A Batteryless RFID Remote Control System

This paper presents a novel eco-friendly batteryless remote control (RC) system based on a multi-RF identification (RFID) scheme. The proposed RC device does not require the use of batteries or other installed power source. Instead, it relies on passive RFID chips that are remotely powered by an RFID reader. The controlled device (e.g., a TV) incorporates an RFID reader to power up and communicate with the RC. The proposed batteryless RC is composed of an antenna, a plurality of N passive RFID chips and N switches, and a multi-port microstrip network that interconnects the various RFID chips, allowing them to share a common antenna. Each key of the RC is associated to an RFID with a unique identifier, which allows the device to be controlled to identify the key pressed by the user. The proposed arrangement ensures that only the chip associated to the pressed key is read by the RFID reader, while the other chips remain inactive. First of all, the system is described including the multi-RFID scheme and the proposed multi-port network. Afterword, a characterization of the contact switches and RFID chips is performed. This is followed by RFID chip impedance matching and switch tuning. A multi-port network is fabricated (in low-cost FR4) and measured in order to access network´s behavior depending on some parameters such as the number of ports and distance from the active port to the antenna. Finally, a four-key RC unit is prototyped, and an RFID reader system is integrated in a TV by using an external RFID-to-infrared interface. Four control functionalities are implemented and tested (CH+, CH-, Vol+, and Vol-). Measurements are also conducted to evaluate the system coverage range and line-of-sight capability.