(Received: 2016-12-29, Revised: 2017-03-08 , Accepted: 2017-04-02)
Rula Alrawashdeh,
Recently, the interest in wireless power transfer (WPT) has significantly increased due to its attractive applications. The power transfer efficiency and communication range of most of the existing WPT systems are still limited, which is due to many technical challenges and regulation limitations. This requires more research and technical efforts to overcome the current limitations and make WPT systems much more efficient and widely used. This paper aims at reviewing recent advances and research progress in the area of WPT for the purposes of addressing current challenges and future research directions. To obtain these purposes, an introduction to WPT is provided. Also, main research themes of WPT in free space and lossy media are discussed. Additionally, the benefits of using split ring resonators WPT in conducting lossy media are investigated. This will be very helpful to boost WPT in lossy media and inspire more optimized structures for further improvement.

[1] J. Zhang, Rectennas for RF Wireless Energy Harvesting, Ph.D. dissertation, Dept. Elect. Eng., University of Liverpool, Liverpool, UK, 2013.

[2], "Wireless Power Transfer,"[Online], Available:

[3], "Wireless Power Transfer,"[Online], Available: ttps://

[4] N. Shinohara, Wireless Power Transfer via Radiowaves, New Jersey: John Wiley & Sons, Inc., 2014.

[5] W. Hayt and J. Buck, Engineering Electromagnetics, USA, New York: McGraw-Hill, 2012. 

[6] H. Sugiyama, "Performance Analysis of Magnetic Resonant System Based on Electrical Circuit Theory," in: Tech., pp. 95-116, Jan. 2012.

[7] ICNIRP Guidelines for Limiting Exposure to Time-Varying Electric, Magnetic and Electromagnetic Fields (up to 300 GHz), Health Physics, vol. 74, no. 4, pp. 494‐522, 1998.

[8] M. A. Hassan and A. Elzawawi, "Wireless Power Transfer through Inductive Coupling," Proc. of 19th International Conference on Circuits (part of CSCC '15), pp.115-118, 2015.

[9] D. M. Pozar, Microwave Engineering, USA, New Jersey, John Wiley & Sons, Inc., 2015.

[10] M. Kesler, "Highly Resonant Wireless Power Transfer: Safe, Efficient and over Distance," Witricity Corporation-White Paper, pp. 1-13, 2017.

[11] X. Mou and H. Sun, "Wireless Power Transfer: Survey and Roadmap," Proc. of 81st Vehicular Technology Conference (VTC2015- Spring), pp. 1-13, 2015.

[12] M. Biswal, P. Sharma, N. Shete, S. Sokande and P. Tayade, "Study and Survey of Wireless Charging Technologies," International Journal of Advanced Research in Computer Engineering & Technology (IJARCET), vol. 5, no. 5, pp. 1450–1453, May 2016.

[13] L. M. M. Tan, Efficient Rectenna Design for Wireless Power Transmission for MAV Applications, Master thesis, Dept. Elect. and Computer Eng., Naval Postgraduate School, California, Dec. 2005.

[14] C-H. Hung, Design and Development of Wireless Power Transmission for Unmanned Air Vehicles, Master thesis, Dept. Elect. and Computer Eng., Naval Postgraduate School, California, Sep. 2012.

[15], "The Friis Equation,"[Online], Available: http://www.antenna-

[16] Y. Huang and K. Boyle, Antennas from Theory to Practice, UK, John Wiley & Sons, Ltd., 2008.

[17] R. Mehrotra, "Cut the Cord: Wireless Power Transfer, Its Applications and Its Limits," pp. 1-11. 2014,[Online], Available:,[Accessed: 5- May- 2014].

[18] M. K. Hosain et al., "Development of a Compact Rectenna for Wireless Powering of a Head-Mountable Deep Brain Stimulation Device," IEEE Journal of Translational Engineering in Health and Medicine, vol. 2, pp. 1-13, 2014.

