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1

Electrically Small Folded Slot Antenna Utilizing Capacitive Loaded Slot Lines  

NASA Technical Reports Server (NTRS)

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

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

2007-01-01

2

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

NASA Astrophysics Data System (ADS)

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

Cutshall, Ryan T.

3

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

Microsoft Academic Search

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

Peng Jin; Richard W. Ziolkowski

2009-01-01

4

Low Q electrically small linear and elliptical polarized spherical dipole antennas  

Microsoft Academic Search

Electrically small antennas are generally presumed to exhibit high impedance mismatch (high VSWR), low efficiency, high quality factor (Q); and, therefore, narrow operating bandwidth. For an electric or magnetic dipole antenna, there is a fundamental lower bound for the quality factor that is determined as a function of the antenna's occupied physical volume. In this paper, the quality factor of

Steven R. Best

2005-01-01

5

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

SciTech Connect

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

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

2011-09-01

6

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

7

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

PubMed

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

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

2012-03-01

8

Some novel design techniques for conformal antennas  

Microsoft Academic Search

Design techniques for conformal antennas are presented including designs for dielectric-loaded cavity radiators quadrature parallel-plate antennas, integrated-random antennas, and edge-slot radiators. Working models designed for a variety of applications have been fabricated for operation in the frequency range from UHF to K-band. It is noted that aside from the weight and space saving features realized and the usage on conformal

H. S. Jones Jr.

1978-01-01

9

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

E-print Network

6 LIST OF FIGURES Figure 1.1 – Antenna dimensions for Meridian configuration ................................... 11 Figure 2.1 – Overview of TSA dimensions and fields................................................ 14 Figure 2.2 – Taper... detailed design procedure that investigates the operational bandwidth effects due to parameter variations. Chapter 4 offers conclusions and future work. 14 CHAPTER 2 OVERVIEW OF TAPERED SLOT ANTENNAS Tapered slot antennas (TSA) first appeared...

Panzer, Benjamin Garrett

2007-12-12

10

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

11

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

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

12

SOME FAR FIELD FEATURES OF CYLINDRICAL MICROSTRIP ANTENNA ON AN ELECTRICALLY SMALL CYLINDER  

Microsoft Academic Search

The far field behavior of a small wave size cylindrical microstrip antenna (CMA) has been originally analyzed for a small elevation angle, where a pronounced maximum has been found. Also it has been found that a similar maximum takes place in the far field of an electric dipole taken instead of the patch. It has been shown that the phenomenon

Alexander Y. Svezhentsev

2008-01-01

13

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

14

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

PubMed

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

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

2008-08-01

15

Wideband embedded/conformal antenna subsystem concept  

NASA Astrophysics Data System (ADS)

The concept for a wideband, embedded/conformal antenna subsystem is presented. A multilayer radome not only protects the antenna from hostile environments, but also is designed to sustain aircraft dynamic loading. The radiating element consists of a planar, dual- flared slot capable of high-performance, multioctave operation. Advanced materials are currently being developed to enhance the low profile and efficient, wideband performance of the radiating element.

Smalanskas, Joseph P.; Valentine, Gary W.; Wolfson, Ronald I.

1991-10-01

16

New Concept Conformal Antennas Utilizing Metamaterial and Transformation Optics  

E-print Network

In this letter, we show by theoretical analysis and computer simulation that conformal antennas can be designed using metamaterial with inhomogeneous constitutive parameters by applying the electromagnetic coordinate ...

Luo, Yu

17

Ultra-wideband conformal helmet antenna  

Microsoft Academic Search

This paper presents the development of an ultra-wideband (300 to 3000 MHz), vertically polarized, nearly omni-directional (in azimuth) communications antenna integrated into the camouflage cover of a standard military-issue Kevlar helmet. The Helmet Camouflage Cover Antenna (referred to as the “helmet antenna”) is one of three antennas (with the combined frequency coverage from 2 to 2000 MHz) based on the

J. Lebaric; Ah-Tuan Tan

2000-01-01

18

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

19

Development of a microstrip UHF conformal antenna  

NASA Technical Reports Server (NTRS)

Low profile, engineering model EMU antennas were constructed. Final data for these antennas meet most of the electrical requirements in a 6 in. x 18 in. x 1.4 in. package which weighs under 2.0 lbs. Coverage data calculated at the design frequencies very nearly meets the design goal of providing a gain greater than or equal to -10 dBi over 80% of a sphere. Recommendations are made for future work directed toward producing an efficient quality design capable of operating in a space environment.

Shields, M. W.; Cassell, R. B.

1977-01-01

20

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

E-print Network

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

Elsherbeni, Atef Z.

21

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

NASA Technical Reports Server (NTRS)

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

Kempel, Leo C.; Volakis, John L.

1992-01-01

22

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

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

23

Calculation of the characteristic impedance of TEM horn antennas using the conformal mapping approach  

Microsoft Academic Search

A new conformal mapping technique for determining the characteristic impedance of TEM horn antennas is presented. The original work by Carrel [1958], on noncoplanar fin antennas of this type, predicts incorrect impedance values which do not agree with experimental results. The present paper discusses fully the source of the error in Carrel and details the successive mappings involved in the

A. P. Lambert; S. M. Booker; P. D. Smith

1995-01-01

24

Scattering from a cylindrically conformal slotted-waveguide array antenna  

Microsoft Academic Search

Slotted-waveguide array antennas are widely used on modern airborne radar. However, conventional planar slotted-waveguide antennas have a significant contribution to the overall radar cross section (RCS) of the host vehicle. Reduction of the antenna's RCS is one of important aspects for the stealth technology. It is well known, the RCS of a flat plate is generally higher than that of

Guoxin Fan; Jian-Ming Jin

1996-01-01

25

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

26

The analysis of wideband conformal microstrip array antenna with cosecant-squared beam shaping  

Microsoft Academic Search

The characteristics of new ultra wideband (UWB) like fractal microstrip patch antenna element and 24×10 elements wideband conformal microstrip array antenna using non-uniform photonic bandgap (PBG) substrate structure whose gap positions enhance some modes and weaken others have been analyzed using a full 3D electromagnetic field inside a structure based on the finite element method (FEM). The cosec2 elevation beam

Yasser M. Madany

2006-01-01

27

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

28

Conformal patch fed stacked triangular dielectric resonator antenna for WLAN applications  

Microsoft Academic Search

A Stacked triangular dielectric resonator antenna (DRA) fed by a conformal patch is proposed for WLAN applications. In this paper, triangular shaped three resonators with same dielectric constant and different sizes are stacked to improve the gain, bandwidth and radiation performances of DRA. An increase in bandwidth is further achieved by using air gaps. This Stacked DRA is excited by

Runa Kumari; Kapil Parmar; S. K. Behera

2010-01-01

29

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

30

Phase-compensated metasurface for a conformal microwave antenna  

NASA Astrophysics Data System (ADS)

The in-phase radiation from a conformal metamaterial surface is numerically and experimentally reported. The LC-resonant metasurface is composed of a simultaneously capacitive and an inductive grid constituted by copper strips printed on both sides of a dielectric board. The metasurface is designed to fit a curved surface by modifying its local phase. The latter phase-compensated metasurface is used as a reflector in a conformal Fabry-Pérot resonant cavity designed to operate at microwave frequencies. Far-field measurements performed on a fabricated prototype allow showing the good performances of such a phase-compensated metasurface in restoring in-phase emissions from the conformal surface and producing a directive emission in the desired direction.

Germain, Dylan; Seetharamdoo, Divitha; Nawaz Burokur, Shah; de Lustrac, André

2013-09-01

31

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

32

CONTROLLABLE CONFORMAL ELECTROMAGNETIC BAND GAP ANTENNA FOR BASE H. BOUTAYEB*, K. MAHDJOUBI, A-C. TAROT and T.DENIDNI*  

E-print Network

CONTROLLABLE CONFORMAL ELECTROMAGNETIC BAND GAP ANTENNA FOR BASE STATION H. BOUTAYEB*, K. MAHDJOUBI. *INRS-Telecommunication, place Bonaventure, H5A1K6, Montreal, Canada. The structure is characterized multi-band (GSM/DCS/UMTS) base station antenna. We call T the transmission coefficient of the structure

Paris-Sud XI, Université de

33

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

Microsoft Academic Search

The use of conformal antenna array in the treatment of superficial diseases can significantly increase patient comfort while enhancing the local control of large treatment area with irregular shapes. Originally a regular square multi-fed slot antenna (Dual Concentric Conductor - DCC) was proposed as basic unit cell of the array. The square DCC works well when the outline of the

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

2009-01-01

34

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

PubMed Central

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

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

2013-01-01

35

Considerations on terminal antenna design and analysis  

Microsoft Academic Search

The explosion of modern wireless services has drastically increased the need for efficient electrically small antennas for the handheld terminals. However and opposite to electronic devices, efficiency in antennas is limited by fundamental physical principles. In this paper we present a short summary on the theoretical limitation of the performances of electrically small antennas, and then present some design strategies.

Anja K. Skrivervik; Juan R. Mosig

2008-01-01

36

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 A.

2006-01-01

37

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

PubMed

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

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

2009-02-23

38

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

PubMed Central

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

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

2013-01-01

39

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

NASA Astrophysics Data System (ADS)

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

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

2009-02-01

40

The cellphone antenna test results  

Microsoft Academic Search

The results of experimental testing near reactive zone of the different kinds the cellphone antennas are presented. Dielectric coating parameters influence on cellphone antenna near reactive zone pattern is studied. The specific absorption rate (SAR) is also measured, presented and discussed in this paper. The properties of electrically small antennas as a function their total length, geometry and effective volume

A. I. Karpov; V. A. Katrych; E. A. Antonenko; S. A. Yarmolchuc

2009-01-01

41

Antennae  

NASA Technical Reports Server (NTRS)

Atlas Image mosaic, covering 7' x 7' on the sky of the interacting galaxies NGC 4038 and NGC 4039, better known as the Antennae, or Ring Tail galaxies. The two galaxies are engaged in a tug-of-war as they collide. The mutual gravitation between them is working to distort each spiral galaxy's appearance as the two merge. The interaction is evidently impetus for an intense burst of new star formation, as can be seen from the many infrared-bright knots and bright galactic nuclei. Compare the 2MASS view of this system with that obtained by the Hubble Space Telescope in the optical. Many of the same features are seen, although 2MASS is able to peer through much of the dust seen in the galaxies' disks. The galaxy light looks smoother. Also, in the near-infrared the bright knots of star formation are likely highlighted by the light of massive red supergiant stars. The much more extended 'tidal tails,' which give the Antennae their name, are quite faint in the 2MASS image mosaic.

1999-01-01

42

Focusing and impedance properties of conformable phased array antennas for microwave hyperthermia  

SciTech Connect

Phased array applicators for microwave hyperthermia are usually developed using planar, layered tissue models, and then evaluated using numerical techniques. The present investigation considers the use of a cylindrical, layered tissue model to replace the first step of the design procedure. This model facilitates an evaluation of the impact of curvature, polarization, and bolus materials on the antenna performance.

Najafabadi, R.M.; Peterson, A.F. [Georgia Inst. of Tech., Atlanta, GA (United States). School of Electrical and Computer Engineering] [Georgia Inst. of Tech., Atlanta, GA (United States). School of Electrical and Computer Engineering

1996-10-01

43

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

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

44

Highly adaptive RF excitation scheme based on conformal resonant CRLH metamaterial ring antennas for 7-Tesla traveling-wave magnetic resonance imaging.  

PubMed

We propose an adaptive RF antenna system for the excitation (and manipulation) of the fundamental circular waveguide mode (TE(11)) in the context of high-field (7T) traveling-wave magnetic resonance imaging (MRI). The system consists of composite right-/left-handed (CRLH) meta-material ring antennas that fully conforms to the inner surface of the MRI bore. The specific use of CRLH metamaterials is motivated by its inherent dispersion engineering capabilities, which is needed when designing resonant ring structures for virtually any predefined diameter operating at the given Larmor frequency (i.e. 298 MHz). Each functional group of the RF antenna system consists of a pair of subsequently spaced and correspondingly fed CRLH ring antennas, allowing for the unidirectional excitation of propagating, circularly polarized B(1) mode fields. The same functional group is also capable to simultaneously mold an incoming, counter-propagating mode. Given these functionalities we are proposing now a compound scheme (i.e. periodically arranged multiple antenna pairs)--termed as "MetaBore"--that is apt to provide a tailored RF power distribution as well as full wave reflection compensation virtually at any desired location along the bore. PMID:22254370

Erni, Daniel; Liebig, Thorsten; Rennings, Andreas; Koster, Norbert H L; Fröhlich, Jürg

2011-01-01

45

Design and performance of small printed antennas  

Microsoft Academic Search

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

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

1998-01-01

46

Planar Microstrip Yagi Antennas  

NASA Technical Reports Server (NTRS)

Developmental class of antennas based on combination of microstrip-patch and Yagi-array concepts. Mutual coupling between microstrip elements, ordinarily considered nuisance, used to advantage. Applicable to both linearly and circularly polarized antennas. Use of fewer driven elements results in less complexity and reduced loss of power in associated transmission lines and other coupling and power-distributing circuitry. Applications include antennas on land vehicles, television receiving antennas, and conformal antennas on aircraft.

Huang, John

1990-01-01

47

Antenna engineering handbook /2nd edition/  

NASA Astrophysics Data System (ADS)

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

Johnson, R. C.; Jasik, H.

48

The ETH (electronically tuned helix) antenna  

Microsoft Academic Search

A new class of electrically small tunable antennas that are highly efficient has been developed. Designs for US Army applications include communications antennas in the HF and VHF bands with frequency tuning ranges in excess of 15:1. Designs operating at moderate power levels (10-40 W) and high power (1 kW) exist or are under development. The antennas are low profile,

G. Ploussios; A. Strugatsky

1995-01-01

49

Multiple frequency printed slot and dipole antennas  

E-print Network

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

Kolsrud, Arild

2012-06-07

50

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

51

Printed Monopole Antennas with Increased Bandwidth and Gain for Wi-Fi Applications  

E-print Network

Printed Monopole Antennas with Increased Bandwidth and Gain for Wi-Fi Applications Nevin Altunyurt, compact antennas that can integrate well into future portable wireless communication devices. Owing, electrically small planar antennas are seen as the favorable candidates to be used in such systems

Swaminathan, Madhavan

52

Standard antennas for electromagnetic interference measurements and methods to calibrate them  

Microsoft Academic Search

This tutorial paper discusses various standard antennas for measuring radio-frequency electric and magnetic fields. A theoretical analysis of each antenna's receiving characteristics is summarized and referenced. The antennas described are an electrically short dipole, a resistively loaded short dipole and halfwave dipole, an electrically small loop, a resistively loaded loop, photonic probes, and a single-turn loop designed for simultaneous measurement

Motohisa Kanda

1994-01-01

53

Design Goals Electrically small a few meters in size  

E-print Network

;CENTER FOR PULSED POWER AND POWER ELECTRONICS HAARP Facility · High Frequency Active Auroral Research POWER AND POWER ELECTRONICS Antenna Dimensions 3/13/2014 4 #12;CENTER FOR PULSED POWER AND POWER.") Inductive Inductive Capacitive 3m 3m 1.5m #12;CENTER FOR PULSED POWER AND POWER ELECTRONICS Circuit Model

Anlage, Steven

54

Experimental demonstration of superdirective dielectric antenna  

SciTech Connect

We propose and demonstrate experimentally a simple approach for achieving superdirectivity of emitted radiation for electrically small antennas based on a spherical dielectric resonator with a notch excited by a dipole source. Superdirectivity is achieved without using complex antenna arrays and for a wide range of frequencies. We also demonstrate the steering effect for a subwavelength displacement of the source. Finally, unlike previously known superdirective antennas, our design has significantly smaller losses, at the operation frequency radiation efficiency attains 80%, and matching holds in the 3%-wide frequency band without any special matching technique.

Krasnok, Alexander E.; Filonov, Dmitry S.; Belov, Pavel A. [National Research University of Information Technologies, Mechanics and Optics (ITMO), St. Petersburg 197101 (Russian Federation); Simovski, Constantin R. [National Research University of Information Technologies, Mechanics and Optics (ITMO), St. Petersburg 197101 (Russian Federation); Aalto University, School of Electric and Electronic Engineering, Aalto FI76000 (Finland); Kivshar, Yuri S. [National Research University of Information Technologies, Mechanics and Optics (ITMO), St. Petersburg 197101 (Russian Federation); Nonlinear Physics Center, Research School of Physics and Engineering, Australian National University, Canberra ACT 0200 (Australia)

2014-03-31

55

Miniaturized telemetry antennas with integrated electronics  

Microsoft Academic Search

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

Thomas Goodwin

2008-01-01

56

Antenna Systems Advanced Antenna Systems  

E-print Network

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

Fang, Yuguang "Michael"

57

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, Allan C.; Tuss, James

1999-07-01

58

User Antennas  

NASA Technical Reports Server (NTRS)

The following subject areas are covered: (1) impact of frequency change of user and spacecraft antenna gain and size; (2) basic personal terminal antennas (impact of 20/30 GHz frequency separation; parametric studies - gain, size, weight; gain and figure of merit (G/T); design data for selected antenna concepts; critical technologies and development goals; and recommendations); and (3) user antenna radiation safety concerns.

Jamnejad, Vahraz; Cramer, Paul

1990-01-01

59

Inflated antennas  

NASA Technical Reports Server (NTRS)

Inflatable space antennas are discussed. A brief history of inflatable structures is given. Several antenna configurations are described. The antenna configuration consisting of a thin film cone and parabolic held to the proper shape by internal pressure is discussed in detail.

Friese, G. J.; Thomas, M.; Hinson, W. F.

1983-01-01

60

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

E-print Network

--Electrically small antennas, genetic algorithm (GA), metamaterials, optimization methods. I. INTRODUCTION ANTENNASIEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 55, NO. 3, MARCH 2007 731 A Hybrid Optimization-MATLAB based hybrid optimization model. The optimized-analytical model is specifically applied to a spherical

Ziolkowski, Richard W.

61

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

62

Linear array of woodpile EBG sectoral horn antennas  

Microsoft Academic Search

A technique is described for creating linear array antennas that conform to the natural stacking sequence of the woodpile electromagnetic bandgap (EBG) material. Each element in the linear array consists of a woodpile EBG sectoral horn antenna. The electromagnetic confinement mechanism within each horn antenna relies wholly on the 3-D EBG of the woodpile material. The array element has a

Andrew R. Weily; Karu P. Esselle; Trevor S. Bird; Barry C. Sanders

2006-01-01

63

Circular and polygonal array antennas for electronic steering  

Microsoft Academic Search

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

Juliano R. Brianeze; Edson Reis

2010-01-01

64

Electrically small particles combining even- and odd-mode currents for microwave energy harvesting  

NASA Astrophysics Data System (ADS)

We present a structure composed of an ensemble of electrically small resonators for harvesting microwave energy. A flower-like structure composed of four electrically small split-ring resonators (SRRs) arranged in a cruciate pattern, each with a maximum dimension of less than ?o/10, is shown to achieve more than 43% microwave-to-alternating current conversion efficiency at 5.67 GHz. Even- and odd-mode currents are realized in the proposed harvester to improve the efficiency and concurrently reduce the dielectric loss in the substrate. An experimental validation is conducted to prove the harvesting capability.

