Unit structure of dual-passband FSR, dual-passband FSR and antenna housing

Abstract

The invention belongs to the technical field of microwaves, and particularly relates to a unit structure of a dual-passband FSR, the dual-passband FSR and an antenna housing, the unit structure comprises an impedance layer and an FSS layer; the impedance layer comprises a first dielectric substrate, double-helix resonance structures, interdigital capacitor structures and connecting wires, the double-helix resonance structures and the interdigital capacitor structures are arranged on the two faces of the first dielectric substrate, the double-helix resonance structures and the interdigital capacitor structures located on the same face are connected through the connecting wires, and resistors are arranged on the connecting wires; the two connecting wires on the two faces of the first dielectric substrate are in a crossed position relation. The FSS layer has a dual annular gap to construct two transport bands. According to the invention, a radar antenna is not influenced at two working frequency bands, radar low detectability is realized through out-of-band wave absorption, dual polarization is realized, the profile is as low as 0.085 # imgabs0 #, and the oblique incidence stability can reach 45 degrees, so that the requirements of low profile, dual polarization and wide-angle performance stability are simultaneously realized.

Description

Technical Field

[0001] The present application belongs to the field of microwave technology, and specifically relates to a unit structure of a dual-passband FSR, a dual-passband FSR and an antenna cover. Background Art

[0002] Traditional radar antenna covers are usually composed of frequency selective surface (FSS) structures, which rely on the frequency selective characteristics of FSS for incident waves to achieve the antenna cover function. FSS (Frequency Selective Surface) is a two-dimensional structure composed of periodically arranged conductive or dielectric units, which can selectively reflect or transmit electromagnetic waves according to the frequency of the incident wave. The basic principle of FSS is to design the shape, size and arrangement of its units so that it exhibits bandpass or bandstop filtering characteristics within a specific frequency range.

[0003] Dual-passband FSR (Frequency Selective Rasorber) refers to a frequency selective structure with two passbands. This frequency selective structure can allow signals to pass in 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. Two transmission windows can be realized when the two transmission bands of the lossy layer coincide with the transmission bands of the low-pass and dual-bandpass FSS. 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 wave absorption rate is greater than 80%, but in actual applications, due to the excessive number of layers of the structure, the thickness reaches 0.15 , It indicates the free space wavelength corresponding to the lowest frequency where 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, it is used for the stealth of broadband antennas. The design combines spiral inductors and interdigital capacitor parallel resonators to meet the wide passband requirements at lower frequencies in 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, the model only has the characteristics of single polarization, and cannot achieve frequency selection under the conditions of horizontally polarized and vertically polarized incident waves, and does not have angle stability, so it cannot be applied in actual engineering.

[0006] In a known technique, the absorber consists of a lossy layer and a lossless layer. The two layers are 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 loss under TE polarization is 0.39 and 0.64 dB, respectively, and the insertion loss under TM polarization is 0.40 and 0.66 dB, respectively. The frequency band where the reflection coefficient is lower than -10 dB is 5-12.8 GHz. In actual tests, the angular stability of this design is only 30°, and stable performance cannot be guaranteed under large angle incidence conditions.

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

[0008] Application Contents The technical problem to be solved by the present application is to provide a unit structure of a dual-passband FSR, a dual-passband 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.

[0009] The present application provides a unit structure of a dual-passband FSR, comprising: The impedance layer comprises a dielectric substrate 1, a double helix resonant structure, an interdigital capacitor structure, and a connecting wire, wherein the double helix resonant structure and the interdigital capacitor structure are arranged on both sides of the dielectric substrate 1, and the double helix resonant structure and the interdigital capacitor structure on the same side are connected by a connecting wire, and a resistor is arranged on the connecting wire, and the connecting wires on the two sides of the dielectric substrate 1 are in a cross position relationship; The FSS layer has double-sided ring gaps to construct two transmission belts; The impedance layer is spaced apart from the FSS layer.

[0010] Optionally, the two connecting wires on two sides of the dielectric substrate are in a cross position relationship.

[0011] 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 1.

[0012] Optionally, the structure of the spiral conductive sheet is a rectangular spiral structure or a circular spiral structure.

