Single pulse forward looking three-dimensional imaging method and system based on adaptive iterative spectrum estimation

Abstract

The application relates to a single-pulse forward-looking three-dimensional imaging method and system based on adaptive iterative spectrum estimation, and relates to a single-pulse forward-looking three-dimensional imaging method and system for static targets. The application aims to solve the problem that, in existing forward-looking SAR imaging of static targets, a radar needs to receive a certain amount of echoes to form an image, which leads to a long receiving time and can only form a two-dimensional image. The process comprises the following steps: (1) obtaining a one-dimensional range image; (2) performing envelope alignment and phase correction on the one-dimensional range images of the sum channel and the difference channels; synchronizing the offset of each pulse to the azimuth difference and the elevation difference one-dimensional range images; (3) performing azimuth desquaring processing on the three channels; (4) obtaining the frequency domain results of the three channels; (5) traversing all units of the frequency domain results of the sum channel; when the IAA spectrum estimation result of the sum channel of (q, m) is less than a threshold value, q is set to q+1 to continue the judgment; otherwise, the azimuth angle and the elevation angle are calculated; energy projection is performed on each (q, m) meeting the condition; and a three-dimensional imaging result is obtained. The application is used in the field of single-pulse forward-looking three-dimensional imaging.

Description

Technical Field

[0001] This invention relates to a method and system for single-pulse forward-looking three-dimensional imaging of stationary targets. Background Technology

[0002] Three-dimensional imaging of forward-looking targets is of great military significance. For example, missile-borne seekers can more quickly and accurately identify enemy target characteristics, enabling precision strikes. Monopulse forward-looking 3D imaging involves transmitting and receiving radar signals through sum and difference channels, processing the echo signals in the range and azimuth directions, and then using monopulse angle measurement technology to invert the target's three-dimensional information. Finally, the image is projected into three-dimensional space. Monopulse angle measurement uses a specific algorithm to obtain the target's angle information relative to the radar from the sum and difference channels. However, because the Doppler frequencies between different scattering points in the forward-looking direction are relatively small, traditional methods (forward-slant SAR) require radar to achieve a long synthetic aperture length, meaning a sufficient number of echoes must be received, resulting in a long imaging time and a two-dimensional image. Summary of the Invention

[0003] The purpose of this invention is to solve the problem that in existing forward-looking SAR imaging of stationary targets, the radar must receive a certain number of echoes in order to form an image, resulting in long reception time and only two-dimensional images. The invention proposes a single-pulse forward-looking three-dimensional imaging method and system based on adaptive iterative spectrum estimation.

[0004] The specific process of the single-pulse forward-looking 3D imaging method based on adaptive iterative spectrum estimation is as follows:

[0005] Step 1: Perform range processing and range migration correction on the echoes of the radar and channel, azimuth difference channel and elevation difference channel respectively to obtain the pulse compression echo results of the and channel, azimuth difference channel and elevation difference channel, i.e., one-dimensional range image;

[0006] Step 2: Perform minimum entropy envelope alignment and phase correction on the one-dimensional range image of the channel; synchronize the offset of each pulse to the one-dimensional range image of azimuth difference and elevation difference;

[0007] Step 3: Based on the oblique angle θ of each distance unit xie With distance R m Construct a reference signal and use the reference signal to perform azimuth deskewing on the three channels;

[0008] Step 4: Select the m-th range cell after azimuth de-skew processing for the azimuth difference channel and pitch difference channel, and perform adaptive iterative spectrum estimation; use the spectrum estimation result as the initial value for the m-th range cell after azimuth de-skew processing for the azimuth difference channel and pitch difference channel, and perform adaptive iterative spectrum estimation; traverse m from 0 to M-1 to obtain the frequency domain results of the three channels;

[0009] Where 0 ≤ m ≤ M-1, and M is the total number of distance cells;

[0010] Step 5: Set the threshold;

[0011] Traverse and channel frequency domain results across all distance cells;

[0012] When the sum channel IAA spectrum estimation result of the qth sub-unit in the mth distance unit is less than the threshold, let q = q + 1 to continue the judgment, 0 ≤ q ≤ Q - 1, where Q is the total number of sub-units after IAA spectrum estimation set manually, and Q ≥ N;

[0013] When the sum channel IAA spectrum estimation result of the qth sub-unit in the m-th range cell is greater than or equal to the threshold, the azimuth and elevation angles are calculated by combining the frequency domain results of the azimuth difference channel and elevation difference channel of the corresponding pulse in the corresponding range cell; energy projection is performed on the qth sub-unit (q,m) in each m-th range cell that meets the conditions according to the geometric relationship; and the final three-dimensional imaging result is obtained.

