Dual-Band Antenna Pair With High Isolation Using Multiple Orthogonal Modes for 5G Smartphones

This communication presents a novel decoupling method to design a dual-band closely arranged multiple-input multiple-output (MIMO) antenna pair with high isolation for fifth-generation (5G) smartphones. By combining a bent loop and a T-shaped monopole into a compact space with a miniaturized size of 21. 8 7 mm2, multiple orthogonal in-phase modes and out-of-phase modes are excited at two different bands, respectively, to decrease the mutual coupling. Although the bent loop is closely spaced to the T-shaped monopole, the proposed antenna pair exhibits high isolation of more than 24 dB in dual bands without any decoupling structures. An 8 8 MIMO system operating at 3. 3–3. 6 GHz and 4. 4–5. 0 GHz is developed by arranging four such antenna pairs. The isolation is more than 12. 8 dB, the envelope correlation coefficients (ECCs) are lower than 0. 18, and the efficiencies are better than 71% and 68% in two bands for the proposed 8 8 MIMO system. The proposed MIMO system features dual-band operation, compact structure, and excellent isolation, which provides a promising solution for the 5G smartphone antenna design.