Patent Description:
Electrical energy used in powering electronic devices comes predominantly from wired sources. Conventional wireless power transfer relies on magnetic inductive effect between two coils placed in close proximity of one another. To increase its efficiency, the coil size is selected to be less than the wavelength of the radiated electromagnetic wave. The transferred power diminishes strongly as the distance between the source and the charging device is increased.

US Application bearing publication number <CIT>appears directed to a wireless power transmission system that includes at least one source of electromagnetic radiation, a multitude of wireless power receivers that receive radiated electromagnetic energy, a beacon collocated with each wireless power receiver and adapted to generate and radiates a pilot signal when the beacon is in an active state, and an array of transmitting antennas connected to the source of electromagnetic radiation that radiates the electromagnetic radiation in the direction of the beacon in the active state. The electromagnetic radiation can be electronically steered from one wireless power receiver to another by activating and deactivating the beacons collocated with each wireless power receiver.

<CIT> B <NUM> appears directed to a system for providing wireless, charging power and/or primary power to electronic/electrical devices. Microwave energy is focused by a power transmitter that includes one or more adaptively-phased microwave array emitters onto a device to be charged. Rectennas within the device to be charged receive and rectify the microwave energy and use it for battery charging and/or for primary power. A locator signal generated by the device to be charged is analyzed by the system to determine the location of the device to be charged relative to the microwave array emitters, permitting the microwave energy to be directed towards the device to be charged. Backscatter detectors respond to backscatter energy reflected off of any obstacle between the device to be charged and the microwave array emitters. Power to any obstructed microwave array emitter is reduced until the obstruction is removed. The data can be modulated onto microwave energy beams produced by the array emitters and demodulated by the device, thereby providing means of data communication from the power transmitter to the device. Similarly, data can be modulated onto the locator signal and demodulated in the power transmitter, thereby providing means of data communication from the device to the power transmitter.

The scope of the present invention is set out in the claims appended hereto.

The Figures included herein are each considered to be useful to aid in the understanding of the present invention and background concepts of the present invention. The Figures included herein are not necessarily according to the present invention. In particular, all Figures except for <FIG> refer primarily to background concepts or other concepts of this disclosure.

An RF lens, for example the RF lens of the present invention, typically includes a multitude of radiators adapted to transmit radio frequency electromagnetic EM waves (hereinafter alternatively referred to as EM waves, or waves) whose phases and amplitudes are modulated so as to concentrate the radiated power in a small volume of space (hereinafter alternatively referred to as focus point or target zone) in order to power an electronic device positioned in that space. Accordingly, the waves emitted by the radiators are caused to interfere constructively at the focus point.

<FIG> shows a multitude of radiators, arranged in an array <NUM>, forming an RF lens. Array <NUM> is shown as including N radiators <NUM><NUM>, <NUM><NUM>, <NUM><NUM>. <NUM>N-<NUM>, <NUM>N each adapted to radiate an EM wave whose amplitude and phase may be independently controlled in order to cause constructive interference of the radiated EM waves at a focus point where a device to be charged is located, where N is integer greater than <NUM>. <FIG> is a side view of the array <NUM> when the relative phases of the waves generated by radiators <NUM>i (i is an integer ranging from <NUM> to N) are selected so as to cause constructive interference between the waves to occur near region <NUM> where a device being wirelessly charged is positioned, i.e., the focus point. Region <NUM> is shown as being positioned at approximately distance d<NUM> from center <NUM> of array <NUM>. The distance between the array center and the focus point is alternatively referred to herein as the focal length. Although the following description of an RF lens is provided with reference to a one or two dimensional array of radiators, it is understood that an RF lens in accordance with the present invention may have any other arrangement of the radiators, such as a circular arrangement <NUM> of radiators <NUM> as shown in <FIG>, or the elliptical arrangement <NUM> of radiators <NUM> shown in <FIG>.

