Research On Coherent Source And Low Complexity DOA Estimation Technology

With the commercialization of the 5th Generation(5G)mobile communication system,its signal detection technology has been widely used in various fields such as military,science and technology,among which DOA estimation technology provides important support for the implementation of positioning technology.Although the existing classic DOA estimation technology has been able to estimate the angle of arrival of independent signals more accurately,its performance is susceptible to factors such as source coherence,low signal-tonoise ratio,and small angular interval,which makes the algorithm resolution lower and leads to estimation failure.In addition,in order to obtain more angle information,it is not only necessary to extend the DOA estimation to two-dimensional space,but with the application of massive MIMO technology,the number of antenna elements increases,which increases the computational complexity of the two-dimensional DOA estimation technology,Which may make the algorithm difficult to implement in actual engineering applications.Therefore,improving the estimation accuracy and reducing the computational complexity is the research focus of DOA estimation technology.Aiming at the problem of coherent source estimation,this thesis firstly analyzes the spatial smoothing algorithm and an improved MUSIC algorithm in a uniform linear array,and proposes a joint DOA algorithm on this basis.The algorithm uses an improved two-way spatial smoothing algorithm to preprocess the received signal of the array element to achieve decoherence,and then uses the DOA algorithm based on feature space to achieve DOA estimation.The simulation results show that the joint DOA estimation algorithm has good decoherence performance,better stability,and higher estimation accuracy,especially when estimating signals with small incident angle differences in a low signal-to-noise ratio environment,the algorithm is compared with the bidirectional spatial smoothing algorithm.The error is smaller and the algorithm success rate is higher.Aiming at the high computational complexity of the algorithm in the two-dimensional DOA estimation,this paper applies the Nystrom algorithm to the two-dimensional DOA estimation,transforming the high-latitude matrix operation into the low-latitude matrix operation,which can effectively reduce the computational complexity of the algorithm.Accordingly,this paper proposes a two-dimensional root finding MUSIC algorithm based on Nystrom's estimation.The algorithm uses the Nystrom algorithm to block the received signal,calculates the noise subspace in the low-latitude matrix,and then constructs the root polynomial to obtain the two-dimensional angle information of the azimuth and elevation angles.The simulation results show that the algorithm can obtain a more accurate estimate when the number of elements is large and the signal-to-noise ratio is high,and the calculation complexity is reduced.However,the algorithm has higher requirements on the signal-to-noise ratio,and its performance is greatly affected by the block parameters.Aiming at the problem that the estimation error of the two-dimensional root finding MUSIC algorithm based on Nystrom's estimation is too large under the condition of low signal-to-noise ratio,this paper proposes a cascaded MUSIC algorithm based on Nystrom's estimation.The algorithm first uses the Nystrom algorithm to estimate the signal subspace,and then uses the idea of cascade to perform initial estimation to obtain part of the angle information,rewrite the spatial spectrum function in the two-dimensional MUSIC algorithm,and transform the two-dimensional angle search into one-dimensional search.The search interval is narrowed,and two-dimensional angle parameters corresponding to one-to-one are obtained,thereby achieving the purpose of reducing computational complexity.The simulation experiment results show that the algorithm has high estimation accuracy,strong stability,and good estimation performance.