Overview

In order to design an MMIC to a given specification, the designer must be able to take ideas for the required circuit topology and accurately predict the performance of this circuit when implemented in MMIC form. This is achieved using computer-aided design (CAD) tools, such as Agilent ADS, ^[1] Ansoft Designer, ^[2] AWR Microwave Office, ^[3] and Cadence Virtuosos, ^[4] to simulate the RF and microwave characteristics. These tools allow the designer to connect together models of the individual component elements into a circuit design and simulate the MMIC circuit performance in the frequency or time domain.

High-yielding MMIC product design requires well characterized and accurately modeled MMIC components implemented within these commercial simulators. This is a time-consuming and costly activity, and it represents a significant investment by the foundry; hence, their model libraries are neither comprehensive nor perfect. Although these component models are usually hidden behind their schematic symbols, understanding how the foundry may have produced the models helps the designer to understand their limitations and use them circumspectly.

The aim of this chapter is to review the concept of s-parameter representation of components and discus how a foundry typically goes about characterizing the individual components and develops a lumped-element equivalent circuit model for them. The chapter continues by describing the commonly used equivalent circuit topologies for both the active and passive components and how they were derived. The chapter also touches on the limitations of s-parameter representation of individual components and...