CN110196415A - A kind of wide null Beamforming Method based on compensation Antenna error - Google Patents
A kind of wide null Beamforming Method based on compensation Antenna error Download PDFInfo
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Abstract
A kind of wide null Beamforming Method based on compensation Antenna error.The present invention relates to wide null Beamforming Methods.The problem of the purpose of the present invention is to solve under Antenna error background, traditional Clutter suppression algorithm can not inhibit the sea clutter broadened by Ship Motion.Process are as follows: one: the Antenna error data that the corresponding all angles of antenna are influenced by error are obtained by active correction；Two: pulse compression being carried out to the echo data of carrier-borne high-frequency ground wave radar and correlative accumulation is handled, obtains the three-dimensional modal data of channel × Doppler × distance；Three: obtaining normalized amendment orthogonal weight method weight coefficient；Four: obtaining wide null Beamforming Method weight coefficient；Five: three-dimensional modal data being handled using wide null Beamforming Method weight coefficient, the three-dimensional modal data of angle × Doppler after the sea clutter that is inhibited × distance.The present invention is used for carrier-borne high-frequency ground wave radar field of signal processing.
Description
Technical Field
The invention relates to the field of signal processing of a ship-borne high-frequency ground wave radar, which can be used for suppressing sea clutter of the ship-borne ground wave radar in the background of antenna directional diagram errors.
Background
The ship-borne high-frequency ground wave radar is a new system radar, the working frequency range is 3MHz-30MHz, compared with the conventional radar such as a microwave radar, the radar has the advantages of over-the-horizon detection of targets below the horizon, anti-stealth, long early warning time, anti-radiation missile resistance, stable equipment, strong anti-interference capability and the like, and plays an important role in the military field of all countries in the world at present.
For a ship-borne high-frequency ground wave radar, the movement of a ship platform can cause the spectrum of a first-order sea clutter to be broadened, so that a ship target with a lower speed is influenced by the broadened spectrum and submerged in the sea clutter, and the information of the target cannot be accurately estimated. The first-order sea clutter spectrum is related to the movement speed of the ship, so that the direction of the sea clutter can be deduced relatively through the movement speed of the ship, and the problem can be converted into the problem of inhibiting the clutter with the known direction. Aiming at the problem, national scholars carry out extensive research, and the research on target detection and estimation of a ship-borne high-frequency ground wave radar [ D ]. Harbin industry university, 2001. an Orthogonal Weighting method (OW) is introduced, so that first-order sea clutter is restrained; sun M, Xie J, Hao Z, et al. target Detection and Estimation for Shipborne HFSWR Based on Objective Projection [ C ]// 201211 th International conference on Signal Processing (ICSP 2012).0. then, aiming at the deficiency of the orthogonal weighting method, an Oblique Projection algorithm (OP) is introduced, and the information of the target Signal is retained to a greater extent while the fixed azimuth clutter is suppressed.
For the traditional ship-based high-frequency ground wave radar, due to the limitation of the antenna arrangement position and the actual environment, the interference of antenna directional diagram errors can occur, the antenna directional diagram can be distorted due to the errors, and the work can not be normally finished. The traditional clutter suppression algorithm such as the orthogonal weighting method and the oblique projection algorithm has a deteriorated effect under the background of antenna directional diagram errors, and cannot sufficiently suppress the broadened sea clutter submerging the ship. In addition, since the amplitude-phase characteristics of the antenna and the channel are slowly changed with the increase of the using time, the actual error of the antenna array may deviate from the original error measurement value, and therefore, the difficulty of correcting the directional diagram error of the antenna is further increased.
When the antenna arrays are arranged into uniform linear arrays along two sides of the ship board and the antennas are not influenced by directional diagram errors, directional diagrams (including null points) synthesized by the antenna arrays are symmetrical about the antenna arrays. The radar array can realize the simultaneous suppression of the sea clutter from both sides of the antenna array. When the antenna directional diagram error exists, the directional diagram synthesized by the antenna array is not symmetrical about the antenna array any more. The traditional zero point forming algorithm can only inhibit a clutter source at one side of the antenna, and the clutter at the other side enters the antenna to influence detection.
