Sample records for electrically-small conformal antenna

  1. Electrically small antennas

    NASA Astrophysics Data System (ADS)

    Richmond, J. H.; Walter, C. H.

    1982-12-01

    The theory and techniques for small antennas mounted on structures, for microstrip antennas, and for k-pulse applications were investigated. The topics discussed include: mutual impedance between vertical dipoles over a flat earth; on the edge mode in the theory of TM scattering by a strip or strip grating; on the edge mode in the theory of thick cylindrical monopole antennas; field of separable electric source current distribution in free space; scattering from cylindrical inhomogeneities in a lossy medium; and propagation of surface waves on a buried coaxial cable with periodic slots.

  2. Metamaterial-based efficient electrically small antennas

    Microsoft Academic Search

    Richard W. Ziolkowski; Aycan Erentok

    2006-01-01

    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

  3. Metamaterial-Inspired Efficient Electrically Small Antennas

    Microsoft Academic Search

    Aycan Erentok; Richard W. Ziolkowski

    2008-01-01

    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

  4. Electrically small split ring resonator antennas

    NASA Astrophysics Data System (ADS)

    Alici, Kamil Boratay; Ozbay, Ekmel

    2007-04-01

    We studied electrically small resonant antennas composed of split ring resonators (SRR) and monopoles. The antennas considered have the same ring radius, but slightly different geometry. The resonance frequency depends on the geometry of the SRRs. Two SRR antennas are designed. The first one, which operates at 3.62 GHz, is demonstrated theoretically and experimentally. The size of this antenna is Q Q (min Q =1.78). The second one is a rather small SRR antenna in which the capacitance between the rings is increased. The size is reduced to 0.074?0×0.079?0. This structure is called serrated SRR (SSRR). Both antennas have similar far-field patterns but the efficiency of the SSRR antenna is less.

  5. Electrically small, complementary electric-field-coupled resonator antennas

    NASA Astrophysics Data System (ADS)

    Odabasi, H.; Teixeira, F. L.; Guney, D. O.

    2013-02-01

    We study the radiation properties of electrically small resonant antennas (ka <1) composed of electric-field-coupled (ELC) and complementary electric-field-coupled (CELC) resonators and a monopole antenna. We use such parasitic ELC and CELC "metaresonators" to design various electrically small antennas. In particular, monopole-excited and bent-monopole-excited CELC resonator antennas are proposed that provide very low profiles on the order of ?0/20. We compare the performance of the proposed ELC and CELC antennas against more conventional designs based upon split-ring resonators.

  6. Electrically Small Folded Slot Antenna Utilizing Capacitive Loaded Slot Lines

    NASA Technical Reports Server (NTRS)

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

    2007-01-01

    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.

  7. Biologically-inspired, electrically small antenna arrays

    NASA Astrophysics Data System (ADS)

    Masoumi, Amir Reza

    First, the motivation behind adding a passive external coupling network after antenna arrays is discussed, the concept of biomimetic antenna arrays (BMAAs) introduced and some of the previous work done in this area have been reviewed. Next, a BMAA which achieves an angular resolution of roughly 15 times its regular counterpart is introduced and fully characterized. The introduced BMAA employs transformers which considerably degrade its performance, namely its output power. To cicumvent this shortcoming a new architecture of a BMAA that does not employ transformers and therefore yields a higher output power for the same angular resolution has been subsequently presented. Moreover, a detailed noise analysis of this BMAA is carried out and the output noise of the new architecture is compared with the output noise of the original design. The modified twoelement BMAA architecture is then extended to multiple elements. A novel nonlinear optimization process is introduced that maximizes the total power captured by the BMAA for a given angular resolution and the concept illustrated for a three-element antenna array. Next an optimum two-element BMAA which achieves the maximum possible angular resolution while obtaining the same output power level of a regular antenna array with the same elements and spacing is introduced. A novel two-element superdirective array based on this optimum BMAA has been also discussed. The passive BMAAs discussed in this thesis have a relatively narrow bandwidth. To extend the bandwidth of BMAAs, non- Foster networks have been employed in their external coupling networks and it has been demonstrated that they can increase their bandwidth by a factor of roughly 33. Finally, the BMAA concept has been extended to nano-antenna arrays and a concept for designing sub-wavelength angle-sensing detectors at optical wavelengths has been introduced.

  8. Electrically small antenna elements using negative permittivity resonators

    Microsoft Academic Search

    Howard R. Stuart; Alex Pidwerbetsky

    2006-01-01

    We show how resonators composed of negative permittivity materials can form the basis of effective small antenna elements. A quasi-static analysis of the resonant properties of a sub-wavelength negative permittivity sphere predicts that such a resonator will have a Q-factor that is only 1.5 times the Chu limit, matching the performance of other known electrically small spherical antenna designs, such

  9. Lower Bounds on the Q of Electrically Small Dipole Antennas

    Microsoft Academic Search

    Arthur D. Yaghjian; Howard R. Stuart

    2010-01-01

    General expressions are obtained for the lower bounds on the quality factor (Q) of electrically small electric- and magnetic-dipole antennas confined to an arbitrarily shaped volume V and excited by general sources or by global electric-current sources alone. The lower-bound expressions depend only on the direction of the dipole moment with respect to V , the electrical size of V

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

    NASA Astrophysics Data System (ADS)

    Cutshall, Ryan T.

    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.

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

    SciTech Connect

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

    2011-09-01

    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.

  12. Analysis and optimization of an electrically small receiving antenna

    NASA Astrophysics Data System (ADS)

    Casey, John P.; Bansal, Rajeev

    1991-08-01

    A theoretical and experimental study of an optimum receiving antenna configuration that fits within certain allocated space requirements is presented. This optimum monopole antenna configuration is applicable for LORAN-C reception. The antenna analysis is based on a quasi-static numerical study of a conducting body of revolution above a perfectly conducting ground plane. A general numerical algorithm is developed to determine the input impedance and the effective height of the antenna. In addition, the amplifier noise and its role in the choice of the optimum antenna are examined. Results are presented for cylindrical and truncated conical structures both with and without a top load.

  13. Electrically small antenna elements using negative permittivity resonators

    Microsoft Academic Search

    Howard R. Stuart; A. Pidwerbetsky

    2005-01-01

    We consider the use of materials with negative electric permittivity as a building block for constructing effective small antenna elements. In this paper, we show that negative permittivity alone is sufficient for constructing an effective small antenna element. Further, we clarify, here the issue of the radiation Q: a quasi-static analysis is used to show that a sub-wavelength spherical negative

  14. Efficiency variations in electrically small, meander line RFID antennas

    Microsoft Academic Search

    Amir Galehdar; David V. Thiel; Steven G. O'Keefe; Simon P. Kingsley

    2007-01-01

    Not all meander line dipole antennas (MLDAs) plotted on the same grid necessarily have similar characteristics. MLDAs can be optimized for best efficiency, lowest resonant frequency or highest impedance. Different structures were investigated using a 5 times 10 array of rectangular grid points in 4times9 mm2 area and, all symmetrical MLDA that incorporate all grids points were modeled to determine

  15. Direct transfer patterning of electrically small antennas onto three-dimensionally contoured substrates.

    PubMed

    Pfeiffer, Carl; Xu, Xin; Forrest, Stephen R; Grbic, Anthony

    2012-03-01

    A direct transfer patterning process is presented that allows metallic patterns to be stamped onto a contoured substrate. This process was used to make some of the most efficient electrically small antennas to date, while maintaining bandwidths approaching the physical limit. PMID:22290732

  16. Theoretical formulation for an electrically small microstrip patch antenna loaded with negative index materials

    Microsoft Academic Search

    J. S. Petko; D. H. Werner

    2005-01-01

    Composite metamaterials that possess simultaneously negative permeability and permittivity, causing them to exhibit a negative index of refraction known, are known as a negative index materials (NIM). An application of NIMs is to increase the power radiated from electrically small antennas. NIMs can also be used to design thin sub-wavelength cavity resonators. We expand on this principle by introducing a

  17. Electric lines of force of an electrically small dipole-loop antenna array

    Microsoft Academic Search

    P. L. Overfelt

    1998-01-01

    The electric lines of force of an electrically small dipole-loop antenna array have been determined analytically for both the near- and far-fields of the array. It has been found that the behavior of the families of electric contours are dependent upon a coupling parameter, which is the ratio of the loop and dipole sizes and currents. This parameter also controls

  18. An electrically-small monopole phased array antenna for wide band applications

    Microsoft Academic Search

    S. Y. Peng; G. A. Pfaff

    1984-01-01

    An electrically-small, lightweight, and low RCS (radar cross-section) Monopole Array Antenna has been developed for wide band application. The monopoles were printed on a low dielectric constant (epsilon sub gamma = 2.3) substrate and fed by a modified meanderline microstrip feed structure, with quarter-wavelength stubs to improve feed efficiency. The operational frequency is from 0.65 to 2.0 GHz. The physical

  19. A Dual-Band Printed Electrically Small Antenna Covered by Two Capacitive Split-Ring Resonators

    Microsoft Academic Search

    Lin Wang; Meng Qing Yuan; Qing Huo Liu

    2011-01-01

    In this letter, we present a dual-band electrically small antenna (ESA) operating at 934 MHz and 1.55 GHz. The miniaturized radiation structure consists of a small ring and two concentric split-ring resonators on an FR-4 substrate. The resonant response of the proposed radiation structure is charac- terized by the coupling among two split-ring resonators and the small ring. A weak

  20. An electrically-small monopole phased array antenna for wide band applications

    NASA Astrophysics Data System (ADS)

    Peng, S. Y.; Pfaff, G. A.

    An electrically-small, lightweight, and low RCS (radar cross-section) Monopole Array Antenna has been developed for wide band application. The monopoles were printed on a low dielectric constant (epsilon sub gamma = 2.3) substrate and fed by a modified meanderline microstrip feed structure, with quarter-wavelength stubs to improve feed efficiency. The operational frequency is from 0.65 to 2.0 GHz. The physical size of the monopole array measures only 0.125 wavelength in height. The weight is about 0.3 pounds. A four-element subarray was built and tested. Its overall physical size is 2.5 inches in height by 10 inches in length by 24.4 inches in width. The measured gain and pattern data are presented, as well as the low RCS property and many applications of the monopole array.

  1. Conformal phased array antenna pattern corrector

    NASA Astrophysics Data System (ADS)

    Antonucci, J. D.

    1984-11-01

    The present invention relates to radar antenna systems and particularly to a pattern corrector for a conformal phased array monopulse antenna system. In certain monopulse radar applications, such as aboard aircraft, it becomes advantageous to mount a phased array antenna onto the curved exterior surface of the host vehicle. Such a conformal phased array antenna, however, produces a distorted radiation pattern when the beam is scanned off of broadside.

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

    E-print Network

    Panzer, Benjamin Garrett

    2007-12-12

    Radar operation from the CReSIS Meridian UAV requires a broadband antenna array composed of lightweight, thin, end-fire antenna elements. Toward this goal four Vivaldi antenna designs were simulated, fabricated, and characterized. The final design...

  3. Electrically small ultra wideband antenna for EMC measurements in vehicles optimized by electromagnetic simulation

    Microsoft Academic Search

    Ingo Schmidt; Martin Schwark; Robert Geise

    2008-01-01

    A monoconical antenna type has been selected and successfully optimized by a electromagnetic field simulation program. A real antenna was constructed with the parameters found by several simulated parameter sweeps. The comparison between simulation and real antenna shows a good agreement and the comparison between an antenna constructed with the optimal half opening angle derived from theory and the new

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

    NASA Astrophysics Data System (ADS)

    Zhu, Ning

    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.

  5. Electromagnetic characterization of conformal antennas

    NASA Technical Reports Server (NTRS)

    Volakis, John L.; Kempel, Leo C.; Alexanian, Angelos; Jin, J. M.; Yu, C. L.; Woo, Alex C.

    1992-01-01

    The ultimate objective of this project is to develop a new technique which permits an accurate simulation of microstrip patch antennas or arrays with various feed, superstrate and/or substrate configurations residing in a recessed cavity whose aperture is planar, cylindrical or otherwise conformed to the substructure. The technique combines the finite element and boundary integral methods to formulate a system suitable for solution via the conjugate gradient method in conjunction with the fast Fourier transform. The final code is intended to compute both scattering and radiation patterns of the structure with an affordable memory demand. With upgraded capabilities, the four included papers examined the radar cross section (RCS), input impedance, gain, and resonant frequency of several rectangular configurations using different loading and substrate/superstrate configurations.

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

    SciTech Connect

    Speer, Pete

    2009-04-15

    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.

  7. Design and measurements of an electrically small, broad bandwidth, non-Foster circuit-augmented protractor antenna

    NASA Astrophysics Data System (ADS)

    Zhu, Ning; Ziolkowski, Richard W.

    2012-07-01

    A broad bandwidth, electrically small, metamaterial-inspired protractor antenna was designed, fabricated and tested around 300 MHz. Its broad bandwidth property was achieved by augmenting the protractor-shaped near-field resonant parasitic (NFRP) element with a non-Foster circuit. The resulting active NFRP element provided the means to surpass the fundamental passive limits. The measurement results for this non-Foster protractor antenna showed more than a 10 times increase of the 10 dB fractional bandwidth (FBW10dB) of the original passive version. The corresponding half-power bandwidth (BW3dB) was more than 8.24 times the passive upper bound.

  8. Hemispherical coil electrically small antenna made by stretchable conductors printing and plastic thermoforming

    NASA Astrophysics Data System (ADS)

    Wu, Zhigang; Jobs, Magnus; Rydberg, Anders; Hjort, Klas

    2015-02-01

    A production scalable technique is presented to make hemispherical coil antennas by using a stretchable printed silver paste conductor and plastic thermoforming. To ease the fabrication process an unbalanced feed-structure was designed for solderless mounting on conductive materials. The manufactured antenna had a resonance frequency of 2.467?GHz with a reflection coefficient of ?33.8?dB. The measured and simulated radiation patterns corresponded to that of monopole structure and the measured efficiency was 40%.

  9. Efficiency of Electrically Small Dipole Antennas Loaded With Left-Handed Transmission Lines

    Microsoft Academic Search

    Qing Liu; Peter S. Hall; Alejandro L. Borja

    2009-01-01

    A study of the efficiency of small dipole antennas loaded with a left-handed transmission line is described. The antenna is composed of a ladder network periodic structure of a number of unit cells. Left-handed performance can be obtained in straight or meandered capacitive-inductive (CL) lumped loading. Its performance is compared to a right-handed dipole with inductive (L) lumped loading. Differently

  10. Investigation of gain enhancement of electrically small antennas using double-negative, single-negative, and double-positive materials.

    PubMed

    Ghosh, B; Ghosh, S; Kakade, A B

    2008-08-01

    In this paper, it is shown that a double-negative or a mu-negative shell can be used to achieve a very high gain for an electrically small loop. It is also seen that together with the high gain, the metamaterial shell can be used to achieve a very uniform gain characteristic with respect to the shell dimensions. This is accomplished by a proper choice of the media parameters of the metamaterial shell and the region surrounding the antenna. This significantly eases the fabrication constraints and the close tolerances on the shell which was a major drawback towards the practical realization of the shell. Also, significant power gain can be obtained when the radiated power from the metamaterial shell is compared to the power radiated by a loop of the same radius as the outer radius of the shell. In addition, it is also found that a double-positive shell of the same dimensions as the metamaterial shell can be used to significantly increase the gain of the infinitesimal antenna. The power gain characteristics show distinct resonant peaks in this case. Excellent matching characteristics are observed corresponding to the radiated power gain. PMID:18850966

  11. Applying soft magnetic materials to conductive surfaces to realise a novel conformal HF antenna concept

    Microsoft Academic Search

    J. Dresel; A. R. Clark; A. P. C. Fourie

    1999-01-01

    This paper presents a novel conformal HF antenna concept. Soft magnetic materials are used to suppress currents on conductive surfaces in order to realise conformal HF antennas. The concept is verified by comparing predicted HF antenna characteristics to measured results. The efficiency of the conformal HF antenna is compared to a tuned whip and loop antenna. The conformal antenna shows

  12. Fast Characterization of Radiation Patterns of Conformal Array Antennas

    E-print Network

    Paris-Sud XI, Université de

    are thus of special interest for imaging radar systems mounted on the fuselage of an Unmanned Aerial Vehicle (UAV) or of an aircraft [1]. This new generation of radar imaging systems is based shaped arrays. II. PROBLEM FORMULATION Consider an antenna array conformal to a surface 3 S R

  13. Performance simulation and analysis of two kinds of cylindrical conformal microstrip Yagi antennas

    Microsoft Academic Search

    Song Lizhong; Fu Shifeng; Fang Qingyuan; Wu Qun

    2009-01-01

    Based on two kinds of traditional planar microstrip Yagi antennas, the radiation performances of corresponding cylindrical conformal microstrip Yagi antennas are discussed and simulated in this paper. In simulations, each kind of microstrip Yagi antenna has three directors. For each kind of microstrip Yagi antenna, the diameter of conductor cylinder is 300 mm and two same antennas are symmetrically mounted

  14. High Data Rate Link from DIVA Using a Conformal Antenna

    NASA Astrophysics Data System (ADS)

    Loeffler, D.; Wiesbeck, W.; Wiesler, A.; Bastian, U.; Roeser, S.; Mandel, H.; Seifert, W.; Wagner, S.

    Like some other small spinning scientific satellites, DIVA has a fixed position of the spinning axis with respect to sun. Due to this alignment, the earth can appear in any angular position relative to the satellite, which causes the need for an antenna with full spherical coverage to maintain a permanent link to the control facilities on earth. Up to now this coverage usually was achieved by the use of ordinary TT&C-antennas, as they are utilized on communication satellites for telemetry, tracing and command. In this control application there is no need for high-data-rate communication, so this antenna neither offers high bandwidth nor high gain. Especially the low gain of this antenna type results in a bad signal-to-noise ratio (SNR) at the receiving antenna on the earth. As a consequence the low SNR limits the data rate to small values. In scientific missions with a high amount of data needed to be transferred to the earth, the use of these antennas results in a bottle neck in the data link and lowers the efficiency of the scientific mission itself. An increase in SNR at the receiving antenna needs an increase in signal strength because the noise figure of commercially used receiving antennas on the earth is already extremely low and cannot be lowered further without major technical effort. Hence the gain of the transmitting antenna on the satellite has to be increased. In this contribution a broadband conformal antenna concept is presented which yields an average gain of 7.6 dBi over the full sphere for the antenna on the satellite. The antenna consists of 26 elements which are located at different positions on the surface of the satellite. By using the knowledge of the earth's angular position from the satellite's navigation system, the element pointing best towards the earth is used for the link. Technically this problem is solved by using a low-loss switching matrix. Slot spirals are used as single elements. The element consists of an etched slot spiral on an RT/duroid 6002 substrate. A honeycomb structure and a carrier complete the simple mechanical setup of the single element. Using this new antenna there appears to be no limitation in the bandwidth of the data link due to the transmitting antenna, because the bandwidth of the used slot spiral can easily be one octave. Besides the large bandwidth, the pure circular polarisation is a major advantage of the spiral antenna. A usable data rate of 1.2 Mbit/s having a BER of 10^{-5} can be achieved using this switched conformal array antenna and an RF-bandwidth of 2 MHz in S-band.

  15. Development of a Low Profile Conformal UHF RFID Tag Antenna for Identification of Water Bottles

    E-print Network

    Elsherbeni, Atef Z.

    Development of a Low Profile Conformal UHF RFID Tag Antenna for Identification of Water Bottles--Development of a low profile conformal RFID tag antenna with an omnidirectional pattern when mounted on a water bottle water bottle is developed. The design challenges discussed include achieving sufficient antenna

  16. Development of a low profile conformal UHF RFID tag antenna for identification of water bottles

    Microsoft Academic Search

    Toni Bjorninen; Leena Ukkonen; Lauri Sydanheimo; Atef Z. Elsherbeni

    2011-01-01

    Development of a low profile conformal RFID tag antenna with an omnidirectional pattern when mounted on a water bottle is discussed. Results from full-wave electromagnetic simulations are presented to explain the design procedure and to evaluate the performance of the prototype tag antenna. The design uncertainty is quantified based on the expected maximum variations in the tag antenna and tag

  17. Wide-band radar front-end calibration for imaging SAR experiments with conformal antenna array

    Microsoft Academic Search

    T. Bertuch; P. Knott; H. Wilden; O. Peters

    2011-01-01

    If specifically designed, one of the advantages of conformal antenna arrays is their large field of view (LFOV) which can be significantly larger than the one of planar arrays. This property was successfully exploited in a radar experiment generating SAR images with an array scanning angle of 70°. For that purpose a conformal antenna array was connected to a radar

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

    NASA Technical Reports Server (NTRS)

    Kempel, Leo C.; Volakis, John L.

    1992-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

    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.

  20. Conformal Frequency Reconfigurable Microstrip Antenna on a Thin Substrate for Wide-Band Applications

    Microsoft Academic Search

    Jun Ouyang; Feng Yang; Shiwen Yang; Zaiping Nie; Zhiqing Zhao

    2008-01-01

    There is a fundamental limit in designing wide-band microstrip antennas on a thin substrate. Frequency reconfigurable structures provide a solution to this problem. A novel conformal frequency reconfigurable microstrip antenna is introduced in this article. The frequency range of 10-dB return loss of the proposed antenna is six times more than that of a corresponding simple rectangular microstrip antenna with

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

    E-print Network

    Arnold, Craig B.

    reduce the time spent in fabricating these #12;structures. When integrated with RF testing hardware as the substrate for the implementation of a conformal GPS antenna (1575 MHz ) design because of its durability

  2. Conformal Asymmetric Meandered Flare (AMF) Antenna for Body-Worn Applications

    Microsoft Academic Search

    Dimitris Psychoudakis; John L. Volakis

    2009-01-01

    A conformal body-worn antenna is presented for communications at 300 MHz. The antenna consists of a thin broadband flared-dipole element printed on a thin (0.1 mm) FR4 substrate without metallic backing or other shielding. The letter presents the design approach for tuning, matching, and mounting the antenna on the human body. Measurements are given for a human body phantom, and

  3. A wideband conformal antenna array for cognitive radio\\/MIMO applications

    Microsoft Academic Search

    J. K. Halpe Gamage; B. Holter; I. A. Jensen; K. Husby; J. Kuhnle

    2011-01-01

    This paper presents performance results of a wideband conformal antenna array consisting of six E-patch antennas placed above a cylindrical metallic ground plane, using air as substrate material. The paper contains simulation results based on a parameterized model developed in CST Microwave Studio, as well as measurement results from a prototype. It is shown that the properties of the prototyped

  4. Design and analysis of a conformal patch antenna for a wearable breast hyperthermia treatment system

    NASA Astrophysics Data System (ADS)

    Curto, Sergio; Ramasamy, Manoshika; Suh, Minyoung; Prakash, Punit

    2015-03-01

    To overcome the limitations of currently available clinical hyperthermia systems which are based on rigid waveguide antennas, a wearable microwave hyperthermia system is presented. A light wearable system can improve patient comfort and be located in close proximity to the breast, thereby enhancing energy deposition and reducing power requirements. The objective of this work was to design and assess the feasibility of a conformal patch antenna element of an array system to be integrated into a wearable hyperthermia bra. The feasibility of implementing antennas with silver printed ink technology on flexible substrates was evaluated. A coupled electromagnetic-bioheat transfer solver and a hemispheric heterogeneous numerical breast phantom were used to design and optimize a 915 MHz patch antenna. The optimization goals were device miniaturization, operating bandwidth, enhanced energy deposition pattern in targets, and reduced Efield back radiation. The antenna performance was evaluated for devices incorporating a hemispheric conformal groundplane and a rectangular groundplane configuration. Simulated results indicated a stable -10 dB return loss bandwidth of 88 MHz for both the conformal and rectangular groundplane configurations. Considering applied power levels restricted to 15 W, treatment volumes (T>410C) and depth from the skin surface were 11.32 cm3 and 27.94 mm, respectively, for the conformal groundplane configuration, and 2.79 cm3 and 19.72 mm, respectively, for the rectangular groundplane configuration. E-field back-radiation reduced by 85.06% for the conformal groundplane compared to the rectangular groundplane configuration. A prototype antenna with rectangular groundplane was fabricatd and experimentally evaluated. The groundplane was created by printing silver ink (Metalon JS-B25P) on polyethylene terephthalate (PET) film surface. Experiments revealed stable antenna performance for power levels up to 15.3 W. In conclusion, the proposed patch antenna with conformal groundplane and prined ink technology shows promising performance to be integrated in a clinical array system.

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

    NASA Astrophysics Data System (ADS)

    Roy, Sayan

    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.

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

    E-print Network

    Tentzeris, Manos

    , the cylindrically curved panels are impacted using a drop-weight impact apparatus with an instrumented spherical tip-lobes and wider beamwidth. The results of impact test indicate that the value of the contact force decreasesImpact Behavior and Radiation Performance of a Structurally Integrated Antenna Array Conformed

  7. Radiation and scattering from printed antennas on cylindrically conformal platforms

    NASA Technical Reports Server (NTRS)

    Kempel, Leo C.; Volakis, John L.; Bindiganavale, Sunil

    1994-01-01

    The goal was to develop suitable methods and software for the analysis of antennas on cylindrical coated and uncoated platforms. Specifically, the finite element boundary integral and finite element ABC methods were employed successfully and associated software were developed for the analysis and design of wraparound and discrete cavity-backed arrays situated on cylindrical platforms. This work led to the successful implementation of analysis software for such antennas. Developments which played a role in this respect are the efficient implementation of the 3D Green's function for a metallic cylinder, the incorporation of the fast Fourier transform in computing the matrix-vector products executed in the solver of the finite element-boundary integral system, and the development of a new absorbing boundary condition for terminating the finite element mesh on cylindrical surfaces.

  8. Engineering antenna radiation patterns via quasi-conformal mappings.

    PubMed

    García-Meca, Carlos; Martínez, Alejandro; Leonhardt, Ulf

    2011-11-21

    We use a combination of conformal and quasi-conformal mappings to engineer isotropic electromagnetic devices that modify the omnidirectional radiation pattern of a point source. For TE waves, the designed devices are also non-magnetic. The flexibility offered by the proposed method is much higher than that achieved with conformal mappings. As a result, it is shown that complex radiation patterns can be achieved, which can combine high directivity in a desired number of arbitrary directions and isotropic radiation in other specified angular ranges. In addition, this technique enables us to control the power radiated in each direction to a certain extent. The obtained results are valid for any part of the spectrum. The potential of this method is illustrated with some examples. Finally, we study the frequency dependence of the considered devices and propose a practical dielectric implementation. PMID:22109400

  9. An investigation of conformable antennas for the astronaut backpack communication system

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

    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.

  10. An investigation of conformable antennas for the astronaut backpack communication system

    NASA Astrophysics Data System (ADS)

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

    1988-06-01

    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.

  11. Locally conformal FDTD modeling of MEMS-Based antenna sensors for melanoma detection

    Microsoft Academic Search

    D. Caratelli; A. Yarovoy; A. Massaro; R. Cingolani; A. Lay-Ekuakille

    2011-01-01

    The full-wave characterization of reconfigurable antenna sensors for non-invasive detection of melanoma is presented. To this end, an enhanced locally conformal finite- difference time-domain numerical procedure, based on a suitable normalization of the electromagnetic field-related quantities, is adopted. In this way, a physical insight in wave diffraction phenomena occurring in the radar monitoring of skin cancers, as well as in

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

    NASA Technical Reports Server (NTRS)

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

    2006-01-01

    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.

  13. Maximum power penetration through an electrically small aperture

    NASA Astrophysics Data System (ADS)

    Lee, K. S. H.

    1983-05-01

    An analysis is presented for the maximum power absorbed by a monopole antenna over a ground plane with a load impedance receiving an external time-harmonic field. The power conservation law is examined in the cases of total or partial absorption of the field power, noting the necessity for the antenna and the electrical field to be parallel and 90 deg out of phase to have a maximized interaction. Consideration of the maximal absorption area leads to a discussion of the EM penetration through an electrically small aperture, which yields an expression for the maximal EM absorption area, as well as the transmission cross-section.

  14. Antenna Technologies for NASA Applications

    NASA Technical Reports Server (NTRS)

    Miranda, Felix

    2007-01-01

    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.

  15. Antenna Technologies for NASA Applications

    NASA Technical Reports Server (NTRS)

    Miranda, Felix A.

    2006-01-01

    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.

  16. Body-Worn E-Textile Antennas: The Good, the Low-Mass, and the Conformal

    Microsoft Academic Search

    Timothy F. Kennedy; Patrick W. Fink; Andrew W. Chu; Nathan J. Champagne; Gregory Y. Lin; Michael A. Khayat

    2009-01-01

    Support of ever increasing applications for wireless data and communications on a body-centric platform requires novel antenna systems that can be integrated with the body-worn environment, while maintaining free-range of movement and minimal mass impact. E-textile antennas show great promise due to their ease of integration with other textile materials, and they are inherently low-mass and flexible relative to conventional

  17. Proceedings ofAsia-Pacific Microwave Conference 2007 Conformal Antennas on Liquid Crystalline Polymer

    E-print Network

    Swaminathan, Madhavan

    of 0.002 up to mm wave frequencies; and good mechanical properties such as mechanical flexibility and a low coefficient of thermal expansion [1]. Prior research on RF SOP focused on embedding high quality the effects of an RF- module package is discussed. Finally, the details of the fabrication ofthe antennas

  18. Body conformal antennas for superficial hyperthermia: the impact of bending contact flexible microstrip applicators on their electromagnetic behavior.

    PubMed

    Correia, Davi; Kok, H Petra; de Greef, Martijn; Bel, Arjan; van Wieringen, Niek; Crezee, Johannes

    2009-12-01

    Hyperthermia is a powerful radiosensitizer for treatment of superficial tumors. This requires body conformal antennas with a power distribution as homogeneous as possible over the skin area. The contact flexible microstrip applicators (CFMA) operating at 434 MHz exist in several sizes, including the large size 3H and 5H. This paper investigates the behavior of the electromagnetic fields for the 3H and 5H CFMA in both flat and curved configurations, and the impact on performance parameters like the penetration depth (PD) and the effective heating depth (EHD). The underlying theory behind the electromagnetic behavior in curved situations is presented as well as numerical simulations of both flat and curved configurations. The results are compared to measurements of the electromagnetic field distributions in a cylindrical patient model. Due to their large size multimode solutions may exist, and our results confirm their existence. These multimode solutions affect both the power distribution and PD/EHD, with a dependence on applicator curvature. Therefore, the performance parameters like PD and EHD need to be carefully assessed when bending large size CFMA applicators to conform to the patient body. This conclusion also holds for other types of large size surface current applicators. PMID:19695983

  19. Design and performance of small printed antennas

    Microsoft Academic Search

    Rod B. Waterhouse; S. D. Targonski; D. M. Kokotoff

    1998-01-01

    Electrically small microstrip patches incorporating shorting posts are thoroughly investigated. These antennas are suitable for mobile communications handsets where limited antenna size is a premium. Techniques to enhance the bandwidth of these antennas are presented and performance trends are established. From these trends, valuable insight to the optimum design, namely broad bandwidth, small size, and ease of manufacturing, is given

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

    PubMed

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

    2009-02-01

    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

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

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

    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.

  2. Superconducting matching networks in monopole antennas

    NASA Astrophysics Data System (ADS)

    Piatnicia, A. Y.; Talisa, S. H.; Buckley, M. J.; Gavaler, J. R.; Janocko, M. A.

    1991-08-01

    The goals of this program were to demonstrate the performance advantages of UHF Super Directive Array using a monopole antenna matching network made of high temperature superconducting (HTS) material over a monopole antenna matching network made of gold and to demonstrate the feasibility of using HTS material matching networks to feed a two element electrically small superdirective monopole array. In both cases only the matching networks were made of HTS material. The radiators were made of silver, copper, and steel. The electrically small monopole antenna and the electrically small element monopole antenna array were operated in the UHF band because the need exists for a high efficiency electrically small array operating in the UHF range as part of a multispectral seeker of an air-to-air missile. To date no antenna system consisting of electrically small conventional metal monopole radiators and HTS material matching networks has been demonstrated. An electrically small superdirective monopole array with superconducting matching networks is a candidate for use in an air-to-air missile as part of a multispectral seeker. The seeker must have a multispectral capability in order to successfully engage advanced Low Observable aircraft and missiles. The air-to-air missile guidance is initially provided by a surveillance and control aircraft.

  3. Development of a structurally integrated conformal load-bearing multifunction antenna: overview of the Air Force Smart Skin Structures Technology Demonstration Program

    NASA Astrophysics Data System (ADS)

    Lockyer, Allen J.; Alt, Kevin H.; Kinslow, Robert W.; Kan, Han-Pin; Kudva, Jayanth N.; Tuss, James; Goetz, Allan C.

