Improved Nested Arrays With Sum-Difference Coarray for DOA Estimation

In this paper, we propose two kinds of improved nested arrays for direction of arrival (DOA) estimation, which are obtained by rearranging physical sensors of the prototype nested array. Specifically, the sum-difference coarrays (SDCAs) of the proposed arrays are constructed by jointly using the temporal and spatial information of the received signal. By systematically analyzing the structures of the proposed two kinds of arrays, we derive the closed-form expressions about their physical sensor positions, SDCAs, consecutive degrees of freedom (DOFs), and maximum physical array apertures, respectively. Compared to the prototype nested array which only considers the difference coarray (DCA), the proposed arrays with SDCAs have a lot more consecutive DOFs. Moreover, all physical sensors of the proposed arrays, except the one at zero point, can be placed at the positions opposite to their original ones, which will not result in a change in the consecutive DOFs. This phenomenon means that the proposed arrays have flexible array configurations with different physical array apertures, which make them more beneficial for practical application. In the end, simulation results demonstrate the superiorities of the proposed arrays in terms of detection performance and estimation accuracy.