An angular stable large-frequency-ratio dual-bandpass frequency selective surface structure

Abstract

This invention relates to the field of electromagnetic wave technology and discloses a frequency selective surface structure with a stable angle and high frequency ratio, comprising multiple identical regular hexagonal FSS units arranged in a periodic equilateral triangle pattern. Each FSS unit includes, from top to bottom, a first dielectric substrate, a metal layer, and a second dielectric substrate. The metal layer, from the outside in, consists of a hexagonal ring, three elongated branches of the same size, and three patches of the same size. The three patches are rotationally symmetrical about the center of the hexagonal ring and are connected to the hexagonal ring through the three elongated branches. The patches are rhomboid patches, with the extension of the shorter diagonal of each rhomboid patch passing through the center of the hexagonal ring; alternatively, the patches can be isosceles triangles, ">" shapes, or "<" shapes. Under perpendicular incidence conditions, this invention achieves a frequency ratio of approximately 4, and with rhomboid patches, the frequency ratio is 4.3. Even at large incident angles, the wave transmission performance remains relatively stable. This structure is simple and easy to manufacture.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic wave technology, and more specifically to a frequency-selective surface structure. Background Technology

[0002] Frequency selective surfaces (FSS) are a typical two-dimensional periodic electromagnetic structure that exhibits spatial filtering characteristics for incident electromagnetic waves, meaning they can selectively transmit or reflect electromagnetic waves in specific frequency bands. Due to their unique frequency selectivity, FSSs have been widely used in radar systems, satellite communications, electromagnetic shielding, modern wireless communications, and electromagnetic compatibility. For example, as radomes, FSSs can effectively suppress out-of-band interference while ensuring transparent signal transmission within the operating frequency band. With the development of multi-frequency technology and the deployment of multi-band radar systems, research on multi-frequency FSSs has gradually attracted widespread attention. However, most existing multi-frequency FSSs operate in close proximity, with the frequency ratio (the ratio of the center frequencies of the two operating bands) typically not exceeding 3:1. Due to harmonics and grating lobes, it is difficult to achieve a multi-frequency or dual-frequency FSS with good performance and a high frequency ratio. Especially for oblique incidence, its transmission and reflection performance decreases rapidly with increasing incidence angle. Therefore, to further meet the needs of multi-frequency communication and detection systems, it is necessary to develop an angle-stable, high-frequency-ratio dual-bandpass frequency selective surface structure. Summary of the Invention

[0003] In most existing multi-frequency FSSs, the operating frequency bands are relatively close together. Due to harmonics and grating lobe effects, it is difficult to achieve a multi-frequency or dual-frequency FSS with good performance and a high frequency ratio. Especially for oblique incidence, its transmission and reflection performance decreases rapidly with increasing incident angle. This invention provides an angle-stable dual-bandpass frequency selective surface structure with a high frequency ratio. Under perpendicular incidence conditions, its frequency ratio can reach about 4. When a diamond-shaped patch is used, its frequency ratio is 4.3. Its transmission performance remains relatively stable even at large incident angles.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A high-ratio dual-bandpass frequency selective surface structure with stable angle is composed of multiple identical regular hexagonal FSS units arranged in a periodic equilateral triangle pattern. Each FSS unit structure includes, from top to bottom, a first dielectric substrate, a metal layer, and a second dielectric substrate. The metal layer consists of, from the outside to the inside: a hexagonal ring, three elongated branches of the same size, and three patches of the same size. The three patches are distributed in a rotationally symmetrical manner about the center of the hexagonal ring, and the three patches are respectively connected to the hexagonal ring through the three elongated branches. The patch is a rhombus-shaped patch, with the extension of the shorter diagonal of each rhombus patch passing through the center of the hexagonal ring. The angle between the shorter diagonals of two adjacent patches is 120°. Three elongated branches connect the three patches to the hexagonal ring along the shorter diagonals of the three patches, respectively; or, The patch is an isosceles triangle, ">" shaped, or "<" shaped patch, and the center line of the triangle, ">" shaped, or "<" shaped patch passes through the center of the hexagonal ring.

[0005] The preferred technical solution for the above-mentioned basic structure is that the outer side length of the hexagonal ring of the metal layer is 4mm and the inner side length is 3.85mm.

[0006] A further preferred technical solution is that the side length of the rhomboid patch in the metal layer is 1.88 mm, the gap width between two adjacent rhomboid patches is 0.2 mm, and the width of the three elongated branches in the metal layer is 0.9 mm.

[0007] A further preferred technical solution is to adjust the first operating frequency band by adjusting the gap size between adjacent patches in the metal layer.

