Whirl target three-dimensional time-frequency spectrum parameter estimation method and system based on vortex electromagnetic wave

Abstract

The application discloses a three-dimensional time-frequency spectrum parameter estimation method and system based on a vortex electromagnetic wave rotating target, and mainly solves the problems of poor azimuth resolution and target parameter cross term interference in the prior art. The implementation scheme comprises the following steps: a radar detection scene is established, an estimated measurement value model of the rotating target is obtained, geometric parameters of the target in a radar coordinate system are obtained, a vortex electromagnetic wave signal model is established and optimized, and expressions of radial Doppler frequency and rotating Doppler frequency are derived; a double-mode vortex echo signal is constructed according to the optimized signal model, and the radial echo signal when the mode is 0 is determined; according to time-frequency spectrums of the radial echo signal and the double-mode vortex echo signal, time-frequency spectrum distributions of the radial echo and the double-mode vortex echo of the target and an optimal azimuth angle are obtained, and then a rotating Doppler frequency curve is obtained, and target parameters are estimated according to the curve. The application can realize optimal solution of the target azimuth angle and the target parameters, improves the estimation accuracy of the rotating target azimuth angle, and can be used for time-frequency spectrum characteristic analysis of the vortex electromagnetic wave.

Description

Technical Field

[0001] This invention belongs to the field of radar signal processing technology, specifically relating to a method and system for estimating the three-dimensional time-spectrum parameters of a rotating target, which can be used for the time-spectrum characteristic analysis of vortex electromagnetic waves. Background Technology

[0002] Vortex electromagnetic waves are electromagnetic waves carrying orbital angular momentum. Their annular radiation field intensity distribution and helical phase wavefront give them the ability to modulate phase information in the azimuth direction. Therefore, vortex electromagnetic waves have received increasing attention in recent years in fields such as radar imaging and rotating target detection. The introduction of the orbital angular momentum (OAM) concept has injected new vitality into the field of sensing. Unlike spin angular momentum, i.e., polarization effect, OAM essentially describes the macroscopic physical characteristics of electromagnetic waves, characterizing the degree of rotation around an axis during electromagnetic wave propagation. Thus, electromagnetic vortex waves are defined. Theoretically, the range of OAM mode values ​​can be infinitely large, becoming a completely new dimension outside the time, frequency, and polarization domains.

[0003] Unlike traditional planar electromagnetic wave illumination, vortex electromagnetic waves, due to their OAM (Optical Aspect-Oriented Array) characteristics, produce not only a linear Doppler frequency shift in the radial direction but also a Doppler frequency shift in the azimuth direction when used for target detection; this is known as rotational Doppler shift. Time-frequency analysis can provide basic information about the frequency components of a signal; however, traditional time-frequency analysis methods still face problems such as cross-term interference and insufficient time-frequency resolution when processing complex signals.

[0004] Patent document CN1176169843A discloses a method for estimating joint parameters of a rotating target based on vortex electromagnetic waves. This method performs time-frequency analysis on the parameters to be estimated based on the echo time-domain signal to obtain the maximum likelihood estimate. Through error analysis, it derives the Cramer-Rao lower bound. While this method can estimate the target's micro-Doppler frequency by detecting local peak points in the echo signal's time-frequency distribution, the micro-Doppler frequency components at different scattering points of the target typically overlap in the time-frequency distribution, making it difficult to obtain the desired frequency components. Furthermore, the resolution of the signal's time-frequency distribution is limited, resulting in poor estimation accuracy of the micro-Doppler frequency.

[0005] Most existing rotating Doppler models are designed for single-scattering point targets, while research on rotating Doppler frequency shift extraction for multi-scattering point targets is still in its early stages. However, real-world rotating components, such as aircraft rotors and engine blades, are often modeled as multi-scattering point models. Therefore, there is an urgent need to study methods for estimating the three-dimensional time-spectrum parameters of rotating targets based on vortex electromagnetic waves, in order to fully explore the potential of vortex electromagnetic waves in the application of three-dimensional parameter estimation for rotating targets. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of the prior art by proposing a method and system for estimating the three-dimensional time-spectrum parameters of a rotating target based on vortex electromagnetic waves, so as to improve the estimation accuracy of micro-Doppler frequencies and optimize the motion parameters of the rotating target.

