Three-dimensional fast imaging method based on cylindrical aperture radar

Abstract

This application relates to a rapid three-dimensional imaging method based on cylindrical aperture radar, comprising: establishing a three-dimensional imaging geometric model of cylindrical aperture radar to obtain at least the distance expression from the antenna array elements to the target point; obtaining a phase-compensated signal based on echo signal preprocessing; performing elevation-based phase stabilization processing to at least eliminate the influence of radar carrier altitude; and constructing a two-dimensional spatial frequency domain to obtain a two-dimensional spatial frequency signal to reconstruct the target's scattering information. This application can improve focusing consistency and imaging robustness across the entire radial range.

Description

Technical Field

[0001] This application relates to the field of radar imaging and synthetic aperture radar (SAR) technology, and in particular to a method for rapid three-dimensional imaging based on cylindrical aperture radar. Background Technology

[0002] Existing radar imaging technology has significant bottlenecks in real-time performance and imaging quality. However, the most commonly used focusing algorithm in traditional near-field 3D imaging is the time-domain algorithm, such as the BP algorithm. While the time-domain algorithm can accurately reconstruct the target image, it has a large computational load and is slow in data processing. Therefore, there is an urgent need for a method that can ensure imaging resolution while further saving algorithm processing time. Summary of the Invention

[0003] This application provides a method for rapid three-dimensional imaging based on cylindrical aperture radar, which can improve focusing consistency and imaging robustness across the entire radial range.

[0004] According to one of the solutions in this application, a method for rapid three-dimensional imaging based on cylindrical aperture radar is provided, including:

[0005] Establish a three-dimensional imaging geometric model for cylindrical aperture radar to at least obtain the distance expression from the antenna array element to the target point; Based on the preprocessing of the echo signal, the phase-compensated signal is obtained; The elevation-based phase-stabilized method can at least eliminate the influence of radar carrier altitude. Two-dimensional spatial frequency domain is constructed to obtain two-dimensional spatial frequency signals, thereby reconstructing the scattering information of the target.

[0006] In some embodiments, establishing a three-dimensional imaging geometric model for cylindrical aperture radar, at least obtaining the distance expression from the antenna array elements to the target point, includes: By approximating the coordinates of the transmitting and receiving array elements to be at the same location, and using the equivalent sampling point coordinates and any target point on the human body surface, the radar transmits a frequency-modulated continuous wave signal. The echo signal received inside the cylindrical aperture is expressed as follows; The distance from the antenna array elements to the target point is determined.

[0007] In some embodiments, obtaining the phase-compensated signal based on echo signal preprocessing includes: Perform frequency mixing and descrambling on the transmitted and received signals; At least by converting the frequency modulated continuous wave intermediate frequency signal into a single frequency signal, a phase-compensated signal can be obtained.

[0008] In some embodiments, the elevation-to-stable phase method processing includes: Based on the wavenumbers of the minimum and maximum frequencies, the corresponding echo signal data is expressed. An estimated representation of the reflectance image is obtained, and the signal is then transferred to the target point height plane for subsequent two-dimensional processing.

[0009] In some embodiments, where the measured corresponding echo signal data is expressed similarly to a Fourier integral: The reflectance image of the target point is estimated by using an integral similar to its inverse transform.

[0010] In some embodiments, the integration of the inverse transform is achieved by performing a one-dimensional convolution in the elevation direction.

[0011] In some embodiments, the two-dimensional spatial frequency domain construction includes: By introducing polar coordinates, a connection is established between the original data and the spatial frequency domain; The signal phase is set in polar coordinate format, based at least on the spatial location and spatial angle of the target point; With radius The cylindrical imaging region is uniformly divided into A series of concentric rings are used to obtain the horizontal radius of the area to be imaged; Retain linear terms representing the target location and filter out terms that include radar location.

[0012] In some embodiments, the signal phase in polar coordinates includes radar position information varying with azimuth angle and target planar information.

[0013] In some embodiments, the two-dimensional spatial frequency domain construction further includes: Obtain a spatial frequency polar coordinate domain signal containing only target location information; By mapping polar coordinate data to rectangular coordinate data through coordinate mapping relationships, a two-dimensional spatial frequency signal can be obtained.

