同轴馈电耦合微带贴片天线的时域有限差分法分析

提出一种融合曲线坐标和直角坐标的区域网格划分方法。在同轴线区域采用曲线坐标网格,用以代替传统的阶梯剖分,在其它区域及边界上采用直角坐标网格,从而极大地提高了计算效率。同时,在时域有限差分法中还采用了非均匀网格划分,PML吸收边界和Prony外推法等技术,对同轴馈电的耦合微带贴片天线进行了分析。     

An Equivalent Feed Model for the FDTD Analysis of Antennas Driven Through a Ground Plane by Coaxial Lines

For the finite-difference time-domain (FDTD) analysis of antennas excited by coaxial lines, an equivalent model of the antenna feed is presented here. Under the quasi-static approximation, the coaxial aperture is simply represented as the equivalent magnetic-frill current and the equivalent load circuit including the effects of the coaxial line. It leads us to a simple modification of the standard FDTD update equation at the aperture without any additional cell modeling of the line. The validity of the proposed model is confirmed by comparing of the FDTD results and the measured data.      

Effective permittivity at the interface of dispersive dielectrics in FDTD

A simple treatment of E-field component tangential to dispersive media interfaces in FDTD is introduced. The method uses concepts from the auxiliary differential equations method to average the constitutive parameters. The cases of a wave propagating in a coaxial line and of an open-ended coaxial line radiating into the dispersive media are investigated. Results show that the simulations could be significantly erroneous if the interface is not handled properly.     

An Efficient FDTD Model for Resistively Loaded Cylindrical Antennas With Coaxial Lines

A full coarse-grid based finite-difference time-domain (FDTD) model is proposed for an efficient analysis of resistively loaded cylindrical antennas driven by coaxial feed lines. In the case of the electrically thin resistive antenna, the thin-wire approximation is applied to the near fields around the antenna. The resistive antenna is equivalently represented by a series connection of piecewisely lumped resistors along the antenna axis. And the coaxial line is replaced by an equivalent source over the feed aperture of the line. Then the corresponding FDTD update equations make it possible to implement the full coarse-grid model without additional grid refinements for the antenna and the feed line. The transient reflected feed voltage and the input impedance of resistive antennas are calculated numerically and compared with those of a full fine-grid.      

采用FDTD法研究微带天线雷达散射截面的减缩

采用时域有限差分法(FDTD)方法以及新的含有内阻的磁流环激励同轴馈电模型研究了微带天线的辐射及散射特性,分析了集总负载加载和贴片表面开槽对微带天线雷达散射截面(RCS)的影响,研究了微带天线RCS减缩前后的回波损耗、增益及方向性的变化.研究表明,集总负载加载能降低谐振频率点的RCS,开槽方法能在天线辐射性能改变不大的情况下对微带天线的RCS具有较好的减缩作用.     

Modelling of coaxial-fed microstrip patch antenna by finite difference time domain method

A direct three-dimensional finite-difference time-domain (FDTD) method is applied to coaxial-fed microstrip antennas. The model is shown to be an efficient and accurate tool for modelling coaxial-fed structures. The reflection coefficient can be determined from the simulated time-domain wave that is reflected down the coaxial line. Excellent agreement over a wide frequency range is shown in two cases between the measured and FDTD derived results.<>     

利用FDTD 法分析同轴馈源性能

本文利用FDTD 方法分析了同轴馈源的性能。文章首先介绍了共形FDTD 的建立方法,利用该方法分析了不 同激励形式时同轴馈源的性能,并给出同时形式和模方向图和差模方向图的工程实现方法。同轴馈源对实现反射面天 线的双频段馈源设计具有重要意义。     

A note on the impedance variation with feed position of a rectangular microstrip-patch antenna

The variation with feed position of the input impedance of a rectangular patch antenna is investigated theoretically. Two different feed types are examined: an inset microstrip line, and a coaxial probe. The finite-difference time-domain (FDTD) technique is used for the calculations. Numerical results are compared with published measurements and other theoretical models.     

