Design method of broadband high-polarization-stability frequency selective surface and frequency selective surface

Abstract

The invention belongs to the field of electromagnetic wave-absorbing frequency selective surface design, and particularly relates to a frequency selective surface design scheme for improving polarization stability and angle stability of an asymmetric FSS (frequency selective surface) patch and simultaneously realizing broadband absorption performance through a central rotational symmetry design, which comprises the following steps of: establishing an FSS model according to design requirements by utilizing simulation software; the FSS model comprises a metal substrate, a wave-absorbing dielectric layer and an FSS functional layer from bottom to top; optimizing the size of the FSS functional layer pattern according to the wave-absorbing performance requirement to obtain an FSS functional layer pattern optimization scheme meeting the wave-absorbing performance requirement; aiming at the obtained FSS function layer pattern optimization scheme, analyzing the polarization performance and the oblique angle incidence performance under the selected FSS feature size to obtain a final FSS function layer pattern; according to the method, the wave absorbing bandwidth is greatly widened, the central symmetry of the FSS pattern is improved, and the polarization stability and the oblique angle incidence stability of the FSS are improved.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic absorption frequency selective surface design. Specifically, it relates to a broadband high polarization stability frequency selective surface design method and a frequency selective surface. Through a central rotational symmetry design, the polarization and angular stability of an asymmetric FSS patch are improved, while simultaneously achieving broadband absorption performance. This results in a broadband frequency selective surface design scheme with high polarization stability and high angular stability. Background Technology

[0002] Currently, absorbing materials are widely used in the aerospace field, especially in equipment where the requirements for absorbing performance are higher. However, due to the structural design of the absorbing materials and their dielectric and magnetic properties, the absorbing materials only have good absorbing performance in specific frequency bands, resulting in a narrow absorbing bandwidth.

[0003] A frequency selective surface (FSS) is a periodic array structure composed of a large number of passive resonant elements. These elements can be metal patches or apertures periodically arranged on metal patches. By adjusting the shape, size, dimensions, and period of the elements in this periodic structure material, the transmission and reflection characteristics of electromagnetic waves can be effectively controlled, significantly broadening the research and application scope of microwave absorbing materials.

[0004] FSS patches, typically used for controlling microwave absorption performance, are rarely symmetrical due to the target requirements for adjusting absorption performance. These complex FSS structures are often designed only for cases where electromagnetic waves are incident perpendicularly. Under perpendicular incidence, the electric and magnetic field components of the electromagnetic wave will generate TE and TM polarization on the FSS patch surface. This leads to polarization problems in asymmetric FSS patches due to inconsistent feature dimensions in the TE and TM polarization directions. Furthermore, in real-world applications, electromagnetic waves are not always incident perfectly perpendicular to the coating surface. Since electromagnetic wave propagation on material surfaces is highly sensitive to the angle of incidence, especially at high frequencies, even slight deviations from the designed angle of incidence can significantly affect propagation and polarization. Inappropriate frequency and angle combinations can lead to decreased transmission efficiency or signal distortion. Therefore, the performance stability under oblique incidence must also be considered when designing FSS patches. Summary of the Invention

[0005] To address the aforementioned problems in the prior art, a broadband frequency selective surface (FSS) design scheme with high polarization stability and high angular stability is provided. The frequency selective surface designed in this scheme maintains high polarization stability and oblique angle incident stability in the overall FSS patch's response to electromagnetic wave incident behavior, while also possessing broadband absorption characteristics, significantly improving the overall performance stability of the FSS broadband absorption design.

[0006] The complete technical solution of this invention includes:

[0007] A frequency-selective surface design scheme that improves the polarization and angular stability of an asymmetric FSS patch through a central rotational symmetry design, while simultaneously achieving broadband absorption performance, includes the following steps:

[0008] Step (1): Use simulation software to establish the corresponding FSS model according to the design requirements (structure, thickness, material parameters, etc.). From bottom to top, they are metal substrate, microwave absorbing medium layer, and FSS functional layer.

[0009] Step (2): Optimize the pattern size of the FSS functional layer according to the absorption performance requirements;

[0010] Step (3): Analyze the polarization performance and oblique angle incident performance under the selected FSS feature size, and obtain the final FSS design scheme;

[0011] Step (4): Prepare the final FSS design using surface processing methods.

[0012] Furthermore, in step (1) above, the FSS model can be established using any HFSS and CST software known to those skilled in the art.

[0013] Furthermore, in step (1), the thickness of the absorbing medium layer in the FSS model ranges from 0.5 mm to 3 mm, the thickness of the FSS pattern layer ranges from 1 μm to 30 μm, and the FSS material is a highly conductive material, including but not limited to platinum, silver, copper, etc.

[0014] Furthermore, step (2) includes:

[0015] 1) Using simulation methods, the period size of the basic unit of FSS with the highest absorption intensity and the largest absorption bandwidth is obtained. Frequency sweep analysis is performed under this period size, and an absorption performance database is constructed.

