A four-way frequency selective surface structure with high selectivity and its unit structure

Abstract

The present invention discloses a four-way frequency selective surface unit structure with high selectivity, comprising: a first metal layer, a first dielectric substrate, a second metal layer, a first air cavity, a third metal layer, a second dielectric substrate, a second air cavity, a fourth metal layer, a third dielectric substrate, and a fifth metal layer, which are sequentially arranged from top to bottom; the first metal layer and the second metal layer are located on the first dielectric substrate; the third metal layer is located on the upper surface of the second dielectric substrate; the fourth metal layer and the fifth metal layer are located on the third dielectric substrate; the first metal layer and the fifth metal layer are provided with curved cross-slot slits; the second metal layer and the fourth metal layer are both square loop patches; and the third metal layer is a square patch. The present invention also discloses a four-way frequency selective surface structure with high selectivity. The frequency selective surface structure of the present invention realizes four-way bands through a multi-level cascading manner, has high passband selectivity, and a wide band suppression range.

Description

Technical Field

[0001] The present invention belongs to the technical field of electromagnetic fields and electromagnetic waves, and particularly relates to a four-band highly selective frequency selective surface structure and its unit structure. Background Art

[0002] A Frequency Selective Surface (FSS) is a two-dimensional periodic array structure composed of identical metal patch units or aperture units arranged periodically. It can control the transmission or reflection characteristics of incident electromagnetic waves and has selective filtering characteristics, so it is regarded as a spatial filter. The frequency response of the FSS is related to various factors such as the unit structure of the periodic structure, the operating frequency, the material selection and thickness of the dielectric substrate, etc. Since the FSS has frequency selection characteristics for electromagnetic waves, it is applied in fields such as filters, radomes, electromagnetic shielding, antenna systems, and safety protection that cover most of the electromagnetic spectrum.

[0003] With the development of communication technologies, the application scenarios of the electromagnetic environment are becoming increasingly complex. The surge in the demand for bandwidth by various terminal devices has made frequency resources scarce. Existing frequency resources have problems such as low utilization rate and mutual interference of noise signals between various communication systems. In order to meet the large channel capacity transmission of communication and solve the limitations of single-frequency technologies, the multi-frequency technology of antennas has become a research hotspot in recent years. It can achieve simultaneous operation in multiple frequency bands in the same system, which replaces the need for multiple antennas operating in different frequency bands in the past. In addition to reducing processing costs, it also enhances the utilization rate of spectrum resources and the integration degree of communication systems.

[0004] Applying the FSS can separate signals of different frequencies within the operating frequency band, suppress signals outside the operating frequency band, and reduce interference between communication systems. As the detectable frequency range increases, traditional FSSs gradually cannot meet the reflection characteristics of higher frequency bands. Using a highly selective FSS can better distinguish the electromagnetic waves output inside and outside the passband, introduce resonant zeros while ensuring the passband characteristics, improve the bilateral steep drop characteristics, suppress electromagnetic waves in a relatively wide range outside the band, and enable the electromagnetic waves to have better selection ability in the high-frequency range to meet the overall operation of the system. Existing four-band FSS structures generally do not consider the suppression problem of higher frequency bands, and the out-of-band suppression effect is not good, affecting the high selectivity characteristics and unable to meet higher performance requirements. Summary of the Invention

[0005] In order to solve the above problems existing in the prior art, the present invention provides a four-band highly selective frequency selective surface structure and its unit structure. The technical problems to be solved by the present invention are achieved through the following technical solutions:

[0006] The first aspect of the embodiment of the present invention provides a four-way frequency selective surface unit structure with high selectivity, including: a first metal layer, a first dielectric substrate, a second metal layer, a first air cavity, a third metal layer, a second dielectric substrate, a second air cavity, a fourth metal layer, a third dielectric substrate, and a fifth metal layer arranged in sequence from top to bottom;

[0007] The first metal layer and the second metal layer are respectively located on the upper surface and the lower surface of the first dielectric substrate;

[0008] The third metal layer is located on the upper surface of the second dielectric substrate;

[0009] The fourth metal layer and the fifth metal layer are respectively located on the upper surface and the lower surface of the third dielectric substrate;

[0010] The structures of the first metal layer and the fifth metal layer are the same, and both are provided with curved cross-slot slits, and the curved cross-slot slits are centrosymmetric structures with the geometric center of the metal layer where they are located;

[0011] The second metal layer and the fourth metal layer are both square loop patches;

[0012] The third metal layer is a square patch.

