Method and device for calculating RCS (Radar Cross-Section) of target wrapped around plasma flow field

Abstract

The invention discloses a plasma surrounding flow field coating target RCS calculation method and device. The method comprises the following steps: determining each scattering center of a target body and distribution of plasma around a flow field; respectively calculating a transmission path of the electromagnetic wave in the plasma after passing through each scattering center; based on the distribution of the plasma around the flow field, plasma parameters on each transmission path are extracted; calculating attenuation constants and phase shift constants of the electromagnetic waves on the corresponding transmission paths based on the plasma parameters on each transmission path; based on the attenuation constant and the phase shift constant, calculating the scattering field intensity after the electromagnetic wave passes through the plasma; calculating scattering echoes of the target body based on the field intensity of the electromagnetic wave after the electromagnetic wave passes through the plasma; and calculating the RCS of the target body based on the scattering echo of the target body. According to the method, the calculation efficiency is high, and the real-time calculation requirement can be met.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electromagnetic characteristic calculation, in particular to a plasma flow field coated target RCS calculation method and device. BACKGROUND

[0002] When a high-speed vehicle moves in the atmosphere, a plasma flow field surrounding the vehicle is formed. The plasma flow field can attenuate and absorb radar waves incident therein, which shows as the reduction of target RCS, and affects the radar's ability to detect, track and identify the target. Accurate acquisition of the electromagnetic characteristics of the plasma flow field coated target is the prerequisite for understanding and mastering the mechanism and variation of the plasma electromagnetic characteristics, and is also the basis for stable tracking and identification of high-speed vehicles. Therefore, the calculation of the electromagnetic characteristics of the plasma flow field coated target has a clear application value. However, the existing calculation methods have the problem of large amount of calculation, which cannot meet the real-time calculation requirements.

[0003] Therefore, there is an urgent need for a plasma flow field coated target RCS calculation method and device to solve the above problems. SUMMARY

[0004] The present application provides a plasma flow field coated target RCS calculation method and device, which has high calculation efficiency and can meet the real-time calculation requirements. The technical solution is as follows:

[0005] On the one hand, a plasma flow field coated target RCS calculation method is provided, which comprises:

[0006] determining each scattering center of a target body and a plasma flow field distribution;

[0007] calculating the transmission path of electromagnetic waves in the plasma after passing through each scattering center, respectively;

[0008] extracting the plasma parameters on each transmission path based on the plasma flow field distribution;

[0009] calculating the attenuation constant and phase shift constant of electromagnetic waves on the corresponding transmission path based on the plasma parameters on each transmission path;

[0010] calculating the scattering field strength of electromagnetic waves after passing through the plasma based on the attenuation constant and the phase shift constant;

[0011] calculating the scattering echo of the target body based on the field strength of electromagnetic waves after passing through the plasma;

[0012] calculating the RCS of the target body based on the scattering echo of the target body.

[0013] In another aspect, a device for calculating RCS of a target coated by a plasma flow field is provided, the device comprising:

[0014] a determining unit configured to determine each scattering center of the target body and a plasma flow field distribution;

[0015] a first calculating unit configured to calculate a transmission path of an electromagnetic wave in the plasma after passing through each scattering center, respectively;

[0016] an extracting unit configured to extract a plasma parameter on each transmission path based on the plasma flow field distribution;

[0017] a second calculating unit configured to calculate an attenuation constant and a phase shift constant of the electromagnetic wave on the corresponding transmission path based on the plasma parameter on each transmission path;

[0018] a third calculating unit configured to calculate a scattering field intensity of the electromagnetic wave after passing through the plasma based on the attenuation constant and the phase shift constant;

[0019] a fourth calculating unit configured to calculate a scattering echo of the target body based on the field intensity of the electromagnetic wave after passing through the plasma;

[0020] a fifth calculating unit configured to calculate the RCS of the target body based on the scattering echo of the target body.

