CN111781603B - Ground clutter suppression method for airborne weather radar - Google Patents
Ground clutter suppression method for airborne weather radar Download PDFInfo
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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
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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
- G01S7/023—Interference mitigation, e.g. reducing or avoiding non-intentional interference with other HF-transmitters, base station transmitters for mobile communication or other radar systems, e.g. using electro-magnetic interference [EMI] reduction techniques
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- G01S7/28—Details of pulse systems
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- 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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- 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
- G01S7/2928—Random or non-synchronous interference pulse cancellers
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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
- G01S7/41—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 invention discloses a ground clutter suppression method of an airborne weather radar, which comprises the following steps: 1) Determining prior knowledge of radar system parameters, ground clutter and meteorological target distribution geometric relations by adopting an area array antenna; 2) Obtaining a ground clutter pitch angle, a ground clutter azimuth angle, a meteorological target pitch angle and a meteorological target azimuth angle through distance circulation and azimuth circulation, and accordingly obtaining respective time domain guide vectors and airspace two-dimensional guide vectors of the ground clutter pitch angle, the ground clutter azimuth angle, the meteorological target pitch angle and the meteorological target azimuth angle; 3) Obtaining a ground clutter and meteorological target three-dimensional space-time guide vector by a time domain guide vector, an azimuth dimension guide vector and a pitching dimension guide vector; 4) Obtaining a snapshot signal and a covariance matrix of ground clutter and a meteorological target by using the three-dimensional guide vector; 5) After the covariance matrix is obtained, full-dimensional optimal processing is carried out to obtain a weight vector, and the weight vector is used for filtering the snapshot signal. The method can improve the estimation precision and the convergence rate, can effectively improve the detection performance of the system in a non-uniform environment, and has good clutter suppression effect.
Description
Technical Field
The invention belongs to the technical field of ground clutter suppression of airborne weather radar and the technical field of array signal processing, and particularly relates to a ground clutter suppression method of airborne weather radar
Background
The airborne weather radar is an important electronic device of the aircraft, and can detect and early warn disaster weather such as thunderstorm, turbulence and wind shear existing in front of a flight path in real time, so that a pilot is guided to avoid a dangerous area. Currently, the manufacturers of airborne weather radars mainly include two companies, collins and Honeywell. The airborne weather radar usually works in a down-looking mode, and at this time, the echo of the airborne weather radar not only contains a weather target, but also contains noise and ground clutter, so that main lobes and side lobe ground clutter must be effectively restrained to identify the weather target, and the false alarm probability is reduced. As shown in fig. 1, when the radar transmits and receives signals downwards at a certain pitch angle, the same distance gate in the echo has both weather clutter and ground clutter signals, but the depression angle of the weather target and the ground clutter is different, so that the ground clutter can be better suppressed by expanding the traditional two-dimensional space-time adaptive processing (2D-STAP) to the three-dimensional space-time adaptive processing (3D-STAP) on the basis of increasing pitch dimension information. The conventional 2D-STAP generally synthesizes a two-dimensional area array into a one-dimensional horizontal linear array by adopting a column weighted synthesis mode, namely, clutter suppression is performed by using only azimuth domain and doppler domain information, and pitch domain information is ignored. The 3D-STAP fully utilizes the pitch dimension information to perform joint self-adaptive processing in the space domain two-dimensional and the time domain, so that not only can the ground clutter suppression performance be improved, but also the robustness is good. However, in the prior art, the application of 3D-STAP technology to ground clutter suppression and weather detection of airborne weather radar has not been described.
