Second-order dual-passband energy selection structure based on passband offset

Abstract

The invention provides a second-order dual-passband energy selection structure based on passband offset, which is a periodic structure and comprises a plurality of independent units which are periodically and seamlessly arranged in x and y directions, each independent unit comprises a laminated structure in the vertical direction, and each laminated structure sequentially comprises a first selectable layer, a first air layer, a second selectable layer, a second air layer, a third selectable layer, a third air layer, a fourth selectable layer, a fourth air layer and a fifth selectable layer from top to bottom; the first selectable layer comprises a first dielectric substrate and a first selectable layer metal zigzag structure; the second selectable layer comprises a second dielectric substrate and a second selectable layer metal zigzag structure; the third selectable layer comprises a third dielectric substrate and a metal square ring structure; the energy selection structure realizes second-order resonance and impedance matching by setting the thickness of an air layer; according to the invention, high-level electromagnetic protection efficiency can be obtained in a broadband range.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic protection technology, and in particular to a second-order dual-passband energy selection structure based on passband offset; specifically, it relates to a second-order dual-passband energy selection surface based on passband offset. This structure can be widely used in scenarios requiring multi-band operation and adaptive power protection, such as electromagnetic stealth platforms and electromagnetic protection systems for electronic equipment. Background Technology

[0002] In complex electromagnetic environments, high-power electromagnetic waves pose a serious threat to sensitive electronic equipment, making the development of protective structures capable of adapting to changes in electromagnetic wave power crucial. Energy selective surfaces (ESS), as a dynamic electromagnetic control structure, can achieve the dual functions of low-power signal transmission and high-power interference shielding by integrating nonlinear devices: they exhibit a passband at low power levels, ensuring normal communication; and at high power levels, the electromagnetic response is altered through the conduction of nonlinear devices, switching to a protective state.

[0003] Currently, most energy selective surface research focuses on single-passband designs, which operate in a limited frequency band and cannot meet the needs of multi-frequency communication and comprehensive electromagnetic protection. Therefore, dual-passband energy selective surfaces have emerged. However, existing dual-passband structures mostly employ first-order resonant units, which suffer from limited freedom in passband modulation, insufficient protection effectiveness during high- and low-power switching, and poor out-of-band suppression performance.

[0004] To overcome the aforementioned limitations, this invention proposes a second-order dual-passband energy selective surface based on passband shift. By employing a second-order resonant structure, passband selectivity and frequency modulation capabilities are significantly enhanced, enabling flexible design of two independent passbands. Furthermore, under high-power conditions, this structure can utilize nonlinear devices such as diodes to induce changes in resonant characteristics, achieving a significant shift in the passband frequency. This allows for high protection performance within the desired frequency band while maintaining structural response stability, better meeting the application requirements of modern multi-band, high-reliability electromagnetic protection. Summary of the Invention

[0005] This invention proposes a second-order dual-passband energy selection structure based on passband offset, which has a second-order dual-passband energy selection surface based on passband offset. This structure uses a second-order resonant unit and combines it with an air layer for impedance matching, which can achieve dual-passband characteristics with low insertion loss at different frequencies under low power incident conditions; while under the action of high power electromagnetic waves, by effectively offsetting the dual passband, a high level of electromagnetic protection performance can be obtained over a wide frequency range.

[0006] The present invention adopts the following technical solution.

[0007] A second-order dual-passband energy selection structure based on passband shift, having a second-order dual-passband energy selection surface based on passband shift, such as...Figure 1 As shown, the macroscopic image of the selection structure is a two-dimensional periodic structure, which includes a plurality of independent units arranged periodically and seamlessly in the x and y directions; Each independent unit includes a stacked structure in the vertical direction, and the stacked structure includes, from top to bottom in sequence: a first selectable layer (1), a first air layer (6), a second selectable layer (2), a second air layer (7), a third selectable layer (3), a third air layer (8), a fourth selectable layer (4), a fourth air layer (9), and a fifth selectable layer (5); The first selectable layer includes a first dielectric substrate and a first selectable layer metal zigzag structure; The second selectable layer includes a second dielectric substrate and a second selectable layer metal zigzag structure; The third selectable layer includes a third dielectric substrate and a metal square ring structure; The energy selection structure realizes second-order resonance and impedance matching by setting the thickness of the air layer.

[0008] When looking down on the independent unit, the sizes of the first selectable layer, the second selectable layer, the third selectable layer, the fourth selectable layer, the fifth selectable layer, the first air layer, the second air layer, the third air layer, and the fourth air layer are all the same as the size of the independent unit; The first to fourth air layers are filled between the respective selectable layers in sequence and are symmetrically distributed, and the planar sizes of all air layers are the same as the size of the independent unit; The top view size of the first selectable layer metal zigzag structure is larger than that of the second selectable layer metal zigzag structure.

[0009] As Figure 2 shown, the first selectable layer metal zigzag structure is located on the upper surface of the first dielectric substrate 1 a and includes a first metal zigzag structure 1 b with the same zigzag metal structure A, a second metal zigzag structure 1 c , a third metal zigzag structure 1 d , and a fourth metal zigzag structure 1 e ; The zigzag metal structure A includes two metal edges and three metal lines, and the two metal edges extend from the center of the first dielectric substrate to form a zigzag continuous "Z" - shaped metal structure with three metal lines; The first selectable layer further includes a first capacitor 1 f , a second capacitor 1 g , a first diode 1 h , a second diode 1 i , a third diode 1 j , and a fourth diode 1 k; The first capacitor is embedded in one metal side of the first metal meandering structure, the second capacitor is embedded in one metal side of the second metal meandering structure, the first diode and the second diode are in parallel and embedded in one metal side of the third metal meandering structure, and the third diode and the fourth diode are in parallel and embedded in one metal side of the fourth metal meandering structure; The first selectable layer has the same structure as the fifth selectable layer; The first to second capacitors (1 f 、1 g ) use CQ0402ARNPO9BNR40; The first to fourth diodes (1 h 、1 i 、1 j 、1 k ) use diodes that are all NSR201MX; The first dielectric substrate 1 a has the same size as the unit size and the dielectric substrate used is Rogers RT5008 with a dielectric constant of 2.2.

[0010] The second selectable layer metal meandering structure is located on the upper surface of the second dielectric substrate 2 a , and includes a fifth metal meandering structure 2 b , a sixth metal meandering structure 2 c , a seventh metal meandering structure 2 d , and an eighth metal meandering structure 2 e ; The meandering metal structure B includes three metal sides and three metal lines. Two metal sides extend from the center of the first dielectric substrate, and the second metal side is perpendicular to the third metal side. There is a gap between the third metal side and the edge of the independent unit. The three metal lines form a meandering metal structure, all of which are in a continuous "Z" shape; The second selectable layer further includes a fifth diode 2 f and a sixth diode 2 g ; The fifth diode 2 f is embedded in one metal side of the seventh metal meandering structure 2 d , and the sixth diode 2 g is embedded in one metal side of the eighth metal meandering structure 2 e .

