Design method of near-field multi-target microwave wireless energy transmission antenna array

Abstract

The application discloses a design method of a near-field multi-target microwave wireless energy transmission antenna array. Firstly, position information between an array element on a transmitting antenna and a focusing plane is obtained based on coordinate transformation; secondly, a mathematical equation of a Poynting vector and a beam collection efficiency is derived based on electromagnetic field theory; thirdly, the mathematical equation is solved, and a corresponding solution is obtained; and finally, the solution is used as a feeding excitation of the antenna array, and a corresponding power directional diagram is obtained. The application can realize multi-target microwave wireless energy transmission, and ensures that a microwave wireless energy transmission system has a high BCE.

Description

Technical Field

[0001] This invention belongs to the field of antenna array design technology, and relates to a design method for a near-field multi-target microwave wireless power transfer antenna array. Background Technology

[0002] In recent years, near-field multi-target microwave wireless power transfer technology has attracted widespread interest in academia and industry. Achieving near-field multi-target microwave wireless power transfer while ensuring high transmission efficiency is a key issue for all microwave wireless power transfer systems. Beam collection efficiency is a crucial indicator for measuring the efficiency of microwave wireless power transfer.

[0003] Currently, domestic and international design methods for near-field multi-target microwave wireless power transfer antenna arrays mainly rely on optimization algorithms. These algorithms optimize the feeding and excitation of the array antenna, such as an active phased array antenna, to radiate the electromagnetic field beam onto a pre-defined focusing area. However, in practical engineering, due to factors such as computing power and cost, these methods have long solution times, making it impossible to quickly evaluate the efficiency of near-field multi-target microwave wireless power transfer systems. Summary of the Invention

[0004] The purpose of this invention is to provide a design method for a near-field multi-target microwave wireless power transmission antenna array. This method is based on the superposition principle and uses numerical methods to quickly solve the feeding excitation of the antenna array, thereby realizing the evaluation of the near-field multi-target microwave wireless power transmission efficiency.

[0005] The technical solution adopted in this invention is a design method for a near-field multi-target microwave wireless power transmission antenna array. First, based on coordinate transformation, the position information between the array elements on the transmitting antenna and the focusing plane is obtained. Second, based on electromagnetic field theory, the mathematical equations of the Poynting vector and beam collection efficiency are derived through mathematical derivation. Third, the mathematical equations obtained above are solved to obtain the corresponding solutions. Finally, the obtained solutions are used as the feeding excitation of the antenna array to obtain the corresponding power pattern.

[0006] The invention is further characterized by:

[0007] Specifically, the steps include the following:

[0008] Step 1: Solve for the distance vector between each element on the array antenna and the observation point;

[0009] Step 2: Solve for the electric and magnetic field vectors of the array antenna elements at the observation point based on the results obtained in Step 1;

[0010] Step 3: Solve for the Poynting vector of the focusing plane based on the results obtained in Step 2;

[0011] Step 4: Calculate the total energy collected by the focusing plane based on the results obtained in Step 3;

[0012] Step 5: Calculate the total transmitted energy of the planar array antenna;

[0013] Step 6: Based on the results obtained in Steps 4 and 5, establish a mathematical equation for beam collection efficiency.

[0014] The specific process of step 1 is as follows:

[0015] Assuming a near-field multi-target microwave wireless power transfer system includes A focusing plane and a planar array antenna, the planar array antenna containing... The same radiating elements, and the array elements along x shaft and y The axes are evenly arranged with a spacing of [missing information]. The power supply excitation is expressed as follows: , Meanwhile, it is assumed that there are on each focal plane. The observation point, of which the first... Each focal plane Upper The position vector of each observation point is represented as: , , No. Each focal plane correspond x , y , z The rotation matrices are respectively , , and They represent circumference respectively. x , y , z The angle of the rotation axis is defined as counterclockwise as positive, where the first... Each focal plane The rotated first The position vector of each observation point is represented as:

[0016] (1)

[0017] (2)

[0018] (3)

[0019] (4)

[0020] No. A rotating focusing plane The translated first The position vector of each observation point is represented as:

[0021] (5)

[0022] in, Indicates the first Translation vectors of a rotating focal plane, , and They represent exist x , y , z The components on;

[0023] Let the first planar array antenna be... The position vector of each array element , No. Individual elements and the first A rotating focusing plane Upper The distance vector between the observation points is Specifically, it is expressed as:

[0024] (6).

