A single-layer wave absorber with evanescent wave absorbing characteristics and a design method thereof

Abstract

The application provides a single-layer wave absorber with evanescent wave absorbing characteristics and a design method thereof. The single-layer evanescent wave absorber comprises a dielectric substrate and a single-layer resistive structure attached to the dielectric substrate, and the resistive structure comprises a plurality of periodically capacitive structures arranged at equal intervals through patterning. The application environment of the wave absorber is the near-field region of a radiation source in a metal waveguide. The environmental configuration of the wave absorber further comprises a metal rectangular waveguide and two noise source feedings, and the wave absorber is arranged at the cross section of the rectangular waveguide. The design method derives the specific physical size of the periodic capacitive structure according to a predefined working frequency f0, a dispersion curve and a capacitive structure equivalent surface impedance calculation formula. The wave absorber has the advantages of simple structure, low profile and easy processing due to the single-layer structure. In addition, the wave absorber is expected to be applied to the near field of an integrated circuit due to the characteristics of customizable working frequency, compact size and the ability to absorb near-field evanescent waves.

Description

Technical Field

[0001] This invention relates to the field of microwave absorber design technology, and in particular to a single-layer absorber with evanescent wave absorption characteristics and its design method. Background Technology

[0002] Microwave absorbers have attracted widespread attention because they can absorb harmful electromagnetic interference, reduce radar cross-section, and prevent electronic systems and components from being affected by noise. These absorbers are widely used in wireless communication systems, including base stations, mobile phones, and satellites. In addition, the rapidly developing three-dimensional high-density integrated circuit environment and the corresponding noise interference have also placed higher standards and requirements on microwave absorbers.

[0003] While traditional microwave absorbers can absorb far-field plane waves, they lack the ability to absorb near-field evanescent waves, making them difficult to apply in the near-field of complex, dense, and rapidly evolving electromagnetic environments. This invention provides an effective and simple method for suppressing near-field noise interference. Summary of the Invention

[0004] One objective of this invention is to provide a design method for a single-layer absorber with evanescent wave absorption characteristics.

[0005] The objective of this invention is achieved through the following technical solution: the single-layer absorber comprises a single-layer resistive structure, which includes a plurality of periodically arranged, patterned capacitive structures. The design method for the single-layer absorber comprises the following specific steps:

[0006] 1) Predefine the operating frequency f0 of the evanescent wave absorber and the operating environment parameters according to the requirements. The operating environment parameters include the cross-sectional dimensions of the rectangular waveguide.

[0007] 2) Based on the operating environment parameters, determine the propagation constant k of the evanescent wave absorber along the Y direction of the rectangular waveguide at a predefined operating frequency f0. y ;

[0008] 3) Calculate the specific impedance Z corresponding to the periodic capacitive structure based on the propagation constant and wave vector matching relationship. s ;

[0009] 4) Based on the impedance Z of the resistive-capacitive structure s Calculate the patch size of the periodic capacitive structure and the gap size between adjacent patches.

[0010] Preferably, in step 2), the propagation constant k of the evanescent wave absorber along the Y direction of the waveguide at the operating frequency f0 is determined. y The specific method is as follows:

[0011]

[0012] In the formula, c is the propagation speed of electromagnetic waves in a vacuum, f0 is the predefined operating frequency of the evanescent wave absorber, a is the dimension of the wide side of the rectangular waveguide cross-section, and k y The propagation constant along the Y direction of the rectangular waveguide at a predefined operating frequency f0.

[0013] Preferably, in step 3), the specific impedance Z corresponding to the periodic capacitive structure is calculated. s The method is as follows:

[0014] According to the propagation constant wave vector matching relationship, that is, let Im(k y )=Im(k l ), k l Let be the propagation constant along the Y direction in a capacitive structure, and the specific mathematical relationship is as follows:

[0015]

[0016] In the formula, β is the propagation constant along the X direction calculated from the surface wave supported by the capacitive surface. Based on the surface wave dispersion curve equation supported by the capacitive surface, the impedance Z of the corresponding periodic resistive capacitive structure is derived. s Z s The mathematical relationship between β and β is:

[0017]

[0018] In the formula, k0 is the propagation constant in free space, η0 is the permeability in free space, and Z... s For the real and imaginary parts of the impedance of a periodic resistive-capacitive structure;

[0019] The impedance Z at the operating frequency f0 is calculated based on the propagation constant and wave vector matching relationship. s The real and imaginary parts.

