A single-layer broadband frequency selective absorber with notch band

Abstract

The present invention provides a single-layer broadband frequency selective absorber with a notch band, comprising an absorber unit, the absorber unit comprising an absorbent frequency selective surface, a dielectric plate, a foam plate and a metal reflector arranged in sequence from top to bottom; the absorbent frequency selective surface is a metal coating layer, comprising an octagonal annular strip, the octagonal annular strip comprising side one and side two; side one and side two are arranged at intervals, and side two is parallel or perpendicular to the four sides of the dielectric plate; four side one of the octagonal annular strip are all electrically connected to a chip resistor in the forward direction; the inner sides of the four side two are all electrically connected to a rectangular annular strip vertically; the inner side of the rectangular annular strip is surrounded and electrically connected to a meander line strip. The frequency selective absorber with a notch band of the present invention has a simple structure, a wide absorption frequency band, an adjustable notch band, stable polarization, stable incident angle, and is easy to manufacture, and can be used for the ground plane of an antenna and to reduce the radar scattering cross section of the antenna.

Description

Technical Field

[0001] The invention relates to the technical field of wave absorbing materials, relates to wave absorbing materials and frequency selective surfaces, and in particular to a single-layer broadband frequency selective wave absorbing body with a notch band. Background Art

[0002] With the rapid development of electromagnetic wave communication equipment, the impact of electromagnetic waves on communication and military fields is increasing. It is necessary to regulate the reflection of electromagnetic waves while ensuring normal communication to improve communication efficiency, improve stealth technology and eliminate electromagnetic wave interference. The emergence of absorbing materials has solved the above problems better. Absorbing materials refer to a type of material that can absorb or significantly reduce the electromagnetic wave energy received on its surface, thereby reducing the interference of electromagnetic waves. In engineering applications, in addition to requiring absorbing materials to have a high absorption rate of electromagnetic waves in a wider frequency band, they are also required to have properties such as light weight, moisture resistance and corrosion resistance. Traditional absorbers, such as wedge-shaped materials, magnetic absorbers and Salisbury absorption screens, have defects such as high density, large thickness or narrow absorption band.

[0003] Frequency Selective Rasorber (FSR) is a multi-resonant broadband absorber with the characteristics of light weight, low profile, significant absorption within the band, low loss transmission or reflection outside the band. Compared with traditional electromagnetic absorbing materials, it is smaller in size and can obtain better absorbing performance. Traditional broadband absorbers can absorb electromagnetic waves within a certain bandwidth and reduce the radar cross section (RCS) of the antenna. However, when sending and receiving signals, the absorber will interfere with the radiation performance of the antenna, affect the radiation pattern of the antenna, and reduce the gain of the antenna.

[0004] Notch-type (or reflective) FSR can generate a reflection band (i.e., notch band) within the absorption band. This type of structure is particularly useful for the design of antenna absorbers. The notch band within the absorption band can be used as the reflection ground plane of the antenna, and the RCS can be reduced through the absorption band. However, the existing notch-type frequency selective absorbers are mainly two-dimensional structures using two-layer dielectric plates. A few absorber structures that use a single-layer dielectric to achieve notch response also have polarization sensitivity problems and cannot meet actual needs. Therefore, it is necessary to continue to explore the absorption and notch mechanisms of notch-type absorbers and optimize the structural units.

[0005] Therefore, how to provide a broadband absorber with a notch band that only requires a single-layer dielectric plate and has polarization stability is a problem that technical personnel in this field urgently need to solve. Summary of the invention

[0006] In view of this, the present invention provides a single-layer broadband frequency selective absorber with a notch band for RCS reduction.

[0007] In order to achieve the above object, the present invention adopts the following technical solution:

[0008] A single-layer broadband frequency selective absorber with a notch band comprises an absorber unit, wherein the absorber unit comprises an absorbent frequency selective surface, a dielectric plate, a foam plate and a metal reflector arranged in sequence from top to bottom;

[0009] The absorptive frequency selective surface is a metal coating layer, comprising an octagonal annular strip, the octagonal annular strip comprising side one and side two; side one is spaced apart from side two, and side two is parallel or perpendicular to the four sides of the dielectric plate; the four side ones of the octagonal annular strip are all electrically connected in a forward direction with chip resistors; the inner sides of the four side twos are all vertically electrically connected with rectangular annular strips; the inner side of the rectangular annular strip is surrounded and electrically connected with a meander strip; the side of the rectangular annular strip electrically connected to the meander strip is opposite to the side of the rectangular annular strip electrically connected to the side two.

