A frequency selective surface with absorption and penetration

Abstract

The present invention discloses an integrated absorption and penetration frequency selective surface (FSS) having a multi-layer sandwich structure, primarily composed of a lossy impedance layer, a dielectric layer, and a reflective layer. The lossy impedance layer comprises two layers, and the reflective layer comprises three layers. The FSS unit structure in the lossy impedance layer is an N-gonal ring structure loaded with N circular spiral structures, with a resistor component loaded at each vertex of the N-gonal ring structure. The difference between the two lossy impedance layers is that the side length of the N-gonal structure in the upper layer is smaller than that of the N-gonal structure in the lower layer. The unit structures of the first and third reflective layers in the reflective layer are N-gonal, while the unit structure of the second reflective layer is Y-shaped, forming a three-layer complementary structure. The FSS in the present invention can achieve the combined performance of high mid-frequency broadband transmission and strong absorption on both sides.

Description

Technical Field

[0001] The present invention belongs to the technical field of stealth of communication systems, and in particular relates to an absorbent and penetrable integrated frequency selective surface. Background Art

[0002] The traditional frequency selective surface antenna cover has a wave-transmitting function within the band, which can ensure that its own antenna can normally transmit and receive electromagnetic waves. However, outside the band, it can be approximated as a fully reflective metal cover, scattering almost all incident electromagnetic waves to other directions. With the development of radar detection systems in recent years, the traditional frequency selective surface antenna cover can be easily captured by multi-station collaborative radar detection systems, greatly increasing the risk of target exposure.

[0003] Compared to traditional frequency selective surfaces, ATFSS combines frequency selection with circuit-simulated absorbers. This not only ensures the proper transmission and transmission of signals within the operating frequency band, but also absorbs, rather than reflects, incident radar waves outside of the band. This comprehensively reduces electromagnetic scattering from targets and significantly enhances radar stealth. Consequently, ATFSS has become an essential material in advanced equipment communication systems.

[0004] Based on the relative positions of the absorbing and transmitting bands, ATFSS can be divided into three types: low-frequency transparent / high-frequency absorbing ATFSS (LT-ATFSS), high-frequency transparent / low-frequency absorbing ATFSS (HT-ATFSS), and medium-frequency transparent / two-sided absorbing ATFSS (MT-ATFSS). The design of LT-ATFSS and HT-ATFSS is relatively simple to implement compared to MT-ATFSS. By placing the absorber structure's lossy impedance surface layer (resistive film FSS, resistive FSS units, or absorbing material) directly on a lossless FSS with a passband significantly below or above the absorbing frequency, a low-insertion-loss transparent band can be created at low / high frequencies. The lossy units then absorb incident waves by converting electromagnetic energy into heat at a greater frequency than the absorbing frequency band. However, the mid-frequency wave-transmitting / double-sided absorbing ATFSS structure has the design difficulty of balancing the wave-transmitting and absorption performances. For the lossy layer, its absorption is generally achieved by adding lossy elements to the electromagnetic resonance structure, and the unit size of the resonance structure must be close to the wavelength of the absorption band. For the transmission layer, in order to allow the incident electromagnetic wave to pass through, it is necessary to design an FSS with a unit size much smaller than the wavelength of the absorption band to avoid strong resonance and absorption. However, in the same unit, the bandpass FSS is usually required to have the same planar size as the lossy layer, which leads to a design contradiction. In addition, the resistive surface of the upper layer of the absorption-transmitting integrated material generally has a certain degree of absorption at high frequencies. Therefore, in the existing MT-ATFSS research, there are defects such as poor wave-transmitting performance, narrow wave-transmitting bandwidth, or unsatisfactory absorption performance on both sides, which makes it difficult to meet the needs of actual applications. Summary of the Invention

[0005] In order to overcome the problems in the prior art, the present invention provides an integrated frequency selective surface with both absorption and transmission. By adopting an impedance surface unit realized by loading resistor components and a circular spiral structure in a metal FSS unit, the loss caused by the lossy upper layer at high frequencies is eliminated as much as possible, thereby improving the transmittance of the frequency band and achieving the comprehensive performance of high transmittance in the medium-frequency broadband and strong absorption on both sides.

