Dual-polarization reconfigurable hidden integrated frequency selective surface and antenna housing

Abstract

The invention belongs to the field of microwave engineering, and particularly relates to a dual-polarization reconfigurable hidden integrated frequency selective surface and an antenna housing, and the frequency selective surface is composed of three layers of structures: an adjustable FSS layer, an adjustable impedance layer and a non-adjustable impedance layer. Wherein the PIN diode is loaded in the adjustable layer, the resistor is loaded in the impedance layer, the spiral resonator and the interdigital capacitor resonator are used for the non-adjustable impedance layer and the adjustable impedance layer respectively, the metal structures arranged in the x direction and the y direction are placed on the two sides of the adjustable impedance layer respectively to achieve dual polarization, and the adjustable FSS layer is used for forming a wave-transparent window. And by utilizing the PIN diode and the multi-layer structure design, the switching between the wave-transparent function and the wave-absorbing function in the X wave band is realized, and the hidden and transparent integrated function design is realized. And an emission mode and an absorption mode can be switched in an X wave band, so that an integrated stealth function is realized. The antenna housing has a wave absorbing and transmitting function and a reconfigurable characteristic through the frequency selective surface.

Description

Technical Field

[0001] The present application belongs to the field of microwave engineering, and specifically relates to a dual-polarization reconfigurable concealed integrated frequency selective surface and antenna cover. Background Art

[0002] Frequency Selective Surface (FSS) is an infinite two-dimensional periodic structure that achieves different functions by artificially regulating electromagnetic waves. The combination of lossy layer and lossless FSS can achieve transmission in the passband and absorption of electromagnetic waves in the stopbands on both sides, which is also called frequency selective absorber (FSR). For traditional passive FSR, once the structural parameters and lumped component parameters are determined, electromagnetic waves can only be transmitted in a fixed passband and absorbed in the stopband. This surface with fixed electromagnetic characteristics is difficult to adapt to the complex and changeable electromagnetic space characteristics of modern information-based electronic warfare. By combining variable components such as varactor diodes and PIN diodes with FSS. On this basis, loading resistors can achieve functions such as passband regulation or passband and stopband switching. This structure is also called active frequency selective surface (AFSR) absorber. Early research on AFSR focused on the design and simulation of frequency selective surface (FSS) structures based on PIN diodes, which exhibited switchable absorption and transmission characteristics. Subsequent research has explored the use of varactors and transistors as active elements, enabling continuous tuning of the AFSR's frequency response. The development of new materials and manufacturing techniques has also led to more compact and efficient AFSR designs, such as those utilizing graphene and metamaterials. In addition, researchers have investigated the application of AFSRs in various fields, including stealth technology, electromagnetic interference (EMI) mitigation, and advanced communication systems.

[0003] The first prior art proposes a single-polarization absorption-transmission-absorption (ATA) switch, which uses a non-parallel resonant structure in the FSS layer and achieves regulation through a PIN diode; in the impedance layer, a spiral resonator and a cross-digital capacitor resonator are used, combined with a resistor and a PIN diode to achieve the switching function of the wave-transmitting window, and ensure the wave-absorbing effect in the wave-transmitting window. However, due to its polarization sensitivity, the switching function cannot match multiple polarization modes.

[0004] In addition, the second prior art uses metal wires of different widths to arrange periodically and load PIN diodes in the FSS layer, and uses a metal square ring to load a resistor structure in the lossy layer to achieve out-of-band wave absorption. This structure constitutes a unipolar TA-type switch. When the diode is turned on, the parallel resonant circuit of the FSS layer is destroyed, the wave-transmitting window disappears, and it becomes a full reflection band. This structure has the disadvantage of being sensitive to polarization, and there is no design for the wave-absorbing function after the wave-transmitting window is closed, which makes the structure unable to be expanded to an ATA-type design. In response to this, a dual-polarized ATA-type switch is designed by combining an electric field-coupled resonator with a PIN diode, and the insertion loss of the wave-transmitting window is reduced to 0.45dB. By adding an adjustable layer combined with a PIN diode to the lower layer of the traditional FSR, a dual-polarized AT-type switch is realized, which reduces the insertion loss and achieves a low-profile design.

