This study explores a battery-free method for monitoring elbow flexion using a printed dipole antenna as a passive sensor. The antenna's resonant frequency and reflection coefficient (S11) change in response to bending, thus offering an innovative alternative to traditional sensor-based systems that require active power. Electromagnetic simulations were performed using CST Microwave Studio over several frequency bands (0-10 GHz, 1.2 – 1.6 GHz, and 0−4GHz) while varying the elbow angle from 0° to 150° in 5° increments. The results indicate that the resonant frequency varies continuously with the flexion angle, especially in the 1.5−2.5GHz band, where high stability and sensitivity were observed. Notable singularities at angles such as 0°,45°,90°, and 135° suggest complex electromagnetic interactions that merit further investigation. Repositioning the feed point proved critical, with optimal measurements obtained on the arm, at 5 mm away from the elbow. These findings confirm that printed dipole antennas can function as passive sensors for joint movement, paving the way for seamless integration into wearable textiles or direct skin applications. Future work will integrate human body models into the simulation, advance prototype development, and incorporate sophisticated signal processing to enhance gesture recognition. This approach represents a promising leap toward lightweight, durable, and energy-efficient wearable sensor technologies.
