Research On Spotlight SAR High Resolution Imaging Technology

Spotlight is a kind imaging mode of synthetic aperture radar (SAR). Spotlight SARwhich has an imaging ability of all-weather and all-time is a very important radarsystem in the high resolution imaging field today. Due to the long irradiation time onthe same target area, the azimuth information of Spotlight SAR is acquired more and theresolution is higher. However, the traditional interpolation algorithm has a lowoperation efficiency in dealing with the azimuth. The phase factor transform algorithmadopts step frequency signal, applies scale transform theory combined with thebroadband synthetic method, and makes a breakthrough in the old weakness. Thealgorithm of this paper which obtains the very high resolution image not only improvesthe computing efficiency, but also realizes the coupling between scale transform andbroadband synthetic. It has a certain application value in both military and civilianbecoming a research focus in the SAR high resolution imaging field gradually.This thesis mainly discusses the improved algorithm of Spotlight SAR highresolution imaging. The key content is as follows:（1） It analyses the basic theory of Spotlight SAR high resolution imaging,shows the signal model, illustrates how radar data is received and processed,and introduces the relevant forms of error.（2） It applies deramp in the step frequency signal, improves the methodconnecting with the broadband synthesis, analyzes the process of resamplingalgorithm, and verifies the necessity of the resampling technique through thesimulation.（3） This thesis introduces the most basic step frequency signal model simplyand improves the model in PFA. It studies the frequency domain syntheticalgorithm with frequency band overlap against the background of SpotlightSAR and focuses on the noise processing method of different noises. Itanalyzes the broadband synthesis method in-depth under the condition ofdifferent noise interferences, and gives the distribution curve of noise’s effectson image quality finally. （4） The concept of scale transform is introduced. It also analyzes the basictheory of phase factor transform algorithm and discusses the choice ofparameter emphatically. This thesis uses the step frequency signal as premise,couples the broadband synthesis method and the phase factor transformalgorithm, improves the algorithm through the range migration correction, andfinally validates the feasibility and efficiency of this algorithm through thetarget simulation of different resolution.This thesis mainly studies high resolution imaging algorithm of Spotlight SAR. Itfocuses on the phase factor transform algorithm based on scale transform and thebroadband synthesis algorithm based on frequency band overlap. What’s more, it alsocouples the two algorithms to achieve the high resolution imaging of both range andazimuth. The research in depth about this aspect will become a hot research topic in thefield of SAR high resolution imaging in the future.