[0005] In addition, the third prior art proposes a three-dimensional ATA type passband adjustable AFSR, which is composed of an FSR and a rectangular waveguide structure, and a variable capacitance diode is loaded inside the lossy layer and the rectangular waveguide to realize the movement of the wave transmission window. This structure can achieve broadband wave absorption, but the wave transmission window is narrow, and the three-dimensional structure processing process is relatively complicated.

[0006] In addition, some structures in the above-mentioned existing technologies are difficult to meet multiple polarization matching and have a single application scenario; some structures cannot achieve wave absorption outside the wave-transmitting window, increasing the probability of target detection; some structures have a large cross-sectional thickness and are difficult to maintain performance under large angle conditions.

[0007] Application Contents The technical problem to be solved by the present application is to provide a dual-polarized reconfigurable hidden integrated frequency selective surface and antenna cover, which has wave absorbing and transmitting function and reconfigurable characteristics, and has a relatively simple structure and is easy to process.

[0008] The present application provides a dual-polarization reconfigurable concealed integrated frequency selective surface and antenna cover, including: An adjustable FSS layer, used to form a wave-transmitting window, wherein the adjustable FSS layer includes a PIN diode 1; An adjustable impedance layer, used to achieve in-band wave absorption after the wave transmission window is closed, the adjustable impedance layer comprising a cross-digital resonator, a second PIN diode and a first resistor; The non-adjustable impedance layer is used to achieve wave absorption outside the wave transmission window, that is, out-of-band wave absorption, and increase the wave absorption bandwidth. The non-adjustable impedance layer includes a spiral resonator and a resistor.

[0009] Optionally, the non-adjustable impedance layer further includes a dielectric substrate three, a cross metal line arranged on the dielectric substrate three, four spiral resonators are centrally symmetrically arranged on the dielectric substrate three, the four spiral resonators are connected by the cross metal line, and four branches of the cross metal line are connected in series with a resistor two for achieving out-of-band wave absorption; The helical resonator includes a rectangular helical patch.

[0010] Optionally, the material of the dielectric substrate three is polytetrafluoroethylene.

[0011] Optionally, the dielectric substrate three is in the shape of a rectangular plate, and the four spiral resonators are respectively arranged at four vertex corners of the dielectric substrate three.

[0012] Optionally, the adjustable FSS layer further comprises a dielectric substrate 1, a square ring metal sheet arranged on one side of the dielectric substrate 1, a square metal sheet arranged on one side of the dielectric substrate 1 and located inside the square ring metal sheet, and a cross metal line arranged on the other side of the dielectric substrate 1, a square ring gap is formed between the square ring metal sheet and the square metal sheet, four PIN diodes 1 are centrally symmetrically arranged in the ring gap, and the positive electrode of the PIN diode 1 is connected to the square metal sheet, the negative electrode of the PIN diode 1 is connected to the square metal sheet, and the square metal sheet is connected to the center of the cross metal line.

[0013] Optionally, the adjustable impedance layer also includes a dielectric substrate 2, two interdigital resonators respectively arranged on both sides of the dielectric substrate 2 and connected in series, the two PIN diodes 2 are respectively arranged at the center positions of the two interdigital resonators, the four resistors 1 are respectively arranged at both ends of the two interdigital resonators, the four resistors 1 are all connected to connecting wires, and the two interdigital resonators are connected to the resistor 1 through the connecting wires.

[0014] Optionally, the interdigital resonator includes a first trident structure and a second trident structure, wherein the first trident structure and the second trident structure are alternately arranged, and the middle tines of the first trident structure and the second trident structure are connected via a second PIN diode.

[0015] Optionally, the material of the dielectric substrate 2 is polytetrafluoroethylene; Optionally, the material of the dielectric substrate 1 is polytetrafluoroethylene; Optionally, the interdigital resonator is made of metal or a conductive composite material.