[0013] In an embodiment of the present invention, the first metal layer, the first dielectric substrate, the second metal layer, the third metal layer, the second dielectric substrate, the fourth metal layer, the third dielectric substrate, and the fifth metal layer are all centrosymmetric structures.

[0014] In an embodiment of the present invention, the curved cross-slot slit includes four pairs of opposite curved slits, and the two opposite curved slits are centrosymmetric structures with the geometric center of the metal layer where they are located, and two adjacent curved slits can coincide after rotating 90°;

[0015] The inner ends of the four curved slits intersect at the geometric center of the metal layer where they are located.

[0016] In an embodiment of the present invention, the curved slit includes: a first straight slit, a first bent slit, a second straight slit, a second bent slit, a third straight slit, and a third side straight slit;

[0017] One end of the first linear slit penetrates through the edge of the metal layer where it is located, and the other end is connected and communicated with one end of the first bent slit. The other end of the first bent slit is connected and communicated with one end of the second linear slit. The other end of the second linear slit is connected and communicated with one end of the second bent slit. The other end of the second bent slit is connected and communicated with one end of the third linear slit. The other end of the third linear slit is connected and communicated with one end of the third side linear slit. The other end of the third side linear slit intersects with the other end of the third side linear slit of another bent slit.

[0018] The first linear slit, the second linear slit, and the third linear slit are located on the same straight line.

[0019] The first bent slit, the second bent slit, and the third side linear slit are all located on the same side.

[0020] In an embodiment of the present invention, the widths of the first linear slit, the first bent slit, the second linear slit, the second bent slit, the third linear slit, and the third side linear slit are all the same.

[0021] In an embodiment of the present invention, the first dielectric substrate, the second dielectric substrate, and the third dielectric substrate are all square and have the same size and material.

[0022] In an embodiment of the present invention, the first dielectric substrate, the second dielectric substrate, and the third dielectric substrate are all made of F4B-2 material.

[0023] The second aspect of the embodiment of the present invention provides a frequency selective surface structure with four-way band high selectivity, which is characterized by including M×N periodically arranged frequency selective surface unit structures described in the first aspect of the embodiment of the present invention, where M and N are both integers greater than or equal to 1.

[0024] Advantages of the present invention:

[0025] 1. The four-way band high selectivity frequency selective surface structure of the present invention adopts a multi-level cascaded air cavity structure. The bent cross-slot structure on the upper surface of the first dielectric substrate and the lower surface of the third dielectric substrate shows passband characteristics. The third metal layer of the square patch on the upper surface of the second dielectric substrate provides high-frequency suppression characteristics. Four-way bands with transmission poles at 6.54 GHz, 8.41 GHz, 10.80 GHz, and 13.06 GHz are achieved through multi-layer coupling, which can ensure that electromagnetic signals in the corresponding frequency bands are not interfered by other frequency signals.

[0026] 2. The transmission coefficient of the frequency selective surface structure of the present invention between the four passbands is less than -10 dB, achieving an out-of-band rejection of less than -10 dB between the four passbands. In the frequency bands of 0 - 5.5 GHz and 14 - 40 GHz, it has an out-of-band rejection effect of -20 dB. While ensuring the four passbands, it has a wide out-of-band rejection frequency range, strong anti-interference ability, improves the selectivity of the structure, and enhances the out-of-band rejection effect.

[0027] 3. The frequency selective surface structure of the present invention adopts a centrosymmetric unit structure, which can achieve strong polarization stability.

