Switchable wave absorbing / transmitting device

Abstract

The invention belongs to the field of electromagnetic materials, and discloses a switchable wave-absorbing / wave-transmitting device, which is characterized in that a loss layer comprises an upper surface copper-clad plate, a first dielectric substrate and a lower surface copper-clad plate; the upper and lower surface copper-clad plates are consistent in structure, and the projection of the upper surface copper-clad plate on the lower surface copper-clad plate and the upper surface copper-clad plate are arranged at an angle of 90 degrees; the pattern structure on each array in the upper surface copper-clad plate comprises N switchable resonant windows and N + 1 fusion type bias networks which are arranged alternately, and the N switchable resonant windows and the N + 1 fusion type bias networks are connected through metal connecting wires; the fusion type bias network is of a central symmetry structure and comprises two parallel metal wires and a metal connecting structure vertically connected between the metal wires, the two parallel metal wires are perpendicular to the metal connecting wire, and a lumped inductor is loaded in the metal connecting structure. By optimizing the fused bias network structure in the loss layer, the absorption performance of the two sides (low frequency and high frequency) of the switching frequency band is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field related to electromagnetic materials, and more specifically, relates to a switchable wave absorbing / transmitting device. Background Art

[0002] The core mechanism of modern radar stealth technology lies in the manipulation of electromagnetic waves. Radar absorbing materials (RAMs) utilize a lossy dielectric structure to dissipate the energy of incident electromagnetic waves into Joule heat, thereby attenuating the reflected signal. Frequency selective surfaces (FSSs), developed based on this technology, utilize a two-dimensional periodic array of cells and achieve precise control of the electromagnetic response frequency band through geometric topology optimization. By adding lossy structures, wide-band electromagnetic wave absorption can be achieved.

[0003] Absorption / transmission structures, consisting of a cascade of multiple lossy layers and frequency-selective surfaces, can simultaneously absorb and transmit waves within a specific frequency band. Therefore, they have the potential to be used in stealth radome designs and have attracted extensive research over the past few decades. Recent advances have focused on broadening the absorption bandwidth, enhancing transmission, and miniaturizing unit designs. However, the persistence of the transmission window prevents the absorption of in-band electromagnetic waves, thus compromising stealth performance. Therefore, to meet the requirements of applications such as transmission-band stealth and intelligent radar systems, reconfigurable absorptive / transmitting structures that dynamically adjust their functionality based on the antenna's operating state have attracted significant interest.

[0004] Switchable aspiration / transmission devices show great potential, particularly in terms of dynamic tuning and functional switching. Multiple functional switching can be achieved by integrating variable materials, liquid media, and mechanical switches, but complex mechanisms and fabrication processes currently limit their engineering applications. Diodes, with their excellent electrical performance and cost-effectiveness, have been widely used as reconfigurable devices in switchable aspiration / transmission devices by embedding PIN diodes in strategic locations to achieve functional switching.

[0005] In recent years, broadband switchable wave absorbing / transmitting devices have attracted research attention. Low-Q resonators are used to achieve broadband transmission, but this negatively impacts absorption performance, making it difficult to maintain stable absorption characteristics during functional switching. To address this issue, a switchable wave absorbing / transmitting device with a non-switchable lossy layer was proposed, achieving stable switching under single polarization (R. Li, J. Tian, ​​B. Jiang, Z. Lin, B. Chen, and H. Hu, “ASwitchable Frequency Selective Rasorber with Wide Passband,” IEEE Antennas Wireless Propag. Lett., vol. 20, no. 8, pp. 1567–1571, Aug. 2021). This approach broadens the absorption range by adding multiple lossy layers, achieving stable absorption on both sides of the passband. To expand the functionality to dual polarization, careful design of the bias circuit and current path, coupled with an orthogonal symmetric patterning on the backside, resulted in a broadband dual-polarization switchable absorber / transmitter with independent polarization control (H. Jiang, S. Liao, R. Li, and Q. Xue, “Independently Switchable Rasorber with Wide Transmission and Low-Reflection Bands Under Dual Polarization,” IEEE Trans. Microw. Theory Techn., vol. 72, no. 2, pp. 863–877, Feb. 2024). However, these designs rely on multiple lossy layers, increasing the complexity and cost of design and fabrication. Therefore, switchable absorbers / transmitters with simple structures and stable absorption capabilities deserve further research. Summary of the Invention

[0006] In response to the above-mentioned defects or improvement needs of the existing technology, the present invention provides a switchable wave absorbing / transmitting device, which aims to improve the absorption performance on both sides of the switching frequency band (low frequency and high frequency) by optimizing the fused bias network structure in the loss layer, thereby solving the problems of the current switchable wave absorbing / transmitting device in that the absorption frequency band is difficult to stabilize and the structural design is complex.

