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1. A New Coupling Insensitive Nonlinear Capacitive Resonant Wireless Power Transfer Circuit

   https://doi.org/10.1109/WPTC51349.2021.9458093  

   Chai, Ruiying; Mortazawi, Amir (January 2021, 2021 IEEE Wireless Power Transfer Conference (WPTC))

   This paper presents a nonlinear capacitive WPT system that automatically compensate for the coupling variation between the transmitter and receiver in a capacitive wireless power transfer (WPT) system with no active circuitry. The system is capable of minimizing the output power variation at a fixed operating frequency of13 MHz as the coupling distance varies. A constant output power is achieved over a wide range of coupling capacitance variation in comparison to the conventional capacitive wireless power transmission circuits. Such an approach is attractive for biomedical implants employing a capacitive WPT system. 

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2. A New Coupling Insensitive Nonlinear Capacitive Resonant Wireless Power Transfer Circuit

   Ruiying Chai; Amir Mortazawi (January 2021, 2021 IEEE Wireless Power Transfer Conference (WPTC))

   This paper presents a nonlinear capacitive WPT system that automatically compensate for the coupling variation between the transmitter and receiver in a capacitive wireless power transfer (WPT) system with no active circuitry. The system is capable of minimizing the output power variation at a fixed operating frequency of13 MHz as the coupling distance varies. A constant output power is achieved over a wide range of coupling capacitance variation in comparison to the conventional capacitive wireless power transmission circuits. Such an approach is attractive for biomedical implants employing a capacitive WPT system. 

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3. A Coupling Factor Independent Wireless Power Transfer System Employing Two Nonlinear Circuits

   Ruiying Chai, Amir Mortazawi (June 2020, IEEE MTTS International Microwave Symposium digest)

   null (Ed.)

   Conventional linear resonant wireless power trnnsfer (WPT) systems suffe1· from a significant pe1•formance degrndation as the coupling factor between the translnit and receive coils varies. In this paper, the performance of a new WPT circuit that takes the advantage of nonlinear resonant circuit is investigated. It employs passive nonlinear resonators in both the trnnslnitter and receiver sides to regulate the output power without using any active or control circuitry, frequency tuning or complicated coil configurntions. A 60 W nonlinear WPT prototype circuit working at 1.5 MHz is designed, fab1icated and compared with a silnilal'ly designed linear \VPT circuit. The nonlinem· \VPT circuit is capable of maintaining almost a constant output power while the distance between the coils changes from 6 cm to 15 cm, a significant performance improvement as compared to the linear WPT circuit tested under the same conditions. 

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4. Design, Modeling, and Analysis of Inductive Resonant Coupling Wireless Power Transfer for Micro Aerial Vehicles (MAVs)

   https://doi.org/10.1109/ICRA.2018.8461162  

   Plaizier, Gregory M.; Andersen, Erik; Truong, Binh; He, Xiang; Roundy, Shad; Leang, Kam K. (May 2018, 2018 IEEE International Conference on Robotics and Automation (ICRA))

   This paper presents the design, modeling, analysis, and experimental validation of an inductive resonant wireless power transfer (WPT) system to power a micro aerial vehicle (MAV). Using WPT, in general, enables longer flight times, virtually eliminates the need for batteries, and minimizes down time for recharging or replacing batteries. The proposed WPT system consists of a transmit coil, which can either be fixed to ground or placed on a mobile platform, and a receive coil carried by the MAV. The details of the WPT circuit design are presented. A power-transfer model is developed for the two-coil system, where the model is used to select suitable coil geometries to maximize the power received by the MAV for hovering. Analysis, simulation, and experimental results are presented to demonstrate the effectiveness of the WPT circuitry. Finally, a wirelessly powered MAV that hovers above the transmit coil is demonstrated in a laboratory setting. 

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5. Enabling Magnetic Beamforming in MIMO Wireless Power Transfer Using Reconfigurable Metasurface

   https://doi.org/10.1109/GLOBECOM42002.2020.9322096  

   Li, Zhangyu; Sun, Zhi (December 2020, IEEE Globecom 2020)

   null (Ed.)

   Wireless power transfer (WPT) has been widely used in IoT applications, such as mobile device charging, biomedical implants communication, and RFID field. Maximizing the power transfer efficiency (PTE) becomes one of the most crucial problems for designing the WPT systems. Magnetic induction (MI) beamforming has been proposed recently to maximize the PTE for the near field MIMO WPT systems. However, conventional magnetic beamforming in WPT systems usually requires accurate magnetic channel estimation, both amplitude and phase control of the charging source, which can not be achieved in an extreme environment. In this paper, we propose a novel magnetic induction beamforming scheme in MIMO WPT system using a reconfigurable metasurface. Instead of controlling the source currents or voltages, the reconfigurable metasurface can achieve near field beamforming only by varying the capacitor and resistance in specific coil array units. The beamforming is modeled as a discrete optimization problem and solved by using the Simulate Anneal (SA) method. Through the analytical and COMSOL simulation results, our proposed beamforming scheme can achieve approximately two times PTE of the conventional beamforming method in a 40 cm charging distance. 

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