[0007] The technical approach to achieve the objective of this invention is as follows: by using a three-dimensional time-frequency spectrum analysis method optimized by adding dual vortex echoes, and by using a genetic algorithm to optimize and solve the micro-Doppler frequency corresponding to the time-frequency spectrum, the estimation accuracy of the micro-Doppler frequency is improved; by coupling azimuth information to the time-frequency spectrum amplitude, and then extracting azimuth information from the amplitude information, the motion parameters of the rotating target are further optimized.

[0008] Based on the above ideas, the technical solution of the present invention includes:

[0009] 1. A method for estimating the three-dimensional time-spectrum parameters of a rotating target based on vortex electromagnetic waves, characterized in that it includes:

[0010] (1) Establish a radar detection scenario and obtain an estimated measurement model of the rotating target in the scenario;

[0011] (2) Obtain the geometric parameters of the target in the radar coordinate system from the estimated measurement value model, and establish the vortex electromagnetic wave echo signal model S(τ,t,l), where τ is the range dimension time, t is the azimuth dimension time, and l is the mode;

[0012] (3) The vortex electromagnetic wave echo signal model is optimized, and the radial Doppler frequency f is derived from the optimized signal model S(t,l). lD (t) and the rotational Doppler frequency f rD The expression for (t);

[0013] (4) Construct a dual-mode vortex echo signal S based on the optimized signal model S(t,l). DMA (t,l);

[0014] (5) Based on the optimized signal model S(t,l), determine the radial echo signal S when mode l is 0. ZM (t), which includes micro-motion parameters such as rotation angular frequency, Euler angle, and rotation radius estimation;

[0015] (6) Based on the radial echo signal S ZM (t) and dual-mode vortex echo signal S DMA The time spectrum of (t,l) is used to obtain the time spectrum distribution of the radial Doppler and dual-mode vortex echo signals of the target;

[0016] (7) Based on the dual-mode vortex echo signal S DMA (t,l) and radial echo signal S ZMThe optimal azimuth angle is obtained by optimizing the azimuth angle based on the time spectrum of (t);

[0017] (8) Combining the optimal azimuth angle with the rotating Doppler frequency f rD The relationship between (t) is used to derive the rotational Doppler frequency curve. From the rotational Doppler frequency curve The target parameter θ is estimated in the middle. rD .

[0018] Furthermore, in step (6), based on the radial echo signal S ZM (t) and dual-mode vortex echo signal S DMA The time-frequency spectrum of (t,l) is used to obtain the time-frequency spectrum distribution of the radial Doppler and dual-mode vortex echo signals of the target. Its implementation includes:

[0019] (6a) For the radial echo signal S ZM (t) Perform a short-time Fourier transform (STFT) to obtain its radial Doppler time-frequency spectrum distribution.

[0020] (6b) For dual-mode vortex echo signal S DMA Performing a Short-Time Fourier Transform (STFT) on (t,l) yields the time-spectral distribution of its dual-mode vortex echo signal.

[0021] Furthermore, in step (8), the optimal azimuth angle and the rotating Doppler frequency f are combined. rD The relationship between (t) is used to derive the rotational Doppler frequency curve. From the rotational Doppler frequency curve The target parameter θ is estimated in the middle. rD Its implementation includes:

[0022] (8a) Derive the rotating Doppler frequency f rD Relationship between (t) and azimuth angle

[0023] (8b) Extract the rotational Doppler frequency curve based on the derived rotational Doppler frequency expression.

[0024] (8c) Estimate the objective parameter θ based on least squares estimation. rD =[β,r P / D,Ω] T Optimization issues:

[0025]

[0026] Among them, f rD (t,θ rD () represents the rotational Doppler frequency.

[0027] 2. A three-dimensional time-spectrum parameter estimation system for a rotating target based on vortex electromagnetic waves, characterized in that it comprises:

[0028] The radar detection scenario modeling module is used to establish radar detection scenarios, simulate the motion characteristics of rotating targets, and generate estimated measurement value models for the scenario.

[0029] The geometric parameter extraction module is used to extract the target geometric parameters;

[0030] The vortex echo modeling module, based on the established geometric model, is used to establish the vortex echo signal model S(τ,t,l);

[0031] The signal optimization and Doppler analysis module is used to optimize the vortex electromagnetic wave echo signal model and derive the radial Doppler frequency f from the optimized vortex electromagnetic wave echo signal model S(t,l). lD (t) and the rotational Doppler frequency f rD (t);

[0032] Dual-mode vortex echo signal synthesis module, used to synthesize dual-mode vortex echo signals S DMA (t,l);

[0033] The radial vortex echo signal synthesis module is used to synthesize the radial vortex echo signal S. ZM (t);

[0034] The time-frequency analysis module combines the generated dual-mode vortex echo signal and radial vortex echo signal to obtain the time spectrum of the echo signal;

[0035] The micro-motion parameter estimation module is used to optimize the target's optimal azimuth angle by combining the time-frequency spectra of the radial echo signal and the dual-mode vortex echo signal. And combined with the optimal azimuth angle With rotational Doppler frequency f rD The relationship between (t) is used to estimate the optimal objective parameter θ. rD .

