Conformal Multiband Antenna for Wearable and Gesture-Sensing Applications

Wireless body-centric communication technology has experienced substantial growth in the wearable device industry, owing to the growing demand for remote health monitoring, military and sensing applications, etc., without compromising the wearer's comfort. This growth is aided by the popularity of wearable antennas for their beneficial features such as low profile, adaptability, durability, and biocompatibility with specific absorption rate (SAR), which make them viable options in wireless body area network (WBAN) deployments. This study introduces a modified T-shaped, stub-loaded planar antenna tailored for wearable applications across WiFi (2.08-2.88 GHz), WLAN (3.55-5.4 GHz), and WiMAX (5.73-5.92 GHz) bands. Leveraging strategically placed slits/stubs, additional resonances are introduced to achieve multiband functionality. This design features a via-less structure, facilitating simplified fabrication process. The effectiveness of the antenna is validated by simulation and equivalent circuit modeling. Bending analysis based on human body radii shows minimal performance deterioration, exhibiting equivalent performance when both flat and bent at 30- to 80-mm radii. The antenna offers a low SAR without introducing additional SAR reduction techniques. SAR values of 0.184, 0.1936, 0.4981, 0.6531, and 0.7339 W/kg were achieved at operating frequencies of 2.45, 3.77, 4.66, 5.23, and 5.83 GHz, respectively, which ensures adherence to safety guidelines. The sensitivity of the antenna sensor is also investigated for different volumes of a tissue model through resonant frequencies shift at varying distances. Moreover, the antenna is demonstrated by experimental validation, which includes wrist placement and gesture recognition trials.