An RF-Powered Self-Locating Flexible Building Environment Sensor System

Wireless, battery-free, peel-and-stick sensors can enable many new capabilities in the Internet-of-Things(IoT). Low-cost sensor hardware and manufacturing together with no-skill installation and commissioning and low maintenance requirements can allow widely distributed sensors for continuous, comprehensive monitoring for structural health, physical health, safety, and industrial and environmental applications. This paper presents a system of RF-powered flexible sensors for building environment sensing with the potential to deliver up to 30% energy savings through improved HVAC controls. The system utilizes a set of electronic hubs that both provide remote power to the sensors and wirelessly relay sensor data to the building management system (BMS). The sensors are flexible electronic labels powered by rectified RF energy received from a hub and can contain multiple printed and conventional sensors including for temperature, humidity, and air quality. The electronic hub includes a programmable multidirectional beam-steering antenna that allows arbitrarily-placed sensors to be automatically located by the system through monitoring of received RF power as a function of transmission angle. The system has achieved extremely low-power operation, wireless sensor data transmission over > 10 meters, remote power delivered across >7 meters and sensor localization to within 0.5 meters.