Low-speed clutter trace point suppression method based on clutter map large-selection updating

Abstract

The invention relates to a low-speed clutter trace point suppression method based on clutter map large-selection updating, and belongs to the technical field of radar data processing. Comprising the following steps: calculating the maximum unambiguous velocity of the ground-based radar, and determining the maximum radial velocity of each Doppler channel based on the maximum unambiguous velocity; acquiring data of each Doppler channel after phase-coherent accumulation of the ground-based radar in the kth search period; performing constant false alarm detection and hidden image threshold detection on data of each Doppler channel in the kth search period in sequence; when a constant false alarm detection threshold and a hidden shadow threshold are satisfied, clutter map detection is carried out based on data of each Doppler channel in the kth search period and the clutter map in the (k-1) th search period, and when a target is detected, a trace point is reported; and updating the clutter maps of the (k-1) search periods by adopting a distance dimension extension selection mode to obtain the clutter map of the kth search period. According to the method, the slow clutter trace point is effectively suppressed, and the normal target detection capability of the ground-based radar is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of radar data processing, and in particular to a ground-based radar of a pulse Doppler system, and proposes a slow clutter point trace suppression method based on clutter map selection and updating, so as to reduce the number of slow clutter points and improve radar detection performance. Background Art

[0002] At present, with the continuous development of electronic technology and aviation technology, the types and numbers of small targets such as various low-flying drones and cruise missiles are increasing. In order to effectively deal with the threats of various low-flying small targets, ground-based radars need stronger small target detection capabilities and better low-altitude detection capabilities. However, the improvement of ground-based radar detection capabilities has led to the detection of various insects and birds flying in the air and air currents in the air by ground-based radars, which in turn generates a large number of traces. Various insects and birds flying in the air and air currents in the air are not the expected detection targets of ground-based radars, but belong to the clutter of ground-based radars. Therefore, the radar traces caused by various insects and birds flying in the air and air currents in the air are called slow clutter traces.

[0003] Due to the huge number of various insects and birds in the air and the air currents, the ground-based radar detects a large number of slow clutter traces. Too many slow-moving clutter traces can easily lead to the saturation of the number of ground-based radar traces, making it impossible to report the traces of normal targets, seriously affecting the normal operation of the ground-based radar. Even when the number of ground-based radar traces is not saturated, the presence of a large number of slow-moving clutter traces can easily lead to track association errors of normal targets, affecting the ground-based radar's tracking of normal targets; at the same time, a large number of slow-moving clutter traces will produce a large number of false tracks, seriously affecting the normal operation of the ground-based radar. Therefore, the slow clutter traces must be suppressed.

[0004] Although artificial intelligence algorithms such as machine learning or deep learning can better identify slow clutter traces and normal target traces, and then suppress slow clutter traces; however, the prerequisite is that the number of ground-based radar traces is not saturated, and slow clutter traces and normal target traces can be reported normally. Since too many slow-moving clutter traces can easily lead to the saturation of the number of ground-based radar traces, at this time, normal target traces can no longer be reported; therefore, it is necessary to suppress slow clutter traces in the target detection stage of the ground-based radar to avoid the saturation of the number of ground-based radar traces. Conventional clutter maps can only suppress fixed ground clutter, but cannot suppress slow clutter. Therefore, new methods must be studied to suppress slow clutter traces in the target detection stage. Summary of the invention

[0005] The technical problems to be solved by the present invention are:

[0006] In order to avoid the shortcomings of the prior art, the present invention provides a slow clutter point trace suppression method based on clutter map selection and updating, which is used to suppress slow clutter point traces in the target detection stage of a ground-based radar with a pulse Doppler system, thereby improving the detection capability of the ground-based radar for normal targets.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0008] A method for suppressing slow clutter traces based on clutter map selection and updating, characterized by comprising:

