FDTD中微带线激励源设置的新方法

ＦＤＴＤ已广泛应用于微带问题的计算中,本文提出了一种新的微带线馈电激励设置方式,同以往的激励设置方法不同,它不仅能计算Ｇａｕｓｓｉａｎ脉冲激励也能计算正弦波激励,计算过程中,源平面无需切换成吸收边界,场区的划分使反射场自然从总场区分离出来。     

基于自适应遗传算法的FDTD中完全匹配层的设置方法

针对时域有限差分算法进行电磁场数值求解时的PML吸收边界层的设置问题,给出了利用自适应遗传算法对吸收层的电导率进行优化确定吸收层电导率的方法,得到了相同激励源下吸收效果最佳的吸收层各层电导率值,该值只是经典边界电导率取值的边界反射场值的1/5不到,而且随着计算时间的增长,吸收稳定性增强,可以更加准确地进行电磁场数值模拟。     

一种新的各向异性介质完全匹配层与矢量有限元的结合

与在有限元中广泛使用的Sacks提出的单轴各向异性介质PML[1]不同,采用一种新型的各向异性介质PML[2].这种PML技术可用于处理双轴各向异性介质的边界截断问题,当然也适用于各向同性介质与单轴各向异性介质.不像文献[1]中的PML技术,文中的PML技术不需要在目标区域与PML层介质之间加一层空气,因此它需要更小的计算区域.将这种新型的PML与矢量有限元VFEM结合,以计算填充各向同性介质、单轴各向异性介质基片的带有背腔结构微带贴片天线的输入阻抗为例,证明了在用VFEM处理开放的无限区域问题时,作为边界截断策略,这种PML技术与边界积分法BI一样有效.     

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。     

采用PML吸收边界条件的FDTD法的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。     

二维光子晶体带隙结构透过率的研究

计算了二维光子晶体TM模透射率频率分布,并用FDTD+PML边界方法对光子晶体传输特性进行分析,直观地给出了光在光子晶体中的光场分布,分析了不同网格精细度和晶体层数对于透过率的影响。     

采用PML的FDTD方法对矩形微带天线的研究

将完全匹配层(PML)吸收边界应用于微带结构中，对矩形微带天线进行了分析计算，给出了其时域和频域的仿真结果。结果表明，与传统的Mur边界相比，采用PML吸收边界具有反射小、馈源模型简单、收敛速度快等优点。     

周期结构FDTD算法的各向异性PML边界条件

本文建立了一种新的适用于周期FDTD计算的边界条件—周期/各向异性PML混合边界条件.计算验证表明,本文的方法改善了原来单向波边界的缺点,具有较高的精度,使周期FDTD算法进一步走向成熟.     

一种新型微带曲折线慢波结构的设计

设计了一种新型微带曲折线慢波结构,该结构采用双介质杆支撑式的V型平面曲折线慢波电路。利用电磁场仿真软件HFSS对这种新型结构和传统微带曲折线慢波结构进行了分析比较,研究结果表明,新型微带曲折线慢波结构在不改变色散强弱的情况下,工作频段向高频端拓展且耦合阻抗有了很大提高,可以更好地工作在短毫米波段。并仿真分析了结构参数对高频特性的影响,所获得的仿真结果为器件的粒子模拟及计算慢波结构的工作效率奠定了基础。     

一种新型超宽带平面天线的FDTD分析

本文分析了一种具有超宽带特性的平面喇叭天线的阻抗和辐射特性.这种平面喇叭采用了新型的平衡馈电方式,结构简单,性能良好.采用时域有限差分方法(FDTD)分析天线时,吸收边界采用了完全匹配层技术(PML),并用环路径分方法(CP)处理了喇叭脊间窄缝,计算结果与实测数据比较,两者十分吻合.     

A full-wave model for EMI prediction in planar microstrip circuitsexcited in the near-field of a short electric dipole

A full-wave model to evaluate the interference induced in planar microstrip lines of arbitrary shape exposed to the near-field of an elementary electric dipole is presented. The analysis of the line response, consisting in the evaluation of the surface current excited along the microstrip line, is based on the electric dyadic Green's function method. The surface current induced on the metal strip which, for the sake of generality, is considered as embedded in the dielectric substrate, is obtained solving by means of the spectral-domain approach (SDA) the electric integral equation, which enforces the boundary condition of zero tangential electric field on the surface of the strip. The induced current is computed for different line geometries and loads, and for various positions (inside or outside the dielectric substrate) and orientations of the dipolar source. Indications towards reducing the level of the signal induced on the loads of the line are inferred     

