Frequency selective surface structure and antenna device including frequency selective surface structure

Abstract

This invention relates to a frequency selective surface (FSS) structure comprising one or more sheet elements, each of which is made of a tunable material (e.g., graphene) that switches between a reflective state and a non-reflective (transparent) state in response to an external input applied thereto. The external input can be represented by an electrical signal, a thermal effect, or a combination thereof. In the presence of multiple sheet elements, the sheet elements are arranged adjacent to each other, and each sheet element is provided with an independently controlled conductive substructure arranged in a manner that does not interfere with the transparent state of the sheet element. The FSS structure can be mounted in an antenna device to enable adjustment of the antenna device's radiation pattern.

Description

Technical Field

[0001] This invention generally relates to the field of antennas that radiate radio waves. Specifically, the invention relates to a frequency selective surface (FSS) structure for reflecting and transmitting radio waves according to external inputs applied to the FSS structure, and also to an antenna device including an FSS structure. Background Technology

[0002] Reconfigurable intelligent surfaces (RIS) can controllably influence antenna radiation patterns, making them highly attractive for upcoming sixth-generation (6G) communication systems. RIS can be based on various metamaterials, electromagnetic bandgap structures, or artificial magnetic conductors. Tunable metamaterials may be particularly advantageous for beam scanning without front-end phase shifters. In addition to planar antenna arrays, antennas realized through 3D printing or 3D molding of dielectric materials (such as dielectric resonator antennas) are likely to be an important research area for high-performance 6G communication systems.

[0003] In general, existing RIS are typically implemented as various types of graphene-based attenuators, absorbing structures, and reflecting surfaces. However, these RIS are all untunable, meaning that for radio waves, these RIS can only be either transparent or reflective. This is because such RIS often use conductor structures that are incompatible with transparent and reflective states, and / or prevent grounding connections (e.g., ground planes) from achieving a transparent state. To solve these problems, a complex multilayer conductor structure is needed.

[0004] Another potential approach is to use PIN diodes to connect the conductor structure to achieve both transparent and reflective states. However, this approach is limited to the frequency range below 10 GHz and results in high insertion losses, typically at least 3 dB. Since PIN diodes exhibit capacitive properties at higher frequencies, their performance is affected, further limiting their operating frequency range. PIN diode-based RIS also require complex voltage-fed networks, potentially comprising thousands of components. When used in the millimeter-wave range, the number of components increases dramatically, rendering the power consumption and practical implementation of voltage-fed networks impractical and infeasible. Summary of the Invention

[0005] This invention provides a brief overview of some concepts, which will be further described in the specific embodiments. This invention is neither intended to identify key features nor to limit the scope of the invention.

[0006] The purpose of this invention is to provide an FSS structure that can enhance the beam steering of radio waves.

[0007] The above objective is achieved through the features of the independent claim in the appended claims. Further embodiments and examples will be apparent from the dependent claims, detailed description, and drawings.

[0008] According to a first aspect, an FSS structure is provided. The FSS structure includes a dielectric substrate and at least one sheet element disposed on the dielectric substrate. Each of the at least one sheet element is made of a tunable material. The tunable material is responsive to an electrical signal applied to it, switching between a first state and a second state. The tunable material is used to reflect radio waves in the first state and to transmit the radio waves in the second state. The FSS structure further includes a conductive substructure for applying the electrical signal to the tunable material of each of the at least one sheet element. The conductive substructure includes at least one first conductor and at least one second conductor. The at least one first conductor is connected to each of the at least one sheet element. The at least one second conductor is disposed near each of the at least one sheet element such that a gap exists between the at least one second conductor and each of the at least one sheet element. By using an FSS structure configured in this way, beam steering can be provided over a wide angular range (e.g., up to 360° for applications below 6 GHz) and high gain can be achieved. Furthermore, by using this conductive substructure in the FSS structure, a simplified voltage feed network can be provided for radio frequency (e.g., millimeter-wave frequencies) (compared to the voltage feed networks used in existing RIS). Additionally, the number of components (e.g., 1 to 4 sheet elements) required by this configured FSS structure to achieve the desired beam steering angle range is reduced (compared to existing RIS). Finally, when the FSS structure is used on the walls and / or roof of a building, if the tunable material is in a second (transparent) state, the FSS structure can provide wireless coverage to users inside the building (e.g., through window glass); if the tunable material is in a first (reflective) state, the FSS structure redirects radio waves to users outside the building.

[0009] In one embodiment of the first aspect, the at least one second conductor comprises a plurality of discrete conductors disposed on the dielectric substrate surrounding each of the at least one sheet element. Implementing the second conductor in this manner reduces the cost of the conductive substructure (and the FSS structure itself) in terms of material consumption.

[0010] In one embodiment of the first aspect, the at least one second conductor is configured as a continuous conductive layer disposed on the dielectric substrate surrounding each of the at least one sheet element. By implementing the second conductor in this way, an electrical signal (e.g., voltage) can be uniformly applied to each tunable material.

[0011] In one embodiment of the first aspect, the at least one second conductor is disposed on each of the at least one sheet element. In this embodiment, the gap between the at least one second conductor and each of the at least one sheet element is filled with a dielectric material layer. This arrangement of the second conductor may be advantageous when a more compact FSS structure is required.

[0012] In one embodiment of the first aspect, the at least one second conductor is configured as a conductive mesh disposed on the dielectric material layer. By using the conductive mesh, electrical signals can be uniformly applied to the entire surface of the tunable material while barely interfering with the second (transparent) state of the tunable material.

