FDTD formalism including a microstrip inside an elementary cell

Analysing microwave millimeter-wave integrated circuits (MMIC) with the FDTD technique can require a large computation space, and, as a consequence, a long computation time. With this technique, accurate frequency responses are obtained by the Fourier transform of very long time domain records. A classical way to lower the computation time is to apply linear, or non-linear, predictors, to short time domain records. We propose another method to lower the computation time: this method consists in reducing the computation space by introducing a formalism of a microstrip inside an elementary cell. We have applied the above formalism to the determination of the S/sub 21/ parameter for the classical double-stub filter. For the computation, the filter is enclosed in a PEC parallelepipedic cavity. This formalism is similar to the thin wire formalism previously introduced by Holland and Simpson (1981).