CN110940953B - Three-dimensional detection method for target in sea clutter of ground wave radar - Google Patents
Three-dimensional detection method for target in sea clutter of ground wave radar Download PDFInfo
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- G—PHYSICS
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- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
- G01S7/28—Details of pulse systems
- G01S7/285—Receivers
- G01S7/292—Extracting wanted echo-signals
- G01S7/2923—Extracting wanted echo-signals based on data belonging to a number of consecutive radar periods
- G01S7/2927—Extracting wanted echo-signals based on data belonging to a number of consecutive radar periods by deriving and controlling a threshold value
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
- G01S7/35—Details of non-pulse systems
- G01S7/352—Receivers
- G01S7/354—Extracting wanted echo-signals
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
- G01S7/41—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00 using analysis of echo signal for target characterisation; Target signature; Target cross-section
- G01S7/414—Discriminating targets with respect to background clutter
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Abstract
The three-dimensional detection method of the target in the sea clutter of the ground wave radar comprises the steps of constructing a ground wave radar channel-distance-Doppler return spectrum, extracting a sea clutter region, and constructing a multi-stage airspace filter by using an oblique projection technology; feeding a ground wave radar channel-distance-Doppler echo spectrum to each spatial filter, and sequentially filtering each azimuth covered by the ground wave radar serving as a potential target direction by each filter; and carrying out minimum synthesis operation on the spectrum data after the spatial domain filtering to obtain a synthesized spectrum, carrying out three-dimensional detection on the distance-Doppler-azimuth spectrum of the synthesized spectrum to inhibit non-uniform sea clutter, searching peak values, and finally outputting azimuth, distance and Doppler parameters of a ship target. According to the invention, the azimuth dimension detection is expanded on the basis of the two-dimensional detection of the traditional distance-Doppler dimension target, so that the azimuth-distance-Doppler dimension target detection is formed, and the target detection capability in the sea clutter is improved by combining the echo difference of the sea clutter and the target in the three combined dimensions.
Description
Technical Field
The invention relates to a method for detecting a target in sea clutter of a ground wave radar, in particular to a three-dimensional detection method for the target in sea clutter of the ground wave radar.
Background
The ground wave radar is a main means for the large-scale, beyond-sight distance and continuous detection of the marine ship targets, and utilizes the characteristic of the diffraction of the vertical polarized high-frequency electromagnetic wave (3-30 MHz) along the sea surface to realize the beyond-sight distance detection of the marine targets. Ground wave radar sea clutter is a signal scattered back by interaction of high-frequency radio waves emitted by the radar and sea waves, and is divided into first-order, second-order and Gao Jiehai clutter. Wherein, the first-order sea clutter is expressed as a pair of stretched double peaks, and has strong energy, thereby causing a ship detection blind area [1] The detection rate is reduced. Therefore, the detection method of the ship target in the sea clutter is required to be developed, the limit of a 'detection blind area' is broken through, and the detection performance of the ground wave radar marine target is improved.
The conventional ground wave radar target detection method generally adopts a two-dimensional threshold detection method, namely, the detection results of two times are respectively detected once in the distance dimension and the Doppler dimension and then are' and then the target detection result is outputAnd outputting the distance and Doppler parameters of the target at the same time. And taking channel data at the corresponding target distance-Doppler spectrum point position in the later stage, and adopting beam forming methods such as amplitude comparison or a lookup table and the like to measure the direction to obtain the azimuth parameters of the target. In the two-dimensional threshold detection process, amplitude detection is mostly adopted. The method comprises a mean value type constant false alarm detector, a sequencing statistics type constant false alarm detector and an adaptive regression constant false alarm detector [2] . The detection method of the average value type constant false alarm detector is suitable for a uniform background, and when the sliding window range of the reference window is larger, the constant false alarm detection loss is smaller, but effective local estimation cannot be formed. The detection method of the sequencing statistics type constant false alarm detector has certain inhibition capability on weak clutter, and the detection performance in a strong clutter region is reduced. The self-adaptive regression constant false alarm detection method has an inhibition effect on the clutter of the ionosphere and the low-speed area, but in a uniform detection background area, the detection performance is inferior to that of a mean value constant false alarm detector and a self-adaptive regression constant false alarm detector. The two-dimensional detection method generally needs to achieve better detection performance by region segmentation in practical application and then adopts different threshold detection methods aiming at different clutter areas and types, but the target detection effect in sea clutter is still not ideal.