[0013] In one embodiment of the first aspect, the dielectric substrate and the at least one sheet element each have a thickness selected based on the wavelength of the radio wave. Thus, a fully transparent FSS structure can be achieved when the tunable material is in a second (transparent) state.

[0014] In one embodiment of the first aspect, the tunable material includes: zero-bandgap semiconductors, metal-insulator transition (MIT) based materials, transition metal oxide (TMO) based materials, or combinations thereof. These materials exhibit better properties at millimeter-wave frequencies, thereby improving the performance of the FSS structure at these frequencies.

[0015] In one embodiment of the first aspect, the tunable material may also switch between the first state and the second state in response to thermal effects on each of the at least one sheet element. By using such a tunable material, the FSS structure can be controlled (alone or in combination) using two different methods (i.e., by applying an electrical input signal and a thermal input signal), thus enabling more flexible use of the FSS structure.

[0016] In one embodiment of the first aspect, the at least one sheet element comprises a plurality of sheet elements disposed adjacent to each other on the dielectric substrate. In this embodiment, the at least one first conductor of the conductive substructure comprises a plurality of first conductors, each of which is connected to one of the plurality of sheet elements. The at least one second conductor of the conductive substructure comprises a plurality of second conductors, each of which is disposed near and gapped from one of the plurality of sheet elements. By using this multi-element FSS structure, radio waves can be simultaneously reflected and transmitted by switching between a first state and a second state of the various sheet elements of the FSS structure. Therefore, the FSS structure can provide wireless coverage to users both inside and outside a building simultaneously.

[0017] In one embodiment of the first aspect, the number of the plurality of sheet elements is chosen such that the electric field generated in each of the plurality of sheet elements in response to the electrical signal is uniformly distributed across the sheet elements. This allows each of the plurality of sheet elements to reflect or transmit radio waves more efficiently.

[0018] According to a second aspect, an antenna device is provided. The antenna device includes a housing and at least one antenna element disposed within the housing and used for transmitting radio waves. The antenna device also includes at least one FSS structure according to a first aspect. Each of the at least one FSS structures is at least partially disposed within the housing along the radio wave propagation path. The antenna device further includes a power source for applying an electrical signal via a conductive element structure to a tunable material of each of the at least one sheet element in each of the at least one FSS structures. By using the FSS structures in the antenna device, the radiation pattern of the antenna device can be efficiently adjusted.

[0019] In one embodiment of the second aspect, each of the at least one FSS structure is disposed between the near field and the far field of the at least one antenna element. By arranging the FSS structures in this way, significant impedance matching degradation can be avoided. Furthermore, this arrangement of the FSS structures ensures that no grating lobes appear in the radiation pattern of the antenna device. Finally, placing the FSS structures somewhere between the near and far fields of the antenna element allows for a more compact antenna device.

[0020] In one embodiment of the second aspect, each of the at least one FSS structure is disposed in the far field of the at least one antenna element. By disposing the FSS structure in the far field of the antenna element, the performance of the antenna device can be improved (compared to the case where the FSS structure is disposed between the far field and near field of the antenna element), but this will increase the overall size of the antenna device.

[0021] In one embodiment of the second aspect, the antenna device further includes a temperature control element for applying heat to each of the at least one sheet element in each of the at least one FSS structure. By using such a temperature control element, other methods for controlling the FSS structure (i.e., by applying heat to the FSS structure) can be provided.

[0022] In one embodiment of the second aspect, the at least one FSS structure is in the shape of a hollow box or hollow tube, and the at least one antenna element is disposed within the hollow box or hollow tube. This configuration of the FSS structure allows for more efficient adjustment of the radiation pattern of the antenna device.

[0023] Other features and advantages of the invention will become apparent from reading the following detailed description and reviewing the accompanying drawings. Attached Figure Description

[0024] The invention is explained below with reference to the accompanying drawings, in which:

[0025] Figure 1 A schematic block diagram of a typical wireless communication system for indoor scenarios is shown.

[0026] Figure 2 A schematic block diagram of a frequency selective surface (FSS) structure according to a first exemplary embodiment is shown.

[0027] Figure 3 A schematic block diagram of a wireless communication system for indoor scenarios is shown, in which wireless communication is used. Figure 2 The FSS structure shown;

[0028] Figure 4 A schematic block diagram of an FSS structure according to a second exemplary embodiment is shown;

[0029] Figure 5 A schematic block diagram of an FSS structure according to a third exemplary embodiment is shown;

[0030] Figure 6 A schematic block diagram of an FSS structure according to a fourth exemplary embodiment is shown;

[0031] Figure 7 A schematic block diagram of a wireless communication system based on multiple indoor CPEs according to an exemplary embodiment is shown;

[0032] Figure 8 A schematic block diagram of an antenna device according to a first exemplary embodiment is shown;

[0033] Figure 9 A schematic block diagram of an antenna device according to a second exemplary embodiment is shown;

[0034] Figure 10 A schematic block diagram of an antenna device according to a third exemplary embodiment is shown;

[0035] Figure 11 A schematic block diagram of an antenna device according to a fourth exemplary embodiment is shown. Detailed Implementation

[0036] Various embodiments of the invention have been described in further detail with reference to the accompanying drawings. However, the invention may be embodied in many other forms and should not be construed as limited to any particular structure or function disclosed in the following description. Rather, these embodiments are provided to make the description of the invention detailed and complete.

