Radar stealth device, system and radar stealth method

Abstract

The present invention provides a radar stealth device, a system and a radar stealth method. The radar stealth device includes a negative bias voltage layer and a plasma generator. The negative bias voltage layer is disposed on the surface layer of the target and is used for forming a negative pressure electric field. The outlet of the plasma generator is located on the side of the negative bias voltage layer away from the target and is used for emitting plasma in a direction away from the target. Free electrons in the plasma move in a directional manner under the action of the negative pressure electric field to form a plasma layer, and the plasma layer is used for modulating the echo frequency of the radar outside the receiving frequency band of the radar. This solution can effectively broaden the stealth frequency band.

Description

Technical Field

[0001] Embodiments of the present invention relate to the field of electromagnetic technology, and particularly to a radar stealth device, a system and a radar stealth method. Background Art

[0002] Radar stealth naturally becomes an important stealth technology. The existing radar stealth technologies mainly reduce the Radar Cross section (RCS) of the target by changing the amplitude and phase of the radar echo signal to achieve the stealth effect. The commonly used technical measures include: shape stealth technology, absorbing material technology, impedance loading stealth technology, etc. However, these existing technologies all have the problem of narrow stealth frequency bands. Summary of the Invention

[0003] Based on the problem of narrow stealth frequency bands in the prior art, embodiments of the present invention provide a radar stealth device, a system and a radar stealth method, which can effectively broaden the stealth frequency band.

[0004] In a first aspect, embodiments of the present invention provide a radar stealth device, including: a negative bias voltage layer and a plasma generator;

[0005] The negative bias voltage layer is disposed on the surface of the target and is used to form a negative pressure electric field;

[0006] The outlet of the plasma generator is located on the side of the negative bias voltage layer away from the target, and is used to emit plasma in a direction away from the target. Moreover, free electrons in the plasma move in a directional manner under the action of the negative pressure electric field to form a plasma layer, and the plasma layer is used to modulate the echo frequency of the radar outside the receiving frequency band of the radar.

[0007] Preferably, it further includes: an insulating layer located between the negative bias voltage layer and the plasma generator; the insulating layer is used to isolate anions of the negative bias voltage layer from cations in the plasma layer.

[0008] Preferably, the plasma in the plasma layer is distributed in a gradient; wherein, the plasma density closer to the plasma generator is greater than the plasma density farther from the plasma generator.

[0009] Preferably, the maximum resonance frequency of the plasma generator is greater than the radar carrier frequency of the radar;

[0010] The maximum resonance frequency of the plasma generator is calculated by the following formula:

[0011]

[0012] where f pis the maximum resonance frequency, N e is the maximum plasma density of the plasma layer, e is the electron charge, m e is the electron mass, and ε0 is the permittivity of free space.

[0013] Preferably, the negative voltage input to the negative bias layer is determined according to the Doppler frequency to be modulated; the Doppler frequency to be modulated is determined according to the receiving bandwidth of the radar; the Doppler frequency is used to modulate the echo frequency of the radar outside the receiving frequency band of the radar.

[0014] Preferably, the following formula is used to calculate the minimum moving speed at which the echo frequency of the radar is modulated outside the receiving frequency band of the radar through the Doppler frequency:

[0015]

[0016] where f dmin is the Doppler frequency; c is the speed of light; f z is the radar carrier frequency; v min is the minimum moving speed of the free electrons in the plasma layer with a resonance frequency greater than the radar carrier frequency under the action of the negative voltage electric field formed by inputting the negative voltage to the negative bias layer, where the negative voltage is positively correlated with the minimum moving speed.

[0017] Preferably, the number of the plasma generators is multiple.

[0018] In a second aspect, an embodiment of the present invention further provides a radar stealth system, including a target and the radar stealth device according to any embodiment of this specification; the radar stealth device is disposed on the surface layer of the target.

