Session 2P4
Near to Mid-range Wireless Power Transfer
Technology: Principles and Applications 2
Wireless Power Transmission by Scalar Waves
Konstantin Meyl, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 382
Study of Transmission Performance on Strong Coupling Wireless Power Transfer System in Free Position
X. L. Huang, W. Wang, L. L. Tan, J. M. Zhao, Y. L. Zhou, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Investigation of Characteristics of the Current for the Maximum Power Transfer in Wireless Power Transmission
Xueliang Huang, Qingjing Ji, Linlin Tan, Wei Wang, Hao Qiang, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
The Coil Misalignment Model of Inductively Coupled Wireless Power Transfer System: Mutual Inductance
Analysis and Transfer Efficiency Optimization
Xueliang Huang, Hao Qiang, Linlin Tan, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Resonant Frequency Splitting Analysis and Optimation of Wireless Power Transfer System
Xueliang Huang, Linlin Tan, Wei Wang, YaLong Zhou, Hao Qiang, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Equivalence of Inductive Coupling and Strongly Coupled Magnetic Resonance in Wireless Power Transfer
383
David S. Ricketts, A. Hillenius, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
A Comparison of Analytical Models for Resonant Inductive Coupling Wireless Power Transfer
Elisenda Bou Balust, Eduard Alarcon, Jordi Gutierrez, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Optimization of Wireless Power Transfer with Intermediate Resonant Coil for Interfacing with the Central
Nervous System
Lingyao Chen, Massood Tabib-Azar, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Undesired Emission from Spiral Resonators for Coupled Resonant Wireless Power Transfer
Hiroshi Hirayama, K. Komatsu, Nobuyoshi Kikuma, Kunio Sakakibara, . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Magnetostrictive Resonators for Wireless Energy Transfer
Alexander Chernokalov, Mikhail Makurin, Nikolay Olyunin, Vladimir Arkhipenkov, Ki Young Kim,
Keum-Su Song, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Resonant Structure Based on Bulk Acoustic Resonator (Metacapacitor)
Pavel A. Turalchuk, Orest G. Vendik, Irina B. Vendik, Dmitry V. Kholodnyak, Ki Young Kim,
Keum-Su Song, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Adaptive Impedance Matching for Magnetically Coupled Resonators
Benjamin H. Waters, Alanson P. Sample, Joshua R. Smith, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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Progress In Electromagnetics Research Symposium Abstracts, Moscow, Russia, August 19–23, 2012
Wireless Power Transmission by Scalar Waves
Konstantin Meyl
Faculty of Computer and Electrical Engineering, Furtwangen University, Germany
Abstract— Current RFID technology explains how the transfer of energy takes place on a chip
card by means of longitudinal wave components in close range of the transmitting antenna. It
is scalar waves which spread towards the electrical or the magnetic field pointer. That provides
the better explanation.
Using the wave equation proposed by Maxwell’s field equations these wave components were set
to zero. Why were only the postulated model computations provided after which the range is
limited to the sixth part of the wavelength.
This text proposes instead the rationale for scalar wave components in the wave equation of
Laplace. Physical conditions for the development of scalar wave transponders become operable
well beyond the close range. Scalar wave information and energy is transferred with the same
carrier wave and not carried over two separated ways as with RFID systems. Bi-directional signal
transmission with energy transfer in both directions is achieved when there is a resonant coupling
between transmitter and receiver.
The first far range transponders developed on the basis of the extended field equations are
already functional as prototypes, according to the US-Patent No. 787,412 of Nikola Tesla: Art
of transmitting electrical energy through the natural medium, New York 1905.
New areas of application with increased requirements are for example:
• In telemetry plants rotary sensors are to be supplied with energy (in the car, e.g., to control
tire-pressure).
• Also with heat meters the energy should come from a central unit and be spreadly wireless
in the whole house to the heating cost meters without the use of batteries (replacing active
RFIDs).
• In airports contents of freight containers are to be seized, without having been opened or the
forwarding trade wants to examine closed truck charges by transponder technology (security
checks).
• In the robot and handling technique the wirings are to be replaced by a wireless technology
due to wear-out problem.
