A land clutter removal method and system

Abstract

The present invention discloses a land clutter removal method and system, belonging to the field of radar technology. The method comprises: setting the radar working mode to clutter collection; fusing the acquired clutter collection data with the digital map, retaining the land part in the 01 vector map; setting the radar working mode to the radiation state, performing pulse pressure calculation on the data after AD sampling according to the distance line, performing bipolar accumulation calculation on the pulse pressure result data, and then calculating the echo power data on the distance line, and finally performing CFAR detection. The present invention effectively combines background clutter collection, data collection and bottom-level data fusion processing to generate a new version of the digital map, effectively reducing the false alarm rate, improving the detection efficiency, and quickly locking the dangerous target.

Description

Technical Field

[0001] The invention relates to a land clutter removal method and system, belonging to the technical field of radar. Background Art

[0002] In the field of water detection, radar technology, as a key means, has always been the focus of research on improving target detection accuracy and reducing false alarm rates. At present, conventional optimization schemes for water detection radars, especially shore-based radar systems, generally adopt a strategy of detecting radiation with radar as the center. During the operation of the radar, the system will first enter the "clutter generation state", at which time the radar will record and save the surrounding environmental echoes. This step is crucial because it provides the basis for subsequent data processing.

[0003] Furthermore, when the radar is in normal radiation mode, it will record and store sea clutter. Sea clutter is radar echo generated by natural phenomena such as sea waves and tides. Its characteristics are complex and changeable, which interferes with target detection. In order to effectively distinguish between targets and clutter, the system will compare and process the previously recorded clutter data, and use algorithms to analyze and identify the real target echo.

[0004] In addition, in order to improve the accuracy of target recognition, the system will also combine the underlying digital map information. Digital maps provide detailed geographical environment data, including coastlines, islands, etc. This information helps the system eliminate shore-based land targets, thereby further reducing the false alarm rate. However, in practical applications, especially in narrow sea areas, it is difficult for the system to accurately eliminate land clutter due to the complex and changeable boundary between land and water. This results in a large number of false alarm targets being misidentified, while the real surface ship targets may not be located in a timely and effective manner due to being covered. Summary of the invention

[0005] In order to reduce the false alarm rate of radar detection targets in narrow sea areas, the present invention provides a land clutter removal method and system, and the technical solution is as follows:

[0006] The land clutter elimination method of the present invention comprises:

[0007] Step 1: Set the radar working mode to clutter collection, calculate the pulse pressure of the data after AD sampling according to the distance line; perform double-pole accumulation calculation on the pulse pressure result data; calculate the echo power data on the current distance line; calculate the storage subscript of the current scanning angle in the graphic storage diagram, and store the echo power value of the current distance line according to the current scanning angle to form the clutter collection table data;

[0008] Step 2: Fusing the clutter data acquired in step 1 with the digital map, including:

[0009] (1) Calculate the echo power value in dB;

[0010] (2) Calculate the average noise power;

[0011] (3) Remove impurity noise points;

[0012] (4) Amplitude quantification:

[0013] Amplitude output value = amplitude output value / RBM coefficient;

[0014] If the amplitude output value is <0, set the amplitude output value = 0;

[0015] If the amplitude output value > 255, set the amplitude output value = 255;

[0016] (5) Perform 01 quantization: if the amplitude output value is >30, the current point value = 1; otherwise, the current point value = 0;

[0017] (6) Keep the land part in the 01 vector map;

[0018] Step 3: Set the radar working mode to radiation state, calculate the pulse pressure of the data after AD sampling according to the distance line, perform double-pole accumulation calculation on the pulse pressure result data, then calculate the echo power data on the distance line, and finally perform CFAR detection:

[0019] If "(current point amplitude / average noise)>fixed noise threshold" and "(current point amplitude / floating noise)>floating noise threshold", the current point is a CFAR target;

[0020] If "the current point is a CFAR target" and "the current point is a water area value of 1 in the 01 clutter map", the current point is an output point target and the point target output is performed.

[0021] Optionally, the pulse pressure calculation result in step 1 is expressed as:

[0022]

[0023] Among them, s(n) represents the discrete data expression of the pulse pressure after zero frequency, and h(n) represents the matched filter.