Array errors have a non-negligible effect on the performance of the array antenna. At present, the research of various national scholars focuses on correcting and analyzing array position errors and mutual coupling errors, and the most common antenna directional diagram errors in actual engineering are rarely researched, so that a method for correcting the antenna directional diagram errors is needed, and the widened first-order sea clutter in the carrier-borne high-frequency ground wave radar can be suppressed.
Disclosure of Invention
The invention aims to solve the problem that a traditional clutter suppression algorithm cannot suppress sea clutter widened due to ship motion under the background of an antenna directional diagram error, and provides a wide zero-trap beam forming method based on antenna directional diagram error compensation.
A method for forming a wide zero-notch beam based on compensating antenna directional diagram errors comprises the following specific processes:
the method comprises the following steps: obtaining antenna directional diagram error data of each angle corresponding to the antenna affected by the error through active correction, and recording the antenna directional diagram error data as r (theta);
step two: performing pulse compression and coherent accumulation processing on echo data of the ship-borne high-frequency ground wave radar to obtain three-dimensional spectrum data of channel multiplied by Doppler multiplied by distance, and recording the three-dimensional spectrum data as CDR;
step three: based on the error data r (theta) obtained in the step one, the original array guide vector (the array guide vector without the error) is corrected to obtain the interfered projection matrixDisturbed based projection matrixGet the normalized correction cross-addWeight method weight coefficientThe specific process is as follows:
step three, firstly: the first-order Bragg frequency is derived from the Bragg resonance scattering principle and the deep water dispersion principle:
wherein f isBIs the Bragg frequency, the Bragg frequency is the Bragg frequency, f0Is the radar operating frequency, which is in MHz;
step three: finding out the Doppler frequency f corresponding to the Doppler unit through the three-dimensional spectral data CDR obtained in the step twodTo obtain fdAzimuth theta of corresponding sea clutteri：
Wherein v ispIs the moving speed of the ship-based platform, thetai∈[0,2π]；
Step three: orientation thetaiArray steering vector a (theta) corresponding to sea clutteri) Comprises the following steps:
step three and four: the azimuth theta obtained by the step oneiAntenna pattern error data r (theta)i) Constructing a corrected array steering vector
Wherein omicron represents the Hadamard product; r (theta)i) Azimuth theta of sea clutter corresponding to the error-affected antennaiAntenna pattern error data of (a);
step three and five: using modified array steering vectorsConstructing disturbed projection matrices
Wherein, IMThe unit array with the order of the array element number M is adopted, and the superscript H represents the conjugate transpose;
step three and six: using disturbed projection matricesObtaining an orientation of thetaiWeight coefficient of normalized correction orthogonal weighting method corresponding to sea clutter
Wherein s (theta) is a scanning circulation vector, and plays a role in scanning all angles by traversing theta (0-360 degrees);
step three, pseudo-ginseng: by traversing thetaiObtaining the normalized correction orthogonal weighting method weight coefficient corresponding to all the sea clutter
Step four: setting the width of the wide null as delta theta and theta in clutter azimuthiReconstructing K nulls in the vicinity of delta theta, and corresponding modified guide vectors to the reconstructed nullsGuide vector replacing correction in step threeObtaining a wide zero-trap beam forming method weight coefficient W according to the method in the third step; the specific process is as follows:
step four, firstly: finding out the corresponding sea clutter azimuth theta in the third step and the second stepiSetting the width of the wide null as delta theta, and constructing the corresponding angle of the improved null, wherein the reconstructed null number is K after improvement:
wherein, thetakThe angle corresponding to the k-th null is improved;
step four and step two: constructing a corresponding ideal array guide vector by using the K angles obtained in the first step:
step four and three, constructing the corrected array guide vector
Wherein, r (theta)k) Theta corresponding to the antenna affected by the errorkAngular antenna pattern error data;
step four: using modified array steering vectorsConstructing a projection matrix J corresponding to the wide zero-trap beam forming method:
wherein,the vector matrix is steered to the array after modification,
step four and five: obtaining a projection matrix J corresponding to the wide null method to obtain the azimuth thetajForming a method weight coefficient W by a wide zero-trap beam corresponding to the sea clutter:
the scanning function is realized by traversing theta (0-360 degrees) so as to scan all angles;
step four and six:by traversing thetaiObtaining wide zero-trapped wave beam forming method weight coefficients W corresponding to all sea clutter;
step five: and (4) processing the three-dimensional spectral data CDR obtained in the step (II) by using the wide zero-notch beam forming method weight coefficient W obtained in the step (IV) to obtain angle multiplied by Doppler multiplied by distance three-dimensional spectral data after sea clutter suppression.
