Lumped Capacitance, Open-Circuit End Effects, and Edge-Capacitance of Microstrip-Like Transmission Lines for Microwave and Millimeter-Wave Applications

A detailed analysis of lumped capacitance, open-circuit end effects, and edge-capacitance of finite-length strip conductors embedded in multilayer, isotropic dielectrics without sidewalls is presented. The analysis uses the well-known variational technique, in conjunction with the transverse transmission-line technique. The lumped capacitances of square and rectangular conductor patches in sandwiched microstrip, inverted microstrip, and suspended microstrip are computed. Further, extensive data on the open-circuit end effects and edge-capacitances of finite-length strip conductors in these rnicrostrip-like transmission lines are generated. Using the method presented, the analysis of lumped capacitance, open-circuit end effects, and edge-capacitances of finite-length strip conductors in various microstrip-like structures reduces to the determination of a single admittance parameter. This parameter can be simply obtained from the transmissionline equivalent circuit.     

Lumped capacitance and open end effects of striplike structures inmultilayered and anisotropic substrates

An accurate calculation of the lumped capacitance of a rectangular microstrip patch and the edge capacitance of an open-circuit microstrip or stripline is carried out. Variational expressions in the spectral domain are developed to analyze these conductors when they are embedded in a multilayered anisotropic substrate. A recurrence algorithm, easy to compute, is proposed to determine the three-dimensional spectral Green's function characterizing the sort of substrates employed. The method makes it possible to study biaxial substrates in the case of the rectangular patch and uniaxial substrates with tilted optical axis in the transverse plane in the case of open-circuit striplike transmission lines. A detailed study of trial functions to approximate the charge density on the conductors is carried out, taking into account the physical features of each problem. The results obtained are compared with those appearing in the literature. Original design graphs are presented, with special emphasis on the use of inhomogeneous and anisotropic substrates     

Capacitance parameters of coupled elliptic microstrip disks inlayered anisotropic media

An algorithm which calculates the modal capacitances and the gap capacitance of coupled microstrip elliptic disks embedded in layered media with dielectric anisotropy is discussed. The capacitance parameters determined are useful in accounting for coupling effects in the design of interacting lumped microstrip components of elliptic shape     

Double-layer microstrip structures—lumped capacitances and open-circuit end correction

The analysis is reported of the lumped capacitance and open-circuit end effects of finite-length strip conductors in double-layer microstrip structures. Two specific configurations, namely double-layer microstrip and microstrip-with-overlay configurations, are considered. The analytical approach uses the variational technique in the Fourier transform domain in conjunction with the transverse transmission line technique. It is identified that the only parameter needed to analyse the lumped capacitances and open-circuit end effects of these microstrip structures is the admittance at the charge plane. This parameter can easily be determined from the two-wire transmission line equivalent circuit. Extensive numerical data are generated for the lumped capacitances and open-circuit end effects of the finite-length strip conductor in double-layer microstrip and microstrip-with-overlay configurations. The data presented should be useful in designing lumped elements and filters in these configurations.     

Scattering matrix of dielectric resonator coupled with twomicrostrip lines

A lumped equivalent circuit is proposed to model the coupling of a dielectric resonator with two microstrip lines terminated by any impedance. A three-dimensional finite-element method is used to determine the resonant frequency, quality factor, and coupling coefficients as functions of the electromagnetic parameters of the structure. Scattering parameters are computed. Methods are presented to evaluate these coefficients from a field analysis. They are shown to give good agreement between computed and experimental results     

Matrix Methods for Microstrip Three-Dimensional Problems

The matrix methods are applied to three-dimensional microstrip problems with emphasis upon the general problem of discontinuities in microstrip. Discontinuities considered are 1) open circuits, 2) change of width, and 3) gap in microstrip. Also, the capacitance of rectangular sections of microstrip is computed. Computed data agree well with experiment and data in the literature.     

An Analysis of Gap in Microstrip Transmission Lines

Although microstrip transmission lines have been widely used in microwave integrated circuits, the discontinuity structures in the microstrip transmission lines such as a gap, an abruptly ended strip conductor, and so on, have hardly been analyzed. An analytical method and numerical results for a gap capacitance in the microstrip transmission line are described. The equivalent circuit parameters are formulated with three-dimensional Green's functions, based on a variational principle. The numerical results are in good agreement with the published experimental data. The fringing effect of an abruptly ended strip conductor is also investigated.     

