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A Comprehensive Method of Ambiguity Suppression for Constellation of Geostationary and Low Earth Orbit SAR (ConGaLSAR)
IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing ( IF 5.5 ) Pub Date : 2020-01-01 , DOI: 10.1109/jstars.2020.3002392
Peng Xiao , Wei Guo , Youming Wu , Bo Liu

ConGalSAR is a novel SAR constellation that has an outstanding performance of revisit and economy. In the system, with the MirrorSAR technology, one geostationary illuminator and several economical low earth orbit transponders work together to achieve a short revisiting interval. Because of the huge difference in the distances of transmitting and receiving, the spatial weighting of the antenna patterns on the ground is quite different, which leads to the deterioration of ambiguity to signal ratio. The multiphase center and digital beamforming antennas can suppress the ambiguity energy; however, they are too expensive and heavy to be equipped on the dozens of transponding nanosatellites. In this article, a comprehensive ambiguity suppression method, including the reflector antenna design and signal processing, is proposed to reduce the ambiguity ratio, which well solves the ambiguity problem under the condition of the low manufacturing costs and lightweight transponders. In terms of the hardware design, the multifeed reflector antenna is applied to the transponder, in which the feeds receive an echo together. Based on this, the low sidelobes beamforming is achieved to well suppress the ambiguity. Meanwhile, the amplitude-modulated chirps are also used here aiming at the residual ambiguity in the large dynamic scene. Through spectral selection and extrapolation processing, range ambiguity energy is suppressed more while preserving the resolution. The digital simulations show that the comprehensive method can realize −20 dB ambiguity ratios at least, which conforms to the ambiguity-to-signal ratio design of ConGaLSAR.

中文翻译:

一种对地球静止轨道和近地轨道SAR(ConGaLSAR)星座模糊度抑制的综合方法

ConGalSAR 是一种新颖的 SAR 星座,具有突出的回访性和经济性。在系统中,通过MirrorSAR技术,一个地球同步照明器和几个经济的低地球轨道转发器协同工作,实现了较短的重访间隔。由于发射和接收距离的巨大差异,地面天线方向图的空间权重差异较大,导致模糊信比恶化。多相中心和数字波束成形天线可以抑制模糊能量;然而,它们太昂贵和太重,无法装备在几十颗转发的纳米卫星上。在本文中,综合模糊抑制方法,包括反射面天线设计和信号处理,提出了降低模糊率的方法,很好地解决了制造成本低、转发器轻量化条件下的模糊问题。在硬件设计方面,多馈源反射器天线应用于转发器,其中馈源一起接收回波。在此基础上,实现了低旁瓣波束成形,以很好地抑制歧义。同时,针对大动态场景中的残余模糊性,这里也使用了调幅chirps。通过光谱选择和外推处理,在保持分辨率的同时,更多地抑制了距离模糊能量。数字仿真表明,综合方法至少可以实现-20 dB的模糊比,符合ConGaLSAR的模糊信比设计。很好地解决了在制造成本低、转发器重量轻的情况下的歧义问题。在硬件设计方面,多馈源反射器天线应用于转发器,其中馈源一起接收回波。在此基础上,实现了低旁瓣波束成形,以很好地抑制歧义。同时,针对大动态场景中的残余模糊性,这里也使用了调幅chirps。通过光谱选择和外推处理,在保持分辨率的同时,更多地抑制了距离模糊能量。数字仿真表明,综合方法至少可以实现-20 dB的模糊比,符合ConGaLSAR的模糊信比设计。很好地解决了在制造成本低、转发器重量轻的情况下的歧义问题。在硬件设计方面,多馈源反射器天线应用于转发器,其中馈源一起接收回波。在此基础上,实现了低旁瓣波束成形,以很好地抑制歧义。同时,针对大动态场景中的残余模糊性,这里也使用了调幅chirps。通过光谱选择和外推处理,在保持分辨率的同时,更多地抑制了距离模糊能量。数字仿真表明,综合方法至少可以实现-20 dB的模糊比,符合ConGaLSAR的模糊信比设计。
更新日期:2020-01-01
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