[0011] The fifth to sixth diodes (2 f 、2 g ) use diodes that are all NSR201MX. The second dielectric substrate 2 aThe size is the same as the unit size, and the dielectric substrate used is Rogers RT5008 with a dielectric constant of 2.2. The second selectable layer 2 and the fourth selectable layer 4 have the same structure.

[0012] The first to fourth metal meandering structures are respectively arranged by rotating 90° along the center of the first selectable layer; the fifth to eighth metal meandering structures are respectively arranged by rotating 90° along the center of the second selectable layer; The first and second diodes and the third and fourth diodes are respectively arranged by rotating 90° along the center of the first selectable layer; The first capacitor and the second capacitor are respectively arranged by rotating 90° along the center of the first selectable layer; The fifth diode and the sixth diode are respectively arranged by rotating 90° along the center of the second selectable layer; The fifth diode and the sixth diode are respectively arranged by rotating 90° along the center of the second selectable layer.

[0013] As Figure 4 shown, the third selectable layer includes a third dielectric substrate 3 a and a metal square ring structure 3 located on its upper surface a ; the metal square ring structure 3 a is seamlessly arranged with the independent units; the metal square ring structure is in the shape of a "mouth"; The third dielectric substrate 3 a has the same size as the unit size, and the dielectric substrate used is Rogers RT5008 with a dielectric constant of 2.2.

[0014] As Figure 5 shown, the selectable layers are seamlessly separated by air layers, that is: the first to fourth air layers (6, 7, 8, 9) are successively located between adjacent selectable layers; The air layers are symmetrically distributed in structure, that is, the first air layer is the same as the fourth air layer 9, and the second air layer is the same as the third air layer. This design helps to achieve symmetric electromagnetic coupling and impedance matching.

[0015] As Figure 6 shown, when the second-order dual-band energy selection structure is expressed by an equivalent circuit model, specifically: The first metal meandering structure 1 in the first selectable layer b , the second metal meandering structure 1 c , the third metal meandering structure 1 d , the fourth metal meandering structure 1 e are equivalent to an inductor L 1; the first diode 1 h , the second diode 1 i are equivalent to parallel diodes D 1 and diodeD 2; First capacitor 1 f Second capacitor 1 g Equivalent to a capacitor C 1; The first dielectric substrate 1 in the first selectable layer 1 a Equivalent to a lossy transmission line; The equivalent circuit parameters of the first selectable layer and the fifth selectable layer are the same; The fifth metallic tortuous structure 2 in the second energy selection layer b 2. Sixth Metal Zigzag Structure c 2. Seventh Metal Zigzag Structure d 2. Eighth Metal Zigzag Structure e Equivalent to an inductor L 2; Fifth diode 2 f 6th diode 2 g Equivalent to a diode D 3; The gaps in the metal tortuous structure between units are equivalent to coupling capacitors. C 2; The second dielectric substrate 2 in the second selectable layer 2 a It is equivalent to a lossy transmission line; the equivalent circuit parameters of the second energy selection layer 2 and the fourth energy selection layer 4 are the same. The metal square ring structure 3 in the third energy selection layer 3 a Equivalent to an inductor L 3; The third dielectric substrate 3 in the third selectable layer 3 a Equivalent to a lossy transmission line; In the equivalent circuit model, the first to fourth air layers (6, 7, 8, 9) are respectively equivalent to lossless transmission lines with different characteristic impedances, propagation constants, and thicknesses.

[0016] Assume the correspondence between the first to fourth air layers in the equivalent circuit model is as follows: The parameters of the first air layer are... Z a1 , β a1 , t a1 The parameters of the second air layer are: Z a2 , β a2 , t a2 The parameters of the third air layer are: Z a2 , β a2 , t a2 The parameters of the fourth air layer are: Z a1 , β a1 , ta1 ; Assuming that the electromagnetic effects of the dielectric can be neglected in the equivalent circuit model, the ABCD transfer matrices of the first, second, and third selectable layers can be obtained from the equivalent circuit model, and are expressed by the following formulas: A 1 B 1 C 1 D 1. The transfer matrix is ​​used to describe the first selectable layer, where Z D1 and Z D2 The impedance of the diode varies with the incidence of electromagnetic waves of different power.

[0017] A 2 B 2 C 2 D 2. The transfer matrix is ​​used to describe the second selectable layer, where Z D3 The impedance of the diode varies with the incidence of electromagnetic waves of different power. A 3 B 3 C 3 D 3. The transfer matrix is ​​used to describe the third selectable layer; A a1 B a1 C a1 D a1 The transfer matrix is ​​used to describe the first and fourth air layers, where Z a1 The impedance of free air ( Z a1 =377Ω); β a1 and t a1 The propagation constants and thicknesses of the first and fourth air layers; A a2 B a2 C a2D a2 The transfer matrix is ​​used to describe the second and third air layers, where Z a2 The impedance of free air ( Z a2 =377Ω); β a2 and t a2 The propagation constants and thicknesses of the second and third air layers; ABCD The transmission matrix is ​​used to describe the surface of a second-order dual-passband energy-selective structure based on passband offset, and the formula for the transmission coefficient is obtained from this matrix: Under ideal conditions, the space characteristic impedance Z 0 is 377Ω; when low-power electromagnetic waves are incident, the diode is in the off state, which is equivalent to a cutoff capacitor; while when high-power electromagnetic waves are incident, the diode enters the on state, which is equivalent to a conduction resistance. Based on this equivalent circuit model and the change in impedance characteristics, two distinct electromagnetic states are achieved through an energy selection structure: one is the working state that allows signals to pass through, and the other is the protective state that achieves electromagnetic shielding.

[0018] The specific structural parameters of the energy-selective structure are as follows: p For the entire unit structure in x, y The length and width in the axial direction are also the first selectable layer 1, the second selectable layer 2, the third selectable layer 3, the fourth selectable layer 4, the fifth selectable layer 5, the first air layer 6, the second air layer 7, the third air layer 8, the fourth air layer 9, and the first dielectric substrate 1. a Second dielectric substrate 2 a Third dielectric substrate 3 a Length and width. w 1 represents the first to fourth metal zigzag structures (1) b 1 c 1 d 1 e The width of ) l 1. w 2 and l 2 represents the length, width, and length of the metal wire and its edge. w 3 represents the first and second diodes connected in parallel (1) h 1 i The width of ). l 3 and l 4. Fifth to eighth metal zigzag structures (2) b 2 c 2d 2 e The length of the metal edge and the length of the metal wire. w 4 and w 5 represents the width of the metal wire and the width of the metal edge. p - l 6) / 2 is a metal square ring structure (3) a The width of ). d 1 and d 2 represents the first to sixth diodes (1) h 1 i 1 j 1 k 2 f 2 g ( ) length and width. c 1 and c 2 represents the first to second capacitors (1) f 1 g ( ) length and width. t d1 First dielectric substrate 1 a thickness, t d2 For the second dielectric substrate 2 a thickness, t d3 For the third dielectric substrate 3 a thickness, t a1 The thicknesses of the first air layer 6 and the fourth air layer 9, t a2 The thickness of the second air layer 7 and the third air layer 8.

