一种双频双极化宽带高温超导微带天线的研究

为了提高天线的性能,本文设计了一种口径耦合馈电的多层介质高温超导微带天线。天线的馈电网络部分采 用了高温超导材料,利用了高温超导材料具有低表面阻抗的特性,提高了天线的效率。高温超导微带天线的衬底介电 常数过高,多层介质的结构引入一层真空衬底,降低平均介电常数,这样能展宽天线的带宽。天线缝隙采用H 型缝 隙,提高了两极化端口间的隔离度。天线的仿真结果表明了设计思路的合理性和可行性。     

高温超导微带天线的谐振特性研究

传输线模型是分析微带天线的一种最简单的方法，但其未将导体的特性参数考虑到天线的分析中去,针对这一缺点,为研究超导体的表面阻抗对高温超导微带天线输入阻抗和谐振频率的影响,把导体特性对天线的影响看作一种微扰来处理,对传统的传输线模型进行了修正,并通过与谱域矩量法相比较,验证了修正后方法的有效性.进而利用修正后的方法计算分析了高温超导矩形微带贴片天线的输入阻抗和谐振频率,给出了关于高温超导微带天线输入阻抗和谐振频率的若干结论.     

高温超导体非线性特性对微带天线性能的影响

主要研究了高温超导(HTS)薄膜非线性特性对微带天线性能的影响。首先介绍了高温超导薄膜的非线性特性现象，以及产生该现象的可能的机理，在此基础上以矩形微带贴片天线为例，采用谱域矩量法对微带天线的辐射效率和输入阻抗进行了计算。结果表明输入功率增大到一定值时，将使天线的辐射效率下降，而且输入功率对输入阻抗也有一定的影响。     

含电磁双各向异性介质衬底的FSS特性分析

运用谱域Galerkin法对含电磁双各向异性介质衬底的频率选择表面(FSS)进行了分析,概述了算法的基本实现过程,直接以Maxwell方程为基础,逐步推导出该周期结构中的谱域格林函数.文中在衬底介质参数的变动下,对一系列FSS反射系数进行了有效计算,计算结果表明了介质衬底的电磁各向异性特性对FSS频率选择特性的影响.     

金属衬底多层各向异性介质电波反射特性研究

通过分析和计算多层各向异性介质的电磁波传输矩阵,导出了金属衬底上多层各向异性介质的电磁波反射系数计算方法,举例验证了该计算方法的正确性.作为一个应用例子,初步分析了金属衬底上各向异性材料的极化转换特性,为复杂电磁材料的电磁散射近似计算提供了理论基础.     

含各向异性介质衬底频率选择表面的直线法分析

运用直线法对一以单轴各向异性介质层为衬底的频率选择表面(FSS)进行了分析,考虑到介质层的各向异性,文中对直线法的常用方式作出了一定的修改,并详细介绍了整个方法实现过程。最后,对几套不同介电参数的FSS进行了计算,考虑了介质衬底的各向异性对FSS电磁特性的影响。     

FDTD应用于各向异性介质及半空间散射问题

介绍FDTD方法应用于各向异性介质散射分析及其并行计算.基于并矢表面阻抗给出金属表面各向异性介质涂层的等效介质参数公式.讨论铁氧体基片偏置磁场对微带天线辐射方向图的影响,模拟研究了板状各向异性材料介质参数的反演途径.将半空间FDTD应用于金属平板上孔缝散射计算和光学材料表面微缺陷散射近场和散射振幅分析,以及介质光栅Floquet模和传输功率的计算.     

背腔双负微带天线的仿真与实验研究

研究了以双负材料为衬底的背腔微带天线的设计方法与电磁特性.采用S参数法提取双负材料异质填充结构的本构电磁参数,基于腔模理论与HFSS仿真相结合的方法设计了背腔双负微带天线,并进行了加工制作和测试.给出了双负材料电磁特性参数的提取结果、背腔双负微带天线的辐射方向图、端口S参数的计算机仿真与实测结果,以及背腔双负微带天线的单站RCS仿真曲线.结果表明:背腔双负微带天线较背腔普通微带天线具有更好的带宽特性和散射特性.     

左手微带天线设计及其RCS计算

基于左手传输线结构,设计了左手微带天线单元及其4×4阵列,并对单元天线和阵列天线的辐射特性和散射特性进行了数值仿真计算与实际测量。数值仿真与实测结果表明,相比于矩形微带天线,左手微带天线在不影响辐射性能的情况下,大幅度地降低了天线带外的雷达散射截面(RCS)。左手微带天线克服了现有微带天线RCS缩减技术中的不足和缺陷,是在不损失天线辐射性能的前提下降低RCS的有效选择方案。     

应用于卫星电视广播接收微带天线的设计

本文设计了一种应用于卫星电视广播接收(Ku波段)的左旋圆极化微带天线,分析并仿真了天线的几何参数对天线工作性能的影响.通过对各几何参数的优化,使天线具有良好的轴比特性和辐射特性,并可作为阵元组成卫星接收微带天线阵列.     

Superconducting microstrip antennas: an experimental comparison oftwo feeding methods

The recent discovery of high-temperature superconductors (HTSs) has generated a substantial amount of interest in microstrip antenna applications. However, the high permittivity of substrates compatible with HTS causes difficulty in feeding such antennas because of the high patch edge impedance. Two methods for feeding HTS microstrip antennas at K- and Ka-band are examined. Superconducting microstrip antennas that are directly coupled and gas-coupled to a microstrip transmission line have been designed and fabricated on lanthanum aluminate substrates using Y-Ba-Cu-O superconducting thin films. Measurements from these antennas, including input impedance, bandwidth, efficiency, and patterns, are presented and compared with published models. The measured results demonstrate that usable antennas can be constructed using either of these architectures, although the antennas suffer from narrow bandwidths. In each case, the HTS antenna shows a substantial improvement over an identical antenna made with normal metals     

Annular Ring Microstrip Antennas for Millimeter Wave Applications

This work presents a fullwave analysis for annular ring microstrip antennas on uniaxial anisotropic substrates. The effect of the anisotropic substrates on the antenna performance at the millimeter wave band is investigated. The analysis is performed in the Hankel transform domain using Hertz vector potentials and Galerkin Method. Numerical results are presented for the antenna main characteristics such as resonant frequency and radiation pattern.     

