基于时域有限差分法的微带天线分析

微带天线具有许多优点,在许多领域得到广泛应用。为精确设计微带天线,需了解描述天线性能的电参数。介绍了一种数值分析方法——时域有限差分法（FDTD）,从Maxwell旋度方程出发推导FDTD差分格式计算过程,总结出分析电磁问题的一般步骤,并采用FDTD分析了一款典型的微带天线。和电磁仿真软件XFDTD仿真结果相比较,可以看出FDTD计算结果与软件仿真结果吻合得很好。     

Analysis of a double step microstrip discontinuity in the substrateusing the 3D-FDTD method

The finite-difference time-domain (FDTD) method has been applied to the analysis of a double step microstrip discontinuity having thickness changes in the longitudinal direction. The discontinuity occurs in patch antenna feeds or interconnections between microwave planar circuit modules. The simulation results are compared with those computed by HFSS to show a good agreement. An equivalent circuit for the double step discontinuity is developed from the scattering parameters computed by the FDTD method     

遗传算法在优化设计宽频微带天线中的应用

将遗传算法与FDTD法结合优化设计出了一种宽频微带天线.文中简要讨论了遗传算法的操作过程,并介绍了减少遗传算法与FDTD法结合优化微带天线计算量的方法.与初始矩形微带天线相比,优化后天线的阻抗带宽增加了三倍多.     

微带可重构天线的初步探讨

引入了一种崭新的天线概念-可重构天线。首先根据传统微带天线腔模理论定性地分析了微带可重构天线的工作机理，然后用时域有限差分（FDTD）法对微带天线的可重构特性进行了仿真分析。仿真和分析表明，矩形微带可重构天线当某一边长大于等于一个工作波长时，能够获得良好的可重构特性。     

Analysis of electromagnetic radiation from shaped-end radiatorsusing the finite difference time domain method

The finite difference time domain (FDTD) technique is a popular method for analyzing electromagnetic scattering, radiation, and penetration problems. Several authors have recently applied the FDTD method to antenna radiation problems. To date, the antenna structures considered have been wire and conical monopole antennas, rectangular waveguides, pyramidal horn antennas, and microstrip antennas. Results from these analysis have been in the form of normalized field patterns and no results showing absolute gain have been presented. The article demonstrates the first staircased application of the FDTD method to the analysis of radiation from circular waveguides and other shaped-end radiators. Results of absolute gain versus angle are shown for a straight-cut circular waveguide and for two different shaped-end radiators. All FDTD analyses are full three-dimensional computations and are compared in each case with measured data     

采用PML吸收边界条件的FDTD法在分析平面微带结构中的应用

本文将理想匹配层(PML)吸收边界条件用于平面微带结构的时域有限差分法(FDTD)分析中,给出平面微带结构的PML吸收边界条件,并编制程序,进行数值计算。结果表明,与传统的Mur吸收边界条件相比,采用PML吸收边界条件只需采用最简单的馈源模型就可明显地减小计算网格空间和加快收敛速度,并且可用于分析任意复杂结构的微带电路。本文方法对微带电路及微带天线的CAD设计将具有实际意义。     

双极化口径耦合微带天线FDTD分析

本文应用时域有限差分法（FDTD）分析了双极化口径耦合多层微带贴片天线。文中结果表明,FDTD在分析多层复杂结构的微带天线时是非常有效的。采用Gauss脉冲激励,通过FFT,一次计算就可得到天线谐振频率、耦合、频带宽度、增益等参数的宽频带特性。计算结果对天线的优化设计具有一定的指导作用。     

Modelling of bow-tie microstrip antennas using modified locallyconformal FDTD method

An analysis of bow-tie microstrip antennas is presented based on the use of the modified locally conformal finite-difference time-domain (FDTD) method. This approach enables the number of cells along the antenna length and width to be chosen independently of the antenna central width, which helps to keep the number of cells required in those directions to a minimum. The analysis results are compared with experimental results and good agreement is observed     

Study of impedance and radiation properties of a concentricmicrostrip triangular-ring antenna and its modeling techniques usingFDTD method

A concentric microstrip triangular-ring antenna structure using the log-periodic principle for increasing the impedance bandwidth of the microstrip patch antenna is described. The finite-difference time-domain (FDTD) method is applied to analyze the proposed structure. A special technique to model the slanted metallic boundaries of the triangular ring has been used in the general FDTD algorithm to avoid the staircase approximation. The method improves the accuracy of the original FDTD algorithm without increasing the complexity. The radiation patterns at different frequencies over a wide bandwidth are obtained experimentally     

同轴馈电耦合微带天线的MPSTD-FDTD分析

将多区域时域伪谱(MPSTD)与时域有限差分(FDTD)相结合的混合算法应用于同轴馈电耦合微带天线的分析,该混合算法充分发挥两种时域算法的优越性,对同轴馈电耦合微带天线进行了准确建模与快速分析,数值仿真验证了该算法的有效性和准确性。     

The theory of a singularity-enhanced FDTD method for diagonal metal edges

The complete theory of a singularity-enhanced finite-difference time-domain (FDTD) method for a sharp diagonal metal edge is presented. This method is very accurate and efficient for modeling printed microwave components with diagonal metal edges including some microstrip patch antennas, various other printed antennas, and printed transmission lines. Considering the singular nature of electromagnetic fields at a sharp metal edge, new FDTD equations are derived for all electric and magnetic nodes near the edge, using a contour-path subcell approach. The new FDTD equations for the affected nodes differ from the standard (Yee's) FDTD equations only by a few additional coefficients, for which complete mathematical expressions are given. Application of this method to several antenna and transmission-line problems demonstrated significantly improved accuracy over previous methods, without any noticeable computing overhead. A coarse grid can be used in conjunction with this method and hence the required computer memory and time can be reduced drastically. We have used the maximum allowed time step in all our applications and the method was always stable.     

