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1

Efficient Radiation from an Electrically Small Antenna.  

National Technical Information Service (NTIS)

Applying the analytic technique, two antenna designs were found for which the radiation Q was below the limit determined by Chu for electrically small antennas. The simplest design is a turnstile antenna comprised of two perpendicularly oriented collocate...

C. A. Grimes

2000-01-01

2

Electrically Small Switchable Chaotic Dipole Antenna.  

National Technical Information Service (NTIS)

An electrically small dipole antenna loaded with Chua's oscillator as a nonlinear load is analyzed. By using certain values for the linear reactive and resistive elements of this circuit, various types of periodic, period- doubled, and chaotic behavior th...

P. L. Overfelt D. J. White

2000-01-01

3

Electrically Small Inductive-Loaded Planar Antenna.  

National Technical Information Service (NTIS)

It is shown that it is possible to design an electrically small inductive-loaded planar antenna, with a matching post, that is matched to a 50- ohm coaxial line. Planar antennas having a wide range of configurations were simulated at UHF. Many of these an...

E. Altshuler

2009-01-01

4

Metamaterial-Inspired Efficient Electrically Small Antennas  

Microsoft Academic Search

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

Aycan Erentok; Richard W. Ziolkowski

2008-01-01

5

An electrically small meander line antenna for wireless applications  

Microsoft Academic Search

The meander line antenna (MLA) is conventionally an electrically small antenna. Electrically small antennas pose several performance related issues such as narrow bandwidth, high VSWR, low gain and high cross polarization levels. In this paper a modified two element MLA is proposed. The modified MLA possesses novelty in terms of its geometrical shape, which is achieved with the unification of

Atif Jamil; Mohd Zuki Yusoff; Noorhana Yahya

2010-01-01

6

Electrically small meanderly folded patch antennas  

Microsoft Academic Search

This paper introduces a novel small antenna structures-meanderly folded patch antennas - and discusses performance properties of several miniaturized versions. All antenna versions operate on the basic mode TM010. The influence of the number of meanders, size of the antenna, quality factor Q, frequency bandwidth BW and directivity is discussed.

Alois Holub; Milan Polivka

2009-01-01

7

An electrically small meandered line antenna with truncated ground plane  

Microsoft Academic Search

An electrically small meandered microstrip line antenna was investigated. The antenna was designed, fabricated and measured for an operating frequency of 2.4 GHz with a 10 dB return loss bandwidth of 2%. In order to improve the efficiency and gain, a truncated ground plane was used, and its effect on balancing the antenna currents has been studied. A Wheeler Cap

Ibrahim T. Nassar; Thomas M. Weller

2011-01-01

8

Aircraft Antennas/Conformal Antennas Missile Antennas,  

National Technical Information Service (NTIS)

The lecture covers three major areas of airborne microwave antennas, namely: Missile conformal telemetry/telecommand and radar-fuze antennas, Missile and aircraft nose radar flatplate antennas, and Aircraft Electronic Warfare antennas.

K. Solbach

1987-01-01

9

A tunable spherical cap microfluidic electrically small antenna.  

PubMed

A highly efficient microfluidic 3D electrically small antenna is created using a simple fabrication technique. It is easy to construct simply by pneumatically inflating a planar microfluidic antenna into a spherical cap. It has premium performance around its hemispherical shape, combining a wide working band with high efficiency. PMID:23606457

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

2013-10-11

10

Novel Electrically Small Antennas and Metamaterial High Impedance Surfaces.  

National Technical Information Service (NTIS)

This final report presents a summary of the work performed on the project 'Novel Electrically Small Antennas and Metamaterial High Impedance Surfaces,' under ONR Grant No. N00014-04-1-0619, over the period of June 1, 2004 to September 30, 2005. The main a...

A. Hoorfar J. McVay J. Zhu H. Huang

2005-01-01

11

Antenna Efficiency Calculations for Electrically Small, RFID Antennas  

Microsoft Academic Search

Radio frequency identification (RFID) antenna efficiency is an important component of link budget design. A method of moments technique based on the summation of segment currents compares favorably with two different results obtained using the finite element method (radiation pattern integration and Wheeler cap). The efficiency of a resonant dipole was found to be proportional to the inverse square root

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

2007-01-01

12

Conformal Faraday Effect Antenna  

US Patent & Trademark Office Database

The device, a conformal antenna, includes an antenna element directly coupled to a layer of gyrotropic material and means for creating a magnetic field, the magnetic field having a component substantially perpendicular to, and passing through, the layer of gyrotropic material and the antenna element. The gyrotropic material may be at least partially disposed on a ground plane and may comprise a material such as yttrium iron garnet. The means for creating a magnetic field can be located within the layer of gyrotropic material and may comprise at least one external magnet. The reflective metal ground plane can be the outer surface of a vehicle. The antenna element could have a dipole antenna configuration, and can produce a wave that is linearly polarized. The operation of the device may be at or above the resonant frequency of the gyrotropic material.

2013-02-05

13

Electrically small self-resonant wire antennas optimized using a genetic algorithm  

Microsoft Academic Search

One of the major limitations of electrically small antennas is that as the size of the antenna is decreased its radiation resistance approaches zero and its reactance approaches plus or minus infinity. Most small antennas are inefficient, nonresonant and, thus, require matching networks. In this investigation, we use a genetic algorithm (GA) in conjunction with the numerical electromagnetics code to

Edward E. Altshuler

2002-01-01

14

An efficient, low profile, electrically small, three-dimensional, very high frequency magnetic EZ antenna  

NASA Astrophysics Data System (ADS)

A very high frequency version of the electrically small, coax-fed, three-dimensional magnetic EZ antenna was designed and tested. The fabricated antenna was formed by integrating a capacitively loaded loop element with a coaxially-fed, electrically small, semicircular loop antenna. This low profile antenna (height ~?/25) had an electrical size that was ka~0.46 at 105.2 MHz (where a is the radius of the minimum enclosing hemisphere). Nearly complete matching to the 50 ? source and a high overall efficiency (nearly 95%) were achieved. The numerically predicted and the measured results were in good agreement.

Lin, Chia-Ching; Ziolkowski, Richard W.; Nielsen, Jean A.; Tanielian, Minas H.; Holloway, Christopher L.

2010-03-01

15

Design and performance of an electrically small slot loop antenna with a miniaturized superconducting matching circuit  

Microsoft Academic Search

In order to realize a small superconducting receiver, we designed an electrically small slot loop antenna with a miniaturized impedance matching circuit. The area of the slot loop antenna is 4 mm × 4 mm on MgO substrate at a frequency of 2.4 GHz. By applying 2-pole bandpass filter technique, we propose a design theory of the miniaturized impedance matching

Y. Tsutsumi; H. Kanaya; K. Yoshida

2005-01-01

16

Aircraft Antennas/Conformal Antennas Missile Antennas.  

National Technical Information Service (NTIS)

Three major areas of airborne microwave antennas are examined. The basic system environment for missile telemetry/telecommand and fuze functions is sketched and the basic antenna design together with practical examples are discussed. The principle require...

K. Solbach

1987-01-01

17

Electrically Small Microstrip Quarter-Wave Monopole Antennas  

NASA Technical Reports Server (NTRS)

Microstrip-patch-style antennas that generate monopole radiation patterns similar to those of quarter-wave whip antennas can be designed to have dimensions smaller than those needed heretofore for this purpose, by taking advantage of a feed configuration different from the conventional one. The large sizes necessitated by the conventional feed configuration have, until now, made such antennas impractical for frequencies below about 800 MHz: for example, at 200 MHz, the conventional feed configuration necessitates a patch diameter of about 8 ft (.2.4 m) . too large, for example, for mounting on the roof of an automobile or on a small or medium-size aircraft. By making it possible to reduce diameters to between a tenth and a third of that necessitated by the conventional feed configuration, the modified configuration makes it possible to install such antennas in places where they could not previously be installed and thereby helps to realize the potential advantages (concealment and/or reduction of aerodynamic drag) of microstrip versus whip antennas. In both the conventional approach and the innovative approach, a microstrip-patch (or microstrip-patch-style) antenna for generating a monopole radiation pattern includes an electrically conductive patch or plate separated from an electrically conductive ground plane by a layer of electrically insulating material. In the conventional approach, the electrically insulating layer is typically a printed-circuit board about 1/16 in. (.1.6 mm) thick. Ordinarily, a coaxial cable from a transmitter, receiver, or transceiver is attached at the center on the ground-plane side, the shield of the cable being electrically connected to the ground plane. In the conventional approach, the coaxial cable is mated with a connector mounted on the ground plane. The center pin of this connector connects to the center of the coaxial cable and passes through a hole in the ground plane and a small hole in the insulating layer and then connects with the patch above one-third of the radial distance from the center. The modified feed configuration of the innovative approach is an inductive-short-circuit configuration that provides impedance matching and that has been used for many years on other antennas but not on microstrip-style monopole antennas. In this configuration, the pin is connected to both the conductive patch and the ground plane. As before, the shield of the coaxial cable is connected to the ground plane, but now the central conductor is connected to a point on the pin between the ground plane and the conductive plate (see figure). The location of the connection point on the pin is chosen so that together, the inductive short circuit and the conductive plate or patch act as components of a lumped-element resonant circuit that radiates efficiently at the resonance frequency and, at the resonance frequency, has an impedance that matches that of the coaxial cable. It should be noted that the innovative design entails two significant disadvantages. One disadvantage is that the frequency bandwidth for efficient operation is only about 1/20 to 1/15 that of a whip antenna designed for the same nominal frequency. The other disadvantage is that the estimated gain is between 3-1/2 and 4-1/2 dB below that of the whip antenna. However, if an affected radio-communication system used only a few adjacent frequency channels and the design of the components of the system other than the antenna provided adequate power or gain margin, then these disadvantages could be overcome.

Young, W. Robert

2004-01-01

18

Efficiency variations in electrically small, meander line RFID antennas  

Microsoft Academic Search

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

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

2007-01-01

19

Antenna element design for a conformal antenna array demonstrator  

Microsoft Academic Search

Conformal and structurally integrated antennas will play an increasing role in future airborne applications in various fields of interest such as Communication, Navigation, Electronic Warfare or RADAR. However, these antennas are subject to static deformations and vibrations caused by aerodynamic loads which significantly diminish the antennas performance. These effects are investigated in the scope of the interdisciplinary NATO Research Task

Peter Knott; Claudius Locker; Stephan Algermissen

2011-01-01

20

S-Band Conformal Array Antenna.  

National Technical Information Service (NTIS)

Requirements for an S-band Conformal Array Antenna are presented. The high gain antenna is designed to receive from a satellite at scan angles as large as 60 degrees. Development status of low loss printed circuit techniques in the areas of array aperture...

C. A. Chuang D. J. Martin

1983-01-01

21

Bilaterally-Etched Cross Meander-line As an Electrically-Small Antenna at VHF Band  

Microsoft Academic Search

To miniaturize thin types of printed antennas, a bilaterally-etched cross meander-line antenna was developed for specified low-power radio applications at 300 MHz. This antenna consists of two meander-line patterns etched on both surfaces of a dielectric substrate, where the meander-line patterns were crossed each other. According to analytical results, the return loss of this antenna was 17 dB and the

S. Kashihara; F. Kuroki

2008-01-01

22

Performance of a meandered line as an electrically small transmitting antenna  

Microsoft Academic Search

For antennas to radiate at maximum efficiency, their dimensions must be on the same order as the radiated wavelength. At frequencies below 30 MHz, antennas with efficient radiation are often too large for mobile and portable applications. Smaller antennas can be made to radiate efficiently by use of matching networks. For installation convenience and ease of adjustment, these networks are

Thomas J. Warnagiris; Thomas J. Minardo

1998-01-01

23

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

SciTech Connect

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

Speer, Pete

2009-04-15

24

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

NASA Astrophysics Data System (ADS)

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

Zhu, Ning

25

Configurable Conformal Impulse Receive Antenna.  

National Technical Information Service (NTIS)

Among leading-edge research concerns in ultra-wideband (UWB) radiofrequency (RF) methods, it has recently become important to devise antennas to satisfy the following conditions as much as possible: (a) be UWB responsive; (b) be preserving of impulse wave...

G. H. Kirk

2005-01-01

26

A re-examination of the fundamental limits on the radiation Q of electrically small antennas  

Microsoft Academic Search

An exact method, which is more straightforward than those previously published, is derived for the calculation of the minimum radiation Q of a general antenna. This expression agrees with the previously published and widely cited approximate expression in the extreme lower limit of electrical size. However, for the upper end of the range of electrical size which is considered electrically

James S. McLean

1996-01-01

27

Shape and excitation optimization for conformal array antennas  

NASA Astrophysics Data System (ADS)

We present a procedure for the optimization of array antennas that conform to circular cylinders in two space dimensions. For a phase-mode excitation of the antenna, a large number of antenna element designs are compared in terms of two objectives: (1) the active reflection coefficient and (2) the far-field distortion with respect to the excited phase-mode. This analysis yields Pareto fronts with respect to the two objectives and appropriate designs are selected based on the information collected for the useful phase modes given a specific frequency band. This antenna element design is used for the pattern synthesis, where we optimize a linear combination of (1) requirements on the directive gain and (2) similar requirements on the power reflected from the array antenna aperture.

HalleröD, T.; Rylander, T.

2008-08-01

28

Thin conformal antenna array for microwave power conversions  

NASA Technical Reports Server (NTRS)

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

Dickinson, R. M. (inventor)

1978-01-01

29

Electrically small supergain end-fire arrays  

Microsoft Academic Search

The theory, computer simulations, and experimental measurements are presented for electrically small, two-element supergain arrays with near-optimal end-fire gains of 7 dB. We show how the difficulties of narrow tolerances, large mismatches, low radiation efficiencies, and reduced scattering of electrically small parasitic elements are overcome by using electrically small resonant antennas as the elements in both separately driven and singly

A. D. Yaghjian; T. H. O'Donnell; E. E. Altshuler; S. R. Best

2008-01-01

30

Electrically small supergain end-fire arrays  

Microsoft Academic Search

The theory, computer simulations, and experimental measurements are presented for electrically small two-element supergain arrays with near optimal endfire gains of 7 dB. We show how the difficulties of narrow tolerances, large mismat ches, low radiation efficiencies, and reduced scattering of elect rically small parasitic elements are overcome by using electrically small resonant antennas as the elements in both separately

Arthur D. Yaghjian; Terry H. O'Donnell; Edward E. Altshuler; Steven R. Best

2008-01-01

31

Design and development of smart skin conformal antenna with MEMS structural sensors and actuators  

NASA Astrophysics Data System (ADS)

Recently there has been considerable interest toward designing and developing `smart skins' for aircraft. The smart skin is a composite layer which may contain conformal radar, conformal microstrip or spiral antennas for electromagnetic applications. These embedded antennas will given rise to very low radar cross section or can be completely `hidden' to tracking radar. In addition, they can be used to detect, monitor or even jam other unwanted electromagnetic field signatures. The conformal electronically steerable antenna may find useful as a communication link between sensors, actuators and controllers in future `smart' aircraft. The smart skin structure containing the antenna should not only compensate for unwanted structural vibration but also maintain the electromagnetic beam steering and power density (beam shaping). This paper is designed to address some technical advances made in the design and development of thin, wideband, conformal antenna architecture that is structurally integratable and both structurally and electronically tunable using multifunctional piezo, ferroelectric and chiral materials.

Varadan, Vijay K.; Varadan, Vasundara V.

1997-06-01

32

Electrically small supergain end-fire arrays  

NASA Astrophysics Data System (ADS)

The theory, computer simulations, and experimental measurements are presented for electrically small, two-element supergain arrays with near-optimal end-fire gains of 7 dB. We show how the difficulties of narrow tolerances, large mismatches, low radiation efficiencies, and reduced scattering of electrically small parasitic elements are overcome by using electrically small resonant antennas as the elements in both separately driven and singly driven (parasitic), two-element, electrically small supergain end-fire arrays. Although rapidly increasing narrow tolerances prevent the practical realization of the maximum theoretically possible end-fire gain of electrically small arrays with many elements, the theory and preliminary numerical simulations indicate that near-maximum supergains are also achievable in practice for electrically small arrays with three (and possibly more) resonant elements if the decreasing bandwidth with increasing number of elements can be tolerated.

Yaghjian, A. D.; O'Donnell, T. H.; Altshuler, E. E.; Best, S. R.

2008-06-01

33

Study of a conformal hidden wire antenna used for the detection of stolen cars  

Microsoft Academic Search

Object of this paper is the analysis of a conformal wire antenna used for the detection of stolen cars. The antenna operates in the low frequency range 0-300 MHz and it is located on the top part of the metallic chassis, over the back tire. Details on the simulation model are provided and results are validated by comparing different numerical

A. Ciccomancini Scogna; J. Wang

2008-01-01

34

Clutter properties for STAP with smooth and faceted cylindrical conformal antennas  

Microsoft Academic Search

Conformal antennas, which assume the shape of the platform, have several advantages; like reduced weight and space, aerodynamic design and increased field of view. We are interested in detection of moving ground targets with air-borne radar with faceted or smooth vertical half-cylinder or planar antennas with different subarray sizes. We simulate radar systems and study clutter properties which are important

Svante Björklund; Tomas Boman; Anders Nelander

2010-01-01

35

Radiation and scattering from cylindrically conformal printed antennas. Ph.D. Thesis Final Report  

NASA Technical Reports Server (NTRS)

Microstrip patch antennas offer considerable advantages in terms of weight, aerodynamic drag, cost, flexibility, and observables over more conventional protruding antennas. These flat patch antennas were first proposed over thirty years ago by Deschamps in the United States and Gutton and Baisinot in France. Such antennas have been analyzed and developed for planar as well as curved platforms. However, the methods used in these designs employ gross approximations, suffer from extreme computational burden, or require expensive physical experiments. The goal of this thesis is to develop accurate and efficient numerical modeling techniques which represent actual antenna structures mounted on curved surfaces with a high degree of fidelity. In this thesis, the finite element method is extended to cavity-backed conformal antenna arrays embedded in a circular, metallic, infinite cylinder. Both the boundary integral and absorbing boundary mesh closure conditions will be used for terminating the mesh. These two approaches will be contrasted and used to study the scattering and radiation behavior of several useful antenna configurations. An important feature of this study will be to examine the effect of curvature and cavity size on the scattering and radiation properties of wraparound conformal antenna arrays.

Kempel, Leo C.; Volakis, John L.

1994-01-01

36

Electrically Small Supergain Arrays  

Microsoft Academic Search

The theory, computer simulations, and experimental measurements are presented\\u000afor electrically small two-element supergain arrays with near optimal endfire\\u000agains of 7 dB. We show how the difficulties of narrow tolerances, large\\u000amismatches, low radiation efficiencies, and reduced scattering of electrically\\u000asmall parasitic elements are overcome by using electrically small resonant\\u000aantennas as the elements in both separately driven and

Arthur D. Yaghjian; Terry H. O'Donnell; Edward E. Altshuler; Steven R. Best

2007-01-01

37

Simulation of Conformal Spiral Slot Antennas on Composite Platforms  

NASA Technical Reports Server (NTRS)

During the course of the grant, we wrote and distributed about 12 reports and an equal number of journal papers supported fully or in part by this grant. The list of reports (title & abstract) and papers are given in Appendices A and B. This grant has indeed been instrumental in developing a robust hybrid finite element method for the analysis of complex broadband antennas on doubly curved platforms. Previous to the grant, our capability was limited to simple printed patch antennas on mostly planar platforms. More specifically: (1) mixed element formulations were developed and new edge-based prisms were introduced; (2) these elements were important in permitting flexibility in geometry gridding for most antennas of interest; (3) new perfectly matched absorbers were introduced for mesh truncations associated with highly curved surfaces; (4) fast integral algorithms were introduced for boundary integral truncations reducing CPU time from O(N-2) down to O(N-1.5) or less; (5) frequency extrapolation schemes were developed for efficient broadband performance evaluations. This activity has been successfully continued by NASA researchers; (6) computer codes were developed and extensively tested for several broadband configurations. These include FEMA-CYL, FEMA-PRISM and FEMA-TETRA written by L. Kempel, T. Ozdemir and J. Gong, respectively; (7) a new infinite balun feed was designed nearly constant impedance over the 800-3000 MHz operational band; (8) a complete slot spiral antenna was developed, fabricated and tested at NASA Langley. This new design is a culmination of the projects goals and integrates the computational and experimental efforts. this antenna design resulted in a U.S. patent and was revised three times to achieve the desired bandwidth and gain requirements from 800-3000 MHz.

Volakis, J. L.; Nurnberger, M. W.; Ozdemir,T.

1998-01-01

38

Radiation and scattering from printed antennas on cylindrically conformal platforms  

NASA Technical Reports Server (NTRS)

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.

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

1994-01-01

39

Design and measurement of conformal antennas on cylindrical and spherical geometries  

Microsoft Academic Search

Conformal antennas on different kinds of surfaces as circular cylinders, elliptic cylinders, spheres, cones and even more complex formed surfaces like wings of aeroplanes have received more and more attention due to their extended beam scanning capabilities in comparison with planar arrays as well as their close mechanical fit to the carrying structure. This contribution discusses the advantages and drawbacks

D. Loffler; E. Gschwendtner; W. Wiesbeck

1999-01-01

40

Inkjet printing of dual band conformal antenna for use in wifi frequency bands  

Microsoft Academic Search

In this paper, a dual-band conformal antenna for use in Wifi frequency bands is designed and developed using conductive inkjet printing technique. Paper as a high frequency substrate is used for low cost reasons. Discussion about the benefits of using inkjet printing is also provided. Measured results are presented showing a good agreement with theoretical ones.

Amin Rida; George Shaker; Farzad Nasri; Trevale Reynolds; Symeon Nikolaou; M. Tenzeris

2010-01-01

41

Triangular prisms for edge-based vector finite element analysis of conformal antennas  

Microsoft Academic Search

This paper deals with the derivation of the edge-based shape functions for the distorted triangular prism and their applications for the analysis of doubly curved conformal antennas in the context of the finite element method (FEM). Although the tetrahedron is often the element of choice for volume tessellation, mesh generation using tetrahedra is cumbersome and the central processing unit (CPU)

T. Ozdemir; J. L. Volakis

1997-01-01

42

Study of inkjet printing as an ultra-low-cost antenna prototyping method and its application to conformal wraparound antennas for sounding rocket sub-payload  

NASA Astrophysics Data System (ADS)

Inkjet printing is an attractive patterning technology that has received tremendous interest as a mass fabrication method for a variety of electronic devices due to its manufacturing exibility and low-cost feature. However, the printing facilities that are being used, especially the inkjet printer, are very expensive. This thesis introduces an extremely cost-friendly inkjet printing method using a printer that costs less than $100. In order to verify its reliability, linearly and circularly polarized (CPd) planar and conformal microstrip antennas were fabricated using this printing method, and their measurement results were compared with copper microstrip antennas. The result shows that the printed microstrip antennas have similar performances to those of the copper antennas except for lower efficiency. The effects of the conductivity and thickness of the ink layer on the antenna properties were studied, and it is found that the conductivity is the main factor affecting the radiation efficiency, though thicker ink yields more effective antennas. This thesis also presents the detailed antenna design for a sub-payload. The sub-payload is a cylindrical structure with a diameter of six inches and a height of four inches. It has four booms coming out from the surface, which are used to measure the variations of the energy flow into the upper atmosphere in and around the aurora. The sub-payload has two types of antennas: linearly polarized (LPd) S-band antennas and right-hand circularly polarized (RHCPd) GPS antennas. Each type of antenna has various requirements to be fully functional for specific research tasks. The thesis includes the design methods of each type of antenna, challenges that were confronted, and the possible solutions that were proposed. As a practical application, the inkjet printing method was conveniently applied in validating some of the antenna designs.

Maimaiti, Maimaitirebike

43

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

PubMed Central

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

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

2013-01-01

44

Antennas  

NASA Astrophysics Data System (ADS)

Articles on the following topics are presented: problems in the design and methods of calculating the parameters of very low frequency and low frequency antennas, quasi-optical transmission lines for millimeter waves, the design of antenna arrays, the theory of mixed problems in antenna design and synthesis, the investigation of binary sources of radio frequency radiation using an interferometer, a method for solving exterior problems in electrodynamics, optimal differential electric field distributions in an antenna aperture, calculating the characteristics of a junction of two waveguides for a round waveguide with an azimuthally magnetized ferrite rod, a spiral line with an azimuthally magnetized ferrite cylinder, and calculation of a y circulator waveguide with a ferrite dielectric element.

1982-05-01

45

Time-Dependent Numerical Method with Boundary-Conforming Curvilinear Coordinates Applied to Wave Interactions with Prototypical Antennas  

NASA Astrophysics Data System (ADS)

A new unstaggered finite-difference time-dependent technique to accurately model scattring from prototypical 2D antenna structures is devised. The unbounded boundary value problems defining these phenomena are redefined over bounded domains using appropriate radiation operators over finite artificial boundaries. Generalized curvilinear coordinates are generated such that physical boundaries correspond to coordinate lines. A numerical procedure to generate almost orthogonal, boundary-conforming, fine grids over these bounded regions is developed. Once the governing equations are written in terms of the new curvilinear coordinates, a time-dependent numerical method is applied to obtain time harmonic steady-state solutions to these problems. The electric field wave amplitude as well as the wave pattern inside the waveguide and the scattered field from the prototypical antennas are obtained. Accuracy and computational cost are compared when almost orthogonal and nonorthogonal grids are in use. An optical theorem for a flanged waveguide antenna with perfect electrical conductor walls is derived. It is verified that the approximate solutions obtained by application of the time-dependent numerical method with boundary-conforming, curvilinear coordinates satisfy the optical theorem.

Villamizar, Vianey; Rojas, Otilio

2002-03-01

46

Antenna Technologies for NASA Applications  

NASA Technical Reports Server (NTRS)

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

Miranda, Felix

2007-01-01

47

Investigation of a Forward Looking Conformal Broadband Antenna for Airborne Wide Area Surveillance.  

National Technical Information Service (NTIS)

The presented work describes an antenna with 2:1 bandwidth (400-800 MHz) that will be used in airborne wide area surveillance. Several designs of the Log-Periodic configuration are introduced in addition to a TEM Horn. Performance parameters like bandwidt...

H. E. Yacoub

2004-01-01

48

Colocated Magnetic Loop, Electric Dipole Array Antenna (Preliminary Results).  

