CN111106858B - Device and method for wireless power transmission based on antenna array design - Google Patents

Abstract

Embodiments of the present disclosure relate to a method, apparatus, and wireless power transfer system for wireless power transfer based on antenna array design. By adopting the embodiment of the disclosure, a plurality of discrete users in the space can be charged simultaneously according to different energy distribution demands, and the transmitting array can rapidly respond and adjust the beam radiation direction when the positions of the users are switched. Compared with a traditional phased array, the array has more accurate beam pointing in a multi-beam pointing scene; compared with a conventional rectangular pulse modulation array, the time modulation is finished by adopting cosine and pulse signals, the number of radiation beams generated by the array is easy to control, the directions of the beams are independently controllable, the waste caused by useless sideband radiation is avoided, and the space transmission efficiency from point to multiple points is improved. The time modulation of the antenna channel is realized in a digital control mode, the multi-beam independent directional control and ultra-low side lobe radiation of the array can be realized under the condition of not needing a phase shifter, and the efficiency of a wireless power transmission system is effectively improved.

Description

Device and method for wireless power transmission based on antenna array design

Technical Field

Embodiments of the present disclosure generally relate to the field of wireless power transmission via antenna arrays, and more particularly, to multi-beam time-modulated inversion arrays applied to wireless power transmission.

Background technique

Wireless power transmission is a technology that can transfer electrical energy from the transmitting source to the receiving load without a wire connection. According to the different energy transmission mechanisms, it can be roughly divided into two methods: near-field transmission based on non-radiative methods and far-field transmission based on radio frequency radiation. Far-field wireless power transmission has broad application prospects due to its longer transmission distance and the ability to take into account the information interaction function of users at both ends of the transmitter and receiver. Far-field wireless power transmission follows the propagation model of electromagnetic waves in free space. According to the Friis formula, the energy obtained at the receiving end will experience path loss. In order to ensure that sufficient energy is obtained in the receiving area, array antennas are usually used as transmitting devices, and array beamforming and other technologies are used to synthesize highly directional narrow beams to accurately point to the receiving target, thereby improving the energy transmission efficiency of the link.

In order to achieve precise beam pointing, a high-precision phase shifter can be introduced into the transmitting antenna array channel, but this method is expensive and requires the angular position of the receiving target to be known in advance, resulting in a complex array feeding network and cumbersome signal processing process. The reverse array is also called a directional self-traceable array. The working principle is that when the phase of the receiving and transmitting signals of the antenna unit in the array meets the generalized conjugation condition, the transmitted signal will return along the direction of the incoming wave, that is, the "reverse" of electromagnetic wave transmission is achieved. The main implementation forms of the reverse array are: Van Atta form, phase conjugate array based on superheterodyne technology (Pon-Type structure), phase conjugate array based on phase detection phase-locked loop, and digital reverse array. The Van Atta array has strict requirements on the symmetry of the array and the consistency of the antenna unit, and is only applicable to planar arrays with plane wave incidence. Compared with the former, the reverse array based on superheterodyne uses a phase conjugate mixing circuit based on a mixer to achieve wavefront reconstruction at each antenna unit, and no longer strictly limits the array form. Therefore, it is widely used in communication, radar, and wireless energy transmission systems.

However, the traditional inverted array is based on a phased array system, and the radiation performance deteriorates seriously when the number of pointing targets increases.

Summary of the invention

The present disclosure overcomes the shortcomings of the prior art and proposes an improved method and device for wireless power transmission.

According to the first aspect of the present disclosure, a method for wireless power transmission based on antenna array design is provided. The method includes: receiving a guide signal from at least one user device with multiple antenna units; for each of the multiple antenna units: mixing the received guide signal with a local oscillator signal, filtering the mixed signal through a low-pass filter to generate a lower sideband signal that is phase-conjugated with the guide signal, determining the value of a pulse control parameter according to the properties of the guide signal and the power requirements of at least one user device, generating at least one non-rectangular pulse control signal - the number of the non-rectangular pulse control signal is determined by the number of the at least one user device - the non-rectangular pulse control signal is a function of the pulse control parameter, modulating the lower sideband signal according to the at least one non-rectangular pulse control signal; and radiating the modulated lower sideband signal with the multiple antenna units. In addition to the mixer and the filter, the phase conjugate mixing circuit has a single sideband modulator that completes the time modulation function, and has a stronger beam pointing capability than the conventional time modulation reverse array.

