Characteristic mode analysis-based array antenna decoupling surface design method

Abstract

The invention discloses an array antenna decoupling surface design method based on characteristic mode analysis, and belongs to the field of array antenna decoupling surface design. The method comprises the following steps: firstly, finding out a main cancellation mode through characteristic mode analysis; and then, in combination with a characteristic mode theory, changing the position of the decoupling surface and regulating and controlling the amplitude and the phase of the patch on the main cancellation mode to realize the decoupling requirement, and obtaining the decoupling surface meeting the decoupling requirement. Compared with a current S parameter-based decoupling surface design method, the method has the advantages that (1) the design is carried out in combination with a characteristic mode theory, so that the design direction is clearer, the optimization frequency and the dependence on experience are reduced, and the design efficiency is improved; and (2) a main cancellation mode is found by analyzing the characteristic modes of the coupling field and the cancellation field, so that the design accuracy is improved, and the decoupling effect of the designed decoupling surface is improved. In addition, due to the wide applicability of the characteristic mode theory, the method is suitable for decoupling surface research and development of various array antennas.

Description

Technical Field

[0001] The present invention belongs to the field of decoupling surface design for array antennas. Specifically, it is a method for designing a decoupling surface for array antennas based on characteristic mode analysis. This method is applicable to the research and development of decoupling surfaces for various array antennas. Background Art

[0002] Antenna arrays have characteristics such as electronic scanning and pattern reconfiguration, so they have been widely used. However, the coupling between elements will seriously affect the performance of the antenna array. Subsequently, a large number of studies have been carried out on the decoupling technology of antenna arrays. Common decoupling technologies include defective ground structures, electromagnetic bandgap decoupling structures, etc. However, these methods all have limitations: the defective ground structure will increase the backward radiation, and adding an electromagnetic bandgap decoupling structure between elements is not applicable to compact antenna arrays. In order to find a more effective decoupling method for antenna arrays, in 2017, Professor Wu Keli proposed a new type of decoupling structure: the decoupling surface of the array antenna. This structure reflects the radiation field of the antenna to obtain a reflected field, and this reflected field cancels the coupling field between the antenna elements, thereby achieving a reduction in coupling. Subsequently, this decoupling structure has been successfully applied to various types of antenna arrays. However, the current decoupling surfaces are all designed based on S-parameters. (1) This leads to a high dependence on experience and optimization, limiting the efficiency of the decoupling surface design; (2) They are analyzed at the macroscopic level and do not specifically analyze the modes of the coupling field and the cancellation field, so it is not known which cancellation mode plays the main cancellation role. This characteristic results in a low accuracy of this design method, limiting the decoupling effect of the designed decoupling surface. Summary of the Invention

[0003] The purpose of the present invention is to improve the deficiencies of the current decoupling surface design method, and a method for designing a decoupling surface for an array antenna based on characteristic mode analysis is proposed. This method designs the decoupling surface of the array antenna based on characteristic mode analysis: First, the main cancellation mode is found through characteristic mode analysis; then, combined with the characteristic mode theory, the position and patch of the decoupling surface are changed to adjust the amplitude and phase of the main cancellation mode to meet the decoupling requirements, and a decoupling surface that meets the decoupling requirements is obtained.

[0004] The purpose of the present invention is achieved as follows:

