介质平面上高频单极天线特性分析

该文用时域有限差分法(Finite Difference Time Domain,FDTD)计算介质平面上单极天线的阻抗特性。用FDTD法计算天线的辐射特性可以使用不同的激励方式,文章比较了采用不同激励方式时,天线的输入阻抗。文章的主要内容是将表面阻抗法用于FDTD中,计算架设在介质平面上单极天线的辐射特性,并用FDTD法计算了介质平面上铺设不同尺寸的导体平面时,天线的阻抗特性。     

基于矩量法对导体板上单极天线特性研究

利用矩量法对有限大导体板上单极天线的阻抗特性进行了研究。基于Pocklington积分方程和Galerkin法，采用分域基正弦函数展开模式，得出了有限尺寸导体板上单极天线的电流分布和输入阻抗，并对单极天线在不同长度及不同导体板上的情况进行了研究。结果表明，单极天线的长度及导体板的形状及大小在一定程度上影响了单极天线的特性。     

一种时间序列预测方法在二维时域有限差分法中的应用

本文将一种时间序列预测方法与二维时域有限差分（ＦＤＴＤ）法相结合,并应用均匀微波平面传输线的特性参数计算,该混合方法特别适用于尺寸很细微的ＭＭＩＣ传输线,而且可以精确地计算非理想导体的损耗。与传统的ＦＤＴＤ法相比,大大节约了计算时间,提高了效率。计算结果与测量非常一致。     

基于矩量法对一种手机天线的特性分析

本文基于矩量法，对一种便携式手机天线的特性进行了研究，利用Pocklington积分方程和Galerkin法，采用分域基函数展开模式，得出了矩形导电机壳及单极天线上的电流分布和输入阻抗，并对几种不同尺寸导电机壳上的天线特性进行了分析。计算结果表明导电机壳尺寸在很大程度上影响天线的性能，合理选择导电机壳尺寸可有效调节便携式手机天线的性能。     

模式匹配分析有限圆盘地面单极天线

本文给出了一种严格分析有限尺寸圆盘地面单极天线的新方法－模式匹配法。该方法通过在天线上、下两边平行放置两个无限大良导电平面,以及合理划分区域,使得每个分区中的场分量能够采用柱谐展开式解析表示,且展开系数由导体表面边界条件及分区交界处场分量连续条件加以确定。在此基础上,进一步分析天线的输入阻抗等电性能。计算结果表明：对不同尺寸圆盘地面单极子天线,理论分析与文献中的实验结果均十分吻合。同时,由于场量的解析表示,使得计算速度较快。     

模式匹配法分析有限圆盘地面单极天线

本文给出了一种严格分析有限尺寸圆盘地面单极天线的新方法———模式匹配法 .该方法通过在天线上、下两边平行放置两个无限大良导电平面 ,以及合理划分区域 ,使得每个分区中的场分量能够采用柱谐展开式解析表示 ,且展开系数由导体表面边界条件及分区交界处场分量连续条件加以确定 .在此基础上 ,进一步分析天线的输入阻抗等电性能 .计算结果表明 :对不同尺寸圆盘地面单极子天线 ,理论分析与文献中的实验结果均十分吻合 .同时 ,由于场量的解析表示 ,使得计算速度较快     

非正交FD—TD法在二维涂敷导体TM散射问题中的应用

本文全面介绍了非正交ＦＤ－ＴＤ方法的基本原理，推导出了其稳定条件和数值色散方程，并对其数值色散特性进行了详细分析研究。用非正交ＦＤ－ＴＤ方法在正弦波激励下对无限长三角形导体柱ＴＭ散射电流进行了计算，与矩量法结果基本吻合，证明了其有效性。在此基础上对涂敷多边形导体柱的ＴＭ散射问题进行了计算，得出远区单站ＲＣＳ结果，同时为了比较给出了分别用非正交ＦＤ－ＴＤ法和等效源法计算涂敷方形导体柱的散射场分布的结     

改进的FD—TD法分析二维理想导体TM近区散射问题

本文针对一般ＦＤ－ＴＤ方法分析计算二维理想导体散射问题所遇到散射体边角处难以精确处理的缺点进行了改进。将边角处总场近似解析解直接引入ＦＤ－ＴＤ法差分公式，得到了有关修正系数，为了检验此方法的有效性，有无限长导体方柱为例分别用一般ＦＤ－ＴＤ法和本文的ＦＤ－ＴＤ方法进行了分析研究，并与ＭＯＭ法进行了比较，所得结果说明改进后的ＦＤ－ＴＤ方法对分析计算导体边角附近电流分布特性是较有效的。     

平板宽带单极与偶极天线的全波分析

采用时域有限差分法（FDTD）计算圆盘天线及宽带变形vivaldi天线的输入阻抗及方向图。利用镜像原理得到三角形单极、圆盘单极天线的输入阻抗。采取激励源区的准静态模型在保证精度的同时又无须将复杂的具体馈电结构建模，三角形单极天线和圆盘单极天线的计算结果与有关文献的比较验证了该方法具有准确、实用性强等优点，对宽带变形vivaldi天线FDTD分析得到电流分布及输入阻抗，经傅立叶变换由近场值得到天线远场方向图，结果表明变形vivaldi天线具有输入阻抗和方向图的宽带特性。     