[0024] Optionally, the calculation formula for the storage subscript is:

[0025] Storage index = (current azimuth + 180°) / (scanning speed * PRI * (number of valid cycles + number of invalid cycles))

[0026] Here, PRI represents the pulse repetition interval.

[0027] Optionally, the formula for calculating the dB value of the echo power value in step 2 is:

[0028] dB value = 20*log 10 (P)

[0029] Wherein, P represents the echo power.

[0030] The present invention provides a land clutter removal system, comprising:

[0031] The clutter data acquisition module is configured to set the radar working mode to clutter acquisition, perform pulse pressure calculation on the data after AD sampling according to the distance line; perform double-pole accumulation calculation on the pulse pressure result data; calculate the echo power data on the current distance line; calculate the storage subscript of the current scanning angle in the graphic storage diagram, and store the echo power value of the current distance line according to the current scanning angle to form clutter acquisition table data;

[0032] The fusion module is configured to fuse the clutter data acquired by the clutter data acquisition module with the digital map, including:

[0033] (1) Calculate the echo power value in dB;

[0034] (2) Calculate the average noise power;

[0035] (3) Remove impurity noise points;

[0036] (4) Amplitude quantification:

[0037] Amplitude output value = amplitude output value / RBM coefficient;

[0038] If the amplitude output value is <0, set the amplitude output value = 0;

[0039] If the amplitude output value > 255, set the amplitude output value = 255;

[0040] (5) Perform 01 quantization: if the amplitude output value is >30, the current point value = 1; otherwise, the current point value = 0;

[0041] (6) Keep the land part in the 01 vector map;

[0042] The point target output module is configured to set the radar working mode to radiation state, calculate the pulse pressure of the AD sampled data according to the distance line, perform double-pole accumulation calculation on the pulse pressure result data, and then calculate the echo power data on the distance line, and finally perform CFAR detection:

[0043] If "(current point amplitude / average noise)>fixed noise threshold" and "(current point amplitude / floating noise)>floating noise threshold", the current point is a CFAR target;

[0044] If "the current point is a CFAR target" and "the current point is a water area value of 1 in the 01 clutter map", the current point is an output point target and the point target output is performed.

[0045] Optionally, the pulse pressure calculation result in the clutter data acquisition module is expressed as:

[0046]

[0047] Among them, s(n) represents the discrete data expression of the pulse pressure after zero frequency, and h(n) represents the matched filter.

[0048] Optionally, the calculation formula for the storage subscript is:

[0049] Storage index = (current azimuth + 180°) / (scanning speed * PRI * (number of valid cycles + number of invalid cycles))

[0050] Here, PRI represents the pulse repetition interval.

[0051] Optionally, the fusion module calculates the echo power value in dB using the following formula:

[0052] dB value = 20*log 10 (P)

[0053] Wherein, P represents the echo power.

[0054] The present invention provides a land clutter removal device, comprising a memory and a processor;

[0055] The memory is used to store computer programs;

[0056] The processor is used to implement the land clutter removal method as described in any one of the above items when executing the computer program.

[0057] The present invention provides a computer-readable storage medium, characterized in that a computer program is stored on the storage medium, and when the computer program is executed by a processor, the land clutter removal method as described in any one of the above items is implemented.

[0058] The beneficial effects of the present invention are:

[0059] The land clutter elimination method of the present invention effectively combines background clutter collection, data processing and bottom-level data fusion processing to generate a new version of the digital map. For unclear and narrow river data in the near-end digital map, the newly generated map can be modified through auxiliary telescopes and photoelectric imaging comparison, and the targets in the land area of ​​the river can be quickly eliminated, effectively reducing the false alarm rate, improving the detection efficiency, and quickly locking the dangerous targets. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0061] Figure 1 This is a flow chart of noise admission in the first embodiment of the present invention.

[0062] Figure 2 This is a flow chart of fusing clutter acquisition data with a digital map in the first embodiment of the present invention. DETAILED DESCRIPTION

[0063] In order to make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0064] Embodiment 1:

[0065] This embodiment provides a land clutter removal method, which generates a 01 digital map by collecting clutter and combining it with the underlying digital map data, and then improves the 01 digital map through auxiliary means such as optoelectronic equipment, so as to clearly identify the difference between the narrow river area and the land, and effectively remove the land false alarm targets. The specific steps are as follows:

[0066] Step 1: Turn on the radar and set the radar working mode to clutter recording.

