A method, system, device and medium for calculating polarization error distortion eigenvalue of a magnetized plasma sheath coated target radar echo

Abstract

A kind of magnetized plasma sheath covering target radar echo polarization error distortion eigenvalue calculation method, system, equipment and medium, method includes: setting plasma sheath parameter, radar frequency and magnetic field intensity, calculating the maximum layer number and maximum depth of radar penetrable plasma sheath, calculating the sheath collision frequency of polarization error distortion point, it is judged whether distortion point exists and the sheath layer number where distortion point is located is output, the distortion position sheath eigenvalue vector in the distortion point existing condition is output;System, equipment and medium: for realizing a kind of magnetized plasma sheath covering target radar echo polarization error distortion eigenvalue calculation method;The present application can realize the accurate calculation of the eigenvalue corresponding to the polarization error distortion point of plasma sheath covering target radar echo signal under magnetized environment, with the characteristics of high calculation precision, strong scalability.

Description

Technical Field

[0001] This invention relates to the field of radar signal transmission technology, and in particular to a method, system, device, and medium for calculating the polarization error distortion characteristic value of radar echoes from targets covered by magnetized plasma sheaths. Background Technology

[0002] When a reentry vehicle returns to Earth, the plasma sheath generated on its surface severely impacts radar signals, causing a series of problems such as navigation failure, data loss, and reduced detection accuracy. Current research by scholars both domestically and internationally primarily focuses on the time-frequency transmission characteristics of radar echoes. However, the impact of the plasma sheath on radar echoes extends beyond time-frequency characteristics to include polarization characteristics. Nevertheless, studies on the polarization characteristics of radar echoes caused by the plasma sheath have limited analysis of radar polarization errors, and there is currently no specific research addressing polarization error distortion.

[0003] Existing methods for calculating the polarization error of radar echo signals under plasma sheath encapsulation mainly involve changing the parameters of the plasma sheath and analyzing the effects of different plasma sheath parameters on the time delay and Doppler effect of electromagnetic waves with different polarizations. A commonly used method is the Improved Scattering Matrix Method (ISMM) (Chen, X.; Shen, F.; Liu, Y.; Ai, W.; Li, X. Improved Scattering-Matrix Method and its Application to Analysis of Electromagnetic Wave Reflected by Reentry PlasmaSheath. IEEE Transactions on Plasma Science. 2018, 46, 1755-1767.). This method characterizes the influence of the unmagnetized plasma sheath on electromagnetic waves from three perspectives: transmission coefficient, reflection coefficient, and absorption coefficient. Then, a ray tracing method is employed (Meng, H.; Dou, W.; Yin, C. Analysis of Radome Using Aperture Integration-surface Integration Method with Modified Transmission Coefficient. Journal). (ofInfrared, Millimeter & Terahertz Waves. 2009, 30, 199-210.) This paper verifies the ISMM method, theoretically derives the reflection and transmission coefficients of electromagnetic waves under oblique incidence in a monolayer homogeneous plasma, and provides calculation formulas for vertically polarized and parallelly polarized waves. It utilizes the field approximation principle to perform an equivalent calculation of the electromagnetic wave propagation process, thereby calculating the polarization error of electromagnetic waves in a non-magnetized plasma sheath (Zhang Xu. Influence Mechanism and Law of Plasma Sheath on Various Polarized Radar Waves [D]. Shaanxi: Xi'an University of Electronic Science and Technology, 2020: 1-76.).

[0004] Existing technologies calculate radar echo polarization errors based on time-frequency analysis, and the ISMM method used calculates the dielectric constant of the layered sheath, and then calculates the reflection and transmission coefficients. However, they do not consider the influence of the Earth's magnetic field on electromagnetic waves from the perspective of the polarization domain, making it impossible to accurately calculate the electromagnetic wave polarization error of the magnetized plasma sheath under actual conditions, and there is currently no research on the polarization error distortion characteristics. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, the present invention aims to provide a method, system, device, and medium for calculating the characteristic value of polarization error distortion in radar echoes from targets encased in magnetized plasma sheaths. This invention utilizes the characteristic values ​​and non-uniform distribution characteristics of the plasma sheath, sets a plasma sheath structure with characteristic values ​​varying with the number of layers, sets the radar frequency and magnetic field strength, then determines the relationship between the characteristic frequency of the layered plasma sheath and the radar frequency, calculates the maximum number of layers and maximum depth that the radar can penetrate, and further calculates the plasma sheath collision frequency when polarization error distortion occurs. Finally, combining the set plasma characteristic values, the existence of the distortion point of the polarization error is determined, and the characteristic value of the sheath at the location of the polarization error distortion when the distortion point exists is output. This invention can accurately calculate the characteristic value corresponding to the polarization error distortion point of the radar echo signal from targets encased in plasma sheaths under magnetized conditions, and features high calculation accuracy and strong scalability.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for calculating the polarization error distortion eigenvalue of radar echo from a target covered by a magnetized plasma sheath includes the following steps:

