Dual-band low-frequency passband independently switchable frequency selective surface

Abstract

The application is a kind of double-passband low-frequency passband independent switchable frequency selective surface, which is composed of a three-layer structure, the upper and lower layers are double-passband metal layers, four p-i-n diodes are placed in the middle slit of each layer, the middle layer is a cross metal structure, and the layers are separated by a dielectric substrate; a metal column passes through the center strip layer to connect the upper and lower layers, the middle layer and the upper and lower layers are connected to the positive and negative electrodes of a direct current power supply respectively, and the p-i-n diodes are fed by the metal column. The three-layer structure can realize independent control of double-passband, and the application of forward voltage to the p-i-n diodes can make the low-frequency passband independently switchable and the high-frequency passband stable, and the structure has good in-band and out-of-band characteristics, wide passband and high frequency ratio characteristics. The application is suitable for dual-frequency and multi-frequency systems, and can adapt to more and more complex electromagnetic environments, and can be used for radar stealth and other applications.

Description

Technical Field

[0001] This invention belongs to the field of communication technology, and further relates to a dual-passband low-frequency passband independently switchable frequency selectable surface in the field of electromagnetic field and microwave technology, which can be used in dual-frequency, multi-frequency systems and stealth radar radome related systems and equipment. Background Technology

[0002] In the application of equipment stealth, on the one hand, it is necessary to improve the detection capability of our radar to help us detect enemy targets earlier; on the other hand, it is necessary to improve the radar stealth function of the equipment to ensure that our equipment is not detected or jammed by the enemy. Radar Cross Section (RCS) is generally used to characterize the stealth capability of a target; the smaller the RCS value, the stronger the radar stealth capability. Stealth radomes based on bandpass frequency selective surfaces can reduce the risk of our equipment being exposed to enemy detection radar while ensuring normal communication between our various devices: allowing electromagnetic waves within the operating frequency band of our equipment to pass through, ensuring the normal operation of our equipment; and reflecting electromagnetic waves outside the operating frequency band. Furthermore, through its shape design, it can scatter electromagnetic waves outside the operating frequency band into directions that are difficult for enemy radar to detect, effectively reducing the RCS of our equipment. A band-stop frequency selective surface can be used as an antenna reflector. It exhibits total reflection characteristics of electromagnetic waves within the operating frequency band of our equipment, ensuring the normal operation of our equipment. It also exhibits total transmission characteristics of electromagnetic waves outside the operating frequency band of our equipment, making it difficult for the enemy radar to receive the reflected electromagnetic waves, thereby effectively reducing the RCS of our equipment.

[0003] With the increasing demand for multi-frequency applications, frequency selectable surfaces with multi-band characteristics are attracting more and more attention. Modern radar antennas and wireless communication systems are constantly evolving towards broadband, ultra-wideband, multi-frequency, and frequency-converting capabilities, making it difficult for traditional frequency selectable surfaces to meet these requirements. Summary of the Invention

[0004] To overcome the shortcomings of the existing technologies and fill the gap in the design of multi-frequency independent controllable frequency selective surfaces, a dual-passband low-frequency passband independent switchable frequency selective surface is proposed. It aims to solve the problems of existing traditional frequency selective surface structures being unable to achieve independent control in multi-frequency systems and having narrow bandwidth. It can be used in dual-frequency, multi-frequency systems and stealth radar radomes and other systems and equipment.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A dual-passband low-frequency passband independently switchable frequency selectable surface, comprising an upper dual-passband metal layer, a middle cross-shaped metal layer, and a lower dual-passband metal layer;

[0007] The upper dual-passband metal layer and the lower dual-passband metal layer have the same structure and both have dual polarization characteristics. A pin diode is provided on each branch, thereby realizing dual-passband characteristics on a single-layer structure.

[0008] External power supplies are installed between each branch of the middle cross metal layer and each branch of the upper dual-passband metal layer, as well as between each branch of the lower dual-passband metal layer. DC power is supplied to each pin diode through the external power supply and the feed line structure. When a positive DC voltage is applied to the pin diode, the low-frequency passband is closed, while the high-frequency passband remains unchanged, achieving independent switching characteristics for the low-frequency passband. When a negative DC voltage is applied to the pin diode, it exhibits dual-passband characteristics, achieving independent switching characteristics for the low-frequency passband.

