A method for suppressing false alarms of tracks of low, small and slow target detection radars

Abstract

The present invention relates to a method for suppressing false alarms of tracks of low, small and slow target detection radars. In a data processor, tracks are established for all the traces reported by signal processors, and judgments are made by comparing the radial velocity of the traces and the track velocity. When the radial velocity of the trace is greater than a certain threshold of the track velocity, it is determined that the current track is clutter and is deleted; otherwise, it is determined as a track of a real target and reported to the radar terminal for display. In the same environment, by adopting this method, false alarms of the tracks displayed on the radar terminal can be effectively suppressed, meeting the user's usage requirements.

Description

Technical Field

[0001] The present invention belongs to the technical field of radar, and particularly relates to a method for suppressing false alarms of tracks of a radar for detecting low, small and slow targets. Background Art

[0002] The radar for detecting "low, small and slow" targets is essentially a moving target detection radar, which requires that the Doppler frequency of background interference clutter is different from that of the target to be detected. The frequency filtering method can filter out the background interference clutter, so that the radar can detect the target signal dots from the clutter background and thus form a target track.

[0003] However, in the actual environment, the Doppler frequencies of interfering clutter such as swaying shrubs or leaves are often the same as or very close to the Doppler frequency of the "low, small and slow" target to be detected, resulting in difficulty in filtering out these background interference clutter by the frequency filtering method. These clutter often form a large number of false tracks, causing difficulties in the use of the radar for customers.

[0004] Generally, the processing method for such problems is that the radar adopts a refined frequency filtering method to suppress these clutter so that these clutter do not form dots as much as possible. However, in complex environment cases, it is very difficult to process these clutter suppression. Summary of the Invention

[0005] The technical problem solved by the present invention is to provide a suppression method for false tracks formed by clutter interference with a Doppler frequency close to that of the target for a radar for detecting "low, small and slow" targets.

[0006] The technical solution of the present invention is: A method for suppressing false alarms of tracks of a radar for detecting "low, small and slow" targets, comprising the following steps:

[0007] Step 1: When the radar is powered on and the antenna makes a 360-degree circumferential scanning movement, and the target H is searched continuously twice, the radar data processor calculates the temporary track of the target H.

[0008] Step 2: When the radar searches for the target again, if the target H is not searched, the temporary track of the target H is deleted, and return to Step 1; if the target H is searched, the radar signal processor calculates the primary dot information of the target H according to the received echo, and calculates the dot radial velocity as V D , and calculates the reliable track of the target H according to the dot information and the temporary track information of the target H, and records the track velocity as V H ;

[0009] Step 3: The radar data processor calculates the difference between V D and V H , and when (V D - V H ) > V 阀值When it is determined that target H is a clutter false target, the radar data processor deletes the reliable track of target H. Conversely, when it is determined that target H is a real target, the radar data processor reports the reliable track of target H to the radar terminal for display.

[0010] A further technical solution of the present invention is that in step 1, the component ZVx of the temporarily tracked speed filtering value in the X-axis direction of the rectangular coordinate system, the component ZVy of the temporarily tracked speed filtering value in the Y-axis direction of the rectangular coordinate system, the component Ex of the temporarily tracked position filtering value in the X-axis direction of the rectangular coordinate system, and the component Ey of the temporarily tracked position filtering value in the Y-axis direction of the rectangular coordinate system are defined. The calculation formulas for each parameter are as follows:

[0011] ZVx = (R2 * sin(B2) - R1 * sin(B1)) / Pt;

[0012] ZVy = (R2 * cos(B2) - R1 * cos(B1)) / Pt;

[0013] Ex = (R1 * sin(B1) + ZVx * Pt) * (1.0 - Ka) + R2 * sin(B2) * Ka;

[0014] Ey = (R1 * cos(B1) + ZVy * Pt) * (1.0 - Ka) + R2 * cos(B2) * Ka;

[0015] R1: The distance value of the first echo point of target H detected by the radar for the first time

[0016] B1: The azimuth value of the first echo point of target H detected by the radar for the first time

[0017] R2: The distance value of the first echo point of target H detected by the radar for the second time

[0018] B2: The azimuth value of the first echo point of target H detected by the radar for the second time

[0019] Ka: Filtering coefficient (0.5)

[0020] Pt: Radar search period.

[0021] A further technical solution of the present invention is that in step 2, the radial velocity of the echo point is V D , and the calculation formula is as follows:

[0022] V D = fd × λ ÷ 2

[0023] Wherein, fd: Doppler frequency of target H relative to the radar detected by the radar again

[0024] λ: Radar emission wavelength.

