Ultra-wideband water-based wave-absorbing structure

Abstract

The invention discloses an ultra-wideband water-based wave-absorbing structure, and belongs to the technical field of metamaterials and wave absorption. The structure comprises a metal back plate, a lower dielectric layer, a water channel layer, a water-based cavity array and an upper dielectric shell array which are sequentially arranged from bottom to top, wherein the water-based cavity unit is in a multi-ridge flat-top tower shape, a plurality of ridges are uniformly distributed, and the included angle between each ridge and the central axis is theta 1; the upper medium shell unit is in a regular polygon frustum shape or a circular truncated cone shape, the included angle between the outer side face of the upper medium shell unit and the central axis is theta2, and theta1 is smaller than theta2. According to the device, ultra-wideband absorption from 7.4 GHz to 200 GHz is achieved, the absorption efficiency exceeds 90%, and the device can meet the application requirement of multiple frequency bands.

Description

Technical Field

[0001] The invention belongs to the technical field of metamaterials and wave absorbing technology, and in particular relates to an ultra-wideband water-based wave absorbing structure. Background Art

[0002] Absorbing structures are widely used in military, aerospace, electromagnetic shielding and other fields to absorb or suppress electromagnetic wave energy, thereby reducing radar reflection cross section or electromagnetic interference. In this field, water-based absorbing structures and 3D printing technology have gradually become research hotspots in recent years.

[0003] The design goals of the absorbing structure are mainly focused on achieving broadband absorption, high absorption efficiency, lightweight design and dynamic regulation performance. Among them, broadband absorption requires that the material has excellent absorbing performance in the range from low frequency to high frequency, such as the wide frequency band coverage of 10GHz to 50GHz in the patent named "A honeycomb cross-band broadband absorber based on a metasurface" (publication number CN 116613539A). High absorption efficiency requires that the absorption rate of the absorber in the target frequency band be maintained above 90% to meet the technical requirements of electromagnetic stealth and electromagnetic compatibility. The design based on metal dielectric resonance to achieve impedance matching is often limited in absorption bandwidth due to the limitation between quality factor and resonance intensity. For example, the patent named "A water-based sandwich metasurface adjustable coherent absorber" (publication number CN 113346249 A), and in order to achieve broadband absorption based on metal resonance, it is necessary to achieve coupled resonance of similar resonance modes, which puts higher requirements on design and preparation. In addition, in order to adapt to space-constrained scenarios, the absorbing structure needs to be lightweight and thin. However, previous water-based absorbing structures still have significant deficiencies in these aspects. For example, the patent named "An Adjustable Ultra-Wideband Salt Water-Based Absorber" (publication number CN 109509985A) achieves ultra-wideband absorption of 1.4-3.3GHz and 4.3-63GHz. However, the overall thickness of the absorber reaches 25mm. The regular and uniform water-based absorber design requires a higher cross-sectional size to achieve impedance matching of broadband multiple resonant modes.

[0004] The high dielectric constant and low magnetic permeability of water make it an ideal absorbing structure. Water-based absorbing structures have received extensive attention in recent years due to their excellent dielectric properties, dynamic regulation capabilities, and environmental friendliness. However, traditional water-based absorbing structures also face technical challenges such as poor mechanical stability, unstable absorber performance due to the fluidity and evaporation of water. In addition, how to optimize the structural design of water-based materials to give full play to their high dielectric properties and achieve combination with other absorbing mechanisms is still a difficult point in research. Summary of the invention

[0005] In order to solve the broadband absorption problem of water-based absorbing structures, the present invention proposes an ultra-broadband water-based absorbing structure, which adopts a multi-ridge flat-top tower-type water-based cavity and non-uniform transition broadband matching to obtain a water-based medium ultra-broadband absorbing structure with excellent performance.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] An ultra-wideband water-based wave absorbing structure comprises a metal back plate, a lower dielectric layer, a water channel layer, a water-based cavity array and an upper dielectric shell array arranged in sequence from bottom to top;

[0008] The metal back plate and the lower dielectric layer are provided with two water injection ports;