[0019] In a third aspect, an embodiment of the present invention further provides a radar stealth method, which is a radar stealth method implemented based on the radar stealth device according to any embodiment of this specification, including:

[0020] Input a negative voltage to the negative bias layer to form a negative voltage electric field;

[0021] Control the plasma generator to emit plasma in a direction away from the target, so that the free electrons in the plasma move in a directional manner under the action of the negative voltage electric field to form a plasma layer, so as to use the plasma layer to modulate the echo frequency of the radar outside the receiving frequency band of the radar.

[0022] Preferably, before inputting the negative voltage to the negative bias layer, it further includes:

[0023] Determine the Doppler frequency to be modulated according to the receiving bandwidth of the radar; the Doppler frequency is used to modulate the echo frequency of the radar outside the receiving frequency band of the radar;

[0024] Calculate the minimum moving speed of free electrons in the plasma layer according to the Doppler frequency to be modulated; determine the value of the negative voltage input to the negative bias layer according to the minimum moving speed.

[0025] An embodiment of the present invention provides a radar stealth device, system and radar stealth method. By setting a negative bias layer on the surface of the target, a negative pressure electric field is formed, so that free electrons in the plasma emitted by the plasma generator on the side of the negative bias layer away from the target move at high speed to form a plasma layer, which is used to cause the Doppler effect of the radar incident wave and modulate the echo frequency of the radar outside the receiving frequency band of the radar, so as to achieve the purpose of stealth. Since the radar has a fixed receiving bandwidth and forms a corresponding receiving frequency band, only when the echo of the radar is within this receiving frequency band can the echo be received. When the echo is received, it indicates that the target is detected. In this solution, even if the frequency band range of the radar receiving bandwidth is relatively wide, the echo can be modulated outside the receiving frequency band of the radar, and the radar cannot receive the echo, so the target cannot be detected, thus realizing the stealth of the target and being able to widen the stealth frequency band. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0027] Figure 1 It is a schematic structural diagram of a radar stealth device provided by an embodiment of the present invention;

[0028] Figure 2 It is a schematic structural diagram of another radar stealth device provided by an embodiment of the present invention;

[0029] Figure 3 It is a schematic structural diagram of yet another radar stealth device provided by an embodiment of the present invention;

[0030] Figure 4 It is a schematic structural diagram of still another radar stealth device provided by an embodiment of the present invention;

[0031] Figure 5 It is an architecture diagram of a radar stealth system provided by an embodiment of the present invention;

[0032] Figure 6 It is a flowchart of a radar stealth method provided by an embodiment of the present invention;

[0033] Reference numerals: 1 - negative bias layer; 2 - plasma generator; 3 - plasma layer; 4 - insulating layer. Specific embodiments

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0035] As mentioned above, existing radar stealth technologies such as shape stealth technology, absorbing material technology, and impedance loading stealth technology mainly reduce the radar cross-section of the target by changing the amplitude and phase of the radar echo signal, achieving the stealth effect, and can only have the function of stealth targets within a certain frequency band range. Therefore, it is considered to generate high-speed moving plasma on the surface of the target, so that the Doppler effect of the plasma directly changes the frequency of the radar echo signal. In this solution, a negative bias layer is provided on the surface layer of the target to form a negative pressure electric field, so that the free electrons in the plasma emitted by the plasma generator away from the target are repelled by the constant negative pressure electric field on the negative bias layer and move away from the negative bias layer at high speed, generating a Doppler effect on the incident radar wave; due to the very high moving speed of the free electrons, its Doppler effect can even modulate the echo frequency of the radar outside the receiving frequency band of the radar, causing the radar to be unable to receive the echo and forming the effect of target stealth. The Doppler characteristic is an inherent property of an object, and only when the incident radar wave can form a reflection in the formed plasma layer to generate a radar echo, can the Doppler effect be used to make the frequency of the reflected radar echo outside the receiving frequency band of the radar to achieve the stealth effect. And only when the incident frequency of the radar wave is less than the maximum resonance frequency of the plasma layer can a reflection be formed. Therefore, this device can achieve the stealth effect on radar waves with frequencies below the maximum resonance frequency of the formed plasma layer. It can not only effectively broaden the frequency band of stealth, but also make the target have the stealth effect in the low frequency band.

