Frequency selection wave absorber based on three-dimensional structure

Abstract

The invention discloses a frequency selection wave absorber based on a three-dimensional structure, and belongs to the technical field of electromagnetic wave absorbers, the frequency selection wave absorber comprises a plurality of periodically distributed three-dimensional structure units, and each three-dimensional structure unit comprises a frequency selection surface layer, a loss layer and a microstrip resonance wave absorbing structure; the micro-strip resonance wave-absorbing structure is parallel to the incident direction of incident waves, and the frequency selection surface layer and the loss layer are both perpendicular to the incident direction of the incident waves; the micro-strip resonance wave-absorbing structure and the loss layer form a cross-shaped structure, and the end part of the micro-strip resonance wave-absorbing structure is propped against the frequency selective surface layer; the frequency selective surface layer comprises an aperture layer and patch layers arranged on the two sides of the aperture layer; the loss layer comprises a metal resonance unit, the middle of the metal resonance unit is provided with a square ring type spiral metal wire, and the periphery of the metal resonance unit is provided with a metal arrow structure loaded with a first lumped resistor; the micro-strip resonance wave-absorbing structure comprises a U-shaped micro-strip line loaded with a second lumped resistor. The wave-absorbing material has a broadband wave-absorbing characteristic and a good radar scattering interface reduction effect.

Description

Technical Field

[0001] The present invention belongs to the technical field of electromagnetic wave absorbers, and particularly relates to a frequency selective absorber based on a three-dimensional structure. Background Art

[0002] The main function of an absorber is to absorb the energy of electromagnetic waves, convert it into heat energy or other forms of energy, so as to weaken or eliminate the reflected wave. Absorbers have a wide range of applications in the fields of electromagnetic wave control and anti-interference. For example, the main function of an absorber in a radar system is to reduce the radar cross section, thereby reducing the possibility of a target being detected by the radar. Since the process of a radar electronic device detecting a target is actually a process of detecting the energy of the radar wave scattered by the target object, the radar cross section reduction technology has always been one of the important research directions of stealth technology.

[0003] A frequency selective absorber (Frequency Selective Radome, FSR) combines the functions of an absorber and a frequency selective surface (FSS). While absorbing electromagnetic waves, it also has a transmission window and has very broad application prospects. With the continuous development of new weaponry and equipment, there are higher requirements for the broadband characteristics of FSR in practical applications. Therefore, it is of great significance to study FSR with broadband absorption characteristics and good radar scattering interface reduction effects. Summary of the Invention

[0004] Aiming at the deficiencies in the prior art, the present invention provides a frequency selective absorber based on a three-dimensional structure, which has broadband absorption characteristics and good radar scattering interface reduction effects.

[0005] The present invention provides the following technical solutions:

[0006] A frequency selective absorber based on a three-dimensional structure includes a plurality of periodically distributed three-dimensional structure units. The three-dimensional structure unit includes a frequency selective surface layer, a loss layer, and a microstrip resonant absorption structure. The microstrip resonant absorption structure is parallel to the incident direction of the incident wave. The frequency selective surface layer and the loss layer are horizontally parallel and both perpendicular to the incident direction of the incident wave. The microstrip resonant absorption structure and the loss layer form a "cross" structure, and the end of the microstrip resonant absorption structure abuts against the frequency selective surface layer. The frequency selective surface layer includes an aperture layer and patch layers provided on both sides of the aperture layer, and has a coupled bandpass frequency selection characteristic. The loss layer includes metal resonant units, a square ring-shaped spiral metal wire is arranged in the middle of the metal resonant unit, and metal arrow structures loaded with first lumped resistors are arranged around. The metal arrow structures are connected to the square ring-shaped spiral metal wire. The microstrip resonant absorption structure includes a U-shaped microstrip line loaded with a second lumped resistor.

[0007] Optionally, the patch layer includes a first metal layer and a first dielectric layer, and the first dielectric layer is adjacent to the aperture layer.

[0008] Optionally, the first dielectric layer is a square sheet structure with a thickness of 1 mm and a dielectric constant of 3.5.

[0009] Optionally, the aperture layer is a metal square ring with a hollow middle, and the outer side length of the metal square ring is 7.5 mm and the inner side length is 3.5 mm.

[0010] Optionally, the patch layer is equivalent to a capacitor layer, the aperture layer is equivalent to an inductor layer, and the two capacitor layers and inductor layers form a parallel LC circuit.

[0011] Optionally, the outer perimeter of the square-ring-shaped spiral metal wire is 7.26 mm.

[0012] Optionally, the loss layer further includes a second dielectric layer; the metal resonant unit is disposed on the second dielectric layer, and the thickness of the second dielectric layer is 0.5 mm; the resistance value of the first lumped resistor is 170 Ω.