[0014] IAA stands for Adaptive Iterative Spectral Estimation.

[0015] The single-pulse forward-looking 3D imaging system based on adaptive iterative spectrum estimation is used to execute the aforementioned single-pulse forward-looking 3D imaging method based on adaptive iterative spectrum estimation.

[0016] A storage medium storing at least one instruction, which is loaded and executed by a processor to implement the single-pulse forward-looking three-dimensional imaging method based on adaptive iterative spectrum estimation.

[0017] The beneficial effects of this invention are as follows:

[0018] Traditional forward-slant SAR static target imaging radars require a certain number of echoes to achieve imaging, resulting in long reception times and limiting them to two-dimensional imaging. This invention proposes a single-pulse forward-looking three-dimensional imaging method based on adaptive iterative spectrum estimation, requiring fewer echoes. The invention employs an azimuth deslant method during signal processing, satisfying the conditions for subsequent adaptive iterative spectrum estimation. Adaptive iterative spectrum estimation is applied to the sum, azimuth difference, and elevation difference channels, reducing the required number of echoes to 25% of the original while still enabling target morphology identification. The time required for echo acquisition is also reduced to 25%. Finally, by setting an amplitude threshold, the number of energy projection elements is controlled, reducing computational load. The use of a single-pulse three-channel system provides three-dimensional imaging capability. In the rapidly changing battlefield, this invention enables three-dimensional imaging with only a small number of echoes, reducing limitations on missile trajectories, improving maneuverability, and lowering the interception rate. Attached Figure Description

[0019] Figure 1 This is a flowchart of the present invention;

[0020] Figure 2 In the geometric scenario for which this invention is applied, x, y, and z are coordinate axes. The x-axis is the direction of movement of the radar platform, the y-axis is perpendicular to the ground and pointing upwards, the z-axis is right-handed with the x and y axes, V is the speed of the radar platform, H is the height of the radar platform, R0 is the initial distance between the target and the radar, α is the downward viewing angle, ψ is the angle between the line connecting the radar and the target and the negative direction of the y-axis, and Target is the target.

[0021] Figure 3 This is a schematic diagram showing the arrangement of echo pulse numbers and distance units;

[0022] Figure 4 A schematic diagram simulating the distribution of scattering points on a ship in a 3D scene;

[0023] Figure 5 The results are from a forward-slant SAR imaging system with a signal-to-noise ratio of 15 dB and a pulse count of 1024.

[0024] Figure 6 The results are from a forward-slant SAR imaging system with a signal-to-noise ratio of 15 dB and a pulse count of 512.

[0025] Figure 7 The results are from a forward-slant SAR imaging system with a signal-to-noise ratio of 30 dB and a pulse count of 1024.

[0026] Figure 8 The results are from a forward-slant SAR imaging system with a signal-to-noise ratio of 30 dB and a pulse count of 512.

[0027] Figure 9 The three-dimensional imaging results of this invention with a signal-to-noise ratio of 15dB and 512 pulses (viewpoint 1);

[0028] Figure 10 The three-dimensional imaging results of this invention with a signal-to-noise ratio of 15dB and 512 pulses (viewpoint 2);

[0029] Figure 11 The top view of the imaging of this invention is shown with a signal-to-noise ratio of 15dB and 512 pulses.

[0030] Figure 12 The imaging front view of this invention is 15dB signal-to-noise ratio -512 pulses;

[0031] Figure 13 The side view of the imaging of this invention is 15dB signal-to-noise ratio -512 pulses;

[0032] Figure 14 The three-dimensional imaging results of this invention with a signal-to-noise ratio of 30dB and 512 pulses (viewpoint 1);

[0033] Figure 15 The three-dimensional imaging results of this invention with a signal-to-noise ratio of 30dB and 512 pulses (viewpoint 2);

[0034] Figure 16 The top view of the imaging of this invention is shown with a signal-to-noise ratio of 30dB and 512 pulses.

[0035] Figure 17 The imaging front view of this invention is shown with a signal-to-noise ratio of 30dB and 512 pulses.

