基于时域调制反射阵列的波束赋形技术

传统的反射阵利用相控器件与微带线实现波束赋形。为了降低相控成本与系统复杂度,提出基于时域调制阵列波束赋形技术。时域调制反射阵列是一种基于简单可重构反射单元的反射阵,它利用控制可重构反射单元的开与关,达到控制阵列输出,实现旁瓣抑制、波束赋形等功能。通过理论推导及仿真,结果表明,时域调制反射阵可以在不采用传统阵列中的相控器件及馈电网络的前提下,采用最小方差无失真响应波束赋形方法与时间调制法,生成理想的方向图,实现波束赋形功能。此特性将有利于推广波束赋形技术在毫米波频段反射阵的应用。     

Modeling and Design of Electronically Tunable Reflectarrays

The reflectarray has significant promise in applications requiring high-gain, low-profile reflectors. Recent advances in tuning technology have raised the possibility of realizing electronically tunable reflectarrays, which can dynamically adjust their radiation patterns. This paper presents an electronically tunable reflectarray based on elements tuned using varactor diodes. Modeling approaches based on an equivalent circuit representation and computational electromagnetics simulations are presented. Both techniques accurately predict the scattering characteristics of the unit cell as compared to experimental measurements. The development of a unit cell with over 320^omicron of phase agility at 5.5 GHz is discussed. Finally, a 70-element electronically tunable reflectarray prototype operating at 5.8 GHz is presented. Radiation pattern measurements with the reflectarray demonstrate its dynamic beam-forming characteristics. Measurements of the gain of the reflectarray correlate well with theoretical expectations.     

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     

Cross-polarisation level of reflectarray with gapped ring elements

A reflectarray with variable-size-gapped-ring elements has been designed. It is proposed to reduce the cross-polarisation level of a reflectarray using concentric ring elements. 11 dB reduction of cross-polarisation level can be achieved     

基于反射阵天线的无线输能系统设计与实验

微波无线输能技术因其传输距离远,易于调控,近年来受到广泛的关注。文中提出一款基于移动馈源的波束扫描平面反射阵天线,该阵列由19×19个移相单元构成,整体尺寸为490.2 mm×490.2 mm。通过仿真验证了提出的移相单元可以覆盖360°全相位,且反射系数大于-0.1 dB(97.7%)。基于CST全波仿真表明,设计的反射阵扫描角度为-28°～+25°。同时,搭建了一个微型的传能系统用于验证反射阵天线的性能。通过实验验证发现在有平面反射阵天线的情况下,在其辐射近场范围内,无线传能系统接收终端获得的功率提高约为无反射阵情况下的700%～1500%,非常有利于传能系统的能量传输。仿真和实验结果均证明该反射阵天线在微波无线传能领域具有一定的应用前景。     

双层微带反射阵单元特性研究

微带反射阵单元是组成微带反射阵的基本元素,其性能的好差直接影响整个阵列的性能。本文首先介绍了仿真微带反射阵单元反射场相位的等效波导法的基本原理;然后分析了双层贴片上下不同宽度比、不同介质层厚度的对反射场相位曲线及频带宽度的影响,并提出如何获得阵列最大频带宽度;最后研究了接地面开槽结构对反射阵单元反射场相位、幅值的影响,计算结果表明适当大小的槽结构能够提高反射场相位曲线的平坦度及增大反射场幅值。     

双频宽带大型微带反射阵天线设计

微带反射阵天线在性能上最主要的缺陷就是窄带,一般情况下其带宽小于5%,对电大口径短焦距馈电时更窄。本文设计并制作出一种由L波段和C波段两个反射面天线组成的6m×2m薄膜双频微带反射阵天线,两个频段的天线共用一层膜面。对该天线的电性能进行了测试,测试结果表明:该天线两个频段的相对带宽均大于10%(副瓣电平≤-18dB)。该天线具有折叠、可展开的结构特征,可以在卫星或航天器上广泛应用。     

基于两种单元贴片的毫米波平面反射阵列天线

针对单层介质单一贴片很难实现360°全域相位变化,文中提出了一种拥有环形贴片和环圆混合型贴片两种贴片组合结构的毫米波平面反射阵列天线,这种结构可以实现更为平滑的360°相位变化.利用这项技术,设计和分析了频率为94GHz的单层毫米波微带平面反射阵列天线,仿真计算验证了该方案的可行性.     

