Fast simulation method of near-field dynamic echo based on time-domain high frequency method

Abstract

This invention provides a rapid simulation method for near-field dynamic echoes based on the time-domain high-frequency method, comprising the following steps: S1, deriving the closed-form expression of the time-domain physical optics method under antenna beam illumination; S2, setting the target mesh model, near-field echo antenna pattern, pulse Doppler system parameters, and ballistic parameters; S3, simulating the near-field echo using the time-domain high-frequency method to obtain the zero intermediate frequency (IF) signal; S4, taking the envelope of the IF signal to obtain the Doppler echo. This invention achieves rapid simulation of near-field dynamic echoes by constructing a closed-form expression of the time-domain physical optics method for transient scattering near-field, combined with near-field dynamic echo simulation methods and signal processing.

Description

Technical Field

[0001] This invention relates to the field of near-field dynamic echo simulation technology, and in particular to a fast near-field dynamic echo simulation method based on the time-domain high-frequency method. Background Technology

[0002] Near-field dynamic echoes, as carriers of target information, directly affect the fuze's ability to perceive and make decisions about targets. For example, the echo Doppler frequency can be used to estimate target velocity, and the echo pulse leading edge can be used to estimate target distance. Obtaining near-field dynamic echoes using testing methods is time-consuming and labor-intensive, and current fuzes require rapid and accurate acquisition of large amounts of near-field dynamic echoes, which testing methods generally cannot meet. Therefore, it is necessary to achieve rapid simulation of near-field dynamic echoes through simulation techniques. Summary of the Invention

[0003] The purpose of this invention is to provide a fast simulation method for near-field dynamic echoes based on the time-domain high-frequency method. It constructs a time-domain physical optics closed-form expression for transient scattering near-field, and combines near-field dynamic echo simulation methods and signal processing to achieve fast simulation of near-field dynamic echoes.

[0004] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0005] A fast simulation method for near-field dynamic echoes based on time-domain high-frequency methods includes the following steps:

[0006] S1. The closed-form expression of the time-domain physical optics method under antenna beam illumination is derived in advance;

[0007] S2. Set the target mesh model, near-field echo antenna pattern, pulse Doppler system parameters, and ballistic parameters;

[0008] S3. The near-field echo is simulated using the time-domain high-frequency method to obtain the zero intermediate frequency signal;

[0009] S4. Take the envelope of the zero intermediate frequency signal to obtain the Doppler echo.

[0010] Optionally, in S1, the process of deriving the closed-form expression of the time-domain physical optics method under antenna beam illumination is as follows:

[0011] S11. The time-domain electromagnetic field integral equation for calculating the near-field scattering of the target is given below:

[0012]

[0013]

[0014] In the above formula, E and H represent the electric and magnetic fields, r and t represent any position and time in space, s represents the surface enveloping the source, and r' and t' represent any position vector and time in space with s as the surface. Let R be the outward normal unit vector of the source surface s, and R be the distance between the field point and the source point. The unit vector from the field point to the source point. Let ds' be the unit dvar, ds' be the integral surface element at r', c be the speed of light, and ε and μ be the permittivity and permeability, respectively.

[0015] S12. Give the expression for the antenna's far-field radiation in the time domain:

[0016]

[0017] In the above formula Let δ be the vector current moment of the antenna, K(t) be the impulse function, η be the arbitrary broadband pulse signal, R be the wave impedance, and R be the distance from the radiation field point to the antenna position. The antenna position here is the source point in formula (1) and (2), and the radiation field point is the field point in formula (1) and (2).

[0018] S13. Substituting equation (3) into equations (1) and (2), we can obtain the time-domain physical optical integral formula for the target under antenna illumination.

[0019] S14. If the surface element S is small enough to satisfy the far-field condition, then R in equation (3) can be simplified to:

[0020]

[0021] In the above formula, r' is the position vector of the radiation field point, r s This is the antenna position vector;

[0022] Substituting equations (3) and (4) into equations (1) and (2), the surface integral of physical optics in the time domain can be transformed into a closed expression, as shown below:

[0023]

[0024] In the above formula, E s H s Let r and t be the electric and magnetic fields, respectively, and r' be any position and time in space. Let r' be the position vector of any point on the target. Let be the unit vector pointing from the origin of the local coordinate system of surface element s to the observation point. Let s be the unit dative vector, s be the surface enclosing the source, ds' be the integral element at r', and r' be the integral element at r'. s Let ds' be the position vector from the origin to the surface element ds. Let ρ be the unit vector pointing from the antenna position to the origin of the local coordinate system of the surface element ds'. n for The modulus, c is the speed of light, η is the wave impedance, δ and δ' are the impulse functions, K(t) is the excitation source, and J is the time-domain pulse. n J is the vector current moment of the antenna. n (n) For J n The nth derivative.