[0016] 2) Based on the absorption bandwidth, bands, absorption intensity in each band, and average absorption intensity requirements of the frequency selective surface, the target performance is decomposed into regional performance indicators according to the absorption peak distribution positions of the absorption curves in the absorption performance database. Then, based on the absorption bandwidth, absorption intensity, and number of characteristic dimensions of the FSS basic unit, the FSS basic units that meet the regional performance indicators are selected and arranged in a centrally symmetrical manner to obtain the frequency selective surface that meets the target performance.

[0017] Furthermore, in step (2), a variety of FSS functional layer patterns that meet performance requirements can be obtained. The FSS pattern is characterized by rotational symmetry around the four-sided periodic center of the FSS, with asymmetric patches, including but not limited to rectangular patches, as basic units.

[0018] Furthermore, in step (3), polarization stabilization requires the FSS pattern to perfectly match the reflection loss curves under TE and TM wave incidence. Oblique angle incidence stabilization requires setting the incident angle according to actual performance needs, and the performance loss should not exceed the performance index. The various FSS functional layer patterns that meet the performance requirements obtained in step (2) are analyzed, and the FSS functional layer pattern that meets both polarization stabilization and oblique angle incidence stabilization is selected.

[0019] Furthermore, the surface processing methods used in step (4) include, but are not limited to, surface processing methods well known to those skilled in the art, such as magnetron sputtering, screen printing and surface laser processing.

[0020] Furthermore, a frequency-selective surface is designed using the above design method.

[0021] The advantages of this invention over the prior art are:

[0022] (1) The central rotationally symmetric FSS structure gives rise to the "double absorption peak" characteristic of the reflection loss curve, which greatly broadens the absorption bandwidth.

[0023] (2) Compared with the existing technology, the central symmetry of the FSS pattern is improved under the premise of achieving FSS broadband absorption performance. The improvement of central symmetry directly leads to the improvement of FSS polarization stability and oblique angle incident stability.

[0024] (3) Magnetron sputtering and screen printing processes can easily prepare complex FSS surface shapes without increasing process complexity by using photomasks. Laser processing, on the other hand, enables the preparation of complex patterns on smaller workpiece surfaces with simpler procedures and higher processing precision. Attached Figure Description

[0025] Figure 1 This is a flowchart of the design method of the present invention.

[0026] Figure 2 This is an example diagram of the FSS model of the design method of this invention.

[0027] Figure 3 This is an example of an FSS unit in the design method of this invention.

[0028] Figure 4 This is the reflection loss performance diagram corresponding to Example 1 of the design method of this invention.

[0029] Figure 5 These are the performance curves of Example 1 of the design method of this invention under TE polarization and TM polarization.

[0030] Figure 6This is the performance change of the reflection loss curve in Example 1 of the design method of the present invention within the angle range of -30° to +30°. Detailed Implementation

[0031] The present invention will now be described in detail with reference to embodiments and accompanying drawings. However, it should be understood that the embodiments and drawings are for illustrative purposes only and do not constitute any limitation on the scope of protection of the present invention. All reasonable modifications and combinations included within the inventive spirit of the present invention fall within the scope of protection of the present invention.

[0032] According to an embodiment of the present invention, based on Figure 1 As shown, the present invention provides a wideband, high polarization stability frequency selective surface design, comprising the following steps:

[0033] Step (1): Model the FSS model according to actual needs. Example of a model: Figure 2 As shown.

[0034] Step (2): Optimize the model to determine a suitable period size. Within this period size, set different FSS patch shapes and sizes and perform parameter sweep analysis. The sweep step size is set according to actual needs, and suitable target shapes and sizes are selected from these. An example of an FSS patch is shown below. Figure 3 As shown.

[0035] Furthermore, including:

[0036] 2.1 Set the same feature size and use models of FSS basic units with different shapes under different period sizes for simulation. Select the period size with the highest intensity and the largest absorption bandwidth according to the output absorption performance intensity and bandwidth. Set different FSS basic unit shapes and sizes under the period size, perform parameter sweep frequency analysis, and use the parameter sweep frequency analysis results to build an absorption performance database.

[0037] 2.2 For the target performance of the frequency-selective surface (absorbing bandwidth, bands, absorption intensity in each band, and average absorption intensity in all bands), based on the absorption peak distribution positions of the absorption curves in the absorption performance database, the target performance is decomposed into regional performance indicators; the absorption intensity in each band is represented by reflection loss, specifically: f i <R Li , where f i For the i-th band, R Li Let be the reflection loss of the i-th band. The average absorption intensity is as follows:

[0038]

[0039] 2.3 Screening FSS basic units that meet the regional performance indicators from the absorption performance database; the screening criteria are absorption bandwidth, absorption intensity, and the number of feature sizes of the FSS basic unit. Under the premise that the absorption bandwidth and absorption intensity meet the requirements, the FSS basic unit with the fewest feature sizes is selected, and the simplicity of the FSS patch shape is characterized by the number of feature sizes.

