Metapocket: A Tri-Band Flexible Metasurface for Smartphone Antenna Performance Enhancement

In this paper, a flexible tri-band reflective metasurface, the metapocket, is presented to work with smartphone antennas to enhance its realized gain, and radiation efficiency and reduce its Specific Absorption Rate (SAR). Considering the limitation of the on-body scenario, the metasurface unit cell number is considered as a variable, and an artificial intelligence-driven method (the self-adaptive Bayesian neural network surrogate-model-assisted differential evolution for antenna optimization (SB-SADEA)) is applied to achieve the optimal performance. The designed reflection phase operates at 2.33-2.44 GHz (WIFI band), 3.39-3.56 GHz (5G N77 band) and 5.05-5.39 GHz (WLAN band). Polydimethylsiloxane (PDMS) substrate is utilized for good flexibility and biocompatibility. A state-of-the-art 5G smartphone (VIVO IQOO) is employed in both simulation and measurement. In free space, realized gain enhancement by 4.23, 4.67, 5.8 dB are achieved, radiation efficiency enhancement by 16.6%, 11.5%, 12.1% are achieved, respectively. Furthermore, calculated SAR reduction by 90.2%, 88.9%, 89.9% are achieved. All results verify that the proposed tri-band metapocket is of significant value to smartphone antenna performance in an on-body scenario.