The method to identify the inner structure of a kind of nonlinear systems with sinusoid signals

A method is described to identify the inner structure of open-loop nonlinear systems using Volterra kernels in the frequency domain. By applying Volterra functional series theory to the systems, one can obtain a criterion for the inner structure of nonlinear systems which contain only one nonlinearity. When the input is a single-frequency sinusoid signal, one can divide this system into five kinds through measuring the Mf loci. After it is shown that the system has an open-loop structure, various models are discussed, and it is proved that the relations between the Volterra kernels of these models can help one to identify the inner structure in more detail.<>