[19] L. Summerer and O. Purcell, "Concepts for Wireless Energy Transmission via Laser,"[Online], Available: laser-WPT.pdf.

[20] A. W. Bett, F. Dimroth, R. Lockenhoff, E. Oliva and J. Schubert, "III–V Solar Cells under Monochromatic Illumination," Proc. of 33rd IEEE Photovoltaic Specialists Conference, pp. 1-5, 2008.

[21] A. Yakovlev, S. Kim and A. Poon, "Implantable Biomedical Devices: Wireless Powering and Communication," IEEE Communications Magazine, vol. 50, no. 4, pp. 152-159, April 2012.

[22] N. W. Bergmann, J. Juergens, L. Hou, Y. Wang and J. Trevathan, "Wireless Underwater Power and Data Transfer," Proc. of 38th Annual IEEE Conference on Local Computer Networks- Workshops, pp. 104-107, 2013.

[23] E. A. Karagianni, "Electromagnetic Waves under Sea: Bow-Tie Antenna Design for Wi-Fi Underwater Communications, " Progress in Electromagnetics Research M, vol. 41, pp. 189–198, 2015.

[24] W. Dargie and C. Poellabauer, Fundamentals of Wireless Sensor Networks: Theory and Practice, USA, New Jersey, John Wiley and Sons, Ltd., 2010.

[25] C. M. Nguyen et al., "Wireless Power Transfer for Autonomous Wearable Neurotransmitter Sensors,'' Sensors, vol. 15, no. 9, pp. 24553-24572, Sep. 2015, doi:10.3390/s150924553.

[26] F. Merli, Implantable Antennas for Biomedical Applications, Ph.D. dissertation, Dept. Elect. Eng., EPFL Univ., Lausanne, Switzerland, 2011.

[27] R. W. P. King and G. S. Smith, Antennas in Matter: Fundamentals, Theory and Applications, Cambridge, Mass: MIT Press, 1981.

[28], "Factors Affecting Inductance,"[Online], Available: 

[29] IEEE Standard for Safety Levels with Respect to Human Exposure to Radio Frequency Electromagnetic Fields, 3 kHz to 300 GHz, IEEE Standard C95.1-1999, 1999.

[30] IEEE Standard for Safety Levels with Respect to Human Exposure to Radio Frequency Electromagnetic Fields, 3 kHz to 300 GHz, IEEE Standard C95.1-2005, 2005.

[31] M. D. Basar, M. Ahmad, J. Cho and F. Ibrahim, "Application of Wireless Power Transmission Systems in Wireless Capsule Endoscopy: An Overview," Sensors, vol. 14, no. 6, pp. 10929–10951, Jun. 2014, doi: 10.3390/s140610929.

[32] M. Fareq, M. Fitra, M. Irwanto, S. Hasan and M. Arinal, "Low Wireless Power Transfer Using Inductive Coupling for Mobile Phone Charger," Journal of Physics: Conference Series 495, pp. 1-7, 2014, doi:10.1088/1742-6596/495/1/012019.

[33] K. A. Kalwar, M. Aamir and S. Mekhilef, "Inductively Coupled Power Transfer (ICPT) for Electric Vehicle Charging – A Review," Renew. and Sustainable Energy Reviews, vol. 47, pp. 462–475, 2015.

[34], "Resonant Inductive coupling," [Online], Available:

[35] C. Reinhold, P. Scholz, W. John and U. Hilleringmann, "Efficient Antenna Design of Inductive Coupled RFID-Systems with High Power Demand,'' Journal of Communications, vol. 2, no. 6, pp. 14- 23, Nov. 2007.

[36] Wirelesspowerconsortium, "Magnetic Rresonance and Magnetic Iinduction,"[Online], Available: making-the-right-choice-for-your-application.html.