AlShareef, Mohammed R.; Ramahi, Omar M.

2014-06-01

65

Land vehicle antennas for satellite mobile communications  

NASA Technical Reports Server (NTRS)

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

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

1985-01-01

66

Smart-skin antenna technology  

NASA Astrophysics Data System (ADS)

Using smart materials and skins, one could design a smart structure with suitable feedback system architecture. This paper is designed to address some technical advances and applications of smart materials, smart skins and coatings covering a broad spectrum of electromagnetic fields. The Smart Skin Antenna Technology Program's objectives are to (1) use smart skin technologies to develop an antenna system architecture which is structurally integratable, wideband, and embedded/conformal; (2) design, develop, and fabricate a thin, wideband, conformal/arrayable radiator that is structurally integratable and which uses advanced Penn State dielectric and absorber materials to achieve wideband ground planes, and together with low RCS, wideband radomes; (3) implement a smart skin antenna system architecture. Traditional practice has been to design radome and antenna as separate entities and then resolve any interface problems during an integration phase. A structurally integratable conformal antenna, however, demands that the functional components be highly integrated both conceptually and in practice. Our concept is to use the lower skin of the radome as a substrate on which the radiator can be made using standard photolithography, thick film, or LTCC techniques.

Varadan, Vijay K.; Varadan, Vasundara V.

1993-07-01

67

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

68

Smart skin spiral antenna with chiral absorber  

NASA Astrophysics Data System (ADS)

Recently there has been considerable interest toward designing 'smart skins' for aircraft. The smart skin is a composite layer which may contain conformal radars, conformal microstrip antennas or spiral antennas for electromagnetic applications. These embedded antennas will give rise to very low radar cross section (RCS) 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. This paper is designed to address some technical advances made to reduce the size of spiral antennas using tunable dielectric materials and chiral absorbers. The purpose is to design, develop and fabricate a thin, wideband, conformal spiral antenna architecture that is structurally integrable and which uses advanced Penn State dielectric and absorber materials to achieve wideband ground planes, and together with low RCS. Traditional practice has been to design radome and antenna as separate entities and then resolve any interface problems during an integration phase. A structurally integrable conformal antenna, however, demands that the functional components be highly integrated both conceptually and in practice. Our concept is to use the lower skin of the radome as a substrate on which the radiator can be made using standard photolithography, thick film or LTCC techniques.

Varadan, Vijay K.; Varadan, Vasundara V.

1995-05-01

69

Micro-electro-mechanical systems (MEMS) integrated frequency reconfigurable antenna  

NASA Astrophysics Data System (ADS)

In this paper, the design, analysis, and characterization of reconfigurable antennas based on radio frequency micro-electro-mechanical systems (RF MEMS) operating in the United States' public safety (PS) bands are presented. The design methodology of these antennas, which are dierent from the normal antenna design, is also reported. In this thesis, two electrically small reconfigurable antenna designs have been presented, with two and three modes of operation, and central frequencies of 718 and 4960 MHz and of 857,809 and 4960 MHz, respectively. The maximum frequency tunable ratio achieved in these designs is 7. The recongurability between the modes is achieved by one and three RF MEMS switches in all three designs. These switches enable a change in the length of the current flow path, thereby changing the resonance frequencies. The measurement results for impedance and radiation characteristics of the fabricated antennas prototypes are also presented, and agree reasonably well with the simulations results from An-soft HFSS.

Zohur, Abdul

70

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

71

IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 54, NO. 7, JULY 2006 2113 Metamaterial-Based Efficient Electrically Small  

E-print Network

the input resistance of this resonant system to 50 . Generally, this matching method uti- lizes passive resistance that is matched to a specified source resistance leading to overall efficiencies approaching unity it has a very small radiation resistance while simultaneously having a very large capacitance reactance

Ziolkowski, Richard W.

72

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

73

Survey of deployable antenna concepts  

NASA Technical Reports Server (NTRS)

Deployable space antenna concepts are surveyed. Precision reflector antennas, stiffened membrane antennas, truss antennas, infrared antennas, and electrostatically figured membrane reflectors are described.

Freeland, R. E.

1983-01-01

74

Performance Analysis of Dipole Antennas Embedded in Core-Shell Spheres: A Green's Function Analysis  

E-print Network

The main goal of this work is to theoretically investigate the behavior of an electrically small antenna enclosed in a concentric sphere. The Greens function analysis is applied to characterize the input impedance of a concentric resonator excited by a dipole located at its center. The method of moments (MoM) with Galrekin's procedure is used to determine the current distribution over the source excitation and hence the input impedance. The behavior of quality factor (Q) and bandwidths of the antenna is studied with the use of input impedance as a function of frequency. We illustrate that by embedding a dipole antenna inside a core-shell structure, with magnetic shell and dielectric core, a Q as low as the Chu limit can be approached. The obtained observations demonstrate how a resonator composed of magnetic shells can provide electrically small antennas with high bandwidths performance.

Shabnam Ghadarghadr; Hossein Mosallaei

2010-05-02

75

Modeling the electromagnetic radiation from electrically small table-top products  

Microsoft Academic Search

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

T. H. Hubing; J. F. Kauffman

1989-01-01

76

Notch Antennas  

NASA Technical Reports Server (NTRS)

Notch antennas, also known as the tapered slot antenna (TSA), have been the topics of research for decades. TSA has demonstrated multi-octave bandwidth, moderate gain (7 to 10 dB), and symmetric E- and H- plane beam patterns and can be used for many different applications. This chapter summarizes the research activities on notch antennas over the past decade with emphasis on their most recent advances and applications. This chapter begins with some discussions on the designs of single TSA; then follows with detailed discussions of issues associated with TSA designs and performance characteristics. To conclude the chapter, some recent developments in TSA arrays and their applications are highlighted.

Lee, Richard Q.

2004-01-01

77

International Conference on Antennas and Propagation (ICAP 89), 6th, University of Warwick, Coventry, England, Apr. 4-7, 1989, Proceedings. Part 1 - Antennas. Part 2 - Propagation  

NASA Astrophysics Data System (ADS)

Various papers on antennas and propagation are presented. The general topics addressed include: phased arrays; reflector antennas; slant path propagation; propagation data for HF radio systems performance; satellite and earth station antennas; radio propagation in the troposphere; propagation data for HF radio systems performance; microstrip antennas; rain radio meteorology; conformal antennas; horns and feed antennas; low elevation slant path propagation; radio millimeter wave propagation; array antennas; propagation effects on satellite mobile, satellite broadcast, and aeronautical systems; ionospheric irregularities and motions; adaptive antennas; transient response; measurement techniques; clear air radio meteorology; ionospheric and propagation modeling; millimeter wave and lens antennas; electromagnetic theory and numerical techniques; VHF propagation modeling, system planning methods; radio propagation theoretical techniques; scattering and diffraction; transhorizon rain scatter effects; ELF-VHF and broadcast antennas; clear air millimeter propagation; scattering and frequency-selective surfaces; antenna technology; clear air transhorizon propagation.

78

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

79

Spacecraft Antennas  

NASA Technical Reports Server (NTRS)

Some of the various categories of issues that must be considered in the selection and design of spacecraft antennas for a Personal Access Satellite System (PASS) are addressed, and parametric studies for some of the antenna concepts to help the system designer in making the most appropriate antenna choice with regards to weight, size, and complexity, etc. are provided. The question of appropriate polarization for the spacecraft as well as for the User Terminal Antenna required particular attention and was studied in some depth. Circular polarization seems to be the favored outcome of this study. Another problem that has generally been a complicating factor in designing the multiple beam reflector antennas, is the type of feeds (single vs. multiple element and overlapping vs. non-overlapping clusters) needed for generating the beams. This choice is dependent on certain system design factors, such as the required frequency reuse, acceptable interbeam isolation, antenna efficiency, number of beams scanned, and beam-forming network (BFN) complexity. This issue is partially addressed, but is not completely resolved. Indications are that it may be possible to use relatively simple non-overlapping clusters of only a few elements, unless a large frequency reuse and very stringent isolation levels are required.

Jamnejad, Vahraz; Manshadi, Farzin; Rahmat-Samii, Yahya; Cramer, Paul

1990-01-01

80

Parallel/Series-Fed Microstrip Array Antenna  

NASA Technical Reports Server (NTRS)

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

Huang, John

1994-01-01

81

Design and performance of a microstrip reflectarray antenna  

Microsoft Academic Search

Microstrip reflectarray antennas present an alternative to conventional directive antennas in that they are flat, inexpensive, easy to install and manufacture, conformal to the mounting surface, easy to package, and they possess high power and beam steering capabilities. For the first time, a comprehensive, experimentally verified design procedure for the microstrip reflectarray is presented. In this design procedure, the microstrip

Ronald D. Javor; Xiao-Dong Wu; Kai Chang

1995-01-01

82

Electronically tunable active antenna using microstrip annular ring  

E-print Network

-state devices, microstrip antennas, and phased arrays, the interest in active antennas has been revived. Recently, a, Gunn diode was incorporated into a, recta. ngular patch by Thomas et ah [11I. They suggested its use in the next generation of conformal...

Miller, Richard Earl

2012-06-07

83

A compact dual band circularly polarized antenna design for Mars rover mission  

Microsoft Academic Search

Microstrip antennas are widely used in wireless communications due to their advantages of low profile, light weight, low production cost, and conformability with RF circuitry. Recently, a novel reconfigurable microstrip antenna design, patch antenna with switchable slots (PASS), has been proposed to realize various functionalities such as dual frequency operation, dual band CP performance, and polarization diversity with only one

Fan Yang; Yahya Rahmat-Samii

2003-01-01

84

Piezoceramic actuated aperture antennae  

Microsoft Academic Search

Recently, it has been demonstrated that aperture antennae can have their performance improved by employing shape control on the antenna surface. The antennae previously studied were actuated utilizing polyvinylidene fluoride (PVDF). Since PVDF is a polymer with limited control authority, these antennae can only be employed in space based applications. This study examines more robust antenna structures devised of a

Hwan-Sik Yoon; Gregory Washington

1998-01-01

85

Statistical Properties of Antenna Impedance in an Electrically Large Cavity  

SciTech Connect

This paper presents models and measurements of antenna input impedance in resonant cavities at high frequencies.The behavior of input impedance is useful in determining the transmission and reception characteristics of an antenna (as well as the transmission characteristics of certain apertures). Results are presented for both the case where the cavity is undermoded (modes with separate and discrete spectra) as well as the over moded case (modes with overlapping spectra). A modal series is constructed and analyzed to determine the impedance statistical distribution. Both electrically small as well as electrically longer resonant and wall mounted antennas are analyzed. Measurements in a large mode stirred chamber cavity are compared with calculations. Finally a method based on power arguments is given, yielding simple formulas for the impedance distribution.

WARNE,LARRY K.; LEE,KELVIN S.H.; HUDSON,H. GERALD; JOHNSON,WILLIAM A.; JORGENSON,ROY E.; STRONACH,STEPHEN L.

2000-12-13

86

Experimental Study of the Effect of Paint on Embedded Automotive Antennas  

Microsoft Academic Search

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

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

2008-01-01

87

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

NASA Technical Reports Server (NTRS)

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

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

2011-01-01

88

Astigmatism in reflector antennas.  

NASA Technical Reports Server (NTRS)

Astigmatic phase error in large parabolic reflector antennas is discussed. A procedure for focusing an antenna and diagnosing the presence and degree of astigmatism is described. Theoretical analysis is conducted to determine the nature of this error in such antennas.

Cogdell, J. R.; Davis, J. H.

1973-01-01

89

Analytical Techniques and Operational Perspectives for a Spherical Inverted-F Antenna  

E-print Network

) David Lee Rolando, B.S., Texas A&M University Chair of Advisory Committee: Dr. Gregory Huff The spherical inverted-F antenna (SIFA) is a relatively new conformal antenna design that consists of a microstrip patch resonator on a spherical... is to present a new model using the cavity method, as employed in microstrip patches. The SIFA cavity model uses a curvilinear coordinate system appropriate to the antenna?s unique geometry and is able to predict the antenna?s performance more accurately than...

Rolando, David Lee

2012-02-14

90

On the Characteristic impedance of the TEM horn antenna  

Microsoft Academic Search

Some time ago, Carrel presented an analytical formula, based on conformal mapping, for the characteristic impedance of the transverse electromagnetic horn antenna . Later, results from this formula were shown to be in error, and Lambert et al. offered a new analytical formula, also based on conformal mapping . This formula also contains an error that is easily corrected. Independently,

R. T. Lee; G. S. Smith

2004-01-01

91

Technique for Solving Electrically Small to Large Structures for Broadband Applications  

NASA Technical Reports Server (NTRS)

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

Jandhyala, Vikram; Chowdhury, Indranil

2011-01-01

92

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

93

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.; Acostia, Roberto J.

2006-01-01

94

Antenna theory: a review  

Microsoft Academic Search

In this review the author traces the history of antennas and some of the most basic radiating elements, demonstrates the fundamental principles of antenna radiation, reviews Maxwell's equations and electromagnetic boundary conditions, and outlines basic procedures and equations of radiation. Modeling of antenna source excitation is illustrated, and antenna parameters and figures-of-merit are reviewed. Theorems, arraying principles, and advanced asymptotic

CONSTANTINE A. BALANIS

1992-01-01

95

Polarization-agile antennas  

Microsoft Academic Search

A polarization-agile antenna is a type of antenna the polarization state of which can be changed dynamically, i.e., it can have either linear (vertical or horizontal) or circular polarization (left hand or right hand), depending on the requirements of its specific application. This special characteristic offers great flexibility for antenna systems, because a single antenna could be used to satisfy

S. Gao; A. Sambell; S. S. Zhong

2006-01-01

96

Highly compact composite antenna  

Microsoft Academic Search

The highly compact antenna proposed in this communication consists of a judicious association of equivalent magnetic current source with equivalent electric current source. This composite antenna presents a directivity radiation pattern analogous to one of the microstrip ceramic antennas but can be used at low frequencies. The antenna measurements confirm the promising performances obtained from electromagnetic simulations.

M. Pigeon; C. Morlaas; H. Aubert; B. Souny

2009-01-01

97

VIRGINIA TECH ANTENNA GROUP  

E-print Network

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

Beex, A. A. "Louis"

98

Antenna deployment mechanism  

NASA Technical Reports Server (NTRS)

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

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

1979-01-01

99

Smart antennas for wireless systems  

Microsoft Academic Search

In this article we discuss current and future antenna technology for wireless systems and the improvement that smart and adaptive antenna arrays can provide. We describe standard cellular antennas, smart antennas using fixed beams, and adaptive antennas for base stations, as well as antenna technologies for handsets. We show the potential improvement that these antennas can provide, including range extension,

JACK H. WINTERS

1998-01-01

100

Antenna technology for wireless communications  

Microsoft Academic Search

This paper discusses antenna technologies for wireless communications and specifically those technologies which will enhance link performance and reduce the visual impact of the antenna tower. A brief discussion of the importance of antenna technology transfer from the aerospace\\/defense sector is made. Antenna technology for wireless communications is categorized into Smart Antenna Systems and Antenna Aperture Technology. Smart antenna technology

P. L. Perini

1997-01-01

101

HF broadcast transmitting antennas  

Microsoft Academic Search

An overview is presented of high-frequency (HF) broadcast transmitting antennas. For long-range broadcasting, high-power wideband directive antennas with slewing and beam shaping capabilities are needed. The design requirements, state-of-the-art, and the future trend of these antennas are discussed. Also discussed are the power-handling capability of the antenna, its mechanical requirements, and siting conditions. Currently available HF broadcast antennas are examined.

A. Paul

1988-01-01

102

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

103

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

104

A Flexible Surface Description for Arbitrarily Shaped Dielectric Lens Antennas  

NASA Astrophysics Data System (ADS)

A method to efficiently describe arbitrarily shaped dielectric lens antennas based on spherical harmonics is proposed. It makes use of a Fourier-Laplace series and requires a low number of expansion coefficients, only. Symmetries can be included to impose special geometries or to further reduce the number of coefficients. The efficiency of the approach enables a fast optimization of the surface. This is particularly useful for electrically small lenses. Three exemplary lens designs based on different specifications are obtained through optimization. The manufacturing is discussed and the radiation characteristics are explored and validated through measurements.

Jaschke, Thomas; Rohrdantz, Benjamin; Jacob, Arne F.

2015-01-01

105

A 35GHz Cone Conformal Microstrip 4??4 Array  

Microsoft Academic Search

Design of a 35 GHz conformal microstrip patch antenna 4 x 4 elements array on a perfectly conducting cone is presented. A new kind of microstrip feed approach, which is hemline feed method (HFM), is used to design the patch element. And this kind of elements is used for forming the conformal microstrip array. The influence of the conical curvature

Min Liu; Zi-Rui Feng; Fan-Yi Meng; Feng-Lin Sun; Qun Wu

2007-01-01

106

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

E-print Network

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

Nam, Sangwook

107

Stored energies in electric and magnetic current densities for small antennas  

E-print Network

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

Jonsson, B L G

2014-01-01

108

Wideband active antenna cancellation  

E-print Network

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

Adaniya, Hana L

2008-01-01

109

Cross resonant optical antenna.  

PubMed

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

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

2009-06-26

110

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

111

EVOLUTION OF ANTENNA PERFORMANCE FOR APPLICATIONS IN THERMAL MEDICNE  

PubMed Central

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

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

2013-01-01

112

A broadband dual polarized antenna feed system  

Microsoft Academic Search

An antenna feed system operating at 3.4-4.8 and 5.85-7.075 GHz has been designed which conforms to the current polarization performance specifications required by the Intelsat. The principal design considerations and concepts are discussed, with particular attention given to the design of the corrugated horn, 4\\/6 GHz diplexer, and polarizers. The concept discussed is the simplest possible circuit which does not

R. Schwerdtfeger; J. Kopal

1984-01-01

113

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

114

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

115

Active retrodirective antenna  

NASA Technical Reports Server (NTRS)

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

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

1977-01-01

116

Piezoceramic actuated aperture antennas  

Microsoft Academic Search

Recently, it has been demonstrated that aperture antennas can have their performance improved by utilizing PVDF as a shape controlling actuator. Since PVDF is a polymer with limited control authority, these antennas can only be employed in space based applications. This study examines more robust antenna structures devised of a thick metalized substrate with surface bonded piezoceramic (PZT) actuators. In

Hwan-Sik Yoon; Gregory Washington

1998-01-01

117

Resonant optical antennas.  

