KR101674112B1 - Method and recording medium for classification of target using jet engine modulation signals - Google Patents

Abstract

The present invention relates to a method for identifying a target using jet engine modulation signals and a recording medium for the same, and more particularly, to a method for identifying the type of a target using jet engine modulation signals and a recording medium for the same. A method for identifying a target using jet engine modulation signals according to an embodiment of the present invention comprises the following steps: irradiating an electromagnetic wave toward the target and receiving a jet engine modulation (JEM) signal reflected from the target; applying a joint time-frequency analysis (JTFA) to the JEM signal to generate a time-frequency wave image representing amplitude information in a time region and a frequency region; converting the time-frequency wave image to a pixel image including a plurality of pixels arranged in a matrix so as to correspond to the time region and the frequency region, respectively; extracting an effective pixel from the pixel image; and identifying the target by using pixel information of the effective pixel.

Description

[0001] METHOD AND RECORDING MEDIUM FOR CLASSIFICATION OF TARGET USING JET ENGINE MODULATION SIGNALS [0002]

The present invention relates to a target identification method using a jet engine modulation signal and a recording medium, and more particularly, to a target identification method using a jet engine modulation signal for identifying a type of a target using a jet engine modulation signal, will be.

A radar is an apparatus that transmits electromagnetic waves to a target and receives electromagnetic waves reflected from the target to detect position information such as distance, direction and altitude from the target, and has an advantage that it can be used regardless of weather and day and night. The radar is used not only for the distance information but also for the identification of the target by obtaining the characteristics of the target using the signal size and phase change information from the reflected signal.

The Jet Engine Modulation (JEM) technique is a technique for classifying aircraft types and types by analyzing radar reflection signals that are modulated by the rotation of a jet engine of an aircraft. The jet engine modulation technique is the oldest method among the aircraft identification methods, but it is known as the most realistic method in operation amount and performance. A jet engine modulation technique is a method of estimating the number of blades of a jet engine from a jet engine modulation signal and comparing the number of blades with a database of the number of wings of the engine to find the type of engine.

In order to identify a target from a jet engine modulation signal, a time-frequency simultaneous analysis technique having many merits can be used by simultaneously analyzing the time domain and the frequency domain. This time-frequency simultaneous analysis technique has the advantage of overcoming the disadvantages of using only one time axis or frequency axis and enhancing the intuitiveness of the signal periodicity.

However, in order to apply the time-frequency simultaneous analysis technique to most jet engine modulation signals, it is difficult to extract the information of the jet engine for target identification due to irregular waveforms. In order to confirm the waveform period directly by the irregular waveform The measurement result is inaccurate and takes a long time, which is inadequate to be applied to an actual war situation requiring identification of a fast target in real time.

KR 10-1494778 B1

The present invention provides a target identification method and recording medium using a jet engine modulation signal that automatically identifies the type of target using a jet engine modulation signal.

A method of identifying a target using a jet engine modulation signal according to an exemplary embodiment of the present invention includes the steps of: radiating an electromagnetic wave toward a target and receiving a jet engine modulation signal (JEM) reflected from the target; Generating a time-frequency waveform image representing amplitude information in a time domain and a frequency domain by applying a time-frequency simultaneous analysis technique (JTFA) to the jet engine modulation signal; Converting the time-frequency waveform image into a pixel image including a plurality of pixels arranged in a matrix corresponding to the time domain and the frequency domain; Extracting an effective pixel from the pixel image; And identifying the target using the pixel information of the effective pixel.

The time-frequency simultaneous analysis technique may include a Smoothed Pseudo Wigner-Ville Distribution (SPWVD) analysis technique.

The step of generating the time-frequency waveform image may include the step of changing the frequency value such that the average frequency value of the jet engine modulation signal has a value of zero.

The process of extracting the effective pixel may include: selecting an effective pixel region from a pixel value of a pixel included in the pixel image; Extracting an outline of the effective pixel region; Selecting a contour corresponding to a frequency having a positive value in the time-frequency waveform image among the extracted contours; And extracting a pixel located at a peak of the selected contour line as an effective pixel.

