Hold the Chips: Chipless Technology, an Alternative Technique for RFID

Entering "RFID" on your Web browser will return you more than 50 million links. This huge number of references is a result of the impact of radio-frequency identification (RFID) technology worldwide [1]. Indeed, RFID technology is exploited in numerous domains, with thousands of applications, including more and more seen in everyday life. The RFID market is worth several billion dollars today, and its growth is more than 10% per year [2], [3]. There are two main classes of RFID devices. Figure 1 illustrates the main features of each class. The most known and broadly used class is the one based on the use of an integrated circuit (IC) chip in which the information is stored and that is connected to an antenna; the two together form the "tag." Such a technology exhibits several advantages, including flexibility and versatility in terms of the application. Nevertheless, it has some drawbacks mostly in terms of cost, robustness, reliability, data security, and poor recyclability of tags. More properties and new functionalities, such as sensing capabilities and tag-totag communication [4], are continually being developed, leading to the new paradigm of Internet of Things [5].