PubMed

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

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

2005-06-10

118

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

119

JPL antenna technology development  

NASA Astrophysics Data System (ADS)

Plans for evaluating, designing, fabricating, transporting and deploying cost effective and STS compatible offset wrap rib antennas up to 300 meters in diameter for mobile communications, Earth resources observation, and for the orbiting VLBI are reviewed. The JPL surface measurement system, intended for large mesh deployable antenna applications will be demonstrated and validated as part of the antenna ground based demonstration program. Results of the offset wrap rib deployable antenna technology development will include: (1) high confidence structural designs for antennas up to 100 meters in diameter; (2) high confidence estimates of functional performance and fabrication cost for a wide range of antenna sizes (up to 300 meters in diameter); (3) risk assessment for fabricating the large size antennas; and (4) 55 meter diameter flight quality hardware that can be cost effectively completed toto accommodate a flight experiment and/or application.

Freeland, R. E.

1981-02-01

120

Uniplanar Wideband Quasi Yagi Antenna for Multiple Antenna Channel Measurements  

E-print Network

of arrival information, and data necessary for the design of smart antennas and spectrally efficient systemsUniplanar Wideband Quasi Yagi Antenna for Multiple Antenna Channel Measurements M. Abdalla and S antenna has gained considerable attention recently as a method of producing a broad bandwidth antenna

Haddadi, Hamed

121

A Compact Annular Ring Microstrip Antenna for WSN Applications  

PubMed Central

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

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

2012-01-01

122

Dipole-Excited Ring Antenna  

NASA Technical Reports Server (NTRS)

Dipole radiator drives ring radiator in compact C-band antenna. Antenna can be mounted flush with surface. Compared with horn or parabolic dish with same aperature, new ring antenna has greater gain, lower side lobes, and narrower beam width. Used on vehicles requiring flush-mounted antennas with very directive signals. Used as radar altimeter antenna for aircraft.

Ellis, H., Jr

1982-01-01

123

Circularly polarized microstrip fractal antennas  

Microsoft Academic Search

A miniaturized circularly polarized antenna based on the Sierpinski gasket is presented. In exchange for size reduction, minimum axial ratio and the bandwidth of this antenna are degraded. An additional new microstrip fractal antenna named the crown square antenna is also introduced and illustrated to have circular polarization when its feed location is near to the center of the antenna.

P. Dehkhoda; A. Tavakoli

2004-01-01

124

Experimental determination of the electromagnetic field in the near-zone of a high power UHF pyramidal horn antenna  

Microsoft Academic Search

The far-zone characteristics (directive gain, main-lobe beamwidth, side-lobe structure) of pyramidal horn antennas are fairly well known and, for the most part, easily predictable. However, as the observation point moves within the far-zone boundary, predicting the radiated field characteristics becomes much more difficult. Preliminary results of an intensive effort utilizing electrically small electric (dipoles) and magnetic (loops) probes to map

T. H. Shumpert; T. A. Blalock; G. R. Edlin

1981-01-01

125

Conical-reflector antennas.  

NASA Technical Reports Server (NTRS)

The mechanical advantages of a singly curved conical reflector are demonstrated by the experimental test of a furlable 1.83 m conical-Gregorian antenna at 16.33 GHz. The measured gain of 47.5 dB corresponds to a net efficiency of over 57%. A ray-optics analysis of conical-reflector antennas is presented, and data useful in the design of conical antennas are given. The conical-Gregorian antenna, in which a subreflector is used in conjunction with a conventional horn feed, is considered in detail. A physical-optics analysis of the conical-Gregorian antenna is used to investigate diffraction and other effects, and to analytically confirm the high performance of the antenna.

Ludwig, A. C.

1972-01-01

126

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

127

Recent results for plasma antennas  

SciTech Connect

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

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

2008-05-15

128

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.

129

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

130

Turnstile slot antenna  

NASA Technical Reports Server (NTRS)

A turnstile slot antenna is disclosed, the antenna being for and integral with a spacecraft having a substantially cylindrical body portion. The antenna comprises a circumferential slot about the periphery of the spacecraft body portion with an annular wave guide cavity defining a radial transmission line disposed within the spacecraft body portion behind and in communication with the circumferential slot. Feed stubs and associated transmission apparatus are provided to excite the annular cavity in quadrature phase such that an omnidirectional, circularly polarized, rotating radiation pattern is generated. The antenna of the instant invention has utility both as a transmitting and receiving device, and ensures continuous telemetry and command coverage with the spacecraft.

Munson, R. E. (inventor)

1974-01-01

131

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

132

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

133

Milestones in Broadcasting: Antennas.  

ERIC Educational Resources Information Center

Briefly describes the development of antennas in the prebroadcast era (elevated antenna, selectivity to prevent interference between stations, birth of diplex, directional properties, support structures), as well as technological developments used in long-, medium-, and short-wave broadcasting, VHF/FM and television broadcasting, and satellite…

Media in Education and Development, 1985

1985-01-01

134

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

135

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

136

Small microstrip patch antenna  

Microsoft Academic Search

A novel small microstrip patch antenna is presented. The probe-fed circular microstrip patch incorporates a single shorting post which significantly reduces the overall size of the antenna. Experimental and theoretical impedance behavior and radiation characteristics of the modified patch are given. Very good agreement between experiment and theory was achieved.

R. Waterhouse

1995-01-01

137

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.

138

Ellipsoidal Balloon Antenna  

NASA Technical Reports Server (NTRS)

Direct-broadcast ellipsoidal antenna 40 percent smaller than spherical reflector. Balloon antenna has feedpoint on surface of ellipsoid outside balloon, simplifying balloon deployment and feed support. Dielectric shrouds used locally to adjust shape of balloon and maintain feed distance at its optimum value.

Cramer, P. W.

1985-01-01

139

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

NASA Astrophysics Data System (ADS)

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

Davidson, Kyle

140

Parabolic torus transreflector antenna  

NASA Astrophysics Data System (ADS)

The possible scan rate of conventional radar antennas using parabolic dishes is limited to about 60 rev/min. This limitation is related to mechanical rotation requirements. Many radar applications require high data renewal rates, including short-range defense systems and systems for reduction of sea clutter. Faster scan rates can be obtained by using phased arrays and electronic scanning. However, the use of the required equipment introduces considerable complexity and cost. The present investigation is concerned with a novel form of antenna permitting high scan rates, taking into account a parabolic torus transreflector antenna. The feed horn illuminates one side of the radome with polarization parallel to the wires, which therefore reflect the radiation like a dish antenna. In the antenna considered, rotation of the beam is effected by mechanical rotation of the horn feed only, and this provides the potential for high scanning rates.

Diaz, L. M.; Smith, M. S.

1984-12-01

141

GPS antenna designs  

NASA Technical Reports Server (NTRS)

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

Laube, Samuel J. P.

1987-01-01

142

Aircraft radar antennas  

NASA Astrophysics Data System (ADS)

Many changes have taken place in airborne radar antennas since their beginnings over forty years ago. A brief historical review of the advances in technology is presented, from mechanically scanned reflectors to modern multiple function phased arrays. However, emphasis is not on history but on the state-of-the-art technology and trends for future airborne radar systems. The status of rotating surveillance antennas is illustrated by the AN/APY-1 Airborne Warning and Control System (AWACS) slotted waveguide array, which achieved a significant breakthrough in sidelobe suppression. Gimballed flat plate arrays in nose radomes are typified by the AN/APG-66 (F-16) antenna. Multifunction phased arrays are presented by the Electronically Agile Radar (EAR) antenna, which has achieved significant advances in performance versatility and reliability. Trends toward active aperture, adaptive, and digital beamforming arrays are briefly discussed. Antennas for future aircraft radar systems must provide multiple functions in less aperture space, and must perform more reliably.

Schrank, Helmut E.

1987-04-01

143

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

144

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

145

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

146

A crown square microstrip fractal antenna  

Microsoft Academic Search

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

P. Dehkhoda; A. Tavakoli

2004-01-01

147

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

148

Satellite Antenna Systems  

NASA Technical Reports Server (NTRS)

Through the Technology Affiliates Program at the Jet Propulsion Laboratory, the ACTS antenna system was transferred from experimental testing status to commercial development with KVH Industries, Inc. The ACTS design enables mobile satellite antennas to remain pointed at the satellite, regardless of the motion or vibration on which it is mounted. KVH's first product based on the ACTS design is a land-mobile satellite antenna system that will enable direct broadcast satellite television aboard moving trucks, recreational vehicles, trains, and buses. Future products could include use in broadcasting, emergency medical and military vehicles.

1997-01-01

149

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

NASA Astrophysics Data System (ADS)

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

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

2009-09-01

150

Robust Hybrid Finite Element Methods for Antennas and Microwave Circuits  

NASA Technical Reports Server (NTRS)

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

Gong, J.; Volakis, John L.

1996-01-01

151

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

152

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

153

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

154

Communication satellite antennas  

Microsoft Academic Search

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

LEON J. RICARDI

1977-01-01

155

Polarized Antenna Splitting Functions  

SciTech Connect

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

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

2009-10-17

156

Multiple antenna technologies  

E-print Network

Multiple antenna technologies have received high attention in the last few decades for their capabilities to improve the overall system performance. Multiple-input multiple-output systems include a variety of techniques capable of not only increase the reliability of the communication but also impressively boost the channel capacity. In addition, smart antenna systems can increase the link quality and lead to appreciable interference reduction.

Mohaisen, Manar; Chang, KyungHi

2009-01-01

157

Deployable antenna reflector  

NASA Technical Reports Server (NTRS)

The first phase in the development of a solid surface, deployable, antenna reflector is outlined and discussed. The deployment concept is described in conjunction with illustrations and photos of the fabricated reflector models. Details and results of the thermal distortion analysis are presented. Results indicate that the discussed reflector concept is an effective approach in satisfying the requirements for large deployable antennas in the 6 GHz to 100 GHz frequency regime.

Palmer, W. B.

1979-01-01

158

The Folded Horn Antenna  

NASA Astrophysics Data System (ADS)

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

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

159

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

160

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

161

47 CFR 95.1013 - Antennas.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Antennas. 95.1013 Section 95.1013 ...General Provisions § 95.1013 Antennas. (a) The maximum allowable...AMTS stations must employ directional antennas. (c) Antennas used with LPRS...

2013-10-01

162

47 CFR 73.753 - Antenna systems.  

...2014-10-01 2014-10-01 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...

2014-10-01

163

47 CFR 95.1013 - Antennas.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Antennas. 95.1013 Section 95.1013 ...General Provisions § 95.1013 Antennas. (a) The maximum allowable...AMTS stations must employ directional antennas. (c) Antennas used with LPRS...

2011-10-01

164

47 CFR 95.1013 - Antennas.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false Antennas. 95.1013 Section 95.1013 ...General Provisions § 95.1013 Antennas. (a) The maximum allowable...AMTS stations must employ directional antennas. (c) Antennas used with LPRS...

2010-10-01

165

47 CFR 73.753 - Antenna systems.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 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...

2011-10-01

166

47 CFR 95.1013 - Antennas.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false Antennas. 95.1013 Section 95.1013 ...General Provisions § 95.1013 Antennas. (a) The maximum allowable...AMTS stations must employ directional antennas. (c) Antennas used with LPRS...

2012-10-01

167

47 CFR 73.753 - Antenna systems.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 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...

2012-10-01

168

47 CFR 73.753 - Antenna systems.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 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...

2010-10-01

169

Octocopter based Calibration of the Butterfly Antenna  

E-print Network

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

Erdmann, Martin

170

Multibeam antenna study, phase 1  

NASA Technical Reports Server (NTRS)

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

Bellamy, J. L.

1972-01-01

171

Development of Leaky Wave Antennas for Layered Ridge Dielectric Waveguide  

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

172

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

173

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

174

Antenna cab interior showing waveguide from external parabolic antenna (later ...  

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

Antenna cab interior showing waveguide from external parabolic antenna (later addition), looking north. - Western Union Telegraph Company, Jennerstown Relay, Laurel Summit Road off U.S. 30, Laughlintown, Westmoreland County, PA

175

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

176

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

Microsoft Academic Search

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

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

2008-01-01

177

Satellite dual antenna pointing system  

NASA Technical Reports Server (NTRS)

A satellite antenna pointing system for separately pointing separated transmit and receive high gain antenna systems includes means for separately and sequentially applying a beacon signal to the transmit and receive antenna systems and a broad beam width antenna which has a coverage area greater than the overall coverage region of the spot beam antenna systems. The system includes ground stations located at or near the periphery of the overall coverage region adapted to receive these beacon signals. At a central control station these beacon signals are compared to provide first signals proportional to the ratio of said beacon signals received from said transmit antenna system and said broad beam width antenna and second signals proportional to the ratio of said beacon signals received from said satellite receive antenna system and said broad beam width antenna. The central station generates from said first signals transmit antenna control signals which are sent to the satellite to control the orientation of said transmit antenna system. Likewise, the central control station generates from the second signals receiver antenna control signals which are applied to the satellite to control the orientation of the satellite receive antenna system.

Keigler, John E. (Inventor); Hartshorne, Frank A. (Inventor)

1986-01-01

178

View north of the antenna array, note the communications antenna ...  

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

View north of the antenna array, note the communications antenna in the middleground - Over-the-Horizon Backscatter Radar Network, Christmas Valley Radar Site Transmit Sector Four Antenna Array, On unnamed road west of Lost Forest Road, Christmas Valley, Lake County, OR

179

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

180

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

181

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

182

Mapping Reconfigurable Antennas Using Graphs  

Microsoft Academic Search

This paper introduces the modeling of reconfigurable antennas using graphs. Several examples are presented and analyzed. Graphs are shown herein to be useful for modeling reconfigurable antennas with different techniques and properties.

J. Costantine; C. G. Christodoulou; S. E. Barbin

2008-01-01

183

A plasma receiving dipole antenna  

SciTech Connect

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

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

2010-10-15

184

Effect of Wire Space and Weaving Pattern on Performance of Microstrip Antennas Integrated in the Three Dimensional Orthogonal Woven Composites  

NASA Astrophysics Data System (ADS)

A conformal load-bearing antenna structure (CLAS) combines the antenna into a composite structure such that it can carry the designed load while functioning as an antenna. Novel microstrip antennas woven into the three dimensional orthogonal woven composite were proposed in our previous study. In order to determine the effect of the space between the conductive wires on the antenna performance, different space ratios of 1.7, 2.3 and 4.6 were considered in the design. Simulation results showed that when the space ratio increased, the frequency shift and return loss of the corresponding antenna became larger. And the antenna had relatively good performance when the space ratio reached 1.7. Two types of antennas were designed and fabricated with the ratio of 1.7 and 1 respectively and both of them obtained agreeable results. It was also demonstrated by the experimental that the orthogonal structure patch antenna had similar radiation pattern with the traditional copper foil microstrip antenna. However, the interlaced patch antenna had large back and side lobes in the radiation pattern because the existence of the curvature of copper wires in interlaced coupons lowered the reflective efficiency of the ground.

Yao, Lan; Wang, Xin; Xu, Fujun; Jiang, Muwen; Zhou, Dongchun; Qiu, Yiping

2012-02-01

185

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

186

Fast Characterization of Radiation Patterns of Conformal Array Antennas  

E-print Network

Vehicle (UAV) or of an aircraft [1]. This new generation of radar imaging systems is based are thus of special interest for imaging radar systems mounted on the fuselage of an Unmanned Aerial on multifunctional Synthetic Aperture Radars that aim at providing high resolution and long range imaging

Paris-Sud XI, Université de

187

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

188

The ACTS multibeam antenna  

NASA Technical Reports Server (NTRS)

The Advanced Communications Technology Satellite (ACTS) to be launched in 1993 is briefly introduced. Its multibeam antenna, consisting of electrically similar 30 GHz receive and 20 GHz transmit offset Cassegrain systems, both utilizing orthogonal 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 degree 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 HEMT low-noise amplifier and a 20 GHz TWT power amplifier.

Regier, Frank A.

1992-01-01

189

Launching large antennas  

NASA Astrophysics Data System (ADS)

Large antennas will provide communication to rural and remote areas in times of need. This is seen as facilitating the work of law enforcement agencies. All mobile radio communications will enjoy advantages in distances covered and information relayed owing to the large number of beams possible from super radio transmitters in space. If the antennas are placed in low-earth orbit, advantages will be realized in the remote sensing of the earth's resources. It is pointed out that with umbrella or bicyclelike antennas turned outward toward space, the universe could be scouted for signals from intelligent life. Various concepts that have been put forward by U.S. companies are described. These include the radial rib, wrap rib, and parabolic erectable truss designs. Others are the mesh hoop column collapsable umbrella made of gold and molybdenum and the maypole design.

Brandli, H. W.

1983-09-01

190

Antenna for Imaging Sea Ice  

NASA Technical Reports Server (NTRS)

Antenna for imaging of polar regions has terrestrial applications. Antenna consists of four horizontally-polarized 19.0 by 0.6-m planar waveguide arrays and appropriate feed networks mounted on single aluminum supporting structure. Antenna suitable for high quality imaging of sea ice in polar regions above 60 degrees latitude.

Barath, F. T.; Jordan, R. L.

1984-01-01

191

Dielectric-loaded horn antenna  

Microsoft Academic Search

A wide-band dual-mode horn, which has a rotationally symmetric beam and extremely low sidelobe levels, can be obtained by loading a dielectric band inside the horn antenna. Measured radiation characteristics of such antennas, including the so-called shaped-beam antenna, are shown.

TOSHIO SATOH

1972-01-01

192

Circularly polarized fractal slot antenna  

Microsoft Academic Search

A circularly polarized fractal slot antenna is proposed in this paper. The design is based on the Sierpinski shape. The conductors and nonconductors configurations have been exchanged to produce a Sierpinski slot antenna configuration. Then, four versions of the developed Sierpinski slot antenna are placed at right angles to each other to form a symmetrical structure in the form of

A. R. El-Damak; H. Ghali; H. F. Ragaie

2005-01-01

193

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

194

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

195

Design considerations for an archimedean slot spiral antenna  

NASA Technical Reports Server (NTRS)

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

Nurnberger, Michael W.; Volakis, John L.

1995-01-01

196

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.

197

Smart base station antenna  

Microsoft Academic Search

This paper presents a novel hybrid beam steering scheme for mobile cellular applications. In this scheme, a linear equispaced sensor array of N antenna elements at the base station is used to form a fixed beam pattern in a fixed number of directions covering the cell area. In addition an adaptive pilot beam also is formed by using the same

K. Rambabu; R. Rajagopal

2000-01-01

198

Aircraft radar antennas  

Microsoft Academic Search

Many changes have taken place in airborne radar antennas since their beginnings over forty years ago. A brief historical review of the advances in technology is presented, from mechanically scanned reflectors to modern multiple function phased arrays. However, emphasis is not on history but on the state-of-the-art technology and trends for future airborne radar systems. The status of rotating surveillance

Helmut E. Schrank

1987-01-01

199

MLS airborne antenna research  

Microsoft Academic Search

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

C. L. Yu; W. D. Burnside

1975-01-01

200

Antenna electrodes for controlling electroluminescence.  