[0036] Figure 18 The side view of the imaging of this invention is shown with a signal-to-noise ratio of 30dB and 512 pulses. Detailed Implementation

[0037] Specific implementation method one: Combining Figure 1 , 2 3. This embodiment describes the specific process of the single-pulse forward-looking three-dimensional imaging method based on adaptive iterative spectrum estimation as follows:

[0038] Step 1: Perform range processing and range migration correction on the echoes of the radar and channel, azimuth difference channel and elevation difference channel respectively to obtain the pulse compression echo results of the and channel, azimuth difference channel and elevation difference channel, i.e., one-dimensional range image;

[0039] Step 2: Perform minimum entropy envelope alignment and phase correction on the one-dimensional range image of the channel; synchronize the offset of each pulse to the one-dimensional range image of azimuth difference and elevation difference;

[0040] Step 3: Based on the oblique angle θ of each distance unit xie With distance R m Construct a reference signal and use the reference signal to perform azimuth deskewing on the three channels;

[0041] Step 4: Select the m-th range cell after azimuth de-skew processing for the azimuth difference channel and pitch difference channel, and perform adaptive iterative spectrum estimation; use the spectrum estimation result as the initial value for the m-th range cell after azimuth de-skew processing for the azimuth difference channel and pitch difference channel, and perform adaptive iterative spectrum estimation; traverse m from 0 to M-1 to obtain the frequency domain results of the three channels;

[0042] Where 0 ≤ m ≤ M-1, and M is the total number of distance cells;

[0043] Step 5: Set the threshold;

[0044] Traverse and channel frequency domain results across all distance cells;

[0045] When the sum channel IAA spectrum estimation result of the qth sub-unit in the mth distance unit is less than the threshold, let q = q + 1 to continue the judgment, 0 ≤ q ≤ Q - 1, where Q is the total number of sub-units after IAA spectrum estimation set manually, and Q ≥ N;

[0046] When the sum channel IAA spectrum estimation result of the qth sub-unit in the m-th range cell is greater than or equal to the threshold, the azimuth and elevation angles are calculated by combining the frequency domain results of the azimuth difference channel and elevation difference channel of the corresponding pulse in the corresponding range cell; energy projection is performed on the qth sub-unit (q,m) in each m-th range cell that meets the conditions according to the geometric relationship; and the final three-dimensional imaging result is obtained.

[0047] IAA (Iterative Adaptive Approach) is an adaptive iterative spectral estimation method.

[0048] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that, in step one, range processing and range migration correction are performed on the echoes of the radar and channel, azimuth difference channel, and elevation difference channel, respectively, to obtain the pulse compression echo results of the and channel, azimuth difference channel, and elevation difference channel, i.e., a one-dimensional range image. The specific process is as follows:

[0049] Step 11: During the movement of the carrier platform (or missile when on a missile), the monopulse radar transmits a linear frequency modulated pulse signal to the target. After being reflected by the target, the signal is received by the radar and processed internally to obtain echo signals from three channels: sum, azimuth difference, and elevation difference.

[0050] Steps 1 and 2: Using the same reference function, perform range-direction matched filtering on the echo signals of the sum, azimuth, and pitch difference channels respectively, and then perform range migration correction to obtain the pulse compression echo results of the sum, azimuth, and pitch difference channels, i.e., a one-dimensional range image.

[0051] The other steps and parameters are the same as in Specific Implementation Method 1.

[0052] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that the reference function expression is the transmission signal delay.

[0053] Where c is the speed of light, R ref The reference distance is Δt, which is the signal transmission delay.

[0054] Other steps and parameters are the same as in specific implementation method one or two.

[0055] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that, in step two, the minimum entropy method is used to align the one-dimensional range image of the channel and perform phase correction; the offset of each pulse is synchronized to the one-dimensional range image of azimuth difference and pitch difference; the specific process is as follows:

[0056] Step 2: Align the one-dimensional distance image of the channel with the minimum entropy method, then perform phase correction, and record the offset of each pulse relative to the original pulse, denoted as d(n).

