Advanced Perspectives on Metamaterial Integration in Wireless Power Transfer: A Review
DOI:
https://doi.org/10.13052/2025.ACES.J.400308Keywords:
Inductive power transfer, metamaterials (MTMs), power transfer efficiency (PTE), wireless power transfer (WPT)Abstract
The field of wireless power transfer (WPT) has recently seen much innovation and improvement and, as a result, there is an ever-increasing need for high power transfer efficiency (PTE) of the WPT systems, as well as enhanced transmission distance for end users. However, some of the currently available WPT systems have a restricted PTE and transfer distance because they use an inductive coupling technique. With this method, the PTE suffers a significant drop as the distance between the transmitter and receiver coils grows. Alternately, magnetic resonance coupling (MRC) is employed as a mid-range WPT solution. For this method, metamaterials (MTMs) are used to increase efficiency by inserting them between the transmitter (Tx) and receiver (Rx) coils. MTMs are artificially manufactured materials that demonstrate unusual electromagnetic properties. These traits include evanescent wave amplification and negative refractive characteristics, both of which have the potential to be employed for the improvement of PTE. This paper offers an in-depth summary of recent research and development in MTM-based WPT systems. In this overview, we examine previously reported MTM-based WPT systems across a range of characteristics, including configuration, operating frequency, size, and PTE. A comparative of the various MTM-based WPT systems is also provided in this paper. PTEs for these systems were also presented against their normalized transfer distances. This study was conducted with the intention of providing a resource for academics studying WPT systems and their practical implementations. This analysis exposes the developments occurring in MTM-based WPT systems.
Downloads
References
S. K. Singh, T. S. Hasarmani, and R. M. Holmukhe, “Wireless transmission of electrical power: Overview of recent research & development,” International Journal of Computer and Electrical Engineering, vol. 4, no. 2, pp. 207-211, 2012.
Qi and Magsafe [Online]. Available: appleinsider.com/articles/21/01/01/qi-and-magsafe—everything-an-iphone-user-needs-to-know-about-wireless-charging
A. Kurs, R. Moffatt, and M. Soljačić, “Simultaneous mid-range power transfer to multiple devices,” Appl. Phys. Lett., vol. 96, no. 4, pp. 2009-2011, 2010.
E. Baghdadi and J. Van Mierlo, “Study of wireless power transfer for electric vehicles,” in Proceedings of the 2018 19th IEEE Mediterranean Electrotechnical Conference (MELECON), Marrakesh, Morocco, pp. 1-6, 2018.
G. Yı
lmaz and C. Dehollain, Wireless Power Transfer, 4th ed. Amsterdam: Elsevier, 2017.
S. Maslovski, S. Tretyakov, and P. Alitalo, “Near-field enhancement and imaging in double planar polariton-resonant structures,” J. Appl. Phys., vol. 96, no. 3, pp. 1293-1300, 2004.
Z. Chen, B. Guo, Y. Yang, and C. Cheng, “Metamaterials-based enhanced energy harvesting: A review,” Phys. B Condens. Matter, vol. 438, pp. 1-8, 2014.
K. Sun, S. V. Georgakopoulos, and M. P. Nikdast, “An overview of metamaterials and their achievements in wireless power transfer,” Journal of Materials Chemistry C, vol. 6, no. 12, pp. 2925-2943, 2018.
B. Wang, W. Yerazunis, and K. H. Teo, “Wireless power transfer: Metamaterials and array of coupled resonators,” Proc. IEEE, vol. 101, no. 6, pp. 1359-1368, 2013.
C. Yee Yong and K. Fen Chen, “Wireless power transfer technology using resonant technique,” IOP Conf. Ser. Earth Environ. Sci., vol. 268, no. 1, 2019.
D. Stepins, J. Zakis, P. Padmanaban, and D. Deveshkumar Shah, “Suppression of radiated emissions from inductive-resonant wireless power transfer systems by using spread-spectrum technique,” Electron., vol. 11, no. 5, 2022.
B. Esmaeili Jamakani, A. Mosallanejad, E. Afjei, and A. Lahooti Eshkevari, “Investigation of triple quadrature pad for wireless power transfer system of electric vehicles,” IET Electr. Syst. Transp., vol. 11, no. 1, pp. 58-68, 2021.
