Before revision: The HOSIDFs bear an intuitive resemblance to the classical frequency response function and define the periodic output of a stable, causal, time invariant nonlinear system to a sinusoidal input signal: This output is denoted by and consists of harmonics of the input frequency: Defining the Fourier transforms of the input and output as and yields the definition of the k-th order HOSIDF: Advantages and Applications The application and analysis of the HOSIDFs is advantageous both when a nonlinear model is already identified and when no model is known yet.
After revision: The HOSIDFs bear an intuitive resemblance to the classical frequency response function and define the periodic output of a stable, causal, time invariant nonlinear system to a sinusoidal input signal: This output is denoted by and consists of harmonics of the input frequency: Defining the single sided spectra, such that of the input and output as and yields the definition of the k-th order HOSIDF: Advantages and Applications The application and analysis of the HOSIDFs is advantageous both when a nonlinear model is already identified and when no model is known yet.