A THZ CSAR Ground Moving Target Parameter Estimation and Refocusing Algorithm

In this paper, an azimuth velocity estimation method based on spectral peak measurement-moving target shadow detection (SPM-SD) is proposed. Compared with the existing methods, this method takes into account the effect of the moving target position on the doppler shift and improves the accuracy of the azimuth velocity estimation value. The doppler modulation frequency of the azimuth phase is then estimated by using the fractional Fourier transform (FrFt), which in combination with the azimuth velocity gives an estimation of the distance velocity of the moving target. Finally, the estimation results are used to construct the first-order and second-order phase compensation functions for azimuth phase compensation, and the phase gradient autofocus algorithm (PGA) is used to compensate for the residual quadratic and higher phase errors. The real CSAR data processing results prove the effectiveness of the proposed method and greatly improve the imaging quality of the moving target.