[0036] The following describes the specific implementation manners of the above concepts.

[0037] Please refer to Figure 1 and Figure 2 wherein, Figure 1 The shown radar stealth device is the structure before applying a negative voltage to the negative bias layer 1. Figure 2The shown radar stealth device is the structure after applying a negative voltage to the negative bias layer 1. An embodiment of the present invention provides a radar stealth device, which includes: a negative bias layer 1 and a plasma generator 2;

[0038] The negative bias layer 1 is disposed on the surface of the target and is used to form a negative voltage electric field;

[0039] The plasma generator 2 has an outlet located on the side of the negative bias layer 1 away from the target, and is used to emit plasma in a direction away from the target. Free electrons in the plasma move in a directed manner under the action of the negative voltage electric field to form a plasma layer 3, and the plasma layer 3 is used to modulate the echo frequency of the radar outside the receiving frequency band of the radar.

[0040] In an embodiment of the present invention, by disposing the negative bias layer 1 on the surface of the target to form a negative voltage electric field, free electrons in the plasma emitted by the plasma generator 2 with an outlet located on the side of the negative bias layer 1 away from the target move at high speed to form a plasma layer 3, which is used to cause the Doppler effect on the radar incident wave and modulate the echo frequency of the radar outside the receiving frequency band of the radar, so as to achieve the purpose of stealth. Since the radar has a fixed receiving bandwidth and forms a corresponding receiving frequency band, only when the radar echo is within this receiving frequency band can the echo be received. When the echo is received, it indicates that the target is detected. In this solution, even if the frequency band range of the radar receiving bandwidth is relatively wide, the echo can be modulated outside the receiving frequency band of the radar, and the radar cannot receive the echo, so the target cannot be detected, thus realizing the stealth of the target and being able to widen the stealth frequency band.

[0041] In an embodiment of the present invention, when the negative bias layer 1 is disposed on the surface of the target, the negative bias layer 1 can wrap the entire target so that radar waves in any direction cannot detect the target, or the negative bias layer 1 can be disposed on one side of the target so that the negative voltage electric field formed when the negative bias layer 1 is applied with a negative voltage can act on the entire target.

[0042] In an embodiment of the present invention, since the function of the negative bias layer 1 is to form a negative voltage electric field, the material of the negative bias layer 1 needs to be conductive, such as metals like iron and aluminum. To facilitate the disposition of the negative bias layer 1 on the surface of the target, the structure of the negative bias layer 1 can be a sheet structure. By connecting a constant negative voltage to the negative bias layer 1, at this time, the negative bias layer 1 can generate a constant negative voltage field.

[0043] In one embodiment of the present invention, the plasma generator 2 is used to emit plasma. The outlet end of the plasma generator 2 faces away from the target. Therefore, when the plasma generator 2 emits plasma, it can emit the plasma in a direction away from the target. The plasma includes: positively charged atomic nuclei, negatively charged free electrons, and un-ionized neutral particles. Under the action of a negative pressure electric field, the free electrons in the plasma are repelled and move at high speed in a region away from the negative bias layer 1, thereby forming a plasma layer 3.

[0044] When the incident radar wave enters the plasma layer 3, due to the high-speed movement of the free electrons in the plasma layer 3, the Doppler effect will be generated on the incident radar wave. The Doppler frequency generated by the Doppler effect causes the frequency of the echo corresponding to the incident radar wave to change. Furthermore, the echo frequency of the radar can be modulated outside the receiving frequency band of the radar by adjusting the Doppler frequency, so that the target is stealthy.

[0045] Among them, the plasma generator 2 can be of any mechanism.

[0046] It should be noted that the device can be arranged on the local or entire outer surface of the target according to the actual situation and requirements. For example, the device can be arranged on the main part of the target where radar waves are reflected, or the negative bias layer 1 can cover the outer surface of the target, so that the plasma layer 3 generated by the plasma emitted by multiple plasma generators 2 under the action of the negative bias layer 1 surrounds the outer surface of the target. No matter which setting method is used, when the target passes through the radar detection area, as long as the device starts to work, the radar cannot detect the information of the target according to the received echo, and the target can achieve the stealth effect.

