Analysis of modulator circuits based on multi-dimensional Fourier transformation

There are many communication circuits driven by multitone signals such as modulators and mixers. If the input frequency components are largely different from each other, the brute force numerical method will take an enormous computation time to obtain the steady-state responses. In this paper, we show a SPICE oriented algorithm based on multi-dimensional Fourier transformation, where all of the circuit analyses such as DC- and AC-analysis in the algorithm are carried out with SPICE. On the other hand, a very simple sensitivity analysis and 2-dimensional FFT are carried out by a Fortran program (or C program). We found that the convergence ratio of our algorithm is sufficiently large, and can be applied to wide class of communication circuits.