Currently, the main ground clutter suppression techniques can be divided into the following categories: 1) Ground clutter suppression techniques based on beam multiscanning. Determining the scanning range of the main beam to the ground according to the aircraft track by utilizing a geometric relation, continuously adjusting the pitch angle of an antenna to generate echoes of different space positions, and then superposing data which are not interfered by clutter on certain range gates together to achieve the aim of suppressing clutter; 2) Frequency domain based ground clutter suppression techniques. According to the model of the meteorological echo and the ground clutter, after Doppler compensation is carried out on the echo, the meteorological target is not zero point in the frequency domain and occupies a large range, and the ground clutter is distributed near the zero point in the frequency domain and has a small range. A proper zero-notch filter is designed according to the characteristics, so that ground clutter components can be effectively restrained; 3) Clutter suppression technology based on airspace adaptive filtering. Because the meteorological target and the ground object have height difference information, the space domain cancellation weight coefficient is accurately estimated according to echo data generated in a two-channel mode, the acquired cancellation weight coefficient is utilized to perform two-channel cancellation, and the components of the meteorological target after cancellation are reserved, so that the aim of ground clutter suppression is fulfilled. 4) Ground clutter suppression in multi-polarization mode. The polarization scattering characteristics of the targets can be utilized to identify non-meteorological signals caused by meteorological and sea clutter, flying birds and insects and the like, and interference of the non-meteorological signals on radar display is reduced, so that clutter suppression capability is further enhanced. In view of the above, many researchers have conducted intensive studies at home and abroad.
In the above disclosed technical solution, the solution 1) is easily limited by flight conditions, and the effect of suppressing the middle-distance clutter is not obvious; scheme 2) because the carrier motion can cause the echo frequency spectrum to be shifted and widened, the difference between the meteorological target frequency spectrum and the ground clutter frequency spectrum is not very large, and therefore the suppression effect is not obvious relative to the ground radar; in the scheme 3), due to the existence of uncertain factors such as channel amplitude-phase errors, antenna direction pointing errors and the like, the estimated airspace cancellation weight coefficient often deviates from an actual value, and the clutter suppression effect is affected; scheme 4) the acquisition of raw data is difficult, and the processing of polarization information generally requires higher clutter polarization, and the movement of the carrier expands the clutter spectrum, so that the application of the polarization information to the airborne weather radar alone increases great difficulty. In view of the above problems, how to achieve effective suppression of ground clutter under various complex conditions is still a key problem to be solved in practical processing.
Disclosure of Invention
The technical problem to be solved by the invention is to provide the ground clutter suppression method for the airborne weather radar, which can overcome the difficulty under the influence of various factors to effectively suppress the ground clutter and overcome the influence of the non-uniform clutter environment and the limitation of independent samples distributed in the same way in practice.
In order to solve the technical problems, the invention adopts the following technical scheme:
an airborne weather radar ground clutter suppression method comprises the following steps:
1) Determining prior knowledge of radar system parameters, ground clutter and meteorological target distribution geometric relations by adopting an area array antenna;
2) Obtaining a ground clutter pitch angle, a ground clutter azimuth angle, a meteorological target pitch angle and a meteorological target azimuth angle through distance circulation and azimuth circulation, and accordingly obtaining respective time domain guide vectors and airspace two-dimensional guide vectors of the ground clutter pitch angle, the ground clutter azimuth angle, the meteorological target pitch angle and the meteorological target azimuth angle;
3) Obtaining a ground clutter and meteorological target three-dimensional space-time guide vector by a time domain guide vector, an azimuth dimension guide vector and a pitching dimension guide vector;
4) Obtaining a snapshot signal and a covariance matrix of ground clutter and a meteorological target by using the three-dimensional guide vector;
5) After the covariance matrix is obtained, full-dimensional optimal processing is carried out to obtain a weight vector, and the weight vector is used for filtering the snapshot signal.
Further, in the step 1), an area array antenna is adopted, and the prior knowledge process of determining the radar system parameters, the ground clutter and the meteorological target distribution geometrical relationship is as follows: each array element in the array antenna system is arranged into an area array at a certain interval in the vertical height and the horizontal direction, then the prior knowledge of the distribution geometrical relationship of radar system parameters, ground clutter and meteorological targets is determined, and the following structured STAP technology is adopted for laying.
