Sequence design for high squint spotlight SAR imaging on manoeuvring descending trajectory

Abstract

Owing to the special geometry and system deviations of missile-borne spotlight SAR with manoeuvring motion, the sequence designed with traditional methods used in airborne and space-borne SAR systems perform low precision. An unequal azimuth and pitch beamwidths will make the beam footprint turn into an irregular ellipse, which consequently renders it difficult to gain the accurate echo bandwidth. In addition, biggish low pulse repetition frequency limit (LPRFL) caused by high velocity of the platform and beamwidth increases the complexity of system sequence design. In this study, a precise and effective sequence design method is developed based on effectual access of accurate LPRFL and high PRF limit with the consideration of ambiguity constraints and system deviations. Specifically, a new scene traversal method is proposed to gain the echo bandwidth with high precision for any azimuth and pitch beamwidths. Finally, a practical trajectory optimisation method is designed to further reduce the transmitted pulse number and lower the load of real-time processing. Plenty of simulation results verify its validity and effectiveness of the sequence design, which can be effectively applied to high manoeuvring spotlight SAR.