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Sparse array broadband beamforming grating lobe suppressing method

A sparse array, grating lobe technology, applied in radio wave measurement systems, instruments, etc., can solve problems such as inapplicability to multi-target detection, and achieve the effect of low application cost and good practicability

Active Publication Date: 2016-02-17
HARBIN ENG UNIV
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Problems solved by technology

[0008] Documents 1 and 2 give a class of methods for resisting the grating lobe effect caused by array sparsity. This method uses the mode of virtual array element to reduce the degree of array sparsity to resist the grating lobe effect caused by array sparsity. The disadvantage is that the target must be known. Approximate orientation, not suitable for multi-target detection

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  • Sparse array broadband beamforming grating lobe suppressing method
  • Sparse array broadband beamforming grating lobe suppressing method
  • Sparse array broadband beamforming grating lobe suppressing method

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specific Embodiment approach 2

[0075] 2. Specific implementation mode two: the difference between this implementation mode and specific implementation mode one is: if Figure 4 As shown, firstly, FFT (Fast Fourier Transform) is performed on the received array signal to convert it into a frequency domain signal, and conventional beamforming is performed on each frequency point signal within the working frequency band bandwidth B of the frequency domain signal to obtain each The spatial spectrum output of the frequency point P(f i ,θ):

[0076] P(f i ,θ)=a(f i ,θ) H R(f i )a(f i ,θ)(12)

[0077] B is the signal frequency band, B=f h -f l , f l is the lower limit frequency of the working frequency band, f h is the upper limit frequency of the working frequency band, f i For FFT transformation, for the i-th frequency in signal frequency band B, i=1,2...L, L is the number of subbands corresponding to FFT in signal bandwidth B, L=B / Δf, B is signal bandwidth, Δf is FFT Frequency resolution when calcula...

specific Embodiment approach 3

[0088] 3. Specific implementation mode three: the difference between this implementation mode and specific implementation mode one or two is: the specific calculation method of the step 2 is as follows:

[0089] If the main lobe orientation is θ k , then the position where each frequency grating lobe appears The calculation formula is:

[0090] θ kfi =arcsin(sinθ k ±mλ i / d), m=1,2,...,0°kfi <180°(15)

[0091] Among them, m is the serial number corresponding to the grating lobe, which is a positive integer, and λ i =C / f i ,λ i for the frequency f i The corresponding wavelength, C is the speed of sound, d is the element spacing of the array, when m=0, the corresponding angle is the main maximum position, that is, the position of the target, and the angular position corresponding to the integer m in the range of other measurement areas is the grid Lobe position, there may be multiple grating lobes in the measurement area, the specific number is given by Under this co...

specific Embodiment approach 4

[0093] 4. Specific implementation mode four: the difference between this implementation mode and one of the specific implementation modes one to three is: the step 3 is specifically:

[0094] For the sound pressure array, the width of the grating lobe of the single-frequency signal is completely equal to the width of the main lobe. Therefore, the width of the grating lobe can be determined by the calculation formula of the width of the main lobe. For an equidistant linear array, the frequency is f i The zero-point main lobe width Δθ formed by the signal k (or zero-point beam width) corresponding to the calculation formula of the half-beam width is:

[0095] Δθ k =arcsin(λ i / Md)(16)

[0096] That is, sin(Δθ k )=λ i / Md, M is the number of array elements, grating lobe angle Then the formula for calculating the starting and ending range of the corresponding grating lobes is:

[0097]

[0098] grating lobe corresponds to the left range start point, grating lobe ...

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Abstract

The invention provides a sparse array broadband beamforming grating lobe suppressing method. The method comprises a step 1 of performing frequency-domain broadband beamforming on array signals received by multiple array elements of a sparse array; a step 2 of predicting a grating lobe angle by using the orientation [theta]k of a strong interference target signal obtained in the step 1; a step 3 of resolving the start-stop range of the grating lobe of each frequency point according to the grating lobe angle [theta]kfj obtained in the step 2 and the main lobe width of each frequency point; a step 4 of computing a grating lobe suppression weight coefficient matrix Wk according to a grating lobe range obtained in the step 3; and a step 5 of suppressing the gratin lobe by using the grating lobe suppression weight coefficient matrix Wk obtained in the step 4 and a spatial spectrum output matrix P of each frequency point obtained in the step 1; and a step 6 of adding the spatial spectrum output matrix Pout after the grating lobe suppression in order to perform broadband spatial spectrum synthesis. The method solves broadband beamforming grating lobe influences caused by a common equal-interval sparse array and is used in signal processing field.

Description

technical field [0001] The invention relates to a grating lobe suppressing method for forming a sparse array broadband beam. Background technique [0002] Sparse array refers to an array whose element spacing is not less than the half-wavelength corresponding to the maximum frequency value within the working frequency range when the array is arranged at equal intervals. It is a well-known physical phenomenon that the sparseness of the array will cause the grating lobe (submaximum) to appear in the beamforming result. For the single-frequency signal, the grating lobe strength formed is the same as the main lobe, which will make the beamforming direction finding result appear azimuth ambiguous. . During broadband signal processing, because the grating lobe of each frequency point in the frequency range is different, and the main lobe appears in the same position, it has a better suppression effect on the grating lobe, which makes the results of broadband beamforming not ambig...

Claims

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Application Information

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IPC IPC(8): G01S7/539
CPCG01S7/539
Inventor 梅继丹孙大军兰华林朱英慧薛芙莲
Owner HARBIN ENG UNIV
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