Flexible frequency selective surface based on geometric kinking and application

Abstract

The invention belongs to the technical field of electromagnetic compatibility, and particularly relates to a flexible frequency selective surface based on geometric kinking and application. The flexible frequency selective surface designed by the invention has the advantages of simple structure, good angle stability and good bending angle, can realize a passband effect in a range of 5.08-6.01 GHz, has good angle stability in an electromagnetic wave incident angle of 0-60 degrees, keeps stable frequency selection performance in a bending angle of 0-180 degrees, and has good application prospects. The method has good curved surface conformal capability, and has application prospects in the technical fields of radar radomes, electromagnetic protection and communication.

Description

Technical Field

[0001] The invention belongs to the technical field of electromagnetic compatibility, and in particular relates to a flexible frequency selective surface based on geometric kinks and applications thereof. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] Frequency selective surface (FSS) is an artificial periodic structure composed of specific resonant units arranged in a two-dimensional periodic manner. This structure can accurately control the frequency, incident angle and polarization mode of electromagnetic waves to achieve a specific filtering effect on electromagnetic waves, namely frequency selectivity. Due to its unique electromagnetic wave control capability, FSS has been widely used in many fields such as radar antenna covers, electromagnetic protection and communication technology. With the advancement of technology and the increase in demand, more complex curved surface structures are required for FSS, such as the streamlined stealth design of aircraft and the conformal design of antennas. These complex curved surface structures have promoted the flexible development of FSS technology.

[0004] At present, research work is mainly focused on enabling FSS to be effectively applied in complex curved surfaces through material selection and structural design. For example, Chen et al. selected ultra-thin polyvinyl chloride (PVC) as a substrate and successfully prepared a flexible FSS that can still maintain a passband transmittance of 70% when the conformal bending angle reaches 77.35°. Yang et al. used polydimethylsiloxane (PDMS) as a substrate material to prepare a flexible FSS that can achieve an angle stability of 60° and a conformal bending angle of 128° while maintaining good frequency selection characteristics. However, for some extreme application scenarios, these conformal bending angles are still not enough to meet the needs, and this type of flexible FSS has complex structural problems in manufacturing.

[0005] At the same time, further exploration of conformal bending angles in this field is often accompanied by high requirements for angle stability. Geometric kinks are considered to be a good solution to the problem of angle stability, but since the resonance peak of a single geometric kink is usually single and narrow, a better solution is needed for FSS that requires broadband characteristics. Summary of the invention

[0006] In order to solve the above technical problems, the purpose of the present invention is to provide a flexible frequency selective surface based on geometric knots and its application. The flexible frequency selective surface has the advantages of simple structure, good angular stability and good bending angle, and can achieve a passband effect in the range of 5.08 to 6.01 GHz. At the same time, it has good angular stability within the electromagnetic wave incident angle of 0 to 60°, and maintains stable frequency selection performance within the bending angle of 0 to 180°, and has good surface conformal capability.

[0007] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0008] In a first aspect, the present invention provides a flexible frequency selective surface based on geometric kinks, the flexible frequency selective surface comprising a dielectric substrate and a geometric kink structural unit attached to the dielectric substrate;

[0009] The geometric knot structure unit comprises a first Möbius knot and a second Möbius knot of different sizes, and the distance d between the two is 14 to 16 mm;

[0010] The radius r of the first Möbius knot and the second Möbius knot are both 4 to 4.9 mm, the coil diameter a is both 1 to 2 mm, and the deviation coefficient b is both 1 to 2 mm;

[0011] The operating frequency of the flexible frequency selective surface is 5.08-6.01 GHz.

[0012] Preferably, the radius r of the first Möbius knot is 4 to 4.1 mm, the coil diameter a is 1 to 2 mm, and the deviation coefficient b is 1 to 2 mm.

[0013] Preferably, the radius r of the second Möbius knot is 4.7-4.9 mm, the coil diameter a is 1-2 mm, and the deviation coefficient b is 1-2 mm.

[0014] Preferably, the geometric knot structure unit is formed by periodic extension in the xy plane.

[0015] Preferably, the material of the dielectric substrate includes PET film and foam, with a relative dielectric constant of 1 to 1.2, a length p of 30 to 35 mm, a width w of 15 to 19.8 mm, and a height h of 12 to 15 mm.

[0016] Preferably, the Möbius knot is obtained by topological transformation of the classic Möbius strip, wherein the middle portion of the Möbius strip is hollowed out, leaving only the edge to form two overlapping edge lines, and the edge lines are replaced by metal wires, namely, a Möbius knot.

