Active frequency selective surface composite wave absorbing device

Abstract

The invention discloses an active frequency selective surface composite wave absorbing device, and belongs to the technical field of composite wave absorbing materials. The N second active frequency selective surface layers are inserted into the dielectric isolation layer of the single-function-layer active frequency selective surface to regulate and control the impedance of the dielectric isolation layer, so that impedance modification of the grounding transmission line is realized; different impedance forms can respectively realize susceptance frequency dispersion form reversion of the grounding transmission line at a low-frequency end and resonance suppression at a half-wavelength position, so that an effect of equivalently regulating and controlling the grounding transmission line is achieved. Through cooperative regulation and control of the first active frequency selection surface layer and the second active frequency selection surface layer, broadband absorption states can be constructed at a low-frequency end and a high-frequency end at the same time, broadband absorption is achieved, and the design mode is evolved into double-variable cooperative regulation and control matching from unilateral regulation and control matching. And synchronous expansion of the low-frequency absorption state bandwidth and the high-frequency absorption state bandwidth can be considered.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite wave-absorbing materials, and more specifically, relates to an active frequency selective surface composite wave-absorbing device. Background Art

[0002] With the advancement of technology, low observability has become a top priority for combat platforms, and the battle between stealth and counter-stealth has become a new arena in information warfare. Iterative upgrades in radar technology have led to a diversification of detection frequency bands, driving the demand for microwave absorbing structures towards wider bandwidths. Coated absorbers can be categorized as magnetic loss or dielectric loss based on their loss mechanisms. Their operating frequency bands are typically related to coating thickness, which limits their application in increasingly low-frequency electromagnetic threat environments. Frequency selective surface (FSS) composite absorbers, as a representative example of structural absorbing materials, have attracted widespread attention due to their flexible design. Among them, active frequency selective surfaces (AFSS) utilize active semiconductor devices such as varistors and varactors to replace traditional passive components. They modulate their response to electromagnetic waves through external signal excitation, opening new avenues for the broadband design of absorbing structures. Therefore, the study of an active frequency selective surface composite absorber is of great significance.

[0003] Existing active frequency selective surface composite absorbers (AFSSs) reconstruct the impedance of the AFSS to match the cotangent dispersion of the grounded transmission line impedance, thereby creating multiple absorption peaks. This results in excellent control at low frequencies, and the resulting multi-matching absorption peak design with the grounded transmission line has achieved promising performance. However, the grounded transmission line and the AFSS have opposite impedance dispersion at low frequencies, resulting in a narrowband match. Furthermore, the transmission line's half-wavelength total internal reflection at high frequencies still limits further expansion of the device's absorption performance. Therefore, transmission line impedance is a major constraint on the broadband performance of existing active frequency selective surface composite absorbers. Consequently, existing technologies are unable to simultaneously expand the bandwidth of both low- and high-frequency absorption states. Summary of the Invention

[0004] In response to the above defects or improvement needs of the existing technology, the present invention provides an active frequency selective surface composite absorbing device to solve the technical problem that the existing technology cannot take into account the simultaneous expansion of the bandwidth of the low-frequency absorption state and the high-frequency absorption state.

[0005] In order to achieve the above-mentioned object, in a first aspect, the present invention provides an active frequency selective surface composite absorbing device, comprising: a total reflection bottom plate layer, an adjustable transmission line module and an adjustable surface module arranged in sequence from bottom to top;

[0006] The adjustable surface module includes: a first active frequency selective surface layer and a first dielectric substrate layer arranged in sequence from bottom to top;

[0007] The adjustable transmission line module includes: N+1 dielectric isolation layers arranged in sequence from bottom to top and a transmission line reconstruction unit arranged between every two adjacent dielectric isolation layers; N≥1;

[0008] The transmission line reconstruction unit includes: a second active frequency selective surface layer and a second dielectric substrate layer arranged in sequence from bottom to top;

[0009] The first active frequency selective surface layer and the second active frequency selective surface layer both include a plurality of periodically arranged FSS units; the patterns of the FSS units in the first active frequency selective surface layer and the second active frequency selective surface layer are different, and / or the devices of the FSS units in the first active frequency selective surface layer and the second active frequency selective surface layer are different;

[0010] The adjustable surface module is used to adjust the surface impedance of the device;

[0011] The transmission line reconstruction unit is used to adjust the impedance of two adjacent dielectric isolation layers.

[0012] Further preferably, the FSS unit is a FSS unit loaded with a PIN diode.

[0013] Further preferably, the impedance Y of the first active frequency selective surface layer is FSS1 for:

[0014]

[0015] Among them, R v The adjustable resistance of the PIN diode on the first active frequency selection surface layer; C p is the parallel parasitic capacitance of the PIN diode on the first active frequency selection surface layer; L and C are the inductance and capacitance of the FSS unit on the first active frequency selection surface layer respectively; ω is the angular frequency.

