Study Of Signal Processing Methods For High-resolution SAR

Synthetic Aperture Radar(SAR) is a kind of high-resolution imaging radar. It could obtain high-resolution radar images which are similar to optical photos. SAR has always been paid high attention by scientific researchers for its capacity of being able to work at all-day and all-weather, identifying camouflage effectively,penetrating obstacles and so on. One of the key targets of SAR imaging technology is how to acquire high-resolution images. But with the increasing of the velocity of the radar platform, the motion of the radar during signal transmission which has been neglected by traditional GO-STOP echo model would lead to the decline of resolution.In spaceborne condition, even no images. Therefore, it is very necessary to construct a SAR echo imaging model of high-speed platform.This essay presents an echo model which is applied to high velocity platform and gives corresponding imaging solutions based on three conventional SAR imaging algorithms which are Range-Doppler algorithm, Chirp-Scaling algorithm and Range-Migration algorithm. Firstly, this essay analyzes theoretically why traditional GO-STOP echo model in high speed platform cannot image precisely. In the meanwhile, an echo model which is applied to high velocity platform is presented.Secondly, Improved Range-Doppler algorithm, Improved Chirp-Scaling algorithm and Improved Range-Migration algorithm combined with high velocity echo model are presented in airborne strip map SAR. Experimental simulations shows that the GO-STOP model will bring non-ignorable error to SAR imaging, which proved that the model given by this essay is effective. Finally, improved R-M imaging algorithm based on space borne spotlight SAR is presented. Although using spotlight mode can improve the azimuth resolution, but it requires a larger bandwidth range. In practice,azimuth pulse repetition frequency cannot be too high for the pressure of data transmission. Therefore, the azimuth spectrum of the received signal is often aliasing.In order to solve this contradiction, two-step algorithm of spotlight SAR has been used for reference, which transferred the spotlight mode to strip map mode to makesure that strip map SAR imaging algorithm could be used. The model presented from this essay is different from the traditional GO-STOP echo model, so reference function in the improved spotlight SAR algorithm must be reorganize to fulfill this algorithm. Dot object simulation based on spaceborne spotlight SAR proved that the improved spotlight SAR algorithm from this paper is feasible.