CURRENTLY, SOFTWARE CIRCUIT simulators are used to analyze the linear behavior of a design in the frequency domain and the nonlinear behavior in the time domain. The two domains and behaviors are resolved through an iterative approach called harmonic balance. Yet designers face additional challenges in compact models. For example, such models may not be able to reliably predict behavior under extreme nonlinear conditions or for circuits with non- 50-O terminations. In a six-page white paper titled, "AWR's Support of PHD and Nonlinear Behavioral Models," Malcolm Edwards points out that recent developments in measurement and modeling technology are focusing on technology-independent, measurement-based black-box models.

The white paper provides an overview of these models, recent developments, and the efforts of participating companies. For example, it includes information on two pertinent industry groups: the Compact Model Council and OpenWave Forum. It then delves into a discussion of nonlinear behavior, S-functions (which are an extension of S-parameters for nonlinear components), the Cardiff measurement system and associated model, and harmonic- balance techniques. The document closes with a discussion of actually using a nonlinear X-parameter/S-function model and multi-tone intermodulation analysis. Overall, it provides a solid summary of how the industry is tackling these design challenges while emphasizing that the Microwave Office software is fully capable of simulating measurement-based, extracted nonlinear models.

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