Array element level echo DBF method of stepped array plane radar

Abstract

The invention belongs to the field of radar information processing, and particularly relates to an array element level echo DBF method of a stepped array plane radar. The method comprises a step of generating a beam pointing direction steering vector and a step of generating an antenna pattern. And a step of generating a DBF of array element level echoes. According to the invention, the array elements are arranged in a step shape, and the main lobe width of an antenna pattern is the same as that of a square matrix with the same length and width on the premise that the number of the array elements is limited.

Description

Technical Field

[0001] The present invention belongs to the field of radar information processing, and particularly relates to an element-level echo DBF method for a stepped array radar. Technical Background

[0002] DBF is an indispensable signal processing step for modern phased array radars. However, when actually building a radar, due to cost issues, the number of array elements of the radar array is too small. If arranged in a two-dimensional square array, the main lobe width of the antenna pattern is too wide.

[0003] Due to the distribution characteristics of each sub-array in the stepped array, the calculation of the steering vector is much more complex than that of a two-dimensional square array. Generally, it is necessary to equivalent the stepped array to a two-dimensional square array with the same length and width for calculation. At the positions where array elements are missing, their weighting values are set to 0 and removed from the steering vector. Although the results obtained by this calculation method are correct, it is very troublesome and error-prone to find the positions of the weighting values of the missing array elements in the steering vector. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the present invention provides an element-level echo DBF method for a stepped array radar. The present invention includes the generation of the steering vector of the stepped array phased array radar, the generation of the antenna pattern, and DBF. The present invention arranges the array elements in a stepped shape. On the premise of limited number of array elements, the main lobe width of the antenna pattern is the same as that of a square array with the same length and width.

[0005] The technical solution of the present invention is: an element-level echo DBF method for a stepped array radar, and the specific steps are as follows:

[0006] Step 1: Generation of the steering vector in the beam pointing direction

[0007] Step 1a): Generation of the sub-array steering vector

[0008] Assume that the number of sub-array elements in the horizontal direction is Ny, the number of sub-array elements in the vertical direction is Nz, and the ratio of the element spacing to the wavelength is dl. Then the sub-array steering vector is:

[0009]

[0010] Vs zn = exp(j * 2 * π * dl * n * sin(θ))

[0011] Vs y = [Vs y0 , Vs y1 , … Vs y(Ny-1)

[0012] Vs z = [Vs z0 , Vs z1 ​,…Vs z(Nz-1)

[0013] Vs = kron(Vs y , Vs z )

[0014] In the above formula, Vs y is the steering vector of the horizontal sub - array, Vs z is the steering vector of the vertical sub - array, Vs is the total steering vector of the sub - array, j is the imaginary unit, j 2 = - 1, kron(x, y) is to calculate the Kronecker product of x and y, m is the element number in the horizontal direction of the sub - array, and its value range is [0, Ny - 1], n is the element number in the vertical direction of the sub - array, and its value range is [0, Nz - 1], θ is the elevation angle of the beam pointing, is the azimuth angle of the beam pointing;

[0015] Step 1b): Generation of the steering vector of the stepped array surface

[0016] The phase shift between adjacent sub - arrays is:

[0017]

[0018] If the number of sub - arrays is Nl, the steering vectors of different sub - arrays are:

[0019] Vs i = Vs * exp(j * i * phs)

[0020] In the above formula, i is the sub - array number, and its value range is [0, Nl - 1], and the total steering vector of the stepped array surface is:

[0021] V = [Vs0, Vs1,... Vs (Nl-1)

[0022] Among them, Vs0, Vs1, etc. are the steering vectors of different sub - arrays, all of which are row vectors. If it is a multi - beam radar, V is the steering matrix. By repeating Step 1, the steering vectors of all beam directions can be obtained and then arranged into the steering matrix.

[0023] The beneficial effect of this step is that it can generate the steering vector of the stepped array as a whole according to the steering vector of the small square array, avoiding the cumbersome problem in the process of obtaining the steering vector of a single element.

