Research on efficient calibration techniques for airborne SAR systems

Radiometric calibration of synthetic aperture radar (SAR) is an important work to relate pixel values to the backscattering coefficient of ground targets. SAR external calibration using point targets and internal calibration using system generated calibration signals can monitor the SAR system transfer function. To improve calibration precision, some efficient calibration techniques are introduced with external calibration approaches considered. Firstly, the pixel sizes both in range and in azimuth are unified by resampling whole data. Secondly, the antenna pattern of airborne SAR is measured and calibrated using the corner reflector array or uniform distributed targets to remove or reduce distortions from the radar data. Finally, airborne SAR data are transformed backscattering coefficient by utilizing the transfer function of SAR system. Theoretic analysis and experimental results show that these techniques are effective and feasible so that they can provide a theoretic support and technical approach for radiometric calibration.