Enhanced Low-Redundancy Restricted Array for Direction of Arrival Estimation

Sensor arrays play a significant role in direction of arrival (DOA) estimation. Specifically, arrays with low redundancy (LR) and reduced mutual coupling are desirable. In this article, we investigate a sensor array configuration that has restricted sensor spacing and propose a closed-form expression. We also propose several classes of LR arrays. Interestingly, compared with super nested arrays (SNA) and maximum interelement spacing constraint (MISC) arrays, one of the proposed arrays $(4r)$-type I has a significant reduction in both redundancy ratio and mutual coupling. Numerical simulations are also conducted to verify the superiority of the proposed array over the known sparse arrays in terms of weight functions, mutual coupling matrices, uniform degrees of freedom, and DOA estimation performance.