Amplitude demodulation of filtered AM/PM signals

The input signal is assumed to be simultaneously amplitude and phase modulated (AM and PM), and the bandpass filter may be unsymmetrical and mistuned. The demodulator output is the magnitude of the filtered signal for an AM receiver or its phase for a PM receiver. For such a system with amplitude demodulation, the results are found and presented in the form of an expansion in which the leading term is the linear (i.e., undistorted) reproduction of the input AM and the successive terms represent the distortion and crossmodulation. The significant effects are given by the first few terms of the expansion because the applications of interest are those in which the distortion is small. A spectral analysis is performed on the output of an AM receiver. The leading DC, linear, and nonlinear terms of the output power spectrum are derived by assuming that the amplitude- and phase-modulating signals are uncorrelated zero-mean random Gaussian processes