I. Alhamrouni, M. Iskandar, M. Salem, L. J. Awalin, A. Jusoh, and T. Sutikno, “Application of inductive coupling for wireless power transfer,” Int. J. Power Electron. Drive Syst., vol. 11, no. 3, pp. 1109-1116, 2020.
K. N. Mude, S. S. Williamson, and S. K. Panda, “Comprehensive review and analysis of two-element resonant compensation topologies for wireless inductive power transfer systems,” Chinese Journal of Electrical Engineering, vol. 5, no. 2, pp. 14-31, 2019.
O. D. Oyeleke, S. Thomas, P. Nzerem, and G. Koyunlu, “Design and construction of a prototype wireless power transfer device,” Int. J. Eng. Manuf., vol. 9, no. 2, pp. 16-30, 2019.
M. Carbajal-Retana, J. Hernández-González, and J. R. Rangel-Magdaleno, “Interleaved buck converter for inductive wireless power transfer in DC-DC converters,” Electronics, vol. 9, no. 6, pp. 1-15, 2020.
A. Mahesh, B. Chokkalingam, and L. Mihet-Popa, “Inductive wireless power transfer charging for electric vehicles-A review,” IEEE Access, vol. 9, pp. 137667-137713, 2021.
P. H. Chen, C. Li, Z. Dong, and M. Priestley, “Inductive power transfer battery charger with IR-based closed-loop control,” Energies, vol. 15, no. 21, 2022.
A. Ragab, M. I. Marei, M. Mokhtar, and A. Abdelsattar, “Design and performance evaluation of a PV interface system based on inductive power transfer,” Int. J. Power Electron. Drive Syst., vol. 12, no. 1, pp. 364-373, 2021.
V. Shevchenko, M. Khomenko, I. Kondratenko, O. Husev, and B. Pakhaliuk, “Experimental comparison of designed inductance coils for wireless power transfer,” Electr. Control Commun. Eng., vol. 16, no. 2, pp. 102-109, 2020.
Electrice, “Actualităţi şi perspective în domeniul maşinilor electrice,” Actualităţi şi Perspective în Domeniul Maşinilor Electrice, pp. 66-75, 2005.
M. H. Misran, M. A. M. Said, M. A. Othman, R. A. Manap, S. Suhaimi, and N. I. Hassan, “A systematic optimization procedure of antenna miniaturization for efficient wireless energy transfer,” International Journal of Electrical and Computer Engineering (IJECE), vol. 9, no. 4, pp. 3159-3166, Aug. 2019.
Y. Yamada, T. Imura, and Y. Hori, “Theorizing a simple ferrite cored coil using image coils in wireless power transfer,” IEEE Access, vol. 11, pp. 8065-8072, 2023.
A. F. Abdul Aziz, M. F. Romlie, and Z. Baharudin, “Review of inductively coupled power transfer for electric vehicle charging,” IET Power Electron., vol. 12, no. 14, 2019.
M. Rehman, P. Nallagownden, and Z. Baharudin, “Efficiency investigation of SS and SP compensation topologies for wireless power transfer,” Int. J. Power Electron. Drive Syst., vol. 10, no. 4, pp. 2157-2164, 2019.
N. T. Diep, N. K. Trung, and T. T. Minh, “Wireless power transfer system design for electric vehicle dynamic charging application,” Int. J. Power Electron. Drive Syst., vol. 11, no. 3, pp. 1468-1480, 2020.
J. Lee, M. Y. Kim, and S. H. Lee, “Novel transformerless multilevel inductive power transfer system,” IEEE Access, vol. 10, pp. 55565-55573, 2022.
Q. T. Vo, Q. T. Duong, and M. Okada, “Load-independent voltage control for multiple-receiver inductive power transfer systems,” IEEE Access, vol. 7, pp. 139450-139461, 2019.
D. M. Roberts, A. P. Clements, R. McDonald, J. S. Bobowski, and T. Johnson, “Mid-range wireless power transfer at 100 MHz using magnetically coupled loop-gap resonators,” IEEE Trans. Microw. Theory Tech., vol. 69, no. 7, pp. 3510-3527, 2021.
J. N. Wandinger, D. M. Roberts, J. S. Bobowski, and T. Johnson, “Inductive power transfer through saltwater,” in 2021 13th Int. Conf. Electromagn. Wave Interact. with Water Moist Subst. ISEMA, vol. 2, no. 4, 2021.
