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

Abstract

The invention relates to a dual-polarization high-selectivity frequency selective surface based on a three-dimensional slot line structure, which comprises a plurality of printed circuit boards which are transversely and longitudinally staggered to form a grid shape, each printed circuit board is formed by a plurality of basic unit arrays, and each basic unit comprises a patch unit, a dielectric substrate and a metal micro-unit which are sequentially stacked; the patch unit comprises two interactive patches, each interactive patch comprises a fixed strip and at least one interactive strip arranged at the end part of the fixed strip, and the interactive strips of different interactive patches are arranged in a staggered manner; each metal micro unit comprises a metal foil, a main groove line and a side groove line which are parallel to each other are etched on the metal foil, each main groove line is composed of two opposite T-shaped groove lines, each T-shaped groove line comprises a long groove strip and a short groove strip, the two short groove strips of each T-shaped groove line are oppositely arranged, and a rectangular groove with the width larger than that of each side groove line is formed in the middle section of each side groove line; the method is better in selectivity and angle stability.

Description

Technical Field

[0001] The 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 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, polarizers, etc. Traditional two-dimensional frequency selective surfaces are usually composed of metal patches or aperture units arranged in a certain period on a dielectric substrate. For example, the common rectangular patch frequency selective surface exhibits passband or stopband characteristics at a specific frequency, and the filtering function of electromagnetic waves of different frequencies is achieved by changing the size, shape and period of the patch. However, there are some limitations of traditional two-dimensional frequency selective surfaces, such as narrow passband, poor passband selectivity, and unstable oblique incidence performance. The use of multi-layer structures for cascading can improve the filtering response to meet the requirements of bandwidth or selectivity, but this often results in a large overall thickness and weight of the structure, which is not easy to conform.

[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 working wavelength, resulting in 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 edge of the passband 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 its 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] The embodiment of the present invention provides 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 sequentially stacked; The patch unit includes two interactive patches, each of which includes a fixed strip and at least one interactive strip arranged at the end of the fixed strip, and the interactive strips of different interactive patches are arranged alternately with each other; The metal micro unit comprises a metal foil, on which parallel main groove lines and side groove lines are etched, wherein the main groove line is composed of two opposite T-shaped groove lines, wherein the T-shaped groove line comprises a long groove bar and a short groove bar, wherein the two short groove bars of the T-shaped groove line are arranged opposite to each other, and a rectangular groove having a width greater than that of the side groove line is arranged in the middle section of the side groove line; The interactive patch and the metal micro-unit are connected via two conductors penetrating the dielectric substrate.

[0007] Optionally, the number of the interactive strips is 2, a connecting strip is provided at the other end of the fixed strip, a fixed patch is provided at the other end of the connecting strip, and the fixed patch is connected to a conductor.

[0008] 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.

[0009] Optionally, one end of the conductor is arranged on a side of the T-slot line.

[0010] 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.

[0011] Optionally, two accommodating through holes are provided on the side of the spacing area, and one end of the conductor is located in the accommodating through hole.

[0012] 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.

[0013] Optionally, one grid of the grid is formed by four printed circuit boards that are staggered in a horizontal and vertical manner, and each printed circuit board of one grid has a basic unit. 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.

[0014] 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.

[0015] The function of the above structure is briefly described. The geometric shapes of the printed circuit board placed along the xz plane and the printed circuit board placed along the yz plane are exactly the same and orthogonal to each other, so as to achieve a stable frequency response when irradiated by electromagnetic waves of different polarizations. Taking the electromagnetic wave incident with TE polarization as an example, the direction of the electric field vector is the y-axis direction, and a voltage difference will be generated on both sides of the main slot line and the side slot line in the printed circuit board placed along the yz plane, forming a specific electromagnetic induction. The incident plane wave is converted into a guided wave and enters the main slot line and the side slot line, so that the electromagnetic wave can effectively pass through the entire structure at a specific passband frequency, and the electromagnetic wave is reflected at other frequencies. The combined shape of the main slot line and the patch unit attached to the lower surface of the dielectric substrate is used to form a broadband transmission characteristic and a transmission zero point higher than the passband. The side slot line is used to form a transmission zero point lower than the passband and a wide stopband characteristic of the low frequency band. The entire three-dimensional slot line structure makes the frequency response of the passband edge steeper in the case of dual polarization through the carefully designed slot line and metal patch shape and size, thereby improving the 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.