[0007] To achieve the purpose of the present invention, the present invention provides a switchable wave absorbing / transmitting device, which comprises, from top to bottom, a lossy layer, a support layer, and a frequency selective surface layer; The lossy layer includes, from top to bottom, an upper copper-clad plate, a first dielectric substrate, and a lower copper-clad plate; the lower copper-clad plate has the same structure as the upper copper-clad plate, and is arranged at 90 degrees to the projection of the upper copper-clad plate on the lower copper-clad plate; The upper surface copper clad board has an array pattern structure; the pattern structure on each array includes N switchable resonant windows and N+1 fused bias networks arranged alternately, and the switchable resonant windows and the fused bias network are connected by metal connecting lines, and N is an integer greater than or equal to 1; wherein the fused bias network is a centrally symmetrical structure, which includes two parallel metal lines and a metal connecting structure vertically connected between the metal lines, the metal lines are arranged perpendicular to the metal connecting lines, and the metal connecting structure is loaded with a lumped inductor.

[0008] As a preferred embodiment of the present invention, the length of the metal wire is 15 mm-18 mm, and the wire width is 0.1 mm-0.3 mm; The value of any lumped inductance in the lossy layer is 30 nH-50 nH.

[0009] As a preferred embodiment of the present invention, the switchable resonant window is composed of a meandering metal pattern and two first PIN diodes, and a lumped capacitor is provided in the meandering metal; The line width of the meandering metal in the switchable resonant window is 3.5 mm-3.8 mm, and the gap is 0.5 mm-0.7 mm; the value of any lumped capacitance in the lossy layer is 3 pF-6 pF.

[0010] As a preferred embodiment of the present invention, the length of the metal connecting wire is 11.5 mm-14 mm, and the width is 1 mm-2 mm; A lumped resistor is embedded in the metal connecting wire; the gap spacing between any lumped resistor in the lossy layer is 0.5 mm, and the value of the lumped resistor is 115 Ohm-175 Ohm.

[0011] As a preferred embodiment of the present invention, the frequency selective surface layer includes four metal patch layers and three dielectric isolation layers arranged alternately.

[0012] As a preferred embodiment of the present invention, the periodic unit structure in the frequency selective surface layer is, from top to bottom, a first metal patch layer, a second dielectric isolation layer, a second metal patch layer, a third dielectric isolation layer, a third metal patch layer, a fourth dielectric isolation layer, and a fourth metal patch layer; the first metal patch layer and the second metal patch layer are both octagonal patterns, the third metal patch layer is a grid pattern, and the fourth metal patch layer is a rectangular patch pattern; the second metal patch layer is connected to a pad embedded in the third dielectric isolation layer through a blind hole; the grid pattern of the third metal patch layer is provided with a notch at the position corresponding to the pad, so that a gap is formed between the pad and the third metal layer, and a second PIN diode is loaded at the gap.

[0013] As a preferred embodiment of the present invention, the support layer is made of aramid paper honeycomb or PMI foam, with a thickness of 15 mm-20 mm, preferably 18 mm.

[0014] As a preferred embodiment of the present invention, the metal used in the metal patch layer is one of gold, aluminum, copper or silver.

[0015] As a preferred embodiment of the present invention, the dielectric isolation layer is made of one of glass fiber reinforced epoxy resin material, polyimide organic polymer material, polytetrafluoroethylene high-frequency board, aramid honeycomb or PMI foam, with a thickness of 0.2 mm-2 mm; wherein the thickness of the first dielectric isolation layer is preferably 0.508 mm; the thickness of the second dielectric isolation layer is preferably 0.203 mm; the thickness of the third dielectric isolation layer and the fourth dielectric isolation layer is preferably 1.524 mm.

[0016] As a preferred embodiment of the present invention, the periodic unit structure in the lossy layer is the area defined by two adjacent switchable resonant windows in the upper copper-clad plate and two adjacent switchable resonant windows in the lower copper-clad plate; the area formed by two periodic unit structures in the frequency selective surface layer is the orthographic projection of one periodic unit structure in the lossy layer on the frequency selective surface layer; The period of any periodic unit structure in the lossy layer is 28 mm to 32 mm; the period of any periodic unit structure in the frequency selective surface layer is 14 mm to 16 mm.

