討論了距離向去調頻聚束模式SAR信號的回波模型及特點，通過對聚束SAR信號的時、頻域關系的分析，給出了適合去調頻后的聚束SAR數據的成像算法。該算法結合了SPECAN算法高效和標離-多普勒算法實現方位精確聚焦，與傳統的距離-多普勒算法相比，成倍地降低處理的數據量，從而可實現聚束SAR的實時成像處理。對Ku波段實際飛行數據采用該算法壓縮得到高分辨率的圖像，驗證了理論分析的正確性和所用方法的可行性。

This article discusses the character of range-dechirped spotlight SAR signal, analyzes the time and frequency domain character of dechirp SAR signal, presents imaging method of spotlight range-dechirped raw data.The new algorithm combines the advantages of two processing approaches: the efficiency of SPECAN algorithm and the precision of stripmap focusing technique, the first step of the proposed algorithm implements deramp technique representing a simplified version of the SPECAN approach, the second processing carries out the residual focusing via the use of a conventional stripmap processing procedure,in comparison with the range doppler method,this algorithm decreases the processed data with a little amount of calculation increased.The Ku band airborne spotlight SAR imaging experiment confirms its availability.