A Novel Compensation Method to Calibrate Dispersion Effect for Spaceborne Synthetic Aperture Radar

The ionospheric dispersion effect introduces additional phase errors to the chirp signal, leading to undesirable deterioration in range compression, including range shift and main lobe broadening. The contrast optimization autofocus (COA), as a representative of parametric-based methods calibrating the dispersion effect, updates the chirp rate empirically and manually. Moreover, it only compensates for quadratic phase errors while failing to address linear and higher-order phase errors. To this end, this paper proposes a novel compensation method. Compared to the COA, two specific step sizes are derived to quantitatively restrict the range shift and quadratic phase errors for accurately updating the chirp rate. Subsequently, the total electron content (TEC) inferred by chirp rate errors is applied to construct the conjugate compensation term associated with range-frequency achieving full-order phase error calibration. The simulated experiment demonstrates the superiority of the proposed method.