The invention has the beneficial effects that:
the invention provides an effective solution for suppressing widened sea clutter by a carrier-borne high-frequency ground wave radar influenced by an antenna directional diagram error. Data of antenna directional diagram errors are obtained in an active correction mode, so that the original array steering vectors are corrected, the influence of the array affected by the errors on sea clutter information is fully considered, the error information is utilized, and the original orthogonal weighting method is improved; according to the problem that the error acquisition precision is not high in the actual environment, a beam forming method of the wide null is provided and is applied to clutter suppression of the carrier-borne high-frequency ground wave radar in the antenna directional diagram error environment for the first time. The method for forming the wide zero-notch beam based on the compensation antenna directional diagram error is used for processing the echo data of the carrier-borne high-frequency ground wave radar, and the problem that the traditional clutter suppression algorithm cannot suppress broadened first-order sea clutter under the condition of the antenna directional diagram error is solved.
From fig. 9 and table 3, the average power for suppressing the front sea clutter is 47.16dB, the target peak power is 61.15dB, and the signal-to-noise-and-noise ratio is 9.48 dB; the average power of the sea clutter obtained by the traditional orthogonal weighting method is 41.50dB, the target peak power is 60.13dB, and the signal-to-noise-and-noise ratio is 9.1 dB; the average power of the sea clutter obtained by the wide zero-notch beam forming method is 23.51dB, the target peak power is 55.02dB, and the signal-to-noise-ratio is 34.49 dB; under the error environment, the traditional orthogonal weighting method has the effect equivalent to that before the suppression, and under the condition of less influence on the target peak power, the method greatly improves two indexes of sea clutter average power and signal-to-noise-and-noise ratio, so that the effectiveness of the method is proved. By utilizing the method for forming the wide zero-notch beam based on the compensation antenna directional diagram error to process the echo data of the ship-borne high-frequency ground wave radar, the problem that the traditional orthogonal weighting method cannot suppress the broadened sea clutter under the error condition is solved.
Drawings
FIG. 1 is an overall flow diagram of the invention;
FIG. 2 is a schematic diagram of a receiving array of a ship-based high-frequency ground wave radar;
fig. 3a is an amplitude error diagram of an actually measured antenna array element 1;
fig. 3b is an amplitude error diagram of the actually measured antenna array element 2;
fig. 3c is an amplitude error diagram of the measured antenna element 3;
fig. 3d is an amplitude error diagram of the actually measured antenna element 4;
fig. 3e is an amplitude error diagram of the actually measured antenna array element 5;
FIG. 3f is a graph of the amplitude error of the measured antenna element 6;
FIG. 3g is an amplitude error diagram of the measured antenna element 7;
FIG. 3h is an amplitude error diagram of the actually measured antenna array element 8;
fig. 4a is a diagram of the phase error of the measured antenna element 1;
fig. 4b is a graph of the phase error of the measured antenna element 2;
fig. 4c is a graph of the phase error of the measured antenna element 3;
fig. 4d is a diagram of the phase error of the measured antenna element 4;
fig. 4e is a diagram of the phase error of the measured antenna element 5;
fig. 4f is a diagram of the phase error of the measured antenna element 6;
fig. 4g is a diagram of the phase error of the measured antenna element 7;
fig. 4h is a diagram of the phase error of the actually measured antenna array element 8;
FIG. 5 is a graph comparing the corrected weight coefficients with the corresponding antenna patterns of the conventional orthogonal weighting method under an error environment;
FIG. 6 is a graph comparing antenna patterns corresponding to the error environment for the method of the present invention and the conventional orthogonal weighting method;
FIG. 7a is a cross-sectional view of a conventional orthogonal weighting method in an error environment;
FIG. 7b is a cross-sectional view of a range-Doppler spectrum in an error environment according to the method of the present invention;
FIG. 8a is a comparison graph of an angular Doppler cross-section of the method of the present invention compared to a conventional orthogonal weighting method in an error environment;
FIG. 8b is a comparison graph of an angular Doppler cross-section of the method of the present invention compared to a conventional orthogonal weighting method in an error environment;
FIG. 9 is a Doppler cross-sectional view of the target under error environment according to the method of the present invention and the conventional orthogonal weighting method.
