The impact of a nonideal return path on differential signalintegrity

Printed circuit board transmission lines propagating high-speed digital signals are susceptible to nonideal return paths which may affect signal integrity. In an attempt to clarify this complex issue, this paper presents a study of differential signal integrity issues for the familiar situation in which two coupled microstrip traces are in close proximity to a common reference plane. Differential signaling on coupled microstrip lines and stripline configurations are investigated. Finite-difference time domain simulations are used to demonstrate the impact a nonideal return path can have on differential signal integrity     

Isolation effects in single- and dual-plane VLSI interconnects

The issue of interline coupling in high-speed VLSI interconnects is addressed. A full-wave-based technique is used to numerically solve for the modes and hence the line voltages and currents for multiconductor microstrip. The accuracy of these results is compared with time-domain experimental data. Isolation lines placed between signal lines and grounded at both ends are considered as a means of significantly reducing crosstalk. It is shown that the performance of such lines depends on several factors such as relative mode velocities, signal rise and fall times, and line length. These points are illuminated by considering the effects of isolation lines in two geometries of interest in high-speed integrated circuits. On the basis of these results one can determine the usefulness of isolation lines for a given geometry     

Dispersion characteristics of open and shielded microstrip linesunder a combined principal axes rotation of electrically andmagnetically anisotropic substrates

This work examines the dispersion properties of microstrip transmission lines whose substrate permittivity and permeability tensors are rotated simultaneously. The analysis takes into account both shielded and open structures, including both single and coupled microstrip line geometries. The spectral-domain method is utilized to formulate the dyadic impedance Green's function, and Galerkin's method is applied to find the propagation constants. Numerical studies are performed when the angular difference between the principal axes of [ϵ] and [μ] tensors is fixed, but both are rotated from 0 to 90°. The dispersion characteristics for all structures are computed over a wide frequency band that ranges from 0.1-100 GHz. The study indicates that propagation properties of microwave integrated circuits (MICs) with dielectrically and magnetically anisotropic substrates (such as composites) can be changed considerably by the misalignment of material and structure coordinates systems     

耦合微带线的散射参数特性分析

针对耦合微带线的散射参数在一些频率点处呈现出波峰、波谷现象,该文根据微波网络理论,从两根平行微带线的奇模和偶模的散射参数出发,推导出四端口网络散射参数的波峰、波谷处频率与并行长度和线间距的关系。同时分别在频域和时域研究了两根平行微带结构的插入损耗对信号传输的影响。经分析发现,由于微带线间的耦合,波峰、波谷处的频率随线间距增大而提高,随长度增大而降低;而且在串扰产生的同时,所传输的信号也有一定程度的衰减。     

Dielectric Waveguide Microwave Integrated Circuits---An Overview

An integrated circuit technique for microwave and millimeter wavelengths which uses refractive-type waveguides and signal processing coupled with planar integration techniques characteristic of microstrip microwave integrated circuits (MIC's) is described. Following a comparison of the optical and millimeter approaches to this circuit technique, a discussion of transmission lines and components for millimeter wavelengths is presented. System applications are also described.     

A novel method for modeling coupling between several microstriplines in MIC's and MMIC's

A technique for modeling the adjacent and nonadjacent couplings between several microstrip lines in microwave integrated circuits (MICs) and monolithic microwave integrated circuits (MMICs) is presented. The technique assumes that the primary transmission paths in the circuit can be modeled with conventional single or coupled microstrip models. A particular four-port model is then superimposed on the existing circuit for each adjacent or nonadjacent coupling that is present. This model uses analytical equations for microstrip coupled lines and is, therefore, fast and easy to compute     

Embedded microstrip interconnection lines for gigahertz digitalcircuits

Transmission line structures are needed for the high-performance interconnection lines of GHz integrated circuits (ICs) and multichip modules (MCMs), to minimize undesired electromagnetic wave phenomena and, therefore, to maximize the transmission bandwidth of the interconnection lines. In addition, correct and simple models of the interconnection lines are required for the efficient design and analysis of the circuits containing the interconnection lines. In this paper, we present electrical comparisons of three transmission line structures: conventional metal-insulator-semiconductor (MIS) and the embedded microstrip structures-embedded microstrip (EM) and inverted embedded microstrip (IEM). In addition, we propose closed-form expressions for the embedded microstrip structures EM and IEM and validate the expressions by comparing with empirical results based on S-parameter measurements and subsequent microwave network analysis. Test devices were fabricated using a 1-poly and 3-metal 0.6 μm Si process. The test devices contained the conventional MIS and the two embedded microstrip structures of different sizes. The embedded microstrip structures were shown to carry GHz digital signals with less loss and less dispersion than the conventional MIS line structures. S-parameter measurements of the test devices showed that the embedded microstrip structures could support the quasi-TEM mode propagation at frequencies above 2 GHz. On the other hand, the conventional MIS structure showed slow-wave mode propagation up to 20 GHz. More than 3-dB/mm difference of signal attenuation was observed between the embedded microstrip structures and the conventional MIS structure at 20 GHz. Finally, analytical RLCG transmission line models were developed and shown to agree well with the empirical models deduced from S-parameter measurements     