[0024] Step 2: Generation of the antenna pattern

[0025] Step 2a): Quantize and sample the elevation angle and azimuth angle within the antenna scanning range to obtain the elevation angle sequence and azimuth angle sequence;

[0026] ​​Step 2b): Select a pair of elevation angle and azimuth angle from the elevation angle sequence and the azimuth angle sequence, and calculate its steering column vector V n ;

[0027] Step 2c): Calculate the matrix multiplication according to the following formula:

[0028] patternData = conj(V) * V n

[0029] In the above formula, patternData is the antenna pattern weighting value in the direction corresponding to the selected elevation angle and azimuth angle;

[0030] Step 2d): Repeat steps 2b and 2c, traverse all the elevation angles and azimuth angles in the elevation angle sequence and the azimuth angle sequence, and arrange the obtained patternData according to elevation and azimuth to obtain a two-dimensional antenna pattern.

[0031] The beneficial effect of this step is that the DBF gain in different azimuths and elevations can be obtained through the generated antenna pattern of the stepped array surface.

[0032] Step 3: DBF of element-level echo

[0033] Step 3a): Receive the element-level echo data of the actual radar or the element-level echo data of the simulated radar, and arrange the echo data into a matrix S according to different elements. The number of rows of S is the number of elements, and the number of columns is the number of sampling points in the range dimension;

[0034] Step 3b): Use the steering vector V obtained in step 1 to calculate according to the following formula:

[0035] echo = conj(V) * S

[0036] In the above formula, echo is the result vector after DBF. If it is a multi-beam radar, echo is the result matrix, and different rows of the matrix store the DBF results of different beams.

[0037] The beneficial effect of this step is that the echo signal received by the stepped array antenna can be DBF, so that the target echo is enhanced.

[0038] The beneficial effect of the present invention is to propose an implementation method of the steering vector, antenna pattern and DBF of the array antenna for the stepped antenna element arrangement. Through the method described in the present invention, the echo signal received by the stepped antenna array can be spatially filtered and the target signal can be enhanced. Brief Description of the Drawings

[0039] Figure 1 Arrangement diagram of elements on the stepped array surface.

[0040] Figure 2 Antenna pattern of Embodiment 2 with beam pointing at an azimuth angle of -30 degrees.

[0041] Figure 3 Antenna pattern of Embodiment 2 with beam pointing at an azimuth angle of 0 degrees.

[0042] Figure 4 Antenna pattern of Embodiment 2 with beam azimuth angle of 20 degrees.

[0043] Figure 5 Azimuthal dimension antenna pattern of Embodiment 2 with beam azimuth angle of 0 degrees.

[0044] Figure 6 Elevation dimension antenna pattern of Embodiment 2 with beam azimuth angle of 0 degrees.

[0045] Figure 7 Azimuthal dimension antenna pattern of a two-dimensional square array with the same length and width as the stepped array in Embodiment 2.

[0046] Figure 8 Elevation dimension antenna pattern of a two-dimensional square array with the same length and width as the stepped array in Embodiment 2.

[0047] Figure 9 Received echo pulse compression result of element 0 without DBF

[0048] Figure 10 DBF result of Embodiment 3 with beam azimuth angle of -30 degrees.

[0049] Figure 11 DBF result of Embodiment 3 with beam azimuth angle of 0 degrees.

[0050] Figure 12 DBF result of Embodiment 3 with beam azimuth angle of 20 degrees.

[0051] Explanation of terms: DBF: Digital Beamforming. Detailed implementation manners

[0052] The technical solutions provided by the present invention will be described in detail below in conjunction with specific embodiments. It should be understood that the following specific implementation manners are only used to illustrate the present invention and not to limit the scope of the present invention.

[0053] As Figures 1 to 12 shown, the element-level echo DBF method of a stepped array radar of the present invention specifically includes the following steps:

[0054] Step 1: Generation of beam pointing direction steering vector

[0055] Step 1a): Generation of sub-array steering vector

[0056] Let the number of elements in the horizontal sub - array be Ny, the number of elements in the vertical sub - array be Nz, and the ratio of the element spacing to the wavelength be dl. Then the sub - array steering vector is as follows:

[0057]

[0058] Vs zn = exp(j * 2 * π * dl * n * sin(θ))

[0059] Vs y = [Vs y0 , Vs y1 , … Vs y(Ny-1)

[0060] Vs z = [Vs z0 , Vs z1 , … Vs z(Nz-1)

[0061] Vs = kron(Vs y , Vs z )

