Microwave wireless power transfer device and design method

Abstract

This application discloses a microwave wireless power transfer device and its design method. The device includes: a microstrip array feed source, comprising a feed network unit and four rectangular microstrip patch units arranged in a 2×2 array. The feed network unit is used to excite the four rectangular microstrip patch units with equal amplitude and in phase. The microstrip array feed source is used to radiate electromagnetic waves. A transmission-focusing metasurface array includes multiple metasurface units arranged in an 11×11 array. Each metasurface unit includes, from top to bottom, an upper complementary square resonant unit, an upper dielectric substrate, a middle complementary square resonant unit, a lower dielectric substrate, and a lower complementary square resonant unit. The transmission-focusing metasurface array is used to control the phase distribution of the electromagnetic waves radiated by the microstrip array feed source to achieve focusing. A support member is also included. This application can stably achieve near-field focusing and energy convergence.

Description

Technical Field

[0001] This application relates to the field of electromagnetic metamaterials technology, and in particular to a microwave wireless power transmission device and its design method. Background Technology

[0002] Microwave power transmission (MPT) typically consists of a transmitter antenna radiating electromagnetic energy, which is then received and converted into direct current (DC) electrical energy at a receiver. Because electromagnetic waves diffuse in space, the power available to the receiver is often limited without energy focusing mechanisms. To improve the power density and received power in the target area, near-field focusing (NFF) or beamforming techniques are commonly used in engineering to coherently superimpose electromagnetic energy near a predetermined location, forming a smaller focal spot and thus improving power transmission efficiency.

[0003] In existing technologies for microwave wireless power transmission devices, horn antennas are often used as feed sources. These are equivalent to radiation sources with a phase center, radiating approximately spherical waves onto a transmissive metasurface. The metasurface is composed of numerous elements, each providing a different transmission phase, allowing the transmitted waves to coherently superimpose at a preset focal length to achieve focusing. However, due to the large size of the horn antenna, it and the metasurface are usually discrete structures, resulting in a bulky system with low integration and poor portability. Furthermore, alignment and assembly errors between the feed source and the metasurface can severely affect focusing performance. Summary of the Invention

[0004] This application aims to propose a microwave wireless power transfer device and design method that can stably achieve near-field focusing and energy convergence.

[0005] The microwave wireless power transfer device according to a first aspect embodiment of this application includes: The microstrip array feed includes a power supply network unit and four rectangular microstrip patch units, which are arranged in a 2×2 array. The power supply network unit is used to excite the four rectangular microstrip patch units with equal amplitude and phase. The microstrip array feed is used to radiate electromagnetic waves. A transmission-focusing metasurface array includes multiple metasurface units arranged in an 11×11 array. Each metasurface unit includes, from top to bottom, an upper complementary square resonant unit, an upper dielectric substrate, a middle complementary square resonant unit, a lower dielectric substrate, and a lower complementary square resonant unit. The upper complementary square resonant unit is located below the microstrip array feed. The transmission-focusing metasurface array is used to control the phase distribution of the electromagnetic waves radiated by the microstrip array feed to achieve focusing. The upper, middle, and lower complementary square resonant units each include a rectangular ring and a square patch located within the rectangular ring. A support member is disposed between the microstrip array feed source and the transmission focusing metasurface array, and the support member is used to limit the distance between the microstrip array feed source and the transmission focusing metasurface array to a preset distance.

[0006] A microwave wireless power transfer device design method according to a second aspect embodiment of this application includes: A microstrip array feed source is established; wherein, the microstrip array feed source includes a feed network unit and four rectangular microstrip patch units; A metasurface unit library is established; wherein, the metasurface unit library records the correspondence between the geometric parameters, transmission phase and transmission amplitude of multiple metasurface units; Set a preset spacing between the microstrip array feed and the transmission focusing metasurface array; The transmission focusing metasurface array is established; wherein the transmission focusing metasurface array includes a plurality of metasurface units, and the geometric parameters of each metasurface unit in the transmission focusing metasurface array are selected from the metasurface unit library; The microstrip array feed and the transmission focusing metasurface are connected by a support member based on the preset spacing to obtain a microwave wireless power transmission device.

[0007] In this embodiment, a microstrip array feed source replaces the traditional horn antenna, effectively reducing the feed source volume. Simultaneously, a support structure connects the microstrip array feed source and the transmission-focusing metasurface array at a preset spacing, achieving an integrated design that significantly reduces the overall device size and improves integration and portability. Furthermore, during the design of the microwave wireless power transfer device, the geometric parameters of the multiple metasurface units included in the transmission-focusing metasurface array are selected from a metasurface unit library, enabling the necessary transmission phase compensation. This allows the designed microwave wireless power transfer device to stably achieve near-field focusing and energy convergence.