National Technical Information Service (NTIS)

We present a detailed electromagnetic analysis of an electrically small colocated electric dipole and magnetic loop antenna array. This antenna is the simplest example of the Grimes multipole class of antenna arrays. We have determined that since the inte...

P. L. Overfelt D. R. Bowling D. J. White

1994-01-01

49

Antenna applications of superconductors  

Microsoft Academic Search

The applicability of superconductors to antennas is examined. Potential implementations that are examined are superdirective arrays; electrically small antennas; tuning and matching of these two; high-gain millimeter-wavelength arrays; and kinetic inductance slow wave structures for array phasers and traveling wave array feeds. It is thought that superdirective arrays and small antennas will not benefit directly, but their tuning\\/matching networks will

R. C. Hansen

1991-01-01

50

Antenna applications of superconductors  

Microsoft Academic Search

The applicability of superconductors to antennas is examined. Potential implementations that are examined are superdirective arrays; electrically small antennas; tuning and matching of these two; high-gain millimeter-wavelength arrays; and kinetic inductance slow wave structures for array phasers and travelling wave array feeds. It is thought that superdirective arrays and small antennas will not benefit directly, but their tuning\\/matching networks will

R. C. Hansen

1991-01-01

51

Applications of superconductors in antenna systems  

Microsoft Academic Search

It is noted that the new ceramic high temperature superconductors are potentially of use in antenna systems, assuming liquid nitrogen cooling is available. A detailed assessment of different antenna systems is presented: (1) electrically small antennas, at VHF\\/UHF, and below 1 MHz, (2) electrically large antennas, for centimeter array feed systems and for millimeter systems; (3) coaxial cables; (4) cavity

M. S. Smith

1989-01-01

52

The Zeaxanthin-Independent and Zeaxanthin-Dependent qE Components of Nonphotochemical Quenching Involve Common Conformational Changes within the Photosystem II Antenna in Arabidopsis1[W  

PubMed Central

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 (?A535) 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.

Johnson, Matthew P.; Perez-Bueno, Maria L.; Zia, Ahmad; Horton, Peter; Ruban, Alexander V.

2009-01-01

53

PCS antenna design: the challenge of miniaturization  

Microsoft Academic Search

PCS (personal communication system) devices have become an important part of everyday life. The pressure to design small, lightweight, and user-friendly mobile-communication devices has increased accordingly, creating the need for optimal antennas for mobile applications. In this paper, we present some basic rules about electrically small antennas, give clues and guidelines about efficient antenna miniaturization, and, finally, show some examples

A. K. Skrivervik; J.-F. Zurcher; O. Staub; J. R. Mosig

2001-01-01

54

Review on recent phased array antenna technologies in Japan  

Microsoft Academic Search

A review on recent phased array antenna technologies is presented. The technologies referred to are antenna calibration, low sidelobe pattern synthesis for conformal array antennas and density tapering for active phased array antennas

Takashi Katagi; Isamu Chiba

2000-01-01

55

Design methodology for multiport antennas  

NASA Astrophysics Data System (ADS)

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

Arceo, Diana

56

Fundamental Aspects of Near-Field Coupling Small Antennas for Wireless Power Transfer  

Microsoft Academic Search

A physical limitation on the power transfer efficiency between two electrically small antennas in the near-field range is presented. By using a Z-parameter which describes the interaction between two antennas for spherical modes in connection with antenna parameters, the maximum power transfer efficiency and the optimum load impedance are shown as functions of the distance between two antennas, the radiation

Jaechun Lee; Sangwook Nam

2010-01-01

57

Mathematical Modeling of Multi-Element Monopole Antennas.  

National Technical Information Service (NTIS)

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 per...

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

1981-01-01

58

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

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

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

2009-01-01

59

A novel compact UHF wideband antenna for near field electrical characterization of Steel Fiber Reinforced Concrete  

Microsoft Academic Search

A novel, electrically small, UHF (350 MHz-750 MHz) microstrip slot antenna is presented. The antenna is designed for the characterization of steel fiber reinforced concrete (SFRC) segments. The antenna consists on a three layer structure headed by the slot ground plane, followed by the feeding microstrip in the central layer with some resistive loading for bandwidth enhancement purposes; finally on

G. Roqueta; S. Irteza; J. Romeu; L. Jofre

2009-01-01

60

Low-Profile Multifrequency HF Antenna Design for Coastal Radar Applications  

Microsoft Academic Search

A novel design for an electrically small high-frequency (HF) antenna suitable for coastal radar applications is presented. The principle design objectives were to develop an HF antenna resonant at multiple frequencies that is also compact and easily transportable for deployment to coastal sites and on floating platforms. The compact antenna achieves practical performance values for radiation resistance, bandwidth, and gain

James Baker; Hyoung-Sun Youn; Nuri Celik; Magdy F. Iskander

2010-01-01

61

Metamaterials and Conformal Antenna Technologies.  

National Technical Information Service (NTIS)

Metamaterials are artificially constructed materials. When electromagnetic waves propagate through metamaterials they display properties different from those found in natural materials. These different properties can include negative refraction (light is ...

H. Mosallaei J. Sokoloff L. Menon M. Dokmeci S. Idhar

2013-01-01

62

Furlable antenna. [antenna design  

NASA Technical Reports Server (NTRS)

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.

Barnett, M. A. (inventor)

1976-01-01

63

The polarizabilities of electrically small apertures of arbitrary shape  

NASA Astrophysics Data System (ADS)

Numerical procedures, based on a method of moments approach, are presented for computing the magnetic and electric polarizabilities of electrically small apertures of arbitrary shape. The magnetic polarizability density is determined by using pulse expansion functions defined over quadrilateral subdomains, while the electric polarizability density is obtained by using basis functions. Each of the basis functions consists of a piecewise arrangement of simple linear functions defined over triangles and having an area coordinate representation. All the subdomains are generated automatically by applying either the Gordon-Hall or the Zienkiewicz-Phillips subdivision methods. Computed results are obtained for several aperture shapes, among them the circle and ellipse.

Okon, E. E.; Harrington, R. F.

1981-11-01

64

Microstrip antennas  

Microsoft Academic Search

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

DAVID M. POZAR

1992-01-01

65

An L-band antenna array with integrated phase shifters  

NASA Astrophysics Data System (ADS)

The design and modus operandi of an L-band microstrip antenna array with integrated phase shifter is described. The array consists of phase shift antenna elements. These elements have power capability and can be integrated with two versions of microstrip antennas to form flat conformal arrays. Phase shifters and antenna elements were integrated into a flat conformal array. Different linear arrays were simulated and successfully tested.

Leich, Martin

1989-06-01

66

Design and development of a conformal load-bearing smart skin antenna: overview of the AFRL Smart Skin Structures Technology Demonstration (S3TD)  

NASA Astrophysics Data System (ADS)

Documented herein is a review of progress for the recently completed 'Smart Skin Structure Technology Demonstration' (S3TD) contract number F33615-93-C-3200 performed by Northrop Grumman Corporation, Hawthorne, California and TRW/ASD, Rancho Bernardo, San Diego, California under the Air Force Research Laboratory, Flight Dynamics Directorate, Structures Division's direction and sponsorship. S3TD was conceived as the first serious attempt, to made a complex antenna become a bone fide aircraft structural panel, without loss of overall structural integrity or electrical performance. The program successfully demonstrated the design, fabrication, and structural validation of a load bearing multifunction antenna component panel subjected to realistic aircraft flight load conditions. The final demonstration article was a structurally effective 36 by 36 inch curved multifunction antenna component panel that withstood running loads of 4,000 pounds per inch, and principal strain levels of 4,700 microstrain. Testing the structural component to ultimate, the panel failed at the predicted limit of 148 kips equating to 150 percent design limit load, after successfully completing one lifetime of fatigue. The load conditions were representative of a mid-fuselage F-18 class fighter component panel installation. The panel was designed not to buckle at ultimate failure, and the dominant failure mode was face sheet pull off, as predicted. Structural test data correlated closely with analysis. Wide band electrical performance for the component antenna panel was validated using anechoic chamber measurements and near field probing techniques, covering avionics communication navigation and identification and electronic warfare functions in the 0.15 to 2.2 GHz frequency regimes.

Lockyer, Allen J.; Alt, Kevin H.; Coughlin, Daniel P.; Durham, Michael D.; Kudva, Jayanth N.; Goetz, Allen C.; Tuss, Jim

1999-07-01

67

Scalable conformal array for multi-gigabit body centric wireless communication  

Microsoft Academic Search

In this work a conceptual design of a conformal antenna array is presented for a millimeter-wave antenna system, optimized for low-cost mass production in PCB technology. The conformal array is constituted by four cube faces with two antennas realized on each face. A printed circuit board (PCB) laminate material was chosen for developing this integrated 60 GHz antenna solution. The

Alexander Vasylchenko; John F. Farserotu; Montserrat Fernandez-Bolanos; Adrian M. Ionescu; Steven Brebels; Walter De Raedt; Guy A. E. Vandenbosch

2011-01-01

68

Deployable antenna  

NASA Technical Reports Server (NTRS)

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.

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

2006-01-01

69

Analysis of Dipole Antenna Eccentered in a Borehole for Borehole Radar  

Microsoft Academic Search

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

S. Ebihara; Y. Inoue

2007-01-01

70

Reconfigurable antenna pattern verification  

NASA Technical Reports Server (NTRS)

A method of verifying programmable antenna configurations is disclosed. The method comprises selecting a desired antenna configuration from a plurality of antenna configuration patterns, with the selected antenna configuration forming at least one reconfigurable antenna from reconfigurable antenna array elements. The method validates the formation of the selected antenna configuration to determine antenna performance of the at least one reconfigurable antenna.

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

2013-01-01

71

Tunable Patch Antennas Using Microelectromechanical Systems.  

National Technical Information Service (NTIS)

Patch antennas are enablers in wireless applications due to their manufacturability, conformability, low cost, and low weight. However, they have narrow bandwidths and fixed operating frequencies that limit their utility when frequency agility is critical...

S. C. Yee

2011-01-01

72

Evaluation of Uncertainty Budget for Antenna Calibration.  

National Technical Information Service (NTIS)

Accurate field strength measurements for EMC conformance testing can be obtained by using antennas which have reliable antenna factors (AF). AF is a major component in calculating the uncertainty budget of an EMC test. So AF must be highly accurate and th...

B. Tueretken I. Araz M. Hekim M. Yazici S. E. San

2002-01-01

73

Radiation field of pentagonal microstrip antenna  

NASA Astrophysics Data System (ADS)

A conformal mapping method has been used to solve the problem of a pentagonal microstrop antenna. The conformal outer mapping is first used to transform the outside area of a polygon into the outside area of a circle and solve the circular boundary problem. The circle parameters are then inversely transformed to the pentagon boundary problem, and solutions to the antenna are obtained. Both experimental study and theoretical analysis are reported, and numerical computer calculations are compared with the experimental results.

Cao, J.-L.; Dong, W.-L.; Li, W.-X.

1986-01-01

74

NEC4 Analysis of a Navy VLF Antenna.  

National Technical Information Service (NTIS)

NEC4 is used to evaluate proposed modifications to a Navy VLF top-loaded monopole. Charge densities are computed and used to calculate the maximum top-load gradient for two wire sizes. Although the antenna is electrically small, a large number of segments...

C. Deneris J. H. Schukantz P. Hansen J. Logan

1994-01-01

75

Planar Miniature RFID Antennas Suitable for Integration With Batteries  

Microsoft Academic Search

A class of planar, electrically-small UHF antennas suitable for direct integration with electronic components such as batteries is introduced. The new design approach combines a meander line section and a capacitive strip section. The geometries of the two sections can together be scaled in size over a wide range of planar form factors while still maintaining self-resonance and practically realizable

Christopher T. Rodenbeck

2006-01-01

76

A Simple Approach for Reducing Mutual Coupling in Two Closely Spaced Metamaterial-Inspired Monopole Antennas  

Microsoft Academic Search

A simple approach for reducing the mutual coupling in two closely spaced electrically small antennas (ESAs) is proposed based on the general idea of field cancellation. The antenna array consists of two metamaterial-inspired small printed monopole antennas. The mutual coupling is reduced by self-cancellation of the induced common ground and near-field currents, without introducing additional structures. A fabricated prototype of

Jiang Zhu; George V. Eleftheriades

2010-01-01

77

Effects of nonlinear loads on antennas and scatterers  

NASA Astrophysics Data System (ADS)

Nonlinear loads on antennas are used to advantage or degrade the performance of a communications system. Nonlinear elements are routinely used to protect sensitive receivers from high-power signals including high-power microwaves and EMP (electromagnetic pulse). Time-varying loading of antennas are used to modulate the radar backscatter cross section to produce sidebands at the modulation frequency. Nonlinear elements are used to detect the electromagnetic energy incident on an antenna, and thus used as a measurement technique. Nonlinear loads are also used for pulse shaping of the fields radiated by pulse-excited antennas. Active loads are used to increase the performance of electrically small antennas and closely coupled arrays. Alternatively, undesired semiconducting junctions on structures near antennas produce intermodulation products that seriously degrade performance (this is often called the ""rusty-bolt'' effect). The techniques available for analyzing these effects are reviewed and representative examples given. A time-stepping procedure is treated in detail.

Landt, J. A.

1983-09-01

78

A Mechanism of Nonphotochemical Energy Dissipation, Independent from PsbS, Revealed by a Conformational Change in the Antenna Protein CP26W?  

PubMed Central

The regulation of light harvesting in higher plant photosynthesis, defined as stress-dependent modulation of the ratio of energy transfer to the reaction centers versus heat dissipation, was studied by means of carotenoid biosynthesis mutants and recombinant light harvesting complexes (LHCs) with modified chromophore binding. The npq2 mutant of Arabidopsis thaliana, blocked in the biosynthesis of violaxanthin and thus accumulating zeaxanthin, was shown to have a lower fluorescence yield of chlorophyll in vivo and, correspondingly, a higher level of energy dissipation, with respect to the wild-type strain and npq1 mutant, the latter of which is incapable of zeaxanthin accumulation. Experiments on purified thylakoid membranes from all three mutants showed that the major source of the difference between the npq2 and wild-type preparations was a change in pigment to protein interactions, which can explain the lower chlorophyll fluorescence yield in the npq2 samples. Analysis of the xanthophyll binding LHC proteins showed that the Lhcb5 photosystem II subunit (also called CP26) undergoes a change in its pI upon binding of zeaxanthin. The same effect was observed in wild-type CP26 upon treatment that leads to the accumulation of zeaxanthin in the membrane and was interpreted as the consequence of a conformational change. This hypothesis was confirmed by the analysis of two recombinant proteins obtained by overexpression of the Lhcb5 apoprotein in Escherichia coli and reconstitution in vitro with either violaxanthin or zeaxanthin. The V and Z containing pigment-protein complexes obtained by this procedure showed different pIs and high and low fluorescence yields, respectively. These results confirm that LHC proteins exist in multiple conformations, an idea suggested by previous spectroscopic measurements (Moya et al., 2001), and imply that the switch between the different LHC protein conformations is activated by the binding of zeaxanthin to the allosteric site L2. The results suggest that the quenching process induced by the accumulation of zeaxanthin contributes to qI, a component of NPQ whose origin was previously poorly understood.

Dall'Osto, Luca; Caffarri, Stefano; Bassi, Roberto

2005-01-01

79

Microstrip Backfire Antenna.  

National Technical Information Service (NTIS)

This invention relates to microstrip antennas and more particularly to a multi-mode antenna using both microstrip antenna elements and a backfire cavity. Compact missile-borne antenna systems require complex antenna beam shapes. At times, these beam shape...

C. M. Kaloi

1981-01-01

80

Land vehicle antennas for satellite mobile communications  

NASA Technical Reports Server (NTRS)

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

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

1985-01-01

81

A colocated magnetic loop, electric dipole array antenna (preliminary results)  

NASA Astrophysics Data System (ADS)

We present a detailed electromagnetic analysis of an electrically small colocated electric dipole and magnetic loop antenna array. This antenna is the simplest example of the Grimes multipole class of antenna arrays. We have determined that since the interaction term between the two elements disappears from the radial complex power, we were able to set the radial reactance to zero by choosing appropriate current magnitudes and phases on the array elements. By driving the two elements in quadrature, we obtained a much increased radiation intensity and directivity as well as increased radiated power.

Overfelt, P. L.; Bowling, D. R.; White, D. J.

1994-09-01

82

Investigating a horizontal helical antenna for use in the phantom monopole configuration  

NASA Astrophysics Data System (ADS)

A phantom monopole was successfully simulated using wire loop antennas prior to this thesis work. These wire loop antennas have an undesirable input impedance, making them difficult to match and implement in physical building. A new type of antenna needs to be found that has a more desirable impedance while still maintaining the same near magnetic field and far field radiation pattern. The research done for this problem focused on a horizontally placed helical antenna. There is little research done on a horizontally placed helical antenna. The fact that there isn't information readily available meant that many different parameters of this antenna were investigated. A normal mode helical antenna was chosen because of its size and impedance. A helical antenna is an electrically small antenna, like the wire loop antenna, with an improved impedance compared to the wire loop. The work done not only dealt with computer simulation of the helical antenna, but also physical building of the antenna. The physical testing was done in order to get real world data and to support the computer modeling of the phantom monopole. Through testing and simulations, it was found that a horizontally placed helical antenna provided an alternative to the wire loop antenna originally used. By placing the helical antenna horizontally, the near magnetic field and far field radiation pattern mimicked those found in the original wire loop configuration. This means the phantom monopole is recreated using a new type of antenna that has an improved input impedance.

LeMieux, Mattison

83

Radar Antenna.  

National Technical Information Service (NTIS)

An antenna is described for range-gated, pulse doppler, radar systems. The antenna includes first and second, shortened, half-wave dipoles and first and second reflecting screens. One dipole is fed through a fixed 22 1/2 degree phase-shift network while t...

O. E. Rittenback

1978-01-01

84

Active antenna  

NASA Technical Reports Server (NTRS)

An antenna, which may be a search coil, is connected to an operational amplifier circuit which provides negative impedances, each of which is in the order of magnitude of the positive impedances which characterize the antenna. The antenna is connected to the inverting input of the operational amplifier; a resistor is connected between the inverting input and the output of the operational amplifier; a capacitor-resistor network, in parallel, is connected between the output and the noninverting input of the operational amplifier; and a resistor is connected from the noninverting input and the circuit common. While this circuit provides a negative resistance and a negative inductance, in series, which appear, looking into the noninverting input of the operational amplifier, in parallel with the antenna, these negative impedances appear in a series loop with the antenna positive impedances, so as to algebraically add. This circuit is tuned by varying the various circuit components so that the negative impedances are very close, but somewhat less, in magnitude, to the antenna impedances. The result is to increase the sensitivity of the antenna by lowering its effective impedance. This, in turn, increases the effective area of the antenna, which may be broadband.

Sutton, John F. (inventor)

1994-01-01

85

Adjoint sensitivity analysis of an ultrawideband antenna  

SciTech Connect

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

Stephanson, M B; White, D A

2011-07-28

86

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

Microsoft Academic Search

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

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

1994-01-01

87

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

Microsoft Academic Search

Electrically small loops and monopoles are modeled over infinite lossy ground planes using a modification to the Sommerfeld approach, in order to assess the performance of YBCO antennas connected to typical 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,

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

1994-01-01

88

Radiation field of pentagonal microstrip antenna  

Microsoft Academic Search

A conformal mapping method has been used to solve the problem of a pentagonal microstrop antenna. The conformal outer mapping is first used to transform the outside area of a polygon into the outside area of a circle and solve the circular boundary problem. The circle parameters are then inversely transformed to the pentagon boundary problem, and solutions to the

J.-L. Cao; W.-L. Dong; W.-X. Li

1986-01-01

89

Array Antenna Design with WIPL-D.  

National Technical Information Service (NTIS)

Array antenna design at Syracuse Research Corporation using WIPL-D is demonstrated by two examples: a switched beam conformal array and a phased array. The conformal array is a cylindrical array of vertical column subarrays. The phased array is planar arr...

H. K. Schuman D. McPherson K. Hinman

2004-01-01

90

Split-Ring Resonator Loaded Miniaturised Slot for the Slotted Waveguide Antenna Stiffened Structure.  

National Technical Information Service (NTIS)

The increasing use carbon fibre reinforced polymer CFRP in modern military aircraft together with the desire for a conformal load-bearing antenna structure, has since inspired the slotted waveguide antenna stiffened structure (SWASS) (concept 1). Conventi...

K. Ghorbani

2011-01-01

91

Split-Ring Resonator for the Slotted Waveguide Antenna and Tuneable BST Varactor.  

National Technical Information Service (NTIS)

The increasing use of carbon fibre reinforced polymer CFRP in modern military aircraft together with the desire for a conformal load-bearing antenna structure, has since inspired the slotted waveguide antenna stiffened structure (SWASS) concept. Conventio...

K. Ghorbani

2012-01-01

92

Antenna Controller  

NASA Technical Reports Server (NTRS)

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

1994-01-01

93

Dipole Moments of Weak, Electrically Small Emitters from TEM-Cell Measurements.  

National Technical Information Service (NTIS)

The report presents a new method for determining the equivalent electric and magnetic dipole moments of an electrically small emitter from TEM-cell measurements. The electric dipole moments are determined from open-circuit measurements, and the magnetic d...

D. A. Hill K. H. Cavcey

1998-01-01

94

Optical antennas and plasmonics  

Microsoft Academic Search

Optical antenna is a nanoscale miniaturisation of radio or microwave antennas that is also governed by the rule of plasmonics. We introduce various types of optical antenna and make an overview of recent developments in optical antenna research. The role of local and surface plasmons in optical antenna is explained through antenna resonance and resonance conditions for specific metal structures

Q-Han Park

2009-01-01

95

L-band antenna array with integrated phase shifters  

NASA Astrophysics Data System (ADS)

The design and operation of an L band microstrip antenna with integrated phase shifters is described. The array consists of phase shifter antenna elements. The phase shifters have power handling capability and can be used with two different versions of microstrip antennas for constructing various phased array systems. The phase shifters and the antenna elements are integrated into a flat conformal unit. Linear arrays are simulated and tested. Promising applications are in mobile satellite communications and L band radar synthetic aperture radar systems. The development of compatible microstrip antenna excited with circular polarization would be useful for extending the application of the concept.

Leich, Martin

1990-11-01

96

Antenna Technologies for Future NASA Exploration Missions  

NASA Technical Reports Server (NTRS)

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

Miranda, Felix A.

2006-01-01

97

Structurally Integrated Antenna Concepts for HALE UAVs  

NASA Technical Reports Server (NTRS)

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

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

2006-01-01

98

Small antennas  

Microsoft Academic Search

A small antenna is one whose size is a small fraction of the wavelength. It is a capacitor or inductor, and it is tuned to resonance by a reactor of opposite kind. Its bandwidth of impedance matching is subject to a fundamental limitation measured by its \\

H. Wheeler

1975-01-01

99

Design and comparative study on planar small antennas using meander and peano line structure  

Microsoft Academic Search

This paper presents two types of electrically small antennas. One of the element has a meander structure and the other one has peano structure. The element size of both are 1\\/50 lambda length and the substrate is 1\\/15 lambda squared for 1GHz. From the measured results, the radiation efficiency was experimentally shown and the both of antenna gain were compared.

T. Fukusako; T. Terada; K. Iwata

2007-01-01

100

Microwave cavity antennas  

Microsoft Academic Search

Advances in the design of microwave cavity antennas are discussed, surveying both Western and Soviet work for the period 1950-1988. The fundamental principles and classification of cavity antennas are reviewed, and particular attention is given to cavity-backed antennas; translucent-aperture cavity antennas; cavity-backed, crossed-dipole-fed, helical, and spiral antennas; short-backfire antennas; and long-backfire antennas. Extensive diagrams, drawings, graphs, and photographs are provided.

A. Kumar; H. D. Hristov

1989-01-01

101

Design of a matching network for dipole antennas  

NASA Astrophysics Data System (ADS)

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.

Park, Jennifer

1993-03-01

102

Offset parabolic reflector antennas  

Microsoft Academic Search

The characteristics of offset parabolic reflector antennas are examined with particular reference to their use in satellite communication systems. Consideration is given to single offset reflector analysis, the electrical performance of the single offset reflector antenna, a design procedure for multiple spot-beam antennas, primary feeds for offset reflector antennas, and dual-reflector offset antennas.

A. W. Rudge

1983-01-01

103

Design and analysis of a compact low cost patch antenna for different wireless operations  

Microsoft Academic Search

Microstrip patch antenna holds many promises for wireless applications. It has advantages like conformability to host surface, light weight, low profile and easy installation. This paper presents a novel design for a low cost, single layer, single feed, compact microstrip patch antenna for multi-band wireless applications. According to the electrical performance, the antenna should find use for high speed wireless

Chitra Singh; R. P. S. Gangwar

2011-01-01

104

Method for Determining Antenna Near-Fields from Measurements on a Spherical Surface.  

National Technical Information Service (NTIS)

A method is given for determining antenna near-fields from measurements on a spherical surface. Phase and intensity values are measured by scanning a probe antenna over a spherical surface. The method applies both to planar or conformal antennas. The sphe...

G. P. Tricoles E. L. Rope

1978-01-01

105

Double-resonance antenna  

NASA Astrophysics Data System (ADS)

This article describes a new kind of microstrip antenna that uses double-resonance phenomenon to radiative as a short dipole. The working wavelength of this antenna is approximately eight times the maximum dimension of the antenna.

Seaux, J. P.; Reineix, A.; Jecko, B.

1991-09-01

106

Threader Microcomputer Antenna Controller.  

National Technical Information Service (NTIS)

The THREADER microcomputer antenna controller is the electrical interface and controller between the THREADER PDP11 and SA antenna pedestal. The antenna controller is slaved to the PDP11; however, the controller contains its own microprocessor, memory and...

L. E. Russo

1979-01-01

107

Receive antenna selection for polarized antennas  

Microsoft Academic Search

In this work we analyze the combined effects of array orientation\\/rotation and antenna cross polarization discrimination on the performance of dual-polarized systems with receive antenna selection. We start our analysis with a 1 out of N selection and extend it to M out of N receive antenna selection, for which we derive numerical expressions for the effective channel gains. These

Aamir Habib; Christian Mehlfuhrer; Markus Rupp

2011-01-01

108

Short backfire antenna research  

Microsoft Academic Search

In this paper, a method is presented for analysis of a short backfire antenna. A new type backfire antenna whose gain is about 2.5 dB higher than that of a normal short backfire antenna is developed successfully, without the increase of size of antenna aperture.

