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。     

非平行微带线间的串扰抵消研究

非平行微带线是印刷电路板(PCB)上不可避免的互连结构。针对PCB 上非平行微带线间的串扰问题,用平行微带线近似非平行微带线,把平行耦合微带线间的串扰抵消方法应用到非平行耦合微带线中,提出了利用耦合传输线信道传输矩阵方法来进行远端串扰抵消,在对非平行耦合传输线信道传输矩阵进行特征值分解的基础上构建串扰抵消电路。仿真了非平行微带线间夹角分别为q=3°、5°、10°时的串扰,结果表明,该方法可以有效改善非平行微带线上信号眼图的质量,串扰抵消效果良好。     

Characterization of V-groove coupled microshield line

A new membrane supported air-filled V-groove coupled microshield has been investigated using finite element method. The even- and odd-mode characteristic impedances and the effective dielectric constants have been computed. The dependence on various dimensions has been studied. The crosstalk levels between adjacent lines have been compared with that in coupled microstrip lines, coupled microstrip lines with lateral ground planes, and V-groove structures with and without metallization in the groove.     

衬底材料对微带线间串扰耦合的影响研究

随着系统频率的提高,衬底材料特性已成为影响信号走线之间串扰的一个不可忽略的因素。该文基于传输线方程和频域S参数对两平行微带线间串扰耦合进行理论分析,并结合全波3维电磁场仿真工具对具有不同介电常数和不同厚度的衬底材料进行了仿真和分析,得到了微带线在不同衬底下的电场分布,以及近端和远端串扰随频率、衬底介电常数和厚度变化的曲线。随着频率的增大,远端串扰将大于近端串扰,并且随着衬底介电常数和厚度的增加,微带线间的串扰呈现正弦上升的变化趋势。     

Méthodes d’analyse et de synthèse de quelques “ microantennes” à large bande en mode quasi transversal électromagnétique

The transmission line model has been utilized to determine the input impedance, the bandwidth, the radiation patterns and the mutual impedance of several microstrip antennas such as the arbitrary shape patch antennas and the wideband flat dipole which is an hybrid radiating source. We suppose that the dominant mode of propagation is the quasiTem one having negligible variation of fields in the transverse direction. Nevertheless a general scattering problem of an arbitrary shaped tridimensional antenna solved by moments method and the finite difference approach applied to integral equations has explained the very large bandwidth microstrip antenna behaviour. The wideband flat dipole has been used in flat arrays, with more than several hundred of such elements, and in microstrip phased arrays with beam steering in a large angular sector.     

面向远端串扰的电路信号降扰研究

电路板信号间的远端串扰对信号的完整性具有较大的影响。为研究降低远端串扰的方法,本文利用Ansoft HFSS软件对线间串扰进行电磁仿真研究。研究表明通过添加防护线、覆盖介质层等措施可以降低远端串扰的影响。在一定频率范围内增加RSR结构中金属贴片的长度和数量,使金属贴片厚度接近微带线厚度等措施,会具有更好的效果;选择具有较高相对介电常数的覆盖介质层材料及增大介质层的厚度也可以降低远端串扰的影响。     

Characterization of picosecond pulse crosstalk between coupledmicrostrip lines with arbitrary conductor width

The propagation and crosstalk properties of picosecond electrical pulses along coupled microstrip lines with arbitrary strip widths are investigated. The current distributions and propagation constants of the dominant c- and π-modes in these asymmetric coupled striplines are calculated using the spectral domain approach; and the full-wave analysis results obtained are incorporated into a fast Fourier transform (FFT) algorithm to simulate pulse distortion and crosstalk in the coupled transmission lines. Several samples of asymmetric coupled microstrip lines are fabricated and their characteristics are measured. The results of experiments are found to be in good agreement with those of computer simulations. For the first time, rigorous results of picosecond pulse distortion and crosstalk in asymmetric coupled transmission lines are provided     

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.     

