Artillery positioning radar clutter suppression method based on double-frame joint detection

Abstract

The invention discloses an artillery positioning radar clutter suppression method based on double-frame joint detection. The artillery positioning radar clutter suppression method comprises the following steps of performing threshold reduction target detection processing on two frames of echoes; carrying out two-over-two criterion detection on the target detected in each frame according to a distance unit; fine speed measurement processing is carried out on the target exceeding the threshold; and carrying out clutter elimination processing based on the target speed. The method has better inhibition performance on slow clutters such as ground features, meteorology, birds and the like and far-area folding clutters, high-speed target detection loss is reduced, occupation of the clutters on system time resources is reduced, and the requirements of high-speed target detection of rapid screen penetration and simultaneous multi-target detection capability on the system time resources are met.

Description

Technical Field

[0001] The invention relates to radar signal processing technology, in particular to a clutter suppression method for artillery positioning radar based on double-frame joint detection. Background Art

[0002] Artillery locating radar needs to detect artillery projectiles with extremely small radar reflection cross-section (usually 0.001-0.1㎡) at low elevation angles. At this time, the ground environment clutter is extremely strong, and the projectile echo signal is covered by slow clutter such as ground objects, weather, and flying birds. In order to achieve the detection of weak targets and improve the ability to detect targets in complex backgrounds, artillery locating radar usually uses moving target detection (MTD) technology.

[0003] MTD is a technology that uses Doppler filter groups to suppress clutter and improve the radar's ability to detect moving targets in a clutter background. It uses FFT (or FIR) to form a narrowband filter group that is adjacent and partially overlapping on the frequency axis to complete the approximate matched filtering of target signals with different Doppler frequencies, so that the signal-to-noise ratio of the target is improved, and the clutter filter is set to a high impedance state to suppress slow clutter. However, when the Doppler frequency caused by the movement of high-speed projectile targets is greater than the repetition frequency of the transmitted pulse, there will be speed ambiguity, that is, in certain speed ranges, it may fall into the clutter filter and cannot be detected, resulting in target detection loss. The current conventional solution is to use multiple groups (usually 3 groups) of timing staggered with different repetition frequencies between circles to make high-speed projectile targets avoid clutter filters, but this method takes up more system time resources and still has a large number of missed alarms for high-speed projectile targets that quickly cross the radar search screen.

[0004] In addition to the above-mentioned slow clutter such as ground objects, weather, and flying birds, far-zone folded clutter will also occupy more system time resources, resulting in reduced simultaneous multi-target detection capabilities. Therefore, it is necessary to improve the radar system's ability to suppress slow clutter and far-zone folded clutter. Summary of the invention

[0005] In view of the problems existing in the prior art, the present invention provides a clutter suppression method for artillery positioning radar based on dual-frame joint detection. Compared with conventional processing methods, the method has better suppression performance for slow clutter such as ground objects, weather, flying birds and far-field folded clutter, reduces the loss of high-speed target detection, reduces the occupation of system time resources by clutter, and meets the requirements of high-speed target detection with fast screen penetration and simultaneous multi-target detection capability for system time resources.

[0006] The purpose of the present invention is achieved through the following technical solutions.

[0007] A method for suppressing clutter of artillery positioning radar based on dual-frame joint detection comprises the following steps:

[0008] 10) Echo data reorganization: In a coherent processing interval, the radar transmits 2P pulses in total, P is an integer, and P≥8, the repetition periods of the first P transmitted pulses and the last P transmitted pulses are PRT1 and PRT2 respectively, PRT1≠PRT2, the radar receives the echo signals of the first P pulses and combines them into the first frame echo, and receives the echo signals of the last P pulses and combines them into the second frame echo;

[0009] 20) Threshold reduction target detection: The two frames of echo data are respectively subjected to threshold reduction detection processing according to the filter distance unit, and the clutter filter is no longer set to high impedance state at this time;

[0010] 30) 2-by-2 criterion joint detection: perform AND operation on the target detection marks of the two frames of echoes according to the distance unit, and obtain the marks of the two frames detecting the target in the same distance unit. If the two frames detect the target in the same distance unit, set the comprehensive detection mark to 1, otherwise the mark is 0;

[0011] 40) Target precision speed measurement processing: For targets with a comprehensive detection mark of 1, the unambiguous speed of the target in two frames is calculated based on the conversion relationship between the filter channel number where the target is located and the speed, after amplitude weighting;

[0012] 50) Clutter removal based on target speed: When the speeds of the targets in the two frames are both less than the set clutter speed threshold, and the speed difference between the targets in the two frames is less than the set speed difference threshold, the target is judged as clutter and the detection mark is set to 0, otherwise the detection mark is set to 1.