[0040] 2.4 The selected FSS basic units are combined and arranged, and the combination arrangement with the smallest overall period size is selected to obtain a frequency selection surface design scheme that meets the target performance.

[0041] Step (3): Analyze the polarization performance and oblique angle incident performance of the selected FSS design scheme, obtain the final reflection loss performance curve, and determine whether the absorption performance, polarization performance and oblique angle incident performance of the obtained broadband absorbing FSS can achieve satisfactory design results.

[0042] Steps (1) to (3) yield a wideband, high-stability frequency selective absorbing surface, which includes: multiple FSS units arranged periodically, each FSS unit containing several FSS patches obtained by rotational symmetry of asymmetric patches.

[0043] To further verify the beneficial effects of the high-coverage frequency selective surface (FSS) designed by the broadband absorbing frequency selective surface design method of the present invention, the following embodiments are provided for further illustration.

[0044] Example 1

[0045] A frequency selective surface with wide bandwidth, high polarization stability, and high angle stability is prepared. Its specific performance requirements are as follows: the absorption frequency band is X-band and Ku-band (8-18GHz), where the absorption intensity in the X-band is <-5dB, the absorption intensity in the Ku-band is <-5dB in the 12-15GHz range, the polarization performance is stable, and the performance loss is less than 1dB at the incident angle in the range of -30° to +30°.

[0046] Step (1): To meet the broadband absorption performance of FSS, we modeled it in a periodic dimension of 10mm × 10mm, as follows: Figure 2 As shown.

[0047] Step (2): The above FSS model was structurally optimized. The sweep step size was set to 0.05mm, and a rotationally symmetric FSS patch obtained by rotating a rectangular patch by 90° was selected. The corresponding broadband absorption performance is as follows: Figure 4 As shown.

[0048] Step (3): Analyze the performance stability of the selected patches under electromagnetic wave TE polarization and TM polarization, such as... Figure 5As shown; calculate the performance loss at incident angles within the range of -30° to +30°, such as... Figure 6 As shown.

[0049] The above description uses an FSS design with broadband absorption in the X-band and Ku-band absorption bands and oblique angle incident stability as an example for detailed explanation. The FSS design of this invention achieves high performance and consistency with the set specifications for broadband absorption and performance stability in any target absorption band. The absorption bandwidth and polarization / angle stability both achieve satisfactory design results. In other words, the FSS design of this invention has the advantages of broadband absorption, polarization stability, and oblique angle incident stability.

[0050] The above-described embodiments are merely some implementation methods of this application. For those skilled in the art, various modifications and improvements can be made without departing from the inventive concept of this application, and these all fall within the protection scope of this application.

Claims

1. A method for designing a wideband, high polarization stability frequency selective surface, characterized in that, The steps include: (1) Use simulation software to build an FSS model according to the design requirements. The FSS model includes a metal substrate, a microwave absorbing medium layer, and an FSS functional layer from bottom to top. (2) Optimize the FSS functional layer pattern size according to the absorption performance requirements to obtain an optimized FSS functional layer pattern that meets the absorption performance requirements. (3) For the FSS functional layer pattern optimization scheme obtained in step (2), analyze the polarization performance and oblique angle incident performance under the selected FSS feature size to obtain the final FSS functional layer pattern. (4) The final FSS functional layer pattern is prepared using surface processing methods.

2. The broadband high polarization stability frequency selective surface design method according to claim 1, characterized in that, In step (1), the design requirements include the structure, thickness and material parameters of the FSS.

3. The broadband high polarization stability frequency selective surface design method according to claim 2, characterized in that, The FSS model was established using HFSS or CST software.

4. The broadband high polarization stability frequency selective surface design method according to claim 3, characterized in that, The thickness of the absorbing medium layer ranges from 0.5 mm to 3 mm, and the thickness of the FSS pattern layer ranges from 1 μm to 30 μm.

5. The broadband high polarization stability frequency selective surface design method according to claim 4, characterized in that, FSS material is a highly conductive material, including but not limited to platinum, silver, and copper.

6. The broadband high polarization stability frequency selective surface design method according to claim 5, characterized in that, The pattern of the FSS functional layer is formed by rotating symmetrically around the four-dimensional center of the FSS, using asymmetric patches as basic units.

7. The broadband high polarization stability frequency selective surface design method according to claim 6, characterized in that, Polarization stabilization requires that the reflection loss curves of the FSS pattern perfectly match under TE and TM wave incidence. Oblique angle incidence stabilization requires setting the incidence angle according to actual performance needs, and the performance loss should not exceed the performance index.

8. The broadband high polarization stability frequency selective surface design method according to claim 7, characterized in that, The surface processing methods include magnetron sputtering, screen printing, and surface laser processing.

9. A frequency-selective surface obtained by the method according to any one of claims 1-8, characterized in that, The frequency selective surface is prepared using the frequency selective surface design scheme described in step (5) and a surface processing method.

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