In one embodiment, the method may further include: determining the modulation frequency of the at least one non-rectangular pulse control signal according to the operating frequency of each antenna unit in the plurality of antenna units, the operating frequency being much greater than the modulation frequency, for example, at least 1000 times, or 10000 times, or higher. Preferably, the pulse control parameter may include: a periodic conduction duration for the at least one non-rectangular pulse control signal, used for time modulation of the antenna unit; and a weight for each non-rectangular pulse control signal in the at least one non-rectangular pulse control signal, used for weighting the time modulation of each non-rectangular pulse control signal. Alternatively, the pulse control parameter may consist of or only include: a periodic conduction duration for the at least one non-rectangular pulse control signal, used for time modulation of the antenna unit; and a weight for each non-rectangular pulse control signal in the at least one non-rectangular pulse control signal, used for weighting the time modulation of each non-rectangular pulse control signal. The phase conjugate relationship between the traceback signal and the incoming wave signal can be ensured without adding additional phase control.

In one embodiment, the attribute of the pilot signal may include the phase of the lower sideband signal.

In one embodiment, the power requirement may include the power required by each user equipment and the range over which the user equipment is distributed.

In one embodiment, the value of the pulse control parameter may also be determined by stochastic optimization.

In one embodiment, the method may further include: amplifying the modulated lower sideband signal before the radiating.

In one embodiment, the method may further include: distributing the local oscillator signal to a loop associated with each antenna unit of the plurality of antenna units by a multi-way equal power divider.

In one embodiment, for each antenna unit in the multiple antenna units, the number of the non-rectangular pulse control signals may be equal to the number of the user equipments.

In one embodiment, the method may also include: on one channel, i.e., the in-phase channel, of the orthogonal dual-channel circuit, modulating the lower sideband signal according to the at least one non-rectangular pulse control signal to obtain a first modulation signal; on another channel, i.e., the orthogonal channel, of the orthogonal dual-channel circuit, modulating the lower sideband signal according to the orthogonal signal of the at least one non-rectangular pulse control signal, and phase shifting by π/2 to obtain a second modulation signal; and merging the first modulation signal with the second modulation signal. By introducing the single-sideband modulation module of the orthogonal dual-channel, the generation of the mirror harmonic beam is suppressed, and the waste of useless radiation is avoided. The non-rectangular pulse modulation is realized by the variable gain amplifier, which is different from the square wave pulse modulation controlled by the conventional RF switch. The number of sideband beams generated is controllable, and the useless radiation generated by a large number of harmonic beams in the square wave modulation is avoided. In addition, the direction of each harmonic beam is independently controllable, which is more flexible than the square wave pulse modulation scheme.

According to another aspect of the present disclosure, a device for wireless power transmission based on an antenna array is provided. The device includes a plurality of antenna loops, each of which includes: an antenna unit for receiving a guide signal from at least one user device; a mixer for mixing the received guide signal with a local oscillator signal; a low-pass filter for filtering the mixed signal to generate a lower sideband signal that is phase-conjugated with the guide signal; a single sideband modulator for modulating the lower sideband signal according to at least one non-rectangular pulse control signal, and the modulated lower sideband signal is suitable for being radiated through the antenna unit; a pulse generator, which is configured to: determine the value of a pulse control parameter according to the properties of the guide signal and the power requirements of at least one user device; and generate the at least one non-rectangular pulse control signal for each of the plurality of antenna loops, the number of which is determined by the number of at least one user device, and the non-rectangular pulse control signal is a function of the pulse control parameter. In addition to the mixer and the filter, the phase conjugate mixing circuit has a single sideband modulator that completes the time modulation function, and has a stronger beam pointing capability than the conventional time modulation reverse array.

In one embodiment, the pulse generator may be configured to determine the modulation frequency of the at least one non-rectangular pulse control signal according to the operating frequency of the antenna unit in the multiple antenna loops, and the operating frequency is much greater than the modulation frequency, for example, at least 1000 times, or 10000 times, or higher. Preferably, the pulse control parameter may include: a periodic conduction duration for the at least one non-rectangular pulse control signal, used to time modulate the antenna unit; and a weight for each non-rectangular pulse control signal in the at least one non-rectangular pulse control signal, used to weight the time modulation of each non-rectangular pulse control signal. Alternatively, the pulse control parameter may consist of or only include: a periodic conduction duration for the at least one non-rectangular pulse control signal, used to time modulate the antenna unit; and a weight for each non-rectangular pulse control signal in the at least one non-rectangular pulse control signal, used to weight the time modulation of each non-rectangular pulse control signal. The phase conjugate relationship between the traceback signal and the incoming signal can be guaranteed without adding additional phase control.

In one embodiment, the attribute of the pilot signal may include the phase of the lower sideband signal.

In one embodiment, the power requirement may include the power required by each user equipment and the range over which the user equipment is distributed.

