A Study On Time Reversal Based Targets Localization Algorithm

Multipath is a commom phenomenon in radar and wireless communication applications. It refers to the phenomenon that the signal travels from the transmitter to the receiver along different paths. But in the design of most radar systems multipath is only treated as undesired clutter noise so that multipath has a negative impact on the resolution of radar systems and the accuracy of locating targets.This paper introduces time reversal(TR) to targets localization and take advantage of the scatting caracteristics of multipath media to improve the existing localization algorithms, then enhances the localization performance of the radar systems.First of all, we elaborated the background and operating principle of TR.Then we studied on TR based target detection and classification in multipath environment. Our focus was on the maximum likeklihood TR detectors, and we analyzed the problem of detecting the presence of the target. We compared the TR classifiers with the conventional classifiers. Experimental results showed that TR classifiers had a better performance of target detection and provided a higher gain than the conventional classifiers. Then we applied TR to Range and Direction-of-Arrival(DOA) estimators. For DOA estimators, we proposed TR based Capon estimation algorithm and compared it with the conventional Capon estimation algorithm. We derived the respective Cramér–Rao bounds(CRB) to compare the performance of the two algorithms. Experimental results showed that TR/DOA estimator had a lower Cramer-Rao lower bound than conventional estimator, and indicated better performance of localization. For Range estimators, we proposed a range estimation algorithm that was based on TR observations and then compared it with the conventional estimation algorithm that was basd on conventional observations. Experimental results showed that TR based estimation algorithm had a more accurate localization. Finally, we applied TR to the detection of a moving target, we studied the impact of target motion on the performance of the conventional detection algorithm and TR based detection algorithm, then we showed the ability of TR based algorithm to detecte moving targets in the presence of Doppler shifts in multipath environment. Experimental results showed that TR based moving targets detection had better performance.We elaborated TR based target localization algorithm and analyzed the localization performance of it in the process of modeling, theoretical analysis and experimental simulation. Furthermore, the conventional localization algorithm was given for comparison. By comparison, we can find that TR based localization algorithm had a higher localization accuracy. Especially in the case of low signal to noise ratio and the strong scattering, the advantages of TR based localization algorithm became more evident with respect to the conventional localization algorithm. We can adapt the signals transmitted from the antenna array to the caracteristics of multipath environment by TR process, and then improve the ability of radar to locate targets by adjusting the probing waveform.