[0014] In some embodiments, the two-dimensional spatial frequency domain construction further includes: performing a three-dimensional inverse Fourier transform on the signal to obtain a profile image, and repeating the same operation on all cylinders within the ring radius range to reconstruct the scattering information of the target.

[0015] This application presents a cylindrical aperture radar-based three-dimensional rapid imaging method, which at least establishes a three-dimensional imaging geometric model of the cylindrical aperture radar and obtains the distance expression from the antenna array elements to the target point. Based on echo signal preprocessing, a phase-compensated signal is obtained. A vertically stabilized phase method is used to at least eliminate the influence of radar carrier altitude. A two-dimensional spatial frequency domain is constructed to obtain a two-dimensional spatial frequency signal to reconstruct the target's scattering information. Addressing the problem of high computational load and slow data processing in traditional time-domain imaging algorithms, this method provides a cylindrical aperture radar three-dimensional rapid imaging method based on polar coordinate frequency domain mapping. By establishing a direct frequency domain mapping relationship between the echo signal and the target's spatial position, and then using a phase-stabilized phase method to effectively separate elevation angle information, efficient spatial frequency domain reconstruction is achieved. Polar coordinate transformation and phase compensation mechanisms are introduced into the spatial frequency domain to achieve efficient three-dimensional reconstruction of the cylindrical aperture radar. Simultaneously, in the two-dimensional frequency domain transformation and phase compensation stages, the geometric distance difference caused by the target's radial position variation is incorporated into phase consistency correction. A radial partitioning reference compensation mechanism suppresses focusing degradation caused by radial spatial variability, thereby improving focusing consistency and imaging robustness across the entire radial range.

[0016] It should be understood that the foregoing general description and the following detailed description are exemplary and illustrative only, and are not intended to limit the scope of this application. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A schematic diagram of the overall process of a three-dimensional fast imaging method based on cylindrical aperture radar according to an embodiment of this application is shown; Figure 2 A schematic diagram of a cylindrical array three-dimensional imaging geometric model according to an embodiment of this application is shown. Detailed Implementation

[0019] Various embodiments and features of this application are described herein with reference to the accompanying drawings.

[0020] It should be understood that various modifications can be made to the embodiments described herein. Therefore, the above description should not be considered as limiting, but merely as an example of embodiments. Other modifications within the scope and spirit of this application will be apparent to those skilled in the art.

[0021] The accompanying drawings, which are included in and form part of this specification, illustrate embodiments of the present application and, together with the general description of the present application given above and the detailed description of the embodiments given below, serve to explain the principles of the present application.

[0022] These and other features of this application will become apparent from the following description of preferred forms of embodiments given as non-limiting examples, with reference to the accompanying drawings.

[0023] It should also be understood that although this application has been described with reference to some specific examples, those skilled in the art can certainly implement many other equivalent forms of this application.

[0024] The above and other aspects, features and advantages of this application will become more apparent when taken in conjunction with the accompanying drawings and in view of the following detailed description.

[0025] Specific embodiments of this application are described thereafter with reference to the accompanying drawings; however, it should be understood that the claimed embodiments are merely examples of this application, which can be implemented in various ways. Well-known and / or repeated functions and structures are not described in detail to avoid unnecessary or redundant details that could obscure the application. Therefore, the specific structural and functional details claimed herein are not intended to be limiting, but merely serve as the basis and representative basis for the claims to teach those skilled in the art to use this application in a variety of substantially any suitable detailed structures.

[0026] This specification may use the phrases “in one embodiment,” “in another embodiment,” “in yet another embodiment,” or “in other embodiments,” all of which may refer to one or more of the same or different embodiments according to this application.

