Two Methods for the Measurement of Substrate Dielectric Constant

Two methods for the accurate and convenient measurement of the dielectric constant of a microwave substrate are proposed. Both methods use the precision measurement capability of the HP-8510 Network Analyzer system and a rigorous theoretical analysis of multilayer transmission lines [6], and hence can also be used for the measurement of the frequency dependence of the relative dielectric constant. Accuracy on the order of 1.0 percent can be obtained by use of these techniques. Measurements were done for various substrates and gave results as predicted.     

A Comprehensive Technique to Determine the Broadband Physically Consistent Material Characteristics of Microstrip Lines

This paper describes a method to extract the relative complex dielectric permittivity from propagation coefficient measurements on microstrip lines. The material characteristics of microstrip lines fabricated on two different types of substrates commonly used in microwave circuit and printed circuit boards are investigated. The mechanisms that cause the effective permittivity of microstrip lines to be dispersive are explored. The technique includes creating closed-form effective permittivity equations to relate the effective permittivity of the microstrip lines to the real part of the dielectric permittivity of the substrate. Curve-fitting methods are used to create causal dielectric material models that relate the imaginary part of the dielectric permittivity to its real part. The methods developed in this paper can be used to characterize low-loss dielectric materials whose polarization is dominantly dipolar within the microwave frequency range in high-speed packaging applications.      

MSTRIP (Parameters of Microstrip) (Computer Program Descriptions)

This program calculates the characteristic impedance, phase velocity, and effective dielectric constant of single or coupled microstrip lines. Parameters to be specified by the user are as follows: range of W/H/sub 1/, S/H/sub 1/, substrate dielectric constant, single or coupled lines with or without an upper ground plane.     

Theoretical and Experimental Investigation of Asymmetric Coplanar Waveguides (Short Papers)

Conformal mapping techniques are used to obtain analytic closed-form expressions for the characteristic impedance and the relative effective dielectric constant of asymmetric coplanar waveguide with infinite or finite dielectric thickness. The line asymmetry leads to a decrease of its characteristic impedance and to an increase of its relative effective dielectric constant. Six asymmetric coplanar waveguides are realized and their characteristic impedances are measured using time-domain reflectometry techniques. The experimental results show very good agreement with the theoretical ones.     

Effects of manufacturing tolerances on the electrical performance of suspended and inverted microstrip lines

Effects of manufacturing tolerances in the dimensions and parameters of suspended and inverted microstrip lines on the electrical performance of these lines have been studied through sensitivity analysis. The closed-form expressions recently given by Pramanick and Bhartia for the analysis of these lines have been used to derive the mathematical expressions for various sensitivities and the dependence of sensitivities on the aspect ratios and on the substrate dielectric constant has been depicted graphically. Generally speaking, the effects of tolerances are seen to be reflected much more sharply in the sensitivities of the characteristic impedance than in those of the effective dielectric constant. Many other useful inferences are also drawn from the sensitivity graphs. The conclusions are presented in tabular form, so as to be of direct help to the user.     

基于介电非线性机制的微带电路无源互调效应研究

微带电路无源互调产生机制尚无定论并且缺乏可靠的理论预测方法,本文基于等效受控源模型,建立了基于介电非线性机制的微带线无源互调的解析计算模型,同时,通过对比测试聚四氟乙烯玻纤布介质微带线和空气介质微带线的三阶互调规律验证了介质非线性是微带电路无源互调的一种主要非线性来源,并提取了非线性参数.实验结果显示聚四氟乙烯玻纤布介质微带线比空气介质微带线的传输互调高了约20dB,反射互调高了约15dB,表明介质非线性是聚四氟乙烯玻纤布介质微带线互调的主要来源.同时,根据本文建立的微带线互调计算解析模型,提取聚四氟乙烯玻纤布介质基板的三阶非线性相对介电常数.本文研究方法可以进一步用于其它微带电路无源互调规律计算研究.     