[0019] like Figure 7 As shown, the structure of this invention exhibits two second-order passbands with insertion losses below 3dB when low-power electromagnetic waves are incident: a low-frequency passband ranging from 2.19 to 2.64 GHz and a high-frequency passband ranging from 5 to 5.47 GHz, with relative bandwidths of 18.6% and 9%, respectively. When high-power electromagnetic waves are incident, the structure forms a protection band with a protection effectiveness higher than 20dB in the frequency ranges of 2.12–3.02 GHz and 4.73–5.8 GHz, with the highest protection effectiveness reaching over 60dB.

[0020] The simulation results of this invention are consistent in both equivalent circuit analysis and full-wave field co-simulation: under low power conditions, two low insertion loss second-order passbands are successfully achieved at low and high frequencies; under high power conditions, excellent electromagnetic protection effect is achieved in the operating frequency band over a wide bandwidth.

[0021] When the second-order dual-passband energy selection structure is working, when a low-power electromagnetic wave is incident on the second-order dual-passband energy selection surface, the diodes in each energy selection layer are in the off state, which is equivalent to a cutoff capacitor. The metal tortuous structure in the first and fifth energy selection layers, together with the diodes and capacitors, is equivalent to a large inductor and a small capacitor. The metal tortuous structure in the second and fourth energy selection layers, together with the diodes, is equivalent to a small inductor and a capacitor. The metal edge of the metal tortuous structure between units is equivalent to a coupling capacitor, which resonates with the metal square ring of the third energy selection layer. Impedance matching is then achieved through the first to fourth air layers, so that the overall structure exhibits two second-order passband characteristics with low insertion loss at low and high frequencies. When high-power electromagnetic waves are incident on a second-order dual-passband energy selective surface, the diodes in each energy selective layer quickly conduct, effectively acting as a very small on-resistance. In this state, the first energy selective layer is equivalent to a combination of a large inductor, resistor, and capacitor, while the second energy selective layer is equivalent to a combination of a small inductor, resistor, and capacitor. These layers work in conjunction with the metal square ring resonator unit of the third energy selective layer, and impedance is modulated through an air layer. This results in the overall structure exhibiting two second-order passband characteristics with low insertion loss at both low and high frequencies. As the diodes in each energy selective layer conduct, the equivalent capacitance of each layer increases, causing the two second-order passbands at low and high frequencies to shift to even lower frequencies, thus giving the structure high protection characteristics within the target frequency band.

[0022] The thickness ratio of the first dielectric substrate to the second dielectric substrate to the third dielectric substrate is 1:1:1; the thickness ratio of the first air layer to the second air layer is 2:5.

[0023] The first dielectric substrate is the same size as the independent unit, and its thickness is... t d1 The range is 0.06 λ L ~ 0.01 λ L The second dielectric substrate is the same size as the independent unit, and its thickness is... t d2 The range is 0.006 λ L ~ 0.01 λ L The third dielectric substrate is the same size as the independent unit, and its thickness is... t d3 The range is 0.006 λ L ~ 0.01 λ L The first air layer is the same size as the unit and has a thickness of [missing information]. t a1 Satisfying 0.008 λ L ~ 0.01 λL The second air layer is the same size as the unit and has a thickness of [missing information]. t a2 Satisfying 0.02 λ L ~ 0.025 λ L , λ L The wavelength corresponds to the starting frequency of the operating frequency band of the structure.

[0024] In this invention, each energy selector layer achieves effective resonant coupling and impedance matching through the adjustment of the intermediate air layer. This design enables the structure to stably generate two low insertion loss second-order passbands (low frequency and high frequency) under low power; when irradiated by high-power electromagnetic waves, the electromagnetic state of the structure switches, and the passband characteristics are shifted to low frequency, thereby obtaining high protection performance in the target frequency band.

[0025] Compared with the prior art, the second-order dual-passband energy selective surface based on passband shift of the present invention has the following advantages: (1) This invention achieves a power-adaptive dual-passband response through an innovative multi-layer structure design. Under low-power conditions, the structure can excite two second-order passbands (low frequency and high frequency) with extremely low insertion loss; while under high-power conditions, the passband characteristics are effectively shifted, transforming into a high-protection state. Among them, the first and fifth selectable layers adopt a thick, long, and tortuous metal structure with diodes and capacitors to generate the low-frequency passband; the second and fourth selectable layers adopt a relatively thin and short tortuous metal structure with a small number of diodes to generate the high-frequency passband, thereby realizing a flexible design of the passband frequency.

[0026] (2) This invention introduces an air layer into the design of an energy selective surface, making full use of the air layer's optimization effect on passband bandwidth in terms of impedance matching. This design is not only simple in structure and clear in principle, but also provides a feasible design idea and theoretical basis for the subsequent development of higher-order (such as third-order or multi-order) electromagnetic protection surfaces, and has broad application prospects in the fields of electromagnetic protection and electromagnetic interference suppression. Attached Figure Description

[0027] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments: Appendix Figure 1 This is a schematic diagram of a three-dimensional structural unit of a second-order dual-passband energy selective surface based on passband offset according to the present invention. Appendix Figure 2 This is a top view schematic diagram of the first / five-energy selection layer of a second-order dual-passband energy selection surface based on passband offset according to the present invention; Appendix Figure 3This is a top view schematic diagram of the second / fourth energy selection layer of a second-order dual-passband energy selection surface based on passband offset according to the present invention; Appendix Figure 4 This is a top view schematic diagram of the third energy selection layer of a second-order dual-passband energy selection surface based on passband offset according to the present invention. Appendix Figure 5 This is a front view schematic diagram of a second-order dual-passband energy selection surface based on passband offset according to the present invention; Appendix Figure 6 This is an equivalent circuit diagram of a second-order dual-passband energy selection surface based on passband offset according to the present invention. Figure 7 This is a schematic diagram of the transmission coefficient curve of a second-order dual-passband energy selective surface based on passband offset under normal incident high and low power electromagnetic wave irradiation. In the diagram: First selectable layer 1, Second selectable layer 2, Third selectable layer 3, Fourth selectable layer 4, Fifth selectable layer 5, First air layer 6, Second air layer 7, Third air layer 8, Fourth air layer 9, First dielectric substrate 1 a First metal tortuous structure 1 b Second metal tortuous structure 1 c Third metal tortuous structure 1 d Fourth metal tortuous structure 1 e First capacitor 1 f Second capacitor 1 g First diode 1 h Second diode 1 i Third diode 1 j Fourth diode 1 k Second dielectric substrate 2 a Fifth metal tortuous structure 2 b 2. Sixth Metal Zigzag Structure c 2. Seventh Metal Zigzag Structure d 2. Eighth Metal Zigzag Structure e Fifth diode 2 f 6th diode 2 g Third dielectric substrate 3 a 3. Metal square ring structure b . Detailed Implementation

