A configuration-oriented SPICE model for multiconductortransmission lines with homogeneous dielectrics

Using the SPICE circuit analysis computer program to simulate a lossless multiconductor transmission line is investigated. It is demonstrated that for the case of a homogeneous dielectric, the multiconductor line can be represented by a system of standard two-wire lines which is not based on modal decomposition. This system is readily modeled with SPICE. While restricted to situations where the dielectric constant can be assumed uniform, the present method has the advantage of an intuitive relationship to the conductor configuration, simpler SPICE input data requirements, and an improvement in computer run time over other methods     

A SPICE model for multiconductor transmission lines excited by anincident electromagnetic field

This paper describes a SPICE model that may be used for predicting the time-domain or frequency-domain voltages and currents induced at the terminations of a multiconductor transmission line (MTL) by an incident electromagnetic held. Explicit results for the entries in the SPICE circuit model are obtained for an incident uniform plane wave that may represent sources such as radio and television transmitters, radars, lightning, etc. The result relies on the transformation of the MTL equations into uncoupled modal lines by similarity transformations. The entries in the similarity transformations are provided for lossless lines. The model is implemented using controlled sources to implement the modal transformations and delay lines to implement the modal lines. If the model is implemented as a SPICE subcircuit model, the time-domain form of the incident field can be implemented as a source external to that subcircuit model so that changes in the line responses due to changes In the incident field waveform can be simulated without changing the subcircuit model. In order to avoid negative line delays, the result is restricted to incident waves having components of the propagation vector in the positive direction along the line. This restriction can be removed by simply reversing the line. The paramount advantages of the model are that both time-domain and frequency-domain results can be easily obtained with the existing SPICE code, and nonlinear loads, such as transistors and digital devices, as well as dynamic loads, such as inductors and capacitors, may be easily incorporated using the existing elements in the SPICE code. Predicted results for MTL's using the method are compared to those of the time-domain to frequency-domain transformation and finite difference-time-domain (FDTD) methods     

Transient field coupling and crosstalk in lossy lines witharbitrary loads

We extend the transient scattering analysis of a lossy multiconductor transmission line to the evaluation of the interference produced by a field illuminating the line. The external interference is described by suitable voltage wave sources that are readily computed in the time domain and do not affect the structure of the transient scattering equations. The proposed formulation fully exploits the advantages of the transient analysis based on the line matched scattering parameters, dealing effectively with low-loss lines and helping the understanding of the interference mechanism through the physical interpretation of the results. The simplicity and efficiency of our approach is evidenced by means of a numerical example of the external interferences on a realistic nonlinearly loaded highly mismatched 3-conductor interconnect     

Comments on "A SPICE model for multiconductor transmission lines excited by an incident electromagnetic field" [and reply]

In a recent paper, C.R. Paul (see ibid., vol.36, p.342, 1994) discusses the concept of using the SPICE circuit analysis code for simulating field-to-wire coupling. He may not be aware that similar work has already been undertaken. A paper by Broyde et al. (1991) appears to be the first published implementation of this idea. The present comments on Paul's mostly theoretical paper emphasize some practical aspects of the simulation of EMC problems using a SPICE simulation program when multiconductor transmission lines (MTL) models are implemented. C.R. Paul responds to the comments.     

Circuit model for plane-wave incidence an multiconductortransmission lines

In the quasi-TEM limit a circuit model is developed to predict the voltages and currents induced on a multilayered microstrip structure illuminated by a low-frequency uniform plane wave. The analysis is based on a low-frequency series expansion rather than on the direct integration of Maxwell's equations     

Fast transient analysis of incident field coupling to multiconductor transmission lines

Due to the rapid surge in operating frequencies and complexity of modern electronic designs, accurate/fast electromagnetic compatibility/interference analysis is becoming mandatory. This paper presents a closed-form SPICE macromodel for fast transient analysis of lossy multiconductor transmission lines in the presence of incident electromagnetic fields. In the proposed algorithm, the equivalent sources due to incident field coupling have been formulated so as to take an advantage of the recently developed delay extraction based passive transmission line macromodels. Also, a method to incorporate frequency-dependent per-unit-length parameters is presented. The time-domain macromodel is in the form of ordinary differential equations and can be easily included in SPICE like simulators for transient analysis. The proposed algorithm while guaranteeing the stability of the simulation by employing passive transmission line macromodel, provides significant speed-up for the incident field coupling analysis of multiconductor transmission line networks, especially with large delay and low losses.     

