Nonlinear disturbance errors in system identification using multisine test signals

The errors introduced into linear system identification by 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. An explanation of previously published practical results is then given. This leads to the definition of a novel class of signals, termed no interharmonic distortion (NID) multisines, with interesting properties. The application of NID multisines to system testing with a recently proposed method of compensating for nonlinearities is examined. This allows the identification of the linear system and the straightforward calculation of the coefficient of the nonlinear term