Synthesizing a wideband waveform by using a phased array

Abstract

A key parameter affecting the ability of many radar to perform target identification is down-range resolution. A large radar instantaneous bandwidth permits the use of high range resolution (HRR) and rotational imaging. However, a narrow bandwidth phased array radar cannot support wideband signals because the array is steered by phase shift rather than time delay. This paper characterizes the array limitations as a function of bandwidth and presents a new methodology for synthesizing a wideband waveform with the use of very few (3 or 4) pulses. The technique is based on forming an inverse filter to reduce the high sidelobes and eliminate the grating lobes that would be generated when combining only a few pulses. It is demonstrated that the achieved HRR results using multiple processed linear frequency modulated (LFM) signals through adaptive inverse filters are about as good as those derived from a single wideband pulse of the same resultant bandwidth.