Varactor-tuned integrated Gunn oscillators

Electronic tuning of Gunn diodes in hybrid integrated circuits has been studied. Microstrip transmission lines were used to form resonant circuits into which a Gunn diode and a varactor diode were mounted to provide the microwave power and frequency tuning, respectively. Basically, two types of circuits have been investigated. The first is a half-wavelength open-circuited microstrip `cavity' with this transmission line and the varactor diode attached between the end of the cavity and an RF ground. The second is a lumped LC circuit in which the inductance of a short high-impedance microstrip line is resonated with the lumped capacitance of the varactor diode. The latter circuit provides a tuning range of over 10 percent at 7.5 GHz. The power output varies within 2 dB in the tuning range.     

基于HFSS的双层宽带微带贴片天线的研究

采用HFSS10电磁场仿真软件设计和仿真了一种新型宽带双层微带贴片天线,天线采用聚四氟乙烯和空气两层介质,通过增加空气介质层的厚度,同时利用圆形金属电容片补偿馈电探针引起的电感,对微带天线进行耦合馈电,仿真结果表明天线的阻抗带宽达到了23%（VSWR≤2）,从而实现了宽频带微带天线的设计.     

Improved tuning prediction for the microstrip coupled dielectricresonator using distributed coupling

In this paper, accurate modeling of the varactor-tuned dielectric resonator (DR) using distributed coupling between the DR and microstrip lines is investigated on the basis of three-dimensional electromagnetic study. The magnetic coupling between the DR and microstrip line is appreciable over a length greater than the diameter of the DR. The distribution of this coupling should be considered when calculating the electronic frequency tuning range. A novel circuit model is introduced to represent the coupling as distributed, with an integral method to calculate equivalent-circuit parameters efficiently. The distributed model provides much better accuracy than the conventional lumped model. A comparison is made between the calculated tuning range of 23 MHz achieved by the distributed model, which agrees closely with a measurement of 20.2 MHz, and that of 89 MHz predicted by the conventional lumped model. The circuit model of distributed coupling is, therefore, valuable in the design of DR oscillators     

基于ADS的数字调谐跳频滤波器设计方法

介绍了基于ADS的数字调谐跳频滤波器仿真设计方法。根据集总元件耦合谐振器滤波器理论计算出滤波器仿真参数,应用ADS对包括微带线、PIN二极管等参数模型的滤波器电路模拟仿真,解决数字调谐跳频滤波器电容阵列的取值问题。结合ADS仿真数据和实物测试结果,验证了该方法的有效性。     

采用FDTD法研究微带天线雷达散射截面的减缩

采用时域有限差分法(FDTD)方法以及新的含有内阻的磁流环激励同轴馈电模型研究了微带天线的辐射及散射特性,分析了集总负载加载和贴片表面开槽对微带天线雷达散射截面(RCS)的影响,研究了微带天线RCS减缩前后的回波损耗、增益及方向性的变化.研究表明,集总负载加载能降低谐振频率点的RCS,开槽方法能在天线辐射性能改变不大的情况下对微带天线的RCS具有较好的减缩作用.     

Variational Method for the Analysis of Microstrip-Like Transmission Lines

A theoretical method is presented by which microstrip-like transmission lines can be analyzed. These transmission lines are characterized by conducting strips, large ground planes, multi-dielectric-layer insulation, and planar geometry. The method is essentially based on a variational calculation of the line capacitance in the Fourier-transformed domain and on the charge density distribution as a trial function. A shielded double-layer microstrip line is analyzed by this method. Derived formulas for this structure are also applicable to simpler structures: a double-layer microstrip line, a shielded microstrip line, and a microstrip line. The calculated values of the line capacitance and the guide wavelength are compared with the measured values where possible. Oxide-layer effects on a silicon microstrip line and shielding effects on a sapphire microstrip line are also discussed based on this theory. The limitations and possible applications of this method are described.     