[0027] In fields such as public safety, counter-terrorism, and riot control, millimeter-wave 3D imaging technology serves as a core support for security checks and target recognition. Its imaging resolution, signal-to-noise ratio, and reconstruction speed directly affect the accuracy and reliability of scene perception. Millimeter-wave 3D imaging technology, with its superior penetration of non-metallic materials such as clothing and its non-contact, non-ionizing radiation detection methods, can accurately and quickly image and detect hidden dangerous objects on or near the human body without infringing on privacy. This makes it irreplaceable in scenarios such as human security checks. Millimeter-wave imaging systems are mainly divided into two imaging geometric models: planar scanning and cylindrical scanning. Cylindrical scanning uses a set of antenna arrays in the vertical direction to move in a circle around the target, thus forming a two-dimensional scanning cylinder. Compared to planar array scanning security equipment, cylindrical array scanning security equipment can obtain a larger observation angle and acquire more detailed information within the observed scene, significantly improving scanning efficiency and attracting widespread attention from researchers both domestically and internationally. Since human security checks require accurate detection of targets within a short time, they are real-time in nature, necessitating rapid judgment and decision-making in real-time situations.

[0028] Based on the background section described above, this application provides illustrative solutions to address the deficiencies in the prior art through embodiments, but these are not intended to limit the scope of patent protection claimed in this application.

[0029] As one of the solutions, comprehensive Figure 1 and Figure 2 As shown, embodiments of this application provide a method for rapid three-dimensional imaging based on cylindrical aperture radar, including: Establish a three-dimensional imaging geometric model for cylindrical aperture radar to at least obtain the distance expression from the antenna array element to the target point; Based on the preprocessing of the echo signal, the phase-compensated signal is obtained; The elevation-based phase-stabilized method can at least eliminate the influence of radar carrier altitude. Two-dimensional spatial frequency domain is constructed to obtain two-dimensional spatial frequency signals, thereby reconstructing the scattering information of the target.

[0030] Regarding the foregoing content, this application aims to provide at least one method for rapid 3D imaging based on cylindrical aperture radar. This method involves acquiring and modeling radar echo signals according to the transceiver mechanism of cylindrical array radar; performing frequency mixing and deskewing processing on the received echo signals; compensating the deskewing signals to convert the frequency-modulated continuous wave signal into a single-frequency signal; separating elevation information to achieve efficient spatial frequency domain reconstruction; and mapping two-dimensional frequency domain data to the polar coordinate spatial frequency domain by introducing polar coordinate transformation and filtering compensation strategies in the horizontal direction, further completing global 3D imaging reconstruction. The 3D rapid imaging method based on near-field millimeter-wave cylindrical aperture radar disclosed in various embodiments of this application effectively separates elevation information using a stationary phase method and completes spatial frequency domain 3D imaging through polar coordinate transformation and filtering compensation strategies. This method is suitable for scenarios such as human security checks, public safety detection, and near-field fine imaging.

[0031] In a specific embodiment of the present disclosure, the three-dimensional fast imaging method based on cylindrical aperture radar can be generally described in two parts: imaging modeling and imaging algorithm. Each part can be illustrated by step S1 to step S4 in the following sections.

[0032] In some implementation schemes, the embodiments of this application may include: establishing a three-dimensional imaging geometric model of a cylindrical aperture radar to obtain at least the distance expression from the antenna array element to the target point, including: approximating the coordinates of the transmitting array element and the receiving array element at the same position, obtaining the radar transmitting frequency-modulated continuous wave signal expression through the equivalent sampling point position coordinates and any target point on the human body surface; obtaining the received echo signal expression within the cylindrical aperture; and determining the distance expression from the antenna array element to the target point.

[0033] Step S1: Establish a three-dimensional imaging geometric model for cylindrical aperture radar.

[0034] Step S11: Establish a three-dimensional imaging geometric model of a cylindrical array, such as... Figure 2 This illustration shows a schematic diagram of a cylindrical array three-dimensional imaging geometric model according to an embodiment of this application. The human body is located in a constructed Cartesian coordinate system OXYZ, where X represents the range direction, Y represents the azimuth direction, and Z represents the altitude direction. M transmitting array elements Tx are vertically and equally spaced on the antenna plane, and M receiving array elements Rx are also vertically and equally spaced on the antenna plane. A cylindrical aperture is formed by circular motion around the Z-axis with radius [missing information]. Based on the principle of equivalent phase center, the coordinates of the transmitting and receiving elements can be approximated as being at the same location. The coordinates of the equivalent sampling point are denoted as [missing information]. Any target point on the human body surface is denoted as The radar transmits frequency-modulated continuous wave signals. Its signal expression is as follows: ; in, The center frequency of the signal. For distance terms, time is a variable, and , For signal duration, The signal is frequency modulated, and the signal bandwidth is... .

