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-[micro]m low-temperature polycrystalline silicon (LTPS) thin-film transistor (TFT) technology. Since the threshold voltages of LTPS 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 LTPS TFT demodulator is 500 [micro]m x 450 [micro]m. Index Terms--Demodulator, low-temperature polycrystalline silicon (LTPS), RF identification (RFID), system on panel (SOP), transponder.