A broadband active frequency selective surface structure and unit structure thereof

Abstract

The application discloses a kind of broadband active adjustable frequency selection surface structure and unit structure thereof, belong to microwave technology and antenna technical field, including multiple periodic arrangement unit structure;Each unit structure includes first tight coupling radiation structure, second tight coupling radiation structure and dielectric slab, the plane where first tight coupling radiation structure and second tight coupling radiation structure each are perpendicular to the plane of dielectric slab, dielectric slab is connected between first tight coupling radiation structure and second tight coupling radiation structure;Dielectric slab is provided with radio frequency transmission path and direct current feed network, active switching device and band-pass filter structure are connected in series in radio frequency transmission path, the two ends of radio frequency transmission path are respectively coupled with first tight coupling radiation structure, second tight coupling radiation structure;Direct current feed network is electrically connected with active switching device, and radio frequency choke structure is provided in direct current feed network.The application has the comprehensive performance of wideband, wide angle, low loss and dynamic adjustable.

Description

Technical Field

[0001] This invention belongs to the field of microwave technology and antenna technology, specifically relating to a broadband active tunable frequency selective surface structure and its unit structure. Background Technology

[0002] A frequency selective surface (FSS) is a periodic electromagnetic structure with frequency filtering characteristics, capable of selectively transmitting or reflecting electromagnetic waves in specific frequency bands. It is widely used in radomes, radar absorbers, and other fields. System applications place higher demands on radomes: they must meet ultra-wideband requirements, high transmittance, and large-angle incident stability. Traditional passive FSSs, once fabricated, have fixed frequency response characteristics and cannot adapt to dynamically changing electromagnetic environments. Therefore, active frequency selective surfaces (AFSSs) have emerged, dynamically controlling their electromagnetic response by loading active devices (such as PIN diodes and varactor diodes) into the FSS unit. However, existing AFSS designs typically integrate active devices directly onto the resonant unit. This tight coupling causes parasitic parameters of the active devices to severely affect the in-band insertion loss and out-of-band rejection characteristics of the FSS. Furthermore, to achieve wideband characteristics, multi-layer cascaded structures are often used, making the overall structure more complex after introducing active control, difficult to design the feeding network, and challenging to achieve fast, synchronous state switching.

[0003] The patent application CN120824547A, entitled "Frequency Selective Surface Radome (FSS) and its Manufacturing Method", published on October 21, 2025, discloses that the FSS consists of, from bottom to top, a lower functional ceramic layer, a capacitive element array, an upper functional ceramic layer, and a resistive element array. However, once the fabrication is completed, its frequency response characteristics are fixed and cannot be dynamically adjusted according to changes in the external environment, making it difficult to meet the modern demand for rapid switching of radome functions.

[0004] Patent application CN117374604A, entitled "An Active Frequency Selective Surface Structure Based on PIN Diode," published on January 9, 2024, discloses a resonant unit comprising at least one periodically arranged resonant element. The resonant element, from top to bottom, consists of a first substrate dielectric layer, a first metal frequency selective surface layer, a first dielectric structure layer, a second metal frequency selective surface layer, a second substrate dielectric layer, a second dielectric structure layer, a third metal frequency selective surface layer, and a third substrate dielectric layer. Both the first and second metal frequency selective surface layers are inductor square ring structures, while the third metal frequency selective surface layer is a PIN diode ring structure. However, when communication is required (passband), the radome needs to ensure high transmittance; when stealth is required (stopband), effective suppression of radar wave reflection is necessary. Existing technologies struggle to achieve high-performance, rapid switching between these two states.

