DOA And Time Delay Estimation In Multipath Environment

Time delay estimation and direction-of-arrival estimation are two important research contents in the field of signal processing regarding target positioning technology.In actual application scenarios,due to the complexity and diversity of channel propagation and the surrounding environment of the receiver,there is a multipath propagation phenomenon between the source and the receiver or the receiving array.In order to solve this problem,the research on anti-multipath and high-resolution time delay estimation has gradually become a hot spot.In addition,the distributed source model has good performance in simulating the characteristics of the signal multipath propagation environment.Therefore,the direction of arrival estimation based on the distributed source model has received widespread attention.Previous studies on time delay estimation and direction of arrival estimation often assumed that the background noise was Gaussian noise.However,in fact,there may be impulsive noise in some complex multipath scattering environments,such as atmospheric environmental noise,radar backscatter echoes,and electromagnetic noise in urban mobile radio channels.At this time,it is more appropriate to describe these noises with Alpha stable distribution.In view of the problems in the current research on time delay estimation and direction of arrival estimation,this paper combines the theory of fractional low-order statistics and correntropy to study the super-resolution time delay estimation of narrowband multipath signals and the angle parameters estimation of the distributed source.In this paper,the methods of time delay estimation and direction-of-arrival estimation under the background of impulsive noise and multipath propagation are proposed.The specific research content includes the following three aspects:(1)Aiming at the problem of performance degradation of traditional time delay estimation algorithms under the conditions of impulsive noise and narrowband multipath propagation,this paper models impulsive noise based on the Alpha stable distribution,combines the subspace method with the phased fractional low-order moment and proposes a super-resolution time delay estimation algorithm for narrow-band multipath signals based on the phased fractional low-order moment.Based on the multipath signal time delay estimation model,the proposed algorithm is theoretically analyzed,and the performance of the algorithm is verified through simulation experiments.It shows that the algorithm has high time delay estimation accuracy under a strong impulsive noise environment.(2)In view of the problem that the angle estimation method of the point source model is not effective in the multipath scattering environment,this paper extends the joint angle estimation method of coherently distributed sources composed of non-circular signals to impulsive noise scenarios.This paper proposes the concept of generalized complex correntropy,and gives a joint angle estimation algorithm of coherently distributed non-circular source based on generalized complex correntropy.Simulation results show that the proposed algorithm can obtain better estimation results under the conditions of highly impulsive noise,low signal-to-noise ratio,and signal multipath propagation.(3)Aiming at the problem of performance degradation of the DOA estimation algorithm for coherently distributed non-circular signals under an impulsive noise environment,this paper combines with the concept of generalized complex correntropy and proposes a low complexity DOA estimation algorithm of the coherently distributed non-circular signal based on ESPRIT method.The generalized complex correntropy operator has the advantage of not relying on prior knowledge of noise and good robustness.It avoids the degradation problem of traditional algorithms based on second-order statistics under impulsive noise.The algorithm does not need to search for spectral peaks,and the calculation complexity is low.The simulation results show that the algorithm proposed in this paper uses non-circular characteristics to improve the accuracy of DOA estimation,at the same time it can effectively suppress impulsive noise and can obtain better estimation performance in the case of the lower signal-to-noise ratio.