Complementary pair radar waveforms–evaluating and mitigating some drawbacks

Abstract

Complementary pulse pair is a radar waveform that achieves the ultimate range sidelobe reduction zero sidelobe. It is an early and simple embodiment of radar waveform diversity (WD), presently a popular topic. However, the use of complementary pulse waveforms is not widely spread because of several drawbacks. The main problem is the sensitivity to Doppler shift. Usually the two complementary coded pulses are separated in time. Doppler shift causes a phase ramp as function of time. That ramp causes two problems: (a) the two pulses in a pair are centered on different average phases; (b) there is a phase ramp during each pulse. Problem (a) also known as slow-time mismatch, is handled by the pulse-topulse conventional Doppler processing, which provides slow-time phase compensation. Problem (b) requires fast-time compensation, not provided by a simple linear Doppler processor. It causes loss of the ideal delay-sidelobe cancellation resulting in near range-sidelobes. Those near sidelobes increase with longer codes and with higher Doppler shifts. At the same time a complementary pulse pair also causes a difficulty at low Doppler shifts.