Design of Small Multiband Full-Screen Smartwatch Antenna for IoT Applications

Smartwatch is a potential candidate for the Internet-of-Things (IoT) hub. However, the performance of smartwatch antennas is severely restricted by the smartwatch structure, especially when the antennas are designed by traditional methods. For adapting smartwatches to the role of IoT hub, a novel method of designing the multiband smartwatch antenna is presented in this article, aiming at increasing the number of frequency bands, omnidirectivity, and structural suitability. First, the fundamental structure (including the full screen and the system PCB) of the smartwatch is analyzed as a whole by characteristic mode analysis (CMA). Thus, abundant resources of characteristic modes are introduced. The fundamental structure is then modified as the radiator of a multiband antenna. Then, a nonradiating capacitive coupling element (CCE) excites the desired four 0.5
${\lambda }$
modes from this structure. This method could fully utilize the intrinsic modes of the smartwatch structure itself, thus exhibiting multiple advantages: significantly small size, smaller ground, omnidirectional radiation, and fitting to the full-screen smartwatch structure.