[0025] A further technical solution of the present invention is that in the step 2, the track speed is V H ;

[0026]

[0027] where ZVx: the component of the temporary track speed filtering value in the X-axis direction of the rectangular coordinate system

[0028] ZVy: the component of the temporary track speed filtering value in the Y-axis direction of the rectangular coordinate system

[0029] Ex: the component of the temporary track position filtering value in the X-axis direction of the rectangular coordinate system

[0030] Ey: the component of the temporary track position filtering value in the Y-axis direction of the rectangular coordinate system

[0031] R: the distance value of the first echo point of the target H detected again by the radar

[0032] B: the azimuth value of the first echo point of the target H detected again by the radar

[0033] Kb: the filtering coefficient (0.33)

[0034] Pt: the radar search period.

[0035] Advantages of the Invention

[0036] The technical effect of the present invention is that the present invention provides a method for suppressing the track false alarm of a low, small and slow target detection radar. In the prior art, the radar solves the track false alarm by detecting the radial velocity difference between the target and the false alarm through a signal processing algorithm to eliminate the detected false alarm first echo points. The false alarm track is generated by the false alarm first echo points. If the number of false alarm first echo points is reduced, the false alarm track will naturally be reduced. However, it is sometimes difficult to eliminate the detected false alarm first echo points in the actual environment.

[0037] In the real environment, even if the false alarm first echo points are detected, this method performs track processing on all the first echo points of the targets (real targets and false alarms) through a data processing algorithm. Before reporting the track, by comparing the target radial velocity and the track speed, it is confirmed whether the target track is a false alarm track. If it is, it is discarded; if not, it is reported.

[0038] Therefore, compared with the prior art, the previous radar reduced false alarms by reducing the false alarm first echo points through a signal processor, while the present invention reduces false alarms by reducing the false alarm tracks through a data processor.

[0039] In summary, in the same environment, by adopting this method, the track false alarm displayed by the radar terminal can be effectively suppressed, meeting the user's usage requirements. Brief Description of the Drawings

[0040] Figure 1 This is the flow chart of the method

[0041] Figure 2 This is the mathematical principle diagram of the method

[0042] Figure 3 These are the actual effect diagrams, where (a) is the effect diagram before adopting this method, and (b) is the effect diagram after adopting this method Specific implementation manners

[0043] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention

[0044] Refer to Figures 1 - 3 , the core idea of the present invention is: in the data processor, establish a track for all the traces reported by the signal processors, and make a judgment by comparing the radial velocity of the trace (also called Doppler velocity, calculated from the Doppler frequency) and the track velocity. When the radial velocity of the trace is greater than a certain threshold of the track velocity, it is determined that the current track is clutter and is deleted. Otherwise, it is determined as the track of a real target and reported to the radar terminal for display. The determination principle is shown in the attached drawings

[0045] The mathematical principle of the present invention is as shown in the attached drawings. The track velocity VH of a moving target can be decomposed into the radial velocity VD (trace Doppler velocity) relative to the radar and the tangential velocity VQ. According to the principle diagram, when the target moves along the radar radial direction, VD = VH; when the target moves in other directions, VD < VH. Therefore, mathematically, it can be considered that the targets with VD > VH are all false targets (for example, for interfering clutter such as shaking shrubs or leaves, they are all shaking in place, and their VH = 0, while the Doppler velocity VD > 0)

[0046] Considering that there is a certain error in the radar signal processor when calculating VD, when the target moves along the radar radial direction, VD may be slightly greater than VH. If only the targets with VD > VH are judged as false targets, it is possible to eliminate the real targets moving along the radar radial direction as false targets. Therefore, in the actual application of the present invention, a threshold needs to be set to eliminate this error. Generally, the error in the radar signal processor when calculating VD will not be greater than a Doppler resolution velocity. Therefore, the V threshold is set to a Doppler resolution velocity

[0047] The specific steps of this method are as follows:

[0048] Step 1: When the radar is turned on and the antenna makes a 360-degree circular scanning motion, when the target H is detected continuously twice, the radar data processor calculates the temporary track of the target H, and calculates the component ZVx of the filtered value of the temporary track speed in the X-axis direction of the rectangular coordinate system, the component ZVy of the filtered value of the temporary track speed in the Y-axis direction of the rectangular coordinate system, the component Ex of the filtered value of the temporary track position in the X-axis direction of the rectangular coordinate system, and the component Ey of the filtered value of the temporary track position in the Y-axis direction of the rectangular coordinate system. The calculation formulas for each parameter are as follows:

[0049] ZVx = (R2 * sin(B2) - R1 * sin(B1)) / Pt; (1)

[0050] ZVy = (R2 * cos(B2) - R1 * cos(B1)) / Pt; (2)

