An echo generation method based on single-frequency MIMO arc scanning

Abstract

This invention provides an echo generation method based on single-frequency MIMO arc scanning. Using simulated single-frequency MIMO arc scanning data as input, the method employs a filtered back projection (BP) algorithm to generate three-dimensional images at different attitudes. Scattering center information from the three-dimensional images is extracted to form a list of all-attitude three-dimensional scattering centers. Echoes are synthesized by weighted superposition of scattering center contributions based on the geometric relationship between the radar and the scattering centers, combined with directivity patterns. This method significantly reduces the amount of broadband data required by traditional imaging methods, improves the modeling efficiency of single-frequency input, and can adapt to echo simulations for arbitrary paths and a large number of attitudes, significantly enhancing echo simulation efficiency.

Description

Technical Field

[0001] The present invention relates to a radar target characteristic simulation technology, and in particular to an echo generation method based on single-frequency MIMO arc scanning. Background Art

[0002] Generating target echoes involves radar transmit and receive waveforms, motion trajectories, and relative attitude. In practical engineering applications, this often requires generating massive amounts of target echoes, making direct electromagnetic computational solutions prohibitively time-consuming. Acquiring echoes based on scattering center models is a common technique, but scattering center acquisition requires both broadband data imaging and full-attitude scattering center modeling, creating significant efficiency challenges. Summary of the Invention

[0003] The purpose of the present invention is to provide an echo generation method based on single-frequency MIMO arc scanning, which drastically reduces the amount of broadband data required by traditional imaging methods, improves the modeling efficiency of single-frequency input, can adapt to arbitrary path and massive attitude echo simulation, and greatly improves the echo simulation efficiency.

[0004] To achieve the above objectives, the present invention provides an echo generation method based on single-frequency MIMO arc scanning. The method uses simulated single-frequency MIMO arc scanning data as input, adopts a filtered back projection (BP) algorithm to form three-dimensional imaging in different postures, extracts scattering center information of the three-dimensional imaging to form a full-pose three-dimensional scattering center list, and synthesizes the echo by weighted superposition of the contributions of the scattering centers based on the geometric relationship between the radar and the scattering centers in combination with the directional diagram.

[0005] The method for obtaining single-frequency MIMO arc scanning data includes: establishing an input model of a target to be determined and arc scanning MIMO, and calculating the single-frequency MIMO arc scanning multi-base scattered electric field using an electromagnetic field calculation method.

[0006] The method of establishing the input model of the target and arc scanning MIMO includes:

[0007] In the electromagnetic simulation software, the geometric center of the target is placed at the coordinate origin, and the arc diameter is set to 2 to 3 times the target size;

[0008] In the simulation calculation, N transmitting antennas and receiving antennas with a distance interval of λ / 2 are set on the arc to form a MIMO system. During the simulation calculation, N×N two-dimensional matrix electric field data is obtained.

[0009] The method for calculating the single-frequency MIMO arc scanning multi-base scattered electric field using the electromagnetic field calculation method includes:

[0010] Select the frequency domain electromagnetic calculation method according to the electrical size of the target. When the target electrical size is less than 100λ, select MLFMM. When the target electrical size is greater than 100λ, select the bouncing ray method.

[0011] The pitch angle of the target is rotated in steps, and two-dimensional matrix electric field data is acquired in sequence to form spherical electric field data surrounding the target.

[0012] The method of using the BP algorithm to form three-dimensional imaging in different postures includes: calculating the distance between each pixel and each antenna position without approximation, performing coherent superposition in the time domain along the trajectory of each scattering point, and realizing multiple three-dimensional imaging of the target at different pitch angles and azimuth angles in the uniform discrete space of the entire spherical surface.

[0013] The method for extracting scattering center information of three-dimensional imaging includes: extracting three-dimensional scattering center information using a CLEAN algorithm from multiple three-dimensional images of a target to form a scattering center list;

[0014] The scattering center information at least includes a position and an amplitude.

[0015] The echo voltage calculation expression is:

[0016]

[0017] Where λ is the wavelength, G T and G R are the transmitting antenna gain and the receiving antenna gain, R m is the distance from the detector to the scattering center, p is the detector emission waveform, A m is the scattering center amplitude, obtained from the scattering center list.

[0018] The present invention can improve the computing efficiency of input and output, and specifically has the following advantages:

[0019] 1. Dramatically reduce the amount of broadband data required by traditional imaging methods;

[0020] 2. MIMO arc scanning further improves the modeling efficiency of single-frequency input;

[0021] 3. Only one acquisition of the full-attitude scattering center list is required, which can adapt to arbitrary paths and massive attitude echo simulations, greatly improving the echo simulation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a flow chart of an echo generation method based on single-frequency MIMO arc scanning provided by the present invention.

[0023] Figure 2 Schematic diagram of the target of the present invention and arc scanning MIMO input model.