[0005] In summary, current frequency selective surface structures still suffer from the shortcomings of traditional passive FSS, such as limited functionality and inability to be dynamically reconfigured. Summary of the Invention

[0006] The purpose of this invention is to overcome the problem that current frequency selective surface structures still have the problem of limited functionality and inability to dynamically reconfigure traditional passive FSSs, and proposes a broadband active tunable frequency selective surface structure and its unit structure.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a broadband active tunable frequency selective surface structure, comprising a plurality of periodically arranged unit structures; Each unit structure includes a first tightly coupled radiating structure, a second tightly coupled radiating structure, and a dielectric plate. The planes of the first tightly coupled radiating structure and the second tightly coupled radiating structure are perpendicular to the plane of the dielectric plate, and the dielectric plate is connected between the first tightly coupled radiating structure and the second tightly coupled radiating structure. The dielectric flat plate is provided with an RF transmission path and a DC feed network. An active switching device and a bandpass filter structure are connected in series in the RF transmission path. The two ends of the RF transmission path are coupled to a first tightly coupled radiation structure and a second tightly coupled radiation structure, respectively. The DC power supply network is electrically connected to the active switching device, and an RF choke structure is provided in the DC power supply network.

[0008] Furthermore, the active switching device is a PIN diode, which is connected in series to the radio frequency transmission path, and the two bias terminals of the DC power supply network are electrically connected to the two electrodes of the PIN diode, respectively.

[0009] Furthermore, the RF choke structure is a fan-shaped RF choke structure, which is connected in series in the feeder of the DC power supply network.

[0010] Furthermore, the bandpass filter structure is a microstrip line bandpass filter, and the bandpass filter structure and the radio frequency transmission path are disposed on the surface of the dielectric plate.

[0011] Furthermore, both the first tightly coupled radiating structure and the second tightly coupled radiating structure include a dielectric substrate and a radiating patch, with the radiating patch formed on the surface of the dielectric substrate and the surface of the dielectric substrate perpendicular to the surface of the dielectric plate.

[0012] Furthermore, a coupling feed section is provided at the end of the radiating patch facing the dielectric plate. The coupling feed section is arranged adjacent to and opposite to the end of the radio frequency transmission path to form an electromagnetic coupling feed.

[0013] Furthermore, the side of the dielectric substrate is mated and fixed to the side of the dielectric plate.

[0014] Furthermore, the radio frequency transmission path is a microstrip transmission line, which is printed on the surface of the dielectric substrate.

[0015] Furthermore, multiple unit structures are arranged in a row and column periodic pattern, and the active switching devices of multiple unit structures in the same row or column are connected in parallel to the same DC bias feeder to form a parallel bias feeder structure.

[0016] In a second aspect, the present invention provides a unit structure of a broadband active tunable frequency selective surface structure, including a first tightly coupled radiating structure, a second tightly coupled radiating structure and a dielectric plate, wherein the planes of the first tightly coupled radiating structure and the second tightly coupled radiating structure are perpendicular to the plane of the dielectric plate, and the dielectric plate is connected between the first tightly coupled radiating structure and the second tightly coupled radiating structure. The dielectric flat plate is provided with an RF transmission path and a DC power supply network. The RF transmission path is connected in series with an active switching device and a bandpass filter structure. The two ends of the RF transmission path are electromagnetically coupled to the first tightly coupled radiation structure and the second tightly coupled radiation structure, respectively. The DC power supply network is electrically connected to the active switching device, and an RF choke structure is provided in the DC power supply network.

[0017] Compared with the prior art, the present invention has the following beneficial technical effects: This invention proposes a broadband active tunable frequency selective surface structure. It employs a three-dimensional architecture with a vertically tightly coupled radiating structure perpendicular to the dielectric plate, achieving decoupling of electromagnetic reception, bandpass filtering, active control, and electromagnetic radiation. This physically separates the radiation function from the active circuit function, allowing independent optimization of radiation and control performance and reducing design coupling complexity. The tightly coupled vertical radiating structure effectively expands the operating bandwidth while significantly improving frequency response stability under large-angle incidence, adapting to the engineering application requirements of wide-angle scanning. The RF transmission path integrates a bandpass filter structure and active switching devices, synergistically ensuring transmission efficiency within the passband and effectively suppressing out-of-band signals. Through optimization of the active circuit, rapid switching between on and off states is achieved while ensuring low insertion loss in the passband and high suppression in the stopband. Electrically controlled switching of the operating state is achieved through a DC feed network with an RF choke structure. The RF choke structure prevents RF signals from leaking to the feed network, ensuring stable and reliable control functionality. The unit can be flexibly and periodically expanded into an array, combining broadband, wide-angle, low-loss, and dynamically adjustable performance. Attached Figure Description

[0018] The accompanying drawings are provided to further understand the invention and constitute a part of this invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0019] Figure 1(a) is an oblique view of the unit structure of the active tunable frequency selective surface of the present invention, viewed from above.

