Broadband electromagnetic cloaking device based on plasma array and radar absorbing material

Abstract

The application relates to a broadband electromagnetic stealth device based on a plasma array and a radar wave absorbing material, which comprises a metal plate, the bottom of which is connected to the surface of a military equipment shell; a radar wave absorbing material, which is coated on the surface of the metal plate or the military equipment shell, and the coating thickness is 2 mm; and a plasma array, which is covered on the radar wave absorbing material; the plasma array forms a combined plasma layer after being excited; and the plasma frequency in the plasma layer presents high-low alternating distribution. The electromagnetic stealth device is jointly formed by a tubular closed low-pressure plasma generator and a carbon-based radar wave absorbing material; the tubular closed cavity is made of a black glass tube, which can effectively block visible light generated by the plasma from diffusing to the outside of the cavity; the new composite wave absorbing material formed by combining the plasma and the wave absorbing material exhibits extremely excellent wave absorbing performance, and can absorb radar waves in a wide frequency band.

Description

Technical Field

[0001] This invention relates to the field of low-temperature plasma application technology, specifically to a broadband electromagnetic stealth device based on plasma arrays and radar absorbing materials. Background Technology

[0002] The widespread use of radar in modern military applications has made it an important detection tool. Radar stealth has naturally become an important stealth technology, and it has always been a research hotspot in the field of space exploration. Plasma stealth technology is gradually moving from the laboratory to practical application, and its applications are expanding from the aviation field to stealth for naval vessels and ground weapons.

[0003] Achieving low observability of targets in increasingly complex electromagnetic environments is a crucial issue that must be considered when designing various equipment systems. The key to radar stealth is primarily reducing the target's radar cross-section to a level undetectable by radar receivers. Common methods for reducing radar cross-section include loading radar-absorbing materials onto the target surface to reduce detection echoes or modifying the object's geometry to redirect scattered waves away from the backscattering direction.

[0004] Achieving radar stealth through target reshaping is an extremely challenging engineering project with very high design costs. It is often only applicable to a small number of critical devices, and the shape design does not effectively achieve stealth at lower frequencies. Applying radar-absorbing materials to the target surface is a common method to reduce radar cross-section. Traditional radar-absorbing materials such as ferrite and carbon-based materials can only effectively absorb electromagnetic waves in specific frequency bands and angles. Furthermore, radar-absorbing material coatings are very thick, making it difficult to absorb X-band microwaves. Therefore, thin-layer radar-absorbing materials are not suitable for reducing radar cross-section over a wide frequency range. Since plasma can absorb electromagnetic waves over a wide frequency range and is easy to control, plasma stealth is used to reduce the electromagnetic wave reflection of targets.

[0005] Much research on plasma stealth revolves around open-plate plasma covering a metal plate. However, due to the short lifetime of plasma in open environments, it is difficult to generate and maintain an ideally distributed plasma electron density. Furthermore, this type of open plasma emits visible light, making it easily detectable by photoelectric detection systems. Therefore, this type of open plasma cannot be directly used for practical stealth applications.

[0006] For the reasons mentioned above, enclosed plasma has been introduced into stealth technology. Enclosed plasma is usually generated using inductive coupling coils or discharge electrodes. Enclosed plasma can maintain a stable electron density and controllable plasma distribution. Plasma generated by inductive coupling coils has problems such as uneven distribution and large device size, making it unsuitable for large-area plasma stealth applications. Summary of the Invention

[0007] The purpose of this invention is to provide a broadband electromagnetic stealth device based on plasma arrays and radar absorbing materials in order to solve the above-mentioned problems.

[0008] To achieve the above objectives, the present invention is implemented through the following technical solution: a broadband electromagnetic stealth device based on plasma array and radar absorbing material, which includes a metal plate whose bottom is connected to the surface of the military equipment shell;

[0009] Radar absorbing material, which is coated on the surface of metal plates or military equipment shells, with a coating thickness of 2 mm;

[0010] A plasma array is covered on radar absorbing material; after being excited, the plasma array forms a composite plasma layer; the plasma frequency within the plasma layer exhibits an alternating distribution of high and low frequencies.