[0025] Optionally, in S2, the target mesh model is a standard format generated by commercial software FEKO or CST, with the suffix nas, stl or msh; the near-field echo antenna is a standard format generated by commercial software FEKO with the suffix ffe.

[0026] Optionally, in S2, the pulse Doppler system parameters include: center frequency, pulse repetition period, pulse width, receiving gate width, and receiving delay; the ballistic parameters include: miss distance, miss azimuth, initial rendezvous distance, final rendezvous distance, relative velocity between missile and target, target attitude, and missile attitude.

[0027] Optionally, S3 specifically includes the following steps:

[0028] S31. Calculate the ballistic sampling points on the trajectory based on the pulse repetition period, pulse width, intersection distance, and relative velocity between the missile and the target. Calculate the missile's position based on the miss distance, miss azimuth, and the position of the ballistic sampling points. Combine this with the target position to calculate the incident direction. Then, obtain the bright area elements based on the antenna pattern. Select a sinusoidal signal as the carrier signal. Modulate the periodic pulse function with the carrier to transform it into a radio frequency pulse signal. Use the radio frequency pulse signal as the excitation source.

[0029] S32. Solve the echo of the pulse Doppler fuze system. Specifically, the radio frequency pulse signal is transmitted through the antenna. When the electromagnetic wave encounters the target, it is scattered. Some of the energy returns to the receiving antenna. For each ballistic sampling point, the near-field echo is obtained by simulation using the time-domain high-frequency method.

[0030] S33. Mix the received echo with the carrier frequency, and then filter out the high-frequency components to obtain a zero-IF signal containing Doppler information.

[0031] Optionally, in step S4, the zero intermediate frequency signal obtained in step S3 is subjected to a second FFT to obtain the DC component in the rectangular pulse, and the Doppler information is retained. This process is envelope detection to obtain the Doppler echo.

[0032] Compared with the prior art, the present invention has the following advantages:

[0033] By combining physical optics with the local Green's function approximation method of surface elements and extending it to the case of antenna beam illumination, this method enables rapid simulation of near-field dynamic echoes, obtaining zero intermediate frequency signals and Doppler echo signals, providing theoretical basis and technical support for the rapid generation of target intersection echoes in batches. Attached Figure Description

[0034] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the description will be briefly introduced below. Obviously, the drawings described below are one embodiment of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort:

[0035] Figure 1 This is a flowchart of a fast simulation method for near-field dynamic echo based on the time-domain high-frequency method in this invention. Detailed Implementation

[0036] The following detailed description, in conjunction with the accompanying drawings and specific embodiments, further illustrates the solution proposed by the present invention. The advantages and features of the present invention will become clearer from the following description. It should be noted that the drawings are in a very simplified form and use non-precise proportions, used only to facilitate and clearly illustrate the embodiments of the present invention. Please refer to the drawings to make the objectives, features, and advantages of the present invention more apparent and understandable. It should be understood that the structures, proportions, sizes, etc., depicted in the accompanying drawings are only for illustrative purposes to aid those skilled in the art and are not intended to limit the implementation conditions of the present invention. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to the size, without affecting the effects and objectives achieved by the present invention, should still fall within the scope of the technical content disclosed in the present invention.

[0037] In existing technologies, numerical algorithms in computational electromagnetics offer high simulation accuracy but are slow, especially for electrically large targets. High-frequency algorithms, on the other hand, are better suited for simulating electrically large targets due to their faster speed, though their accuracy differs slightly from numerical algorithms. The time domain, compared to the frequency domain, can more accurately simulate the time relationship during projectile-target rendezvous, and a single simulation in the time domain yields a wideband result. Therefore, this invention employs a time-domain high-frequency method to achieve rapid simulation of near-field dynamic echoes.

