Magnetoinductive wave control

Abstract

A method of configuring a metamaterial structure comprising a plurality of electrical resonators (110) that support magnetoinductive waves is disclosed. The method comprises: powering at least one of the electrical resonators (110) with an alternating current at an excitation frequency, the at least one powered electrical resonator providing a source of magnetoinductive waves in the structure; adjusting parameters of the metamaterial structure to create constructive interference of one- two- or three-dimensional magnetoinductive waves at one or more target resonators of the electrical resonators (110), to improve power transfer from the at least one powered electrical resonator to the one or more target resonators (110).

1 . A method of configuring a metamaterial structure comprising a plurality of electrical resonators that support magnetoinductive waves, the method comprising:
 powering at least one of the electrical resonators with an alternating current at an excitation frequency, the at least one powered electrical resonator providing a source of magnetoinductive waves in the structure;   adjusting parameters of the metamaterial structure to create constructive interference of one- two- or three-dimensional magnetoinductive waves at one or more target resonators of the electrical resonators, to improve power transfer from the at least one powered electrical resonator to the one or more target resonators.   
     
     
         2 . The method of  claim 1 , wherein improving power transfer comprises increasing current intensity in a target resonator and/or improving the efficiency of power transfer from the at least one powered electrical resonator to the one or more target resonators. 
     
     
         3 . The method of  claim 1  or  2 , wherein there are a plurality of target resonators, and improving power transfer comprises increasing the uniformity of current intensity in the target resonators. 
     
     
         4 . The method of any preceding claim, wherein the metamaterial structure comprises a lattice of resonators, and adjusting parameters of the metamaterial structure comprises creating one or more lattice defect in the metamaterial structure from which MIWs are scattered and/or reflected. 
     
     
         5 . The method of  claim 4 , wherein the configuration of the lattice defects is temporally periodic. 
     
     
         6 . The method of  claim 5 , wherein the defects are configured to produce a checkerboard pattern of alternating high and low currents in the neighbouring lattice elements in a region of the electrical resonators of the structure, and the method comprises switching the configuration of the defects from a first configuration with a first checkerboard pattern of high current resonators, and a second configuration with a second pattern that is substantially an inverted version of the first pattern 
     
     
         7 . The method of any of  claims 4  to  6 , comprising placing a defect on a symmetry axis/plane of the Brillouin zone of the metamaterial structure to reflect and/or scatter a beam formed along the symmetry axis/plane. 
     
     
         8 . The method of  claim 7 , wherein the metamaterial structure approximates a square 2D array, the method comprising placing a defect on a diagonal from a powered electrical resonator. 
     
     
         9 . The method of any of  claims 4  to  8 , comprising placing a pattern of defects along at least one edge of the array to create a specific standing MIW pattern over the structure. 
     
     
         10 . The method of  claim 9 , wherein the standing wave pattern approximates a checkerboard pattern of alternating high and low current intensity over a region of the structure. 
     
     
         11 . The method of  claim 9  or  10 , wherein the pattern of defects along at least one edge comprises defects in each corner of the structure. 
     
     
         12 . The method of  claim 11 , wherein the defects in each corner together form triangular shapes in each corner. 
     
     
         13 . The method of any of  claims 4  to  12 , wherein creating one or more defect in the array comprises creating a plurality of lambda-periodic defects in that have a spatial period in at least one direction corresponding with a wavelength of the MIWs from the at least one powered electrical resonator. 
     
     
         14 . The method of  claim 13 , wherein the lambda-periodic defects comprise, or consist entirely of, features at edge regions of the structure. 
     
     
         15 . The method of  claim 13  or  14 , wherein the lambda-periodic defects comprise a lambda-grid of defects across a region, or all of, the array. 
     
     
         16 . The method of any of  claims 4  to  15 , wherein creating one or more defect in the array comprises creating a defect at every second electrical resonator along the edges of the array. 
     
     
         17 . The method of any of  claims 4  to  16 , wherein at least one electrical resonator is a controllable resonator that comprises part of a controllable element, the controllable resonator being switchable from an on state to an off state using a control signal, wherein creating one or more defects in the metamaterial structure comprises using a control signal to switch a controllable resonator from an on state to an off state. 
     
     
         18 . The method of  claim 17 , wherein the controllable resonator has a resonant frequency in the on state and a first impedance at the resonant frequency in the on state, and in the off state has a second impedance at the resonant frequency that is at least 10 times less than the first impedance. 
     
     
         19 . The method of  claim 17  or  18 , wherein the controllable resonator comprises a primary resonator and the controllable element comprises a control device that further comprises an active control element that is configured to adjust the impedance and/or resonant frequency of the primary resonator in response to the control signal. 
     
