EPC Gen-2 UHF RFID tags with low-power CMOS temperature sensor suitable for gas applications

This paper presents a passive RFID tag with an embedded temperature sensor intended for the EPC Gen-2 protocol operating in the 902-928 MHz ISM band. The design is implemented as a node of a low cost temperature sensors network. The system is powered by a remote power through the RF energy received from the reader in order to create autonomous temperature measurement micro systems. The temperature sensor is based on ring oscillator using CMOS thyristor delay element. The energy recovery and power distribution unit of the RFID tag provides different supply voltages in order to optimize the performance and the power consumption of each building block. Amplitude Shift Keying (ASK) modulation architecture is adopted for Radio Frequency (RF) link which uses an envelope detector and non-coherent demodulation technique. For the temperature sensor, Low power operation is achieved by eliminating the use of power hungry Analog to Digital Converters (ADCs) at the sensor output. The design architecture is fully compliant to the EPC Gen-2 standard. The error in temperature sensing is around -1.8°C/+1°C, with a resolution of 0.3°C. The RFID tag achieves a sensitivity of -11 dBm with an input data rate up to 200 kbps from 1.8V. 0.5Vwas used as supply voltage for the temperature sensor to ensure the low power consumption as well as robustness. The proposed UHF RFID tag is implemented and simulated in 0.18μmCMOS process.