Fully Textile Dual-Band Logo Antenna for IoT Wearable Devices

In recent years, the interest in the Internet of Things (IoT) has been growing because this technology bridges the gap between the physical and virtual world, by connecting different objects and people through communication networks, in order to improve the quality of life. New IoT wearable devices require new types of antennas with unique shapes, made on unconventional substrates, which can be unobtrusively integrated into clothes and accessories. In this paper, we propose a fully textile dual-band logo antenna integrated with a reflector for application in IoT wearable devices. The proposed antenna’s radiating elements have been shaped to mimic the logo of South-West University “Neofit Rilski” for an unobtrusive integration in accessories. A reflector has been mounted on the opposite side of the textile substrate to reduce the radiation from the wearable antenna and improve its robustness against the loading effect from nearby objects. Two antenna prototypes were fabricated and tested in free space as well as on three different objects (human body, notebook, and laptop). Moreover, in the two frequency ranges of interest a radiation efficiency of 25–38% and 62–90% was achieved. Moreover, due to the reflector, the maximum local specific-absorption rate, which averaged over 10 g mass in the human-body phantom, was found to be equal to 0.5182 W/kg at 2.4 GHz and 0.16379 W/kg at 5.47 GHz. Additionally, the results from the performed measurement-campaign collecting received the signal-strength indicator and packet loss for an off-body scenario in real-world use, demonstrating that the backpack-integrated antenna prototype can form high-quality off-body communication channels

Wearable Antennas for Sensor Networks and IoT Applications: Evaluation of SAR and Biological Effects

In recent years, there has been a rapid development in the wearable industry. The growing number of wearables has led to the demand for new lightweight, flexible wearable antennas. In order to be applicable in IoT wearable devices, the antennas must meet certain electrical, mechanical, manufacturing, and safety requirements (e.g., specific absorption rate (SAR) below worldwide limits). However, the assessment of SAR does not provide information on the mechanisms of interaction between low-intensity electromagnetic fields emitted by wearable antennas and the human body. In this paper, we presented a detailed investigation of the SAR induced in erythrocyte suspensions from a fully textile wearable antenna at realistic (net input power 6.3 mW) and conservative (net input power 450 mW) conditions at 2.41 GHz, as well as results from in vitro experiments on the stability of human erythrocyte membranes at both exposure conditions. The detailed investigation showed that the 1 g average SARs were 0.5758 W/kg and 41.13 W/kg, respectively. Results from the in vitro experiments demonstrated that the short-term (20 min) irradiation of erythrocyte membranes in the reactive near-field of the wearable antenna at 6.3 mW input power had a stabilizing effect. Long-term exposure (120 min) had a destabilizing effect on the erythrocyte membrane