[0009] Obtain the working parameters of the ground-based radar with pulse Doppler system, including the working carrier frequency, search period, pulse repetition interval, the number of signal sampling points within the pulse repetition interval, the number of pulses within a coherent accumulation period and the signal sampling rate;

[0010] The maximum unambiguous velocity of the ground-based radar is calculated according to the operating carrier frequency, the pulse repetition interval and the speed of light, and the maximum radial velocity of each Doppler channel is determined based on the maximum unambiguous velocity;

[0011] Obtain the data of each Doppler channel after coherent accumulation of the ground-based radar in the kth search cycle;

[0012] The data of each Doppler channel in the k-th search cycle are sequentially subjected to constant false alarm detection and shadow threshold detection; when the constant false alarm detection threshold and shadow threshold are met, clutter map detection is performed based on the data of each Doppler channel in the k-th search cycle and the clutter map of the k-1-th search cycle, and a point trace is reported when a target is detected;

[0013] The clutter map of the k-1 search period is updated by using the distance dimension expansion and selection method to obtain the clutter map of the k-th search period. The updated clutter map of the k-th search period is used for clutter map detection of the k+1-th search period.

[0014] A further technical solution of the present invention is as follows: the maximum unambiguous speed of the ground-based radar is calculated based on the carrier frequency, pulse repetition interval and speed of light, using the following formula:

[0015] V max =c / (2f0T r )

[0016] Where f0 is the carrier frequency, T r is the pulse repetition interval and c is the speed of light.

[0017] A further technical solution of the present invention is as follows: the step of determining the maximum radial velocity of each Doppler channel based on the maximum unambiguous velocity comprises:

[0018] When m≤N p / 2, Vm =(m-0.5)V max / N p ;

[0019] When m>N p / 2, V m =(mN p -1.5)V max / N p ;

[0020] Where m = 1, 2, ..., N p , N p Represents N after coherent accumulation p Doppler channels, n = 1, 2, ..., N s N s sampling points, V m is the maximum radial velocity.

[0021] A further technical solution of the present invention: the data of each Doppler channel includes:

[0022] When the local radar adopts linear detection, the data of each Doppler channel is N p The linear detection value of each Doppler channel; when the local radar adopts square law detection, the data of each Doppler channel is N p The square-law detection value of a Doppler channel.

[0023] A further technical solution of the present invention is as follows: the clutter map detection based on the data of each Doppler channel in the kth search period and the clutter map in the k-1th search period comprises:

[0024] When the data S of each Doppler channel in the kth search cycle k (m,n)≥C e M k-1 (m,n), m=1,2,…,N p ,n=1,2,…,N s When , the target is considered to be detected and the trace is reported; among them, C e is the threshold coefficient for clutter image detection, M k-1 (m,n) is the clutter map of the k-1th search cycle.

[0025] A further technical solution of the present invention is as follows: the clutter map of k-1 search periods is updated by adopting a distance dimension expansion and selection method to obtain the clutter map of the kth search period, comprising:

[0026] The number of expansion points of the distance dimension of each channel is determined based on the maximum radial velocity of each Doppler channel and the maximum radial velocity of the slow clutter point trace;

[0027] Determine the range dimension expansion selection result based on the data of each Doppler channel and the number of expansion points of the range dimension;

[0028] The clutter map is updated based on the distance dimension expansion and selection result and the clutter map of the k-1th search period to obtain the clutter map of the kth search period.

[0029] A further technical solution of the present invention is as follows: the number of expansion points of each channel distance dimension is determined based on the maximum radial velocity of each Doppler channel and the maximum radial velocity of the slow clutter point trace, including:

[0030] When |V m |≤V c When the distance dimension is extended, the number of points R m =ceil[4|V m |T s f s / c],m=1,2,…,N p , when |V m |>V c When the distance dimension is extended, the number of points R m =0, m=1,2,…,N p ; where |·| represents the modulus value, ceil[·] represents rounding up, and V c is the maximum radial velocity of the slow clutter point, f s is the signal sampling rate.