[0038] High-frequency time-domain methods can be categorized into physical optics (PSO) and shot-bounce ray (SBR) methods. SBR tracks the ray until it leaves the target element, while PSO tracks the ray only once. Generally, SBR offers higher accuracy but is slower. Since fuses are typically narrow-beam antennas, only a portion of the target element is illuminated during rendezvous, so using SBR has little impact on simulation accuracy. Therefore, the difficulty in using PSO to solve near-field dynamic echoes lies in the need for integration across the target element. In the far-field condition, the time-domain PSO integration can be simplified to a closed-form expression. However, in the near-field condition, the accuracy of the closed-form expression is positively correlated with the distance between the target and the observation point. Therefore, numerical integration is usually used to obtain better computational accuracy. However, numerical integration requires very small sampling intervals, increasing the computational load. In projectile-target rendezvous calculations, a single trajectory typically requires tens of thousands of calculations, making it difficult for numerical integration to achieve rapid simulation of near-field dynamic echoes. The local Green's function approximation method for target elements assumes that the distance between the integrating element and the observation point satisfies R > 2D. 2 / λ (where D is the maximum size of the surface element and λ is the wavelength), meaning the observation point is considered to be in the far-field region of the surface element's scattering field, the near-field physical optics integral can be simplified to a closed expression. This invention combines the physical optics method with the local Green's function approximation method for surface elements and extends it to the case of antenna beam illumination, obtaining a time-domain physical optics closed expression for the transient scattering near field. Combined with near-field dynamic echo simulation methods and signal processing, rapid simulation of near-field dynamic echoes is achieved.

[0039] like Figure 1 As shown, the present invention provides a fast simulation method for near-field dynamic echoes based on the time-domain high-frequency method, comprising the following steps:

[0040] S1. The closed-form expression of the time-domain physical optics method under antenna beam illumination is derived in advance.

[0041] Specifically, the derivation process is as follows:

[0042] S11. First, the time-domain electromagnetic field integral equation for calculating the near-field scattering of the target is given, as shown in the following equation:

[0043]

[0044]

[0045] In the above formula, E and H represent the electric and magnetic fields, r and t represent any position and time in space, s represents the surface enveloping the source, and r' and t' represent any position vector and time in space with s as the surface. Let R be the outward normal unit vector of the source surface s, and R be the distance between the field point and the source point. The unit vector from the field point to the source point. Let ds' be the unit dvar, ds' be the integral surface element at r', c be the speed of light, and ε and μ be the permittivity and permeability, respectively.

[0046] The above two formulas do not use any approximations and can theoretically calculate the electromagnetic field distribution at any point in space. Combined with the physical optics assumptions, the time-domain PO near-field integral formula can be obtained.

[0047] S12. Give the expression for the antenna's far-field radiation in the time domain:

[0048]

[0049] In the above formula Let η be the vector current moment of the antenna, δ be the impulse function, K(t) be any broadband pulse signal, η be the wave impedance, and R be the distance from the radiation field point to the antenna position. Here, the antenna position is the source point in formula (1) and (2), and the radiation field point is the field point in formula (1) and (2).

[0050] S13. Substituting equation (3) into equations (1) and (2), we can obtain the time-domain physical optical integral formula for the target under antenna illumination.

[0051] S14. If the surface element S is small enough to satisfy the far-field condition, then R in equation (3) can be simplified to:

[0052]

[0053] In the above formula, r' is the position vector of the radiation field point, r s This is the antenna position vector.

[0054] Substituting equations (3) and (4) into equations (1) and (2), the surface integral of physical optics in the time domain can be transformed into a closed expression, as shown below:

[0055]

[0056] In the above formula, E s H s Let r and t be the electric and magnetic fields, respectively, and r' be any position and time in space. Let r' be the position vector of any point on the target. Let be the unit vector pointing from the origin of the local coordinate system of surface element s to the observation point. Let s be the unit dative vector, s be the surface enclosing the source, ds' be the integral element at r', and r' be the integral element at r'. s Let ds' be the position vector from the origin to the surface element ds. Let ρ be the unit vector pointing from the antenna position to the origin of the local coordinate system of the surface element ds'. n for The modulus, c is the speed of light, η is the wave impedance, δ and δ' are the impulse functions, K(t) is the excitation source, and J is the time-domain pulse. nJ is the vector current moment of the antenna. n (n) For J n The nth derivative;

[0057] Understandably, combining the physical optics method with the local Green's function approximation method for surface elements can simplify the two-dimensional surface integral into a closed expression, avoiding numerical integration calculations. Furthermore, since the formula is derived theoretically, it can also guarantee simulation accuracy. Therefore, this method can achieve rapid simulation of near-field dynamic echoes and ensure simulation accuracy, providing theoretical basis and technical support for the rapid generation of missile-eye rendezvous echoes in batches.

