On the design of passive RFID tags for ASK modulation

Design of passive UHF RFID tag for ASK modulation is investigated. It is shown that tag antenna structural mode strongly affects the tag´s backscattered field, shaping the phase and magnitude of the modulated signal. In contrast to prior art, the proposed circuit design can manipulate the effects of the tag antenna structural term, ensuring phase continuity of the backscattered field, which is a necessary condition for ASK modulation. Furthermore, the structural field can be favourably exploited, increasing the total backscattered power, by properly selecting the circuit´s parameters within realistic values as shown herein. Identification range, maximum power transfer, BER and total backscattered power with respect to the parameters of the circuit are evaluated and optimised.