[0036] Compared with the prior art, the present invention has the following advantages:

[0037] Firstly, this invention calculates the time-spectrum distribution of the target radial Doppler and dual-mode vortex echo signals based on the time-spectrum of the radial echo signal and the dual-mode vortex echo signal. This not only allows for more effective separation and analysis of the rotating Doppler component, significantly improving the accuracy and reliability of parameter estimation, but also enables optimization of the azimuth angle to obtain the optimal azimuth angle.

[0038] Secondly, this invention extracts the radial Doppler information of the target from the time spectrum by performing a short-time Fourier transform on the zero-mode vortex echo signal and combining it with the Hough transform, thus avoiding the loss of skeleton extraction when extracting the time-frequency curve and optimizing the motion parameters of the rotating target.

[0039] Third, this invention improves the estimation accuracy of target parameters by obtaining the rotating Doppler frequency curve of the vortex echo signal based on the time-spectrum distribution of the dual-mode vortex echo signal and the radial echo signal, and extracting target parameters from the rotating Doppler frequency curve.

[0040] Fourth, this invention optimizes the rotation target parameters based on genetic algorithms and least squares estimation, which can achieve more accurate estimation of the rotation target parameters. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of a vortex electromagnetic wave radar detection scenario used in an embodiment of the present invention;

[0042] Figure 2 This is a flowchart illustrating the implementation of the three-dimensional time-spectrum parameter estimation method for a rotating target based on vortex electromagnetic waves according to the present invention.

[0043] Figure 3 This is a block diagram of the three-dimensional time-spectrum parameter estimation system for rotating targets based on vortex electromagnetic waves according to the present invention;

[0044] Figure 4 This is a diagram showing the optimal azimuth angle estimated by a genetic algorithm in an embodiment of the present invention.

[0045] Figure 5 This is a diagram showing the result of target parameter estimation in an embodiment of the present invention. Detailed Implementation

[0046] Reference Figure 1 This example is based on a vortex electromagnetic wave radar detection scenario, which includes:

[0047] A radar coordinate system (X,Y,Z), a reference coordinate system (X',Y',Z'), and a local coordinate system (x,y,z) are established to obtain a mathematical model of the target's range, azimuth, and elevation angles in the radar coordinate system. The radar coordinate system is a Cartesian coordinate system with the receiver element O as its origin, and the local coordinate system has the target's rotation center O as its origin, sharing the same origin as the reference coordinate system.

[0048] The coordinates of radar coordinate system O are (X) o ,Y o Z o The rotating target point P rotates with an angular velocity and a radius r. PRotate counterclockwise. The Euler angles between the two coordinate systems are (α, β, γ). Obtain the rotation matrix expression for the target point in this coordinate system:

[0049]

[0050] Among them, a 11 =cosαcosγ-sinαcosβsinγ

[0051] a 12 =-cosαsinγ-sinαcosβcosγ

[0052] a 13 =sinαsinβ

[0053] a 21 =sinαcosγ+cosαcosβsinγ

[0054] a 22 =-sinαsinγ+cosαcosβcosγ,

[0055] a 23 = -cosαsinβ

[0056] a 31 =sinβsinγ

[0057] a 32 =sinβcosγ

[0058] a 33 =cosβ

[0059] R r Let R be the rotation matrix of the target point, (α,β,γ) be the Euler angles between the local coordinate system and the radar coordinate system, and R be the rotation matrix of the target point. rz (α),R rx (β),R rz (γ) are the rotation matrices of the coordinate axes corresponding to the Euler angles;

[0060] In one embodiment of the present invention, based on the rotation matrix of the rotating target, an estimated measurement model of the rotating target in the coordinate system is obtained, namely, the coordinates of point target P in the local coordinate system and the coordinates of point target P in the radar coordinate system, and a vortex electromagnetic wave echo signal model S(τ,t,l) is established, including:

[0061] The coordinates of point target P in the local coordinate system are:

[0062] (x P (t),y P (t),z P (t)) T =[rP cos(Ωt+φ P ),r P sin(Ωt+φ P ),0] T

[0063] The coordinates of point target P in the radar coordinate system are:

[0064]

[0065] Where, φ P r P Ω and Ω represent the initial azimuth, rotation radius, and rotation angular velocity of the point target in its local coordinate system, respectively.

