A hybrid FDTD-SPICE method for the analysis of microwave circuits

Abstract

A hybrid full-wave electromagnetic (EM) field-circuit simulation method, which aims at accurately analyzing microwave circuits, is proposed. This method adopts the finite-difference time-domain (FDTD) algorithm for the EM simulation, the sophisticated equivalent models in a general circuit simulato r SPICE for the circuit simulation, and hybridizes the FDTD and SPICE by using the equivalent current source (ECS) approach. Moreover, three techniques, which map a lumped circuit into FDTD cells as a wire, surface or volume structure respectively, are thoroughly studied. The formulae of the ECS with these three techniques are derived and introduced in detail, and their influences on the simulation accuracy are analyzed. The proposed method is applied to two sample circuits, a microstrip line and a frequency selective surface (FSS), both of which are loaded with diode pairs. The simulation results are compared with the measurement ones, and good agreement is observed, indicating the accuracy and versatility of the method.