A dual-band FSR unit structure, a dual-band FSR and a radome

Abstract

The application belongs to the technical field of microwave, and particularly relates to a unit structure of double-passband FSR, double-passband FSR and antenna cover. The unit structure comprises an impedance layer and an FSS layer. The impedance layer comprises a dielectric substrate one, double-helix resonance structures, interdigital capacitance structures and connecting wires. The double-helix resonance structures and the interdigital capacitance structures are arranged on two surfaces of the dielectric substrate one. The double-helix resonance structures and the interdigital capacitance structures on the same surface are connected through the connecting wires. The connecting wires are provided with resistors. The two connecting wires on the two surfaces of the dielectric substrate one are in a cross position relationship. The FSS layer has double-side ring slits to construct two transmission bands. The radar antenna is not affected in two working frequency bands, and the radar is low-probe in the out-of-band wave absorption. The unit structure has dual polarization, a profile as low as 0.085, and a stable performance of oblique incidence up to 45 degrees, so as to simultaneously realize the requirements of low profile, dual polarization and large-angle performance stability.

Description

Technical Field

[0001] The present application belongs to the field of microwave technology, and in particular relates to a unit structure of a dual-band FSR, a dual-band FSR and a radome. Background Art

[0002] Traditional radar radomes are typically constructed using a frequency selective surface (FSS) structure, relying on the FSS's frequency-selective properties to achieve their radome function. An FSS (Frequency Selective Surface) is a two-dimensional structure composed of periodically arranged conductive or dielectric elements that selectively reflects or transmits electromagnetic waves based on the frequency of the incident wave. The fundamental principle of an FSS is to achieve bandpass or bandstop filtering characteristics within a specific frequency range by designing the shape, size, and arrangement of its elements.

[0003] A dual-passband FSR (Frequency Selective Rasorber) is a frequency selective structure with two passbands. This frequency selective structure allows signals to pass within two specific frequency ranges while attenuating or blocking signals in other frequency ranges.

[0004] In a known technology, two transmission windows are realized within a wider operating frequency range by cascading two similar lossy layers, a low-pass FSS and a dual-bandpass multilayer FSS from top to bottom. The low-pass FSS acts as the ground for the lossy layer, and a bent conductive line is used to produce a high-frequency absorption band. The interaction between the dual-bandpass FSS and the two lossy layers results in low-frequency and mid-frequency absorption bands. When the two transmission bands of the lossy layer coincide with the transmission bands of the low-pass and dual-bandpass FSS, two transmission windows can be realized. The FSR has two -3dB transmission bands with fractional bandwidths of 45.98% and 23.31%, respectively, and three absorption bands with fractional bandwidths of 81.11%, 13.67% and 3.36%, respectively. The absorption rate is greater than 80%, but in actual application, due to the excessive number of layers of the structure, the thickness reaches 0.15, The free space wavelength corresponds to the lowest frequency at which the reflection coefficient is less than -10dB. The thickness of this structure is fixed and complicated to process, and it does not meet the requirements of low profile in practical applications.

[0005] In a known technology, a broadband antenna is used for stealth. The design combines a spiral inductor and an interdigitated capacitor parallel resonator to meet the wide passband requirements at the lower frequencies of the operating band. In actual tests, the design was able to achieve two passbands between 4.9-6 GHz (20.0%) and 8.6-9 GHz (6.3%). The device also achieved three absorption bands with fractional bandwidths of 48.4%, 25.7%, and 22.0%, respectively. However, this model only has single-polarization characteristics and cannot achieve frequency selection under both horizontally and vertically polarized incident wave conditions. It also lacks angular stability, making it unsuitable for practical engineering applications.

[0006] In one known technique, the absorber consists of a lossy layer and a lossless layer separated by an air gap. The upper lossy layer consists of four square rings with two branches, achieving a dual-band transmission response. At 8 and 11.9 GHz, the insertion losses are 0.39 and 0.64 dB for TE polarization, and 0.40 and 0.66 dB for TM polarization, respectively. The reflection coefficient falls below -10 dB in the 5-12.8 GHz frequency range. In actual testing, this design exhibited only 30° angular stability, making stable performance impossible at high angles of incidence.

[0007] In summary, the dual-passband frequency selective metasurface in the existing technology cannot simultaneously meet the characteristics of low profile, dual polarization and large-angle stability.

[0008] Application Contents

[0009] The technical problem to be solved by the present application is to provide a unit structure of a dual-band FSR, a dual-band FSR and an antenna cover, so as to solve the problem in the prior art that the passive frequency selective surface cannot simultaneously achieve low profile, dual polarization and stable performance at a large angle.

[0010] The present application provides a dual-band FSR unit structure, comprising:

[0011] The impedance layer includes a first dielectric substrate, a double-helix resonant structure, an interdigital capacitor structure, and connecting wires. The double-helix resonant structure and the interdigital capacitor structure are provided on both sides of the first dielectric substrate. The double-helix resonant structure and the interdigital capacitor structure on the same side are connected by connecting wires. The connecting wires are provided with resistors. The connecting wires on the two sides of the first dielectric substrate are in a cross-positioned relationship.

