A Battery-Free Wireless Temperature Sensing Chip for Food Monitoring

This work presents a battery-free wireless temperature sensing chip for long-termly monitoring the food production environment. A calibrated oscillator-based CMOS temperature sensor is proposed instead of the ADC-based power-hungry circuits in conventional works. In addition, the sensor chip can harvest the power transferred by a remote reader to eliminate the use of battery. Meanwhile, the system conduct wireless bidirectional communication between the sensor chip and reader. In this way, the temperature sensing chip is fabricated in 55 nm CMOS process, and the reader chip is implemented in 65 nm CMOS technology. Experimental results show that the temperature measurement error achieves $\pm 1.6^{\circ} \mathrm{C}$ from $25^{\circ} \mathrm{C}$ to $50^{\circ} \mathrm{C}$, with battery-free readout by a remote reader.