A method for extracting fast time-frequency features of a target coated with a plasma sheath
By combining intrapulse fast-time frequency analysis and Radon transform, the frequency modulation period and width features of the plasma sheath are extracted, solving the problem of extracting the instantaneous features of the plasma sheath in the prior art and realizing the effective extraction of plasma sheath features.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- BEIJING INST OF ENVIRONMENTAL FEATURES
- Filing Date
- 2026-04-21
- Publication Date
- 2026-06-12
Smart Images
Figure CN122194093A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of data processing technology, and in particular to a method for extracting fast time-frequency features of a target covered by a plasma sheath. Background Technology
[0002] The radar target echo spectrum contains target motion characteristic information and plasma sheath characteristic information. Among these, the most critical are the time and frequency characteristics of the modulation features, which reflect the micro-motion characteristics of the target and the plasma sheath. The plasma sheath exhibits rapidly changing time-varying characteristics and frequency modulation characteristics.
[0003] However, there is currently no research on the extraction of transiently changing plasma sheath features. Summary of the Invention
[0004] This invention provides a method for extracting fast time-frequency features of a target covered by a plasma sheath. The technical solution is as follows: On the one hand, a method for extracting fast time-frequency features of a target covered by a plasma sheath is provided, the method comprising: The linear frequency modulated narrowband echo signal of the target covered by the plasma sheath is acquired, and the time-frequency distribution of the target is obtained by performing an intra-pulse short-time Fourier transform on the echo signal. Perform a Radon transform on the time-frequency distribution to obtain the transform domain distribution; The slope angle of the line is determined based on the peak position in the transform domain distribution; this slope angle is the angle from the positive x-axis to the normal vector of line L. Based on the projections of the time-frequency distribution onto the straight line at an angle and at 90°, the frequency modulation periodicity and width characteristics of the plasma sheath are obtained.
[0005] On the other hand, a device for extracting fast time-frequency features of a target covered by a plasma sheath is provided, the device comprising: The time-frequency processing unit is used to acquire the linear frequency modulated narrowband echo signal of the target covered by the plasma sheath, and to perform an intra-pulse short-time Fourier transform on the echo signal to obtain the time-frequency distribution of the target. Radon transform unit is used to perform Radon transform on the time-frequency distribution to obtain the transform domain distribution; The unit is used to determine the slope angle of a straight line based on the peak position in the transform domain distribution; the slope angle is the angle from the positive x-axis to the normal vector of the straight line L; The acquisition unit is used to obtain the frequency modulation periodicity and width characteristics of the plasma sheath based on the projections of the time-frequency distribution onto the oblique angle of the straight line and 90°, respectively.
[0006] On the other hand, a computer device is provided, the computer device including a memory and a processor, the memory for storing a computer program, and the processor for executing the computer program stored in the memory to implement the steps of the plasma sheath-encased target fast time-frequency feature extraction method described above.
[0007] On the other hand, a computer-readable storage medium is provided, wherein a computer program is stored therein, and when the computer program is executed by a processor, it implements the steps of the above-described method for extracting fast time-frequency features of a plasma sheath-covered target.
[0008] On the other hand, a computer program product is provided, including a computer program that, when executed by a processor, implements the steps of the above-described method for extracting fast time-frequency features of a plasma sheath-covered target.
[0009] The technical solution provided by this invention can bring at least the following beneficial effects: This invention combines intrapulse fast-time frequency analysis with Radon transform to extract the frequency modulation periodicity and spectral width characteristics of the plasma sheath, effectively solving the problem of extracting the instantaneous characteristics of the plasma sheath. Attached Figure Description
[0010] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0011] Figure 1 This is a flowchart of a method for extracting fast time-frequency features of a target covered by a plasma sheath, provided by an embodiment of the present invention. Figure 2 This is a schematic diagram of the Radon transform in two dimensions; Figure 3 It is the time-frequency diagram within the pulse of a rigid body target; Figure 4 It is a time-frequency diagram of the target pulse covered by a sheath; Figure 5 This is a schematic diagram of the projection of the fast time-frequency characteristics of the sheath-enclosed target into the Radon domain; Figure 6 This is a schematic diagram of sheath coverage feature extraction; Figure 7 This is a structural diagram of a plasma sheath-encased target fast time-frequency feature extraction device according to an embodiment of the present invention; Figure 8This is a hardware architecture diagram of a computer device provided in an embodiment of the present invention. Detailed Implementation
[0012] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.