In one embodiment, the value of the pulse control parameter may also be determined by stochastic optimization.

In one embodiment, each of the plurality of antenna loops may further include: an amplifier, configured to amplify the modulated lower sideband signal.

In one embodiment, the device may further include: a multi-way equal power divider, configured to distribute the local oscillator signal to the mixer of each antenna loop in the plurality of antenna loops.

In one embodiment, for each antenna unit in the multiple antenna units, the number of the non-rectangular pulse control signals may be equal to the number of the user equipments.

In one embodiment, the single sideband modulator can be composed of an orthogonal dual-channel circuit, which includes: a first variable gain amplifier on one channel, i.e., the in-phase channel, of the orthogonal dual-channel circuit, for receiving the at least one non-rectangular pulse control signal and thereby modulating the lower sideband signal to obtain a first modulation signal; a second variable gain amplifier on another channel, i.e., the orthogonal channel, of the orthogonal dual-channel circuit and a phase shifter connected in series therewith, the second variable gain amplifier being used to receive the orthogonal signal of the at least one non-rectangular pulse control signal and thereby modulating the lower sideband signal, the phase shifter being used to phase shift the modulated lower sideband signal by π/2 to obtain a second modulation signal; and a combiner, being used to combine the first modulation signal with the second modulation signal. By introducing the single sideband modulation module of the orthogonal dual-channel, the generation of the image harmonic beam is suppressed, and the waste of useless radiation is avoided. The non-rectangular pulse modulation is realized by the variable gain amplifier, which is different from the square wave pulse modulation controlled by the conventional RF switch, and the number of the generated sideband beams is controllable, thereby avoiding the useless radiation generated by a large number of harmonic beams in the square wave modulation. In addition, the direction of each harmonic beam is independently controllable, which is more flexible than the square wave pulse modulation scheme.

According to another aspect of the present disclosure, a wireless power transmission system based on antenna array design is provided. The system includes a device for wireless power transmission based on antenna array design as described above, and at least one user device that sends a guidance signal to the device for wireless power transmission and receives a radiation signal from the device for wireless power transmission.

The advantages brought by the embodiments of the present disclosure are generally: combining the reverse technology with the time modulation technology, utilizing the automatic tracking advantage of the former and the low sidelobe and multi-beam characteristics of the latter, to realize a transmitting array with low sidelobe, multi-beam and automatic direction tracing in space. At the same time, a variable gain amplifier is used in the time modulation part to generate an appropriate non-rectangular pulse modulation signal, thereby avoiding the problem of useless sideband radiation caused by traditional rectangular square wave modulation, improving the energy utilization efficiency of the transmitting array, and bringing greater advantages to wireless power transmission applications. In addition, the multiple harmonic beams generated by the time modulation array have a slight frequency difference, which is consistent with the frequency of the modulation signal, thereby reducing the beam pointing error caused by signal interference in the multi-beam direction tracing array.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the embodiments of the present disclosure will become more easily understood through the following detailed description with reference to the accompanying drawings. In the accompanying drawings, various embodiments of the present disclosure will be described in an exemplary and non-limiting manner, in which:

FIG1 shows a flow chart of a power transmission method according to an embodiment of the present disclosure;

FIG2 shows a schematic diagram of a power transmission system according to an embodiment of the present disclosure;

FIG3 shows a system block diagram of a wireless power transmission device according to an embodiment of the present disclosure;

FIG4 is a schematic diagram showing an example of equal power transmission according to an embodiment of the present disclosure;

FIG5 shows the optimized cosine pulse component weight distribution and channel on-time distribution of the equal power transmission example of FIG4 ;

FIG6 shows a single-station test diagram and a dual-station test diagram of the array radar cross-section area of the equal-power transmission example of FIG4 ;

FIG7 shows the optimized array normalized single-station pattern and dual-station pattern of the equal-power transmission example of FIG4 ;

FIG8 is a schematic diagram showing an example of unequal power transmission according to another embodiment of the present disclosure;

FIG9 shows the optimized cosine pulse component weight distribution and channel on-time distribution of the non-equal power transmission example of FIG8; and

FIG. 10 shows the optimized array normalized single-station pattern and dual-station pattern of the unequal power transmission example of FIG. 8 .

Detailed ways

The principles of the present disclosure will now be described with reference to the various exemplary embodiments shown in the accompanying drawings. It should be understood that the description of these embodiments is only to enable those skilled in the art to better understand and further implement the present disclosure, and is not intended to limit the scope of the present disclosure in any way. It should be noted that similar or identical reference numerals may be used in the figures where feasible, and similar or identical reference numerals may represent similar or identical functions. Those skilled in the art will readily recognize from the following description that alternative embodiments of the structures and methods described herein may be adopted without departing from the principles of the embodiments of the present disclosure described herein.