C. Y. Liu, G. Bin Wang, C. C. Wu, E. Y. Chang, S. Cheng, and W. H. Chieng, “Derivation of the resonance mechanism for wireless power transfer using class-e amplifier,” Energies, vol. 14, no. 3, 2021.
B. A. Rayan, U. Subramaniam, and S. Balamurugan, “Wireless power transfer in electric vehicles: A review on compensation topologies, coil structures, and safety aspects,” Energies, vol. 16, no. 7, 2023.
Z. Despotovic, D. Reljic, V. Vasic, and D. Oros, “Steady-state multiple parameters estimation of the inductive power transfer system,” IEEE Access, vol. 10, pp. 46878-46894, 2022.
H. Sadeghi Gougheri and M. Kiani, “An inductive voltage-/current-mode integrated power management with seamless mode transition and energy recycling,” IEEE Journal of Solid-State Circuits, vol. 54, no. 3, pp. 874-884, Mar. 2019.
C. Rong, W. Li, Z. Zhou, C. Zhu, and Z. Deng, “A critical review of metamaterial in wireless power transfer system,” IET Power Electronics, vol. 14, no. 9, pp. 1541-1559, 2021.
R. Jyosthna, R. A. Sunny, A. A. Jugale, and M. R. Ahmed, “Microstrip patch antenna design for space applications,” in Proceedings of the 2020 International Conference on Communication and Signal Processing (ICCSP), Chennai, India, pp. 406-410, 2020.
M. H. Misran, M. A. M. Said, M. A. Othman, R. Abd Manap, S. Suhaimi, and N. I. Hassan, “DGS based CP antenna for 5G communication with harmonic,” International Journal of Integrated Engineering, vol. 16, no. 1, pp. 301-311, 2024.
D. Ahn and S. Hong, “A study on magnetic field repeater in wireless power transfer,” IEEE Trans. Ind. Electron., vol. 60, no. 1, pp. 360-371, 2013.
M. Liu, M. Fu, Y. Wang, and C. Ma, “Battery cell equalization via megahertz multiple-receiver wireless power transfer,” IEEE Trans. Power Electron., vol. 33, no. 5, pp. 4135-4144, 2018.
Z. Dong, S. Liu, X. Li, Z. Xu, and L. Yang, “A novel long-distance wireless power transfer system with constant current output based on domino-resonator,” IEEE J. Emerg. Sel. Top. Power Electron., vol. 9, no. 2, pp. 2343-2355, 2021.
W. X. Zhong, C. K. Lee, and S. Y. R. Hui, “Wireless power domino-resonator systems with noncoaxial axes and circular structures,” IEEE Trans. Power Electron., vol. 27, no. 11, pp. 4750-4762, 2012.
C. Cheng, Z. Zhou, W. Li, C. Zhu, and Z. Deng, “A multi-load wireless power transfer system with series-parallel-series compensation,” IEEE Transactions on Power Electronics, vol. 34, no. 8, pp. 7126-7130, 2019.
Y. H. Kim, S. Y. Kang, S. Cheon, M. L. Lee, J. M. Lee, and T. Zyung, “Optimization of wireless power transmission through resonant coupling,” in SPEEDAM 2010 Int. Symp. Power Electron. Electr. Drives, Autom. Motion, pp. 1069-1073, 2010.
Q. Ke, W. Luo, G. Yan, and K. Yang, “Analytical model and optimized design of power transmitting coil for inductively coupled endoscope robot,” IEEE Trans. Biomed. Eng., vol. 63, no. 4, pp. 694-706, 2016.
A. L. F. Stein, P. A. Kyaw, and C. R. Sullivan, “Wireless power transfer utilizing a high-Q self-resonant structure,” IEEE Trans. Power Electron., vol. 34, no. 7, pp. 6722-6735, 2019.
J. O. Mur-Miranda, J. H. Lang, K. A. Gilhousen, and J. P. Florance, “Wireless power transfer using weakly coupled magnetostatic resonators,” in Proceedings of the 2010 IEEE Energy Conversion Congress and Exposition (ECCE), pp. 4179-4186, 2010.
J. H. Park, B. C. Park, J. H. Lee, Y. H. Ryu, E. S. Park, and S. W. Kwon, “Optimum frequency of high Q-factor resonator for magnetic resonance coupling,” in Proceedings of the 41st European Microwave Conference (EuMC), pp. 61-63, 2011.