[0017] In general, the above technical solutions conceived by the present invention have the following technical advantages compared with the existing technology: The switchable absorber / transmitter device of the present invention achieves improved absorption performance in the switching frequency band through a single lossy layer. Specifically, in the specific design of the lossy layer of the present invention, the structure of the fused feed network is optimized. This fused feed network is a centrosymmetrical structure comprising two parallel metal wires and a metal connection structure perpendicularly connected between the metal wires. The metal wires and the metal connection wires are arranged perpendicularly, and the metal connection structure is loaded with a lumped inductor. This introduces resonance on both sides of the wide transmission band, thereby improving absorption performance on both sides of the switching frequency band (low and high frequencies). The fused design expands the impedance range of the original single capacitive or inductive device, thereby effectively enhancing absorption matching. Furthermore, the polarization selection of the present invention enables independent regulation of TE and TM electromagnetic waves. By controlling the state of the diode in different directions, switching between three states of absorption and transmission, polarization-independent regulation, and absorption is achieved. Compared with designs that rely on multiple lossy layers, the structural design of the present invention is simpler and has lower manufacturing costs. In summary, this design achieves a transmission bandwidth of 3.8-4.29 GHz (11.8%) and an absorption bandwidth of more than 110% with only a single loss layer and a thickness of only 0.107λ L , it can perform stable switching of functions and stable absorption, with a simple structural design, and has an absolute advantage in the existing field of switchable wave absorbing / transmitting device design.

[0018] The fused feed network of the present invention has a centrally symmetrical structure. The preferred metal wire length is 315-18 mm and the wire width is 0.1-0.3 mm. The wire length and lumped inductance on both sides of the symmetrical structure control the impedance matching of high and low frequencies respectively to adapt to stable absorption in more frequency bands. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 3D structural diagram of a unit pattern in the switchable wave absorbing / transmitting device exemplified in the present invention.

[0020] Figure 2 It is a two-dimensional planar schematic diagram of the extended lossy layer unit structure in the switchable wave absorbing / transmitting device according to an example of the present invention.

[0021] Figure 3 is a two-dimensional plan view of the frequency selective surface layer in the switchable wave absorbing / transmitting device according to an example of the present invention; wherein, Figure 3 (a) corresponds to the side view of the unit, (b) corresponds to the first metal patch layer unit pattern, (c) corresponds to the second metal patch layer unit pattern, (d) corresponds to the third metal patch layer unit pattern, and (e) corresponds to the fourth metal patch layer unit pattern.

[0022] Figure 4 It is an equivalent circuit diagram of the entire switchable wave absorbing / transmitting device according to an example of the present invention.

[0023] Figure 5Schematic diagram of the feeding method and current path with a lossy layer according to an example of the present invention.

[0024] Figure 6 Schematic diagram of a lossy layer array according to an example of the present invention.

[0025] Figure 7 FIG. 1 is a schematic diagram of a frequency selective surface layer array according to an example of the present invention.

[0026] Figure 8 This is an S-parameter simulation result diagram of a switchable wave absorbing / transmitting device in a commercial electromagnetic simulation software according to an example of the present invention, wherein Figure 8 (a) is the S parameter simulation data under the integrated absorption and penetration working state, (b) is the S parameter simulation data under the absorption working state, and (c) and (d) are the S parameter simulation data under the polarization selection mode.

[0027] Figure 9 This is a graph showing the S parameter test results of the switchable wave absorbing / transmitting device in a microwave darkroom according to an example of the present invention, wherein Figure 9 (a) is the S parameter simulation data under the integrated absorption and penetration working state, (b) is the S parameter simulation data under the absorption working state, and (c) and (d) are the S parameter simulation data under the polarization selection mode.

[0028] Figure 10 This is the S parameter simulation result diagram of the unloaded fusion bias network of the present invention, where Figure 10 (a) is the S parameter simulation data in the absorption and penetration integrated state, and (b) is the S parameter simulation data in the absorption working state.

[0029] Figure 11 This is a diagram of the S-parameter simulation results of the device with different parameters of the fusion bias network in the example of the present invention under the working state of absorption and penetration. Figure 11 (a) is the S-parameter simulation data of the device under different lumped inductance values, and (b) is the S-parameter simulation data of the device under different metal wire lengths.

