Sum and Difference Beam Imaging Target Detection and Accurate Angle Measurement Method

Abstract

The present invention relates to the technical field of optical imaging, microwave imaging, radar detection, wireless communication, sonar, ultrasonic imaging, and target detection and imaging recognition based on sound, light, electricity and other media, and specifically to a sum and difference beam imaging target detection and precise angle measurement method and its application in the above-mentioned fields. The method of the present invention first performs sum beam imaging processing on the echo signal received by the array unit, and performs target detection and amplitude ratio angle measurement on the obtained sum beam imaging result; then performs difference beam imaging processing on the echo signal, and on this basis, combines the sum beam target detection result and its angle measurement data, and uses the difference beam null corresponding to the target to accurately determine its angle coordinate, thereby avoiding the influence of the difference beam coverage, shape and linearity on the detection accuracy, and using one difference beam imaging to obtain the precise angle coordinates of all targets, thereby achieving precise and rapid target angle coordinate measurement.

Description

Technical Field

[0001] The present invention relates to the fields of optical imaging, microwave imaging, radar detection, wireless communication, sonar, ultrasonic imaging, and target detection and imaging recognition technology based on sound, light, electricity and other media, and specifically to a sum and difference beam imaging target detection and precise angle measurement method and its application in the above-mentioned fields. Background Art

[0002] In traditional radar detection technology, the amplitude ratio method is usually used to determine the target coordinates, that is, the direction of the target signal with the strongest angle is used as its angle coordinate. Generally speaking, the coordinate measurement accuracy of the amplitude ratio method is relatively low, which is difficult to meet the tracking needs of high-precision tracking radar for targets.

[0003] In order to measure the target angle coordinates more accurately, active phased array radar usually uses spatial difference beam to obtain accurate angle tracking parameters, that is, it uses multiple beams with different spatial distributions to detect the target and obtain the precise coordinates of the target by taking the difference, as shown in the attached figure. Figure 1 As shown, 9 spatial beams are used to cover the target area, and the target echo intensity obtained by each different detection beam is A n , then the precise angle tracking coordinates of the target are:

[0004]

[0005]

[0006] However, the above active phased array radar detection technology still has many defects and shortcomings. On the one hand, the use of spatial multi-beam transmission technology requires the generation of multiple detection pulses, which is time-consuming and greatly affected by the target movement, especially for high-speed moving targets, which may lead to detection failure; on the other hand, the use of spatial multi-beam receiving technology, although the real-time performance is good, the coverage, shape and linearity of the synthetic difference beam will seriously affect the detection accuracy. At the same time, although most passive phased array radars use multi-mode and differential feed sources to achieve single pulse tracking, this technology cannot be used for active phased arrays, and currently passive phased arrays have been gradually replaced by active phased arrays. Summary of the invention

[0007] In order to overcome the above-mentioned defects and shortcomings of active phased array radar and passive phased array radar detection technology, the present invention provides a set of solutions: the present invention first adopts sum beam imaging for target detection, first determines the number of targets, and uses the amplitude ratio method to measure the coordinates of the targets, and then performs difference beam imaging, and uses the difference beam null corresponding to the target to accurately measure its angular coordinate, thereby avoiding the influence of the difference beam coverage range, shape and linearity on the detection accuracy, and the accurate angular coordinates of all targets can be obtained by using one difference beam imaging.

[0008] Imaging theory proves that the result of two-dimensional IFFT transformation of the complex signal distributed in the array is the image of the target.

[0009]

[0010] in, As the target image, is the array unit receiving signal, φ F is the focusing phase weighted value, A is the complex weighting coefficient of the array unit, and different A constitutes different array patterns. When A is replaced by the complex weighting coefficient corresponding to the needle beam pattern, the above imaging result is the sum beam imaging result. Using a high-gain needle beam pattern for sum beam imaging can obtain the maximum signal-to-noise ratio and the best target detection performance.

[0011] Sum beam imaging can be used to measure angles, usually using the amplitude ratio method, that is, using the maximum value direction as the target direction. However, the amplitude ratio method is easily affected by various errors, noise, etc., and because the target amplitude distribution changes little in the maximum value direction, it is difficult to obtain the precise angle coordinate value of the target.

