xMISC: Improved Sparse Linear Array via Maximum Inter-Element Spacing Concept

In this letter, we propose a new improved sparse array design via the maximum inter-element spacing constraint (MISC) concept. The array, called enhanced MISC array (xMISC), is developed by filling the holes in the conventional improved MISC array (IMISC). First, the hole locations in the IMISC array are analyzed, then a simplified hole-filling strategy is proposed. The hole-filling strategy does not require any additional sensors but rather leverages the inter-element spacing terms adjustment. Compared to the existing MISC and IMISC arrays, the xMISC array exhibits enhanced uniform degrees of freedom (uDOF) and relatively reduced mutual coupling. Besides, the xMISC retains a hole-free difference co-array. Moreover, the closed-form expressions for sensor locations, weight functions, and achievable DOF are derived in detail. Numerical examples validated the merits of the xMISC array.