[0013] The step 10) is specifically as follows:

[0014] The radar receives the echo signals of the first P pulses and combines them into the first frame echo :

[0015] ;

[0016] The radar receives the echo signals of the last P pulses and combines them into the second frame echo :

[0017] .

[0018] The step 20) is specifically as follows:

[0019] ;

[0020] ;

[0021] In the above formula:

[0022] , N is the total number of distance units;

[0023] Detecting a target mark for each range unit of the first frame echo;

[0024] a target detection mark for each range cell of the second frame echo;

[0025] is the detection threshold.

[0026] The step 30) is specifically as follows:

[0027] ;

[0028] In the above formula:

[0029] , N is the total number of distance units;

[0030] is the detection result of the distance sampling point n of the first frame echo;

[0031] is the detection result of the distance sampling point n of the second frame echo;

[0032] It is the result of the detection results of the distance sampling point n of the two frames of echo.

[0033] The step 40) is specifically as follows:

[0034] ;

[0035] ;

[0036] In the above formula:

[0037] , N is the total number of distance units;

[0038] is the filter number where the target is located;

[0039] is the echo amplitude corresponding to the filter number where the target is located;

[0040] is the target left filter number;

[0041] is the echo amplitude corresponding to the filter number on the left side of the target;

[0042] Target right filter number;

[0043] is the echo amplitude corresponding to the filter number on the right side of the target;

[0044] is the single filter velocity scale corresponding to the first frame;

[0045] is the single filter velocity scale corresponding to the second frame.

[0046] The step 50) is specifically as follows:

[0047] ;

[0048] In the above formula:

[0049] , N is the total number of distance units;

[0050] It is the clutter removal mark, and the clutter marked as 0 is removed;

[0051] is the unambiguous velocity of the target calculated in the first frame;

[0052] is the unambiguous velocity of the target calculated in the second frame;

[0053] is the unambiguous speed difference threshold of the target in two frames;

[0054] is the clutter velocity threshold to be suppressed.

[0055] Compared with the prior art, the advantages of the present invention are:

[0056] 1) When detecting a target, the clutter filter is no longer set to a high impedance state, which reduces the target detection loss caused by high-speed targets falling into the clutter filter due to speed ambiguity.

[0057] 2) It has better suppression performance for slow clutter such as ground objects, weather, and flying birds, greatly reducing the occupation of system time resources by clutter, and meeting the needs of high-speed target detection with fast screen penetration and simultaneous multi-target detection for system time resources.

[0058] 3) It can effectively suppress far-field folded clutter. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 This is a signal flow chart of the present invention.

[0060] Figure 2 The unambiguous velocity curve of a target ranging from 0 to 1000 m / s at two repetition rates.

[0061] Figure 3Schematic diagram of far-zone folded clutter suppression based on dual-frame joint detection. DETAILED DESCRIPTION

[0062] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0063] like Figure 1 As shown, the clutter suppression method of artillery positioning radar based on double-frame joint detection of the present invention includes the following steps:

[0064] 10) Echo data reconstruction. In a coherent processing interval, the radar transmits a total of 2P (P is an integer, and P ≥ 8) pulses, and the repetition periods of the first P transmitted pulses and the last P transmitted pulses are PRT1 and PRT2 respectively (PRT1 ≠ PRT2).

[0065] The radar receives the echo signals of the first P pulses and combines them into the first frame echo :

[0066] ;

[0067] The radar receives the echo signals of the last P pulses and combines them into the second frame echo :

[0068] .

[0069] 20) Threshold reduction target detection. The two frames of data after CFAR processing are subjected to threshold reduction detection processing according to the filter distance unit, and the clutter filter is no longer set to high impedance state. Suppose the detection sequences of the first frame and the second frame are: , perform target detection, if there is a target, the detection mark is 1, otherwise it is 0. The main algorithm formula is as follows:

[0070] ;

[0071] ;

[0072] In the above formula:

[0073] , N is the total number of distance units;

[0074] Detecting a target mark for each range unit of the first frame echo;

[0075] a target detection mark for each range cell of the second frame echo;

[0076] is the detection threshold.

[0077] 30) 2-by-2 criterion joint detection. The target detection marks of the two frames of echo are ANDed according to the distance unit to obtain the marks of the two frames detecting the target in the same distance unit. If the two frames detect the target in the same distance unit, the comprehensive detection mark is set to 1, otherwise it is set to 0. The main algorithm formula is as follows:

[0078] ;

[0079] In the above formula:

[0080] , N is the total number of distance units;

[0081] is the detection result of the distance sampling point n of the first frame echo;

[0082] is the detection result of the distance sampling point n of the second frame echo;

[0083] It is the result of the detection results of the distance sampling point n of the two frames of echo.

