Digital beamforming in sar systems

Abstract

The rapid progression in digital hardware and signal processing capabilities stimulates the development of radar systems. The tendency is to move the digital interface toward the antenna, replacing, whenever possible, analog RF-hardware. Based on software codes, these digital systems are more flexible and easier to reconfigure than RF-hardware. This letter illustrates the general concept for digital beamforming (DBF) in synthetic aperture radar systems and investigates their principle capabilities, limitations, and performance parameters. It is shown that using DBF a simultaneous improvement in azimuth coverage and resolution can be achieved.Index Terms-Digital beamforming, digital radar, digital synthetic aperture radar (SAR), software-defined radar sensors.

Recent Trend and Advance of Synthetic Aperture Radar with Selected Topics

“…A basic design of achieving high resolution in wide swath is DBF on receive with the conventional analogue beam forming on transmit, where a wide swath is illuminated using either a small part of an antenna or a small separate antenna, and the scattered signal is received by multiple independent sub-apertures; these signals are then processed independently to produce images of multiple swaths and to produce a wide-swath image by combining them. Several different approaches have been proposed, including a squinted geometry, a displace phase center antenna technique, both of which use sub-apertures aligned in the azimuth direction, a quad-element rectangular array system, and a high-resolution wide-swath (HRWS) system employing multiple sub-aperture elements split into both the azimuth and range directions [192][193][194][197][198][199], as well as the use of a large reflector antenna with feed arrays [158,200,201]. As mentioned in Section 2.2, Tandem-L will have 10 m resolution covering 350 km swath with repeat cycle of 8 days [22,158].…”

ASTC-MIMO-TOPS Mode with Digital Beam-Forming in Elevation for High-Resolution Wide-Swath Imaging

“…The steering raw in azimuth and the scanning vector in elevation can be preloaded onboard with the system requirement according to the designed SAR imaging geometry. Echoes from multiple along-track (in azimuth) spatial channels can be combined coherently via azimuth signal reconstruction algorithms in [19][20][21][22] to suppress azimuth ambiguity energy, while signals received by all sub-apertures in elevation are combined to form a sharp and high gain steering beam to extract spatial diversity and suppress range ambiguous energy. Azimuth beam steering is implemented by an analog beam-forming (ABF), and elevation beam scanning is achieved by a DBF net for each sub-antenna as shown in Figure 5.…”

Near-Space Microwave Radar Remote Sensing: Potentials and Challenge Analysis

“…Another promising configuration is digital beamforming on receive [50]. As shown in Figure 4, the satellite antenna footprint exceeds by far the size of the near-space receiver footprint.…”