[0008] Other features and advantages of this application will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing this application. Attached Figure Description

[0009] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is a schematic diagram of the structure of a microstrip array feed source according to an embodiment of this application; Figure 2 This is a schematic diagram of the structure of a metasurface unit according to an embodiment of this application; Figure 3 This is a schematic diagram of the structure of a transmission focusing metasurface array according to an embodiment of this application; Figure 4 This is a schematic diagram of the structure of a microwave wireless power transmission device according to an embodiment of this application; Figure 5 This is a schematic flowchart of a microwave wireless power transfer device design method according to an embodiment of this application. Figure 6 This is a schematic diagram of the phase compensation distribution result according to an embodiment of this application; Figure 7 This is a schematic diagram of the focused electric field at the focal point of an embodiment of this application. Detailed Implementation

[0010] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0011] In the description of this application, the use of terms such as "first," "second," etc., is for the purpose of distinguishing technical features only and should not be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated or the order of the technical features indicated.

[0012] In the description of this application, it should be understood that the orientation descriptions, such as up, down, etc., are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0013] In the description of this application, it should be noted that, unless otherwise explicitly defined, terms such as "setup," "installation," and "connection" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this application in conjunction with the specific content of the technical solution.

[0014] The technical solution of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are some embodiments of this application, not all embodiments.

[0015] See below. Figures 1 to 7 The embodiments of this application will be further described below.

[0016] like Figures 1 to 4 As shown in the figure, this application proposes a microwave wireless power transmission device, including a microstrip array feed, a transmission focusing metasurface array, and a support component; The microstrip array feed includes a feed network unit and four rectangular microstrip patch units. The four rectangular microstrip patch units are arranged in a 2×2 array. The feed network unit is used to excite the four rectangular microstrip patch units with equal amplitude and phase. The microstrip array feed is used to radiate electromagnetic waves. The transmission-focusing metasurface array comprises multiple metasurface units arranged in an 11×11 array. Each metasurface unit includes, from top to bottom, an upper complementary square resonant unit, an upper dielectric substrate, a middle complementary square resonant unit, a lower dielectric substrate, and a lower complementary square resonant unit. The upper complementary square resonant unit is positioned below the microstrip array feed. The transmission-focusing metasurface array is used to control the phase distribution of the electromagnetic waves radiated by the microstrip array feed to achieve focusing. The upper, middle, and lower complementary square resonant units each include a rectangular ring and a square patch located within the rectangular ring. A support is disposed between the microstrip array feed and the transmission focusing metasurface array. The support is used to limit the distance between the microstrip array feed and the transmission focusing metasurface array to a preset distance.

[0017] In this embodiment, a microstrip array feed source replaces the traditional horn antenna, effectively reducing the feed source volume. Simultaneously, a support structure connects the microstrip array feed source and the transmission-focusing metasurface array at a preset spacing, achieving an integrated design that significantly reduces the overall device size and improves integration and portability. Furthermore, during the design of the microwave wireless power transfer device, the geometric parameters of the multiple metasurface units included in the transmission-focusing metasurface array are selected from a metasurface unit library, enabling the necessary transmission phase compensation. This allows the designed microwave wireless power transfer device to stably achieve near-field focusing and energy convergence.

[0018] The aforementioned microstrip array feed is a 2×2 microstrip array feed network, ensuring that the four rectangular microstrip patch cells are excited with equal amplitude and in phase. This feed network can employ a T-type power divider, comprising an input trunk, a quarter-wavelength impedance transformer, and power distribution branches. (See reference...) Figure 1 As shown; The aforementioned transmission-focusing metasurface array comprises multiple metasurface units, the unit structure of which can be referred to as follows: Figure 2 As shown, it consists of three layers of complementary square resonant units (upper, middle, and lower) and two layers of dielectric material. The upper and lower dielectric layers are located between the upper and middle complementary square resonant units and the middle and lower complementary square resonant units, respectively. Each of the upper, middle, and lower complementary square resonant units includes a rectangular ring and a square patch located within the rectangular ring, as shown. Figure 2 As shown, the square patch is located in the center of the rectangular ring. The rectangular rings in each layer of complementary square resonant units have the same dimensions, but the side lengths of the square patches within them are not identical. This allows us to understand that the metasurface unit can achieve 0–360° transmission phase coverage at the operating frequency by adjusting the side lengths a1 and a3 of the square patches in the upper and lower complementary square resonant units. For some units with relatively low transmission amplitude, the impedance matching characteristics of the intermediate layer can be utilized to adjust the side length a2 of the square patch in the intermediate layer's complementary square resonant unit, ensuring a transmission amplitude greater than 0.8 and achieving efficient energy transmission. Multiple metasurface units are arranged in an 11×11 array, as shown... Figure 3 As shown. Specifically, the upper, middle, and lower complementary square resonant units are all made of copper, with a thickness of 35 μm.

[0019] The aforementioned support structure can be a nylon support column positioning structure. This structure can constrain the distance between the feed and the metasurface, improve assembly repeatability, and ensure the parallelism between the feed and the metasurface, thereby maintaining the effectiveness of phase compensation. This allows for stable focus and controllable sidelobes even in close-range coupling scenarios, thus enhancing the safety and consistency of the microwave wireless power transfer device's operation. It is understood that nylon material has a low dielectric constant and low loss; using nylon can reduce the disturbance of the electromagnetic field distribution caused by the support structure. The aforementioned nylon support column positioning structure can include multiple nylon columns to achieve more stable positioning and support for the entire microwave wireless power transfer device. For details, the structure of the microwave wireless power transfer device can be found in [reference needed]. Figure 4 As shown.