[0028] The present invention will be further described in detail below in conjunction with the drawings and embodiments. Description of the Drawings

[0029] Figure 1 It is a schematic structural diagram of a unit structure of a four-passband high-selectivity frequency selective surface structure provided by an embodiment of the present invention;

[0030] Figure 2 It is a side view of a unit structure of a four-passband high-selectivity frequency selective surface structure provided by an embodiment of the present invention;

[0031] Figure 3 It is a front view of the first metal layer and the fifth metal layer provided by an embodiment of the present invention;

[0032] Figure 4 It is a front view of the second metal layer provided by an embodiment of the present invention;

[0033] Figure 5 It is a front view of the third metal layer provided by an embodiment of the present invention;

[0034] Figure 6 It is a three-dimensional view of a four-passband high-selectivity frequency selective surface structure provided by an embodiment of the present invention;

[0035] Figure 7 It is a simulation diagram of the transmission coefficient of a four-passband high-selectivity frequency selective surface structure provided by an embodiment of the present invention in TE and TM polarization modes;

[0036] Figure 8 It is a simulation diagram of the angular stability performance of a four-passband high-selectivity frequency selective surface structure provided by an embodiment of the present invention in TE polarization mode;

[0037] Figure 9 It is a simulation diagram of the angular stability performance of a four-passband high-selectivity frequency selective surface structure provided by an embodiment of the present invention in TM polarization mode;

[0038] Figure 10An equivalent circuit model of a four-band frequency selective surface structure with high selectivity provided by an embodiment of the present invention;

[0039] Figure 11 A transmission coefficient curve obtained from the full-wave simulation and equivalent circuit model of a four-band frequency selective surface structure with high selectivity provided by an embodiment of the present invention.

[0040] Explanation of reference numerals:

[0041] 1 - First dielectric substrate; 11 - First metal layer; 110 - Curved slit; 111 - First straight slit; 112 - First bent slit; 113 - Second straight slit; 114 - Second bent slit; 115 - Third straight slit; 116 - Third side straight slit; 12 - Second metal layer; 2 - First air cavity; 3 - Second dielectric substrate; 31 - Third metal layer; 4 - Second air cavity; 5 - Third dielectric substrate; 51 - Fourth metal layer; 52 - Fifth metal layer. Detailed implementation manners

[0042] The following further describes the present invention in detail with reference to specific embodiments, but the implementation manners of the present invention are not limited thereto.

[0043] Embodiment 1

[0044] As Figure 1 、 Figure 2 、 Figure 3 、 Figure 4 and Figure 5 shown, a four-band frequency selective surface unit structure with high selectivity includes: a first metal layer 11, a first dielectric substrate 1, a second metal layer 12, a first air cavity 2, a third metal layer 31, a second dielectric substrate 3, a second air cavity 4, a fourth metal layer 51, a third dielectric substrate 5, and a fifth metal layer 52, which are arranged in sequence from top to bottom.

[0045] The first metal layer 11 and the second metal layer 12 are respectively located on the upper surface and the lower surface of the first dielectric substrate 1. The third metal layer 31 is located on the upper surface of the second dielectric substrate 3. The fourth metal layer 51 and the fifth metal layer 52 are respectively located on the upper surface and the lower surface of the third dielectric substrate 5.

[0046] The first metal layer 11 and the fifth metal layer 52 have the same structure. Curved cross-slot slits are formed on both the first metal layer 11 and the fifth metal layer 52. The curved cross-slot slits on the first metal layer 11 are centrosymmetric with respect to the geometric center of the first metal layer 11; the curved cross-slot slits on the fifth metal layer 52 are centrosymmetric with respect to the geometric center of the fifth metal layer 52. The second metal layer 12 and the fourth metal layer 51 are square loop patches with the same size; the third metal layer 31 is a square patch.

[0047] The first metal layer 11, the first dielectric substrate 1, the second metal layer 12, the third metal layer 31, the second dielectric substrate 3, the fourth metal layer 51, the third dielectric substrate 5, and the fifth metal layer 52 are all centrosymmetric structures.

