A Hybrid CN-FDTD-SPICE Solver for Field-Circuit Analyses in Low-Frequency Wideband Problems

The conventional finite-difference time-domain (FDTD) method is efficient for microwave frequencies, but requires a large number of time steps for low frequencies. In this work, a hybrid Crank-Nicolson (CN) FDTD-SPICE method is applied to field-circuit analyses in low- frequency wideband problems. The unconditionally stable CN-FDTD method is used to give a rapid full wave solution by overcoming the Courant-Friedrichs-Lewy (CFL) condition that constrains the conventional FDTD method at low frequencies. The hybrid CN-FDTD-SPICE method can be used for simulating the interactions between modern electronic circuit systems and a 3-D structure supporting field radiation and interferences. It can greatly improve the computational efficiency over the conventional FDTD method at low frequencies because its time increment can be significantly larger. Three numerical examples are presented to verify the accuracy and efficiency of this hybrid method. Its CPU time is much shorter than that of the conventional FDTD-SPICE method. This CN-FDTD-SPICE method becomes increasingly advantageous when the radiation fields are required as the system integration continues to accelerate.