[0020] The operating frequency of the aforementioned microwave wireless power transmission device can be 2.45 GHz.

[0021] This application also proposes a design method for a microwave wireless power transfer device, such as... Figure 5 As shown, it includes: Step 101: Establish a microstrip array feed source; wherein, the microstrip array feed source includes a feed network unit and four rectangular microstrip patch units; Step 102: Establish a metasurface unit library; wherein, the metasurface unit library records the correspondence between the geometric parameters, transmission phase and transmission amplitude of multiple metasurface units; Step 103: Set the preset spacing between the microstrip array feed and the transmission focusing metasurface array; Step 104: Establish a transmission focusing metasurface array; wherein, the transmission focusing metasurface array includes multiple metasurface units, and the geometric parameters of each metasurface unit in the transmission focusing metasurface array are selected from the metasurface unit library; The microstrip array feed and the transmission focusing metasurface are connected by a support structure based on a preset spacing to obtain a microwave wireless power transmission device.

[0022] In the embodiments of this application, during the design process of the microwave wireless power transfer device, when establishing the transmission focusing metasurface array, the geometric parameters of the multiple metasurface units included in the transmission focusing metasurface array are all selected from the metasurface unit library, which can achieve the required transmission phase compensation, so that the designed microwave wireless power transfer device can stably achieve near-field focusing and energy convergence.

[0023] In some implementations, establishing a microstrip array feed includes determining the radiating element size and array parameters of the microstrip array feed; determining the radiating element size and array parameters of the microstrip array feed includes: First, select the thickness of the dielectric substrate. With relative permittivity Then, the initial width of the rectangular microstrip patch unit is calculated based on the transmission line principle. The equivalent dielectric constant of a microstrip line is calculated using the formula for calculating the equivalent dielectric constant. This allows for the calculation of the initial length of the rectangular microstrip patch unit. Furthermore, the rectangular microstrip patch unit adopts an embedded structure, requiring adjustment of the embedding depth. The input impedance was adjusted, and subsequent simulation optimization was used to ensure that the rectangular microstrip patch unit resonated at the operating frequency and that the input impedance met the design requirements.

[0024] Secondly, a 2×2 microstrip array feed network is designed to ensure that the four rectangular microstrip patch cells are excited with equal amplitude and in phase. The feed network can adopt a T-type power divider, which includes an input trunk, a quarter-wavelength impedance transformer, and power distribution branches.

[0025] Specifically, taking a design operating frequency of 2.45 GHz and a microstrip array antenna input port of 50Ω as an example, the feed network adopts a T-type power divider, which includes a 50Ω input trunk line, a quarter-wavelength impedance transformer, and a power distribution branch. By adjusting the transformer line width and length and compensating for microstrip discontinuities, the array input port satisfies the input reflection coefficient at 2.45 GHz. Below -15dB, the input impedance Z is 50Ω. At this point, most of the power is fed into the entire microstrip array antenna, and the input impedance is matched with the port, which can reduce reflection.

[0026] In addition, an excitation port can be set at the feed input end, and a far-field monitor can be established to obtain the array's gain, radiation pattern, and polarization characteristics at 2.45 GHz.

[0027] In some embodiments, the transmission focusing metasurface array includes multiple metasurface units arranged in an 11×11 array; each metasurface unit includes, from top to bottom, an upper complementary square resonant unit, an upper dielectric substrate, a middle complementary square resonant unit, a lower dielectric substrate, and a lower complementary square resonant unit. Establishing a transmission-focusing metasurface array includes: Calculate the phase compensation distribution required for the transmission focusing metasurface array; wherein, the phase compensation distribution includes the compensation phase required for each metasurface unit in the 11×11 array arrangement; Based on the phase compensation distribution results, unit mapping is performed, and corresponding geometric parameters are selected from the metasurface unit library for each metasurface unit arranged in an 11×11 array to establish a transmission focusing metasurface array; wherein, the geometric parameters include the side lengths of the square patches in the upper layer complementary square resonant unit, the middle layer complementary square resonant unit, and the lower layer complementary square resonant unit.

[0028] In this embodiment, the phase compensation distribution required for achieving phase in-phase superposition of electromagnetic waves at a preset focal point is pre-calculated for the transmission focusing metasurface array at the operating frequency. After obtaining the phase compensation distribution result, for each metasurface unit in the 11×11 array, a search and matching is performed in the established metasurface unit library according to its required compensation phase value. The metasurface unit library stores the transmission phase and transmission amplitude data of metasurface units with different geometric parameters (i.e., the side length a1 of the square patch in the upper complementary square resonator unit, the side length a2 of the square patch in the middle complementary square resonator unit, and the side length a3 of the square patch in the lower complementary square resonator unit) at the operating frequency. By comparing the required compensation phase of each metasurface unit with the transmission phase of each unit in the unit library, the geometric parameters of the metasurface unit whose transmission phase is closest to the compensation phase and whose transmission amplitude meets the design requirements are selected, thus completing the parameter configuration of the metasurface unit at that position. In summary, by performing the above-described unit mapping process on each metasurface unit in the 11×11 array, the entire transmission focusing metasurface array can be established, enabling it to have preset phase modulation capabilities, thereby achieving efficient focusing of electromagnetic waves radiated from the microstrip array feed source.

