A spatial plane electric field customized field distribution shaping method

Abstract

The application discloses a spatial plane electric field customized field distribution shaping method, which converts an arbitrary complex target shaping pattern into a focus point set by determining the structural parameters, working frequency and near-field shaping height of an array antenna unit and adopting an equidistant gridding discrete mode; the amplitude and phase distribution of all array elements are calculated by using a MATLAB point source model in combination with an improved extended maximum power transmission efficiency method (I-EMMPTE), and an electric field distribution diagram at a specified shaping height is generated; the electric field distribution diagram is subjected to automatic identification of sidelobe peak points by MATLAB, all sidelobe suppression points are extracted, and the focus points and the sidelobe suppression points are set with a fixed weight ratio which can be flexibly regulated according to actual suppression requirements in the I-EMMPTE, the electric field distribution is recalculated, and the above-mentioned identification-weight configuration-recomputation steps are iterated and circulated until no sidelobe suppression point can be identified, so that the sidelobes are completely eliminated; finally, the optimized array element amplitude and phase distribution is directly output to an array antenna feeding system; the application can effectively balance the precision of near-field focusing shaping and the sidelobe suppression performance by strengthening the energy distribution in the focusing area to suppress the electromagnetic energy in the sidelobe area, and can realize high-precision near-field shaping of an arbitrary complex pattern, and has strong engineering practicability.

Description

Technical Field

[0001] This invention relates to the field of array antenna technology, specifically to a method for shaping the customized electric field distribution in a spatial plane. Background Technology

[0002] With the rapid development of technologies such as wireless power transmission, near-field high-precision sensing, and microwave medical applications, industry and academia have put forward higher technical requirements for the spatial distribution control of near-field electromagnetic energy: not only is it necessary to accurately focus electromagnetic energy to a designated near-field region, but it is also necessary to achieve field strength shaping of user-defined arbitrarily complex patterns, while suppressing energy leakage in the sidelobe region to the maximum extent, thereby improving energy utilization efficiency and reducing electromagnetic interference to the surrounding area.

[0003] Existing near-field focusing shaping technology still has many technical shortcomings and cannot meet the above high requirements. Specifically, the shortcomings are reflected in the following two aspects:

[0004] 1. Traditional focusing methods lack flexibility: Traditional methods based on Fourier transform, delay summation beamforming, etc., can usually only achieve focusing on a single point or simple geometric shape (such as a circle or rectangle), and it is difficult to support field strength shaping of user-defined arbitrarily complex patterns (such as characters or irregular shapes), which cannot meet the needs of diverse application scenarios.

[0005] 2. It is difficult to balance the sidelobe suppression effect with computational efficiency: Some shaping schemes based on intelligent optimization such as convex optimization and genetic algorithms can reduce the sidelobe level to a certain extent, but they have problems such as high computational complexity, slow convergence speed and poor real-time performance, which are difficult to adapt to the rapid iteration requirements in engineering applications; another scheme achieves sidelobe suppression by constraining the amplitude and phase range of array elements, but sacrifices the shaping accuracy of the target area, resulting in pattern distortion.

[0006] In summary, existing near-field focusing shaping techniques generally suffer from insufficient shaping flexibility, poor sidelobe suppression, high computational complexity, and weak engineering adaptability. They cannot simultaneously meet the dual requirements of "precise shaping of arbitrarily complex patterns" and "efficient sidelobe suppression," thus restricting the application of near-field electromagnetic control technology in high-end scenarios. Summary of the Invention

[0007] Purpose of the invention: The purpose of this invention is to provide a method for shaping the customized field distribution of a spatial planar electric field. Existing near-field focusing shaping techniques generally suffer from problems such as insufficient shaping flexibility, poor sidelobe suppression, high computational complexity, and weak engineering adaptability, and cannot simultaneously meet the dual requirements of "precise shaping of arbitrarily complex patterns" and "efficient sidelobe suppression".

[0008] Technical solution: The present invention provides a method for customizing the electric field distribution in a spatial plane, comprising the following steps:

[0009] Step 1: Discretize the target shaping pattern into a set of equally spaced focal points. The set of focal points can be adapted to any complex pattern, including characters and irregular shapes.