Rectangular resonators in inverted microstrip and suspended microstrip

Resonant frequency characteristics of rectangular resonators in a generalized shielded suspended substrate line are analysed using a rigorous spectral domain technique. The computed dominant mode resonant frequency of rectangular resonators in a suspended microstrip with centred dielectric, inverted microstrip and suspended microstrip are presented as a function of various structural parameters. These characteristics are distinct from those obtained for a conventional microstrip rectangular resonator. Experiments are carried out in the frequency range 4-18 GHz to verify the computed resonant frequencies for a suspended microstrip with a centred dielectric using first-order basis functions. The results should find applications in the design of inverted microstrip and suspended microstrip passive microwave and millimetre wave integrated circuits.     

基于介质集成悬置槽线的差分至单端功分器北大核心CSCD

设计了一种基于介质集成悬置槽线的宽带差分至单端功分器。采用槽线与微带线耦合的差分过渡结构,实现了差分电路与单端电路的互连。在较宽的工作频率范围内实现了较好的共模噪声抑制。在10.52~15.58 GHz的频率范围内,测得差分端口处的回波损耗优于10 dB。输出端口在10.1~15 GHz的频率范围内保持15 dB以上的隔离度。差分工作模式下,功分器输出的两路信号具有幅值相等、相位相反的特点。所设计的电路基于多层板结构,将槽线及其核心电路悬置于多层板内置的腔体中,具有自封装、低辐射损耗等优势。     

耦合传输线信道传输矩阵建模及串扰抵消效果分析

针对高速互连系统中传输线上的串扰问题,基于电磁耦合理论,研究了耦合传输线信道传输矩阵的性质,建立了以下两种情况的耦合传输线信道传输矩阵模型及其矩阵分解形式,分别是：（1）考虑受扰线两边各一条相邻微带线对受扰线的串扰;（2）考虑受扰线两边各两条相邻微带线对受扰线的串扰.给出了上述两种情况下基于耦合传输线信道传输矩阵分解形式的串扰抵消方案,并利用仿真工具ADS对其进行了验证.结果表明：信号抖动和失真大幅下降,串扰抵消效果良好,并且第二种情况下的串扰抵消效果优于第一种情况.该结果说明了在基于耦合传输线信道传输矩阵进行串扰抵消时,考虑两边各两条相邻微带线的串扰效果较好,对保持高速信号完整性具有一定的实际应用价值.     

微带线中光敏带隙的电磁模型

微带线中的光敏带隙常被用于光控微波开关和皮秒光电测试系统中。文中描述了微带线中的光敏带隙的动态特性。在充分考虑波导中的表面电流和光受激域中体电流的相互耦合作用后，给出了完整的波导理论模型。文中讨论了激励光功率、受激载流子扩散、光辐射、表面波和不连续区的边缘效应等因素对微带线中微波传输的影响。     

Simulation des régimes transitoires sur des sections de lignes microruban par une technique de filtrage numérique

This paper deals with a method for analysis of pulse transmission and reflection on microstrips sections that can be used as interconnection lines in or between high-speed digital integral circuits. It is shown that z-transform, which defines an intermediate domain between time and frequency, leads to a very general simulation method of the transient properties of the line sections. The line characteristics can be frequency dependent because of the propagation losses. The validity of the model is established from direct measurements on microstrip sections etched on alumina and GaAs substrates.     

Finite-Difference Time-Domain Analysis of Electromagnetic Modes Inside Printed Coupled Lines and Quantification of Crosstalk

Detailed analysis of mode structures inside coupled microstrip lines and their correlation with crosstalk between traces has been performed. The use of finite-difference time-domain and singular value decomposition methods for modal identification followed by cross correlation for crosstalk prediction is demonstrated in this paper. The combination of these methods is robust, versatile, and ideal for pulsed applications in an inhomogeneous, anisotropic multilayer substrate with complex 3-D structures. Moreover, all possible modes are extracted in a single analysis. This novel approach provides a quantitative measurement of crosstalk by establishing correlation between modes evolving inside the source line and the field waveforms coupled with the victim line. The effects of line topology, material properties, and pulse characteristics are examined. At the near end, transverse electromagnetic mode of the source line dictates coupling; however, as the pulse advances, the higher order transverse magnetic mode dominates and exhibits significant contribution to the evolution of the waveform coupled with the victim line at the far end, which is confirmed by cross correlation. This paper has physical significance in devising systems for suppressing unwanted modes responsible for crosstalk and radiation leakage due to fast pulses.      

