Ka-band reflectarray using ring elements

A simple ring structure to realise a Ka-band circularly polarised microstrip reflectarray is presented. With rotation techniques employed to focus the reflected wave at a focal point, a 0.5 m right-hand circularly polarised microstrip reflectarray is developed and tested at 31.75 GHz resulting in 50% aperture efficiency. The cross-polarisation levels measured are 40.7 dB down at broadside, showing the validity of the structure.     

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.     

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。     

A C/ka dual frequency dual Layer circularly polarized reflectarray antenna with microstrip ring elements

This paper reports a dual frequency dual layer circularly polarized reflectarray operating in the C and Ka bands. A 0.5-m right-hand circularly polarized planar reflectarray antenna is designed using microstrip ring elements of variable rotations to achieve a cophasal beam at broadside. The microstrip ring elements are more compact than the traditional reflectarray elements and can minimize blockage for the multilayer multifrequency applications. The highest efficiencies measured are 46% at 7.3 GHz and 38% at 31.75 GHz. The tested cross-polarization levels are -21 dB at 7.3 GHz and -29.2 dB at 31.75 GHz at the broadside direction. The tested results show that the designed ring element is suitable for both the single and dual layer applications with good bandwidth and circularly polarized performance.     

Design of millimeter wave microstrip reflectarrays

This paper discusses the theoretical modeling and practical design of millimeter wave reflectarrays using microstrip patch elements of variable size. A full-wave treatment of plane wave reflection from a uniform infinite array of microstrip patches is described and used to generate the required patch-design data and to calculate the radiation patterns of the reflectarray. The critical parameters of millimeter wave reflectarray design, such as aperture efficiency, phase errors, losses, and bandwidth are also discussed. Several reflectarray feeding techniques are described, and measurements from four reflectarray design examples at 28 and 77 GHz are presented     

Novel Broadband Reflectarray Antenna with Windmill-Shaped Elements for Millimeter-Wave Application

A novel broadband millimeter-wave reflectarray antenna composed of windmill-shaped elements of variable lengths is proposed. Compared to the conventional single-layer reflectarray elements, the windmill-shaped elements can realize much larger phase variation range (over 600°), leading to broader bandwidth. Using this technique, a 15°-beam-steering reflectarray operating at 30 GHz is designed. The computed results demonstrate the agreement of the main beam steering with the design requirement, and a 1-dB gain bandwidth close to 20% is obtained. The validity of the obtained results is verified by comparing the ones generated by Ansoft High Frequency Structure Simulator (HFSS) with those produced by Ansoft Designer. The antenna is useful for millimeter-wave applications.     

微带反射阵天线的分析与设计

介绍了微带反射阵天线的基本原理,分析了天线设计中阵元单元尺寸和间隔的计算、相位延迟线的选择、基片厚度的选取、误差分析、仿真验证等,根据分析结果提出了低副瓣微带反射阵天线的设计方法。实例测试结果表明,反射阵天线的总体性能接近抛物面天线的性能,易于折叠、携带方便。     

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。     

Broadband reflectarray with combination of cross and rectangle loop elements

A reflectarray antenna composed of a combination of cross and rectangle loops of variable size printed on a conductor-backed substrate is presented. Using this type of cell element, a wideband, single-layer reflectarray is fabricated and measured. The bandwidth performance of this reflectarray is comparable to the previously reported best figures for reflectarrays using stacked-patch cell elements. Measured results demonstrate a radiation efficiency close to 60% and a 1 dB gain bandwidth of 24%, centred at Ku-band.     

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.     

新型宽频带微带反射阵单元相位特性研究

分析由两个弯曲振子及一个普通振子构成的单层三谐振单元的相位特性。对三种基板结构下单元的相移特性进行了研究。结果表明,采用混合基板,增加泡沫的厚度,可以在较宽频带内获得平滑的相移特性,同时相位动态范围大于360°。与三层堆叠结构的相移特性进行了比较,仿真结果表明可以达到与其相近的效果。最后给出了一种改进型单元结构,能够在6-10GHz带宽内得到基本一致的相移特性曲线。利用该结构组成一个12×13单元的反射阵列,带宽内效率约为50%。     

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.     

Wideband reflectarrays using artificial impedance surfaces

The gain bandwidth of a microstrip reflectarray can be substantially improved by replacing the usual layer of near-resonant patches with a simple artificial impedance surface consisting of closely spaced electrically small patches on a grounded dielectric substrate. It is shown that this approach can lead to reflectarray gain bandwidths (1 dB) in excess of 20% with a single layer of printed elements     

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.     

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.     

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     

太赫兹液晶反射阵列移相单元的设计与分析

为了满足高增益天线大的移相度和可工作在太赫兹频段,设计了一种基于液晶的双偶极子反射移相单元结构。采用液晶的等效介电常数模型,在频率为335~345 GHz频段均产生360o以上的相移,在342 GHz实现最大相移390o。为了减小液晶不均匀性对相移产生的影响,建立了单元的精确模型,该模型在频率范围为330~338 GHz时均产生了250o以上的相移,在336 GHz实现最大相移285o。与均匀液晶等效介电常数模型相比,产生最大相移的频率点发生了变化,并且产生了最大为105o的移相差值,这在相控反射阵列天线的设计中是不可忽略的。     

一种渐变槽线作馈源的新型微带反射阵

提出了利用渐变槽线天线物理截面小的特点与变极化技术相结合的方法来改善微带反射阵馈源的遮挡效应,并设计了用于变极化微带反射阵馈源的渐变槽线天线及含37单元的微带反射阵。鉴于这些特点,该类天线在雷达、移动通信等领域具有潜在工程应用。文中给出了部分的理论分析和实例佐证。     

Cassegrain Offset Subreflector-Fed X/Ka Dual-Band Reflectarray With Thin Membranes

The development of a 0.75-m Cassegrain offset subreflector-fed X/Ka dual-band reflectarray antenna is presented. The subreflector (SR) is fabricated using combinations of prescribed geometric parameters and two left-hand circularly polarized microstrip patch arrays are designed as feed networks with one covering X-band and the other covering Ka-band. The phase corrections in the reflectarray required to form a planar phase front are realized by rotating microstrip ring elements. Low-dielectric constant foam layers are inserted below both the X- and Ka-band membranes to act as support structures and to minimize the degrading effects of thin substrates. It is believed that this is the first Cassegrain offset-fed reflectarray ever been developed. The measured results show efficiencies around 50% for both frequency bands with room for improvements.     

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。