[0029] In some implementations, the phase compensation distribution required for the transmission focusing metasurface array is calculated, including: Establish a reference coordinate system; Based on the preset spacing, preset focal length and reference coordinate system, determine the center position of the required microstrip array feed source, the metasurface plane where the transmission focusing metasurface array is located, and the coordinate information corresponding to the center position and focal position of each metasurface unit; Based on the center position of the microstrip array feed, the metasurface plane where the transmission focusing metasurface array is located, and the coordinate information corresponding to the center position of each metasurface unit, the first phase that needs to be compensated from the microstrip array feed to each metasurface unit is obtained. Based on the coordinate information of the metasurface plane where the transmission focusing metasurface array is located, the center position of each metasurface unit and the focal position, calculate the second phase that each metasurface unit needs to compensate for from the focal point. Based on the reference phase constant and the first and second phases corresponding to each metasurface unit, the compensation phase required for each metasurface unit is obtained. Based on the compensation phase of all metasurface units, the phase compensation distribution results are obtained.

[0030] In this embodiment, a microstrip array feed is used instead of a horn antenna in conventional solutions. Furthermore, when the microstrip array feed and the metasurface are close together, the incident electric field exhibits significant near-field characteristics, resulting in a large difference in incident phase distribution compared to an ideal point source spherical wave. If the ideal wavefront model is still used to directly calculate the compensation phase and map it to the metasurface elements, it can easily lead to focus drift, sidelobe enhancement, and reduced energy transfer efficiency. Therefore, this embodiment proposes a different method for calculating the compensation phase, which is more suitable for microstrip array feeds. This method considers both the first phase compensation required from the microstrip array feed to each metasurface element and the second phase compensation required from each metasurface element to the focus, ultimately yielding a more accurate phase compensation distribution.

[0031] In some implementations, the compensation phase required for each metasurface unit is obtained based on the reference phase constant and the first and second phases corresponding to each metasurface unit, subject to the following expression: ; in, To compensate for the phase, As a reference phase constant, For the first phase, This is the second phase.

[0032] In this embodiment, since the sum of the incident phase (first phase) and the compensation phase should be equal to the sum of the focusing phase (second phase) and the reference phase constant, the above-mentioned metasurface compensation phase formula can be obtained. This calculation method fully considers the characteristics of near-field radiation from the microstrip array feed. Compared with the traditional phase compensation method based on the ideal point source assumption, it can obtain a more accurate compensation phase, effectively improving the focusing effect and energy transmission efficiency.

[0033] The aforementioned reference phase constant can be used to optimize the selection of cell structure and reduce phase abrupt changes in order to improve focusing performance.

[0034] In some implementations, based on the center position of the microstrip array feed, the metasurface plane where the transmission focusing metasurface array is located, and the coordinate information corresponding to the center position of each metasurface unit, the first phase that needs to be compensated from the microstrip array feed to each metasurface unit is obtained, including: Based on the coordinate information corresponding to the center position of the microstrip array feed, the microstrip array feed is simulated separately. Based on the coordinate information corresponding to the metasurface plane where the transmission focusing metasurface array is located, a field monitor is set at the metasurface plane to obtain the electric field distribution data of the microstrip array feed at the metasurface plane. The electric field distribution data is interpolated, and the real part and imaginary part of the electric field corresponding to the center position of each metasurface unit are obtained based on the coordinate information corresponding to the center position of each metasurface unit. Based on the real and imaginary electric field data corresponding to the center position of each metasurface unit, the first phase that needs to be compensated from the microstrip array feed to each metasurface unit is obtained.

[0035] In this embodiment, by simulating the microstrip array feed separately in electromagnetic simulation software, the actual electric field distribution at the metasurface plane can be accurately obtained. Setting a field monitor on the metasurface plane allows for comprehensive capture of the electric field distribution information of the electromagnetic waves radiated by the microstrip array feed on that plane. Interpolation of the electric field distribution data is performed to obtain a continuous electric field distribution between discrete sampling points on the metasurface plane, thereby accurately extracting the electric field parameters at the center of each metasurface unit. Finally, based on the coordinates of the center of each metasurface unit, the corresponding real and imaginary parts of the electric field can be extracted from the interpolated electric field distribution data, and the electric field phase at that point can be calculated. This phase is the first phase that needs to be compensated from the microstrip array feed to the metasurface unit. This method, based on actual simulation and interpolation extraction, accurately reflects the phase distribution characteristics of the microstrip array feed under near-field conditions, laying a solid foundation for the subsequent accurate calculation of the total compensation phase of the metasurface unit.