[0005] A method for designing a decoupling surface for an array antenna based on characteristic mode analysis specifically includes the following steps: Step 1, preliminarily design the decoupling surface of the array antenna; the patch of the decoupling surface of the array antenna adopts a form of a combination of multiple rectangular patches, and the arrangement direction of the rectangular patches is consistent with the polarization direction of the antenna; Step 2: Use the electromagnetic simulation software FEKO to perform eigenmode analysis on the coupling field between array elements to obtain the amplitudes and phases of each mode of the coupling field; perform eigenmode analysis on the cancellation field to obtain the amplitudes and phases of each mode of the cancellation field; Coupling field mode of component is set as , cancellation field mode of component is set as ; Calculate the cancellation degree of each mode to find the main cancellation mode; where ; Calculate the cancellation degree of each mode to find the main cancellation mode; among them, , , represents the eigenmode , represents the , , components of the field, and respectively represent the amplitude and phase of the component of the coupling field mode , and respectively represent the amplitude and phase of the component of the cancellation field mode , represents the cancellation degree caused by the component of the cancellation field mode on the component of the coupling field mode ; Step 3: Change the position of the decoupling surface of the array antenna and analyze the change of the cancellation degree after the position change; if the cancellation degree increases, continue to adjust the position in the same direction, otherwise adjust the position in the opposite direction until the position of the decoupling surface of the antenna that meets the decoupling requirements is obtained; Step 4: Use the electromagnetic simulation software FEKO to simulate the eigenvalues of the main cancellation mode, and judge whether the main cancellation mode stores net electric energy or net magnetic energy according to the eigenvalues; then, modify the patches on the decoupling surface of the array antenna to change the ability of the main cancellation mode to store net electric energy / net magnetic energy, thereby changing its eigenvalues and reducing the ; Step 5: Repeat Step 2 to Step 4 until the decoupling requirements are met.

[0006] Furthermore, in the above Step 2, the amplitudes and phases of each mode of both the coupling field and the cancellation field are obtained through the following process: Step 201: Use the electromagnetic simulation software FEKO to simulate the coupling field between array elements, and obtain the amplitude and phase of the mode weight coefficients of each mode of the coupling field, and the amplitude and phase of the characteristic field. Step 202: Multiply the amplitude of the mode weight coefficient by the amplitude of the characteristic field and add the phases to obtain the amplitude and phase of each mode of the coupling field. Step 203: Use the electromagnetic simulation software FEKO to simulate the cancellation field, and obtain the amplitude and phase of the mode weight coefficients of each mode of the cancellation field, and the amplitude and phase of the characteristic field. Step 204: Multiply the amplitude of the mode weight coefficient by the amplitude of the characteristic field and add the phases to obtain the amplitude and phase of each mode of the cancellation field.

[0007] Further, in Step 2 during simulation, the coupling field is the radiation field of one unit at another unit; the cancellation field is the reflected field of the radiation field of the antenna unit at the coupled unit after being reflected by the ADS unit.

[0008] Further, in Step 2, the mode of the cancellation field of the component causing the cancellation degree ; wherein, is the of the component of the coupling field mode of , is the of the cancellation field mode of ; that is, the amplitude of the coupling field after cancellation; is defined as the energy ratio of the coupling field after cancellation to the original coupling field, so is obtained.

[0009] Further, in Step 3, the position of the decoupling surface of the array antenna is obtained through the following process: Step 301: Change the position of the decoupling surface of the array antenna, and analyze the change of the cancellation degree of the main cancellation mode after the position change; Step 302: If the cancellation degree increases, continue to perform position adjustment in the same direction; otherwise, perform position adjustment in the opposite direction.

[0010] Further, in step 4, the patches on the decoupling surface of the array antenna are obtained through the following process: Step 401: Use the electromagnetic simulation software FEKO to simulate and obtain the eigenvalues of the main cancellation mode, and judge whether the main cancellation mode stores net electric energy or net magnetic energy according to the eigenvalues; Step 402: By modifying the patches on the decoupling surface of the array antenna or adding inductance / capacitance elements, change the ability of the main cancellation mode to store net electric energy / net magnetic energy, and then change its eigenvalue, so that the decreases.

