Investigation of tapered multiple microstrip lines for VLSI circuits

Abstract

Tapered, coupled, microstrip transmission lines are an increasingly important part of high-speed digital circuits. These lines, used as interconnects between integrated circuit devices, are modeled using an iteration-perturbation approach applied in the spatial domain. The approach is used first to solve the static problem, and then to iterate on the static solution to obtain the charge and current distributions on the lines at different frequencies. From this model, a frequency-dependent scattering parameter characterization is determined. Results for typical geometries are presented and are compared with those published by other authors.

A time-domain simulation of pulse propagation through the tapered, coupled, microstrip lines is performed. The frequency-domain scattering parameters are inverse Fourier transformed to obtain the time-domain Green's function. The input pulse is convolved with the Green's function, and a Newton-Raphson algorithm is applied to account for nonlinear loads. Good agreement is found with other published results.

Finally, some experimental results are shown and an equivalent circuit is proposed. The experimental results verify the model, while the equivalent circuit allows the time-domain simulation to be performed in less time with a negligible loss in accuracy. Results show that the equivalent circuit gives essentially the same time-domain response in about one-tenth of the simulation time.