Hexagonal dual-polarization high-selectivity frequency selective surface

Abstract

The hexagonal dual-polarization high-selectivity frequency selective surface comprises a middle filtering layer and two magnetoelectric dipole antennas, and the section of the hexagonal dual-polarization high-selectivity frequency selective surface is hexagonal; the two magnetoelectric dipole antennas have the same structure and are symmetrically arranged relative to the middle filtering layer, the middle filtering layer is a middle metal layer with a central slot, the appearance of the middle metal layer is a regular hexagon, the central slot is hollowed out by a hexagon located in the center, and the middle metal layer is a rectangular metal layer. The six edge grooves extend outwards from the six edges of the hexagonal hollowed-out part respectively, and each edge groove faces one end point of the regular hexagon appearance of the middle metal layer. The middle filtering layer serves as a band-pass filter, electromagnetic waves penetrate through the middle filtering layer during resonance, suppression of low-frequency and high-frequency stop bands is achieved, and meanwhile the middle filtering layer serves as a common ground plane of the two magnetoelectric dipole antennas. According to the invention, the problems of high insertion loss in a wave-transparent window, insufficient out-of-band suppression, over-wide transition zone, poor angle stability and the like of the existing frequency selective surface can be solved.

Description

Technical Field

[0001] The invention belongs to the field of electromagnetic field and microwave technology, and particularly relates to a hexagonal dual-polarization high-selectivity frequency selective surface. Background Art

[0002] High Selective Frequency Selective Surfaces (HFSS) refers to the high selectivity of frequency selective surfaces achieved by introducing resonant cavities, multi-layer cascades, and other methods. High selectivity usually means that the filter response has a flatter passband, steeper sidebands, and no higher-order resonances in a wider frequency band outside the band. It is usually achieved by introducing multiple transmission poles in the passband to improve the passband flatness and introducing transmission zeros at the edge of the passband to achieve sideband jitter cutoff and out-of-band suppression. Highly selective frequency selective surface antenna covers can reduce the impact on the working ability of the in-band antenna and improve the out-of-band stealth performance, which is of great research value.

[0003] Patent CN114498061A discloses a frequency selective surface unit, a frequency selective surface and a frequency selection method. The high-selectivity frequency selective surface proposed in this patent has the advantages of wide passband, low profile, dual-polarization application, etc., but the disadvantages are that the stopband bandwidth is narrow and only the TE polarization has angle stability.

[0004] In the article “Filtenna-Filter-Filtenna-Based FSS With Simultaneous Wide Passbandand Wide Out-of-Band Rejection Using Multiple-Mode Resonators”, a quadrilateral FA-F-FA-based high-selectivity frequency selective surface is proposed. The advantages of its FSS structure are wide passband and stopband and narrow transition band, and the disadvantage is that it only has angular stability of TE polarization.

[0005] There are many high-selectivity frequency selective surfaces currently under research, but there are still problems such as high insertion loss in the wave-transmitting window, insufficient out-of-band suppression, and poor angle stability, resulting in the performance of current high-selectivity frequency selective surfaces to be improved. Summary of the invention

[0006] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a hexagonal dual-polarization high-selectivity frequency selective surface, in order to solve one or all of the problems of the existing frequency selective surface, such as high insertion loss in the wave transmission window, insufficient out-of-band suppression, too wide transition band, poor angle stability, etc.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] A hexagonal dual-polarization high-selectivity frequency selective surface, comprising a middle filter layer and two magneto-electric dipole antennas, with a hexagonal cross section;

[0009] The two magnetoelectric dipole antennas have the same structure and are symmetrically arranged about an intermediate filter layer. The intermediate filter layer is an intermediate metal layer with a central slot. The shape of the intermediate metal layer is a regular hexagon. The central slot consists of a hexagonal hollow located in the center and six side slots extending outward from the six sides of the hexagonal hollow, and each side slot faces an end point of the regular hexagonal shape of the intermediate metal layer. The intermediate filter layer acts as a bandpass filter, which transmits electromagnetic waves and suppresses low-frequency and high-frequency stopbands when in resonance, and at the same time serves as a common ground plane for the two magnetoelectric dipole antennas.

