Fast Estimation of Main Intermodulation Products Using Volterra Series

The most accurate procedure for computing the intermodulation products is to find a steady-state period of the signal, and then to determine the spectrum by means of fast Fourier transform. However, this method needs a time-consuming numerical integration over many periods of the faster signal even for accelerated extrapolation methods for determining the steady state. In the paper, an efficient method for a fast estimation of the main intermodulation products is presented. The method uses higher-order Volterra series in a simple multistep algorithm, which is compatible with a typical structure of the frequency-domain part of software tools. The method is demonstrated by an illustrative example first, which clearly shows possible incorrect interpretation of the Volterra series. Afterwards, the efficiency of the algorithm is demonstrated by a fast estimation of the main intermodulation products of a low-voltage low-power CMOS RF four-quadrant multiplier.