    1996-05-01

    The Structures Division of the Air Force's Wright Laboratory is sponsoring the development and demonstration of a new high pay-off technology termed CLAS--Conformal Load Bearing Antenna Structures. Northrop Grumman Corporation and TRW/ASD are developing the technology under the `Smart-Skin Structure Technology Demonstration (S3D)' program, contract, No. F33615-93-C-3200. The program goal is to design, develop, fabricate, and test a CLAS component and lay the foundation for future work where potential benefits from structurally integrated antennas may be realized. Key issues will focus but are not limited to the design, structures, and manufacturing aspects of antenna embedment into load bearing aircraft structures. Results from Phase I of the program have been previously reported, where initial pay-offs in reducing overall airframe acquisition and support cost, weight, signature, and drag were quantitatively and qualitatively identified. A full-sized CLAS component, featuring a broadband multi-arm spiral embedded in sandwich stiffened structure, will be fabricated and tested for static strength, durability, and damage tolerance. Basic electrical performance, (e.g. radiation patterns, gain, and impedance) will also be verified; however, extensive electrical validation will be the subject of further work. Key aspects of the work and progress to date are detailed below.

  4. Antenna engineering handbook /2nd edition/

    NASA Astrophysics Data System (ADS)

    Johnson, R. C.; Jasik, H.

    Essential principles, methods, and data for solving a wide range of problems in antenna design and application are presented. The basic concepts and fundamentals of antennas are reviewed, followed by a discussion of arrays of discrete elements. Then all primary types of antennas currently in use are considered, providing concise descriptions of operating principles, design methods, and performance data. Small antennas, microstrip antennas, frequency-scan antennas, conformal and low-profile arrays, adaptive antennas, and phased arrays are covered. The major applications of antennas and the design methods peculiar to those applications are discussed in detail. The employment of antennas to meet the requirements of today's complex electronic systems is emphasized, including earth station antennas, satellite antennas, seeker antennas, microwave-relay antennas, tracking antennas, radiometer antennas, and ECM and ESM antennas. Finally, significant topics related to antenna engineering, such as transmission lines and waveguides, radomes, microwave propagation, and impedance matching and broadbanding, are addressed.

  5. Multiple frequency printed slot and dipole antennas 

    E-print Network

    Kolsrud, Arild

    1997-01-01

    Multiple frequency antennas are becoming more and more important as the technology advances. Printed circuit antennas can be designed to achieve multiple frequency operation. The advantages like low cost, conformal and planar, and a possible...

  6. X-Antenna: A graphical interface for antenna analysis codes

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

    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.

  7. High power very low frequency\\/low frequency transmitting antennas

    Microsoft Academic Search

    PEDER HANSEN

    1990-01-01

    Very-low-frequency (VLF) and low-frequency (LF) transmitting antennas are small with respect to the wavelength and are required to radiate substantial power levels. Design parameters for these antennas are discussed, including the impact of technical advances in high-voltage design and bandwidth enhancement. Most of these antennas are various realizations of electrically small monopoles that can be modeled by a simple series

  8. Application for smart skin technologies to the development of a conformal antenna installation in the vertical tail of a military aircraft

    Microsoft Academic Search

    Kevin H. Alt; Allen J. Lockyer; Christopher A. Martin; Jayanth N. Kudva; Allan C. Goetz

    1995-01-01

    Recent developments in smart skins technology at Northrop Grumman have paved the way toward incorporating avionics communication functions, previously provided by blade antennas, into the vertical tail of a military aircraft. Radio frequency communication link ranges can be significantly improved by structurally integrating the antenna radiating element into the tail region. Excitation of the large vertical tail surface improves radiation

  9. The Zeaxanthin-Independent and Zeaxanthin-Dependent qE Components of Nonphotochemical Quenching Involve Common Conformational Changes within the Photosystem II Antenna in Arabidopsis 1(W)

    Microsoft Academic Search

    Matthew P. Johnson; Ahmad Zia; Peter Horton; Alexander V. Ruban

    2009-01-01

    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

  10. Miniaturized telemetry antennas with integrated electronics

    Microsoft Academic Search

    Thomas Goodwin

    2008-01-01

    Microstrip wrap antennas have been used for telemetry applications since the 1960's. Robert Munson published a seminal paper describing wrap antenna theory and design in 1974. The basic antenna concept consists of a continuous radiating element and a corporate feed network printed on a thin dielectric substrate, which is then formed to be conformal to a cylindrical or conical surface.

  11. Analysis of Dipole Antenna Eccentered in a Borehole for Borehole Radar

    Microsoft Academic Search

    S. Ebihara; Y. Inoue

    2007-01-01

    In this paper, we analyze response of borehole radar that use an electrically small dipole antenna in an eccentric borehole. Our approach is an extended version of the pseudoanalytic formulation, which was previously applied for analysis of an induction logging tool. In order to verify the calculation method, we did two experiments. The first one is measurement of monopole antenna

  12. Antenna Systems Advanced Antenna Systems

    E-print Network

    Fang, Yuguang "Michael"

    EEL4461 EEL5462 Fall 2014 Antenna Systems Advanced Antenna Systems Instructor Dr. Jenshan Lin://lss.at.ufl.edu/) Textbooks Required: Balanis, Antenna Theory - Analysis and Design, 3rd ed. 2005 Prerequisite EEL3472 principles of antenna and to apply them to the design and analysis of antenna systems. Students will learn

  13. Design and performance of a microstrip reflectarray antenna 

    E-print Network

    Javor, Ronald David

    1994-01-01

    Microstrip reflectarray antennas present an alternative to conventional directive antennas in that they are flat, easy to install and manufacture, are conformal to the mounting surface and posses high power capabilities. For the first time...

  14. Furlable antenna. [antenna design

    NASA Technical Reports Server (NTRS)

    Barnett, M. A. (inventor)

    1976-01-01

    An improved furlable antenna particularly suited for use in a celestial space environment is described. The antenna is characterized by an actuator comprising an elastomeric member of an annular configuration, an annular array of uniformly spaced antenna ribs rigidly affixed at the base ends to an actuator which enables it to be supported for pivotal displacement from a deployed configuration. The ribs are radially extended from the actuator to a furled configuration. The ribs are extended parallel to the axis of the actuator with flexible reflecting web affixed to the ribs, with angularly spaced bearing blocks.

  15. Synthesis of Conformal Arrays With Optimized Polarization

    Microsoft Academic Search

    Christof Dohmen; Johann W. Odendaal; Johan Joubert

    2007-01-01

    Adaptive array theory is applied to a conformal antenna array to synthesize a main beam with optimized polarization employing dual polarized patch antennas as radiators. The required polarization in the main beam region of the array is realized by combining the weighted individual feeding ports of the patch antennas before the beam forming optimization is performed. This significantly reduces the

  16. Spiral microstrip antenna with resistance

    NASA Astrophysics Data System (ADS)

    Shively, David G.

    1994-06-01

    The present invention relates to microstrip antennas, and more particularly to wide bandwidth spiral antennas with resistive loading. A spiral microstrip antenna having resistor element embedded in each of the spiral arms is provided. The antenna is constructed using a conductive back plane as a base. The back plane supports a dielectric slab having a thickness between one-sixteenth and one-quarter of an inch. A square spiral, having either two or four arms, is attached to the dielectric slab. Each arm of the spiral has resistor elements thereby dissipating an excess energy not already emitted through radiation. The entire configuration provides a thin, flat, high gain, wide bandwidth antenna which requires no underlying cavity. The configuration allows the antenna to be mounted conformably on an aircraft surface.

  17. Tunable Miniaturized Patch Antennas With Self-Biased Multilayer Magnetic Films

    Microsoft Academic Search

    Guo-Min Yang; X. Xing; A. Daigle; M. Liu; O. Obi; S. Stoute; K. Naishadham; Nian X. Sun

    2009-01-01

    Magneto-dielectric substrates with thin magnetic films show great potential in realizing electrically small tunable antennas with enhanced bandwidth, improved directivity, and high efficiency. This communication introduces self-biased NiCo-ferrite magnetic films as a practical mean to tune a patch antenna by loading single layer and multilayer self-biased ferrite films. The central resonant frequency of the unloaded patch antenna is measured at

  18. VHF/UHF low profile antenna analysis

    NASA Astrophysics Data System (ADS)

    Adams, J. D.; Cotton, Rickey B.; Tripp, Victor K.

    1995-07-01

    This report describes the results of an analytical and experimental study to determine the feasibility of developing octave bandwidth, electrically small, low profile antennas in UHF and VHF bands from 20 to 1200 MHz. The combination of achieving both small size and octave bandwidths in the frequency range from 20-160 MHz presents the most difficult challenge. Antenna elements examined include loops, disk cones, conical monopoles, Goubau, and microstrip spiral antennas. Results presented include experimental data on disk-cones, a scaled conical monopole, and a scaled microstrip spiral antenna. More work remains to be done, especially in the 20-40 MHz band. However, it is projected that, with continued development efforts, the desired results can be achieved.

  19. Deployable antenna

    NASA Technical Reports Server (NTRS)

    Fink, Patrick W. (Inventor); Dobbins, Justin A. (Inventor); Lin, Greg Y. (Inventor); Chu, Andrew W. (Inventor); Scully, Robert C. (Inventor)

    2006-01-01

    A deployable antenna and method for using wherein the deployable antenna comprises a collapsible membrane having at least one radiating element for transmitting electromagnetic waves, receiving electromagnetic waves, or both.

  20. Circular and polygonal array antennas for electronic steering

    Microsoft Academic Search

    Juliano R. Brianeze; Edson Reis

    2010-01-01

    The circular (ring) array antenna may be considered as one of the building blocks of a whole family of conformal array antennas, which are antennas structurally integrated to a given surface (Visser, 2005). A cylindrical or circular array of elements has a potential of 360° coverage, either with an omnidirectional beam, multiple beams, or a narrow beam that can be

  1. IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 55, NO. 4, APRIL 2007 1051 Multilayer Effects on Microstrip Antennas for

    E-print Network

    Tentzeris, Manos

    IN THE LAST TEN years, research has been undertaken on the embedding of antennas in load-bearing structural sur- faces of aircraft to improve both structural efficiency and an- tenna performance (Fig. 1) [1 called conformal load-bearing antenna struc- ture (CLAS) [3]. Innovative integration of antenna elements

  2. Predictions of the efficiencies of supeconducting small antennas connected to lossy ground planes using a Sommerfeld integral technique

    NASA Astrophysics Data System (ADS)

    Cook, G. G.; Khamas, S. K.; Bowling, D. R.; Overfeltm, P. L.; Hageman, L.

    1994-07-01

    Electrically small loops and monopoles are modeled over infinite lossy ground planes using a modification to the Sommerfeld approach, in order to asses the performance of YBCO antennas connected to typically metallic ground planes. Calculated results suggest that for antennas with low-radiation resistances, significant efficiency improvements can be obtained with YBCO elements even if the ground planes remain lossy, and that little is to begained by making th ground planes superconducting if the antenna remain lossy.

  3. Land vehicle antennas for satellite mobile communications

    NASA Technical Reports Server (NTRS)

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

    1985-01-01

    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.

  4. Meander antennas

    NASA Astrophysics Data System (ADS)

    Rashedmohassel, J. A.

    Meander antennas are a class of wire structures made from meander sections intended to reduce the resonant length of the antenna. Each half section is formed when the wire is folded three times over its course and a complete section is made when two half sections are connected back to back. The resonant frequency and other antenna characteristics depend primarily on the number of sections per wavelength N and the separation of the folded arms w. Usually w is kep small in comparison to the length of the antenna and therefore the undesirable radiation due to the horizontal portions are negligible. In this case the reduction in the resonant length depends on N and is typically 25 to 50 percent. The efficiency is affected only by the ohmic losses in the wire and the bandwidth of the antenna is generally less than a conventional monopole but comparable to that of other size reduction techniques such as base loaded antennas.

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

    NASA Astrophysics Data System (ADS)

    Schmitt, Franz-Josef

    2010-08-01

    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.

  6. UMass Antenna Lab Antennas Studies for

    E-print Network

    Southern California, University of

    UMass Antenna Lab Antennas Studies for UWB Radio Program Review May 23, 2002 Professor David M@ecs.umass.edu #12;UMass Antenna Lab UWB Radio Antenna and Electromagnetics Tasks - progress on original tasks - 1. Full-Wave Calculation of Receive Antenna Voltage (arbitrary input voltage waveform, antenna types

  7. A NOVEL RADIATION PATTERN AND FREQUENCY RECONFIGURABLE MICROSTRIP ANTENNA ON A THIN SUBSTRATE FOR WIDE-BAND AND WIDE-ANGLE SCANNING APPLICATION

    Microsoft Academic Search

    Jun OuYang; F. Yang; S. W. Yang; Z. P. Nie; Z. Q. Zhao

    2008-01-01

    A novel radiation pattern and frequency reconfigurable microstrip antenna is introduced in this paper. This antenna is designed on a thin substrate for the application of conformal phased antenna future. The proposed antenna make the operating frequency range 6 times larger than that of a simple rectangular microstrip antenna, and make the beam covering from ?70? ?70? compared with the

  8. Antenna Technologies for Future NASA Exploration Missions

    NASA Technical Reports Server (NTRS)

    Miranda, Felix A.

    2006-01-01

    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.

  9. Design of a matching network for dipole antennas

    NASA Astrophysics Data System (ADS)

    Park, Jennifer

    1993-03-01

    The input impedance of an antenna is highly dependent on the frequency range in which it operates. For an electrically small antenna to operate in a broad frequency range, the antenna must be properly matched. This thesis presents the design of a matching network for a 1-meter monopole antenna, operating over 30-90 MHz using the real frequency method (RFM). It outlines the mathematical steps needed to determine the equalizer function, which ultimately leads to the circuit design. The goal of the RFM, given the real frequency data, is to optimize the Transducer Power Gain (TPG) and minimize the reflection coefficient or power lost due to the impedance mismatch. Complete design including network realization is given. However, no experimental results are presented.

  10. UMass Antenna Lab Antennas Studies for

    E-print Network

    Southern California, University of

    UMass Antenna Lab Antennas Studies for UWB Radio of Massachusetts at Amherst Amherst, MA 01003 schaubert@ecs.umass.edu #12;UMass Antenna Lab UWB Radio Antenna and Electromagnetics Tasks 1. Full-Wave Calculation of Receive Antenna Voltage (arbitrary input voltage waveform

  11. RANDOM SAMPLE ANTENNA SELECTION WITH ANTENNA SWAPPING

    E-print Network

    Blostein, Steven D.

    RANDOM SAMPLE ANTENNA SELECTION WITH ANTENNA SWAPPING by Edmund Chun Yue Tam A thesis submitted.) Wireless communications employing multiple transmit and receive antennas can bring promising improvements technique known as antenna selection can be applied. In antenna selection, only a subset of the full array

  12. Conformal microstrip patch circular array with orthogonal conformal stripline feed and all-angle transition

    Microsoft Academic Search

    R. T. Cock; R. D. Cook

    1997-01-01

    A prototype Ku-band, 32-element, circular microstrip patch array connected to a conformal stripline feed with an orthogonal all-angle transition was designed, fabricated and tested. The low cost antenna uses standard printed circuit technology. The antenna consists of a stripline feed conformally encased in a metal ring orthogonal to microstrip patch radiating elements which are etched on the front Duriod 5880

  13. Polydimethylsiloxane membranes for millimeter-wave planar ultra flexible antennas

    Microsoft Academic Search

    Nicolas Tiercelin; Philippe Coquet; Ronan Sauleau; Vincent Senez; Hiroyuki Fujita

    2006-01-01

    We present here the use of polydimethylsiloxane (PDMS) membranes as a new soft polymer substrate (?r ap 2.67 at 77 GHz) for the realization of ultra-flexible millimeter-wave printed antennas thanks to the extremely low Young's modulus (EPDMS < 2 MPa). Ultimately this peculiar property enables one to design wide-angle mechanically beam-steering antennas and flexible conformal antennas. The experimental characterization of

  14. Steerable Risley Prism antennas with low side lobes in the Ka band

    Microsoft Academic Search

    B. J. Tame; N. A. Stutzke

    2010-01-01

    The Risley Prism antenna is a steerable beam antenna that is light weight, compact, conformal if desired and can be used on a wide variety of platforms. Small mobile platforms have limited real estate and this antenna technology is a viable solution. Some potential applications include UAV's, Humvee's and other ground mobile vehicles as well as larger platforms such as

  15. 176 IEEE ANTENNAS AND WIRELESS PROPAGATION LETTERS, VOL. 3, 2004 FDTD Analysis of Bow-Tie Antenna by Incorporating

    E-print Network

    Park, Seong-Ook

    176 IEEE ANTENNAS AND WIRELESS PROPAGATION LETTERS, VOL. 3, 2004 FDTD Analysis of Bow-Tie Antenna-domain (FDTD) method, locally conformal grid, static field solution. I. INTRODUCTION THE finite-difference time-domain (FDTD) method is com- monly used for calculating various electromagnetic prob- lems because of its

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

    SciTech Connect

    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

    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.

  17. A source of E and H fields for antenna-factor calibration

    NASA Astrophysics Data System (ADS)

    Fitzgerrell, R. G.

    1984-05-01

    The loop cell used for calibration is fabricated using two intersecting metal sheets joined at the intersection and forming a 36-deg angle. A section of a loop is mounted between two coaxial panel jacks, one on each sheet located at a distance equal to the loop radius from the intersection. A known current through this section of electrically small loop produces calculable E and H fields between the sheets in the plane of the loop. These known fields may be used to determine the antenna factor of small E and H antennas placed in the field if the mutual impedance due to the antenna images in the sheets is negligible and the antenna is not close to the open edges of the cell. Measured and calculated antenna factors agree within + or - 2 dB between 0.25 and 1000 MHz.

  18. Experimental Study of the Effect of Paint on Embedded Automotive Antennas

    Microsoft Academic Search

    Brendan Pell; Wayne Rowe; Edin Sulic; Kamran Ghorbani; Sabu John; Rahul Gupta; Kefei Zhang; Brian Hughes

    2008-01-01

    In years have seen the advent of new types of automotive antennas, such as blade or 'shark-fin' antennas and conformal planar roof mounted antennas. In many cases it is desirable to paint these antennas to improve the appearance of the vehicle. In this communication we present an investigation of the effect that both metallic and non-metallic two-pack polyurethane paint has

  19. The conical antenna as a sensor or probe

    NASA Astrophysics Data System (ADS)

    King, R. W. P.

    1983-02-01

    It is shown that the electrically small wide-angled spherically capped conical monopole has frequency-related properties closely resembling those of the electrically thin cylindrical dipole. It is pointed out that the frequency dependence of the current in the load of a conical receiving antenna can be determined by applying the reciprocal theorem. At each frequency, there are three steps to be followed. The first is determining the radiation field of the conical antenna when driven by unit voltage. The second is locating a thin cylindrical dipole in the far field of the conical antenna and determining the current in its load. The application of the reciprocal theorem demonstrates that this is also the current in an equal load in the conical antenna when the cylindrical dipole is driven by unit voltage. The third step is determining the field arising from the cylindrical dipole at the location of the conical antenna. This, it is pointed out, is the incident field that excites the current in the load of the conical antenna.

  20. Technique for Solving Electrically Small to Large Structures for Broadband Applications

    NASA Technical Reports Server (NTRS)

    Jandhyala, Vikram; Chowdhury, Indranil

    2011-01-01

    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.

  1. Electrically-small quarter-wave, and resonant monopole elements with disk ground plans in free space

    NASA Astrophysics Data System (ADS)

    Weiner, M. M.

    1990-12-01

    This paper extends previously reported results for a quarterwave monopole element on a disk ground plane in free space to include electrically-small and resonant elements. Numerical results are obtained by utilizing Richmond's method of moments computer program for disk ground planes in free space.

  2. IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 60, NO. 1, JANUARY 2012 421 Extended Mode-Based Bandwidth Analysis for Asymmetric

    E-print Network

    Nam, Sangwook

    , a method for estimating 3 dB bandwidth of near-field communication (NFC) systems with non, electrically small antenna, near-field communication (NFC), near-field coupling. I. INTRODUCTION According, the method for estimating the 3 dB bandwidth of the near-field communication (NFC) system is proposed

  3. IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 59, NO. 8, AUGUST 2011 3131 [3] E. Boch, "Backhaul for WiMax and LTE: High bandwidth ethernet

    E-print Network

    Nam, Sangwook

    . 2005, pp. 125­128. Mode-Based Estimation of 3 dB Bandwidth for Near-Field Communication Systems Youndo estimation, capacity, electrically small antenna, near-field communication (NFC), near-field coupling. I on the bandwidth and the capacity of a near-field communication (NFC) system was reported using the equivalent

  4. VIRGINIA TECH ANTENNA GROUP

    E-print Network

    Beex, A. A. "Louis"

    VIRGINIA TECH ANTENNA GROUP Development of New Antennas and Applications: Applications of UWB - 21, 2005 Sheraton Crystal City, Arlington, VA Virginia Tech1872 #12;IDGA - 20-21 September 2005Military Antenna Systems, Arlington, VA Virginia Tech1872 VIRGINIA TECH ANTENNA GROUP1 Outline · - Impulse

  5. Self-structuring antennas

    Microsoft Academic Search

    C. M. Coleman; E. J. Rothwell; J. E. Ross

    2000-01-01

    This paper presents a new antenna concept with potential For use in a variety of difficult antenna situations. The term “self-structuring” implies that the antenna changes its electrical shape in response to its environment. The shape change is not made by altering the position or physical geometry of the antenna structure, but rather by controlling the electrical connections between the

  6. Phase scan antenna array

    Microsoft Academic Search

    Richard A. Stern; Richard W. Babbitt; Gerald Mikucki

    1986-01-01

    A phase scan antenna array for planar radar scanning in a single plane with a pencil-shaped beam is provided comprising a plurality of ferrite rod line source antennas. Each rod antenna has a plurality of beam-emitting slots spaced along one side thereof and is end fed in phase with the other antennas from a single hollow metallic waveguide by means

  7. 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

  8. Overview of GPS antennas

    Microsoft Academic Search

    E. Levine

    2009-01-01

    GPS antennas should cover most of the sky and see as much satellites as possible. The antenna should have a broad radiation beam and low gain. The antenna must be well-matched in the relevant frequencies and be Right Hand Circular Polarized. The key factor in GPS systems for high position accuracy and for short acquisition time is the antenna. It

  9. Information for Antenna Group

    E-print Network

    Beex, A. A. "Louis"

    Information for VISITORS To Antenna Group Virginia Tech Bradley Department of Electrical-800-388-7005 www.smartwaybus.com Campus Electrical Engineering Building Whittemore Hall (housing the Antenna Group Offices/Lab and the Antenna Lab) and Durham Hall are shown on the attached map. The Virginia Tech Antenna

  10. Automatic antenna-tuning unit for software-defined and cognitive radio

    Microsoft Academic Search

    Oh Sung-hoon; Hang Song; James T. Aberle; Bertan Bakkaloglu; Chaitali Chakrabarti

    2007-01-01

    Summary Thispaperdiscussestheimplementationofanautomaticantennatuningunitsystem(ATU)forsoftware-definedand cognitive radio. The ATU simplifies radio frequency (RF) front-end design for multi-band, multi-mode radios by allowing an electrically small reconfigurable antenna to become a frequency-agile selective component (essentially a tunable filter). In implementing the ATU, impedance synthesizers (tunable matching networks) using RF MEMS switches as the control elements are used to match a more or less arbitrary load

  11. Monopole antenna decoupling with a radial-transmission-line choke

    NASA Astrophysics Data System (ADS)

    Dalby, T. G.

    A method of decoupling a monopole antenna from surrounding conductive elements is demonstrated using a radial- transmission-line equivalent of a lambda/4 choke mounted at the base of, and concentrically with the monopole. The arrangement can provide a structure smaller in dimension and more convenient than a conventional lambda/4 choke at wavelengths greater than 1 m. The radial line performance is extremely tolerant of dissymmetry in the configuration of either the monopole or the inner termination. Measurements of radiation patterns of monopoles with electrically small radial-line chokes indicate variations as expected, which can be controlled through changes in monopole configuration.

  12. Pattern synthesis for a conformal wing array

    Microsoft Academic Search

    Hans Steyskal; Hanscom AFB

    2002-01-01

    Future aircraft may utilize the large aerodynamic areas of the wings also for electrodynamics by structurally embedding conformal phased array antennas. We explore this concept with a computer model for a line array wrapped around a wing. The model uses a realistic wing profile and array element patterns which include the effects of mutual coupling and the local radius of

  13. DIPLOMA THESIS VECTOR ANTENNA FOR

    E-print Network

    DIPLOMA THESIS VECTOR ANTENNA FOR ULTRAHIGH ENERGY COSMIC NEUTRINO DETECTION IN THE ANTARCTIC ICE Contents iii List of Figures v 1 Introduction 1 2 Introduction to Antennas 5 2.1 Wire antennas 5 2.2 Dipole antennas 6 2.3 Half-wavelenght Dipole 8 2.4 Radiation Pattern of a Dipole Antenna 8 2.5 Antenna

  14. Wideband active antenna cancellation

    E-print Network

    Adaniya, Hana L

    2008-01-01

    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 ...

  15. JPL antenna technology development

    NASA Technical Reports Server (NTRS)

    Freeland, R. E.

    1982-01-01

    Systems-level technology for evolving cost-effective, STS compatible antennas that will be automatically deployed in orbit to perform a variety of missions in the 1985 to 2000 time period is discussed. For large space-based antenna systems, the LSST program has selected deployable antennas for development. The maturity of this class of antenna, demonstrated by the success of smaller size apertures, provides a potential capability for satisfying a significant number of near-term, space-based applications. The offset wrap-rib concept development is the basis of the JPL LSST antenna technology development program. Supporting technology to the antenna concept development include analytical performance prediction, the capability for measuring and evaluating mechanical antenna performance in the intended service environment, and the development of candidate system-level configurations for potential applications utilizing the offset wrap-rib antenna concept.

  16. Conformal House

    NASA Astrophysics Data System (ADS)

    Ryttov, Thomas A.; Sannino, Francesco

    We investigate the gauge dynamics of nonsupersymmetric SU(N) gauge theories featuring the simultaneous presence of fermionic matter transforming according to two distinct representations of the underlying gauge group. We bound the regions of flavors and colors which can yield a physical infrared fixed point. As a consistency check we recover the previously investigated bounds of the conformal windows when restricting to a single matter representation. The earlier conformal windows can be imagined to be part now of the new conformal house. We predict the nonperturbative anomalous dimensions at the infrared fixed points. We further investigate the effects of adding mass terms to the condensates on the conformal house chiral dynamics and construct the simplest instanton induced effective Lagrangian terms.

  17. Cross resonant optical antenna.

    PubMed

    Biagioni, P; Huang, J S; Duò, L; Finazzi, M; Hecht, B

    2009-06-26

    We propose a novel cross resonant optical antenna consisting of two perpendicular nanosized gold dipole antennas with a common feed gap. We demonstrate that the cross antenna is able to convert propagating fields of any polarization state into correspondingly polarized, localized, and enhanced fields and vice versa. The cross antenna structure therefore opens the road towards the control of light-matter interactions based on polarized light as well as the analysis of polarized fields on the nanometer scale. PMID:19659107

  18. Resonant Optical Antennas

    Microsoft Academic Search

    P. Mühlschlegel; H.-J. Eisler; O. J. F. Martin; B. Hecht; D. W. Pohl

    2005-01-01

    We have fabricated nanometer-scale gold dipole antennas designed to be resonant at optical frequencies. On resonance, strong field enhancement in the antenna feed gap leads to white-light supercontinuum generation. The antenna length at resonance is considerably shorter than one-half the wavelength of the incident light. This is in contradiction to classical antenna theory but in qualitative accordance with computer simulations

  19. JPL antenna technology development

    Microsoft Academic Search

    R. E. Freeland

    1981-01-01

    Plans for evaluating, designing, fabricating, transporting and deploying cost effective and STS compatible offset wrap rib antennas up to 300 meters in diameter for mobile communications, Earth resources observation, and for the orbiting VLBI are reviewed. The JPL surface measurement system, intended for large mesh deployable antenna applications will be demonstrated and validated as part of the antenna ground based

  20. UWB antenna characterization

    Microsoft Academic Search

    James S. McLean; Robert Sutton

    2008-01-01

    The characterization of UWB antennas is considered with emphasis placed on the determination of compact descriptors appropriate for UWB communications antennas. All of the descriptors can be derived from the antenna transfer function, thus providing a unified approach in which the transfer function is the basis for all of the subsequent computations. It is shown that the unambiguous determination of

  1. UWB magnetic antennas

    Microsoft Academic Search

    Hans Gregory Schantz

    2003-01-01

    Many commercial applications call for UWB antennas that are less prone to near-field coupling. Magnetic antennas are well suited for these applications, because the relatively large magnetic fields tend not to couple as strongly with near-by objects. The purpose of this article is to provide a brief overview of some UWB magnetic antennas. In particular, this paper will discuss large

  2. Active retrodirective antenna

    NASA Technical Reports Server (NTRS)

    Chernoff, R. C.; Tausworthe, R. C.

    1977-01-01

    Active antenna is self-phasing array which transmits signal in direction of remote pilot source. Word "active" means that transmitted power is generated by sources associated with antenna rather than by reflection of incident signal, as in passive retrodirective antenna. Array is also known as self-focusing array.

  3. Antenna development at DARPA

    NASA Astrophysics Data System (ADS)

    Corey, Larry; Jaska, Esko

    2004-09-01

    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.

  4. Optical antenna thermal emitters

    Microsoft Academic Search

    Jon A. Schuller; Thomas Taubner; Mark L. Brongersma

    2009-01-01

    Optical antennas are a critical component in nanophotonics research and have been used to enhance nonlinear and Raman cross-sections and to make nanoscale optical probes. In addition to their ‘receiving’ properties, optical antennas can operate in ‘broadcasting’ mode, and have been used to modify the emission rate and direction of individual molecules. In these applications the antenna must operate at

  5. Optical antenna thermal emitters

    Microsoft Academic Search

    Jon A. Schuller; Thomas Taubner; Mark L. Brongersma

    2009-01-01

    Optical antennas are a critical component in nanophotonics research and have been used to enhance nonlinear and Raman cross-sections and to make nanoscale optical probes. In addition to their `receiving' properties, optical antennas can operate in `broadcasting' mode, and have been used to modify the emission rate and direction of individual molecules. In these applications the antenna must operate at

  6. Antenna Theory Midterm Exam

    E-print Network

    Ida, Nathan

    Antenna Theory 2nd Midterm Exam November 21, 2005 Answer the following 3 questions. Questions have. It is required to produce an endfire antenna pattern with a single null at /2. Assuming you are free to use any. 2. An antenna array must produce a main beam and two, smaller side lobes as follows: f(!) = 1, " 3

  7. ANTENNA ARRAYS FOR SYNCHRONIZATION

    E-print Network

    Swindlehurst, A. Lee

    Chapter 1 EXPLOITING ANTENNA ARRAYS FOR SYNCHRONIZATION Gonzalo Seco1 Department of Signal Theory, attention has recently shifted to the use of antenna arrays for addressing these problems. The spatial selectivity o ered by an antenna array can dramatically improve performance in environments with severe

  8. Synthesis of multiple shaped beam antenna patterns

    NASA Technical Reports Server (NTRS)

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

    1973-01-01

    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.

  9. Resonant optical antennas.

    PubMed

    Mühlschlegel, P; Eisler, H-J; Martin, O J F; Hecht, B; Pohl, D W

    2005-06-10

    We have fabricated nanometer-scale gold dipole antennas designed to be resonant at optical frequencies. On resonance, strong field enhancement in the antenna feed gap leads to white-light supercontinuum generation. The antenna length at resonance is considerably shorter than one-half the wavelength of the incident light. This is in contradiction to classical antenna theory but in qualitative accordance with computer simulations that take into account the finite metallic conductivity at optical frequencies. Because optical antennas link propagating radiation and confined/enhanced optical fields, they should find applications in optical characterization, manipulation of nanostructures, and optical information processing. PMID:15947182

  10. Antenna Controller Replacement Software

    NASA Technical Reports Server (NTRS)

    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

    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.

  11. The Fourpoint Antenna as a LEDA Outrigger Antenna Steve Ellingson

    E-print Network

    Ellingson, Steven W.

