A radar two-dimensional angular imaging method and system based on difference-sum beam

Abstract

The present invention discloses a radar two-dimensional angular imaging method and system based on difference-sum beam, and relates to the field of radar imaging. The method comprises: obtaining incident signals in the main lobe received by each subarray in an array antenna; estimating the initial value of the wave direction of each incident signal; based on the initial value of the wave direction of each incident signal, using digital beamforming technology to generate a corresponding sum beam and a corresponding difference beam; based on the initial value of the wave direction of each incident signal, the sum beam and the difference beam, using an iterative algorithm to obtain the estimated value of the wave direction of each incident signal; determining the grayscale corresponding to each incident signal according to the estimated value of the wave direction of each incident signal; generating a pitch-azimuth two-dimensional image of an observed target according to the estimated value of the wave direction of the incident signal and the corresponding grayscale. The present invention can achieve high-resolution imaging.

Description

Technical Field

[0001] The present invention relates to the field of radar imaging, and in particular to a radar two-dimensional angular imaging method and system based on difference-sum beams. Background Art

[0002] At present, the imaging methods for precision tracking imaging radar to achieve imaging sampling include one-dimensional range imaging, real beam imaging, and inverse synthetic aperture radar (ISAR) imaging. Among them, one-dimensional range imaging cannot identify multiple scattering points within the same range unit, which reduces the resolution and makes the imaging difficult to read; real beam imaging cannot identify multiple scattering points within the main lobe of the same beam, and the main lobe width is limited by the antenna aperture and cannot be very large; for ISAR imaging, the information on the target's motion state is unknown for non-cooperative targets. Therefore, it is difficult to compensate for the target's translational component, and the quality of motion compensation is also the key to whether ISAR imaging can be applied in practice. In addition, ISAR requires that the target has rotational motion relative to the radar platform. For targets that do not meet this motion condition or are stationary, ISAR technology cannot perform high-resolution imaging. Summary of the invention

[0003] Based on this, an embodiment of the present invention provides a radar two-dimensional angular imaging method and system based on difference-sum beam to achieve high-resolution imaging.

[0004] To achieve the above object, the present invention provides the following solutions:

[0005] A radar two-dimensional angular imaging method based on difference-sum beam, comprising:

[0006] Acquire an incident signal in a main lobe received by each subarray in the array antenna; the incident signal is a signal reflected by each scattering point on an observation target in the main lobe after the array antenna sends a detection signal;

[0007] estimating an initial value of the direction of arrival of each incident signal; the direction of arrival is characterized by an incident angle; the incident angle includes an azimuth angle and an elevation angle;

[0008] Based on the initial value of the direction of arrival of each of the incident signals, a corresponding sum beam and a corresponding difference beam are generated using a digital beamforming technique;

[0009] Based on the initial value of the direction of arrival of each incident signal, the sum beam and the difference beam, an iterative algorithm is used to obtain an estimated value of the direction of arrival of each incident signal;

[0010] Determining the grayscale corresponding to each of the incident signals according to the estimated value of the direction of arrival of each of the incident signals;

[0011] A pitch-azimuth two-dimensional image of the observed target is generated according to the estimated value of the arrival direction of the incident signal and the corresponding grayscale.

[0012] Optionally, determining the grayscale corresponding to each of the incident signals according to the estimated value of the direction of arrival of each of the incident signals specifically includes:

[0013] Determining the intensity amplitude of each incident signal according to the estimated value of the direction of arrival of each incident signal;

[0014] The grayscale corresponding to each of the incident signals is determined according to the intensity amplitude of each of the incident signals.

[0015] Optionally, the obtaining the estimated value of the direction of arrival of each incident signal by using an iterative algorithm based on the initial value of the direction of arrival of each incident signal, the sum beam, and the difference beam specifically includes:

[0016] Calculating a sum signal and a difference signal based on the sum beam, the difference beam and the incident signal;

[0017] Constructing a direction of arrival iterative equation based on the sum signal and the difference signal;

[0018] Based on the initial value of the direction of arrival of each incident signal, the direction of arrival iteration equation is adopted to iteratively update the direction of arrival of each incident signal with the incident angle accuracy set as the target, so as to obtain an estimated value of the direction of arrival of each incident signal.

