Microwave imaging and scatter source separation method based on revolution-revolution composite motion system

Abstract

The application discloses a microwave imaging and scattering source separation method based on a revolution-rotation composite motion system, and the revolution-rotation composite motion system is used for radar microwave measurement on a target system to be measured, wherein the target system to be measured comprises a target to be measured, a hanging rope, a rotating rhombic support rod and a revolving turntable, and the rotating rhombic support rod is located above the revolving turntable, that is, the rotating rhombic support rod and the revolving turntable perform revolution-rotation composite motion, so that the tip of the rotating rhombic support rod always faces the radar incident direction, thereby reducing the rhombic support rod scattering; meanwhile, a point target model is used to verify the influence of the self-rotation of other targets on the revolving turntable on the measurement of the revolution scattering characteristics of the target to be measured, the real situation of the target motion during the measurement is analyzed theoretically, and the calculation and analysis of a two-dimensional image are carried out, and the image subtraction method is further used to reduce the rhombic support rod scattering, so that the microwave imaging and the scattering source separation can be realized.

Description

Technical Field

[0001] This invention relates to the field of scattering measurement technology, and more specifically to a microwave imaging and scattering source separation method based on a combined revolution and rotation system. Background Technology

[0002] Currently, for scattering measurements of large-sized targets, the required target rhomboid support rods are also quite large. The aircraft under test adopts a "two-support-one-suspension" support method, that is, a suspension rope is used at the front and two rhomboid support rods are used at the rear. The target under test and the rhomboid support rods are located on a turntable. Therefore, effectively reducing the scattering of the rhomboid support rods is a necessary way to accurately measure the scattering of the target.

[0003] However, since the rhomboid support rod will bend when a large target is erected, the carrier or background cancellation method is not applicable. Because the rhomboid support rod is large in size, even if absorbing material is laid, it will have a significant impact on the scattering of the large target, thereby reducing the accuracy of scattering measurement.

[0004] Therefore, how to improve the accuracy of large-size target scattering measurement, reduce the influence of rhomboid straight rod scattering, and realize microwave imaging and scattering source separation are problems that urgently need to be solved by those skilled in the art. Summary of the Invention

[0005] In view of this, this invention provides a microwave imaging and scattering source separation method based on a combined revolution and rotation motion system. It proposes that while the turntable revolves, the rhomboid support rotates, and the angular velocities of the two are opposite, ensuring that the tip of the rhomboid support always faces the radar incident direction, thereby reducing scattering from the rhomboid support. Simultaneously, a point target model is used to investigate the influence of the rotational motion of other targets on the turntable on the measurement of the revolution scattering characteristics of the target under test. Target echo calculations and two-dimensional image calculations are performed on the actual target motion during measurement, and an image clipping cancellation method is used to further reduce scattering from the rhomboid support.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A microwave imaging and scattering source separation method based on a combined revolution and rotation system includes the following steps:

[0008] Step 1: Collect the combined target echo of the revolution and rotation composite motion system;

[0009] Step 2: Perform phase compensation on the combined target echo according to the combined revolution and rotation motion to obtain a two-dimensional image of the rotating target with clutter from the scattering source of the revolution target;

[0010] Step 3: Determine the location of the scattering source of the rotating target based on the two-dimensional image of the rotating target, and normalize the imaging values ​​within a preset range of the rotating target location to obtain the self-scattering of the rotating target; the normalized scattering value obtained by the normalization process is the self-scattering of the rotating target.

[0011] Step 4: Perform phase compensation on the self-scattering of the rotating target according to the combined motion of revolution and rotation to obtain the self-echo of the rotating target;

[0012] Step 5: Subtract the combined target echo and the self-echo of the rotating target to obtain the canceled target echo;

[0013] Step 6: Perform phase compensation on the canceled target echo according to the orbital motion mode to obtain a two-dimensional image of the orbiting target; at this time, the scattering effect of the rotating target is very small. If the scattering coefficients of the orbiting and rotating targets are the same, then in the canceled two-dimensional image of the orbiting target, the scattering of the orbiting target and the scattering of the rotating target will differ by more than 40dB.

[0014] Preferably, the combined revolution and rotation motion system includes a turntable, a target under test, a suspension rope, and rhomboid supports. The target under test and the rhomboid supports are located on the turntable. The suspension rope suspends the front of the target under test, and the two sets of rhomboid supports can rotate to support the rear of the target under test. While the turntable revolves around the Earth, the rhomboid supports rotate on their own axes, and the angular velocities of the two rotations are opposite. The rotation of the turntable and the rhomboid supports constitutes a combined revolution and rotation motion. The tips of the rhomboid supports are always facing the radar incident direction. The radar emits radar waves to the combined revolution and rotation motion system and collects the combined target echo. The rhomboid supports are the rotating target, and the target under test is the revolving target.