    The Fourpoint Antenna as a LEDA Outrigger Antenna Steve Ellingson Aug 6, 2011 Contents 1 Introduction 2 2 The EDGES Fourpoint Antenna 2 3 NEC Model for the EDGES Fourpoint Antenna 2 4 A Candidate LEDA Outrigger Antenna 8 5 Considerations for Future Work 8 6 Acknowledgments 13 Bradley Dept. of Electrical

  12. Advanced design methodologies and novel applications of reflectarray antennas

    NASA Astrophysics Data System (ADS)

    Nayeri, Payam

    Reflectarray antennas combine the numerous advantages of printed antenna arrays and reflector antennas and create a hybrid high-gain antenna with a low-profile, low-mass, and diversified radiation performance. Reflectarrays are now emerging as the new generation of high-gain antennas for long-distance communications. In this dissertation, some advanced concepts demonstrating novel features of reflectarray antennas are presented. • First, various approaches for radiation analysis of reflectarray antennas are described and implemented. Numerical results are then presented for a variety of systems and the advantages, limitations, and accuracy of these approaches are discussed and compared with each other. • A broadband technique by using sub-wavelength elements is proposed and prototypes are fabricated and tested. This technique enables the reflectarray to achieve a significant bandwidth improvement with no additional cost. • Infrared reflectarrays antennas are studied for possible applications in concentrating solar power systems. Material losses, an important design issue at infrared frequencies, are investigated and reflectarrays consisted of dielectric resonant elements are proposed with low-loss features at infrared. • Multi-beam reflectarray antennas are studied and it is demonstrated that by optimizing the phase of the elements, a desirable multi-beam performance can be achieved using a single-feed. Local and global phase-only optimization techniques have been implemented. Two Ka-band quad-beam prototypes with symmetric and asymmetric beams have been fabricated and tested. • Different approaches for beam-scanning with reflectarray antennas are also reviewed and it is shown that for moderately wide angle beam-scanning, utilizing a feed displacement technique is more suitable than an aperture phase tuning approach. A feed displacement beam-scanning design with novel aperture phase distribution is proposed for the reflectarray antenna, and is further optimized to improve the performance. A high-gain Ka-band prototype achieving 60 degrees scan range with side-lobe levels below 15 dB is demonstrated. • The feasibility of designing reflectarray antennas on conformal surfaces is also studied numerically. A generalized analysis approach is presented and the radiation performance of reflectarray antennas on singly-curved conformal cylindrical platforms are studied and compared with their planar counterpart. It is revealed that conformal reflectarray antennas are a suitable choice for a high-gain antenna where curved platforms are required. In summary, different challenges in reflectarray analysis and design are addressed in this dissertation. On the element design challenges, bandwidth improvement and infrared operation of reflectarray antennas have been studied. On the system level challenges, multi-beam designs, beam-scanning performance, and conformal platforms have been investigated. Several prototypes have been fabricated and tested, demonstrating the novel features and potential applications of reflectarray antennas.

  13. Linearly tapered slot antenna circular array for mobile communications

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    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.

  14. Cellular Reflectarray Antenna

    NASA Technical Reports Server (NTRS)

    Romanofsky, Robert R.

    2010-01-01

    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.

  15. The single antenna interferometer

    SciTech Connect

    Fitch, J.P.

    1990-01-15

    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.

  16. MSU Antenna Pattern Data

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

    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.

  17. Flexible sixteen monopole antenna array for microwave breast cancer detection.

    PubMed

    Bahrami, H; Porter, E; Santorelli, A; Gosselin, B; Popovic, M; Rusch, L A

    2014-01-01

    Radar based microwave imaging (MI) has been widely studied for breast cancer detection in recent times. Sensing dielectric property differences of tissues over a wide frequency band has been made possible by ultra-wideband (UWB) techniques. In this paper, a flexible, compact monopole antenna on a 100 ?m Kapton polyimide is designed, using a high frequency structure simulator (HFSS), to be in contact with biological breast tissues over the 2-5GHz frequency range. The antenna parameters are optimized to obtain a good impedance match over the required frequency range. The designed antenna size is 18mm × 18mm. Further, a flexible conformal 4×4 ultra-wideband antenna array, in a format similar to that of a bra, was developed for a radar-based breast cancer detection system. PMID:25570813

  18. Radiation by cavity-backed antennas on a circular cylinder

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

    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.

  19. Conformality lost

    SciTech Connect

    Kaplan, David B.; Lee, Jong-Wan; Son, Dam T.; Stephanov, Mikhail A. [Institute for Nuclear Theory, University of Washington, Seattle, Washington 98195-1550 (United States); Department of Physics, University of Illinois, Chicago, Illinois 60607-7059 (United States)

    2009-12-15

    We consider zero-temperature transitions from conformal to nonconformal phases in quantum theories. We argue that there are three generic mechanisms for the loss of conformality in any number of dimensions: (i) fixed point goes to zero coupling, (ii) fixed point runs off to infinite coupling, or (iii) an IR fixed point annihilates with a UV fixed point and they both disappear into the complex plane. We give both relativistic and nonrelativistic examples of the last case in various dimensions and show that the critical behavior of the mass gap behaves similarly to the correlation length in the finite temperature Berezinskii-Kosterlitz-Thouless (BKT) phase transition in two dimensions, {xi}{approx}exp(c/|T-T{sub c}|{sup 1/2}). We speculate that the chiral phase transition in QCD at large number of fermion flavors belongs to this universality class, and attempt to identify the UV fixed point that annihilates with the Banks-Zaks fixed point at the lower end of the conformal window.

  20. General properties of antennas

    Microsoft Academic Search

    Cari E. Baum; Kirtland AFB

    2002-01-01

    In antenna design there are some fundamental relationships based on reciprocity. The equivalence of antenna pattern in transmission and reception is well known. Less well known is the time-derivative relationship going from reception to transmission. These relationships are derived here and expressed in various useful forms. Electric and magnetic dipoles are given special consideration, and the combined form constructed as

  1. Active UWB antenna

    Microsoft Academic Search

    Mithilesh Kumar; Ananjan Basu; Shiban K. Koul

    2010-01-01

    This paper presents a novel scheme for development of an active Ultra-Wide Band (UWB) antenna. A single pulse of 133 ps and amplitude 530 mV peak to peak was obtained using High Electron Mobility Transistor (HEMT) as a generation circuit. This generation circuit was next integrated with a newly proposed UWB planar microstrip antenna. Transmission and reception characteristics of the

  2. UWB antenna array

    Microsoft Academic Search

    Dau-Chyrh Chang; Chao-Hsiang Liao; Powen Hsu

    2011-01-01

    This paper compares the performances of ultra wideband (UWB) arrays that use sinusoidal waveform for power pattern and ultra-short pulse waveform for energy pattern. In general, antenna arrays cannot have element spacing larger than one wavelength in any plane because the resulting grating lobes absorb much power, which will limit the bandwidth of antenna arrays. In particular, there are substantial

  3. Deployable antennae design alternatives

    Microsoft Academic Search

    E. Frisch; L. Heichele; W. Nagl; H. Popp; W. Schaefer

    1975-01-01

    To have a large spectrum of design and decision criteria, some RF configurations of microwave reflector antennas which seem to achieve the best RF properties, especially in a deployable configuration, are considered. Antenna concepts suitable for the 12 GHz range (high surface accuracy, low weight, and high stiffness) were considered. An RF configuration with about 3m diameter and 12 GHz

  4. GPS antenna designs

    NASA Technical Reports Server (NTRS)

    Laube, Samuel J. P.

    1987-01-01

    Application of the current GPS NAVSTAR system to civilian service requires that a right hand, circularly polarized, -160 dBW spread spectrum signal be received from an orbiting satellite, where the antenna environment is also moving. This presents a design challenge when inexpensive antennas are desired. The intent of this survey is to provide information on the antennas mentioned and to construct and test prototypes to determine whether the choice made by the industry, the quadrifilar helix, is the best. The helix antenna is currently the low cost standard for GPS. Prototype versions were constructed using 12 gauge wire and subminiature coaxial hardline. The constructed antennas were tested using a signal generator and a reference turnstile. A spectrum analyzer was used to measure the level of the received signal.

  5. UHF coplanar-slot antenna for aircraft-to-satellite data communications

    NASA Technical Reports Server (NTRS)

    Myhre, R. W.

    1979-01-01

    A lightweight low drag coplanar slot antenna was developed for use on commercial jet aircraft that will provide upper hemisphere coverage in the UHF band at frequencies of 402 and 468 MHz is described. The antenna is designed to transmit meteorological data from wide body jet aircraft to ground users via synchronous meteorological data relay satellites. The low profile antenna (23.5 cm wide by 38.1 cm long slot by 1.9 cm high) is a conformal antenna utilizing the coplanar approach with the advantages of broad frequency bandwidth and improved electrical integrity over wide range of temperature. The antenna is circular polarized, has anon axis gain of near +2.5 dB, and a HPBW greater than 90 deg. Areas discussed include antenna design, radiation characteristics, flight testing, and system performance.

  6. Antenna location design for generalized distributed antenna systems

    Microsoft Academic Search

    Xinzheng Wang; Pengcheng Zhu; Ming Chen

    2009-01-01

    A squared distance criterion for antenna location design in generalized distributed antenna systems (GDAS) is proposed to maximize the cell averaged ergodic capacity. The criterion requires the antenna port locations minimize the expectation of the squared distance between a randomly distributed user and the nearest antenna port. This is equivalent to codebook design in vector quantization. For uniform user distribution,

  7. AN ANTENNA SOLUTION FOR MIMO CHANNELS: THE SWITCHED PARASITIC ANTENNA

    E-print Network

    1 AN ANTENNA SOLUTION FOR MIMO CHANNELS: THE SWITCHED PARASITIC ANTENNA Mattias WennstrË? om Signals Chalmers University of Technology tomaso@s2.chalmers.se Technical area: Antenna and RF subsystems ABSTRACT We investigate the switched parasitic antenna (SPA), which is a novel technique for electronically

  8. Random Antenna Selection & Antenna Swapping Combined with OSTBCs

    E-print Network

    Blostein, Steven D.

    1 Random Antenna Selection & Antenna Swapping Combined with OSTBCs *Hani Mehrpouyan, Dr. Steven D iterative antenna selection algorithm based on an SNR selection criterion for a multi. The proposed algorithm addresses the open problem of finding a suboptimal set of transmit and receive antennas

  9. AN ANTENNA SOLUTION FOR MIMO CHANNELS: THE SWITCHED PARASITIC ANTENNA

    E-print Network

    AN ANTENNA SOLUTION FOR MIMO CHANNELS: THE SWITCHED PARASITIC ANTENNA Mattias Wennstr¨om Signals Chalmers University of Technology tomaso@s2.chalmers.se Technical area: Antenna and RF subsystems ABSTRACT We investigate the switched parasitic antenna (SPA), which is a novel technique for electronically

  10. Microstrip antenna couplers and active antenna amplifying arrays 

    E-print Network

    Yang, Yao-Chou (Angus)

    1997-01-01

    amplifier is designed and tested to integrate with the patch-fed antenna coupler. With FET amplifiers serving as active components, two compact active antenna amplifying linear arrays (Chebyshev and uniform) are designed and tested. The active patch...-fed antenna coupler array has the advantages of single input port, satisfactory transmitting radiation patterns, ease of bias, and compactness. The active patch-fed antenna coupler may find applications in power combining. For the line-fed antenna coupler...

  11. Autonomous omnidirectional spacecraft antenna system

    NASA Technical Reports Server (NTRS)

    Taylor, T. H.

    1983-01-01

    The development of a low gain Electronically Switchable Spherical Array Antenna is discussed. This antenna provides roughly 7 dBic gain for receive/transmit operation between user satellites and the Tracking and Data Relay Satellite System. When used as a pair, the antenna provides spherical coverage. The antenna was tested in its primary operating modes: directed beam, retrodirective, and Omnidirectional.

  12. Antenna Theory October 9, 2000

    E-print Network

    Ida, Nathan

    Antenna Theory Exam No. 1 October 9, 2000 Solve the following 4 problems. Each problem is 20, thin wire dipole antenna is given. Assuming a peak current of 1A at 600 MHz calculate: a. The radiated power of the antenna. b. The radiation resistance of the antenna. c. The directivity and maximum

  13. Antenna Position Calibration Melvyn Wright

    E-print Network

    Antenna Position Calibration Melvyn Wright Radio Astronomy laboratory, University of California, Berkeley, CA, 94720 ABSTRACT This memo summarizes the antenna position calibration used at Hat Creek of HA and DEC provide data from which the antenna positions are determined. If the antenna positions

  14. VLA Antenna Pad Transformer Breaker

    E-print Network

    Groppi, Christopher

    NRAO VLA Antenna Pad Transformer Breaker Survey C-Array, April 2012, Bob Broilo #12;C-Array Antenna Breaker Repair Priority: Before next C array E10_IR000157_CE5.IS2 Visible Light Image Notes: Antenna moves000156_CE6.IS2 Visible Light Image Notes: Phase A was warm in survey during May 2011 #12;C-Array Antenna

  15. VLA Antenna Pad Transformer Breaker

    E-print Network

    Groppi, Christopher

    NRAO VLA Antenna Pad Transformer Breaker Survey D-Array, April 5th 2013 #12;VLA Antenna Pad2 Visible Light Image Notes: #12;VLA Antenna Pad Transformer Breaker Survey D-Array, April 2013, Bob Priority: N/A E06_IR000205_DE6.IS2 Visible Light Image Notes: #12;VLA Antenna Pad Transformer Breaker

  16. VLA Antenna Pad Transformer Breaker

    E-print Network

    Groppi, Christopher

    NRAO VLA Antenna Pad Transformer Breaker Survey C-Array, August 20th 2013 #12;VLA Antenna Pad. Antenna is scheduled to move off this pad soon, so replacement can probably wait until next D-array when: #12;VLA Antenna Pad Transformer Breaker Survey C-Array, August 2013, Bob Broilo 3 Inspected by: Bob

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

    NASA Astrophysics Data System (ADS)

    Mazady, Md. Anas Boksh

    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.

  18. Robust Hybrid Finite Element Methods for Antennas and Microwave Circuits

    NASA Technical Reports Server (NTRS)

    Gong, J.; Volakis, John L.

    1996-01-01

    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.

  19. Antenna pattern study

    NASA Technical Reports Server (NTRS)

    Harper, Warren

    1988-01-01

    Prediction of antenna radiation patterns has long been an important function in the design of command, communication, and tracking systems for rocket vehicles and spacecraft. An acceptable degree of assurance that a radio link will provide the required quality of data or certainty of correct command execution must be acquired by some means if the system is to be certified as reliable. Two methods have been used to perform this function: (1) Theoretical analysis, based on the known properties of basic antenna element types and their behavior in the presence of conductive structures of simple shape, and (2) Measurement of the patterns on scale models of the spacecraft or rocket vehicle on which the antenna is located. Both of these methods are ordinarily employed in the antenna design process.

  20. Coaxial phased array antenna

    NASA Technical Reports Server (NTRS)

    Ellis, H., Jr. (inventor)

    1980-01-01

    A coaxial antenna array for communicating circularly polarized electromagnetic radiation is disclosed. A pair of open ended antenna cavities is coaxially constructed and operates by excitation of linear radiation elements arranged within each of the cavities. A pair of crossed dipole radiation devices is centered within the inner cavity and operated by means of a phase shifting network circuit to transmit as well as receive circularly polarized radiation. Four monopole radiation devices are symmetrically arranged to operate in the outer cavity in phase quadrature by means of the phase shifting network circuit to both transmit and receive circularly polarized electromagnetic radiation. Combined operation of the two antenna cavities with a 180 deg phase differential between the fields related to the two antenna cavities provides a broad beam, relatively wide frequency bandwidth communication capability. Particular embodiments disclosed feature a generally square cavity array as well as a circular cavity array.

  1. Dielectric Covered Planar Antennas

    NASA Technical Reports Server (NTRS)

    Llombart Juan, Nuria (Inventor); Lee, Choonsup (Inventor); Chattopadhyay, Goutam (Inventor); Gill, John J. (Inventor); Skalare, Anders J. (Inventor); Siegel, Peter H. (Inventor)

    2014-01-01

    An antenna element suitable for integrated arrays at terahertz frequencies is disclosed. The antenna element comprises an extended spherical (e.g. hemispherical) semiconductor lens, e.g. silicon, antenna fed by a leaky wave waveguide feed. The extended spherical lens comprises a substantially spherical lens adjacent a substantially planar lens extension. A couple of TE/TM leaky wave modes are excited in a resonant cavity formed between a ground plane and the substantially planar lens extension by a waveguide block coupled to the ground plane. Due to these modes, the primary feed radiates inside the lens with a directive pattern that illuminates a small sector of the lens. The antenna structure is compatible with known semiconductor fabrication technology and enables production of large format imaging arrays.

  2. Communication satellite antennas

    Microsoft Academic Search

    LEON J. RICARDI

    1977-01-01

    During the previous two decades, communication satellites have developed from the pioneering Telstar to the highly sophisticated ATS-6. Concurrrently, the spacecraft antennas have developed from a low-gain \\

  3. MLS airborne antenna research

    NASA Technical Reports Server (NTRS)

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

    1975-01-01

    The geometrical theory of diffraction was used to analyze the elevation plane pattern of on-aircraft antennas. The radiation patterns for basic elements (infinitesimal dipole, circumferential and axial slot) mounted on fuselage of various aircrafts with or without radome included were calculated and compared well with experimental results. Error phase plots were also presented. The effects of radiation patterns and error phase plots on the polarization selection for the MLS airborne antenna are discussed.

  4. Development of Leaky Wave Antennas for Layered Ridge Dielectric Waveguide

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    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.

  5. Mathematical modeling of multi-element monopole antennas

    NASA Astrophysics Data System (ADS)

    Puri, N. N.; Goubau, G.; Stavridis, A.; Fich, S.

    1981-03-01

    This research document presents a new theory for the analysis of multi-element antennas which consists of interconnected conductive structure elements of electrically small dimensions. The theory is based on the retarded electromagnet potentials which permit a diakoptic approach to the problem. The antenna is broken up into its individual structure elements. Each element is assumed to be excited, (a) by currents which are impressed at its terminals, i.e., junctions with adjacent elements (current coupling), and (b) by the electric fields of the currents and charges on all the other elements (field coupling). Both excitations are treated independently. Each impressed current produces a 'dominant' current distribution, a characteristic of the element, which can be readily computed. Current coupling is formulated by 'intrinsic' impedance matrices which relate the scalar potentials at the terminals of an element, caused by its dominant current distributions, to the impressed currents of the element. Field coupling produces 'scatter' currents on all the elements, and is formulated by a 'field coupling' matrix which relates the scalar potentials at the terminals, caused by field coupling, to the impressed currents at all the terminals. Intrinsic and 'field coupling' are combined to form the 'complete' impedance matrix of the diakopted antenna. Enforcing continuity of the currents and equality of the scalar potentials at all the interconnections between the elements yields a system of linear equations for the junction currents and the input impedance of the antenna. Current coupling dominates over field coupling. Field coupling due to the dominant current distributions of the elements is of primary importance while field coupling due to the scatter currents is, in general, negligible.

  6. The Folded Horn Antenna

    NASA Astrophysics Data System (ADS)

    Farr, E. G.; Bowen, L. H.; Baum, C. E.; Prather, W. D.

    Antennas for radiating high-power mesoband (medium-bandwidth) electromagnetic signals are critical to the mission of upsetting electronics at a distance. When operated at frequencies of a few hundred megahertz, RF weapons require highly efficient antennas that can fit into a small volume. Most of the existing antennas, such as pyramidal horns, are too large to fit onto certain platforms of interest. To address this challenge, we investigate the folded horn, which has aperture dimensions of 0.5 × 2 wavelengths, and a depth of 1.5-2 wavelengths. This antenna has a nearly focused aperture field, due to a parabolic fold in the H-plane. We report here on the fabrication and testing of the first folded horn, operating at 3 GHz. After a number of iterations, we obtained a realized gain of at least 10 dBi over 3-5 GHz, an aperture efficiency of 80%, and a return loss below -10 dB over 2.8-3.35 GHz. This design could be adapted to high-voltages, and it could work well in a two-antenna array, with two antennas positioned back to back, driven by a differential source.

  7. Near-field testing of the 15-meter hoop-column antenna

    NASA Technical Reports Server (NTRS)

    Schroeder, Lyle C.; Adams, Richard R.; Bailey, M. C.; Belvin, W. Keith; Butler, David H.; Campbell, Thomas G.

    1989-01-01

    A 15-m-diameter antenna was tested to verify that dimensional tolerances for acceptable performance could be achieved and to verify structural, electromagnetic, and mechanical performance predictions. This antenna utilized the hoop column structure, a gold plated molybdenum mesh reflector, and 96 control cables to adjust the reflector conformance with a paraboloid. The dimensional conformance of the antenna structure and surface was measured with metric camera and theodolites. Near field pattern data were used to assess the electromagnetic performance at five frequencies from 2.225 to 11.6 GHz. The reflector surface was adjusted to greatly improve electromagnetic performance with a finite element model and the surface measurements. Measurement results show that antenna surface figure and adjustments and electromagnetic patterns agree well with predictions.

  8. Octocopter based Calibration of the Butterfly Antenna

    E-print Network

    Erdmann, Martin

    Octocopter based Calibration of the Butterfly Antenna for the Pierre Auger Observatory von Raphael Mechanical Structure of the Butterfly Antenna 45 5.1 Description of the Butterfly Antenna . . . . . . . . . . . . . . . . . . . . . . . . . . 45 5.2 Improvement of the Butterfly Antenna . . . . . . . . . . . . . . . . . . . . . . . . 46 5

  9. Design of a ring resonator-based optical beam forming network for phased array receive antennas

    Microsoft Academic Search

    Klooster van't J. W; C. G. H. Roeloffzen; A. Meijerink; L. Zhuang; D. A. I. Marpaung; Etten van W. C; R. G. Heideman; A. Leinse; H. Schippers; J. Verpoorte; M. Wintels

    2008-01-01

    A novel squint-free ring resonator-based optical beam forming network (OBFN) for phased array antennas (PAA) is proposed. It is intended to provide broadband connectivity to airborne platforms via geostationary satellites. In this paper, we present the design of the OBFN and its control system. Our goal is to deliver large bandwidth Ku-band connectivity between antennas, mount conformal to the airplane

  10. Microstrip antenna couplers and active antenna amplifying arrays

    E-print Network

    Yang, Yao-Chou (Angus)

    1997-01-01

    to the patch and it becomes a line-fed antenna coupler. This configuration could exhibit dual frequency operation (different mode excited: TMpipand TMipp). A simple 3x4 uniform traveling array is designed using line-fed antenna couplers. Its tapering...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...

  11. Concepts and cost trade-offs for land vehicle antennas in satellite mobile communications

    NASA Technical Reports Server (NTRS)

    Haddad, H. A.

    1948-01-01

    Several antenna design concepts, operating at UHF (821 to 825 MHz transmit and 866 to 870 MHz receive bands), with gain ranging between 6 and 12 dBic, that are suitable for land mobile vehicles are presented. The antennas may be used within CONUS and ALASKA to communicate to and from a geosynchronous satellite. Depending on the type of steering mechanism, the antennas are broken down into three categories; (1) electronically scanned arrays with phase shifters, (2) electronically switched arrays with switchable power dividers/combiners, and (3) mechanically steered arrays. The operating characteristics of two of these design concepts, one a conformal antenna with electronic beam steering and the other a nonconformal design with mechanical steering, were evaluated with regard to two and three satellite system. Cost estimates of various antenna concepts were made and plotted against their overall gain performance.

  12. Imaging antenna arrays

    NASA Technical Reports Server (NTRS)

    Rutledge, D. B.; Muha, M. S.

    1982-01-01

    Many millimeter and far-infrared imaging systems are limited in sensitivity and speed because they depend on a single scanned element. Because of recent advances in planar detectors such as Schottky diodes, superconducting tunnel junctions, and microbolometers, an attractive approach to this problem is a planar antenna array with integrated detectors. A planar line antenna array and optical system for imaging has been developed. The significant advances are a 'reverse-microscope' optical configuration and a modified bow-tie antenna design. In the 'reverse-microscope' configuration, a lens is attached to the bottom of the substrate containing the antennas. Imaging is done through the substrate. This configuration eliminates the troublesome effects of substrate surface waves. The substrate lens has only a single refracting surface, making possible a virtually aplanatic system, with little spherical aberration or coma. The array is characterized by an optical transfer function that is easily measured. An array with 19 dB crosstalk levels between adjacent antennas has been tested and it was found that the array captured 50 percent of the available power. This imaging system was diffraction limited.

  13. Industrial Plasma Antennas

    NASA Astrophysics Data System (ADS)

    Alexeff, Igor

    2007-11-01

    This presentation summarizes an extensive program on plasma antennas. Plasma antennas are just as effective as metal antennas. In addition, they can transmit, receive and reflect lower frequency signals while being transparent to higher frequency signals. When de-energized, they electrically disappear. Plasma noise does not appear to be a problem. New technology that has been developed include a method of operating at high plasma density at minimal power consumption, a novel technique of noise reduction, and a method of opening a plasma window in a plasma microwave barrier on a time scale of microseconds rather than the usual time scale of milliseconds due to plasma decay. We are at present testing an intelligent plasma antenna in which a plasma ``window'' in a circular plasma barrier surrounding an antenna rotates azimuthally, seeking a radio transmitter. When located, a computer locks onto the transmitter. When the transmitter is de-energized, the plasma window recommences scanning. Commercial interest is strong, with invited papers being presented for 4 years in succession at the SMi Stealth Conference in London, UK, an operating model on permanent exhibition at the Booze-Allen headquarters in Alexandria, VA, and strong interest from Lockheed-Martin. In collaboration with Ted Anderson, Haleakala R&D Corp.; Esmaeil Farshi, Fred Dyer, Jeffrey Peck, Eric Pradeep, Nanditha Pulasani, and Naresh Karnam, University of Tennessee.

  14. A plasma receiving dipole antenna

    SciTech Connect

    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

    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.

  15. Hemispheric ultra-wideband antenna.

    SciTech Connect

    Brocato, Robert Wesley

    2006-04-01

    This report begins with a review of reduced size ultra-wideband (UWB) antennas and the peculiar problems that arise when building a UWB antenna. It then gives a description of a new type of UWB antenna that resolves these problems. This antenna, dubbed the hemispheric conical antenna, is similar to a conventional conical antenna in that it uses the same inverted conical conductor over a ground plane, but it also uses a hemispheric dielectric fill in between the conductive cone and the ground plane. The dielectric material creates a fundamentally new antenna which is reduced in size and much more rugged than a standard UWB conical antenna. The creation of finite-difference time domain (FDTD) software tools in spherical coordinates, as described in SAND2004-6577, enabled this technological advance.

  16. Pattern diversity compact patch antenna

    Microsoft Academic Search

    M. S. Ruiz Palacios; M. J. Martinez Silva

    2010-01-01

    Diversity is a required property for antennas in Multiple Input-Multiple Output (MIMO) systems. In this paper a pattern diversity antenna is presented for operation in the 2.4 band of IEEE 802.11n WLAN MIMO standard. This compact antenna is formed by two shorted air substrate patch antennas located back to back in order to produce two lobes oriented in different directions.

  17. Ionospheric effects to antenna impedance

    NASA Technical Reports Server (NTRS)

    Bethke, K. H.

    1986-01-01

    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.

  18. VLA Antenna Pad Transformer Breaker

    E-print Network

    Groppi, Christopher

    NRAO VLA Antenna Pad Transformer Breaker Survey A-Array, July 2011, Bob Broilo #12;A-Array Antenna at this time Repair Priority: N/A E48_IR000096_AE6.IS2 Visible Light Image Notes: #12;A-Array Antenna Pad at this time Repair Priority: N/A E64_IR000093_AE8.IS2 Visible Light Image Notes: #12;A-Array Antenna Pad

  19. VLA Antenna Pad Transformer Breaker

    E-print Network

    Groppi, Christopher

    NRAO VLA Antenna Pad Transformer Breaker Survey B-Array, May 2011, Bob Broilo #12;B-array Antenna Action Monitor Repair Priority: N/A E04_IR000050_DE4_DE5.IS2 Visible Light Image Notes: Antenna moving at this time Repair Priority: N/A E08_IR000051_DE8.IS2 Visible Light Image Notes: #12;B-array Antenna Pad

  20. Dielectric coated wire antennas

    NASA Technical Reports Server (NTRS)

    Richmond, J. H.; Newman, E. H.

    1976-01-01

    An electrically thin dielectric insulating shell on an antenna composed of electrically thin circular cylindrical wires is examined. A moment method solution is obtained, and the insulating shell is modeled by equivalent volume polarization currents. These polarization currents are related in a simple manner to the surface charge density on the wire antenna. In this way the insulating shell causes no new unknowns to be introduced, and the size of the impedance matrix is the same as for the uninsulated wires. The insulation is accounted for entirely through a modification of the symmetric impedance matrix. This modification influences the current distribution, impedance, efficiency, field patterns, and scattering properties. The theory is compared with measurement for dielectric coated antennas in air.

  1. Antenna radome sample test report

    Microsoft Academic Search

    Leonard H. Baker; Thomas D. Bratton

    1991-01-01

    The antenna radome sample test conducted at the Federal Aviation Administration (FAA) Technical Center by the Secondary Surveillance Systems Branch, ACN-220 is documented. The test configuration consisted of the antenna radome sample centered between the Discrete Address Beacon System's (DABS) antenna and its remote Calibration Performance Monitor Equipment (CPME). The Range and Azimuth Accuracy (RAA) diagnostic program was used to

  2. Design of reconfigurable slot antennas

    Microsoft Academic Search

    Dimitrios Peroulis; Kamal Sarabandi; Linda P. B. Katehi

    2005-01-01

    In this paper the design of a compact, efficient and electronically tunable antenna is presented. A single-fed resonant slot loaded with a series of PIN diode switches constitute the fundamental structure of the antenna. The antenna tuning is realized by changing its effective electrical length, which is controlled by the bias voltages of the solid state shunt switches along the

  3. LF and VLF antenna modeling

    Microsoft Academic Search

    D. E. Hurdsman; P. M. Hansen; J. W. Rockway

    2003-01-01

    The 60 kHz timing station in Fort Collins, Colorado known as WWVB and a 21.4 kHz Navy VLF transmit antenna at Lualualei, Hawaii were modeled using the method of moments wire modeling code, Expert MININEC Broadcast Professional. An accurate computational antenna model was needed in order to evaluate proposed antenna modifications. The evaluation criteria for defining an \\

  4. VLA Antenna Pad Transformer Breaker

    E-print Network

    Groppi, Christopher

    NRAO VLA Antenna Pad Transformer Breaker Survey D-Array, October 2011, Bob Broilo #12;D-Array Antenna Pad Transformer Survey October 2011, Bob Broilo 2 Inspected by: Bob Broilo Inspection Date: 10-hand) feeds DE2. #12;D-Array Antenna Pad Transformer Survey October 2011, Bob Broilo 3 Inspected by: Bob

  5. VLA Antenna Pad Transformer Breaker

    E-print Network

    Groppi, Christopher

    NRAO VLA Antenna Pad Transformer Breaker Survey A-Array, May 20, 2014 Summary: The breakers at AN5 and AN6 show clear signs of degradation since 2011 and should be replaced. #12;VLA Antenna Pad Notes: #12;VLA Antenna Pad Transformer Breaker Survey A-Array, May 2014, Bob Broilo 3 Inspected by: Bob

  6. VLA Antenna Pad Transformer Breaker

    E-print Network

    Groppi, Christopher

    NRAO VLA Antenna Pad Transformer Breaker Survey B-Array, November 22nd , 2013 Summary: None the breakers. #12;VLA Antenna Pad Transformer Breaker Survey B-Array, November 2013, Bob Broilo 2 Inspected by Visible Light Image Notes: #12;VLA Antenna Pad Transformer Breaker Survey B-Array, November 2013, Bob

  7. Antenna Theory Exam No. 1.

    E-print Network

    Ida, Nathan

    Antenna Theory Exam No. 1. October 11, 2002 Answer the following four questions. Each has equal resistance of a 3/2 dipole antenna with sinusoidal current. Solution: Using the formula for a general length antenna, the radiation resistance may be written directly as: Rrad = 2 =0 (cos((L/)cos) - cos(L/))2 sin

  8. Antenna Theory December 1, 2003

    E-print Network

    Ida, Nathan

    Antenna Theory Exam No. 2 December 1, 2003 Solve the following two problems. These are written angle. b. Sketch the antenna array pattern (that is, the combine array factor and element pattern). At what angles are the nulls of the pattern? e18.99. In chapter18.problems.extra 2. An antenna is required

  9. Galileo satellite antenna modeling

    NASA Astrophysics Data System (ADS)

    Steigenberger, Peter; Dach, Rolf; Prange, Lars; Montenbruck, Oliver

    2015-04-01

    The space segment of the European satellite navigation system Galileo currently consists of six satellites. Four of them belong to the first generation of In-Orbit Validation (IOV) satellites whereas the other two are Full Operational Capability (FOC) satellites. High-precision geodetic applications require detailed knowledge about the actual phase center of the satellite and receiver antenna. The deviation of this actual phase center from a well-defined reference point is described by phase center offsets (PCOs) and phase center variations (PCVs). Unfortunately, no public information is available about the Galileo satellite antenna PCOs and PCVs, neither for the IOV, nor the FOC satellites. Therefore, conventional values for the IOV satellite antenna PCOs have been adopted for the Multi-GNSS experiment (MGEX) of the International GNSS Service (IGS). The effect of the PCVs is currently neglected and no PCOs for the FOC satellites are available yet. To overcome this deficiency in GNSS observation modeling, satellite antenna PCOs and PCVs are estimated for the Galileo IOV satellites based on global GNSS tracking data of the MGEX network and additional stations of the legacy IGS network. Two completely independent solutions are computed with the Bernese and Napeos software packages. The PCO and PCV values of the individual satellites are analyzed and the availability of two different solutions allows for an accuracy assessment. The FOC satellites are built by a different manufacturer and are also equipped with another type of antenna panel compared to the IOV satellites. Signal transmission of the first FOC satellite has started in December 2014 and activation of the second satellite is expected for early 2015. Based on the available observations PCO estimates and, optionally PCVs of the FOC satellites will be presented as well. Finally, the impact of the new antenna model on the precision and accuracy of the Galileo orbit determination is analyzed.

  10. DSN Microwave Antenna Holography

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

    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.

  11. Design considerations for an archimedean slot spiral antenna

    NASA Technical Reports Server (NTRS)

    Nurnberger, Michael W.; Volakis, John L.