[0084] 40) Target precision speed measurement processing. For the target marked as 1 in the figure, the unambiguous speed of the target in two frames is calculated based on the conversion relationship between the filter channel number and the speed, after amplitude weighting. The main algorithm formula is as follows:

[0085] ;

[0086] ;

[0087] In the above formula:

[0088] , N is the total number of distance units;

[0089] is the filter number where the target is located;

[0090] is the echo amplitude corresponding to the filter number where the target is located;

[0091] is the target left filter number;

[0092] is the echo amplitude corresponding to the filter number on the left side of the target;

[0093] Target right filter number;

[0094] is the echo amplitude corresponding to the filter number on the right side of the target;

[0095] is the single filter velocity scale corresponding to the first frame;

[0096] is the single filter velocity scale corresponding to the second frame.

[0097] 50) Clutter removal based on target speed. When the speed of the target in the two frames is less than the set clutter speed threshold, and the speed difference of the target in the two frames is less than the set speed difference threshold, the target is judged as clutter and the detection mark is set to 0, otherwise the detection mark is set to 1. The main algorithm formula is as follows.

[0098] ;

[0099] In the above formula:

[0100] , N is the total number of distance units;

[0101] It is the clutter removal mark, and the clutter marked as 0 is removed;

[0102] is the unambiguous velocity of the target calculated in the first frame;

[0103] is the unambiguous velocity of the target calculated in the second frame;

[0104] is the unambiguous speed difference threshold of the target in two frames;

[0105] is the clutter velocity threshold to be suppressed.

[0106] Algorithm Principle

[0107] The Doppler frequency generated by the echo signal will vary depending on the speed of the target. Therefore, targets of different speeds can be identified based on the Doppler frequency. Greater than the repetition frequency of the transmitted pulse There will be velocity ambiguity when the target is measured. The unambiguous velocity measurement range of the target depends on the pulse repetition frequency, and its corresponding velocity is , considering the target's moving direction, the unambiguous speed range is .

[0108] In the conventional single-frame detection and processing method, the radar transmits P (P is an integer, and P ≥ 8) pulses in a coherent processing interval. Assuming that the radar operates at a carrier frequency of 3.1 GHz and a pulse repetition frequency of 2000 Hz, the maximum unambiguous speeds are calculated to be ±48.4 m / s. Usually, the Doppler speed of meteorological clutter and sea clutter is below 30 m / s, while the Doppler speed of artillery targets is usually between 30 and 1000 m / s. Therefore, there is no speed ambiguity for slow clutter such as meteorology, while for high-speed artillery targets, due to the existence of speed ambiguity, they may fall into the clutter filter. During the detection process, the clutter filter is set to a high impedance state, resulting in detection loss of artillery targets in certain speed ranges.

[0109] The clutter suppression method for artillery positioning radar based on dual-frame joint detection is that within a coherent processing interval, the radar transmits a total of 2P (P is an integer, and P≥8) pulses, the repetition periods of the first P transmission pulses and the last P transmission pulses are PRT1 and PRT2 (PRT1≠PRT2), respectively, the echo signals of the first P pulses are received and combined into the first frame echo, and the echo signals of the last P pulses are received and combined into the second frame echo. Independent target detection is performed on the two frames of echo respectively, and at this time the clutter filter is no longer set to a high impedance state, avoiding the loss of detection of high-speed targets. Then, precise speed measurement processing is performed on the targets detected in the same distance unit in the two frames respectively. Since there is no speed ambiguity for slow clutter, the difference in speed measured in the two frames should theoretically be 0. For high-speed targets, due to the existence of speed ambiguity, the difference in speed measured by the two frames of echo data with different pulse repetition periods may be large. Using the characteristic that there is a large difference in the speed difference between clutter and target, the formula is used to convert Targets marked as 0 are judged as clutter and eliminated, so that slow clutter can be suppressed.

[0110] ;

[0111] In the above formula:

[0112] , N is the total number of distance units;

[0113] It is the clutter removal mark, and the clutter marked as 0 is removed;

[0114] is the unambiguous velocity of the target calculated in the first frame;

[0115] is the unambiguous velocity of the target calculated in the second frame;

[0116] is the unambiguous speed difference threshold of the target in two frames;

[0117] is the clutter velocity threshold to be suppressed.

