In-Flight Multi-Channel Calibration for Along-Track Interferometric Airborne Radar

Abstract

Multi-channel calibration is essential for detecting moving targets and for estimating their positions and velocities accurately. This paper presents a fast and efficient calibration algorithm for along-track multi-channel systems, in particular for space-time adaptive processing (STAP) techniques. The proposed algorithm corrects the phase and magnitude offsets of the receive channels, and also takes into account the Doppler centroid variation (e.g., caused by atmospheric turbulences) along slant range and azimuth time. The knowledge of the Doppler centroid variation is especially important for an accurate clutter covariance matrix estimation, which is required by STAP for efficient clutter suppression. Important calibration parameters and offsets are estimated directly from range-compressed training data. The proposed algorithm is evaluated based on real multi-channel X-band radar data acquired with DLR’s airborne system F-SAR and compared with the state-of-the-art digital channel balancing technique. The experimental results show the potential of the proposed calibration algorithm towards real-time applications.