Chipless RFID Based on Micro-Doppler Effect

This article demonstrates how motion effect can be exploited to read moving chipless radio frequency identification (RFID) tags at larger distances compared to what has been reached without taking into account the movement. According to the Doppler effect, due to the time-variant behavior of moving chipless tags, the tag backscattered field contains frequency components different from those that are transmitted. These motion-induced frequency components can be utilized to efficiently detect the tag at large distances, in a real environment composed of stationary objects. A circuit-based analytical model verified by full-wave simulations is presented to effectively predict the quasi-stationary backscattered field from moving scatterers, with fast computation process. The developed analytic model is applied to rotating dipole scatterers and is used to design chipless tags, including an identifier. In terms of identification, good agreement is observed between the measurement results and those are predicted by the model. Finally, read range enhancement is proven experimentally by a real environment measurement where the chipless tags are readable at distances up to several meters.