[0062] Among them, Vs y is the steering vector of the horizontal sub - array, Vs z is the steering vector of the vertical sub - array, Vs is the total steering vector of the sub - array, j is the imaginary unit, j 2 = - 1, kron(x, y) is to calculate the Kronecker product of x and y, m is the element serial number in the horizontal direction of the sub - array, and its value range is [0, Ny - 1], n is the element serial number in the vertical direction of the sub - array, and its value range is [0, Nz - 1], θ is the elevation angle of the beam pointing, is the azimuth angle of the beam pointing;

[0063] Step 1b): Generation of the stepped array surface steering vector

[0064] The phase shift between adjacent sub - arrays is:

[0065]

[0066] If the number of sub - arrays is Nl, the number of sub - arrays is greater than or equal to 2, and the sub - arrays form a step. The steering vectors of different sub - arrays are:

[0067] Vs i = Vs * exp(j * i * phs)

[0068] Among them, i is the sub - array serial number, and its value range is [0, Nl - 1]. The total stepped array surface steering vector is:

[0069] V = [Vs0, Vs1, … Vs​​(Nl-1)

[0070] Among them, Vs0, Vs1, etc. are different sub-array steering vectors, all of which are row vectors. If it is a multi-beam radar, V is the steering matrix. By repeating step 1, the steering vectors in all beam directions can be obtained and then arranged into a steering matrix.

[0071] The beneficial effect of this step is that it can generate the steering vectors of the stepped array as a whole based on the steering vectors of the small square array, avoiding the cumbersome problem of obtaining the steering vectors for each individual array element.

[0072] Step 2: Generation of antenna pattern

[0073] Step 2a): Quantize and sample the elevation angle and azimuth angle within the antenna scanning range to obtain an elevation angle sequence and an azimuth angle sequence;

[0074] Step 2b): Select a pair of elevation angle and azimuth angle from the elevation angle sequence and azimuth angle sequence, and calculate its steering column vector V n ;

[0075] Step 2c): Calculate the matrix multiplication according to the following formula:

[0076] patternData = conj(V)*V n

[0077] In the above formula, patternData is the weighted value of the antenna pattern in the direction corresponding to the selected elevation angle and azimuth angle;

[0078] Step 2d): Repeat steps 2b and 2c, traverse all elevation angles and azimuth angles in the elevation angle sequence and azimuth angle sequence, and arrange the obtained patternData according to elevation and azimuth to obtain a two-dimensional antenna pattern.

[0079] The beneficial effect of this step is that it can obtain the DBF gain in different azimuths and elevations through the generated antenna pattern of the stepped array surface.

[0080] Step 3: DBF of element-level echo

[0081] Step 3a): Receive the element-level echo data of the actual radar or the element-level echo data generated by simulation, and arrange the echo data into a matrix S according to different elements. The number of rows of S is the number of elements, and the number of columns is the number of sampling points in the range dimension;

[0082] Step 3b): Use the steering vector V obtained in step 1 and calculate according to the following formula:

[0083] echo = conj(V)*S

[0084] ​In the above test, echo is the result vector after DBF. If it is a multi-beam radar, echo is the result matrix, and different rows of the matrix store the DBF results of different beams.

[0085] Such as Figure 9 and Figure 11 , it can be known that after DBF, the target echo signal is enhanced by 40 dB, which is the same as the gain when the azimuth angle given by the antenna pattern in Figure 5 is 0 degree.

[0086] For a stepped radar array, as shown in the appendix Figure 1 , theoretically, the number of horizontal array elements Ny and the number of vertical array elements Nz can be different, and their value ranges are generally greater than or equal to 2. The horizontal array element spacing, vertical array element spacing, and horizontal and vertical spacings between adjacent different sub-arrays can also be different. For the convenience of calculating the steering vector, in the present invention, the horizontal array element spacing, vertical array element spacing, and horizontal and vertical spacings between adjacent different sub-arrays are all taken as the same value, which is d.

[0087] The advantage of the stepped array is that it expands the geometric size of the antenna by using a limited number of array elements, increasing the length and width of the antenna. Compared with a two-dimensional square array of the same length and width, the main lobe width of the antenna pattern is the same, the number of array elements is reduced a lot, and the subsequent device complexity is greatly reduced. However, since the number of array elements of the stepped array is less than that of a two-dimensional square array of the same length and width, the gain after DBF is not as good as that of a two-dimensional square array of the same length and width.