Further, in the step 2), a ground clutter pitch angle, a ground clutter azimuth angle, a meteorological target pitch angle and a meteorological target azimuth angle are obtained through distance circulation and azimuth circulation, so that the time domain guide vector and the airspace two-dimensional guide vector of the ground clutter pitch angle, the ground clutter azimuth angle, the meteorological target pitch angle and the meteorological target azimuth angle are respectively obtained, and the process is as follows: obtaining pitch angles and azimuth angles of ground clutter and meteorological targets from distance to azimuth, and respectively constructing a time domain guide vector, a pitch dimension guide vector and an azimuth dimension guide vector of the ground clutter and the meteorological targets; the time domain guide vector consists of M pulses; the pitching dimension guide vector consists of P pitching arrays; the azimuth dimension guide vector is composed of N azimuth arrays.
Further, in the step 3), the three-dimensional space-time guiding vector process of the ground clutter and the meteorological target can be obtained by using the time domain guiding vector, the azimuth guiding vector and the pitch guiding vector is as follows: after obtaining a time domain guide vector, an azimuth guide vector and a pitch dimension guide vector from distance to azimuth, carrying out Kronecker direct product on the time domain guide vector, the azimuth guide vector and the pitch dimension guide vector to obtain a three-dimensional space-time guide vector.
Further, in the step 4), the process of obtaining the snapshot signals and the covariance matrix of the ground clutter and the meteorological target from the three-dimensional guide vector is as follows: and performing conjugate transposition on the time domain guiding vector, the azimuth guiding vector and the elevation guiding vector, and performing Kronecker direct product to obtain covariance matrixes of the time domain guiding vector, the azimuth guiding vector and the elevation guiding vector.
Further, after the covariance matrix is obtained in the step 5), performing full-dimensional optimization to obtain a weight vector, and performing a filtering process on the snapshot signal by using the weight vector, wherein the filtering process comprises the following steps: according to step 4), obtaining weight values by the covariance matrix of ground clutter and noise and the meteorological target guide vector according to the full-dimensional self-adaptive processing, and multiplying the weight values with the snapshot signals to obtain filtered signals
The invention discloses a ground clutter suppression method of an airborne weather radar, which is based on a three-dimensional space-time adaptive processing algorithm, can overcome the influence of a non-uniform clutter environment in practice and the limitation of independent and uniformly distributed samples, and can fully utilize priori information, namely directly construct a vector matrix model of ground clutter and a vector matrix model of a weather target according to known clutter structures, weather target characteristics, system parameters and space geometric relations. According to the principle of the airborne weather radar ground clutter suppression method based on the three-dimensional space-time adaptive processing algorithm, the three-dimensional space-time adaptive processing is utilized, and the weather target is optimally separated from the ground clutter and the noise environment through the combined processing of the pitching domain, the Doppler domain and the azimuth domain. The method solves the problems of radar scanning limitation, doppler spectrum broadening, inaccurate airspace estimation of the cancellation coefficient, influence of a non-uniform clutter environment in practice, limitation of independent samples with the same distribution and the like in the traditional method, ground clutter suppression performance reduction caused by the factors and the like, and simulation results show that the airborne weather radar ground clutter suppression method based on the three-dimensional space-time adaptive processing algorithm is a feasible ground clutter suppression method.
