Dual-polarized reconfigurable invisible-transparency integrated frequency selective surface and antenna cover

Abstract

This application belongs to the field of microwave engineering, specifically relating to a dual-polarization, reconfigurable, stealthy, and transparent integrated frequency selective surface and radome. The frequency selective surface consists of a three-layer structure: an adjustable FSS layer, an adjustable impedance layer, and a non-adjustable impedance layer. A PIN diode is loaded in the adjustable layer, while a resistor is loaded in the impedance layer. A spiral resonator and an interdigital capacitor resonator are used in the non-adjustable and adjustable impedance layers, respectively. Metal structures arranged in the x and y directions are placed on both sides of the adjustable impedance layer to achieve dual polarization. The adjustable FSS layer forms a transmission window and has reconfigurable functionality. Utilizing the PIN diode and multi-layer structure design, the switching between transmission and absorption functions in the X-band is achieved, realizing a stealthy and transparent integrated design. Transmission and absorption modes can be switched in the X-band, achieving integrated stealth functionality. The radome, through this frequency selective surface, possesses both transmission and absorption capabilities and reconfigurable characteristics.

Description

Technical Field

[0001] This application belongs to the field of microwave engineering, specifically relating to a dual-polarization reconfigurable concealed transparent integrated frequency selective surface and radome. Background Technology

[0002] A frequency selective surface (FSS) is an infinitely large two-dimensional periodic structure that can achieve different functions by artificially controlling electromagnetic waves. The combination of a lossy layer and a lossless FSS can achieve electromagnetic wave transmission within the passband and absorption within the stopbands on both sides, and is also known as a frequency selective absorber (FSR). For traditional passive FSSs, once the structural parameters and lumped component parameters are determined, they can only transmit electromagnetic waves within a fixed passband and absorb electromagnetic waves within the stopband. This type of surface with fixed electromagnetic properties is difficult to adapt to the complex and ever-changing electromagnetic space characteristics of modern information-based electronic warfare. By combining variable components such as varactor diodes and PIN diodes with the FSS, and adding resistors, functions such as passband control or passband / stopband switching can be achieved. This structure is also known as an active frequency selective absorber (AFSR). Early research on AFSRs mainly focused on the design and simulation of PIN diode-based frequency selective surface (FSS) structures, which demonstrated switchable absorption and transmission characteristics. Subsequent research explored the use of varactors and transistors as active components, enabling continuous tuning of the AFSR's frequency response. Advances in new materials and manufacturing technologies have also led to more compact and efficient AFSR designs, such as those utilizing graphene and metamaterials. Furthermore, researchers have investigated the applications of AFSRs in various fields, including stealth technology, electromagnetic interference (EMI) mitigation, and advanced communication systems.

[0003] Existing technology 1 proposes a single-polarization absorption-transmission-absorption (ATA) switch. It employs a non-parallel resonant structure in the FSS layer, using a PIN diode for modulation. In the impedance layer, a spiral resonator and a cross-linked capacitor resonator, combined with a resistor and a PIN diode, are used to achieve the switching function of the transmission window, ensuring the absorption effect within the transmission window. However, due to its polarization sensitivity, the switching function cannot be matched with multiple polarization modes.

[0004] Furthermore, existing technology two uses a periodic arrangement of metal lines of varying widths in the FSS layer and loads PIN diodes, while employing a metal square ring resistor structure in the lossy layer to achieve out-of-band absorption. This structure constitutes a single-polarized TA-type switch. When the diode is turned on, the parallel resonant circuit of the FSS layer is disrupted, the transmission window disappears, and it becomes a total reflection zone. This structure suffers from the disadvantage of polarization sensitivity and lacks an absorption function after the transmission window is closed, preventing its extension to an ATA-type design. To address this, a dual-polarized ATA-type switch was designed by combining a PIN diode with an electric field-coupled resonator, reducing the insertion loss of the transmission window to 0.45dB. By adding an adjustable layer with PIN diodes under the traditional FSR, a dual-polarized AT-type switch was achieved, reducing insertion loss while realizing a low-profile design.

[0005] Furthermore, existing technology 3 proposes a three-dimensional ATA-type passband tunable AFSR, consisting of an FSR and a rectangular waveguide structure. A varactor diode is loaded inside the lossy layer and the rectangular waveguide to achieve the movement of the transmission window. This structure can achieve broadband absorption, but the transmission window is relatively narrow, and the fabrication process of the three-dimensional structure is quite complex.