[0066] The distance, elevation angle, and azimuth angle between point target P and the origin O of the radar coordinate system are as follows:

[0067]

[0068] Specifically, firstly, the echo signal of vortex electromagnetic waves in an N-transmitter single-receiver pulse radar system can be expressed as:

[0069]

[0070] Where, σ P Let f0 be the scattering coefficient of a point target, c be the radar carrier frequency, n(τ,t) be the speed of light, and r be the noise level. p (t), θ p (t), These represent the distance between the point target and the origin of the radar coordinate system, the elevation angle, and the azimuth angle, respectively.

[0071] In one embodiment of the present invention, the vortex electromagnetic wave echo signal model is optimized, and the radial Doppler frequency f is derived from the optimized signal model S(t,l). lD (t) and the rotational Doppler frequency f rD The expressions for (t) include:

[0072] The radial and rotational Doppler frequencies of the target are derived from the echo phase. The study of the rotational Doppler effect is based on micro-Doppler theory, so it studies the modulation law based on the detection of the target; therefore, the range dimension information can be omitted.

[0073] By removing all information except the phase term, i.e., leaving only the phase term, we obtain the normalized backscattering coefficients:

[0074]

[0075] Based on the normalized backscattering coefficient, the vortex electromagnetic wave echo signal is optimized as follows:

[0076]

[0077] Where, σ P Let f0 be the scattering coefficient of a point target, f0 be the radar carrier frequency, c be the speed of light, n(t) be the noise, and r be the scattering coefficient of the point target. p (t), These represent the distance and azimuth angle between the point target and the origin of the radar coordinate system, respectively.

[0078] As shown in the above equation, the phase of the echo includes an azimuth modulation term and a radial range modulation term. Therefore, the radial micro-Doppler frequency and the rotational Doppler frequency of the target are each determined by two terms:

[0079]

[0080] Where ζ0, ζ1, ζ2, ζ3, ζ4, ζ5, ζ6 are curve parameters, (α, β, γ) are the Euler angles between the local coordinate system and the radar coordinate system, and r p (t), θ p (t), These represent the distance between the point target and the origin of the radar coordinate system, the elevation angle, and the azimuth angle, respectively. P r P Ω and Ω represent the initial azimuth, rotation radius, and rotation angular velocity of the point target in its local coordinate system, respectively.

[0081] Example 1: A method for estimating the three-dimensional time-spectrum parameters of a rotating target based on vortex electromagnetic waves.

[0082] Reference Figure 2 The implementation steps of this example include the following:

[0083] Step 1: Establish vortex electromagnetic waves of different modes.

[0084] In one embodiment of the present invention, a dual-mode vortex echo signal S is constructed based on the optimized signal model S(t,l). DMA (t,l):

[0085] Establish the echo signal S(t,+l) when using positive mode vortex electromagnetic waves to detect multiple targets:

[0086]

[0087] Establish the echo signal S(t,-l) when using negative-mode vortex electromagnetic waves to detect multiple targets:

[0088]

[0089] Based on the above S(t,+l) and S(t,-l), a dual-mode vortex echo signal S is established. DMA (t,l):

[0090]

[0091] Where, r p (t), θ p (t), These represent the distance between the point target and the origin of the radar coordinate system, the elevation angle, and the azimuth angle, respectively. P r P Ω and σ represent the initial azimuth, rotation radius, and rotation angular velocity of the point target in the local coordinate system, respectively. P denoted as scattering coefficient of a point target, f0 as radar carrier frequency, and c as speed of light.

[0092] Since the rotating Doppler frequency is relatively smaller than the radial Doppler frequency, a dual-mode vortex echo signal S is added. DMA (t,l) can extract the rotational Doppler effect and convert it into amplitude variation. This method can more effectively separate and analyze the rotational Doppler component, hence DMA is simply referred to as dual-mode addition.

[0093] In another embodiment of the present invention, the single-mode echo signal S when mode l is 0 is determined based on the optimized signal model S(t,l). ZM (t):

[0094]

[0095] Where, r p (t) represents the distance between the point target and the origin of the radar coordinate system, σ P Let f0 be the scattering coefficient of the point target, c be the radar carrier frequency, and c be the speed of light. When the transmission mode of the vortex wave is zero, its properties are similar to those of a traditional plane wave. In this case, only radial Doppler information can be detected.