[0011] Furthermore, the military equipment includes stealth weapons and equipment or important radar antenna components for land, sea, and air applications.

[0012] Furthermore, the radar absorbing material is a non-magnetic dielectric absorbing material made of carbon-based materials or a magnetic ferrite absorbing material.

[0013] Furthermore, each plasma unit in the plasma array can be arbitrarily turned on and off. By adjusting the parameters of the plasma, the tunability of the absorption frequency band can be achieved. By controlling the on / off state of the plasma units, the spatial distribution of the plasma can be changed, thereby adjusting the attenuation bandgap and attenuation amplitude.

[0014] Furthermore, the plasma array is connected to an adjustment and control module and a plasma excitation module on the outside; the adjustment and control module is used to regulate the on / off state of the plasma units, and the plasma excitation module is used to regulate the parameters of the plasma.

[0015] Furthermore, the plasma array is generated by a tubular closed low-pressure plasma generator; the tubular closed low-pressure plasma generator is composed of multiple sets of gas discharge tubes with black tubular closed cavities.

[0016] Furthermore, the gas discharge tube is filled with a low-pressure mixture of inert gas and mercury, with a gas pressure of 500 Pa to 1500 Pa; the diameter of the gas discharge tube is 15 mm, and the plasma excitation module is controlled by a ballast.

[0017] Specifically, the frequencies of the alternating plasma distribution within the gas discharge tube are 5.18e10 rad / s and 1.8e10 rad / s, respectively.

[0018] Compared with existing technologies, the beneficial effects of this invention are reflected in:

[0019] This invention utilizes a tubular closed low-pressure plasma generator to produce plasma, which, together with carbon-based radar-absorbing materials, constitutes an electromagnetic stealth device. The tubular closed cavity is made of black glass tubes, which can effectively block the visible light generated by the plasma from diffusing outside the cavity. The radar-absorbing material is made of carbon-based materials. The combination of plasma and absorbing materials forms a novel composite absorbing material that exhibits extremely excellent absorption performance. It can absorb radar waves over a wide frequency band. When the plasma density exhibits an alternating high and low distribution pattern, the absorption rate of the plasma absorber for 8-18GHz microwaves can reach over 90%. Furthermore, by changing the type of radar-absorbing material and the on / off state of the plasma unit, different absorption frequency bands can be adjusted for different scenario requirements, ultimately achieving wide-bandwidth, large-angle, tunable electromagnetic absorption within the 8-18GHz frequency band. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of the present invention;

[0021] Figure 2 The distribution diagram of plasma under the three modes of the present invention is shown.

[0022] Figure 3 This is a comparison of the absorption rates of plasma and radar absorbing materials with three different distribution patterns. Detailed Implementation

[0023] The present invention will be further described in detail below with reference to the embodiments shown in the accompanying drawings, but this does not constitute any limitation on the present invention.

[0024] This invention aims to broaden the microwave stealth capabilities of radar-absorbing materials in the X-band, while simultaneously achieving tunable electromagnetic absorption. It is generally believed that when the electromagnetic wave frequency is higher than the plasma frequency, there are certain frequency bands in which electromagnetic waves cannot propagate within the plasma, known as the photonic bandgap; conversely, when the electromagnetic wave frequency is lower than the plasma frequency, it cannot propagate within the plasma, a phenomenon called the cutoff frequency. Generally, Wp / 2π (Hz) is considered the cutoff frequency for electromagnetic wave propagation within the plasma. Electromagnetic waves below this frequency will be totally reflected and cannot enter the plasma. Since the plasma density inside the gas discharge tube exhibits a radial Gaussian distribution, meaning the plasma frequency at the tube wall is lower than the plasma frequency at the tube center, when electromagnetic waves couple into a large-scale plasma array, phenomena such as electromagnetic diffraction will not occur. (Refer to...) Figure 2As shown, the thin plasmas arranged in Mode 2 and Mode 3 are relatively uniformly distributed and can only transmit electromagnetic waves in specific frequency bands. Therefore, by arranging the thin plasmas in a non-uniform manner, more electromagnetic waves can be coupled into the plasma layer, thereby increasing the possibility of electromagnetic wave multiple scattering, dissipating electromagnetic energy, and improving the electromagnetic wave absorption rate.