[0016] Further preferably, the impedance Y of the i-th second active frequency selective surface layer from bottom to top is FSS2(i) satisfy:

[0017]

[0018] Y TL(1) =-jY0cot(βh1)

[0019] Where Y0 is the free space admittance; Y TL(i) is the admittance from the i-th dielectric isolation layer from bottom to top to the total reflection bottom plate layer; j is the imaginary number sign; β is the propagation constant; h iis the thickness of the i-th dielectric isolation layer from bottom to top; Γ is the preset reflection coefficient of the device; cot(·) is the cotangent function.

[0020] More preferably, N=1.

[0021] Further preferably, the pattern types of the FSS units in the first active frequency selective surface include: a polygonal ring pattern, a cross pattern, a polygonal pattern, a dipole pattern, a polygonal ring-cross composite pattern or a polygonal ring-triangle composite pattern;

[0022] The polygonal ring-cross composite pattern is a centrally symmetrical structure based on a polygonal ring with T-shaped short arms connected at each vertex;

[0023] The polygonal ring-triangle composite pattern is a centrally symmetrical structure based on the polygonal ring, with trapezoids cut out from the center of each vertex and / or side.

[0024] Further preferably, the pattern types of the FSS units in the second active frequency selective surface include: a polygonal ring pattern, a cross pattern, a polygonal pattern, a dipole pattern, a polygonal ring-cross composite pattern or a polygonal ring-triangle composite pattern;

[0025] The polygonal ring-cross composite pattern is a centrally symmetrical structure based on a polygonal ring with T-shaped short arms connected at each vertex;

[0026] The polygonal ring-triangle composite pattern is a centrally symmetrical structure based on the polygonal ring, with trapezoids cut out from the center of each vertex and / or side.

[0027] Further preferably, the period of the FSS unit in the first active frequency selective surface is an integer multiple of the period of the FSS unit in the second active frequency selective surface;

[0028] The period of the FSS unit in the first active frequency selective surface and the period of the FSS unit in the second active frequency selective surface are 5 to 50 mm.

[0029] Further preferably, in the first active frequency selective surface and the second active frequency selective surface, the pattern line width of the FSS unit is 0.1-10 mm, the gap between the FSS unit patterns is 0.2-1.5 mm, and the capacitance between the FSS unit patterns is gap capacitance or lumped capacitance.

[0030] Further preferably, the material of the first dielectric substrate layer is glass fiber reinforced epoxy resin or polyimide film, with a thickness of 0.025-0.8 mm.

[0031] Further preferably, the material of the second dielectric substrate layer is glass fiber reinforced epoxy resin or polyimide film, with a thickness of 0.025-0.8 mm.

[0032] Further preferably, the material of the first dielectric isolation layer is aramid paper honeycomb material or foam composite material, with a thickness of 5-40 mm.

[0033] Further preferably, the material of the second dielectric isolation layer is aramid paper honeycomb material or foam composite material, with a thickness of 5-40 mm.

[0034] Further preferably, the total reflection bottom plate is a solid or hollow total reflection bottom plate.

[0035] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects:

[0036] 1. The present invention provides an active frequency selective surface composite absorbing device. N second active frequency selective surface layers are inserted into the dielectric isolation layer of an original single-functional layer active frequency selective surface to control the dielectric isolation layer impedance, thereby achieving impedance modification of a grounded transmission line. The different impedance forms can respectively achieve inversion of the grounded transmission line's susceptance dispersion form at the low-frequency end and resonance suppression at half the wavelength, thereby achieving the equivalent effect of controlling the grounded transmission line. Through the coordinated control of the first and second active frequency selective surface layers, broadband absorption states can be constructed at both the low-frequency and high-frequency ends, achieving broadband absorption. The design model evolves from unilateral control matching to dual-variable coordinated control matching, ensuring that the susceptance of the grounded transmission line at both the low-frequency and high-frequency ends meets the matching requirements of the original single-functional layer active frequency selective surface, and can simultaneously expand the bandwidth of both the low-frequency and high-frequency absorption states.

[0037] 2. In the active frequency selective surface composite absorbing device provided by the present invention, since the second active frequency selective surface layer in the introduced transmission line reconstruction unit is mainly composed of FSS units, and the thickness of the FSS units is extremely thin and can be ignored, the thickness of the transmission line reconstruction unit mainly depends on the thickness of the second dielectric substrate layer, which is also relatively thin. Therefore, the present invention can effectively expand the overall absorption bandwidth without significantly increasing the thickness of the original single-functional layer active frequency selective surface.