[0088] Due to the distribution characteristics of each sub-array of the stepped array, the calculation of the steering vector is much more complex than that of a two-dimensional square array. Generally, it is necessary to equivalent the stepped array to a two-dimensional square array of the same length and width for calculation. At the position where the array elements are missing, their weighting values are set to 0 and removed from the steering vector. Although the result obtained by this calculation method is correct, it is very troublesome and error-prone to find the position of the weighting value of the missing array element in the steering vector. The method for calculating the steering vector proposed in the present invention uses the phase relationship of different sub-arrays to directly solve the steering vector of the stepped array, avoiding this problem.

[0089] Example 1. Generation of the steering vector in the beam pointing direction

[0090] (1) The number of horizontal array elements of the sub-array array of the radar array is 5, the number of vertical array elements is 5, the number of sub-arrays is 4, the ratio of the array element spacing to the wavelength is 0.5, the number of radar beams is 3, the elevation angles of the three beams are all 0, and the direction angles are -30 degrees, 0 degrees, and 20 degrees respectively. First, calculate the steering vector of the beam pointing in the -30-degree direction, and its sub-array steering vector:

[0091]

[0092] Vszn = exp(j * 2 * π * dl * n * sin(θ))

[0093] Vs y = [Vs y0 , Vs y1 , … Vs y(Ny-1)

[0094] Vs z = [Vs z0 , Vs z1 , … Vs z(Nz-1)

[0095] Vs = kron(Vs y , Vs z )

[0096] where θ = -30, dl = 0.5, the ranges of m and n are both [0, 4], Ny and Nz are both 5, and the calculated Vs is a row vector with a dimension of 25.

[0097] (2) Calculate the steering vector of the total stepped array surface at -30 degrees:

[0098]

[0099] Vsi = Vs * exp(j * i * phs)

[0100] V* = [Vs0, Vs1, … Vs (Nl-1)

[0101] where Nl = 4, the value range of i is [0, 3], and V * is the steering vector corresponding to the beam in the -30 degree direction.

[0102] (3) Calculate the steering vectors of the beams in the 0 degree and 20 degree directions, and form a matrix V with V * . Each row of V corresponds to the steering vector of a different azimuth beam.

[0103] Example 2, Generation of Antenna Pattern

[0104] (1) The elevation angle sequence takes 512 points between 0 degrees and 60 degrees, and the azimuth angle sequence takes 1024 points between -60 degrees and 60 degrees;

[0105] (2) Select a pair of elevation angle and azimuth angle from the elevation angle sequence and azimuth angle sequence, and calculate its steering column vector V n ;

[0106] (3) Calculate the matrix multiplication according to the following formula:

[0107] ​​​patternData = conj(V) * V n

[0108] In the above test, patternData is the weighted value of the antenna pattern in the direction corresponding to the selected pitch angle and azimuth angle;

[0109] (4) Traverse all the pitch angles and azimuth angles in the pitch angle sequence and azimuth angle sequence, arrange the obtained patternData according to pitch and azimuth to obtain a 1024 * 512 matrix, and the two-dimensional antenna pattern is stored in the matrix.

[0110] Embodiment 3, DBF of element-level echo

[0111] (1) Perform DBF using simulation data. The transmitted signal is a linear frequency modulation signal. Set a target echo at the pointing where both the azimuth angle and the pitch angle are 0 degrees, 80 kilometers away from the radar; set a clutter at the spatial pointing where the azimuth angle is -30 degrees and the pitch angle is 0 degrees, 150 kilometers away from the radar array surface; set a dense false target interference at the spatial pointing where the azimuth angle is 20 degrees and the pitch angle is 0 degrees, 200 kilometers away from the radar; the echo data is stored in matrix S, and each row of S is the echo data received by the corresponding element;

[0112] (2) Use the beam steering matrix V generated in Embodiment 1 to perform DBF, and the formula is as follows:

[0113] echo = conj(V) * S

[0114] The result of DBF is stored in matrix echo.