[0025] Furthermore, when an electromagnetic wave is incident normally onto a plasma absorber, the low-frequency electromagnetic wave propagates within the low-electron-density plasma, as referenced. Figure 2 As shown, the plasma unit with an electron density of Ne1 strongly couples with low-frequency electromagnetic waves. As the electromagnetic wave frequency increases, more electromagnetic energy can couple into the high-electron-density plasma, resulting in a stronger coupling effect between high-frequency electromagnetic waves and the plasma with an electron density of Ne2. Electromagnetic waves in the X-KU band can completely couple into the plasma layer and be dissipated and absorbed by the RAM. The electromagnetic waves react with the RAM, and the radar-absorbing material on the metal surface exhibits an induced electric field. This indicates that such radar-absorbing materials have good absorption performance for high-frequency electromagnetic waves. As the frequency increases, electromagnetic energy is concentrated in the gaps between the plasma units. Electromagnetic waves undergo multiple scattering between the gas discharge tube and the radar-absorbing material and are dissipated and absorbed.

[0026] Based on the above theory, alternating plasma frequencies on radar absorbing materials can form novel composite absorbing materials that exhibit extremely excellent absorption performance. The specific structure is as follows:

[0027] Reference Figure 1 As shown, a broadband electromagnetic stealth device based on plasma array and radar absorbing material is disclosed. It includes a metal plate 100, the bottom of which is connected to the surface of the outer shell of military equipment. The military equipment includes land, sea and air-based weapons and equipment that need to be stealthed or important radar antenna components. Such radars are not easy to steal through their shape, and protruding parts cannot achieve radar stealth well. Traditional radar absorbing materials are coated on radar antennas, which cannot achieve wide-band absorption. The plasma screen + absorbing material of this invention can achieve this well. For flying targets, parts that are not easy to steal, such as landing gear parts and aircraft engine parts, the stealth method of this invention can also be used.

[0028] Radar absorbing material 200 is coated on the surface of a metal plate or the outer shell of military equipment, with a coating thickness of 2 mm.

[0029] Radar absorbing materials can be non-magnetic dielectric absorbing materials made of carbon-based materials or magnetic ferrite absorbing materials.

[0030] A plasma array 300 is covered on a radar absorbing material; after being excited, the plasma array forms a combined plasma layer; the plasma frequency within the plasma layer exhibits an alternating distribution of high and low frequencies.

[0031] To achieve wide-bandwidth, large-angle, tunable electromagnetic wave absorption within the 8-18 GHz frequency range, and to adjust the absorption frequency band for different scenarios, each plasma unit in the plasma array can be arbitrarily turned on and off. By adjusting the plasma parameters, the absorption frequency band can be made adjustable. By controlling the on / off state of the plasma units, the spatial distribution of the plasma can be changed, thereby adjusting the attenuation bandgap and attenuation amplitude. Therefore, a corresponding control module is set up. An adjustment control module 400 and a plasma excitation module 500 are connected to the outside of the plasma array. The adjustment control module 400 is used to control the on / off state of the plasma units, and the plasma excitation module 500 is used to control the plasma parameters.

[0032] The plasma array is configured as follows: it is generated by a tubular closed low-pressure plasma generator; the tubular closed low-pressure plasma generator is composed of multiple sets of gas discharge tubes with black tubular closed cavities, the gas discharge tubes are filled with a low-pressure mixture of inert gas and mercury, the gas pressure is 500 Pa-1500 Pa; the diameter of the gas discharge tube is 15 mm, and the plasma excitation module is controlled by a ballast.