[0015] Preferably, in step 2, a two-dimensional reconstruction algorithm is used to construct a two-dimensional image. Two revolution target points are taken on the turntable, namely A and C, and three rotation target points are taken on the rhomboid support rod, namely B, D and E, as point target models.

[0016] The combined target echo is represented as follows:

[0017] E s (f,θ)=E As (f,θ)+E Cs (f,θ)+E Bs (f,θ)+E Ds (f,θ)+E Es (f,θ);

[0018]

[0019]

[0020]

[0021]

[0022]

[0023] Where f is the radar wave; θ is the clockwise rotation angle of the radar; E As (f,θ), E Bs (f,θ), E Cs (f,θ), E Ds (f,θ) and E Es (f, θ) represent the echoes from points A, B, C, D, and E, respectively; (x) A ,y A (x) represents the position coordinates of the first revolution target point A; C ,y C (x) represents the position coordinates of the second revolution target point C; B ,y B (x) represents the position coordinates of the first rotation target point B; D ,y D (x) represents the position coordinates of the second rotation target point D; E ,y E ) represents the position coordinates of the third rotating target point E; s(x,y) is the target scattering coefficient, which is set to 1 in the simulation calculation; the phase delay generated by the radar wave after being reflected by the target is 2kd; k=2πf / c, c is the speed of light;

[0024]

[0025]

[0026]

[0027]

[0028]

[0029] Where R represents the distance between the radar and the target; θ is the clockwise rotation angle of the radar; R B R D R E Let B, D, and E be the radii of rotation around the first revolution target point A, respectively. Their expressions are:

[0030]

[0031]

[0032]

[0033] θ B θ D θ E Let B, D, and E be the initial values ​​of the angles between the target point B, the second target point D, and the third target point E and the negative y-axis, respectively. The expression is:

[0034]

[0035]

[0036]

[0037] The target scattering coefficient, which is phase-compensated according to the combined motion of revolution and rotation, is expressed as:

[0038] s(x,y)=∫∫E s (f,θ)e j2kd dfdθ

[0039] In this process, a two-dimensional image is formed based on the target scattering coefficient using either revolution or a combination of revolution and rotation. The value of d only needs to be taken accordingly. A or d C or d B or d D or d E The target scattering coefficient is a two-dimensional matrix, similar to the value of a pixel. A two-dimensional image can be obtained by applying a plotting function to this two-dimensional matrix.

[0040] Preferably, the specific process of step 4 is as follows:

[0041] Based on the motion pattern of the first rotating target point B, the two-dimensional image of the first rotating target point B is subtracted, and the echo electric field of the first rotating target point B is obtained in reverse.

[0042] Preferably, the specific process of step 5 is as follows:

[0043] The echo electric field of the first rotation target point B, which was obtained in reverse step 4, is subtracted from the echo electric fields of the three target points: the first orbital target point A, the first rotation target point B, and the second orbital target point C. The echo electric field of the orbital target is obtained by subtracting the echo electric field of the first rotation target point B from the echo electric fields of the three target points: the first orbital target point A, the first rotation target point B, and the second orbital target point C.

[0044] Preferably, the specific process of step 6 is as follows:

[0045] The electric field of the orbiting target obtained in step 5 is imaged in two dimensions using the orbital motion to obtain a two-dimensional image of the orbiting target after the scattering source is separated.

[0046] As can be seen from the above technical solution, compared with the prior art, the present invention discloses a microwave imaging and scattering source separation method based on a combined revolution and rotation motion system. Radar microwave measurement is performed based on this combined revolution and rotation motion system, ensuring that the tip of the rotating rhomboid support is always directly facing the radar incident direction, thereby reducing scattering from the rhomboid support. Simultaneously, a point target model is used to verify the influence of the rotational motion of other targets on the turntable on the measurement of the revolution scattering characteristics of the target under test. Theoretical analysis and two-dimensional image calculation analysis are performed on the actual target motion during measurement, and an image clipping cancellation method is used to further reduce scattering from the rhomboid support, achieving microwave imaging and scattering source separation. Attached Figure Description

[0047] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0048] Figure 1 The attached figure is a schematic diagram of the microwave imaging and scattering source separation method based on a combined revolution and rotation system provided by the present invention.

[0049] Figure 2 The attached figure is a schematic diagram of large-size target scattering measurement provided by the present invention;

[0050] Figure 3 The attached diagram is a schematic diagram showing the out-of-phase angular velocities of the turntable's revolution and rotation when there are five point targets provided by the present invention;

[0051] Figure 4 The attached figure is a schematic diagram of the actual motion state of five point targets when their angular velocities are in the same direction, as provided by the present invention.

