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Vyas R, Li S, Ghannouchi F. 2019. Using 2.4 GHz load-side voltage standing waves to passively boost RF-DC voltage conversion in RF rectifier. Wireless Power Transfer 6(2): 113-125 doi: 10.1017/wpt.2019.12 
Using 2.4 GHz load-side voltage standing waves to passively boost RF-DC voltage conversion in RF rectifier
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Author Bio:
Rushi Vyas received his B.Sc., M.Sc., and Ph.D. degrees in electrical and computer engineering from the Georgia Institute of Technology, Atlanta, GA, USA. He is currently an Assistant Professor in the Schulich School of Engineering, and a Researcher with the Pipeline Engineering Center (PEC), University of Calgary, Calgary, AB, Canada. His work has been covered in over 27 research publications in peer-reviewed journals and conference proceedings, and three book chapters covering topics in ambient RF -energy harvesting, inkjet-printed electronics, wireless gas and structural-health sensors, and real-time-localization systems (RTLS). Prior to joining academia, he worked on cellular radios at Apple Inc. and Blackberry. Prof. Vyas has received finalist and honorable-mention awards at the 2008 and 2012 IEEE International Microwave Symposia and the 2008 and 2009 IEEE Antennas and Propagation Society International Symposia (APS). His work on RF-energy harvesting and battery-less sensors has also been covered in media forums such as MSN News, Engadget, IEEE Institute, Energy Harvesting Journal, and New Energy and Fuel. 
Fadhel Ghannouchi (S'84-M'88-SM'93-F'07) is currently a Professor, an Alberta Innovates/Canada Research Chair, and the Founding Director of the iRadio Laboratory, Department of Electrical and Computer Engineering, University of Calgary, Calgary, AB, Canada. He has held several invited positions with several academic and research institutions in Europe, North America, and Japan. He has provided consulting services to many microwave and wireless communication companies. He has authored or co-authored over 650 publications and holds 16 U.S. patents with four pending. His current research interests include microwave instrumentation and measurements, non-linear modeling of microwave devices and communications systems, design of power- and spectrum-efficient microwave amplification systems, and design of intelligent RF transceivers for wireless and satellite communications - Corresponding author: Rushi Vyas, E-mail: rushi.vyas@ucalgary.ca
Abstract: A novel, dual-band, voltage-multiplying (RF-DC) rectifier circuit with load-tuned stages resulting in a 50 Ω input-impedance and high RF-DC conversion in 2.4 and 5.8 GHz bands for wireless energy-harvesting is presented. Its novelty is in the use of optimal-length transmission lines on the load side of the 4 half-wave rectifying stages within the two-stage voltage multiplier topology. Doing so boosts the rectifier's output voltage due to an induced standing-wave peak at each diode's input, and gives the rectifier a 50 Ω input-impedance without an external-matching-network in the 2.4 GHz band. Comparisons with other rectifiers show the proposed design achieving a higher DC output and better immunity to changing output loads for similar input power levels and load conditions. The second novelty of this rectifier is a tuned secondary feed that connects the rectifier's input to its second stage to give dual-band performance in the 5.8 GHz band. By tuning this feed such that the second stage and first stage reactances cancel, return-loss resonance in the 5.8 GHz band is achieved in addition to 2.4 GHz. Simulations and measurements of the design show RF-DC sensitivity of −7.2 and −3.7 dBm for 1.8V DC output, and better than 10 dB return-loss, in 2.4 and 5.8 GHz bands without requiring an external-matching-network.