高温超导耦合微带线动态电感模型

应用单根微带线内部电感计算的“增值电感规则”，提出一种计算高温超导耦合微带线动态电感的方法，即从无限簿的奇、偶模特性阻抗出发，求出无限薄耦合微带线的外部奇、偶模电感，经修正后得到有限厚的外部电感公式，再利用增值的电感规则及不同厚度时电感增值的不同特点，提出4种情况下电感增值的不同偏导形式，进而求出其相应的动态电感。该公式对超导电路元器件的设计和分析具有指导作用，其正确性通过两个计算实例得到了验证。     

An evaluation of materials and processes for integrated microwave circuits

This paper presents an evaluation of materials and processes applicable to the fabrication of hybrid microstrip microwave circuits. Substrate materials evaluated included aluminas, beryllias, quartz, and glass of varying purities and surface finishes. Conductor materials evaluated included silver, copper, gold, and aluminum. Fabrication processes studied included vacuum deposition sputtering electroless and electroplating, thick-film screening and firing, and photoetching. Sapphire and high-purity alumina (99.5 percent pure or better) substrates were found superior as substrates for microstrip circuits. Conductor materials and processing methods found best were 1) vacuum deposited chromium-gold thin film which was gold electroplated and photoetched; 2) thick-film silver which was photoetched to delineate the microwave pattern.     

Design of Aperture-Coupled Filters

A procedure for the design of aperture-coupled Filters is presented, based on the theory of conventional coupled circuits. This design procedure accounts for the relatively low insertion loss of aperture-coupled filters as compared with other known designs of microwave filters. The factors which contribute to this low value of insertion loss are the following: 1) Use of a high Q-mode configuration such as a cylindrical cavity in the TE/sub 011/ mode. 2) Aperture coupling of elements eliminating the losses of impedance transforming sections of transmission line. 3) A mechanical design which eliminates joints at critical points and also provides control over interior surface finishes.     

一种基于耦合线和环形微带线的负群时延电路

负群时延电路(NGDC)在微波系统中有着广泛应用,文中提出了一种基于有损耦合线和环形微带线的负群时延电路。该电路由耦合线和微带传输线组成。基于射频领域中偶模-奇模分析方法,分析该电路的偶模和奇模的输入导纳,得到电路的S 参数。利用HFSS 电磁仿真软件对该负群时延电路结构做了优化设计,实物加工并测试。测试结果表明:在中心频率2.36 GHz 时,该电路的负群时延值约为-1.4 ns,插入损耗S21约为-3.9 dB,反射系数S11约为-9.5 dB,实测与仿真结果吻合。这种新颖的负群时延电路结构简单、信号损耗小、易于加工,可用于微波和无线通信等领域。     

Novel microstrip multifunction directional couplers and filters formicrowave and millimeter-wave applications

The design of a particular class of microstrip couplers and filters is presented. The synthesis functions obtained from the solution of first-order nonlinear differential equation of nonuniform lines with a loose coupling assumption are modified and validated for higher coupling values. The design employs a nonuniform coupled line configuration along which a realizable continuous coupling coefficient is obtained by modifying the reflection coefficient distribution function. This modification results in a frequency-selective coupling which minimizes the out-of-band coupling in the specified frequency range. As a result, it is possible to realize -3 dB directional couplers using double-coupled lines without the need for tandem connections or extreme photolithographic techniques. Experimental results for microwave band-pass and periodic couplers are presented together with the computed results. Potential applications of these components are discussed, and the work is extended to include millimeter-wave realization     

On The Problem of Using Guard Traces for High Frequency Differential Lines Crosstalk Reduction

In this paper, the problem of using guard traces for reducing crosstalk between differential transmission line pairs is investigated, both experimentally and by full-wave electromagnetic (EM) simulations. Different cases of differential lines crosstalk are treated with and without guard trace separation between the differential line pairs. Coated microstrip printed circuit board test structures including thru-reflect-line calibration standards are designed and fabricated on a high frequency laminate material, allowing direct measurement of crosstalk between adjacent differential line pairs in the absence and in the presence of guard traces stitched with vias of regular spacing. The test structures are characterized with mixed-mode scattering parameters using a physical layer test system. Different configurations (of differential line pairs) without guard trace, with floating guard traces (which are terminated and nonterminated) and with a solid guard trace separation are investigated using a High Frequency Structure Simulator (a commercial full-wave 3-D EM simulation tool). The experimental data are compared with the simulation results, and some conclusions and guidelines on the effect of guard traces for alleviating crosstalk between differential transmission lines are presented     

Rigorous analysis of planar MIS transmission lines

The realisation of distributed microwave integrated circuits can be expected by using very low phase velocity propagation modes on MIS and Schottky planar transmission lines. Up to now, the frequency behaviour of such lines has been obtained by using analytical models. We present a rigorous analysis of a MIS microstrip line, the validity of which is testified by comparison to experimental values.