Y. Kawamura and M. Shoyama, “Wireless power transmission using LC cancellation,” in 2013 IEEE ECCE Asia Downunder 5th IEEE Annu. Int. Energy Convers. Congr. Exhib. IEEE ECCE Asia 2013, pp. 1041-1045, 2013.
K. Tashiro, H. Wakiwaka, S. I. Inoue, and Y. Uchiyama, “Energy harvesting of magnetic power-line noise,” IEEE Trans. Magn., vol. 47, no. 10, pp. 4441-4444, 2011.
B. H. Soong, Y. L. Sum, W. Liu, and S. Ramachandran, “Characterizing wire wound inductor coils for optimized wireless power transfer,” in IEEE/ASME Int. Conf. Adv. Intell. Mechatronics (AIM), pp. 469-474, 2009.
M. Takato, T. Yamada, T. Nishikawa, and K. Saito, “Multilayer ceramic coil for wireless power transfer system by photo resist film process,” in Proceedings of the 2014 International Conference on Electronics Packaging (ICEP), pp. 326-331, 2014.
N. S. Artan, R. C. Patel, C. Ning, and H. J. Chao, “High-efficiency wireless power delivery for medical implants using hybrid coils,” in Proc. Annu. Int. Conf. IEEE Eng. Med. Biol. Soc. (EMBS), no. 3, pp. 1683-1686, 2012.
C. Zhu, K. Liu, C. Yu, R. Ma, and H. Cheng, “Simulation and experimental analysis on wireless energy transfer based on magnetic resonances,” in 2008 IEEE Veh. Power Propuls. Conf. (VPPC) 2008, pp. 18-21, 2008.
S. A. Chowdhury, S. Kim, S. Kim, J. Moon, I. Cho, and D. Ahn, “Automatic tuning resonant capacitor to fix the bidirectional detuning with ZVS in wireless power transfer,” IEEE Transactions on Industrial Electronics, vol. 71, no. 6, pp. 5683-5692, June 2024.
G. Giovannetti and D. De Marchi, “Capacitors quality effect in magnetic resonance radiofrequency coils,” J. Med. Biol. Eng., vol. 37, pp. 639-643, 2017.
M. I. A. Abdel Maksoud, R. A. Fahim, A. E. Shalan, M. A. Abd Elkodous, M. A. Olojede, M. M. Allam, and H. O. M. Ibrahim, “Advanced materials and technologies for supercapacitors used in energy conversion and storage: A review,” Environmental Chemistry Letters, vol. 19, pp. 375-439, 2021.
A. Boardman, “Pioneers in metamaterials: John Pendry and Victor Veselago,” Journal of Optics, vol. 13, no. 2, p. 020401, 2010.
K. Sun, J. Wang, Y. Ma, Z. Wu, and Y. Zhang, “Random copper/yttrium iron garnet composites with tunable negative electromagnetic parameters prepared by in situ synthesis,” RSC Advances, vol. 5, no. 75, pp. 61155-61160, 2015.
N. Engheta and R. W. Ziolkowski, “A positive future for double-negative metamaterials,” IEEE Trans. Microw. Theory Tech., vol. 53, no. 4 II, pp. 1535-1555, 2005.
J. Shin, A. Akyurtlu, M. Deshpande, and R. W. Ziolkowski, “Comments on ‘design, fabrication, and testing of double negative metamaterials’,” IEEE Trans. Antennas Propag., vol. 53, no. 2, pp. 891-892, 2005.
S. White, “The transmission of electrical energy without wires as a means for furthering peace,” Electrical World and Engineer, Mar. 5, 1904.
A. A. Eteng, S. K. A. Rahim, C. Y. Leow, S. Jayaprakasam, and B. W. Chew, “Low-power near-field magnetic wireless energy transfer links: A review of architectures and design approaches,” Renew. Sustain. Energy Rev., vol. 77, pp. 486-505, Apr. 2017.
W. Li, P. Wang, C. Yao, Y. Zhang, and H. Tang, “Experimental investigation of 1D, 2D, and 3D metamaterials for efficiency enhancement in a 6.78MHz wireless power transfer system,” in 2016 IEEE Wirel. Power Transf. Conf. (WPTC) 2016, pp. 19-22, 2016.
M. S. Yusri, M. H. Misran, N. Yusop, M. A. M. Said, M. A. Othman, and S. Suhaimi, “Transfer efficiency enhancement on wireless power transfer using metamaterial,” in 2023 International Conference on Information Technology (ICIT), Amman, Jordan, pp. 724-729, 2023.
