Batteryless wireless tilt sensor with self-calibration capability for structural health monitoring

Aging infrastructures require constant monitoring to prevent major disasters. Accurate tilt detection is vital in determining the instability of bridges and foundations; however, existing systems depend on batteries, cables, and periodic calibration. We present a battery-free wireless tilt sensor based on a dual-band microwave structure that allows self-calibration against varying environmental effects and distance ambiguity. The sensor uses harvested energy from signals transmitted by a reader and integrates sensing, communication, and antenna functionalities into one device. The measurement results show that tracking the phase difference between two bands mitigates environmental factors. A 36° phase shift over a tilt range of -10° to +10° is observed, corresponding to a sensitivity of 1.8° of measured phase per 1° of actual tilt. The system is fully integrated, IoT-ready, and facilitates easy integration into a sensor network. It also creates a reliable platform for monitoring critical infrastructures in real-time to ensure rapid measurement of tilts from multiple sensors.