[0028] As shown in the figure, a second-order dual-passband energy selection structure based on passband shift has a second-order dual-passband energy selection surface based on passband shift, such as... Figure 1 As shown, the macroscopic appearance of the selected structure is a two-dimensional periodic structure, which includes multiple independent units arranged periodically and seamlessly in the x and y directions. Each independent unit includes a stacked structure in the vertical direction, and the stacked structure successively includes from top to bottom: a first selectable layer 1, a first air layer 6, a second selectable layer 2, a second air layer 7, a third selectable layer 3, a third air layer 8, a fourth selectable layer 4, a fourth air layer 9, and a fifth selectable layer 5; The first selectable layer includes a first dielectric substrate and a first selectable layer metal meandering structure; The second selectable layer includes a second dielectric substrate and a second selectable layer metal meandering structure; The third selectable layer includes a third dielectric substrate and a metal square ring structure; The energy selection structure realizes second-order resonance and impedance matching by setting the thickness of the air layer.

[0029] When looking down on the independent unit, the sizes of the first selectable layer, the second selectable layer, the third selectable layer, the fourth selectable layer, the fifth selectable layer, the first air layer, the second air layer, the third air layer, and the fourth air layer are all the same as the size of the independent unit; The first to fourth air layers are successively filled between the respective selectable layers and are symmetrically distributed, and the planar sizes of all the air layers are the same as the size of the independent unit; The size of the first selectable layer metal meandering structure in the downward view is larger than that of the second selectable layer metal meandering structure.

[0030] As Figure 2 shown, the first selectable layer metal meandering structure is located on the upper surface of the first dielectric substrate 1 a and includes a first metal meandering structure 1 with the same meandering metal structure A b , a second metal meandering structure 1 c , a third metal meandering structure 1 d , and a fourth metal meandering structure 1 e ; ’ The meandering metal structure A includes two metal edges and three metal wires, and the two metal edges extend from the center of the first dielectric substrate to form a meandering metal structure in the shape of a continuous "Ji" character with three metal wires; The first selectable layer further includes a first capacitor 1 f , a second capacitor l g , a first diode 1 h , a second diode 1 i , a third diode 1 j ’ a fourth diode 1 k; The first capacitor is embedded in one metal side of the first metal meandering structure, the second capacitor is embedded in one metal side of the second metal meandering structure, the first diode and the second diode are connected in parallel and embedded in one metal side of the third metal meandering structure, and the third diode and the fourth diode are connected in parallel and embedded in one metal side of the fourth metal meandering structure; The first selectable layer has the same structure as the fifth selectable layer; The first to second capacitors 1 f 、1 g adopt CQ0402ARNPO9BNR40; The first to fourth diodes 1 h 、1 i 、1 j 、1 k adopt diodes that are all NSR201MX; The first dielectric substrate 1 a has the same size as the unit size and the adopted dielectric substrate is Rogers RT5008 with a dielectric constant of 2.2.

[0031] The metal meandering structure of the second selectable layer is located on the upper surface of the second dielectric substrate 2 a and includes a fifth metal meandering structure 2 b 、a sixth metal meandering structure 2 c 、a seventh metal meandering structure 2 d 、an eighth metal meandering structure 2 e ; The meandering metal structure B includes three metal sides and three metal lines. Two metal sides extend from the center of the first dielectric substrate, and the second metal side is perpendicular to the third metal side. There is a gap between the third metal side and the edge of the independent unit. The three metal lines form a meandering metal structure, all in a continuous "Z" shape; The second selectable layer further includes a fifth diode 2 f 、a sixth diode 2 g ; The fifth diode 2 f is embedded in one metal side of the seventh metal meandering structure 2 d and the sixth diode 2 g is embedded in one metal side of the eighth metal meandering structure 2 e .

[0032] The fifth to sixth diodes 2 f 、2 g adopt diodes that are all NSR201MX. The second dielectric substrate 2 aThe size is the same as the unit size, and the dielectric substrate used is Rogers RT5008 with a dielectric constant of 2.2. The second selectable layer 2 and the fourth selectable layer 4 have the same structure.

[0033] The first to fourth metal meandering structures are respectively arranged by rotating 90° along the center of the first selectable layer; the fifth to eighth metal meandering structures are respectively arranged by rotating 90° along the center of the second selectable layer; The first and second diodes and the third and fourth diodes are respectively arranged by rotating 90° along the center of the first selectable layer; The first capacitor and the second capacitor are respectively arranged by rotating 90° along the center of the first selectable layer; The fifth diode and the sixth diode are respectively arranged by rotating 90° along the center of the second selectable layer; The fifth diode and the sixth diode are respectively arranged by rotating 90° along the center of the second selectable layer.

[0034] As Figure 4 shown, the third selectable layer includes a third dielectric substrate 3 a and a metal square ring structure 3 located on its upper surface a ; the metal square ring structure 3 a is seamlessly arranged with the independent units; the metal square ring structure is in the shape of a "mouth"; the third dielectric substrate 3 a has the same size as the unit size, and the dielectric substrate used is Rogers RT5008 with a dielectric constant of 2.2.

[0035] As Figure 5 shown, each selectable layer is seamlessly separated by an air layer, that is: the first to fourth air layers 6, 7, 8, 9 are successively located between adjacent selectable layers; The air layers are symmetrically distributed in structure, that is, the first air layer is the same as the fourth air layer 9, and the second air layer is the same as the third air layer. This design helps to achieve symmetric electromagnetic coupling and impedance matching.