[0010] Preferably, the plurality of absorbing units are periodically arranged to form the single-layer broadband frequency selective absorbing body. The absorbing unit area of ​​the single-layer broadband frequency selective absorbing body with a notch band for RCS reduction is 16 mm×16 mm.

[0011] Preferably, the foam board is a polymethacrylimide (PMI for short) foam board, which is bonded between the dielectric board and the metal reflective board, and the thickness of the PMI foam board is 12 mm.

[0012] Preferably, the material of the dielectric plate is a lossy dielectric, and the thickness of the dielectric plate is 0.5 mm.

[0013] Preferably, the cross section of the wave absorbing unit is square.

[0014] Preferably, the width of the octagonal ring strip is 0.8 mm.

[0015] Preferably, the rectangular ring strip is a closed square ring strip with a width of 0.3 mm.

[0016] Preferably, the rectangular ring strip is electrically connected to the second side through a first strip, and the first strip is vertically electrically connected to the midpoints of the two side edges of the rectangular ring strip and is also vertically electrically connected to the corresponding midpoints of the second side.

[0017] Preferably, the length and width of the first strip are both 0.3 mm.

[0018] Preferably, the meander strip is electrically connected to the midpoint of the inner side of the rectangular ring strip through a second strip, and the second strip is perpendicular to the inner side of the rectangular ring strip.

[0019] Preferably, the meander strip comprises a plurality of bending segments of the same length, and the ends of adjacent bending segments are electrically connected via a vertical connecting segment to form a complete meander strip, wherein the midpoint of one bending segment is vertically electrically connected to the second strip.

[0020] Preferably, the width of the second strip is 0.3 mm.

[0021] Preferably, the resistance values ​​of the four chip resistors loaded on the octagonal ring of the absorptive frequency selective surface are all 140Ω.

[0022] It can be seen from the above technical solution that, compared with the prior art, the beneficial effects of the present invention include:

[0023] 1. The absorptive frequency selective surface of the present invention adopts an octagonal ring structure with a meander strip surrounded by a rectangular ring strip connected inside, and the octagonal ring structure loaded with four patch resistors realizes a wide absorption band. The meander strip structure surrounded by the rectangular ring strip and the octagonal ring constitute a parallel series LC resonator with a high equivalent inductance value. According to the impedance equal to zero when the series LC resonator resonates, when it resonates, the patch resistor loaded on the octagonal ring strip is short-circuited to prevent the loaded resistor from consuming electromagnetic wave energy, thereby realizing a broadband absorber with a notch band that only requires a single-layer dielectric plate. Moreover, the position of the notch band can be adjusted by changing the length of the meander strip structure and the number of bending nodes.

[0024] 2. The present invention adjusts the size of each part of the structural unit so that the structure produces an absorption band with a 90% absorption rate covering the frequency bands of 2.26GHz to 7.34GHz and 8.48GHz to 8.89GHz, and the working bandwidth is 118.9%. In the frequency band of 7.78GHz to 8.3GHz, a notch band with a reflection loss of less than 3dB is obtained, which has the advantages of stable incident angle and polarization of electromagnetic waves. Compared with the wavelength λ0 of the lowest operating frequency, the unit area of ​​the structure is only 0.12λ0×0.12λ0, and the unit thickness is only 0.09λ0, achieving small unit size and ultra-thin characteristics. At the same time, the structure only includes a single-layer printed circuit board (absorptive frequency selective surface), a PMI foam board and a metal reflector plate structure, which has the advantages of low cost and easy processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art are briefly introduced below. Obviously, the drawings in the following description are only embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on the provided drawings without creative work.