[0019] Optionally, the calculating the sum signal and the difference signal based on the sum beam, the difference beam and the incident signal specifically includes:

[0020] Determine the array pattern of the sum beam, and calculate the sum signal from the array pattern of the sum beam and the incident signal;

[0021] An array pattern of the difference beam is determined, and a difference signal is calculated from the array pattern of the difference beam and the incident signal.

[0022] Optionally, the calculation formula of the sum signal is:

[0023]

[0024] Among them, y Σi (t) represents the sum signal received when the main lobe of the beam points to the i-th incident angle; represents the array pattern of the sum beam corresponding to the i-th incident angle; X(t) represents the incident signal; θ represents the azimuth angle; t represents time;

[0025] The calculation formula of the difference signal is:

[0026]

[0027] Among them, y Δi (t) represents the difference signal received when the main lobe of the beam points to the i-th incident angle; Represents the array pattern of the difference beam corresponding to the i-th incident angle.

[0028] Optionally, the direction of arrival iteration equation is:

[0029]

[0030] Among them, y Σi (t) represents the sum signal received when the main lobe of the beam points to the i-th incident angle; y Δi (t) represents the difference signal received when the main lobe of the beam points to the i-th incident angle; Δ x The spacing of the antenna subarrays in the x-axis direction; Δ y represents the spacing of the antenna subarray in the y-axis direction; λ represents the wavelength of the incident signal; g x represents the attenuation coefficient in the x-axis direction; g y represents the attenuation coefficient in the y-axis direction; j represents the imaginary unit; represents the estimated azimuth of the i-th incident signal at the previous iteration number; represents the estimated azimuth of the i-th incident signal at the current number of iterations; represents the estimated pitch angle of the i-th incident signal at the previous iteration number; It represents the estimated pitch angle of the i-th incident signal at the current iteration number.

[0031] The present invention also provides a radar two-dimensional angular imaging system based on difference-sum beam, comprising:

[0032] An incident signal acquisition module is used to acquire an incident signal in a main lobe received by each subarray in the array antenna; the incident signal is a signal reflected by each scattering point on the observation target in the main lobe after the array antenna sends a detection signal;

[0033] An initial estimation module, used to estimate the initial value of the direction of arrival of each incident signal; the direction of arrival is characterized by an incident angle; the incident angle includes an azimuth angle and a pitch angle;

[0034] A sum and difference beam forming module, configured to generate a corresponding sum beam and a corresponding difference beam using a digital beam forming technique based on an initial value of the direction of arrival of each of the incident signals;

[0035] A direction of arrival estimation module, configured to obtain an estimated value of the direction of arrival of each incident signal by using an iterative algorithm based on an initial value of the direction of arrival of each incident signal, the sum beam and the difference beam;

[0036] A grayscale determination module, used to determine the grayscale corresponding to each of the incident signals according to the estimated value of the direction of arrival of each of the incident signals;

[0037] The two-dimensional imaging module is used to generate a pitch-azimuth two-dimensional image of the observed target according to the estimated value of the arrival direction of the incident signal and the corresponding grayscale.

[0038] Optionally, the grayscale determination module specifically includes:

[0039] an amplitude determination unit, configured to determine the intensity amplitude of each incident signal according to an estimated value of the direction of arrival of each incident signal;

[0040] A grayscale calculation unit is used to determine the grayscale corresponding to each of the incident signals according to the intensity amplitude of each of the incident signals.

[0041] Optionally, the direction of arrival estimation module specifically includes:

[0042] a sum and difference signal calculation unit, configured to calculate a sum signal and a difference signal based on the sum beam, the difference beam and the incident signal;

[0043] An iterative equation determination unit, used for constructing a direction of arrival iterative equation based on the sum signal and the difference signal;

[0044] The iterative updating unit is used to iteratively update the direction of arrival of each incident signal based on the initial value of the direction of arrival of each incident signal, using the direction of arrival iterative equation, with the incident angle accuracy set as the target, to obtain an estimated value of the direction of arrival of each incident signal.