[0012] The FSS layer has two double ring gaps to construct two transmission belts;

[0013] The impedance layer is spaced apart from the FSS layer.

[0014] Optionally, the two connecting wires on one side and the other side of the dielectric substrate are in a cross-shaped position relationship.

[0015] Optionally, the double helix resonant structure includes two spiral conductive plates surrounding each other, and a spiral gap is provided between the two spiral conductive plates, wherein the outer end of one of the spiral conductive plates is connected to a connecting wire, and the outer end of the other spiral conductive plate is connected to a T-shaped conductive plate.

[0016] Optionally, the structure of the spiral conductive sheet is a rectangular spiral structure or a circular spiral structure.

[0017] Optionally, the spiral gap width between the two spiral conductive sheets is g , the width of the spiral conductive sheet is c The width of the horizontal line part and the vertical line part of the T-shaped conductive piece 1 are both w 2. The length of the connecting wire is l 3. The distance between the horizontal line portion of the T-shaped conductive sheet 1 and the spiral conductive sheet not connected to the T-shaped conductive sheet 1 is l 4. The width of the interdigital capacitor structure is f_l , the length is f_w ;

[0018] and g : c : w 2: l 3: l 4: f_l : f_w =0.1:0.15:0.25:5.2:1.15:2.5:2;

[0019] And / or, the connecting wire is made of metal or a conductive composite material;

[0020] And / or, the spiral conductive sheet is made of metal or a conductive composite material;

[0021] And / or, the material of the T-shaped conductive piece 1 is metal or a conductive composite material.

[0022] Optionally, the spiral gap width between the two spiral conductive sheets is 0.1±10% mm;

[0023] And / or, the width of the spiral conductive sheet is 0.15±10% mm;

[0024] And / or, the width of the horizontal line part and the vertical line part of the T-shaped conductive piece 1 are both 0.25±10% mm;

[0025] And / or, the length of the connecting wire is 5.2±10% mm;

[0026] And / or, the distance between the horizontal line portion of the T-shaped conductive sheet 1 and the spiral conductive sheet not connected to the T-shaped conductive sheet 1 is 1.15±10% mm;

[0027] And / or, the width of the interdigital capacitor structure is 2.5±10% mm, and the length is 2±10% mm.

[0028] Optionally, the interdigitated capacitor structure includes a multi-tooth structure 1 and a multi-tooth structure 2 that are meshed with each other, the multi-tooth structure 1 is connected to the multi-tooth structure 2, the side of the multi-tooth structure 1 facing away from the multi-tooth structure 2 is connected to the connecting wire, and the side of the multi-tooth structure 2 facing away from the multi-tooth structure 1 is connected to the T-shaped conductive plate 2.

[0029] Optionally, the multi-tooth structure 1 includes a plurality of conductive strips 1 distributed at intervals and a conductive connecting piece 1 connecting the plurality of conductive strips 1; the multi-tooth structure 2 includes a plurality of conductive strips 2 distributed at intervals and a conductive connecting piece 2 connecting the plurality of conductive strips 2; the plurality of conductive strips 1 and the plurality of conductive strips 2 are alternately distributed, and one of the conductive strips 1 is extended and connected to the conductive connecting piece 2;

[0030] And / or, the width of the horizontal line part and the vertical line part of the T-shaped conductive piece 2 are both w 1. The length of the horizontal line portion of the second T-shaped conductive piece is l 5. The distance between the horizontal line portion of the T-shaped conductive sheet 2 and the edge of the dielectric substrate 1 is l 1; w 1: l 5: l 1=0.2:4:0.75;

[0031] And / or, the material of the multi-tooth structure 1 and the multi-tooth structure 2 is metal or a conductive composite material;

[0032] And / or, the material of the T-shaped conductive piece 2 is metal or a conductive composite material.

[0033] Optionally, the FSS layer includes a second dielectric substrate, a first square ring conductive sheet disposed on the second dielectric substrate, a second square ring conductive sheet disposed on the second dielectric substrate and located within the first square ring conductive sheet, and a square conductive sheet disposed on the second dielectric substrate and located within the second square ring conductive sheet, a first square ring gap being defined between the first square ring conductive sheet and the second square ring conductive sheet, and a second square ring gap being defined between the second square ring conductive sheet and the square conductive sheet.

[0034] And / or, the distance between the impedance layer and the FSS layer is 10±10% mm.

[0035] The present application provides a dual-band FSR comprising one or more of the aforementioned unit structures.

[0036] The present application provides a radome comprising one or more frequency selective surfaces.

[0037] The beneficial effect of the present application is that the unit structure of the dual-band FSR provided by the present application and the structural design of the impedance layer avoid the coupling influence of the double-helix resonant structure and the interdigitated capacitor structure, and the performance is superimposed, so that the absorption rate of the absorption frequency band is improved, while the stability of the structure is enhanced, and it has the performance of achieving low profile, dual polarization and stable performance at a large angle at the same time.

