TLCODE方法在多路传输线并联电路中的应用

 介绍了TLCODE方法对多路传输线并联电路的模拟情况。根据TLCODE方法的要求,在引入接地电阻的条件下推导了多路传输线并联时的界面电压公式,同时构建了一个多路传输线并联的PSPICE电路模型,将该模型计算得到的传输线输入端电压作为TLCODE方法的输入电压,通过比较发现两种方法计算的传输线任意处的电流、电压波形完全符合。这表明利用TLCODE方法模拟多路传输线并联问题取得了成功,标志着开发多路并联磁绝缘传输线电路模型取得了重要进展。     

腔体内传输线耦合的电磁仿真软件与传输线方程的混合算法

研究了一种有限积分法软件与传输线方程相结合的混合算法,用于解决复杂电磁环境下屏蔽腔体内传输线的电磁耦合问题。利用有限积分法软件实现屏蔽腔体的建模,仿真得到腔体内部空间电磁场分布,并设置电场探针提取出传输线的激励场。利用传输线方程建立腔体内传输线的耦合模型,将得到的传输线激励场引入到传输线方程作为等效分布电压和电流源。利用时域有限差分(FDTD)格式对传输线方程进行离散,从而迭代求解出传输线终端负载上的电压和电流响应。通过与文献以及传统数值算法的计算结果进行对比,验证混合算法的正确性。研究表明,该混合算法在模拟电大尺寸腔体内传输线的电磁耦合方面,具有较高的精度和计算效率。     

Electrodynamic modelling of waveguide properties of the transmission lines based on flat waveguide splitters

The capability of the H-plane waveguide joints to maintain natural [1] and quasi-natural modes [2] of Hpso type brings about an idea of possibility to develop transmission lines with E-modes based on them. From the physical point of view, the said property of the splitter allows to conclude that, to some extent, this structure is a resonator whose cut-off orthogonal waveguides serve as reflecting surfaces cutting off the electromagnetic field at a certain distance from the splitter area. Whereas the transmission line losses of lowest E-modes are higher than those of H- modes, still one could expect that, due to the semi-open character in both transverse directions, at least the cross-shaped line [3,4], with regard for its loss criterion, will be competitive with the groove waveguide [5,6].     

The contribution of a lateral wave in simulating low-frequency sound fields in an irregular waveguide with a liquid bottom

A further development of a previously proposed approach to calculating the sound field in an arbitrarily irregular ocean is presented. The approach is based on solving the first-order causal mode equations, which are equivalent to the boundary-value problem for acoustic wave equations in terms of the cross-section method. For the mode functions depending on the horizontal coordinate, additional terms are introduced in the cross-section equations to allow for the multilayer structure of the medium. A numerical solution to the causal equations is sought using the fundamental matrix equation. For the modes of the discrete spectrum and two fixed low frequencies, calculations are performed for an irregular two-layer waveguide model with fluid sediments, which is close to the actual conditions of low-frequency sound propagation in the coastal zone of the oceanic shelf. The calculated propagation loss curves are used as an example for comparison with results that can be obtained for the given waveguide model with the use of adiabatic and one-way propagation approximations.     

Statistical characteristics of nonstationary backscattering in randomly irregular media

Using the method of invariant immersion, we perform numerical simulations of the statistical characteristics of a plane nonstationary wave reflected from a one-dimensional, randomly irregular medium due to multiple scattering. The statistical effects in the mean reflected field are considered, and the behavior of its higher moments is analyzed. The possibility of obtaining the solution of the statistical inverse wave problem is discussed. Pacific Oceanological Institute of the Far-East Branch of the Russian Academy of Sciences, Vladivostok, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 42, No. 12, pp. 1153–1164, December, 1999.     

