Joint frequency and time coded chipless UWB-RFID tag for bit data enhancement

In this paper, a chipless UWB-RFID tag is proposed that is possessed of digital signatures coded in frequency domian and time domain both. The tag is composed of an UWB antenna attached by a U-slot and a microstrip feed line, all of them are decorated by the resistive ON/OFF switches tailored for the application of digitization. Simulation show the proposed tag can be achieved by two discrete pulses in the backscattered wave, one is the structural mode, owning band gap in its spectrum that is probable to be coded by one digit bit “0” or “1” according to the status of the ON/OFF switch going across the U-slot; Another is the antenna mode, the phase of which is determined by the status of ON/OFF switch being probably coded by one digit bit “0” or “1” in time domian. As a result, the bit data of the tag can be enhanced by arraying a multiple of them with different length of U-slots and feed lines. As a paradigm, a tag with three such configurations is validated with joint frequency and time coded by 6 digit bit achieving data capacity by 64.