Decoupling of Inverted-F Antennas With High-Order Modes of Ground Plane for 5G Mobile MIMO Platform

This paper presents a novel method of decoupling inverted-F antennas (IFAs) with high-order modes of a ground plane in 5G mobile multiple-input multiple-output (MIMO) platform. The proposed method is illustrated in a dual-antenna 5G mobile platform operating at 3.5 GHz. An IFA excites a high-order mode of the field distribution in the ground plane at 3.5 GHz. The electric field of the excited high-order mode forms several stable null-amplitude field points located on the edge of the ground plane. The other IFA is then placed in one of the stable null points. By doing this, the two IFAs are decoupled with high isolation. The simulated results show that isolation improvements of 20–40 dB can be achieved when the positions and orientations of the two IFAs are optimized. The measured results confirm that the fabricated antennas have peak isolations of 45–56 dB. Finally, the proposed method is applied to design a three-IFA-based MIMO platform which verifies that the suggested concept can effectively simplify the decoupling mechanism and works well in a multiantenna-based mobile MIMO terminal.