[0045] Optionally, the sum-difference signal calculation unit specifically includes:

[0046] A sum signal calculation subunit, used for determining the array pattern of the sum beam, and calculating the sum signal from the array pattern of the sum beam and the incident signal;

[0047] The difference signal calculation subunit is used to determine the array pattern of the difference beam and calculate the difference signal from the array pattern of the difference beam and the incident signal.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] The embodiment of the present invention proposes a radar two-dimensional angular imaging method and system based on difference-sum beam, which uses digital beamforming technology to generate sum beams and difference beams corresponding to the initial values ​​of the wave direction of each incident signal, and uses an iterative algorithm to obtain the estimated values ​​of the azimuth and elevation angles of each incident signal based on the initial values ​​of the wave direction of each incident signal, the sum beam and the difference beam, and combines the estimated values ​​of the azimuth and elevation angles and the corresponding grayscale to generate an elevation-azimuth two-dimensional image of the observed target, and the two-dimensional image contains two-dimensional information of the elevation and azimuth. Compared with ISAR imaging, the embodiment of the present invention has a fast imaging speed and can achieve high-resolution imaging. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0051] Figure 1 A flowchart of a radar two-dimensional angular imaging method based on a difference-sum beam provided in an embodiment of the present invention;

[0052] Figure 2 A schematic diagram of the structure of an array antenna provided in an embodiment of the present invention;

[0053] Figure 3 A structural diagram of a radar two-dimensional angular imaging system based on a difference-sum beam provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0054] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0055] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0056] The embodiment of the present invention utilizes digital beamforming technology, relies on a two-dimensional array antenna, and performs operations on the signals received by the array to sharpen the beam, thereby identifying multiple echo signals in the main lobe of the beam, thereby achieving the purpose of high-resolution imaging. This embodiment has no special requirements for the attitude, trajectory, and motion state of the observed target. Compared with Doppler domain imaging methods such as ISAR, it has obvious advantages, fast imaging speed, high-resolution imaging, and intuitive imaging results with better readability.

[0057] Figure 1 A flowchart of a radar two-dimensional angular imaging method based on difference-sum beams provided in an embodiment of the present invention.

[0058] See also Figure 1 The radar two-dimensional angular imaging method based on difference-sum beam in this embodiment includes:

[0059] Step 101: Acquire an incident signal in the main lobe received by each subarray in the array antenna; the incident signal is a signal reflected from each scattering point on the observation target in the main lobe after the array antenna sends a detection signal. The incident signal is an echo signal.

[0060] In this step, the array antenna is composed of four uniform arrays (subarrays) with the same structure, such as Figure 2 As shown, the spacing of the antenna subarrays in the x-axis direction and the spacing of the antenna subarrays in the y-axis direction are Δ x and Δ y , the number of array elements is N x ×N y , the spacing between the array elements in the x-axis direction and the array elements in the y-axis direction is d x and d y , the array elements are all omnidirectional antennas, and the wavelength of the incident signal is λ. There are K incident signals in the main lobe directed to each subarray, s1(t),…,s k (t), the incident angles of the K incident signals in the main lobe received by each sub-array (the incident signal received by the sub-array contains noise) are respectively Among them, the four sub-arrays are numbered 00, 01, 10 and 11 respectively.

[0061] The incident signal in the main lobe received by each subarray in the array antenna is:

[0062]

[0063]

[0064]

[0065] X 11 (t) = A1(θ, φ)Dxy S(t)+N 11 (t)

[0066] Among them, X 00 (t) represents the incident signal in the main lobe received by the subarray numbered 00; X 01 (t) represents the incident signal in the main lobe received by the subarray numbered 01; X 10 (t) represents the incident signal in the main lobe received by the subarray numbered 10; X 11 (t) represents the incident signal in the main lobe received by the subarray numbered 11; represents the array manifold of the subarray numbered 00; represents the incident angle; θ represents the azimuth; represents the pitch angle; S(t) represents the K incident signals (without noise) directed to each subarray, s1(t),…,s k (t) constitutes the matrix; N 00 (t), N 01 (t), N 10 (t) and N 11 (t) represent the noise signals of the subarray numbered 00, the subarray numbered 01, the subarray numbered 10, and the subarray numbered 11, respectively; D x , D y , D xy They are all intermediate parameters that prove the correlation of sub-array received signals.

[0067] D x D is the diagonal matrix formed by the phase difference of the received signals of the two sub-arrays in the x-axis direction of the array antenna; y D is the diagonal matrix formed by the phase difference of the received signals of the two sub-arrays in the y-axis direction of the array antenna; xy It is a diagonal matrix formed by the phase difference of the received signals of two sub-arrays on the diagonal line. Specifically:

[0068]

[0069]

[0070] D xy =D x D y

[0071] Step 102: estimating an initial value of the direction of arrival of each incident signal; the direction of arrival is represented by an incident angle; the incident angle includes an azimuth angle and an elevation angle.