[0013] Please refer to Figure 1 The present invention provides a method for extracting fast time-frequency features of a target covered by a plasma sheath, the method comprising: Step 100: Obtain the linear frequency modulated narrowband echo signal of the target covered by the plasma sheath, and perform an intra-pulse short-time Fourier transform on the echo signal to obtain the time-frequency distribution of the target. Step 102: Perform Radon transform on the time-frequency distribution to obtain the transform domain distribution; Step 104: Determine the slope angle of the line based on the peak position in the transform domain distribution; the slope angle of the line is the angle from the positive x-axis to the normal vector of the line L; Step 106: Based on the projections of the time-frequency distribution onto the straight line at an angle and at 90°, respectively, the frequency modulation periodicity and width characteristics of the plasma sheath are obtained.
[0014] In this embodiment of the invention, by combining intrapulse fast-time frequency analysis with Radon transform, the frequency modulation periodicity and spectral width characteristics of the plasma sheath can be extracted, effectively solving the problem of extracting the instantaneous characteristics of the plasma sheath.
[0015] The following description Figure 1 The execution method for each step is shown.
[0016] First, for step 100, the linear frequency modulated narrowband echo signal of the target covered by the plasma sheath is acquired, and the intra-pulse short-time Fourier transform is performed on the echo signal to obtain the time-frequency distribution of the target.
[0017] In this embodiment of the invention, the time-frequency distribution of the target is obtained using a time-frequency analysis method. Specifically, performing an intra-pulse short-time Fourier transform on the echo signal includes: The echo signal is divided into several time intervals using a window function; Fourier transform is used to analyze each time interval to determine the frequency present in each time interval; the time-frequency distribution is the spectrum that varies with time.
[0018] Performing a Fourier transform on each time interval yields the short-time Fourier transform, which is achieved using the following formula: in, h ( τ ) represents the selected window function. s ( τ () represents the time-domain echo signal. τ For time delay, w t is the Doppler frequency, t is time, and j is the imaginary number.
[0019] Multiplying the echo signal by a window function can effectively suppress signals outside the neighborhood of the analysis time, therefore the STFT is a signal... s ( τ The local spectrum at time t. Due to the uncertainty principle in time-frequency analysis, namely: in, , These are the signal's time width and bandwidth, respectively. Defined as the covariance of the signal. The uncertainty principle states that the minimum lower bound of the time-width-bandwidth product is 1 / 2, meaning the time width and bandwidth of a signal cannot be arbitrarily small. Good frequency resolution requires filters with narrow bandwidths, i.e., longer [filters / filters]. On the other hand, good temporal resolution requires a shorter time frame. However, the two cannot be satisfied at the same time; there is a trade-off between time resolution and frequency resolution.
[0020] Then, for step 102, a Radon transform is performed on the time-frequency distribution to obtain the transform domain distribution.
[0021] The Radon transform is a type of integral transform. In the two-dimensional case, the Radon transform is shown in Figure 2. Figure 2 Middle function f exist xOy Area on a plane D It is defined above. For xOy any straight line on the plane L Both can be represented by a pair of parameters. (α,l) Uniquely determined. Among them... α for x positive axis to straight line L The size of the angle of the normal vector , l Origin of coordinates O to the straight line L distance.
[0022] If the line L AND function f domainD If they intersect, then they are opposite lines. L function above f Integrate the value of as a straight line. L The values of the Radon transform for the parameters: straight line L parameters (α,l) It can be represented as: In this embodiment of the invention, for a single rigid target linear frequency-modulated narrowband echo, its intrapulse fast time-frequency characteristics do not exhibit periodic brightness changes, as shown in Figure 3, which is an intrapulse fast time-frequency diagram of a rigid target, with the horizontal axis representing fast time and the vertical axis representing frequency. However, for a target encased in a sheath, at certain angles, the plasma sheath becomes an important scattering source, leading to regular brightness changes in the intrapulse fast time-frequency characteristics, such as... Figure 4 As shown, this is the intra-pulse time-frequency diagram of the target covered by the sheath, with the horizontal axis representing fast time and the vertical axis representing frequency. Furthermore, compared to rigid targets, the sheath modulates the target's echo. Therefore, intra-band fast time-frequency analysis is performed on the narrowband data, and then the period number characteristics of its intra-band fluctuations and the spectral width characteristics of the time-frequency signal are extracted to reflect the changes in the target sheath characteristics as the target moves.
[0023] To extract the periodic features of sheath variation, a Radon transform can be performed on the time-frequency distribution to extract the transform domain features of the target.
[0024] The Radon transform can be performed using the following formula, and the distribution of the domain of change is as follows: Figure 5 As shown, the horizontal axis Angle represents the angle of the transform domain, and the vertical axis represents the distribution of the transform domain. in, R STFT (α,l) The result is a transformation domain distribution. STFT(t,w) This is the time-frequency distribution result, where t is time. w For Doppler frequency, α For the angle information in the transform domain, l This refers to the positional information in the transform domain.