Drawings
FIG. 1 is a schematic diagram of the spatial geometry of the data received by a weather radar;
FIG. 2 is a schematic diagram of three-dimensional space-time adaptive data processing;
FIG. 3 is a process flow of ground clutter suppression for three-dimensional space-time adaptive processing;
FIG. 4 is a slice of a three-dimensional power spectrum at a meteorological target;
FIG. 5 (a) is an azimuth sine value-Doppler frequency two-dimensional planar weather and ground clutter power spectrum;
FIG. 5 (b) is a pitch angle sine value-Doppler frequency two-dimensional planar meteorological and ground clutter power spectrum;
FIG. 5 (c) is an azimuth sine value-pitch sine value two-dimensional planar weather and ground clutter power spectrum;
FIG. 6 is a slice of a three-dimensional adaptive antenna pattern at a meteorological target;
fig. 7 (a) is a pitch angle sine value-doppler frequency two-dimensional planar adaptive antenna pattern;
fig. 7 (b) is an azimuth sine value-elevation sine value two-dimensional planar adaptive antenna pattern;
FIG. 7 (c) is a 2D-STAP azimuthal sine value-Doppler frequency two-dimensional planar antenna pattern;
FIG. 7 (D) is a 3D-STAP azimuthal sine value-Doppler frequency two-dimensional planar antenna pattern;
FIG. 8 (a) is an azimuth section at a meteorological target;
FIG. 8 (b) is a Doppler frequency profile at a meteorological target;
FIG. 9 is a three-dimensional improvement factor slice;
FIG. 10 (a) is a diagram of azimuth dimension improvement factors;
fig. 10 (b) is a doppler domain improvement factor graph.
FIG. 11 (a) is a graph of residual power after filtering that the meteorological target is near the primary clutter;
FIG. 11 (b) is a graph of residual power after filtering the meteorological target near side lobe clutter.
Detailed Description
The following describes a control algorithm for the contour error of a servo system according to the present invention in detail with reference to the accompanying drawings.
The invention discloses a ground clutter suppression method of an airborne weather radar, which adopts an area array antenna to determine prior knowledge of radar system parameters, ground clutter and weather target distribution geometric relations, and then obtains a ground clutter pitch angle, a ground clutter azimuth angle, a weather target pitch angle and a weather target azimuth angle through distance circulation and azimuth circulation, thereby respectively obtaining respective time domain guide vectors and space domain two-dimensional guide vectors of the ground clutter pitch angle, the ground clutter azimuth angle, the weather target pitch angle and the weather target azimuth angle. The three-dimensional space-time guide vector of the ground clutter and the aerial image target is obtained by the time domain guide vector, the azimuth dimension guide vector and the elevation dimension guide vector, and the snapshot signal and the covariance matrix of the ground clutter and the aerial image target are obtained by the three-dimensional guide vector. After the covariance matrix is obtained, full-dimensional optimal processing is carried out to obtain a weight vector, and the weight vector is used for filtering the snapshot signal.
In view of the principle, the invention provides an airborne weather radar ground clutter suppression method based on a three-dimensional space-time adaptive processing algorithm, which can fully utilize the height difference of ground clutter and a meteorological target to suppress the ground clutter in actual processing, and the simulation result shows that the 3D-STAP technology has greater superiority compared with the 2D-STAP technology by applying the airspace filtering principle in array signal processing and the moving target detection and clutter suppression characteristics of STAP technology.
The three-dimensional space-time adaptive processing adopts an area array to receive data. As shown in FIG. 1, the working wavelength is lambda, the radar antenna is positioned on yoz plane, P×N units are adopted to form a two-dimensional planar array, and the distance between array elements is d respectively z And d y The height of the carrier from the ground is H, and the speed v is the same as the speed v a Flying parallel to the direction of the antenna plane array (front side view). In the diagram, the meteorological target and ground clutter appear in the same range gate, θ c Represents the ground clutter pitch angle, and the depression angle of the meteorological target is theta w Phi is azimuth angle (theta appearing hereinafter c_i An ith pitch angle, θ, representing ground clutter w_ι Iota pitch angle, phi representing meteorological target c_j Indicating the jth azimuth of the ground clutter,indicating weather object->A number of azimuth angles). The process flow is shown in fig. 3, and the main steps are as follows:
1) Determining prior knowledge of radar system parameters, ground clutter and meteorological target distribution geometric relations by adopting an area array antenna;
in order to overcome the problems of the influence of the non-uniform clutter environment and the limitation of independent samples distributed in the same way in practice, priori knowledge can be fully utilized, so that a three-dimensional structured space-time self-adaptive method is adopted to pad the following steps.