[0035] Step S12: Within the diameter of the cylindrical cavity The received echo signal It is expressed as follows: ; in It is the reflectivity of the target point. It is the time difference between when the signal is emitted from the transmitting element, reaches the target, and returns to the receiving element. This represents the speed of electromagnetic wave propagation.

[0036] Step S13: Distance from antenna element to target point The expression is: .

[0037] In some implementations, the embodiments of this application may be as follows: obtaining a phase-compensated signal based on echo signal preprocessing, including: performing frequency mixing and descrambling processing on the transmitted and received signals; at least by converting the frequency-modulated continuous wave intermediate frequency signal into a single-frequency signal to obtain the phase-compensated signal.

[0038] In this embodiment, step S2 can be added on top of step S1.

[0039] Step S2: Echo signal preprocessing.

[0040] Step S21: Perform frequency mixing and de-chewing processing on the transmitted and received signals: .

[0041] Step S22: Perform phase compensation processing. Because the intermediate frequency signal obtained after the mixing and de-skewing process contains residual video phase, i.e. The residual video phase causes the echo signal phase to deviate, interfering with the reflectivity phase information of the target point. Therefore, phase compensation is required, converting the FM continuous wave intermediate frequency signal into a single-frequency signal, with the phase compensation factor set as follows: .

[0042] Step S23: Obtain the phase-compensated signal: .

[0043] In some implementations, the embodiments of this application may be: elevation-based steady-state processing, including: obtaining the corresponding echo signal data representation based on the wavenumbers of the minimum and maximum frequencies; obtaining an estimated representation of the reflectivity image, thereby the signal is transmitted to the target point height plane for subsequent two-dimensional processing.

[0044] In cases where the measured echo signal data is expressed similarly to a Fourier integral, the estimate of the reflectivity image of the target point is obtained by using an integral similar to its inverse transform. The integral of the inverse transform can be achieved by performing a one-dimensional convolution in the elevation direction.

[0045] In this embodiment, step S3 can be added on top of step S2.

[0046] Step S3: Elevation-based stable phase method processing.

[0047] Step S31: Acquired backscattering data It is a function of two spatial coordinates and one time variable. The time variable is related to the frequency and wavenumber. Directly related, among which , and These are the wavenumbers at the minimum and maximum frequencies, respectively. Therefore, the measured corresponding echo signal data can also be expressed as... As shown below: .

[0048] Step S32: The above equation is similar to a Fourier integral. The estimate of the reflectance image of the target point can be obtained by using an integral similar to its inverse transform, i.e.: .

[0049] Step S33: To calculate the integral in the above equation that is similar to its inverse transform, let .

[0050] Step S34: The estimation expression for the reflectance image can then be expressed as: .

[0051] Step S35: The integral, similar to its inverse transform, can be calculated by performing a one-dimensional convolution in the elevation direction, i.e.: .

[0052] Step S36: To improve computational efficiency, the Fast Fourier Transform (FFT) can be used to reduce computational complexity. Therefore, the convolution in the elevation domain can be performed as a complex product in the Fourier domain, i.e.: ; ; in, It is an echo signal Fourier transform in the elevation domain.

[0053] Step S37: Subsequently, the above one-dimensional convolution in the elevation direction can be expressed as: .

[0054] Step S38: Perform complex product calculations in the Fourier domain, which can be solved using the MSP method. .

[0055] Step S39: Therefore, the above It can be represented as: .

[0056] Step S310: The estimation expression for the reflectance image can then be written as: .

[0057] Step S311: Wherein let .

[0058] Step S312: At this point, the influence of radar carrier altitude has been eliminated, and the signal is transmitted to the target point altitude plane. Next, two-dimensional processing is performed.