[0025] Finally, explanations are given for step 104, "Determine the straight line angle based on the peak position in the transform domain distribution; the straight line angle is the angle from the positive x-axis to the normal vector of the straight line L" and step 106, "Obtain the frequency modulation period characteristics and width characteristics of the plasma sheath based on the projections of the time-frequency distribution onto the straight line angle and 90° respectively".
[0026] Find the location of the maximum value in the transformed domain distribution. The maximum value corresponds to α The coordinates are the inclination angle of a straight line. l The intercept is the time-frequency distribution plot at the angle. α The projection onto the surface is a periodically fluctuating curve. Therefore, the projection curve of the time-frequency distribution on the oblique angle of the straight line can be determined, and this projection curve is a periodically fluctuating curve. Based on the projection curve, the number of peaks is determined, and this number of peaks is used to define the frequency modulation periodicity characteristic of the plasma sheath. The projection of the time-frequency distribution on 90° is determined, and the spectral width characteristic occupied by the peaks is extracted based on this projection. A schematic diagram of feature extraction is shown below. Figure 6 As shown.
[0027] It should be noted that finding the location of the maximum value can be achieved by performing a grid search across the entire transform domain to find the point with the largest modulus.
[0028] In summary, the feature extraction method of this invention can be described as follows: The fast time transform domain features of the plasma sheath can be obtained through the embodiments of the present invention, thereby extracting the frequency modulation period and width features of the plasma sheath.
[0029] Please refer to Figure 7 This invention provides a device for extracting fast time-frequency features of a target covered by a plasma sheath, the device comprising: The time-frequency processing unit 700 is used to acquire the linear frequency modulated narrowband echo signal of the target covered by the plasma sheath, and to perform an intra-pulse short-time Fourier transform on the echo signal to obtain the time-frequency distribution of the target. Radon transform unit 702 is used to perform Radon transform on the time-frequency distribution to obtain the transform domain distribution; The determining unit 704 is used to determine the slope angle of a straight line based on the peak position in the transform domain distribution; the slope angle of the straight line is the angle from the positive x-axis to the normal vector of the straight line L; The acquisition unit 706 is used to obtain the frequency modulation periodicity and width characteristics of the plasma sheath based on the projections of the time-frequency distribution onto the straight line at an angle and 90°, respectively.
[0030] In one embodiment of the present invention, the time-frequency processing unit is specifically used to: divide the echo signal into several time intervals using a window function; analyze each time interval using Fourier transform to determine the frequency present in each time interval; and the time-frequency distribution is a spectrum that varies with time.
[0031] In one embodiment of the present invention, the Radon transform unit is specifically used to perform Radon transform using the following formula: in,R STFT (α,l) The result is a transformation domain distribution. STFT(t,w) This is the time-frequency distribution result, where t is time. w For Doppler frequency, α For the angle information in the transform domain, l This refers to the positional information in the transform domain.
[0032] In one embodiment of the present invention, the acquisition unit is configured to: determine the projection curve of the time-frequency distribution on the oblique angle of a straight line, wherein the projection curve is a periodically fluctuating curve; and determine the number of peaks based on the projection curve, so as to determine the number of peaks as the frequency modulation periodic feature of the plasma sheath; determine the projection of the time-frequency distribution on 90°, and extract the spectral width feature occupied by the peaks based on the projection.
[0033] It should be noted that the plasma sheath-covered target fast time-frequency feature extraction device provided in the above embodiments is only an example of the division of the above functional modules. In practical applications, the above functions can be assigned to different functional modules as needed, that is, the internal structure of the device can be divided into different functional modules to complete all or part of the functions described above. In addition, the plasma sheath-covered target fast time-frequency feature extraction device and the plasma sheath-covered target fast time-frequency feature extraction method embodiment provided in the above embodiments belong to the same concept, and the specific implementation process is detailed in the method embodiment, which will not be repeated here.
[0034] Embodiments of this application also provide a computer device, please refer to... Figure 8 The computer device includes a processor and a memory, the memory storing at least one instruction, at least one program, code set or instruction set, the at least one instruction, at least one program, code set or instruction set being loaded and executed by the processor to implement the fast time-frequency feature extraction method for plasma sheath-covered targets provided in the above-described method embodiments.
[0035] Embodiments of this application also provide a computer-readable storage medium storing at least one instruction, at least one program, code set, or instruction set, wherein the at least one instruction, at least one program, code set, or instruction set is loaded and executed by a processor to implement the fast time-frequency feature extraction method for plasma sheath-covered targets provided in the above-described method embodiments.