[0037] As will be apparent to those skilled in the art from the detailed description, the scope of this invention includes any embodiment of the invention disclosed herein, whether implemented independently or in combination with any other embodiment of the invention. For example, the apparatus disclosed herein can be implemented in practice using any number of the embodiments provided herein. Furthermore, it should be understood that any embodiment of the invention can be implemented using one or more features set forth in the appended claims.

[0038] As used herein, the term "exemplary" means "for illustration." Unless otherwise stated, any embodiment described herein as "exemplary" should not be construed as preferred or having an advantage over other embodiments.

[0039] This document may use any positioning terms, such as "left," "right," "top," "bottom," "above," "below," "upper," "lower," "horizontal," "vertical," etc., to facilitate the description of the relationship of an element or feature to one or more other elements or features in accordance with the accompanying drawings. Clearly, positioning terms are intended to include different orientations of the device disclosed herein beyond those depicted in the drawings. For example, if the device in the drawings is envisioned to be rotated 90 degrees clockwise, the element or feature described as being "left" and "right" relative to other elements or features would be located "above" and "below" of those other elements or features, respectively. Therefore, the positioning terms used herein should not be construed as any limitation on the invention.

[0040] Although numerical terms such as "first," "second," "third," and "fourth" may be used herein to describe various embodiments and features, it should be understood that these embodiments and features should not be limited by these numerical terms. The numerical terms used herein are only used to distinguish one feature or embodiment from another. For example, the first state and the second state discussed herein may be renamed the second state and the first state, respectively, without departing from the teachings of the invention.

[0041] As used in the embodiments disclosed herein, an antenna device can refer to a device for radiating and receiving radio waves. Radio waves can refer to electromagnetic radiation occurring in the centimeter-wave (cm-wave) and millimeter-wave (mm-wave) bands. For example, radio waves have been used in wireless communications such as point-to-point communication, inter-satellite links, and point-to-multipoint communication. However, the applications of radio waves are not limited to wireless communications; they can also be used for applications such as vehicle navigation and control (air, ground, or sea), road obstacle detection, etc. Therefore, the antenna device according to the embodiments disclosed herein can be used in the same application scenarios as radio waves. More specifically, the antenna device can be implemented as part of user equipment (UE) (which may refer to customer premises equipment (CPE), such as wireless routers, switches, etc.), mobile devices, mobile stations, terminals, user units, mobile phones, cellular phones, smartphones, cordless phones, personal digital assistants (PDAs), wireless communication devices, desktop computers, laptop computers, tablet computers, single-board computers (SBCs) (e.g., Raspberry Pi devices), gaming devices, netbooks, smartbooks, ultrabooks, medical devices or medical equipment, biometric sensors, wearable devices (e.g., smartwatches, smart glasses, smart wristbands, etc.), entertainment devices (e.g., audio players, video players, etc.), vehicle components or sensors (e.g., driver assistance systems), smart meters / sensors, unmanned vehicles (e.g., industrial robots, quadcopters, etc.) and their components (e.g., autonomous vehicle computers), industrial manufacturing equipment, global positioning systems (GPS). System (GPS) device, Internet of Things (IoT) device, Industrial IoT (IIoT) device, Machine-type Communication (MTC) device, a group of Massive IoT (MIoT) or Massive MTC (mMTC) devices / sensors, or any other suitable device that operates using radio waves. In some embodiments, UE may refer to at least two juxtaposed and interconnected UEs as defined herein.

[0042] As used in the embodiments disclosed herein, a frequency selective surface (FSS) structure can refer to a structure that can be used to control the propagation of radio waves by altering the electrical and magnetic properties of the FSS structure. More specifically, an FSS structure can be used to reflect, transmit, or absorb radio waves of a specific frequency or frequency sub-band (e.g., from the millimeter-wave band).

[0043] Figure 1 A schematic block diagram of a typical wireless communication system 100 for indoor scenarios is shown. Figure 1 As shown, system 100 includes a first CPE (e.g., a wireless router) 102 mounted on a wall 104 within a room (e.g., a conference room). The first CPE 102 has a limited wireless coverage area 106, and it is initially assumed that two users are within the wireless coverage area 106 of the first CPE 102. If these two users decide to move around the room (e.g., ... Figure 1 As indicated by the middle arrow, they will move beyond the wireless coverage area 106 of the first CPE 102, resulting in a loss of wireless connectivity. To address this issue, system 100 includes a second CPE 108, which is similar to, for example, the first CPE 102. However, if both users continue to move further in the same direction, they will also leave the wireless coverage area of ​​the second CPE 108, thus requiring at least one additional CPE. This approach, based on using multiple CPEs within a room, is costly and undesirable from the user's perspective.

[0044] The exemplary embodiments disclosed herein provide a technical solution that can mitigate or even eliminate the aforementioned disadvantages inherent in the prior art. Specifically, the exemplary embodiments disclosed herein relate to an FSS structure comprising one or more sheet elements, each of which is made of a tunable material (e.g., graphene) that can switch between a reflective state and a non-reflective (transparent) state in response to an external input applied thereto. This external input can be represented by an electrical signal, a thermal effect, or a combination thereof. In the case of multiple sheet elements, the multiple sheet elements are arranged adjacent to each other, and each of the multiple sheet elements is provided with an independently controlled conductive substructure arranged in a manner that does not interfere with the transparent state of the sheet element. The FSS structure can be installed in an antenna device to make it possible to adjust the radiation pattern of the antenna device. Furthermore, such an configured FSS can provide an extended coverage area for a user, allowing the user to be served by only one such FSS structure (e.g., even if the user moves around the room, such as...). Figure 1 (As shown).

