Limiting of Several Signals and Its Effect on Communication System Performance

In a typical satellite communication system, several modulated carriers pass through a transponder simultaneously. If limiting action is present, signal suppression may occur, and cross products are produced. An equation is derived for the power spectrum of the output of a hard limiter when the input consists of angle modulated sinusoids plus random noise. Based upon this equation, the magnitude of any term can be determined; numerical results are presented for the magnitudes of the signals, suppression, and crossproducts for a large number of cases. When the signals are demodulated at a ground station, the crossproduct terms falling near the desired signal cause distortion. A method for computing this distortion and some numerical results are presented.