Microwave Encoders and Application to Near-Field Chipless-RFID: a Review

Recently, electromagnetic encoders operating at microwave frequencies have been reported. Such encoders can be useful for measuring linear and angular displacements and velocities, but also as near-field chipless-RFID tags. In both cases, encoder reading is carried out by proximity, through near field, by using a microwave interrogation signal. This paper reports the recent advances relative to such microwave encoders, with special emphasis on chipless-RFID applications. Two types of encoders are considered: (i) those with printed metallic elements on a dielectric substrate, and (ii) full dielectric encoders, where the metallic elements are replaced with dielectric inclusions.