An AC-DC rectifier for RF energy harvesting system

This paper presents an AC-DC rectifier that can provide high output voltage and power conversion efficiency (PCE), especially in low RF input power. In order to maximize the output voltage and PCE, the key design parameters optimization of the charge pump is discussed. Besides, to reduce the threshold voltage, the conventional Schottky-diodes are replaced by diode-connected MOSFETs which utilize native transistors with ultra low threshold voltage. A 5-stage rectifier is simulated by using harmonic balance nonlinear circuit analysis and implemented in 0.18 μm 1P6M CMOS technology with 0.06 sq mm die size. Measurement results showed that if a 150 kΩ load resistance is parallel with the rectifier output, DC voltage can reach to 2.6 V and PCE reaches as high as 46.43 % with input power of -10 dBm at a frequency of 900 MHz so as to light up a 2.4 V light-emitting diode (LED) lamp.