[0016] Optionally, the side length of the square metal sheet is S1; the width of the annular gap is S2, the length of the co-digital resonator is W1, the width of the trident structure one is W2, the spacing between the adjacent side teeth of the trident structure one and the side teeth of the trident structure two is W3, the end of the side teeth of the trident structure one and the end of the trident structure two are spaced, and the width of the spacing is W4, the width of the connecting line is W5, the distance between the rectangular spiral patch and the edge of the dielectric substrate three is N1, the width of the rectangular spiral patch is N2, the number of turns of the rectangular spiral patch is three, and the spacing between adjacent turns is N 3， The inner width of the innermost circle is N5, and the width of the cross metal wire is N4; Among them, 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.

[0017] The present application provides a radome comprising one or more frequency selective surfaces as described above.

[0018] The beneficial effect of the present application is that the frequency selective surface provided by the present application is composed of a three-layer structure: an adjustable FSS layer, an adjustable impedance layer and a non-adjustable impedance layer. Among them, the PIN diode (PIN diode 1 and PIN diode 2) is loaded in the adjustable layer (adjustable impedance layer and adjustable FSS layer), and the resistor (resistor 1 and resistor 2) is loaded in the impedance layer. The spiral resonator and the interdigital capacitor resonator are respectively used for the non-adjustable impedance layer and the adjustable impedance layer. 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 is used to form a wave-transmitting window and has a reconfigurable function. The PIN diode and multi-layer structure design are used to realize the switching between the wave-transmitting function and the wave-absorbing function in the X-band, and realize the integrated stealth function design. The emission and absorption modes can be switched in the X-band to realize the integrated stealth function. And it can maintain good performance under large angle conditions.

[0019] The antenna cover provided in the present application has a wave absorbing and transmitting function and a reconfigurable characteristic through the frequency selective surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A schematic diagram of the structure of the frequency selective surface provided in this application; Figure 2 A schematic diagram of the structure of the adjustable FSS layer provided for this application; Figure 3 A schematic diagram of a single-layer structure of an adjustable impedance layer provided in this application; Figure 4A complete structural diagram of the adjustable impedance layer provided in this application; Figure 5 A schematic diagram of the structure of the non-adjustable impedance layer provided in this application; Figure 6 CST and ADS simulation result diagram of the non-adjustable impedance layer provided in this application; Figure 7 CST and ADS simulation result diagram of the adjustable FSS layer provided for this application; Figure 8 Comparison chart of CST and ADS simulation results of the ON / OFF state of the adjustable FSS layer provided in this application; Fig. 9 CST and ADS simulation result diagram of the adjustable impedance layer provided in this application; Fig.10 A comparison chart of CST and ADS simulation results of the ON / OFF state of the adjustable impedance layer provided in this application; Fig.11 An equivalent circuit model of the frequency selective surface provided for this application; Fig.12 This is a diagram of CST and ADS simulation results of the frequency selective surface provided in this application in the "ON" state; Fig.13 This is a diagram of CST and ADS simulation results of the frequency selective surface provided in this application in the "OFF" state.

[0021] In the figure: 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 wire; 16, annular gap; 20, adjustable impedance layer; 21, dielectric substrate two; 22, cross-shaped resonator; 221, trident structure one; 222, trident 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 wire; 34, resistor two. DETAILED DESCRIPTION

[0022] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein are only for the purpose of describing the embodiments of this application and are not intended to limit this application.

[0024] Before describing the embodiments of the present application in detail, some nouns and terms involved in the embodiments of the present application are first described. The nouns and terms involved in the embodiments of the present application are subject to the following interpretations: In FSS, S parameters usually include S11, S21, etc., where: S11: Indicates the return loss at port 1, also known as the input reflection coefficient. It measures the proportion of the signal energy reflected back at the input port (port 1). The closer the S11 value is to 0 (usually expressed in dB, such as -25dB, -40dB, etc.), the smaller the reflection, that is, the smaller the reflection loss in the transmission path.