[0025] The specific process of step 2 is as follows:

[0026] No. Individual elements and the first A rotating focusing plane Upper The electric and magnetic field vectors at each observation point are respectively and Specifically, it is expressed as:

[0027] (7)

[0028] (8)

[0029] in, Indicates the feed excitation of the array antenna, superscript H Represents the conjugate of a matrix. Represents the space wavenumber. and They represent the first The electric and magnetic field radiation patterns of each array element. , and Indicates the first The electric field of each element is x , y , z The amount on, , and Indicates the first The magnetic field of each array element is x , y , z The components on;

[0030] No. The relationship between the electric and magnetic field radiation patterns of each array element is expressed as follows:

[0031] (9)

[0032] in, Indicates spatial wave impedance, express The unit vector, where "×" indicates the cross product calculation.

[0033] The specific process of step 3 is as follows:

[0034] No. Each focal plane Upper At each observation point x , y , z The Poynting vectors in the directions are represented as follows:

[0035] (10)

[0036] (11)

[0037] (12)

[0038] in, superscript * Represents the conjugate transpose of a matrix; .

[0039] The specific process of step 4 is as follows:

[0040] No. Each focal plane The energy collected is defined as , No. Each focal plane Upper Poynting vector at each observation point ,but Represented as:

[0041] (13)

[0042] in, Indicates the first Each focal plane Upper The receiving area of ​​each observation point; , Indicates the first Each focal plane unit vector, , and Indicates the unit vector in x , y , z Substituting equations (10), (11), and (12) into equation (13), the components above, then the first... Each focal plane The collected energy is rewritten as:

[0043] (14)

[0044] (15)

[0045] If equation (14) is expressed in Hermitian matrix form, then equation (14) can be rewritten as:

[0046] (16)

[0047] (17)

[0048] The specific process of step 5 is as follows:

[0049] Imagine a spherical receiving surface at a distance from the array antenna. The total energy collected by this spherical receiving surface is equivalent to the total transmitted energy of the planar array antenna. Specifically, it is expressed as:

[0050] (18)

[0051] (19)

[0052] (20)

[0053] (twenty one)

[0054] (twenty two)

[0055] (twenty three)

[0056] (twenty four)

[0057] in, , Represents the radial unit vector in spherical coordinates.

[0058] The specific process of step 6 is as follows:

[0059] According to the definition of BCE, the ratio of equations (17) and (24) is the BCE of the near-field multi-target microwave wireless power transfer system, expressed as:

[0060] (25).

[0061] The beneficial effects of this invention are:

[0062] 1. It can realize the calculation of the feeding excitation of multi-target antenna array to maximize beam collection efficiency, which is more convenient and faster than optimization algorithms;

[0063] 2. This method can be used to accurately calculate the arbitrary position and pose of multiple targets, ultimately maximizing the beam collection efficiency of the near-field multi-target microwave wireless power transmission system. Attached Figure Description

[0064] Figure 1 This invention relates to the design method of a near-field multi-target microwave wireless power transfer antenna array.

[0065] Schematic diagram of near-field multi-target microwave wireless power transfer;

[0066] Figure 2 This invention relates to a design method for near-field multi-target microwave wireless power transfer antenna arrays.

[0067] A schematic diagram of the calculation model for the center-focusing receiving plane;

[0068] Figure 3 This is a diagram showing the amplitude distribution of the feed excitation of the planar array antenna in the design method of the near-field multi-target microwave wireless power transfer antenna array of the present invention.

[0069] Figure 4 This is a feed excitation phase distribution diagram of the planar array antenna in the design method of the near-field multi-target microwave wireless power transfer antenna array of the present invention;

[0070] Figure 5 The normalized power distribution map is obtained through the design method of the near-field multi-target microwave wireless power transfer antenna array of the present invention. Detailed Implementation

[0071] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0072] This invention relates to a design method for near-field multi-target microwave wireless power transfer antenna arrays, which can be used to guide the feed excitation design of near-field multi-target microwave wireless power transfer antenna arrays.