[0006] In order to solve the above technical problems, the technical solutions proposed by the present invention are as follows:

[0007] A frequency selective surface that is both absorbent and penetrating comprises, from top to bottom, a lossy impedance layer, a dielectric layer and a reflective layer.

[0008] The lossy impedance layer is composed of a first dielectric substrate and a periodic FSS unit structure and a resistor component located on the upper surface of the first dielectric substrate. The FSS unit structure is a regular N-gonal ring structure loaded with N circular spiral structures. The N circular spiral structures are respectively arranged at the center of each side of the regular N-gonal ring structure. The two end points of any circular spiral structure are respectively connected to the disconnected sides of the regular N-gonal ring structure. A resistor component is loaded at each vertex of the regular N-gonal ring structure. The lossy impedance layer includes a first lossy impedance layer and a second lossy impedance layer from top to bottom. In the same unit period, the side length of the regular N-gonal ring structure in the first lossy impedance layer is smaller than the side length of the regular N-gonal ring structure in the second lossy impedance layer.

[0009] Preferably, the regular N-gon is a regular hexagon.

[0010] The reflective layer is composed of a second dielectric substrate and a periodic unit structure located on the upper surface of the second dielectric substrate. The reflective layer includes a first reflective layer, a second reflective layer, and a third reflective layer from top to bottom. The unit structures of the first reflective layer and the third reflective layer are hexagonal, and the unit structure of the second reflective layer is Y-shaped.

[0011] A medium is provided between the first lossy impedance layer and the second lossy impedance layer, between the first reflection layer and the second reflection layer, and between the second reflection layer and the third reflection layer.

[0012] The frequency-selective material of the present invention, which transmits mid-frequency waves and absorbs waves on both sides, has a multi-layer sandwich structure consisting of a lossy impedance layer, a dielectric layer, and a reflective layer. The reflective layer at the bottom layer transmits within a relatively wide frequency band in the middle and reflects within adjacent frequency bands at both ends. The lossy impedance layer at the top layer matches the transmission band of a portion of the reflective surface and forms an impedance surface for the reflection band of a portion of the reflective surface, absorbing the reflected energy. Therefore, electromagnetic waves within the mid-frequency passband can pass through the reflective layer and the lossy impedance layer with low insertion loss. Within the adjacent frequency bands at both ends, the reflective layer acts as an ideal metal plate, reflecting electromagnetic waves to the lossy impedance layer, which then dissipates the electromagnetic waves within this frequency band. The reflective layer and the lossy impedance layer jointly achieve the electromagnetic characteristics of mid-frequency transmission and absorption on both sides.

[0013] The reflective layer in the present invention is composed of a second-order non-resonant structure, and the lossy impedance layer is composed of a periodic FSS unit structure loaded with resistor elements, and the FSS unit structure is a hexagonal ring structure loaded with 6 circular spiral structures, so that the equivalent surface impedance of the impedance surface of the lossy loss layer at the parallel resonant frequency reaches infinity, thereby improving the wave transmission performance of the lossy layer in the wave transmission frequency band. At the same time, two lossy impedance layers are provided, and the side length of the hexagonal ring structure in the first lossy impedance layer is smaller than the side length of the hexagonal ring structure in the second lossy impedance layer, that is, the first lossy impedance layer is a high-frequency absorbing structure, and the second lossy impedance layer is a low-frequency absorbing structure. Through the cooperation of the two, the problem of requiring two-side absorption in the present application is solved for different absorption frequency bands.

[0014] The reflective layer is set to three layers, and the unit structure of the first reflective layer and the third reflective layer is hexagonal, and the unit structure of the second reflective layer is Y-shaped. It is set to a three-layer complementary structure, which can achieve intermediate wave transmission performance.

[0015] As an optional embodiment, in the absorbing material provided by the present invention, at the two end points of the circular spiral structure, the outer circle end point is directly connected to the disconnected side of the hexagonal ring structure, and the inner circle end point passes through the bottom surface of the dielectric substrate and is connected to the other disconnected side of the hexagonal ring structure.

[0016] In order to connect the circular spiral structure with the hexagonal ring structure, the present invention directly connects the outer circle endpoint of the circular spiral structure to the disconnected side when the circular spiral structure is placed at the center of one side of the hexagonal ring structure. In order to prevent the inner circle endpoint of the circular spiral structure from affecting the periodic FSS unit structure when it is directly connected to the other disconnected side, the inner circle endpoint is passed through the bottom surface of the dielectric substrate and then connected to the other disconnected side of the hexagonal ring structure.