[0031] A further technical solution of the present invention is as follows: the maximum radial velocity of the slow clutter point trace cannot exceed the minimum detectable velocity of the ground-based radar.

[0032] A further technical solution of the present invention is as follows: the distance dimension expansion selection result is determined based on the data of each Doppler channel and the number of expansion points of the distance dimension, using the following formula:

[0033]

[0034] Among them, max[·] means taking the maximum value, and min[·] means taking the minimum value.

[0035] A further technical solution of the present invention is that the clutter map is updated based on the distance dimension expansion and selection result and the clutter map of the k-1th search period to obtain the clutter map of the kth search period, using the following formula:

[0036] Among them, a is the clutter map iteration coefficient, M k-1 (m,n) is the clutter map of the k-1th search cycle, M k (m,n) is the clutter map of the kth search cycle.

[0037] The beneficial effects of the present invention are:

[0038] The invention provides a method for suppressing slow clutter traces based on clutter map selection and updating. For a ground-based radar of a pulse Doppler system, the clutter map is updated in a distance dimension expansion and selection manner according to the speed of each Doppler channel, so that the clutter map established by the slow clutter itself suppresses itself, thereby effectively suppressing the slow clutter traces and improving the detection capability of the ground-based radar for normal targets. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0040] Figure 1 The present invention is a flow chart for realizing the method for suppressing slow clutter traces based on the clutter map selection and updating. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0042] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchangeable where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0043] In the description of the present invention, it is necessary to understand that the terms "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship are based on the orientation or position relationship shown in the drawings, and are 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 cannot be understood as a limitation on the present invention.

[0044] In order to enable those skilled in the art to better understand the present invention, the present invention is described in detail below in conjunction with specific embodiments.

[0045] Example 1

[0046] The present invention provides a method for suppressing slow clutter traces based on clutter map selection and updating, such as Figure 1 As shown, the following steps are included:

[0047] Step 1: Given a ground-based radar with a pulse Doppler system, obtain the radar's operating carrier frequency f0 and search period T s , pulse repetition interval T r , the number of signal sampling points N within the pulse repetition interval s , the number of pulses in a coherent integration cycle N p and signal sampling rate f s .

[0048] Among them, the carrier frequency f0 and the signal sampling rate f s The unit is Hertz, the search period is T s and the pulse repetition interval T r The unit is seconds.

[0049] Step 2: The ground-based radar searches for a period of time T. s The detection of the entire mission airspace is completed through multiple scans within the ground-based radar; the processing process of each scan of the ground-based radar is the same, and the first scan is taken as an example here to illustrate; M0(m,n) is the clutter map at the initial moment of the first scan, and M0(m,n)=0, where m=1,2,…,N p Represents N after coherent accumulation p Doppler channels, n = 1, 2, ..., N s N s sampling points; denoted by M k (m,n) is the clutter map of the kth search cycle in the first scan.

[0050] N in a coherent integration cycle p After coherent integration, the pulses are converted into N p Doppler channel data.

[0051] Step 3: Based on the carrier frequency f0 and pulse repetition interval T r The maximum unambiguous velocity V of the ground-based radar is calculated by the speed of light c max =c / (2f0T r ), and then get N p The maximum radial velocity V of each Doppler channel m ,m=1,2,…,N p , when m≤N p / 2, Vm =(m-0.5)V max / N p , when m>N p / 2, V m =(mN p -1.5)V max / N p .

[0052] The speed of light c is equal to 3×10 8 m / s, maximum unambiguous speed V max and N p The maximum radial velocity V of the Doppler channel m The unit is meter / second.

[0053] Step 4: Set the maximum radial velocity of the slow clutter point to V c .

[0054] Among them, the maximum radial velocity V of the slow clutter point is c The unit is meter per second; its value cannot exceed the minimum detectable speed of the ground-based radar. It is generally set based on experience, and its value can be adjusted according to the number of slow clutter points.

