Study On Weak Targets Detection Algorithms Based On Multi-frame Echoes

Recent years, with the further decrease of the targets’ RCS, the detection of weak targets has been an important and difficult problem in the field of radar technology. Whether a radar can detect weak targets efficiently in time or not is crucial to its performance. Because of the extremely low SNR(signal-to-noise ratio) of weak targets’ radar echoes, traditional radar signal processing methods can not achieve ideal detection and tracking for such targets. Increasing the time of integration can improve the SNR of weak targets efficiently. And the continuous long time integration technology has been a research focus in the field of the weak targets detection.However, for the traditional mechanical scanning radar, continuous long time integration can not be achieved generally. Only the continuous multi-frame radar echoes which are received in multiple antenna scanning periods can be used. In this dissertation, the algorithms that how to realize the detection of weak targets based on multi-frame radar echoes are discussed deeply on the basis of the multi-frame echoes signal model of non-fluctuated target. The main contents can be summarized as follows:1. The basic radar signal processing concepts and methods are reviewed. The definition of Chirp signal and pulse compression are presented in detail. Incoherent integration and coherent integration are emphasized, and the performance of the two signal integration methods are proved and compared through the computer simulation experiments. Two Track-Before-Detect(TBD) algorithms are introduced deeply. The dissertation also gives the simulation experiment results of the two TBD algorithms.2. For the loss of energy results from the incoherent integration of multi-frame echoes in the TBD methods, the dissertation researches how to realize the coherent integration of multi-frame echoes. On the basis of the detailed analysis of moving targets’ multi-frame echoes, three multi-frame coherent integration methods: coherent integration method based on envelope interpolation and replacement; coherent integration method based on frequency domain compensation; and coherent integration method base on Keystone transform are introduced. And the performance of the three coherent integration methods are validated and compared via computer simulation experiments.3. The measured data from a certain radar are processed and analyzed using the methods which are presented in this dissertation. The processing methods include single-frame echo’s coherent integration, multi-frame echoes’ TBD, multi-frame echoes’ coherent integration. The dissertation analyzes the factors that affect the result of the multi-frame echoes’ coherent integration in detail. Aim at the factors, the dissertation presents corresponding solutions and the result of the simulation experiments. Finally, the dissertation presents a novel multi-frame echoes’ coherent integration algorithm based on space-slow-time. The dissertation also conducts the computer simulation experiments and processes the measured data using this new method.