[0036] In some implementations, the first phase to be compensated from the microstrip array feed to each metasurface unit is obtained based on the real and imaginary parts of the electric field corresponding to the center position of each metasurface unit, and is constrained by the following expression: ; in, For the imaginary part of the electric field, This represents the real part of the electric field.

[0037] In this embodiment, by substituting the imaginary and real part data of the electric field at the center of the metasurface unit into the arctangent function, the first phase corresponding to the metasurface unit can be directly calculated. This phase accurately reflects the phase state of the electromagnetic wave radiated by the microstrip array feed when it reaches the metasurface unit, laying the foundation for subsequent accurate calculation of the total compensation phase.

[0038] In some implementations, based on the coordinate information corresponding to the metasurface plane where the transmission focusing metasurface array is located, the center position of each metasurface unit, and the focal position, the second phase that needs to be compensated from the focal point to each metasurface unit is calculated, subject to the following expression: ; Among them, the The coordinate information corresponding to the center position of each metasurface unit is: , The focal length is [value], and the coordinates of the focal point are [value]. .

[0039] In this embodiment, focal length Represents the distance from the metasurface plane z=0 to the focus. Distance along the z-axis, the first The coordinate information corresponding to the center position of each metasurface unit is: , For the first The x-axis coordinates corresponding to the center position of each metasurface unit. For the first The y-axis coordinates corresponding to the center position of each metasurface unit. The wavelength is denoted as λ. This part calculates the electromagnetic wave propagating from the center of the metasurface unit cell to the focal point, compared to propagation from the center of the metasurface plane. The phase difference corresponding to the optical path difference propagating to the focal point is the second phase that needs to be compensated from the metasurface unit to the focal point. By introducing the second phase compensation, it is possible to ensure that the electromagnetic waves modulated by the metasurface achieve phase in-phase superposition at the focal point, thereby enhancing the focusing effect.

[0040] In some implementations, the phase compensation distribution required for the transmission focusing metasurface array is calculated, including: First, establish a reference coordinate system. In the reference coordinate system, the metasurface plane is... The feed phase center is located at The expected focus is on ,in Let the first The center coordinates of each metasurface unit are .

[0041] Secondly, since the feed is a microstrip array antenna and the distance between the feed and the metasurface is relatively short, the electromagnetic field radiated by the feed cannot be approximated as a point source. Therefore, existing phase compensation formulas cannot be used directly for compensation; precise phase compensation is required. Specifically, it is necessary to calculate the first phase from the feed to the center of each metasurface unit that needs precise compensation. And the second phase that needs to be compensated from each metasurface unit to the focal point .

[0042] The precise phase compensation from the feed to the metasurface includes the following steps: First, the microstrip array antenna feed is simulated separately in electromagnetic simulation software, with the center position of the microstrip array feed being... A field monitor is placed in the z=0 plane, and the electric field data of the feed at the z=0 plane is obtained through simulation. Then, the electric field data is processed. Since the microstrip array antenna is x-polarized, the real part Re(Ex) and imaginary part Im(Ex) of the electric field Ex in the electric field data are needed. The number of metasurface elements in the focusing metasurface is 11×11. The center coordinates of each metasurface element need to be calculated in advance. Then, the electric field data is interpolated using numerical calculation methods to obtain the real part Re(Ex) and imaginary part Im(Ex) of Ex at the center of each metasurface element. Finally, the first phase that needs to be accurately compensated from the feed to the center of each metasurface element is calculated. ; The metasurface-to-focal-point phase compensation includes the following steps: Based on the center coordinates and focal length of each metasurface unit, the phase compensation required for each metasurface unit to reach the focal point is calculated using the following formula: ; Finally, the total phase value that needs to be compensated for for each metasurface unit is calculated: ; in, To compensate for the phase, As a reference phase constant, For the first phase, This is the second phase.

[0043] Finally, based on the compensated phases of all metasurface units, the phase compensation distribution results are obtained, as follows: Figure 5 As shown.

[0044] In some implementations, element mapping is performed based on the phase compensation distribution results, and corresponding geometric parameters are selected from the metasurface element library for each metasurface element arranged in an 11×11 array to establish a transmission focusing metasurface array, including: For each metasurface unit, its compensated phase is compared with the transmission phase recorded in the metasurface unit library, and the transmission phase that is closest to the compensated phase is selected as the target transmission phase. Based on the correspondence between multiple geometric parameters and transmission phases recorded in the metasurface unit library, for each metasurface unit, the geometric parameter corresponding to its target transmission phase is determined as the target geometric parameter. Based on the target geometric parameters corresponding to each metasurface unit, an 11×11 array of transmission focusing metasurfaces is established.

[0045] In this embodiment, by traversing each metasurface unit in the 11×11 array, phase comparison and target geometric parameter selection operations are performed one by one. Once the target geometric parameters of each metasurface unit are determined, that is, according to the 11×11 array arrangement, these metasurface units with specific geometric parameters, namely sizes a1, a2, and a3, are spatially combined and arranged to construct a complete transmission-focusing metasurface array. This unit mapping method ensures that each unit in the array can provide phase modulation closest to its required compensation phase, while guaranteeing high transmission efficiency, laying a key foundation for achieving efficient near-field focusing in the entire microwave wireless power transmission device.

