A power distribution method for improving the uniformity of electromagnetic field distribution in a resonant cavity

Abstract

The application discloses a power distribution method for improving the uniformity of electromagnetic field distribution in a resonant cavity, and belongs to the field of microwave energy transmission. The application adopts superposition of multiple degenerate resonant modes, obtains the electromagnetic field distribution in the resonant cavity under a single resonant mode through electromagnetic simulation, and characterizes the accurate field distribution expression under different resonant modes by means of MATLAB; then, the power distribution of each resonant mode is carried out in MATLAB, and the variance of the magnetic field amplitude at the sample point under different power distribution modes is calculated, so that the power distribution mode when the electromagnetic field distribution in the resonant cavity is most uniform can be quickly and accurately obtained. The method of the application effectively improves the uniformity of the electromagnetic field distribution in the resonant cavity under the condition that the total input power is unchanged, reduces the occurrence of resonant zero points, thereby reduces the area with low energy transmission efficiency in the resonant cavity, and makes it possible to realize stable and high-efficiency wireless energy transmission.

Description

Technical Field

[0001] This invention belongs to the field of microwave power transmission, specifically relating to a power distribution method for improving the uniformity of electromagnetic field distribution within a resonant cavity. Background Technology

[0002] With the rise of mobile internet and the Internet of Things (IoT) and the continuous innovation of wireless communication technology, wireless interconnection technologies and products have profoundly impacted people's production and lifestyles at all levels. To solve the "last mile" problem of power transmission, researchers have proposed the concept of wireless power transmission. Wireless power transmission refers to the process of wirelessly transferring energy from a source to a load. Currently, wireless power transmission technologies mainly include electromagnetic induction, magnetic resonance, and radiation types. In recent years, these technologies have achieved mature theoretical frameworks and have been commercially applied in some fields. However, when the distance between the transceiver and receiver is too great or there are obstacles in between, the efficiency of the wireless power transmission system will drop sharply. Furthermore, most of these systems can only perform one-to-one wireless power transmission, which greatly restricts the further development of wireless power transmission technology in the civilian sector. Therefore, to solve the above problems, based on these technologies, researchers have proposed a cavity resonant wireless power transmission technology, which theoretically can achieve full-space, multi-target energy transmission and has broad application prospects.

[0003] However, currently commonly used microwave resonators are mainly single-mode resonators, such as the "Cavity Resonator Wireless Power Transfer System for Freely Moving Animal Experiments," which uses TM... 110 Resonant mode. A drawback of this structure is the uneven electromagnetic field distribution within the resonant cavity, resulting in a magnetic field zero-point and significant differences in the energy received at different locations within the cavity. Currently, researchers mostly improve efficiency at each point through dynamic impedance matching, but this greatly increases system complexity and cost. There are also some wireless power transfer systems based on multimode resonant cavities, known as "Three-Dimensional Charging via MultimodeResonant Cavity Enabled Wireless Power Transfer," which utilize TE... 011 and TE 012Two resonant modes operate at two different frequencies, and corresponding receivers are designed for each mode. Each time, the appropriate resonant mode needs to be manually selected based on the receiver's location, increasing design complexity and hindering practical applications. Therefore, improving the uniformity of the field distribution inside the resonant cavity while simultaneously eliminating resonant nulls and reducing regions of low wireless power transmission efficiency within the cavity is a current research hotspot. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art by proposing a power allocation method that improves the uniformity of the electromagnetic field distribution within a resonant cavity by superimposing multiple degenerate resonant modes. The method first obtains the electromagnetic field distribution within the resonant cavity under a single resonant mode through electromagnetic simulation, and then accurately characterizes the field distribution expressions under different resonant modes using MATLAB. Next, in MATLAB, power allocation is performed for each resonant mode, and the variance of the magnetic field amplitude at sample points under different power allocation methods is calculated, thereby quickly and accurately determining the power allocation method that achieves the most uniform electromagnetic field distribution within the resonant cavity. With a constant total input power, this method improves the uniformity of the electromagnetic field distribution within the resonant cavity, reduces the occurrence of resonant zeros, and thus reduces the region of low power transmission efficiency within the resonant cavity, making stable and high-efficiency wireless power transmission possible.

[0005] The above-mentioned technical objective of the present invention is achieved through the following technical solution:

[0006] A power distribution method for improving the uniformity of electromagnetic field distribution within a resonant cavity, characterized by comprising the following steps:

[0007] S1. Establish a resonant cavity, determine the operating frequency and the corresponding set of degenerate resonant modes, with a total number of resonant modes of N.