[0052] Figure 5 The attached figure is a schematic diagram of the actual motion trajectories of the three target points A, B, and C provided by this invention;

[0053] Figure 6 The attached figure is a schematic diagram of the two-dimensional imaging results of three point targets A, B, and C when the incident angle is -10° to 10°, provided by the present invention.

[0054] Figure 7 The attached figure is a schematic diagram of the two-dimensional imaging results of three point targets A, B, and C when the incident angle is -45° to 45°, as provided by the present invention.

[0055] Figure 8 The attached figure is a schematic diagram of the two-dimensional imaging result of the rotation of point target B provided by the present invention;

[0056] Figure 9 The attached figure is a schematic diagram of the two-dimensional imaging results of point targets A, B, and C rotating according to point B, provided by the present invention.

[0057] Figure 10 The attached figure is a schematic diagram of the incident angle of -10° to 10° provided by the present invention;

[0058] Figure 11 The attached figure is a schematic diagram of the incident angle of -10° to 10° provided by the present invention;

[0059] Figure 12 The attached figure is a schematic diagram of the incident angle of -10° to 10° provided by the present invention;

[0060] Figure 13 The attached figure is a schematic diagram of the incident angle of -45° to 45° provided by the present invention. Detailed Implementation

[0061] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0062] This invention discloses a microwave imaging and scattering source separation method based on a combined revolution and rotation system, comprising the following steps:

[0063] S1: Collect the combined target echo of the combined revolution and rotation motion system;

[0064] The combined revolution and rotation motion system includes a turntable 1, a target 2, a suspension rope 3, and rhomboid support rods 4. The target 2 and the rhomboid support rods 4 are located on the turntable 1. The suspension rope 3 suspends the front of the target 2, and the two sets of rhomboid support rods 4 can rotatably support the rear of the target 2. While the turntable 1 revolves around the target, the rhomboid support rods 4 rotate on their own axis, and the angular velocities of the two rotations are opposite. The rotation of the turntable 1 and the rhomboid support rods 4 constitutes the combined revolution and rotation motion. The tip of the rhomboid support rods 4 always faces the radar incident direction. The radar emits radar waves to the combined revolution and rotation motion system and collects the combined target echo.

[0065] The radar emits a frequency sweep signal with linear frequency variation and receives the echo signal reflected by the test object system, which is composed of a combined system of revolution and rotation.

[0066] Simultaneously with emitting a frequency sweep signal, the test object system revolves around the center of the turntable, while the rhomboid support rotates around its own axis. Within a preset azimuth angle range, the angular velocities of the revolution and rotation are equal in magnitude but opposite in direction.

[0067] The echo signals of the target under test at different rotation azimuth angles are sampled to obtain the echo data of the sampling points at all azimuth angles;

[0068] S2: Perform phase compensation on the combined target echo according to the combined revolution and rotation motion to obtain a two-dimensional image of the rotating target with clutter from the scattering source of the revolution target;

[0069] A two-dimensional image is constructed using a two-dimensional reconstruction algorithm. Two revolution target points, A and C, are taken on the turntable, and three rotation target points, B, D and E, are taken on the rhomboid support.

[0070] The combined target echo is represented as:

[0071] E s (f,θ)=E As (f,θ)+E Cs (f,θ)+E Bs (f,θ)+E Ds (f,θ)+E Es (f,θ);

[0072]

[0073]

[0074]

[0075]

[0076]

[0077] Where f is the radar wave; θ is the clockwise rotation angle of the radar; E As (f,θ), E Bs (f,θ), E Cs (f,θ), E Ds (f,θ) and E Es (f, θ) represent the echoes from points A, B, C, D, and E, respectively; (x) A ,y A (x) represents the position coordinates of the first revolution target point A; C ,y C (x) represents the position coordinates of the second revolution target point C; B ,y B (x) represents the position coordinates of the first rotation target point B; D ,y D (x) represents the position coordinates of the second rotation target point D; E ,y E) represents the position coordinates of the third rotating target point E; s(x,y) is the target scattering coefficient, set to 1 in the simulation calculation; the phase delay of the radar wave after reflection from the target is 2kd; k=2πf / c, c is the speed of light; d are respectively:

[0078]

[0079]

[0080]

[0081]

[0082]

[0083] Where R represents the distance between the radar and the target; θ is the clockwise rotation angle of the radar; R B R D R E Let B, D, and E be the radii of rotation around the first revolution target point A, respectively. Their expressions are:

[0084]

[0085]

[0086]

[0087] θ B θ D θ E Let B, D, and E be the initial values ​​of the angles between the target point B, the second target point D, and the third target point E and the negative y-axis, respectively. The expression is:

[0088]

[0089]

[0090]

[0091] The target scattering coefficient, which is phase-compensated according to the combined motion of revolution and rotation, is expressed as:

[0092] s(x,y)=∫∫E s (f,θ)e j2kd dfdθ

[0093] In this process, based on the target scattering coefficient, a two-dimensional image is generated using either revolution or a combination of revolution and rotation. The value of d only needs to be taken accordingly. A or d Cor d B or d D or d E .

