at an elevation of 2900 m in Atacama desert in northern Chile since 2007. The pointing performance has been verified with a dedicated optical pointing telescope, the servo performance is tested with angle encoders, and the surface accuracy has been measured with a radio holography method. Both ACA 12-m antennas and 7-m antennas have been successfully demonstrated to meet the very stringent ALMA specifications.

Saito, M.; Inatani, J.; Nakanishi, K.; Saito, H.; Iguchi, S.

2012-09-01

69

Serpentine Buoyant Cable Antenna.  

National Technical Information Service (NTIS)

The present invention relates to an improved buoyant cable antenna system. The system includes a buoyant cable transmission line segment and an antenna segment formed from a flexible memory structure comprised of at least one segment of coiled compression...

E. M. Gerhard

2006-01-01

70

Space-Frame Antenna  

NASA Technical Reports Server (NTRS)

The space-frame antenna is a conceptual antenna structure that would be lightweight, deployable from compact stowage, and capable of deforming itself to a size, shape, and orientation required for a specific use. The space-frame antenna would be a trusslike structure consisting mostly of a tetrahedral mesh of nodes connected by variable-length struts. The deformation of the antenna to a desired size, shape, and orientation would be effected through coordinated lengthening and shorting of the struts.

Curtis, Steven A.

2010-01-01

71

Modeling of fractal antennas  

Microsoft Academic Search

Results on the numerical analysis of the Sierpinski and Koch fractal antennas are presented. It is shown that self-similarity\\u000a of fractal structures affects electromagnetic properties of antenna structures created on the basis of these fractals. It\\u000a is demonstrated that the Sierpinski and Koch fractal antennas are multiband structures; therefore, these antennas can be used\\u000a for the development of radar and

S. V. Krupenin

2006-01-01

72

Dielectrically Loaded Biconical Antennas  

Microsoft Academic Search

Biconical antennas are of great interest to those who deal with broadband applications including the transmission\\/reception of pulses. In particular, wide-angle conical antennas are an attractive choice in many applications including Electronic Support Measures (ESM) and the measurements of transient surface currents and charge densities on aircraft. Dielectric loading in the interior region of a conical antenna can be used

Fouad Ahmed Nusseibeh

1995-01-01

73

Nonlinear antenna technology  

Microsoft Academic Search

Nonlinear antennas combine advances in nonlinear dynamics, active antenna design, and analog microelectronics to generate beam steering and beam forming across an array of nonlinear oscillators. Nonlinear antennas exploit two phenomena typically shunned in traditional designs: nonlinear unit cells and interelement coupling. The design stems from nonlinear coupled differential equation analysis that by virtue of the dynamic control is far

BRIAN K. MEADOWS; TED H. HEATH; JOSEPH D. NEFF; EDGAR A. BROWN; DAVID W. FOGLIATTI; MICHAEL GABBAY; V. In; P. Hasler; S. P. Deweerth; W. L. Ditto

2002-01-01

74

Antenna development at DARPA  

NASA Astrophysics Data System (ADS)

This paper reviews recent and ongoing antenna technology and systems development in the Special Projects Office of the Defense Advanced Research Projects Agency (DARPA/SPO). These programs fall into two categories: development and application of antenna component technologies and development of transportable phased-array radar antennas. These development programs are presented in a chronological order.

Corey, Larry; Jaska, Esko

2004-09-01

75

Wearable textile antennas  

Microsoft Academic Search

Owing to the rapid progress in fabrication technologies of conductive fibrous materials and the increasing demand for wireless communications in smart clothing systems, the potential application of wearable textile antennas in this field continues to increase. This article reviews a variety of wearable textile antennas in order to provide background information and application ideas for designing such antennas. The various

Jung-Sim Roh; Yong-Seung Chi; Tae Jin Kang

2010-01-01

76

Hexagonal fractal multiband antenna  

Microsoft Academic Search

The design of a new fractal multiband antenna, based on the hexagon, is presented. Three iterations of the hexagonal fractal multiband antenna, arranged in the dipole configuration, are examined. Experimental results are compared with those obtained using the method of moments and the fractal antenna is found to possess predictable multiband characteristics.

P. W. Tang; P. F. Wahid

2004-01-01

77

Microstrip antenna array with multi-octave bandwidth  

NASA Astrophysics Data System (ADS)

Up to the present time, electronic warfare (EW) systems have employed spiral antennas, wide bandwidth horns, or log periodic dipole arrays to meet the multioctave bandwidth antenna requirements. In the context of requirements to mount such antennas conformally on the bodies of missiles and aircraft, investigations have been conducted regarding the wide bandwidth capabilities of microstrip antennas. However, the bandwidths achieved so far have been limited. Attention is given to the possibility of multioctave operation on the basis of the formation of a log periodic array of patch elements. The basic action of a log periodic array is discussed, and the design of the log periodic overlaid patch array is described. It is pointed out that the log periodic microstrip patch array can now be considered for wide bandwidth EW application where the low profile, ruggedness, and conformal mounting properties of microstrip are important system advantages.

Hall, P. S.

1986-03-01

78

The ALMA antenna procurement  

NASA Astrophysics Data System (ADS)

Visitors who come to the OSF at regular intervals find a growing population of antennas at various stages of assembly and testing. The long path from the start of the definition of antenna specifications to the start of science operations with the antennas was and still is a formidable endeavor. When completed, ALMA will comprise a 12-meter diameter antennas array, the bilateral interferometer array, of a minimum of fifty antennas and in addition, the ACA (Atacama Compact Array), composed of four 12-meter diameter antennas and twelve 7-meter diameter antennas. Out of the fifty antennas of the bilateral interferometer array, one-half are provided by the North American partners of ALMA, the other half by the European partners. The sixteen antennas that will comprise the ACA are provided by the East Asian Partners of ALMA. Here we review some key points of this challenging process and we provide a brief history and status of the ALMA antennas. Because of the length of the description, we will present this in a series of two articles. In this first part we concentrate mostly on the bilateral antenna procurement. A detailed description of the ACA will be presented in the next newsletter.

Stanghellini, S.; Zivick, Jeff; Inatani, Junji

2009-10-01

79

Antenna Controller Replacement Software  

NASA Technical Reports Server (NTRS)

The Antenna Controller Replacement (ACR) software accurately points and monitors the Deep Space Network (DSN) 70-m and 34-m high-efficiency (HEF) ground-based antennas that are used to track primarily spacecraft and, periodically, celestial targets. To track a spacecraft, or other targets, the antenna must be accurately pointed at the spacecraft, which can be very far away with very weak signals. ACR s conical scanning capability collects the signal in a circular pattern around the target, calculates the location of the strongest signal, and adjusts the antenna pointing to point directly at the spacecraft. A real-time, closed-loop servo control algorithm performed every 0.02 second allows accurate positioning of the antenna in order to track these distant spacecraft. Additionally, this advanced servo control algorithm provides better antenna pointing performance in windy conditions. The ACR software provides high-level commands that provide a very easy user interface for the DSN operator. The operator only needs to enter two commands to start the antenna and subreflector, and Master Equatorial tracking. The most accurate antenna pointing is accomplished by aligning the antenna to the Master Equatorial, which because of its small size and sheltered location, has the most stable pointing. The antenna has hundreds of digital and analog monitor points. The ACR software provides compact displays to summarize the status of the antenna, subreflector, and the Master Equatorial. The ACR software has two major functions. First, it performs all of the steps required to accurately point the antenna (and subreflector and Master Equatorial) at the spacecraft (or celestial target). This involves controlling the antenna/ subreflector/Master-Equatorial hardware, initiating and monitoring the correct sequence of operations, calculating the position of the spacecraft relative to the antenna, executing the real-time servo control algorithm to maintain the correct position, and monitoring tracking performance.

Chao, Roger Y.; Morgan, Scott C.; Strain, Martha M.; Rockwell, Stephen T.; Shimizu, Kenneth J.; Tehrani, Barzia J.; Kwok, Jaclyn H.; Tuazon-Wong, Michelle; Valtier, Henry; Nalbandi, Reza; Wert, Michael; Leung, Patrick

2010-01-01

80

EVOLUTION OF ANTENNA PERFORMANCE FOR APPLICATIONS IN THERMAL MEDICNE  

PubMed Central

This presentation provides an overview of electromagnetic heating technology that has proven useful in clinical applications of hyperthermia therapy for cancer. Several RF and microwave antenna designs are illustrated which highlight the evolution of technology from simple waveguide antennas to spatially and temporally adjustable multiple antenna phased arrays for deep heating, conformal arrays for superficial heating, and compatible approaches for radiometric and magnetic resonance image based non-invasive thermal monitoring. Examples of heating capabilities for several recently developed applicators demonstrate highly adjustable power deposition that has not been possible in the past. PMID:23487445

Stauffer, P.R.; Maccarini, P.F.

2013-01-01

81

Control of electromagnetic edge effects in electrically-small rectangular plasma reactors  

SciTech Connect

Electromagnetic fields supported by rectangular reactors for plasma enhanced chemical vapor deposition are studied theoretically. Expressions for the fields in an electrically-small rectangular reactor with plasma in the chamber are derived. Modal field decompositions are employed under the homogeneous plasma slab approximation. The amplitude of each mode is determined analytically. It is shown that the field can be represented by the standing wave, evanescent waves tied to the edges, and an evanescent wave tied to the corners of the reactor. The impact of boundary conditions at the plasma edge on nonuniformity is quantified. Uniformity may be improved by placing a lossy magnetic layer on the reactor sidewalls. It is demonstrated that nonuniformity is a decreasing function of layer thickness.

Trampel, Christopher P.; Stieler, Daniel S. [Department of Electrical and Computer Engineering, Iowa State University, 2215 Coover Hall, Ames, Iowa 50011 (United States); PowerFilm, Inc., 2337 230th Street, Ames, Iowa 50014 (United States)

2012-09-15

82

Synthesis of multiple shaped beam antenna patterns  

NASA Technical Reports Server (NTRS)

Results are presented of research into the problem of finding an excitation of a given antenna such that the desired radiation pattern is approximated to within acceptable limits. This is to be done in such a fashion that boundary conditions involving hardware limitations may be inserted into the problem. The intended application is synthesis of multiple shaped beam antennas. Since this is perhaps the most difficult synthesis problem an antenna engineer is likely to encounter, the approach taken was to include as a by-product capability for synthesizing simpler patterns. The synthesis technique has been almost totally computerized. The class of antennas which may be synthesized with the computer program are those which may be represented as planar (continuous or discrete) current distributions. The technique is not limited in this sense and could indeed by extended to include, for example, the synthesis of conformal arrays or current distributions on the surface of reflectors. The antenna types which the program is set up to synthesize are: line source, rectangular aperture, circular aperture, linear array, rectangular array, and arbitrary planar array.

Stutzman, W. L.; Coffey, E. L.

1973-01-01

83

Log-Periodic Microstrip Patch Antenna Miniaturization Using Artificial Magnetic Conductor Surfaces.  

E-print Network

??Microstrip patch antennas are attractive for numerous military and commercial applications due to their advantages in terms of low-profile, broadside radiation, low-cost, low-weight and conformability.… (more)

Almutawa, Ahmad Tariq

2011-01-01

84

Stored energies in electric and magnetic current densities for small antennas  

E-print Network

Electric and magnetic currents are essential to describe electromagnetic stored energy, as well as the associated quantities of antenna Q and the partial directivity to antenna Q-ratio, D/Q, for general structures. The upper bound of previous D/Q-results for antennas modeled by electric currents is accurate enough to be predictive, this motivates us here to extend the analysis to include magnetic currents. In the present paper we investigate antenna Q bounds and D/Q-bounds for the combination of electric- and magnetic-currents, in the limit of electrically small antennas. This investigation is both analytical and numerical, and we illustrate how the bounds depend on the shape of the antenna. We show that the antenna Q can be associated with the largest eigenvalue of certain combinations of the electric and magnetic polarizability tensors. The results are a fully compatible extension of the electric only currents, which come as a special case. The here proposed method for antenna Q provides the minimum Q-value...

Jonsson, B L G

2014-01-01

85

Spiral antennas for ESM  

NASA Astrophysics Data System (ADS)

In the absence of any published mathematical analyses of the cavity-backed spiral antennas that have become popular in Electronic Support Measures systems, the functions and operating principles of the antenna's spiral radiator, backing cavity, and balun transformer components are treated by means of elementary reasoning. As an illustration of the performance quality currently achievable with these antennas, an evaluation is conducted for the cases of a reduced size square antenna for the 0.4-4.0 GHz frequency band, a 52-mm diameter antenna covering the standard 2.0-18.0 GHz band, and an in-line, 16-mm diameter antenna and integral radome for the 18.0-40.0 GHz band, where the output is by means of a double ridge waveguide.

Morgan, T. E.

1985-07-01

86

Combined fast multipole-QR compression technique for solving electrically small to large structures for broadband applications  

NASA Technical Reports Server (NTRS)

An approach that efficiently solves for a desired parameter of a system or device that can include both electrically large fast multipole method (FMM) elements, and electrically small QR elements. The system or device is setup as an oct-tree structure that can include regions of both the FMM type and the QR type. An iterative solver is then used to determine a first matrix vector product for any electrically large elements, and a second matrix vector product for any electrically small elements that are included in the structure. These matrix vector products for the electrically large elements and the electrically small elements are combined, and a net delta for a combination of the matrix vector products is determined. The iteration continues until a net delta is obtained that is within predefined limits. The matrix vector products that were last obtained are used to solve for the desired parameter.

Jandhyala, Vikram (Inventor); Chowdhury, Indranil (Inventor)

2011-01-01

87

MSU Antenna Pattern Data  

NASA Technical Reports Server (NTRS)

The Microwave Sounding Unit (MSU) antenna pattern data for nine MSU Flight Models (FMs) have been successfully rescued from 22-year old 7-track and 9-track magnetic tapes and cartridges. These antenna pattern data were unpacked into user-friendly ASCII format, and are potentially useful for making antenna pattern corrections to MSU antenna temperatures in retrieving the true brightness temperatures. We also properly interpreted the contents of the data and show how to convert the measured antenna signal amplitude in volts into relative antenna power in dB with proper normalization. It is found that the data are of high quality with a 60-dB drop in the co-polarized antenna patterns from the central peak value to its side-lobe regions at scan angles beyond 30 deg. The unpacked antenna pattern data produced in this study provide a useful database for data users to correct the antenna side-lobe contribution to MSU measurements. All of the data are available to the scientific community on a single CD-ROM.

Mo, Tsan; Kleespies, Thomas J.; Green, J. Philip

2000-01-01

88

The single antenna interferometer  

SciTech Connect

Air and space borne platforms using synthetic aperture radars (SAR) have made interferometric measurements by using either two physical antennas mounted on one air-frame or two passes of one antenna over a scene. In this paper, a new interferometric technique using one pass of a single-antenna SAR system is proposed and demonstrated on data collected by the NASA-JPL AirSAR. Remotely sensed L-band microwave data are used to show the sensitivity of this technique to ocean surface features as well as a baseline for comparison with work by others using two-antenna systems. 7 refs., 3 figs.

Fitch, J.P.

1990-01-15

89

Cellular Reflectarray Antenna  

NASA Technical Reports Server (NTRS)

The cellular reflectarray antenna is intended to replace conventional parabolic reflectors that must be physically aligned with a particular satellite in geostationary orbit. These arrays are designed for specified geographical locations, defined by latitude and longitude, each called a "cell." A particular cell occupies nominally 1,500 square miles (3,885 sq. km), but this varies according to latitude and longitude. The cellular reflectarray antenna designed for a particular cell is simply positioned to align with magnetic North, and the antenna surface is level (parallel to the ground). A given cellular reflectarray antenna will not operate in any other cell.

Romanofsky, Robert R.

2010-01-01

90

A Compact Annular Ring Microstrip Antenna for WSN Applications  

PubMed Central

A compact annular ring microstrip antenna was proposed for a wireless sensor network (WSN) application in the 2.4 GHz band. In this paper the major considerations of the conformal antenna design were the compact size and the impact on antenna's performance of a steel installation base. By using a chip resistor of large resistance (120 ?) the antenna size was reduced to 38% of that a conventional annular ring patch antenna. With the addition of the steel installation base the resonant frequency of the antenna increases about 4.2% and the bandwidth reduces from 17.5% to 11.7% by adjusting the load resistance simultaneously. Several key parameters were discussed and optimized, and the antenna was fabricated and its performance measured. The antenna is well matched at 2.4 GHz with 34.2 dB return loss and –2.5 dBi peak gain. Meanwhile, it exhibits excellent radiation patterns with very low cross-polarization levels. PMID:23012510

Wang, Daihua; Song, Linli; Zhou, Hanchang; Zhang, Zhijie

2012-01-01

91

Technique for Solving Electrically Small to Large Structures for Broadband Applications  

NASA Technical Reports Server (NTRS)

Fast iterative algorithms are often used for solving Method of Moments (MoM) systems, having a large number of unknowns, to determine current distribution and other parameters. The most commonly used fast methods include the fast multipole method (FMM), the precorrected fast Fourier transform (PFFT), and low-rank QR compression methods. These methods reduce the O(N) memory and time requirements to O(N log N) by compressing the dense MoM system so as to exploit the physics of Green s Function interactions. FFT-based techniques for solving such problems are efficient for spacefilling and uniform structures, but their performance substantially degrades for non-uniformly distributed structures due to the inherent need to employ a uniform global grid. FMM or QR techniques are better suited than FFT techniques; however, neither the FMM nor the QR technique can be used at all frequencies. This method has been developed to efficiently solve for a desired parameter of a system or device that can include both electrically large FMM elements, and electrically small QR elements. The system or device is set up as an oct-tree structure that can include regions of both the FMM type and the QR type. The system is enclosed with a cube at a 0- th level, splitting the cube at the 0-th level into eight child cubes. This forms cubes at a 1st level, recursively repeating the splitting process for cubes at successive levels until a desired number of levels is created. For each cube that is thus formed, neighbor lists and interaction lists are maintained. An iterative solver is then used to determine a first matrix vector product for any electrically large elements as well as a second matrix vector product for any electrically small elements that are included in the structure. These matrix vector products for the electrically large and small elements are combined, and a net delta for a combination of the matrix vector products is determined. The iteration continues until a net delta is obtained that is within the predefined limits. The matrix vector products that were last obtained are used to solve for the desired parameter. The solution for the desired parameter is then presented to a user in a tangible form; for example, on a display.

Jandhyala, Vikram; Chowdhury, Indranil

2011-01-01

92

Recent results for plasma antennas  

SciTech Connect

Plasma antennas are just as effective as metal antennas. They can transmit, receive, and reflect radio waves just as well as metal antennas. In addition, plasma generated noise does not appear to be a problem.

Alexeff, Igor; Anderson, Ted; Farshi, Esmaeil; Karnam, Naresh; Pulasani, Nanditha Reddy [Department of Electrical Engineering, University of Tennessee, Knoxville, Tennessee 37996 (United States)

2008-05-15

93

Conformable seal  

DOEpatents

Sealing apparatus and method, comprising first and second surfaces or membranes, at least one of which surfaces is deformable, placed in proximity to one another. Urging means cause these surfaces to contact one another in a manner such that the deformable surface deforms to conform to the geometry of the other surface, thereby creating a seal. The seal is capable of undergoing multiple cycles of sealing and unsealing.

Neef, W.S.; Lambert, D.R.

1982-08-10

94

HF Antenna Optimization Study.  

National Technical Information Service (NTIS)

The report presents a summation of a study to determine the optimum log periodic dipole array design for a high gain, low coverage HF antenna over real and/or ground screen covered earth. The major problem encountered is one of determining antenna electri...

C. T. Elfving, D. L. Johnstone, U. R. Embry, V. R. Arens

1969-01-01

95

Types of Antennae  

NSDL National Science Digital Library

This illustrated guide is designed to help students recognize and learn the different types of antennae found on arthropods. The single Web page, which can be easily printed for use at field sites or in the lab, shows 8 types of antennae.

96

Probe Station Antenna Range  

NASA Technical Reports Server (NTRS)

This summer I was given the task of programming a Probe Station to collect near field antenna patterns and convert them to far field patterns. The purpose of this project is to provide NASA with another means of antenna characterizing. Currently, NASA Glenn can measure near field and far field patterns of many different types of antennas. The antennas targeted for this lab are small patch antennas at high frequencies that require probe biasing. The Probe Station contains two probes for RF signals and another two for DC Biasing. The way this lab works is as follows: A patch antenna is placed on the probe station and biased properly for testing. This antenna is known as the Antenna Under Test (AUT). The AUT is supplied with an RF signal from a probe that is connected to a network analyzer. Above the AUT hangs a probe for measuring the electric field emitted by the AUT. The probe is controlled by four axis. The axis of movements for this probe are back and forth, left and right, up and down, and rotation. The network analyzer and axis controllers are tied into a computer for reading commands and recording data. The probe scans a rectangular pattern above the AUT to measure the electric field emitted by the AUT. This data is then recorded and analyzed back at the computer.

Zaman, Afroz

2004-01-01

97

Microstrip Reflectarray Antenna  

NASA Technical Reports Server (NTRS)

Proposed microstrip reflectarray antenna provides two or more beams in different directions, without power-dividing circuitry. Because antenna flat, mass and cost of fabrication less than paraboloidal reflector with aperture of equal size, and mounted easier with less supporting structure. Designed to be mounted on ground or surfaces of ships, land vehicles, and buildings.

Huang, John

1992-01-01

98

Antenna Scan Considerations  

Microsoft Academic Search

This paper consists of three parts, each treating a single type of antenna scan. Part I is devoted to the spiral scan, deriving the equations of motion for searching a region of space in a minimum period of time. Power relations required for the antenna drive also are derived. Part II discusses a simple conical scan; the development concerns the

Daniel Levine

1954-01-01

99

Highly Miniaturized Fractal Antennas  

Microsoft Academic Search

In this paper, the use of fractal elements in miniaturized antenna applications is discussed. Hilbert grounded wires are studied and a simple design routine is outlined. Using commercial software tools, the design of groundless fractals is shown to be simple and fast. We present grounded and groundless Hilbert and Meander antennas for 250 MHz, 400 MHz and 2 GHz applications.

George S. A. Shaker; Safieddin Safavi-Naeini

2007-01-01

100

47 CFR 73.68 - Sampling systems for antenna monitors.  

Code of Federal Regulations, 2011 CFR

...environmental disturbances). (2) Sampling lines for directional antennas...3) Other configurations of sampling systems may be used upon demonstration...performance based on moment method modeling, as described in § 73.151(c), shall install a sampling system conforming to the...

2011-10-01

101

47 CFR 73.68 - Sampling systems for antenna monitors.  

Code of Federal Regulations, 2010 CFR

...environmental disturbances). (2) Sampling lines for directional antennas...3) Other configurations of sampling systems may be used upon demonstration...performance based on moment method modeling, as described in § 73.151(c), shall install a sampling system conforming to the...

2010-10-01

102

47 CFR 73.68 - Sampling systems for antenna monitors.  

Code of Federal Regulations, 2012 CFR

...environmental disturbances). (2) Sampling lines for directional antennas...3) Other configurations of sampling systems may be used upon demonstration...performance based on moment method modeling, as described in § 73.151(c), shall install a sampling system conforming to the...

2012-10-01

103

47 CFR 73.68 - Sampling systems for antenna monitors.  

Code of Federal Regulations, 2013 CFR

...environmental disturbances). (2) Sampling lines for directional antennas...3) Other configurations of sampling systems may be used upon demonstration...performance based on moment method modeling, as described in § 73.151(c), shall install a sampling system conforming to the...

2013-10-01

104

Linearly tapered slot antenna circular array for mobile communications  

NASA Technical Reports Server (NTRS)

The design, fabrication and testing of a conformal K-band circular array is presented. The array consists of sixteen linearly tapered slot antennas (LTSA). It is fed by a 1:16 microstrip line power splitter via electromagnetic coupling. The array has an omni-directional pattern in the azimuth plane. In the elevation plane the beam is displaced above the horizon.

Simons, Rainee N.; Kelly, Eron; Lee, Richard Q.; Taub, Susan R.

1993-01-01

105

Size reduction and multi-resonance effects of slotted single-layer edge-fed patch antennas  

NASA Astrophysics Data System (ADS)

In this work, easy to fabricate edge-fed, single-substrate, slotted, square-patch antennas were designed, fabricated, and measured. Effects of slots on patch antenna, such as the size reduction effect and the multi-resonance effect, are demonstrated by examples. Measurements show that up to four additional resonant frequencies below the original patch antenna's TM020 frequency are obtainable and that the size of the antenna can be reduced to less than approximately 40% its original size. The size reduction property of the proposed antenna may be suitable for miniaturized planar and conformal antennas that are needed for personal communication devices, and the multifrequency property of the proposed antenna has the advantage of serving multiple frequencies with one antenna.

Park, Zivin; Cho, Chun-Hyung

2012-08-01

106

Radiation by cavity-backed antennas on a circular cylinder  

NASA Technical Reports Server (NTRS)

Conformal antenna arrays are popular antennas for aircraft, spacecraft and land vehicle platforms due to their inherent low weight, cost and drag properties. However, to date there has been a dearth of rigorous analytical or numerical solutions to aid the designer. In fact, it has been common practice to use limited measurements and planar approximations in designing such non-planar antennas. The finite element-boundary integral method is extended to radiation by cavity-backed structures in an infinite, metallic cylinder. The formulation is used to investigate the effect of cavity size on the radiation pattern for typical circumferentially and axially polarized patch antennas. Curvature effect on the gain, pattern shape, and input impedance is also studied. Finally, the accuracy of the FE-BI approach for a microstrip patch array is demonstrated.

Kempel, Leo C.; Volakis, John L.; Sliva, Randy

1994-01-01

107

Multiband PIFA vehicle telematics antennas  

Microsoft Academic Search

Compact, low-cost antennas for multiband telematics applications on vehicles are described. The multifrequency band antennas are variations on the printed inverted-F antenna (PIFA) principle. One type of PIFA is a compact variation of a conventional antenna while the other is a novel planar version customized for different mounting positions such as bumpers, window, and roof mount. In both derivations the

Rusiru Leelaratne; Richard Langley

2005-01-01

108

Modeling panel antenna in NEC  

Microsoft Academic Search

The paper deals with the panel antenna modeling using NEC Win PRO v. 1.1 package. Base of antenna modeling would be wire construction. To achieve better performance and characteristics, several solutions for reflector and dipole are proposed. Antenna with best results and attributes will be compared with technical data of APX907016 RFS antenna given by producer. The challenge in the

Tihomir Pusnik; Dragan Poljak

2006-01-01

109

Shorted fractal Sierpinski monopole antenna  

Microsoft Academic Search

This paper describes novel configurations of shorted fractal Sierpinski gasket antenna. The antenna uses half the structure of a conventional Sierpinski gasket antenna and is folded over to be parallel to the ground plane, to form an element similar to that of the inverted L antenna. A quasi log periodic resonance behavior is obtained with a shorting pin placed at

C. T. P. Song; Peter S. Hall; H. Ghafouri-Shiraz

2004-01-01

110

Generalized Sierpinski fractal multiband antenna  

Microsoft Academic Search

A new set of fractal multiband antennas called mod-p Sierpinski gaskets is presented. Mod-p Sierpinski fractal antennas derive from the Pascal triangle and present a log-periodic behavior, which is a consequence of their self-similarity properties. Mod-p Sierpinski fractal antennas constitute a generalization of the classical Sierpinski antenna

Jordi Romeu; Jordi Soler

2001-01-01

111

SPS antenna pointing control  

NASA Technical Reports Server (NTRS)

The pointing control of a microwave antenna of the Satellite Power System was investigated emphasizing: (1) the SPS antenna pointing error sensing method; (2) a rigid body pointing control design; and (3) approaches for modeling the flexible body characteristics of the solar collector. Accuracy requirements for the antenna pointing control consist of a mechanical pointing control accuracy of three arc-minutes and an electronic phased array pointing accuracy of three arc-seconds. Results based on the factors considered in current analysis, show that the three arc-minute overall pointing control accuracy can be achieved in practice.

Hung, J. C.

1980-01-01

112

A crown square microstrip fractal antenna  

Microsoft Academic Search

Fractal antennas have been demonstrated to enhance antenna properties due to their self-similarity behavior. We introduce a new self-similar fractal antenna based on nearly square shape with a circular polarization. This new antenna which is called the crown square fractal antenna displays lower first mode frequency than a normal nearly square microstrip patch antenna which results in reduced antenna size.

P. Dehkhoda; A. Tavakoli

2004-01-01

113

Magneto-Dielectric Wire Antennas Theory and Design  

NASA Astrophysics Data System (ADS)

There is a pervasive need in the defense industry for conformal, low-profile, efficient and broadband (HF-UHF) antennas. Broadband capabilities enable shared aperture multi-function radiators, while conformal antenna profiles minimize physical damage in army applications, reduce drag and weight penalties in airborne applications and reduce the visual and RF signatures of the communication node. This dissertation is concerned with a new class of antennas called Magneto-Dielectric wire antennas (MDWA) that provide an ideal solution to this ever-present and growing need. Magneto-dielectric structures (mur > 1; epsilon r > 1) can partially guide electromagnetic waves and radiate them by leaking off the structure or by scattering from any discontinuities, much like a metal antenna of the same shape. They are attractive alternatives to conventional whip and blade antennas because they can be placed conformal to a metallic ground plane without any performance penalty. A two pronged approach is taken to analyze MDWAs. In the first, antenna circuit models are derived for the prototypical dipole and loop elements that include the effects of realistic dispersive magneto-dielectric materials of construction. A material selection law results, showing that: (a) The maximum attainable efficiency is determined by a single magnetic material parameter that we term the hesitivity: Closely related to Snoek's product, it measures the maximum magnetic conductivity of the material. (b) The maximum bandwidth is obtained by placing the highest amount of mu" loss in the frequency range of operation. As a result, high radiation efficiency antennas can be obtained not only from the conventional low loss (low mu") materials but also with highly lossy materials (tan(deltam) >> 1). The second approach used to analyze MDWAs is through solving the Green function problem of the infinite magneto-dielectric cylinder fed by a current loop. This solution sheds light on the leaky and guided waves supported by the magneto-dielectric structure and leads to useful design rules connecting the permeability of the material to the cross sectional area of the antenna in relation to the desired frequency of operation. The Green function problem of the permeable prolate spheroidal antenna is also solved as a good approximation to a finite cylinder.

Sebastian, Tom

114

Efficient rectifying antenna  

NASA Technical Reports Server (NTRS)

Rectifying antenna comprised of 17 subarrays positioned closely together to intercept microwave beam features low cost, high conversion efficiency, and high power handling capability. Tests demonstrate efficiency level of 82 percent in converting RF to dc.

Dickinson, R. M.; Brown, W. C.

1979-01-01

115

Parallel Plate Antenna.  

National Technical Information Service (NTIS)

The invention as disclosed is a parallel plate antenna having a number of stacked horizontal plates and two vertical plates. Alternating ones of the horizontal plates are electrically coupled to one vertical plate such that the horizontal plates coupled t...

D. F. Rivera

2009-01-01

116

Microwave antenna holography  

NASA Technical Reports Server (NTRS)

This microwave holography technique utilizes the Fourier transform relation between the complex far field radiation pattern of an antenna and the complex aperture field distribution. Resulting aperture phase and amplitude distribution data can be used to precisely characterize various crucial performance parameters, including panel alignment, panel shaping, subreflector position, antenna aperture illumination, directivity at various frequencies, and gravity deformation effects. The methodology of data processing presented here was successfully applied to the Deep Space Network (DSN) 34-m beam waveguide antennas. The antenna performance was improved at all operating frequencies by reducing the main reflector mechanical surface rms error to 0.43 mm. At Ka-band (32 GHz), the estimated improvement is 4.1 dB, resulting in an aperture efficiency of 52 percent. The performance improvement was verified by efficiency measurements and additional holographic measurements.

Rochblatt, David J.; Seidel, Boris L.

1992-01-01

117

Polarized Antenna Splitting Functions  

SciTech Connect

We consider parton showers based on radiation from QCD dipoles or 'antennae'. These showers are built from 2 {yields} 3 parton splitting processes. The question then arises of what functions replace the Altarelli-Parisi splitting functions in this approach. We give a detailed answer to this question, applicable to antenna showers in which partons carry definite helicity, and to both initial- and final-state emissions.

Larkoski, Andrew J.; Peskin, Michael E.; /SLAC

2009-10-17

118

Spaceborne distributed SAR antenna  

NASA Technical Reports Server (NTRS)

The MSAR c-band array panel was developed and tested. Each element of the antenna system is discussed individually as well as collectively. Textual descriptions together with test data are both used to enable a clear understanding of the antenna system performance. In general, test data has confirmed or exceeded expectations. Of particular note is the excellent cross polarization achieved with a field cancelling geometry.

Mckenna, D. B.

1984-01-01

119

Efficient Co-design of Composite Smart Structures (Antennas and Mechanical Structures) Using a Novel Hybrid Optimization Technique  

E-print Network

antennas are commonly used because they are conformable to planar and nonplanar surfaces, while sandwich structures composed of composite faces and honeycomb core are used as the basic supporting mechanical are presented in Fig. 1. The fundamental idea of the CSS panel is inserting the antennas in a composite sandwich

Tentzeris, Manos

120

Investigation of a wideband dual via fed circularly polarized patch antenna for applications in retrodirective arrays  

NASA Astrophysics Data System (ADS)

Retrodirective arrays are an ongoing topic of research, particularly for applications on air mobile platforms such as Unmanned Aerial Vehicles (UAV). To perform their task of establishing a broadband communications link in a dynamic environment requires electrically small, inexpensive, wideband antennas that are Circularly Polarized (CP). However most antennas that provide the bandwidth required with CP utilize non-standard components that cannot be manufactured in contemporary Computer Aided Manufacturing (CAM) facilities. This thesis explores ways to eliminate these non-standard components, principally air gaps and probes, and replace them with vias and multi-layer dielectrics. This investigation lead to the development of four configurations of a dual via fed circular patch antenna, with three different designs for the feed network: a two stage branch line coupler, a Wilkinson power divider with a 90 degree delay line, and a 90 degree hybrid. The experimental results included a version of this antenna operating at 3.0 GHz with a 33 % bandwidth across both the reflection coefficient and its axial ratio, comparing very well with simulations in Ansoft HFSS, and exceeding the performance of any published microstrip antenna that did not use non-standardard PCB components. This dual via fed design was then investigated in a 2 by 5 element linear array in order to develop an understanding of the coupling behaviour between elements. Keywords: microstrip antenna, mutual coupling, retrodirective arrays, circular polarization.