Detailed Description
The first embodiment is as follows: the present embodiment is described with reference to fig. 1, and a method for forming a wide zero-notch beam based on compensating an antenna pattern error according to the present embodiment specifically includes:
the method comprises the following steps: obtaining antenna directional diagram error data of each angle corresponding to the antenna affected by the error through active correction, and recording the antenna directional diagram error data as r (theta);
step two: performing pulse compression and coherent accumulation processing on echo data of the ship-borne high-frequency ground wave radar to obtain three-dimensional spectrum data of channel multiplied by Doppler multiplied by distance, and recording the three-dimensional spectrum data as CDR;
step three: based on the error data r (theta) obtained in the step one, the original array guide vector (the array guide vector without the error) is corrected to obtain the interfered projection matrixDisturbed based projection matrixObtaining normalized modified orthogonal weighting method weight coefficientsThe specific process is as follows:
step three, firstly: the first-order Bragg frequency is derived from the Bragg resonance scattering principle and the deep water dispersion principle:
wherein f isBIs the Bragg frequency, the Bragg frequency is the Bragg frequency, f0Is the radar operating frequency, which is in MHz;
step three: finding out the Doppler frequency f corresponding to the Doppler unit through the three-dimensional spectral data CDR obtained in the step twodTo obtain fdAzimuth theta of corresponding sea clutteri：
Wherein v ispFor movement of ship-based platformsSpeed, thetai∈[0,2π]；
Step three: orientation thetaiArray steering vector a (theta) corresponding to sea clutteri) Comprises the following steps:
step three and four: the azimuth theta obtained by the step oneiAntenna pattern error data r (theta)i) Constructing a corrected array steering vector
Wherein omicron represents the Hadamard product; r (theta)i) Azimuth theta of sea clutter corresponding to the error-affected antennaiAntenna pattern error data of (a);
step three and five: using modified array steering vectorsConstructing disturbed projection matrices
Wherein, IMThe unit array with the order of the array element number M is adopted, and the superscript H represents the conjugate transpose;
step three and six: using interfered projectionShadow matrixObtaining an orientation of thetaiWeight coefficient of normalized correction orthogonal weighting method corresponding to sea clutter
Wherein s (theta) is a scanning circulation vector, and plays a role in scanning all angles by traversing theta (0-360 degrees);
step three, pseudo-ginseng: by traversing thetaiObtaining the normalized correction orthogonal weighting method weight coefficient corresponding to all the sea clutter
Step four: setting the width of the wide null as delta theta and theta in clutter azimuthiReconstructing K nulls in the vicinity of delta theta, and corresponding modified guide vectors to the reconstructed nullsGuide vector replacing correction in step threeObtaining a wide zero-trap beam forming method weight coefficient W according to the method in the third step; the specific process is as follows:
step four, firstly: finding out the corresponding sea clutter azimuth theta in the third step and the second stepiSetting the width of the wide null as delta theta, and constructing the corresponding angle of the improved null, wherein the reconstructed null number is K after improvement:
wherein, thetakThe angle corresponding to the k-th null is improved;
step four and step two: constructing a corresponding ideal array guide vector by using the K angles obtained in the first step:
step four and step three: constructing a modified array steering vector
Wherein, r (theta)k) Theta corresponding to the antenna affected by the errorkAngular antenna pattern error data;
step four: using modified array steering vectorsConstructing a projection matrix J corresponding to the wide zero-trap beam forming method:
wherein,the vector matrix is steered to the array after modification,
step four and five: obtaining a projection matrix J corresponding to the wide null method to obtain the azimuth thetajForming a method weight coefficient W by a wide zero-trap beam corresponding to the sea clutter:
the scanning function is realized by traversing theta (0-360 degrees) so as to scan all angles;
step four and six: by traversing thetaiObtaining wide zero-trapped wave beam forming method weight coefficients W corresponding to all sea clutter;
step five: and (4) processing the three-dimensional spectral data CDR obtained in the step (II) by using the wide zero-notch beam forming method weight coefficient W obtained in the step (IV) to obtain angle multiplied by Doppler multiplied by distance three-dimensional spectral data after sea clutter suppression.