[0010] In one embodiment, the two magnetoelectric dipole antennas are antenna one and antenna two, antenna one includes a top metal layer, and antenna two includes a bottom metal layer. The top metal layer and the bottom metal layer have the same shape and structure, both of which are hexagons composed of six completely identical isosceles triangular metal patches. There is a first gap between adjacent isosceles triangular metal patches on the same horizontal plane, and the two isosceles triangular metal patches on the same projection plane are connected by a metal column, and the metal column passes through the middle metal layer.

[0011] In one embodiment, the top metal layer is located on the upper surface of the hexagonal first dielectric layer, the bottom metal layer is located on the lower surface of the hexagonal third dielectric layer, and there are second gaps of equal size between the six isosceles triangular metal patches constituting the top metal layer and the edge of the first dielectric layer, and between the six isosceles triangular metal patches constituting the bottom metal layer and the edge of the third dielectric layer.

[0012] In one embodiment, the intermediate metal layer is located on the lower surface of the first dielectric layer or the upper surface of the hexagonal second dielectric layer, and the first dielectric layer, the second dielectric layer and the third dielectric layer have the same shape and size, and their projections are opposite.

[0013] In one embodiment, the first dielectric layer has the same relative dielectric constant as the third dielectric layer, and is different from the relative dielectric constant of the second dielectric layer; the first dielectric layer has the same loss tangent as the third dielectric layer, and is different from the loss tangent of the second dielectric layer.

[0014] In one embodiment, a metal ring is disposed in each of the six side grooves, and the intermediate metal layer is composed of a metal sheet obtained by performing a center groove, edge holes, and end holes on a hexagonal metal block, and the metal ring;

[0015] The metal ring is connected to the metal sheet, the edge openings are respectively provided at the midpoints of the six sides of the hexagonal metal block, and the end point openings are respectively provided at the six end points of the hexagonal metal block.

[0016] The sizes of the opening 1 and the opening 2 are different. The opening 1 and the opening 2 introduce new transmission zero points at high frequencies to enhance the out-of-band suppression effect of the high-frequency stopband.

[0017] In one embodiment, the opening 1 and the opening 2 are both rectangular, the length of the opening 1 is smaller than the length of the opening 2, and the width is smaller than the width of the opening 2.

[0018] In one embodiment, six circular openings are formed on the metal sheet, each of which is located at a line connecting the center of the hexagonal metal block and the center of opening one, and the circular openings are used for metal columns to pass through to connect two magnetoelectric dipole antennas.

[0019] In one embodiment, the metal ring is composed of five metal strips connected in sequence, wherein metal strip one, metal strip three and metal strip five are parallel and perpendicular to metal strip two and metal strip four, and are located on the same side of metal strip two, and metal strip two and metal strip four are located on the same side of metal strip three;

[0020] The lengths of the metal strips 3 and 5 are equal and less than the length of the metal strip 1, and the length of the metal strip 4 is less than the length of the metal strip 2;

[0021] One end of the metal strip one is connected to the metal sheet, and the other end is connected to the metal strip two, the metal strip three, the metal strip four and the metal strip five in sequence. The end of the metal strip five is connected to the metal strip two and is spaced apart from the metal strip one.

[0022] In one embodiment, the metal strip 1 is vertically connected to the metal sheet, that is, the metal strip 1 is vertically connected to the edge groove where it is located.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] First, compared with the general antenna-filter-antenna type high-selectivity frequency selective surface based on magnetoelectric dipole, the present invention adopts a hexagonal structure as a whole, which can achieve the angle stability of TE and TM dual polarization. Specifically, when the TM wave is obliquely incident, the antenna-filter-antenna type high-selectivity frequency selective surface based on magnetoelectric dipole with a quadrilateral structure will excite common mode resonance in the passband, or excite differential mode resonance in the high-frequency stopband, thereby causing the performance of the passband and stopband to deteriorate, that is, the transmission zero point appears in the passband or the transmission pole appears in the stopband. The hexagonal structure can greatly suppress the common mode resonance in the passband or the differential mode resonance in the high-frequency stopband, thereby achieving the angle stability of TE and TM dual polarization.