[0010] Step 2: Based on the point source model and the improved maximum power transmission efficiency method, calculate the excitation amplitude and phase distribution of each element of the array antenna and generate the initial electric field distribution map on the shaping plane; the improved maximum power transmission efficiency method achieves differentiated energy allocation between the target region and the sidelobe region by independently setting the weight control factors of the focal point and the suppression point.

[0011] Step 3: Automatically identify the sidelobe peak points of the initial electric field distribution map, extract all sidelobe suppression points, and configure a dynamically adjustable fixed weight ratio for the focal point and the sidelobe suppression points. Recalculate the updated electric field distribution map using the improved maximum power transmission efficiency method. Repeat the identification, configuration, and recalculation steps until no new sidelobe suppression points can be identified, thereby achieving the successive elimination of sidelobes.

[0012] Step 4: Output the final optimized amplitude and phase distribution of the array elements to the antenna feeding system, or for a metasurface array, map the amplitude and phase distribution by adjusting the geometric parameters of the metasurface elements.

[0013] Furthermore, in step 1, the discretization of the target shaping pattern adopts an equally spaced grid division, and the number and distribution density of focal points are not limited by the pattern complexity, which can completely preserve the detailed features of the pattern.

[0014] Furthermore, in step 2, the improved maximum power transmission efficiency method adds a focusing weight diagonal matrix and a suppression weight diagonal matrix to the traditional maximum power transmission efficiency method, so as to independently adjust the energy weights of the focusing point set and the suppression point set, thereby achieving the decoupling of the main lobe energy enhancement and the side lobe energy suppression.

[0015] Furthermore, in step 3, the automatic identification of sidelobe peak points is based on background threshold determination. Only local maxima points in the electric field distribution map with field strength values ​​higher than the background threshold and not belonging to the focusing region are extracted as effective suppression points to avoid over-control of non-peak regions.

[0016] Furthermore, in step 3, the fixed weight ratio between the focal point and the sidelobe suppression point is not a preset constant, and can be continuously adjusted according to the actual sidelobe suppression level requirements and the shaping accuracy requirements of the target area, so as to dynamically balance the sidelobe suppression effect and the pattern fidelity.

[0017] Furthermore, in step 3, the termination condition of the loop iteration is that no effective sidelobe suppression point can be identified in the current electric field distribution map, rather than relying on the preset number of iterations. This allows the iteration process to adaptively converge to the state of complete sidelobe elimination, while reducing unnecessary computational overhead.

[0018] Furthermore, in step 4, the optimization process of the amplitude and phase distribution of the array elements is based on the closed-form analytical calculation of the point source model and the improved maximum power transmission efficiency method. It does not rely on random search or iterative optimization algorithms and has the characteristic of fast convergence.

[0019] Furthermore, the method is applicable to both traditional phased array antennas and metasurface array antennas; for traditional phased array antennas, the optimized amplitude and phase distribution is directly fed to each array element channel; for metasurface arrays, the optimized amplitude and phase distribution is achieved by adjusting the variable geometric parameters of the metasurface elements without changing the feed network architecture.

[0020] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: By discretizing the target pattern into a set of focal points, the present invention can realize near-field shaping of any custom pattern such as characters and irregular graphics. It can be applied to near-field electromagnetic energy spatial distribution control scenarios, including but not limited to wireless power transmission, near-field high-precision sensing, microwave thermotherapy and radio frequency identification. It can realize field strength shaping of any user-defined pattern and simultaneously achieve the effect of complete suppression of side lobes.

[0021] This invention achieves precise control of the energy in the main and sidelobe regions by using the weight ratio of the focal point to the sidelobe suppression point in I-EMMPTE. This avoids energy loss in the target region while suppressing energy in the sidelobe region, effectively solving the problem of "contradiction between sidelobe suppression and shaping accuracy". It significantly improves the utilization efficiency of near-field electromagnetic energy and reduces electromagnetic interference to the surrounding area.