[0096] Step 2: Obtain the time-spectrum distribution of vortex electromagnetic waves in different modes.

[0097] In one embodiment of the present invention, it is based on the single-mode echo signal S ZM (t) and dual-mode vortex echo signal S DMA The time spectrum of (t,l) is used to obtain the time spectrum distribution of the target's single-mode vortex echo signal and dual-mode vortex echo signal.

[0098] 2.1) For single-mode echo signal S ZM (t) Perform a short-time Fourier transform (STFT) to obtain the time-varying single-mode vortex echo signal.

[0099] 2.2) Establish a single-mode vortex echo signal S ZM (t) and the dual-mode vortex echo signal S DMAThe following relationship exists between (t,l):

[0100]

[0101] 2.3) Perform a Short-Time Fourier Transform (STFT) on the relation obtained in 2.2) to obtain the time-spectrum distribution of the dual-mode vortex echo signal.

[0102]

[0103] Where l represents the mode, Let be the azimuth angle of the target, and fft(·) be the Fourier transform.

[0104] Step 3, based on the time spectrum of the single-mode vortex echo signal Time spectrum of dual-mode vortex echo signal The target's azimuth angle is optimized to obtain the optimal azimuth angle.

[0105] Existing algorithms for optimizing target azimuth angles include genetic algorithms, particle swarm optimization, simulated annealing, etc. This embodiment selects, but is not limited to, genetic algorithms.

[0106] The genetic algorithm gradually approaches the optimal solution through operations such as selection, crossover, and mutation.

[0107] This step utilizes a genetic algorithm to optimize the target's azimuth angle. The implementation of obtaining the target's optimal azimuth angle includes:

[0108] 3.1) Generate an initial population, that is, obtain the time-spectrum distribution of single-mode vortex echo signals for multiple targets based on the relationship between the time-spectrum distribution of dual-mode vortex echo signals and the time-spectrum distribution of single-mode vortex echo signals. The following is the relationship between azimuth and time-frequency distribution:

[0109]

[0110] 3.2) Iterate the target azimuth angle based on the initial population, that is, iterate and optimize using the following formula until the iteration result approaches 0, thus obtaining the optimal azimuth angle of the target.

[0111]

[0112] Step 4, solve for the objective parameter θ rD .

[0113] 4.1) Establish the rotating Doppler frequency f rD (t) and optimal azimuth angle Relationship:

[0114]

[0115] Where ζ0, ζ1, ζ2, ζ3, ζ4, ζ5, and ζ6 are the parameters of the rotating Doppler frequency curve, and γ is the Euler angle between the local coordinate system and the radar coordinate system. Let φ be the azimuth angle between the point target and the origin of the radar coordinate system. P Ω represents the initial azimuth angle of the point target in its local coordinate system, and Ω represents the rotational angular velocity.

[0116] 4.2) According to the above expression for the rotating Doppler frequency f rD (t), extract the rotational Doppler frequency curve. And from the extracted rotational Doppler frequency curve In the middle, estimate the target parameters:

[0117] θ rD =[β,r P / D,Ω] T ,

[0118] Where β is the Euler angle, r p Let be the distance between the point target and the origin of the radar coordinate system, and D be the radius of rotation.

[0119] 4.3) Based on the least squares method, the rotating Doppler frequency curve is calculated. The residual between the target parameter and the objective parameter is minimized to obtain the objective parameter θ. rD Its formula is expressed as follows:

[0120]

[0121] Using the parameters obtained from the rotational Doppler frequency curve, the motion parameters and geometric information of the rotating target can be determined. At this point, the extraction of the rotational Doppler signal and the estimation of the micro-motion parameters are complete.

[0122] The flowchart representations or method representations of the above embodiments can be understood as representing modules, segments, or portions of code comprising one or more executable instructions configured to implement a specific logical function or process. This invention is not limited to the disclosed preferred embodiments, and its implementation may not follow the order shown or discussed. That is, the step numbers in the specification and claims are only for clear description and ease of understanding of the embodiments of this invention, and their order is not limited.

[0123] Example 2: A three-dimensional time-spectrum parameter estimation system for a rotating target based on vortex electromagnetic waves.

[0124] Reference Figure 3This example includes: Radar detection scene modeling module 1, geometric parameter extraction module 2, vortex echo modeling module 3, signal optimization and Doppler analysis module 4, dual-mode vortex echo signal synthesis module 5, radial vortex echo signal synthesis module 6, time-frequency analysis module 7, and micro-motion parameter estimation module 8.

