Frequency-selective surface unit cell, frequency selective surface, antenna system and communication device

Abstract

The embodiments of the present application belong to the technical field of communications. Provided are a frequency-selective surface unit cell, a frequency selective surface, an antenna system, and a communication device. The frequency-selective surface unit cell comprises a dielectric layer, a central metal, and at least two annular metals. The central metal is disposed on the dielectric layer. The at least two annular metals are disposed on the dielectric layer, and each of the at least two annular metals has an inner metal and an outer metal, wherein in a plane perpendicular to the thickness direction of the dielectric layer, the orthographic projection of any one of the annular metals surrounds the orthographic projection of the central metal and is spaced apart from the orthographic projection of the central metal, the orthographic projections of any two of the annular metals are spaced apart from each other, the orthographic projection of the inner metal and the orthographic projection of the central metal define a first gap, the orthographic projections of two adjacent annular metals define a second gap, and the orthographic projection of the outer metal and the edge of the orthographic projection of the dielectric layer define a third gap. In this way, the passband bandwidth of the frequency selective surface can be increased.

Description

Frequency selective surface unit, frequency selective surface, antenna system and communication equipment

[0001] This application claims priority to Chinese Patent Application No. 202510467701.4, filed on April 14, 2025, entitled "Frequency Selective Surface Unit, Frequency Selective Surface, Antenna System and Communication Equipment", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of communication technology, and in particular to a frequency selective surface unit, a frequency selective surface, an antenna system, and a communication device. Background Technology

[0003] To achieve high integration in antenna systems, antenna element arrays from multiple frequency bands are integrated into a single antenna system, forming a multi-band antenna system. In related technologies, a multi-band antenna system includes a first-band antenna array, a second-band antenna array, a third-band antenna array, and a frequency selective surface (FSS). The radiating elements of the first-band antenna array are located on the first side of the FSS, while the radiating elements of the second and third-band antenna arrays are located on the second side. The first and second sides of the FSS are opposite sides of the surface. The FSS acts as a reflector for the first-band antenna array and also as an electromagnetically transparent plate for the second and third-band antenna arrays. However, the dual-passband bandwidth of the FSS in related technologies is insufficient in the second and third frequency bands. Summary of the Invention

[0004] This application provides a frequency selective surface unit, a frequency selective surface, an antenna system, and a communication device, which can solve the problem of insufficient dual-passband bandwidth of frequency selective surfaces in related technologies.

[0005] In a first aspect, embodiments of this application provide a frequency selective surface unit, which includes a dielectric layer, a central metal, and at least two annular metals. The central metal is disposed in the dielectric layer. At least two annular metals are disposed in the dielectric layer, and the at least two annular metals have inner metals and outer metals. The inner metal is the annular metal closest to the central metal among the at least two annular metals, and the outer metal is the annular metal farthest from the central metal among the at least two annular metals. In a plane perpendicular to the thickness direction of the dielectric layer, the orthographic projection of any one annular metal surrounds the orthographic projection of the central metal and is spaced apart from the orthographic projection of the central metal. The orthographic projections of any two annular metals are spaced apart. The orthographic projections of the inner metal and the central metal form a first gap, the orthographic projections of two adjacent annular metals form a second gap, and the orthographic projection of the outer metal and the edge of the orthographic projection of the dielectric layer form a third gap.

[0006] In the embodiments of this application, the central metal, the ring metal, and the dielectric layer can form an N-ring (N+1) slot structure, where N is greater than or equal to 2. The N-ring (N+1) slot structure can form high stopband suppression characteristics in the low-frequency band while forming multi-passband transmission characteristics in multiple high-frequency bands. The frequency-selective surface has high stopband suppression and large passband bandwidth, which can solve the problem of insufficient stopband suppression in the prior art and can also solve the problem of insufficient dual passband bandwidth in the prior art.

[0007] In some possible implementations, the frequency selective surface unit also includes a coupling metal disposed on the dielectric layer, with the coupling metal spaced apart from the outer metal, and the coupling metal and the outer metal forming a coupling capacitor.

[0008] In this way, by loading coupling metal onto the outer metal, the position of the stopband resonant point is adjusted, thereby further increasing the stopband bandwidth and further improving the stopband suppression.

[0009] In some possible implementations, the coupling metal and the outer metal are located in the same plane, and the orthographic projections of the coupling metal and the outer metal are spaced apart in a plane perpendicular to the thickness direction of the dielectric layer.

[0010] In this way, the coupling metal and the outer metal are arranged adjacent to each other on the same plane. The coupling metal and the outer metal form a coupling capacitor through adjacent coupling, so as to adjust the resonant point position of the stopband, further increase the stopband bandwidth, and further improve the stopband suppression.

[0011] In some possible implementations, the coupling metal and the outer metal are spaced apart along the thickness direction of the dielectric layer, and in a plane perpendicular to the thickness direction of the dielectric layer, the orthographic projection of the coupling metal and the orthographic projection of the outer metal at least partially overlap.

[0012] In this way, the coupling metal and the outer metal are on different planes, and the coupling metal and the outer metal form a plate coupling capacitor to adjust the position of the stopband resonant point, further increase the stopband bandwidth, and further improve the stopband suppression.

[0013] In some possible implementations, the coupling metal and the outer metal constitute a distributed capacitor.

[0014] In this way, the coupling metal of the appropriate structure can be selected according to the layout scenario, which can broaden the degree of freedom in adjusting the performance of the frequency-selectable surface.

[0015] In some possible implementations, the frequency selective surface unit also includes an inductor structure connected in series with an outer metal element.

[0016] In this way, by connecting an inductor structure in series within the loop formed by the outer metal, the inductance can be increased, thereby further increasing the passband bandwidth. Furthermore, when designing the inductor structure, the width of the outer metal can be made larger, which reduces machining tolerance requirements, simplifies manufacturing, and improves yield and production efficiency.

[0017] In some possible implementations, the inductor structure is a distributed inductor.

[0018] This expands the flexibility in adjusting the performance of frequency selective surfaces. Furthermore, distributed inductance can be formed on the dielectric layer using PCB manufacturing processes, improving the production efficiency of frequency selective surfaces.

[0019] In some possible implementations, the frequency selective surface unit also includes a removal structure coupled to an outer metal, the orthographic projection of which lies inside the second slit in a plane perpendicular to the thickness direction of the dielectric layer.

[0020] In this way, removing the structure can remove the non-ideal resonant points that fall into the passband at large angles, thereby improving stability at large angles and broadening the degree of freedom in adjusting the performance of the frequency-selective surface unit.

[0021] In some possible implementations, the orthographic projection of the removed structure in a plane perpendicular to the thickness direction of the dielectric layer is in the shape of a "1", "L", "S", fan, or sawtooth.