The term "including" and its variations are to be interpreted as open terms meaning "including but not limited to". Unless the context clearly indicates otherwise, the term "or" should be understood as "and/or". In addition, the terms "based on" or "according to" should be understood as "based at least in part on" or "based at least in part on". The terms "one embodiment" and "embodiment" should be understood as "at least one embodiment". The term "another embodiment" should be interpreted as "at least one other embodiment". Unless otherwise specified or limited, the terms "mounted", "connected", "supported" and "coupled" and their variations are used broadly and include direct and indirect mounting, connection, support and coupling. In addition, "connected" and "coupled" are not limited to physical or mechanical connections or couplings.

Fig. 1 shows a flow chart of a power transmission method 100 according to an embodiment of the present disclosure. First, in step 101, a plurality of antenna units are used to receive a guidance signal from at least one user equipment. The guidance signal is usually a position guidance signal in the uplink phase of the signal, and in this phase, the plurality of antenna units are in a receiving state.

Afterwards, steps 102 to 106 are performed for each antenna unit in the plurality of antenna units. In step 102, the received pilot signal is mixed with the local oscillator signal. The frequency of the local oscillator signal is related to the frequency of the pilot signal, specifically, it is twice the frequency of the pilot signal. In step 103, the mixed signal is filtered by a low-pass filter to obtain a lower sideband signal that is phase-conjugated with the pilot signal, that is, a phase-conjugated component of the received pilot signal. In step 104, the value of the pulse control parameter is determined according to the attributes of the pilot signal and the power requirement of at least one user device. Such attributes may be all or part of the attributes of the pilot signal or related to the pilot signal, such as the phase of the filtered lower sideband signal; the power requirement includes the absolute value of the power requirement and the relative value of the power requirement between multiple user devices (in other words, the power required by each user device) and the user area area (in other words, the range in which the user devices are distributed), corresponding to the radiation pattern peak level of the antenna array (corresponding to the absolute value of the power requirement), the sidelobe level (corresponding to the relative value of the power requirement between multiple user devices) and the beam width parameter (corresponding to the user area area). In step 105, at least one non-rectangular pulse control signal is generated, the number of which is determined by the number of the at least one user device, and the non-rectangular pulse control signal is a function of a pulse control parameter. In other words, the number of non-rectangular pulse control signals is related to, for example, the same as, the number of user devices. Thus, one component in the non-rectangular pulse control signal corresponds to one user device and is used to modulate a signal to be radiated to the user device. In one example, the non-rectangular pulse control signal may be a cosine pulse control signal or other non-rectangular pulse control signal. In step 106, the lower sideband signal is modulated according to at least one non-rectangular pulse control signal. Therefore, if there are multiple non-rectangular pulse control signals, the lower sideband signal is also divided into multiple components to be modulated by corresponding non-rectangular pulse control signals, respectively.

After the lower sideband signal is modulated, it is radiated by multiple antenna elements in step 107. The steps in the above method 100 are not limited in order, and the order of some steps can be adjusted, for example, step 104 can be placed before step 103.

FIG2 shows a schematic diagram of a power transmission system 20 according to an embodiment of the present disclosure. The power transmission system 20 includes a wireless power transmission device 200 and at least one user device. The wireless power transmission device 200 is generally used as a receiving and transmitting terminal for signals and includes multiple antenna loops, i.e., multiple antenna units. There are generally multiple user devices, for example, P user devices 300 ₁ , 300 ₂ …… 300 _P as shown in FIG2 . In the left figure of FIG2 , each user device 300 ₁ , 300 ₂ …… 300 _P transmits a guide signal to the wireless power transmission device 200, and this process is generally referred to as uplink. After phase conjugation and time modulation of the received signal, in the right figure of FIG2 , the modulated lower sideband signal is forwarded to the free space via the antenna, and the signal will automatically trace back to each user device, and this process is generally referred to as downlink.

FIG3 shows a system block diagram of a wireless power transmission device 200 according to an embodiment of the present disclosure. The wireless power transmission device 200 includes a pulse generator 220 and a plurality of antenna loops 210. Each antenna loop 210 includes an antenna unit 211 for receiving a pilot signal from a user equipment and radiating a modulated lower sideband signal, a mixer 212 for mixing the received pilot signal with a local oscillator signal, a low-pass filter 213 for filtering the mixed signal to generate a lower sideband signal that is phase-conjugated with the pilot signal, and a single sideband modulator 214 for modulating the lower sideband signal according to at least one non-rectangular pulse control signal. The pulse generator 220 is used to generate a non-rectangular pulse control signal to modulate the lower sideband signal.