[0036] Embodiments of this application also provide a computer program product, which includes a computer program. A processor of a computer device reads the computer program from a computer-readable storage medium and executes the computer program, causing the computer device to perform the fast time-frequency feature extraction method for plasma sheath-encased targets described in any of the above embodiments.
[0037] For ease of description, the above systems or devices are described separately as various modules or units based on their functions. Of course, in implementing this application, the functions of each unit can be implemented in one or more software and / or hardware components.
[0038] As can be seen from the above description of the embodiments, those skilled in the art can clearly understand that this application can be implemented by means of software plus necessary general-purpose hardware platforms. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in various embodiments or some parts of the embodiments of this application.
[0039] Finally, it should be noted that in this document, relational terms such as first, second, third, and fourth 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.
[0040] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.
Claims
1. A method for extracting fast time-frequency features of a target encased in a plasma sheath, characterized in that, The method includes: The linear frequency modulated narrowband echo signal of the target covered by the plasma sheath is acquired, and the time-frequency distribution of the target is obtained by performing an intra-pulse short-time Fourier transform on the echo signal. Perform a Radon transform on the time-frequency distribution to obtain the transform domain distribution; The slope angle of the line is determined based on the peak position in the transform domain distribution; this slope angle is the angle from the positive x-axis to the normal vector of line L. Based on the projections of the time-frequency distribution onto the straight line at an angle and at 90°, the frequency modulation periodicity and width characteristics of the plasma sheath are obtained.
2. The method according to claim 1, characterized in that, Perform an intra-pulse short-time Fourier transform on the echo signal, including: The echo signal is divided into several time intervals using a window function; Fourier transform is used to analyze each time interval to determine the frequency present in each time interval; the time-frequency distribution is the spectrum that varies with time.
3. The method according to claim 2, characterized in that, Performing a Radon transform on the time-frequency distribution yields a transform domain distribution, including: The Radon transform is performed using the following formula: in, R STFT (α,l) The result is a transformation domain distribution. STFT(t,w) This is the time-frequency distribution result, where t is time. w For Doppler frequency, α For the angle information in the transform domain, l This refers to the positional information in the transform domain.
4. The method according to any one of claims 1-3, characterized in that, The process of obtaining the frequency modulation periodicity and width characteristics of the plasma sheath based on the projections of the time-frequency distribution onto the straight line at an angle and at 90° includes: The projection curve of the time-frequency distribution on the oblique angle of a straight line is determined, and the projection curve is a periodically fluctuating curve; and the number of peaks is determined based on the projection curve, so as to determine the number of peaks as the frequency modulation periodic characteristics of the plasma sheath; The projection of the time-frequency distribution onto 90° is determined, and the spectral width feature occupied by the peak is extracted based on this projection.
5. A device for extracting fast time-frequency features of a target covered by a plasma sheath, characterized in that, The device includes: The time-frequency processing unit is used to acquire the linear frequency modulated narrowband echo signal of the target covered by the plasma sheath, and to perform an intra-pulse short-time Fourier transform on the echo signal to obtain the time-frequency distribution of the target. Radon transform unit is used to perform Radon transform on the time-frequency distribution to obtain the transform domain distribution; The unit is used to determine the slope angle of a straight line based on the peak position in the transform domain distribution; the slope angle is the angle from the positive x-axis to the normal vector of the straight line L; The acquisition unit is used to obtain the frequency modulation periodicity and width characteristics of the plasma sheath based on the projections of the time-frequency distribution onto the oblique angle of the straight line and 90°, respectively.
6. The apparatus according to claim 5, characterized in that, The acquisition unit is configured to: determine the projection curve of the time-frequency distribution on the oblique angle of a straight line, wherein the projection curve is a periodically fluctuating curve; and determine the number of peaks based on the projection curve, so as to determine the number of peaks as the frequency modulation periodic characteristics of the plasma sheath; The projection of the time-frequency distribution onto 90° is determined, and the spectral width feature occupied by the peak is extracted based on this projection.
7. A computer device, characterized in that, The computer device includes a memory and a processor. The memory is used to store computer programs, and the processor is used to execute the computer programs stored in the memory to implement the steps of the method according to any one of claims 1-4.
8. A computer-readable storage medium, characterized in that, The storage medium stores a computer program, which, when executed by a processor, implements the steps of the method described in any one of claims 1-4.
9. A computer program product, characterized in that, Includes a computer program, which, when executed by a processor, implements the steps of the method according to any one of claims 1-4.