Progress In Electromagnetics Research Symposium Abstracts, Moscow, Russia, August 19–23, 2012
383
Study of Transmission Performance on Strong Coupling Wireless
Power Transfer System in Free Position
X. L. Huang, W. Wang, L. L. Tan, J. M. Zhao, and Y. L. Zhou
School of Electrical Engineering, Southeast University, Nanjing 210096, China
Abstract— With power frequency fixed, the output power and transmission efficiency maximum points of wireless power transmission system do not appear simultaneously under SeriesParallel (SP) resonance model. However, output power and transmission efficiency have key
relationships with the impedance matching of system. With the change of spatial free position
of two coils, the mutual inductance between two coils will change, which have a further influence
on impedance matching of system. Therefore, an optimization scheme has been proposed which
is based on pursuit of the maximum transmission efficiency or output power. That is to say,
in different free position, power ascension or efficiency improving can be achieved through the
appropriate regulation of axial distance, radial distance or offset angle.
It shows relationships between power, efficiency and axial distance, radial distance or offset angle
in Figure 1 and Figure 2, which is achieved by theoretical simulation, and simulation parameters:
two identical spiral copper laps r = 10 cm, N = 31. Results show that the change of the
axial distance, radial distance or offset angle has an apparent effect on the output power and
transmission efficiency of system, which suggests that by changing the axial distance, radial
distance or offset angle we can realize the adjustment of the power and efficiency of the system.
So, the feasibility of the above conclusions theoretically has been proved. From the experimental
results of Figure 3 and Figure 4, it is known that when the axial distance d = 5 cm and radial
offset distance increases from 0 to 5 cm, output power increases 6 W. Offset angle ranges from 0◦
to 10◦ , the transmission efficiency decreases 3% and when the angle continues increasing to 30◦ ,
the efficiency has a sudden 4% increment. The feasibility of the above theories has been proved
by experiment.
Meanwhile, another comparative experiment is designed to verify the impact of the surrounding
environment upon the performance of the system. Two iron panels have been added to both
sides of the 10 cm symmetry of the system in the case of fixed power frequency. It is found
Figure 1: P with L and d, simulation.
Figure 2: η with α and d, simulation.
Figure 3: d = 5 cm, P with L, experiment.
Figure 4: d = 5 cm, η with α, experiment.
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Progress In Electromagnetics Research Symposium Abstracts, Moscow, Russia, August 19–23, 2012
that transmission performance (transmission efficiency and output power) of system has declined
(blue wire in Figures 3, 4), but the trend is the same as it with no obstacles. To sum up, this
paper puts forward a way of adjustment to achieve the maximum output power and transmission
efficiency of the system through changing axial distance, radial distance or offset angle between
two coils. It will have a good significance for the design and control of practical applications.
Progress In Electromagnetics Research Symposium Abstracts, Moscow, Russia, August 19–23, 2012
385
Investigation of Characteristics of the Current for the Maximum
Power Transfer in Wireless Power Transmission
X. L. Huang, Q. J. Ji, L. L. Tan, W. Wang, and H. Qiang
School of Electrical Engineering, Southeast University, Nanjing 210096, China
Abstract— The electromagnetic field distribution between the two coils of wireless power transmission (WPT) is investigated by the way of numerical calculation. Meanwhile the relationship
between the current phase difference of the two coils (transmitting Tx coil and receiving Rx coil)
and the transferred power is revealed and discussed.
In the WPT system, the energy is transferred with the aid of a coupling electromagnetic field
between the two coils. The main working principles of WPT that are mostly referred and discussed are the electromagnetic induction and the magnetic resonance coupled mode theory. In
this paper, the electromagnetic field distribution is obtained by the numerical calculation of finite
element method. For the special coils, the electromagnetic field distribution is determined by the
amplitude and phases of the current in two coils, labeled as I˙1 = A∠0, I˙2 = B∠ϕ (ϕ is the phase
angle difference). With the numerical calculation of the Maxwell equation, the distribution of
the Poynting vector between the Tx coil and Rx coil is obtained (Fig. 1). It can be seen that the
power is transferred from one coil to another. Integrating the Poynting vector in the surface that
in the middle of the two coils (as seen in the Fig. 1), the power (Pt ) transferred from Tx coil to
Rx could be obtained. Setting the current amplitudes of A and B, and adjusting the ϕ, we could
find that the peak of Pt occurs when the ϕ = π2 (Fig. 2). The relation of Pt and other factors,
such as the frequency of work, current amplitudes, are also discussed. The conclusions proposed
in this paper are deduced based on the theory of electromagnetic field, so it is universal to be
benefit to understand the working principle of WPT and carry out the further researches.