[0006] In addition, some of the existing technologies mentioned above have difficulty satisfying multiple polarization matching requirements and have limited application scenarios; some structures cannot absorb waves outside the wave transmission window, increasing the probability of the target being detected; and some structures have a large cross-sectional thickness, making it difficult to maintain performance under large angle conditions.

[0007] Application content

[0008] The technical problem to be solved by this application is to provide a dual-polarization reconfigurable transparent integrated frequency selective surface and radome, which has wave absorption and transmission function and reconfigurability, and has a relatively simple structure and is easy to process.

[0009] This application provides a dual-polarized reconfigurable, transparent, integrated frequency selective surface and radome, including:

[0010] An adjustable FSS layer is used to form a wave-transparent window, the adjustable FSS layer including a PIN diode;

[0011] An adjustable impedance layer is used to achieve in-band absorption after the transmission window is closed. The adjustable impedance layer includes a cross-type resonator, a second PIN diode, and a first resistor.

[0012] A non-adjustable impedance layer is used to achieve out-of-band absorption outside the transmission window and increase the absorption bandwidth. The non-adjustable impedance layer includes a spiral resonator and a resistor.

[0013] Optionally, the non-adjustable impedance layer further includes a dielectric substrate three, a cross-shaped metal line disposed on the dielectric substrate three, four spiral resonators are centrally symmetrically disposed on the dielectric substrate three, the four spiral resonators are connected by the cross-shaped metal line, and a resistor two is connected in series on each of the four branches of the cross-shaped metal line to achieve out-of-band absorption.

[0014] The spiral resonator includes a rectangular spiral patch.

[0015] Optionally, the dielectric substrate three is made of polytetrafluoroethylene.

[0016] Optionally, the dielectric substrate three is in the shape of a rectangular plate, and the four spiral resonators are respectively disposed at the four apex corners of the dielectric substrate three.

[0017] Optionally, the adjustable FSS layer further includes a dielectric substrate, a square ring metal sheet disposed on one side of the dielectric substrate, a square metal sheet disposed on one side of the dielectric substrate and located within the square ring metal sheet, and a cross-shaped metal line disposed on the other side of the dielectric substrate. A square annular gap is formed between the square ring metal sheet and the square metal sheet. Four PIN diodes are centrally symmetrically disposed within the annular gap. The positive terminal of each PIN diode is connected to the square metal sheet, the negative terminal of each PIN diode is connected to the square metal sheet, and the square metal sheet is connected to the center of the cross-shaped metal line.

[0018] Optionally, the adjustable impedance layer further includes a dielectric substrate II, two interdigitated resonators disposed on both sides of the dielectric substrate II in parallel and in series, two PIN diodes II respectively disposed at the center of the two interdigitated resonators, four resistors I respectively disposed at both ends of the two interdigitated resonators, each of the four resistors I being connected to a connecting wire, and the two interdigitated resonators being connected to the resistors I through the connecting wire.

[0019] Optionally, the interdigitated resonator includes a trident tooth structure one and a trident tooth structure two, wherein the trident tooth structure one and the trident tooth structure two are staggered, and the middle trident teeth of the trident tooth structure one and the trident tooth structure two are connected by a PIN diode two.

[0020] Optionally, the dielectric substrate second is made of polytetrafluoroethylene;

[0021] Optionally, the dielectric substrate is made of polytetrafluoroethylene;

[0022] Optionally, the material of the interdigitated resonator is metal or conductive composite material.

[0023] Optionally, the side length of the square metal sheet is S1; the width of the annular gap is S2; the length of the interdigitated resonator is W1; the width of the first triangular tooth structure is W2; the distance between the adjacent side teeth of the first and second triangular tooth structures is W3; the ends of the side teeth of the first and second triangular tooth structures are spaced apart, and the width of the space is W4; the width of the connecting line is W5; the distance between the rectangular spiral patch and the edge of the third dielectric substrate is N1; the width of the rectangular spiral patch is N2; the rectangular spiral patch has three turns; and the spacing between adjacent turns is N. 3， Furthermore, the innermost circle has an inner width of N5, and the cross-shaped metal wire has a width of N4.

[0024] Wherein, S1:S2:W1:W2:W3:W4:W5:N1:N2:N3:N4:N5=6.6:0.2:2.7:2.0:0.3:0.3:0.2:0.2:0.1:0.1:0.14:0.4.

[0025] This application provides an antenna radome including one or more frequency selective surfaces as described above.