Lin Changlu; Song Ximing

1983-01-01

109

Three-Element Antenna.  

National Technical Information Service (NTIS)

A three-element directional/omnidirectional antenna adapted for use in both transmitting and receiving modes. Crossed loop antennas are mounted on top of a monopole whip antenna and are electrically coupled thereto. Each of the loop antennas consists of a...

A. R. Carr

1982-01-01

110

Full polarimetric pattern synthesis for an active conformal array  

Microsoft Academic Search

Conformal arrays offer a maximal sensor surface area for a given platform which in turn provides larger array aperture and array gain. When considering such an antenna for an airborne radar, the classical requirements for an electronically scanned antenna pattern remain, such as low sidelobe level and low cross polarization level for both sum and difference beams. This paper presents

M. Dinnichert

2000-01-01

111

A reconfigurable plasma antenna  

NASA Astrophysics Data System (ADS)

An experiment aimed at investigating the antenna properties of different plasma structures of a plasma column as a reconfigurable plasma antenna, is reported. A 30 cm long plasma column is excited by surface wave, which acts as a plasma antenna. By changing the operating parameters, e.g., working pressure, drive frequency, input power, radius of glass tube, length of plasma column, and argon gas, single plasma antenna (plasma column) can be transformed to multiple small antenna elements (plasma blobs). It is also reported that number, length, and separation between two antenna elements can be controlled by operating parameters. Moreover, experiments are also carried out to study current profile, potential profile, conductivity profile, phase relations, radiation power patterns, etc. of the antenna elements. The effect on directivity with the number of antenna elements is also studied. Findings of the study indicate that entire structure of antenna elements can be treated as a phased array broadside vertical plasma antenna, which produces more directive radiation pattern than the single plasma antenna as well as physical properties and directivity of such antenna can be controlled by operating parameters. The study reveals the advantages of a plasma antenna over the conventional antenna in the sense that different antennas can be formed by tuning the operating parameters.

Kumar, Rajneesh; Bora, Dhiraj

2010-03-01

112

A reconfigurable plasma antenna  

SciTech Connect

An experiment aimed at investigating the antenna properties of different plasma structures of a plasma column as a reconfigurable plasma antenna, is reported. A 30 cm long plasma column is excited by surface wave, which acts as a plasma antenna. By changing the operating parameters, e.g., working pressure, drive frequency, input power, radius of glass tube, length of plasma column, and argon gas, single plasma antenna (plasma column) can be transformed to multiple small antenna elements (plasma blobs). It is also reported that number, length, and separation between two antenna elements can be controlled by operating parameters. Moreover, experiments are also carried out to study current profile, potential profile, conductivity profile, phase relations, radiation power patterns, etc. of the antenna elements. The effect on directivity with the number of antenna elements is also studied. Findings of the study indicate that entire structure of antenna elements can be treated as a phased array broadside vertical plasma antenna, which produces more directive radiation pattern than the single plasma antenna as well as physical properties and directivity of such antenna can be controlled by operating parameters. The study reveals the advantages of a plasma antenna over the conventional antenna in the sense that different antennas can be formed by tuning the operating parameters.

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

2010-03-15

113

A Review of Antenna Technologies for Future NASA Exploration Missions  

NASA Technical Reports Server (NTRS)

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

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

2007-01-01

114

Mutual Elements and Substrate Effect Analysis on Patch Antenna Arrays  

NASA Astrophysics Data System (ADS)

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

Wallace, Matthew J.

115

Pattern synthesis for a conformal wing array  

Microsoft Academic Search

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

Hans Steyskal; Hanscom AFB

2002-01-01

116

Development of pulse radiation antennas  

Microsoft Academic Search

In this paper, the development of pulse radiation antennas is summarized. Loaded dipole antennas, TEM horn antennas and its variations, and reflector impulse radiating antennas are discussed as the main forms of antennas which can radiate pulse. The advantages and disadvantages concerning pulse radiation antennas are reviewed as well as the history of this technology. Also the improving methods and

Bo Sun; Jinghui Qiu; Chun Zhang; Weibo Deng

2008-01-01

117

Standardized Modular Antenna System.  

National Technical Information Service (NTIS)

For use in a submarine, an easily reconfigurable mast antenna system disposed within an RF transparent radome is disclosed where modularly, interchangeably designed antenna of the system are detachably attached to each other via an electronic interface co...

D. J. Saleem

1997-01-01

118

Atacama compact array antennas  

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

119

Serpentine Buoyant Cable Antenna.  

National Technical Information Service (NTIS)

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

E. M. Gerhard

2006-01-01

120

JPL antenna technology development  

NASA Technical Reports Server (NTRS)

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.

Freeland, R. E.

1982-01-01

121

Antenna Height Gain Experiment.  

National Technical Information Service (NTIS)

The report presents the results of the antenna height gain experiment performed in the Chicago Region at four different sites. Two bands, VHF and UHF, are analyzed for their signal strength and occupancy variation versus antenna heights. These results are...

O. Efremov

1976-01-01

122

Space-Frame Antenna  

NASA Technical Reports Server (NTRS)

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

Curtis, Steven A.

2010-01-01

123

Resonant Optical Antennas  

Microsoft Academic Search

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

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

2005-01-01

124

[Conformal radiotherapy].  

PubMed

Conformal radiotherapy is a new irradiation technique made possible by technological improvements, especially progress in imaging and 3D dosimetry. By conforming the volume irradiated as closely as possible to the clinical anatomical target volume, conformal radiotherapy is designed to deliver a higher dose to the tumour volume, while more effectively sparing the adjacent tissues from the adverse effects of irradiation. Conformal radiotherapy may therefore constitute a progress comparable to the contribution of high-energy radiotherapy in the 1960s or the impact of computer-assisted dosimetry in the 1970s. Evaluation of the results, definition of its indications, standardisation of practices, and study of the impact of dose escalation require further studies in the field of prostate cancer, as the superiority of this new technique over conventional radiotherapy has not been formally established due to the limited follow-up. PMID:10434334

Hubert, J; Rossi, D; Beckendorf, V

1999-06-01

125

Antenna development at DARPA  

NASA Astrophysics Data System (ADS)

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

Corey, Larry; Jaska, Esko

2004-09-01

126

Deep space antennas  

Microsoft Academic Search

Three 26-m tracking antennas operated by the NASA Deep Space Network at Goldstone, Calif.; Madrid, Spain; and near Canberra, Australia, will cease operations on Dec. 1, 1981. The stations will continue to operate 64-m and 34-m deep space tracking antennas. Ending operation of the 26-m antennas will cause a reduction of about 30%; of the Deep Space Network tracking and

Peter M. Bell

1981-01-01

127

Undersized long backfire antenna  

Microsoft Academic Search

Using an approximate synthesis procedure, a practical undersized backfire antenna (BFA) with a nonuniform corrugated rod structure was developed. Many backfire antenna designs with synthesized corrugated surface-wave rods were manufactured and tested. A comparison between the parameters of two long backfire antennas having the same basic dimensions but differing in the surface-wave (SW) structures (uniform and modulated) is presented. It

H. D. Hristov; G. S. Kirov; J. R. Urumov

1989-01-01

128

Coherently combining antennas  

NASA Technical Reports Server (NTRS)

An apparatus includes antenna elements configured to receive a signal including pseudo-random code, and electronics configured to use the pseudo-random code to determine time delays of signals incident upon the antenna elements and to compensate the signals to coherently combine the antenna elements.

Dybdal, Robert B. (Inventor); Curry, Samuel J. (Inventor)

2009-01-01

129

A Tripolarization Antenna Fed by Proximity Coupling and Probe  

Microsoft Academic Search

The design and characterization of a conformal tripolarization antenna with three independent ports and three orthogonal polarizations is presented. The antenna uses both proximity (slot) coupling and probe-fed ports to reduce isolation and improve polarization purity. The measured bandwidth of the -10-dB return loss is found to be 190 MHz (2.4-2.59 GHz). Measurements across the working bandwidth also show that

Hua Zhong; Zhijun Zhang; Wenhua Chen; Zhenghe Feng; Magdy F. Iskander

2009-01-01

130

Microstrip patch antenna receiving array operating in the Ku band  

NASA Technical Reports Server (NTRS)

Microstrip patch antennas were first investigated from the idea that it would be highly advantageous to fabricate radiating elements (antennas) on the same dielectric substrate as RF circuitry and transmission lines. Other advantages were soon discovered to be its lightweight, low profile, conformability to shaped surfaces, and low manufacturing costs. Unfortunately, these same patches continually exhibit narrow bandwidths, wide beamwidths, and low antenna gain. This thesis will present the design and experimental results of a microstrip patch antenna receiving array operating in the Ku band. An antenna array will be designed in an attempt to improve its performance over a single patch. Most Ku band information signals are either wide band television images or narrow band data and voice channels. An attempt to improve the gain of the array by introducing parasitic patches on top of the array will also be presented in this thesis.

Walcher, Douglas A.

1996-01-01

131

Analysis of a microstrip reflectarray antenna for microspacecraft applications  

NASA Technical Reports Server (NTRS)

A microstrip reflectarray is a flat reflector antenna that can be mounted conformally onto a spacecraft's outside structure without consuming a significant amount of spacecraft volume and mass. For large apertures (2 m or larger), the antenna's reflecting surface, being flat, can be more easily and reliably deployed than a curved parabolic reflector. This article presents the study results on a microstrip reflect-array with circular polarization. Its efficiency and bandwidth characteristics are analyzed. Numerous advantages of this antenna system are discussed. Three new concepts using this microstrip reflectarray are also proposed.

Huang, J.

1995-01-01

132

EVOLUTION OF ANTENNA PERFORMANCE FOR APPLICATIONS IN THERMAL MEDICNE  

PubMed Central

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

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

2013-01-01

133

The ALMA antenna procurement  

NASA Astrophysics Data System (ADS)

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

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

2009-10-01

134

Synthesis of multiple shaped beam antenna patterns  

NASA Technical Reports Server (NTRS)

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

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

1973-01-01

135

A generalized crossed dipole antenna, the Fourtear antenna  

Microsoft Academic Search

A generalized form of a crossed dipole antenna, the Fourtear antenna, has been designed and tested. The Fourtear antenna is a promising dual-polarized broadband antenna element. The antenna consists of four identical teardrop elements, but the horizontal elements are positioned perpendicular to the vertical elements. The radiating element is printed on a dielectric material that is backed with a finite

Seong-Youp Suh; W. Stutzman; W. Davis; A. Waltho; J. Schiffer

2004-01-01

136

Polarization tracking phased array antenna with cross dipole antenna  

Microsoft Academic Search

Conclusions In this paper, a phased array antenna (PAA) using crossed dipole antenna elements is examined. A partially driven array technique is used for the array antenna. From the analyzed results, it is shown that the element antenna has conical radiation pattern. Using the element antenna, the beam scanning characteristics of the PAA is investigated. It is found that this

S. Hasegawa; T. Yasuzumi; O. Hashimoto; Y. Kazama

2009-01-01

137

A Low Profile Dual Band Antenna for Implanted ZigBee Based Biosensors  

Microsoft Academic Search

In this paper, a low profile uniplanar monopole dual band antenna was developed for implanted Zigbee based biosensors. The proposed antenna is consisted of T type monopole radiating part and four rectangular inductive loading spirals structure. The operating resonant frequencies are designed to conform to ZigBee dual bands, 886~924MHz and 2.4~2.45GHz, respectively. While the proposed antenna was immersed in fresh

Chih-Kuang Wu; Tsung-Fu Chien; Hung-Chi Yang; Chien-Min Cheng; Ching-Hsing Luo

2011-01-01

138

Received Voltage Versus Antenna Height  

Microsoft Academic Search

Relative received voltage versus antenna height above ground is a function of field intensity height gain and the height dependent antenna effective length and impedance. The results of an empirical investigation of relative received voltage versus antenna height using typical EMI antennas in the frequency range 2.5 MHz to 1 GHz are presented. In a theoretical analysis field and antenna

ALBERT A. SMITH

1969-01-01

139

Conformal technicolor  

Microsoft Academic Search

We point out that the flavor problem in theories with dynamical electroweak symmetry breaking can be effectively decoupled if the physics above the TeV scale is strongly conformal, and the electroweak order parameter has a scaling dimension d = 1+epsilon with epsilon simeq 1\\/few. There are many restrictions on small values of epsilon: for epsilon << 1, electroweak symmetry breaking

Markus A. Luty; Takemichi Okui

2006-01-01

140

Technique for Solving Electrically Small to Large Structures for Broadband Applications  

NASA Technical Reports Server (NTRS)

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

Jandhyala, Vikram; Chowdhury, Indranil

2011-01-01

141

ALMA Antenna Contract Signed  

NASA Astrophysics Data System (ADS)

On December 6, ESO signed a contract with the consortium led by Alcatel Alenia Space and composed also of European Industrial Engineering (Italy) and MT Aerospace (Germany), to supply 25 antennas for the Atacama Large Millimeter Array (ALMA) project, along with an option for another seven antennas. The contract, worth 147 million euros, covers the design, manufacture, transport and on-site integration of the antennas. It is the largest contract ever signed in ground-based astronomy in Europe.

2005-12-01

142

Cellular Reflectarray Antenna  

NASA Technical Reports Server (NTRS)

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

Romanofsky, Robert R.

2010-01-01

143

MASTER TELEVISION ANTENNA SYSTEM.  

ERIC Educational Resources Information Center

SPECIFICATIONS FOR THE FURNISHING AND INSTALLATION OF TELEVISION MASTER ANTENNA SYSTEMS FOR SECONDARY AND ELEMENTARY SCHOOLS ARE GIVEN. CONTRACTOR REQUIREMENTS, EQUIPMENT, PERFORMANCE STANDARDS, AND FUNCTIONS ARE DESCRIBED. (MS)

Rhode Island State Dept. of Education, Providence.

144

MSU Antenna Pattern Data  

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

145

Installation of T-306 Antenna  

NSF Publications Database

... Installation of T-306 ALE Antenna at Black Island) To: Facilities Engineering Projects Manager, DPP ... Black Island include attaching the HF antennae to an existing rhombic antenna at Black Island ...

146

Stripline Beacon and Telemetry Antenna.  

National Technical Information Service (NTIS)

The major development goal for this antenna was to add an S-band beacon array to an existing S-band telemetry antenna. The resultant antenna was to be flush mounted on a nine inch diameter vehicle. (Author)

A. Waterman D. G. Henry

1976-01-01

147

Compact Fully Overlapping Subarray Antenna.  

National Technical Information Service (NTIS)

This paper describes a new limited scan antenna technique for electronic scanning arrays. The antenna uses a novel coupling network to achieve fully overlapping subarrays with minimal antenna depth. The coupling network is comprised of contraposed input a...

P. A. Valentino J. J. Stangel S. Milazzo

1984-01-01

148

Mm-wave scanning antenna  

US Patent & Trademark Office Database

In general, in one aspect, the disclosure describes a semiconductor antenna having a plurality of antenna elements and a switching network formed in the same semiconductor die. The switching network is to control activation of the antenna elements.

2010-03-23

149

Conformable seal  

DOEpatents

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

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

1982-08-10

150

Conformality lost  

SciTech Connect

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.

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

151

Tapered Direct Fed Quadrifilar Helix Antenna.  

National Technical Information Service (NTIS)

A quadrifilar helical antenna is provided having a feedpoint for the antenna connecting to individual helical antenna elements. Each antenna element tapers from a maximum width at the feedpoint to a minimum width. The tapered antenna elements provide impe...

M. J. Josypenko

2000-01-01

152

Robust Hybrid Finite Element Methods for Antennas and Microwave Circuits.  

National Technical Information Service (NTIS)

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 equ...

J. Gong J. L. Volakis

1996-01-01

153

What's new in antennas?  

Microsoft Academic Search

Innovative designs, novelty, and creative ideas, currently reported in the international antenna literature, are highlighted in the areas of elements, traveling-wave arrays, apertures, arrays, measurements, and material development. Manufacturing and operational aspects are noted and the driving forces identified. The extent to which antenna technology is mature, the role of research, and degrees of design freedom are considered in some

James R. James; Swindon Wilts

1990-01-01

154

Coaxial Horn Antenna System.  

National Technical Information Service (NTIS)

An antenna feed system includes a plurality of RF born antennas (201, 202) for operating on a plurality of RF frequency bands. A first one of the feed horns (202) can have a bore-sight axis and is configured for operating at a first one of the frequency b...

J. A. Kralovec G. K. Gothard T. E. Durham

2003-01-01

155

Deployable Ground Plane Antenna.  

National Technical Information Service (NTIS)

A deployable ground plane antenna for use aboard a satellite or the like, with the antenna and erection mechanism being compactly stowable within the confines of a launch vehicle prior to and during launch thereof is described. After ejection of the satel...

L. Schwerdtfeger

1977-01-01

156

Microstrip Backfire Antenna.  

National Technical Information Service (NTIS)

A microstrip backfire antenna which combines the microstrip type antenna element with a backfire cavity to provide more than three times the gain over a single microstrip element and thereby be capable of replacing four or more elements of a conventional ...

C. M. Kaloi

1982-01-01

157

Backfire bifilar helix antenna  

Microsoft Academic Search

A backfire bifilar helix antenna is disclosed having two helically wound conductors made of coaxial cable wherein the two conductors comprise the shield portion of the cable. The coaxial cable of one of the conductors serves as a transmission line for supplying signals to the feed end of the antenna and has its center conductor connected to the shield of

C. W. Webster

1984-01-01

158

Experiments with Dipole Antennas  

ERIC Educational Resources Information Center

Employment of a data-acquisition system for data collection and calculations makes experiments with antennas more convenient and less time consuming. The determined directional patterns of the dipole antennas of different lengths are in reasonable agreement with theory. The enhancement of the signal by using a reflector is demonstrated, and a…

Kraftmakher, Yaakov

2009-01-01

159

Deformations in VLBI antennas  

NASA Technical Reports Server (NTRS)

A study is presented of deformations in antennas with the emphasis on their influence on VLBI measurements. The GIFTS structural analysis program has been used to model the VLBI antenna in Fairbanks (Alaska). The report identifies key deformations and studies the effect of gravity, wind, and temperature. Estimates of expected deformations are given.

Clark, T. A.; Thomsen, P.

1988-01-01

160

Satellite horn antennas design  

Microsoft Academic Search

Telecommunication satellite horn antennas require now-a-days more and more stringent requirements based mainly in the increased bandwidth necessary to accommodate more transponders to increase the capacity of the new satellite services. In this aspect horn antennas play a key role in the development of wider bandwidth services on board satellites because they are usually the reason that limits bandwidth in

Jorge Teniente; Ramón Gonzalo; Carlos del Río

2009-01-01

161

Multibeam satellite antenna design  

Microsoft Academic Search

This paper describes the antenna design of the multi-beam for communication satellites. The paper deals with a method to determine design core parameters of optimal antenna diameter, feed horn type and horn size, F\\/D, and the coordinate of offset horns, and the performance of the design results.

Jeom-Hun Lee

2005-01-01

162

Yagi Antenna Design.  

National Technical Information Service (NTIS)

The report presents data, using modeling techniques, for the optimum design of different length Yagi antennas. This information is presented in graphical form to facilitate the design of practical length antennas--from 0.2 wavelength to 4.2 wavelengths lo...

P. P. Viezbicke

1976-01-01

163

Antenna design simplified  

NASA Astrophysics Data System (ADS)

A 73% cost saving is reported for the manufacture of an RF antenna for the detection of plastic and metallic mines, through the fabrication of its antenna/septum assembly by either the rotational molding of FRP or plastic thermoforming of an aluminum-base zinc alloy sheet. These procedures were chosen after consideration of roll forming, hydroforming, stamping, and plastic injection molding.

Origlio, G. F.

164

Types of Antennae  

NSDL National Science Digital Library

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

165

Radiation by cavity-backed antennas on a circular cylinder  

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

166

Terahertz antenna based on graphene  

NASA Astrophysics Data System (ADS)

We have investigated several configurations of antennas based on graphene. We show that patterned metallic dipole antennas or arrays of dipole antennas deposited on graphene highly benefit from the reversible high-resistivity-to-low-resistivity transition in graphene, tuned by a gate voltage. The radiation pattern and the efficiency of such antennas are changed via the gate voltage applied on graphene.

Dragoman, M.; Muller, A. A.; Dragoman, D.; Coccetti, F.; Plana, R.

2010-05-01

167

RF MEMS Based Reconfigurable Antennas  

NASA Technical Reports Server (NTRS)

The presentation will first of all address the advantages of RF MEMS circuit in antenna applications and also the need for electronically reconfigurable antennas. Next, discuss some of the recent examples of RF MEMS based reconfigurable microstrip antennas. Finally, conclude the talk with a summary of MEMS antenna performance.

Simons, Rainee N.

2004-01-01

168

Platform tolerant RFID tag antenna  

Microsoft Academic Search

A passive radio-frequency identification (RFID) tag antenna for UHF applications is proposed. An inductively coupled feed for the tag, employed previously in an earlier design, is modified to realize a new RFID tag antenna. A ground plane is used in the design to make the tag antenna platform-tolerant. The read range and percentage power transfer of the tag antenna are

Y. C; K. W. Leung; R. Mittra; K. V. S. Rao

2007-01-01

169

Terahertz antenna based on graphene  

Microsoft Academic Search

We have investigated several configurations of antennas based on graphene. We show that patterned metallic dipole antennas or arrays of dipole antennas deposited on graphene highly benefit from the reversible high-resistivity-to-low-resistivity transition in graphene, tuned by a gate voltage. The radiation pattern and the efficiency of such antennas are changed via the gate voltage applied on graphene.

M. Dragoman; A. A. Muller; D. Dragoman; F. Coccetti; R. Plana

2010-01-01

170

Autonomous omnidirectional spacecraft antenna system  

NASA Technical Reports Server (NTRS)

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.

Taylor, T. H.

1983-01-01

171

SPS antenna pointing control  

NASA Technical Reports Server (NTRS)

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

Hung, J. C.

1980-01-01

172

Magneto-Dielectric Wire Antennas Theory and Design  

NASA Astrophysics Data System (ADS)

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

Sebastian, Tom

173

NASA technology for large space antennas  

NASA Technical Reports Server (NTRS)

Some leading concepts for deployable antennas are described and an assessment of the state of the art in deployable antennas is presented. The advanced sunflower precision antenna, the radial rib antenna and the maypole (hoop/column) antenna, the wrap rib antenna and the parabolic erectable truss antenna are covered. In addition, a discussion on the technology development program for two deployable antenna concepts that are responsive to the antenna mission requirements as defined in the NASA mission model is presented.

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

1980-01-01

174

Shaped single reflector offset antenna with low cross-polarization fed by a lens horn  

NASA Astrophysics Data System (ADS)

A novel compact primary-fed offset reflector antenna with the potential of radiating circular as well as elliptical beams with low cross-polarization, is proposed. The reflector is fed by a horn with a phase-correcting lens in the aperture. Compared to the dual-reflector offset antenna, the concept is easier to assemble and mechanically more robust. The antenna has been synthesized and analyzed by computer programs resulting from modifications of corresponding PO programs for dual-reflector offset antennas. The synthesized antenna exhibits similar cross-polarization, side-lobe level, and aperture efficiency as those of dual-reflector offset antennas, although the one-to-one correspondence between zero cross-polarization and conformal mapping from the feed to the aperture, is not exactly valid for this approach.

Lier, Erik; Skyttemyr, Svein A.

1994-04-01

175

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

NASA Technical Reports Server (NTRS)

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.

Myhre, R. W.

1979-01-01

176

Antenna pattern study  

NASA Technical Reports Server (NTRS)

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.

Harper, Warren

1988-01-01

177

Telemetry Ring Antenna.  

National Technical Information Service (NTIS)

A quarter-wavelength ring antenna was developed to telemeter active fuzes in flight with a minimum modification to fuze or artillery round. Using principles of strip transmission line theory, general design criteria were established to maximize radiation ...

H. Bassen R. Jantz

1966-01-01

178

Lightweight Antenna Techniques.  

National Technical Information Service (NTIS)

The report presents results of a study to determine the feasibility of constructing a very lightweight, highly-transportable, efficient, high-gain satellite communications antenna system subject to certain design specifications. In the first part of the r...

E. N. Schopke L. Pietsch M. L. Livingston R. E. Moseley

1967-01-01

179

Coaxial phased array antenna  

NASA Technical Reports Server (NTRS)

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.

Ellis, H., Jr. (inventor)

1980-01-01

180

ACTS Multibeam Antenna.  

National Technical Information Service (NTIS)

The Advanced Communications Technology Satellite (ACTS) to be launched in 1993 introduces several new technologies including a multibeam antenna (MBA) operating at Ka-band. The satellite is introduced briefly, and then the MBA, consisting of electrically ...

F. A. Regier

1992-01-01

181

Microwave antenna holography  

NASA Technical Reports Server (NTRS)

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

Rochblatt, David J.; Seidel, Boris L.

1992-01-01

182

MLS airborne antenna research  

NASA Technical Reports Server (NTRS)

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.

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

1975-01-01

183

Vehicle antenna on AMC  

Microsoft Academic Search

In this paper a novel dual band EBG based on the conventional double square patch EBG but with more band flexibility is presented combined with a small antenna aimed at the automotive market where antennas may be placed on the metal bodywork. Multifrequency band flexibility for the UMTS 1.9 GHz band, WLAN 2.45 GHz band, WiFi at 5.15 GHz and

Nisar Ahmad Abbasi; Richard Langley

2010-01-01

184

A Metamaterial Inspired Compact Patch Antenna with Frequency Continuously Reconfigurable Performance for Cognitive Radio  

NASA Astrophysics Data System (ADS)

A new rectangular cavity loaded with metamaterial structure is proposed. Its properties of resonant frequency and the distributing of near field are analyzed. Simulated results show that it not only can resonate at subwavelength but that it has also a good radiation feature used as antenna. The speciality that the resonant frequency will change with different value of negative permeability enlightens us to design a frequency continuously reconfigurable antenna for cognitive radio instead of conventional methods used MEMS to reconfigure the shape of radiator. SRRs integer with capacity and varactor diode are used to realize changing mu-negative material by controlling the voltage. According to the near field magnetic orientation, a proper alignment is chosen. At last, a simple antenna is designed. Dimensions of this antenna are very small compared to resonant wavelength (about 10%) and its frequency can be reconfigured continuously in a broadband from 342MHz to 463 MHz. Radiation patterns of the antenna are stable and the maximum gain is above 0 dBi in all operation bands. This may indeed open interesting venues for the design of electric small antennas with continuous frequency reconfigurable performance.

