基于液晶的太赫兹反射式波束扫描天线

提出了一种基于液晶的太赫兹电控反射式移相器及其构成的波束扫描阵列天线。通过采用液晶调控的开槽结构移相器,解决了液晶调控过程中谐振层覆盖面不足造成的液晶取向不均、边缘效应和饱和电压增大等问题。设计了工作在380 GHz三开槽的移相器,对谐振频点的表面电流分布和谐振频点进行了仿真分析。数值计算结果表明当液晶相对介电常数在2.47~3.26范围内变化,377~392 GHz频率范围内移相器能够实现360°的相移。采用三开槽结构反射相移单元,设计了工作于380 GHz的电控波束扫描阵列天线,实现了30°范围内的一维波束扫描,主瓣增益大于20 dBi。     

一种基于超介质覆层加载的LTE天线设计

将弧形微带线、圆形开口谐振环和方型DGS(Defected Ground Structure)组建了一种平面微带型超介质单元,该单元在微波频段内具有等效介电常数和等效磁导率均小于0的特性。同时在双层贴片与接地板之间利用短路针加载技术,设计了一种结构简单的普通微带天线。MATLAB和HFSS软件仿真结果表明,设计的平面型超介质单元在1~10 GHz频段内具有多个等效介电常数和等效磁导率均小于0的频段。将由超介质单元构成的覆层加载到天线辐射贴片前方,构建一种工作频段完全覆盖1.92~1.98 GHz,2.11~2.17 GHz的LTE(Long Term Evolution)超介质天线。仿真结果表明,加载超介质覆层后微带天线的工作频段分别扩展为1.91~2.05 GHz、2.09~2.19 GHz频段,增益也提高了至少2 dB。     

基于复合超介质基板的微带天线设计与分析

利用方形开口谐振环、微带线和缺陷地结构建构了一种结构较为简单、便于调节的腔体型结构超介质。仿真结果表明,设计的超介质在1.0~3.6 GHz、3.8~7.1 GHz和7.2~8.0 GHz三个频段内均具有等效介电常数和等效磁导率小于零的左手材料特性。将超介质单元周期性地镶嵌在一种普通多频微带天线的介质基板内,实现了基于复合超介质基板天线。测试结果表明,在工作频率为1.61,3.44和3.9 GHz的微带天线中加载这种超介质结构覆层后,其谐振频率分别降低了60,70和40 MHz,同时将4.53~4.80 GHz和4.97~6.00 GHz两个工作频段扩展为4.6~6.0 GHz的超宽带。所设计的天线整体性能良好,且满足了WLAN在5 GHz通信频段的要求。     

一种纯介质结构的宽带反射阵天线单元特性分析

提出一种基于纯介质结构的宽带反射阵单元结构。首先通过改变介质基片的介电常数,研究了纯介质单元的移相特性,然后采用阻抗匹配层技术,获得了宽带范围内平坦的相移曲线。由于自然材料的介电常数难以连续变化,这里使用介质基片开孔结构,实现了等效的介电常数非均匀分布。目前主流的反射阵天线使用微带贴片作为阵列单元,它存在工作带宽窄、相移范围受限的问题。提出的纯介质单元则为宽带反射阵天线的设计提供了一种新思路。     

基于加载线型Ka频段的五位数字移相器

数字移相器广泛应用于相控阵雷达中,本文采用一前一后加载支线的方法设计了 11.25°,22.5°和45°移相单元,以3 dB支线耦合器的形式设计90°和180°移相单元,在Ka频段研制出五位数字移相器。该移相器在30 GHz~31 GHz工作频带内,各移相单元实测相移误差最大为6.5°,最小为0.2°;插入损耗最大为11.8 dB,最小为8.6 dB;输入驻波比小于2,整个电路尺寸为110 mm×55 mm×25 mm。     

基于复合超介质基板的微带天线设计与分析

利用方形开口谐振环、微带线和缺陷地结构建构了一种结构较为简单、便于调节的腔体型结构超介质.仿真结果表明,设计的超介质在1.0～3.6GHz、3.8～7.1GHz和7.2～8.0GHz三个频段内均具有等效介电常数和等效磁导率小于零的左手材料特性.将超介质单元周期性地镶嵌在一种普通多频微带天线的介质基板内,实现了基于复合超介质基板天线.测试结果表明,在工作频率为1.61,3.44和3.9GHz的微带天线中加载这种超介质结构覆层后,其谐振频率分别降低了60,70和40MHz,同时将4.53～4.80GHz和4.97～6.00GHz两个工作频段扩展为4.6～6.0GHz的超宽带.所设计的天线整体性能良好,且满足了WLAN在5GHz通信频段的要求.     

基于平面微带结构超介质天线设计与分析

利用开槽曲流技术构建了一种工作频段位于S、C波段内的多频微带贴片天线,根据传统立体左手材料的变型结构设计了一种新型平面微带结构的超介质。在微带贴片天线的介质基板内加载超介质覆层后,天线工作频率降低,频带展宽以及辐射性能得到改善。HFSS和Matlab仿真实验结果表明,新型平面微带结构的超介质在2.7~4.9GHz和5.0~5.5 GHz两个频段内具有等效介电常数和等效磁导率均小于0的左手特性,工作频率在2.66,3.67,4.66和5.49 GHz的微带贴片天线加载超介质覆层后,其谐振频率分别降低了140,140,210和270 MHz,同时4.60~4.78GHz的工作频带展宽了160 MHz。该超介质微带天线可以运用于实际的WLAN或WIMAX通信中。     

宽带低副瓣微带反射阵列天线

为了实现便携式雷达设备的轻小型化,系统采用微带反射阵列天线替代传统的抛物反射面天线.该天线设计的难点是如何实现雷达工作频带内的天线低副瓣特性.采用微带延迟线的移相方案,并提出微带贴片与延迟线满足线性相移关系的匹配原则,实现了反射阵列天线的宽带低副瓣特性.实测结果表明,在X频段3.2%的带宽内,天线副瓣电平低于-25 dB,并且天线效率不低于50%.     