[0047] In addition, since the plasma layer 3 is formed by the negative pressure electric field generated by the negative bias layer 1 repelling the free electrons in the plasma and making them move at high speed, but the cations in the plasma will generate electromagnetic attraction with the negative bias layer 1, thus affecting the Doppler effect. Therefore, in one embodiment of the present invention, a schematic structural diagram before the operation of another radar stealth device is provided, as Figure 3 shown. The device may further include: an insulating layer 4 located between the negative voltage layer 1 and the plasma generator 2; the insulating layer 4 is used to isolate the anions of the negative bias layer 1 from the cations in the plasma layer 3. Thereby reducing or blocking the neutralization of the cations in the plasma with the anions in the negative bias layer 1, and further reducing the influence on the Doppler effect.

[0048] After the insulating layer 4 is added to the radar stealth device, when a negative voltage is applied to the negative bias layer 1 at this time, the result can be obtained as shown in Figure 4The structure of the radar stealth device shown, where the insulating layer 4 isolates the anions in the negative bias layer 1 from the cations in the plasma layer 3. After the device operates, when the applied negative voltage remains unchanged, a constant negative pressure electric field can still be formed. The insulating layer 4 can not only make the Doppler effect generated by the device more stable, but also ensure the normal operation of the target.

[0049] In an embodiment of the present invention, the plasma in the plasma layer 3 is distributed in a gradient; among them, the plasma density closer to the plasma generator 2 is greater than the plasma density farther from the plasma generator 2.

[0050] Assume that the plasma layer 3 is equivalent to 100 layers of homogeneous media, and the plasma density in the plasma layer 3 decreases layer by layer in the direction away from the negative bias layer 1 from the plasma generator. Among them, the plasma density of the innermost layer, which is the layer closest to the plasma generator 2, is the largest, and the plasma density of the outermost layer, which is the farthest from the plasma generator, is the smallest.

[0051] It should be noted that when the incident radar wave enters the plasma layer 3, reflection and attenuation effects will occur, that is, when the frequency of the incident radar wave is less than the resonance frequency of the plasma layer, the reflection effect occurs, and when the frequency of the incident radar wave is greater than the resonance frequency of the plasma layer 3, the incident radar wave will undergo absorption and attenuation effects in the plasma layer 3, thus reducing the radar cross-section of the target. In order to enable the radar incident wave to produce a reflection effect to form an echo, and then modulate the Doppler frequency to make the radar echo frequency modulated outside the receiving frequency band of the radar, it is necessary to ensure that when the incident radar wave reaches the innermost layer of the plasma layer 3, it has been completely reflected back. Therefore, it is necessary to ensure that the maximum resonance frequency of the plasma layer 3, that is, the resonance frequency of the innermost layer, is greater than the frequency of the radar incident wave. In the embodiment of the present invention, it is necessary to ensure that the plasma density of the plasma layer 3 formed by the plasma generator 2 in the innermost layer can make the generated maximum resonance frequency meet the requirements, so that the device can play a stealth role for radars with carrier frequencies below the maximum resonance frequency.

[0052] In an embodiment of the present invention, the plasma density of the plasma generator 2 in the innermost layer needs to meet the following conditions: the maximum resonance frequency of the plasma generator 2 is greater than the radar carrier frequency of the radar; among them, the maximum resonance frequency of the plasma generator 2 is calculated by the following formula:

[0053]

[0054] where, f p is the maximum resonance frequency, N e is the maximum plasma density of the plasma layer, e is the electron charge, m eis the electron mass, and ε0 is the permittivity of free space.

