The reflectarray antenna

A class of antennas that utilizes arrays of elementary antennas as reflecting surfaces has been investigated. An antenna of this type is here called a Reflectarray. It has been found that the Reflectarray combines much of the simplicity of the reflector-type antenna with the performance versatility of the array type. The reflecting surfaces employed in these antennas are characterized by a surface impedance that can be synthesized to produce a variety of radiation patterns. The equations of the surface impedance as a function of the desired reflected phase front is derived for the lossless case and methods of realizing this surface impedance are presented. Experimental results of a waveguide array type Reflectarray are given including pencil beam, broad beam and scanning modes. Data on the effects of specific phase errors are presented.     

Cylindrical and three-dimensional corner reflector antennas

Two reflector antennas are proposed. The first is constructed by adding a cylindrical reflecting surface of suitable radius to theV-shaped corner reflector antenna. The feeding element is a half-wavelength dipole. The resulting cylindrical corner reflector provided a 2 dB increase in gain, minimum sidelobe level, low input reactance, and uncritical dependence of performance on frequency. The second antenna is constructed by adding a cylindrical surface to the three-dimensional corner reflector. This extension provided an increase in gain of at least 6.5 dB, an input resistance compatible with the commercially available 50- or75-Omegacoaxial cables, low input reactance, and uncritical dependence of performance on frequency. A grid-type cylindrical corner reflector antenna, and a three-dimensional corner reflector antenna with a cylindrical subsurface of finite reflecting surfaces were designed, and the measured input impedances, gains, and field patterns showed excellent agreement with the theoretical results for both antennas.     

Spectrum Signature Modeling and Data Reduction Techniques Applicable to Airborne Antennas

Information is presented on a modeling technique and on data reduction techniques applicable to obtaining the spectrum signatures of low-gain, low-frequency airborne antennas. The modeling technique demonstrates the degree of simplicity permissible in the fabrication of aircraft scale models on which test antennas are mounted. It is shown that simple geometric shapes employed to represent an aerodynamically shaped aircraft will yield sufficiently accurate information for antenna signature evaluation, thus allowing far-field antenna characteristics to be obtained at a relatively low cost. A brief discussion of an analog-digital converter unit is also included. This unit is employed in the placing of antenna pattern data in a format that is applicable to the Electromagnetic Compatibility Analysis Center (ECAC) computer facilities.     

Evolution of the large Deep Space Network antennas

The evolution of the largest antenna of the US NASA Deep Space Network (DSN) is described. The design, performance analysis, and measurement techniques, beginning with its initial 64-m operation at S-band (2295 MHz) in 1966 and continuing through the present Ka-band (32-GHz) operation at 70 m, is described. Although their diameters and mountings differ, these parabolic antennas all employ a Cassegrainian feed system, and each antenna dish surface is constructed of precision-shaped perforated-aluminum panels that are secured to an open steel framework     

The development of radial line slot array antenna for direct broadcast satellite reception

Microwave antennas are extensively used in communications systems such as satellite, television and high-speed data transmission due to their wide and absolute bandwidth. Among the variety of microwave antennas, satellite communication commonly adopts an antenna of parabolic dish type, despite some drawbacks. In a primary fed design, there is considerable aperture blockage. An offset parabolic antenna design, which then eliminates the blockage, is susceptible to physical damage as its feed is significantly exposed from the body of reflector. The radial line slot array (RLSA) type antenna is thus designed to cope with the problems encountered in parabolic antennas. RLSA is a planar antenna suitable for direct broadcast satellite (DBS) reception, with advantages including high radiation efficiency (high gain), low profile, low cost and feed rear-mounted. The prototype development started with the selection of the cavity's dielectric material and construction of the feeding structure of coaxial-to-waveguide transition. Within the frequency band of interest, between 10.95 and 11.7?GHz, results, is showed a lower than ?10?dB of return loss. A DBS receiver test-bed had been developed to test the constructed antenna prototypes and it revealed that the prototype has the capability of receiving TV programs from DBS.     

Antenna development in China

A brief review of the history and geography of antenna developments in China is presented. Aperture antennas and array antennas together with antenna measurements are discussed in particular. Antenna developments in Taiwan, Hong Kong, and Macao are not included     

Frequency Selective Surfaces for Extended Bandwidth Backing Reflector Functions

This paper deals with the use of frequency selective surfaces (FSS) to increase the efficiency $,times,$ bandwidth product in wideband antenna arrays, whose efficiency is limited by the front-to-back ratio. If the backing reflector for the antenna is realized through a single metal plane solution, its location will be suitable only on a relatively limited frequency range especially if wide angle scanning is required. In order to extend the frequency range of usability, an FSS can be sandwiched between the antenna and the ground plane, providing an additional reflecting plane for an higher frequency band. The possibility to integrate in the antenna different functionalities, otherwise performed by several antennas, is also discussed in the paper. The proposed backing structure composed by the FSS and the ground plane has been designed to be used in conjunction with a wideband antenna consisting of an array of connected dipoles. A hardware demonstrator of the backing structure has also been manufactured and tested.      

