The effect of pulse phase errors on the chirp scaling SAR processing algorithm

The chirp scaling (CS) SAR processing algorithm uses the linear FM property of the transmitted pulses to provide accurate range cell migration correction. However, when the transmitted pulse is not linear FM, or if the FM rate is not known exactly, processing errors due to chirp scaling will result. This paper presents the resulting processing error in the CS algorithm, given pulse phase errors that exceed those expected in SAR systems. The registration and phase error that result in chirp scaling are negligible for typical or stable pulse phase errors, or can be avoided if phase modulation coefficients are estimated from the replica. A fast Fourier transformed pulse replica is sufficient to form the range matched filter in the CS algorithm, giving slightly better range resolution than the range/Doppler (R/D) algorithm.