Dual-polarization high-selectivity frequency selective surface based on three-dimensional slotline structure

Abstract

The present invention relates to a dual-polarization high-selectivity frequency selective surface based on a three-dimensional slot line structure, comprising a plurality of printed circuit boards that are staggered horizontally and vertically to form a grid shape, wherein the printed circuit board is formed by a plurality of basic unit arrays, wherein the basic unit comprises a patch unit, a dielectric substrate and a metal micro unit that are stacked in sequence; the patch unit comprises two interactive patches, each comprising a fixed strip and at least one interactive strip arranged at the end of the fixed strip, wherein the interactive strips of different interactive patches are staggered with each other; the metal micro unit comprises a metal foil, wherein parallel main slot lines and side slot lines are etched on the metal foil, wherein the main slot line comprises two opposite T-shaped slot lines, wherein the T-shaped slot line comprises a long slot strip and a short slot strip, wherein the two short slot strips of the T-shaped slot line are arranged opposite to each other, and wherein the middle section of the side slot line is provided with a rectangular slot having a width greater than that of the side slot line; the present invention has better selectivity and angular stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of metamaterials and antenna covers, and in particular relates to a dual-polarization high-selectivity frequency selective surface based on a three-dimensional slot line structure. Background Art

[0002] Frequency-selective surfaces (FSSs) are spatial filters that selectively reflect or transmit electromagnetic waves. Due to their excellent filtering properties, they are widely used in radar and antenna systems, including radomes, reflectors, absorbers, and polarizers. Traditional two-dimensional FSSs are typically composed of metal patches or aperture units arranged at a certain period on a dielectric substrate. For example, the common rectangular patch FSS exhibits passband or stopband characteristics at specific frequencies. By varying parameters such as the size and shape of the patches and the period of the units, the filtering function for electromagnetic waves of different frequencies is achieved. However, traditional two-dimensional FSSs have some limitations, such as narrow passbands, poor passband selectivity, and unstable oblique-incidence performance. Cascading multilayer structures can improve the filtering response to meet bandwidth or selectivity requirements, but this often results in a thick and heavy structure that is not easily conformal.

[0003] In recent years, in order to improve the performance of frequency selective surfaces, researchers have begun to explore three-dimensional frequency selective surfaces. Compared with two-dimensional frequency selective surfaces, three-dimensional frequency selective surfaces provide additional degrees of freedom for forming multiple transmission paths. Based on this feature, it becomes easier and more flexible for three-dimensional frequency selective surfaces to introduce transmission zeros and transmission poles at specific frequencies. In addition, the unit size and thickness of the three-dimensional frequency selective surface can be designed to be much smaller than the operating wavelength, thereby producing an angularly stable frequency response. Based on microstrip lines or slot arrays, some three-dimensional frequency selective surfaces with one or more transmission zeros have been proposed, but these zeros are not close to the passband, or are all located on one side of the passband. Its roll-off characteristics at the passband edge are not steep enough, which leads to the inability to effectively screen out the signals in the required frequency band in some application scenarios that require high-precision frequency selection, such as multi-band multiplexing in modern communication systems, and easily causes interference between frequency bands.

[0004] In general, in the current design of two-dimensional and three-dimensional frequency-selective surfaces, it is often difficult to simultaneously take into account performance such as broadband, high selectivity and high angular stability, which greatly limits their scope of application. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a dual-polarization high-selectivity frequency selective surface based on a three-dimensional slot line structure, which has better selectivity and angular stability.

[0006] An embodiment of the present invention provides a dual-polarization high-selectivity frequency selective surface based on a three-dimensional slotline structure, comprising a plurality of printed circuit boards interlaced horizontally and vertically to form a grid. The printed circuit boards are formed by an array of multiple basic units, each of which includes a patch unit, a dielectric substrate, and a metal micro-unit stacked in sequence.

[0007] The patch unit includes two interactive patches, each of which includes a fixed strip and at least one interactive strip arranged at an end of the fixed strip, and the interactive strips of different interactive patches are staggered with each other;

[0008] The metal micro unit includes a metal foil, on which parallel main groove lines and side groove lines are etched. The main groove line is composed of two opposite T-shaped groove lines, and the T-shaped groove line includes a long groove bar and a short groove bar. The two short groove bars of the T-shaped groove line are arranged opposite to each other, and the middle section of the side groove line is provided with a rectangular groove with a width greater than the width of the side groove line.

