Abstract
The multiple-input multiple-output (MIMO) technique can improve the high-resolution wide-swath imaging capacity of synthetic aperture radar (SAR) systems. Beamspace MIMO-SAR utilizes multiple subpulses transmitted with different time delays by different transmit beams to obtain more spatial diversities based on the relationship between the time delay and the elevation angle in the side-looking radar imaging geometry. This paper presents a beamspace MIMO-SAR imaging approach, which takes advantage of real time digital beamforming (DBF) with null steering in elevation and azimuth multichannel raw data reconstruction. Echoes corresponding to different subpulses in the same subswath are separated by DBF with null steering onboard, while echoes received and stored by different azimuth channels are reconstructed by multiple Doppler reconstruction filters on the ground. Afterwards, the resulting MIMO-SAR raw data could be equivalent to the raw data of the single-channel burst mode, and classical burst mode imaging algorithms could be adopted to obtain final focused SAR images. Simulation results validate the proposed imaging approach.
Highlights
High-resolution wide-swath (HRWS) imaging capacity is one of the most important aims of future spaceborne microwave remote sensing [1, 2]
Different transmitted subpulses are transmitted with different elevation beams and time delays, and their corresponding echoes could be separated by digital beamforming (DBF) in elevation based on the relation between the short transmitted time delay and the elevation angle in the side-looking synthetic aperture radar (SAR) imaging geometry [15]
Based on the relationship between the transmitted time delay and the SAR side-looking imaging geometry, echoes corresponding to different subpulses are separated by a DBF processor with null steering onboard
Summary
High-resolution wide-swath (HRWS) imaging capacity is one of the most important aims of future spaceborne microwave remote sensing [1, 2]. To overcome the inherent limitation between azimuth resolution and unambiguous swath width in conventional single-channel spaceborne synthetic aperture radar (SAR) systems [2], multiple innovative multichannel imaging modes are proposed and investigated [3,4,5,6,7,8,9,10,11,12,13,14,15,16,17]. The resulting raw data after DBF onboard and azimuth multichannel reconstruction could be focused by classical burst mode imaging algorithms [20,21,22,23,24,25].
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