High-Order Generic-Coarray for MIMO Array Design With Reduced Mutual Coupling

Sparse multiple-input and multiple-output (MIMO) systems have received considerable attention due to their capability to increase uniform degrees of freedom (uDOFs) and suppress mutual coupling. Previous work has devised numerous array configurations based on both nested-type and coprime-type arrays, while they require the difference coarrays (DCA) of the transmitter (Tx) and receiver (Rx) to be hole-free or central-consecutive, resulting in severe mutual coupling. In this letter, a high-order generic-coarray (HOGC) is proposed for MIMO system design, which introduces two additional variables into the generic-coarray. We employ the HOGC to construct an extended difference coarray of the sum coarray utilizing a central-inconsecutive Tx DCA, significantly suppressing the mutual coupling while maintaining high uDOFs. Moreover, closed-form expressions are derived for the range of uDOFs and the number of DOFs. Simulation results demonstrate the superiority of the proposed systems in direction of arrival estimation, particularly under strong mutual coupling conditions.