[0025] Secondly, compared with the general high-selectivity frequency selective surface, the present invention introduces two types of through holes on the edge. Since the high-order resonance in the high-frequency stopband affects the high-frequency stopband suppression effect, two high-order resonance frequency points appear in the front and back, so two openings of different sizes are made to generate transmission zeros at two different frequency points, which respectively suppress the high-order resonances of the two frequency points, thereby enhancing the high-frequency out-of-band suppression effect and making the structure have better out-of-band suppression and a wider stopband.

[0026] Third, compared with the general high-selectivity frequency selective surface, the present invention has a narrower transition band, a wider passband and a lower insertion loss. The narrower transition band is achieved by controlling the position of the low-frequency transmission zero point generated by the magnetoelectric dipole and the high-frequency transmission zero point generated by the "e"-shaped metal ring in the middle layer, and the wider passband and lower insertion loss are achieved by exciting the four modes of the magnetoelectric dipole antenna through multi-mode resonance technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the overall structure of the high-selectivity frequency selective surface of the present invention.

[0028] Figure 2 It is a diagram of the top / bottom metal layer structure of the high-selectivity frequency selective surface of the present invention.

[0029] Figure 3 It is a schematic diagram of the dimensions of the top / bottom metal layers of the high-selectivity frequency selective surface of the present invention.

[0030] Figure 4 This is a structural diagram of the second metal layer of the high-selectivity frequency selective surface of the present invention.

[0031] Figure 5 This is a structural diagram of the dimensioning of the second metal layer of the high-selectivity frequency selective surface of the present invention.

[0032] Figure 6 It is a transmission coefficient curve under TE / TM polarization when the incident wave is incident at an incident angle of 0° in Example 1 of the present invention.

[0033] Figure 7 1 is a transmission coefficient curve of Example 1 of the present invention at different incident angles of the incident wave, wherein (a) is the transmission coefficient curve under TE polarization, and (b) is the transmission coefficient curve under TM polarization. DETAILED DESCRIPTION

[0034] The embodiments of the present invention are described in detail below with reference to the accompanying drawings and examples.

[0035] As mentioned above, the existing high-selectivity frequency selective surfaces still face some problems in terms of wave-transmitting window, out-of-band suppression and angle stability. To this end, the present invention provides a hexagonal dual-polarized high-selectivity frequency selective surface based on multi-mode resonance technology, which has a wide passband and a wide stopband, and maintains the polarization stability and angle stability of the passband and the stopband, and is suitable for wireless communication systems in complex electromagnetic environments, such as radars, radomes, aircraft stealth, etc.

[0036] For details, please refer to Figure 1 to Figure 5 As shown, the present invention is a hexagonal dual-polarization high-selectivity frequency selective surface, which includes two magnetoelectric dipole antennas and an intermediate filter layer. The device as a whole is a hexagonal prism structure, that is, the cross-section is hexagonal. Obviously, the hexagon referred to in the present invention is preferably a regular hexagon in actual engineering.

[0037] The two magnetoelectric dipole antennas of the present invention have the same structure and are connected back to back, that is, they are arranged symmetrically about the middle filter layer and connected through the middle filter layer by a connecting component. Thus, an antenna-filter-antenna (AFA) structure is formed. The present invention has an inherent high-pass filter response and a wide working bandwidth by combining the magnetic (M) dipole mode and the electric (E) dipole mode through two back-to-back magnetoelectric dipole antennas and a ground plane embedded in the filter. The broadband out-of-band suppression of the low and high bands is controlled by the central slot of the middle filter layer and six rotationally symmetrical closed "e"-shaped rings. In addition, two through holes of different sizes form an additional "LC" series resonance to eliminate the high-order mode resonance to further enhance the high-frequency out-of-band suppression. The ground plane also plays a vital role in the impedance matching of the FSS.