[0057] Where n is the pulse number, 0≤n≤N-1, and N is the total number of echo pulses;

[0058] Step 22: Synchronize (the offset of each pulse in the difference channel is the same as the offset of the corresponding pulse in the sum channel. For example, if the offset of the first pulse in the sum channel is 5, then the offset of the first pulse in the azimuth difference and pitch difference channels should also be 5). The offset of each pulse is used to correct the one-dimensional range image of the azimuth difference and pitch difference channels (equivalent to the azimuth difference and pitch difference channels also undergoing the same envelope alignment and phase correction), that is, use d(n) to correct the one-dimensional range image of the azimuth difference and pitch difference channels;

[0059] The azimuth error correction formula is:

[0060]

[0061]

[0062] Where n is the pulse sequence number, m is the range cell sequence number, v is the range cell sequence number, N is the total number of echo pulses, and M is the total number of range cells; s a0 S is a one-dimensional range image of the azimuth difference channel. a ′0 represents the row-wise DFT result of the one-dimensional range image of the azimuth difference channel, s a This is a one-dimensional range image after azimuth error correction; j is the imaginary unit, j 2 =-1;

[0063] The pitch difference correction formula is:

[0064]

[0065]

[0066] Where n is the pulse sequence number, m is the range cell sequence number, v is the range cell sequence number, N is the total number of echo pulses, and M is the total number of range cells; This is a one-dimensional range image of the pitch difference channel. The one-dimensional range image of the pitch difference channel is obtained by row-wise DFT. This is a one-dimensional range image after pitch error correction;

[0067] DFT stands for Discrete Fourier Transform.

[0068] The other steps and parameters are the same as those in one of the specific implementation methods one to three.

[0069] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that, in step three, the oblique angle θ of each distance unit is used... xie With distance R mConstruct a reference signal and use it to perform azimuth deskewing on the three channels; the specific process is as follows:

[0070] Step 3: 1. Obtain the oblique angle θ of the m-th range cell in the N / 2-th pulse (center pulse) using inertial navigation. xie With distance R m Construct a reference signal

[0071]

[0072] in The Doppler center frequency of the m-th distance unit; t is the Doppler modulation frequency of the m-th distance unit; n =nT r For slow time, T r λ is the pulse repetition time, n is the pulse number; v′ is the radar platform velocity; λ is the wavelength; 0≤m≤M-1;

[0073] Step 3.2: Multiply the m-th range cell of the one-dimensional range image of the azimuth and pitch difference channels after envelope alignment and phase correction in Step 2 by the conjugate of the reference signal:

[0074]

[0075]

[0076]

[0077] Where s sm (t n ), s am (t n ), s pm (t n () represents the echo of the m-th range cell of the envelope-aligned sum, azimuth difference, and elevation difference channel signals; The reference signal is conjugate; · represents multiplication; s s (n,m), s a (n,m), s p (n,m) represent the sum channel, azimuth channel, and pitch difference channel data of the m-th range unit of the n-th pulse, respectively;

[0078] Step 33: Repeat steps 31 and 32 until m is traversed from 0 to M-1, completing the azimuth and oblique directions of the three channels.

[0079] The other steps and parameters are the same as those in one of the specific implementation methods one to four.

[0080] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that: in step four, the m-th range cell after azimuth de-skew processing is selected for adaptive iterative spectrum estimation; the spectrum estimation result is used as the initial value for iterating the m-th range cell after azimuth de-skew processing for the azimuth difference channel and elevation difference channel, and adaptive iterative spectrum estimation is performed; m is traversed from 0 to M-1 to obtain the frequency domain results for the three channels; the specific process is as follows:

[0081] Step 4: Select the m-th range cell signal after channel azimuth deskewing, use the unit matrix as the initial value for iteration, and perform 15 IAA iterations.

[0082] Among them, IAA (Iterative Adaptive Approach) is an adaptive iterative spectral estimation method;

[0083] Step 42: Select the m-th range cell signal after azimuth deskewing processing of the azimuth difference channel, and use the result in Step 41 as the initial value for iteration to perform 10 IAA iterations.

[0084] Select the m-th range cell signal after azimuth deskewing processing of the pitch difference channel, and use the result in step 4.1 as the initial value for iteration to perform 10 IAA iterations.

[0085] Step 43: Repeat steps 41 and 42 until m is traversed from 0 to M-1 to complete the IAA spectrum estimation of the three channels and obtain the frequency domain results of the three channels.

[0086] The other steps and parameters are the same as those in one of the specific implementation methods one to five.