Converting the time-frequency waveform image into a pixel image including a plurality of pixels having at least one value of R (Red), G (Green), and B (Blue) In the selecting of the effective pixel region, a pixel having a G (Green) value among a plurality of pixels included in the pixel image may be extracted to determine an effective pixel region.

The step of identifying the target can identify the target by calculating at least one of the number of wings and the length of the wings of the jet engine mounted on the target.

The time domain of the time-frequency waveform image is transformed so that the initial time axis corresponds to the first axis of the pixel image, and the number of blades (BN) of the jet engine can be calculated from the following equation (1).

[Equation 1]

(Where R [·] denotes an operator for rounding down the decimal point to convert to an integer, HPN denotes the total number of pixels in the first axis, FR denotes an interval between the effective pixels in the first axis direction , TR is the time-time domain of the frequency waveform image size, _R f represents the rotational frequency of the jet engine, the modulating signal).

The frequency domain of the time-frequency waveform image is transformed so that the maximum frequency axis corresponds to the second axis of the pixel image, and the blade length BL of the jet engine can be calculated from the following equation (2).

&Quot; (2) "

MP is the minimum distance between the second axis and the effective pixel, FR is the time-axis distance between the first axis and the second axis,? Is the wavelength of the electromagnetic wave,? Is the angular velocity of the jet engine modulation signal,? Is the angle of incidence of the electromagnetic wave, Frequency Indicates the frequency domain magnitude of the waveform image.)

In addition, the recording medium according to the embodiment of the present invention stores a computer program for performing the method of identifying a target using the jet engine modulation signal.

According to an embodiment of the present invention, a target identification method and a recording medium using a jet engine modulation signal convert a time-frequency waveform image generated from a jet engine modulation signal into a pixel image, The number of wings of the jet engine and the wing length can be automatically extracted from the maximum Doppler frequency corresponding to the maximum Doppler frequency.

Further, in the process of converting the time-frequency waveform image into the pixel image, by performing the operation only on the specific component corresponding to the effective jet engine modulated signal component based on the image processing technique to obtain the jet engine information, It is possible to quickly perform the identification process of the target having the efficiency.

1 is a flow chart schematically illustrating a method of identifying a target using a jet engine modulation signal according to an embodiment of the present invention.
Figure 2 shows a jet engine modulated signal reflected from a target;
3 is a diagram illustrating a process of applying an empirical mode separation method to a jet engine modulated signal;
4 is a diagram showing a waveform image generated by applying a time-frequency simultaneous analysis technique;
5 is a diagram illustrating a principle for identifying a target from a waveform image;
6 is a diagram illustrating a process of selecting an effective pixel region from a pixel value;
7 is a diagram showing a process of selecting a contour line of an effective pixel region and extracting a pixel located at a peak of the contour line with an effective pixel.
8 is a view showing a process of calculating the number of wings of a jet engine mounted on a target;
9 is a view showing a process of calculating a blade length of a jet engine mounted on a target;

A target identification method and a recording medium using a jet engine modulation signal according to the present invention convert a time-frequency waveform image generated from a jet engine modulation signal into a pixel image and output a maximum Doppler The technical features that can automatically extract the number of wings and the wing length of the jet engine from the frequency are presented.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, Is provided to fully inform the user. Wherein like reference numerals refer to like elements throughout.

1 is a flowchart schematically illustrating a method of identifying a target using a jet engine modulation signal according to an embodiment of the present invention.

Referring to FIG. 1, a method of identifying a target using a jet engine modulation signal according to an exemplary embodiment of the present invention includes the steps of: radiating an electromagnetic wave toward a target; receiving a jet engine modulation signal (JEM) reflected from the target; (S100); A step (S200) of generating a time-frequency waveform image representing amplitude information in a time domain and a frequency domain by applying a time-frequency simultaneous analysis technique (JTFA: Joint Time-Frequency Analysis) to the jet engine modulation signal; A step (S300) of converting the time-frequency waveform image into a pixel image including a plurality of pixels arranged in a matrix so as to correspond to the time domain and the frequency domain, respectively; Extracting an effective pixel from the pixel image (S400); And identifying a target using pixel information of the effective pixel (S500).

