Performance evaluation of left-handed delay lines for RFID backscatter applications

The operation principle of a passive RFID tag on the basis of delay lines is presented and the performance of left- and right-handed lines for this application is compared. Additionally, limitations due to the dispersion properties of left-handed lines for the maximum number of usable cells are discussed. In conclusion, an expression relating the maximum number of usable bits for the tag impulse response to system parameters like bandwidth, centre frequency etc. is given. A proof of concept is realized with a 100 cell four bit backscatter tag. The set up of the tag is described and the performance analysed.