Novel soil environment monitoring system based on RFID sensor and LoRa

This work proposes a novel soil environment monitoring system based on RFID sensor and LoRa to realize long term and low cost monitoring. The monitoring system consists of patrol car, RFID sensor, farmland monitoring center and cloud platform. The proposed patrol car is responsible for collecting the information of embedded RFD sensors and communicate with the monitoring center through LoRa. The proposed RFID sensor is comprised of a power management section, a communication section, and a digital section. The power management section employs a whip antenna for energy harvesting, and a novel boost rectifier, consisting of a single stage rectifier and a DC-DC charge pump, is introduced to rectify the harvested RF power for high efficiency. A voltage regulator is used to generate a stable DC voltage supply. In the communication section, a novel monopole antenna is propose to minimize the size of antenna. It can be concluded from the experimental results that our RFID sensor can work under the maximum communication distance of 1.3 m. The errors of the measured temperature and moisture content are 1.5% and 1.0% respectively when the embedding depth of RFID sensor is 60 cm and the moisture content of soil is smaller than 30%. The optimum speed of patrol car is 33 km/h when the communication success rate is above 90% and the coverage area is above 10 km(2).