[0051] Ex = (R1 * sin(B1) + ZVx * Pt) * (1.0 - Ka) + R2 * sin(B2) * Ka; (3)

[0052] Ey = (R1 * cos(B1) + ZVy * Pt) * (1.0 - Ka) + R2 * cos(B2) * Ka; (4)

[0053] R1: The distance value of the first echo point of the target H detected by the radar for the first time

[0054] B1: The azimuth value of the first echo point of the target H detected by the radar for the first time

[0055] R2: The distance value of the first echo point of the target H detected by the radar for the second time

[0056] B2: The azimuth value of the first echo point of the target H detected by the radar for the second time

[0057] Ka: Filtering coefficient (0.5)

[0058] Pt: Radar search period

[0059] Step 2: Then the radar searches for the target again. When the target H is not detected, the temporary track of the target H is deleted, and step 1 is returned; when the target H is detected, the radar signal processor calculates the first echo point information of the target H according to the received echo, and calculates the radial velocity of the echo point as VD. The calculation formula is as follows:

[0060] V D = fd × λ ÷ 2 (5)

[0061] fd: Doppler frequency of the target H relative to the radar detected by the radar again

[0062] λ: Radar emission wavelength

[0063] Based on the primary echo information and the temporary track information of target H, calculate the reliable track of target H, and calculate the track speed as VH;

[0064]

[0065] ZVx: Component of the filtered value of the temporary track speed in the X-axis direction of the rectangular coordinate system

[0066] ZVy: Component of the filtered value of the temporary track speed in the Y-axis direction of the rectangular coordinate system

[0067] Ex: Component of the filtered value of the temporary track position in the X-axis direction of the rectangular coordinate system

[0068] Ey: Component of the filtered value of the temporary track position in the Y-axis direction of the rectangular coordinate system

[0069] R: Distance value of the primary echo of target H detected again by the radar

[0070] B: Azimuth value of the primary echo of target H detected again by the radar

[0071] Kb: Filter coefficient (0.33)

[0072] Pt: Radar search period

[0073] Step 3: Before reporting the track, the radar data processor calculates the difference between VD and VH. When (VD - VH) > V threshold (a Doppler resolution speed), it is determined that target H is a clutter false target, and the radar data processor deletes the reliable track of target H. Otherwise, it is determined that target H is a real target, and the radar data processor reports the reliable track of target H to the radar terminal for display.

[0074] The following lists a specific example to further explain the technical solution of the present invention:

[0075] Radar parameters: Search period Pt = 3 s, emission wavelength 3 cm, speed resolution 0.9 m / s;

[0076] The radar is powered on and searches at a speed of 3 seconds per circle. Target H is detected in two consecutive circles. For the target H detected in the first circle, R1 is 1380 m and B1 is 30 degrees. For the target H detected in the second circle, R2 is 1410 m and B2 is 30.5 degrees. Calculate ZVx, ZVy, Ex, and Ey of target H according to Formulas 1 - 4;

[0077] ZVx = (1410 * sin(30.5) - 1380 * sin(30)) / 3 = 8.543 m / s;

[0078] ZVy = (1410 * cos(30.5) - 1380 * cos(30)) / 3 = 6.594 m / s;

[0079] Ex = (1380 * sin(30) + 8.543 * 3) * (1 - 0.5) + 1410 * sin(30.5) * 0.5 = 715.6 m;

[0080] Ey = (1380 * cos(30) + 6.594 * 3) * (1 - 0.5) + 1410 * cos(30.5) * 0.5 = 1214.9 m;

[0081] The Doppler frequency fd of target H detected by the radar in the third circle is 660 Hz, R3 is 1440 m, B3 is 31 degrees. Calculate VD and VH of target H according to Formulas 5 and 6;

[0082] VD = 660 * 0.03 / 2 = 9.9 m / s;

[0083] VH = √((8.543 * (1 - 0.33) + 0.33 * (1440 * sin(31) - 715.6) / 3)² + (6.594 * (1 - 0.33) + 0.33 * (1440 * cos(31) - 1214.9) / 3)²)

[0084] = 10.8 m / s;

[0085] Compare VD and VH. VD of target H is less than VH, determine that target H is a real target, and the radar data processor reports the reliable track of target H to the radar terminal for display.

