Long-range batteryless RF sensor for monitoring the freshness of packaged vegetables

A compact and long measurement range batteryless radio frequency sensor tag is designed and implemented for monitoring the freshness of packaged vegetables based on measured temperature and humidity values. The proposed system consists of a server personal computer, an RFID reader operating at a frequency of 13.56 MHz, and a temperature- and humidity-sensor tag. The proposed reader is equipped with a boost circuit to boost the circuit power up to 1 W and a 17 cm × 22 cm loop antenna to enhance the amplitude of the transceiver signal. Therefore, the proposed reader can read RF sensor tags at a distance of up to 30 cm, that is, relatively very long-range in 13.56 MHz. The proposed batteryless passive sensor tag can simultaneously measure temperature and humidity inside packaged vegetables, with accuracies of 97.8% and 98.5%, respectively. By measuring the temperature and humidity of the vegetables storage environment, we can predict the freshness of vegetables. This system implemented by using batteryless RF sensor that is expected to be a promising tool to help customers choose fresh vegetables.