The second embodiment is as follows: the first difference between the present embodiment and the specific embodiment is: obtaining antenna directional diagram error data of each angle corresponding to the antenna affected by the error through active correction in the first step, and recording the antenna directional diagram error data as r (theta); the specific process is as follows:
the method comprises the following steps: the receiving array of the ship-borne high-frequency ground wave radar adopts a uniform linear array as shown in figure 2, the number of array elements is M, the spacing between the array elements is d, and the wavelength of the radar is lambda ═ c/f0C is the speed of light, f0Setting a target for a radar working carrier frequency in a direction with an included angle theta with the radar array;
the first step is: the array receives the echo data of the target, and based on the data amplitude obtained by the first array element, the data amplitudes obtained by other array elements are respectively compared with the number of the first array elementMaking difference according to the amplitude, and recording the obtained difference as the amplitude disturbance rho in the theta directionm(θ),m＝1,2,...,M，
Wherein m represents the mth array element, and theta represents the arrangement included angle between the target and the radar array;
based on the data phase obtained by the first array element, the data phases obtained by other array elements are respectively differenced with the data phase obtained by the first array element, and then the original phase difference d/lambda (m-1) · cos theta among the array elements is subtracted, and the difference is recorded as the phase perturbation in the theta direction
Step one is three: processing the obtained amplitude disturbance and phase disturbance to obtain antenna directional diagram error data with the direction of thetaThe superscript T stands for transpose, j is an imaginary unit, j2＝-1；
And rotating the target placement angle by 0-360 degrees, and scanning the target placement angle at intervals of 1 degree to obtain antenna directional diagram error data of each angle.
Other steps and parameters are the same as those in the first embodiment.
The third concrete implementation mode: the present embodiment differs from the first or second embodiment in that: in the second step, the echo data of the ship-borne high-frequency ground wave radar is subjected to pulse compression and coherent accumulation processing to obtain three-dimensional spectrum data of channel multiplied by Doppler multiplied by distance, and the three-dimensional spectrum data is recorded as CDR; the specific process is as follows:
step two, firstly: carrying out pulse compression on echo data of a target received by the array, and carrying out appropriate N-1 section truncation processing to obtain N distance units;
step two: performing FFT processing on all accumulated echoes of each distance unit, performing coherent accumulation to obtain L Doppler units, and finally obtaining three-dimensional spectral data of channels (array element number) multiplied by Doppler multiplied by distance, which is recorded as CDR;
the FFT is a fast fourier transform.
Other steps and parameters are the same as those in the first or second embodiment.
The fourth concrete implementation mode: the difference between this embodiment mode and one of the first to third embodiment modes is: scanning cycle vector s (theta) ═ s in the third step and the sixth step1θ(θ),...,smθ(θ),...,sMθ(θ)]TThe size of which is Mx 1, smθ(θ) is the m-th element in the scan cycle vector, smθ(θ)＝ej·2π·(m-1)·d·cosθ/λM1, 2.., M, the superscript T representing transposition.
Other steps and parameters are the same as those in one of the first to third embodiments.
The fifth concrete implementation mode: the difference between this embodiment and one of the first to fourth embodiments is: processing the three-dimensional spectral data CDR obtained in the step two by using the weight coefficient W of the wide zero-trap beam forming method obtained in the step four to obtain angle multiplied by Doppler multiplied by distance three-dimensional spectral data after sea clutter is suppressed; the specific process is as follows:
step five, first: selecting the CDR data acquired in the step two, selecting a certain range-Doppler unit, finding the position of the sea clutter according to the Doppler corresponding unit, and processing the data of the certain range-Doppler unit by using the wide zero notch beam forming method weight coefficient W obtained in the step four to obtain an angle spectrum with one range-Doppler unit clutter filtered;
step five two: and traversing the range-Doppler unit to obtain angle multiplied by Doppler multiplied by range three-dimensional spectral data after sea clutter is inhibited.
