Research On DOA Estimation Algorithms For Nested Array

Array signal processing is an important branch in the field of modern signal processing,which utilizes the sensor array to receive the signal.Compared with the traditional single sensor,sensor arrays have the advantages of more flexible beam control,higher signal gain,stronger interference suppression ability and higher spatial resolution.Direction of arrival(DOA)estimation of received signals is an important research direction of array signals processing.DOA estimation uses the difference of received signals of each sensor in the array and designs corresponding algorithms to obtain the incident angle of the signals.Nested array is a novel geometric shape of non-uniform array,which can significantly increase the degree of freedom,improve the performance of DOA estimation,and deal with under-determined source estimation.In recent years,nested array has been widely used in array signal parameter estimation.This paper mainly studies the DOA estimation algorithm of array signal under nested array.The topic selection has theoretical significance and application value.The main work in this paper is summarized as follows.1)The spatial smoothing DOA estimation algorithms under nested array are studied in this paper,including spatial smoothing multiple signal classification(SS-MUSIC)algorithm,spatial smoothing estimating signal parameters via rotational invariance techniques(SS-ESPRIT)algorithm and spatial smoothing propagator method(SS-PM)algorithm.With the help of nested array,these three algorithms can greatly improve the degree of freedom of the whole array,which allows them to deal with more sources.Compared with uniform linear array,the angle estimation performance of the proposed algorithm is improved,and it can deal with under-determined source angle estimation.2)The discrete fourier transform(DFT)DOA estimation algorithms under nested array are proposed in this paper,including DFT algorithm and DFT-MUSIC algorithm.The DFT algorithm firstly performs vectorization operation on the received data covariance matrix,sorts the received data after the vectorization to remove redundancy,and obtains the received data of the expanded array element number.Then,the DFT method is used to obtain the DOA initial estimation,and finally the accurate DOA estimate can be obtained via local peak searching.Compared with the spatial smoothing algorithm which only utilizes nearly half of the degree of freedom of the virtual array,the DFT algorithm makes full use of the complete degree of freedom virtual array,thereby reducing the loss of the aperture and improving the performance of angle estimation.Based on the DFT algorithm,the DFT-MUSIC algorithm firstly uses DFT method to realize the initial estimation of DOA,and then only one-dimensional local spectral peak search is needed to obtain accurate DOA estimation by the SS-MUSIC method.Therefore,its complexity is much lower than that of SS-MUSIC algorithm,and the DOA estimation performance of the two algorithms is similar.3)Two-dimensional DOA estimation algorithms under double parallel nested array are studied in this paper,including unitary ESPRIT algorithm and unitary PM algorithm.The two algorithms combine the bi-parallel model with nesting theory,and transform the two-dimensional angle estimation into twice one-dimensional angle estimation processes.The proposed algorithms use cross-covariance of parallel nested arrays to generate longer virtual arrays,thus increasing the degree of freedom of arrays.In addition,the two algorithms introduce the concept of unitary matrix to transform the signal covariance matrix into real matrix,which reduces the complexity of the algorithm,and can automatically pair two-dimensional DOA estimation without additional pairing process.The angle estimation performance of this kind of algorithm is better than that of DOA estimation matrix method with two parallel matrices,and it can identify more sources.4)Two-dimensional DOA estimation algorithms based on MIMO radar with nested array are proposed in this paper,including MUSIC algorithm,ESPRIT algorithm,PM algorithm and subspace-based algorithm.This kind of algorithms combine two parallel MIMO array with nested arrays,and use the two parallel arrays with nested relations as transceiver and receiver arrays,thus increasing the degree of freedom of the array.Then,virtual snapshots are added by data reconstruction,and two-dimensional DOA estimation of signals is extracted by using the characteristics of signal subspace and noise subspace.This kind of algorithm introduces unitary matrix operation based on signal subspace,which reduces the computational complexity of the algorithm.The proposed algorithm can obtain two-dimensional angle estimation of pairs.At the same time,compared with the traditional DOA algorithm of dual parallel uniform MIMO radar array,the proposed algorithm has better angle estimation performance.