[0046] In some implementations, the transmission phase of multiple metasurface units in the metasurface unit library is distributed in the range of 0–360°; the transmission amplitude of all metasurface units in the metasurface unit library is greater than or equal to a preset first threshold.

[0047] In this embodiment, multiple metasurface units in the metasurface unit library need to achieve full phase coverage at the operating frequency, i.e., full transmission phase coverage from 0 to 360°. Only in this way can it be ensured that each required compensation phase can find a close transmission phase value in the metasurface unit library when selecting metasurface units and their geometric parameters according to the compensation phase required at the corresponding position during the establishment of the transmission focusing metasurface array, thereby enabling the selection of suitable metasurface units and their geometric parameters. At the same time, the transmission amplitude of the metasurface units in the metasurface unit library is greater than or equal to a preset first threshold, which can ensure that the transmission energy is not too weak. The preset first threshold can be set according to actual needs.

[0048] In some implementations, taking an operating frequency of 2.45 GHz and a preset first threshold of 0.8 as an example, a metasurface unit library is established, including: First, select the metasurface unit period. And select the thickness of the dielectric substrate in the metasurface unit. The structure of metasurface units is as follows Figure 2 As shown.

[0049] Secondly, simulations were performed in the time-domain solver of the electromagnetic simulation software. By adjusting the geometric parameters a1 and a3 of the square patches in the upper and lower complementary square resonant units of the metasurface element, 0–360° transmission phase coverage at 2.45 GHz was achieved. For some elements with relatively low transmission amplitude, the impedance matching characteristics of the intermediate layer could be utilized to adjust the geometric parameter a2 of the square patch in the complementary square resonant unit of the intermediate layer, ensuring that the transmission amplitude is greater than 0.8, thus achieving efficient energy transmission. The range of geometric parameters a1, a2, and a3 of the square patches in the complementary square resonant unit that meet the above conditions was obtained, and the transmission coefficient of the element at 2.45 GHz can be obtained. Establish a metasurface unit library, namely the "geometric parameter - transmission phase / transmission amplitude" unit library, which records the metasurfaces that satisfy the transmission amplitude. 8 and transmission phase The corresponding geometric parameters a1, a2, and a3 when covering 0–360° conditions.

[0050] In addition, oblique incidence caused by near-range radiation can be considered to maintain high transmission and controllable phase error of the unit within a certain incident angle range.

[0051] In some cases, element mapping is performed based on the phase compensation distribution results. Corresponding geometric parameters are selected from the metasurface element library for each metasurface element arranged in an 11×11 array to establish a transmission focusing metasurface array. Specifically, the total phase compensation required for each metasurface element is determined. Mapping to the "Geometric Parameters - Transmission Phase / Transmission Amplitude" database, select the phase that needs to be compensated for each metasurface. With transmission phase The geometric parameters a1, a2, a3 of the complementary square resonant units of the closest metasurface units with |T|≥0.8 are used to form an 11×11 metasurface array.

[0052] In some implementations, a full-wave simulation model of the overall device, "2×2 microstrip array feed - 11×11 transmission focusing metasurface array," can be established in electromagnetic simulation software. The overall structural model is as follows: Figure 4 As shown, the electric field intensity distribution, focal spot size, side lobe level, and focal position deviation at the focal point are extracted.

[0053] In some implementations, the microwave wireless power transmission device can also be used as a microwave hyperthermia device. Therefore, after the design is completed, hyperthermia verification is required. Specifically, an equivalent tissue model or a tissue stack model is placed on the metasurface output side to perform electromagnetic-thermal coupling simulation, calculate parameters such as SAR, temperature rise distribution, and focusing efficiency; verify that the target area temperature rise reaches the hyperthermia threshold and control hot spots in non-target areas, and complete the feasibility verification of the device for microwave hyperthermia.

[0054] In some implementations, taking a 2×2 microstrip array feed and an 11×11 focusing metasurface as examples, the entire method flow is described in detail, including the following steps: (1) Establish a 2×2 microstrip array feed model in electromagnetic simulation software. Its structural schematic diagram is shown below. Figure 1 As shown, F4B was selected as the feed substrate material, and the substrate thickness was taken as... Four rectangular microstrip patch units are arranged on the top layer of the substrate, forming a 2×2 array. A T-type power divider is used to feed the rectangular microstrip patch units with equal amplitude and phase power. A grounding metal layer is placed on the bottom layer. The patch size parameters are used to determine the optimal power supply. With embedding depth The parameters are adjusted in combination to select the width of the rectangular microstrip patch. and length The selected patch embedding depths are 48.4mm and 39.25mm respectively. The width of the 50Ω main line is selected as 4.6mm (W50), and the width of the quarter-wavelength impedance transformer is selected as 2.6mm (W70), with a length of 21.25mm (L70). (2) Determine the feed-metasurface spacing Select It is 20cm; (3) Establish a library of transmissive metasurface units, such as metasurface units like Figure 2 As shown, F4B can be selected as the dielectric substrate for the metasurface unit, with a thickness of... The metasurface unit period p is 40 mm, and the geometric parameter b of the rectangular ring in the complementary square resonator unit is 37 mm. By changing the side lengths a1 and a3 of the square patches in the upper and lower complementary square resonator units, the phase coverage is made from 0 to 360 degrees. Then, the side length a2 of the square patch in the middle complementary square resonator unit is adjusted to make the transmission amplitude greater than 0.8. The transmission amplitude is extracted. With phase Establish a parameter scanning database and select parameters that meet the requirements. And the phase covers a set of units from 0 to 360°.