    1995-01-01

    The design goal is to develop a 118-157 MHz, vertically polarized, low-profile (or conformal) antenna as a replacement for VHF AM blade antennas on aircraft. This design is to be arrived at by scaling the dimensions of an antenna designed for a center frequency of 1.1 GHz. The design prior to scaling may have the following maximum dimensions: diameter less than 3.70 in. and thickness less than 0.50 in. Although a four-arm spiral design was originally suggested, a two-arm spiral may also be used, as both mode-1 and mode-2 (sum and difference) radiation patterns aren't required. While a four-arm spiral can easily be designed should both sum and difference patterns be required, the two-arm design will provide the required sum pattern and simplify the design problem somewhat: only one feed is required, and the feed area geometry is more straightforward. Polarization requirements dictate that a slot spiral be used, as opposed to a wire spiral. Two similar radiating structures were considered. The first is the standard archimedean spiral antenna. The second is a hollow archimedean spiral antenna, essentially a standard archimedean spiral with the inner portion removed.

  12. Antenna mathematical modeling (GTD)

    Microsoft Academic Search

    R. G. Kouyoumjian; R. J. Luebbers; L. Ton-That

    1976-01-01

    The primary objective of this effort has been to employ the geometrical theory of diffraction in combination with the moment method to develop a user-oriented computer code to calculate the radiation pattern of wire antennas in the presence of perturbing structures. The work accomplished can be divided into two parts. A theoretical and experimental investigation of the effect of edges

  13. Phase scan antenna array

    NASA Astrophysics Data System (ADS)

    Stern, Richard A.; Babbitt, Richard W.; Mikucki, Gerald

    1986-11-01

    A phase scan antenna array for planar radar scanning in a single plane with a pencil-shaped beam is provided comprising a plurality of ferrite rod line source antennas. Each rod antenna has a plurality of beam-emitting slots spaced along one side thereof and is end fed in phase with the other antennas from a single hollow metallic waveguide by means of coupling slots in the waveguide which are spaced apart one wavelength of the radar frequency. The rods are mounted in a two-dimensional columnar array with the beam-emitting slots of each rod aligned in rows with the corresponding slots of the other rods by a mounting member having a plurality of mutually-parallel slots in which the rods are disposed. The walls of the mounting member slots suppress Faraday rotation of the waves in the rods and the bottom of the slots enhance the single beam emitted from the face of the array. The array rods are simultaneously magnetically biased by a plurality of serially-interconnected biasing coils which are helically wound around the mounting member and disposed between the rows of beam-emitting rod slots.

  14. Candidate Design for a Multiband LMR Antenna System Using a Rudimentary Antenna Tuner

    E-print Network

    Ellingson, Steven W.

    Candidate Design for a Multiband LMR Antenna System Using a Rudimentary Antenna Tuner Steve of Figures 1 Block diagram of the candidate antenna system. . . . . . . . . . . . . . . . . . . . . 3 2 diagram of the antenna tuner. . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 6 Candidate monopole

  15. Antennas - Our electronic eyes and ears

    Microsoft Academic Search

    John D. Kraus

    1989-01-01

    Although the number of antenna types is vast, all antenna properties may be characterized in terms of the same basic parameters of radiation pattern, impedance, radar cross-section, and temperature. A comprehensive introduction is presented to antenna configurations; these encompass, among antennas constructed of wire or tubing, such wideband and circularly polarized types as helices, linear conductors, and loops. Sheet-conductor antenna

  16. JPL Large Advanced Antenna Station Array Study

    NASA Technical Reports Server (NTRS)

    1978-01-01

    In accordance with study requirements, two antennas are described: a 30 meter standard antenna and a 34 meter modified antenna, along with a candidate array configuration for each. Modified antenna trade analyses are summarized, risks analyzed, costs presented, and a final antenna array configuration recommendation made.

  17. RFI Reduction by Control of Antenna Sidelobes

    Microsoft Academic Search

    L. Peters; R. C. Rudduck; L. Du

    1964-01-01

    This paper describes measurements and theoretical developments on the far sidelobe or backlobe region of three basic antenna types:the horn antenna, the parabolic reflector antenna and the Luneberg lens antenna. The application is for RFI reduction with emphasis on the use of radar absorber materials. A technique for design of nulls in the Fresnel Zone of an aperture antenna is

  18. ANTENNA DESIGN AND RADIATION PATTERN VISUALIZATION

    E-print Network

    Elsherbeni, Atef Z.

    ANTENNA DESIGN AND RADIATION PATTERN VISUALIZATION Atef Z. Elsherbeni, Matthew J. Inman, R and radiation patterns of many antenna geometries and antenna arrays can be evaluated but not easily visualized of the radiation patterns for many different types of antennas and antenna arrays. The package allows the user

  19. Global conformal surface parameterization

    Microsoft Academic Search

    Xianfeng Gu; Shing-tung Yau

    2003-01-01

    We solve the problem of computing global conformal parameterizations for surfaces with nontrivial topologies. The parameterization is global in the sense that it preserves the conformality everywhere except for a few points, and has no boundary of discontinuity. We analyze the structure of the space of all global conformal parameterizations of a given surface and find all possible solutions by

  20. Irrational conformal field theory

    Microsoft Academic Search

    M. B. Halpern; E. Kiritsis; N. A. Obers; K. Clubok

    1996-01-01

    This is a review of irrational conformal field theory, which includes rational conformal field theory as a small subspace. Central topics of the review include the Virasoro master equation, its solutions and the dynamics of irrational conformal field theory. Discussion of the dynamics includes the generalized Knizhnik-Zamolodchikov equations on the sphere, the corresponding heat-like systems on the torus and the

  1. Conformal or Confining

    E-print Network

    da Silva, Tiago Nunes; Robroek, Lasse

    2015-01-01

    We present a lattice study of the zero-temperature line of chiral symmetry breaking phase transitions in the conformal window of QCD for varying number of flavors. We argue that it is consistent with a lower edge of the conformal window at $N_fpoint merging as a mechanism for the loss of conformality.

  2. Microsecond switchable thermal antenna

    SciTech Connect

    Ben-Abdallah, Philippe, E-mail: pba@institutoptique.fr; Benisty, Henri; Besbes, Mondher [Laboratoire Charles Fabry, UMR 8501, Institut d'Optique, CNRS, Université Paris-Sud 11, 2, Avenue Augustin Fresnel, 91127 Palaiseau Cedex (France)

    2014-07-21

    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 (VO{sub 2}). This thermal source is made of a periodically patterned tunable VO{sub 2} 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 VO{sub 2} 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 VO{sub 2} 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.

  3. Microsecond switchable thermal antenna

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

    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.

  4. Circularly polarized microstrip antennas

    NASA Technical Reports Server (NTRS)

    Lo, Y. T.; Engst, B.; Lee, R. Q. H.

    1985-01-01

    A simple microstrip antenna can be made to radiate EM waves of any polarization, in particular, the circular polarization (CP) without any phasing network and power divider. A simple and accurate theory for this family of antennas was developed. However, the CP bandwidth, (CPBW) the bandwidth in which the axial ratio (AR) is less than a certain specified value, is very small. Most of the experimental designs were made for a feed placed along the diagonal of the patch. It is shown that there are practically infinitely many possible designs with different feed location. The speculation that other designs might give a wider bandwidth is clarified and an effective method for broadening the bandwidth is shown.

  5. Antenna structure with distributed strip

    DOEpatents

    Rodenbeck, Christopher T. (Albuquerque, NM)

    2008-10-21

    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.

  6. Antenna structure with distributed strip

    DOEpatents

    Rodenbeck, Christopher T. (Albuquerque, NM)

    2008-03-18

    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.

  7. Efficient Placement of Directional Antennas

    SciTech Connect

    Pan, Feng [Los Alamos National Laboratory; Kasiviswanathan, Shiva [Los Alamos National Laboratory

    2010-09-20

    Directional antenna is an technology for the proliferation of wireless networks. In centralized wireless network, wireless devices communicate through base stations. Directed antennas are placed on base stations and form a backbone of communication. The communication between base stations and wireless devices can be interfered due to a large number of wireless device. Methodically positioning and orienting directed antennas can help to reduce the interference while saving energy. An integer linear programming is developed for siting and directing antennas on multiple base stations, and this formulation can be extended to model non-overlapping channels. Through the integer programming formulation, optimal antenna positions can be used to analyze the performance of directed antennas with different parameters like the number base stations and the number of non-overlapping channels.

  8. Microstrip antenna theory and design

    NASA Astrophysics Data System (ADS)

    James, J. R.; Hall, P. S.; Wood, C.

    Microstrip is the name given to a type of open waveguiding structure which is now commonly used in present-day electronics, not only as a transmission line but for circuit components such as filters, couplers, and resonators. The idea of using microstrip to construct antennas is a much more recent development. The purpose of this monograph is to present the reader with an appreciation of useful antenna design approaches and the overall state-of-the art situation. Flat-plate antenna techniques and constraints on performance are considered along with microstrip design equations and data, the radiation mechanism of an open-circuit microstrip termination and the resulting design implications, the basic methods of calculation and design of patch antennas, and linear array techniques. Attention is also given to techniques and design limitations in two-dimensional arrays, circular polarization techniques, manufacturing and operational problems of microstrip antennas, recent advances in microstrip antenna analysis, and possible future developments.

  9. Antenna Calibration and Measurement Equipment

    NASA Technical Reports Server (NTRS)

    Rochblatt, David J.; Cortes, Manuel Vazquez

    2012-01-01

    A document describes the Antenna Calibration & Measurement Equipment (ACME) system that will provide the Deep Space Network (DSN) with instrumentation enabling a trained RF engineer at each complex to perform antenna calibration measurements and to generate antenna calibration data. This data includes continuous-scan auto-bore-based data acquisition with all-sky data gathering in support of 4th order pointing model generation requirements. Other data includes antenna subreflector focus, system noise temperature and tipping curves, antenna efficiency, reports system linearity, and instrument calibration. The ACME system design is based on the on-the-fly (OTF) mapping technique and architecture. ACME has contributed to the improved RF performance of the DSN by approximately a factor of two. It improved the pointing performances of the DSN antennas and productivity of its personnel and calibration engineers.

  10. Adaptive antenna systems

    Microsoft Academic Search

    B. Widrow; P. E. Mantey; L. J. Griffiths; B. B. Goode

    1967-01-01

    A system consisting of an antenna array and an adaptive processor can perform filtering in both the space and the frequency domains, thus reducing the sensitivity of the signal-receiving system to interfering directional noise sources. Variable weights of a signal processor can be automatically adjusted by a simple adaptive technique based on the least-mean-squares (LMS) algorithm. During the adaptive process

  11. Wimpy Radar Antenna

    NSDL National Science Digital Library

    Center for Engineering Educational Outreach,

    Students reinforce an antenna tower made from foam insulation so that it can withstand a 480 N-cm bending moment (torque) and a 280 N-cm twisting moment (torque) with minimal deflection. During one class period, students discuss the problem, run the initial bending and torsion tests and graph the results. During the following class periods, students design, construct and test sturdier towers, and graph the results.

  12. Helicopter Rotor Antenna

    NASA Technical Reports Server (NTRS)

    Pogorzelski, Ronald J.; Cable, Vaughn P.

    2001-01-01

    This effort was directed toward demonstration of the efficacy of a concept for mitigation of the rotor blade modulation problem in helicopter communications. An antenna is envisioned with radiating elements mounted on the rotor and rotating with it. The rf signals are coupled to the radio stationary with respect to the airframe via a coupler of unique design. The coupler has an rf cavity within which a mode is established and the field distribution of this mode is sampled by probes rotating with the radiating elements. In this manner the radiated pattern is "despun" with respect to the rotor. Theoretical analysis has indicated that this arrangement will be less susceptible to rotor blade modulation that would be a conventional fixed mounted antenna. A small coupler operating at S-band was designed, fabricated, and mounted on a mockup representative of a helicopter body. A small electric motor was installed to rotate the rotor portion of the coupler along with a set of radiating elements during testing. This test article was be evaluated using the JPL Mesa Antenna Measurement Facility to establish its ability to mitigate rotor blade modulation. It was found that indeed such a coupler will result in a despun pattern and that such a pattern can be effective in mitigation of rotor blade modulation.

  13. MEMS-switched reconfigurable antennas

    Microsoft Academic Search

    William H. Weedon; William J. Payne; Gabriel M. Rebeiz

    2001-01-01

    The integration and use of RF MEMS switches in microstrip patch antennas and feed structures were investigated for developing reconfigurable multi-band antennas. The current application focuses on the development of a dual L\\/X-band antenna that would support several satellite or UAV-based communications and radar applications such as SAR, terrain mapping, GMTI, AMTI, etc. A reconfigurable patch module (RPM) was designed

  14. Deployable antenna phase A study

    NASA Technical Reports Server (NTRS)

    Schultz, J.; Bernstein, J.; Fischer, G.; Jacobson, G.; Kadar, I.; Marshall, R.; Pflugel, G.; Valentine, J.

    1979-01-01

    Applications for large deployable antennas were re-examined, flight demonstration objectives were defined, the flight article (antenna) was preliminarily designed, and the flight program and ground development program, including the support equipment, were defined for a proposed space transportation system flight experiment to demonstrate a large (50 to 200 meter) deployable antenna system. Tasks described include: (1) performance requirements analysis; (2) system design and definition; (3) orbital operations analysis; and (4) programmatic analysis.

  15. Large Space Antenna Systems Technology, 1984

    NASA Technical Reports Server (NTRS)

    Boyer, W. J. (compiler)

    1985-01-01

    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.

  16. Ferrite attenuator modulation improves antenna performance

    NASA Technical Reports Server (NTRS)

    Hooks, J. C.; Larson, S. G.; Shorkley, F. H.; Williams, B. T.

    1970-01-01

    Ferrite attenuator inserted into appropriate waveguide reduces the gain of the antenna element which is causing interference. Modulating the ferrite attenuator to change the antenna gain at the receive frequency permits ground tracking until the antenna is no longer needed.

  17. Full-wave analysis and wide-band design of probe-fed multilayered cylindrical-rectangular microstrip antennas

    Microsoft Academic Search

    H. Mang; X. Xiaowen

    2004-01-01

    The input impedance and radiation pattern of the probe-fed multilayered cylindrical-rectangular microstrip antennas (PMCMSA) are analyzed by using a novel approach which combines the conformal finite-difference time-domain (FDTD) and Gedney's unsplit version of the perfectly matched layer absorbing boundary condition method and the Green's functions in cylindrically stratified media. The near fields of such antennas and the current distributions on

  18. Compact space-multimode diversity stacked circular microstrip antenna array for 802.11n MIMO-OFDM WLANs

    Microsoft Academic Search

    A. Ocalan; A. Savasinabes; I. Gorge; O. Ertug; E. Yazgan

    2009-01-01

    The support of MIMO communication in OFDM-WLAN systems conforming to IEEE 802.11n standard requires the design and use of compact antennas and arrays with low correlation ports. In this paper, the design and analysis of a compact space-multimode diversity provisioning stacked circular microstrip patch uniform linear antenna array (SCP-ULA) for MIMO-OFDM WLAN systems and the associated spatial and modal correlation,

  19. Metamaterial-based "sabre" antenna

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    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.

  20. Antenna system for MSAT mission

    NASA Technical Reports Server (NTRS)

    Karlsson, Ingmar; Patenaude, Yves; Stipelman, Leora

    1988-01-01

    Spar has evaluated and compared several antenna concepts for the North American Mobile Satellite. The paper describes some of the requirements and design considerations for the antennas and demonstrates the performance of antenna concepts that can meet them. Multiple beam reflector antennas are found to give best performance and much of the design effort has gone into the design of the primary feed radiators and beam forming networks to achieve efficient beams with good overlap and flexibility. Helices and cup dipole radiators have been breadboarded as feed element candidates and meausured results are presented. The studies and breadboard activities have made it possible to proceed with a flight program.

  1. Inflatable antenna for cubesats: Motivation for development and antenna design

    NASA Astrophysics Data System (ADS)

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

    2013-10-01

    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.

  2. Application of the minimum scattering antenna theory to mismatched antennas

    NASA Astrophysics Data System (ADS)

    Rogers, P. Glynn

    1986-10-01

    The invisibility condition for mismatched antennas is examined theoretically, and the question of its realization in practical antennas is discussed. The mutual impedance between two antennas satisfying the invisibility requirement is derived by modifying the corresponding derivation for canonical minimum scattering antennas due to Wasylkiwskyj and Kahn (1970). The theory is applied to the mutual impedance in an array of small monopoles in a parallel plate waveguide. The active impedance of the central element as a function of scan angle is calculated and the results compared with experiment. It is demonstrated that antennas whose scattering behavior is dominated by a single characteristic mode can be made invisible by the addition of a suitable reactive termination.

  3. UWB antennas: Design and application

    Microsoft Academic Search

    Zhi Ning Chen

    2007-01-01

    Since FCC released the extremely wide spectrum with emission masks for commercial ultra-wideband (UWB) applications in 2002, much effort of research and development has been paid for the design of UWB antennas for a variety of applications from wireless or wired communications to non-communications such as imaging, location, and radar systems. Many UWB antennas have been developed to cover the

  4. Astronaut space suit communication antenna

    NASA Technical Reports Server (NTRS)

    Lindsey, J. F., III; Nason, G. H.

    1968-01-01

    Astronaut space suit communication antenna consists of a spring steel monopole in a blade-type configuration. This antenna is mounted in a copper cup filled with a potting compound that is recessed in the center to facilitate bending the blade flat for stowing when not in use.

  5. GHz Broadband High Power Antennas

    NASA Astrophysics Data System (ADS)

    Podgorski, Andrew S.

    The purpose of this publication is to demonstrate the latest achievements in the area of broadband antennas operating in the frequency range up to 100 GHz. Emphasis is directed towards the application of broadband antennas into EMI/EMC/EMP testing, time domain material testing and possible future applications.

  6. RADARSAT elevation antenna pattern determination

    Microsoft Academic Search

    T. I. Lukowski; R. K. Hawkins; C. Cloutier; J. Wolfe; L. D. Teany; S. K. Srivastava; B. Banik; R. Jha; M. Adamovic

    1997-01-01

    The operations plan for RADARSAT is based on implicit calibration of the imagery products from this sensor system. The determination of the antenna gain patterns in elevation for RADARSAT is a critical step in the radiometric calibration of this imagery. The shapes of the antenna patterns in elevation were derived from imagery collected over the South American rain forests of

  7. Scattering by cavity-backed antennas on a circular cylinder

    NASA Technical Reports Server (NTRS)

    Kempel, Leo C.; Volakis, John L.

    1994-01-01

    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.

  8. Patch antenna terahertz photodetectors

    NASA Astrophysics Data System (ADS)

    Palaferri, D.; Todorov, Y.; Chen, Y. N.; Madeo, J.; Vasanelli, A.; Li, L. H.; Davies, A. G.; Linfield, E. H.; Sirtori, C.

    2015-04-01

    We report on the implementation of 5 THz quantum well photodetector exploiting a patch antenna cavity array. The benefit of our plasmonic architecture on the detector performance is assessed by comparing it with detectors made using the same quantum well absorbing region, but processed into a standard 45° polished facet mesa. Our results demonstrate a clear improvement in responsivity, polarization insensitivity, and background limited performance. Peak detectivities in excess of 5 × 1012 cmHz1/2/W have been obtained, a value comparable with that of the best cryogenic cooled bolometers.

  9. The ICRF antennas for TFTR

    SciTech Connect

    Hoffman, D.J.; Colestock, P.L.; Gardner, W.L.; Hosea, J.C.; Nagy, A.; Stevens, J.; Swain, D.W.; Wilson, J.R.

    1988-01-01

    Two compact loop antennas have been designed to provide ion cyclotron resonant frequency (ICRF) heating for TFTR. The antennas can convey a total of 10 MW to accomplish core heating in either high-density or high-temperature plasmas. The near-term goal of heating TFTR plasmas and the longer-term goals of ease in handling (for remote maintenance) and high reliability (in an inaccessible tritium tokamak environment) were major considerations in the antenna designs. The compact loop configuration facilitates handling because the antennas fit completely through their ports. Conservative design and extensive testing were used to attain the reliability required for TFTR. This paper summarizes how these antennas will accomplish these goals. 5 figs, 1 tab.

  10. Electrically connected resonant optical antennas.

    PubMed

    Prangsma, Jord C; Kern, Johannes; Knapp, Alexander G; Grossmann, Swen; Emmerling, Monika; Kamp, Martin; Hecht, Bert

    2012-08-01

    Electrically connected resonant optical antennas hold promise for the realization of highly efficient nanoscale electro-plasmonic devices that rely on a combination of electric fields and local near-field intensity enhancement. Here we demonstrate the feasibility of such a concept by attaching leads to the arms of a two-wire antenna at positions of minimal near-field intensity with negligible influence on the antenna resonance. White-light scattering experiments in accordance with simulations show that the optical tunability of connected antennas is fully retained. Analysis of the electric properties demonstrates that in the antenna gaps direct current (DC) electric fields of 10(8) V/m can consistently be achieved and maintained over extended periods of time without noticeable damage. PMID:22800440

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

    NASA Technical Reports Server (NTRS)

    Zakrajsek, Robert J.

    2000-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

    Olsson, T.

    1972-01-01

    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.

  13. Optimal Antenna Cluster Size in Cell-Free Large-Scale Distributed-Antenna Systems with

    E-print Network

    1 Optimal Antenna Cluster Size in Cell-Free Large-Scale Distributed-Antenna Systems with Imperfect, and Zhisheng Niu, Fellow, IEEE Abstract--In a cell-free Large-Scale Distributed-Antenna Sys- tems (L-DAS), the antennas are distributed over the intended coverage area. Introducing cooperation among the antennas can

  14. Transcatheter Microwave Antenna

    NASA Technical Reports Server (NTRS)

    Arndt, Dickey G. (Inventor); Carl, James R. (Inventor); Ngo, Phong (Inventor); Raffoul, George W. (Inventor)

    2001-01-01

    A method, simulation, and apparatus are provided that are highly suitable for treatment of benign prostatic hyperplasia (BPH). A catheter is disclosed that includes a small diameter disk loaded monopole antenna surrounded by fusion material having a high heat of fusion and a melting point preferably at or near body temperature. Microwaves from the antenna heat prostatic tissue to promote necrosing of the prostatic tissue that relieves the pressure of the prostatic tissue against the urethra as the body reabsorbs the necrosed or dead tissue. The fusion material keeps the urethra cool by means of the heat of fusion of the fusion material. This prevents damage to the urethra while the prostatic tissue is necrosed. A computer simulation is provided that can be used to predict the resulting temperature profile produced in the prostatic tissue. By changing the various control features of the catheter and method of applying microwave energy a temperature profile can be predicted and produced that is similar to the temperature profile desired for the particular patient.

  15. Soret fishnet metalens antenna.

    PubMed

    Orazbayev, Bakhtiyar; Beruete, Miguel; Pacheco-Peña, Víctor; Crespo, Gonzalo; Teniente, Jorge; Navarro-Cía, Miguel

    2015-01-01

    At the expense of frequency narrowing, binary amplitude-only diffractive optical elements emulate refractive lenses without the need of large profiles. Unfortunately, they also present larger Fresnel reflection loss than conventional lenses. This is usually tackled by implementing unattractive cumbersome designs. Here we demonstrate that simplicity is not at odds with performance and we show how the fishnet metamaterial can improve the radiation pattern of a Soret lens. The building block of this advanced Soret lens is the fishnet metamaterial operating in the near-zero refractive index regime with one of the edge layers designed with alternating opaque and transparent concentric rings made of subwavelength holes. The hybrid Soret fishnet metalens retains all the merits of classical Soret lenses such as low profile, low cost and ease of manufacturing. It is designed for the W-band of the millimeter-waves range with a subwavelength focal length FL = 1.58?mm (0.5?0) aiming at a compact antenna or radar systems. The focal properties of the lens along with its radiation characteristics in a lens antenna configuration have been studied numerically and confirmed experimentally, showing a gain improvement of ~2?dB with respect to a fishnet Soret lens without the fishnet metamaterial. PMID:25950243

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

    Microsoft Academic Search

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

    2008-01-01

    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

  17. SMART ANTENNAS FOR WIRELESS COMMUNICATION SYSTEMS

    Microsoft Academic Search

    Mustafa KARAKOÇ; Adnan KAVAK

    2004-01-01

    Smart antennas are considered to be promising technology for increasing the performance of wireless communication systems. A smart antenna consists of several antenna elements, whose signals are processed adaptively in order to exploit the spatial domain of the mobile radio channel (1). Usually, the signals received at the different antenna elements are multiplied with complex weights w, and then summed

  18. Specific antenna for Ultra Wide Band applications

    Microsoft Academic Search

    J.-C. Diot; B. Beillard; J. Andrieu; M. Lalande; B. Jecko

    2005-01-01

    The development of ultra wide band (UWB) systems required the design of specific antennas. These antennas must have a very wide band and not disperse or distort the pulses. This paper describe in a first part a transient method to design UWB antennas for transient application. In a second part, it gives some examples of antennas for radar and communication

  19. Helix Antennas Dr. Sandra Cruz-Pol

    E-print Network

    Cruz-Pol, Sandra L.

    , circular or linear (vertical), depending on which receiver is being used. Narrow Band Antennas Circularly11 Helix Antennas Dr. Sandra Cruz-Pol INEL 5305 UPRM Antenna Theory and Design Helix antenna geométricas. Axial Mode Most widely used mode Pattern has form: where Axial Mode 3/4

  20. Wide-band antennas: Theory and applications

    Microsoft Academic Search

    G. Dubost; S. Zisler

    1976-01-01

    Progress in the development of antennas having frequency bandwidths comparable to the carrier frequency is reviewed. The bases of the up-to-date antenna theory and advanced calculation methods are examined. Detailed attention is given to such technical constraints in antenna design as high directivity, small overall size, ease of electric adaptation, and possibility of feeding antennas by lines of a great

  1. Time Domain Responses of Printed UWB Antennas

    Microsoft Academic Search

    Yiqiong Shi; Sheel Aditya; C. L. Law

    2005-01-01

    Ultra-wideband (UWB) technology deals with generating, transmitting and receiving short pulses of sub-nanosecond duration. Thus, the time domain response of an antenna for UWB applications is as important as the traditional frequency domain antenna parameters. This paper discusses the time domain responses of two types of printed UWB antennas. It is shown that a smaller antenna with a shorter distance

  2. Time Domain Behaviors of Artimi's UWB Antenna

    Microsoft Academic Search

    L. Guo; J. Liang; X. Chen; C. G. Parini

    2006-01-01

    In this paper, a time domain study of Artimi's UWB antenna is presented. Firstly, the antenna's frequency domain behavior is illustrated. Thereafter, a detailed time domain investigation of the antenna is highlighted. It has been shown that Artimi's UWB antenna generally exhibits a good performance in both frequency and time domain. Wireless communications have been advancing with an astonishing rate

  3. High capacity antennas for MIMO radio systems

    Microsoft Academic Search

    V. Jungnickel; V. Pohl; H. Nguyen; U. Kruger; T. Haustein; C. von Helmolt

    2002-01-01

    The capacity of radio systems with multiple-transmit and multiple-receive antennas may be improved by antenna arrangements which reduce the effective Rician factor. Channel measurements indicate that the capacity in indoor environments may then be close to the independent Rayleigh fading channel even for large numbers of antennas. High capacities may be achieved with such antennas also in outdoor environments. Experiments

  4. 'Invisible' antenna takes up less space

    Microsoft Academic Search

    M. Shelley; K. Bond

    1986-01-01

    A compensated microstrip patch design is described that also uses grounded coplanar waveguide to permit a second, independent antenna to be mounted on any type of existing primary radar antenna aboard an aircraft without affecting its radiation. Successful integration of the IFF (identification friend or foe) antenna, which works at D-band, and the primary radar antenna is possible because of

  5. UWB module with antenna using organic substrates

    Microsoft Academic Search

    Koichiro Gomi; Masaaki Ishida; Shigeru Hiura

    2005-01-01

    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

  6. UWB module with antenna using organic substrates

    Microsoft Academic Search

    Koichiro Gomi; Masaaki Ishida; Shigeru Hiura

    2005-01-01

    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

  7. Miniaturized multipurpose dual UHF RFID band antenna

    Microsoft Academic Search

    A. Ali Babar; L. Ukkonen; L. Sydanheimo

    2010-01-01

    In this paper, the design, development and performance of a miniaturized multipurpose dual band planar antenna is discussed. This dual band antenna is destined to work on two UHF RFID bands, which are, 433MHz and the European RFID band (865MHz–868MHz). The main objective to design such an antenna was to have an antenna design having a small size, with an

  8. Reconfigurable MEMS Antennas Nakul Haridas1

    E-print Network

    Arslan, Tughrul

    Reconfigurable MEMS Antennas Nakul Haridas1 , Ahmet T. Erdogan1 , Tughrul Arslan1 , Anthony J carried out in the field of reconfigurable antennas, and in specific the reconfigurable MEMS (Micro-Electro-Mechanical Systems) antennas. The application of MEMS to antennas is studied and compared with the various

  9. GBES Antenna Efficiency Measurements Glen Langston

    E-print Network

    Groppi, Christopher

    1 GBES Antenna Efficiency Measurements Glen Langston Draft -- 94 April 28 Overview This document describes a set of measurements and calculations of the OVLBI GBES antenna gain. The antenna efficiency was measured by observations of radio sources of known brightness and small angular size. The antenna

  10. 1 Joint Antenna Combining and Multiuser Detection

    E-print Network

    Müller, Ralf R.

    1 Joint Antenna Combining and Multiuser Detection Ralf Muller y and Laura Cottatellucci y Smart antenna technology combined with code-division multiple-access (CDMA) is common in 3rd generation cellular with multiple element antennas, is exemplarily explored. Multiple reception due to multiple receive antennas

  11. 26 MHz 1300 MHz Log periodic antenna

    E-print Network

    26 MHz ­ 1300 MHz Log periodic antenna 1000 MHz ­ 4000 MHz Log periodic antenna Pre Supply Control cable to computer USB port USB to GPIB Cable RF cables from antennas to pre-selector should be as short as possible. Pre-selector should be mounted near the antennas. Pre-selector control

  12. Wire-antenna designs using genetic algorithms

    Microsoft Academic Search

    Edward E. Altshuler; Derek S. Linden

    1997-01-01

    There is a large class of electromagnetic radiators designated as wire antennas. As a rule, an inductive process is used to design these antennas. Either an integral equation is formulated or a simulator is used that gives the current distributions on the wires of the antenna, from which the electromagnetic properties of the antenna can then be determined. Once the

  13. Performance of Beverage antennas at low angles

    NASA Astrophysics Data System (ADS)

    Burke, G. J.; King, R. J.; Lytle, R. J.; Miller, E. K.

    1983-11-01

    Numerical modeling of Beverage and monopole antennas shows the fields of both antennas to have a similar dependence on range and height above ground, with the Beverage antenna having slightly greater gain in the forward direction due to its directivity. The use of multiple Beverage antennas closely spaced was found to increase the efficiency and gain in the forward direction for short Beverage antennas. For the longer antenna considered for the HF bistatic radar, the decrease in directivity for two closely spaced antennas reduced the forward gain.

  14. Ion source with external RF antenna

    DOEpatents

    Leung, Ka-Ngo; Ji, Qing; Wilde, Stephen

    2005-12-13

    A radio frequency (RF) driven plasma ion source has an external RF antenna, i.e. the RF antenna is positioned outside the plasma generating chamber rather than inside. The RF antenna is typically formed of a small diameter metal tube coated with an insulator. An external RF antenna assembly is used to mount the external RF antenna to the ion source. The RF antenna tubing is wound around the external RF antenna assembly to form a coil. The external RF antenna assembly is formed of a material, e.g. quartz, which is essentially transparent to the RF waves. The external RF antenna assembly is attached to and forms a part of the plasma source chamber so that the RF waves emitted by the RF antenna enter into the inside of the plasma chamber and ionize a gas contained therein. The plasma ion source is typically a multi-cusp ion source.

  15. A compact MIMO antenna for wireless communication

    Microsoft Academic Search

    Haili Zhang; Zhihong Wang; Jiawel Yu; Jia Huang

    2008-01-01

    This paper presents the design of a 2.65 GHz MIMO antenna with three equilateral triangular microstrip patches as the antenna elements. The wide-beam characteristics of a triangular-patch antenna, combined with the high gain of each antenna element, improve the SNR and interference rejection of the MIMO system. Through the analysis of mutual coupling and correlation between each pair of antenna

  16. Smart antennas based on graphene

    SciTech Connect

    Aldrigo, Martino; Dragoman, Mircea, E-mail: mircea.dragoman@imt.ro [National Institute for Research and Development in Microtechnology (IMT), P.O. Box 38-160, 023573 Bucharest (Romania); Dragoman, Daniela [Physics Faculty, University of Bucharest, P.O. Box MG-11, 077125 Bucharest (Romania)

    2014-09-21

    We report two configurations of smart graphene antennas, in which either the radiation pattern of the antenna or the backscattering of the periodic metallic arrays is controlled by DC biases that induce metal-insulator reversible transitions of graphene monolayers. Such a transition from a high surface resistance (no bias) to a low surface resistance state (finite bias voltage) causes the radiation pattern of metallic antennas backed with graphene to change dramatically, from omnidirectional to broadside. Moreover, reflectarrays enhance the backscattered field due to the same metal-dielectric transition.