[0013] Optionally, the spiral gap width between the two spiral conductive sheets is g , the width of the spiral conductive sheet is c The widths of the horizontal line part and the vertical line part of the T-shaped conductive sheet 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 ; 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 is made of metal or a conductive composite material; And / or, the spiral conductive sheet is made of metal or a conductive composite material; And / or, the material of the T-shaped conductive sheet 1 is metal or a conductive composite material.

[0014] Optionally, the spiral gap width between the two spiral conductive sheets is 0.1±10% mm; And / or, the width of the spiral conductive sheet is 0.15±10% mm; And / or, the width of the horizontal line part and the vertical line part of the T-shaped conductive sheet 1 are both 0.25±10% mm; And / or, the length of the connecting wire is 5.2±10% mm; And / or, the spacing 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; And / or, the width of the interdigital capacitor structure is 2.5±10% mm, and the length is 2±10% mm.

[0015] 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 a T-shaped conductive sheet 2.

[0016] 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, and 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; And / or, the width of the horizontal line part and the vertical line part of the T-shaped conductive sheet 2 are both w 1. The length of the horizontal line portion of the second T-shaped conductive sheet 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; And / or, the material of the multi-tooth structure 1 and the multi-tooth structure 2 is metal or a conductive composite material; And / or, the material of the T-shaped conductive sheet 2 is metal or a conductive composite material.

[0017] Optionally, the FSS layer includes a dielectric substrate 2, a square ring conductive sheet 1 disposed on the dielectric substrate 2, a square ring conductive sheet 2 disposed on the dielectric substrate 2 and located inside the square ring conductive sheet 1, and a square conductive sheet disposed on the dielectric substrate 2 and located inside the square ring conductive sheet 2, a square ring gap 1 is provided between the square ring conductive sheet 1 and the square ring conductive sheet 2, and a square ring gap 2 is provided between the square ring conductive sheet 2 and the square conductive sheet; And / or, the distance between the impedance layer and the FSS layer is 10±10% mm.

[0018] The present application provides a dual-passband FSR, comprising one or more of the unit structures.

[0019] The present application provides a radome comprising one or more frequency selective surfaces.

[0020] 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.

[0021] The dual-passband FSR of this application can make the radar antenna unaffected in two working frequency bands, absorb waves outside the band to achieve radar low detectability, have dual polarization, and the profile is 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

[0022] Figure 1 A schematic diagram of the structure of a unit structure of a dual-passband FSR provided in this application; Figure 2 A schematic diagram of the structure of the impedance layer provided in this application; Figure 3 A schematic diagram of the structure of the interdigital capacitor provided in this application; Figure 4 A schematic diagram of the structure of the FSS layer provided for this application; Figure 5 An equivalent circuit diagram of the unit structure provided for this application; Figure 6 The full-wave simulation and equivalent circuit simulation result diagram of the impedance layer provided in this application; Figure 7 The full-wave simulation and equivalent circuit simulation result diagram of the FSS layer provided for this application; Figure 8 The full-wave simulation and equivalent circuit simulation result diagram of the unit structure of the dual-passband FSR provided in this application; Fig. 9 The electric field distribution and current distribution diagram of the impedance layer provided in this application; Fig.10 Figure (a) is a simulation result diagram of the oblique incidence performance under TE polarization conditions of the unit structure of the dual-band FSR provided by the present application, and Figure (b) is a simulation result diagram of the oblique incidence performance under TM polarization conditions; Fig.11 Figures (a) and (b) show the unit structure of the dual-band FSR provided by the present application and the conductive plate. f A1 The RCS comparison diagram of the two stations at (c) and (d) is f A2 RCS comparison chart of two stations at ; Fig.12 A comparison diagram of the unit structure of the dual-passband FSR provided in this application and the single-station RCS of the conductive plate; Fig.13 Figure (a) is a dual-passband FSR measurement environment diagram provided by this application, and Figure (b) is a sample diagram; Fig.14Figure (a) is a comparison diagram of the measured results and simulation results of the S parameters of the sample provided in this application, and Figure (b) is a comparison diagram of the measured results and simulation results of the wave absorption rate; Fig.15 Figure (a) is a comparison chart of the measured performance results and simulation results of the sample provided in this application under TE polarization conditions at 45° oblique incidence, and Figure (b) is a comparison chart of the measured performance results and simulation results under TM polarization conditions at 45° oblique incidence.