The process of receiving the jet engine modulation signal (S100) uses a radar to emit electromagnetic waves toward a target, such as an aircraft, and receives jet engine modulated signals reflected from the target. Here, the radar emits an electromagnetic wave to a target, receives electromagnetic waves reflected from the target within the range of the radar, and the electromagnetic wave radiated from the radar has a certain wavelength (?). Further, the electromagnetic wave radiated from the radar is radiated at a certain incidence angle?, Where the angle of incidence? Is the angle between the rotation axis of the wing of the target jet engine and the central axis of the electromagnetic wave radiated by the radar it means.

Figure 2 is a diagram showing jet engine modulated signals reflected from a target.

In the jet engine mounted on a target such as an airplane, a plurality of blades are fixed around a rotation axis for air compression. As described above, the signal reflected from the target by electromagnetic waves radiated by the radar is complex Size and phase modulation. Thus, the reflected signal, which is subjected to complicated magnitude and phase modulation by the rotation of each wing, is referred to as a Jet Engine Modulation (JEM) signal.

The time-frequency waveform image generation step S200 includes applying a time-frequency simultaneous analysis method (JTFA) to the jet engine modulation signal to generate a time- Generate a frequency waveform image.

3 is a diagram illustrating a process of applying an empirical mode separation method to a jet engine modulation signal.

As described above, the jet engine modulation signal received from the target is reflected in a complicated form by magnitude and phase modulation by rotation of each wing. Therefore, first, a first chopping frequency that is directly connected to the number information of the wing of the jet engine is found with respect to the jet engine modulation signal, and a low-pass filter that uses the frequency of the harmonic component as a cut- (LPF: Low Pass Filter) is applied (Fig. 3 (a)).

Thereafter, the signal filtered by the low-pass filter is separated into several intrinsic mode functions (IMFs) using Empirical Mode Decomposition (EMD), while the signal filtered by the jet engine modulated signal The final eigenmode function (IMF 1) with the highest contribution and the last eigenmode function (last IMF) are combined to restore the final jet engine modulated signal (Fig. 3 (b)).

In relation to the process of reconstructing the final jet engine modulated signal using the empirical mode separation method, it is described in various papers such as "Extraction of JEM component in the observation range of weak JEM using complex EMD" And a detailed description thereof will be omitted.

4 is a diagram showing a waveform image generated by applying the time-frequency simultaneous analysis technique.

When the final jet engine modulation signal is restored by the above process, a time-frequency simultaneous analysis technique is applied to the jet engine modulation signal, and time-frequency simultaneous analysis of the amplitude information in the time domain and the frequency domain, Create a waveform image.

Time-frequency simultaneous analysis techniques for generating time-frequency waveform images are STFT (Short Time Fourier Transform) and SPWVD (Smoothed Pseudo Wigner-Ville Distribution) techniques.

The STFT technique is a technique that is performed by sequentially executing a Fourier transform while moving a window with time using an appropriate window function for a purpose. Unlike a general Fourier transform, At the same time, it is a spectral method that can observe the occurrence of an event. However, the STFT has low time and frequency resolution, which makes it difficult to accurately analyze transient signals.

On the other hand, the SPWVD technique has the advantage of analyzing transient abnormal signals with high time-frequency resolution. In an embodiment of the present invention, a time-frequency waveform image was generated by applying the SPWVD, that is, the Smoothing-Pseudo-Wigner-Bill distribution scheme, in order to independently improve time and frequency resolution to produce a clear time-frequency waveform image.

A time-frequency waveform image is a tool for visualizing and identifying signal information, which combines features of waveform and spectrum. That is, in the waveform, the change of the amplitude axis according to the change of the time axis can be seen. In the spectrum, the change of the amplitude axis according to the change of the frequency axis can be seen. On the other hand, As a difference in printing density or a difference in display color. That is, as shown in FIG. 4, the difference in amplitude can be expressed as a difference in display color according to the change of the time axis and the frequency axis according to the time-frequency waveform image. You can see the value of relative amplitude with color.