[0055] Step 5: In the kth search cycle, record the coherent accumulation of the echo signals of the ground-based radar and the beam N p The data of the Doppler channel is S k (m,n), m=1,2,…,N p ,n=1,2,…,N s .

[0056] When the local radar adopts linear detection, S k (m,n) is N p The linear detection value of a Doppler channel; when the local radar adopts square law detection, S k (m,n) is N p The square-law detection value of a Doppler channel.

[0057] Step 6, for N p The data of the Doppler channel S k (m,n), m=1,2,…,N p ,n=1,2,…,N s First, perform constant false alarm detection and blanking threshold detection. When S k When (m,n) exceeds the constant false alarm detection threshold and the blanking threshold, the clutter map detection is performed again. Only S k (m,n)≥C e M k-1 (m,n), m=1,2,…,N p,n=1,2,…,N s When , the target is considered to be detected and the trace is reported; among them, C e is the threshold coefficient of clutter image detection, M k-1 (m,n) is the clutter map of the k-1th search cycle.

[0058] Step 7: Update the clutter map by expanding the distance dimension.

[0059] Step 7 specifically includes the following sub-steps:

[0060] (7a) According to N p The maximum radial velocity V of each Doppler channel m ,m=1,2,…,N p , the maximum radial velocity of the slow clutter point is V c , search period T s , speed of light c and signal sampling rate f s Calculate the number of expansion points R of each channel distance dimension m ,m=1,2,…,N p ; When |V m |≤V c When the distance dimension is extended, the number of points R m =ceil[4|V m |T s f s / c],m=1,2,…,N p , where |·| represents the modulus value, and ceil[·] represents rounding up; when |V m |>V c When the distance dimension is extended, the number of points R m =0,m=1,2,…,N p ;

[0061] (7b) According to N p The data of the Doppler channel S k (m,n), m=1,2,…,N p ,n=1,2,…,N s And the number of expansion points R of the distance dimension m ,m=1,2,…,N p , and get the result after the distance dimension is expanded and selected Calculate according to the following formula:

[0062]

[0063] Among them, max[·] means taking the maximum value, and min[·] means taking the minimum value;

[0064] (7c) The result after expanding the distance dimension and the clutter map M of the k-1th search cycle k-1 (m,n), m=1,2,…,N p ,n=1,2,…,N s , update the clutter map to obtain the clutter map of the kth search cycle Among them, a is the clutter map iteration coefficient, which is generally taken as 0.125.

[0065] Step 8, let k=k+1, and repeat steps 5 to 7 until the ground-based radar operation is completed.

[0066] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should be included in the protection scope of the present invention.

Claims

1. A method for suppressing slow clutter traces based on clutter map selection and updating, characterized in that: include: Obtain the working parameters of the ground-based radar with pulse Doppler system, including the working carrier frequency, search period, pulse repetition interval, the number of signal sampling points within the pulse repetition interval, the number of pulses within a coherent accumulation period and the signal sampling rate; The maximum unambiguous velocity of the ground-based radar is calculated according to the operating carrier frequency, the pulse repetition interval and the speed of light, and the maximum radial velocity of each Doppler channel is determined based on the maximum unambiguous velocity; Obtain the data of each Doppler channel after coherent accumulation of the ground-based radar in the kth search cycle; The data of each Doppler channel in the k-th search cycle are sequentially subjected to constant false alarm detection and shadow threshold detection; when the constant false alarm detection threshold and shadow threshold are met, clutter map detection is performed based on the data of each Doppler channel in the k-th search cycle and the clutter map of the k-1-th search cycle, and a point trace is reported when a target is detected; The clutter map of the k-1 search period is updated by using the distance dimension expansion and selection method to obtain the clutter map of the k-th search period. The updated clutter map of the k-th search period is used for clutter map detection of the k+1-th search period.

