Amplitude and Phase Modulated Pulse Trains for Clutter Rejection in Radar

Abstract

In radar systems the very low side-lobes that can be achieved with amplitude and phase modulated pulse trains make their use particularly attractive in systems requiring a large dynamic range. Moreover, the excellent self-clutter rejection performance is obtained without sacrificing the ability for the separation of close targets (no main lobe widening). The additional expense of encoding and decoding in amplitude and phase may be justified for radars that must cope with land clutter or operate in a dense-target environment. This paper presents a method for generating finite length sequences that have high energy ratio and low sidelobe energy in their autocorrelation function. The method is computer based and generates the desired sequence of any given length in an iterative manner starting with a sequence that has relatively low sidelobes in its autocorrelation function. It is shown that energy ratio of polyphase sequences that have low sidelobe energy , is improved through the process of clipping.