5 is a diagram showing a principle for identifying a target from a waveform image.

5, a chopping rate at which one wing of a jet engine mounted on the target moves to an adjacent point can be obtained from a cycle repeated in the time axis of the time-frequency waveform image, The maximum Doppler frequency can be obtained by the size of the outer component. Such a chopping period and maximum Doppler frequency can be confirmed by the user's eyes, but it is required to automatically perform the above process in order to measure accurate information and to obtain quick results.

In order to automatically identify the target by measuring the chopping period and the maximum Doppler frequency, the process of generating the time-frequency waveform image is a process of changing the frequency value such that the average frequency value of the jet engine modulation signal has a value of 0 .

In the case of the time-frequency waveform image shown in FIGS. 4 and 5, the upper time-frequency waveform image and the lower time-frequency waveform image are displayed in a substantially symmetrical form with respect to the axis having a frequency value of 0. However, in the case of a general time-frequency waveform image, the time-frequency waveform image at the upper part and the time-frequency waveform image at the lower part are symmetric with respect to the axis having the constant value (C) Respectively. In this case, in order to make the time-frequency waveform image of the upper part and the time-frequency waveform image of the lower part symmetrical with respect to the axis having the value of 0 by removing the constant C due to the pore effect, The frequency value of the modulated signal can be changed to a value obtained by subtracting the average frequency value from each frequency value. The reason why the frequency value of the jet engine modulation signal is changed so that the average frequency value of the jet engine modulation signal is changed to 0 by changing the frequency value of each frequency value to the value obtained by subtracting the average frequency value, Will be described later with respect to the process of obtaining the blade length of the jet engine mounted on the target.

A step S300 of transforming the time-frequency waveform image into the pixel image includes applying a time-frequency simultaneous analysis technique to a time-frequency waveform image representing amplitude information in a time domain and a frequency domain to include a plurality of pixels arranged in a matrix Into a pixel image. Here, the initial time axis (time = 0) of the time-frequency waveform image is transformed to correspond to the first axis of the pixel image and the maximum frequency axis (frequency = max) is transformed to correspond to the second axis of the pixel image, The pixel image comprises a plurality of pixels arranged in a matrix on a plane consisting of a first axis and a second axis.

6 to 9, a time-frequency waveform image having a time range of 0 sec to 0.5 sec and having a frequency range of -299 Hz to +299 Hz includes 365 pixels (The horizontal axis in Fig. 6) and the second axis (the vertical axis in Fig. 6) having 339 pixel numbers. Also, in the time-frequency waveform image, the difference in the printing density or the amplitude represented by the display color is converted into the pixel value of each pixel included in the pixel image.

Here, in the case where the difference in amplitude appears as a difference in printing density, the pixel image may be configured by arranging pixels having pixel values corresponding to respective printing densities, but in general, the time-frequency waveform image is represented by the difference in display color Frequency waveform image to a pixel image in step S300, the time-frequency waveform image is converted into a pixel value of R (Red), G (Green), and B (Blue) Into a pixel image containing a plurality of pixels having at least one value. That is, it is possible to convert a pixel image having a pixel value in which R (Red), G (Green), and B (Blue) values are combined according to the display color of the time-frequency waveform image.

In step S400 of extracting an effective pixel, an effective pixel having information for obtaining a chopping rate and a size of an outer component required for identifying a target from a pixel image including a plurality of pixels arranged in a matrix Pixels are extracted. In addition, the step of extracting an effective pixel (S400) includes the steps of: selecting an effective pixel region from the pixel values of the pixels included in the pixel image; Extracting an outline of the effective pixel region; Selecting a contour corresponding to a frequency having a positive value in the time-frequency waveform image among the extracted contours; And extracting a pixel located at a peak of the selected contour line as an effective pixel.

FIG. 6 illustrates a process of selecting an effective pixel region from a pixel value, FIG. 7 illustrates a process of selecting a contour line of an effective pixel region, and extracting a pixel positioned at a peak of the contour line with an effective pixel.

