Microstrip reflectarray with QUAD-EMC element

This paper shows the performance of a reflect array using the QUAD-EMC patch as the radiating element. The phase adjustment is made at a sub-array level by tuning the length of each driven patch. Therefore, this new design uses fewer of the required phase shifter elements. The phase diagram provides the shared phase to each QUAD-EMC unit. The return loss plot of a radiating unit excited by the microstrip line is studied. The connection between the phase diagram and the return loss plot is also discussed. Experiments have shown that we can get comparable results with those obtained by controlling the phase on each individual element. Bandwidth of 23% with 1.5 dB gain variation can be achieved when built on an FR4 substrate. The cross polarization level may be improved since there is enough room to place the straight delay lines.     

毫米波赋形偏馈双反射面天线技术

为了实现一种具有高口面辐射效率、斜波束出射能力的口径天线,采用几何光学方法设计了一种偏馈双反射面天线.天线主反射面采用赋形设计,副反射面的设计过程中采用Snell定理作为约束条件.通过理论公式、数值模拟仿真和实验测试研究,实现了一种出射波束口径为110 cm、天线口面场分布为抛物形分布、波束出射方向与竖直方向成20°夹角的赋形偏馈双反射面天线.在中心频率95 GHz下,实测天线增益为59.7 dB,第一副瓣电平为-19dB,天线口径效率达到78%.     

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.     

Folded reflectarray antenna

A novel folded reflectarray antenna is presented. This antenna combines a twist and focusing reflector concept in a single printed structure. Together with a printed grid, a low profile and high gain antenna results. A test antenna in the 20 GHz range was designed, fabricated and tested     

Novel photonically-controlled reflectarray antenna

A novel method for generating a reconfigurable reflectarray based on the creation of photoinduced plasma inside the semiconductor substrate of a reflectarray is presented in this paper. A reflectarray antenna prototype is fabricated and measured to demonstrate the validity of the design methodology. Measurements were carried out to characterize the bandwidth and the gain of the antenna in both the OFF and ON states of an optical flash lamp that was used to induce photoconductivity inside the silicon substrate.     

Broadband reflectarray antenna with double cross loops

A reflectarray antenna composed of double crossed loops of variable lengths printed on a conductor backed substrate is introduced. Using this technique, a single-layer reflectarray with wider bandwidth compared to conventional single-layer reflectarrays is fabricated and measured. Measured results demonstrate a radiation efficiency close to 55% and 1 dB gain-bandwidth of 10%, centred at 22 GHz.     

Multi-feed single-beam power-combining reflectarray antenna

A design procedure is described for multi-feed single-beam power-combining reflectarray antennas. The method is applied to a two-feed case and is then validated experimentally.     

Circularly polarised reflectarray with linearly polarised feed

A design procedure for a circularly polarised (CP) reflectarray with linearly polarised feed is presented. It is validated by simulation and experiment results that exhibit the cross-polar level of -20 dB at the designed frequency, and -10 dB in 14% bandwidth. This type of CP reflectarray can be used as a good substitution for those with a CP feed.     

Liquid-crystal-based reflectarray antenna with electronically switchable monopulse patterns

A printed reflectarray antenna, which generates a beam that can be electronically switched from a sum to a difference radiation pattern, is presented. This is achieved by applying a bias voltage of 20 V to one- half of the aperture, which is constructed above a 500 mum cavity containing liquid crystals. Simulated results are shown to be in good agreement with measurements at X-band.     

星载赋形波束单馈源单偏置反射面天线设计

为了使星载赋形波束天线远场方向图与服务区形状匹配良好,并且在波束覆盖区内具有较平坦的方向性系数,将表征反射面形状的Zernike多项式展开系数作为优化变量,建立基于最小P乘法和Minmax方法的适应度函数,利用进化算法进行赋形反射面天线优化。利用该方法设计了覆盖中国大陆和巴西的赋形波束反射面天线。仿真结果表明,天线远场方向图与服务区形状均匹配良好,服务区内的方向性系数波动量分别为2.31 dB和11.23 dB,该值比现有方法小,并且该方法具有较高自由度及收敛性好的特点。     

Pattern synthesis of the offset reflector antenna system with lesscomplicated phased array feed

The performance degradation of an offset reflector antenna with off-axis scanning feed and distorted reflector surface can be improved by using a phased array feed. Generally, both analog attenuators and phase shifters are used in phased array feed. Yet, it seems to make the feed system very complicated. In this paper, a phase-only gradient search (POGS) algorithm is developed to optimize the performance of offset reflector antenna systems using phased array feed that is equipped with phase shifters only. This technique not only can greatly simplify the complexity of phased array feed, but also can provide the reflector antenna with better antenna gain and sidelobe level control capability. Simulation and experimental results are presented to illustrate the excellent performance of offset reflector, with limited beam scanning capability, can be obtained by using this less complicated phased array feed     

Dual polarisation of microstrip reflectarray antenna

Dual polarisation of a microstrip reflectarray was demonstrated for the first time. A 16 element array of square microstrip patch antennas operating in the X-band was used to reflect the main beam 20" off broadside in both the E-plane and H-plane     

Multiple-polarization microstrip reflectarray antenna with highefficiency and low cross-polarization