Sea clutter is sea surface radar echoes from random orientations that appear in the channel-range-doppler spectrum as implying different airspace echo information at different range and doppler locations. Given that the resonating waves may be distributed over a large ocean surface, there may be multiple and random potential sea clutter echo directions, while the target comes from a particular orientation. This airspace echo difference between sea clutter and ship targets is now in the channel data acquired by the ground wave radar receiving array. Thus, the spatial difference should be exploited in conjunction with range and Doppler domain information during target detection, which is lacking in the prior art.
The relevant references are as follows:
[1]Leong H,Ponsford A.The effects of sea clutter on the performance of HF surface wave radar in ship detection.IEEE Radar Conference.Rome:IEEE,2008:1-6.
[2]Ji Yonggang,Xu Leda,Wang Yiming,and Chu Xiaoliang.Ship Detection in Strong Clutter Environment Based on Adaptive Regression Thresholding for HFSWR,2014International Conference on Computer Science and Electronic Technology(ICCSET 2014),Atlantis Press,pp.352-355.
disclosure of Invention
The invention aims to provide a three-dimensional detection method for targets in sea clutter of a ground wave radar, which is different from the traditional distance-Doppler two-dimensional target detection, increases azimuth dimension detection, and further forms azimuth-distance-Doppler target detection. The method fully utilizes the difference of the combined dimensions of the space, the distance and the frequency of the target and the sea clutter to realize the target detection in the sea clutter.
In order to achieve the above purpose, the present invention provides a technical solution of a three-dimensional detection method for a target in sea clutter of a ground wave radar, which is characterized by comprising the following steps:
step 1: constructing a ground wave radar channel-distance-Doppler return spectrum, and extracting a sea clutter region:
pulse compression and coherent accumulation are sequentially carried out on down-conversion time domain sampling signals acquired by a ground wave radar receiving channel to obtain a ground wave radar channel-distance-Doppler return spectrum, a two-dimensional signal-to-noise ratio method is adopted to extract a sea clutter region, the sea clutter region is marked as x (c, r, f), and the physical quantity is amplitude, and the unit is dB; c represents a receiving channel, r represents a distance, and f represents Doppler;
step 2: constructing a multistage spatial filter:
in the ship detection scenario of the ground wave radar, sea clutter may have various doppler and azimuth, and may even have multiple azimuth for each doppler. But each vessel produces echoes from a particular different doppler and azimuth. Therefore, a plurality of notches need to be provided to eliminate clutter interference in all directions other than the target direction angle.
In order to provide the notches in these directions, it is necessary to construct a plurality of spatial filters, each having a corresponding notch, thereby constructing a multi-stage spatial filter. The cascade multiplication of the oblique projection spatial filters has equivalent filtering effect, namely, the signals from the target azimuth angle are not distorted, and sea clutter is removed by continuous notches. The spatial filters are constructed by adopting an oblique projection technology, target signals are reserved, and clutter interference is suppressed.
Step 3: and (3) spectrum synthesis:
feeding the ground wave radar channel-distance-Doppler echo spectrum to each spatial filter, sequentially filtering each azimuth covered by the ground wave radar as a potential target direction by each filter, reserving a spectrum signal of the direction after filtering each direction, and recording asThe physical quantity is amplitude, and the unit is dB; a represents an azimuth; and (3) performing minimum synthesis operation on each spatial domain filtered spectrum data, namely only retaining the minimum value in the filtering result of each spatial domain filter, wherein the obtained result is called a synthesized spectrum. After spectral synthesis, the desired signal from the target bearing is preserved without introducing amplitude and phase distortions, and most of the clutter is eliminated except for clutter that is the same as the target bearing. It should be noted that the non-directional noise cannot be suppressed. Since noise is gaussian and relatively weak, its effect on the target spectrum is negligible. When one direction is set as the potential direction of the target, only the range-Doppler spectrum and nondirectional noise of the direction are reserved, and spectrum signals of other directions are restrained;
step 4: target detection and parameter estimation:
and (3) respectively setting thresholds for the distance dimension, the Doppler dimension and the azimuth dimension of the synthesized spectrum generated in the step (3), wherein each threshold is determined by a mean value type constant false alarm detector, and carrying out three-dimensional detection on the distance-Doppler-azimuth spectrum of the synthesized spectrum so as to inhibit non-uniform sea clutter, then carrying out a peak searching process, and finally outputting the azimuth, the distance and the Doppler parameters of the ship target.