[0020] Preferably, the specific method for calculating the patch size of the periodic capacitive structure and the gap size between adjacent patches in step 4) is as follows:

[0021] According to a specific impedance Z s The imaginary part is used to calculate the capacitance C at the corresponding operating frequency f0. s :

[0022] Im(Z s )=-1 / (2πfC s )

[0023] According to a specific capacitance C s By deducing this, we can find the patch size D corresponding to the periodic capacitive structure and the gap size g between adjacent patches:

[0024]

[0025] In the formula, Z0 is the eigenimpedance of free space, and ε eff is the equivalent dielectric constant of the dielectric layer.

[0026] Preferably, the specific method for calculating the patch size of the periodic capacitive structure and the gap size between adjacent patches in step 4) is as follows:

[0027] The scattering parameters of a periodic capacitive structure with patch size D and gap size g for a vertically incident electromagnetic wave are simulated using periodic boundary modeling. Then, the scattering parameters S at the upper and lower boundaries of the periodic resistive-capacitive structure are obtained using the de-embedding method. Finally, the equivalent surface impedance Z of the periodic capacitive structure is calculated. s ′:

[0028]

[0029] In the formula, S 11 S 21 S 22 All are scattering parameters S;

[0030] Compare the Z inferred in step 3) s The imaginary part and the simulated Z s The imaginary part of ′, if Z s The imaginary part of ′ and Z s If the imaginary parts are consistent, then the patch size D of the periodic capacitive structure and the gap size g between adjacent patches are output.

[0031] One object of the present invention is to provide a single-layer absorber with evanescent wave absorption characteristics.

[0032] The objective of this invention is achieved through the following technical solution: a dielectric substrate and a single-layer resistive structure attached to the dielectric substrate, wherein the single-layer resistive structure includes a plurality of periodic capacitive structures arranged in a patterned manner at equal intervals.

[0033] Both the dielectric substrate and the single-layer resistive structure are located in the near-field region of the radiation source within the metal waveguide.

[0034] Preferably, the periodic capacitive structure is a "square" patch, and the gap size between adjacent "square" patches is equal.

[0035] Preferably, the size of the "square" patch and the gap size between adjacent "square" patches are designed using the above-described design method for a single-layer absorber with evanescent wave absorption characteristics.

[0036] Because of the adoption of the above technical solution, the present invention has the following advantages:

[0037] 1. The single-layer microwave absorber of this application is designed based on multiple periodic capacitive structures of the same size and structure and patterned. While ensuring that the number of periods of the capacitive structure remains unchanged, the operating frequency of the absorber can be adjusted simply by changing the specific size and gap size of the capacitive structure.

[0038] 2. Compared with traditional microwave absorbers, which absorb far-field plane waves but do not have the ability to absorb near-field evanescent waves, this application has the following characteristics: since this absorber actually operates below the cutoff frequency of the metal rectangular waveguide, it means that the absorber absorbs near-field evanescent waves. Therefore, it is defined as an "evanescent wave absorber". It has the characteristics of simple structure, easy processing and single-layer metal structure.

[0039] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained from the following description and claims. Attached Figure Description

[0040] The accompanying drawings of this invention are described below.

[0041] Figure 1 This is a three-dimensional view of a single-layer absorber with evanescent wave absorption characteristics under "dual-port" excitation according to the present invention.

[0042] Figure 2 This is a front view of a single-layer absorber with evanescent wave absorption characteristics under "dual-port" excitation according to the present invention.

[0043] Figure 3 This is a top view of a single-layer absorber with evanescent wave absorption characteristics under "dual-port" excitation according to the present invention.

[0044] Figure 4 This is a top view of the single-layer resistive structure under "dual-port" excitation of the present invention.

[0045] Figure 5 This relates the operating frequency, propagation constant, equivalent surface impedance of the capacitive structure, and the dimensions of the capacitive structure under the "dual-port" excitation of this invention.

[0046] Figure 6 This describes the correspondence between the operating frequency, transmission coefficient, absorption coefficient amplitude, and capacitive structure size of the periodic capacitive structure under "dual-port" excitation of the present invention.

[0047] Figure 7This is a three-dimensional view of a single-layer absorber with evanescent wave absorption characteristics under "single-port" excitation according to the present invention.

[0048] Figure 8 This is a front view of a single-layer absorber with evanescent wave absorption characteristics under "single-port" excitation according to the present invention.

[0049] Figure 9 This is a top view of a single-layer absorber with evanescent wave absorption characteristics under "single-port" excitation according to the present invention.