[0022] This invention uses I-EMMPTE as the core optimization model and combines it with the MATLAB point source model to complete the amplitude and phase distribution calculation. Compared with intelligent optimization methods such as convex optimization and genetic algorithms, it has a fast calculation convergence speed and good real-time performance. At the same time, the method is compatible with traditional array antennas and metasurface arrays, and can be directly connected to existing feeding systems without large-scale modifications. It has low engineering implementation difficulty and strong practicality.

[0023] This invention continuously optimizes the amplitude and phase distribution of array elements through iterative processes until sidelobes are completely eliminated, ensuring clear edges and complete details of the target shaped pattern, and significantly improving the accuracy and pattern reproduction of near-field shaping. Attached Figure Description

[0024] Figure 1 This is a flowchart of the present invention;

[0025] Figure 2 This is a schematic diagram of the shaped pattern of the present invention being discretized into equally spaced focal points;

[0026] Figure 3 This is a schematic diagram illustrating the identification of sidelobe suppression points according to the present invention;

[0027] Figure 4 This is a schematic diagram showing the distribution of the pattern "0" focal point and sidelobe suppression points of the present invention;

[0028] Figure 5 This is a schematic diagram showing the distribution of the focal point and sidelobe suppression points of the pattern "LOVE" in this invention;

[0029] Figure 6 This is a diagram illustrating the near-field shaping effect of the 12-key numeric keypad pattern (0-9, *, #) of the present invention through a conventional array antenna.

[0030] Figure 7 This is a diagram illustrating the near-field shaping effect of the 12-key numeric keypad pattern (0-9, *, #) of the present invention through a metasurface array antenna.

[0031] Figure 8 This is a diagram illustrating the near-field shaping effect of the pattern "LOVE" from this invention using a conventional array antenna.

[0032] Figure 9 This is an image showing the effect of near-field shaping of the pattern "LOVE" in this invention through a metasurface array antenna;

[0033] Figure 10 This is a schematic diagram of the structure of the active radiation metasurface unit in this invention;

[0034] Figure 11 This is a schematic diagram of the upper metal patch structure of the active radiative metasurface unit in this invention;

[0035] Figure 12 This is a schematic diagram of the middle metal patch structure of the active radiative metasurface unit in this invention;

[0036] Figure 13 This is a schematic diagram of the lower metal patch structure of the active radiative metasurface unit in this invention;

[0037] Figure 14 This is a schematic diagram of the ground plane structure of the active radiative metasurface unit in this invention;

[0038] Figure 15 This is a schematic diagram of the lower dielectric substrate structure of the active radiative metasurface unit in this invention;

[0039] Figure 16 This is a schematic diagram illustrating the amplitude control of the active radiative metasurface unit in this invention;

[0040] Figure 17 This is a schematic diagram of the phase modulation of the active radiative metasurface unit in this invention. Detailed Implementation

[0041] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0042] like Figure 1 As shown, this embodiment of the invention provides a method for customizing the electric field distribution in a spatial plane, comprising the following steps:

[0043] S1. Determine the structural parameters, operating frequency and near-field shaping height of the array antenna element, and use an equal-spacing grid discretization method to transform any complex target shaping pattern into a set of focal points;

[0044] S2. Calculate the amplitude and phase distribution of all array elements using the MATLAB point source model combined with I-EMMPTE, and generate the electric field distribution map at the specified shaping height.

[0045] S3. Automatically identify the sidelobe peak points of the electric field distribution map using MATLAB, extract all sidelobe suppression points, and set a fixed weight ratio that can be flexibly adjusted for the focus point and the sidelobe suppression points in I-EMMPTE according to the actual suppression requirements. Recalculate the electric field distribution and iterate the above steps until no sidelobe suppression points can be identified, thus achieving complete elimination of sidelobes.

[0046] S4. The optimized amplitude and phase distribution of the array elements is directly output to the array antenna feeding system. If it is a metasurface array, the corresponding amplitude and phase distribution is achieved by adjusting the geometric parameters of the metasurface elements.

[0047] Preferably, the structural parameters of the array antenna element include the element coordinate vector and the element spacing. These parameters are the sole input basis for the array mutual coupling response matrix in I-EMMPTE, and the matrix directly characterizes the electromagnetic coupling characteristics between array elements. The focal point set has no limitations on pattern complexity or the number of patterns, and can adapt to custom patterns such as characters and irregular graphics.

