Generalised nonlinear theory for one-port microwave active circuits

A nonlinear model characterising two-terminal microwave active circuits under dynamic and steady-state conditions is developed from a generalised circuit approach. The model considers the active circuit as a black box consisting of a one-port passive circuit and a one-port active device. The response of the active and passive circuits to modulated time-dependent signals with slowly varying amplitude and phase is derived. The model takes into consideration the nonlinear dependence of the active-device currents on RF voltage amplitude and frequency; also it considers the effects of nonlinearities of the passive circuit on frequency. This makes the model suitable for applications which employ strongly modulated signals for which Van der Pol´s cubic nonlinearity model fails.