Additionally or in a specific embodiment, each antenna loop 210 may include only one antenna unit 211. In the specific example shown in FIG. 3 , each antenna loop 210 may also include a circulator connected to the antenna unit 211 to isolate the transmit and receive signals. In the specific example shown in FIG. 3 , each antenna loop 210 may also include an amplifier 215 to amplify the modulated lower sideband signal to the required power before radiation. In the specific example shown in FIG. 3 , the wireless power transmission device 200 may also include a multi-way equal power divider 230, which is used to distribute the local oscillator signal to the mixer 212 in each antenna loop 210 in the multiple antenna loops. In addition, the pulse generator 220 is also connected to the single sideband modulator 214 in each antenna loop 210. There are multiple antenna loops 210, for example, N.

In a specific embodiment, the pulse generator 220 can be controlled by a field programmable gate array (FPGA) to generate multiple non-rectangular pulse control signals for each antenna loop 210. The number of non-rectangular pulse control signals is determined by the number of user devices. For example, if there are ten user devices, ten non-rectangular pulse control signals can be allocated to each antenna loop 210. The single sideband modulator 214 in each antenna loop 210 can be, for example, an orthogonal dual-channel circuit structure shown in Figure 3. In this example, a first variable gain amplifier 216 is provided on one channel, i.e., the in-phase channel, for receiving the non-rectangular pulse control signal and thereby modulating the lower sideband signal to obtain a first modulated signal. A second variable gain amplifier 217 and a phase shifter 218 connected in series therewith are provided on another channel, i.e., the orthogonal channel. The second variable gain amplifier 217 is used to receive the orthogonal non-rectangular pulse control signal and thereby modulate the lower sideband signal, and the phase shifter 218 is used to phase shift the modulated lower sideband signal by π/2 to obtain a second modulated signal. The orthogonal dual-channel circuit structure also includes a combiner 219 for combining the first modulated signal with the second modulated signal, thereby outputting the first modulated signal to the optional amplifier 215. By introducing the orthogonal dual-channel single-sideband modulation structure, the generation of image harmonic beams is suppressed, and the waste of useless radiation is avoided. In this example, the pulse generator 220 is connected to the first variable gain amplifier 216 and the second variable gain amplifier 217 in the single-sideband modulator 214 in each antenna loop 210, and feeds a non-rectangular pulse control signal to them.

The following describes two embodiments in conjunction with Figures 4 to 10 to explain the inventive concept and working principle of the present disclosure. The devices corresponding to the two embodiments can be referred to Figures 2 and 3. However, it should be understood that the embodiments in the specification are only used to better understand the principles of the present disclosure, and are not intended to limit the scope of protection of the present disclosure.

In the first embodiment below, the number of antenna elements N = 16, and the antenna unit 211 is an omnidirectional antenna element operating at f ₀ = 2.45 GHz, which means that the frequency of the uplink pilot signal transmitted by the user equipment is 2.45 GHz. The element spacing is half a wavelength: d = λ ₀ /2, where λ ₀ = c/f ₀ , c is the speed of light. The system modulation frequency f _p should be selected to be much smaller than the operating frequency of the antenna unit, for example, one thousandth or less, for example, 25 kHz. The local oscillator signal frequency f _LO is related to the operating frequency of the antenna unit, specifically f _LO = 2f ₀ .

The scenario of this embodiment is set as follows: there are P = 3 user devices 300 ₁ , 300 ₂ , and 300 3 to be charged in space, which are equidistant r = 6m from the transmitting terminal array (i.e., the array formed by the antenna unit 211 in the wireless power transmission device 200 ₎ . Taking the axial direction of the transmitting array as the reference direction, the three user devices are distributed in the direction of θ = [40°, 60°, 110°], as shown in FIG4 . The center frequency of the uplink signal sent from the user device is f ₀ . Taking a single-frequency signal as an example, the signal reaching the transmitting terminal array is:

V _in,l , θ _in,l represent the strength and incident angle of the lth signal reaching the antenna array, n represents the nth user equipment, t represents time, and k represents the free space wave number of the electromagnetic wave, k=2π/λ ₀ , where λ ₀ =c/f ₀ . V _LO represents the local oscillator signal strength, and the signal after the received pilot signal and the local oscillator signal are mixed at the mixer 212 is:

The lower sideband signal obtained by filtering with the low-pass filter 213 is:

The phase of the signal is conjugate with the phase of the pilot signal. The single-sideband modulator 214 performs amplitude weighting on the time modulation of the signal. _Un (t) represents the periodic modulation signal generated by the pulse generator 220, i.e., the non-rectangular pulse control signal. _An represents the amplitude weight of the nth transmission channel (i.e., for the nth antenna loop or antenna unit). In order to avoid loss of generality or generally speaking, _An can be set to 1. The modulated signal is:

This embodiment adopts a time modulation scheme based on weighted cosine and pulse signals. The generation process of the non-rectangular pulse control signal _Un (t) will be described below.

