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The electromagnetic transmission of electric power is not feasible
use the results of numerical magnetic resonance, the LC resonator circuit Q value in the field radius of 30 cm 4,000 contracts. Resonance frequency of 9MHz, converted into a wavelength of 33 meters. When the distance between 1.5 meters, the energy transfer efficiency of 90%. If 3 meters away, transfer efficiency of 45%, κ / Γ greater than 1.

Massachusetts Institute of Technology (MIT) research team in November 2006 launched a code of WiTricity (Wireless Electricity) research program, attempts to develop in a few meters away from each other systems for wireless transmission of electric power technology. Recently, MIT team outside its findings publicly, has been able to reach through wireless transmission means 60 watt light bulb two meters outside the initial purpose.
Figure 5 κ value associated with the interval
If the LC resonator used in imitation of the office room above, assuming that the transmitter using an LC resonator radius of 1 meter and 3 from the bed to settle in meter-high ceiling, connected to the 10MHz switching power supply. The absorption edge side of the resonator was 30 cm radius, Q is about 1,000. In this state, the power transmission and the effectiveness of the use of high dielectric disc similar levels, but the body energy is simply to receive zero, and thus insured a lot of humans.
Figure 4 2-D high-dielectric electromagnetic vibration disk
impact of the human body can be said whether the wireless power technology into the practical application of the barrier. Because it directly to the living to the experiment will lead to morale problems that guide the use of the MIT team responsible for clean up in his office books of the robot to simulate the human body. In this experiment, MIT team is still based on high dielectric body as a disk to send the receiver. Transmitter placed in the center of the ceiling, install the receiver on the robot, the robot from walking. The room is a cube, beds, walls and ceiling are the same material. The shape of the transmitter output, less constrained elasticity, the internal transmitter set aside consideration of energy loss, the focus at the receiving end of energy loss.
However, even temperature no matter how small, has a potential risk, and therefore must be taken before magnetic resonance systems, such as LC resonator, rather than high dielectric disks to achieve wireless power transmission (Figure 6). Using LC coil is in the best interests of the external coil LC how much almost all the energy of magnetic energy and magnetic field in the space of human life everywhere, minimal impact on the human body. For example, the use of medical MRI (Magnetic Resonance Imaging, MRI) review the installation of the firing of the human body magnetic field strength will be very strong, there are other linear motors, and even magnetic immersed bed, etc., will environment in human life caused by the strong magnetic field, but the facts confirm that the magnetic field on the human body and will not cause health concerns.
than the dielectric constant dielectric loss Im (ε) / εTiO2
Secondly, look at practical applications obstructions. This point can be the solution of Maxwell equations to get values. Using coupled mode theory to obtain approximate.
3 Tesla effect was designed to test the system architecture diagram
MIT transmission system, a transmitter and receiver installed on the resonance of their body, and the transmitter into energy. When the transmitter and receiver at the beginning of a consensus, decreasing the energy of the transmitter, the receiver gradually accumulated. Really a transmitter until the energy is exhausted, the resonance has come to an end. The idea of ??mechanical energy can be used to drive or to charge the battery.
energy transfer efficiency for the system design crucial
κ value greater bonding strength of the higher, the higher the energy exchange. Energy loss is small it means Γ is small, that a large Q value. Value is inversely proportional to Q and Γ. Netease blog
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and MIT but the method applied electromagnetic resonance. Is applied in detail the so-called “Evanescent Tail” close-field energy transfer between two objects as a medium. Evanescent Tail can be seen as a follow from the rapid decay of the electromagnetic field.
the results of calculations based on data, even if the transmitter or the receiver and other vibrating body closer to the wall, Q value is only a little less, that the energy loss is not too great. Even if buried in the wall next to the transmitter, Q value is only reduced by about half.
If the consideration of the practical use of context, during the system design must be some costly work, in particular the size and shape of the transmitter, to be put to good thinking.