[0067] (1) In the clutter recording state, the pulse pressure is calculated according to the distance line for the data after AD sampling. The discrete data expression of the pulse pressure after zero frequency is:

[0068]

[0069] Where n represents the sampling point, represents the signal amplitude, rect() represents the rectangular function, t represents time, T represents the total time of a pulse, that is, the total time of a distance line, K m represents the frequency modulation slope, M represents the total number of sampling points of a distance line, and f d Indicates the initial frequency of the signal.

[0070] Digital pulse compression generally uses the frequency domain compression method, that is, the input signal is multiplied by the matched filter in the frequency domain and then transformed to the time domain. This method is adopted because the efficient calculation of FFT can be utilized. If the time domain convolution method is performed directly, the amount of calculation will be much larger than the frequency domain method, especially when the signal time domain bandwidth is large.

[0071] The mathematical expression of the matched filter for digital pulse compression is the complex conjugate function of the linear frequency modulation signal:

[0072]

[0073] Considering that the main-sidelobe ratio can be improved, the calculation of the Hamming window can be increased, so in summary, the pulse pressure process can be simplified as follows:

[0074]

[0075] (2) Performing double-pole accumulation calculation on the pulse pressure result data;

[0076] (3) Calculate the echo power data on the distance line:

[0077] P=I 2 +Q 2

[0078] I represents the real part of the complex sampled data, and Q represents the imaginary part of the complex sampled data.

[0079] (4) Calculate the storage subscript of the current scanning angle in the graphic storage diagram:

[0080] Storage index = (current azimuth + 180°) / (scanning speed * PRI * (number of valid cycles + number of invalid cycles))

[0081] PRI is a pulse cycle length. The effective cycle is the number of effective pulse cycles, and the invalid cycle is the number of invalid pulses, also called the transition cycle.

[0082] (5) The echo power value of the current distance line is stored according to the current scanning angle to form clutter recording table data.

[0083] Step 2: Fusion of clutter data with digital maps.

[0084] (1) Calculate the echo power value in dB:

[0085] dB value = 20*log 10 (P)

[0086] (2) Calculate the average noise power:

[0087]

[0088] Where i represents the i-th sampling point, P(i) represents the power of the i-th sampling point, and N represents the total number of sampling points involved in the calculation.

[0089] (3) Remove impurity noise points:

[0090] Amplitude output value = dB value - average noise power value

[0091] (4) Amplitude quantification:

[0092] Amplitude output value = amplitude output value / RBM coefficient

[0093] If "amplitude output value < 0", amplitude output value = 0;

[0094] If "amplitude output value>255", amplitude output value = 255

[0095] (5) Perform 01 quantization:

[0096] If "amplitude output value>30", current point value = 1;

[0097] Otherwise, the current point value = 0

[0098] (6) Compare the digital map with the actual situation and refine the water area in the 01 vector map; the newly generated map can be modified through auxiliary telescopes and photoelectric imaging comparison.

[0099] (7) Keep the land part in the 01 vector map.

[0100] Step 3: Set the radar working mode to radiation state and output point target. The specific steps are as follows:

[0101] (1) Calculate the pulse pressure of the AD sampled data according to the distance line:

[0102]

[0103] The mathematical expression of the matched filter for digital pulse compression is the complex conjugate function of the linear frequency modulation signal:

[0104]

[0105] Considering that the main-sidelobe ratio can be improved, the calculation of the Hamming window can be increased, so in summary, the pulse pressure process can be simplified as follows:

[0106]

[0107] (2) Performing double-pole accumulation calculation on the pulse pressure result data;

[0108] After the pulse pressure is processed, the double-pole accumulation mainly accumulates the amplitude of the current range line echo data and the previous two range line data to improve the detection signal-to-noise ratio. The calculation formula is as follows:

[0109] OutOut(:,n)=K1*abs(OutOut(:,n-2))+K2*abs(OutOut(:,n-1))+abs(OutOut(:,n))

[0110] Among them, OutOut(:,n) represents the echo amplitude of the current range line, OutOut(:,n-1) represents the echo amplitude of the previous range line, OutOut(:,n-2) represents the echo amplitude of the first two range lines, K1 represents the weighting coefficient, K2 represents the weighting coefficient, and (:,n) represents: the nth range line.