[0024] Figure 3 Schematic diagram of the detector irradiating a target according to the present invention. DETAILED DESCRIPTION

[0025] As described in the background technology, there is currently no efficient full-attitude three-dimensional scattering center extraction and echo generation method. Research has found that the Beijing Institute of Environmental Characteristics has implemented a recursive solution transformation of single-frequency radar echoes, lateral distribution history diagrams, spatial parameter domain images, target scattering point positions, and target scattering point amplitudes in the patent "A Single-Frequency Radar Imaging Method and Device" (Publication No.: CN109444843A); in the patent "A Single-Frequency Radar Imaging Method for Spinning Targets" (Publication No.: CN105353374A), the radar echo is divided into N sub-apertures, and Fourier transform and inverse Radon transform are performed in sequence to reconstruct the first image of the target, and the CLEAN algorithm is used to reconstruct the second image of the target. In the patent "Azimuth Imaging Method of MIMO Curved Array in Terahertz Band" (publication number: CN109001754A) of the Institute of Electronics of the Chinese Academy of Sciences, a geometric transformation relationship between MIMO curved array and MIMO linear array is established. Combining compensation function and spatial spectrum, imaging is performed in the azimuth direction of the equivalent MIMO linear array to obtain the target reflection coefficient function.

[0026] Of the three patents mentioned above, the first patent uses single-base electric field data as the input for the entire processing process. The second patent uses sub-aperture partitioning technology, and the rest is consistent with the first patent. The third patent only forms azimuth two-dimensional imaging, and the imaging method adopts a modified Omega-K algorithm. The present invention is a three-dimensional imaging method based on frequency domain BP.

[0027] In the current public literature, Qiao Cheng focused on analyzing the resolution of several imaging algorithms in the single-frequency data mode in his IEEE conference paper "Resolution Analysis of Compressed Sensing Based Methods for Single Frequency Radar Imaging". Wu Shiyou introduced the equivalent conversion between MIMO arc arrays and MIMO linear arrays in his paper "Research on Azimuth Imaging Algorithms for Terahertz MIMO Arc Arrays" in the Journal of Electronics and Information Technology, established a corresponding new imaging model, and designed a single-frequency azimuth imaging algorithm. At the same time, in the IEEE journal paper "A Modified Omega-K Algorithm for Near-Field Single-Frequency MIMO-Arc-Array-Based Azimuth Imaging", the focus was on making corrections at the imaging algorithm level. The above three papers did not involve echo calculation based on the scattering center model, which is different from the present invention.

[0028] The present invention proposes a fast echo simulation calculation method for obtaining full-attitude scattering centers and forming a scattering center model based on 3D imaging of single-frequency MIMO arc scanning data. It can adapt to arbitrary path and massive attitude echo simulation, greatly improving the echo simulation efficiency.

[0029] The following is based on Figures 1 to 3 , specifically describe the preferred embodiments of the present invention.

[0030] like Figure 1 As shown, the present invention provides an echo generation method based on single-frequency MIMO arc scanning, comprising the following steps:

[0031] Step S1: establishing an input model of a target and arc scanning MIMO;

[0032] In the electromagnetic simulation software, the geometric center of the target is placed at the coordinate origin, and the arc diameter is generally set to 2-3 times the target size;

[0033] In the simulation, N transmitting and receiving antennas with a spacing of λ / 2 are set on the arc to form a MIMO system. During the simulation, N×N multi-base scattered electric field data (two-dimensional matrix) are obtained.

[0034] Figure 2 Schematic diagram of the target and arc scanning MIMO input model of the present invention, where × represents the MIMO transmit / receive position, and the circle in the XoZ plane is the target rotation step rotation path;

[0035] Step S2, using an electromagnetic field calculation method to calculate the single-frequency MIMO arc scanning multi-base scattered electric field;

[0036] Select the frequency domain electromagnetic calculation method according to the electrical size of the target. Generally speaking, when the electrical size of the target is less than 100λ, select MLFMM, and when the electrical size is greater than 100λ, select the bouncing ray method;

[0037] Step the pitch angle of the rotating target to obtain two-dimensional matrix electric field data in sequence, thereby forming spherical electric field data surrounding the target, providing data input for three-dimensional imaging in step S3;

[0038] Step S3: performing three-dimensional imaging of the entire space at different incident directions using a BP imaging algorithm;

[0039] The BP algorithm is used to process the scattered electric field calculated in step S2. BP calculates the distance between each pixel and each antenna position without approximation and performs coherent superposition in the time domain along the trajectory of each scattering point, thereby achieving high-resolution imaging. In the uniformly discrete space of the entire sphere, multiple three-dimensional images of the target at different pitch angles and azimuth angles are achieved, which serves as input for the scattering center extraction in step S4.