[0073] Example 1

[0074] The present invention discloses a design method for a near-field multi-target microwave wireless power transmission antenna array. First, based on coordinate transformation, the positional information between the array elements on the transmitting antenna and the focusing plane is obtained. Second, based on electromagnetic field theory, the mathematical equations for the Poynting vector and beam collection efficiency are derived through mathematical derivation. Third, the mathematical equations obtained above are solved to obtain the corresponding solutions. Finally, the obtained solutions are used as the feeding excitation for the antenna array to obtain the corresponding power pattern.

[0075] Example 2

[0076] The specific process is as follows:

[0077] Step 1: Calculate the distance vector between each element on the array antenna and the observation point.

[0078] Assuming a near-field multi-target microwave wireless power transfer system includes A focusing plane and a planar array antenna. The planar array antenna includes... The same radiating elements, and the array elements along x shaft and y The axes are evenly arranged with a spacing of [missing information]. ,like Figure 1 As shown. It is also assumed that all elements are isotropic and that the mutual coupling between elements is negligible. Figure 1 Show the first Each radiating element, its position coordinates, and its feeding excitation are respectively expressed as: , . No. Each focal plane The computational model for coordinate transformation, such as Figure 2 As shown. It is also assumed that there are on each focal plane. The observation point, of which the first... Each focal plane Upper The position vector of each observation point is represented as: , . No. Each focal plane correspond x , y , z The rotation matrices are respectively . , and They represent circumference respectively. x ,y , z The angle of the rotation axis is defined as counterclockwise as positive. Wherein, the... Each focal plane The rotated first The position vector of each observation point is represented as:

[0079] (1)

[0080] (2)

[0081] (3)

[0082] (4)

[0083] No. A rotating focusing plane The translated first The position vector of each observation point is represented as:

[0084] (5)

[0085] in, Indicates the first Translation vectors of a rotating focal plane, , and They represent exist x , y , z The components on the surface. Furthermore, unlike far-field electromagnetic radiation, near-field electric field radiation needs to consider the effect of distance. Therefore, the first component on the planar array antenna... The position vector of each array element , No. Individual elements and the first A rotating focusing plane Upper The distance vector between the observation points is Specifically, it can be expressed as:

[0086] (6)

[0087] Step 2: Calculate the electric and magnetic field vectors of the array antenna elements at the observation point.

[0088] No. Individual elements and the first A rotating focusing plane Upper The electric and magnetic field vectors at each observation point are respectively and Specifically, it can be expressed as:

[0089] (7)

[0090] (8)

[0091] in, Indicates the feed excitation of the array antenna, superscript H Represents the conjugate of a matrix. Represents the space wavenumber. and They represent the first The electric and magnetic field radiation patterns of each array element. It is important to note that... , and Indicates the first The electric field of each element is x , y , z The amount on, , and Indicates the first The magnetic field of each array element is x , y , z The portion on top.

[0092] No. The relationship between the electric and magnetic field radiation patterns of each array element can be expressed as:

[0093] (9)

[0094] in, Indicates spatial wave impedance, express The unit vector, where "×" indicates the cross product calculation.

[0095] Step 3, calculate the Poynting vector of the focal plane.

[0096] No. Each focal plane Upper The Poynting vectors of the observation points in the x, y, and z directions are respectively represented as follows:

[0097] (10)

[0098] (11)

[0099] (12)

[0100] in, Superscript *This represents the conjugate transpose of a matrix. Additionally, please note:

[0101] .

[0102] Step 4: Calculate the total energy collected by the focusing plane;

[0103] No. Each focal plane The energy collected is defined as , No. Each focal plane Upper Poynting vector at each observation point ,but It can be represented as:

[0104] (13)

[0105] in, Indicates the first Each focal plane Upper The receiving area of ​​each observation point. Furthermore, , Indicates the first Each focal plane unit vector, , and Indicates the unit vector in x , y , z The components on. Substituting equations (10), (11), and (12) into equation (13), then the first component... Each focal plane The collected energy can be rewritten as:

[0106] (14)

[0107] (15)

[0108] Further expressing equation (14) in Hermitian matrix form, equation (14) can be rewritten as:

[0109] (16)

[0110] (17)

[0111] Step 5: Calculate the total transmitted energy of the planar array antenna.