[0087] Specific Implementation Method Seven: This implementation method differs from one of Specific Implementation Methods One to Six in that a threshold is set in step five;

[0088] Traverse and channel frequency domain results across all distance cells;

[0089] When the sum channel IAA spectrum estimation result of the qth sub-unit in the mth distance unit is less than the threshold, let q = q + 1 to continue the judgment, 0 ≤ q ≤ Q - 1, where Q is the total number of sub-units after IAA spectrum estimation set manually, and Q ≥ N;

[0090] When the sum channel IAA spectrum estimation result of the qth sub-unit in the m-th range cell is greater than or equal to the threshold, the azimuth and elevation angles are calculated by combining the frequency domain results of the azimuth difference channel and elevation difference channel of the corresponding pulse in the corresponding range cell; energy projection is performed on the qth sub-unit (q,m) in each m-th range cell that meets the conditions according to the geometric relationship; and the final three-dimensional imaging result is obtained.

[0091] Among them, IAA (Iterative Adaptive Approach) is an adaptive iterative spectral estimation method;

[0092] The specific process is as follows:

[0093] The q-th sub-unit (q,m) in each of the m-th distance units that meet the conditions is: the (q,m) whose sum channel IAA spectrum estimation result is greater than or equal to the threshold D;

[0094] Step 51: Set the threshold D to the median amplitude of all cells in the channel IAA spectrum estimation results;

[0095] Step 52, when When calculating the azimuth angle Pitch angle

[0096]

[0097] in The sum of channels IAA spectral estimation results for (q,m) are given. The results are the IAA spectrum estimation results for the azimuth difference channel. This is the IAA spectrum estimation result for the pitch difference channel; real(.) is the operation of taking the real part; k a k p These are the slopes of the single-pulse azimuth and elevation angle detection curves, respectively.

[0098] Step 53: Based on the actual geometric relationship between the radar and the target, calculate the three coordinates (x, y, z) of point (q, m) using the azimuth, elevation, and slant range. As the intensity value projected onto the point (x,y,z);

[0099] Step 54: Traverse 0≤q≤Q-1, 0≤m≤M-1 to complete the energy projection, and use point cloud to display the final imaging result.

[0100] The other steps and parameters are the same as those in one of the specific implementation methods one to six.

[0101] Specific Implementation Method 8: This implementation method is a single-pulse forward-looking 3D imaging system based on adaptive iterative spectrum estimation. The system is used to execute the single-pulse forward-looking 3D imaging method based on adaptive iterative spectrum estimation.

[0102] Specific Implementation Method Nine: This implementation method is a storage medium that stores at least one instruction. The at least one instruction is loaded and executed by a processor to implement the single-pulse forward-looking three-dimensional imaging method based on adaptive iterative spectrum estimation.

[0103] It should be understood that any method described in this invention can be provided as a computer program product, software, or computerized method, which may include a non-transitory machine-readable medium on which instructions are stored, which can be used to program a computer system or other electronic device. The storage medium may include, but is not limited to, magnetic storage media, optical storage media; magneto-optical storage media include: read-only memory (ROM), random access memory (RAM), erasable programmable memory (e.g., EPROM and EEPROM), and flash memory layers; or other types of media suitable for storing electronic instructions.

[0104] The beneficial effects of the present invention are verified using the following embodiments:

[0105] Example 1:

[0106] This embodiment of a single-pulse forward-looking 3D imaging method based on adaptive iterative spectrum estimation is prepared according to the following steps:

[0107] To simulate a real-world environment, signal-to-noise ratios were set to 30dB and 15dB, with the scenario being a stationary ship. Figure 2 For the geometric relationships of the scene, Figure 4 This shows the distribution of ship scattering points in the simulation scenario.

[0108] Establish a spatial coordinate system xyz, where the positive x-axis represents the radar platform's motion direction, the positive y-axis points vertically upwards, and the z-axis is obtained from the x and y axes using the right-hand rule. The antenna's half-power beamwidth is 3 degrees, and the antenna beam center is aligned with the scene center. The linear frequency modulated pulse signal has a carrier frequency of 33 GHz, a pulse repetition rate of 1000 Hz, a pulse width of 10 μs, a bandwidth of 160 MHz, and a sampling frequency of 200 MHz.

[0109] The radar's initial position is [-5000, 4000, -400], all in meters; the target's position is the origin, 6.5 km from the radar; the radar's velocity is V = 100 m / s.