[0030] Throughout the drawings, the same reference numerals are used to denote the same elements or structures, wherein: 1-Loss layer, 2-Support layer, 3-Frequency selective surface layer, 4-Switchable resonant window, 5-Fused bias network, 6-Metal connection line, 7-Lumped resistor, 8-Lumped inductor, 9-Lumped capacitor, 10-First PIN diode, 11-First metal patch layer, 12-Second dielectric isolation layer, 13-Second metal patch layer, 14-Third dielectric isolation layer, 15-Third metal patch layer, 16-Fourth dielectric isolation layer, 17-Fourth metal patch layer, 18-Pad, 19-Second PIN diode. DETAILED DESCRIPTION

[0031] 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.

[0032] like Figure 1 As shown, the switchable wave absorbing / transmitting device of the present invention comprises a loss layer 1, a support layer 2, and a frequency selective surface layer 3 from top to bottom.

[0033] The unit patterns of the loss layer 1 and the frequency selective surface layer 3 are as follows: Figure 2 and Figure 3 shown.

[0034] like Figure 2 As shown, the lossy layer 1 comprises, from top to bottom, a double-sided copper-clad structure consisting of an upper copper-clad laminate, a first dielectric isolation layer, and a lower copper-clad laminate. The lower copper-clad laminate has the same structure as the upper copper-clad laminate, and is arranged 90° around its center, starting from the projection of the upper copper-clad laminate on the lower copper-clad laminate.

[0035] The copper clad board on the upper surface is an array pattern structure; the pattern structure on each array includes N switchable resonant windows 4 and N+1 fused bias networks 5 arranged alternately, and the switchable resonant windows 4 and the fused bias network 5 are connected by metal connecting lines 6, where N is an integer greater than or equal to 1; wherein, the fused bias network 5 is a centrally symmetrical structure, which includes two parallel metal wires and a metal connecting structure vertically connected between the metal wires, the metal wires are arranged perpendicular to the metal connecting lines 6, and the metal connecting structure is loaded with a lumped inductor 8.

[0036] The array pattern structure comprises multiple periodic unit structures, which are formed by replicating and translating the periodic unit structures along the length direction of the two-dimensional plane in which they are located. Each periodic unit structure is composed of the area bounded by two adjacent switchable resonant windows in the upper copper-clad laminate and two adjacent switchable resonant windows in the lower copper-clad laminate, namely, the left portion of the switchable resonant window 4 and the right portion of the adjacent switchable resonant window 4, as well as four quarter-fused bias networks 5 connecting the two adjacent switchable resonant windows 4.

[0037] In some embodiments, the length of the metal wire is 315 mm-18 mm, and the wire width is 0.1 mm-0.3 mm; On either surface of the lossy layer, the lumped inductor 8 has a value of 30 nH to 50 nH. The fused bias network 5 is a centrosymmetrical structure, with the line lengths and lumped inductors on either side controlling the impedance matching at high and low frequencies, respectively, thereby affecting the absorption range of the corresponding frequency bands.

[0038] In some embodiments, the switchable resonant window 4 is composed of a meandering metal pattern and two first PIN diodes 10 ; the meandering metal has a line width of 3.5 mm to 3.8 mm and a gap of 0.5 mm to 0.7 mm.

[0039] Two first PIN diodes 10 are connected in series and embedded in the switchable resonant window 4, ensuring the switching characteristics of the PIN diodes; a lumped capacitor 9 is loaded on the meandering metal connection line in the switchable resonant window 4. On the two surfaces of the lossy layer, any one of the lumped capacitors has a value of 3 pF-6 pF, which is used to isolate DC and ensure the state switching of the first PIN diode 10.

[0040] Metal connecting wire 6 connects the switchable resonant window to the feed network. Lumped resistors are embedded within the metal connecting wire 6 for electromagnetic wave absorption. The length of the connecting metal patch is 11.5 mm to 14 mm, and the width is 1 mm to 2 mm. The gap between any lumped resistors 7 on either surface of the lossy layer is 0.3 mm to 0.7 mm, and the lumped resistors range from 115 ohms to 175 ohms.

[0041] In some embodiments, the frequency selective surface layer 3 includes four metal patch layers and three dielectric isolation layers stacked alternately. In some embodiments, the metal patch should be made of a metal material with good electrical conductivity, such as gold, aluminum, or copper.

