TerraSAR-X Dual Receive Antenna Mode - Channel Reconstruction and Impact on the GMTI Performance

Synthetic aperture radar with multiple channels separated in along-track direction allows for GMTI such as detection of road traffic [1]. With TerraSAR-X two receive channels separated in along-track direction can either be realized through switching between the fore and aft antenna halves from pulse to pulse, or with the dual receive antenna (DRA) mode [2]. While the switching in the single channel switched aperture mode is implemented by alternately applying attenuation to the fore and aft antenna halves, in the DRA mode the signals of the fore and aft antenna halves are combined by a hybrid coupler generating the sum and difference channel data. By use of the redundant receiver unit both channels are sampled separately. Fore and aft channel signals have to be reconstructed in the signal processing step. In this paper a method for an adaptive fore and aft channel reconstruction based on calibration pulses and calibration beams is presented. The imbalances related to the TerraSAR-X hardware implementation of the DRA mode are modeled into the transfer functions of the data acquisition and the processing in order to analyze the quality of signal reconstruction and draw conclusions on the impact on the ground moving target indication (GMTI) performance of this two-channel mode. The theoretical results derived are validated with experimental data and GMTI results are shown.