[0013] Optionally, the microstrip resonant absorber structure includes a third dielectric layer, the U-shaped microstrip line is disposed on the third dielectric layer, and the thickness of the third dielectric layer is 0.5 mm; the second lumped resistor is located in the middle of the U-shaped microstrip line, and the resistance value is 150 Ω.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0015] Compared with the traditional two-dimensional radar absorber with low-frequency absorption and high-frequency transmission, the present invention adds a three-dimensional structure along the incident direction of the incident wave, which not only enriches the functionality and application range of the absorber, but also significantly improves its absorption performance and stealth effect. The three-dimensional U-shaped microstrip resonant absorber structure parallel to the incident direction of the incident wave in the present invention has less influence on the absorption band of the low-frequency part, is easier to impedance match, and is easier to optimize in design; in addition, the U-shaped microstrip resonant absorber structure of the present application is mainly used to absorb the high-frequency absorption band, and at the same time has a certain frequency band expansion effect on the low-frequency absorption band, so that the overall structure has good transmittance (transmission efficiency higher than 90%) in the middle frequency band (9-11 GHz), and has absorption bands on both the low-frequency and high-frequency sides of the transmission band, and the reflection coefficient in the relatively wide frequency band from 3 GHz to 19.6 GHz is lower than -10 dB, making the present application have good stealth ability. Description of the Drawings

[0016] Figure 1 is the overall structure schematic diagram of a frequency selective absorber based on a three-dimensional structure of the present invention;

[0017] Figure 2It is a schematic diagram of the layering of the three-dimensional structural unit of the present invention;

[0018] Figure 3 It is a structural diagram of the metal resonant unit of the present invention;

[0019] Figure 4 It is the transmission coefficient curve of a frequency selective absorber based on a three-dimensional structure of the present invention;

[0020] Figure 5 It is the reflection coefficient curve of a frequency selective absorber based on a three-dimensional structure of the present invention.

[0021] In the figure, the markings are as follows: 10 is the frequency selective surface layer, 11 is the patch layer, 12 is the aperture layer, 111 is the first metal layer, 112 is the first dielectric layer, 20 is the loss layer, 21 is the metal resonant unit, 22 is the second dielectric layer, 211 is the square-ring-shaped spiral metal wire, 212 is the metal arrow structure, 213 is the first lumped resistor, 30 is the microstrip resonant absorbing structure, 31 is the U-shaped microstrip line, 32 is the second lumped resistor, and 33 is the third dielectric layer. Detailed implementation manners

[0022] Now, the present invention will be further described in detail with reference to the accompanying drawings.

[0023] It should be noted that the terms such as "upper", "lower", "left", "right", "front", "rear", etc. cited in the invention are only for the convenience of description and are not used to limit the scope of implementation of the present invention. The change or adjustment of their relative relationship, without substantial change in the technical content, should also be regarded as the scope of implementation of the present invention. In addition, the terms "first", "second", etc. in the specification and claims of the present invention are used to distinguish similar objects and do not necessarily need to describe a specific order or sequence. It should be understood that such terms can be interchanged under appropriate circumstances so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein.

[0024] As Figure 1 and Figure 2 shown, a frequency selective absorber based on a three-dimensional structure is provided, which includes a plurality of periodically distributed three-dimensional structural units. The three-dimensional structural unit includes a frequency selective surface layer 10, a loss layer 20, and a microstrip resonant absorbing structure 30. Optionally, the period of the three-dimensional structural unit is 22.5 mm.

[0025] The microstrip resonant absorbing structure 30 is parallel to the incident direction of the incident wave. The frequency selective surface layer 10 and the loss layer 20 are distributed horizontally in parallel and are both perpendicular to the incident direction of the incident wave; in Figure 2In the coordinate system shown, the frequency selective surface layer 10 and the loss layer 20 are both located on the XOY surface, and the microstrip resonant absorbing structure 30 is located on the XOZ surface; the microstrip resonant absorbing structure 30 and the loss layer 20 form a "cross" structure, and the end of the microstrip resonant absorbing structure 30 abuts against the frequency selective surface layer 10; the connection methods of the microstrip resonant absorbing structure 30, the loss layer 20, and the frequency selective surface layer 10 can all refer to the prior art, such as bonding, etc.

[0026] As Figure 2 shown, the frequency selective surface layer 10 includes an aperture layer 12 and patch layers 11 provided on both sides of the aperture layer 12, that is, the structure of the frequency selective surface layer 10 is patch layer 11 - aperture layer 12 - patch layer 11; the frequency selective surface layer 10 has a coupled band - pass frequency selection characteristic; the interaction between the patch layer 11 and the aperture layer 12 and between them and the incident electromagnetic wave is coupling, and the coupling enables the FSS to transmit electromagnetic waves within a specific frequency range, that is, the band - pass frequency selection characteristic.