Referring to FIGS. 6 and 7, the process of extracting effective pixels (S400) will be described in detail. First, an effective pixel region is selected from the pixel values of the pixels included in the pixel image. As described above, the time-frequency waveform image shows the difference in amplitude according to the change of the time axis and the frequency axis as a difference in print density or a difference in display color. Here, when the amplitude difference appears as a difference in printing density, the process of selecting an effective pixel region may select a region having a pixel value corresponding to a time-frequency waveform image having a predetermined printing density. However, Frequency waveform image is converted into a pixel image having a pixel value in which R (Red), G (Green), and B (Blue) values are combined, a green component (Refer to FIG. 5). Here, the reason why the pixels including the green component are selected and the effective pixel area is selected is that the red component of the time-frequency waveform image, which is represented by the difference of the display colors, is a part of the Doppler frequency component (about 70% ), And the blue component includes a plurality of external frequency components other than the Doppler frequency component.

The process of selecting an effective pixel region to select a pixel including a green component may determine a valid pixel region by extracting a pixel having a G (Green) value among a plurality of pixels included in the pixel image. That is, a pixel having a non-zero G (Green) value among a plurality of pixels having values of R (Red), G (Green), and B (Blue) of 0 to 255 is extracted to determine an effective pixel region, Green component can be extracted quickly and accurately.

As shown in FIG. 7, the outline of the effective pixel region is extracted when the effective pixel region including the green component is selected as described above. The extracted contour includes an upper contour corresponding to a frequency having a positive value in the time-frequency waveform image and a lower contour corresponding to a frequency having a negative value in the time-frequency waveform image, Selects a large upper contour. This is because a faster moving contour is advantageous for peak detection, and a lower contour may be selected if the lower contour has a large variance, but this is only applied to the process of calculating the number of blades of a jet engine mounted on the target, In order to calculate the blade length, a process of selecting the upper contour line is separately required.

When the upper contour line is selected by the above-described process, a pixel located at the peak of the selected contour line, i.e., the peak pixel, is extracted as an effective pixel. That is, each pixel located at the peak of the upper contour on the pixel image is an effective pixel necessary to calculate the target identification, i.e., the number of wings and the wing length of the target.

Hereinafter, the process of calculating the number of wings and the wing length of a jet engine mounted on the target using pixel information of effective pixels, that is, pixel values and pixel positions, will be described in detail.

8 is a view showing a process of calculating the number of wings of a jet engine.

Referring to FIG. 8, according to the method of identifying a target using a jet engine modulation signal according to an embodiment of the present invention, the number of wings of a jet engine mounted on a target can be calculated by the following equation (1).

(Where R [·] denotes an operator for rounding down the decimal point to convert to an integer, HPN denotes the total number of pixels in the first axis, FR denotes an interval between the effective pixels in the first axis direction , TR is the time-time domain of the frequency waveform image size, _R f represents the rotational frequency of the jet engine, the modulating signal).

The number of blades BN of the jet engine can be calculated by measuring one rotation cycle of the rotation axis of the jet engine and a time when each blade moves to the next blade position by rotation. That is, the value obtained by dividing the rotation period of the rotation axis of the jet engine by the time for each wing to move to the position of the next wing is the number of wing of the jet engine.

That is, FR in Equation (1) means an interval between effective pixels located at a peak on a pixel image. In order to more accurately measure the number of blades (BN) of the jet engine, it is possible to select an interval represented by the greatest frequency among the various intervals between effective pixels and determine the interval as FR.

Further, a factor for converting the domain time domain (8 (a) Fig.) Corresponding to the first axis of HPN and TR is a pixel image in Equation 1, f _R is a rotation frequency of the jet-modulated signal f _R It is possible to calculate the rotation period of the rotation axis of the jet engine. f _R can be estimated from the jet engine modulation signal using an autocorrelation method or a cepstrum method, and a detailed description thereof will be omitted.