This paper presents the study and prototype demonstration of the concepts of antenna focusing, cross-polarization reduction, and multiple-polarization capability of a planar microstrip reflectarray antenna. A square patch with two equal microstrip delay lines connected to its two orthogonal feeding points is used as the antenna element of the planar reflectarray. The length of the delay lines, which varies from patch to patch, is schematically designed to focus the plane wave to the feed point. The measured overall efficiency of the prototype antenna is above 50% in the normal operating band, and in some frequency ranges the efficiency has reached 70%. The experimental patterns show that the measured cross polarization due to special arrangement of the delay lines is quite low at the direction of the main beam. X-polarization and Y-polarization measured data show that the antenna is suitable for multiple-polarization applications (dual linear and dual circular). Surprisingly, the antenna has achieved approximately greater than 7% of gain bandwidth (-3 dB gain drop). These results demonstrate the feasibility of such an antenna for radar and communication system applications     

折合式平面反射阵天线的研究进展

折合式平面反射阵天线(folded reflectarray antenna,FRA)作为一种高增益天线形式,在雷达、通信等领域有着良好的应用前景.在继承平面反射阵天线易加工、低成本、平面化等特点的同时,FRA巧妙地利用了光路折合原理,具有更低剖面、无馈源口径遮挡等优点,自其概念提出以来便一直受到学术界和工业界的广泛关...     

一体化馈源大角度扫描折叠式反射阵列天线

卫星通讯服务的快速增长催生了对于“动中通”设备旺盛的需求.由于具有低剖面、加工方便、功能实现多样等特点, 折叠式反射阵列具有应用于“动中通”系统的巨大潜力.针对这一应用需求, 提出了一种具有大角度扫描能力的折叠式反射阵列设计方案, 基于多层印刷电路板(Printed Circuit Board, PCB)技术,设计了一种工作在C波段可用于折叠式反射阵列具有60°扫描能力的微带缝隙单元, 利用该单元设计了0°、45°和60°波束指向的固定波束折叠式反射阵列.此外, 使用阵列馈源替代传统喇叭馈源, 完成了馈源与主反射面的一体化设计, 实现了折叠式反射阵列天线结构的平面化.固定波束折叠式反射阵列的仿真和实测结果表明在4.85~5.15 GHz的频率范围内, 阵列具有60°波束扫描的能力.     

Microstrip antenna technology

A survey of microstrip antenna elements is presented, with emphasis on theoretical and practical design techniques. Available substrate materials are reviewed along with the relation between dielectric constant tolerance and resonant frequency of microstrip patches. Several theoretical analysis techniques are summarized, including transmission-line and modal-expansion (cavity) techniques as well as numerical methods such as the method of moments and finite-element techniques. Practical procedures are given for both standard rectangular and circular patches, as well as variations on those designs including circularly polarized microstrip patches. The quality, bandwidth, and efficiency factors of typical patch designs are discussed. Microstrip dipole and conformal antennas are summarized. Finally, critical needs for further research and development for this antenna are identified.     

Microstrip circular-segment antenna

The analysis of the electromagnetic properties of the circular-segment microstrip antenna with microstrip feed is presented. The theory employs an equivalent magnetic wall model, treating the antenna as a lossy flat cavity. A series expansion in resonant modes yields an approximation of input impedance, radiation characteristics and near field data of the antenna.     

波束扫描反射阵列天线偏焦特性

针对波束扫描反射阵列天线在大角度扫描时增益下降及方向图恶化等问题,提出通过馈源偏焦来改善反射阵列天线的扫描性能。采用方形贴片结构设计了一款工作在X频段的反射阵列天线。研究馈源在15°,30°,45°扫描角的纵向偏焦以及10°,20°和30°扫描角的横向偏焦对波束扫描反射阵列天线性能的影响。测试结果显示,在扫描角度较小时,横向偏焦引起波束指向的改变,波束宽度变化不大。减小馈源纵向偏焦尺寸,旁瓣电平减小,中心频率处的增益提高,尤其是在较大的扫描角度时效果更加明显,有利于提高波束扫描反射阵列天线的大角度扫描能力。     

Impulse-radiating antenna with an offset geometry

An offset impulse-radiating antenna (IRA) is numerically analyzed and compared with a typical centered IRA. In the typical centered IRA, the transverse electromagnetic (TEM) feed arms block the aperture because they are located at the center of the aperture. This blockage causes multiple reflections inside the antenna and, thus, ripples in the tail of the radiated waveform. In the offset IRA, the TEM feed arms are removed from the aperture, lowering the tail ripples caused by multiple reflections between the TEM feed arms and the reflector. The boresight gains and the impulse amplitudes are seen to be essentially the same for both IRAs. The monostatic radar cross section of the offset IRA is significantly lower than that of the centered IRA for the plane wave incident from the boresight direction because the wave incident to the offset IRA is diverted toward the focal point of the reflector, which is away from the boresight direction. The offset IRA has a shadow behind the reflector. This feature can be useful in bistatic radar applications because the antennas can be placed in the shadows of each other.     

Design and performance of a microstrip reflectarray antenna

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 reflectarray has been shown to be an effective linear array capable of beam switching and dual polarization. The design procedure also allows the array to be fed from a feed-horn offset at any given angle to the plane of the array. The design procedure is well suited for CAD programs