[0058] S2. Set the target mesh model, near-field echo antenna pattern, pulse Doppler system parameters, and ballistic parameters.

[0059] Specifically, the target mesh model can be a standard format generated by commercial software such as FEKO and CST, with the suffixes nas, stl, or msh; the near-field echo antenna can be a standard format generated by commercial software FEKO with the suffix ffe; the pulse Doppler system parameters can include: center frequency (GHz), pulse repetition period (ns), pulse width (ns), receiver gate width (ns), and receiver delay (ns); the ballistic parameters typically include: miss distance (m), miss azimuth (°), initial rendezvous distance (m), final rendezvous distance (m), relative velocity between missile and target (m / s), target attitude (°), and missile attitude (°).

[0060] S3. Near-field echoes are simulated using the time-domain high-frequency method to obtain zero intermediate frequency signals.

[0061] The specific process is as follows:

[0062] S31. Calculate the ballistic sampling points on the trajectory based on the pulse repetition period, pulse width, intersection distance, and relative velocity between the missile and the target. Calculate the missile's position based on the miss distance, miss azimuth, and the position of the ballistic sampling points. Combine this with the target position to calculate the incident direction. Then, obtain the bright area elements based on the antenna pattern. Select a sinusoidal signal as the carrier signal. Modulate the periodic pulse function with the carrier to transform it into a radio frequency pulse signal. Use the radio frequency pulse signal as the excitation source.

[0063] S32. Solve the echo of the pulse Doppler fuze system. Specifically, the radio frequency pulse signal is transmitted through the antenna. When the electromagnetic wave encounters the target, it is scattered. Some of the energy returns to the receiving antenna. For each ballistic sampling point, the near-field echo is obtained by simulation using the time-domain high-frequency method.

[0064] S33. Mix the received echo with the carrier frequency, and then filter out the high-frequency components to obtain a zero-IF signal containing Doppler information.

[0065] Assuming the period of the periodic pulse function is T and the pulse width is τ, the expression for the periodic pulse function is as follows:

[0066]

[0067] Choosing a sinusoidal signal as the carrier signal with a center frequency of f0, the periodic pulse function modulated by the carrier is used as the excitation source, as expressed below:

[0068]

[0069] In the above two equations, δ(t-NT) is the impact function, and N = 1, 2, 3, ... For the initial phase, U m This represents the amplitude of the transmitted signal.

[0070] Radio frequency signals are transmitted through an antenna. When the electromagnetic waves encounter a target, they are scattered, and some energy returns to the receiving antenna. The time-domain expression of the received signal can be written as:

[0071]

[0072] In the formula, τ(m) represents the signal delay time, which is determined by the distance between the target and the antenna. For complex targets, the scattering mechanism between electromagnetic waves and the various surface elements of the target is very complex and cannot be described by a simple formula. Here, the method in S1 is used to simulate and obtain U. r (t). The received echo is mixed with the carrier frequency, and then filtered to remove high-frequency components, yielding a zero-IF signal containing Doppler information. The zero-IF signal is amplified and sent to the receiving gate; it can only be received when the receiving gate is open.

[0073] S4. Take the envelope of the zero intermediate frequency signal to obtain the Doppler echo.

[0074] Specifically, based on the zero intermediate frequency signal obtained in step S3, the zero intermediate frequency signal is subjected to a second filtering by FFT to obtain the DC component in the rectangular pulse, while retaining the Doppler information. This process is called envelope detection to obtain the Doppler echo.

[0075] In summary, this invention combines physical optics with the local Green's function approximation method for surface elements and extends it to the case of antenna beam illumination to obtain a time-domain physical optics closed-form expression for transient scattering near-field. Combined with near-field dynamic echo simulation methods and signal processing, it realizes rapid simulation of near-field dynamic echoes, which can obtain zero intermediate frequency signals and Doppler echo signals, providing a theoretical basis and technical support for the rapid generation of target intersection echoes in batches.