According to the embodiment of FIG. 8, it can be seen that the spacing (FR), which is the most common among the effective pixels on the pixel image shown in FIG. 8 (b), is 17. Further, the total number of pixels (HPN) of the first axis of the pixel image is 365, and the size (TR) of the time domain of the time-frequency waveform image has a value of 0.5. Also, the rotation frequency f _R of the jet engine modulation signal derived by the autocorrelation method has a value of 1.0345.

Accordingly, it can be seen that the number of blades (BN) of the jet engine is calculated as 42 as a result of substituting each of the above values into the equation (1) and rounding down the decimal point to integers.

On the other hand, the blade length BL of the jet engine can be calculated from the maximum Doppler shift frequency (f _{d, max} ) represented by the following expression (2) of the jet engine modulation signal.

Where? Is the wavelength of the electromagnetic wave,? Is the angular velocity of the jet engine modulation signal,? Is the angle of incidence of the electromagnetic wave, BL is the blade length of the jet engine, and C is a constant value due to the above-

In the case of a general jet engine, the wing of the jet engine is installed not to be exposed to the outside, but to a certain depth into the interior of the jet engine. Therefore, due to the pore effect due to such a pull-in installation, a constant value (C) is included in the maximum Doppler frequency of the jet engine modulation signal.

However, as described above, when the frequency value of the jet engine modulation signal is changed to a value obtained by subtracting the average frequency value from each frequency value and the frequency value is changed so that the average frequency value of the jet engine modulation signal has a value of 0 In the time-frequency waveform image, the upper time-frequency waveform image and the lower time-frequency waveform image can be symmetrically adjusted with respect to the axis having a frequency value of 0, and the constant (C) value due to the pore effect Has a value of zero.

Therefore, in this case, the maximum Doppler frequency (f _{d, max} ) value can be expressed by the following equation (3), and the blade length BN of the jet engine can be calculated from the following equation (3).

9 is a view showing a process of calculating the blade length of the jet engine mounted on the target.

Referring to FIG. 9, in the target identification method using the jet engine modulation signal according to the embodiment of the present invention, the blade length of the jet engine mounted on the target is calculated by the following Equation 4 derived from Equation (3) .

MP is the minimum distance between the second axis and the effective pixel, FR is the time-axis distance between the first axis and the second axis,? Is the wavelength of the electromagnetic wave,? Is the angular velocity of the jet engine modulation signal,? Is the angle of incidence of the electromagnetic wave, Frequency Indicates the frequency domain magnitude of the waveform image.)

The maximum Doppler frequency (f _{d, max} ) in Equation (3) can be calculated from the VPN, MP, FR values. That is, since the maximum Doppler frequency (f _{d, max} ) corresponds to the maximum outline component in the frequency axis direction from the time-frequency waveform image as shown in FIG. 5, The interval between the peaks of the upper contour line from the central axis on the pixel image can be obtained from a value obtained by dividing the pixel image into upper and lower portions excluding the central axis and subtracting MP corresponding to the length in the second axial direction of the upper pixel image. In Equation (4), FR and VPN are factors for converting the area corresponding to the second axis of the pixel image into the frequency domain (Fig. 9 (a)).

According to the embodiment of Fig. 9, the minimum spacing (MP) of the spacing between the second axis and each effective pixel on the pixel image shown in Fig. 9 (b) In addition, since the total number of pixels (VPN) of the second axis of the pixel image is 339, the number of pixels of the upper pixel image excluding the central axis in the second axis direction is 169, and the size of the frequency domain of the time- Respectively. Further, the angular velocity (?) Of the jet engine modulation signal can be obtained by multiplying the rotation frequency (f _R ) of the jet engine modulation signal by 2?.

Therefore, when the value of the electromagnetic wave radiated from the radar is 0.03 and the angle of incidence of the electromagnetic wave is 50 °, the blade length BL of the jet engine is 0.394 m. < / RTI >

As described above, according to the target identification process using the jet engine modulation signal according to the embodiment of the present invention, only the specific component corresponding to the effective jet engine modulation signal component is calculated based on the image processing technique, The identification process of the target having high reliability and efficiency can be performed quickly.

