Radar Ambiguity Function

Abstract

Range resolution for a given radar can be significantly improved by using very short pulses. Unfortunately, utilizing very short pulses decreases the average transmitted power, which can hinder the radar's normal modes of operation particularly for multi-function and surveillance radars. Since the average transmitted power is directly linked to the receiver SNR, it is often desirable to increase the pulse width (i.e., increase the average transmitted power) while simultaneously maintaining adequate range resolution (i.e., use short pulses). This can be made possible by using pulse compression techniques. Pulse compression allows us to achieve the average transmitted power of a relatively long pulse, while obtaining the range resolution corresponding to a short pulse. This chapter takes the reader into the world of most common radar signal types, both analog and discrete. The ambiguity functions for both types of waveforms are analyzed. The analog waveforms discussed include the single unmodulated pulse, linear frequency modulation (LFM) pulse, unmodulated pulse train, LFM pulse train, stepped frequency waveforms, and nonlinear FM waveforms. The rest of the chapter is concerned with common discrete radar waveform types. Unmodulated pulse-train codes as well as binary codes, polyphase codes, and frequency codes are analyzed.