An RF Wireless Power Transfer system to power battery-free devices for asset tracking

Internet of Things (IoT) and Wireless Sensor Networks (WSN) infrastructures are becoming more and more available and diffused. One major outcome is the development of new services that help to make everyday life easier and better. One of those to which this paper reserves special attention is asset tracking which refers to the method of tracking physical assets. This service is very well based on IoT infrastructure and, due to the enormous number of objects to be traced, desperately needs the availability of inexpensive tags with sensing capabilities, that can be conveniently monitored from a long distance and require no maintenance. For this, engineers are called to face very challenging issues. One of these is how to power a maintenance-free tag that consequently must be battery-free. This paper deals with the investigation of a system based on radio frequency (RF) Wireless Power Transfer (WPT) that powers a battery-free tag for asset tracking, in which the major challenge is that the WPT deals with dynamic objects at different speeds. The performances and key features of a system on chip (SoC) specifically designed to power a tag by means of RF WPT will be investigated. The aim is to provide a strategy and a model to design the infrastructure by providing the number of hot-spots needed to perform successfully the identification of an asset. Validation of the model has been done by means of specific tests and experimental results are provided.