[0012] When A is replaced by the complex weighting coefficient corresponding to the difference beam pattern, the above imaging result is the difference beam imaging result. Although the target signal level obtained by the difference beam imaging result is reduced, its difference beam null accurately represents the angular coordinate of the target. At the same time, the position of the difference beam null is not easily affected by errors and noise, and is easy to measure. Therefore, the difference beam imaging technology can accurately and stably determine the target angular coordinate.

[0013] Based on the above understanding, the present invention provides a method for target detection and precise angle measurement using sum and difference beam imaging. The method first performs sum beam imaging processing on the echo signals received by the array unit to obtain sum beam imaging data, and performs target detection and amplitude ratio angle measurement on the obtained sum beam imaging results; then, difference beam imaging processing is performed on the echo signals received by the array unit to obtain difference beam imaging data, and on this basis, the sum beam target detection results and their angle measurement data are combined to accurately determine the angular coordinates of each target.

[0014] Specifically, the sum and difference beam imaging target detection and accurate angle measurement method of the present invention comprises the following steps:

[0015] Step 1: Design a beam pattern that matches the detection target;

[0016] Step 2: Perform beamforming processing on the echo signals received by the array unit;

[0017] Step 3: Target detection and angular coordinate measurement;

[0018] Step 4: Design a difference beam pattern that matches the detection target;

[0019] Step 5: Performing difference beam imaging processing on the echo signal received by the array unit;

[0020] Step 6: Determine the angle coordinates of the detection target;

[0021] Step 7: Output the measured data of the detection target.

[0022] Furthermore, the sum beam pattern designed in the method of the present invention is a low-sidelobe high-gain needle-shaped sum beam pattern, and the low-sidelobe high-gain needle-shaped sum beam pattern is designed and obtained by an array amplitude weighting or phase weighting method;

[0023] The array amplitude weighting method includes but is not limited to uniform distribution, cosine weighting, Hamming window, Taylor distribution, Chebyshev distribution and mixed weighting;

[0024] The phase weighting method includes but is not limited to a genetic algorithm, a particle swarm optimization algorithm, a neural network, and a hybrid optimization method.

[0025] Furthermore, in step 2 of the method of the present invention, the following method is used to perform sum beam imaging when performing sum beam imaging processing on the echo signal received by the array unit:

[0026]

[0027] Where: j is the imaginary unit, e is the Euler constant, is the sum beam image, A is the target echo signal received by the array unit; ∑ is the complex weight value of the array element corresponding to the beam; is the focusing phase weighting coefficient. When the target is far enough, directly take φ F =0,(x m ,y n ) is the coordinate of the array unit, R is the target slant range, is the wave number, λ is the wavelength, η=1 for passive imaging, semi-active imaging or phased array beam scanning imaging, η=2 for active holographic imaging or synthetic aperture imaging, and the symbol IFFT stands for two-dimensional inverse fast Fourier transform.

[0028] Furthermore, when performing target detection and angular coordinate measurement in step 3 of the method of the present invention, the constant false alarm method is used to detect the target on the sum beam imaging result, and for the target exceeding the detection threshold, the target coordinate is determined by the amplitude ratio method, that is, the maximum value direction of the target image is used as the angular coordinate of the target; the noise threshold is obtained by the unit average method:

[0029]

[0030] in: is the noise threshold; S i is the image field value, Ω is the number of units for averaging operation, and the symbol ∑ represents the summation operation;

[0031] When the ratio of the image field value to the noise threshold is greater than the system detection signal-to-noise ratio SNR, it is considered that the target is detected at the image field position.