A cylindrical multiconductor stripline-like microstrip transmissionline

An analytical expression for the Maxwell capacitance matrix of a class of cylindrical inhomogeneous, multiconductor transmission lines is provided. This class includes cylindrical structures symmetrical with respect to the circuit circle and having a symmetry axis. The effective dielectric constant of the line is found to be the arithmetical mean of the dielectric constants of the two media. Hence, this structure enjoys the main advances of the planar stripline-like microstrip systems. It is also pointed out how to obtain elliptical stripline-like microstrip transmission lines     

Some Characteristics of Dielectric Image Lines at Millimeter Wavelengths

The attenuation characteristics of several dielectric image lines have been calculated for the frequency range extending from 24 to 100 kmc and have been checked experimentally at 35 and 70 kmc. To obtain low attenuation at these high frequencies, dielectric materials with little loss and small size of cross section are required, while low values of the dielectric constant are also desirable. The effects of the size and shape of the dielectric cross section and of low dielectric constant are treated separately. To find proper materials with low dielectric constants several new foam plastics were investigated. Three types were found suitable for image line use, and in fact, these plastics have such good electrical and physical properties that they should be useful in many microwave applications. A qualitative measure of field extent is given for several image lines at 35 or 70 kmc, and various image lines and associated components are discussed. A new type of image line, called the tape line, is described.     

A class of artificial materials isorefractive with free space

A new class of dispersion-free artificial material that is isorefractive with free space is presented. Materials can be fabricated by composing an array of conducting inclusions in a tenuous host medium that are symmetric with respect to the direction of propagation. Strategies are proposed for both longitudinal and radial propagation. In the presence of the transverse electromagnetic mode, the inclusions are transversely polarized and hence raise the effective relative dielectric constant of the material. The inclusions simultaneously constrict the magnetic field lines, lowering the effective permeability by the same factor. The net effect is to make an artificial material with the same speed of propagation as the host material, but with a lower effective impedance. Such a material can be used to improve aperture efficiency in impulse radiating antennas. Limitations of the materials including field enhancement due to the inclusions and skin losses due to finite conductivities are also discussed.     

Determination of capacitances and inductances of the uniformcoupled lines in the anisotropic inhomogeneous medium by resistive sheet

Many filters, power dividers and nonreciprocal circuits such as a lumped element circulators used for broadcasting, communications and CATV, are using parallel coupled lines together with the high dielectric constant ceramics and ferrite. It is important to design such a devices, that the capacitance and inductance per unit length of the multi-distributed lines are determined by simple methods. This paper shows a simple method of determining the values of the multi-lines in an anisotropic medium by using the two dimensional resistive sheet or equivalent computer method. The values are used for obtaining the effective dielectric constant and the effective permeability which are required for the estimation of the quasi-TEM mode in the case of a small sectional dimension compared with the wavelength. The method used to obtain the inductance is based on the Babinet' principle     

The bilocal approximation for the effective dielectric constant of an isotropic random medium

The bilocal approximation in strong fluctuation theory leads to an expression for the effective dielectric constant of a random medium. A detailed study of this expression is made for the case of a medium characterized by an isotropic correlation function. The effective dielectric constant is shown to obey an equation involving an integral containing the correlation function, the free space propagation constant, the quasistatic dielectric constant, and the effective dielectric constant itself, Numerical methods for solution are suggested. The low frequency behavior is also examined. The leading correction term to the quasistatic dielectric constant is shown to be different than previously deduced expressions.     

Millimeter wave twist reflector design aspects

A millimeter-wave twist reflector design procedure is described. An effective dielectric constant for capacitive susceptance correction for a unidirectional planar grating at the interface of free space and dielectric material in the twist reflector environment is introduced. The loss factor of the dielectric material is taken into account for the prediction of twist reflector performance. With the introduction of these corrections experimental results are found to be in close agreement with the theory. Normalized curves for the design of twist reflectors in terms of grating parameters, dielectric substrate relative permittivity, and dielectric material thickness are presented. Experimental results are given     

Finite-element analysis of generalized V- and W-shaped edge andbroadside-edge-coupled shielded microstrip lines on anisotropic medium

