传输/反射法测量复介电常数的若干问题

研究了传输／反射法测量线性材料复介电常数εr的厚度谐振、多值性等问题，得到了解决这些问题的有效方法。通过改进NRW传输／反射法，由散射参数直接得到了归一化特性阻抗与传播常数，从而可以把已有的三个确定复介电常数的方程用到NRW传输／反射法中。联合应用这三个方程解决了上述问题，这使得人们可以用传输／反射法对任意厚度的样品在任意频率上进行复介电常数的稳定测量。用波导取样器与同轴线取样器分别得到的实验结果证明了此方法的有效性与可实现性。     

40～110 GHz介质材料自由空间法电磁参数测量

为研究介质材料40～110 GHz频段下的电磁参数,搭建了自由空间测量系统并进行TRL(直通、反射、传输线)校准,聚四氟乙烯标准样的电磁参数实际测量为εr=2.25±0.15,μr=1.01±0.01.测量结果及不确定分析结果显示,在40～110 GHz频段内基于该方法的测量系统具有较好的测量精度.     

用双端口网络理论求均匀传输线特性阻抗和传输常数

用双端口网络理论来分析研究均匀传输线，可以将复杂的分布参数问题化解为简单的双端口网络问题。本文阐明了如何利用双端口网络的有关计算公式和极限运算法则，求出均匀传输线的特性阻抗Zc和传输常数γ0的方法。     

双轴各向异性介质特征参数的测试模型

介质参数测试的关键理论步骤是求解相应的电磁逆问题。本文利用等效传输线法导出了已知双轴各向异性电磁材料复介电常数张量ε^-和复磁导率张量μ^-，计算出反射系数和透射系数（正问题）的理论公式后，提出了一种新的求解逆问题的理论方法。由介质对正入射TE、TM波的反射系数与透射系数，可用公式直接反演得到ε^-和μ^-的复分量εx、μy和εy,μx然后利用介质对斜入射TE、TM波的透射系数由大为简化的反演算法迭代求解它们的z分量εz和μz。计算机模拟实验给出了比较理想的结果。     

线性互易媒质电磁参数的计算机辅助测量

本文研究任意媒质的电磁参数测量。一般地,把媒质样品看作一段均匀有耗网络,利用所测得的S参数反演出媒质的完全电磁参数(?)=ε_0(ε′-jε″)和(?)=μ_0(μ′-jμ″)。全部过程采用计算机辅助分析。文中给出了实验结果。     

材料

0203897材料电磁参数测量误差传递流程图分析法[刊]/田步宇//西安电子科技大学学报.—2001,28(5).—569～572,583(K)介绍了一种分析材料电磁参数测量不确定度的新方法——误差传递流程图分析法,该方法根据所用测量技术的物理模型与数学模型,找出切合实际的误差传递关系,建立误差流程图,据此编程计算,求得各种误差因素引起的定量结果以及综合误差。利用此方法分析了多端口材料电磁参数测试系统的测量不确定度,得到了一些重要结论。结果表明,对于复杂测试系统,该方法十分有效。参80203898梯度功能材料研究进展[刊]/王慧//河北工业科技.—2001,18(5).—44～48(K)     

怎样分辨电缆的特性阻抗?

在实验中,我们必须用特定的电缆把仪器、设备和被测对象联接起来才能实现匹配,否则将使实验不能准确.因此需要正确辨认各种电缆的特性阻抗.我们可以通过同轴电缆的特性阻抗计算公式来辨认: Z_c60(μ_r/ε_r)~(1/2)In(R/r)(1) 式中:R为外导体半径,r为内导体半径,ε_r为两导体间所充介质的相对介电常数,μ_r为相对导磁系数. 但是,实验室里的电缆大多数是已经装有电缆头的成品电缆,混杂在一起,无法从外表结构上辨认.必须设法在不拆卸的情况下,测量出它的特性阻抗,加以辨认.我们知道,同轴电缆的特性阻抗     

传输/反射法测量微波吸收材料电磁参数的研究

通过从HP8722ET网络分析仪提取散射参数,研究了以乙丙橡胶为基体,磁性材料羰基铁粉为吸收剂的微波吸收材料同轴测试样品在同轴夹具中位置L1与样品长度L2的测量误差对其电磁参数测量结果的影响,提出了减小测量误差的方法.结果表明：在2.6～18GHz范围内,L1存在-0.08mm的绝对误差使得相对介电常数实部ε′与虚部ε″,相对磁导率实部μ′与虚部μ″的测量值与真实值的最大相对误差值分别达3.1%、168.0%、3.7%和-10.0%;L2存在-2%的相对误差使得ε′、ε″、μ′和μ″的测量值与真实值的最大相对误差值分别达3.5%、30.0%、4.0%和5.0%.采用光学显微镜的静态方法测量样品长度和使用辅助定位夹具可以减小测量误差，提高电磁参数测试结果的精确度。     

PCB的特性阻抗与电磁干扰（Ⅱ）

1 特性阻抗对基板材料之要求现以特性阻抗值较高和广泛采用的微带线结构为例图4中的(a)。特性阻抗(Z_0)为Z_0=87/(εr 1.41)~(1/2)ln5.98H/(0.8ω T)(6)式中的εr—介质常数,H—介质厚度,ω—导线宽度,T—导线厚度。结合图3和图4可以看出:影响特性阻抗的主要因素是:(一)介质常数;(二)介质厚度;(三)导线宽度和(四)导线厚度等。因而可知,特性阻抗与基板材料(覆铜板材)关系是非常密切的,相关的便有(一),(二)和(四)三个因素,故选择基板材料在 PCB 设计中     

用矢网测量非50Ω传输线特性阻抗的方法

1引言 传输线特别是同轴传输线在射频系统或测试系统的外接线中得到很广泛的应用,而在评估传输线时,通常需要测鼍的参数包括特性阻抗Z0,单何长度C,传播常数γ=α＋β,其中α—相位常数,β—衰减常数。     

Dynamic Three-Dimensional TLM Analysis of Microstriplines on Anisotropic Substrate

The frequency-dependent propagation characteristics of a hybrid mode along microstriplines on anisotropic substrates are presented for the case where the constitutive parameter tensors maybe diagonalized. A generalization of the three-dimensional transmission-line-matrix (TLM) numerical procedure is used to obtain results for the phase constant Beta, effective permittivity epsilon/sub eff/, and the characteristic impedance Z, all as functions of frequency and the shape ratio (w/h). Also shown are results for coupled microstrips on a sapphire substrate.     

