Alexander Choo

This paper presents a cross-coupled CMOS rectifier for ambient RF energy harvesting, which utilizes an advanced topology amalgamation technique to significantly improve the rectifier’s power conversion efficiency (PCE) and power dynamic range (PDR), also known as the high-PCE range. Our novel technique involves adaptively self-biasing the rectifying PMOS in the last stage of the proposed rectifier, which deactivates the cross-coupled counterpart and enables the subsequent diode-based rectifier circuitry to operate efficiently during high-power operation and extends the high-PCE range by mitigating the leakage current. Fabricated in a 65-nm CMOS process, our proposed rectifier scores a wide PDR of 21 dB at 900 MHz and 15 dB at 1.8 GHz with a peak PCE of 79.77% and 51.3%, respectively, under a 100-kΩ load. Moreover, we perform a Monte Carlo simulation to showcase the impact of transistor variations. Our proposed rectifier, which offers the widest PDR compared to recently-reported designs operating at a similar frequency, is highly adaptable to the varying RF environment, enabling efficient and reliable energy harvesting for Internet of Things devices.

This brief reports a dual-topology CMOS rectifier with an extended power dynamic range (PDR) for radio frequency (RF)-based hybrid energy harvesting (RF-HEH) systems. By leveraging both the cross-coupled differential drive (CCDD) and the Dickson topologies with high forward conduction and low reverse leakage, we obtain an extension of the rectifier’s PDR by adaptively disabling the CCDD counterpart and enabling the Dickson counterpart to dominate the rectifier’s performance during high-power operation. Apart from that, we formulate a rectifier-performance index (RPI), which accounts for the power conversion efficiency (PCE), the PDR, the sensitivity, and the load resistance of the rectifier to provide an adequate performance benchmark with the state-of-the-art rectifiers. Fabricated in a 130-nm CMOS, the proposed dual-topology rectifier measures a wide PDR of 19.5 dB with a peak PCE of 78.4% for a 100-k $\Omega $ load operating at 900 MHz. Besides, our prototype records the highest RPI of 19.2 compared to the recent arts operating at GSM900.

The increasing demand for wireless Internet of Things (IoT) calls for power efficient RF energy harvesting approach. The current dominant single-band RF energy harvesting front-end system restricts itself to a single frequency, which is at the risk of ineffective operation when the harvesting frequency is unavailable. This paper reviews and explores the alternative approach of a multiband RF energy-harvesting front-end system. It covers all essential circuitry of a multiband RF energy harvesting front-end system, starting from the recent RF surveys which investigate the typical, usable, and high-strength RF input, to the overview of the state-of-the-art antenna, impedance matching network (IMN), and RF-DC rectifier. The recent advancement of the multiple RF input harvesting abilities, reflection loss minimization, and performance improvement are comprehensively reviewed for different operating conditions, and this review also presents the advantages and disadvantages of the different circuit architecture combinations for multiband RF energy harvesting front-end systems. In summary, this review aims to fill the research gap in the further advancement of multiband RF energy harvesting towards enhancing its performance through optimal circuit integration of the front-end system.

This brief presents a novel circuit architecture for a Dickson-based reconfigurable rectifier with wide power dynamic range (PDR). Besides, a novel figure of merit (FoM) concerning the reconfigurable rectifiers is formulated to provide a more comprehensive assessment of the rectifier’s performance. The proposed reconfigurable design improves the operating range of the rectifier by adaptively switching between the six-stage configuration during low-power operation and the 12-stage configuration during high-power operation. Fabricated in 130-nm CMOS, the proposed reconfigurable rectifier measures a PDR of 14 dB with a peak power conversion efficiency (PCE) of 34.93% for 1- $\text{M}\Omega $ load operating at 900 MHz. Relative to the recently published reconfigurable rectifiers, our design records the highest FoM of 36.98 dB/mm2, with minimum harvesting downtime.

This article investigates the latest research outcomes on the wide power dynamic range (PDR) CMOS RF-DC rectifier for on-chip radio frequency energy harvesting (RFEH) system as a viable approach to extend the high power conversion efficiency (PCE) operating range which is limited by the varying nature of the available far-field RF power. The significance of enhancing the rectifier’s PDR is that it offers a more reliable operation of RFEH in real-life applications. Therefore, this review seeks to navigate the research and development focus of the RFEH system towards extending the PDR of the CMOS RF-DC rectifier by providing analysis of the effect of state-of-the-art PDR extension techniques and their design tradeoffs. The review encapsulates the transmission of the RF power, a brief overview of the RFEH front-end circuit, and a comprehensive review of the CMOS rectifier design focusing on PDR. At the end of this article, we discuss the future design aspects to address the limitation of the RFEH system. Recent research shows that extending the rectifier’s PDR will enhance the overall performance of the RFEH system.