[0050] Figure 10 This is a top view of the single-layer resistive structure under "single-port" excitation according to the present invention.

[0051] Figure 11 This invention presents the correspondence between the operating frequency, transmission coefficient, absorption coefficient amplitude, and capacitive structure size of the periodic capacitive structure under "single-port" excitation.

[0052] In the figure: 1-Dielectric substrate; 2-Single-layer resistive structure; 3-"Square" patch; 4-Metal rectangular waveguide; 5-Noise source feed. Detailed Implementation

[0053] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0054] Example 1:

[0055] like Figure 1-4 The single-layer absorber with evanescent wave absorption characteristics under "dual-port" excitation shown includes a dielectric substrate 1 and a single-layer resistive structure 2 attached to the dielectric substrate 1. The single-layer resistive structure includes a plurality of periodic capacitive structures arranged in a patterned and equally spaced manner.

[0056] Both the dielectric substrate 1 and the single-layer resistive structure 2 are disposed in the near-field region of the radiation source within the metal waveguide.

[0057] In an example of the present invention, the near-field region of the radiation source within the metal waveguide includes a metal rectangular waveguide 4 and two noise source feeds 5. The evanescent wave absorber is fed using a waveguide coaxial conversion feeding method. The single-layer evanescent wave absorber is disposed between the two noise source feeds 5, and the single-layer evanescent wave absorber is disposed at the cross-section of the metal rectangular waveguide 4 near one of the noise source feeds 5.

[0058] In the embodiments of the present invention, the single-layer resistive structure is a capacitive surface, including but not limited to interdigital structures, lumped parameter capacitors, periodic patch structures, etc.

[0059] As one embodiment of the present invention, the periodic capacitive structure is a "square" patch 3, and the gap size between adjacent "square" patches 3 is equal.

[0060] In this embodiment of the invention, the dielectric substrate 1 is a cuboid substrate, and the length and width of the substrate are the cross-sectional dimensions of the metal rectangular waveguide 4. The waveguide model is selected as WR-187. The length a of the dielectric substrate 1 is 47.55 mm, the width b is 22.15 mm, and the thickness t is... sub The thickness is 0.125mm, and the material selected is polyethylene terephthalate (PET) with a relative permittivity of 3.1. The single-layer evanescent wave absorber resistive structure 2 on the upper surface of the dielectric substrate 1 is an indium tin oxide (ITO) thin film of the same thickness.

[0061] The gap size between adjacent "square" patches 3 is g, and the size of "square" patch 3 is D; the probe diameter r of the two noise source feeds 5 is 2.98 mm, the probe height h1 of the two noise source feeds 5 is 13.2 mm, the distance l between the two noise source feeds 5 is 86 mm, the distance l3 between the two noise source feeds 5 and the waveguide backplane is 16.5 mm, the length l2 of the metal rectangular waveguide 4 is 119 mm, and the distance l1 between the dielectric substrate 1 and the vertical center of one of the noise source feeds 5 is 3.0 mm.

[0062] The dimensions of the "square" patch 3 and the gap dimensions between adjacent "square" patches 3 are designed using a single-layer absorber design method with evanescent wave absorption characteristics.

[0063] A design method for a single-layer absorber with evanescent wave absorption characteristics is provided, which is used to design the size of the "square" patch 3 and the gap size between adjacent "square" patches 3 of the single-layer absorber with evanescent wave absorption characteristics under the above-mentioned "dual-port" excitation. The specific steps are as follows:

[0064] 1) Predefine the operating frequency f0 of the evanescent wave absorber and the operating environment parameters according to the requirements. The operating environment parameters include the cross-sectional dimensions of the rectangular waveguide.

[0065] In this invention, the required evanescent wave absorber operating frequencies f0 are predefined as 2.78 GHz, 2.88 GHz, and 2.96 GHz, respectively; the rectangular waveguide cross-sectional dimensions a are 47.55 mm in length and 22.15 mm in width.

[0066] 2) Based on the operating environment parameters, determine the propagation constant k of the evanescent wave absorber along the Y direction of the rectangular waveguide at a predefined operating frequency f0. y The specific method is as follows:

[0067]

[0068] In the formula, c is the propagation speed of electromagnetic waves in a vacuum, f0 is the predefined operating frequency of the evanescent wave absorber, a is the dimension of the wide side of the rectangular waveguide cross-section, and k y The propagation constant along the Y direction of the rectangular waveguide at a predefined operating frequency f0.

