平板裂缝天线阻抗匹配设计的研究

本文对平板裂缝天线阻抗匹配设计方法进行了讨论。采用微波网络理论,在内部馈电情况下,分别对一条辐射波导上辐射裂缝的归一化导纳和为２的匹配设计准则,以及对串一并形式馈电装置,对耦合裂缝的归一化阻抗和为２的匹配设计准则进行了证明。按照同样方法,对串一串、并一串形式的馈电装置,导出了新的耦合裂缝匹配设计准则。     

Integral equation analysis of a sheet impedance coated window slotantenna

Presents an integral equation and method of moments analysis of a window slot antenna. The antenna is modeled by a sheet admittance coated rectangular aperture in an infinite ground plane. It is shown that the sheet admittance coated aperture is complementary to a sheet impedance plate, which permits the window slot antenna to be analyzed with existing computer programs. Numerical results are compared with measurements for input impedance and radiation efficiency     

Dielectric image line groove antennas for millimeter waves, Part I: Theoretical background

Dielectric image line groove antennas are very useful for the application in the millimeter-wave region. In this first part of a two-part paper, three different types of groove discontinuities under a dielectric image line for application in millimeterwave antennas are investigated: the equivalent circuits of 1) a slot discontinuity in a metallic ground plane and 2) a slot discontinuity in the metallization of a substrate material under a dielectric image line are derived theoretically using an approximation for the electromagnetic fields of the slots. 3)The equivalent circuit of cylindrical holes in a metallic ground plane under a dielectric image line is derived from measurements. The results are used to synthesize millimeterwave dielectric image line antenna arrays as described in part II of the paper.     

A waveguide transverse slot for array applications

The characteristics of a radiating rectangular transverse slot in a rectangular waveguide have been studied. A moment method solution is used with entire basis expansion and testing functions (Galerkin) including the effect of wall thickness. The results are presented in terms of normalized resistance and reactance versus slot length and frequency. Excellent agreement with a previous pulse basis solution is found, as well as with measured data. An array of resonantly spaced transverse slots radiates large grating lobes. A spatial filter using baffles to suppress the grating lobes is described, suppressed. The effect of the baffles on the transverse slot impedance is analyzed for the case of baffles with infinite height     

Radiation from a slot in an impedance surface

The effects of a lossy-ground plane on the radiation from a slot are analyzed by using a Green's function of an impedance surface. Numerical results of the radiation field, radiated power, and loss power are presented for various lossy ground planes. In particular, the radiation field and the radiated power from a short slot are given by simple closed expressions. The analytical model of a slot in an impedance surface is validated by radiation field measurements     

Theoretical and experimental study of the input impedance of thecylindrical cavity-backed rectangular slot antennas

The authors study the input impedance of a cylindrical cavity-backed slot antenna based on mode matching and the complex Poynting theorem. Two cavity-backed slot antennas were fabricated to verify the theory. The numerical results agree very well with measurements. Two resonant frequencies were found from the input impedance. One resonant frequency is attributed to the rectangular slot and the other is due to the cavity. The slot length controls the first resonant frequency and has a much stronger effect on the input impedance at the antenna operating frequency as compared with the cavity length     

Theory and experiment of the hemispherical cavity-backed slotantenna

The hemispherical cavity-backed slot antenna is studied theoretically and experimentally. The exact magnetic field Green's function of the cavity is derived rigorously and expressed in a form convenient for numerical computation. The moment method is used to find the equivalent magnetic current in the slot and, hence, the input impedance of the antenna configuration. The effects of the cavity size, of the slot length, and of the slot offset on the input impedance are studied and very good agreement between theory and experiment is obtained. The variation of the magnetic current around the slot and cavity resonances are discussed. Comparisons between the rigorous solution and the single-mode theory are given and the limitation of the single-mode theory is discussed     

Theory and experiment of the cavity-backed slot-excited dielectricresonator antenna

A slot-excited hemispherical dielectric resonator antenna backed by a rectangular cavity is studied theoretically and experimentally. The magnetic-type dyadic Green's function for the rectangular cavity is derived using the mode-matching method. An integral equation for the equivalent magnetic current is obtained by enforcing the boundary condition across the slot. The moment method with the Galerkin's procedure is then used to find the magnetic current in the slot and, hence, the input impedance of the antenna. Measurements were carried out to verify the theory and good agreement is obtained. The effects of the slot inclination angle, of the slot offset, and of the cavity size on the input impedance are discussed     

Equivalent surface impedance of an infinite periodic array of slot impedance loads based on a semicylinder cavity

A problem of finding the equivalent surface impedance of an infinite periodic array of slot impedance loads based on a semicylinder cavity. The problem is solved by the integral-equation method. As the numerical method for solving the integral equation, the Krylov-Bogoliubov method is used. The results of the numerical experiment are presented in the form of dependences of the impedance on the cavity radius, slot width, conductor width, and angle of electromagnetic-wave incidence. The angular dependences of the impedance are compared to the earlier results obtained for an array of rectangular grooves and a single impedance load based on a semicylinder cavity.     

