A metamaterial structure that absorbs low-frequency waves and transmits high-frequency waves

Abstract

This invention proposes a metamaterial structure that absorbs low-frequency waves while transmitting high-frequency waves. This structure, belonging to the field of electromagnetic fields and microwave technology, consists of six layers stacked sequentially: the first layer is a dielectric layer; the second layer is composed of a dielectric substrate layer and a metal microstructure layer on top of the dielectric substrate layer; the third layer is a dielectric layer; the fourth layer is a ferrite material layer; the fifth layer is a metal microstructure layer; and the sixth layer is a dielectric layer. This metamaterial structure combines the wave transmission / reflection properties of the metal structure array with the electromagnetic loss effects of chip resistors and ferrite materials. This combination of these two loss effects helps expand the low-frequency absorption bandwidth and achieves integrated absorption and transmission of the entire structure.

Description

Technical Field

[0001] The present invention relates to an integrated metamaterial structure that absorbs low-frequency waves and transmits high-frequency waves, and belongs to the field of electromagnetic field and microwave technology. Background Art

[0002] Metamaterials refer to artificial composite structures or composite materials that do not exist in nature and are artificially designed and manufactured to have extraordinary physical properties that natural materials do not possess. In a narrow sense, metamaterials specifically refer to left-handed materials (LHM), also known as double-negative materials, which are artificial periodic dielectric materials with negative dielectric constants ε and magnetic permeability μ. Due to their extraordinary physical properties that natural materials do not possess, they have become a research hotspot in the fields of applied physics, optics, microwaves, and materials engineering. With the continuous deepening of research, the study of metamaterials has expanded from the initial microwave band to the optical wave band and the acoustic wave band. In addition to the original left-handed materials, the metamaterials included also include photonic crystals, supermagnetic materials, frequency selective surfaces, and so on.

[0003] With the continuous advancement of modern radar detection technology, radar detection range and accuracy have continued to increase, significantly reducing the battlefield survivability and penetration capabilities of weapons and equipment. To address this change, the design of high-definition stealth weapons and equipment has attracted increasing attention. Metamaterial technology has been widely applied in the stealth field due to its unique advantages in electromagnetic control. The earliest and most widely used is frequency-selective surface metamaterial technology. Frequency-selective surfaces are spatial electromagnetic wave filtering structures. They use a periodically arranged metal unit structure to transmit or reflect electromagnetic waves in specific frequency bands. Combined with the low-scattering shape of the antenna cover, they reduce the radar cross-section of a single station in the radar module, thereby ensuring the normal operation of friendly radars while providing stealth against radar waves in specific frequency bands. However, with the development and use of multi-station detection radar technology and the continuous improvement of radar detection capabilities, the requirements for single-station and dual-station stealth performance and anti-interference performance of equipment are constantly increasing. Traditional frequency-selective surfaces based on wave transmission / reflection cannot meet these requirements, and the design of metamaterial structures with higher performance, integrating wave absorption and wave transmission, is needed. Summary of the Invention

[0004] The purpose of the present invention is to overcome the shortcomings of the existing technology and provide a metamaterial structure that has high transmittance to electromagnetic waves in the C band and strong absorption characteristics of electromagnetic waves in frequency bands below the C band.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A metamaterial structure that absorbs low-frequency waves and transmits high-frequency waves is composed of six layers laid in sequence; the first, third, and sixth layers are dielectric layers; the fourth layer is a ferrite material layer; the second layer is composed of a dielectric substrate layer and a metal microstructure layer on the dielectric substrate layer, the metal microstructure layer being composed of a periodic arrangement of square grid units, each grid unit including a metal square ring, two microstrip capacitors and two microstrip inductors being provided on the four sides of the square ring, and a chip resistor being welded to each of the four corners of the square ring; the fifth layer is a metal microstructure layer being composed of a periodic arrangement of square grid units, each grid unit being a square metal patch with a circular hole etched in the middle.

[0007] Furthermore, the thickness of the first layer and the sixth layer are 0.1 to 0.5 mm respectively.

[0008] Furthermore, the width of the gap between the two patches of the microstrip capacitor of the second layer is 0.2-0.4 mm, the patch length is 1-3 mm, and the patch width is 0.1-0.5 mm.

[0009] Furthermore, the line width of the microstrip inductor of the second layer is 0.1-0.5 mm, and the length is 2-5 mm.

[0010] Furthermore, the thickness of the second dielectric substrate layer is selected to be 0.5 mm or 1 mm according to the PCB board specification.

[0011] Furthermore, the side length of the grid unit of the second layer is p=26-32 mm, the side length of the square ring of the second layer is 0.8p-0.9p, and the ring width of the square ring is 0.5-1 mm.

[0012] Furthermore, the thickness of the third layer is 0.3p to 0.5p.

