In order to solve the problem due to the double-square-root terms of the range history and degrade the phase error caused by the range history approximation, the method of displacement phase center approximation is modified continually and the range history is approximated into the sum of a monostatic term, a range-variant term and an azimuth-variant term. In the processing of deriving the azimuth phase stationary point using the conventional principle of stationary phase, the azimuth-variant term is considered sufficiently to obtain a more accurate phase stationary point. Thus, a more accurate point target response two-dimensional frequency expression is obtained. Based on that, a high resolution range Doppler algorithm for the multiple-receiver synthetic aperture sonar imaging is proposed. With the presented method, the echo signals corresponding to each receiver are processed firstly. Next, a high resolution SAS complex image can be obtained by coherently superposing each individual processing result. The result of simulation and real data imaging shows the effectiveness of the proposed algorithm.
