Performance Comparison of Reflector- and Planar-Antenna Based Digital Beam-Forming SAR

Abstract

The trend in the conception of future spaceborne radar remote sensing is clearly toward the use of digital beamforming techniques. These systems will comprise multiple digital channels, where the analog-to-digital converter is moved closer to the antenna. This dispenses the need for analog beam steering and by this the used of transmit/receive modules for phase and amplitude control. Digital beam-forming will enable Synthetic Aperture Radar (SAR) which overcomes the coverage and resolution limitations applicable to state-of-the-art systems. On the other hand, new antenna architectures, such as reflectors, already implemented in communication satellites, are being considered for SAR applications. An open question is the benefit of combining digital beam-forming techniques with reflector antennas. The paper answers this question by comparing the system architecture and digital beam-forming requirements of a planar and a reflector antenna SAR. Further elaboration yields the resulting SAR performance of both systems. This paper considers multiple novel aspects of digital beam-forming SAR system design, which jointly flow into the presented system performance.

System Performance Analysis for Multi-Band SweepSAR Operating Mode

“…SweepSAR 모드로 운용하기 위한 반사판 안테나 및 RF 송․수신 모듈의 구성은 그림 3과 같다 [14] . 송신 시에는 모든 급전 배열 안테나에 신호를 여기하여 넓은 빔으로 조사하고, 수신 타이밍을 고려하여 각 급전의 ON/OFF를 제어하여 순차적으로 반향신호를 수신한다.…”

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].…”

A novel ultra-wide swath SAR based on variable PRF and digital beamforming

“…To resolve the problem, diverse multi-aperture SAR concepts combined with the advanced DBF technique in elevation or/and in azimuth are designed by increasing the system complexity and the freedom degrees, as suggested in [1]- [3]. Various DBF forms, such as SCan-On-REceive (SCORE), enable higher Signal-toNoise Ratio (SNR) and lower Ambiguity-to-Signal Ratio (ASR).…”

“…Various DBF forms, such as SCan-On-REceive (SCORE), enable higher Signal-toNoise Ratio (SNR) and lower Ambiguity-to-Signal Ratio (ASR). And they can be effectuated based either on the planar array or on the reflector antenna, as elaborated in [3]- [4].…”

“…In this paper, the DBF technique is adopted for the improvement of the SNR and the suppression of ambiguity. And the reflector antenna is preferred, due to its light weight for large-size antenna and its low handling complexity for DBF [3]- [4]. Another inherent bottleneck for the strip-mapping ultra-wide swath SAR is the blind-range problem [7], which entails the discontinuous mapping.…”