A single-passband FSR unit structure, a single-passband FSR and a radome

Abstract

The application belongs to the technical field of microwave, and particularly relates to a single-passband FSR unit structure, a single-passband FSR and a radome, which comprise an impedance layer and an FSS layer. The impedance layer comprises a dielectric substrate one, two double-helix resonant structures arranged on two surfaces of the dielectric substrate one respectively, four connecting wires connected to four ends of the two double-helix resonant structures respectively, four resistors arranged on the dielectric substrate one and connected to the four connecting wires respectively, and T-shaped metal sheets arranged on the dielectric substrate one and connected to the four resistors respectively. The FSS layer has a single square ring gap to construct a single transmission band. The unit structure provided in the application is used to enhance the polarization stability in a vertical stacking mode of the double-layer structure of the impedance layer, so that the unit structure greatly reduces the insertion loss and has stable dual-polarization characteristics and certain angular 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 single-band FSR, a single-band FSR and a radome. Background Art

[0002] A radome not only protects the radar's internal antenna system from environmental conditions such as rain, snow, wind, and sand, but also ensures that the antenna system operates normally within the required frequency band and achieves stealth. The core of radome low observable technology is to reduce the radar cross section. A frequency selective absorber (FSE) is a composite structure that combines a frequency selective surface with a circuit mode absorber. It typically consists of a multi-layer periodic structure consisting of a lossy impedance surface layer, a dielectric layer, an air layer, and a lossless FSS transmission layer.

[0003] A single-band FSR (Frequency Selective Rasorbeer) is a frequency selective structure with a single passband and two absorbing bands on either side. This frequency selective structure allows signals to pass within a specific frequency range, while attenuating or blocking signals in other frequency ranges.

[0004] In a known technology, the lossy layer consists of a Jerusalem element with a parallel resonant unit in the center, and resistors are loaded on the metal branches. The lossless layer is integrated by a multi-layer frequency selective surface, achieving high selectivity and a wide transmission band. Simulation results show that a 1 dB transmission window is obtained at 7.9-9.0 GHz, and the lowest insertion loss is 1 dB. Its -10 dB absorption band is 3.3-7.1 GHz and 9.4-12.0 GHz, and the angle stability reaches 20° in actual measurement. The structure has a large cross-section in practical applications, with a thickness of 0.1 , This represents the free-space wavelength corresponding to the lowest frequency where the reflection coefficient is less than -10dB. It exhibits unstable performance under wide angles of incidence and exhibits high insertion loss, leaving room for optimization.

[0005] In a known technique, the design uses an open circular resonator in the top layer combined with a metal strip loaded with resistors to realize the resistor. At the bottom layer, a slotted frequency selective surface with two slots is designed to match the passband of the resistor. Full-wave simulation results show that an anisotropic transmission band with low insertion loss under transverse electric (TE) and transverse magnetic (TM) polarization is achieved, and absorption is achieved on both sides of the passband, with a -10 dB reflection bandwidth of 61.3%. The design thickness is 0.125 , The free-space wavelength is the lowest frequency at which the reflection coefficient is less than -10 dB. Given its anisotropy, this design can only achieve single-polarization performance for a stable antenna system, with an insertion loss of 0.81 dB.

[0006] In summary, the single-passband frequency-selective metasurface in the existing technology cannot simultaneously take into account insertion loss, thickness, and angular stability, and there is room for optimization.

[0007] Application Contents

[0008] The technical problem to be solved by the present application is to provide a unit structure of a single-band FSR, a single-band FSR and an antenna cover, which have low insertion loss, stable dual-polarization characteristics and a certain angle stability.

[0009] The present application provides a unit structure of a single-passband FSR, comprising:

[0010] The impedance layer includes a dielectric substrate 1, two double-helix resonant structures respectively disposed on two sides of the dielectric substrate 1, four connecting wires respectively connected to four ends of the two double-helix resonant structures, four resistors disposed on the dielectric substrate 1 and respectively connected to the four connecting wires, and a T-shaped conductive sheet disposed on the dielectric substrate 1 and respectively connected to the four resistors;

[0011] FSS layer, with a single square ring gap to construct a single transmission belt;

[0012] The impedance layer is spaced apart from the FSS layer.