Davidson, Kyle

121

Robust Hybrid Finite Element Methods for Antennas and Microwave Circuits  

NASA Technical Reports Server (NTRS)

One of the primary goals in this dissertation is concerned with the development of robust hybrid finite element-boundary integral (FE-BI) techniques for modeling and design of conformal antennas of arbitrary shape. Both the finite element and integral equation methods will be first overviewed in this chapter with an emphasis on recently developed hybrid FE-BI methodologies for antennas, microwave and millimeter wave applications. The structure of the dissertation is then outlined. We conclude the chapter with discussions of certain fundamental concepts and methods in electromagnetics, which are important to this study.

Gong, J.; Volakis, John L.

1996-01-01

122

Multibeam antenna study, phase 1  

NASA Technical Reports Server (NTRS)

A multibeam antenna concept was developed for providing spot beam coverage of the contiguous 48 states. The selection of a suitable antenna concept for the multibeam application and an experimental evaluation of the antenna concept selected are described. The final analysis indicates that the preferred concept is a dual-antenna, circular artificial dielectric lens. A description of the analytical methods is provided, as well as a discussion of the absolute requirements placed on the antenna concepts. Finally, a comparative analysis of reflector antenna off-axis beam performance is presented.

Bellamy, J. L.

1972-01-01

123

Fabrication and impact performance of three-dimensionally integrated microstrip antennas with microstrip and coaxial feeding  

NASA Astrophysics Data System (ADS)

A conformal load-bearing antenna structure (CLAS) combines the antenna into a composite structure such that it can carry the designed load while functioning as an antenna. In this paper, two types of new 3D integrated microstrip antennas (3DIMAs) with different feeding methods are designed to work at the radar L-band. Different from the conventional CLAS, the radiating patch and the ground plane of the 3DIMA are both composed of woven conductive wires and are bonded into the 3D composite physically by Z-yarns, greatly improving the damage tolerance of the antenna. The return loss of the coaxial-fed antenna is -13.15 dB with a resonant frequency of 1.872 GHz, while that of the microstrip-fed antenna is -31.50 dB with a resonant frequency of 1.33 GHz. Both of the 3DIMAs have similar radiation patterns to that of the traditionally designed microstrip antenna. In addition, an experimental investigation of the impact response of the coaxial-fed 3DIMA was carried out and the results showed the radiation pattern had almost no change even when the antenna received an impact energy of 15 J, exhibiting superior impact resistance to that of a conventional microstrip antenna.

Yao, Lan; Wang, Xin; Xu, Fujun; Zhao, Da; Jiang, Muwen; Qiu, Yiping

2009-09-01

124

Antenna cab interior showing equipment rack and fiberglass antenna panels, ...  

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

Antenna cab interior showing equipment rack and fiberglass antenna panels, looking west. - Western Union Telegraph Company, Jennerstown Relay, Laurel Summit Road off U.S. 30, Laughlintown, Westmoreland County, PA

125

Antenna cab interior showing equipment rack and fiberglass antenna panels, ...  

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

Antenna cab interior showing equipment rack and fiberglass antenna panels, looking southeast. - Western Union Telegraph Company, Jennerstown Relay, Laurel Summit Road off U.S. 30, Laughlintown, Westmoreland County, PA

126

Cup Cylindrical Waveguide Antenna  

NASA Technical Reports Server (NTRS)

The cup cylindrical waveguide antenna (CCWA) is a short backfire microwave antenna capable of simultaneously supporting the transmission or reception of two distinct signals having opposite circular polarizations. Short backfire antennas are widely used in mobile/satellite communications, tracking, telemetry, and wireless local area networks because of their compactness and excellent radiation characteristics. A typical prior short backfire antenna contains a half-wavelength dipole excitation element for linear polarization or crossed half-wavelength dipole elements for circular polarization. In order to achieve simultaneous dual circular polarization, it would be necessary to integrate, into the antenna feed structure, a network of hybrid components, which would introduce significant losses. The CCWA embodies an alternate approach that entails relatively low losses and affords the additional advantage of compactness. The CCWA includes a circular cylindrical cup, a circular disk subreflector, and a circular waveguide that serves as the excitation element. The components that make it possible to obtain simultaneous dual circular polarization are integrated into the circular waveguide. These components are a sixpost polarizer and an orthomode transducer (OMT) with two orthogonal coaxial ports. The overall length of the OMT and polarizer (for the nominal middle design frequency of 2.25 GHz) is about 11 in. (approximately equal to 28 cm), whereas the length of a commercially available OMT and polarizer for the same frequency is about 32 in. (approximately equal to 81 cm).

Acosta, Roberto J.; Darby, William G.; Kory, Carol L.; Lambert, Kevin M.; Breen, Daniel P.

2008-01-01

127

Aperture excited dielectric antennas  

NASA Technical Reports Server (NTRS)

The results of a comprehensive experimental and theoretical study of the effect of placing dielectric objects over the aperture of waveguide antennas are presented. Experimental measurements of the radiation patterns, gain, impedance, near-field amplitude, and pattern and impedance coupling between pairs of antennas are given for various Plexiglas shapes, including the sphere and the cube, excited by rectangular, circular, and square waveguide feed apertures. The waveguide excitation of a dielectric sphere is modeled using the Huygens' source, and expressions for the resulting electric fields, directivity, and efficiency are derived. Calculations using this model show good overall agreement with experimental patterns and directivity measurements. The waveguide under an infinite dielectric slab is used as an impedance model. Calculations using this model agree qualitatively with the measured impedance data. It is concluded that dielectric loaded antennas such as the waveguide excited sphere, cube, or sphere-cylinder can produce directivities in excess of that obtained by a uniformly illuminated aperture of the same cross section, particularly for dielectric objects with dimensions of 2 wavelengths or less. It is also shown that for certain configurations coupling between two antennas of this type is less than that for the same antennas without dielectric loading.

Crosswell, W. F.; Chatterjee, J. S.; Mason, V. B.; Tai, C. T.

1974-01-01

128

Microstrip antenna couplers and active antenna amplifying arrays  

E-print Network

MICROSTRIP ANTENNA COUPLERS AND ACTIVE ANTENNA AMPLIFYING ARRAYS A Thesis by YAO-CHOU (ANGUS) YANG Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of MASTER... OF SCIENCE December 1997 Major Subject: Electrical Engineering MICROSTRIP ANTENNA COUPLERS AND ACTIVE ANTENNA AMPLIFYING ARRAYS A Thesis by YAO-CHOU (ANGUS) YANG Submitted to the Office of Graduate Studies of Texas AkM University in partial...

Yang, Yao-Chou (Angus)

2012-06-07

129

The Fourpoint Antenna as a LEDA Outrigger Antenna Steve Ellingson  

E-print Network

The Fourpoint Antenna as a LEDA Outrigger Antenna Steve Ellingson Aug 6, 2011 Contents 1. A useful description of the EDGES fourpoint antenna is given in Rogers & Bowman (2008) [3]. From Figure 1 imply c = 50.30 cm and = 1.35. A drawing provided separately by Alan Rogers confirms b = 30.48 cm

Ellingson, Steven W.

130

PASS Spacecraft Antenna Technology Assessment  

NASA Technical Reports Server (NTRS)

The purpose was to generate estimates of mechanical performance for the classes of spacecraft antenna under construction for application to the Personal Access Satellite System (PASS). These performance data are needed for the support of trade studies involving antenna system development. The classes of antenna considered included: (1) rigid non-deployable antenna structures; (2) mechanical deployable antenna concepts; (3) inflatable deployable antenna concepts; and (4) mesh deployable antenna concepts. The estimates of mechanical performance are presented in terms of structural weight and cost as a function of the reflector size. Estimates of aperture surface precision are presented for a few discrete antenna sizes. The range of reflector size is 1 to 4 meters for non-deployable structures and 2 to 8 meters for deployable structures. The range of reflector surface precision is lambda/30 to lambda/50 for 20 and 30 GHz, respectively.

Freeland, R. E.

1990-01-01

131

A plasma receiving dipole antenna  

SciTech Connect

Results from experimental studies of a short-wave plasma dipole transceiver antenna are presented. The efficiency of the plasma receiving antenna is estimated, and the optimal frequency range for excitation and reception under the given experimental conditions is determined.

Minaev, I. M.; Gusein-zade, N. G. [Russian Academy of Sciences, Prokhorov Institute of General Physics (Russian Federation); Rukhadze, K. Z. [Moscow State Institute of Radio Engineering, Electronics, and Automation (Russian Federation)

2010-10-15

132

A novel small fractal patch antenna  

Microsoft Academic Search

A novel fractal patch antenna is introduced to reduce the antenna size in this paper. Compared to the conventional square patch antenna, the proposed antenna exhibits lower resonant frequency. A fractal patch antenna is simulated and measured. The miniaturizing benefits of using this fractal antenna are proved by the results of experiments and simulations.

Jingjing Huang; Fuqi Shan; Jingzhao She; Zhenghe Feng

2005-01-01

133

Electromagnetic exposure in a phantom in the near and far fields of wire and planar antennas  

NASA Astrophysics Data System (ADS)

Due to the wide availability and usage of wireless devices and systems there have been and are concerns regarding their effects on the human body. Respective regulatory agencies have developed safety standards based on scientific research on electromagnetic (EM) exposure from wireless devices and antennas. The metric that quantifies the exposure level is called the Specific Absorption Rate (SAR). Wireless devices must satisfy the regulatory standards before being marketed. In the past, researchers have primarily focused on investigating the EM exposure from wireless devices that are used very near to the user's head or body (less than 25 mm). But as time progressed many more wireless devices have become ubiquitous (vehicular wireless devices, laptop PCMCIA cards, Bluetooth dongles, wireless LAN routers, cordless phone base stations, and pico base stations are to name a few) and are operated at distances greater than 25 mm yet smaller than 200 mm. Given the variations in operating frequency, distance, and antenna size and type it is challenging to develop an approach using which EM exposure from a wide variety of wireless devices can be evaluated. The problem becomes more involved owing to the difficulties in identifying the antenna zone boundaries, e.g. reactive near-field, radiating near-field, far-field etc. The focus of this thesis is to investigate a large class of low and highly directive antennas and evaluate the EM exposure from them into a large elliptical phantom. The objective is to be able to predict threshold power levels that meet the SAR limits imposed by the regulatory agencies. It was observed that among the low directivity antennas at close near-field distances, electrically small antennas induced distinguishably higher SAR than electrically larger antennas. But differences in SAR were small as the phantom moved into the far-fields of the antennas. SAR induced by highly directive antennas were higher when the phantom was in the far-field of the antennas and was facing the antenna frontal plane. The same was not true when the phantom was in the near-field of the antennas. Finally, by analyzing the simulation and measurement data threshold power formulas were developed for low directivity antennas using which power levels corresponding to the safe exposure limits independent of device type or geometry can be estimated.

Mazady, Md. Anas Boksh

134

Ionospheric effects to antenna impedance  

NASA Technical Reports Server (NTRS)

The reciprocity between high power satellite antennas and the surrounding plasma are examined. The relevant plasma states for antenna impedance calculations are presented and plasma models, and hydrodynamic and kinetic theory, are discussed. A theory from which a variation in antenna impedance with regard to the radiated power can be calculated for a frequency range well above the plasma resonance frequency is give. The theory can include photo and secondary emission effects in antenna impedance calculations.

Bethke, K. H.

1986-01-01

135

Super wideband fractal antenna design  

Microsoft Academic Search

Fractals have very unique properties, therefore in recent years, antenna designers use fractal geometry in multi-band and broad-band antennas designing. In this paper, I have achieved to a 40 GHz super wideband antenna with applying a fractal geometry to a wire square loop antenna and choosing appropriate size and location for feeding. Modelling and simulation is performed via SuperNEC electromagnetic

Abolfazl Azari

2009-01-01

136

Satellite communication antenna technology  

NASA Technical Reports Server (NTRS)

A general overview of current technology in the field of communication satellite antennas is presented. Among the topics discussed are: the design of multiple beam systems; frequency reuse; and polarization control of antenna measurements. Consideration is also given to: contour beam synthesis; dual shaped reflector synthesis; beam shaping; and offset reflector design. The applications of the above technologies to present and future generations of communications satellites is considered, with emphasis given to such systems as: the Intelsats; the Defense Satellite Communications System, (DSCS-III); Satellite Business System (SBS), and Comstar.

Mittra, R. (editor); Imbriale, W. A. (editor); Maanders, E. J. (editor)

1983-01-01

137

DSN Microwave Antenna Holography  

NASA Technical Reports Server (NTRS)

The DSN microwave antenna holography project will obtain three-dimensional pictures of the large DSN antenna surfaces. These pictures must be of suffi icient resolution to allow adjustment of the reflector panels to an rms surface of 0.5 mm (0.25 mm, goal). The major parameters and equations needed to define a holographic measurement system are outlined and then the proof of concept demonstration measurement that was made at DSS-43 (Australia) that resulted in contour maps with spatial resolution of 7 m in the aperture plane and resolution orthogonal to the aperture plane of 0.7 mm was discussed.

Rochblatt, D. J.; Seidel, B. L.

1984-01-01

138

Furlable spacecraft antenna development  

NASA Technical Reports Server (NTRS)

The development of large furlable spacecraft antennas using conical main reflectors is described. Two basic antenna configurations which utilize conical main reflectors have been conceived and are under development. In the conical-Gregorian configuration each ray experiences two reflections in traveling from the feed center to the aperture plane. In the Quadreflex (four reflection) configuration, each ray experiences four reflections, one at each of two subreflector surfaces and two at the main conical reflector surface. The RF gain measurements obtained from 6-ft and 30-in. models of the conical-Gregorian and Quadreflex concepts respectively were sufficiently encouraging to warrant further development of the concepts.

Oliver, R. E.; Wilson, A. H.

1972-01-01

139

A Simple, Efficient TV Antenna  

NSDL National Science Digital Library

This website, provided by Professor Rick Matthews of Wake Forest University, contains instructions on how to build an inexpensive but effective TV antenna. The site includes formulas for converting channel number to frequency, and frequency to wavelength (that is, wavelength in "twin-lead," the standard antenna lead wire). A diagram shows that the distance across antenna is half wavelength.

2007-05-03

140

Low-sidelobe radar antennas  

NASA Astrophysics Data System (ADS)

The advances that made sidelobes of -50 dB possible are recounted, and the factors determining whether the sidelobes can be carried into wider bandwidths are discussed. Attention is also given to the use of sidelobes in agile and active arrays. That slotted arrays were the first to achieve ultra-low sidelobes is not considered an accident. Each point in the distribution is determined individually by slot location and shape, and these can be readily milled with exactness. Also described are corporate-fed planar arrays, reflectors and lenses, and conformal arrays. In discussing tolerance and bandwidth, it is pointed out that for any antenna the key to achieving low sidelobes is to recognize and control the sources of error that degrade sidelobe levels. In general, the error sources are in the structure, mutual coupling, component manufacturing tolerance, and frequency response, and they give rise to errors of three types: gradual distortion, random errors, and systematic errors. Each of these is discussed.

Evans, G. E.; Schrank, H. E.

1983-07-01

141

Infrared antenna metrology  

NASA Astrophysics Data System (ADS)

Infrared antennas are a novel type of detectors that couples electromagnetic radiation into metallic structures and feed it to a rectifying element. As their radio and millimeter counterparts, they can be characterized by parameters explaining their response in a variety of situations. The size of infrared antennas scales with the detected wavelength. Then, specifically designed experimental set-ups need to be prepared for their characterization. The measurement of the spatial responsivity map of infrared antennas is one of the parameters of interest, but other parameters can be defined to describe, for example, their directional response, or polarization response. One of the inputs to measure the spatial responsivity map is the spatial distribution of the beam irradiance illuminating the antenna-coupled detector. The measured quantity is actually a map of the response of the detector when it moves under the beam illumination. This measurement is given as the convolution of the actual responsivity map and the beam irradiance distrbution. The uncertainties, errors, and artifacts incorporated along the measurement procedure are analyzed by using the Principal Component Analysis (PCA). By means of this method is possible to classify different sources of uncertainty. PCA is applied as a metrology tool to characterize the accuracy and repeatability of the experimental set-up. Various examples are given to describe the application of the PCA to the characterization of the deconvolution procedure, and to define the responsivity and the signal-to-noise ratio of the measured results.

López-Alonso, José M.; Mandviwala, Tasneem; Alda, Javier; Lail, B.; Boreman, Glenn

2005-10-01

142

Collapsible corrugated horn antenna  

Microsoft Academic Search

A horn antenna that is readily collapsible while not in use is described. A number of different sized annular metal rings are arranged in a sequence such that each ring is larger than the one that precedes it in the sequence. A number of thin flexible electrically conductive members attach successive metal rings together physically and connect them together electrically.

D. E. Barthlome

1978-01-01

143

Compact WLAN disc antennas  

Microsoft Academic Search

A novel conical beam patch antenna design, suitable for local area network applications, uses a central cylindrical connection from the disc to ground to achieve a large reduction in resonant size. Results on efficiency, bandwidth, and pattern are reported for several prototypes.

Neil J. McEwan; Raed A. Abd-Alhameed; Embarak M. Ibrahim; Peter S. Excell; Nazar T. Ali

2002-01-01

144

Adaptive dome antenna array  

NASA Astrophysics Data System (ADS)

The class of antenna arrays examined consists of a plane multielement array emitting through a hemispherical dome which acts as a lens. Computer simulation studies were conducted for such an adaptive dome array having 21 isotropic elements. The studies simulated the effects of one and two narrow-band interference signals as well as white noise. The adaptation criterion corresponded to a generalized SNR.

Samoilenko, V. I.; Grubrin, I. V.

1981-02-01

145

Development of Leaky Wave Antennas for Layered Ridge Dielectric Waveguide  

NASA Technical Reports Server (NTRS)

The millimeter wave, especially above 100 GHz, and the submillimeter wave frequency spectrum offers the possibility for narrow-beam, high-resolution antennas which are critical for high definition radars required for space debris tracking, airport ground avoidance radars, and missile tracking. In addition, the frequency which most atmospheric constituents may be detected lie in this part of the frequency spectrum. Therefore, the development of electronic components for millimeter/submillimeter wave passive sensors is required for environmental monitoring of the Earth's atmosphere. Typical microwave transmission lines such as microstrip and coplanar waveguide rely on two or more electrical conductors to concentrate and guide the electromagnetic energy. Unfortunately, the surface resistance of the conductors increases as the square root of frequency. In addition, the circuit dimensions must be decreased with increasing frequency to maintain a single mode transmission line which further increases the conductor loss. An alternative family of transmission lines are formed from two or more insulating materials and rely on the differences in the permittivities between the two materials to guide the wave. No metal conductors are required although some dielectric waveguides do utilize a metallic ground plane to facilitate the interconnections of active electrical elements or to reduce the transmission line size. Examples of such transmission lines are image guides, insulated image guides, trapped image guides, ridge guide, and layered ridge dielectric waveguide (LRDW). Although most dielectric waveguides have dimensions on the order of lambda to provide sufficient field confinement, the LRDW has been shown to provide good field confinement for electrically small lines. This offers an advantage in circuit integration. It has been shown that a periodic array of metallic strips placed either along or on top of a dielectric waveguide forms an effective radiator. This antenna is easy to fabricate and there is good background of microstrip type antenna design information in the literature. This paper reports the development of the first frequency scanning antenna fed by a LRDW.

Ponchak, George E.; Katehi, Linda P. B.

1993-01-01

146

Mobile terminal antennas for helicopters  

NASA Astrophysics Data System (ADS)

In this paper, the feasibility of using an L-band low gain antenna (LGA) as a mobile terminal antenna for helicopters is described. The objective is to select the lowest cost antenna system which can be easily mounted on a helicopter and capable of communicating with a geosynchronous satellite. To ensure that all the antenna options are being considered, the steerable high gain reflector and medium gain array antennas as well as LGA are studied and compared in an exhaustive survey. The high gain reflector antenna in L-band is usually very large in size and heavy in weight. In addition, a bulky and expensive tracking system is needed to steer the antenna beam to the satellite direction. The medium gain antennas (including mechanically and electronically steered arrays) are also more expensive and less reliable than an LGA due to the addition of a beam steering system to track the satellite. The omni-directional LGA is simple, reliable, and inexpensive. It is typically ten times smaller than the medium gain antenna. This makes the position, selection, and mounting on the helicopter relatively easier. Therefore, the LGA is selected as a mobile terminal antenna for helicopters. Among the many LGA's (cross-dipole, helix, spiral, and slot antennas), the helix antenna is the most inexpensive. One can also change the size, shape, or pitch angle of the helix to optimize the gain in the desired direction. Therefore, the helix antenna is selected for further study. Both 2-arm and 4-arm helices are studied theoretically and experimentally to determine the antenna's performance and the scattering effects from the helicopter body and the blades. The multipath, Doppler, and Doppler rate issues as well as the periodic fading effects caused by the helicopter rotor blades will be briefly discussed in the paper.

Wu, Te-Kao; Farazian, K.; Golshan, N.; Divsalar, D.; Hinedi, S.; Woo, K.

147

Mobile terminal antennas for helicopters  

NASA Technical Reports Server (NTRS)

In this paper, the feasibility of using an L-band low gain antenna (LGA) as a mobile terminal antenna for helicopters is described. The objective is to select the lowest cost antenna system which can be easily mounted on a helicopter and capable of communicating with a geosynchronous satellite. To ensure that all the antenna options are being considered, the steerable high gain reflector and medium gain array antennas as well as LGA are studied and compared in an exhaustive survey. The high gain reflector antenna in L-band is usually very large in size and heavy in weight. In addition, a bulky and expensive tracking system is needed to steer the antenna beam to the satellite direction. The medium gain antennas (including mechanically and electronically steered arrays) are also more expensive and less reliable than an LGA due to the addition of a beam steering system to track the satellite. The omni-directional LGA is simple, reliable, and inexpensive. It is typically ten times smaller than the medium gain antenna. This makes the position, selection, and mounting on the helicopter relatively easier. Therefore, the LGA is selected as a mobile terminal antenna for helicopters. Among the many LGA's (cross-dipole, helix, spiral, and slot antennas), the helix antenna is the most inexpensive. One can also change the size, shape, or pitch angle of the helix to optimize the gain in the desired direction. Therefore, the helix antenna is selected for further study. Both 2-arm and 4-arm helices are studied theoretically and experimentally to determine the antenna's performance and the scattering effects from the helicopter body and the blades. The multipath, Doppler, and Doppler rate issues as well as the periodic fading effects caused by the helicopter rotor blades will be briefly discussed in the paper.

Wu, Te-Kao; Farazian, K.; Golshan, N.; Divsalar, D.; Hinedi, S.; Woo, K.

1993-01-01

148

Antenna modeling and analysis for ELF/VLF/LF applications  

NASA Astrophysics Data System (ADS)

This paper presents a numerical procedure which can be effectively used for the analysis/design of a very-low frequency capacitive antenna system on complex platforms and for charge distribution computation. The 'quasi static' radiation problem was solved by means of the corresponding electrostatic solution, by using a Method Of Moments (MOM) procedure. Pulse basis functions, defined on surface patch domains, and the point-matching test procedure are used in conjunction with a powerful postprocessing numerical tool. Given the platform model, the postprocessing tool allows us to analyze all possible antenna configurations by running the MOM computer code only once. The following parameters can be evaluated: (1) antenna radiation pattern; (2) antenna Norton equivalent circuit, from which the effective voltage at the input of the receiver can be evaluated; (3) induced charge distribution; and (4) scattered electric field distribution near the platform. The proposed solution is particularly useful for applications where the criticality of the structure requires a peculiar attention in defining structural elements that constitute the 'electrical doublet' (conformal antenna).

Bandinelli, M.; Chiti, S.; Cioni, R.

1993-05-01

149

Microsecond switchable thermal antenna  

NASA Astrophysics Data System (ADS)

We propose a thermal antenna that can be actively switched on and off at the microsecond scale by means of a phase transition of a metal-insulator material, the vanadium dioxide (VO2). This thermal source is made of a periodically patterned tunable VO2 nanolayer, which support a surface phonon-polariton in the infrared range in their crystalline phase. Using electrodes properly registered with respect to the pattern, the VO2 phase transition can be locally triggered by ohmic heating so that the surface phonon-polariton can be diffracted by the induced grating, producing a highly directional thermal emission. Conversely, when heating less, the VO2 layers cool down below the transition temperature, the surface phonon-polariton cannot be diffracted anymore so that thermal emission is inhibited. This switchable antenna could find broad applications in the domain of active thermal coatings or in those of infrared spectroscopy and sensing.

Ben-Abdallah, Philippe; Benisty, Henri; Besbes, Mondher

2014-07-01

150

Printed Monopole Slot Antenna for Internal Multiband Mobile Phone Antenna  

Microsoft Academic Search

A new internal multiband mobile phone antenna formed by two printed monopole slots of different lengths cut at the edge of the system ground plane of the mobile phone is presented. The antenna can generate two wide bands centered at about 900 and 2100 MHz to cover the GSM850\\/GSM900\\/DCS\\/PCS\\/UMTS bands and the 2.4-GHz WLAN band. Further, the antenna has a

Chun-I. Lin; Kin-Lu Wong

2007-01-01

151

Principles of antennas - Wire and aperture  

NASA Astrophysics Data System (ADS)

A quantitative approach is taken in this textbook on wire and aperture antennas. The topics addressed include: planar sources of uniform plane waves, current element sources, dipole and monopole antennas, computer solutions of dipole and monopole antennas, loop antennas, helical antennas, Yagi-Uda antennas, and freqeuncy-independent and logarithmically periodic antennas. Also discussed are: noise power delivered by wire antennas, aperture antennas, angular spectrum of plane waves, waveguide radiators, paraboloidal reflectors, receiving paraboloidal reflectors with feeds, analysis of transmitting paraboloids, and Cassegrain and offset reflector analysis.

Maclean, T. S. M.

152

Redshift antenna project  

NASA Technical Reports Server (NTRS)

The layout of a center frequency 2203.1 MHz antenna is presented. The four to one taped layout was photograph reduced and a single section was etched. Initial impedance and frequency mismatches were corrected, and impedance plots of each of the two sections are shown. With the 2203.1 MHz layout as a reference, initial layouts were made for the remaining two frequencies 2117.7 and 2299.7 MHz, and single sections were fabricated.

1974-01-01

153

Modular antenna design study  

NASA Technical Reports Server (NTRS)

The mechanical design of a modular antenna concept was developed sufficiently to allow manufacture of a working demonstration model of a module, to predict mass properties, and to make performance estimates for antenna reflectors composed of these modules. The primary features of this concept are: (1) each module is an autonomous structural element which can be attached to adjacent modules through a three point connection; (2) the upper surface is a folding hexagonal truss plate mechanism which serves as the supporting structure for a reflective surface; and (3) the entire truss and surface can be folded into a cylindrical envelope in which all truss elements are essentially parallel. The kinematic studies and engineering demonstration model fully verified the deployment kinematics, stowing philosophy, and deployment sequencing for large antenna modules. It was established that such modules can be stowed in packages as small as 25 cm in diameter, using 1.27 cm diameter structural tubes. The development activity indicates that this deployable modular approach towards building large structures in space will support erection of 450 m apertures for operation up to 3 GHz with a single space shuttle flight.

Ribble, J. W.

1981-01-01

154

Wideband Planar Log-Periodic Antenna  

Microsoft Academic Search

A compact planar wideband microstrip antenna is introduced. The antenna is a log-periodic antenna with 7 dipole elements. The antenna is designed to function in the frequency range of 500 to 700 MHz. It has a dimension of 268 mm by 145 mm by 3 mm. The matching is better than -10 dB in the working bandwidth. The proposed antenna

M. M. Tajdini; M. Shahabadi

2007-01-01

155

Printed millimeter wave vertical patch antenna  

Microsoft Academic Search

A new form of millimeter wave antenna element by embedding a vertical patch antenna into a microwave substrate is presented. The antenna is fed by the special grounded CPW\\/microstrip\\/printed ring combination. An air cavity is employed to enhance the antenna gain. The designed antenna is ease of fabrication and the simple in structure. It has an impedance bandwidth of 26%

Hang Wong; Kung Bo Ng; Kwai Man Luk; Chi Hou Chan; Quan Xue

2010-01-01

156

The Koch island fractal microstrip patch antenna  

Microsoft Academic Search

The Koch island fractal patch antenna is introduced in order to reduce the antenna size. By the space-filling property of fractal geometry, this antenna reveals lower resonant frequency than that of a normal square patch antenna. Based on experimental results, it is found that as iteration and iteration factor increases, the resonant frequency of this patch antenna decreases, while maintaining

Ilk won Kim; TacHoon Yoo; JongGwan Yook; HanKyu Park

2001-01-01

157

Frequency independent parabolic phased antenna array of log periodic antennas  

NASA Astrophysics Data System (ADS)

A frequency-independent phased array antenna made of log-periodic radiators is presented which, in contrast to the Duhamel array, does not employ phase shifters at the antenna inputs to produce radiation in the main direction. The array considered here is a system of radial log-periodic radiators that form a parabolic phased-array antenna. The dipoles of all the radiators having the same size are located along a parabolic line. The operation of the parabolic array at various frequencies is equivalent to that of a series of confocal parabolic mirror antennas excited from a single source.

Veriga, B. A.; Vyakhirev, N. I.

1984-03-01

158

Antenna structure with distributed strip  

DOEpatents

An antenna comprises electrical conductors arranged to form a radiating element including a folded line configuration and a distributed strip configuration, where the radiating element is in proximity to a ground conductor. The folded line and the distributed strip can be electrically interconnected and substantially coplanar. The ground conductor can be spaced from, and coplanar to, the radiating element, or can alternatively lie in a plane set at an angle to the radiating element. Embodiments of the antenna include conductor patterns formed on a printed wiring board, having a ground plane, spacedly adjacent to and coplanar with the radiating element. Other embodiments of the antenna comprise a ground plane and radiating element on opposed sides of a printed wiring board. Other embodiments of the antenna comprise conductors that can be arranged as free standing "foils". Other embodiments include antennas that are encapsulated into a package containing the antenna.

Rodenbeck, Christopher T. (Albuquerque, NM)

2008-10-21

159

Antenna structure with distributed strip  

DOEpatents

An antenna comprises electrical conductors arranged to form a radiating element including a folded line configuration and a distributed strip configuration, where the radiating element is in proximity to a ground conductor. The folded line and the distributed strip can be electrically interconnected and substantially coplanar. The ground conductor can be spaced from, and coplanar to, the radiating element, or can alternatively lie in a plane set at an angle to the radiating element. Embodiments of the antenna include conductor patterns formed on a printed wiring board, having a ground plane, spacedly adjacent to and coplanar with the radiating element. Other embodiments of the antenna comprise a ground plane and radiating element on opposed sides of a printed wiring board. Other embodiments of the antenna comprise conductors that can be arranged as free standing "foils". Other embodiments include antennas that are encapsulated into a package containing the antenna.

Rodenbeck, Christopher T. (Albuquerque, NM)

2008-03-18

160

A Mars Riometer: Antenna Considerations  

NASA Technical Reports Server (NTRS)

This is the final report on NASA Grant NAG5-9706. This project explored riometer (relative ionospheric opacity meter) antenna designs that would be practical for a Mars surface or balloon mission. The riometer is an important radio science instrument for terrestrial aeronomy investigations. The riometer measures absorption of cosmic radio waves by the overhead ionosphere. Studies have shown the instrument should work well on Mars, which has an appreciable daytime ionosphere. There has been concern that the required radio receiver antenna (with possibly a 10 meter scale size) would be too large or too difficult to deploy on Mars. This study addresses those concerns and presents several antenna designs and deployment options. It is found that a Mars balloon would provide an excellent platform for the riometer antenna. The antenna can be incorporated into the envelope design, allowing self-deployment of the antenna as the balloon inflates.

Fry, Craig D.

2001-01-01

161

Dual-frequency patch antennas  

Microsoft Academic Search

Dual-frequency patch antennas may provide an alternative to large-bandwidth planar antennas, in applications in which large bandwidth is really needed for operating at two separate transmit-receive bands. When the two operating frequencies are far apart, a dual-frequency patch structure can be conceived to avoid the use of separate antennas. In this paper, a critical overview of possible solutions for dual-frequency

S. Maci; G. BifJi Gentili

1997-01-01

162

Inflatable antenna for cubesats: Motivation for development and antenna design  

NASA Astrophysics Data System (ADS)

CubeSats and small satellites have potential to provide means to explore space and to perform science in a more affordable way. As the goals for these spacecraft become more ambitious in space exploration, moving from Low Earth Orbit (LEO) to Geostationary Earth Orbit (GEO) or further, the communication systems currently implemented will not be able to support those missions. One of the bottlenecks in small spacecraft communication systems is represented by antennas' size, due to the close relation between antenna gain and dimensions. Current antennas for CubeSats are mostly dipole or patch antennas with limited gain. Deployable (not inflatable) antennas for CubeSats are currently being investigated, but these solutions are affected by the challenge of packaging the whole deployable structure in a small spacecraft. The work that we propose represents the first attempt to develop an inflatable antenna for CubeSats. Inflatable structures and antennas can be packaged efficiently occupying a small amount of space, and they can provide, once deployed, large dish dimension and correspondent gain. Inflatable antennas have been previously tested in space (Inflatable Antenna Experiment, STS-77). However they have never been developed for small spacecraft such as CubeSats, where the packaging efficiency, the deployment, and the inflation represent a challenge. Our study explores for the first time the possibility of developing such antenna in a way compatible with CubeSat dimensions and constraints. The research provides answers on the possible dimensions for an inflatable antenna for small satellites, on the gain and resolution that can be achieved, and on the deployment and inflation mechanism compatible with CubeSat. Future work in the development of the antenna will include the test of the antenna in flight during a specific technical demonstration mission. The article is structured as follows: context and motivation for Cubesat inflatable antenna are described; then a study to design the antenna which achieves the required performance metrics, while respecting the constraints imposed by CubeSat structure, is presented.

