A high precision FPGA-based active radar calibrator

This study design a high precision active radar calibrator (ARC) with programmable echo points which served as control points for both geometric and radiometric calibrations or other applications. The echo delay and Doppler shift of ARC system are fully digitally controlled. Specification and performance of the digital ARC were tested on C-band ERS-2 SAR image. From the experimental results, the FPGA circuit can produce several calibration points of desired range or azimuth direction. In InSAR application, the echo points of ARC system can estimate squint angle difference in two co-registration images. Compared to analog time delay ARC system, the current ARC generates delay error less than 10ns, greatly reduced from 30-50 ns that analog time delay has. In addition, the stability of the time delay and output power in the FPGA based ARC are both much better than the traditional analog delay ARC.