[0022] In this way, removing the structure can remove the non-ideal resonant points that fall into the passband at large angles, thus broadening the degree of freedom in adjusting the performance of the frequency-selective surface.

[0023] In some possible implementations, the frequency-selective surface element is a rotationally symmetric structure.

[0024] In this way, the frequency-selective surface unit (FSS) is insensitive to the polarization direction of electromagnetic waves, avoiding performance fluctuations caused by changes in polarization direction. Furthermore, rotational symmetry allows the FSS to exhibit more consistent frequency response characteristics for electromagnetic waves at different incident angles. For example, at oblique incidence, the performance difference between TE (transverse electric) and TM (transverse magnetic) polarized waves is smaller, reducing angle sensitivity. In addition, rotationally symmetric structures make tolerance control easier during manufacturing, especially in printing processes, where symmetrical patterns reduce directional errors and improve yield.

[0025] In some possible implementations, the dielectric layer is a single-layer structure, which can reduce the thickness of the frequency selective surface elements and thus help reduce the thickness of the frequency selective surface. Additionally, the cost of the dielectric layer can be reduced, thereby reducing the cost of the frequency selective surface elements and ultimately the cost of the frequency selective surface.

[0026] In some possible implementations, the dielectric layer is a multilayer structure, which can further improve the stopband suppression of the frequency selective surface and further improve the passband bandwidth of the frequency selective surface.

[0027] Secondly, embodiments of this application provide a frequency selective surface, which includes a plurality of frequency selective surface units as described in any of the first aspects. The plurality of frequency selective surface units are arranged in an array, and in a plane perpendicular to the thickness direction of the dielectric layer, the orthographic projections of the outer metal of two adjacent frequency selective surface units form a fourth slit.

[0028] In some possible implementations, the dielectric layers of any two frequency selective surface units are integrated into a single structure. Fabricating structures such as a central metal or ring-shaped metal within this integrated dielectric layer can improve the production efficiency of the frequency selective surface. Furthermore, it can reduce the volume of the frequency selective surface units.

[0029] In some possible implementations, the coupling metal between the outer metals of two adjacent frequency-selective surface units is a single structure.

[0030] This reduces the amount of coupling metal, eliminates the need to separate the coupling metal between the outer metals of two adjacent frequency selective surface units, reduces the manufacturing difficulty of the frequency selective surface, and improves the manufacturing efficiency of the frequency selective surface.

[0031] Thirdly, embodiments of this application provide an antenna system comprising multiple antenna arrays and a frequency selective surface as described in any of the second aspects. Any two antenna arrays operate at different frequency bands. Each antenna array includes at least one antenna element, and each antenna element includes a radiating element. The radiating element of one of the multiple antenna arrays is located on one side of the frequency selective surface, while the radiating elements of the remaining antenna arrays are located on the other side of the frequency selective surface. The operating frequency band of one antenna array is lower than that of the remaining antenna arrays. The frequency selective surface is used to reflect the radiated signal of one of the antenna arrays and to transmit the radiated signals of the remaining antenna arrays.

[0032] Fourthly, embodiments of this application provide a communication device that includes an antenna system as described in the third aspect. Attached Figure Description

[0033] Figure 1 is a schematic diagram of the base station antenna architecture in related technologies;

[0034] Figure 2 is a schematic diagram of the insertion loss of the frequency-selective surface in Figure 1;

[0035] Figure 3 is a top view of a frequency selective surface provided in an embodiment of this application;

[0036] Figure 4 is a three-dimensional schematic diagram of the frequency selective surface unit in Figure 3;

[0037] Figure 5 is a top view of the frequency selection surface shown in Figure 4;

[0038] Figure 6 is a schematic diagram of point A in Figure 3;

[0039] Figure 7 is a three-dimensional structural schematic diagram of the second frequency selective surface unit provided in the embodiment of this application;

[0040] Figure 8 is a top view of the frequency-selective surface unit in Figure 7;

[0041] Figure 9 is a schematic diagram of point C in Figure 8;

[0042] Figure 10 is a three-dimensional structural schematic diagram of the third frequency selective surface unit provided in the embodiment of this application;

[0043] Figure 11 is a top view of the frequency-selective surface unit in Figure 10;

[0044] Figure 12 is a schematic diagram of point E in Figure 11;

[0045] Figure 13 is a three-dimensional structural schematic diagram of the fourth frequency selective surface unit provided in the embodiments of this application;

[0046] Figure 14 is a top view of the frequency-selective surface unit in Figure 13;

[0047] Figure 15 is a schematic diagram of point D in Figure 14;

[0048] Figure 16 is a three-dimensional structural schematic diagram of the fifth frequency selective surface unit provided in the embodiments of this application;

[0049] Figure 17 is a top view of the frequency-selective surface unit in Figure 16;

[0050] Figure 18 is a schematic diagram of point D in Figure 17;

[0051] Figure 19 is a schematic diagram of the insertion loss of a frequency selective surface constructed from the frequency selective surface elements shown in Figure 16.

[0052] Explanation of reference numerals in the attached figures: 100, Frequency selective surface; 10, Frequency selective surface element; 11, Dielectric layer; 12, Central metal; 131, First annular metal; 132, Second annular metal; 13a, Inner metal; 13b, Outer metal; 14, Coupling metal; 15, Inductor structure; 16, Removal structure; 171, First slot; 172, Second slot; 173, Third slot; 174, Fourth slot; X, Length direction; Y, Width direction; Z, Thickness direction. Detailed Implementation

[0053] The terminology used in the implementation section of this application is for the purpose of explaining specific embodiments of this application only, and is not intended to limit this application.

[0054] The following explains the terms that may be used in the embodiments of this application:

[0055] A frequency selective surface (FSS) is a two-dimensional periodic array structure, essentially a spatial filter that interacts with electromagnetic waves and exhibits distinct bandpass or bandstop filtering characteristics. A FSS can transmit or reflect waves of different frequencies, thus providing specific frequency selection.

[0056] Frequency selective surface (FSS) elements are the basic periodic structural units that constitute a frequency selective surface.

[0057] Coupling can be understood as direct coupling and / or indirect coupling. "Coupled connection" can be understood as a direct coupling connection and / or indirect coupling connection. Direct coupling can also be called "electrical connection," which can be understood as physical contact and electrical conduction between components; it can also be understood as the form of connection between different components in a circuit structure through physical lines that can transmit electrical signals, such as copper foil or wires on a printed circuit board (PCB). "Indirect coupling" can be understood as electrical conduction between two conductors through a gap / non-contact method. In one embodiment, indirect coupling can also be called capacitive coupling, for example, signal transmission is achieved by forming an equivalent capacitance through coupling between the gaps between two conductive parts.