[0023] 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

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] TE polarization: Indicates the polarization state in which the electric field vector E of the electromagnetic wave is perpendicular to the propagation direction and the angle between the electric field vector E and a 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 structures such as waveguides and antennas.

[0029] TM polarization: Indicates the polarization state in which the magnetic field vector H of the electromagnetic wave is perpendicular to the propagation direction and the angle between the magnetic field vector H and a specific direction (usually the reference direction) is 0°. In RF and microwave technology, TM polarization is often used to describe the propagation characteristics of electromagnetic waves in structures such as waveguides and antennas.

[0030] Taking "±10%" in the text as an example, it means that the value before ±10% is used as the benchmark, and the range is between the value minus 10% of the value and the value plus 10% of the value.

[0031] like Figure 1-5 As shown, the present application provides a unit structure of a dual-passband FSR, 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 arranged 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, a resistor 15 is arranged on the connecting wire 14, and 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; the impedance layer 10 and the FSS layer 20 are spaced apart.

[0032] In one embodiment, in order to avoid the coupling effect of the double helix resonant structure 12 and the interdigital capacitor structure 13, the performance is superimposed, the wave absorption rate of the wave absorption band is improved, and the stability of the structure is enhanced. 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 expanded as much as possible, that is, the two connecting wires 14 on the two sides of the dielectric substrate 11 are in a cross-cross position relationship. It can be understood that the two connecting wires 14 are vertically crossed on the projection perpendicular to the dielectric substrate 11, and can also be a cross position relationship not limited to 45°, 60°, and 70°. The double helix resonant structure 12 and the interdigital capacitor structure 13 need to be connected in the same polarization direction, that is, respectively on the same surface of the dielectric substrate 11, to achieve dual-polarization wave transmission of two passbands. If the double helix resonant structure 12 and the interdigital capacitor structure 13 are respectively arranged on the two surfaces of the dielectric substrate 11, it is equivalent to having two identical structures in one polarization direction, and different polarization results will appear to respectively show a single passband effect, but cannot achieve a dual passband effect.

[0033] 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, resulting in grating lobes and other factors that affect the wave transmission and absorption effects.

[0034] In one embodiment, the resistor 15 is located in the middle of the connecting wire 14. It can be understood that the two resistors 15 on both sides of the dielectric substrate 11 overlap in the projection perpendicular to the dielectric substrate 11, and are located in the middle of the double helix resonant structure 12 and the interdigital capacitor structure 13, so that it is helpful to reduce the coupling effect of the double helix resonant structure 12 and the interdigital capacitor structure 13, and the current and electric field are mainly concentrated on the connecting wire 14 connecting the double helix resonant structure 12 and the interdigital capacitor structure 13, and loss absorption is generated when flowing through the lumped resistor 15. In some embodiments, the resistor 15 is also located at any position of the connecting wire 14, and the two resistors 15 can also be staggered.

[0035] In one embodiment, Figure 2 As shown, the double helix resonant structure 12 includes two spiral conductive sheets 121 that surround each other, and there is a spiral gap between the two spiral conductive sheets 121, wherein the outer end of one spiral conductive sheet 121 is connected to the connecting wire 14, and the outer end of the other spiral conductive sheet 121 is connected to the T-shaped conductive sheet 16. Specifically, one end of the two spiral conductive sheets 121 is at the diagonal position of the rectangle, and is wound multiple times in the same plane in the same direction spiral path, and the other ends of the two spiral conductive sheets 121 are at opposite positions, and the two maintain a uniform spacing. The number of turns of the spiral conductive sheet 121 is 3, 4 or more turns.

[0036] Compared with the single helix structure, the double helix resonant structure 12 has higher wave transmittance and better passband selectivity. In addition, the other end of the single helix structure is usually inside the helix, and it is not easy to connect the two sides.

