Study On The Array SAR GMTI Techniques

As one of the functions of Multi-mode Array SAR,the main purpose of Ground Moving Target Indication(GMTI)is to search and find the moving targets on ground,determine the velocity and location of the moving target and draw the track of it.Mark the moving target and its track on the SAR map so as to combine the GMTI mode and SAR mode,which is known as SAR-GMTI mode.In order to realize the real-time target indication and location,in this dissertation the method of azimuth digital scan based on digital beam-forming is adopted.The procedure starts by illuminating the wide area by a wide beam and receive the signal by 24 channels so as to form a narrow beam.Control the direction of the narrow beam digitally and scan the area illuminated.After detecting the moving target,determine the position of the target by phase comparison.Compared with the Space-Time Adaptive Processing(STAP)technique,the algorithm proposed has the feature of easy-calculating and real-time.The main contend and the progress achieved is presented below:1.Study on the parameters and system characteristics of the array radar.Due to the combination of the GMTI mode and SAR mode,the need of the SAR mode ought to be taken into consideration when designing the parameters,like the bandwidth and pulse width of the signal and the pulse repeat frequency(PRF).Then,analyze the radiation plot of the antenna under different conditions of the direction of the beam and the number of the receive channels in order to give way to the analysis of the performance of moving target indication and location.2.Study on the coherent clutter model for airborne array radar.The method of modeling is stated detailed,including the separation of the ground units,the transform of the coordinates,the model of the RCS and the model of the receive signal.By simulations of the clutter in different PRFs,the effectiveness of the model is proved and it can be used as the base of the analysis of the performance of moving target indication.3.Study on the algorithms of the moving target indication of the array radar and the analysis of the performance of it.Considering the feature of the system and the mode of operation of the array radar,the proper algorithms for moving target indication is proposed and the procedure of it is given.The main clutter track technique is studied and the frequency estimation method is improved so as to determine the center of the spectrum of the signal of the moving target.Meanwhile,the performance of moving target indication is analyzed.4.Study on the algorithms of the moving target location of the array radar and the analysis of the performance of it.According to the feature of the array,the phase comparison algorithm is adopted.The error of the estimation of the location of the moving target is given quantitatively by formulation derivation.The angle ambiguity is analyzed qualitatively and the method of using the rough location of the detection to solve the angel ambiguity is proposed.The work in this dissertation is of great significance in theory and reference for the real-time GMTI of airborne array radar.