[0048] Preferably, the first dielectric substrate 1, the second dielectric substrate 3, and the third dielectric substrate 5 are made of F4B-2 flame-retardant material with a relative dielectric constant of 2.65 and a dielectric loss tangent of 0.003. The first metal layer 11, the second metal layer 12, the third metal layer 31, the fourth metal layer 51, and the fifth metal layer 52 are all made of Cu metal. The surface sizes of the first metal layer 11, the first dielectric substrate 1, the second dielectric substrate 3, the third dielectric substrate 5, and the fifth metal layer 52 are all squares with a size of 6mm×6mm. Among them, the thickness h1 of the first dielectric substrate 1, the second dielectric substrate 3, and the third dielectric substrate 5 is 1mm, the thickness h2 of the first air cavity 2 and the second air cavity 4 is 2.6mm, and the thicknesses of the first metal layer 11, the second metal layer 12, and the third metal layer 31 are in the range of 0.017mm - 0.035mm. The structural size of the frequency selective surface unit in this embodiment is 0.13λ×0.13λ, which can meet the requirements of the miniaturized structure of the device. The four sides of the first metal layer 11, the first dielectric substrate 1, the second metal layer 12, the first air cavity 2, the third metal layer 31, the second dielectric substrate 3, the second air cavity 4, the fourth metal layer 51, the third dielectric substrate 5, and the fifth metal layer 52 are correspondingly formed.

[0049] Specifically, the bent cross-slot includes four pairs of opposite bent slots 110. The four bent slots 110 on the same metal layer are opposite to each other in pairs. The two opposite bent slots 110 are centrosymmetric structures centered on the geometric center of the metal layer where they are located, and the adjacent two bent slots 110 can coincide after rotating 90°. The four bent slots 110 on the same metal layer form a centrosymmetric structure. The inner ends of the four bent slots 110 on the first metal layer 11 intersect at the geometric center of the first metal layer 11, and the inner ends of the four bent slots 110 on the fifth metal layer 52 intersect at the geometric center of the fifth metal layer 52.

[0050] Furthermore, as Figure 3 shown, the bent slot 110 includes: a first straight slot 111, a first bent slot 112, a second straight slot 113, a second bent slot 114, a third straight slot 115, and a third side straight slot 116.

[0051] One end of the first straight gap 111 penetrates through the edge of the metal layer (the first metal layer 11 or the fifth metal layer 52) where it is located. The other end of the first straight gap 111 is connected and communicated with one end of the first bent gap 112. The other end of the first bent gap 112 is connected and communicated with one end of the second straight gap 113. The other end of the second straight gap 113 is connected and communicated with one end of the second bent gap 114. The other end of the second bent gap 114 is connected and communicated with one end of the third straight gap 115. The other end of the third straight gap 115 is connected and communicated with one end of the third side straight gap 116. The other end of the third side straight gap 116 intersects with the other end of the third side straight gap 116 of another bent gap 110. The third side straight gaps 116 of the four bent gaps 110 on the same metal layer intersect and are communicated at the geometric center of the metal layer. The first straight gap 111, the second straight gap 113, and the third straight gap 115 are located on the same straight line. The first bent gap 112, the second bent gap 114, and the third side straight gap 116 are all located on the same side.

[0052] Specifically, both the first bent gap 112 and the second bent gap 114 include two side straight gaps and one middle straight gap. The two ends of the middle straight gap are respectively connected and communicated with the other ends of the two side straight gaps, and the two side straight gaps and the middle straight gap are perpendicular. The lengths of the two side straight gaps of the first bent gap 112 are the same. The lengths of the two side straight gaps of the second bent gap 114 are the same. The lengths of the two side straight gaps of the first bent gap 112 are greater than the lengths of the two side straight gaps of the second bent gap 114. The middle straight gap of the first bent gap 112 is parallel to the middle straight gap of the second bent gap 114. The first straight gap 111, the second straight gap 113, and the third straight gap 115 are all parallel to the middle straight gap. The other end of the first straight gap 111 is connected and communicated with one end of a side straight gap of the first bent gap 112. The other end of a side straight gap of the first bent gap 112 is connected and communicated with one end of the second straight gap 113. The other end of the second straight gap 113 is connected and communicated with one end of the second bent gap 114. The other end of the second bent gap 114 is connected and communicated with one end of the third straight gap 115. The other end of the third straight gap 115 is connected and communicated with one end of the third side straight gap 116. The third side straight gap 116 is parallel to the side straight gap.