[0042] For example, a periodic unit structure in the frequency selective surface layer 3 corresponds vertically to two periodic unit structures in the upper surface copper clad board, and the periodic unit structures in the frequency selective surface layer 3 are, from top to bottom, the first metal patch layer 11, the second dielectric isolation layer 12, the second metal patch layer 13, the third dielectric isolation layer 14, the third metal patch layer 15, the fourth dielectric isolation layer 16, and the fourth metal patch layer 17. The first metal patch layer and the second metal patch layer are irregular octagons processed on the copper foil (the long side of the patch is 11 mm-13 mm, the short side is 8 mm-9 mm, and the four corners are cut off to form an irregular octagon), the third metal patch layer is a grid pattern processed on the copper foil (the side length in the middle of the grid is 6 mm-7 mm), and the fourth metal patch layer is a rectangular patch pattern processed on the copper foil (the side length of the rectangular patch is 13 mm-14 mm). The second metal patch layer is connected to the pad 18 embedded in the third dielectric isolation layer 14 through a blind hole, and the second PIN diode 19 is loaded in the narrow gaps in different directions to form a frequency selective surface unit.

[0043] In some embodiments, the support layer mentioned herein is made of aramid paper honeycomb or PMI foam, with a thickness of 15 mm to 20 mm, and mainly serves as an isolation loss layer and a frequency selective surface layer as well as a support.

[0044] In some embodiments, the metal patch layer is made of gold, aluminum, copper, or silver. The dielectric isolation layers are made of materials such as glass fiber reinforced epoxy resin (FR-4), polyimide organic polymer material (Polyimide), polytetrafluoroethylene high-frequency board (F4BM265), aramid honeycomb, or PMI foam. The thickness ranges from 0.2 mm to 2 mm, depending on the dielectric constant. These layers primarily support the metal patch and provide impedance matching.

[0045] The glass cloth-reinforced, ceramic-filled hydrocarbon composite material (Rogers RO4003C) and low-loss PMI foam used in this invention can be replaced with commercially available materials such as glass fiber-reinforced epoxy resin (FR-4), polyimide organic polymer materials (Polyimide), polytetrafluoroethylene high-frequency board (F4BM265), and aramid paper honeycomb materials. In addition to the above embodiments, the present invention can also use other dielectric materials with relatively small variations in relative permittivity, dielectric loss factor, relative magnetic permeability, and magnetic loss factor as the substrate. The metal patch layer should be made of a highly conductive metal material, and metals such as gold and aluminum can also be used. The period of the lossy layer structure can also be other values ​​within the range of 28 mm to 32 mm, and the period of the frequency selective surface structure can also be other values ​​within the range of 14 mm to 16 mm. Variations in the periodicity will affect the overall performance of the device, and simulations can be performed accordingly.

[0046] Among them, the periodic unit structure in the loss layer 1 is the area defined by two adjacent switchable resonant windows 4 in the upper surface copper-clad board and two adjacent switchable resonant windows 4 in the lower surface copper-clad board; the area composed of two periodic unit structures in the frequency selective surface layer 3 is the orthographic projection of a periodic unit structure in the loss layer 1 on the frequency selective surface layer 3.

[0047] like Figure 1-Figure 3 This switchable wave-absorbing / wave-transmitting device operates at a center frequency of approximately 4 GHz. When PIN diodes 10 and 19 are off, the device is in a transmission state, with electromagnetic waves sequentially passing through lossy layer 1 and frequency selective surface 3, achieving a transmission effect. When PIN diodes 10 and 19 are on, the transmission window closes, and the electromagnetic waves, after passing through frequency selective surface 3, are reflected back to lossy layer 1 and absorbed by resistor 7, achieving an absorption effect. At both low and high frequencies, impedance matching is achieved by adjusting the parameters of the fused bias network 5, ensuring stable absorption in both states. Furthermore, by controlling the PIN diodes 10 and 19 in different directions, the polarization of the incident electromagnetic wave can be selected.

[0048] Specifically, the switchable absorber / transmitter device can absorb electromagnetic waves in the microwave frequency band of 1.48-6.48 GHz and transmit electromagnetic waves in the microwave frequency band of 3.81-4.29 GHz in the absorber-transmitter working state; in the absorber working state, the absorption frequency band ranges from 1.5-5.5 GHz. The switchable absorber / transmitter device can achieve polarization selection working state by controlling diodes in different directions, allowing only single-polarization electromagnetic wave transmission. x and y represent the diodes in the vertical direction, respectively, and 0 and 1 represent the diode's open and closed states, respectively. There are four working modes: xy-00: All diodes in the x and y directions are turned off; xy-11: All diodes in the x and y directions are turned on; xy-10: the diode in the x direction is on, and the diode in the y direction is off; xy-01: The diode in the x direction is off, and the diode in the y direction is on; Specific functions implemented in the working frequency band: xy-00 mode: both the x and y directions are in the suction / penetration integrated state; xy-11 mode: both x and y directions are absorbing; xy-10 mode: absorption in the x direction, absorption / transmission in the y direction, and y polarization selection state; xy-01 mode: the x direction is absorption / transmission integrated, the y direction is absorption state, and the x polarization selection state.

