Background
Electronic countermeasure is an important combat means for attack and defense in modern war, and radar signal sorting is to sort radar radiation signals with unknown parameters under a complex electromagnetic environment, and is an important component of an electronic countermeasure system.
Modern radars have developed in the direction of multifunctional and multipurpose new systems and new technologies, one radar may have multiple working states and multiple systems, and various complex waveforms are often designed, so that regularity of signal sorting and identification is destroyed, a radar reconnaissance system is greatly challenged, the number of various electronic countermeasure equipment is increased, the radar reconnaissance system is in a complex and intensive electromagnetic signal environment, complexity and operation of signal processing are mainly concentrated on signal sorting, and the level of signal sorting is an important index for measuring the advancement of electronic countermeasure equipment.
For a complex electromagnetic environment, radar radiation source signals are often overlapped in a time domain, a space domain and a frequency domain, the traditional radar signal sorting method has serious batch increasing and batch missing phenomena, the high density of the signal environment also causes the traditional sorting processing to have large calculation amount, and the phenomena can cause the failure of signal sorting, so that a new signal sorting method needs to be explored urgently. The invention adopts the method of positioning first and then pre-sorting, reduces the operation amount of subsequent signal sorting processing, and can achieve the purpose of correctly sorting signals.
Disclosure of Invention
The invention aims to: in view of the above problems, a method is provided which can improve the accuracy of sorting with a small amount of calculation.
The invention provides a signal pre-sorting method based on self-adaptive two-dimensional clustering, which comprises the following steps:
1) two-dimensionally positioning a target by using an antenna array to obtain a distance and direction (R, theta) information sequence;
2) setting initial values of threshold values (delta R, delta theta) of distance and azimuth;
3) calculating the similarity (d) between the target distance dimension and the orientation dimensionR,dθ);
4) According to the calculated similarity and the threshold value, two-dimensional clustering of the distance and the direction is obtained;
5) self-adaptively adjusting the threshold values of the distance and the orientation, and counting the similarity mean value of the distance dimension and the orientation dimension after clustering
And when the average value is smaller than the threshold value of the distance or the direction, finishing signal pre-sorting.
The method comprises the following steps: the two-dimensional positioning of the array antenna on the target specifically comprises the following steps: by using a large-caliber sparse array, when R is less than or equal to 2D2The target processing array near field area at lambda is used for simultaneously obtaining target distance and azimuth information based on the array spherical wave model, wherein R is the target distance, D is the array caliber, and lambda is the target wavelength; positioning is firstly carried out on unsorted signals of the broadband radar, scanning is carried out on different distances R and azimuth angles theta, and a space spectrum is calculated for each stepping frequency point k:
wherein N is a covariance matrix of the noise,
the array flow vector under different frequency points is obtained, and the space spectrum of the broadband radar signal is as follows:
in the above formula, K is the number of the stepping frequency points; and searching a peak value of the radar signal space spectrum, wherein the scanning distance and the direction corresponding to the peak value are the distance and direction information of the target.
In the step 2), initial values of distance and orientation thresholds are set according to the precision of the sparse array for target distance measurement and direction finding.
More specifically, in step 3), the similarity between the distance dimension and the orientation dimension is calculated by using the euclidean distance:
wherein d is
REuclidean distance in the distance dimension, M is the number of pulse sequences, R
refTaking the distance measured for the first time as a reference distance;
wherein d is
θEuclidean distance, θ, in the azimuthal dimension
refFor the reference orientation, the first measured orientation is typically taken as the reference orientation.
More specifically, in the step 4), when the pulse sequence satisfies d at the same time in the distance dimension and the azimuth dimensionRΔ R and d ≤θWhen the pulse sequence is less than or equal to delta theta, the pulse sequences are grouped into one class, otherwise, a new class is reconstructed, and the like is performed until all the pulse sequences complete two-dimensional clustering.
More specifically, in the step 5), an average value of the pulse sequence distance and the azimuth dimension similarity is calculated by using the following formula:
while at the same timeSatisfy the requirement of
And
and (3) adjusting the threshold values of the distance and the direction, and repeating the steps 3), 4) and 5) until the threshold values do not need to be adjusted again, and finishing signal pre-sorting.