[0110] (a) Performing forward-slant SAR imaging of the scene (traditional)

[0111] Calculations show that forward-slant SAR requires at least 1024 pulses to roughly image; too few pulses will result in severe defocusing; the final result is a two-dimensional image.

[0112] Figure 5 , Figure 6 , Figure 7 , Figure 8The images show the imaging results of 1024 pulses and 512 pulses of forward-slant SAR at signal-to-noise ratios of 15dB and 30dB, respectively. It can be seen that even at high signal-to-noise ratios, 256 pulses are still insufficient to form an image, making it difficult to determine the shape of the target; while receiving 1024 pulses can generate a clearer two-dimensional image.

[0113] Figure 5 , Figure 7 The images show the imaging results of 1024 pulses for forward-slant SAR at signal-to-noise ratios of 15dB and 30dB, respectively. It can be seen that the signal-to-noise ratio has little impact on the imaging results of forward-slant SAR.

[0114] (ii) Performing single-pulse forward-looking 3D imaging of the scene based on adaptive iterative spectrum estimation

[0115] Signal processing is performed according to the above-described invention process to obtain imaging results.

[0116] Figure 9 , Figure 10 The images show the three-dimensional imaging results of the present invention from different perspectives. Figure 11 , Figure 12 , Figure 13 The images shown are a top view, a front view, and a side view of the three-dimensional imaging result. It can be seen that even with a small number of pulses (256 pulses), the present invention can still roughly image the outline of the target ship, and the mast, bow, and stern can all be identified.

[0117] Figure 9 , Figure 10 , Figure 11 , Figure 12 , Figure 13 , Figure 14 , Figure 15 , Figure 16 , Figure 17 , Figure 18 The images show the three-dimensional, top, front, and side views at signal-to-noise ratios of 30dB and 15dB, respectively. It can be seen that although some areas are slightly out of focus at low signal-to-noise ratios, the images still identify the ship, indicating that the invention is still applicable under low signal-to-noise ratio conditions.

[0118] In summary, this invention can better display the target shape and contour under low pulse number conditions compared with traditional forward-slant SAR, reducing the required pulse number by 75% and the time required to acquire echoes by 75%. Secondly, compared with traditional forward-slant SAR, which can only perform two-dimensional imaging, the three-dimensional imaging capability of this invention increases the information in the imaging results and improves the target recognition, which is of great significance for identifying enemy targets. In addition, the energy projection threshold can be dynamically adjusted as needed, increasing it can reduce the amount of computation, while decreasing it can enrich the image details.

[0119] This invention can be applied to flight platforms equipped with monopulse radar, including but not limited to missile-borne seekers.

[0120] This invention may have other embodiments. Without departing from the spirit and essence of this invention, those skilled in the art can make various corresponding changes and modifications according to this invention, but these corresponding changes and modifications should all fall within the protection scope of the appended claims.

Claims

1. A single-pulse forward-looking three-dimensional imaging method based on adaptive iterative spectral estimation, characterized in that: The specific process of the method is as follows: Step 1: Perform range processing and range migration correction on the echoes of the radar and channel, azimuth difference channel and elevation difference channel respectively to obtain the pulse compression echo results of the and channel, azimuth difference channel and elevation difference channel, i.e., one-dimensional range image; Step 2: Perform minimum entropy envelope alignment and phase correction on the one-dimensional range image of the channel; synchronize the offset of each pulse to the one-dimensional range image of azimuth difference and elevation difference; Step 3: Based on the oblique angle θ of each distance unit xie With distance R m Construct a reference signal and use the reference signal to perform azimuth deskewing on the three channels; Step 4: Select the m-th distance cell after channel azimuth deskewing and perform adaptive iterative spectrum estimation; The spectrum estimation results are used as the initial values ​​for the m-th range cell iteration after azimuth deskewing processing of the azimuth and elevation difference channels, and adaptive iterative spectrum estimation is performed; m is traversed from 0 to M-1 to obtain the frequency domain results of the three channels; Where 0 ≤ m ≤ M-1, and M is the total number of distance cells; Step 5: Set the threshold; Traverse and channel frequency domain results across all distance cells; When the sum channel IAA spectrum estimation result of the qth sub-unit in the mth distance unit is less than the threshold, let q = q + 1 to continue the judgment, 0 ≤ q ≤ Q - 1, where Q is the total number of sub-units after IAA spectrum estimation set manually, and Q ≥ N; When the IAA spectrum estimation result of the sum channel of the qth sub-unit in the mth range cell is greater than or equal to the threshold, the azimuth and elevation angles are calculated by combining the frequency domain results of the azimuth difference channel and elevation difference channel of the corresponding pulse of the corresponding range cell. Based on geometric relationships, energy projection is performed on the q-th sub-unit (q,m) in the m-th distance unit that meets the conditions; the final three-dimensional imaging result is obtained. IAA stands for Adaptive Iterative Spectral Estimation.

