Design of a MIMO Antenna With High Isolation for Smartwatch Applications Using the Theory of Characteristic Modes

This paper describes the design and testing of a multiple-in multiple-out (MIMO) antenna for metal-frame smartwatch applications. The antenna operates from 2.4 to 2.49 GHz, which can cover Bluetooth/WiFi band. The design procedure is based on the theory of characteristic modes and it is discussed thoroughly. By employing a pair of degenerated modes to design the MIMO antenna, a high port-to-port isolation can be achieved over the operating frequency band. Simulated and measured results are presented to verify the antenna design. Furthermore, the antenna has a low envelope correlation coefficient and a high effective diversity gain even when it is mounted on the human phantom. Hence, the proposed antenna proves to be a good candidate for smartwatch applications.