The method has the advantages that the method of positioning firstly and then pre-sorting is adopted, the limitation of traditional radar signal sorting is broken through, the phenomena of increasing batches and missing batches which are increasingly serious in signal sorting are effectively solved by utilizing two-dimensional clustering processing of distance and direction, and the effectiveness of radar signal sorting is improved.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings. All other methods, which can be obtained by a person skilled in the art without any inventive step based on the method of the present invention, are within the scope of the present invention.
Fig. 1 is a flowchart of a signal pre-sorting method based on adaptive two-dimensional clustering according to the present invention, and as shown in the figure, the method includes the following steps:
step S1, two-dimensionally positioning the target by using the antenna array to obtain a distance and direction (R, theta) information sequence;
the two-dimensional positioning of the target utilizes a large-caliber sparse array, and when R is less than or equal to 2D2Target processing array at/lambda timeIn the near field region, target distance and azimuth information can be simultaneously obtained based on an array spherical wave model, wherein R is the target distance, D is the array caliber, and lambda is the target wavelength. Positioning is firstly carried out on unsorted signals of the broadband radar, scanning is carried out on different distances R and azimuth angles theta, and a space spectrum is calculated for each stepping frequency point k:
where N is the covariance matrix of the noise, αfk(R, theta) is an array flow vector under different frequency points, and then the space spectrum of the broadband radar signal is as follows:
in the above formula, K is the number of the stepped frequency points. And searching a peak value of the radar signal space spectrum, wherein the scanning distance and the direction corresponding to the peak value are the distance and direction information of the target.
Step S2, setting initial values of threshold values (delta R, delta theta) of distance and orientation;
the threshold is an initial value of a distance threshold and an orientation threshold which are set according to the precision of the sparse array for measuring distance and direction of the target.
Step S3, calculating the similarity of the target distance dimension and the orientation dimension;
and calculating the similarity between the distance dimension and the orientation dimension by adopting the Euclidean distance:
wherein d is
REuclidean distance in the distance dimension, M is the number of pulse sequences, R
refFor the reference distance, the first measured distance is generally taken as the reference distance.
Wherein d is
θEuclidean distance, θ, in the azimuthal dimension
refFor reference orientation, takeThe first measured orientation is the reference orientation.
Step S4, according to the calculated similarity and threshold, obtaining two-dimensional clustering of distance and orientation;
the two-dimensional clustering is to utilize the pulse sequence to simultaneously satisfy d in the distance dimension and the azimuth dimensionRΔ R and d ≤θWhen the pulse sequence is less than or equal to delta theta, the pulse sequences are grouped into one class, otherwise, a new class is reconstructed, and the like is performed until all the pulse sequences complete two-dimensional clustering.
Step S5, self-adaptively adjusting the threshold values of the distance and the orientation, and counting the similarity mean value of the distance dimension and the orientation dimension after clustering
And finishing signal pre-sorting until the mean value is smaller than the threshold value of the distance or the direction.
Calculating the mean value of the pulse sequence distance dimension and the azimuth dimension similarity by the following formula:
when simultaneously satisfying
And
and adjusting the threshold values of the distance and the orientation, and repeating the steps S3, S4 and S5 until the threshold values do not need to be adjusted again, and finishing the signal pre-sorting.
The technical effects achieved by the present invention are illustrated by simulation experiments.
The distance-direction information of the four broadband frequency agile radar radiation sources simultaneously existing in an airspace is respectively (10200m,1 degree), (10400m,2 degrees), (10600m,3 degrees) and (10800m,4 degrees), a first target (3260MHz,3290MHz) is separated by 10MHz frequency agile, a second target (3300MHz,3340MHz) is separated by 40MHz frequency agile, a third target (3340MHz,3370MHz) is separated by 10MHz frequency agile, and a fourth target (3220MHz,3250MHz) is separated by 10MHz frequency agile and 20MHz frequency agile. The number of pulses M is 100, the initial threshold values of the distance and the direction are 100M and delta theta is 0.5 degrees, and the results of frequency pre-sorting, distance pre-sorting and direction pre-sorting in two-dimensional clustering are respectively shown in fig. 2, fig. 3 and fig. 4, so that the purpose of correctly pre-sorting multiple radar signals with mutually overlapped airspace, time domain and frequency domain in a complex electromagnetic environment is achieved.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.