PubMed

Optical antennas can control the emission from quantum emitters by modifying the local density of optical states via the Purcell effect. A variety of nanometallic antennas have been implemented to enhance and control key photoluminescence properties, such as the decay rate, directionality and polarization. However, their implementation in active devices has been hampered by the need to precisely place emitters near an antenna and to efficiently excite them electrically. Here we illustrate a design methodology for antenna electrodes that for the first time facilitates simultaneous operation as electrodes for current injection and as antennas capable of optically manipulating the electroluminescence. We show that by confining the electrically excited carriers to the vicinity of antenna electrodes and maximizing the optical coupling of the emission to a single, well-defined antenna mode, their electroluminescence can be effectively controlled. This work spurs the development of densely integrated, electrically driven light sources with tailored emission properties. PMID:22893129

Huang, Kevin C Y; Seo, Min-Kyo; Huo, Yijie; Sarmiento, Tomas; Harris, James S; Brongersma, Mark L

2012-01-01

201

Novel metamaterial based antennas for flexible wireless systems  

NASA Astrophysics Data System (ADS)

Recent years have witnessed a great deal of interest from both academia and industry in the field of flexible electronic systems. This research topic tops the pyramid of research priorities requested by many national research agencies. Consistently, flexible electronic systems require the integration of flexible antennas operating in specific frequency bands to provide wireless connectivity which is highly demanded by today's information oriented society. On the other hand, metamaterials have become very popular in the design of contemporary antenna and microwave devices due to their wide range of applications derived from their unique properties which significantly enhances the performance of antennas and RF systems. Accordingly, the integration of metamaterial structures within flexible wireless systems is very beneficial in this growing field of research. A systematic approach to the analysis and design of flexible and conformal antennas and metamaterials is ultimately needed. The research reported in this thesis focuses on developing flexible low profile antennas and metamaterial structures in addition to characterizing their performance when integrated within flexible wireless systems. Three flexible, compact, and extremely low profile (50.8 microm) antennas intended for WLAN, Bluetooth and Ultra Wide Band (UWB) applications are presented. Next, a novel miniaturized Artificial Magnetic Conductor (AMC) and a new technique to enhance the bandwidth of micro-Negative (MNG) metamaterial are reported. Furthermore, the effect of bending on the AMC and MNG metamaterial is investigated in this thesis for the first time. Finally, the findings of this research are utilized in practical applications with specific design constraints including mutual coupling reduction between radiating elements in antenna arrays and MIMO systems and Specific Absorption Rate (SAR) reduction in telemedicine systems.

Khaleel, Haider Raad

202

Theory and experiment of circularly polarized dielectric resonator antenna with a parasitic patch  

Microsoft Academic Search

The use of a single parasitic patch for circular polarization (CP) excitation of the dielectric resonator antenna (DRA) is investigated. For demonstration, the technique is applied to the conformal-strip fed hemispherical DRA, excited at the fundamental TE111 mode. Using the Green's function approach, the integral equations for the conformal-strip and parasitic-patch currents are formulated by matching the appropriate boundary conditions.

Kwok Wa Leung; Hoi Kuen Ng

2003-01-01

203

Design and Development of Aerogel-Based Antennas for Aerospace Applications: A Final Report to the NARI Seedling  

NASA Technical Reports Server (NTRS)

As highly porous solids possessing low density and low dielectric permittivity combined with good mechanical properties, polyimide (PI) aerogels offer great promise as an enabling technology for lightweight aircraft antenna systems. While they have been aggressively explored for thermal insulation, barely any effort has been made to leverage these materials for antennas or other applications that take advantage of their aforementioned attributes. In Phase I of the NARI Seedling Project, we fabricated PI aerogels with properties tailored to enable new antenna concepts with performance characteristics (wide bandwidth and high gain) and material properties (low density, environmental stability, and robustness) superior to the state of practice (SOP). We characterized electromagnetic properties, including permittivity, reflectivity, and propagation losses for the aerogels. Simple, prototype planar printed circuit patch antennas from down-selected aerogel formulations were fabricated by molding the aerogels to net shapes and by gold-metalizing the pattern onto the templates via electron beam evaporation in a clean room environment. These aerogel based antennas were benchmarked against current antenna SOP, and exhibited both broader bandwidth and comparable or higher gain performance at appreciably lower mass. Phase II focused on the success of the Phase I results pushing the PI aerogel based antenna technology further by exploring alternative antenna design (i.e., slot coupled antennas) and by examining other techniques for fabricating the antennas including ink jet printing with the goal of optimizing antenna performance and simplifying production. We also examined new aerogel formulations with better moisture and solvent resistance to survive processing conditions. In addition, we investigated more complex antenna designs including passive phased arrays such as 2x4 and 4x8 element arrays to assess the scalability of the aerogel antenna concept. Furthermore, we explored the possibility of developing these arrays in thin, flexible form to make conformable antennas.

Meador, Mary Ann B.; Miranda, Felix A.

2014-01-01

204

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

205

NRL Low-Frequency Antenna Development  

E-print Network

using cross-polarized LF antenna design. #12;NRL Low Frequency Antenna Development Genuine TasmanianNRL Low-Frequency Antenna Development Brian Hicks W. Erickson, K. Stewart #12;NRL Low Frequency Antenna Development Our goal has been to research and develop wide- bandwidth low-frequency antennas

Ellingson, Steven W.

206

Antennas - Our electronic eyes and ears  

Microsoft Academic Search

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

John D. Kraus

1989-01-01

207

Dielectric loaded aperture antennas.  

NASA Technical Reports Server (NTRS)

This paper describes a primarily experimental study of the effect of placing dielectric obstacles having various geometries directly upon the aperture of circular and rectangular waveguide antennas. It is found that plexiglas spheres, and in some cases plexiglas cubes, one to four wavelengths in dimension, produce directive patterns with low sidelobes. The measured gain in some cases is 6 dB greater than the gain of an optimum horn having an equal aperture size.

Croswell, W. F.; Chatterjee, J. S.

1972-01-01

208

Wimpy Radar Antenna  

NSDL National Science Digital Library

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

Center for Engineering Educational Outreach,

209

Adaptive antenna systems  

Microsoft Academic Search

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

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

1967-01-01

210

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

211

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

212

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

213

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

214

Large furlable antenna study  

NASA Technical Reports Server (NTRS)

The parametric study of the performance of large furlable antennas is described and the availability of various size antennas is discussed. Three types of unfurlable reflector designs are considered: the wrapped rib, the polyconic, and the maypole. On the basis of these approaches, a space shuttle launch capability, and state-of-the-art materials, it is possible to design unfurlable reflectors as large as 130 feet (40 meters) in diameter to operate at 10 GHz and 600 feet (183 meters) in diameter at 0.5 GHz. These figures can be increased if very low thermal coefficient of expansion materials can be developed over the next 2-5 years. It is recommended that a special effort be made to develop light weight materials that would provide nearly zero thermal coefficient of expansion and good thermal conductivity within the next 10 years. A conservative prediction of the kinds of unfurlable spacecraft antennas that will be available by 1985 with orbital performance predicted on the basis of test data and with developed manufacturing processes is summarized.

Campbell, G. K. C.

1975-01-01

215

Antenna Subtraction at NNLO  

E-print Network

The computation of exclusive QCD jet observables at higher orders requires a method for the subtraction of infrared singular configurations arising from multiple radiation of real partons. We present a subtraction scheme relevant for NNLO perturbative calculations in $e^+e^- \\to $ jets. The building blocks of the scheme are antenna functions derived from the matrix elements for tree-level $1\\to 3$ and $1 \\to 4$ and one-loop $1 \\to 3$ processes. By construction, these building blocks have the correct infrared behaviour when one or two particles are unresolved. At the same time, their integral over the antenna phase space is straightforward. As an example of how to use the scheme we compute the NNLO contributions to the subleading colour QED-like contribution to $e^+e^- \\to 3$ jets. To illustrate the application of NNLO antenna subtraction for different colour structures, we construct the integrated forms of the subtraction terms needed for the five-parton and four-parton contributions to $e^+e^- \\to 3$ jets at NNLO in all colour factors, and show that their infrared poles cancel analytically with the infrared poles of the two-loop virtual correction to this observable.

A. Gehrmann--De Ridder; T. Gehrmann; E. W. N. Glover

2007-11-21

216

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

217

Printed antenna for satellite communications  

Microsoft Academic Search

An antenna which has been conceived as a portable system for satellite communications based on the recommendations ITU-R S.580–6 [1] and ITU-R S.465–5 [2] for small antennas, i.e., with a diameter lower than 50 wavelengths, is introduced. It is a planar and a compact structure with a size of 40×40×2 cm. The antenna is formed by an array of 256

Andres Garcia-Aguilar; Jose Manuel Inclan-Alonso; Jose Manuel Fernandez-Gonzalez; Manuel Sierra-Perez

2010-01-01

218

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

219

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

220

Analyzing Large Reflector Antenna Structures  

NASA Technical Reports Server (NTRS)

Iterative Design of Antenna Structures (IDEAS) computer program performs finite-element analysis and optimization of design, with special features for analysis and design of microwave antennas and associated structural components. Primary feature to perform root-mean-square-best-fitting path-length-error and boresight-pointing-error analyses for Cassegrain microwave antenna structure loaded by gravity, wind, or other environmental effects. Flexible and easy to use. Written in ATHENA FORTRAN and ASSEMBLER.

Levy, Roy; Strain, Douglas M.

1991-01-01

221

47 CFR 73.816 - Antennas.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 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...

2010-10-01

222

47 CFR 80.923 - Antenna system.  

Code of Federal Regulations, 2010 CFR

... 5 2010-10-01 2010-10-01 false Antenna system. 80.923 Section 80.923 Telecommunication...Installations for Small Passenger Boats § 80.923 Antenna system. An antenna must be provided in accordance with the...

2010-10-01

223

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

224

47 CFR 101.517 - Antennas.  

Code of Federal Regulations, 2011 CFR

...5 2011-10-01 2011-10-01 false Antennas. 101.517 Section 101.517 Telecommunication...Digital Electronic Message Service § 101.517 Antennas. (a) Transmitting antennas may be omnidirectional or directional,...

2011-10-01

225

47 CFR 80.866 - Spare antenna.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 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...

2012-10-01

226

47 CFR 74.1237 - Antenna location.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false Antenna location. 74.1237 Section 74...Broadcast Booster Stations § 74.1237 Antenna location. (a) An applicant...the primary station. The transmitting antenna should be placed above growing...

2012-10-01

227

47 CFR 80.866 - Spare antenna.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 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...

2010-10-01

228

47 CFR 101.517 - Antennas.  

Code of Federal Regulations, 2010 CFR

...5 2010-10-01 2010-10-01 false Antennas. 101.517 Section 101.517 Telecommunication...Digital Electronic Message Service § 101.517 Antennas. (a) Transmitting antennas may be omnidirectional or directional,...

2010-10-01

229

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

230

47 CFR 15.203 - Antenna requirement.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 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...

2012-10-01

231

47 CFR 73.1675 - Auxiliary antennas.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false Auxiliary antennas. 73.1675 Section 73.1675 Telecommunication...Broadcast Stations § 73.1675 Auxiliary antennas. (a)(1) An auxiliary antenna is one that is permanently installed and...

2010-10-01

232

47 CFR 73.816 - Antennas.  

...2014-10-01 2014-10-01 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...

2014-10-01

233

47 CFR 95.1213 - Antennas.  

Code of Federal Regulations, 2011 CFR

...Telecommunication 5 2011-10-01 2011-10-01 false Antennas. 95.1213 Section 95.1213 Telecommunication...Radiocommunication Service (MedRadio) § 95.1213 Antennas. No antenna for a MedRadio transmitter shall be...

2011-10-01

234

47 CFR 73.1680 - Emergency antennas.  

...2014-10-01 2014-10-01 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...

2014-10-01

235

47 CFR 73.69 - Antenna monitors.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Antenna monitors. 73.69 Section 73.69...SERVICES AM Broadcast Stations § 73.69 Antenna monitors. (a) Each station using a directional antenna must have in operation at the...

2011-10-01

236

47 CFR 101.117 - Antenna polarization.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 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...

2012-10-01

237

47 CFR 101.517 - Antennas.  

Code of Federal Regulations, 2012 CFR

...5 2012-10-01 2012-10-01 false Antennas. 101.517 Section 101.517 Telecommunication...Digital Electronic Message Service § 101.517 Antennas. (a) Transmitting antennas may be omnidirectional or directional,...

2012-10-01

238

47 CFR 73.816 - Antennas.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 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...

2011-10-01

239

47 CFR 73.1675 - Auxiliary antennas.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false Auxiliary antennas. 73.1675 Section 73.1675 Telecommunication...Broadcast Stations § 73.1675 Auxiliary antennas. (a)(1) An auxiliary antenna is one that is permanently installed and...

2012-10-01

240

47 CFR 73.816 - Antennas.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 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...

2012-10-01

241

47 CFR 74.1237 - Antenna location.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Antenna location. 74.1237 Section 74...Broadcast Booster Stations § 74.1237 Antenna location. (a) An applicant...the primary station. The transmitting antenna should be placed above growing...

2011-10-01

242

47 CFR 101.115 - Directional antennas.  

Code of Federal Regulations, 2013 CFR

... 2013-10-01 false Directional antennas. 101.115 Section 101.115 ...Standards § 101.115 Directional antennas. (a) Unless otherwise authorized...of this part must employ a directional antenna adjusted with the center of the...

2013-10-01

243

47 CFR 101.117 - Antenna polarization.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 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...

2010-10-01

244

47 CFR 73.1680 - Emergency antennas.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 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...

2011-10-01

245

47 CFR 73.1675 - Auxiliary antennas.  

...2014-10-01 2014-10-01 false Auxiliary antennas. 73.1675 Section 73.1675 Telecommunication...Broadcast Stations § 73.1675 Auxiliary antennas. (a)(1) An auxiliary antenna is one that is permanently installed and...

2014-10-01

246

47 CFR 74.1237 - Antenna location.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Antenna location. 74.1237 Section 74...Broadcast Booster Stations § 74.1237 Antenna location. (a) An applicant...the primary station. The transmitting antenna should be placed above growing...

2013-10-01

247

47 CFR 80.866 - Spare antenna.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 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...

2011-10-01

248

47 CFR 73.1675 - Auxiliary antennas.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Auxiliary antennas. 73.1675 Section 73.1675 Telecommunication...Broadcast Stations § 73.1675 Auxiliary antennas. (a)(1) An auxiliary antenna is one that is permanently installed and...

2011-10-01

249

47 CFR 73.1675 - Auxiliary antennas.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Auxiliary antennas. 73.1675 Section 73.1675 Telecommunication...Broadcast Stations § 73.1675 Auxiliary antennas. (a)(1) An auxiliary antenna is one that is permanently installed and...

2013-10-01

250

47 CFR 80.923 - Antenna system.  

Code of Federal Regulations, 2011 CFR

... 5 2011-10-01 2011-10-01 false Antenna system. 80.923 Section 80.923 Telecommunication...Installations for Small Passenger Boats § 80.923 Antenna system. An antenna must be provided in accordance with the...

2011-10-01

251

47 CFR 73.69 - Antenna monitors.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false Antenna monitors. 73.69 Section 73.69...SERVICES AM Broadcast Stations § 73.69 Antenna monitors. (a) Each station using a directional antenna must have in operation at the...

2012-10-01

252

47 CFR 101.517 - Antennas.  

Code of Federal Regulations, 2013 CFR

...5 2013-10-01 2013-10-01 false Antennas. 101.517 Section 101.517 Telecommunication...Digital Electronic Message Service § 101.517 Antennas. (a) Transmitting antennas may be omnidirectional or directional,...

2013-10-01

253

47 CFR 73.69 - Antenna monitors.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Antenna monitors. 73.69 Section 73.69...SERVICES AM Broadcast Stations § 73.69 Antenna monitors. (a) Each station using a directional antenna must have in operation at the...

2013-10-01

254

47 CFR 80.923 - Antenna system.  

Code of Federal Regulations, 2013 CFR

... 5 2013-10-01 2013-10-01 false Antenna system. 80.923 Section 80.923 Telecommunication...Installations for Small Passenger Boats § 80.923 Antenna system. An antenna must be provided in accordance with the...

2013-10-01

255

47 CFR 101.115 - Directional antennas.  

Code of Federal Regulations, 2010 CFR

... 2010-10-01 false Directional antennas. 101.115 Section 101.115 ...Standards § 101.115 Directional antennas. (a) Unless otherwise authorized...of this part must employ a directional antenna adjusted with the center of the...

2010-10-01

256

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

257

47 CFR 95.1213 - Antennas.  

Code of Federal Regulations, 2010 CFR

...Telecommunication 5 2010-10-01 2010-10-01 false Antennas. 95.1213 Section 95.1213 Telecommunication...Radiocommunication Service (MedRadio) § 95.1213 Antennas. No antenna for a MedRadio transmitter shall be...

2010-10-01

258

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

259

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

260

47 CFR 15.203 - Antenna requirement.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 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...

2010-10-01

261

47 CFR 74.1237 - Antenna location.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false Antenna location. 74.1237 Section 74...Broadcast Booster Stations § 74.1237 Antenna location. (a) An applicant...the primary station. The transmitting antenna should be placed above growing...

2010-10-01

262

47 CFR 74.1237 - Antenna location.  

...2014-10-01 2014-10-01 false Antenna location. 74.1237 Section 74...Broadcast Booster Stations § 74.1237 Antenna location. (a) An applicant...the primary station. The transmitting antenna should be placed above growing...

2014-10-01

263

47 CFR 15.203 - Antenna requirement.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 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...

2011-10-01

264

47 CFR 15.203 - Antenna requirement.  

...2014-10-01 2014-10-01 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...

2014-10-01

265

47 CFR 73.69 - Antenna monitors.  

...2014-10-01 2014-10-01 false Antenna monitors. 73.69 Section 73.69...SERVICES AM Broadcast Stations § 73.69 Antenna monitors. (a) Each station using a directional antenna must have in operation at the...

2014-10-01

266

47 CFR 80.923 - Antenna system.  

Code of Federal Regulations, 2012 CFR

... 5 2012-10-01 2012-10-01 false Antenna system. 80.923 Section 80.923 Telecommunication...Installations for Small Passenger Boats § 80.923 Antenna system. An antenna must be provided in accordance with the...

2012-10-01

267

47 CFR 73.1680 - Emergency antennas.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 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...

2010-10-01

268

47 CFR 73.1680 - Emergency antennas.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 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...

2012-10-01

269

47 CFR 73.69 - Antenna monitors.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false Antenna monitors. 73.69 Section 73.69...SERVICES AM Broadcast Stations § 73.69 Antenna monitors. (a) Each station using a directional antenna must have in operation at the...

2010-10-01

270

47 CFR 80.1017 - Antenna system.  

Code of Federal Regulations, 2012 CFR

...Bridge-to-Bridge Act § 80.1017 Antenna system. (a) An antenna must be provided for nonportable...which is nondirectional and vertically polarized. The construction and installation of this antenna must insure proper operation in...

2012-10-01

271

47 CFR 80.1017 - Antenna system.  

Code of Federal Regulations, 2011 CFR

...Bridge-to-Bridge Act § 80.1017 Antenna system. (a) An antenna must be provided for nonportable...which is nondirectional and vertically polarized. The construction and installation of this antenna must insure proper operation in...

