Abstract
Smart watch antenna design is challenging due to the limited available area and the contact with the human body. The strap of smart watch can be utilized effectively for integration of the antenna. In this study, an antenna integrated on a smart watch strap model using computer simulation technology (CST) was designed. The antenna was designed for industrial, scientific, and medical (ISM) frequency bands at 2.45 and 5.8 GHz. Roger 3003C was used as substrate due to its semi-flexible nature. The antenna size is 28.81 × 19.22 × 1.58 mm3 and it has a gain of 1.03 and 5.97 dB, and efficiency of 80% and 95%, at 2.45 and 5.8 GHz, on the smart watch strap, respectively. A unit cell was designed having a dimension of 19.19 × 19.19 × 1.58 mm3 to mitigate the effect of back radiation and to enhance the gain. The antenna backed by the unit cell exhibited a gain of 2.44 and 6.17 dB with efficiency of 50% and 72% at 2.45 and 5.8 GHz, respectively. The AMC-backed antenna was integrated into a smart watch strap and placed on a human tissue model to study its human proximity effects. The specific absorption rate (SAR) values were calculated to be 0.19 and 1.18 W/kg at the designed ISM frequencies, and are well below the permissible limit set by the FCC and ICINPR. Because the antenna uses flexible material for wearable applications, bending analysis was also undertaken. The indicated results prove that bending along the x- and y-axes has a negligible effect on the antenna’s performance and the antenna showed excellent performance in the human proximity test. The measured results of the fabricated antenna were comparable with the simulated results. Thus, the designed antenna is compact, has high gain, and can be used effectively for wireless IoT applications.
Highlights
In the future, the greatest challenge in networks will be to connect everything everywhere, and millions of devices will be interconnected with each other
A simple square patch was designed, a parasitic patch on the right side of substrate was added, and two resonators were introduced inside the ground plane on the top to resonate the antenna at 2.45 and 5.8 GHz
The rubber strap of the smart watch had a thickness of 2 mm
Summary
The greatest challenge in networks will be to connect everything everywhere, and millions of devices will be interconnected with each other. The antenna had a low gain of 1.8 dB and a single band operating at 2.4 GHz. A Bluetooth antenna for smart watch applications was previously proposed. Another tri-band antenna having a size of 35 × 35 × 5 mm was proposed and had efficiency from 76 to 86% and gain up to 1.84 dB It was designed for the metal frame of a smart watch. 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.
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