[0038] The intermediate filter layer of the present invention is an intermediate metal layer 13 with a central slot. The outer shape of the intermediate metal layer 13 is a regular hexagon. The central slot is located at the center of the regular hexagon. Its shape is similar to the shape of a snowflake, and is composed of a hexagonal hollow located in the center and six side slots extending outward from the six sides of the hexagonal hollow. Specifically, it can be formed by rotating a rectangular slot co-centered with the intermediate metal layer 13 around the center by 60°, 120°, and 180°. The angle definition here is based on the upper and lower sides of the regular hexagonal hollow as the 0° reference, that is, each side slot is respectively facing an end point of the regular hexagonal outer shape of the intermediate metal layer 13. In other words, each end point of the regular hexagonal outer shape corresponds to the midpoint of each side of the hexagonal hollow.

[0039] According to the above structure, the middle filter layer acts as a bandpass filter, which can transmit electromagnetic waves and suppress low-frequency and high-frequency stopbands when resonating. At the same time, the filter acts as a common ground plane for two magnetoelectric dipole antennas, and plays an important role in the impedance matching of the antenna. Therefore, the present invention can achieve transmission characteristics with both wide passband and wideband external suppression, and maintain the polarization stability of the resonant frequency and the angle stability of dual polarization, and is suitable for wireless communication systems in complex electromagnetic environments, and can be applied to antenna covers.

[0040] In a further embodiment of the present invention, the two magnetoelectric dipole antennas are antenna one and antenna two. Figure 1 to Figure 5 As shown, antenna 1 includes a top metal layer 11, and antenna 2 includes a bottom metal layer 16. The top metal layer 11 and the bottom metal layer 16 have the same shape and structure, both of which are hexagons composed of six identical isosceles triangular metal patches, that is, Figure 2 The patch one 111, patch two 112, patch three 113, patch four 114, patch five 115 and patch six 116 are all symmetrical in center. On the same horizontal plane, that is, in the top metal layer 11 or the bottom metal layer 16, there is a first gap 117 between two adjacent isosceles triangular metal patches, and the two patches of the top metal layer 11 and the bottom metal layer 16 on the same projection plane are tightly connected to the upper and lower surfaces of a metal column 17, and the metal column 17 passes through the middle metal layer 13. In the present invention, the upper half of the metal column 17 and the top metal layer 11 constitute the antenna one, and the lower half of the metal column 17 and the bottom metal layer 16 constitute the antenna two.

[0041] By adopting the above-mentioned patch combination method, the preliminary design of the back-to-back hexagonal magnetoelectric dipole antenna was completed, realizing the basic functions of the receiving antenna-transmitting antenna.

[0042] In a further embodiment of the present invention, dielectric layers are designed for the top metal layer 11 and the bottom metal layer 16, respectively. Figure 1 to Figure 5 As shown, the top metal layer 11 is located on the upper surface of the first dielectric layer 12, and the bottom metal layer 16 is located on the lower surface of the third dielectric layer 15. The cross-sections of the first dielectric layer 12 and the third dielectric layer 15 are obviously hexagonal, and their cross-sectional dimensions are larger than the cross-sectional dimensions of the top metal layer 11 and the bottom metal layer 16. Therefore, between the six patches of the top metal layer 11 and the edge of the first dielectric layer 12, and between the six patches of the bottom metal layer 16 and the edge of the third dielectric layer 15, second gaps 118 of equal size are formed.

[0043] Since the frequency selective surface is a periodic structure, the second gap 118 can separate adjacent magneto-electric dipole units, so that the frequency selective surface can work normally.

