探针馈电印刷线天线的矩量法分析——（Ⅱ）多臂天线

通过应用模式分解法,本文将单臂探针馈电印刷线天线的分析方法推广到具有旋转对称性的任意多臂探针馈电印刷线天线的分析计算。首先给出探针馈电N臂印刷线天线的电流积分方程、矩量方程及远区辐射场计算公式;通过一个中心馈电螺旋天线的分析计算验证方法和计算程序的正确性;设计出具有良好圆极化特性的开口双圆环印刷线天线;最后分析了一探针馈电四臂印刷螺旋天线的辐射特性。     

基于RWG法分析考虑互耦的阵列方向特性

RWG(Rao-Wihon-Glisson)三角基函数为基础的矩量法是分析偶极子天线阵列的有效方法.通过求解阻抗矩阵和矩量方程,可分析天线互耦特性.偶极子模型法是将包含2个三角的RWG边元的表面电流分布用具有等效偶极子矩量的无穷小偶极子代替来求解天线辐射场.运用偶极子模型法替代传统的电场积分法来求解阵列方向图,对考虑互耦偶极子阵列的方向图进行了仿真,并对比分析了和理想情况下的差异.同通常的电场积分方程法相比,此方法具有计算简便,物理意义明确,可分析任意形状的天线等特点.     

基于不同积分方程的线天线矩量法分析

首先扼要地阐述矩量法(MoM)分析天线的一般概念和基本思想，然后分别采用3种不同的积分方程对线天线进行矩量法分析，并与解析计算结果进行比较，两者的一致性说明了计算结果的正确性。     

一种宽带圆形阵列天线的矩量法分析

利用矩量法对宽带圆形阵列天线的互耦特性进行分析。为了对较粗线天线进行精确分析,矩量法采用正弦差值基函数与点配法,并采用全域线天线积分核计算Pocklington方程,得到天线的广义散射矩阵,实现互耦分析。为了验证其计算结果,对所设计阵列天线进行了CST软件仿真和实验测试。仿真和测试结果表明：矩量法计算与CST仿真结果基本相同,实验测试结果在主波束方向、主波瓣宽度、副瓣电平等特性上与计算和仿真结果近似一致,说明此方法能够有效的对宽带阵列天线进行互耦分析。     

线天线的小波矩阵变换法求解

本文研究天线的小波矩阵变换法求解。首先采用三角插值基函数和线天线的一种精确计算模型,利用矩量法得到矩阵方程,然后通过Daubechies离散小波变换进行快速求解。计算结果表明,该方法能够使阻抗矩阵稀疏化,从而提高了求解速度。     

近地半菱形天线地波场强的计算

针对平面镜像法不能准确计算近地复杂线天线地波场强的问题,提出将平面分层媒质的格林函数法和前苏联学者Fock地波留数级数计算模型相结合,并以近地半菱形天线为例来进行计算.首先,推导了半空间并矢格林函数的空域形式,并采用加强离散复镜像法对表达式中Sommerfeld积分进行计算验证,之后采用矩量法求解半菱形天线的电流;其次,给出了偶极子在球形表面的Fock留数级数波场模型,并把模式方程变换为微分方程进行求解,考虑到大气的指数型模型,采用等效地球半径对偶极子地波场进行计算并同ITU-R推荐的指数型地波计算软件GRWAVE的计算结果进行对比验证.最后,推导了地球表面任意方向偶极子的地波场计算表达式,并根据求取的半菱形天线电流对地波场进行计算.提供了一种近地复杂线天线地波场的求解思路.     

细螺旋天线的近场分析

用矩量法得到螺旋天线的电流分布,并在此基础上进一步确定了螺旋天线的近场分布.提出了用来度量线天线近场耦合强度的一种方法.针对螺旋天线的近场计算并描绘出了耦合度随收发间距变化的曲线图.     

双臂圆锥对数螺旋天线的矩量法分析

用矩量法将Nakano方程化为矩阵方程,给出了广义阻抗矩阵、电压矩阵的表达式,并以双臂圆锥对数螺旋天线为例,研究了天线上的电流分布和辐射特性.此方法精度高,编程容易,解决了任意形状的线天线的分析问题.     

双位积分方程在分析地面上线天线中的应用

导出了任意取向线天线在基于sommerfeld积分的反射系数近似条件下的双位积分方程,采用多项式基函数和点匹配的矩量法对该方程求解,给出阻抗元素计算的一般表达式.计算结果表明了该方法的有效性.     

矩量法结合AWE技术分析阵列天线

从工程角度出发,应用AWE技术结合矩量法分析阵列天线的辐射特性。首先采用投量法求解阵列天线的电场积分方程,得到某一频率点的电流分布和输入阻抗;然后通过Pade逼近获得任意频率的导纳,从而得到阵列天线的频率响应;最后针对一六单元八木阵列天线进行分析,给出了天线上的电流分布、输入导纳以及辐射方向图,并对AWE/MOM与MOM的计算结果进行比较,两者比较接近,但AWE/MOM可大大加快计算速度。     

Numerical analysis of arbitrarily shaped probe-excited single-armprinted wire antennas

A general integral equation technique is described for analysis of an arbitrarily shaped single-arm printed wire antenna excited through a vertical probe. A unified current integral equation is formulated on the basis of dyadic Green's functions and the reciprocity theorem. The current distribution is obtained by using a parametric moment method in which parameter segments are adopted for the printed wire instead of the commonly employed wire length segments. The radiation field solution involving both the printed antenna and vertical probe is also presented. The validity of the formulation is verified by comparing the numerically obtained input impedance and radiation patterns for a linear antenna and a meander antenna with measured data. A circular open loop and an Archimedian spiral are investigated to illustrate the applicability of the present technique     

Accurate characterization of planar printed antennas usingfinite-difference time-domain method