This paper presents detailed finite-element analysis of generalized V- and W-shaped shielded microstrip lines in an anisotropic medium. The computed results show detailed quasistatic characteristics of the effective dielectric constant, characteristic impedance, and conductor loss of the lines. The broadside edge coupled lines are proposed for the first time in this paper. Unlike the previous analysis based on the conformal mapping method, this analysis takes into account the top walls and sidewalls, finite metallization thickness, and dielectric anisotropy. The results presented in this paper will considerable advance microwave-integrated-circuit technology using V- and W-shaped shielded microstrip lines     

Microwave dielectric properties of DNA based polymers between 10 and 30 GHz

Deoxyribonucleic acid (DNA) based polymer thin-films were characterized at microwave frequencies for the first time. The dielectric properties of the film were extracted from comparison of the propagation constants of the co-planar waveguide (CPW) lines on bare MgO substrates and the DNA based films on MgO substrates. The insertion loss introduced by the DNA film is only 0.1 dB at 10 GHz and 0.5 dB at 30 GHz. The relative dielectric constant of the DNA based film averages to four at microwave frequencies, and the loss-tangent was below 0.1 up to 30 GHz.     

On the Radiation from Microstrip Discontinuities

The method of an earlier paper by Lewin is used to calculate, more accurately, the radiated power from a microstrip termination. The substrate dielectric constant epsilon is used instead of the effective dielectric constant epsilon/sub e/ in the polarization term. The open-circuit, short-circuit, and matched coaxial terminations are deduced as particular cases of the general termination. On comparison with Lewin's results, differences of up to 30 percent have been found, but the differences are much smaller for the larger values of the actual relative dielectric constant epsilon. Curves show that the short-circuit termination radiates less than a quarter that of the open circuit, and can be considered as a means of reducing losses in microstip resonators. The parallel post configuration is also considered.     

宽边侧边耦合四微带传输线的频率特性

本文用谱域阻纳分析法研究了普遍的多层介质宽边侧边耦合多微带线的频率特性,给出了三层介质宽边侧边耦合四微带线的特性阻抗及等效介电常数的设计曲线。结果还表明该结构的偶-奇模特性阻抗Zeo随频率变化很大,当相对介电常数r较小时,变化更大。     

带调谐隔板耦合微带线色散特性的直线法分析

本文采用直线法与等效传输线法相结合分析了带调谐隔板耦合微带线的色散特性。通过在电路的两侧人为地插入电壁或磁壁,分别解出电路的偶模与奇模有效介电常数。     

Guided Waves in Limit Cases of Microstrip (Correspondence)

The great difficulty in solving for the propagation constant and effective characteristic impedance for microstrip transmission lines is invariably avoided by assuming quasi-TEM propagation and solving Laplace's equation rather than the wave equation. Deschamps and Wu have qualitatively discussed aspects of the hybrid-mode problem. Zysman and Varon have presented a solution for the related but distinctly different problem of closed microstrip. In this communication we present the basis through which the quasi-TEM analysis may be justified for the limit cases of guided waves on microstrip in which the dielectric constant approaches that of free space or becomes very large. The guided wave problem is formulated exactly in terms of longitudinal electric and magnetic field components satisfying the wave equation and coupled through the boundary conditions at the dielectric interface.     

Electromagnetic coupling of coplanar waveguides and microstriplines to highly lossy dielectric media

The spectral-domain technique is utilized to analyze the coupling characteristics of coplanar waveguides and microstrip lines coupled with multilayer lossy dielectric media. Numerical results illustrating the dispersion characteristics of coplanar and microstrip lines, as well as the various electric field components coupled to highly lossy dielectric media, are presented. It is shown that the presence of a superstrate of lossless dielectric between the coplanar waveguide and the lossy medium plays a key role in setting up an axial electric field component that facilitates leaky-wave-type coupling to the lossy medium. The thickness of the superstrate relative to the gap width in the coplanar waveguide is important in controlling the magnitude of this axial electric field component. The coupling characteristics of the microstrip and coplanar lines are compared, and results generally show improved coupling if coplanar waveguides are utilized. Values of the attenuation constant α are higher for coplanar waveguide than for microstrip line, and for both structures α decreases with frequency