[0008] Step 1, set the plasma sheath parameters, radar frequency, and magnetic field strength: Set the total thickness L of the plasma sheath, the number of layers M, the thickness of the i-th plasma sheath layer d(i) = L / M, the plasma sheath electron density Ne = [Ne(1), Ne(2), ..., Ne(M)] (Ne(i) is the electron density of the i-th plasma sheath layer, i = 1, 2, 3, ..., M), the plasma sheath collision frequency υ = [υ(1), υ(2), ..., υ(M)] (υ(i) is the collision frequency of the i-th plasma sheath layer, i = 1, 2, 3, ..., M), the electron charge e, the electron mass m, the vacuum dielectric constant ε0, the radar frequency f, and the geomagnetic field strength B. z ;

[0009] Step 2, calculate the maximum number of plasma sheath layers and the maximum depth that the radar can penetrate: Calculate the characteristic frequency f of each plasma layer based on the parameters in Step 1. p (i) Determine the characteristic frequency f of each plasma layer based on the radar frequency f. p (i) By analyzing the relationship between the radar frequency f and the maximum number of plasma sheath layers N that the radar wave can penetrate, and calculating the maximum depth D that the radar wave can penetrate the plasma sheath, we can obtain the maximum number of plasma sheath layers N that the radar wave can penetrate. max ;

[0010] Step 3: Calculate the sheath collision frequency υ at the polarization error distortion point based on the relevant parameters from Step 1. s ;

[0011] Step 4: Determine whether a distortion point exists and output the sheath layer number where the distortion point is located: According to the maximum number of layers N that radar waves can penetrate in Step 2 and the sheath collision frequency υ of the polarization error distortion point in Step 3 s , determine the magnitude relationship between the sheath collision frequency υ of the polarization error distortion point s and the collision frequency of the first N layers of the plasma sheath υ=[υ(1), υ(2), ..., υ(M)]; if υ s <υ(N), the distortion point exists; if the distortion point exists, output the sheath layer number K where the distortion point is located, and calculate the sheath thickness D at the distortion point s ;

[0012] Step 5: Output the sheath characteristic value vector at the distortion position when the distortion point exists: According to the calculation result of Step 4, output the sheath characteristic value vector T=[Ne of the distortion position composed of electron density Ne s , collision frequency υ s , sheath layer number K, and sheath thickness D s s υ s K D s .

[0013] Step 2 is specifically as follows:

[0014] Step 2.1: Let the layer number of the plasma sheath i=1, the electron density of the first layer of the plasma sheath is Ne(1), calculate the plasma characteristic frequency f of the first layer p (1), compare the plasma characteristic frequency f of the first layer p (1) with the radar frequency f=5GHz, if it is determined that f p (1)<f, the radar wave can penetrate the first layer of the plasma sheath;

[0015] The calculation formula of the plasma characteristic frequency f p (i) is:

[0016]

[0017] f p (i)=ω p (i) / (2π)

[0018] In the formula, Ne(i) represents the electron density of the i-th layer, e represents the electron charge, m represents the electron mass, ε0 represents the permittivity in vacuum, and ω p (i) represents the plasma characteristic angular frequency of the i-th layer;

[0019] Step 2.2: By analogy, let the layer number of the plasma sheath i=2, repeat the calculation and judgment process of Step 2.1, until f p ​(N)>f, which is considered as radar waves being unable to penetrate the Nth plasma sheath, where 1≤N≤M, yielding the maximum number of penetration layers N, and calculating the maximum penetration depth D based on the number of penetration layers. max The calculation formula is:

[0020]

[0021] In the formula, N represents the maximum number of penetration layers, and d(i) represents the thickness of the i-th plasma sheath.

[0022] In step 3, the sheath collision frequency υ of the polarization error distortion point s The calculation formula is:

[0023] ω=2πf

[0024]

[0025] In the formula, ω represents the radar angular frequency, f represents the radar frequency, m represents the electron mass, e represents the electron charge, and B... z It represents the intensity of the Earth's magnetic field.