[0013] Optionally, the two double-helix resonant structures are both arranged in the middle of the dielectric substrate 1, and the two double-helix resonant structures are arranged to be deflected from each other.

[0014] Optionally, the double helix resonant structure includes two spiral conductive plates surrounding each other, with a spiral gap between the two spiral conductive plates, and the outer ends of the two spiral conductive plates are respectively connected to two connecting wires, and the two connecting wires are in the same straight line direction.

[0015] Optionally, the structure of the spiral conductive sheet is a rectangular spiral structure or a circular spiral structure;

[0016] And / or, the connecting wire is made of metal or a conductive composite material;

[0017] And / or, the spiral conductive sheet is made of metal or a conductive composite material;

[0018] And / or, the material of the T-shaped conductive sheet is metal or a conductive composite material;

[0019] And / or, the material of the dielectric substrate 1 is polytetrafluoroethylene.

[0020] Optionally, the side length of the dielectric substrate 1 is p , 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 connecting wire is w 1. The width of the horizontal line part and the vertical line part of the T-shaped conductive sheet are both w 1. The length of the horizontal line portion of the T-shaped conductive sheet is l 1. The distance between the horizontal line part of the T-shaped conductive sheet and the double helix resonant structure is l 2. The distance between the horizontal line portion of the T-shaped conductive sheet and the side edge of the dielectric substrate is w 2;

[0021] described p:g:c:w 1 ：l 1 ：l 2 ：w 2=16:0.1:0.15:0.2:4:5.3:0.75.

[0022] Optionally, the side length of the dielectric substrate 1 is 16±10% mm;

[0023] And / or, the spiral gap width between the two spiral conductive sheets is 0.1±10% mm;

[0024] And / or, the width of the spiral conductive sheet is 0.15±10% mm;

[0025] And / or, the width of the connecting wire is 0.2±10% mm;

[0026] And / or, the width of the horizontal line part and the vertical line part of the T-shaped conductive sheet are both 0.2±10% mm;

[0027] And / or, the length of the horizontal line portion of the T-shaped conductive sheet is 4±10% mm;

[0028] And / or, the distance between the horizontal line portion of the T-shaped conductive sheet and the double helix resonant structure is 5.3±10% mm;

[0029] And / or, the distance between the horizontal line portion of the T-shaped conductive sheet and the side edge of the dielectric substrate is 0.75±10% mm.

[0030] Optionally, the FSS layer includes a second dielectric substrate, a square ring metal sheet disposed on the second dielectric substrate, and a square metal sheet disposed on the second dielectric substrate and located within the square ring metal sheet, with square ring gaps being formed between the square ring metal sheets.

[0031] Optionally, the material of the dielectric substrate 2 is polytetrafluoroethylene;

[0032] And / or, the material of the square ring metal sheet is metal or a conductive composite material;

[0033] And / or, the square metal sheet is made of metal or a conductive composite material.

[0034] Optionally, the size of the interval between the impedance layer and the FSS layer is 10±10% mm.

[0035] The present application provides a single-passband FSR, comprising one or more of the above-mentioned unit structures.

[0036] The present application provides a radome comprising one or more single-band FSRs.

[0037] The beneficial effect of the present application is that the unit structure of the single-band FSR provided by the present application, the double-helix resonant structure, the connecting wire and the resistor in the impedance layer constitute a series RLC circuit to generate an absorbing frequency band, the middle double-helix resonant structure constitutes a parallel LC circuit, the two double-helix resonant structures enable the insertion of a passband in the absorbing band, and the impedance layer adopts a double-layer structure vertically stacked in a manner to enhance the polarization stability performance, so that the unit structure significantly reduces the insertion loss and has stable dual-polarization characteristics and a certain angle stability.