A Ka-band microstrip reflectarray with elements having variablerotation angles

This paper demonstrates a novel means of achieving cophasal far-field radiation for a circularly polarized microstrip reflectarray with elements having variable rotation angles. Two Ka-band half-meter microstrip reflectarrays have been fabricated and tested. Both are believed to be the electrically largest reflectarrays ever developed using microstrip patches. One, a conventional design, has identical square patches with variable-length microstrip phase-delay lines attached. The other has identical square patches with identical microstrip phase-delay lines but different element rotation angles. Both antennas demonstrated excellent performance with more than 55% aperture efficiencies, but the one with variable rotation angles resulted in better overall performance. A brief mathematical analysis is presented to validate this “rotational element” approach. With this approach, a means of scanning the main beam of the reflectarray over a wide angular region without any RF beamformer by using miniature or micromachined motors is viable     

Spiraphase-type reflectarrays based on loaded ring slot resonators

Reflective periodic arrays based on loaded ring slot resonators are analyzed. A full-wave mathematical model is developed and numerical results are presented. It is proven that the reflection angle for the normally incident circularly polarized wave can be effectively controlled by proper positioning of reactive loads in ring slot resonators. Analysis of the reflection characteristics of the Ka band one-layer reflectarray results in a conclusion that the incident wave can be effectively redirected in the directions determined by elevation angles as high as 65/spl deg/ with conversion coefficient better than -1.5 dB. It is also shown that the usage of the multilayer reflectarray leads to a considerable improvement in the reflection characteristics when it is compared with the one-layer reflectarray. The method of the waveguide simulator has been used to verify the developed mathematical model.     

Three-layer printed reflectarrays for contoured beam space applications

A procedure for designing contoured beam reflectarrays in a defined frequency band is proposed. The reflectarray consists of three layers of rectangular patch arrays backed by a ground plane. The phase of the reflection coefficient for both linear polarizations is controlled at each reflective element by adjusting the patch dimensions. To overcome the frequency band limitation of reflectarrays, the patch dimensions are adjusted to match the required phase distribution and its variation with frequency. A phase-only synthesis technique based on the intersection approach has been applied to obtain the phase distribution on the reflectarray surface. An experimental demonstration is presented by means of a medium-size two-layer reflectarray that radiates two pencil beams separated by 55/spl deg/. An 80-cm three-layer reflectarray has been designed for typical South America DBS coverage at Ku-band for dual polarization. After the optimization of the patch dimensions to match the phase distribution in the 12.8-14.2 GHz band significant improvements have been achieved in the contoured patterns. As a result, the theoretical radiation patterns practically fulfill the requirements in the coverage region within a 10% bandwidth.     

Design and fabrication of a wideband reflectarray antenna in Ku and K bands

The purpose of this paper is design of a wide band single layer reflectarray antenna using a new broadband cell. The proposed cell consists of two parts. The first part is a circular patch and the second one is a ring with some additional stubs, which are attached to the patch and ring in a symmetrical form. The circular patch and ring elements are designed at frequencies of 20 GHz and 15 GHz respectively. In order to increase the reflectarray antenna bandwidth, at first the dimensions of the patch, ring and stubs are optimized to attain uniform phase response in the frequency range from 11 GHz to 20 GHz. Then an air layer is considered under the dielectric substrate. The reflectarray antenna is designed based on this optimized wideband unit cell. A wideband horn antenna is also designed as a feed antenna for the proposed reflectarray structure. The reflectarray antenna with horn are simulated. The 1 dB gain-bandwidth of 4.66 GHz is obtained (27.4% fractional bandwidth) in the frequency band of 14.72 GHz to19.38 GHz. Finally, the reflectarray antenna is fabricated and tested. It can be seen that there is a good agreement between simulation and measurement results.     

Reflectarray element using variable ring with slot on ground plane

A novel structure using a variable microstrip ring with a slot ring on part of the ground plane is proposed as an auxiliary unit cell in a reflectarray. A progressive phase range larger than 682° has been achieved by changing the sizes of the microstrip rings and adding slot rings on part of the ground plane. A K-band reflectarray has been fabricated and shows very good performance.     