[0053] Among them, the widths of the first straight gap 111, the first bent gap 112, the second straight gap 113, the second bent gap 114, the third straight gap 115, and the third side straight gap 116 are all the same. The length of the side straight gap of the first bent gap 112 is greater than the length of the side straight gap of the second bent gap 114.

[0054] Preferably, the width of the curved slot 110 is w1, the length of the first straight slot 111 is l1, the length of the second straight slot 113 is l2, the length of the third rectangular slot 115 is (2×l3 + w1), the widths of the first bent slot 112 and the second bent slot 114 are l2. Among them, the depth (the length of the side straight slot) of the first bent slot 112 is (2×l3 + w1), the depth (the length of the side straight slot) of the second bent slot 114 is (l3 + w1), and the depth (length) of the third side straight slot 116 is the same as the depth (the length of the side straight slot of the second bent slot 114) of the second bent slot 114.

[0055] In addition, the inner side length of the square loop patch is d1, and the width is w2. The side length of the square patch is d2.

[0056] The geometric parameters of the unit structure are shown in Table 1:

[0057] Parameter <![CDATA[w1]]> <![CDATA[w2]]> <![CDATA[l1]]> <![CDATA[l2]]> <![CDATA[l3]]> <![CDATA[d1]]> Value 0.15 0.57 0.55 0.57 0.625 3.86 Parameter <![CDATA[d2]]> D <![CDATA[h1]]> <![CDATA[h2]]> Value 4.85 6 1 2.6

[0058] Table 1.

[0059] Embodiment 2

[0060] A frequency selective surface structure with four-way band and high selectivity includes M×N periodically arranged frequency selective surface unit structures of Embodiment 1, where M and N are both integers greater than or equal to 1. Among them, the unit structures are in close contact with each other pairwise.

[0061] As Figure 6 shown, the frequency selective surface structure includes 5×5 unit structures. Of course, the frequency selective surface structure can include 10×10, 20×20, 40×40, or even more unit structures in Embodiment 1.

[0062] In the present invention, two passbands are generated through the interaction between four curved slots 110 and the square loop patch. Therefore, four-way bands can be generated on the upper and lower dielectric substrates. By cascading multiple metal layers and dielectric substrates, four-way bands are achieved between 6 GHz and 14 GHz. While ensuring the four-way bands, it has a strong out-of-band rejection effect, realizing a high-selectivity frequency selective surface, reducing the transmission coefficient between the four-way bands to below -10 dB, and reducing the transmission coefficient in the frequency bands of 0 - 5.5 GHz and 14 - 40 GHz to below -20 dB. There are steep cut-off characteristics and ultra-wideband suppression outside the passbands. The unit structure of the present invention is 0.13λ×0.13λ, reducing the size of the unit structure and realizing the miniaturization of the structure. The transmission coefficient of the surface structure of the present invention varies with the frequency of the electromagnetic wave and is basically the same in TE polarization and TM polarization, having good polarization stability. The transmission coefficient of the surface structure of the present invention varies with the frequency of the electromagnetic wave and shows good angular stability characteristics when the incident angle is 0°, 15°, and 30°.

[0063] In addition, the patterns of the first metal layer 11 and the fifth metal layer 52 of the frequency selective surface unit structure of the present invention are the same, and the patterns of the second metal layer 12 and the fourth metal layer 51 are the same, which reduces the manufacturing difficulty and is easy to process.

[0064] Furthermore, in order to verify the performance of the frequency selective surface structure (FSS structure) of this embodiment, a number of performance simulation analyses were carried out on this FSS structure using the commercial simulation software HFSS.