The finite-difference-time-domain method (FD-TD) is used to characterize complex planar printed antennas with various feed structures, which include coaxial probe feed, microstrip line feed, and aperture coupled feed structures. A coaxial probe model is developed by using a three-dimensional FD-TD technique. This model is shown to be an efficient and accurate tool for modeling coaxial line fed structures. A novel use of a dispersive absorbing boundary condition is presented for a printed antenna with a high dielectric constant. All the numerical results obtained by the FD-TD method are compared with experimental results, and the comparison shows excellent agreement over a wide frequency band     

A broad-band U-slot rectangular patch antenna on a microwavesubstrate

A broad-band U-slot rectangular patch antenna printed on a microwave substrate is investigated. The dielectric constant of the substrate is 2.33. The antenna is fed by a coaxial probe. The characteristics of the U-slot patch antenna are analyzed by the finite-difference time-domain (FDTD) method. Experimental results for the input impedance and radiation patterns are obtained and compared with numerical results. The maximum impedance bandwidth achieved is 27%, centered around 3.1 GHz, with good pattern characteristics     

MAR analysis of a spherical-circular printed antenna with finite ground excited by an axially symmetric probe

The paper deals with an accurate mathematical and numerical analysis of a spherical-circular antenna printed over a coaxial spherical-circular ground conductor. A coaxial probe simulated by a radial driving current placed between two conductors excites the antenna. Consideration is done in terms of the spherical vector wave function expansions of the field in each partial domain. The problem is cast into a coupled set of the dual-series equations for the expansion coefficients, and then to an infinite-matrix equation having favorable features. This is achieved by following the Method of Analytical Regularization developed earlier for the analysis of spherical reflectors.     

Very compact double C-patch antenna

A miniaturised C-patch antenna excited by means of a coaxial probe is described. The antenna consists of two stacked C-shaped elements connected together with a vertical conducting plane. The antenna is designed on an air substrate and offers attractive dimensions, being five times lower than those of a conventional half wavelength microstrip patch antenna operating at the same frequency. A 10 dB bandwidth of 3% is obtained. The voltage standing wave ratio, radiation patterns, and electric surface current density are presented     

Input impedance of a probe-fed circular microstrip antenna with thick substrate

A method of computing the input impedance for the probe fed circular microstrip antenna with thick dielectric substrate is presented. Utilizing the framework of the cavity model, the fields under the microstrip patch are expanded in a set of modes satisfying the boundary conditions on the eccentrically located probe, as well as on the cavity magnetic wall. A mode-matching technique is used to solve for the electric field at the junction between the cavity and the coaxial feed cable. The reflection coefficient of the transverse electromagnetic (TEM) mode incident in the coaxial cable is determined, from which the input impedance of the antenna is computed. Measured data are presented to verify the theoretical calculations. Results of the computation of various losses for the circular printed antenna as a function of substrate thickness are also included.     

Rigorous Analysis of Rectangular Dielectric Resonator Antenna With a Finite Ground Plane

A probe-fed rectangular dielectric resonator antenna (RDRA) placed on a finite ground plane is numerically investigated using method of moments (MoM). The whole structure of the antenna is exactly modeled in our simulation. The feed probe, coaxial cable and ground plane are modeled as surface electric currents, while the dielectric resonator (DR) and the internal dielectric of coaxial cable is modeled as volume polarization currents. Each of the objects is treated as a set of combined field integral equations. The associated couplings are then formulated with sets of integral equations. The coupled integral equations are solved using MoM in spatial domain. The effects of ground plane size, air gap between dielectric resonator and ground plane, probe length, and position on the radiation performance of the antenna including resonant frequency, input impedance, radiation patterns, and bandwidth are investigated. The results obtained for the antenna parameters based on the MoM investigation shows that there is a close agreement with those obtained by measurement. Moreover it is shown that the MoM results are more accurate than other simulation results using software package such as High Frequency Structure Simulator (HFSS).      

Covert dual-band wearable button antenna

A novel dual-band antenna for wearable WLAN computing applications is introduced. This antenna comprises three discs and a coaxial post. Its appearance is of a standard metal button of the type used in denim jeans. The antenna is easily disguised and less sensitive to clothing than printed patches, which use the textile fabric as a substrate or superstrate. The antenna requires no external matching circuitry and operates at 2400 and 5200 MHz. The radiation patterns are omnidirectional around the central post of the antenna.     

Analysis of linear coaxial antennas

Two types of linear coaxial antennas, coaxial-colinear antennas, and slotted coaxial antennas are studied to check the possibility of using them as the base-station antenna in personal communication systems. The slot voltages and input impedance of linear coaxial antennas are obtained by using a transmission-line analysis where the radiation effect is accounted by a shunt and a serial admittance, respectively. The current distribution is obtained by solving an integral equation using the method of moments. The radiation pattern and directivity are then obtained from the current distribution and the reflection coefficient inside the coaxial cable. Factors analyzed include frequency, coaxial filling permittivity and segment number     

Analysis of dielectric-resonator antennas with emphasis onhemispherical structures

An overview is given for the development of dielectric-resonator antennas. A detailed analysis and study of the hemispherical structure, excited by a coaxial probe or a slot aperture, is then given, using the dyadic Green's functions pertaining to an electric-current source or a magnetic-current source, located in a dielectric sphere. The integral equation for a hemispherical dielectric-resonator antenna (DRA), excited by either a coaxial probe or a slot aperture, is obtained. The integral equation is solved using the method of moments. The antenna characteristics, such as input impedance, radiation patterns, directivity, and efficiency, are computed numerically, around the resonant frequency of the TE₁₁₁ mode (the HEM₁₁ mode for cylindrical coordinates). The computed input impedance is compared with numerical and experimental data available in the literature