[0026] In step 4, the sheath thickness D at the distortion point s The calculation formula is:

[0027]

[0028] In the formula, d(i) represents the thickness of the i-th plasma sheath.

[0029] A system for calculating the polarization error distortion eigenvalues ​​of radar echoes from targets encased in magnetized plasma sheaths includes:

[0030] Parameter setting module: Set the total thickness L of the plasma sheath, the number of layers M, the thickness of the i-th plasma sheath layer d(i) = L / M, the electron density of the plasma sheath Ne = [Ne(1), Ne(2), ..., Ne(M)] (Ne(i) is the electron density of the i-th plasma sheath layer, i = 1, 2, 3, ..., M), the collision frequency of the plasma sheath υ = [υ(1), υ(2), ..., υ(M)] (υ(i) is the collision frequency of the i-th plasma sheath layer, i = 1, 2, 3, ..., M), the electron charge e, the electron mass m, the vacuum dielectric constant ε0, the radar frequency f, and the geomagnetic field strength B. z ;

[0031] Maximum number of layers calculation module: Calculates the plasma characteristic frequency f of each layer according to the parameters in the parameter setting module. p (i) Determine the characteristic frequency f of each plasma layer based on the radar frequency f. p(i) By analyzing the relationship between the radar frequency f and the maximum number of plasma sheath layers N that the radar wave can penetrate, and calculating the maximum depth D that the radar wave can penetrate the plasma sheath, we can obtain the maximum number of plasma sheath layers N that the radar wave can penetrate. max ;

[0032] Sheath Collision Frequency Calculation Module: Calculates the sheath collision frequency υ at the polarization error distortion point based on the relevant parameters in the parameter setting module. s ;

[0033] Distortion point judgment module: Based on the maximum number of layers N that radar waves can penetrate in the maximum layer calculation module and the sheath collision frequency υ of the polarization error distortion point in the sheath collision frequency calculation module. s Determine the sheath collision frequency υ at the polarization error distortion point. s The magnitude of the collision frequencies υ=[υ(1),υ(2),…,υ(M)] with the first N layers of plasma sheath are related, if υ s If the value is less than υ(N), then the distortion point exists; if the distortion point exists, output the number of sheath layers K where the distortion point is located, and calculate the sheath thickness D at the distortion point. s ;

[0034] Distortion location sheath eigenvalue vector output module: The output is based on the calculation results of the distortion point judgment module, which is derived from the electron density Ne. s Collision frequency υ s Number of sheath layers K, sheath thickness D s The sheath eigenvalue vector T = [Ne] at the distorted location s υ s KD s ].

[0035] A device for calculating the polarization error distortion eigenvalues ​​of radar echoes from targets encased in magnetized plasma sheaths includes:

[0036] Memory: Used to store the computer program for implementing the method for calculating the polarization error distortion characteristic value of radar echo of a target covered by a magnetized plasma sheath;

[0037] Processor: Used to implement the method for calculating the polarization error distortion characteristic value of radar echo of a target covered by a magnetized plasma sheath when executing the computer program.

[0038] A computer-readable storage medium:

[0039] The computer-readable storage medium stores a computer program that, when executed by a processor, enables a method for calculating the polarization error distortion characteristic value of radar echoes from targets covered by magnetized plasma sheaths.

[0040] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0041] 1. This invention features high accuracy in calculating distortion point eigenvalues. Because it considers the influence of the actual Earth's magnetic field on the plasma sheath, compared to existing methods for calculating radar echo signal detection and polarization errors based on the assumption of no magnetism, the method proposed in this invention can calculate radar echo signal polarization error distortion more accurately than in reality.

[0042] 2. This invention features a simple calculation process. Since the polarization distortion error calculation method is based on Maxwell's equations and the Appleton-Hartree formula, the calculation process only requires simple mathematical operations such as summation, integration, and exponentiation. Compared with time-frequency analysis-based calculation methods that require model transformation and substitution and multiple Fourier transforms, this invention proposes a very simple calculation method.

[0043] 3. This invention features strong scalability. Because the plasma sheath parameters and radar frequency in this calculation method can be flexibly set, it can be flexibly applied to various plasma sheaths under different temperature and pressure conditions, radar systems in various frequency bands, and various magnetization environments, such as S-band, C-band, and L-band radar systems. Furthermore, this calculation method is applicable to most magnetized plasma environments, such as in fusion energy, plasma medicine, and space exploration scenarios, thus possessing extremely strong scalability.