[0037] In some embodiments, the structure of the double helix conductive sheet 121 is a rectangular helix structure or a circular helix structure. It should be noted that in the study, it was found that the square helix structure is easier to control individual parameters for optimization during simulation, and is easy to design and process. In terms of effect, the square and the circle can achieve the same effect, and the square is easier to adjust.

[0038] 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 line part and the vertical line part 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 ; 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; 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 line part and the vertical line part of the T-shaped conductive sheet 16 are both w 2 is 0.25±10% mm, the length of the connecting wire 14 l 3 is 5.2±10% mm, and 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.

[0039] In one embodiment, the dielectric substrate 11 is in the shape of a square with a side length of p 16±10% mm; 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.

[0040] In some embodiments, the spiral conductive sheet 121 is made of metal or a conductive composite material; the spiral conductive sheet 121 and the T-shaped conductive sheet 16 are made of the same or different materials. 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.

[0041] 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 mesh 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 that is 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 that is 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.

[0042] In one embodiment, Figure 3 As shown, the multi-tooth structure 131 includes five conductive strips 1311 distributed at intervals and a conductive connecting piece 1312 connecting the five conductive strips 1311. The multi-tooth structure 2 132 includes four conductive strips 1321 distributed at intervals and a conductive connecting piece 2 1322 connecting the four conductive strips 1321. The five conductive strips 1311 and the four conductive strips 1321 are alternately distributed, and one of the conductive strips 1311 is extended and connected to the conductive connecting piece 2 1322. Specifically, the structural shapes of the conductive strips 1311 and the conductive strips 1321 are long strips, triangles, or trapezoids.

[0043] In some embodiments, the multi-tooth structure 131 may also be a three-finger structure, a four-finger structure, or a six-finger structure, and the multi-tooth structure 132 may be a two-finger structure, a three-finger structure, or a five-finger structure.

[0044] In some embodiments, the material of the multi-tooth structure 1 131 and the multi-tooth structure 2 132 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.

[0045] In some embodiments, the material of the T-shaped conductive sheet 2 17 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.

[0046] The width of the horizontal line part and the vertical line part of the T-shaped conductive sheet 17 are both w 1. The length of the horizontal line portion of the T-shaped conductive sheet 17 is l 5. The distance between the horizontal line portion of the T-shaped conductive sheet 17 and the edge of the dielectric substrate 11 is l 1; w 1: l 5: l 1=0.2:4:0.75.

[0047] In one embodiment, the width of the horizontal line part and the vertical line part of the T-shaped conductive sheet 17 is w 1 is 0.2±10% mm, the length of the horizontal line portion of the T-shaped conductive sheet 17 l 5 is 4±10% mm, and the distance between the horizontal line portion of the T-shaped conductive sheet 17 and the edge of the dielectric substrate 11 is l 1 is 0.75±10% mm.

[0048] In one embodiment, Figure 4 As shown, the FSS layer 20 includes a dielectric substrate 21, a square ring conductive sheet 1 22 disposed on the dielectric substrate 21, a square ring conductive sheet 23 disposed on the dielectric substrate 21 and located inside the square ring conductive sheet 1 22, and a square conductive sheet 24 disposed on the dielectric substrate 21 and located inside the square ring conductive sheet 23, a square ring gap 1 25 is provided between the square ring conductive sheet 1 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.

[0049] 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.

[0050] In one embodiment, the dielectric substrate 21 is in the shape of a square with a side length of pThe outer side of the square ring conductive sheet 22 coincides with the edge of the dielectric substrate 21, and the inner side length of the square ring conductive sheet 22 is a 4; The outer side length of the square ring conductive sheet 23 is a 3. The inner side length is a 2; The side length of the square conductive sheet 24 is a 1; and h : p : a 4: a 3: a 2: a 1=10:16:10.08:9.27:6.72:6.05.

[0051] In one embodiment, the distance between the impedance layer 10 and the FSS layer 20 is h 10±10% mm, the dielectric substrate 21 is in the shape of a square with a side length p The outer side of the square ring conductive sheet 22 coincides with the edge of the dielectric substrate 21, and the inner side length of the square ring conductive sheet 22 is a 4 is 10.08±10% mm; the outer side length of the square ring conductive sheet 23 a 3 is 9.27±10% mm, inner side length a 2 is 6.72±10% mm; the side length of the square conductive sheet 24 a 1 is 6.05±10% mm.