As seen from <FIG>, each radiator <NUM>i is assumed to be positioned at distance yi from center <NUM> of array <NUM>. The amplitude and phase of the wave radiated by radiator <NUM>i are assumed to be represented by Ai and θi respectively. Assume further that the wavelength of the waves being radiated is represented by λ. To cause the waves radiated by the radiators to interfere constructively in region <NUM> (i.e., the desired focus point), the following relationship is satisfied between various phases θi and distances yi: <MAT>.

Since the phase of an RF signal may be accurately controlled, power radiated from multiple sources may be focused, in accordance with the present invention, onto a target zone where a device to be wirelessly charged is located. Furthermore, dynamic phase control enables the tracking of the device as it moves from its initial location. For example, as shown in <FIG>, if the device moves to a different position-along the focal plane-located at a distance d<NUM> from center point <NUM> of the array, in order to ensure that the target zone is also located at distance d<NUM>, the phases of the sources may be adjusted in accordance with the following relationship: <MAT>.

Referring to <FIG>, if the device moves to a different position away from the focal plane (e.g., to a different point along the y-axis) the radiators' phases are dynamically adjusted, as described below, so as to track and maintain the target zone focused on the device. Parameter yc represents the y-component of the device's new position, as shown in <FIG>, from the focal plane of the array (i. e, the plane perpendicular to the y-axis and passing through center <NUM> of array <NUM>).

The amount of power transferred is defined by the wavelength λ of the waves being radiated by the radiators, the array span or array aperture A as shown in <FIG>, and the focal length, i.e. (λF/A).

In one example, the distance between each pair of radiators is of the order of the wavelength of the signal being radiated. For example, if the frequency of the radiated wave is <NUM> (i.e., the wavelength is <NUM>), the distance between each two radiators may be a few tenths to a few tens of the wavelengths, that may vary depending on the application.

An RF lens, in accordance with the present invention, is operative to transfer power wirelessly in both near-field and far field regions. In the optical domain, a near field region is referred to as the Fresnel region and is defined as a region in which the focal length is of the order of the aperture size. In the optical domain, a far field region is referred to as the Fraunhofer region and is defined as a region in which the focal length (F) is substantially greater than (2A<NUM>/λ).

To transfer power wirelessly to a device, in accordance with the present invention, the radiator phases are selected so as to account for differences in distances between the target point and the radiators. For example, assume that the focal length d<NUM> in <FIG> is of the order of the aperture size A. Therefore, since distances S<NUM>, S<NUM>, S<NUM>. SN are different from one another, corresponding phases θ<NUM>, θ<NUM>, θ<NUM>. θN of radiators <NUM><NUM>, <NUM><NUM>, <NUM><NUM>. <NUM>N are varied so as to satisfy expression (<NUM>), described above. The size of the focus point (approximately λF/A) is relatively small for such regions because of the diffraction limited length.

A radiator array, in accordance with the present invention, is also operative to transfer power wirelessly to a target device in the far field region where the focal length is greater than (2A<NUM>/λ). For such regions, the distances from the different array elements to the focus spot are assumed be to be the same. Accordingly, for such regions, S<NUM> = S<NUM> = S<NUM>. = SN, and θ<NUM> = θ<NUM> = θ<NUM>. The size of the focus point is relatively larger for such regions and thus is more suitable for wireless charging of larger appliances.

<FIG> shows an RF lens <NUM>. RF lens <NUM> is shown as including a two dimensional array of radiators <NUM>i,j arranged along rows and columns. Although RF lens <NUM> is shown as including <NUM> radiators <NUM>i,j disposed along <NUM> rows and <NUM> columns (integers i and j are indices ranging from <NUM> to <NUM>) it is understood that an RF lens may have any number of radiators disposed along U rows and V columns, where U and V are integers greater one. In the following description, radiators <NUM>i,j may be collectively or individually referred to as radiators <NUM>.