Figure 1: The Poynting vector distribution between
the two coils.
Figure 2: The Pt change with the ϕ.
Progress In Electromagnetics Research Symposium Abstracts, Moscow, Russia, August 19–23, 2012
386
The Coil Misalignment Model of Inductively Coupled Wireless
Power Transfer System: Mutual Inductance Analysis and Transfer
Efficiency Optimization
X. L. Huang1 , H. Qiang1, 2 , and L. L. Tan1
1
2
School of Electrical Engineering, Southeast University, Nanjing 210096, China
School of Information Science and Engineering, Changzhou University, Changzhou 213164, China
Abstract— A novel means of optimizing transfer efficiency of the inductively coupled wireless
power transfer (ICWPT) system is presented for the first time by looking for the partial optimal
solution of mutual inductance of coil misalignment.
Inductive coupling is one major technology of wireless power transfer, which transfers power from
a primary transmitter (Tx) coil to a secondary receiver (Rx) coil with the aid of an alternating
magnetic field. Many researches have deduced the expression of the transfer efficiency and results
show that the high transfer efficiency is associated with the great mutual inductance. To the
general knowledge, the Tx and Rx coils would be ideally coaxially orientated so that maximum
coupling such as the maximum mutual inductance and the optimal transfer efficiency results.
Meanwhile the mutual inductance is correlated with the parameters of coils and the separate
distance, lateral distance and tilt angle between the two coils. In the applications envisaged, such
as electric vehicles and biomedical implants, generally the receiving coil is laterally and angularly
misaligned from the transmitting coil. The numerical solution of the mutual inductance between
the two coils is derived and simulation result shows that there is a partial optimal solution in
the ranges of lateral and angular misalignments with the special system parameters, as shown
in Fig. 1. Then a novel means is presented for the first time to design the coil to be removable
and rotatable for optimizing transfer efficiency by looking for the maximum mutual inductance
in a special rangs. Finally the experimental results show it is accordant with the theory analysis
and the proposed means is efficient and greatly improves the transfer efficiency. If the transfer
distance is 15 cm and there is no lateral misalignment, the transfer efficiency can be improved
about from 38.6% to 60.5% by turning the transmitting coil to vary the tilt angle from 0 to π/4,
as shown in Fig. 2. This introduced technique can be widely applied to wireless power transfer
system to optimize the transfer efficiency.
×10
-7
Figure 1: Mutual inductance M of coil misalignment
with lateral distance l and tilt angle θ.
Figure 2: The measured transfer efficiency, where
the Tx coil is removable and rotatable while the Rx
coil is fixed.
Progress In Electromagnetics Research Symposium Abstracts, Moscow, Russia, August 19–23, 2012
387
Resonant Frequency Splitting Analysis and Optimation of Wireless
Power Transfer System
X. L. Huang, L. L. Tan, W. Wang, Y. L. Zhou, and H. Qiang
School of Electrical Engineering, Southeast University, Nanjing 210096, China
Abstract— Studies reveal that while at long-distance transmission, the wireless power transfer
system has only one stable resonant frequency and under this frequency the transmitting and
receiving coils circuits in their self-resonance respectively, meanwhile, the system achieves efficient
performance. But, at close transfer distance, the system resonant frequency will give rise to three
resonant frequencies which increase the power transfer instability. Because of the system has more
than one resonant frequency which means resonant frequency splitting occurs, it is difficult to
determine an ideal frequency controlling points. So it is necessary to solve the resonant frequency
splitting problem to improve the system stability and control ability at whole transfer distance.