[0115] For convenient observation, pulse compression is performed on the results of each beam after DBF. From Appendix Figure 5 and Appendix Figure 7 By comparison, it can be seen that the main lobe width in the azimuth dimension of the antenna pattern of the stepped array is the same as that of the antenna pattern of a two-dimensional square array with the same length and width. From Appendix Figure 6 and Appendix Figure 8 By comparison, it can be seen that the main lobe width in the pitch dimension of the antenna pattern of the stepped array is the same as that of the antenna pattern of a two-dimensional square array with the same length and width; from Appendix Figure 10 , Appendix Figure 11 and Appendix Figure 12 It can be seen that after DBF, the response signals (target signal, clutter signal, and interference signal) in the echo corresponding to the beam pointing are amplified, and the signals in other directions are suppressed, realizing spatial domain filtering.

[0116] As described above, this is only the best specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

[0117] The content not described in detail in the specification of the present invention belongs to the well-known technology of those skilled in the art.

Claims

1. An element-level echo DBF method for a stepped array radar, arranging the elements in a stepped shape, characterized in that, Including the following steps: Step 1: Generation of the steering vector of the beam pointing direction Step 1a): Generation of the steering vector of the sub-array The number of elements in the horizontal direction of the sub-array is Ny, the number of elements in the vertical direction of the sub-array is Nz, and the ratio of the element spacing to the wavelength is dl. Then the sub-array steering vector is: Vs zn = exp(j * 2 * π * dl * n * sin(θ)) Vs y = [Vs y0 , Vs y1 , … Vs y(Ny-1) ​ Vs z = [Vs z0 , Vs z1 , … Vs z(Nz-1) ​ Vs = kron(Vs y , Vs z ) Among them, Vs y is the steering vector of the horizontal subarray, Vs z is the steering vector of the vertical subarray, Vs is the total steering vector of the subarray, the value range of m is [0, Ny - 1], the value range of n is [0, Nz - 1], θ is the elevation angle of the beam pointing, is the azimuth angle of the beam pointing; Step 1b): Generation of the stepped array surface steering vector The phase shift between adjacent sub-arrays is: The number of sub-arrays is Nl, and the steering vectors of different sub-arrays are: Vs i = Vs * exp(j * i * phs) where the value range of i is [0, Nl - 1], and the total stepped array surface steering vector is: V = [Vs0, Vs1,... Vs (Nl-1) ; Step 2: Generation of the antenna pattern Step 2a): Quantitatively sample the elevation angle and azimuth angle within the antenna scanning range to obtain an elevation angle sequence and an azimuth angle sequence; Step 2b): Select a pair of pitch angle and azimuth angle from the pitch angle sequence and the azimuth angle sequence, and calculate its steering column vector V n ; Step 2c): Calculate the matrix multiplication according to the following formula: patternData = conj(V) * V n patternData is the weighted value of the antenna pattern in the direction corresponding to the selected elevation angle and azimuth angle; Step 2d): Repeat steps 2b and 2c, traverse all the elevation angles and azimuth angles in the elevation angle sequence and azimuth angle sequence, and arrange the obtained patternData according to elevation and azimuth to obtain a two-dimensional antenna pattern; Step 3: DBF of the element-level echo Step 3a): Arrange the echo data into a matrix S according to different elements. The number of rows of S is the number of elements, and the number of columns is the number of sampling points in the range dimension; Step 3b): Use the steering vector V obtained in Step 1 to calculate according to the following formula: echo = conj(V)*S In the above formula, echo is the result vector after DBF.

2. The element-level echo DBF method of a stepped array radar according to claim 1, characterized in that In Step 1b, the radar is a multi-beam radar, and the steering vector V becomes a steering matrix. The number of rows of the matrix is the number of beams. By repeating Step 1, the steering vectors in different beam directions are all obtained and then arranged into a steering matrix.

3. The element-level echo DBF method of a stepped array radar according to claim 2, wherein In Step 3b, the result vector echo becomes a matrix, and each row of the matrix stores the DBF result corresponding to the beam.

4. The array element level echo DBF method of a stepped array radar according to claim 1, characterized in that The number of horizontal elements is greater than or equal to 2.

5. The method for array element level echo DBF of a stepped array radar according to claim 1, characterized in that, The number of vertical elements is greater than or equal to 2.

6. The method for array element level echo DBF of a stepped array radar according to claim 1, wherein, The number of sub-arrays is greater than or equal to 2.

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