[0036] As Figure 6 shown, when the second-order dual-band energy selection structure is expressed by an equivalent circuit model, specifically: The first metal meandering structure 1 in the first selectable layer b , the second metal meandering structure 1 c , the third metal meandering structure 1 d , the fourth metal meandering structure 1 e are equivalent to an inductor L 1; the first diode 1 h , the second diode 1 i are equivalent to parallel diodes D 1 and diodeD 2; First capacitor 1 f Second capacitor 1 g Equivalent to a capacitor C 1; The first dielectric substrate 1 in the first selectable layer 1 a Equivalent to a lossy transmission line; The equivalent circuit parameters of the first selectable layer and the fifth selectable layer are the same; The fifth metallic tortuous structure 2 in the second energy selection layer b 2. Sixth Metal Zigzag Structure c 2. Seventh Metal Zigzag Structure d 2. Eighth Metal Zigzag Structure e Equivalent to an inductor L 2; Fifth diode 2 f 6th diode 2 g Equivalent to a diode D 3; The gaps in the metal tortuous structure between units are equivalent to coupling capacitors. C 2; The second dielectric substrate 2 in the second selectable layer 2 a It is equivalent to a lossy transmission line; the equivalent circuit parameters of the second energy selection layer 2 and the fourth energy selection layer 4 are the same. The metal square ring structure 3 in the third energy selection layer 3 a Equivalent to an inductor L 3; The third dielectric substrate 3 in the third selectable layer 3 a Equivalent to a lossy transmission line; In the equivalent circuit model, the first to fourth air layers 6, 7, 8, and 9 are respectively equivalent to lossless transmission lines with different characteristic impedances, propagation constants, and thicknesses.

[0037] Assume the correspondence between the first to fourth air layers in the equivalent circuit model is as follows: The parameters of the first air layer are... Z a1 , β a1 , t a1 The parameters of the second air layer are: Z a2 , β a2 , t a2 The parameters of the third air layer are: Z a2 , β a2 , t a2 The parameters of the fourth air layer are: Z a1 , β a1 , ta1 ; Assuming that the electromagnetic effects of the dielectric can be neglected in the equivalent circuit model, the ABCD transfer matrices of the first, second, and third selectable layers can be obtained from the equivalent circuit model, and are expressed by the following formulas: A 1 B 1 C 1 D 1. The transfer matrix is ​​used to describe the first selectable layer, where Z D1 and Z D2 The impedance of the diode varies with the incidence of electromagnetic waves of different power.

[0038] A 2 B 2 C 2 D 2. The transfer matrix is ​​used to describe the second selectable layer, where Z D3 The impedance of the diode varies with the incidence of electromagnetic waves of different power. A 3 B 3 C 3 D 3. The transfer matrix is ​​used to describe the third selectable layer; A a1 B a1 C a1 D a1 The transfer matrix is ​​used to describe the first and fourth air layers, where Z a1 Resistance of free air Z a1 =377Ω; β a1 and t a1 The propagation constants and thicknesses of the first and fourth air layers; A a2 B a2 C a2 Da2 The transfer matrix is ​​used to describe the second and third air layers, where Z a2 Resistance of free air Z a2 =377Ω; β a2 and t a2 The propagation constants and thicknesses of the second and third air layers; ABCD The transmission matrix is ​​used to describe the surface of a second-order dual-passband energy-selective structure based on passband offset, and the formula for the transmission coefficient is obtained from this matrix: Under ideal conditions, the space characteristic impedance Z 0 is 377Ω; when low-power electromagnetic waves are incident, the diode is in the off state, which is equivalent to a cutoff capacitor; while when high-power electromagnetic waves are incident, the diode enters the on state, which is equivalent to a conduction resistance. Based on this equivalent circuit model and the change in impedance characteristics, two distinct electromagnetic states are achieved through an energy selection structure: one is the working state that allows signals to pass through, and the other is the protective state that achieves electromagnetic shielding.

[0039] The specific structural parameters of the energy-selective structure are as follows: p For the entire unit structure in x, y The length and width in the axial direction are also the first selectable layer 1, the second selectable layer 2, the third selectable layer 3, the fourth selectable layer 4, the fifth selectable layer 5, the first air layer 6, the second air layer 7, the third air layer 8, the fourth air layer 9, and the first dielectric substrate 1. a Second dielectric substrate 2 a Third dielectric substrate 3 a Length and width. w 1 represents the first to fourth metal zigzag structures. b 1 c 1 d 1 e width, l 1. w 2 and l 2 represents the length, width, and length of the metal wire and its edge. w 3 represents the first and second diodes connected in parallel. h 1 i The width. l 3 and l 4. Fifth to Eighth Metal Zigzag Structure 2 b 2 c 2 d 2 eThe length of the metal edge and the length of the metal wire. w 4 and w 5 represents the width of the metal wire and the width of the metal edge. p - l 6) / 2 is a metal square ring structure 3 a The width. d 1 and d 2 represents the first to sixth diodes 1 h 1 i 1 j 1 k 2 f 2 g Length and width. c 1 and c 2 represents the first to second capacitors 1 f 1 g Length and width. t d1 First dielectric substrate 1 a thickness, t d2 For the second dielectric substrate 2 a thickness, t d3 For the third dielectric substrate 3 a thickness, t a1 The thicknesses of the first air layer 6 and the fourth air layer 9, t a2 The thickness of the second air layer 7 and the third air layer 8.

[0040] like Figure 7 As shown, the structure of this invention exhibits two second-order passbands with insertion losses below 3dB when low-power electromagnetic waves are incident: a low-frequency passband ranging from 2.19 to 2.64 GHz and a high-frequency passband ranging from 5 to 5.47 GHz, with relative bandwidths of 18.6% and 9%, respectively. When high-power electromagnetic waves are incident, the structure forms a protection band with a protection effectiveness higher than 20dB in the frequency ranges of 2.12–3.02 GHz and 4.73–5.8 GHz, with the highest protection effectiveness reaching over 60dB.

[0041] The simulation results of this invention are consistent in both equivalent circuit analysis and full-wave field co-simulation: under low power conditions, two low insertion loss second-order passbands are successfully achieved at low and high frequencies; under high power conditions, excellent electromagnetic protection effect is achieved in the operating frequency band over a wide bandwidth.

[0042] When the second-order dual-passband energy selection structure is working, when a low-power electromagnetic wave is incident on the second-order dual-passband energy selection surface, the diodes in each energy selection layer are in the off state, which is equivalent to a cutoff capacitor. The metal tortuous structure in the first and fifth energy selection layers, together with the diodes and capacitors, is equivalent to a large inductor and a small capacitor. The metal tortuous structure in the second and fourth energy selection layers, together with the diodes, is equivalent to a small inductor and a capacitor. The metal edge of the metal tortuous structure between units is equivalent to a coupling capacitor, which resonates with the metal square ring of the third energy selection layer. Impedance matching is then achieved through the first to fourth air layers, so that the overall structure exhibits two second-order passband characteristics with low insertion loss at low and high frequencies. When high-power electromagnetic waves are incident on a second-order dual-passband energy selective surface, the diodes in each energy selective layer quickly conduct, effectively acting as a very small on-resistance. In this state, the first energy selective layer is equivalent to a combination of a large inductor, resistor, and capacitor, while the second energy selective layer is equivalent to a combination of a small inductor, resistor, and capacitor. These layers work in conjunction with the metal square ring resonator unit of the third energy selective layer, and impedance is modulated through an air layer. This results in the overall structure exhibiting two second-order passband characteristics with low insertion loss at both low and high frequencies. As the diodes in each energy selective layer conduct, the equivalent capacitance of each layer increases, causing the two second-order passbands at low and high frequencies to shift to even lower frequencies, thus giving the structure high protection characteristics within the target frequency band.