[0072] In step 102, the array antenna transmits a detection signal and receives an incident signal (echo signal), and estimates the initial values ​​of the directions of arrival of K incident signals in the main lobe in sequence. The estimation formula of the initial value is:

[0073]

[0074]

[0075] …

[0076]

[0077] …

[0078] in, represents the initial value of the direction of arrival of the first incident signal, represents the initial estimate of the azimuth angle of the first incident signal, represents the initial estimate of the elevation angle of the first incident signal; represents the initial value of the direction of arrival of the second incident signal, represents the initial estimate of the azimuth angle of the second incident signal, represents the initial estimate of the elevation angle of the second incident signal; represents the initial value of the direction of arrival of the nth incident signal, represents the initial estimate of the azimuth angle of the nth incident signal, represents the initial estimate of the elevation angle of the nth incident signal; represents the two-dimensional steering vector of the first incident signal, represents the two-dimensional steering vector of the second incident signal, represents the two-dimensional steering vector of the nth incident signal, X(t) is the incident signal in the main lobe received by the array antenna (denoted by X 00 (t), X 01 (t), X 10 (t) and X 11 (t) composition). express The conjugate matrix of express The conjugate matrix of represents the two-dimensional steering vector after the first incident signal is estimated, express The conjugate matrix of express The conjugate matrix of express The conjugate matrix of represents the two-dimensional steering vector after estimation of the i-th incident signal.

[0079] Step 103: Based on the initial value of the direction of arrival of each incident signal, a corresponding sum beam and a corresponding difference beam are generated using a digital beamforming technique.

[0080] Step 104: Based on the initial value of the direction of arrival of each incident signal, the sum beam and the difference beam, an iterative algorithm is used to obtain an estimated value of the direction of arrival of each incident signal.

[0081] The step 104 specifically includes:

[0082] 1) Based on the sum beam, the difference beam and the incident signal, a sum signal and a difference signal are calculated. Specifically:

[0083] ① Determine the array pattern of the sum beam, and calculate the sum signal from the array pattern of the sum beam and the incident signal; the calculation formula of the sum signal is:

[0084]

[0085] Among them, y Σi (t) represents the sum signal received when the main lobe of the beam points to the i-th incident angle; represents the array pattern of the sum beam corresponding to the i-th incident angle; X(t) represents the incident signal; θ represents the azimuth angle; t represents time.

[0086] in,

[0087]

[0088]

[0089] represents the initial value of the direction of arrival of the pth incident signal; represents the initial estimate of the azimuth angle of the pth incident signal, represents the initial estimate of the elevation angle of the pth incident signal; represents the two-dimensional steering vector after the estimation of the p-th incident signal; express The conjugate matrix of ; For beam pointing hour, The array gain at . Where,

[0090]

[0091] For beam pointing hour, The array gain at , similarly, can be calculated

[0092] ② Determine the array pattern of the difference beam, and calculate the difference signal from the array pattern of the difference beam and the incident signal. The calculation formula of the difference signal is:

[0093]

[0094] Among them, y Δi (t) represents the difference signal received when the main lobe of the beam points to the i-th incident angle; Represents the array pattern of the difference beam corresponding to the i-th incident angle.

[0095] in,

[0096]

[0097]

[0098] 2) Constructing a direction of arrival iterative equation based on the sum signal and the difference signal. The direction of arrival iterative equation is:

[0099]

[0100] Among them, y Σi (t) represents the sum signal received when the main lobe of the beam points to the i-th incident angle; y Δi (t) represents the difference signal received when the main lobe of the beam points to the i-th incident angle; Δ x The spacing of the antenna subarrays in the x-axis direction; Δ y represents the spacing of the antenna subarray in the y-axis direction; λ represents the wavelength of the incident signal; g x represents the attenuation coefficient in the x-axis direction; g y Represents the attenuation coefficient in the y-axis direction, g y The closer it is to 1, the higher the imaging accuracy, but this value is affected by the signal-to-noise ratio; j represents the imaginary unit; represents the estimated azimuth of the i-th incident signal at the previous iteration number; represents the estimated azimuth of the i-th incident signal at the current number of iterations; represents the estimated pitch angle of the i-th incident signal at the previous iteration number; It represents the estimated pitch angle of the i-th incident signal at the current iteration number.

