A passive UHF tag for RFID-based train axle temperature measurement system

A fully integrated passive UHF RFID tag with embedded temperature sensor, compatible with the ISO/IEC 18000 type 6C protocol, is developed in a standard 0.18μm CMOS process, which is designed to measure the axle temperature of a running train. The consumption of RF/analog front-end circuits is 1.556μA@1.0V, and power dissipation of digital part is 5μA@1.0V. The CMOS temperature sensor exhibits a conversion time under 2 ms, less than 7 μW power dissipation, resolution of 0.31°C/LSB and error of +2.3/-1.1°C with a 1.8 V power supply for range from -35°C to 105°C. Measured sensitivity of tag is -5dBm at room temperature.