[0021] In another aspect, a computer device is provided, the computer device comprising a memory and a processor, the memory being configured to store a computer program, and the processor being configured to execute the computer program stored in the memory to implement the steps of the above-mentioned method for calculating RCS of a target coated by a plasma flow field.

[0022] In another aspect, a computer readable storage medium is provided, the storage medium storing a computer program, the computer program being executed by a processor to implement the steps of the above-mentioned method for calculating RCS of a target coated by a plasma flow field.

[0023] In another aspect, a computer program product is provided, the computer program product comprising a computer program, the computer program being executed by a processor to implement the steps of the above-mentioned method for calculating RCS of a target coated by a plasma flow field.

[0024] The embodiment of the present application provides a plasma flow field coated target RCS calculation method. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0026] Figure 1 is a flow chart of a plasma flow field coated target RCS calculation method provided by an embodiment of the present application;

[0027] Figure 2 is a structure diagram of a plasma flow field coated target RCS calculation device provided by an embodiment of the present application;

[0028] Figure 3 is a hardware architecture diagram of a computer device provided by an embodiment of the present application;

[0029] Figure 4 is a simulation result schematic diagram of a metal ball plasma flow field provided by an embodiment of the present application;

[0030] Figure 5 is a transmission path schematic diagram of electromagnetic waves in plasma provided by an embodiment of the present application. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the following will combine the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are some of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present application.

[0032] The specific implementation of the method of the present application will be described in detail below.

[0033] Reference is made to Figure 1The embodiment of the present application provides a method for calculating RCS of a target coated by a plasma flow field, which comprises the following steps:

[0034] In step 100, each scattering center of the target body and the distribution of the plasma flow field are determined.

[0035] In step 102, the transmission path of the electromagnetic wave in the plasma after passing through each scattering center is calculated respectively.

[0036] In step 104, the plasma parameters on each transmission path are extracted based on the distribution of the plasma flow field.

[0037] In step 106, the attenuation constant and the phase shift constant of the electromagnetic wave on the corresponding transmission path are calculated based on the plasma parameters on each transmission path.

[0038] In step 108, the scattering field intensity of the electromagnetic wave after passing through the plasma is calculated based on the attenuation constant and the phase shift constant.

[0039] In step 110, the scattering echo of the target body is calculated based on the field intensity of the electromagnetic wave after passing through the plasma.

[0040] In step 112, the RCS of the target body is calculated based on the scattering echo of the target body.

[0041] In this embodiment, the target body is equivalent to a limited number of scattering centers based on the scattering center theory, and the RCS characteristics of the target coated by the plasma flow field are quickly generated by calculating the attenuation of the amplitude of each scattering center by the plasma flow field. Therefore, the present application can solve the problems of low calculation efficiency and inability to perform real-time simulation of the RCS characteristics of the target coated by the plasma flow field, and realizes accurate and fast acquisition of the electromagnetic characteristics of the target coated by the plasma flow field.

[0042] The execution mode of each step is described below. Figure 1

[0043] Firstly, for step 100:

[0044] In the high-frequency region of the target body, the target scattering is not contributed by the whole target surface, but has locality, and can be completely characterized by a plurality of isolated scattering centers, so the target body can be equivalent to a limited number of scattering centers. In this step, a three-dimensional scattering center forward parameterization modeling method based on the shooting and bouncing ray (SBR) technology can be used to calculate the scattering center of the target body.

[0045] ​Furthermore, the plasma flow field distribution is closely related to factors such as the target shape, velocity, material, and atmospheric conditions. When solving for the flow field's physical parameters, a model where both thermodynamic and chemical equilibrium are used can be employed. A seven-component model is used for high-temperature air, with chemical components including N2, O2, N, O, NO, NO+, and e-. Under a dual-temperature approximation, different control temperatures are used for different reactions. For example... Figure 4 The figure shows a schematic diagram of the simulation results of the plasma flow field around a metal sphere. The distribution of the plasma flow field can be seen from the figure.

