Analysis of communication circuits based on multidimensional Fourier transformation

There are many communication circuits driven by multitone signals such as m odulators and mixers, and so on. In this case, if frequency components of t he modulators are largely different, the brute force numerical integration will take an enormous computation time to get the steady-state responses, b ecause the step size must be chosen depending on the highest frequency inpu t. The same situation happens to mixer circuits which generate very low fre quency output. In this paper, an efficient algorithm is shown to solve the communication c ircuits driven by multitone signals which is based on the frequency-domain relaxation method and the multidimensional Fourier transformation. Attenuat ion of the transient phenomena mainly depends on the reactive elements such as capacitors and inductors, so that we partition the circuit into two gro ups of the nonlinear resistive subnetworks and the reactive elements using the substitution sources. The steady-state response can be calculated in su ch a manner that the responses at each partitioning point have the same wav eform, We have developed a simple simulator carrying out our algorithm that only uses the transient, de-analysis and ac-analysis of SPICE. It can be e asily applied to relatively large scale integrated circuits, efficiently, W e found from many simulation results that the convergence ratio at the iter ation of our relaxation method is sufficiently large, and can be applied to wide class of the communication circuits.