[0069] In this embodiment of the invention, since it operates below the cutoff frequency, the waveguide's intrinsic propagation constant exhibits a negative correlation with the predefined operating frequency. That is, as the operating frequency gradually increases from low to near the cutoff frequency, the waveguide's intrinsic propagation constant k... y The modulus gradually decreases from large to small; at three predefined operating frequencies f0, the waveguide intrinsic propagation constant k y The imaginary part ranges from 22.7j to 31.1j (1 / m).

[0070] 3) Calculate the specific impedance Z corresponding to the periodic capacitive structure based on the propagation constant and wave vector matching relationship. s The specific method is as follows:

[0071] According to the propagation constant wave vector matching relationship, that is, let Im(k y )=Im(k l ), k l Let be the propagation constant along the Y direction in a capacitive structure, and the specific mathematical relationship is as follows:

[0072]

[0073] In the formula, β is the propagation constant along the X direction calculated from the surface wave supported by the capacitive surface. Based on the surface wave dispersion curve equation supported by the capacitive surface, the impedance Z of the corresponding periodic resistive capacitive structure is derived. s Z s The mathematical relationship between β and β is:

[0074]

[0075] In the formula, k0 is the propagation constant in free space, η0 is the permeability in free space, and Z... s For the real and imaginary parts of the impedance of a periodic resistive-capacitive structure;

[0076] The impedance Z at the operating frequency f0 is calculated based on the propagation constant and wave vector matching relationship. s The real and imaginary parts.

[0077] In this invention example, at predefined operating frequencies f0 equal to 2.78, 2.88, and 2.96 GHz, the waveguide intrinsic propagation constant k yThe imaginary part ranges from 22.7j to 31.1j, so the longitudinal (along the Y direction) propagation constant k is calculated. l The imaginary part ranges from 22.7j to 31.1j (1 / m), where the transverse (along the X direction) propagation constant β of the surface wave supported by the capacitive surface is directly calculated from the dispersion curve. Therefore, the transverse propagation constant β and the impedance Z are used to determine the propagation constant. s The impedance Z under the action of f0 can be obtained from the relationship. s .

[0078] The waveguide intrinsic propagation constant k y Substituting the imaginary part of 22.7j~31.1j(1 / m) into the above k... l The range of β is obtained by calculating the relationship with β, and then the equivalent surface impedance Z of the capacitive structure mentioned above is used. s The mathematical relationship between β and impedance Z is used to determine the peak absorption coefficient of over 90%. s Range: Roughly determine the impedance Z s The real part is 3.3–12 (Ω), and in this example, the impedance Z s Designed to be 6 (Ω); impedance Z was precisely calculated. s The imaginary part of the impedance is -520j to -350j (Ω). It should be noted that the operating frequency and the imaginary part of the impedance are closely related, while the amplitude of the absorption coefficient is mainly contributed by the real part of the impedance. Therefore, after calculating the imaginary part of the impedance at a given operating frequency, the real part of the impedance can be determined based on the magnitude of the imaginary part of the transverse propagation constant β.

[0079] 4) Based on the impedance Z of the resistive-capacitive structure s Calculate the patch size of the periodic capacitive structure and the gap size between adjacent patches; use the two methods in 4-1) and 4-2) respectively for calculation.

[0080] 4-1) Based on the specific impedance Z s The imaginary part is used to calculate the capacitance C at the corresponding operating frequency f0. s :

[0081] Im(Z s )=-1 / (2πfC s )

[0082] According to a specific capacitance C s By deducing this, we can find the patch size D corresponding to the periodic capacitive structure and the gap size g between adjacent patches:

[0083]

[0084] In the formula, Z0 is the eigenimpedance of free space, and ε eff is the equivalent dielectric constant of the dielectric layer.

[0085] In this invention, at predefined operating frequencies f0 equal to 2.78, 2.88, and 2.96 GHz, its specific impedance Z s Given (-j350 / 420 / 520 Ohm / sq), the patch size of the periodic capacitive structure and the gap size between adjacent patches are calculated according to the above method, firstly by Z. s and C s The one-to-one correspondence allows us to calculate C. s The values ​​are 0.164 / 0.134 / 0.104pF, respectively. Furthermore, the corresponding capacitive structure and gap dimensions can be calculated as D = 5.38 / 5.28 / 5.22mm and g = 0.15 / 0.31 / 0.39mm, respectively.