[0055] The maximum resonance frequency of the plasma generator 2 can be determined according to the radar carrier frequency of the radar. For example, if the radar stealth device needs to achieve stealth of the target under the radar incident wave with a radar carrier frequency below 4 GHz, then the maximum resonance frequency of the plasma generator 2 can be greater than 4 GHz. Substituting this radar carrier frequency into the maximum resonance frequency calculation formula, the minimum value of the maximum plasma density N can be calculated. e Therefore, the plasma generator 2 used in this embodiment needs to be able to satisfy that the maximum plasma density N e is greater than this minimum value.

[0056] Furthermore, in order to make the target stealth to the radar, it is also necessary to adjust the negative voltage input to the negative bias layer 1 to modulate the radar echo frequency outside the receiving frequency band of the radar.

[0057] In an embodiment of the present invention, the negative voltage input to the negative bias layer 1 is determined according to the Doppler frequency to be modulated; the Doppler frequency is used to modulate the echo frequency of the radar outside the receiving frequency band of the radar.

[0058] In actual applied radars, most radars are narrowband radars, and the receiving bandwidth of narrowband radars is generally 5 - 10 MHz. In the embodiment of the present invention, in order to prevent the influence of the radar incident wave angle, radar transmitter parameters, etc. on the effect of this device, the Doppler frequency to be modulated is selected as 20 - 40 MHz to modulate the echo frequency of the narrowband radar outside the receiving frequency band of the narrowband radar. The Doppler frequency to be modulated is the Doppler frequency generated when the incident radar wave enters the plasma layer 3. The Doppler frequency is determined by the movement speed of free electrons in the plasma layer 3, and the movement speed of free electrons is determined by the negative voltage electric field intensity generated by the negative bias layer 1. Therefore, determining the negative voltage input to the negative bias layer 1 according to the Doppler frequency to be modulated also needs to be determined by the movement speed of free electrons in the plasma layer 3.

[0059] Specifically, the following formula can be used to calculate the minimum movement speed for modulating the echo frequency of the radar outside the receiving frequency band of the radar through the Doppler frequency:

[0060]

[0061] where f dmin is the Doppler frequency; c is the speed of light; f z is the radar carrier frequency; v minUnder the action of the negative voltage input to the negative bias layer 1 to form a negative voltage electric field, the minimum movement speed of free electrons in the plasma layer 3 with a resonance frequency greater than the radar carrier frequency, where the negative voltage is positively correlated with the minimum movement speed.

[0062] For example, the maximum resonance frequency of the plasma generator 2 is 4 GHz. When passing through the detection range of a narrowband radar with a carrier frequency of 3 GHz, the Doppler frequency is selected to be 20 - 40 MHz according to the receiving bandwidth of the narrowband radar. Therefore, when substituting the minimum Doppler frequency of 20 MHz into the above formula, it can be calculated that under the action of the negative voltage input to the negative bias layer 1 to form a negative voltage electric field, the minimum movement speed of free electrons in the plasma layer 3 is 10 6 m / s. Therefore, as long as the minimum Doppler frequency is greater than the receiving bandwidth of the narrowband radar, it can ensure the realization of target stealth.

[0063] Among them, the negative voltage is positively correlated with the minimum movement speed. Then the relationship between the negative voltage and the minimum movement speed can be: minimum movement speed = initial speed + k * value of the negative voltage. Where k is a constant and can be obtained through a large number of experiments.

[0064] Moreover, the movement speed of free electrons in the plasma layer 3 that is farthest from the plasma generator 2, i.e., the outermost layer, is the minimum movement speed in the plasma layer 3 generated by this device, and the movement speed of free electrons in the plasma layer 3 that is closest to the plasma generator, i.e., the innermost layer, is the maximum movement speed in the plasma layer 3 generated by this device. Similarly, substituting 40 MHz into the above formula, the maximum movement speed of free electrons in the plasma layer 3 can be obtained as 2 * 10 6 m / s. Therefore, the movement speed of free electrons in the plasma layer 3 increases in an arithmetic progression from the outermost layer to the innermost layer within the range of 10 6 m / s to 2 * 10 6 m / s.