[0032] Furthermore, the difference beam pattern designed in the method of the present invention is formed by two equal-amplitude, anti-phase illumination plane waves; when the 3dB beam width of the sum beam pattern is φ, the azimuth difference beam plane wave illumination source is {(-θ h ,0),(θ h ,0)}, the elevation difference beam plane wave illumination source is {(0,-θ v ),(0,θ v )}, where: θ h =θ v =γφ, select the γ value according to the null depth, and require γ∈(0,2]; then obtain the complex weighted value of the array element corresponding to the difference beam pattern:

[0033]

[0034]

[0035] in: are the complex weighted values ​​of the azimuth difference beam and the elevation difference beam respectively. The symbol exp represents an exponential function with e as the base, and the symbol sin represents a sine function. m and n represent the position numbers of the array elements in the x and y directions respectively. Δ x , Δ y are the array unit spacing in the x and y directions, respectively.

[0036] Furthermore, in step 5 of the method of the present invention, when performing difference beam imaging processing on the echo signal received by the array unit, the following method is used to perform azimuth and elevation difference beam imaging:

[0037]

[0038]

[0039] in: They are the azimuth difference beam image and the elevation difference beam image, are the complex weighted values ​​of the azimuth and elevation difference beam arrays respectively, and A is the weighted value of the low sidelobe amplitude.

[0040] Furthermore, in step seven of the method of the present invention, the data outputted from the measured data of the detected target includes the amplitude, phase and angle coordinate information of the target.

[0041] More specifically, the sum and difference beam imaging target detection and precise angle measurement method of the present invention performs precise measurement of the target angular coordinates based on the difference beam imaging results; based on the sum beam imaging results and the angle measurement results of the amplitude ratio method, the coordinates of the zero sink of the target difference beam imaging are measured, and the coordinates are the precise angular coordinates of the target.

[0042] At the same time, the present invention also relates to the application of the above method in the fields of optical imaging, microwave imaging, radar detection, wireless communication, sonar, ultrasonic imaging, as well as acoustic, optical, and electrical target detection, imaging recognition, and wireless communication.

[0043] In summary, the sum and difference beam imaging target detection and precise angle measurement method of the present invention organically combines sum beam imaging and difference beam imaging technologies, and on the basis of sum beam imaging target detection and amplitude ratio method angle measurement, uses the difference beam null corresponding to the target through difference beam imaging to accurately determine its angular coordinates, thereby avoiding the influence of the difference beam coverage, shape and linearity on the detection accuracy, and the precise angular coordinates of all targets can be obtained by using one difference beam imaging, thereby realizing accurate and fast target angular coordinate measurement.

[0044] In addition, the method of the present invention has good application prospects and can be widely used in the field of target detection and communication technology using sound, light, electricity, etc. as media. When the detection medium is electromagnetic waves, the technology is suitable for microwave imaging, radar detection, wireless communication, synthetic aperture radar, and inverse synthetic aperture radar; when the detection medium is sound waves or ultrasonic waves, the technology is suitable for sonar, ultrasonic imaging, and synthetic aperture sonar; when the detection medium is light, the technology is suitable for optical imaging and synthetic aperture optical imaging. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the technical solutions of the prior art and the embodiments of the present invention, the drawings required for describing the prior art and the embodiments of the present invention are briefly introduced below. Obviously, the following drawings are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0046] Figure 1 Schematic diagram of active phased array radar using spatial difference beam to obtain angle tracking parameters.

[0047] Figure 2 The figure is a flow chart of the algorithm of the method of the present invention.

[0048] Figure 3 It is a schematic diagram of the present invention and beam imaging results.

[0049] Figure 4 It is a schematic diagram of the difference beam imaging result of the present invention. DETAILED DESCRIPTION

[0050] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. The present invention can also be implemented or applied through other different specific implementation methods. The details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0051] At the same time, it should be understood that the protection scope of the present invention is not limited to the specific embodiments described below; it should also be understood that the terms used in the embodiments of the present invention are for describing specific embodiments rather than for limiting the protection scope of the present invention.

[0052] Embodiment 1: A method for target detection and accurate angle measurement using sum and difference beam imaging (see Appendix Figure 2-4 ),include:

[0053] Step 1: Design a beam pattern that matches the detection target;

[0054] The designed sum beam pattern is a low sidelobe high gain needle-shaped sum beam pattern, and the low sidelobe high gain needle-shaped sum beam pattern is designed and obtained by an array amplitude weighting method;

[0055] The array amplitude weighting methods include uniform distribution, cosine weighting, Hamming window, Taylor distribution, Chebyshev distribution and mixed weighting.

