A global finite-element time-domain analysis of active nonlinear microwave circuits

An extension of the finite-element time-domain (FETD) method for mixed electromagnetic and circuit simulation of complex active microwave circuits is proposed in this paper. The passive distributed part of the circuit is analyzed using FETD and its interaction with lumped passive/active linear/nonlinear components is modeled via an equivalent-current generator whose value and internal capacitive admittance are computed at each time step by the FETD solver. Benchmark tests on a microwave amplifier and a injection-locked oscillator indicate that this extended FETD is not only superior in mesh flexibility, but also gives more accurate results than the similar FDTD-based algorithm.