[0052] In one embodiment, the material of the dielectric substrate 1 1 and the dielectric substrate 2 21 is polytetrafluoroethylene.

[0053] In one embodiment, the material of the square ring conductive sheet 1 22, the square ring conductive sheet 23 and the square conductive sheet 24 is metal or a conductive composite material; wherein 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.

[0054] Example 1 The size parameters of the unit structure of the dual-passband FSR are shown in Table 1. An equivalent circuit with a double parallel LC structure of the impedance layer 10 and the FSS layer 20 is established in the circuit simulation software ADS. The equivalent circuit is as follows: Figure 5 shown.

[0055] Table 1

[0056] It should be noted that in the physical structure model ( Figure 1), the impedance layer double helix structure and the interdigital capacitor structure are equivalent to equivalent circuit models ( Figure 5 ) in the figure, the two parallel capacitor-inductor structures on the lower left side transmit waves at a specific frequency. The vertical conductive wires connected to it are inductor structures, and the horizontal conductive wires form capacitor structures, forming a series capacitor-inductor-resistor structure to absorb waves. Each square ring gap in the FSS layer is equivalent to two parallel capacitor-inductor structures on the right side, which transmit waves at a specific frequency.

[0057] For ease of understanding, full-wave simulation and equivalent circuit simulation are performed on the unit structure of the impedance layer 10, the FSS layer 20 and the dual-passband FSR provided in this embodiment. The simulation results are shown in FIG. Figure 6 , 7 As shown in 8, it can be seen that the absorption frequency is obtained by the combined design of the impedance layer 10. = 4.7 GHz and =8.3 GHz, and the transmission frequency =6.3 GHz and =9.8GHz. The double helix resonant structure 12 generates a low-frequency transmission pole As well as the double-sided absorption band, the interdigital capacitor structure 13 generates a high-frequency transmission pole The two structures avoid coupling effects during the design process, achieve superposition of performance, improve the absorption rate of the absorption frequency band, and enhance the stability of the structure.

[0058] 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, so as to realize the ATAT type dual-passband FSR design.

[0059] Fig. 9 This is 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 the 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 loss absorption occurs when flowing through the lumped resistor 15. 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 free space, generating a transmission band; in the transmission band At , the current is mainly concentrated on the interdigital capacitor structure 13 to generate parallel resonance, generating transmission poles to transmit electromagnetic waves. The distribution of surface current confirms the performance realization method of the structure proposed in the above practical design process.

[0060] The unit structure of the dual-band FSR has the following characteristics: oblique incidence performance within 45° and polarization stability. Fig.10 shown. Fig.10 (a) and Fig.10 (b) are the oblique incident performance curves of the unit structure under TE polarization and TM polarization conditions, respectively. It can be seen that the performance of the unit structure under TE polarization 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 it does not appear in the working frequency band due to the limitation of the structural size design, showing good polarization stability. From the oblique incident performance, it can be seen that under TE polarization conditions, the performance of the unit structure is almost not affected by the oblique incident angle. Under TM polarization, as the oblique incident angle increases, the low-frequency and high-frequency absorption bandwidths gradually shrink, the high-frequency transmission band shifts to high frequency, and the insertion loss increases.

[0061] The unit structure is designed by superposition of the interdigital capacitor structure 13 and the double helix resonant structure 12. The superposition of the absorption bands of the two 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°.

[0062] like Fig.11 As shown in Figure 2, the dual-band FSR and the conductive reflector have a dual-station RCS reduction effect. f A1 and f A2 Compare the two absorption frequencies. Fig.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. Fig.11 (b) In Compared with the conductive reflector, FSR can be achieved at The RCS reduction of the main lobe within 100° can reach 11.9 dB at 0°.

[0063] Fig.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 FSR and conductive plate increases accordingly. At 6 GHz and 9 GHz near the two absorption bands, the RCS has 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.

[0064] Example 2 The present application provides a dual-passband FSR, comprising one or more unit structures.