[0065] Assume that the plasma layer 3 is equivalent to 100 layers. The transmission coefficient between every two adjacent layers in these 100 layers of homogeneous medium is 0.9, and the reflection coefficient is 0.1. The collision absorption of radar waves by the plasma is ignored, and the reflection of radar waves more than once between different plasma layers is ignored. When the receiving bandwidth of the narrowband radar is 10 MHz and the carrier frequency is 3 GHz, the receiving frequency band of the narrowband radar is 2.995 GHz to 3.005 GHz. In order to make the radar echo frequency exceed the receiving frequency band of the narrowband radar, the required modulated Doppler frequency needs to be greater than the receiving bandwidth of the narrowband radar. Therefore, the Doppler frequency is determined to be 20 - 40 MHz when the incident radar wave is 3 GHz. Since the moving speed of the target is very small compared with the moving speed of free electrons in the plasma layer 3, the influence of the moving speed of the target on the Doppler frequency can be ignored. Then, when the target moves towards the direction close to the narrowband radar, due to the Doppler frequency generated by the Doppler effect of the high-speed moving free electrons in the plasma layer 3 generated by this device on the incident wave of the narrowband radar, the echo frequency of this incident radar wave is modulated to 3.02 - 3.04 GHz. It can be understood that no matter what speed the target approaches the narrowband radar, the plasma layer 3 of this device will modulate the echo frequency of this narrowband radar outside the receiving frequency band of this narrowband radar.

[0066] In the embodiment of the present invention, in order to generate a plasma density that meets the requirements and make the plasma layer 3 be able to be relatively uniformly distributed, the number of plasma generators 2 is multiple. The number and distribution mode of the plasma generators 2 can be determined according to the actually required coverage area and the required stealth effect.

[0067] For low-frequency radar, in the existing radar stealth technology, it is necessary to cover a thick absorbing material on the surface of the target. Not only is the stealth effect not good, but its weight has already affected the normal operation and flight of the target. However, this device can achieve a stealth effect on radar waves with frequencies below the maximum resonance frequency of the formed plasma layer 3, and can achieve full-band stealth below the maximum resonance frequency.

[0068] Please refer to Figure 5 , the embodiment of the present invention provides a radar stealth system, including a target 10 and the radar stealth device 20 described in any embodiment of this specification; the radar stealth device is arranged on the surface layer of the target.

[0069] Please refer to Figure 6 , the embodiment of the present invention provides a radar stealth method implemented based on the radar stealth device described in any embodiment of this specification. This method may include:

[0070] Step 600, input a negative voltage to the negative bias layer 1 to form a negative voltage electric field;

[0071] Step 602: Control the plasma generator 2 to emit plasma in a direction away from the target, so that the free electrons in the plasma move directionally under the action of the negative pressure electric field to form a plasma layer 3, and use the plasma layer 3 to modulate the echo frequency of the radar outside the receiving frequency band of the radar.

[0072] Since this method requires the radar incident wave to form a radar echo beyond the radar receiving frequency band through the Doppler effect, the prerequisite for the feasibility of this method is that the radar incident wave with a frequency less than the maximum resonance frequency of the plasma layer 3 can form a reflection. In order to ensure that the radar with a carrier frequency below the maximum resonance frequency can be stealth, it is necessary to determine the maximum resonance frequency of the plasma layer, that is, the plasma density of the plasma layer 3 formed by the plasma generator 2 in the innermost layer needs to meet the requirements.

[0073] Specifically, the plasma density of the plasma generator 2 in the innermost layer needs to meet the following conditions: the maximum resonance frequency of the plasma generator 2 is greater than the radar carrier frequency of the radar; among them, the maximum resonance frequency of the plasma generator 2 is calculated by the following formula:

[0074]

[0075] where f p is the maximum resonance frequency, N e is the maximum plasma density of the plasma layer, e is the electron charge, m e is the electron mass, and ε0 is the permittivity of free space.

