Metal-Frame Antenna for Big-Screen Smartphones Using Characteristic Mode Analysis

In previously published papers about the metal-frame smartphone antennas, the screen is usually not included in the antenna model. As the big-screen, or even full-screen (also called all-screen or bezel-less) smartphones become the trend in recent and foreseeable future years, the effect of the very close screen to metal-frame antennas becomes prominent, e.g., the antenna's bandwidth is significantly narrowed. In this paper, a metal-frame antenna for the big-screen smartphone covering 824-960 MHz (GSM850/900), 1452-1496 MHz (LTE1500), 1710-2690 MHz (DCS, PCS, UMTS2100, LTE2300/2500), and 3400-3600 MHz (3.5 GHz 5G) is introduced. For the first time, the screen is fully considered, even designed as part of the antenna. The theory of characteristic modes (TCM) is applied in the design method. A prototype is made and measured for verifying the proposed methodology. Some key parameters of this antenna design are also discussed. This methodology helps to improve the degraded performance of smartphone antennas due to the big-screen industrial design.