Curvature-Induced Performance Variations in Conformal Antennas of Wireless Sensing of Smart Jewelry

Conformal antennas are designed to accommodate different special curved surfaces and have shown advantages in areas such as aerospace and the Internet of Things (IoT), including wearables and automation technology of smart Jewelry sensing. In this study, the effect of antenna curvature on radiation efficiency and impedance matching is investigated by measuring the reflection coefficient S<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</inf> at different curvatures using a vector network analyser (VNA). The results show that although the resonant frequency is stable, the magnitude of S<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</inf> decreases with decreasing intermediate curvature and then changes with increasing curvature, which is attributed to the enhanced capacitance effect of the compensating inductive reactance. The best performance is achieved when the curvature is between 120 and 150 degrees, with minimal reflection and increased transmission.