[0025] S21: Indicates the insertion loss of the signal from port 1 to port 2. It measures the loss of the signal during the transmission process. The closer the S21 value is to 1 (0dB), the smaller the loss during the transmission process.

[0026] S11-TE-0°: indicates the reflection coefficient of port 1 for electromagnetic waves in the transverse electric mode at a specific angle (0°).

[0027] S11-TE-36°: indicates the reflection coefficient of port 1 for electromagnetic waves in the transverse electric mode at a specific angle (36°).

[0028] S11-TM-0°: represents the reflection coefficient of port 1 for electromagnetic waves in the transverse magnetic mode in the 0° polarization direction.

[0029] S11-TM-36°: indicates the reflection coefficient of port 1 for electromagnetic waves in the transverse magnetic mode in the 36° polarization direction.

[0030] S21-TE-0°: represents the transmission coefficient from port 1 to port 2 for electromagnetic waves in the transverse electric mode at a specific angle (0°).

[0031] S21-TE-36°: indicates the transmission coefficient from port 1 to port 2 for electromagnetic waves in the transverse electric mode at a specific angle (36°).

[0032] S21-TM-0°: indicates the reflection coefficient from port 1 to port 2 for electromagnetic waves in the transverse magnetic mode in the 0° polarization direction.

[0033] S21-TM-36°: indicates the reflection coefficient from port 1 to port 2 for electromagnetic waves in the transverse magnetic mode in the 36° polarization direction.

[0034] like Figure 1-5As shown, the present application provides a dual-polarization reconfigurable hidden 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 wave-transmitting 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 wave-transmitting window is closed, and the adjustable impedance layer 20 includes a co-digital resonator 22, a PIN diode 23 and a resistor 24; the non-adjustable impedance layer 30 is used to achieve absorption outside the wave-transmitting window, i.e., out-of-band absorption, and increase the absorption bandwidth, and the non-adjustable impedance layer 30 includes a spiral resonator 32 and a resistor 34.

[0035] Compared with the prior art, the frequency selective surface provided by the present application is composed of a three-layer structure: an adjustable FSS layer 10, an adjustable impedance layer 20 and a non-adjustable impedance layer 30. Among them, PIN diodes (PIN diode 1 14 and PIN diode 2 23) are loaded in the adjustable layer (adjustable impedance layer 20 and adjustable FSS layer 10), and resistors (resistor 1 24 and resistor 2 34) are loaded in the impedance layer. The spiral resonator 32 and the interdigital capacitor resonator are respectively used for the non-adjustable impedance layer 30 and the adjustable impedance layer 20. 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 is used to form a wave-transmitting window and has a reconfigurable function. The PIN diode and multi-layer structure design are used to realize the switching between the wave-transmitting function and the wave-absorbing function in the X-band, and realize the integrated stealth function design. The emission and absorption modes can be switched in the X-band to realize the integrated stealth function.

[0036] It should be noted that the selection of the PIN diode mainly takes into account the cost, operating frequency band and equivalent electrical parameters. This structure requires the PIN diode to operate in the X-band and have a relatively small equivalent capacitance.

[0037] In one embodiment, Figure 5 As shown, the non-adjustable impedance layer 30 also includes a dielectric substrate 31, a cross metal wire 33 arranged on the dielectric substrate 31, four spiral resonators 32 are centrally symmetrically arranged on the dielectric substrate 31, the four spiral resonators 32 are connected by the cross metal wire 33, and the four branches of the cross metal wire 33 are all connected in series with a resistor 2 34 for achieving out-of-band absorption; the spiral resonator includes a rectangular spiral patch.

[0038] Specifically, in order to better achieve the out-of-band wave absorption effect and further expand the wave absorption bandwidth, a non-adjustable impedance layer 30 with a fixed frequency band is designed to correspond to the wave transmission window with the adjustable FSS layer 10 and the adjustable impedance layer 20, and the out-of-band wave absorption is achieved at the same time. The non-adjustable impedance layer 30 uses a spiral resonator 32 to realize the wave transmission window, and the spiral resonators 32 are symmetrically loaded at the four corners of the dielectric substrate 31, and are connected by cross metal wires 33. The central symmetric structural characteristics ensure the realization of dual polarization. The out-of-band wave absorption is achieved by loading the lumped resistor 2 34 on the cross metal wires 33.

