Research And Implementation Of Key Technologies For A Passive UHF RFID Tag

RFID is a technology that incorporates the use of electromagnetic or electrostatic coupling in the radio frequency portion of the electromagnetic spectrum to uniquely identify an object. It’s becoming a hot topic, and has very wide application fields.Firstly, the component of passive UHF RFID chips and the fundamental theory of RFID system are discussed in this dissertation. We had deeply researched in the key technologies of UHF RFID system including demodulation, modulation, memory, reception and radiation.In order to improve the sensitivity of demodulator, the threshold voltage compensation technology was used to reduce voltage loss on the charge transfer transistor in envelope detector circuit and a voltage reference circuit without diode and resistance was designed. In order to transfer data from RFID tags to readers, a modulator which controls the impedance of chips is needed. Using the switching characteristic of CMOS transistor, a modulator with simple structure and small size was designed.Considering process compatibility and the cost of tag chips, a memory cell was designed with parallel double floating gates and based on standard CMOS process. It has lower power and program voltage. A method, in which both the gate and the substrate of the charge transfer transistor are dynamically biased by the internal high voltages of the charge pump, is proposed. In this way, the threshold voltage loss on the charge transfer transistor is eliminated and the substrate leakage is also reduced, as a result, the PCE of the charge pump is improved.This dissertation proposed a meander-line dipole antenna for the tag chips designed by our research group. We preferably solved the problems of impedance matching and antenna miniaturization.This paper accomplished the designing and testing of passive UHF RFID. The result shows that the chip performance indicators achieved the expected goals.