Considerations on performance evaluation of cavity-backed slotantenna using the FDTD technique

The finite-difference time-domain (FDTD) method is considered a versatile and efficient tool for the solution of Maxwell's equations in complex structures for any time dependence. We show an antenna feed model suitable for performance evaluation of a cavity-backed slot antenna using the FDTD technique. The gap voltage and the coaxial feed models are examined, and their input characteristics and absolute gains are compared. Analytical results show that the input characteristics are estimated with fewer time steps for the coaxial model than for the conventional gap voltage model. Furthermore, we show how to calculate absolute gains and radiation patterns using the coaxial model and a sinusoidal voltage source at the desired frequency. The computed results of the absolute gain converge after the fifteenth period of the voltage source for the coaxial model and are in good agreement with the experimental results. On the other hand, the absolute gain is observed to fluctuate when the gap voltage model is used. The performance evaluation and comparison reveals that the coaxial model is an appropriate feed model for use in the analysis of the performance of the cavity-backed slot antenna using the FDTD technique. The good agreement of the FDTD results with the experimental measurements demonstrates the effectiveness of the model and the method proposed     

On Solving TM0n Modal Excitation in a Ka-Band Overmoded Circular Waveguide by the Conservation of Complex Power Technique

To measure the radiation properties of relativistic diffraction generator (RDG) in Ka-band, a TM0n modal excitation model is established, which consists of an overmoded circular waveguide and a coaxial line feeding probe. Using the transverse E-field mode matching and the conservation of complex power technique (CCPT), we deduce the scattering matrix at coaxial line to coaxial line and coaxial line to circular waveguide junctions. Then using the overall cascaded junction scattering matrix, the numerical results for the reflection coefficient of the coaxial line and the power distribution of TM0n multi-modal are presented. The numerical results are in agreement with HFSS simulation results and experimental results. The analysis shows that by choosing the appropriate position of coaxial line probe, the power proportion of the device operating mode excited in circular waveguide could be the largest.     

On Solving TM0n Modal Excitation in a Ka-Band Overmoded Circular Waveguide by the Conservation of Complex Power Technique

To measure the radiation properties of relativistic diffraction generator (RDG) in Ka-band, a TM0n modal excitation model is established, which consists of an overmoded circular waveguide and a coaxial line feeding probe. Using the transverse E-field mode matching and the conservation of complex power technique (CCPT), we deduce the scattering matrix at coaxial line to coaxial line and coaxial line to circular waveguide junctions. Then using the overall cascaded junction scattering matrix, the numerical results for the reflection coefficient of the coaxial line and the power distribution of TM0n multi-modal are presented. The numerical results are in agreement with HFSS simulation results and experimental results. The analysis shows that by choosing the appropriate position of coaxial line probe, the power proportion of the device operating mode excited in circular waveguide could be the largest.     

一种基于FDTD的简单有效的天线阻抗计算方法

本文从有源区的软激励时Yee差分方程出发,推导了一种适用于理想的间隙激励(δ-gap source)和探针激励的天线输入阻抗新的计算公式,该方法简洁、有效,公式物理意义明确,能够有效地消除硬激励(hard source).计算天线阻抗时,在频率很低接近零时阻抗值的严重失真,使得应用时域有限差分法计算天线输入阻抗变得更加快捷适用.最后,本文应用该方法分别计算了一个单极子天线和同轴馈电的微带天线,单极子天线的计算结果和前人的计算结果吻合得很好,并且消除了频率接近零时以前计算结果的严重失真,微带天线和已有软件的计算结果进行了比较,得到了满意的结果.     

二元喇叭天线阵列的互耦研究

通过同轴线给天线馈电的方式,采用细导线FDTD方法模拟同轴线,研究了同轴传输线口径处内、外场之间的耦合,并分析了二元TEM喇叭天线阵的耦合问题,通过对单一喇叭进行馈电计算了天线阵单元的自阻抗和互阻抗.结果表明.在所考虑的频段内自阻抗和互阻抗不随频率的变化而变化,具有很好的宽带性能.     

