Dual-band 8 × 8 MIMO antenna with enhanced isolation and efficiency for 5G smartphone applications

Abstract

In this paper, a dual-band 8 × 8 multiple-input multiple-output (MIMO) antenna is presented for 5G smartphone applications operating at 3.5 GHz and 5.5 GHz bands. Each antenna element consists of a modified F-shaped radiator, installed at the rim of the smartphone PCB with a size 140 × 70 mm2. The size of each element is 4.5 × 11 mm2 (0.05λ × 0.16λ), where λ is a free-space wavelength at 3.5 GHz. Two types of isolators have been employed to achieve higher isolation in both bands. A defected ground structure is used to isolate the closely spaced antenna elements whereas T- and L-shaped isolators are utilized to isolate antennas with larger inter-element spacing. The simulated results are in good agreement with the measured results indicating sufficient matching bandwidth in both bands. The mutual couplings less than −20 dB and –22 dB are achieved in the lower and higher bands, respectively. Envelope correlation coefficient between all the antenna elements is<0.11, whereas the radiation efficiencies higher than 68% and 78% are achieved in the lower and higher bands, respectively. The results presented justify that the proposed antenna is a suitable choice for 5G smartphone applications.