32-$\mu{\rm W}$ Wirelessly-Powered Sensor Platform With a 2-m Range

In this paper, the experimental results of a complete battery-less wirelessly-powered 2.45-GHz temperature sensor system with a microcontroller (μC) and an ISM-band transmitter on FR-4 is presented. As the measured results show, the energy harvesting system can provide 2.4 V to turn on the μC , temperature sensor and transmitter with only -15 dBm (32μW) radio frequency input power and up to 0.2°C temperature resolution. The system is able to transmit 32-bit sensor data back to the base station with an extra 16 bits for cyclic redundancy check check at regular intervals. The battery-less μC can be wirelessly powered when located up to a distance of 2 m from a power transmitter supplying less than 50 mW of microwave power using a patch array.