Analyzing Strongly Nonlinear Multitone Circuits by Multi-Time Methods

Harmonic balance and traditional time-domain simulation techniques are limited in their applicability when strong nonlinearities and multi-tone signals are both present. In this paper, new simulation algorithms are described and used to analyse strongly nonlinear microwave circuits with multi-tone excitations. The techniques are based on representing multi-tone waveforms as functions of several 'time' variables, and solving a partial differential form of the circuit equations using time-domain methods. The methods scale linearly with increasing circuit size, regardless of the number of nonlinearities. A switching mixer is analyzed using the new methods. Speedups of over two orders of magnitude over traditional techniques are obtained. Moreover, the multi-time representations obtained from the new methods provide intuitive and powerful visualisations of the operation of the circuit.