[0038] The single-band FSR provided by this application has a high-transmittance transmission band and two absorption bands, and the thickness is 0.085 , Indicates the free space wavelength corresponding to the lowest frequency where the reflection coefficient is less than -10dB. The range where the reflection coefficient is less than -10dB is 3.9-9.3GHz, and the relative bandwidth is 82%. The transmission band is higher than -3dB in the range of 5.8-7GHz, and at the transmission pole f T1 = 6.3GHz, the insertion loss is 0.3dB, and the angular stability is 30°. Actual tests show stable dual-polarization characteristics and a certain degree of angular stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a schematic diagram of the unit structure of the single-band FSR of this application.

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

[0041] Figure 3 Schematic diagram of the structure of the FSS layer provided by this application;

[0042] Figure 4 Equivalent circuit diagram of the unit structure provided in this application;

[0043] Figure 5 The full-wave simulation and equivalent circuit simulation results of the unit structure of the single-band FSR 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 single-layer and double-layer double-helix impedance layers provided in this application;

[0046] Figure 8 The electric field distribution and current distribution diagram of the impedance layer provided in this application;

[0047] Figure 9 (a) is a simulation result diagram of the oblique incidence performance of the unit structure of the dual-band FSR provided in this application under TE polarization conditions, and (b) is a simulation result diagram of the oblique incidence performance under TM polarization conditions;

[0048] Figure 10 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 ;

[0049] Figure 11 A comparison chart of the unit structure of the single-passband FSR provided in this application and the single-station RCS of the metal plate;

[0050] Figure 12 Figure (a) is a diagram of the dual-band FSR measurement environment provided by this application, and Figure (b) is a sample diagram;

[0051] Figure 13 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;

[0052] Figure 14 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.

[0053] In the figure: 10, impedance layer; 11, dielectric substrate 1; 12, double helix resonant structure; 121, spiral conductive sheet; 13, connecting wire; 14, resistor; 15, T-shaped conductive sheet; 20, FSS layer; 21, dielectric substrate 2; 22, square ring metal sheet; 23, square metal sheet; 24, square ring gap. DETAILED DESCRIPTION

[0054] 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.

[0055] 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.

[0056] Before describing the embodiments of the present application in detail, some of the nouns and terms involved in the embodiments of the present application are first explained. The nouns and terms involved in the embodiments of the present application are subject to the following interpretations:

[0057] In FSS, S parameters usually include S11, S21, etc., where:

[0058] S11: Return loss at port 1, also known as the input reflection coefficient. It measures the proportion of signal energy reflected back from the input port (port 1). The closer the S11 value is to 0 (usually expressed in dB, such as -25dB or -40dB), the lower the reflection, indicating lower return loss in the transmission path.

[0059] S21: Indicates the insertion loss of a signal from port 1 to port 2. It measures the signal loss during transmission. The closer the S21 value is to 1 (0dB), the smaller the loss during transmission.

[0060] TE polarization: A polarization state in which the electric field vector E of an electromagnetic wave is perpendicular to the direction of propagation and the angle between the electric field vector E and a specific direction (usually a 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.

[0061] TM polarization: This refers to a polarization state in which the magnetic field vector H of an electromagnetic wave is perpendicular to the propagation direction and the angle between the magnetic field vector H and a specific direction (usually a 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.

[0062] Parallel LC circuit: A circuit structure formed by connecting an inductor and a capacitor in parallel.

[0063] Series RLC circuit: A circuit consisting of a resistor (R), an inductor (L), and a capacitor (C) connected in series.

[0064] FR4: Mainly composed of glass fiber and epoxy resin.

[0065] RO4003C: Made of glass fiber reinforced polytetrafluoroethylene (PTFE) and ceramic composite material.

[0066] RO4350B: Also made of glass fiber reinforced PTFE and ceramic composite material.

[0067] Taking "±10%" in the text as an example, it means that the value before ±10% is used as the benchmark, and the range is from the value minus 10% of the value to the value plus 10% of the value.