[0009] In one embodiment, the upper dual-pass metal layer is printed on the upper surface of the upper dielectric substrate, the lower dual-pass metal layer is printed on the lower surface of the lower dielectric substrate, the middle cross metal layer is printed on the lower surface of the upper dielectric substrate or the upper surface of the lower dielectric substrate, and the metal pillar passes through the middle cross metal layer to connect the upper dual-pass metal layer and the lower dual-pass metal layer, thus serving as the feed line structure.

[0010] In one embodiment, the upper dual-pass metal layer and the lower dual-pass metal layer have the same structure, shape and size, are symmetrically arranged, and are each composed of an inner cross metal structure, an outer metal frame, a pin diode and a first circular aperture.

[0011] The first circular aperture is located at the center of the inner cross metal structure, allowing the feeder structure to pass through and connect with the inner cross metal structure.

[0012] A pin diode is placed at the first gap between each branch of the inner cross metal structure and the outer metal frame.

[0013] In one embodiment, the inner cross metal structure consists of a central disk structure and a centrally symmetrical cross structure connected to the disk radially, with the first circular aperture located at the center of the central disk structure.

[0014] In one embodiment, the outer metal frame is a hollow square structure, with the midpoints of the four sides corresponding to the four branches of the inner cross metal structure. A strip structure extends from the midpoints of the four sides into the frame, forming a first gap with the corresponding branch of the inner cross metal structure. A portion of the strip structure extends to the adjacent side, and / or a portion of the adjacent side extends to the strip structure, thereby forming a second gap between the strip structure and the adjacent side.

[0015] In one embodiment, the strip structure extends into a wing-like structure in the middle. The wing-like structure is composed of a first rectangle, a trapezoid, and a second rectangle. The length directions of the first and second rectangles are perpendicular to the length of the strip structure. The length of the first rectangle is greater than the length of the second rectangle. The lower base of the trapezoid is connected to the side of the first rectangle closest to the inner cross metal structure, and the upper base is connected to the side of the second rectangle away from the inner cross metal structure. The second rectangle and the inner cross metal structure form the first gap.

[0016] In one embodiment, a square structure extends inward from each of the four corners of the outer metal frame, and a second gap is formed between the first rectangle and a square structure.

[0017] In one embodiment, the intermediate cross metal layer includes a cross metal structure and a central metal disk. The cross metal structure is connected to the central metal disk and is a centrally symmetrical cross structure extending radially outward along the central metal disk. A second circular aperture is located at the center of the central metal disk, allowing the feeder structure to pass through and connect with the central metal disk.

[0018] In one embodiment, the length of the second rectangle is d2 = 1 mm and the width is L2 = 0.5 mm; the length of the first rectangle is d3 = 3 mm and the width is L4 = 0.5 mm; the length of the strip structure is L5 = 0.8 mm and the width is d4 = 1.7 mm; the height of the trapezoid is 1 mm; the side length of the square structure is L6 = 2.4 mm, the distance of the second gap is D = 0.9 mm, and the side length of the outer metal frame is S = 10 mm; the width of each branch of the inner cross metal structure is d1 = 0.7 mm and the length is L1 = 0.66 mm, the distance of the first gap is A = 0.3 mm, the radius of the central disk structure is R2 = 0.25 mm, and the radius of the first circular hole is R1 = 1.1 mm; the length of the metal column is P = 4.4 mm and the radius is R3 = 0.2 mm; the width of each branch of the cross metal structure is W = 0.38 mm and the length is L = 4.5 mm, and the radius of the second circular hole is R4 = 0.5 mm.