[0044] In a further embodiment of the present invention, the intermediate metal layer 13 can be directly arranged on the lower surface of the first dielectric layer 12, or a second dielectric layer 14 can be added thereto and arranged on the upper surface of the second dielectric layer 14. Obviously, the cross section of the second dielectric layer 14 is also hexagonal. When the intermediate metal layer 13 is arranged on the lower surface of the first dielectric layer 12, the intermediate metal layer 13 is directly connected to the first dielectric layer 12 without an air layer in between.

[0045] In this embodiment, the intermediate metal layer 13 is arranged on the upper surface of the second dielectric layer 14. At this time, the lower surface of the second dielectric layer 14 is in direct contact with the third dielectric layer 15. The first dielectric layer 12, the second dielectric layer 14 and the third dielectric layer 15 have the same shape and size, and their projections are relative. The first dielectric layer 12 and the third dielectric layer 15 have the same relative dielectric constant and the same loss tangent. However, the relative dielectric constant of the second dielectric layer 14 is different from that of the first dielectric layer 12 and the third dielectric layer 15, and the loss tangent is different from that of the first dielectric layer 12 and the third dielectric layer 15.

[0046] In this embodiment, a second dielectric layer 14 is added, and the intermediate metal layer 13 is arranged on the upper surface thereof. The characteristic is that the intermediate metal layer 13 is directly connected to the second dielectric layer 14 without an air layer in between.

[0047] In a further embodiment of the present invention, again referring to Figure 1 to Figure 5 As shown, a metal ring 135 is respectively arranged in the six side grooves. At this time, the intermediate metal layer 13 is composed of a metal sheet 136 obtained by performing center slotting, edge hole opening and end point hole opening on the hexagonal metal block, and the metal ring 135. Among them: the metal ring 135 is connected to the metal sheet 136, the edge hole opening refers to the opening 1 131 being respectively arranged at the midpoint position of the six sides of the hexagonal metal block, and the end point hole opening refers to the opening 2 132 being respectively arranged at the six end points of the hexagonal metal block. In the present invention, the opening 131 and the opening 2 132 have different sizes, and the opening 131 and the opening 2 132 introduce new transmission zeros at high frequencies, further enhancing the out-of-band suppression effect of the high-frequency stopband.

[0048] The metal ring 135 has two functions. One is to introduce a transmission zero point close to the passband in the high-frequency stopband, enhance the high-frequency out-of-band suppression effect and shorten the transition band range from the passband to the high-frequency stopband to improve selectivity. The other is to generate a fundamental transmission mode and participate in the construction of a flat passband of the frequency selection surface. Since the high-order resonance in the high-frequency stopband affects the high-frequency stopband suppression effect, firstly, a transmission zero point is constructed at this high-order resonance through the opening 2 132 to suppress this high-order resonance; but it is found that after suppressing this high-order resonance, a new high-order resonance is generated at another frequency point, and the transmission zero point is continued to be constructed at the newly generated high-order resonance through the opening 1 131 to complete the final design. Therefore, the opening 1 131 and the opening 2 132 are used to construct a transmission zero point, suppress high-order resonance, and thus enhance the high-frequency out-of-band suppression effect. In addition, the opening 1 131 and the opening 2 132 can also improve the impedance matching of the antenna 1 and the antenna 2 and reduce the insertion loss of the passband.

[0049] The first opening 131 and the second opening 132 of the present invention are both in a rectangular shape, and the first opening 131 is smaller than the second opening 132. Specifically, its length is smaller than the length of the second opening 132, and its width is smaller than the width of the second opening 132. Since the high-order resonance in the high-frequency stopband affects the high-frequency stopband suppression effect, two high-order resonance frequency points appear before and after, so two different sizes of openings are made to generate transmission zeros at two different frequency points, respectively suppressing the high-order resonance of the two frequency points, thereby enhancing the high-frequency out-of-band suppression effect.

[0050] In a further embodiment of the present invention, again referring to Figure 1 to Figure 5 As shown, six circular openings 133 are formed on the metal sheet 136, each of which is located on the line connecting the center of the hexagonal metal block and the center of the opening 131. One circular opening 133 is used for a metal column 17 to pass through, thereby connecting two magnetoelectric dipole antennas.