[0009] The water-based cavity array comprises a plurality of periodically arranged water-based cavity units;

[0010] The upper dielectric shell array includes a plurality of upper dielectric shells arranged periodically, and the bottoms of the upper dielectric shell units are connected and correspond to the water-based cavity units one by one;

[0011] The water-based cavity unit is a multi-ridge flat-top tower; the multi-ridge flat-top tower is convergent at the top and wide at the bottom, and multiple ridges are evenly distributed and the angles with the central axis are all θ 1 ;

[0012] The upper dielectric housing unit is a regular polygonal cone or truncated cone, and the angle between its outer side and the central axis is θ 2 , and θ 1 <θ 2 .

[0013] Furthermore, θ 2 The value range is 10°~30°.

[0014] Furthermore, the periodic side length of the water-based cavity unit is 0.5λ~λ, where λ is the wavelength corresponding to the lowest frequency of the working frequency band.

[0015] Furthermore, the water-based cavity unit is a multi-ridge flat-top tower type, and the bottom ridgeline design is defined as follows:

[0016]

[0017] Among them, t∈[0, 2π], b is the reference radius of the bottom of the water-based cavity, a is the ridge perturbation factor, n is the number of periods (i.e., the number of ridges), and n ranges from 4 to 6.

[0018] Furthermore, the reference radius b of the bottom of the water-based cavity is related to the wavelength corresponding to the lowest frequency of the working frequency band, and has a value of 0.2λ to 0.4λ.

[0019] Furthermore, the height of the water-based cavity unit is 0.2λ to 0.4λ.

[0020] Furthermore, the thickness of the water channel layer is 0.05 to 0.1 times of the unit period size to ensure that the water flow distribution is satisfied without significantly increasing the structure height.

[0021] The device performance advantages of the present invention are:

[0022] 1. Through the optimized multi-layer structure design, including metal backplane, lower dielectric layer, water channel layer, water-based cavity array and upper dielectric shell array, the device achieves ultra-wideband absorption from 7.4GHz to 200GHz, with an absorption efficiency of more than 90%, and can adapt to multi-band application requirements.

[0023] 2. The non-uniform angle matching design of the upper dielectric shell unit and the water-based cavity unit, combined with the multi-ridged flat-top tower structure of the water-based cavity, forms a gradually changing impedance transition area, effectively reducing the reflected waves in different frequency bands and significantly improving the broadband absorption efficiency.

[0024] 3. The multi-ridge flat-top tower structure significantly broadens the absorption bandwidth through the multi-mode resonance effect (including the coupling of low-order and high-order modes), enabling the device to achieve efficient absorption in different frequency bands, especially excellent performance in the high frequency band.

[0025] 4. Through the design of the water channel layer, the complete sealing of the water-based cavity and the uniform distribution of pure water are ensured, eliminating possible problems of uneven filling or leakage, and providing a guarantee for long-term stable operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a three-dimensional schematic diagram of the water-based absorbing unit in this embodiment.

[0027] Figure 2 It is a side view of the water-based absorbing unit in this embodiment.

[0028] Figure 3 This is a top view of the water-based absorbing unit in this embodiment.

[0029] Figure 4 Schematic diagram of the overall structure of the water-based wave absorbing structure in the embodiment.

[0030] Figure 5 TE / TM absorption efficiency results in the embodiment.

[0031] Explanation of the reference numerals: 1 is a metal back plate, 2 is a lower dielectric layer, 3 is a water channel layer, 4 is a water-based cavity unit, 5 is an upper dielectric shell unit, and 6 is a back water injection port. DETAILED DESCRIPTION

[0032] In order to better illustrate the purpose, advantages and technical ideas of the present invention, the technical scheme of the present invention is further described below in conjunction with the accompanying drawings and specific examples. It should be noted that the specific examples given below only serve to explain the present invention, and the protection scope of the present invention is not limited to the following.

[0033] This embodiment designs a wide-angle broadband water-based absorbing structure operating in the 7.4 GHz to 200 GHz frequency band. The design goal is to achieve ultra-wideband, high-efficiency absorbing performance, while taking into account the adaptability to large-angle incidence and complex polarization environments.

