Results of flight tests of a two-channel radar system with real-time MTI processing

Abstract

In synthetic aperture radar (SAR), only fixed targets are mapped on their correct positions. Moving targets are displaced in azimuthal direction due to the Doppler frequency shift caused by target velocities. The detection and correct positioning of moving targets within SAR images is a problem that can be solved by using multiple antennas and multi-channel receivers. For the detection of slow moving targets or moving targets that are backfolded into the clutter spectrum, a good suppression of fixed target echoes is necessary to gain subclutter visibility. Space-time adaptive processing (STAP) shows good performance in clutter suppression and is state of the art. However, the main disadvantage of conventional STAP techniques is the very high computational load. Therefore, performing STAP in real-time for the purpose of on-board subclutter moving target indication (MTI) requires special techniques. To estimate the true azimuthal positions of moving targets, phase differences between receiver channels can be evaluated e.g. by using the well-known monopulse method. Alternatively, STAP can be applied to solve this problem as well. STAP in real-time is discussed for two applications. First, STAP can be used for suppressing clutter and jammers. Moreover, clutter filter coefficients gained by STAP can be used for the purpose of correct positioning of moving targets within SAR images. Results of this real-time STAP technique as well as results of the moving target repositioning technique are presented: the clutter suppression quality and the moving target repositioning accuracy are demonstrated with real SAR data and moving targets recorded during a measurement campaign.