[0094] S3: Determine the specific location of the scattering source of the rotating target based on the two-dimensional image of the rotating target. Select a certain range of areas at the specific location and normalize the imaging values ​​of the selected range. This normalized scattering value is the scattering of the rotating target itself.

[0095] Based on the two-dimensional image, the scattering source of the rotating part (i.e., the scattering source of the rhomboid support rod) is extracted;

[0096] S4: Perform opposite phase compensation on the scattering of the rotating target to obtain the echo of the rotating target;

[0097] By performing opposite phase compensation using a combined revolution and rotation motion, the echo data of the rotating part (i.e., the rhomboid support rod) is obtained; the image is formed according to the motion mode of the first rotating target point B, and the two-dimensional image of the first rotating target point B is subtracted to obtain the echo electric field of the first rotating target point B.

[0098] S5: Cancel the combined target echo and the rotating target echo to obtain the target echo;

[0099] Subtract the echo data from S1 and S3 to obtain the canceled echo data; subtract the echo electric field of the first rotation target point B obtained in reverse S4 from the echo electric fields of the first orbit target point A, the first rotation target point B, and the second orbit target point C.

[0100] S6: Perform phase compensation on the canceled target echo according to the orbital motion mode to obtain a two-dimensional image of the orbiting target after the scattering source is separated; perform phase compensation on the canceled echo data according to the orbital motion mode, and use a two-dimensional reconstruction algorithm to construct a two-dimensional image;

[0101] Two-dimensional imaging of the echo electric field obtained from S5 in a revolution motion mode can obtain a two-dimensional image of the revolving target after the scattering source is separated.

[0102] Example

[0103] In a specific embodiment, taking a point target as an example, where the radar is stationary and the turntable revolves and rotates, the target's motion is as follows: Figure 3 As shown, the arrow indicates the direction of the turntable's rotation, and the radar is marked below, emitting radar waves directly towards the turntable.

[0104] Figure 3The target motion is as follows: Point targets A and C rotate counterclockwise around the turntable's revolution center point O, with the coordinates of the first revolution target point A being (1, 1) and the coordinates of the second revolution target point C being (-1, -1). Point targets B, D, and E rotate clockwise around the target's rotation center point A, with the coordinates of the first rotation target point B being (1, 0.5), the coordinates of the second rotation target point D being (1.35, 0.65), and the coordinates of the third rotation target point E being (1.5, 1). That is, the turntable's revolution and the target's rotation are in opposite angular directions. The scattering coefficient of all point targets is set to 1.

[0105] Regarding the specific motions of the turntable's revolution and the target's rotation, firstly, the scattering characteristics of five target points A, B, C, D, and E are studied when the angular velocities of the turntable's revolution and the target's rotation are opposite in direction but equal in magnitude. Then, the echo data of the first rotating target point B is obtained by using the image matting method, and then canceled with the overall echo data of the first revolution target point A, the second revolution target point C, and the first rotating target point B to obtain two-dimensional images of the revolution targets A and C after separating the scattering sources.

[0106] (1) Two-dimensional imaging using revolution motion

[0107] The two-dimensional imaging calculations used the X-band, i.e., 8GHz to 12GHz, with a frequency interval of 20MHz. The turntable's rotation aperture angle was 20°, i.e., the azimuth angle was -10° to 10°, with an angular interval of 0.1°. The revolution and rotation angular velocities were of the same magnitude, θ. The distance R between the radar and the target was considered sufficiently large, satisfying the far-field condition.

[0108] First, such as Figure 5 The diagram shows the actual trajectories of the first revolution target point A, the first rotation target point B, and the second revolution target point C. During the motion, the trajectories of the first revolution target point A and the second revolution target point C lie on the same circle. The first rotation target point B rotates on its own axis while simultaneously revolving around the revolution, and the angular velocities of its rotation and revolution are opposite in direction and equal in magnitude. Therefore, it can be concluded that the first rotation target point B and its center of rotation, i.e., the first rotation target point A, are relatively stationary. This leads to the following... Figure 5 The actual motion trajectory shown.

[0109] When the angular velocities of the turntable's revolution and the target's rotation are in opposite directions, by Figure 4 It can be seen that, assuming the turntable remains stationary, the radar rotates clockwise around the first orbital target point A and the second orbital target point C. At the same time, the first rotational target point B, the second rotational target point D, and the third rotational target point E rotate clockwise around A. This is consistent with... Figure 3 The relative motions are the same. At this point, the actual motion states of points A, B, C, D, and E can be obtained as follows: Figure 4 As shown.