[0033] Furthermore, the plasma frequency is limited, with alternating plasma frequencies of 5.18e10 rad / s and 1.8e10 rad / s within the gas discharge tube. The plasma cylindrical array is assumed to be infinitely distributed on a perfect electrical conductor (metal plate) covered with conventional radar absorbing material. By adjusting the rectifier voltage, plasmas with different electron densities can be obtained. To analyze the influence of plasma spatial distribution on radar absorption, reference is made... Figure 2 As shown, the distributions of two plasmas with different frequencies were tested in three different modes (single low-electron-density plasma, single high-electron-density plasma, and alternating distributions of the two densities). (Ne1 and Ne2 represent the corresponding plasma electron densities). The electron collision frequency was fixed at 1.256e10 rad / s. Figure 2 The simulation results show that when the ballast is loaded with voltages of 220V and 160V respectively, the plasma frequency in the gas discharge tube is 5.18e10 rad / s (for high electron density plasma corresponding to Ne2) and 1.8e10 rad / s (for low electron density plasma corresponding to Ne1). Adjusting the voltage can change the electron density of the plasma, thereby changing the plasma frequency.

[0034] Comparison of the absorption rates of three plasma stealth devices with different distribution patterns and radar absorbing materials (reference) Figure 3 As shown, when the plasma frequency of the plasma absorber is distributed in an alternating pattern of high and low frequencies, it can effectively absorb low-frequency electromagnetic waves.

[0035] The above-described embodiments are preferred embodiments of the present invention and are only used to facilitate the illustration of the present invention. They are not intended to limit the present invention in any way. Any person skilled in the art who makes local modifications or alterations to the technical content disclosed in the present invention without departing from the scope of the technical features of the present invention shall still fall within the scope of the technical features of the present invention.

Claims

1. A broadband electromagnetic cloaking device based on plasma array and radar absorbing material, characterized in that: It comprises a metal plate, the bottom of which is connected to the surface of the military equipment shell; A radar wave absorbing material is coated on the surface of the metal plate or the military equipment shell, with a coating thickness of 2 mm; A plasma array is covered on the radar wave absorbing material; the plasma array forms a combined plasma layer after being excited; the plasma frequency in the plasma layer presents high-low alternating distribution; The plasma array is generated by a tubular closed low-pressure plasma generator; the tubular closed low-pressure plasma generator is composed of multiple groups of gas discharge tubes with black tubular closed cavities; The plasma frequencies in the gas discharge tubes are 5.18e10 rad / s and 1.8e10 rad / s, respectively.

2. The broadband electromagnetic cloaking device based on plasma array and radar absorbing material according to claim 1, characterized in that: The radar wave absorbing material is made of a non-magnetic medium wave absorbing material or a magnetic ferrite wave absorbing material.

3. The broadband electromagnetic cloaking device based on plasma array and radar absorbing material of claim 1, wherein: Each plasma unit in the plasma array can be turned on and off at will; by adjusting the parameters of the plasma, the tunability of the wave absorbing band is realized; by controlling the on-off of the plasma units, the spatial distribution of the plasma is changed, so that the adjustment of the attenuation band gap and the attenuation amplitude is realized.

4. The broadband electromagnetic cloaking device based on plasma array and radar absorbing material of claim 3, wherein: The outer side of the plasma array is connected with an adjusting control module and a plasma excitation module; the adjusting control module is used to control the on-off of the plasma units, and the plasma excitation module is used to control the parameters of the plasma.

5. The broadband electromagnetic cloaking device based on plasma array and radar absorbing material according to claim 4, characterized in that: The gas discharge tube is filled with low-pressure mixed gas of inert gas and mercury, with a gas pressure of 500 Pa-1500 Pa; the diameter of the gas discharge tube is 15 mm, and the plasma excitation module is controlled by a ballast.

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