[0038] 3. Furthermore, in the active frequency selective surface composite absorbing device provided by the present invention, the material of the dielectric substrate layer is glass fiber reinforced epoxy resin or polyimide film, and the material of the dielectric isolation layer is aramid paper honeycomb material or foam composite material. These materials are all characterized by light weight. Therefore, compared with traditional dielectric absorbing materials, the composite absorbing device provided by the present invention is a lightweight absorbing device and is suitable for carriers requiring low additional weight. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 A schematic diagram of an active frequency selective surface composite absorbing device provided by an embodiment of the present invention;

[0040] Figure 2 A schematic diagram of a single-period 3D structure of the active frequency selective surface composite absorbing device provided in Example 1 of the present invention;

[0041] Figure 3 A schematic diagram of the topological structure of the FSS unit provided in Example 1 of the present invention;

[0042] Figure 4 A schematic diagram of a single-period 3D structure of the active frequency selective surface composite absorbing device provided in Example 2 of the present invention;

[0043] Figure 5 A schematic diagram of the topological structure of the FSS unit provided in Example 2 of the present invention;

[0044] Figure 6 A schematic diagram of a single-period 3D structure of the active frequency selective surface composite absorbing device provided in Example 3 of the present invention;

[0045] Figure 7 A schematic diagram of the topological structure of the FSS unit provided in Example 3 of the present invention;

[0046] Figure 8 1 is a schematic diagram of a reflectivity characteristic curve of the active frequency selective surface composite absorbing device under normal incidence provided by Example 1 of the present invention;

[0047] Figure 9 1 is a schematic diagram of a reflectivity characteristic curve of the active frequency selective surface composite absorbing device under normal incidence provided by Example 2 of the present invention;

[0048] Figure 10 1 is a schematic diagram of a reflectivity characteristic curve of the active frequency selective surface composite absorbing device provided in Example 3 of the present invention under normal incidence. DETAILED DESCRIPTION

[0049] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention 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 merely for the purpose of explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0050] In order to achieve the above-mentioned object, in a first aspect, the present invention provides an active frequency selective surface composite absorbing device, comprising: a total reflection bottom plate layer, an adjustable transmission line module and an adjustable surface module arranged in sequence from bottom to top;

[0051] The adjustable surface module includes: a first active frequency selective surface layer and a first dielectric substrate layer arranged in sequence from bottom to top;

[0052] The adjustable transmission line module includes: N+1 dielectric isolation layers arranged in sequence from bottom to top and a transmission line reconstruction unit arranged between every two adjacent dielectric isolation layers; N≥1;

[0053] The transmission line reconstruction unit includes: a second active frequency selective surface layer and a second dielectric substrate layer arranged in sequence from bottom to top;

[0054] The first active frequency selective surface layer and the second active frequency selective surface layer both include a plurality of periodically arranged FSS units; the patterns of the FSS units in the first active frequency selective surface layer and the second active frequency selective surface layer are different, and / or the devices of the FSS units in the first active frequency selective surface layer and the second active frequency selective surface layer are different;

[0055] The adjustable surface module is used to adjust the surface impedance of the device;

[0056] The transmission line reconstruction unit is used to adjust the impedance of two adjacent dielectric isolation layers, thereby adjusting the transmission line impedance of the device.

[0057] The present invention achieves dynamic reconfiguration of the impedance of the dielectric isolation layer by inserting a second active frequency selective surface layer (multiple second active frequency selective surface layers or a single second frequency selective surface layer with a complex impedance form can be introduced, with flexible design and diverse control methods, not limited here) into the dielectric isolation layer of the first active frequency selective surface composite absorber in a conventional active frequency selective surface composite absorber. The second active frequency selective surface acts as an impedance modification layer of the dielectric isolation layer, and its different impedance forms can respectively achieve inversion of the susceptance dispersion form of the grounded transmission line at the low-frequency end and resonance suppression at half the wavelength, thereby achieving the effect of equivalently controlling the grounded transmission line. Through the coordinated control of the first and second active frequency selective surface layers, broadband absorption can be simultaneously established at both the low-frequency and high-frequency ends, achieving broadband absorption. The design mode has evolved from unilateral control matching to dual-variable collaborative control matching, so that the electrical susceptance of the grounded transmission line at the low-frequency and high-frequency ends meets the matching requirements of the original single-functional layer active frequency selective surface, and can take into account the simultaneous expansion of the low-frequency absorption state and high-frequency absorption state bandwidth, so as to achieve the purpose of simultaneously expanding the low-frequency absorption state bandwidth and the high-frequency absorption state bandwidth, and can effectively expand the absorption bandwidth and realize ultra-wideband electromagnetic absorption performance.

[0058] Preferably, in an optional implementation manner, the FSS unit is a FSS unit loaded with a PIN diode, and has a reconfigurable impedance characteristic.