[0034] like Figure 1-Figure 4 As shown, an ultra-wideband water-based absorbing structure of the present embodiment includes a metal backplane, a lower dielectric layer, a water channel layer, a water-based cavity array and an upper dielectric shell array arranged in sequence from bottom to top.

[0035] The metal back panel uses red copper as a reflective mirror to provide total reflection and ensure absorption efficiency.

[0036] The lower dielectric layer has a thickness of 1 mm and is used for unit support and water-based cavity sealing.

[0037] The metal back plate and the lower dielectric layer are provided with two water injection ports, and gas is discharged during the water injection process to ensure that the water-based cavity is fully filled.

[0038] The water-based cavity array includes 10×10 periodically arranged water-based cavity units; according to frequency band requirements, the unit period is set to 10 mm.

[0039] The upper dielectric shell array includes 10×10 upper dielectric shells arranged in a period, and the bottoms of the upper dielectric shell units are connected and correspond to the water-based cavity units one by one.

[0040] The water-based cavity unit is a six-ridge flat-top tower with a convergent top and a wide bottom. The bottom ridge design is defined as follows:

[0041] x(t)=cost*(b+a*cos(n*t))

[0042] y(t)=sint*(b+a*cos(n*t))

[0043] Where t∈[0, 2π], bottom ridge parameter settings: b=3.5mm, a=-0.4mm, n=6; ridge inclination angle θ 1 The angle is 12° and the height of the water-based cavity is 2.26 mm.

[0044] In this embodiment, the edges and tips of the six-ridge flat-top tower structure can change the boundary conditions of the water-based cavity. When electromagnetic waves are incident on the cavity, a strong electric field focusing effect is formed at the edges and vertices, thereby improving the dielectric loss capacity of pure water and effectively absorbing electromagnetic wave energy in the high-frequency band. Secondly, the six-ridge flat-top tower structure optimizes the distribution of electromagnetic energy in the cavity, forming an xy-axis symmetrical electric field distribution, which brings dual-polarized absorption performance to the absorption unit. In addition, the six-ridge flat-top tower structure excites multiple resonant modes in a wide frequency band through its geometric characteristics. The coupling between these modes significantly enhances the broadband response capability of the cavity and further broadens the absorption bandwidth.

[0045] Ridgeline inclination angle θ 1 Generally between 10° and 20°, the steeper angle helps to enhance the local electric field and improve the high-frequency absorption efficiency. At the same time, it forms a non-uniform angle matching structure with the upper dielectric shell with a gentle inclination, achieving smooth impedance matching in a wide frequency range. Through the precise optimization of the above geometric parameters, the six-ridge flat-top tower-type water-based cavity ensures the basis for efficient absorption in a wide frequency range.

[0046] The water-based cavity is filled with pure water, which uses its high dielectric constant and dielectric loss characteristics to enhance the absorption of electromagnetic waves, ensuring efficient electromagnetic energy dissipation in the entire working frequency band. A 1mm thick water channel layer is designed between the water-based cavity and the lower dielectric layer to ensure that pure water can evenly fill the cavity and avoid electromagnetic performance fluctuations caused by uneven filling.

[0047] The upper dielectric shell adopts a square pyramid shape, with a top width of 5.63mm, a dielectric layer height of 6mm, and an inclination angle of θ 2 The bottom of the upper dielectric shell is set to a square dielectric layer with a width of 10mm and a height of 1mm, and its main function is to avoid the breakage of the connecting parts between the units.

