Beam-Space Based MIMO SAR Digital Beamforming with Array-Fed Reflector Antennas

In a Multiple-Input Multiple-Output Synthetic Aperture Radar (MIMO SAR) system, the miniaturization and high gain of the antenna has been pursued all the time. At the same time, it is common to partially transfer the pressure of suppressing azimuth ambiguity to range so as to balance antenna size, and thereupon following a problem that the radar echoes in elevation are sensitive to terrain undulation. A promising candidate is the combination of array-fed reflector antenna and Digital Beamforming (DBF) technique. Therefore, this paper establishes an echo model for array-fed reflector antenna and proposes a beamspace based DBF method applied to array-fed reflector antennas. Simulations taking use of the proposed DBF method are carried out to verify the effect on range ambiguity suppression. Aiming at the terrain-undulation-sensitive problem, a derivative constraint to steering vector is added during the DBF process, which greatly improves the robustness of DBF in elevation.