[0013] Furthermore, the thickness of the fourth layer is 0.06p to 0.15p.

[0014] Furthermore, the side length of the grid unit of the fifth layer is 0.5p, and the radius of the circular hole is 3 to 8 mm.

[0015] Furthermore, the resistance of the chip resistor is 100-400Ω.

[0016] Furthermore, the dielectric layer materials of the first and sixth layers are made of quartz fiber reinforced cyanate resin composite materials, the dielectric substrate layer of the second layer is made of FR4 resin substrate, the dielectric layer of the third layer is made of PMI foam, and the fifth layer is a metal microstructure layer etched on a PI film substrate using PCB processing technology.

[0017] The beneficial effects of the present invention compared with the prior art are as follows:

[0018] (1) The low-frequency wave-absorbing and high-frequency wave-transmitting metamaterial structure of the present invention combines the wave-transmitting / reflecting characteristics of the metal structure array with the electromagnetic loss effects of the chip resistor and ferrite material. The combination of the two loss effects is conducive to expanding the low-frequency wave-absorbing bandwidth and realizing the integrated wave-absorbing / wave-transmitting performance of the entire structure.

[0019] (2) In the second layer of the low-frequency wave-absorbing and high-frequency wave-transmitting metamaterial structure of the present invention, microstrip capacitors and inductors are added to the square ring. On the one hand, the adjustment of the capacitor and inductor loading is conducive to the realization of low-frequency resonant absorption characteristics. On the other hand, it is also conducive to the adjustment of the absorption band under the loading of strong dispersive media such as ferrite. By designing a microstrip line structure with capacitor and inductor characteristics to realize the loading of equivalent capacitors and inductors, the impedance matching characteristics are adjusted, avoiding the problems of increased processing complexity caused by loading chip capacitors and chip inductors and reduced welding reliability during use.

[0020] (3) Ferrite material is added to the fourth layer of the low-frequency absorbing and high-frequency transmitting metamaterial structure of the present invention. Although the difficulty of matching design is increased due to the dispersion characteristics of ferrite, the low-frequency absorption characteristics can be further enhanced by utilizing its relatively large low-frequency loss.

[0021] (4) The second and fifth layers of the low-frequency wave-absorbing and high-frequency wave-transmitting metamaterial structure of the present invention adopt different periodic arrangements, which is beneficial to reducing the influence of low-frequency resonance on high-frequency wave transmission.

[0022] (5) The special structure of the low-frequency wave-absorbing and high-frequency wave-transmitting metamaterial structure of the present invention and the proportional relationship between the structures (including the side length of the grid unit of the second layer being p, the side length of the square ring of the second layer being 0.8p~0.9p, the thickness of the third layer being 0.3p~0.5p, the thickness of the fourth layer being 0.06p~0.15p, and the side length of the grid unit of the fifth layer being 0.5p) achieve the characteristics of wave transmission and low-frequency wave absorption in the C band, and can be applied to various wave-transmitting structures such as antenna covers and antenna windows to improve the structural stopband suppression characteristics to meet the application requirements in stealth, electromagnetic compatibility, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the low-frequency wave-absorbing and high-frequency wave-transmitting metamaterial structure of the present invention;

[0024] Figure 2 This is a schematic diagram of the second layer of the low-frequency wave-absorbing and high-frequency wave-transmitting metamaterial structure of the present invention;

[0025] Figure 3 This is a schematic diagram of the fifth layer of the low-frequency wave-absorbing and high-frequency wave-transmitting metamaterial structure of the present invention;

[0026] Figure 4The transmission and reflection characteristics of the low-frequency wave-absorbing and high-frequency wave-transmitting metamaterial structure of Example 1 of the present invention in the range of 0.1 GHz to 8 GHz are shown. DETAILED DESCRIPTION

[0027] In order to make the above features and advantages of the present invention more clearly understood, embodiments are given below and described in detail with reference to the accompanying drawings.

[0028] The present invention provides a low-frequency wave-absorbing and high-frequency wave-transmitting metamaterial structure, which consists of a six-layer structure, such as Figure 1 As shown. From top to bottom, the first layer is the dielectric layer with a thickness of h1; the second layer is composed of a dielectric substrate layer and a metal microstructure layer located thereon. The substrate thickness is h2. The metal microstructure layer is composed of a periodic arrangement of square grid units. The side length of the grid unit is p. Each grid unit is composed of a metal square ring. Two microstrip capacitors and two inductors are added to the four sides of the square ring respectively. A chip resistor is welded to each of the four corners of the square ring, as shown Figure 2 As shown, the side length of the square ring is a1, the ring width is w1, the gap between the two capacitor patches is cg, the patch length is cl, the patch width and the inductor line width are both cw, the length is l1, and the patch resistor value is R; the third layer is the dielectric layer with a thickness of h3; the fourth layer is the ferrite material layer with a thickness of h4; the fifth layer is the metal microstructure layer, which is also composed of a periodic arrangement of square grid units. The side length of the grid unit is 0.5p, and the grid unit is a square metal patch with a circular hole etched in the middle. The radius of the circular hole is r1, as shown Figure 3 The sixth layer is a dielectric layer with a thickness of h6. The first and sixth dielectric layers act as skin layers, providing both isolation and support, as well as impedance matching.

