Measurement of aliasing distortions and quantization noise in multirate systems

A method to measure linear and nonlinear distortions in implemented digital multirate systems is presented. The system to be measured is modeled as a parallel connection of a linear system, described by its bifrequency system function, and a nonlinear system producing the observed deviations from linearity. The output signal of the latter system, being cyclostationary in general, is described by a bifrequency spectral density, a generalization of the power spectral density. The bifrequency system function includes both the linear time-invariant transfer function of the system and further transmissions from the input to the output which result from aliasing and/or imaging distortions