[0058] Operating Frequency Band: Regardless of the type of antenna, it always operates within a certain frequency range (bandwidth). For example, an antenna supporting the B40 band operates within the frequency range of 2300MHz to 2400MHz, or in other words, its operating frequency band includes the B40 band. The frequency range that meets the specifications can be considered the antenna's operating frequency band. The width of the operating frequency band is called the operating bandwidth. The operating bandwidth of an omnidirectional antenna may reach 3-5% of the center frequency. The operating bandwidth of a directional antenna may reach 5-10% of the center frequency. Bandwidth can be considered as a frequency range on both sides of the center frequency (e.g., the resonant frequency of a dipole), where the antenna characteristics are within the acceptable range of the center frequency.

[0059] This application provides a communication device, which includes, but is not limited to, base stations, radars, switches, routers, gateways, servers, network interface cards, wireless access points, modems, optical transceivers, fiber optic transceivers, mobile phones, tablets, laptops, and wearable devices (such as smart glasses, smart bracelets, smartwatches, and wireless headphones). The following description uses a base station as an example.

[0060] The base station can be a base transceiver station (BTS) in a Global System for Mobile Communications (GSM) or Code Division Multiple Access (CDMA) system, a Node B (NB) in a Wideband Code Division Multiple Access (WCDMA) system, an Evolutionary Node B (eNB) in a Long Term Evolution (LTE) system, or a radio controller in a Cloud Radio Access Network (CRAN) scenario. Alternatively, the base station can also be a relay station, access point, vehicle-mounted equipment, wearable device, or a g node (gNodeB or gNB) in a new radio (NR) system, or a base station in a future evolved network, etc., and the embodiments in this application are not limited to these.

[0061] Base stations are used to provide wireless signal coverage within a cell to enable communication between terminal devices and the wireless network. A base station includes a base station antenna, which is a type of antenna system used to transmit and receive radio frequency signals, thus facilitating communication between the terminal device and the wireless network.

[0062] The terminal device can be a mobile phone (as shown in Figure 1), a tablet computer, a laptop computer, or other devices.

[0063] Base station antennas are fundamental to current mobile communications and play a crucial role. To meet the ever-increasing demands for mobile communication speeds and bandwidth, higher-speed and larger-capacity communication systems need to be designed. Base station antenna systems are currently evolving from 5th-generation (5G) mobile communication technology to 5th-generation-Advanced (5G-A) commercialization acceleration technology. A key technology at present is providing operators with multi-band integrated antenna array solutions, namely, common-aperture antenna array technology.

[0064] Figure 1 is a schematic diagram of the base station antenna architecture in the related technology, and Figure 2 is a schematic diagram of the insertion loss of the frequency selection surface in Figure 1.

[0065] In related technologies, a base station antenna includes a first-band antenna array, a second-band antenna array, a third-band antenna array, a frequency selective surface 24, a reflector 25, and an radome 26. The operating frequency band of the first-band antenna array is lower than that of the second and third-band antenna arrays. Both the second and third-band antenna arrays are located inside the radome 26. The second radiating element 22 of the second-band antenna array and the third radiating element 23 of the third-band antenna array are located on the same side of the reflector 25, which reflects the radiated signal from the first-band antenna array. The first radiating element 21 of the first-band antenna array is located on the first side of the frequency selective surface 24, while the second radiating element 22 of the second-band antenna array and the third radiating element 23 of the third-band antenna array are both located on the second side of the frequency selective surface 24. The first and second sides of the frequency selective surface 24 are opposite sides of the surface. The frequency selective surface 24 acts as a reflector for the first-band antenna array, reflecting its radiated signal. The frequency selective surface 24 also serves as an electromagnetic transparent plate for the second and third frequency band antenna arrays. The frequency selective surface 24 transmits the radiated signals of the second and third frequency band antenna arrays, exhibiting electromagnetic transparency characteristics (i.e., electromagnetic waves can pass through freely) to the radiated signals of the second and third frequency band antenna arrays.

[0066] The frequency selection surface 24 has a stopband and a passband. The passband can be understood as the frequency range where electromagnetic waves can pass freely, and the stopband as the frequency range where electromagnetic waves are reflected. Here, we use the insertion loss frequency response curve of an FSS as an example to illustrate the definitions of the passband and stopband, as shown in Figure 2. Assuming the dielectric loss of the FSS is 0, the insertion loss of this FSS in the stopband is ≤-15dB (or the stopband suppression is 15dB), which can be understood as most of the electromagnetic energy being reflected back by the FSS in the stopband. Corresponding to the architecture in Figure 1, this FSS can serve as a reflector 25 for the first-band antenna array. Furthermore, Figure 2 shows that the insertion loss of this FSS in the passband is close to 0dB, which can be understood as almost all electromagnetic energy passing freely through the FSS. Corresponding to the architecture in Figure 1, this FSS can serve as an electromagnetic transparent plate for the first-band antenna array and the second-band antenna array.

[0067] However, the passband bandwidth of the frequency selective surface 24 in the related technology is insufficient in the second and third frequency bands, and the frequency range (passband) that the frequency selective surface 24 allows signals to pass through effectively cannot meet the requirements of practical applications. In addition, the stopband suppression of the frequency selective surface 24 in the first frequency band is insufficient. Within the stopband frequency range designed for the frequency selective surface 24, the attenuation capability of the FSS for electromagnetic waves does not meet the expected target, resulting in the inability to effectively suppress or block electromagnetic wave energy in specific frequency bands. Furthermore, the frequency selective surface 24 has insufficient large-angle stability in the first, second, and third frequency bands.

[0068] In view of this, embodiments of this application provide a frequency selective surface unit 10, a frequency selective surface 100, and an antenna system. The frequency selective surface unit 10 can form an N-ring (N+1) slot structure, enabling the frequency selective surface 100 to have both high stopband suppression and multi-passband transmission characteristics. This solves the problem of insufficient stopband suppression in the prior art and also addresses the problem of insufficient dual-passband bandwidth in the prior art. Furthermore, the frequency selective surface unit 10 includes a removal structure 16 for removing non-ideal resonant points that fall into the passband at large angles, improving stability at large angles. In addition, the frequency selective surface unit 10 uses a single-layer dielectric layer 11 to support the metal material, achieving a low-cost frequency selective surface 100. Wherein, N is greater than or equal to 2.

[0069] The antenna system provided in this application includes multiple antenna arrays and a frequency selective surface 100. Any two antenna arrays operate at different frequency bands. Each antenna array includes at least one antenna element, and each antenna element includes a radiating element. The radiating element of one of the multiple antenna arrays is located on one side of the frequency selective surface 100, while the radiating elements of the remaining antenna arrays are located on the other side of the frequency selective surface 100. The operating frequency band of one antenna array is lower than that of the remaining antenna arrays. The frequency selective surface 100 is used to reflect the radiated signal of one antenna array and to transmit the radiated signals of the remaining antenna arrays.

