Study On FMCW SAR Imaging And Moving Target Detection

Frequency Modulated Continuous Wave(FMCW) Synthetic Aperture Radar(SAR) not only has the the capability of obtaining high-resoulution images under all-time and all the meteorological conditions, but also has the characteristics of light weight, small volume, low cost and low power consumption. Therefore, FMCW SAR can be mounted in a variety of detection platforms, even suitable for small unmanned aricraft. It has been widely appplied in both military and civil areas ranging from the battledfield reconnaissance to resource remote sensing. However, FMCW SAR system usually transmits continuous wave and receives Dechirp signal, and thus the platform motion can not be ignored. Therefore, the tradional “stop-go-stop” assumption for the pulse SAR is not valid. Its echo expression is more complicated, and is required to give detail analysis, and studies the corresponding imaging formation algorithm and moving target detection algorithm for FMCW SAR. Therefore, related researches on these issues have become a hot topic in radar society, which is of great value for theory derivation and practical application.At first, we start with establishing the echo model of FMCW SAR, and then studying an imaging algorithm under squint mode. Then, the echo model of moving target is derived, and the detection method is discussed. Further, considering the fact that wide-area GMTI has wide observation area, high revisit rate and relative low resolution, it is a good candidate for rapid monitoring and investigation of the illumilated scene. It is the emphasis of ground target detection technology. Therefore, this thesis provides in-depth study on the wide area GMTI algorithms under the FMCW SAR configureation. Finally, simulated experiments verify the effectiveness of the relevant methods. This thesis is organized as follows:(1) Firstly, for FMCW SAR echo, we build the echo model, analyze the echo signal characteristics and the operation principles, and illustrate the essential difference with pulsed SAR. Based on the detail analysis of the FMCW SAR under squint mode, an effective imaging algorithm is investigated, and the subsequent simulation experiments verify its vadility.(2) Upon the establishment and analysis of the echo of moving target in the mode of FMCW SAR system, coarse imaging and detection can be realized in by incorporating the Doppler shift compensation and DPCA technique. Then, the moving target information is extracted, and inverse transformed to the original raw data domain for secondary focusing imaging processing. By combining Doppler shift compensation, azimuth deramp, ambiguity number estimation, as well as the Keystone transformation, the well-focused image the moving target can be obtained. The effectiveness of the method is verified by the computer simulation.(3) Firstly, by establishing the signal mode of moving target for FMCW wide area GMTI, the conditions and theories of FMCW-DBS are analyzed. Secondly, each wave subregion's imaging result can be obtained by DBS imaging technology. Then, the image combination is realized based on the fast correlation method and the coordinates transition are applied on each subimage. Further, clutter suppression and moving targets detection is implemented through the technology of Displaced Phase center Anenna(DPCA) and Constant FalseAlarm Rate(CFAR). The angular relocation of the targets in the image can be accomplished by using the interferometric phase information. Finally, simulated experiments proves the effectiveness.