J. Park, Y. Tak, Y. Kim, Y. Kim, and S. Nam, “Investigation of adaptive matching methods for near-field wireless power transfer,” IEEE Trans. Antennas Propag., vol. 59, no. 5, pp. 1769-1773, 2011.
T. C. Beh, M. Kato, T. Imura, S. Oh, and Y. Hori, “Automated impedance matching system for robust wireless power transfer via magnetic resonance coupling,” IEEE Trans. Ind. Electron., vol. 60, no. 9, pp. 3689-3698, 2013.
F. Zhang, S. A. Hackworth, W. Fu, C. Li, Z. Mao, and M. Sun, “Relay effect of wireless power transfer using strongly coupled magnetic resonances,” IEEE Trans. Magn., vol. 47, no. 5, pp. 1478-1481, 2011.
A. K. Singh, M. P. Abegaonkar, and S. K. Koul, “High-gain and high-aperture-efficiency cavity resonator antenna using metamaterial superstrate,” IEEE Antennas Wirel. Propag. Lett., vol. 16, pp. 2388-2391, 2017.
N. Rajak, N. Chattoraj, and R. Mark, “Metamaterial cell inspired high gain multiband antenna for wireless applications,” AEU Int. J. Electron. Commun., vol. 109, pp. 23-30, 2019.
G. Varamini, A. Keshtkar, N. Daryasafar, and M. Naser-Moghadasi, “Microstrip Sierpinski fractal carpet for slot antenna with metamaterial loads for dual-band wireless application,” AEU Int. J. Electron. Commun., vol. 84, pp. 93-99, Oct. 2018.
B. Wang, T. Nishino, and K. H. Teo, “Wireless power transmission efficiency enhancement with metamaterials,” in 2010 IEEE Int. Conf. Wirel. Inf. Technol. Syst. (ICWITS 2010), no. 1, pp. 2-5,2010.
J. Liu, Z. Gong, S. Yang, H. Sun, and J. Zhou, “Practical model for metamaterials in wireless power transfer systems,” Appl. Sci., vol. 10, p. 8506, 2020.
W. Lee and Y.-K. Yoon, “Wireless power transfer systems using metamaterials: A review,” IEEE Access, vol. 8, pp. 147930-147947, 2020.
W. Li, F. Yu, X. Rong, and H. Qin, “Optimization of low-frequency magnetic metamaterials for efficiency improvement in magnetically coupled resonant wireless power transfer systems,” IEEE Access, vol. 10, pp. 125445-125457,2022.
M. J. Chabalko, J. Besnoff, and D. S. Ricketts, “Magnetic field enhancement in wireless power with metamaterials and magnetic resonant couplers,” IEEE Antennas Wirel. Propag. Lett., vol. 15, pp. 452-455, 2016.
X. Wang, Y. Wang, Y. Hu, Y. He, and Z. Yan, “Analysis of wireless power transfer using superconducting metamaterials,” IEEE Trans. Appl. Supercond., vol. 29, no. 2, 2019.
D. R. Smith, D. Schurig, J. J. Mock, P. Kolinko, and P. Rye, “Partial focusing of radiation by a slab of indefinite media,” Appl. Phys. Lett., vol. 84, no. 13, pp. 2244-2246, 2004.
K. A. Cota, P. A. Gray, M. Pathmanathan, and P. W. Lehn, “An approach for selecting compensation capacitances in resonance-based EV wireless power transfer systems with switched capacitors,” IEEE Trans. Transp. Electrif., vol. 5, no. 4, pp. 1004-1014, 2019.
Y. Liu, U. K. Madawala, R. Mai, and Z. He, “Zero-phase-angle controlled bidirectional wireless EV charging systems for large coil misalignments,” IEEE Trans. Power Electron., vol. 35, no. 5, pp. 5343-5353, 2020.
K. Zhang, C. Liu, Z. H. Jiang, Y. Zhang, X. Liu, H. Guo, and X. Yang, “Near-field wireless power transfer to deep-tissue implants for biomedical applications,” IEEE Transactions on Antennas and Propagation, vol. 68, no. 2, pp. 1098-1106, 2020.