First, the system modulation frequency _fp = 25kHz is determined. When there are P = 3 targets to be charged, 3 non-rectangular pulse control signals (cosine pulse control signals in this example) are required, with frequencies of: _fp , _2fp , _3fp . _τn represents the conduction time (normalized) of the nth antenna unit in one cycle for time modulation of the non-rectangular pulse control signal; _anp represents the weight of the time modulation of the pth non-rectangular pulse control signal for the nth antenna unit for weighting the time modulation of each non-rectangular pulse control signal, in the following form:

in rect represents a rectangular pulse function. _Uni (t), _Unq (t) represent the modulation signals of the in-phase channel and the orthogonal channel, respectively, and are generated by the FPGA control circuit at the pulse generator 220. The pulse control parameters _τn , _anp are obtained according to the optimization target by using a random optimization method. For example, genetic algorithm, differential evolution, artificial bee colony algorithm, etc. The optimization target can be a reference value of several specified performance indicators (side lobe level, peak level, beam width) related to the attribute. The optimization target function is formed according to a certain function form, which will be explained below.

Next, construct an objective function and determine the pulse modulation parameters according to the sidelobe level SLL, peak level PL and beam width BW in the antenna radiation pattern parameters. SLL, PL and BW are the antenna radiation performance indicators corresponding to the power requirements of the user equipment. According to these properties, the pulse control parameters can be determined by random optimization such as the Artificial Bee Colony (ABC) algorithm. The optimization target SLL _des is used to represent the expected maximum sidelobe level value or index, thereby reducing energy leakage in non-target areas; the optimization target PL _des is used to represent the expected peak level value or index, thereby allocating beam energy or power to each user; the optimization target BW _des is used to represent the expected beam width value or index, thereby avoiding energy dispersion to non-target areas. Thus, the objective function is constructed as follows:

w ₁ , w ₂ , w ₃ represent the weight values of their respective optimization targets, and H represents the Heaviside step function. According to the target scenario of this embodiment, three independent user equipments in the space are of equal power transmission, the normalized peak level values of the optimization targets are all PL _des = 0 dB, the 3 dB beam width values of the optimization targets are all BW _des = ₅ °, and the maximum sidelobe level value of the optimization target is SLL _des = -40 dB. Make SLL _p , PL _p , and BW _p as close as possible to their respective optimization target values, and the corresponding pulse control parameters τ _n , _anp values are their optimized values. For example, in this example, the optimized pulse control parameters τ n , _anp (normalized) distribution is shown in FIG5 - the left figure shows the normalized weight _anp for three user equipments in 16 antenna units, and the right figure shows the normalized on-time τ _n for 16 antenna units. As defined above, for example, as can be seen in the left diagram of FIG. 5 , for the nth antenna element, the sum of the time modulation weights a _n1 , a _n2 and a _n3 of the three non-rectangular pulse control signals is equal to 1.

The directional tracing performance of the reverse array is measured by the beam pointing error (Beam Pointing Error, BPE), which needs to be determined by measuring the array radar scattering cross-section, a physical quantity that characterizes the scattering strength of the antenna array. The single-station directional pattern characterizes the beam tracing angle range of the antenna array, and its test method is shown in the left figure in Figure 6, that is, the transmitting antenna and the receiving antenna are synchronously moved at different angles relative to the antenna array so that the receiving antenna detects the normalized power. The dual-station directional pattern characterizes the beam pointing error, and its test method is shown in the right figure in Figure 6, that is, the transmitting antenna is fixed, and the receiving antenna is individually moved at different angles relative to the antenna array so that the receiving antenna detects the normalized power. In the above embodiment, the single and dual-station directional patterns of the antenna array after optimization are shown in Figure 7. Under the effect of the optimized modulation timing, the array tracing field radiates along the incoming wave direction of each user, and the energy is evenly distributed.