[0065] Please refer to Figure 7 、 Figure 8 and Figure 9 , Figure 7 which are the simulation diagrams of the transmission coefficients of a four-band highly selective frequency selective surface structure provided by the embodiments of the present invention in TE and TM polarization modes.

[0066] As Figure 7 shown, the FSS structure of the present invention realizes four passbands with transmission poles at 6.54 GHz, 8.41 GHz, 10.80 GHz, and 13.06 GHz through multi-layer coupling. The -3 dB bandwidths are 6.42 - 6.63 GHz, 8.23 - 8.62 GHz, 10.75 - 10.95 GHz, and 12.97 - 13.26 GHz respectively. And the transmission coefficient of this structure between the four passbands is less than -10 dB, and it has an out-of-band rejection effect of -20 dB in the frequency bands of 0 - 5.5 GHz and 14 - 40 GHz. The transmission coefficient curves of electromagnetic waves in TE / TM two polarization modes are in good fit, showing excellent polarization stability.

[0067] Furthermore, in order to study the angular stability of the FSS structure of the present invention, it is irradiated with incident waves at incident angles of 0°, 15°, and 30° in TE mode and TM mode, and the frequency characteristics of this structure can be obtained. Please refer to Figure 8 and Figure 9 . Under the irradiation of electromagnetic incident waves at different angles, the frequency deviation is within an acceptable range, showing excellent signal transmission ability and anti-interference ability.

[0068] In order to further illustrate the mechanism of the electromagnetic characteristics of the four-band highly selective frequency selective surface structure of the present invention, an equivalent circuit model of this frequency selective surface structure was established and simulated and analyzed:

[0069] As Figure 10As shown, the four curved slots can be equivalent to an LC parallel circuit (L1 - C1), and the square loop patch can be equivalent to an LC series circuit (L2 - C2). The interaction between the four curved slots and the square loop patch generates two passbands. Therefore, the upper and lower dielectric layers can generate four passbands. In our design, a metal square sheet is used to suppress the high - frequency band range, which can be equivalent to C3. Here, the dielectric substrate can be equivalent to a short transmission line, composed of an inductor L t and a capacitor C t connected in series. The calculation formulas for the inductor L t and the capacitor are respectively: L t = μ0μ r d, C t = ε0ε r d / 2. However, since the value of C t is very small, it can be ignored. Here, the transmission line is simplified to an inductor L t . The values of the capacitor and inductor in this equivalent circuit can be optimized through transmission line theory and curve fitting. The full - wave simulation is carried out by HFSS simulation, and the equivalent circuit is simulated by ADS. This frequency - selective surface structure has four passbands with transmission poles at 6.54 GHz, 8.41 GHz, 10.80 GHz, and 13.06 GHz respectively, and the out - of - band suppression effect is obvious. Figure 11 is the transmission coefficient curve obtained from the full - wave simulation and equivalent circuit model of the frequency - selective surface designed in the present invention. With the help of the equivalent circuit model, its simulation results are basically in agreement with the full - wave simulation, and this figure can verify the feasibility and accuracy of the frequency - selective surface model of the present invention.

[0070] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present invention.

[0071] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "a plurality" means two or more unless otherwise specifically defined.

[0072] In the present invention, unless otherwise clearly defined or limited, terms such as "installed", "connected", "coupled", "fixed", etc. shall be construed broadly. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the internal communication of two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0073] In the present invention, unless otherwise clearly defined or limited, the first feature being "on" or "under" the second feature may include the direct contact between the first and second features, or may include the situation where the first and second features are not in direct contact but in contact through other features therebetween. Moreover, the first feature being "above", "over" and "on top of" the second feature includes that the first feature is directly above and obliquely above the second feature, or simply means that the first feature has a higher horizontal height than the second feature. The first feature being "under", "beneath" and "underneath" the second feature includes that the first feature is directly below and obliquely below the second feature, or simply means that the first feature has a lower horizontal height than the second feature.