Equivalent circuit modelling of lossy coupled lines using SPICE software

A new skin effect equivalent circuit and a propagation line equivalent circuit for time domain simulation on a single line have been presented in previous work (T. Vu Dinh et al., 1990) SPICE simulations have proved the accuracy and efficiency of the proposed method. This concept is extended for coupled line modelling. A dual line device is analysed as a typical example of the usual cases. The method has successfully been extended to N lossy coupled lines. The results show a good agreement with those obtained by other methods.<>     

Comparison of FDTD and SPICE simulations for lossy and dispersivenonlinear transmission lines

For the first time, a simulation has been carried out of lossy and dispersive nonlinear transmission lines (NLTLs) used for pulse compression, by two different time-domain approaches: SPICE and a full wave 3D finite difference time domain method. Results show good agreement between the two approaches. The output pulse risetime is strongly affected by DC and skin-effect losses     

A parallel-plate waveguide model of lossy microstrip lines

An improved semi-analytical model of a lossy microstrip transmission line is proposed. The model is based on the theory of the fundamental transverse magnetic mode of a lossy parallel-plate waveguide whose dielectric medium is assigned the effective permittivity of the respective lossless microstrip line. The complex propagation constant of the fundamental mode is computed by imposing the Leontovitch boundary condition at the upper and lower plates whose impedances take into account the thickness of the conductors and the current crowding effect. The dielectric loss is computed by perturbation formulas. The proposed model features high accuracy and computational efficiency at frequencies up to 100 GHz.     

Plane wave coupling to multiple conductor transmission lines abovea lossy earth

The current induced on an infinite multiple conductor transmission line located above a lossy homogeneous medium due to a transient plane wave is discussed. An exact solution is formulated in the frequency domain using a spatial transform technique. The widely utilized quasi-TEM approximation is derived directly from the exact solution with emphasis on the physical consequences of the assumptions made. Both frequency domain and time domain numerical results are presented for typical transmission structures and documented electromagnetic pulse (EMP) excitations. Comparison of the quasi-TEM approximation to the exact solution is made in order to study the validity of its application in EMP coupling problems. The modeling of the EMP source as an incident plane wave is examined by comparing the induced current due to a dipole source with its steepest-descent contribution     

Distributed equivalent sources for the analysis of multiconductortransmission lines excited by an electromagnetic field

The interaction of multiconductor lines with electromagnetic radiation is commonly studied in terms of field-induced voltage and current sources distributed along the line. The author presents the relationships between these sources and the incident fields for the general case of a transmission line with its conductors embedded in different dielectric volumes of arbitrary shape. It is shown that the sources can be expressed directly in terms of the incident fields and some vector parameters which are determined from the solution of a series of electrostatic problems with appropriate boundary conditions independent of the incident electric fields. It is noted that the multiconductor lines are suitable for direct applications in microwave transmission lines with rather arbitrary configurations     

Clarification of a decoupling method for multiconductortransmission lines

The authors provide a clarification of a decoupling method employed in the analysis of multiconductor transmission lines. They show that the use of a similarity transformation yields more efficient and stable numerical algorithms for computation of eigenvalues and characteristic impedance/admittance matrices of the telegrapher's equations than those based on a congruence transformation. The algorithms are easy to implement in existing software and, thus, their utilization is recommended     

Analysis of crosstalk and field coupling to lossy MTLs in a SPICEenvironment

This paper proposes a circuit model for lossy multiconductor transmission lines (MTLs) suitable for implementation in modern SPICE simulators, as well as in any simulator supporting differential operators. The model includes the effects of a uniform or nonuniform disturbing field illuminating the line and is especially devised for the transient simulation of electrically long wideband interconnects with frequency dependent per-unit-length parameters. The MTL is characterized by its transient matched scattering responses, which are computed including both dc and skin losses by means of a specific algorithm for the inversion of the Laplace transform. The line characteristics are then represented in terms of differential operators and ideal delays to improve the numerical efficiency and to simplify the coding of the model in existing simulators. The model can be successfully applied to many kinds of interconnects ranging from micrometric high-resistivity metallizations to low-loss PCBs and cables, and can be considered a practical extension of the widely appreciated lossless MTL SPICE model, which maintains the simplicity and efficiency     

