| The angle and position information of target signals is one of the important parameters required by modern communication,which makes the direction of arrival(DOA)estimation techniques get great attention and development.In recent years,DOA estimation techniques have developed relatively well.However,it needs to be further studied in some complex scenes,such as urban environment with dense high-rise buildings,underwater environment full of noise,etc.The signals will be subject to multipath interference and noise interference in the process of transmission,which increases the difficulty of extracting angle information from the signals received by the antenna array.In addition,the array will also affect the DOA estimation.On the one hand,if the array shape is different,the corresponding array steering vector is different,which will affect the DOA results;on the other hand,the actual array will inevitably suffer mutual coupling error,that is,the actual array steering vector does not match the ideal steering vector.These factors have become the reason why the theoretical algorithm research is difficult to apply to practice.In order to tackle this thorny problem,this thesis comprehensively considers these factors,models them into the received signals,and proposes a sparse angle estimation algorithm in complex environment.(1)In terms of the problem that antenna array will affect the DOA estimation results,the estimation performance of non-uniform linear array and its mutual coupling are studied.Based on the induced electromotive force(EMF)method,the electromagnetic mutual coupling phenomenon of non-uniform array is modeled.Under the fair conditions of the same array element number or the same array aperture,the non-uniform linear array is designed.The mean square error of DOA estimation results with or without mutual coupling is simulated and compared.The simulation results show that in general,the performance of minimum redundant array is better when the array is with or without mutual coupling.(2)Based on the complex propagation environment where coherent signal problem caused by multipath propagation and the noise is Gaussian colored noise,a sparse angle estimation algorithm in complex scenes is proposed considering the adverse effects of array mutual coupling error.Firstly,the received signals of the array are modeled,and then the mutual coupling of the array is preprocessed after extracting the received signal of the middle subarray to separate the mutual coupling error.Then,the higher-order cumulant is used to suppress the Gaussian colored noise,and the Toeplitz matrix is constructed to obtain the full rank matrix containing array steering vector to tackle with coherent signals.Based on the obtained Toeplitz matrix,a sparse angle estimation optimization problem is constructed.From the simulation results,we can see that the proposed algorithm can successfully solve signal decoherence and suppress noise,and has a good performance in the scene with low signal-to-noise ratio and less snapshots.Furthermore,it can correctly estimate the angle information in the presence of mutual coupling error. |