采用FDTD/FVTD混合算法分析蝶形微带天线

用FDTD和FVTD混合算法分析了蝶形微带天线的反射损失.在适于矩形网格的区域采用常规的非均匀FDTD算法,在微带贴片天线的斜边或PEC弯曲表面处采用FVTD算法,重叠区域的场通过邻近场的线性插值得到.程序仿真和实际测量结果的比较表明在较宽的频带内,该算法在不损失精度,不显著增加CPU时间和内存的情况下,极大地降低了常规FDTD所要求的网格密度.     

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     

Optimization of a buried microstrip antenna for simultaneous communication and sensing of soil moisture

Imbedded microstrip antennas have been previously demonstrated for use either as sensing elements or as components of a wireless communication system. This paper presents a method and dual use designs for simultaneous sensing of soil moisture and communication from the buried antenna to an external receiver. Using the genetic algorithm and the finite-difference time domain (FDTD) method, the sensing band is designed to have maximum sensitivity to the moisture of the surrounding soil, while the communication band is designed to have minimal detuning due to changes in soil moisture. Single layer and stacked microstrip antennas are shown.     

内嵌结构光子晶体在F 型微带天线中的应用

对常用的正方晶格光子晶体结构进行改进优化,设计出一种新型内嵌结构式二维光子晶体,即在普 通正方晶格光子晶体内部嵌入同类晶格的光子晶体。将该结构光子晶体应用到F 型微带天线中,采用平面波展开 法,进行大量仿真计算。结果表明:与传统的微带天线相比,加入该结构光子晶体后的微带天线回波损耗由 -18. 2465dB 降低到-41. 0624dB。天线具有更好的阻抗特性和辐射效率,方向图有所改善,背瓣辐射最大处减少约 5dB。这种新型的光子晶体微带天线达到了提高天线性能的目的。     

A VHF Microstrip Antenna With Wide-Bandwidth and Dual-Polarization for Sea Ice Thickness Measurement

A VHF microstrip patch antenna was developed to achieve a bandwidth of 45 MHz (30%) from 127 to 172 MHz with dual-linear-polarization capability. This microstrip antenna, having a size of 117 cm times 117 cm times 27 cm, used low-dielectric-constant foam substrates and dual-stacked patches with capacitive probe feeds to achieve the required wide bandwidth. Four such capacitive feeds were used to achieve dual polarizations with less than -20 dB of cross-polarization level. Twenty-four shorting pins were uniquely used here on the lower patch to achieve 40 dB of isolation between the two polarization ports. This antenna has a measured gain of 8.5 dB at 137 MHz and 10.3 dB at 162 MHz. One advantage observed here at the low frequencies of VHF is that more electrical structures can be easily integrated into the microstrip antenna to improve its performance.     

35GHZ Patch Antenna Array Based on the Electromagnetic Band‐Gap Structure

The electromagnetic band‐gap (EBG) structure, also called photonic band‐gap structure, consisted by triangular arrays of air columns on the dielectric structure is designed and studied by using the FDTD method. According to the simulated and measured results, the EBG structure effectively suppressing surface wave for TE and TM modes is designed. The optimized EBG structure is presented.The proposed EBG structure is applied to the four‐element microstrip patch array antenna. As results of simulation and measurements, the impedance bandwidth and the gain of proposed EBG patch array antenna are improved.     

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.     

Design and Experiment on Differentially-Driven Microstrip Antennas

Design and experiment is given of differentially-driven microstrip antennas. First, the design formulas to determine the patch dimensions and the location of the feed point for single-ended microstrip antennas are examined to design differentially-driven microstrip antennas. It is found that the patch length can still be designed using the formulas for the required resonant frequency but the patch width calculated by the formula usually needs to be widen to ensure the excitation of the fundamental mode using the probe feeds. The condition that links the patch width, the locations of the probe feeds, and the excitation of the fundamental mode is given. Second, the wideband techniques for single-ended microstrip antennas are evaluated for differentially-driven microstrip antennas. A novel H-slot is proposed for differentially-driven microstrip antennas to improve impedance bandwidth. Third, the effects of imperfect differential signal conditions on the performance of differentially-driven microstrip antennas are investigated for the first time. It is found that they only degrade the polarization purity in the -plane with an increased radiation of cross-polarization. Finally, both differentially-driven and single-ended microstrip antennas were fabricated and measured. It is shown that the simulated and measured results are in acceptable agreement. More importantly, it is also shown that the differentially-driven microstrip antenna has wider impedance bandwidth of measured 4.1% and simulated 3.9% and higher gain of measured 4.2 dBi and simulated 3.7 dBi as compared with those of measured 1.9% and simulated 1.3% and gain of measured 1.2 dBi and simulated 1.2 dBi of the single-ended microstrip antenna.     

一种新型小型化微带天线的全波分析

本文介绍了一种新颖的小型化微带天线.利用在贴片上面开一个C型缝隙,使得谐振频率明显降低,尺寸仅是传统的半波长微带天线的33%,阻抗带宽略有增加,并且加工相对简单.利用时域有限差分法(FDTD)对这种天线进行了较为全面的理论分析,给出了输入端反射损耗特性和辐射特性.同时给出了矩量法(MoM)分析结果和测量结果,具有较好的一致性.此种天线可应用于对天线尺寸有严格限制的场合.