[0020] Figure 1(b) is a perspective view of the unit structure of the active tunable frequency selective surface of the present invention, viewed from below.

[0021] Figure 2 This is a front view of the active tunable frequency selective surface unit of the present invention.

[0022] Figure 3 This is a top view of the active tunable frequency selective surface unit of the present invention.

[0023] Figure 4 This is a schematic diagram of the proposed final overall design of the active tunable frequency selective surface of the present invention, with a scale of 16×16. Among them, 1 is the upper vertical tightly coupled antenna structure, 2 is the lower vertical tightly coupled antenna structure, 3 is the X-band bandpass filter, 4 is the PIN diode, 5 is the DC feed line, 6 is the cross-sectional fan-shaped structure, 7 is the metallized via, 8 is the control voltage interface, and 9 is the ground.

[0024] Figure 5 The diagram shows the transmission frequency response curves of the present invention under different incident angles (0°, 30°, 45°, 60°) of a plane electromagnetic wave; wherein (a) is a schematic diagram of the transmission frequency response curve of the active tunable frequency selective surface under 0° incident angle, (b) is a schematic diagram of the transmission frequency response curve of the active tunable frequency selective surface under 30° incident angle, (c) is a schematic diagram of the transmission frequency response curve of the active tunable frequency selective surface under 45° incident angle, and (d) is a schematic diagram of the transmission frequency response curve of the active tunable frequency selective surface under 60° incident angle. Detailed Implementation

[0025] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0026] It should be noted that when an element is referred to as being "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only embodiments.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0028] It should be noted that the terms "first," "second," etc., in the specification and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0029] Example 1 A broadband active tunable frequency selective surface structure includes multiple periodically arranged unit structures. Each unit structure includes a first tightly coupled radiating structure, a second tightly coupled radiating structure, and a dielectric plate. The planes of the first and second tightly coupled radiating structures are perpendicular to the plane of the dielectric plate, which connects the first and second tightly coupled radiating structures. This invention employs a three-dimensional architecture with the vertical radiating structure perpendicular to the dielectric plate, structurally decoupling electromagnetic reception, signal processing, and electromagnetic radiation functions. This avoids the parasitic parameters of active switching devices directly interfering with the resonant characteristics of the radiating units, effectively reducing transmission loss within the passband and improving out-of-band signal suppression. The dielectric plate has an RF transmission path and a DC feed network. The RF transmission path contains an active switching device and a bandpass filter structure connected in series. The two ends of the RF transmission path are coupled to the first and second tightly coupled radiating structures, respectively. This invention uses a tightly coupled radiating structure in conjunction with a bandpass filter structure integrated into the dielectric plate to effectively expand the operating bandwidth and maintain a stable frequency response even under large-angle electromagnetic wave incidence, adapting to wide-angle scanning application requirements. The DC power supply network is electrically connected to the active switching device, and an RF choke structure is provided in the DC power supply network. This invention, by integrating the active switching device and the DC power supply network with the RF choke structure, enables rapid switching between wave-transmitting and wave-blocking operating states via bias voltage, achieving dynamic control of electromagnetic characteristics; the RF choke structure blocks RF signal leakage to the DC power supply network, ensuring stable and reliable control functionality.

[0030] The active switching device is a PIN diode, which is connected in series to the radio frequency transmission path. The two bias terminals of the DC power supply network are electrically connected to the two electrodes of the PIN diode. As an electronically controlled switching element, the PIN diode has a fast switching speed between on and off states and controllable parasitic parameters. After being connected in series to the radio frequency transmission path, the on and off of the radio frequency signal path can be directly controlled by the DC bias voltage. It is the core actuator for realizing the active adjustable characteristics of the frequency selective surface.

[0031] The RF choke structure is a fan-shaped RF choke structure, which is connected in series in the feeder of the DC power supply network. The fan-shaped RF choke structure has wide-band DC isolation characteristics. When connected in series in the DC feeder, it can effectively block the leakage of RF signals to the power supply network, avoid interference of the power supply line with the transmission performance of the RF path, and at the same time ensure the stable transmission of DC bias current, thus achieving effective isolation between RF signals and DC control signals.