[0039] In this embodiment, the dielectric substrate 31 is a PTFE substrate with a thickness of 0.2 mm, a relative dielectric constant of 2.1, and an electric loss tangent of 0.002. The non-adjustable impedance layer 30 is subjected to 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 with the optimized parameters. The simulation results are as follows: Figure 6 The fitting curve is shown.

[0040] In one embodiment, Figure 2 As shown, the adjustable FSS layer 10 also includes a dielectric substrate 11, a square ring metal sheet 12 arranged on one side of the dielectric substrate 11, a square metal sheet 13 arranged on one side of the dielectric substrate 11 and located in the square ring metal sheet 12, and a cross-shaped metal line 15 arranged 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 arranged in the ring gap 16, and 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; 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, and the square ring gap 16 structure and the cross-shaped metal line 15 with through holes are used in the adjustable FSS layer 10 to realize feeding.

[0041] Specifically, the frequency selective surface is composed of an adjustable FSS layer 10, an adjustable impedance layer 20 and a non-adjustable impedance layer 30 from the bottom to the top. Among them, the adjustable FSS layer 10 is mainly used for the realization of the wave transmission window; the adjustable impedance layer 20 mainly realizes the in-band absorption after the wave transmission window is closed; the non-adjustable impedance layer 30 mainly realizes the absorption outside the wave transmission window, that is, the out-of-band absorption, and increases the absorption bandwidth. A lumped resistor is loaded in the impedance layer, and the loss of the resistor is used to realize the absorption function. A PIN diode is used in the adjustable layer to realize the adjustable switch function: the on-off characteristic is used to change the resonant frequency and move the passband; the out-of-band characteristic is used to realize the switch function.

[0042] The adjustable FSS layer 10 realizes the functions of a bandpass surface and a total reflection surface in two different states. Therefore, the on-off characteristics of the PIN diode 14 are utilized to shift the passband, that is, the bandpass function is realized in the "ON" state, when the PIN diode 14 is in the on state; in the "OFF" state, the passband is shifted to a higher frequency, when the PIN diode 14 is in the off state, and the total reflection characteristics at the original passband are realized by utilizing the out-of-band characteristics after the shift.

[0043] Based on the above scheme, a square annular gap 16 structure (such as Figure 2 As shown). Since the structure is a symmetrical structure, it can achieve polarization insensitivity. The dielectric substrate 11 adopts a PTFE substrate with a thickness of 0.2 mm, a relative dielectric constant of 2.1, and an electric loss tangent of 0.002. Four PIN diodes 14 are loaded symmetrically at the center of the annular gap 16, wherein the positive electrode of the PIN diode 14 is connected to the square metal patch at the center of the unit, and the negative electrode is connected to the square ring metal at the edge of the unit. In order to realize the feeding of the PIN diode, the square metal patch at the center of the unit is connected to the cross-shaped metal line 15 (width S3) on the other side of the dielectric substrate through a metal through hole. At this point, the feeding of the PIN diode 14 of the adjustable FSS layer 10 is realized.

[0044] It should be noted that other lossless FSS structures were considered during the structural design process, but the results were poor. The square ring structure has better overall performance (insertion loss, relative bandwidth, and size).

[0045] In one embodiment, the outer side length of the square ring metal sheet 12 is D.

[0046] In this embodiment, the adjustable FSS layer 10 uses CST and ADS to perform full-wave simulation and equivalent circuit simulation, and the simulation results are compared to optimize the parameters. The simulation results are as follows: Figure 7 The fitting curve is shown in Figure 2. Using the on-off characteristics of the PIN diode, such as Figure 8As shown, the wave-transmitting window at 9 GHz is moved to a high frequency, and the out-of-band characteristics are used to realize the total reflection characteristics at the original passband.