[0074] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine the different embodiments or examples described in this specification.

[0075] The above content is a further detailed description of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention pertains, without departing from the concept of the present invention, several simple deductions or substitutions can still be made, and all should be regarded as belonging to the protection scope of the present invention.

Claims

1. A four-way frequency selective surface unit structure with high selectivity, characterized in that Including: A first metal layer (11), a first dielectric substrate (1), a second metal layer (12), a first air cavity (2), a third metal layer (31), a second dielectric substrate (3), a second air cavity (4), a fourth metal layer (51), a third dielectric substrate (5), and a fifth metal layer (52) which are arranged in sequence from top to bottom; The first metal layer (11) and the second metal layer (12) are respectively located on the upper surface and the lower surface of the first dielectric substrate (1); The third metal layer (31) is located on the upper surface of the second dielectric substrate (3); The fourth metal layer (51) and the fifth metal layer (52) are respectively located on the upper surface and the lower surface of the third dielectric substrate (5); The first metal layer (11) and the fifth metal layer (52) have the same structure, both are provided with curved cross-slot slits, and the curved cross-slot slits are centrosymmetric structures with respect to the geometric center of the metal layer where they are located; The second metal layer (12) and the fourth metal layer (51) are both square loop patches; The third metal layer (31) is a square patch.

2. The frequency selective surface unit structure with a four-way and high selectivity according to claim 1, characterized in that The first metal layer (11), the first dielectric substrate (1), the second metal layer (12), the third metal layer (31), the second dielectric substrate (3), the fourth metal layer (51), the third dielectric substrate (5), and the fifth metal layer (52) are all centrosymmetric structures.

3. A four-way frequency selective surface unit structure with high selectivity according to claim 1, characterized in that The curved cross-slot slits include four pairs of opposite curved slits (110), and the two opposite curved slits (110) are centrosymmetric structures with respect to the geometric center of the metal layer where they are located, and two adjacent curved slits (110) can coincide after rotating 90°; The inner ends of the four curved slits (110) intersect at the geometric center of the metal layer where they are located.

4. The frequency selective surface unit structure with four ports and high selectivity according to claim 3, characterized in that The curved slit (110) includes: a first straight slit (111), a first bent slit (112), a second straight slit (113), a second bent slit (114), a third straight slit (115), and a third side straight slit (116); One end of the first straight slit (111) penetrates through the edge of the metal layer where it is located, and the other end is connected and communicated with one end of the first bent slit (112). The other end of the first bent slit (112) is connected and communicated with one end of the second straight slit (113). The other end of the second straight slit (113) is connected and communicated with one end of the second bent slit (114). The other end of the second bent slit (114) is connected and communicated with one end of the third straight slit (115). The other end of the third straight slit (115) is connected and communicated with one end of the third side straight slit (116). The other end of the third side straight slit (116) intersects with the other end of the third side straight slit (116) of another curved slit (110); The first straight slit (111), the second straight slit (113), and the third straight slit (115) are located on the same straight line; The first bending gap (112), the second bending gap (114), and the third side straight gap (116) are all located on the same side.

5. A four-way frequency selective surface unit structure with high selectivity according to claim 4, characterized in that, The widths of the first straight gap (111), the first bending gap (112), the second straight gap (113), the second bending gap (114), the third straight gap (115), and the third side straight gap (116) are all the same.

6. The frequency selective surface unit structure with four-way and high selectivity according to claim 1, characterized in that, The first dielectric substrate (1), the second dielectric substrate (3), and the third dielectric substrate (5) are all square and have the same size and material.

7. A four-way frequency selective surface unit structure with high selectivity according to claim 1, characterized in that The first dielectric substrate (1), the second dielectric substrate (3), and the third dielectric substrate (5) are all made of F4B-2 material.

8. A four-way frequency selective surface structure with high selectivity, characterized in that, It includes M×N periodically arranged frequency selective surface unit structures as described in any one of claims 1 to 7, where M and N are both integers greater than or equal to 1.

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