[0125] The working principle of the entire system is as follows:

[0126] The radar detection scenario modeling module 1 is used to establish a radar detection scenario, simulate the motion characteristics of a rotating target, and generate an estimated measurement value model under the scenario.

[0127] The geometric parameter extraction module 2 is used to extract the geometric parameters of the target, including the initial azimuth angle, rotation radius, rotation angular velocity, distance between the point target P and the origin O of the radar coordinate system, elevation angle, azimuth angle, and output the geometric parameters of the target to the vortex echo modeling module 3.

[0128] The vortex echo modeling module 3 is used to establish a vortex echo signal model S(τ,t,l) based on the geometric parameters of the target, and output the vortex echo signal to the signal optimization and Doppler analysis module 4.

[0129] The signal optimization and Doppler analysis module 4 is used to optimize the vortex electromagnetic wave echo signal model and derive the radial Doppler frequency f from the optimized vortex electromagnetic wave echo signal model S(t,l). lD (t) and the rotational Doppler frequency f rD (t), and output the optimized vortex echo signal S(t,l) to the dual-mode vortex echo signal synthesis module 5 and the radial vortex echo signal synthesis module 6 respectively;

[0130] The dual-mode vortex echo signal synthesis module 5 is used to synthesize a dual-mode vortex echo signal S based on the vortex echo signal. DMA (t,l), and outputs the generated dual-mode vortex echo signal to the time-frequency analysis module 7;

[0131] The radial vortex echo signal synthesis module 6 is used to synthesize a radial vortex echo signal S based on the vortex echo signal. ZM (t), the generated radial vortex echo signal is output to the time-frequency analysis module 7;

[0132] The time-frequency analysis module 7 is used to obtain the time spectrum of the echo signal based on the dual-mode vortex echo signal and the radial vortex echo signal, and output the obtained echo signal time spectrum to the micro-motion parameter estimation module 8.

[0133] The micro-motion parameter estimation module 8 is used to optimize the target's optimal azimuth angle by combining the time spectrum of the radial echo signal and the dual-mode vortex echo signal. And combined with the optimal azimuth angle With rotational Doppler frequency f rD The relationship between (t) is used to estimate the optimal objective parameter θ. rD .

[0134] It should be noted that the above functional modules can be implemented, in whole or in part, through software, hardware, firmware, or any combination thereof. When implemented in software, they can be implemented, in whole or in part, as program instruction products. A program instruction product includes one or a set of program instructions. When the program instructions are loaded and executed on a computer, the described process or function is generated, in whole or in part. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The program instructions can be stored in a computer-readable and writable storage medium, or transferred from one computer's readable and writable storage medium to another.

[0135] The direct coupling or communication connections between the modules shown or discussed in this embodiment can be achieved through indirect coupling or communication connections via interfaces, devices, or modules. The various functional modules and sub-modules in this embodiment can dynamically reside within a single processing unit, or each module can exist physically independently, or two or more modules can dynamically reside within a single processing unit. When these dynamic components are implemented as software functional modules and sold or used as independent products, they can also be stored in a computer-readable and writable storage medium. This storage medium can be a memory, disk, or optical disc, etc.

[0136] The effects of this invention can be further illustrated by the following simulation results.

[0137] 1. Simulation conditions

[0138] Assume that the vortex electromagnetic wave radar transmits a signal at a frequency of 3 GHz and lasts for 2 seconds to illuminate the target.

[0139] Assume the eddy current electromagnetic wave echo mode after receiving the multi-element echo is 5;

[0140] Assume there are 3 rotating targets;

[0141] The rotation frequency is 20.95 rad / s, the rotation radius is 0.26 m, the offset distance is 0.57 m, and the Euler angle is (0, 0.9, 0).

[0142] 2. Simulation Results

[0143] Simulation 1: Based on the above simulation conditions, the optimal azimuth angle of the target is solved using the method of this invention. The optimal azimuth angle of each target point throughout the entire period is obtained, and the results are as follows. Figure 4 As shown.

[0144] from Figure 4As can be seen, the theoretical curve fits the actual estimated curve very well, meaning the iterative result approaches 0. By iteratively optimizing using the method of this invention until the iterative result approaches 0, the solved azimuth angle is the optimal azimuth angle for the target.

[0145] Simulation 2: Based on the above simulation conditions, the target parameters are solved using the method of this invention to obtain the target parameters of each point target throughout the entire period. The results are as follows: Figure 5 As shown.