[0051] In a further embodiment of the present invention, again referring to Figure 1 to Figure 5 As shown, the metal ring 135 is shaped like the letter "e", and is specifically composed of five metal strips, namely, metal strip 1 1351, metal strip 2 1352, metal strip 3 1353, metal strip 4 1354 and metal strip 5 1355, which are connected in sequence. In the order of connection, the adjacent metal strips are perpendicular to each other. That is, metal strip 1 1351, metal strip 3 1353 and metal strip 5 1355 are parallel and perpendicular to metal strip 2 1352 and metal strip 4 1354. Moreover, metal strip 1 1351, metal strip 3 1353 and metal strip 5 1355 are located on the same side of metal strip 2 1352, and metal strip 2 1352 and metal strip 4 1354 are located on the same side of metal strip 3 1353. The lengths of metal strip 3 1353 and metal strip 5 1355 are equal and less than the length of metal strip 1 1351, and the length of metal strip 4 1354 is less than the length of metal strip 2 1352.

[0052] One end of the metal strip 1351 is connected to the metal sheet 136, which can be specifically connected vertically, that is, the metal strip 1351 is vertically connected to the side groove in which it is located. If the description form of the rectangular slot is used, the metal strip 1351 is perpendicular to the long side 1342 of the rectangular slot in which it is located, and parallel to the short side 1341 of the rectangular slot in which it is located. The other end of the metal strip 1351 is connected to the metal strip 2 1352, the metal strip 3 1353, the metal strip 4 1354 and the metal strip 5 1355 in sequence, and the end of the metal strip 5 1355 is connected to the metal strip 2 1352 and has a spacing with the metal strip 1 1351.

[0053] There are a total of 6 "e"-shaped metal rings 135 used in this embodiment, with exactly the same structure. They can be formed by an "e"-shaped metal ring cocentric with the intermediate metal layer 13 and rotating around the center by 60°, 120°, 180°, 240°, or 300°.

[0054] In general, in a detailed embodiment of the present invention, from top to bottom it mainly includes a top metal layer 11, a first dielectric layer 12, an intermediate metal layer 13, a second dielectric layer 14, a third dielectric layer 15, a bottom metal layer 16 and a metal column 17. The bottom metal layer 16 is located on the lower surface of the third dielectric layer 15 and is exactly the same as the top metal layer 11. The radius of the metal column 17 is the radius of the circular opening 131, and the top metal layer 11 and the bottom metal layer 16 are connected through the circular opening 131.

[0055] Among them, the first dielectric layer 12 and the third dielectric layer 15 adopt a regular hexagonal structure of Rogers RO4350 with a relative dielectric constant of 3.66, with a side length W1=7.5mm, a thickness H1=2.9mm of the first dielectric layer 12, and a thickness H3=2.9mm of the third dielectric layer 15. The second dielectric layer 14 adopts a regular hexagonal structure of Rogers RO4003 with a relative dielectric constant of 3.55, with a side length W1=7.5mm, and a thickness H2=0.1mm of the second dielectric layer 14.

[0056] The height a1 of the isosceles triangle patch of the top metal layer 11 is 6.065 mm, the distance from the vertex to the edge of the hexagonal dielectric plate is a2 = 6.195 mm, the length of the bottom side is W2 = 7 mm, and the width of the first gap 117 is W3 = 0.3 mm.

[0057] The rectangular slot of the middle metal layer 13 is Lr=6.8mm, Wr=2mm, the width of each metal strip in the metal ring 135 is W4=0.2mm, the lengths of metal strip one 1351, metal strip two 1352, metal strip three 1353, metal strip four 1354 and metal strip five 1355 are L1=1.85mm, L2=1.51mm, L3=1.7mm, L4=1.15mm, L5=1.5mm respectively, the size of opening one 131 is WS1=1.5mm, LS1=1.8mm, the size of opening two 132 is WS2=1.6mm, LS2=2.3mm, the diameter of the circular opening 133 is Dvia=1.4mm, and the distance between two symmetrical circular openings 133 is Dele=7mm.