[0038] The dual-band FSR of this application can make the radar antenna unaffected in two working frequency bands, and achieve radar low detectability by absorbing waves outside the band, with dual polarization and a profile as low as 0.085 , and the oblique incidence stability can reach 45°, thus simultaneously achieving the requirements of low profile, dual polarization and large-angle performance stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 A schematic structural diagram of the unit structure of the dual-band FSR provided in this application;

[0040] Figure 2 A schematic diagram of the structure of the impedance layer provided in this application;

[0041] Figure 3 A schematic diagram of the structure of the interdigital capacitor provided in this application;

[0042] Figure 4 Schematic diagram of the structure of the FSS layer provided by this application;

[0043] Figure 5 Equivalent circuit diagram of the unit structure provided in this application;

[0044] Figure 6 The full-wave simulation and equivalent circuit simulation results of the impedance layer provided in this application;

[0045] Figure 7 The full-wave simulation and equivalent circuit simulation results of the FSS layer provided by this application;

[0046] Figure 8 The full-wave simulation and equivalent circuit simulation results of the unit structure of the dual-band FSR provided by this application;

[0047] Figure 9 The electric field distribution and current distribution diagram of the impedance layer provided in this application;

[0048] Figure 10 Figure (a) is a simulation result diagram of the oblique incidence performance of the unit structure of the dual-band FSR provided by this application under TE polarization conditions, and Figure (b) is a simulation result diagram of the oblique incidence performance under TM polarization conditions;

[0049] Figure 11 Figures (a) and (b) show the unit structure of the dual-band FSR provided by this application and the conductive plate. f A1 The RCS comparison diagram of the two stations at (c) and (d) is f A2 The RCS comparison chart of the two stations at ;

[0050] Figure 12 A comparison chart of the unit structure of the dual-band FSR provided in this application and the single-station RCS of the conductive plate;

[0051] Figure 13 Figure (a) is a diagram of the dual-band FSR measurement environment provided by this application, and Figure (b) is a sample diagram;

[0052] Figure 14 Figure (a) is a comparison between the measured S parameter results and the simulation results of the sample provided in this application, and Figure (b) is a comparison between the measured and simulation results of the absorption rate;

[0053] Figure 15 Figure (a) is a comparison between the measured and simulated performance results of the sample provided in this application at 45° oblique incidence under TE polarization conditions, and Figure (b) is a comparison between the measured and simulated performance results at 45° oblique incidence under TM polarization conditions.

[0054] In the figure: 10, impedance layer; 11, dielectric substrate 1; 12, double helix resonant structure; 121, spiral conductive sheet; 13, interdigital capacitor structure; 131, multi-tooth structure 1; 1311, conductive strip 1; 1312, conductive connecting sheet 1; 132, multi-tooth structure 2; 1321, conductive strip 2; 1322, conductive connecting sheet 2; 14, connecting wire; 15, resistor; 16, T-shaped conductive sheet 1; 17, T-shaped conductive sheet 2; 20, FSS layer; 21, dielectric substrate 2; 22, square ring conductive sheet 1; 23, square ring conductive sheet 2; 24, square conductive sheet; 25, square ring gap 1; 26, square ring gap 2. DETAILED DESCRIPTION

[0055] In order to make the technical problems, technical solutions and beneficial effects to be solved by this application more clearly understood, this application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0056] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application pertains. The terms used herein are for the purpose of describing the embodiments of this application only and are not intended to limit this application.

[0057] Before the embodiments of the present application are described in detail, first, some of the terms and terminology involved in the embodiments of the present application are explained, and the terms and terminology involved in the embodiments of the present application are applicable to the following explanations:

[0058] In FSS, S parameters usually include S11, S21, etc., wherein:

[0059] S11: represents the return loss at port 1, also known as the input reflection coefficient. It measures the proportion of energy reflected back at the input port (port 1). The closer the value of S11 to 0 (usually expressed in dB, such as -25 dB, -40 dB, etc.), the smaller the reflection, i.e. the smaller the reflection loss in the transmission path.

[0060] S21: represents the insertion loss of the signal from port 1 to port 2 during transmission. It measures the loss of the signal during transmission. The closer the value of S21 to 1 (0 dB), the smaller the loss during transmission.

[0061] TE polarization: represents the polarization state in which the electric field vector E of the electromagnetic wave is perpendicular to the direction of propagation, and the angle between the electric field vector E and a certain specific direction (usually the reference direction) is 0°. In radio frequency and microwave technology, TE polarization is often used to describe the propagation characteristics of electromagnetic waves in waveguides, antennas and other structures.

[0062] TM polarization: represents the polarization state in which the magnetic field vector H of the electromagnetic wave is perpendicular to the direction of propagation, and the angle between the magnetic field vector H and a certain specific direction (usually the reference direction) is 0°. In radio frequency and microwave technology, TM polarization is often used to describe the propagation characteristics of electromagnetic waves in waveguides, antennas and other structures.

[0063] For example, "±10%" in this article refers to the range from the value minus 10% of the value to the value plus 10% of the value based on the value before ±10%.

