An eight-element ultra-wideband multiple-input multiple-output antenna system is proposed for the 5G mobile terminals. Each radiating branch is composed of a Loop and a monopole antenna. The ultra-wideband characteristics of the antenna are obtained by a T-shaped feed branch coupling a radiation branch. Furthermore, the isolation is lower than −15 dB by introducing a Tshaped neutralization line structure. The results of simulation and measurement show that the antenna system can cover 3.3-5.6 GHz, and the antenna efficiency is 45%-80%. At the same time, the envelope correlation coefficient between any two elements is lower than 0.03. Therefore, the proposed antenna in this study is very suitable for the eight-element MIMO antenna system as a reference.

In this paper co-polarization spatial Goos–Hänchen (GH) shifts (Δss/λ and Δpp/λ) of periodic chiral metamaterials are investigated. The numerical results show that the enhancement of GH shifts is affected by the incident frequency, the incident angle, the period and the volume fraction of the dispersive chiral layer. For s polarized waves, GH shifts are always enhanced negatively with one Brewster angle, but two Brewster angles arise when the period is large and specific. For p polarized waves there are two Brewster angles in general, at which the GH shifts can be greatly enhanced with negative and positive peaks. More Brewster angles appear when the period is sufficiently large and specific. The transition of negatively and positively enhanced GH shifts is sensitive to large frequencies, and can be tuned by changing the frequency slightly. The transition can also be adjusted by varying the volume fraction of the dispersive chiral layer and the period of the structure.

A dual-band wideband circularly polarized (CP) microstrip antenna is proposed for sub-6G application. The antenna consists of an upper L-shaped radiator and two circular strips on the ground. This produces the right-handed circular polarization (RHCP) in the Wi-Fi (2.4-2.48 GHz) and n77 (3.3-4.2 GHz) band with the help of two circular strips at the left and right corners on the lower ground. The antenna occupies a small radiating area of 45 × 45 × 1.0 mm 3 . The measured results show wide −10 dB reflection coefficient bandwidths of 46.4% (1.82-2.92 GHz) and 40. . The 3-dB axial ratio bandwidths of the antenna are 25.1% (1.88-2.42 GHz) and 40. . The measured peak gains are 4.8 and 7.5 dBi at the lower and higher bands, respectively. Therefore, the proposed antenna in this study is suitable for the dual-band wideband CP antenna as a reference.

An eight-element multiple-input-multiple-output antenna system which consists of Hshaped slot antennas is presented around the handset frame for 5G applications. Each antenna element consists of an H-shaped radiating surface and an L-shaped microstrip feeder. In the frequency bands of 3.4-3.6 GHz and 4.7-5.1 GHz, the isolation is lower than −15 dB by introducing the ladder-shaped defect ground structure. The antenna efficiency is 50%-81%, and the envelope correlation coefficient is lower than 0.02 among antenna elements. The measurement results agree well with the simulation ones, indicating that the proposed antenna can satisfy the requirements of 5G communication.