  17. Semi hemi antenna. [balloon parachuted microwave antenna for stratospheric testing

    NASA Technical Reports Server (NTRS)

    Repucci, T. A.; Ferris, J. E.

    1978-01-01

    The University of Michigan minipod, which is released from a balloon and floats down on a parachute, is designed for stratospheric testing. The present paper briefly describes the evolution of antenna designs for the minipod 1.5 GHz transceiver, which communicates with and relays information to an aircraft and ground station. The following stages are noted: ordinary monopole, crossed dipole, capacitative antenna, fat monopole, the addition of parasitic elements, and a thinner monopole with taper.

  18. Antenna sunshield membrane

    NASA Technical Reports Server (NTRS)

    Bogorad, Alexander (Inventor); Bowman, Jr., Charles K. (Inventor); Meder, Martin G. (Inventor); Dottore, Frank A. (Inventor)

    1994-01-01

    An RF-transparent sunshield membrane covers an antenna reflector such as a parabolic dish. The blanket includes a single dielectric sheet of polyimide film 1/2-mil thick. The surface of the film facing away from the reflector is coated with a transparent electrically conductive coating such as vapor-deposited indium-tin oxide. The surface of the film facing the reflector is reinforced by an adhesively attached polyester or glass mesh, which in turn is coated with a white paint. In a particular embodiment of the invention, polyurethane paint is used. In another embodiment of the invention, a layer of paint primer is applied to the mesh under a silicone paint, and the silicone paint is cured after application for several days at room temperature to enhance adhesion to the primer.

  19. Evolutionary optimization of optical antennas.

    PubMed

    Feichtner, Thorsten; Selig, Oleg; Kiunke, Markus; Hecht, Bert

    2012-09-21

    The design of nanoantennas has so far been mainly inspired by radio-frequency technology. However, the material properties and experimental settings need to be reconsidered at optical frequencies, which would entail the need for alternative optimal antenna designs. Here we subject a checkerboard-type, initially random array of gold cubes to evolutionary optimization. To illustrate the power of the approach, we demonstrate that by optimizing the near-field intensity enhancement, the evolutionary algorithm finds a new antenna geometry, essentially a split-ring-two-wire antenna hybrid that surpasses by far the performance of a conventional gap antenna by shifting the n=1 split-ring resonance into the optical regime. PMID:23005987

  20. Omni-directional Antenna Pattern

    E-print Network

    Kansas, University of

    antennas base on GPS derived location information. IMPACT 1) Provide the basis for ATM end-to-end wireless the benefits of GPS derived location information for wireless network operations. SCHEDULE Architecture Testing DM FR #12;

  1. Numerical modeling techniques for antennas

    SciTech Connect

    Miller, E.K.

    1983-07-19

    An overview of wire-antenna computer modeling is given for infinite media and half-space type problems. The formulation and numerical solution methods are summarized, and applications are demonstrated with numerous examples.

  2. Microstrip antenna developments at JPL

    Microsoft Academic Search

    John Huang

    1991-01-01

    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,

  3. Large communication-satellite antenna

    Microsoft Academic Search

    J. Schultz

    1977-01-01

    Antennas planned for future space satellites will be too large to be carried aloft in an assembled configuration. They will therefore have to be deployable. A design concept for such antennas, usable at UHF-to-microwave frequencies, is discussed with reference to communications system parameters, and structural analysis. Various possibilities for the electrical configuration of a flat-faced phased-array are presented, including space

  4. Ultra Wide Band Miniature Antenna

    Microsoft Academic Search

    B. Bonnet; F. Dupont; F. Berens

    2007-01-01

    This article presents the simulation, manufacturing and measurement of the miniaturized ultra wide band IPADtrade (Integrated Passive Device) chip antenna for ultra wide band (UWB) applications. The proposed antenna has a compact size of 8.4*3.l*0.7 mm and has been mounted on an evaluation board. It offers an impedance bandwidth of 2.49 GHz (3 to 5.5 GHz) at VSWR 3:1 and

  5. Fin-line horn antenna

    DOEpatents

    Reindel, John (San Diego, CA)

    1990-01-01

    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.

  6. Box truss antenna technology status

    NASA Technical Reports Server (NTRS)

    Coyner, J. V.; Bachtell, E. E.

    1987-01-01

    Recent technology development activities for box truss structures and box truss antennas are summarized. Three primary activities are discussed: the development of an integrated analysis system for box truss mesh antennae; dynamic testing to characterize the effect of joint free play on the dynamic behavior of box truss structures; and fabrication of a 4.5 meter diameter offset fed mesh reflector integrated to an all graphite epoxy box truss cube.

  7. Conformal Carroll groups

    E-print Network

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

    2014-07-02

    Conformal extensions of Levy-Leblond's Carroll group, based on geometric properties analogous to those of Newton-Cartan space-time are proposed. The extensions are labelled 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.

  8. Conformal Carroll groups

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

    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.

  9. 'Invisible' antenna takes up less space

    NASA Astrophysics Data System (ADS)

    Shelley, M.; Bond, K.

    1986-06-01

    A compensated microstrip patch design is described that also uses grounded coplanar waveguide to permit a second, independent antenna to be mounted on any type of existing primary radar antenna aboard an aircraft without affecting its radiation. Successful integration of the IFF (identification friend or foe) antenna, which works at D-band, and the primary radar antenna is possible because of the diversity in frequency between the two antennas. Construction of a microstrip radiating element, electromagnetically invisible to the primary antenna, requires orthogonal grating elements and use of the primary antenna as the ground plane. Coplanar mounting of a stripline array with the primary antenna reduces the manufacturing costs and increases the functional performance of the IFF antenna.

  10. Aperture Coupled Microstrip Short Backfire Antenna

    NASA Astrophysics Data System (ADS)

    Kirov, Georgi S.; Chervenkov, Georgi T.; Kalchev, Chavdar D.

    2012-03-01

    A broadband aperture coupled microstrip short backfire antenna is described herein. It consists of a feed part (a microstrip feed line and a coupling slot in a metal ground) and a radiating part with two radiators: a patch antenna and a backfire antenna. The bandwidth widening of the antenna is achieved by use of two resonances: a patch resonance and a backfire resonance. The antenna is designed to operate within the Ku-band. It has a frequency bandwidth of about 15% and a maximum gain of 11.5 dBi. Within the antenna bandwidth the gain and the radiation efficiency have values more than 9 dBi and 82.1%, respectively. The designed antenna has a simple and compact construction and high mechanical and electrical characteristics. It can be used as a single antenna or as an element of microstrip antenna arrays with various applications in the contemporary communication systems.

  11. NASA technology for large space antennas

    NASA Technical Reports Server (NTRS)

    Russell, R. A.; Campbell, T. G.; Freeland, R. E.

    1979-01-01

    Technology developed by NASA in conjunction with industry for potential large, deployable space antennas with applications in communication, radio astronomy and earth observation is reviewed. Concepts for deployable antennas that have been developed to the point of detail design are summarized, including the advanced sunflower precision antenna, the radial rib antenna, the maypole (hoop/column) antenna and the parabolic erectable truss antenna. The assessment of state-of-the-art deployable antenna technology is discussed, and the approach taken by the NASA Large Space Systems Technology (LSST) Program to the development of technology for large space antenna systems is outlined. Finally, the further development of the wrap-rib antenna and the maypole (hoop/column) concept, which meet mission model requirements, to satisfy LSST size and frequency requirements is discussed.

  12. Antennas for mobile satellite communications

    NASA Technical Reports Server (NTRS)

    Huang, John

    1991-01-01

    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.

  13. E-Textile Antennas for Space Environments

    NASA Technical Reports Server (NTRS)

    Kennedy, Timothy F.; Fink, Patrick W.; Chu, Andrew W.

    2007-01-01

    The ability to integrate antennas and other radio frequency (RF) devices into wearable systems is increasingly important as wireless voice, video, and data sources become ubiquitous. Consumer applications including mobile computing, communications, and entertainment, as well as military and space applications for integration of biotelemetry, detailed tracking information and status of handheld tools, devices and on-body inventories are driving forces for research into wearable antennas and other e-textile devices. Operational conditions for military and space applications of wireless systems are often such that antennas are a limiting factor in wireless performance. The changing antenna platform, i.e. the dynamic wearer, can detune and alter the radiation characteristics of e-textile antennas, making antenna element selection and design challenging. Antenna designs and systems that offer moderate bandwidth, perform well with flexure, and are electronically reconfigurable are ideally suited to wearable applications. Several antennas, shown in Figure 1, have been created using a NASA-developed process for e-textiles that show promise in being integrated into a robust wireless system for space-based applications. Preliminary characterization of the antennas with flexure indicates that antenna performance can be maintained, and that a combination of antenna design and placement are useful in creating robust designs. Additionally, through utilization of modern smart antenna techniques, even greater flexibility can be achieved since antenna performance can be adjusted in real-time to compensate for the antenna s changing environment.

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

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

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

  15. [Conformers of carnosine].

    PubMed

    Kliuev, S A

    2006-01-01

    The geometric and energetic parameters of most stable conformations of carnosine were calculated by the semiempirical guantum-chemical method PM3. The carnosine-water-zinc (II) clusters were simulated. PMID:16909845

  16. Assemblies of Conformal Tanks

    NASA Technical Reports Server (NTRS)

    DeLay, Tom

    2009-01-01

    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.

  17. Broadband monopole optical nano-antennas

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

    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.

  18. Vehicle antenna development for mobile satellite applications

    NASA Technical Reports Server (NTRS)

    Woo, K.

    1988-01-01

    The paper summarizes results of a vehicle antenna program at JPL in support of a developing U.S. mobile satellite services (MSS) designed to provide telephone and data services for the continental United States. Two classes of circularly polarized vehicle antennas have been considered for the MSS: medium-gain, satellite-tracking antennas with 10-12-dBic gain; and low-gain, azimuthally omnidirectional antennas with 3-5-dBic gain. The design and performance of these antennas are described, and the two antennas are shown to have peculiar advantages and disadvantages.

  19. A trajectory preprocessor for antenna pointing

    NASA Technical Reports Server (NTRS)

    Tyler, S. R.

    1994-01-01

    A trajectory-preprocessing algorithm has been devised which matches antenna angular position, velocity, and acceleration to those of a target. This eliminates vibrations of the antenna structure caused by discontinuities in velocity and acceleration commands, and improves antenna-pointing performance by constraining antenna motion to a linear regime. The algorithm permits faster acquisition times and preserves antenna-tracking capability in situations where there would otherwise be an unacceptably sudden change in antenna velocity or acceleration. A simulation of DSS 13 shows that this preprocessor would reduce servo error to 1 mdeg during acquisition of a low-Earth-orbiting satellite.

  20. Conformal invariance of curvature perturbation

    E-print Network

    Jinn-Ouk Gong; Jai-chan Hwang; Wan Il Park; Misao Sasaki; Yong-Seon Song

    2011-07-10

    We show that in the single component situation all perturbation variables in the comoving gauge are conformally invariant to all perturbation orders. Generally we identify a special time slicing, the uniform-conformal transformation slicing, where all perturbations are again conformally invariant to all perturbation orders. We apply this result to the delta N formalism, and show its conformal invariance.

  1. Ambient connections realising conformal Tractor

    E-print Network

    Olver, Peter

    Ambient connections realising conformal Tractor holonomy Thomas Leistner, University of Adelaide 17-August 4, Poster session, July 24, 2006 #12;Conformal Structures and Tractor bundles A conformal is the normal conformal Tractor bundle. It is a vector bundle which is associated to the principle fibre bundle

  2. Antenna for passive RFID tags

    NASA Astrophysics Data System (ADS)

    Schiopu, Paul; Manea, Adrian; Cristea, Ionica; Grosu, Neculai; Vladescu, Marian; Craciun, Anca-Ileana; Craciun, Alexandru

    2015-02-01

    Minuscule devices, called RFID tags are attached to objects and persons and emit information which positioned readers may capture wirelessly. Many methods of identification have been used, but that of most common is to use a unique serial number for identification of person or object. RFID tags can be characterized as either active or passive [1,2]. Traditional passive tags are typically in "sleep" state until awakened by the reader's emitted field. In passive tags, the reader's field acts to charge the capacitor that powers the badge and this can be a combination of antenna and barcodes obtained with SAW( Surface Acoustic Wave) devices [1,2,3] . The antenna in an RFID tag is a conductive element that permits the tag to exchange data with the reader. The paper contribution are targeted to antenna for passive RFID tags. The electromagnetic field generated by the reader is somehow oriented by the reader antenna and power is induced in the tag only if the orientation of the tag antenna is appropriate. A tag placed orthogonal to the reader yield field will not be read. This is the reason that guided manufacturers to build circular polarized antenna capable of propagating a field that is alternatively polarized on all planes passing on the diffusion axis. Passive RFID tags are operated at the UHF frequencies of 868MHz (Europe) and 915MHz (USA) and at the microwave frequencies of 2,45 GHz and 5,8 GHz . Because the tags are small dimensions, in paper, we present the possibility to use circular polarization microstrip antenna with fractal edge [2].

  3. Wide scanning spherical antenna

    NASA Technical Reports Server (NTRS)

    Shen, Bing (Inventor); Stutzman, Warren L. (Inventor)

    1995-01-01

    A novel method for calculating the surface shapes for subreflectors in a suboptic assembly of a tri-reflector spherical antenna system is introduced, modeled from a generalization of Galindo-Israel's method of solving partial differential equations to correct for spherical aberration and provide uniform feed to aperture mapping. In a first embodiment, the suboptic assembly moves as a single unit to achieve scan while the main reflector remains stationary. A feed horn is tilted during scan to maintain the illuminated area on the main spherical reflector fixed throughout the scan thereby eliminating the need to oversize the main spherical reflector. In an alternate embodiment, both the main spherical reflector and the suboptic assembly are fixed. A flat mirror is used to create a virtual image of the suboptic assembly. Scan is achieved by rotating the mirror about the spherical center of the main reflector. The feed horn is tilted during scan to maintain the illuminated area on the main spherical reflector fixed throughout the scan.

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

    NASA Technical Reports Server (NTRS)

    Fichter, W. B.

    1989-01-01

    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.

  5. A New UWB Skeletal Antenna for EMC Applications

    Microsoft Academic Search

    A. R. Mallahzadeh; R. Pazoki; S. Karimkashi

    2007-01-01

    In this paper a new UWB antenna structure is introduced for EMC applications. This antenna is the skeletal form of the teardrop antenna. As the frequency decreases, the usual teardrop antenna is not applicable since the weight of such antenna as well as its ground dimension considerably increases and such antenna has not a good resistance against the wind. The

  6. A Compact Meander Microstripe Antenna for Bluetooth Headset

    Microsoft Academic Search

    Alpha Fan

    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,

  7. Progress on conformal microwave array applicators for heating chestwall disease

    NASA Astrophysics Data System (ADS)

    Stauffer, P. R.; Maccarini, P. F.; Juang, T.; Jacobsen, S. K.; Gaeta, C. J.; Schlorff, J. L.; Milligan, A. J.

    2007-02-01

    Previous studies have reported the computer modeling, CAD design, and theoretical performance of single and multiple antenna arrays of Dual Concentric Conductor (DCC) square slot radiators driven at 915 and 433 MHz. Subsequently, practical CAD designs of microstrip antenna arrays constructed on thin and flexible printed circuit board (PCB) material were reported which evolved into large Conformal Microwave Array (CMA) sheets that could wrap around the surface of the human torso for delivering microwave energy to large areas of superficial tissue. Although uniform and adjustable radiation patterns have been demonstrated from multiple element applicators radiating into simple homogeneous phantom loads, the contoured and heterogeneous tissue loads typical of chestwall recurrent breast cancer have required additional design efforts to achieve good coupling and efficient heating from the increasingly larger conformal array applicators used to treat large area contoured patient anatomy. Thus recent work has extended the theoretical optimization of DCC antennas to improve radiation efficiency of each individual aperture and reduce mismatch reflections, radiation losses, noise, and cross coupling of the feedline distribution network of large array configurations. Design improvements have also been incorporated into the supporting bolus structure to maintain effective coupling of DCC antennas into contoured anatomy and to monitor and control surface temperatures under the entire array. New approaches for non-invasive monitoring of surface and sub-surface tissue temperatures under each independent heat source are described that make use of microwave radiometry and flexible sheet grid arrays of thermal sensors. Efforts to optimize the clinical patient interface and move from planar rectangular shapes to contoured vest applicators that accommodate entire disease in a larger number of patients are summarized. By applying heat more uniformly to large areas of contoured anatomy, the CMA applicator resulting from these enhancements should expand the number of patients that can benefit from effective heating of superficial disease in combination with radiation or chemotherapy.

  8. The Effect of Antenna Physics on Fading Correlation and the Capacity of Multielement Antenna Systems

    Microsoft Academic Search

    Jianmin Gong; Jeremiah F. Hayes; Mohammad Reza Soleymani

    2007-01-01

    In this paper, we investigate the effects of antenna directivity and antenna orientation on fading correlation and, therefore, the channel capacity in multiple-input-multiple-output communication systems by means of a spherical simulation model. The correlation is caused by the mutual interaction of the scattering environment and antenna elements. To study the effect of antenna directivity and orientations on the correlation and

  9. A new ultrawideband printed monopole antenna: the planar inverted cone antenna (PICA)

    Microsoft Academic Search

    Seong-Youp Suh; Warren L. Stutzman; William A. Davis

    2004-01-01

    A new antenna, the planar inverted cone antenna (PICA), provides ultrawideband (UWB) performance with a radiation pattern similar to monopole disk antennas , but is smaller in size. Extensive simulations and experiments demonstrate that the PICA antenna provides more than a 10:1 impedance bandwidth (for VSWR<2) and supports a monopole type omnidirectional pattern over 4:1 bandwidth. A second version of

  10. Power Control and Number of Antenna Elements in CDMA Distributed Antenna Systems \\Lambda

    E-print Network

    Yanikomeroglu, Halim

    Power Control and Number of Antenna Elements in CDMA Distributed Antenna Systems \\Lambda Halim, the dynamic range of the power control decreases. It is demonstrated that by using a DA system with as small of antenna elements in a CDMA dis­ tributed antenna (DA) system and the yielding reverse link SIR

  11. An Original Antenna for Transient High Power UWB Arrays: The Shark Antenna

    Microsoft Academic Search

    Laurent Desrumaux; Adrien Godard; Michèle Lalande; Valérie Bertrand; Joël Andrieu; Bernard Jecko

    2010-01-01

    A novel ultrawideband (UWB) antenna, called the Shark antenna, and designed especially for transient applications is proposed in this paper. A Shark antenna array is also conceived in order to obtain a high power UWB pulse radiation source through the frequency band [800 MHz-8 GHz]. For this application, the elementary antenna must be compact, non-dispersive, and the array must have

  12. Multiple-Antenna Interference Channels with Real Interference Alignment and Receive Antenna

    E-print Network

    Wang, Zhengdao

    1 Multiple-Antenna Interference Channels with Real Interference Alignment and Receive Antenna Joint of freedom (DoF) regions of constant coefficient multiple antenna interference channels are investigated. First, we consider a K-user Gaussian interference channel with Mk antennas at transmitter k, 1 k K

  13. Unicast Multi-antenna Relay Beamforming with Per-Antenna Power Control: Optimization and Duality

    E-print Network

    Liang, Ben

    1 Unicast Multi-antenna Relay Beamforming with Per-Antenna Power Control: Optimization and Duality amplify-and-forward multi-antenna re- laying between a single pair of source and destination under relay per-antenna power constraints. We design the optimal relay processing matrix to minimize the maximum

  14. Analysis and design of aircraft antennas

    NASA Technical Reports Server (NTRS)

    Balanis, C. A.

    1975-01-01

    Recording systems and other associated electronic equipment were engineered, calibrated, and used to measure antenna radiation patterns of aircraft structures. Antenna design, measured and computed results, and performance are discussed. Data show measured and computer data to be in agreement.

  15. Mechanisms of the Rosetta high gain antenna

    NASA Astrophysics Data System (ADS)

    Pereira, Carlos

    2001-09-01

    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.

  16. A COGNITIVE COMPENSATION MECHANSIM FOR DEFORMABLE ANTENNAS 

    E-print Network

    Long, Stephen A.

    2010-07-14

    This thesis presents the design, theory, and measurement of a linearly polarized microstrip patch antenna with a novel substrate-integrated mechanism that can compensate the detuning effects from a physical deformation. Specifically, this antenna...

  17. Integrated resonant tunneling diode based antenna

    DOEpatents

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

    2000-01-01

    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.

  18. 47 CFR 15.317 - Antenna requirement.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    47 ? Telecommunication ? 1 ? 2010-10-01 ? 2010-10-01 ? false ? Antenna requirement. ? 15.317 ? Section 15.317 ? Telecommunication ? FEDERAL COMMUNICATIONS COMMISSION ? GENERAL ? RADIO FREQUENCY DEVICES ? Unlicensed Personal Communications Service Devices ? § 15.317 ? Antenna requirement. ?...

  19. 47 CFR 15.317 - Antenna requirement.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    47 ? Telecommunication ? 1 ? 2012-10-01 ? 2012-10-01 ? false ? Antenna requirement. ? 15.317 ? Section 15.317 ? Telecommunication ? FEDERAL COMMUNICATIONS COMMISSION ? GENERAL ? RADIO FREQUENCY DEVICES ? Unlicensed Personal Communications Service Devices ? § 15.317 ? Antenna requirement. ?...

  20. 47 CFR 80.1017 - Antenna system.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    (a) An antenna must be provided for nonportable bridge-to-bridge radiotelephone installations which is nondirectional and vertically polarized. The construction and installation of this antenna must insure proper operation in time of an...

  1. 47 CFR 80.1017 - Antenna system.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    (a) An antenna must be provided for nonportable bridge-to-bridge radiotelephone installations which is nondirectional and vertically polarized. The construction and installation of this antenna must insure proper operation in time of an...

  2. 47 CFR 15.317 - Antenna requirement.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    47 ? Telecommunication ? 1 ? 2013-10-01 ? 2013-10-01 ? false ? Antenna requirement. ? 15.317 ? Section 15.317 ? Telecommunication ? FEDERAL COMMUNICATIONS COMMISSION ? GENERAL ? RADIO FREQUENCY DEVICES ? Unlicensed Personal Communications Service Devices ? § 15.317 ? Antenna requirement. ?...

  3. 47 CFR 15.317 - Antenna requirement.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    47 ? Telecommunication ? 1 ? 2011-10-01 ? 2011-10-01 ? false ? Antenna requirement. ? 15.317 ? Section 15.317 ? Telecommunication ? FEDERAL COMMUNICATIONS COMMISSION ? GENERAL ? RADIO FREQUENCY DEVICES ? Unlicensed Personal Communications Service Devices ? § 15.317 ? Antenna requirement. ?...

  4. 47 CFR 15.317 - Antenna requirement.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    47 ? Telecommunication ? 1 ? 2014-10-01 ? 2014-10-01 ? false ? Antenna requirement. ? 15.317 ? Section 15.317 ? Telecommunication ? FEDERAL COMMUNICATIONS COMMISSION ? GENERAL ? RADIO FREQUENCY DEVICES ? Unlicensed Personal Communications Service Devices ? § 15.317 ? Antenna requirement. ?...

  5. Left-handed leaky wave antenna for millimeter-wave applications

    Microsoft Academic Search

    Shin-ichiro Matsuzawa; K. Sato; A. Sanada; H. Kubo; S. Aso

    2005-01-01

    In this paper, we have designed microstrip left-handed leaky wave antennas (LH LWAs) working from 75 to 82 GHz, and we have conformed beam scanning by MoM simulation. A conventional LH LWA for microwave applications consists of series interdigital capacitors and shunt stubs connected with vias to the ground. Manufacturing the interdigital capacitor and meander-line inductor working at mm-wave frequencies

  6. Killing Tensors and Conformal Killing Tensors from Conformal Killing Vectors

    E-print Network

    Raffaele Rani; S. Brian Edgar; Alan Barnes

    2003-03-12

    Koutras has proposed some methods to construct reducible proper conformal Killing tensors and Killing tensors (which are, in general, irreducible) when a pair of orthogonal conformal Killing vectors exist in a given space. We give the completely general result demonstrating that this severe restriction of orthogonality is unnecessary. In addition we correct and extend some results concerning Killing tensors constructed from a single conformal Killing vector. A number of examples demonstrate how it is possible to construct a much larger class of reducible proper conformal Killing tensors and Killing tensors than permitted by the Koutras algorithms. In particular, by showing that all conformal Killing tensors are reducible in conformally flat spaces, we have a method of constructing all conformal Killing tensors (including all the Killing tensors which will in general be irreducible) of conformally flat spaces using their conformal Killing vectors.

  7. Antenna Control Systems: From PI to H

    Microsoft Academic Search

    Wodek Gawronski

    2009-01-01

    This paper discusses the compensation of antenna-pointing errors following the recent analysis and retrofit of the NASA Deep Space Network antenna-control systems. The desired high-frequency communications with spacecraft (at Ka-band) require improved pointing precision over lower-frequency communications (at X-band). The quality of the antenna drives (hardware), the control algorithm (software), and the physical structure of the antenna (in terms of

  8. The Multi-Cross UWB Antenna

    Microsoft Academic Search

    Guan-Yu Chen; Sheng-Yi Huang; Jwo-Shiun Sun; Shuang-Yuan Chen

    This paper proposes an omni-directional UWB antenna pattern in azimuth cut, low voltage standing wave ratio (VSWR), and easy to construct antenna for ultra wideband (UWB) systems. The designed antenna uses the multi circular blade configuration with a radiating element and on two different ground planes (square and circular ground shape). The multi-circular blades UWB antenna suitable for IEEE 802.15.3a

  9. Characteristics of UWB antenna and wave propagation

    Microsoft Academic Search

    Guan-Yu Chen; Jwo-Shiun Sun; Sheng-Yi Huang; Y. D. Chen; Cheng-Hung Lin

    2005-01-01

    This paper proposes an omni-directional UWB antenna pattern in azimuth cut, low voltage standing wave ratio (VSWR), and easy to construct antenna for ultra wideband (UWB) systems. The designed antenna uses the multi circular blade configuration with a radiating element and on two different ground planes (square and circular ground shape). The multi-circular blades UWB antenna suitable for IEEE 802.15.3a

  10. Research and development of planar UWB antennas

    Microsoft Academic Search

    Zhi Ning Chen; Xianming Qing

    2005-01-01

    This paper addresses the advanced progress in research and development of planar antennas for promising ultra-wideband (UWB) applications within 3.1 GHz-10.6 GHz. The special design considerations for UWB antennas are introduced first. Secondly, newly developed omnidirectional designs, especially the antennas on PCBs are reviewed. Thirdly, the characteristics of a directional modified antipodal tapered slot antenna are shown for UWB applications.

  11. Wearable Yagi microstrip antenna for telemedicine applications

    Microsoft Academic Search

    Haider R. Khaleel; Hussain M. Al-Rizzo; Daniel G. Rucker; Taha A. Elwi

    2010-01-01

    This paper presents a button shaped antenna based on a microstrip Yagi array. The proposed antenna is suitable for Wireless Body Area Network (WBAN) and telemedicine applications operating at 2.45 GHz. Antenna properties, such as far-field radiation patterns, coupling coefficient, measured by the scattering parameter S11, and gain are provided. Moreover, the simulated performance of the proposed antenna is compared

  12. A fractal circular polarized RFID tag antenna

    NASA Astrophysics Data System (ADS)

    Chaouki, Guesmi; Ferchichi, Abdelhak; Gharsallah, Ali

    2013-09-01

    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.

  13. Microstrip patch antenna for RFID applications

    Microsoft Academic Search

    Raied A. R. Ibrahim; Mustapha C. E. Yagoub; Riadh W. Y. Habash

    2009-01-01

    The microstrip patch antenna is a popular printed resonant antenna for narrow-band microwave wireless link applications such as radio frequency identification (RFID) systems that require semi-hemispherical coverage. In this paper, a 865 MHz microstrip patch antenna fed by a microstrip line designed on a substrate is considerably studied and thoroughly analyzed. The antenna has been designed using the 3D High

  14. Flexible printed monopole antennas for WLAN applications

    Microsoft Academic Search

    Haider R. Khaleel; Hussain M. Al-Rizzo; Daniel G. Rucker; Yahiea Al-Naiemy

    2011-01-01

    In this paper, we present two thin\\/flexible printed monopole antennas for Wireless Local Area Network (WLAN) applications. The first design is a single band antenna which operates at 2.4 GHz while the second one is a dual band antenna operates at 2.5 GHz and 5.2 GHz. The dimensions of the proposed antennas are: (26.5 mm x 25) and (35 mm

  15. Performance assessment of printed RFID reader antenna

    Microsoft Academic Search

    Ailian Cai; Xianming Qing; Zhi Ning Chen; Boon Keng Lok

    2007-01-01

    In this paper, we characterize a printed loop antenna at high frequency (HF). The low-cost printed antenna will be used in a HF RFID smart shelf system for a low cost solution. The performance of the printed antenna is compared with an antenna made of PCB (copper) at 13.56 MHz in terms of impedance matching, field response, Q-factor, and detection

  16. The Galileo high gain antenna deployment anomaly

    NASA Technical Reports Server (NTRS)

    Johnson, Michael R.

    1994-01-01

    On April 11, 1991, the Galileo spacecraft executed a sequence that would open the spacecraft's High Gain Antenna. The Antenna's launch restraint had been released just after deployment sequence, the antenna, which opens like an umbrella, never reached the fully deployed position. The analyses and tests that followed allowed a conclusive determination of the likely failure mechanisms and pointed to some strategies to use for recovery of the high gain antenna.

  17. Single- and dual-polarized slot and patch antennas with wide tuning ranges

    NASA Astrophysics Data System (ADS)

    White, Carson R.

    Frequency- and polarization-agile antennas are of great interest for multi-function, software-defined, and cognitive radios. Frequency tuning over an octave is challenging because the radiation conductance changes as the antennas are tuned. In this work, single- and dual-polarized antennas are tuned over frequency ranges of up to 2:1 and 1.7:1, respectively, while remaining impedance matched. The impedance match over tuning is maintained by a properly chosen reactive element in series with the antenna. Both polarizations of the dual-polarized antennas are tuned independently, enabling either simultaneous frequency- and polarization-agility, or operation at two independent frequencies on orthogonal polarizations. First, the tunability of the slot-ring antenna is demonstrated with fixed-capacitor loading, and then, single and dual-polarized slot-ring antennas are tuned from 0.95-1.8 GHz and 0.93-1.6 GHz, respectively, using varactor diodes. Microstrip reactive loads are developed to maintain >20 dB port-to-port isolation over most of the tuning range of the dual-polarized antenna. This may be the first dual-polarized tunable antenna with independent control of both polarizations over a 1.7:1 frequency range. Single-sided radiation is desirable for many applications, and varactor-tuned cavity-backed slots are investigated for this purpose. A shallow cavity-backed slot is tuned from 1.0 to 1.9 GHz with <-20 dB return loss. The antenna operates either in free-space or conformally mounted with minimal change in input impedance. Finally, a dual-polarized cavity-backed patch antenna is tuned from 0.6-1 GHz. Differential feeds are employed to achieve >30 dB port-to-port isolation (differential- differential mode) over the tuning range, and the measured cross-polarization level at 0.65, 0.8, and 0.95 GHz is <-25 dB. This may be the first demonstration of dual-polarized independent tuning over a 1.7:1 frequency range with single-sided radiation.

  18. Optically addressed ultra-wideband phased antenna array

    NASA Astrophysics Data System (ADS)

    Bai, Jian

    Demands for high data rate and multifunctional apertures from both civilian and military users have motivated development of ultra-wideband (UWB) electrically steered phased arrays. Meanwhile, the need for large contiguous frequency is pushing operation of radio systems into the millimeter-wave (mm-wave) range. Therefore, modern radio systems require UWB performance from VHF to mm-wave. However, traditional electronic systems suffer many challenges that make achieving these requirements difficult. Several examples includes: voltage controlled oscillators (VCO) cannot provide a tunable range of several octaves, distribution of wideband local oscillator signals undergo high loss and dispersion through RF transmission lines, and antennas have very limited bandwidth or bulky sizes. Recently, RF photonics technology has drawn considerable attention because of its advantages over traditional systems, with the capability of offering extreme power efficiency, information capacity, frequency agility, and spatial beam diversity. A hybrid RF photonic communication system utilizing optical links and an RF transducer at the antenna potentially provides ultra-wideband data transmission, i.e., over 100 GHz. A successful implementation of such an optically addressed phased array requires addressing several key challenges. Photonic generation of an RF source with over a seven-octave bandwidth has been demonstrated in the last few years. However, one challenge which still remains is how to convey phased optical signals to downconversion modules and antennas. Therefore, a feed network with phase sweeping capability and low excessive phase noise needs to be developed. Another key challenge is to develop an ultra-wideband array antenna. Modern frontends require antennas to be compact, planar, and low-profile in addition to possessing broad bandwidth, conforming to stringent space, weight, cost, and power constraints. To address these issues, I will study broadband and miniaturization techniques for both single and array antennas. In addition, a prototype transmitting phased array system is developed and shown to demonstrate large bandwidth as well as a beam steering capability. The architecture of this system can be further developed to a large-scale array at higher frequencies such as mm-wave. This solution serves as a candidate for UWB multifunctional frontends.

