A reliable demodulator and a power regulation circuit with an accurate and small-size voltage reference in UHF RFID

Abstract

Key blocks used for Ultra High Frequency (UHF) Radio Frequency Identification (RFID) are designed in this paper, including a power regulation circuit and an ASK demodulator. The power regulation circuit is composed of a current mode voltage reference and a voltage regulator. The proposed current mode voltage reference is featured by the merits of small-size and high-accuracy. By optimizing the feedback factor of the voltage regulator, the chip size of the voltage reference is further reduced. The system design ensures the ASK demodulator has good performance in rejecting distortion and error-demodulation. Moreover, the threshold voltage compensation technology greatly improves the sensitivity of the demodulator. The proposed circuits have been fabricated under a SMIC 0.18μm 2P4M EEPROM process. The power consumption of the voltage reference is 0.83μW, the minimum operating voltage is 0.85V, and the active area is 0.028mm2. The chip size of the ASK demodulator is 0.0078mm2. All of the proposed circuits were verified in a full UHF RFID chip, and tested through a commercial reader. Under a wireless circumstance, the power regulation circuit provides a stable 1V power supply for the chip. The ASK demodulator correctly translates a full set of inventory command sent by the reader. According to the demodulated command, the tag chip feeds back the required data to reader.