Airborne Synthetic Aperture Radar Imaging Algorithm

Synthetic Aperture Radar(SAR)is a sort of high resolution imaging radar．It worksby flying carriers’ movement to form some virtual antennas of the radar, to obtainhigh-resolution image data. SAR makes use of microwave remote sensing technologyand therefore can work in all day and under all whether conditions. And SAR can formhigh resolution images over long distances. Because of these advantages, SAR haswidely application value in military and civilian areas. The performance of conventionalSAR imaging algorithms is limited by system’s achievable bandwidth. And the qualityof the imagery is influenced by noise and side lobe. So we need improve the quality ofthe imagery.The main contributions of the paper are as follows:(1) According to pulse compression theory and SAR principle，the paper firstlygives an analysis on the principle of high—resolution SAR imaging，then，notes that theSAR range resolution is dependent of signal bandwidth，while SAR azimuth resolutionis dependent of the bandwidth of the LFM-featured Doppler signal generated from therelative movement between aircraft carrying the radar and the fixed ground target，thus，high azimuth resolution can be realized through pulse compression．(2) In this thesis，two widely used imaging algorithms are studied following theanalysis of the basic principles of SAR imaging，including Range-Doppler algorithm，Chirp Scaling algorithm. Considering the characteristics of the large squint side-lookingSAR，improved algorithms are discussed．The simulation results confirm the algorithmsvalidity．(3) Doppler center frequency is an important parameter necessary for SAR imagingand has a great impact on the effect of imaging. So it must be estimated precisely．Theestimating methods contain time domain method and frequency domain method.At thelast of this paper the principle of these algorithms is studied.