Linear cancellation technique for suppressing impulse noise

Abstract

At the present time, known techniques for suppressing the effects of impulsive disturbances can be identified with one of three general approaches: (a) The use of nonlinear saturating elements or noise clippers; (b) Disturbance-triggered, gating-out schemes; (c) The use of special signal design such as special coding, or linear premodulation waveform alteration and postdemodulation correction of the message. In this paper a new technique that is fun&- mentally simple and hear is described; it is effective even when the i-f filter responses to the various impulses overlap, as long as the number of overlapping responses is not great. The only important assumption made is the one that is fundamental in all impulse-noise studies - that the individual bursts have durations that are substantially shorter than the duration of the shortest important message element. This technique (which we call the linear-cancellation technique") makes use of an important property of the impulse response of a linear filter - that its maximum value is directly proportional to the filter bandwidth. This technique is applicable to the reception of all types of modulation, even to pulsed transmissions, subject, of course, to the fundamental assumption about the duration of the input noise pulse relative to the duration of the shortest important message element.