[0101] 3) Based on the initial value of the direction of arrival of each incident signal, the direction of arrival iteration equation is used to iteratively update the direction of arrival of each incident signal with the incident angle accuracy set as the target, so as to obtain an estimated value of the direction of arrival of each incident signal. Specifically:

[0102] In the first iteration, the initial value of the direction of arrival of the first incident signal is input into the direction of arrival iteration equation, and it is determined whether the estimated value of the direction of arrival of the first incident signal obtained after the first iteration is less than the set incident angle accuracy ε. If so, the estimated value obtained after the first iteration is used as the final estimated value of the direction of arrival of the first incident signal, and then the first iteration is performed on the remaining K-1 directions of arrival of the incident signals in turn. After the first iteration is completed, the directions of arrival of the incident signals that have not obtained the final estimated value are estimated, and the estimated value after the first iteration is input into the direction of arrival iteration equation as the initial value of the second iteration, and the directions of arrival of the remaining incident signals are iterated for the second time in turn, and after multiple iterations and updates, the final estimated values ​​of the directions of arrival of all incident signals are obtained.

[0103] Step 105: Determine the grayscale corresponding to each of the incident signals according to the estimated value of the direction of arrival of each of the incident signals.

[0104] The step 105 specifically includes:

[0105] Determine the intensity amplitude of each incident signal according to the estimated value of the direction of arrival of each incident signal; and determine the grayscale corresponding to each incident signal according to the intensity amplitude of each incident signal. Specifically:

[0106] According to the iterative calculation results (the estimated value of the direction of arrival of the incident signal), multiple sharpened beams are formed respectively, pointing to multiple echo directions and measuring the intensity amplitudes σ1, σ2, ..., σ K According to the corresponding relationship between the intensity amplitude and the gray level, the gray level corresponding to each scattering point echo signal (incident signal) received is determined. Among them, the intensity amplitude σ of the i-th incident signal i The calculation formula is:

[0107]

[0108] Among them, s i (t) represents the i-th incident signal directed to the array antenna.

[0109] Step 106: Generate a pitch-azimuth two-dimensional image of the observed target according to the estimated value of the arrival direction of the incident signal and the corresponding grayscale.

[0110] Wherein, step 106 specifically includes:

[0111] According to the estimated value of the direction of arrival of the incident signal The pitch-azimuth two-dimensional image of the observed target is generated by using the corresponding grayscale. The two-dimensional image can be generated by using an existing imaging method, which is not limited here.

[0112] This embodiment is based on the radar two-dimensional angular imaging method of difference-sum beam, and extends the beam sharpening method based on difference-sum signal to the two-dimensional case. After the detection signal is transmitted, multiple strong scattering points in the main lobe of the beam are encountered to form multiple incident signals; the echo signal is received, and multiple sum and difference beams are adaptively formed in the two-dimensional plane through the receiving end, and each echo signal is received and the signal amplitude is measured. At this time, the direction of the beam is the location of the strong scattering point, and the echo signal amplitude is the scattering intensity; then the target in the main lobe of the beam can be imaged in two dimensions.

[0113] The radar two-dimensional angular imaging method based on difference-sum beam of the present invention has the following advantages:

[0114] This imaging method can use single snapshot data to measure the amplitude of the strong scattering point in the main lobe, convert it into grayscale value, and combine it with the azimuth-elevation two-dimensional information of the radiation point to perform imaging. Compared with ISAR, it has the characteristics of fast imaging speed, insensitivity to relative motion attitude, and can achieve high-resolution imaging.

[0115] The present invention also provides a radar two-dimensional angular imaging system based on difference-sum beam, see Figure 3 , the system comprising:

[0116] The incident signal acquisition module 201 is used to acquire the incident signal in the main lobe received by each sub-array in the array antenna; the incident signal is the signal reflected by each scattering point on the observation target in the main lobe after the array antenna sends a detection signal.

[0117] The initial estimation module 202 is used to estimate the initial value of the direction of arrival of each incident signal; the direction of arrival is represented by an incident angle; the incident angle includes an azimuth angle and a pitch angle.

[0118] The sum and difference beam forming module 203 is used to generate a corresponding sum beam and a corresponding difference beam by using a digital beam forming technology based on the initial value of the direction of arrival of each incident signal.