[0048] Preferably, the I-EMMPTE adds a focusing diagonal matrix and a suppression diagonal matrix to the traditional EMMPTE, enabling independent control of the weights of the focusing and suppression points. Traditional EMMPTE dynamically adjusts the excitation amplitude and phase distribution of the array elements to achieve the theoretical extreme value for the ratio of the total electric field energy received by the target area to the total array input power. Its physical essence is to utilize the coherent superposition effect of electromagnetic waves to enhance the electromagnetic field in the focusing area, achieving spatial energy convergence. This method is applicable to multiple fields such as wireless power transmission, radio frequency energy harvesting, radio frequency identification, and microwave hyperthermia. The specific mathematical expression for traditional EMMPTE is:

[0049] ,

[0050] The specific mathematical expression for I-EMMPTE is as follows:

[0051] ;

[0052] in It is the optimal excitation vector of the array, representing the excitation amplitude and phase of the N array elements; It is the array mutual coupling response matrix, which is determined by the coordinates, spacing, and operating frequency of the array elements, and characterizes the electromagnetic coupling characteristics between the array elements; It is a field target matrix, where rows correspond to target points, columns correspond to array elements, and elements correspond to the electric field intensity of the array element at the target point. It is a focused diagonal matrix, where the first P (number of focal points) values ​​on the diagonal are equal to K (focal point weights), and the last Q (number of suppression points) values ​​are equal to 1. It is a suppression diagonal matrix, where the first P (number of focal points) values ​​on the diagonal are equal to 1, and the last Q (number of suppression points) values ​​are equal to 1 (suppression point weights). It is the basic constraint column vector of field strength, with all elements equal to 1.

[0053] Preferably, the automatic identification of sidelobe peak points implemented in MATLAB can be used to determine the background threshold benchmark for sidelobes, which can be set according to the actual scenario requirements. Typically, a field strength value 20dB lower than the main lobe peak value is selected as the screening threshold. The entire electric field data is scanned and retrieved, and all local maxima points with field strength values ​​higher than the preset background threshold are automatically extracted and marked as potential sidelobe suppression point locations. The signal peaks in the main lobe are removed from the identified maxima points, and the remaining points are the sidelobe suppression points that need to be suppressed.

[0054] Preferably, the fixed weight ratio between the focal point and the sidelobe suppression point is not a fixed constant. It can be continuously adjusted according to the actual requirements for sidelobe suppression level and shaping accuracy, achieving a dynamic balance between sidelobe suppression and the shaping accuracy of the focal region. There is no fixed formula for selecting the K value; it requires iterative simulation testing. The core principle is to find a balance between "main lobe fidelity" and "sidelobe suppression," fine-tuning in real time based on the field pattern feedback from each simulation until the application specifications are met. It is recommended to start testing with a larger value, typically K=100. A high initial value can quickly highlight the main lobe characteristics, facilitating subsequent targeted parameter reduction or fine-tuning based on the actual performance of the sidelobe and main lobe. If the main lobe is clear but the sidelobe is too high, it indicates that the focusing weight is too strong, and K needs to be reduced; if the sidelobe is low but the main lobe is distorted, K needs to be increased to improve the focusing concentration and achieve precise field pattern control.

[0055] Preferably, the cyclic iteration is an adaptive termination iteration, and the iteration termination condition is that MATLAB cannot identify the sidelobe suppression point, rather than a fixed number of iterations to ensure that the computational load is minimized while meeting the sidelobe suppression requirements.

[0056] Preferably, the MATLAB point source model, combined with I-EMMPTE, calculates the amplitude and phase distribution of all array elements. The MATLAB point source model requires specifying the array size, operating frequency, element spacing, target shaping height, and inputting the coordinates of the target focal point and suppression point. This establishes the basic constraints and array mutual coupling response matrix for subsequent field strength calculations. Each antenna element in the array is treated as an omnidirectional ideal point source. Based on electromagnetic radiation theory, the electric field vector generated by each element at the sampling point in the focusing region is calculated to construct a complete electric field matrix. Then input the focus diagonal matrix. and suppression diagonal matrix The optimal excitation vector for the array can be calculated using I-EMMPTE by taking the K, Q, and P values. That is, the amplitude and phase corresponding to each array element.