[0065] In order to verify the performance of the dual-passband FSR proposed in this section, a sample was fabricated. Fig.13 The figure shows the test environment and the schematic diagram of the dual-passband FSR processing sample. The sample is an array composed of 20×20 units with a size of 320mm×320mm. The impedance layer 10 is printed on the F4B220 material, and the conductive structure on it is etched on both sides of the dielectric substrate using the immersion gold process. The lumped resistor 15 is a 300mm 0201 package. Resistor 15 and FSS layer 20 are printed on one side of F4B350 material. The air layer between the two layers is replaced by a 10mm foam board.

[0066] The measurement method of the processed samples in this section is consistent with the above measurement method, and the reflection coefficient and transmission coefficient are measured respectively. The angle stability measurement result is obtained by changing the oblique incident angle, and the polarization angle of the incident is changed by changing the angle of the horn antenna to obtain the polarization stability measurement result.

[0067] Fig.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. Fig.14 (a), the reflection coefficient bandwidth of the measured results is 4.85-11.28 GHz, the relative bandwidth is 80%, there are two transmission bands at 6.25 GHz and 9.8 GHz, and the insertion losses are 1.2 dB and 1.1 dB respectively. Fig.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%.

[0068] Fig.15 The figure shows the comparison between the measurement results and the simulation results of the processed sample in the 45° oblique incidence range. Fig.15 (a) is the measurement result of TE polarized incident electromagnetic wave, Fig.15 (b) is the measurement result of TM polarized incident electromagnetic wave. It can be seen that under 45° oblique incidence, the processed sample can still maintain stable absorption and penetration performance with excellent angle stability. The results of TE and TM polarizations are basically consistent, verifying that it has dual polarization characteristics. Under TM polarization conditions, high frequencies are greatly affected by high-order harmonics, but do not affect the working frequency band performance.

[0069] 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 is the lowest frequency at which the reflection coefficient is less than -10 dB. The range of reflection coefficient less than -10 dB is 4.4-11.1 GHz, and the relative bandwidth is 86.5%. The transmission band above -3 dB is 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. The actual test shows stable dual-polarization characteristics and large-angle stability.

[0070] The present application provides a radome comprising one or more frequency selective surfaces.

[0071] 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.

[0072] 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 unit structure of a dual-passband FSR, 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 arranged 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); a resistor (15) is arranged on the connecting wire (14); and 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 belts; The impedance layer (10) and the FSS layer (20) are spaced apart.

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

3. The unit structure according to claim 1, characterized in that: The double helix resonant structure (12) comprises two spiral conductive sheets (121) surrounding each other, and a spiral gap is provided 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 1 (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 parts of the T-shaped conductive sheet 1 (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 1 (16) and the spiral conductive sheet (121) not connected to the T-shaped conductive sheet 1 (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, characterized in that: The interdigital capacitor structure (13) comprises a multi-tooth structure 1 (131) and a multi-tooth structure 2 (132) that mesh with each other, the multi-tooth structure 1 (131) being 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) being connected to a connecting wire (14), and the side of the multi-tooth structure 2 (132) facing away from the multi-tooth structure 1 (131) being connected to a T-shaped conductive sheet 2 (17).

7. The unit structure according to claim 6, characterized in that: The multi-tooth structure 1 (131) comprises 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) comprises 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 distributed alternately, and one of the conductive strips 1 (1311) is extended and connected to the conductive connecting piece 2 (1322); And / or, the widths of the horizontal line part and the vertical line part of the T-shaped conductive sheet 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, characterized in that: The FSS layer (20) comprises a dielectric substrate 2 (21), a square ring conductive sheet 1 (22) arranged on the dielectric substrate 2 (21), a square ring conductive sheet 2 (23) arranged on the dielectric substrate 2 (21) and located inside the square ring conductive sheet 1 (22), and a square conductive sheet (24) arranged on the dielectric substrate 2 (21) and located inside the square ring conductive sheet 2 (23); a square ring gap 1 (25) is provided between the square ring conductive sheet 1 (22) and the square ring conductive sheet 2 (23); and a square ring gap 2 (26) is provided between the square ring conductive sheet 2 (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-passband FSRs as claimed in claim 9.

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