[0044] 4. This invention features high computational efficiency. The method achieves accurate calculation of radar echo polarization distortion characteristic values ​​under magnetized conditions through only five steps, with a simple and clear approach.

[0045] In summary, this invention utilizes the characteristic values ​​and non-uniform distribution characteristics of the plasma sheath to define a plasma sheath structure with characteristic values ​​varying with the number of layers. It sets the radar frequency and magnetic field strength, then determines the relationship between the characteristic frequency of the layered plasma sheath and the radar frequency, calculates the maximum number of layers and maximum depth that the radar can penetrate, and further calculates the plasma sheath collision frequency when polarization error distortion occurs. Finally, combining the set plasma characteristic values, it determines the existence of the polarization error distortion point and outputs the sheath characteristic value at the location of the polarization error distortion point when the distortion point exists. Compared with existing technologies, this invention can more simply and accurately analyze the influence of magnetized plasma sheaths on radar echo polarization characteristics and has strong scalability. Attached Figure Description

[0046] Figure 1 This is a flowchart of the method of the present invention.

[0047] Figure 2 This is a polarization characteristic distortion diagram obtained from simulation in an embodiment of the present invention. Detailed Implementation

[0048] The technical solution of the present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0049] With reference to Figure 1 , a method for calculating the polarization error distortion characteristic value of radar echo from a target covered by a magnetized plasma sheath comprises the following steps:

[0050] Step 1: set plasma sheath parameters, radar frequency and magnetic field strength: set the total thickness L of the plasma sheath, the number of layers M, the thickness of the i-th layer of the plasma sheath as d(i)=L / M, the electron density of the plasma sheath as Ne=[Ne(1),Ne(2),…,Ne(M)] (Ne(i) is the electron density of the i-th layer of the plasma sheath, i=1,2,3,…,M), the collision frequency of the plasma sheath as υ=[υ(1),υ(2),…,υ(M)] (υ(i) is the collision frequency of the i-th layer of the plasma sheath, i=1,2,3,…,M), the electron charge as e, the electron mass as m, the permittivity in vacuum as ε0, the radar frequency f and the geomagnetic field strength B z ; since the plasma sheath parameters and radar frequency in this calculation method can be flexibly set, it can be flexibly applied to plasma sheaths under various different temperature and pressure conditions, radar systems of various frequency bands, and various magnetization environments, such as S-band, C-band and L-band radar systems. In addition, this calculation method is applicable to most magnetized plasma environments, such as scenarios of fusion energy, plasma medicine, space exploration, etc., and therefore has extremely strong scalability.

[0051] Step 2: calculate the maximum number of layers and maximum depth that the radar can penetrate the plasma sheath: calculate the characteristic frequency f of each layer of plasma respectively according to the parameters in Step 1 p (i), judge the magnitude relationship between the characteristic frequency f of each layer of plasma p (i) and the radar frequency f according to the radar frequency f, obtain the maximum number of layers N that the radar wave can penetrate the plasma sheath, and calculate the maximum depth D that the radar wave can penetrate the plasma sheath max ;

[0052] Said Step 2 is specifically as follows:

[0053] Step 2.1: let the number of layers of the plasma sheath i=1, then the electron density of the first layer of the plasma sheath is Ne(1), calculate the plasma characteristic frequency f of the first layer p (1), compare the plasma characteristic frequency f of the first layer p (1) with the radar frequency f=5GHz, if it is determined that f p (1)<f, the radar wave can penetrate the first layer of the plasma sheath;

[0054] The plasma characteristic frequency f pThe formula for calculating (i) is:

[0055]

[0056] f p (i)=ω p (i) / (2π)

[0057] In the formula, Ne(i) represents the electron density of the i-th layer, e represents the electron charge, m represents the electron mass, ε0 represents the vacuum dielectric constant, and ω p (i) represents the characteristic angular frequency of the plasma in the i-th layer;

[0058] Step 2.2, and so on, let the number of plasma sheath layers i = 2, and repeat the calculation and judgment process of step 2.1 until f p (N)>f, which is considered as radar waves being unable to penetrate the Nth plasma sheath, where 1≤N≤M, yielding the maximum number of penetration layers N, and calculating the maximum penetration depth D based on the number of penetration layers. max The calculation formula is:

[0059]

[0060] In the formula, N represents the maximum number of penetration layers, and d(i) represents the thickness of the i-th plasma sheath.