[0008] S2. Set the magnetic field amplitude variance function To characterize the uniformity of the field distribution within the resonant cavity; where H q This represents the magnetic field amplitude at the q-th sample point within the resonant cavity. Q represents the average magnetic field amplitude at all sample points within the resonant cavity, where Q = K. 3 This represents the total number of sample points when K sample points are uniformly taken in the X, Y, and Z directions within the resonant cavity.

[0009] S3-1. Simulate the i-th resonant mode of the excitation cavity, then extract the magnetic field amplitude at Q sample points to obtain the variance D of the magnetic field amplitude of the i-th resonant mode. i ;

[0010] Based on the general field distribution expression of the i-th resonant mode, calculate the variance D′ of the magnetic field amplitude corresponding to the Q sample points. i .

[0011] S3-2. Adjust the amplitude H in the field distribution expression of the i-th resonant mode. i The value of D makes i With D′ i The same, thus determining H in the i-th resonant mode. i The accurate value is obtained, and then the accurate field distribution expression of the i-th resonant mode is determined.

[0012] S3-3. Repeat steps S3-1 to S3-2 to determine the accurate field distribution expressions for the N resonant modes.

[0013] S4. Based on the principle of resonant mode superposition, linearly superimpose the accurate field distribution expressions of N resonant modes, and then calculate the distribution variance function D of the superimposed magnetic field inside the resonant cavity under different power distributions, obtaining the P corresponding to the minimum of D. i This ultimately determines the power allocation method; among which, P i P represents the power of the i-th resonant mode. i The value ranges from 0 to 1.

[0014] Furthermore, in steps S3-1 and S3-2, the variance of the magnetic field amplitude D′ is calculated using MATLAB. i In step S4, MATLAB is used to calculate the variance function D of the superimposed magnetic field distribution inside the resonant cavity under different power distributions.

[0015] Furthermore, the resonant cavity is a metal-enclosed resonant cavity or a metasurface resonant cavity.

[0016] The beneficial effects of this invention are:

[0017] The power distribution method for improving the uniformity of electromagnetic field distribution in a resonant cavity proposed in this invention is applicable to resonant cavities of different sizes and metasurface resonant cavities, and has a wide range of applications and strong practicality.

[0018] The power distribution method proposed in this invention to improve the uniformity of electromagnetic field distribution in the resonant cavity adopts a degenerate resonance mode, that is, each resonance mode has the same resonant frequency. In this way, the receiver does not need to operate at multiple frequencies, thereby reducing the design complexity of the system.

[0019] The power allocation method proposed in this invention to improve the uniformity of electromagnetic field distribution in resonant cavities can be calculated using the commercial mathematical software MATLAB, thereby accurately characterizing the electromagnetic field distribution after the superposition of multiple modes, and quickly and accurately determining the optimized power allocation method for different resonant modes, avoiding the repetitive work of frequently deriving magnetic fields, and saving time and effort.

[0020] The power distribution method proposed in this invention for improving the uniformity of electromagnetic field distribution within a resonant cavity can enhance the uniformity of electromagnetic field distribution inside the resonant cavity, making the energy received by the receiver at each position within the resonant cavity as consistent as possible. This avoids large fluctuations in the output voltage of the circuit as the receiver moves to different positions within the resonant cavity, thereby enabling efficient and stable wireless power transmission within the resonant cavity.

[0021] The power distribution method proposed in this invention to improve the uniformity of electromagnetic field distribution in the resonant cavity can reduce the occurrence of resonant zeros, thereby effectively reducing the region with low energy transmission efficiency in the resonant cavity and avoiding the inability to perform wireless energy transmission at certain locations in the resonant cavity. Attached Figure Description

[0022] Figure 1 A flowchart of a power distribution method for improving the uniformity of electromagnetic field distribution within a resonant cavity;

[0023] Figure 2 This is a schematic diagram of the metal resonant cavity in the embodiment;

[0024] Figure 3 The variance of the magnetic field amplitude under different power distributions in the embodiments;

[0025] Figure 4 The TE generated by simulation in the example 203 A comparison of the overall magnetic field distribution in resonant mode (a) and magnetic field distribution under optimal power distribution ratio (b);

[0026] Figure 5 The TE generated by simulation in the example 203 A comparison of the front views of the magnetic field distribution in the resonant mode (a) and the magnetic field distribution under the optimal power distribution ratio (b);

[0027] Figure 6 The TE generated by simulation in the example 203 A comparison of the side views of the magnetic field distribution in the resonant mode (a) and the magnetic field distribution under the optimal power distribution ratio (b);

[0028] Figure 7 The TE generated by simulation in the example 203 A comparison of top views of the magnetic field distribution in resonant mode (a) and the magnetic field distribution under optimal power distribution ratio (b);

[0029] Figure 8 A comparison diagram of the magnetic field distribution along a line segment taken in the X direction at the center of the resonant cavity;

[0030] Figure 9 This is a comparison diagram of the magnetic field distribution along a line segment taken in the Z direction at the center of the resonant cavity. Detailed Implementation

[0031] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments. The present invention includes, but is not limited to, the following embodiments.