[0076] The maximum resonance frequency of the plasma generator 2 can be determined according to the radar carrier frequency of the radar. For example, if it is necessary to achieve stealth for the target under the radar incident wave with a radar carrier frequency below 4 GHz, then the maximum resonance frequency of the plasma generator 2 can be greater than 4 GHz. Substituting this radar carrier frequency into the maximum resonance frequency calculation formula, the minimum value of the maximum plasma density N e can be calculated. Therefore, the plasma generator 2 used in this embodiment needs to be able to satisfy that the maximum plasma density N e is larger than this minimum value, so that the radar incident wave with a radar carrier frequency below 4 GHz can form a reflected echo.

[0077] To ensure that a reflected echo can be formed, it is also necessary to ensure that the negative voltage input to the negative bias layer 1 can make the movement speed of the free electrons in the plasma layer 3 large enough, so that the frequency of the reflected echo formed by the incident radar wave is modulated outside the receiving frequency band of the radar through the Doppler effect.

[0078] In the embodiment of the present invention, before inputting a negative voltage to the negative bias layer 1, it further includes:

[0079] Determine the Doppler frequency to be modulated according to the receiving bandwidth of the radar; the Doppler frequency is used to modulate the echo frequency of the radar outside the receiving frequency band of the radar; calculate the minimum moving speed of free electrons in the plasma layer 3 according to the Doppler frequency; determine the value of the negative voltage input to the negative bias layer 1 according to the minimum moving speed.

[0080] In an embodiment of the present invention, the negative voltage input to the negative bias layer 1 is determined according to the Doppler frequency; the Doppler frequency is used to modulate the echo frequency of the radar outside the receiving frequency band of the radar.

[0081] The Doppler frequency is generated by the incident radar wave entering the plasma layer 3. The Doppler frequency is determined by the moving speed of free electrons in the plasma layer 3, and the moving speed of free electrons is determined by the negative voltage electric field strength generated by the negative bias layer 1. Therefore, to determine the negative voltage input to the negative bias layer 1 according to the Doppler frequency, it is also necessary to determine through the moving speed of free electrons in the plasma layer 3.

[0082] Specifically, the following formula can be used to calculate the minimum moving speed for modulating the echo frequency of the radar outside the receiving frequency band of the radar through the Doppler frequency:

[0083]

[0084] where f dmin is the Doppler frequency; c is the speed of light; f z is the radar carrier frequency; v min is the minimum moving speed of free electrons in the plasma layer 3 with a resonance frequency greater than the radar carrier frequency under the action of the negative voltage electric field formed by inputting the negative voltage to the negative bias layer 1, where the negative voltage is positively correlated with the minimum moving speed.

[0085] For example, assume that the plasma layer 3 is equivalent to 100 layers. When the receiving bandwidth of the narrowband radar is 10 MHz and the carrier frequency is 3 GHz, the receiving frequency band of the narrowband radar is 2.995 GHz to 3.005 GHz. To make the frequency of the radar echo exceed the receiving frequency band of the narrowband radar, the Doppler frequency needs to be greater than the receiving bandwidth of the narrowband radar. Therefore, the Doppler frequency is determined to be 20 - 40 MHz when the incident radar wave is 3 GHz. Since the moving speed of the target is very small compared to the moving speed of the free electrons in the plasma layer 3, the influence of the moving speed of the target on the Doppler frequency can be ignored. When the target moves towards the narrowband radar, due to the Doppler effect of the fast-moving free electrons in the plasma layer 3 on the incident wave of the narrowband radar, the Doppler frequency modulates the echo frequency of the incident radar wave to 3.02 - 3.04 GHz. Thus, it can be seen that as long as the Doppler frequency is greater than the receiving bandwidth of the narrowband radar, the plasma layer 3 will modulate the echo frequency of the narrowband radar outside the receiving frequency band of the narrowband radar.

[0086] Therefore, as long as the minimum Doppler frequency is greater than the receiving bandwidth of the narrowband radar, it can ensure the realization of target stealth. Thus, the Doppler frequency can be determined according to the receiving bandwidth of the radar. Then, using the above formula, the minimum moving speed of the free electrons in the plasma layer 3 can be calculated based on the minimum value of the Doppler frequency under the action of the negative voltage electric field formed by inputting a negative voltage to the negative bias layer 1.