[0017] As an optional embodiment, in the absorbing material provided by the present invention, the inner ring endpoint is connected to the first metal via located on the dielectric substrate, and then is routed through the back side and then passes through the second metal via located on the dielectric substrate to be connected to the other side of the hexagonal ring structure that is disconnected.

[0018] In the present invention, all metal patterns in the periodic FSS unit structure are obtained by etching, so the outer circle endpoints are directly connected to the hexagonal structure, and the inner circle endpoints are provided with metal vias on the dielectric substrate below. The metal vias are used to connect the FSS unit structure above the dielectric substrate with the metal traces below (i.e., the back traces). Then, another metal via is provided at the position of the other side of the break in the hexagonal ring structure, thereby realizing the connection between the circular spiral structure and the hexagonal structure without affecting the FSS unit structure.

[0019] As an optional embodiment, in the absorbing material provided by the present invention, the side length of the hexagonal ring structure in the first lossy impedance layer is 4.0 mm to 5.0 mm, and the side length of the hexagonal ring structure in the second lossy impedance layer is 7.0 mm to 8.0 mm.

[0020] In one cycle, the side length of the hexagonal ring structure in the first lossy impedance layer is 4.0mm~5.0mm, which is a high-frequency absorbing structure. The side length of the hexagonal ring structure in the second lossy impedance layer is 7.0mm~8.0mm, which is a low-frequency absorbing structure. Through the mutual cooperation of low frequency and high frequency, the absorption effect on both sides is achieved.

[0021] As an optional embodiment, in the absorbing material provided by the present invention, the line width of the hexagonal ring structure is 0.6mm~1.2mm, the inner diameter, line width and line spacing of the circular spiral ring are all 0.05mm~0.1mm, the number of spiral turns is 2~3 turns, the loaded resistance range is 10Ω~500Ω, and the period size of the FSS unit structure is 8.0mm~10.0mm.

[0022] As an optional embodiment, in the absorbing material provided by the present invention, the period of the unit structure in the first reflecting layer and the second reflecting layer is 8.0mm-10.0mm, the side length of the hexagon is 5.5mm-6.5mm, and the line width is 0.5mm-1.5mm.

[0023] As an optional embodiment, in the absorbing material provided by the present invention, the period of the unit structure in the second reflective layer is 8.0 mm to 10.0 mm, and the width of the Y-shaped line is 2.5 mm to 3.5 mm.

[0024] As an optional embodiment, in the absorbing material provided by the present invention, the first dielectric substrate and the second dielectric base are one of PI film, FR4 or Rogers board, and the thickness of the first dielectric substrate and the second dielectric base is 0.025mm to 0.5mm.

[0025] As an optional embodiment, in the absorbing material provided by the present invention, the dielectric layer or the dielectric is one of aramid paper honeycomb, PMI foam, PVC foam or PET foam.

[0026] The integrated absorption and transmission frequency selective surface of the present invention is composed of a lossy impedance layer, a dielectric layer and a reflective layer. The reflective layer has the characteristics of transmitting in a relatively wide frequency band in the middle and reflecting in adjacent frequency bands at both ends. The lossy impedance layer has the characteristics of matching the transmission frequency band of part of the reflective surface, forming an impedance surface for the reflection band of part of the reflective surface, and absorbing the reflected energy. Therefore, electromagnetic waves within the intermediate frequency passband can pass through the reflective layer and the lossy layer with low insertion loss. In the adjacent frequency bands at both ends, the reflective layer can be equivalent to an ideal metal plate, reflecting the electromagnetic waves to the lossy layer, and the electromagnetic waves in this frequency band are lost by the lossy layer. The reflective layer and the lossy layer jointly realize the electromagnetic characteristics of absorbing waves on both sides of the middle wave transmission.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) The present invention provides a medium-frequency wave-transmitting / two-side wave-absorbing integrated frequency selective surface structure, which realizes the performance of medium-frequency broadband wave transmission and strong wave absorption on both sides through an overall structure provided with two lossy impedance layers and three reflective layers.