[0032] The bandpass filter structure is a microstrip line bandpass filter, which is mounted on the surface of a dielectric planar substrate on the same plane as the RF transmission path. Microstrip line bandpass filters are small in size and highly integrated; their co-mounted placement with the RF transmission path simplifies the fabrication process. This structure can precisely define the operating passband range, and in conjunction with active switches, it constrains frequency selectivity, effectively improving the signal suppression capability outside the passband.

[0033] Both the first and second tightly coupled radiating structures include a dielectric substrate and a radiating patch. The radiating patch is formed on the surface of the dielectric substrate, with the substrate surface perpendicular to the dielectric plate surface. The sides of the dielectric substrate are mated and fixed to the sides of the dielectric plate. This vertical architecture, with the radiating patch supported by the dielectric substrate and arranged perpendicularly to the dielectric plate, forms a three-dimensional coupled structure. The tightly coupled layout effectively expands the operating bandwidth and improves frequency response stability under large-angle incident light. The side-matting fixing method ensures structural strength and coupling position accuracy.

[0034] A coupling feed section is provided at the end of the radiating patch facing the dielectric plate. The coupling feed section is arranged adjacent to and opposite the end of the RF transmission path to form an electromagnetic coupling feed. Through the adjacent and opposite arrangement of the coupling feed section and the end of the RF transmission path, energy transfer is achieved by near-field electromagnetic coupling without the need for direct conductor connection. This design can prevent DC bias signals from entering the radiating structure, making the RF transmission function and DC control function independent and non-interfering with each other.

[0035] The radio frequency (RF) transmission path is a microstrip transmission line, which is printed on the surface of a dielectric substrate. Using microstrip transmission lines as the RF signal transmission carrier results in a thin and lightweight structure with mature manufacturing technology, facilitating integration with active devices and filtering structures. It also enables precise impedance matching, reduces RF signal transmission loss, and ensures signal transmission efficiency within the passband.

[0036] Multiple unit structures are arranged in a row-column periodic pattern. The active switching devices of multiple unit structures in the same row or column are connected in parallel to the same DC bias feeder, forming a parallel bias feeder structure. The row-column periodic arrangement of unit structures is suitable for large-scale array applications. The active switches in the same row or column are connected in parallel to the same bias feeder, forming a parallel control architecture. This design can synchronously control the operating state of multiple units, significantly improving the overall state switching speed, while simplifying the wiring complexity of the array feeder network.

[0037] Example 2 A unit structure of a broadband active tunable frequency selective surface structure includes a first tightly coupled radiating structure, a second tightly coupled radiating structure, and a dielectric plate. The planes of the first tightly coupled radiating structure and the second tightly coupled radiating structure are perpendicular to the plane of the dielectric plate, and the dielectric plate is connected between the first tightly coupled radiating structure and the second tightly coupled radiating structure. The dielectric flat plate is provided with an RF transmission path and a DC power supply network. The RF transmission path is connected in series with an active switching device and a bandpass filter structure. The two ends of the RF transmission path are electromagnetically coupled to the first tightly coupled radiation structure and the second tightly coupled radiation structure, respectively. The DC power supply network is electrically connected to the active switching device, and an RF choke structure is provided in the DC power supply network.

[0038] This unit structure is based on a decoupled working mechanism of electromagnetic coupling reception—active channel control and filtering—electromagnetic coupling radiation. It achieves physical separation of radiation and control / filtering functions through a three-dimensional architecture. The three-dimensional layout, with a vertically aligned radiating structure perpendicular to the intermediate dielectric plate, structurally decouples the electromagnetic wave transmission / reception function from signal processing and active control functions. The vertically aligned, tightly coupled radiating structure is only responsible for the spatial coupling of electromagnetic energy. The active switch and filtering structure are all integrated into the RF transmission path of the intermediate dielectric plate. Energy is transferred between them through near-field electromagnetic coupling, avoiding direct interference of parasitic parameters of active devices with the resonant characteristics of the radiating unit. This reduces the design coupling between radiation and control performance, allowing for independent optimization of bandwidth, angular stability, and switching control performance.