2011-10-01

272

47 CFR 80.1017 - Antenna system.  

Code of Federal Regulations, 2010 CFR

...Bridge-to-Bridge Act § 80.1017 Antenna system. (a) An antenna must be provided for nonportable...which is nondirectional and vertically polarized. The construction and installation of this antenna must insure proper operation in...

2010-10-01

273

47 CFR 80.1017 - Antenna system.  

Code of Federal Regulations, 2013 CFR

...Bridge-to-Bridge Act § 80.1017 Antenna system. (a) An antenna must be provided for nonportable...which is nondirectional and vertically polarized. The construction and installation of this antenna must insure proper operation in...

2013-10-01

274

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

275

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

276

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

277

Active Tuning Antennas for Wireless Communication  

NASA Astrophysics Data System (ADS)

Latest technologies in wireless communications present new challenges on antenna design. Reduced size antennas with self reconfigurable ability are characteristical of smart antennas. This paper presents the practical implementation issues of making an automatic smart antenna tuning system varying the resonant frequency of the antenna using a varactor. The primary parameter for changing varactor's value is antenna's VSWR which is monitored by a uC. Additionally, the uC also controls the varactor's value.

Raptis, Vasilis; Tatsis, Giorgos; Votis, Constantinos; Chronopoulos, Spyridon K.; Christofilakis, Vasilis; Kostarakis, Panos

2010-01-01

278

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

279

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

280

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

NASA Astrophysics Data System (ADS)

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

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

281

New massive conformal gravity  

E-print Network

We investigate the new massive conformal gravity which is not invariant under conformal transformations, in comparison to the massive conformal gravity. We find five polarization modes of gravitational waves propagating on the Minkowski spacetimes. The stability of Minkowski spacetimes is guaranteed if the mass squared is not negative and the linearized Ricci tenor is employed to describe a massive spin-2 graviton. However, the small Schwarzschild black hole is unstable against the $s$-mode massive graviton perturbations.

Yun Soo Myung

2014-02-09

282

Circularly polarized metallic EBG antenna  

Microsoft Academic Search

This letter describes the concept and the realization of a directive and circularly polarized antenna using an electromagnetic band gap material whose circular polarization is generated by the structure itself. Experimental and simulated results are presented for an antenna operating at 5GHz.

Michael Diblanc; Emmanuel Rodes; Eric Arnaud; Marc Thevenot; Thierry Monediere; Bernard Jecko

2005-01-01

283

DUALBAND WEARABLE UHF RFID ANTENNA  

Microsoft Academic Search

Based on a system study of the ability to use a commercial RFID system operating in 869 MHz band for the identification of moving sportsmen (1), TAG antennas has been recognized as one of the most sensitive component that affect the proper function of the whole system, especially in case when TAG antenna has to operate in the close vicinity

Milan Svanda; Milan Polivka

284

Optical antenna enhanced spontaneous emission  

PubMed Central

Atoms and molecules are too small to act as efficient antennas for their own emission wavelengths. By providing an external optical antenna, the balance can be shifted; spontaneous emission could become faster than stimulated emission, which is handicapped by practically achievable pump intensities. In our experiments, InGaAsP nanorods emitting at ?200 THz optical frequency show a spontaneous emission intensity enhancement of 35× corresponding to a spontaneous emission rate speedup ?115×, for antenna gap spacing, d = 40 nm. Classical antenna theory predicts ?2,500× spontaneous emission speedup at d ? 10 nm, proportional to 1/d2. Unfortunately, at d < 10 nm, antenna efficiency drops below 50%, owing to optical spreading resistance, exacerbated by the anomalous skin effect (electron surface collisions). Quantum dipole oscillations in the emitter excited state produce an optical ac equivalent circuit current, Io = q?|xo|/d, feeding the antenna-enhanced spontaneous emission, where q|xo| is the dipole matrix element. Despite the quantum-mechanical origin of the drive current, antenna theory makes no reference to the Purcell effect nor to local density of states models. Moreover, plasmonic effects are minor at 200 THz, producing only a small shift of antenna resonance frequency. PMID:25624503

Eggleston, Michael S.; Messer, Kevin; Zhang, Liming; Yablonovitch, Eli; Wu, Ming C.

2015-01-01

285

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

286

A Milstar low profile antenna  

Microsoft Academic Search

A low profile antenna\\/pedestal system for the Milstar program was developed at Raytheon under an Air Force contract. The system was designed to have minimum intrusion inside the aircraft and no protrusion outside the aircraft so that the radome is flush to the fuselage. The main drivers of this antenna design include low cost, minimum height, and high efficiencies for

Y. Chang; M. Sarcione; F. Beltran

1999-01-01

287

Electronically steerable antenna for aircraft  

Microsoft Academic Search

The design of an electronically steerable medium gain antenna for aircraft able to provide voice communication via satellite is presented. The antenna consists of 5 radiating facets and the coverages achieved, including the effect of the aircraft fuselage, are based on the experimental results obtained with the actual components of the beam forming network (switches, phase shifters, power dividers) and

J. Barbero; M. L. Hernanz; C. Martin; J. Vassallo; B. Hedge

1991-01-01

288

Analysis of Vivaldi antennas  

NASA Astrophysics Data System (ADS)

This paper presents a hybrid-mode solution for the guide wavelength of the exponentially tapered (Vivaldi) slot-line antenna, with particular attention given to the method of analysis. The solution to the hybrid-mode equations is obtained by applying the transverse equivalent transmission-line concept in the spectral domain in conjunction with a simple coordinate transformation rule. Results calculated for the variation of the guide wavelength against the z coordinate are compared with those found by using the Galerkin method in the Fourier domain, showing very good agreement.

Huang, Jingxi; Fan, Zhibo

289

Galilean conformal electrodynamics  

NASA Astrophysics Data System (ADS)

Maxwell's Electrodynamics admits two distinct Galilean limits called the Electric and Magnetic limits. We show that the equations of motion in both these limits are invariant under the Galilean Conformal Algebra in D = 4, thereby exhibiting non-relativistic conformal symmetries. Remarkably, the symmetries are infinite dimensional and thus Galilean Electrodynamics give us the first example of an infinitely extended Galilean Conformal Field Theory in D > 2. We examine details of the theory by looking at purely non-relativistic conformal methods and also use input from the limit of the relativistic theory.

Bagchi, Arjun; Basu, Rudranil; Mehra, Aditya

2014-11-01

290

Optical antennas as nanoscale resonators  

E-print Network

Recent progress in nanotechnology has enabled us to fabricate subwavelength architectures that function as antennas for improving the exchange of optical energy with nanoscale matter. We describe the main features of optical antennas for enhancing quantum emitters and review designs that increase the spontaneous emission rate by orders of magnitude from the ultraviolet up to the near-infrared spectral range. To further explore how optical antennas may lead to unprecedented regimes of light-matter interaction, we draw a relationship between metal nanoparticles, radio-wave antennas and optical resonators. Our analysis points out how optical antennas may function as nanoscale resonators and how these may offer unique opportunities with respect to state-of-the-art microcavities.

Mario Agio

2011-11-05

291

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

292

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

293

Thermo-mechanical Characteristics of Smart Skin Antenna Structures  

NASA Astrophysics Data System (ADS)

Analysis on the thermo-mechanical behaviors of smart skin antenna structures under air flow is performed. The model is a conformal load-bearing structure, reducing radar cross section and increasing stealth functions are very important. The skin is modeled as a multi-layer sandwich structure composed of carbon/epoxy, glass/epoxy and a dielectric polymer. Furthermore, a dielectric layer is embedded on the middle surface of the sandwich structure to act as antenna or radars. The formulation of the structural model is based on the first-order shear deformation plate theory. Lastly, Newton-Raphson iterative method applied for solving the nonlinear equations of the thermal postbuckling analysis and numerical results are calculated by finite element method.

Lee, Chang-Yull; Yoo, Kwang-Kyu; Kim, Ji-Hwan

294

IEEE ANTENNAS AND WIRELESS PROPAGATION LETTERS, VOL. 3, 2004 45 A Wideband Monopole Antenna for  

E-print Network

IEEE ANTENNAS AND WIRELESS PROPAGATION LETTERS, VOL. 3, 2004 45 A Wideband Monopole Antenna for PCS--A triple-band stubby antenna fed by a coaxial probe and tuning technique are proposed for operating at PCS, IMT-2000, and Bluetooth bands. The proposed antenna shielded by the antenna cover consists of the two

Park, Seong-Ook

295

Microstrip antenna couplers and active antenna amplifying arrays  

E-print Network

, Figure 34, and Figure 36 . . 43 S21 (Ang) vs. length variations (l/L) among 49 50 Figure 15, Figure 34, and Figure 36 . . 50 44 Geometry of the patch-fed antenna coupler on 31-mil substrate . . . 53 FIGURE Page 45 S1 I (dB) vs. gap variations (mm...) of the line-fed antenna coupler on 31-mil substrate. . . . . 95 Surface current distribution at 7. 9 GHz (TMJgp) of the line-fed antenna coupler on 31-mil substrate. . . . . . . . 110 . . . . 112 . . . 112 96 E-plane radiation pattern of TMwp mode...

Yang, Yao-Chou (Angus)

2012-06-07

296

Folded Conformations of Maitotoxin  

Microsoft Academic Search

We used classical molecular mechanics and dynamics simulations to sample the conformational space of maitotoxin, the largest and most lethal natural product. Among the set of minima obtained, the five conformers with the lowest energies show folded structures with an intramolecular hole. We found the folding mainly due to hydrogen bonds that fasten the mobile zones of the molecule. The

Myrna H. Matus; Laura Escobar; Marcelo Galván

2008-01-01

297

Fusion of conformal interfaces  

Microsoft Academic Search

We study the fusion of conformal interfaces in the c = 1 conformal field theory. We uncover an elegant structure reminiscent of that of black holes in supersymmetric theories. The role of the BPS black holes is played by topological interfaces, which (a) minimize the entropy function, (b) fix through an attractor mechanism one or both of the bulk radii,

C. Bachas; I. Brunner

2008-01-01

298

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

299

Forthcoming Publications: Science, PRL Optical Antennas  

E-print Network

Forthcoming Publications: Science, PRL Optical Antennas D.W. Pohl This work presented here.nano-optics.ch Schweizerischer Nationalfonds FNSNF #12;My definition of an antenna....: #12;...adopts that of radio wave technology. antenna arms feed gap antenna cable connecting to load reflectors directors radiation lobes #12

300

Wireless@Virginia Tech Antennas and Propagation  

E-print Network

Wireless@Virginia Tech SWIM Antennas and Propagation Need for Research The success of any wireless communications device is integrally tied to the antennas used to transmit the signal. The antenna design must with a myriad of environmental elements, such as multipath, path loss, reflection, and scattering makes antenna

Beex, A. A. "Louis"

301

26 MHz 1300 MHz Log periodic antenna  

E-print Network

An, Computer and Power Supplies 2000 MHz ­ 8000 MHz Horn Antenna 3000 MHz High Pass Filter Low Noise26 MHz ­ 1300 MHz Log periodic antenna 1000 MHz ­ 4000 MHz Log periodic antenna Pre Supply Control cable to computer USB port USB to GPIB Cable RF cables from antennas to pre

302

A novel ultra-wideband microstrip antenna  

Microsoft Academic Search

This paper describes the design of a novel ultra-wideband (UWB) antenna for UWB applications. The design is based on planar rectangular monopole microstrip antenna. The optimum antenna geometry is obtained by computation calculation, and the results were simulated by using electromagnetic simulation software CST MWS(CST microwave studio). The results show that the microstrip antenna can get in the range of

Xiaodong Deng; Xiaodong Yang; Bingcai Chen; Yu Bai

2011-01-01

303

Fractal GPS antenna design on piezoelectric substrate  

Microsoft Academic Search

This paper presents a study of fractal GPS antenna design on piezoelectric substrate. The antenna size is reduced by using piezoelectric materials with high dielectric constant and the fractal structure in antenna design. The desired high effective dielectric constant can be obtained by the special arrangement of the ground. The Koch fractal structure is employed in antenna design. With the

Tzu-Chun Tang; Cheng-Han Tsai; Ken-Huang Lin; Yu-Tung Huang; Chi-Yun Chen

2010-01-01

304

Smart antennas for wireless communications systems  

Microsoft Academic Search

The fundamental idea behind smart antennas is to improve the performance of the wireless communication system by increasing the gain in a chosen direction. This can be achieved by pointing the main lobes of the antenna-beam patterns towards the desired users. Smart antenna system combines multiple antenna elements with a signal processing capability to automatically optimise its radiation and\\/or reception

Ioan Nicolaescu; Dan Stoica

2010-01-01

305

Millimeter-Wave Substrate Mounted Antenna Measurements  

Microsoft Academic Search

A substrate mounted antenna is a type of integrated circuit antenna that, unlike the microstrip antenna, does not have a ground plane on the bottom surface of the substrate. The measurement apparatus is described, and the rerults of field pattern and absolute gain measurements at 230 GHz w+&-+e presented I. INTRODUCTION The long range goals of the substrate mounted antenna

M. Couker; J. J. Gallagher

1990-01-01

306

1 Joint Antenna Combining and Multiuser Detection  

E-print Network

1 Joint Antenna Combining and Multiuser Detection Ralf Muller y and Laura Cottatellucci y Smart diversity intrinsically present in CDMA systems. Antenna arrays provide spatial diversity and smart antennas antenna technology combined with code-division multiple-access (CDMA) is common in 3rd generation cellular

Müller, Ralf R.

307

Antenna topology impacts on measured MIMO capacity  

Microsoft Academic Search

The achievable spectral efficiency of multiple antenna radios is greatly improved by Multiple Input Multiple Output (MIMO) signaling. However, the benefit of MIMO is lessened in practice due to mutual coupling in the antenna arrays. This problem is exacerbated by the size restrictions on antenna arrays in portable devices. We present a compact antenna array that is designed to limit

David W. Browne; Majid Manteghi; Michael P. Fitz; Yahya Rahmat-Samii

2005-01-01

308

DEPLOYABLE ANTENNA KINEMATICS USING TENSEGRITY STRUCTURE DESIGN  

E-print Network

DEPLOYABLE ANTENNA KINEMATICS USING TENSEGRITY STRUCTURE DESIGN By BYRON FRANKLIN KNIGHT .........................................................................................................5 Tensegrity Overview

Florida, University of

309

Conformity index: A review  

SciTech Connect

We present a critical analysis of the conformity indices described in the literature and an evaluation of their field of application. Three-dimensional conformal radiotherapy, with or without intensity modulation, is based on medical imaging techniques, three-dimensional dosimetry software, compression accessories, and verification procedures. It consists of delineating target volumes and critical healthy tissues to select the best combination of beams. This approach allows better adaptation of the isodose to the tumor volume, while limiting irradiation of healthy tissues. Tools must be developed to evaluate the quality of proposed treatment plans. Dosimetry software provides the dose distribution in each CT section and dose-volume histograms without really indicating the degree of conformity. The conformity index is a complementary tool that attributes a score to a treatment plan or that can compare several treatment plans for the same patient. The future of conformal index in everyday practice therefore remains unclear.

Feuvret, Loic [Institut Curie, Orsay (France)]. E-mail: loic.feuvret@cpo.curie.net; Noel, Georges [Institut Curie, Orsay (France); Mazeron, Jean-Jacques [Institut Curie, Orsay (France); Pitie Salpetriere Hospital, Paris (France); Bey, Pierre [Institut Curie, Orsay (France); Institut Curie, Paris (France)

2006-02-01

310

Antenna system for UWB GPR for landmine detection  

Microsoft Academic Search

The paper describes the design of an antenna system for a video impulse radar dedicated to landmine detection. The developed antenna system consists of a dielectric wedge antenna as transmit antenna and loop antennas as receive ones. The receive antennas are situated below the transmit one. The dielectric wedge antenna has been designed on the basis of the transmission line

Alexander G. Yarovoy; Alexander Schukin; Igor Kaploun; Leo P. Ligthart

2001-01-01

311

Antennas for Ubiquitous Sensor Network  

NASA Astrophysics Data System (ADS)

Recent advancements in the ubiquitous sensor network field have brought considerable feasibility to the realization of a ubiquitous society. A ubiquitous sensor network will enable the cooperative gathering of environmental information or the detection of special events through a large number of spatially distributed sensor nodes. Thus far, radio frequency identification (RFID) as an application for realizing the ubiquitous environment has mainly been developed for public and industrial systems. To this end, the most existing applications have demanded low-end antennas. In recent years, interests of ubiquitous sensor network have been broadened to medical body area networks (BAN), wireless personal area networks (WPAN), along with ubiquitous smart worlds. This increasing attention toward in ubiquitous sensor network has great implications for antennas. The design of functional antennas has received much attention because they can provide various kinds of properties and operation modes. These high-end antennas have some functions besides radiation. Furthermore, smart sensor nodes equipped with cooperated high-end antennas would allow them to respond adaptively to environmental events. Therefore, some design approaches of functional antennas with sensing and reconfigurability as high-end solution for smart sensor node, as well as low-end antennas for mobile RFID (mRFID) and SAW transponder are presented in this paper.

Chang, Kihun; Yoon, Young Joong

312

Multiple-Beam Communications Antenna  

NASA Technical Reports Server (NTRS)

System has both fixed-spot and scanning coverage. Advanced offset-fed spacecraft antenna systems operating in 30/20 GHz frequency bands developed to provide multiple-radiating fixed-spot and regional-coverage scanning beams for use on communications satellites. Operating at higher frequencies, provides alternate frequency bands for expansion of existing satellite services and achieving frequency reuse capability for conservation of frequency spectrum. 20-GHz transmitting antenna is offset-fed, dual-reflector configuration. 30-GHz receiving antenna has orthogonal polarized feeds, hyperbolic reflectors, and two subreflectors.

Myhre, R. W.; Roberts, T. E.; Wong, W. C.

1989-01-01

313

Smart antennas based on graphene  

SciTech Connect

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

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

2014-09-21

314

Smart antennas based on graphene  

NASA Astrophysics Data System (ADS)

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

Aldrigo, Martino; Dragoman, Mircea; Dragoman, Daniela

2014-09-01

315

Optical antenna enhanced graphene photodetector  

NASA Astrophysics Data System (ADS)

We report on the integration of an individual, metal-based, plasmonic nano-antenna on a graphene photodetector. The device exhibits an electromagnetic resonance at a wavelength of 580 nm with well-defined polarization sensitivity. With no applied bias voltage, this antenna-coupled graphene photodetector features a responsivity of ˜17 nA/?W, which is four orders of magnitude higher than previously studied single antenna enhanced detectors. Finally, we measure a signal-to-noise ratio of ˜200 in a 1-Hz bandwidth, with an average photocurrent value of 1.2 nA.

Chakraborty, Chitraleema; Beams, Ryan; Goodfellow, Kenneth M.; Wicks, G. W.; Novotny, Lukas; Nick Vamivakas, A.