[0058] The structure of the bottom metal layer 16 is completely the same as that of the top metal layer 11 .

[0059] The effect of the present invention can be further illustrated by the following simulation:

[0060] 1. Simulation software:

[0061] Commercial Ansoft HFSS19.0 software.

[0062] 2. Simulation content:

[0063] Simulation 1, embodiment 1 of the present invention, transmission coefficient curve when the incident wave is incident at an incident angle of 0°, simulation results under TE polarization / TM polarization are as follows Figure 6 As shown. Figure 6 It can be seen that Example 1 achieves a -1dB passband of 4.56-7.33 GHz, a -1dB bandwidth of 46.6%, a low-frequency -10dB stopband bandwidth of 0.1-4.35 GHz, a high-frequency -10dB stopband bandwidth of 7.54-17.96 GHz, a relative bandwidth of 175.2%, a low-frequency transition band (-3dB to -10dB) of 0.06 GHz, and a high-frequency transition band (-3dB to -10dB) of 0.12 GHz.

[0064] Simulation 2, transmission coefficient curve of Example 1 of the present invention when the incident wave is incident at different incident angles, the simulation results under TE polarization are as follows Figure 7 As shown in (a), the simulation results under TM polarization are as follows Figure 7 As shown in (b). Figure 7 It can be seen that Example 1 can maintain a good passband (S) within a 30° incident angle under TE polarization. 21 >-3dB), the insertion loss in the band drops to 3.38dB at 45°, but the insertion loss at most frequency points in the passband is still less than 3dB, and the stopband angle stability is good. Under TM polarization oblique incidence, it can 21>-3dB) maintains a good passband within the incident angle of 45°, and the insertion loss in the band drops to 4.64dB at 45°, but the insertion loss of most frequency points in the passband is still less than 3dB. Although the suppression ability outside the band is not as good as that under TE polarization, it can basically achieve a suppression effect of -10dB within 18GHz. Therefore, the proposed FSS can maintain a relatively stable response within the oblique incident angle range of 30°, which enables it to be flexibly applied to various forms of radomes, and both the passband and the stopband have good angular stability.

[0065] The above description is only an embodiment of the present invention and does not constitute any limitation to the present invention. It is obvious that for professionals in this field, after understanding the content and principles of the present invention, it is possible to make various modifications and changes in form and details without departing from the principles and structures of the present invention. However, these modifications and changes based on the ideas of the present invention are still within the scope of the claims and protection of the present invention.

Claims

1. A hexagonal dual-polarization high-selectivity frequency selective surface, characterized in that: It includes a middle filter layer and two magneto-electric dipole antennas, and has a hexagonal cross section; The two magnetoelectric dipole antennas have the same structure and are symmetrically arranged about an intermediate filter layer. The intermediate filter layer is an intermediate metal layer (13) with a central slot. The intermediate metal layer (13) has a regular hexagonal shape. The central slot is composed of a hexagonal hollow located in the center and six side slots extending outward from six sides of the hexagonal hollow, respectively. Each side slot faces an end point of the regular hexagonal shape of the intermediate metal layer (13). The intermediate filter layer acts as a bandpass filter, which transmits electromagnetic waves and suppresses low-frequency and high-frequency stopbands when in resonance, and at the same time acts as a common ground plane for the two magnetoelectric dipole antennas.

2. The hexagonal dual-polarization high-selectivity frequency selective surface according to claim 1, characterized in that: The two magnetoelectric dipole antennas are antenna one and antenna two. Antenna one includes a top metal layer (11), and antenna two includes a bottom metal layer (16). The top metal layer (11) and the bottom metal layer (16) have the same shape and structure, and are both hexagons composed of six identical isosceles triangular metal patches. There is a first gap (117) between adjacent isosceles triangular metal patches on the same horizontal plane. Two isosceles triangular metal patches on the same projection plane are connected by a metal column (17), and the metal column (17) passes through the middle metal layer (13).

