A Highly Integrated Design of Dual-band HF Band (13.56MHz) / UHF Band (915MHz) Rectifier for Wireless Power Transfer

In this study, we proposed a new design for a dual-band, four-stage complementary metal–oxide–semiconductor (CMOS) rectifier. A design concept based on coupling and radiation energy translation theory is employed to reuse the same rectifier circuits for both the HF band (13.56MHz) and the UHF band (915MHz) energy harvesting modes by re-configuring impedance matching between the DC and RF ports. To optimize the efficiency of the rectifier under low input voltage swing, we utilized an improved cross-coupled bridge configuration capable of boosting the input signal to improve the energy harvesting capability and driven by a differential RF input. A differential-drive active gate bias mechanism accomplishes both low ON resistance and small reverse leakage in MOS transistors with diode connections. To demonstrate the viability of the proposed design methodology, we designed a power-harvesting receiver with a dual-band, four-stage rectifier using a 0.18 um CMOS process. Within the UHF/HF frequencies, the input power range was -10 dBm to 8.5 dBm/3.5 mW, the maximum efficiency was 51.78%/40.15%, and the output DC voltage was measured at 2.85 V/2.52 V.