[0049] The following example illustrates a specific switchable wave absorbing / transmitting device. In the lossy layer 1, the gap spacing between the welded lumped resistors in the unit pattern is 0.5 mm; the gap spacing between the lumped capacitors is 0.5 mm; the gap spacing between the PIN diodes is 0.5 mm; and the gap spacing between the lumped inductors is 1 mm. In the frequency selective surface layer, the gap spacing between the welded PIN diodes in the unit pattern is 0.5 mm. The first dielectric isolation layer in the lossy layer 1 is Rogers RO4003C (relative permittivity 3.55, loss tangent 0.0027), with a thickness of 0.508 mm. The support layer 2 is low-loss PMI foam. The dielectric substrates used for the second, third, and fourth dielectric isolation layers 12, 14, and 16 in the frequency selective surface layer 3 are all Rogers RO4003C, with thicknesses of 0.203 mm, 1.524 mm, and 1.524 mm, respectively. The upper and lower metal patches in lossy layer 1, as well as the first, second, third, and fourth metal patches 11, 13, 15, and 17, are all thin copper sheets. The gap between the lumped resistor 7, lumped capacitor 9, first PIN diode 10, and second PIN diode 19 is 0.5 mm. The gap between the lumped inductor 8 is 1 mm. Using printed circuit board (PCB) processing technology, specific lumped components are soldered into the gaps to form the responsive unit structure of the switchable wave absorbing / transmitting device.

[0050] The lossy layer design of the present invention includes a switchable resonant window 4, a fused bias network 5, and a metal connection line 6. The switchable resonant window 4 is equivalent to a parallel PIN-LC structure, used to form a transmission window at a specific location, and the transmission window can be opened and closed by controlling the state of the diode. The fused bias network 5 is equivalent to the series connection of two parallel LC structures, introducing resonance at the high and low frequency sides, respectively, driving the overall impedance of the lossy layer to match the general absorption region, achieving absorption characteristics. The connecting metal patch 6 is equivalent to an inductor L and inserts a lumped resistor to absorb electromagnetic waves. In the frequency selective surface 3, the first and second metal patch layers are equivalent to capacitors, and the PIN diode loaded on the surface is equivalent to a parallel PIN-C structure. The third metal patch layer is equivalent to an inductor; the fourth metal patch layer is equivalent to a capacitor. Considering that each layer is separated from each other, the entire structure is equivalent to a second-order filter circuit. The equivalent circuit functions to provide a transmission window and acts as a metal floor to absorb electromagnetic waves in the absorption frequency band. The support layer 2 between the lossy layer 1 and the frequency selective surface 3 is a quarter wavelength away from the center frequency, making its impedance characteristics well matched to air. The absorption bandwidth of the switchable absorber / transmitter can be controlled by adjusting the resonance points of the fused bias network at low and high frequencies.

[0051] Example 1: The copper-clad laminates on the upper and lower surfaces of the lossy layer have a meandering metal line width of 3.65 mm and a gap of 0.6 mm in the center switchable resonant window. The fused bias network has two arms with sides of 16.5 mm and a line width of 0.2 mm. The connecting metal patch is 12.6 mm long and 1.4 mm wide. The copper-clad laminate pattern on the lower surface is identical and symmetrical by 90 degrees. On both surfaces of the lossy layer, the lumped resistance of any soldered element in the gap between cells is 143 ohms; the lumped inductance is 47 nH; and the lumped capacitance is 4 pF. The PIN diode is a Skyworks SMP1345-040LF, which is equivalent to a 0.1 pF capacitor in series with a 0.45 nH inductor in the off state and a 2 ohm resistor in series with a 0.45 nH inductor in the on state.

[0052] The first and second metal patches of the frequency selective surface shown have long sides of 12.5 mm and short sides of 9 mm, and are chamfered to form irregular octagons. The third metal patch layer has a grid with a center side length of 6.3 mm. The fourth metal patch layer has rectangular patches with sides of 13.9 mm.

[0053] The height of the separation between the lossy layer and the frequency selective surface is shown to be 18 mm.

