Chipless RFID for Identification and Sensing

This chapter deals with an overview of the chipless RFID technology. The topic is initially introduced by presenting a comparison of this item-tagging technique with existing technologies such as the UHF RFID and the barcode. The advantages and drawbacks are discussed. Afterward, the most popular approaches to synthesize a chipless RFID are addressed both in time domain (TD) and in frequency domain (FD). The former approach is described in detail with several examples related to information encoding schemes and sensing applications. Both passive or semi-passive TD tags are described. The last part of the chapter is dedicated to the description of FD tags, where the information is usually encoded in the presence or absence of a frequency peak at a predetermined frequency. It is also shown that FD tags can be employed as sensors if the resonator is loaded with a material sensible to an environmental variable such as the humidity level.