Variance analysis of frequency response function measurements using periodic excitations

The influence of disturbing noise and non-linear distortions on frequency response function (FRF) measurements using periodic excitations has been studied in detail in the literature. A variance analysis method has been developed that allows to detect and quantify the non-linear distortions and the disturbing noise. In this paper the variance analysis is generalised to detect and quantify the following non-stationary disturbances: (i) non-synchronous periodic signals, for example the 50Hz mains and its harmonics, and (ii) non-stationary behaviour of the device under test, for example phase or frequency modulation.