2014-12-01

316

Electrically floating, near vertical incidence, skywave antenna  

SciTech Connect

An Electrically Floating, Near Vertical Incidence, Skywave (NVIS) Antenna comprising an antenna element, a floating ground element, and a grounding element. At least part of said floating ground element is positioned between said antenna element and said grounding element. The antenna is separated from the floating ground element and the grounding element by one or more electrical insulators. The floating ground element is separated from said antenna and said grounding element by one or more electrical insulators.

Anderson, Allen A.; Kaser, Timothy G.; Tremblay, Paul A.; Mays, Belva L.

2014-07-08

317

Experimental Multiport Bicone Antenna  

NASA Astrophysics Data System (ADS)

A practical, easily manufactured multiport bicone antenna suitable for many receiving tasks such as direction finding systems can be made by using sharp-edged metal fins on the feeding coax center conductor to provide a tapered transition and connection path to coaxial probes. This construction resembles an arrow's tail. Already four mutually orthogonal fins can give full 360 degree azimuth coverage with suitable -3 dB port pattern overlap. Five experimental constructions working at Ku and Ka bands, each with fractional bandwidths of 23 to 31 per cent, are shown with full dimensional details. Suitable fin tapering is close to the full air gap in the coax and fin thickness should be less than 1/16th of the outer conductor diameter.

Eskelinen, Pekka; Ylinen, Juhana

2013-01-01

318

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

319

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

320

Conformal Carroll groups  

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

321

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

322

Inflatable Antennas Support Emergency Communication  

NASA Technical Reports Server (NTRS)

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

2010-01-01

323

Planar microstrip YAGI antenna array  

NASA Technical Reports Server (NTRS)

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

Huang, John (inventor)

1993-01-01

324

Box truss antenna technology status  

NASA Technical Reports Server (NTRS)

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

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

1987-01-01

325

VHF-UHF aircraft antenna  

Microsoft Academic Search

A broadband, circularly polarized antenna system suitable for use on WP-3 aircraft and operating in the VHF-UHF frequency region has been designed and fabricated. This airborne radiometer system will operate over a 3 to 1 frequency range without tuning. The installation contains a high- and low-frequency hemispherical coverage antenna and a high- and low-frequency fan-beam array. The entire installation is

F. Fine

1976-01-01

326

Conformal and non conformal dilaton gravity  

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

327

Characterizing Protein Conformation Space  

E-print Network

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

Nigham, Anshul

328

Multiple band circularly polarized microstrip antenna  

NASA Technical Reports Server (NTRS)

A multiple antenna assembly for communicating electromagnetic radiation is disclosed. An antenna element stack is constructed of a plurality of elliptical lamina antenna elements mutally separated by layers of dielectric material, and separated from a ground plane by dielectric material. The antenna assembly is coupled through a feed line in contact with the top antenna element. A conductor joins the remaining antenna elements to the ground plane. Each individual antenna element is operable for communication reception and transmission within a frequency band determined by the size of the particular antenna element. The sizes of the antenna elements may be selected to provide electromagnetic radiation communication over several distinct frequency bands, or to connect the individual bands into a broad band.

Yu, I. P. (inventor)

1980-01-01

329

Aperture Coupled Microstrip Short Backfire Antenna  

NASA Astrophysics Data System (ADS)

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

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

2012-03-01

330

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

331

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

332

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

333

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

334

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

335

Satellite Communications with NRAO Green Bank Antennas  

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

336

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

337

Magnetic antenna excitation of whistler modes. II. Antenna arrays  

NASA Astrophysics Data System (ADS)

The excitation of whistler modes from magnetic loop antennas has been investigated experimentally. The field topology of the excited wave driven by a single loop antenna has been measured for different loop orientations with respect to the uniform background field. The fields from two or more antennas at different locations are then created by superposition of the single-loop data. It is shown that an antenna array can produce nearly plane waves which cannot be achieved with single antennas. By applying a phase shift along the array, oblique wave propagation is obtained. This allows a meaningful comparison with plane wave theory. The Gendrin mode and oblique cyclotron resonance are demonstrated. Wave helicity and polarization in space and time are demonstrated and distinguished from the magnetic helicity of the wave field. The superposition of two oblique plane whistler modes produces in a "whistler waveguide" mode whose polarization and helicity properties are explained. The results show that single point measurements cannot properly establish the wave character of wave packets. The laboratory observations are relevant for excitation and detection of whistler modes in space plasmas.

Stenzel, R. L.; Urrutia, J. M.

2014-12-01

338

Feed Structure For Antennas  

NASA Technical Reports Server (NTRS)

A novel feed structure, for an antenna having a resonant electric field structure, comprising a patch element, an integrated circuit attached to the patch element, at least one inner conductor electrically connected to and terminating at the integrated circuit on a first end of the at least one inner conductor, wherein the at least one inner conductor extends through and is not electrically connected to the patch element, and wherein the at least one inner conductor is available for electrical connectivity on a second end of the at least one inner conductor, and an outer conductor electrically connected to and terminating at the patch element on a first end of the outer conductor, wherein the outer conductor is available for electrical connectivity on a second end of the outer conductor, and wherein the outer conductor concentrically surrounds the at least one inner conductor from the second end of the at least one inner conductor available for electrical connectivity to the first end of the outer conductor terminating at the patch element.

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

2005-01-01

339

Dr. S. X-Pol Intro to Antennas 1  

E-print Network

into two groups ­ Wire antennas: · dipoles, loops, Yagi-Uda... ­ Aperture antennas: · parabolic, horns feed Dipole with parabolic and corner reflector Reflector and Pyramidal horn antennas Outline AntennaDr. S. X-Pol Intro to Antennas 1 Introduction to Antennas Dr. Sandra Cruz-Pol Electricaland

Cruz-Pol, Sandra L.

340

The inverted-F antenna height effects on bandwidth  

Microsoft Academic Search

The inverted-F antenna is widely used in mobile applications due to its simple design, flexibility, low cost and reliable performance. The paper studies the relationships between antenna impedance bandwidth and its vertical dimension (height) based on measurements. The measurement results indicate the antenna SWR bandwidth increases nearly linearly with the antenna height. Increasing the antenna height increases the antenna area,

Duixian Liu; B. Gaucher

2005-01-01

341

Conformal supermultiplets without superpartners  

E-print Network

We consider polynomial deformations of Lie superalgebras and their representations. For the class A(n-1,0) ~ sl(n/1), we identify families of superalgebras of quadratic and cubic type, consistent with Jacobi identities. For such deformed superalgebras we point out the possibility of zero step supermultiplets, carried on a single, irreducible representation of the even (Lie) subalgebra. For the conformal group SU(2,2) in 1+3-dimensional spacetime, such irreducible (unitary) representations correspond to standard conformal fields (j_1,j_2;d), where (j_1,j_2) is the spin and d the conformal dimension; in the massless class j_1 j_2=0, and d=j_1+j_2+1. We show that these repesentations are zero step supermultiplets for the superalgebra SU_(2)(2,2/1), the quadratic deformation of conformal supersymmetry SU(2,2/1). We propose to elevate SU_(2)(2,2/1) to a symmetry of the S-matrix. Under this scenario, low-energy standard model matter fields (leptons, quarks, Higgs scalars and gauge fields) descended from such conformal supermultiplets are not accompanied by superpartners.

Peter Jarvis

2011-06-24

342

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

343

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

344

IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION 1 Gain Enhancement of a Microstrip Patch Antenna  

E-print Network

IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION 1 Gain Enhancement of a Microstrip Patch Antenna, Senior Member, IEEE, Abstract-- In this paper, the performance of a circular mi- crostrip patch antenna is improved using a new cylindrical Electromagnetic Bandgap (EBG) substrate. The microstrip patch antenna

Paris-Sud XI, Université de

345

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

346

IEEE ANTENNAS AND WIRELESS PROPAGATION LETTERS, VOL. 7, 2008 569 A Compact Tunable Internal Antenna for  

E-print Network

switching techniques such as RF switches, MEMS switches, PIN diodes, and varactors [7]­[11]. In this letter is available for the antenna structure. The conventional passive multiband antennas often require large size of antenna dimension [1]­[5]. Moreover, passive multiband antennas might be less efficiency in term

Park, Seong-Ook

347

Mechanisms of the Rosetta high gain antenna  

NASA Astrophysics Data System (ADS)

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

Pereira, Carlos

2001-09-01

348

Antenna beamforming for infrastructureless wireless networks  

E-print Network

Our work studies the impact of antenna beamforming on the performance of infrastructureless wireless networks. Based on examination of the beampattern for a uniform circular antenna array (UCAA) utilizing beamforming under ...

Godoy, Elizabeth C

2007-01-01

349

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

350

A 60 GHz Conical Horn Antenna Excited with Quasi-Yagi Antenna Mikko Sironen, Yongxi Qian, and Tatsuo Itoh  

E-print Network

A 60 GHz Conical Horn Antenna Excited with Quasi-Yagi Antenna Mikko Sironen, Yongxi Qian Abstract -- A conical horn antenna excited with a quasi- Yagi antenna is presented. This antenna comprise radiator is thus desirable. A horn antenna is in this perspective in favor. In [1] a planar quasi

Itoh, Tatsuo

351

Conformal Random Geometry  

E-print Network

In these Notes, a comprehensive description of the universal fractal geometry of conformally-invariant scaling curves or interfaces, in the plane or half-plane, is given. The present approach focuses on deriving critical exponents associated with interacting random paths, by exploiting their underlying quantum gravity structure. The latter relates exponents in the plane to those on a random lattice, i.e., in a fluctuating metric, using the so-called Knizhnik, Polyakov and Zamolodchikov (KPZ) map. This is accomplished within the framework of random matrix theory and conformal field theory, with applications to geometrical critical models, like Brownian paths, self-avoiding walks, percolation, and more generally, the O(N) or Q-state Potts models and, last but not least, Schramm's Stochastic Loewner Evolution (SLE_kappa). These Notes can be considered as complementary to those by Wendelin Werner (2006 Fields Medalist!), ``Some Recent Aspects of Random Conformally Invariant Systems,'' arXiv:math.PR/0511268.

Bertrand Duplantier

2006-08-23

352

Compact conformal manifolds  

NASA Astrophysics Data System (ADS)

In this note we begin a systematic study of compact conformal manifolds of SCFTs in four dimensions (our notion of compactness is with respect to the topology induced by the Zamolodchikov metric). Supersymmetry guarantees that such manifolds are Kähler, and so the simplest possible non-trivial compact conformal manifold in this set of geometries is a complex one-dimensional projective space. We show that such a manifold is indeed realized and give a general prescription for constructing complex N-dimensional projective space conformal manifolds as certain small breaking deformations of strongly interacting SCFTs. In many cases, our prescription reduces the construction of such spaces to a study of the chiral ring. We also give an algorithm for constructing more general compact spaces of SCFTs.

Buican, Matthew; Nishinaka, Takahiro

2015-01-01

353

Random Conformal Weldings  

E-print Network

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

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

2009-09-07

354

Random Conformal Weldings  

E-print Network

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

Astala, K; Kupiainen, A; Saksman, E

2009-01-01

355

Horn Antennas Dr. Sandra Cruz-Pol  

E-print Network

1 Horn Antennas INEL 6069 Dr. Sandra Cruz-Pol ECE, UPRM Horn Antennas Invented in late 1800's. Types H-plane E-plane PyramidalPyramidal Conical H-plane horn Antenna DH/bD a1 / [ ] [ ]{ }22 1 2max. 13.7. / 50 e E E Ga D = / 501 e b B = E plane horn antenna DE/aD b1 / 2e Gregorian feed Arecibo

Cruz-Pol, Sandra L.

356

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

357

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

358

Non-Reciprocal Optical Antennas  

E-print Network

Plasmonics aims to interface photonics and electronics. Finding optical, near-field analogues of much used electro-technical components is crucial to the success of such a platform. Here we present the plasmonic analogue of a non-reciprocal antenna. For non-reciprocality in a plasmonic context, the optical excitation and emission resonances of the antenna need to be an orthogonal set. We show that nonlinear excitation of metal nanoantennas creates a sufficient shift between excitation and emission wavelengths that they can be interpreted as decoupled, allowing for independent tuning of excitation and emission properties along different spatial dimensions. This leads, for given excitation wavelength and polarization, to independent optimization of emission intensity, frequency spectrum, polarization and angular spectrum. Non-reciprocal optical antennas of both gold and aluminum are characterized and shown to be useful as e.g. nonlinear signal transducers or nanoscale sources of widely tunable light.

Castro-Lopez, Marta; van Hulst, Niek F

2014-01-01

359

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

360

Offset unfurlable antenna, phase 1  

NASA Astrophysics Data System (ADS)

The configuration, technology requirements, development aspects, and experimental activities for satellite reflectors for fixed and mobile communications and television broadcasting are outlined. A 4.5 m antenna for 4 GHz, and an 8 m antenna for 1.6 GHz were studied, assuming an L-Sat type satellite. A radial rib concept with auxiliary adjustment ribs, and a three dimensional scissors concept (spatial framework) with mesh adjustment elements were compared concerning mass, stowage, volume, development risk, and reliability. For antennas of diameter from 3.6 to 12 m (12 GHz to 800 MHz) the radial rib reflector is preferred. Main advantages (with rib folding for larger reflector diameters) are: lower costs; less critical technology problems; lower development risks; high deployment reliability; lightweight intermediate ribs can adapt surface accuracy to higher frequency requirements (high application flexibility); and folded main ribs provide high package capability at larger diameters. The scissors concept is advantageous for applications requiring reflectors from 12 m diameter onwards.

1984-03-01

361

Antenna Technology Shuttle Experiment (ATSE)  

NASA Technical Reports Server (NTRS)

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

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

1987-01-01

362

Electronically steerable antenna for aircraft  

NASA Astrophysics Data System (ADS)

The design of an electronically steerable medium gain antenna for aircraft able to provide voice communication via satellite is presented. The antenna consists of 5 radiating facets and the coverages achieved, including the effect of the aircraft fuselage, are based on the experimental results obtained with the actual components of the beam forming network (switches, phase shifters, power dividers) and the radiating facets including the matching network. One hundred percent of the mandatory coverage (colatitude 0 to 85 degrees) is achieved with a gain greater than 10 dBi and 12 dBi are achieved in 60 percent of it. Concerning the goal coverage (colatitude 0 to 105 degrees) a gain greater than 7 dBi is achieved in 84 percent of it. The dimensions of the radome required for this antenna are: length 1780 mm, width 255 mm, height 197 mm.

Barbero, J.; Hernanz, M. L.; Hernanz, M.; Martin, C.; Vassallo, J.; Hedge, B.

1991-10-01

363

Charged conformal Killing spinors  

NASA Astrophysics Data System (ADS)

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

Lischewski, Andree

2015-01-01

364

Ethyl anion preferred conformation  

NASA Astrophysics Data System (ADS)

Ab initio architecture and torsional barrier for ethyl anion, C2H -5 are analyzed using natural bond orbital methodology. The B3LYP/6-311++G(3df,2p) 2-kcal/mol torsional barrier between the preferred staggered and higher-energy eclipsed conformer is calculated to be one-third lower than for ethane. This decrease is largely attributed to reduced hyperconjugative stabilization of the equilibrium anion conformer compared to that for ethane. Proton removal is also predicted to cause opening of the ethane central CCH angle by 7°, attributed to decreased steric repulsion and to increased hyperconjugative stabilization accompanying angle widening in the ion.

Goodman, Lionel; Sauers, Ronald R.

365

47 CFR 95.859 - Antennas.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 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...

2012-10-01

366

47 CFR 74.641 - Antenna systems.  

...2014-10-01 2014-10-01 false Antenna systems. 74.641 Section 74.641...Broadcast Auxiliary Stations § 74.641 Antenna systems. (a) For fixed stations...auxiliary stations shall use directional antennas that meet the performance...

2014-10-01

367

47 CFR 101.115 - Directional antennas.  

Code of Federal Regulations, 2012 CFR

... 2012-10-01 false Directional antennas. 101.115 Section 101.115 ...Standards § 101.115 Directional antennas. Link to an amendment published at...of this part must employ a directional antenna adjusted with the center of the...

2012-10-01

368

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

369

47 CFR 78.105 - Antenna systems.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false Antenna systems. 78.105 Section 78.105... Technical Regulations § 78.105 Antenna systems. (a) For fixed stations...Fixed CARS stations shall use directional antennas that meet the performance standards...

2012-10-01

370

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

371

47 CFR 74.737 - Antenna location.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false Antenna location. 74.737 Section 74.737...and TV Booster Stations § 74.737 Antenna location. (a) An applicant...retransmitted. (b) The transmitting antenna should be placed above growing...

2012-10-01

372

47 CFR 74.641 - Antenna systems.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false Antenna systems. 74.641 Section 74.641...Broadcast Auxiliary Stations § 74.641 Antenna systems. (a) For fixed stations...auxiliary stations shall use directional antennas that meet the performance...

2012-10-01

373

47 CFR 95.51 - Antenna height.  

Code of Federal Regulations, 2013 CFR

... 5 2013-10-01 2013-10-01 false Antenna height. 95.51 Section 95.51 Telecommunication...General Mobile Radio Service (GMRS) § 95.51 Antenna height. (a) Certain antenna structures used in a GMRS system and...

2013-10-01

374

47 CFR 95.51 - Antenna height.  

Code of Federal Regulations, 2010 CFR

... 5 2010-10-01 2010-10-01 false Antenna height. 95.51 Section 95.51 Telecommunication...General Mobile Radio Service (GMRS) § 95.51 Antenna height. (a) Certain antenna structures used in a GMRS system and...

2010-10-01

375

47 CFR 73.510 - Antenna systems.  

...2014-10-01 2014-10-01 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...

2014-10-01

376

47 CFR 80.863 - Antenna system.  

Code of Federal Regulations, 2011 CFR

... 5 2011-10-01 2011-10-01 false Antenna system. 80.863 Section 80.863 Telecommunication...Vessels Not Subject to Subpart W § 80.863 Antenna system. (a) An antenna system must be installed which is as...

2011-10-01

377

47 CFR 95.51 - Antenna height.  

Code of Federal Regulations, 2012 CFR

... 5 2012-10-01 2012-10-01 false Antenna height. 95.51 Section 95.51 Telecommunication...General Mobile Radio Service (GMRS) § 95.51 Antenna height. (a) Certain antenna structures used in a GMRS system and...

2012-10-01

378

47 CFR 78.105 - Antenna systems.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Antenna systems. 78.105 Section 78.105... Technical Regulations § 78.105 Antenna systems. (a) For fixed stations...Fixed CARS stations shall use directional antennas that meet the performance standards...

2011-10-01

379

47 CFR 80.863 - Antenna system.  

Code of Federal Regulations, 2012 CFR

... 5 2012-10-01 2012-10-01 false Antenna system. 80.863 Section 80.863 Telecommunication...Vessels Not Subject to Subpart W § 80.863 Antenna system. (a) An antenna system must be installed which is as...

2012-10-01

380

47 CFR 73.510 - Antenna systems.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 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...