[0011] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention proposes a design method for the decoupling surface of an array antenna based on characteristic mode analysis: First, find the main cancellation mode through characteristic mode analysis; then, combine the characteristic mode theory to change the position and patches of the decoupling surface to adjust the amplitude and phase of the main cancellation mode to meet the decoupling requirements, and obtain a decoupling surface that meets the decoupling requirements. Compared with the traditional S-parameter-based design method, this method (1) combines the characteristic mode theory for design, making the design direction clearer, thus reducing the number of optimizations and the dependence on experience, and improving the design efficiency; (2) By analyzing the characteristic modes of the coupling field and the cancellation field, the main cancellation mode is found, thus improving the design accuracy and enhancing the decoupling effect of the designed decoupling surface. Description of the Drawings

[0012] Figure 1 It is an axonometric view of the antenna element structure.

[0013] Figure 2 It is a top view of the antenna element structure.

[0014] Figure 3 It is a side view of the antenna element structure.

[0015] Figure 4 It is a schematic diagram of the initially designed decoupling surface.

[0016] Figure 5 It is a schematic diagram of the initially designed decoupling surface and a two-element array composed of two adjacent elements with the initially designed decoupling surface loaded.

[0017] Figure 6 For the component amplitudes of each mode of the coupling field and the cancellation field.

[0018] Figure 7 For the Component amplitude.

[0019] Figure 8 Are the coupling field, cancellation field, and coupled field after cancellation under different decoupling surface heights.

[0020] Figure 9 Are the coupling field, cancellation field, and coupled field after cancellation before and after shortening the patch spacing.

[0021] Figure 10 Are the decoupling surface patches before and after shortening the slot.

[0022] Figure 11 Is the 8-element linear array before loading the final decoupling surface.

[0023] Figure 12 Is the 8-element linear array after loading the final decoupling surface.

[0024] Figure 13 Are the Scd before and after loading the decoupling surface during normal radiation.

[0025] Figure 14 Are the Scf before and after loading the decoupling surface during normal radiation.

[0026] Figure 15 Are the active reflection coefficients of elements a, b, c, and d before and after loading the final decoupling surface.

[0027] Figure 16 Are the array patterns at the 2.1 GHz frequency point before and after loading the final decoupling surface.

[0028] Figure 17 Are the array patterns at the 2.25 GHz frequency point before and after loading the final decoupling surface.

[0029] Figure 18 Are the array patterns at the 2.4 GHz frequency point before and after loading the final decoupling surface. Detailed implementation

[0030] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0031] The present invention first performs characteristic mode analysis on the coupling field and the cancellation field to find the main cancellation modes. Then, it analyzes the influence of the position of the decoupling surface on the amplitude and phase of the main cancellation mode, and further obtains the influence of the position of the decoupling surface on the cancellation effect. Based on the analysis results, the position of the decoupling surface is designed. Next, in combination with the characteristic mode theory, it analyzes the influence of the patch on the amplitude and phase of the main cancellation mode, and further finds the influence of the patch on the cancellation effect. According to the analysis results, the patch is designed. Finally, a decoupling surface that meets the decoupling requirements is obtained.

[0032] A method for designing a decoupling surface of an array antenna based on characteristic mode analysis includes the following steps: Step 1, preliminarily design the decoupling surface of the array antenna. The patch of the decoupling surface of the array antenna adopts a form of a combination of multiple rectangular patches, and the arrangement direction of the rectangular patches is the same as the polarization direction of the antenna; Step 2, use characteristic mode analysis to find the main cancellation modes. Use the electromagnetic simulation software FEKO to simulate and obtain the amplitude and phase of the mode weight coefficients of each mode of the coupling field and the amplitude and phase of the characteristic field. Then, multiply the amplitudes of the two and add the phases to obtain the amplitude and phase of each mode of the coupling field. Use the electromagnetic simulation software FEKO to simulate and obtain the amplitude and phase of the mode weight coefficients of each mode of the cancellation field and the amplitude and phase of the characteristic field. Then, multiply the amplitudes of the two and add the phases to obtain the amplitude and phase of each mode of the cancellation field. Calculate the cancellation degree of each mode , and find the main cancellation modes; Step 3, design the position of the decoupling surface of the array antenna. Change the position of the decoupling surface of the array antenna, and analyze the change in the cancellation degree of the main cancellation mode after the position change . If the cancellation degree increases, continue to adjust the position in the same direction; otherwise, adjust the position in the opposite direction; Step 4, design the patch of the decoupling surface of the array antenna. First, use the electromagnetic simulation software FEKO to simulate and obtain the eigenvalues of the main cancellation mode, and judge whether the main cancellation mode stores net electric energy or net magnetic energy according to the eigenvalues. Then, by modifying the patch of the decoupling surface of the array antenna, adding inductance / capacitance elements, etc., change the ability of the main cancellation mode to store net electric energy / net magnetic energy, and further change its eigenvalues to make the decrease; Step 5, after completing the above steps, if further decoupling is required, repeat the above steps 2 to 4 until the decoupling requirements are met.