[0056] Step 2: Perform beamforming processing on the echo signals received by the array unit;

[0057] When performing sum beam imaging processing on the echo signal received by the array unit, the following method is used to perform sum beam imaging:

[0058]

[0059] Where: j is the imaginary unit, e is the Euler constant, is the sum beam image, A is the target echo signal received by the array unit; ∑ is the complex weight value of the array element corresponding to the beam; is the focusing phase weighting coefficient. When the target is far enough, directly take φ F =0,(x m ,y n ) is the coordinate of the array unit, R is the target slant range, is the wave number, η=1 for passive imaging, semi-active imaging or phased array beam scanning imaging, and η=2 for active holographic imaging or synthetic aperture imaging. The symbol IFFT stands for two-dimensional inverse fast Fourier transform.

[0060] Sum beam imaging case: operating frequency 60GHz, antenna unit spacing is half wavelength, array size 100*100, set 5 long-distance targets in different directions and different amplitudes, Sum beam imaging results are attached Figure 3 .

[0061] Step 3: Target detection and amplitude-comparison normal angle coordinate measurement;

[0062] When performing target detection and angular coordinate measurement, the constant false alarm method is used for target detection on the sum beam imaging results. For targets exceeding the detection threshold, the amplitude ratio method is used to determine the target coordinates, that is, the maximum value direction of the target image is used as the angular coordinate of the target; the noise threshold is obtained using the unit average method:

[0063]

[0064] in: is the noise threshold; S i is the image field value, Ω is the number of units for averaging operation, and the symbol ∑ represents the summation operation;

[0065] When the ratio of the image field value to the noise threshold is greater than the system detection signal-to-noise ratio SNR, it is considered that the target is detected at the image field position.

[0066] Step 4: Design a difference beam pattern that matches the detection target;

[0067] The designed difference beam pattern is formed by two equal-amplitude, anti-phase illumination plane waves. When the 3dB beam width of the sum beam pattern is φ, the azimuth difference beam plane wave illumination source is {(-θ h ,0),(θ h ,0)}, the elevation difference beam plane wave illumination source is {(0,-θ v ),(0,θ v )}, where: θ h =θ v =γφ, select the γ value according to the null depth, and require γ∈(0,2]; then obtain the complex weighted value of the array element corresponding to the difference beam pattern:

[0068]

[0069]

[0070] in: are the complex weighted values ​​of the azimuth difference beam and the elevation difference beam respectively. The symbol exp represents an exponential function with e as the base, and the symbol sin represents a sine function. m and n are the position numbers of the array units respectively. x , Δ y are the array unit spacing in the x and y directions respectively.

[0071] Step 5: Performing difference beam imaging processing on the echo signal received by the array unit;

[0072] When performing difference beam imaging processing on the echo signals received by the array unit, the following method is used to perform azimuth and elevation difference beam imaging:

[0073]

[0074]

[0075] in: They are the azimuth difference beam image and the elevation difference beam image, are the complex weighted values ​​of the azimuth and elevation difference beam arrays respectively, and A is the weighted value of the low sidelobe amplitude.

[0076] Differential beam imaging case: operating frequency 60GHz, antenna unit spacing is half wavelength, array size 100*100, set 5 long-distance targets in different directions and different amplitudes, differential beam imaging results are attached Figure 4 .

[0077] Step 6: Determine the angle coordinates of the detection target;

[0078] According to the difference beam imaging results, combined with the sum beam target detection results and its angle measurement data, the coordinates of the null of the target difference beam imaging are measured, and the coordinates are the precise angle coordinates of the target.

[0079] Step 7: Output the measured data of the detection target;

[0080] The output data includes the amplitude, phase and angle coordinate information of the target.

[0081] Embodiment 2: A method for target detection and accurate angle measurement using sum and difference beam imaging, comprising:

[0082] Step 1: Design a beam pattern that matches the detection target;

[0083] The designed sum beam pattern is a low sidelobe high gain needle-shaped sum beam pattern, and the low sidelobe high gain needle-shaped sum beam pattern is designed and obtained by a phase weighting method;

[0084] The phase weighting method includes genetic algorithm, particle swarm optimization algorithm, neural network and hybrid optimization method.