[0045] Figure 2A schematic block diagram of an FSS structure 200 according to a first exemplary embodiment is shown. Figure 2 As shown, the FSS structure 200 includes a dielectric substrate 202 (e.g., SiO2) and a sheet element 204 disposed on the dielectric substrate 202. The sheet element 204 is made of a tunable material having a first state and a second state. In the first state, the tunable material is used to reflect radio waves incident on the sheet element 204. In the second state, the tunable material is used to transmit radio waves incident on the sheet element 204. The transition between the first and second states can be responsive to an electrical signal applied to the tunable material. The tunable material can be represented by a zero-bandgap semiconductor, an MIT-based material, a TMO-based material, any combination of these materials, or any other material having similar switchable properties. A non-limiting example of a zero-bandgap semiconductor may be graphene. Examples of MIT-based and TMO-based materials may include, but are not limited to, vanadium dioxide and molybdenum disulfide. The sheet element 204 can be transferred onto the dielectric substrate 202 in a solid state or deposited onto the dielectric substrate 202 by any suitable fabrication method. The choice of manufacturing method depends on the tunable material involved, and may include, but is not limited to, chemical vapor deposition (CVD) and physical vapor deposition (PVD).

[0046] To apply an electrical signal to the tunable material of the sheet element 204, the FSS structure 200 also includes a conductive substructure formed by a combination of a first conductor 206 and a second conductor 208. The first conductor 206 is implemented as an electrode directly connected to the sheet element 204 (i.e., connected to the tunable material). The second conductor 208 is implemented as a continuous thin conductive layer surrounding the sheet element 204, such that a gap 210 exists between the second conductor 208 and the sheet element 204. More specifically, the second conductor 208 is implemented as a conductive ring or loop surrounding the sheet element 204. The first conductor 206 and the second conductor 208 can each be made of any metal (e.g., gold, silver, aluminum, copper, titanium, hafnium, nickel, zirconium, or any alloy thereof or combination thereof), conductive polymer, conductive copolymer, or semiconductor material. The gap 210 has a width suitable for the wavelength of radio waves and is optimized to generate a desired voltage difference between the first conductor 206 and the second conductor 208, or in other words, between the sheet element 204 and the second conductor 208.

[0047] It is worth noting that the dielectric substrate 202 and the sheet element 204 each have a thickness selected based on the wavelength of radio waves. In this case, the FSS structure 200 can be completely transparent when the tunable material is in the second (transparent) state. More specifically, to provide transparent operation of the FSS structure 200, the thickness of the dielectric substrate 202 on which the tunable material (e.g., graphene) is grown needs to be considered; otherwise, the FSS structure 200 will always be reflective (even if the tunable material is in the second state). To achieve both reflective and transparent operation of the FSS structure 200, the thickness of the dielectric substrate 202 with a dielectric constant dk > 3 (e.g., dk = 12 for Si / SiO2 used as a common substrate for graphene) can be (n*λ_g) / 2, where, dk is the wavelength of the radio wave in the guiding medium, f is the frequency of the radio wave, c is the speed of light in a vacuum, and n is any multiple of λ_g, meaning the material will be periodically transparent at multiple frequencies. When dk is small, or the thickness of the dielectric substrate 202 is extremely small, the thickness of the dielectric substrate 202 may not correspond to half the wavelength of the radio wave, as described above.

[0048] Generally, graphene is chosen as a tunable material because of its unique quantum properties, which lead to the phenomenon that the number of charge carriers in graphene depends on the polarity and value of the gate voltage (i.e., the voltage fed through the first conductor 206). If a voltage difference exists between the graphene and the toroidal or loop-shaped second conductor 208 separated from the graphene by the gap 310, the resulting electric field alters the number of mobile charge carriers (e.g., electrons), resulting in an excess of charge carriers compared to the neutral state (i.e., when no such voltage difference exists). The concentration of charge carriers is proportional to the applied voltage. Graphene is neutral when the gate voltage is zero, at which point its resistivity is at its maximum. The dependence of resistivity on gate voltage may vary with defects present in the graphene layers and is not significant in multilayer structures.

[0049] When the state transition of the tunable material is based on the gate voltage, the presence of a ring-shaped or loop-shaped second conductor 208 in the FSS structure 200 is advantageous because the ring-shaped or loop-shaped second conductor 208 can provide multiple voltage feed points to achieve a constant surface resistance of the tunable material. Therefore, a single chip element 204 may be sufficient, without the need to use multiple smaller elements on the same area. In some cases, a single voltage feed point (i.e., the second conductor 208 implemented as a point electrode) may not be sufficient to provide a constant surface resistance because the surface resistance in the middle of the chip element 204 may be smaller than that at the edges of the chip element 204.

[0050] As an alternative or complement to graphene, vanadium dioxide (VO2) can be used as a phase-change switch, providing the aforementioned transition from a first state to a second state. Phase-change switches utilize the abrupt MIT transition that occurs in TMOs, such as vanadium dioxide. The two distinct material states of vanadium dioxide (i.e., the metallic state and the insulating state) have different crystal structures and are defined as two distinct phases of vanadium dioxide, one being a conductive phase (and therefore reflective), and the other a dielectric phase (and therefore transparent). Unlike graphene, state transitions or phase transitions in vanadium dioxide or similar MIT-based materials can be controlled not only by using electrical signals but also by thermal effects (e.g., applied via a laser pointer). MIT-based materials are extremely fast, thus MIT-based phase-change devices can achieve deep subthermal switching (<10 mV / decade at room temperature). Vanadium dioxide can achieve low-temperature phase-change transitions, where its state changes from "dielectric" to "conductor," while simultaneously improving its energy efficiency and scalability.