[0118] Assuming that the radar operating carrier frequency is 3.1 GHz, the pulse repetition frequency of the first frame is 2000 Hz, the pulse repetition frequency of the second frame is 2100 Hz, and the total number of pulses per frame is 16, the maximum unambiguous speed of each frame is calculated to be ±48.4 m / s and ±50.8 m / s respectively. Figure 2 The unambiguous velocity curves, velocity difference curves and the removed low-speed clutter markers (when ), it can be seen that slow clutter below 30 m / s is marked and removed, while high-speed target detection is not lost and is retained.

[0119] like Figure 3 As shown in the figure, for far-field folded clutter, due to the different pulse repetition frequencies of the two frames, the folded clutter will appear in different distance units. In the 2-by-2 target joint detection criterion, the target is considered to be output only when the two frames detect the target in the same distance unit. Therefore, the far-field folded clutter can be eliminated.

[0120] During dual-frame joint detection, in order not to increase system time resources, the total number of pulses in one frame during conventional single-frame processing can be divided into two groups (such as 32 pulses divided into two groups of 16 pulses, and the two groups have different repetition rates). At the same time, in order to ensure the original detection power of the system, the target detection threshold value is 3 decibels lower than the detection threshold of the conventional processing method to compensate for the accumulated loss of target signal-to-noise ratio due to halving the number of pulses.

Claims

1. A clutter suppression method for artillery positioning radar based on dual-frame joint detection, characterized in that The steps include: 10) Echo data reorganization: In a coherent processing interval, the radar transmits 2P pulses in total, P is an integer, and P≥8, the repetition periods of the first P transmitted pulses and the last P transmitted pulses are PRT1 and PRT2 respectively, PRT1≠PRT2, the radar receives the echo signals of the first P pulses and combines them into the first frame echo, and receives the echo signals of the last P pulses and combines them into the second frame echo; 20) Threshold reduction target detection: The two frames of echo data are respectively subjected to threshold reduction detection processing according to the filter distance unit, and the clutter filter is no longer set to high impedance state at this time; 30) 2-by-2 criterion joint detection: perform AND operation on the target detection marks of the two frames of echoes according to the distance unit, and obtain the marks of the two frames detecting the target in the same distance unit. If the two frames detect the target in the same distance unit, set the comprehensive detection mark to 1, otherwise the mark is 0; 40) Target precision speed measurement processing: For targets with a comprehensive detection mark of 1, the unambiguous speed of the target in two frames is calculated based on the conversion relationship between the filter channel number where the target is located and the speed, after amplitude weighting; 50) Clutter removal based on target speed: When the speeds of the targets in the two frames are both less than the set clutter speed threshold, and the speed difference between the targets in the two frames is less than the set speed difference threshold, the target is judged as clutter and the detection mark is set to 0, otherwise the detection mark is set to 1.

2. The method for suppressing clutter of artillery positioning radar based on dual-frame joint detection according to claim 1 is characterized in that: The step 10) is specifically as follows: The radar receives the echo signals of the first P pulses and combines them into the first frame echo : ； The radar receives the echo signals of the last P pulses and combines them into the second frame echo : 。 3. The method for suppressing clutter of artillery positioning radar based on dual-frame joint detection according to claim 1 is characterized in that: The step 20) is specifically as follows: ； ； In the above formula: , N is the total number of distance units; Detecting a target mark for each range unit of the first frame echo; a target detection mark for each range cell of the second frame echo; is the detection threshold.

4. The method for suppressing clutter of artillery positioning radar based on dual-frame joint detection according to claim 1 is characterized in that: The step 30) is specifically as follows: ； In the above formula: , N is the total number of distance units; is the detection result of the distance sampling point n of the first frame echo; is the detection result of the distance sampling point n of the second frame echo; It is the result of the detection results of the distance sampling point n of the two frames of echo.

5. The method for suppressing clutter of artillery positioning radar based on dual-frame joint detection according to claim 1 is characterized in that: The step 40) is specifically as follows: ； ； In the above formula: , N is the total number of distance units; is the filter number where the target is located; is the echo amplitude corresponding to the filter number where the target is located; is the target left filter number; is the echo amplitude corresponding to the filter number on the left side of the target; Target right filter number; is the echo amplitude corresponding to the filter number on the right side of the target; is the single filter velocity scale corresponding to the first frame; is the single filter velocity scale corresponding to the second frame.

6. The method for suppressing clutter of artillery positioning radar based on dual-frame joint detection according to claim 1 is characterized in that: The step 50) is specifically as follows: ； In the above formula: , N is the total number of distance units; It is the clutter removal mark, and the clutter marked as 0 is removed; is the unambiguous velocity of the target calculated in the first frame; is the unambiguous velocity of the target calculated in the second frame; is the unambiguous speed difference threshold of the target in two frames; is the clutter velocity threshold to be suppressed.

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