Compared with the prior art, the innovation of the invention is embodied in the following aspects:
the method breaks through the limitation of 'detection blind areas' caused by sea clutter in the traditional sense by developing a ship target detection method in the sea clutter, and improves the detection performance of the ground wave radar marine targets.
Unlike conventional range-doppler two-dimensional target detection, azimuth-dimensional detection is added, thereby forming azimuth-range-doppler target detection. The method fully utilizes the difference of the combined dimensions of the space, the distance and the frequency of the target and the sea clutter to realize the target detection in the sea clutter.
This airspace echo difference between sea clutter and ship targets is now in the channel data acquired by the ground wave radar receiving array. Thus, the spatial difference should be exploited in conjunction with the range and Doppler domain information during target detection. However, the receiving array aperture of the ground wave radar is too small relative to the wavelength thereof, so that even if a conventional beam forming method is adopted, the spatial filtering effect is limited, and effective three-dimensional detection cannot be formed. The invention adopts a multi-stage oblique projection airspace filtering mode, achieves better airspace filtering effect, and enables three-dimensional combined detection to be possible.
Drawings
FIG. 1 shows the target detection process of the present invention.
Figure 2 is a ground wave radar range-doppler spectrum of one receive channel.
Signal to interference and noise ratio improvement and interference and noise ratio at different spatial principal angles of fig. 3.
The spatial principal angles and orientations at different filter notch spacings of fig. 4.
Figure 5 shows the result of the actual measurement of the ground wave radar,
wherein, (a) azimuth-range-doppler spectrum after conventional DBF, (b) azimuth-range-doppler spectrum of the present patent, (c) doppler dimension result contrast, (d) range dimension result contrast, (e) azimuth dimension result contrast.
Detailed Description
The method of the present invention is further described below with reference to the formulas and drawings:
as shown in fig. 1, the first-order echo spectrum extraction method in the strong interference environment using the multi-domain information of the high-frequency ground wave radar mainly comprises the steps of echo spectrum construction and sea clutter region extraction, multi-stage spatial filtering, spectrum synthesis, target detection and parameter estimation, and finally outputs the detected target distance, doppler and azimuth information. The method comprises the following specific steps:
step 1: a channel-distance-Doppler spectrum is formed by using a ground wave radar multichannel down-conversion signal with a period of T seconds (291 s is taken as an example in the invention) through matched filtering and coherent accumulation processing. Extracting a sea clutter region by adopting a two-dimensional signal-to-noise ratio method, and marking the sea clutter region as x (c, r, f), wherein the physical quantity is amplitude, and the unit is dB; c represents the receive channel, r represents the range, and f represents the Doppler. In the form shown in figure 2.
Step 2: the step adopts an oblique projection method to construct a multi-stage airspace filter, and when the airspace guiding vector in the target direction is A and the airspace guiding vector in other observation directions is potential sea clutter airspace guiding vector B, a single oblique projection airspace filter E projected to A along B is defined AB Is that
Wherein the superscript -1 Is the generalized inverse of the matrix, superscript H Is the hermitian conjugate transpose of the matrix,is an orthogonal complement projection of matrix B, defined as
The oblique projection filtering E AB Has the following characteristics:
the characteristics lay a foundation for constructing the multi-stage spatial filter, and the specific steps for realizing the multi-stage filter are as follows:
1) The number of the used multi-stage filters is determined, the number P of which is determined by the space range of the coverage azimuth angle of the ground wave radar,
the spatial sampling interval is calculated as
P＝int(|θ L -θ T +Δθ|+|θ T +Δθ-θ R |)/Δθ (4)
Wherein int (, θ) represents an integer L And theta R θ is the left-right azimuth boundary covered by the ground wave radar T Is the potential target direction and Δθ is the notch spacing selected for filtering.