[0087] Moreover, the moving speed of the free electrons in the plasma layer 3 that is farthest from the plasma generator 2, i.e., the outermost layer, is the minimum moving speed in the plasma layer 3, and the moving speed of the free electrons in the plasma layer 3 that is closest to the plasma generator, i.e., the innermost layer, is the maximum moving speed in the plasma layer 3.

[0088] Among them, the negative voltage is positively correlated with the minimum moving speed. Then, the relationship between the negative voltage and the minimum moving speed can be: minimum moving speed = initial speed + k * value of the negative voltage. Where k is a constant and can be obtained through a large number of experiments.

[0089] Therefore, as long as the minimum Doppler frequency is known, the value of the negative voltage to be input to the negative bias layer 1 can be determined.

[0090] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A radar stealth device, characterized in that, Comprising: A negative bias voltage layer and a plasma generator; The negative bias voltage layer is disposed on the target surface layer for forming a negative voltage electric field; The plasma generator has an outlet on the side of the negative bias voltage layer away from the target, and is used for emitting plasma in a direction away from the target. Free electrons in the plasma move in a directional manner under the action of the negative voltage electric field to form a plasma layer, and the plasma layer is used for modulating the echo frequency of the radar outside the receiving frequency band of the radar; It further comprises: an insulating layer located between the negative bias voltage layer and the plasma generator; the insulating layer is used for isolating anions of the negative bias voltage layer from cations in the plasma layer; The maximum resonance frequency of the plasma generator is greater than the radar carrier frequency of the radar; The negative voltage input to the negative bias voltage layer is determined according to the Doppler frequency to be modulated; the Doppler frequency is determined according to the receiving bandwidth of the radar; the Doppler frequency is used for modulating the echo frequency of the radar outside the receiving frequency band of the radar.

2. The radar stealth device according to claim 1, wherein The plasma in the plasma layer is distributed in a gradient; wherein, the plasma density closer to the plasma generator is greater than the plasma density farther from the plasma generator.

3. The radar stealth device according to claim 2, characterized in that, The maximum resonance frequency of the plasma generator is calculated by the following formula: where f p is the maximum resonance frequency, N e is the maximum plasma density of the plasma layer, e is the electron charge, m e is the electron mass, and ε0 is the permittivity of free space.

4. The radar stealth device according to claim 1, wherein The following formula is used to calculate the minimum moving speed for modulating the echo frequency of the radar outside the receiving frequency band of the radar through the Doppler frequency: where f dmin is the Doppler frequency; c is the speed of light; f z is the radar carrier frequency; v min is the minimum motion speed of free electrons in the plasma layer whose resonance frequency is greater than the radar carrier frequency under the action of the negative voltage electric field formed by inputting the negative voltage to the negative bias layer, where the negative voltage is positively correlated with the minimum motion speed.

5. The radar stealth device according to any one of claims 1-4, characterized in that, The number of the plasma generators is multiple.

6. A radar stealth system, characterized in that, Comprising a target and the radar stealth device according to any one of claims 1-5; the radar stealth device is disposed on the target surface layer.

7. A radar stealth method implemented based on the radar stealth device described in any one of claims 1-5, characterized in that, Comprising: Input a negative voltage to the negative bias voltage layer to form a negative voltage electric field; Control the plasma generator to emit plasma in a direction away from the target, so that free electrons in the plasma move in a directional manner under the action of the negative voltage electric field to form a plasma layer, in order to use the plasma layer to modulate the echo frequency of the radar outside the receiving frequency band of the radar.

8. The radar stealth method according to claim 7, characterized in that, Before inputting the negative voltage to the negative bias voltage layer, it further comprises: Determine the Doppler frequency to be modulated according to the receiving bandwidth of the radar; the Doppler frequency is used for modulating the echo frequency of the radar outside the receiving frequency band of the radar; According to the Doppler frequency to be modulated, calculate the minimum moving speed of free electrons in the plasma layer; determine the value of the negative voltage input to the negative bias voltage layer according to the minimum moving speed.

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