Intermodulation performance of biased-nonlinearities

A general formula, using a Fourier-series representation for the transfer characteristic of biased-nonlinearities, is presented. Using this formula, general expressions, involving the ordinary Bessel functions, can be obtained for calculating the amplitudes of the output products of a biased-non-linearity excited by a multisinusoidal signal plus Gaussian noise. In contrast with previously published results, the implementation of the proposed expressions requires the computation of simple mathematical functions that are available in most mathematical library subroutines and can even be implemented using programmable pocket calculators. The special case of an input consisting of a weak signal plus strong interference plus Gaussian noise is considered in detail. This case is of special importance as it shows that when the input is formed of a weak signal and a strong interference, the biased-nonlinearity can provide a large enhancement in the output signal-to-interference ratio if the bias is set equal to or close to the amplitude of the strong interference.