[0119] The direction of arrival estimation module 204 is used to obtain an estimated value of the direction of arrival of each incident signal by using an iterative algorithm based on the initial value of the direction of arrival of each incident signal, the sum beam and the difference beam.

[0120] The grayscale determination module 205 is used to determine the grayscale corresponding to each of the incident signals according to the estimated value of the direction of arrival of each of the incident signals.

[0121] The two-dimensional imaging module 206 is used to generate a pitch-azimuth two-dimensional image of the observed target according to the estimated value of the arrival direction of the incident signal and the corresponding grayscale.

[0122] In one example, the grayscale determination module 205 specifically includes:

[0123] The amplitude determination unit is used to determine the intensity amplitude of each incident signal according to the estimated value of the wave arrival direction of each incident signal.

[0124] A grayscale calculation unit is used to determine the grayscale corresponding to each of the incident signals according to the intensity amplitude of each of the incident signals.

[0125] In one example, the direction of arrival estimation module 204 specifically includes:

[0126] A sum and difference signal calculation unit is used to calculate a sum signal and a difference signal based on the sum beam, the difference beam and the incident signal.

[0127] The iterative equation determination unit is used to construct a direction of arrival iterative equation based on the sum signal and the difference signal.

[0128] The iterative updating unit is used to iteratively update the direction of arrival of each incident signal based on the initial value of the direction of arrival of each incident signal, using the direction of arrival iterative equation, with the incident angle accuracy set as the target, to obtain an estimated value of the direction of arrival of each incident signal.

[0129] In one example, the sum-difference signal calculation unit specifically includes:

[0130] The sum signal calculation subunit is used to determine the array pattern of the sum beam and calculate the sum signal based on the array pattern of the sum beam and the incident signal.

[0131] The difference signal calculation subunit is used to determine the array pattern of the difference beam and calculate the difference signal from the array pattern of the difference beam and the incident signal.

[0132] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the system disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0133] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A radar two-dimensional angular imaging method based on difference-sum beam, characterized in that: include: Acquire an incident signal in a main lobe received by each subarray in the array antenna; the incident signal is a signal reflected by each scattering point on an observation target in the main lobe after the array antenna sends a detection signal; estimating an initial value of the direction of arrival of each incident signal; the direction of arrival is characterized by an incident angle; the incident angle includes an azimuth angle and a pitch angle; Based on the initial value of the direction of arrival of each of the incident signals, a corresponding sum beam and a corresponding difference beam are generated using a digital beamforming technique; Based on the initial value of the direction of arrival of each incident signal, the sum beam and the difference beam, an iterative algorithm is used to obtain an estimated value of the direction of arrival of each incident signal; Determining the grayscale corresponding to each of the incident signals according to the estimated value of the direction of arrival of each of the incident signals; A pitch-azimuth two-dimensional image of the observed target is generated according to the estimated value of the arrival direction of the incident signal and the corresponding grayscale.

2. The radar two-dimensional angular imaging method based on difference-sum beam according to claim 1, characterized in that: Determining the grayscale corresponding to each of the incident signals according to the estimated value of the direction of arrival of each of the incident signals specifically includes: Determining the intensity amplitude of each incident signal according to the estimated value of the direction of arrival of each incident signal; The grayscale corresponding to each of the incident signals is determined according to the intensity amplitude of each of the incident signals.

3. The radar two-dimensional angular imaging method based on difference-sum beam according to claim 1, characterized in that: The step of obtaining an estimated value of the direction of arrival of each incident signal by using an iterative algorithm based on the initial value of the direction of arrival of each incident signal, the sum beam and the difference beam specifically includes: Calculating a sum signal and a difference signal based on the sum beam, the difference beam and the incident signal; Constructing a direction of arrival iterative equation based on the sum signal and the difference signal; Based on the initial value of the direction of arrival of each incident signal, the direction of arrival iteration equation is adopted to iteratively update the direction of arrival of each incident signal with the incident angle accuracy set as the target, so as to obtain an estimated value of the direction of arrival of each incident signal.

4. The radar two-dimensional angular imaging method based on difference-sum beam according to claim 3, characterized in that: The calculating the sum signal and the difference signal based on the sum beam, the difference beam and the incident signal specifically includes: Determine the array pattern of the sum beam, and calculate the sum signal from the array pattern of the sum beam and the incident signal; An array pattern of the difference beam is determined, and a difference signal is calculated from the array pattern of the difference beam and the incident signal.