[0046] For step 102, the propagation path of the electromagnetic wave in the plasma after passing through each scattering center is calculated, including:

[0047] Starting from the scattering center, the direction opposite to the incident electromagnetic wave is used to calculate the transmission path;

[0048] The calculation interval is determined based on the wavelength of electromagnetic waves;

[0049] Based on the calculation interval, the elevation angle and azimuth angle of the radar incident, the recursive step size of the transmission path in three-dimensional space is determined.

[0050] Based on the recursive step size, the transmission path corresponding to each scattering center is calculated.

[0051] In this step, such as Figure 5 As shown, the dots represent scattering centers, the solid lines represent the incident direction of the electromagnetic wave, and the dashed lines represent the propagation path calculation direction starting from the scattering center. Furthermore, the calculation interval is preferably one-tenth of the electromagnetic wave wavelength, thus ensuring both calculation accuracy and computational efficiency.

[0052] In some implementations, the recursive step size (dx, dy, dz) is calculated using the following formula:

[0053]

[0054] dz = dr·cos(θ)

[0055] In the formula, dr is the recursive step size of the transmission path in three-dimensional space, dr=(dx,dy,dz), where dx, dy, and dz are the step size components in the x, y, and z directions, respectively; θ is the elevation angle of the radar incident. This is the azimuth angle at which the radar incident.

[0056] The expression for the transmission path r is:

[0057] r=(x0+i·dx,y0+i·dy,z0+i·dz),i=1,…N

[0058] Wherein, (x0, y0, z0) represents the spatial coordinates of the scattering center P0, i represents the i-th step; N is the total number of steps of calculation.

[0059] Through the above formula, the transmission path corresponding to each scattering center as the starting point is calculated respectively.

[0060] For step 104, since the spatial distribution of the plasma flow field around the target body has been determined, when the transmission path is determined, the corresponding plasma parameters can be extracted according to the spatial position of each point on the transmission path.

[0061] For step 106, the plasma parameters at least include electron density and collision frequency and plasma collision frequency;

[0062] The attenuation constant is calculated by the following formula:

[0063]

[0064] The phase shift constant is calculated by the following formula:

[0065]

[0066] Wherein, α is the attenuation constant; β is the phase shift constant; μ0 is the permeability in vacuum; ω is the electromagnetic wave frequency; ν is the plasma collision frequency; ε0 is the dielectric constant in vacuum; ω p is the plasma resonance frequency; n is the free electron density in the plasma; e is the electron charge; m is the electron mass.

[0067] In this step, the permeability in vacuum is taken as 4π×10 -7 H / m.

[0068] For step 108, the scattered field intensity of the electromagnetic wave after passing through the plasma is calculated by the following formula:

[0069] E = E0e -αz-jβz

[0070] Wherein, E is the scattered field intensity of the electromagnetic wave after passing through the plasma; E0 is the initial incident field intensity; Z is the transmission distance.

[0071] It should be noted that the single-pass attenuation of the electromagnetic wave after passing through the plasma can be calculated by the above formula, and when the double-pass attenuation needs to be calculated, the calculated attenuation constant and phase shift constant need to be increased by one time respectively, and then the scattering intensity calculation formula is used for calculation.

[0072] For step 110, the scattered echo of the target body is calculated by the following formula:

[0073]

[0074] wherein E s is the scattering echo of the target body; E i is the scattering intensity of the i-th scattering center; k is the wave number; k0 is the wave beam of the central frequency point; I is the number of scattering centers; a i is the frequency dependence of the i-th scattering center; (x i ,y i ,z i ) is the three-dimensional position parameter of the i-th scattering center; and θ and are the pitch angle and the azimuth angle of the radar, respectively.

[0075] For step 112, the RCS of the target body is calculated using the following formula:

[0076] RCS = 20log10(E s )

[0077] As can be seen from the above, starting from the target electromagnetic scattering mechanism, the target is equivalent to a scattering center, based on the idea of ray tracing, the traditional massive ray tracing starting from the target is simplified to the tracing and calculation of a limited number of electromagnetic wave propagation paths starting from the scattering center, and the path tracing and attenuation calculation of the non-intersecting rays with the target scattering center are omitted, so that the calculation efficiency can be significantly improved, and the real-time calculation requirement can be met.