[0068] like Figure 1-5 As shown, the present application provides a single-band FSR unit structure, which can be applied to the radome design of a single-band radar antenna system on a weapon platform such as an aircraft, including: an impedance layer 10 and an FSS layer 20; wherein, the impedance layer 10 includes a dielectric substrate 11, two double-helix resonant structures 12 respectively arranged on two sides of the dielectric substrate 11, four connecting wires 13 respectively connected to the four ends of the two double-helix resonant structures 12, four resistors 14 arranged on the dielectric substrate 11 and respectively connected to the four connecting wires 13, and a T-shaped conductive sheet 15 arranged on the dielectric substrate 11 and respectively connected to the four resistors 14; the FSS layer 20 has a unilateral ring gap 24 to construct a single transmission band; the impedance layer 10 and the FSS layer 20 are spaced apart.

[0069] Compared with the prior art, the unit structure of the single-band FSR provided by the present application comprises a double-helix resonant structure 12, a connecting wire 13 and a resistor 14 in the impedance layer 10, which constitute a series RLC circuit to generate an absorbing frequency band. The middle double-helix resonant structure 12 constitutes a parallel LC circuit. The two double-helix resonant structures 12 allow a passband to be inserted into the absorbing band. The impedance layer 10 adopts a double-layer structure vertically stacked to enhance polarization stability, so that the unit structure significantly reduces insertion loss and has stable dual-polarization characteristics and a certain degree of angular stability.

[0070] It should be noted that in the physical structure model ( Figure 1 ), the double helix structure of the impedance layer is equivalent to an equivalent circuit model ( Figure 4 The parallel capacitor-inductor structure on the lower left side of the image transmits waves at specific frequencies. The vertical metal wires connected to it form an inductor structure, while the horizontal metal wires form a capacitor structure, creating a series capacitor-inductor-resistor structure for wave absorption. The square ring-shaped gap in the FSS layer is equivalent to the parallel capacitor-inductor structure on the right, transmitting waves at specific frequencies.

[0071] The double-helix structure is primarily advantageous for connection at both ends, enabling effective polarization in both directions. Multiple interleaved helices are possible, but the resulting complexity increases, without significantly improving performance. Furthermore, this complexity can lead to coupling between structures, resulting in grating lobes and other issues.

[0072] In one embodiment, two double-helix resonant structures 12 are disposed in the middle of dielectric substrate 11, and the two double-helix resonant structures 12 are arranged to be offset from each other. It is understood that when one of the two double-helix resonant structures 12 is offset by a certain angle, the two double-helix resonant structures 12 can overlap in a direction perpendicular to dielectric substrate 11. The deflection angle is 90°, but may also be, but is not limited to, 45°, 60°, or 70°.

[0073] The two double-helix resonant structures 12 are arranged 90° apart to achieve electromagnetic response in both horizontal and vertical polarization directions. Any polarization direction can be synthesized from the two polarization directions. If they are parallel, only a single polarization effect is achieved, achieving performance in one direction but not in the other. Other angles are similar to parallelism, but cannot achieve full performance in the other polarization direction alone, and therefore cannot synthesize the same performance at any polarization angle.

[0074] In one embodiment, the double-helix resonant structure 12 includes two spiral conductive sheets 121 that surround each other, with a spiral gap between them. The outer ends of the two spiral conductive sheets 121 are respectively connected to two connecting wires 13, and the two connecting wires 13 are arranged in the same linear direction. Specifically, one end of each spiral conductive sheet 121 is wound multiple times in the same plane at opposite corners of a rectangle, with the other ends of the spiral conductive sheets 121 at opposite ends, and a uniform spacing is maintained between them. The number of turns of the spiral conductive sheet 121 can be three, four, or more, and the spiral conductive sheet 121 can be a square spiral resonant structure or a rectangular spiral resonant structure.

[0075] In some embodiments, the spiral conductive sheet 121 can be configured as a rectangular spiral or a circular spiral. Research has found that a square spiral structure is easier to control and optimize individual parameters during simulation, and is also easier to design and manufacture. While a square and a circular structure can achieve the same effect, the square is easier to adjust.