In practical applications, the principal angle of space between the target orientation and the filter notch position has a great influence on the signal-to-interference-and-noise ratio. Therefore, before the oblique projection spatial filtering parameter is selected, the improvement amount of the signal to interference and noise ratio under different interference and noise ratios is determined, which is closely related to the main angle of space. The principal spatial angle is determined by the notch spacing Δθ of the filter orientations.
From figure 3, which shows the numerical analysis, it is difficult to improve the signal-to-interference-plus-noise ratio SINR when the principal angle is very small at 1 ° and the signal-to-noise ratio SIR is-10 dB. And when the main angle is 90 deg. and the interference is greater than the noise, the improvement of SINR can be ensured. When the main angle is 13 degrees and the INR is larger than 15B, the SINR is improved, and the practical application situation of the ground wave radar is met. In this case, as can be seen from fig. 4, the space main angle increases with an increase in azimuth interval and a proximity of the target azimuth. Therefore, in order to maintain a principal angle above 13 ° in the azimuthal coverage range of [ -40 °,40 ° ], a spatial filtering notch spacing of at least 2 ° should be selected.
2) In the azimuth angle range covered by the ground wave radar, clutter angle or interference azimuth angle is selected for spatial filtering, and one time is performed
An angle, delta theta is used as interval, and clutter angle or interference azimuth angle is satisfied
θ C ∈[θ L ,θ T -Δθ]∪[θ T +Δθ,θ R ] (5)
3) For the clutter angle or interference azimuth selected in step 2, the target subspace and the clutter subspace are recorded as respectivelyIs->Then each spatial filter E is constructed according to (1) AB ；
4) Repeating the steps 2) and 3) for P times, thereby obtaining P filters based on oblique projection, and multiplying each filter based on oblique projection to form a multi-stage spatial filter.
Where p represents the p-th filter.
Step 3: feeding the sea clutter channel-distance-Doppler spectrum extracted in the step 1 to a multi-stage spatial filter E formed in the step 3 cas A range-doppler-azimuth spectrum of the ground wave radar is obtained, see fig. 5.
The specific way to feed the channel-range-doppler spectrum to the multi-stage spatial filter is as follows: synthesizing the spectrum data after the plurality of airspace filtering by utilizing a logical product, wherein the final three-dimensional target spectrum is
Where a, r, f represent azimuth, range and Doppler, min () represents the minimum value in brackets, s (r, f) j ) And i (r, f) k ) Representing the ship target and sea clutter distance-doppler spectrum, respectively; k represents the Doppler frequency point number of the sea clutter, and K represents the Doppler frequency point of the kth sea clutter; j represents the Doppler frequency point number of the target, and K & gtJ implies that the echo frequency point of the ship is smaller than the sea clutter frequency point; n (r, f) is gaussian white noise; a is that j Representing steering vectors of vessels, B k Representing the steering vector of the sea clutter.
The steering vectors of the ship and sea clutter are respectively
B k ＝[a(θ k ) … a(θ K )] T (9)
Wherein θ is the azimuth angle, and θ j Expressing the azimuth angle of the Doppler frequency point of the jth target, wherein J is a natural number from 1 to J; θ k Represents the azimuth angle of the kth sea clutter Doppler frequency point, K is a natural number with values of 1 to K, and when K is the value K, the formula 9 is [ a (theta K )] T The method comprises the steps of carrying out a first treatment on the surface of the d is the array element spacing, M is the array element number, f 0 Is the radar carrier frequency, c is the speed of light, [.] T Transpose the matrix.
From equation (7), after spectral synthesis, the desired signal from the target bearing is recovered without introducing amplitude and phase distortions, and most of the clutter is eliminated except for the clutter that is the same as the target bearing. It should be noted that the non-directional noise cannot be suppressed. Since noise is gaussian and relatively weak, its effect on the target spectrum is negligible. When one bearing is set as the potential direction of the target, only the range-doppler spectrum and non-directional noise of that direction are preserved, while the spectral signals of the other directions are suppressed. The filtering in turn selects each azimuth of the ground wave radar coverage as a potential target direction and preserves the spectral signal of that direction.