[0008] The edges of the hexagonal rings in the metal layer are equivalent to inductors, and adjacent patches constitute an equivalent capacitor. The parallel resonance of the aforementioned inductors and capacitors generates the first operating frequency band. The first operating frequency band can be adjusted by adjusting the gap size between adjacent patches.

[0009] A further preferred technical solution is to adjust the second operating frequency band by adjusting the width of the elongated branch in the metal layer and the side length of the patch.

[0010] The hexagonal ring in the metal layer has an equivalent inductance. The hexagonal ring, the elongated stub, and the patch constitute an equivalent capacitance. The parallel resonance of the inductor and capacitor generates a second operating frequency band. The second operating frequency band can be adjusted by adjusting the width of the elongated stub and the side length of the patch.

[0011] A further preferred technical solution is that the material and size of the second dielectric substrate are exactly the same as those of the first dielectric substrate.

[0012] A further preferred technical solution is that the thickness of the first dielectric substrate is 0.1-2 mm, the dielectric constant is 2-5, and the loss tangent is 0.008.

[0013] A further preferred technical solution is that the thickness of the first dielectric substrate is 0.5 mm and the dielectric constant is 3.5.

[0014] A further preferred technical solution is that the material of the metal layer is copper, and the thickness is 0.015-0.050mm.

[0015] A further preferred technical solution is that the thickness of the metal layer is 0.015 mm.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention achieves a frequency-selective surface structure with a stable angle and high frequency ratio by introducing elongated branches and patches into the metal layer. Under perpendicular incidence conditions, its frequency ratio can reach 4, and when using diamond-shaped patches, the frequency ratio is 4.3. Its wave transmission performance remains relatively stable even at large incident angles. The structure is simple, easy to process, has good performance, and is easy to promote and apply. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a cross-sectional schematic diagram of the frequency selective surface unit according to an embodiment of the present invention.

[0019] Figure 2 This is a schematic diagram of the structure of the metal layer 2 in the frequency selective surface unit of this embodiment of the invention when using a diamond-shaped patch.

[0020] Figure 3 The transmittance curves of the frequency-selective surface structure of Embodiment 1 of this application under different TE polarization incident angles are shown.

[0021] Figure 4 This is a transmittance curve of the frequency-selective surface structure in Embodiment 1 of this application under different TM polarization incident angles.

[0022] Among them, 1. dielectric substrate; 2. metal layer; 3. dielectric substrate; 21. hexagonal ring; 22. elongated branch; 23. diamond patch. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0024] The embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0025] like Figure 1 As shown in the figure, the high-ratio dual-bandpass frequency selective surface structure with angle stability provided in this embodiment is composed of multiple identical FSS units arranged periodically. The FSS units are regular hexagons, and the periodic arrangement is equilateral triangles. The FSS unit structure includes: a metal layer 2, a first dielectric substrate 1 located on the upper surface of the metal layer 2, and a second dielectric substrate 3 located on the lower surface of the metal layer 2.

[0026] Figure 2 The diagram shown is a schematic of the structure of metal layer 2 in this embodiment, including: a hexagonal ring 21 on the outer side, three elongated branches 22 in the middle, and three patches on the inner side.

[0027] The three elongated branches 22 are of the same size, the three patches are of the same size, and the three patches are distributed in rotational symmetry about the center of the hexagonal ring 21. The three patches are connected to the hexagonal ring 21 through the three elongated branches 22 respectively.

[0028] For the shape of the patch, a rhombus-shaped patch 23 is preferred. When a rhombus-shaped patch 23 is used, the extension of the shorter diagonal of each rhombus-shaped patch 23 passes through the center of the hexagonal ring 21, and the angle between the shorter diagonals of two adjacent rhombus-shaped patches 23 is 120°. Three elongated branches 22 connect the three rhombus-shaped patches 23 to the hexagonal ring 21 along the direction of the shorter diagonals of the three rhombus-shaped patches 23, respectively. The patch can also be an isosceles triangle, ">" shaped, or "<" shaped patch, with the center line of the isosceles triangle, ">" shaped, or "<" shaped patch passing through the center of the hexagonal ring 21.

[0029] For the dimensions of the hexagonal ring 21 of the metal layer 2, preferably, the outer side length of the hexagonal ring 21 is 4mm and the inner side length is 3.85mm.

[0030] For the dimensions of the diamond patch 23 of the metal layer 2, preferably, the side length of the diamond patch 23 is 1.88mm, and the gap width between two adjacent diamond patches 23 is 0.2mm.

[0031] The width of the three elongated branches 22 in the metal layer 2 is preferably 0.9 mm.

