Compact Four-Element MIMO Antenna System for 5G Laptops

This paper presents a compact dual-band four-element multiple-input multiple-output (MIMO) antenna system for the fifth-generation (5G) laptops with a large display-to-body ratio. The four antenna elements, each being a three-dimensional inverted-F antenna (IFA) of the same structure and size, are constructed on the same T-cross-sectioned substrate, the vertical part of which is embedded in the $1\times64$ mm2 clearance area created from the upper edge of the display ground plane. They are configured into two dual-antenna units. Within each unit, the two IFAs are arranged to be skew-symmetric with respect to the display ground plane, and their short-circuit points are brought close to each other to achieve the so-called short-circuit decoupling. In addition, the two units are mirror imaged of each other with a small gap in between and are connected by two decoupling chip inductors to form a high-isolation four-element MIMO antenna system. In the operating bands of 3300–3600 and 4800–5000 MHz required by 5G, the measured isolation is larger than 10 dB, and the measured antenna efficiency is beyond 35 %, both being large enough for practical applications. In particular, the proposed MIMO antenna system has a profile height of only 1.4 mm, which is very small, making it suitable for laptops with a large display-to-body ratio.