The Effects of Video Clipping on the Performance of an Active Satellite PSK Communication System

A phase-shift-keying (PSK) satellite communication system is considered in which 1) clutter (other users and/or jamming) is added to the desired signal on the up-link, 2) the repeater contains a hard-limiter, 3) thermal noise is added on the down-link, 4) the receiver consists of a synchronous detector followed by an infinite clipper, and 5) the output of the clipper is sampled at the Nyquist rate, and the decision is based upon whether the majority of the samples are positive or negative. The error probability of this system is given by a binomial distribution, the parameters of which are determined by the clutter and noise statistics. Explicit results are obtained for the case where the down-link noise may be neglected and the clutter is Gaussian. It is shown that the video clipper results in a degradation of performance of at most 2 dB relative to an ideal linear system and only about 1 dB relative to a system in which a limiting repeater is employed without clipping on the ground. For the case of strong clutter and strong noise, the degradation relative to an ideal linear system is shown to be 3 dB. The use of infinite clipping provides a two-fold advantage: 1) The error analysis can be performed at all signal-to-clutter and signal-to-noise ratios, not only in an asymptotic limit; 2) Digital signal processing of large time-bandwidth product signals is facilitated. (Infinite clipping corresponds to one-bit quantization.)