In order to achieve system resonance, varieties of capacitor compensated modes can be used in
transmitting and receiving circuits. In this paper the bilateral capacitor parallel-compensated
topology (PP) is studied, and the system load equivalent model is established to analyze the
variation characteristics of the system input impedance. Then the threshold conditions of the
transfer distance and load are given while the system resonant frequency splitting occurs. In
conclusion, an optimization control method is proposed to ensure the system a single stable
resonant frequency and effective work in resonant status.
Based on the above analysis, it can be found that at close distance, a single stable resonant
frequency of the transfer system for an easy control can be achieved through the following two
methods: (1) with resonant frequency ω0 and load RL fixed, adjusting α to achieve the system’s
operation on ω0 , which ω = βω0 , which α for capacitance ratio α = C1 /C2 , C1 , C2 are the
capacitor compensated of system coils. This method has less requirements on power source
frequency output and only needs change in small range. However, a too large α will cause a large
gap between the system’s transmitting and receiving circuits self-resonant frequency, which is
not conducive to the effective power transfer; (2) with α fixed, and adjusting RL to achieve only
one resonant frequency at the whole distance under the context of d < dc , where, dc denoted as
a threshold distance which makes the system has only one resonant frequency.
Figure 1: Frequency splitting, which ω = βω0 .
Figure 2: The curve of RL varied with d.
Figure 3: Load received power varied with d.
Figure 4: Transfer efficiency varied with d.
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Progress In Electromagnetics Research Symposium Abstracts, Moscow, Russia, August 19–23, 2012
Equivalence of Inductive Coupling and Strongly Coupled Magnetic
Resonance in Wireless Power Transfer
D. S. Ricketts and A. Hillenius
Carnegie Mellon University, Pittsburgh, USA
Abstract— Recent demonstrations of mid-range wireless power transfer using strongly coupled
magnetic resonance [1] has created a resurgence in research activity in wireless power delivery
using magnetoquasistatic fields. Inductively coupled wireless power transfer has been extensively
studied and used over the past 100 years, in particular the last 50 years in biomedical and charging
applications [2]. Works using coupled magnetic resonance have purported that the coupled resonance produces increased efficiency over non-resonant approaches [1, 3], e.g., inductive coupling.
Several modeling papers have shown that the coupled magnetic resonance can be modeled by a
simple mutual inductance and RLC network using standard network theory [4]. In particular,
they show that the use of resonance can be interpreted simply as an optimal impedance matching
of load and source, just as is done routinely in inductively coupled wireless power transfer. These
works are very useful for modeling and calculations; however, they do not show explicitly or
experimentally that that the maximum possible power transfer is dictated by coil geometry and
separation only, and that optimum power transfer can be achieved with an optimally impedance
matched inductively coupled 2-coil system or with a strongly coupled magnetic resonance 4-coil
system. In this work we present experimental results of a non-resonant source coil (no resonating capacitor) impedance matched with a discrete T -matching network and a strongly coupled
magnetic resonant source coil system tuned for optimal efficiency. We show that the maximum
power transfer is the same for both systems and that the maximum power is determined by
the geometry of the coils, i.e., inductors, only. We also show experimentally that the use of an
external impedance matching network or a 2-coil strongly coupled magnetic resonant system is
simply a different implementation of the same physical principles.
(a)
(b)
(c)
Figure 1: (a) Strongly coupled magnetic resonance. d1 is adjusted for maximum power transfer d2 is fixed
at 10 in. (25.4 cm). (b) Input impedance of part (a) as a function of d1 . (c) Same loop as in (a) but without
a resonance capacitor. Impedance match is achieved with discrete T -match circuit. Measured impedances
shown. Both loops have identical loads and generate approximately the same output power (30 mW in this
example).
REFERENCES
1. Kurs, A., et al., “Wireless power transfer via strongly coupled magnetic resonances,” Science,
Vol. 317, 83–86, July 2007.
2. Donaldson, N. de N. and T. A. Perkins, “Analysis of resonant coupled coils in the design of
radio frequency transcutaneous links,” Med. & Biol. Eng. & Comput., Vol. 21, 612–627, 1983.