[0070] One of the antenna arrays operates in a frequency band that can be called the low-frequency band, and there is one low-frequency band. The remaining antenna arrays operate in frequency bands that can be called the high-frequency bands, and there is at least one high-frequency band.

[0071] For example, there are three antenna arrays: a first antenna array, a second antenna array, and a third antenna array. The operating frequency band of the first antenna array is lower than that of the second antenna array, and the operating frequency band of the third antenna array is also lower than that of the second antenna array. The first radiating element of the first antenna array is located on one side of the frequency selective surface 100, while the second radiating element of the second antenna array and the third radiating element of the third antenna array are located on the other side of the frequency selective surface 100. The frequency selective surface 100 serves as a reflector for the first antenna array and also as an electromagnetically transparent plate for the second and third antenna arrays.

[0072] It should be noted that the number of antenna arrays located on the other side of the frequency selection surface 100 can be more than two, such as three, four, or five.

[0073] In addition to radiating elements, an antenna unit may also include carrier components, feeding units, etc. The feeding unit is used to be electrically connected to the feeding network and to feed power to the radiating elements. The feeding method of the feeding unit to the radiating elements can be direct feeding or coupled feeding. The carrier component is used to carry the feeding unit, radiating elements, etc.

[0074] In addition to the antenna array and frequency selective surface 100, the antenna system may also include other structures. For example, the antenna array may also include a reflector, a feed network, a radome, etc. The feed network is used to electrically connect the transceiver and the antenna array, and the reflector is used to reflect the radiated signal of the antenna array located on the other side of the frequency selective surface 100.

[0075] The frequency selective surface unit 10 and frequency selective surface 100 provided in this application embodiment will be described in detail below with reference to specific embodiments.

[0076] Example 1

[0077] Figure 3 is a top view of a frequency selective surface provided in an embodiment of this application; Figure 4 is a three-dimensional schematic diagram of the frequency selective surface unit in Figure 3; Figure 5 is a top view of the frequency selective surface shown in Figure 4; and Figure 6 is a schematic diagram of point A in Figure 3.

[0078] The frequency selective surface 100 includes multiple frequency selective surface units 10, such as nine as shown in Figure 3. Of course, the number of frequency selective surface units 10 can be less or more than nine. The multiple frequency selective surface units 10 are arranged in an array, for example, the multiple frequency selective surface units 10 form a 3x3 array.

[0079] Referring to Figure 4, the frequency selective surface unit 10 includes a dielectric layer 11, a central metal 12, and at least two annular metals (13a or 13b in Figure 4). The central metal 12 and the at least two annular metals are disposed on the dielectric layer 11, or in other words, the dielectric layer 11 carries the central metal 12 and all the annular metals.

[0080] For example, as shown in FIG5, there are two annular metals, namely a first annular metal 131 and a second annular metal 132. In a plane perpendicular to the thickness direction of the dielectric layer 11, the orthographic projection of the first annular metal 131 surrounds the orthographic projection of the second annular metal 132, that is, the orthographic projection of the second annular metal 132 is located inside the orthographic projection of the first annular metal 131. Of course, the number of annular metals can also be more than two, for example, the number of annular metals can also be four.

[0081] At least two annular metals have an inner metal 13a and an outer metal 13b. Along a direction perpendicular to the thickness direction of the central metal 12 (as shown in Figure 5, either the X or Y direction), the inner metal 13a is the annular metal closest to the central metal 12, and the outer metal 13b is the annular metal furthest from the central metal 12. Referring to Figure 5, along a direction perpendicular to the thickness direction of the central metal 12 (as shown in Figure 5, either the X or Y direction), the distance between the first annular metal 131 and the central metal 12 is greater than the distance between the second annular metal 132 and the central metal 12. Therefore, the first annular metal 131 is the annular metal closest to the central metal 12, and the second annular metal 132 is the annular metal furthest from the central metal 12.

[0082] Referring to Figures 4 and 5, in a plane perpendicular to the thickness direction of the dielectric layer 11 (Z direction in Figure 5), the orthographic projection of any one annular metal (13a or 13b in Figure 5) surrounds the orthographic projection of the central metal 12 and is spaced apart from the orthographic projection of the central metal 12. The orthographic projections of any two annular metals are spaced apart. The orthographic projection of the inner metal 13a and the orthographic projection of the central metal 12 form a first gap 171. The orthographic projections of two adjacent annular metals form a second gap 172. The orthographic projection of the outer metal 13b and the edge of the orthographic projection of the dielectric layer 11 form a third gap 173.

[0083] In this embodiment, the central metal 12, the annular metal, and the dielectric layer 11 can form an N-ring (N+1) slot structure. For example, as shown in Figure 5, the central metal 12, the annular metal, and the dielectric layer 11 form a two-ring three-slot structure. The N-ring (N+1) slot structure can form high stopband suppression characteristics in the low-frequency band while forming multi-passband transmission characteristics in multiple high-frequency bands. The frequency selective surface 100 has high stopband suppression and large passband bandwidth, which can solve the problem of insufficient stopband suppression in the prior art and can also solve the problem of insufficient dual passband bandwidth in the prior art.

[0084] In this context, "N rings" refers to the number of ring-shaped metal elements, where N is greater than or equal to 2. For example, N is 2, but N can also be greater than or equal to 2. The low-frequency band refers to the operating frequency band of an antenna array that radiates electromagnetic waves reflected by the frequency-selective surface 100, while the high-frequency band refers to the operating frequency band of an antenna array that radiates electromagnetic waves transmitted by the frequency-selective surface 100.

[0085] In this embodiment, the frequency selection surface 100 has i passbands, where i is an integer greater than or equal to 2. The gap between the inner metal 13a and the central metal 12 in a direction perpendicular to the thickness of the central metal 12 forms a coupling capacitor, which adjusts the position of the resonant point of one of the i passbands to meet usage requirements. The gap between any two adjacent annular metal rings in a direction perpendicular to the thickness of the central metal 12 forms a coupling capacitor, which can adjust the position of the resonant point of one of the remaining passbands of the i passbands.

[0086] Referring to Figure 5, the orthographic projection of the outer metal 13b and the edge of the orthographic projection of the dielectric layer 11 form a third gap 173, meaning that the orthographic projection of the outer metal 13b is located inside the orthographic projection of the dielectric layer 11, and there is a gap between the side edge of the outer metal 13b and the edge of the dielectric layer 11. Therefore, when multiple frequency selective surface units 10 are arranged in an array, in a plane perpendicular to the thickness direction of the dielectric layer 11, as shown in Figure 6, the orthographic projections of the outer metal 13b of two adjacent frequency selective surface units 10 form a fourth gap 174. At this time, the fourth gap 174 includes a portion of the third gap 173 of the two adjacent frequency selective surface units 10.

