An LTPS TFT Demodulator for RFID Tags Embeddable on Panel Displays

This paper presents an amplitude-shift-keying (ASK) demodulator for RF identification tags, which can be embedded on panel displays. The ASK demodulator was implemented in 3-mu m low-temperature polycrystalline silicon (LTPS) thin-film transistor (TFT) technology. Since the threshold voltages of UPS TFTs are higher than CMOS transistors, the conventional demodulator implementation will degrade the demodulator sensitivity significantly. The novel full-wave demodulator circuit was proposed to resolve the issue of high threshold voltage and reduce the ripples of the demodulated envelope. Operated at 8 V, the demodulator consumes 1.6 mW of power. The input carrier frequency was tested up to 13.56 MHz, and the highest ASK modulated data rate is 100 kb/s. The circuit size of the UPS TFT demodulator is 500 mu m x 450 mu m.