3. Ho, S. L., et al., “A comparative study between novel witricity and traditional inductive magnetic coupling in wirless charging,” IEEE Tran. on Mag., Vol. 47, 1522–25, May 2011.
4. Dionigi, M. and M. Mongiardo, “CAD of wireless resonant energy links (WREL) realized by
coils,” IEEE Int. Microw. Symp., 1760–1763, 2010.
Progress In Electromagnetics Research Symposium Abstracts, Moscow, Russia, August 19–23, 2012
A Comparison of Analytical Models for Resonant Inductive
Coupling Wireless Power Transfer
E. Bou1 , E. Alarcon1 , and J. Gutierrez2
1
Electronic Engineering Department, Technical University of Catalonia UPC BarcelonaTech, Spain
2
Applied Physics Department, Technical University of Catalonia UPC BarcelonaTech, Spain
Abstract— Recent research in wireless power transfer (WPT) using resonant inductive coupling
has demonstrated very high efficiencies (above 40%) at large distances compared to the antenna
dimensions, which has exponentially increased the number of potential applications of WPT.
Since resonant inductive coupling is a very multidisciplinary field, different approaches have been
proposed to predict the behaviour of these systems from physical theory of resonators, reflected
load theory and the circuit point of view. However, the relation between these methods is
still obscure. In this article, we compare the results of these models to find the efficiency of a
Resonant Inductive Coupling WPT system under Steady-State conditions and to analyze the
relation between the optimal load values obtained from this perspectives and the ones obtained
using impedance matching techniques.
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Progress In Electromagnetics Research Symposium Abstracts, Moscow, Russia, August 19–23, 2012
Optimization of Wireless Power Transfer with Intermediate
Resonant Coil for Interfacing with the Central Nervous System
Lingyao Chen and Massood Tabib-Azar
University of Utah, 50 S. Central Campus Dr., Rm. 3280 MEB Salt Lake City, UT 84112-9206, USA
Abstract— Sensing and stimulating neurons using wireless telemetry systems are extensively
used for prosthetics and mapping the circuitry of the brain [1]. In these systems, the preferred
method for power and signal transmissions is to use an open-transformer configuration (Fig. 1)
also known as magnetic dipole or inductive coupling [2]. Here we show that a third resonant coil
can be used in-between the transmitting and receiving coils (Fig. 2) to enhance the telemetry
efficiency by X5 in the inductive coupling scheme. Inductors and capacitors in all three coil
circuits had the same value of 1 µH and 100 nF, respectively, yielding the same resonant frequency
for the transmitter (TX), intermediate (IM) and receiving coils (RX). Furthermore, the RX coil’s
radius was fixed at 0.6 mm. Fig. 3 shows the output voltage as a function of TX coil’s location
for different radii of TX coils (all much larger than RX coil’s) with no IM coil present. It can
be seen that for each distance ZRT , there is an optimized TX coil radius to achieve maximum
Vout . Closer the distance ZRT , smaller the radius of TX coil for optimum transmission. As with
2
2
µ0 NTX RTX
πRRX
di
magnetic dipole theory, when RTX À RRX , Vout = NRX 2(R
2 +Z 2 )3/2 dt . The behavior of Vout
TX
RT
3
as a function of ZRT follows the 1/ZRT
law when ZRT À RTX , as expected.
Figure 4 shows Vout vs. IM coil’s location for different IM radii, while TX and RX coils’ distance
(ZRT ) were fixed at 70 mm and TX and RX radii were 44.5 mm and 0.6 mm, respectively. When
there was no IM coil, the transmitted Vout was 10.8 mVpp; when the IM coil was introduced,
Vout increased by a factor of 2 to 5 for different IM coil radii and location. For different IM coil
location (ZRM ), there was an optimized IM coil radius to maximize Vout . Closer the IM coil to
Figure 1: Schematic of coils transmitting and receiving inside/outside human brain with intermediate
coil as power booster.
Figure 2: Circuit diagram of three transmitting, receiving and intermediate coils.
Figure 3: Output voltage vs. transmitting coil location (ZRT ) for two coils transmission with different
transmitting coil radius. RRX was fixed at 0.6 mm.