As described further blow, the array radiators are locked to a reference frequency, which may be a sub-harmonic (n=<NUM>, <NUM>, <NUM>. ) of the radiated frequency, or at the same frequency as the radiated frequency. The phase of the wave radiated by each radiator are controlled independently in order to enable the radiated waves to constructively interfere and concentrate their power onto a target zone within any region in space.

<FIG> is a simplified block diagram of a radiator <NUM> disposed in RF lens <NUM>. As seen, radiator <NUM> is shown as including, in part, a programmable delay element (also referred to herein as phase modulator) <NUM>, a phase/frequency locked loop <NUM>, a power amplifier <NUM>, and an antenna <NUM>. Programmable delay element <NUM> is adapted to delay signal W<NUM> to generate signal W<NUM>. The delay between signals W<NUM> and W<NUM> is determined in accordance with control signal Ctrl applied to the delay element. In one example, phase/frequency locked loop <NUM> receives signal W<NUM> as well as a reference clock signal having a frequency Fref to generate signal W<NUM> whose frequency is locked to the reference frequency Fref. In another example, signal W<NUM> generated by phase/frequency locked loop <NUM> has a frequency defined by a multiple of the reference frequency Fref. Signal W<NUM> is amplified by power amplifier <NUM> and transmitted by antenna <NUM>. Accordingly and as described above, the phase of the signal radiated by each radiator <NUM> may be varied by an associated programmable delay element <NUM> disposed in the radiator.

<FIG> is a simplified block diagram of a radiator <NUM> disposed in RF lens <NUM>. As seen, radiator <NUM> is shown as including, in part, a programmable delay element <NUM>, a phase/frequency locked loop <NUM>, a power amplifier <NUM>, and an antenna <NUM>. Programmable delay element <NUM> is adapted to delay the reference clock signal Fref thereby to generate a delayed reference clock signal Fref_Delay. The delay between signals Fref and Fref_Delay is determined in accordance with control signal Ctrl applied to the delay element <NUM>. Signal W<NUM> generated by phase/frequency locked loop <NUM> has a frequency locked to the frequency of signal Fref_Delay or a multiple of the frequency of signal Fref_Delay. In other examples (not shown), the delay element is disposed in and is part of phase/frequency locked loop <NUM>. In yet other examples (not shown), the radiators may not have an amplifier.

<FIG> shows a number of components of a device <NUM> adapted to be charged wirelessly. Device <NUM> is shown as including, in part, an antenna <NUM>, a rectifier <NUM>, and a regulator <NUM>. Antenna <NUM> receives the electromagnetic waves radiated by a radiator, in accordance with the present invention. Rectifier <NUM> is adapted to convert the received AC power to a DC power. Regulator <NUM> is adapted to regulate the voltage signal received from rectifier <NUM> and apply the regulated voltage to the device. High power transfer efficiency is obtained if the aperture area of the receiver antenna is comparable to the size of the target zone of the electromagnetic field. Since most of the radiated power is concentrated in a small volume forming the target zone, such a receiver antenna is thus optimized to ensure that most of the radiated power is utilized for charging up the device. The device may be retro-fitted externally with components required for wireless charging. In another example, existing circuitry present in the charging device, such as antenna, receivers, and the like, may be used to harness the power.

<FIG> is a schematic diagram of RF lens <NUM> wirelessly charging device <NUM>. <FIG> shows RF lens <NUM> concurrently charging devices <NUM>, and <NUM> using focused waves of similar or different strengths. <FIG> shows RF lens <NUM> wireless charging mobile devices <NUM>, <NUM> and stationary device <NUM> all of which are assumed to be indoor.