[0033] The following gives a specific example of the design of the decoupling surface of the array antenna:

[0034] The structure of the selected antenna element is as Figures 1 to 3As shown, the dimensions are W = L = 65 mm, Wp = Lp = 42.5 mm, W1 = 21.7 mm, L1 = 1.8 mm, W2 = 4 mm, L2 = 8 mm, R = 1.3 mm, R1 = 2.17 mm, H1 = 13 mm, H2 = 4 mm, H3 = 1 mm, H4 = 23.09 mm. The operating frequency range of the antenna is from 2 GHz to 2.5 GHz. The decoupling surface of the initially designed array antenna consists of a dielectric plate and four rectangular patches arranged along the polarization direction of the antenna. The size of each patch is 15 mm × 15 mm, and the height of the decoupling surface is set to 19 mm, as Figure 4 shown.

[0035] Next, the characteristic mode analysis is used to find the main cancellation modes. Since the coupling between adjacent units is much greater than that between non-adjacent units, for the study of two adjacent antenna units, they are respectively set as unit a and unit b, as Figure 5 shown. According to the electromagnetic field boundary conditions, the coupling received by the antenna unit is generated by the component and component of the coupling field. Therefore, only the component and component are studied. (1) At 2.32 GHz, the characteristic mode analysis of the coupling field between adjacent units is carried out using the electromagnetic simulation software FEKO. The coupling field selected during the simulation is the radiation field of unit a at unit b. The amplitude and phase of the mode weight coefficients of each mode of the coupling field, as well as the amplitude and phase of the characteristic field, are obtained through simulation. Then, the amplitude of each mode of the coupling field is obtained by multiplying the amplitudes and adding the phases of the two. The amplitude is as Figure 6 shown. (2) At 2.32 GHz, the characteristic mode analysis of the cancellation field is carried out using the electromagnetic simulation software FEKO. The cancellation field selected during the simulation is the reflected field at unit b obtained by the unit of the decoupling surface reflecting the radiation field of unit a. Using the same method as the characteristic mode analysis of the coupling field, the amplitude and phase of each mode of the cancellation field are obtained. The amplitude is as Figure 7 shown. (3) According to Figure 6 and Figure 7 , it can be seen that the coupling between adjacent units is mainly generated by modes a, b, c, d, and e of the coupling field. Combining the amplitudes of each mode of the cancellation field, it can be seen that the cancellation mainly occurs between the component of mode a of the coupling field and the component of mode a of the cancellation field. Therefore, the main cancellation effect is caused by the component of mode a of the cancellation field.

[0036] Then, the position design of the decoupling surface of the array antenna is carried out. The height of the decoupling surface is changed to 23 mm, and the method in step 2 is used to calculate the The amplitudes and phases of the components are shown in Table 1. After changing the height, the components of the cancellation field mode a and the components of the coupling field mode a, and the components of the coupling field after cancellation are represented on the complex plane, as shown in Figure 8 . According to Table 1 and Figure 8 , the cancellation degree increases after increasing the height. Therefore, the height of the decoupling surface is further adjusted in the increasing direction. The height of the decoupling surface is adjusted to 27 mm. The amplitudes and phases of the components of the cancellation mode a, the generated cancellation degree, and the decoupling amplitude are shown in Table 1. It can be seen that both the cancellation degree and the coupling reduction amplitude are further increased. The cancellation degree increases from 7.99% to 12.05%, and the coupling reduction amplitude increases from 6.22 dB to 9.21 dB.