[0019] In one embodiment, the DC power supply of the pin diode is achieved through a frequency-selective surface self-power supply. The middle cross metal layer, the upper double-pass metal layer, and the lower double-pass metal layer are connected to the positive and negative terminals of the power supply to power the pin diode. When the pin diode is conducting, it acts as a resistor, and when it is not conducting, it acts as a capacitor. All pin diodes are powered synchronously.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] First, the dual-passband metal layer in this invention achieves dual-passband characteristics on a single-layer structure. To achieve independent control of the dual passbands, the frequency characteristics of the capacitor are utilized; that is, a small capacitor can be equivalent to an open circuit in the low-frequency range, and a large capacitor can be equivalent to a short circuit in the high-frequency range. The pin diode provides the large capacitor, and the second gap provides the small capacitor. Therefore, this dual-passband layer can be equivalent to two circuit structures in the low-frequency and high-frequency ranges, realizing that the low-frequency passband is controlled by the pin diode, and the high-frequency passband is controlled by the second gap. This overcomes the problem of traditional frequency-selective surfaces in the prior art being unable to achieve independent multi-frequency control, giving this invention the advantages of independently controllable dual passbands and a small thickness.

[0022] Secondly, because the overall structure of this invention employs a multi-layer structure consisting of an upper dual-passband metal layer, a middle cross-shaped metal layer, and a lower dual-passband metal layer, designing the dual-passband layer as a dual-layer structure facilitates bandwidth expansion. Simultaneously, the cascaded coupling between the middle layer and the dual-passband layer improves the characteristics within the passband, making the dual-passband flatter. This allows the invention to achieve the advantages of wide passband and low insertion loss while maintaining independent switchability of the low-frequency dual-passband.

[0023] Third, because the pin diode in this invention uses a frequency-selective surface self-feeding method, the metal pillar is regarded as a feed line structure connecting the upper and lower layers. Active control of the pin diode is achieved by applying DC voltages to the intermediate layer and the dual-passband layer, respectively. This gives the invention the advantages of simple structure and easy feeding. Attached Figure Description

[0024] Figure 1 This is an exploded view of the overall structure of the dual-passband low-frequency passband independently switchable frequency selectable surface of the present invention.

[0025] Figure 2 This is a schematic diagram of the upper dual-passband metal layer and the lower dual-passband metal layer structure in an embodiment of the present invention.

[0026] Figure 3 This is a schematic diagram showing the dimensions of the upper and lower dual-passband metal layers in an embodiment of the present invention.

[0027] Figure 4 This is a schematic diagram of the intermediate metal layer structure and metallized pillars of the present invention.

[0028] Figure 5 This is a schematic diagram of the power supply method of the present invention.

[0029] Figure 6 This is a transmission coefficient curve of the pin diode when it is turned on and off in a simulation experiment according to an embodiment of the present invention. Detailed Implementation

[0030] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings and examples.

[0031] Reference Figure 1 The overall structure of the electromagnetic surface of the present invention will be described in further detail below.

[0032] In this embodiment of the invention, the dual-passband low-frequency passband independently switchable frequency selectable surface includes an upper dual-passband metal layer 12, a middle cross-shaped metal layer 17, and a lower dual-passband metal layer 15. The upper dual-passband metal layer 12 and the lower dual-passband metal layer 15 have dual-polarization characteristics, identical structures, and each branch of both layers is provided with a pin diode 11, thereby enabling dual-passband characteristics in a single-layer structure.

[0033] The present invention provides a first external power supply between each branch of the intermediate cross metal layer 17 and each branch of the upper double-pass metal layer 12, specifically by controlling the current application between the branches through a first external power supply. A second external power supply is provided between each branch of the intermediate cross metal layer 17 and each branch of the lower double-pass metal layer 15, specifically by controlling the current application between the branches through a second external power supply.

[0034] Therefore, through an external power supply and feeder structure, DC power can be supplied to each pin diode 11: when a positive DC voltage is applied to each pin diode 11 of the upper dual-passband metal layer 12 or the lower dual-passband metal layer 15, the low-frequency passband is closed, while the high-frequency passband remains unchanged, thus achieving independent switching characteristics for the low-frequency passband; when a negative DC voltage is applied to each pin diode 11 of the upper dual-passband metal layer 12 or the lower dual-passband metal layer 15, dual-passband characteristics are exhibited, thus achieving independent switching characteristics for the low-frequency passband.