[0017] Preferably, the material of the Möbius knot is metal; further preferably, the metal is selected from one or more of silver, gold, aluminum, iron, tin, copper, and stainless steel.

[0018] Preferably, the processing technology of the Möbius knot is one or more of 3D printing, printed circuit board technology, and mechanical processing.

[0019] A second aspect of the present invention provides an application of the above-mentioned flexible frequency selective surface based on geometric kinks in the fields of radar antenna covers, electromagnetic protection and communication technology.

[0020] According to a second aspect of the present invention, a radar antenna cover is provided, which is used to cover the radiation direction of an antenna system. The radar antenna cover is composed of the flexible frequency selective surface based on geometric kink according to the first aspect.

[0021] The beneficial effects achieved by one or more technical solutions of the present invention are as follows:

[0022] (1) The geometric knot-based flexible frequency selective surface prepared in the present invention has a passband -3dB bandwidth of 0.93GHz (5.08-6.01GHz), a relative bandwidth of 16.77%, an insertion loss of less than 1dB in the frequency band of 5.11-5.80GHz, and two -10dB stopbands with bandwidths of 0.03 and 0.04GHz at 5.02-5.05GHz and 6.06-6.10GHz, respectively.

[0023] (2) The flexible frequency selective surface based on geometric kink prepared by the present invention has good angular stability within the electromagnetic wave incident angle range of 0 to 60°, including TE polarization mode and TM polarization mode.

[0024] (3) The flexible frequency selective surface based on geometric kinks prepared by the present invention maintains stable frequency selection performance within a bending angle of 0 to 180° and has good surface conformality. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic diagram of the construction of a flexible frequency selective surface based on geometric knots in Example 1 of the present invention, wherein: 1: a first Möbius knot; 2: a second Möbius knot; 3: a foam substrate;

[0026] Figure 2 The schematic diagram of the structure of the Möbius knot obtained by topological transformation of the classical Möbius tie;

[0027] Figure 3Partial schematic diagrams of flexible frequency selective surfaces based on geometric knots in Examples 1 to 3 of the present invention, wherein (a) a geometric knot structure unit, (b) a top view of the flexible frequency selective surface, and (c) a side view of the flexible frequency selective surface;

[0028] Figure 4 It is a simulation result diagram of Example 1 of the present invention, and a curve diagram of transmission coefficient variation with incident angle under TE and TM polarizations;

[0029] Figure 5 It is a simulation result diagram of Example 2 of the present invention, and a curve diagram of transmission coefficient changing with incident angle under TE and TM polarizations;

[0030] Figure 6 It is a simulation result diagram of Example 3 of the present invention, and a curve diagram showing the transmission coefficient changing with the incident angle under TE and TM polarizations;

[0031] Figure 7 It is a simulation result diagram of the comparative example of the present invention, and a curve diagram of transmission coefficient variation with incident angle under TE and TM polarization;

[0032] Figure 8 This is a graph of the measured results in an embodiment of the present invention, and a graph showing the transmission coefficient changing with the bending angle. DETAILED DESCRIPTION

[0033] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0034] The inventor obtained the Möbius knot structure in the previous research of this research group (a Möbius knot with topological resonance characteristics, metamaterial design based on metal Möbius knot and its electromagnetic topological properties, Zhang Wenjin, Master's thesis of Shandong University, May 20, 2021, Chapter 3), and designed a flexible frequency selective surface based on geometric knots, which solved the problems of limited bending angle and complex structure of flexible frequency selective surfaces.

[0035] The present invention will be further described in detail below in conjunction with specific embodiments. It should be noted that the specific embodiments are intended to explain the present invention rather than to limit it.

[0036] Example 1 :This embodiment provides a flexible frequency selective surface based on geometric kink and analyzes its transmittance simulation curve

[0037] like Figure 1 As shown, the flexible frequency selective surface based on geometric kink includes a dielectric substrate 3 and a geometric kink structural unit attached to the dielectric substrate;

[0038] Among them, the geometric knot structure unit includes the first Möbius knot and the second Möbius knot. The Möbius knot is prepared using the content of Chapter 3 of "Metamaterial Design Based on Metal Möbius Knot and Its Electromagnetic Topological Properties·Zhang Wenjin·Master's Thesis of Shandong University·May 20, 2021";

[0039] like Figure 2 As shown, the Möbius knot is obtained by topological transformation of the classic Möbius strip. The middle part of the Möbius strip is hollowed out, leaving only the edge, forming two overlapping edge lines, and the edge lines are replaced by metal wires, which is the Möbius knot.