Time-domain skin-effect model for transient analysis of lossy transmission lines

A skin-effect equivalent circuit consisting of resistors and inductors is derived from the skin-effect differential equations for simulating the loss of a transmission line. A numerical method is used to analyze the transmission-line differential equations and the skin-effect equivalent circuit, yielding a model which relates the new values of node voltages and line currents to their values at the previous time step. Based on this model, a very simple program was written on a desk-top computer for the transient analysis of lossy trammission lines. Two examples are presented. The first example is an analysis of the step and pulse responses of a 600-m RG-8/U coaxial cable. The computed results show excellent agreement with measured data. The second example studies the current at the end of a 12-in 7-Ω strip line under different loading conditions. Very good agreement has been obtained between the calculated steady-state solution and that obtained by the frequency-domain method.     

A universal model for lossy and dispersive transmission lines fortime domain CAD of circuits

Branin's method of characteristics has been extended to obtain a universal equivalent model for lossy and dispersive transmission lines. Existing CAD software packages, such as SPICE, can be used for this implementation. The starting point for obtaining the model is the analog filters that approximate the characteristic impedance Z₀ (s) and the propagation function F(s)=exp(-γl) of the transmission line. The circuits are synthesized using conventional network synthesis techniques. An examination of the validity of the model is carried out by analyzing an example of RLCG lines driven by bipolar logic gates and the distortion of a DC Gaussian pulse as it propagates along a microstrip line     

A versatile SPICE model for quantum-well lasers

A SPICE equivalent-circuit model for the design and analysis of quantum-well lasers is described. The model is based on the three-level rate equations which include, in their characterization of charge dynamics, the role of gateway states at the quantum well. The model is versatile in that it permits both small- and large-signal simulations to be performed. Emphasis here is placed on validating the model via a comparison of simulated results with measured data of the small-signal modulation response, obtained over a wide range of optical output powers from two lasers with different lengths of the separate-confinement heterostructure (SCH). Using a set of tightly specified model parameters, all the important trends in the experimental data are reproduced. The consideration of gateway states is found to be important, with regard to predicting the small-signal response, only for the laser with the longer SCH. This highlights the significance of the interplay between the roles of transport through the SCH and capture/release via the gateway states at the quantum well     

A Zener diode model with application to SPICE2

A Zener diode model for use with circuit analysis programs is described, and the implementation of the model in SPICE2 is explained. Breakdown is modeled as a sum of one or two exponential terms. If breakdown is neglected, the model reduces to an ordinary diode model. A new limiting algorithm is presented to ensure numerical stability.     

A SPICE model for a novel brushless adjustable-speed drive

A SPICE circuit model was developed to accurately simulate the i-v characteristics of a brushless AC motor commutated by semiconductor switches. The model is based on Fourier curve fits to measured mutual inductance interactions between all combinations of field and armature windings, as well as coil resistance and inductance. The model is able to accurately predict current and voltage characteristics, both statically, and dynamically when interfaced with a commutation model. The model has been demonstrated to agree with electrical tests of an inverted motor on a large time scale. It has also given reliable predictions of small time-scale details, where it is desirable to predict power MOSFET switch behavior after a command to open or close. Data were collected and analyzed for simulations of the motor model combined with a commutation model containing MOSFET switches. Metrics were compared to data collected from an inverted brushless motor with good agreement.     

A SPICE model for near-field transient analysis of ferromagneticgrids

Ferromagnetic grids are becoming more and more popular for electromagnetic shielding applications in avionics, satellite design, and power electronic systems. This paper presents an equivalent homogeneous but anisotropic model of a planar ferromagnetic grid. The nonlinear characteristic and the hysteresis of the material are taken into account. The field source is a low frequency magnetic dipole placed in the proximity of the grid. Both grid and source models are given in the form of multiconductor transmission line (TL) equations. They are solved, in the time domain, by the circuit simulator SPICE