| The problem of detecting and tracking low-altitude targets is one of the main research topics in radar. Multipath can cause echo amplitude fluctuate. And then targets’ detection performance descends quickly. Otherwise, the high mobility of low-altitude targets can cause the tracking filter diverge.The detection method based on frequency diversity and tracking method based on the first order Extended Kalman filter are proposed to solve the problem of low-altitude targets detection and tracking. These methods can promote the detection and tracking performance.In the light of high speed moving target of low-altitude radar detection and tracking problem, this thesis analyzes the target’s detection performance by using the frequency diversity detection method based on Keystone transformation and compares the performance metrics between different tracking filter methods. Finally, the low-altitude target detection radar signal processing system based on FPGA implementation is realized. The main work is listed as follows:1. By building the echo signal model of multipath, this thesis analyzes the influence on targets’ detection performance including echo amplitude attenuation.2. These low-altitude targets can be detected accurately by using the frequency diversity detection method based on Keystone transformation. This method eliminates the impact of echo amplitude due to the multipath and utilizes different channels to accumulate targets information. Compared with the method of single channel measurement, this method increases the signal noise ratio and promotes the detection performance.3. These four tracking filters including α-β filter, Kalman filter based on uniform motion state model, Kalman filter based on uniformly accelerated motion state model, and the first order Extended Kalman filter can effectively track the low-altitude targets. Compared with these four methods, this thesis proves the performance of the first order Extended Kalman filter is the best.4. Based on the low-altitude target detection radar project background, this thesis provides the more specific scheme of the implementation of signal processing and completes the algorithm design and FPGA realization including pulse compression module, MTI module, MTD module, CFAR processing module, cohesion of distance and doppler information module, and target tracking module. The logic validity and realizability of this FPGA system have been proved by functional simulation and joint debugging with other radar subsystems. By testing outfield, the system can detect and track the civil aircraft, and the practicability of this system is now proved.Through the analysis of detecting and tracking low-altitude targets, the more applicable detection and tracking method on the FPGA implementation of guidance radar signal processing system is found. What’s more, the implementation of this system is accomplished. |