Figure 4: Output voltage vs. intermediate coil location (ZRM ) for three coils transmission with different
intermediate coil radius. ZRT = ZRM + ZMT , and
was fixed at 70 mm.
Progress In Electromagnetics Research Symposium Abstracts, Moscow, Russia, August 19–23, 2012
391
the RX coil, smaller was its radius for optimized Vout , but the value was always between the radii
of TX and RX coils. This can be explained noting that Vout is maximized when magnetic fluxes
2
2
2
2
µ0 IRRX
NRX πRTX
µ0 IRRX
NRX πRIM
(φ’s) are equal: φRT = 2(R
= φRM = 2(R
2 +Z 2 )3/2
2 +Z 2 )3/2 .
TX
RT
IM
RM
REFERENCES
1. Murari, K., et al., “Wireless multichannel integrated potentiostat for distributed neurotransmitter sensing,” Engineering in Medicine and Biology Society, 7329–7332, 2005.
2. Lenaerts, B. and R. Puers, Omnidirectional Inductive Powering for Biomedical Implants,
Springer, 2009.
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Progress In Electromagnetics Research Symposium Abstracts, Moscow, Russia, August 19–23, 2012
Undesired Emission from Spiral Resonators for Coupled Resonant
Wireless Power Transfer
H. Hirayama, K. Komatsu, N. Kikuma, and K. Sakakibara
Department of Computer Science and Engineering
Nagoya Institute of Technology, Japan
Abstract—
Introduction: Wireless power transfer (WPT) technology is expected to realize ubiquitous
power system. Since the WPT system handles power of kW order, it is necessary to assess
undesired emission. Various kinds of resonators, such as helical coil or meander lines are possible
for the WPT antenna. Spiral resonator has an advantage of low-profile structure. In this report,
we discuss undesired emission from a spiral resonator.
Consideration Model: Spiral antenna model in which transmitting(TX) and receiving(RX)
antennas are set in the same direction is shown in Fig. 1(a). It was reported that arrangement of
TX and RX antenna in opposite direction increases coupling coefficient [2]. Fig. 2(b) shows the
reverse arranged model. A power source and load were connected to the port 1 and 2, respectively.
The source and load impedance were 50 ohm.
Results: S21 characteristics with respect to the transfer distance was calculated by method of
moment (MoM). Although the self resonant frequency of the spiral antenna itself is 36.7 MHz,
low-frequency and high-frequency resonances were caused because of a coupling [3]. S21 at the
high-frequency mode is used in the Fig. 2. Transfer distance was extended by 19% by arranging
antenna in reverse direction.
Far-field radiation power can be calculated through a gain as an antenna, where both TX and RX
spirals are considered as a TX antenna. Calculation result is shown in Fig. 3. Far-field radiation
was decreased by 4.5 dB in high-frequency mode resonant.
Conclusions: We show that transfer distance was extended by 19% and far-field radiation
decreased by 4.5 dB by arranging spiral resonator in opposite direction.
(a)
(b)
Figure 1: Consideration model.
Figure 2: Distance characteristics of S21 .
Figure 3: Gain as a TX antenna.
Progress In Electromagnetics Research Symposium Abstracts, Moscow, Russia, August 19–23, 2012
393
REFERENCES
1. Kurs, A., A. Karalis, et al., “Wireless power transfer via strongly coupled magnetic resonances,”
Science Magazine, Vol. 317, No. 5834, 83–86, 2007.
2. Awai, I., Nikkei Electronics, 11–14, 100–108, Nov. 2011.
3. Hirayama, H., et al., “A consideration of electromagnetic-resonant coupling mode in wireless
power transmission,” IEICE ELEX, Vol. 6, No. 19, 1421–1425, Oct. 2009.
Progress In Electromagnetics Research Symposium Abstracts, Moscow, Russia, August 19–23, 2012
394
Magnetostrictive Resonators for Wireless Energy Transfer
Alexander Chernokalov1 , Mikhail Makurin1 , Nikolay Olyunin1 ,
Vladimir Arkhipenkov1 , Ki Young Kim2 , and Keum-Su Song2
1
2
Samsung Moscow Research Center, Russia
Future IT Research Center, Samsung Advanced Institute of Technology, Yongin 446-712, Korea
Abstract— Magnetostrictive resonators are proposed to be used for wireless energy transfer in
the sub-MHz range.