[0016] The beneficial effects of the present invention are that the dual-polarized highly selective three-dimensional frequency selective surface in the present invention can enable the antenna to maintain good radiation characteristics in the frequency band of 5.2GHz to 7.75GHz, and can freely send and receive communications; it has a steep roll-off characteristic at the edge of the passband, and can effectively suppress interference from adjacent frequency bands; when the incident angle reaches 60°, the filtering performance is still stable, and can adapt to signals with different incident angles to ensure 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.

[0017] 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 a plurality of strips interacting with each other, and a side slot line is arranged on the side of the main slot line. The side slot line is simpler than the main slot line, and a rectangular slot line with a width greater than the side slot line is arranged in the middle of the side slot line. Compared with a single slot line, or with a metal patch arranged in the shape of a slot line, the structure of the present invention has higher selectivity and angular stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the overall structure of an embodiment of the present invention.

[0019] Figure 2 This is a schematic diagram of the structure of a 2*2 grid.

[0020] Figure 3 It is a schematic diagram of the structure of the basic unit placed along the yz plane.

[0021] Figure 4 It is a schematic diagram of the structure of a metal microunit attached to a dielectric substrate.

[0022] Figure 5 It is a schematic diagram of the structure of the patch unit attached to the dielectric substrate.

[0023] Figure 6 The S parameter simulation results varying with frequency are obtained in the microwave studio of the three-dimensional high-frequency electromagnetic simulation software CST when the TE wave and the TM wave are respectively incident vertically on the dual-polarization highly selective three-dimensional frequency selective surface within a frequency range of 2 GHz to 12 GHz, wherein the S parameter simulation results include the simulation results of the transmission coefficient (i.e., S21) and the reflection coefficient (i.e., S11); 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.

[0024] Figure 7 is the transmission coefficient (i.e., S21) measured when the TE wave irradiates the three-dimensional frequency selective surface at different angles; where the incident angle They are , , and .

[0025] Figure 8 is the transmission coefficient (i.e., S21) measured when the TM wave irradiates the three-dimensional frequency selective surface at different angles; where the incident angle They are , , and .

[0026] 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; 16 conductor I, 17 conductor II, 18 main slot line, 19 side slot line, 20 fixed patch, 21 connecting strip, 22 fixed strip, 23 alternating strip, 231 alternating strip I, 232 alternating strip II, 233 alternating strip III, 234 alternating strip IV, 24 accommodating through hole; 181 long slots, 182 short slots, 191 rectangular slots. DETAILED DESCRIPTION

[0027] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0028] Example 1 A dual-polarization high-selectivity frequency selective surface based on a three-dimensional slot line structure, comprising a plurality of printed circuit boards 1 that are staggered horizontally and vertically to form a grid shape, wherein the printed circuit board is formed by an array of a plurality of basic units 11, wherein the basic unit 11 comprises a patch unit 12, a dielectric substrate 13 and a metal micro unit 14 that 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 disposed at the end of the fixed strip 22, and the interactive strips 23 of different interactive patches are arranged alternately with each other; The metal micro unit 14 includes a metal foil 15, on which a parallel main groove line 18 and a side groove line 19 are etched, 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 oppositely, and the middle section of the side groove line 19 is provided with a rectangular groove 191 whose width is greater than that of the side groove line 19; The interactive patch and the metal micro-unit 14 are connected via two conductors penetrating the dielectric substrate 13 .

[0029] 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.

[0030] The printed circuit board is formed by an array of multiple basic units 11, each grid is surrounded by 4 printed circuit boards, and each printed circuit board is provided with a basic unit, which is rectangular, 12-16 mm long, and 6-8 mm wide.

[0031] 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.

[0032] The interactive strip 23 is perpendicular to the fixed strip 22 , the fixed strip 22 is perpendicular to the connecting strip 21 , and the fixed patch 20 is rectangular, and a through hole for accommodating a conductor is provided in the rectangle.

[0033] The interactive patch of the present invention is composed of metal patches.