[0009] The interactive patch and the metal micro unit are connected via two conductors that penetrate the dielectric substrate.

[0010] Optionally, the number of the interactive strips is 2, a connecting strip is provided at the other end of the fixed strip, a fixing patch is provided at the other end of the connecting strip, and the fixing patch is connected to the conductor.

[0011] Optionally, the interactive strips are perpendicular to the fixed strips, the fixed strips are perpendicular to the connecting strips, and the fixed patch is rectangular, with a through hole for accommodating a conductor provided in the rectangle.

[0012] Optionally, one end of the conductor is arranged on a side of the T-slot line.

[0013] Optionally, the area between the short slots of the two T-slot lines is a spacing area, and one end of the conductor is arranged on a side of the spacing area.

[0014] Optionally, two accommodating through holes are provided on a side of the spacer area, and one end of the conductor is located in the accommodating through hole.

[0015] Optionally, the end of the long groove strip is located at the end of the metal foil, one end of the side groove line is located at the end of the metal foil and the other end is located inside the metal foil, and the rectangular groove is located on the side of one of the T-slots.

[0016] Optionally, one grid of the grid is formed by four printed circuit boards staggered in a horizontal and vertical direction, and each printed circuit board in one grid has a basic unit.

[0017] Optionally, two adjacent printed circuit boards in a grid are provided with metal micro units, and another two adjacent printed circuit boards are provided with patch units.

[0018] Optionally, the thickness of the dielectric substrate is 0.5-0.7 mm; the thickness of the metal foil is 0.01-0.02 mm.

[0019] To briefly explain the function of the above structure, the geometric shapes of the printed circuit boards (PCBs) arranged along the xz plane and the yz plane are identical and orthogonal to each other, achieving a stable frequency response when exposed to incident electromagnetic waves of different polarizations. For example, for TE-polarized electromagnetic waves, with the electric field vector oriented along the y-axis, a voltage difference is generated across the main and side slots in the PCB arranged along the yz plane, generating a specific electromagnetic induction. The incident plane wave is converted into a guided wave and enters the main and side slots, allowing the electromagnetic wave to effectively transmit through the structure at specific passband frequencies while being reflected at other frequencies. The combined shape of the main slot and the patch elements attached to the bottom surface of the dielectric substrate creates broadband transmission characteristics with a transmission zero above the passband. The side slots create a transmission zero below the passband and a wide stopband at low frequencies. Through the carefully designed shape and dimensions of the slots and metal patches, the entire three-dimensional slot structure achieves a steeper frequency response at the passband edge in dual-polarization conditions, improving passband selectivity. At the same time, this structure can maintain relatively stable frequency selection performance under different incident angles because the period of its unit cell is relatively small.

[0020] The beneficial effects of the present invention are as follows: the dual-polarized highly selective three-dimensional frequency selective surface in the present invention enables the antenna to maintain good radiation characteristics within the frequency band of 5.2 GHz to 7.75 GHz, and can freely transmit and receive communications; it has a steep roll-off characteristic at the passband edge, and can effectively suppress interference from adjacent frequency bands; when the incident angle reaches 60°, the filtering performance remains stable, and can adapt to signals with different incident angles, ensuring the reliability of communication; at the same time, it also has good out-of-band suppression performance outside the passband, which can reduce the RCS of the antenna and achieve the stealth purpose of the antenna.

[0021] The main slot line of the present invention is designed to be composed of two T-shaped slot lines, which are connected to the patch unit on the back. The patch unit is formed by the interaction of multiple strips, and side slot lines are provided on the sides of the main slot lines. The side slot lines are simpler than the main slot lines, and a rectangular slot line with a width greater than the side slot line is provided in the middle of the side slot line. Compared with a single slot line, or compared with setting the metal patch in the shape of a slot line, this structure of the present invention has higher selectivity and angular stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the overall structure of an embodiment of the present invention.

[0023] Figure 2 This is a schematic diagram of the structure of a 2*2 grid.

[0024] Figure 3 It is a structural diagram of the basic unit placed along the yz plane.

[0025] Figure 4 It is a schematic diagram of the structure of a metal micro unit attached to a dielectric substrate.