The operation in the sub-MHz frequency range is preferable for wireless energy transfer in the
presence of lossy media: biological tissue, water, soil, conductive objects, and other. Low operating frequency allows reducing the losses in such media. One more issue in biological applications
of wireless energy transfer is the EM field exposure level. The maximum permissible exposure
levels for sub-MHz and MHz frequencies are less restrictive than for higher frequencies.
Most of the resonators used for wireless energy transfer via magnetic field are coil-based. At
the same time there exists a problem of designing a compact coil-based resonator with high
Q-factor for sub-MHz frequency range. There are few ideas of non coil-based resonator design
suitable for low frequencies [1, 2]. The idea closest to the proposed one is described in [2], where
a magnetoelectric resonating device is used for energy transmission comprising of piezoelectric
and magnetostrictive layers. There exist two problems with this approach: first the Q-factor of
the resonator is reduced because of composite structure of the device, and second this device is
difficult to match to a variable load.
Instead of using a composite structure we propose to use a solid-state resonator composed of
magnetostrictive material. The resonator is assumed to be biased by an external permanent
magnet. The advantage of this approach is the intrinsically high Q-factor of the resonator (∼ 103 ).
The mechanical energy of the resonator is converted to electric energy using a coil wound around
the resonator, which plays a role of energy transducer. The coil is connected to a load. Optimal
load resistance depends on the number of turns in the coil. Therefore we can match the device
to a wide range of load resistances by changing the number of turns in the coil.
REFERENCES
1. Cook, N. P., S. Dominiak, L. Sieber, and H. Widmer, “Transmitters and receivers for wireless
energy transfer,” US Patent App., 12/211, 706, September 16, 2008.
2. Liu, Y., J. Simon, R. C. O’handley, and J. Huang, “Wireless transfer of information using
magneto-electric devices,” US Patent App., 12/505, 151, July 17, 2009.
Progress In Electromagnetics Research Symposium Abstracts, Moscow, Russia, August 19–23, 2012
Resonant Structure Based on Bulk Acoustic Resonator
(Metacapacitor)
Pavel Turalchuk1 , Orest Vendik1 , Irina Vendik1 ,
Dmitry Kholodnyak1 , Ki Young Kim2 , and Keum-Su Song2
1
2
St. Petersburg Electrotechnical University, St. Petersburg 197376, Russia
Future IT Research Center, Samsung Advanced Institute of Technology, Yongin 446-712, Korea
Abstract— The resonant structure based on Bulk Acoustic Resonator (BAR) is a planar multilayer structure, comprising the conducting loop and the BAR structure. The BAR (metacapacitor) structure consists of a thin layer of the piezoelectric ceramics terminated in thin metal upper
and lower electrodes. The metacapacitor structure is mounted on silicon substrates. In this case,
the silicon is used as a dielectric substrate. On the both sides of the metacapacitor structure, the
dielectric substrates are etched in the center in order to provide almost free acoustic boundary
conditions. In this case, the metacapacitor structure provides a high-Q shear-wave bulk acoustic resonance excited between two electrodes. At the operating frequency the equivalent input
impedance of the metacapacitor exhibits a capacitive reactance, which corresponds to the capacitor with a high value of capacitance. The high value of the capacitance of the metacapacitor in
combination with a small inductance of the loop provides a resonant response of the advanced
resonant structure at the desired frequency in the MHz frequency range. Conducting loop formed
as a round strip is located on the upper dielectric layer of the metacapacitor. The loop edges are
connected to the metacapacitor electrodes by means of metallized “via” interconnections. The
designed miniature resonator exhibits a high value of capacitance and a high Q-factor.