[0059] It should be noted that the key to generating the absorption peak lies in constructing the composite absorber's susceptance zero point. The first active frequency-selective surface layer is equivalent to the series connection of L1, C1, and PIN1. The isolation layer, with a thickness of d, exhibits a periodic impedance variation in the form of a cotangent with frequency. This impedance is divided into regions I (f < 1 / 4 (c / d)), II (f = 1 / 4 (c / d)), III (f = 1 / 2 (c / d)), and IV (f = 3 / 4 (c / d)). The isolation layer near regions II and IV is equivalent to an open circuit, which has little effect on the composite structure's susceptance. When the resistance of PIN1 is properly matched, good absorption can be achieved. The impedance of the isolation layer in region I is of increasing strong inductance. By adjusting the resistance value of PIN1 to enhance the capacitance of the FSS unit (denoted as AFSS1) in the first active frequency selective surface layer, susceptance cancellation can be achieved, thereby generating a low-frequency narrowband absorption peak. The opposite susceptance dispersion of the dielectric isolation layer and AFSS1 limits its absorption bandwidth; in region III, the admittance of the isolation layer is infinite, the composite structure cannot produce a susceptance zero point, and there is an inherent total reflection point. The high-frequency absorption bandwidth constraint comes from the half-wavelength impedance resonance of the isolation layer.

[0060] The introduced second active frequency selective surface is equivalent to the series connection of L2, C2 and PIN2, which is used to control the impedance of the dielectric isolation layer. When observed from AFSS1, the FSS units in the N second active frequency selective surface layer 2-2 (denoted as AFSS2) divide a complete dielectric isolation layer with an original thickness of d into N+1 relatively thin dielectric isolation layers (thicknesses d1, d2, ..., d N+1 , are all less than d); a grounded transmission line in the form of a T-type circuit is formed between each AFSS2 and the two adjacent dielectric isolation layers, and its impedance resonance frequency is controlled by the size of C2. It is generally regulated to the absorption peak at the low-frequency end to generate impedance local dispersion torsion in the resonance zone. When PIN2 is in a relatively small resistance state, the T-type impedance can produce controllable resonance at the low-frequency end of region I, so that the impedance trend of the grounded transmission line in the resonance zone is close to that of AFSS1, and the susceptance of the composite structure can be maintained near 0 in a wide band, forming a broadband low-frequency absorption state. When PIN2 is in a relatively large resistance state, the half-wavelength resonance at region III can be balanced, the total reflection point is effectively suppressed, and the high-frequency absorption state is expanded. Therefore, the purpose of simultaneously constructing a low-frequency broadband absorption state and a high-frequency broadband absorption state can be achieved through the coordinated regulation of AFSS1 and AFSS2.

[0061] It should be noted that the parameters of the first active frequency selective surface layer and the second active frequency selective surface layer can be flexibly designed according to different target frequency bands, and the design is flexible, simple and convenient.

[0062] In an optional embodiment, the impedance Y of the first active frequency selective surface layer is FSS1 for:

[0063]

[0064] Among them, R v The adjustable resistance of the PIN diode on the first active frequency selection surface layer; C p is the parallel parasitic capacitance of the PIN diode on the first active frequency selection surface layer; L and C are the inductance and capacitance of the FSS unit on the first active frequency selection surface layer respectively; ω is the angular frequency.

[0065] In an optional embodiment, the impedance Y of the i-th second active frequency selective surface layer from bottom to top is FSS2(i) satisfy:

[0066]

[0067] Y TL(1) =-jY0cot(βh1)

[0068] Where Y0 is the free space admittance; Y TL(i) is the admittance from the i-th dielectric isolation layer from bottom to top to the total reflection bottom plate layer; j is the imaginary number sign; β is the propagation constant; h i is the thickness of the i-th dielectric isolation layer from bottom to top; Γ is the preset reflection coefficient of the device, which can be set by the user. Generally, Γ < 0.326, so that the reflectivity of the device is less than -10 dB. cot(·) is the cotangent function.

[0069] Preferably, in an optional embodiment, N=1, and the corresponding active frequency selective surface composite absorbing device is as follows: Figure 1 As shown, it includes, from top to bottom, a first dielectric substrate layer 101, a first active frequency selective surface layer 102, a first dielectric isolation layer 103, a second dielectric substrate layer 104, a second active frequency selective surface layer 105, a second dielectric isolation layer 106 and a total reflection bottom plate layer 107;

[0070] The first dielectric substrate layer 101 and the first active frequency selective surface layer 102 constitute an adjustable transmission line module; the second dielectric substrate layer 104 and the second active frequency selective surface layer 105 constitute a transmission line reconstruction unit. The first dielectric isolation layer 103, the second dielectric substrate layer 104, the second active frequency selective surface layer 105, and the second dielectric isolation layer 106 constitute an adjustable transmission line module.

[0071] Impedance Y of the second active frequency selective surface layer FSS2 for:

[0072]

[0073] Where Y0 is the free space admittance; Y TL(2) is the admittance from the second dielectric isolation layer to the total reflection bottom plate layer; j is the imaginary number sign; β is the propagation constant; h2 is the thickness of the second dielectric isolation layer; Γ is the preset reflection coefficient of the device, which can be set by the user. Generally, Γ<0.326, so that the reflectivity of the device is less than -10dB.

[0074] It should be noted that the material of the dielectric isolation layer is air, aramid honeycomb, PMI foam, etc., which is not limited here.