[0078] As Figure 2 , Figure 3 indicated, the embodiment of the present application provides a plasma flow field coated target RCS calculation device. The device embodiment can be realized by software, or realized by hardware or a combination of software and hardware. From the hardware layer, as Figure 2 indicated, it is a hardware architecture diagram of a computing device where a plasma flow field coated target RCS calculation device provided by the embodiment of the present application is located. In addition to the processor, the memory, the network interface, and the non-volatile memory shown in Figure 2 , the computing device where the device in the embodiment is usually also can include other hardware, such as a forwarding chip responsible for processing packets and the like. Taking the software implementation as an example, as Figure 3 indicated, as a logically meaningful device, it is formed by the CPU of the computing device where it is located to read the corresponding computer program in the non-volatile memory into the memory for running.

[0079] Please refer to Figure 3 , the embodiment of the present application provides a plasma flow field coated target RCS calculation device, which comprises:

[0080] A determination unit 300 is configured to determine each scattering center of the target body and the plasma flow field distribution.

[0081] The first calculation unit 302 is configured to calculate a transmission path of the electromagnetic wave in the plasma after passing through each scattering center, respectively.

[0082] The extraction unit 304 is configured to extract a plasma parameter on each transmission path based on the plasma flow field distribution.

[0083] The second calculation unit 306 is configured to calculate an attenuation constant and a phase shift constant of the electromagnetic wave on the corresponding transmission path based on the plasma parameter on each transmission path.

[0084] The third calculation unit 308 is configured to calculate a scattering field intensity of the electromagnetic wave after passing through the plasma based on the attenuation constant and the phase shift constant.

[0085] The fourth calculation unit 310 is configured to calculate a scattering echo of the target object based on the field intensity of the electromagnetic wave after passing through the plasma.

[0086] The fifth calculation unit 312 is configured to calculate the RCS of the target object based on the scattering echo of the target object.

[0087] In some embodiments, the first calculation unit 302 is configured to perform the following operations:

[0088] The calculation direction of the transmission path is determined from the position of the scattering center to the opposite direction of the incident direction of the electromagnetic wave.

[0089] The calculation interval is determined based on the wavelength of the electromagnetic wave.

[0090] The recursive step length of the transmission path in the three-dimensional space is determined based on the calculation interval, the pitch angle and the azimuth angle of the radar incidence.

[0091] The transmission path corresponding to each scattering center is calculated based on the recursive step length.

[0092] In some embodiments, the recursive step length (dx, dy, dz) is calculated by the following formula:

[0093]

[0094] dz = dr cos(θ)

[0095] In the formula, dr is the recursive step length of the transmission path in the three-dimensional space, dr = (dx, dy, dz), dx, dy and dz are step length components in x, y and z directions, respectively; θ is the pitch angle of the radar incidence; and φ is the azimuth angle of the radar incidence. In the formula, dr is the recursive step length of the transmission path in the three-dimensional space, dr = (dx, dy, dz), dx, dy and dz are step length components in x, y and z directions, respectively; θ is the pitch angle of the radar incidence; and φ is the azimuth angle of the radar incidence.

[0096] In some embodiments, the expression of the transmission path r is as follows:

[0097] r = (x0 + i dx, y0 + i dy, z0 + i dz), i = 1,... N

[0098] where (x0, y0, z0) represents the spatial coordinates of the scattering center P0, i represents the i-th step; N is the total number of steps of calculation.

[0099] In some embodiments, the plasma parameters include at least electron density and collision frequency and plasma collision frequency;

[0100] The attenuation constant is calculated by the following formula:

[0101]

[0102] The phase shift constant is calculated by the following formula:

[0103]

[0104] where a is the attenuation constant; β is the phase shift constant; μ0 is the permeability in vacuum; ω is the electromagnetic wave frequency; v is the plasma collision frequency; ε0 is the permittivity in vacuum; ω p is the plasma resonance frequency; n is the free electron density in the plasma; e is the electron charge; m is the electron mass.

