Digital Beamforming for Spaceborne Reflector-Based Synthetic Aperture Radar, Part 2: Ultrawide-swath imaging mode

Abstract

Utilizing digital beamforming techniques in conjunction with the feed array of large deployable reflector antennas can boost the performance of synthetic aperture radar (SAR) systems. Multi-channel SAR overcomes the constraints of classical singlechannel SAR allowing for wide-swath imaging at fine azimuth resolution. Part 1 of this tutorial provided an introduction to the instrument structure of a digital beamforming (DBF) imaging radar and the particularities/variants of its basic operation mode, known as a single-beam scan-on-receive (SCORE) system.The underlying part 2 of the tutorial paper addresses the topic of ultra-wide swath imaging in the order of a few hundred kilometers, enabled through DBF. A detailed insight into simultaneous multiple sub-swath imaging is given; gaps (blind ranges) that occur in this operation mode are addressed; and the data streams management at the various on-board processing stages is explained, put in relation to the imaging mode, and expressions for the data rates are provided.A further beamforming topic seized in part 2 of this tutorial trilogy is the feed array excitation (complex weights) and the resulting primary and secondary radiation patterns. This is explained in the context of a reference reflector-feed antenna system providing numerous example cases aiming to foster the understanding of the topic.Index Terms-synthetic aperture radar (SAR), digital-beam forming, reflector-based SAR.Parameter Values: For a f prf = 1770 Hz and T echo = 1.52 ms the number of beams can be computed using (1) which results in N beam = 3. The diamond diagram in Fig. 1 shows that three sub-swaths are required to image a 355 km swath (look angle range from 26.4 • to 42.5 • ). The typical number of beams for reflector SAR is in the range of N beam = 3 to 6.

Comprehensive Review: Effectiveness of MIMO and Beamforming Technologies in Detecting Low RCS UAVs

“…[65] investigates the complexities of designing transmit and receive beamforming in MIMO radar systems among signal-dependent interference, highlighting computational challenges and proposing innovative solutions. The authors in [66,67] highlight the transition from traditional analog beamforming methods to advanced digital beamforming techniques in radar systems. This evolution is significant for spaceborne SAR and FMCW MIMO radar networks, marking a pivotal point in the development of radar technology.…”

A Synthetic Aperture Radar Imaging Mode Utilizing Frequency Scan for Time-of-Echo Compression

“…Conventionally, the imaged swath width and position is determined from the timing (diamond) diagram so as to avoid an overlap of the signal echo and the transmit pulse (cf. [39] for details on the imaging gap caused by the transmit pulses). It turns out, that the identical approach is not applicable to f-STEC SAR, because of the inherent interrelation between the swath width and various operational parameters.…”

“…However, in general the ambiguity level is low for all three systems, since the performance is timing limited. Nevertheless, both SCORE and f-STEC systems could be operated in a multi-swath imaging mode [39], without sacrificing RASR.…”

Experimental Demonstration of Staggered Ambiguous SAR Mode for Ship Monitoring With TerraSAR-X

“…It is worth noting the differences between the staggered ambiguous mode, shown in the right panel of Fig. 1, and the staggered SAR system in [27]- [37] that employs DBF techniques, shown in the left panel of Fig. 1.…”