NISAR S‐SAR Digital Beamforming Architecture and Implementation

Abstract

AbstractISRO(Indian Space Research Organization) and JPL(Jet Propulsion Laboratory), NASA are jointly developing a state‐of‐the‐art L&S band SAR, planned to be launched through GSLV during 2023‐24. The conventional SAR systems has a limitation of providing higher spatial resolution as well as wider swath coverage simultaneously[6]. The NASA‐ISRO Synthetic Aperture Radar (NISAR) is based on a novel SAR concept, which will be utilized to image wide swath as high resolution of stripmap SAR, also called SweepSAR[1]. NISAR uses Digital Beam Forming on receive along with SweepSAR concept to get the advantage of lesser transmit power, immunity to range ambiguities with narrower receive beams, improved SNR and noise equivalent sigma naught as compared to conventional SAR system and directly radiating arrays with digital beamforming[5].In this paper, digital beamforming (DBF)[2] technique being used in NISAR S‐SAR receive chain is presented. The paper focuses on the DBF architecture, methodology, mathematical equations, practical implementation challenges and strategies used for mitigation of such challenges in order to achieve desired performance. Subsequently, DBF Hardware implementation algorithm and improvement in S‐SAR performance as a result of DBF technique is discussed.