[0112] Similar to the process described above for calculating the total energy collected by the focusing plane, the only difference is that a spherical receiving surface needs to be assumed at a distance from the array antenna. The total energy collected by this spherical receiving surface can be equivalent to the total transmitted energy of the planar array antenna. Specifically, it can be expressed as:

[0113] (18)

[0114] (19)

[0115] (20)

[0116] (twenty one)

[0117] (twenty two)

[0118] (twenty three)

[0119] (twenty four)

[0120] in, . Represents the radial unit vector in spherical coordinates.

[0121] Step 6: Establish the mathematical equation for beam collection efficiency.

[0122] According to the definition of BCE, the ratio of equations (17) and (24) is the BCE of the near-field multi-target microwave wireless power transfer system, which can be expressed as:

[0123] (25)

[0124] Clearly, the problem of solving the BCE is rewritten as a generalized eigenvalue problem. The maximum eigenvalue of Equation (25) is equal to the maximum BCE of the array antenna, and the relevant eigenvector corresponding to the maximum eigenvalue of Equation (25) is equal to the feed excitation of the array antenna. Finally, the feed excitation can be obtained using Equation (25), and then applied to the array antenna to realize near-field multi-target microwave wireless power transmission.

[0125] Example 3

[0126] The advantages of this invention can be further illustrated by the following simulation experiments:

[0127] 1) Simulation parameters: The near-field multi-target microwave wireless power transfer system includes one transmitting antenna and two focusing receiving antennas. Both transmitting and receiving antennas have square apertures. The transmitting array contains 256 elements, with a side length of [missing information]. , The array element spacing is 0.5 wavelengths, and the operating frequency is 5.8 GHz. Table 1 shows the relevant parameters and BCE of the two-target near-field microwave wireless power transfer system; Figure 3 The feed amplitude obtained after solving equation (25) is shown. Figure 4 The feed phase obtained after solving equation (25) is shown. Figure 5 The electromagnetic field distribution obtained after solving equation (25) is shown.

[0128] 2) Simulation content and results: Table 1 shows the relevant parameters and BCE of the two-target near-field microwave wireless power transfer system; Figure 3 The distribution of the feed amplitude of a near-field two-target microwave wireless power transmission antenna array is shown. It can be seen that the feed amplitude distribution of the antenna array is large in the middle and small around the edges. Figure 4 The feed phase distribution of the near-field two-target microwave wireless power transmission antenna array shows that the feed phase distribution of the antenna array exhibits symmetry, which is consistent with the symmetrical distribution of the poses of the two receiving antenna targets in space. Figure 5 The electromagnetic radiation field distribution of a near-field two-target microwave wireless power transfer antenna array is shown. It can be seen that after applying the feed excitation obtained by equation (25) to the antenna array, its electromagnetic radiation field is mainly distributed on receiving antenna 1 and receiving antenna 2. It should be noted that the first and third columns of Table 1 represent the phase positions of the first and second focusing receiving planes from the planar array antenna, respectively, and the second and fourth columns represent the relative rotation angles of the first and second focusing receiving planes from the planar array antenna, respectively.

[0129] Table 1. Relevant parameters of the near-field microwave wireless power transfer system

[0130]

