OTFS Based SAR With Low Complexity Receiver
Gaurav Sharma, A. Arockia Bazil Raj
Abstract
Synthetic aperture radar (SAR) are exploiting millimeter-wave (mmWave) band for imaging applications. However, with the conventional pulse-width of few tens of microseconds the receive SAR signal experiences intra-pulse Doppler shift in mmWave band which results in severe image degradation. The recently proposed, orthogonal time frequency space (OTFS) modulation has shown to be resilient against the Doppler impairments. In this work, we propose a cyclic-prefix (CP)-OTFS modulation with practical pulse shaping waveforms for SAR applications. We present a novel delay-Doppler domain based pulse compression technique to mitigate the intra-pulse Doppler impairments. The traditional pulse compression techniques in SAR are known to have inter-range-cell-interference (IRCI) due to the presence of range side-lobes which leads to low resolution imaging. The proposed receiver algorithm effectively exploits the diagonalization property of factor-circulant matrix and eliminates IRCI. The receiver algorithm is shown to have a lower computational complexity vis-a-vis the state-of-the-art matched-filter OTFS radar receiver thus, making it suitable for real-time SAR applications. Finally, simulated SAR images show the effectiveness of our methodology in eliminating the distortion caused by intra-pulse Doppler shift and removal of IRCI for high resolution imaging.