Input impedance of a probe-fed stacked circular microstrip antenna

The input impedance of a microstrip antenna consisting of two circular microstrip disks in a stacked configuration driven by a coaxial probe is investigated. A rigorous analysis is performed using a dyadic Green's function formulation whereby the mixed boundary value problem is reduced to a set of coupled vector integral equations using the vector Hankel transform. Galerkin's method is used in the spectral domain, using two sets of disk current expansions. One set is based on the complete set of orthogonal modes of the magnetic cavity, and the other uses Chebyshev polynomials with the proper edge condition for the disk currents. An additional term is added to the disk current expansion to model the current properly in the vicinity of the probe/disk junction. The input impedance of the antenna, including the probe self-impedance, is calculated as a function of the layered parameters and the ratio of the two disk radii. Disk current distributions and radiation patterns are presented. The calculated results are shown to be in good agreement with experimental data     

Propagation in layered biased semiconductor structures based ontransport analysis

A transport-field parallel-plate formulation and solution method to determine the small-signal propagation constant is given for wide microstrip lines over an inhomogeneously doped semiconductor substrate of small transverse dimensions. Included in the detailed transport model are two carrier species, recombination-generation mechanisms, DC and AC field-dependent mobilities and diffusion constants, and boundary condition contact effects. A transverse DC bias condition is applied. Structures numerically simulated are a voltage-variable GaAs distributed Schottky-barrier phase shifter and a transmission line over an Si bipolar junction. Numerical data based on a finite-difference technique are generated on carrier densities, electric potentials and fields, and current densities. Propagation constant calculations compared favorably to those calculated by both full-wave field analysis and moments-of-the-Boltzmann-equation analysis for some less general cases. Propagation constant results for the GaAs structure are compared with available experimental data, and good agreement is obtained     

Spectral-domain analysis of shielded microstrip lines on biaxiallyanisotropic substrates

The spectral-domain technique is extended to the study of shielded microstrip lines on biaxial substrates. The analysis simultaneously includes dielectric and magnetic anisotropy effects. A fourth-order formulation leads to the determination of the appropriate Green's function for the structure. The characteristic equation is formed through the application of the Galerkin method to the equations resulting from the boundary conditions on the strip. Numerical results calculated by this method for isotropic as well as dielectrically anisotropic substrates are compared with the existing data, and in both cases a very good agreement is observed. New data on the propagation constant of the shielded microstrip with different substrate permittivities and permeabilities are presented to illustrate the effects of the material parameters on the characteristics of the microstrip line     

Quasi-analytical static solution of the boxed microstrip lineembedded in a layered medium

A quasi-analytical method to carry out the quasi-TEM study of a microstrip line embedded in a general layered substrate with rectangular enclosure is presented. Electric walls, magnetic walls, and periodic boundary conditions are considered. The analysis is based on the spectral-domain formulation and the use of a proper expansion of the free charge distribution (Chebyshev polynomials with edge condition). Two different approaches are proposed to speed up the evaluation of the spectral series in such a way that only a few spectral terms must be retained in the numerical computations of the mentioned series. The propagation parameters and the charge distribution are obtained with extreme accuracy in fractions of one second on a personal computer     

网络分解直线法结合周期边界条件分析开域微带结构

本文用网络分解直线法结合周期边界条件,以平面波激励,通过贴片电流提取相关参数的方法,分析开域微带结构。阻抗元素计算和减缩方程求解,分别使用快速傅里叶变换和网络分解技术,从而大大提高了计算效率。周期边界模拟开域的收敛性研究和计算时间的比较表明了该方法的有效性。最后计算了矩形贴片平面谐振器的谐振频率,其结果与已发表的值吻合很好。     

Propagation characteristics of microstrip transmission line on ananisotropic material ridge

A microstrip transmission line residing on an electrically anisotropic material ridge embedded in a multilayered environment is studied using a coupled set of integral equations (IE's). The full-wave IE formulation easily accommodates arbitrary material anisotropy and inhomogeneity in the finite ridge region using equivalent polarization currents residing in a multilayered isotropic background. New results are presented for uniaxially anisotropic ridge structures which show that the transmission line propagation constant is sensitive to anisotropy for certain ridge structures and insensitive for others, compared to the conventional line on an infinite substrate. Results are also presented for a transmission line printed on a nonreciprocal solid-state magnetoplasma ridge. The current distribution associated with the dominant microstrip mode is investigated, where it is found that the transverse component of current is much larger for the ridge geometry than for the infinite substrate case, although the transverse component is still small compared to the longitudinal component     

ANALYSIS OF OPEN MICROSTRIP STRUCTURES BY USING DIAKOPTIC METHOD OF LINES COMBINED WITH PERIODIC BOUNDARY CONDITIONS

This paper presents the analysis of open microstrip structures by using diakoptic method of lines (ML) combined with periodic boundary conditions (PBC). The parameters of microstrip patch are obtained from patch current excited by plane wave. Impedance matrix elements are computed by using fast Fourier transform(FFT), and reduced equation is solved by using diakoptic technique. Consequently, the computing time is reduced significantly. The convergence property of simulating open structure by using PBC and the comparison of the computer time between using PBC and usual absorbing boundary condition (ABC) show the validity of the method proposed in this paper. Finally, the resonant frequency of a microstrip patch is computed. The numerical results obtained are in good agreement with those published.