[0064] For example, as Figure 1-5As shown, the present application provides a dual-band FSR unit structure, including: an impedance layer 10 and an FSS layer 20; wherein the impedance layer 10 includes a dielectric substrate 11, a double helix resonant structure 12, an interdigital capacitor structure 13, and a connecting wire 14. The double helix resonant structure 12 and the interdigital capacitor structure 13 are provided on both sides of the dielectric substrate 11. The double helix resonant structure 12 and the interdigital capacitor structure 13 located on the same side are connected by a connecting wire 14. The connecting wire 14 is provided with a resistor 15. The connecting wires 14 on both sides of the dielectric substrate 11 are in a cross position relationship; the FSS layer 20 has a double ring gap to construct two transmission bands; and the impedance layer 10 and the FSS layer 20 are separated by a gap.

[0065] In one embodiment, to avoid the coupling effect between the double-helix resonant structure 12 and the interdigital capacitor structure 13, achieve performance superposition, improve the absorption rate of the absorption frequency band, and enhance the stability of the structure, the double-helix resonant structure 12 and the interdigital capacitor structure 13 are arranged on both sides of the diagonal of the dielectric substrate 11 and the spacing is maximized, that is, the two connecting wires 14 on the two sides of the dielectric substrate 11 are in a cross-intersection relationship. It is understood that the two connecting wires 14 are perpendicularly crossed in the projection perpendicular to the dielectric substrate 11, and can also be in a cross-intersection relationship not limited to 45°, 60°, or 70°. The double-helix resonant structure 12 and the interdigital capacitor structure 13 need to be connected in the same polarization direction, that is, on the same surface of the dielectric substrate 11, to achieve dual-polarization wave transmission in two passbands. If the double-helix resonant structure 12 and the interdigital capacitor structure 13 are arranged on two surfaces of the dielectric substrate 11, it is equivalent to having two identical structures in one polarization direction, resulting in different polarization results, each showing a single passband effect, and failing to achieve a dual passband effect.

[0066] Providing more double-helix resonant structures 12 and interdigital capacitor structures 13 on a single surface of the dielectric substrate 11 will cause electromagnetic coupling between the structures, generating grating lobes and affecting the wave transmission and absorption effects.

[0067] In one embodiment, resistor 15 is located in the middle of connecting wire 14. It will be appreciated that the two resistors 15 on either side of dielectric substrate 11 overlap in a projection perpendicular to dielectric substrate 11 and are located between the double-helix resonant structure 12 and the interdigital capacitor structure 13. This helps reduce the coupling effect between the double-helix resonant structure 12 and the interdigital capacitor structure 13. Current and electric field are primarily concentrated on the connecting wire 14 connecting the double-helix resonant structure 12 and the interdigital capacitor structure 13, generating loss and absorption when flowing through the lumped resistor 15. In some embodiments, resistor 15 can also be located at any position on connecting wire 14, and the two resistors 15 can also be staggered.

[0068] In one embodiment, Figure 2As shown, the double-helix resonant structure 12 includes two spiral conductive sheets 121 that surround each other, with a spiral gap between them. The outer end of one spiral conductive sheet 121 is connected to the connecting wire 14, while the outer end of the other spiral conductive sheet 121 is connected to the T-shaped conductive sheet 16. Specifically, one end of each spiral conductive sheet 121 is wound multiple times in the same direction on the same plane at opposite corners of a rectangle. The other ends of each spiral conductive sheet 121 are wound at opposite ends, with a uniform spacing between them. The number of turns of each spiral conductive sheet 121 can be three, four, or more.

[0069] Compared with a single helix structure, the double helix resonant structure 12 has higher wave transmittance and better passband selectivity. In addition, the other end of a single helix structure is usually inside the helix, making it difficult to connect the two sides.

[0070] In some embodiments, the double-helix conductive sheet 121 has a rectangular or circular helix structure. It should be noted that research has found that a square helix structure is easier to control and optimize individual parameters during simulation, and is also easier to design and manufacture. While square and circular structures can achieve the same effect, the square structure is easier to adjust.

[0071] In one embodiment, the spiral gap width between the two spiral conductive sheets 121 is g , the width of the spiral conductive sheet 121 is c The width of the horizontal and vertical parts of the T-shaped conductive sheet 16 is w 2. The length of the connecting wire 14 is l 3. The distance between the horizontal line portion of the T-shaped conductive sheet 16 and the spiral conductive sheet 121 not connected to the T-shaped conductive sheet 16 is l 4. The width of the interdigital capacitor structure 13 is f_l , the length is f_w ;

[0072] g : c : w 2: l 3: l 4: f_l : f_w =0.1:0.15:0.25:5.2:1.15:2.5:2;

[0073] In one embodiment, the spiral gap width between the two spiral conductive sheets 121 is g The width of the spiral conductive sheet 121 is 0.1±10% mm. c The width of the horizontal and vertical parts of the T-shaped conductive sheet 16 is 0.15±10% mm. w2 is 0.25±10% mm, the length of the connecting wire 14 l 3 is 5.2±10% mm, the distance between the horizontal line portion of the T-shaped conductive sheet 16 and the spiral conductive sheet 121 not connected to the T-shaped conductive sheet 16 is l 4 is 1.15±10% mm, the width of the interdigital capacitor structure 13 f_l 2.5±10% mm, length f_w 2±10% mm.