[0086] 4-2) The scattering parameters of a periodic capacitive structure with patch size D and gap size g for a vertically incident electromagnetic wave are simulated using periodic boundary simulation. The scattering parameters S of the upper and lower boundaries of the periodic resistive capacitive structure are obtained using the de-embedding method, and then the equivalent surface impedance Z of the periodic capacitive structure is calculated. s ′:

[0087]

[0088] In the formula, S 11 S 21 S 22 All are scattering parameters S;

[0089] Compare the Z inferred in step 3) s The imaginary part and the simulated Z s The imaginary part of ′, if Z s The imaginary part of ′ and Z s If the imaginary parts are consistent, then the patch size D of the periodic capacitive structure and the gap size g between adjacent patches are output.

[0090] In this invention, at predefined operating frequencies f0 equal to 2.78, 2.88, and 2.96 GHz, its specific impedance Z s For (-j350 / 420 / 520 Ohm / sq), at a predefined operating frequency f0 equal to 2.78, 2.88, and 2.96 GHz, its specific impedance Z s Given (-j350 / 420 / 520 Ohm / sq), the dimensions of the corresponding periodic resistive-capacitive structure and gap can be deduced from the above method. Thus, at operating frequencies of 2.78 / 2.88 / 2.96 GHz, the corresponding capacitive structure dimensions and gap are D = 5.38 / 5.28 / 5.22 mm and g = 0.15 / 0.31 / 0.39 mm, respectively.

[0091] In this embodiment of the invention, the operating frequency f0 and the intrinsic propagation constant k of the rectangular waveguide are predefined. y The equivalent surface impedance Z of a real periodic resistive-capacitive structure s The relationship between the actual size D of the periodic resistive-capacitive structure and the size g of the etched gap is shown in Table 1.

[0092] Table 1 Operating frequencies f0 and k y k l ,β,Z s Correspondence table between D and g

[0093]

[0094]

[0095] Based on the above parameters, HFSS2022 was used to simulate and analyze the -10-dB reflection coefficient curve (S11), transmission coefficient curve (S21), and absorption coefficient A of the designed single-layer absorber with evanescent wave absorption characteristics. The analysis results are as follows:

[0096] like Figure 5 The figure shows the reflection coefficient (S11) curves for three specific capacitive structure sizes under the "two-port" configuration, corresponding to the waveguide intrinsic propagation constant k. y The curve corresponds to the longitudinal propagation constant k. l The imaginary part of the curve, and the corresponding surface impedance Z of the periodic capacitive structure. s The imaginary part curve; in addition, by Figure 5 It can be clearly observed that the operating frequency under three-dimensional simulation can be well matched with the operating frequency predicted by the mathematical expression, and the correctness of the design theory is further verified from three different frequency points.

[0097] In this invention, the effective parameter for measuring the ability of an absorber to absorb electromagnetic waves is the absorption coefficient A. The relationship between the absorption coefficient A and the S-parameter can be determined by the following formula:

[0098] A = 1 - S 11 2 -S 21 2

[0099] like Figure 6 The figure shows the reflection coefficient (S11) curve, transmission coefficient (S21) curve, and corresponding absorption coefficient A curve for three specific capacitive structure sizes under the "dual-port" design. At the resonant frequency, the peak absorption coefficient A is close to 98%. In addition, since the operating frequency of this absorber is below the cutoff frequency of the rectangular waveguide, it has evanescent wave absorption characteristics.

[0100] Example 2:

[0101] To more effectively illustrate the absorption capability of this absorber, its application in a rectangular waveguide with an "open end" was also investigated. For example... Figure 7-10 The image shows a single-layer absorber with evanescent wave absorption characteristics under "single-port" excitation, including a dielectric substrate 1 and a single-layer resistive structure 2 attached to the dielectric substrate 1. The single-layer resistive structure includes a plurality of periodic capacitive structures arranged in a patterned and equally spaced manner.

[0102] Both the dielectric substrate 1 and the single-layer resistive structure 2 are disposed in the near-field region of the radiation source within the metal waveguide.

[0103] In an example of the present invention, the near-field region of the radiation source within the metal waveguide includes a rectangular waveguide 4 with an open end and a noise source feed 5. The evanescent wave absorber is fed using a waveguide coaxial conversion feeding method, and the single-layer evanescent wave absorber is disposed at the cross-section of the metal rectangular waveguide 4 near the noise source feed 5.

[0104] In the embodiments of the present invention, the single-layer resistive structure is a capacitive surface, including but not limited to interdigital structures, lumped parameter capacitors, periodic patch structures, etc.

[0105] As one embodiment of the present invention, the periodic capacitive structure is a "square" patch 3, and the gap size between adjacent "square" patches 3 is equal.

