An ultra-wideband MIMO system with multi-loop mode for full-screen smartphone applications

In this letter, an ultra-wideband (UWB) eight-element multiple-input multiple-output (MIMO) antenna system with multi-loop modes for fifth-generation (5G) smartphones is presented. The antenna unit has a simple structure and is composed of an inverted U-shaped feeding strip and an L-shaped grounding radiation strip with a hollow out in the middle. Owing to the generation of two coupling loop modes, the working bandwidth of the proposed antenna unit covers 3.2-6.4 GHz. Besides, the simulated and measured results show that the isolation between any two antennas is better than 12.0 dB, and the total efficiency of each element is higher than 50%. Meanwhile, the measured radiation pattern, envelope correlation coefficients, channel capacity loss, mean effective gain, and diversity gain are also given in this letter. The above results demonstrate that the MIMO system has the advantages of simple structure, convenient manufacture, and superior performance.