Research On DBS Imaging Technique For MMW Terminal Guidance Radar

After successive developments of four generations, anti-ship missile has become one of the main weapons to attack enemies'warships. For terminal guidance of anti-ship missiles, radar terminal guidance is a widely-used solution. However, how to quickly obtain 2-D high-resolution radar images of warships remains to be a difficult problem, which limits the detection and recognition performances of anti-ship missile's terminal guidance radar. This thesis focuses on radar imaging techniques of millimeter-wave anti-ship terminal guidance radar, and systematically studies the DBS (Doppler Beam Sharpening) parameter design, Doppler parameter estimation and DBS imaging algorithms during the terminal guidance period of an anti-ship missile. The main work is outlined as follows.In the introduction, The role of anti-ship missiles in modern high-tech regional wars is clarified, with an emphasis on radar terminal guidance techniques of anti-ship missiles by which the concept of DBS is introduced. Then, the state of the art of DBS imaging and Doppler parameter estimation techniques is summarized. The major work of the whole thesis is described at last.Chapter 2 focuses on the parameter design of DBS concerning the application of DBS into anti-ship missile terminal guidance radar. At first, the operation principle of DBS is introduced. Then, typical terminal trajectories of anti-ship missiles are summarized and analyzed. Thirdly, according to the characteristics of DBS imaging in the terminal guidance radar of anti-ship missile, the parameter design of range resolutions and azimuth resolutions both on the slant range plane and the ground range plane, the PRF (pulse repetition frequency) and the beam scanning speed, etc., are studied in detail.Chapter 3 studies the methods of Doppler parameter estimation. Firstly, the correlation function method is adopted to estimate the base-band Doppler centroid. Secondly, to solve the Doppler centroid ambiguity due to DBS imaging at great forward-squint angle, it is proposed that Radon transform be applied to estimate the Doppler centroid based on the approximate linear characteristic of the range migration under the condition of great forward-squint angle. Meanwhile, the Radon based method is compared with the energy center method. Thirdly, the estimation algorithms of Doppler frequency rate are discussed. Simulation results verify the validity of the methods above.Chapter 4 studies the imaging algorithm of DBS. First of all, given the requirement of real-time DBS imaging for missile borne radar, the fast azimuth synthesis method based on Dechirp– SPECAN, i.e., spectral analysis algorithm - is analyzed, and the adaptability of SPECAN to DBS imaging in great squint situation is deeply researched. Secondly, to solve the problem of the spatial variation of the azimuth resolution in great-squint DBS imaging, under the constraint of invariant PRF, the pre-filtering method and the frequency-domain interpolation method are utilized to lock the sharpening ratio, based on which the method of azimuth resolution modification is proposed. Thirdly, to solve the problem of imaging wide region using scan DBS technique, the sub-image geometric correction and stitching techniques are researched. Finally, the whole-flow simulation for great squint, wide region scan DBS imaging is conducted to verify the validation of the techniques above.In the end, the whole work of this thesis is summarized, and some conclusions are presented. In addition, some directions for further research are pointed out at last.