[0061] Step 3: Calculate the sheath collision frequency υ at the polarization error distortion point based on the relevant parameters from Step 1. s The sheath collision frequency υ at the polarization error distortion point s The calculation formula is:

[0062] ω=2πf

[0063]

[0064] In the formula, ω represents the radar angular frequency, f represents the radar frequency, m represents the electron mass, e represents the electron charge, and B... z It represents the intensity of the Earth's magnetic field.

[0065] Since the polarization distortion error calculation method is based on Maxwell's equations and Appleton-Hartree formulas, the calculation process only requires simple mathematical operations such as summation, integration, and exponentiation. Compared with the time-frequency analysis-based calculation method that requires model transformation and substitution and multiple Fourier transforms, the method proposed in this invention is a very simple calculation method.

[0066] Step 4: Determine if the distortion point exists and output the sheath layer number where the distortion point is located: Based on the maximum number of layers N that the radar wave can penetrate in Step 2 and the sheath collision frequency υ of the polarization error distortion point in Step 3. sDetermine the sheath collision frequency υ at the polarization error distortion point. s The magnitude of the collision frequencies υ=[υ(1),υ(2),…,υ(M)] with the first N layers of plasma sheath are related, if υ s If the value is less than υ(N), then the distortion point exists; if the distortion point exists, output the number of sheath layers K where the distortion point is located, and calculate the sheath thickness D at the distortion point. s ;

[0067] The sheath thickness D at the distortion point s The calculation formula is:

[0068]

[0069] In the formula, d(i) represents the thickness of the i-th plasma sheath.

[0070] Step 5, output the distortion position sheath eigenvector when the distortion point exists: based on the calculation results of Step 4, output the eigenvector of the electron density Ne. s Collision frequency υ s Number of sheath layers K, sheath thickness D s The sheath eigenvalue vector T = [Ne] at the distorted location s υ s KD s ].

[0071] A system for calculating the polarization error distortion eigenvalues ​​of radar echoes from targets encased in magnetized plasma sheaths includes:

[0072] Parameter setting module: Set the total thickness L of the plasma sheath, the number of layers M, the thickness of the i-th plasma sheath layer d(i) = L / M, the electron density of the plasma sheath Ne = [Ne(1), Ne(2), ..., Ne(M)] (Ne(i) is the electron density of the i-th plasma sheath layer, i = 1, 2, 3, ..., M), the collision frequency of the plasma sheath υ = [υ(1), υ(2), ..., υ(M)] (υ(i) is the collision frequency of the i-th plasma sheath layer, i = 1, 2, 3, ..., M), the electron charge e, the electron mass m, the vacuum dielectric constant ε0, the radar frequency f, and the geomagnetic field strength B. z This module corresponds to step 1;

[0073] Maximum number of layers calculation module: Calculates the plasma characteristic frequency f of each layer according to the parameters in the parameter setting module. p (i) Determine the characteristic frequency f of each plasma layer based on the radar frequency f. p (i) By analyzing the relationship between the radar frequency f and the maximum number of plasma sheath layers N that the radar wave can penetrate, and calculating the maximum depth D that the radar wave can penetrate the plasma sheath, we can obtain the maximum number of plasma sheath layers N that the radar wave can penetrate. max This module corresponds to step 2;

[0074] Sheath Collision Frequency Calculation Module: Calculates the sheath collision frequency υ at the polarization error distortion point based on the relevant parameters in the parameter setting module. s This module corresponds to step 3;

[0075] Distortion point judgment module: Based on the maximum number of layers N that radar waves can penetrate in the maximum layer calculation module and the sheath collision frequency υ of the polarization error distortion point in the sheath collision frequency calculation module. s Determine the sheath collision frequency υ at the polarization error distortion point. s The magnitude of the collision frequencies υ=[υ(1),υ(2),…,υ(M)] with the first N layers of plasma sheath are related, if υ s If the value is less than υ(N), then the distortion point exists; if the distortion point exists, output the number of sheath layers K where the distortion point is located, and calculate the sheath thickness D at the distortion point. s This module corresponds to step 4;

[0076] Distortion location sheath eigenvalue vector output module: The output is based on the calculation results of the distortion point judgment module, which is derived from the electron density Ne. s Collision frequency υ s Number of sheath layers K, sheath thickness D s The sheath eigenvalue vector T = [Ne] at the distorted location s υ s KD s This module corresponds to step 5.