[0029] (2) The two lossy impedance layers in the present invention introduce a circular spiral structure into the hexagonal ring structure of the loaded resistor element, so that the equivalent surface impedance of the impedance surface of the lossy layer at the parallel resonant frequency reaches infinity, thereby improving the wave transmission performance of the lossy layer in the wave transmission frequency band.

[0030] (3) The medium-frequency wave-transmitting / two-side wave-absorbing integrated frequency selective surface structure proposed in the present invention uses foam or honeycomb as the sandwich layer between the layers. Compared with the air sandwich used in the prior art, this structure has certain structural strength performance and can better meet the conditions of engineering applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0032] Figure 1This is a schematic structural diagram of the absorption-through integrated frequency selective surface of the present invention;

[0033] Figure 2 Schematic diagram of the structure of the first lossy impedance layer in the present invention;

[0034] Figure 3 Schematic diagram of the structure of the second lossy impedance layer in the present invention;

[0035] Figure 4 Schematic diagram of the structure of the first reflective layer and the third reflective layer in the present invention;

[0036] Figure 5 Schematic diagram of the structure of the first reflective layer and the second reflective layer in the present invention;

[0037] Figure 6 Graph showing the wave transmittance and reflectivity results of the frequency selective surface with absorption and transmission in Example 1 of the present invention;

[0038] Figure 7 This is a graph showing the absorptivity results of the absorbent-through integrated frequency selective surface in Example 1 of the present invention;

[0039] Figure 8 Graph showing the transmittance and reflectance results of the frequency selective surface with absorption and transmission in Example 2 of the present invention;

[0040] Figure 9 This is a graph showing the absorptivity results of the absorbent-through integrated frequency selective surface in Example 2 of the present invention;

[0041] Figure 10 Graph showing the wave transmittance and reflectivity results of the frequency selective surface with absorption and transmission in Example 3 of the present invention;

[0042] Figure 11 This is a graph showing the absorptivity results of the absorbent-through integrated frequency selective surface in Example 3 of the present invention;

[0043] Figure 12 Schematic diagram of the structure of the first lossy impedance layer in Comparative Example 1 of the present invention;

[0044] Figure 13 Schematic diagram of the structure of the second lossy impedance layer in Comparative Example 1 of the present invention;

[0045] Figure 14 Graph showing the wave transmittance and reflectivity results of the frequency selective surface with absorption and penetration in Comparative Example 1 of the present invention;

[0046] Figure 15 This is a graph showing the absorption rate of the frequency selective surface with absorption and penetration in comparative example 1 of the present invention.

[0047] Reference numerals:

[0048] 1. Lossy impedance layer; 2. Dielectric layer; 3. Reflective layer. DETAILED DESCRIPTION

[0049] To facilitate understanding of the present invention, the present invention will be described in more comprehensive and detailed form below in conjunction with the accompanying drawings and preferred embodiments. However, the protection scope of the present invention is not limited to the following specific embodiments.

[0050] Unless otherwise defined, all technical terms used hereinafter have the same meanings as those generally understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0051] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0052] Example 1

[0053] This embodiment provides an integrated absorption and penetration frequency selective surface, which includes a lossy impedance layer 1, a dielectric layer 2 and a reflective layer 3 from top to bottom. The structural diagram is shown in FIG. Figure 1 As shown, specifically, there are two lossy impedance layers and three reflective layers.

[0054] The lossy impedance layer 1 consists of a first dielectric substrate and a periodic FSS unit structure and a resistor component located on the upper surface of the first dielectric substrate. The FSS unit structure is a hexagonal ring structure loaded with 6 circular spiral structures. The 6 circular spiral structures are respectively arranged at the center of each edge of the hexagonal ring structure. The two end points of any circular spiral structure are respectively connected to the disconnected edges of the hexagonal ring structure. A resistor component is loaded at each vertex of the hexagonal ring structure.

[0055] The lossy impedance layer 1 includes a first lossy impedance layer and a second lossy impedance layer from top to bottom. In the same unit period, the side length of the hexagonal ring structure in the first lossy impedance layer is smaller than the side length of the hexagonal ring structure in the second lossy impedance layer.

[0056] In this embodiment, both the first and second lossy impedance layers consist of a dielectric substrate and a periodic FSS unit structure located on the dielectric substrate. The FSS unit structure consists of a 0.018 mm thick copper layer, onto which 0603 packaged resistor components are soldered. A dielectric layer is also provided between the two lossy impedance layers. The dielectric substrate is 0.5 mm thick FR4 with a dielectric constant of 4.3 (1 + 0.025i).