In the following second embodiment, it is assumed that there are three users to be charged in space that are not equidistant from the transmitting terminal array (i.e., the array formed by the antenna unit 211 in the wireless power transmission device 200). With the axial direction of the transmitting array as the reference direction, they are distributed in the direction of θ = [40°, 60°, 110°], and the distances from the transmitting terminal are: r = [9.5m, 3m, 4.5m], as shown in Figure 8. The uplink stage of the user guidance signal is consistent with the aforementioned first embodiment. After the signal is received, it is processed by the mixer 212 and the low-pass filter 213 and fed into the single-sideband modulator 214. The objective function form in this scenario is the same as that in the aforementioned first embodiment, but the optimization target is different:

The normalized peak level values of the optimization targets are PL _1,des = 0dB, PL _2,des = -10dB, PL _3,des = -6dB, the beam width values of the optimization targets are all BW _des = 5°, and the maximum sidelobe level value of the optimization target is SLL _des = -40dB. The distribution of the optimized weight _anp and the conduction time _τn are shown in the left and right figures of FIG9 , respectively. The single-station and dual-station radiation patterns of the above second embodiment after optimization are shown in FIG10 . Under the action of the pulse control parameters obtained through optimization, the array traceback field radiates along the incoming wave direction of each user, and the energy is reconfigured. The beam gain of the long-distance user is high, and the beam gain of the short-distance user is low, which solves the "near-far effect" often encountered in multi-user transmission to a certain extent.

It is worth noting that, according to an embodiment of the present disclosure, the pulse control parameters may only include the weight _anp and the on-time τ _n . In other words, no additional phase control is added during the time modulation process to ensure the phase conjugate relationship between the traceback signal and the incoming signal.

The advantages of the various embodiments disclosed in the present invention are: 1) controlling the turn-on time and turn-on duration of the switch is equivalent to performing amplitude-phase weighting on the antenna unit. Therefore, the switch replaces the role of the RF phase shifter in the traditional array to realize beam pointing and scanning functions, which avoids the pointing error problem caused by the quantization accuracy of the phase shifter on the one hand, and greatly reduces the hardware cost of the antenna system on the other hand; 2) The amplitude weighting equivalent to the time-controlled switch expands the dynamic range of the channel gain control in the traditional amplitude weighting method, and it is easy to realize ultra-low sidelobe weighting; 3) Due to the periodic switching action in the time domain, the energy radiated by the antenna unit is distributed in discrete intervals in the frequency domain. After the related superposition of these energies, radiation components of multiple frequencies will be generated in space (the frequency interval is related to the period of time modulation), that is, simultaneous multi-beams are generated. Compared with the transmitting array realized by the traditional multi-beam network, the design complexity of the feeding network is greatly reduced.

In addition, compared to phased array antennas and smart antennas, the antenna array disclosed in the present invention does not need to predict the direction information of the user's incoming wave, nor does it require complex digital signal processing to automatically forward energy to the direction of the target user; it has application advantages in multi-user scenarios, and generates independent response beams for multiple uplink signals with low hardware cost and low processing complexity, which can realize flexible point-to-multipoint energy transmission. The time modulation of the antenna array disclosed in the present invention adopts a non-rectangular pulse modulation signal. The number of radiation beams generated by the array is easy to control, and the direction of each beam is independently controllable, avoiding the waste caused by useless harmonic radiation caused by traditional rectangular square wave modulation, and improving the transmission efficiency of the wireless power transmission system. Furthermore, the multiple harmonic beams generated by the time modulation array have a slight frequency difference, which is consistent with the frequency of the modulation signal, thereby reducing the beam pointing error caused by the signal mutual interference of the multi-beam direction tracing array.

Although the claims in this application have been formulated to particular combinations of features, it should be understood that the scope of the present disclosure also includes any novel feature or any novel combination of features disclosed herein, whether explicitly or implicitly or in any generalization thereof, whether or not it relates to the same scheme in any claim currently claimed. Applicants hereby give notice that new claims may be formulated to such features and/or combinations of such features during the prosecution of this application or in any further application derived therefrom.

Claims (17)

1. A method of wireless power transfer based on an antenna array, comprising:

Receiving (101) a pilot signal from at least one user equipment with a plurality of antenna elements;

For each antenna element of the plurality of antenna elements:

mixing (102) the received pilot signal with a local oscillator signal;

Filtering (103) the mixed signal by a low pass filter to generate a lower sideband signal phase conjugated with the pilot signal;

Determining (104) a value of a pulse control parameter based on a property of the pilot signal and a power requirement of the at least one user equipment, wherein the pulse control parameter comprises:

for the period conduction duration of the at least one non-rectangular pulse control signal, the period conduction duration is used for modulating the antenna unit in time; and

A weight for each of the at least one non-rectangular pulse control signal for weighting a time modulation of each non-rectangular pulse control signal;

-generating (105) at least one non-rectangular pulse control signal, the number of non-rectangular pulse control signals being equal to the number of user equipments;

modulating (106) the lower sideband signal according to the at least one non-rectangular pulse control signal; and

The modulated lower sideband signal is radiated (107) with the plurality of antenna elements.