[0026] The beneficial effects of this application are that the frequency selective surface provided consists of a three-layer structure: an adjustable FSS layer, an adjustable impedance layer, and a non-adjustable impedance layer. PIN diodes (PIN diode one and PIN diode two) are loaded in the adjustable layers (adjustable impedance layer and adjustable FSS layer), while resistors (resistor one and resistor two) are loaded in the impedance layer. A spiral resonator and an interdigital capacitor resonator are used in the non-adjustable impedance layer and the adjustable impedance layer, respectively. Metal structures arranged in the x and y directions are placed on both sides of the adjustable impedance layer to achieve dual polarization. The adjustable FSS layer forms a transmission window and has reconfigurable functionality. Utilizing PIN diodes and a multi-layer structure design, the switching between transmission and absorption functions in the X-band is achieved, realizing an integrated stealth and concealment design. The emission and absorption modes can be switched in the X-band to achieve integrated stealth functionality. Furthermore, it maintains good performance under large angle conditions.

[0027] The radome provided in this application has wave-absorbing and wave-transmitting functions and reconfigurable characteristics through its frequency-selective surface. Attached Figure Description

[0028] Figure 1 A schematic diagram of the structure of the frequency selection surface provided in this application;

[0029] Figure 2 This is a schematic diagram of the adjustable FSS layer provided in this application;

[0030] Figure 3A schematic diagram of the single-layer structure of the adjustable impedance layer provided in this application;

[0031] Figure 4 A complete structural schematic diagram of the adjustable impedance layer provided in this application;

[0032] Figure 5 A schematic diagram of the structure of the non-adjustable impedance layer provided in this application;

[0033] Figure 6 CST and ADS simulation results of the non-adjustable impedance layer provided for this application;

[0034] Figure 7 CST and ADS simulation results of the adjustable FSS layer provided for this application;

[0035] Figure 8 Comparison of simulation results of ON / OFF states CST and ADS for the adjustable FSS layer provided in this application;

[0036] Figure 9 CST and ADS simulation results of the adjustable impedance layer provided for this application;

[0037] Figure 10 Comparison of CST and ADS simulation results for the ON / OFF states of the adjustable impedance layer provided in this application;

[0038] Figure 11 The equivalent circuit model of the frequency selection surface provided in this application;

[0039] Figure 12 The simulation results of CST and ADS for the frequency selection surface in the "ON" state provided in this application are shown.

[0040] Figure 13 The simulation results of CST and ADS for the frequency selection surface provided in this application in the "OFF" state are shown in the figure.

[0041] In the diagram: 10. Adjustable FSS layer; 11. Dielectric substrate one; 12. Square ring metal sheet; 13. Square metal sheet; 14. PIN diode one; 15. Cross-shaped metal line; 16. Annular gap; 20. Adjustable impedance layer; 21. Dielectric substrate two; 22. Interdigitated resonator; 221. Trident tooth structure one; 222. Trident tooth structure two; 23. PIN diode two; 24. Resistor one; 25. Connecting line; 30. Non-adjustable impedance layer; 31. Dielectric substrate three; 32. Spiral resonator; 33. Cross-shaped metal line; 34. Resistor two. Detailed Implementation

[0042] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0043] 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 application belongs. The terminology used herein is for the purpose of describing embodiments of this application only and is not intended to limit this application.

[0044] Before providing a detailed description of the embodiments of this application, some of the nouns and terms used in the embodiments of this application will be explained first. The nouns and terms used in the embodiments of this application shall be interpreted as follows:

[0045] In FSS, S-parameters typically include S11, S21, etc., where:

[0046] S11: Represents the return loss at port 1, also known as the input reflection coefficient. It measures the proportion of signal energy reflected back at the input port (port 1). The closer the value of S11 is to 0 (usually expressed in dB, such as -25dB, -40dB, etc.), the smaller the reflection, meaning the smaller the reflection loss in the transmission path.

[0047] S21: Represents the insertion loss during signal transmission from port 1 to port 2. It measures the loss of the signal during transmission. The closer the value of S21 is to 1 (0dB), the smaller the loss during transmission.

[0048] S11-TE-0°: This indicates the reflection coefficient of port 1 for electromagnetic waves in transverse electric mode at a specific angle (0°).

[0049] S11-TE-36°: This indicates the reflection coefficient of port 1 for electromagnetic waves in transverse electric mode at a specific angle (36°).

[0050] S11-TM-0°: Represents the reflection coefficient of port 1 for electromagnetic waves in transverse magnetic mode in the 0° polarization direction.