[0047] In one embodiment, the adjustable impedance layer 20 is designed mainly for the in-band and out-band wave absorption after the wave transmission window is closed, such as Figure 3 and Figure 4 As shown, the adjustable impedance layer 20 also includes a dielectric substrate 21, two interdigital resonators 22 respectively arranged on both sides of the dielectric substrate 21 and connected in series, two PIN diodes 23 respectively arranged at the center positions of the two interdigital resonators 22, four resistors 1 24 respectively arranged at both ends of the two interdigital resonators 22, the four resistors 1 24 are all connected to a connecting line 25, and the two interdigital resonators 22 are connected to the resistor 1 24 through the connecting line 25.

[0048] Specifically, a co-chi type resonator 22 is used to make the resonant frequency correspond to the center frequency of the wave transmission window generated by the adjustable FSS. The co-chi type resonators 22 are connected by metal wires, and the wave absorption function is realized by loading a lumped resistor 24. A PIN diode 23 is loaded at the center of the co-chi type resonator 22, and a metal wire is used to realize the series connection of the PIN diode 23 in each polarization direction, so that the feeding network is integrated into the functional structure, avoiding the influence of the additional feeding structure on the material properties. This bias network is also called a fusion bias network, which means that two co-chi type resonators 22 are connected to each other by metal wires, so that all diodes 2 can be connected through the co-chi type resonator 22 and the metal wire. Therefore, it is only necessary to connect the positive and negative poles of the voltage source at both ends of the overall structure of the adjustable impedance layer 20, that is, all PIN diodes can be controlled. The fusion bias network is divided into a series fusion bias network and a parallel fusion bias network. The series fusion bias network needs to connect a voltage source that satisfies the conduction voltage condition of all PIN diodes 23 in a circuit at two ends of the structure, while the parallel fusion bias network only needs to provide a voltage that satisfies the conduction condition of a single PIN diode 23.

[0049] Considering the requirements of dual polarization characteristics, the adjustable impedance layer 20 needs to have equivalent structures in the x and y directions. The adjustable impedance layer 20 includes adjustable characteristics, so the design of the feeder needs to be considered in the design structure. The double-layer structure can facilitate the feeding of each polarization direction without adding additional feeders. The prior art puts the structures of the two polarization directions on the same layer, but requires additional feeders to be led out on both layers, and requires a lumped inductor to be connected in series, which is complex in structure and has a large impact.

[0050] In one embodiment, the dielectric substrate 21 is a PTFE substrate with a thickness of 0.3 mm, a relative dielectric constant of 2.1, and an electric loss tangent of 0.002. In order to achieve dual polarization, mutually perpendicular periodic unit structures (a structure consisting of a cross-shaped resonator 22, a PIN diode 23, and two resistors 24) are arranged on both sides of the dielectric substrate 21, and the center positions correspond to each other (such as Figure 4 as shown).

[0051] In one embodiment, Figure 3 As shown, the co-digital resonator 22 includes a trident structure 1 221 and a trident structure 222 . The trident structure 1 221 and the trident structure 222 are alternately arranged, and the middle teeth of the trident structure 1 221 and the trident structure 2 222 are connected via a PIN diode 2 23 .

[0052] The side length of the square metal sheet 13 is S1; the width of the annular gap 16 is S2, the length of the co-digital resonator 22 is W1, the width of the trident structure 1 221 is W2, the spacing between the side teeth of the adjacent trident structure 1 221 and the side teeth of the trident structure 2 222 is W3, the end of the side teeth of the trident structure 1 221 and the end of the trident structure 2 222 are spaced, and the width of the spacing 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 3 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 spacing between adjacent turns is N 3， The inner width of the innermost circle is N5, and the width of the cross metal wire 33 is N4; Among them, 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.

[0053] In this embodiment, the adjustable impedance layer 20 is subjected to full-wave simulation and equivalent circuit simulation using CST and ADS, such as Fig. 9 As shown in the figure, it can be seen that the equivalent circuit simulation results do not have the additional resonance point at 13GHz in the full-wave simulation results. This is because the coupling effect between the upper and lower layers of metal is taken into account in the full-wave simulation, which leads to the appearance of grating lobes, while the equivalent circuit simulation does not take the coupling effect into account. Fig.10 As shown, when in the "OFF" state, the PIN diode is in the on state and the wave transmission window at 9 GHz is closed.