[0057] The difference between the first lossy impedance layer and the second lossy impedance layer is that the side length of the hexagonal ring structure in the first lossy impedance layer is smaller than the side length of the hexagonal ring structure in the second lossy impedance layer. The side length of the hexagonal ring structure in the first lossy impedance layer is smaller than the side length of the hexagonal ring structure in the second lossy impedance layer, that is, the periodic structure in the first lossy impedance layer is smaller than the periodic structure in the second lossy impedance layer. Specifically, the FSS unit structure of the first lossy impedance layer is as follows: Figure 2 As shown, the outer ring side length of the hexagonal ring is R1 = 4.4mm, the inner ring side length is R2 = 3.6mm, the resistance of the resistor welded at the hexagonal vertex is 200Ω, the line width and line spacing of the circular spiral structure are both 0.1, the number of turns is 2, the inner ring radius is 0.1, and the unit period is R = 8mm. The second lossy impedance layer FSS unit structure is as follows Figure 3 As shown, the outer ring side length of the hexagonal ring is R3 = 7.6 mm, the inner ring side length is R4 = 6.6 mm, the resistance of the resistor welded at the hexagonal vertex is 500 Ω, the line width and line spacing of the circular spiral structure are both 0.1 mm, the number of turns is 2, the inner ring radius is 0.1 mm, and the unit period is R = 8 mm.

[0058] The reflective layer 3 is composed of a second dielectric substrate and a periodic unit structure located on the upper surface of the second dielectric substrate. The reflective layer 3 includes a first reflective layer, a second reflective layer, and a third reflective layer from top to bottom. The unit structures of the first reflective layer and the third reflective layer are hexagonal, and the unit structure of the second reflective layer is Y-shaped.

[0059] In this embodiment, the reflective layer 3 is composed of a second dielectric substrate and a periodic FSS unit structure located on the upper surface of the second dielectric substrate. The FSS unit structure is composed of a 0.018 mm copper layer. The second dielectric substrate is composed of a 0.05 mm PI film. The dielectric constant of the PI film is 3.5 (1 + 0.014i). The unit structures of the first and third reflective layers are the same, both hexagonal. The structural diagram is shown in FIG. Figure 4 As shown, the unit period is R = 8mm, and the side length of the hexagonal patch is R5 = 6mm. The unit structure of the second reflective layer is the same as the "Y-shaped" structure, and the structural diagram is shown in Figure 5 As shown, the unit line width W = 3mm.

[0060] A medium is provided between the first lossy impedance layer and the second lossy impedance layer, between the first reflection layer and the second reflection layer, and between the second reflection layer and the third reflection layer.

[0061] In this embodiment, the dielectric layer 2 between the dielectric and the lossy impedance layer 1 and the reflective layer 3 is made of the same material, a foam material, with a dielectric constant of 1.1(1+0.009i). The thickness between the first and second lossy impedance layers is 13 mm, the thickness between the second lossy impedance layer and the first reflective layer is 13 mm, the thickness between the first and second reflective layers is 1.5 mm, and the thickness between the second and third reflective layers is 1.5 mm. The entire structure is designed to have a thickness of 30.24 mm. The entire structure is arranged in an equilateral triangle with a period of √3*R.

[0062] Both the reflective layer and the lossy layer are prepared using an etching process. After etching, the lossy layer is welded with the resistor components and circular spiral resonant structure in each unit using automatic welding technology, and is connected to the metal structure through two metal vias and a short trace on the back of the dielectric at the innermost turn of the unit. After processing, the reflective layer and the lossy layer are bonded with adhesive and foam to form an absorbent and transparent integrated frequency selective surface sample.

[0063] The performance of the absorbent and penetrating frequency selective surface prepared in Example 1 was tested, and the results are shown below.

