Towards multi-bit, long range and eco-friendly implementation of tag sensors

Internet of Things (IoT) is becoming a driving paradigm for the Information and Communication Technology (ICT) evolution. Beyond the well known sensing and communication features that must equip objects to become smart and thus to insert them into IoT world, energy autonomy and the largest available compatibility with hosting objects must be pursued. Chipless sensor tags are one of the most promising solution to cope with all these features concurrently; in fact, they have in-herent sensing and communication capabilities, they are passive, thus autonomous, they are extremely simple to allow an easy integration with the object manufacturing processes, and they can be still easily implementable by using eco-friendly materials. The main limit of classic chipless architectures, however, is that they are usually static (information is stored once the tag is built) and in any case sensing and dynamic information can be recovered only in presence of a stationary environment. This paper presents a review of some 'multi-bit' sensor tag architectures based on the harmonic radar principle that can overcome this limitations and thus be profitably used to support the massive deployment of IoT devices.