Babuscia, Alessandra; Corbin, Benjamin; Knapp, Mary; Jensen-Clem, Rebecca; Van de Loo, Mark; Seager, Sara

2013-10-01

163

Development of inflatable antenna structures  

NASA Technical Reports Server (NTRS)

Self-rigidizable spring-tape-reinforced (STR) booms were used to develop structural systems for large-aperture space inflatable radar antennas. The lightweight planar frames built with STR booms can be compactly stowed for launch, deployed by inflation pressure in space, and used to tension the RF membrane apertures of the antennas. Engineering models of a Ka-band reflectarray antenna and a L-band synthetic-aperture radar antenna were developed and have successfully demonstrated stowage and deployment, as well as RF performance. A design improvement was also being implemented to enhance long-term configuration stability and widen the application range of the STR booms.

Lou, M. C.; Fang, H.

2002-01-01

164

Metamaterial-based "sabre" antenna  

NASA Astrophysics Data System (ADS)

The "sabre" antenna is an array of two monopole elements, vertically polarized with omnidirectional radiation patterns, and placed on either side of a composite material on the tail of an airplane. As an in-phase reflector plane, the antenna uses a compact dual-layer high-impedance surface (DL-HIS) with offset mushroom-like Sivenpiper square shape unit cells. This topology allows one to control both operational frequency and bandgap width, while reducing the total height of the antenna to under ?0/36. The designed antenna structure has a wide bandwidth higher than 24% around 1.4 GHz. The measurements and numerical simulations agree very well.

Hafdallah Ouslimani, Habiba; Yuan, Tangjie; Kanane, Houcine; Priou, Alain; Collignon, Gérard; Lacotte, Guillaume

2014-05-01

165

Fiber based phased array antennas  

NASA Astrophysics Data System (ADS)

A phased array antenna is a multielement antenna capable of agile electronic beam forming and steering requiring several hundred high frequency, wide bandwidth, interconnections. Conventional distribution methods using waveguide or coax are impractical because they exhibit high attenuation, limited bandwidth, sensitivity to EMI, temperature drifts, and phase instability. Additionally, for large numbers of antenna elements, the size and weight of such systems make them impossible for large scale implementation on communication satellites. RF signal distribution via fiber optic technology is a potential solution to these phased array antenna problems.

Guggenmos, Joel L.; Johnson, Ronald L.

1987-01-01

166

47 CFR 80.866 - Spare antenna.  

Code of Federal Regulations, 2013 CFR

...erection must be provided. If the installed transmitting antenna is suspended between supports, this spare antenna must be a single-wire transmitting antenna of the same length and must also include suitable...

2013-10-01

167

Large Space Antenna Systems Technology, 1984  

NASA Technical Reports Server (NTRS)

Mission applications for large space antenna systems; large space antenna structural systems; materials and structures technology; structural dynamics and control technology, electromagnetics technology, large space antenna systems and the Space Station; and flight test and evaluation were examined.

Boyer, W. J. (compiler)

1985-01-01

168

47 CFR 73.816 - Antennas.  

Code of Federal Regulations, 2010 CFR

...Stations (LPFM) § 73.816 Antennas. (a) Permittees and...may employ nondirectional antennas with horizontal only polarization, vertical only polarization, circular...polarization. (b) Directional antennas will not be...

2010-10-01

169

47 CFR 73.1680 - Emergency antennas.  

Code of Federal Regulations, 2010 CFR

...stations may use a horizontal or vertical wire or a nondirectional vertical element of a directional antenna as an emergency antenna. AM...using an emergency nondirectional antenna or a horizontal or vertical wire pursuant to this...

2010-10-01

170

47 CFR 101.517 - Antennas.  

Code of Federal Regulations, 2010 CFR

...Message Service § 101.517 Antennas. (a) Transmitting antennas may be omnidirectional or...b) The use of horizontal or vertical plane wave polarization...stations. (c) Directive antennas must be used at all...

2010-10-01

171

47 CFR 73.1680 - Emergency antennas.  

Code of Federal Regulations, 2011 CFR

...stations may use a horizontal or vertical wire or a nondirectional vertical element of a directional antenna as an emergency antenna. AM...using an emergency nondirectional antenna or a horizontal or vertical wire pursuant to this...

2011-10-01

172

47 CFR 73.1680 - Emergency antennas.  

Code of Federal Regulations, 2012 CFR

...stations may use a horizontal or vertical wire or a nondirectional vertical element of a directional antenna as an emergency antenna. AM...using an emergency nondirectional antenna or a horizontal or vertical wire pursuant to this...

2012-10-01

173

47 CFR 73.816 - Antennas.  

Code of Federal Regulations, 2012 CFR

...Stations (LPFM) § 73.816 Antennas. (a) Permittees and...may employ nondirectional antennas with horizontal only polarization, vertical only polarization, circular...polarization. (b) Directional antennas will not be...

2012-10-01

174

47 CFR 101.517 - Antennas.  

Code of Federal Regulations, 2012 CFR

...Message Service § 101.517 Antennas. (a) Transmitting antennas may be omnidirectional or...b) The use of horizontal or vertical plane wave polarization...stations. (c) Directive antennas must be used at all...

2012-10-01

175

47 CFR 73.816 - Antennas.  

Code of Federal Regulations, 2011 CFR

...Stations (LPFM) § 73.816 Antennas. (a) Permittees and...may employ nondirectional antennas with horizontal only polarization, vertical only polarization, circular...polarization. (b) Directional antennas will not be...

2011-10-01

176

47 CFR 101.517 - Antennas.  

Code of Federal Regulations, 2011 CFR

...Message Service § 101.517 Antennas. (a) Transmitting antennas may be omnidirectional or...b) The use of horizontal or vertical plane wave polarization...stations. (c) Directive antennas must be used at all...

2011-10-01

177

Analysis and suppression for nonstationary clutter in airborne conformal array radar  

Microsoft Academic Search

The characteristics of clutter nonstationarity for airborne radar with conformal antennas array (CAA) are analyzed, and an improved angle-Doppler compensation method is proposed based on above analysis. Unlike the uniform linear antennas array (LAA), the elements of CAA distribute in three-dimension space which lead to that the clutter angle-Doppler spectrum distribution should be described in four-dimension space. According to this

Duan Ke-qing; Xie Wen-chong; Wang Yong-liang

2010-01-01

178

Microelectromechanical Systems Actuator Based Reconfigurable Printed Antenna  

NASA Technical Reports Server (NTRS)

A polarization reconfigurable patch antenna is disclosed. The antenna includes a feed element, a patch antenna element electrically connected to the feed element, and at least one microelectromechanical systems (MEMS) actuator, with a partial connection to the patch antenna element along an edge of the patch antenna element. The polarization of the antenna can be switched between circular polarization and linear polarization through action of the at least one MEMS actuator.

Simons, Rainee N. (Inventor)

2005-01-01

179

Antenna configurations provide polarization diversity  

NASA Technical Reports Server (NTRS)

Compact back-to-back trapezoidal tooth log-periodic /TTLP/ antenna with frequency-independent characteristics is formed by reducing the angle between the two elements of a basic TTLP to zero. The back-to-back antenna, arranged in various configurations, provides monopulse operations in one or two planes and in various polarizations.

Schumacher, C. N.

1966-01-01

180

DIPLOMA THESIS VECTOR ANTENNA FOR  

E-print Network

DIPLOMA THESIS VECTOR ANTENNA FOR ULTRAHIGH ENERGY COSMIC NEUTRINO DETECTION IN THE ANTARCTIC ICE or Environment 35 5.1.1 Electromagnetic Wave in Ice 35 5.2 UHEC Antenna Amplification 35 5.3 Vector Measurements) detection in the Antarctic ice. Neutrinos are elementary parti- cles that travel close to the speed of light

181

Emergency-vehicle VHF antenna  

NASA Technical Reports Server (NTRS)

Helical VHF antenna mounts on roof of moving vehicle to communicate with distant stations via earth satellites. Antenna requires no pointing and can provide two-way communication while vehicle moves at high speed. Device has proved extremely successful in electrocardiogram transmission tests between medical services vehicle and hospital emergency room.

Anderson, R. E.; Carlson, A. W.; Lewis, J.

1977-01-01

182

Wideband Fractal Vertical Patch Antenna  

Microsoft Academic Search

A wideband vertical patch antenna (VPA) is depicted, which is devised from fractal antenna technology. By using a dual-Koch loop structure, a wideband VPA with 42% bandwidth and 8 dBi gain at the center frequency is designed and tested. Symmetrical broadside patterns are obtained at the passband.

T. P. Wong; Carmen K. L. Lau; Kwai-Man Luk; Kai-Fong Lee

2007-01-01

183

Multiband Sierpinskl fractal patch antenna  

Microsoft Academic Search

The multiband behavior of the Sierpinski patch antenna is described, and a new technique to improve the multiband behavior from the point of view of the radiation patterns is introduced. The technique suppresses the effects of the high order modes and a patch antenna with similar radiation patterns can be designed. Once the high order mode has been suppressed for

C. Borja; J. Romeu

2000-01-01

184

Small high directivity ferrite antennas  

NASA Astrophysics Data System (ADS)

A centimeter-wavelength antenna of millimetric dimensions, which uses the intrinsic angular sensitivity of ferrites, is described, with an emphasis on the modification of the material's permeability. The construction of both the ferrite film lens antenna and the ferrite film cassegrain antenna are detailed; both can be devised in a number of configurations for appropriate beam positioning and rf filtering. The antenna design, discussed primarily in the context of smart missiles, electronic warfare, and satellite systems, presents the possibility of magnetically switching between the transmit and receive modes within the antenna structure itself. Finally, it is noted that for a simple 2-dipole array the angular resolution can be two orders of magnitude higher than with the conventional techniques.

Wright, T. M. B.

185

A Novel Class of Reconfigurable Spherical Fermat Spiral Multi-port Antennas  

NASA Astrophysics Data System (ADS)

Reconfigurability in antenna systems is a desired characteristic that has attracted attention in the past years. In this work, a novel class of spherical Fermat spiral multi-port antennas for next-generation wireless communications and radar applications is presented. The device modelling is carried out by using a computationally enhanced locally conformal finite-difference time-domain full-wave procedure. In this way, the circuital characteristics and radiation properties of the antennas are investigated accurately. The structure reconfigurability, in terms of frequency of operation and radiation efficiency, is technically performed by a suitable solid-state tuning circuitry adopted to properly change the feeding/loading conditions at the input ports of the antenna.

Caratelli, D.; Yarovoy, A.; Haider, N.

186

L-band orthogonal-mode crossed-slot antenna and VHF crossed-loop antenna  

NASA Technical Reports Server (NTRS)

A low gain, circularly polarized, L-band antenna; a low gain, linealy polarized, L-band antenna; and a low gain, circularly polarized, upper hemisphere, VHF satellite communications antenna intended for airborne applications are described. The text includes impedance and antenna radiation pattern data, along with physical description of the construction of the antennas.

Olsson, T.

1972-01-01

187

Input optimization for multi-antenna broadcast channels with per-antenna power constraints  

Microsoft Academic Search

This work considers a Gaussian multi-antenna broadcast channel with individual power constraints on each antenna, rather than the usual sum power constraint over all antennas. Per-antenna power constraints are more realistic because in practical implementations each antenna has its own power amplifier. The main contribution of this paper is a new derivation of the duality result for this class of

Tian Lan; Wei Yu

2004-01-01

188

Millimetre wave antennas for future vehicle communications  

Microsoft Academic Search

This paper describes an investigation into millimetric antennas for future telematic applications. System studies have been performed on the basis of current transponder technology at 63 GHz and have shown that for adequate communications to roadside beacons and other vehicles two or three antennas will be needed. The required antenna gain and efficiency can be met with microstrip antenna types.

Christodoulos Kykkotis; Peter S. Hall; Robert A. Lewis; Alan D. Searle

1999-01-01

189

Site attenuation with log-periodic antennas  

Microsoft Academic Search

Site attenuation measurements made with biconical antennas below 200 MHz are found to agree rather well with calculations based on point dipole antennas. The log-periodic dipole antennas used above 200 MHz differ more drastically than the biconical from an ideal point dipole. Discrepancies arising from the use of log-periodic antennas are examined, and a simple modification of the site attenuation

J. D. Gavenda

1993-01-01

190

Microstrip log periodic antenna using circuit simulator  

Microsoft Academic Search

This paper described the method of designing the quasi log periodically scaled microstrip antenna using S parameter of the antenna and microstrip transmission line circuit. The novelty of this antenna structure is a combination of a small number of elements to create a log periodic array with modest bandwidth. The radiating element is a square patch antenna. The input impedance

M. K. A. Rahim; P. Gardner

2003-01-01

191

UWB module with antenna using organic substrates  

Microsoft Academic Search

This paper presents the ultra wideband (UWB) module which contains an antenna, switches and a low noise amplifier (LNA). In order to accomplish small size and low cost, the antenna is designed using organic substrates and other parts are fabricated on the same printed circuit board (PCB) as the antenna. Size of the antenna is 20 mm × 15 mm

Koichiro Gomi; Masaaki Ishida; Shigeru Hiura

2005-01-01

192

UWB module with antenna using organic substrates  

Microsoft Academic Search

This paper presents the ultra wideband (UWB) module which contains an antenna, switches and a low noise amplifier (LNA). In order to accomplish small size and low cost, the antenna is designed using organic substrates and other parts are fabricated on the same printed circuit board (PCB) as the antenna. Size of the antenna is 20 mm times 15 mm

Koichiro Gomi; Masaaki Ishida; Shigeru Hiura

2005-01-01

193

FM wide band panel dipole antenna  

Microsoft Academic Search

It is very common that when a broadcaster needs to install an FM transmitting antenna within a large metropolitan area he places it on the tallest structure or building available. When the rooftop is already occupied by a large number of other types of transmitting and receiving antennas, the panel dipole antenna should be chosen. This antenna is secured to

Valentín Trainotti; N. Dalmas Di Giovanni

2002-01-01

194

Square loop antenna miniaturization using fractal geometry  

Microsoft Academic Search

Antenna design is a very tricky problem. Common designs are sensitive to only a narrow range of frequencies, and are not efficient if they are smaller that a quarter of the wavelength. This is a problem for small, portable antennas, such as those on cellular phones. Fractal antenna designs can overcome some of these problems. Experiments have shown that antennas

Hassan M. Elkamchouchi; Mona N. Abd El-Salam

2003-01-01

195

Hilbert curve fractal antennas with reconfigurable characteristics  

Microsoft Academic Search

Fractal Hilbert curve is one of the most recent geometries to be studied for antennas. This geometry results in an antenna with low resonant frequency compared to other configurations. The antenna consists of line segments arranged in a predictable fractal order, thus enabling easy generation and reproducible results compared to an arbitrary shrinkage of antenna size. This can be modeled

K. J. Vinoy; K. A. Jose; V. K. Varadan; V. V. Varadan

2001-01-01

196

Metal Patch Antenna  

NASA Technical Reports Server (NTRS)

Disclosed herein is a patch antenna comprises a planar conductive patch attached to a ground plane by a support member, and a probe connector in electrical communication with the conductive patch arranged to conduct electromagnetic energy to or from the conductive patch, wherein the conductive patch is disposed essentially parallel to the ground plane and is separated from the ground plane by a spacing distance; wherein the support member comprises a plurality of sides disposed about a central axis oriented perpendicular to the conductive patch and the ground plane; wherein the conductive patch is solely supported above the ground plane by the support member; and wherein the support member provides electrical communication between the planer conductive patch and the ground plane.

Chamberlain, Neil F. (Inventor); Hodges, Richard E. (Inventor); Zawadzki, Mark S. (Inventor)

2012-01-01

197

Conformal Radii for Conformal Loop Ensembles  

NASA Astrophysics Data System (ADS)

The conformal loop ensembles CLE ? , defined for 8/3 ? ? ? 8, are random collections of loops in a planar domain which are conjectured scaling limits of the O( n) loop models. We calculate the distribution of the conformal radii of the nested loops surrounding a deterministic point. Our results agree with predictions made by Cardy and Ziff and by Kenyon and Wilson for the O( n) model. We also compute the expectation dimension of the CLE ? gasket, which consists of points not surrounded by any loop, to be 2 - {(8 - kappa)(3kappa - 8)}/{32kappa} , which agrees with the fractal dimension given by Duplantier for the O( n) model gasket.

Schramm, Oded; Sheffield, Scott; Wilson, David B.

2009-05-01

198

Scattering by cavity-backed antennas on a circular cylinder  

NASA Technical Reports Server (NTRS)

Conformal arrays are popular antennas for aircraft, spacecraft, and land vehicle platforms due to their inherent low weight and drag properties. However, to date there has been a dearth of rigorous analytical or numerical solutions to aid the designer. In fact, it has been common practice to use limited measurements and planar approximations in designing such non-planar antennas. The finite element-boundary integral method is extended to scattering by cavity-backed structures in an infinite, metallic cylinder. In particular, the formulation specifics such as weight functions, dyadic Green's function, implementation details and particular difficulties inherent to cylindrical structures are discussed. Special care is taken to ensure that the resulting computer program has low memory demand and minimal computational requirements. Scattering results are presented and validated as much as possible.

Kempel, Leo C.; Volakis, John L.

1994-01-01

199

Conformations of Substituted Ethanes.  

ERIC Educational Resources Information Center

Reviews state-of-the-art of conformational analysis and factors which affect it. Emphasizes sp-3 hybridized acrylic molecules. Provides examples on the importance of certain factors in determining conformation. Purpose, is to provide examples for examination questions. (Author/SA)

Kingsbury, Charles A.

1979-01-01

200

Crime and Conformism  

Microsoft Academic Search

We propose a simple conformism model that explains how parental education and peer pressure impact on criminal activities. We then test the model using the U.S. National Longitudinal Survey of Adolescent Health (AddHealth), which contains unique information on friendship relationships among delinquent teenagers. We find that conformity is very strong within groups of delinquents and that the higher the taste

Eleonora Patacchini; Yves Zenou

2005-01-01

201

Antennas Designed for Advanced Communications for Air Traffic Management (AC/ATM) Project  

NASA Technical Reports Server (NTRS)

The goal of the Advanced Communications for Air Traffic Management (AC/ATM) Project at the NASA Glenn Research Center at Lewis Field is to enable a communications infrastructure that provides the capacity, efficiency, and flexibility necessary to realize a mature free-flight environment. The technical thrust of the AC/ATM Project is targeted at the design, development, integration, test, and demonstration of enabling technologies for global broadband aeronautical communications. Since Ku-band facilities and equipment are readily available, one of the near-term demonstrations involves a link through a Kuband communications satellite. Two conformally mounted antennas will support the initial AC/ATM communications links. Both of these are steered electronically through monolithic microwave integrated circuit (MMIC) amplifiers and phase shifters. This link will be asymmetrical with the downlink to the aircraft (mobile vehicle) at a throughput rate of greater than 1.5 megabits per second (Mbps), whereas the throughput rate of the uplink from the aircraft will be greater than 100 kilobits per second (kbps). The data on the downlink can be narrow-band, wide-band, or a combination of both, depending on the requirements of the experiment. The AC/ATM project is purchasing a phased-array Ku-band transmitting antenna for the uplink from the test vehicle. Many Ku-band receiving antennas have been built, and one will be borrowed for a short time to perform the initial experiments at the NASA Glenn Research Center at Lewis Field. The Ku-band transmitting antenna is a 254-element MMIC phased-array antenna being built by Boeing Phantom Works. Each element can radiate 100 mW. The antenna is approximately 43-cm high by 24-cm wide by 3.3-cm thick. It can be steered beyond 60 from broadside. The beamwidth varies from 6 at broadside to 12 degrees at 60 degrees, which is typical of phased-array antennas. When the antenna is steered to 60 degrees, the beamwidth will illuminate approximately five satellites on the orbital arc. Spread spectrum techniques will be employed to keep the power impinging on the adjacent satellites below their noise floor so that no interference results. This antenna is power limited. If the antenna elements (currently 254) are increased by a factor of 4 (1024) or 16 (4096), the gain will increase and the beamwidth will decrease in proportion. For the latter two antenna sizes, the power must be "backed off" to prevent interference with the neighboring satellites. The receiving antenna, which is approximately 90-cm high, 60-cm wide, and 3.5-cm thick, is composed of 1500 phased-array elements. The system phased-array controller can control both a 1500-element receiving antenna and a 500-element transmitting antenna. For ground testing, this controller will allow manual beam pointing and polarization alignment. For normal operation, the system can be connected to the receiving antenna and the navigation system for real-time autonomous track operation. This will be accomplished by first pointing both antennas at the satellite using information from the aircraft data bus. Then, the system phased-array controller will electronically adjust the antenna pointing of the receiving antenna to find the peak signal. After the peak signal has been found, the beam of the transmitting antenna will be pointed to the same steering angles as the receiving antenna. For initial ground testing without an aircraft, the ARINC 429 data bus (ARINC Inc., Annapolis, Maryland) will be simulated by a gyro system purchased for the follow-on to the Monolithic Microwave Integrated Circuit (MMIC) Arrays for Satellite Communication on the Move (MASCOM) Project. MASCOM utilized the Advanced Communications Technology Satellite (ACTS) with a pair of Ka-band experimental phased-array antennas.

Zakrajsek, Robert J.

2000-01-01

202

Expected antenna utilization and overload  

NASA Technical Reports Server (NTRS)

The trade-offs between the number of antennas at Deep Space Network (DSN) Deep-Space Communications Complex and the fraction of continuous coverage provided to a set of hypothetical spacecraft, assuming random placement of the space craft passes during the day. The trade-offs are fairly robust with respect to the randomness assumption. A sample result is that a three-antenna complex provides an average of 82.6 percent utilization of facilities and coverage of nine spacecraft that each have 8-hour passes, whereas perfect phasing of the passes would yield 100 percent utilization and coverage. One key point is that sometimes fewer than three spacecraft are visible, so an antenna is idle, while at other times, there aren't enough antennas, and some spacecraft do without service. This point of view may be useful in helping to size the network or to develop a normalization for a figure of merit of DSN coverage.

Posner, Edward C.

1991-01-01

203

Inflatable Antennas Support Emergency Communication  

NASA Technical Reports Server (NTRS)

Glenn Research Center awarded Small Business Innovation Research (SBIR) contracts to ManTech SRS Technologies, of Newport Beach, California, to develop thin film inflatable antennas for space communication. With additional funding, SRS modified the concepts for ground-based inflatable antennas. GATR (Ground Antenna Transmit and Receive) Technologies, of Huntsville, Alabama, licensed the technology and refined it to become the world s first inflatable antenna certified by the Federal Communications Commission. Capable of providing Internet access, voice over Internet protocol, e-mail, video teleconferencing, broadcast television, and other high-bandwidth communications, the systems have provided communication during the wildfires in California, after Hurricane Katrina in Mississippi, and following the 2010 Haiti earthquake.

2010-01-01

204

NASA Antenna Gets its Bearings  

NASA Video Gallery

The historic "Mars antenna" at NASA's Deep Space Network site in Goldstone, Calif. has finished a major, delicate surgery that lasted seven months. The operation on the giant, 70-meter-wide (230-fo...

205

Planar microstrip YAGI antenna array  

NASA Technical Reports Server (NTRS)

A directional microstrip antenna includes a driven patch surrounded by an isolated reflector and one or more coplanar directors, all separated from a ground plane on the order of 0.1 wavelength or less to provide end fire beam directivity without requiring power dividers or phase shifters. The antenna may be driven at a feed point a distance from the center of the driven patch in accordance with conventional microstrip antenna design practices for H-plane coupled or horizontally polarized signals. The feed point for E-plane coupled or vertically polarized signals is at a greater distance from the center than the first distance. This feed point is also used for one of the feed signals for circularly polarized signals. The phase shift between signals applied to feed points for circularly polarized signals must be greater than the conventionally required 90 degrees and depends upon the antenna configuration.

Huang, John (inventor)

1993-01-01

206

Fin-line horn antenna  

DOEpatents

A fin line circuit card containing a fin line slot feeds a dipole antenna ich extends a quarterwave outside the waveguide and provides an energy beam focal point at or near the open end of the waveguide. The dipole antenna thus maintains a wide and nearly constant beamwidth, low VSWR and a circular symmetric radiation pattern for use in electronic warfare direction finding and surveillance applications.

Reindel, John (San Diego, CA)

1990-01-01

207

Microstrip antenna developments at JPL  

Microsoft Academic Search

The in-house development of microstrip antennas, initiated in 1981, when a spaceborne lightweight and low-profile planar array was needed for a satellite communication system, is described. The work described covers the prediction of finite-ground-plane effects by the geometric theory of diffraction, higher-order-mode circularly polarized circular patch antennas, circularly polarized microstrip arrays with linearly polarized elements, an impedance-matching teardrop-shaped probe feed,

John Huang

1991-01-01

208

Novel Fractal Monopole Wideband Antenna  

Microsoft Academic Search

In this paper, two new types of fractal monopole antennas named Penta-Gasket-Khoch (PGK) and Complementary-Penta-Gasket-Khoch (CPGK) are introduced. My designs have achieved a good input impedance match throughout the pass band (2–20 GHz), but some occasional irregular small mismatch exists. These antennas are suitable for applications in picocell environments for the operating bands of ICMS, UMTS, Bluetooth, WLAN and HIPERLAN

M. Naghshvarian-Jahromi; N. Komjani

2008-01-01

209

Antennas for mobile satellite communications  

NASA Astrophysics Data System (ADS)

A NASA sponsored program, called the Mobile Satellite (MSAT) system, has prompted the development of several innovative antennas at L-band frequencies. In the space segment of the MSAT system, an efficient, light weight, circularly polarized microstrip array that uses linearly polarized elements was developed as a multiple beam reflector feed system. In the ground segment, a low-cost, low-profile, and very efficient microstrip Yagi array was developed as a medium-gain mechanically steered vehicle antenna. Circularly shaped microstrip patches excited at higher-order modes were also developed as low-gain vehicle antennas. A more recent effort called for the development of a 20/30 GHz mobile terminal antenna for future-generation mobile satellite communications. To combat the high insertion loss encountered at 20/30 GHz, series-fed Monolithic Microwave Integrated Circuit (MMIC) microstrip array antennas are currently being developed. These MMIC arrays may lead to the development of several small but high-gain Ka-band antennas for the Personal Access Satellite Service planned for the 2000s.

Huang, John

1991-12-01

210

Antennas for mobile satellite communications  

NASA Technical Reports Server (NTRS)

A NASA sponsored program, called the Mobile Satellite (MSAT) system, has prompted the development of several innovative antennas at L-band frequencies. In the space segment of the MSAT system, an efficient, light weight, circularly polarized microstrip array that uses linearly polarized elements was developed as a multiple beam reflector feed system. In the ground segment, a low-cost, low-profile, and very efficient microstrip Yagi array was developed as a medium-gain mechanically steered vehicle antenna. Circularly shaped microstrip patches excited at higher-order modes were also developed as low-gain vehicle antennas. A more recent effort called for the development of a 20/30 GHz mobile terminal antenna for future-generation mobile satellite communications. To combat the high insertion loss encountered at 20/30 GHz, series-fed Monolithic Microwave Integrated Circuit (MMIC) microstrip array antennas are currently being developed. These MMIC arrays may lead to the development of several small but high-gain Ka-band antennas for the Personal Access Satellite Service planned for the 2000s.

Huang, John

1991-01-01

211

A design of 120-degree vertical polarized sector antenna using very short balanced antipodal Vivaldi antenna  

Microsoft Academic Search

The Vivaldi antenna is a very popular antenna element for those applications requiring a high-gain and a wideband traveling wave antenna element. The antenna usually has very long length L (?3?0). Following basic traveling-wave antenna principles, the longer L, the higher the gain and narrower the beamwidth. Very few references appear in the literature where this antenna element is used

Chen Wu; J. Litva

2002-01-01

212

Mobile antenna development at JPL  

NASA Technical Reports Server (NTRS)

The Jet Propulsion Laboratory (JPL), under the sponsorship of NASA, has pioneered the development of land vehicle antennas for commercial mobile satellite communications. Several novel antennas have been developed at L-band frequencies for the Mobile Satellite (MSAT) program initiated about a decade ago. Currently, two types of antennas are being developed at K- and Ka-band frequencies for the ACTS (Advanced Communications Technology Satellite) Mobile Terminal (AMT) project. For the future, several hand-held antenna concepts are proposed for the small terminals of the Ka-band Personal Access Satellite System (PASS). For the L-band MSAT program, a number of omni-directional low-gain antennas, such as the crossed drooping-dipoles, the higher-order-mode circular microstrip patch, the quadrifilar helix, and the wrapped-around microstrip 'mast' array, have been developed for lower data rate communications. Several medium-gain satellite tracking antennas, such as the electronically scanned low-profile phased array, the mechanically steered tilted microstrip array, the mechanically steered low-profile microstrip Yagi array, and the hybrid electronically/mechanically steered low-profile array, have been developed for the MSAT's higher data rate and voice communications. To date, for the L-band vehicle application, JPL has developed the world's lowest-profile phased array (1.8 cm height), as well as the lowest-profile mechanically steered antenna (3.7 cm height). For the 20/30 GHz AMT project, a small mechanically steered elliptical reflector antenna with a gain of 23 dBi has recently been developed to transmit horizontal polarization at 30 GHz and receive vertical polarization at 20 GHz. Its hemispherical radome has a height of 10 cm and a base diameter of 23 cm. In addition to the reflector, a mechanically steered printed MMIC active array is currently being developed to achieve the same electrical requirements with a low profile capability. These AMT antenna developments, along with other Ka-band technologies, will lead to the development of several compact hand-held terminals for the PASS program. A few antenna concepts, such as the lap-top or desk-top terminal's printed array, the hand-held phased array, and the head-mounted low-profile array, have been proposed to achieve a future vision for the personal access communications system.

Huang, J.; Jamnejad, V.; Densmore, A.; Tulintseff, A.; Thomas, R.; Woo, K.

1993-01-01

213

Conformal radii for conformal loop ensembles  

E-print Network

The conformal loop ensembles CLE(k), defined for k in [8/3, 8], are random collections of loops in a planar domain which are conjectured scaling limits of the O(n) loop models. We calculate the distribution of the conformal radii of the nested loops surrounding a deterministic point. Our results agree with predictions made by Cardy and Ziff and by Kenyon and Wilson for the O(n) model. We also compute the expectation dimension of the CLE(k) gasket, which consists of points not surrounded by any loop, to be 2-(8-k)(3k-8)/32k, which agrees with the fractal dimension given by Duplantier for the O(n) model gasket.

Oded Schramm; Scott Sheffield; David B. Wilson

2006-11-22

214

Conformal Carroll groups  

NASA Astrophysics Data System (ADS)

Conformal extensions of Lévy-Leblond's Carroll group, based on geometric properties analogous to those of Newton-Cartan space-time are proposed. The extensions are labeled by an integer k. This framework includes and extends our recent study of the Bondi-Metzner-Sachs (BMS) and Newman-Unti (NU) groups. The relation to conformal Galilei groups is clarified. Conformal Carroll symmetry is illustrated by ‘Carrollian photons’. Motion both in the Newton-Cartan and Carroll spaces may be related to that of strings in the Bargmann space.

Duval, C.; Gibbons, G. W.; Horvathy, P. A.

2014-08-01

215

PATTERN SYNTHESIS OF CYLINDRICAL CONFORMAL ARRAY BY THE MODIFIED PARTICLE SWARM OPTIMIZATION ALGORITHM  

Microsoft Academic Search

In order to overcome drawbacks of standard particle swarm optimization (PSO) algorithm, such as prematurity and easily trapping in local optimum, a modified PSO algorithm which adopts a global best perturbation, is used to optimize the pattern of cylindrical conformal antenna array for sidelobe level (SLL) suppression and null control in certain directions.The convergence speed and accuracy of the algorithm

Zhan-Bo Lu; An Zhang; Xin-Yu Hou

2008-01-01

216

Conformal and non conformal dilaton gravity  

NASA Astrophysics Data System (ADS)

The quantum dynamics of the gravitational field non-minimally coupled to an (also dynamical) scalar field is studied in the broken phase. For a particular value of the coupling the system is classically conformal, and can actually be understood as the group averaging of Einstein-Hilbert's action under conformal transformations. Conformal invariance implies a simple Ward identity asserting that the trace of the equation of motion for the graviton is the equation of motion of the scalar field. We perform an explicit one-loop computation to show that the DeWitt effective action is not UV divergent on shell and to find that the Weyl symmetry Ward identity is preserved on shell at that level. We also discuss the fate of this Ward identity at the two-loop level — under the assumption that the two-loop UV divergent part of the effective action can be retrieved from the Goroff-Sagnotti counterterm — and show that its preservation in the renormalized theory requires the introduction of counterterms which exhibit a logarithmic dependence on the dilaton field.