[37] B. Wang, K. H. Teo, S. Yamaguchi, T. Takahashi and Y. Konishi, "Flexible and Mobile Near-Field Wireless Power Transfer Using an Array of Resonators", WPT, pp.73-77, Oct. 2010.

[38] S. Han and D. D. Wentzloff, "Wireless Power Transfer Using Resonant Inductive Coupling for 3D Integrated ICs," 2010 IEEE International 3D Systems Integration Conference (3DIC), pp. 1-5, 2010.

[39] B. Wang, T. Nishino and K. H. Teo, "Wireless Power Transmission Efficiency Enhancement with Metamaterials," Proc. of the IEEE International Conference on Wireless Information Technology and Systems, pp. 1-4, 2010.

[40] B. Wang, K. H. Teo, T. Nishino, W. Yerazunis, J. Barnwell and J. Zhang, "Wireless Power Transfer with Metamaterials," Proc. of the 5th European Conference on Antennas and Propagation (EUCAP), pp. 3905-3908, 2011.

[41] A. Rajagopalan, A. K. RamRakhyani, D. Schurig and G. Lazzi, "Improving Power Transfer Efficiency of a Short-Range Telemetry System Using Compact Metamaterials," IEEE Transactions on Microwave Theory and Techniques, vol. 62, no. 4, pp. 947-955, April 2014.

[42] A. P. Sample, D. T. Meyer and J. R. Smith, "Analysis, Experimental Results and Range Adaptation of Magnetically Coupled Resonators for Wireless Power Transfer," IEEE Transactions on Industrial Electronics, vol. 58, no. 2, pp. 544-554, Feb. 2011.

[43] J. Park, Y. Tak, Y. Kim, Y. Kim and S. Nam, "Investigation of Adaptive Matching Methods for Near- Field Wireless Power Transfer," IEEE Transactions on Antennas and Propagation, vol. 59, no. 5, pp. 1769-1773, May 2011.

[44] W. Q. Niu, J. X. Chu, W. Gu and A. D. Shen, "Exact Analysis of Frequency Splitting Phenomena of Contactless Power Transfer Systems," IEEE Transactions on Circuits and Systems I: Regular Papers, vol. 60, no. 6, pp. 1670-1677, June 2013.

[45] N. Y. Kim et al., "Automated Adaptive Frequency Tracking System for Efficient Mid-Range Wireless Power Transfer via Magnetic Resonance Coupling, " Proc. of the 42nd European Microwave Conference, pp. 221-224, 2012.

[46] M. Schormans, V. Valente and A. Demosthenous, "Frequency Splitting Analysis and Compensation Method for Inductive Wireless Powering of Implantable Biosensors", Sensors, vol. 16, no. 8, pp. 1-14, Aug. 2016.

[47] W. S. Lee, W. I. Son, K. S. Oh and J. W. Yu, "Contactless Energy Transfer Systems Using Antiparallel Resonant Loops," IEEE Transactions on Industrial Electronics, vol. 60, no. 1, pp. 350-359, Jan. 2013.

[48] Y. L. Lyu et al., "A Method of Using Nonidentical Resonant Coils for Frequency Splitting Elimination in Wireless Power Transfer," IEEE Trans. on Power Electronics, vol. 30, no. 11, pp. 6097-6107, 2015. 

[49] J-G. Shi, D-J. Li and C-J. Yang, "Design and Analysis of an Underwater Inductive Coupling Power Transfer System for Autonomous Underwater Vehicle Docking Applications," Journal of Zhejiang University-SCIENCE C, vol. 15, no. 1, pp. 51-62, Jan. 2014.

[50] V. Bana, G. Anderson, L. Xu, D. Rodriguez, A. Phipps and J. D. Rockway, "Characterization of Coupled Coil in Seawater for Wireless Power Transfer," Technical Report 2026, pp. 1-18, Sep. 2013.

[51] M. Kesler, "Highly Resonant Wireless Power Transfer in Subsea Applications," Colin McCarthy WiTricity Corporation,[Online], Available: Applications.pdf.