2011-10-01

381

47 CFR 73.510 - Antenna systems.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 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...

2012-10-01

382

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

383

47 CFR 80.863 - Antenna system.  

Code of Federal Regulations, 2013 CFR

... 5 2013-10-01 2013-10-01 false Antenna system. 80.863 Section 80.863 Telecommunication...Vessels Not Subject to Subpart W § 80.863 Antenna system. (a) An antenna system must be installed which is as...

2013-10-01

384

47 CFR 74.641 - Antenna systems.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Antenna systems. 74.641 Section 74.641...Broadcast Auxiliary Stations § 74.641 Antenna systems. (a) For fixed stations...auxiliary stations shall use directional antennas that meet the performance...

2011-10-01

385

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

386

47 CFR 73.510 - Antenna systems.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 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...

2010-10-01

387

47 CFR 74.641 - Antenna systems.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false Antenna systems. 74.641 Section 74.641...Broadcast Auxiliary Stations § 74.641 Antenna systems. (a) For fixed stations...auxiliary stations shall use directional antennas that meet the performance...

2010-10-01

388

47 CFR 74.737 - Antenna location.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Antenna location. 74.737 Section 74.737...and TV Booster Stations § 74.737 Antenna location. (a) An applicant...retransmitted. (b) The transmitting antenna should be placed above growing...

2013-10-01

389

47 CFR 95.51 - Antenna height.  

Code of Federal Regulations, 2011 CFR

... 5 2011-10-01 2011-10-01 false Antenna height. 95.51 Section 95.51 Telecommunication...General Mobile Radio Service (GMRS) § 95.51 Antenna height. (a) Certain antenna structures used in a GMRS system and...

2011-10-01

390

47 CFR 95.859 - Antennas.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 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...

2010-10-01

391

47 CFR 95.1213 - Antennas.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false Antennas. 95.1213 Section 95.1213...Service (MedRadio) § 95.1213 Antennas. Link to an amendment published...FR 55733, Sept. 11, 2012. No antenna for a MedRadio transmitter...

2012-10-01

392

47 CFR 74.737 - Antenna location.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Antenna location. 74.737 Section 74.737...and TV Booster Stations § 74.737 Antenna location. (a) An applicant...retransmitted. (b) The transmitting antenna should be placed above growing...

2011-10-01

393

47 CFR 74.737 - Antenna location.  

...2014-10-01 2014-10-01 false Antenna location. 74.737 Section 74.737...and TV Booster Stations § 74.737 Antenna location. (a) An applicant...retransmitted. (b) The transmitting antenna should be placed above growing...

2014-10-01

394

47 CFR 74.641 - Antenna systems.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Antenna systems. 74.641 Section 74.641...Broadcast Auxiliary Stations § 74.641 Antenna systems. (a) For fixed stations...auxiliary stations shall use directional antennas that meet the performance...

2013-10-01

395

Stacked optical antennas Dieter W. Pohl,1  

E-print Network

Stacked optical antennas Dieter W. Pohl,1 Sergio G. Rodrigo,2 and Lukas Novotny2,a 1 Institute; published online 13 January 2011 We propose and analyze a stacked optical antenna SOA . It is characterized in microscopy. © 2011 American Institute of Physics. doi:10.1063/1.3541544 Optical antennas are devices

Novotny, Lukas

396

47 CFR 95.859 - Antennas.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 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...

2011-10-01

397

47 CFR 78.105 - Antenna systems.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Antenna systems. 78.105 Section 78.105... Technical Regulations § 78.105 Antenna systems. (a) For fixed stations...Fixed CARS stations shall use directional antennas that meet the performance standards...

2013-10-01

398

47 CFR 78.105 - Antenna systems.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false Antenna systems. 78.105 Section 78.105... Technical Regulations § 78.105 Antenna systems. (a) For fixed stations...Fixed CARS stations shall use directional antennas that meet the performance standards...

2010-10-01

399

Antenna Construction and Propagation of Radio Waves.  

ERIC Educational Resources Information Center

Developed as part of the Marine Corps Institute (MCI) correspondence training program, this course on antenna construction and propagation of radio waves is designed to provide communicators with instructions in the selection and/or construction of the proper antenna(s) for use with current field radio equipment. Introductory materials include…

Marine Corps Inst., Washington, DC.

400

47 CFR 74.737 - Antenna location.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false Antenna location. 74.737 Section 74.737...and TV Booster Stations § 74.737 Antenna location. (a) An applicant...retransmitted. (b) The transmitting antenna should be placed above growing...

2010-10-01

401

47 CFR 78.105 - Antenna systems.  

...2014-10-01 2014-10-01 false Antenna systems. 78.105 Section 78.105... Technical Regulations § 78.105 Antenna systems. (a) For fixed stations...Fixed CARS stations shall use directional antennas that meet the performance standards...

2014-10-01

402

47 CFR 80.967 - Antenna system.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Antenna system. 80.967 Section 80.967...Vessels on the Great Lakes § 80.967 Antenna system. The antenna must be omni-directional, vertically polarized and located as high as practicable...

2011-10-01

403

Circularly Polarized Microstrip Antenna for Cordless Phones  

E-print Network

Circularly Polarized Microstrip Antenna for Cordless Phones By: Rachael Moore, Maria-Carmen Parejo;RESULTS Radiation Pattern of Right Handed Circularly Polarized Antenna #12;RESULTS Radiation Pattern of Left Handed Circularly Polarized Antenna #12;DISCUSSION OF RESULTS Axial ratios of right and left

404

47 CFR 80.967 - Antenna system.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false Antenna system. 80.967 Section 80.967...Vessels on the Great Lakes § 80.967 Antenna system. The antenna must be omni-directional, vertically polarized and located as high as practicable...

2012-10-01

405

47 CFR 80.967 - Antenna system.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Antenna system. 80.967 Section 80.967...Vessels on the Great Lakes § 80.967 Antenna system. The antenna must be omni-directional, vertically polarized and located as high as practicable...

2013-10-01

406

Microstrip Antenna System for Arbitrary Polarization Reconfigurability  

E-print Network

Microstrip Antenna System for Arbitrary Polarization Reconfigurability Jarrah Bergeron, Bernard, Victoria, BC, Canada Abstract--A microstrip antenna system is presented that allows polarization of 3.9 dB and 8.8 dB between individual polarization states. Index Terms--microstrip antenna

Bornemann, Jens

407

An optimized dual polarization global beam antenna  

Microsoft Academic Search

A satellite antenna has been developed which provides, from a synchronous orbit position, a shaped beam for earth coverage with improved gain and a high degree of polarization purity. This shaped beam antenna is somewhat larger than the conventional global coverage horn antenna. However, for a fixed e.i.r.p. requirement, the increased gain can lead to a significant mass reduction due

E. Carpenter

1982-01-01

408

Design of a wideband TEM horn antenna  

Microsoft Academic Search

A novel design method for a TEM horn antenna is proposed on the basis of parallel plate waveguide theory. This TEM horn antenna has an exponentially tapered structure to increase the matching bandwidth. The measurement shows that the TEM horn antenna has the frequency band of 75 MHz to 1200 MHz for VSWR less than 2.0.

Kyung-Ho Chung; Sung-Ho Pyun; S.-Y. Chung; Jae-Hoon Choi

2003-01-01

409

Planar Differential Elliptical UWB Antenna Optimization  

Microsoft Academic Search

A recently proposed optimization procedure, based on the time domain characteristics of an antenna, is exploited to design a planar differential elliptical antenna for ultrawideband (UWB) applications. The optimization procedure aims at finding an antenna not only with low VSWR but also one exhibiting low-dispersion characteristics over the relevant frequency band. Furthermore, since in pulse communications systems the input signal

Nikolay Telzhensky; Yehuda Leviatan

2006-01-01

410

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

411

Mechanisms of the Rosetta high gain antenna  

Microsoft Academic Search

This paper describes the antenna pointing mechanism (APM) and the hold down and release mechanism (HRM) used in the high gain antenna of the ROSETTA mission. The hold down and release mechanism consists of three units which compensate the tolerance mismatch between antenna and spacecraft through incorporation of potting rings. Given that the activation mode is pyrotechnic, release shock is

Carlos Pereira

2001-01-01

412

Eigencombining: A Unified Approach to Antenna Array  

E-print Network

algorithms for receive-side smart antennas, and compares their performance and numerical complexity with analyses of conventional smart antenna algorithms, i.e., statistical beamforming (BF) and maximal, etc. Such benefits can be achieved with smart antennas, i.e., SIMO, MISO, and MIMO systems

Blostein, Steven D.

413

Fractal theory for large lacunar antenna arrays  

Microsoft Academic Search

The complexity of the arrays is directly tied to the number of antennas of which they are composed. The laws of radiation in the far field are well known and are inferred from the law of illumination of the antenna. The worry of the inventor is, as always, to determine, for a number of possible antennas, their spatial partition which

C. Goutelard

1992-01-01

414

Dale Haracre Ceramics In a Patch Antenna  

E-print Network

Dale Haracre Ceramics In a Patch Antenna #12;Abstract A patch antenna is also known on a flat surface. Ceramic based patched antennas can be used for a wide range of applications.They can a ground plate.Typically dielectric materials are proposed such as Zinc titanate (ZnTiO3) based ceramics

Mukhopadhyay, Sharmila M.

415

Beauty of fractals design of fractal antennas  

Microsoft Academic Search

In this paper, beauty of fractals, some bases of its, processes, parameters and pictures of Mandelbrot and Julia sets are represented. Algorithms of computer-aided design of the dipole and planar fractal antennas of different orders are described. Current distribution, characteristics of impedance, distribution of near electromagnetic field and radiation of the fractal antennas are analyzed. Represented antennas structures may be

G. G. Chavka

2007-01-01

416

Genetically engineered dual-band fractal antennas  

Microsoft Academic Search

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

D. H. Werner; P. L. Werner

2001-01-01

417

An overview of fractal antenna engineering research  

Microsoft Academic Search

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

Douglas H. Werner; S. Ganguly

2003-01-01

418

Investigation of microwave antennas with improved performances  

Microsoft Academic Search

This dissertation presents the investigation of antennas with improved performances at microwave frequencies. It covers the following three topics: the study of the metamaterial with near-zero index of refraction and its application in directive antenna design, the design technique of a wideband circularly polarized patch antenna for 60GHz wireless application and the investigation of a novel direction of arrival (DOA)

Rongguo Zhou

2010-01-01

419

A capacitively coupled polymeric internal antenna  

Microsoft Academic Search

A capacitively-coupled polymeric internal antenna is introduced for Bluetooth or GPS applications. Such an antenna can be easily fabricated on a flexible film substrate and attached to the inside surface of the plastic housing of a portable wireless device, such as a PDA. The proposed antenna saves critical space on the printed circuit board (PCB) and eliminates the need for

Khan M. Z. Shams; M. Ali

2004-01-01

420

Automatic Phasing for Active Antenna Elements  

NASA Technical Reports Server (NTRS)

Automatic phasing system periodically interrupts antenna operation for calibration intervals and measures phase and amplitude response at each active antenna element. Using these measurements, system adjusts phase shift and possibly gain of active elements during operating intervals to give desired antenna-gain pattern.

Wu, C.

1984-01-01

421

Passive and active Reconfigurable antenna design  

E-print Network

Passive and active Reconfigurable antenna design Doctoral course ­ Ulm, Germany - October 8-12 2012 antennas in Cognitive radio applications, Combining Photonics and RF to produce more versatile of Reconfiguration Devices and Technology (Semiconductors ­ MEMS) - Integration of devices into antennas (including

Pfeifer, Holger

422

Performance analysis of radar antenna systems  

Microsoft Academic Search

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

J. J. Kim; O. B. Kesler

1999-01-01

423

Installed performance analysis of radar antenna systems  

Microsoft Academic Search

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

Jacob J. Kim; Oren B. Kesler

1998-01-01

424

Phased array aircraft antennas for satellite communications  

Microsoft Academic Search

A number of critical issues facing designers of aircraft antenna terminals for satellite communication are considered, taking into account a number of efforts aimed at the development of high gain, flush mounted phased array antennas which would eliminate the need for a cumbersome radome. An investigation is conducted regarding the geometrical requirements of a pencil beam aircraft antenna for satellite

R. J. Mailloux

1977-01-01

425

Antenna technologies for 60 GHz applications  

Microsoft Academic Search

In this paper, the wafer transfer technology (WTT) and the low-temperature co-fired ceramic (LTCC) technology are employed for 60 GHz antenna designs. A coplanar waveguide (CPW) fed coplanar strip (CPS) dipole antenna using the WTT technology is presented. Meanwhile, two antenna arrays using the LTCC technology are reported.

Yong-Xin Guo; Siew Bee Yeap; Zhi Ning Chen

2009-01-01

426

The diamond dipole: a Gaussian impulse antenna  

Microsoft Academic Search

When a typical narrowband antenna is excited by an ultra-wideband (UWB) impulse, the antenna rings at its resonant frequency, stretching out the waveform in time. A resonant antenna, like the bow tie, discone, or bicone have been available for years. A bow tie has a relatively high input impedance, and requires a matching balun to make it useable with a

H. G. Schantz; L. Fullerton

2001-01-01

427

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.

428

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

429

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

430

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

431

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

432

Antenna systems requirements definition study  

NASA Astrophysics Data System (ADS)

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

Golden, C. T.

1981-02-01

433

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

434

DIGITAL IMPLEMENTATION OF DIRECTION-OF-ARRIVAL ESTIMATION TECHNIQUES FOR SMART ANTENNA SYSTEMS  

E-print Network

DIGITAL IMPLEMENTATION OF DIRECTION-OF-ARRIVAL ESTIMATION TECHNIQUES FOR SMART ANTENNA SYSTEMS .........................................................................................................1 Smart Antennas..............................................................................................................1 Antenna Arrays

Lawrence, Rick L.

435

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

436

Galilean conformal and superconformal symmetries  

NASA Astrophysics Data System (ADS)

Firstly we discuss briefly three different algebras named as nonrelativistic (NR) conformal: Schrödinger, 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?? from relativistic conformal algebra O( 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.

2012-10-01

437

ADVANCED PRECIPITATION RADAR ANTENNA SINGLY CURVED PARABOLIC ANTENNA REFLECTOR DEVLEOPMENT  

Microsoft Academic Search

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

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

2003-01-01

438

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

439

Massive conformal gravity  

E-print Network

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

F. F. Faria

2013-12-19

440

Conformal transformation optics  

NASA Astrophysics Data System (ADS)

The field of transformation optics shows that media containing gradients in optical properties are equivalent to curved geometries of spacetime for the propagation of light. Conformal transformation optics -- a particular variant of this feature -- can be used to design devices with novel functionalities from inhomogeneous, isotropic dielectric media.

Xu, Lin; Chen, Huanyang

2015-01-01

441

Metamaterials with conformational nonlinearity  

E-print Network

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

442

Conforming polygonal finite elements  

Microsoft Academic Search

SUMMARY In this paper, conforming finite elements on polygon meshes are developed. Polygonal finite elements provide greater flexibility in mesh generation and are better-suited for applications in solid mechanics which involve a significant change in the topology of the material domain. In this study, recent advances in meshfree approximations, computational geometry, and computer graphics are used to construct different trial

N. Sukumar; A. Tabarraei

2004-01-01

443

Nanorod optical antennas for dipolar transitions  

E-print Network

Optical antennas link objects to light. Here, we analyze metal nanorod antennas as cavities with variable reflection coefficients to derive the interaction of dipolar transitions with radiation through the antenna modes. The presented analytical model accurately describes the complete emission process, and is summarized in a phase-matching equation. We show how antenna modes evolve as they become increasingly more bound, i.e. plasmonic. The results illustrate why efficient antennas should not be too plasmonic, and how subradiant even modes can evolve into weakly-interacting dark modes. Our description is valid for the interaction of nanorods with light in general, and is thus widely applicable.

Tim H. Taminiau; Fernando D. Stefani; Niek F. van Hulst

2009-12-10

444

Benchmark simulations of ICRF antenna coupling  

SciTech Connect

The paper reports on ongoing benchmark numerical simulations of antenna input impedance parameters in the ion cyclotron range of frequencies with different coupling codes: CST Microwave Studio, TOPICA and ANTITER 2. In particular we study the validity of the approximation of a magnetized plasma slab by a dielectric medium of suitably chosen permittivity. Different antenna models are considered: a single-strap antenna, a 4-strap antenna and the 24-strap ITER antenna array. Whilst the diagonal impedances are mostly in good agreement, some differences between the mutual terms predicted by Microwave Studio and TOPICA have yet to be resolved.

Louche, F.; Lamalle, P. U.; Messiaen, A. M.; Compernolle, B. van [Laboratory for Plasma Physics-Association 'Euratom-Belgian State', Trilateral Euregio Cluster Ecole Royale Militaire-Koninklijke Militaire School, B-1000 Brussels (Belgium); Milanesio, D.; Maggiora, R. [Politecnico di Torino, Turin (Italy)

2007-09-28

445

Benchmark simulations of ICRF antenna coupling  

NASA Astrophysics Data System (ADS)

The paper reports on ongoing benchmark numerical simulations of antenna input impedance parameters in the ion cyclotron range of frequencies with different coupling codes: CST Microwave Studio, TOPICA and ANTITER 2. In particular we study the validity of the approximation of a magnetized plasma slab by a dielectric medium of suitably chosen permittivity. Different antenna models are considered: a single-strap antenna, a 4-strap antenna and the 24-strap ITER antenna array. Whilst the diagonal impedances are mostly in good agreement, some differences between the mutual terms predicted by Microwave Studio and TOPICA have yet to be resolved.

Louche, F.; Lamalle, P. U.; Messiaen, A. M.; Van Compernolle, B.; Milanesio, D.; Maggiora, R.

2007-09-01

446

Low gain and steerable vehicle antennas for communications with land mobile satellite  

NASA Technical Reports Server (NTRS)

Current development activities at JPL for ground mobile vehicle antennas to be used with the Land Mobile Satellite Service (LMSS) system are described. Both low gain and electronically steerable high gain type antennas are discussed in terms of their design concept and RF performance. For the low gain type, three classes of antennas are under various stages of development. These are the crossed-drooping dipole, quadrifilar helix, and microstrip patch designs. The antennas are intended to provide circularly-polarized radiation with a minimum of 3-dB gain in the angular region from 19 degrees to 60 deg from the horizon in elevation plane and with an omnidirectional pattern in azimuthal plane. For the electronically steerable high gain type, circularly-polarized microstrip patch phased arrays formed on a planar surface and on the surface of a truncated cone are under study. The arrays are intended to provide a minimum of 12 dB gain in the same angular region in elevation plane at all azimuthal angles. This coverage is accomplished by scanning the high gain pencil beam in both elevation and azimuthal directions. Both types of antennas are to transmit at 821-831 MHz band and to receive at 866-876 MHz band. They must be of low cost design and reasonably conformal to the vehicle.

Woo, K.

