Batteryless UHF RFID technology for iot-based ambient sensing

The Internet of Things (IOT) is the logical further development of today’s internet and envisions a future on billions of smart connected devices. Devices that senses their surroundings and which when combined into the cloud will provide informations on the environment from microscopic to global scaling. Therefore, the IOT will require enabling sensor hardware in addition to the cloud computing services: smart connected devices that have on-board sensors in order to provide metrics for ambient intelligence. It is predicted that smart mobile devices in the future will be equipped with a limited range of physical sensors but will be able to read a wide range of new sensors as separated accessories. Wireless sensors are widely developed in order to remotely detect, measure, monitor and control several entities in logistics, food quality and agriculture, environment, healthcare, homeland security, and process monitoring and control. The selection of a particular sensor technology or radio-architecture has to account for the physical/chemical process to be measured, the location of the measurement site, the sensor size, the read range, the power consumption, the type of network and the cost. Among the different short-range radio technologies that potentially converge to this scenario, Radio Frequency Identification (RFID) systems may represent a strategic enabling component for the true pervasive diffusion of IOT-based Ambient Sensing. RFID is particularly attractive for the energy autonomy of battery-less (passive) tags, for the low-cost, the inter-operability and the relatively low-complexity. A passive RFID system is composed of a digital device called tag, embedding an antenna and an IC-chip with a unique identification code (ID), and a radio scanner device, called reader. Despite the RFID technology is currently mostly applied to logistics of goods, the very recent research is exploring other paths with the common goal of extracting physical information about 3 tagged objects and nearby environment through low-level processing of electromagnetic signals received and backscattered by the tags. RFID tags can be equipped with a large variety of passive digital and analog sensors for measuring environmental parameters such as temperature, pressure, light intensity, strain, accelerations and humidity or gases and thus performing the sensing activity without any local power supply. Body area networks (Bans) and wearable sensors are also an attractive area for smart tags applications, e.g. for motion recognition monitoring. RFID systems could therefore permit to implement, in a simple and efficient way, the last few meters of the Internet of Things concerning the pervasive quantification of environmental parameters of interest. Ambient sensors, in particular, could permit to quantify the wellness of the environment itself and to analyze its correlation with the people health-state. The application of the RFID technology to the Pervasive ambient sensing is a rather new topic. The subject of this Ph.D thesis deals with the study of RFID ambient sensing feasibility through of a multidisciplinary vision, which merges together Electromagnetics, Wireless Communication, Electronics, Sensors and Chemical Materials. From the perspective of IoT the research will cover passive (i.e. battery-less) devices in the UHF band (860-960MHz) which are capable to provide services and enough read-ranges to implement a network of sensors for monitoring the quality of the local environment. Each sensor-tag can be processed individually or together with those from the other distributed nodes in order to extract information in the most comprehensive way. Theoretical aspects will be addressed by studying the communication links of RFID devices for sensing purposes and validated by an extensive and targeted campaign of measurements for temperature and gas sensing.