Shoujun, Zhao; Zuping, Qian; Guohong, Zhao; Xiaohong, Jiang; Dongqian, Lv

2011-03-01

185

47 CFR 73.753 - Antenna systems.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Antenna systems. 73.753 Section 73.753...International Broadcast Stations § 73.753 Antenna systems. All international broadcasting stations shall operate with directional antennas. Such antennas shall be...

2013-10-01

186

View of Antenna #1 (foreground), and Antenna #2 surface doors. ...  

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

View of Antenna #1 (foreground), and Antenna #2 surface doors. Image looking northeast - Titan One Missile Complex 2A, .3 miles west of 129 Road and 1.5 miles north of County Line Road, Aurora, Adams County, CO

187

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

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

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

188

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

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

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

189

Cup Cylindrical Waveguide Antenna  

NASA Technical Reports Server (NTRS)

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

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

2008-01-01

190

Industrial Plasma Antennas  

NASA Astrophysics Data System (ADS)

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.

Alexeff, Igor

2007-11-01

191

Aperture excited dielectric antennas  

NASA Technical Reports Server (NTRS)

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

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

1974-01-01

192

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

NASA Astrophysics Data System (ADS)

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

Mazady, Md. Anas Boksh

193

Antennas made simple: making antennas with recycled materials  

Microsoft Academic Search

The fabrication of antennas with recycled materials but with good performance is possible by using the classical formulation from textbooks. Several antenna designs built with materials found at home are shown, and their performance is measured with professional equipment to assess an acceptable agreement between simulations and measurements. Practical design and fabrication of antennas made with used materials and operating

H. Martinez; J. M. Gonzalez-Arbesu; S. Blanch

2004-01-01

194

View of antenna tunnel end. Right to Antenna Silo #1, ...  

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

View of antenna tunnel end. Right to Antenna Silo #1, left to Antenna Silo #2 - Titan One Missile Complex 2A, .3 miles west of 129 Road and 1.5 miles north of County Line Road, Aurora, Adams County, CO

195

RESEARCH ARTICLE Optical antennas and plasmonics  

Microsoft Academic Search

Optical antenna is a nanoscale miniaturization of radio or microwave antennas that is also governed by the rule of plasmonics. We introduce various types of optical antenna and make an overview of recent developments in optical antenna research. The role of local and surface plasmons in optical antenna is explained through antenna resonance and resonance conditions for specific metal structures

Q-Han Park

196

Hemispheric ultra-wideband antenna.  

SciTech Connect

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.

Brocato, Robert Wesley

2006-04-01

197

Antenna Radome Sample Test Report.  

National Technical Information Service (NTIS)

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 ...

L. H. Baker T. D. Bratton

1991-01-01

198

Low Profile Circularly Polarized Antenna.  

National Technical Information Service (NTIS)

A low profile antenna assembly is described for communicating electromagnetic radiation. In a particular embodiment shown, a microstrip assembly is formed with an antenna element provided in the shape of an elliptical lamina. The location of the feed poin...

I. P. Yu

1977-01-01

199

The grid array antenna  

NASA Technical Reports Server (NTRS)

Attention is called to the grid array as a possible useful antenna design for UHF clear air radars. This type of antenna integrates radiating elements and the feed network into a single structure so that a fairly large array can be driven from a single feed point. Figures are given which demonstrate the basic principle of the grid array, which are adapted from Conti et al. (1981). Conductors are arranged above a ground plane in a repeating, staggered array of connected rectangles. Each rectangular element is approximately one by one-half wavelength in size. The currents on the conductors at resonance is indicated. The grid array illustrated can be expanded in both vertical and horizontal directions about the feed point by adding additional rectangular conductors. The design eliminates the feed network and would provide a thin, panel-like antenna that could be easily built and transported.

Ecklund, W. L.

1986-01-01

200

A 96-antenna radioheliograph  

NASA Astrophysics Data System (ADS)

Here we briefly present some design approaches for a multifrequency 96-antenna radioheliograph. The configuration of the array antenna, transmission lines and digital receivers is the main focus of this work. The radioheliograph is a T-shaped centrally condensed radiointerferometer operating in the frequency range 4–8 GHz. The justification for the choice of such a configuration is discussed. The signals from antennas are transmitted to a workroom by analog optical links. The dynamic range and phase errors of the microwave-over-optical signal are considered. The signals after downconverting are processed by digital receivers for delay tracking and fringe stopping. The required step of delay tracking and data rates are considered. Two 3-bit data streams (I and Q) are transmitted to a correlator with the transceivers embedded in Field Programmed Gate Array chips and with PCI Express cables.

Lesovoi, Sergey V.; Altyntsev, Alexander T.; Ivanov, Eugene F.; Gubin, Alexey V.

2014-07-01

201

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

NASA Technical Reports Server (NTRS)

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.

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

1989-01-01

202

Time-domain antenna characterizations  

Microsoft Academic Search

A set of time-domain characterizations that can efficiently describe wireband antennas is proposed. The experimentally measured responses of transverse electromagnetic horn antennas are used to evaluate the utility of these characterizations. Comparisons are made between the antennas' frequency-domain response and their time-domain characterizations. The comparisons show that the time-domain characterizations can provide significant insight into an antenna's behavior as well

Oliver E. Allen; David A. Hill; Arthur R. Ondrejka

1993-01-01

203

An active downlink photonic antenna  

Microsoft Academic Search

This paper presents an active photonic antenna concept whereby an interface circuit is introduced in order to integrate the antenna with the photodiode. The operating frequencies ranges are 1.8 to 3.5 GHz which support the GSM 1800, WLAN and WiMAX applications. The simulated and measured results of interface circuit and antenna are presented. Thus, the photonic antenna is developed by

N. F. Nanyan; R. Ngah; T. Prakoso; Y. Rahayu; T. A. Rahman

2010-01-01

204

DSN microwave antenna holography  

NASA Technical Reports Server (NTRS)

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

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

1984-01-01

205

Anechoic chamber wideband antenna measurements  

Microsoft Academic Search

The method is considered which consists of measurements of output antenna signals on a number of frequencies and Fourier transformation of data into time domain for separation of own antenna field and interference fields. The results of testing at serial facility for antenna measurements in an anechoic chamber are presented as for diagnosis of scattered fields, as for improvement of

A. V. Kalinin

2006-01-01

206

Antenna diversity in mobile communications  

Microsoft Academic Search

The conditions for antenna diversity action are investigated. In terms of the fields, a condition is shown to be that the incident field and the far field of the diversity antenna should obey (or nearly obey) an orthogonality relationship. The role of mutual coupling is central, and it is different from that in a conventional array antenna. In terms of

R. G. Vaughan; J. B. Andersen

1987-01-01

207

Parametric Modeling of Ultrawideband Antennas  

Microsoft Academic Search

Compared to narrowband antennas, ultrawideband (UWB) antennas have particular characteristics which involve new ways to model them. This paper introduces the use of parametric modeling to efficiently model transfer functions (and associated impulse responses) of UWB antennas, and to determine an equivalent circuit of their input impedance.

Y. Duroc; A. Ghiotto; T. P. Vuong; S. Tedjini

2007-01-01

208

The JPL mechanically steered antenna  

NASA Technical Reports Server (NTRS)

The Jet Propulsion Laboratory has designed and developed a mechanically steered antenna for tracking satellites in a mobile environment. This antenna was used to track an L-band beacon on the MARISAT satellite. A description of the antenna and the results of the satellite experiment are given.

Berner, Jeff B.; Bell, David J.

1988-01-01

209

Low-sidelobe radar antennas  

NASA Astrophysics Data System (ADS)

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

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

1983-07-01

210

Quartz antenna with hollow conductor  

DOEpatents

A radio frequency (RF) antenna for plasma ion sources is formed of a hollow metal conductor tube disposed within a glass tube. The hollow metal tubular conductor has an internal flow channel so that there will be no coolant leakage if the outer glass tube of the antenna breaks. A portion of the RF antenna is formed into a coil; the antenna is used for inductively coupling RF power to a plasma in an ion source chamber. The antenna is made by first inserting the metal tube inside the glass tube, and then forming the glass/metal composite tube into the desired coil shape.

Leung, Ka-Ngo (Hercules, CA); Benabou, Elie (Alameda, CA)

2002-01-01

211

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

NASA Technical Reports Server (NTRS)

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.

Haddad, H. A.

1948-01-01

212

Microstrip backfire antenna  

NASA Technical Reports Server (NTRS)

Microstrip resonator is improvement over dipole-fed waveguide-fed backfire designs. Advantages include simpler construction with reduction in weight and size over other backfire designs. Microstrip backfire concept has potential in dual-polarization antenna systems, array-thinning designs, and feed designs for larger parabolic reflectors.

Campbell, T. G.; Cohen, N. V.

1978-01-01

213

Modified Short Backfire Antenna.  

National Technical Information Service (NTIS)

Measurements have shown it possible to increase the gain of the short backfire antenna significantly in different ways: (1) By increasing the size of the reflectors. (2) By placing extra reflectors in multiples of a half wavelength from the surface wave r...

F. A. Hass

1971-01-01

214

Compact antenna range analysis  

Microsoft Academic Search

This preliminary design study (methodology investigation) established the feasibility and cost of the reflector for an outdoor compact range with 50 foot diameter quiet zone. The U.S. Army at Ft. Huachuca, Arizona would use the range to measure patterns of microwave antennas mounted on vehicles and aircraft. Considerations included reflector configuration, size, focal length, surface accuracy, edge treatment, feed, quiet

R. W. Moody; O. D. Asbell; E. B. Joy

1986-01-01

215

Community Antenna Television (CATV).  

ERIC Educational Resources Information Center

The number of households hooked up to cable television or community antenna television (CATV) is expanding rapidly, and Federal Communications Commission (FCC) has been developing regulations since 1962 to guide the growth of the industry. By 1965 the FCC had claimed jurisdiction over all CATV systems in the U. S. This jurisdiction was challenged…

Federal Communications Commission, Washington, DC.

216

Antenna Deployment Mechanism.  

National Technical Information Service (NTIS)

A mechanism is described for the powered deployment of an antenna mast on a spacecraft or the like, and for caging or latching the mast in a retracted position. A redundant drive rotates a drum to reel in a cable for deploying a multi-section telescoping ...

W. A. Leavy C. R. Griffin

1978-01-01

217

Multiplate Antenna Feed.  

National Technical Information Service (NTIS)

The report describes the design of a multiplate antenna feed system which consists of tower- and ground-mounted equipment. The feed illuminates each of four elliptical multiplate apertures on the ground, producing a single beam on transmit, and a square c...

S. Milazzo J. Lory C. Rothenberg J. Kearney

1964-01-01

218

Switched fragmented aperture antennas  

Microsoft Academic Search

This paper introduces a reconfigurable aperture concept derived from fragmented aperture design where the configuration of the fragmented aperture may be switched by the user to obtain different functionalities. A fragmented aperture antenna is a patchwork of discrete conducting and dielectric units distributed over the specified aperture. The arrangement of the units is determined using an efficient, multistage procedure that

James C. Maloney; Morris P. Kesler; Lisa M. Lust; Lon N. Pringle; T. Lynn Fountain; Paul H. Harms; Glenn S. Smith

2000-01-01

219

Multi-Purpose Antenna.  

National Technical Information Service (NTIS)

A description is given of a microwave antenna, useful on a spacecraft, which utilizes a single dish reflector and single coaxial horn structure to transmit at two frequencies, and to receive signals at a third frequency that allow tracking. The horn struc...

K. E. Woo

1970-01-01

220

TV Transmitting Antenna Selection  

Microsoft Academic Search

In the selection of a transmitting antenna, factors such as power gain, height above terrain, horizontal pattern directivity, amount of null fill, and beam tilt of the vertical pattern have to be taken into consideration to best satisfy the equipment availability and intended market coverage. A critical analysis of all these factors with possible tradeoffs is presented and the station

Jose Perini

1969-01-01

221

System design and performance of a wideband photonic array antenna  

NASA Astrophysics Data System (ADS)

Presented in this paper is an overview of the development of a wideband photonic array antenna. The presentation will focus on the performance of a unique L-band 24 X 4 element conformal array, supported by a photonic true-time-delay beamforming network. A 2-ns pulse was injected into the system and the round trip impulse response was measured to demonstrate the array's 550 MHz instantaneous bandwidth.

Lee, J. J.; Livingston, Stan; Loo, Robert Y.; Jones, V. L.; Foster, C.; Yen, Huan-Wun; Tangonan, Gregory L.

1994-06-01

222

Mobile terminal antennas for helicopters  

NASA Astrophysics Data System (ADS)

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

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

223

Printed Monopole Slot Antenna for Internal Multiband Mobile Phone Antenna  

Microsoft Academic Search

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

Chun-I. Lin; Kin-Lu Wong

2007-01-01

224

Design of Short Backfire Antennas [Antenna Designer's Notebook  

Microsoft Academic Search

The design proposed in this article is dedicated to short backfire antennas fed by a dipole or a crossed dipole. The studies were carried out with different types of short backfire antennas. The directivity of the antennas designed ranged between 12 and 20.5 dB, The presented design procedure may be very useful for the creation of high-efficiency and compact microwave

G. S. Kirov

2009-01-01

225

Miniatured annular ring loaded patch antennas  

Microsoft Academic Search

The proliferation of wireless communication systems has promoted the development of miniaturized antenna designs. Annular ring patch antennas are reported to reduce antenna size. In this paper, several novel compact probe-fed annular-ring microstrip patch antennas are presented. In order to reduce the antenna size and provide a suitable input impedance match, two techniques are employed; the insertion of strips into

Max Ammann; Xiulong Bao

2007-01-01

226

Backfire antennas with conical dielectric structures  

Microsoft Academic Search

A theoretical analysis is presented of a multimode backfire antenna with conical dielectric waveguide, with particular attention given to the radiation pattern of the antenna. Experimental results are presented on a multimode backfire antenna, designed for the feeding of small reflector antennas. It is found that the use of a backfire feed enables the attainment of a reflector-antenna gain coefficient

N. A. Bei; V. N. Mitrokhin

1978-01-01

227

JPL Large Advanced Antenna Station Array Study  

NASA Technical Reports Server (NTRS)

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.

1978-01-01

228

Wideband slotted patch antennas using EBG structures  

Microsoft Academic Search

A slotted microstrip patch antenna is designed with Electromagnetic Band gap (EBG) structures. The performance parameters of the presented antenna are then compared with the conventional patch antenna. It is realized that there is a significant increase of bandwidth and better suppression of harmonics than the normal patch antenna. This antenna is thus operating in the frequency band 5 -

Utsav Chandra; H. F. AbuTarboush; H. S. Al-Raweshidy; R. Nilavalan

2010-01-01

229

Optical antennas for nano-photonic applications  

Microsoft Academic Search

Antenna-coupled optical detectors, also named optical antennas, are being developed and proposed as alternative detection devices for the millimetre, infrared, and visible spectra. Optical and infrared antennas represent a class of optical components that couple electromagnetic radiation in the visible and infrared wavelengths in the same way as radioelectric antennas do at the corresponding wavelengths. The size of optical antennas

Javier Alda; José M Rico-García; José M López-Alonso; G Boreman

2005-01-01

230

Balanced backfire zigzag antennas  

Microsoft Academic Search

Linearly polarized backfire antennas are described which have high front-to-back ratio and very low sidelobes. The backfire radiation is produced from a meandering conductor. The principal directional characteristics can be determined by using linear array theory. When the conductor is periodic this can be related to a series expansion of the fields in space harmonics. A simple first-order theory for

P. Mayes

1964-01-01

231

A New Backfire Antenna  

Microsoft Academic Search

Measurements have shown that it is possible to increase the gain of the short backfire antenna significantly in different ways: 1.By increasing the size of the reflectors. 2.By placing extra reflectors in multiples of a half wave-length from the surface wave reflector. 3.By placing a quarter-wave ring in front of the surface wave reflector. The surface of the ring is

F. A. Hass

1971-01-01

232

Two advanced solar antenna \\  

Microsoft Academic Search

A novel hybrid technology where amorphous silicon (a-Si:H) solar cells are either integrated or physically combined with printed slot antennas is presented. This basic idea is demonstrated with the help of two innovative designs where the solar cells are directly grown on a stainless steel ground-plane or glued onto a standard copper layer printed on a dielectric substrate. To show

Stefano Vaccaro; Juan R. Mosig; Peter de Maagt

2003-01-01

233

Antenna axis drive torques for the 70-meter antenna  

NASA Technical Reports Server (NTRS)

Antenna axis speeds versus wind speeds are given in terms of dish size, hydraulic motor size, and the number of servo valves. An increase in the dish diameter of antenna is usually accompanied by increases in the axis torques required to drive the antenna against wind. The proposed increase in the diameters of the 64-m antenna dishes to 70 m (plus a noise shield) does require increased axis torques. The increased dish diameter causes the maximum azimuth and elevation torques to increase 48% and 43% respectively.

Mcginness, H. D.

1985-01-01

234

Numerical evaluation of antenna noise temperature for optimal reflector antenna designs  

Microsoft Academic Search

Antenna noise temperature is crucial to an optimal antenna design. In this paper a systematic evaluation of the antenna noise temperature for arbitrary antenna pointing angles and noise temperature profiles is presented. Its numerical implementation is discussed. Simulation results of a single offset reflector and an offset Gregorian antenna are used to validate the effectiveness in the antenna design phase.

Shenheng Xu; Yahya Rahmat-Samii

2011-01-01

235

Novel Ka-band microstrip antenna fed circular polarized horn array antenna  

Microsoft Academic Search

This paper introduces a novel microstrip antenna fed circular polarized array antenna composed of 8-element horn antennas. This horn can be divided into two parts, microstrip antenna and square horn. The microstrip antenna has the role of feeder and polarizer of the horn antenna, and it is designed for stacked type having a metal spacer for high gain, high isolation

Young-Bae Jung; Soon-Young Eom; Soon-Ik Jeon; Chang-Joo Kim

2004-01-01

236

Helicopter Rotor Antenna  

NASA Technical Reports Server (NTRS)

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.

Pogorzelski, Ronald J.; Cable, Vaughn P.

2001-01-01

237

The ACTS multibeam antenna  

NASA Technical Reports Server (NTRS)

The Advanced Communications Technology Satellite (ACTS) to be launched in 1993 introduces several new technologies including a multibeam antenna (MBA) operating at Ka-band. The satellite is introduced briefly, and then the MBA, consisting of electrically similar 30 GHz received and 20 GHz transmit offset Cassegrain systems utilizing orthogonal linear polarizations, is described. Dual polarization is achieved by using one feed assembly for each polarization in conjunction with nested front and back subreflectors, the gridded front subreflector acting as a window for one polarization and a reflector for the other. The antennas produce spot beams with approximately 0.3 deg beamwidth and gains of approximately 50 dbi. High surface accuracy and high edge taper produce low sidelobe levels and high cross-polarization isolation. A brief description is given of several Ka-band components fabricated for ACTS. These include multiflare antenna feedhorns, beam-forming networks utilizing latching ferrite waveguide switches, a 30 GHz high mobility electron transmitter (HEMT) low-noise amplifier and a 20 GHz TWT power amplifier.

Regier, Frank A.

1992-01-01

238

Modular antenna design study  

NASA Technical Reports Server (NTRS)

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

Ribble, J. W.

1981-01-01

239

Antenna structure with distributed strip  

DOEpatents

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

Rodenbeck, Christopher T. (Albuquerque, NM)

2008-10-21

240

Antenna Calibration and Measurement Equipment  

NASA Technical Reports Server (NTRS)

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.

Rochblatt, David J.; Cortes, Manuel Vazquez

2012-01-01

241

Antenna structure with distributed strip  

DOEpatents

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

Rodenbeck, Christopher T. (Albuquerque, NM)

2008-03-18

242

Efficient Placement of Directional Antennas  

SciTech Connect

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.

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

2010-09-20

243

On conformal biharmonic immersions  

Microsoft Academic Search

This paper studies conformal biharmonic immersions. We first study the transformations of Jacobi operator and the bitension\\u000a field under conformal change of metrics. We then obtain an invariant equation for a conformal biharmonic immersion of a surface\\u000a into Euclidean 3-space. As applications, we construct a two-parameter family of non-minimal conformal biharmonic immersions\\u000a of cylinder into $${\\\\mathbb{R}^3}$$ and some examples of

Ye-Lin Ou

2009-01-01

244

Deployable antenna phase A study  

NASA Technical Reports Server (NTRS)

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.

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

1979-01-01

245

MEMS-switched reconfigurable antennas  

Microsoft Academic Search

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

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

2001-01-01

246

Hemispherical coverage antenna for spacecraft  

NASA Astrophysics Data System (ADS)

A hemispherical-coverage antenna for spacecraft is described. The antenna has excellent impedance, axial ratio, and gain characteristics over a + or - 10-percent frequency bandwidth. This type of antenna is applicable to telemetry and control for spacecraft, missiles, aircraft, Inmarsat small terminals for ships and boats, and M-sat ground terminals in cars and satellite systems, where high efficiency performance of hemispherical radiation is required.

Kumar, A.

1988-05-01

247

Simulation of conformational transitions  

Microsoft Academic Search

Conformational transitions are essential for the functioning of many proteins, and understanding this dynamical behavior is a central goal in molecular biology. Computer simulations are playing an important role towards this aim by providing insights into how the conformational changes are induced, propagated and used. Popular methods for the simulation of conformational transitions will be reviewed, with a focus on

Arjan van der Vaart

2006-01-01

248

Metamaterial-based "sabre" antenna  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

249

Detecting Deformations in Phased-Array Antennas  

NASA Technical Reports Server (NTRS)

Doppler technique detects deformation of large phased array radar antenna. Antenna electrically split into subarrays; individual phases measured when examination of antenna stability and provides information for correcting deformation.

Li, F. K.; Held, D. N.

1984-01-01

250

Large Space Antenna Systems Technology, 1984  

NASA Technical Reports Server (NTRS)

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

Boyer, W. J. (compiler)

1985-01-01

251

Vlasov Antenna Data for Electromagnetic Code Validation.  

National Technical Information Service (NTIS)

Measured antenna data is provided for validating computational electromagnetic (CEM) computer programs. The subject antenna is the Vlasov antenna, which is formed by cutting a hollow circular cylindrical waveguide at an oblique angle. Measurements are sho...

A. Greenwood K. Hendricks

2003-01-01

252

Out of Band Performance of Antennas.  

National Technical Information Service (NTIS)

The out of band performance of antennas is considered. The types covered are cylindrical, biconical, horn and parabolic antennas. Both measured and theoretical data are presented. The antenna parameters covered are radiation and input impedances, gain, an...

W. R. Lind

1965-01-01

253

47 CFR 15.317 - Antenna requirement.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Antenna requirement. 15.317 Section 15...Communications Service Devices § 15.317 Antenna requirement. An unlicensed PCS device must meet the antenna requirement of §...

2013-10-01

254

47 CFR 73.1680 - Emergency antennas.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Emergency antennas. 73.1680 Section 73.1680 Telecommunication...Broadcast Stations § 73.1680 Emergency antennas. (a) An emergency antenna is one that is erected for temporary use...

2013-10-01

255

47 CFR 73.816 - Antennas.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Antennas. 73.816 Section 73.816 Telecommunication...Broadcast Stations (LPFM) § 73.816 Antennas. (a) Permittees and licensees may employ nondirectional antennas with horizontal only...

2013-10-01

256

Ferrite attenuator modulation improves antenna performance  

NASA Technical Reports Server (NTRS)

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.

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

1970-01-01

257

Microelectromechanical Systems Actuator Based Reconfigurable Printed Antenna  

NASA Technical Reports Server (NTRS)

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

Simons, Rainee N. (Inventor)

2005-01-01

258

Millimeter and submillimeter wave antenna structure  

NASA Technical Reports Server (NTRS)

An integrated circuit antenna structure for transmitting or receiving millimeter and/or submillimeter wave radiation having an antenna relatively unimpaired by the antenna mounting arrangment is disclosed herein. The antenna structure of the present invention includes a horn disposed on a substrate for focusing electromagnetic energy with respect to an antenna. The antenna is suspended relative to the horn to receive or transmit the electromagnetic energy focused thereby.

Rebiez, Gabriel M. (Inventor); Rutledge, David B. (Inventor)

1989-01-01

259

Time-domain three antenna method for biconical antenna  

Microsoft Academic Search

We apply our proposed method for evaluating the free-space antenna factor of a Biconical antenna. The method is based on the techniques of a time domain analysis and a pulse compression technique. The method enables us to isolate the direct wave from the reflected waves on the ground plane in an open area test site, and to evaluate the free-space

Satoru Kurokawa; Michitaka Ameya; Masanobu Hirose

2010-01-01

260

Random Antenna Selection & Antenna Swapping Combined with OSTBCs  

Microsoft Academic Search

This paper proposes a novel and efficient iterative antenna selection algorithm based on an SNR selection criterion for a multi-input-multi-output (MIMO) system employing orthogonal space time block codes (OST- BCs), specifically Alamouti codes. The proposed algorithm addresses the open problem of finding a suboptimal set of transmit and receive antennas that performs close to the globally optimum configuration selection solution

Hani Mehrpouyan; Steven D. Blostein; Edmund C. Y. Tam

2009-01-01

261

Random Antenna Selection & Antenna Swapping Combined with OSTBCs  

Microsoft Academic Search

This paper proposes a novel and efficient iterative antenna selection algorithm based on an SNR selection criterion for a multi-input-multi-output (MIMO) system employing orthogonal space time block codes (OSTBCs), specifically Alamouti codes. The proposed algorithm addresses the open problem of finding a suboptimal set of transmit and receive antennas that performs close to the globally optimum configuration selection solution at

Hani Mehrpouyan; Steven D. Blostein; Edmund C. Y. Tam

2007-01-01

262

The software defined antenna: Microstrip antennas with gaps  

Microsoft Academic Search

The goal of this research is to develop an unconstrained reconfigurable programmable array antenna. The concept is to build microstrip patch antenna arrays using individual controllable pixels. A 16 by 16 array of mechanically actuated pixels has been constructed. Air gaps exist in the ground plane, substrate, and conductor layer. This prototype is controlled through software to build an array

Eugene Y. Lee; E. K. Walton; Jon Young; Steve Gemeny; Teh-hong Lee; Nathen Roberts; Evan Bosso; Eduard Huang

2010-01-01

263

View of Antenna #1 (foreground), and Antenna #2 surface doors. ...  