[0026] Figure 1 is a schematic structural diagram of an absorber unit according to an embodiment of the present invention;

[0027] Figure 2 is a top view of an absorber unit according to an embodiment of the present invention;

[0028] Figure 3 is a schematic diagram of an arrangement of absorber units according to an embodiment of the present invention;

[0029] Figure 4 is an equivalent circuit model diagram of an absorber according to an embodiment of the present invention;

[0030] Figure 5 It is a simulation result of reflection coefficient of an absorber according to an embodiment of the present invention when TE polarized waves are incident at different angles;

[0031] Figure 6 is a simulation result of reflection coefficient of an absorber according to an embodiment of the present invention when TM polarized waves are incident at different angles;

[0032] Figure 7 It is a comparison between the simulation and the measured results of the reflection coefficient of the absorber of one embodiment of the present invention when the TE polarized wave is vertically incident;

[0033] Figure 8 1 is a graph showing the influence of different sideline lengths (i.e., the longest side length (L) of the meander line structure of the absorber according to one embodiment of the present invention) parallel to the sideline connected to the octagonal ring on the reflection coefficient;

[0034] Fig. 9 1 is a graph showing the influence of different numbers of bending nodes (N) of the meander line structure of the absorber on the reflection coefficient in one embodiment of the present invention.

[0035] In the figure:

[0036] 1 is a metal coating layer, 2 is a dielectric plate, 3 is a PMI foam board, 4 is a metal reflector, 5 is a side one, 6 is a side two, 11 is a chip resistor, 12 is an octagonal ring strip, 13 is a first strip, 14 is a rectangular ring strip, 15 is a second strip, and 16 is a meander strip. DETAILED DESCRIPTION

[0037] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] Reference Figure 1 As shown, the present invention includes providing a notch type frequency selective absorber, the smallest unit of the absorber is an absorber unit. The absorber unit includes a dielectric plate 2, an absorptive frequency selective surface arranged on the upper surface of the dielectric plate, a metal reflector 4 and a PMI foam plate 3 arranged between the dielectric plate and the metal reflector.

[0039] The absorptive frequency selective surface is a metal coating layer 1, including an octagonal annular strip 12, the octagonal annular strip 12 includes a side 1 5 and a side 2 6; the side 1 5 and the side 2 6 are spaced apart, and the side 2 6 is parallel or perpendicular to the four sides of the dielectric plate 2.

[0040] It should be noted that the parallel or vertical space mentioned in the embodiments refers to a two-dimensional space parallel to the plane where the surface of the dielectric plate is located.

[0041] Reference Figure 2 As shown, the four side edges 1 5 of the octagonal ring strip 12 are electrically connected to the chip resistors 11 in the forward direction; the inner sides of the four side edges 2 6 are electrically connected to the rectangular ring strips 14 vertically; the inner side of the rectangular ring strip 14 is surrounded and electrically connected to the meander line strip 16; the side of the rectangular ring strip 14 electrically connected to the meander line strip 16 is opposite to the side of the rectangular ring strip 14 electrically connected to the side edge 2 6.

[0042] The side 26 of the octagonal ring strip 12, i.e., the horizontal or vertical side of the octagonal ring strip 12 relative to the edge of the dielectric plate 2, extends inwardly to be electrically connected to the rectangular ring strip 14, and the innermost side of the rectangular ring strip 14 close to the center position of the octagonal ring strip 12 extends inwardly to be electrically connected to the meander line strip 16.

[0043] In one embodiment, the rectangular ring strip 14 is vertically connected to the horizontal or vertical side of the octagonal ring strip 12 through the first strip 13 , and the meander strip 16 is vertically connected to the innermost side of the rectangular ring strip 14 through the second strip 15 .

[0044] In this embodiment, the rectangular ring strip 14 is a square ring strip, the outer dimensions of the square ring strip 14 are 4.5 mm×2.5 mm, and the width of the square ring strip 14 is 0.3 mm. The first strip 13 is a first square strip, and the second strip 15 is a second square strip. The first square strip has a length of 0.3 mm and a width of 0.3 mm, and the second square strip has a length of 0.3 mm and a width of 0.3 mm.