[0034] The patch unit 12 includes a fixed patch 20 with through holes etched therein, a connecting strip 21, a fixed strip 22 and an interactive strip 23 connected in sequence. The fixed patch 20 is square, the connecting strip 21, the fixed strip 22 and the interactive strip 23 are rectangular, the number of the interactive strips 23 is preferably 2-3, more preferably 2, and the plurality of interactive strips are arranged at one end of the fixed strip 22, and the connecting strip 21, the fixed strip 22 and the interactive strip 23 are vertically connected to each other.

[0035] 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.

[0036] 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.

[0037] like Figure 5 As shown, the interactive strip 23 includes four toothed interactive strips I 231, II 232, III 233 and 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.

[0038] One end of the conductor is arranged on a side of the T-slot line.

[0039] 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 at a side of the spacing area.

[0040] 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 .

[0041] 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.

[0042] 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 .

[0043] 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.

[0044] The side groove line 19 is divided into two sections by a rectangular groove 191. The two sections have the same size, with a length of 2 mm to 3 mm and a width of 0.1 mm to 0.3 mm. The rectangular groove 191 has a length of 4 mm to 5 mm and a width of 2 mm to 2.5 mm.

[0045] One grid of the grid is formed by four printed circuit boards 1 that are staggered in a horizontal and vertical manner, and each printed circuit board 1 of the grid has a basic unit 11 .

[0046] Two adjacent printed circuit boards 1 in one grid are provided with metal micro units 14 , and another two adjacent printed circuit boards 1 are provided with patch units 12 .

[0047] 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.

[0048] 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.

[0049] 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.

[0050] The non-conductive material used to make the dielectric substrate 13 in Example 1 is FR4, with 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.

[0051] Example 2 In the high-frequency electromagnetic simulation software CST, when the TE wave and TM wave are incident vertically on the electromagnetic model of the printed circuit board 1, the simulation results of the S parameters varying with frequency are obtained, including the transmission coefficient S21 and the reflection coefficient S11, as shown in Figure 6 As shown in the figure, it can be seen that the three-dimensional frequency selective surface forms a stable dual-polarization passband in the range of 5.2 GHz to 7.75 GHz, forms a sharp roll-off on both sides of the passband, and at the same time, forms a good stopband suppression performance outside the passband.

[0052] Figure 7 and Figure 8These are the simulation results of the transmission coefficients that vary with frequency when TE waves and TM waves with frequencies in the range of 2-12 GHz are incident on the invented three-dimensional frequency selective surface structure at different angles. As can be seen from the figure, as the incident angle changes from Increase to , the transmission performance remains basically stable and has good filtering characteristics.

[0053] A person 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 concept of 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.

[0054] One or more embodiments of the present application are intended to cover all such substitutions, modifications and variations that fall within the broad scope of the present application. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of one or more embodiments of the present application should be included in the protection scope of the present application.

Claims

1. A dual-polarization high-selectivity frequency selective surface based on a three-dimensional slot line structure, characterized in that: It 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) comprises two interactive patches, wherein the interactive patches comprise a fixed strip (22) and at least one interactive strip (23) arranged at the end of the fixed strip (22), and the interactive strips (23) of different interactive patches are arranged in an alternating manner; The metal micro-unit (14) comprises a metal foil (15), on which parallel main groove lines (18) and side groove lines (19) are etched, the main groove lines (18) are composed of two opposite T-shaped groove lines, the T-shaped groove lines include 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) having a width greater than that of the side groove line (19); The interactive patch and the metal micro-unit (14) are connected via a conductor that penetrates the dielectric substrate (13), and the number of the conductors is two.

2. The dual-polarization high-selectivity frequency selective surface as claimed in claim 1, characterized in that: 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 as claimed in claim 2, characterized in that: 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 being provided in the rectangle.

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

5. The dual-polarization high-selectivity frequency selective surface as claimed in claim 4, characterized in that: 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 as claimed in claim 5, characterized in that: Two accommodating through holes (24) are arranged 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 groove strip (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.

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

9. The dual-polarization high-selectivity frequency selective surface as claimed in claim 8, characterized in that: Two adjacent printed circuit boards (1) of 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 millimeters; the thickness of the metal foil (15) is 0.01-0.02 millimeters.

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