Research On Nested Array Structure Design And DOA Estimation Algorithm

Direction of arrival(DOA)estimation is one of the key concerns in the field of electronic countermeasures.Most traditional DOA estimation algorithms are proposed for uniform arrays,while the adjacent antenna spacing and physical aperture of uniform arrays are limited by the signal half-wavelength,and their maximum estimable sources are small and DOA estimation accuracy is low.Compared with uniform array,the continuous virtual array generated by nested array has higher degree of freedom,which can achieve DOA estimation with more sources than array elements,and can improve DOA estimation accuracy when the number of array elements is the same.Therefore,this paper investigates the nested array structure and its DOA estimation algorithm,and proposes an improved nested array structure and DOA estimation algorithm to further improve the DOA estimation performance.The main research contents as follows:1.In this paper,the spatial spectral estimation system model is briefly described,the signal model of uniform array is given,and the classical Multiple Signal Classification(MUSIC)algorithm based on subspace,Root-MUSIC algorithm and rotation-invariant subspace algorithm are analyzed theoretically and simulated.The basic concept of nested arrays and the corresponding signal model are introduced,and the DOA estimation algorithm of nested arrays is derived theoretically and the DOA estimation performance of nested arrays is analyzed in detail through simulation experiments.2.To address the problem that there are more redundancies in the sum-and-difference virtual arrays of the second-level nested arrays under the vectorized conjugate-enhanced MUSIC algorithm,two sum-and-difference translational nested array structures are proposed in this paper.Both arrays consist of a single array element and a second-level nested array,and this single array element is used as the reference array element.The two arrays are able to translate the continuous range of the sum virtual array while the continuous range of the differential virtual array remains unchanged,thus reducing the redundancy between them to a large extent,increasing the continuous degrees of freedom and the virtual array aperture,and thus improving the maximum estimable source number and DOA estimation accuracy.3.To address the problem of low efficiency of DOA estimation by spatially smoothed MUSIC algorithm,this paper proposes two algorithms based on improved spatially smoothed spectral decomposition Root-MUSIC and spectral decomposition propagation operator RootMUSIC under nested arrays.In the case that the number of sources is unknown,this paper uses the Root-MUSIC algorithm instead of the MUSIC algorithm and uses the spectral decomposition algorithm to accelerate the root finding process of the Root-MUSIC algorithm,improves the spatial smoothing technique and combines it with the spectral decomposition Root-MUSIC,thus reducing the complexity of the algorithm.For the case where the number of sources is known,the computational complexity of the algorithm is further reduced by replacing the eigenvalue decomposition with the propagation operator algorithm in the computation of the improved spatially smoothed spectral decomposition Root-MUSIC algorithm.