[0085] Step 2: Perform beamforming processing on the echo signals received by the array unit;

[0086] When performing sum beam imaging processing on the echo signal received by the array unit, the following method is used to perform sum beam imaging:

[0087]

[0088] Where: j is the imaginary unit, e is the Euler constant, is the sum beam image, A is the target echo signal received by the array unit; ∑ is the complex weight value of the array element corresponding to the beam; is the focusing phase weighting coefficient. When the target is far enough, directly take φ F =0,(x m ,y n ) is the coordinate of the array unit, R is the target slant range, is the wave number, η=1 for passive imaging, semi-active imaging or phased array beam scanning imaging, and η=2 for active holographic imaging or synthetic aperture imaging. The symbol IFFT stands for two-dimensional inverse fast Fourier transform.

[0089] Step 3: Target detection and amplitude-comparison normal angle coordinate measurement;

[0090] When performing target detection and angular coordinate measurement, the constant false alarm method is used for target detection on the sum beam imaging results. For targets exceeding the detection threshold, the amplitude ratio method is used to determine the target coordinates, that is, the maximum value direction of the target image is used as the angular coordinate of the target; the noise threshold is obtained using the unit average method:

[0091]

[0092] in: is the noise threshold; S i is the image field value, Ω is the number of units for averaging operation, and the symbol ∑ represents the summation operation;

[0093] When the ratio of the image field value to the noise threshold is greater than the system detection signal-to-noise ratio SNR, it is considered that the target is detected at the image field position.

[0094] Step 4: Design a difference beam pattern that matches the detection target;

[0095] The designed difference beam pattern is formed by two equal-amplitude, anti-phase illumination plane waves. When the 3dB beam width of the sum beam pattern is φ, the azimuth difference beam plane wave illumination source is {(-θ h ,0),(θ h ,0)}, the elevation difference beam plane wave illumination source is {(0,-θ v),(0,θ v )}, where: θ h =θ v =γφ, select the γ value according to the null depth, and require γ∈(0,2]; then obtain the complex weighted value of the array element corresponding to the difference beam pattern:

[0096]

[0097]

[0098] in: are the complex weighted values ​​of the azimuth difference beam and the elevation difference beam respectively. The symbol exp represents an exponential function with e as the base, and the symbol sin represents a sine function. m and n are the position numbers of the array units respectively. x , Δ y are the array unit spacing in the x and y directions respectively.

[0099] Step 5: Performing difference beam imaging processing on the echo signal received by the array unit;

[0100] When performing difference beam imaging processing on the echo signals received by the array unit, the following method is used to perform azimuth and elevation difference beam imaging:

[0101]

[0102]

[0103] in: They are the azimuth difference beam image and the elevation difference beam image, are the complex weighted values ​​of the azimuth and elevation difference beam arrays respectively, and A is the weighted value of the low sidelobe amplitude.

[0104] Step 6: Determine the angle coordinates of the detection target;

[0105] According to the difference beam imaging results, combined with the sum beam target detection results and its angle measurement data, the coordinates of the null of the target difference beam imaging are measured, and the coordinates are the precise angle coordinates of the target.

[0106] Step 7: Output the measured data of the detection target;

[0107] The output data includes the amplitude, phase and angle coordinate information of the target.

[0108] The above description is only an embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, replacement, etc. made within the spirit and principle of the present invention should be included in the scope of protection of the claims of the present invention.

Claims

1. A method for target detection and accurate angle measurement using sum and difference beam imaging, characterized in that: The method first performs sum beam imaging processing on the echo signals received by the array unit to obtain sum beam imaging data, and performs target detection and angle measurement using the amplitude ratio method on the obtained sum beam imaging results; then performs difference beam imaging processing on the echo signals received by the array unit to obtain difference beam imaging data, and on this basis, combines the sum beam target detection results and the angle measurement data to accurately determine the angular coordinates of each target; The method comprises the following steps: Step 1: Design a beam pattern that matches the detection target; Step 2: Perform beamforming processing on the echo signals received by the array unit; Step 3: Target detection and angular coordinate measurement; Step 4: Design a difference beam pattern that matches the detection target; Step 5: Performing difference beam imaging processing on the echo signal received by the array unit; Step 6: Determine the angle coordinates of the detection target; Step 7: Output the measured data of the detection target.