  19. An LTE-Band Dual-Antenna Design with an Enhanced Antenna Efficiency

    NASA Astrophysics Data System (ADS)

    Kim, Jinyong; Chung, Kyungho; Ho, Yochuol; Kim, Moonil

    A neutralization line is internally added to a 770MHz LTE-band miniature dual-antenna system to improve its antenna efficiency. The odd-mode antenna impedance simulations indicate that the position of the neutralization line along the radiating structure determines the operation frequency. Measurement results show that the line reduces the antenna coupling loss from -6 to -17dB while improving the individual antenna efficiency from 42 to 65 percent at 770MHz.

  20. Antenna Technology Shuttle Experiment (ATSE)

    NASA Technical Reports Server (NTRS)

    Freeland, R. E.; Mettler, E.; Miller, L. J.; Rahmet-Samii, Y.; Weber, W. J., III

    1987-01-01

    Numerous space applications of the future will require mesh deployable antennas of 15 m in diameter or greater for frequencies up to 20 GHz. These applications include mobile communications satellites, orbiting very long baseline interferometry (VLBI) astrophysics missions, and Earth remote sensing missions. A Lockheed wrap rip antennas was used as the test article. The experiments covered a broad range of structural, control, and RF discipline objectives, which is fulfilled in total, would greatly reduce the risk of employing these antenna systems in future space applications. It was concluded that a flight experiment of a relatively large mesh deployable reflector is achievable with no major technological or cost drivers. The test articles and the instrumentation are all within the state of the art and in most cases rely on proven flight hardware. Every effort was made to design the experiments for low cost.

  1. Compact Low Frequency Radio Antenna

    DOEpatents

    Punnoose, Ratish J. (Hayward, CA)

    2008-11-11

    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.

  2. Antenna coupled photonic wire lasers.

    PubMed

    Kao, Tsung-Yu; Cai, Xiaowei; Lee, Alan W M; Reno, John L; Hu, Qing

    2015-06-29

    Slope efficiency (SE) is an important performance metric for lasers. In conventional semiconductor lasers, SE can be optimized by careful designs of the facet (or the modulation for DFB lasers) dimension and surface. However, photonic wire lasers intrinsically suffer low SE due to their deep sub-wavelength emitting facets. Inspired by microwave engineering techniques, we show a novel method to extract power from wire lasers using monolithically integrated antennas. These integrated antennas significantly increase the effective radiation area, and consequently enhance the power extraction efficiency. When applied to wire lasers at THz frequency, we achieved the highest single-side slope efficiency (~450 mW/A) in pulsed mode for DFB lasers at 4 THz and a ~4x increase in output power at 3 THz compared with a similar structure without antennas. This work demonstrates the versatility of incorporating microwave engineering techniques into laser designs, enabling significant performance enhancements. PMID:26191717

  3. Advanced zone plate antenna design

    NASA Astrophysics Data System (ADS)

    Wiltse, James C.

    2000-12-01

    The phase-correcting Fresnel zone plate antenna has been studied extensively at microwave and millimeter-wave frequencies in the past few years, in part because it offers advantages of low weight, cost, and loss. Scores of articles have appeared describing fundamental characteristics and methods of improving the efficiency, gain, and multiple- frequency band performance. As a result of these studies, one can now optimize the design, and an optimized zone plate antenna can provide performance superior to a standard lens or paraboloid antenna, especially at millimeter wavelengths. There are many differences between performance at optical wavelengths and microwaves/millimeter-waves, and these differences are described. A new planar design with non- parallel surfaces is discussed. This configuration offers further improvement in diffraction efficiency.

  4. Spinning grating antenna for MMW imaging

    Microsoft Academic Search

    Vladimir A. Manasson; Robert M. Mino; Lev S. Sadovnik

    1997-01-01

    MMW Scanning Antenna remains one of the most challenging components in the imaging radar design. Electronically steered antennas require sophisticated fabrication and become prohibitively expensive if a large array is considered. Mechanically scanning antennas typically involve one or more hinged parts (lenses, mirrors or feeds). In operation they experience mechanical acceleration and forces that sharply limit scanning rate. We present

  5. UMTS WCDMA Network Planning with Smart Antennas

    Microsoft Academic Search

    D. Tsilimantos; G. Tsoulos; D. I. Kaklamani

    2007-01-01

    The issue of UMTS WCDMA radio network planning with smart antennas is presented in this paper. First the complexity of 3G network planning is discussed in the context of 2G and smart antennas. Then the impact that smart antennas can have on key WCDMA network parameters, such as capacity and coverage probability is demonstrated with the help of a radio

  6. Study of a Differential - Fed UWB Antenna

    Microsoft Academic Search

    E. Pancera

    2007-01-01

    This article introduces a study of tapered slot antennas with ultra wideband applications. The contribute of this work is double. Firstly, a novel low profile, planar UWB antenna has been presented. Secondly, from this design, a novel differential -fed UWB antenna has been developed. The possibility of having a differential feeding structure is very useful since it permits to simplify

  7. Slot antenna for ultra-wideband applications

    Microsoft Academic Search

    H. M. Jafari; M. J. Deen; S. Hranilovic; N. K. Nikolova

    2006-01-01

    An ultra-wideband (UWB) antenna is designed for communications applications. Parameters that affect the antenna performance are investigated using both simulations and measurements. The same antenna is redesigned for use in a UWB cancer detection system, and its performance characteristics are investigated in a lossy biological coupling medium

  8. Very small UWB antenna for WBAN applications

    Microsoft Academic Search

    Kamya Yekeh Yazdandoost; Kiyoshi Hamaguchi

    2011-01-01

    The increasing demand for lightweight and miniature size of Ultra-Wideband (UWB) applications in wireless communications such as Body Area Network (BAN), requires the design of very small UWB antennas. One of the main element of wireless body area network is an antenna, and there are numerous concerns to consider while designing an on-body antenna, including power consumption, size, frequency, required

  9. HANDSET ANTENNA DESIGN: PRACTICE AND THEORY

    Microsoft Academic Search

    Wen Geyi; Qinjiang Rao; Shirook Ali; Dong Wang

    2008-01-01

    In this paper, an attempt is made to present a theory for the design of handset antennas, which results from the long experience that the authors have in the field of handset antenna design. The proposed theory is based on the well-known skin effect and constructs the antenna using a thin wire model that represent the backbone of the final

  10. Capacity of linear rectangular microstrip antenna arrays

    Microsoft Academic Search

    Christos Kalialakis; Ana Collado; Apostolos Georgiadis

    2009-01-01

    In this work, the dependence of the capacity of 2timesM MIMO systems on the mutual coupling between the transmitting and receiving antennas is investigated taking into account the correlation coefficient given by Clarke's model. Linear arrays of microstrip rectangular antennas are considered both in the transmitting and the receiving ends. The effect of the mutual coupling between microstrip antenna elements

  11. Advanced control technology for LSST antennas

    NASA Technical Reports Server (NTRS)

    Lin, Y. H.

    1981-01-01

    The control technology for the realization of large space system technology (LSST) antenna systems was identified and developed. Emphasis was directed at the control of LSST wrap-rib offset-feed antenna. The overall dynamic and control performance of offset-feed antenna was evaluated. Quantitative definitions of control problems were provided and control concepts for future development were identified.

  12. Printed UWB antenna for portable devices

    Microsoft Academic Search

    Emmi Kaivanto

    2008-01-01

    The shape of the radiator of an UWB antenna has a very strong effect to the impedance bandwidth of the antenna. This paper showed that the -10 dB bandwidth of an UWB antenna can be increased even 60 % using elliptical edges instead of straight edges in the radiator and without increasing the largest dimensions of the radiator. Is was

  13. Installed performance analysis of radar antenna systems

    Microsoft Academic Search

    Jacob J. Kim; Oren B. Kesler

    1998-01-01

    If modern airborne radar systems are to function properly, the radar antenna radiation patterns must meet certain specifications. Previously, most radar antennas were designed and tested in a clean antenna environment, i.e., there are no near field scattering from host structures, or radome effects. However, these higher order effects are a matter of increasing concern with added performance demands in

  14. Performance analysis of radar antenna systems

    Microsoft Academic Search

    J. J. Kim; O. B. Kesler

    1999-01-01

    If modern airborne radar systems are to function properly, the radar antenna radiation patterns must meet certain specifications. Until recently, most radar antennas were designed and tested in a clean antenna environment, i.e., there is no near field scattering from host structures or radome effects. However, these higher order effects are the matter of increasing concern with added performance demands

  15. Millimetre wave high efficiency photonic crystal antennas

    Microsoft Academic Search

    Gerard Burns; Harold Chong; David Edgar; Alex Ross; Khaled Elgaid; Helen McLelland; Susan Ferguson; F. McEwan; I. Thayne

    2002-01-01

    For a considerable time, the efficiency of planar antennas at high frequency has failed to reach its full potential. Since the planar antenna is an important element in an MMIC transceiver system, this poses a major problem. Due to the nature of the electromagnetic environment the antenna operates in, a large amount of the propagating radiation is coupled into the

  16. Photonic crystal horn and array antennas

    Microsoft Academic Search

    Andrew R. Weily; Karu P. Esselle; Barry C. Sanders

    2003-01-01

    We introduce a defect-based horn antenna in a two-dimensional photonic crystal. Our numerical simulations demonstrate the efficient, highly directional nature of the antenna. It has a large operating bandwidth, low loss, and an operating frequency that is scalable to various regions of the electromagnetic spectrum. We also show that the photonic crystal horn antenna can be successfully used in an

  17. Millimetre wave high efficiency photonic crystal antennas

    Microsoft Academic Search

    Gerard Burns; I. Thayne

    2003-01-01

    For a considerable time, the efficiency of planar antennas at high frequency has failed to reach its full potential. Since the planar antenna is an important element in an MMIC transceiver system, this poses a major problem. Due to the nature of the electromagnetic environment the antenna operates in, a large amount of the propagating radiation is coupled into the

  18. An overview of fractal antenna engineering research

    Microsoft Academic Search

    Douglas H. Werner; S. Ganguly

    2003-01-01

    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

  19. Wireless link design using a patch antenna

    SciTech Connect

    Hall, E

    2000-08-11

    A wireless link was designed using a patch antenna. In the process, several different models were tested. Testing proved a patch antenna was a viable solution for building a wireless link within the design specifications. Also, this experimentation provided a basis for future patch antenna design.

  20. Fundamental transmitting properties of carbon nanotube antennas

    Microsoft Academic Search

    G. W. Hanson

    2005-01-01

    Fundamental properties of dipole transmitting antennas formed by carbon nanotubes are investigated. Since carbon nanotubes can be grown to centimeter lengths, and since they can be metallic, the properties of carbon nanotubes as antenna elements are of fundamental interest. In this paper, dipole carbon nanotube antennas are investigated via a classical Hallen's-type integral equation, based on a quantum mechanical conductivity.

  1. Vector Antenna Array Configurations for Advanced

    E-print Network

    Vector Antenna Array Configurations for Advanced Synthesis Imaging on the Moon Jonatan Danielsson.80.332 053 0009002605 Antenna Array ConfigurationDense array located on the ground improved sensitivity and Resolution Improving Sensitivity More antennas Longer integration time Dual polarization data Averaging

  2. Optical Antenna Effect in Semiconducting Nanowires

    E-print Network

    Xiong, Qihua

    Optical Antenna Effect in Semiconducting Nanowires G. Chen,,,§ Jian Wu,,§ Qiujie Lu,§ H. R with nanoscale antennae made from crystalline GaP nanowires (NWs). Using Raman scattering, we have observed strong optical antenna effects which we identify with internal standing wave photon modes of the wire

  3. Antenna Devices and Measurement of Radio Emission

    E-print Network

    Erdmann, Martin

    Antenna Devices and Measurement of Radio Emission from Cosmic Ray induced Air Showers at the Pierre . . . . . . . . . . . . . . . . . . . . . . . 53 6 Antenna Theory 55 6.1 Vector Effective Length Effective Height in a Measurement Setup . . . . . . . 64 6.6.1 Thevenin Equivalent Antenna Description

  4. GBES Antenna Pointing Offsets Glen Langston

    E-print Network

    Groppi, Christopher

    1 GBES Antenna Pointing Offsets Glen Langston 95 January 30 Overview This document describes the measurement of OVLBI GBES antenna pointing corrections. The pointing offset function is described and previous. Introduction Bright compact radio sources were observed with the GBES antenna on 94 April 7, 12, 15, 21, 29

  5. Conformal General Relativity

    E-print Network

    V. Pervushin; D. Proskurin

    2001-06-03

    The inflation-free solution of problems of the modern cosmology (horizon, cosmic initial data, Planck era, arrow of time, singularity,homogeneity, and so on) is considered in the conformal-invariant unified theory given in the space with geometry of similarity where we can measure only the conformal-invariant ratio of all quantities. Conformal General Relativity is defined as the $SU_c(3)\\times SU(2)\\times U(1)$-Standard Model where the dimensional parameter in the Higgs potential is replaced by a dilaton scalar field described by the negative Penrose-Chernikov-Tagirov action. Spontaneous SU(2) symmetry breaking is made on the level of the conformal-invariant angle of the dilaton-Higgs mixing, and it allows us to keep the structure of Einstein's theory with the equivalence principle. We show that the lowest order of the linearized equations of motion solves the problems mentioned above and describes the Cold Universe Scenario with the constant temperature T and z-history of all masses with respect to an observable conformal time. A new fact is the intensive cosmic creation of $W,Z$-vector bosons due to their mass singularity. In the rigid state, this effect is determined by the integral of motion $(m_w^2H_{\\rm hubble})^{1/3}=2.7 K k_B$ that coincides with the CMB temperature and has the meaning of the primordial Hubble parameter. The created bosons are enough to consider their decay as an origin of the CMB radiation and all observational matter with the observational element abundances and the baryon asymmetry. Recent Supernova data on the relation between the luminosity distance and redshift (including the point $z=1.7$) do not contradict the dominance of the rigid state of the dark matter in the Conformal Cosmology.

  6. Antenna systems requirements definition study

    NASA Technical Reports Server (NTRS)

    Golden, C. T.

    1981-01-01

    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.

  7. Optimization of Antenna Structure Design

    NASA Technical Reports Server (NTRS)

    Levy, R.

    1984-01-01

    Optimality criteria design is applied for large antenna structures with multiple constraints on microwave performance. The constraints are on accuracy of the structure: restrictions on the microwave pathlength error, and the antenna pointing error. The examples given show convergence to low-weight feasible designs that satisfy the constraints. Truss-member sizes are automatically selected from tables of commercially available structural shapes, and approximations results from the method of selection are found moderate. The multiple constraint design is shown to be more effective in meeting constraints than the old envelop method. For practical structures, the new design method can be performed within reasonable core size and computation time.

  8. High Resolution Scanning Reflectarray Antenna

    NASA Technical Reports Server (NTRS)

    Romanofsky, Robert R. (Inventor); Miranda, Felix A. (Inventor)

    2000-01-01

    The present invention provides a High Resolution Scanning Reflectarray Antenna (HRSRA) for the purpose of tracking ground terminals and space craft communication applications. The present invention provides an alternative to using gimbaled parabolic dish antennas and direct radiating phased arrays. When compared to a gimbaled parabolic dish, the HRSRA offers the advantages of vibration free steering without incurring appreciable cost or prime power penalties. In addition, it offers full beam steering at a fraction of the cost of direct radiating arrays and is more efficient.

  9. Antenna systems requirements definition study

    NASA Astrophysics Data System (ADS)

    Golden, C. T.

    1981-02-01

    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.

  10. Charged Conformal Killing Spinors

    E-print Network

    Andree Lischewski

    2014-08-10

    We study the twistor equation on pseudo-Riemannian $Spin^c-$manifolds whose solutions we call charged conformal Killing spinors (CCKS). We derive several integrability conditions for the existence of CCKS and study their relations to spinor bilinears. A construction principle for Lorentzian manifolds admitting CCKS with nontrivial charge starting from CR-geometry is presented. We obtain a partial classification result in the Lorentzian case under the additional assumption that the associated Dirac current is normal conformal and complete the Classification of manifolds admitting CCKS in all dimensions and signatures $\\leq 5$ which has recently been initiated in the study of supersymmetric field theories on curved space.

  11. Conformally coupled dark matter

    E-print Network

    Mark Israelit

    1996-08-15

    Dark matter is obtained from a scalar field coupled conformally to gravitation; the scalar being a relict of Dirac's gauge function. This conformally coupled dark matter includes a gas of very light ($m\\approx 2.25\\times 10^{-34} eV$) neutral bosons having spin 0, as well as a time-dependent global scalar field, both pervading all of the cosmic space. The time-development of this dark matter in the expanding F-R-W universe is investigated, and an acceptable cosmological behaviour is obtained.

  12. AN ANTENNA SOLUTION FOR MIMO CHANNELS: THE SWITCHED PARASITIC ANTENNA

    Microsoft Academic Search

    Mattias Wennstr; Thomas Svantesson

    2000-01-01

    We investigate the switched parasitic antenna (SPA), which is a novel technique for electronically directing the radiation pat- tern, in a MIMO system. The correlation between the received signal modes are shown to be sufficiently low to yield a diver- sity gain. The capacity limit using the SPA is investigated for different SPA configurations and it is found that the

  13. Fractal antennas: a novel antenna miniaturization technique, and applications

    Microsoft Academic Search

    J. P. Gianvittorio; Yahya Rahmat-Samii

    2002-01-01

    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

  14. Galilean conformal and superconformal symmetries

    SciTech Connect

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

    2012-10-15

    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.

  15. Atmospheric icing and broadcast antenna reflections

    NASA Astrophysics Data System (ADS)

    Ryerson, Charles C.

    1988-08-01

    This study assesses the effects of atmospheric icing on broadcast transmission reflections on two mountains-Mount Mansfield in northern Vermont and Mount Washington in New Hampshire. Experience and theory suggest that antenna ice accretions produce large signal reflections. Correlations between reflection coefficients and ice accretions on Rosemount ice detectors adjacent to antennas were low and occasionally negative. The unexpected correlations may be due to factors not measured, such as antenna tuning, ice type and ice location on the antenna system. Other confounding factors may include ice detector performance and methods used to compute antenna ice accretions from the ice detectors.

  16. Antenna of the space radiotelescope KRT-3

    NASA Technical Reports Server (NTRS)

    Kostenko, V. I.; Matveyenko, L. I.

    1979-01-01

    The questions of antenna design with a diameter of 3 m for space radio-interferometry are examined. The basic characteristics of the antenna are determined, on the basis of which a model of the antenna of a space radiotelescope of 3.1 m KRT-3 is developed and prepared. The technological peculiarities of the antenna preparation are examined. The results of measurement of the reflecting surfaces of the telescope are cited, which point to the fact that the antenna may operate to wave lengths in the order of 2 mm.

  17. The 34-meter antenna drive control system

    NASA Technical Reports Server (NTRS)

    1981-01-01

    Detailed definitions of the baseline antenna drive and control/instrumentation equipment for 34 meter antennas included in Network Consolidation Program of the Deep Space Network are presented. The overall antenna control and monitor system and its interfaces with other higher level control and monitor equipment is described. Explicit descriptions of the antenna axis drive motors and motor controllers, the axis angle encoding systems, and miscellaneous antenna located components are presented, and related to system functional and performance requirements. Some potential alternates to the baseline system configuration are described and discussed.

  18. Taming the conformal zoo

    Microsoft Academic Search

    Gregory Moore; Nathan Seiberg

    1989-01-01

    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.

  19. 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

  20. Massive conformal gravity

    E-print Network

    F. F. Faria

    2014-12-15

    In this article we construct a massive theory of gravity that is invariant under conformal transformations. The massive action of the theory depend on the metric tensor and a scalar field, which are considered as the only field variables. We find the vacuum field equations of the theory and the solution of its Newtonian limit.

  1. Design of broadband single polarized antenna

    NASA Astrophysics Data System (ADS)

    Shin, Phoo Kho; Aziz, Mohamad Zoinol Abidin Abd.; Ahmad, Badrul Hisham; Ramli, Mohamad Hafize Bin; Fauzi, Noor Azamiah Md; Malek, Mohd Fareq Abd

    2015-05-01

    In practical wireless communication application, bandwidth enhancement becomes one of the major design considerations. At the same time, circular polarized (CP) antenna received much attention for the applications of modern wireless communication system when compared to linear polarized (LP) antenna. This is because CP antenna can reduce the multipath effect. Hence, broadband antenna with operating frequency at 2.4GHz for WLAN application is proposed. The proposed antenna is done by using L-probe amendment with rectangular patch. The rectangular patch and copper ground plane is separated with 10mm air gap. This approach is used to enhance the bandwidth and the gain of the proposed antenna. The bandwidth of the designed antenna is more than 200MHz which meet broadband application. The return loss for the antenna is below -10dB to achieved 90% matching efficiency. The position of L-probe feed is altered in order to obtained different polarizations. The broadband antenna had been designed and simulated by using Computer Simulation Technology (CST) software. In this paper, the comparison for single polarized antenna with the design of non-inverted patch and inverted patch is discussed. The characteristics of the S-parameter, axial ratio, gain, surface current for each designed antenna are analyzed.

  2. Conformational changes in biopolymers

    NASA Astrophysics Data System (ADS)

    Ivanov, Vassili

    2005-12-01

    Biopolymer conformational changes are involved in many biological processes. This thesis summarizes some theoretical and experimental approaches which I have taken at UCLA to explore conformational changes in biopolymers. The reversible thermal denaturation of the DNA double helix is, perhaps, the simplest example of biopolymer conformational change. I have developed a statistical mechanics model of DNA melting with reduced degrees of freedom, which allows base stacking interaction to be taken into account and treat base pairing and stacking separately. Unlike previous models, this model describes both the unpairing and unstacking parts of the experimental melting curves and explains the observed temperature dependence of the effective thermodynamic parameters used in models of the nearest neighbor type. I developed a basic kinetic model for irreversible thermal denaturation of F-actin, which incorporates depolymerization of F-actin from the ends and breaking of F-actin fiber in the middle. The model explains the cooperativity of F-actin thermal denaturation observed by D. Pavlov et al. in differential calorimetry measurements. CG-rich DNA sequences form left-handed Z-DNA at high ionic strength or upon binding of polyvalent ions and some proteins. I studied experimentally the B-to-Z transition of the (CG)6 dodecamer. Improvement of the locally linearized model used to interpret the data gives evidence for an intermediate state in the B-to-Z transition of DNA, contrary to previous research on this subject. In the past 15 years it has become possible to study the conformational changes of biomolecules using single-molecule techniques. In collaboration with other lab members I performed a single-molecule experiment, where we monitored the displacement of a micrometer-size bead tethered to a surface by a DNA probe undergoing the conformational change. This technique allows probing of conformational changes with subnanometer accuracy. We applied the method to detect, for the first time, single hybridization events of label-free target oligomers. This demonstrates a new paradigm of molecule detection where, hybridization of the target is detected through the conformational change of the probe.

  3. Foldable nanopaper antennas for origami electronics.

    PubMed

    Nogi, Masaya; Komoda, Natsuki; Otsuka, Kanji; Suganuma, Katsuaki

    2013-05-21

    Foldable antennas are required for small-sized electronic devices with high portability. Antennas on plastic substrates provide high flexibility and high sensitivity but are not foldable. Antennas on paper substrates are foldable, but their sensitivity is poor because of their coarse surfaces. In this paper, nanopapers with smooth surfaces and high foldability are fabricated from 30 nm wide cellulose nanofibers for use as foldable antenna substrates. Silver nanowires are then printed on the nanopapers to act as antenna lines. These nanopaper antennas with silver nanowires exhibit high sensitivity because of their smooth surfaces and high foldability because of their network structures. Also, their high foldability allows the mechanical tuning of their resonance points over a wide frequency range without using additional components such as condensers and coils. Nanopaper antennas with silver nanowires are therefore suitable for the realization of future foldable electronics. PMID:23575553

  4. Dynamic interrogation of wireless antenna sensor

    NASA Astrophysics Data System (ADS)

    Yao, J.; Tjuatja, S.; Huang, H.; Sanders, J.

    2014-03-01

    This paper presents the dynamic interrogation of a wireless antenna sensor for mechanical vibration monitoring. In order to interrogate the antenna resonant frequency at sufficient high speeds, a wireless interrogator that consists of a Frequency Modulated Continuous Wave (FMCW) synthesizer, a signal demodulation unit, and a real-time digital signal processing program was developed. The principle of operation of the dynamic wireless sensing system is first described, followed by the description of the design and implementation of the antenna sensor and the wireless interrogator. After calibrate the antenna sensor response using static tensile tests, dynamic interrogation of the wireless antenna sensor was carried out by subjecting the test specimen to a sinusoidal tensile load. The resonant frequency shifts of the antenna sensor were compared with the strains calculated from the applied loads. A good agreement between the antenna sensor readings and the strain values were achieved. A sampling rate of up to 50 Hz was demonstrated.

  5. Solid state NMR measurements of conformation and conformational

    E-print Network

    Weliky, David

    Solid state NMR measurements of conformation and conformational distributions in the membrane Lansing, MI, USA The solid state NMR lineshape of a protein backbone carbonyl nucleus is a general conformation in the distri- bution. These types of solid state NMR methodologies have been applied

  6. Multi-frequency resonant antenna

    NASA Technical Reports Server (NTRS)

    Temps, A. J., Jr.; Visscher, J.

    1970-01-01

    Antenna is simultaneously resonant at 8.75 MHz, 11.825 MHz, and 20.562 MHz. It provides a near-field radiator which has a constant current distribution across its radiating elements for each of the resonant frequencies.

  7. Gradiometer antennas for tunnel detection

    Microsoft Academic Search

    David A. Hill

    1992-01-01

    The use of gradiometer antennas for detection of long conductors and detection of empty tunnels is analyzed. For reception in vertical boreholes, the gradiometer consists of two vertical electric or magnetic dipoles with a vertical separation. Both sum and difference responses are useful, but the difference responses has the potential advantage of suppressing the primary field and making the scattered

  8. An ultrawideband photonic crystal antenna

    Microsoft Academic Search

    K. Agi; M. Mojahedi; K. J. Malloy; E. Schamiloglu

    1997-01-01

    We present the development of a novel ultrawideband antenna structure that uses photonic crystals as a substrate to reflect the energy normally trapped within a substrate into free space. Photonic crystals are three-dimensional periodic structures that exhibit spatial three-dimensional filter properties. In order to achieve an ultrawideband photonic crystal, two photonic crystals with different periodicities are stacked in tandem. The

  9. IMPULSE RADIATING ANTENNAS, PART II

    Microsoft Academic Search

    Everett G. Farr; Carl E. Baum; C. Jerald Buchenauer

    In this continuation of our paper in the last conference proceedings1, we consider further developments in the area of Impulse Radiating Antennas (IRAs). First, we consider definitions of gain in the time domain, which are important for optimizing the performance of IRAs. A reasonable definition of gain must be equally valid in transmission as in reception. Such a definition leads

  10. RF/Optical Hybrid Antenna

    NASA Astrophysics Data System (ADS)

    Torrez, T. M.

    2015-05-01

    This article details analyses performed on several variations of a proposed radio frequency (RF)/optical hybrid antenna. The goal was to determine the structural impact of adding an assembly of optical mirrors to the antenna; stresses in the structural members and reflector surface deformation were used to assess this impact. The results showed that the structure could handle the added assembly, and the surface RMS increased, as expected, with larger increases seen as the antenna translates in elevation from the rigging angle of 45 deg (a predetermined location chosen to optimize panel settings during installation). In addition, actuators are located behind each optical mirror to reoptimize the mirror positions after they deflect due to the antenna being tipped in elevation. The necessary actuator motion was calculated for each mirror for a range of elevation angles, and it was found that the required motions are achievable by commonly used actuators. Resonant frequency analysis was also performed on the quadripod and tripod (for DSS-13 at Goldstone) to determine the effect that adding optical components on the apex has on the structure and its first mode; it was found that the impact is minimal to both the stresses seen in the structure and its first mode.

  11. Photogrammetry Of A Parabolic Antenna

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

    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.

  12. DSS 13 microprocessor antenna controller

    NASA Technical Reports Server (NTRS)

    Gosline, R. M.

    1988-01-01

    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.

  13. Non-Gimbaled Antenna Pointing

    NASA Technical Reports Server (NTRS)

    Vigil, Jeannine S.

    1997-01-01

    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.

  14. Loop Virasoro Lie conformal algebra

    SciTech Connect

    Wu, Henan, E-mail: wuhenanby@163.com; Chen, Qiufan; Yue, Xiaoqing [Department of Mathematics, Tongji University, Shanghai 200092 (China)] [Department of Mathematics, Tongji University, Shanghai 200092 (China)

    2014-01-15

    The Lie conformal algebra of loop Virasoro algebra, denoted by CW, is introduced in this paper. Explicitly, CW is a Lie conformal algebra with C[?]-basis (L{sub i} | i?Z) and ?-brackets [L{sub i}?{sub ?}?L{sub j}] = (???2?)L{sub i+j}. Then conformal derivations of CW are determined. Finally, rank one conformal modules and Z-graded free intermediate series modules over CW are classified.

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

    NASA Astrophysics Data System (ADS)

    Mohammad, Irshad

    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.

  16. From Antenna to Assay

    PubMed Central

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

    2009-01-01

    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

  17. Conformal mappings involving curvilinear quadrangles

    E-print Network

    Craster, Richard

    1 Conformal mappings involving curvilinear quadrangles By R.V. Craster Department of Theoretical Mechanics, University of Nottingham, Nottingham, NG7 2RD, U.K. Conformally mapping a curvilinear quadrangle and there are usually no obvious solutions. In this paper conformal mappings involving a special class of curvilinear

  18. Radiation characteristics of ring antennas for electron plasma waves

    Microsoft Academic Search

    Shigeru Egashira; Yuzuru Morita; Yoshinori Yoshida

    1982-01-01

    For ionospheric measurements and laboratory plasma studies, an antenna with good radiating or receiving efficiency for plasma waves is needed. Egashira et al. (1978) have proposed a ring antenna. It was demonstrated that such an antenna excites plasma waves more easily than a disk antenna of identical radius if the ratio of the antenna radius to the Debye length is

  19. Broadband terahertz antenna for wide band gap semiconductor photoconductive switches

    Microsoft Academic Search

    Yu-Jiun Ren; Pengcheng Lv; Kai Chang

    2008-01-01

    A study of the bowtie antenna fed by a coplanar stripline for terahertz applications is presented in this paper. The purpose of designing the antennas is to use it as the antenna elements of the photoconductive switch devices. The broadband and radiation characteristics of the bowtie antenna are compared with a dipole antenna in the same dimension scale. The bowtie

  20. Circularly polarized textile antenna for personal satellite communication

    Microsoft Academic Search

    E. Kaivanto; J. Lilja; M. Berg; E. Salonen; P. Salonen

    2010-01-01

    This paper describes how the performance of wearable textile antenna is affected by antenna bending. Here, we will focus on the resonance frequency fluctuation and input-match bandwidth variation due to the antenna bending as well as the changes in radiation pattern and antenna efficiency. This study is carried out for a circularly polarized textile patch antenna operating at Iridium satellite

  1. A multi octaves directive dielectric lens: the pyramid antenna

    Microsoft Academic Search

    S. Bruni; A. Neto; F. Marliani

    2005-01-01

    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

  2. A rectangular cavity for cell phone antenna efficiency measurement

    Microsoft Academic Search

    A. P. Raiva; J. Fabrega-Sanchez

    2005-01-01

    Electromagnetic cavities can be used to measure antenna efficiency. Enclosing an antenna within a conducting rectangular or spherical cavity can eliminate the radiation resistance from the impedance without changing the loss resistance of the antenna. The cavity size should avoid both the disturbance of the field near the antenna and the cavity's resonance. The efficiency of the antenna is calculated

  3. Advanced technology in satellite communication antennas: Electrical and mechanical design

    Microsoft Academic Search

    Takashi Kitsuregawa

    1990-01-01

    Antenna technology for earth stations and satellites is discussed. The fundamentals, including common analysis methods, for antenna technology for satellite communication are reviewed. Details of the analysis method for beam waveguide feeds are shown, and electrical and mechanical designs for earth station antennas are examined. Offset dual-reflector antennas and offset reflector antennas with beam waveguide feed are examined, giving comprehensive

  4. Layout Of Antennas And Cables In A Large Array

    NASA Technical Reports Server (NTRS)

    Logan, Ronald T., Jr.

    1995-01-01

    Layout devised to minimize total land area occupied by large phased array of antennas and to minimize total length of cables in array. In original intended application, array expanded version of array of paraboloidal-dish microwave communication antennas of Deep Space Network. Layout also advantageous for other phased arrays of antennas and antenna elements, including notably printed-circuit microwave antenna arrays.

  5. Negative ion source with external RF antenna

    DOEpatents

    Leung, Ka-Ngo; Hahto, Sami K.; Hahto, Sari T.