5. The radar two-dimensional angular imaging method based on difference-sum beam according to claim 4, characterized in that: The calculation formula of the sum signal is: Among them, y Σi (t) represents the sum signal received when the main lobe of the beam points to the i-th incident angle; represents the array pattern of the sum beam corresponding to the i-th incident angle; X(t) represents the incident signal; θ represents the azimuth angle; t represents time; The calculation formula of the difference signal is: Among them, y Δi (t) represents the difference signal received when the main lobe of the beam points to the i-th incident angle; Represents the array pattern of the difference beam corresponding to the i-th incident angle.

6. The radar two-dimensional angular imaging method based on difference-sum beam according to claim 3, characterized in that: The direction of arrival iteration equation is: Among them, y Σi(t) represents the sum signal received when the main lobe of the beam points to the i-th incident angle; y Δi(t) represents the difference signal received when the main lobe of the beam points to the i-th incident angle; Δ x Indicates the spacing of the antenna subarray in the x-axis direction; Δ y represents the spacing of the antenna subarray in the y-axis direction; λ represents the wavelength of the incident signal; g x represents the attenuation coefficient in the x-axis direction; g y represents the attenuation coefficient in the y-axis direction; j represents the imaginary unit; represents the estimated azimuth of the i-th incident signal at the previous iteration number; represents the estimated azimuth of the i-th incident signal at the current number of iterations; represents the estimated elevation angle of the i-th incident signal at the previous iteration number; It represents the estimated pitch angle of the i-th incident signal at the current iteration number.

7. A radar two-dimensional angular imaging system based on difference-sum beam, characterized in that: include: An incident signal acquisition module is used to acquire an incident signal in a main lobe received by each subarray in the array antenna; the incident signal is a signal reflected by each scattering point on the observation target in the main lobe after the array antenna sends a detection signal; An initial estimation module, used to estimate the initial value of the direction of arrival of each incident signal; the direction of arrival is characterized by an incident angle; the incident angle includes an azimuth angle and a pitch angle; A sum and difference beam forming module, configured to generate a corresponding sum beam and a corresponding difference beam using a digital beam forming technique based on an initial value of the direction of arrival of each of the incident signals; A direction of arrival estimation module, configured to obtain an estimated value of the direction of arrival of each incident signal by using an iterative algorithm based on an initial value of the direction of arrival of each incident signal, the sum beam and the difference beam; A grayscale determination module, used to determine the grayscale corresponding to each of the incident signals according to the estimated value of the direction of arrival of each of the incident signals; The two-dimensional imaging module is used to generate a pitch-azimuth two-dimensional image of the observed target according to the estimated value of the arrival direction of the incident signal and the corresponding grayscale.

8. The radar two-dimensional angular imaging system based on difference-sum beam according to claim 7, characterized in that: The grayscale determination module specifically includes: an amplitude determination unit, configured to determine the intensity amplitude of each incident signal according to an estimated value of the direction of arrival of each incident signal; A grayscale calculation unit is used to determine the grayscale corresponding to each of the incident signals according to the intensity amplitude of each of the incident signals.

9. The radar two-dimensional angular imaging system based on difference-sum beam according to claim 7, characterized in that: The direction of arrival estimation module specifically includes: a sum and difference signal calculation unit, configured to calculate a sum signal and a difference signal based on the sum beam, the difference beam and the incident signal; An iterative equation determination unit, used for constructing a direction of arrival iterative equation based on the sum signal and the difference signal; The iterative updating unit is used to iteratively update the direction of arrival of each incident signal based on the initial value of the direction of arrival of each incident signal, using the direction of arrival iterative equation, with the incident angle accuracy set as the target, to obtain an estimated value of the direction of arrival of each incident signal.

10. The radar two-dimensional angular imaging system based on difference-sum beam according to claim 9, characterized in that: The sum-difference signal calculation unit specifically comprises: A sum signal calculation subunit, used for determining the array pattern of the sum beam, and calculating the sum signal from the array pattern of the sum beam and the incident signal; The difference signal calculation subunit is used to determine the array pattern of the difference beam and calculate the difference signal from the array pattern of the difference beam and the incident signal.

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