[0051] Those skilled in the art will recognize that graphene and vanadium dioxide are merely two examples and should not be considered as limiting the invention in any way. Other potential materials, such as molybdenum disulfide, other zero-bandgap semiconductors, MIT-based materials, TMO-based materials, and 2D materials with similar switchable properties, or any combination of these or other potential materials (e.g., a combination of graphene and vanadium dioxide), can be used as tunable materials in the FSS structure 200. The only requirement is that the candidate tunable material has the property that it is possible to transition from a first (reflective) state to a second (transparent) state in response to an external input. As mentioned above, the external input can be an electrical signal or a thermal effect, etc. Depending on one of the two control methods used for the tunable material, the sheet element 204 may be surrounded by a ring-shaped or loop-shaped second conductor 208, or there may be some integrated or separate devices (e.g., optical infrared heaters) for applying heat to the tunable material to provide the transition between the aforementioned states.

[0052] Because the surface resistance of the tunable material used in the FSS structure 200 is significantly higher in the second (transparent) state than in the first (reflective) state, the tunable material can act as a conductor or dielectric (or insulator). In the second state, virtually all the electromagnetic (EM) energy of the radio waves is transmitted through the FSS structure 200, and the resistance of the entire FSS structure 200 can be higher than 700 Ω / sq (e.g., 1000 Ω / sq). However, when an electrical signal (or any other state-switching input depending on the tunable material used) is applied, the FSS structure 200 becomes conductive (i.e., provides the first state), thereby reflecting all the EM energy of the radio waves. In the first state, the resistance of the entire FSS structure 200 can be lower than 50 Ω / sq (e.g., 20 Ω / sq).

[0053] It should also be noted that, such as Figure 2 The number, shape, and arrangement of the structural elements constituting the FSS structure 200 shown are not intended to be any limitation of the invention, but only to provide a general idea of ​​implementing structural elements within the FSS structure 200. For example, in some other embodiments, the FSS structure 200 may include a plurality of sheet elements 204 disposed adjacent to each other on a dielectric substrate 202, and each of the plurality of sheet elements 204 may be provided with the same conductive substructure as described above. Generally, the number (and correspondingly, the size) of the plurality of sheet elements 204 can be selected such that the electric field generated in each of the plurality of sheet elements in response to an electrical signal is uniformly distributed on the sheet elements 204. Furthermore, the shape of the ring-shaped or loop-shaped second conductor 208 may be different. For example, the shape of the second conductor 208 may be similar to the shape of the sheet element 204 it surrounds.

[0054] Figure 3 A schematic block diagram of a wireless communication system 300 for indoor scenarios is shown, in which an FSS structure 200 is used. Figure 3 As shown, system 300 includes a CPE (e.g., a wireless router) 302 mounted on a wall 304 within a room (e.g., a conference room). Assume the CPE 302 is equipped with an FSS structure 200. Therefore, with... Figure 1 Unlike the CPE 102 shown, the CPE 302 has an extended wireless coverage range 306, which allows all users in the room to connect to the wireless network regardless of their location within the room. In other words, all users can be served by a single CPE 302.

[0055] Figure 4 A schematic block diagram of an FSS structure 400 according to a second exemplary embodiment is shown. Figure 4As shown, the FSS structure 400 includes a dielectric substrate 402 (e.g., Si / SiO2) and two identical sheet elements 404 disposed adjacent to each other on the dielectric substrate 402. The dielectric substrate 402 may have a thickness selected in the manner described above, i.e., by making the thickness correspond to half the wavelength of the incident radio wave. Each of the two sheet elements 404 is implemented in a similar manner to the sheet element 204 of the FSS structure 200. The FSS structure 400 also includes two identical conductive substructures, each for applying an electrical signal to one of the sheet elements 404. Each of the two conductive substructures has a first conductor 406 and a second conductor 408. The first conductor 406 and the second conductor 408 are implemented in a similar manner to the first conductor 206 and the second conductor 208, respectively. In other words, the first conductor 406 is implemented as an electrode directly connected to the sheet element 404, while the second conductor 408 is implemented as a conductive ring or loop around the sheet element 404 and has a gap 410 with the sheet element 404.

[0056] Unlike FSS structure 100, FSS structure 400 can be both reflective and transparent to incident radio waves. This is because the presence of two independent conductive electronic structures allows the two sheet elements 404 to be controlled in different ways. That is, one sheet element 404 can be switched to a first state, while the other sheet element 404 can be switched to a second state.