[0054] In one embodiment, the frequency selective surface provided by the present application is subjected to full-wave simulation and equivalent circuit simulation using CST and ADS. So far, the adjustable FSS layer 10 has been used to generate a wave-transmitting window with a center frequency of 9 GHz, and the adjustable impedance layer 20 and the non-adjustable impedance layer 30 have been used to introduce in-band and out-of-band wave absorbing functions. The three-layer structure is cascaded to obtain the following: Figure 1 , Fig.11 The overall model arrangement and equivalent circuit model are shown in Table 1, and the geometric parameters of each component after optimization are shown in Table 2.

[0055] Table 1

[0056] Table 2

[0057] When the PIN diode 14 of the adjustable FSS layer 10 is turned on and the PIN diode 23 of the adjustable impedance layer 20 is turned off, the frequency selective surface (the frequency selective surface provided in this application is a switch-type AFSR) is in the "ON" state; otherwise, it is in the "OFF" state. The two states and two polarization modes are simulated respectively, and the following are obtained: Fig.12 , 13 Curve shown. When in the "ON" state, the reflection coefficient of the electromagnetic wave is less than -10dB in the frequency range of 4.32-13.75GHz (104.37%), and there is almost no difference between the TE and TM polarization modes; the transmission 3dB passband 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 the two polarized incident waves 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 makes the results of the two polarizations not completely consistent. At the same time, considering that the dielectric substrate will absorb 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 wave absorption bandwidth of the frequency selective surface almost covers 4GHz-12GHz, achieving broadband stealth performance.

[0058] Under oblique incidence, the performance of the frequency selective surface provided by the present application is analyzed. Fig.11 , 12 It can be seen from the simulation results that for both TE and TM polarization modes, the frequency selective surface can basically maintain the switching function of integrated stealth and transparency within the oblique incidence angle range of 36°, ensuring the maintenance of the wave-transmitting window and the basic wave-absorbing effect inside and outside the band, and ensuring the stealth performance under large-angle incidence conditions and the transmission performance within the wave-transmitting window.

[0059] In the "ON" state, as the incident angle increases, the electric field of the TE wave remains parallel to the surface of the structure; the electric field of the TM wave forms an angle with the surface of the structure, so the projection component of the electric field on the surface of the structure decreases as the incident angle increases. Therefore, under oblique incidence conditions, there is almost no effect on the TE wave, but there is an effect on the TM, which is manifested as a decrease in the horizontal projection component of the electric field, so that the induced current on the metal changes, further changing the equivalent capacitance and equivalent inductance of the metal, resulting in a shift in the resonance point; the vertical projection component of the electric field increases, generating a new equivalent capacitance between the metal layers, and then generating a new resonant circuit in the passband, reflecting part of the incident wave back, causing S21 to decrease, and thus a non-ideal depression appears in the passband.

[0060] In the "OFF" state, as the incident angle increases, the absorption effect in the original wave transmission window, that is, in the band, gradually weakens, and the absorption bandwidth outside the band gradually decreases. The reduction degree of the absorption bandwidth in the TM polarization mode is greater than that in the TE polarization mode. Overall, the performance in the TE polarization mode is better than that in the TM polarization mode.

[0061] The frequency selective surface provided in this application can maintain good performance under large angle conditions. The loss layer is designed by combining spiral inductors, cross-digital capacitors with lumped resistors and PIN diodes. The annular gap 16 is used to load the PIN diode 14 in the FSS layer, and a fused bias network and a cross-shaped metal wire 15 are used for feeding. The three-layer structure is equivalent to a circuit model using electromagnetic theory, and simulation analysis and comparison are performed separately to optimize the structural parameters. This structure has both wave absorption and transmission functions and reconfigurable characteristics, and can be applied to future smart antenna cover systems.