[0035] Based on the above structure, this invention utilizes a dual-passband metal layer to achieve dual-passband characteristics on a single-layer structure. The cascaded structure of the upper dual-passband metal layer 12, the lower dual-passband metal layer 15, and the cross-shaped metal layer 17 enables the dual-passband to have wide passband characteristics, realizing the function of independent switching of the low-frequency passband. Simultaneously, since the overall structure employs a multi-layer design, setting the dual-passband layer as a dual-layer structure is beneficial for expanding the bandwidth, and the cascaded coupling between adjacent layers can improve the characteristics within the passband, making the dual-passband flatter.

[0036] In one specific embodiment, the structure employs a double-layer substrate, wherein the upper dual-passband metal layer 12 is printed on the upper surface of the upper dielectric substrate 13, the lower dual-passband metal layer 15 is printed on the lower surface of the lower dielectric substrate 14, and the middle cross-shaped metal layer 17 can be printed on either the lower surface of the upper dielectric substrate 13 or the upper surface of the lower dielectric substrate 14. A metal pillar 16 passes through and connects to the middle cross-shaped metal layer 17, and extends through both the upper and lower dielectric substrates 13 and 14, connecting the upper dual-passband metal layer 12 and the lower dual-passband metal layer 15. The metal pillar 16 serves as the feed structure for the controlled pin diode 11 of this invention, and its symmetrical design enables uniform power feeding. Furthermore, by applying DC voltages to the middle cross-shaped metal layer 17 and the dual-passband layer respectively, active control of the pin diode 11 can be achieved.

[0037] In this invention, the upper dual-passband metal layer 12 and the lower dual-passband metal layer 15 have identical structures, shapes, and dimensions, and are symmetrically arranged vertically. Both possess dual-passband characteristics and can achieve independent control of the dual passesbands. Specifically, both are composed of an inner cross-shaped metal structure 114, an outer metal frame 111, a pin diode 11, and a first circular aperture 115, as shown below. Figure 2 As shown.

[0038] The outer metal frame 111 is a closed metal frame, preferably a square frame. The inner cross-shaped metal structure 114 is located inside the metal frame and has four centrally symmetrical branches. A first circular aperture 115 is provided at the center of the inner cross-shaped metal structure 114, allowing the feeder structure to pass through and connect to the inner cross-shaped metal structure 114. The pin diodes 11 are respectively located at the first gap 113 between each branch of the inner cross-shaped metal structure 114 and the outer metal frame 111.

[0039] Furthermore, the inner cross metal structure 114 is mainly composed of a central disk structure and a centrally symmetrical cross structure connected to the disk. The four branches of the centrally symmetrical cross structure constitute the four centrally symmetrical branches of the inner cross metal structure 114, and the first circular hole 115 is located at the center of the central disk structure.

[0040] In one embodiment of the present invention, the outer metal frame 111 is a hollow square metal frame, with the midpoints of its four sides corresponding to the four branches of the inner cross-shaped metal structure 114. A strip structure extends from the midpoints of each of the four sides into the frame, and each strip structure forms a first gap 113 with a corresponding branch of the inner cross-shaped metal structure 114. A portion of the strip structure extends to an adjacent side, forming a second gap 112 between the strip structure and the adjacent side. Alternatively, a portion of the strip structure extends to an adjacent side, and simultaneously, a portion of the adjacent side also extends into the strip structure, forming a second gap 112 between the strip structure and the adjacent side. Or, a portion of the adjacent side also extends into the strip structure, forming a second gap 112 between the strip structure and the adjacent side. Here, the adjacent side refers to the two sides of the hollow square adjacent to the side from which the strip structure extends.

[0041] In this embodiment, the frequency characteristics of the capacitor are used to achieve independent control of the dual passbands. Specifically, the small capacitor can be equivalent to an open circuit in the low-frequency range, and the large capacitor can be equivalent to a short circuit in the high-frequency range. In this embodiment, the pin diode 11 provides a large capacitor (e.g., 0.15pF in this embodiment), and the second gap 112 provides a small capacitor (e.g., 0.006pF in this embodiment). The corresponding dual passband layer can be equivalent to two circuit structures in the low-frequency and high-frequency regions, respectively, achieving control of the low-frequency passband by the pin diode 11 and the high-frequency passband by the second gap 112. Combined with the cascaded structure of the upper dual passband metal layer 12, the cross-shaped metal layer 17, and the lower dual passband metal layer 15, this embodiment achieves the advantages of a wide passband and low insertion loss while maintaining independent switching capability of the dual passband low-frequency passband.