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

View of Antenna #1 (foreground), and Antenna #2 surface doors. Orientation Target #2 in background. Image looking northeast - Titan One Missile Complex 2A, .3 miles west of 129 Road and 1.5 miles north of County Line Road, Aurora, Adams County, CO

264

View of Antenna #2 (foreground), and Antenna #1 surface doors. ...  

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

View of Antenna #2 (foreground), and Antenna #1 surface doors. Orientation Target #1 in background. Image looking northwest - Titan One Missile Complex 2A, .3 miles west of 129 Road and 1.5 miles north of County Line Road, Aurora, Adams County, CO

265

Reconfigurable Antenna and RF Circuits Using Multi-Layer Stretchable Conductors  

Microsoft Academic Search

The growth of flexible electronics industry has given rise to light-weight, flexible devices which have a wide range of applications such as wearable electronics, flexible sensors, conformal antennas, bio-medical applications, solar cells etc. Though several techniques exist to fabricate flexible devices, the limiting factors have been durability, cost and complexity of the approach. In this research, the focus has been

Riaz Ahmed Liyakath

2012-01-01

266

Design and Optimization of Broadband High Impedance Ground Planes (HIGP) for Surface Mount Antennas.  

National Technical Information Service (NTIS)

Gain and bandwidth metrics of broad-band low-profile antennas severely deteriorate when they are placed conformally onto the conductive skins of air, sea, and ground platforms. This detrimental effect is primarily due to out-of-phase reflections from the ...

M. Dogrul

2008-01-01

267

High temperature permittivity measurements of Alumina Enhanced Thermal Barrier (AETB-8) material for CEV antenna radomes  

Microsoft Academic Search

Alumina Enhanced Thermal Barrier (AEBT-8) material is currently being considered as a potential radome material for phased array antennas that will be conformally mounted to the outer surface of NASA's Orion Crew Exploration Vehicle. Accordingly, there is a need to establish if the dielectric properties of the AEBT-8 material change as a function of temperature. In this paper we discuss

C. H. Mueller; F. A. Miranda

2010-01-01

268

Tolerance theory of large antennas  

Microsoft Academic Search

The design of an antenna calls for definite amplitudes and phases of the currents, but when the antenna has been constructed and adjusted, there will be departures from the design currents because of several factors. The customary procedure of taking radiation patterns and making the final adjustments semi-empirically has usually been satisfactory, but two difficulties have been setting in with

R. Bracewell

1961-01-01

269

Small size wearable button antenna  

Microsoft Academic Search

A novel small size wearable antenna for WLAN applications is proposed in this paper. The antenna structure is based on a previous development and achieves lower size by implementing different miniaturization techniques. The radiating structure has the shape and dimensions of a standard denim jeans button and is made up of a button shaped cylindrical structure and a top metal

B. Sanz-Izquierdo; F. Huang; J. C. Batchelor

2006-01-01

270

Antenna Quadripod With Reduced Blockage  

NASA Technical Reports Server (NTRS)

Design study for subreflector support of 64-m-diameter paraboloidal microwave antenna described in 19-page report. Objective of study to upgrade existing antenna quadripod, subject to mechanical and electromagnetic design requirements and optimization criteria. Principal effort directed toward reducing signal blockage by quadripod legs while minimizing structural weight.

Cucchissi, J. J.

1986-01-01

271

Antenna configurations provide polarization diversity  

NASA Technical Reports Server (NTRS)

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

Schumacher, C. N.

1966-01-01

272

Backfire antennas with dipole elements  

Microsoft Academic Search

A method is set up for a theoretical investigation of arbitrary backfire antennas based upon dipole structures. The mutual impedance between the dipole elements of the antenna is taken into account, and the field radiated due to a surface wave reflector of finite extent is determined by calculating the surface current distribution on the reflector plate. Numerical results obtained for

E. Nielsen; K. Pontoppidan

1970-01-01

273

Remote Tracking Antenna Study (TAGGANT).  

National Technical Information Service (NTIS)

The final report includes the progress report for the months of October, November and December 1992. The main emphasis remained on packaging and improving the RF performance of an antenna/receiver for Satcom. Additionally, many other type of antennas were...

1992-01-01

274

Surface accuracy of Cassegrain antennas  

Microsoft Academic Search

For a Cassegrain antenna system, a simple and general procedure is presented for computing the effective surface root mean square (rms) and beam deviations considering primary surface distortions and relative translations and rotations of the antenna components. It is shown that certain primary reflector distortions can be compensated for by an appropriate adjustment of the subreflector position. Different methods in

M. S. Zarghamee; J. Antebi

1985-01-01

275

Emergency-vehicle VHF antenna  

NASA Technical Reports Server (NTRS)

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

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

1977-01-01

276

Adaptive reactance parasitic antenna array  

Microsoft Academic Search

This paper presents initial experiences with the design and implementation of a low-cost beam steering antenna for long-distance WIFI applications. The antenna system has three components: (1) an adaptive parabolic reflector constructed from an array of passive scatterers with tunable reactive loads, (2) an optimizer that runs on a host computer that adjusts the phases and amplitudes of their currents

Vladimir Filimonov; Alan Mainwaring; Ivan Shishalov; Maxim Shuralev; Alexey Umnov

2007-01-01

277

Positioning Fixture For Survey Antenna  

NASA Technical Reports Server (NTRS)

Improved positioning fixture designed to simplify and accelerate accurate alignment of antenna for use in land survey aided by satellites of Global Positioning System. Holds antenna at fixed height and orientation over station monument so survey measurements made with accuracy and precision.

Dinardo, Steven J.; Smith, Mark A.

1994-01-01

278

Antennas for distributed nanosatellite networks  

Microsoft Academic Search

Distributed nanosatellite networks have the advantage of being reconfigurable, redundant, and readily deployable. Two types of antennas designed for this application are presented: a flexible UHF antenna for Earth-to-satellite communications, and an X-band retrodirective array for secure satellite-to-satellite crosslink communications.

T. J. Mizuno; J. D. Roque; B. T. Murakami; L. K. Yoneshige; G. S. Shiroma; R. Y. Miyamoto; W. A. Shiroma

2005-01-01

279

Development of a new type of beam-steerable earth station antenna - Offset Spherical Antenna  

Microsoft Academic Search

The Offset Spherical Antenna, a beam-steerable earth station antenna, is introduced. The architecture and configuration of the antenna are described. The antenna is compared to other types of multibeam and\\/or beam-steerable antennas. The Offset Spherical Antenna consists of a feed subsystem, a spherical main reflector, and two subreflectors with special and unique curved profiles. The antenna's beam-steering capability is independent

Fumio Watanabe

1989-01-01

280

Electrically connected resonant optical antennas.  

PubMed

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

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

2012-08-01

281

The ICRF antennas for TFTR  

SciTech Connect

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.

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

282

Graphene-antenna sandwich photodetector.  

PubMed

Nanoscale antennas sandwiched between two graphene monolayers yield a photodetector that efficiently converts visible and near-infrared photons into electrons with an 800% enhancement of the photocurrent relative to the antennaless graphene device. The antenna contributes to the photocurrent in two ways: by the transfer of hot electrons generated in the antenna structure upon plasmon decay, as well as by direct plasmon-enhanced excitation of intrinsic graphene electrons due to the antenna near field. This results in a graphene-based photodetector achieving up to 20% internal quantum efficiency in the visible and near-infrared regions of the spectrum. This device can serve as a model for merging the light-harvesting characteristics of optical frequency antennas with the highly attractive transport properties of graphene in new optoelectronic devices. PMID:22703522

Fang, Zheyu; Liu, Zheng; Wang, Yumin; Ajayan, Pulickel M; Nordlander, Peter; Halas, Naomi J

2012-07-11

283

Test methodology for adaptive antenna systems  

NASA Astrophysics Data System (ADS)

Conventional antenna evaluations to determine gain, pattern, polarization, and terminal impedance characteristics are conducted on a component level. Adaptive antenna evaluations extend conventional antenna evaluations to system-level tests that quantify the performance of a receiving antenna system in both interference-free and interference environments. Test procedures for conventional antenna evaluations are well established. Test procedures for adaptive antennas expand the scope of antenna testing, tend to be system specific, and represent particular scenarios for interference. Adaptive antenna evaluations require additional instrumentation having more general spectral capabilities than conventional antenna test equipment, as well as an RF measurement facility capable of simultaneously generating both desired and interference signal components arriving from differing directions. The expansion of antenna testing for adaptive antenna designs is reviewed.

Dybdal, Robert B.

1987-01-01

284

Transcatheter Microwave Antenna  

NASA Technical Reports Server (NTRS)

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.

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

2001-01-01

285

Time-domain three antenna method for evaluation of antenna factors of log-periodic antenna  

Microsoft Academic Search

we have proposed the method for evaluating the free- space antenna factor of a log-periodic broadband antenna (LPDA) with time-domain technique [1]. Our method is based on the techniques of time domain analysis and pulse compression technology. The introduced function enables us to isolate the direct wave from the reflected waves on the ground plane in an open area test

Satoru Kurokawa; Masanobu Hirose; Koji Komiyama

2007-01-01

286

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

NASA Technical Reports Server (NTRS)

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

Olsson, T.

1972-01-01

287

A phased array antenna using cross dipole antenna for mobile satellite communications  

Microsoft Academic Search

In this paper, we propose a phased array antenna which consists of crossed dipole antenna with a reflector as an element antenna. The element antenna is designed by optimizing its parameters. The main and cross polarization characteristics of the right and left side beam scanning of the fabricated 19-element array antenna is measured. Next, the experimental results of the beam

S. Hasegawa; T. Yasuzumi; O. Hashimoto; Y. Kazama

2010-01-01

288

Measurement of Antenna Gain with Transmitting and Receiving Antennas on a Finite Ground Plane.  

National Technical Information Service (NTIS)

The gain of an antenna is usually measured by placing a transmitting antenna in the far field of the antenna under test (AUT) and then comparing the power received by that antenna with that received by a reference antenna (RA). Rather than having a separa...

E. E. Altshuler T. H. O'Donnell

2008-01-01

289

Scattering by cavity-backed antennas on a circular cylinder  

NASA Technical Reports Server (NTRS)

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

Kempel, Leo C.; Volakis, John L.

1994-01-01

290

Analysis method of parabolic reflector antenna  

Microsoft Academic Search

This paper describes the analysis method of parabolic reflector antenna. The analysis parameters of the antenna system are optimal antenna diameter, offset height, focal point length, feed horn type and horn size, F\\/D and the coordinate of offset horns. The paper deals with the method to determine design core parameters of optimal antenna diameter, feed horn type and horn size,

Jcom-Hun Lee; Seong-Pal Lee

2005-01-01

291

Automated Time Domain Antenna Range Initial Implementation  

Microsoft Academic Search

For organizations engaged in the development of antenna designs, conventional fre- quency domain antenna measurement systems represent a huge initial cost, and a significant bar- rier to entry into the field. When characterizing ultra-wideband antennas, the cost of frequency domain measurements is even greater, because data must be taken at many frequencies, requiring additional time. A time domain antenna range

W. Scott Bigelow; Everett G. Farr; Leland H. Bowen; Tyrone C. Tran; Carl E. Baum; William D. Prather

292

Time Domain Behaviors of Artimi's UWB Antenna  

Microsoft Academic Search

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

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

2006-01-01

293

Time domain aperture antenna study, volume 2  

Microsoft Academic Search

This research employs a direct time domain model applicable to aperture antennas of any shape excited by fields of any form in space and time to study theoretically the electromagnetic far fields of a paraboloid reflector when fed by a transverse electromagnetic (TEM) horn antenna. First, the TEM horn antenna is considered as an aperture antenna with an arbitrary excitation

H. C. Maddocks

1974-01-01

294

Time Domain Responses of Printed UWB Antennas  

Microsoft Academic Search

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

Yiqiong Shi; Sheel Aditya; C. L. Law

2005-01-01

295

Characterization of a Time Domain Antenna Range  

Microsoft Academic Search

We characterize here the performance of a time domain antenna range by measuring a number of antennas, comparing the results to frequency domain measurements. Our time domain antenna range consists of a fast pulser and a sampling oscilloscope. We have demonstrated good performance of this range for all types of antennas (resonant and non-resonant) that operate between 900 MHz and

Lanney M. Atchley; Everett G. Farr; Leland H. Bowen; W. Scott Bigelow; Harald J. Wagnon; Donald E. Ellibee; Tyrone C. Tran

296

High accuracy deployable antenna for communications satellite  

Microsoft Academic Search

High frequency multi-beam satellite antennas have been studied to realize increased communication capacity, simplified earth stations, and multiple frequency reuse. The satellite antenna needs a highly accurate and large reflector. To overcome the launching vehicle's constraints in size and weight, a solid deployable antenna is under development. A petal antenna (PETAL), composed of solid shell elements, has been studied as

M. Watanabe; M. Misawa; M. Minomo; T. Yasaka

1982-01-01

297

Folded dipole antenna near metal plate  

Microsoft Academic Search

The paper presents the effects on antenna parameters when an antenna is placed horizontally near a metal plate. The plate has finite size and rectangular shape. A folded dipole antenna is used and it is placed symmetrically above the plate. The FEM (finite element method) is used to simulate the dependency of antenna parameters on the size of the plate

P. Raumonen; L. Sydanheimo; L. Ukkonen; M. Keskilammi; M. Kivikoski

2003-01-01

298

Wireless interrogation of passive antenna sensors  

Microsoft Academic Search

Recently, we discovered that the resonant frequency of a microstrip patch antenna is sensitive to mechanical strains or crack presence in the ground plane. Based on this principle, antenna sensors have been demonstrated to measure strain and detect crack in metallic structures. This paper presents a wireless method to remotely interrogate a dual-frequency antenna sensor. An interrogation horn antenna was

S. Deshmukh; H. Huang

2010-01-01

299

G-band bowtie dipole antenna  

Microsoft Academic Search

In this paper we propose a 3D micromachined 210 GHz elevated bowtie dipole antenna fed by coplanar waveguide. The antenna is designed for MMICs applications at G-band (140 GHz to 220 GHz). The antenna topology effectively creates a low dielectric substrate and undesired substrate effects can be eliminated, since the antenna substrate is essentially air (the lowest possible dielectric constant)

Adel S. Emhemmed; K. Elgaid

2009-01-01

300

The research on short backfire antenna  

Microsoft Academic Search

A method to analyze the short backfire antenna was presented. The method interpreted the working principle of the backfire antenna relatively well. The gain of a backfire antenna developed by this method was approximately 2.5 dB higher than that of an ordinary short backfire antenna.

C. L. Lin; X. M. Song

1983-01-01

301

High frequency techniques for antenna analysis  

Microsoft Academic Search

A summary of various high-frequency techniques is presented for analyzing the electromagnetic radiation from antennas in the presence of their host environment. These techniques provide physical insight into antenna radiation mechanisms and are found to be highly efficient and accurate for treating a variety of practical antenna configurations. Examples to which these techniques have been applied include open-ended waveguide antennas,

PRABHAKAR H. PATHAK

1992-01-01

302

System and Circuit Models for Microwave Antennas  

Microsoft Academic Search

This paper describes how circuit and system models are derived for antennas from measurement of the input reflection coefficient. Circuit models are used to optimize the antenna performance and to calculate the radiated power and the transfer function of the antenna. System models are then derived for transmitting and receiving antennas. The most important contribution of this study is to

Mohamed I. Sobhy; Benito Sanz-Izquierdo; John C. Batchelor

2007-01-01

303

Decoupling and descattering networks for antennas  

Microsoft Academic Search

The possibilities of connecting a lossless network between input ports and antenna ports such that there is no coupling and scattering between the antennas are discussed. A necessary condition for complete decoupling and descattering is power orthogonality between the patterns of the individual antennas. Numerical and experimental results are presented for monopole antennas.

J. BACH ANDERSEN; HENRIK HASS RASMUSSEN

1976-01-01

304

Tunability of Liquid Dielectric Resonator Antennas  

Microsoft Academic Search

Dielectric resonator antennas (DRAs) have in the past been used most often at frequencies in the GHz portion of the spectra. This letter presents a novel 50-MHz DRA that uses water as the dielectric. For purposes of keeping the antenna tuned to a specific frequency, ande for using the antenna at different frequencies, this antenna can utilize a pump to

Steven G. O'Keefe; Simon P. Kingsley

2007-01-01

305

Wire-antenna designs using genetic algorithms  

Microsoft Academic Search

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

Edward E. Altshuler; Derek S. Linden

1997-01-01

306

Metal Patch Antenna  

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

307

Antenna sunshield membrane  

NASA Technical Reports Server (NTRS)

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.

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

1994-01-01

308

Composite antenna feed  

NASA Technical Reports Server (NTRS)

A composite antenna feed subsystem concentrated in a small area at the prime focus of the parabola of a satellite parabolic reflector accomodates a plurality of frequency bands. The arrays comprising the subsystem are mounted on the top cover of a communication module. A multimode horn is arranged at the center of the subsystem axis which functions at X- And C-band frequencies, and a cross array consisting of individual elements form the S-band feed, with one arm of the S-band array containing an element mutually shared with the L-band array. Provision is also made for UHF frequencies, and a dipole arrangement for VHF frequencies is arranged around the S-band arms.

Jakstys, V. J. (inventor)

1973-01-01

309

The collinear coaxial array antenna  

NASA Astrophysics Data System (ADS)

A design of a coaxial vertical antenna proposed in the ARRL antenna handbook is analyzed. A numerical analysis was carried out using the moment method. A variety of antenna configurations in the 160 MHz design frequency are analyzed and current distribution, gain, polar diagrams and impedances are calculated. The analysis is carried out for simple configurations and extended to a case with 16 repeated center sections. The effects of using lossy cable in the construction is also investigated. A defect in the original ARRL design is rectified. An array of an overall length 5.33 wavelengths is shown to have a gain of 10.69 dB.

Brammer, D. J.; Williams, D.

1981-03-01

310

Active antennas for satellite communications  

NASA Astrophysics Data System (ADS)

The feasibility of replacing the high-power traveling-wave tube amplifiers (TWTA's) of a satellite antenna transmit system by many low-power solid-state power amplifiers (SSPA's) each driving a feed radiating element is examined in this paper. In view of the requirement of a one watt output power from each such low-power SSPA, the design, fabrication, and performance of a 1-watt SSPA are also described in this paper. In addition, the suitability of a number of antenna configurations as active antennas has been evaluated for C-Band shaped beam Intelsat applications.

Parekh, S. V.; Soule, H. H.; Cummings, M.; Bornemann, W.

311

Computer design of antenna reflectors.  

NASA Technical Reports Server (NTRS)

Performance of paraboloidal antenna reflectors is adversely influenced by surface distortions from a perfect paraboloid, which cause pathlength variations of the RF energy beam. The structural design objective for the surface backup structure is to minimize the rms pathlength deviations for gravity loading. Two design approaches are illustrated and applied to sample antenna structure designs. These are a sectional search method and a virtual work/Lagrange multiplier method. Both are shown to provide useful performance improvements. The second, however, appears to be more suited for application to design of large antenna structures.

Levy, R.

1973-01-01

312

Time-domain analysis of antennas used for EMC  

Microsoft Academic Search

The article consists of a Powerpoint presentation on time-domain analysis of antennas. The areas discussed include: time-domain antenna; time-frequency relationship; biconical dipole antenna; dual ridged horn antenna; log periodic dipole array antenna; half-wave dipole antenna; EMC and DRG antenna.

D. Camell

2008-01-01

313

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

NASA Technical Reports Server (NTRS)

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

Zakrajsek, Robert J.

2000-01-01

314

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

NASA Technical Reports Server (NTRS)

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.

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

1978-01-01

315

Conformations of Substituted Ethanes.  

ERIC Educational Resources Information Center

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

Kingsbury, Charles A.

1979-01-01

316

Microwave sensing of protein conformation and binding  

NASA Astrophysics Data System (ADS)

Dielectric spectroscopy of biological macromolecules has not been pursued with the same vigor as fluorescence. One reason for this is the difficulty in measuring dielectric dispersion of biological species. All biological macromolecules are weakly dielectric, but in solution they are surrounded by a high concentration of weakly bound and bulk water. Bound water may be distinguished from bulk solution, however, and may act as a reporter for macromolecular conformation. Here we report dielectric measurements in the range 0.5 to 20 GHz made with a planar slot antenna attached to a fused-quartz cuvette, allowing simultaneous measurements of optical and dielectric spectra. Two sets of experiments demonstrate our ability to detect changes in protein conformation and binding of small ligands. In the first set, the reversible thermal unfolding of bovine pancreatic ribonuclease (RNase A), a small globular protein, was monitored using both UV/VIS and dielectric spectroscopies. In the second set of experiments, the binding of fluormone (a synthetic fluorescent estrogen) and other hormones to human estrogen receptor ? was measured using fluorescence polarization and dielectric spectroscopies. Similar results are obtained from optical and dielectric spectroscopy for both experiments. These two sets of experiments demonstrate that: 1) dielectric spectroscopy in the microwave range is a viable technique for detection of changes in protein conformation and ligand binding; 2) protein and/or ligand is not grossly perturbed by the presence of microwave radiation.

Taylor, Kimberly

2003-03-01

317

Radar cross section measurement by compact range method using 8-element small antenna array instead of one large antenna  

Microsoft Academic Search

RCS (radar cross section) measurement by the compact range method was performed using an 8-element small antenna array instead of one large antenna. The span of each antenna is 800 mm; 4 of the 8 antennas are used for transmission and the other 4 antennas are used for receiving. The transmission antennas and the receiving antennas are placed in cross

H. Suzuki; K. Saito; T. Yoshizawa; S. Uwabe; M. Inoue

2009-01-01

318

Structure and Conformation of Carbohydrates  

NASA Astrophysics Data System (ADS)

The conformational analysis of monosaccharides, disaccharides, and oligosaccharides is reviewed. Conformational terms are introduced through examination of the conformations of cyclohexane and cyclopentane then applied to the pyranose, furanose , and septanose rings. Concepts such as the anomeric effect are discussed. Topics of current interest, such as hydroxymethyl group and hydroxyl group rotation and disaccharide conformations are summarized. Physical methods for studying conformation are outlined.

Grindley, T. Bruce

319

Microstrip Antenna with Polarization Diversity.  

National Technical Information Service (NTIS)

This invention comprises an inexpensive, flush-mounted microstrip antenna the polarization of which is easily changed from vertical linear to horizontal linear, left-circular, right-circular or any desired elliptical sense. This enables the designer to se...

D. H. Schaubert

1979-01-01

320

Evolutionary Optimization of Optical Antennas  

NASA Astrophysics Data System (ADS)

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.

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

2012-09-01

321

Large space systems antenna technology  

NASA Technical Reports Server (NTRS)

Program objectives; approach; surface characterization of large scale antennas; adaptive feed-multimode horn and array configuration; and technology benefits of CSEI program are outlined. This presentation is represented by viewgraphs only.

Campbell, Thomas G.

1989-01-01

322

Dual-frequency microwave antenna  

NASA Technical Reports Server (NTRS)

Single antenna using two feed horns (one for receiving and radiation X-band signals, and one for S-band signals), in conjunction with ellipsoid reflector and dichronic plate, can accommodate two different frequencies simultaneously.

Bathker, D. A.; Brunstein, S. A.; Ludwig, A. C.; Potter, P. D.

1980-01-01

323

NASA Antenna Gets its Bearings  

NASA Video Gallery

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

324

Evolutionary optimization of optical antennas.  

PubMed

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

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

2012-09-21

325

Reflection-Zone-Plate Antenna  

NASA Technical Reports Server (NTRS)

Microwave antenna, based on reflection holography, designed and tested. Modified to produce arbitrary beam patterns by controlling relief pattern. Antenna planar or contoured to supporting structure. Low off-axis radar cross section at frequencies removed from operational frequency. Interference pattern produced by spherical wave intersecting plane wave consists of concentric circles similar to Newton's rings. Pattern identical to Fresnel zone plate, which has lens properties. Plane wave incident on hologram, or zone plate, focused to point.

Franke, John M.; Leighty, Bradley D.

1989-01-01

326

Fin-line horn antenna  

DOEpatents

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

Reindel, John (San Diego, CA) [San Diego, CA

1990-01-01

327

Microstrip antenna developments at JPL  

Microsoft Academic Search

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

John Huang

1991-01-01

328

Trees performing as RF antennas  

Microsoft Academic Search

This paper describes how shrubs have been used as transmitting and receiving RF antennas. The variations of transmitting and receiving characteristics with moist and dry conditions have been studied extensively. It has been found out that the two sets of observations differ by 5-7dB. Modulated wave transmissions and receptions have been studied as well. The behaviour of such antennas are

Shuva Jyoti Kar; Ajay Chakrabarty; B. K. Sarkar

2010-01-01

329

Field Computations of Optical Antennas  

Microsoft Academic Search

Antenna-based near-field optical microscopy and spectroscopy makes use of locally enhanced opti- cal fields created near laser-irradiated metal nanostructures acting as local probes. Using three- dimensional simulations based on the finite element method we study the electromagnetic fields near various optical antennas and we optimize their geometry in order to bring out a strong enhance- ment in a selected frequency

Roman Kappeler; Daniel Erni; Cui Xudong; Lukas Novotny

330

Omnidirectional antenna for radar applications  

NASA Astrophysics Data System (ADS)

The development of an omnidirectional antenna for sidelobe blanking is described. The results of electrical measurements for an S-band and L-band configuration are given. The antenna architecture consists of eight printed radiating elements arranged in a biconical fashion. The single radiating element is a pseudo log periodic microstrip array fed by means of capacitive coupling. Modularity and flexibility are the outstanding characteristics of the design.

Vitiello, R.

