Two-dimensional Target Azimuth Estimation Technology Based On Difference Co-array

The spatial spectrum estimation technology receives and processes the spatial signal through the antenna array,and obtains the Direction of Arrival(DOA)of the signal according to the energy distribution of the signal.The Degree of Freedom(DOF)of the antenna array has a decisive influence on the identifiable performance of the signal parameters and the accuracy of the angle estimation.The traditional uniform linear array can only provide the same degree of freedom as the number of array elements in the array system,so that the direction of arrival estimation cannot be effectively performed in the case where the number of signal sources is more than the number of array elements(underdetermined conditions).The same is true for the two-dimensional array system angle estimation.Difference co-array can provide much more virtual array elements than actual arrays to increase the degree of freedoms of the array system.In view of this,the thesis uses difference co-array to solve the two-dimensional array system angle estimation problem combining Direction of Departure(DOD)and Direction of Arrival in underdetermined conditions.The research work of this thesis mainly involves two levels:(1)Starting from the level of designing the array structure,a new array structure called cascade array is proposed,which is composed of a uniform linear array and a non-uniform linear array connection,and give an accurate mathematical definition of the cascaded array.The properties of the cascaded array and its difference co-array are summarized,i.e.,the cascaded array can provide more degrees of freedom in the case of a fixed number of array elements than the existing array structure and no holes.The array structure is applied to the angle estimation under normal and underdetermined conditions to verify its performance.The experimental simulation results show that the designed cascaded array can obtain more degrees of freedom,thus improving the parameter identifiability of the array system and the accuracy of the angle estimation.(2)Starting from the algorithm research level,a DOD-DOA angle estimation algorithm based on weighted subspace fitting technique is proposed for the traditional two-dimensional array system angle estimation algorithm with high computational complexity and large computational complexity.The algorithm parameterizes the orthogonal projection of the two-dimensional joint array manifold zero space,and transforms the optimization problem of the two-dimensional weighted subspace fitting into a one-dimensional problem,and estimates the angle information of the target through automatic pairing.The final experimental simulation results show that the proposed algorithm with the cascaded array are more accurate than the traditional estimation of signal parameters via rotational invariance technique algorithm with the existing array structure,and the computational complexity is lower.Therefore,based on the difference co-array,starting from the two levels of designing the array structure and algorithm research,this thesis effectively solves the problem of target azimuth estimation of two-dimensional array system in underdetermined conditions.