Anestis Dounavis

A general class of passive macromodels for lossy multiconductor transmission lines

This paper presents a general class of passive macromodeling algorithm for multiport distributed interconnects. A new theorem is described that specifies sufficient conditions for matrix-rational approximation of exponential functions in order to generate a passive macromodel. A proof is given showing that the currently existing passive matrix-rational approximation of exponential functions is a subclass of the generic approach presented in this paper. In addition, a technique to obtain a compact passive macromodel with predetermined coefficients, based on near-optimal approximation, is presented. The proposed model can be easily incorporated with recently developed passive model-reduction techniques.

Efficient passive circuit models for distributed networks with frequency-dependent parameters

This paper presents an efficient method for the analysis of multiconductor transmission lines with frequency-dependent parameters. The proposed technique generates positive-real representations for the frequency dependency of transmission line parameters as well as closed-form expressions based on exponential Pade approximants. The new model is suitable for inclusion in general purpose circuit simulators and overcomes the difficulty of mixed frequency/time simulation encountered during transient analysis. In addition, the proposed model can be easily incorporated with the recently developed passive model-reduction techniques. Numerical examples are presented to demonstrate the validity and efficiency of the proposed method.

DEPACT: delay extraction-based passive compact transmission-line macromodeling algorithm

With the continually increasing operating frequencies, signal integrity and interconnect analysis in high-speed designs is becoming increasingly important. Recently, several algorithms were proposed for macromodeling and transient analysis of distributed transmission line interconnect networks. The techniques such as method-of-characteristics (MoC) yield fast transient results for long delay lines. However, they do not guarantee the passivity of the macromodel. It has been demonstrated that preserving passivity of the macromodel is essential to guarantee a stable global transient simulation. On the other hand, methods such as matrix rational approximation (MRA) provide efficient macromodels for lossy coupled lines, while preserving the passivity. However, for long lossy delay lines this may require higher order approximations, making the macromodel inefficient. To address the above difficulties, this paper presents a new algorithm for passive and compact macromodeling of distributed transmission lines. The proposed method employs delay extraction prior to approximating the exponential stamp to generate compact macromodels, while ensuring the passivity. Validity and efficiency of the proposed algorithm is demonstrated using several benchmark examples

Passive closed-form transmission-line model for general-purpose circuit simulators

A passive closed-form model for multiconductor lossy transmission line analysis is presented in this paper. The proposed model is suitable for inclusion in general-purpose circuit simulators and overcomes the mixed frequency/time simulation difficulties encountered during the transient analysis. In addition, the model can handle frequency-dependent line parameters. This method offers an efficient means to discretize transmission lines compared to the conventional lumped discretization, while preserving the passivity of the discrete model. Coefficients describing the discrete model are computed a priori and analytically, using closed-form Pade approximants of exponential matrices. Numerical examples are presented to demonstrate the validity of the proposed model and to illustrate its application to a variety of interconnect structures.

A comparative study of two transient analysis algorithms for lossy transmission lines with frequency-dependent data

Two general algorithms for the modeling of lossy transmission lines with frequency-dependent parameters are contrasted and compared. The first is based on the generalized method of characteristics while the second is based on the more recent Pade macromodeling approach. The different approximations made in these two algorithms are contrasted and computational evidence is presented to show that these two methods complement rather than compete with each other.

Passive closed-form transmission-model for general purpose circuit simulators

A passive closed-form model for multiconductor lossy transmission line analysis is presented. The proposed model is suitable for inclusion in general purpose circuit simulators and overcomes the mixed frequency/time simulation difficulties encountered during the transient analysis. The method offers an efficient means to discretize the transmission lines compared to the conventional lumped discretization while preserving the passivity of the discrete model. Coefficients describing the discrete model are computed a priori and analytically, using closed-form Pade approximants of exponential matrices.

Passive model reduction of multiport distributed interconnects

Signal integrity analysis has become imperative for high-speed designs. In this paper, we present a new technique to advance Krylov-space-based passive model-reduction algorithms to include distributed interconnects described by telegraphers equations. Interconnects can be lossy, coupled, and can include frequency-dependent parameters. In the proposed scheme, transmission-line subnetworks are treated with closed-form stamps obtained using matrix-exponential Pade, where the coefficients describing the model are computed a priori and analytically. In addition, a technique is given to guarantee that the contribution of these stamps to the modified nodal analysis formulation leads to a passive macromodel.

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

A SPICE model for incident field coupling to lossy multiconductor transmission lines

An efficient time-domain macromodel for incident field coupling to lossy multiconductor transmission lines is presented. The model takes the form of ordinary differential equations and can be easily included in SPICE like simulators for transient analysis. The model is based on the closed-form matrix-rational approximation of the exponential matrix describing telegraphers equations and semi-analytic rational approximation of forcing functions.

Delay extraction and passive macromodeling of lossy coupled transmission lines

Recently, several algorithms were proposed for time-domain macromodeling of distributed transmission line networks. It has been demonstrated that preserving passivity of the macromodel is essential to guarantee a stable global transient simulation. Techniques such as method-of-characteristics yield fast transient results for long delay lines. However, they do not guarantee the passivity of the macromodel. On the other hand, methods such as matrix rational approximation provide efficient macromodels for lossy coupled lines, while preserving passivity. However, for long lossy delay lines this may require higher order approximations, making the macromodel inefficient. In order to address the above difficulty, this paper presents a new algorithm for efficient macromodeling of lossy coupled lines with long delay. The proposed method employs delay extraction prior to approximating the exponential stamp of the line and guarantees the macromodel passivity. The paper also provides guidelines on the practical applicability of the delay extraction and the matrix rational approximation, based on the knowledge of line parameters.