[0051] S11-TM-36°: This indicates the reflection coefficient of port 1 for electromagnetic waves in transverse magnetic mode in the 36° polarization direction.

[0052] S21-TE-0°: This indicates the transmission coefficient from port 1 to port 2 for electromagnetic waves in transverse electric mode at a specific angle (0°).

[0053] S21-TE-36°: This indicates the transmission coefficient from port 1 to port 2 for electromagnetic waves in transverse electric mode at a specific angle (36°).

[0054] S21-TM-0°: Represents the reflection coefficient from port 1 to port 2 for electromagnetic waves in transverse magnetic mode in the 0° polarization direction.

[0055] S21-TM-36°: This indicates the reflection coefficient from port 1 to port 2 for electromagnetic waves in transverse magnetic mode, in the 36° polarization direction.

[0056] like Figure 1-5 As shown, this application provides a dual-polarization reconfigurable transparent integrated frequency selective surface, including: an adjustable FSS layer 10, an adjustable impedance layer 20, and a non-adjustable impedance layer 30; wherein, the adjustable FSS layer 10 is used to form a transmission window, and the adjustable FSS layer 10 includes a PIN diode 14; the adjustable impedance layer 20 is used to achieve in-band absorption after the transmission window is closed, and the adjustable impedance layer 20 includes a cross-type resonator 22, a PIN diode 23, and a resistor 24; the non-adjustable impedance layer 30 is used to achieve out-of-band absorption outside the transmission window and increase the absorption bandwidth, and the non-adjustable impedance layer 30 includes a spiral resonator 32 and a resistor 34.

[0057] Compared with existing technologies, the frequency selective surface provided in this application consists of a three-layer structure: an adjustable FSS layer 10, an adjustable impedance layer 20, and a non-adjustable impedance layer 30. PIN diodes (PIN diode 14 and PIN diode 23) are loaded in the adjustable layers (adjustable impedance layer 20 and adjustable FSS layer 10), while resistors (resistor 24 and resistor 34) are loaded in the impedance layer. A spiral resonator 32 and an interdigital capacitor resonator are used in the non-adjustable impedance layer 30 and the adjustable impedance layer 20, respectively. Metal structures arranged in the x and y directions are placed on both sides of the adjustable impedance layer 20 to achieve dual polarization. The adjustable FSS layer 10 forms a transmission window and has a reconfigurable function. Utilizing PIN diodes and a multi-layer structure design, the switching between transmission and absorption functions in the X-band is achieved, realizing an integrated stealth and transparency design. The emission and absorption modes can be switched in the X-band to achieve integrated stealth functionality.

[0058] It should be noted that the selection of PIN diodes mainly takes into account cost, operating frequency band, and equivalent electrical parameters. This structure requires the PIN diodes to operate in the X-band and have relatively small equivalent capacitance.

[0059] In one embodiment, such as Figure 5As shown, the non-adjustable impedance layer 30 also includes a dielectric substrate 31, a cross-shaped metal line 33 disposed on the dielectric substrate 31, and four spiral resonators 32 centrally symmetrically disposed on the dielectric substrate 31. The four spiral resonators 32 are connected through the cross-shaped metal line 33. Resistors 34 are connected in series on each of the four branches of the cross-shaped metal line 33 to achieve out-of-band absorption. The spiral resonator includes a rectangular spiral patch.

[0060] Specifically, to better achieve out-of-band absorption and further extend the absorption bandwidth, a fixed-band, non-adjustable impedance layer 30 is designed to address this requirement. The transmission window corresponds to the adjustable FSS layer 10 and the adjustable impedance layer 20, simultaneously achieving out-of-band absorption. The non-adjustable impedance layer 30 uses spiral resonators 32 to realize the transmission window. Spiral resonators 32 are symmetrically loaded at the four corners of the dielectric substrate 31 and connected by cross-shaped metal lines 33. The centrally symmetrical structure ensures dual polarization. Out-of-band absorption is achieved by loading a lumped resistor 34 on the cross-shaped metal lines 33.

[0061] In this embodiment, the dielectric substrate 31 is a PTFE substrate with a thickness of 0.2 mm, a relative permittivity of 2.1, and an electrical loss tangent of 0.002. The non-adjustable impedance layer 30 undergoes full-wave simulation and equivalent circuit simulation using CST (Computer Simulation Technology, electromagnetic simulation analysis software) and ADS (Advanced Design System, electronic design automation (EDA) software developed by Keysight Technologies). The simulation results are compared and the parameters are optimized. The simulation results are as follows: Figure 6 The fitted curve is shown.

