Wideband Decoupling of Integrated Slot Antenna Pairs for 5G Smartphones

This communication proposes a wideband decoupling technique to suppress the strong coupling between two extremely closely spaced open-slot antennas and implements a wideband integrated slot antenna pair for fifth-generation (5G) metal-rimmed smartphones. By simply inserting a connecting line between two closely spaced open-slot antennas, a top slot structure can be constituted with odd- and even-mode resonances in the lower and higher bands, respectively, to cancel the original strong mutual coupling. In addition to the decoupling effect, the top slot can also expand the effective radiation aperture of the antenna pair for the bandwidth improvement. The proposed slot antenna pair, with a compact footprint of 28 ×7 ×1.8 mm
³
, shows good impedance matching, isolated and diversity performance across 3.3-5.0 GHz. Then, an 8 ×8 multiple-input multiple-output (MIMO) system, constituted by four sets of slot antenna pairs, is simulated, fabricated, and measured. Both the simulated and experimental results show that the 8 ×8 MIMO system can offer isolations of better than 10.8 dB and envelope correlation coefficients (ECCs) of less than 0.14 between all eight ports across 3.3-5.0 GHz. Also, a total efficiency of 55.0%-83.1% and 52.5%-83.1% is achieved for Ant1 and Ant2, respectively. Featuring wide bandwidth, compact size, high integration level, and metal rim compatibility, we forecast the proposed solution has great potential for future 5G smartphones.