[0032] The first working frequency band adjustment method for the angle-stable, high-ratio dual-band pass frequency selection surface structure is as follows: the first working frequency band is adjusted by adjusting the gap size between adjacent patches in the metal layer 2.

[0033] The second working frequency band of the angle-stable, high-ratio dual-band pass frequency selection surface structure is adjusted by adjusting the width of the long strip branch 22 in the metal layer 2 and the side length of the patch.

[0034] For the first dielectric substrate 1, preferably, the thickness of the first dielectric substrate 1 is 0.1-2 mm, the dielectric constant is 2-5, and the loss tangent is 0.008. More preferably, the thickness of the first dielectric substrate 1 is 0.5 mm, and the dielectric constant is 3.5.

[0035] Regarding the material and size of the two dielectric substrates, preferably, the second dielectric substrate 3 is exactly the same as the first dielectric substrate 1 in terms of material and size.

[0036] Regarding the material and dimensions of metal layer 2, preferably, the material of metal layer 2 is copper, and the thickness is 0.015-0.050 mm. More preferably, the thickness of metal layer 2 is 0.015 mm.

[0037] Specific implementation case 1: The frequency selective surface structure is composed of the same FSS unit arranged periodically. The FSS unit is a regular hexagon and the periodic arrangement is an equilateral triangle.

[0038] The FSS unit structure includes: a metal layer 2, a first dielectric substrate 1 located on the upper surface of the metal layer 2, and a second dielectric substrate 3 located on the lower surface of the metal layer 2.

[0039] The first dielectric substrate 1 has a thickness of 0.5 mm, a dielectric constant of 3.5, and a loss tangent of 0.008. The material and dimensions of the second dielectric substrate 3 are exactly the same as those of the dielectric substrate 1.

[0040] The metal layer 2 is made of copper and has a thickness of 0.015 mm. From the outside to the inside, the metal layer 2 consists of a hexagonal ring 21, three elongated branches 22, and three rhomboid patches 23.

[0041] The three rhombus-shaped patches 23 are identical in size and are rotationally symmetrical about the center of the hexagonal ring 21. The extension of the shorter diagonal of each rhombus-shaped patch 23 passes through the center of the hexagonal ring 21, and the angle between the shorter diagonals of two adjacent rhombus-shaped patches 23 is 120°.

[0042] Three elongated branches 22 are of the same size and are located between the hexagonal ring 21 and the three rhombus patches 23. The three elongated branches 22 connect the three rhombus patches 23 to the hexagonal ring 21 along the shorter diagonal of the three rhombus patches 23, respectively.

[0043] The outer side of the hexagonal ring 21 of the metal layer 2 is 4 mm and the inner side is 3.85 mm. The three rhomboid patches 23 of the metal layer 2 have a side length of 1.88 mm and the gap width between two adjacent rhomboid patches 23 is 0.2 mm. The width of the three elongated branches 22 of the metal layer 2 is 0.9 mm.

[0044] Figure 3This is a transmittance curve of the frequency-selective surface structure of Embodiment 1 of the present invention under different TE polarization incident angles. The horizontal axis represents frequency, and the vertical axis represents transmittance. TE polarization indicates that the direction of the incident electric field is perpendicular to the incident plane, which is the plane formed by the electromagnetic wave incident direction and the dielectric normal (i.e., the normal shared by the first dielectric substrate 1, the metal layer 2, and the second dielectric substrate 3). At an incident angle of 0°, the -3dB passband (frequency band with transmittance greater than 50%) of this structure is 4.04-5.69GHz and 17.10-24.91GHz, with a frequency ratio of 4.3; at an incident angle of 30°, the -3dB passband is 4.16-5.58GHz and 17.45-24.26GHz; and at an incident angle of 60°, the -3dB passband is 4.49-5.29GHz and 18.55-22.38GHz. As the incident angle increases, the passband bandwidth gradually decreases.

[0045] Figure 4 This is a transmittance curve of the frequency-selective surface structure of Embodiment 1 of the present invention under different TM polarization incident angles. The horizontal axis represents frequency, and the vertical axis represents transmittance. TM polarization indicates that the direction of the incident electric field is parallel to the incident plane, which is the plane formed by the electromagnetic wave incident direction and the dielectric normal (i.e., the normal shared by the first dielectric substrate 1, the metal layer 2, and the second dielectric substrate 3). At an incident angle of 0°, the -3dB passband of this structure is 4.04-5.69GHz and 17.10-24.91GHz, with a frequency ratio of 4.3; at an incident angle of 30°, the -3dB passband is 3.93-5.83GHz and 16.63-24.13GHz; and at an incident angle of 60°, the -3dB passband is 3.33-6.43GHz and 15.19-23.72GHz. As the incident angle increases, the bandwidth of the first passband gradually increases, while the second passband shifts slightly to the left.