[0043] The thickness ratio of the first dielectric substrate to the second dielectric substrate to the third dielectric substrate is 1:1:1; the thickness ratio of the first air layer to the second air layer is 2:5.

[0044] The first dielectric substrate is the same size as the independent unit, and its thickness is... t d1 The range is 0.06 λ L ~ 0.01 λ L The second dielectric substrate is the same size as the independent unit, and its thickness is... t d2 The range is 0.006 λ L ~ 0.01 λ L The third dielectric substrate is the same size as the independent unit, and its thickness is... t d3 The range is 0.006 λ L ~ 0.01 λ L The first air layer is the same size as the unit and has a thickness of [missing information]. t a1 Satisfying 0.008 λ L ~ 0.01 λL The second air layer is the same size as the unit and has a thickness of [missing information]. t a2 Satisfying 0.02 λ L ~ 0.025 λ L , λ L The wavelength corresponds to the starting frequency of the operating frequency band of the structure.

[0045] In this example, the first and second diodes are connected in a forward parallel configuration and embedded in a metal edge of the third metal zigzag structure. The third and fourth diodes are also connected in the same forward parallel configuration and embedded in a metal edge of the fourth metal zigzag structure. The first to sixth diodes and the first to second capacitors are integrated by soldering their surface mount pads to the metal strips pre-reserved on the metal zigzag structure to achieve electrical connection.

[0046] Example: In this example, as Figure 1 As shown, a second-order dual-passband energy selectable surface based on passband offset has a vertically arranged structure, including periodically distributed and seamlessly filled units. Each unit includes, from top to bottom, a first energy selectable layer 1, a first air layer 6, a second energy selectable layer 2, a second air layer 7, a third energy selectable layer 3, a third air layer 8, a fourth energy selectable layer 4, a fourth air layer 9, and a fifth energy selectable layer 5.

[0047] like Figure 2 As shown, the first selectable layer 1 includes a first dielectric substrate 1. a and the first metal zigzag structure 1 located on its upper surface b Second metal tortuous structure 1 c Third metal tortuous structure 1 d Fourth metal tortuous structure 1 e First capacitor 1 f Second capacitor 1 g First diode 1 h Second diode 1 i Third diode 1 j Fourth diode 1 k ; the first to fourth metal tortuous structures (1 b 1 c 1 d 1 e The structures are identical, each consisting of two metal edges and three metal lines; the first to second metal zigzag structures (1 b 1 c From the first to the second capacitor (1) f 1 gThe third to fourth metal zigzag structures (1) are connected to the structure. d 1 e ) from the first to the fourth diode (1 h 1 i 1 j 1 k ) connected; the first to second capacitors (1 f 1 g The first to fourth diodes (1) are CQ0402ARNPO9BNR40. h 1 i 1 j 1 k The diodes used are all NSR201MX; the first dielectric substrate 1 a The size is the same as the unit size, and the dielectric substrate used is Rogers RT5008 with a dielectric constant of 2.2. The first selectable layer 1 and the fifth selectable layer 5 have the same structure.

[0048] like Figure 3 As shown, the second selectable layer 2 includes a second dielectric substrate 2. a And the fifth metal zigzag structure 2 located on its upper surface b 2. Sixth Metal Zigzag Structure c 2. Seventh Metal Zigzag Structure d 2. Eighth Metal Zigzag Structure e Fifth diode 2 f 6th diode 2 g The fifth metal tortuous structure 2 b 2. Sixth Metal Zigzag Structure c 2. Seventh Metal Zigzag Structure d 2. Eighth Metal Zigzag Structure e The structure is the same; the fifth diode 2 f Embedded in the seventh metal tortuous structure 2 d The sixth diode 2 g Embedded in the eighth metal tortuous structure 2 e The fifth and sixth diodes (2) f 2 g The diodes used are all NSR201MX. The second dielectric substrate 2 a The size is the same as the unit size, and the dielectric substrate used is Rogers RT5008 with a dielectric constant of 2.2. The second selectable layer 2 and the fourth selectable layer 4 have the same structure.

[0049] like Figure 4 As shown, the third selectable layer 3 includes a third dielectric substrate 3. a and the metal square ring structure 3 located on its upper surfacea The metal square ring structure 3 a Seamlessly arranged with the unit; the third dielectric substrate 3 a The size is the same as the cell size and the dielectric substrate used is Rogers RT5008 with a dielectric constant of 2.2.

[0050] like Figure 5 As shown, each selectable layer is seamlessly separated by an air layer: the first to fourth air layers (6, 7, 8, 9) are located sequentially between adjacent selectable layers. The air layers are structurally symmetrically distributed, that is, the first air layer 6 is the same as the fourth air layer 9, and the second air layer 7 is the same as the third air layer 8. This design helps to achieve symmetrical electromagnetic coupling and impedance matching.

[0051] like Figure 6 As shown, the second-order dual-passband energy selective surface based on passband offset of the present invention can be equivalent to a specific equivalent circuit model.

[0052] The first metal zigzag structure 1 in the first selectable layer 1 b Second metal tortuous structure 1 c Third metal tortuous structure 1 d Fourth metal tortuous structure 1 e It can be equivalent to an inductor L 1; First diode 1 h Second diode 1 i It can be equivalent to diodes in parallel. D 1 and diode D 2; First capacitor 1 f Second capacitor 1 g It can be equivalent to a capacitor. C 1; First dielectric substrate 1 in the first selectable layer 1 a It can be equivalent to a lossy transmission line; the equivalent circuit parameters of the first energy selection layer 1 and the fifth energy selection layer 5 are the same; The fifth metal zigzag structure 2 in the second energy selection layer 2 b 2. Sixth Metal Zigzag Structure c 2. Seventh Metal Zigzag Structure d 2. Eighth Metal Zigzag Structure e It can be equivalent to an inductor L 2; Fifth diode 2 f 6th diode 2 g It can be equivalent to a diode. D 3; The gaps in the tortuous metal structure between units can be considered equivalent to coupling capacitors. C 2; The second dielectric substrate 2 in the second selectable layer 2 a It can be equivalent to a lossy transmission line; the equivalent circuit parameters of the second energy selection layer 2 and the fourth energy selection layer 4 are the same; The metal square ring structure 3 in the third energy selection layer 3 a It can be equivalent to an inductor L 3; The third dielectric substrate 3 in the third selectable layer 3 a It can be equivalent to a lossy transmission line; The first to fourth air layers (6, 7, 8, 9) can be represented in circuits as lossless transmission lines with different characteristic impedances, propagation constants, and thicknesses. Their corresponding relationships are as follows: The parameters of the first air layer 6 are... Z a1 , β a1 , t a1 The parameters of the second air layer are 7. Z a2 , β a2 , t a2 The parameters of the third air layer are 8. Z a2 , β a2 , t a2 The parameters of the fourth air layer are 9. Z a1 , β a1 , t a1 .