[0077] A device for calculating the polarization error distortion eigenvalues ​​of radar echoes from targets encased in magnetized plasma sheaths includes:

[0078] Memory: Used to store the computer program for implementing the method for calculating the polarization error distortion characteristic value of radar echo of a target covered by a magnetized plasma sheath;

[0079] Processor: Used to implement the method for calculating the polarization error distortion characteristic value of radar echo of a target covered by a magnetized plasma sheath when executing the computer program.

[0080] A computer-readable storage medium:

[0081] The computer-readable storage medium stores a computer program that, when executed by a processor, enables a method for calculating the polarization error distortion characteristic value of radar echoes from targets covered by magnetized plasma sheaths.

[0082] The application effects of the present invention will be described in detail below with reference to the embodiments.

[0083] The embodiment uses simulation to obtain the polarization error distortion characteristic values ​​of the radar echo signal of the target covered by the plasma sheath under magnetization. Since it is currently impossible to directly obtain the relevant parameters of the plasma sheath on the reentry vehicle surface, the parameter range taken in this embodiment refers to the experimental results of RAM-C (Radio Attenuation Measurement) (Beck, FB; Castellow; Swift, CT; Thomson, J. RAM C-3 S-band diagnostic experiment. NASA Special Publication, 1970, 1.). The parameters involved in the processing are shown in Table 1:

[0084] Table 1 Parameters of the Example

[0085]

[0086]

[0087] A method for calculating the polarization error distortion eigenvalue of radar echo from a target covered by a magnetized plasma sheath includes the following steps:

[0088] Step 1, set the plasma sheath parameters, radar frequency, and magnetic field strength: Set the plasma sheath thickness L to 10cm, the number of layers M to 100, the electron density of the i-th layer to Ne(i), the plasma collision frequency to υ(i), the thickness d(i) = 0.1cm, and the electron density range to 10. 16 m -3 ~10 18 m -3 The electron density per i-th shell is Ne(i) = i × 10 16 m -3 (i = 1, 2, ..., 100), the plasma collision frequency range is 30 GHz to 39.9 GHz, the collision frequency of each i-th layer is υ(i) = (30 + (i-1) × 0.1) GHz (i = 1, 2, ..., 100), and the electron charge e is 1.6 × 10⁻⁶. -19 C, electron mass m is 9.1 × 10 -31 kg, vacuum dielectric constant ε0 is 8.85 × 10 -12 F / m, radar frequency f is 5GHz, geomagnetic field strength B z 30000nT;

[0089] Step 2, calculate the maximum number of plasma sheath layers and the maximum depth that the radar can penetrate: calculate the plasma characteristic frequency f of each layer based on the parameters in Step 1. p (i) The relationship between the radar frequency f and the radar wave frequency is used to calculate the maximum penetration depth D and the number of layers N of the radar wave. Specifically:

[0090] Step 2.1, let i=1, then the electron density of the first layer of the sheath Ne(1)=10 16 m -3 , calculate the plasma characteristic frequency f of this layer p (1)=0.89GHz, compare the plasma characteristic frequency f p (1)=0.89GHz of the first layer with the radar frequency f=5GHz, and determine that f p (1)<f, so the first layer is penetrable;

[0091] The calculation formula is:

[0092]

[0093] f p (i)=ω p (i) / (2π)

[0094] In the formula, Ne(i) represents the electron density of the i-th layer, e represents the electron charge, m represents the electron mass, ε0 represents the permittivity in vacuum, ω p (i) represents the plasma characteristic angular frequency of the i-th layer;

[0095] Step 2.2, and so on, let i=2, repeat the above calculation and judgment process until f p (N)>f, which is regarded as the N-th layer being impenetrable (1≤N≤M); through layer-by-layer judgment, it is found that when the electron density Ne(N)=31.05×10 16 m -3 , the radar wave cannot penetrate, and the maximum number of penetrable layers is 31, with a penetration depth D=3.1cm;

[0096] Step 3, calculate the sheath collision frequency υ of the polarization error distortion point s =31.42GHz, the calculation formula is:

[0097] ω=2πf

[0098]

[0099] In the formula, ω represents the radar angular frequency, f represents the radar frequency, m represents the electron mass, e represents the electron charge, B z represents the geomagnetic field intensity;