[0076] In some embodiments, the material of the connecting wire 13 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.

[0077] In some embodiments, the spiral conductive sheet 121 is made of 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.

[0078] In some embodiments, the material of the T-shaped conductive sheet 15 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.

[0079] In some embodiments, the dielectric substrate 11 is made of PTFE (polytetrafluoroethylene), or may be made of FR4, RO4003C, RO4350B, silicon nitride ceramics, or silicon carbide ceramics.

[0080] In one embodiment, the thickness of the dielectric substrate 11 is d 1 is 0.2-0.5mm.

[0081] In one embodiment, the side length of the dielectric substrate 11 is p , the spiral gap width of the two spiral conductive sheets 121 is g , the width of the spiral conductive sheet 121 is c , the width of the connecting wire 13 is w 1. The width of the horizontal and vertical parts of the T-shaped conductive sheet 15 is w 1. The length of the horizontal line portion of the T-shaped conductive sheet 15 is l 1. The distance between the horizontal line part of the T-shaped conductive sheet 15 and the double helix resonant structure 12 is l 2. The distance between the horizontal line portion of the T-shaped conductive sheet 15 and the side edge of the dielectric substrate 11 is w 2;

[0082] p:g:c:w 1：l 1 ：l 2 ：w 2 = 16:0.1:0.15:0.2:4:5.3:0.75. The above parameters have a proportional relationship, and can achieve functions of different frequency bands when they are enlarged or reduced in proportion.

[0083] In one embodiment, the side length of the dielectric substrate 11 is p 16±10% mm;

[0084] The spiral gap width between the two spiral conductive sheets 121 is g 0.1±10% mm;

[0085] The width of the spiral conductive sheet 121 c 0.15±10% mm;

[0086] Width of connecting wire 13 w 1 is 0.2±10% mm;

[0087] The width of the horizontal and vertical parts of the T-shaped conductive sheet 15 is w 1 is 0.2±10% mm;

[0088] The length of the horizontal line portion of the T-shaped conductive piece 15 l 1 is 4±10% mm;

[0089] The distance between the horizontal line of the T-shaped conductive sheet 15 and the double helix resonant structure 12 is l 2 is 5.3±10% mm;

[0090] The distance between the horizontal line portion of the T-shaped conductive sheet 15 and the side edge of the dielectric substrate 11 is w 2 is 0.75±10% mm.

[0091] Under the above parameter ratio determination conditions, it is still feasible to change the parameters within a certain range. The table shows the preferred parameters selected in the parameter scan, but the variation range should not exceed ±10% of the value in the table, otherwise it will affect the performance.

[0092] In one embodiment, the FSS layer 20 includes a dielectric substrate 21, a square ring metal sheet 22 disposed on the dielectric substrate 21, and a square metal sheet 23 disposed on the dielectric substrate 21 and within the square ring metal sheet 22. A square ring gap 24 is defined between the square ring metal sheets 22 and 23. Specifically, the dielectric substrate 21 is made of PTFE (polytetrafluoroethylene), or alternatively, FR4, RO4003C, RO4350B, silicon nitride ceramic, or silicon carbide ceramic. The dielectric substrate 21 is square in shape, with side lengths equal to those of the dielectric substrate 11, and a thickness of 1.5 mm. d1 is 0.3-1mm. The outer side of the square ring metal sheet 22 coincides with the edge of the dielectric substrate 21, and the inner side length of the square ring metal sheet 22 is a 2 is 10.88±10% mm, and the side length of the square metal sheet 23 is a 1 is 9.8±10% mm.

[0093] In one embodiment, the distance between the impedance layer 10 and the FSS layer 20 is h 10±10% mm.

[0094] In some embodiments, the material of the dielectric substrate 21 is polytetrafluoroethylene, and may also be FR4, RO4003C, RO4350B, silicon nitride ceramics, or silicon carbide ceramics.

[0095] In some embodiments, the material of the square ring metal sheet 22 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.

[0096] In some embodiments, the square metal sheet 23 is a 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.

