Coprime MIMO Architecture for Mixed Near- and Far-Field Source Localization

As is well known, sparse multiple-input–multiple-output (MIMO) arrays have obvious superiorities in array aperture, degrees of freedom, and mutual coupling effects over uniform MIMO arrays. In this article, we design a symmetric displaced coprime MIMO array (SDCMA) to locate mixed near-field and far-field sources. The SDCMA architecture consists of three sparse uniform linear arrays (ULAs), where the ULA in the middle is considered as the transmit array, and the other two ULAs and the center sensor are used as the receive array. Moreover, both transmit and receive arrays are centro-symmetric and together form a symmetric displaced coprime array. Under the given number of sensors, the SDCMA is determined only by a closed-form expression and its contiguous lags range in the difference coarray of sum coarray (DCSC) can also be expressed analytically. Furthermore, we derive the optimum SDCMA architectures and the corresponding DCSCs by maximizing the numbers of contiguous and unique coarray lags. Compared to the existing MIMO architectures, the SDCMA provides a greater number of contiguous and unique lags as well as a larger coarray aperture. Simulation results demonstrate the advantages of the SDCMA over several existing MIMO architectures.