[0053] like Figure 7 As shown, the structure of this invention exhibits two second-order passbands with insertion losses below 3dB when low-power electromagnetic waves are incident: a low-frequency passband ranging from 2.19 to 2.64 GHz and a high-frequency passband ranging from 5 to 5.47 GHz, with relative bandwidths of 18.6% and 9%, respectively. When high-power electromagnetic waves are incident, the structure forms a protection band with a protection effectiveness higher than 20dB in the frequency ranges of 2.12–3.02 GHz and 4.73–5.8 GHz, with the highest protection effectiveness reaching over 60dB.

[0054] It can be seen that the simulation results of this invention are consistent in both equivalent circuit analysis and full-wave field co-simulation: under low power conditions, two low insertion loss second-order passbands are successfully achieved at low and high frequencies; under high power conditions, excellent electromagnetic protection effect is achieved in the operating frequency band over a wide frequency range.

[0055] The above description is merely a preferred embodiment of the present invention. It should be noted that for those skilled in the art, without departing from the principle of the present invention, the types or parameters of diodes, capacitors, and other components used in the first to fifth selectable layers can be replaced, the dielectric properties or structural forms of the first to fourth air layers can be adjusted, or the overall size can be reasonably scaled. All such equivalent substitutions, structural modifications, or parameter improvements should be considered to fall within the protection scope defined by the claims of the present invention.

Claims

1. A second-order dual-passband energy selection structure based on passband shift, having a second-order dual-passband energy selection surface based on passband shift, characterized in that: The selection structure is a periodic structure, which includes a plurality of independent units arranged periodically and seamlessly in the x and y directions; Each independent unit includes a stacked structure in the vertical direction, and the stacked structure includes, from top to bottom in sequence: a first selectable layer (1), a first air layer (6), a second selectable layer (2), a second air layer (7), a third selectable layer (3), a third air layer (8), a fourth selectable layer (4), a fourth air layer (9), and a fifth selectable layer (5); The first selectable layer includes a first dielectric substrate and a first selectable layer metal meandering structure; The second selectable layer includes a second dielectric substrate and a second selectable layer metal meandering structure; The third selectable layer includes a third dielectric substrate and a metal square ring structure; The energy selection structure realizes second-order resonance and impedance matching by setting the thickness of the air layer.

2. The second-order dual-passband energy selection structure based on passband shift according to claim 1, characterized in that: When looking down on the independent unit, the sizes of the first selectable layer, the second selectable layer, the third selectable layer, the fourth selectable layer, the fifth selectable layer, the first air layer, the second air layer, the third air layer, and the fourth air layer are all the same as the size of the independent unit; The first to fourth air layers are sequentially filled between the selectable layers and are symmetrically distributed, and the planar sizes of all air layers are the same as the size of the independent unit; The top view size of the first selectable layer metal meandering structure is larger than that of the second selectable layer metal meandering structure.

3. The second-order dual-passband energy selection structure based on passband shift according to claim 1, characterized in that: The first selectable layer metal zigzag structure is located on the first dielectric substrate 1. a The upper surface includes a first metal zigzag structure 1 having the same zigzag metal structure A. b Second metal tortuous structure 1 c Third metal tortuous structure 1 d Fourth metal tortuous structure 1 e ; The meandering metal structure A includes two metal edges and three metal lines. The two metal edges extend from the center of the first dielectric substrate, and the three metal lines form a meandering continuous "Z" - shaped metal structure; The first selectable layer also includes a first capacitor 1 f Second capacitor 1 g First diode 1 h Second diode 1 i Third diode 1 j Fourth diode 1 k ; The first capacitor is embedded in one metal edge of the first metal meandering structure, the second capacitor is embedded in one metal edge of the second metal meandering structure, the first diode and the second diode are connected in parallel and embedded in one metal edge of the third metal meandering structure, and the third diode and the fourth diode are connected in parallel and embedded in one metal edge of the fourth metal meandering structure; The first selectable layer and the fifth selectable layer have the same structure; First dielectric substrate 1 a The size is the same as the unit size.

4. A second-order dual-passband energy selection structure based on passband shift according to claim 2, characterized in that: The second selectable layer metal tortuous structure is located on the second dielectric substrate 2. a The upper surface includes a fifth metal zigzag structure 2 having the same zigzag metal structure B. b 2. Sixth Metal Zigzag Structure c 2. Seventh Metal Zigzag Structure d 2. Eighth Metal Zigzag Structure e ; The meandering metal structure B includes three metal edges and three metal lines. Two metal edges extend from the center of the first dielectric substrate, and the second metal edge is perpendicular to the third metal edge. There is a gap between the third metal edge and the edge of the independent unit, and the three metal lines form a meandering metal structure, all of which are in a continuous "Z" - shaped; The second selectability layer also includes a fifth diode 2. f 6th diode 2 g The fifth diode 2 f Embedded in the seventh metal tortuous structure 2 d A metal edge, the sixth diode 2 g Embedded in the eighth metal tortuous structure 2 e A metal edge; The second dielectric substrate 2 a The size is the same as the unit size.

5. A second-order dual-passband energy selection structure based on passband shift according to claim 3, characterized in that: The first to fourth metal meandering structures are respectively arranged by rotating 90° around the center of the first selectable layer; the fifth to eighth metal meandering structures are respectively arranged by rotating 90° around the center of the second selectable layer; The first and second diodes and the third and fourth diodes are respectively arranged by rotating 90° around the center of the first selectable layer; The first capacitor and the second capacitor are respectively arranged by rotating 90° around the center of the first selectable layer; The fifth diode and the sixth diode are respectively arranged by rotating 90° around the center of the second selectable layer; The fifth diode and the sixth diode are respectively arranged by rotating 90° around the center of the second selectable layer.

6. A second-order dual-passband energy selection structure based on passband shift according to claim 3, characterized in that: The third selectable layer includes a third dielectric substrate 3 a and a metal square ring structure 3 located on its upper surface a ; the metal square ring structure 3 a is seamlessly arranged with the independent units; the metal square ring structure is in the shape of a "square frame" The third dielectric substrate 3 a Size is the same as unit size; The selectable layers are seamlessly separated by air layers, that is: the first to fourth air layers are sequentially located between adjacent selectable layers; The air layers are symmetrically distributed in structure, that is, the first air layer is the same as the fourth air layer 9, and the second air layer is the same as the third air layer, so as to achieve symmetrical electromagnetic coupling and impedance matching.