Meanwhile, the target identification method using the jet engine modulation signal according to the embodiment of the present invention can also be applied to a recording medium storing a computer program for performing the above method.

In addition, the target identification method using the jet engine modulation signal according to the embodiment of the present invention may be implemented in the form of a computer-readable programming language code recorded in a computer-readable recording medium. The computer-readable recording medium is any data storage device that can be read by a computer and can store data. For example, the computer-readable recording medium may be a ROM, a RAM, a CD-ROM, a magnetic tape, a floppy disk, an optical disk, a hard disk drive, a flash memory, a solid state disk (SSD), or the like. In addition, the computer readable code or program stored in the computer readable recording medium may be transmitted through a network connected between the computers.

While the preferred embodiments of the present invention have been described and illustrated above using specific terms, such terms are used only for the purpose of clarifying the invention, and the embodiments of the present invention and the described terminology are intended to be illustrative, It will be obvious that various changes and modifications can be made without departing from the spirit and scope of the invention. Such modified embodiments should not be individually understood from the spirit and scope of the present invention, but should be regarded as being within the scope of the claims of the present invention.

Claims (9)

Radiating an electromagnetic wave toward the target and receiving jet engine modulation (JEM) signals reflected from the target;
Generating a time-frequency waveform image representing amplitude information in a time domain and a frequency domain by applying a time-frequency simultaneous analysis technique (JTFA) to the jet engine modulation signal;
Converting the time-frequency waveform image into a pixel image including a plurality of pixels arranged in a matrix corresponding to the time domain and the frequency domain;
Extracting an effective pixel from the pixel image; And
And identifying the target using the pixel information of the effective pixel.
The method according to claim 1,
Wherein the time-frequency simultaneous analysis technique includes a Smoothed Pseudo Wigner-Ville Distribution (SPWVD) analysis technique.
The method according to claim 1,
Wherein the generating the time-frequency waveform image comprises:
And modifying the frequency value so that the average frequency value of the jet engine modulation signal has a value of zero.
The method according to claim 1,
The step of extracting the valid pixels may include:
Selecting an effective pixel region from a pixel value of a pixel included in the pixel image;
Extracting an outline of the effective pixel region;
Selecting a contour corresponding to a frequency having a positive value in the time-frequency waveform image among the extracted contours; And
And extracting a pixel positioned at a peak of the selected contour line with an effective pixel.
The method of claim 4,
Converting the time-frequency waveform image into a pixel image including a plurality of pixels having at least one value of R (Red), G (Green), and B (Blue)
Wherein the step of selecting an effective pixel region comprises the step of extracting a pixel having a G value among a plurality of pixels included in the pixel image to determine an effective pixel region.
The method according to claim 1,
The process of identifying the target may comprise:
And a jet engine modulated signal that identifies a target by calculating at least one of a number of wings and a wing length of the jet engine mounted on the target.
The method of claim 6,
Wherein the time domain of the time-frequency waveform image is transformed such that an initial time axis corresponds to a first axis of the pixel image,
Wherein the number of blades (BN) of the jet engine is calculated from the following equation (1).
[Equation 1]

(Where R [·] denotes an operator for rounding down the decimal point to convert to an integer, HPN denotes the total number of pixels in the first axis, FR denotes an interval between the effective pixels in the first axis direction , TR is the time-time domain of the frequency waveform image size, _R f represents the rotational frequency of the jet engine, the modulating signal).
The method of claim 6,
Wherein the frequency domain of the time-frequency waveform image is transformed such that a maximum frequency axis corresponds to a second axis of the pixel image,
Wherein the blade length (BL) of the jet engine is calculated from the following equation (2).
&Quot; (2) "

MP is the minimum distance between the second axis and the effective pixel, FR is the time-axis distance between the first axis and the second axis,? Is the wavelength of the electromagnetic wave,? Is the angular velocity of the jet engine modulation signal,? Is the angle of incidence of the electromagnetic wave, Frequency Indicates the frequency domain magnitude of the waveform image.)
A recording medium storing a computer program for performing a target identification method using the jet engine modulation signal according to any one of claims 1 to 8.

Images