3. The hexagonal dual-polarization high-selectivity frequency selective surface according to claim 2, characterized in that: The top metal layer (11) is located on the upper surface of the hexagonal first dielectric layer (12), and the bottom metal layer (16) is located on the lower surface of the hexagonal third dielectric layer (15). There are second gaps (118) of equal size between the six isosceles triangular metal patches forming the top metal layer (11) and the edge of the first dielectric layer (12), and between the six isosceles triangular metal patches forming the bottom metal layer (16) and the edge of the third dielectric layer (15).

4. The hexagonal dual-polarization high-selectivity frequency selective surface according to claim 3, characterized in that: The intermediate metal layer (13) is located on the lower surface of the first dielectric layer (12) or the upper surface of the hexagonal second dielectric layer (14); the first dielectric layer (12), the second dielectric layer (14) and the third dielectric layer (15) have the same shape and size and are projected relative to each other.

5. The hexagonal dual-polarization high-selectivity frequency selective surface according to claim 4, characterized in that: The relative dielectric constant of the first dielectric layer (12) is the same as that of the third dielectric layer (15), and is different from that of the second dielectric layer (14); the loss tangent of the first dielectric layer (12) is the same as that of the third dielectric layer (15), and the loss tangent of the second dielectric layer (14) is different.

6. The hexagonal dual-polarization high-selectivity frequency selective surface according to any one of claims 1 to 5, characterized in that: A metal ring (135) is arranged in each of the six side grooves, and the intermediate metal layer (13) is composed of a metal sheet (136) obtained by performing center groove, edge hole and end hole drilling on a hexagonal metal block, and the metal ring (135); The metal ring (135) is connected to the metal sheet (136), the edge openings are respectively provided at the midpoints of the six sides of the hexagonal metal block as openings one (131), and the end point openings are respectively provided at the six end points of the hexagonal metal block as openings two (132); The sizes of the opening 1 (131) and the opening 2 (132) are different. The opening 1 (131) and the opening 2 (132) introduce a new transmission zero point at high frequency to enhance the out-of-band suppression effect of the high-frequency stop band.

7. The hexagonal dual-polarization high-selectivity frequency selective surface according to claim 6, characterized in that: The opening 1 (131) and the opening 2 (132) are both rectangular, the length of the opening 1 (131) is smaller than the length of the opening 2 (132), and the width is smaller than the width of the opening 2 (132).

8. The hexagonal dual-polarization high-selectivity frequency selective surface according to claim 6, characterized in that: The metal sheet (136) is provided with six circular openings (133), each of which is located at a line connecting the center of the hexagonal metal block and the center of the first opening (131), and the circular openings (133) are used for allowing the metal column (17) to pass through to connect the two magnetoelectric dipole antennas.

9. The hexagonal dual-polarization high-selectivity frequency selective surface according to claim 8, characterized in that: The metal ring (135) is composed of five metal strips connected in sequence, wherein the metal strip one (1351), the metal strip three (1353) and the metal strip five (1355) are parallel and perpendicular to the metal strip two (1352) and the metal strip four (1354), and are located on the same side of the metal strip two (1352), and the metal strip two (1352) and the metal strip four (1354) are located on the same side of the metal strip three (1353); The lengths of the metal strip three (1353) and the metal strip five (1355) are equal and smaller than the length of the metal strip one (1351), and the length of the metal strip four (1354) is smaller than the length of the metal strip two (1352); One end of metal strip one (1351) is connected to the metal sheet (136), and the other end is connected to metal strip two (1352), metal strip three (1353), metal strip four (1354) and metal strip five (1355) in sequence. The end of metal strip five (1355) is connected to metal strip two (1352) and is spaced apart from metal strip one (1351).

10. The hexagonal dual-polarization high-selectivity frequency selective surface according to claim 8, characterized in that: The metal strip 1 (1351) is vertically connected to the metal sheet (136), that is, the metal strip 1 (1351) is vertically connected to the side groove where it is located.

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