[0100] Step 4, determine whether the distortion point exists and output the sheath layer where the distortion point is located: according to the maximum number of layers that the radar wave can penetrate in Step 2 is 31, υ(31)=33GHz, while the sheath collision frequency υ of the polarization error distortion point s =31.42GHz<33GHz, so the distortion point exists;

[0101] Step 5, output the sheath eigenvector of the distortion location when the distortion point exists: According to the settings in Step 1, the collision frequency of the 15th layer is 31.4 GHz, so the layer where the distortion point occurs is the 16th layer, and the electron density Ne s =1.6×10 17 m -3 Collision frequency υ s =31.42GHz, number of sheath layers K=16, sheath thickness D s =1.6cm, output distortion point sheath eigenvalue vector T=[Ne s υ s KD s ] = [1.6 × 10 17 m -3 31.42GHz 16 1.6cm).

[0102] Figure 2 The polarization distortion diagram obtained after this embodiment shows that when the angular frequency of the radar wave is equal to the collision frequency of the 16th layer of plasma sheath, the polarization deflection angle changes direction, indicating that the polarization characteristics of the echo signal are distorted. It is evident that the method for calculating the characteristic value of polarization error distortion of radar echoes from targets covered by magnetized plasma sheaths proposed in this invention can accurately calculate the sheath collision frequency when the polarization error of the radar echo is distorted. Furthermore, by combining the set sheath structure and parameters, it outputs the sheath electron density, collision frequency, number of sheath layers, and sheath thickness at the distortion point location, verifying the correctness of the results obtained in this embodiment.

[0103] In summary, the above embodiments demonstrate that the method for calculating the characteristic value of radar echo polarization error of a target covered by a magnetized plasma sheath according to the present invention can analyze the influence of the magnetized plasma sheath on the polarization characteristics of the radar echo in a relatively simple and accurate manner, and has strong scalability.

Claims

1. A method for calculating the characteristic value of polarization error distortion of radar echo from a target covered by a magnetized plasma sheath, characterized in that, Includes the following steps: Step 1, Set plasma sheath parameters, radar frequency, and magnetic field strength: Set the total thickness of the plasma sheath. L The number of layers is M , No. i The thickness of the plasma sheath is d ( i )= L / M Plasma sheath electron density Ne =[ Ne (1), Ne (2),…, Ne ( M )]( Ne ( i ) is the first i Electron density of the plasma sheath layer, i =1,2,3,…, M Plasma sheath collision frequency υ =[ υ (1), υ (2),…, υ ( M )]( υ ( i ) is the first i The collision frequency of the plasma sheath. i =1,2,3,…, M ), electron charge is e Electron mass is m The vacuum dielectric constant is ε 0. Radar frequency f and geomagnetic field strength B z ; Step 2, calculate the maximum number of plasma sheath layers and the maximum depth that the radar can penetrate: calculate the characteristic frequency of each plasma layer based on the parameters in Step 1. According to radar frequency f Determine the characteristic frequency of each plasma layer With radar frequency f The size relationship was used to determine the maximum number of plasma sheath layers that radar waves could penetrate. N And calculate the maximum depth to which radar waves can penetrate the plasma sheath. D max ; Step 3: Calculate the sheath collision frequency at the polarization error distortion point based on the relevant parameters from Step 1. υ s ; Step 4: Determine if the distortion point exists and output the sheath layer number where the distortion point is located: based on the maximum number of layers that the radar wave can penetrate in Step 2. N The sheath collision frequency with the polarization error distortion point in step 3 υ s Determine the sheath collision frequency at the polarization error distortion point υ s and before N Collision frequency of the plasma sheath υ =[ υ (1), υ (2),…, υ ( N The size relationship of )], if υ s < υ ( N If the distortion point exists, then the distortion point exists. If a distortion point exists, output the number of sheath layers containing the distortion point. K And calculate the sheath thickness at the distortion point. D s ; Step 5, Output the distortion location sheath eigenvector when the distortion point exists: Based on the calculation results of Step 4, output the electron density... Ne s Collision frequency υ s Number of sheath layers K Sheath thickness D s The sheath eigenvalue vector T = [ ] at the distorted location Ne s υ s KD s ].