[0062] In one embodiment, such as Figure 2 As shown, the adjustable FSS layer 10 also includes a dielectric substrate 11, a square ring metal sheet 12 disposed on one side of the dielectric substrate 11, a square metal sheet 13 disposed on one side of the dielectric substrate 11 and located within the square ring metal sheet 12, and a cross-shaped metal line 15 disposed on the other side of the dielectric substrate 11. A square ring gap 16 is formed between the square ring metal sheet 12 and the square metal sheet 13. Four PIN diodes 14 are centrally symmetrically disposed within the ring gap 16, and the positive terminal of the PIN diodes 14 is connected to the square metal sheet 13, the negative terminal of the PIN diodes 14 is connected to the square metal sheet 13, and the square metal sheet 13 is connected to the center of the cross-shaped metal line 15. In order to realize the reconfigurable function, a fused bias network is used in the adjustable impedance layer 20, that is, no additional feed line is required. The adjustable FSS layer 10 uses the square ring gap 16 structure and the cross-shaped metal line 15 with through holes to realize the power supply.

[0063] Specifically, the frequency selection surface consists of an adjustable FSS layer 10, an adjustable impedance layer 20, and a non-adjustable impedance layer 30, from bottom to top. The adjustable FSS layer 10 primarily handles the implementation of the transmission window; the adjustable impedance layer 20 primarily handles in-band absorption after the transmission window is closed; and the non-adjustable impedance layer 30 primarily handles out-of-band absorption outside the transmission window, increasing the absorption bandwidth. A lumped resistor is loaded in the impedance layer, utilizing the resistor's losses to achieve the absorption function. In the adjustable layer, PIN diodes are used to implement an adjustable switching function: the on / off characteristics are used to change the resonant frequency, shifting the passband; and the out-of-band characteristics are used to achieve the switching function.

[0064] The adjustable FSS layer 10 functions as both a bandpass surface and a total reflection surface in two different states. Therefore, by utilizing the switching characteristics of the PIN diode 14, the passband is shifted. In the "ON" state, the bandpass function is achieved, with the PIN diode 14 in a conducting state; in the "OFF" state, the passband is shifted to a higher frequency, with the PIN diode 14 in a de-energized state. The shifted out-of-band characteristics are then used to achieve the total reflection characteristic of the original passband.

[0065] Based on the above scheme, a square annular slit 16 structure (such as...) with relatively good working bandwidth characteristics and angular stability was selected. Figure 2 (As shown). Due to its symmetrical structure, this structure achieves polarization insensitivity. The dielectric substrate 11 is a 0.2 mm thick PTFE substrate with a relative permittivity of 2.1 and a loss tangent of 0.002. Four PIN diodes 14 are symmetrically loaded at the center of the annular gap 16. The positive terminal of the PIN diode 14 is connected to the square metal patch at the center of the cell, and the negative terminal is connected to the square annular metal patch at the edge of the cell. To feed the PIN diodes, the square metal patch at the center of the cell is connected to the cross-shaped metal line 15 (width S3) on the other side of the dielectric substrate through a metal via. This achieves the feeding of the PIN diodes 14 in the tunable FSS layer 10.

[0066] It should be noted that other lossless FSS structures were considered during the structural design process, but the results were not satisfactory, while the square ring structure has better overall performance (insertion loss, relative bandwidth, size).

[0067] In one embodiment, the outer side length of the square ring metal sheet 12 is D.

[0068] In this embodiment, the adjustable FSS layer 10 uses CST and ADS to perform full-wave simulation and equivalent circuit simulation, and compares the simulation results to optimize the parameters. The simulation results are as follows: Figure 7 The fitted curve is shown. Utilizing the switching characteristics of a PIN diode, such as... Figure 8As shown, the transmission window at 9 GHz was moved to a higher frequency, and the total reflection characteristics at the original passband were realized by utilizing out-of-band characteristics.

[0069] In one embodiment, primarily targeting in-band and out-of-band absorption after the transmission window is closed, an adjustable impedance layer 20 is designed, such as... Figure 3 and Figure 4 As shown, the adjustable impedance layer 20 also includes a dielectric substrate 21, two interdigitated resonators 22 disposed in parallel and connected in series on both sides of the dielectric substrate 21, two PIN diodes 23 disposed at the center of the two interdigitated resonators 22, and four resistors 24 disposed at both ends of the two interdigitated resonators 22. Each of the four resistors 24 is connected to a connecting line 25, and the two interdigitated resonators 22 are connected to the resistors 24 through the connecting line 25.

