Nonlinear disturbance errors in system identification using multisine test signals

The errors introduced into linear system identification by a class of nonlinear distortions are examined. A theoretical framework is presented for the distortion generated by odd-power-nonlinearities when using multisine test signals for frequency-domain identification. It is shown that the distortion is a function of the number of test harmonics, their harmonic values, and their phases. This leads to the definition of a novel class of signals, termed no interharmonic distortion (NID) multisines, with interesting properties. An explanation of previously published practical results is then given. Application of multisines to system testing with a method of compensating for nonlinearities is illustrated with practical results