A 65-nm CMOS battery-less temperature sensor node for RF-powered Wireless Sensor Networks

This work presents the design of a temperature sensor in a 65nm CMOS technology, which is powered by harvesting the electromagnetic energy in the ISM frequency band (2.4GHz). The power consumption of the sensor was substantially reduced so that the energy required to operate could be stored in a 50 mu F external capacitor. The rectifier sensitivity has been improved so as to allow autonomous operation from a distance of 2m to a conventional Wi-Fi transmitter (2.4GHz@ 100mW). To achieving these features, all circuits were designed for operating at 0.5V supply voltage. The measured temperature value is transmitted within another frequency band, the European UHF (867 MHz), by using 4-FSK modulation.