[0045] In one embodiment, the horizontal or vertical side length of the octagonal ring strip 12 is 7 mm, the angle between the inclined side and the horizontal or vertical direction is 45°, the length of the oblique side is 5.66 mm, and the width is 0.8 mm.

[0046] In one embodiment, a chip resistor 11 is disposed on the oblique side of the octagonal ring strip 12, and is located at the midpoint of the oblique side. The resistance of the chip resistor 11 is 140Ω.

[0047] In one embodiment, the meander strip 16 includes multiple bending segments of the same length, and the ends of adjacent bending segments are electrically connected via vertical connecting segments to form a complete meander strip 16 , wherein the midpoint of one bending segment is vertically electrically connected to the second strip 15 .

[0048] In this embodiment, the width of the meander strip 16 is 0.3 mm, the number of bending nodes N of the longest side is 3, the length (L) of the longest side is 3.2 mm, the length of the gap between the longest sides is 2.9 mm, and the width of the gap between the longest sides is 0.2 mm.

[0049] In one embodiment, the material of the dielectric plate 2 is Rogers 4350B, the dielectric constant is 3.66, the loss tangent is 0.0037, and the unit size of the dielectric plate 2 is 16 mm×16 mm×0.5 mm.

[0050] In one embodiment, the metal coating layer material is copper, and the electrical conductivity is 5.8×10 7 S / m, thickness is 0.035mm.

[0051] In one embodiment, the PMI foam plate 3 between the dielectric plate 2 and the metal reflective plate 4 has a thickness of 12 mm and a dielectric constant ≈1.

[0052] In one embodiment, the metal reflector 4 is made of copper, and its electrical conductivity is 5.8×10 7 S / m, thickness is 1.6mm.

[0053] Reference Figure 3 As shown, a plurality of absorbing units are periodically arranged to form the single-layer broadband frequency selective absorbing body, and the period is 16 mm. The unit area of ​​the single-layer broadband frequency selective absorbing body with a notch band for RCS reduction is 16 mm×16 mm.

[0054] Reference Figure 4As shown, by adjusting the structure according to the transmission line theory, surface current and equivalent circuit theory, the equivalent circuit model diagram of the absorber of one embodiment of the present invention can be determined. Wherein, Z1 is the characteristic impedance of the equivalent transmission line of the dielectric plate 2, h1 is the corresponding transmission line length, Z0 is the characteristic impedance of the equivalent transmission line of the PMI foam board 3, h2 is the corresponding transmission line length, R = 201Ω, L1 = 3.84nH, L2 = 8.01nH, C1 = 0.017pF, C2 = 0.084pF, C3 = 0.174pF.

[0055] Reference Figure 5 As shown, the CST Studio Suite software is used to perform simulation calculations according to the model structure size. The reflection coefficient of the absorber of one embodiment of the present invention when the TE polarized wave is incident at different angles shows that the notch band of the absorber at different incident angles is stable within 0 to 45°, and the absorption band and reflection band of the absorber at different incident angles are both stable within 0 to 30°.

[0056] Reference Figure 6 As shown, the CST Studio Suite software is used to perform simulation calculations according to the model structure size. The reflection coefficients of the absorber of one embodiment of the present invention when the TM polarized wave is incident at different angles indicate that the notch band of the absorber at different incident angles is stable within the range of 0 to 45°, and the absorption band and reflection band of the absorber at different incident angles are both stable within the range of 0 to 30°.

[0057] Combination Figure 5 and Figure 6 It can be seen that the absorption band and the reflection band of the present invention are consistent under TE and TM polarizations, and the present invention has polarization stability.

[0058] Reference Figure 7 As shown, when the TE polarized wave is vertically incident, the frequency range in which the reflection coefficient of the structure is less than -10dB, that is, the absorption band is 2.26GHz to 7.34GHz and 8.48GHz to 8.89GHz, the operating bandwidth is 118.9%, and the frequency band in which the reflection coefficient is greater than -3dB, that is, the notch band range is 7.78GHz to 8.3GHz. The simulation results are in good agreement with the measured results.

