Design of Smartwatch Integrated Antenna With Polarization Diversity

Abstract

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. INDEX TERMS Wireless body area network (WBAN), wearable antenna, Smartwatch integrated antenna, polarization diversity, cubic tissue model, wrist model, specific absorption rate (SAR), Envelope correlation coefficient (ECC).

A wideband isolation technique using bezel coupled T‐type isolator for smartwatch MIMO applications

“…Accordingly, various designs for smartwatch MIMO applications have been proposed in the literature. [10][11][12][13][14] To achieve high port-to-port isolation covering a wideband frequency range, characteristic mode theory was utilized in Wen et al 10 The characteristic mode theory is used to excite degenerate modes by employing ground modification and orthogonal T-shaped monopoles. However, the geometry lacks coplanar design requirements.…”

“…Polarization diversity was employed in a two-port system using smartwatch annular integrated ring. 11 Dual-polarized colocated slots were etched on a wedge profile cavity 12,13 and a cuboid cavity 14 to achieve polarization diversity resulting in higher isolation for wider bandwidth. However, the design is unsuitable for low-profile smartwatch applications.…”

“…However, compact sizes of smartwatches are much smaller as compared to smartphones and USB dongles, which poses another design challenge to smartwatch MIMO antennas resulting in strong mutual coupling. Accordingly, various designs for smartwatch MIMO applications have been proposed in the literature 10–14 …”

“…However, the geometry lacks coplanar design requirements. Polarization diversity was employed in a two‐port system using smartwatch annular integrated ring 11 . Dual‐polarized colocated slots were etched on a wedge profile cavity 12,13 and a cuboid cavity 14 to achieve polarization diversity resulting in higher isolation for wider bandwidth.…”

An Artificial Magnetic Conductor-Backed Compact Wearable Antenna for Smart Watch IoT Applications

“…The antenna efficiency, and had low gain, but it was also not tested on a watch or a human tissue model [23]. An annual ring type smart watch antenna integrated into a watch's metal frame was proposed in [24], having a gain of 4 dBi and radiation efficiency of 62% at an operating frequency 2.4 GHz. The SAR value of the designed antenna was below the permissible limit set by the FCC.…”