2. According to claim 1, a method for suppressing slow clutter traces based on clutter map selection and updating is characterized in that: The maximum unambiguous velocity of the ground-based radar is calculated based on the carrier frequency, pulse repetition interval and speed of light, using the following formula: V max =c / (2f0T r ) Where f0 is the carrier frequency, T r is the pulse repetition interval and c is the speed of light.

3. According to claim 2, a method for suppressing slow clutter traces based on clutter map selection and updating is characterized in that: The determining of the respective maximum radial velocity of each Doppler channel based on the maximum unambiguous velocity comprises: When m≤N p / 2, V m =(m-0.5)V max / N p ; When m>N p / 2, V m =(mN p -1.5)V max / N p ; Where m = 1, 2, ..., N p , N p Represents N after coherent accumulation p Doppler channels, n = 1, 2, ..., N s N s sampling points, V m is the maximum radial velocity.

4. According to claim 3, a method for suppressing slow clutter traces based on clutter map selection and updating is characterized in that: The data of each Doppler channel includes: When the local radar adopts linear detection, the data of each Doppler channel is N p The linear detection value of each Doppler channel; when the local radar adopts square law detection, the data of each Doppler channel is N p The square-law detection value of a Doppler channel.

5. According to claim 4, a method for suppressing slow clutter traces based on clutter map selection and updating is characterized in that: The clutter map detection is performed based on the data of each Doppler channel in the kth search period and the clutter map in the k-1th search period, including: When the data S of each Doppler channel in the kth search cycle k (m,n)≥C e M k-1 (m,n), m=1,2,…,N p ,n=1,2,…,N s When , the target is considered to be detected and the trace is reported; among them, C e is the threshold coefficient for clutter image detection, M k-1 (m,n) is the clutter map of the k-1th search cycle.

6. According to claim 1, a method for suppressing slow clutter traces based on clutter map selection and updating is characterized in that: The method of updating the clutter map of k-1 search periods by expanding the distance dimension to obtain the clutter map of the kth search period includes: The number of expansion points of the distance dimension of each channel is determined based on the maximum radial velocity of each Doppler channel and the maximum radial velocity of the slow clutter point trace; Determine the range dimension expansion selection result based on the data of each Doppler channel and the number of expansion points of the range dimension; The clutter map is updated based on the distance dimension expansion and selection result and the clutter map of the k-1th search period to obtain the clutter map of the kth search period.

7. According to claim 6, a method for suppressing slow clutter traces based on clutter map selection and updating is characterized in that: The method of determining the number of expansion points of the distance dimension of each channel based on the maximum radial velocity of each Doppler channel and the maximum radial velocity of the slow clutter point trace includes: When |V m |≤V c When the distance dimension is extended, the number of points R m =ceil[4|V m |T s f s / c],m=1,2,…,N p , when |V m |>V c When the distance dimension is extended, the number of points R m =0, m=1,2,…,N p ; where |·| represents the modulus value, ceil[·] represents rounding up, and V c is the maximum radial velocity of the slow clutter point, f s is the signal sampling rate.

8. According to claim 7, a method for suppressing slow clutter traces based on clutter map selection and updating is characterized in that: The maximum radial velocity of the slow clutter point trace cannot exceed the minimum detectable velocity of the ground-based radar.

9. According to claim 7, a method for suppressing slow clutter traces based on clutter map selection and updating is characterized in that: The distance dimension expansion selection result is determined based on the data of each Doppler channel and the number of expansion points of the distance dimension, using the following formula: Among them, max[·] means taking the maximum value, and min[·] means taking the minimum value.

10. The method for suppressing slow clutter traces based on clutter map selection and updating according to claim 9, characterized in that: The clutter map is updated based on the distance dimension expansion result and the clutter map of the k-1th search period to obtain the clutter map of the kth search period, using the following formula: Among them, a is the clutter map iteration coefficient, M k-1 (m,n) is the clutter map of the k-1th search cycle, M k (m,n) is the clutter map of the kth search cycle.

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