Design and analysis of wideband MIMO antenna arrays for 5G smartphone application

A new wideband multiple-input/multiple-output (MIMO) antenna system able to operate in a frequency band ranging between 3.3 and 7.1 GHz is proposed for fifth-generation (5G) new radio applications for future smartphones. The design structure contains four pairs of compact microstrip-fed slot antennas, located at the corners of an FR-4 printed circuit board. Each pair of antennas consists of a radiator with two concentric annular slots, fed by two L-shaped microstrip-feeding lines and provides polarization and radiation pattern diversity function due to the orthogonal placement of their feed-line. In order to reduce the mutual coupling characteristic, we have inserted a rectangular slot under each microstrip feed-line. Besides, we have coupled and linked the two rings by a small gap to combine and move the resonant modes so as to achieve wideband coverage. The measured and simulated results show that the proposed design achieves the desired performance, such as isolation >12 dB, a total efficiency >48%, and an envelope correlation coefficient <0.07. In addition, the radiation pattern, the total efficiency, the realized gain, and the channel capacity are also studied. According to the reached results, the proposed MIMO antenna may be a suitable application-oriented design for 5G mobile communication.