[0064] Figure 6 This is a result diagram of the wave transmission coefficient and reflectivity of the structure under normal incidence of electromagnetic waves under vertical polarization. From the wave transmission curve in the figure, it can be seen that the wave transmission of the integrated frequency selective surface of absorption and transmission in this embodiment is greater than -1.35dB at 8GHz~10GHz, and the relative bandwidth is 22.2%, which is a broadband wave transmission structure. In addition, at 2GHz-6GHz and 13GHz-18GHz, the wave transmission is less than or equal to -10dB, which is equivalent to a total reflection state. From the reflectivity curve, it can be seen that the ATFSS structure in this embodiment has a wave absorption effect at 2GHz-6GHz and 13GHz-18GHz, and the reflectivity is basically less than or equal to -10dB.

[0065] Figure 7 This is a graph showing the absorptivity of the absorbent-transmitting frequency selective surface of the present invention under normal incidence of electromagnetic waves under vertical polarization. It can be seen from the graph that at frequencies of 2GHz-6GHz and 13GHz-18GHz, the absorptivity of the structure is greater than 90% in all frequency bands, except for a few frequency points where the absorptivity is above 83%.

[0066] Example 2

[0067] The difference from Example 1 is that the outer ring side length of the hexagonal ring in the first impedance layer is R1 = 4.0 mm, the inner ring side length is R2 = 3.4 mm, the resistance of the resistor welded at the hexagonal vertex is 100 Ω, the line width and line spacing of the circular spiral structure are both 0.1, the number of turns is 2, the inner ring radius is 0.1, and the unit period is R = 9 mm. The second lossy impedance layer FSS unit structure is as follows Figure 3 As shown, the outer ring side length of the hexagonal ring is R3 = 7.0 mm, the inner ring side length is R4 = 6.4 mm, the resistance of the resistor welded at the hexagonal vertex is 500 Ω, the line width and line spacing of the circular spiral structure are both 0.1 mm, the number of turns is 2, the inner ring radius is 0.1 mm, and the unit period is R = 9 mm.

[0068] The reflective layer is composed of a second dielectric substrate and a periodic FSS unit structure located on the upper surface of the second dielectric substrate. The FSS unit structure is composed of a 0.018mm copper layer. The second dielectric substrate is composed of a 0.05mm PI film. The dielectric constant of the PI film is 3.5 (1 + 0.014i). Among them, the unit structure of the first reflective layer and the third reflective layer is the same, both are hexagonal. The structural diagram is shown as follows: Figure 4 As shown, the unit period is R = 9mm, and the side length of the hexagonal patch is R5 = 5.5mm. The unit structure of the second reflective layer is the same as the "Y-shaped" structure, and the structural diagram is shown in Figure 5 As shown, the unit line width W = 2.5 mm.

[0069] The dielectric layers between the dielectric, lossy impedance layer, and reflective layer are all foam materials with a dielectric constant of 1.1(1+0.009i). The thickness between the first and second lossy impedance layers is 13mm, the thickness between the second lossy impedance layer and the first reflective layer is 13mm, the thickness between the first and second reflective layers is 1.5mm, and the thickness between the second and third reflective layers is 1.5mm. The entire structure is designed to be 30.24mm thick and arranged in an equilateral triangle with a period of √3*R.

[0070] The remaining structures are the same as those in Example 1.

[0071] Figure 8 This is a result diagram of the wave transmission coefficient and reflectivity of the structure under normal incidence of electromagnetic waves under vertical polarization. From the wave transmission curve in the figure, it can be seen that the wave transmission of the integrated absorption and transmission frequency selective surface in this embodiment is greater than -1.25dB at 8.5GHz to 10.5GHz, and the relative bandwidth is 21%. It is a broadband wave-transmitting structure, and has an absorbing effect at 3.7GHz-6.7GHz and 13.5GHz-17.5GHz, and the reflectivity is basically less than or equal to -8dB.

[0072] Figure 9This is a graph showing the absorptivity of the absorbent-transmitting frequency selective surface of the present invention under normal incidence of electromagnetic waves under vertical polarization. It can be seen from the graph that at frequencies of 3.7GHz-6.7GHz and 13.5GHz-17.5GHz, the absorptivity of the structure is greater than 80% in all frequency bands except for a few frequency points.