Alvarez, Enrique; Herrero-Valea, Mario; Martín, C. P.

2014-10-01

217

Satellite Communications with NRAO Green Bank Antennas  

NASA Astrophysics Data System (ADS)

The National Radio Astronomy Observatory's Green Bank facility has several medium and large antennas that are available for satellite communications. The 100 meter Robert C. Byrd Green Bank Telescope (GBT), the largest and most sensitive antenna on site, is capable of receiving signals at frequencies as high as 86 GHz. In addition to the GBT are the fully operational 43 meter, 20 meter, and 13.7 meter antennas, and three mothballed 26 meter antennas. A transmitter could be fitted to any of these antennas for spacecraft uplinks. We discuss the characteristics of these antennas and possible operational models for future planetary science mission support.

Ford, John M.; Ford, H. Alyson; Watts, Galen

2014-11-01

218

Fixed beam and mechanically steerable antennas  

NASA Astrophysics Data System (ADS)

The principal design features and performance characteristics of fixed-beam and mechanically scanned antennas that are commonly found in today's operational electronic countermeasures (ECM) and electronic support measures (ESM) equipment are reviewed. The requirements driving the design of steerable ECM antennas are wide bandwidth, high efficiency, and the ability to handle high average power levels. The main types of antennas include spirals, helices, horns, and waveguide radiators. ESM antennas are characterized by wide bandwidth and multiple polarization responses to insure reception of all signals of interest. The types of ESM antennas discussed here include log periodic dipole arrays, spiral antennas, and wideband horns.

Hardie, G. S.; Sefton, H. B., Jr.

1984-09-01

219

Broadband monopole optical nano-antennas  

NASA Astrophysics Data System (ADS)

In this paper, a novel design of broadband monopole optical nano-antennas is proposed. It consists of a corrugated halfelliptical patch inside an elliptical aperture. Full-wave electromagnetic simulations have been used to investigate the performance of the nano-antenna. The predicted performance of the proposed monopole nano-antenna is remarkably broadband. Moreover, the proposed broadband nano-antenna can respond to light waves with different polarizations. The proposed optical antenna will pave the way towards the development of high performance optical antennas and optical systems.

Zhou, Rongguo; Ding, Jun; Arigong, Bayaner; Lin, Yuankun; Zhang, Hualiang

2014-03-01

220

Systems analysis for DSN microwave antenna holography  

NASA Technical Reports Server (NTRS)

Proposed systems for Deep Space Network (DSN) microwave antenna holography are analyzed. Microwave holography, as applied to antennas, is a technique which utilizes the Fourier Transform relation between the complex far-field radiation pattern of an antenna and the complex aperture field distribution to provide a methodology for the analysis and evaluation of antenna performance. Resulting aperture phase and amplitude distribution data are used to precisely characterize various crucial performance parameters, including panel alignment, subreflector position, antenna aperture illumination, directivity at various frequencies, and gravity deformation. Microwave holographic analysis provides diagnostic capacity as well as being a powerful tool for evaluating antenna design specifications and their corresponding theoretical models.

Rochblatt, D. J.

1989-01-01

221

Characterizing Protein Conformation Space  

E-print Network

In this work, we propose a radical approach for exploring the space of all possible protein structures. We present techniques to explore the clash-free conformation space, which comprises all protein structures whose atoms ...

Nigham, Anshul

222

Assemblies of Conformal Tanks  

NASA Technical Reports Server (NTRS)

Assemblies of tanks having shapes that conform to each other and/or conform to other proximate objects have been investigated for use in storing fuels and oxidizers in small available spaces in upper stages of spacecraft. Such assemblies might also prove useful in aircraft, automobiles, boats, and other terrestrial vehicles in which space available for tanks is limited. The basic concept of using conformal tanks to maximize the utilization of limited space is not new in itself: for example, conformal tanks are used in some automobiles to store windshield -washer liquid and coolant that overflows from radiators. The novelty of the present development lies in the concept of an assembly of smaller conformal tanks, as distinguished from a single larger conformal tank. In an assembly of smaller tanks, it would be possible to store different liquids in different tanks. Even if the same liquid were stored in all the tanks, the assembly would offer an advantage by reducing the mechanical disturbance caused by sloshing of fuel in a single larger tank: indeed, the requirement to reduce sloshing is critical in some applications. The figure shows a prototype assembly of conformal tanks. Each tank was fabricated by (1) copper plating a wax tank mandrel to form a liner and (2) wrapping and curing layers of graphite/epoxy composite to form a shell supporting the liner. In this case, the conformal tank surfaces are flat ones where they come in contact with the adjacent tanks. A band of fibers around the outside binds the tanks together tightly in the assembly, which has a quasi-toroidal shape. For proper functioning, it would be necessary to maintain equal pressure in all the tanks.

DeLay, Tom

2009-01-01

223

47 CFR 24.55 - Antenna structures; air navigation safety.  

Code of Federal Regulations, 2013 CFR

... 2013-10-01 false Antenna structures; air navigation safety. 24.55...Technical Standards § 24.55 Antenna structures; air navigation safety. Licensees that own their antenna structures must not allow these antenna...

2013-10-01

224

47 CFR 73.1213 - Antenna structure, marking and lighting.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Antenna structure, marking and lighting. 73.1213...Broadcast Stations § 73.1213 Antenna structure, marking and lighting. (a) The...Construction, Marking, and Lighting of Antenna Structures), requires certain antenna...

2011-10-01

225

47 CFR 24.55 - Antenna structures; air navigation safety.  

Code of Federal Regulations, 2011 CFR

... 2011-10-01 false Antenna structures; air navigation safety. 24.55...Technical Standards § 24.55 Antenna structures; air navigation safety. Licensees that own their antenna structures must not allow these antenna...

2011-10-01

226

47 CFR 73.1213 - Antenna structure, marking and lighting.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false Antenna structure, marking and lighting. 73.1213...Broadcast Stations § 73.1213 Antenna structure, marking and lighting. (a) The...Construction, Marking, and Lighting of Antenna Structures), requires certain antenna...

2012-10-01

227

47 CFR 22.365 - Antenna structures; air navigation safety.  

Code of Federal Regulations, 2013 CFR

... 2013-10-01 false Antenna structures; air navigation safety. 22.365...Requirements § 22.365 Antenna structures; air navigation safety. Licensees that own their antenna structures must not allow these antenna...

2013-10-01

228

47 CFR 22.365 - Antenna structures; air navigation safety.  

Code of Federal Regulations, 2011 CFR

... 2011-10-01 false Antenna structures; air navigation safety. 22.365...Requirements § 22.365 Antenna structures; air navigation safety. Licensees that own their antenna structures must not allow these antenna...

2011-10-01

229

47 CFR 24.55 - Antenna structures; air navigation safety.  

Code of Federal Regulations, 2012 CFR

... 2012-10-01 false Antenna structures; air navigation safety. 24.55...Technical Standards § 24.55 Antenna structures; air navigation safety. Licensees that own their antenna structures must not allow these antenna...

2012-10-01

230

47 CFR 73.1213 - Antenna structure, marking and lighting.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Antenna structure, marking and lighting. 73.1213...Broadcast Stations § 73.1213 Antenna structure, marking and lighting. (a) The...Construction, Marking, and Lighting of Antenna Structures), requires certain antenna...

2013-10-01

231

47 CFR 22.365 - Antenna structures; air navigation safety.  

Code of Federal Regulations, 2012 CFR

... 2012-10-01 false Antenna structures; air navigation safety. 22.365...Requirements § 22.365 Antenna structures; air navigation safety. Licensees that own their antenna structures must not allow these antenna...

2012-10-01

232

47 CFR 73.316 - FM antenna systems.  

Code of Federal Regulations, 2010 CFR

...degrees. Sufficient vertical patterns to indicate...characteristics of the antenna above and below the...antenna, and that no antenna of any type is mounted...any horizontal or vertical distance specified by the antenna manufacturer as...

2010-10-01

233

47 CFR 73.316 - FM antenna systems.  

Code of Federal Regulations, 2011 CFR

...degrees. Sufficient vertical patterns to indicate...characteristics of the antenna above and below the...antenna, and that no antenna of any type is mounted...any horizontal or vertical distance specified by the antenna manufacturer as...

2011-10-01

234

47 CFR 17.4 - Antenna structure registration.  

Code of Federal Regulations, 2012 CFR

...the proposed new antenna structure or modification of an existing antenna structure...proposed antenna structure or physical modification of an existing antenna structure may...Structure Registration Number must be weather-resistant and of sufficient size...

2012-10-01

235

47 CFR 17.4 - Antenna structure registration.  

Code of Federal Regulations, 2013 CFR

...the proposed new antenna structure or modification of an existing antenna structure...proposed antenna structure or physical modification of an existing antenna structure may...Structure Registration Number must be weather-resistant and of sufficient size...

2013-10-01

236

Patch antenna based temperature sensor  

NASA Astrophysics Data System (ADS)

In this paper, we studied the microstrip patch antenna for the purpose of temperature sensing. The relationship between the antenna resonant frequency shift and temperature variation is first derived based on the transmission line model. A substrate material was selected to achieve a linear sensor response. Temperature chamber tests on patch antenna sensors bonded to three different test samples were carried out. Preliminary experimental results indicated a linear relation between the normalized antenna resonant frequency changes and temperature variations. However, a large discrepancy between the measured and predicted sensitivities was observed, which indicated that the thermal strain might have a significant influence on the dielectric constant of the substrate. To account for this effect, we introduced a strain coefficient of dielectric constant to quantify the effect of strain on the dielectric constant. With the modified theoretical predictions, the errors between the measurements and predictions were within the systematic error of the reference thermocouple, which validates the feasibility of using a microstrip patch antenna for temperature sensing.

Jiang, Hao; Sanders, Jeremiah; Yao, Jun; Huang, Haiying

2014-04-01

237

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

NASA Technical Reports Server (NTRS)

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 steer the beam. The array of phased ring radiators is unique in that it provides improved gain for a small rocket or missile that uses spin stabilization for stability. The antenna pattern created is symmetric about the roll axis (like an omnidirectional wraparound), and is thus capable of providing continuous coverage that is compatible with very fast spinning rockets. For larger ELVs with roll control, a linear array of elements can be used for the 1D scanned beamformer and phased array, or a 2D scanned beamformer can be used with an NxN element array.

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

2012-01-01

238

Compact Low Frequency Radio Antenna  

DOEpatents

An antenna is disclosed that comprises a pair of conductive, orthogonal arches and a pair of conductive annular sector plates, wherein adjacent legs of each arch are fastened to one of the annular sector plates and the opposite adjacent pair of legs is fastened to the remaining annular sector plate. The entire antenna structure is spaced apart from a conductive ground plane by a thin dielectric medium. The antenna is driven by a feed conduit passing through the conductive ground plane and dielectric medium and attached to one of the annular sector plates, wherein the two orthogonal arched act as a pair of crossed dipole elements. This arrangement of elements provides a radiation pattern that is largely omni-directional above the horizon.

Punnoose, Ratish J. (Hayward, CA)

2008-11-11

239

Integrated resonant tunneling diode based antenna  

DOEpatents

An antenna comprising a plurality of negative resistance devices and a method for making same comprising employing a removable standoff layer to form the gap between the microstrip antenna metal and the bottom contact layer.

Hietala, Vincent M. (Placitas, NM); Tiggers, Chris P. (Albuquerque, NM); Plut, Thomas A. (Albuquerque, NM)

2000-01-01

240

DEPLOYABLE ANTENNA KINEMATICS USING TENSEGRITY STRUCTURE DESIGN  

E-print Network

DEPLOYABLE ANTENNA KINEMATICS USING TENSEGRITY STRUCTURE DESIGN By BYRON FRANKLIN KNIGHT This research has been a labor of love, beginning with my first job as a "new grad" building deployable antenna .........................................................................................................5 Tensegrity Overview

Florida, University of

241

47 CFR 101.117 - Antenna polarization.  

Code of Federal Regulations, 2010 CFR

...Standards § 101.117 Antenna polarization...polarization (horizontal and vertical) shall be used. For LMDS...its service area, but only vertical and/or horizontal polarization for antennas located within 20...

2010-10-01

242

47 CFR 101.117 - Antenna polarization.  

Code of Federal Regulations, 2011 CFR

...Standards § 101.117 Antenna polarization...polarization (horizontal and vertical) shall be used. For LMDS...its service area, but only vertical and/or horizontal polarization for antennas located within 20...

2011-10-01

243

47 CFR 101.117 - Antenna polarization.  

Code of Federal Regulations, 2012 CFR

...Standards § 101.117 Antenna polarization...polarization (horizontal and vertical) shall be used. For LMDS...its service area, but only vertical and/or horizontal polarization for antennas located within 20...

2012-10-01

244

Mechanisms of the Rosetta high gain antenna  

NASA Astrophysics Data System (ADS)

This paper describes the antenna pointing mechanism (APM) and the hold down and release mechanism (HRM) used in the high gain antenna of the ROSETTA mission. The hold down and release mechanism consists of three units which compensate the tolerance mismatch between antenna and spacecraft through incorporation of potting rings. Given that the activation mode is pyrotechnic, release shock is a major concern and is minimised through integration of shock absorbers which allow stroking of the separation nuts. The antenna pointing mechanism is a dual drive (azimuth over elevation) unit which allows controlled rotation of the antenna. The drive units incorporate spring loaded end stops to prevent the antenna from hitting the spacecraft, and optical encoders which register the absolute position of the antenna. The pointing and the hold down mechanisms of the ROSETTA antenna are fully qualified and will withstand the high launch loads of the Ariane-5 and the environmental demands of deep space operation.

Pereira, Carlos

2001-09-01

245

An antenna coupling model for cross-polarized antennas for radar electromagnetic compatibility analysis  

Microsoft Academic Search

A statistically based antenna coupling model for linearly polarized, cross-polarized antennas is presented. The antenna gains are defined as random variables. It is assumed that the probability density functions of the gains can be estimated from the antenna patterns. From the density functions, a method is developed to calculate the combined density function. This method accounts for angular motion that

Terry L. Foreman

1993-01-01

246

Contraves' Antenna Tip Hinge Mechanism for Selenia Spazio's 20/30 Ghz Antenna.  

National Technical Information Service (NTIS)

A mechanism which can deploy a folded tip of an antenna in orbit, the Antenna Tip Hinge Mechanism (ATHM) was developed. The ATHM consists of two hinges, each near the edge of the antenna main body and tip interface. Following a command, the antenna tip is...

D. Stella, F. Morganti, G. Nielsen

1986-01-01

247

Millimeter-Wave Printed Antenna Arrays for Covering Various Sector Widths - [Antenna Designer's Notebook  

Microsoft Academic Search

In this paper, we introduce new millimeter-wave corner antenna arrays (MWCA) with eight axially placed printed dipoles fed by an integrated symphase network. The antenna array is placed between two metal plates that make the corner reflector. The antennas were simulated and realized in the frequency range about 26 GHz, which is popular for microwave communication networks. Three antennas, with

Tom Milligan

2007-01-01

248

A Compact Meander Microstripe Antenna for Bluetooth Headset  

Microsoft Academic Search

The meander Antenna is a conventional type antenna. By correct shape size and outline design, the meander antenna can obtain good antenna parameter and fact performance. Modern consumption product with wireless function becomes increasingly more small and light. This fashion trend challenges small antenna design .This Letter describes how to achieve the good antenna performance worked on the Industrial, Scientific,

Alpha Fan

249

Ion cyclotron range of frequencies antenna design for R tokamak  

Microsoft Academic Search

The ion cyclotron range of frequencies antenna design for the R tokamak (a proposal by the Institute of Plasma Physics, Nagoya University) is described. The design involves three types of antennas: a standard loop antenna, a panel heater antenna, and a waveguide antenna for ion Bernstein wave heating (IBWH). The standard loop antenna is made of aluminum alloy and has

E. Kako; R. Ando; M. Ichimura; Y. Ogawa; T. Amano; T. Watari

1987-01-01

250

Large Space Antenna Systems Technology, 1984  

NASA Technical Reports Server (NTRS)

Papers are presented which provide a comprehensive review of space missions requiring large antenna systems and of the status of key technologies required to enable these missions. Topic areas include mission applications for large space antenna systems, large space antenna structural systems, materials and structures technology, structural dynamics and control technology, electromagnetics technology, large space antenna systems and the space station, and flight test and evaluation.

Boyer, W. J. (compiler)

1985-01-01

251

A fractal circular polarized RFID tag antenna  

NASA Astrophysics Data System (ADS)

In this paper, we present a novel fractal antenna for radiofrequency identification (RFID) tags. The proposed antenna has a resonant frequency equal to 2.45GHz and circular polarization. The fractal technique was very useful to obtain a miniaturization of antenna size by more than 30%. The gain and directivity of the antenna are acceptable for the desired RFID application. All the results are obtained using CST Microwave simulation tool.

Chaouki, Guesmi; Ferchichi, Abdelhak; Gharsallah, Ali

2013-09-01

252

Fractal antenna applications in wireless telecommunications  

Microsoft Academic Search

Applying fractals to antenna elements allows for smaller, resonant antennas which are multiband\\/broadband and may be optimized for gain. They do not use additional loading components and are simple and cost-effective to fabricate. They can be mounted to constraining form factors, such as the casing of hand-held transceivers. Fractal antennas prove worthwhile, high performance, resonant antennas for many practical applications.

Nathan Cohen; Fractal Antenna

1997-01-01

253

Antenna reconfiguration verification and validation  

NASA Technical Reports Server (NTRS)

A method of testing the electrical functionality of an optically controlled switch in a reconfigurable antenna is provided. The method includes configuring one or more conductive paths between one or more feed points and one or more test point with switches in the reconfigurable antenna. Applying one or more test signals to the one or more feed points. Monitoring the one or more test points in response to the one or more test signals and determining the functionality of the switch based upon the monitoring of the one or more test points.

Becker, Robert C. (Inventor); Meyers, David W. (Inventor); Muldoon, Kelly P. (Inventor); Carlson, Douglas R. (Inventor); Drexler, Jerome P. (Inventor)

2009-01-01

254

Antenna systems requirements definition study  

NASA Technical Reports Server (NTRS)

A plan to use a 55m wrap rib antenna in a second generation land mobile satellite service application as a specific mission to define a large space structure technology system and its interfaces is described. The system design aims to examine the launch phase of the mission including interface with the space transportation system and the orbital transfer vehicle, and the deployment from the spacecraft of the boom, antennas, and solar panels. Methods for determining the effect of system configuration on the interfaces and of the space environment and operational events on the system and its subsystem interfaces are discussed.

Golden, C. T.

1981-01-01

255

Interleaved array antenna technology development  

NASA Technical Reports Server (NTRS)

This is the third phase of a program to establish an antenna concept for shuttle and free flying spacecraft earth resources experiments using Synthetic Aperture Radar. The feasibility of a plated graphite epoxy waveguide for a space antenna was evaluated. A quantity of flat panels and waveguides were developed, procured, and tested for electrical and mechanical properties. In addition, processes for the assembly of a unique waveguide array were investigated. Finally, trades between various configurations that would allow elevation (range) electronic scanning and that would minimize feed complexity for various RF bandwidths were made.

1985-01-01

256

Conformal equivalence of triangle meshes  

Microsoft Academic Search

We present a new algorithm for conformal mesh parameterization. It is based on a precise notion of discrete conformal equivalence for triangle meshes which mimics the notion of conformal equivalence for smooth surfaces. The problem of finding a flat mesh that is discretely conformally equivalent to a given mesh can be solved efficiently by minimizing a convex energy function, whose

Boris Springborn; Peter Schröder; Ulrich Pinkall

2008-01-01

257

ADVANCED PRECIPITATION RADAR ANTENNA SINGLY CURVED PARABOLIC ANTENNA REFLECTOR DEVLEOPMENT  

Microsoft Academic Search

NASA and JPL have recognized space inflatable and thin film technologies as the enabling innovations for the advancement of the next generation of Advanced Precipitation Radar Antenna (APRA). 1,2 However, the utilization of these Gossamer technologies in this type of application (i.e. a large thin film parabolic cylindrical reflector deployed and supported by a space inflatable structure) has never been

John K. Lin; George H. Sapna III; Stephen E. Scarborough; Bernardo C. Lopez

2003-01-01

258

Fractal antennas: a novel antenna miniaturization technique, and applications  

Microsoft Academic Search

Fractal geometry involves a recursive generating methodology that results in contours with infinitely intricate fine structures. This geometry, which has been used to model complex objects found in nature such as clouds and coastlines, has space-filling properties that can be utilized to miniaturize antennas. These contours are able to add more electrical length in less volume. In this article, we

J. P. Gianvittorio; Yahya Rahmat-Samii

2002-01-01

259

Fixed beam and mechanically steerable antennas  

Microsoft Academic Search

The principal design features and performance characteristics of fixed-beam and mechanically scanned antennas that are commonly found in today's operational electronic countermeasures (ECM) and electronic support measures (ESM) equipment are reviewed. The requirements driving the design of steerable ECM antennas are wide bandwidth, high efficiency, and the ability to handle high average power levels. The main types of antennas include

G. S. Hardie; H. B. Sefton Jr.

1984-01-01

260

Coplanar waveguide feed for microstrip patch antennas  

NASA Technical Reports Server (NTRS)

A coplanar waveguide (CPW) loop is shown to be an effective low VSWR feed for microstrip antennas. The low VSWR transition between the CPW and the antenna is obtained without the use of a matching circuit, and it is relatively insensitive to the position of the antenna and the feed.

Smith, R. L.; Williams, J. T.

1992-01-01

261

Transients in wide-angle conical antennas  

Microsoft Academic Search

The response of an antenna to dc pulse excitation, both in reception and in transmission, can be determined by use of Fourier transforms provided the complex impedance and complex effective height of the antenna are known over the frequency range where the excitation has significant components. We have computed the time history of the response of a wide-angle conical antenna

1965-01-01

262

IN!STEP INFLATABLE ANTENNA DESCRIPTION  

Microsoft Academic Search

Large size space deployable antenna structures are needed for a variety of applications. Current resources limitations within the antenna user community have resulted in the need for low cost, light weight and mechanically reliable space structures. An inflatable deployable antenna concept, under development at L'Garde has such great potential for satieing these requirements; it was selected for a NASA sponsored

Gordon Veal

263

GBES Antenna Efficiency Measurements Glen Langston  

E-print Network

completely transparent at 2cm. One of the inner panels of the antenna was removed to allow access to the optics. There are 24 inner panels on the antenna and 48 outer panels. Removing one inner panel1 GBES Antenna Efficiency Measurements Glen Langston Draft -- 94 April 28 Overview This document

Groppi, Christopher

264

47 CFR 95.51 - Antenna height.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Antenna height. 95.51 Section 95.51 Telecommunication...Service (GMRS) § 95.51 Antenna height. (a) Certain antenna structures...that are more than 60.96 m (200 ft) in height, or are located near or at a...

2013-10-01

265

47 CFR 95.51 - Antenna height.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false Antenna height. 95.51 Section 95.51 Telecommunication...Service (GMRS) § 95.51 Antenna height. (a) Certain antenna structures...that are more than 60.96 m (200 ft) in height, or are located near or at a...

2012-10-01

266

47 CFR 95.51 - Antenna height.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Antenna height. 95.51 Section 95.51 Telecommunication...Service (GMRS) § 95.51 Antenna height. (a) Certain antenna structures...that are more than 60.96 m (200 ft) in height, or are located near or at a...

2011-10-01

267

An overview of fractal antenna engineering research  

Microsoft Academic Search

Recent efforts by several researchers around the world to combine fractal geometry with electromagnetic theory have led to a plethora of new and innovative antenna designs. In this report, we provide a comprehensive overview of recent developments in the rapidly growing field of fractal antenna engineering. Fractal antenna engineering research has been primarily focused in two areas: the first deals

Douglas H. Werner; S. Ganguly

2003-01-01

268

Resonant frequency of Hilbert curve fractal antennas  

Microsoft Academic Search

An approximate formulation for the resonant frequency of a dipole Hilbert curve fractal antenna (HCFA) is derived here. These can be used as small resonant antennas, useful in VHF\\/UHF communication. The formulas presented here can be appropriately inverted to obtain the design equations for the antenna, for a given resonant frequency

K. J. Vinoy; K. A. Jose; V. K. Varadan; V. V. Varadan

2001-01-01

269

Genetically engineered dual-band fractal antennas  

Microsoft Academic Search

Fractal antenna engineering concepts have been successfully combined with genetic algorithms to develop a powerful design optimization tool. The genetic optimization approach developed can simultaneously optimize the geometry of a fractal antenna, locations of loads, component values of loads, and the projected length of the fractal antenna. The results suggest that a 30-55% size reduction can be achieved by optimizing

D. H. Werner; P. L. Werner

2001-01-01

270

Random Conformal Weldings  

E-print Network

We construct a conformally invariant random family of closed curves in the plane by welding of random homeomorphisms of the unit circle. The homeomorphism is constructed using the exponential of $\\beta X$ where $X$ is the restriction of the two dimensional free field on the circle and the parameter $\\beta$ is in the "high temperature" regime $\\betawelding problem is solved by studying a non-uniformly elliptic Beltrami equation with a random complex dilatation. For the existence a method of Lehto is used. This requires sharp probabilistic estimates to control conformal moduli of annuli and they are proven by decomposing the free field as a sum of independent fixed scale fields and controlling the correlations of the complex dilation restricted to dyadic cells of various scales. For uniqueness we invoke a result by Jones and Smirnov on conformal removability of H\\"older curves. We conjecture that our curves are locally related to SLE$(\\kappa)$ for $\\kappa<4$.

Astala, K; Kupiainen, A; Saksman, E

2009-01-01

271

Random Conformal Weldings  

E-print Network

We construct a conformally invariant random family of closed curves in the plane by welding of random homeomorphisms of the unit circle. The homeomorphism is constructed using the exponential of $\\beta X$ where $X$ is the restriction of the two dimensional free field on the circle and the parameter $\\beta$ is in the "high temperature" regime $\\betawelding problem is solved by studying a non-uniformly elliptic Beltrami equation with a random complex dilatation. For the existence a method of Lehto is used. This requires sharp probabilistic estimates to control conformal moduli of annuli and they are proven by decomposing the free field as a sum of independent fixed scale fields and controlling the correlations of the complex dilation restricted to dyadic cells of various scales. For uniqueness we invoke a result by Jones and Smirnov on conformal removability of H\\"older curves. We conjecture that our curves are locally related to SLE$(\\kappa)$ for $\\kappa<4$.

K. Astala; P. Jones; A. Kupiainen; E. Saksman

2009-09-07

272

Gravity on Conformal Superspace  

NASA Astrophysics Data System (ADS)

The configuration space of general relativity is superspace - the space of all Riemannian 3-metrics modulo diffeomorphisms. However, it has been argued that the configuration space for gravity should be conformal superspace - the space of all Riemannian 3-metrics modulo diffeomorphisms and conformal transformations. Taking this conformal nature seriously leads to a new theory of gravity which although very similar to general relativity has some very different features particularly in cosmology and quantisation. It should reproduce the standard tests of general relativity. The cosmology is studied in some detail. The theory is incredibly restrictive and as a result admits an extremely limited number of possible solutions. The problems of the standard cosmology are addressed and most remarkably the cosmological constant problem is resolved in a natural way. The theory also has several attractive features with regard to quantisation particularly regarding the problem of time.

Kelleher, Bryan

2003-11-01

273

Measured and predicted root-mean-square errors in square and triangular antenna mesh facets  

NASA Technical Reports Server (NTRS)

Deflection shapes of square and equilateral triangular facets of two tricot-knit, gold plated molybdenum wire mesh antenna materials were measured and compared, on the basis of root mean square (rms) differences, with deflection shapes predicted by linear membrane theory, for several cases of biaxial mesh tension. The two mesh materials contained approximately 10 and 16 holes per linear inch, measured diagonally with respect to the course and wale directions. The deflection measurement system employed a non-contact eddy current proximity probe and an electromagnetic distance sensing probe in conjunction with a precision optical level. Despite experimental uncertainties, rms differences between measured and predicted deflection shapes suggest the following conclusions: that replacing flat antenna facets with facets conforming to parabolically curved structural members yields smaller rms surface error; that potential accuracy gains are greater for equilateral triangular facets than for square facets; and that linear membrane theory can be a useful tool in the design of tricot knit wire mesh antennas.

Fichter, W. B.

1989-01-01

274

Conformal Orthosymplectic Quantum Mechanics  

E-print Network

We present the most general curvature obstruction to the deformed parabolic orthosymplectic symmetry subalgebra of the supersymmetric quantum mechanical models recently developed to describe Lichnerowicz wave operators acting on arbitrary tensors and spinors. For geometries possessing a hypersurface-orthogonal homothetic conformal Killing vector we show that the parabolic subalgebra is enhanced to a (curvature-obstructed) orthosymplectic algebra. The new symmetries correspond to time-dependent conformal symmetries of the underlying particle model. We also comment on generalizations germane to three dimensions and new Chern--Simons-like particle models.

J. Burkart; A. Waldron

2008-12-20

275

Conformal orthosymplectic quantum mechanics  

NASA Astrophysics Data System (ADS)

We present the most general curvature obstruction to the deformed parabolic orthosymplectic symmetry subalgebra of the supersymmetric quantum mechanical models recently developed to describe Lichnerowicz wave operators acting on arbitrary tensors and spinors. For geometries possessing a hypersurface-orthogonal homothetic conformal Killing vector we show that the parabolic subalgebra is enhanced to a (curvature-obstructed) orthosymplectic algebra. The new symmetries correspond to time-dependent conformal symmetries of the underlying particle model. We also comment on generalizations germane to three dimensions and new Chern-Simons-like particle models.

Burkart, Joshua; Waldron, Andrew

2009-05-01

276

Micromachined Antennas for Integration with  

E-print Network

DEPARTMENT OF ENGINEERING SCIENCES UPPSALA UNIVERSITY UPPSALA, SWEDEN Submitted to the Faculty of Science of Technology. #12;c Erik ¨Ojefors, 2004 Printed in Sweden by Eklundshofs Grafiska AB, Uppsala, 2004 #12;To my fed patch antenna, manufactured using a thick organic dielectric, is modelled with a modified

277

Photogrammetry Of A Parabolic Antenna  

NASA Technical Reports Server (NTRS)

Surface measured with accuracy better than 10 to the negative fifth power times diameter. Report describes use of advanced close-range photogrammetry to determine deviations of 34-m-diameter antenna main reflector and subreflector from nominal paraboloidal shapes. Measurements enable removal of linear offsets and angular misalignments of subreflector, with consequent increase of 4 percent in aperture efficiency.

Merrick, W. D.; Lansing, F. L.; Stoller, F. W.; Lobb, V. B.

1988-01-01

278

DSS 13 microprocessor antenna controller  

NASA Technical Reports Server (NTRS)

A microprocessor-based antenna monitor and control system with multiple CPUs are described. The system was developed as part of the unattended station project for DSS 13 and was enhanced for use by the SETI project. The operational features, hardware, and software designs are described, and a discussion is provided of the major problems encountered.

Gosline, R. M.

1988-01-01

279

White Paper Pulsed Antenna Measurements  

E-print Network

White Paper Agilent Pulsed Antenna Measurements Using PNA Network Analyzers #12;Abstract This paper is described. Measurements made using an Agilent E8360 PNA series Microwave Network Analyzer are presented of the pulsed RF signal spectrum, and will therefore measure the pulsed signal as though it were a CW signal. 2

del Barco, Enrique

280

Antenna analysis using neural networks  

Microsoft Academic Search

Conventional computing schemes have long been used to analyze problems in electromagnetics (EM). The vast majority of EM applications require computationally intensive algorithms involving numerical integration and solutions to large systems of equations. The feasibility of using neural network computing algorithms for antenna analysis is investigated. The ultimate goal is to use a trained neural network algorithm to reduce the

William T. Smith

1992-01-01

281

Insulated vertical antennas above ground  

Microsoft Academic Search

A fast efficient method is proposed to solve the problem of a vertical dielectric-coated antenna located in free space above ground. The solution is a moment method solution. The influence of lossy ground is taken into account via equivalent images due to Popovic, and the currents of images are expressed by the source current. The dielectric coating is modeled by

Xianshan Li; Khalil El Khamlichi Drissi; Françoise Paladian

2004-01-01

282

From Antenna to Assay  

PubMed Central

Conspectus Ligand-sensitized, luminescent lanthanide(III) complexes are of considerable importance because their unique photophysical properties (microsecond to millisecond lifetimes, characteristic and narrow emission bands, and large Stokes shifts) make them well suited as labels in fluorescence-based bioassays. The long-lived emission of lanthanide(III) cations can be temporally resolved from scattered light and background fluorescence to vastly enhance measurement sensitivity. One challenge in this field is the design of sensitizing ligands that provide highly emissive complexes with sufficient stability and aqueous solubility for practical applications. In this Account, we give an overview of some of the general properties of the trivalent lanthanides and follow with a summary of advances made in our laboratory in the development of highly luminescent Tb(III) and Eu(III) complexes for applications in biotechnology. A focus of our research has been the optimization of these compounds as potential commercial agents for use in Homogeneous Time-Resolved Fluorescence (HTRF) technology. Our approach involves developing high-stability octadentate Tb(III) and Eu(III) complexes that rely on all-oxygen donor atoms and using multi-chromophore chelates to increase molar absorptivity; earlier examples utilized a single pendant chromophore (that is, a single “antenna”). Ligands based on 2-hydroxyisophthalamide (IAM) provide exceptionally emissive Tb(III) complexes with quantum yield values up to ?60% that are stable at the nanomolar concentrations required for commercial assays. Through synthetic modification of the IAM chromophore and time-dependent density functional theory (TD-DFT) calculations, we have developed a method to predict absorption and emission properties of these chromophores as a tool to guide ligand design. Additionally, we have investigated chiral IAM ligands that yield Tb(III) complexes possessing both high quantum yield values and strong circularly polarized luminescence (CPL) activity. To efficiently sensitize Eu(III) emission, we have used the 1-hydroxypyridin-2-one (1,2-HOPO) chelate to create remarkable ligands that combine excellent photophysical properties and exceptional aqueous stabilities. A more complete understanding of this chromophore has been achieved by combining low-temperature phosphorescence measurements with the same TD-DFT approach used with the IAM system. Eu(III) complexes with strong CPL activity have also been obtained with chiral 1,2-HOPO ligands. We have also undertaken the kinetic analysis of radiative and non-radiative decay pathways for a series of Eu(III) complexes; the importance of the metal ion symmetry on the ensuing photophysical properties is clear. Lastly, we describe a Tb(III)-IAM compound—now carried through to commercial availability—that offers improved performance in the common HTRF platform and has the potential to vastly improve sensitivity. PMID:19323456

Moore, Evan G.; Samuel, Amanda P. S.; Raymond, Kenneth N.