[0074] In one embodiment, the dielectric substrate 11 is in the shape of a square with a side length of p 16±10% mm;

[0075] In some embodiments, the material of the connecting wire 14 is metal or a conductive composite material; the metal includes copper, silver, and gold, but is not limited to copper, silver, and gold; the conductive composite material includes a composite material mixed with carbon fiber and resin, a composite material mixed with graphite and resin, or a composite material mixed with graphene and resin.

[0076] In some embodiments, the spiral conductive sheet 121 is made of metal or a conductive composite material. The spiral conductive sheet 121 may be made of the same or different materials as the T-shaped conductive sheet 16. Examples of metals include, but are not limited to, copper, silver, and gold. Examples of conductive composite materials include composite materials made of carbon fiber and resin, graphite and resin, or graphene and resin.

[0077] In one embodiment, Figure 2 As shown, the interdigital capacitor structure 13 includes a multi-tooth structure 1 131 and a multi-tooth structure 2 132 that are meshed with each other. The multi-tooth structure 1 131 is connected to the multi-tooth structure 2 132. The side of the multi-tooth structure 1 131 facing away from the multi-tooth structure 2 132 is connected to the connecting wire 14, and the side of the multi-tooth structure 2 132 facing away from the multi-tooth structure 1 131 is connected to the T-shaped conductive sheet 2 17. Specifically, the multi-tooth structure 1 131 and the multi-tooth structure 2 132 are connected at one point, and the rest of the parts have a gap; preferably, the multi-tooth structure 1 131 and the multi-tooth structure 2 132 are connected at the middle position. The material of the interdigital capacitor structure 13 is the same as that of the spiral conductive sheet 121; of course, the material of the interdigital capacitor structure 13 and the spiral conductive sheet 121 can also be different.

[0078] In one embodiment, Figure 3As shown, the multi-tooth structure one 131 includes five conductive strips one 1311 distributed at intervals, and a conductive connecting sheet one 1312 connecting the five conductive strips one 1311. The multi-tooth structure two 132 includes four conductive strips two 1321 distributed at intervals, and a conductive connecting sheet two 1322 connecting the four conductive strips two 1321. The five conductive strips one 1311 and the four conductive strips two 1321 are alternately distributed, and one of the conductive strips one 1311 is extended to be connected to the conductive connecting sheet two 1322. Specifically, the conductive strips one 1311 and the conductive strips two 1321 are in the shape of a long strip, a triangle, or a trapezoid.

[0079] In some embodiments, the multi-tooth structure one 131 can also be a three-finger structure, a four-finger structure, or a six-finger structure, and the multi-tooth structure two 132 is a two-finger structure, a three-finger structure, or a five-finger structure.

[0080] In some embodiments, the multi-tooth structure one 131 and the multi-tooth structure two 132 are made of metal or conductive composite material; the metal includes copper, silver, and gold, but is not limited to copper, silver, and gold; the conductive composite material includes a composite material mixed by carbon fiber and resin, a composite material mixed by graphite and resin, or a composite material mixed by graphene and resin.

[0081] In some embodiments, the T-shaped conductive sheet two 17 is made of metal or conductive composite material; the metal includes copper, silver, and gold, but is not limited to copper, silver, and gold; the conductive composite material includes a composite material mixed by carbon fiber and resin, a composite material mixed by graphite and resin, or a composite material mixed by graphene and resin.

[0082] The width of the horizontal line part and the vertical line part of the T-shaped conductive sheet two 17 is 0.2 mm. w 1The length of the horizontal line part of the T-shaped conductive sheet two 17 is 4 mm. l 5The distance between the horizontal line part of the T-shaped conductive sheet two 17 and the edge of the dielectric substrate one 11 is 0.75 mm. l 1; w 1: l 5: l 1=0.2:4:0.75.

[0083] In one embodiment, the width of the horizontal line part and the vertical line part of the T-shaped conductive sheet two 17 is 0.2±10% mm. w 1The length of the horizontal line part of the T-shaped conductive sheet two 17 is 4±10% mm. l 5The distance between the horizontal line part of the T-shaped conductive sheet two 17 and the edge of the dielectric substrate one 11 is 0.75±10% mm. l 1

[0084] In one embodiment, as shown in FIG. 1, the width of the horizontal line part and the vertical line part of the T-shaped conductive sheet two 17 is 0.2 mm. Figure 4As shown, the FSS layer 20 includes a second dielectric substrate 21, a first square ring conductive patch 22 disposed on the second dielectric substrate 21, a second square ring conductive patch 23 disposed on the second dielectric substrate 21 and located within the first square ring conductive patch 22, and a square conductive patch 24 disposed on the second dielectric substrate 21 and located within the second square ring conductive patch 23. The first square ring conductive patch 22 and the second square ring conductive patch 23 have a first square ring gap 25 therebetween, and the second square ring conductive patch 23 and the square conductive patch 24 have a second square ring gap 26 therebetween.

[0085] In one embodiment, the distance between the impedance layer 10 and the FSS layer 20 is h ; preferably, the distance between the impedance layer 10 and the FSS layer 20 is 10 ± 10% mm.