2) Obtaining a ground clutter pitch angle, a ground clutter azimuth angle, a meteorological target pitch angle and a meteorological target azimuth angle through distance circulation and azimuth circulation, and accordingly obtaining respective time domain guide vectors and airspace two-dimensional guide vectors of the ground clutter pitch angle, the ground clutter azimuth angle, the meteorological target pitch angle and the meteorological target azimuth angle;
for a given range gate, NPM echoes can be obtained from M pulses, N azimuth dimension antenna elements, P elevation dimension antenna elements. The following definitionsPitch-dimensional steering vector for ground clutterTime-dimensional steering vector->And an azimuth dimension steering vector a (ζ) ij ) Their expressions are as follows:
in the above formula, the symbol "e" represents an exponential function based on e, the superscript T represents a matrix transpose,represents pitch dimensional spatial frequency, ζ, at the ith pitch angle of ground clutter ij Represents the azimuth dimensional space frequency at the ith pitch angle and the jth azimuth angle of ground clutter, +.>The normalized Doppler frequency generated by the ground clutter at the ith pitch angle and the jth azimuth angle is represented as follows:
in the above, f c_ij ＝2v a cosθ c_i sinφ c_j Lambda is the Doppler shift of the ground clutter, f r Is the pulse repetition frequency and lambda is the wavelength. Similarly, the meteorological target pitch dimension guide vector ε (ρ ι ) Direction-dimensional guide vectorAnd a time-dimensional steering vector->They are represented as follows:
in the above, ρ ι The pitch dimensional spatial frequency at the iota pitch angle of the meteorological target is represented,indicating the first pitch angle, the first ∈>Azimuth dimensional space frequency at azimuth, +.>Indicating the first pitch angle, the first ∈>Normalized Doppler frequencies generated at each azimuth are expressed as follows:
in the above-mentioned method, the step of,is the iota pitch angle, the +.>Doppler shift of meteorological target at each azimuth.
3) Obtaining a ground clutter and meteorological target three-dimensional space-time guide vector by a time domain guide vector, an azimuth dimension guide vector and a pitching dimension guide vector;
three-dimensional space-time steering vector S of ground clutter at ith pitch angle and jth azimuth angle c_ij Can be expressed as:
similarly, the meteorological target is at the first pitch angle and the first pitch angleThree-dimensional space-time steering vector of individual azimuth angles>Can be expressed as:
in the above-mentioned method, the step of,represents the Kronecker direct product, wherein +.>Representing the disturbance amplitude, sigma, of the time domain of a meteorological target v The motion variance of the meteorological target is reflected in the motion intensity of the meteorological target, G is the number of distance gates distributed by the meteorological target, and the Hadamard product is indicated by the following weight.
4) Obtaining a snapshot signal and a covariance matrix of ground clutter and a meteorological target by using the three-dimensional guide vector;
ground clutter snapshot signal X c The sum of echoes of all clutter scattering points within the equidistant ring for all range gates is expressed as:
in the above description, nr is the number of distance gates for generating ground clutter (the number of the distance gates for the ground clutter is the same as the number of pitch angles), J is the number of clutter azimuth directions, η ij The ground clutter amplitude for the ith range gate, the jth azimuth.
Ground clutter covariance matrix R c Can be expressed as:
in the above equation, the symbol "E" indicates a mathematical expectation.
Similarly, meteorological target snapshot signal X w Expressed as:
in the above formula, G is the number of distance gates of the meteorological distribution (the number of distance gates of the meteorological target is consistent with the number of pitch angles), J is the number of azimuth directions of the meteorological distribution,for the iota distance gate, the +.>The magnitude of the meteorological target amplitude for each bearing.
The covariance matrix of the meteorological target is expressed as:
5) After the covariance matrix is obtained, full-dimensional optimal processing is carried out to obtain a weight vector, and the weight vector is used for filtering the snapshot signal.