I used to evaluate the energy loss of QR. QR bigger, the performance of the smaller energy loss. Assuming QR = 1,992, the symbol of the vibration cycle time, all the electromagnetic energy of 1 / 1992 to electromagnetic jet. If the complete formation of the object only by electromagnetic waves, the object in a period of time, all the energy will be dissipated. Easy to get to the information in the discretion of, the application of about 100M ~ 1GHz down the resonance frequency for wireless power transmission should be the most feasible. To 1GHz, the ratio of the frequency dielectric (Dielectric Permittivity) of large sectors of real numbers, imaginary part of the material has a very small lot, and the receiver can be used as delivery devices, such as titanium dioxide (TiO2) (Table 1).
use of directional antennas or laser so that the direction of the electromagnetic emission is concentrated towards the unity of a viable approach in practice, in fact, it was also proposed in 1968 the track solar power (Solar Power Station) concept, intended to carry There are ambitious solar power satellite systems, microwave transmission to Earth of the idea. But because the satellite transmitter must stop following the receiver, so the actual use of too many limitations on the subject.
Another interesting question is whether both the absolute position of the coil will affect the strength of links, that is, to examine changes in the value of κ. Experiment is the use of coaxial parallel way, if one end of the tilt 45 degrees, κ values ??persist in Bacheng level. If two wire axis parallel to surface, κ value is the 70% level. Thus, the relative position of point of view or a little impact, if the applicable conditions to enter the system design is still to spend doing something.
wireless power systems have minimal impact on the human body
To progress the delivery of energy efficiency, MIT team used “strong-coupling region,” the natural world will be presented in the resonance picture. Strong coupling region is a way to get κ / Γ is much greater than one place. Jane Lueyan Zhi, κ and Γ is the crux of the resolution efficiency of energy transfer parameters. In details, κ quantified with intensity, Γ is the absorption of electromagnetic radiation or energy loss caused by system size, the ratio of the amount. In short, κ / Γ Hong far in breaking into the strong-binding domain, the energy transfer rate is much higher than the rate of loss, in other words, the energy transfer efficiency comparable to high.
magnetic resonance more efficient than electromagnetic induction transmission
then look away. κ / Γ is much larger than 1 is the experimental focus of the MIT team, and lead to strong coupling region is to achieve high energy transfer efficiency of the physical basis. κ / Γ is the transmission efficiency in addition to a function of distance is a function of its own. When the resonance of the two objects gradually distanced themselves from, the combination of weaker degree. According to the experiment shows that when κ / Γ is less than 1, the energy loss becomes very large (Figure 5).
obstructions block in Figure 7 and reduce the receiving coil test the premise, two meters of light can still shine.
First, the use of electromagnetic waves transmitted power subject to the robot, the robot relative to the results of the Office of the invention is much smaller, receiving only a small part. Use of high dielectric resonance between the disk, the robot reached the room, the shortest distance, to receive the maximum power, while the robot went to the room corner, the receive power smaller. If the robot as a human to calculate the simulation, the energy absorbed by humans is very small, will only result in a little tepid, which is the electric field induced in the human skin surface Joule heating.
WiTricity applications is widespread. Like all kinds of home use or military use mechanical devices, electric vehicles, portable devices, medical instruments, sensors, electric blankets, or have the greenhouse effect of the device, etc. are possible.
Great Leap Forward WiTricity wireless power transmission techniques may be new traffic light infinite in September 2008, No. 91
To use magnetic resonance theory to electric power transmission, transmission efficiency, the effective transmission distance, obstacles for the energy transfer effects, in particular, the main thing is whether the human body have an adverse impact, etc., all require specific test and evaluation.
a few meters to tens of meters distance transmission of data, is the most popular wireless networking technology. It has been also thought why not properly take advantage of these cheap and over the wireless network to transmit electricity. But in fact the wireless network to transmit power is not feasible, because the electromagnetic waves are not suitable for transferring energy or electricity. To broadcast reception, for example, the base station radio broadcast station to tens or hundreds of kilowatts (kW) 360 degrees toward the direction of high-power radio transmitter signals, but compared with the power of the transmitter, the receiver can receive only with negligible to describe the energy transfer efficiency to effectively too low.

κ calculation formula can be used coupled mode theory (Coupled-Mode Theory, CMT) to obtain approximate. Q value of the joint model theory verge on ω/2Γ.