2. The single-pulse forward-looking three-dimensional imaging method based on adaptive iterative spectrum estimation according to claim 1, characterized in that: In step one, range processing and range migration correction are performed on the echoes of the radar and channel, azimuth difference channel, and elevation difference channel, respectively, to obtain the pulse compression echo results of the and channel, azimuth difference channel, and elevation difference channel, i.e., the one-dimensional range image. The specific process is as follows: Step 11: During the movement of the carrier platform, the monopulse radar transmits linear frequency modulated pulse signals to the target. After being reflected by the target, the signals are received by the radar and processed to obtain echo signals from three channels: azimuth difference, elevation difference, and pitch difference. Steps 1 and 2: Using the same reference function, perform range-direction matched filtering on the echo signals of the sum, azimuth, and pitch difference channels respectively, and then perform range migration correction to obtain the pulse compression echo results of the sum, azimuth, and pitch difference channels, i.e., a one-dimensional range image.

3. The single-pulse forward-looking three-dimensional imaging method based on adaptive iterative spectrum estimation according to claim 2, characterized in that: The reference function expression is the transmission signal delay. Where c is the speed of light, R ref The reference distance is Δt, which is the signal transmission delay.

4. The single-pulse forward-looking three-dimensional imaging method based on adaptive iterative spectral estimation according to claim 3, characterized in that: In step two, the minimum entropy method is used to align the one-dimensional range image of the channel with the envelope and phase correction; the offset of each pulse is synchronized to the one-dimensional range image of azimuth difference and pitch difference. The specific process is as follows: Step 2: Align the one-dimensional distance image of the channel with the minimum entropy method, then perform phase correction, and record the offset of each pulse relative to the original pulse, denoted as d(n). Where n is the pulse number, 0≤n≤N-1, and N is the total number of echo pulses; Step 22: Synchronize the offset of each pulse to the one-dimensional range image of the azimuth difference channel and the pitch difference channel, that is, use d(n) to correct the one-dimensional range image of the azimuth difference channel and the pitch difference channel; The azimuth error correction formula is: Where n is the pulse sequence number, m is the range cell sequence number, v is the range cell sequence number, N is the total number of echo pulses, and M is the total number of range cells; s a0 S is a one-dimensional range image of the azimuth difference channel. a ′0 represents the row-wise DFT result of the one-dimensional range image of the azimuth difference channel, s a This is a one-dimensional range image after azimuth error correction; j is the imaginary unit, j 2 =-1; The pitch difference correction formula is: Where n is the pulse sequence number, m is the range cell sequence number, v is the range cell sequence number, N is the total number of echo pulses, and M is the total number of range cells; This is a one-dimensional range image of the pitch difference channel. The one-dimensional range image of the pitch difference channel is obtained by row-wise DFT. This is a one-dimensional range image after pitch error correction; DFT stands for Discrete Fourier Transform.

5. The single-pulse forward-looking three-dimensional imaging method based on adaptive iterative spectrum estimation according to claim 4, characterized in that: In step three, the oblique angle θ of each distance unit is used as a reference. xie With distance R m Construct a reference signal and use the reference signal to perform azimuth deskewing on the three channels; The specific process is as follows: Step 3:

1. Obtain the oblique angle θ of the m-th range cell in the N / 2-th pulse using inertial navigation. xie With distance R m Construct a reference signal in The Doppler center frequency of the m-th distance unit; t is the Doppler modulation frequency of the m-th distance unit; n =nT r For slow time, T r Where n is the pulse repetition time, n is the pulse number, and v′ is the radar platform speed. λ is the wavelength; 0 ≤ m ≤ M⁻¹; Step 3.2: Multiply the m-th range cell of the one-dimensional range image of the azimuth and pitch difference channels after envelope alignment and phase correction in Step 2 by the conjugate of the reference signal: Where s sm (t n ), s am (t n ), s pm (t n () represents the echo of the m-th range cell of the envelope-aligned sum, azimuth difference, and elevation difference channel signals; The reference signal is conjugate; · represents multiplication; s s (n,m), s a (n,m), s p (n,m) represent the sum channel, azimuth channel, and pitch difference channel data of the m-th range unit of the n-th pulse, respectively; Step 33: Repeat steps 31 and 32 until m is traversed from 0 to M-1, completing the azimuth and oblique directions of the three channels.