M. Song, K. Baryshnikova, A. Markvart, P. Belov, E. Nenasheva, C. Simovski, and P. Kapitanova, “Smart table based on a metasurface for wireless power transfer,” Physical Review Applied, vol. 11, no. 5, p. 054046, 2019.
A. L. A. K. Ranaweera, T. S. Pham, H. N. Bui, V. Ngo, and J. W. Lee, “An active metasurface for field-localizing wireless power transfer using dynamically reconfigurable cavities,” Sci. Rep., vol. 9, no. 1, pp. 1-12, 2019.
M. A. Badwey, N. H. Abbasy, and G. M. Eldallal, “An efficient design of LC-compensated hybrid wireless power transfer system for electric vehicle charging applications,” Alexandria Eng. J., vol. 61, no. 8, pp. 6565-6580, 2022.
S. Wang, C. Jiang, X. Tao, F. Chen, C. Rong, C. Lu, Y. Zeng, X. Liu, R. Liu, B. Wei, and M. Liu, “Enhancing the stability of medium range and misalignment wireless power transfer system by negative magnetic metamaterials,” Materials, vol. 13, 2020.
J. Wang, R. Chen, C. Cai, J. Zhang, and C. Wang, “An onboard magnetic integration-based WPT system for UAV misalignment-tolerant charging with constant current output,” IEEE Transactions on Transportation Electrification, vol. 9, pp. 1973-1984, 2023.
Z. Yuan, Q. Yang, X. Zhang, R. Wang, X. Ma, C. Cai, P. Zhang, and H. Lin, “A power-enhancing complementary coupling integration strategy for misalignment-tolerant WPT systems,” IEEE Transactions on Power Electronics, vol. 38, pp. 14689-14701, 2023.
B. Wang, K. H. Teo, T. Nishino, W. Yerazunis, J. Barnwell, and J. Zhang, “Experiments on wireless power transfer with metamaterials,” Appl. Phys. Lett., vol. 98, no. 25, pp. 1-4, 2011.
Y. Z. Cheng, J. Jin, W. L. Li, J. F. Chen, B. Wang, and R. Z. Gong, “Indefinite-permeability metamaterial lens with finite size for miniaturized wireless power transfer system,” AEU Int. J. Electron. Commun., vol. 70, no. 9, pp. 1282-1287, 2016.
Y. Cho, S. Lee, J. Lee, and J. Lee, “Hybrid metamaterial with zero and negative permeability to enhance efficiency in wireless power transfer system,” in Proceedings of the 2016 IEEE Wireless Power Transfer Conference (WPTC), Aveiro, Portugal, pp. 1-3, 2016.
W. Xin, C. C. Mi, F. He, M. Jiang, and D. Hua, “Investigation of negative permeability metamaterials for wireless power transfer,” AIP Adv., vol. 7, no. 11, 2017.
J. Chen and H. Tan, “Metamaterial for wireless power transfer system at 13.56 MHz with coil misalignment,” in Proc. 2017 7th IEEE Int. Symp. Microwave, Antenna, Propagation, EMC Technol. (MAPE 2017), pp. 313-317, 2017.
C. Lu, X. Huang, C. Rong, Z. Hu, J. Chen, X. Tao, S. Wang, B. Wei, and M. Liu, “Shielding the magnetic field of wireless power transfer system using zero-permeability metamaterial,” The Journal of Engineering, vol. 2019, no. 16, pp. 1812-1815, 2019.
A. L. A. K. Ranaweera, T. P. Duong, and J. W. Lee, “Experimental investigation of compact metamaterial for high efficiency mid-range wireless power transfer applications,” J. Appl. Phys., vol. 116, no. 4, 2014.
C. Rong, X. Tao, C. Lu, Z. Hu, X. Huang, Y. Zeng, and M. Liu, “Analysis and optimized design of metamaterials for mid-range wireless power transfer using a Class-E RF power amplifier,” Appl. Sci., vol. 9, no. 1, p. 26, 2018.
J. Chen, X. Liu, Y. Zhao, and Y. Sun, “Metamaterial-based high-efficiency wireless power transfer system at 13.56 MHz for low power applications,” Progress in Electromagnetics Research B, vol. 72, pp. 17-30, 2017.
T. Shaw, A. Roy, and D. Mitra, “Efficiency enhancement of wireless power transfer system using MNZ metamaterials,” Prog. Electromagn. Res. C, vol. 68, pp. 11-19, Aug. 2016.