[0105] In some embodiments, the scattered field intensity of the electromagnetic wave after passing through the plasma is calculated by the following formula:

[0106] E = E0e -αz-jβz

[0107] where E is the scattered field intensity of the electromagnetic wave after passing through the plasma; E0 is the initial incident field intensity; Z is the transmission distance.

[0108] In some embodiments, the scattering echo of the target body is calculated by the following formula:

[0109]

[0110] where E s is the scattering echo of the target body; E i is the scattering intensity of the i-th scattering center; k is the wave number; k0 is the wave beam of the center frequency point; I is the number of scattering centers; a i is the frequency dependence of the i-th scattering center; (x i , y i , z i ) is the three-dimensional position parameter of the i-th scattering center; θ and are the pitch angle and azimuth angle of the radar, respectively.

[0111] It should be noted that the above embodiment provides the plasma flow field around the target RCS calculation device, and only the above functional modules are used as examples for illustration. In actual application, the above functions can be completed by different functional modules according to needs, that is, the internal structure of the device is divided into different functional modules to complete all or part of the functions described above. In addition, the plasma flow field around the target RCS calculation device and the plasma flow field around the target RCS calculation method provided by the above embodiment belong to the same concept, and the specific implementation process is described in the method embodiment, which will not be repeated here.

[0112] Embodiments of the present application also provide a computer device, which refers to Figure 3 The computer device includes a processor and a memory, and the memory stores at least one instruction, at least one program, a code set or an instruction set. The at least one instruction, at least one program, code set or instruction set is loaded and executed by the processor to implement the plasma flow field around the target RCS calculation method provided by the above method embodiments.

[0113] Embodiments of the present application also provide a computer readable storage medium, which stores at least one instruction, at least one program, a code set or an instruction set. The at least one instruction, at least one program, code set or instruction set is loaded and executed by the processor to implement the plasma flow field around the target RCS calculation method provided by the above method embodiments.

[0114] Embodiments of the present application also provide a computer program product, which includes a computer program. The processor of the computer device reads the computer program from the computer readable storage medium, and the processor executes the computer program to make the computer device execute the plasma flow field around the target RCS calculation method described in any of the above embodiments.

[0115] For the convenience of description, the above system or device is described as various modules or units in function. Of course, in the implementation of the present application, the functions of each unit can be implemented in the same or multiple software and / or hardware.

[0116] From the above description of the embodiments, those skilled in the art can clearly understand that the present application can be implemented by means of software and necessary general hardware platforms. Based on such understanding, the technical solutions of the present application can be embodied in the form of a software product, which can be stored in a storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes a plurality of instructions for making a computer device (which can be a personal computer, server, or network device, etc.) execute the methods described in the various embodiments or some parts of the embodiments.

[0117] Finally, it is to be understood that the phraseology or terminology such as "first", "second", "third", "fourth", etc. is merely used to distinguish or identify a specific entity or step from another entity or step without necessarily requiring or implying any actual such relationship or order between such entities or steps. Moreover, the terms "comprises", "comprising", or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can also include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by "comprises... a" does not, without more constraints, exclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the recited element.

[0118] The above description is merely that of the preferred embodiments of the application and modifications and alterations are possible without departing from the principles of the application as set forth in the claims.

Claims

1. A method for calculating the RCS of a target enveloped by a plasma flow field, characterized in that, The method includes: Determine each scattering center of the target body and the distribution of the plasma flow field around it; Calculate the propagation path of the electromagnetic wave in the plasma after passing through each scattering center; Based on the plasma flow field distribution, plasma parameters are extracted for each of the transmission paths; Based on the plasma parameters on each transmission path, the attenuation constant and phase shift constant of the electromagnetic wave on the corresponding transmission path are calculated; Based on the attenuation constant and the phase shift constant, the scattered field strength of the electromagnetic wave after passing through the plasma is calculated; The scattered echo of the target body is calculated based on the field strength after the electromagnetic wave passes through the plasma. The RCS of the target body is calculated based on the scattered echo of the target body.