    2007-02-13

    A radio frequency (RF) driven plasma ion source has an external RF antenna, i.e. the RF antenna is positioned outside the plasma generating chamber rather than inside. The RF antenna is typically formed of a small diameter metal tube coated with an insulator. An external RF antenna assembly is used to mount the external RF antenna to the ion source. The RF antenna tubing is wound around the external RF antenna assembly to form a coil. The external RF antenna assembly is formed of a material, e.g. quartz, which is essentially transparent to the RF waves. The external RF antenna assembly is attached to and forms a part of the plasma source chamber so that the RF waves emitted by the RF antenna enter into the inside of the plasma chamber and ionize a gas contained therein. The plasma ion source is typically a multi-cusp ion source. A converter can be included in the ion source to produce negative ions.

  6. Transparent antennas for solar cell integration

    NASA Astrophysics Data System (ADS)

    Yasin, Tursunjan

    Transparent patch antennas are microstrip patch antennas that have a certain level of optical transparency. Highly transparent patch antennas are potentially suitable for integration with solar panels of small satellites, which are becoming increasingly important in space exploration. Traditional patch antennas employed on small satellites compete with solar cells for surface area. However, a transparent patch antenna can be placed directly on top of solar cells and resolve the issue of competing for limited surface real estate. For such an integration, a high optical transparency of the patch antenna is required from the solar cells' point of view. On the other hand, the antenna should possess at least acceptable radiation properties at the same time. This dissertation focuses on some of the most important concerns from the perspective of small satellite applications. For example, an optimization method to simultaneously improve both optical transparency and radiation efficiency of the antenna is studied. Active integrated antenna design method is extended to meshed patch applications in an attempt to improve the overall power efficiency of the front end communication subsystem. As is well known, circular polarization is immune from Faraday rotation effect in the ionosphere and thus can avoid a 3-dB loss in geo-satellite communication. Therefore, this research also aims to present design methods for circularly polarized meshed patch antennas. Moreover, a meshed patch antenna capable of supporting a high communication data rate is investigated. Lastly, other types of transparent patch antennas are also analyzed and compared to meshed patches. In summary, many properties of transparent patch antennas are examined in order to meet different design requirements.

  7. Conformal Complementarity Maps

    E-print Network

    Jose L. F. Barbon; Eliezer Rabinovici

    2013-08-08

    We study quantum cosmological models for certain classes of bang/crunch singularities, using the duality between expanding bubbles in AdS with a FRW interior cosmology and perturbed CFTs on de Sitter space-time. It is pointed out that horizon complementarity in the AdS bulk geometries is realized as a conformal transformation in the dual deformed CFT. The quantum version of this map is described in full detail in a toy model involving conformal quantum mechanics. In this system the complementarity map acts as an exact duality between eternal and apocalyptic Hamiltonian evolutions. We calculate the commutation relation between the Hamiltonians corresponding to the different frames. It vanishes only on scale invariant states.

  8. Conformal superalgebras via tractor calculus

    E-print Network

    Andree Lischewski

    2014-08-10

    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.

  9. Multiple Antenna Performance of Quarter-Wavelength Monopole Antennas for Card-Type Terminal

    NASA Astrophysics Data System (ADS)

    Okano, Yoshiki; Cho, Keizo

    This paper investigates the performance of multiple monopole antennas mounted on a card-type terminal, which is expected to be used in the systems beyond 3G, based on the calculated and measured radiation patterns for the 2.0GHz. We characterize the feasible performance of quarter-wavelength monopole antennas mounted on a card-type terminal in a multiple antenna configuration with narrow element spacing of less than a half-wavelength assuming that the antennas used must satisfy the space restrictions of the mobile terminal. Performance figures of merit for the multiple antenna performance include the beamforming gain, correlation coefficient, and MIMO channel capacity. Furthermore, we investigate the influence of a finite ground plane on the characteristics of multiple monopole antennas using a typical antenna configuration comprising a simple finite ground plane and multiple monopole antennas to discuss the fundamental characteristics.

  10. Research on MLS airborne antenna

    NASA Technical Reports Server (NTRS)

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

    1976-01-01

    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.

  11. 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.

  12. Plasmonic Antenna Coupling for QWIPs

    NASA Technical Reports Server (NTRS)

    Hong, John

    2007-01-01

    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.

  13. Slotted antenna waveguide plasma source

    NASA Technical Reports Server (NTRS)

    Foster, John (Inventor)

    2007-01-01

    A high density plasma generated by microwave injection using a windowless electrodeless rectangular slotted antenna waveguide plasma source has been demonstrated. Plasma probe measurements indicate that the source could be applicable for low power ion thruster applications, ion implantation, and related applications. This slotted antenna plasma source invention operates on the principle of electron cyclotron resonance (ECR). It employs no window and it is completely electrodeless and therefore its operation lifetime is long, being limited only by either the microwave generator itself or charged particle extraction grids if used. The high density plasma source can also be used to extract an electron beam that can be used as a plasma cathode neutralizer for ion source beam neutralization applications.

  14. Photonic crystal horn and array antennas.

    PubMed

    Weily, Andrew R; Esselle, Karu P; Sanders, Barry C

    2003-07-01

    We introduce a defect-based horn antenna in a two-dimensional photonic crystal. Our numerical simulations demonstrate the efficient, highly directional nature of the antenna. It has a large operating bandwidth, low loss, and an operating frequency that is scalable to various regions of the electromagnetic spectrum. We also show that the photonic crystal horn antenna can be successfully used in an array configuration that uses a feed network made from photonic crystal waveguide circuits. The feed network and antennas have been integrated into a single photonic crystal device. This photonic crystal array antenna is shown to have high directivity and compact size while retaining the advantages of the photonic crystal horn antenna. PMID:12935272

  15. Antenna pattern control using impedance surfaces

    NASA Technical Reports Server (NTRS)

    Balanis, Constantine A.; Liu, Kefeng; Tirkas, Panayiotis A.

    1993-01-01

    During the period of this research project, a comprehensive study of pyramidal horn antennas was conducted. Full-wave analytical and numerical techniques were developed to analyze horn antennas with or without impedance surfaces. Based on these full-wave analytic techniques, research was conducted on the use of impedance surfaces on the walls of the horn antennas to control the antenna radiation patterns without a substantial loss of antenna gain. It was found that the use of impedance surfaces could modify the antenna radiation patterns. In addition to the analytical and numerical models, experimental models were also constructed and they were used to validate the predictions. Excellent agreement between theoretical predictions and the measured data was obtained for pyramidal horns with perfectly conducting surfaces. Very good comparisons between numerical and experimental models were also obtained for horns with impedance surfaces.

  16. Antenna development for astroparticle and radioastronomy experiments

    NASA Astrophysics Data System (ADS)

    Charrier, Didier; CODALEMA Collaboration

    2012-01-01

    An active dipole antenna is in operation since five years at the Nançay radio Observatory (France) in the CODALEMA experiment. A new version of this active antenna has been developed, whose shape gave its name of “Butterfly” antenna. Compared to the previous version, this new antenna has been designed to be more efficient at low frequencies, which could permit the detection of atmospheric showers at large distances. Despite a size of only 2 m×1 m in each polarization, its sensitivity is excellent in the 30-80 MHz bandwidth. Three antennas in dual polarization were installed on the CODALEMA experiment, and four other have been recently installed on the Auger area in the scope of the AERA project. The main characteristics of the Butterfly antenna are detailed with an emphasis on its key features which make it a good candidate for the low frequency radioastronomy and the radio detection of transients induced by high energy cosmic rays.

  17. Miniaturization of UWB Antennas and its Influence on Antenna-Transceiver Performance

    Microsoft Academic Search

    Soheil Radiom; H. Aliakbarian; G. Vandenbosch; G. Gielen

    2008-01-01

    A modified small-size tapered monopole antenna is optimized for ultra wideband applications in co-design with the transceiver. Our optimization procedure aims at finding an antenna not only with low VSWR, but also miniaturizing the antenna at the same time. Our proposed optimization algorithm, real-coded compact genetic algorithm, RCCGA, has lowered the antenna area more than 48% compared to previous work

  18. Link quality based MIMO antenna selection in RoF ubiquitous antenna

    Microsoft Academic Search

    Takeshi Higashino; Takuya Yamakami; Katsutoshi Tsukamoto; Shozo Komaki

    2010-01-01

    Recently, multi-antenna technology is used in almost new radio communication technology such as MIMO (multiple-input multiple-output). The centralized signal processing is one of features of the Radio-on-Fiber distributed antenna application. This paper proposes a link quality based antenna selection in Radio-on-Fiber ubiquitous antenna system. In this system, the channel state information is gathered by the centralized control station (CCS). Proposed

  19. Transmitter Optimization for the Multi-Antenna Downlink With Per-Antenna Power Constraints

    Microsoft Academic Search

    Wei Yu; Tian Lan

    2007-01-01

    This paper considers the transmitter optimization problem for a multiuser downlink channel with multiple transmit antennas at the base-station. In contrast to the conventional sum-power constraint on the transmit antennas, this paper adopts a more realistic per-antenna power constraint, because in prac- tical implementations each antenna is equipped with its own power amplifier and is limited individually by the linearity

  20. DSS 13 Microprocessor Antenna Controller

    NASA Technical Reports Server (NTRS)

    Gosline, R. M.

    1984-01-01

    A microprocessor based antenna controller system developed as part of the unattended station project for DSS 13 is described. Both the hardware and software top level designs are presented and the major problems encounted are discussed. Developments useful to related projects include a JPL standard 15 line interface using a single board computer, a general purpose parser, a fast floating point to ASCII conversion technique, and experience gained in using off board floating point processors with the 8080 CPU.

  1. Asymmetric Coplanar Strip fed wide band antenna

    Microsoft Academic Search

    D. Laila; V. Deepu; R. Sujith; P. Mohanan; C. K. Anandan; K. Vasudevan

    2008-01-01

    An Asymmetric Coplanar Strip (ACS) fed uniplanar antenna for wide band applications is presented. The resulting antenna offers a 2:1 VSWR bandwidth greater than 100% from 1.65 GHz to 5.06 GHz covering the DCS\\/PCS\\/IEEE 802.11a\\/WiMAX bands. The antenna has an overall dimension of 44 mm X 35 mm when printed on a substrate of dielectric constant 4.4 and height 1.6

  2. UWB antennas with enhanced performances (invited)

    Microsoft Academic Search

    Zhi Ning Chen

    2008-01-01

    This paper updates the latest progress in research and development (R&D) of ultra-wideband (UWB) antennas in Institute for Infocomm Research (I2R), Singapore in 2007. All projects aim to enhance the performance of UWB antennas for specific applications besides the basic design considerations such as broadband impedance response and small size. First, the UWB antenna with diversity performance is briefly introduced

  3. A Small UWB Antenna for Wireless USB

    Microsoft Academic Search

    Terence S. P. See; Zhi Ning Chen

    2007-01-01

    A printed ultra-wideband (UWB) antenna operating within a frequency range of 3.1-5 GHz is proposed for wireless USB dongle applications. The antenna consists of a triangular radiating element with a notch at the center and an L-shaped strip extended from the end of the radiator to reduce the antenna size. The ground plane is etched on the reverse side of

  4. A compact CPW fed serrated UWB antenna

    Microsoft Academic Search

    V. A Shameena; Sarah Jacob; C. K Aanandan; K Vasudevan; P. Mohanan

    2011-01-01

    A compact CPW-fed planar monopole antenna for ultra-wideband applications is presented and investigated. The proposed antenna with a small size of 20 mm x26 mm x 1.6 mm is composed of a staircase shaped radiating element fed by a CPW feed line, and an inverted stair-style ground. The measured results agree reasonably with the simulated ones. The proposed antenna yields

  5. Distortion compensation techniques for large reflector antennas

    Microsoft Academic Search

    W. A. Imbriale

    2001-01-01

    The high-frequency limit of reflector antennas is usually governed by the magnitude of the surface error. Whereas little can be done for the high-spatial frequency portion of this error, there are various techniques that can be employed to compensate for large-scale surface errors due to gravity induced distortions for ground antennas or thermally induced distortions for spacecraft antennas. This somewhat

  6. Finding the Focal Axes of Offset Antennas

    NASA Technical Reports Server (NTRS)

    Schmidt, R. F.

    1982-01-01

    Focal axis of offset paraboloidal reflector antennas determined by direct measurement instead of trial and error. Two feed horns transmit sum or difference pattern to antenna under test, which reflects energy to far-field detector. When axis of feed horns coincides with focal axis of antenna reflector, far-field detector records minimum in amplitude difference and maximum in absolute-magnitude phase difference between sum and difference signals.

  7. Multi-Mode Broadband Patch Antenna

    NASA Technical Reports Server (NTRS)

    Romanofsky, Robert R. (Inventor)

    2001-01-01

    A multi-mode broad band patch antenna is provided that allows for the same aperture to be used at independent frequencies such as reception at 19 GHz and transmission at 29 GHz. Furthermore, the multi-mode broadband patch antenna provides a ferroelectric film that allows for tuning capability of the multi-mode broadband patch antenna over a relatively large tuning range. The alternative use of a semiconductor substrate permits reduced control voltages since the semiconductor functions as a counter electrode.

  8. Frequency-Reconfigurable Antenna Using Metasurface

    Microsoft Academic Search

    H. L. Zhu; X. H. Liu; S. W. Cheung; T. I. Yuk

    2014-01-01

    A frequency-reconfigurable antenna designed using metasurface (MS) to operate at around 5 GHz is proposed and studied. The frequency-reconfigurable metasurfaced (FRMS) an- tennaiscomposedofasimplecircularpatchantennaandacircular MS with the same diameter of 40 mm (0.67 ) and implemented using planar technology. The MS is placed directly atop the patch antenna, making the FRMS antenna very compact and low pro- file with a thickness

  9. Quasi-optical slot antenna SIS mixers

    Microsoft Academic Search

    Jonas Zmuidzinas; H. G. LeDuc

    1992-01-01

    A quasi-optical SIS mixer designed for efficient radiation coupling is described. The mixer uses a twin-slot antenna which has the advantages of a good beam pattern and a low impedance. The radiation and impedance characteristics of the antenna were obtained from a moment-matched calculation. Tapered superconducting microstrip transmission lines are used to carry the radiation from the slot antennas to

  10. Dielectric optical antenna thermal emitters and metamaterials

    Microsoft Academic Search

    Jonathan Aaron Schuller

    2010-01-01

    Optical antennas are critical components in nanophotonics research due to their unparalleled ability to concentrate electromagnetic energy into nanoscale volumes. Researchers typically construct such antennas from wavelength-size metallic structures. However, recent research has begun to exploit the scattering resonances of high-permittivity particles to realize all-dielectric optical antennas, emitters, and metamaterials. In this thesis, we experimentally and theoretically characterize the resonant

  11. Dielectric Optical Antenna Emitters and Metamaterials

    Microsoft Academic Search

    Jon Schuller

    2009-01-01

    Optical antennas are critical components in nanophotonics research due to their unparalleled ability to concentrate electromagnetic energy into nanoscale volumes. Researchers typically construct such antennas from wavelength-size metallic structures. However, recent research has begun to exploit the scattering resonances of high-permittivity particles to realize all-dielectric optical antennas, emitters, and metamaterials. In this talk, we experimentally and theoretically characterize the resonant

  12. Fundamental transmitting properties of carbon nanotube antennas

    Microsoft Academic Search

    G. W. Hanson

    2005-01-01

    P.J. Burke et al. (see http:\\/\\/xxx.lanl.gov\\/abs\\/cond-mat\\/0408418) considered carbon nanotube dipole antennas based on a transmission-line model. This paper investigates fundamental properties of dipole antennas formed by carbon nanotubes using a Halle´n's-type integral equation. The input impedance, radiation pattern, and current profiles are presented and compared to those of ordinary metallic antennas of the same size and shape. Possible applications of

  13. Computed performance of the half-scale accurate antenna reflector

    NASA Technical Reports Server (NTRS)

    Lambert, Kevin M.

    1989-01-01

    The performance of the half-scale, accurate antenna reflector was studied. The antenna is evaluated for use as a compact range reflector. The reflector is studied for use with three separate feed antennas.

  14. 47 CFR 95.1315 - Antenna height restriction.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...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...

  15. RCS of circular carbon NANO tube antenna array

    Microsoft Academic Search

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

    2009-01-01

    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.

  16. Dual-Polarization, Multi-Frequency Antenna Array for use with Hurricane Imaging Radiometer

    NASA Technical Reports Server (NTRS)

    Little, John

    2013-01-01

    Advancements in common aperture antenna technology were employed to utilize its proprietary genetic algorithmbased modeling tools in an effort to develop, build, and test a dual-polarization array for Hurricane Imaging Radiometer (HIRAD) applications. Final program results demonstrate the ability to achieve a lightweight, thin, higher-gain aperture that covers the desired spectral band. NASA employs various passive microwave and millimeter-wave instruments, such as spectral radiometers, for a range of remote sensing applications, from measurements of the Earth's surface and atmosphere, to cosmic background emission. These instruments such as the HIRAD, SFMR (Stepped Frequency Microwave Radiometer), and LRR (Lightweight Rainfall Radiometer), provide unique data accumulation capabilities for observing sea surface wind, temperature, and rainfall, and significantly enhance the understanding and predictability of hurricane intensity. These microwave instruments require extremely efficient wideband or multiband antennas in order to conserve space on the airborne platform. In addition, the thickness and weight of the antenna arrays is of paramount importance in reducing platform drag, permitting greater time on station. Current sensors are often heavy, single- polarization, or limited in frequency coverage. The ideal wideband antenna will have reduced size, weight, and profile (a conformal construct) without sacrificing optimum performance. The technology applied to this new HIRAD array will allow NASA, NOAA, and other users to gather information related to hurricanes and other tropical storms more cost effectively without sacrificing sensor performance or the aircraft time on station. The results of the initial analysis and numerical design indicated strong potential for an antenna array that would satisfy all of the design requirements for a replacement HIRAD array. Multiple common aperture antenna methodologies were employed to achieve exceptional gain over the entire spectral frequency band while exhibiting superb VSWR (voltage standing wave ratio) values. Element size and spacing requirements were addressed for a direct replacement of the thicker, lower-performance, stack ed patch antenna array currently employed for the HIRAD application. Several variants to the multiband arrays were developed that exhibited four, equally spaced, high efficiency, "sweet spot" frequency bands, as well as the option for a high-performance wideband array. The 0.25-in. (˜6.4- mm) thickness of the antenna stack-up itself was achieved through the application of specialized antenna techniques and meta-materials to accomplish all design objectives.

  17. UWB stacked patch antenna design for near-field imaging radar antenna array

    Microsoft Academic Search

    B. Yang; A. G. Yarovoy; L. P. Ligthart

    2009-01-01

    In this paper a design of UWB aperture-coupled stacked patch (ASP) antenna to be used as an array element in a short range imaging radar is presented. The antenna operates in the frequency band from 10 GHz to 18 GHz. Antenna optimization is done using two different numerical techniques in order to cross-verify the simulated results. Experimental results agree very

  18. The effect of antenna physics on fading correlation and the capacity of multielement antenna systems

    Microsoft Academic Search

    J. Gong; J. F. Hayes; M. R. Soleymani

    2005-01-01

    In this paper, we develop a three dimensional model to evaluate the effects of antenna pattern and orientation on the fading correlation in multiple input-multiple output wireless systems. The channel transfer function and its correlation matrix are derived. Two kinds of antenna are deployed in our simulation, dipole and patch microstrip antennas. The simulation results show that the patch microstrip

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

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

    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).

  20. 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

  1. Distributed Antenna-Coupled Cold-Electron Bolometers for Focal Plane Antenna

    Microsoft Academic Search

    Leonid Kuzmin

    2008-01-01

    Novel concepts of the parallel and series array of Cold-Electron Bolometers (CEB) with Superconductor- Insulator-Normal (SIN) Tunnel Junctions have been proposed for distributed focal plane antenna. The arrays are developed for a pixel design based on arrays of CEBs coupled to a distributed slot antenna or dipole antenna. Two variants of the CEB arrays have been considered for both types

  2. Structures for remotely deployable precision antennas

    NASA Technical Reports Server (NTRS)

    Hedgepeth, John M.

    1989-01-01

    There is a need for completely deployable large antenna reflectors capable of efficiently handling millimeter-wave electromagnetic radiation. The structural concepts and technologies that are appropriate to fully automated deployment of dish-type antennas with solid reflector surfaces were studied. First, the structural requirements are discussed. Then, existing concepts for fully deployable antennas are 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.

  3. MILA Antenna Control Unit Replacement Project

    NASA Technical Reports Server (NTRS)

    Bresette, Jeremy

    2007-01-01

    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.

  4. Beamforming of Joint Polarization-Space Matched Filtering for Conformal Array

    PubMed Central

    Liu, Lutao; Jiang, Yilin; Tian, Zuoxi

    2013-01-01

    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

  5. 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

    Davies, John N.

    3318 IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 56, NO. 10, OCTOBER 2008 [3] Microstrip Antennas: The Analysis and Design of Microstrip Antennas and Arrays, D. M. Pozar and D. H. Schaubert, Eds- tennas. Boston, MA: Artech House, 1991. [5] Advances in Microstrip and Printed Antennas, K. F. Lee, Ed

  6. Subtleties Concerning Conformal Tractor Bundles

    E-print Network

    Graham, C Robin

    2012-01-01

    The realization of tractor bundles as associated bundles in conformal geometry is studied. It is shown that different natural choices of principal bundle with normal Cartan connection corresponding to a given conformal manifold can give rise to topologically distinct associated tractor bundles for the same inducing representation. Consequences for homogeneous models and conformal holonomy are described. A careful presentation is made of background material concerning standard tractor bundles and equivalence between parabolic geometries and underlying structures.

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

    PubMed Central

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

    2014-01-01

    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

  8. Antenna systems for the Aryabhata mission

    Microsoft Academic Search

    S. P. Kosta; S. Pal; P. K. Reddy; V. K. Lakshmeesha; K. N. S. Rao; K. N. Shamanna; V. Mahadevan; V. S. Rao; L. Nicholas

    1979-01-01

    The onboard ground antenna system employed in the Aryabhata mission for telemetry and telecommand operations are described. The onboard antenna system common to telemetry and telecommand frequencies consists of four monopoles fed in turnstile configuration and generates a near isotropic pattern with worst dips of the order of -10 dB over approximately 0.2% of the total radiation sphere area. The

  9. Lightweight adaptive antennas for EHF payloads

    Microsoft Academic Search

    D. R. McElroy; W. C. Cummings; D. P. Kolba

    1992-01-01

    In an antijam military satellite communications system, the service provided by a geosynchronous altitude satellite can be significantly enhanced through the use of lightweight, adaptive EHF antennas to provide theater coverage. The communications capabilities provided by payloads with these EHF antennas can include both low data rate services (75 to 2400 b\\/s per channel) and medium data rate links (with

  10. A slot antenna with electronically tunable length

    Microsoft Academic Search

    Shigeo Kawasaki; T. Itoh

    1991-01-01

    The authors describe a 1? slot antenna with a layered structure loaded with two 1-port reactive FET components electromagnetically. By changing bias voltages, the reactance of the FETs varies and the length of the slot is tuned electronically. The resonant points of S11 measurements were shifted over a range of 1 GHz around 10 GHz. The antenna patterns are essentially

  11. Antenna 3D Pad printing solution evaluation

    Microsoft Academic Search

    Ye Xiong; Zengchao Qu

    2011-01-01

    Diversification, styling, miniaturization and cost reduction are trends in the field of portable electronics. The 3D technology is an innovative way to meet this demand. This paper evaluated the Pad printing 3D antenna manufacture technology which offers versatile and cost effective interconnection platform compared to the flex-antenna or sheet metal technologies. The basic Pad Printing process was introduced firstly, the

  12. Ultra Wide Band Planar Slot Antenna

    Microsoft Academic Search

    S. Noghanian; M. K. Jung

    2008-01-01

    In this paper a set of compact planar slot antennas for ultra wide band applications are presented. These antennas provide bandwidth of more than 7 GHz and are designed for microwave imaging and wireless communication applications for frequency range of 3–10 GHz. Both simulated and measured results are presented.

  13. Fractal Microstrip Antenna Aids Wideband Applications

    Microsoft Academic Search

    Abolfazl Azari

    2011-01-01

    ULTRAWIDEBAND (UWB) communications systems work across broad bandwidths and can provide an effective means of transferring large amounts of data. But these systems also place great demands on the operating bandwidths of their components, including the antennas, forcing designers to develop structures that are not only small in size but capable of extremely wide bandwidths. Fortunately, fractal microstrip antenna structures

  14. Polarization Measurements and Antenna Orientation Optimization

    E-print Network

    Southern California, University of

    propagation measurements. · The estimation process is applicable to any type of narrowband/wideband/UWB UWB radio receiver. · By reciprocity theorem, the optimal receiving antenna orientation in receivingPolarization Measurements and Antenna Orientation Optimization in Multipath Channels SangHyun Chang

  15. A perspective on array antenna developments

    Microsoft Academic Search

    Lars Josefsson

    2006-01-01

    Although the first array antennas were developed long ago, it took considerable time and effort before the electronically phased array antennas reached the marketplace. Their full potential could initially not be exploited without the availability of advanced integrated circuits and computer technology. The developments of electromagnetic analysis methods and simulation tools have of course also played a significant role. Still,

  16. Empirical comparison of MIMO antenna configurations

    Microsoft Academic Search

    Pasi Suvikunnas; Jari Salo; Jarmo Kivinen; Pertti Vainikainen

    2005-01-01

    By now, it is well known that multiple-input multiple-output (MIMO) communications systems are able to bring considerable performance gains for wireless communications. It is also evident that both the propagation channel and the antenna characteristics influence the MIMO capacity. In this paper, we consider the problem of comparing MIMO antenna configurations using measured radio channels. We introduce a new figure

  17. Design of a broadband ESPAR antenna

    Microsoft Academic Search

    Bashir Alshami; Hassan Aboulnour; M. Dib

    2009-01-01

    The design of a broadband electrically steerable passive array radiator (BB-ESPAR) antenna as a uniform structure, for broadband modern communication systems, is proposed in this paper. ESPAR antenna, in a typical consideration, is constructed from seven monopole elements with a ground plane. The middle element is active and the others are parasitic and have variable reactance loads for direction pattern

  18. Advances in multibeam communications satellite antennas

    Microsoft Academic Search

    A. I. Zaghloul; Y. Hwang; R. M. Sorbello; F. T. Assal

    1990-01-01

    The evolution of satellite antennas over the past quarter of a century is presented. Five major areas of advances in communications satellite antenna technology are reviewed: single offset reflectors with feed arrays, shaped reflector systems, active phased arrays, phased-array-fed dual reflector systems, and lightweight feed elements. Examples are given of existing systems and of the ongoing development of new technologies

  19. Thermal control considerations in satellite antennas

    Microsoft Academic Search

    N. Fernandez

    1980-01-01

    A generalized, dimensional thermal analysis of antenna reflectors, specifically of the type used on telecommunication and direct television satellites, is presented. An optimal thermal configuration (coatings, insulation, etc.) for a paraboloid antenna 1 m in diameter was calculated. The drawbacks of mathematical modeling insofar as temperature field determination is concerned are pointed out. Calculation predictions are compared with space simulation

  20. Metamaterial properties, designs, and antenna applications

    Microsoft Academic Search

    R. W. Ziolkowski

    2005-01-01

    Metamaterials have the potential to allow engineers to tailor the electromagnetic responses of the materials incorporated in antenna systems to enhance their performance. Several examples of the exotic properties of electromagnetic metamaterials will be given. One class of metamaterials that has already demonstrated its usefulness with antennas is the artificial magnetic conductor (AMC). It has been demonstrated that this metamaterial

  1. Simplified Fabrication of Helical Copper Antennas

    NASA Technical Reports Server (NTRS)

    Petro, Andrew

    2006-01-01

    A simplified technique has been devised for fabricating helical antennas for use in experiments on radio-frequency generation and acceleration of plasmas. These antennas are typically made of copper (for electrical conductivity) and must have a specific helical shape and precise diameter.

  2. Microstrip antenna-coupled infrared detectors

    NASA Astrophysics Data System (ADS)

    Codreanu, Iulian

    Microstrip antennas, where a dipole or patch structure is located above a metallic ground plane, are widely used for communications applications in the microwave portion of the spectrum. Combining numerical-electromagnetic design tools derived from finite-difference time-domain analysis with the high resolution capabilities of direct- write electron-beam lithography (DEBL), we have extended the functionality of microstrip antennas to much shorter wavelengths, in the 9- to 11-micron band of the infrared (IR). We have fabricated antenna-coupled detectors for this band by integrating a submicron-sized niobium bolometer with the microstrip antennas. Sensor performance of various antenna designs was characterized experimentally in terms of spatial response, angular response, wavelength response, polarization purity, temporal response, responsivity, and signal-to-noise ratio. The proximity-dependent interaction between the antenna and the ground plane was investigated, as well as the impact of different transmission-line configurations for baseband signal extraction. The feasibility of using layered dielectric media for the supporting structures was shown, and increases in responsivity in excess of 40 were demonstrated, compared to monolithic-substrate designs. Microelectromechanical (MEM) structures employing movable metallic elements adjacent to the antennas were investigated as possible approaches for active wavelength tuning. Finally, we explored the consequence of residual sensor-antenna contact nonlinearities on the measured noise spectra and spatial response.

  3. Tuning of microstrip antenna on ferrite substrate

    Microsoft Academic Search

    R. K. Mishra; S. S. Pattnaik; N. Das

    1993-01-01

    The permeability variation of a ferrite substrate with an axial DC magnetic bias field along with the RF excitation of a microstrip antenna leads to multiresonant behavior. A study of tuning the patch antenna on a ferrite substrate to exploit this feature is reported, along with the associated theoretical analysis and experimental findings

  4. CPW-fed active slot antennas

    Microsoft Academic Search

    Brian K. Kormanyos; William Harokopus; Linda P. B. Katehi; Gabriel M. Rebeiz

    1994-01-01

    We have combined microwave oscillator design with theoretical characterization of planar antennas to build active slot-oscillators. The design is uniplanar, does not require via holes and is compatible with monolithic transistor technology. The coplanar waveguide (CPW) fed antenna impedance is calculated using the space domain integral equation technique (SDIE), a full wave method of moments approach. Slot-oscillators were built at

  5. Planar antenna system for direction finding

    NASA Astrophysics Data System (ADS)

    Mardale, Iulia-Cezara; Cocias, Gabriela; Dumitrascu, Ana; Tamas, Razvan; Berescu, Serban

    2015-02-01

    Applications of direction finding techniques include detection and localization of pulsed electromagnetic sources. This paper presents the design and analysis of a planar antenna system for direction finding. Our proposed system includes 4 hybrid couplers that generate 900 shifted signals, 2 crossover couplers also known as 0dB couplers, two 450 phase shifters, two 00 phase shifters and 4 patch antennas.

  6. Optimization of Antenna-Structure Design

    NASA Technical Reports Server (NTRS)

    Levy, R.

    1986-01-01

    Conference paper describes application of optimality criterion to design of microwave dish antenna. For purpose of study, overall design objective is to minimize structural weight, subject to design constraints that antenna-pointing and microwave-path-length errors not exceed specified values. Design constraints and optimality criterion satisfied in same procedure.

  7. Structures for remotely deployable precision antennas

    NASA Technical Reports Server (NTRS)

    Hedgepeth, J. M.

    1989-01-01

    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.

  8. Microelectromechanical Systems (MEMS) Actuators for Antenna Reconfigurability

    NASA Technical Reports Server (NTRS)

    Simons, Rainee N.; Chun, Donghoon; Katehi, Linda P. B.

    2001-01-01

    A novel microelectromechanical systems (MEMS) actuator for patch antenna reconfiguration, is presented for the first time. A key feature is the capability of multi-band operation without greatly increasing the antenna element dimensions. Experimental results demonstrate that the center frequency can be reconfigured from few hundred MHz to few GHz away from the nominal operating frequency.

  9. Reconfigurable Antennas for Wireless and Space Applications

    Microsoft Academic Search

    Christos G. Christodoulou; Youssef Tawk; Scott R. Erwin

    2012-01-01

    Reconfigurable antennas, with the ability to radiate more than one pattern at different frequencies and polarizations, are necessary in modern telecommunication systems. The requirements for increased functionality (e.g., direction finding, beam steering, radar, control, and command) within a confined volume place a greater burden on today's transmitting and receiving systems. Reconfigurable antennas are a solution to this problem. This paper

  10. Antenna system providing a spherical radiation pattern

    NASA Technical Reports Server (NTRS)

    Sickles, II, Louis (Inventor)

    1993-01-01

    An antenna system provides a substantially spherical radiation pattern about a structure located above ground level, by locating the individual radiation pattern of each of a plurality of individual antennae, each positioned to have a radiation pattern covering only a portion of the desired sphere, and then applying all antenna signals, during either transmission or reception time intervals, through space-diversity and/or time-diversity apparatus, to cause the patterns of all of the antennae to combine into the desired substantially-spherical pattern. The antennae may have substantially hemispherical patterns, with each antenna of a pair thereof being directed in a direction generally opposite to the other antenna of that pair. Time domain multiple access (TDMA) operation of a master system station, with transmission in different time slots for different portions of the coverage sphere, and selection of the strongest received signal from among all of the plurality N of signals simultaneously received by the plurality N of antennae, can provide the desired spherical radiation pattern in both the transmission and reception modes of operation.