脉冲功率传输线磁绝缘的建立与特性分析

 分析了脉冲功率传输线建立磁绝缘的暂态过程,对暂态过程中传输线的击穿与磁绝缘关系、电子的分布规律及其与建立磁绝缘的关系进行了阐述。分析了磁绝缘传输线电极间的电子分布改变传输线工作阻抗值的现象,给出了传输线稳态工作阻抗的求解方法和用稳态工作阻抗计算传输线暂态工作阻抗的方法。研究了截面尺寸变化时传输线中电子的分布和电磁波传播的折反射情况。结果表明:传输线在建立磁绝缘的过程中损失电子是必然的,损失电子是建立磁绝缘的必要条件。截面半径沿轴向变化时,其工作特性与极间距的变化有关。极间距增大时,后半段的电子电流增大,使其工作阻抗增大并与前半段相等,因而在尺寸变化处不产生反射波。极间距减小时,由于后半段提前产生损失电子,因而尺寸变化处产生反射波。     

Three-dimensional vectorial analysis of waveguide structures with the method of lines

The method of lines (MoL) a special eigenmode algorithm has been proven as an efficient tool for the analysis of waveguide structures in optics and microwaves. The electric and magnetic fields in the cross-section and their derivatives with respect to the cross-section coordinates are discretized with finite differences (FD) while analytic expressions are used in the direction of propagation. The numerical effort for analyzing three-dimensional structures with a two-dimensional discretization can be very high, particularly if vectorial characteristics have to be taken into account. In this paper we introduce a reduction of the eigenmode system to keep the effort moderate. Only a certain number of eigenmodes is determined with the Arnoldi algorithm. We will show then how the electric field distribution of the eigenmodes can be computed from the magnetic field and vice versa. To match the fields at the interfaces we introduce left eigenvectors which are the inverse of the field distributions. The formulas were applied to the analysis of a polarization converter consisting of a periodical perturbation of a waveguide structure. A rotation angle greater than 80° was determined.     

脉冲功率传输线磁绝缘的建立与特性分析

分析了脉冲功率传输线建立磁绝缘的暂态过程,对暂态过程中传输线的击穿与磁绝缘关系、电子的分布规律及其与建立磁绝缘的关系进行了阐述。分析了磁绝缘传输线电极间的电子分布改变传输线工作阻抗值的现象,给出了传输线稳态工作阻抗的求解方法和用稳态工作阻抗计算传输线暂态工作阻抗的方法。研究了截面尺寸变化时传输线中电子的分布和电磁波传播的折反射情况。结果表明:传输线在建立磁绝缘的过程中损失电子是必然的,损失电子是建立磁绝缘的必要条件。截面半径沿轴向变化时,其工作特性与极间距的变化有关。极间距增大时,后半段的电子电流增大,使其工作阻抗增大并与前半段相等,因而在尺寸变化处不产生反射波。极间距减小时,由于后半段提前产生损失电子,因而尺寸变化处产生反射波。     

非线性拟合方法用于透射式脉冲红外技术测试碳/碳复合材料的热扩散系数

为了测试碳/碳复合材料的热扩散系数,本文提出了非线性拟合用于透射式脉冲红外检测的数据处理方法.非线性拟合通过循环迭代的方法持续调整拟合参数,让理论值不断逼近实验值,直至获得最佳结果.传统的透射式脉冲红外成像技术利用半高时间法测试材料的热扩散系数,但通常会受到采集时间不足和信噪比差的限制.本文提出的非线性拟合方法可以有效消除或减弱这两种影响.在使用该方法之前,首先选用常见的304不锈钢评估了该方法的测量精度及拟合长度对测试结果的影响.结果显示304不锈钢的测量精度达到0.3%,且当拟合长度不小于半高时间法采集时间的1/5时,拟合长度对非线性拟合结果影响很小.随后使用该拟合方法测试了不同厚度的碳/碳复合材料试件,并通过热扩散系数测量结果分析了试件之间的热参数差异性和材料自身的均匀性.     

Demonstration of mode conversion in an irregular waveguide

Communications wavelength waveguide mode conversion is demonstrated in an irregular metal-walled structure that was designed by using multiresolution optimization. Strong scatter and a large number of degrees of freedom allowed high-efficiency conversion in a device having a length of just a few wavelengths. The fabrication approach draws on standard semiconductor processing. Mode-selective reflectors, splitters, phase shifters, and other elements can be achieved by using this principle.     