Other steps and parameters are the same as in one of the first to fourth embodiments.
The following examples were used to demonstrate the beneficial effects of the present invention:
the first embodiment is as follows:
the method for forming the wide zero notch beam based on the compensation of the antenna pattern error is implemented by the following steps:
the simulation parameters are shown in the following table:
TABLE 1 shipboard HFSWR System parameter settings
TABLE 2 simulation target parameter settings
The method comprises the following steps: and measuring the antenna directional diagram of the array in an active correction mode to obtain antenna directional diagram error data r (theta) of each angle of the antenna. The obtained measured antenna amplitude error and phase error are shown in fig. 3a, 3b, 3c, 3d, 3e, 3f, 3g, 3h and fig. 4a, 4b, 4c, 4d, 4e, 4f, 4g, 4 h.
Step two: the method comprises the steps of performing pulse compression and coherent accumulation processing on echo data of the ship-borne high-frequency ground wave radar to obtain three-dimensional spectral data of a channel multiplied by Doppler multiplied by distance, and recording the three-dimensional spectral data as CDR, wherein the size of the three-dimensional spectral data is 8 multiplied by 512 multiplied by 120.
Step three: correcting the original array guide vector through the acquired error data r (theta) to obtain an interfered projection matrixFurther obtaining the normalized correction orthogonal weighting method weight coefficientThe corrected weight coefficients and the corresponding antenna pattern pairs of the conventional orthogonal weighting method under the error environment are shown in fig. 5.
Step four: and near the direction of clutter formation, the width of the wide null is delta theta to be 2 degrees, the number of the reconstructed nulls after improvement is K to be 3, and the reconstructed array guide vector replaces the original array guide vector in the step three to obtain a wide null trapped wave beam formation method weight coefficient W. The antenna pattern pairs corresponding to the wide null notch beamforming method and the conventional orthogonal weighting method under an error environment are shown in fig. 6.
Step five: the CDR data are processed by utilizing the weight coefficient of the obtained wide zero notch beam forming method, and the processing result of the wide zero notch beam forming method on the echo data of the carrier-borne high-frequency ground wave radar is obtained, the comparison of the AD spectrum cross section of the method disclosed by the invention and the RD spectrum cross section of the traditional orthogonal weighting method are shown in figures 7a and 7b, and the comparison of the corresponding target Doppler cross section of the method disclosed by the invention is shown in figure 9.
The simulation result proves that:
as can be seen from fig. 5, the target azimuth is 120 °, the azimuth of the sea clutter corresponding to the front of the radar is 60 °, and the azimuth of the sea clutter corresponding to the back of the radar is 300 °. According to the figure, under the error condition, the antenna directional diagram is distorted in the traditional orthogonal weighting method, and the null cannot be formed at the position corresponding to the clutter; the corrected orthogonal weighting method effectively estimates the orientation of 120 degrees of the target signal, and forms nulls at 60 degrees and 300 degrees of the two sea clutter orientations, so that clutter can be effectively filtered.
As can be seen from fig. 6, the target azimuth is 120 °, the azimuth of the sea clutter corresponding to the front of the radar is 60 °, and the azimuth of the sea clutter corresponding to the back of the radar is 300 °. As can be seen, the wide null notch beamforming method has wider nulls than the conventional orthogonal weighting method; when influenced by the antenna directional diagram error, the traditional orthogonal weighting method fails, and the wide null forming method can still form wide nulls in the corresponding clutter azimuth, so that the purpose of suppressing the clutter is achieved.
See fig. 7a, 7b and fig. 8a, 8 b. As can be seen from the figure, the traditional orthogonal weighting method cannot suppress the broadened sea clutter in the antenna directional diagram error environment, and the target is submerged in the sea clutter; the method provided by the invention can inhibit the sea clutter under the error condition, and the target is obviously exposed.
