Threshold voltage compensation scheme for RF-to-DC converter used in RFID applications

A threshold voltage (V_th) compensation scheme is proposed. In this scheme, the bias voltage required to compensate the V_th has been acquired from the input radio-frequency (RF) signal voltage and the output DC voltage. The proposed rectifier and the self V_th-cancellation (SVC)-based rectifier have been designed and fabricated in a standard 0.18 μm CMOS technology. Measurements have been performed for various resistive loads at the ISM 433 MHz frequency. The maximum PCE value achieved by the proposed rectifier is 30% at an input RF power level of -5 dBm whereas the maximum PCE achieved by the SVC is 22% at -9 dBm. These PCEs have been measured at a load resistance of value of 10 kΩ.