Distortion noise in frequency-dependent nonlinear networks

Formulas are derived for the computation of distortion-noise power in frequency-dependent nonlinear networks represented by a Volterra series. The integrals for the distortion-power spectrum contain higher-dimensional Laplace transforms of the corresponding kernels of the Volterra series. An analysis of the frequency-dependent nonlinearity is carried out for transistor feedback amplifiers and f.m. radio-relay amplifiers used in frequency-division-multiplex transmission systems. The nonlinearity of a given order for transistor feedback amplifiers is characterised by a distortion term, and its frequency characteristic, which can be computed or determined from certain intermodulation measurements. A linear f.m. amplifier is completely characterised by its transfer immittance W12 (jω).