Effect of the Dielectric Anisotropy on the Propagation Properties of Microstrip Tapers with Height Variations

This paper deals with the design and application of nonuniform microstrip transmission lines on anisotropic substrates. A rigorous analysis is based on the use of Hertz vector potentials, moment method and transmission line theory to determine the dispersion characteristics of single and coupled tapered microstrip lines for accurate performance prediction. Results are presented for the main parameters providing the necessary information to design several devices on tapered microstrip, with variation on the strip width and dielectric height, for (M)MIC and antennas applications. A good agreement was observed with the results available in the literature for tapered lines on isotropic substrates.     

Radiation and scattering characteristics of microstrip antennas onnormally biased ferrite substrates

Radiation and scattering characteristics of microstrip antennas and arrays printed on ferrite substrates with a normal magnetic bias field are described. The extra degree of freedom offered by the biased ferrite can be used to obtain a number of novel characteristics, including switchable and tunable circularly polarized radiation from a microstrip antenna having a single feed point, dynamic wide-angle impedance matching for phased arrays of microstrip antennas, and a switchable radar cross section reduction technique for microstrip antennas. Results are obtained from full-wave moment method solutions for single microstrip antennas and infinite arrays of microstrip antennas. A cavity model solution for a circular patch antenna on a biased ferrite substrate is also presented, to aid in understanding the operation of these antennas     

含有负参数媒质双层基底的宽带微带天线设计

将谐振腔引入微带结构,分析和设计了含有负参数媒质双层基底的微带天线.利用腔体内各本征模式频率参量的消除,此新型微带天线突破了传统的窄带局限.对于负参数媒质固有损耗所带来的天线性能的改变也进行了考虑.最后,将此设计应用于单负参数媒质双层基底微带天线中,同样获得了大幅度提高的带宽特性.     

Theory and analysis of differentially-driven microstrip antennas

This paper studies differentially-driven microstrip antennas. The theory of microstrip antennas based on the improved cavity model is expanded to analyze the input impedance and radiation characteristics of the differentially-driven microstrip antennas. The differentially-driven microstrip antennas were fabricated. Their performances were experimentally verified. Results show that the occurrence of resonance for the differentially-driven microstrip antennas also depends on the ratio of the separation /spl xi/ of the dual feeds to the free-space wavelength /spl lambda//sub o/. When the dual feeds are located far from each other /spl xi///spl lambda//sub o/>0.1, the resonance occurs, and the input resistance at resonance is rather large. However, when the dual feeds are located near to each other /spl xi///spl lambda//sub o/<0.1, the resonance does not occur, the input resistance is quite small, and the input impedance is inductive. Compared with single-ended microstrip antennas, the differentially-driven microstrip antennas have larger resonant resistance, similar co-polar radiation patterns, and lower cross-polar radiation component.     

Broad-band cavity-backed and capacitively probe-fed microstrippatch arrays

A hybrid full wave method for the analysis of probe-fed infinite phased arrays of single and stacked microstrip patches, backed by metallic cavities, is applied to investigate the combined utilization of the capacitive probe-feeding technique and the cavity enclosure of microstrip patches. The goal is to obtain broad-band microstrip antennas on thick substrates without the limitations due to the generation of surface waves of the conventional microstrip antennas on infinite substrates. A design procedure for the capacitive coupling is investigated and theoretical results for the active input impedance and radiation characteristics of different wide-band antenna designs are presented     

双频／双极化贴片天线的研究进展

本文报道了近年来双频／双极化贴片天线的研究进展。给出了一些新型的天线结构及其性能和应用。对微带天线的理论分析作了归纳     

Miniaturized high-temperature superconductor microstrip patchantenna

Experimental as well as computational results are presented for 2.4 GHz microstrip antennas which are miniaturized (total length, 6 mm) by both a new, stepped impedance patch shape and a relatively high substrate permittivity. The antennas investigated were fabricated from YBa₂Cu₃O_7-δ thin films epitaxially grown on single-crystalline LaAlO₃ substrates by pulsed excimer laser ablation or by high-pressure oxygen DC sputtering and, for comparison, from copper on the same substrate material. It is shown that the radiation efficiency of this antenna structure is only about 1% to 6% for copper at 77 K but is increased to values between 35% and 65% for HTS films. From experimental investigations of the power dependence of the antenna gain at 77 K, nonlinearities, especially a sharp drop at a current density of about 2×10⁶ A/cm², were observed     

Comparative study on the mutual coupling between different sized cylindrical dielectric resonators antennas and circular microstrip patch antennas

A systematic comparative study on the mutual coupling (S/sub 21/) between dielectric resonator antennas (DRAs) and microstrip patch antennas is presented. The mutual coupling between two cylindrical probe-fed DRAs is studied for different radius to height (a/L) ratios. It is found that the mutual coupling decreases with the radius to height ratio. Comparison between mutual coupling of probe-fed cylindrical DRAs and circular microstrip patch antennas with different dielectric substrates are also studied. The mutual coupling between DRAs is 2 dB stronger than between microstrip patch antennas when the patch is etched on a dielectric substrate of a dielectric constant close to the permittivity of the DRA. The mutual coupling of the circular patch antennas reduces with the dielectric constant of the substrate.