[0054] Figure 4 The equivalent circuit model of the present invention is shown in the figure. The lossy layer 1 and the frequency selective surface 3 are separated by an air transmission line with an electrical length of 18 mm. The equivalent circuit of the PIN diode is shown in the figure. The switchable resonant window is equivalent to a parallel PIN-L1-C1; the fused bias network is composed of a parallel L a -C a and parallel L b -C b The lumped resistor R is used to absorb electromagnetic waves; the equivalent inductor L2 of the metal is connected. The frequency selective surface design adopts a non-resonant switchable second-order bandpass frequency selective surface architecture, which consists of C s1 -L s -C s2 Cascade formation, C s1 Represents the first metal patch layer and the second metal patch layer, and is in parallel with the second PIN diode; L s Represents the third metal patch layer; C s2 The fourth metal patch layer. The dielectric isolation layer is equivalent to an air transmission line with a length of t1 and a characteristic impedance of Z0 = 377 Ohm. By adjusting the parallel L a -C a and parallel L b -C b The specific value of can control the absorption frequency range.

[0055] Figure 5 Schematic diagram of the power feeding of the switchable wave absorbing / transmitting device of the present invention. Figure 5 (a) shows the lossy layer 2×2 unit structure and feeding method. Figure 5 (b) shows a schematic diagram of the current path of its equivalent circuit, and the integrated fusion bias network feeds the PIN by applying voltage in each column, and the polarization selection function can be achieved by independently applying voltage in different directions.

[0056] The schematic diagram of the 10×10 array structure of the lossy layer 1 and the 20×20 array structure of the frequency selective surface 3 is shown in FIG. Figure 6 、 Figure 7 shown.

[0057] This example was simulated in a commercial electromagnetic simulation software. The S parameters of the switchable wave absorbing / transmitting device are as follows: Figure 8 In the absorption-transmission integrated working state, within the range of 3.81-4.29 GHz (11.8%), there is a 1 dB transmission band at the TE and TM polarizations, namely |S 21 |<-1 dB, absorption bands 1.48-3.4 GHz and 4.7-6.48 GHz, e.g. Figure 8 In addition, in the absorption working state, the absorption band covers the range of 1.61-5.47 GHz (110%) and |S 21 |<22 dB, e.g. Figure 8 The polarization selection mode is shown in (b). Figure 8 As shown in (c)-(d) in the figure, the absorption band performance is stable, and different polarizations have independent transmission windows. The simulation results show the excellent absorption performance of the designed switchable absorber / transmitter device, and it realizes three working states. At the same time, the reflectivity / transmittance of this example was measured in a microwave darkroom. The measurement results show that the device can switch between different working states while maintaining stable absorption performance. This is consistent with the expected goal and verifies the proposed design method. Figure 9 shown.

[0058] This example compares the S parameter results without loading the fusion bias network results, such as Figure 10 As shown in Figure 3 , the device without the fused bias network can still switch between the absorption and absorption states, but the absorption performance is stable at -8 dB, and the absorption intensity is poor. Adding the fused bias network 5 enhances the absorption performance on both sides and stabilizes it during the state switching process. Furthermore, controlling the diode state in the device without the fused bias network requires the design of a separate bias network.

[0059] In this example, the structural parameters of the fusion bias network 5 are adjusted, and the S parameter results are as follows: Figure 11 By increasing the metal wire length (arm length), the high-frequency -10 dB absorption band is reduced, thus achieving regulation of the high-frequency side; by reducing the lumped inductance value, the low-frequency -10 dB absorption band is reduced, thus achieving regulation of the low-frequency side.

[0060] Obviously, those skilled in the art may make various modifications and variations to the present invention without departing from the spirit and scope of the present invention. Thus, if such modifications and variations fall within the scope of protection of the present invention and its equivalents, the present invention is intended to include such modifications and variations. The above-described embodiments are merely preferred embodiments for the purpose of fully illustrating the present invention and are not intended to limit the scope of protection. Any equivalent substitutions or modifications made by those skilled in the art based on the present invention are also within the scope of protection of the present invention.