6. The single-pulse forward-looking three-dimensional imaging method based on adaptive iterative spectral estimation according to claim 5, characterized in that: In step four, the m-th range cell after azimuth deskewing of the channel is selected and adaptive iterative spectrum estimation is performed. The spectrum estimation result is used as the initial value for the iteration of the m-th range cell after azimuth deskewing of the azimuth difference channel and the elevation difference channel, and adaptive iterative spectrum estimation is performed. m is traversed from 0 to M-1 to obtain the frequency domain results of the three channels. The specific process is as follows: Step 4: Select the m-th range cell signal after channel azimuth deskewing, use the unit matrix as the initial value for iteration, and perform 15 IAA iterations. IAA stands for Adaptive Iterative Spectral Estimation Method; Step 42: Select the m-th range cell signal after azimuth deskewing processing of the azimuth difference channel, and use the result in Step 41 as the initial value for iteration to perform 10 IAA iterations. Select the m-th range cell signal after azimuth deskewing processing of the pitch difference channel, and use the result in step 4.1 as the initial value for iteration to perform 10 IAA iterations. Step 43: Repeat steps 41 and 42 until m is traversed from 0 to M-1 to complete the IAA spectrum estimation of the three channels and obtain the frequency domain results of the three channels.

7. The single-pulse forward-looking three-dimensional imaging method based on adaptive iterative spectral estimation according to claim 6, characterized in that: In step five, a threshold is set; Traverse and channel frequency domain results across all distance cells; When the sum channel IAA spectrum estimation result of the qth sub-unit in the mth distance unit is less than the threshold, let q = q + 1 to continue the judgment, 0 ≤ q ≤ Q - 1, where Q is the total number of sub-units after IAA spectrum estimation set manually, and Q ≥ N; When the IAA spectrum estimation result of the sum channel of the qth sub-unit in the mth range cell is greater than or equal to the threshold, the azimuth and elevation angles are calculated by combining the frequency domain results of the azimuth difference channel and elevation difference channel of the corresponding pulse of the corresponding range cell. Based on geometric relationships, energy projection is performed on the q-th sub-unit (q,m) in the m-th distance unit that meets the conditions; the final three-dimensional imaging result is obtained. IAA stands for Adaptive Iterative Spectral Estimation Method; The specific process is as follows: The q-th sub-unit (q,m) in each of the m-th distance units that meet the conditions is: the (q,m) whose sum channel IAA spectrum estimation result is greater than or equal to the threshold D; Step 51: Set the threshold D to the median amplitude of all cells in the channel IAA spectrum estimation results; Step 52, when When calculating the azimuth angle Pitch angle in The sum of channels IAA spectral estimation results for (q,m) are given. The results are the IAA spectrum estimation results for the azimuth difference channel. This is the IAA spectrum estimation result for the pitch difference channel; real(.) is the operation of taking the real part; k a k p These are the slopes of the single-pulse azimuth and elevation angle detection curves, respectively. Step 53: Based on the actual geometric relationship between the radar and the target, calculate the three coordinates (x, y, z) of point (q, m) using the azimuth, elevation, and slant range. As the intensity value projected onto the point (x,y,z); Step 54: Traverse 0≤q≤Q-1, 0≤m≤M-1 to complete the energy projection, and use point cloud to display the final imaging result.

8. A single-pulse forward-looking three-dimensional imaging system based on adaptive iterative spectral estimation, characterized in that, The system is used to perform the single-pulse forward-looking three-dimensional imaging method based on adaptive iterative spectrum estimation as described in any one of claims 1 to 7.

9. A storage medium, characterized in that, The storage medium stores at least one instruction, which is loaded and executed by a processor to implement the single-pulse forward-looking three-dimensional imaging method based on adaptive iterative spectrum estimation as described in any one of claims 1 to 7.

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