[0097] Example 1

[0098] The size parameters of the unit structure of the single-band FSR are shown in Table 1. In the circuit simulation software ADS, an equivalent circuit with a parallel LC circuit of the impedance layer 10 and the FSS layer 20 is established. The equivalent circuit is as follows: Figure 4 shown.

[0099] Table 1

[0100]

[0101] Comparison of simulation results with calculation results of equivalent circuit Figure 5 As shown in the figure, the reflection coefficient is less than -10 dB from 3.9 to 9.3 GHz, with a relative bandwidth of 82%. The transmission band is greater than -3 dB from 5.8 to 7 GHz, with a minimum insertion loss of 0.007 dB at 6.3 GHz, significantly reducing insertion loss. The results obtained from the equivalent circuit calculation are generally consistent with the model simulation results, verifying the correctness of the design.

[0102] Figure 6The corresponding relationship of the equivalent circuit on the impedance layer 10 and its simulation results are shown. It can be seen that the gap between the spiral conductive sheets 121 is equivalent to a capacitor, the spiral conductive sheet 121 is equivalent to an inductor, and the double spiral inductor is a parallel LC circuit that generates a transmission band. At the transmission pole =6.3 GHz, the equivalent impedance of the impedance layer 10 and the frequency selective layer tends to infinity. =4.1 GHz, =8.6 GHz. The FSS layer 20 (also called the frequency selective layer) has a square ring slot 24 structure. By adjusting the size parameters, the passband of the FSS layer 20 is matched with the passband of the impedance layer 10, realizing an ATA-type FSR design.

[0103] Compared with other structures, the spiral resonant structure can reduce interlayer coupling when it is stacked on both sides of the dielectric substrate and the spiral direction is consistent. From the simulation results, a single-layer double-helix resonant structure 12 can achieve the wave absorption-wave transmission-wave absorption performance in one polarization direction. Figure 7 The figure shows the comparison of the simulation results of the impedance layer 10 with the spiral absorption structure printed on only one side of the dielectric substrate and the double-layer impedance layer 10. It can be seen that the overall performance only has a slight shift in the transmission frequency point, and the overall performance remains unchanged.

[0104] Figure 8 The electric field distribution and surface current of the impedance layer 10 in the absorption band and transmission band under TE polarization conditions are shown.

[0105] It can be seen that there are double-sided absorption bands and At this point, the current and electric field are mainly concentrated on the spiral conductive sheet 121 connected to the double helix resonant structure 12, and when flowing through the resistor 14, loss absorption occurs. At this point, the current and electric field are mainly concentrated on the double-helix resonant structure 12. The incident electromagnetic wave induces a current on it, which then radiates the electromagnetic wave into the free space on the nearly lossless metal structure, generating a transmission belt.

[0106] The FSR performance under oblique incidence within 30° and the polarization stability based on the double helix resonant structure 12 are shown in Figure 1. Figure 9 shown. Figure 9 (a) and Figure 9 (b) The oblique-incidence performance curves of the FSR under TE and TM polarization conditions, respectively, show that the performance of the FSR under TE and TM polarization conditions is basically consistent, showing good polarization stability. Compared with TE polarization, the high-order harmonics at high frequencies appear earlier at low frequencies in TM polarization. From the perspective of oblique-incidence performance, as the oblique-incidence angle increases, the low-frequency absorption bandwidth gradually decreases, the transmission band shrinks, and the insertion loss increases. The FSR can maintain stable performance within a range of 30°.

[0107] In CST (CST Studio Suite, a professional 3D electromagnetic field simulation software), an 8×8 element array was simulated to study the RCS reduction effect of FSR. The array size was 128mm×128mm, and the simulation results of the array were compared with those of a metal reflector of the same size. Figure 10 As shown in Figure 2, the RCS reduction effect of combining FSR with metal reflectors is Comparison at two absorbing frequency points. Figure 10 (a) It can be seen that Compared with metal reflectors, FSR can be achieved at The RCS reduction of the main lobe within 140° is the best at 0°, reaching 7.68 dB. Figure 10 In (b), Compared with metal reflectors, FSR can be achieved at The main lobe RCS is reduced within 60°, and the RCS reduction effect can reach 20.72 dB at 0°. It can be seen that due to the increase in high-frequency electrical size, the simulation of the unit array is closer to the ideal period infinite plane. Therefore, in terms of the main lobe RCS reduction range and the amplitude of RCS reduction, the high frequency Frequency is better than low frequency .