[0039] When the DC power supply network applies a bias voltage to the active switching device, the active switching device is in a low-impedance conducting state, and the radio frequency transmission path is turned on. When the incident electromagnetic wave irradiates the first tightly coupled radiating structure, it excites an induced current on the radiating structure. The electromagnetic energy is coupled from the radiating structure into the radio frequency transmission path on the dielectric plate through the near-field electromagnetic coupling effect. The radio frequency signal propagates along the transmission path, and after the bandpass filter structure completes the frequency band selection, it continues to be transmitted through the turned-on active switching device. Finally, the radio frequency signal reaches the other end of the transmission path and is fed into the second tightly coupled radiating structure again through near-field electromagnetic coupling. The second tightly coupled radiating structure radiates the electromagnetic energy into space in the form of electromagnetic waves, completing the transmission of electromagnetic waves in the target frequency band.

[0040] When the DC power supply network applies a cutoff bias voltage (or zero bias) to the active switching device, the active switching device is in a high-impedance cutoff state, and the radio frequency transmission path is cut off. After the incident electromagnetic wave couples to the first tightly coupled radiation structure, the electromagnetic energy cannot be transmitted to the second tightly coupled radiation structure through the cutoff active switching device. Most of the electromagnetic energy is reflected and cannot pass through the unit structure, thereby achieving the blocking of electromagnetic waves and forming a stopband characteristic.

[0041] The DC power supply network provides bias voltage to the active switching devices, enabling electronically controlled switching between on / off states. The RF choke structure in the DC power supply network utilizes its high-frequency, high-impedance, and DC-low-pass impedance characteristics to present extremely high impedance to RF signals in the operating frequency band, effectively preventing RF signal leakage along the DC feed line and avoiding interference from the power supply network to the performance of the RF transmission path. Simultaneously, it presents extremely low impedance to the DC bias signal, ensuring a stable DC current supply to the active switching devices and achieving mutual isolation between the RF signal and the DC control signal.

[0042] Example 3 See Figure 1(a) and Figure 1(b). Figure 4 This is an overall structure of a broadband active tunable frequency selective surface (AFSS) structure, which adopts a "sandwich" layered architecture. The architecture consists of the following components stacked sequentially in the vertical direction: Upper vertical tightly coupled antenna structure 1: Located at the top of the unit, it is responsible for the termination and / or retransmission of electromagnetic waves.

[0043] Lower vertical tightly coupled antenna structure 2: Located at the bottom of the unit, it is responsible for receiving and forwarding electromagnetic waves.

[0044] When electromagnetic waves are incident from the top, the upper vertical tightly coupled antenna structure 1 is responsible for receiving electromagnetic waves, and the lower vertical tightly coupled antenna structure 2 is responsible for forwarding electromagnetic waves; when electromagnetic waves are incident from the bottom, the lower vertical tightly coupled antenna structure 2 is responsible for receiving electromagnetic waves, and the upper vertical tightly coupled antenna structure 1 is responsible for forwarding electromagnetic waves.

[0045] Middle plate: Connects the upper and lower vertical structures, integrating active circuits and filtering structures.

[0046] The element period size is 11.3 mm; the overall section height is 13.8 mm.

[0047] To control the state of PIN diode 4, an independent DC feed network was designed. This network includes a DC feed line 5 (divided into high and low levels) and an AC-blocking sector structure 6 (RFC, Radio Frequency Choke). The function of the AC-blocking sector structure 6 is to prevent radio frequency signals from leaking into the DC feed line 5, while allowing DC current to flow smoothly to drive PIN diode 4.

[0048] Figure 2 A microstrip line circuit with a PIN diode 4 is designed on the intermediate plate. The PIN diode 4 serves as the core switching element, and its conduction and cutoff are controlled by applying different DC bias voltages, thereby achieving the "opening" and "closing" of the electromagnetic signal channel.