2009-01-01

283

A new class of resonant antennas  

NASA Astrophysics Data System (ADS)

A new class of wire antennas called meander antennas is introduced as possible elements for size reduction. Efficiency is affected only by the ohmic losses in the wire, and cross polarization is negligible. An increase in the number of meander sections introduces less size reduction in return for an improved bandwidth. These antennas can be used to reduce the size of existing wire antennas such as Yagi-Uda antennas and log-periodic dipole arrays. A size reduction in the resonant length typically from 25-40 percent is obtained. More size reduction is obtained by decreasing the radius of the wire or increasing the separation of the folded arms.

Rashed, Jalil; Tai, Chen-To

1991-09-01

284

Antenna pattern control using impedance surfaces  

NASA Technical Reports Server (NTRS)

The implementation of a moment method code for the analysis of horn antennas was accomplished. The code can analyze the antenna with or without lossy material coatings. It predicts the antenna gain, voltage standing wave ratio (VSWR) on the feeding waveguide, the existing modes on the radiating aperture, and radiation patterns of the antenna. Many computations were performed on three pyramidal horn antennas, and their radiation and VSWR's are presented and compared with experimental data. Although the code is still being finalized, some discussions on using the code are included.

Balanis, Constantine A.; Liu, Kefeng

1991-01-01

285

Non-Gimbaled Antenna Pointing  

NASA Technical Reports Server (NTRS)

The small satellite community has been interested in accessing fixed ground stations for means of space-to-ground transmissions, although a problem arises from the limited global coverage. There is a growing interest for using the Space Network (SN) or Tracking and Data Relay Satellites (TDRS) as the primary support for communications because of the coverage it provides. This thesis will address the potential for satellite access of the Space Network with a non-gimbaled antenna configuration and low-power, coded transmission. The non-gimbaled antenna and the TDRS satellites, TDRS-East, TDRS-West, and TDRS-Zone of Exclusion, were configured in an orbital analysis software package called Satellite Tool Kit to emulate the three-dimensional position of the satellites. The access potential, which is the average number of contacts per day and the average time per contact, were obtained through simulations run over a 30-day period to gain all the possible orientations. The orbital altitude was varied from 600 km through 1200 km with the results being a function of orbital inclination angles varying from 20 deg through 100 deg and pointing half-angles of I0 deg through 40 deg. To compare the validity of the simulations, Jet Propulsion Laboratory granted the use of the TOPEX satellite. The TOPEX satellite was configured to emulate a spin-stabilized antenna with its communications antenna stowed in the zenith-pointing direction. This mimicked the antenna pointing spin-stabilized satellite in the simulations. To make valid comparisons, the TOPEX orbital parameters were entered into Satellite Tool Kit and simulated over five test times provided by Jet Propulsion Laboratory.

Vigil, Jeannine S.

1997-01-01

286

Low Cost Large Space Antennas  

NASA Technical Reports Server (NTRS)

The mobile communication community could significantly benefit from the availability of low-cost, large space-deployable antennas. A new class of space structures, called inflatable deployable structures, will become an option for this industry in the near future. This new technology recently made significant progress with respect to reducing the risk of flying large inflatable structures in space. This progress can be attributed to the successful space flight of the Inflatable Antenna Experiment in May of 1996, which prompted the initiation of the NASA portion of the joint NASA/DOD coordinated Space Inflatables Program, which will develop the technology to be used in future mobile communications antennas along with other users. The NASA/DOD coordinated Space Inflatables Program was initiated in 1997 as a direct result of the Inflatable Antenna Experiment. The program adds a new NASA initiative to a substantial DOD program that involves developing a series of ground test hardware, starting with 3 meter diameter units and advancing the manufacturing techniques to fabricate a 25 meter ground demonstrator unit with surface accuracy exceeding the requirements for mobile communication applications. Simultaneously, the program will be advancing the state of the art in several important inflatable technology areas, such as developing rigidizable materials for struts and tori and investigating thin film technology issues, such as application of coatings, property measurement and materials processing and assembly techniques. A very important technology area being addressed by the program is deployment control techniques. The program will sponsor activities that will lead to understanding the effects of material strain energy release, residual air in the stowed structure, and the design of the launch restraint and release system needed to control deployment dynamics. Other technology areas directly applicable to developing inflatable mobile communication antennas in the near future are analytical performance prediction tools, configuration studies and miniaturizing the inflation systems.

Chmielewski, Artur B.; Freeland, Robert

1997-01-01

287

Random Conformal Weldings  

Microsoft Academic Search

We construct a conformally invariant random family of closed curves in the plane by welding of random homeomorphisms of the unit circle. The homeomorphism is constructed using the exponential of $\\\\beta X$ where $X$ is the restriction of the two dimensional free field on the circle and the parameter $\\\\beta$ is in the \\

K. Astala; P. Jones; A. Kupiainen; E. Saksman

2009-01-01

288

Metamaterials with conformational nonlinearity  

E-print Network

Metamaterials with conformational nonlinearity Mikhail Lapine1,2 , Ilya V. Shadrivov1,2 , David A development, metamaterials became a prominent area of research, bridging theoretical and applied electrodynamics, electrical engineering and material science. Being man-made structures, metamaterials offer

289

CHAPTER TWO Conformational Ensemble  

E-print Network

35 3. Generating Starting Structures Based on Templates 36 4. BiHelix: TM Bundle Conformational Sampling of Helix Rotation Angles 38 5. SuperBiHelix TM Bundle Sampling of All Helix Orientation Angles 40 to control G protein-mediated pathways, which gave them their original name. Overwhelming evidence has shown

Goddard III, William A.

290

Taming the conformal zoo  

Microsoft Academic Search

All known rational conformal field theories may be obtained from (2+1) dimensional Chern-Simons gauge theories by appropriate choice of gauge group. We conjecture that all rational field theories are classified by groups via (2+1)-dimensional Chern-Simons gauge theories. On leave of absence from the Department of Physics, Weizmann Institute of Science, Rehovot 76100, Israel.

Gregory Moore; Nathan Seiberg

1989-01-01

291

Design and analysis of an electronically steerable microstrip patch and a novel Coplanar Waveguide (CPW) fed slot antenna array  

NASA Astrophysics Data System (ADS)

Conformal Phased Array Antennas (CPAAs) are very attractive for their high gain, low profile, and beam scanning ability while being conformal to their mounting surface. Among them are microstrip patch phased arrays and wideband slot phased arrays which are of particular significance. In this work, first the study, design, and implementation of a conformal microstrip patch phased array is presented which consists of a high gain beam scanning array implemented using microstrip delay lines controlled using GaAs SPDT switches. Then the study and design of a wideband Coplanar Waveguide (CPW)-fed slot phased array antenna is presented. In both cases the array beam scanning properties are elucidated by incorporating the measured delay line scattering parameters inside Ansys Designer simulation models and then computing and presenting their full-wave radiation characteristics.

Aldossary, Hamad

292

Galilean conformal and superconformal symmetries  

SciTech Connect

Firstly we discuss briefly three different algebras named as nonrelativistic (NR) conformal: Schroedinger, Galilean conformal, and infinite algebra of local NR conformal isometries. Further we shall consider in some detail Galilean conformal algebra (GCA) obtained in the limit c{yields}{infinity} from relativistic conformal algebraO(d+1, 2) (d-number of space dimensions). Two different contraction limits providing GCA and some recently considered realizations will be briefly discussed. Finally by considering NR contraction of D = 4 superconformal algebra the Galilei conformal superalgebra (GCSA) is obtained, in the formulation using complexWeyl supercharges.

Lukierski, J., E-mail: lukier@ift.uni.wroc.pl [University of Wroclaw, Institute for Theoretical Physics (Poland)

2012-10-15

293

Hexagonal and Pentagonal Fractal Multiband Antennas  

NASA Technical Reports Server (NTRS)

Multiband dipole antennas based on hexagonal and pentagonal fractals have been analyzed by computational simulations and functionally demonstrated in experiments on prototypes. These antennas are capable of multiband or wide-band operation because they are subdivided into progressively smaller substructures that resonate at progressively higher frequencies by virtue of their smaller dimensions. The novelty of the present antennas lies in their specific hexagonal and pentagonal fractal configurations and the resonant frequencies associated with them. These antennas are potentially applicable to a variety of multiband and wide-band commercial wireless-communication products operating at different frequencies, including personal digital assistants, cellular telephones, pagers, satellite radios, Global Positioning System receivers, and products that combine two or more of the aforementioned functions. Perhaps the best-known prior multiband antenna based on fractal geometry is the Sierpinski triangle antenna (also known as the Sierpinski gasket), shown in the top part of the figure. In this antenna, the scale length at each iteration of the fractal is half the scale length of the preceding iteration, yielding successive resonant frequencies related by a ratio of about 2. The middle and bottom parts of the figure depict the first three iterations of the hexagonal and pentagonal fractals along with typical dipole-antenna configuration based on the second iteration. Successive resonant frequencies of the hexagonal fractal antenna have been found to be related by a ratio of about 3, and those of the pentagonal fractal antenna by a ratio of about 2.59.

Tang, Philip W.; Wahid, Parveen

2005-01-01

294

Research on MLS airborne antenna  

NASA Technical Reports Server (NTRS)

Numerical solutions for the radiation patterns of antennas mounted on aircraft are developed. The airborne antenna problems associated with the Microwave Landing System (MLS) are emphasized. Based on the requirements of the MLS, volumetric pattern solutions are essential. Previous attempts at solving for the volumetric patterns were found to be far too complex and very inefficient. However as a result of previous efforts, it is possible to combine the elevation and roll plane pattern solutions to give the complete volumetric pattern. This combination is described as well as the aircraft simulation models used in the analysis. A numerical technique is presented to aid in the simulation of the aircraft studied. Finally, a description of the input data used in the computer code is given.

Yu, C. L.; Burnside, W. D.

1976-01-01

295

Science Museum: Antenna Science News  

NSDL National Science Digital Library

The Web site of the London's Science Museum (last mentioned in the April 21, 2000 Scout Report) now offers Antenna, a section of frequently updated popular science news delivered with a decidedly British sense of humor. Antenna offers both short (about 3 screens of information) and longer features (6 or more pages), some with video. Recent short features are "First human clone - or is it?"; "Bond robot," examining real world uses of James Bond technology; and "Cod and chips at risk," a look at the causes of reduced availability of fish and chips as cod is overfished. An example of a longer feature is "Tiny tickers fixed before birth," an offering about heart surgery performed while Baby is still safe inside Mum. Be sure to check the archives for past articles, both long and short.

296

Plasmonic Antenna Coupling for QWIPs  

NASA Technical Reports Server (NTRS)

In a proposed scheme for coupling light into a quantum-well infrared photodetector (QWIP), an antenna or an array of antennas made of a suitable metal would be fabricated on the face of what would otherwise be a standard QWIP. This or any such coupling scheme is required to effect polarization conversion: Light incident perpendicularly to the face is necessarily polarized in the plane of the face, whereas, as a matter of fundamental electrodynamics and related quantum selection rules, light must have a non-zero component of perpendicular polarization in order to be absorbed in the photodetection process. In a prior coupling scheme, gratings in the form of surface corrugations diffract normally gles, thereby imparting some perpendicular polarization. Unfortunately, the corrugation- fabrication process increases the overall nonuniformity of a large QWIP array. The proposed scheme is an alternative to the use of surface corrugations.

Hong, John

2007-01-01

297

Automated Antenna Design with Evolutionary Algorithms  

NASA Technical Reports Server (NTRS)

Current methods of designing and optimizing antennas by hand are time and labor intensive, and limit complexity. Evolutionary design techniques can overcome these limitations by searching the design space and automatically finding effective solutions. In recent years, evolutionary algorithms have shown great promise in finding practical solutions in large, poorly understood design spaces. In particular, spacecraft antenna design has proven tractable to evolutionary design techniques. Researchers have been investigating evolutionary antenna design and optimization since the early 1990s, and the field has grown in recent years as computer speed has increased and electromagnetic simulators have improved. Two requirements-compliant antennas, one for ST5 and another for TDRS-C, have been automatically designed by evolutionary algorithms. The ST5 antenna is slated to fly this year, and a TDRS-C phased array element has been fabricated and tested. Such automated evolutionary design is enabled by medium-to-high quality simulators and fast modern computers to evaluate computer-generated designs. Evolutionary algorithms automate cut-and-try engineering, substituting automated search though millions of potential designs for intelligent search by engineers through a much smaller number of designs. For evolutionary design, the engineer chooses the evolutionary technique, parameters and the basic form of the antenna, e.g., single wire for ST5 and crossed-element Yagi for TDRS-C. Evolutionary algorithms then search for optimal configurations in the space defined by the engineer. NASA's Space Technology 5 (ST5) mission will launch three small spacecraft to test innovative concepts and technologies. Advanced evolutionary algorithms were used to automatically design antennas for ST5. The combination of wide beamwidth for a circularly-polarized wave and wide impedance bandwidth made for a challenging antenna design problem. From past experience in designing wire antennas, we chose to constrain the evolutionary design to a monopole wire antenna. The results of the runs produced requirements-compliant antennas that were subsequently fabricated and tested. The evolved antenna has a number of advantages with regard to power consumption, fabrication time and complexity, and performance. Lower power requirements result from achieving high gain across a wider range of elevation angles, thus allowing a broader range of angles over which maximum data throughput can be achieved. Since the evolved antenna does not require a phasing circuit, less design and fabrication work is required. In terms of overall work, the evolved antenna required approximately three person-months to design and fabricate whereas the conventional antenna required about five. Furthermore, when the mission was modified and new orbital parameters selected, a redesign of the antenna to new requirements was required. The evolutionary system was rapidly modified and a new antenna evolved in a few weeks. The evolved antenna was shown to be compliant to the ST5 mission requirements. It has an unusual organic looking structure, one that expert antenna designers would not likely produce. This antenna has been tested, baselined and is scheduled to fly this year. In addition to the ST5 antenna, our laboratory has evolved an S-band phased array antenna element design that meets the requirements for NASA's TDRS-C communications satellite scheduled for launch early next decade. A combination of fairly broad bandwidth, high efficiency and circular polarization at high gain made for another challenging design problem. We chose to constrain the evolutionary design to a crossed-element Yagi antenna. The 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 getic algorithm and stochastic hill-climbing has been fabricated and tested. Laboratory results cor

Linden, Derek; Hornby, Greg; Lohn, Jason; Globus, Al; Krishunkumor, K.

2006-01-01

298

Microstrip antennas for SAR applications  

Microsoft Academic Search

This paper discusses various methods of implementing a shared-aperture dual-frequency dual-polarized array antenna for spaced-based synthetic aperture radar (SAR) applications. After evaluating the use of several potential array architecture concepts and radiating elements, a design using interlaced C-band microstrip patches and X-band printed slot elements was chosen as the best choice for the present system requirements. Layout considerations for the

Ralph Pokuls; Jaroslaw Uher; D. M. Pozar

1998-01-01

299

Conformal superspace ?-models  

NASA Astrophysics Data System (ADS)

We review recent developments in the context of two-dimensional conformally invariant ?-models. These quantum field theories play a prominent role in the covariant superstring quantization in flux backgrounds and in the analysis of disordered systems. We present supergroup WZW models as primary examples of logarithmic conformal field theories, whose structure is almost entirely determined by the underlying supergeometry. In particular, we discuss the harmonic analysis on supergroups and supercosets and point out the subtleties of Lie superalgebra representation theory that are responsible for the emergence of logarithmic representations. Furthermore, special types of marginal deformations of supergroup WZW models are studied which only exist if the Killing form is vanishing. We show how exact expressions for anomalous dimensions of boundary fields can be derived using quasi-abelian perturbation theory. Finally, the knowledge of the exact spectrum is used to motivate a duality between the OSP(4|2) symmetric Gross-Neveu model and the S supersphere ?-model.

Mitev, Vladimir; Quella, Thomas; Schomerus, Volker

2011-09-01

300

Quantum conformal fluctuations revisited  

Microsoft Academic Search

The conformal quantization method of Narlikar and Padmanabhan is reformulated with a view to take into account theexact propagator and to provide explicitnumerical estimates of various predictions for dust cosmologies. It is found that in spite of the divergence of quantum fluctuations at the big-bang epoch it is possible to construct wave packets which remain sharp fromt=10?70s, say, up to

J. Lahiri; V. J. Menon

1988-01-01

301

Conformal scalar field wormholes  

NASA Technical Reports Server (NTRS)

The Euclidian Einstein equations with a cosmological constant and a conformally coupled scalar field are solved, taking the metric to be of the Robertson-Walker type. In the case Lambda = 0, solutions are found which represent a wormhole connecting two asymptotically flat Euclidian regions. In the case Lambda greater than 0, the solutions represent tunneling from a small Tolman-like universe to a large Robertson-Walker universe.

Halliwell, Jonathan J.; Laflamme, Raymond

1989-01-01

302

Transcatheter Antenna For Microwave Treatment  

NASA Technical Reports Server (NTRS)

Method and apparatus are provided for propagating microwave energy into heart tissues to produce a desired temperature profile therein at tissue depths sufficient for thermally ablating arrhythmogenic cardiac tissue to treat ventricular tachycardia and other arrhythmias while preventing excessive heating of surrounding tissues, organs, and blood. A wide bandwidth double-disk antenna is effective for this purpose over a bandwidth of about six gigahertz. A computer simulation provides initial screening capabilities for an antenna such as antenna, frequency, power level, and power application duration. The simulation also allows optimization of techniques for specific patients or conditions. In operation, microwave energy between about 1 Gigahertz and 12 Gigahertz is applied to monopole microwave radiation having a surface wave limiter. A test setup provides physical testing of microwave radiators to determine the temperature profile created in actual heart tissue or ersatz heart tissue. Saline solution pumped over the heart tissue with a peristaltic pump simulates blood flow. Optical temperature sensors disposed at various tissue depths within the heart tissue detect the temperature profile without creating any electromagnetic interference. The method may he used to produce a desired temperature profile in other body tissues reachable by catheter such as tumors and the like.

Arndt, G. Dickey (Inventor); Carl, James R. (Inventor); Raffoul, George W. (Inventor); Karasack, Vincent G. (Inventor); Pacifico, Antonio (Inventor); Pieper, Carl F. (Inventor)

2000-01-01

303

Compact chip monopole antenna with parasitic patch for GPS applications  

Microsoft Academic Search

A chip monopole antenna with a parasitic patch is proposed for GPS applications. To reduce the dimensions of the antenna, the chip monopole antenna is composed of stacked meander, helix structures, and a parasitic patch. The impedance and radiation characteristics of the antenna are investigated. The measured results show that the proposed antenna, having compact dimensions of 3.6 ?? 5

Jinwoo Jung; Kyoungkeun Kim; Jahyeon Lee; Hyeonjin Lee; Yeongseog Lim

2009-01-01

304

A multi octaves directive dielectric lens: the pyramid antenna  

Microsoft Academic Search

Leaky wave antennas have been investigated for a long time and are typically an inexpensive solution for beam scanning antennas. We have designed a novel antenna topology, named the pyramid antenna, based on the broadband leaky concept. The pyramid antenna, currently covered by a patent application, has unparalleled bandwidth performances that can be briefly summarized as follows: 1) input impedance

S. Bruni; A. Neto; F. Marliani

2005-01-01

305

Optically transparent conductive polymer RFID meandering dipole antenna  

Microsoft Academic Search

In this paper, we present optically transparent flexible conductive polymer antennas for radio frequency identification systems. The designs for these antennas are presented along with simulated and measured results of antenna radiating properties. These conductive polymer antennas are compared to antennas with the same design fabricated out of copper. Finally, we include an analysis of the optical transparency of the

Nicholas J. Kirsch; Nicholas A. Vacirca; Elizabeth E. Plowman; Timothy P. Kurzweg; Adam K. Fontecchio; Kapil R. Dandekar

2009-01-01

306

Textile UWB Antennas for Wireless Body Area Networks  

Microsoft Academic Search

A new ultrawideband (UWB) textile antenna designed for UWB wireless body area network (WBAN) applications is presented. Unlike previous textile antennas, these antennas offer a direct integration into clothing due to a very small thickness (0.5 mm) and flexibility. We have realized two different designs of textile antennas: coplanar waveguide fed printed UWB disc monopole and UWB annular slot antenna.

Maciej Klemm; Gerhard Troester

2006-01-01

307

Vertically polarized antenna system for television broadcasting services  

Microsoft Academic Search

In the paper, the design and simulation of a transmit antenna system with vertical polarization is discussed. The antenna is designed for television broadcasting services. The improvement of antenna properties is achieved by using a special balun with a shunt matching and an inner compensation transmission line. The feeding network of the antenna is deeply discussed. The antenna is simulated

Kamil Pitra; Vladimir Sporik; Zbynek Lukes; Zbynek Raida; Vladislav Dlouhy; Jan Bartyzal

2011-01-01

308

Gain measurements of vertically polarized antennas over imperfect ground  

Microsoft Academic Search

A technique is described for measuring the absolute gain of vertically polarized HF antennas. A horizontal half-wave dipole, located near the antenna being measured (test antenna), is used as a reference in a comparison type of gain measurement. A rotatable, linearly polarized, transmitting antenna is mounted on an airplane and used to illuminate the test-reference antenna location. With the airborne

R. Fitzgerrell

1967-01-01

309

Cylindrical CPW-fed and CPS-fed slot antennas  

Microsoft Academic Search

Cylindrical antennas are needed in applications which require mounting on curved surfaces. This article presents two new designs of antennas printed on cylindrical substrates. The first antenna is a dual frequency coplanar waveguide (CPW)-fed double folded slot antenna operating at 5 and 7 GHz. This antenna is matched to the feed line without external matching circuitry and exhibits a gain of

Amjad A. Omar; Maximilian C. Scardelletti; Nihad Dib; Raed Shubair

2009-01-01

310

Advanced ICRF antenna design for R-TOKAMAK  

Microsoft Academic Search

The advanced ICRF antennas designed for the R-TOKAMAK (a proposal in the Institute of Plasma Physics, Nagoya University) are described. They are a standard loop antenna and a panel heater antenna for fast wave heating, and a waveguide antenna for ion Bernstein wave heating. The standard loop antenna is made of Al-alloy and has a simple structure to install because

E. Kako; R. Ando; M. Ichimura; Y. Ogawa; T. Amano; T. Watari

1986-01-01

311

Compact frequency notched ultra-wideband fractal printed slot antenna  

Microsoft Academic Search

A novel frequency notched ultra-wideband (UWB) fractal printed slot antenna is proposed. The antenna is similar in configuration to a conventional microstrip-fed wide slot antenna, however, by introducing a Koch fractal slot, not only the size of the antenna is reduced significantly but also frequency notched function is achieved. Several properties of the antenna such as impedance bandwidth, frequency notched

W. J. Lui; C. H. Cheng; H. B. Zhu

2006-01-01

312

Advanced microwave radiometer antenna system study  

NASA Technical Reports Server (NTRS)

The practicability of a multi-frequency antenna for spaceborne microwave radiometers was considered in detail. The program consisted of a comparative study of various antenna systems, both mechanically and electronically scanned, in relation to specified design goals and desired system performance. The study involved several distinct tasks: definition of candidate antennas that are lightweight and that, at the specified frequencies of 5, 10, 18, 22, and 36 GHz, can provide conical scanning, dual linear polarization, and simultaneous multiple frequency operation; examination of various feed systems and phase-shifting techniques; detailed analysis of several key performance parameters such as beam efficiency, sidelobe level, and antenna beam footprint size; and conception of an antenna/feed system that could meet the design goals. Candidate antennas examined include phased arrays, lenses, and optical reflector systems. Mechanical, electrical, and performance characteristics of the various systems were tabulated for ease of comparison.

Kummer, W. H.; Villeneuve, A. T.; Seaton, A. F.

1976-01-01

313

Microfluidic serpentine antennas with designed mechanical tunability.  

PubMed

This paper describes the design and characterization of microfluidic serpentine antennas with reversible stretchability and designed mechanical frequency modulation (FM). The microfluidic antennas are designed based on the Poisson's ratio of the elastomer in which the liquid alloy antenna is embedded, to controllably decrease, stabilize or increase its resonance frequency when being stretched. Finite element modelling was used in combination with experimental verification to investigate the effects of substrate dimensions and antenna aspect ratios on the FM sensitivity to uniaxial stretching. It could be designed within the range of -1.2 to 0.6 GHz per 100% stretch. When the aspect ratio of the serpentine antenna is between 1.0 and 1.5, the resonance frequency is stable under stretching, bending, and twisting. The presented microfluidic serpentine antenna design could be utilized in the field of wireless mobile communication for the design of wearable electronics, with a stable resonance frequency under dynamic applied strain up to 50%. PMID:25144304

Huang, YongAn; Wang, Yezhou; Xiao, Lin; Liu, Huimin; Dong, Wentao; Yin, Zhouping

2014-09-30

314

Lower Hybrid Antenna Design for MST  

SciTech Connect

Inter-digital line antennas are being used to test the feasibility of lower hybrid current drive in MST. The antennas use {lambda}/4 resonators and launch slow waves at 800 MHz with n parallel {approx} 7.5. Routine operation has been achieved with a good impedance match between antenna and plasma. High power antenna design improvements include larger vacuum feed-throughs, better impedance matching, and rf instrumentation on all resonators. The antenna and feed-through modeling was performed with CST Microwave Studio{sup TM}. The pulse-forming network that powers the klystron is being upgraded to a 50 kV - 30 ms pulse. The goal for the LHCD system on MST is a modular design that can handle 300 kW per antenna.

Goetz, J.A.; Thomas, M.A.; Kaufman, M.C.; Oliva, S.P. [Department of Physics, University of Wisconsin, Madison, WI 53706 (United States)

2005-09-26

315

Passive wireless antenna sensors for crack detection and shear/compression sensing  

NASA Astrophysics Data System (ADS)

Despite the fact that engineering components and structures are carefully designed against fatigue failures, 50 to 90% of mechanical failures are due to fatigue crack development. The severity of the failure depends on both the crack length and its orientation. Many types of sensors are available that can detect fatigue crack propagation. However, crack orientation detection has been rarely reported in the literature. We evaluated a patch antenna sensor capable of detecting crack propagation as well as crack orientation changes. The aim of these sensors would be to evaluate the real-time health condition of metallic structures to avoid catastrophic failures. The proposed crack sensing system consists of a dielectric substrate with a ground plane on one side of the substrate and an antenna patch printed on the other side of the substrate. The ground plane and the antenna patch, both conductive in nature, form an electromagnetic resonant cavity that radiates at distinct frequencies. These frequencies are monitored to evaluate the condition of cracks. A wireless sensor array can be realized by implementing a wireless interrogation unit. The scientific merits of this research are: 1) high sensitivity: it was demonstrated that the antenna sensors can detect crack growth with a sub-millimeter resolution; 2) passive wireless operation: based on microstrip antennas, the antenna sensors encode the sensing information in the backscattered antenna signal and thus can transmit the information without needing a local battery; 3) thin and conformal: the entire sensor unit is less than a millimeter thick and highly conformal; 4) crack orientation detection: the crack orientation on the structure can be precisely evaluated based on a single parameter, which only few sensors can accomplish. In addition to crack detection, the patch antenna sensors are also investigated for measuring shear and pressure forces, with an aim to study the formation, diagnostics and prevention of foot ulcers in diabetic patients. These sensors were vertically integrated and embedded in the insole of shoes for measuring plantar pressure/shear distribution. The scientific merits of this proposed research are: 1) simultaneous shear/pressure measurement : current smart shoe technology can only measure shear and pressure separately due to the size of the shear sensor. The proposed sensor can measure shear and pressure deformation simultaneously; 2) high sensitivity and spatial resolution: these sensors are very sensitive and have compact size that enables measuring stress distribution with fine spatial resolution; 3) passive and un-tethered operation: the sensor transponder was mounted on the top surface of the shoe to facilitate wireless interrogation of the sensor array embedded in the insole of the shoe, eliminating external wiring completely.

Mohammad, Irshad

316

Mechanical Measurements of the ALMA Prototype Antennas  

E-print Network

The specifications of the Atacama Large Millimeter Array (ALMA) have placed stringent requirements on the mechanical performance of its antennas. As part of the evaluation process of the VertexRSI and Alcatel EIE Consortium (AEC) ALMA prototype antennas, measurements of the path length, thermal, and azimuth bearing performance were made under a variety of weather conditions and observing modes. The results of mechanical measurements, reported here, are compared to the antenna specifications.

A. Greve; J. G. Mangum

2007-10-30

317

The development of inflatable array antennas  

Microsoft Academic Search

Inflatable array antennas are being developed to significantly reduce the mass, the launch vehicle stowage volume, and the cost of future spacecraft systems. Three inflatable array antennas, previously developed for spacecraft applications, are a 3.3 m×1.0 m L-band synthetic-aperture radar (SAR) array, a 1.0 m-diameter X-band telecom reflectarray, and a 3 m-diameter Ka-band telecom reflectarray. All three antennas are similar

John Huang; Michael Lou

2001-01-01

318

Construction of 21cm Cosmic Radio Antenna  

Microsoft Academic Search

We made a pyramidal horn antenna system for 21cm cosmic radio wave. The antenna system has a rectangular waveguide with TE10 mode and a copper probe to detect the electromagnetic wave in waveguide. The parameters of the probe are obtained by experiments using two waveguides. Pyramidal horn antenna is designed to get a gain of 20dB. The size of the

Jong Ae Park; Jong-Man Yang; Seog Tae Han; Yong Sun Park

1993-01-01

319

A circular patch antenna for radio LAN's  

Microsoft Academic Search

A TM02-mode circular patch antenna for the application of radio LANs is reported. An experimental prototype operating at 5.2 GHz is designed and tested. The antenna pattern is omnidirectional in azimuth and has a notch in the normal direction. A 3.3% bandwidth of VSWR ⩽2 and 4.2-dB antenna gain were measured. Experimental results agree well with theoretical predictions

Y. J. Guo; A. Paez; R. A. Sadeghzadeh; S. K. Barton

1997-01-01

320

Gravitational event search with five resonant antennas  

E-print Network

Five cryogenic resonant gravitational antennas are now in operation. This is the first time that such a large number of high sensitive antennas are taking data and an agreement on data exchange has been signed by the responsible groups. The data exchanged will consist essentially in lists of ''candidate events''. In this paper the procedure used by the Rome group in order to obtain ''candidate events'' is presented. Some methods of analyzing the data of the "network" of the five antennas are shown.

S. Frasca

2000-02-02

321

Microstrip base station antennas for cellular communications  

Microsoft Academic Search

Four base-station antenna products using microstrip technology have been developed for use in cellular communications. The antennas operate in the 800-900-MHz range and are designed to work in a 60° sectored arrangement. The main product is a half-cylinder three-beam radome-enclosed antenna. There are three microstrip planar array panels within the half-cylindrical radome. Each microstrip planar array panel illuminates one 60°

Peter Strickland; Fazal Bacchus

1991-01-01

322

Emission of terahertz radiations from fractal antennas  

NASA Astrophysics Data System (ADS)

We investigate the emission of terahertz radiation from a photoconductive fractal antenna fabricated on a semi-insulating gallium arsenide substrate. Owing to the self-similarity of fractal structures, our fractal antenna shows a multiband emission of terahertz radiation. The emission intensity at peak frequency is about twice that from a bow-tie antenna. We also investigate the mechanism of the multiband emission by using the finite-difference time-domain calculation.

Miyamaru, F.; Saito, Y.; Takeda, M. W.; Liu, L.; Hou, B.; Wen, W.; Sheng, Ping

2009-11-01

323

ULTRA WIDEBAND FRACTAL MICROSTRIP ANTENNA DESIGN  

Microsoft Academic Search

Abstract—Newfractal geometry for microstrip antennas is presented in this paper. This fractal structure is implemented on hexagonal and,several iteration is applied on initial shape.,This antenna has lowprofile, lightw eight and is easy to be fabricated and has successfully demonstrated multiband and broadband characteristics. The simulated results showthat proposed antenna has very good performance in impedance bandwidth and radiation pattern.

Abolfazl Azari; Javad Rowhani

2008-01-01

324

Pseudo full-duplex phased array antennas  

NASA Astrophysics Data System (ADS)

High data rate networks are now being designed to rapidly exchange high value sensor and video information among various users located on the surface and airborne. Phased array antennas can provide rapid switching amongst the members in addition to the gain necessary to connect these members. For many applications, these antennas would be configured to either transmit or receive. Designing a phased array antenna that is full duplex significantly complicates the design because much of the emphasis in the design is placed on keeping the transmit energy out of the receive channel. A phased array antenna could be designed to receive only when the antenna is not transmitting; thus the design would only need to protect the receiver components during the transmission. The antenna would be then full duplex. This paper describes a small pseudo full duplex wideband multi-frequency band (X, Ku and K) phased array antenna with +/-27 degrees of the beam scanning, using a novel multi-line time delay phase shifter controlled by a piezoelectric transducer (PET). This antenna design is simple, and would use no more space than an antenna used solely for either transmit or receive. Also, some of the isolation between the transmit and receive channels is achieved using novel low-cost fabrication techniques.