[0110] Depend on Figure 4 It can be seen that: the two point targets, the first orbital target point A and the second orbital target point C, are stationary, while the radar rotates clockwise around the center of the turntable. Based on their motion, the distances between the first orbital target point A, the second orbital target point C, and the radar can be obtained as follows:

[0111]

[0112] Among them, (x A ,y A ), (x C ,y C ) are the coordinates of the first orbital target point A and the second orbital target point C, respectively; R is the distance from the radar to the center of the turntable; and θ is the clockwise rotation angle of the radar.

[0113] At this time, the first rotation target point B and the second rotation target point D are not stationary, but are rotating clockwise around the first revolution target point A. Let's assume the initial values ​​of the angles between the first rotation target point B, the second rotation target point D, and the negative y-axis are θ. B ,θ D And the magnitude of the angular velocity of the rotation is θ. At this time, the distance between the first rotating target point B and the radar is:

[0114]

[0115] in, It is the radius of rotation of the first rotation target point B around the first revolution target point A, (x A ,y A (x) represents the coordinates of point target A. B ,y B () represents the coordinates of the first rotation target point B.

[0116] Similarly, the distance between the second rotating target point D and the radar at this time is:

[0117]

[0118] in, It is the radius of rotation of the second rotation target point D around the first revolution target point A, (x D ,y D () represents the coordinates of the second rotation target point D.

[0119] Similarly, the distance between the third rotating target point E and the radar at this time is:

[0120]

[0121] in, It is the radius of rotation of the third rotation target point E around the first revolution target point A, (x E ,y E () represents the coordinates of the third rotation target point E.

[0122] For every angular interval the target rotates, the radar emits a stepped-frequency electromagnetic wave f. Assuming the target position is (x, y), the phase delay of the signal after reflection from the target is 2kd, where c is the speed of light. Assuming the target's scattering coefficient is s(x, y), the signal received by the radar is:

[0123]

[0124] From this, the echo signal E can be obtained. s (f,θ):

[0125] E s (f,θ)=E As (f,θ)+E Cs (f,θ)+E Bs (f,θ)+E Ds (f,θ)+E Es (f,θ) (6)

[0126] With echo signal E s (f,θ) can be used to represent the target scattering coefficient s(x,y) when "phase compensation is performed based on the motion mode of the first orbital target point A":

[0127] s(x,y)=∫∫E s (f,θ)e j2kd dfdθ (7)

[0128] Among them, the two-dimensional image is formed by revolution, and the value of d is selected as d A or d C .

[0129] Based on the imaging algorithm described above, two-dimensional imaging calculations of the target can be achieved.

[0130] To achieve two-dimensional imaging using a combination of revolution and rotation, phase compensation is required based on the distance between the rotating target point and the radar. Similarly, to achieve two-dimensional imaging using revolution, phase compensation is required based on the distance between the revolution target point and the radar. This type of imaging is also the traditional two-dimensional imaging method.

[0131] Based on the above echo signal calculation process, after obtaining accurate target echoes, phase compensation is performed on the echo data using the distance d between the first orbiting target point A and the radar. Two-dimensional imaging is then performed on the first orbiting target point A, the first rotating target point B, and the first orbiting target point C, as shown below. Figure 6 As shown, the angles of rotation and revolution are both -10° to 10°.

[0132] Depend on Figure 6 It can be seen that the two target positions, the first orbital target point A and the second orbital target point C, can be accurately imaged, and the scattering values ​​of the targets are the same. However, target B is out of focus, and its maximum scattering value is less than that of target A.

[0133] To further verify the theoretical analysis, the rotation and revolution angles were increased to -45° to 45°, and two-dimensional images were then created of the first revolution target point A, the first rotation target point B, and the first revolution target point C. Figure 7 As shown.

[0134] Depend on Figure 7 It can be seen that the positions of the first orbital target point A and the second orbital target point C can be accurately imaged, but... Figure 6 In comparison, the imaging sidelobes are significantly reduced, and the scattering values ​​of the first orbiting target point A and the second orbiting target point C are not significantly different. However, significant defocusing occurs at the first rotating target point B, distributed between -45° and 45° below the first orbiting target point A, with a maximum vertical distance of 0.5 from the first orbiting target point A. The maximum scattering value at B differs from that at the first orbiting target point A by approximately 25 dB. However, some low-scattering clutter also appears within the imaging range. Using the same type of target (three targets A, B, and C) and two different aperture angles, imaging results for targets moving in a revolution pattern are obtained.