[0070] Specifically, a cross-type resonator 22 is used to correspond the resonant frequency to the center frequency of the transmission window generated by the adjustable FSS. The cross-type resonators 22 are connected by metal wires, and the absorption function is achieved by loading a lumped resistor 24. A PIN diode 23 is loaded at the center of the cross-type resonator 22, and the PIN diodes 23 are connected in series in each polarization direction using metal wires, integrating the feed network into the functional structure and avoiding the impact of an additional feed structure on material properties. This bias network is also called a fused bias network, which means that the two cross-type resonators 22 are interconnected by metal wires. Therefore, all the diodes can be connected through the cross-type resonators 22 and the metal wires. Thus, only the positive and negative terminals of the voltage source need to be connected to both ends of the overall structure of the adjustable impedance layer 20 to control all the PIN diodes. Fusion bias networks are further divided into series fused bias networks and parallel fused bias networks. The series-connected fusion bias network requires voltage sources connected at both ends of the structure to satisfy the conduction voltage condition of all PIN diodes 223 in a circuit, while the parallel-connected fusion bias network only needs to provide the voltage to satisfy the conduction of a single PIN diode 223.

[0071] Considering the requirements of dual polarization characteristics, the adjustable impedance layer 20 needs to be structurally equivalent in both the x and y directions. This adjustable impedance layer 20 incorporates adjustable characteristics; therefore, the design of the feed lines needs to be considered in the structural design. A double-layer structure facilitates feeding in each polarization direction without requiring additional feed lines. Existing technology places the structures for both polarization directions on the same layer, but this requires additional feed lines to be led out from both layers and a series lumped inductor, resulting in a complex structure and significant impact.

[0072] In one embodiment, the dielectric substrate 21 is a PTFE substrate with a thickness of 0.3 mm, a relative permittivity of 2.1, and a loss tangent of 0.002. To achieve dual polarization, mutually perpendicular periodic unit structures (a structure consisting of a cross-type resonator 22, a PIN diode 23, and two resistors 24) are arranged on both sides of the dielectric substrate 21, with their centers corresponding to each other (e.g., ...). Figure 4 (As shown).

[0073] In one embodiment, such as Figure 3 As shown, the interdigitated resonator 22 includes a trident tooth structure 1 221 and a trident tooth structure 222. The trident tooth structure 1 221 and the trident tooth structure 222 are arranged alternately, and the middle trident teeth of the trident tooth structure 1 221 and the trident tooth structure 222 are connected by a PIN diode 23.

[0074] The square metal sheet 13 has a side length of S1; the annular gap 16 has a width of S2; the interdigitated resonator 22 has a length of W1; the trident tooth structure 1 has a width of W2; the distance between the edge teeth of adjacent trident tooth structure 1 221 and the edge teeth of trident tooth structure 222 is W3; the ends of the edge teeth of trident tooth structure 1 221 and the ends of trident tooth structure 222 are spaced apart, and the width of the spaced distance is W4; the connecting line 25 has a width of W5; the distance between the rectangular spiral patch and the edge of the dielectric substrate 31 is N1; the width of the rectangular spiral patch is N2; the rectangular spiral patch has three turns; and the distance between adjacent turns is N. 3， The innermost circle has an inner width of N5, and the cross metal wire 33 has a width of N4.

[0075] Wherein, S1:S2:W1:W2:W3:W4:W5:N1:N2:N3:N4:N5=6.6:0.2:2.7:2.0:0.3:0.3:0.2:0.2:0.1:0.1:0.14:0.4.

[0076] In this embodiment, the adjustable impedance layer 20 is simulated using CST and ADS for full-wave simulation and equivalent circuit simulation, such as... Figure 9 As shown, the equivalent circuit simulation results do not exhibit the additional resonant point at 13 GHz seen in the full-wave simulation. This is because the full-wave simulation considers the coupling effect between the upper and lower metal layers, leading to the appearance of gate lobes, while the equivalent circuit simulation does not consider this coupling effect. Figure 10 As shown, when in the "OFF" state, the PIN diode is in the conducting state, and the transmission window at 9GHz is closed.