In order to minimize the power of the remaining clutter plus noise in the output and obtain the maximum output signal to noise ratio (SCNR), according to the minimum output energy criterion of Linear Constraint (LCMV), there is the constraint equation:
in the above formula, r=r c +R w Representing the sum of the ground clutter covariance matrix and the meteorological target covariance matrix. S is S w Is expressed in any iota pitch angleAnd the three-dimensional space-time guiding vector of the meteorological target obtained by the azimuth angles. w represents a weight vector, and the optimal weight vector is obtained by a Lagrangian multiplier method:
w opt ＝ηR -1 (12)
where η is the high resolution spectral estimate (Capon spectrum) that constitutes the beamformer, expressed as:
in the above, R -1 Is the inverse of R.
Array output of full-dimensional optimization:
in the above formula, x=x c +X w Representing the sum of the ground clutter snapshot and the meteorological target snapshot.
The airborne weather radar ground clutter suppression method based on the three-dimensional space-time adaptive processing algorithm provided by the invention is used for simulation verification, and experimental results fully prove the effectiveness of the method.
The experiment adopts a rectangular plane array 8 multiplied by 8, the pitching beam is directed to be 8 degrees away from the normal direction of the array surface, and the horizontal beam is directed to be 0 degree away from the normal direction of the array surface. Because of the internal motion of the meteorological target, the motion variance of the meteorological target is assumed to be sigma v =2, pitch of 30km, azimuth angle 5 °, pitch angle θ w =8°, doppler frequency 200Hz. The clutter generating distance range is 25 km-35 km, the distance is 100m, the azimuth generating range is-13 degrees, and each azimuth range is divided into 200 clutter scattering units at equal intervals on each range gate.
Table 1 radar simulation parameters
Fig. 4 is a slice view of a three-dimensional power spectrum at a meteorological target during a front side view movement of an airborne radar, and fig. 5 is a cross-sectional view of the three-dimensional power spectrum. Ground clutter and meteorological targets can be well distinguished by using pitch dimension information. FIG. 6 shows a slice of a three-dimensional adaptive antenna pattern at a meteorological target. Fig. 7 (a), (b) and (D) are cross-sectional views of three-dimensional space-time adaptive antenna patterns, fig. 7 (c) and (D) are azimuth sine value-doppler frequency two-dimensional planar adaptive antenna patterns obtained by 2D-STAP and 3D-STAP, respectively, fig. 8 is a cross-sectional view of both fig. 7 (c) and (D), the 3D-STAP adaptive antenna patterns can obtain the highest gain at the target, whereas the 2D-STAP ignores the pitch dimension information, cannot form the highest gain at the target, resulting in the filtering of the meteorological signals, and a higher gain in the clutter region will result in clutter retention. Fig. 9 shows a three-dimensional improvement factor slice. FIG. 10 is a graph comparing improvement factors of 3D-STAP and 2D-STAP, and it can be seen that 3D-STAP achieves a maximum improvement factor of about 18dB greater than 2D-STAP and a minimum improvement factor of about 19dB greater than 2D-STAP. FIG. 11 (a) is a comparison of the 3D-STAP method and the 2D-STAP method filtered residual power output of a meteorological target near the main clutter, FIG. 11 (b) is a comparison of the 3D-STAP method and the 2D-STAP method filtered residual power output of a meteorological target near the sidelobe clutter, where the solid line is the 3D-STAP process and the dashed line is the 2D-STAP process. When the meteorological signals are in the main clutter region, the meteorological signals processed by the 2D method are submerged in the clutter, and the meteorological signals processed by the 3D method are 13dB higher than the clutter, so that the meteorological signals can be completely detected. When the meteorological signals are near the side lobe clutter, the meteorological signals processed by the 2D method are 6dB higher than the clutter and can be detected, and the meteorological signals processed by the 3D method are 19dB higher than the clutter and can be completely detected.
