Low power RF rectifiers based on class-E/F2 architecture for energy harvesting applications

Abstract

This article introduces a new low-power Class-E/F₂ shunt rectifier and voltage doubler (VD) for energy harvesting (EH) applications, employing RO4003C substrate. These circuits achieve high efficiency and produce a substantial DC voltage. The proposed designs are suitable for LTE, IoT, WSN, GSM 900, and low-power EH systems. The innovative designs are depending on a Class-E/F₂ circuit structure, which combines Class-E and inverse Class-F configurations with a second harmonic resonance circuit. This configuration effectively eliminates the second harmonic current component by employing a $\lambda /8$ transmission line (TL) linked to the anode terminal of the diode. At low values of input power ($P_{in}$), the voltage and efficiency-boosting are achieved by designing two coupling transmission lines (CTLs). The proposed rectifier and voltage doubler circuits include a DC-pass filter designed to eliminate high-frequency components. The rectifier and VD circuits are manufactured using the HSMS-285x series Schottky diodes. When a radio input power ($P_{in}$) is equal to −10 dBm, the rectifier and VD circuits demonstrate experimental conversion efficiencies larger than 40 %. The DC voltage is 0.6 V at both 650 MHz and 900 MHz, with terminal resistances ($R_L$) of 4.3 kΩ and 8 kΩ for rectifier and VD, respectively. The rectifier design achieves a maximum measured efficiency equal to 50 %, maintaining a constant DC-voltage equal to 1.7 V at$R_L$ = 4.3 kΩ and 900 MHz. Additionally, the proposed VD demonstrates a peak experimental efficiency equal to 57 %, with a constant DC-voltage equal to 3.2 V at $P_{in}=0dBm$ and $R_L=8K\Omega$, operating in two bands of 650 MHz and 900 MHz. It also achieves a measured efficiency equal to 45 % at $P_{in}=-10dBm$. Finally, the PCB sizes of the suggested rectifier and VD are 3 cm² and 3.37 cm², respectively.