[0087] In a plane perpendicular to the thickness direction of the dielectric layer 11, the orthographic projection of the annular metal can be a square ring, a circular ring, a polygonal ring, or other shapes.

[0088] In some embodiments, in the same frequency selection surface unit 10, the shapes of the orthographic projections of at least two annular metals on a plane perpendicular to the thickness direction of the dielectric layer 11 may be different. For example, as shown in FIG. 5, the shapes of the orthographic projections of the two annular metals on a plane perpendicular to the thickness direction of the dielectric layer 11 are different.

[0089] In some embodiments, within the same frequency-selective surface unit 10, the orthographic projections of any two annular metal rings onto a plane perpendicular to the thickness direction of the dielectric layer 11 can also have the same shape.

[0090] In some embodiments, the annular metal is a first metal sheet. Thus, the annular metal is a metal layer disposed on the dielectric layer 11, which can be manufactured using PCB technology, thereby improving the manufacturing efficiency of the frequency selection surface 100.

[0091] In a plane perpendicular to the thickness direction of the dielectric layer 11, the orthographic projection of the central metal 12 can be a rectangle, trapezoid, circle, polygon, or an annular shape (as shown in Figure 5).

[0092] In some embodiments, the central metal 12 is a second metal sheet, thus the central metal 12 is a metal layer disposed on the dielectric layer 11, which can be manufactured using PCB technology, thereby improving the manufacturing efficiency of the frequency selection surface 100.

[0093] In one embodiment, the central metal 12 and the inner metal 13a may be located in the same plane. In another embodiment, the central metal 12 and the inner metal 13a may also be located in two planes spaced apart along the thickness direction of the dielectric layer 11.

[0094] In one embodiment, two adjacent annular metals forming the second gap 172 may be located on the same plane. In another embodiment, two adjacent annular metals forming the second gap 172 may also be located on two planes spaced apart along the thickness direction of the dielectric layer 11.

[0095] In one embodiment, the outer metal 13b of two adjacent frequency selective surface units 10 constituting the fourth slot 174 may be located on the same plane. In another embodiment, the outer metal 13b of two adjacent frequency selective surface units 10 constituting the fourth slot 174 may also be located on two planes spaced apart along the thickness direction of the dielectric layer 11.

[0096] In this embodiment, the dielectric layer 11 is made of an insulating material, such as glass, ceramic, foam, or plastic. Alternatively, the dielectric layer 11 can be a flame-retardant (FR-4) dielectric substrate, a Rogers dielectric substrate, or a hybrid of Rogers and FR-4 dielectric substrates, etc. Here, FR-4 is a designation for a flame-retardant material grade, and a Rogers dielectric substrate is a high-frequency board.

[0097] In some possible implementations, as shown in Figure 4, the dielectric layer 11 is a single-layer structure, which can reduce the thickness of the frequency selective surface unit 10 and help reduce the thickness of the frequency selective surface 100. Additionally, the cost of the dielectric layer 11 can be reduced, thereby reducing the cost of the frequency selective surface unit 10 and consequently the cost of the frequency selective surface 100.

[0098] When the dielectric layer 11 is a single-layer structure, in one embodiment, the central metal 12 and the annular metal can be located on the same side of the dielectric layer 11, for example, as shown in FIG. 5, where both the central metal 12 and the annular metal are located on the lower surface of the dielectric layer 11. Alternatively, in one embodiment, the central metal 12 and a portion of at least two annular metals are located on one side of the dielectric layer 11, and the other portion of at least two annular metals is located on the other side of the dielectric layer 11.

[0099] In some possible implementations, the dielectric layer 11 can also be a multilayer structure (not shown in the figure). In this case, the dielectric layer 11 may include at least two dielectric sublayers, which are stacked along the thickness direction of the dielectric layer 11. When the dielectric layer 11 is a multilayer structure, the stopband suppression of the frequency selective surface 100 can be further improved, and the passband bandwidth of the frequency selective surface 100 can be further improved.

[0100] When the dielectric layer 11 has a multilayer structure, in one embodiment, the central metal 12 and at least one annular metal can be disposed in the same dielectric sublayer; for example, the central metal 12 and any one of the annular metals can be disposed on the same side of the same dielectric sublayer. In one embodiment, the central metal 12 and the annular metals can be disposed in different dielectric sublayers. In one embodiment, all annular metals can be located in the same dielectric sublayer. In one embodiment, annular metals are disposed on at least two dielectric sublayers.

[0101] In some possible implementations, as shown in Figures 3 and 4, the dielectric layers 11 of any two frequency selective surface units 10 are integral structures. Fabricating structures such as the central metal 12 and ring-shaped metal within the integral dielectric layer 11 can improve the production efficiency of the frequency selective surface 100. Furthermore, it can also reduce the volume of the frequency selective surface unit 10.

[0102] In some possible implementations, as shown in Figure 5, the frequency selective surface unit 10 further includes a coupling metal 14 disposed on the dielectric layer 11. The coupling metal 14 is spaced apart from the outer metal 13b, and the coupling metal 14 and the outer metal 13b form a coupling capacitor. In this way, by loading the coupling metal 14 onto the outer metal 13b, the resonant point position of the stopband is adjusted, further increasing the stopband bandwidth and further improving the stopband rejection.

[0103] For example, as shown in FIG5, the number of coupling metals 14 is four. Of course, the number of coupling metals 14 may be less than or more than four.

[0104] In one embodiment, the coupling metal 14 is capacitively coupled with the outer metal 13b to form a distributed capacitor. In this way, the coupling metal 14 with the appropriate structure can be selected according to the layout scenario, which can broaden the degree of freedom for adjusting the performance of the frequency selectable surface 100.

[0105] The coupling metal 14 can be a third metal sheet or a metal wire, etc. In addition, the orthographic projection of the coupling metal 14 on a plane perpendicular to the thickness direction of the dielectric layer 11 can be a trapezoidal, square, or rectangular structure (as shown in Figure 5).

[0106] When the coupling metal 14 is a third metal sheet or metal line, the coupling metal 14 is equivalent to a metal layer disposed on the dielectric layer 11. In this case, it can be manufactured by PCB process, which can improve the manufacturing efficiency of the frequency selection surface 100.

[0107] Of course, in addition to forming a distributed capacitance with the outer metal 12b, in some possible implementations, the coupling metal 14 can also be a lumped capacitor, which refers to a capacitive component, such as a capacitor element.