<FIG> shows computer-simulated electromagnetic field profiles generated by a one-dimensional RF lens at a distance <NUM> meters away from the RF lens having an array of <NUM> isotropic radiators. The beam profiles are generated for three different frequencies, namely <NUM> (wavelength <NUM>), <NUM> (wavelength <NUM>), and <NUM> (wavelength <NUM>). Since the distance between each pair of adjacent radiators of the RF lens is assumed to be <NUM>, the RF lens has an aperture of <NUM>. Therefore, the wavelengths are of the order of aperture size and focal length of the radiator. <FIG> is a simplified schematic view of such an RF lens <NUM> having <NUM> radiators <NUM>k that are spaced <NUM> apart from one another, where K is an integer ranging from <NUM> to <NUM>.

Plots <NUM>, <NUM> and <NUM> are computer simulations of the electromagnetic field profiles respectively for <NUM>, <NUM>, and <NUM> signals radiated by radiator <NUM> when the relative phases of the various radiators are selected so as to account for the path differences from each of radiators <NUM>k to the point located <NUM> meters away from radiator <NUM><NUM> in accordance with expression (<NUM>) above. For each of these profiles, the diffraction limited focus size is of the order of the wavelengths of the radiated signal. Plots <NUM>, <NUM> and <NUM> are computer simulations of the electromagnetic field profiles at a distance <NUM> meters away from the radiator array for <NUM>, <NUM>, and <NUM> signals respectively when the phases of radiators <NUM>k were set equal to one another.

As seen from these profiles, for the larger wavelength having a frequency of <NUM> (i. e, plots <NUM>, <NUM>), because the path differences from the individual radiators to the focus point are not substantially different, the difference between profiles <NUM> and <NUM> is relatively unpronounced. However, for each of <NUM> and <NUM> frequencies, the EM confinement (focus) is substantially more when the relative phases of the various radiators are selected so as to account for the path differences from the radiators <NUM>k to the focus point than when radiator phases are set equal to one another. Although the above examples are provided with reference to operating frequencies of <NUM>, <NUM>, and <NUM>, it is understood that any other operating frequency, such as <NUM>, <NUM>, and <NUM> may be used.

<FIG> shows the variations in computer simulated electromagnetic field profiles generated by RF lens <NUM>-at a distance of <NUM> meters away from the RF lens-as a function of the spacing between each adjacent pair of radiators. The RF lens is assumed to operate at a frequency of <NUM>. Plots <NUM>, <NUM>, and <NUM> are computer simulations of the field profiles generated respectively for radiator spacings of <NUM>, <NUM>, and <NUM> after selecting the relative phases of the various radiators to account for the path differences from various radiators <NUM>k to the point <NUM> meters away from the RF lens, in accordance with expression (<NUM>) above. Plots <NUM>, <NUM>, and <NUM> are computer simulations of the field profiles generated respectively for radiator spacings of <NUM>, <NUM>, and <NUM> assuming all radiators disposed in RF lens <NUM> have equal phases. As is seen from these plots, as the distance between the radiators increases-thus resulting in a larger aperture size-the EM confinement also increases thereby resulting in a smaller focus point.

<FIG> is the computer simulation of the EM profile of an RF lens at a distance <NUM> meters away from an RF lens having disposed therein a two-dimensional array of Hertzian dipoles operating at a frequency of <NUM>, such as RF lens <NUM> shown in <FIG>. The spacing between the dipole radiators are assumed to be <NUM>. The relative phases of the radiators were selected so as to account for the path differences from the radiators to the focal point, assumed to be located <NUM> meters away from the RF lens. In other words, the relative phases of the radiators is selected to provide the RF lens with a focal length of approximately <NUM> meters. The scale used in generating <FIG> is -<NUM> dB to <NUM> dB. <FIG> shows the EM profile of <FIG> using a scale of -<NUM> dB to <NUM> dB.

<FIG> is the computer simulation of the EM profile of the RF lens of <FIG> at a distance <NUM> meters away from the focal point, i.e., <NUM> meters away from the RF lens. As is seen from <FIG>, the radiated power is diffused over a larger area compared to those shown in <FIG>. The scale used in generating <FIG> is -<NUM> dB to <NUM> dB. <FIG> shows the EM profile of <FIG> using a scale of -<NUM> dB to <NUM> dB.