Foshee, James J.; Tahim, Raghbir S.; Chang, Kai

2002-06-01

325

Antenna pattern control using impedance surfaces  

NASA Technical Reports Server (NTRS)

The modification of a moment method code is described. Analyses of horn antennas were conducted extensively. Excellent agreements with measured results were observed for pyramidal horn antennas with perfectly conducting surfaces. The predicted results are so accurate that even the finest ripple structures in the far-field radiation patterns are computed correctly. Preliminary results for the radiation patterns of pyramidal horns with impedance surfaces were also obtained. Discussions of using the code in accurate modeling of practical pyramidal horn antennas are also included. After the code for the analysis of the horn antennas with impedance materials is finalized, the synthesis problem will be examined in the coming research period.

Balanis, Constantine A.; Liu, Kefeng

1992-01-01

326

Considerations for millimeter wave printed antennas  

NASA Technical Reports Server (NTRS)

Calculated data are presented on the performance of printed antenna elements on substrates which may be electrically thick, as would be the case for printed antennas at millimeter wave frequencies. Printed dipoles and microstrip patch antennas on polytetrafluoroethylene (PTFE), quartz, and gallium arsenide substrates are considered. Data are given for resonant length, resonant resistance, bandwidth, loss due to surface waves, loss due to dielectric heating, and mutual coupling. Also presented is an optimization procedure for maximizing or minimizing power launched into surface waves from a multielement printed antenna array. The data are calculated by a moment method solution.

Pozar, D. M.

1983-01-01

327

Antenna-coupled infrared focal plane array  

NASA Astrophysics Data System (ADS)

In this dissertation a new type of infrared focal plane array (IR FPA) was investigated, consisting of antenna-coupled microbolometers fabricated using electron-beam lithography. Four different antenna designs were experimentally demonstrated at 10-micron wavelength: dipole, bowtie, square-spiral, and log-periodic. The main differences between these antenna types were their bandwidth, collection area, angular reception pattern, and polarization. To provide pixel collection areas commensurate with typical IR FPA requirements, two configurations were investigated: a two-dimensional serpentine interconnection of individual IR antennas, and a Fresnel-zone-plate (FZP) coupled to a single-element antenna. Optimum spacing conditions for the two-dimensional interconnect were developed. Increased sensitivity was demonstrated using a FZP-coupled design. In general, it was found that the configuration of the antenna substrate material was critical for optimization of sensitivity. The best results were obtained using thin membranes of silicon nitride to enhance the thermal isolation of the antenna-coupled bolometers. In addition, choice of the bolometer material was also important, with the best results obtained using vanadium oxide. Using optimum choices for all parameters, normalized sensitivity (D*) values in the range of mid 108 [cm Hz /W] were demonstrated for antenna-coupled IR sensors, and directions for further improvements were identified. Successful integration of antenna-coupled pixels with commercial readout integrated circuits was also demonstrated.

Gonzalez, Francisco Javier

328

MILA Antenna Control Unit Replacement Project  

NASA Technical Reports Server (NTRS)

The Air to Ground Subsystem (AGS) Antenna Control Units at the MILA Ground Network Tracking Station are at end-of-life and are being replaced. AGS consists of two antennas at MILA (Quad-Helix and Teltrac). Software was taken from the existing Subsystem Controller and modified for the Antenna Control Unit (ACU). The software is capable of receiving and sending commands to and from the ACU. Moving the azimuth clockwise, counterclockwise, moving the elevation up or down, turning servo power on and off, and inputting azimuth and elevation angles are commands that the antenna can receive.

Bresette, Jeremy

2007-01-01

329

Small antennas for communication over sea ice  

NASA Astrophysics Data System (ADS)

The invention described herein relates to an antenna system which makes use of the waveguide properties of sea ice. The antenna system broadly includes at least one antenna wire extending along and preferably in contact with a sea ice surface for transmitting and receiving substantially vertically polarized radio waves. In a first embodiment, the antenna system has a single antenna wire connected to a tuner at one end and grounded to seawater at a second end. The antenna system also has a second length of wire attached to the tuner. The second wire passes through a hole in the sea ice and is also grounded to the seawater beneath the sea ice. In an alternative embodiment, only the second wire is grounded to the seawater beneath the sea ice. The single antenna wire in this embodiment is ungrounded. In yet another embodiment, the antenna system comprises a dipole antenna wire laying on the surface of the sea ice and being connected to a radio for transmitting and receiving radio signals.

Mileski, Paul

1993-10-01

330

Submillimeter-wave antennas on thin membranes  

NASA Technical Reports Server (NTRS)

Submillimeter-wave antennas have been fabricated on 1-micron thick silicon-oxynitride membranes. This approach results in better patterns than previous lens-coupled antennas, and eliminates the dielectric loss associated with the substrate lens. Measurements on a wideband log-periodic antenna at 700 GHz, 370 GHz and 167 GHz show no sidelobes and 3-dB beamwidths between 40 and 60 deg. A linear imaging array has similar patterns at 700 GHz. Possible applications for membrane antennas include wideband superconducting tunnel-junction receivers for radio astronomy and imaging arrays for radiometry and plasma diagnostics.

Rebeiz, Gabriel M.; Regehr, Wade G.; Rutledge, David B.; Savage, Richard L.; Luhmann, Neville C., Jr.

1987-01-01

331

COMPUTER MODELING ANALYSIS OF BROADBAND MOBILE ANTENNAS  

E-print Network

possible without the assistance from New Hampshire Public Television and Brian Shepperd. The work reported ­ Selecting a Datacast Receiver Antenna............................................. 46 Commercial Off

New Hampshire, University of

332

47 CFR 95.1013 - Antennas.  

Code of Federal Regulations, 2012 CFR

...1013 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES PERSONAL RADIO SERVICES Low Power Radio Service (LPRS) General Provisions § 95.1013 Antennas. (a) The maximum...

2012-10-01

333

47 CFR 95.1013 - Antennas.  

Code of Federal Regulations, 2013 CFR

...1013 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES PERSONAL RADIO SERVICES Low Power Radio Service (LPRS) General Provisions § 95.1013 Antennas. (a) The maximum...

2013-10-01

334

47 CFR 95.1013 - Antennas.  

Code of Federal Regulations, 2011 CFR

...1013 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES PERSONAL RADIO SERVICES Low Power Radio Service (LPRS) General Provisions § 95.1013 Antennas. (a) The maximum...

2011-10-01

335

47 CFR 73.816 - Antennas.  

Code of Federal Regulations, 2013 CFR

...Section 73.816 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Low Power FM Broadcast Stations (LPFM) § 73.816 Antennas. (a) Permittees and...

2013-10-01

336

THz patterned antennas for THz-TDS  

NASA Astrophysics Data System (ADS)

We report on a comprehensive investigation of radiation characteristics of THz emitters using structures based on the Sierpinski fractal. Self-similarity present in the geometrical properties of these antennas improves the coupling of emitted radiation to free space. Using THz-TDS it is shown that these novel antennas produce higher radiation power when compared to the bow-tie antenna. To the best of our knowledge this is the first time that Sierpinski fractal antennas have been used as emitters for generating THz radiation.

Maraghechi, P.; Elezzabi, A. Y.

2011-02-01

337

Allen Telescope Array Antennas from an ATA PerspectiveAntennas from an ATA Perspective  

E-print Network

Allen Telescope Array Antennas from an ATA PerspectiveAntennas from an ATA Perspective FASR InstDavid DeBoer, Project Engineer/Deputy Project Manager, SETI Instituteitute #12;Allen Telescope Array OutlineOutline · ATA Overview · Antenna · Costing/timeline #12;Allen Telescope Array ATA Team

338

An antenna-pointing mechanism for the ETS-6 K-band Single Access (KSA) antenna  

NASA Technical Reports Server (NTRS)

Both the design philosophy for the Antenna Pointing Mechanism (APM) to be used for the K-band Single Access (KSA) antenna system and experimental results of the APM Engineering Model (EM) tests are described. The KSA antenna system will be flown on the Engineering Test Satellite 6 (ETS-6).

Takada, Noboru; Amano, Takahiro; Ohhashi, Toshiro; Wachi, Shigeo

1991-01-01

339

Determining weather radar antenna pointing using signals detected from the sun at low antenna elevations  

E-print Network

Determining weather radar antenna pointing using signals detected from the sun at low antenna radiation of the sun for checking of the antenna alignment and of the sensitivity of the receiver chain is a well established method in weather radar maintenance, and radar manufacturers offer sun calibration

Stoffelen, Ad

340

An iterative model for fractal antennas: application to the Sierpinski gasket antenna  

Microsoft Academic Search

A simple model that explains the behavior of the Sierpinski fractal antenna is presented. This model shows that the multiband behavior of the Sierpinski fractal antenna is a consequence of its fractal nature. The model is applied to predict the behavior of the Sierpinski fractal antenna when the flare angle is modified and its validity is assessed by comparing its

Carles Puente Baliarda; Carmen Borja Borau; Mònica Navarro Rodero; Jordi Romeu Robert

2000-01-01

341

Conformal superalgebras via tractor calculus  

E-print Network

We use the manifestly conformally invariant description of a Lorentzian conformal structure in terms of a parabolic Cartan geometry in order to introduce a superalgebra structure on the space of twistor spinors and normal conformal vector fields formulated in purely algebraic terms on parallel sections in tractor bundles. Via a fixed metric in the conformal class, one reproduces a conformal superalgebra structure which has been considered in the literature before. The tractor approach, however, makes clear that the failure of this object to be a Lie superalgebra in certain cases is due to purely algebraic identities on the spinor module and to special properties of the conformal holonomy representation. Moreover, it naturally generalizes to higher signatures. This yields new formulas for constructing new twistor spinors and higher order normal conformal Killing forms out of existing ones, generalizing the well-known spinorial Lie derivative. Moreover, we derive restrictions on the possible dimension of the space of twistor spinors in any metric signature.

Andree Lischewski

2014-08-10

342

New carbon nanotube antenna array simulation and fabrication  

NASA Astrophysics Data System (ADS)

A novel THz antenna structure, made of carbon nanotube arrays is suggested. Using CST MICROWAVE STUDIO (CST MWS), the capabilities of carbon nanotube terahertz (THz) antenna arrays have been simulated and this CNT antenna array has been fabricated.

Zareie, Hosein; Davoudzadeh, Nima; Koohsorkhi, Javad; Mohajerzadeh, Shamsoddin; Rouhi, Nima

2009-03-01

343

47 CFR 74.22 - Use of common antenna structure.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 false Use of common antenna structure. 74.22 Section 74.22 Telecommunication...74 § 74.22 Use of common antenna structure. The simultaneous use of a common antenna structure by more than one station...

2012-10-01

344

47 CFR 74.22 - Use of common antenna structure.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 false Use of common antenna structure. 74.22 Section 74.22 Telecommunication...74 § 74.22 Use of common antenna structure. The simultaneous use of a common antenna structure by more than one station...

2013-10-01

345

47 CFR 17.4 - Antenna structure registration.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Antenna structure registration. 17.4 Section 17...CONSTRUCTION, MARKING, AND LIGHTING OF ANTENNA STRUCTURES General Information § 17.4 Antenna structure registration. (a) Effective...

2011-10-01

346

47 CFR 74.22 - Use of common antenna structure.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 false Use of common antenna structure. 74.22 Section 74.22 Telecommunication...74 § 74.22 Use of common antenna structure. The simultaneous use of a common antenna structure by more than one station...

2011-10-01

347

Log Periodic Antennas Dr. S. X-Pol  

E-print Network

3/26/2009 1 Log Periodic Antennas INEL 5305 Dr. S. X-Pol Canal Frecuencia (MHz) Banda Frecuencia of the Log-Periodic Dipole Antenna" Variaciones used as a feed in reflector antennas Compact ultra broadband

Cruz-Pol, Sandra L.

348

47 CFR 73.54 - Antenna resistance and reactance measurements.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 false Antenna resistance and reactance measurements. 73.54 Section 73... § 73.54 Antenna resistance and reactance measurements. (a) The resistance...transmitter. (b) The resistance and reactance of a directional antenna shall be...

2010-10-01

349

47 CFR 74.1235 - Power limitations and antenna systems.  

Code of Federal Regulations, 2011 CFR

...TPO. (f) Composite antennas and antenna arrays may be used where...Either horizontal, vertical, circular or elliptical...Separate transmitting antennas are permitted if both horizontal and vertical polarization is to...

2011-10-01

350

47 CFR 74.1235 - Power limitations and antenna systems.  

Code of Federal Regulations, 2010 CFR

...TPO. (f) Composite antennas and antenna arrays may be used where...Either horizontal, vertical, circular or elliptical...Separate transmitting antennas are permitted if both horizontal and vertical polarization is to...

2010-10-01

351

47 CFR 73.6025 - Antenna system and station location.  

Code of Federal Regulations, 2011 CFR

...degrees of the antenna vertical axis and the...direction. Sufficient vertical plane patterns...characteristics of the antenna above and below...horizontal and vertical plane patterns...complete directional antenna system. In...

2011-10-01

352

47 CFR 74.1235 - Power limitations and antenna systems.  

Code of Federal Regulations, 2012 CFR

...TPO. (f) Composite antennas and antenna arrays may be used where...Either horizontal, vertical, circular or elliptical...Separate transmitting antennas are permitted if both horizontal and vertical polarization is to...

2012-10-01

353

47 CFR 73.685 - Transmitter location and antenna system.  

Code of Federal Regulations, 2012 CFR

...tilting of the major vertical radiation lobe...category. Directional antennas may be employed...degrees of the antenna vertical axis and the orientation...horizontal and vertical plane patterns...complete directional antenna system. In...

2012-10-01

354

47 CFR 73.6025 - Antenna system and station location.  

Code of Federal Regulations, 2010 CFR

...degrees of the antenna vertical axis and the...direction. Sufficient vertical plane patterns...characteristics of the antenna above and below...horizontal and vertical plane patterns...complete directional antenna system. In...

2010-10-01

355

47 CFR 73.6025 - Antenna system and station location.  

Code of Federal Regulations, 2012 CFR

...degrees of the antenna vertical axis and the...direction. Sufficient vertical plane patterns...characteristics of the antenna above and below...horizontal and vertical plane patterns...complete directional antenna system. In...

2012-10-01

356

47 CFR 73.685 - Transmitter location and antenna system.  

Code of Federal Regulations, 2011 CFR

...tilting of the major vertical radiation lobe...category. Directional antennas may be employed...degrees of the antenna vertical axis and the orientation...horizontal and vertical plane patterns...complete directional antenna system. In...

2011-10-01

357

47 CFR 73.685 - Transmitter location and antenna system.  

Code of Federal Regulations, 2010 CFR

...tilting of the major vertical radiation lobe...category. Directional antennas may be employed...degrees of the antenna vertical axis and the orientation...horizontal and vertical plane patterns...complete directional antenna system. In...

2010-10-01

358

Antennas for the Vlf Region and Lf Region.  

National Technical Information Service (NTIS)

A description is given of all the transmitting and receiving antennas that have been used for VLF project studies. The antenna efficiency is discussed and helical transmitting antennas are described in a special chapter. Various diagrams plotted in accord...

R. Klein

1970-01-01

359

47 CFR 22.1011 - Antenna height limitations.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Antenna height limitations. 22.1011 Section 22.1011...Radiotelephone Service § 22.1011 Antenna height limitations. The antenna height of offshore stations must not exceed 61...

2013-10-01

360

47 CFR 101.125 - Temporary fixed antenna height restrictions.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 false Temporary fixed antenna height restrictions. 101.125 Section 101...Standards § 101.125 Temporary fixed antenna height restrictions. The overall antenna structure heights employed by mobile stations in the...

2011-10-01

361

47 CFR 101.125 - Temporary fixed antenna height restrictions.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 false Temporary fixed antenna height restrictions. 101.125 Section 101...Standards § 101.125 Temporary fixed antenna height restrictions. The overall antenna structure heights employed by mobile stations in the...

2012-10-01

362

47 CFR 95.1315 - Antenna height restriction.  

Code of Federal Regulations, 2011 CFR

...Telecommunication 5 2011-10-01 2011-10-01 false Antenna height restriction. 95.1315 Section 95.1315 Telecommunication...Service (MURS) General Provisions § 95.1315 Antenna height restriction. The highest point of any MURS antenna...

2011-10-01

363

47 CFR 73.614 - Power and antenna height requirements.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 false Power and antenna height requirements. 73.614 Section 73...Stations § 73.614 Power and antenna height requirements. (a) Minimum requirements...horizontal direction. No minimum antenna height above average terrain is specified....

2013-10-01

364

47 CFR 22.1011 - Antenna height limitations.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false Antenna height limitations. 22.1011 Section 22.1011...Radiotelephone Service § 22.1011 Antenna height limitations. The antenna height of offshore stations must not exceed 61...

2012-10-01

365

47 CFR 22.1011 - Antenna height limitations.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Antenna height limitations. 22.1011 Section 22.1011...Radiotelephone Service § 22.1011 Antenna height limitations. The antenna height of offshore stations must not exceed 61...

2011-10-01

366

47 CFR 95.1315 - Antenna height restriction.  

Code of Federal Regulations, 2012 CFR

...Telecommunication 5 2012-10-01 2012-10-01 false Antenna height restriction. 95.1315 Section 95.1315 Telecommunication...Service (MURS) General Provisions § 95.1315 Antenna height restriction. The highest point of any MURS antenna...

2012-10-01

367

47 CFR 95.1315 - Antenna height restriction.  

Code of Federal Regulations, 2013 CFR

...Telecommunication 5 2013-10-01 2013-10-01 false Antenna height restriction. 95.1315 Section 95.1315 Telecommunication...Service (MURS) General Provisions § 95.1315 Antenna height restriction. The highest point of any MURS antenna...

2013-10-01

368

RCS of circular carbon NANO tube antenna array  

Microsoft Academic Search

A novel THz antenna structure, made of carbon nanotube arrays is suggested. Using CST MICROWAVE STUDIO (CST MWS), the capabilities of carbon nanotube terahertz (THz) antenna arrays have been simulated and this CNT antenna array has been fabricated.

H. Zareie; N. Davoudzadeh; M. Tafazoli; G. Fard; M. Hasan; Shamsoddin

2009-01-01

369

Conformal Fluid Dynamics  

E-print Network

We present a conformal theory of a dissipationless relativistic fluid in 2 space-time dimensions. The theory carries with it a representation of the algebra of 2-$D$ area-preserving diffeomorphisms in the target space of the complex scalar potentials. A complete canonical description is given, and the central charge of the current algebra is calculated. The passage to the quantum theory is discussed in some detail; as a result of operator ordering problems, full quantization at the level of the fields is as yet an open problem.

P. D. Jarvis; J. W. van Holten

2005-01-28

370

A microstrip array antenna with omnidirectional pattern fed by CPW  

Microsoft Academic Search

Colinear array antennas constructed from coaxial elements such as sleeve dipoles or patch antennas using parasitic cylinders are employed as omnidirectional antennas in mobile communication. In microcellular and wireless LAN systems, simple, small-size, and low-cost antennas for base stations are desired. The paper proposes a base station antenna that satisfies these requirements. The proposed antenna configuration is a back-to-back narrow-width

Hisao Iwasaki; Komukai Toshiba-cho

1996-01-01

371

Beam-steerable flat-panel reflector antenna  

Microsoft Academic Search

Many space applications require a high-gain antenna that can be easily deployable in space. Currently, the most common high-gain antenna for space-borne applications is an umbrella-type reflector antenna that can be folded while being lifted into Earth orbit. We propose a different type of high-gain antenna for easy space deployment. The proposed antenna is similar to reflector antennas except the

Choon Sae Lee; Chanam Lee; F. A. Miranda

2005-01-01

372

Sierpi?ski fractal plasmonic antenna: a fractal abstraction of the plasmonic bowtie antenna.  

PubMed

A new class of bowtie antennas with Sierpi?ski fractal features is proposed for sensing molecular vibration modes in the near- to mid-infrared. These antennas offer a compact device footprint and an enhanced confinement factor compared to a bowtie antenna. Through extensive simulations, it is shown that these characteristics are related to the ability of this fractal geometry to become polarized. Simulation results demonstrate that these antennas may be tuned between 700 nm ? ? ? 3.4 µm and that electric field enhancement by 56 is possible at the center of the antenna gap. PMID:21643300

Sederberg, Shawn; Elezzabi, A Y

2011-05-23

373

The Intelsat 4 antenna positioner  

NASA Technical Reports Server (NTRS)

The Intelsat 4 communications satellite has two spot beam antennas which are pointed to selected land masses by gimbaled positioners. The positioners employ drive motors with electromagnetic brakes and jackscrews that are self-caging during the launch. The positioner uses dry lubricants for ball bearings, spur gears, screw and nut, and various journal bearings. A coefficient of friction of approximately 0.05 was demonstrated in vacuum operation. Success of the positioner was demonstrated on the first Intelsat 4 placed in orbit in January 1971. The developmental problems that were encountered and their solutions are discussed.

Glassow, F. A.

1972-01-01

374

Interleaved arrays antenna technology development  

NASA Technical Reports Server (NTRS)

Phase one and two of a program to further develop and investigate advanced graphite epoxy waveguides, radiators, and components with application to space antennas are discussed. The objective of the two phases were to demonstrate mechanical integrity of a small panel of radiators and parts procured under a previous contract and to develop alternate designs and applications of the technology. Most of the emphasis was on the assembly and test of a 5 x 5 element module. This effort was supported by evaluation of adhesives and waveguide joint configurations. The evaluation and final assembly considered not only mechanical performance but also producibility in large scale.

1986-01-01

375

Optimum optical limited scan antenna  

NASA Astrophysics Data System (ADS)

An optical limited scan antenna system is considered for applications such as spot coverage of a small portion of the earth from a satellite. The optimum criterion relating aperture efficiency, number of control elements, and angular coverage is revisited briefly. The optical scheme advocated utilizes a bootlace aperture lens, a generalized Luneberg lens focused to the near field, and a small array of active elements. The operation of the system is described first in terms of geometrical optics and elementary diffraction principles. Numerical computations for a case of practical interest verify the expectation of near optimum performance.

Dufort, E. C.

1986-09-01

376

Antenna analysis using neural networks  

NASA Technical Reports Server (NTRS)

Conventional computing schemes have long been used to analyze problems in electromagnetics (EM). The vast majority of EM applications require computationally intensive algorithms involving numerical integration and solutions to large systems of equations. The feasibility of using neural network computing algorithms for antenna analysis is investigated. The ultimate goal is to use a trained neural network algorithm to reduce the computational demands of existing reflector surface error compensation techniques. Neural networks are computational algorithms based on neurobiological systems. Neural nets consist of massively parallel interconnected nonlinear computational elements. They are often employed in pattern recognition and image processing problems. Recently, neural network analysis has been applied in the electromagnetics area for the design of frequency selective surfaces and beam forming networks. The backpropagation training algorithm was employed to simulate classical antenna array synthesis techniques. The Woodward-Lawson (W-L) and Dolph-Chebyshev (D-C) array pattern synthesis techniques were used to train the neural network. The inputs to the network were samples of the desired synthesis pattern. The outputs are the array element excitations required to synthesize the desired pattern. Once trained, the network is used to simulate the W-L or D-C techniques. Various sector patterns and cosecant-type patterns (27 total) generated using W-L synthesis were used to train the network. Desired pattern samples were then fed to the neural network. The outputs of the network were the simulated W-L excitations. A 20 element linear array was used. There were 41 input pattern samples with 40 output excitations (20 real parts, 20 imaginary). A comparison between the simulated and actual W-L techniques is shown for a triangular-shaped pattern. Dolph-Chebyshev is a different class of synthesis technique in that D-C is used for side lobe control as opposed to pattern shaping. The interesting thing about D-C synthesis is that the side lobes have the same amplitude. Five-element arrays were used. Again, 41 pattern samples were used for the input. Nine actual D-C patterns ranging from -10 dB to -30 dB side lobe levels were used to train the network. A comparison between simulated and actual D-C techniques for a pattern with -22 dB side lobe level is shown. The goal for this research was to evaluate the performance of neural network computing with antennas. Future applications will employ the backpropagation training algorithm to drastically reduce the computational complexity involved in performing EM compensation for surface errors in large space reflector antennas.

Smith, William T.

1992-01-01

377

Design and development of novel fractal antennas for wireless applications; -.  

E-print Network

??The emerging wireless standards are imposing more and more newlineperformance constraints on antenna size efficiency frequency of operation newlineand reconfigurablity This has motivated antenna researchers… (more)

Manimegalai, B

2014-01-01

378

Modeling active GPCR conformations.  

PubMed

The most significant advance in modeling GPCR active states has been the ?(2)-adrenergic receptor-Gs complex as this essentially transforms active-state modeling into homology modeling. Various different molecular dynamics-based approaches for modeling active states are presented, and a number of key applications discussed. These simulations have given insights into the activation pathway, conformational changes, dimerization, hydration, the ionic lock, ligand binding, protonation, and sodium binding. Crystallography and simulations have shown that the presence of agonist alone is unlikely to be sufficient to form the active state and that restraints applied to the G protein-binding region are required. The role of various microswitches in activation is discussed, including the controversial rotamer toggle switch. The importance of explicitly simulating experimental molecular probes to understand activation is highlighted, along with the need to ensure that such molecules are well parameterized. Approaches to loop modeling are discussed. We argue that the role of successful virtual screening against active models should not be overestimated as the main conformational changes on activation occur in the intracellular region. PMID:23374178

Taddese, Bruck; Simpson, Lisa M; Wall, Ian D; Blaney, Frank E; Reynolds, Christopher A

2013-01-01

379

Antenna Allocation in MIMO Radar with Widely Separated Antennas for Multi-Target Detection.  

PubMed

In this paper, we explore a new resource called multi-target diversity to optimize the performance of multiple input multiple output (MIMO) radar with widely separated antennas for detecting multiple targets. In particular, we allocate antennas of the MIMO radar to probe different targets simultaneously in a flexible manner based on the performance metric of relative entropy. Two antenna allocation schemes are proposed. In the first scheme, each antenna is allocated to illuminate a proper target over the entire illumination time, so that the detection performance of each target is guaranteed. The problem is formulated as a minimum makespan scheduling problem in the combinatorial optimization framework. Antenna allocation is implemented through a branch-and-bound algorithm and an enhanced factor 2 algorithm. In the second scheme, called antenna-time allocation, each antenna is allocated to illuminate different targets with different illumination time. Both antenna allocation and time allocation are optimized based on illumination probabilities. Over a large range of transmitted power, target fluctuations and target numbers, both of the proposed antenna allocation schemes outperform the scheme without antenna allocation. Moreover, the antenna-time allocation scheme achieves a more robust detection performance than branch-and-bound algorithm and the enhanced factor 2 algorithm when the target number changes. PMID:25350505

Gao, Hao; Wang, Jian; Jiang, Chunxiao; Zhang, Xudong

2014-01-01

380

Structures for remotely deployable precision antennas  

Microsoft Academic Search

Future space missions such as the Earth Science Geostationary Platform (ESGP) will require highly accurate antennas with apertures that cannot be launched fully formed. The operational orbits are often inaccessible to manned flight and will involve expendable launch vehicles such as the Delta or Titan. There is therefore a need for completely deployable antenna reflectors of large size capable of

J. M. Hedgepeth

1989-01-01

381

Structures for remotely deployable precision antennas  

NASA Astrophysics Data System (ADS)

Future space missions such as the Earth Science Geostationary Platform (ESGP) will require highly accurate antennas with apertures that cannot be launched fully formed. The operational orbits are often inaccessible to manned flight and will involve expendable launch vehicles such as the Delta or Titan. There is therefore a need for completely deployable antenna reflectors of large size capable of efficiently handling millimeter wave electromagnetic radiation. The parameters for the type of mission are illustrated. The logarithmic plot of frequency versus aperture diameter shows the regions of interest for a large variety of space antenna applications, ranging from a 1500-meter-diameter radio telescope for low frequencies to a 20-meter-diameter infrared telescope. For the ESGP, a major application is the microwave radiometry at high frequencies for atmospheric sounding. Almost all existing large antenna reflectors for space employ a mesh-type reflecting surface. Examples are shown and discussed which deal with the various structural concepts for mesh antennas. Fortunately, those concepts are appropriate for creating the very large apertures required at the lower frequencies for good resolution. The emphasis is on the structural concepts and technologies that are appropriate to fully automated deployment of dish-type antennas with solid reflector surfaces. First the structural requirements are discussed. Existing concepts for fully deployable antennas are then described and assessed relative to the requirements. Finally, several analyses are presented that evaluate the effects of beam steering and segmented reflector design on the accuracy of the antenna.

Hedgepeth, J. M.

1989-07-01

382

DESIGN CONSIDERATIONS FOR INTEGRATED MOBILE PHONE ANTENNAS  

Microsoft Academic Search

In this paper some of these relations will be discussed. Based on these design guidelines a concept for a GShUDCSPCS antenna suitable for the integration into a mobile will be resented. The investigation is carried out using EMPIRE which IS a commercial FDTD software from IMST GmbH. Interaction of the antenna with the board

D. Manteuffel; A. Bahr; D. Heberling; I. Wolff

2009-01-01

383

Plasmonic Laser Antennas and Related Devices  

Microsoft Academic Search

This paper reviews recent work on device applications of optical antennas. Localized surface plasmon resonances of gold nanorod antennas resting on a silica glass substrate were modeled by finite difference time-domain simulations. A single gold nanorod of length 150 or 550 nm resonantly generates enhanced near fields when illuminated with light of 830 nm wavelength. A pair of these nanorods

Ertugrul Cubukcu; Nanfang Yu; E. J. Smythe; L. Diehl; K. B. Crozier; Federico Capasso

2008-01-01

384

Scattered and absorbed powers in receiving antennas  

Microsoft Academic Search

This paper discusses the amount of power, which is scattered and absorbed by a receiving antenna and in particular, whether an antenna can absorb the entire power incident upon it. The absorbed and scattered power from dipole arrays in either free space, or over ground plane is considered. By defining a suitable \\

David Pozar

2004-01-01

385

Microstrip antennas and arrays on chiral substrates  

Microsoft Academic Search

Results are presented for isolated microstrip antennas and infinite arrays of microstrip antennas printed on chiral substrates, computed from full-wave spectral domain moment method solutions. Data for resonant length, impedance, directivity, efficiency, cross-polarization level, and scan performance are compared to results obtained for a dielectric substrate of the same thickness and permittivity. It is concluded that, from the point of

D. M. Pozar

1992-01-01

386

Antenna bias rigging for performance objective  

NASA Technical Reports Server (NTRS)

An optimum bias rigging for a paraboloidal antenna can be used to minimize the expected average mean-square half-pathlength surface deviations. Statistics of deep space planetary missions are employed to develop weighting factors for antenna elevation angles during these missions. A procedure is shown to compute the optimum rigging angle from these weights.

Levy, R.

1977-01-01

387

A planar log-periodic antenna  

Microsoft Academic Search

A planar log-periodic antenna structure that has radiation characteristics similar to those of a half-wave dipole has been found. The bandwidth can be as large as desired, and antennas can be easily fabricated by using printed circuit techniques. When fed with a suitable balun, VSWR's lower than 1.8:1 can be obtained over a wide-frequency band.