[0057] Figure 5 A schematic block diagram of an FSS structure 500 according to a third exemplary embodiment is shown. Figure 5As shown, the FSS structure 500 includes a dielectric substrate 502 (e.g., SiO2) and a sheet element 504 disposed on the dielectric substrate 502. The dielectric substrate 502 and the sheet element 504 can be implemented in a similar manner to the dielectric substrate 202 and the sheet element 204, respectively. Similar to the FSS structure 200, the FSS structure 500 also includes a conductive substructure for applying electrical signals to the sheet element 504 (i.e., the tunable material used to fabricate the sheet element 504). However, the conductive substructure of the FSS structure 500 differs from that of the FSS structure 200. Specifically, the conductive substructure of the FSS structure 500 includes a first conductor 506 and four second conductors 508-1, 508-2, 508-3, and 508-4. Similar to the first conductor 206, the first conductor 506 is implemented as an electrode directly connected to the sheet element 504. The second conductors 508-1, 508-2, 508-3, and 508-4 are implemented as discrete conductors, disposed on the dielectric substrate 502, located near the sheet element 504, and having an equal gap 510 with the sheet element 504. The gap 510 can be selected in the same manner as the selected gap 201. It should be noted that... Figure 5 The number and shape of the second conductors shown should not be considered as any limitation on the invention. In another embodiment, the FSS structure 500 may include two second conductors, wherein one second conductor is configured as a semi-loop around the sheet element 504 from the left, and the other second conductor is configured as a similar semi-loop around the sheet element 504 from the right. In yet another embodiment, the FSS structure 500 may include a plurality of second conductors uniformly or non-uniformly arranged around the periphery of the sheet element 504. Furthermore, in some other embodiments, the FSS structure 500 may include a plurality of first conductors and a plurality of second conductors, wherein each first conductor is disposed between two adjacent second conductors (similar to the first conductor 506 disposed between adjacent second conductors 508-1 and 508-4).

[0058] Figure 6 A schematic block diagram of an FSS structure 600 according to a fourth exemplary embodiment is shown. Figure 6As shown, the FSS structure 600 includes a dielectric substrate 602 (e.g., Si / SiO2) and a sheet element 604 disposed on the dielectric substrate 602. The dielectric substrate 602 and the sheet element 604 can be implemented in a similar manner to the dielectric substrate 202 and the sheet element 304, respectively. Similar to the FSS structure 200, the FSS structure 600 also includes a conductive substructure for applying electrical signals to the sheet element 604 (i.e., the tunable material used to fabricate the sheet element 604). However, the conductive substructure of the FSS structure 600 differs from that of the FSS structure 200. Specifically, the conductive substructure of the FSS structure 600 includes a first conductor 606 and a second conductor 608. Similar to the first conductor 206, the first conductor 606 is implemented as an electrode directly connected to the sheet element 604. The second conductor 608 is configured as a conductive mesh disposed on the sheet element 604, such that a gap exists between the second conductor 608 and the sheet element 604. Figure 6 (Not shown). This gap can be selected in the same manner as selection gap 210. This gap can be filled with a dielectric material layer, such that the second conductor 608 is disposed on this dielectric material layer. When using a dielectric material layer, its thickness (in addition to the thickness of the dielectric substrate 602 and the sheet element 604) should also be considered to provide transparent operation of the FSS structure 600 when the tunable material is in the second state. It is worth noting that... Figure 6 The configuration and shape of the second conductor shown should not be considered as any limitation of the invention. In other embodiments, the second conductor 608 may be implemented as a plurality of separate conductors disposed on the sheet element 604 in a uniform or non-uniform manner (e.g., disposed on the edge regions of the sheet element 604). Furthermore, the mesh configuration of the second conductor 608 may be implemented in different ways. For example, if desired, the conductive mesh may have cells of any polygonal shape, such as triangles, squares, rectangles, rhombuses, etc., depending on the specific application. Generally, the shape and size of the conductive mesh cells (e.g., square cells) may be based on the installation location of the FSS structure 600 (e.g., if the FSS structure 600 is intended to be installed on a window slab, the conductive mesh may be configured to be optically invisible).

[0059] Figure 7A schematic block diagram of a wireless communication system 700 based on multiple indoor CPEs is shown. More specifically, system 700 includes two network nodes 702-1 and 702-2, and three indoor CPEs, each installed in one of the houses 704-1, 704-2, and 704-3. Each network node in network nodes 702-1 and 702-2 can refer to a CPE in a specific wireless communication network or any other communication fixed point of a UE. A network node can be called a base transceiver station (BTS) in 2G communication technology, a NodeB in 3G communication technology, an evolved NodeB (eNodeB) in 4G communication technology, and a gNB in ​​5G new radio (NR) communication technology. It is assumed that each of the three indoor CPEs is equipped with any one of FSS structures 200, 400, 500, and 600. In this case, the energy of the radio waves radiated by each indoor CPE can be directed in almost any direction. like Figure 7 As shown, radio waves from the CPE installed in house 704-1 are directed to network node 702-1, while radio waves from the CPE installed in house 704-3 are directed to network node 702-2. Radio waves from the CPE installed in house 704-2 are simultaneously directed to both network nodes 702-1 and 702-2, as well as other desired directions (i.e., a multiple-input multiple-output (MIMO) scheme is possible). Therefore, by using any of the FSS structures 200, 400, 500, and 600, improved beam steering can be performed, and increased gain (e.g., from 2dBi to 3dBi to 7dBi to 8dBi) can be achieved. If the indoor CPE is not equipped with any of the FSS structures 200, 400, 500, and 600, the indoor CPE will provide an omnidirectional radiation pattern (in all directions), which may be useless in some use cases because the achievable gain may be very low compared to a CPE with an FSS structure.