[0086] In one embodiment, the second dielectric substrate 21 is square-shaped with a side length of p ; the outer side of the first square ring conductive patch 22 coincides with the edge of the second dielectric substrate 21, and the inner side of the first square ring conductive patch 22 has a length of a 4; the outer side of the second square ring conductive patch 23 has a length of a 3, and the inner side of the second square ring conductive patch 23 has a length of a 2; the square conductive patch 24 has a side length of a 1; and h : p : a 4: a 3: a 2: a 1=10:16:10.08:9.27:6.72:6.05.

[0087] In one embodiment, the distance between the impedance layer 10 and the FSS layer 20 is h 10 ± 10% mm, the second dielectric substrate 21 is square-shaped with a side length of p 16 ± 10% mm; the outer side of the first square ring conductive patch 22 coincides with the edge of the second dielectric substrate 21, and the inner side of the first square ring conductive patch 22 has a length of a 4 10.08 ± 10% mm; the outer side of the second square ring conductive patch 23 has a length of a 3 9.27 ± 10% mm, and the inner side of the second square ring conductive patch 23 has a length of a 2 6.72 ± 10% mm; the square conductive patch 24 has a side length of a 1 6.05 ± 10% mm.

[0088] In one embodiment, the material of the first dielectric substrate 11 and the second dielectric substrate 21 is polytetrafluoroethylene.

[0089] In one embodiment, the material of the square ring conductive sheet 22, the square ring conductive sheet 23 and the square conductive sheet 24 is metal or conductive composite material; wherein the metal includes copper, silver, gold, but is not limited to copper, silver and gold; the conductive composite material includes a composite material formed by mixing carbon fibers and resin, a composite material formed by mixing graphite and resin or a composite material formed by mixing graphene and resin.

[0090] Embodiment 1

[0091] The size parameters of the unit structure of the dual-passband FSR are shown in Table 1. The equivalent circuit of the impedance layer 10 and the FSS layer 20 having a dual-parallel LC structure is established in the circuit simulation software ADS, and the equivalent circuit is as shown in Figure 5 .

[0092] Table 1

[0093]

[0094] It should be noted that in the physical structure model, Figure 1 , the impedance layer double helix structure and the interdigital capacitor structure are respectively equivalent to the two parallel capacitor-inductor structures on the left lower side in the equivalent circuit model Figure 5 , which are transparent at a specific frequency. The longitudinal conductive lines connected thereon are inductance structures, and the transverse conductive lines constitute capacitor structures, which constitute a series capacitor-inductor-resistor structure to absorb waves. Each square ring gap of the FSS layer is equivalent to the two parallel capacitor-inductor structures on the right, which are transparent at a specific frequency.

[0095] In order to facilitate understanding, the impedance layer 10, the FSS layer 20 and the unit structure of the dual-passband FSR provided in the embodiment are subjected to full-wave simulation and equivalent circuit simulation, and the simulation results are as shown in Figure 6 , 7 and 8. It can be seen that through the combined design of the impedance layer 10, the wave absorption frequency points = 4.7 GHz and = 8.3 GHz, and the transmission frequency points = 6.3 GHz and = 9.8 GHz are obtained. Among them, the double helix resonant structure 12 generates a low-frequency transmission pole and a double-sided wave absorption band, and the interdigital capacitor structure 13 generates a high-frequency transmission pole and a double-sided wave absorption band. The two structures avoid coupling influence in the design process, the performance is superimposed, the wave absorption rate of the wave absorption band is improved, and the stability of the structure is enhanced.

[0096] When designing the FSS layer 20 , a double-ring gap-type bandpass FSS of appropriate size is selected, and the two transmission bands of the FSS layer 20 are matched with the two passbands of the impedance layer 10 respectively, thereby realizing an ATAT type dual-passband FSR design.

[0097] Figure 9 The surface current distribution of the dual-band FSR impedance layer 10 in the absorption band and transmission band under TE polarization conditions. and At this point, the current and electric field are mainly concentrated on the conductive line connecting the double helix resonant structure 12 and the interdigital capacitor structure 13, and when flowing through the lumped resistor 15, loss absorption occurs. At this point, the current is mainly concentrated on the double helix structure, where the incident electromagnetic wave generates parallel resonance and induces current, causing the free electrons in the conductive wire to oscillate and then radiate electromagnetic waves into the free space, generating a transmission band. In the transmission band At , the current is mainly concentrated on the interdigital capacitor structure 13, which causes parallel resonance and generates a transmission pole to transmit electromagnetic waves. The distribution of surface current confirms the performance realization method of the structure proposed in the above actual design process.

[0098] The unit structure of the dual-band FSR has the following characteristics: oblique incidence performance within 45° and polarization stability. Figure 10 shown. Figure 10 (a) and Figure 10 (b) The oblique incidence performance curves of the unit structure under TE and TM polarization conditions, respectively, show that the performance of the unit structure under TE and TM polarization conditions is basically consistent. In the simulation results of TM polarization, the high-frequency part is affected by the grating lobe, but due to the limitations of the structural size design, it does not appear within the operating frequency band, showing good polarization stability. From the oblique incidence performance, it can be seen that under TE polarization conditions, the performance of the unit structure is almost unaffected by the oblique incidence angle. Under TM polarization, as the oblique incidence angle increases, the low-frequency and high-frequency absorption bandwidths gradually shrink, the high-frequency transmission band shifts toward high frequencies, and the insertion loss increases.