[52] M. Ryu, J. D. Kim, H. U. Chin, J. Kim and S. Y. Song, "Three-Dimensional Power Receiver for in Vivo Robotic Capsules," Medical and Biological Engineering and Computing, vol. 45, no.10, pp. 997– 1002, Oct. 2007.

[53] J. Gao, G. Yan, Z. Wang, P. Jiang and D. Liu, "A Capsule Robot Powered by Wireless Power Transmission: Design of Its Receiving Coil," Sensors and Actuators A: Physical, vol. 234, pp. 133-142, Oct. 2015.

[54] R. Carta, R. J. Thone' and R. Puers, "A Wireless Power Supply System for Robotic Capsular Endoscopes," Sensors and Actuators A: Physical, vol.162, no. 2, pp. 177–183, Aug. 2010.

[55] R. Carta, J. Thone and R. Puers, "A 3D Ferrite Coil Receiver for Wireless Power Supply of Endoscopic Capsules," Procedia Chemistry, vol. 1, no. 1, pp. 477–480, Sep. 2009.

[56] J. Zhiwei, Y. Guozheng, J. Pingping, W. Zhiwu and L. Hua, "Efficiency Optimization of Wireless Power Transmission Systems for Active Capsule Endoscopes," Physiological Measurement, vol. 32, no. 10, pp. 1561–1573, Aug. 2011.

[57] Y. Huang et al., "An Efficiency-Enhanced Wireless Power Transfer System with Segmented Transmitting Coils for Endoscopic Capsule," Proc. of the IEEE International Symposium on Circuits and Systems (ISCAS2013), pp. 2279-2282, 2013.

[58] R. Beiranvand, "Analyzing the Uniformity of the Generated Magnetic Field by a Practical One- Dimensional Helmholtz Coils System," Review of Scientific Instruments, vol. 84, no. 7, 2013.

[59] N. Vidal, S. Courto, J. M. Lopez Villegas, J. Siero and F.M. Ramos, "Detuning Study of Implantable Antennas Inside the Human Body," Progress in Electromagnetics Research (PIER), vol. 124, pp. 265- 283, 2012.

[60] Virtual Medical Centre, "Wireless Capsule Enteroscopy Capsule Endoscopy,"[Online], Available: cam/.

[61] Computer Simulation Technology,[Online], Available:

[62] J. Hartford, Wireless Power for Medical Devices, Electronic Components, 2013,[Online], Available:

[63] A. E. Czarnecki, Efficient Inductively Coupled Resonant Power Transfer for an Implantable Electroencephalography Recording Device, Master thesis, Dept. Elect. Comp. Eng., Northeastern University, Boston, Massachusetts, July 2012.

[64] X. Li et al., "A Wireless Magnetic Resonance Energy Transfer System for Micro Implantable Medical Sensors," Sensors, vol. 12, no. 8, pp. 10292-10308, July 2012.

[65] U-M. Jow and M. Ghovanloo, "Design and Optimization of Printed Spiral Coils for Efficient Transcutaneous Inductive Power Transmission," Proc. of the IEEE Transactions on Biomedical Circuits and Systems, vol. 1, no. 3, pp. 193-202, Sept. 2007.

[66] A. Usman, J. Bito and M. M. Tentzeris, "Flexible & Planar Implantable Resonant Coils for Wireless Power Transfer Using Inkjet Masking Technique," Proc. of the IEEE Topical Conference on Biomedical Wireless Technologies, Networks and Sensing Systems (BioWireleSS), pp. 97-99, 2016.

[67] F. Zhang et al., "Design of a Compact Planar Rectenna for Wireless Power Transfer in the ISM Band," International Journal of Antennas and Propagation, pp. 1-9, Feb. 2014.