<FIG> is the computer simulation of the EM profile of an RF lens at a distance <NUM> meters away from the RF lens having disposed therein a two-dimensional array of Hertzian dipoles operating at a frequency of <NUM>. The spacing between the dipole radiators are assumed to be <NUM>. The relative phases of the radiators are selected so as to account for the path differences from the radiators to the focal point, assumed to be located <NUM> meters away from the RF lens and at an offset of <NUM> from the focal plane of the RF lens, i.e., the focus point has a y-coordinate of <NUM> meters from the focal plane (see <FIG>). The scale used in generating <FIG> is -<NUM> dB to <NUM>. <FIG> shows the EM profile of <FIG> using a scale of -<NUM> dB to <NUM> dB.

<FIG> is the computer simulation of the EM profile of the RF lens of <FIG> at a distance <NUM> meters away from the focal point, i.e., <NUM> meters away from the x-y plane of the RF lens. As is seen from <FIG>, the radiated power is diffused over a larger area compared to that shown in <FIG>. The scale used in generating <FIG> is -<NUM> dB to <NUM> dB. <FIG> shows the EM profile of <FIG> using a scale of -<NUM> dB to <NUM> dB. The EM profiles shown in <FIG>, <FIG> <FIG>, <FIG> demonstrate the versatility of an RF lens, in accordance with the present invention, in focusing power at any arbitrary point in 3D space.

In accordance with one aspect of the present invention, the size of the array forming an RF lens is configurable and may be varied by using radiator tiles each of which may include one or more radiators. <FIG> shows an example of a radiator tile <NUM> having disposed therein four radiators <NUM><NUM>, <NUM><NUM>, <NUM><NUM>, and <NUM><NUM>. Although radiator tile <NUM> is shown as including four radiators, it is understood that a radiator tile, in accordance with one aspect of the present invention, may have fewer (e.g., one) or more than (e.g., <NUM>) four radiators. <FIG> shown an RF lens <NUM> initially formed using <NUM> radiator tiles, namely radiator tiles <NUM><NUM>, <NUM><NUM>, <NUM><NUM>, <NUM><NUM>, <NUM><NUM>, <NUM><NUM>, <NUM><NUM>-each of which is similar to radiator tile <NUM> shown in <FIG>-and being provided with two more radiator tiles <NUM><NUM> and <NUM><NUM>. Although not shown, it is understood that each radiator tile includes the electrical connections necessary to supply power to the radiators and deliver information from the radiators as necessary. In one example, the radiators formed in the tiles are similar to radiator <NUM> shown in <FIG>.

In accordance with one aspect of the present invention, the RF lens is adapted to track the position of a mobile device in order to continue the charging process as the mobile device changes position. To achieve this, a subset or all of the radiators forming the RF lens include a receiver. The device being charged also includes a transmitter adapted to radiate a continuous signal during the tracking phase. By detecting the relative differences between the phases (arrival times) of such a signal by at least three different receivers formed on the RF lens, the position of the charging device is tracked.

<FIG> is a simplified block diagram of a radiator <NUM> disposed in an RF lens, such as RF lens <NUM> shown in <FIG>. Radiator <NUM> is similar to radiator <NUM> shown in <FIG>, except that radiator <NUM> has a receiver amplifier and phase recovery circuit <NUM>, and a switch S<NUM>. During power transfer, switch S<NUM> couples antenna <NUM> via node A to power amplifier <NUM> disposed in the transmit path. During tracking, switch S<NUM> couples antenna <NUM> via node B to receiver amplifier and phase recovery circuit <NUM> disposed in the receive path to receive the signal transmitted by the device being charged.