[0106] In this embodiment of the invention, the dielectric substrate 1 is a cuboid substrate, and the length and width of the substrate are the cross-sectional dimensions of the metal rectangular waveguide 4. The waveguide model is selected as WR-187. The length a of the dielectric substrate 1 is 47.55 mm, the width b is 22.15 mm, and the thickness t is... sub The thickness is 0.125mm, and the material selected is polyethylene terephthalate (PET) with a relative permittivity of 3.1. The single-layer evanescent wave absorber resistive structure 2 on the upper surface of the dielectric substrate 1 is an indium tin oxide (ITO) thin film of the same thickness.

[0107] The gap size between adjacent "square" patches 3 is g, and the size of "square" patch 3 is D; the probe diameter r of the two noise source feeds 5 is 2.98 mm, the probe height h1 of the two noise source feeds 5 is 13.2 mm, the distance l between the two noise source feeds 5 is 86 mm, the distance l3 between the two noise source feeds 5 and the waveguide backplane is 16.5 mm, the length l2 of the metal rectangular waveguide 4 is 119 mm, and the distance l1 between the dielectric substrate 1 and the vertical center of one of the noise source feeds 5 is 3.0 mm.

[0108] The dimensions of the "square" patch 3 and the gap dimensions between adjacent "square" patches 3 are designed using a single-layer absorber design method with evanescent wave absorption characteristics.

[0109] A design method for a single-layer absorber with evanescent wave absorption characteristics is provided, which is used to design the size of the "square" patch 3 and the gap size between adjacent "square" patches 3 of the single-layer absorber with evanescent wave absorption characteristics under the above-mentioned "end-opening" excitation. The specific steps are as follows:

[0110] 1) Predefine the operating frequency f0 of the evanescent wave absorber and the operating environment parameters according to the requirements. The operating environment parameters include the cross-sectional dimensions of the rectangular waveguide.

[0111] In this invention example, the required evanescent wave absorber operating frequency f0 is predefined as 2.78 GHz; the rectangular waveguide cross-sectional dimensions are: length a = 47.55 mm and width b = 22.15 mm.

[0112] 2) Based on the operating environment parameters, determine the propagation constant k of the evanescent wave absorber along the Y direction of the rectangular waveguide at a predefined operating frequency f0. y The specific method is as follows:

[0113]

[0114] In the formula, c is the propagation speed of electromagnetic waves in a vacuum, f0 is the predefined operating frequency of the evanescent wave absorber, a is the dimension of the wide side of the rectangular waveguide cross-section, and k y The propagation constant along the Y direction of the rectangular waveguide at a predefined operating frequency f0.

[0115] In this embodiment of the invention, since it operates below the cutoff frequency, the waveguide's intrinsic propagation constant exhibits a negative correlation with the predefined operating frequency. That is, as the operating frequency gradually increases from low to near the cutoff frequency, the waveguide's intrinsic propagation constant k... y The modulus gradually decreases from large to small; at the predefined operating frequency f0, the waveguide intrinsic propagation constant k y The imaginary part is 31.1j(1 / m).

[0116] 3) Calculate the specific impedance Z corresponding to the periodic capacitive structure based on the propagation constant and wave vector matching relationship. s The specific method is as follows:

[0117] According to the propagation constant wave vector matching relationship, that is, let Im(k y )=Im(k l ), k l Let be the propagation constant along the Y direction in a capacitive structure, and the specific mathematical relationship is as follows:

[0118]

[0119] In the formula, β is the propagation constant along the X direction calculated from the surface wave supported by the capacitive surface. Based on the surface wave dispersion curve equation supported by the capacitive surface, the impedance Z of the corresponding periodic resistive capacitive structure is derived. s Z s The mathematical relationship between β and β is:

[0120]

[0121] In the formula, k0 is the propagation constant in free space, η0 is the permeability in free space, and Z... s For the real and imaginary parts of the impedance of a periodic resistive-capacitive structure;

[0122] The impedance Z at the operating frequency f0 is calculated based on the propagation constant and wave vector matching relationship. s The real and imaginary parts.

[0123] In this embodiment of the invention, at a predefined operating frequency f0 equal to 2.78 GHz, the waveguide intrinsic propagation constant k y The value is 31.1j(1 / m), from which the longitudinal propagation constant k is derived. l The imaginary part is 31.1j(1 / m) and the real part is 0.54(1 / m). The transverse propagation constant β, which supports surface wave propagation on a capacitive surface, is directly calculated from the dispersion curve. Therefore, the transverse propagation constant β and the impedance Z... s The impedance Z under the action of f0 can be obtained from the relationship. s .