[0075] It should be noted that the FSS units in the same active frequency selective surface layer are generally the same.

[0076] The patterns of the FSS units in the first and second active frequency selective surface layers are not limited, as long as they meet the corresponding impedance requirements. The patterns / devices of the FSS units in each second active frequency selective surface layer can be the same or different, as long as they meet the corresponding impedance requirements, and are not limited here.

[0077] In an optional embodiment, the optional FSS unit patterns in the first active frequency selective surface layer and the second active frequency selective surface layer can be a polygonal ring pattern, a cross pattern, a polygonal pattern, a dipole pattern, or a pattern obtained by performing a Boolean operation based on the aforementioned patterns or any combination thereof (e.g., a polygonal ring-cross composite pattern, a polygonal ring-triangle composite pattern, etc.), etc., without limitation herein. The polygonal ring-cross composite pattern is a centrally symmetrical structure based on a polygonal ring with T-shaped short arms connected at each vertex; the polygonal ring-triangle composite pattern is a centrally symmetrical structure based on a polygonal ring with trapezoids cut out of the center area of ​​each vertex and / or edge.

[0078] In an optional embodiment, the period of the FSS unit in the first active frequency selective surface is an integer multiple of the period of the FSS unit in the second active frequency selective surface; specifically, they can be the same, or the period of the FSS unit in the first active frequency selective surface can be an integer multiple of the period of the FSS unit in the second active frequency selective surface, or the period of the FSS unit in the second active frequency selective surface can be an integer multiple of the period of the FSS unit in the first active frequency selective surface, which is not limited here.

[0079] Preferably, in an optional implementation manner, the period of the FSS units in the first active frequency selective surface and the period of the FSS units in the second active frequency selective surface are 5-50 mm, preferably 10-40 mm.

[0080] In an optional implementation manner, in the first active frequency selective surface and the second active frequency selective surface, the pattern line width of the FSS unit is 0.1-10 mm, and the gap between the FSS unit patterns is 0.2-1.5 mm.

[0081] PIN diodes are distributedly loaded on the FSS pattern topology. The FSS unit patterns are connected by capacitors. To feed the PIN diodes, 50-300nH inductors are loaded between the FSS units to achieve DC conduction and AC isolation. The capacitor type can be gap capacitors, lumped capacitors, etc.

[0082] In an optional embodiment, the material of the first dielectric substrate layer is glass fiber reinforced epoxy resin or polyimide film, with a thickness of 0.025-0.8 mm.

[0083] In an optional embodiment, the material of the first dielectric isolation layer is aramid paper honeycomb material or foam composite material, with a relative dielectric constant ranging from 1.07 to 1.15, a loss tangent ranging from 0.0017 to 0.0039, and a thickness of 5 to 40 mm.

[0084] In an optional embodiment, the second dielectric isolation layer is made of aramid paper honeycomb material or foam composite material, with a relative dielectric constant ranging from 1.07 to 1.15, a loss tangent ranging from 0.0017 to 0.0039, and a thickness of 5 to 40 mm.

[0085] In an optional implementation manner, the above-mentioned total reflection bottom plate can be a solid total reflection bottom plate or a hollow total reflection bottom plate, which is not limited here.

[0086] It should be noted that the active frequency selective surface composite absorbing device provided by the present invention has an introduced transmission line reconstruction unit composed of an FSS unit (including a metal pattern and a device) and a second dielectric substrate layer. The thickness of the FSS metal pattern is extremely thin, generally 5-105um (preferably 35um), which can be ignored. Therefore, the thickness of the transmission line reconstruction unit mainly depends on the thickness of the loaded device and the second dielectric substrate layer. The thickness of the loaded device is generally 0.2-0.4mm (preferably 0.2mm), and the thickness of the second dielectric substrate layer is generally 0.025-0.8mm (preferably 0.15mm). Both are relatively thin. Even if multiple transmission line reconstruction units are introduced, the present invention can effectively expand the overall absorption bandwidth without significantly increasing the thickness of the original single-functional layer active frequency selective surface.

[0087] In order to further illustrate the active frequency selective surface composite absorbing device provided by the present invention, the following is a detailed description in conjunction with specific embodiments:

[0088] Example 1

[0089] This embodiment provides an active frequency selective surface composite absorbing device, comprising: from top to bottom: a first dielectric substrate layer 1-1, a first active frequency selective surface layer 1-2, a first dielectric isolation layer 1-3, a second dielectric substrate layer 1-4, a second active frequency selective surface layer 1-5, a second dielectric isolation layer 1-6, and a total reflection bottom plate layer 1-7.

[0090] The first dielectric substrate layer 1-1 and the first active frequency selective surface layer 1-2 constitute an adjustable transmission line module; the second dielectric substrate layer 1-4 and the second active frequency selective surface layer 1-5 constitute a transmission line reconstruction unit; and the first dielectric isolation layer 1-3, the second dielectric substrate layer 1-4, the second active frequency selective surface layer 1-5, and the second dielectric isolation layer 1-6 constitute an adjustable transmission line module.