Step 4: and 3, respectively setting thresholds in the distance, azimuth and Doppler domains by the average value type constant false alarm detector to perform three-dimensional detection on the azimuth-distance-Doppler spectrum. Three-dimensional composite object detection using peak detection is represented as
D＝peak(D r ||D a ||D f ) (10)
Wherein D stores azimuth, range and Doppler position parameters of the vessel being probed, peak () indicates a search for amplitude peaks in brackets, D r ，D a And D f Spectral amplitude values stored in the range, azimuth and Doppler dimensions, respectively, which are each greater than the detection threshold T of the respective range, azimuth and Doppler domain r ,T a And T f The expression "logical sum" means a logical sum operation,is the distance dimension amplitude value at a specific Doppler of f and azimuth of a,/>Is the azimuth dimension amplitude value at doppler f and range r,is the doppler amplitude value at a particular bearing a and range r.
And finally outputting the azimuth, distance and Doppler parameters of the ship target through the peak detection of the formula (10).
Fig. 5 shows the measured ground wave radar processing results of the method of this patent and a comparison with the conventional DBF method. From the azimuth-range-Doppler spectrum after the conventional DBF of FIG. 5 (a), the band characteristics of sea clutter are still very obvious, and point targets (the azimuth of the targets is 10 degrees, the distance is 82.5-85 Km, and the Doppler is 0.2198-0.2266 Hz) are difficult to find. Fig. 5 (b) azimuth-range-doppler spectrum of the present patent, the banding features of sea clutter are eliminated and punctiform targets appear. The signal-to-interference-and-noise ratio of the patent to the target is improved by approximately 10dB and is higher than 5dB adopting the DBF method. The detected target bearing was 8 °, the distance was 84Km, and the doppler was 0.2266Hz. Fig. 5 (c), (d), and (e) show comparison of the results of the doppler dimension, the distance dimension, and the azimuth dimension, further showing the effectiveness of the method of the present patent.
Claims (4)
1. The three-dimensional detection method of the target in the sea clutter of the ground wave radar is characterized by comprising the following steps of:
step 1: constructing a ground wave radar channel-distance-Doppler return spectrum, and extracting a sea clutter region:
pulse compression and coherent accumulation are sequentially carried out on down-conversion time domain sampling signals acquired by a ground wave radar receiving channel to obtain a ground wave radar channel-distance-Doppler return spectrum, a two-dimensional signal-to-noise ratio method is adopted to extract a sea clutter region, the sea clutter region is marked as x (c, r, f), and the physical quantity is amplitude, and the unit is dB; c represents a receiving channel, r represents a distance, and f represents Doppler;
step 2: constructing a multistage spatial filter:
constructing a multi-stage airspace filter by adopting an oblique projection technology;
step 3: and (3) spectrum synthesis:
feeding the ground wave radar channel-distance-Doppler echo spectrum to each spatial filter, sequentially filtering each azimuth covered by the ground wave radar as a potential target direction by each filter, reserving a spectrum signal of the direction after filtering each direction, and recording asThe physical quantity is amplitude, and the unit is dB; a represents an azimuth;
performing minimum synthesis operation on each spatial domain filtered spectrum data, namely only reserving the minimum value in the filtering result of each spatial domain filter, wherein the obtained result is called synthesized spectrum;
after spectrum synthesis, the expected signal from the target azimuth is reserved under the condition of not introducing amplitude and phase distortion, and most clutter is eliminated except clutter which is the same as the target azimuth;
when one direction is set as the potential direction of the target, only the range-Doppler spectrum and nondirectional noise of the direction are reserved, and spectrum signals of other directions are restrained;
step 4: target detection and parameter estimation:
and (3) respectively setting thresholds for the distance dimension, the Doppler dimension and the azimuth dimension of the synthesized spectrum generated in the step (3), wherein each threshold is determined by a mean value type constant false alarm detector, and carrying out three-dimensional detection on the distance-Doppler-azimuth spectrum of the synthesized spectrum so as to inhibit non-uniform sea clutter, then carrying out a peak searching process, and finally outputting the azimuth, the distance and the Doppler parameters of the ship target.