[0108] In some possible implementations, the coupling metal 14 and the outer metal 13b are located in the same plane. In a plane perpendicular to the thickness direction of the dielectric layer 11, the orthographic projections of the coupling metal 14 and the outer metal 13b are spaced apart. In this way, the coupling metal 14 and the outer metal 13b are arranged adjacent to each other on the same plane, and the coupling metal 14 and the outer metal 13b form a coupling capacitor through adjacent coupling to adjust the resonant point position of the stopband, further increasing the stopband bandwidth and further improving the stopband suppression.

[0109] In some embodiments, the dielectric layer 11 is a single-layer structure. In this case, the coupling metal 14 and the outer metal 13b are located on the same side of the surface of the dielectric layer 11. For example, as shown in FIG5, the coupling metal 14 and the outer metal 13b are both located on the lower surface of the dielectric layer 11, which allows the coupling metal 14 and the outer metal 13b to form a coupling capacitor through adjacent coupling.

[0110] In some embodiments, when the dielectric layer 11 is a multilayer structure, the coupling metal 14 and the outer metal 13b are both located on one side surface of one of the dielectric sublayers of the dielectric layer 11. In this case, the coupling metal 14 and the outer metal 13b can be located on the surface or inside of the dielectric layer 11.

[0111] Figure 7 is a three-dimensional structural schematic diagram of the second frequency selective surface unit provided in the embodiment of this application, Figure 8 is a top view schematic diagram of the frequency selective surface unit in Figure 7, and Figure 9 is a schematic diagram of point C in Figure 8.

[0112] In some possible implementations, as shown in Figures 7 and 9, the coupling metal 14 and the outer metal 13b are spaced apart along the thickness direction of the dielectric layer 11 (Z direction in Figure 9). In a plane perpendicular to the thickness direction of the dielectric layer 11, the orthographic projection of the coupling metal 14 and the orthographic projection of the outer metal 13b at least partially coincide. Thus, the coupling metal 14 and the outer metal 13b are on different planes, forming a planar coupling capacitor to adjust the resonant point position of the stopband, further increasing the stopband bandwidth and further improving the stopband suppression.

[0113] In some embodiments, the dielectric layer 11 is a single-layer structure, with the coupling metal 14 and the outer metal 13b located on opposite sides of the dielectric layer 11. For example, as shown in FIG8, the coupling metal 13 is disposed on the upper surface of the dielectric layer 11, and the outer metal 13b is disposed on the lower surface of the dielectric layer 11, such that the coupling metal 14 and the outer metal 13b are spaced apart along the thickness direction of the dielectric layer 11.

[0114] In some embodiments, when the dielectric layer 11 is a multilayer structure, the coupling metal 14 and the outer metal 13b can be located on opposite sides of the same dielectric sublayer, or the coupling metal 14 and the outer metal 13b can be located on two different dielectric sublayers.

[0115] In some possible implementations, as can be seen from Figures 3 and 6, the coupling metal 14 between the outer metal 13b of two adjacent frequency selective surface units 10 is an integral structure, which can reduce the number of coupling metals 14, eliminate the need to divide the coupling metal 14 between the outer metal 13b of two adjacent frequency selective surface units 10, reduce the manufacturing difficulty of the frequency selective surface 100, and improve the manufacturing efficiency of the frequency selective surface 100.

[0116] It should be noted that, in addition to being an integral structure, the coupling metal 14 between the outer metal 13b of two adjacent frequency selective surface units 10 can also be set separately in some scenarios. That is to say, the coupling metal 14 between the outer metal 13b of two adjacent frequency selective surface units 10 is set at intervals.

[0117] In some possible implementations, as shown in Figure 5, the frequency selective surface element 10 is a rotationally symmetric structure. This makes the frequency selective surface element 10 insensitive to the polarization direction of electromagnetic waves, avoiding performance fluctuations caused by changes in polarization direction. Furthermore, rotational symmetry allows the FSS to exhibit more consistent frequency response characteristics for electromagnetic waves with different incident angles. For example, at oblique incidence, the performance difference between TE (transverse electric) and TM (transverse magnetic) polarized waves is smaller, reducing angle sensitivity. In addition, rotationally symmetric structures make it easier to control tolerances during manufacturing, especially in printing processes, where symmetrical patterns can reduce directional errors and improve yield.

[0118] For example, as shown in FIG5, the frequency selective surface unit 10 is a rotationally symmetric structure that rotates 90° around a central axis parallel to the thickness direction of the dielectric layer 11 (Z direction in FIG5). In this case, the rotation angle is 90°. Of course, the rotation angle of the frequency selective surface unit 10 can also be less than or greater than 90°. For example, the rotation angle of the frequency selective surface unit 10 can also be 45°.

[0119] When the frequency selective surface unit 10 has a rotationally symmetric structure, both the central metal 12 and the annular metal are rotationally symmetric, and the number of coupling metals 14 is at least two, with the at least two coupling metals 14 distributed in a rotationally symmetric manner. The specific number of coupling metals 14 depends on the rotation angle of the frequency selective surface unit 10. For example, as shown in Figure 5, if the rotation angle of the frequency selective surface unit 10 is 90°, the corresponding number of coupling metals 14 can be four, with the four coupling metals 14 distributed in a rotationally symmetric manner at the four corners of the frequency selective surface unit 10.

[0120] It should be noted that, in addition to being a rotationally symmetric structure, the frequency selective surface unit 10 can also be a non-rotationally symmetric structure in some scenarios.

[0121] Example 2

[0122] Figure 10 is a three-dimensional structural schematic diagram of the third type of frequency selective surface unit provided in the embodiment of this application; Figure 11 is a top view schematic diagram of the frequency selective surface unit in Figure 10; Figure 12 is a schematic diagram of point E in Figure 11; Figure 13 is a three-dimensional structural schematic diagram of the fourth type of frequency selective surface unit provided in the embodiment of this application; Figure 14 is a top view schematic diagram of the frequency selective surface unit in Figure 13; and Figure 15 is a schematic diagram of point D in Figure 14.

[0123] The difference between Embodiment 2 and Embodiment 1 is that, as shown in Figure 10 or Figure 13, the frequency selective surface unit 10 further includes an inductor structure 15, which is connected in series with the outer metal 13b. By connecting the inductor structure 15 in series in the loop formed by the outer metal 13b, the inductance can be increased, further increasing the passband bandwidth. Furthermore, while setting the inductor structure 15, the width of the outer metal 13b can be designed to be large, reducing processing tolerance requirements, lowering processing difficulty, and improving yield and production efficiency.

[0124] It is understood that the inductor structure 15 is connected in series with the outer metal 13b, which means that the inductor structure 15 and the outer metal 13b form a ring structure. Referring to Figures 11 and 14, the orthographic projection of this ring structure on the plane perpendicular to the thickness direction of the dielectric layer 11 is a ring, and it surrounds the orthographic projection of the central metal 12 on the plane perpendicular to the thickness direction of the dielectric layer 11.

