Ultrawideband MIMO Array With Self-Decoupled Building Blocks for 5G Smartphones

In this paper, an ultrawideband self-decoupled building block with two antennas is constructed, which achieves high isolation between bandwidths without any decoupling structures. An ultrawideband operation is achieved by exciting two 0.25λ open slot modes and a loop mode. The wideband decoupling is usually a thorny problem, and our self-decoupling design within ultrawideband is verified by canceling the common and differential mode currents of every resonant mode. As a result, the proposed broadband building block not only operates in a wide bandwidth of 3.39–8.2 GHz (83%), including LTE band 42 (3.4–3.6 GHz), n79 (4.4–5 GHz), and both the n46 (5.15–5.925 GHz) and n96 (5.925–7.125 GHz), but also demonstrates high isolation (> 15.2 dB) over the entire bandwidth. An eight-element MIMO array consisting of four building blocks is designed, processed, and tested. The measured results demonstrate that the antenna system can provide good isolation in the 3.39–8.2 GHz operating band with good efficiencies (> 58%) and low ECCs (< 0.09). The proposed building block, with its benefits of ultrawideband, high isolation, self-decoupling, and simple structure, is very promising for 5G mobile communications.