[0073] Example 3

[0074] The difference from Example 1 is that the outer ring side length of the hexagonal ring is R1 = 5.0 mm, the inner ring side length is R2 = 4.0 mm, the resistance of the resistor welded at the hexagonal vertex is 200Ω, the line width and line spacing of the circular spiral structure are both 0.1, the number of turns is 2, the inner ring radius is 0.1, and the unit period is R = 10 mm. The second lossy impedance layer FSS unit structure is as follows Figure 3 As shown, the outer ring side length of the hexagonal ring is R3 = 8.0 mm, the inner ring side length is R4 = 7.0 mm, the resistance of the resistor welded at the hexagonal vertex is 500 Ω, the line width and line spacing of the circular spiral structure are both 0.1 mm, the number of turns is 2, the inner ring radius is 0.1 mm, and the unit period is R = 10 mm.

[0075] The reflective layer is composed of a second dielectric substrate and a periodic FSS unit structure located on the upper surface of the second dielectric substrate. The FSS unit structure is composed of a 0.018mm copper layer. The second dielectric substrate is composed of a 0.05mm PI film. The dielectric constant of the PI film is 3.5 (1 + 0.014i). Among them, the unit structure of the first reflective layer and the third reflective layer is the same, both are hexagonal. The structural diagram is shown as follows: Figure 4 As shown, the unit period is R = 10mm, and the side length of the hexagonal patch is R5 = 6.5mm. The unit structure of the second reflective layer is the same as the "Y-shaped" structure, and the structural diagram is shown in Figure 5 As shown, the unit line width W = 3.5 mm.

[0076] The dielectric layers between the dielectric, lossy impedance layer, and reflective layer are all foam materials with a dielectric constant of 1.1(1+0.009i). The thickness between the first and second lossy impedance layers is 13mm, the thickness between the second lossy impedance layer and the first reflective layer is 13mm, the thickness between the first and second reflective layers is 1.5mm, and the thickness between the second and third reflective layers is 1.5mm. The entire structure is designed to be 30.24mm thick and arranged in an equilateral triangle with a period of √3*R.

[0077] The remaining structures are the same as those in Example 1.

[0078] Figure 10The result diagram of the wave transmission coefficient and reflectivity of the structure under normal incidence of electromagnetic waves under vertical polarization. From the wave transmission curve in the figure, it can be seen that the wave transmission of the integrated absorption and transmission frequency selective surface in this embodiment is greater than -0.92dB at 7.5GHz to 10GHz, and the relative bandwidth is 28.6%. It is a broadband wave-transmitting structure, and has an absorbing effect at 3GHz-6GHz and 12.8GHz-15.8GHz, and the reflectivity is basically less than or equal to -10dB.

[0079] Figure 11 This is a graph showing the absorptivity of the absorbent-transmitting frequency selective surface of the present invention under normal incidence of electromagnetic waves under vertical polarization. It can be seen from the graph that at frequencies of 3GHz-6GHz and 12.8GHz-15.8GHz, the absorptivity of the structure is greater than 80% in all frequency bands except for a few individual frequency points.

[0080] Comparative Example 1

[0081] The difference from Example 1 is that the first lossy impedance layer and the second lossy impedance layer do not have a circular spiral structure, and are only composed of hexagonal structure loaded resistor components. The structural diagram is shown in FIG. Figure 12 and Figure 13 As shown, the rest of the structure remains the same as that of Example 1.

[0082] The performance of the absorbent-through integrated frequency selective surface prepared in Comparative Example 1 was tested, and the results are shown below.

[0083] Figure 14 The result graph of the wave transmission coefficient and reflectivity of the structure under normal incidence of electromagnetic waves under vertical polarization can be seen from the wave transmission curve in the figure: compared with the wave transmission results in the embodiment, the wave transmission rate of the structure in Comparative Example 1 is less than or equal to -8dB in the frequency band of 1GHz-20GHz, which is basically equivalent to a full reflection state and has no wave transmission effect. From the reflectivity curve, it can be seen that the structure has an absorbing effect at 2GHz-6GHz and 13GHz-18GHz, but the absorbing effect is reduced compared with the results of the embodiment.

[0084] Figure 15 This graph shows the absorptivity of a frequency selective surface with vertical polarization under normal incidence for a vertically polarized electromagnetic wave. The graph shows that at frequencies between 2 GHz and 6 GHz and between 13 GHz and 18 GHz, the absorptivity of this structure is greater than 75%, with the exception of a few frequency points where the absorptivity exceeds 53%. Compared to the results in the example, the absorptive performance of this structure has declined.