[0048] During the impedance matching transition process, the gentle inclination angle of the shell provides a preliminary match to the free space, reducing the impedance difference between the incident electromagnetic wave and the absorbing structure, while the steep angle design of the water-based cavity enhances the focusing and dissipation of the electromagnetic wave through its tip and ridges. The non-uniform angle design between the two ensures the impedance gradient from the free space to the inside of the water-based cavity, avoids the strong reflection of the electromagnetic wave, and enables the incident energy to enter the water-based cavity more efficiently. This non-uniform angle matching design not only achieves good impedance matching in the low-frequency band, but also effectively improves the absorption efficiency in the high-frequency band through the tip effect of the steep-angle part and the local electric field enhancement. In addition, this angle transition design also guides the propagation path of the electromagnetic wave, optimizes the energy distribution in the water-based cavity, further stimulates a variety of resonance modes, and achieves the improvement of broadband absorption performance, laying the foundation for the improvement of overall absorbing performance.

[0049] The lower dielectric layer and the upper dielectric shell are made of resin, which has low dielectric loss and excellent mechanical stability. It not only optimizes the impedance matching performance in the low frequency band, but also improves the long-term reliability of the absorbing structure in complex environments.

[0050] Based on the above design, the electromagnetic simulation software CST was used to establish a complete wave absorbing structure simulation model, and the periodic boundary conditions and Floquet port mode were used to perform full-wave electromagnetic simulation analysis. Figure 5 As shown, the absorbing structure achieves an absorption efficiency of over 90% in a wide frequency range of 7.4 GHz to 200 GHz and maintains stable absorption performance throughout the entire frequency band.

[0051] The simulation and test results show that the absorbing structure has excellent absorbing performance in an ultra-wide frequency range and maintains efficient absorption in dual-polarization mode, which fully verifies the effectiveness of the design method proposed in this invention. By further adjusting the cavity geometry parameters, water channel distribution and angle matching, its applicable frequency band can be further expanded, showing its wide application potential in the fields of electromagnetic stealth, broadband absorbing materials and electromagnetic compatibility in complex environments.

Claims

1. An ultra-wideband water-based wave absorbing structure, characterized in that: It includes a metal back plate, a lower dielectric layer, a water channel layer, a water-based cavity array and an upper dielectric shell array which are arranged in sequence from bottom to top; The metal back plate and the lower dielectric layer are provided with two water injection ports; The water-based cavity array comprises a plurality of periodically arranged water-based cavity units; The upper dielectric shell array includes a plurality of upper dielectric shells arranged periodically, and the bottoms of the upper dielectric shell units are connected and correspond to the water-based cavity units one by one; The water-based cavity unit is a multi-ridge flat-top tower type; the multi-ridge flat-top tower type is convergent at the top and wide at the bottom, and multiple ridges are evenly distributed and the angles between them and the central axis are all θ1; The upper dielectric shell unit is in the shape of a regular polygonal cone or a truncated cone, and the angle between the outer side surface and the central axis is θ2, and θ1<θ2.

2. The ultra-wideband water-based wave absorbing structure according to claim 1, characterized in that: The value range of θ2 is 10°~30°.

3. The ultra-wideband water-based wave absorbing structure according to claim 2, characterized in that: The periodic side length of the water-based cavity unit is 0.5λ-λ, where λ is the wavelength corresponding to the lowest frequency in the working frequency band.

4. The ultra-wideband water-based wave absorbing structure according to claim 3, characterized in that: The height of the water-based cavity unit is 0.2λ to 0.4λ.

5. An ultra-wideband water-based wave absorbing structure as claimed in claim 3 or 4, characterized in that: The water-based cavity unit is a multi-ridge flat-top tower, and its bottom ridge design is defined as follows: x(t)=cost*(b+a*cos(n*t)) y(t)=sint*(b+a*cos(n*t)) Among them, t∈[0, 2π], b is the reference radius of the bottom of the water-based cavity, a is the ridge perturbation factor, and n is the number of cycles.

6. The ultra-wideband water-based wave absorbing structure according to claim 5, characterized in that: The reference radius b of the bottom of the water-based cavity is related to the wavelength corresponding to the lowest frequency of the working frequency band, and the value is 0.2λ~0.4λ.

7. The ultra-wideband water-based wave absorbing structure according to claim 6, characterized in that: The value of n is 4 to 6.

8. The ultra-wideband water-based wave absorbing structure according to claim 7, characterized in that: The thickness of the water channel layer is 0.05 to 0.1 times the unit period size.

Images