[0146] from Figure 5 As can be seen, by using the parameters obtained from the rotated Doppler frequency curve, the theoretical Doppler frequency curve fits the actual estimated value curve very well; from Figure 5 As can be seen from b, the theoretical curve parameters are close to the actual estimated curve parameters. The target parameters of the rotating target can be determined by using the parameters obtained from the estimated rotating Doppler frequency curve.

[0147] The simulation results above show that the present invention can effectively solve the optimal azimuth angle and target parameters of the target, give full play to the potential of vortex electromagnetic waves in the three-dimensional parameter estimation of rotating targets, and can effectively improve the estimation accuracy of the azimuth angle of the rotating target, thereby optimizing the rotating target parameters.

[0148] It should be noted that the above description is only two specific examples of the present invention and does not constitute any limitation on the present invention. Obviously, those skilled in the art, after understanding the content and principle of the present invention, may make various modifications and changes in form and details without departing from the principle and structure of the present invention. However, these modifications and changes based on the idea of ​​the present invention are still within the scope of protection of the claims of the present invention.

Claims

1. A method for estimating the three-dimensional time-spectrum parameters of a rotating target based on vortex electromagnetic waves, characterized in that, include: (1) Establish a radar detection scenario and obtain an estimated measurement model of the rotating target under this scenario; (2) Obtain the geometric parameters of the target in the radar coordinate system from the estimated measurement model, and establish the vortex electromagnetic wave echo signal model. ,in For distance and time, For the orientation dimension and time, Modal; (3) Optimize the vortex electromagnetic wave echo signal model, and then optimize the signal model. Derivation of radial Doppler frequency and rotational Doppler frequency The expression; (4) Based on the optimized signal model Constructing dual-mode vortex echo signals It is represented as follows: ； in, , These are the vortex echo signals corresponding to the positive and negative modes, respectively. , , These represent the distance between the point target and the origin of the radar coordinate system, the elevation angle, and the azimuth angle, respectively. , , These represent the initial azimuth, rotation radius, and rotation angular velocity of the point target in its local coordinate system. Let be the scattering coefficient of the point target. For radar carrier frequency, The speed of light; (5) Based on the optimized signal model Determine when the mode Radial echo signal when it is 0 It includes micro-motion parameters such as rotation angular frequency, Euler angles, and rotation radius estimation; specifically expressed as follows: ； in, The distance between the point target and the origin of the radar coordinate system. Let be the scattering coefficient of the point target. For radar carrier frequency, The speed of light; (6) Based on the radial echo signal and dual-mode vortex echo signal The time spectrum of the target is obtained by obtaining the radial Doppler and dual-mode vortex echo signal time spectrum distributions. (7) Based on the dual-mode vortex echo signal and radial echo signal The time spectrum is used to optimize the azimuth angle to obtain the optimal azimuth angle; (8) Combining the optimal azimuth angle and the rotating Doppler frequency The relationship between them yields the rotational Doppler frequency curve. From the rotational Doppler frequency curve Estimate the target parameters .

2. The method according to claim 1, characterized in that, Step (1) establishes a radar detection scenario and obtains an estimated measurement model of the rotating target in this scenario, including: (1a) Establishing the radar coordinate system Reference coordinate system and local coordinate system : The radar coordinate system is based on the receiving array element. A rectangular coordinate system with the origin as the origin. The local coordinate system is centered on the target rotation center. With the origin as the reference point, the motion of the target includes both translation and rotation. (1b) Based on the established coordinate system, obtain the rotation matrix expression for the target point in that coordinate system: ； in, Let be the rotation matrix of the target point. The Euler angles between the local coordinate system and the radar coordinate system. These are the rotation matrices for the coordinate axes corresponding to Euler angles; ； (1c) Based on the rotation matrix of the rotating target, obtain the estimated measurement model of the rotating target in this coordinate system, i.e., the point target. Coordinates and point targets in the local coordinate system Coordinates in the radar coordinate system: Point Target The coordinates in the local coordinate system are: ； Point Target The coordinates in the radar coordinate system are: ； in, , , These are the initial azimuth, rotation radius, and rotation angular velocity of the point target in its local coordinate system.

3. The method according to claim 1, characterized in that, In step (2), the geometric parameters of the target in the radar coordinate system are obtained from the estimated measurement model, including: point target relative to the origin of the radar coordinate system distance Pitch angle azimuth They are represented as follows: ； ； ； in, Point targets The coordinates in the radar coordinate system.