[0040] Step S4: extracting scattering centers to form a full-pose three-dimensional scattering center list;

[0041] For the multiple three-dimensional images obtained in step S3 above, the CLEAN algorithm is used to extract the three-dimensional scattering center information (position, amplitude), thereby forming a scattering center list;

[0042] Step S5: Based on the geometric relationship between the radar and the scattering center, the contribution of the scattering center is weighted and superimposed in combination with the directivity pattern to synthesize the echo;

[0043] The echo voltage calculation expression is:

[0044]

[0045] Where λ is the wavelength, G T and G R are the transmitting antenna gain and the receiving antenna gain, R m is the distance from the detector to the scattering center, p is the detector emission waveform, A m is the scattering center amplitude, which can be obtained from the scattering center list calculated in step S4.

[0046] Figure 3 This is a schematic diagram of the detector of the present invention illuminating a target. The black dots represent the three-dimensional scattering center distribution of the target in this state. The antenna pattern irradiates the target, and the scattering center amplitude and the antenna gain weight are superimposed to form an echo.

[0047] Compared with the prior art, the present invention has the following advantages:

[0048] The present invention has extremely high solution efficiency in solving the fully diffused foil cloud echo, and the simulation time is improved by orders of magnitude compared with the accurate low-frequency modeling method.

[0049] The present invention adopts single-frequency imaging technology. Traditional imaging methods (three-dimensional) generally require scanning in three dimensions of frequency, pitch and azimuth. Single-frequency imaging reduces the amount of data from three dimensions to two dimensions, which is an order of magnitude reduction.

[0050] The present invention adopts MIMO arc scanning. MIMO speeds up the speed of simulating and acquiring data, and arc scanning increases the angle range of the observed target, laying the foundation for fast and accurate three-dimensional imaging.

[0051] The present invention forms a list of all-attitude scattering centers through full-space scanning imaging, which has broad practical value. The all-attitude scattering centers are only a function of frequency. Once established, they can adapt to arbitrary paths and massive attitude echo simulations, meet the actual needs of engineering applications, and can be reused in obtaining a large number of target echoes.

[0052] The present invention can be directly expanded to form a physical device. The target is placed on a low-scattering bracket and is rotated stepwise along the target's geometric center and a circle orthogonal to the MIMO arc to obtain test data consistent with the simulation properties of the present invention.

[0053] It should be noted that in the embodiments of the present invention, the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate the description of the embodiments. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0054] Although the present invention has been described in detail through the above preferred embodiments, it should be understood that the above description is not intended to limit the present invention. After reading the above description, various modifications and substitutions of the present invention will become apparent to those skilled in the art. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. An echo generation method based on single-frequency MIMO arc scanning, characterized in that: Using the single-frequency MIMO arc scanning data obtained through simulation as input, the filtered back projection (BP) algorithm is used to generate three-dimensional images at different postures. The scattering center information of the three-dimensional imaging is extracted to form a list of three-dimensional scattering centers in all postures. Based on the geometric relationship between the radar and the scattering centers, the contributions of the scattering centers are weighted and superimposed in combination with the directional pattern to synthesize the echo. The method for obtaining single-frequency MIMO arc scanning data includes: establishing an input model of a target to be determined and arc scanning MIMO, and calculating the single-frequency MIMO arc scanning multi-base scattered electric field using an electromagnetic field calculation method; The method of establishing the input model of the target and arc scanning MIMO includes: In the electromagnetic simulation software, the geometric center of the target is placed at the coordinate origin, and the arc diameter is set to 2 to 3 times the target size; In the simulation calculation, N transmitting antennas and receiving antennas with a distance interval of λ / 2 are set on the arc to form a MIMO system. During the simulation calculation, N×N two-dimensional matrix electric field data is obtained; The method for calculating the single-frequency MIMO arc scanning multi-base scattered electric field using the electromagnetic field calculation method includes: Select the frequency domain electromagnetic calculation method according to the target electrical size. When the target electrical size is less than 100λ When the target electrical size is greater than 100λ, the bouncing ray method is selected. The pitch angle of the rotating target is stepped to obtain two-dimensional matrix electric field data in sequence, forming spherical electric field data surrounding the target; The method of using the BP algorithm to form 3D images in different postures includes: calculating the distance between each pixel and each antenna position, performing coherent superposition in the time domain along the trajectory of each scattering point, and achieving multiple 3D images of the target at different pitch angles and azimuth angles in a uniformly discrete space across the entire sphere; The method for extracting scattering center information of three-dimensional imaging includes: extracting three-dimensional scattering center information using a CLEAN algorithm from multiple three-dimensional images of a target to form a scattering center list; The scattering center information at least includes position and amplitude; The echo voltage calculation expression is: Where λ is the wavelength, G T and G R are the transmitting antenna gain and the receiving antenna gain, R m is the distance from the detector to the scattering center, p is the detector emission waveform, A m is the scattering center amplitude, which is obtained from the scattering center list, and f0 refers to the center frequency of the radar operation.

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