Analysis of hemispherical cavity-backed slot antenna

The input impedance of the hemispherical cavity-backed slot antenna is investigated theoretically and experimentally. The mode-matching method and moment method are used to find the Green's function of the cavity and the equivalent magnetic current of the slot, respectively. The effects of slot length and cavity radius on the input impedance are studied     

波导宽边辐射缝隙的全波分析

使用时域有限差分法 (FDTD法 )对矩形波导上单个辐射缝隙的特性进行了严格分析 ,得出在不同缝隙偏置、缝隙宽度和波导壁厚条件下缝隙的谐振长度、散射参数以及等效归一化导纳等特性 ,并对‘谐振状态’的定义做了讨论 ,为高性能波导缝隙天线阵的设计提供参考     

Analysis and design of coplanar waveguide-fed slot antenna array

A method for analyzing and designing the slot antenna array excited by a coplanar waveguide (CPW) is presented. The slots are etched on the conducting plane of the CPW and placed in the direction perpendicular to the transmission line. Moment-method analysis and matrix-pencil approach are adopted to calculate the scattering parameters and hence the self-admittance of each slot. The mutual admittances between the slots are calculated from the formulas derived for the complementary strip dipoles based on the reciprocity theorem and via Booker's relation. Then the transmission line theory is used to calculate the input impedance of the array, and an iterative process is employed to obtain a matched design for a desired slot-voltage distribution. A four-element slot array is fabricated and measured using this design procedure. Calculated results are in good agreement with measurements     

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.     

可见光与红外图像增强融合算法研究

提出了自适应图像增强算法，用于可见光和红外图像的融合。首先对输入的可见光图像和红外图像进行自适应增强，然后采用基于图像空间能量窗及归一化互相关测度构造融合图像，利用图像的信息熵评估算法的融合效果，最后给出了一组可见光和红外图像融合的试验结果，表明该算法十分有效，融合图像有丰富的互补信息，有利于人眼观察和目标识别。     

Analysis of aperture-coupled microstrip antenna using thesegmentation method

The authors present an original analysis of an aperture-coupled microstrip antenna. The theory is based on the segmentation method, which considers the patch as a multiport network whose impedance matrix is deduced from a hybrid matrix, and the use of analytical expressions of the cavity admittance at the slot centre. The theory is presented for the first time, and the theoretical results are in good agreement with previous published measurements     

基于自适应加权的超光谱图像分类方法

为了进一步提高已有的加权超光谱图像分类方法的识别性能,以支持向量机(SVM)作为基本框架,结合超光谱图像的谱间与空域信息,提出了一种自适应加权的超光谱图像分类方法.所提方法的自适应权值是由两部分构成,即改进的具有归一化取值的互信息(MI)与一定量的归一化图像标准方差之和,不仅考虑到了超光谱图像的谱间信息对分类会产生的作...     

一种计算波导耦合缝隙有源阻抗的方法

 针对耦合波导缝隙馈电时波导内电磁场复杂且不利于工程应用的问题,提出一种耦合波导缝隙有源阻抗计算方法.根据耦合波导端口处S矩阵与端口处输入阻抗矩阵的关系建立关于耦合波导缝隙有源阻抗方程,且采用牛顿法求解此非线性高阶分式方程,得到计及缝隙间互耦的耦合波导缝隙有源阻抗值.通过提取HFSS软件中耦合缝隙馈电的裂缝天线S矩阵进行仿真计算,结果表明该计算耦合缝隙有源阻抗的方法是有效的且适合大型裂缝天线耦合裂缝设计.     

X波段带线波导缝隙天线阻抗的精确测量

本文用等效短路面代替短路活塞的方法,实现短路法测量两端口网络的S参数;用不等间距的有限数据点,通过计算机统计回归解处理数据,得到了两端口网络S参数的准确值,从而可消除同轴一带线波导转换接头的影响,在X波段精确地测量了带线波导缝隙天线的阻抗及其随结构的变化。这种方法同样适用于类似结构的微带天线的阻抗测量。     

A mathematical model for the impedance of the cavity-backed slot antenna

A mathematical model is derived that relates the impedance of a cavity-backed slot antenna to that of an identical slot which is free to radiate on both sides of a large ground plane. The model, which utilizes empirical constants from a previous experimental investigation, provides a continuously variable function of frequency and cavity depth for the impedance of a cavity-backed slot of fixed length and cavity cross section. This function is then compared with previously found experimental values and two theoretical solutions, one using a variational method and the other using the complex Poynting theorem.     

Full-wave analysis of a two slot microstrip filter using a newalgorithm for computation of the spectral integrals

An integral equation is formulated in the spectral domain for a two slot microstrip filter using the exact Green's function for the grounded dielectric substrate. Using a moment method (MM) procedure, the integral equation has been discretized. The elements of the impedance matrix and the excitation vector are given by two dimensional Sommerfeld-type integrals in closed form. An efficient and accurate numerical integration scheme for computation of the elements is presented. The S parameters obtained from the MM procedure have been found to be in excellent agreement with measurements