一种宽频带微带天线的设计

介绍了宽频带渐变式微带缝隙天线的工作原理、设计参数及其对电性能的影响，设计了一种结构简单的天线形式，给出了该天线工作于S、C频段的结构尺寸以及VSWR、辐射方向图的仿真和测试数据曲线，两者之间有很好的一致性，并对影响天线性能的关键参数进行了误差计算。结果表明：在加工精度可达到的范围内，对天线性能的影响不大。该天线可应用于宽频带单极化、双极化阵列天线单元或反射面天线馈源。     

大型空间桁架面天线的结构 —电磁耦合优化设计

 由于载荷变化及各种随机干扰,大型空间桁架面天线必须保持非常精确的形状.基于提高空间天线电磁性能以及降低作动器能耗的目的,结合大型空间桁架天线结构的特点,建立了以天线轴向增益和作动器能耗为目标函数,以结构强度、作动器变形和轴力为约束条件的多目标优化模型.数值试验结果表明,结构—电磁耦合优化设计模型只需较低的作动器能耗,就能明显提高天线电性能,很好地满足了天线结构与电磁设计要求.     

A Note on the Difference Between Equiangular and Archimedes Spiral Antennas (Correspondence)

There seems to exist in the literature considerable confusion about the various types of spiral antennas, their characteristics, and their bandwidth capabilities. One evidence of this confusion appeared in a paper by Bower and Wolfe, in which they state that the Archimedes spiral antenna can be specified in terms of angles and hence belongs in the class of "frequency--independent antennas. "Frequency--independent antennas are relatively new; in fact, until 1955 there was no evidence that a "frequency-independent" antenna did, indeed, exist. Therefore, it would appear appropriate to delineate the characteristics and the terminology of the antennas involved. Perhaps this brief report of some recent work at the University of Illinois Antenna Laboratory will aid in pointing up the differences in operation of the logarithmic (i.e., equiangular) and Archimedean spiral antennas.     

FPGA在SAR实时运动补偿系统中的应用

机载SAR要获得高分辨率的图像,必须保证天线波束的指向恒定.提出了一种基于FPGA与二维电扫相控阵天线实现SAR实时运动补偿的方案,并结合FPGA的特点采用了CORDIC算法做为超越函数处理模块.通过实时控制相控阵天线,实现了载机在姿态发生变化时依然保证波束稳定地指向测绘带中心,从而得到高分辨率的图像.     

Analysis of active surface reflector antenna for a large millimeterwave radio telescope

The authors analyze the effects of imperfect segment alignment on the aperture efficiency of a large millimeter telescope. A 50 meter diameter instrument of this type specified to operate to wavelengths as short as 1 mm is being designed with an actively controlled main surface. By simulating the performance of the control system, they generate samples of tilt and piston errors for the segments from which the antenna radiation patterns and aperture efficiencies are calculated. They make a comparison of these results with models of antenna tolerance theory developed by Ruze (1966), which relate the aperture efficiency to the RMS phase error. They find that Ruze's formulas have a different range of validity when the aperture RMS phase error, rather than the RMS surface error, is used as a parameter. When appreciable tilt errors are present in large segmented antennas, the aperture RMS phase error tends to a constant value, independent of the aperture illumination and of the shape of the segments. They conclude that the antenna RMS surface error is a better tracer of the aperture efficiency than is the aperture RMS phase error when Ruze's formula is used. They find that this well-known expression stands as a lower limit to the performance of large segmented reflector antennas     

轴向模螺旋天线方向性系数分析

传统的轴向模螺旋天线的方向性系数公式只考虑了螺旋直径、螺距及圈数等几个变量,忽略了反射板的尺寸和形状以及馈电方式对方向性系数的影响。简要介绍了轴向模螺旋天线的工作原理,仿真计算了反射板的尺寸和形状以及馈电方式等几个变量与螺旋天线的方向性系数的关系,加工制作了其中一种天线。实测结果与仿真结果基本一致,因此验证了仿真结果的正确性。为轴向模螺旋天线的设计提供了有价值的参考。     

