New method for preprocessing in airborne SAR system

Generally the pulse repetition frequency in airborne SAR system is much higher than signal bandwidth to guarantee the maximum slant range requested. In order to reduce the large processing amount caused by high PRF, we always preprocess the echo signal in azimuth before the whole processing procedure. The conventional method is pre-filtering, which has some approximation and relatively large computation amount. This paper mainly studies pre-accumulation as another preprocessing method with relatively small computation amount. On the basis of SAR signal processing theory, we analyze and simulate the result of direct accumulation of incoherent signal in azimuth, as well as the phase loss caused by incoherence and the factors affecting the phase loss. Furthermore, present a resolution to eliminate the phase loss, which adjusting signal phase by multiplying phase difference before accumulating, and compare the computation amount with that of pre-filtering. After that, point out the condition suitable to use this method. Finally, we apply this method to raw data processing of airborne SAR and the result shows that the proposed method can achieve the image result with the similar quality to that of original processing, while reduce the computation amount considerably.