[0037] Table 1 Amplitudes and phases of the components of the cancellation mode a, the generated cancellation degree, and the decoupling amplitude at different heights

[0038] Then, the patch design of the decoupling surface of the array antenna is carried out. Considering the profile height of the antenna, the height of the decoupling surface is selected as 23 mm. The eigenvalue of the cancellation mode a obtained by simulation is -44.06, which is less than 0. So the cancellation mode a stores net electric energy. The gaps between the metal patches on the decoupling surface play a role in storing electric energy. Therefore, shortening these gaps can reduce the ability of the cancellation mode a to store electric energy, and further reduce the ability of the cancellation mode a to store net energy, and further reduce .

[0039] According to the characteristic mode theory, there is ; ; ; , where is the mode weight coefficient of the cancellation field mode ; is 's phase; is the corresponding to the cancellation field mode component of the characteristic magnetic field. So, there is ; ; Therefore, becoming smaller makes increase, and then makes increase; is less than 0, so becoming smaller means becoming smaller, becomes smaller, resulting in becomes smaller, thus leading to becomes smaller. Therefore, shortening the patch slot will increase and decrease By simulation and calculation, it is obtained that and , so shortening the patch slot will cause an increase in the angle between the component of the cancellation field mode a and the component of the coupled field mode a. The component of the cancellation field mode a, the component of the coupled field mode a, and the component of the coupled field after cancellation before and after shortening the slot are represented in the complex plane, as shown in Figure 9 . It can be seen from Figure 9 that the cancellation degree has been improved after shortening the slot. In this example, the patch length changes from 15mm×15mm to 15mm×12mm, and at the same time, a narrow metal strip is added to the slot between the patches, as shown in Figure 10 . Through simulation, it is obtained that the decoupling degree increases from 6.22dB to 8.85dB after shortening the slot.

[0040] The decoupling surface of the finally designed array antenna is loaded on the eight-element linear array composed of antenna elements to verify the proposed method. The eight-element linear array before and after loading is shown in Figure 11 and Figure 12 .

[0041] First, study the coupling reduction situation, the matching change situation of the antenna, and the change situation of the array pattern during normal radiation.

[0042] (1) Coupling reduction situation during normal radiation. The mutual coupling is divided into the mutual coupling between adjacent elements and the mutual coupling between non-adjacent elements. For adjacent elements, select element c and element d, and for non-adjacent elements, select element c and element f. During normal radiation, the Scd and Scf before and after loading the designed decoupling surface are obtained through HFSS simulation, as shown in Figure 13 and Figure 14 . During normal radiation, Scd drops by up to 28.56dB in the frequency band, and Scf drops by 1.7dB to 7.61dB in the frequency band. It can be seen that the coupling between adjacent elements and non-adjacent elements during normal radiation is effectively reduced.

[0043] (2) Matching change situation of the antenna during normal radiation. Elements e, f, g, h and elements a, b, c, d are symmetric, so it is sufficient to select elements a, b, c, d for simulation. During normal radiation, the active reflection coefficients of elements a, b, c, d before and after loading the designed decoupling surface are shown in Figure 15As shown, it can be seen that the active reflection coefficients of elements a, b, c, and d within the frequency band are lower than -12.5 dB after loading the designed decoupling surface, indicating good antenna matching after loading.