Claims (5)
1. The ground clutter suppression method for the airborne weather radar is characterized by comprising the following steps of: the method comprises the following steps:
1) Determining prior knowledge of radar system parameters, ground clutter and meteorological target distribution geometric relations by adopting an area array antenna;
2) Obtaining a ground clutter pitch angle, a ground clutter azimuth angle, a meteorological target pitch angle and a meteorological target azimuth angle through distance circulation and azimuth circulation, and accordingly obtaining respective time domain guide vectors and airspace two-dimensional guide vectors of the ground clutter pitch angle, the ground clutter azimuth angle, the meteorological target pitch angle and the meteorological target azimuth angle;
3) Obtaining a ground clutter and meteorological target three-dimensional space-time guide vector by a time domain guide vector, an azimuth dimension guide vector and a pitching dimension guide vector;
4) Obtaining a snapshot signal and a covariance matrix of ground clutter and a meteorological target by using the three-dimensional guide vector;
5) After obtaining the covariance matrix, carrying out full-dimensional optimal processing to obtain a weight vector, and filtering the snapshot signal by using the weight vector;
in the step 4), the process of obtaining the snapshot signals of the ground clutter and the meteorological target and the covariance matrix by the three-dimensional guide vector is as follows: and performing conjugate transposition on the time domain guiding vector, the azimuth guiding vector and the elevation guiding vector, and performing Kronecker direct product to obtain covariance matrixes of the time domain guiding vector, the azimuth guiding vector and the elevation guiding vector.
2. The airborne weather radar ground clutter suppression method according to claim 1, wherein: the prior knowledge process for determining the geometrical relationship among radar system parameters, ground clutter and meteorological target distribution by adopting an area array antenna in the step 1) is as follows: each array element in the array antenna system is arranged into an area array at a certain interval in the vertical height and the horizontal direction, then the prior knowledge of the distribution geometrical relationship of radar system parameters, ground clutter and meteorological targets is determined, and the following structured STAP technology is adopted for laying.
3. The airborne weather radar ground clutter suppression method according to claim 1, wherein: in the step 2), a ground clutter pitch angle, a ground clutter azimuth angle, a meteorological target pitch angle and a meteorological target azimuth angle are obtained through distance circulation and azimuth circulation, so that the time domain guide vector and the space domain two-dimensional guide vector of the ground clutter pitch angle, the ground clutter azimuth angle, the meteorological target pitch angle and the meteorological target azimuth angle are respectively obtained, and the process is as follows: obtaining pitch angles and azimuth angles of ground clutter and meteorological targets from distance to azimuth, and respectively constructing a time domain guide vector, a pitch dimension guide vector and an azimuth dimension guide vector of the ground clutter and the meteorological targets; the time domain guide vector consists of M pulses; the pitching dimension guide vector consists of P pitching arrays; the azimuth dimension guide vector is composed of N azimuth arrays.
4. The airborne weather radar ground clutter suppression method according to claim 1, wherein: in the step 3), the three-dimensional space-time guiding vector process of the ground clutter and the meteorological target can be obtained by using the time domain guiding vector, the azimuth guiding vector and the pitching guiding vector, and the three-dimensional space-time guiding vector process comprises the following steps: after obtaining a time domain guide vector, an azimuth guide vector and a pitch dimension guide vector from distance to azimuth, carrying out Kronecker direct product on the time domain guide vector, the azimuth guide vector and the pitch dimension guide vector to obtain a three-dimensional space-time guide vector.
5. The airborne weather radar ground clutter suppression method according to claim 1, wherein: after the covariance matrix is obtained in the step 5), carrying out full-dimensional optimal processing to obtain a weight vector, and then carrying out a filtering process on the snapshot signal by using the weight vector, wherein the filtering process comprises the following steps: according to the step 4), the weight is obtained by the covariance matrix of the ground clutter and the noise and the meteorological target guide vector according to the full-dimensional self-adaptive processing, and then the filtered signal is obtained by multiplying the weight with the snapshot signal.
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