Abstract
Accurate position estimation of ground-moving targets is a crucial requirement for any radar-based surveillance system. For a multi-channel airborne radar, the target position on the ground can be accurately obtained by estimating the direction-of-arrival (DOA) angle of the moving targets. However, in practice, the aircraft motion caused by atmospheric turbulence tilts the antenna array and introduces undesired phase differences among the multiple receive channels. As a result, the accuracy of the estimated DOA angles can be severely affected. This letter presents a robust and efficient algorithm that corrects the undesired phase differences among the multiple receive channels. By doing this, accurate DOA angles and, therefore, accurate target positions on the ground can be estimated. Important inputs of the proposed algorithm are the precise absolute positions of the receive channels and the elevation of the terrain. The performance of the proposed algorithm is validated using simulated data as well as radar data acquired with the DLR’s multi-channel airborne system with digital beamforming capabilities digital beamforming SAR (DBFSAR).
Highlights
A IRBORNE radars are very attractive for surveillance applications due to their weather-independent and day– night acquisition capabilities
When the aircraft has an antenna array with multiple receive (Rx) channels, the target position on the ground can be obtained by estimating the direction-ofarrival (DOA) angle [1]
The term d is the beamforming vector and uarray is the directional cosine with respect to the antenna array axis and t is the azimuth time
Summary
A IRBORNE radars are very attractive for surveillance applications due to their weather-independent and day– night acquisition capabilities. When the aircraft has an antenna array with multiple receive (Rx) channels, the target position on the ground can be obtained by estimating the direction-ofarrival (DOA) angle [1]. The calibration is accurate, the phase offsets are not adaptively estimated and, this algorithm is robust only for low-squint-angle acquisitions and for moderately flat terrains Another algorithm was proposed in [3] for compensating the undesired phases among the Rx channels. This method handles effectively the high-squint-angle acquisitions and terrain’s high topographic variations. Even though it gives reliable detection results, the achieved target position accuracy is poor since only two Rx channels are used. The performance of the proposed algorithm is validated using both simulated and X-band radar datasets acquired with the DLR’s multi-channel airborne system digital beamforming SAR (DBFSAR) [4]
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