Tag Design for RFID AC Current Sensing System

This study describes the development of an RFID tag system and antenna for real-time ac current sensing of individual appliances in smart homes. The operating principle of the tag system is based on the tag antenna tuning via a tuning circuit. The auto-tuning chip is embedded to compensate the antenna matching and stores the impedance tuning in the form of a 5–bit sensor code. The tag wirelessly streams the 5–bit sensor code that represents the ac current drawn by the electrical load, to the dedicated RFID reader in the range of 3 m at 868 MHz. The tag device is an energy harvester and a cost-effective ac current sensing solution compared to commercial smart meters in smart power metering systems. The antenna is designed to fit around the housing of the current sensor.