[0108] Figure 11 The figure shows the single-station RCS comparison of FSR and metal plate. It can be seen that in the simulated 3-13GHz frequency range, FSR has a relatively obvious RCS reduction effect. As the frequency increases, high frequency leads to an increase in electrical size, and the RCS of FSR and metal plate increases accordingly. FSR has a relatively obvious RCS reduction effect at 5GHz and 8GHz near the two absorption bands. =The RCS reduction effect near 6.3 GHz is relatively weakened.

[0109] Example 2

[0110] The present application provides a single-passband FSR including one or more unit structures.

[0111] In order to verify the effectiveness of the proposed 12FSR design based on the double helix resonant structure, a sample was manufactured. Figure 12 The figure shows the test environment and the sample processing. The sample is a 20×20 array with a size of 320mm×320mm. The lossy layer is printed on F4B220 material, and the metal structure is etched on the dielectric substrate using the immersion gold process. Resistor 14 is a 300mm 0201 package. The resistor 14 and FSS layer 20 are printed on F4B350 material. The air layer between the two layers is replaced by a 10mm foam board, the material is polymethacrylimide ( The actual test was carried out in a standard microwave darkroom, where three identical standard horn antennas were used as transmitting antenna, reflecting receiving antenna and transmitting receiving antenna respectively. Figure 12 (a) The sample is located below the absorbing material. The three antennas are connected to corresponding ports of a vector network analyzer (VNA). A VNA time-domain gate is used to eliminate environmental signal interference, making the actual measurement results more accurate.

[0112] Actual testing was conducted in a microwave anechoic chamber, with actual measurement results obtained using a vector network analyzer. When measuring the reflection coefficient, a metal plate was used for calibration. After normalization, the sample was placed before measurement to obtain the true reflection coefficient. Measurements were made with the sample's impedance layer 10 facing the transmitting antenna and the reflected receiving antenna. When measuring the transmission coefficient, the transmitting antenna and the transmitted receiving antenna were aligned. The transmission coefficient was first measured without the sample, then normalized, and then the sample was placed before measurement to obtain the true transmission coefficient measurement result.

[0113] Figure 13 The following is a comparison of the measurement results and simulation results of the processed sample. It can be seen that the measurement results are slightly different from the simulation results. Compared with the idealized simulation results, the high-order modes of electromagnetic coupling and transmission in the actual measurement process cannot be calculated by simulation. At the same time, the errors in actual processing and the influence of environmental variables will also lead to deviations in the measurement results. Figure 13 The reflection coefficient bandwidth of the measured results remains essentially unchanged, shifting slightly toward higher frequencies within the 4-9.7 GHz range, with a relative bandwidth of 83.2%. The transmission band increases slightly from 5.65-7.1 GHz, reaching a minimum insertion loss of 0.3 dB at 6.3 GHz. This increase in insertion loss may be due to processing errors, measurement errors, and actual dielectric loss. The low-frequency absorption band narrows to 4-5 GHz, while the high-frequency absorption band shifts to the right to the 7.9-9.7 GHz range. Figure 13 (b) It can be seen that the absorption rate is greater than 90% in the range of 3.3-5.4 GHz and 7.3-10.5 GHz.

[0114] Figure 14 The figure shows the comparison between the measurement results and simulation results of the sample processed with the incident wave in the 30° oblique incidence range.

[0115] Figure 14 (a) is the measurement result of TE polarized incident electromagnetic wave, Figure 14(b) shows the measurement results for TM-polarized incident electromagnetic waves. It can be seen that at 30° 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, with minimal offset in the resonance point, verifying its polarization stability.

