Waveform and Receiver Design for OTFS-Based SAR Under Interference and Low SNR Conditions

Orthogonal time-frequency space (OTFS)-based synthetic aperture radar (SAR) is resilient to intrapulse Doppler shift and provides inter-range-cell interference (IRCI)-free imaging. Narrowband interference (NBI) is a common cause of SAR image distortion. To mitigate NBI, we formulate a multiobjective waveform design optimization problem, where we generate a sequence for waveform design using the state-of-the-art improved-gray wolf optimization (I-GWO) algorithm. It is demonstrated that the sequence generated to eliminate NBI suffers noise enhancement under low signal-to-noise ratio (SNR) conditions using state-of-the-art OTFS-based SAR receiver. To obviate the noise enhancement for any general SAR sequence, we propose a novel low-complexity linear minimum mean square error (LMMSE) receiver algorithm to enhance imaging quality under low SNR conditions. Finally, performance of the proposed waveform and receiver design technique is validated under NBI and low SNR conditions, and the results are analyzed.