[0111] (3) Calculate the echo power data on the distance line:

[0112] P=I 2 +Q 2

[0113] Wherein, I represents the real part of the complex sampled data, and Q represents the imaginary part of the complex sampled data.

[0114] (4) Perform CFAR detection:

[0115]

[0116]

[0117] Where i represents the i-th sampling point, P(i) represents the power amplitude of the i-th sampling point, N represents the total number of sampling points involved in the calculation, the reference half window refers to the reference length around the i-th target, and the protection half window refers to the length of the i-th target amplitude extension.

[0118] If "(current point amplitude / average noise)>fixed noise threshold" and "(current point amplitude / floating noise)>floating noise threshold", the current point is a CFAR target; if "the current point is a CFAR target" and "the current point is a water area value 1 in the 01 clutter map", the current point is an output point target and the point target output is performed.

[0119] The land clutter elimination method of this embodiment effectively combines background clutter collection, data processing and underlying data fusion processing to generate a new version of the digital map. For unclear and narrow river data in the near-end digital map, the newly generated map can be modified through auxiliary telescopes and photoelectric imaging comparison, and the targets in the land area of ​​the river can be quickly eliminated, effectively reducing the false alarm rate, improving the detection efficiency, and quickly locking the dangerous targets.

[0120] Embodiment 2:

[0121] This embodiment provides a land clutter removal system, comprising:

[0122] The clutter data acquisition module is configured to set the radar working mode to clutter acquisition, perform pulse pressure calculation on the data after AD sampling according to the distance line; perform double-pole accumulation calculation on the pulse pressure result data; calculate the echo power data on the current distance line; calculate the storage subscript of the current scanning angle in the graphic storage diagram, and store the echo power value of the current distance line according to the current scanning angle to form clutter acquisition table data;

[0123] The fusion module is configured to fuse the clutter data acquired by the clutter data acquisition module with the digital map, including:

[0124] (1) Calculate the echo power value in dB;

[0125] (2) Calculate the average noise power;

[0126] (3) Remove impurity noise points;

[0127] (4) Amplitude quantification:

[0128] Amplitude output value = amplitude output value / RBM coefficient;

[0129] If the amplitude output value is <0, set the amplitude output value = 0;

[0130] If the amplitude output value > 255, set the amplitude output value = 255;

[0131] (5) Perform 01 quantization: if the amplitude output value is >30, the current point value = 1; otherwise, the current point value = 0;

[0132] (6) Keep the land part in the 01 vector map;

[0133] The point target output module is configured to set the radar working mode to radiation state, calculate the pulse pressure of the AD sampled data according to the distance line, perform double-pole accumulation calculation on the pulse pressure result data, and then calculate the echo power data on the distance line, and finally perform CFAR detection:

[0134] If "current point average noise > fixed noise threshold" and "current point floating noise > floating noise threshold", the current point is a CFAR target;

[0135] If "the current point is a CFAR target" and "the current point is a water area value of 1 in the 01 clutter map", the current point is an output point target and the point target output is performed.

[0136] Some steps in the embodiments of the present invention may be implemented using software, and the corresponding software program may be stored in a readable storage medium, such as a CD or a hard disk.