2. The method according to claim 1, characterized in that, The calculation of the propagation path of the electromagnetic wave in the plasma after passing through each scattering center includes: Starting from the scattering center, the direction opposite to the incident electromagnetic wave is used to calculate the transmission path; The calculation interval is determined based on the wavelength of electromagnetic waves; Based on the calculation interval, the elevation angle and azimuth angle of the radar incident, the recursive step size of the transmission path in three-dimensional space is determined. Based on the recursive step size, the transmission path corresponding to each scattering center is calculated.

3. The method according to claim 2, characterized in that, The recursive step size (dx, dy, dz) is calculated using the following formula: dz = dr·cos(θ) In the formula, dr is the recursive step size of the transmission path in three-dimensional space, dr=(dx,dy,dz), where dx, dy, and dz are the step size components in the x, y, and z directions, respectively; θ is the elevation angle of the radar incident. This is the azimuth angle at which the radar incident.

4. The method according to claim 3, characterized in that, The expression for the transmission path r is: r=(x0+i·dx,y0+i·dy,z0+i·dz),i=1,…N In the formula, (x0, y0, z0) represents the spatial coordinates of the scattering center P0, i represents the i-th step, and N is the total number of calculation steps.

5. The method according to claim 1, characterized in that, The plasma parameters include at least electron density and collision frequency, and plasma collision frequency; The attenuation constant is calculated using the following formula: The phase shift constant is calculated using the following formula: In the formula, α is the attenuation constant; β is the phase shift constant; μ0 is the permeability in vacuum; ω is the electromagnetic wave frequency; and ν is the plasma collision frequency. ε0 is the vacuum dielectric constant; ω p denoted as , where n is the plasma resonant frequency; n is the free electron density in the plasma; e is the electron charge; and m is the electron mass.

6. The method according to claim 5, characterized in that, The scattered field strength of electromagnetic waves after passing through plasma is calculated using the following formula: E=E0e -αz-jβz In the formula, E is the scattered field strength of the electromagnetic wave after passing through the plasma; E0 is the initial incident field strength; and Z is the transmission distance.

7. The method according to claim 1, characterized in that, The scattered echo of the target body is calculated using the following formula: In the formula, E s E is the scattered echo of the target body; i The scattering intensity is denoted by k; k is the wavenumber; k0 is the beam at the center frequency; I is the number of scattering centers; a i The frequency dependence of the i-th scattering center; (x i ,y i ,z i ) represents the three-dimensional position parameters of the i-th scattering center; θ and These are the radar's elevation and azimuth angles, respectively.

8. A device for calculating the RCS of a target enveloped by a plasma flow field, characterized in that, The device includes: A determining element is used to determine each scattering center of the target body and the distribution of the plasma flow field around it. The first calculation unit is used to calculate the propagation path of electromagnetic waves in the plasma after passing through each scattering center; An extraction unit is used to extract plasma parameters on each of the transmission paths based on the plasma flow field distribution. The second calculation unit is used to calculate the attenuation constant and phase shift constant of the electromagnetic wave in the corresponding transmission path based on the plasma parameters in each transmission path; The third calculation unit is used to calculate the scattered field strength of the electromagnetic wave after passing through the plasma based on the attenuation constant and the phase shift constant. The fourth calculation unit is used to calculate the scattered echo of the target body based on the field strength after the electromagnetic wave passes through the plasma; The fifth calculation unit is used to calculate the RCS of the target body based on the scattered echo of the target body.

9. A computer device, characterized in that, The computer device includes a memory and a processor. The memory is used to store computer programs, and the processor is used to execute the computer programs stored in the memory to implement the steps of the method according to any one of claims 1-7.

10. A computer-readable storage medium, characterized in that, The storage medium stores a computer program, which, when executed by a processor, implements the steps of the method described in any one of claims 1-7.

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