A systematic approach for extracting lumped circuit parameters of microstrip discontinuities from their S-parameter characteristics

✍ Scribed by R. Mittra; A. Suntives; M. S. Hossain; J. Ma

• Publisher: John Wiley and Sons
• Year: 2002
• Tongue: English
• Weight: 541 KB
• Volume: 15
• Category: Article
• ISSN: 0894-3370
• DOI: 10.1002/jnm.431

✦ Synopsis

Abstract

This paper describes a systematic approach for extracting the lumped circuit parameters of microstrip discontinuities from their S‐parameter characteristics—which are assumed to be known—by using a three‐ step procedure. We begin by computing the lumped equivalent circuit parameters, e.g., L, C, R and/or G, with a direct extraction procedure, which relates the S‐parameters to the Z‐ (or Y‐) parameters of the discontinuity. Next, we use these values as initial guesses for an optimization code based on the genetic algorithm, to obtain circuit parameters that are invariant over a specified frequency range. Finally, we develop an artificial neural network model for predicting the values of these circuit elements rapidly as we change the physical and electrical parameters of the discontinuity, for instance the width or height of the etch, and the complex dielectric constant of the substrate. The application of the direct extraction technique is first illustrated by considering a number of representative two‐port microstrip discontinuities, viz., the chamfered bend and gap discontinuities. It is then extended to three‐port structures, for instance, a T‐junction. The validation is given for the case examples investigated by comparing the S‐parameter calculated from the equivalent circuit with those obtained from a full‐wave EM solver. We also use the chamfered bend as a case example to illustrate the application of this three‐step procedure. Copyright © 2002 John Wiley & Sons, Ltd.