[0099] The unit structure is designed by superposition of interdigital capacitor structure 13 and double helix resonant structure 12. The superposition of the two absorption bands makes the generated FSR The absorption rate increases, the stability of oblique incidence is improved, and stable performance can be maintained within the range of 45°.

[0100] like Figure 11 As shown, the dual-band FSR and the conductive reflector have a bistatic RCS reduction effect. f A1 and f A2 Comparison at two absorbing frequency points. Figure 11(a) It can be seen that Compared with the conductive reflector, FSR can be achieved at The RCS reduction of the main lobe within 140° is the best at 0°, which can reach 9.8 dB. Figure 11 In (b), Compared with the conductive reflector, FSR can be achieved at The main lobe RCS is reduced within 100°, and the RCS reduction effect can reach 11.9 dB at 0°.

[0101] Figure 12 The figure shows the single-station RCS comparison of FSR and conductive plate. It can be seen that the dual-passband FSR has a relatively obvious RCS reduction effect within the simulated frequency band. As the frequency increases, the RCS of both FSR and conductive plate increases. At 6 GHz and 9 GHz near the two absorption bands, the RCS shows a relatively obvious reduction effect. In the transmission band, = The RCS reduction effect near 6.3GHz is relatively weak. =9.8 GHz, the weakening trend slows down.

[0102] Example 2

[0103] The present application provides a dual-passband FSR including one or more unit structures.

[0104] In order to verify the performance of the dual-passband FSR proposed in this section, a sample was manufactured, such as Figure 13 The figure shows the test environment and a schematic diagram of the dual-band FSR fabricated sample. The sample is a 20×20 element array, measuring 320mm×320mm. The impedance layer 10 is printed on F4B220 material, and the conductive structure is etched on both sides of the dielectric substrate using an immersion gold process. The lumped resistor 15 is a 300Ω 0201 package. The resistor 15 and FSS layer 20 are printed on one side of the F4B350 material. The air gap between the two layers is replaced by a 10mm foam board.

[0105] The measurement method for the processed samples in this section is consistent with the above measurement method, measuring the reflection coefficient and transmission coefficient respectively. The angular stability measurement results are obtained by changing the oblique incident angle, and the polarization stability measurement results are obtained by changing the angle of the horn antenna to change the incident polarization angle.

[0106] Figure 14 The following is a comparison of the measurement results and the simulation results. It can be seen that within the allowable error range, the measurement results are basically consistent with the simulation results. The slight deviations can be attributed to processing errors and measurement accuracy. Figure 14(a) The reflection coefficient bandwidth of the measured results is 4.85-11.28 GHz, the relative bandwidth is 80%, and there are two transmission bands at 6.25 GHz and 9.8 GHz, with insertion losses of 1.2 dB and 1.1 dB respectively. Figure 14 (b) It can be seen that the absorption rate is greater than 90% in the range of 3.6-5.8 GHz and 6.6-9.1 GHz, and the absorption rate is close to 100%.

[0107] Figure 15 The figure shows the comparison between the measurement results and simulation results of the processed sample in the range of 45° oblique incidence. Figure 15 (a) is the measurement result of TE polarized incident electromagnetic wave, Figure 15 (b) shows the measurement results for TM-polarized incident electromagnetic waves. It can be seen that even at 45° oblique incidence, the fabricated sample maintains stable absorption and penetration performance, demonstrating excellent angular stability. The results for TE and TM polarizations are largely consistent, confirming its dual-polarization characteristics. Under TM polarization, high frequencies are significantly affected by higher-order harmonics, but this does not affect performance across the operating frequency band.

[0108] In summary, based on the simulation results, the dual-band FSR of the present invention has two transmission bands and two absorption bands, and the thickness is 0.085 , The free-space wavelength corresponds to the lowest frequency where the reflection coefficient is less than -10 dB. The range where the reflection coefficient is less than -10 dB is 4.4-11.1 GHz, and the relative bandwidth is 86.5%. The transmission bands above -3 dB are 6.03-6.64 GHz and 9.39-10.25 GHz, respectively. f T1 = 6.3 GHz, the insertion loss is 0.5 dB, at the transmission pole f T2 = The insertion loss is 0.8 dB at 9.8 GHz. Actual tests show stable dual-polarization characteristics and wide-angle stability.

[0109] The present application provides a radome comprising one or more frequency selective surfaces.

[0110] Those 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 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.

[0111] It is intended that the embodiments of the application herein disclosed meet all the written requirements of the patent statutes and come within the judicial doctrines of equivalents and will not be construed to be limited to the embodiments shown and described and by the keeping within the spirit and scope of the embodiments of the application.