[0040] like Figure 3 As shown in (a), the specific parameters of the geometric knot structure unit are set as follows:

[0041] The first Möbius knot has a knot radius of r = 4 mm, a coil diameter a = 1 mm and a deviation coefficient b = 1 mm;

[0042] The second Möbius knot has a knot radius of r = 4.8 mm, a coil diameter a = 1 mm, and a deviation coefficient b = 1 mm;

[0043] The distance between the first Möbius knot and the second Möbius knot is d=15 mm.

[0044] like Figure 3 As shown in (b) and (c), the relative dielectric constant of the foam substrate is 1, the length p is 30 mm, the width w is 15 mm, and the height h is 13 mm.

[0045] The simulation frequency range is 4 to 8 GHz, and the results are as follows Figure 4 As shown, when the incident angle of the electromagnetic wave is 0°, the transmission coefficient S in the TE polarization mode and the TM polarization mode 21 In the frequency band range of 5.08~6.01GHz, it is greater than -3dB, and the relative bandwidth is 16.77%. In the frequency band range of 5.11~5.80GHz, the insertion loss is less than 1dB. On the left and right sides of the passband, there are -10dB stop bands with bandwidths of 0.03GHz (5.02~5.05GHz) and 0.04GHz (6.06~6.10GHz) respectively. 5.05~5.08GHz and 6.01~6.06GHz are transition bands with bandwidths of 0.03 and 0.05GHz respectively.

[0046] At the same time, if Figure 4 As shown, the structure has good angular stability within the electromagnetic wave incident angle range of 0 to 60°, and can still maintain more than 89.24% of the -3dB passband when the incident angle is 60°, including the TE polarization mode and the TM polarization mode.

[0047] Example 2 :This embodiment provides a flexible frequency selective surface based on geometric kink and analyzes its transmittance simulation curve

[0048] The difference between the flexible frequency selective surface obtained in this embodiment and that in Embodiment 1 lies in the difference in parameters of the geometric kink structure unit and the dielectric substrate.

[0049] The specific parameters of the geometric knot structure unit in this embodiment are set as follows:

[0050] The first Möbius knot has a knot radius of r = 4.1 mm, a coil diameter a = 1.5 mm and a deviation coefficient b = 1.5 mm;

[0051] The second Möbius knot has a knot radius of r = 4.7 mm, a coil diameter a = 1.5 mm and a deviation coefficient b = 1.5 mm;

[0052] The distance between the first Möbius knot and the second Möbius knot is d=14 mm.

[0053] The relative dielectric constant of the foam substrate is 1.2, the length p is 30.6 mm, the width w is 17.2 mm, and the height h is 15 mm.

[0054] The simulation frequency range is 4 to 8 GHz, and the results are as follows Figure 5 As shown, when the incident angle of the electromagnetic wave is 0°, the transmission coefficient S in the TE polarization mode and the TM polarization mode 21 In the frequency range of 5.24~5.84GHz, the relative bandwidth is greater than -3dB, and the relative bandwidth is 10.83%. Figure 5 As shown, the structure has good angular stability within the electromagnetic wave incident angle range of 0 to 60°, and can still maintain more than 73.33% of the -3dB passband when the incident angle is 60°, including the TE polarization mode and the TM polarization mode.

[0055] Example 3 :This embodiment provides a flexible frequency selective surface based on geometric kink and analyzes its transmittance simulation curve

[0056] The difference between the flexible frequency selective surface obtained in this embodiment and that in Embodiment 1 lies in the difference in parameters of the geometric kink structure unit and the dielectric substrate.

[0057] The specific parameters of the geometric knot structure unit in this embodiment are set as follows:

[0058] The first Möbius knot has a knot radius of r = 4.1 mm, a coil diameter a = 2 mm, and a deviation coefficient b = 2 mm;

[0059] The second Möbius knot has a knot radius of r = 4.9 mm, a coil diameter a = 2 mm, and a deviation coefficient b = 2 mm;

[0060] The distance between the first Möbius knot and the second Möbius knot is d=16 mm.

[0061] The relative dielectric constant of the foam substrate is 1.1, the length p is 35 mm, the width w is 19.8 mm, and the height h is 12 mm.