Figure 4 shows a simple example, that two-dimensional high-dielectric disc (Dielectric Disk) the use of resonance. In the field inside the proximity region is not spread to distant areas. The arrangements outside the scope of electromagnetic waves. Electromagnetic energy loss is too large, not with the energy transfer medium.
Figure 6 LC resonator using a wireless power transmission system
2 tesla pylons photos
text. Nai Tong
MIT experimental configuration is as follows: a 30 cm radius of the LC resonator, two meters away from each other, and configured on the receiving end 60-watt bulb (Figure 7). First of all, from the Colpitts resonator using electromagnetic induction to power to the transmitter coil, then the magnetic field due to resonance, the power transmitted to the receiver coil, after the supply of electricity to induce the use of electromagnetic light and shiny. At first glance, as if all the system can not find the capacitor, but it is scattered in the electrostatic capacity of the wire is the capacitor. Experimental system the resonance frequency of about 10MHz, and the solution of Maxwell equations are commensurate with the theoretical value out of the same. Must further clarify the unique Q-value of pure copper is 2,300, while the actual measurement system is 1,000. Currently leads the research team thought it was caused by oxidation of the name. As the frequency of 10MHz would cause the skin effect conductor (Skin Effect), the current in the wire surface is only 10 microns thin layer flow.
In fact, wireless power transmission (Wireless Power Transmission) or wireless energy transmission (Wireless Energy Transfer) is a very old study. Early in the 19th century, Thomas Edison (Thomas Edison) and Nicola. Tesla (Nikola Tesla) would have consumed time and spirit of the great research includes a variety of long distance wireless power transmission, including transmission technology. Tesla back in 1891 attempted to demonstrate its feasibility, in 1904, construct a Tesla Power Tower (Telsa Tower) (Figure 2) in an attempt to achieve long-distance power transmission. While this plan ultimately failed, but the effects of future generations still to Tesla (Telsa Effect) (Figure 3) who have tried the word pictures wirelessly transmit electricity transmission avant-garde engineers.
because of MIT wireless power system design uses two coils, so there is a very easy to misinterpret people premises, that is, the system uses the principle of individual electromagnetic induction. Although the two systems is somewhat similar at first glance, but the magnetic resonance occurs in the link efficiency million times higher than the electromagnetic induction. This is because the former is in the loop with the capacitor can cause resonance effects, the distance between the coil and longer.
2011 年 09 月 07 日
achieve wireless transmission power is the key to the magnetic field coupled resonators (Magnetically Coupled Resonator), is shown in Figure 1 left and right ends of the coil device. The two resonators are a pair of 5.25 with a 6 mm copper wire around the ring, with inductor-capacitor (LC) characteristics of the coil antenna, the LC resonance frequency of 9.90MHz.
9610-3BaTi4O9
3710-4LiTaO3
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material / material
Figure 1 MIT WiTricity discuss the design team and their experimental device. Photo left for the power of the transmitter, the receiver is located right on the device lamp is lit.
in real life environment, obstacles than the dielectric constant of small most of the real value. For example, concrete is about 4.5, 1.2 to 5 wood, quartz glass is 4, so the dielectric loss caused by abnormal small. Nothing more than there are exceptions, the water is obvious example. When the transmitter near commensurate with the water, the resonance Q-value dropped to about one third of abnormal values. But even this predicament, the practical point of view or perverting can receive.
Table 1 high dielectric material

The MIT approach is to use the resonance phenomenon. Resonance is a very extraordinary phenomenon of artificial world, a wide variety. Musical instruments with sound resonance, children swing the mechanical resonance, electromagnetic resonance, NMR resonance gas. This common feature of some resonance, equal to the energy exchange will occur in the same frequency between the two objects, while the frequency is not inconsistent with the transfer of energy between two objects. Such as acoustic resonance, the assumption in the room placed one hundred birds feast, the number of individual liquid into a little different, so that each glass has a different fixed frequency. When there is a trained opera singer loud sound when the tone with the same frequency is the same glass, the emergence of a strong resonance, but the other is the vibration frequency of different glass does not produce anything.
4010-4 imaginary part of dielectric constant real part of the ratio, the claim that the “dielectric loss.” The smaller the ratio, of course, the smaller the energy loss.