Extremely Low-Profile Tunable Multiport Handset Antenna

This article presents an extremely low-profile tunable antenna design for smartphones with height of only 0.75 mm. The proposed antenna is integrated into the back cover of the device to utilize the existing gap between the battery and the back cover as efficiently as possible. By utilizing both tunable components and adjustable feeding weights, the designed multiport antenna system covers 3300–4200 MHz frequency range with 100 MHz instantaneous bands. In addition to just frequency tuning, these tunable elements can be utilized to adapt the antenna for different operation environments, such as changes in the structure of the device or the user effect. We show that the proposed antenna can be extended for two- and four-element multiple-input multiple-output (MIMO) operation. The proposed design is manufactured and measured, and the results confirm good antenna performance with average total efficiencies of 35% and 25% in free space and with a hand phantom, respectively.