[0029] As a preferred embodiment, the unit grid side length p=26-32 mm.

[0030] As a preferred embodiment, the dielectric thickness in the first layer and the sixth layer is h1 = 0.1-0.5 mm, and h6 = 0.1-0.5 mm.

[0031] As a preferred embodiment, the size of the microstrip capacitor in the second layer is a1=0.8p~0.9p, w1=0.5~1mm, cl=1~3mm, cw=0.1~0.5mm, cg=0.2~0.4mm, l1=2~5mm, the thickness of the dielectric layer h2 can be selected as 0.5mm, 1mm, etc. according to the specifications of the PCB board, and the resistance value R=100~400Ω.

[0032] As a preferred embodiment, the dielectric thickness in the third layer is h3 = 0.3p to 0.5p.

[0033] As a preferred embodiment, the thickness of the ferrite material in the fourth layer is h4=0.06p~0.15p.

[0034] As a preferred embodiment, the radius r1 of the circular hole in the fifth layer is 3-8 mm.

[0035] The low-frequency wave absorption and high-frequency wave transmission metamaterial structure of the present invention combines the electromagnetic filtering effect of the metallized microstructure array of the second and fifth layers with the electromagnetic wave absorption loss effect of the chip resistor and the third layer of ferrite material to simultaneously achieve the high-frequency wave transmission and low-frequency wave absorption characteristics of the metamaterial structure. For C-band electromagnetic waves, the electromagnetic filtering characteristics of the two microstructure layers are utilized, and the special size design of the microstructure makes the electromagnetic waves in this frequency band have less loss in the chip resistor and ferrite, thereby achieving high transmission characteristics for electromagnetic waves; for electromagnetic waves in frequency bands below the C-band, the reflection effect of the fifth layer of microstructure on low-frequency electromagnetic waves is first combined with the electromagnetic modulation effect of the second layer of metal microstructure layer containing chip resistors to achieve the loss of low-frequency electromagnetic waves. At the same time, the low-frequency loss characteristic of the ferrite material of the fourth layer is further enhanced by the large low-frequency loss, ultimately achieving the high transmission and low absorption characteristics of the metamaterial structure. The wave transmission passband and wave absorption band characteristics can be adjusted by adjusting the parameters.

[0036] The technical solution of the present invention is described in detail below with reference to specific embodiments.

[0037] Example 1

[0038] In this embodiment, the first and sixth dielectric layers are made of quartz fiber reinforced cyanate resin composite materials with a dielectric constant of 3.4 and a loss tangent of 0.008. The second layer is a metal microstructure etched on an FR4 substrate, and then chip resistors are soldered at the four corners of the ring. The third layer is a PMI foam layer with a dielectric constant of 1.2 and a loss tangent of 0.003. The fourth layer is a ferrite material layer. The fifth layer is a metal microstructure layer etched on a PI film substrate using PCB processing technology.

[0039] Preferably, the side length of the grid unit of the second layer is p = 30 mm, and the other structural parameters are a1 = 28 mm, w1 = 0.8 mm, cl = 2 mm, cw = 0.2 mm, cg = 0.6 mm, l1 = 2.5 mm, r1 = 7 mm, the resistance of the chip resistor is 249 Ω, the thicknesses of the first and sixth dielectric layers are h1 = 0.2 mm and h6 = 0.2 mm respectively, the thickness of the substrate in the second layer is h2 = 0.5 mm, the thickness of the third PMI foam layer is h3 = 10 mm, and the thickness of the fourth ferrite material layer is h4 = 2 mm.

[0040] Figure 4The figure shows the electromagnetic transmission and reflection coefficient curve of this structure from 0.1 to 8 GHz. The S parameter on the vertical axis is the scattering parameter, which is an important parameter in microwave transmission. S21 is the forward transmission coefficient, i.e., gain; and S11 is the input reflection coefficient, i.e., input return loss. Figure 4 It can be seen that around 5.3 GHz in the C-band, there is a transmission passband with a transmission loss of less than -3 dB, covering a bandwidth of 1.5 GHz. Around 1.6 GHz in the L-band, electromagnetic transmission and reflection are both low, indicating that most electromagnetic waves are absorbed and lost, with a reflectivity of less than -10 dB covering a bandwidth of 1 GHz. In the S-band from 2 to 4 GHz, transmission and reflection coefficients are also low, with the reflection coefficient below -6 dB. This demonstrates that this structure absorbs low-frequency waves while transmitting high-frequency waves.