[0059] In some implementations, embodiments of this application may include: two-dimensional spatial frequency domain construction, comprising: introducing a polar coordinate format to establish a connection between the original data and the spatial frequency domain; setting the signal phase in polar coordinate format based at least on the spatial location and spatial angle of the target point; and setting the signal phase with a radius of... The cylindrical imaging region is uniformly divided into A concentric ring is formed to obtain the horizontal radius of the observation area to be imaged; the linear term of the target position is retained, and the term containing the radar position is filtered out.

[0060] The polar coordinate format of the signal phase includes radar position information that varies with azimuth angle and target planar information.

[0061] In this embodiment, step S4 can be added on top of step S3.

[0062] Step S4: Two-dimensional spatial frequency domain construction.

[0063] Step S41: Analyze the signal phase: .

[0064] Step S42: In order to link the original data with the spatial frequency domain, introduce... In polar coordinate format , and At this point, the signal phase is represented in polar coordinates as follows: .

[0065] Step S43: Setting , in For the spatial location of the target point, The target space angle.

[0066] Step S44: Phase It includes radar position information that varies with azimuth angle, phase... Including planar information of the target, filtering and compensation processing is required to obtain a spatial frequency domain signal containing only the target's linear phase. However, when the target's radial position changes within the horizontal plane, the radar's geometric distance to the target will significantly alter, leading to increased radial spatial variability and deterioration in focusing performance with position. Therefore, a partitioned compensation approach is subsequently adopted in the radial dimension to improve imaging consistency and robust focusing capability across the entire radial range. A radius of... The cylindrical imaging region is uniformly divided into With a series of concentric rings, the formula for calculating the radius of the horizontal plane of the area to be imaged can be obtained as follows: , in, and These are the closest distance to the imaging observation horizontal plane and the farthest distance to the imaging observation horizontal plane, respectively. Indicates the ground distance resolution. This indicates the angle of incidence for the transmitting and receiving antenna arrays.

[0067] Step S45: The distance term for the m-th ring is: , in, Use the target as a reference angle.

[0068] Step S46: Set the filter for: .

[0069] Step S47: Setting , in, , The horizontal angle of the scene.

[0070] Step S48: The linear term representing the target position is retained, while the term containing the radar position is filtered out. The signal expression is: .

[0071] Step S49: At this stage, obtain a spatial frequency polar coordinate domain signal containing only target location information. Then through coordinate mapping relationships By mapping polar coordinate data to Cartesian coordinates, a two-dimensional spatial frequency signal can be obtained. This data format conversion can be achieved through two-dimensional interpolation. Finally, the signal... Performing a three-dimensional inverse Fourier transform (3-D IFT) yields a profile image. Repeating the same operation on all cylinders within the annular radius reconstructs the target's scattering information.

[0072] This disclosure also provides a three-dimensional rapid imaging device based on cylindrical aperture radar, including one or more processing modules configured to execute the three-dimensional rapid imaging method based on cylindrical aperture radar described above, and at least configured to execute specific implementations of steps S1 to S4.

[0073] Based on the above-mentioned inventive concept, the cylindrical aperture radar-based three-dimensional rapid imaging method and apparatus of various embodiments disclosed herein at least establish a three-dimensional imaging geometric model of the cylindrical aperture radar and obtain at least the distance expression from the antenna array elements to the target point; obtain the phase-compensated signal based on the echo signal preprocessing; perform elevation-oriented phase stabilization processing to at least eliminate the influence of radar carrier altitude; construct a two-dimensional spatial frequency domain to obtain a two-dimensional spatial frequency signal to reconstruct the target's scattering information. Therefore, addressing the problem of large computational load and slow data processing in traditional time-domain imaging algorithms, this invention provides a cylindrical aperture radar three-dimensional rapid imaging method based on polar coordinate frequency domain mapping. By establishing a direct frequency domain mapping relationship between the echo signal and the target's spatial position, and then using a phase stabilization method to effectively separate elevation angle information, efficient spatial frequency domain reconstruction is achieved. Polar coordinate transformation and phase compensation mechanisms are introduced into the spatial frequency domain to achieve efficient three-dimensional reconstruction of the cylindrical aperture radar. Simultaneously, in the two-dimensional frequency domain transformation and phase compensation stages, the geometric distance difference caused by the target's radial position variation is incorporated into the phase consistency correction. A radial partitioning reference compensation mechanism is used to suppress focusing degradation caused by radial spatial variability, thereby improving focusing consistency and imaging robustness across the entire radial range.