[68] M. I. Anju, R. Siva, S. Abisha, V. Nandhini and R. Priya, "A Linearly Polarized Rectenna for Far-Field Wireless Power Transfer," International Journal of Advanced Research in Electrical, Electronics and Instrumentation Engineering, vol. 4, no. 3, March 2015. 

[69] R. Tanaka, H. Sakaki, M. Kuroki, F. Kuroiwa and K. Nishikawa, "Wide Dynamic Range Rectifier with Adaptive Power Control Technique," Asian Wireless Power Transfer Workshop, pp. 1-6, Feb. 2015.

[70] O. Ramahi, "Metasurfaces for Far-Field Wireless Power Transfer and Energy Harvesting," Proc. of Qatar Foundation Annual Research Conference, 2016: EEPP3120 EEPP3120.

[71] M. Abu, M. S. A. Jamil Kher, N. H. Izahar, A. F. Ab. Latif and S. N. Zabri, "Enhancement of Rectenna Performance Using Artificial Magnetic Conductor for Energy Harvesting Applications," Journal of Telecommunication, Electronic and Computer Engineering (JTEC), vol. 7, no. 2, pp. 77-82, Dec. 2015.

[72] J-S. Sun, R-H. Chen, S-K. Liu and C-F. Yang, "Wireless Power Transmission with Circularly Polarized Rectenna," Microwave Journal, pp. 1-15, Jan. 2011.

[73] D-Y. Choi, S. Shrestha, J-J. Park and S-K. Noh, "Design and Performance of an Efficient Rectenna Incorporating a Fractal Structure," International Journal of Communication Systems, vol. 27, no. 4, pp. 661-679, April 2014.

[74] G. Andia Vera, A. Georgiadis, A. Collado and S. Via, "Design of a 2.45 GHz Rectenna for Electromagnetic (EM) Energy Scavenging," Proc. of the IEEE Radio and Wireless Symposium (RWS), pp. 61-64, 2010.

[75] S. Shrestha, S-K. Noh and D-Y. Choi, "Comparative Study of Antenna Designs for RF Energy Harvesting," International Journal of Antennas and Propagation, pp.1-10, Jan. 2013.

[76] S. Keyrouz and H. Visser, "Efficient Direct-Matching Rectenna Design for RF Power Transfer Applications," Journal of Physics: Conference Series, pp.1-5, 2013.

[77] J-W. Zhang, Y. Huang and P. Cao, "An Investigation of Wideband Rectennas for Wireless Energy Harvesting", Wireless Engineering and Technology, pp. 107-116, Aug. 2014.

[78] M. A. Sennouni, J. Zbitou, A. Benaissa, A. Tribak, O. Elmrabet and M. Latrach, "Development of a New Slit-Slotted Shaped Microstrip Antenna Array for Rectenna Application," Journal of Emerging Technologies in Web Intelligence, vol. 6, no. 1, pp. 49-53, Feb. 2014.

[79] F. Mohammad and M. Saed, "A Retrodirective Array with Reduced Surface Waves for Wireless Power Transfer Applications," Progress in Electromagnetics Research C, vol. 55, pp. 179–186, 2014.

[80] D. Arnitz and M. S. Reynolds, "MIMO Wireless Power Transfer for Mobile Devices," Proc. of the IEEE Pervasive Computing, vol. 15, no. 4, pp. 36-44, 2016.

[81] Y-Y. Gao, X-X. Yang, C. Jiang and J-Y. Zhou, "A Circularly Polarized Rectenna with Low Profile for Wireless Power Transmission," Progress in Electromag. Research Letters, vol. 13, pp. 41–49, 2010.

[82] Z. Harouni, L. Cirio, L. Osman, A. Gharsallah and O. Picon, "A Dual Circularly Polarized 2.45-GHz Rectenna for Wireless Power Transmission," Proc. of the IEEE Antennas and Wireless Propagation Letters, vol. 10, pp. 306-309, 2011.