[0055] (4) Calculate the phase compensation required for the 11×11 array and map the cells: Extract the near-field incident electric field of the feed on the metasurface in the electromagnetic simulation software. The real and imaginary parts of the electric field data are interpolated using numerical calculation methods to obtain the first phase that needs to be accurately compensated from the feed source to the center of each metasurface unit. Then, the second phase that needs to be compensated from the metasurface to the focal point is obtained through the phase compensation formula. Finally, the overall phase compensation formula is obtained. ,in =0 Metasurfaces require overall phase compensation, such as Figure 6 As shown, select the cell with the closest phase from the cell library and The elements are filled into the corresponding element positions to form an 11×11 focused metasurface array, as shown in the schematic diagram below. Figure 3 As shown; (5) Overall verification and iteration: The 2×2 array feed and the 11×11 metasurface array are combined and modeled, as follows: Figure 4 As shown, the simulation yielded the electric field distribution at f = -10 cm on the output side of the metasurface, and the electric field distribution at the focal point is as follows. Figure 7As shown, if focus shift or sidelobe overshoot occurs, the spacing is iteratively adjusted. Reference phase Parameters such as array edge element selection strategy (prioritizing elements with high transmission or smaller phase error).

[0056] In some embodiments, under near-field conditions where the distance between the feed and the metasurface is relatively close, this application no longer relies solely on the ideal spherical wave assumption to calculate the incident phase of "feed → metasurface". Instead, it extracts the actual incident phase distribution from the feed to the metasurface plane through simulation, calculates the phase that needs to be compensated from the metasurface to the focal point based on the focusing formula, and combines the two phases to obtain the transmission phase required for each unit, thereby achieving stable near-field focusing and energy convergence.

[0057] Specifically, under near-field conditions with an operating frequency of 2.45 GHz and a close feed-metasurface spacing of approximately 20 cm, how can we characterize and compensate for the phase deviation caused by non-ideal wavefronts to eliminate focus point offset, addressing the complex radiation characteristics and unclear phase center of low-profile array feeds at close range? Under a focal length of approximately 10 cm, how can we combine "true incident phase compensation" with "target focusing phase compensation" to obtain the required transmission phase distribution suitable for transmission-type focusing metasurfaces, thereby improving focusing position accuracy and focal spot quality? Furthermore, when using a 2×2 microstrip array as a low-profile feed, how can we realize a compact, easily integrated, and easily reproducible transmission near-field focusing device and its design method, while improving robustness to assembly errors and reducing the cost of repeated iterative calibrations?

[0058] In the description of this specification, the references to terms such as "an embodiment," "some implementations," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0059] Although the embodiments of this application have been described in detail above with reference to the accompanying drawings, this application is not limited to the above embodiments. Those skilled in the art will understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application. The scope of this application is defined by the claims and their equivalents.

Claims

1. A microwave wireless power transmission device, characterized in that, include: The microstrip array feed includes a power supply network unit and four rectangular microstrip patch units, which are arranged in a 2×2 array. The power supply network unit is used to excite the four rectangular microstrip patch units with equal amplitude and phase. The microstrip array feed is used to radiate electromagnetic waves. A transmission-focusing metasurface array includes multiple metasurface units arranged in an 11×11 array. Each metasurface unit includes, from top to bottom, an upper complementary square resonant unit, an upper dielectric substrate, a middle complementary square resonant unit, a lower dielectric substrate, and a lower complementary square resonant unit. The upper complementary square resonant unit is located below the microstrip array feed. The transmission-focusing metasurface array is used to control the phase distribution of the electromagnetic waves radiated by the microstrip array feed to achieve focusing. The upper, middle, and lower complementary square resonant units each include a rectangular ring and a square patch located within the rectangular ring. A support member is disposed between the microstrip array feed source and the transmission focusing metasurface array, and the support member is used to limit the distance between the microstrip array feed source and the transmission focusing metasurface array to a preset distance.

2. A design method for a microwave wireless power transfer device, characterized in that, include: A microstrip array feed source is established; wherein, the microstrip array feed source includes a feed network unit and four rectangular microstrip patch units; A metasurface unit library is established; wherein, the metasurface unit library records the correspondence between the geometric parameters, transmission phase and transmission amplitude of multiple metasurface units; Set a preset spacing between the microstrip array feed and the transmission focusing metasurface array; The transmission focusing metasurface array is established; wherein the transmission focusing metasurface array includes a plurality of metasurface units, and the geometric parameters of each metasurface unit in the transmission focusing metasurface array are selected from the metasurface unit library; The microstrip array feed and the transmission focusing metasurface are connected by a support member based on the preset spacing to obtain a microwave wireless power transmission device.

