An echo time-delay compensation method combining correlation with pulse compression for synthetic aperture sonar

A raw echo time-delay compensation method combining pulse compression with correlation function is proposed to solve the problem that the improvement effect of cross-correlation time-delay compensation algorithm for SAS(synthetic aperture sonar) image quality is limited by decreasing phase congruence of the array elements.Phase distortion of the raw echo is compensated by its pulse compression echo.Subsequently,the echo with rough time-delay compensation can be obtained.Then the echo with accurate time-delay compensation can be got by combining pulse compression with Displaced Phase Center(DPC) algorithm.Moreover,the time-delay of each array element echo at different positions during aperture synthetizing can be achieved.Finally,the proposed algorithm can improve the image quality much better than only using the DPC algorithm.After the processing of experiment data,the raw echo obtains more accurate time-delay compensation by the proposed method.The new image result of anthropogenic landform shows that the brightness and contrast ratio are increased significantly and more details can be seen.The cable-target was focused more deeply and its length error was reduced from 5%to 0.8% approximately after used the proposed method.Results of experiment show that the proposed algorithm can promote the cross-correlation time-delay compensation algorithm significantly;the feasibility and validity of the method are consequently demonstrated.