331

Integrated multifrequency phased array antenna  

Microsoft Academic Search

A new wideband small size, multifrequency phased array antenna with beam scanning capability has been designed and developed at X-, K- and Ku-band frequency ranges. The phased array design utilizes multi-function wideband RF antenna (T\\/R modules) elements, which are realized by integrating a wideband transmitter source (RF amplifiers), low noise amplifier (LNA), a diplexer and a multi-octave band planar linear

R. S. Tahim; J. Foshee; K. Chang

2001-01-01

332

Characteristics of a multibeam antenna using quasi-optical hybrid ring antenna-mixer array  

Microsoft Academic Search

This paper addresses a principle of multibeam quasi-optical antenna mixer array. At first, the multibeam antenna using this technique is presented. The multibeam antenna, composed of quasi-optical hybrid ring antenna-mixer, is measured at K-band. The antenna element consists of back-to-back aperture coupled patch antenna to couple the RF signal at 18.4 GHz to the sigma port of a hybrid ring

S. Janin; P. Dangrattanawong; K. Sripimanwat; C. Phongcharoenpanichand; M. Krairiksh

2005-01-01

333

Electromagnetic antenna modeling (EAM) system  

NASA Astrophysics Data System (ADS)

The determination of foreign communications capabilities and intent is an important assessment function performed by the USAF National Air Intelligence Center (NAIC). In this context, Rome Laboratory became the NAIC engineering agent for the development of an NAIC requirement for the rapid analysis and evaluation of antenna structures based on often vague to sometimes detailed dimensional information. To this end, the Rome Laboratory sponsored development of the Electromagnetic Antenna Modeling (EAM) System, a state-of-the-art Pascal program with an MS Windows graphical user interface (GUI) pre- and post-processor. Users of NAIC capabilities initiate antenna analysis efforts that range from simple parametric studies to more complex, detailed antenna design and communication-system evaluations. Accordingly, EAM provides a modeling capability 'matched' to the sophistication of the individual analyst, with features appropriate for users ranging from nontechnical analysts to experienced antenna engineers. This capability is particularly valuable in the military-intelligence environment, in which high-speed assessments are required. In particular, EAM meets the specific antenna-analysis requirements of NAIC with a versatile graphical user interface.

Packer, Malcolm; Powers, Robert; Tsitsopoulos, Paul

1994-12-01

334

Antennas for mobile satellite communications  

NASA Astrophysics Data System (ADS)

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

Huang, John

1991-12-01

335

Architecture and interconnect technologies for a novel conformal active phased array radar module  

Microsoft Academic Search

Highly integrated transmit\\/receive modules are key components for modern active phased array radar systems. This paper describes architecture and related interconnect technologies for a novel transmit\\/receive module with integrated radiating element and circulator for X-band applications. It allows the realization of future planar or conformal active antenna arrays with low installation depth as well as high maintainability performance.

Marc Schreiner; Helmut Leier; Wolfgang Menzel; H.-P. Feldle

2003-01-01

336

Principles and applications of a controllable electromagnetic band gap material to a conformable spherical radome  

NASA Astrophysics Data System (ADS)

This paper presents the principle of two types of conformable and controllable spherical radome based on Electromagnetic Band Gap (EBG) materials operating at around 10 GHz. The EBG structure is composed of a grid of metallic wires conformed on a hollow spherical object. Two switching control configurations are considered: (1) between an EBG structure made of electrically continuous wires and another one made of discontinuous wires, and (2) between two EBG structures made of discontinuous wires where each has a different period of discontinuities. Both switching configurations are simulated and experimentally characterized on passive prototypes. An excellent agreement is observed between simulations and measurements. The radiation patterns of two types of antennas, a horn antenna and a meteorological antenna, are also measured in the presence of the radome.

Haché, S.; Burokur, S. N.; de Lustrac, A.; Gadot, F.; Cailleu, P.; Piau, G.-P.

2009-06-01

337

NASA technology for large space antennas  

NASA Technical Reports Server (NTRS)

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.

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

1979-01-01

338

E-Textile Antennas for Space Environments  

NASA Technical Reports Server (NTRS)

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.

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

2007-01-01

339

Mobile antenna development at JPL  

NASA Astrophysics Data System (ADS)

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

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

340

Mobile antenna development at JPL  

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

341

The frequency response of phased-array antennas  

SciTech Connect

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

Brock, B.C.

1989-02-01

342

Wide scanning spherical antenna  

NASA Technical Reports Server (NTRS)

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.

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

1995-01-01

343

CONFORM/SPECIFOR.  

National Technical Information Service (NTIS)

This paper has a twofold purpose: first, it describes the recently developed constrained forced model, CONFORM, currently operational and in use at the United States Army Management System Support Agency for structuring theater forces for the outyears. Th...

R. H. Gramann

1973-01-01

344

Conformational Characteristics of Polystyrene.  

National Technical Information Service (NTIS)

Conformational energies of meso and racemic dyads of polystyrene have been computed as functions of skeletal bond rotations. Confinement of rotations of the phenyl groups to a small range within which they are nearly perpendicular to the plane defined by ...

D. Y. Yoon P. R. Sundararajan P. J. Flory

1975-01-01

345

Loaded horizontal antenna over an imperfect ground  

NASA Technical Reports Server (NTRS)

The effect of loading for antennas over an imperfect ground is analyzed. The Fresnel reflection coefficient technique is used to derive an E-integral equation for the antenna current. An optimization method is employed to determine the critical loading parameter which enforces a traveling wave current on the antenna. Results are given for the critical loading parameters, antenna currents, input impedances, and radiation patterns for various antenna dimensions and ground parameters. Calculations of the time-domain behavior of the current are presented to show the effect of loading on antenna transient response.

Rahmat-Samii, Y.; Parhami, P.; Mittra, R.

1978-01-01

346

Multilayer Microstrip Slot And Dipole Array Antenna  

NASA Technical Reports Server (NTRS)

Multilayer antenna structure contains interleaved linear subarrays of microstrip dipole and slot radiating antenna elements to provide compact, dual-band antenna. Structure also contains associated microstrip transmission lines, plus high-power amplifiers for transmission and low-noise amplifiers for reception. Overall function is to transmit in horizontal polarization at frequency of 29.634 GHz and receive in vertical polarization at 19.914 GHz, in direction 44 degrees from broadside to antenna. Antenna structure is part of apparatus described in "Steerable K/Ka-band Antenna for Land-Mobile Satellite Applications," NPO-18772.

Tulintseff, Ann N.

1994-01-01

347

Broadband monopole optical nano-antennas  

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

348

Systems analysis for DSN microwave antenna holography  

NASA Technical Reports Server (NTRS)

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

Rochblatt, D. J.

1989-01-01

349

Vehicle antenna development for mobile satellite applications  

NASA Technical Reports Server (NTRS)

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.

Woo, K.

1988-01-01

350

Representations of conformal supersymmetry  

NASA Astrophysics Data System (ADS)

The superalgebras of (generalized) conformal supersymmetry have some very interesting unitarizable representations that contain only massless representations of the conformal subalgebra, in spite of contrary claims that have recently been made Castell, L., and Heidenreich, W., Phys. Rev. D25, 1745 (1982). , Castell, L. and Kunemund, Th., Phys. Rev. D26, 1485 (1982). .

Flato, Moshé; Fronsdal, Christian

1984-03-01

351

Assemblies of Conformal Tanks  

NASA Technical Reports Server (NTRS)

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

DeLay, Tom

2009-01-01

352

Patch antenna based temperature sensor  

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

353

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

NASA Technical Reports Server (NTRS)

A low-cost beamformer phased array antenna has been developed for expendable launch vehicles, rockets, and missiles. It utilizes a conformal array antenna of ring or individual radiators (design varies depending on application) that is designed to be fed by the recently developed hybrid electrical/mechanical (vendor-supplied) phased array beamformer. The combination of these new array antennas and the hybrid beamformer results in a conformal phased array antenna that has significantly higher gain than traditional omni antennas, and costs an order of magnitude or more less than traditional phased array designs. Existing omnidirectional antennas for sounding rockets, missiles, and expendable launch vehicles (ELVs) do not have sufficient gain to support the required communication data rates via the space network. Missiles and smaller ELVs are often stabilized in flight by a fast (i.e. 4 Hz) roll rate. This fast roll rate, combined with vehicle attitude changes, greatly increases the complexity of the high-gain antenna beam-tracking problem. Phased arrays for larger ELVs with roll control are prohibitively expensive. Prior techniques involved a traditional fully electronic phased array solution, combined with highly complex and very fast inertial measurement unit phased array beamformers. The functional operation of this phased array is substantially different from traditional phased arrays in that it uses a hybrid electrical/mechanical beamformer that creates the relative time delays for steering the antenna beam via a small physical movement of variable delay lines. This movement is controlled via an innovative antenna control unit that accesses an internal measurement unit for vehicle attitude information, computes a beam-pointing angle to the target, then points the beam via a stepper motor controller. The stepper motor on the beamformer controls the beamformer variable delay lines that apply the appropriate time delays to the individual array elements to properly steer the beam. The array of phased ring radiators is unique in that it provides improved gain for a small rocket or missile that uses spin stabilization for stability. The antenna pattern created is symmetric about the roll axis (like an omnidirectional wraparound), and is thus capable of providing continuous coverage that is compatible with very fast spinning rockets. For larger ELVs with roll control, a linear array of elements can be used for the 1D scanned beamformer and phased array, or a 2D scanned beamformer can be used with an NxN element array.

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

2012-01-01

354

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

Microsoft Academic Search

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

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

2004-01-01

355

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

Microsoft Academic Search

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

Terry L. Foreman

1993-01-01

356

THz Broadband High-Power Antennas - Results of Modeling and Antennas Future Applications  

NASA Astrophysics Data System (ADS)

The purpose of this publication is to demonstrate the results of supercomputer modeling of broadband antennas operating up to 100 THz. The aim of modeling was to achieve the highest possible antenna gain and peak power, the highest gain uniformity and lowest sidelobes, while maintaining the smallest antenna aperture and lowest multi-antenna coupling.

Podgorski, A.; Prather, W.; Yakura, S.; MacGillivray, J.

357

A FREQUENCY-INVARIANT ARRAY ANTENNA FED BY LOG PERIODIC DIPOLE ANTENNAS  

Microsoft Academic Search

Software radio applications demand extremely broadband antennas. An unequally spaced array antenna composed of log periodic dipole antennas (LPDAs) is proposed. First, the concept of an unequally spaced array elements is explained. Next, LPDAs are designed so as to achieve almost constant radiation patterns in 2 GHz to 10 GHz. Finally, radiation patterns of the LPDA array antenna are obtained.

Yoshihide Yamada; Teruhisa Itagaki; Makoto Kijima; Yoshio Ebine

358

A miniature broadband multilayer microstrip antenna  

Microsoft Academic Search

A novel compact broadband multilayer microstrip antenna is presented in this paper. The VSWR, gain and radiation pattern of this antenna are simulated. The measured VSWR of it is also shown in the paper. The results are discussed in detail.

Zhiwei Shi; Xi Deng; Yunlin Liu; Kun Chao

2008-01-01

359

Optimum design of a scavenging antenna system  

Microsoft Academic Search

This paper presents some guidelines for the design procedure of an optimum scavenging antenna system. Based on these guidelines, a scavenging antenna has been fabricated and characterized, achieving very good results in comparison to the traditional designs.

Raquel Serrano; Albert Aguasca; Jordi Romeu; Lluis Jofre

2010-01-01

360

A Dielectric-Rod Backfire Antenna.  

National Technical Information Service (NTIS)

A backfire antenna is described which incorporates a dielectric slow-wave structure in place of the parasitic directors of earlier models. Using previously investigated optimum dimensions, this antenna uses new techniques of energizing in a cross polarize...

J. A. Strom

1969-01-01

361

Antenna using a Photonic Bandgap Structure.  

National Technical Information Service (NTIS)

A microstrip patch antenna utilizes a microstrip patch antenna substrate formed of photonic bandgap material. One or more periodic patterns may be used therewith to produce multiple bandgaps into the photonic bandgap material. The periodic patterns may be...

J. A. LaComb

2006-01-01

362

Wireless interrogation of passive antenna sensors  

NASA Astrophysics Data System (ADS)

Recently, we discovered that the resonant frequency of a microstrip patch antenna is sensitive to mechanical strains or crack presence in the ground plane. Based on this principle, antenna sensors have been demonstrated to measure strain and detect crack in metallic structures. This paper presents a wireless method to remotely interrogate a dual-frequency antenna sensor. An interrogation horn antenna was used to irradiate the antenna sensor with a linear chirp microwave signal. By implementing a light-activated switch at the sensor node and performing signal processing of the backscattered signals, the resonant frequencies of the antenna sensor along both polarizations can be measured remotely. Since the antenna sensor does not need a local power source and can be interrogated wirelessly, electric wiring can be eliminated. The sensor implementation, the signal processing and the experimental setup that validate the remote interrogation of the antenna sensor are presented. A power budget model has also been established to estimate the maximum interrogation range.

Deshmukh, S.; Huang, H.

2010-03-01

363

Integrated resonant tunneling diode based antenna  

DOEpatents

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

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

2000-01-01

364

Combination Antenna Receive-Transmit System (CARTS).  

National Technical Information Service (NTIS)

A system that allows simultaneous transmission and reception on a common antenna is designed. A simple decoupling network that provides decoupling from a transmitting antenna nearly independent of transmitter-multicoupler off-resonance impedance is design...

I. C. Olson

1970-01-01

365

Performance of Antennas in Their Operational Environment.  

National Technical Information Service (NTIS)

Lecture Series 131 on the performance of antennas in their operational environment is sponsored by the Electromagnetic Wave Propagation Panel of AGARD and implemented by the Consultant and Exchange Programme. Antennas can provide gain in any direction, an...

1983-01-01

366

Large Deployable Antenna Shuttle Experiment  

NASA Technical Reports Server (NTRS)

An experiment designed to use the Space Shuttle in tests of the mechanical and electrical properties of spaceborne deployable antennas under zero-gravity conditions is outlined. Space-erectable 20-meter diameter phased arrays or reflector/feed systems, and self-deploying mechanisms, are to be tested. Reflector surface integrity will be tested by an AM laser technique, and electrical behavior will be tested by a spin-stabilized RF beacon injected into orbit prior to unfurlment of the antenna. Focusing and gain measurements, static pattern measurements, dynamic RF gain measurements, and measurements of cross-polarized signals will be conducted, and the reflector will be illuminated by separate feeds for the S-, X-, and K-bands. Mechanical features of the mesh-wrapped rib furlable antenna design are described.

Freeland, R. E.; Smith, J. G.; Springett, J. C.; Woo, K. E.

1975-01-01

367

Compact Low Frequency Radio Antenna  

DOEpatents

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

Punnoose, Ratish J. (Hayward, CA)

2008-11-11

368

Compact size ultra wideband Hexagonal Fractal antenna  

Microsoft Academic Search

A compact size ultra wide-band coplanar waveguide (CPW) fed, fractal antenna is presented. A rectangular slot antenna is excited by a 50?-CPW with a fractal patch. The antenna was studied experimentally regarding impedance bandwidth, radiation patterns and gain. For the proposed antenna, the -10 dB return loss bandwidth could reach 7.45 GHz (2.85 GHz - 10.3 GHz). Details of the

A. A. Lotfi-Neyestanak; M. R. Azadi; A. Emami-Forooshani

2010-01-01

369

A novel time-domain UWB antenna  

Microsoft Academic Search

A planar monopole UWB antenna with good time-domain performance is presented, calculation and analysis are made through time-domain pattern descriptors. The profile of antenna is simple and easy to be implemented. The proposed antenna is simulated by CST Microwave Studio, some factors which can affect the time-domain performance such as pulse fidelity are studied and taken into account in antenna

Yong Li; Zeming Xie; Qingxin Chu

2008-01-01

370

Advances in time domain antenna measurements  

Microsoft Academic Search

This paper presents some previous and novel developments in time domain antenna measurements. In particular, their implementation in compact ranges for antenna pattern measurements, the development of time domain holography together with their application to non-destructive reverse engineering and antenna diagnostics, and a pattern error correction method using super-resolution techniques are addressed. Measurement results for the phased-array antenna of the

J. Marti-Canales; L. P. Ligthart

2001-01-01

371

Fabrication of Antenna-Coupled Microbolometers  

Microsoft Academic Search

Fabrication conditions of antenna-coupled microbolometers which function in the far-infrared (FIR) frequency region are discussed. A bow-tie antenna-coupled microbolometer was fabricated on a 300 nm Si3N4 membrane, and detection experiments for 118 µ m CH3OH laser radiation were performed. The measured antenna pattern indicated that the fabricated device functions as an antenna-coupled device which receives the laser radiation by means

Takashi Shimizu; Haruhito Moritsu; Yoshizumi Yasuoka; Kenji Gamo

1995-01-01

372

Green Antenna for Solar Energy Collection  

Microsoft Academic Search

For the first time, the idea of using a light-reflecting metallic antenna for design of a solar-cell system is proposed. The antenna for this new concept is named Green Antenna for its association with renewable energy. Both the Green Antenna and its ground plane simultaneously act as light-reflecting surfaces for the solar-cell system. To demonstrate the idea, a suspended plate

E. H. Lim; K. W. Leung; C. C. Su; H. Y. Wong

2010-01-01

373

A fractal circular polarized RFID tag antenna  

NASA Astrophysics Data System (ADS)

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

Chaouki, Guesmi; Ferchichi, Abdelhak; Gharsallah, Ali

2013-09-01

374

Dual-band wearable textile antenna  

Microsoft Academic Search

Future utilization of smart clothing will necessitate applications of multi-function and multifrequency wearable antennas. This work addresses the development of a dual-band textile antenna for wearable applications. The antenna is for GSM operation in the 1900 MHz band and for WLAN operation in the 2.4 GHz band. The proposed antenna has a U-shaped slot-structure mounted on the surface of fleece

Pekka Salonen; Yahya Rahmat-Samii; Heli Hurme; Markku Kivikoski

2004-01-01

375

Broadbanding of a plate antenna with slits  

Microsoft Academic Search

Handset antennas for mobile radio communications have been small, and its high-performance characteristics over a broadband have been required. With the spread of multimedia, broadband small handset antennas are required too for video communications. In our previous studies, two-wire meander-line, two-wire helical and two-plate antennas have been investigated for the purpose of the broadbanding of the small antennas. By making

Keisuke NOGUCHI; M. Mizusawa; S. Betsudan

2000-01-01

376

Large Space Antenna Systems Technology, 1984  

NASA Technical Reports Server (NTRS)

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

Boyer, W. J. (compiler)

1985-01-01

377

Conformational flexibility of mephenesin.  

PubMed

The mephenesin molecule (3-(2-methylphenoxy)propane-1,2-diol) serves as a test bank to explore several structural and dynamical issues, such as conformational flexibility, the orientation of the carbon linear chain relative to the benzene plane, or the effect of substituent position on the rotational barrier of a methyl group. The molecule has been studied by rotational spectroscopy in the 4-18 GHz frequency range by Fourier-transform methods in a supersonic expansion. The experiment has been backed by a previous conformational search plus optimization of the lowest energy structures by ab initio and density functional quantum calculations. The three lowest-lying conformers that can interconvert to each other by simple bond rotations have been detected in the jet. Rotational parameters for all structures have been obtained, and methyl torsional barriers have been determined for the two lowest-lying rotamers. The lowest-lying structure of mephenesin is highly planar, with all carbon atoms lying nearly in the benzene ring plane, and is stabilized by the formation of cooperative intramolecular hydrogen bonding. An estimation of the relative abundance of the detected conformers indicates that the energetically most stable conformer will have an abundance near 80% at temperatures relevant for biological activity. PMID:24754523

Ecija, Patricia; Evangelisti, Luca; Vallejo, Montserrat; Basterretxea, Francisco J; Lesarri, Alberto; Castaño, Fernando; Caminati, Walther; Cocinero, Emilio J

2014-05-22

378

Nested-cone transformer antenna  

DOEpatents

A plurality of conical transmission lines are concentrically nested to form an output antenna for pulsed-power, radio-frequency, and microwave sources. The diverging conical conductors enable a high power input density across a bulk dielectric to be reduced below a breakdown power density at the antenna interface with the transmitting medium. The plurality of cones maintain a spacing between conductors which minimizes the generation of high order modes between the conductors. Further, the power input feeds are isolated at the input while enabling the output electromagnetic waves to add at the transmission interface. Thus, very large power signals from a pulse rf, or microwave source can be radiated. 6 figures.

Ekdahl, C.A.

1991-05-28

379

Nested-cone transformer antenna  

DOEpatents

A plurality of conical transmission lines are concentrically nested to form n output antenna for pulsed-power, radio-frequency, and microwave sources. The diverging conical conductors enable a high power input density across a bulk dielectric to be reduced below a breakdown power density at the antenna interface with the transmitting medium. The plurality of cones maintain a spacing between conductors which minimizes the generation of high order modes between the conductors. Further, the power input feeds are isolated at the input while enabling the output electromagnetic waves to add at the transmission interface. Thus, very large power signals from a pulse rf, or microwave source can be radiated.

Ekdahl, Carl A. (Santa Fe, NM)

1991-01-01

380

Interleaved array antenna technology development  

NASA Technical Reports Server (NTRS)

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

1985-01-01

381

High Resolution Scanning Reflectarray Antenna  

NASA Technical Reports Server (NTRS)

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.

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

2000-01-01

382

Adaptive Antenna Control (AAC) program  

NASA Astrophysics Data System (ADS)

This is the test report for the Adaptive Antenna Control Program (Contract No. DAAB07-76-C-8085). The program is under the management of the U.S. Army Communications Systems Agency and monitored by the U.S. Army Communications R D Command both of Ft. Monmouth, New Jersey. SIGNATRON, Inc. and RF Systems, Inc. (as antenna sub-contractor) had the responsibility for executing the program tasks. This report summarizes these tasks and includes the results of the factory and field test phases.

Monsen, P.; Eschle, J.

1980-09-01

383

Nested-cone transformer antenna  

SciTech Connect

A plurality of conical transmission lines are concentrically nested to form an output antenna for pulsed-power, radio-frequency, and microwave sources. The diverging conical conductors enable a high power input density across a bulk dielectric to be reduced below a breakdown power density at the antenna interface with the transmitting medium. The plurality of cones maintain a spacing between conductors which minimizes the generation of high order modes between the conductors. Further, the power input feeds are isolated at the input while enabling the output electromagnetic waves to add at the transmission interface. Thus, very large power signals from a pulse rf, or microwave source can be radiated. 6 figs.

Ekdahl, C.A.

1989-10-18

384

Microstrip Patch Antenna And Method  

NASA Technical Reports Server (NTRS)

Method and apparatus are provided for a microstrip feeder structure for supplying properly phased signals to each radiator element in a microstrip antenna array that may be utilized for radiating circularly polarized electromagnetic waves. In one disclosed embodiment. the microstrip feeder structure includes a plurality of microstrip sections many or all of which preferably have an electrical length substantially equal to one-quarter wavelength at the antenna operating frequency. The feeder structure provides a low loss feed structure that may be duplicated multiple times through a set of rotations and translations to provide a radiating array of the desired size.

Fink, Patrick W. (Inventor)

2001-01-01

385

Advanced antennas for SAR spacecraft  

NASA Technical Reports Server (NTRS)

Single and multi-frequency antenna concepts were developed to evaluate the feasibility of building large aperture polarimetric synthetic aperture radar (SAR) systems to be launched in low cost vehicles such as the Delta 2. The antennas are 18.9 m long by 2.6 m wide (L-band) and achieve single polarization imaging to an incidence angle of 55 degrees and dual/quad imaging to 42 degrees. When combined with strawman spacecraft designs, both concepts meet the mass and volume constraints imposed by a Delta 2 launch.

Gail, William B.

1993-01-01

386

Antenna reconfiguration verification and validation  

NASA Technical Reports Server (NTRS)

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

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

2009-01-01

387

The MultiBand Dipole Antenna  

Microsoft Academic Search

In this paper, the vehicle antenna design is suitable for wireless LAN, radio identification, wireless sensor and short rage intelligent wireless communication. In this design, the multi band dipole antenna feed network with wide bandwidth tapered coplanar waveguide (CPW) balun is studied. The design and experimental results of low profile embedded multi band dipole antenna with tapered CPW balun shows

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

388

Offset-parabolic-reflector antennas: A review  

Microsoft Academic Search

Although used for some decades, the offset-parabolicreflector antenna's electrical properties and performance were not accurately modeled and optimized until the 1960's. This paper reviews, in a tutorial fashion, the state of the art of this important antenna for readers who are not necessarily experts in antenna theory and technology. After a discussion of fundamentals, the performances of both single- and

A. W. Rudge; N. A. Adatia

1978-01-01

389

A feederlink antenna for broadcasting satellites  

Microsoft Academic Search

We have successfully designed an onboard feederlink (17 GHz band) antenna for future Japanese direct broadcasting satellites (DBS) not only to efficiently cover the major part of Japan at a high gain but also to effectively suppress the antenna gain toward interference earth stations in the neighbor countries. The feederlink antenna consists of a single offset shaped reflector and a

Hayato Nishida; Kazuyoshi Shogen; Noboru Toyama

1992-01-01

390

Performance of Beverage Antennas at Low Angles.  

National Technical Information Service (NTIS)

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. T...

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

1983-01-01

391

47 CFR 95.51 - Antenna height.  

Code of Federal Regulations, 2013 CFR

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

2013-10-01

392

Lightweight S-band helix antenna  

NASA Technical Reports Server (NTRS)

Pyrotechnically operated S-band helical antenna is developed in which helix is deployed subsequent to antenna placement. Antenna is small, lightweight, and novel in that deployable helix is used in place of fixed dish or horn. It can be designed to cover L- and X-band frequencies.

Cribb, H. E.