[0027] In this embodiment, the patch layer 11 includes a first metal layer 111 and a first dielectric layer 112, the aperture layer 12 is a metal layer, and the first dielectric layer 112 is adjacent to the aperture layer 12, that is, the frequency selective surface layer 10 is, from left to right: first metal layer 111, first dielectric layer 112, aperture layer 12, first dielectric layer 112, and first metal layer 111; both first dielectric layers 112 are square sheet - like structures with a thickness of 1 mm and a dielectric constant of 3.5; the aperture layer 12 is a metal square ring with a hollow in the middle, and the outer side length of the metal square ring is 7.5 mm and the inner side length is 3.5 mm, so that the frequency selective surface can have good transmittance in the middle frequency band (9 - 11 GHz).

[0028] Specifically, in this embodiment, the patch layer 11 is equivalent to a capacitance layer, the aperture layer 12 is equivalent to an inductance layer, and the two capacitance layers sandwich the inductance layer to form a parallel LC circuit, that is, the frequency selective surface layer 10 is a band - pass type FSS formed by the parallel connection of capacitance - inductance - capacitance, thereby allowing electromagnetic waves within a specific frequency range to pass through while blocking electromagnetic waves of other frequencies.

[0029] The loss layer 20 includes a metal resonant unit 21 and a second dielectric layer 22. The metal resonant unit 21 is disposed on the second dielectric layer 22, and the thickness of the second dielectric layer 22 is 0.5 mm. A square-ring-shaped spiral metal wire 221 is arranged in the middle of the metal resonant unit 21, and metal arrow structures 212 loaded with a first lumped resistor 213 are arranged on all four sides. The metal arrow structures 212 are connected to the square-ring-shaped spiral metal wire 221. The metal arrow is a metal strip in the shape of an arrow, that is, the four metal arrow structures 212 point to the four corners of the second dielectric layer 22, and the outer combined side length of the square-ring-shaped spiral metal wire 221 is 7.26 mm. A first lumped resistor 213 is loaded at the tail of each metal arrow. Preferably, the resistance value of the first lumped resistor 213 is 170 Ω. The square-ring-shaped spiral metal wire 221 can extend the resonant current for miniaturization design and at the same time can introduce a low insertion loss passband as a parallel resonant structure.

[0030] The microstrip resonant absorber structure 30 includes a U-shaped microstrip line 31 loaded with a second lumped resistor 32 and a third dielectric layer 33. The U-shaped microstrip line 31 is disposed on the third dielectric layer 33, and the thickness of the third dielectric layer 33 is 0.5 mm. The second lumped resistor 32 is located in the middle of the U-shaped microstrip line 31, and the resistance value of the second lumped resistor 32 is 150 Ω, forming a high-frequency absorption band. The microstrip resonant absorber structure 30 is mainly used to absorb high-frequency electromagnetic waves, and has less influence on the absorption band of the low-frequency part, is more conducive to impedance matching, and is easier to optimize in design. That is, the U-shaped resonant absorber structure loaded with the second lumped resistor 32 can not only expand the absorption bandwidth of the low frequency, but also turn the original high-frequency reflection band into an absorption band.

[0031] The present invention adds a three-dimensional structure along the incident direction of the incident wave to the traditional two-dimensional radar absorber with low-frequency absorption and high-frequency transmission, realizing the three-dimensional design of the absorber. This design not only greatly enriches the functionality and application range of the absorber, but also significantly improves its absorption performance and stealth effect. Specifically, the present invention utilizes the resonant characteristics of the U-shaped microstrip, so that the influence of its absorption band in the low-frequency part is controlled within a very small range, making it easier to achieve impedance matching and greatly simplifying the optimization steps in the design process. In addition, the U-shaped microstrip resonant absorber structure also undertakes the important task of absorbing the high-frequency absorption band. It has excellent absorption performance in the high-frequency band, effectively improving the stealth ability of the overall structure in the high-frequency band. At the same time, while the U-shaped microstrip resonant absorber structure absorbs the high-frequency absorption band, it also has a certain frequency band expansion effect on the low-frequency absorption band.

