A fast counting method for generic order intermodulation products

Non linear devices such as amplifiers and electro-optical transducers introduce spurious signals known as intermodulations, especially when multiple signals at different frequencies access the system. In this paper an extension to the well known Fast Counting Algorithm (FCA) for the intermodulations is presented and a comparison with slow counting algorithms is done. Carrier configuration is represented by means of indicator polynomials, and high-order intermodulation products distribution can be computed in a fast way, extending the results restricted to third order intermodulations. Moreover, no particular assumption is done on the distribution of the carriers (i.e. they are not required to be equispaced). Comparisons are made in terms of accuracy and speed with slow direct counting algorithms.