[0085] In the present invention, high wave transmission performance within the passband can be achieved by loading a circular spiral structure on the lossy layer, and high absorption function outside the passband can be achieved by loading a resistance component at the same time.

[0086] The above is a further detailed description of the present invention in conjunction with specific preferred embodiments, and the specific implementation of the present invention should not be considered to be limited to these descriptions. For those skilled in the art to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, and all of these should be considered to fall within the scope of protection of the present invention.

Claims

1. A frequency selective surface with an absorbent structure, characterized in that: From top to bottom, it includes a lossy impedance layer, a dielectric layer and a reflective layer; The lossy impedance layer is composed of a first dielectric substrate and a periodic FSS unit structure and a resistor component located on the upper surface of the first dielectric substrate. The FSS unit structure is a regular N-gonal ring structure loaded with N circular spiral structures. The N circular spiral structures are respectively arranged at the center of each side of the regular N-gonal ring structure. The two end points of any circular spiral structure are respectively connected to the disconnected sides of the regular N-gonal ring structure. A resistor component is loaded at each vertex of the regular N-gonal ring structure. The lossy impedance layer includes a first lossy impedance layer and a second lossy impedance layer from top to bottom. In the same unit period, the side length of the regular N-gonal ring structure in the first lossy impedance layer is smaller than the side length of the regular N-gonal ring structure in the second lossy impedance layer. The reflective layer is composed of a second dielectric substrate and a periodic unit structure located on the upper surface of the second dielectric substrate. The reflective layer includes, from top to bottom, a first reflective layer, a second reflective layer, and a third reflective layer. The unit structures of the first reflective layer and the third reflective layer are hexagonal, and the unit structure of the second reflective layer is Y-shaped. A medium is provided between the first lossy impedance layer and the second lossy impedance layer, between the first reflection layer and the second reflection layer, and between the second reflection layer and the third reflection layer.

2. The absorbent and penetrating frequency selective surface according to claim 1, characterized in that: The regular N-gon is a regular hexagon.

3. The absorbent-through integrated frequency selective surface according to claim 2, characterized in that: Of the two end points of the circular spiral structure, the outer end point is directly connected to one side of the hexagonal ring structure that is disconnected, and the inner end point passes through the bottom surface of the dielectric substrate and is connected to the other side of the hexagonal ring structure that is disconnected.

4. The absorbent and penetrating frequency selective surface according to claim 3, characterized in that: The inner ring end point is connected to a first metal via located on the dielectric substrate, and then is routed through a back surface and then passes through a second metal via located on the dielectric substrate to be connected to the other side of the hexagonal ring structure that is disconnected.

5. The absorbent-through integrated frequency selective surface according to claim 2, characterized in that: The side length of the hexagonal ring structure in the first lossy impedance layer is 4.0 mm to 5.0 mm, and the side length of the hexagonal ring structure in the second lossy impedance layer is 7.0 mm to 8.0 mm.

6. The absorbent and penetrating integrated frequency selective surface according to claim 3, characterized in that: The hexagonal ring structure has a line width of 0.6mm~1.2mm, the inner diameter, line width and line spacing of the circular spiral ring are all 0.05mm~0.1mm, the number of spiral turns is 2~3, the loaded resistance range is 10Ω~500Ω, and the period size of the FSS unit structure is 8.0mm~10.0mm.

7. The absorbent and penetrating integrated frequency selective surface according to claim 2, characterized in that: The period of the unit structure in the first reflective layer and the second reflective layer is 8.0 mm to 10.0 mm, the side length of the hexagon is 5.5 mm to 6.5 mm, and the line width is 0.5 mm to 1.5 mm.

8. The absorbent and penetrating frequency selective surface according to claim 1, characterized in that: The period of the unit structure in the second reflective layer is 8.0 mm to 10.0 mm, and the width of the Y-shaped line is 2.5 mm to 3.5 mm.

9. The absorbent and penetrating integrated frequency selective surface according to claim 1, characterized in that: The first dielectric substrate and the second dielectric substrate are one of PI film, FR4 or Rogers board, and the thickness of the first dielectric substrate and the second dielectric substrate is 0.025mm-0.5mm.

10. The absorbent and penetrating integrated frequency selective surface according to claim 1, characterized in that: The medium layer is one of aramid paper honeycomb, PMI foam, PVC foam or PET foam.

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