3. The method according to claim 2, characterized in that, The transmission focusing metasurface array includes multiple metasurface units arranged in an 11×11 array; each metasurface unit includes, from top to bottom, an upper complementary square resonant unit, an upper dielectric substrate, a middle complementary square resonant unit, a lower dielectric substrate, and a lower complementary square resonant unit. The establishment of the transmission focusing metasurface array includes: Calculate the phase compensation distribution required for the transmission focusing metasurface array; wherein, the phase compensation distribution includes the compensation phase required for each metasurface unit in the 11×11 array arrangement; Based on the phase compensation distribution, unit mapping is performed, and the corresponding geometric parameters are selected from each of the metasurface units arranged in an 11×11 array from the metasurface unit library to establish the transmission focusing metasurface array; wherein, the geometric parameters include the side lengths of the square patches in the upper complementary square resonant unit, the middle complementary square resonant unit and the lower complementary square resonant unit.

4. The method according to claim 3, characterized in that, The calculation of the phase compensation distribution required for the transmission focusing metasurface array includes: Establish a reference coordinate system; Based on the preset spacing, preset focal length, and reference coordinate system, determine the required center position of the microstrip array feed source, the metasurface plane where the transmission focusing metasurface array is located, and the coordinate information corresponding to the center position and focal position of each metasurface unit; Based on the center position of the microstrip array feed source, the metasurface plane where the transmission focusing metasurface array is located, and the coordinate information corresponding to the center position of each metasurface unit, the first phase that needs to be compensated from the microstrip array feed source to each metasurface unit is obtained; Based on the coordinate information of the metasurface plane where the transmission focusing metasurface array is located, the center position of each metasurface unit and the focal position, the second phase that needs to be compensated from the focal point to each metasurface unit is calculated. Based on the reference phase constant and the first phase and the second phase corresponding to each of the metasurface units, the compensation phase that needs to be compensated for each of the metasurface units is obtained; The phase compensation distribution result is obtained based on the compensation phase of all the metasurface units.

5. The method according to claim 4, characterized in that, The process of obtaining the compensation phase required for each metasurface unit based on the reference phase constant and the first and second phases corresponding to each metasurface unit is constrained by the following expression: ； in, For the compensation phase, The reference phase constant is... For the first phase, This is the second phase.

6. The method according to claim 4, characterized in that, The step of obtaining the first phase compensation required from the microstrip array feed to each metasurface unit based on the center position of the microstrip array feed, the metasurface plane where the transmission focusing metasurface array is located, and the coordinate information corresponding to the center position of each metasurface unit includes: Based on the coordinate information corresponding to the center position of the microstrip array feed, the microstrip array feed is simulated separately, and based on the coordinate information corresponding to the metasurface plane where the transmission focusing metasurface array is located, a field monitor is set at the metasurface plane to obtain the electric field distribution data of the microstrip array feed at the metasurface plane. The electric field distribution data is interpolated, and the real part and imaginary part of the electric field corresponding to the center position of each metasurface unit are obtained based on the coordinate information corresponding to the center position of each metasurface unit. Based on the real and imaginary electric field data corresponding to the center position of each metasurface unit, the first phase that needs to be compensated from the microstrip array feed to each metasurface unit is obtained.

7. The method according to claim 6, characterized in that, The process of obtaining the first phase compensation required from the microstrip array feed to each metasurface unit based on the real and imaginary electric field data corresponding to the center position of each metasurface unit is constrained by the following expression: ； in, The imaginary part of the electric field is given. This represents the real part of the electric field.

8. The method according to claim 4, characterized in that, The calculation of the second phase compensation required from the metasurface unit to the focal point, based on the coordinate information of the metasurface plane where the transmission focusing metasurface array is located, the center position of each metasurface unit, and the focal position, is constrained by the following expression: ； Among them, the The coordinate information corresponding to the center position of each of the metasurface units is: , The focal length is given, and the coordinate information corresponding to the focal position is given. .

9. The method according to claim 3, characterized in that, Based on the phase compensation distribution, element mapping is performed, and the corresponding geometric parameters are selected from each of the metasurface elements arranged in an 11×11 array from the metasurface element library to establish the transmission focusing metasurface array, including: For each metasurface unit, its compensation phase is compared with the transmission phase recorded in the metasurface unit library, and the transmission phase that is closest to the compensation phase is selected as the target transmission phase. Based on the correspondence between the geometric parameters and the transmission phase recorded in the metasurface unit library, for each metasurface unit, the geometric parameter corresponding to its target transmission phase is determined as the target geometric parameter; Based on the target geometric parameters corresponding to each metasurface unit, an 11×11 array of transmission focusing metasurfaces is established.

10. The method according to claim 2, 3, or 9, characterized in that, The transmission phase of the multiple metasurface units in the metasurface unit library is distributed in the range of 0–360°; the transmission amplitude of the metasurface units in the metasurface unit library is greater than or equal to a preset first threshold.

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