High precision analysis of finlines on semiconductor substrate

In this study, the effect of the metallization thickness in finlines on semiconcuctor substrate is researched. The propagation parameters are computed to measure the inluence of the metallization. The theory and numerical results are presented to the propagation constant and characteristic impedance of the bilateral and unilateral finlines. The full wave analysis of the transverse transmission line — TTL method is used to determine the electromagnetic fields of the structure in Fourier transform domain — FTD. Applying the suitable boundary conditions, the moment method and expanding the fields in a set of suitable bases functions, a homogeneous matrix system is obtained and the propagation constant is computed. The characteristic impedance is obtained using the relation of the voltage in the slot and the transmitted power by the structure. Computational programs are developed to obtain numerical results to the propagation parameters composed by the propagation constant and characteristic impedance.     

对具体结构复介电常数测试的研究

根据微波材料的设计结构（如圆波导结构、非均匀加载结构）建立对应的模型,并以矢量网络分析仪测量的S参数为基础,通过HFSS仿真优化,最终给出相对应的相对复介电常数。由于传统的测试平台只能实现对微波材料样品的测试,因此这里所述方法一方面对于缩短设计周期具有重要意义,另一方面避免了对复杂结构的特性阻抗及传播常数繁琐的求解过程。通过经典的NRW算法所得结果与仿真所得结果相比较,验证了该方法的有效性。     

Dispersion in finlines on semiconductor and the S-parameters of a step discontinuity

The Transverse Transmission Line method is used for the characterization of bilateral and unilateral finlines on a semiconductor substrate and in conjunction with the modal method, for the calculation of the scattering parameters due to a step discontinuity on a unilateral finline with a lossless dielectric substrate. Numerical results of the effective dielectric constant, attenuation constant and characteristic impedance for the bilateral and unilateral finlines on semiconductor substrates, and results of scattering parameters of a step discontinuity for unilateral finline, are presented.     

由散射系数反演电磁参量的一种改进算法

传输/反射法中存在的多值性问题多年来颇受关注。本文考察了两套由散射系数反演电磁参量的公式,表明在满足折射率虚部不小于零、阻抗实部大于零和折射率正切角取值范围受阻抗正切角限制关系三条件时,两套公式均可确定阻抗和折射率虚部,并给出数量有限的、可能的折射率实部。在此基础上,利用相邻频率点电磁参量的连续性,可分别求出数个差异显著的电磁响应谱。依据对材料电磁性能的初步认识,不难选出合适的介电常数和磁导率。最后,通过实例检验了上述方法的有效性。     

Attenuation and propagation in various finline structures

The theory and numerical results of the asymmetric single and coupled bilateral and unilateral finlines and arbitrary antipodal finline considering the attenuation of the substrate are presented. Results are given to the complex propagation constant. The full wave analysis of the Transverse Transmission Line — TTL method is used in the FTD. Applying the moment method the complex propagation constant, including the attenuation constant and the phase constant, are obtained. The effective dielectric constant, ?_eff,, and the characteristic impedance are also calculated. The results are compared with the references, and news results are presented for these parameters.     

A novel transmission line characterisation based on measurement data reconfirmation

Due to inherent resonance effects and frequency-variant dielectric properties, it is very difficult to experimentally determine the stable and accurate circuit model parameters of thin film transmission line structures over a broad frequency band. In this article, a new, simple and straightforward frequency-variant transmission line circuit model parameter determination method is presented. Experimental test patterns for high-frequency transmission line characterisations are designed and fabricated using a package process. The S-parameters for the test patterns are measured using a vector network analyzer (VNA) from 100 MHz to 26.5 GHz. The parasitic effects due to contact pads are de-embedded. The frequency-variant complex permittivity and resonance-effect-free transmission line parameters (i.e., the propagation constant and characteristic impedance) are then determined in a broad frequency band.     

Unified method for determining the complex propagation constant of reflecting and nonreflecting transmission lines

In this letter, a unified method for computing the complex propagation constant /spl gamma/ of reflecting and nonreflecting lines is presented. The method uses a new matrix representation of the wave cascade matrix of a line having any characteristic impedance. To overcome the sign ambiguity problem inherent to the classical method some parameters of the fictitious X/sub AM/ matrix are used and determined by the method itself. The success of the new procedure to resolve the sign ambiguity problem lies in the new matrix representation of the wave cascade matrix of a line having any characteristic impedance and in the reliable criterion to determine the a/sub m//c/sub m/ and b/sub m/ parameters of the fictitious X/sub AM/ matrix.     

Slow wave propagation using interconnections for IC technologies

A microstrip slow wave transmission line, based on a periodic structure made with the two metallic levels used in ICs, is described. Using on-wafer measurements, an effective permittivity as high as 20 in a wide microwave frequency range is reported. The transmission line has also been measured to obtain the characteristic impedance and the losses. Using the basic periodic structure theory the propagation constant of this media has been computed and good agreement has been obtained with that of the measurement. This slow wave structure is very promising for use in MMIC because of its very compact design.<>