Linear lumped loads in the FDTD method using piecewise linear recursive convolution method

This letter gives a new algorithm to include linear lumped elements into finite difference time domain algorithm. The proposed method can efficiently account for two-terminal networks made of several lumped elements. The piecewise linear recursive convolution (PLRC) technique is used to implement lumped loads into Yee cells. Using this method, it is possible to simulate equivalent circuits of terminations for microstrip structures, integrated circuits, or digital devices. The advantage of the PLRC technique is addressed and simulation results validating this method are presented.     

Rigorous evaluation of the vertex effects on thefrequency-dependent circuit parameters of an open-ended microstrip line

This study presents the original inclusion of right singular vertex conditions in integral equations solved by the method of moments for accurate evaluation of the frequency-dependent microstrip discontinuity models required in microwave integrated circuits (MIC) and monolithic microwave integrated circuits (MMIC) design. The 90° wedges singularity function for the current density, weighted with a novel sampling function for “corner cells,” and the harmonic Green's function for shielded structures, is accurately and efficiently integrated in the conical geometry of the 90° sector. The frequency-dependent effective length and excess equivalent capacitance of a shielded open-ended microstrip line are calculated to a higher accuracy with respect to previous two-dimensional and three-dimensional “full wave analyses”     

一种贴片电感电容测量新方法的研究

为了得到贴片电感电容在微带电路中的精确值,提出一种基于矢量网络分析仪的电感电容自动测量系统.依据LC谐振电路和微带传输线理论设计制作测量夹具,通过Matlab编写田口优化算法计算得到已知电感电容值,并基于GPIB接口对矢量网络分析仪实现程控,采用VC ＋＋6.0工具开发自动测量系统的用户界面.给出了具体的设计思路和测量方法,实测结果表明,该系统实现了对微带电路中电感电容的快速精准测量,具有很高的实用价值.     

Miniaturized ring coupler of arbitrary reduced size

A simple and successful method for miniaturizing a ring coupler is proposed. The size of the ring coupler is reduced by connecting multiple open stubs on the inside of the ring. There is no need of any lumped element, via hole or wire bond, but only microstrip lines. The reduced size is arbitrary and the results of the miniaturized ring coupler coincide with that of the traditional one.     

MIM shunt-capacitor model using black boxes of EM-simulatedcritical parts

A new model for metal-insulator-metal shunt capacitors is introduced in this paper. The main difference between the new model and known models is that critical parts of the capacitor's geometry are represented by black boxes. These boxes contain S-parameter files generated with an electromagnetic field solver. The capacitor parts, which depend on the capacitance value, are represented by microstrip and lumped elements. The new model combines the advantages of field simulations with those of lumped- or microstrip-based models. It can easily be used in circuit simulators utilizing their features for design development such as optimizations. The model is compared with two shunt capacitors on microwave monolithic integrated circuits to show the excellent fit     

A planar-lumped model for coupled microstrip lines anddiscontinuities

A convenient model for analyzing coupled microstrip line discontinuities is presented. A planar-lumped model similar to the planar waveguide model for single microstrip lines is developed for coupled microstrip lines. Fields underneath the two strips and those fringing at the outer edge are modeled by two equivalent planar waveguides. Electric and magnetic field coupling in the gap region is modeled by a lumped network. The lumped network parameters are evaluated such that [C] and [L] matrices for the model are identical with those for coupled lines. The model is verified by comparing coupler characteristics with those obtained by the conventional coupled line analysis. Just as the planar model of a single microstrip has been used for characterizing microstrip discontinuities, the planar-lumped model developed is used for coupled line discontinuities. Examples given include coupled microstrip sections with chamfered bends located at right angles to single microstrip lines, for which the results are in good agreement with experimental values     

A study on stray capacitance modeling of inductors by using thefinite element method

Stray capacitance modeling of an inductor is essential for its RF equivalent circuit modeling and inductor design. Stray capacitance determines an inductor's performance and upper frequency limit. A method has been proposed for modeling the distributed stray capacitance of inductors by the finite element method and a node-to-node lumped capacitance network. The effects of wire insulation layer, ferrite core, number of segments used to model the circumference of a wire cross section, pitch and coil-to-core distances, and the capacitance between nonadjacent turns, etc., an an inductors' self-capacitance and calculation accuracy, have all been considered. The calculated equivalent lumped stray capacitance for a rod inductor with a ferrite core is compared to that estimated from measurement. Good agreement between them has been observed