A Long-Range and Self-Powered Intelligent Food Monitoring System Based on Far-Field Energy Harvesting and Pressure Measurement

Abstract

Introduction In recent decades, food safety is becoming a top concern in the world because it is directly related to human health. According to World Health Organization statistics, about 550 million people are poisoned each year because of unsafe food consumption. One of the leading causes of foodborne illnesses is the consumption of rotten and expired foods. Therefore, the development of a food monitoring system is essential. Indeed, many studies have focused on developing battery-free food monitoring systems based on radio frequency energy harvesting (RFEH) technology due to its benefits such as durability, low cost, and safety for stored food [1]-[2]. The major disadvantage of these studies is that they estimated food quality using gas sensors, which require large energy consumption (typically over 10mW). Moreover, the gas sensors need a long time to heat up to obtain accurate sensor data. These drawbacks reduce the feasibility of implementing these systems in practice.This paper aims to develop a self-powered battery-free food monitoring system based on far-field RFEH technique and pressure measurement, which can overcome the problems with the conventional methods. Methods and Experiments The overview architecture of our proposed system is depicted in Fig.1. The self-powering capability of the sensor tag is provided by converting the radio wave transmitted from an RF generator into electrical signals. The antenna is the first component and plays a vital role in an energy harvesting system. To improve the received power and enhance the distance of power transfer, we have developed a printed Yagi-Uda Three element (driver, director, and reflector) because of its simplicity in design, high gain, compact size, and low cost [3]. The operating frequency of the antenna is chosen at the unlicensed Industrial Scientific Medical (ISM) band of 915MHz. Besides, in this study, we focus on monitoring the gradual increase of the air pressure inside the food container due to gas emission during food degradation. The air pressure sensor has ultra-low energy consumption and high precision, suitable for the limited energy condition of far-field RFEH system. Finally, we conduct a set of experiments with different sorts of food, such as pork, fish, and chicken, to demonstrate the feasibility of the proposed method. Results and Conclusions As a result, the designed Yagi antenna has a high gain of 6.54dBi in the direction of the maximum radiation, better than the isotropic antenna in some conventional systems that usually achieve about 1.7 dBi [1]. The reflection coefficient of the Yagi-Uda antenna achieved -26.8dB and voltage standing wave ratio (VSWR) better than 1.3 in approximately 60 band (890-950 MHz). At a distance of 6 meters, the harvested RF power reach -10.9dBm , and the rectifying voltage was obtained at 380mV , which is high enough for the tag to launch its functions. The sensor unit is designed with ultra-low power components and consumes only 300μW on average. The air pressure, temperature, and humidity data obtained from the sensor tag are used to evaluate and estimate the food quality, demonstrating the proposed method's effectiveness.