[0060] Figure 8 A schematic block diagram of an antenna device 800 according to a first exemplary embodiment is shown. Figure 8 As shown, the antenna device 800 includes an antenna element 802, which is disposed in the housing ( Figure 8 (Not shown) and used for transmitting radio waves. The antenna device 800 also includes an FSS structure 804, which is disposed in a housing along the radio wave propagation path (i.e., Figure 8(On the antenna element 802 in the illustrated device configuration). The FSS structure 804 can be implemented as any of FSS structures 200, 400, 500, and 600. The FSS structure 804 can be additionally disposed in the far field of the antenna element 802, or disposed between the near field and the far field of the antenna element 802. The antenna device 800 is also intended to include a power supply ( Figure 8 (Not shown), this power source is used to apply an electrical signal to the tunable material used in the FSS structure 804, thereby providing a transition between the aforementioned states and thus providing beam steering. When the tunable material of the FSS structure 804 is in the first (reflective) state, the radio waves emitted by the antenna element 802 are reflected to the left by the FSS structure 804, i.e., the antenna device 800 has an end-fire radiation pattern 806-1. When the tunable material of the FSS structure 804 is in the second (transparent) state, the radio waves emitted by the antenna element 802 are transmitted through the FSS structure 804, i.e., the antenna device 800 has a side-fire radiation pattern 806-2.

[0061] Figure 9 A schematic block diagram of an antenna device 900 according to a second exemplary embodiment is shown. The antenna device 900 can be implemented as a CPE or any other UE. Figure 9 As shown, the antenna device 900 includes an antenna element 902, which is disposed in the housing ( Figure 9 (Not shown) and used for transmitting radio waves. The antenna device 900 also includes three independently controlled FSS structures 904-1, 904-2, and 904-3, which are disposed in a housing along the radio wave propagation path (i.e., Figure 9 (On the antenna element 902 in the illustrated device configuration). Similarly, FSS structures 904-1, 904-2, and 904-3 can be disposed in the far field of the antenna element 902, or between the near field and far field of the antenna element 902. The antenna device 900 is also intended to include a power supply ( Figure 9(Not shown), the power supply is used to apply an electrical signal to the tunable material used in each of the FSS structures 904-1, 904-2, and 904-3, thereby providing a transition between the aforementioned states and thus providing beam steering. More specifically, each of the FSS structures 904-1, 904-2, and 904-3 can be independently turned on / off for reflective / transparent operation. When the tunable material of FSS structure 904-3 is in the first (reflective) state and the tunable materials of FSS structures 904-1 and 904-2 are in the second (transparent) state, the antenna device 900 has an end-fire radiation pattern 906-1. Further, when the tunable materials of FSS structures 904-1, 904-2, and 904-3 are all in the second state, the antenna device 900 has a side-fire radiation pattern 906-2. Finally, when the tunable material of FSS structure 904-1 is in the first state and the tunable materials of FSS structures 904-2 and 904-3 are in the second state, the antenna device 900 has an end-fire radiation pattern 906-3.

[0062] Figure 10 A schematic block diagram of an antenna device 1000 according to a third exemplary embodiment is shown. The antenna device 1000 can be implemented as a CPE or any other UE. Figure 10 As shown, the antenna device 1000 includes a housing 1002 and an antenna module 1004. The antenna module 1004 is disposed within the housing 1002 and includes multiple antenna elements, each of which is used to transmit radio waves. The antenna device 1000 also includes three independently controlled FSS structures 1006-1, 1006-2, and 1006-3, which are completely disposed within the housing 1002 along the propagation path of the radio waves transmitted by the antenna elements (i.e., Figure 10 (On antenna module 1004 in the illustrated device configuration). Similarly, FSS structures 1006-1, 1006-2, and 1006-3 can be disposed in the far field of antenna module 1004, or between the near field and far field of antenna module 1004. Antenna device 1000 is also intended to include a power supply ( Figure 10 (Not shown), this power supply is used to apply an electrical signal to the tunable material used in each of the FSS structures 1006-1, 1006-2, and 1006-3, thereby providing a transition between the aforementioned states and thus providing beam steering. Generally, the operation of antenna device 1000 can be similar to that of antenna device 900.

[0063] Figure 11 A schematic block diagram of an antenna device 1100 according to a fourth exemplary embodiment is shown. The antenna device 1100 can be implemented as a CPE or any other UE. Figure 11As shown, the antenna device 1100 includes a housing 1102 and an antenna module 1104. The antenna module 1104 is disposed within the housing 1102 and includes multiple antenna elements, each of which is used to transmit radio waves. The antenna device 1100 also includes three independently controlled FSS structures 1106-1, 1106-2, and 1106-3, which are positioned along the propagation path of the radio waves transmitted by the antenna elements (i.e., Figure 11 (On the antenna module 1104 in the device configuration shown). However, with Figure 10 The devices shown have different configurations. The FSS structures 1106-1, 1106-2, and 1106-3 are positioned further away from the antenna module 1104, so that each FSS structure in FSS structures 1106-1 and 1106-3 extends partially by a certain distance b (i.e., Figure 11 The height of the device in the illustrated configuration extends beyond housing 1102, and the FSS structure 1106-2 is entirely outside housing 1102. Figure 10 Compared to the device configuration shown, the configuration of FSS structures 1106-1, 1106-2, and 1106-3 yields better operational results, but requires a larger overall device size. Generally, the optimal location for FSS structures 1106-1, 1106-2, and 1106-3 is in the far field of antenna module 1104. However, for example, to minimize the overall device size, FSS structures 1106-1, 1106-2, and 1106-3 can also be positioned in the near field of antenna module 1104, which still yields satisfactory operational results. Furthermore, besides positioning FSS structures 1106-1, 1106-2, and 1106-3 further away from antenna module 1104, antenna module 1104 can also be pushed downwards within antenna device 1100 to achieve the same operational results as antenna device 1100.