Claims

1. A design method for a near-field multi-target microwave wireless power transfer antenna array, characterized in that: First, based on coordinate transformation, the positional information between the array elements on the transmitting antenna and the focusing plane is obtained. Second, based on electromagnetic field theory, the mathematical equations relating the Poynting vector and beam collection efficiency are derived mathematically. Third, the obtained mathematical equations are solved to obtain the corresponding solutions. Finally, the obtained solutions are used as the feed excitation for the antenna array, and the corresponding power pattern is obtained. The specific steps include the following: Step 1: Solve for the distance vector between each element on the array antenna and the observation point; Step 2: Based on the results obtained in Step 1, calculate the electric and magnetic field vectors of the array antenna elements at the observation point; the specific process of Step 2 is as follows: No. Individual elements and the first A rotating focusing plane Upper The electric and magnetic field vectors at each observation point are respectively and Specifically, it is expressed as: （7） （8） in, This indicates the feeding excitation of the array antenna. Represents the space wavenumber. and They represent the first The electric and magnetic field radiation patterns of each array element. , and Indicates the first The electric field of each element is x , y , z The amount on, , and Indicates the first The magnetic field of each array element is x , y , z The components above; the first Individual elements and the first A rotating focusing plane Upper The distance vector between the observation points is ; No. The relationship between the electric and magnetic field radiation patterns of each array element is expressed as follows: （9） in, Indicates spatial wave impedance, express The unit vector, "×" indicates the cross product calculation; Step 3: Solve for the Poynting vector of the focusing plane based on the results obtained in Step 2; Step 4: Calculate the total energy collected by the focusing plane based on the results obtained in Step 3; Step 5: Calculate the total transmitted energy of the planar array antenna; Step 6: Based on the results obtained in Steps 4 and 5, establish a mathematical equation for beam collection efficiency.

2. The design method for a near-field multi-target microwave wireless power transfer antenna array according to claim 1, characterized in that: The specific process of step 1 is as follows: Assuming a near-field multi-target microwave wireless power transfer system includes A focusing plane and a planar array antenna, the planar array antenna containing... The same radiating elements, and the array elements along x shaft and y The axes are evenly arranged with a spacing of [missing information]. The power supply excitation is expressed as follows: , Meanwhile, it is assumed that there are on each focal plane. The observation point, of which the first... Each focal plane Upper The position vector of each observation point is represented as: , , No. Each focal plane correspond x , y , z The rotation matrices are respectively , , and They represent circumference respectively. x , y , z The angle of the rotation axis is defined as counterclockwise as positive, where the first... Each focal plane The rotated first The position vector of each observation point is represented as: （1） （2） （3） （4） No. A rotating focusing plane The translated first The position vector of each observation point is represented as: （5） in, Indicates the first Translation vectors of a rotating focal plane, , and They represent exist x , y , z The components on; Let the first planar array antenna be... The position vector of each array element , No. Individual elements and the first A rotating focusing plane Upper The distance vector between the observation points is Specifically, it is expressed as: （6）。 3. The design method for a near-field multi-target microwave wireless power transfer antenna array according to claim 2, characterized in that: The specific process of step 3 is as follows: Each focal plane Upper The Poynting vectors of the observation points in the x, y, and z directions are respectively represented as: （10） （11） （12） in, The superscripts * and H represent the conjugate and conjugate transpose of the matrix, respectively; 。 4. The design method for a near-field multi-target microwave wireless power transfer antenna array according to claim 3, characterized in that: The specific process of step 4 is as follows: No. Each focal plane The energy collected is defined as , No. Each focal plane Upper Poynting vector at each observation point ,but Represented as: （13） in, Indicates the first Each focal plane Upper The receiving area of ​​each observation point; , Indicates the first Each focal plane unit vector, , and Indicates the unit vector in x , y , z Substituting equations (10), (11), and (12) into equation (13), the components above, then the first... Each focal plane The collected energy is rewritten as: （14） （15） If equation (14) is expressed in Hermitian matrix form, then equation (14) can be rewritten as: （16） （17）。 5. The design method for a near-field multi-target microwave wireless power transfer antenna array according to claim 4, characterized in that: The specific process of step 5 is as follows: Imagine a spherical receiving surface at a distance from the array antenna. The total energy collected by this spherical receiving surface is equivalent to the total transmitted energy of the planar array antenna. Specifically, it is expressed as: （18） （19） （20） （21） （22） （23） （24） in: , Represents the radial unit vector in spherical coordinates.

6. The design method for a near-field multi-target microwave wireless power transfer antenna array according to claim 5, characterized in that: The specific process of step 6 is as follows: According to the definition of BCE, the ratio of equations (17) and (24) is the BCE of the near-field multi-target microwave wireless power transfer system, expressed as: （25）。

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