Novel Broadband Reflectarray Antenna with Two-Type Elements for Millimeter-Wave Application

A novel broadband millimeter-wave microstrip reflectarray antenna with square-annular patches and combined patches has been presented, aiming to solve the problem of how to obtain a full 360° range of phase shifts for single-layer. The choice of these two-type elements can make the phase shift smoother and increased up to 360°, leading to broader bandwidth. Based on this technique, a single-layer microstrip reflectarray antenna operating at 94 GHz has been designed. The computed results demonstrate the agreement of the main beam steering with the design requirement, and a 1-dB gain bandwidth close to 10% is obtained. The simulation results verify the feasibility of this design.     

A shaped-beam microstrip patch reflectarray

This paper describes a microstrip reflectarray antenna designed to produce a shaped-beam coverage pattern using phase synthesis. The concept is demonstrated with a Ku-band linearly polarized reflectarray designed to provide coverage of the European continent and measured results are compared to those obtained for a previously designed shaped-reflector antenna designed for the same coverage specifications. Results validate the shaped-beam reflectarray concept, although there are disadvantages to the reflectarray such as narrow bandwidth and reduced aperture efficiency that may offset the mechanical and cost advantages of the flat surface of the reflectarray     

Bandwidth of reflectarrays

It is shown that the dominant factor controlling reflectarray bandwidth is the bandwidth of the radiating element, and that the effect of non-constant path delays over the surface of the flat reflector has little significance unless the aperture is electrically very large and the f/D ratio is small. An example of a polarisation-twist reflectarray using aperture coupled elements with time delay lines is used to demonstrate this conclusion.     

Investigations into a power-combining structure using areflectarray of dual-feed aperture-coupled microstrip patchantennas

This paper details an investigation of a power combiner that uses a reflectarray of dual-feed aperture-coupled microstrip patch antennas and a corporate-fed dual-polarized array as a signal distributing/combining device. In this configuration, elements of the reflectarray receive a linearly polarized wave and retransmit it with an orthogonal polarization using variable-length sections of microstrip lines connecting receive and transmit ports. By applying appropriate lengths of these delay lines, the array focuses the transmitted wave onto the feed array. The operation of the combiner is investigated for a small-size circular reflectarray for the cases of -3 dB, -6 dB and -10 dB edge illumination by the 2×2-element dual-polarized array     

一种微带反射阵列天线单元带宽拓展方法

在微带反射阵列天线设计中,采用大小不同、结构相似的多个空心单元于同一层面上嵌套形成组合单元,可以拓展单元带宽.通过几种单元实例计算对比和实验阵面性能的仿真分析,结果表明采用此组合单元可有效拓展阵中单元及微带反射阵列天线系统的工作带宽.应用此组合单元法步骤简单,具有一定的通用性,可为各种反射阵列天线设计和工程实践参考.     

Mechanically controlled reflectarray antenna for beam switching and beam shaping in millimetre-wave applications

A novel method is proposed to shape or switch the radiating beam of a reflectarray antenna by slight displacement of its layers with respect to each other. A reflectarray, which is a quasi-periodic structure composed of microstrip patches loaded by slot elements, is used in this scheme. The required phase shift at each position on the reflectarray surface is obtained by varying the slot length on the ground plane. Several groups of slots are etched on the slot layer and each group corresponds to one and the same beam. Mechanical alignment of the slots that belong to a certain group with the patch leads to activation of the corresponding beam. This method was used to design a reflectarray antenna with three beams at /spl plusmn/30/spl deg/ and 0/spl deg/. Measurement results demonstrated the validity of the design procedure.     

宽带缝隙堆叠贴片微带反射阵天线的研究

微带反射阵天线具有易折叠、易携带等特点,结合缝隙堆叠贴片（ASP）微带单元频带较宽的优势,能进一步展宽缝隙耦合反射阵的带宽。通过求解相位计算公式,得到反射阵表面相位分布。给出了ASP微带天线的设计参数、S参数曲线及对应ASP单元的反射相位曲线,用所设计单元组成225元反射阵模型,结果显示该模型中心频率最大增益为26.03dBi,1.5dB增益带宽为33.3%,在整个带宽内具有良好的工作性能。