[0042] Furthermore, in this embodiment of the invention, the strip structure extends to both sides in a wing-like structure at its middle position. This wing-like structure is composed of a first rectangle, a trapezoid, and a second rectangle. The first rectangle is close to the side of the metal frame it is connected to, and the second rectangle is away from the side of the metal frame it is connected to. If the direction perpendicular to the length of the strip structure is taken as the length direction of the first rectangle and the second rectangle, then the length of the first rectangle is greater than the length of the second rectangle. The lower base of the trapezoid is connected to the side of the first rectangle close to the inner cross metal structure 114, and the upper base is connected to the side of the second rectangle away from the inner cross metal structure 114. The second rectangle and the inner cross metal structure 114 form the aforementioned first gap 113. The first rectangle and the aforementioned adjacent side or the extension of the adjacent side into the frame form the aforementioned second gap 112. By extending the wing-like structure on the strip structure, this structure can better form the second gap 112 with the adjacent side, and the wing-like structure can also play a control role for the double-passage strip.

[0043] Furthermore, the aforementioned extension of adjacent sides into the metal frame specifically refers to the four square structures extending inward from the four corners of the outer metal frame 111, totaling four square metal pieces. When the aforementioned wing-shaped structure is adopted, the first rectangle and a square structure form a second gap 112, resulting in a total of eight second gaps 112 on a single dual-band metal layer. There are four first gaps 113 between the inner cross-shaped metal structure 114 and the outer metal frame 111, and four pin diodes 11 are placed in these four first gaps 113.

[0044] This invention also provides a feasible parameter, such as... Figure 3 As shown, in the outer metal frame 111 of the dual-band metal layer, the length d2 of the second rectangle is 1 mm, the width L2 is 0.5 mm, the length d3 is 3 mm, and the width L4 is 0.5 mm. The length L5 of the strip structure is 0.8 mm, and the width d4 is 1.7 mm. The height of the trapezoid is 1 mm. The side length L6 of each square metal sheet is 2.4 mm, the distance of the second gap 112 is D = 0.9 mm, and the side length of the outer metal frame 111 is S = 10 mm. The width of each branch of the inner cross metal structure 114 is d1 = 0.7 mm, the length is L1 = 0.66 mm, and the distance of the first gap 113 is A = 0.3 mm. The radius R2 of the central disk structure is 0.25 mm, slightly larger than the radius of the metal pillar 16, and the radius R1 of the first circular hole 115 is 1.1 mm. The upper dielectric substrate 13 and the lower dielectric substrate 14 are made of a material with a thickness of 2.2 mm and a dielectric constant of ε. r =2.2, a dielectric substrate with a loss tangent of tanδ = 0.0009.

[0045] Reference Figure 4 As shown, the intermediate cross-shaped metal layer 17 includes a cross-shaped metal structure 116, a central metal disk 117, and a second circular aperture 118. The central metal disk 117 is located at the center of the cross-shaped metal structure 116, and the cross-shaped metal structure 116 is connected to the central metal disk 117. It is a centrally symmetrical cross structure extending radially outward along the central metal disk 117. This centrally symmetrical cross structure is projected one-to-one with each branch on the upper and lower dual-pass metal layers. The width of each branch of the cross-shaped metal structure 116 is W = 0.38 mm, and the length is L = 4.5 mm. There is a second circular aperture 118 at the center of the metal disk 117, through which the feeder structure passes and connects to the central metal disk 117. The aperture has a size of R4 = 0.5 mm. The metal pillar 16 passes through the circular aperture and connects the upper dual-pass metal layer 12 and the lower dual-pass metal layer 15. Its length is P = 4.4 mm, and its radius is R3 = 0.2 mm.