  11. Compact wideband multiple conductor monopole antenna

    NASA Astrophysics Data System (ADS)

    Royce, R. K.

    1984-08-01

    A wideband trap-loaded monopole antenna having small structural dimensions in a plane normal to the polarization axis. The traps are resistively-terminated quarter wavelength transmission lines. The locations and anti-resonant frequencies of the traps are selected to make the antenna's input impedance and gain nominally uniform parameters with respect to frequency.

  12. Small antenna measurements using a GTEM cell

    Microsoft Academic Search

    Ping Hui

    2003-01-01

    In this work, two balanced dipole antennas in both the cellular band and the PCS band have been measured using a GTEM (Gigahertz transverse electromagnetic mode) cell and the results have been compared with those obtained using an anechoic room. It is pointed out that correct rotation plane of the antenna under test (AUT) inside the GTEM cell is essential

  13. Phased array antennas for applications on spacecraft.

    NASA Technical Reports Server (NTRS)

    Kummer, W. H.; Kampinsky, A.

    1972-01-01

    This is a survey paper wherein phased array antenna systems, now operating on spacecraft, are reviewed so as to reveal their basic techniques of beam formation, steering, and receive/transmit (transponder) functions. Laboratory developmental antennas, designed for ultimate spacecraft flight qualification, are assessed in terms of the needs of communications, earth resources instrumentation, and area surveillance.

  14. Multiple-antenna microwave ablation: analysis of non-parallel antenna implants

    NASA Astrophysics Data System (ADS)

    Mukherjee, Souvick; Curto, Sergio; Albin, Nathan; Natarajan, Bala; Prakash, Punit

    2015-03-01

    Microwave ablation is a minimally invasive modality increasingly being used for thermal treatment of cancer in various organs. During ablation procedures, treatment planning is typically restricted to vendor specifications of expected ablation zone volumes based on experiments in unperfused ex vivo tissues, presuming parallel insertion of antennas. However, parallel antenna implants are not always clinically possible due to the restricted control of flexible antennas and presence of intervening organs. This paper aims to quantify the effect of non-parallel antenna implants on the ablation volume. 3D electromagnetic-bioheat transfer models were implemented to analyze ablation zone profiles created by dual antenna arrays. Parallel and non-parallel implants spaced 10-25 mm with antenna tips deviated to create converging or diverging configurations were analyzed. Volumetric Dice Similarity Coefficients (DSC) were calculated to compare ablation zone volumes for parallel and non-parallel configuration. Antenna tip displacements of 3 mm/antenna yielded an average DSC of 0.78. Tip displacements of 5 mm/antenna yielded a DSC of 0.78 and 0.64 for 15 mm and 20 mm antenna spacing, respectively. For ablation with dipole antennas as the frequency of operation decreases from 2.45 GHz to 915 MHz the similarity between the ablation zones for parallel and angled cases increased significantly. In conclusion, ablation volumes with non-parallel antenna implants may differ significantly from the parallel configuration. Patient-specific treatment planning tools may provide more accurate predictions of 3D-ablation volumes based on imaging data of actual implanted antenna configurations. Methods to compare ablation zone volumes incorporating uncertainty in antenna positions and experimental results to validate the numerical modelling are also presented.

  15. TRANSIENT MESH ADAPTATION USING CONFORMING AND NON CONFORMING MESH MODIFICATIONS

    E-print Network

    Frey, Pascal

    TRANSIENT MESH ADAPTATION USING CONFORMING AND NON CONFORMING MESH MODIFICATIONS Jean refinements, both in 2D and 3D. Keywords: mesh adaptation, discontinuous Galerkin, anisotropy 1. INTRODUCTION multiple mesh adaptations in order to follow complex features of the flow. The discontinuous Galerkin

  16. ARCHITECTURE OF A CHARGE-TRANSFER STATE REGULATING LIGHT HARVESTING IN A PLANT ANTENNA PROTEIN

    SciTech Connect

    Fleming, Graham; Ahn, Tae Kyu; Avenson, Thomas J.; Ballottari, Matteo; Cheng, Yuan-Chung; Niyogi, Krishna K.; Bassi, Roberto; Fleming, Graham R.

    2008-04-02

    Energy-dependent quenching of excess absorbed light energy (qE) is a vital mechanism for regulating photosynthetic light harvesting in higher plants. All of the physiological characteristics of qE have been positively correlated with charge-transfer between coupled chlorophyll and zeaxanthin molecules in the light-harvesting antenna of photosystem II (PSII). In this work, we present evidence for charge-transfer quenching in all three of the individual minor antenna complexes of PSII (CP29, CP26, and CP24), and we conclude that charge-transfer quenching in CP29 involves a de-localized state of an excitonically coupled chlorophyll dimer. We propose that reversible conformational changes in CP29 can `tune? the electronic coupling between the chlorophylls in this dimer, thereby modulating the energy of the chlorophylls-zeaxanthin charge-transfer state and switching on and off the charge-transfer quenching during qE.

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

    NASA Technical Reports Server (NTRS)

    Kempel, Leo C.; Volakis, John L.

    1993-01-01

    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.

  18. Low cost antennas for MSAT vehicular applications

    NASA Technical Reports Server (NTRS)

    Shafai, L.; Barakat, M.

    1993-01-01

    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.

  19. A Ka-band helical antenna

    NASA Technical Reports Server (NTRS)

    deLeseleuc, Michel; Hindson, Dan

    1995-01-01

    A number of Ka-band satellite systems have been proposed to provide wide band personal communications services to terminals employing small antennas. Work has been performed looking at the use of helical antenna elements to provide an efficient low-cost antenna at these frequencies. Although helices are not planar, at Ka-band they are less than 2.5 cm in height and thus are suitable for these applications. This paper describes the design and development of a broadband helical antenna element. The work performed on: feed configurations, matching techniques, ground plane structures, broadbanding, and the effects of dielectric loading are discussed. Experimental measurements performed during the development of the helical antenna element are presented.

  20. Sinuous antennas for cosmic microwave background polarimetry

    NASA Astrophysics Data System (ADS)

    O'Brient, Roger; Edwards, Jennifer; Arnold, Kam; Engargiola, Greg; Holzapfel, William; Lee, Adrian T.; Myers, Michael; Quealy, Erin; Rebeiz, Gabriel; Richards, Paul; Spieler, Helmuth; Tran, Huan

    2008-07-01

    We are developing antenna-coupled Transition Edge Sensor (TES) bolometers to be used in the focal planes of telescopes mapping Cosmic Microwave Background (CMB) polarization anisotropies. These detectors will be both dual-polarized and ultra-wide band, each containing several frequency channels. Arrays of such detectors could realize mapping speeds nearly an order of magnitude higher than previously deployed technology while naturally facilitating foreground removal. For such detectors to be useful, the antennas must have a high gain and a low cross-polarization. We have designed a novel modification of DuHamel's Sinuous antenna that couples to a contacting lens and is driven by integrated microstrip feed-lines. The integrated feed lines allow the antenna to interface with microstrip circuits and bolometers in a way that is planar and scalable to kilo-pixel arrays. We have demonstrated the polarization and beam properties with scale model antennas that operate at 1-12 GHz.

  1. Baseline antenna design for space exploration initiative

    NASA Technical Reports Server (NTRS)

    Chen, Y. L.; Nasir, M. A.; Lee, S. W.; Zaman, Afroz

    1993-01-01

    A key element of the future NASA Space Exploration Initiative (SEI) mission is the lunar and Mars telecommunication system. This system will provide voice, image, and data transmission to monitor unmanned missions to conduct experiments, and to provide radiometric data for navigation. In the later half of 1991, a study was conducted on antennas for the Mars Exploration Communication. Six antenna configurations were examined: three reflector and three phased array. The conclusion was that due to wide-angle scan requirement, and multiple simultaneous tracking beams, phased arrays are more suitable. For most part, this report studies phased array antenna designs for two different applications for Space Exploration Initiative. It also studies one design for a tri-reflector type antenna. These antennas will be based on a Mars orbiting satellite.

  2. Theoretical aspects of sounder antenna operation

    NASA Technical Reports Server (NTRS)

    Fredricks, R. W.

    1977-01-01

    The fundamental problem of calculating the radiation from an electric dipole immersed in a magnetoplasma is one of solving Maxwell's equations coupled to the self-consistent field-particle equations describing the plasma. For very small applied antenna voltages, the plasma dynamics may be linearized, and the plasma reaction currents computed self-consistently in terms of the voltage on the antenna. Thus, the short dipole can be idealized as a point dipole of moment P sub o = C sub a, V sub o el, where C sub a is the antenna element-to-plasma capacitance for a sheath of dimensions roughly several plasma Debye lengths and el is the dipole element's length. In actual practice, it is at this point that the first difficulty with the antenna theory arises. Even for small signals, the sheath around such an antenna will exhibit a complex impedance. For larger signals, nonlinear effects appear. Attemps are made to solve this problem.

  3. Evolutionary Optimization of Yagi-Uda Antennas

    NASA Technical Reports Server (NTRS)

    Lohn, Jason D.; Kraus, William F.; Linden, Derek S.; Colombano, Silvano P.

    2001-01-01

    Yagi-Uda antennas are known to be difficult to design and optimize due to their sensitivity at high gain, and the inclusion of numerous parasitic elements. We present a genetic algorithm-based automated antenna optimization system that uses a fixed Yagi-Uda topology and a byte-encoded antenna representation. The fitness calculation allows the implicit relationship between power gain and sidelobe/backlobe loss to emerge naturally, a technique that is less complex than previous approaches. The genetic operators used are also simpler. Our results include Yagi-Uda antennas that have excellent bandwidth and gain properties with very good impedance characteristics. Results exceeded previous Yagi-Uda antennas produced via evolutionary algorithms by at least 7.8% in mainlobe gain. We also present encouraging preliminary results where a coevolutionary genetic algorithm is used.

  4. Replacement between conformity and counter-conformity in consumption decisions.

    PubMed

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

    2013-02-01

    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

  5. Evolutionary Optimization of a Quadrifilar Helical Antenna

    NASA Technical Reports Server (NTRS)

    Lohn, Jason D.; Kraus, William F.; Linden, Derek S.; Clancy, Daniel (Technical Monitor)

    2002-01-01

    Automated antenna synthesis via evolutionary design has recently garnered much attention in the research literature. Evolutionary algorithms show promise because, among search algorithms, they are able to effectively search large, unknown design spaces. NASA's Mars Odyssey spacecraft is due to reach final Martian orbit insertion in January, 2002. Onboard the spacecraft is a quadrifilar helical antenna that provides telecommunications in the UHF band with landed assets, such as robotic rovers. Each helix is driven by the same signal which is phase-delayed in 90 deg increments. A small ground plane is provided at the base. It is designed to operate in the frequency band of 400-438 MHz. Based on encouraging previous results in automated antenna design using evolutionary search, we wanted to see whether such techniques could improve upon Mars Odyssey antenna design. Specifically, a co-evolutionary genetic algorithm is applied to optimize the gain and size of the quadrifilar helical antenna. The optimization was performed in-situ in the presence of a neighboring spacecraft structure. On the spacecraft, a large aluminum fuel tank is adjacent to the antenna. Since this fuel tank can dramatically affect the antenna's performance, we leave it to the evolutionary process to see if it can exploit the fuel tank's properties advantageously. Optimizing in the presence of surrounding structures would be quite difficult for human antenna designers, and thus the actual antenna was designed for free space (with a small ground plane). In fact, when flying on the spacecraft, surrounding structures that are moveable (e.g., solar panels) may be moved during the mission in order to improve the antenna's performance.

  6. Optimal antenna spacings in interferometric SAR

    NASA Astrophysics Data System (ADS)

    Xiao, Shu; Munson, David C., Jr.

    2000-08-01

    In practice, a synthetic aperture radar (SAR) reconstructs the complex reflectivity function of a scene, modulated by phase terms that capture 3-D imaging geometry. INSAR (interferometric SAR) attempts to obtain the geometric information by interfering two images (from two antennas) to cancel the same scene reflectivity and recover the scene topography transduced by the image-phase data. This approach, however, leads to a phase-unwrapping problem, which causes ambiguities in estimates of elevation. The phase-unwrapping problem can be solved in a pointwise fashion by using more than two antennas. This approach can effectively prevent error propagation which occurs in traditional phase-unwrapping algorithms. In this work, we study the optimal antenna spacings for pointwise terrain height estimation. In particular, we start from the maximum likelihood estimates of the phase using neighborhood pixels collected by any pair of antennas. The phase estimation noise is approximated as Gaussian with variance prescribed by the Cramer-Rao lower bound on the phase estimate. The ambiguous terrain height derived from any pair of antennas is modeled by a periodic waveform with each period having an approximately Gaussian shape. For multiple pairs of antennas, the corresponding functions describing the ambiguous elevation have different periods, which acts to help resolve the ambiguity. We derive and analyze the ML estimate of elevation at each scene point using multiple pairs of antennas. For the three-antenna case, by analyzing the tradeoff between cycle errors and measurement errors, a closed-form formula approximating the mean squared error (MSE) of the estimated terrain height is derived as a function of antenna spacing. By minimizing the MSE, we determine the optimal antenna spacing. The algorithm is tested with simulated data.

  7. Capturing Chromosome Conformation

    NASA Astrophysics Data System (ADS)

    Dekker, Job; Rippe, Karsten; Dekker, Martijn; Kleckner, Nancy

    2002-02-01

    We describe an approach to detect the frequency of interaction between any two genomic loci. Generation of a matrix of interaction frequencies between sites on the same or different chromosomes reveals their relative spatial disposition and provides information about the physical properties of the chromatin fiber. This methodology can be applied to the spatial organization of entire genomes in organisms from bacteria to human. Using the yeast Saccharomyces cerevisiae, we could confirm known qualitative features of chromosome organization within the nucleus and dynamic changes in that organization during meiosis. We also analyzed yeast chromosome III at the G1 stage of the cell cycle. We found that chromatin is highly flexible throughout. Furthermore, functionally distinct AT- and GC-rich domains were found to exhibit different conformations, and a population-average 3D model of chromosome III could be determined. Chromosome III emerges as a contorted ring.

  8. Conformal Aspects of QCD

    SciTech Connect

    Brodsky, S

    2003-11-19

    Theoretical and phenomenological evidence is now accumulating that the QCD coupling becomes constant at small virtuality; i.e., {alpha}{sub s}(Q{sup 2}) develops an infrared fixed point in contradiction to the usual assumption of singular growth in the infrared. For example, the hadronic decays of the {tau} lepton can be used to determine the effective charge {alpha}{sub {tau}}(m{sub {tau}{prime}}{sup 2}) for a hypothetical {tau}-lepton with mass in the range 0 < m{sub {tau}{prime}} < m{sub {tau}}. The {tau} decay data at low mass scales indicates that the effective charge freezes at a value of s = m{sub {tau}{prime}}{sup 2} of order 1 GeV{sup 2} with a magnitude {alpha}{sub {tau}} {approx} 0.9 {+-} 0.1. The near-constant behavior of effective couplings suggests that QCD can be approximated as a conformal theory even at relatively small momentum transfer and why there are no significant running coupling corrections to quark counting rules for exclusive processes. The AdS/CFT correspondence of large N{sub c} supergravity theory in higher-dimensional anti-de Sitter space with supersymmetric QCD in 4-dimensional space-time also has interesting implications for hadron phenomenology in the conformal limit, including an all-orders demonstration of counting rules for exclusive processes and light-front wavefunctions. The utility of light-front quantization and light-front Fock wavefunctions for analyzing nonperturbative QCD and representing the dynamics of QCD bound states is also discussed.

  9. Algebraic orbifold conformal field theories

    Microsoft Academic Search

    Feng Xu

    2000-01-01

    The unitary rational orbifold conformal field theories in the algebraic quantum field theory and subfactor theory framework are formulated. Under general conditions, it is shown that the orbifold of a given unitary rational conformal field theory generates a unitary modular category. Many new unitary modular categories are obtained. It is also shown that the irreducible representations of orbifolds of rank

  10. Methods for Numerical Conformal Mapping

    Microsoft Academic Search

    Ralph Menikoff; Charles Zemach

    1980-01-01

    Nonlinear integral equations for the boundary functions which determine conformal transformations in two dimensions are developed and analyzed. One of these equations has a nonsingular logarithmic kernel and is especially well suited for numerical computations of conformal maps including those which deal with regions having highly distorted boundaries. Numerical procedures based on interspersed Gaussian quadrature for approximating the integrals and

  11. Conformal mapping: Methods and applications

    Microsoft Academic Search

    R. Schinzinger; P. A. A. Laura

    1991-01-01

    This book exhibits its best qualities as a readily accessible, desk-top source reference on conformal mapping applications for the practicing engineer and applied scientist who may beunfamiliar with the topic or uninformed about its utility in solving problems of contemporary interest. On the other hand, it is not an applied or operational mathematics textbook on conformal transformation methods. The authors

  12. Counselor Identity: Conformity or Distinction?

    ERIC Educational Resources Information Center

    McLaughlin, Jerry E.; Boettcher, Kathryn

    2009-01-01

    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.

  13. Conformal Transformations and Space Travel

    Microsoft Academic Search

    Suraj N. Gupta

    1961-01-01

    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.

  14. First two ALMA antennas successfully linked

    NASA Astrophysics Data System (ADS)

    2009-05-01

    Scientists and engineers working on the world's largest ground-based astronomical project, the Atacama Large Millimeter/submillimeter Array (ALMA), have achieved another milestone -- the successful linking of two ALMA astronomical antennas, synchronised with a precision of one millionth of a millionth of a second -- to observe the planet Mars. ALMA is under construction by an international partnership in the Chilean Andes. ESO PR Photo 18a/09 The two ALMA antennas On 30 April, the team observed the first "interferometric fringes" of an astronomical source by linking two 12-metre diameter ALMA antennas, together with the other critical parts of the system. Mars was chosen as a suitable target for the observations, which demonstrate ALMA's full hardware functionality and connectivity. This important milestone was achieved at the ALMA Operations Support Facility, high in Chile's Atacama region, at an altitude of 2900 metres. "We're very proud and excited to have made this crucial observation, as it proves that the various hardware components work smoothly together. This brings us another step closer to full operations for ALMA as an astronomical observatory," says Wolfgang Wild, the European ALMA Project Manager. The two antennas used in this test will be part of ALMA's array of 66 giant 12-metre and 7-metre diameter antennas that will observe in unison as a single giant telescope, under construction on the Chajnantor plateau above the Operations Support Facility, at an altitude of 5000 metres. ALMA will operate as an interferometer, capturing millimetre and submillimetre wavelength signals from the sky with multiple antennas, and combining them to create extremely high resolution images, similar to those that would be obtained by a single, giant antenna with a diameter equal to the distance between the antennas used. "This can only be achieved with the perfect synchronisation of the antennas and the electronic equipment: a precision much better than one millionth of a millionth of a second between equipment located many kilometers apart. The extreme environment where the ALMA observatory is located, with its strong winds, high altitude, and wide range of temperatures, just adds to the complexity of the observatory and to the fascinating engineering challenges we face", comments Richard Murowinski, ALMA Project Engineer. The astronomical target in this scientific milestone was the planet Mars. The astronomers measured the distinctive "fringes" -- a regular pattern of alternating strong and weak signals -- detected by the interferometer as the planet moved across the sky. The hardware used in this successful first test included two 12-metre diameter ALMA antennas as well as the complex series of electronic processing components needed to combine the signals. Such pairs of antennas are the basic building blocks of imaging systems that enable radio telescopes to deliver pictures that approach or even exceed the resolving power of visible light telescopes. Each antenna is combined electronically with every other antenna to form a multitude of antenna pairs. Each pair contributes unique information that is used to build a highly detailed image of the astronomical object under observation. When completed in early in the next decade, ALMA's 66 antennas will provide over a thousand such antenna pairings, with distances between antennas up to 16 kilometres. This will enable ALMA to see with a sharpness surpassing that of the best space telescopes, and to complement ground-based optical interferometers such as the ESO Very Large Telescope Interferometer (VLTI). "We are on target to do the first interferometry tests at the 5000-metre high-altitude site by the end of this year, and by the end of 2011 we plan to have at least 16 antennas working together as a single giant telescope," said Thijs de Graauw, ALMA Director. Notes for editors ALMA is a revolutionary astronomical telescope, comprising an array of 66 giant 12-metre and 7-metre diameter antennas observing at millimetre and submi

  15. Conformational flexibility in dodecasubstituted porphyrins

    SciTech Connect

    Nurco, D.J.; Medford, C.J.; Forsyth, T.P.; Olmstead, M.M.; Smith, K.M. [Univ. of California, Davis, CA (United States)] [Univ. of California, Davis, CA (United States)

    1996-11-06

    In contrast to regular porphyrins, dodecasubstituted porphyrins have not so far been demonstrated to possess a high degree of conformational flexibility. To determine if this is a general feature of dodecasubstituted porphyrins, we have undertaken an investigation of the conformational properties of the dodecaarylporphyrins 4-6. We show herein that crystal structures of these porphyrins provide ample evidence of the significant conformational flexibility that can be observed for dodecasubstituted porphyrins; the structures we report include the first highly ruffled dodecasubstituted porphyrin, the first examples of multiple conformations in a single dodecasubstituted porphyrin, and the first `wave` core structure of a dodecasubstituted porphyrin, which is also the most nonplanar wave structure reported to date for any porphyrin. The structure reported herein for nickel(II) complexes and metal-free porphyrins 4-6 clearly indicate that these porphyrins possess a higher degree of conformational flexibility than has previously been observed for other dodecasubstituted porphyrins. 6 refs., 2 figs.

  16. An active, C-band array antenna with integrated electronics

    Microsoft Academic Search

    M. Eriksson; K. Axelsson; A. Wikstrom; B. Svensson

    2009-01-01

    A concept of building a low cost integrated AESA has been investigated. A C-band active array antenna board has been designed, built and tested. A printed circuit board with active receiving circuits and antenna feed is mounted on an aluminum plate including the antenna elements. Measurements of the C-board antenna agree well with the simulated results. A bandwidth of about

  17. An uplink antenna for electronic beam steering and interference reduction

    Microsoft Academic Search

    R. B. Dybdal; S. J. Curry

    2002-01-01

    High data rate satellite communication systems require satellite antennas with high gain to obtain link closure. These narrow beamwidth antennas can suffer performance loss because of antenna pointing errors. Interference susceptibility is also a concern and a means of reducing interference is desired. An uplink antenna system concept is described for such requirements.

  18. On connectivity analysis of smart antenna capable wireless sensor networks

    Microsoft Academic Search

    Adnan Kavak; Kerem Kucuk

    2009-01-01

    Advancements in directional antennas or adaptive antenna arrays (AAA) provide potential benefits in solving various problems in wireless sensor network (WSN). Our earlier studies have investigated feasibility of applying smart antennas for task dissemination and localization purposes [4], [6]. Network connectivity or connectivity probability is also an important issue for smart antenna capable WSN as it relies on received ldquoresponserdquo

  19. Analysis and design of Ultra Wide Band Planar monopole antenna

    Microsoft Academic Search

    Yan-Chun Hou; Dong-Lin Su; Jin-Ping Ma

    2008-01-01

    A planar monopole antenna for ultra wide band application is studied comprehensively in this paper. Firstly, based on the transmission line theory, the equivalent circuit model of the planar monopole antenna is presented according to the current distribution on the antenna. Some techniques to widen bandwidth of the antenna, like beveling and shorting post are discussed from a qualitatively point

  20. Small internal ceramic chip antenna for IMT-2000 handsets

    E-print Network

    Park, Seong-Ook

    antenna to be reduced in size and to have an impedance bandwidth wide enough to cover the IMT-2000 band to that of a monopole antenna. These features make the proposed antenna suitable for handset applications. Introduction that the antenna demonstrates suitable performance to be used in mobile communication applications. Fig. 1 Geometry

  1. ELECTRON AND PHOTONTUNNELING TRANSDUCERS FOR GRAVITATIONAL WAVE ANTENNAE

    E-print Network

    Presilla, Carlo

    -crystal silicon cylinders have been grown.7 3. Wide-band Antenna In order to verify these ideas we have built a prototype aluminum (5056) wide-band antenna. Its effective mass is 75 kg. It is a three-mode antenna madeELECTRON AND PHOTONTUNNELING TRANSDUCERS FOR GRAVITATIONAL WAVE ANTENNAE M.F.BOCKOI, F.BORDONJ2, M

  2. A Circular Wire Antenna for Ultra Wideband Applications

    Microsoft Academic Search

    Z. Zhang; J. T. Bernhard

    2007-01-01

    A novel circular wire antenna suitable for ultra wideband (UWB) applications is presented in this paper. It consists of a circularly curved wire over a ground plane. The wire structure is designed to deliver approximately the same benefits as a circular disc antenna. Effective length is introduced to analyze the operation of the antenna. Experimental results of the antenna have

  3. A Compact Monopole UWB Antenna for Ultra Wideband Applications

    Microsoft Academic Search

    Akkala Subbarao; S. Raghavan

    2009-01-01

    A novel compact Ultra wideband antenna fed by CPW is presented. The antenna has a size of 29 mm ?? 32 mm. It provides band width ranging from 2.9 GHz to 11.1 GHz. The antenna can be easily integrated with radio frequency circuit for low cost. Details of antenna are presented with parametric study. The bandwidth is varied by varying

  4. Dual-shorted monopole antenna for Ultra-Wideband application

    Microsoft Academic Search

    Chun-I Lin; Tzung-Wern Chiou; Sheng-Chih Lin; Fu-Ren Hsiao

    2008-01-01

    A novel dual-shorted monopole antenna suitable for UWB application, especially as an internal antenna for notebook or tablet PC has been proposed. The proposed antenna has a simple structure with a dual-shorted strip and is easy to implement at a low cost. Prototypes of the proposed antenna have been constructed and studied. A very uniform surface current distribution in the

  5. Multiple Antenna Time Reversal Transmission In Ultra-Wideband Communications

    E-print Network

    Moura, José

    Multiple Antenna Time Reversal Transmission In Ultra-Wideband Communications Yuanwei Jin, Yi Jiang Abstract-- In this paper we study the multiple antenna time reversal downlink transmission in an ultra-wideband antennas and the user has a single antenna. We design the UWB beamformer that focuses on the intended user

  6. Transmission and Reception by Ultra-Wideband (UWB) Antennas

    Microsoft Academic Search

    Debalina Ghosh; Arijit de; Mary Taylor; Tapan Sarkar; Michael Wicks; Eric Mokole

    2006-01-01

    Broadband antennas are very useful in many applications because they operate over a wide range of frequencies. The objective of this paper is to study the transient responses of various well-known antennas over broad frequency ranges. As such, the phase responses of these antennas as a function of frequency are of great interest. In the ensuing analysis, each antenna is

  7. Low profile antennas and arrays for satellite navigation

    NASA Astrophysics Data System (ADS)

    Smith, M. S.; Neal, L.; Thomas, R. R.; Walker, G. H.

    Low profile antennas and arrays, suitable for use with the GPS satellite navigation system, can be made using microstrip antenna technology. A novel dual-frequency, microstrip-crossed slot antenna is demonstrated. This antenna is suitable for use either alone or as an element in an adaptive array.

  8. PATTERN RECONFIGURABLE CIRCULAR PATCH ANTENNA FOR MIMO COMMUNICATIONS

    Microsoft Academic Search

    D. Piazza; P. Mookiah; M. D'Amico; K. R. Dandekar

    This paper presents a reconfigurable two-port circular patch antenna that improves the performance of a MIMO wireless communications system through pattern diversity. Different modes of the circular patch antenna can be excited by varying its radius with PIN diode switches. Based on this antenna architecture a practical algorithm that exploits the wireless channel spatial selectivity to select the antenna radiation

  9. A dual-polarized parasitic patch antenna for MIMO systems

    Microsoft Academic Search

    Daniele Pinchera; Fulvio Schettino

    2009-01-01

    A preliminary analysis of a reconfigurable parasitic patch antenna for MIMO applications is presented. The proposed antenna is able to work on two different polarizations, providing a separate control of the antenna pattern of each of the two polarization. A number of numerical results, showing the adaptive capabilities of the antenna, is given.

  10. S band dual polarized antenna for DAB application

    Microsoft Academic Search

    Young-Pyo Hong; Jung-Min Kim; Soon-Chul Jeong; Dong-Hyun Kim; Jong-Gwan Yook

    2004-01-01

    This paper presents a dual polarized antenna system incorporating a low profile annular ring patch antenna fed by short circuit pins incorporating 90° phase delay element for circular polarization (CP) and a reactive-loaded monopole linear polarized (LP) antenna which is connected to the circular patch and two additional wires. The simulated return loss characteristics of the proposed antennas reveal bandwidth

  11. Development of a fishbone travelling wave antenna for LHD

    Microsoft Academic Search

    Y. Takase; C. P. Moeller; T. Seki; N. Takeuchi; T. Watari; R. Callis; A. Ejiri; H. Ikezi; H. Kasahara; N. Kasuya; R. Kumazawa; T. Mutoh; K. Ohkubo; R. A. Olstad; M. Saigusa; K. Saito; S. Shiraiwa; T. Taniguchi; H. Torii; H. Wada; K. Yamagishi; T. Yamamoto

    2004-01-01

    The 'fishbone' fast wave travelling wave antenna was developed for LHD to provide a capability for rotational transform profile control by current drive. The fishbone antenna is equivalent to two combline antennae stacked vertically. The antenna operates around 75 MHz and excites a wavenumber of 14 m-1 when the phase difference between adjacent current straps is 90°. A test of

  12. Compact folded monopole antenna with LC-loadings

    Microsoft Academic Search

    S. H. Kim; J. H. Jang

    2010-01-01

    An LC-loaded folded monopole antenna including two meander-line inductors and an interdigitated capacitor was designed for a miniaturization of antenna. The operating frequency of the antenna was essentially determined by the resonant characteristics of the uniquely arranged distributed inductors and capacitor, not by the length of the radiator, so that the size of the antenna can be designed to be

  13. UWB radiating antenna arrays with strong coupling between the elements

    Microsoft Academic Search

    G. P. Pochanin; T. N. Ogurtsova

    2007-01-01

    Various layouts of the UWB radiating antenna array consisting of the large current radiators as antenna array elements are discussed in the paper. Influence of the mutual coupling between the antenna elements for the strong and weak coupling cases is investigated. Obtained dependencies of the radiation efficiency versus the mutual coupling factor and the antenna array layout (the vertical array

  14. Wideband dual-linear polarized microstrip patch antenna 

    E-print Network

    Smith, Christopher Brian

    2009-05-15

    Due to the recent interest in broadband antennas a microstrip patch antenna was developed to meet the need for a cheap, low profile, broadband antenna. This antenna could be used in a wide range of applications such as in the communications industry...

  15. Characteristics of the wire biconical antenna used for EMC measurements

    Microsoft Academic Search

    Brian A. Austin; Andre P. C. Fourie

    1991-01-01

    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

  16. Wideband slablike folded dipole antenna for low frequency airborne radar

    Microsoft Academic Search

    Yufeng Fang; Xuequan Yan; Zhanbo Lu

    2011-01-01

    A slablike folded dipole antenna is proposed for low frequency airborne radar applications. The proposed antenna has a wide impedance bandwidth, low profile, and small size. Without ground plane (GP), the antenna relative bandwidth is over 54% (VSWR?2). The relative bandwidth of the embedded antenna in the leading edges of fighter wings is also more than 45% (VSWR?2), notwithstanding smaller

  17. Research of circular disc ultra wideband EMC measuring antenna

    Microsoft Academic Search

    Jinghui Qiu; Lingling Zhong; Bo Sun; Zhang Ning

    2008-01-01

    Electromagnetic compatibility (EMC) measuring antenna can be used for EMC radiation disturbed and noise immunity test. Its bandwidth requirement is relatively high, and the antenna needs to cover a wide frequency range. In this paper, the conventional circular disc ultra wideband antenna was expanding researched, and a new method to increase the high frequency of the circular disc antenna was

  18. The design of dipole and monopole antennas with low uncertainties

    Microsoft Academic Search

    Martin J. Alexander; Martin J. Salter

    1997-01-01

    Close agreement between the measured and predicted insertion loss between dipole antennas above a conducting ground plane has produced a calculable standard dipole antenna. Antenna factors of dipole antennas in the frequency range 30 MHz to 500 MHz have been determined to an uncertainty of ±0.1 dB. Though the design of the dipole is not new, the key achievements are:

  19. WIDEBAND BOW-TIE SLOT ANTENNA WITH TUNING STUBS

    E-print Network

    Elsherbeni, Atef Z.

    WIDEBAND BOW-TIE SLOT ANTENNA WITH TUNING STUBS Abdelnasser A. Eldek, Atef Z. Elsherbeni Senior, USA Abstract Printed bow-tie and bow-tie slot antennas are planar-type variations of the biconical stub to a bow-tie slot antenna design to enhance the antenna bandwidth for X-band operation. Our study

  20. High dielectric constant composites for high power antennas

    Microsoft Academic Search

    K. A. O'Connor; R. D. Curry

    2011-01-01

    The volume and weight of high power antennas can be a limiting factor for compact pulsed power transmitters. Options for antenna minimization are limited due to the relationship between an antenna's physical dimensions and the frequencies which can be transmitted. Thus, low frequency antennas often require dimensions on the order of meters. An effort undertaken at the University of Missouri