Design of Smartwatch Integrated Antenna with Polarization Diversity

A design of smartwatch integrated antenna with polarization diversity is proposed. An annular ring is integrated in the framework of smartwatch, and excited by two ports. One port is fed by a coplanar waveguide (CPW) line loaded with a T-shaped matching network, and the other is fed by a coplanar strip line (CPS). The overall model of the proposed antenna has a cylindrical shape with 38 mm diameter and 7.5 mm thickness. A metallic plate is located at the backside of the antenna to mimic the shell of smartwatch. The prototype is fabricated and measured, and the measured results agree well with the numerical ones. The two ports have orthometric radiation patterns and can cover the 2.4 GHz wireless local area network (WLAN) band. The gain of the antenna is higher than 3.2 dBi in free space. The proposed antenna is also analyzed with a cubic tissue model and a wrist model in different distances between the proposed antenna and human models. The performances on body scenarios are also acceptable. The values of specific absorption rate (SAR) in the cubic tissue model and wrist model are below the limitations set by both the Federal Communication Commission (FCC) and the European Telecommunication Standards Institute (ETSI). Envelope correlation coefficient (ECC) shows proposed antenna can be used in multiple input multiple output (MIMO) applications. The influence of battery and printed circuits board assembly (PCBA) on S parameters is obvious, and gain and radiation efficiency are not much affected.