Design and Performance Analysis of a Low-Profile Dual-Band Antenna with Low Specific Absorption Rate Using Textile Materials for Wearable and RF Energy Harvesting Applications

This study presents a low-profile, dual-band microstrip patch antenna (MPA) optimized for wearable applications, with a focus on achieving a low specific absorption rate (SAR). The antenna operates efficiently in the 5.8 GHz ISM (industrial, scientific, and medical) band and the 8.3 GHz X-band. A strategically designed C-shaped slot adjusts the resonant frequencies to align with these operational bands. The performance characteristics are evaluated across various textile substrates, including polyester-cotton, felt, denim, polyester, and Cordura, to determine the most suitable material for specific application needs. Constructed from conductive textile materials on a single poly-cotton substrate layer, the antenna combines flexibility and conformity to the human body, making it ideal for wearable technology. The compact design measures 40 mm3 x 45 mm3 x 1.17 mm3 (0.77 lambda 0 x 0.87 lambda 0 x 0.022 lambda 0 at 5.8 GHz), and it demonstrates simulated peak gains of 8.73 dBi and 4.64 dBi for the 5.8 GHz and 8.3 GHz bands, respectively. The antenna achieves bandwidths of 150 MHz at 5.8 GHz and 190 MHz at 8.3 GHz. Experimental results confirm stable return loss (S11) performance despite structural deformations and proximity to the human body. Additionally, the antenna maintains SAR values within the European Union's standard limit of 2 W/kg, attributed to its full ground plane structure. These attributes highlight the antenna's potential for reliable and efficient operation in wearable technologies and RF energy harvesting systems, particularly in indoor environments.