基于加载寄生带的双频天线设计

文中提出了一种双频印刷天线设计方法,覆盖2.4 GHz和5.2 GHz频段。该天线通过在偶极子天线振臂旁平行放置寄生单元,降低天线在高频段的输入阻抗(通常输入阻抗远大于50Ω),从而实现良好的阻抗匹配,在主谐振频段外产生新的寄生谐振频点,达到双频段工作的目的。为了验证所提出的天线设计方案,建立了仿真模型,并加工了天线实物。通过仿真分析和实测发现,改变寄生金属单元的位置和尺寸只影响高频段谐振频点,几乎不影响低频段谐振频点,而偶极子天线尺寸的改变只影响低频段谐振频点,不影响高频段谐振频点。文中设计的天线具有双频段相互独立特性,因此天线的两个谐振频段可根据需求独立设计。     

一种单面双L型异向介质的设计及分析

针对目前已有的异向介质带宽窄,结构复杂的缺点,设计了一种工作在Ku波段的单面双L型异向介质结构。通过采用电磁仿真方法,建立平面电磁波垂直入射异向介质平板的模型,并提取其传输和反射数据;借助MATLAB工具,根据NRW（Niconlson－Ross－Weir）方法从中提取出该新型结构的等效介电常数和等效磁导率。仿真结果表明,这种单面双"L"型的结构在频段为14．2~15．9 GHz的等效介电常数与等效磁导率同时为负,其有效绝对带宽1．9 GHz;在11~17 GHz频段内的有效相对带宽为31．7%。因为这种异向介质结构在特定工作频率下电磁参数同时为负值,并且通过计算频率为15 GHz时的电磁波的相速为－2×107 m/s,验证了该异向介质的结构具有后向波特性。这种结构具有便于制造及可控两大优势,具有很大的应用前景。     

Design of an Electronically Beam Scanning Reflectarray Using Aperture-Coupled Elements

The design of a C-band electronically beam scanning reflectarray is presented. The reconfigurable reflectarray element consists of a microstrip patch, printed on a flexible membrane substrate, aperture-coupled to a transmission line loaded with two varactor diodes. The designed element allows continuous tuning of the reflected signal's phase over a 360deg range with a maximum loss of 2.4 dB at 5.4 GHz. The measured results on a 30-element reflectarray breadboard show that by varying the bias voltages on each element the main beam can be steered to large angles, up to 40deg from broadside in the H-plane. A loss analysis of the proposed reflectarray is also presented     

Amplitude and Phase Controlled Reflectarray Element Based on an Impedance Transformation Unit

An architecture to simultaneously affect both amplitude and phase control from a reflectarray element using an impedance transformation unit is demonstrated. It is shown that a wide range of control is possible from a single element, removing the conventional necessity for variable sized elements across an array in order to form a desired reflectarray far-field pattern. Parallel plate waveguide measurements for a 2.2 GHz prototype element validate the phase and amplitude variation available from the element. It is demonstrated that there is sufficient control of the element's reflection response to allow Dolph-Tschebyscheff weighting coefficients for major-lobe to side-lobe ratios of up to 36 dB to be implemented.      

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.     

Electrically Tunable Reflective Terahertz Phase Shifter Based on Liquid Crystal

We present a reflective spatial phase shifter which operates at terahertz regime above 325 GHz. The controllable permittivity of the nematic liquid crystals was utilized to realize a tunable terahertz (THz) reflective phase shifter. The reflective characteristics of the terahertz electromagnetic waves and the liquid crystal parameters were calculated and analyzed. We provide the simulation results for the effect of the incident angle of the plane wave on the reflection. The experiment was carried out considering an array consisting of 30?×?30 patch elements, printed on a 20?×?20 mm quartz substrate with 1-mm thickness. The phase shifter provides a tunable phase range of 300° over the frequency range of 325 to 337.6 GHz. The maximum phase shift of 331° is achieved at 330 GHz. The proposed phase shifter is a potential candidate for THz applications, particularly for reconfigurable reflectarrays.     

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.     

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.     

Design and Measurement of Reconfigurable Millimeter Wave Reflectarray Cells With Nematic Liquid Crystal

Numerical simulations are used to study the electromagnetic scattering from phase agile microstrip reflectarray cells which exploit the voltage controlled dielectric anisotropy property of nematic state liquid crystals (LCs). In the computer model two arrays of equal size elements constructed on a 15 mum thick tuneable LC layer were designed to operate at center frequencies of 102 GHz and 130 GHz. Micromachining processes based on the metallization of quartz/silicon wafers and an industry compatible LCD packaging technique were employed to fabricate the grounded periodic structures. The loss and the phase of the reflected signals were measured using a quasi-optical test bench with the reflectarray inserted at the beam waist of the imaged Gaussian beam, thus eliminating some of the major problems associated with traditional free-space characterization at these frequencies. By applying a low frequency AC bias voltage of 10 V, a 165deg phase shift with a loss 4.5-6.4 dB at 102 GHz and 130deg phase shift with a loss variation between 4.3-7 dB at 130 GHz was obtained. The experimental results are shown to be in close agreement with the computer model.     

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     

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.