7. A second-order dual-passband energy selection structure based on passband shift according to claim 6, characterized in that: The second-order dual-passband energy selection structure, when expressed in terms of an equivalent circuit model, is specifically as follows: The first metallic tortuous structure 1 in the first energy selectable layer b Second metal tortuous structure 1 c Third metal tortuous structure 1 d Fourth metal tortuous structure 1 e Equivalent to an inductor L 1; First diode 1 h Second diode 1 i Equivalent to diodes in parallel D 1 and diode D 2; First capacitor 1 f Second capacitor 1 g Equivalent to a capacitor C 1; The first dielectric substrate 1 in the first selectable layer 1 a Equivalent to a lossy transmission line; The equivalent circuit parameters of the first selectable layer and the fifth selectable layer are the same; The fifth metallic tortuous structure 2 in the second energy selection layer b 2. Sixth Metal Zigzag Structure c 2. Seventh Metal Zigzag Structure d 2. Eighth Metal Zigzag Structure e Equivalent to an inductor L 2; Fifth diode 2 f 6th diode 2 g Equivalent to a diode D 3; The gaps in the metal tortuous structure between units are equivalent to coupling capacitors. C 2; The second dielectric substrate 2 in the second selectable layer 2 a It is equivalent to a lossy transmission line; the equivalent circuit parameters of the second energy selection layer 2 and the fourth energy selection layer 4 are the same. The metal square ring structure 3 in the third energy selection layer 3 a Equivalent to an inductor L 3; The third dielectric substrate 3 in the third selectable layer 3 a Equivalent to a lossy transmission line; In the equivalent circuit model, the first to fourth air layers are respectively equivalent to lossless transmission lines with different characteristic impedances, propagation constants, and thicknesses.

8. A second-order dual-passband energy selection structure based on passband shift according to claim 7, characterized in that: Assume the correspondence between the first to fourth air layers in the equivalent circuit model is as follows: The parameters of the first air layer are... Z a1 , β a1 , t a1 The parameters of the second air layer are: Z a2 , β a2 , t a2 The parameters of the third air layer are: Z a2 , β a2 , t a2 The parameters of the fourth air layer are: Z a1 , β a1 , t a1 ; Assuming that the electromagnetic effects of the dielectric can be neglected in the equivalent circuit model, the ABCD transfer matrices of the first, second, and third selectable layers can be obtained from the equivalent circuit model, and are expressed by the following formulas: ； A 1 B 1 C 1 D 1. The transfer matrix is ​​used to describe the first selectable layer, where Z D1 and Z D2 The impedance of the diode varies with the incidence of electromagnetic waves of different power. ； A 2 B 2 C 2 D 2. The transfer matrix is ​​used to describe the second selectable layer, where Z D3 The impedance of the diode varies with the incidence of electromagnetic waves of different power. A 3 B 3 C 3 D 3. The transfer matrix is ​​used to describe the third selectable layer; A a1 B a1 C a1 D a1 The transfer matrix is ​​used to describe the first and fourth air layers, where Z a1 The impedance of free air; β a1 and t a1 The propagation constants and thicknesses of the first and fourth air layers; A a2 B a2 C a2 D a2 The transfer matrix is ​​used to describe the second and third air layers, where Z a2 The impedance of free air; β a2 and t a2 The propagation constants and thicknesses of the second and third air layers; ABCD The transmission matrix is ​​used to describe the surface of a second-order dual-passband energy-selective structure based on passband offset, and the formula for the transmission coefficient is obtained from this matrix: When low-power electromagnetic waves are incident, the diode is in the off state, equivalent to a cutoff capacitor; while when high-power electromagnetic waves are incident, the diode enters the on state, equivalent to a conduction resistor. Based on this equivalent circuit model and the change in impedance characteristics, two electromagnetic states are achieved through an energy selection structure: one is the working state that allows signals to pass through, and the other is the protective state that achieves electromagnetic shielding.

9. A second-order dual-passband energy selection structure based on passband shift according to claim 8, characterized in that: When the second-order dual-passband energy selection structure is working, when a low-power electromagnetic wave is incident on the second-order dual-passband energy selection surface, the diodes in each energy selection layer are in the off state, which is equivalent to a cutoff capacitor. The metal tortuous structure in the first and fifth energy selection layers, together with the diodes and capacitors, is equivalent to a large inductor and a small capacitor. The metal tortuous structure in the second and fourth energy selection layers, together with the diodes, is equivalent to a small inductor and a capacitor. The metal edge of the metal tortuous structure between units is equivalent to a coupling capacitor, which resonates with the metal square ring of the third energy selection layer. Impedance matching is then achieved through the first to fourth air layers, so that the overall structure exhibits two second-order passband characteristics with low insertion loss at low and high frequencies. When a high-power electromagnetic wave is incident on a second-order dual-passband energy selective surface, the diodes in each energy selective layer conduct, effectively acting as a very small on-resistance. In this state, the first energy selective layer is equivalent to a combination of a large inductor, resistor, and capacitor, while the second energy selective layer is equivalent to a combination of a small inductor, resistor, and capacitor. These layers work in conjunction with the metal square ring resonator unit of the third energy selective layer, and impedance is modulated through an air layer. This results in the overall structure exhibiting two second-order passband characteristics with low insertion loss at both low and high frequencies. Because the diodes in each energy selective layer are conducting, the equivalent capacitance of each layer increases, causing the two second-order passbands at low and high frequencies to shift to even lower frequencies. This gives the structure high protection characteristics within the target frequency band.

10. A second-order dual-passband energy selection structure based on passband shift according to claim 1, characterized in that: The thickness ratio of the first dielectric substrate to the second dielectric substrate to the third dielectric substrate is 1:1:1; the thickness ratio of the first air layer to the second air layer is 2:

5. The first dielectric substrate is the same size as the independent unit, and its thickness is... t d1 The range is 0.06 λ L ~ 0.01 λ L The second dielectric substrate is the same size as the independent unit, and its thickness is... t d2 The range is 0.006 λ L ~ 0.01 λ L The third dielectric substrate is the same size as the independent unit, and its thickness is... t d3 The range is 0.006 λ L ~ 0.01 λ L The first air layer is the same size as the individual unit, and its thickness is... t a1 The range is 0.008 λ L ~ 0.01 λ L ; The second air layer is the same size as the individual unit, and its thickness is... t a2 The range is 0.02 λ L ~ 0.025 λ L , λ L The wavelength corresponding to the starting frequency of the operating band of the energy-selective structure.

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