[0124] The waveguide intrinsic propagation constant k y Substitute 31.1j(1 / m) into the above k. l The value of β is calculated from the relationship with β, which is 66.1-0.25j(1 / m). Then, the equivalent surface impedance Z of the capacitive structure mentioned above is used to calculate the value of β. s The mathematical relationship between β and impedance Z is used to determine the peak absorption coefficient of over 90%. s Range: Roughly determine the impedance Z s The real part is 3.3–12 (Ω), and in this example, the impedance Z s Designed to be 6 (Ω); impedance Z was precisely calculated. s The imaginary part is -350j (Ω). It should be noted that the operating frequency and the imaginary part of the impedance are closely related, while the amplitude of the absorption coefficient is mainly contributed by the real part of the impedance. Therefore, after calculating the imaginary part of the impedance at a given operating frequency, the real part of the impedance can be determined based on the imaginary part of the transverse propagation constant β.

[0125] 4) Based on the impedance Z of the resistive-capacitive structure s Calculate the patch size of the periodic capacitive structure and the gap size between adjacent patches; use the two methods in 4-1) and 4-2) respectively for calculation.

[0126] 4-1) Based on the specific impedance Z s The imaginary part is used to calculate the capacitance C at the corresponding operating frequency f0. s :

[0127] Im(Z s )=-1 / (2πfC s )

[0128] According to a specific capacitance C s By deducing this, we can find the patch size D corresponding to the periodic capacitive structure and the gap size g between adjacent patches:

[0129]

[0130] In the formula, Z0 is the eigenimpedance of free space, and ε eff is the equivalent dielectric constant of the dielectric layer.

[0131] In this embodiment of the invention, at a predefined operating frequency f0 equal to 2.78 GHz, its specific impedance Z s Given (-j350 Ohm / sq), the patch size of the periodic capacitive structure and the gap size between adjacent patches are calculated according to the above method, firstly by Z. s and C s The one-to-one correspondence allows us to calculate C. s The value is 0.164pF. Furthermore, the corresponding capacitive structure and gap size can be calculated to be D = 5.38mm and g = 0.15mm, respectively.

[0132] 4-2) The scattering parameters of a periodic capacitive structure with patch size D and gap size g for a vertically incident electromagnetic wave are simulated using periodic boundary simulation. The scattering parameters S of the upper and lower boundaries of the periodic resistive capacitive structure are obtained using the de-embedding method, and then the equivalent surface impedance Z of the periodic capacitive structure is calculated. s ′:

[0133]

[0134] In the formula, S 11 S 21 S 22 All are scattering parameters S;

[0135] Compare the Z inferred in step 3) s The imaginary part and the simulated Z s The imaginary part of ′, if Zs The imaginary part of ′ and Z s If the imaginary parts are consistent, then the patch size D of the periodic capacitive structure and the gap size g between adjacent patches are output.

[0136] In this embodiment of the invention, at a predefined operating frequency f0 equal to 2.78 GHz, its specific impedance Z s Given (-j350 Ohm / sq), the dimensions of the corresponding periodic resistive-capacitive structure and the gap can be deduced from the above method. Thus, at an operating frequency of 2.78 GHz, the corresponding capacitive structure dimensions and gap are D = 5.38 mm and g = 0.15 mm, respectively.

[0137] In this embodiment of the invention, it is obvious that since the environment configuration under "single port" is exactly the same as that under "dual port", and the predefined operating frequency and design principle are also exactly the same, the capacitive structure size D and the gap size g in this embodiment are also the same as those under "dual port".

[0138] In this invention, the purpose of designing a "single-port" evanescent wave absorber can be achieved based on the above content and implementation steps, and the specific dimensions of the actual capacitive structure can be deduced from the operating frequency.

[0139] In this invention example, since a "single-port" excitation is used, a new absorption coefficient A' will be used for analysis: Assuming that the incident power, received power, and radiated power of this system are P1, P2, and P3 respectively, and P0 represents the absorbed power of the absorber in this system, the following relationship is satisfied:

[0140] P0 = P2 - P3

[0141]

[0142] Based on the above parameters, HFSS2022 was used to simulate and analyze the -10-dB reflection coefficient curve (S11) and absorption coefficient A' and other characteristic parameters of the designed single-layer absorber with evanescent wave absorption characteristics. The results are as follows:

[0143] like Figure 11 The figure shows the reflection coefficient (S11) curve and the corresponding absorption coefficient A' curve at a predefined frequency point under the "single port" of the present invention. At the resonant frequency, its peak absorption coefficient is greater than 95%. Since the operating frequency of the absorber is below the cutoff frequency of the rectangular waveguide, it has evanescent wave absorption characteristics.