K. Keen

1974-01-01

388

Mutual coupling between log-periodic antennas  

Microsoft Academic Search

Numerical techniques are used for the analysis of mutual coupling in arrays of log-periodic dipole antennas. The analysis is formulated in terms of impedance and admittance matrices for the dipole and transmission line networks. Approximations are made to allow the solution for moderately sized arrays to be practical with the existing generation of computers. Antenna patterns for the array are

R. Kyle

1970-01-01

389

Stagger tuned microstrip log-periodic antenna  

Microsoft Academic Search

Log-periodic dipole antennas (LPDA) have been extensively used since 1960 when their properties were described by Isbell, whose work was followed by the detailed analysis of Carrel (1961). Progress in microwave integrated circuits in the last decade has created a demand for compact antennas, along with the requirement that the systems have a large bandwidth. The approach for broadband configuration

Rajesh Kakkar; Girish Kumar

1996-01-01

390

Antenna design using Transformation Electromagnetics (TEM)  

Microsoft Academic Search

We present two different points of approaches to a class of antenna designs, based on two variations of the Transformation Electromagnetics (T-EM) approach, both of which have been introduced recently in the literature. The first of these addresses the antenna and absorber design problems from the Transformation Optics viewpoint, while the second looks at the same problem from a Field

Raj Mittra; King Fahd

2011-01-01

391

Antenna performance measurements using wireless sensor networks  

Microsoft Academic Search

In this paper, we present the results of an experimental test methodology that was used to characterize the performance of various test antennas (commercially available and developed in-house) within a wireless sensor network node. The test method employed measures the relative performance of a number of test antennas when incorporated within a wireless sensor network node in an open-field test

John Buckley; Kevin Aherne; B. O'Flynn; J. Barton; A. Murphy; C. O'Mathuna

2006-01-01

392

Antenna systems for mobile satellite applications  

Microsoft Academic Search

In the beginning of radio development, mobile communication systems were conceived for the transmission and receiving of telegraphy and telephony signals via mobile antenna at first from ships, and then from cars, trains and aircraft. The consideration of antenna transmission is inevitable, especially in Global Mobile Satellite Communications (GMSC), where their propagation characteristics are much affected by different and changeable

S. D. Ilcev

2009-01-01

393

Smart radome improves reflector antenna directivity  

Microsoft Academic Search

To ensure protection from dust, wind, rain and snow, reflector antennas are covered with spherical dielectric radomes. However, normally it is considered that the presence of the radome in the near zone of the reflector is a negative factor in the electromagnetic sense. The antenna performance suffers: the main beam is typically distorted, and the sidelobe level increases and the

A. Altintas; V. Yurchenko; Alexander Nosich

1997-01-01

394

Antenna arrays technologies for advanced wireless systems  

Microsoft Academic Search

Phased array antennas have and will continue to be a critically important component in the development of future wireless systems with applications in communications, radar, and satellite technologies. In spite of the significant advances in the design of modern phased array antennas, there continue to be significant and growing need for developing high performance systems that are also low cost

Magdy F. Iskander; Wayne Kim; Jodie Bell; Nuri Celik; Zhengqing Yun; Hyoung-sun Youn

2009-01-01

395

Optimum Current Distributions on Vertical Antennas  

Microsoft Academic Search

The theoretical optimum current distribution on a vertical antenna of given length is defined as that current distribution giving the maximum possible field strength on the horizon for a given power output. The problem of determining such distributions is set up as a problem in the calculus of variations, and solution functions are derived for antennas varying in length from

G. A. Miller

1943-01-01

396

Wideband Circularly Polarized Vertical Patch Antenna  

Microsoft Academic Search

A compact circularly polarized (CP) vertical patch antenna is presented that employs a microstrip to slot-line transition for a wideband operation. The antenna is composed of two vertical patches, which are shaped as helix to obtain a broadband CP performance. The loop structure and the vertical overlap configuration lead to significant size reduction as much as 48% when compared to

Ze-Hai Wu; Edward Kai-Ning Yung

2008-01-01

397

Rectangular Microstrip Antenna with Slot Embedded Geometry  

NASA Astrophysics Data System (ADS)

In this paper, a novel design that improves the performance of conventional rectangular microstrip antenna is discussed. Design adopts basic techniques such as probe feeding technique with rectangular inverted patch structure as superstrate, air filled dielectric medium as substrate and slot embedded patch. Prototype of the proposed antenna has been fabricated and various antenna performance parameters such as impedance bandwidth, return loss, radiation pattern and antenna gain are considered for Electromagnetic-study. The antennas are designed for the wireless application operating in the frequency range of 3.3 GHz to 3.6 GHz, and UK based fixed satellite service application (3 GHz to 4 GHz), and are named as single inverted patch conventional rectangular microstrip antenna (SIP-CRMSA) and slots embedded inverted patch rectangular microstrip antenna (SEIP-RMSA), respectively. Measurement outcomes for SEIP-RMSA1 and SEIP-RMSA2 showed the satisfactory performance with an achievable impedance bandwidth of 260 MHz (7 %) and 250 MHz (6.72 %), with return loss (RL) of -11.06 dB and -17.98 dB, achieved gain of 8.17 dB and 5.17 dB with 10% and 8% size reduction in comparison with the conventional patch antenna.

Ambresh, P. A.; Hadalgi, P. M.; Hunagund, P. V.; Sujata, A. A.

2014-09-01

398

Integrated SIW filter and microstrip antenna  

Microsoft Academic Search

A novel design of integrated Substrate Integrated Waveguide (SIW) filter and microstrip antenna is proposed. In the first step, the methodology consists of synthesising the subsystems combining a filter and an antenna using lumped lowpass prototype networks. To realise the concept, the filtering and radiating functions are combined using multilayer technology on a printed circuit board (PCB). The design is

Hizamel M. Hizan; Ian C. Hunter; Alaa I. Abunjaileh

2010-01-01

399

Calculating Electromagnetic Fields Of A Loop Antenna  

NASA Technical Reports Server (NTRS)

Approximate field values computed rapidly. MODEL computer program developed to calculate electromagnetic field values of large loop antenna at all distances to observation point. Antenna assumed to be in x-y plane with center at origin of coordinate system. Calculates field values in both rectangular and spherical components. Also solves for wave impedance. Written in MicroSoft FORTRAN 77.

Schieffer, Mitchell B.

1987-01-01

400

Microwave holographic metrology of large reflector antennas  

Microsoft Academic Search

A microwave holographic technique for the determination of amplitude and phase of the principal and cross-polarized aperture fields of large reflector antennas is described. The hologram formation process utilizes the elevation over azimuth scanning system normally associated with these antennas, and, in this respect, appears to be unique among other proposed methods of field probing. The present work describes the

J. Bennett; A. Anderson; P. McInnes; A. Whitaker

1976-01-01

401

Low-cost printed collinear array antenna  

Microsoft Academic Search

This paper presents the design and antenna-prototype measurements of a low-cost antenna for DECT and LMDS system base stations (3400 to 3600 MHz). The specified pattern must be omnidirectional in the horizontal plane, having a maximum at the horizon. To produce this pattern, a linear array of printed patches, placed on both sides of a planar feeding structure, is designed

M. Sierra-Perez; F. L. Heras-Andres; J. A. G. de Lope

2001-01-01

402

Helmet-mounted smart array antenna  

Microsoft Academic Search

With the advent of wireless telecommunications, efforts to develop personnel-carried personal communications equipment are being very vigorously pursued. For the personal antenna needed in this application, the area around the skull is a prime location and the future of a head-mount antenna has been envisioned. For firefighters, forest rangers, border patrols, and military personnel, the helmet provides a natural platform

J. J. H. Wang; J. K. Tillery; K. E. Bohannan; G. T. Thompson

1997-01-01

403

Antennas For Receiving Signals Broadcast Via Satellites  

NASA Technical Reports Server (NTRS)

Four different antennas designed for use in receiving radio AM and FM signals broadcast via Earth-orbiting satellites at carrier frequency of 2.05 GHz in right-hand circular polarization. Antennas small, lightweight, inexpensive units with low-to-medium-gain, quasi-omnidirectional radiation patterns. Designed for outdoor and indoor uses.

Wu, Te-Kao; Huang, John

1996-01-01

404

Forthcoming Publications: Science, PRL Optical Antennas  

E-print Network

, 115433 (2003). #12;Spectra Quin Yuo Chin.Phys White-light supercontinuum generation in normally Generation of dipole antennas with "optical" dimensions glass cover slip ITO (10nm) gold (40nm) e-beam lithography gold patches 1000 x 500 nm2 (FIB: Stephan Meier, EMPA Dübendorf) #12;Generation of dipole antennas

405

A Self-Affine Fractal Multiband Antenna  

Microsoft Academic Search

The design of a new fractal multiband antenna based on the self-affinity property is presented in this letter. Experimental return loss has been compared with that obtained using the method of moments and the fractal antenna is found to possess predictable multiband characteristics

Sachendra N. Sinha; Manish Jain

2007-01-01

406

Dual-band Sierpinski fractal monopole antenna  

Microsoft Academic Search

A new top-loaded reduced-sized dual-band (1.9 GHz and 3.5 GHz) monopole antenna for wireless communications is presented. The antenna provides better than -15 dB input return loss and keeps the same radiation pattern over both bands. In addition, a low-profile performance is achieved

J. Soler; J. Romeu

2000-01-01

407

Experiences on tuned multiband fractal antennas  

Microsoft Academic Search

This paper presents a study of reconfigurable fractal antennas employing capacitance variations in the fractal structure. The input characteristics of this kind of antenna can be made frequency-agile using capacitive elements in a manner that partially modify an iteration or a group of iterations. By modifying that capacitance, a wideband via tuning could be achieved.

Carlos Redondo Arrieta; L. de Haro

2005-01-01

408

Low cost antennas for MSAT vehicular applications  

NASA Technical Reports Server (NTRS)

For Mobile MSAT applications a number of vehicular antennas have been developed that meet the program requirements. They are, however, costly to manufacture. Two antenna candidates are described here that provide adequate gain in the coverage zone and are also lower cost. One is the mast antenna that uses three or four element arrays of aquadrifilar helices. It generates omnidirectional pattern in azimuth and its beam is scanned in elevation. The second unit is a planar spiral antenna; it generates directional beams by a summation of the azimuthal modes. A variation of this antenna uses conical spirals to fulfill the same task. In both cases beam scanning is achieved by means of electronic switches rather than phase shifters, thus resulting in simpler configurations.

Shafai, L.; Barakat, M.

1993-01-01

409

Antenna organization in green photosynthetic bacteria  

SciTech Connect

This project is concerned with the structure and function of the unique antenna system found in the green photosynthetic bacteria. The antenna system in these organisms is contained within a vesicle known as a chlorosome, which is attached to the cytoplasmic side of the cell membrane. Additional antenna pigments and reaction centers are contained in integral membrane proteins. Energy absorbed by the bacteriochlorophyll c (BChl c) pigments in the chlorosome is transferred via a baseplate'' array of BChl a antenna pigments into the membrane and to the reaction center. A schematic model of chlorosome structure is shown. This project is aimed at increasing our understanding of the organization of the pigments in the chlorosome and how the antenna system functions.

Blankenship, R.E.

1987-01-01

410

Omnidirectional, circularly polarized, cylindrical microstrip antenna  

NASA Technical Reports Server (NTRS)

A microstrip cylindrical antenna comprised of two concentric subelements on a ground cylinder, a vertically polarized (E-field parallel to the axis of the antenna cylinder) subelement on the inside and a horizontally polarized (E-field perpendicular to the axis) subelement on the outside. The vertical subelement is a wraparound microstrip radiator. A Y-shaped microstrip patch configuration is used for the horizontally polarized radiator that is wrapped 1.5 times to provide radiating edges on opposite sides of the cylindrical antenna for improved azimuthal pattern uniformity. When these subelements are so fed that their far fields are equal in amplitude and phased 90.degree. from each other, a circularly polarized EM wave results. By stacking a plurality of like antenna elements on the ground cylinder, a linear phased array antenna is provided that can be beam steered to the desired elevation angle.

Stanton, Philip H. (Inventor)

1985-01-01

411

Logarithmic Conformal Field Theory Through Nilpotent Conformal Dimensions  

E-print Network

We study logarithmic conformal field theories (LCFTs) through the introduction of nilpotent conformal weights. Using this device, we derive the properties of LCFT's such as the transformation laws, singular vectors and the structure of correlation functions. We discuss the emergence of an extra energy momentum tensor, which is the logarithmic partner of the energy momentum tensor.

Moghimi-Araghi, S; Saadat, M

2001-01-01

412

Replacement between conformity and counter-conformity in consumption decisions.  

PubMed

This study assessed, in a Chinese context, how self-esteem interacts with perceived similarity and uniqueness to yield cognitive dissonance, and whether the dissonance leads to self-reported conformity or counter-conformity behavior. Participants were 408 respondents from 4 major Chinese cities (M age = 33.0 yr., SD = 4.3; 48% men). Self-perceptions of uniqueness, similarity, cognitive dissonance, self-esteem and need to behave in conformity or counter-conformity were measured. A theoretical model was assessed in four situations, relating the ratings of self-esteem and perceived similarity/uniqueness to the way other people at a wedding were dressed, and the resultant cognitive dissonance and conformity/ counter-conformity behavior. Regardless of high or low self-esteem, all participants reported cognitive dissonance when they were told that they were dressed extremely similarly to or extremely differently from the other people attending the wedding. However, the conforming/counter-conforming strategies used by participants to resolve the cognitive dissonance differed. When encountering dissonance induced by the perceived extreme uniqueness of dress, participants with low self-esteem tended to say they would dress next time so as to conform with the way others were dressed, while those with high self-esteem indicated they would continue their counter-conformity in attire. When encountering dissonance induced by the perceived extreme similarity to others, both those with high and low self-esteem tended to say they would dress in an unorthodox manner to surprise other people in the future. PMID:23654033

Chou, Ting-Jui; Chang, En-Chung; Dai, Qi; Wong, Veronica

2013-02-01

413

Beamforming of Joint Polarization-Space Matched Filtering for Conformal Array  

PubMed Central

Due to the polarization mismatch of the antenna, the received signal suffers from energy loss. The conventional beamforming algorithms could not be applied to the conformal array because of the varying curvature. In order to overcome the energy loss of the received signal, a novel joint polarization-space matched filtering algorithm for cylindrical conformal array is proposed. First, the snapshot data model of the conformal polarization sensitive array is analyzed. Second, the analytical expression of polarization sensitive array beamforming is derived. Linearly constrained minimum variance (LCMV) beamforming technique is facilitated for the cylindrical conformal array. Third, the idea of joint polarization-space matched filtering is presented, and the principle of joint polarization-space matched filtering is discussed in detail. Theoretical analysis and computer simulation results verify that the conformal polarization sensitive array is more robust than the ordinary conformal array. The proposed algorithm can improve the performance when signal and interference are too close. It can enhance the signal-to-noise ratio (SNR) by adjusting the polarization of the elements of the conformal array, which matches the polarization of the incident signal. PMID:24501582

Liu, Lutao; Jiang, Yilin; Tian, Zuoxi

2013-01-01

414

Piecewise-Planar Parabolic Reflectarray Antenna  

NASA Technical Reports Server (NTRS)

The figure shows a dual-beam, dualpolarization Ku-band antenna, the reflector of which comprises an assembly of small reflectarrays arranged in a piecewise- planar approximation of a parabolic reflector surface. The specific antenna design is intended to satisfy requirements for a wide-swath spaceborne radar altimeter, but the general principle of piecewise-planar reflectarray approximation of a parabolic reflector also offers advantages for other applications in which there are requirements for wideswath antennas that can be stowed compactly and that perform equally in both horizontal and vertical polarizations. The main advantages of using flat (e.g., reflectarray) antenna surfaces instead of paraboloidal or parabolic surfaces is that the flat ones can be fabricated at lower cost and can be stowed and deployed more easily. Heretofore, reflectarray antennas have typically been designed to reside on single planar surfaces and to emulate the focusing properties of, variously, paraboloidal (dish) or parabolic antennas. In the present case, one approximates the nominal parabolic shape by concatenating several flat pieces, while still exploiting the principles of the planar reflectarray for each piece. Prior to the conception of the present design, the use of a single large reflectarray was considered, but then abandoned when it was found that the directional and gain properties of the antenna would be noticeably different for the horizontal and vertical polarizations.

Hodges, Richard; Zawadzki, Mark

2009-01-01

415

Antenna Miniaturization Using Koch Snowflake Fractal Geometry  

NASA Astrophysics Data System (ADS)

The Wireless Industry is witnessing an volatile emergence today in present era. Also requires the performance over several frequency bands or are reconfigurable as the demands on the system changes. This Paper Presents Rectangular, Koch Fractal Patch Antennas on Single and Multilayer Substrate With and Without Air-Gap using Advanced Design System Simulator (ADS). Fractal Antenna provides Miniaturization over conventional microstrip Antennas. The Antennas Have Been Designed on FR4 substrate with ? = 4.2, h = 1.53 and the initial Dimension of the simple Rectangular Patch is 36.08 * 29.6 mm. The experimental Resonant Frequencies of the Fractal Patch with 1st, 2nd & 3rd are observed 2.22, 2.14 & 2.02 GHz Respectively in comparison to Rectangular Patch with 2.43 GHz. The reduced Impedance bandwidth of the Fractal Patch has been improved by designing the patch over multilayer substrate with varying Air-gap between two Substrate. As we increase the air- gap between the two substrate layer further enhancement in impedance bandwidth of Fractal antenna has been Obtained. The Radiation pattern of Koch Fractal antenna is as similar to rectangular patch antenna but with better H-plane Cross Polarization for fractal patch. The all simulated Results are in close Agreement with experimental Results.

Minal, Dhama, Nitin

2010-11-01

416

Conformal Transformations and Space Travel  

Microsoft Academic Search

Conformal transformations are applied to the motion of a space ship experiencing a constant acceleration. The role of proper time is interpreted in terms of atomic periods, and the relationship between the conformal transformations and the general theory of relativity is clarified.

Suraj N. Gupta

1961-01-01

417

Counselor Identity: Conformity or Distinction?  

ERIC Educational Resources Information Center

The authors explore 3 debates in other disciplines similar to counseling's identity debate in order to learn about common themes and outcomes. Conformity, distinction, and cohesion emerged as common themes. They conclude that counselors should retain their distinctive, humanistic approach rather than conforming to the dominant, medical approach.

McLaughlin, Jerry E.; Boettcher, Kathryn

2009-01-01

418

Implanted antennas inside a human body: simulations, designs, and characterizations  

Microsoft Academic Search

Antennas implanted in a human body are largely applicable to hyperthermia and biotelemetry. To make practical use of antennas inside a human body, resonance characteristics of the implanted antennas and their radiation signature outside the body must be evaluated through numerical analysis and measurement setup. Most importantly, the antenna must be designed with an in-depth consideration given to its surrounding

Jaehoon Kim; Yahya Rahmat-Samii

2004-01-01

419

Characteristics of the wire biconical antenna used for EMC measurements  

Microsoft Academic Search

The characteristics of a wire biconical antenna that determine its antenna factor were computed by using the method of moments code NEC-2. A fairly extensive validation exercise was conducted from which a suitable computer model was derived. The input impedance, gain, and radiation patterns of the antenna were computed for special cases where the biconical antenna is used above a

Brian A. Austin; Andre P. C. Fourie

1991-01-01

420

Compact Helical Ring Antenna for Iridium Communication C. Morlaas1  

E-print Network

Compact Helical Ring Antenna for Iridium Communication on UAV C. Morlaas1 , A. Chabory1 , B. Souny1 (Fly2Corsica project), the ENAC UAV team plans to use the Iridium satellite service. To render circular polarization antenna, Iridium antenna, helical ring antenna. 1. Introduction The ENAC UAV team

Paris-Sud XI, Université de

421

General view looking northnorthwest at antenna array. Troposhperic scatter communications ...  

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

General view looking north-northwest at antenna array. Troposhperic scatter communications antennas are seen at far left, transmitter building is in center, antenna array at right - Over-the-Horizon Backscatter Radar Network, Moscow Radar Site Transmit Sector One Antenna Array, At the end of Steam Road, Moscow, Somerset County, ME

422

Design and Characterization of Purely Textile Patch Antennas  

Microsoft Academic Search

In this paper, we present four purely textile patch antennas for Bluetooth applications in wearable computing using the frequency range around 2.4 GHz. The textile materials and the planar antenna shape provide a smooth integration into clothing while preserving the typical properties of textiles. The four antennas differ in the deployed materials and in the antenna polarization, but all of

Ivo Locher; Maciej Klemm; Tünde Kirstein; Gerhard Tröster

2006-01-01

423

A novel circularly polarized textile antenna for wearable applications  

Microsoft Academic Search

A novel circularly polarized (CP) textile patch antenna is presented in this paper. To our knowledge, it is the first textile antenna with circular polarization and for the first time, we show that more sophisticated design methods are also applicable to flexible textile antennas. The antenna uses a single inset microstrip feed-line. To achieve proper CP operation, truncated corners along

Maciej Klemm; Ivo Locher; Gerhard Tröster

2004-01-01

424

RFID tag antennas with stable impedance to mounted material  

Microsoft Academic Search

The following study presents two UHF RFID tag antennas for the identification of mass retailing produces. The antenna is composed of two elements, a planar dipole based antenna matched with a small inductive coil. These tags have the particularity to have stable performances to mounted material. Simulations studied the performance of tag antennas depending on the permittivity and thickness of

T. Deleruyelle; P. Pannier; J. Alarcon; M. Egels; E. Bergeret

2010-01-01

425

Dual-band operation vertical patch antenna for WLAN applications  

Microsoft Academic Search

In this paper, a novel design of the dual-band operation vertical patch antenna are proposed. The structure of proposed antenna consists of two vertical patches which is different from the architecture of traditional planar antennas. By utilizing the broadband feeding mechanism, the antenna bandwidth is significantly increased. And, two separate wide resonant modes for WLAN applications can be generated by

Kuo-Chien Chao; Fa-Shian Chang; Hong-Twu chen; Chia-Hung Lu; Yung-Tao Liu

2007-01-01

426

Radically new design of SAR satellite: short vertical antenna approach  

Microsoft Academic Search

The idea of this work is the use of a vertical antenna (antenna placed in the orbit plane) for a spaceborne radar. This surprising geometry is proven to work properly and to simplify the design of the instrument, particularly when it is associated with a short antenna length (<5 m, along speed vector). The number of antenna control points is

JEAN-PAUL AGUTTES

2001-01-01

427

Investigation of parameters of antenna settings for radioheliograph operation  

Microsoft Academic Search

Algorithms of calculation of the antenna settings and antenna patterns for RATAN-600 operation as a radioheliograph are considered in the paper. Results of modeling the number of panels in the antenna settings and the structure of the antenna patterns are presented.

G. B. Gelfreikh; L. V. Opeikina

2000-01-01

428

Efficient models for base station antennas for human exposure assessment  

Microsoft Academic Search

Two simple and accurate models for base-station (BS) panel antennas are proposed for human-exposure assessment. Panel antennas comprise an antenna array with low coupling between its unit cells. The proposed model is based on the superposition of shifted radiating field contributions in amplitude and phase of a unit cell of the panel antenna. In the first model, the electric field

Zwi Altman; Brigitte Begasse; Christian Dale; Andrzej Karwowski; Joe Wiart; Man-Fai Wong; Laroussi Gattoufi

2002-01-01

429

Circularly Polarized Transmitting Antenna For U. H. F  

Microsoft Academic Search

This paper describes a combined panel antenna with an aperture of about eight wavelengths The combined antenna consists of a zigzag antenna and two collinear arrays. This antenna can be used to radiate vertically polarized, horizontally polarized waves or both, When properly phased it can be used to transmit or receive circularly polarized waves,

Andrew Alford

1978-01-01

430

Multi band patch antenna on conjugate-omega slotted ground  

Microsoft Academic Search

A multi-band patch antenna on complementary conjugate omega ground is proposed. The proposed antenna utilizes complementary conjugate omega resonator (CCOR) in the ground plane altering the effective medium parameters of the substrate. The antenna features a multi frequency behavior (four operating bands) with similar gain. To characterize the performance of the CCOR loaded microstrip antenna, the metamaterial substrate has been

Sudhakar Sahu; Rabindra K. Mishra; D. R. Poddar

2010-01-01

431

An annular-ring reduced surface wave microstrip antenna  

Microsoft Academic Search

Previously, a class of microstrip antennas called reduced surface wave (RSW) antennas was introduced, which consists of antenna geometries that are variations of a circular patch design (Jackson et al. 1993). Although these RSW designs demonstrated good reduction in the surface-wave and lateral-wave excitation, one disadvantage of these designs is that the antenna radius is significantly larger than that of

Amit R. Mehrotra; David R. Jackson; Jeffery T. Williams; Stuart A. Long

1999-01-01

432

Fractal antenna with RF MEMS switches for multiple frequency applications  

Microsoft Academic Search

A new concept of combining RF MEMS switches with fractal antennas is presented. The idea is to connect several antenna configurations together using RF MEMS switches to cover several frequency bands. By using a 'smart combination' of fractal shaped antennas, wideband coverage can be achieved for satellite and wireless communications. Moreover, the same antennas can be used for phased array

D. Anagnostou; Majid Khodier; J. C. Lyke; C. G. Christodoulou

2002-01-01

433

A Novel Fractal Patch Antenna with Low RCS  

Microsoft Academic Search

The special space filling capability of Koch fractal is used in the Radar Cross Section (RCS) reduction of microstrip patch antenna. Compared with normal rectangular microstrip patch antenna, the resonance sides are designed in the shape of Koch fractal, while two Koch fractal shape slots are cut in the antenna. Based on the design, antenna prototypes were fabricated and tested,

G. Cui; Y. Liu; S. Gong

2007-01-01

434

Magnetic antenna using metallic glass  

NASA Technical Reports Server (NTRS)

A lightweight search-coil antenna or sensor assembly for detecting magnetic fields and including a multi-turn electromagnetic induction coil wound on a spool type coil form through which is inserted an elongated coil loading member comprised of metallic glass material wrapped around a dielectric rod. The dielectric rod consists of a plastic or a wooden dowel having a length which is relatively larger than its thickness so as to provide a large length-to-diameter ratio. A tri-axial configuration includes a housing in which is located three substantially identical mutually orthogonal electromagnetic induction coil assemblies of the type described above wherein each of the assemblies include an electromagnetic coil wound on a dielectric spool with an elongated metallic glass coil loading member projecting therethrough.

Desch, Michael D. (Inventor); Farrell, William M. (Inventor); Houser, Jeffrey G. (Inventor)

1996-01-01

435

Antenna beamforming using optical processing  

NASA Technical Reports Server (NTRS)

This work concerns itself with the analytical investigation into the feasibility of optical processor based beamforming for microwave array antennas. The primary focus is on systems utilizing the 20 and 30 GHz communications band and a transmit configuration exclusively to serve this band. A mathematical model is developed for computation of candidate design configurations. The model is capable of determination of the necessary design parameters required for both spatial aspects of the microwave footprint (beam) formation as well as transmitted signal quality. Computed example beams transmitted from geosynchronous orbit are presented to demonstrate network capabilities. A comprehensive device/component survey is also conducted in parallel to determine the feasibility of breadboarding a transmit processor. Recommendations are made for the configuration of such a processor and the components which would comprise such a network.

Anderson, L. P., Jr.; Boldissar, F.; Chang, D. C. D.

1987-01-01

436

Simulation of patch and slot antennas using FEM with prismatic elements and investigations of artificial absorber mesh termination schemes  

NASA Technical Reports Server (NTRS)

Year 1 progress can be characterized with four major achievements which are crucial toward the development of robust, easy to use antenna analysis code on doubly conformal platforms. (1) A new FEM code was developed using prismatic meshes. This code is based on a new edge based distorted prism and is particularly attractive for growing meshes associated with printed slot and patch antennas on doubly conformal platforms. It is anticipated that this technology will lead to interactive, simple to use codes for a large class of antenna geometries. Moreover, the codes can be expanded to include modeling of the circuit characteristics. An attached report describes the theory and validation of the new prismatic code using reference calculations and measured data collected at the NASA Langley facilities. The agreement between the measured and calculated data is impressive even for the coated patch configuration. (2) A scheme was developed for improved feed modeling in the context of FEM. A new approach based on the voltage continuity condition was devised and successfully tested in modeling coax cables and aperture fed antennas. An important aspect of this new feed modeling approach is the ability to completely separate the feed and antenna mesh regions. In this manner, different elements can be used in each of the regions leading to substantially improved accuracy and meshing simplicity. (3) A most important development this year has been the introduction of the perfectly matched interface (PMI) layer for truncating finite element meshes. So far the robust boundary integral method has been used for truncating the finite element meshes. However, this approach is not suitable for antennas on nonplanar platforms. The PMI layer is a lossy anisotropic absorber with zero reflection at its interface. (4) We were able to interface our antenna code FEMA_CYL (for antennas on cylindrical platforms) with a standard high frequency code. This interface was achieved by first generating equivalent magnetic currents across the antenna aperture using the FEM code. These currents were employed as the sources in the high frequency code.

Gong, J.; Ozdemir, T.; Volakis, J; Nurnberger, M.

1995-01-01

437

The logarithmic conformal field theories  

E-print Network

We study the correlation functions of logarithmic conformal field theories. First, assuming conformal invariance, we explicitly calculate two- and three- point functions. This calculation is done for the general case of more than one logarithmic field in a block, and more than one set of logarithmic fields. Then we show that one can regard the logarithmic field as a formal derivative of the ordinary field with respect to its conformal weight. This enables one to calculate any n-point function containing the logarithmic field in terms of ordinary n-point functions. At last, we calculate the OPE coefficients of a logarithmic conformal field theory, and show that these can be obtained from the corresponding coefficients of ordinary conformal theory by a simple derivation.

Tabar, M R R; Khorrami, M

1996-01-01

438

Radiation and scattering by cavity-backed antennas on a circular cylinder  

NASA Technical Reports Server (NTRS)

Conformal arrays are popular antennas for aircraft and missile platforms due to their inherent low weight and drag properties. However, to date there has been a dearth of rigorous analytical or numerical solutions to aid the designer. In fact, it has been common practice to use limited measurements and planar approximations in designing such non-planar antennas. The finite element-boundary integral method is extended to scattering and radiation by cavity-backed structures in an infinite, metallic cylinder. In particular, the formulation specifics such as weight functions, dyadic Green's function, implementation details, and particular difficulties inherent to cylindrical structures are discussed. Special care is taken to ensure that the resulting computer program has low memory demand and minimal computational requirements. Both scattering and radiation parameters are computed and validated as much as possible.

Kempel, Leo C.; Volakis, John L.

1993-01-01

439

Robustness of antenna-coupled distributed bolometers.  

PubMed

This Letter shows the effect of the geometrical and material properties of lead lines and connections on the robustness and reliability of optical antennas working as distributed bolometers. We analyze the operational limits of the biasing voltage using a mutiphysics finite element method. We demonstrate that, after evaluating the effect of the electromagnetic irradiance falling on the device, biasing voltage is the main limiting factor to maintain operative titanium optical antennas. Results have been experimentally verified by finding the biasing values needed to destroy optical antennas working as distributed bolometers. Structural damage has been identified from scanning electron microscopy images. PMID:24081052

Cuadrado, Alexander; Silva-López, Manuel; González, Francisco Javier; Alda, Javier

2013-10-01

440

Detection of electromagnetic waves using MEMS antennas  

SciTech Connect

We describe the design, fabrication and characterization of simple micromechanical structures that are capable of sensing static electric time varying electromagnetic fields. Time varying electric field sensing is usually achieved using an electromagnetic antenna and a receiver. However, these antenna-based approaches do not exhibit high sensitivity over a broad frequency (or wavelength) range. An important aspect of the present work is that, in contrast to traditional antennas, the dimensions of these micromechanical oscillators can be much smaller than the wavelength of the electromagnetic wave. We characterized the fabricated micromechanical oscillators by measuring their responses to time varying electric and electromagnetic fields.

Lavrik, Nickolay V [ORNL] [ORNL; Tobin, [Oak Ridge National Laboratory (ORNL)] [Oak Ridge National Laboratory (ORNL); Bowland, Landon T [ORNL] [ORNL

2011-01-01

441

Circuit models for Sierpinski gasket antennas  

E-print Network

A lumped-parameter impedor-oriented and a 2-port-network-oriented circuit models for the Sierpinski gasket prefractal antenna are presented. With the former, the voltage and current patterns give a detailed understanding of the electromagnetic fields' self-similar distribution throughout the antenna geometry; on the other hand model complexity exponentially increases with the prefractal iteration order. The latter "black-box" model only controls port-oriented global parameters which are the ones commonly used in antennas' circuit models and its complexity is independent of prefractal order. The "black-box" model is also shown to converge, at fractal limit, to a reciprocal triangular network.

Arrighetti, W; Gerosa, G

2005-01-01

442

Wireless communication capability of a reconfigurable plasma antenna  

SciTech Connect

A 30 cm long plasma column is excited by a surface wave, which acts as a plasma antenna. Using plasma properties (pattern formation/striations in plasmas) single plasma antenna can be transformed into array, helical, and spiral plasma antenna. Experiments are carried out to study the power patterns, directivity, and half power beam width of such different plasma antennas. Moreover, field properties of plasma and copper antenna are studied. Further, wireless communication and jamming capability of plasma antenna are tested. Findings of this study suggest that directivity and communication range can be increased by converting single plasma antenna in to array/helical/spiral plasma antenna. Field frequencies of plasma antenna determine the communication and jamming of radio frequency waves. Therefore, this study invokes applications of pattern formation or striations of plasmas in plasma antenna technology.

Kumar, Rajneesh [Institute for Plasma Research, Bhat, Gandhinagar - 382428 (India); Bora, Dhiraj [ITER Organisation, Cadarache-13108 (France)

2011-03-15

443

6d Conformal Matter  

E-print Network

A single M5-brane probing G, an ADE-type singularity, leads to a system which has G x G global symmetry and can be viewed as "bifundamental" (G,G) matter. For the A_N series, this leads to the usual notion of bifundamental matter. For the other cases it corresponds to a strongly interacting (1,0) superconformal system in six dimensions. Similarly, an ADE singularity intersecting the Horava-Witten wall leads to a superconformal matter system with E_8 x G global symmetry. Using the F-theory realization of these theories, we elucidate the Coulomb/tensor branch of (G,G') conformal matter. This leads to the notion of fractionalization of an M5-brane on an ADE singularity as well as fractionalization of the intersection point of the ADE singularity with the Horava-Witten wall. Partial Higgsing of these theories leads to new 6d SCFTs in the infrared, which we also characterize. This generalizes the class of (1,0) theories which can be perturbatively realized by suspended branes in IIA string theory. By reducing on a circle, we arrive at novel duals for 5d affine quiver theories. Introducing many M5-branes leads to large N gravity duals.

Michele Del Zotto; Jonathan J. Heckman; Alessandro Tomasiello; Cumrun Vafa

2014-07-23

444

Dynamics of protein conformations  

NASA Astrophysics Data System (ADS)

A novel theoretical methodology is introduced to identify dynamic structural domains and analyze local flexibility in proteins. The methodology employs a multiscale approach combining identification of essential collective coordinates based on the covariance analysis of molecular dynamics trajectories, construction of the Mori projection operator with these essential coordinates, and analysis of the corresponding generalized Langevin equations [M.Stepanova, Phys.Rev.E 76(2007)051918]. Because the approach employs a rigorous theory, the outcomes are physically transparent: the dynamic domains are associated with regions of relative rigidity in the protein, whereas off-domain regions are relatively soft. This also allows scoring the flexibility in the macromolecule with atomic-level resolution [N.Blinov, M.Berjanskii, D.S.Wishart, and M.Stepanova, Biochemistry, 48(2009)1488]. The applications include the domain coarse-graining and characterization of conformational stability in protein G and prion proteins. The results are compared with published NMR experiments. Potential applications for structural biology, bioinformatics, and drug design are discussed.