2. The three-dimensional detection method of targets in sea clutter of ground wave radar according to claim 1, wherein the step 2 adopts oblique projection technology to construct a multistage spatial filter as follows:
when the airspace guiding vector of the target direction is A and the other observing directions are potential sea clutter airspace guiding vectors B, defining a single oblique projection airspace filtering E projected to A along B AB Is that
Where superscript-1 is the generalized inverse of the matrix, superscript H is the hermitian conjugate transpose of the matrix,is an orthogonal complement projection of matrix B, defined as
The oblique projection filtering E AB Has the following characteristics:
the characteristics lay a foundation for constructing the multi-stage spatial filter, and the specific steps for realizing the multi-stage filter are as follows:
1) Determining the number of multi-stage filters, wherein the number P is determined by the space range of the coverage azimuth angle of the ground wave radar, and the space sampling interval is calculated as
P＝int(|θ L -θ T +Δθ|+|θ T +Δθ-θ R |)/Δθ (4)
Wherein int (, θ) represents an integer L And theta R θ is the left-right azimuth boundary covered by the ground wave radar T Is the potential target direction, Δθ is the notch spacing selected for filtering;
2) In the azimuth angle range covered by the ground wave radar, clutter angles or interference azimuth angles are selected for spatial filtering, one angle at a time, delta theta is used as interval, and the clutter angles or the interference azimuth angles meet
θ C ∈[θ L ,θ T -Δθ]∪[θ T +Δθ,θ R ] (5)
3) For the clutter angle or interference azimuth selected in step 2, the target subspace and the clutter subspace are recorded as respectivelyIs->Then each spatial filter E is constructed according to (1) AB ；
4) Repeating the steps 2) and 3) for P times, thereby obtaining P filters based on oblique projection, and multiplying each filter based on oblique projection to form a multistage airspace filter;
where p represents the p-th filter.
3. The method for three-dimensional detection of an object in sea clutter of a ground wave radar according to claim 1, wherein said step 3 is performed by feeding a channel-distance-doppler spectrum to a multi-stage spatial filter as follows: synthesizing the spectrum data after the plurality of airspace filtering by utilizing a logical product, wherein the final three-dimensional target spectrum is
Where a, r, f represent azimuth, range and Doppler, min () represents the minimum value in brackets, s (r, f) j ) And i (r, f) k ) Representing the ship target and sea clutter distance-doppler spectrum, respectively; k represents the Doppler frequency point number of the sea clutter, and K represents the Doppler frequency point of the kth sea clutter; j represents the Doppler frequency point number of the target, and K & gtJ implies that the echo frequency point of the ship is smaller than the sea clutter frequency point; n (r, f) is gaussian white noise; a is that j Representing steering vectors of vessels, B k A steering vector representing sea clutter;
the steering vectors of the ship and sea clutter are respectively
B k ＝[a(θ k )…a(θ K )] T (9)
Wherein θ is the azimuth angle, and θ j Expressing the azimuth angle of the Doppler frequency point of the jth target, wherein J is a natural number from 1 to J; θ k Represents the azimuth angle of the kth sea clutter Doppler frequency point, K is a natural number with values of 1 to K, and when K is the value K, the formula 9 is [ a (theta K )] T The method comprises the steps of carrying out a first treatment on the surface of the d is the array element spacing, M is the array element number, f 0 Is the radar carrier frequency, c is the speed of light, [.] T Transpose the matrix.
4. The three-dimensional detection method of an object in sea clutter of a ground wave radar according to claim 1, wherein said step 4: the synthesized spectrum of the step 3 is respectively set with threshold values in the distance, azimuth and Doppler domain by a mean value type constant false alarm detector, the azimuth-distance-Doppler spectrum is three-dimensionally detected,
three-dimensional composite object detection using peak detection is represented as
D＝peak(D r ||D a ||D f ) (10)
Wherein D stores azimuth, range and Doppler position parameters of the vessel being probed, peak () indicates a search for amplitude peaks in brackets, D r ，D a And D f Spectral amplitude values stored in the range, azimuth and Doppler dimensions, respectively, which are each greater than the detection threshold T of the respective range, azimuth and Doppler domain r ,T a And T f The expression "logical sum" means a logical sum operation,is the distance dimension amplitude value at a specific Doppler of f and azimuth of a,/>Is the azimuth dimension amplitude value at Doppler f and distance r, < >>Is the Doppler amplitude value at a particular bearing a and range r;
and finally outputting the azimuth, distance and Doppler parameters of the ship target through the peak detection of the formula (10).
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