Looking at fig. 9, calculated results of inhibition for both methods are shown in table 3. As can be seen from fig. 9 and table 3, in an error environment, the conventional orthogonal weighting method has an effect equivalent to that before suppression, but the method of the present invention greatly improves two indexes, namely, the average power of the sea clutter and the signal-to-noise ratio, under the condition of having a small influence on the target peak power, thereby proving the effectiveness of the present invention. The method for forming the wide zero-notch beam based on the compensation antenna directional diagram error is used for processing the echo data of the ship-borne high-frequency ground wave radar, and the problem that the traditional orthogonal weighting method cannot suppress the broadened sea clutter under the error condition is solved.
TABLE 3 method inhibition results
The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof, and it should be understood that various changes and modifications can be effected therein by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (5)
1. A wide zero notch beam forming method based on compensation antenna directional diagram errors is characterized in that: the method comprises the following specific processes:
the method comprises the following steps: obtaining antenna directional diagram error data of each angle corresponding to the antenna affected by the error through active correction, and recording the antenna directional diagram error data as r (theta);
step two: performing pulse compression and coherent accumulation processing on echo data of the ship-borne high-frequency ground wave radar to obtain three-dimensional spectrum data of channel multiplied by Doppler multiplied by distance, and recording the three-dimensional spectrum data as CDR;
step three: based on the error data r (theta) obtained in the step one, the original array guide vector is corrected to obtain the interfered projection matrixDisturbed based projection matrixObtaining normalized modified orthogonal weighting method weight coefficientsThe specific process is as follows:
step three, firstly: the first-order Bragg frequency is derived from the Bragg resonance scattering principle and the deep water dispersion principle:
wherein f isBIs the Bragg frequency, the Bragg frequency is the Bragg frequency, f0Is the radar operating frequency, which is in MHz;
step three: finding out the Doppler frequency f corresponding to the Doppler unit through the three-dimensional spectral data CDR obtained in the step twodTo obtain fdAzimuth theta of corresponding sea clutteri：
Wherein v ispIs the moving speed of the ship-based platform, thetai∈[0,2π]；
Step three: orientation thetaiArray steering vector a (theta) corresponding to sea clutteri) Comprises the following steps:
step three and four: the azimuth theta obtained by the step oneiAntenna pattern error data r (theta)i) Constructing a corrected array steering vector
Wherein,represents a Hadamard product; r (theta)i) Azimuth theta of sea clutter corresponding to the error-affected antennaiAntenna pattern error data of (a);
step three and five: using modified array steering vectorsConstructing disturbed projection matrices
Wherein, IMThe unit array with the order of the array element number M is adopted, and the superscript H represents the conjugate transpose;
step three and six: using disturbed projection matricesObtaining an orientation of thetaiNormalized corrected orthogonal weighting method weight coefficient corresponding to sea clutter
Wherein s (theta) is a scanning circulation vector, and all angles are scanned by traversing theta;
step three, pseudo-ginseng: by traversing thetaiObtaining the normalized correction orthogonal weighting method weight coefficient corresponding to all the sea clutter
Step four: setting the width of the wide null as delta theta and theta in clutter azimuthiReconstructing K nulls in the vicinity of delta theta, and corresponding modified guide vectors to the reconstructed nullsGuide vector replacing correction in step threeObtaining a wide zero-trap beam forming method weight coefficient W according to the method in the third step; the specific process is as follows:
step four, firstly: finding out the corresponding sea clutter azimuth theta in the third step and the second stepiSetting the width of the wide null as delta theta, and constructing the corresponding angle of the improved null, wherein the reconstructed null number is K after improvement:
wherein, thetakThe angle corresponding to the k-th null is improved;
step four and step two: constructing a corresponding ideal array guide vector by using the K angles obtained in the first step:
step four and step three: constructing a modified array steering vector
Wherein, r (theta)k) Theta corresponding to the antenna affected by the errorkAngular antenna pattern error data;
step four: using modified array steering vectorsConstructing a projection matrix J corresponding to the wide zero-trap beam forming method:
wherein,the vector matrix is steered to the array after modification,
step four and five: obtaining a projection matrix J corresponding to the wide null method to obtain the azimuth thetajForming a method weight coefficient W by a wide zero-trap beam corresponding to the sea clutter:
scanning all angles by traversing theta;
step four and six: by traversing thetaiObtaining wide zero-trapped wave beam forming method weight coefficients W corresponding to all sea clutter;
step five: and (4) processing the three-dimensional spectral data CDR obtained in the step (II) by using the wide zero-notch beam forming method weight coefficient W obtained in the step (IV) to obtain angle multiplied by Doppler multiplied by distance three-dimensional spectral data after sea clutter suppression.