[0026] Figure 5 It is a schematic diagram of the structure of the patch unit attached to the dielectric substrate.

[0027] Figure 6 The frequency-dependent S-parameter simulation results obtained in the microwave studio of CST, a three-dimensional high-frequency electromagnetic simulation software, within a frequency range of 2 GHz to 12 GHz when TE waves and TM waves are respectively incident perpendicularly on the dual-polarization highly selective three-dimensional frequency selective surface. The S-parameter simulation results include the simulation results of the transmission coefficient (i.e., S21) and the reflection coefficient (i.e., S11);

[0028] TE wave (i.e. s wave): has a magnetic field component but no electric field component in the propagation direction, which is called a transverse electric wave. TM wave (i.e. p wave): has an electric field component but no magnetic field component in the propagation direction, which is called a transverse magnetic wave.

[0029] Figure 7 is the transmission coefficient (i.e., S21) measured when the TE wave illuminates the three-dimensional frequency selective surface at different angles; where the incident angle They are 、 、 and .

[0030] Figure 8 is the transmission coefficient (i.e., S21) measured when the TM wave illuminates the three-dimensional frequency selective surface at different angles; where the incident angle They are 、 、 and .

[0031] In the figure, 1 is a printed circuit board, 11 is a base unit, 12 is a patch unit, 13 is a dielectric substrate, 14 is a metal micro unit, and 15 is a metal foil;

[0032] 16 conductor I, 17 conductor II, 18 main slot line, 19 side slot line, 20 fixed patch, 21 connecting strip, 22 fixed strip, 23 interactive strip, 231 interactive strip I, 232 interactive strip II, 233 interactive strip III, 234 interactive strip IV, 24 accommodating through hole;

[0033] 181 long slots, 182 short slots, 191 rectangular slots. DETAILED DESCRIPTION

[0034] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0035] Example 1

[0036] A dual-polarization, highly selective frequency selective surface based on a three-dimensional slotted structure comprises a plurality of printed circuit boards 1 arranged in a grid pattern, the printed circuit board 1 being formed by an array of a plurality of basic units 11, each of which comprises a patch unit 12, a dielectric substrate 13, and a metal micro-unit 14 stacked in sequence.

[0037] The patch unit 12 includes two interactive patches, each of which includes a fixed strip 22 and at least one interactive strip 23 provided at the end of the fixed strip 22. The interactive strips 23 of different interactive patches are arranged in an interlaced manner.

[0038] The metal micro unit 14 includes a metal foil 15, on which parallel main groove lines 18 and side groove lines 19 are etched. The main groove line 18 is composed of two opposite T-shaped groove lines, and the T-shaped groove line includes a long groove bar 181 and a short groove bar 182. The two short groove bars 182 of the T-shaped groove line are arranged opposite to each other. The middle section of the side groove line 19 is provided with a rectangular groove 191 with a width greater than that of the side groove line 19.

[0039] The interactive patch and the metal micro unit 14 are connected via two conductors that penetrate the dielectric substrate 13 .

[0040] The printed circuit boards 1 are staggered horizontally and vertically, that is, a plurality of parallel horizontal printed circuit boards and a plurality of parallel vertical printed circuit boards are perpendicular to each other, and two adjacent parallel horizontal printed circuit boards and two adjacent parallel vertical printed circuit boards form a grid.

[0041] The printed circuit board is formed by an array of multiple basic units 11. Each grid is surrounded by four printed circuit boards. Each printed circuit board is provided with a basic unit. The basic unit is rectangular, 12-16 mm long and 6-8 mm wide.

[0042] The number of the interactive strips 23 is two. The other end of the fixed strip 22 is provided with a connecting strip 21 . The other end of the connecting strip 21 is provided with a fixing patch 20 . The fixing patch 20 is connected to a conductor.

[0043] The interactive strips 23 are perpendicular to the fixed strips 22 , and the fixed strips 22 are perpendicular to the connecting strips 21 . The fixed patch 20 is rectangular, and a through hole for accommodating a conductor is provided in the rectangle.

[0044] The interactive patch of the present invention is composed of metal patches.