[0049] Figure 3This is a bandpass filter. An X-band bandpass filter 3 structure is integrated on the middle plate. This filter, along with the PIN diode 4, is connected in series through a metallized via 7, and together they determine the passband characteristics of the entire unit. When the PIN diode 4 is on, the signal passes through the filter; when the PIN diode 4 is off, the signal path is blocked.

[0050] like Figure 4 This diagram illustrates a 16×16 active frequency selective surface array. To achieve a large-area radome, the aforementioned unit structures are arranged periodically to form a 16×16 or larger array. A parallel control scheme is employed; for example, every 8 PIN diodes are controlled by a single DC signal, requiring only 32 parallel control signals for the entire 256-element array. Compared to the traditional serial shift register method, this parallel feeding method achieves faster switching speeds and meets low-latency switching requirements.

[0051] Figure 5 (a) is a schematic diagram of the transmission frequency response curve of an active tunable frequency selective surface under 0-degree incident angle.

[0052] Passband state (communication mode): When a forward bias voltage is applied to PIN diode 4 to turn it on, the entire unit structure forms a passband in the X-band (8GHz-12GHz). The incident electromagnetic wave is captured by the upper receiving structure, passes through the turned-on PIN diode 4 and the bandpass filter, and is then radiated out by the lower relay structure, achieving high transmittance (simulation results >90%). Passband transmittance: ≥90% (8GHz~12GHz, within adjustable bandwidth).

[0053] Stopband state (stealth mode): When PIN diode 4 is unbiased or reverse biased and cut off, the electromagnetic signal channel is cut off. The incident electromagnetic wave cannot pass through the unit and is reflected back. Stopband rejection: ≥15dB (8GHz~12GHz, adjustable bandwidth, bilateral transition band ≤2GHz).

[0054] Figure 5 Figures (b), (c), and (d) show the transmission frequency response curves of the active tunable frequency-selective surface when electromagnetic waves are incident at 30°, 45°, and 60°, respectively. Verification of the electromagnetic characteristics shows that the transmission frequency response curve remains highly stable within the incident angle θ ≤ 60°. This design successfully extends the stable operating range to ±60°, meeting the practical application requirements of most radar radomes for wide-angle scanning.

[0055] This invention boasts superior performance, featuring a wide bandwidth and angle, rapid switching capabilities, and specific characteristics: It achieves a transmittance greater than 90% (insertion loss less than 0.89dB) in the passband and a suppression greater than 15dB in the stopband, outperforming traditional AFSS. Thanks to the tightly coupled unit design, it exhibits excellent frequency response in the X-band and maintains stable performance even at E-plane and H-plane scanning angles reaching 45°. Employing a parallel DC-DC feed network, it achieves nanosecond-level state switching speeds (measured at approximately 200ns), far exceeding the millisecond-level speeds of traditional solutions, thus meeting the requirements for rapid stealth / communication switching.

[0056] This invention provides a broadband active tunable frequency selective surface (AFSS) structure that can be used in radar stealth and communication systems. Through a decoupled design concept of "electromagnetic reception—active channel processing + bandpass filtering—electromagnetic radiation," the electromagnetic wave reception, active modulation, filtering, and radiation functions are structurally decoupled, facilitating independent optimization and rapid design. This achieves high transmittance (>90%), high out-of-band rejection (>15dB), and large-angle incident stability over a wide bandwidth (e.g., X-band). The unique three-dimensional form, composed of a vertically tightly coupled structure and a central plate, facilitates broadband and wide-angle characteristics. By optimizing the active circuit design and integrating the active circuit with the filter, a PIN diode 4 and a bandpass filter are integrated on the central plate, achieving rapid on / off switching (approximately 200ns) while ensuring low insertion loss in the passband and high rejection in the stopband. The DC feed network includes a DC feed line 5 and an AC-isolated fan-shaped structure 6, ensuring effective control of active devices without affecting RF performance.

[0057] This invention proposes a broadband active tunable frequency selective surface structure that can be used as an radome, showing broad application prospects in the field of next-generation communications. This technology can be widely applied to conformal radomes for UAVs and phased array radars, with high transmittance and ±60° wide-angle stability ensuring omnidirectional sensing performance for airborne radar and communication links under large-angle scanning. This technology can empower 5G / 6G millimeter-wave base stations, vehicle-mounted autonomous driving radar, and low-orbit satellite internet terminals. Its low-loss design significantly improves signal transmission efficiency, while the active tunable characteristic provides the hardware foundation for intelligent reflector (RIS) technology, effectively solving the problem of signal obstruction in urban areas.