[0076] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0077] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A fast simulation method for near-field dynamic echoes based on the time-domain high-frequency method, characterized in that, Includes the following steps: S1. The closed-form expression of the time-domain physical optics method under antenna beam illumination is derived in advance; S2. Set the target mesh model, near-field echo antenna pattern, pulse Doppler system parameters, and ballistic parameters; S3. The near-field echo is simulated using the time-domain high-frequency method to obtain the zero intermediate frequency signal; S4. Take the envelope of the zero intermediate frequency signal to obtain the Doppler echo; In S1, the process of deriving the closed-form expression of the time-domain physical optics method under antenna beam illumination is as follows: S11. The time-domain electromagnetic field integral equation for calculating the near-field scattering of the target is given below: （1） （2） In the above formula , For electric and magnetic fields, , For any location and time in space, For the surface of the wrapping source, , For Let the vector be any position vector in space on the surface and time. For the surface of the wrapping source Outward normal unit vector, The distance between the field point and the source point. The unit vector from the field point to the source point. For unit vector, for The integral element at that location, At the speed of light, Here are the dielectric constant and magnetic permeability; S12. Give the expression for the antenna's far-field radiation in the time domain: （3） In the above formula The vector current moment of the antenna. Let be the impulse function. For any broadband pulse signal, Wave impedance; S13. Substituting equation (3) into equations (1) and (2), we can obtain the time-domain physical optical integral formula for the target under antenna illumination. S14. If the surface element S is small enough to satisfy the far-field condition, then for equation (3) It can be simplified to: （4） In the above formula This is the antenna position vector; Substituting equations (3) and (4) into equations (1) and (2), the surface integral of physical optics in the time domain can be transformed into a closed expression, as shown below: （5） In the above formula, Let S be the unit vector pointing from the origin of the local coordinate system of surface element S to the observation point. From the antenna position to the surface element The unit vector at the origin of the local coordinate system. for The modulus, The derivative of the impulse function. The vector current moment of the antenna. for The nth derivative.

2. The fast simulation method for near-field dynamic echo based on the time-domain high-frequency method as described in claim 1, characterized in that, In S2, the target mesh model is a standard format generated by commercial software FEKO or CST, with the suffix nas, stl or msh; the near-field echo antenna is a standard format generated by commercial software FEKO with the suffix ffe.

3. The fast simulation method for near-field dynamic echo based on the time-domain high-frequency method as described in claim 1, characterized in that, In S2, the pulse Doppler system parameters include: center frequency, pulse repetition period, pulse width, receiving gate width, and receiving delay; the ballistic parameters include: miss distance, miss azimuth, initial rendezvous distance, final rendezvous distance, relative velocity between missile and target, target attitude, and missile attitude.

4. The fast simulation method for near-field dynamic echo based on the time-domain high-frequency method as described in claim 3, characterized in that, S3 specifically includes the following steps: S31. Calculate the ballistic sampling points on the trajectory based on the pulse repetition period, pulse width, intersection distance, and relative velocity of the projectile and target; calculate the missile's position based on the miss distance, miss azimuth, and the position of the ballistic sampling points; calculate the incident direction by combining the target position; and obtain the bright area element based on the antenna pattern; select a sinusoidal signal as the carrier signal, and transform it into a radio frequency pulse signal after modulation of the periodic pulse function and the carrier; use the radio frequency pulse signal as the excitation source. S32. Solve the echo of the pulse Doppler fuze system. Specifically, the radio frequency pulse signal is transmitted through the antenna. When the electromagnetic wave encounters the target, it is scattered. Some of the energy returns to the receiving antenna. For each ballistic sampling point, the near-field echo is obtained by simulation using the time-domain high-frequency method. S33. Mix the received echo with the carrier frequency, and then filter out the high-frequency components to obtain a zero-IF signal containing Doppler information.

5. The fast simulation method for near-field dynamic echo based on the time-domain high-frequency method as described in claim 1, characterized in that, In step S4, the zero intermediate frequency signal obtained in step S3 is subjected to secondary filtering by FFT to obtain the DC component in the rectangular pulse, and the Doppler information is retained. This process is envelope detection to obtain the Doppler echo.

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