[0045] The patch unit 12 comprises a fixed patch 20 with through holes etched therein, a connecting strip 21, a fixed strip 22, and an interactive strip 23, which are connected in sequence. The fixed patch 20 is square, and the connecting strip 21, the fixed strip 22, and the interactive strip 23 are rectangular. The number of interactive strips 23 is preferably 2-3, more preferably 2. The multiple interactive strips are all arranged at one end of the fixed strip 22, and the connecting strip 21, the fixed strip 22, and the interactive strip 23 are connected perpendicularly to each other.

[0046] There are two patch units 12, and the interactive strips 23 of the two patch units 12 are staggered and connected to each other, that is, adjacent to each other. The direction in which the connecting strip 21 protrudes from the fixed strip 22 is the same as the direction in which the interactive strip 23 protrudes from the fixed strip 22.

[0047] The side length of the fixing patch 20 is 0.2 mm to 1 mm; the length of the connecting strip 21 is 0.5 mm to 1 mm, and the width is 0.1 mm to 0.3 mm; the length of the fixing strip 22 is 0.8 mm to 1.5 mm, and the width is 0.1 mm to 0.3 mm.

[0048] like Figure 5 As shown, the interactive strip 23 includes four tooth-shaped interactive strips I 231 , interactive strips II 232 , interactive strips III 233 and interactive strips IV 234 , with a length of 1.6 mm to 2 mm, a width of 0.1 mm to 0.2 mm, and a gap between each interactive strip of 0.1 mm to 0.15 mm.

[0049] One end of the conductor is arranged on a side of the T-slot line.

[0050] The area between the short slots 182 of the two T-slot lines is a spacing area, and one end of the conductor is arranged on a side of the spacing area.

[0051] Two accommodating through holes 24 are provided on the side of the spacer area, and one end of the conductor is located in the accommodating through hole 24 .

[0052] The end of the long groove bar 181 is located at the end of the metal foil 15, one end of the side groove line 19 is located at the end of the metal foil 15, and the other end is located inside the metal foil 15, and the rectangular groove 191 is located on the side of one of the T-shaped grooves.

[0053] like Figure 4 As shown, the main slot line 18 includes two groups of symmetrically placed T-shaped slot lines, and the T-shaped slot line includes a long slot bar 181 and a short slot bar 182. The long slot bar 181 and the short slot bar 182 are perpendicular, and the long slot bar 181 is perpendicular to the middle of the short slot bar 182.

[0054] The length of the long slot 181 is 6 mm to 7 mm, and the width is 0.1 mm to 0.2 mm. The length of the short slot 182 is 0.5 mm to 0.9 mm, and the width is 0.1 mm to 0.2 mm.

[0055] The side groove line 19 is divided into two sections by a rectangular groove 191. The two sections have the same size, 2 mm to 3 mm in length and 0.1 mm to 0.3 mm in width. The rectangular groove 191 is 4 mm to 5 mm in length and 2 mm to 2.5 mm in width.

[0056] Each grid in the grid-like shape is formed by four printed circuit boards 1 that are staggered in the horizontal and vertical directions. Each printed circuit board 1 in a grid has a basic unit 11 .

[0057] Two adjacent printed circuit boards 1 in a grid are both provided with metal micro units 14 , and another two adjacent printed circuit boards 1 are provided with patch units 12 .

[0058] The thickness of the dielectric substrate 13 is 0.5-0.7 mm; the thickness of the metal foil 15 is 0.01-0.02 mm; and the diameter of the accommodating through hole 24 is 0.1-0.5 mm.

[0059] There are two accommodating through holes 24 , and the distance between the centers of the two accommodating through holes 24 is 1 mm to 2 mm.

[0060] The distance between the centers of the main groove line 18 and the side groove line 19 ranges from 2 mm to 3.5 mm.

[0061] In Example 1, the non-conductive material used to make the dielectric substrate 13 is FR4, which has a relative dielectric constant of 4.3 and a dielectric loss of 0.025. The metal foil 15 can be made of any material, such as gold foil, silver foil, or copper foil.

[0062] Example 2

[0063] In the high-frequency electromagnetic simulation software CST, when TE waves and TM waves are incident vertically on the electromagnetic model of the printed circuit board 1, the simulation results of its S parameters varying with frequency are obtained, including the transmission coefficient S21 and the reflection coefficient S11, as shown in the following example: Figure 6 As shown in the figure, the three-dimensional frequency selective surface forms a stable dual-polarization passband in the range of 5.2 GHz to 7.75 GHz, with sharp roll-offs on both sides of the passband, while also achieving good stopband suppression performance outside the passband.