[0091] like Figure 2 Shown is a schematic diagram of the 3D structure of a single cycle of the device in this embodiment.

[0092] In this embodiment, the active frequency selective surface is a single-sided copper-clad laminate, and a topological pattern arranged in rows and columns is processed on the copper foil by wet etching. The first dielectric substrate layer 1-1 and the second dielectric substrate layer 1-4 are made of glass fiber reinforced epoxy resin with a relative dielectric constant of 4.4 and a thickness of 0.15 mm.

[0093] The size of the first active frequency selective surface layer 1-2 and the second active frequency selective surface layer 1-5 is 500mm*500mm, and includes 25*25 periods of FSS units. The pattern of the FSS unit in this embodiment is a dipole pattern. The topological structure diagram of the FSS unit is shown in FIG. Figure 3 As shown, the left figure is a schematic diagram of the topological structure of the FSS unit in the first active frequency selective surface layer, and the right figure is a schematic diagram of the topological structure of the FSS unit in the second active frequency selective surface layer. 1-1 =0.8pF, C 1-2=3.0pF. The first active frequency selective surface layer unit 1-2 has a period of 20mm and is loaded with three PIN diodes distributed on the dipole structure. The second active frequency selective surface layer unit 1-5 has a period of 20mm and is loaded with three PIN diodes distributed on the dipole structure. This functional layer works together with the upper and lower dielectric isolation layers to reverse the susceptance dispersion of the grounded transmission line in the low frequency band when PIN2 is at a low resistance value, achieving broadband matching. When PIN2 is at a high resistance value, half-wavelength resonance is suppressed and the total reflection point of the high-frequency absorption state is eliminated, thereby achieving the purpose of simultaneously constructing broadband low-frequency absorption states and broadband high-frequency absorption states.

[0094] It should be noted that, depending on the designed frequency band, the thickness of the first dielectric isolation layer and the second dielectric isolation layer can be flexibly designed, the FSS unit topology can be flexibly designed and the lumped capacitance value of the corresponding parameters can be selected to achieve impedance control in the required frequency band, thereby achieving a broadband absorption effect.

[0095] In this embodiment, the first dielectric isolation layer and the second dielectric isolation layer are both made of aramid paper honeycomb, and both have dimensions of 500mm*500mm*16.5mm. The dimension of the total reflection bottom plate is 500mm*500mm.

[0096] The model of the active frequency selective surface composite absorber device is modeled and simulated in the electromagnetic simulation software HFSS. The simulation performance is as follows: Figure 8 As shown in the figure, it can be seen that the proposed dual-functional layer cooperatively controlled broadband active frequency selective surface composite absorber produces a good bandwidth expansion effect in the low-frequency absorption state and the high-frequency absorption state. Due to the introduction of a new resonance mechanism, the low-frequency absorption state evolves into a dual resonance peak. When PIN1 = 3Ω and PIN2 = 18Ω, a good low-frequency absorption effect is produced, and the low-frequency absorption state bandwidth covers 0.51-1.00GHz (66.7%); when PIN1 = 100Ω and PIN2 = 100Ω, the total reflection point at 4.5GHz is suppressed, and the high-frequency absorption bandwidth reaches 1.0-8.20GHz (156.5%). The overall absorption bandwidth is extended to 0.51-8.20GHz without changing the thickness, and the frequency multiplication number is 16.08.

[0097] Example 2

[0098] The structure of the active frequency selective surface composite absorbing device provided in this embodiment is the same as that of Example 1, including: from top to bottom: a first dielectric substrate layer 2-1, a first active frequency selective surface layer 2-2, a first dielectric isolation layer 2-3, a second dielectric substrate layer 2-4, a second active frequency selective surface layer 2-5, a second dielectric isolation layer 2-6, and a total reflection bottom plate layer 2-7.

[0099] The first dielectric substrate layer 2-1 and the first active frequency selective surface layer 2-2 constitute an adjustable transmission line module; the second dielectric substrate layer 2-4 and the second active frequency selective surface layer 2-5 constitute a transmission line reconstruction unit; and the first dielectric isolation layer 2-3, the second dielectric substrate layer 2-4, the second active frequency selective surface layer 2-5, and the second dielectric isolation layer 2-6 constitute an adjustable transmission line module.

[0100] like Figure 4 Shown is a schematic diagram of the 3D structure of a single cycle of the device in this embodiment.

[0101] In this embodiment, the pattern of the FSS unit (denoted as AFSS1) in the first active frequency selective surface layer 2-2 is a polygonal ring-cross composite pattern; the pattern of the FSS unit (denoted as AFSS2) in the second active frequency selective surface layer 2-2 is a polygonal ring-triangle composite pattern.