2. The method of claim 1, wherein the wide null notch beamforming method is based on compensating antenna pattern errors, and comprises: obtaining antenna directional diagram error data of each angle corresponding to the antenna affected by the error through active correction in the first step, and recording the antenna directional diagram error data as r (theta); the specific process is as follows:
the method comprises the following steps: the receiving array of the ship-borne high-frequency ground wave radar adopts a uniform linear array, the number of array elements is M, the spacing between the array elements is d, and the wavelength of the radar is lambda ═ c/f0C is the speed of light, f0Setting a target for a radar working carrier frequency in a direction with an included angle theta with the radar array;
the first step is: the array receives echo data of a target, on the basis of the data amplitude obtained by the first array element, the data amplitudes obtained by other array elements are respectively differed with the data amplitude of the first array element, and the obtained difference is recorded as the amplitude disturbance rho in the theta directionm(θ),m＝1,2,...,M；
Wherein m represents the mth array element, and theta represents the arrangement included angle between the target and the radar array;
based on the data phase obtained by the first array element, the data phases obtained by other array elements are respectively differenced with the data phase obtained by the first array element, and then the original phase difference d/lambda (m-1) · cos theta among the array elements is subtracted, and the difference is recorded as the phase perturbation in the theta direction
Step one is three: processing the obtained amplitude disturbance and phase disturbance to obtain antenna directional diagram error data with the direction of thetaThe superscript T stands for transpose, j is an imaginary unit, j2＝-1；
And rotating the target placement angle by 0-360 degrees, and scanning the target placement angle at intervals of 1 degree to obtain antenna directional diagram error data of each angle.
3. The method of claim 2, wherein the wide null notch beamforming method is based on compensating antenna pattern errors, and comprises: in the second step, the echo data of the ship-borne high-frequency ground wave radar is subjected to pulse compression and coherent accumulation processing to obtain three-dimensional spectrum data of channel multiplied by Doppler multiplied by distance, and the three-dimensional spectrum data is recorded as CDR; the specific process is as follows:
step two, firstly: performing pulse compression on echo data of a target received by the array, and performing N-1 section truncation processing to obtain N distance units;
step two: performing FFT processing on all accumulated echoes of each distance unit, and performing coherent accumulation to obtain L Doppler units, and finally obtaining three-dimensional spectral data of channel multiplied by Doppler multiplied by distance, which is recorded as CDR;
the FFT is a fast fourier transform.
4. The method of claim 3, wherein the wide null notch beamforming method is based on compensating antenna pattern errors, and comprises: scanning cycle vector s (theta) ═ s in the third step and the sixth step1θ(θ),...,smθ(θ),...,sMθ(θ)]TThe size of which is Mx 1, smθ(theta) is the mth element in the scan cycle vector,the superscript T stands for transpose.
5. The method of claim 4, wherein the wide null notch beamforming method comprises: processing the three-dimensional spectral data CDR obtained in the step two by using the weight coefficient W of the wide zero-trap beam forming method obtained in the step four to obtain angle multiplied by Doppler multiplied by distance three-dimensional spectral data after sea clutter is suppressed; the specific process is as follows:
step five, first: selecting the CDR data acquired in the step two, selecting a certain range-Doppler unit, finding the position of the sea clutter according to the Doppler corresponding unit, and processing the data of the certain range-Doppler unit by using the wide zero notch beam forming method weight coefficient W obtained in the step four to obtain an angle spectrum with one range-Doppler unit clutter filtered;
step five two: and traversing the range-Doppler unit to obtain angle multiplied by Doppler multiplied by range three-dimensional spectral data after sea clutter is inhibited.
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