Doppler Ambiguity Suppression for Multichannel RoSAR Imaging With Doubly Constrained Robust Capon Beamformer

Rotating synthetic aperture radar (RoSAR) employs rotating antennas to provide a 360(degrees) panoramic image of the surroundings from a stationary platform. A multichannel in azimuth RoSAR antenna has been used; the system transmits chirp signals with a low pulse repetition frequency (PRF), and all channels simultaneously receive the echo, resulting in an image sequence with the same frame rate as the video. In the main lobe of the azimuth beam, the recorded echo of the single channel is ambiguous, which makes steering vector errors inevitable in real systems and causes both nonadaptive and adaptive beamforming to perform noticeably worse or even fail. In this letter, we propose a Doppler ambiguity suppression algorithm with the doubly constrained robust Capon beamformer (DCRCB) for multichannel RoSAR that overcomes a number of nonideal factors such as amplitude-phase errors and array element displacement errors between channels. In order to obtain a high-resolution scene image, RoSAR imaging procedures are performed. To clearly demonstrate the proposed approach, the experimental results using simulated data are shown.