2. The method according to claim 1, characterized in that The sum beam pattern is a low-sidelobe high-gain needle-shaped sum beam pattern, and the low-sidelobe high-gain needle-shaped sum beam pattern is designed and obtained by an array amplitude weighting or phase weighting method; The array amplitude weighting method includes uniform distribution, cosine weighting, Hamming window, Taylor distribution, Chebyshev distribution and mixed weighting; The phase weighting method includes genetic algorithm, particle swarm optimization algorithm, neural network and hybrid optimization method.

3. The method according to claim 1, characterized in that In step 2, the following method is used to perform sum beam imaging on the echo signal received by the array unit: Where: j is the imaginary unit, e is the Euler constant, is the sum beam image, A is the target echo signal received by the array unit; ∑ is the complex weight value of the array element corresponding to the beam; is the focusing phase weighting coefficient. When the target is far enough, directly take φ F =0,(x m ,y n ) is the coordinate of the array unit, R is the target slant range, is the wave number, λ is the wavelength, η=1 for passive imaging, semi-active imaging or phased array beam scanning imaging, η=2 for active holographic imaging or synthetic aperture imaging, and the symbol IFFT stands for two-dimensional inverse fast Fourier transform.

4. The method according to claim 1, characterized in that When performing target detection and angular coordinate measurement in step 3, the constant false alarm method is used for target detection on the sum beam imaging results. For targets exceeding the detection threshold, the amplitude ratio method is used to determine the target coordinates, that is, the maximum value direction of the target image is used as the angular coordinate of the target; the noise threshold is obtained using the unit average method: in: is the noise threshold; S i is the image field value, Ω is the number of units for averaging operation, and the symbol ∑ represents the summation operation; When the ratio of the image field value to the noise threshold is greater than the system detection signal-to-noise ratio SNR, it is considered that the target is detected at the image field position.

5. The method according to claim 1, characterized in that The difference beam pattern is formed by two equal-amplitude, anti-phase illumination plane waves; when the 3dB beam width of the sum beam pattern is φ, the azimuth difference beam plane wave illumination source is {(-θ h ,0),(θ h ,0)}, the elevation difference beam plane wave illumination source is {(0,-θ v ),(0,θ v )}, where: θ h =θ v =γφ, select the γ value according to the null depth, and require γ∈(0,2]; then obtain the complex weighted value of the array element corresponding to the difference beam pattern: in: are the complex weighted values ​​of the azimuth difference beam and the elevation difference beam respectively. The symbol exp represents the exponential function with the Euler constant e as the base, the symbol sin represents the sine function, m and n are the position numbers of the array unit in the x-direction and y-direction respectively, Δ x , Δ y are the array unit spacing in the x and y directions respectively.

6. The method according to claim 1, characterized in that In step 5, when performing difference beam imaging processing on the echo signal received by the array unit, the following method is used to perform azimuth and elevation difference beam imaging: in: They are the azimuth difference beam image and the elevation difference beam image, are the complex weighted values ​​of the azimuth and elevation difference beam arrays respectively, and A is the weighted value of the low sidelobe amplitude.

7. The method according to claim 1, characterized in that Step 7: Output the measured data of the detected target. The output data includes the amplitude, phase and angle coordinate information of the target.

8. The method according to claim 1, characterized in that The method accurately measures the target angular coordinates according to the difference beam imaging result; and measures the coordinates of the null of the target difference beam imaging according to the sum beam imaging result and the angle measurement result of the amplitude ratio method, and the coordinates are the accurate angular coordinates of the target.

9. Application of the method according to any one of claims 1 to 8 in the fields of optical imaging, microwave imaging, radar detection, sonar, ultrasonic imaging, and acoustic, optical, and electrical target detection, imaging recognition, and wireless communication.

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