Stepanova, Maria

2010-10-01

445

Warped conformal field theory  

NASA Astrophysics Data System (ADS)

We study field theories in two spacetime dimensions invariant under a chiral scaling symmetry that acts only on right-movers. The local symmetries include one copy of the Virasoro algebra and a U(1) current algebra. This differs from the two-dimensional conformal group but in some respects is equally powerful in constraining the theory. In particular, the symmetries on a torus lead to modular covariance of the partition function, which is used to derive a universal formula for the asymptotic density of states. For an application we turn to the holographic description of black holes in quantum gravity, motivated by the fact that the symmetries in the near-horizon geometry of any extremal black hole are identical to those of a two-dimensional field theory with chiral scaling. We consider two examples: black holes in warped AdS3 in topologically massive gravity and in string theory. In both cases, the density of states in the two-dimensional field theory reproduces the Bekenstein-Hawking entropy of black holes in the gravity theory.

Detournay, Stéphane; Hartman, Thomas; Hofman, Diego M.

2012-12-01

446

Technique for Radiometer and Antenna Array Calibration with Two Antenna Noise Diodes  

NASA Technical Reports Server (NTRS)

This paper presents a new technique to calibrate a microwave radiometer and phased array antenna system. This calibration technique uses a radiated noise source in addition to an injected noise sources for calibration. The plane of reference for this calibration technique is the face of the antenna and therefore can effectively calibration the gain fluctuations in the active phased array antennas. This paper gives the mathematical formulation for the technique and discusses the improvements brought by the method over the existing calibration techniques.

Srinivasan, Karthik; Limaye, Ashutosh; Laymon, Charles; Meyer, Paul

2011-01-01

447

IEEE ANTENNAS AND WIRELESS PROPAGATION LETTERS, VOL. 6, 2007 25 A Compact Broadband Planar Antenna for GPS,  

E-print Network

is developed for global positioning system (GPS), DCS-1800, IMT-2000, and WLAN handsets. The planar antenna, global positioning system (GPS), mobile handset, planar antenna, WLAN. I. INTRODUCTION FOR an antenna that a linearly polarized antenna can be also used for a global positioning system (GPS) (1570­1580 MHz) receiver

Tentzeris, Manos

448

Microwave mode shifting antenna system for regenerating particulate filters  

DOEpatents

A regeneration system comprises a particulate matter (PM) filter including a microwave energy absorbing surface, and an antenna system comprising N antennas and an antenna driver module that sequentially drives the antenna system in a plurality of transverse modes of the antenna system to heat selected portions of the microwave absorbing surface to regenerate the PM filter, where N is an integer greater than one. The transverse modes may include transverse electric (TE) and/or transverse magnetic (TM) modes.

Gonze, Eugene V [Pinckney, MI; Kirby, Kevin W [Calabasas Hills, CA; Phelps, Amanda [Malibu, CA; Gregoire, Daniel J [Thousand Oaks, CA

2011-04-26

449

Performance comparison between rectangular and circular patch antenna array  

Microsoft Academic Search

This paper described the design of multiple element of microstrip patch antenna array operating at 2.45 GHz for WLAN and 5.85 GHz for WiMAX applications. The design and development also focus on different type antenna such as rectangular and circular patch antennas. Microstrip antennas have the attractive features of low profile and light weight. However the antennas may be too

O. Hazila; S. A. Aljunid; Fareq Malek; A. Sahadah

2010-01-01

450

Antenna deployment mechanism for use with a spacecraft. [extensible and retractable telescopic antenna mast  

NASA Technical Reports Server (NTRS)

A mechanical system is disclosed to deploy an antenna on a support which may, for example, be a spacecraft. A series of telescoping tubes are nested one within the other when the antenna is in a retracted stowed position. The outermost tube is rigidly attached to the support and the inner tubes are latched in the stowed position by a caging mechanism. The antenna is driven toward a deployed position by a dual motor driven cable which is terminated in a driving tube at the lower end of the innermost tube, from whence the cable is trained about pulleys at the tops and bottoms of successively large tubes of the antenna. The cable is wound on a drum at the lower end of the antenna and coaxial therewith. During deployment of the antenna, the drum rotates, thereby reeling in the deployment cable. The initial movement of the cable causes cam releasing of the latches in the caging device. Thereafter, the antenna tubes are extended until the final deployed position of the antenna is reached. A ratchet attached to the drum prevents reverse rotation of the drum and locks the antenna in the deployed position until the ratchet is released.

Leavy, W. A.; Griffin, C. R. (inventor)

1979-01-01

451

Antenna Technology for QUASAT application. [radio antenna for very long base interferometry missions  

NASA Technical Reports Server (NTRS)

A hybrid growth version of the advanced Sunflower, or precision deployable, antenna was adopted as the configuration proposed for the QUASAT very long baseline interferometry mission. The antenna consists of rigid panels of graphite-epoxy facesheets covering aluminum honeycomb sandwich. The six main folding panels are hinged to a cantilevered support ring attached to the periphery of the center section. Six pairs of intermediate panels are located between these panels and are hinged to each other and to the main panels. The flight configuration, antenna weight, a mass properties, frequency, and contour tolerance are discussed. The advantages of the solid antenna surface cover an all-mesh contour are examined.

Archer, J. S.; Palmer, W. B.

1985-01-01

452

An Overview of Antenna R&D Efforts in Support of NASA's Space Exploration Vision  

NASA Technical Reports Server (NTRS)

This presentation reviews the research and development work being conducted at Glenn Research Center in the area of antennas for space exploration. In particular, after reviewing the related goals of the agency, antenna technology development at GRC is discussed. The antennas to be presented are large aperture inflatable antennas, phased array antennas, a 256 element Ka-band antenna, a ferroelectric reflectarray antenna, multibeam antennas, and several small antennas.

Manning, Robert M.

2007-01-01

453

Satellite broadcasting: Requirements for the receiving antenna  

NASA Astrophysics Data System (ADS)

The receiving antenna plays a significant part in the reception of television signals broadcast from a satellite in so-called Direct Broadcasting by Satellite (DBS). The performance of the antenna must be sufficiently good to ensure that signals are received without suffering adverse effects of noise or interference. A hypothetical receiver specification was used during the planning of satellite broadcasting at the World Administrative Radio Conference in 1977 (WARC-77), but while this is in general sufficient it may not always be necessary. Furthermore, the different trade-offs involved in the antenna designs (including flat-plate types) may mean that the same result can most effectively be obtained with a very different specification. The various requirements are explained, and examples are given for incomplete or lower-power use of the WARC-77 allocations. It provides a useful background to related research reports which describe work on flat-plate antennas.

Stott, J. H.

454

47 CFR 80.863 - Antenna system.  

Code of Federal Regulations, 2011 CFR

...installed which is as nondirectional and as efficient as is practicable for the transmission and reception of radio ground waves over seawater. The installation and construction of the required antenna must insure operation in time of emergency. (b) If...

2011-10-01

455

47 CFR 80.863 - Antenna system.  

Code of Federal Regulations, 2010 CFR

...installed which is as nondirectional and as efficient as is practicable for the transmission and reception of radio ground waves over seawater. The installation and construction of the required antenna must insure operation in time of emergency. (b) If...

2010-10-01

456

Directional VLF antenna for communicating with submarines  

NASA Astrophysics Data System (ADS)

High-power, very low frequency transmitters for communicating with submarines use electrically short, top-loaded, vertical monopoles. These are efficient radiators of the lateral surface wave, but since they are omnidirectional, they expose residents of neighboring urban areas to possibly harmful effects. A possible alternative, the horizontal traveling-wave antenna of the Beverage type, is analyzed, and the design for the frequency range from 10 to 30 kHz is described. The antenna is highly directive in the horizontal plane. Although the field of the unit horizontal dipole over the earth is much smaller than that of the unit vertical dipole, the large effective length of the traveling-wave antenna makes its field comparable to that of the electrically short vertical monopole. Furthermore, since the radiated field in all directions except within a 30° to 60° angle out to sea is small, there is no exposure risk when the electrically long horizontal antenna is located near inhabited areas.

King, Ronold W. P.

1997-01-01

457

Dielectric Resonator Antennas : theory and design  

E-print Network

Theoretical models for the analysis of Dielectric Resonator Antenna (DRA) are developed. There are no exact solutions to many of the problems in analytical form, therefore a strong focus on the physical interpretation of ...

Lim, Beng-Teck, 1974-

1999-01-01

458

Large Space Antenna Systems Technology, part 1  

NASA Technical Reports Server (NTRS)

A compilation of the unclassified papers presented at the NASA Conference on Large Space Antenna Systems Technology covers the following areas: systems, structures technology, control technology, electromagnetics, and space flight test and evaluation.

Lightner, E. B. (compiler)

1983-01-01

459

47 CFR 74.737 - Antenna location.  

Code of Federal Regulations, 2010 CFR

...if any, that will be retransmitted. (b) The transmitting antenna should be placed above growing vegetation and trees lying in the direction of the area intended to be served, to minimize the possibility of signal absorption by foliage....

2010-10-01

460

47 CFR 74.1237 - Antenna location.  

Code of Federal Regulations, 2010 CFR

...available a suitable signal from the primary station. The transmitting antenna should be placed above growing vegetation and trees lying in the direction of the area intended to be served, to minimize the possiblity of signal absorption by foliage....

2010-10-01

461

The flat antenna - Now a reality  

NASA Astrophysics Data System (ADS)

A practical, high-performance, low-cost, consumer-oriented flat antenna is described. Advantages of the flat antenna include a thin profile which is less obtrusive than a parabolic dish, features less expensive shipping and installation costs due to its light weight, has the ability to squint the beam, and has improved aperture control for sidelobe suppression. R&D focuses on development of monolithic microwave integrated circuts which will be embedded into the array, thus adding the potential features of amenability to integrated electronics (which will improve noise performance and avoid the necessity of appending an external low-noise converter), and electronic steerability to the list of flat antenna advantages. The basic construction of the flat panel and the intended market for the first flat antennas and the subsequent effect on product design are discussed. Initial market results in Japan, and planned development of European and American markets are discussed.

Wells, Daniel R.

1989-09-01

462

Radio Astronomy Antennas by the Thousands  

NASA Astrophysics Data System (ADS)

Large number of microwave antennas of size and surface accuracy appropriate for the Square Kilometre Array (SKA) have not been manufactured previously. To minimize total cost, the design needs to be much more carefully considered and optimized than would be affordable for a small number of antennas. The required surface area requires new methods of manufacture and production-line type assembly to be considered. A blend of past antenna construction technology, creativity, and new technology is needed to provide the best possible telescope for the proposed SKA science goals. The following key concepts will be discussed with respect to reflector antennas and many supporting photographs, figures and drawings will be included. Surface and supporting structure comparison of panels with a one-piece shell as produced by hydroforming.

Schultz, Roger

2004-06-01

463

94 GHz integrated horn monopulse antennas  

NASA Technical Reports Server (NTRS)

A monolithic azimuthal monopulse antenna for 94 GHz applications has been developed. The structure consists of a single dipole suspended in one plane of an integrated horn cavity to obtain the sum pattern, and an antiparallel pair of dipoles suspended in a different plane of the same horn cavity to achieve the difference pattern. Pattern measurements of microwave models and on the millimeter-wave antennas show good agreement with theory and exhibit symmetry with a sharp -30 dB null at broadside for the difference antenna. Microwave model measurements show input impedances close to 50 Ohms, with greater than -25 dB isolation between sum and difference antennas across a 10 percent bandwidth.

Ling, Curtis C.; Rebeiz, Gabriel M.

1992-01-01

464

Dale Haracre Ceramics In a Patch Antenna  

E-print Network

a ground plate.Typically dielectric materials are proposed such as Zinc titanate (ZnTiO3) based ceramics of the antenna Near zero temperature coefficient of resonant frequency ZnTiO3-based ceramics is a promising

Mukhopadhyay, Sharmila M.

465

Wideband Circularly-Polarized Patch Antenna  

Microsoft Academic Search

A novel wideband circularly-polarized patch antenna is presented. First, a new broadband 90deg hybrid feed network is proposed to have a bandwidth of 75% for the 10-dB return loss, good two output ports amplitude balance and a consistent 90deg (plusmn3deg) phase difference between two output ports. Then, a circular patch antenna fed by four sequential-rotation proximity-coupled L-probes orientated to have

Lei Bian; Yong-Xin Guo; L. C. Ong; Xiang-Quan Shi

2006-01-01

466

Dual S/X-band RV antenna  

SciTech Connect

This paper provides specifications and conceptual design of reentry vehicle antennas. A comparison of the types of shared aperture antennas (single cavity-multiple probe; single cavity-single probe; and multiple cavity-individual probe) is discussed. A description of the multiple cavity configuration and fabrication details are presented. Also shown are tuning conditions, VSWR vs frequency plots, isolation vs frequency plots; radiation patterns, and environmental requirements. (FI)

Sena, M.D.; Bentz, R.D.

1987-01-01

467

Accuracy potentials for large space antenna structures  

NASA Technical Reports Server (NTRS)

The relationships among materials selection, truss design, and manufacturing techniques in the interest of surface accuracies for large space antennas are discussed. Among the antenna configurations considered are: tetrahedral truss, pretensioned truss, and geodesic dome and radial rib structures. Comparisons are made of the accuracy achievable by truss and dome structure types for a wide variety of diameters, focal lengths, and wavelength of radiated signal, taking into account such deforming influences as solar heating-caused thermal transients and thermal gradients.

Hedgepeth, J. M.

1980-01-01

468

Deep Space Network Antenna Logic Controller  

NASA Technical Reports Server (NTRS)

The Antenna Logic Controller (ALC) software controls and monitors the motion control equipment of the 4,000-metric-ton structure of the Deep Space Network 70-meter antenna. This program coordinates the control of 42 hydraulic pumps, while monitoring several interlocks for personnel and equipment safety. Remote operation of the ALC runs via the Antenna Monitor & Control (AMC) computer, which orchestrates the tracking functions of the entire antenna. This software provides a graphical user interface for local control, monitoring, and identification of faults as well as, at a high level, providing for the digital control of the axis brakes so that the servo of the AMC may control the motion of the antenna. Specific functions of the ALC also include routines for startup in cold weather, controlled shutdown for both normal and fault situations, and pump switching on failure. The increased monitoring, the ability to trend key performance characteristics, the improved fault detection and recovery, the centralization of all control at a single panel, and the simplification of the user interface have all reduced the required workforce to run 70-meter antennas. The ALC also increases the antenna availability by reducing the time required to start up the antenna, to diagnose faults, and by providing additional insight into the performance of key parameters that aid in preventive maintenance to avoid key element failure. The ALC User Display (AUD) is a graphical user interface with hierarchical display structure, which provides high-level status information to the operation of the ALC, as well as detailed information for virtually all aspects of the ALC via drill-down displays. The operational status of an item, be it a function or assembly, is shown in the higher-level display. By pressing the item on the display screen, a new screen opens to show more detail of the function/assembly. Navigation tools and the map button allow immediate access to all screens.

Ahlstrom, Harlow; Morgan, Scott; Hames, Peter; Strain, Martha; Owen, Christopher; Shimizu, Kenneth; Wilson, Karen; Shaller, David; Doktomomtaz, Said; Leung, Patrick

2007-01-01

469

Adjusting Surfaces Of Large Antenna Reflectors  

NASA Technical Reports Server (NTRS)

New approach more effective than traditional rms-surface-distortion approach. Optimization procedure for control of shape of reflector of large space antenna (LSA). Main feature is shape-controlling mathematical mechanism driven by need to satisfy explicit EM design requirements. Uses standard finite-element structural analysis, aperture-integration EM analysis, and constrained optimization techniques to predict set of actuator inputs that improves performance of antenna while minimizing applied control effort. Procedure applicable to wide variety of LSA concepts.

Padula, Sharon L.; Adelman, Howard M.; Bailey, Marion C.; Hoftka, Raphael T.

1989-01-01

470

64-meter to 70-meter Antenna Extension  

NASA Technical Reports Server (NTRS)

The Deep Space Network 64-m antennas are being upgraded to improve their performance by increasing the diameter to 70 m, installing precision panels, and using a shaped surface. Performance improvement is expected to be 1.9 dB at X-band and 1.4 dB at S-band. The design and capabilities of the antenna are discussed.

Mcclure, D. H.; Mclaughlin, F. D.

1984-01-01

471

Time-Zone-Pattern Satellite Broadcasting Antenna  

NASA Technical Reports Server (NTRS)

Direct-broadcast satellite antenna designs provide contoured beams to match four time zones in 48 contiguous states and spot beams for Alaska, Hawaii, and Puerto Rico presented in 29-page report. Includes descriptions of procedures used to arrive at optimized designs. Arrangements, amplitudes, and phases of antenna feeds presented in tables. Gain contours shown graphically. Additional tables of performance data given for cities in service area of Eastern satellite.

Galindo, Victor; Rahmat-Samii, Yahya; Imbriale, William A.; Cohen, Herb; Cagnon, Ronald R.

1988-01-01

472

A novel broadband printed antenna element  

Microsoft Academic Search

A novel broadband printed antenna element, the printed counterpart of a conventional TV UHF panel antenna with very large bandwidth, has been studied. A design method and realization are presented in the paper. More than one octave measured bandwidth with VSWR less then 1.8 and directivity between 9.0 and 11.0 dBi has been achieved. Properties of the radiator as an

M. Mikavica; B. M. Kolundzija; A. Nesic; M. Marjanovic

1998-01-01

473

Dual-Beam Microstrip Array Antenna  

NASA Technical Reports Server (NTRS)

Microstrip array antenna similar to one described in "Parallel/Series-Fed Microstrip Array Antenna" (NPO-18678), except one array produces two off-broadside beams with no additional complication of feeds. Adjacent elements spaced and phased to radiate coherently in desired beam squint directions. In original application, two beams used in airborne synthetic-aperture interferometric radar to measure along-track and cross-track velocities simultaneously. Other potential applications include multiple-beam communications and tracking of aircraft at airports.

Huang, John; Madsen, Soren N.

1994-01-01

474

Improved Dual-Polarized Microstrip Antenna  

NASA Technical Reports Server (NTRS)

Dual-polarized microstrip antenna features microstrip transmission-line feeds arranged in such configuration that cross-polarized components of radiation relatively low and degree of isolation between feed ports relatively high. V and H feed ports offset from midpoints of feed lines to obtain required opposite phases at feed-point connections to microstrip patches. Two independent beams of same frequency with electric fields polarized orthogonally to each other transmitted or received via antenna. Improved design saves space.

Huang, John

1993-01-01

475

Microstrip fractal antennas for multistandard terminals  

Microsoft Academic Search

A novel microstrip patch antenna with a Koch prefractal edge and a U-shaped slot is proposed for multi-standard use in GSM1800, UMTS, and HiperLAN2. Making use of an inverted-F antenna (PIFA) structure, an interesting size reduction is achieved. The multi-band behavior has been obtained by broadening the lower frequency resonance of the fractal patch to cover GSM1800 and UMTS, and

Jerzy Guterman; António A. Moreira; Custódio Peixeiro

2004-01-01

476

A review of performance characteristics of satellite antennas and some observations on future directions in satellite antenna design  

NASA Technical Reports Server (NTRS)

A general review of the state-of-the-art and new directions in research and development of spacecraft antennas is presented. Three general classes of antennas are discussed: phased arrays, lenses (dielectric and waveguide), and reflector antennas. Presently, the antenna with most applications is the reflector with considerable research being performed to improve its scan and multiple beam characteristics. Future applications for spacecraft antennas and research goals to meet these projected needs also are discussed.

Mittra, R.; Galindo-Israel, V.; Bathker, D. A.; Moule, W. N.

1977-01-01

477

40 CFR 51.854 - Conformity analysis.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 2010-07-01 false Conformity analysis. 51.854 Section 51...OF IMPLEMENTATION PLANS Determining Conformity of General Federal Actions to State...Implementation Plans § 51.854 Conformity analysis. Link to an amendment...

2010-07-01

478

40 CFR 93.154 - Conformity analysis.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 2010-07-01 false Conformity analysis. 93.154 Section...PROGRAMS (CONTINUED) DETERMINING CONFORMITY OF FEDERAL ACTIONS TO STATE OR...IMPLEMENTATION PLANS Determining Conformity of General Federal Actions...

2010-07-01

479

40 CFR 52.2133 - General conformity.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 2010-07-01 false General conformity. 52.2133 Section 52.2133 Protection...CONTINUED) South Carolina § 52.2133 General conformity. The General Conformity regulations adopted into the South...

2010-07-01

480

40 CFR 52.138 - Conformity procedures.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 2010-07-01 false Conformity procedures. 52.138 Section 52...IMPLEMENTATION PLANS Arizona § 52.138 Conformity procedures. (a) Purpose...organizations (MPOs) to use when determining conformity of transportation plans,...

2010-07-01

481

40 CFR 52.938 - General conformity.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 2010-07-01 false General conformity. 52.938 Section 52.938 Protection...IMPLEMENTATION PLANS Kentucky § 52.938 General conformity. The General Conformity regulations were submitted on November...

2010-07-01

482

40 CFR 52.799 - Transportation conformity.  

Code of Federal Regulations, 2013 CFR

...PROMULGATION OF IMPLEMENTATION PLANS Indiana § 52.799 Transportation conformity. On June 4, 2010, Indiana submitted the Transportation Conformity...the Transportation Conformity SIP from Indiana. [75 FR 50710, Aug. 17,...

2013-07-01

483

40 CFR 52.799 - Transportation conformity.  

Code of Federal Regulations, 2011 CFR

...PROMULGATION OF IMPLEMENTATION PLANS Indiana § 52.799 Transportation conformity. On June 4, 2010, Indiana submitted the Transportation Conformity...the Transportation Conformity SIP from Indiana. [75 FR 50710, Aug. 17,...

2011-07-01

484

40 CFR 52.799 - Transportation conformity.  

Code of Federal Regulations, 2012 CFR

...PROMULGATION OF IMPLEMENTATION PLANS Indiana § 52.799 Transportation conformity. On June 4, 2010, Indiana submitted the Transportation Conformity...the Transportation Conformity SIP from Indiana. [75 FR 50710, Aug. 17,...

2012-07-01

485

40 CFR 52.799 - Transportation conformity.  

...PROMULGATION OF IMPLEMENTATION PLANS Indiana § 52.799 Transportation conformity. On June 4, 2010, Indiana submitted the Transportation Conformity...the Transportation Conformity SIP from Indiana. [75 FR 50710, Aug. 17,...

2014-07-01

486

Hunting for the Conformal Window  

E-print Network

Undeniably, the imminent activity of LHC and the quest for the nature of physics beyond the standard model have raised renewed interest in the conformal and quasi-conformal behaviour of gauge field theories with matter content. Theoretically driven questions seem to now acquire a strong experimental appeal and might guide us towards a more realistic string theory to field theory connection, originally inspired by the AdS/CFT conjecture. In this brief report, we discuss the state of the art of our search for the conformal window in the SU(3) colour-gauge theory with fermions in the fundamental representation.

A. Deuzeman; M. P. Lombardo; E. Pallante

2008-10-17

487

ADMR of carotenoid triplet states in bacterial photosynthetic antenna and reaction center complexes  

NASA Astrophysics Data System (ADS)

Using absorption detected magnetic resonance (ADMR) the triplet states of carotenoids have been detected in B880—RC complexes of the purple photosynthetic bacteria Rhodocyclus gelatinosus 149, Rhodopseudomonas acidophila 7050, Rhodopseudomonas palustris 8252, and Rhodospirillum rubrum S1, and in reaction center (RC) complexes of Rhodospirillum rubrum S1. The triplet states were identified as belonging to antenna carotenois in the all-trans conformation with conjugated chain lengths ranging from 10 to 13 double bonds, and to the RC carotenoid 15,15'-cis spirilloxanthin. Carotenoids with different numbers of conjugated double bonds have similar ability to quench the triplet states of the bacteriochlorophylls.

Aust, V.; Angerhofer, A.; Ullrich, J.; von Schütz, J. U.; Wolf, H. C.; Cogdell, R. J.

1991-06-01

488

3318 IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 56, NO. 10, OCTOBER 2008 [3] Microstrip Antennas: The Analysis and Design of Microstrip Antennas  

E-print Network

Antennas: The Analysis and Design of Microstrip Antennas and Arrays, D. M. Pozar and D. H. Schaubert, Eds York: Wiley, 2005, pp. 727­752. [10] D. M. Pozar, "Input impedance and mutual coupling of rectangular

Davies, John N.

489

Lattice Simulations and Infrared Conformality  

We examine several recent lattice-simulation data sets, asking whether they are consistent with infrared conformality. We observe, in particular, that for an SU(3) gauge theory with 12 Dirac fermions in the fundamental representation, recent simulation data can be described assuming infrared conformality. Lattice simulations include a fermion mass m which is then extrapolated to zero, and we note that this data can be fit by a small-m expansion, allowing a controlled extrapolation. We also note that the conformal hypothesis does not work well for two theories that are known or expected to be confining and chirally broken, and that it does work well for another theory expected to be infrared conformal.

Appelquist, Thomas; Fleming, George T.; Lin, Meifeng; Neil, Ethan T.; Schaich, David A.

2011-09-01

490

Conformal mapping of rectangular heptagons  

SciTech Connect

A new effective approach to calculating the direct and inverse conformal mapping of rectangular polygons onto a half-plane is put forward; it is based on the use of Riemann theta functions. Bibliography: 14 titles.

Bogatyrev, Andrei B

2012-12-31

491

CONFORMANCE IMPROVEMENT USING GELS  

SciTech Connect

This report describes work performed during the third and final year of the project, ''Conformance Improvement Using Gels.'' Corefloods revealed throughput dependencies of permeability reduction by polymers and gels that were much more prolonged during oil flow than water flow. This behavior was explained using simple mobility ratio arguments. A model was developed that quantitatively fits the results and predicts ''clean up'' times for oil productivity when production wells are returned to service after application of a polymer or gel treatment. X-ray computed microtomography studies of gels in strongly water-wet Berea sandstone and strongly oil-wet porous polyethylene suggested that oil penetration through gel-filled pores occurs by a gel-dehydration mechanism, rather than gel-ripping or gel-displacement mechanisms. In contrast, analysis of data from the University of Kansas suggests that the gel-ripping or displacement mechanisms are more important in more permeable, strongly water-wet sandpacks. These findings help to explain why aqueous gels can reduce permeability to water more than to oil under different conditions. Since cement is the most commonly used material for water shutoff, we considered when gels are preferred over cements. Our analysis and experimental results indicated that cement cannot be expected to completely fill (top to bottom) a vertical fracture of any width, except near the wellbore. For vertical fractures with apertures less than 4 mm, the cement slurry will simply not penetrate very far into the fracture. For vertical fractures with apertures greater than 4 mm, the slurry may penetrate a substantial distance into the bottom part of the fracture. However, except near the wellbore, the upper part of the fracture will remain open due to gravity segregation. We compared various approaches to plugging fractures using gels, including (1) varying polymer content, (2) varying placement (extrusion) rate, (3) using partially formed gels, (4) using combinations of high and low molecular weight (Mw) polymers, (5) using secondary crosslinking reactions, (6) injecting un-hydrated polymer particles, and (7) incorporating particulates. All of these methods showed promise in some aspects, but required performance improvements in other aspects. All materials investigated to date showed significant performance variations with fracture width. High pressure gradients and limited distance of penetration are common problems in tight fractures. Gravity segregation and low resistance to breaching are common problems in wide fractures. These will be key issues to address in future work. Although gels can exhibit disproportionate permeability reduction in fractures, the levels of permeability reduction for oil flow are too high to allow practical exploitation in most circumstances. In contrast, disproportionate permeability reduction provided by gels that form in porous rock (adjacent to the fractures) has considerable potential in fractured systems.

Randall S. Seright

2004-09-30

492

Chameleonic dilaton and conformal transformations  

E-print Network

We recently proposed a chameleonic solution to the cosmological constant problem - Phys. Rev. D82 (2010) 044006. One of the results of that paper is a non-equivalence of different conformal frames at the quantum level. In this letter we further discuss our proposal focusing our attention on the conformal transformation. Moreover, we point out that a different choice of parameters is necessary in the model.

Andrea Zanzi

2012-06-20

493

Superconducting microstrip antennas - An experimental comparison of two feeding methods  

NASA Technical Reports Server (NTRS)

The recent discovery of high-temperature superconductors (HTSs) has generated a substantial amount of interest in microstrip antenna applications. However, the high permittivity of substrates compatible with HTS causes difficulty in feeding such antennas because of the high patch edge impedance. Two methods for feeding HTS microstrip antennas at K- and Ka-band are examined. Superconducting microstrip antennas that are directly coupled and gap-coupled to a microstrip transmission line have been designed and fabricated on lanthanum aluminate substrates using Y-Ba-Cu-O superconducting thin films. Measurements from these antennas, including input impedance, bandwidth, efficiency, and patterns, are presented and compared with published models. The measured results demonstrate that usable antennas can be constructed using either of these architectures, although the antennas suffer from narrow bandwidths. In each case, the HTS antenna shows a substantial improvement over an identical antenna made with normal metals.

Richard, M. A.; Bhasin, Kul B.; Claspy, Paul C.

1993-01-01

494

Superconducting Microstrip Antennas: An Experimental Comparison of Two Feeding Methods  

NASA Technical Reports Server (NTRS)

The recent discovery of high-temperature superconductors (HTSs) has generated a substantial amount of interest in microstrip antenna applications. However, the high permittivity of substrates compatible with HTS causes difficulty in feeding such antennas because of the high patch edge impedance. Two methods for feeding HTS microstrip antennas at K- and Ka-band are examined. Superconducting microstrip antennas that are directly coupled and gas-coupled to a microstrip transmission line have been designed and fabricated on lanthanum aluminate substrates using Y-Ba-Cu-O superconducting thin films. Measurements from these antennas, including input impedance, bandwidth, efficiency, and patterns, are presented and compared with published models. The measured results demonstrate that usable antennas can be constructed using either of these architectures, although the antennas suffer from narrow bandwidths. In each case, the HTS antenna shows a substantial improvement over an identical antenna made with normal metals

Richard, Mark A.; Claspy, Paul C.; Bhasin, Kul B.

1993-01-01

495

Shear sensing based on a microstrip patch antenna  

NASA Astrophysics Data System (ADS)

A microstrip patch antenna sensor was studied for shear sensing with a targeted application of measuring plantar shear distribution on a diabetic foot. The antenna shear sensor consists of three components, namely an antenna patch, a soft foam substrate and a slotted ground plane. The resonant frequency of the antenna sensor is sensitive to the overlapping length between the slot in the ground plane and the antenna patch. A shear force applied along the direction of the slot deforms the foam substrate and causes a change in the overlapping length, which can be detected from the antenna frequency shift. The antenna shear sensor was designed based on simulated antenna frequency response and validated by experiments. Experimental results indicated that the antenna sensor exhibits high sensitivity to shear deformation and responds to the applied shear loads with excellent linearity and repeatability.

Mohammad, I.; Huang, H.

2012-10-01

496

Ion cyclotron range of frequencies antenna design for R tokamak  

SciTech Connect

The ion cyclotron range of frequencies antenna design for the R tokamak (a proposal by the Institute of Plasma Physics, Nagoya University) is described. The design involves three types of antennas: a standard loop antenna, a panel heater antenna, and a waveguide antenna for ion Bernstein wave heating (IBWH). The standard loop antenna is made of aluminum alloy and has a simple structure because it has to be installed under radioactive conditions by deuterium-tritium neutrons. A new type of antenna called a panel heater antenna has been designed for high-power heating. It has a wide radiation area and is able to select a parallel wave number kappa/sub parallel/. The feasibility of the waveguide antenna is also discussed in association with IBWH. The radiation from the aperture of the double ridge waveguide is estimated in a model experiment, where calculated surface plasma impedance is simulated by a dielectric load.

Kako, E.; Ando, R.; Ichimura, M.; Ogawa, Y.; Amano, T.; Watari, T.

1987-09-01

497

Numerical simulation of a phased-array antenna consisting of asymmetric log-periodic antennas  

NASA Astrophysics Data System (ADS)

The problem of calculating the electrodynamic characteristics of a finite phased-array antenna made up of log-periodic dipole antennas is solved. An iterative method that makes possible a substantial speed-up of the solution is considered. The calculation results are confirmed experimentally.

Strizhkov, V. A.

1991-07-01

498

Antenna Designer's Notebook-asymmetric vertical dipole antennas for MF AM transmitting  

Microsoft Academic Search

An asymmetric vertical dipole is proposed as a surface wave transmitting antenna for low-, medium-, and high-frequency applications, where a strong vertically polarized wave is needed. This kind of vertical dipole antenna uses the supporting guys as part of the radiating structure, permitting a very high radiation efficiency, without the classical buried-wire artificial ground plane. It is basically intended for

T. Trainotti

1993-01-01

499

Conical Slot Antenna and Related Antennas Suitable for Use with an Aircraft with Inflatable Wings.  

National Technical Information Service (NTIS)

Airborne UWB radar systems require receive antennas that can be printed or mounted onto an inflatable wing. Such antennas need to reach as low as VHF frequencies, and must be positioned to look to the side of the aircraft. To satisfy these requirements, a...

E. G. Farr, W. S. Bigelow

2005-01-01

500

666 IEEE ANTENNAS AND WIRELESS PROPAGATION LETTERS, VOL. 10, 2011 Compact Coplanar Waveguide Spiral Antenna With  

E-print Network

uniplanar array of spirals. It is found that a thick substrate of high dielectric con- stant absorbs most- tions. Therefore, this antenna structure is fabricated on a substrate of high dielectric constant and critical parts of radar and communication systems. Designing antennas on substrates with high dielectric

Bornemann, Jens