High-order extended coprime array design for direction of arrival estimation

Nonuniform linear arrays, such as coprime array and nested array, have received great attentions because of the increased degrees of freedom (DOFs) and weakened mutual coupling. In this paper, inspired by the existing coprime array, we propose a high-order extended coprime array (HoECA) for improved direction of arrival (DOA) estimation. We first derive the closed-form expressions for the range of consecutive lags. Then, by changing the inter-element spacing of a uniform linear array (ULA), three cases are proposed and discussed. It is indicated that the HoECA can obtain the largest number of consecutive lags when the spacing takes the maximum value. Finally, by comparing it with the other sparse arrays, the optimized HoECA enjoys a larger number of consecutive lags with mitigating mutual coupling. Simulation results are shown to evaluate the superiority of HoECA over the others in terms of DOF, mutual coupling leakage and estimation accuracy.