[0044] (3) The variation of the array pattern during normal radiation. When the array operates at 2.1 GHz, 2.25 GHz, and 2.4 GHz and is in normal radiation, the array patterns before and after loading the designed decoupling surface are as Figures 16 to 18 shown. At 2.1 GHz, the array gain decreases from 14.59 dB to 14.48 dB after loading the decoupling surface, a decrease of 0.11 dB; at 2.25 GHz, the array gain decreases from 15.04 dB to 14.94 dB after loading the decoupling surface, a decrease of 0.1 dB; at 2.4 GHz, the array gain increases from 15.27 dB to 15.47 dB after loading the decoupling surface, an increase of 0.2 dB. It can be seen that the array pattern within the frequency band remains basically unchanged after loading the designed decoupling surface.

[0045] Next, study the decoupling situation and antenna matching situation during scanning.

[0046] can be used to characterize the strength of the total coupling received by port m, where is the active reflection coefficient of port m, is the passive reflection coefficient of port m. When the antenna operates at 2.32 GHz, before and after loading the designed decoupling surface, and at different scanning angles are shown in Table 2. According to Table 2, it can be seen that: (1) When the scanning angles are -50 degrees, -30 degrees, 0 degrees, 30 degrees, and 50 degrees, the designed decoupling surface reduces , indicating that the designed decoupling surface can continuously play a role in suppressing coupling during scanning; (2) As the scanning angle increases increases, because the increase in the scanning angle will lead to an increase in coupling and then a deterioration in matching. After loading the designed decoupling surface, the increase amplitude of is greatly reduced and is lower than that of the original antenna array at large-angle scanning , so this decoupling surface can improve the antenna matching deterioration problem caused by scanning. (3) During large-angle scanning (±50 degrees), after loading the designed decoupling surface, is less than -10 dB, while that of the original antenna is greater than -6 dB. Therefore, the designed decoupling surface greatly improves the matching situation during large-angle scanning.

[0047] Table 2 and at different scanning angles before and after loading the designed decoupling surface at 2.32 GHz; 。

[0048] Based on the above results, it can be seen that: (1) During normal radiation, after loading the designed decoupling surface, within the frequency band, the maximum decrease of Scd is 28.56 dB and the maximum decrease of Scf is 7.61 dB. Whether for adjacent units or non-adjacent units, the coupling is effectively suppressed; (2) The designed decoupling surface can continuously play the role of suppressing mutual coupling during the scanning process, and can also improve the matching deterioration problem caused by scanning and the matching situation during large-angle scanning.

[0049] The present invention first finds the main cancellation modes through eigenmode analysis. Then, in combination with the eigenmode theory, the position of the decoupling surface and the patch are changed to adjust the amplitude and phase of the main cancellation modes to meet the decoupling requirements, and a decoupling surface meeting the decoupling requirements is obtained. Compared with the traditional design method of the decoupling surface of array antennas based on S-parameters, this method: (1) is designed in combination with the eigenmode theory, making the design direction clearer, thereby reducing the number of optimizations and the dependence on experience, and improving the design efficiency; (2) By analyzing the eigenmodes of the coupling field and the cancellation field, the main cancellation modes are found, thereby improving the design accuracy and the decoupling effect of the designed decoupling surface.

[0050] It should be noted that the above are only preferred application examples of the present invention and are not used to limit the protection scope of the present invention. All technical solutions using equivalent substitution or equivalent transformation forms are within the protection scope of the present invention.