[0046] Specific Implementation Case 2: Unlike Specific Implementation Case 1, the thickness of the first dielectric substrate 1 and the second dielectric substrate 3 is 0.1-2mm, while the rest is the same as in Specific Implementation Case 1.

[0047] Specific Implementation Case 3: Unlike Specific Implementation Case 1, the dielectric constant of the first dielectric substrate 1 and the second dielectric substrate 3 is 2-5, while the rest are the same as in Specific Implementation Cases 1-2.

[0048] Specific implementation case 4: Unlike specific implementation case 1, the thickness of metal layer 2 is 0.015-0.050mm, while the rest is the same as specific implementation cases 1-3.

[0049] Specific Implementation Case 5: Unlike Specific Implementation Case 1, the material of metal layer 2 is gold, silver or aluminum, while the rest is the same as in Specific Implementation Cases 1-4.

[0050] Specific Implementation Case 6: Unlike Specific Implementation Case 1, the three patches of metal layer 2 are isosceles triangles, ">" shapes, or "<" shapes, while the rest are the same as in Specific Implementation Cases 1-5.

[0051] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0052] In the description of this application, it should be noted that the terms "upper," "lower," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Unless otherwise expressly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two elements. For those skilled in the art, the specific meaning of the above terms in this application can be understood according to the specific circumstances.

[0053] It should be noted that in this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0054] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A high-ratio dual-bandpass selective surface structure with stable angle, characterized in that, It is composed of multiple identical regular hexagonal FSS units arranged in a periodic equilateral triangle pattern. Each of the FSS unit structures includes, from top to bottom, the following: a first dielectric substrate (1), a metal layer (2), and a second dielectric substrate (3); The metal layer (2) consists of, from the outside to the inside: a hexagonal ring (21), three long strips (22) of the same size, and three patches of the same size. The three patches are distributed in a rotationally symmetrical manner about the center of the hexagonal ring (21). The three patches are connected to the hexagonal ring (21) through the three long strips (22) respectively. The patch is a rhombus-shaped patch (23), the extension of the shorter diagonal of each rhombus-shaped patch (23) passes through the center of the hexagonal ring (21), the angle between the shorter diagonals of two adjacent rhombus-shaped patches (23) is 120°, and three elongated branches (22) connect the three rhombus-shaped patches (23) to the hexagonal ring (21) along the shorter diagonals of the three rhombus-shaped patches (23); or, The patch is an isosceles triangle, ">", or "<" shaped patch, and the center line of the isosceles triangle, ">", or "<" shaped patch passes through the center of the hexagonal ring (21).

2. The angle-stable, high-ratio dual-bandpass selective surface structure as described in claim 1, characterized in that, The outer side length of the hexagonal ring (21) of the metal layer (2) is 4 mm, and the inner side length is 3.85 mm.

3. The angle-stable, high-ratio dual-bandpass selective surface structure as described in claim 2, characterized in that, The diamond patch (23) of the metal layer (2) has a side length of 1.88 mm and a gap width of 0.2 mm between two adjacent diamond patches (23); the width of the three elongated branches (22) in the metal layer (2) is 0.9 mm.

4. The angle-stable, high-ratio dual-bandpass selective surface structure as described in any one of claims 1 to 3, characterized in that, The first operating frequency band is adjusted by adjusting the gap size between adjacent patches in the metal layer (2).

5. The angle-stable, high-ratio dual-bandpass selective surface structure as described in claim 4, characterized in that, The second operating frequency band is adjusted by adjusting the width of the elongated branch (22) in the metal layer (2) and the side length of the patch (23).

6. The angle-stable, high-ratio dual-bandpass selective surface structure as described in claim 5, characterized in that, The material and size of the second dielectric substrate (3) are exactly the same as those of the first dielectric substrate (1).

7. The angle-stable, high-ratio dual-bandpass selective surface structure as described in claim 6, characterized in that, The first dielectric substrate (1) has a thickness of 0.1-2 mm, a dielectric constant of 2-5, and a loss tangent of 0.

008.

8. The angle-stable, high-ratio dual-bandpass selective surface structure as described in claim 7, characterized in that, The first dielectric substrate (1) has a thickness of 0.5 mm and a dielectric constant of 3.

5.

9. The angle-stable, high-ratio dual-bandpass selective surface structure as described in claim 8, characterized in that, The metal layer (2) is made of copper and has a thickness of 0.015-0.050 mm.

10. The angle-stable, high-ratio dual-bandpass selective surface structure as described in claim 9, characterized in that, The thickness of the metal layer (2) is 0.015 mm.

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