[0137] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A land clutter removal method, characterized in that: The method comprises: Step 1: Set the radar working mode to clutter collection, calculate the pulse pressure of the data after AD sampling according to the distance line; perform double-pole accumulation calculation on the pulse pressure result data; calculate the echo power data on the current distance line; calculate the storage subscript of the current scanning angle in the graphic storage diagram, and store the echo power value of the current distance line according to the current scanning angle to form the clutter collection table data; Step 2: Fusing the clutter data acquired in step 1 with the digital map, including: (1) Calculate the echo power value in dB; (2) Calculate the average noise power; (3) Remove impurity noise points; (4) Amplitude quantification: Amplitude output value = amplitude output value / RBM coefficient; If the amplitude output value is <0, set the amplitude output value = 0; If the amplitude output value > 255, set the amplitude output value = 255; (5) Perform 01 quantization: if the amplitude output value is >30, the current point value = 1; otherwise, the current point value = 0; (6) Keep the land part in the 01 vector map; Step 3: Set the radar working mode to radiation state, calculate the pulse pressure of the data after AD sampling according to the distance line, perform double-pole accumulation calculation on the pulse pressure result data, then calculate the echo power data on the distance line, and finally perform CFAR detection: If "(current point amplitude / average noise)>fixed noise threshold" and "(current point amplitude / floating noise)>floating noise threshold", the current point is a CFAR target; If "the current point is a CFAR target" and "the current point is a water area value of 1 in the 01 clutter map", the current point is an output point target and the point target output is performed.

2. The land clutter removal method according to claim 1, characterized in that: The pulse pressure calculation result in step 1 is expressed as: Among them, s(n) represents the discrete data expression of the pulse pressure after zero frequency, and h(n) represents the matched filter.

3. The land clutter removal method according to claim 1, characterized in that: The calculation formula for the storage subscript is: Storage index = (current azimuth + 180°) / (scanning speed * PRI * (number of valid cycles + number of invalid cycles)) Here, PRI represents the pulse repetition interval.

4. The land clutter removal method according to claim 1, characterized in that: The formula for calculating the dB value of the echo power value in step 2 is: dB value = 20*log 10 (P) Wherein, P represents the echo power.

5. A land clutter removal system, characterized in that: The system comprises: The clutter data acquisition module is configured to set the radar working mode to clutter acquisition, perform pulse pressure calculation on the data after AD sampling according to the distance line; perform double-pole accumulation calculation on the pulse pressure result data; calculate the echo power data on the current distance line; calculate the storage subscript of the current scanning angle in the graphic storage diagram, and store the echo power value of the current distance line according to the current scanning angle to form clutter acquisition table data; The fusion module is configured to fuse the clutter data acquired by the clutter data acquisition module with the digital map, including: (1) Calculate the echo power value in dB; (2) Calculate the average noise power; (3) Remove impurity noise points; (4) Amplitude quantification: Amplitude output value = amplitude output value / RBM coefficient; If the amplitude output value is <0, set the amplitude output value = 0; If the amplitude output value > 255, set the amplitude output value = 255; (5) Perform 01 quantization: if the amplitude output value is >30, the current point value = 1; otherwise, the current point value = 0; (6) Keep the land part in the 01 vector map; The point target output module is configured to set the radar working mode to radiation state, calculate the pulse pressure of the AD sampled data according to the distance line, perform double-pole accumulation calculation on the pulse pressure result data, and then calculate the echo power data on the distance line, and finally perform CFAR detection: If "(current point amplitude / average noise)>fixed noise threshold" and "(current point amplitude / floating noise)>floating noise threshold", the current point is a CFAR target; If "the current point is a CFAR target" and "the current point is a water area value of 1 in the 01 clutter map", the current point is an output point target and the point target output is performed.

6. The land clutter removal system according to claim 5, characterized in that: The pulse pressure calculation result in the clutter data acquisition module is expressed as: Among them, s(n) represents the discrete data expression of the pulse pressure after zero frequency, and h(n) represents the matched filter.

7. The land clutter removal system according to claim 5, characterized in that: The calculation formula for the storage subscript is: Storage index = (current azimuth + 180°) / (scanning speed * PRI * (number of valid cycles + number of invalid cycles)) Here, PRI represents the pulse repetition interval.

8. The land clutter removal system according to claim 5, characterized in that: The formula for calculating the dB value of the echo power value by the fusion module is: dB value = 20*log 10 (P) Wherein, P represents the echo power.

9. A land clutter removal device, characterized in that: including memory and processor; The memory is used to store computer programs; The processor is used to implement the land clutter removal method according to any one of claims 1 to 4 when executing the computer program.

10. A computer-readable storage medium, characterized in that: The storage medium stores a computer program, and when the computer program is executed by the processor, the land clutter removal method according to any one of claims 1 to 4 is implemented.

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