[0074] This application also provides a computer-readable storage medium storing computer-executable instructions thereon. When executed by a processor, the computer-executable instructions mainly implement the above-described three-dimensional fast imaging method based on cylindrical aperture radar, including: Establish a three-dimensional imaging geometric model for cylindrical aperture radar to at least obtain the distance expression from the antenna array element to the target point; Based on the preprocessing of the echo signal, the phase-compensated signal is obtained; The elevation-based phase-stabilized method can at least eliminate the influence of radar carrier altitude. Two-dimensional spatial frequency domain is constructed to obtain two-dimensional spatial frequency signals, thereby reconstructing the scattering information of the target.

[0075] The above embodiments are merely exemplary embodiments of this application and are not intended to limit this application. The scope of protection of this application is defined by the claims. Those skilled in the art can make various modifications or equivalent substitutions to this application within its substance and scope of protection, and such modifications or equivalent substitutions should also be considered to fall within the scope of protection of this application.

Claims

1. A rapid three-dimensional imaging method based on cylindrical aperture radar, including: Establish a three-dimensional imaging geometric model for cylindrical aperture radar to at least obtain the distance expression from the antenna array element to the target point; Based on the preprocessing of the echo signal, the phase-compensated signal is obtained; The elevation-based phase-stabilized method can at least eliminate the influence of radar carrier altitude. Two-dimensional spatial frequency domain is constructed to obtain two-dimensional spatial frequency signals, thereby reconstructing the scattering information of the target.

2. The method according to claim 1, establishing a three-dimensional imaging geometric model for cylindrical aperture radar, and obtaining at least the distance expression from the antenna array elements to the target point, includes: By approximating the coordinates of the transmitting and receiving array elements to be at the same location, and using the equivalent sampling point coordinates and any target point on the human body surface, the radar transmits a frequency-modulated continuous wave signal. The echo signal received inside the cylindrical aperture is expressed as follows; The distance from the antenna array elements to the target point is determined.

3. The method according to claim 2, wherein, Based on the echo signal preprocessing, the phase-compensated signal is obtained, including: Perform frequency mixing and descrambling on the transmitted and received signals; At least by converting the frequency modulated continuous wave intermediate frequency signal into a single frequency signal, a phase-compensated signal can be obtained.

4. The method according to claim 3, wherein, The elevation-oriented stable phase method includes: Based on the wavenumbers of the minimum and maximum frequencies, the corresponding echo signal data is expressed. An estimated representation of the reflectance image is obtained, and the signal is then transferred to the target point height plane for subsequent two-dimensional processing.

5. The method according to claim 4, wherein, When the measured echo signal data is expressed similarly to a Fourier integral: The reflectance image of the target point is estimated by using an integral similar to its inverse transform.

6. The method according to claim 5, wherein, The integral of the inverse transform is achieved by performing a one-dimensional convolution in the elevation direction.

7. The method according to claim 6, wherein the two-dimensional spatial frequency domain construction comprises: By introducing polar coordinates, a connection is established between the original data and the spatial frequency domain; The signal phase is set in polar coordinate format, based at least on the spatial location and spatial angle of the target point; With radius The cylindrical imaging region is uniformly divided into A series of concentric rings are used to obtain the horizontal radius of the area to be imaged; Retain linear terms representing the target location and filter out terms that include radar location.

8. The method according to claim 7, wherein, The signal phase in polar coordinates format includes radar position information that varies with azimuth angle and target planar information.

9. The method according to claim 8, wherein, Two-dimensional spatial frequency domain construction also includes: Obtain a spatial frequency polar coordinate domain signal containing only target location information; By mapping polar coordinate data to rectangular coordinate data through coordinate mapping relationships, a two-dimensional spatial frequency signal can be obtained.

10. The method according to claim 9, wherein, The two-dimensional spatial frequency domain construction also includes: performing a three-dimensional inverse Fourier transform on the signal to obtain a profile image, and repeating the same operation on all cylinders within the ring radius range to reconstruct the target's scattering information.

Images