Compact Sub 6 GHz Dual Band Twelve-Element MIMO Antenna for 5G Metal-Rimmed Smartphone Applications

Abstract

In this paper, a twelve-antenna system is designed for 5G smartphones with metal frames. The system is compact and operates on dual bands within the sub-6 GHz frequency range using multiple-input multiple-output (MIMO) technology. Two sets of six-antenna units are included in the system, arranged in a diagonal mirror-image configuration, and positioned at the center of the circuit board’s longer edges. The profile height of each of the six-antenna units is only 3 mm, and the overall array dimensions are 105 × 3 × 3.1 mm3. A single antenna unit is 15 × 3 × 3.1 mm3 (0.173 λ × 0.035 λ × 0.036 λ, where λ equals the free-space wavelength of 3450 MHz). The arrangement of the antennas in the six-antenna units is parallel, with a 3 mm separation between adjacent antennas. The antenna structure comprises of an inverted L-shaped feed branch and two inverted L-shaped short-circuit branches integrated into part of the metal frame. The proposed array can form multiple resonance paths, achieving dual-band operation at 3300–3600 MHz and 4800–5000 MHz. The measured isolation of this twelve-antenna system within the operating frequency band is over 10 dB, and the measured antenna efficiency is greater than 36%. Therefore, the system is suitable for use in smartphones with high screen-to-body ratios and metal frames.

Design and Performance Evaluation of a 6×6 MIMO Array with Partial Ground Plane for Sub-6 GHz Mobile Applications

“…Also, the ECC is high about 0.42 and the peak gain is as low as 3.2dBi only. Similarly, it can be seen from the results in [16] that the array has only -10dB of lowest isolation, the ECC is higher than 0.4 at 3.5GHz and the TE drops to 36% only. Furthermore, in both of these 12-element MIMO designs no SAR analysis is presented.…”

“…In recent times the researchers have also made several approaches to propose innovative designs consisting of six [9], eight [10][11][12][13], ten [14] and twelve [15,16] element MIMO array antennas to improve the parameter of MIMO for mobile phone for sub-6 GHz (5G) communications. In [9], the authors have proposed a six-element MIMO array that operates below 2.5 GHz.…”

“…Reaching for higher element in [15,16], the authors have proposed 12-element MIMO array both for 5G smart phones at 3.5GHz. Both proposals use side edge positioning technique to gain advantage on MIMO performances.…”