Optimization of bow-tie antennas for pulse radiation

Resistively loaded bow-tie antennas are considered as radiators for temporally short, broad-bandwidth pulses. Analysis is by the finite-difference time-domain (FDTD) method. The geometrical details of the antenna and the resistive loading along the antenna are chosen to optimize this antenna for pulse radiation. Theoretical results for the reflected voltage in the coaxial feed line and the time-varying radiated electric field are compared throughout with experimental measurements. The optimized, resistive bow-tie antenna is shown to radiate a pulse that more closely resembles that of the excitation than is radiated by a metallic bow tie of comparable size. Issues involving the use of the FDTD method for modeling fully three-dimensional antennas are also discussed. These issues include the use of a simple feed model and the staircasing of the edges of the antenna     

圆柱腔内多导体传输线的瞬态电磁响应

为提高系统抗强电磁脉冲毁伤能力,采用时域有限差分法(Finite Difference Tim e Domain,FDTD)和通用电路仿真器(SPICE)相结合的协同仿真方法,以圆柱腔内由单导线、 双绞线、普通双线和同轴线组成的线束为研究对象,重点研究了导线类型、导线间距、捆扎 和RC滤波电路对耦合特性的影响。结果表明：耦合系数受腔体和传输线的双重影响,同轴线 耦合系数较其他两类线缆降低约40 dB;线间相互屏蔽是捆扎降低耦合系数的主要原因 ;随着导线间距增大,耦合系数幅值增大;RC滤波电路是降低电磁耦合的有效手段。所得结 论对电子系统进行抗电磁脉冲加固具有重要意义。     

Leaky coaxial cable with adjustable coupling loss for mobilecommunications in complex environments

A new kind of leaky coaxial cable composed of an axially-slotted line covered with periodic metallic patches is proposed. The basic cable sets up a surface wave and does not radiate itself, but excites the patch apertures into radiation. The direction of the radiation field can be changed by adjusting the size and period of the patches according to the environmental application. A combined method that involves FDTD iteration and integration of the equivalent surface magnetic current is introduced in order to determine the radiation field accurately     

Full-Wave Analyses of Coaxial to Waveguide Adapters by the FDTD Method

The finite-difference time-domain (FDTD) method is applied to the full-wave analyses of the electrical properties of millimeter wave coaxial to waveguide adapters. The results are useful for the design of wideband coaxial to waveguide adapter.     

Artificial Neural Network Models for Coaxial to Waveguide Adapters

Artificial neural networks provide fast and accurate models for the modeling, simulation, and optimization of microwave and millimeter wave components. In this paper, a multilayer perceptron neural network (MLPNN) is used to model a millimeter wave coaxial to waveguide adapter. The MLPNN is electromagnetically developed with a set of training data that are produced by the full-wave finite-difference time-domain (FDTD) method. One type of the designs of experiments, the central composite technique, is used to allow for a minimum number of FDTD simulations that is needed to be performed. The MLPNN models are useful for the CAD of wideband coaxial to waveguide adapter.     

卫星赋形天线矩形同轴线馈电网络的FDTD分析

采用时域有限差分（FDTD）方法分析了构成卫星赋形天线馈电网络（BFN）的矩形同轴线各种不连续性结构的散射特性。该方法通过模拟波的传播过程直接求解结构的散射参数,与模匹配方法相比,分析过程大为简化,将计算结果与实验值进行了比较,二者吻合很好,充分证明了本文方法的有效性和精确性。     

开口式微波加热器的研究

应用时域有限差分法(FDTD)分析和计算了一种开口式同轴加热装置。同时讨论和计算了为防止微波泄漏而设计在腔体外围的扼流槽的作用。测量结果与计算结果有相当高的一致性。表明这种装置可以在中心处产生高温,而在设计相关的微波装置时,使用时域有限差分法又是十分有效的。