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Progress In Electromagnetics Research Symposium Abstracts, Moscow, Russia, August 19–23, 2012
Adaptive Impedance Matching for Magnetically Coupled Resonators
Benjamin H. Waters1 , Alanson P. Sample1, 2 , and Joshua R. Smith1, 2
1
2
Department of Electrical Engineering, University of Washington, USA
Departments of Computer Science Engineering, University of Washington, USA
Abstract— Wireless power technology using magnetically coupled resonators (MCRs) is becoming more prevalent in common applications including electric vehicle charging, consumer
electronics, and implantable biomedical devices [1, 2]. These applications require a practical endto-end wireless power system that can achieve high efficiency for a volume of space and operate
within the bandwidth limitations defined by wireless communication standards and regulations
in various countries.
To maximize efficiency at a single operating frequency for a volume of space (corresponding to
a full range of coupling coefficients), the constant source impedance of a power amplifier must
be matched to the variable impedance of the MCRs which changes as a function of the coupling
coefficient between the transmit (TX) and receive (RX) resonators. Previous work has demonstrated wideband frequency tracking techniques that automatically tunes the operating frequency
to maximize wireless power transfer efficiency [2]. However, frequency-tuning may violates the
regulated frequency bandwidths where commercial wireless power systems can operate.
A framework has been developed to accurately model any adaptive impedance matching (AIM)
network in a high Q MCR wireless power system. AIM networks are critical blocks for these
systems because maximum efficiency can be achieved for a full volume of space at a single
operating frequency. First, a vector network analyzer (VNA) is used to extract S-parameters
from a set of MCRs. After the admittance Y matrices for any AIM network has been defined,
these S and Y matrices are converted into ABCD transmission matrices. A single ABCD matrix
for the entire system can be defined by multiplying the cascaded ABCD matrices [3]. This system
ABCD matrix is then converted back to an S matrix using complex termination impedances to
match a source impedance (typically 50 Ω) to a defined load impedance [4]. Finally, a constrained
non-linear optimization algorithm in Matlab extracts the circuit component values in each AIM
network that maximize S21 for any range of coupling coefficients.
To verify the algorithm, a low-pass π-match network has been implemented as the AIM network
with the MCRs shown in Figure 1(a). Figure 1(b) shows the smith chart of S11 and Figure 1(c)
shows |S21 |2 (efficiency) for two scenarios where 1) the MCRs are terminated in 50 Ω source
and load impedances and 2) AIM networks are placed at both the TX and RX sides. The plot
in Figure 1(c) also compares the efficiency at a single frequency to that of wideband frequency
tuning. Since nearly all parasitics have been accounted for, these efficiencies are achievable at
a single frequency for a full range of coupling coefficients between any TX and RX resonator.
Therefore this tool can be used to design and accurately model a practical end-to-end wireless
power system using any AIM network with any set of MCRs.
(a)
(b)
(c)
Figure 1: (a) Image of the TX and RX magnetically coupled resonators used for wireless power transfer. (b)
Smith chart showing S11 for the actual set of MCRs terminated in 1) 50 Ω source and load impedances (blue
circles) and 2) simulated TX and RX AIM π-match networks (red squares). (c) Plot comparing |S21 |2 for
the actual set of MCRs using 1) frequency tuning (green circles), 2) 50 Ω termination impedances (blue x’s)
and 3) TX and RX AIM π-match networks (red squares).
Progress In Electromagnetics Research Symposium Abstracts, Moscow, Russia, August 19–23, 2012
397
REFERENCES
1. Waters, B. H., A. P. Sample, P. Bonde, and J. R. Smith, “Powering a ventricular assist device
(VAD) with the free-range resonant electrical energy delivery (FREE-D) system,” Proceedings
of the IEEE , Vol. 100, No. 1, 138–149, Jan. 2012.
2. Sample, A. P., D. 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, 544–554, Feb. 2011.
3. Pozar, F. M., Microwave Engineering, Wiley, New York, 2004.
4. Frickey, D. A., “Conversions between S, Z, Y , h, ABCD, and T parameters which are valid
for complex source and load impedances,” IEEE Transactions on Microwave Theory and Techniques, Vol. 42, No. 2, 205–211, Feb. 1994.
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Progress In Electromagnetics Research Symposium Abstracts, Moscow, Russia, August 19–23, 2012