背腔式缝隙天线混合方法降耦研究

运用混合降耦方法,提出了一种简单但高效率的减小背腔式缝隙天线耦合的结构,通过放置两对称寄生单元和去介质的降耦方法,经点频优化,与无附加结构的天线相比,在反射系数小于-10dB 的1. 7% 带宽范围内(中心频率为12GHz)互耦降低了9. 7dB,天线的方向图得到了改善,端射方向的能量减小。在点频优化的基础上,通过带宽内的优化进一步改善了耦合性能,在反射系数小于-10dB 的2. 2%带宽范围内互耦降低了11. 5dB。该降耦方法结构简单、成本低、易加工。     

双L型背腔式圆极化缝隙天线的设计

针对新型室内嵌入式天线的应用前景,提出了一种新颖的双L型背腔式圆极化缝隙天线.该天线底面由两个对称的L型缝隙组成,顶层由微带馈线网络馈电.天线底部放置一个金属腔体,既适合嵌入式安装,便于与室内其他接口集成,同时减少了墙体对天线的影响,增强了天线的正向辐射.给出了天线的阻抗带宽、辐射方向图、增益以及圆极化率的仿真结果,并对天线的阻抗带宽进行了测量.结果表明,该天线针对900MHz频段的室内嵌入式应用有良好的性能.     

Investigation Into the Effects of the Patch-Type FSS Superstrate on the High-Gain Cavity Resonance Antenna Design

Results of modeling, design, simulation and fabrication are presented for a high-gain cavity resonance antenna (CRA), employing highly-reflective patch-type superstrates. In order to determine the resonant conditions, the antenna is first analyzed using the transverse equivalent network (TEN) model, as well as the well known simple ray-tracing method. Prior to that, a highly-reflective patch-type frequency selective surface (FSS) is designed in order to be employed as the superstrate layer of the CRA. Next, a 2.5-D full-wave analysis software package, based on the method of moments (ANSOFT Designer v4.0), is utilized to analyze the antenna structure. Using this full-wave analyzer, the input impedance properties of an actual antenna are investigated as well. Then, a 3-D full-wave analyzer, based on the finite element method (ANSOFT HFSS), is used to extract the directivity and radiation patterns of the CRA, taking into account the finiteness of the substrate, superstrate and ground plane. Some previously unaddressed issues, such as the effects of the FSS superstrate on the input impedance characteristics of the probe-fed microstrip patch antenna, acting as the excitation source of the CRA are also studied. The effects of the highly-reflective FSS superstrate size on the CRA directivity, and explicitly its aperture efficiency, are investigated as well. A comparative study is also performed between CRAs with patch-type FSS and high permittivity dielectric superstrates. Measurement results are provided to support the modelings and simulations.      

Development of a Cavity-Backed Broadband Circularly Polarized Slot/Strip Loop Antenna With a Simple Feeding Structure

A cavity-backed loop antenna is developed for producing broadband circularly polarized (CP) radiation. The antenna configuration consists of a slot loop and a strip loop. The slot loop radiates a CP wave at a lower frequency while the strip loop produces CP radiation at a higher frequency. A combination of the two frequencies leads to a bandwidth enhancement. The slot/strip loop antenna is fed by a single straight microstrip line. It is demonstrated that the cavity-backed slot/strip loop antenna can achieve an axial ratio (les 3 dB) bandwidth of 19% with good impedance matching. The antenna configuration is described and the operating principles for broadband circular polarization and impedance matching are analyzed. The antenna performance is confirmed by experimental results.     

Radiation Patterns of a Noise-Excited Thin Slot

Theoretical and experimental radiation patterns are given in spectral form for the thermal radiation from a cylindrical discharge column which is adjacent to a long thin slot in a metallic plane. A spatial distribution is predicted which exhibits interference minima and maxima when the length of the slot and the wavelength of the emission are the same order of magnitude. The analysis is based on Maxwell's equations and the Leontovich-Rytov distributed source generalization of Nyquist's noise formula. Fraunhofer pattern measurements are presented in which an argon source is used to excite slots of 7.3pi and 9.5pi radians in length. Data are also presented to show the effects of variations in the pressure and the dc current of the discharge. The pattern measuring apparatus is a Dicke radiometer, having the following characteristics: frequency 9200 Mc, bandwidth to the detector 16 mc, modulation frequency 1000 cps, and residual noise level 0.3 rms°K. An interference phenomenon is predicted by the theory and demonstrated by an experiment, even though the source excitation is spatially distributed and essentially uncorrelated in time and in space. The patterns are not even approximately Lambertian, e.g., a thin slot of 9.5pi radians exhibits a pattern having nine relative maxima in 180°, with the maximum emission at 63° from the normal.     

Rectangular Bars Coupled Through a Finite-Thickness Slot

A rigorous new solution, based on fringing capacitances and conformal mapping, is presented for the coupling problem in the parallel-coupled TEM transmission-line structure formed by two rectanguIar bars coupled through a rectangular slot, cut Iongitudinatly in a finite-thickness ground plane. The conformal mapping solution is summarized in Appendix I and is based on the procedure published by Getsinger [1]. Graphs of the capacitances needed to calculate the coupling for a given physicat geometry, without solving the complicated equations associated with the theoretical solution, are also presented. A measurement procedure and experimental results are presented which verify the accuracy of the theoretical coupling data.     