[0057] For details on S1 to S3, please refer to [link / reference]. Figures 2 to 5 , Figure 2 This is a schematic diagram illustrating the discretization of a target pattern into equally spaced focal points. Figure 3 A schematic diagram for identifying sidelobe suppression points; Figures 4 to 5 This is a distribution diagram of the focal point and sidelobe suppression points in a specific embodiment.

[0058] In the simulation software CST2025, models of a conventional antenna array and a metasurface array were built to demonstrate a spatial planar electric field custom field distribution shaping method of the present invention.

[0059] Figure 6 The image shows the focusing plane electric field effect of shaping a 12-key numeric keypad pattern (0-9, *, #) using a conventional array antenna. In this example, the antenna operates at 5.8 GHz, with an element spacing of 12 mm, an array size of 20 × 20, a shaping height of 30 mm, and a focal point spacing of 20 mm. The amplitude and phase distribution of each element is calculated using EMMPTE combined with a MATLAB point source and implemented through feeding.

[0060] Figure 7 The image shows the focusing plane electric field effect of shaping a 12-key numeric keypad pattern (0-9, *, #) using a metasurface array antenna. In this example, the antenna operates at 5.8 GHz, with an element spacing of 12 mm, an array size of 20 × 20, a shaping height of 30 mm, and a focal point spacing of 20 mm. The amplitude and phase distribution of each element is calculated using EMMPTE combined with MATLAB point source and implemented using metasurface elements.

[0061] Figure 8The image shows the focused plane electric field effect of shaping a "LOVE" shape for a conventional array antenna. In this example, the antenna operates at 5.8 GHz, with an element spacing of 12 mm, an array size of 32×32, and a shaping height of 30 mm. The "L" and "E" points are spaced 20 mm apart, the "V" points are spaced 21 mm apart, and the "O" points are spaced 19 mm apart. The amplitude and phase distribution of each element is calculated using EMMPTE combined with MATLAB point sources and implemented through feeding.

[0062] Figure 9 The image shows the focused plane electric field effect of shaping "LOVE" for a metasurface array antenna. In this example, the antenna operates at 5.8 GHz, with an element spacing of 12 mm, an array size of 32×32, and a shaping height of 30 mm. The "L" and "E" points are spaced 20 mm apart, the "V" points are spaced 21 mm apart, and the "O" points are spaced 19 mm apart. The amplitude and phase distribution of each element is calculated using EMMPTE combined with MATLAB point sources and implemented using a metasurface.

[0063] Figures 10 to 15 This is a schematic diagram of the metasurface element structure of this example metasurface array antenna. All three dielectric substrates are made of FR4_epoxy (glass epoxy resin) with a dielectric constant of 4.5, a loss tangent of 0.001, a thickness of 1.5mm, and dimensions of 12mm (length and width). φ represents the angle of rotation of the metal patch around the Z-axis (directly above the center of the metasurface element). The metal patch structures on the front of the top, middle, and bottom dielectric substrates are all made of copper with a thickness of 0.035mm. The centers of all three metal patches are aligned with the overall metasurface element along the Z-axis, where α = 175°, R1 = 4.5mm, R2 = R1 - 1.9mm, K = 1mm, W = 1mm, and P = 12mm. The ground plane is made of copper with a thickness of 0.035mm. The coaxial line is also made of copper and located at the center of the ground plane, aligned with the center of the element along the Z-axis, where h = 1.5mm, D... n =0.8mm, R y =1.84mm.

[0064] Figures 16-17 This is a schematic diagram of the amplitude and phase modulation of the metasurface element in this example metasurface array antenna. R1 modulates the phase and φ modulates the amplitude. The range of R1 is 4.35mm to 5.7mm and the range of φ is -180° to 0°.

[0065] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," 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 the invention. In this specification, 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.