[0062] The simulation frequency range is 4 to 8 GHz, and the results are as follows Figure 6 As shown, when the incident angle of the electromagnetic wave is 0°, the transmission coefficient S in the TE polarization mode and the TM polarization mode 21 In the 5.14~5.93GHz frequency band, the relative bandwidth is greater than -3dB, and the relative bandwidth is 14.27%. Figure 6 As shown, the structure has good angular stability within the electromagnetic wave incident angle range of 0 to 60°, and can still maintain more than 62.03% of the -3dB passband when the incident angle is 60°, including the TE polarization mode and the TM polarization mode.

[0063] Comparative Example 1 :

[0064] The difference between this comparative example and Example 1 is that only a single-size geometric kink structure unit is constructed, that is, an array formed by periodic extension in the xy plane is taken as an example of a unit with a kink radius r of 4 mm, a coil diameter a of 1 mm and a deviation coefficient b of 1 mm. A foam substrate (the material and size are the same as those in Example 1) is attached below the structure unit, with a relative dielectric constant of 1, a length p of 30 mm, a width w of 15 mm and a height of 13 mm.

[0065] The simulation frequency range is 4 to 8 GHz, and the results are as follows Figure 7 The figure shows that the transmission coefficient S of a single-size geometric kink structure unit 21 There is only a single resonance peak, located at 6.08GHz, which means that electromagnetic waves cannot pass through the structure at the resonance frequency. The single frequency point is blocked, which is the left or right arm of the passband FSS, but the passband FSS cannot be formed by only a single-size geometric kink structure unit.

[0066] Test example :This test example measures the bending performance of the flexible frequency selective surface obtained in Example 1

[0067] This test example verifies the bending performance of the designed flexible frequency selective surface. The free space method is used to measure the transmittance of the sample in Example 1 in a bent state. The test frequency range is 4 to 8 GHz. The bending performance is mainly defined by the bending angle α. Figure 8The test results show that the structure maintains stable frequency selection performance within the bending angle range of α = 0 to 180° and has good surface conformality.

[0068] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A flexible frequency selective surface based on geometric kinks, characterized in that: The flexible frequency selective surface comprises a dielectric substrate and a geometric kink structure unit attached to the dielectric substrate; The geometric knot structure unit comprises a first Möbius knot and a second Möbius knot of different sizes, and the distance d between the two is 14 to 16 mm; The radius r of the first Möbius knot and the second Möbius knot are both 4 to 4.9 mm, the coil diameter a is both 1 to 2 mm, and the deviation coefficient b is both 1 to 2 mm; The operating frequency of the flexible frequency selective surface is 5.08-6.01 GHz.

2. The flexible frequency selective surface based on geometric kink according to claim 1, characterized in that: The radius r of the first Möbius knot is 4-4.1 mm, the coil diameter a is 1-2 mm, and the deviation coefficient b is 1-2 mm; the radius r of the second Möbius knot is 4.7-4.9 mm, the coil diameter a is 1-2 mm, and the deviation coefficient b is 1-2 mm.

3. The flexible frequency selective surface based on geometric kink according to claim 1, characterized in that: The geometric knot structure unit is formed by periodic extension in the xy plane.

4. The flexible frequency selective surface based on geometric kink according to claim 1, characterized in that: The material of the dielectric substrate includes PET film and foam, with a relative dielectric constant of 1 to 1.2, a length p of 30 to 35 mm, a width w of 15 to 19.8 mm, and a height h of 12 to 15 mm.

5. The flexible frequency selective surface based on geometric kink according to claim 1, characterized in that: The Möbius knot is obtained by topological transformation of the classic Möbius strip. The middle part of the Möbius strip is hollowed out, leaving only the edge to form two overlapping edge lines, and the edge lines are replaced by metal wires, which is the Möbius knot.

6. The flexible frequency selective surface based on geometric kink according to claim 1, characterized in that: The material of the Mobius knot is metal.

7. The flexible frequency selective surface based on geometric kink according to claim 6, characterized in that: The metal is selected from one or more of silver, gold, aluminum, iron, tin, copper and stainless steel.

8. The flexible frequency selective surface based on geometric kink according to claim 1, characterized in that: The processing technology of the Mobius knot is one or more of 3D printing, printed circuit board technology, and mechanical processing.

9. Application of the flexible frequency selective surface based on geometric kinks as claimed in any one of claims 1 to 8 in the fields of radar antenna covers, electromagnetic protection and communication technology.

10. A radar antenna cover, used to cover the radiation direction of the antenna system, characterized in that: The radar antenna cover is composed of the flexible frequency selective surface based on geometric kinks as described in any one of claims 1 to 8.

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