[0046] refer to Figure 5The DC power supply for pin diode 11 is frequency-selective, self-powered. The intermediate layer 17, upper double-pass metal layer 12, and lower double-pass metal layer 15 are connected to the positive and negative terminals of the power supply to power pin diode 11. When pin diode 11 is conducting, it acts as a small resistor; when it is not conducting, it acts as a capacitor. All pin diodes 11 are synchronously powered, meaning they are synchronously conducting or not conducting. The DC voltage value depends on the pin diode 11 model. When the pin diode 11 model is MA4P303, the resistance is 1.5Ω when conducting and the capacitance is 0.15pF when cut off. The DC voltage value must be greater than 1V and less than 400V.

[0047] The technical effects of the present invention will be further explained below with reference to simulation experiments:

[0048] The S-parameter curves obtained by modeling and simulating the embodiments of the present invention using the commercial simulation software Ansoft HFSS19.0 are shown below. Figure 6 As shown. Figure 6 The horizontal axis represents the frequency value in GHz, and the vertical axis represents the transmission coefficient S. 21 The unit is dB. From Figure 6 The two solid lines in the diagram show that the pin diode in this embodiment of the invention can achieve independent switching of the low-frequency passband and maintain the high-frequency passband when it is on and off, respectively. The low-frequency passband switching range is 5.96GHz-6.7GHz, and the high-frequency passband is basically maintained at 14.9GHz-18.5GHz, with an insertion loss of less than -1dB. This structure has the characteristics of high frequency ratio, wide passband, and independent switching of the low-frequency passband.

[0049] In summary, this invention enables independent control of both passbands. Applying a forward voltage to the pin diodes allows for independent switching of the low-frequency passband while maintaining a stable high-frequency passband. Furthermore, this structure exhibits excellent in-band and out-of-band characteristics, a wide passband, and a high frequency ratio. This invention can be applied to dual-frequency and multi-frequency systems. In this case, by feeding eight pi-n11 diodes, the low-frequency passband can be flexibly controlled. This invention can also serve as a reflector for multi-frequency antennas, simultaneously facing a multi-frequency radar detection system, enabling flexible dual-frequency control. It has significant application value in fields such as electromagnetic stealth, electromagnetic compatibility, communication, and electronic warfare.

[0050] Although specific embodiments of the present invention have been described in detail with reference to the accompanying drawings, this should not be construed as limiting the scope of protection of this patent. Various modifications and variations that can be made by those skilled in the art without inventive effort within the scope described in the claims still fall within the scope of protection of this patent.

[0051] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A dual-passband low-frequency passband independently switchable frequency selective surface, characterized in that, The upper double-passband metal layer (12), the intermediate cross metal layer (17) and the lower double-passband metal layer (15) are provided. The upper double-passband metal layer (12) and the lower double-passband metal layer (15) have the same structure and have dual-polarization characteristics, and each branch is provided with a p-i-n diode (11), so that the double-passband characteristics are realized on a single-layer structure. External power sources are provided between each branch of the intermediate cross metal layer (17) and each branch of the upper double-passband metal layer (12) and the lower double-passband metal layer (15), and direct current feeding of each p-i-n diode (11) is realized through the external power sources and the feeding line structure; when a positive direct current voltage is applied to the p-i-n diode (11), the low-frequency passband is closed and the high-frequency passband remains unchanged, so that the independent switching characteristics of the low-frequency passband are realized; when a negative direct current voltage is applied to the p-i-n diode (11), the double-passband characteristics are presented, so that the independent switching characteristics of the low-frequency passband are realized.

2. The dual passband low frequency passband independently switchable frequency selective surface of claim 1, wherein, The upper double-passband metal layer (12) is printed on the upper surface of the upper dielectric substrate (13), the lower double-passband metal layer (15) is printed on the lower surface of the lower dielectric substrate (14), and the intermediate cross metal layer (17) is printed on the lower surface of the upper dielectric substrate (13) or the upper surface of the lower dielectric substrate (14); the metal column (16) passes through the intermediate cross metal layer (17) to connect the upper double-passband metal layer (12) and the lower double-passband metal layer (15), and serves as the feeding line structure.

