Advanced Nested Array Configuration Achieving Large-Scale Hole-Free Co-Array in MIMO System

Generally, a large number of antennas are used in the multiple-input multiple-output (MIMO) system for various desirable merits. This paper introduces the advanced nested antenna array (ANAA), a sparse array structure, into the MIMO system to increase the spatial resolution and provide more degrees of freedom (DOFs). The ANAA effectively configures two uniform linear arrays (ULAs) and places two antennas between them. As such, the ANAA produces a hole-free difference co-array. Compared with the existing designs, the ANAA benefits from simple closed-form expressions for its construction and optimized distribution of the total number of antennas. Meanwhile, it provides more DOFs with a wider hole-free co-array aperture. The theoretical propositions are proved, and performance results confirm the superiority of the proposed ANAA configuration.