[0077] In one embodiment, the frequency selective surface provided in this application is subjected to full-wave simulation and equivalent circuit simulation using CST and ADS. Thus far, a transmission window with a center frequency of 9 GHz has been generated using the tunable FSS layer 10, and in-band and out-of-band absorption functions have been introduced using the tunable impedance layer 20 and the non-tunable impedance layer 30. Cascading the three layers yields the following structure: Figure 1 , Figure 11 The overall model layout and equivalent circuit model are shown in Table 1. The optimized geometric parameters of each component are shown in Table 2.

[0078] Table 1

[0079]

[0080] Table 2

[0081]

[0082] When PIN diode 14 of the adjustable FSS layer 10 is turned on and PIN diode 23 of the adjustable impedance layer 20 is turned off, the frequency selection surface (the frequency selection surface provided in this application is a switch-type AFSR) is in the "ON" state; otherwise, it is in the "OFF" state. Simulations were performed for the two states and the two polarization modes, and the results are as follows: Figure 12 , 13 The curves are shown. When in the "ON" state, the reflection coefficient of electromagnetic waves in the frequency range of 4.32-13.75GHz (104.37%) is less than -10dB, with almost no difference for both TE and TM polarizations; the 3dB transmission bandwidth is 8.66-9.59GHz, and the transmission bandwidth is 1.13GHz. The minimum insertion loss under TE polarization is 0.91dB (8.99GHz); the minimum insertion loss under TM polarization is 1.11dB (8.99GHz). When incident waves of the two polarizations with the same initial phase are induced on the upper and lower surfaces of the adjustable impedance layer 20, the phase difference caused by the path difference leads to the results of the two polarizations not being completely consistent. Considering that the dielectric substrate absorbs a certain amount of electromagnetic waves, the 0.2dB difference in insertion loss under different polarizations can be explained. When in the "OFF" state, the absorption bandwidth of the frequency-selective surface almost covers 4GHz-12GHz, achieving broadband stealth performance.

[0083] The performance of the frequency-selective surface provided in this application is analyzed under oblique incidence conditions. Figure 11 , 12Simulation results show that for both TE and TM polarization modes, the frequency selection surface can basically maintain the integrated stealth and transmission switching function within a 36° oblique incident angle range, ensuring the maintenance of the transmission window and the basic absorption effect inside and outside the band, thus guaranteeing stealth performance under large incident angle conditions and transmission performance within the transmission window.

[0084] In the "ON" state, as the incident angle increases, the electric field of the TE wave remains parallel to the structural surface; the electric field of the TM wave forms an angle with the structural surface, so the projected component of the electric field on the structural surface decreases as the incident angle increases. Therefore, oblique incidence has almost no effect on the TE wave, but it does affect the TM wave. This manifests as a decrease in the horizontal projected component of the electric field, which in turn changes the induced current in the metal, further altering the equivalent capacitance and equivalent inductance of the metal, leading to a shift in the resonant point. The vertical projected component of the electric field increases, generating new equivalent capacitance between the metal layers, which in turn creates a new resonant circuit within the passband, reflecting some of the incident wave back and reducing S21, thus resulting in a non-ideal dip within the passband.

[0085] In the "OFF" state, as the incident angle increases, the absorption effect within the original transmission window (i.e., the in-band) gradually weakens, and the out-of-band absorption bandwidth gradually decreases. The reduction in absorption bandwidth is greater in TM polarization mode than in TE polarization mode. Overall, TE polarization mode outperforms TM polarization mode.

[0086] The frequency selective surface provided in this application maintains good performance under large angle conditions. A loss layer is designed using a combination of spiral inductors, cross-toe capacitors, lumped resistors, and PIN diodes. A PIN diode 14 is loaded onto the FSS layer using a ring-shaped slot 16, and feeding is achieved using a fused bias network and a cross-shaped metal line 15. The three-layer structure is modeled as an equivalent circuit using electromagnetic theory, and simulation analysis and comparison are performed to optimize the structural parameters. This structure possesses both wave absorption and transmission capabilities and reconfigurability, making it applicable to future smart radome systems.

[0087] This application provides a radome including one or more frequency selective surfaces. The radome has wave-absorbing and reconfigurable characteristics through the frequency selective surfaces.

[0088] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of protection of this application is limited to these examples; within the framework of this application, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of different aspects of one or more embodiments of this application as described above, which are not provided in detail for the sake of brevity.

[0089] One or more embodiments in this application are intended to cover all such substitutions, modifications, and variations that fall within the broad scope of this application. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of one or more embodiments in this application should be included within the protection scope of this application.