1970-01-01

393

A unidirectionally radiating monopole slot antenna  

Microsoft Academic Search

A wideband planar antenna with unidirectional characteristics is demonstrated based on the monopole slot antenna. By utilizing a stub-protruded feedline and adding two symmetrical stubs at the slot edge, the impedance-matching condition is improved. The resonance frequency of the monopole slot antenna is significantly shifted down, and the impedance bandwidth is enlarged. By changing the width of the ground plane,

Tz-Hsiung Lin; Te-Liang Sun; Chien-Jen Wang

2011-01-01

394

Numerical analysis of double antennas, volume 2  

Microsoft Academic Search

The Double Delta antenna is an HF communication antenna which exists in many forms throughout military communication command. Performance characteristics for existing designs are presently unknown and are required in order to recommend an optimum design. This thesis investigates Double Delta antennas used by the U.S. Army (lowband and highband), the U.S. Air Force (lowband and highband), and a commercial

Achmad Chafid

1988-01-01

395

Experimental results of compact microstrip antennas  

Microsoft Academic Search

Due to its low profile, the microstrip antenna has found many applications in personal communication systems. And, owing to the miniaturization of communication equipment, designs for reducing the size of the microstrip antenna have received much attention. One of the effective ways to reduce the patch size of the microstrip antenna is to introduce a shorting pin at the edge

Hong-Twu Chen

1997-01-01

396

Patch Antenna on a High Impedance Wire  

Microsoft Academic Search

This paper presents a novel design for the implementation of a patch antenna over a high impedance wire (HIW). The proposed configuration enhances the efficiency of the patch antenna to 98% together with size reduction of 75%. The performance of the patch antenna over HIW has been analyzed using both electromagnetic and circuit models. Simulated investigations have been verified by

Angie R. El-Damak; Amr M. E. Safwat; Sergei A. Tretyakov; Hadia S. El-Hennawy

2008-01-01

397

Carbon fibre reinforced plastic slotted waveguide antenna  

Microsoft Academic Search

Ten-slot slotted waveguide antennas manufactured from aluminium and carbon fibre reinforced plastic were designed, manufactured and tested. The carbon fibre reinforced plastic was commercially available aerospace grade prepreg tape and metallic lining was not used in the waveguides. The antennas operated at X-band with uniform aperture distribution a uniform aperture distribution. The only difference in antenna performance was an additional

Derek Gray; Kelvin Nicholson; Kamran Ghorbani; Paul Callus

2010-01-01

398

Experimental investigation of a dielectric resonator antenna  

NASA Astrophysics Data System (ADS)

The electrodynamic charactertistics of an antenna consisting of a cylindrical dielectric resonator excited by a microstripline were measured. An analysis is made of the characteristics of the equivalent circuit which has the form of a parallel oscillatory circuit corresponding to the antenna. It is noted that dielectric resonator antennas can be used in receiver modules to improve selectivity.

Agamalian, N. N.; Karapetian, G. G.

399

Planar Monopole Antenna With Attached Sleeves  

Microsoft Academic Search

The analysis of a new printed antenna is presented and discussed. This antenna consists of a printed monopole, with one or two sleeves on each side, fed by a coplanar waveguide (CPW) line. Switches are used to control the length of the monopole and the sleeves and to tune the resonant frequencies of the antenna. In the case of the

V. Zachou; C. G. Christodoulou; M. T. Chryssomallis; D. Anagnostou; S. Barbin

2006-01-01

400

ITER-Like Antenna electrical performance  

Microsoft Academic Search

The future integration on Tore Supra (TS) of the new Ion Cyclotron Heating (ICRH) ITER-like prototype antenna will be performed to achieve the final validation within plasma conditions. Along the few years of developments and electrical optimizations, this antenna went through series of thermo\\/mechanical and electrical tests. This paper presents the latest electrical results of the ITER Like antenna under

A. Argouarch; S. Brémond; G. Lombard; L. Millon; P. Mollard; D. Volpe; K. Vulliez

2007-01-01

401

Small X-Band Oscillator Antennas  

NASA Technical Reports Server (NTRS)

A small, segmented microstrip patch antenna integrated with an X-band feedback oscillator on a high-permittivity substrate has been built and tested. This oscillator antenna is a prototype for demonstrating the feasibility of such devices as compact, low-power-consumption building blocks of advanced, lightweight, phased antenna arrays that would generate steerable beams for communication and remotesensing applications.

Lee, Richard Q.; Miranda, Felix A.; Clark, Eric B.; Wilt, David M.; Mueller, Carl H.; Kory, Carol L.; Lambert, Kevin M.

2009-01-01

402

Microstrip line fed broadband suspended plate antenna  

Microsoft Academic Search

A suspended plate antenna fed by a novel printed feed consisting of a 50 ? transmission line loaded with a rectangular printed loop is presented. The antenna exhibits an impedance bandwidth of 12.4 % for VSWR?2 over a frequency range of 2.14 to 2.42 GHz. Finite element method simulations have been used in designing the antenna.

M. R. Ranjith; P. H. RaoZ; R. SivaRamaKrishnan

2004-01-01

403

Research on the short backfire antenna  

Microsoft Academic Search

A method of analysing the short backfire antenna is proposed. With this method, a new type backfire antenna is developed.\\u000a Its gain is about 2.5dB higher than that of a normal short backfire antenna.

Lin Changlu; Song Ximing

1984-01-01

404

Backfire antennas constructed with coaxial circular loops  

Microsoft Academic Search

The radiation characteristics of backfire antennas constructed entirely of circular loops are studied. A comparison between this type of backfire antenna and the conventional one, made of a solid reflector, reveals that the optimum dimensions of the reflector and the peripheral rim are approximately the same for both kinds of antennas. In addition, it is found that as few as

A. Shoamanesh; L. Shafai

1980-01-01

405

Investigation of backfire monofilar helical antenna  

Microsoft Academic Search

This paper presents a numerical investigation of the electromagnetic properties of the backfire monofilar helical antenna. The current distribution along the helical conductor, the input impedance, and the front-to-back ratio are calculated and analyzed for the backfire operation of the antenna. A para- metric study of the helical geometry and the resulting antenna characteristics will be described and discussed. The

Thomas Gunst Smith; Niels Vesterdal Larsen; Ulrich Vesterager Gothelf; Oleksiy S. Kimy; Olav Breinbjergy

2011-01-01

406

ATCRBS improvement program reflector antenna development  

Microsoft Academic Search

The results of a program to investigate improved antennas for the air traffic control radar beacon system (ATCRBS) are described. An engineering model of a new ATCRBS reflector antenna system was developed and tested. The antenna system was designed primarily for use in terminal area air traffic control, collocated with an airport surveillance radar (ASR). Also developed during this program

P. N. Richardson

1976-01-01

407

GPS antenna characterization in an anechoic chamber  

Microsoft Academic Search

This paper is part of a continuing work with the FAA to develop an antenna testing methodology to characterize antenna performance in a multipath environment. This paper presents a case study to determine the characterization of two GPS antennas of varying performance in real world deployment. Power and phase measurements were acquired at the Wireless and Electromagnetic Compliance and Design

Nick J. LaSorte; Hazem H. Refai; John E. Fagan

2008-01-01

408

Microstrip dipole antenna for WLAN application  

Microsoft Academic Search

This paper describes numerical simulation, fabrication and experimental measurement of microstrip dipole antenna at 2.4 GHz for WLAN application. In this antenna design, Agilent's ADS software using momentum simulation is employed to analyze the entire structure. The properties of antenna such as bandwidth, radiation pattern and half power beamwidth have been investigated and compared between simulation and measurements. The cross-polar

M. H. Jamaluddin; M. K. A. Rahim; M. Z. A. Abd. Aziz; A. Asrokin

2005-01-01

409

Whip antenna design for portable rf systems  

Microsoft Academic Search

Whip type antennas are probably the most commonly used antennas in portable rf systems, such as cordless and cellular phones, rf enabled laptop computers, personal digital assistants (PDAs), and handheld computers. Whip antennas are almost always mounted on the chassis which contains the radio and other electronics. The chassis is usually a molded plastic which is coated with a conducting

Saila Ponnapalli; Frank J. Canora

1995-01-01

410

Microwave performance characterization of large space antennas  

NASA Technical Reports Server (NTRS)

Performance capabilities of large microwave space antenna configurations with apertures generally from 100 wavelengths upwards are discussed. Types of antennas considered include: phased arrays, lenses, reflectors, and hybrid combinations of phased arrays with reflectors or lenses. The performance characteristics of these broad classes of antennas are examined and compared in terms of applications.

Bathker, D. A. (editor)

1977-01-01

411

Ultra wideband L-loop antenna  

Microsoft Academic Search

The antenna design for ultra wideband (UWB) signal radiation is one of the main challenges of the UWB system, especially when low-cost, geometrically small and radio efficient structures are required for typical applications. This study presents a novel printed loop antenna with introducing an L shape portion to its arms. The antenna offers excellent performance for lower-band frequency of UWB

K. Y. Yazdanboost; R. Kohno

2005-01-01

412

A simple wideband antenna for mobile handset  

Microsoft Academic Search

A low cost, simple broadband planar inverted F antenna (PIFA) is presented in this paper. The size of the proposed antenna is 40times 10 times 12 mm3 and is suitable to be embedded in a mobile phone as an internal antenna. It can be achieved a broad bandwidth at VSWR <2 about 830 MHz (1780-2610 MHz) covering DCS, PCS, DECT,

Houda Halheit; André Vander Vorst

2009-01-01

413

Broadband High Frequency Sky-Wave Antenna.  

National Technical Information Service (NTIS)

A broadband H.F. directional sky-wave antenna system comprises a plurality of interconnected, vertical, zig-zag, antenna sections of predetermined increasing height. A counterpoise is utilized to balance the antenna. Power is coupled to the shortest zig-z...

B. E. Feigenbaum

1986-01-01

414

47 CFR 15.203 - Antenna requirement.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Antenna requirement. 15.203 Section 15... Intentional Radiators § 15.203 Antenna requirement. An intentional radiator shall be designed to ensure that no antenna other than that furnished by the...

2013-10-01

415

47 CFR 101.117 - Antenna polarization.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Antenna polarization. 101.117 Section 101... Technical Standards § 101.117 Antenna polarization. Except as...vertical and/or horizontal polarization for antennas located within 20 kilometers of the...

2013-10-01

416

47 CFR 95.859 - Antennas.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Antennas. 95.859 Section 95.859 ...Technical Standards § 95.859 Antennas. (a) The overall height from ground to topmost tip of the CTS antenna shall not exceed the height...

2013-10-01

417

47 CFR 80.866 - Spare antenna.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Spare antenna. 80.866 Section 80.866 Telecommunication...Vessels Not Subject to Subpart W § 80.866 Spare antenna. A spare transmitting antenna completely assembled for immediate erection...

2013-10-01

418

47 CFR 73.510 - Antenna systems.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Antenna systems. 73.510 Section 73.510...Educational FM Broadcast Stations § 73.510 Antenna systems. (a) All noncommercial...the provisions of § 73.316 concerning antenna systems contained in subpart B of...

2013-10-01

419

47 CFR 95.1213 - Antennas.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Antennas. 95.1213 Section 95.1213 Telecommunication...Radiocommunication Service (MedRadio) § 95.1213 Antennas. Except for the 2390-2400 MHz band, no antenna for a MedRadio transmitter shall be...

2013-10-01

420

Extending antenna theory to the optical domain  

Microsoft Academic Search

We describe an algorithm that yields new design rules for linear wire optical antennas. The ground work of our analysis is to derive first, and then solve, an integro-differential equation that gives the current on the wire antenna, at optical frequencies. Consequently, we compute the near field of these antennas, and thereby determine their equivalent-circuit parameters. An illustrative example is

C. De Angelis; A. Locatelli; D. Modotto; S. Boscolo; M. Midrio; F. Sacchetto; A.-D. Capobianco; F. M. Pigozzo; C. G. Someda

2009-01-01

421

RFID tag antenna mountable on metallic plates  

Microsoft Academic Search

RFID tag antenna which could be mountable on metallic plate is designed and measured for 900MHz band. The proposed antenna consists of ground plane, substrate (?r = 4.7), feed line with shorted circuit and radiating patch with L-shaped slit. The feed line with shorted circuit is designed for the direct impedance matching between the antenna and the RFID microchip. Especially,

Sung-Joo Kim; Byongkil Yu; Ho-Jun Lee; Myun-Joo Park; Frances J. Harackiewicz; Byungje Lee

2005-01-01

422

Dual Band UHF and Microwave RFID Antenna  

Microsoft Academic Search

This paper presents a new topology for RFID antenna matched on all UHF and one of the microwave RFID's band. The antenna can be implemented on different standards of tag's sizes as credit card, 85 times 54 mm, or other common sizes 50 times 50 mm. The most criticals parameters of the antenna are studied in order to predict design

T. Deleruyelle; P. Pannier; E. Bergeret; S. Bourdel

2008-01-01

423

Transmit\\/receive MIMO antenna subset selection  

Microsoft Academic Search

The paper discusses antenna subset selection in MIMO wireless systems. The subsets of transmit and receive antennas are selected so as to maximise the channel capacity. First of all, we establish the relationship between the multiplexing gain and the diversity gain achievable with adaptive antenna subset selection. Second, we indicate a selection rule that allows a full diversity advantage to

A. Gorokhov; M. Collados; D. Gore; A. Paulraj

2004-01-01

424

Fast antenna subset selection in MIMO systems  

Microsoft Academic Search

Multiple antenna wireless communication systems have recently attracted significant attention due to their higher capacity and better immunity to fading as compared to systems that employ a single-sensor transceiver. Increasing the number of transmit and receive antennas enables to improve system performance at the price of higher hardware costs and computational burden. For systems with a large number of antennas,

Mohammad Gharavi-Alkhansari; Alex B. Gershman

2004-01-01

425

Predictive Algorithm For Aiming An Antenna  

NASA Technical Reports Server (NTRS)

Method of computing control signals to aim antenna based on predictive control-and-estimation algorithm that takes advantage of control inputs. Conceived for controlling antenna in tracking spacecraft and celestial objects, near-future trajectories of which are known. Also useful in enhancing aiming performances of other antennas and instruments that track objects that move along fairly well known paths.

Gawronski, Wodek K.

1993-01-01

426

A new class of resonant antennas  

Microsoft Academic Search

A new class of wire antennas called meander antennas is introduced as possible elements for size reduction. Efficiency is affected only by the ohmic losses in the wire, and cross polarization is negligible. An increase in the number of meander sections introduces less size reduction in return for an improved bandwidth. These antennas can be used to reduce the size

Jalil Rashed; Chen-To Tai

1991-01-01

427

Compact embedded antenna design and its applications  

Microsoft Academic Search

This work proposes a compact antenna design for various terminal devices application. Good agreement between the simulated and measured results validates the design. I. Introduction A known challenge in designing the embedded antenna for terminal devices application is always the compromise between the antenna size and its performance under a specified working scenario. More specifically, users have come to expect

Cheng-Nan Hu; Jing-Wei Huang; D. C. Chang

2011-01-01

428

FRACTAL ANTENNA FOR PASSIVE UHF RFID APPLICATIONS  

Microsoft Academic Search

This paper addresses the design of fractal antennas placed onto dielectric object in the UHF RFID band and introduces a tag antenna conflguration of simple geometry having impedance tuning capability. Through the paper, the dimensions of the fractal antenna are optimized to improve the impedance matching with the chip impedance. The tag performance changes are studied when it is placed

Saber Helmy Zainud-Deen; Hend Abd El-Azem Malhat; Kamal Hassan Awadalla

2009-01-01

429

Antenna Model for Conductive Omega Particles  

Microsoft Academic Search

Analytical models for small ?-shaped conductive particles in free space or embedded in isotropic materials are presented and discussed. The electromagnetic analysis is based on the antenna theory for circular loop antennas and dipole wire antennas. Analytical expressions for the polarizabilities valid in the frequency area covering the two lower resonances are given. Mutual coupling between two portions of the

C. R. Simovski; S. A. Tretyakov; A. A. Sochava; B. Sauviac; F. Mariotte; T. G. Kharina

1997-01-01

430

Advanced control technology for LSST antennas  

NASA Technical Reports Server (NTRS)

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.

Lin, Y. H.

1981-01-01

431

Research in large adaptive antenna arrays  

NASA Technical Reports Server (NTRS)

The feasibility of microwave holographic imaging of targets near the earth using a large random conformal array on the earth's surface and illumination by a CW source on a geostationary satellite is investigated. A geometrical formulation for the illuminator-target-array relationship is applied to the calculation of signal levels resulting from L-band illumination supplied by a satellite similar to ATS-6. The relations between direct and reflected signals are analyzed and the composite resultant signal seen at each antenna element is described. Processing techniques for developing directional beam formation as well as SNR enhancement are developed. The angular resolution and focusing characteristics of a large array covering an approximately circular area on the ground are determined. The necessary relations are developed between the achievable SNR and the size and number of elements in the array. Numerical results are presented for possible air traffic surveillance system. Finally, a simple phase correlation experiment is defined that can establish how large an array may be constructed.

Berkowitz, R. S.; Dzekov, T.

1976-01-01

432

Differential time-domain single-antenna method for ultra-wide band antenna measurements  

Microsoft Academic Search

Antenna radiation can be experimentally investigated by using the single-antenna method that consists of a virtual transmission between the antenna under test and its image in a conducting reflector. This paper presents a time-domain approach of the single-antenna method for the characterization of ultra-wide band (UWB) antennas. A differential technique was considered in order to discriminate the reflected signal due

Razvan D. Tamas; Laurence Babour; Mihai Alexa; Gabriel Vladu; Pierre Saguet; Jean Chilo

2009-01-01

433

A new quasi-Yagi antenna for planar active antenna arrays  

Microsoft Academic Search

In this paper, a novel broadband planar antenna based on the classic Yagi-Uda dipole antenna is presented, and its usefulness as an array antenna is explored. This “quasi-Yagi” antenna is realized on a high dielectric-constant substrate, and is completely compatible with microstrip circuitry and solid-state devices. This antenna achieves a measured 48% frequency bandwidth for voltage standing-wave ratio <2, better

William R. Deal; Noriaki Kaneda; James Sor; Yongxi Qian; Tatsuo Itoh

2000-01-01

434

Visual analysis in a deployable antenna experiment [satellite antenna  

Microsoft Academic Search

To establish a large deployable antenna, monitoring and collimation are essential for reliable and precise deployment. We have developed an analysis method to detect shifts in several images, in which the combination of cross-correlations between images and approximations at subpixel precision enables us to detect shifts in images with a precision of up to 0.01 pixels. The LDREX mission; which

SHINICHI KIMURA; MAKOTO TAKEUCHI; KOICHI HARIMA; YUTARO FUKASE; HITOSHI SATO; TETSUJI YOSHIDA; AKIHIRO MIYASAKA; HIROYUKI NODA; KEI SUNAKAWA; MASANORI HOMMA

2004-01-01

435

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

NASA Technical Reports Server (NTRS)

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

Fichter, W. B.

1989-01-01

436

[Conformational fluctuations in chloroplasts].  

PubMed

Characteristic features of conformational changes in chloroplasts have been studied by microfilm technique at BMI-13 installation. The oscillatory character of changes in chloroplast cross-section area in time, determined earlier by the tele-lazer microscopy technique, has been confirmed by our data. When chloroplasts are simultaneously seen in the microscope it is possible to observe their synchronous oscillation. The stationarity check of conformational changes shows that is a non-stationary process in the general case. So it is concluded that the standard technique of analysing accidental non-stationary processes can be used for study of conformational changes in chloroplasts provided that the corresponding parts of their kinetics are selected or trends are eliminated depending on the type of non-stationarity. PMID:623830

Rudenko, T I; Makarov, A D; Budnitski?, A A

1978-01-01

437

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

NASA Astrophysics Data System (ADS)

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.

White, Carson R.

438

Antenna pattern control using impedance surfaces  

NASA Technical Reports Server (NTRS)

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

Balanis, Constantine A.; Liu, Kefeng

1991-01-01

439

Error margin for antenna gain measurements  

NASA Technical Reports Server (NTRS)

The specification of measured antenna gain is incomplete without knowing the error of the measurement. Also, unless gain is measured many times for a single antenna or over many identical antennas, the uncertainty or error in a single measurement is only an estimate. In this paper, we will examine in detail a typical error budget for common antenna gain measurements. We will also compute the gain uncertainty for a specific UHF horn test that was recently performed on the Jet Propulsion Laboratory (JPL) antenna range. The paper concludes with comments on these results and how they compare with the 'unofficial' JPL range standard of +/- ?.

Cable, V.

2002-01-01

440

Phased array antenna for space shuttle orbiter  

NASA Astrophysics Data System (ADS)

The National Aeronautics and Space Administration is developing a distributed phased array antenna at the Lyndon B. Johnson Space Center as a possible upgrade for the Space Shuttle Orbiter S-band phase modulation communications system. The antenna consists of an eight-element transmit section, eight-element receive section, and a single L-band receive element. The antenna design is constrained by the existing Orbiter system and space environment. The solution to the interface design problems led to an antenna system which provides improved link margins and yet supports previous operational configurations. This paper describes the system development, antenna hardware, and the interface consideration which led to the final design.

Davidson, Shayla E.

1987-02-01

441

Phased array antenna for space shuttle orbiter  

NASA Technical Reports Server (NTRS)

The National Aeronautics and Space Administration is developing a distributed phased array antenna at the Lyndon B. Johnson Space Center as a possible upgrade for the Space Shuttle Orbiter S-band phase modulation communications system. The antenna consists of an eight-element transmit section, eight-element receive section, and a single L-band receive element. The antenna design is constrained by the existing Orbiter system and space environment. The solution to the interface design problems led to an antenna system which provides improved link margins and yet supports previous operational configurations. This paper describes the system development, antenna hardware, and the interface consideration which led to the final design.

Davidson, Shayla E.

1987-01-01

442

Endfire tapered slot antennas on dielectric substrates  

NASA Technical Reports Server (NTRS)

Endfire-tapered slot antennas are suitable for many integrated circuit applications, imaging and phased arrays. An investigation of single elements of such antennas, including slots which are exponentially tapered (Vivaldi), linearly tapered, and constant width. For antennas of all types, a good general agreement is obtained for curves of beamwidth-versus-length, normalized to wavelength, when one compares the data with that for traveling-wave antennas published by Zucker (1961). An important condition for this agreement is that the effective dielectric thickness, defined in the text, is in a certain optimum range. This condition is qualitatively explained in terms of the theory for traveling-wave antennas.

Yngvesson, K. S.; Schaubert, D. H.; Korzeniowski, T. L.; Kollberg, E. L.; Thungren, T.

1985-01-01

443

The Antenna Bride and Bridegroom  

NASA Astrophysics Data System (ADS)

ALMA Achieves Major Milestone With Antenna-Link Success The Atacama Large Millimeter/submillimeter Array (ALMA), an international telescope project, reached a major milestone on 2 March, when two 12-m ALMA prototype antennas were first linked together as an integrated system to observe an astronomical object. "This achievement results from the integration of many state-of-the-art components from Europe and North America and bodes well for the success of ALMA in Chile", said Catherine Cesarsky, ESO's Director General. ESO PR Photo 10/07 ESO PR Photo 10/07 The Prototype Antennas The milestone achievement, technically termed 'First Fringes', came at the ALMA Test Facility (ATF), located near Socorro in New Mexico. Faint radio waves emitted by the planet Saturn were collected by two ALMA prototype antennas, then processed by new, high-tech electronics to turn the two antennas into a single, high-resolution telescope system, called an interferometer. The planet's radio emissions at a frequency of 104 gigahertz were tracked by the ALMA system for more than an hour. Such pairs of antennas are the basic building blocks of the multi-antenna imaging system ALMA. In such a system, the signals recorded by each antenna are electronically combined with the signals of every other antenna to form a multitude of pairs. Each pair contributes unique information that is used to build a highly detailed image of the astronomical object under observation. When completed in the year 2012, ALMA will have 66 antennas. "Our congratulations go to the dedicated team of scientists, engineers and technicians who produced this groundbreaking achievement for ALMA. Much hard work and many long hours went into this effort, and we appreciate it all. This team should be very proud today," said NRAO Director Fred K.Y. Lo. "With this milestone behind us, we now can proceed with increased confidence toward completing ALMA," he added. ALMA, located at an elevation of 5,000m in the Atacama Desert of northern Chile, will provide astronomers with the world's most advanced tool for exploring the Universe at millimetre and submillimetre wavelengths. ALMA will detect fainter objects and be able to produce much higher-quality images at these wavelengths than any previous telescope system. Scientists are eager to use this transformational capability to study the first stars and galaxies that formed in the early Universe, to learn long-sought details about how stars are formed, and to trace the motion of gas and dust as it whirls toward the surface of newly-formed stars and planets. "The success of this test is fundamental proof that the hardware and software now under development for ALMA will work to produce a truly revolutionary astronomical tool," said Massimo Tarenghi, the ALMA Director. In addition to the leading-edge electronic and electro-optical hardware and custom software that proved itself by producing ALMA's first fringes, the system's antennas are among the most advanced in the world. The stringent requirements for the antennas included extremely precise reflecting surfaces, highly accurate ability to point at desired locations in the sky, and the ability to operate reliably in the harsh, high-altitude environment of the ALMA site. The ALMA Test Facility operates the two prototype antennas built by Alcatel Alenia Space and European Industrial Engineering in Europe, and by VertexRSI (USA). These antennas were evaluated individually at the ATF. Both prototypes were equipped with electronic equipment for receiving, digitizing and transmitting signals to a central facility, where the signals are combined to make the antennas work together as a single astronomical instrument. "The successful achievement of recording the first fringes with two ALMA antennas is certainly an important milestone in the scientific program," said Hans Rykaczewski, the European ALMA Project Manager. "It is encouraging and adds to our motivation to see that the principles of ALMA work - not only scientifically, but also from the po

2007-03-01

444

Mutual coupling between microstrip antennas  

NASA Astrophysics Data System (ADS)

A theoretical study of mutual coupling between microstrip antennas is presented. The cavity method is used, and from the equivalence theorem application the problem is reduced to interaction of two magnetic loops. The mutual impedance is then calculated from the reaction theorem. Theoretical results and measurements are in good agreement

Penard, E.; Daniel, J.-P.

1982-07-01

445

Expected Antenna Utilization and Overload.  

National Technical Information Service (NTIS)

The trade-offs between the number of antennas at Deep Space Network (DSN) Deep-Space Communications Complex and the fraction of continuous coverage provided to a set of hypothetical spacecraft, assuming random placement of the space craft passes during th...

E. C. Posner

1991-01-01

446

Mathematics of Antennas: Annotated Bibliography.  

National Technical Information Service (NTIS)

This annotated bibliography deals with theoretical aspects of antennas. The 199 entries are arranged in alphabetical order by year with the following breakdown: 1961--52 entries, 1962--38 entries, 1963--49 entries, and 1964--60 entries. Other information ...