Claims

1. A dual-band FSR unit structure, characterized in that: include: The impedance layer (10) comprises a dielectric substrate (11), a double helix resonant structure (12), an interdigital capacitor structure (13), and a connecting wire (14). The double helix resonant structure (12) and the interdigital capacitor structure (13) are provided on both sides of the dielectric substrate (11). The double helix resonant structure (12) and the interdigital capacitor structure (13) located on the same side are connected via the connecting wire (14). The double helix resonant structure (12) and the interdigital capacitor structure (13) need to be connected in the same polarization direction. A resistor (15) is provided on the connecting wire (14). The connecting wires (14) on both sides of the dielectric substrate (11) are in a cross position relationship. The FSS layer (20) has a double-sided ring gap to construct two transmission belts; The impedance layer (10) and the FSS layer (20) are spaced apart; The interdigitated capacitor structure (13) includes a multi-tooth structure 1 (131) and a multi-tooth structure 2 (132) that are meshed with each other. The multi-tooth structure 1 (131) is connected to the multi-tooth structure 2 (132). The multi-tooth structure 1 (131) and the multi-tooth structure 2 (132) are connected at one point, and the rest of the parts have a gap.

2. The unit structure according to claim 1, wherein: The two connecting wires (14) on both sides of the dielectric substrate (11) are in a cross-intersection position relationship.

3. The unit structure according to claim 1, wherein: The double helix resonant structure (12) comprises two spiral conductive sheets (121) surrounding each other, with a spiral gap between the two spiral conductive sheets (121), wherein the outer end of one of the spiral conductive sheets (121) is connected to a connecting wire (14), and the outer end of the other spiral conductive sheet (121) is connected to a T-shaped conductive sheet (16).

4. The unit structure according to claim 3, characterized in that The structure of the spiral conductive sheet (121) is a rectangular spiral structure or a circular spiral structure.

5. The unit structure according to claim 3, characterized in that The spiral gap width between the two spiral conductive sheets (121) is g , the width of the spiral conductive sheet (121) is c The widths of the horizontal and vertical lines of the T-shaped conductive sheet (16) are both w 2. The length of the connecting wire (14) is l 3. The distance between the horizontal line portion of the T-shaped conductive sheet (16) and the spiral conductive sheet (121) not connected to the T-shaped conductive sheet (16) is l 4. The width of the interdigital capacitor structure (13) is f_l , the length is f_w ,and g : c : w 2: l 3: l 4: f_l : f_w =0.1:0.15:0.25:5.2:1.15:2.5:2; And / or, the connecting wire (14) is made of metal or a conductive composite material; And / or, the spiral conductive sheet (121) is made of metal or a conductive composite material; And / or, the material of the T-shaped conductive sheet 1 (16) is metal or a conductive composite material.

6. The unit structure according to claim 1, wherein: The side of the multi-tooth structure 1 (131) facing away from the multi-tooth structure 2 (132) is connected to the connecting wire (14), and the side of the multi-tooth structure 2 (132) facing away from the multi-tooth structure 1 (131) is connected to the T-shaped conductive sheet 2 (17).

7. The unit structure according to claim 6, characterized in that The multi-tooth structure 1 (131) includes a plurality of conductive strips 1 (1311) distributed at intervals, and a conductive connecting piece 1 (1312) connecting the plurality of conductive strips 1 (1311). The multi-tooth structure 2 (132) includes a plurality of conductive strips 2 (1321) distributed at intervals, and a conductive connecting piece 2 (1322) connecting the plurality of conductive strips 2 (1321). The plurality of conductive strips 1 (1311) and the plurality of conductive strips 2 (1321) are alternately distributed, and one of the conductive strips 1 (1311) is extended and connected to the conductive connecting piece 2 (1322). And / or, the width of the horizontal line part and the vertical line part of the T-shaped conductive piece 2 (17) are both w 1. The length of the horizontal line portion of the T-shaped conductive sheet 2 (17) is l 5. The distance between the horizontal line portion of the second T-shaped conductive sheet (17) and the edge of the first dielectric substrate (11) is l 1; w 1: l 5: l 1=0.2:4:0.75; And / or, the material of the multi-tooth structure 1 (131) and the multi-tooth structure 2 (132) is metal or a conductive composite material; And / or, the material of the T-shaped conductive sheet 2 (17) is metal or a conductive composite material.

8. The unit structure according to claim 1, wherein: The FSS layer (20) comprises a dielectric substrate (21), a square ring conductive sheet (22) arranged on the dielectric substrate (21), a square ring conductive sheet (23) arranged on the dielectric substrate (21) and located inside the square ring conductive sheet (22), and a square conductive sheet (24) arranged on the dielectric substrate (21) and located inside the square ring conductive sheet (23), wherein a square ring gap (25) is provided between the square ring conductive sheet (22) and the square ring conductive sheet (23), and a square ring gap (26) is provided between the square ring conductive sheet (23) and the square conductive sheet (24); And / or, the distance between the impedance layer (10) and the FSS layer (20) is 10±10% mm.

9. A dual-passband FSR, characterized in that: Comprising one or more unit structures according to any one of claims 1 to 8.

10. A radome, characterized in that: Comprising one or more dual-band FSRs as claimed in claim 9.

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