圆极化微带贴片天线辐射和散射特性研究

提出了一种改进的宽带圆极化微带天线。该天线采用单端口、共面波导馈电。通过仿真优化,获得了32.7%的圆极化轴比带宽(AR<3dB),和47.6%的阻抗带宽(VSWR<2.0)。测量天线样机的阻抗带宽为44.4%,较好地吻合了仿真计算结果。最后,以设计天线为例,研究了圆极化微带贴片天线的辐射特性和散射特性,为圆极化天线雷达截面减缩技术打下了良好的理论和实验基础。     

宽带圆极化微带天线的几种实现方法

在简要概述圆极化微带天线工作原理的基础上,重点介绍了目前国内外较为先进的圆极化微带天线实现宽带的多种方法,包括微带贴片天线、缝隙天线,以及采用PBG结构的圆极化天线。这些方法分别采用单点馈电,多点馈电或多元组合实现圆极化,均有效拓展了圆极化天线的阻抗匹配带宽和圆极化轴比带宽。参考一些实例验证了这些方法的可行性,然后展望了其可能的发展趋势。     

一种小型化宽带圆极化微带天线的设计

设计并加工了一种采用同轴背馈方式馈电的小型化宽带圆极化微带天线。针对单点馈电微带天线轴比带宽窄的问题,通过增加馈电网络对天线辐射贴片进行双点馈电以展宽轴比带宽,得到了良好的效果。馈电网络根据带状线理论设计,利用U形接地板巧妙地实现了宽带天线的结构小型化。通过对辐射贴片的双点馈电获得了令人满意的电压驻波比带宽和良好的圆极化性能。通过仿真和实际测试表明,该天线VSWR≤2的带宽达到了30％,3dB圆极化带宽约为26％,同时频带内天线的增益达到4dB。     

基于MEMS技术的共面耦合式圆极化微带天线的设计与仿真

研究了一种工作在Ka波段,基于MEMS微加工工艺的圆极化微带天线.采用微带馈线与贴片辐射单元非接触、共面临近耦合的馈电方式,可以在不改变贴片与馈线本身的尺寸且无需额外增加匹配网络的情况下调节阻抗匹配,有效地提高了馈线与辐射元的阻抗匹配度与可调性,简化了天线结构.使用3dB电桥移相器实现圆极化,结构规范,圆极化效果好.使用有限元仿真软件Ansoft HFSS对其进行了仿真优化,得出了一组较优参数,此时天线中心频率为35GHz,增益为6.86dB,驻波比≤2时阻抗带宽为4GHz(约11.4%),轴比<3dB时带宽约为5.9GHz(约16.9%).     

具有二次Koch分形边界的圆极化微带天线

设计了一种单馈点圆极化微带天线。微带贴片采用二次Koch分形边界的贴片结构,通过底馈方法激励起两个相互正交的简并模实现圆极化;采用CSTMicrowaveStudio@软件进行了仿真,其结果表明,在微带贴片的对角线上适当位置用探针馈电,可以实现圆极化辐射。对具有介质损耗的天线进行了仿真,结果与理想介质的差异较大。设计了一个右旋圆极化微带天线,并进行了测试。该天线工作于1．575GHz;VSWR小于2的阻抗带宽为51MHz;轴比为4dB;增益为3．8dB;贴片尺寸为42．4mm×42．4mm,可以用作GPS天线。     

LTCC宽频圆极化环形微带贴片天线研究

设计了一种低温共烧陶瓷( LTCC)宽频带圆极化环形微带贴片天线.该天线采用环形辐射贴片结构,在环形内部利用L型匹配支节连接以拓展带宽.通过使用威尔金森功分器加移相器对辐射贴片馈电,使耦合馈电端口的正交电场相位差90.来实现微带天线的圆极化.该天线设计剖面厚度仅2.4 mm.仿真结果显示该天线工作于1.268 GHz时,实现阻抗带宽超过80 MHz,天线的轴比小于1.5 dB且增益达到4.9 dB.实测结果与仿真结果相近.     

便携式MSS地面站终端圆极化微带天线

介绍了一种Ｌ－波段移动通信卫星系统用便携式地面站终端圆极化微带贴片天线的研制结果。设计采用了一对圆形贴片天线拼阵结构,为了实现圆极化,两个圆形贴片都带有一对缺口。对这两个辐射单元等幅度馈电,但馈电相位相差９０°,两个辐射单元在空间上共面正交放置,以改善圆极化轴比。设计同时还使用了共轴寄生圆形微带元,以扩展反射损耗的频带宽度。实验测试结果表明,根据这种方案设计的圆极化微带天线,增益较高,轴比和反射损     

一种新型互补结构的宽带圆极化印刷天线北大核心CSCD

设计了一种新型的宽带圆极化微带天线,天线由两个完全相同的矩形微带贴片组成,采用微带线馈电方式为天线的上层微带贴片进行不对称馈电,下层贴片作为天线的部分地。天线从整体上是一个互补结构,根据圆极化产生的原理,在与馈电微带线相垂直的地方,开一条缝隙,产生正交的表面电流,调节天线的主要参数,使产生等幅正交的空间电场分量,从而产生圆极化波。通过增加十字形调谐结构,调节天线高频段的阻抗带宽和轴比带宽。天线在中心频率2.55 GHz处阻抗带宽(S11<-10 dB)为151%(0.8 GHz^4.5 GHz),天线的轴比带宽(AR<3 dB)为82.3%(1.5 GHz^3.6 GHz)。     

一种卫星接收天线的研究

介绍了一种宽带宽、轴比带宽宽的卫星接收天线的设计,天线采用微带线共面馈电的微带天线形式,利用增加寄生贴片展宽天线单元的电压驻波比带宽和圆极化轴比带宽,利用旋转馈电技术扩展了天线阵列的圆极化轴比带宽.天线设计得到了实验的验证.     