[0032] Since a changing electric field can generate a magnetic field, and a changing magnetic field can generate an electric field, this embodiment only presents the entire process by optimizing the magnetic field amplitude. The flowchart of this embodiment is as follows: Figure 1 As shown, it includes the following steps:

[0033] S1. Create a system in ANSYS HFSS as follows: Figure 2 The metal-enclosed resonant cavity shown has a length of a, a width of b, and a height of d. Where a is 1000 mm, b is 1000 mm, and d is 1000 mm.

[0034] The resonant frequencies corresponding to different resonant modes are calculated based on the size of the resonant cavity, and the calculation formula is shown in (1):

[0035]

[0036] Where ε is the vacuum dielectric constant, μ is the vacuum permeability, and each set of m, n, p values ​​represents a resonant mode.

[0037] Calculations can yield the resonant frequencies of the resonant cavity from the dominant mode to higher-order modes. Here, to maximize the uniformity of the electromagnetic field distribution within the cavity and for ease of explanation, a set of degenerate resonant modes with a relatively large number of degenerate modes is selected: TE. 023 / TE 032 / TE 203 / TE 302 / TM 230 / TM 320 The resonant frequency is 540.4MHz.

[0038] S2. Eleven sample points were uniformly selected in the X, Y, and Z directions within the resonant cavity, for a total of Q = 1331 sample points.

[0039] S3. In ANSYS HFSS, excite the above-mentioned degenerate resonance modes respectively, extract the magnetic field amplitude at these sample points under different resonance modes, and calculate the magnetic field distribution variance D of different resonance modes. i .

[0040] In MATLAB, based on the field distribution expressions for each resonance mode, the variance D′ of the magnetic field amplitude at these sample points under different resonance modes is calculated. i .

[0041] The general magnetic field distribution expression for the i-th resonant mode at (x,y,z) is:

[0042] TE mnp Resonance mode:

[0043]

[0044]

[0045]

[0046] TM mnp Resonance mode:

[0047]

[0048]

[0049] H zi =0 (7)

[0050]

[0051] Where j is the imaginary sign, H i H is the magnetic field amplitude of the i-th resonant mode. xi H yi H zi Let k represent the magnetic field components in the X, Y, and Z directions of the sample point at coordinates (x, y, z) for the i-th resonant mode. c ω is the cutoff wavenumber of the resonant mode, and ω is the resonant angular frequency of the resonant mode.

[0052] In Equations 2-8, once the resonant cavity size and resonant mode are determined, most parameters are known. The only unknown quantity is H. i Its magnitude is related to the excitation signal strength; by adjusting H i The value of H is such that the variance of the magnetic field amplitude at the sample points calculated by MATLAB is the same as the variance of the magnetic field amplitude at the sample points obtained from simulation. i The accurate value of TE can be obtained, thus allowing for accurate simulation results using MATLAB. In this embodiment, TE is ultimately obtained. 023 / TE 032 / TE 203 / TE 302 / TM 230 / TM 320 H corresponding to the resonant mode i The values ​​are 5.95, 8.86, 5.66, 8.63, 4052.75, and 4101.76, respectively.

[0053] S4. Based on the principle of resonant mode superposition, as shown in Equations 9-12, using MATLAB, the accurate field distribution expressions of different resonant modes are linearly superimposed to obtain the magnetic field amplitude at each sample point under the superimposed field. The variance of the magnetic field amplitude at these sample points under different power allocations is then calculated, thereby quickly determining the power allocation method corresponding to the most uniform superimposed field. In this embodiment, the final TE is obtained. 023 / TE 032 / TE 203 / TE 302 / TM 230 / TM 320 The optimal power distribution for these six resonant modes is 0W, 0W, 0.85W, 0W, 0W, and 0.15W.

[0054]

[0055]

[0056]

[0057]

[0058] Among them, H x H y H z Let X, Y, and Z be the magnetic field components of the superimposed field at the sample point (x, y, z), respectively, and H represent the magnetic field amplitude of the superimposed field at the sample point (x, y, z).