一种基于缝隙天线阻抗的带缝腔体谐振频率计算方法

电磁波经缝隙进入机箱腔体后,会在某些频率点形成驻波而发生电磁谐振,导致腔体屏蔽效能急剧下降.为快速准确预测谐振频率以指导屏蔽腔体设计,本文基于缝隙天线阻抗理论提出一种带缝腔体谐振频率的计算方法.将电磁场用自由空间和腔体格林函数表示,根据缝隙处的边界条件建立等效磁流源的积分方程.通过矩量法求解积分方程,计算出腔体输入阻抗.根据谐振发生时电抗为零或电阻最小,可从频率-阻抗曲线获得谐振频率.本文方法不仅能预测缝隙谐振和低阶模式腔体谐振,还能预测出高阶谐振.与实验和CST仿真结果对比验证了本文方法的准确性及快速性.最后用本文方法分析了腔体和缝隙尺寸以及缝隙位置对谐振频率的影响.     

Excitation of a Coaxial Line Through a Transverse Slot

A rocket with removed access plate is simulated by a section of coaxial transmission line with a transverse elliptical slot cut in its sheath. The internal circuit consists of two arbitrary impedances in series with the inner conductor at its ends. The object is to find the currents in these impedances when the cylinder is illuminated from the outside by an electromagneticfield that enters the aperture and excites the internal circuit. The problem is solved by application of the reciprocal theorem. The current in a dipole antenna is determined when this is inthe far field maintained by the slotted coaxial line when driven by a generator in series with one of the load impedances. The field in the aperture is replaced by equivalent electric and magnetic dipoles. The reciprocal theorem gives the current in the load impedance when the distantdipole is driven. A numerical example is given.     

波导窄边缝隙阵列天线的分析与设计

波导窄边缝隙阵列天线由于效率高、功率容量大、稳定性好及副瓣电平低等特性,在雷达体制上使用广泛。对于单一波导窄边缝的隙线阵,根据设计指标,首先分析其理论模型并给定理想的设计参数,再利用Ansoft公司的HFSS软件的参数扫描及优化功能,通过局部调整设计参数就可以方便地得到缝隙的谐振结构。利用这种设计方法可以快速得出所需要的低副瓣窄边波导缝隙阵列天线。     

新型X波段波导缝隙阵列天线的设计

为了克服传统波导缝隙阵列天线重量大、副瓣偏高等问题,提出一种小型化、低副瓣X波段波导缝隙阵列天线的设计方法。首先采用高斯分布实现其幅度加权,快速完成低副瓣波导缝隙阵列天线的设计;然后结合HFSS 软件对传统压缩波导的窄边尺寸进行优化,减小窄边尺寸;同时采用3D 打印技术制造ABS 塑料波导缝隙框架和金属电镀工艺实现天线的加工,通过仿真分析和实物加工测试验证了所设计天线的有效性。所设计的天线方位面副瓣电平可达到-25 dB 以下,重量从25 kg 减小到2.5 kg,减重比达到了90%。最后,详细分析了不同金属电镀层厚度对天线性能的影响。     

Radiation Characteristics of Bent-Wire Antennas

A mathematical model, which predicts the far-field power pattern of a wire antenna bent in one plane, is developed, and the classical approximation of a sinusoidal current distribution along the arc length is employed, neglecting all end and mutual coupling effects. General expressions for the complex Poynting vector, electric- and magnetic-field intensities are also derived in terms of the retarded vector potential. Although the theory for parabolically-bent antennas compares favorably with experiment, it is shown that the agreement is more favorable when the current distribution is computed by the method of moments. In contrast to the figure-eight ?-plane pattern of the conventional straight dipole, the circularly and parabolically bent antennas operating at the first resonance are shown to have radiation patterns approaching omnidirection as the bending curvature is optimized, thus lending themselves to use as replacements for many common dipole applications for gain standards, field probing, reflector feeds, as well as mobile and broadcast antennas.     

Analysis of Planar Ultrawideband Antennas With On-Ground Slot Band-Notched Structures

Planar ultrawideband (UWB) antennas with on-ground band-notched structures are studied in this paper. Two different slot resonators, which feature quarter-wavelength and half-wavelength configurations, are embedded into the arc shaped ground plane of the circular disk patch antennas in order to obtain the desired band-rejection around 5.8 GHz. Their principles and characteristics are analyzed and compared in detail providing designers with in-depth understanding and useful design information. By choosing the quarter-wavelength slot resonator, the first spurious stopband can be pushed up to 3 $f _{0}$ ($f _{0}$ stands for the center frequency of the notch) and this antenna retains a super wide working band which spans from 1.62 GHz to 17.43 GHz. Performance in both the frequency domain and time domain for this antenna has been investigated carefully. The transmission response of a transceiving antenna system and their corresponding transient analysis are discussed at the end of this paper.      