L. Kacinskas

1966-01-01

447

Implanted antenna for biomedical applications  

Microsoft Academic Search

In this paper we present the design, realization and measurements of a first prototype of a complete implantable device. The RF system, working over the medical implanted communication systems (MICS) bandwidth and composed of the antenna, the battery, the transceiver for the data communication and the insulation material, has been designed and realized in order to be integrated with an

F. Merli; L. Bolomey; E. Meurville; A. K. Skrivervik

2008-01-01

448

Fundamental Limitations of Small Antennas  

Microsoft Academic Search

A capacitor or inductor operating as a small antenna is theoretically capable of intercepting a certain amount of power, independent of its size, on the assumption of tuning without circuit loss. The practical efficiency relative to this ideal is limited by the \\

H. A. Wheeler

1947-01-01

449

Optimum optical limited scan antenna  

Microsoft Academic Search

An optical limited scan antenna system is considered for applications such as spot coverage of a small portion of the earth from a satellite. The optimum criterion relating aperture efficiency, number of control elements, and angular coverage is revisited briefly. The optical scheme advocated utilizes a bootlace aperture lens, a generalized Luneberg lens focused to the near field, and a

E. C. Dufort

1986-01-01

450

Dualband Split Dielectric Resonator Antenna  

Microsoft Academic Search

A dualband dielectric resonator antenna (DRA) is designed by splitting a rectilinear dielectric resonator (DR) and carving notches off the DR. It is observed that notches engraved at different positions affect different modes. Removal of dielectric material from where the electric field is strong incurs a significant increase in resonant frequency. The abrupt change of normal electric field across the

Tze-Hsuan Chang; Jean-Fu Kiang

2007-01-01

451

Low profile antennas for MSAT applications  

NASA Technical Reports Server (NTRS)

For MSAT applications, a number of different antennas have been designed and investigated. They include low gain omnidirectional antennas and medium gain to high gain directional antennas. The latter include both portable and vehicular antennas. While portable units are desirable to be low profile and low cost, the vehicular antennas have proved to be the most challenging antenna types for the mobile satellite application. The results of our efforts in design of such antennas are described briefly. Low profile designs are emphasized in most cases, and microstrip type radiators are therefore selected. The single radiator provides low gain omnidirectional patterns and is optimized for low cost applications. It provides low gains around 2-6 dBic and is useful mostly for the data transmission. Medium to high gain antennas are developed as arrays of omnidirectional elements. Again, different designs are optimized to meet the needs of different applications. For portable units, the array configuration can be flexible and is optimized for maximum broadside gains. For vehicular units, however the configurations are desirable to be low profile, or compact, and have means for scanning the antenna beam. For simplicity, fixed beam antennas with mechanical beam scan are selected. For these antennas, as well, different designs, having low profile or compact size, are selected and optimized to meet the MSAT gain and G/T requirements.

Shafai, L.; Moheb, H.; Chamma, W.; Barakat, M.

1995-01-01

452

Taming the conformal zoo  

Microsoft Academic Search

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

Gregory Moore; Nathan Seiberg

1989-01-01

453

Conformally Flat FRW Metrics  

Microsoft Academic Search

We find a new family of non-separable coordinate transformations bringing the FRW metrics into the manifestly conformally flat form. Our results are simple and complete, while our derivation is quite explicit. We also calculate all the FRW curvatures, including the Weyl tensor.

Masao Iihoshi; Sergei V. Ketov; Atsushi Morishita

2007-01-01

454

Conformal cloak for waves  

NASA Astrophysics Data System (ADS)

Conformal invisibility devices are only supposed to work within the valid range of geometrical optics. Here, we show by numerical simulations and analytical arguments that for certain quantized frequencies, they are nearly perfect even in a regime that clearly violates geometrical optics. The quantization condition follows from the analogy between the Helmholtz equation and the stationary Schrödinger equation.

Chen, Huanyang; Leonhardt, Ulf; Tyc, Tomáš

2011-05-01

455

Conformal cloak for waves  

SciTech Connect

Conformal invisibility devices are only supposed to work within the valid range of geometrical optics. Here, we show by numerical simulations and analytical arguments that for certain quantized frequencies, they are nearly perfect even in a regime that clearly violates geometrical optics. The quantization condition follows from the analogy between the Helmholtz equation and the stationary Schroedinger equation.

Chen Huanyang [School of Physical Science and Technology, Soochow University, Suzhou, 215006 Jiangsu (China); Leonhardt, Ulf [School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews KY16 9SS (United Kingdom); Tyc, Tomas [Faculty of Science, Kotlarska 2, and Faculty of Informatics, Botanicka 68a, Masaryk University, CZ-61137 Brno (Czech Republic)

2011-05-15

456

Low Cost Large Space Antennas  

NASA Technical Reports Server (NTRS)

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

Chmielewski, Artur B.; Freeland, Robert

1997-01-01

457

Non-Gimbaled Antenna Pointing  

NASA Technical Reports Server (NTRS)

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

Vigil, Jeannine S.

1997-01-01

458

A phased array tracking antenna for vehicles  

NASA Technical Reports Server (NTRS)

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

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

1990-01-01

459

Foldable nanopaper antennas for origami electronics  

NASA Astrophysics Data System (ADS)

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.

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

2013-05-01

460

Dynamic interrogation of wireless antenna sensor  

NASA Astrophysics Data System (ADS)

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.

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

2014-03-01

461

Conformational changes in biopolymers  

NASA Astrophysics Data System (ADS)

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.

Ivanov, Vassili

2005-12-01

462

Galilean conformal and superconformal symmetries  

SciTech Connect

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

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

2012-10-15

463

Full scale LANDSAT-D antenna pattern measurements  

NASA Technical Reports Server (NTRS)

The design verification of the LANDSAT-D antenna subsystem is addressed. In particular, the analysis of the antenna radiation patterns utilizing a full scale mockup of the LANDSAT-D satellite is discussed. Test antennas included two S-Band shaped beam antennas, two S-Band omni unit radiators (to operate in array), a GPS antenna, an X-Band shaped beam antenna, and one S-Band high-gain parabolic antenna.

1979-01-01

464

User's Manual for Program CONFORM (CONFORMal Contact Stress Problems).  

National Technical Information Service (NTIS)

CONFORM (Conformal Contact of Two Elastic Bodies) is an all Fortran Computer program for the solution of contact stress between two elastic bodies in conformal contact. It is used to find the pressure distribution between the two bodies, the boundary of c...

B. Paul J. Hashemi

1978-01-01

465

Structural Analysis of the JET TAE Antenna  

SciTech Connect

In this paper the mechanical design of the new active MHD antennas for JET is described and the structural/mechanical analysis for the antennas is presented. These new antennas replace the existing n = 1 or 2 saddle coils with a set of eight smaller antennas designed to excite Toroidal Alfven Eigenmodes (TAE's) with high toroidal mode number (n {approx} 10) in the frequency range of 30 kHz-500 kHz. TAE's with these higher mode numbers are expected in ITER and could enhance the loss of fast alpha particles in a burning plasma regime. By studying the properties of stable TAE's excited actively by these antennas, high performance regimes of operation avoiding unstable fast particle driven modes can be found. A more complete overview of the experiment may be found in Reference 1. Two antenna assemblies will be installed at toroidally opposite positions. Antenna wires are protected from the plasma heat flux by CFC tiles mounted on mini-limiters, located between the individual windings. The main structural element is a box section. The support scheme utilizes cantilevered brackets that connect to the saddle coils, and 'wing' brackets which add support to the top of the frame. Conservative estimates of the disruption currents in the MHD antennas and frame were used to calculate loading and resulting stress in the antenna structure. Fields, field transients, and halo current specifications were provided by JET. The frame originally was designed as a continuous loop, and was converted to an open structure to break eddy current loops. Antenna eddy currents were computed assuming the antenna is shorted. In the final design, frame forces primarily result from halo currents entering around the mini limiters that now protect the antenna windings. Accelerations due to the vessel disruption dynamic response were included in the loading. The antenna mechanical design has been shown to perform adequately for all identified disruption loading.

Titus, P.H. [MIT Plasma Science and Fusion Center (United States); Snipes, J. [MIT Plasma Science and Fusion Center (United States); Fasoli, A.F. [MIT Plasma Science and Fusion Center (United States); Testa, D. [Centre de Recherches en Physique des Plasmas (United States); Walton, B. [Culham Science Center (United Kingdom)

2005-05-15

466

Transparent antennas for solar cell integration  

NASA Astrophysics Data System (ADS)

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.

Yasin, Tursunjan

467

Conformal scalar field wormholes  

NASA Technical Reports Server (NTRS)

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

Halliwell, Jonathan J.; Laflamme, Raymond

1989-01-01

468

Wind-induced Dynamics Of A Deep Space Network Antenna  

Microsoft Academic Search

Accurate spacecraft tracking by the NASA Deep Space Network (DSN) antennas must be assured during changing weather conditions. Wind disturbances are the main source of antenna vibrations, and consequently tracking errors. A wind force model is developed, and simulation results of wind-induced vibrations and pointing errors of the DSN antennas are presented. The antenna model includes the antenna structure, the

W. Gawronski; B. Bienkiewicz; R. E. Hill

1994-01-01

469

Short-backfire antenna with circular waveguide feed element  

Microsoft Academic Search

An X-band short-backfire antenna has been constructed and tested to optimize its radiation characteristics. The antenna comprises a backfire structure illuminated by an open-ended circular waveguide. The antenna has a high directivity, and symmetrical radiation pattern. The optimized parameters of the antenna have been measured and compared with that of a cup antenna of similar structure.

J. KOMISARCZUK; S. D. MAROUGI

1983-01-01

470

Antenna Composition and Technology for Cognitive Wireless Communications  

Microsoft Academic Search

Antenna composition that can be applied for cognitive wireless communications is classified into switching antennas, wideband\\u000a antennas and tunable antennas in this article. Some techniques to realize those multi-band antennas are proposed and they\\u000a are numerically or experimentally examined.

Kyoichi Iigusa; Hiroshi Harada

2009-01-01

471

Downlink Optimization of Indoor Wireless Networks Using Multiple Antenna Systems  

Microsoft Academic Search

We compare the performance of two multiple antenna systems to be used in quality of service (QoS) supported indoor wireless networks. While a conventional array antenna system (AAS) has collocated, closely spaced antenna elements, a distributed antenna system (DAS) has largely spaced antennas over the entire area of radio coverage. To support multimedia applications requiring high bandwidth and on time

Bongyong Song; Rene L. Cruz; Bhaskar D. Rao

2004-01-01

472

Broadband terahertz antenna for wide band gap semiconductor photoconductive switches  

Microsoft Academic Search

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

Yu-Jiun Ren; Pengcheng Lv; Kai Chang

2008-01-01

473

Flexible printed circuit board (FPC) antennas for mobile phone operation  

Microsoft Academic Search

In this paper suggestion FPC for antenna design not only easy to control the antenna pattern on desired direction and radiation magnitude but also effective and quickly solved the complex tuning parameters of antenna application. Flexible printer circuit (FPC) board serves planar wireless antenna design. Effectively to supersede the antenna based on the traditional fixed printer circuit board (PCB) implement,

Kuo-Liang Wu; Jwo-Shiun Sun; Guan-Yu Chen

2010-01-01

474

Layout Of Antennas And Cables In A Large Array  

NASA Technical Reports Server (NTRS)

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.

Logan, Ronald T., Jr.

1995-01-01

475

Textile UWB Antennas for Wireless Body Area Networks  

Microsoft Academic Search

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

Maciej Klemm; Gerhard Troester

2006-01-01

476

A rectangular cavity for cell phone antenna efficiency measurement  

Microsoft Academic Search

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

A. P. Raiva; J. Fabrega-Sanchez

2005-01-01

477

Microwave mode shifting antenna system for regenerating particulate filters  

Microsoft Academic Search

A regeneration system comprises a particulate matter (PM) filter including a microwave energy absorbing surface, and an antenna system comprising N antennas and an antenna driver module that sequentially drives the antenna system in a plurality of transverse modes of the antenna system to heat selected portions of the microwave absorbing surface to regenerate the PM filter, where N is

Eugene V. Gonze; Paratore Jr. Michael J; Kevin W. Kirby; Amanda Phelps; Daniel J. Gregoire

2011-01-01

478

Photo-generated THz antennas  

PubMed Central

Electromagnetic resonances in conducting structures give rise to the enhancement of local fields and extinction efficiencies. Conducting structures are conventionally fabricated with a fixed geometry that determines their resonant response. Here, we challenge this conventional approach by demonstrating the photo-generation of THz linear antennas on a flat semiconductor layer by the structured optical illumination through a spatial light modulator. Free charge carriers are photo-excited only on selected areas, which enables the realization of different conducting antennas on the same sample by simply changing the illumination pattern, thus without the need of physically structuring the sample. These results open a wide range of possibilities for the all-optical spatial control of resonances on surfaces and the concomitant control of THz extinction and local fields.

Georgiou, G.; Tyagi, H. K.; Mulder, P.; Bauhuis, G. J.; Schermer, J. J.; Rivas, J. Gomez

2014-01-01

479

Nonlinear Model of Photoconductive Antennas  

NASA Astrophysics Data System (ADS)

The terahertz radiations generated through a slab of GaAs-based photoconductive antennas are calculated from the nonlinear model and measured by a time domain spectroscopy system. The calculated spectra for the different pulses are in agreement with our experimental observations. This consistency suggests that the description of the nonlinear model captures the basic features of this photoelectrical terahertz emission mechanism. Furthermore, 1/f background noise dominates the terahertz detection in our experiments when the frequency is larger than 3 THz.

Li, Liang-Sheng; Yin, Hong-Cheng; Zheng, Ning

2013-06-01

480

Circular short backfire antenna modeling  

Microsoft Academic Search

The first three-dimensional analysis of a short backfire antenna (SBA) is described using the vector-mode-matching method. The computation is efficient for a model that uses only the first harmonic, cos ? , and that deforms the path of numerical integration. This model is useful for SBA computer-aided designs. A larger directivity than previously reported is obtained with the aid of

Gregory P. Otto; Caicheng Lu; Weng Cho Chew

1992-01-01

481

Simulation of Gravitational Radiation Antennas  

NASA Astrophysics Data System (ADS)

The large complexity associated with the design of spherical resonant mass gravitational radiation antennas, necessitates the use of reliable simulation tools, that can accurately predict consequences of specific design choices. For this purpose, we have implemented three different methods; an analytical solution for the displacement field in spherical homogeneous objects, a method utilizing a polynomial expansion of this same displacement field, which is suitable for more complex shaped objects, and a finite element simulation. It is shown that the latter method is best suited to answer critical design issues, whereas the first two can serve as a calibration for the finite element simulation. Since the computational complexity of the finite element kernel requires significant computing power, it has been tailored for execution on parallel computer systems. The simulation program is used to model the influences on the frequency spectrum of the antenna, resulting from varying important design parameters, like the size, material, suspension system and read-out system. Furthermore, we simulate the antenna's response to seismic and thermal noise, cosmics and gravitational radiation.

de Ronde, J. F.; van Albada, G. D.; Sloot, P. M. A.

1997-08-01

482

Transcatheter Antenna For Microwave Treatment  

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

483

Membrane Shell Reflector Segment Antenna  

NASA Technical Reports Server (NTRS)

The mesh reflector is the only type of large, in-space deployable antenna that has successfully flown in space. However, state-of-the-art large deployable mesh antenna systems are RF-frequency-limited by both global shape accuracy and local surface quality. The limitations of mesh reflectors stem from two factors. First, at higher frequencies, the porosity and surface roughness of the mesh results in loss and scattering of the signal. Second, the mesh material does not have any bending stiffness and thus cannot be formed into true parabolic (or other desired) shapes. To advance the deployable reflector technology at high RF frequencies from the current state-of-the-art, significant improvements need to be made in three major aspects: a high-stability and highprecision deployable truss; a continuously curved RF reflecting surface (the function of the surface as well as its first derivative are both continuous); and the RF reflecting surface should be made of a continuous material. To meet these three requirements, the Membrane Shell Reflector Segment (MSRS) antenna was developed.

Fang, Houfei; Im, Eastwood; Lin, John; Moore, James

2012-01-01

484

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

NASA Astrophysics Data System (ADS)

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.

Okano, Yoshiki; Cho, Keizo

485

Transients in Resistively Loaded Antennas and Their Comparison with Conical Antennas and TEM Horns.  

National Technical Information Service (NTIS)

The receiving and transmitting transient responses for a relatively short, linear antenna with continuous resistive loading are investigated theoretically and experimentally. The antenna considered is a nonconducting cylinder with continuously deposited, ...

M. Kanda

1978-01-01

486

Mathcad computer applications predicting antenna parameters from antenna physical dimensions and ground characteristics  

NASA Astrophysics Data System (ADS)

This report provides the documentation for a set of computer applications for the evaluation of antenna parameters. The applications are written for the Mathcad personal computer software for various antenna types listed in the thesis index. Antenna dimensions and, in some cases, ground parameters are the only required inputs for each application. No new antenna parameter equations were developed as a part of this research. The chapters of this thesis are intended to provide Mathcad antenna application users with the background information necessary to readily use and interpret the software for each antenna type. Appendices are provided with examples of each antenna application. Each application has an introductory paragraph and a table of required inputs. The Mathcad software provides various numerical outputs and performance predictions, as well as a graphical representation of radiation patterns in the far-field. Mathcad application results are consistent with the predictions of applicable publications, as well as other antenna numerical analysis programs.

Gerry, Donald D.

1993-06-01

487

Plasmonic nanowire antennas: experiment, simulation, and theory.  

PubMed

Recent advances in nanolithography have allowed shifting of the resonance frequency of antennas into the optical and visible wavelength range with potential applications, for example, in single molecule spectroscopy by fluorescence and directionality enhancement of molecules. Despite such great promise, the analytical means to describe the properties of optical antennas is still lacking. As the phase velocity of currents at optical frequencies in metals is much below the speed of light, standard radio frequency (RF) antenna theory does not apply directly. For the fundamental linear wire antenna, we present an analytical description that overcomes this shortage and reveals profound differences between RF and plasmonic antennas. It is fully supported by apertureless scanning near-field optical microscope measurements and finite-difference time-domain simulations. This theory is a starting point for the development of analytical models of more complex antenna structures. PMID:20726567

Dorfmüller, Jens; Vogelgesang, Ralf; Khunsin, Worawut; Rockstuhl, Carsten; Etrich, Christoph; Kern, Klaus

2010-09-01

488

High accuracy deployable antenna for communications satellite  

NASA Astrophysics Data System (ADS)

High frequency multi-beam satellite antennas have been studied to realize increased communication capacity, simplified earth stations, and multiple frequency reuse. The satellite antenna needs a highly accurate and large reflector. To overcome the launching vehicle's constraints in size and weight, a solid deployable antenna is under development. A petal antenna (PETAL), composed of solid shell elements, has been studied as a high frequency use deployable antenna. It is an axi-symmetric antenna composed of a fixed central shell and deployable triangular and square shells. During the launch phase, a restraining cable is bound around the periphery of deployable elements stowed in a hexagonal configuration. Deployment is initiated by pyrotechnic cable cutters, and the shells are deployed by spring action.

Watanabe, M.; Misawa, M.; Minomo, M.; Yasaka, T.

489

Numerical analysis of double antennas, volume 1  

NASA Astrophysics Data System (ADS)

The Double Delta antenna is an HF communication antenna which exists in many forms throughout military communication commands. Performance characteristics for existing designs are presently unknown and are required in order to recommend an optimum design. This thesis investigates Double Delta antennas used by the U.S. Army (lowband and highband), the U.S. Air Force (lowband and highband), and a commercial model. Selected models are analyzed by a computer simulation method using the Numerical Electromagnetics Code (NEC). The antenna designs are investigated to determine optimum performance characteristics over the 2 - 30 MHz range of frequencies. The parameters calculated were input impedance, VSWR, and antenna gain radiation patterns. For the performance of the antennas when sited near lossy ground, the Sommerfeld method was employed. Finally the results of the evaluation are presented and recommendations are made.

Chafid, Achmad

1988-12-01

490

Numerical analysis of double antennas, volume 2  

NASA Astrophysics Data System (ADS)

The Double Delta antenna is an HF communication antenna which exists in many forms throughout military communication command. Performance characteristics for existing designs are presently unknown and are required in order to recommend an optimum design. This thesis investigates Double Delta antennas used by the U.S. Army (lowband and highband), the U.S. Air Force (lowband and highband), and a commercial model. Selected models are analyzed by a computer simulation method using the Numerical Electromagnetics Code (NEC). The antenna designs are investigated to determine optimum performance characteristics over the 2 to 30 MHz range of frequencies. The parameters calculated were input impedance, VSWR, and antenna gain radiation patterns. For the performance of the antennas when sited near lossy ground, the Sommerfeld method was employed. Finally the results of the evaluation are presented and recommendations are made.

Chafid, Achmad

1988-12-01

491

Advanced microwave radiometer antenna system study  

NASA Technical Reports Server (NTRS)

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

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

1976-01-01

492

Antenna pattern control using impedance surfaces  

NASA Technical Reports Server (NTRS)

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.

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

1993-01-01

493

Compact Miniaturized Antenna for 210 MHz RFID  

NASA Technical Reports Server (NTRS)

This paper describes the design and simulation of a miniaturized square-ring antenna. The miniaturized antenna, with overall dimensions of approximately one tenth of a wavelength (0.1 ), was designed to operate at around 210 MHz, and was intended for radio-frequency identification (RFID) application. One unique feature of the design is the use of a parasitic element to improve the performance and impedance matching of the antenna. The use of parasitic elements to enhance the gain and bandwidth of patch antennas has been demonstrated and reported in the literature, but such use has never been applied to miniaturized antennas. In this work, we will present simulation results and discuss design parameters and their impact on the antenna performance.

Lee, Richard Q.; Chun, Kue

2008-01-01

494

Mobile satellite communications - Vehicle antenna technology update  

NASA Astrophysics Data System (ADS)

This paper discusses options for vehicle antennas to be used in mobile satellite communications systems. Two types of antennas are identified. A non-steerable, azimuthally omnidirectional antenna with a modest gain of 3 to 5 dBi is suggested when a low cost is desired. Alternatively, mechanically or electronically steerable antennas with a higher gain of 10 to 12 dBi are suggested to alleviate power and spectrum scarcity associated with mobile satellite communications. For steerable antennas, both open-loop and closed-loop pointing schemes are discussed. Monopulse and sequential lobing are proposed for the mechanically steered and electronically steered antennas, respectively. This paper suggests a hybrid open-loop/closed-loop pointing technique as the best performer in the mobile satellite environment.

Bell, D.; Naderi, F. M.

495

Distributed control of large space antennas  

NASA Technical Reports Server (NTRS)

A systematic way to choose control design parameters and to evaluate performance for large space antennas is presented. The structural dynamics and control properties for a Hoop and Column Antenna and a Wrap-Rib Antenna are characterized. Some results of the effects of model parameter uncertainties to the stability, surface accuracy, and pointing errors are presented. Critical dynamics and control problems for these antenna configurations are identified and potential solutions are discussed. It was concluded that structural uncertainties and model error can cause serious performance deterioration and can even destabilize the controllers. For the hoop and column antenna, large hoop and long meat and the lack of stiffness between the two substructures result in low structural frequencies. Performance can be improved if this design can be strengthened. The two-site control system is more robust than either single-site control systems for the hoop and column antenna.

Cameron, J. M.; Hamidi, M.; Lin, Y. H.; Wang, S. J.

1983-01-01

496

Status of the ALMA Antenna Production  

NASA Astrophysics Data System (ADS)

The design of the ALMA antennas began in 1999 with a prototyping phase. Two antenna prototypes were built, extensively tested at the VLA site in New Mexico and evaluated in 2003. It was decided to proceed to procurement with two parallel calls for tenders based on the two prototypes. In 2005 contracts were placed with the US VertexRSI and the European AEM Consortium for 25 antennas each. An update on the two designs and the production progress is presented. The Japanese antennas (both 7 and 12 m) are being built by Mitsubishi, which also built an additional antenna prototype. The first antennas have recently arrived at the integration facility at the ALMA Operations Support Facility (OSF).

Stanghellini, Stefano

2007-12-01

497

Detecting crack orientation using patch antenna sensors  

NASA Astrophysics Data System (ADS)

Crack orientation is a very important parameter for structural integrity analysis. Even though many sensors have been developed to detect crack presence and length, very few sensors can detect crack orientation. Recently, we have demonstrated a patch antenna sensor that can detect crack propagation with sub-millimeter resolution. In this paper, the capability of the antenna sensors for crack orientation detection is studied. An antenna sensor with a rectangular antenna patch radiates at two fundamental modes. The effect of a ground-plane crack on these two resonant frequencies depends on its orientation. Hence, the crack orientations can be monitored by analyzing the crack-induced shifts of both antenna resonant frequencies. The principle of operation will be discussed first, followed by detailed descriptions on the numerical simulation, sensor fabrication, experimental procedure, results and analysis. Simulation as well as experimental results confirmed that the antenna sensor is capable of providing quantified information about the crack orientation.

Mohammad, I.; Gowda, V.; Zhai, H.; Huang, H.

2012-01-01

498

Gradual change of conformational disorder  

SciTech Connect

The basic step of crystallization of linear macromolecules is conformational ordering. If the ordering is completed during crystallization, the entropy of fusion is a measure of the gain of conformational disorder on melting. In this lecture the possibility is discussed that in some cases conformational order changes below the glass or disordering transitions (T{sub g} and T{sub d}, respectively). Changes in conformational order below T{sub g} were observed for some flexible macromolecules without side-chains, like polyethylene. Changes below T{sub d} are found among main-chain liquid-crystalline polymers, conformationally disordered (condis) crystals, and related small-molecule model-compounds.

Wunderlich, B

1994-12-31

499

Wrapped Microstrip Antennas for Laptop Computers  

Microsoft Academic Search

The objective of this article is to provide a comprehensive and unified description of the authors' work on the development of wrapped microstrip antennas for laptop applications. The first contribution is the introduction of quasi-omnidirectional wrapped-microstrip antenna elements to be integrated into the display rim of laptops. Single- and dual-band antennas are presented to demonstrate the capabilities of wrapped microstrip

J. Guterman; A. A. Moreira; C. Peixeiro; Y. Rahmat-Samii

2009-01-01

500

New band-notched UWB antenna  

Microsoft Academic Search

A simple and compact ultra wideband (UWB) printed monopole antenna with band-notched performance is proposed in this paper.\\u000a The antenna is partially grounded so that the Q value is depressed and the impedance bandwidth is broadened. A small strip bar is loaded on each arm of the similar U-shaped\\u000a radiator. The impedance bandwidth of the antenna overlap with IEEE 802.11a

Xiao-xiang He; Hong-wei Deng

2009-01-01