Design And Implementation Of The Target Detection Algorithm For Pulse-synthesized Wide-band Radar

Stepped-frequency radar is one of the wide-band radar systems that can achieve high range resolution by synthetizing multiple pulses. It works by transmitting a series of bursts of narrowed pulses, where each burst consists of N pulses whose frequencies are increased from pulse to pulse by a fixed frequency. The echo pulses can obtain high resolution range profile(HRRP) by the IFFT processing. The transmitting, receiving and processing procedures of stepped-frequency radar can be completed by narrow-band pulse that can reduce the requirements for instantaneous bandwidth of radar and decrease the difficulties in the design of digital signal processor. Due to its good performance, stepped-frequency has been widely used in project implementation.This paper starts with the introduction of the mathematical model of the stepped-frequency signal. After derivation and analysis of the model, the principle of high range resolution is developed. With regards to the redundancy and defect brought by the parameter setting, this paper proposes a high resolution range profile algorithm of stepped-frequency radar which evolves from existing techniques. This profile spelling algorithm can reduce the distance bias and suppress the generation of false targets. Both the simulation data and the experimental measurements are used to attain one-dimension HRRP, hence the accomplishment of the study.The one-dimension HRRP of a radar target is described as composed of several kinds of scattering centers with different geometric shapes and structures. These characteristics can be used to improve the detection performance. Because of the difference between the point target and the range extended target, a new constant false alarm rate(CFAR) detector for the range extended target is needed. Based on the introduction and performance analysis of the traditional point target CFAR detectors, three detectors for range extended target are proposed. Then, the detection performances of the proposed detectors with different signal to clutter ratios(SNR) are discussed. Finally, the measured data shows that the Order-Statistic-Based and Multi-Channel detector has better performance than the other two detectors under the Lognormal clutter background.According to the analysis of different CFAR detectors, Cell Averaging Constant False Alarm Rate(CA-CFAR) detector is chosen for the low resolution radar system because of its good performance and so is Order-Statistic-Based and Multi-Channel detector in the high resolution situation. These two algorithms are used for project implementation with Field Programmable Gate Array(FPGA) which has high integration level, speed, reliability and stability. FPGA can deal with the complex timing design. Taking the amount of data, speed and resources into account, FPGA can get the task done according to the characteristics of the two algorithms with the parallel processing method.Finally, this paper makes a summing up of the profile spelling algorithm and the CFAR algorithm, which accomplish the data processing procedure that transforms the stepped-frequency signal to the one-dimension HRRP for the target detection.