RF to DC CMOS rectifier with high efficiency over a wide input power range for RFID applications

Abstract

In this paper we present a RF-DC rectifier which operates over a wide range of input power by providing a regulated output DC voltage. The circuit solution we propose is based on a novel active load circuit which adjusts the output current as a function of the incoming RF power. This allows maximizing both the efficiency and sensitivity of the circuit. Circuit prototypes fabricated in 130nm CMOS technology start to operate at -14dBm, providing a regulated output voltage of 1.6÷1.8V in the -14÷1dBm RF input power at 868MHz. Noticeably, the circuit efficiency of the rectifier peaks at 45%, remaining above 30% in the -12÷+1dBm input power range

An Efficient RF Rectifier for Energy Harvesting Systems with Applications to Wireless Dosimetry

“…A third method of voltage regulation was introduced in [121]. This topology, depicted in Figure 3.13, is known as the Smart Voltage Regulator (SVR), and was designed specifically for semi-passive and active RFID systems which employ energy harvesting.…”

“…The SVR is placed in parallel to the output of a charge pump-based rectifier, such that the output node (denoted by V out ) represents both the output of the rectifier and the regulator. A reference voltage, V ref , meanwhile, is required for the SVR to function properly, and may be supplied by a bandgap voltage reference [121]. The SVR's voltage regulation mechanism stems from transistor MP2.…”

“…Since MP2 is operating in the saturation region, an increase in the effective voltage causes an increase in current flowing through the transistor (I sd2 ). Consequently, the output impedance of the right-hand circuit branch of the SVR (as seen by the rectifier) decreases, while the excess input power is stored in the buffer capacitor, C buf f er [121].…”

“…Unlike linear regulators, the SVR's power efficiency remains constant irrespective of the input power. This is due to the relatively constant power dissipation of MP2 [121].…”

“…However, like linear regulators, it also requires a bandgap voltage reference. Furthermore, its ability to regulate the output voltage is fairly limited [121].…”