A 12-port antenna array operating in the long term evolution (LTE) band 42 (3400–3600 MHz), LTE band 43 (3600–3800 MHz) and LTE band 46 (5150–5925 MHz) for 5G massive multiple-input multiple-output (MIMO) applications in mobile handsets is presented. The proposed MIMO antenna is composed of three different antenna element types, namely, inverted π-shaped antenna, longer inverted L-shaped open slot antenna and shorter inverted L-shaped open slot antenna. In total, eight antenna elements are used for the 8 ×8 MIMO in LTE bands 42/43, and six antenna elements are designed for the 6 ×6 MIMO in LTE band 46. The proposed antenna was simulated, and a prototype was fabricated and tested. The measured results show that the LTE bands 42/43/46 are satisfied with reflection coefficient better than –6 dB, isolation lower than –12 dB, and total efficiencies of higher than 40%. In addition to that, the proposed antenna array has also shown good MIMO performances with envelope correlation coefficient (ECC) lower than 0.15, and ergodic channel capacities higher than 34 bps/Hz and 26.5 bps/Hz in the LTE bands 42/43 and LTE band 46, respectively. The hand phantom effects are also investigated, and the results show that the proposed antenna array can still exhibit good radiation and MIMO performances when operating under data mode and read mode conditions.

The design of a novel practical 28 GHz beam steering phased array antenna for future fifth generation (5G) mobile device applications is presented in this paper. The proposed array antenna has 16 cavity-backed slot antenna elements that are implemented via the metallic back casing of the mobile device, in which two 8-element phased arrays are built on the left- and right-side edges of the mobile device. Each 8–element phased array can yield beam steering at broadside and gain of >15 dBi can be achieved at boresight. The measured 10-dB return loss bandwidth of the proposed cavity-backed slot antenna element was approximately 27.5 GHz to over 30 GHz. In addition, the impacts of user’s hand effects are also investigated.

A multi-band 10-antenna array working at the sub-6-GHz spectrum (LTE bands 42/43 and LTE band 46) for massive multiple-input multiple-output (MIMO) applications in future 5G smartphones is proposed. To realize 10 × 10 MIMO applications in three LTE bands, 10 T-shaped coupled-fed slot antenna elements that can excite dual resonant modes are integrated into a system circuit board. Spatial and polarization diversity techniques are implemented on these elements so that the improved isolation and mitigated coupling effects can be achieved. The proposed antenna array was manufactured and experimentally measured. Desirable antenna efficiencies of higher than 42% and 62% were measured in the low band and high band, respectively. Vital results, such as the envelope correlation coefficient, channel capacity, and mean effective gain ratio, have also been computed and analyzed. The calculated ergodic channel capacities of the 10 × 10 MIMO system working in the LTE bands 42/43 and LTE band 46 reached up to 48 and 51.4 b/s/Hz, respectively.

In this paper, a compact building block composed of a slot antenna and a loop antenna is proposed. The slot antenna and the loop antenna share a rectangular clearance, which improves the compactness of the building block effectively. Although the slot and the loop have overlapped completely, the proposed building block exhibits good isolation (better than 19 dB) without any external decoupling structure. Four such building blocks are used to implement a compact eight-port multiple-input multiple-output (MIMO) array operating at 3.5 GHz band (3.4-3.6 GHz) for fifth-generation (5G) metal-rimmed smartphone applications. The proposed eight-antenna MIMO array exhibits good isolation of better than 16 dB across the whole operating band. The measured efficiencies of the proposed MIMO array were between 59% and 73%, and its corresponding measured envelope correlation coefficients (ECCs) were better than 0.05. Furthermore, the calculated channel capacity of the proposed MIMO array with 20 dB signal-to-noise ratio (SNR) was about 38.2-39.8 bps/Hz across the desired bands (3.4-3.6 GHz). The measured results confirm that the proposed MIMO array is a good candidate for 5G terminals.