1982-01-01

447

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

448

Dual polarization antennas for OTS  

Microsoft Academic Search

The development of a set of dual-polarized antennas for the Orbital Test Satellite (OTS) is discussed. Optimization studies led to the initial selection of a circular parabolic reflector front fed by a corrugated cylindrical horn for the circularly symmetrical beam (Spot beam). A parabolic reflector was selected for the elliptical beam (Eurobeam). An edge taper of -15 dB and an

G. Doro; A. Saitto

1975-01-01

449

Fractal and multiband communication antennas  

Microsoft Academic Search

In this paper we present two novel multiband antenna designs for multiple frequency applications. The first of these, which is based on fractal concepts, is a Sierpinski gasket type of fractal configuration, printed on a dielectric substrate backed by a ground plane. We propose a novel approach to enhancing its multiband performance, in terms of impedance matching characteristics as well

Y. Lee; J. Yeo; R. Mittra; S. Ganguly; J. Tenbarge

2003-01-01

450

DSS 13 microprocessor antenna controller  

NASA Technical Reports Server (NTRS)

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

Gosline, R. M.

1988-01-01

451

Gradiometer antennas for tunnel detection  

Microsoft Academic Search

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

David A. Hill

1992-01-01

452

DSS 13 antenna subsystem automation  

Microsoft Academic Search

Unattended station operation was implemented that permitted full operational control from the network operations center (NOCC). Sensors were installed in the mechanical subsystem to monitor critical functions and to permit automated premission checkout of the subsystem, automated reaction to component failure, and identification of failed components under control of the antenna pointing computer. This monitoring installation is a prototype for

H. Phillips; I. Crane; P. Lipsius

1978-01-01

453

High-directivity acoustic antenna  

NASA Technical Reports Server (NTRS)

Acoustic antenna with unique electronic steering control is used to identify and define aerodynamic noise sources in free field, particularly in wind tunnel which is quite reverberant. Provision is made for high directivity as well as improved discrimination against unwanted background noise such as reverberation or echoes.

El-Sum, H. M. A.

1974-01-01

454

Compact Three-Port Orthogonally Polarized MIMO Antennas  

Microsoft Academic Search

Two designs for three-port orthogonally polarized antennas using dipole antennas and half-slot antennas are proposed in this letter. Each of the antennas constitutes three mutually perpendicular radiating elements to achieve good isolation and low antenna signal correlation between ports. The antennas are fabricated on FR4 epoxy boards and experimental results are provided. Experimental results show that the antennas resonate at

Chi-Yuk Chiu; Jie-Bang Yan; Ross D. Murch

2007-01-01

455

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

456

Antenna subtraction with hadronic initial states  

E-print Network

The antenna subtraction method for the computation of higher order corrections to jet observables and exclusive cross sections at collider experiments is extended to include hadronic initial states. In addition to the already known antenna subtraction with both radiators in the final state (final-final antennae), we introduce antenna subtractions with one or two radiators in the initial state (initial-final or initial-initial antennae). For those, we derive the phase space factorization and discuss the allowed phase space mappings at NLO and NNLO. We present integrated forms for all antenna functions relevant to NLO calculations, and describe the construction of the full antenna subtraction terms at NLO on two examples. The extension of the formalism to NNLO is outlined.

A. Daleo; T. Gehrmann; D. Maitre

2006-12-20

457

Foldable nanopaper antennas for origami electronics.  

PubMed

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

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

2013-05-21

458

Loop Virasoro Lie conformal algebra  

SciTech Connect

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

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

2014-01-15

459

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

460

From Antenna to Assay  

PubMed Central

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

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

2009-01-01

461

Conformal Relativity: Theory and Observations  

Microsoft Academic Search

Theoretical and observational arguments are listed in favor of a new principle of relativity of units of measurements as the basis of a conformal-invariant unification of General Relativity and Standard Model by replacement of all masses with a scalar (dilaton) field. The relative units mean conformal observables: the coordinate distance, conformal time, running masses, and constant temperature. They reveal to

V. Pervushin; V. Zinchuk; A. Zorin

2004-01-01

462

CONFORMATIONS OF ALKANES AND CYCLOALKANES  

E-print Network

89 CHAPTER 3 CONFORMATIONS OF ALKANES AND CYCLOALKANES H ydrogen peroxide is formed in the cells this chapter we'll examine the conformations of various alkanes and cycloal- kanes, focusing most of our that are placed symmetrically around it. 90 CHAPTER THREE Conformations of Alkanes and Cycloalkanes Eclipsed

Ferreira, Márcia M. C.

463

Conformal gripping device  

NASA Technical Reports Server (NTRS)

The present invention relates to a conformal gripping device. In an embodiment of the present invention a conformal gripper device may be disclosed comprising a frame that includes an array of movable pins. The device may also include a roller locking and unlocking system within the frame. The system may comprise a pair of locking rollers for each row of gripper pins to facilitate locking and unlocking the array of gripper pins on a column-by-column basis. The system may also include a striker element that may force the locking rollers to roll along an angled roll surface to facilitate unlocking of the array of pins on a column-by-column basis. The system may further include an electromagnetic actuator or solenoid and permanent magnets to facilitate movement of the striker element and the locking rollers.

Vranish, John M. (Inventor)

2009-01-01

464

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

NASA Astrophysics Data System (ADS)

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

Mohammad, Irshad

465

Hexagonal and Pentagonal Fractal Multiband Antennas  

NASA Technical Reports Server (NTRS)

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

Tang, Philip W.; Wahid, Parveen

2005-01-01

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

Intravascular Extended Sensitivity (IVES) MRI Antennas Robert C. Susil,1  

E-print Network

Intravascular Extended Sensitivity (IVES) MRI Antennas Robert C. Susil,1 Christopher J. Yeung,1 antenna is described. The device is a loopless antenna design that incorporates both an insulating, dielectric coating and a winding of the antenna whip into a helical shape. Because this antenna produces

Atalar, Ergin

468

Tone based MAC protocol for use with Adaptive Array Antennas  

E-print Network

1 Tone based MAC protocol for use with Adaptive Array Antennas Harkirat Singh and Suresh Singh are equipped with adaptive array antennas. The protocol relies on the ability of the antenna and Angle antenna arrays. The impact of using different number of antenna elements is also studied

Singh, Suresh

469

A circular polarization MIMO antenna system applied for RFID management  

Microsoft Academic Search

In this paper, a CP MIMO antenna system design capable of UHF band operation is presented. By using circular polarization and antenna diversity by selection of the antenna supported by RFID reader chip sets, This MIMO antenna system can have high receiving signal strength and larger antenna beam coverage area, making this design a suitable candidate for RFID application in

Wei He; Yinlong Huang; Zhanbing Wang; Yijian Zhao

2008-01-01

470

Advanced technology in satellite communication antennas: Electrical and mechanical design  

Microsoft Academic Search

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

Takashi Kitsuregawa

1990-01-01

471

Radiation characteristics of ring antennas for electron plasma waves  

Microsoft Academic Search

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

Shigeru Egashira; Yuzuru Morita; Yoshinori Yoshida

1982-01-01

472

Small internal ceramic chip antenna for IMT-2000 handsets  

E-print Network

to that of a monopole antenna. These features make the proposed antenna suitable for handset applications. Introduction), meander-line antenna (MLA) and ceramic chip antenna (CCA), have been introduced [1­3]. The antenna proposed in this Letter has been designed into a type of CCA with modified meander line. For the proposed

Park, Seong-Ook

473

Conformal higher spin theory  

NASA Astrophysics Data System (ADS)

We construct gauge theory of interacting symmetric traceless tensors of all ranks s=0,1,2,3,… which generalizes Weyl-invariant dilaton gravity to the higher spin case, in any dimension d>2. The action is given by the trace of the projector to the subspace with positive eigenvalues of an arbitrary Hermitian differential operator overlineH, and the symmetric tensors emerge after expansion of the latter in power series in derivatives. After decomposition in perturbative series around conformally flat point overlineH=? with Euclidean metric, the action functional describes conformal higher spin theory. Namely, the linear in fluctuation term cancels, while the one quadratic in fluctuation breaks up as a sum of conformal higher spin theories, the latter being free gauge theories of symmetric traceless tensors of rank s with actions of d-4+2 s order in derivatives (in odd dimensions they are boundary terms), for all integer s, introduced in 4d case by Fradkin and Tseytlin and studied at the cubic order level by Fradkin and Linetsky. Higher orders in interaction are well-defined. The action appears to be the unique functional invariant w.r.t. general similarity transformations overlineH'=e ??<†overlineHe ??, the latter invariance plays the role of gauge symmetry group of the model. In the framework of the perturbative decomposition, the Hermitian part of ? gauges away the trace parts of the symmetric tensors parameterizing the fluctuation, while the anti-Hermitian one provides standard linearized gauge transformations of conformal higher spin fields. The action can be calculated as a semiclassical series in ? which counts the number of space-time derivatives and thereby exhibits itself as a parameter of low-energy expansion, like ?' in string theory, in so doing the classical term is given by the volume of the domain H( x, p)>0 (where H( x, p) is the Weyl symbol of overlineH), it does not contain derivatives and is interpreted as a cosmological term. At the same time, further terms of the ?-expansion are given by integrals of distributions localized on the constraint surface H( x, p)=0, and the conformal higher spin- s action arises from the ? d-4+2 s-correction. The full gauge invariance of the model is interpreted as covariance algebra of generalized Klein-Gordon equation overlineH|?>=0 for complex scalar field ?.

Segal, Arkady Y.

2003-08-01

474

Conformal superalgebras via tractor calculus  

NASA Astrophysics Data System (ADS)

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

Lischewski, Andree

2015-01-01

475

Linear Low Density Polyethylene (LLDPE) as Flexible Substrate for Wrist and Arm Antennas in C-Band  

NASA Astrophysics Data System (ADS)

This paper focuses on the development and study of linear low density polyethylene as a flexible substrate for conformal antennas for body-worn applications. Thermal stability, tensile strength and elongation at break of the substrate were studied. The permittivity of the substrate was 2.2 and tan ? was found to be 0.0003 at 6 GHz. Since the antenna is being developed for wrist and arm wearing in C-band, the performance of the antenna, such as the S 11 parameter and radiation pattern, were studied with different bending axes and with bending curvature approximating that of the arm and wrist. The performance of a 6 GHz rectangular patch antenna with bending was found to be consistent with the flat profile antenna at the same frequency. A maximum shift in the resonant frequency of ˜20 MHz was observed. The -10 dB bandwidth and directivity of the antenna did not change much with bending. The maximum bending radius in the present study is 10 mm, and S 11 was found to be -17.53 dB at 5.94 GHz and -14.02 dB at 6.06 GHz for a bending axis parallel to the radiating and non-radiating edge, respectively.

Gogoi, Pragyan Jyoti; Bhattacharyya, Satyajib; Bhattacharyya, Nidhi S.

2015-01-01

476

106 IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 52, NO. 1, JANUARY 2004 Smart Antennas Based on Spatial Multiplexing  

E-print Network

106 IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 52, NO. 1, JANUARY 2004 Smart Antennas for reducing mutual coupling in a smart antenna array using patch antenna elements is proposed. In a recently introduced smart antenna architecture, the spatial mul- tiplexing of local elements (SMILE) scheme, the newly

Itoh, Tatsuo

477

Plasmonic Antenna Coupling for QWIPs  

NASA Technical Reports Server (NTRS)

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

Hong, John

2007-01-01

478

Distributed antenna system and method  

NASA Technical Reports Server (NTRS)

System and methods are disclosed for employing one or more radiators having non-unique phase centers mounted to a body with respect to a plurality of transmitters to determine location characteristics of the body such as the position and/or attitude of the body. The one or more radiators may consist of a single, continuous element or of two or more discrete radiation elements whose received signals are combined. In a preferred embodiment, the location characteristics are determined using carrier phase measurements whereby phase center information may be determined or estimated. A distributed antenna having a wide angle view may be mounted to a moveable body in accord with the present invention. The distributed antenna may be utilized for maintaining signal contact with multiple spaced apart transmitters, such as a GPS constellation, as the body rotates without the need for RF switches to thereby provide continuous attitude and position determination of the body.

Fink, Patrick W. (Inventor); Dobbins, Justin A. (Inventor)

2004-01-01

479

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. PMID:24394920

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

2014-01-01

480

Slotted antenna waveguide plasma source  

NASA Technical Reports Server (NTRS)

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

Foster, John (Inventor)

2007-01-01

481

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

482

DSS 13 Microprocessor Antenna Controller  

NASA Technical Reports Server (NTRS)

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

Gosline, R. M.

1984-01-01

483

Adaptive antenna arrays for weak interfering signals  

NASA Technical Reports Server (NTRS)

The interference protection provided by adaptive antenna arrays to an Earth station or satellite receive antenna system is studied. The case where the interference is caused by the transmission from adjacent satellites or Earth stations whose signals inadverently enter the receiving system and interfere with the communication link is considered. Thus, the interfering signals are very weak. To increase the interference suppression, one can either decrease the thermal noise in the feedback loops or increase the gain of the auxiliary antennas in the interfering signal direction. Both methods are examined. It is shown that one may have to reduce the noise correlation to impractically low values and if directive auxiliary antennas are used, the auxiliary antenna size may have to be too large. One can, however, combine the two methods to achieve the specified interference suppression with reasonable requirements of noise decorrelation and auxiliary antenna size. Effects of the errors in the steering vector on the adaptive array performance are studied.

Gupta, I. J.

1985-01-01

484

Patch antennas with new artificial magnetic layers  

E-print Network

A new type of high-impedance surfaces (HIS) has been introduced by C.R. Simovski et al. recently. In this paper, we propose to use such layers as artificial magnetic materials in the design of patch antennas. The new HIS is simulated and patch antennas partially filled by these composite layers are measured in order to test how much the antenna dimensions can be reduced. In order to experimentally investigate the frequency behavior of the material, different sizes of the patches are designed and tested with the same material layer. Also the height of the patch is changed in order to find the best possible position for minimizing the antenna size. This composite layer of an artificial magnetic material has made the antenna smaller while keeping the bandwidth characteristics of the antenna about the same. About 40% of size reduction has been achieved.

M. Ermutlu; C. R. Simovski; M. Karkainen; P. Ikonen; A. A. Sochava; S. A. Tretyakov

2005-04-11

485

Phased array antennas for radar and telecommunications  

NASA Astrophysics Data System (ADS)

The state of the art in phased array antenna technology, research and applications is explored. Phased arrays feature individual elements fed exciting radio frequency inputs that are phased in arithmetic progression. A plane wave is emitted by the array in a determinable direction. Array lobes are avoided by sending near-half wave impulses. Sidelobes are decreased in the far field by control of coupling effects, tolerances in the components during manufacture of the array, and phase shift. Phased array configurations thus far utilized include disk antennas, electronically scanning, rotating rectilinear arrays, and vertical scanning flat arrays. Research is being performed on fixed angle scanning directive antennas, toroidal or hemispherical covered antennas, and auto-adaptive grid antennas. Two main goals of radar research are to define antennas that are resistant to jamming and that can do all-azimuth tracking.

Drabowitch, S.

1985-04-01

486

Ultra directive antenna via transformation optics  

E-print Network

Spatial coordinate transformation is used as a reliable tool to control electromagnetic fields. In this paper, we derive the permeability and permittivity tensors of a metamaterial able to transform an isotropically radiating source into a compact ultradirective antenna in the microwave domain. We show that the directivity of this antenna is competitive with regard to conventional directive antennas horn and reflector antennas, besides its dimensions are smaller. Numerical simulations using finite element method are performed to illustrate these properties. A reduction in the electromagnetic material parameters is also proposed for an easy fabrication of this antenna from existing materials. Following that, the design of the proposed antenna using a layered metamaterial is presented. The different layers are all composed of homogeneous and uniaxial anisotropic metamaterials, which can be obtained from simple metal-dielectric structures. When the radiating source is embedded in the layered metamaterial, a high...

Tichit, Paul-Henri; de Lustrac, Andre; 10.1063/1.3131843

2009-01-01

487

Lower Hybrid Antenna Design for MST  

SciTech Connect

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

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

2005-09-26

488

Orthogonal feeding techniques for tapered slot antennas  

NASA Technical Reports Server (NTRS)

For array of "brick" configuration there are electrical and mechanical advantages to feed the antenna with a feed on a substrate perpendicular to the antenna substrate. Different techniques have been proposed for exciting patch antennas using such a feed structure.Rncently, an aperture-coupled dielectric resonator antenna using a perpendicular feed substrate has been demonstrated to have very good power coupling efficiency. For a two-dimensional rectangular array with tapered slot antenna elements, a power combining network on perpendicular substrate is generally required to couple power to or from the array. In this paper, we will describe two aperture-coupled techniques for coupling microwave power from a linearly tapered slot antenna (LTSA) to a microstrip feed on a perpendicular substrate. In addition, we will present measured results for return losses and radiation patterns.

Lee, Richard Q.; Simons, Rainee N.

1998-01-01

489

Smart Antenna for Cellular Mobile Communication  

E-print Network

The adoption of smart / adaptive antenna techniques in future wireless systems is expected to have a significant impact on the efficient use of the spectrum, the minimization of the cost of establishing new wireless networks, the optimization of service quality and realization of transparent operation across multi technology wireless networks [1]. This paper presents brief account on smart antenna (SA) system. SAs can place nulls in the direction of interferers via adaptive updating of weights linked to each antenna element. SAs thus cancel out most of the co-channel interference resulting in better quality of reception and lower dropped calls. SAs can also track the user within a cell via direction of arrival algorithms [2]. This paper explains the architecture, evolution and how the smart / adaptive antenna differs from the basic format of antenna. The paper further explains about the radiation pattern of the antenna and why it is highly preferred in its relative field. The capabilities of smart / adaptive ...

Jain, R K; Agrawal, N K

2012-01-01

490

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

491

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

492

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

493

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

494

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

495

Photonic crystal horn and array antennas.  

PubMed

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

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

2003-07-01

496

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

497

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

Microsoft Academic Search

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

Wei Yu; Tian Lan

2007-01-01

498

Planar High-Gain WLAN PCB Antenna  

Microsoft Academic Search

A simple design for a low-profile high-gain planar antenna has been presented in the letter. The antenna has the realized gain between 9 and 11 dBi and the return loss better than 10 dB over the 5.6-6.3-GHz frequency band, i.e. 11% bandwidth. A numerical study highlighting effects of key geometrical parameters on the gain and return loss of the antenna

Dmitry E. Zelenchuk; Vincent F. Fusco

2009-01-01

499

Mechanical Measurements of the ALMA Prototype Antennas  

E-print Network

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

A. Greve; J. G. Mangum

2007-10-30

500

Wideband Circularly Polarized Stacked Microstrip Antennas  

Microsoft Academic Search

A simple technique is developed to improve the axial ratio (AR)-bandwidth and quality of circularly polarized stacked microstrip antennas (CPSMAs) using a new C-type single feed. The proposed antenna has been optimized and fabricated, and the computed results agree very well with measurements. The antenna has a 3 dB AR bandwidth of 13.5%, gain is more than 7.5 dBi over

Nasimuddin; Karu P. Esselle; A. K. Verma

2007-01-01