In this paper, a grade nested array constituted by a uniform linear array and a grade linear array with uniformly increasing inter-element is presented. The closed-form expression of the proposed array geometries and corresponding direction-of-arrival (DOA) estimation algorithm are derived. Theory analysis certifies that the proposed grade nested array can provide higher degrees of freedom (DOF) than some existing nested arrays. Some simulations are also presented to demonstrate the improved performance of the proposed nested array for DOA estimation of quasi-stationary signals.
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