A Study Of Chirp Z-Transform Algorithm For Synthetic Aperture Radar

We can describe the echo that synthetic aperture radar (SAR) received as radar backscatter coefficients of the target field convoluted with two impulse response functions. Either on range or azimuth direction, echo of each target on field is dispersive. We can consider echo receive process as a transformation from target space to signal space. SAR signal processing's purpose is to carry out the reverse transformation from signal space to target space via two dimensions inverse convolution. Then we can rebuild the target space and get radar image.In this paper, author introduced the basic theory of SAR. She derived frequency domain expression of SAR system transfer function from it's time domain expression, and then explained the main cause of range cell migration (RCM). She proved SAR echo was the Chirp Z-transform of radar backscatter coefficients of target field on range dimension.Base on inverse Laplace transform theory, author derived calculating method of a kind of inverse Chirp Z-transform. We can calculate the inverse Chirp Z-transform of SAR echo on range dimension use this method to compensate the RCM. And then we calculate the inverse discrete Fourier transform of the signal on azimuth dimension, the processing result is the SAR image. This method of SAR imaging processing called Chirp Z-Transform (CZT) imaging algorithm, what was the main point of this paper.Nowadays, people who work in radar field pay more and more attention on the non-linear frequency modulation (NLFM) signals. Because use it as SAR transmit signal can improve the pulse compression performance, safety and anti-interference property ofthe radar system. This paper expounded a kind of improved CZT imaging algorithm which permits processing SAR echo when SAR sends NLFM signals. This improved CZT imaging algorithm can process range compressed signals and the RCM compensation is independent of linear frequency modulation (LFM) characteristic of LFM signals.Author chose a group of parameters form NLFM functions family and use the improved CZT imaging algorithm to process the signal. The result of RCM compensation is as good as LFM SAR signals.