<FIG> shows a number of components of a device <NUM> adapted to be charged wirelessly. Device <NUM> is similar to device <NUM> shown in <FIG>, except that device <NUM> has a transmit amplifier <NUM>, and a switch S<NUM>. During power transfer, switch S<NUM> couples antenna <NUM> via node D to rectifier <NUM> disposed in receive path. During tracking, switch S<NUM> couples antenna <NUM> via node C to transmit amplifier <NUM> to enable the transmission of a signal subsequently used by the RF lens to detect the position of device <NUM>. <FIG> shows RF lens <NUM> tracking device <NUM> by receiving the signal transmitted by device <NUM>.

In another example, a pulse based measurement technique is used to track the position of the mobile device. To achieve this, one or more radiators forming the RF lens transmit a pulse during the tracking phase. Upon receiving the pulse, the device being tracked sends a response which is received by the radiators disposed in the array. The travel time of the pulse from the RF lens to the device being tracked together with the travel times of the response pulse from the device being tracked to the RF lens is representative of the position of the device being tracked. In the presence of scatterers, the position of the device could be tracked using such estimation algorithms as maximum likelihood, or least-square, Kalman filtering, a combination of these techniques, or the like. The position of the device may also be determined and tracked using WiFi and GPS signals.

The presence of scattering objects, reflectors and absorbers may affect the RF lens' ability to focus the beam efficiently on the device undergoing wireless charging. For example, <FIG> shows an RF lens <NUM> transferring power to device <NUM> in the presence of a multitude of scattering objects <NUM>. To minimize such effects, the amplitude and phase of the individual radiators of the array may be varied to increase power transfer efficiency. Any one of a number of techniques may be used to vary the amplitude or phase of the individual radiators.

In accordance with one such technique, to minimize the effect of scattering, a signal is transmitted by one or more of the radiators disposed in the RF lens. The signal(s) radiated from the RF lens is scattered by the scattering objects and received by the radiators (see <FIG>). An inverse scattering algorithm is then used to construct the scattering behavior of the environment. Such a construction may be performed periodically to account for any changes that may occur with time. In accordance with another technique, a portion or the entire radiator array may be used to electronically beam-scan the surroundings to construct the scattering behavior from the received waves. In accordance with yet another technique, the device undergoing wireless charging is adapted to periodically send information about the power it receives to the radiator. An optimization algorithm then uses the received information to account for scattering so as to maximize the power transfer efficiency.

Claim 1:
An RF lens (<NUM>) comprising:
a first plurality of radiators (<NUM><NUM>,<NUM>-<NUM><NUM>,<NUM>) adapted to radiate electromagnetic waves to power a device (<NUM>, <NUM>) positioned away from the RF lens (<NUM>), wherein the plurality of radiators (<NUM><NUM>,<NUM>-<NUM><NUM>,<NUM>) operate at a first frequency; and
a plurality of locked loop circuits adapted to control phases of the electromagnetic waves radiated by the first plurality of radiators (<NUM><NUM>,<NUM>-<NUM><NUM>,<NUM>) such that the phase of the electromagnetic wave radiated by each of the plurality of radiators (<NUM><NUM>,<NUM>-<NUM><NUM>,<NUM>) is set in accordance with a distance between the radiator and the device (<NUM>, <NUM>), wherein said plurality of locked loop circuits are further adapted to lock a phase or a frequency of the electromagnetic wave radiated by each of the first plurality of radiators (<NUM><NUM>,<NUM>-<NUM><NUM>,<NUM>) to a phase or a frequency of a reference signal;
wherein each radiator comprises an antenna (<NUM>);
characterised in that each radiator comprises a switch (S<NUM>) configured to switch the radiator between power transfer, wherein the switch (S<NUM>) couples the antenna (<NUM>) to a power amplifier (<NUM>), and tracking, wherein the switch (S<NUM>) couples the antenna (<NUM>) to a receiver amplifier and a phase recovery circuit (<NUM>).