     
         20 . The method of  claim 19 , wherein the control device comprises a secondary resonator, inductively coupled to the primary resonator, the active control component configured to vary the electrical properties of the secondary resonator in response to the control signal, thereby adjusting the impedance of the primary resonator. 
     
     
         21 . The method of  claim 20 , wherein the coupling between the primary resonator and secondary resonator results in the coupled system of the primary and secondary resonator having two modes: a first mode in which the currents in the controllable and secondary resonator are in phase, and a second mode in which the currents in the controllable and secondary resonator are out of phase. 
     
     
         22 . The method of  claim 21 , wherein the secondary resonator is operable in the off state to cause an anti-resonance in the system of the primary resonator and the secondary resonator, at the resonant frequency of the primary resonator. 
     
     
         23 . The method of any of  claims 17  to  22 , wherein adjusting parameters comprises communicating the control signal. 
     
     
         24 . The method of  claim 23 , wherein the control signal is communicated by an in-band communication channel that propagates as a modulated MIW through the structure. 
     
     
         25 . The method of any preceding claim, further comprising locating the target resonator by determining which electrical resonator has the best coupling to a target device placed in proximity to the structure. 
     
     
         26 . The method of  claim 25 , wherein locating the target resonator comprises:
 establishing a communication channel between a system controller and the target device;   receiving information from the target device about whether the target device is receiving power from the structure;   conducting a search for the target device by adjusting the parameters of the structure to vary the distribution of current therein, while monitoring the received power at the target device.   
     
     
         27 . The method of  claim 26 , comprising using a model to simulate the propagation of MIWs in the structure to determine how to adjust the parameters of the metamaterial structure to improve power transfer. 
     
     
         28 . The method of any preceding claim, wherein adjusting the parameters of the metamaterial structure comprises adjusting a location and/or amplitude and/or phase of a further powered electrical resonator, wherein the location and or/phase of the further powered electrical resonator is selected to provide constructive interference at the one or more target resonator. 
     
     
         29 . The method of  claim 28 , wherein the phase and/or ampitude of the at least one powered electrical resonator and the further powered electrical resonator is different. 
     
     
         30 . The method of any preceding claim, wherein improving power transfer comprises at least one of:
 i) increasing current intensity in the one or more target resonators;   ii) improving the efficiency of power transfer between the at least one powered electrical resonator and the one or more target resonators;   ii) where there is more than one target resonator, improving the uniformity of current intensity in the target resonators and/or increasing the average current intensity in the target resonators.   
     
     
         31 . An apparatus comprising:
 a plurality of electrical resonators that are configurable to form a metamaterial structure which supports MIWs;   a power source for powering at least one of the electrical resonators with an alternating current at an excitation frequency, so that the at least one powered electrical resonator provides a source of magnetoinductive waves in the structure;   a system controller configured to adjust parameters of the metamaterials structure to create constructive interference of two or three dimensional magnetoinductive waves at one or more target resonators of the electrical resonators, to improve power transfer from the powered at least one electrical resonator to the one or more target electrical resonators.   
     
     
         32 . The apparatus of  claim 31 , wherein improving power transfer comprises increasing current intensity in a target resonator and/or improving the efficiency of power transfer from the at least one powered electrical resonator to the one or more target resonators. 
     
     
         33 . The apparatus of  claim 31  or  32 , wherein there are a plurality of target resonators, and improving power transfer comprises increasing the uniformity of current intensity in the target resonators. 
     
     
         34 . The apparatus of any of  claims 31  to  33 , wherein adjusting parameters of the metamaterial structure comprises creating one or more defect in the metamaterial structure from which MIWs are scattered and/or reflected. 
     
     
         35 . The apparatus of  claim 34 , wherein the configuration of the defects is temporally periodic. 
     
     
         36 . The apparatus of  claim 35 , wherein the defects are configured to produce a checkerboard pattern of alternating high and low currents in a region of the electrical resonators of the structure, and the system controller is configured to switch the configuration of the defects from a first configuration with a first checkerboard pattern of high current resonators, and a second configuration with a second pattern that is substantially an inverted version of the first pattern 
     
     
         37 . The apparatus of any of  claims 34  to  36 , comprising placing a defect on a symmetry axis/plane of the Brillouin scattering zone of the metamaterial structure to reflect and/or scatter a beam formed along the symmetry axis/plane. The apparatus of  claim 37 , wherein the metamaterial structure approximates a square 2D array, the method comprising placing a defect on a diagonal from a powered electrical resonator. 
     
     
         39 . The apparatus of any of  claims 34  to  38 , wherein the system controller is configured to place a pattern of defects along at least one edge of the array to create a specific standing wave pattern over the structure. 
     
