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Design Automation

Macromodeling of Lossy, Dispersive Transmission Lines

Project Overview

As propagated signal transitions become comparable to propagation delays, high speed on-chip and packaging interconnect design now requires that the transmission line properties of an increasing number of critical wires be analyzed carefully before committing the designed system to production. Signal timing and integrity will be greatly compromised if the chip and system design ignores the inductive, lossy, and dispersive nature of the interconnect network.

The analysis of such networks at both the chip and system level imposes stringent requirements on the circuit simulator in terms of architecture, accuracy, and performance. Lossy, dispersive transmission lines are distributed systems that are better described in the frequency domain yet their nonlinear drivers and loads are better analyzed and simulated, as lumped systems, in the time domain.

The aim of this project is to augment and extend the current capabilities of IBM's circuit simulator, PowerSpice, in the simulation of transmission lines. We are currently investigating and extending novel macromodeling techniques based on the transfer matrix of the muticonductor system that includes the modeling of the frequency-dependent behavior of the system's inductive impedance and dielectric loss. The main feature of these techniques is that they do not require the costly time-domain convolutions typically used by circuit simulators to simulate transmission lines. An R & D macromodeling prototype has been coded and run on industrial examples, proving the feasibility of the novel algorithms and confirming their accuracy and efficiency.

This prototype along with the expertise developed during the research phase will soon be incorporated in IBM's PowerSpice using its device API to provide it with an on-the-fly capability for the fast, accurate macromodeling of lossy, dispersive transmission lines.

University partners: Carleton University

Reference: Elfadel, I.M., H. Huang, A. E. Ruehli, A. Dounavis, and M. S. Nakhla, "A comparative Study of Two Transient Analysis Algorithms for Lossy Transmission Lines with Frequency-Dependent Data," to appear in the Proceeding of the Electrical Performance of Electronic Packaging Conference, Boston, MA, October 2001.

For further information contact:

Abe Elfadel <>

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