三平板传输线结构的解析分析方法北大核心CSCD

在考虑不等宽度三平板传输线的极板边缘效应和极板厚度的条件下,建立了单位长度电容、特性阻抗和各位置电场强度幅值的解析求解方法。该方法利用保角变换,将三平板传输线的不规则场边界变换为规则边界,所得结果是不带有任何近似的准确值。该方法计算结果与利用商业软件Ansoft进行模拟所得结果一致,证明该方法正确且可行。     

A reduction modeling method to assess the electromagnetic emission of multiconductor transmission lines

This article deals with the extension of the so-called “equivalent cable-bundle method” to assess the electromagnetic emission of a cable-bundle. As in the immunity case, the purpose of the method is to reduce the complexity of a reference cable-bundle by creating a “reduced cable-bundle” composed of a limited number of “equivalent conductors”. The significant reduction of the thereby obtained model makes possible its introduction in 3D models without any real increase of their size. To cite this article: G. Andrieu et al., C. R. Physique 10 (2009).     

Application of the gradient heat flux sensor to study pulsed processes in a shock tube

The surface temperature of a model body of revolution placed in a pulsed supersonic nitrogen flow is measured with the help of a gradient heat flux sensor. From the measured temperature, a heat flux toward the surface of the body is determined. The steady flow of a viscous transcalent gas about the body is numerically calculated. The results of the numerical calculation and measuring data are in good agreement.     

Linked-cluster expansions in the equations of motion method for nonequilibrium processes

For an arbitrary irreversible process taking place in a closed physical system equations of motion are derived directly from the Liouville equation without introducing any projection operator. These equations are of nonmarkowian nature and are exactly valid for any system arbitrarily far from equilibrium. Using field-theoretical techniques the integral kernels in these equations are expanded into a diagram perturbation series which is proved to be linked. For a system having short memory it is shown that the secular divergent terms cancel each other. Then, using the diagram language the equations of motion are obtained in a much simpler form.     

Application of the Beilis-Tappert parabolic equation method to sound propagation over irregular terrain

The Beilis-Tappert (1979) parabolic equation method is attractive for irregular terrain because it treats surface variations in terms of a simple multiplicative factor ("phase screen"). However, implementing the exact sloping-surface impedance condition is problematic if one wants the computational efficiency of a Fourier parabolic equation algorithm. This article investigates an approximate flat-ground impedance condition that allows the Beilis-Tappert phase screen method to be used with a Fourier algorithm without any added complications. The exact sloping-surface impedance condition is derived and applied to propagation predictions over hills with maximum slopes from 5° to 22°. The predictions with the exact impedance condition are compared to predictions using the approximate flat-ground impedance condition. It is found that for slopes less than 15°-20°, the flat-ground impedance condition is sufficiently accurate. For slopes greater than approximately 20°, the limiting factor on numerical accuracy is not the flat-ground impedance approximation, but rather the narrow-angle approximation required by the Beilis-Tappert method. Thus, within the 20° limitation and using the flat-ground impedance condition with a Fourier parabolic equation, sound propagation over irregular terrain can be computed simply, efficiently, and accurately.     

高频电磁干扰对传输线耦合全波建模方法

对于场线耦合问题,经典传输线理论不适用于求解高频电磁干扰辐照下传输线负载上的电压和电流响应。针对这一问题,首先介绍了一种基于天线理论和模拟行为建模（ABM）的时域全波建模方法。该方法利用Harrington矩量法将电流积分方程离散并推导得到宏模型时域表达式,然后利用ABM频域功能实现频变参数的傅里叶逆变换和时域卷积计算。利用电路求解器,该建模方法可直接求解任意结构传输线耦合的负载处瞬态响应;与传统全波算法相比,模型一旦建立便可应用于任意入射场和线性/非线性负载的情况,无需重复耗时地求解电流积分方程。该方法可简化全波算法求解过程,提高仿真计算效率,尤其便于在入射场和负载存在不确定参数时进行高效重复抽样计算以获得统计特性。然后以高频电磁干扰耦合有损大地上的双导体传输线为例,通过与数值电磁代码和传统传输线理论方法的求解结果对比,验证了所提宏模型的有效性以及传输线理论在解决场线耦合问题时的局限性。结果表明,基于全波方法构建的宏模型可在时域内高效准确地求解高频电磁干扰辐照下任意形状传输线负载上的瞬态响应。