A High-Efficiency Microstrip Antenna Pair with Similar Pi-Shaped Decoupling Structure for 3.5 GHz 5G Ultrathin Smartphones

Abstract

In this paper, a low profile and high-efficiency decoupling antenna pair for multiunit smartphones is proposed using a similar π-shaped feed structure that can excite the dipole radiation mode of microstrip antenna. Ordinarily, symmetrical single-port T-shaped microstrip antennas can only excite monopole modes of bilateral radiation. This paper changes the vertical feeding microstrip structure into two oblique, similar π-shaped feeding structures. This oblique feeding structure can excite the dipole mode of unilateral radiation of the microstrip antenna. Using this method, the antenna design can be simplified, and the low-coupling independent radiation on both sides of the microstrip antenna can be freely controlled without the need for additional structures. Considering the ultra-thin characteristics of 5G smartphone devices, the parameters of the antenna are further optimized: the optimized antenna profile is only 3.7 mm. The measured results show that the 2 × 2 microstrip antenna pairs can effectively cover the 3.5 GHz band (3.4–3.6 GHz), with a coupling that varies from −16.14 dB to −11.01 dB and an efficiency that varies from 80% to 94.1%. The 8 × 8 MIMO smartphone antenna results show that the coupling varies from −20.1 dB to −12.17 dB, the efficiency varies from 79.72% to 93.7%, and the envelope correlation coefficient (ECC) is lower than 0.05. The microstrip antenna decoupling pair with a similar π-shaped feed structure proposed in this paper has high efficiency and low-profile characteristics have important application value in the decoupling design of 3.5 GHz 5G ultra-thin smartphone antennas.