[0125] For example, as shown in FIG11, the number of inductor structures 15 is four. Of course, the number of four inductor structures 15 may be less or more than four.

[0126] In one embodiment, as shown in FIG11, the frequency selection surface unit 10 is a rotationally symmetric structure. In this case, the number of inductor structures 15 is at least two, and the at least two inductor structures 15 are distributed in a rotationally symmetric manner, and any two inductor structures 15 have the same structure.

[0127] In one embodiment, when the frequency selection surface unit 10 is a non-rotationally symmetric structure, the number of inductor structures 15 can be one or more. When the number of inductor structures 15 is at least two, the at least two inductor structures 15 can be distributed in a rotationally symmetric or non-rotationally symmetric manner. Wherein, when at least two inductor structures 15 are distributed in a rotationally symmetric manner, any two inductor structures 15 have the same structure. When at least two inductor structures 15 are distributed in a non-rotationally symmetric manner, the at least two inductor structures 15 can have the same structure, or any two inductor structures 15 can have different structures.

[0128] In some possible implementations, as shown in Figure 12, the inductor structure 15 can be a distributed inductor, which can broaden the degree of freedom in adjusting the performance of the frequency selective surface 100. Alternatively, the distributed inductor can be formed on the dielectric layer 11 using PCB fabrication, improving the manufacturing efficiency of the frequency selective surface 100.

[0129] Among them, the distributed inductor can be any distributed structure that can be equivalent to an inductor, such as thin straight line, double fan-shaped winding on the same layer (as shown in Figure 16), single fan-shaped winding (as shown in Figure 12), spiral winding (as shown in Figure 15), wall-head winding, double-sided inductor winding with metallized vias vertically connected.

[0130] When the distributed inductor is a spiral winding, as shown in Figures 13 and 15, the spiral winding and the outer metal 13b are spaced apart along the thickness direction of the dielectric layer 11. In this case, the frequency selective surface unit 10 also includes at least two electrical connectors. The spiral winding corresponds to two electrical connectors. One end of the spiral winding is electrically connected to the outer metal 13b through one of the electrical connectors, and the other end of the spiral winding is connected to the outer metal 13b through the other electrical connector. At this time, at least a portion of the electrical connector is located between the spiral winding and the outer metal 13b.

[0131] In one embodiment, the electrical connector may be a metallized via disposed in the dielectric layer 11. Alternatively, in another embodiment, the electrical connector may be a metal pillar penetrating at least a portion of the dielectric layer 11.

[0132] When the distributed inductor is a thin straight line, a double-fan-shaped winding on the same layer, a single-fan-shaped winding, or a wall-head winding, the distributed inductor and the outer metal 13b can be located on the same plane and directly connected, or the distributed inductor and the outer metal 13b can be located on different planes and indirectly connected through structures such as metallized vias.

[0133] When the distributed inductor is a double-sided inductor winding with metallized vias connected vertically, the outer metal 13b and the winding on one side of the double-sided inductor winding can be located on the same plane, or the outer metal 13b and the double-sided inductor winding can be spaced apart along the thickness direction of the dielectric layer 11.

[0134] Of course, in addition to being a distributed inductor, in some possible implementations, the inductor structure 15 can also be a lumped inductor, which is a single inductor element.

[0135] In one embodiment, the lumped inductor and the outer metal 13b may be located on the same plane. In another embodiment, the lumped inductor and the outer metal 13b may be located on different planes.

[0136] It should be noted that the inductor structure 15 and the central metal 12 can be located in the same plane, or they can be located in different planes. Additionally, at least one of the at least two ring metals, excluding the outermost metal 13b, can be located in the same plane as the inductor structure 15, or the remaining ring metals, excluding the outermost metal 13b, can be located in different planes from the inductor structure 15. The coupling metal 14 and the inductor structure 15 can be located in the same plane, or they can be located in different planes.

[0137] Example 3

[0138] Figure 16 is a three-dimensional structural schematic diagram of the fifth frequency selective surface unit provided in the embodiment of this application; Figure 17 is a top view schematic diagram of the frequency selective surface unit of Figure 16; Figure 18 is a schematic diagram of point D in Figure 17; and Figure 19 is a schematic diagram of the insertion loss of the frequency selective surface constructed by the frequency selective surface unit shown in Figure 16. In Figure 19, R0 represents the insertion loss curve with an incident angle of 0°, and R60 represents the insertion loss curve with an incident angle of 60°.

[0139] The difference between Embodiment 3 and Embodiment 2 is that, as shown in Figure 16, the frequency selective surface unit 10 further includes a removal structure 16. The removal structure 16 is coupled to the outer metal 13b, and the orthographic projection of the removal structure 16 is located inside the second slit 172 in a plane perpendicular to the thickness direction of the dielectric layer 11 (as shown in Figure 17). In this way, the removal structure 16 can remove non-ideal resonant points that fall into the passband at large angles, thereby improving large-angle stability and expanding the degree of freedom for adjusting the performance of the frequency selective surface unit 10.

[0140] As shown in Figure 19, when the frequency is 0.96 GHz, the insertion loss is -11.22 dB when the incident angle is 0° and -13.06 dB when the incident angle is 60°. Therefore, by setting the removal structure 16, the stability at large angles can be improved.

[0141] Furthermore, the frequency selective surface unit 10, while forming a two-ring, three-slot structure, also incorporates a coupling metal 14 and an inductor structure 15, as shown in Figure 19. This achieves a stopband rejection ratio of <-11dB in the 0.69–0.96GHz range, and two passbands in the 2.3–2.7 and 3.3–3.8GHz ranges with a worst-case in-band loss of <0.37dB. This configuration enables high stopband rejection and increases the bandwidth of both passbands.

[0142] In one embodiment, as shown in FIG18, the removal structure 16 can be directly connected to the outer metal 13b, that is, the removal structure 16 is directly coupled to the outer metal 13b.

[0143] In one embodiment, the removal structure 16 is spaced apart from the outer metal 13b (not shown in the figure), and there is a gap between the removal structure 16 and the outer metal 13b, through which the removal structure 16 is indirectly coupled to the outer metal 13b.

[0144] For example, as shown in FIG16, the removal structure 16 is a fourth metal sheet. The removal structure 16 is equivalent to a metal layer disposed on the dielectric layer 11. The removal structure 16 can be formed on the dielectric layer 11 by PCB process, thereby reducing the manufacturing difficulty of the frequency selection surface 100.

[0145] In a plane perpendicular to the thickness direction of the dielectric layer 11, the shape of the orthographic projection of the removal structure 16 can be a "1" shape, an "L" shape (as shown in Figure 18), an "S" shape, a fan shape, or a sawtooth shape, etc.

[0146] For example, as shown in Figure 17, the number of structures 16 removed is eight. Of course, the number of structures 16 removed can also be less or more than eight.

