《磁共振(磁谐振耦合)无线充电技术鼻祖级文章-英文原文》由会员分享，可在线阅读，更多相关《磁共振(磁谐振耦合)无线充电技术鼻祖级文章-英文原文（8页珍藏版）》请在金锄头文库上搜索。
1、Wireless Power Transfer via Strongly Coupled Magnetic ResonancesAndr Kurs,1* Aristeidis Karalis,2 Robert Moffatt,1 J. D. Joannopoulos,1 Peter Fisher,3 Marin Soljai11Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA. 2Department of Electrical Engineering and Compu
2、ter Science, Massachusetts Institute of Technology, Cambridge, MA 02139, USA. 3Department of Physics and Laboratory for Nuclear Science, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.*To whom correspondence should be addressed. E-mail: 8 / 8Using self-resonant coils in a strongly c
3、oupled regime, we experimentally demonstrate efficient non-radiative power transfer over distances of up to eight times the radius of the coils. We demonstrate the ability to transfer 60W with approximately 40% efficiency over distances in excess of two meters. We present a quantitative model descri
4、bing the power transfer which matches the experimental results to within 5%. We discuss practical applicability and suggest directions for further studies.At first glance, such power transfer is reminiscent of the usual magnetic induction (10); however, note that the usual non- resonant induction is
5、 very inefficient for mid-range applications.Overview of the formalism. Efficient mid-range power transfer occurs in particular regions of the parameter space describing resonant objects strongly coupled to one another. Using coupled-mode theory to describe this physical system (11), we obtain the f
6、ollowing set of linear equationsIn the early 20th century, before the electrical-wire grid, Nikola Tesla (1) devoted much effort towards schemes toa& m(t) = (im - Gm )am (t) + imnan (t) + Fm (t) nm (1)transport power wirelessly. However, typical embodiments (e.g. Tesla coils) involved undesirably la
7、rge electric fields. During the past decade, society has witnessed a dramatic surge of use of autonomous electronic devices (laptops, cell- phones, robots, PDAs, etc.) As a consequence, interest in wireless power has re-emerged (24). Radiative transfer (5), while perfectly suitable for transferring
8、information, poses a number of difficulties for power transfer applications: the efficiency of power transfer is very low if the radiation is omnidirectional, and requires an uninterrupted line of sight and sophisticated tracking mechanisms if radiation is unidirectional. A recent theoretical paper
9、(6) presented a detailed analysis of the feasibility of using resonant objects coupled through the tails of their non-radiative fields for mid- range energy transfer (7). Intuitively, two resonant objects of the same resonant frequency tend to exchange energy efficiently, while interacting weakly wi
10、th extraneous off- resonant objects. In systems of coupled resonances (e.g. acoustic, electro-magnetic, magnetic, nuclear, etc.), there is often a general “strongly coupled” regime of operation (8). If one can operate in that regime in a given system, the energy transfer is expected to be very effic
11、ient. Mid-range power transfer implemented this way can be nearly omnidirectional and efficient, irrespective of the geometry of the surrounding space, and with low interference and losses into environmental objects (6).Considerations above apply irrespective of the physicalnature of the resonances.
12、 In the current work, we focus on one particular physical embodiment: magnetic resonances (9). Magnetic resonances are particularly suitable for everyday applications because most of the common materials do not interact with magnetic fields, so interactions with environmental objects are suppressed
13、even further. We were able to identify the strongly coupled regime in the system of two coupled magnetic resonances, by exploring non-radiative (near-field) magnetic resonant induction at MHz frequencies.where the indices denote the different resonant objects. The variables am(t) are defined so that
14、 the energy contained in object m is |am(t)|2, wm is the resonant frequency of that isolated object, and Gm is its intrinsic decay rate (e.g. due to absorption and radiated losses), so that in this framework an uncoupled and undriven oscillator with parameters w0 and G0 would evolve in time as exp(i
15、w0t G0t). The kmn = knm are coupling coefficients between the resonant objects indicated by the subscripts, and Fm(t) are driving terms.We limit the treatment to the case of two objects, denoted by source and device, such that the source (identified by the subscript S) is driven externally at a cons
16、tant frequency, and the two objects have a coupling coefficient k. Work is extracted from the device (subscript D) by means of a load (subscript W) which acts as a circuit resistance connected to the device, and has the effect of contributing an additional term GW to the unloaded device objects decay rate GD. The overall decay rate at the device is therefore GD = GD + GW. The work extracted is determined by the power dissipated i