[0102] The materials and dimensions of each dielectric substrate layer and isolation layer are the same as those in Example 1. The unit period of each active frequency selective surface layer is 27 mm. The size of the active frequency selective surface layer is 500 mm*500 mm, and it contains 18*18 periodic units. The topological structure diagram of the FSS unit in this embodiment is shown in FIG. Figure 5 As shown, the left figure is a schematic diagram of the topological structure of the FSS unit AFSS1 in the first active frequency selective surface layer, and the right figure is a schematic diagram of the topological structure of the FSS unit AFSS2 in the second active frequency selective surface layer. 2-1 =0.7pF, C 2-2 =2.7pF. Eight PIN diodes are distributed across the FSS unit AFSS1 in the first active frequency selective surface layer and the FSS unit AFSS2 in the second active frequency selective surface layer. AFSS2 works together with the upper and lower dielectric isolation layers to reverse the susceptance dispersion of the grounded transmission line at low frequencies when the PIN2 resistance is low, resulting in broadband matching. When the PIN2 resistance is high, the half-wavelength resonance of the grounded transmission line is suppressed, eliminating the total reflection point in the high-frequency absorption state. This achieves the goal of simultaneously constructing both broadband low-frequency absorption states and broadband high-frequency absorption states.

[0103] The model of the active frequency selective surface composite absorber device is modeled and simulated in the electromagnetic simulation software HFSS. The simulation performance is as follows: Figure 9 As shown, the same low-frequency bandwidth expansion effect as Example 1 is achieved. The low-frequency absorption state evolves from a single resonance peak to a dual resonance peak, and the high-frequency absorption state has a suppressed total reflection point. Overall, the two states achieve an absorption effect with a reflectivity S11 <-10dB in the 0.51-8.16GHz range, with a frequency multiplication factor of 16.

[0104] Example 3

[0105] The structure of the active frequency selective surface composite absorbing device provided in this embodiment is the same as that of Example 1, including: from top to bottom: a first dielectric substrate layer 3-1, a first active frequency selective surface layer 3-2, a first dielectric isolation layer 3-3, a second dielectric substrate layer 3-4, a second active frequency selective surface layer 3-5, a second dielectric isolation layer 3-6, and a total reflection bottom plate layer 3-7.

[0106] The first dielectric substrate layer 3-1 and the first active frequency selective surface layer 3-2 constitute an adjustable transmission line module; the second dielectric substrate layer 3-4 and the second active frequency selective surface layer 3-5 constitute a transmission line reconstruction unit; and the first dielectric isolation layer 3-3, the second dielectric substrate layer 3-4, the second active frequency selective surface layer 3-5, and the second dielectric isolation layer 3-6 constitute an adjustable transmission line module.

[0107] like Figure 6 Shown is a schematic diagram of the 3D structure of a single cycle of the device in this embodiment.

[0108] In this embodiment, the pattern of the FSS unit (denoted as AFSS1) in the first active frequency selective surface layer 3-2 is a diamond pattern; the pattern of the FSS unit (denoted as AFSS2) in the second active frequency selective surface layer 3-2 is a polygonal ring-triangle composite pattern.

[0109] The materials and dimensions of each dielectric substrate layer and isolation layer are the same as those in Example 1. The unit period of each active frequency selective surface layer is 27 mm. The size of the frequency selective surface layer is 500 mm*500 mm, and it contains 18*18 periodic units. The topological structure diagram of the FSS unit in this embodiment is shown in FIG. Figure 7 As shown, the left figure is a schematic diagram of the topological structure of the FSS unit AFSS1 in the first active frequency selective surface layer, and the right figure is a schematic diagram of the topological structure of the FSS unit AFSS2 in the second active frequency selective surface layer. 3-1 =0.68pF, C 3-2 = 2.7pF. Eight PIN diodes are distributed across both AFSS1 and AFSS2. AFSS2, in conjunction with the upper and lower isolation layers, reverses the susceptance dispersion of the grounded transmission line at low frequencies when PIN2 is at a low resistance value, resulting in broadband matching. When PIN2 is at a high resistance value, it suppresses the half-wavelength resonance of the grounded transmission line and eliminates the total reflection point in the high-frequency absorption state, thereby simultaneously creating both broadband low-frequency and broadband high-frequency absorption states.

[0110] The model is simulated in the electromagnetic simulation software HFSS. The simulation performance is as follows: Figure 10As shown, the same low-frequency bandwidth expansion effect as Example 1 is achieved. The low-frequency absorption state evolves from a single resonance peak to a dual resonance peak, and the high-frequency absorption state has a suppressed total reflection point. Overall, the two states achieve an absorption effect with a reflectivity S11 <-10dB in the 0.51-8.23GHz range, with a frequency multiplication factor of 16.14.

[0111] In summary, the active frequency selective surface composite absorbing device provided by the present invention is a dual-functional layer collaboratively controlled broadband active frequency selective surface composite absorbing device. Its purpose is to reconstruct the impedance of the grounded transmission line by inserting an active frequency selective surface in the dielectric isolation layer, and collaboratively control it with the first active frequency selective surface in the adjustable surface module, thereby solving the problem of the difficulty in balancing high and low frequencies in the existing absorber design, and realizing the simultaneous expansion of the bandwidth of the low-frequency absorption state and the high-frequency absorption state.