2. The method for calculating the polarization error distortion characteristic value of radar echo from a target covered by a magnetized plasma sheath according to claim 1, characterized in that, Step 2 specifically involves: Step 2.1, set the number of layers of the plasma sheath. i =1, then the electron density of the first plasma sheath is Ne (1) Calculate the plasma characteristic frequency of the first layer. f p (1) The plasma characteristic frequency of the first layer f p (1) with radar frequency f =5 GHz compared to, if determined f p (1)< f Then the radar waves can penetrate the first plasma sheath; plasma characteristic frequency The calculation formula is: In the formula, Ne ( i ) indicates the first i electron density of the layer e Indicates the amount of electron charge. m Indicates electron mass, ε 0 represents the vacuum dielectric constant. ω p ( i ) indicates the first i The characteristic angular frequency of the plasma in the layer; Step 2.2, and so on, let the number of plasma sheath layers be... i =2, repeat the calculation and judgment process in step 2.1 until... f p ( i )> f To obtain the maximum number of penetration layers N Calculate the maximum penetration depth based on the number of layers penetrated. D max The calculation formula is: In the formula, N Indicates the maximum number of layers penetrated. d ( i ) indicates the first i The thickness of the plasma sheath.

3. The method for calculating the polarization error distortion characteristic value of radar echo from a target covered by a magnetized plasma sheath according to claim 1, characterized in that, The sheath collision frequency of the polarization error distortion point in step 3 υ s The calculation formula is: In the formula, ω Indicates the radar angular frequency. f Indicates the radar frequency. m Indicates electron mass, e Indicates the amount of electron charge. Bz It represents the intensity of the Earth's magnetic field.

4. The method for calculating the polarization error distortion characteristic value of radar echo from a target covered by a magnetized plasma sheath according to claim 1, characterized in that, The thickness of the sheath at the distortion point in step 4 D s The calculation formula is: In the formula, d ( i ) indicates the first i The thickness of the plasma sheath.

5. A system for calculating the characteristic value of polarization error distortion of radar echo from a target covered by a magnetized plasma sheath, characterized in that, include: Parameter setting module: Sets the total thickness of the plasma sheath. L The number of layers is M , No. i The thickness of the plasma sheath is d ( i )= L / M Plasma sheath electron density Ne =[ Ne (1), Ne (2),…, Ne ( M )]( Ne ( i ) is the first i Electron density of the plasma sheath layer, i =1,2,3,…, M Plasma sheath collision frequency υ =[ υ (1), υ (2),…, υ ( M )]( υ ( i ) is the first i The collision frequency of the plasma sheath. i =1,2,3,…, M ), electron charge is e Electron mass is m The vacuum dielectric constant is ε 0. Radar frequency f and geomagnetic field strength B z ; Maximum number of layers calculation module: Calculates the plasma characteristic frequency of each layer according to the parameters in the parameter setting module. According to radar frequency f Determine the characteristic frequency of each plasma layer With radar frequency f The size relationship was used to determine the maximum number of plasma sheath layers that radar waves could penetrate. N And calculate the maximum depth to which radar waves can penetrate the plasma sheath. D max ; Sheath Collision Frequency Calculation Module: Calculates the sheath collision frequency at the polarization error distortion point based on the relevant parameters in the parameter setting module. υ s ; Distortion point detection module: Calculates the maximum number of layers that radar waves can penetrate based on the maximum layer count module. N The sheath collision frequency at the polarization error distortion point in the sheath collision frequency calculation module υ s Determine the sheath collision frequency at the polarization error distortion point υ s and before N Collision frequency of the plasma sheath υ =[ υ (1), υ (2),…, υ ( N The size relationship of )], if υ s < υ ( N If the distortion point exists, then the distortion point exists. If a distortion point exists, output the number of sheath layers containing the distortion point. K And calculate the sheath thickness at the distortion point. D s ; Distortion location sheath eigenvalue vector output module: The output is based on the calculation results of the distortion point judgment module, which is derived from the electron density. Ne s Collision frequency υ s Number of sheath layers K Sheath thickness D s The sheath eigenvalue vector T = [ ] at the distorted location Ne s υ s KD s ].

6. A device for calculating the characteristic value of polarization error distortion of radar echo from a target covered by a magnetized plasma sheath, characterized in that, include: Memory: Used to store a computer program for implementing the method for calculating the polarization error distortion characteristic value of radar echo of a target covered by a magnetized plasma sheath, as described in claims 1-4; Processor: Used to implement the method for calculating the polarization error distortion characteristic value of radar echo of a target covered by a magnetized plasma sheath, as described in claims 1-4, when executing the computer program.

7. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program that, when executed by a processor, enables the calculation of the polarization error distortion characteristic value of a target radar echo covered by a magnetized plasma sheath, as described in claims 1-4.

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