[0086] The radar continues to search and detects target H1 in two consecutive circles. R1 of target H1 detected in the first circle is 580 m, B1 is 10 degrees, R2 of target H1 detected in the second circle is 590 m, B2 is 9.5 degrees. Calculate ZVx, ZVy, Ex, and Ey of target H1 according to Formulas 1 - 4;

[0087] ZVx = (590 * sin(9.5) - 580 * sin(10)) / 3 = -1.1126 m / s;

[0088] ZVy = (590 * cos(9.5) - 580 * cos(10)) / 3 = 3.5733 m / s;

[0089] Ex = (580 * sin(10) - 1.1126 * 3) * (1 - 0.5) + 590 * sin(9.5) * 0.5 = 97.4 m;

[0090] Ey = (580 * cos(10) + 3.5733 * 3) * (1 - 0.5) + 590 * cos(9.5) * 0.5 = 581.9 m;

[0091] The Doppler frequency fd of target H1 detected in the third circle of the radar is 660 Hz, R3 is 580 m, and B3 is 9.5 degrees. Calculate VD and VH of target H1 according to Formulas 5 and 6.

[0092] VD = 660 * 0.03 / 2 = 9.9 m / s;

[0093] VH = √((-1.1126 * (1 - 0.33) + 0.33 * (580 * sin(9.5) - 97.4) / 3)² + (3.5733 * (1 - 0.33) + 0.33 * (580 * cos(9.5) - 581.9) / 3)²)

[0094] = 1.6 m / s;

[0095] Compare VD and VH. For target H1, (VD - VH) = 8.3 m / s, which is greater than the velocity resolution of 0.9 m / s. Determine that target H1 is a clutter false target, and the radar data processor deletes the reliable track of target H1.

[0096] Through the analysis of targets H and H1, the present invention can effectively suppress track false alarms.

[0097] Effect comparison is as Figure 3 shown below:

[0098] Using a set of data, after software processing without the present invention, the effect is as shown in the left figure. There are three targets in the figure. Among them, the two UAV targets are within the yellow circle, the track false alarm is within the blue circle, and the white dots are the target traces detected by the radar. After software processing of this set of data using the present invention, the effect is as shown in the right figure. There are only two targets in the figure. Among them, the two UAV targets are within the yellow circle, and the track false alarm within the blue circle is not reported. By comparing the two figures, the track false alarms displayed by the radar terminal can be effectively suppressed.

Claims

1. A method for suppressing false alarms of tracks of low, small and slow target detection radar, characterized in that, It includes the following steps: Step 1: Turn on the radar. When the antenna makes a 360-degree circular scanning motion and the target H is detected continuously twice, the radar data processor calculates the temporary track of the target H. Define the component ZVx of the temporary track speed filtering value in the X-axis direction of the rectangular coordinate system, the component ZVy of the temporary track speed filtering value in the Y-axis direction of the rectangular coordinate system, the component Ex of the temporary track position filtering value in the X-axis direction of the rectangular coordinate system, and the component Ey of the temporary track position filtering value in the Y-axis direction of the rectangular coordinate system. The calculation formulas for each parameter are as follows: R1: The distance value of the first echo point of the target H detected by the radar for the first time; B1: The azimuth value of the first echo point of the target H detected by the radar for the first time; R2: The distance value of the first echo point of the target H detected by the radar for the second time; B2: The azimuth value of the first echo point of the target H detected by the radar for the second time; Ka: Filtering coefficient; Pt: Radar search period; Step 2: The radar searches for the target again. When the target H cannot be found, the temporary track of the target H is deleted, and Step 1 is returned; when the target H is found, the radar signal processor calculates the primary point track information of the target H based on the received echo, calculates the point track radial velocity as VD, calculates the reliable track of the target H based on the point track information and the temporary track information of the target H, and records the track velocity as V H ; The track velocity V H is: Among them, ZVx: The component of the temporary track speed filtering value in the X-axis direction of the rectangular coordinate system; ZVy: The component of the temporary track speed filtering value in the Y-axis direction of the rectangular coordinate system; Ex: The component of the temporary track position filtering value in the X-axis direction of the rectangular coordinate system; Ey: The component of the temporary track position filtering value in the Y-axis direction of the rectangular coordinate system; R: The distance value of the first echo point of the target H detected by the radar again; B: The azimuth value of the first echo point of the target H detected by the radar again; Kb: Filtering coefficient; Pt: Radar search period; Step 3: The radar data processor calculates the difference between VD and V H . When (VD - V H ) > V threshold, it is determined that target H is a clutter false target, and the radar data processor deletes the reliable track of target H. Otherwise, it is determined that target H is a real target, and the radar data processor reports the reliable track of target H to the radar terminal for display.

2. The method for suppressing false alarms of tracks of low, small and slow target detection radar according to claim 1, characterized in that, In the said Step 2, the radial velocity of the echo point is VD, and the calculation formula is as follows: VD = fd × λ ÷ 2 Among them, fd: The Doppler frequency of the target H detected by the radar again relative to the radar; λ: Radar emission wavelength.

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