[0112] It will be easily understood by those skilled in the art that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An active frequency selective surface composite absorbing device, characterized in that: include: A total reflection bottom plate layer, an adjustable transmission line module and an adjustable surface module are arranged in sequence from bottom to top; The adjustable surface module comprises: a first active frequency selective surface layer and a first dielectric substrate layer arranged in sequence from bottom to top; The adjustable transmission line module includes: N+1 dielectric isolation layers arranged in sequence from bottom to top and a transmission line reconstruction unit arranged between every two adjacent dielectric isolation layers; N≥1; The transmission line reconstruction unit comprises: a second active frequency selective surface layer and a second dielectric substrate layer arranged in sequence from bottom to top; Wherein, the first active frequency selective surface layer and the second active frequency selective surface layer both include a plurality of periodically arranged FSS units; the patterns of the FSS units in the first active frequency selective surface layer and the second active frequency selective surface layer are different, and / or the devices of the FSS units in the first active frequency selective surface layer and the second active frequency selective surface layer are different; The adjustable surface module is used to adjust the surface impedance of the device; The transmission line reconstruction unit is used to adjust the impedance of two adjacent dielectric isolation layers.

2. The active frequency selective surface composite absorbing device according to claim 1, characterized in that: The FSS unit is a FSS unit loaded with a PIN diode.

3. The active frequency selective surface composite absorbing device according to claim 2, characterized in that: The impedance Y of the first active frequency selective surface layer FSS1 for: Among them, R v The adjustable resistance of the PIN diode on the first active frequency selection surface layer; C p is the parallel parasitic capacitance of the PIN diode on the first active frequency selection surface layer; L and C are the inductance and capacitance of the FSS unit on the first active frequency selection surface layer respectively; ω is the angular frequency.

4. The active frequency selective surface composite absorbing device according to claim 3, characterized in that: The impedance Y of the second active frequency selective surface layer from bottom to top FSS2(i) satisfy: Y TL(1) =-jY0cot(βh1) Where Y0 is the free space admittance; Y TL(i) is the admittance from the i-th dielectric isolation layer from bottom to top to the total reflection bottom plate layer; j is the imaginary number sign; β is the propagation constant; h i is the thickness of the i-th dielectric isolation layer from bottom to top; Γ is the preset reflection coefficient of the device; cot(·) is the cotangent function.

5. The active frequency selective surface composite absorbing device according to any one of claims 1 to 4, characterized in that: N＝1。 6. The active frequency selective surface composite absorbing device according to any one of claims 1 to 4, characterized in that: The pattern types of the FSS units in the first active frequency selective surface include: a polygonal ring pattern, a cross pattern, a polygonal pattern, a dipole pattern, a polygonal ring-cross composite pattern or a polygonal ring-triangle composite pattern; The pattern types of the FSS units in the second active frequency selective surface include: a polygonal ring pattern, a cross pattern, a polygonal pattern, a dipole pattern, a polygonal ring-cross composite pattern or a polygonal ring-triangle composite pattern; The polygonal ring-cross composite pattern is a centrally symmetrical structure based on a polygonal ring with T-shaped short arms connected at each vertex. The polygonal ring-triangle composite pattern is a centrally symmetrical structure based on the polygonal ring, with trapezoids cut out from the central area of ​​each vertex and / or side.

7. The active frequency selective surface composite absorbing device according to any one of claims 1 to 4, characterized in that: The period of the FSS unit in the first active frequency selective surface is an integer multiple of the period of the FSS unit in the second active frequency selective surface; The period of the FSS units in the first active frequency selective surface and the period of the FSS units in the second active frequency selective surface are 5 to 50 mm.

8. The active frequency selective surface composite absorbing device according to any one of claims 1 to 4, characterized in that: In the first active frequency selective surface and the second active frequency selective surface, the pattern line width of the FSS unit is 0.1-10 mm, the gap between the FSS unit patterns is 0.2-1.5 mm, and the capacitance between the FSS unit patterns is gap capacitance or lumped capacitance.

9. The active frequency selective surface composite absorbing device according to any one of claims 1 to 4, characterized in that: The material of the first dielectric substrate layer is glass fiber reinforced epoxy resin or polyimide film, with a thickness of 0.025-0.8 mm; The second dielectric substrate layer is made of glass fiber reinforced epoxy resin or polyimide film, and has a thickness of 0.025-0.8 mm.

10. The active frequency selective surface composite absorbing device according to any one of claims 1 to 4, characterized in that: The material of the first dielectric isolation layer is aramid paper honeycomb material or foam composite material, with a thickness of 5-40 mm; The second dielectric isolation layer is made of aramid paper honeycomb material or foam composite material with a thickness of 5-40 mm.

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