[0059] Figure 8 1 is an influence diagram of the length of different longest sides (L) of the meander strip 16 of the absorber of the embodiment of the present invention. It is found that the length of the longest side L of the meander strip 16 mainly affects the frequency of the notch band. The longer the longest side L is, the greater its equivalent inductance value is, and the smaller the resonance frequency of the notch band is.

[0060] Fig. 91 is an influence diagram of different bending node numbers (N) of the meander strip 16 of the absorber of the embodiment of the present invention. It is found that the bending node number N of the meander strip 16 mainly affects the frequency of the notch band. The larger the bending node number N, the larger the equivalent inductance value and the smaller the resonance frequency of the notch band.

[0061] Through the simulation and measurement results comparison analysis of the single-layer broadband frequency selective absorber with notch band for RCS reduction provided by the present invention, the single-layer broadband frequency selective absorber with notch band for RCS reduction finally works in the absorption bands of 2.26GHz to 7.34GHz and 8.48GHz to 8.89GHz with a relative bandwidth of 118.9%, and the notch band of 7.78GHz to 8.3GHz. In addition, the frequency selective absorber has a simple structure, a wide absorption frequency band, an adjustable notch band, stable polarization, stable incident angle, and is easy to manufacture, and can be used for the ground plane of the antenna and to reduce the radar scattering cross section of the antenna.

[0062] The single-layer broadband frequency selective absorber with a notch band provided by the present invention is introduced in detail above. Specific examples are used herein to illustrate the principle and implementation mode of the present invention. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation mode and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

[0063] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A single-layer broadband frequency selective absorber with a notch band, characterized in that: The invention comprises a wave absorbing unit, wherein the wave absorbing unit comprises an absorptive frequency selective surface, a dielectric plate, a foam plate and a metal reflecting plate arranged in sequence from top to bottom; The absorptive frequency selective surface is a metal coating layer, comprising an octagonal annular strip, the octagonal annular strip comprising side one and side two; side one is spaced apart from side two, and side two is parallel or perpendicular to the four sides of the dielectric plate; the four side ones of the octagonal annular strip are all electrically connected in a forward direction with chip resistors; the inner sides of the four side twos are all vertically electrically connected with rectangular annular strips; the inner side of the rectangular annular strip is surrounded and electrically connected with a meander strip; the side of the rectangular annular strip electrically connected to the meander strip is opposite to the side of the rectangular annular strip electrically connected to the side two.

2. The single-layer broadband frequency selective absorber with a notch band according to claim 1, characterized in that: A plurality of the absorbing units are periodically arranged to form the single-layer broadband frequency selective absorbing body.

3. The single-layer broadband frequency selective absorber with a notch band according to claim 1, characterized in that: The cross section of the wave absorbing unit is square.

4. The single-layer broadband frequency selective absorber with a notch band according to claim 1, characterized in that: The width of the octagonal annular strip is 0.8 mm.

5. The single-layer broadband frequency selective absorber with a notch band according to claim 1, characterized in that: The rectangular ring strip is a closed square ring strip with a width of 0.3 mm.

6. The single-layer broadband frequency selective absorber with a notch band according to claim 1, characterized in that: The rectangular ring strip is electrically connected to the second side through a first strip, and the first strip is vertically electrically connected to the midpoints of the two side edges of the rectangular ring strip, and is also vertically electrically connected to the corresponding midpoints of the second side.

7. The single-layer broadband frequency selective absorber with a notch band according to claim 6, characterized in that: The first strip is a square strip.

8. The single-layer broadband frequency selective absorber with a notch band according to claim 1, characterized in that: The meander strip is electrically connected to the midpoint of the inner side of the rectangular ring strip through a second strip, and the second strip is perpendicular to the inner side of the rectangular ring strip.

9. The single-layer broadband frequency selective absorber with a notch band according to claim 8, characterized in that: The meander strip includes multiple bending segments of the same length, and the ends of adjacent bending segments are electrically connected via vertical connecting segments to form a complete meander strip, wherein the midpoint of one bending segment is vertically electrically connected to the second strip.

10. The single-layer broadband frequency selective absorber with a notch band according to claim 8, characterized in that: The second strip is a square strip.

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