Nonlinear Circuit Simulation in the Frequency-domain∗

Simulation in the frequency-domain avoids many of the severe problems experienced when trying to use traditional time-domain simulators such as Spice [1] to find the steady-state behavior of analog, RF, and microwave circuits. In particular, frequency-domain simulation eliminates problems from distributed components and high-Q circuits by forgoing a nonlinear differential equation representation of the circuit in favor of a complex algebraic representation. This paper describes the spectral Newton technique for performing simulation of nonlinear circuits in the frequency-domain, and its implementation in Harmonica. Also described are the techniques used by Harmonica to exploit both the structure of the spectral Newton formulation and the characteristics of the circuits that would be typically seen by this type of simulator. These techniques allow Harmonica to be used on much larger circuits than were normally attempted by previous nonlinear frequency-domain simulators, making it suitable for use on Monolithic Microwave Integrated Circuits (MMICs).