[0062] The present application provides a radome, comprising one or more frequency selective surfaces. The radome has a wave absorbing and penetrating function and a reconfigurable characteristic through the frequency selective surfaces.

[0063] A person skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of protection of the present application is limited to these examples. In line with the concept of the present application, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of different aspects of one or more embodiments of the present application as described above, which are not provided in detail for the sake of simplicity.

[0064] One or more embodiments of the present application are intended to cover all such substitutions, modifications and variations that fall within the broad scope of the present application. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of one or more embodiments of the present application should be included in the protection scope of the present application.

Claims

1. A dual-polarization reconfigurable hidden and transparent integrated frequency selective surface, characterized in that: include: An adjustable FSS layer (10) is used to form a wave-transmitting window, wherein the adjustable FSS layer (10) comprises a PIN diode 1 (14); An adjustable impedance layer (20) is used to achieve in-band wave absorption after the wave transmission window is closed, the adjustable impedance layer (20) comprising a co-digital resonator (22), a second PIN diode (23) and a first resistor (24); The non-adjustable impedance layer (30) is used to achieve wave absorption outside the wave transmission window, i.e., out-of-band wave absorption, and to increase the wave absorption bandwidth. The non-adjustable impedance layer (30) comprises a spiral resonator (32) and a second resistor (34).

2. The frequency selective surface according to claim 1, characterized in that The non-adjustable impedance layer (30) further comprises a dielectric substrate three (31), a cross metal line (33) arranged on the dielectric substrate three (31), four spiral resonators (32) are centrally symmetrically arranged on the dielectric substrate three (31), the four spiral resonators (32) are connected via the cross metal line (33), and four branches of the cross metal line (33) are connected in series with a resistor two (34) for achieving out-of-band wave absorption.

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

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

5. The frequency selective surface according to claim 4, characterized in that The adjustable FSS layer (10) further comprises a dielectric substrate (11), a square ring metal sheet (12) arranged on one side of the dielectric substrate (11), a square metal sheet (13) arranged on one side of the dielectric substrate (11) and located inside the square ring metal sheet (12), and a cross-shaped metal wire (15) arranged 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 arranged 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 wire (15).

6. The frequency selective surface according to claim 5, characterized in that The adjustable impedance layer (20) further comprises a dielectric substrate 2 (21), two interdigital resonators (22) respectively arranged on two sides of the dielectric substrate 2 (21) and connected in parallel in series, the two PIN diodes 2 (23) respectively arranged at the center positions of the two interdigital resonators (22), the four resistors 1 (24) respectively arranged at the two ends of the two interdigital resonators (22), the four resistors 1 (24) are all connected to a connecting line (25), and the two interdigital resonators (22) are connected to the resistors 1 (24) via the connecting line (25).

7. The frequency selective surface according to claim 6, characterized in that The co-digital resonator (22) comprises a first trident structure (221) and a second trident structure (222), wherein the first trident structure (221) and the second trident structure (222) are arranged in an alternating manner, and the middle tines of the first trident structure (221) and the second trident structure (222) are connected via a second PIN diode (23).

8. The frequency selective surface according to claim 6 or 7, characterized in that: The material of the dielectric substrate 2 (21) is polytetrafluoroethylene; And / or, the dielectric substrate 1 (11) is made of polytetrafluoroethylene; And / or, the material of the co-digital resonator (22) is metal or a conductive composite material.

9. The frequency selective surface according to claim 7, 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 co-digital resonator (22) is W1; the width of the trident structure one (221) is W2; the spacing between the adjacent side teeth of the trident structure one (221) and the side teeth of the trident structure two (222) is W3; the end of the side teeth of the trident structure one (221) and the end of the trident structure two (222) are spaced apart, and the width of the spacing 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 three (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 spacing between adjacent turns is N. 3， The inner width of the innermost circle is N5, and the width of the cross metal wire (33) is N4; Among them, 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.

10. A radome, characterized in that: Comprising one or more frequency selective surfaces according to any one of claims 1-9.

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