4. The method according to claim 1, characterized in that: In step (2), a vortex electromagnetic wave echo signal model is established. It is represented as follows: ； in, Let be the scattering coefficient of the point target. For radar carrier frequency, At the speed of light, For noise, , , These represent the distance between the point target and the origin of the radar coordinate system, the elevation angle, and the azimuth angle, respectively. The optimization of the vortex electromagnetic wave echo signal model in step (3) includes: By removing all information except the phase term, i.e., leaving only the phase term, we obtain the normalized backscattering coefficients: ； Based on the normalized backscattering coefficient, the vortex electromagnetic wave echo signal is optimized as follows: ； in, Let be the scattering coefficient of the point target. For radar carrier frequency, At the speed of light, For noise, , These represent the distance and azimuth angle between the point target and the origin of the radar coordinate system, respectively.

5. The method according to claim 1, characterized in that, In step (3), the optimized signal model Derivation of radial Doppler frequency and rotational Doppler frequency The expression is represented as follows: ； in For curve parameters, The Euler angles between the local coordinate system and the radar coordinate system. , These represent the distance and azimuth angle between the point target and the origin of the radar coordinate system, respectively. , , These are the initial azimuth, rotation radius, and rotation angular velocity of the point target in its local coordinate system.

6. The method according to claim 1, characterized in that, In step (6), based on the radial echo signal and dual-mode vortex echo signal The time-frequency spectrum of the target is obtained by calculating the radial Doppler and dual-mode vortex echo signals. This is achieved through the following methods: (6a) Radial echo signal Perform a short-time Fourier transform (STFT) to obtain its radial Doppler time-frequency spectrum distribution. ; (6b) For dual-mode vortex echo signals Performing a short-time Fourier transform (STFT) yields the time-spectral distribution of its dual-mode vortex echo signal. .

7. The method according to claim 1, characterized in that, In step (7), the time spectrum of the radial echo signal is used as a basis. Time spectrum of dual-mode vortex echo signal To obtain the optimal azimuth angle, the following steps are taken: (7a) Based on the time spectrum of the radial echo signal Time spectrum of dual-mode vortex echo signal The relationship between the azimuth angle and the spectrum is obtained, and it is expressed as follows: ； in, For point target The spectrum of the radial echo signal, For point target The location, For the Fast Fourier Transform function, Modal; (7b) The azimuth angle is optimized using a genetic algorithm through the following process. Optimize to obtain the target's optimal azimuth angle. : 。 8. The method according to claim 1, characterized in that, In step (8), the optimal azimuth angle and the rotating Doppler frequency are combined. The relationship between them yields the rotational Doppler frequency curve. From the rotational Doppler frequency curve Estimate the target parameters Its implementation includes: (8a) Combining the relationship between the rotating Doppler frequency and the azimuth angle, the following formula is derived: ； in For the parameters of the rotating Doppler frequency curve, The Euler angles between the local coordinate system and the radar coordinate system. , , These represent the distance, elevation angle, and azimuth angle between the point target and the origin of the radar coordinate system, respectively. The initial azimuth angle of the point target in the local coordinate system. It is the rotational angular velocity; (8b) Extract the rotational Doppler frequency curve based on the derived rotational Doppler frequency expression. ; (8c) Estimate the target parameters based on least squares estimation. The optimization problem is described as follows: ； in, The frequency is the rotational Doppler frequency.

9. A system for estimating the three-dimensional temporal spectrum parameters of a rotating target for implementing any one of the methods of claims 1-8, characterized in that, include: The radar detection scenario modeling module is used to establish radar detection scenarios, simulate the motion characteristics of rotating targets, and generate estimated measurement value models for the scenario. The geometric parameter extraction module is used to extract the target geometric parameters; The vortex echo modeling module, based on the established geometric model, is used to create a vortex echo signal model. ; The signal optimization and Doppler analysis module is used to optimize the vortex electromagnetic wave echo signal model and analyze the optimized vortex electromagnetic wave echo signal model. Derivation of radial Doppler frequency and rotational Doppler frequency ; Dual-mode vortex echo signal synthesis module, used to synthesize dual-mode vortex echo signals. ; Radial vortex echo signal synthesis module, used to synthesize radial vortex echo signals. ; The time-frequency analysis module combines the generated dual-mode vortex echo signal and radial vortex echo signal to obtain the time spectrum of the echo signal; The micro-motion parameter estimation module is used to optimize the target's optimal azimuth angle by combining the time-frequency spectra of the radial echo signal and the dual-mode vortex echo signal. And combined with the optimal azimuth angle With rotational Doppler frequency The relationship between the two parameters is used to estimate the optimal objective parameters. .

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