Self coupled harmonics: stationary and cyclostationary approaches

Self coupled harmonics offer a practical means for testing for the presence of nonlinearities. A computationally attractive method to detect frequency and phase coupling is derived based on a slice of the Fourier series moment polyspectrum, and is capable of handling constant amplitude harmonics as well as harmonics observed in additive and nonzero mean multiplicative noise. The zero-mean case is addressed using cyclic statistics, and contrary to existing approaches, both methods rely on a single record of data and do not assume the additive noise to be Gaussian