High-frequency, low-crosstalk modulator arrays based on FTC polymersystems

A novel electro-optic polymer Furan TetraCyano Indane (FTC) has been utilised in the fabrication of low V_π, high-speed travelling-wave Mach-Zehnder modulator arrays. The modulators were realised with microstrip transmission lines that were optimised resulting in a line loss of 3.64 dB/cm at 40 GHz. Mach-Zehnder modulators based on this design with 1.6 cm interaction length resulted in devices with V_π<5 V and a reasonably fiat frequency response up to 40 GHz. Electrical crosstalk measurements were also conducted on adjacent modulators separated by 400 μm in a modulator array. Without the implementation of any crosstalk reduction techniques, the measurement results indicated a crosstalk level of <-40 dB in the frequency band between 0 and 40 GHz. These impressive results were a consequence of the low dielectric constant of the polymer material at microwave frequencies and of the small lateral dimensions of the microstrip lines     

Behavior of Short Pulses on Tightly Coupled Microstrip Lines and Reduction of Crosstalk by Using Overlying Dielectric

Forward crosstalk can be a problem in the design of printed circuit boards. We explore two aspects of forward crosstalk in tightly coupled microstrip lines. First, we demonstrate, as far as we are aware, the first direct experimental verification of different velocities of propagation in tightly coupled microstrip lines. (These are the even and odd modes for symmetric lines.) Second, we verify by modeling and by experiments the reduction in forward crosstalk when microstrip lines are covered by the proper overlying thickness of dielectric and the simultaneous reduction in differences in modal velocities. In 1981, Anderson introduced a clever means to reduce forward crosstalk in microstrip lines to zero by burying the lines under a relatively thin dielectric layer of an appropriate thickness. At this critical overlayer thickness, the capacitive and inductive crosstalk components are equal even for inhomogeneous media. Anderson's work is not well known to most packaging engineers because it appeared only in the patent literature and in the review of scientific instruments, an excellent journal, but not one usually read by the packaging community. We extend Anderson's results by demonstrating that at the critical thickness of the overlying dielectric the velocities of the two modes become equal. We verify that Anderson's argument extends to the case where the lines are so tightly coupled that the modal velocities differ by more than 10%. We also generalize his results to the case where the lines are asymmetric. Experimental results on microstrip lines approximately 61 cm in length confirm the modeling predictions.     

Investigation of Crosstalk and Coupling Effects of Incident Plane Waves in Orthogonal Microstrips in High-Speed Integrated Circuits Using Full-Wave and Quasi-Static Methods

The crosstalk and coupling of the external fields on orthogonal microstrip transmission lines in different layers have significant effects on signal quality in MMIC and PCBs. In this paper the crosstalk is analyzed in detail using both full-wave and quasi-static methods. The used full wave method is mixed potential integral equation method of moment (MPIEMoM). Because of the weak coupling between lines, the effect of the incident plane-wave is studied by applying transmission line theory in a scattered voltage formulation uses quasi-TEM propagation model for each interconnection and the exact distribution of the incident electric field within the layers. Afterward, by using the predetermined lumped circuit model of the cross-region, the effect of coupling between two lines is calculated and then applied to terminal voltages in 1–20 GHz frequency range which results in the final terminal voltages.     

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     

Quasi-static analysis of shielded microstrip transmission lineswith thick electrodes

An extended point-matching method for analyzing the shielded microstrip transmission lines with thick electrodes has been developed based on the method by Marcuse (1989). This method provides a simple and fast approach to the quasi-static analysis of the structures. The calculated fields are used to estimate the characteristic impedance and effective dielectric constant of the structures. The results agree well with available theoretical results obtained using other methods, such as the finite element method and the boundary element method. This method can be further applied to other microstrip lines widely used in monolithic microwave integrated circuits (MMICs) applications     

非均匀传输线间的串扰研究

应用时域有限差分法对非均匀传输线间的串扰耦合进行分析。基于细线散射的时域有限差分法分析非均匀结构时,采用阶梯式均匀传输线模型,对非均匀传输线进行分段逼近。针对不等长、线径变化、非平行线和交叉线4种情况分析其参数变化对串扰的影响。研究表明：不等长电缆超出部分长度对串扰耦合幅度影响较小,对谐振频率影响较大;电缆线径的变化对其串扰耦合影响较小;非平行线和交叉线的角度对电缆间串扰的影响较大。     

