A passive UHF RFID tag with a dynamic-V_th-cancellation rectifier

Abstract

This paper presents a passive UHF RFID tag with a dynamic-V th -cancellation (DVC) rectifier. In the rectifier, the threshold voltages of MOSFETs are cancelled by applying gate bias voltages, which are dynamically changed according to the states of the MOSFETs. The DVC rectifier enables both low ON-resistance and small reverse leakage of the MOSFETs, resulting in high power conversion efficiency (PCE). An area-efficient demodulator with a novel average detector is also designed, which takes advantage of the rectifier's first stage as the envelope detector. The whole tag chip is implemented in a 0.18 m CMOS process with a die size of 880 950 m 2 . Measurement results show that the rectifier achieves a maximum PCE of 53.7% with 80 k resistor load.

Flexible diodes for radio frequency (RF) electronics: a materials perspective

“…Furthermore, the V th in a transistor tends to be significantly higher than the on-voltage for a Schottky diode (typically < 0.5 V), thus leading to lower values of η rectifier when using transdiode transistors. Several efforts have been made to boost the latter by either lowering the V th [38] or by using self-V th cancellation techniques [39,40]. With these less ideal device characteristics, as compared to Schottky diodes, the question arises as to why one would employ transistors in DC rectifiers at all.…”