[0032] When low-frequency electromagnetic waves are incident on the frequency selective absorber of the present application, the frequency selective surface layer 10 interacts with the loss layer 20 as a metal floor, generating strong resonance at low frequencies, thereby effectively absorbing low-frequency electromagnetic waves. In addition, the metal resonance units 21 and the first lumped resistor 213 of the loss layer 20 absorb the energy of low-frequency electromagnetic waves, and the microstrip resonance absorbing structure 30 has a certain frequency band expansion effect on the low-frequency absorption band;

[0033] When medium-frequency electromagnetic waves are incident on the frequency selective absorber of the present application, due to the coupled band-pass frequency selection characteristic of the frequency selective surface layer 10, and at the same time the metal resonance unit 211 of the loss layer 20 is equivalent to a parallel LC circuit and also has a band-pass characteristic, the medium-frequency electromagnetic waves can smoothly pass through the frequency selective surface to form medium-frequency transmission;

[0034] When high-frequency electromagnetic waves are incident on the frequency selective absorber of the present application, the high-frequency electromagnetic waves interact with the frequency selective surface layer 10 to cause reflection; the microstrip resonance absorbing structure 30 absorbs the energy of most high-frequency electromagnetic waves, thereby transforming the original high-frequency reflection band into an absorption band.

[0035] Such as Figure 4 and Figure 5 shown, the simulation curves of the reflection coefficient and absorption coefficient of the frequency selective absorber of this embodiment changing with frequency are given. It can be seen from the figure that the frequency band with a transmission coefficient greater than 80% is about 8.5 - 11 GHz, and the reflection coefficient is below 0.4 for about 2.6 - 20 GHz. Therefore, while the present invention has ultra-wideband absorption, it can form a good transmission window in the medium frequency range and has broad application prospects in the radar radome system.

[0036] It should be noted that the materials of the metal layer and the dielectric layer can refer to the prior art.

[0037] The above is only the preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions falling within the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for those of ordinary skill in the art, several improvements and refinements made without departing from the principle of the present invention should be regarded as within the protection scope of the present invention.

Claims

1. A frequency selective absorber based on a three-dimensional structure, characterized in that: The invention comprises a plurality of periodically distributed three-dimensional structural units, wherein the three-dimensional structural units comprise a frequency selective surface layer (10), a loss layer (20) and a microstrip resonant wave absorbing structure (30); the microstrip resonant wave absorbing structure (30) is parallel to the incident direction of the incident wave, the frequency selective surface layer (10) and the loss layer (20) are distributed in parallel on the left and right and are both perpendicular to the incident direction of the incident wave; the microstrip resonant wave absorbing structure (30) and the loss layer (20) form a "cross" structure, and the end of the microstrip resonant wave absorbing structure (30) abuts against the frequency selective surface layer (10); the frequency selective surface The layer (10) comprises an aperture layer (12) and patch layers (11) arranged on both sides of the aperture layer (12), and has coupled bandpass frequency selection characteristics; the loss layer (20) comprises a metal resonance unit (21), a square ring-shaped spiral metal wire (211) is arranged in the middle of the metal resonance unit (21), and metal arrow structures (212) loaded with a first lumped resistor (213) are arranged around the metal resonance unit (211); the metal arrow structure (212) is connected to the square ring-shaped spiral metal wire (211); and the microstrip resonant absorbing structure (30) comprises a U-shaped microstrip line (31) loaded with a second lumped resistor (32).

2. The frequency selective absorber based on a three-dimensional structure according to claim 1, characterized in that: The patch layer (11) comprises a first metal layer (111) and a first dielectric layer (112), wherein the first dielectric layer (112) is adjacent to the aperture layer (12).

3. The frequency selective absorber based on a three-dimensional structure according to claim 2, characterized in that: The first dielectric layer (112) is a square sheet structure with a thickness of 1 mm and a dielectric constant of 3.

5.

4. The frequency selective absorber based on a three-dimensional structure according to claim 1, characterized in that: The aperture layer (12) is a metal square ring with a hollow center, and the outer side length of the metal square ring is 7.5 mm, and the inner side length is 3.5 mm.

5. The frequency selective absorber based on a three-dimensional structure according to claim 1, characterized in that: The patch layer (11) is equivalent to a capacitor layer, the aperture layer (12) is equivalent to an inductor layer, and the two capacitor layers and the inductor layer form a parallel LC circuit.

6. The frequency selective absorber based on a three-dimensional structure according to claim 1, characterized in that: The outer side length of the square ring-shaped spiral metal wire (211) is 7.26 mm.

7. The frequency selective absorber based on a three-dimensional structure according to claim 1, characterized in that: The lossy layer (20) further comprises a second dielectric layer (22); the metal resonance unit (21) is arranged on the second dielectric layer (22), the thickness of the second dielectric layer (22) is 0.5 mm; and the resistance value of the first lumped resistor (213) is 170Ω.

8. The frequency selective absorber based on a three-dimensional structure according to claim 1, characterized in that: The microstrip resonant absorbing structure (30) comprises a third dielectric layer (33), the U-shaped microstrip line (31) is arranged on the third dielectric layer (33), and the thickness of the third dielectric layer (33) is 0.5 mm; the second lumped resistor (32) is located in the middle of the U-shaped microstrip line (31) and has a resistance value of 150Ω.

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