2. The method of claim 1, further comprising:

And determining a modulation frequency of the at least one non-rectangular pulse control signal according to an operating frequency of each antenna unit in the plurality of antenna units, wherein the operating frequency is at least 1000 times of the modulation frequency.

3. The method of claim 1, wherein the property of the pilot signal comprises a phase of the lower sideband signal.

4. The method of claim 1, wherein the power requirements include a power required by each user device and a range over which the user devices are distributed.

5. The method according to any of claims 1 to 4, wherein the values of the pulse control parameters are determined by means of random optimization.

6. The method of any one of claims 1 to 4, further comprising:

the modulated lower sideband signal is amplified before the radiation (107).

7. The method of any one of claims 1 to 4, further comprising:

the local oscillator signal is distributed by a multipath equalizer to loops associated with each of the plurality of antenna elements.

8. The method according to any one of claims 1 to 4, wherein the modulating (106) comprises:

modulating the lower sideband signal on an in-phase channel in a quadrature dual-channel circuit according to the at least one non-rectangular pulse control signal to obtain a first modulated signal;

modulating the lower sideband signal according to the orthogonal signal of the at least one non-rectangular pulse control signal on an orthogonal channel in the orthogonal two-channel circuit, and phase shifting pi/2 to obtain a second modulated signal; and

The first modulated signal is combined with the second modulated signal.

9. An apparatus for wireless power transfer based on an antenna array, comprising:

a plurality of antenna loops (210), each of the plurality of antenna loops comprising:

An antenna unit (211) for receiving a pilot signal from at least one user equipment;

A mixer (212) for mixing the received pilot signal with a local oscillator signal;

A low pass filter (213) for filtering the mixed signal to generate a lower sideband signal phase conjugated with the pilot signal;

A single sideband modulator (214) modulating the lower sideband signal according to at least one non-rectangular pulse control signal, the modulated lower sideband signal adapted to be radiated through the antenna element;

a pulse generator (220) configured to:

Determining a value of a pulse control parameter according to the attribute of the pilot signal and the power requirement of the at least one user equipment, wherein the pulse control parameter comprises:

for the period conduction duration of the at least one non-rectangular pulse control signal, the period conduction duration is used for modulating the antenna unit in time; and

A weight for each of the at least one non-rectangular pulse control signal for weighting a time modulation of each non-rectangular pulse control signal; and

The at least one non-rectangular pulse control signal is generated for each antenna loop of the plurality of antenna loops, the number of non-rectangular pulse control signals being equal to the number of user equipments.

10. The apparatus of claim 9, wherein the pulse generator is configured to determine a modulation frequency of the at least one non-rectangular pulse control signal from an operating frequency of the antenna elements in the plurality of antenna loops, the operating frequency being at least 1000 times the modulation frequency.

11. The apparatus of claim 9, wherein the property of the pilot signal comprises a phase of the lower sideband signal.

12. The apparatus of claim 9, wherein the power requirements include a power required by each user device and a range over which the user devices are distributed.

13. The apparatus according to any of claims 9 to 12, wherein the values of the pulse control parameters are determined by means of random optimization.

14. The apparatus of any of claims 9-12, wherein each antenna loop of the plurality of antenna loops further comprises:

an amplifier (215) for amplifying the modulated lower sideband signal.

15. The apparatus of any of claims 9 to 12, further comprising:

A multipath equalizer (230) for distributing the local oscillator signal to the mixer of each of the plurality of antenna loops.

16. The apparatus of any of claims 9 to 12, wherein the single sideband modulator is comprised of an orthogonal dual channel circuit comprising:

A first variable gain amplifier (216) on an in-phase channel in the quadrature dual-channel circuit for receiving the at least one non-rectangular pulse control signal and modulating the lower sideband signal thereby to obtain a first modulated signal;

A second variable gain amplifier (217) on a quadrature channel in the quadrature dual-channel circuit and a phase shifter (218) in series therewith, the second variable gain amplifier (217) for receiving a quadrature signal of the at least one non-rectangular pulse control signal and thereby modulating the lower sideband signal, the phase shifter (218) for phase shifting the modulated lower sideband signal by pi/2 to obtain a second modulated signal; and

-A combiner (219) for combining the first modulated signal with the second modulated signal.

17. A wireless power transfer system based on an antenna array, comprising:

The antenna array based wireless power transfer apparatus of any of claims 9 to 16; and

At least one user equipment that sends a pilot signal to the devices of the wireless power transfer and receives a radiated signal from the devices of the wireless power transfer.