一种小型化弹载共形天线的设计

精确制导导弹的隐蔽性以及抗干扰特性对弹载天线的带宽提出了更高的要求,而且在安装空间受限的弹载应用场合,弹载天线必须具有较低的剖面高度才能保证导弹的气动外形及飞行性能,因此,性能优越的超宽带天线以及共形天线成为重要的研究方向。文章以圆台形金属弹体为载体,设计了对数周期天线以及小型化改进的对数周期天线共形于圆台金属弹体表面,并能够组成六元天线阵列。仿真与实验测试结果说明了该设计的合理性。     

ANSERLIN. a broad-band, low-profile, circularly polarized antenna

A technique is presented for improving the performance of low-profile, circularly polarized (CP) radiating-line antennas. The essential elements of the technique pertain to establishing a single traveling wave on an annular sector of conducting strip that is positioned parallel and close to a large conducting surface. The antenna is named the annular sector, radiating-line (ANSERLIN) antenna. Using this technique, the impedance bandwidth becomes so large that it no longer has any bearing on the operating bandwidth. Instead, the pattern shape and axial ratio become the factors that limit the bandwidth. Both senses of circular polarization can be transmitted or received from the same structure. Experimental results for two-port ANSERLIN antennas are presented. The method of exciting a traveling wave on the annular sector is discussed. Design parameters are given for an antenna that will produce a broadside axial ratio that is less than 0.5 dB at a specified frequency     

Precision DSN radiometer systems: impact on microwave calibrations

The NASA Deep Space Network (DSN) has a long history of providing large parabolic dish antennas with precision surfaces, low-loss feeds, and ultra-low noise amplifiers for deep-space telecommunications. To realize the benefits of high sensitivity, it is important that receiving systems are accurately calibrated and monitored to maintain peak performance. A method is described to measure system performance and to calibrate the receiving system using procedures, software, and commercial instruments that are easy to implement and efficient to use. The utility of the measurement procedures and the precision of the receiver calibration technique were demonstrated by performing tests at Ka-band (32 and 33.68 GHz) frequencies at Goldstone on a 34-m beam-waveguide antenna. Observations of multiple calibration radio sources are used to measure the dependence of antenna gain and system noise temperature on source elevation and derive the performance parameters. The experimental results described illustrate some of the ways that receiving system nonlinearity can negatively impact system performance. A simple radiometer calibration technique and analysis provide quantitative information that enables the system engineer to adjust and linearize the receiving system. When that is not practical, the experimenter or the operator can apply connection coefficients to the measured values of system noise temperature and thereby compensate for the receiving system nonlinearity     

Geometric and Compaction Dependence of Printed Polymer-Based RFID Tag Antenna Performance

Radio frequency identification (RFID) tags with printed antennas are lower in cost but have lower performance than those with metal antennas. Printed antennas can replace metal ones if the performance is increased without raising cost. The performance of printed antennas can be increased if the series resistance in the antennas is lowered. The resistance is dependent on the line thickness and the resistivity of the conductive ink. Printed antennas with different line thicknesses were fabricated to investigate the effect of compaction and thickness on the resistance. The resistance of the printed antenna coils decreased by more than 40% after compaction, while the inductance and the parasitic capacitance were unchanged. RFIDs with compacted printed antennas were found to have significantly increased read range. RFIDs with thick printed antennas were fabricated and tested. These RFIDs were shown to have read ranges comparable to the RFIDs with copper wire antennas. Moreover, a geometry-independent plateau for the read range was found. The presence of a plateau is valuable for thick-line printed antenna since the plateau will enable the usage of low precision printing techniques to lower tag fabrication cost.     

Theoretical analysis and some experiments on Vierergruppe Antenne (Two-dipole antennas)

A center-fed full-wave dipole antenna located one-quarter wavelength above a reflecting plate has a very low potential relative to the plate, at the center of each half-wave element. When metal support bars are attached between these center points and the reflector plate to support the antenna, the structure is called a "metal supported full-wave dipole antenna." An antenna made up of two such full-wave dipole antennas has four half-wavelength antenna elements and has been named "Vierergruppe Antenne." This antenna and the "Achterergruppe Antenne" were invented in Germany. Vierergruppe antenne (sometimes called two-dipole antennas) can be rugged because they are made entirely of metal and do not require insulator supports. They also have excellent electrical characteristics over a very wide frequency range, and are widely used by TV and FM broadcasting stations around the world. Since the full-wave dipole antenna element is composed of a conductor having a diameter as large as 1/20 of the operating wavelength, it is unsuitable to use conventional thin conductor theory to analyze the antenna behavior. In particular, the current at the end of the thick solid antenna element will not be zero, as in the case of the thin one. Flat end-face currents are determined by using a quasi-static approximation and the moment method of analysis. Accordingly the excellent characteristics of this antenna have been found theoretically and fully clarified in the quarter century since its invention.