[0059] Figure 3 The variance of the magnetic field amplitude at the sample point inside the resonant cavity under different power allocation methods is shown. It can be seen that the power allocation method optimized using MATLAB improves the uniformity of the magnetic field distribution by 45.2% compared to the magnetic field distribution of a single resonant mode, significantly improving the uniformity of the magnetic field distribution inside the resonant cavity.

[0060] Figures 4-7 The comparison between the magnetic field distribution under the final optimized power allocation method and the magnetic field distribution under a single resonant mode is shown from different perspectives. It can be seen that the magnetic field distribution under the power allocation method optimized by the present invention reduces the occurrence of resonant zeros and the overall magnetic field distribution is more uniform. This means that the superimposed field of the resonant mode under the power allocation method of the present invention can effectively reduce the region of low energy transfer efficiency within the resonant cavity compared to the magnetic field distribution of a single resonant mode, enabling efficient and stable wireless energy transmission throughout the entire resonant cavity.

[0061] Figures 8-9The magnetic field distributions are shown on line segments taken along the X and Z directions at the center of the resonant cavity, respectively. It can be seen that the magnetic field distribution under multimode superposition can maintain the maximum amplitude of a single resonant mode while increasing the minimum amplitude and eliminating as many resonant zeros as possible.

[0062] In summary, the method of this invention can quickly determine the optimal power allocation method for different resonant modes in a short period of time, which greatly improves efficiency, avoids the repetitive work of frequently deriving magnetic fields, and saves time and effort.

[0063] It is worth noting that this embodiment is merely an illustration of the method of the present invention, and different higher-order degenerate resonant modes can be selected to achieve different effects. Furthermore, within the allowable error range, the present invention can further simplify the process, eliminating the need for electromagnetic simulation; H corresponding to different resonant modes can be determined solely through MATLAB calculations based on the conservation of electromagnetic energy. i The proportional relationship between them can still yield optimized results. This simplified method is a qualitative research method. Its advantage is that it is faster, but its disadvantage is that it is too idealistic and its accuracy is somewhat worse, with an error of about 5%.

[0064] The above description is merely a specific embodiment of the present invention. Any feature disclosed in this specification may be replaced by other equivalent or similar features unless otherwise specified. All disclosed features, or steps in all methods or processes, may be combined in any way except for mutually exclusive features and / or steps.

Claims

1. A power distribution method for improving the uniformity of electromagnetic field distribution within a resonant cavity, characterized in that, Includes the following steps: S1. Establish a resonant cavity, determine the operating frequency and the corresponding set of degenerate resonant modes, with a total of N resonant modes; S2. Set the magnetic field amplitude variance function To characterize the uniformity of the field distribution within the resonant cavity; where H q This represents the magnetic field amplitude at the q-th sample point within the resonant cavity. Q represents the average magnetic field amplitude at all sample points within the resonant cavity, where Q = K. 3 This represents the total number of sample points when K sample points are uniformly taken in the X, Y, and Z directions within the resonant cavity. S3-1. Simulate the i-th resonant mode of the excitation cavity, then extract the magnetic field amplitude at Q sample points to obtain the variance D of the magnetic field amplitude of the i-th resonant mode. i ; Based on the general field distribution expression of the i-th resonant mode, calculate the variance D′ of the magnetic field amplitude corresponding to the Q sample points. i ; S3-2. Adjust the amplitude H in the field distribution expression of the i-th resonant mode. i The value of D makes i With D′ i The same, thus determining H in the i-th resonant mode. i The accurate value is then used to determine the accurate field distribution expression for the i-th resonant mode; S3-3. Repeat steps S3-1 to S3-2 to determine the accurate field distribution expressions for the N resonant modes; S4. Based on the principle of resonant mode superposition, linearly superimpose the accurate field distribution expressions of N resonant modes, then calculate the variance function D of the superimposed magnetic field distribution inside the resonant cavity under different power distributions, and obtain the P corresponding to the minimum of D. i This ultimately determines the power allocation method; among which, P i P represents the power of the i-th resonant mode. i The value ranges from 0 to 1.

2. The power distribution method for improving the uniformity of electromagnetic field distribution within a resonant cavity as described in claim 1, characterized in that, In steps S3-1 and S3-2, the variance of the magnetic field amplitude D′ is calculated using MATLAB. i In step S4, MATLAB is used to calculate the variance function D of the superimposed magnetic field distribution inside the resonant cavity under different power distributions.

3. A power distribution method for improving the uniformity of electromagnetic field distribution within a resonant cavity as described in claim 1 or 2, characterized in that, The resonant cavity is a metal-enclosed resonant cavity or a metasurface resonant cavity.

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