Claims

1. A method for shaping the customized electric field distribution in a spatial plane, characterized in that, Includes the following steps: Step 1: Discretize the target shaping pattern into a set of equally spaced focal points. The set of focal points can be adapted to any complex pattern, including characters and irregular shapes. Step 2: Based on the point source model and the improved maximum power transmission efficiency method, calculate the excitation amplitude and phase distribution of each element of the array antenna and generate the initial electric field distribution map on the shaping plane; The improved maximum power transfer efficiency method achieves differentiated energy distribution between the target region and the sidelobe region by independently setting the weight control factors of the focal point and the suppression point; Step 3: Automatically identify the sidelobe peak points of the initial electric field distribution map, extract all sidelobe suppression points, and configure a dynamically adjustable fixed weight ratio for the focal point and the sidelobe suppression points. Recalculate the updated electric field distribution map using the improved maximum power transmission efficiency method. Repeat the identification, configuration, and recalculation steps until no new sidelobe suppression points can be identified, thereby achieving the successive elimination of sidelobes. Step 4: Output the final optimized amplitude and phase distribution of the array elements to the antenna feeding system, or for a metasurface array, map the amplitude and phase distribution by adjusting the geometric parameters of the metasurface elements.

2. The method for shaping the customized electric field distribution in a spatial plane according to claim 1, characterized in that, In step 1, the discretization of the target shaping pattern adopts an equally spaced grid division. The number and distribution density of focal points are not limited by the pattern complexity, and the detailed features of the pattern can be completely preserved.

3. The method for shaping the customized electric field distribution in a spatial plane according to claim 1, characterized in that, In step 2, the improved maximum power transmission efficiency method adds a focusing weight diagonal matrix and a suppression weight diagonal matrix to the traditional maximum power transmission efficiency method, so as to independently adjust the energy weights of the focusing point set and the suppression point set, thereby achieving the decoupling of the main lobe energy enhancement and the side lobe energy suppression.

4. The method for shaping the customized electric field distribution in a spatial plane according to claim 1, characterized in that, In step 3, the automatic identification of sidelobe peak points is based on background threshold determination. Only local maxima points in the electric field distribution map with field strength values ​​higher than the background threshold and not belonging to the focal region are extracted as effective suppression points to avoid over-control of non-peak regions.

5. The method for shaping the customized electric field distribution in a spatial plane according to claim 1, characterized in that, In step 3, the fixed weight ratio of the focal point to the sidelobe suppression point is not a preset constant. It can be continuously adjusted according to the actual sidelobe suppression level requirements and the shaping accuracy requirements of the target area, so as to dynamically balance the sidelobe suppression effect and the pattern fidelity.

6. The method for shaping the customized electric field distribution in a spatial plane according to claim 1, characterized in that, In step 3, the termination condition of the loop iteration is that no effective sidelobe suppression point can be identified in the current electric field distribution map, rather than relying on the preset number of iterations. This allows the iteration process to adaptively converge to the state of complete sidelobe elimination, while reducing unnecessary computational overhead.

7. The method for shaping the customized electric field distribution in a spatial plane according to claim 1, characterized in that, In step 4, the optimization process of the amplitude and phase distribution of the array elements is based on the closed-form analytical calculation of the point source model and the improved maximum power transfer efficiency method. It does not rely on random search or iterative optimization algorithms and has the characteristic of fast convergence.

8. The method for shaping the customized electric field distribution in a spatial plane according to claim 1, characterized in that, The method is applicable to both traditional phased array antennas and metasurface array antennas. For traditional phased array antennas, the optimized amplitude and phase distribution is directly fed to each array element channel. For metasurface arrays, the optimized amplitude and phase distribution is achieved by adjusting the variable geometric parameters of the metasurface elements without changing the feed network architecture.

9. The method for shaping the customized electric field distribution in a spatial plane according to claim 1, characterized in that, It can be applied to near-field electromagnetic energy spatial distribution control scenarios, including but not limited to wireless power transmission, near-field high-precision sensing, microwave thermotherapy and radio frequency identification. It can realize field strength shaping of user-defined arbitrary patterns and achieve complete suppression of sidelobe at the same time.

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