[0147] As shown in Figure 18, the frequency selective surface unit 10 is a rotationally symmetric structure. Therefore, the number of removal structures 16 is at least two, and the at least two removal structures 16 are rotationally symmetric about the central axis of the frequency selective surface unit 10.

[0148] In one embodiment, when the frequency-selective surface unit 10 is a non-rotationally symmetric structure, the number of removed structures 16 can be one or more. When the number of removed structures 16 is at least two, the at least two removed structures 16 can be distributed in a rotationally symmetric or non-rotationally symmetric manner. Wherein, when the at least two removed structures 16 are distributed in a rotationally symmetric manner, any two removed structures 16 have the same structure. When the at least two removed structures 16 are distributed in a non-rotationally symmetric manner, the at least two removed structures 16 can have the same structure, or any two removed structures 16 can have different structures.

[0149] In one embodiment, as shown in FIG18, the removal structure 16 and the outer metal 13b are located on the same plane. At this time, both the removal structure 16 and the outer metal 13b are located on the lower surface of the dielectric layer 11.

[0150] In another embodiment, the removal structure 16 and the outer metal 13b may also be located on different planes. In this case, the removal structure 16 and the outer metal 13b are spaced apart along the thickness direction of the dielectric layer 11.

[0151] It should be noted that the removal structure 16 and the central metal 12 can be located in the same plane, or they can be located in different planes. Additionally, at least one of the at least two annular metals, excluding the outer metal 13b, can be located in the same plane as the removal structure 16, or the remaining annular metals, excluding the outer metal 13b, can be located in different planes from the removal structure 16. The coupling metal 14 and the removal structure 16 can be located in the same plane, or they can be located in different planes. The inductor structure 15 and the removal structure 16 can be located in the same plane, or they can be located in different planes.

[0152] In the description of the embodiments of this application, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, an indirect connection through an intermediate medium, or the internal connection of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application according to the specific circumstances. The terms "first," "second," "third," "fourth," etc. (if present) are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0153] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the embodiments of this application, and are not intended to limit them. Although the embodiments of this application have been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A frequency selective surface unit (10), characterized by include: Dielectric layer (11); A central metal (12) is disposed on the dielectric layer (11); At least two annular metals are disposed in the dielectric layer (11). Each annular metal has an inner metal (13a) and an outer metal (13b). The inner metal (13a) is the annular metal closest to the central metal (12) among the at least two annular metals, and the outer metal (13b) is the annular metal furthest from the central metal (12) among the at least two annular metals. In a plane perpendicular to the thickness direction of the dielectric layer (11), any one of the annular metals... The orthographic projections of the annular metals surround the orthographic projection of the central metal (12) and are spaced apart from the orthographic projection of the central metal (12). The orthographic projections of any two annular metals are spaced apart. The orthographic projection of the inner metal (13a) and the orthographic projection of the central metal (12) form a first gap (171). The orthographic projections of two adjacent annular metals form a second gap (172). The orthographic projection of the outer metal (13b) and the edge of the orthographic projection of the dielectric layer (11) form a third gap (173).

2. The frequency selective surface unit (10) according to claim 1, characterized in that The frequency selective surface unit (10) further includes a coupling metal (14), which is disposed on the dielectric layer (11). The coupling metal (14) is spaced apart from the outer metal (13b), and the coupling metal (14) and the outer metal (13b) form a coupling capacitor.

3. The frequency selective surface unit (10) according to claim 2, characterized in that The coupling metal (14) and the outer metal (13b) are located in the same plane. In a plane perpendicular to the thickness direction of the dielectric layer (11), the orthographic projection of the coupling metal (14) and the orthographic projection of the outer metal (13b) are spaced apart.

4. The frequency selective surface unit (10) according to claim 2, characterized in that The coupling metal (14) and the outer metal (13b) are spaced apart along the thickness direction of the dielectric layer (11). In a plane perpendicular to the thickness direction of the dielectric layer (11), the orthographic projection of the coupling metal (14) and the orthographic projection of the outer metal (13b) at least partially overlap.

5. The frequency selective surface unit (10) according to any one of claims 2-4, characterized in that, The coupling metal (14) and the outer metal (13b) constitute a distributed capacitor.

6. The frequency selective surface unit (10) according to any one of claims 1-5, characterized in that, The frequency selective surface unit (10) further includes an inductor structure (15) connected in series with the outer metal (13b).

7. The frequency selective surface unit (10) according to claim 6, characterized in that The inductor structure (15) is a distributed inductor.

8. The frequency selective surface unit (10) according to any one of claims 1-7, characterized in that, The frequency selective surface unit (10) further includes a removal structure (16) coupled to the outer metal (13b), and the orthographic projection of the removal structure (16) is located inside the second slit (172) in a plane perpendicular to the thickness direction of the dielectric layer (11).

9. The frequency selective surface unit (10) according to claim 8, characterized in that In a plane perpendicular to the thickness direction of the medium layer (11), the orthographic projection of the removal structure (16) is in the shape of a "1", "L", "S", fan, or sawtooth.

10. The frequency selective surface unit (10) according to any one of claims 1-9, characterized in that, The frequency-selective surface unit (10) has a rotationally symmetric structure.

11. The frequency selective surface unit (10) according to any one of claims 1-10, characterized in that, The dielectric layer (11) is a single-layer structure or a multi-layer structure.

12. A frequency selective surface (100), characterized in that Includes a plurality of frequency selective surface units (10) as described in any one of claims 1 to 11; Multiple frequency selective surface units (10) are arranged in an array, and in a plane perpendicular to the thickness direction of the dielectric layer (11), the orthographic projections of the outer metal (13b) of two adjacent frequency selective surface units (10) form a fourth slit (174).

13. The frequency selective surface (100) according to claim 12, characterized in that The dielectric layer (11) of any two frequency selective surface units (10) is an integral structure.

14. The frequency selective surface (100) according to claim 12 or 13, characterized in that The coupling metal (14) between the outer metal (13b) of two adjacent frequency selective surface units (10) is an integral structure.

15. An antenna system, characterized by It includes multiple antenna arrays and a frequency selective surface (100) as described in any one of claims 12-14; Any two antenna arrays operate at different frequency bands. The antenna array includes at least one antenna element, and the antenna element includes a radiating element. The radiating element of one of the multiple antenna arrays is located on one side of the frequency selection surface (100), and the radiating elements of the remaining antenna arrays are located on the other side of the frequency selection surface (100). The operating frequency band of one of the antenna arrays is lower than the operating frequency band of the remaining antenna arrays. The frequency selective surface (100) is used to reflect the radiated signal of one of the antenna arrays and to transmit the radiated signal of the remaining antenna arrays.

16. A communication device, characterized by Including the antenna system as described in claim 15.

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