Claims

1. A dual-polarization reconfigurable, transparent, integrated frequency selective surface, characterized in that, include: An adjustable FSS layer (10) is used to form a wave-transparent window. The adjustable FSS layer (10) includes a PIN diode (14), a dielectric substrate (11), a square ring metal sheet (12) disposed on one side of the dielectric substrate (11), a square metal sheet (13) disposed on one side of the dielectric substrate (11) and located in the square ring metal sheet (12), and a cross-shaped metal line (15) disposed on the other side of the dielectric substrate (11). A square ring gap (16) is formed between the square ring metal sheet (12) and the square metal sheet (13). Four PIN diodes (14) are centrally symmetrically disposed in the ring gap (16). The positive electrode of the PIN diode (14) is connected to the square metal sheet (13), the negative electrode of the PIN diode (14) is connected to the square metal sheet (13), and the square metal sheet (13) is connected to the center of the cross-shaped metal line (15). An adjustable impedance layer (20) is used to achieve in-band absorption after the transmission window is closed. The adjustable impedance layer (20) includes a dielectric substrate (21), a cross-type resonator (22), a PIN diode (23), and a resistor (24). The two cross-type resonators (22) connected in series are respectively disposed on both sides of the dielectric substrate (21). The two PIN diodes (23) are respectively disposed at the center of the two cross-type resonators (22). The four resistors (24) are respectively disposed at both ends of the two cross-type resonators (22). Each of the four resistors (24) is connected to a connecting line (25). The two cross-type resonators (22) are connected to the resistors (24) through the connecting line (25). The two sides of the dielectric substrate (21) are respectively arranged with mutually perpendicular periodic unit structures. The periodic unit structure is a structure composed of a cross-type resonator (22), a PIN diode (23), and two resistors (24). The non-adjustable impedance layer (30) is used to achieve out-of-band absorption outside the transmission window and increase the absorption bandwidth. The non-adjustable impedance layer (30) includes a spiral resonator (32) and a resistor (34). The non-adjustable impedance layer (30) also includes a dielectric substrate (31) and a cross-shaped metal line (33) disposed on the dielectric substrate (31). The four spiral resonators (32) are centrally symmetrically disposed on the dielectric substrate (31). The four spiral resonators (32) are connected by the cross-shaped metal line (33). Each of the four branches of the cross-shaped metal line (33) is connected in series with a resistor (34) to achieve out-of-band absorption.

2. The frequency selective surface according to claim 1, characterized in that, The spiral resonator (32) includes a rectangular spiral patch; And / or, the dielectric substrate three (31) is made of polytetrafluoroethylene.

3. The frequency selective surface according to claim 2, characterized in that, The dielectric substrate three (31) is rectangular plate in shape, and the four spiral resonators (32) are respectively disposed at the four apex corners of the dielectric substrate three (31).

4. The frequency selective surface according to claim 3, characterized in that, The interdigitated resonator (22) includes a trident tooth structure one (221) and a trident tooth structure two (222). The trident tooth structure one (221) and the trident tooth structure two (222) are interleaved, and the middle trident teeth of the trident tooth structure one (221) and the trident tooth structure two (222) are connected by a PIN diode two (23).

5. The frequency selective surface according to claim 3, characterized in that, The dielectric substrate 2 (21) is made of polytetrafluoroethylene; And / or, the dielectric substrate (11) is made of polytetrafluoroethylene; And / or, the material of the interdigitated resonator (22) is metal or conductive composite material.

6. The frequency selective surface according to claim 4, characterized in that, The side length of the square metal sheet (13) is S1; the width of the annular gap (16) is S2; the length of the interdigitated resonator (22) is W1; the width of the first triangular tooth structure (221) is W2; the distance between the side teeth of the adjacent first triangular tooth structure (221) and the side teeth of the second triangular tooth structure (222) is W3; the ends of the side teeth of the first triangular tooth structure (221) and the ends of the second triangular tooth structure (222) are spaced apart, and the width of the space is W4; the width of the connecting line (25) is W5; the distance between the rectangular spiral patch and the edge of the dielectric substrate (31) is N1; the width of the rectangular spiral patch is N2; the number of turns of the rectangular spiral patch is three; and the distance between adjacent turns is N. 3， The innermost circle has an inner width of N5, and the cross metal wire (33) has a width of N4. Wherein, S1:S2:W1:W2:W3:W4:W5:N1:N2:N3:N4:N5=6.6:0.2:2.7:2.0:0.3:0.3:0.2:0.2:0.1:0.1:0.14:0.

4.

7. An antenna radome, characterized in that, Includes one or more frequency selective surfaces as described in any one of claims 1-6.

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