3. The dual-band low-frequency passband independently switchable frequency selective surface according to claim 1 or 2, characterized in that, The upper double-passband metal layer (12) and the lower double-passband metal layer (15) have the same structure, shape and size, and are symmetrically arranged, and each is composed of an inner cross metal structure (114), an outer metal frame (111), a p-i-n diode (11) and a first circular aperture (115). The first circular aperture (115) is arranged at the center of the inner cross metal structure (114) and is used for the feeding line structure to pass through and connect with the inner cross metal structure (114). Each p-i-n diode (11) is arranged at the first gap (113) between each branch of the inner cross metal structure (114) and the outer metal frame (111).

4. The dual passband low frequency passband independently switchable frequency selective surface of claim 3, wherein, The inner cross metal structure (114) is composed of a center disc structure and a center-symmetric cross structure connected with the disc along the disc radial direction, and the first circular aperture (115) is arranged at the center of the center disc structure.

5. A dual passband low frequency passband independently switchable frequency selective surface according to claim 3 or 4, wherein, The outer metal frame (111) is a hollow square structure, the midpoints of the four sides are opposite to the four branches of the inner cross metal structure (114), respectively, and a strip structure is extended from each midpoint to the inside of the frame, so that the first gap (113) is formed between the strip structure and the corresponding branch of the inner cross metal structure (114); a part of the strip structure is extended to the adjacent side, and / or a part of the adjacent side is extended to the strip structure, so that the second gap (112) is formed between the strip structure and the adjacent side.

6. The dual passband low frequency passband independently switchable frequency selective surface of claim 5, wherein, The strip structure is expanded into a wing structure in the middle, which is composed of a first rectangle, a trapezoid and a second rectangle, the length direction of the first rectangle and the second rectangle is perpendicular to the length direction of the strip structure, the length of the first rectangle is greater than that of the second rectangle, the lower base of the trapezoid is connected with one side of the first rectangle close to the inner cross metal structure (114), the upper base is connected with one side of the second rectangle away from the inner cross metal structure (114), and the first gap (113) is formed between the second rectangle and the inner cross metal structure (114).

7. The dual passband low frequency passband independently switchable frequency selective surface of claim 6, wherein, A square structure is extended into the frame from each corner of the outer metal frame (111), and the second gap (112) is formed between the first rectangle and the square structure.

8. The dual passband low frequency passband independently switchable frequency selective surface of claim 7, wherein, The middle cross metal layer (17) includes a cross metal structure (116) and a center metal disc (117), the cross metal structure (116) is connected to the center metal disc (117) and is a center-symmetric cross structure extending outward along the radial direction of the center metal disc (117), and a second circular aperture (118) is arranged at the center of the center metal disc (117) to pass through the feeder structure and connect with the center metal disc (117).

9. The dual passband low frequency passband independently switchable frequency selective surface of claim 8, wherein, The length d2 of the second rectangle is 1 mm, the width L2 is 0.5 mm, the length d3 of the first rectangle is 3 mm, the width L4 is 0.5 mm, the length L5 of the strip structure is 0.8 mm, the width d4 is 1.7 mm, the height of the trapezoid is 1 mm, the side length L6 of the square structure is 2.4 mm, the distance D of the second gap (112) is 0.9 mm, the side length S of the outer metal frame (111) is 10 mm, the width d1 of each branch of the inner cross metal structure (114) is 0.7 mm, the length L1 is 0.66 mm, the distance A of the first gap (113) is 0.3 mm, the radius R2 of the center disc structure is 0.25 mm, the radius R1 of the first circular aperture (115) is 1.1 mm, the length P of the metal column (16) is 4.4 mm, the radius R3 is 0.2 mm, the width W of each branch of the cross metal structure (116) is 0.38 mm, the length L is 4.5 mm, and the radius R4 of the second circular aperture (118) is 0.5 mm.

10. The dual passband low frequency passband independently switchable frequency selective surface of claim 1, wherein, The direct current feeding of the p-i-n diode (11) is fed by the frequency selective surface itself, the middle cross metal layer (17) and the upper double-passband metal layer (12) and the lower double-passband metal layer (15) are connected to the positive and negative poles of the power supply to feed the p-i-n diode (11), the p-i-n diode (11) is a resistance when it is turned on, and is a capacitor when it is not turned on, and each p-i-n diode (11) is synchronously fed.

Images