     
         40 . The apparatus of  claim 39 , wherein the standing wave pattern approximates a checkerboard pattern of alternating high and low current intensity over a region of the structure. 
     
     
         41 . The apparatus of  claim 39  or  40 , wherein the pattern of defects along at least one edge comprises defects in each corner of the structure. 
     
     
         42 . The apparatus of  claim 41 , wherein the defects in each corner together form triangular shapes in each corner. 
     
     
         43 . The apparatus of any of  claims 34  to  42 , wherein creating one or more defect in the array comprises creating a plurality of lambda-periodic defects in that have a spatial period in at least one direction corresponding with a wavelength of the MIWs from the at least one powered electrical resonator. 
     
     
         44 . The apparatus of  claim 43 , wherein the lambda-periodic defects comprise, or consist entirely of, features at edge regions of the structure. 
     
     
         45 . The apparatus of  claim 43  or  44 , wherein the lambda-periodic defects comprise a lambda-grid of defects across a region, or all of, the array. 
     
     
         46 . The apparatus of any of  claims 34  to  45 , wherein creating one or more defect in the array comprises creating a defect at every second electrical resonator along the edges of the array. 
     
     
         47 . The apparatus of any of  claims 34  to  46 , wherein at least one electrical resonator is a controllable resonator that comprises part of a controllable element, the controllable resonator being switchable from an on state to an off state using a control signal, wherein creating one or more defects in the metamaterial structure comprises using a control signal to switch a controllable resonator from an on state to an off state. 
     
     
         48 . The apparatus of  claim 47 , wherein the controllable resonator has a resonant frequency in the on state and a first impedance at the resonant frequency in the on state, and in the off state has a second impedance at the resonant frequency that is at least 10 times less than the first impedance. 
     
     
         49 . The apparatus of  claim 47  or  48 , wherein the controllable resonator comprises a primary resonator and the controllable element comprises a control device that further comprises an active control element that is configured to adjust the impedance of the primary resonator in response to the control signal. 
     
     
         50 . The apparatus of  claim 49 , wherein the control device comprises a secondary resonator, inductively coupled to the primary resonator, the active control component configured to vary the electrical properties of the secondary resonator in response to the control signal, thereby adjusting the impedance of the primary resonator. 
     
     
         51 . The apparatus of  claim 50 , wherein the coupling between the primary resonator and secondary resonator results in the coupled system of the primary and secondary resonator having two modes: a first mode in which the currents in the controllable and secondary resonator are in phase, and a second mode in which the currents in the controllable and secondary resonator are out of phase. 
     
     
         52 . The apparatus of  claim 51 , wherein the secondary resonator is operable in the off state to cause an anti-resonance in the impedance of the primary resonator at the resonant frequency. 
     
     
         53 . The apparatus of any of  claims 47  to  52 , wherein adjusting parameters comprises communicating the control signal. 
     
     
         54 . The apparatus of  claim 53 , wherein the controllable resonator and the system controller comprise a modem configured to establish an in-band communication channel between the system controller and the controllable resonator that propagates as a modulated MIW via the structure, wherein the control signal is communicated by the in-band communication channel. 
     
     
         55 . The apparatus of any of  claims 30  to  54 , further comprising locating the target resonator by determining which electrical resonator has the best coupling to a target device placed in proximity to the structure. 
     
     
         56 . The apparatus of  claim 55 , wherein the system controller is configured to locate the target resonator by:
 establishing a communication channel between a system controller and the target device;   receiving information from the target device about whether the target device is receiving power from the structure;   conducting a search for the target device by adjusting the parameters of the structure to vary the distribution of current therein, while monitoring the received power at the target device.   
     
     
         57 . The apparatus of  claim 56 , wherein the system controller comprises a model operable to simulate the propagation of MIWs in the structure, and the system controller is configured to use the model to determine how to adjust the parameters of the metamaterial structure to improve power transfer. 
     
     
         58 . The apparatus of any of  claims 30  to  57 , wherein the system controller is configured to adjust the parameters of the metamaterial structure by adjusting a location and/or phase of a further powered electrical resonator, wherein the location and or/phase of the further powered electrical resonator is selected to provide constructive interference at the one or more target resonator. 
     
     
         59 . The apparatus of any of  claims 58 , wherein system controller is configured to apply power with a first phase to the at least one powered electrical resonator and to apply power with a second, different phase to the further powered electrical resonator. 
     
     
         60 . The apparatus of any of  claims 30  to  59 , wherein the system controller is configured to improve power transfer by at least one of:
 i) increasing current intensity in the one or more target resonators; 
 ii) improving the efficiency of power transfer between the at least one powered electrical resonator and the one or more target resonators; 
 ii) where there is more than one target resonator, improving the uniformity of current intensity in the target resonators and/or increasing the average current intensity in the target resonators.