Crosstalk between microstrip transmission lines

Methods for prediction of crosstalk between microstrip transmission lines are reviewed and simplified for the weak-coupling case. Classical coupled transmission line theory is used for uniform lines, and potential and induced EMF methods are used for crosstalk between nonuniform lines. It is shown that the potential method is equivalent to classical coupled transmission line theory for the case of uniform lines. An experiment was performed for uniform coupled microstrip lines for frequencies from 50 MHz to 5 GHz, and good agreement between theory and measurement was obtained for both near- and far-end crosstalk     

Analytical and Experimental Study on Suppression of Electromagnetic Interference on High Speed Printed Circuit Board for Wireless Communication Systems

In this paper, a novel routing topology is proposed to reduce crosstalk between parallel links used for high data rate application. Generally, microstrip lines are used in high frequency RF printed circuit boards for propagating high speed signals in wireless communication. Since RF front end modules in wireless system supports a wide ultra wide band frequency range from 700 MHz to 12 GHz, package density parasitic effects have been a major issue which degrades system performance. The close proximity of signal transmission lines with a high packing density results signal integrity problems such as crosstalk and timing jitter. A modified coupled microstrip line is proposed to reduce crosstalk by means of increasing capacitive coupling ratio. Our proposed structure reduced far end crosstalk by 4 dB and near end crosstalk by 4 dB than existing structures. The proposed microstrip line increased the maximum data rate from 1 to 3.3 Gb/s and reduced timing jitter by 51 ps at 3.3 Gb/s.     

A frequency-domain approach to interconnect crosstalk simulation and minimization

A frequency-domain approach to efficiently simulate and minimize the crosstalk between high speed interconnects is proposed in this paper. Several methods for modeling coupled microstrip transmission lines are discussed. Several possible simulation strategies are also considered. A straightforward yet rigorous frequency-domain approach is followed. This approach can be used for linearly and non-linearly terminated microstrip coupled lines, since it exploits the harmonic balance technique. A typical example of microstrip interconnects is simulated and the results are compared with those obtained in previous work by other authors using time-domain methods. The simulation method proposed in this work yields good accuracy. A crosstalk minimization problem is formulated and solved following the method proposed.     

耦合微带线间串扰问题的FDTD法分析

在模拟和数字电路中,耦合微带线间的串扰会降低设备的性能。为了降低线间串扰,在攻击线两边各插入了一列用金属填充的、顶端用微带连接的接地孔。利用FDTD方法对该结构进行模拟,给出了接地孔的有效放置方法。     

Time-domain analysis of lossy coupled transmission lines

A novel method based on numerical inversion of the Laplace transform is presented for the analysis of lossy coupled transmission lines with arbitrary linear terminal and interconnecting networks. The formulation of the network equations is based on a Laplace-domain admittance stamp for the transmission line. The transmission line stamp can be used to formulate equations representing arbitrarily complex networks of transmission lines and interconnects. These equations can be solved to get the frequency-domain response of the network. Numerical inversion of the Laplace transform allows the time-domain response to be calculated directly from Laplace-domain equations. This method is an alternative to calculating the frequency-domain response and using the fast Fourier transform to obtain the time-domain response. The inversion technique is equivalent to high-order, numerically stable integration methods. Numerical examples showing the general application of the method are presented. It is shown that the inverse Laplace technique is able to calculate the step response of a network. The time-domain independence of the solution is exploited by an efficient calculation of the propagation delay of the network     

A Frequency-Dependent Coupled-Mode Analysis of Multiconductor Microstrip Lines with Application to VLSI Interconnection Problems

The spectral Galerkin procedure is used to calculate the dispersion properties of multiple conductor microstrip lines. The resulting propagation constants are then used in a coupled-mode theory which demonstrates a frequency-dependent coupling of current in a five-conductor system. These results should he useful in the study of crosstalk between parallel microstrip lines used in VLSI interconnections.