[0116] Based on the simulation results, the present invention has a high-transmittance transmission band and two absorption bands, with a thickness of 0.085 , The free space wavelength corresponds to the lowest frequency where the reflection coefficient is less than -10dB. The range where the reflection coefficient is less than -10dB is 3.9-9.3GHz, and the relative bandwidth is 82%. The transmission band is above -3dB in the range of 5.8-7GHz, and at the transmission pole f T1 = 6.3 GHz, the insertion loss is 0.3 dB, and the angular stability is 30°. Actual tests show stable dual-polarization characteristics and a certain degree of angular stability.

[0117] The present application provides a radome comprising one or more single-band FSRs.

[0118] 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 above, which are not provided in detail for the sake of simplicity.

[0119] The one or more embodiments of this application are intended to encompass all such substitutions, modifications, and variations that fall within the broad scope of this application. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of one or more embodiments of this application should be included in the scope of protection of this application.

Claims

1. A unit structure of a single-passband FSR, characterized in that: include: The impedance layer (10) comprises a dielectric substrate (11), two double-helix resonant structures (12) respectively arranged on two sides of the dielectric substrate (11), four connecting wires (13) respectively connected to four ends of the two double-helix resonant structures (12), four resistors (14) arranged on the dielectric substrate (11) and respectively connected to the four connecting wires (13), and a T-shaped conductive sheet (15) arranged on the dielectric substrate (11) and respectively connected to the four resistors (14); An FSS layer (20) having a single square ring gap (24) to construct a single transmission belt; The impedance layer (10) and the FSS layer (20) are spaced apart; The two double helix resonant structures (12) are both arranged in the middle of a dielectric substrate (11), 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), the outer ends of the two spiral conductive sheets (121) are respectively connected to two connecting wires (13), and the two connecting wires (13) are in the same straight line direction.

2. The unit structure according to claim 1, wherein: The two double helix resonant structures (12) are arranged to be deflected relative to each other.

3. The unit structure according to claim 2, characterized in that The structure of the spiral conductive sheet (121) is a rectangular spiral structure or a circular spiral structure; And / or, the connecting wire (13) 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 (15) is metal or a conductive composite material; And / or, the material of the dielectric substrate 1 (11) is polytetrafluoroethylene.

4. The unit structure according to claim 2, characterized in that The side length of the dielectric substrate 1 (11) is p , 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 connecting wire (13) is w 1. The widths of the horizontal and vertical lines of the T-shaped conductive sheet (15) are both w 1. The length of the horizontal line portion of the T-shaped conductive sheet (15) is l 1. The distance between the horizontal line portion of the T-shaped conductive sheet (15) and the double helix resonant structure (12) is l 2. The distance between the horizontal line portion of the T-shaped conductive sheet (15) and the side edge of the dielectric substrate (11) is w 2; p : g : c : w 1: l 1: l 2: w 2=16:0.1:0.15:0.2:4:5.3:0.75。 5. The unit structure according to claim 1, wherein: The FSS layer (20) comprises a second dielectric substrate (21), a square ring metal sheet (22) arranged on the second dielectric substrate (21), and a square metal sheet (23) arranged on the second dielectric substrate (21) and located within the square ring metal sheet (22), wherein a square ring gap (24) is provided between the square ring metal sheet (22) and the square metal sheet (23).

6. The unit structure according to claim 5, characterized in that The material of the dielectric substrate 2 (21) is polytetrafluoroethylene; And / or, the material of the square ring metal sheet (22) is metal or a conductive composite material; And / or, the square metal sheet (23) is metal or a conductive composite material.

7. The unit structure according to claim 1, wherein: The size of the interval between the impedance layer (10) and the FSS layer (20) is 10±10% mm.

8. A single-passband FSR, characterized in that Comprising one or more unit structures according to any one of claims 1 to 7.

9. A radome, characterized in that: Comprising one or more single-passband FSRs as claimed in claim 8.

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