任意截面导体柱电磁散射特性的时域分析

本文采用共形网格的ＦＤＴＤ法对任意截面导体柱的电磁散射特性进行了分析。首先采用广义环路积分法导出共形网格上的时域有限差分方程,然后针对共形网格导出其一阶和二阶吸收边界条件。这种吸收边界条件在曲率半径趋于无穷大时分别退化为一阶和二阶Ｍｕｒ 吸收边界条件。由于采用共形网格,网格节点数远少于普通ＦＤＴＤ法中的节点数,从而大大节省了计算时间和存储空间。在时谐平面波和高斯脉冲激励下,首先计算了导体柱表面的时域感应电流,然后运用Ｆｏｕｒｉｅｒ变换计算导体柱的ＲＣＳ,其结果与其它文献结果一致。     

Input impedance, radiation pattern, and radar cross section ofspiral antennas using FDTD

A finite-difference time-domain (FDTD) analysis of spiral antennas is performed to calculate input impedance, antenna gain, and scattering. A semicircular spiral mounted on a dielectric substrate was simulated for computing the input impedance versus frequency. The gain and scattering computations were performed on a square Archimedean spiral mounted in a ground plane with a cavity backing. Total-field FDTD calculations are used to compute the impedance and gain patterns, while a specially modified scattered-field approach for aperture antennas in infinite ground planes is used for the scattering results. Comparisons are made with published impedance measurements and gain and scattering calculations done with a finite element method. Good results were obtained for impedance, radiation, and scattering     

Numerical analysis of two-arm spiral antennas printed on afinite-size dielectric substrate

A two-arm spiral antenna (SA) printed on a dielectric substrate backed by a conducting plane is analyzed under the condition that the dielectric substrate has a finite side length of L. The analysis is performed using the finite-difference time-domain (FDTD) method. The computation space for the FDTD method is reduced to one-half of the full computation space by virtue of the antenna arm symmetry with respect to the feed point. The numerical evaluations for the radiation characteristics are briefly described, and the SA_∞ (the spiral antenna with a conducting plane of infinite extent) is analyzed. It is found that the input impedance remains constant with side length L⩾0.8 wavelength in this analysis model. It is also found that as L increases, the axial ratio improves with the gain remaining relatively constant (the gain variation is within 1 dB). The SA_finite (the spiral with a conducting plane having the same finite size as the dielectric substrate) is also analyzed. It is revealed that the effects of L on the axial ratio and gain are relatively large compared with those on the former SA_∞     

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).      

Aperture coupled dielectric resonator antenna with a thick groundplane

The aperture-coupled hemispherical dielectric resonator antenna with a thick ground plane is investigated theoretically and experimentally. The effects of the ground plane thickness on the input impedance, resonant frequency, and front-to-back radiation ratio are studied     

A study on wideband gap-coupled microstrip antenna arrays

A method for increasing the bandwidth of microstrip antenna arrays by using gap-coupled patches is described. The input impedance properties of gap-coupled patches are analyzed by the use of the spectral dyadic Green's function for a grounded dielectric slab and the moment method. The dependence of different parameters such as s, L and ϵr on the impedance characteristics is investigated. In considering the effect of feed network, the impedance bandwidth for a VSWR<2 of two-element gap-coupled patch array is as large as 2.5 times that of an ordinary array. The radiation patterns over this bandwidth are measured and discussed. All the microstrip antenna arrays are fabricated on a substrate with ϵr=2.86, h=1.5 mm. A comparison of theoretical and experimental results for both input impedance and radiation patterns are given     

The resonant cylindrical dielectric cavity antenna

An experimental investigation of the radiation and circuit properties of a resonant cylindrical dielectric cavity antenna has been undertaken. The radiation patterns and input impedance have been measured for structures of various geometrical aspect ratios, dielectric constants, and sizes of coaxial feed probes. A simple theory utilizing the magnetic wall boundary condition is shown to correlate well with measured results for radiation patterns and resonant frequencies.     

Theory and experiment of a coaxial probe fed hemisphericaldielectric resonator antenna

A hemispherical dielectric resonator antenna fed by a coaxial probe is studied both theoretically and experimentally. The Green's function for the evaluation of the input impedance is derived rigorously and expressed in a form convenient for numerical computations. The method of moments is used to obtain the probe current from which the input impedance of the DR antenna is calculated. Both delta gap and magnetic frill source models are considered. Moreover, the results using a reduced kernel as well as the exact kernel are presented. Both entire basis (EB) and piecewise sinusoidal (PWS) expansion modes are used and the results are compared. The effects of the probe length, feed position, and dielectric constant on the input impedance are discussed. Finally, the theoretical radiation patterns for the first three resonant modes (TE₁₁₁, TM₁₀₁, and TE₂₂₁) of the DR antenna are presented     

Broadband CPW fed stacked patch antenna

A broadband CPW fed stacked patch antenna well suited for integration with monolithic and optical integrated circuits is presented. The antenna is designed with a bandwidth of 40% on a high dielectric constant feed substrate. The predicted and measured input impedance and far field radiation patterns are given     

Resonant hemispherical dielectric antenna

An antenna consisting of a resonant dielectric hemisphere on top of a ground plane is investigated. Calculations of the internal and external fields are made with emphasis on the lowest-order mode that results in efficient radiation in the direction perpendicular to the ground plane. Measured input impedance data are also presented for a practical radiator.