[0041] Example 2

[0042] The basic structure of this embodiment is consistent with that of Example 1. The first and sixth dielectric layers are made of quartz fiber reinforced cyanate resin composite materials with a dielectric constant of 3.4 and a loss tangent of 0.008. The second layer is a metal microstructure etched on an FR4 substrate, and then chip resistors are soldered at the four corners of the ring. The third layer is a PMI foam layer with a dielectric constant of 1.2 and a loss tangent of 0.003. The fourth layer is a ferrite material layer. The fifth layer is a metal periodic structure etched on a PI film substrate using PCB processing technology, except that the structural parameters are adjusted.

[0043] Preferably, the side length of the grid unit of the second layer is p = 28 mm, and the other structural parameters are a1 = 25 mm, w1 = 0.9 mm, cl = 2.2 mm, cw = 0.2 mm, cg = 0.6 mm, l1 = 2.7 mm, r1 = 6 mm, the resistance of the chip resistor is 249 Ω, the thicknesses of the first and sixth dielectric layers are h1 = 0.3 mm and h6 = 0.3 mm respectively, the thickness of the substrate in the second layer is h2 = 0.5 mm, the thickness of the third PMI foam layer is h3 = 12 mm, and the thickness of the fourth ferrite material layer is h4 = 2.1 mm.

[0044] Similarly, this structure has a transmission passband in the C band, and the bandwidth is 1.4 GHz within the transmission loss of -3 dB. At the same time, the L and S bands maintain low transmission coefficients and reflection coefficients, indicating the existence of an absorption band, and the bandwidth is 1.2 GHz below the reflectivity of -10 dB. It can be seen that this structure has the characteristics of low-frequency absorption and high-frequency transmission.

[0045] The parts not described in detail herein are well known to those skilled in the art.

[0046] Although the present invention has been disclosed as above by way of embodiments, they are not intended to limit the present invention. Any appropriate modification or equivalent substitution of the technical solution of the present invention by a person skilled in the art should be included in the protection scope of the present invention. The protection scope of the present invention shall be based on that defined in the claims.

Claims

1. A metamaterial structure capable of absorbing low-frequency waves and transmitting high-frequency waves, characterized in that: It consists of six layers laid in sequence; among them, the first, third and sixth layers are dielectric layers; the fourth layer is a ferrite material layer; the second layer is composed of a dielectric substrate layer and a metal microstructure layer on the dielectric substrate layer, the metal microstructure layer is composed of a periodic arrangement of square grid units, each grid unit includes a metal square ring, two microstrip capacitors and two microstrip inductors are respectively arranged on the four sides of the square ring, and a chip resistor is welded on each of the four corners of the square ring; the fifth layer is a metal microstructure layer, which is composed of a periodic arrangement of square grid units, each grid unit is a square metal patch with a circular hole etched in the middle; the second and fifth layers adopt different periodic arrangements; the side length of the grid unit of the second layer is p, the side length of the grid unit of the fifth layer is 0.5p, and the radius of the circular hole is 3~8mm.

2. The metamaterial structure according to claim 1, wherein: The thickness of the first layer and the sixth layer are 0.1~0.5mm respectively.

3. The metamaterial structure according to claim 1, wherein: The gap width between the two patches of the microstrip capacitor in the second layer is 0.2~0.4mm, the patch length is 1~3mm, and the patch width is 0.1~0.5mm.

4. The metamaterial structure according to claim 1, wherein: The line width of the microstrip inductor of the second layer is 0.1~0.5mm and the length is 2~5mm.

5. The metamaterial structure according to claim 1, wherein: The thickness of the second dielectric substrate layer is selected to be 0.5 mm or 1 mm according to the PCB board specifications.

6. The metamaterial structure according to claim 1, wherein: The side length of the grid unit of the second layer is p=26~32mm, the side length of the square ring of the second layer is 0.8p~0.9p, and the ring width of the square ring is 0.5~1mm.

7. The metamaterial structure according to claim 6, wherein: The thickness of the third layer is 0.3p~0.5p; the thickness of the fourth layer is 0.06p~0.15p.

8. The metamaterial structure according to claim 1, wherein: The resistance of the chip resistor is 100~400Ω.

9. The metamaterial structure according to claim 1, wherein: The dielectric layer materials of the first and sixth layers are made of quartz fiber reinforced cyanate resin composite materials, the dielectric substrate layer of the second layer is made of FR4 resin substrate, the dielectric layer of the third layer is made of PMI foam, and the fifth layer is a metal microstructure layer etched on the PI film substrate using PCB processing technology.

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