[83] Z. Harouni, L. Osman and A. Gharsallah, "Efficient 2.45 GHz Rectenna Design with High Harmonic Rejection for Wireless Power Transmission," IJCSI, vol. 7, no. 5, Sep. 2010.

[84] Y. Xu, S. Gong and Y. Guan, "Coaxially Fed Microstrip Antenna for Harmonic Suppression," Electronics Letters, vol. 48, no. 15, pp. 895-896, July 2012.

[85] J. Ahn, W. Lee, Y. Yoon and Y-D. Kim, "Planar Inverted F-antenna with Suppressed Harmonics," Proc. of the Asia-Pacific Microwave Conference, pp. 1-4, 2008.

[86] J. Yeo and D. Kim, "Harmonic Suppression Characteristic of a CPW-Fed Circular Slot Antenna Using Single Slot on a Ground Conductor," Progress in Electromag. Research Lett., vol. 11, pp. 11–19, 2009.

[87] S. M. Asif and B. D. Braaten, "Design of a Compact Implantable Rectenna for Wireless Pacing Applications," Proc. of the IEEE International Symposium on Antennas and Propagation (APSURSI), pp. 167-168, 2016.

[88] R. S. Alrawashdeh, Y. Huang, M. Kod and A. Sajak, "A Broadband Flexible Implantable Loop Antenna with Complementary Split Ring Resonators," Proc. of the IEEE Antennas and Wireless Propagation Letters, vol. 14, pp. 1506 – 1509, Feb. 2015.

[89] T. Kumagai, K. Saito, M. Takahashi and K. Ito, "A 430MHz Band Receiving Antenna for Microwave Power Transmission to Capsular Endoscope," Proc. of the IEEE URSI General Assembly and Scientific Symposium, pp. 1-4, 2011. 

[90] M. K. Kumar, S. Rajkumar and J. J. Paul, "Miniaturized Planar Inverted F Antenna for Tri-Band Bio- Telemetry Communications," International Journal of Scientific & Engineering Research, vol. 4, no. 5, pp. 982-987, May 2013.

[91]F. Gozasht and A. S. Mohan, "Miniaturized Slot PIFA Antenna for Triple Band Implantable Biomedical Applications," Proc. of the IEEE MTT-S International Microwave Workshop Series on RF and Wireless Technologies for Biomedical and Healthcare Applications (IMWS-BIO), pp. 1-3, 2013.

[92] A. Y. S. Jou, H. Pajouhi, R. Azadegan and S. Mohammadi, "A CMOS Integrated Rectenna for Implantable Applications," Proc. of the IEEE MTT-S Int. Microwave Symposium (IMS), pp. 1-3, 2016.

[93] O. Kazanc, G. Yilmaz, F. Maloberti and C. Dehollain, "Remote Powering Platform for Implantable Sensor Systems at 2.45 GHz," Proc. of the 36th IEEE Annual International Conference of the Engineering in Medicine and Biology Society (EMBC), pp. 2028-2031, 2014.

[94] R. Moore, "Effects of a Surrounding Conducting Medium on Antenna Analysis," Proc. of the IEEE Transactions on Antennas and Propagation, vol. 11, no. 3, pp. 216–225, May 1963.

[95] JB. Pendry, "Metamaterials and the Control of Electromagnetic Fields,"[Online], Available:

[96] R. Marque's, F. Martin and M. Sorolla, Metamaterials with Negative Parameters: Theory, Design and Microwave Applications, Hoboken, New Jersey, USA, Wiley & Sons, Ltd., 2008. 

[97] C. Calos and T. Itoh, Electromagnetic Metamaterials: Transmission Line Theory and Microwave Applications, Hoboken, New Jersey, USA, Wiley & Sons, Ltd., 2005.

[98] Agilent 85070E Dielectric Probe Kit Printed Version of 85070E Help File, 2013,[Online], Available:,[Accessed: 16- July- 2013].