Claims

1. A switchable wave absorbing / transmitting device, characterized in that: From top to bottom, it includes a loss layer (1), a support layer (2), and a frequency selective surface layer (3); The lossy layer (1) comprises, from top to bottom, an upper surface copper-clad plate, a first dielectric isolation layer, and a lower surface copper-clad plate; The structure of the lower surface copper clad plate is consistent with that of the upper surface copper clad plate, and the projection of the upper surface copper clad plate on the lower surface copper clad plate is arranged at 90 degrees; The upper surface copper clad plate is an array pattern structure; the pattern structure on each array includes N switchable resonant windows (4) and N+1 fusion type bias networks (5) arranged alternately, and the switchable resonant windows (4) and the fusion type bias network (5) are connected by metal connecting lines (6), and N is an integer greater than or equal to 1; wherein, the fusion type bias network (5) is a central symmetrical structure, which includes two parallel metal lines and a metal connection structure vertically connected between the metal lines, the metal lines are vertically arranged to the metal connection lines (6), and the metal connection structure is loaded with a lumped inductor (8).

2. The switchable wave absorbing / transmitting device according to claim 1, characterized in that: The length of the metal wire is 15 mm to 18 mm, and the wire width is 0.1 mm to 0.3 mm; The value of any one of the lumped inductors (8) in the lossy layer (1) is 30 nH-50 nH.

3. The switchable wave absorbing / transmitting device according to claim 1, characterized in that: The switchable resonant window (4) is composed of a meandering metal pattern and two first PIN diodes (10), and a lumped capacitor (9) is provided in the meandering metal; The line width of the meandering metal in the switchable resonant window (4) is 3.5 mm to 3.8 mm, and the gap is 0.5 mm to 0.7 mm; the lumped capacitance of any one of the lossy layers (1) is 3 pF to 6 pF.

4. The switchable wave absorbing / transmitting device according to claim 1, characterized in that: The metal connecting wire (6) has a length of 11.5 mm to 14 mm and a width of 1 mm to 2 mm; A lumped resistor (7) is embedded in the metal connecting wire (6); the gap spacing between any one of the lumped resistors (7) in the lossy layer (1) is 0.5 mm, and the value of the lumped resistor is 115 Ohm-175 Ohm.

5. The switchable wave absorbing / transmitting device according to claim 1, characterized in that: The frequency selective surface layer (3) comprises four metal patch layers and three dielectric isolation layers that are alternately stacked.

6. The switchable wave absorbing / transmitting device according to claim 5, characterized in that: The periodic unit structure in the frequency selective surface layer (3) is, from top to bottom, a first metal patch layer (11), a second dielectric isolation layer (12), a second metal patch layer (13), a third dielectric isolation layer (14), a third metal patch layer (15), a fourth dielectric isolation layer (16), and a fourth metal patch layer (17); the first metal patch layer (11) and the second metal patch layer (13) are both octagonal patterns, the third metal patch layer is a grid pattern, and the fourth metal patch layer is a rectangular patch pattern; The second metal patch layer (13) is connected to a pad (18) embedded in the third dielectric isolation layer (14) through a blind hole; the grid pattern of the third metal patch layer (15) is provided with a notch at a position corresponding to the pad (18), so that a gap is formed between the pad (18) and the third metal layer (15), and a second PIN diode (19) is loaded at the gap.

7. The switchable wave absorbing / transmitting device according to claim 1, characterized in that: The support layer (2) is made of either aramid paper honeycomb or PMI foam, with a thickness of 15 mm to 20 mm; preferably 18 mm.

8. The switchable wave absorbing / transmitting device according to claim 6, characterized in that: The metal used in the metal patch layer is one of gold, aluminum, copper or silver.

9. The switchable wave absorbing / transmitting device according to claim 6, characterized in that: The dielectric isolation layer is made of one of glass fiber reinforced epoxy resin material, polyimide organic polymer material, polytetrafluoroethylene high-frequency board, aramid honeycomb or PMI foam, with a thickness of 0.2 mm-2 mm; wherein the thickness of the first dielectric isolation layer is preferably 0.508 mm; the thickness of the second dielectric isolation layer is preferably 0.203 mm; the thickness of the third dielectric isolation layer and the fourth dielectric isolation layer is preferably 1.524 mm.

10. The switchable wave absorbing / transmitting device according to claim 1, characterized in that: The periodic unit structure in the loss layer (1) is an area defined by two adjacent switchable resonant windows (4) in the upper surface copper-clad plate and two adjacent switchable resonant windows (4) in the lower surface copper-clad plate; the area formed by two periodic unit structures in the frequency selective surface layer (3) is an orthographic projection of one periodic unit structure in the loss layer (1) on the frequency selective surface layer (3); The period of any periodic unit structure in the loss layer (1) is 28 mm to 32 mm; the period of any periodic unit structure in the frequency selective surface layer (3) is 14 mm to 16 mm.

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