[0135] Therefore, we can preliminarily conclude that when a rotating and orbiting target is imaged, defocus will occur within a corresponding angular range depending on the aperture angle. The defocused imaging position roughly appears below the rotation center, and the defocused area is approximately circular, with the rotation center as the center and the radius equal to the difference between the longitudinal distance between the rotation center and the rotating target. Furthermore, simulation calculations show that the larger the aperture angle, the more pronounced the defocusing phenomenon, and the smaller the scattering value at the imaging position, with a maximum difference of about 25 dB compared to the scattering value of the orbiting target. Conversely, the smaller the aperture angle, the less pronounced the defocusing phenomenon, and the larger the scattering value at the imaging position, with the maximum value approximating the scattering value of the orbiting target.

[0136] (2) Two-dimensional imaging using a combination of revolution and rotation.

[0137] First, a two-dimensional image of the first rotating target point B(1, 0.5) is performed according to the motion pattern of B, using the aforementioned echo signal E. s(f,θ) can be used to represent the target scattering coefficient s(x,y) for "phase compensation based on the motion of the first rotating target point B":

[0138] s(x,y)=∫∫E s (f,θ)e j2kd dfdθ (8)

[0139] Among them, the two-dimensional image is formed by a combination of revolution and rotation, and the value of d is selected as d. B or d D or d E Based on the research background that the tip of the rhomboid support always faces the radar incident direction, the value of d in this embodiment is selected as d. B .

[0140] Based on the imaging algorithm described above, two-dimensional imaging calculations of the target can be achieved.

[0141] The results obtained for different aperture angles are as follows: Figure 8 As shown, this is a two-dimensional image of a composite motion of revolution and rotation at point B.

[0142] The point shown in the image is the image of the first rotation target point B, which is... Figure 8 It can be seen that when imaging is performed according to the motion of the rotating target B, the imaging position and scattering value of target B can be accurately imaged.

[0143] Then, two-dimensional imaging is performed on the first orbital target point A, the first rotational target point B, and the second orbital target point C according to the motion mode of the first rotational target point B. The results obtained for different aperture angles are as follows: Figure 9 As shown, the points displayed in the image are the images of the first rotating target point B and the defocused images of the first revolving target point A and the second revolving target point C.

[0144] Depend on Figure 9 It can be seen that when imaging is performed according to the motion of the first rotating target point B, the imaging positions of the first orbiting target point A and the second orbiting target point C exhibit circular defocusing at the position of the scattering source itself, with the rotation center as the center and the radius being the difference between the ordinates of the first orbiting target point A and the first rotating target point B.

[0145] A comparison of the two-dimensional image results and those obtained using a revolution-rotation composite motion reveals that the phenomena observed in imaging using this combined motion are inversely related. In the revolution-rotation composite motion imaging method, the position and scattering of the rotating target point can be imaged, while the revolution target point will exhibit defocusing with corresponding position and scattering values ​​depending on the aperture angle. Conversely, in the revolution-rotation composite motion imaging method, the position and scattering of the revolution target point can be imaged, while the rotation target point will exhibit defocusing with corresponding position and scattering values ​​depending on the aperture angle.

[0146] (3) After keying and cancellation, perform two-dimensional imaging using a revolution motion.

[0147] To eliminate the influence of the rotating target on the revolving target during imaging, the image is now formed according to the motion of the first rotating target point B. The image of the first rotating target point B is subtracted (by extracting a 9*9 (0.4m*0.4m) matrix centered at point B). Then, the echo electric field of the first rotating target point B is calculated, and a two-dimensional image is formed of it using its revolving motion. Figure 10 The image shown is a comparison of the first rotating target point B before and after chroma keying when the incident angle is between -10° and 10°, and the target point B is in a revolution motion. Figure 10 (a) is a two-dimensional image of the object before keying, which moves around point A with an incident angle of -10° to 10°. The point shown in the image is the image of the first rotating target point B after defocusing. Figure 10 (b) is a two-dimensional image after keying, moving around point A with an incident angle of -10° to 10°. The point shown in the image is the image of the first rotating target point B after defocusing.

[0148] Depend on Figure 10 It can be seen that the imaging position and imaging scattering value of the first rotating target point B are not much different before and after matting, which lays the foundation for canceling the scattering of the first rotating target point B in the subsequent combination of target points.

[0149] Next, the echo electric field of the first rotating target point B is subtracted from the echo electric field of the first orbital target point A, the first rotating target point B, and the second orbital target point C, thereby eliminating the scattering effect of the first rotating target point B. Figure 11 The image shown is a comparison of the first orbiting target point A, the first rotating target point B, and the second orbiting target point C before and after image cancellation, when the incident angle is between -10° and 10°. Figure 11 (a) is a two-dimensional image of the object before keying, moving around point A with an incident angle of -10° to 10°. The points shown in the image are the images of the first rotating target point B after defocusing and the images of the first revolving target point A and the second revolving target point C. Figure 11(b) is a two-dimensional image after keying, moving around point A with an incident angle of -10° to 10°. The points shown in the image are the images of the first rotating target point B after defocusing and the images of the first revolving target point A and the second revolving target point C.