[0064] The table below shows a comparison of the performance (i.e., beam steering range) of different antenna devices. Specifically, "Reference" corresponds to an antenna device similar to antenna device 1000 but without the FSS structure, "Case 1" corresponds to antenna device 1000, and "Case 2" corresponds to antenna device 1100 with a distance b equal to 5 mm. Furthermore, "H-Pol" indicates horizontal polarization, and "V-Pol" indicates vertical polarization. To obtain the results shown in the table below, the FSS structure for each case is compared with the reference above. Figure 9The same approach is used to switch between transparent and reflective states. It can be seen that antenna devices 1000 and 1100 offer better beam steering range compared to antenna devices without an FSS structure (see "Improvements compared to the 'Reference' case" in the table below). Conversely, antenna device 1100 offers the best beam steering range, but the overall size of the device increases.

[0065]

[0066] It should be noted that any of the antenna devices 800 to 1100 is not limited to the number, shape, and arrangement of the FSS structures shown. In some other embodiments, each of the antenna devices 800 to 1100 may have an FSS structure in the shape of a hollow box or hollow tube, in which one or more antenna elements are disposed, or may have multiple FSS structures connected to each other to achieve the hollow box or hollow tube configuration. Furthermore, the size, shape, and number of FSS structures may vary depending on the specific application and the position of the FSS structures relative to each other and relative to the antenna elements.

[0067] In one embodiment, each of the antenna devices 800 to 1100 may further include a temperature control element for applying heat to the tunable material in each FSS structure. Examples of the temperature control element may include, but are not limited to, heat sources, heat sinks, optical heat sources, etc. Of course, the use of a temperature control element is only reasonable if the tunable material can provide a transition between the aforementioned states in response to temperature changes (e.g., when vanadium dioxide is used as the tunable material).

[0068] Although exemplary embodiments of the invention have been described herein, it should be noted that various changes and modifications may be made to the embodiments of the invention without departing from the scope of legal protection defined by the appended claims. In the appended claims, the word "comprising" does not exclude other elements or operations, and the terms "a" or "an" do not exclude multiple elements. The enumeration of certain measures in dissimilar appended claims does not imply that combinations of these measures cannot be used advantageously.

Claims

1. A frequency selective surface (FSS) structure, characterized in that, include: Dielectric substrate; At least one sheet element disposed on the dielectric substrate, each of the at least one sheet element being made of a tunable material, the tunable material being switchable between a first state and a second state in response to an electrical signal applied to the tunable material, the tunable material being used to reflect radio waves in the first state and transmit the radio waves in the second state; A conductive substructure for applying the electrical signal to the tunable material of each of the at least one sheet element, the conductive substructure including at least one first conductor and at least one second conductor, the at least one first conductor being connected to each of the at least one sheet element, and the at least one second conductor being disposed near each of the at least one sheet element such that a gap exists between the at least one second conductor and each of the at least one sheet element; Wherein, the at least one second conductor comprises a plurality of separate conductors disposed on the dielectric substrate surrounding each of the at least one sheet element; or, The at least one second conductor is configured as a continuous conductive layer disposed on the dielectric substrate surrounding each of the at least one sheet element; or... The at least one second conductor is disposed on each of the at least one sheet element, the gap between the at least one second conductor and each of the at least one sheet element is filled with a dielectric material layer, and the at least one second conductor is configured as a conductive mesh disposed on the dielectric material layer.

2. The FSS structure according to claim 1, characterized in that, The dielectric substrate and the at least one sheet element each have a thickness selected based on the wavelength of the radio wave.

3. The FSS structure according to claim 1 or 2, characterized in that, The tunable material includes at least one of the following: zero-bandgap semiconductor, metal-insulator transition (MIT) based material, and transition metal oxide (TMO) based material.

4. The FSS structure according to claim 1 or 2, characterized in that, The tunable material can also switch between the first state and the second state in response to thermal effects on each of the at least one sheet element.

5. The FSS structure according to claim 1 or 2, characterized in that, The at least one sheet element includes a plurality of sheet elements disposed adjacent to each other on the dielectric substrate. The at least one first conductor of the conductive substructure includes a plurality of first conductors, each of which is connected to one of the sheet elements. The at least one second conductor of the conductive substructure includes a plurality of second conductors, each of which is disposed near one of the sheet elements and has the gap with the sheet element.

6. The FSS structure according to claim 5, characterized in that, The number of the plurality of sheet elements is selected such that the electric field generated in each of the plurality of sheet elements in response to the electrical signal is uniformly distributed on the sheet elements.

7. An antenna device, characterized in that, include: case; At least one antenna element, which is disposed in the housing and used to transmit radio waves; At least one frequency selective surface (FSS) structure according to any one of claims 1 to 6, each of the at least one FSS structures is at least partially disposed in the housing along the radio wave propagation path; A power source for applying electrical signals via a conductive electronic structure to the tunable material of each sheet element in at least one sheet element of each of the at least one FSS structure.

8. The antenna device according to claim 7, characterized in that, Each of the at least one FSS structure is disposed between the near field and the far field of the at least one antenna element.

9. The antenna device according to claim 7, characterized in that, Each of the at least one FSS structure is disposed in the far field of the at least one antenna element.

10. The antenna device according to any one of claims 7 to 9, characterized in that, It also includes a temperature control element for applying heat to each of the at least one sheet element in each of the at least one FSS structure.

11. The antenna device according to any one of claims 7 to 9, characterized in that, The shape of the at least one FSS structure is a hollow box or a hollow tube, and the at least one antenna vibrator is disposed in the hollow box or hollow tube.

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