Claims

1. A decoupling surface design method for array antennas based on characteristic mode analysis, characterized in that Specifically, it includes the following steps: Step 1, preliminarily design the decoupling surface of the array antenna; The patches of the decoupling surface of the array antenna adopt the form of a combination of multiple rectangular patches, and the arrangement direction of the rectangular patches is the same as the polarization direction of the antenna; Step 2, use the electromagnetic simulation software FEKO to perform eigenmode analysis on the coupling field between array elements to obtain the amplitudes and phases of each mode of the coupling field; perform eigenmode analysis on the cancellation field to obtain the amplitudes and phases of each mode of the cancellation field; Coupled field mode of the component is set to ; for the cancellation field mode of the component is set to ; through ； Calculate the cancellation degree of each mode and find the main cancellation mode. Among them, 、 , represent the characteristic mode , represents the 、 、 components of the field, and represent the amplitude and phase of the component of the coupled field mode respectively, and represent the amplitude and phase of the component of the cancellation field mode respectively, represents the cancellation degree caused by the component of the cancellation field mode to the component of the coupled field mode ; Step 3: Change the position of the decoupling surface of the array antenna and analyze the degree of cancellation after the position change; if the degree of cancellation increases, continue to adjust the position in the same direction, otherwise adjust the position in the opposite direction until the position of the antenna decoupling surface that meets the decoupling requirements is obtained; If the degree of cancellation increases, continue to adjust the position in the same direction, otherwise adjust the position in the opposite direction until the position of the antenna decoupling surface that meets the decoupling requirements is obtained; Step 4: The electromagnetic simulation software FEKO is used to simulate the eigenvalues of the main cancellation mode, and based on the eigenvalues, it is determined whether the main cancellation mode stores net electric energy or net magnetic energy; then, by modifying the patches on the decoupling surface of the array antenna, the ability of the main cancellation mode to store net electric energy / net magnetic energy is changed, thereby changing its eigenvalues and reducing the ; Step 5, repeat Step 2 to Step 4 until the decoupling requirements are met.

2. The design method of the decoupling surface of the array antenna based on the characteristic mode analysis according to claim 1, characterized in that In the said Step 2, the amplitudes and phases of each mode of both the coupling field and the cancellation field are obtained through the following process: Step 201, use the electromagnetic simulation software FEKO to simulate the coupling field between array elements to obtain the amplitudes and phases of the mode weight coefficients of each mode of the coupling field, and the amplitudes and phases of the eigenfields; Step 202, multiply the amplitudes of the mode weight coefficients and the eigenfields and add the phases to obtain the amplitudes and phases of each mode of the coupling field; Step 203, use the electromagnetic simulation software FEKO to simulate the cancellation field to obtain the amplitudes and phases of the mode weight coefficients of each mode of the cancellation field, and the amplitudes and phases of the eigenfields; Step 204, multiply the sum of the mode weight coefficients and the amplitudes of the eigenfields and add the phases to obtain the amplitudes and phases of each mode of the cancellation field.

3. A method for designing a decoupling surface of an array antenna based on characteristic mode analysis according to claim 1, characterized in that, In the said Step 2, during simulation, the coupling field is the radiation field of one element at another element; the cancellation field is the reflected field of the radiation field of the antenna element at the coupled element after being reflected by the ADS element.

4. A method for designing a decoupling surface of an array antenna based on characteristic mode analysis according to claim 1, characterized in that In the said step 2, the mode of the cancellation field of the component of the mode of the coupling field is defined as: ； Among them, is the component of the coupled field mode ; is the component of the cancellation field mode ; is the component of the cancellation field mode .

5. A decoupling surface design method for an array antenna based on characteristic mode analysis according to claim 1, characterized in that In the said Step 3, the position of the decoupling surface of the array antenna is obtained through the following process: Step 301: Change the position of the decoupling surface of the array antenna and analyze the cancellation degree of the main cancellation mode after the position change of the change; Step 302, if the cancellation degree increases, continue to adjust the position in the same direction, otherwise adjust the position in the opposite direction.

6. A decoupling surface design method for an array antenna based on characteristic mode analysis according to claim 1, characterized in that In the said Step 4, the patches of the decoupling surface of the array antenna are obtained through the following process: Step 401, use the electromagnetic simulation software FEKO to simulate and obtain the eigenvalues of the main cancellation mode, and judge whether the main cancellation mode stores net electric energy or net magnetic energy according to the eigenvalues; Step 402, by modifying the patches of the decoupling surface of the array antenna or adding inductive / capacitive elements, change the ability of the main cancellation mode to store net electric energy / net magnetic energy, and further change its eigenvalue, so that the is reduced.

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