[0150] Depend on Figure 11 It can be seen that the scattering at the first rotating target point B before and after cancellation is reduced by a maximum of 25dB, and has no effect on the first orbital target point A and the second orbital target point C. Although the defocus still exists at the first rotating target point B, the difference between the scattering values ​​at the first orbital target point A, the second orbital target point C and the first rotating target point B is at least 25dB.

[0151] To further eliminate scattering from the first rotating target point B and narrow the matting range of B, such as Figure 12 The image shown is a comparison of the first orbiting target point A, the first rotating target point B, and the second orbiting target point C before and after image cancellation, when the incident angle is -10° to 10°. Figure 12 To select different keying ranges, a two-dimensional image after keying, moving in a revolution around point A, with an incident angle of -10° to 10°, is shown in the image. The points displayed are the defocused images of the first rotating target point B and the images of the first and second revolution target points A and C. Figure 12 (a) The keying area is a 9x9 matrix. Figure 12 (a) The chroma keying area is a 3x3 matrix. Figure 12 (a) The chroma keying range is a 1*1 matrix.

[0152] Depend on Figure 12 It can be seen that the keyed area has a significant impact on eliminating the scattering value of the first rotating target point B. If the scattering source can be accurately deducted, the influence of the first rotating target point B on the first orbiting target point A and the second orbiting target point C can be reduced to a very low level.

[0153] Next, we investigate the differences in imaging before and after cancellation when the incident angle is between -45° and 45° for the first orbiting target point A, the first rotating target point B, and the second orbiting target point C, according to their orbital motion. (We extract a 9*9 (0.4m*0.4m) matrix centered at point B). Figure 13 As shown, Figure 13 (a) is a two-dimensional image of the object before keying, which is moving around point A with an incident angle of -45° to 45°. The point shown in the image is the image of the first rotating target point B after defocusing. Figure 13 (b) is a two-dimensional image after keying, moving around point A with an incident angle of -45° to 45°. The point shown in the image is the image of the first rotating target point B after defocusing. Figure 13(c) is a two-dimensional image of the object before keying, moving around point A with an incident angle of -45° to 45°. The points shown in the image are the images of the first rotating target point B after defocusing and the images of the first revolving target point A and the second revolving target point C. Figure 13 (d) is a two-dimensional image after keying, moving around point A with an incident angle of -45° to 45°. The points shown in the image are the images of the first rotating target point B after defocusing, and the images of the first revolving target point A and the second revolving target point C.

[0154] Depend on Figure 13 It can be seen that the scattering value and scattering position of the first rotating target point B before and after keying are not much different. The scattering at the first rotating target point B is eliminated by at least 15dB before and after cancellation, and has no effect on the first orbital target point A and the second orbital target point C. At this time, the difference between the scattering values ​​of the first orbital target point A, the second orbital target point C and the first rotating target point B is at least 40dB, that is, the scattering at the first rotating target point B is effectively eliminated. Figures 6-13 The horizontal axis represents the imaging range of -3 to 3m, the vertical axis represents the longitudinal imaging range of -3 to 3m, and the bar colorimetric chart on the right represents the scattering value at various points in the image.

[0155] As can be seen from the above comparison, when imaging in a revolution-based manner, the rotating target point will exhibit defocus within a corresponding angular range depending on the aperture angle. If the rotating target point is located below the rotation center (a certain revolution target), the defocused image will appear below the rotation center; conversely, it will appear above the rotation center. The defocused area is approximately circular, with the rotation center as the center and the radius being the difference between the longitudinal distance between the rotation center and the rotating target point. Other rotating target points exhibit the same defocusing condition as this rotating target point. Conversely, when imaging in a combined revolution-rotation method, the revolution target point will exhibit defocus within a corresponding angular range depending on the aperture angle. If the revolution target point is located below the rotating target point determined by the combined motion, the defocused image will appear below the rotating target point; conversely, it will appear above the rotating target point. The defocused area is approximately circular, with the rotating target point as the center and the radius being the difference between the longitudinal distance between the rotation center and the rotating target point. Other revolution target points exhibit the same defocusing condition as this revolution target point.

[0156] Furthermore, simulation calculations show that the larger the aperture angle, the more obvious the defocusing phenomenon, and the smaller the scattering value at the imaging position, which can differ from the scattering value at the orbiting target point by up to 30dB; conversely, the smaller the aperture angle, the less obvious the defocusing phenomenon, and the larger the scattering value at the imaging position, which at its maximum approximates the scattering value at the orbiting target point.