[0144] Examples of this invention also demonstrate that the absorber has the same high absorption capacity in a "single-port" rectangular waveguide.

[0145] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0146] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0147] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0148] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0149] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A design method for a single-layer absorber with evanescent wave absorption characteristics, wherein the single-layer absorber comprises a single-layer resistive structure, the single-layer resistive structure comprising a plurality of periodically arranged, patterned capacitive structures, characterized in that, The specific steps for designing a single-layer absorber are as follows: 1) Predefine the operating frequency of the evanescent wave absorber according to requirements. And operating environment parameters, including the cross-sectional dimensions of the rectangular waveguide; 2) Determine the operating frequency of the evanescent wave absorber based on the operating environment parameters. The propagation constant of the intrinsic waveguide along the Y direction of the lower rectangular waveguide ; 3) Calculate the specific impedance corresponding to the periodic capacitive structure based on the propagation constant and wave vector matching relationship. ; 4) Based on the impedance of resistive-capacitive structures Calculate the patch size of the periodic capacitive structure and the gap size between adjacent patches; In step 2), the operating frequency of the evanescent wave absorber is determined. Propagation constant of the lower waveguide along the Y direction The specific method is as follows: In the formula, Let $\mathbf{a}$ be the speed at which electromagnetic waves propagate in a vacuum. The dimension of the wider side of the rectangular waveguide cross-section; Step 3) calculates the specific impedance corresponding to the periodic capacitive structure. The method is as follows: According to the propagation constant wave vector matching relationship, that is, let , Let be the propagation constant along the Y direction in a capacitive structure, and the specific mathematical relationship is as follows: In the formula, Given the propagation constant along the X-direction calculated from the surface wave supported by the capacitive surface, and based on the surface wave dispersion curve equation supported by the capacitive surface, the impedance of the corresponding periodic resistive capacitive structure is derived. ,in and The mathematical relationship is as follows: In the formula, Let be the propagation constant in free space. Permeability in free space For the real and imaginary parts of the impedance of a periodic resistive-capacitive structure; The operating frequency is calculated based on the propagation constant and wave vector matching relationship. impedance under action The real and imaginary parts; The specific method for calculating the patch size of the periodic capacitive structure and the gap size between adjacent patches in step 4) is as follows: According to a specific impedance Z s The imaginary part is used to calculate the capacitance C at the corresponding operating frequency f0. s : According to a specific capacitance C s By deducing this, we can find the patch size D corresponding to the periodic capacitive structure and the gap size g between adjacent patches: In the formula, For the intrinsic impedance of free space, is the equivalent dielectric constant of the dielectric layer.

2. The design method of a single-layer absorber with evanescent wave absorption characteristics as described in claim 1, characterized in that, The specific method for calculating the patch size of the periodic capacitive structure and the gap size between adjacent patches in step 4) is as follows: The scattering parameters of a periodic capacitive structure with patch size D and gap size g for a vertically incident electromagnetic wave are simulated using periodic boundary modeling. Then, the scattering parameters S at the upper and lower boundaries of the periodic resistive-capacitive structure are obtained using the de-embedding method, and finally, the equivalent surface impedance of the periodic capacitive structure is calculated. : In the formula, , , All are scattering parameters S; Compare the Z inferred in step 3) s The imaginary part and the simulated The imaginary part, if The imaginary part of Z s If the imaginary parts are consistent, then the patch size D of the periodic capacitive structure and the gap size g between adjacent patches are output.

3. A single-layer absorber with evanescent wave absorption characteristics, characterized in that, It includes a dielectric substrate (1) and a single-layer resistive structure (2) attached to the dielectric substrate (1), wherein the single-layer resistive structure includes a plurality of periodic capacitive structures arranged in a patterned and equally spaced manner. The dielectric substrate (1) and the single-layer resistive structure (2) are both located in the near-field region of the radiation source inside the metal waveguide. The periodic capacitive structure is a "square" patch (3). The size of the "square" patch (3) and the gap size between adjacent "square" patches (3) are designed using the design method of a single-layer absorber with evanescent wave absorption characteristics as described in any one of claims 1-2.

4. A single-layer absorber with evanescent wave absorption characteristics as described in claim 3, characterized in that, The gap size between adjacent "square" patches (3) is equal.

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