一种LTCC叠层耦合馈电圆极化微带天线的设计

设计了一种低温共烧陶瓷(LTCC)低剖面圆极化叠层耦合微带贴片天线.该天线采用层叠结构,在辐射基板正面采用分形的辐射贴片来降低天线尺寸并拓展带宽;在馈电层基板正面开“十字”槽,在其反面通过使用威尔金森功分器加移相器网络对“十字”槽馈电,使得耦合馈电端口的正交电场相位差90°来实现微带天线的圆极化.该天线设计剖面厚度仅3 mm.仿真结果显示该天线工作于1.268 GHz时,实现阻抗带宽超过60 MHz,天线的轴比小于1.5 dB且增益达到5 dB.     

Conformal microstrip antennas and microstrip phased arrays

A new class of antennas using microstrips to form the feed networks and radiators is presented in this communication. These antennas have four distinct advantages: 1) cost, 2) performance, 3) ease of installation, and 4) the low profile conformal design. The application of these antennas is limited to small bandwidths. Phased arrays using these techniques are also discussed.     

Rectangular resonators in inverted microstrip and suspended microstrip

Resonant frequency characteristics of rectangular resonators in a generalized shielded suspended substrate line are analysed using a rigorous spectral domain technique. The computed dominant mode resonant frequency of rectangular resonators in a suspended microstrip with centred dielectric, inverted microstrip and suspended microstrip are presented as a function of various structural parameters. These characteristics are distinct from those obtained for a conventional microstrip rectangular resonator. Experiments are carried out in the frequency range 4-18 GHz to verify the computed resonant frequencies for a suspended microstrip with a centred dielectric using first-order basis functions. The results should find applications in the design of inverted microstrip and suspended microstrip passive microwave and millimetre wave integrated circuits.     

Inverted microstrip and suspended microstrip with anisotropic substrates

This letter presents characteristics of the inverted microstrip and the suspended microstrip, with anisotropic substrates. The transverse transmission-line method combined with the mapping method and the variational technique in the space domain are used to analyze the impedance characteristics. The data presented should find application in the design of MIC components at millimeter-wave frequencies.     

Broadband microstrip branch-line coupler Broadband microstrip branch-line coupler

The design and measured performances of a broadband branch-line coupler are presented. The broadband coupler was designed by using a four-section branch line topology with a structure of the defected ground. Such a structure can make the impedance of the microstrip line much larger than that without defected structure, even using a normal PCB process. More than 231 Omega was easily achieved by such a defected structure. The measured performance of the broadband coupler agrees well with the results from simulation     

Magnetically scannable microstrip antenna employing a leakygyromagnetic microstrip line

Rigorous full-wave spectral-domain analyses of a magnetically scannable gyromagnetic microstrip leaky-wave antenna are presented. Varying the DC magnetic bias field by ~6.5%, the maximum radiation angle of the leaky-wave antenna, measured from the horizon, shifts from zero to almost 90°     

Self-adjusting microstrip antenna

A microstrip circuit operating in the G band is presented. It allows all emitting printed antenna to self-tune its resonance frequency when it is disturbed, in order to stay resonant and matched at the desired transmit frequency. The principle, design and experimental results of the circuit are presented     

Nonplanar microstrip arrays

Pattern synthesis using planar arrays was done extensively in the past, mainly in the context of radar antennas where a cosec² beam is required in the elevation plane. The synthesis leads to a set of coefficients for the array elements which may be difficult to realize and which, if realizable, may lead to a very narrow-band performance. In this paper, a new type of array is proposed. The shaped-beam nonplanar array is an array of microstrip elements, where the phasing is not generated through the feeding network, but by shaping the substrate. Microstrip arrays lend themselves well to a configuration similar to the one proposed, and as it is shown, the final thickness of the array does not exceed a few substrate thicknesses     

Parameters of microstrip

The program computes the capacitance, effective permittivity, characteristic impedance and phase velocity of single strips, and of the normal modes of coupled pairs of strips, in an approximation in which the longitudinal components of the fields and the thickness of the conducting strips are neglected. Within this model, the inhomogeneous dielectric is treated in a rigorous manner.     

All-garnet-substrate microstrip circulators

Data on a microstrip [1] circulator fabricated on an all-garnet substrate is presented. Fabrication involves only evaporation of copper lines, disk, and ground plane on the substrate. The implications for microwave integrated circuits are discussed briefly.     

The microstrip laser

We present a novel semiconductor laser structure, the microstrip laser, where the epitaxial laser layers sit directly above a thick gold layer, instead of on a conventional semiconductor substrate. This design provides advantages for both high frequency and high-power performance compared to conventional ridge waveguide structures. Results indicative of an improved structure are presented, including a factor of 3 reduction in the thermal resistance of the microstrip laser compared to a conventional laser