[0064] Figure 7 and Figure 8The simulation results of the transmission coefficients of the invented three-dimensional frequency selective surface structure are shown in Figure 1. Increase to , the transmission performance remains basically stable and has good filtering characteristics.

[0065] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of protection of the present application is limited to these examples. In line with the present application, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of different aspects of one or more embodiments of the present application as described above, which are not provided in detail for the sake of simplicity.

[0066] The one or more embodiments of this application are intended to encompass all such substitutions, modifications, and variations that fall within the broad scope of this application. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of one or more embodiments of this application should be included in the scope of protection of this application.

Claims

1. A dual-polarization high-selectivity frequency selective surface based on a three-dimensional slotline structure, characterized by: The invention comprises a plurality of printed circuit boards (1) which are staggered in a grid-like manner, wherein the printed circuit board is formed by an array of a plurality of basic units (11), wherein the basic units (11) comprise patch units (12), dielectric substrates (13) and metal micro units (14) which are stacked in sequence; The patch unit (12) includes two interactive patches, each of which includes a fixed strip (22) and at least one interactive strip (23) arranged at an end of the fixed strip (22), and the interactive strips (23) of different interactive patches are arranged in a staggered manner. The metal micro unit (14) includes a metal foil (15), and the metal foil (15) is etched with parallel main groove lines (18) and side groove lines (19), the main groove line (18) is composed of two opposite T-shaped groove lines, the T-shaped groove line includes a long groove bar (181) and a short groove bar (182), the two short groove bars (182) of the T-shaped groove line are arranged opposite to each other, and the middle section of the side groove line (19) is provided with a rectangular groove (191) with a width greater than the width of the side groove line (19); The interactive patch and the metal micro unit (14) are connected via a conductor that passes through the dielectric substrate (13), and the number of the conductors is two.

2. The dual-polarization high-selectivity frequency selective surface according to claim 1, wherein: The number of the interactive strips (23) is two, the other end of the fixed strip (22) is provided with a connecting strip (21), the other end of the connecting strip (21) is provided with a fixing patch (20), and the fixing patch (20) is connected to a conductor.

3. The dual-polarization high-selectivity frequency selective surface according to claim 2, wherein: The interactive strip (23) and the fixed strip (22) are perpendicular to each other, the fixed strip (22) and the connecting strip (21) are perpendicular to each other, and the fixed patch (20) is rectangular, with a through hole for accommodating a conductor provided in the rectangle.

4. The dual-polarization high-selectivity frequency selective surface according to any one of claims 1 to 3, wherein: One end of the conductor is arranged on a side of the T-slot line.

5. The dual-polarization high-selectivity frequency selective surface according to claim 4, wherein: The area between the short slots (182) of the two T-slot lines is a spacing area, and one end of the conductor is arranged on the side of the spacing area.

6. The dual-polarization high-selectivity frequency selective surface according to claim 5, wherein: Two accommodating through holes (24) are provided on the side of the spacing area, and one end of the conductor is located in the accommodating through hole (24).

7. The dual-polarization high-selectivity frequency selective surface according to any one of claims 1 to 3, characterized in that: The end of the long slot strip (181) is located at the end of the metal foil (15), one end of the side slot line (19) is located at the end of the metal foil (15), and the other end is located inside the metal foil (15), and the rectangular slot (191) is located on the side of one of the T-slots.

8. The dual-polarization high-selectivity frequency selective surface according to any one of claims 1 to 3, wherein: A grid of the grid-like structure is formed by four printed circuit boards (1) that are staggered in the horizontal and vertical directions, and each printed circuit board (1) in a grid has a basic unit (11).

9. The dual-polarization high-selectivity frequency selective surface according to claim 8, wherein: Two adjacent printed circuit boards (1) in a grid are both provided with metal micro units (14), and another two adjacent printed circuit boards (1) are provided with patch units (12).

10. The dual-polarization high-selectivity frequency selective surface according to any one of claims 1 to 3, characterized in that: The thickness of the dielectric substrate (13) is 0.5-0.7 mm; the thickness of the metal foil (15) is 0.01-0.02 mm.

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