[0058] The above content provides a further detailed description of the present invention. It should not be construed that the specific embodiments of the present invention are limited to this. For those skilled in the art, several simple deductions or substitutions can be made without departing from the concept of the present invention, and all such deductions or substitutions should be considered as falling within the protection scope of the present invention as determined by the submitted content.

Claims

1. A broadband active tunable frequency selective surface structure, characterized in that, It includes multiple unit structures arranged in a periodic manner; Each of the unit structures includes a first tightly coupled radiating structure, a second tightly coupled radiating structure, and a dielectric plate. The planes of the first tightly coupled radiating structure and the second tightly coupled radiating structure are perpendicular to the plane of the dielectric plate, and the dielectric plate is connected between the first tightly coupled radiating structure and the second tightly coupled radiating structure. The dielectric flat plate is provided with an RF transmission path and a DC power supply network. An active switching device and a bandpass filter structure are connected in series in the RF transmission path. The two ends of the RF transmission path are respectively coupled to the first tightly coupled radiation structure and the second tightly coupled radiation structure. The DC power supply network is electrically connected to the active switching device, and the DC power supply network is provided with an RF choke structure.

2. The broadband active tunable frequency selective surface structure according to claim 1, characterized in that, The active switching device is a PIN diode, which is connected in series to the radio frequency transmission path. The two bias terminals of the DC power supply network are respectively electrically connected to the two electrodes of the PIN diode.

3. The broadband active tunable frequency selective surface structure according to claim 1, characterized in that, The radio frequency choke structure is a fan-shaped radio frequency choke structure, which is connected in series in the feed line of the DC power supply network.

4. The broadband active tunable frequency selective surface structure according to claim 1, characterized in that, The bandpass filter structure is a microstrip line bandpass filter, and the bandpass filter structure is disposed on the same side as the radio frequency transmission path on the surface of the dielectric plate.

5. The broadband active tunable frequency selective surface structure according to claim 1, characterized in that, Both the first tightly coupled radiating structure and the second tightly coupled radiating structure include a dielectric substrate and a radiating patch. The radiating patch is formed on the surface of the dielectric substrate, and the surface of the dielectric substrate is perpendicular to the surface of the dielectric plate.

6. The broadband active tunable frequency selective surface structure according to claim 5, characterized in that, The radiating patch has a coupling feed section at one end facing the dielectric plate. The coupling feed section is arranged adjacent to and opposite to the end of the radio frequency transmission path to form an electromagnetic coupling feed.

7. The broadband active tunable frequency selective surface structure according to claim 5, characterized in that, The side of the dielectric substrate is fixedly connected to the side of the dielectric plate.

8. The broadband active tunable frequency selective surface structure according to claim 1, characterized in that, The radio frequency transmission path is a microstrip transmission line, which is printed on the surface of the dielectric plate.

9. The broadband active tunable frequency selective surface structure according to claim 1, characterized in that, The multiple unit structures are arranged in rows and columns periodically, and the active switching devices of multiple unit structures in the same row or column are connected in parallel to the same DC bias feeder to form a parallel bias feeder structure.

10. A unit structure for a broadband active tunable frequency selective surface structure, characterized in that, It includes a first tightly coupled radiating structure, a second tightly coupled radiating structure, and a dielectric plate. The planes of the first tightly coupled radiating structure and the second tightly coupled radiating structure are perpendicular to the plane of the dielectric plate. The dielectric plate is connected between the first tightly coupled radiating structure and the second tightly coupled radiating structure. The dielectric flat plate is provided with a radio frequency transmission path and a DC power supply network. An active switching device and a bandpass filter structure are connected in series in the radio frequency transmission path. The two ends of the radio frequency transmission path are electromagnetically coupled to the first tightly coupled radiation structure and the second tightly coupled radiation structure, respectively. The DC power supply network is electrically connected to the active switching device, and the DC power supply network is provided with an RF choke structure.

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