MEMS开关可重构矩形缝隙环天线的设计

提出一种基于MEMS开关的可重构矩形缝隙环天线设计.其关键部件之一是射频微波MEMS开关,选取了接触式MEMS开关.该天线为用共面波导馈电的多频率可重构天线,通过多个MEMS开关来改变矩形缝隙环天线的拓扑结构,按照一定的规则控制开关可实现多频率可重构.其结构简单,剖面低,易于与电路集成.     

圆形波导中线天线的辐射和互阻抗＊

本文采用并矢格林函数,场量变换和反应原理讨论了圆形波导中线天线的辐射和互耦合,给出了场强和互阻抗的普遍公式。波导是半无限长的,端面反射系数为Γ.天线的长度、馈电点和它们在波导中的位置都是任意的。作为例子,我们给出了四种特殊情况下的互阻抗公式,并进行了讨论。     

Design of 45-degree Linearly Polarized Substrate Integrated Waveguide-fed Slot Array Antennas

This paper presents a method of designing substrate integrated waveguide-fed (SIW-fed) slot array antennas. The design theory is based on the circuit model of slot and via as well as the reflection canceling. To prove the feasibility of this method, a 10-element K-band SIW-fed 45-degree linearly polarized slot array antenna with uniform power distribution is designed. By full-wave simulation, the antenna has a good impedance bandwidth of 7.5% and uniform power distribution. Besides, a maximum gain of 15.3dBi is obtained in the broadside and the cross polarization is suppressed below -23.5dB in the boresight. This type of SIW-fed slot array antennas can be a good candidate for microwave and millimeter-wave applications, especially for auto-motive collision-avoidance radar systems.     

基于缝隙效应的几种宽带微带天线的设计

利用缝隙对天线带宽的影响设计了四种宽带微带天线。主要研究了缝隙的形状和大小以及与馈电的距离对天线带宽的影响。首先,宽缝机构可以较大的展宽天线的频带,如果同时配合在贴片上适当的开缝,带宽将进一步展宽;其次,相同缝隙结构的嵌套可使天线同时谐振在很多的频率,从而增加带宽。设计表明这几种微带天线都具有宽带特性,尤其是前两种天线具有超宽带（UWB）的特性,后两种天线的带宽也达到了48％以上。     

Electromagnetic Radiation by Antennas of Arbitrary Shape in a Layered Spherical Media

A unified method of moments model is developed for the analysis of arbitrarily shaped antennas that are radiating next to a multilayered dielectric sphere. The curvilinear Rao-Wilton-Glisson triangular basis functions and dyadic Green's functions have been used in the model. Antennas of various geometries including spherical, circular and rectangular microstrip antennas as well as hemispherical dielectric resonators have been modeled. Input impedance and radiation pattern results are presented and shown to be in good agreement with published data.      

表面波放电狭缝天线辐射电磁场的三维数值分析

针对平板型表面波放电等离子体源,建立了表面波放电狭缝天线辐射电磁波模型,对狭缝天线辐射电磁场分布进行了三维数值计算,并与表面波电磁场进行对比分析,讨论了平板型表面波放电机理。结果表明:整个狭缝天线阵激发的电磁场是每个狭缝天线激发电磁场的线性叠加;狭缝天线阵直接激发的电磁场强度在临近波导壁面处很大,并且随着空间距离的增大迅速衰减;狭缝天线阵直接激发和表面波的电场均远大于各自的磁场,分析电、磁场对带电粒子的力作用时可以忽略磁场力的作用;表面波电磁场远大于狭缝天线阵直接辐射的电磁场,强电磁场范围也远大于狭缝天线阵直接激发的强电磁场范围,等离子体有增强电磁场强度、扩大强电磁场范围的作用。     

基于基片集成波导馈电的Ka波段渐变缝隙天线设计

在被动毫米波 (PMMW) 成像焦平面阵列 (FPA) 馈源的天线中,直线渐变缝隙天线 (LTSA) 相对于传统的喇叭天线、介质棒天线具有其独特的优势。该文优化设计了一种新型的对跖直线渐变缝隙天线 (ALTSA),通过加载超材料结构使天线的增益得到了改善,天线采用基片集成波导 (SIW) 技术进行馈电。通过仿真与测试分析,该天线在较宽的频带内具有良好的阻抗特性、较低的副瓣电平及较高且平稳的增益,所设计的天线具有较小的口径宽度,在焦平面中易于组成较为密集的馈源阵列,以提高被动毫米波成像的空间分辨率。

     

馈线不对称性对多层超宽带缝隙天线性能的

利用等效原理和电-磁组合振子理论简析了具有低交叉极化特性的多层超宽带对跖缝隙天线的工作原理.通过数值仿真,详细研究了馈线不对称性对带内匹配、交叉极化特性和天线增益的影响.结果表明,馈线不对称性对超宽带天线的带内辐射特性有一定的影响.所研究的工作将为多层超宽带对跖缝隙天线的优化设计与实现提供理论依据.