[0157] Specifically, when moving in the manner of the first rotating target point B, the images of the first orbital target point A and the second orbital target point C exhibit defocusing. The defocused area is approximately circular, with the first rotating target point B as the center and a radius equal to the difference in longitudinal distance between the first orbital target point A and the first rotating target point B. Next, using image matting, the echo electric field at the first rotating target point B is extracted. Then, the extracted echo electric field of the first rotating target point B is subtracted from the echo electric fields of the three targets: the first orbital target point A, the first rotating target point B, and the second orbital target point C. Finally, the results of two-dimensional imaging in the orbital motion mode show that the scattering of the first rotating target point B is effectively reduced, with a difference of more than 40 dB compared to the scattering value of the orbital target point. In actual measurement, the tip of the rhomboid support rod is always facing the radar incident direction. The scattering of the rhomboid support rod is mainly concentrated at the tip, which corresponds to the positional relationship between the first orbital target point A and the first rotational target point B in the embodiment. The first orbital target point A can be regarded as the target being measured, and the first rotational target point B can be regarded as the tip of the rhomboid support rod.

[0158] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0159] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A microwave imaging and scattering source separation method based on a combined revolution and rotation system, characterized in that, Includes the following steps: Step 1: Collect the combined target echo of the combined revolution and rotation motion system; Step 2: Perform phase compensation on the combined target echo according to the combined revolution and rotation motion to obtain a two-dimensional image of the rotating target with clutter from the scattering source of the revolution target; Step 3: Determine the location of the scattering source of the rotating target based on the two-dimensional image of the rotating target, and normalize the imaging values ​​within a preset range of the rotating target location to obtain the self-scattering of the rotating target. Step 4: Perform phase compensation on the self-scattering of the rotating target according to the combined motion of revolution and rotation to obtain the self-echo of the rotating target; Step 5: Subtract the combined target echo and the self-echo of the rotating target to obtain the canceled target echo; Step 6: Perform phase compensation on the canceled target echo according to the orbital motion mode to obtain a two-dimensional image of the orbiting target; The combined revolution and rotation motion system includes a turntable, the target under test, a suspension rope, and rhomboid supports. The target under test and the rhomboid supports are located on the turntable. The suspension rope suspends the front of the target under test, and the two sets of rhomboid supports can rotate to support the rear of the target under test. While the turntable revolves around the Earth, the rhomboid supports rotate on their own axes, and the angular velocities of the two rotations are opposite. The rotation of the turntable and the rhomboid supports constitutes the combined revolution and rotation motion. The tips of the rhomboid supports always face the radar incident direction. The radar emits radar waves to the combined revolution and rotation motion system and collects the combined target echo. The rhomboid supports are the rotating target, and the target under test is the revolving target. In step 2, a two-dimensional reconstruction algorithm is used to construct a two-dimensional image. Two revolution target points are taken on the turntable, namely A and C, and three rotation target points are taken on the rhomboid support, namely B, D and E. The combined target echo is represented as follows: ； in, Radar waves; This represents the clockwise rotation angle of the radar. , , , and The echoes are from points A, B, C, D, and E, respectively. Indicates the position coordinates of the first revolution target point A; Indicates the position coordinates of the second revolution target point C; This indicates the position coordinates of the first rotation target point B; Indicates the position coordinates of the second rotation target point D; Indicates the position coordinates of the third rotation target point E; The target scattering coefficient is ; the phase delay caused by the radar wave being reflected from the target is . ; c is the speed of light; in, Indicates the distance between the radar and the target; Let B, D, and E be the radii of rotation around the first revolution target point A, respectively. Their expressions are: Let B, D, and E be the initial values ​​of the angles between the target point B, the second target point D, and the third target point E and the negative y-axis, respectively. The expression is: The target scattering coefficient, which is phase-compensated according to the combined motion of revolution and rotation, is expressed as: Specifically, a two-dimensional image is formed based on the target scattering coefficient using either revolution or a combination of revolution and rotation. Take corresponding or or or or ; The specific process of step 4 is as follows: image the first rotating target point B according to its motion mode, subtract the two-dimensional image of the first rotating target point B, and inversely obtain the echo electric field of the first rotating target point B. The specific process of step 5 is as follows: subtract the echo electric field of the first rotation target point B obtained in step 4 from the echo electric fields of the first revolution target point A, the first rotation target point B, and the second revolution target point C to obtain the revolution target echo electric field. The specific process of step 6 is as follows: the electric field of the orbiting target obtained in step 5 is subjected to two-dimensional imaging in the orbiting motion mode to obtain a two-dimensional image of the orbiting target after the scattering source is separated.

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