A dynamic background suppression method for circular SAR

Abstract

The present invention relates to the field of electromagnetic scattering technology, and in particular to a dynamic background suppression method for circular SAR. An embodiment of the present invention provides a dynamic background suppression method for circular SAR, comprising: placing a test target on a foam support; placing the foam support in a circular arc track so that the center point of the test target coincides with the center point of the circular arc track; wherein a radar transmitting device and a receiving device are provided on the circular arc track, the electromagnetic wave emitted by the transmitting device is always directed toward the center point of the circular arc track, and the angle between the line connecting the transmitting device and the center point of the circular arc track and the horizontal plane is recorded as the ground grazing angle; setting the measurement range of the range gate, the range of the range gate is determined according to the ground grazing angle; and performing circular SAR data acquisition. An embodiment of the present invention provides a dynamic background suppression method for circular SAR, which can improve the accuracy of the test data of the test target.

Description

Technical Field

[0001] The present invention relates to the field of electromagnetic scattering technology, and in particular to a dynamic background suppression method for circular SAR. Background Art

[0002] As various RCS research projects progress, the demand for electromagnetic scattering measurements has gradually expanded from horizontal illumination within a compact indoor field to measurements at larger grazing angles. This inevitably requires adjustments to the measurement system. The measurement chamber adopts an arc-shaped structure. The main body consists of a sphere with an arc-shaped track installed along the sphere's longitudinal axis. A trolley is mounted on the track and slides along the curved track. The radar transmitter and receiver are housed on the trolley. A turntable is installed on the ground perpendicular to the curved track, with foam supports supporting the test target. The trolley's movement allows the electromagnetic scattering properties of the target to be measured at different grazing angles. Processing techniques such as range gating are employed during the measurement process to reduce background levels and improve measurement accuracy.

[0003] In the prior art, the midpoint of the test target coincides with the midpoint of the circular track, and the electromagnetic wave receiving range of the range gate is set to reduce the impact of the environment on the test data. In order to include all test targets and reduce interference from the surrounding environment, the receiving length of the range gate is the length of the test target, and the receiving range of the range gate is a line segment on the line connecting the transmitter and the test target, with the center point of the test target as the midpoint and the length of the test target as the length. As the transmitter moves, the receiving range trajectory of the range gate forms a circle. However, the foam support at the bottom of the test piece is located within the circular area of ​​the range gate. The propagation of electromagnetic waves to the foam support will affect the generation of strong radiation points, reducing the accuracy of the test data of the test target.

[0004] Therefore, in view of the above shortcomings, a dynamic background suppression method for circular SAR is urgently needed. Summary of the Invention

[0005] The embodiment of the present invention provides a dynamic background suppression method for circular SAR, which can improve the accuracy of test data of a test target.

[0006] An embodiment of the present invention provides a method for dynamic background suppression of a circular SAR, comprising:

[0007] Place the test target on the foam support;

[0008] The foam support is placed in a circular track so that the center point of the test target coincides with the center of the circular track. The circular track is provided with a radar transmitter and a receiver. The electromagnetic waves emitted by the transmitter are always directed toward the center of the circular track. The angle between the line connecting the transmitter and the center of the circular track and the horizontal plane is recorded as the ground contact angle.

[0009] Setting a measurement range of a distance gate, wherein the range of the distance gate is determined according to the ground scraping angle;

[0010] Perform circular SAR data collection.

[0011] In one possible design, the range of the range gate is determined according to the grazing angle, including:

[0012] Determining the length and thickness of the test object;

[0013] The receiving range of the range gate is determined according to the length, the thickness and the ground scraping angle.

[0014] In one possible design, determining the range gate receiving range based on the length, the thickness, and the ground-grabbing angle includes:

[0015] Determining the lengths of the front and rear ends of the test target, wherein the test target is divided into two parts of equal length along the length direction, wherein the part close to the launch device is the front end, and the part away from the launch device is the rear end;

[0016] On the connecting line, a point that is 1 / 2 the length of the test target away from the center point of the test target is determined as the first endpoint of the receiving range of the range gate;

[0017] A line segment is drawn from the first endpoint through the center point of the test target, with the end point of the line segment being the second endpoint. The range between the first endpoint and the second endpoint is the measurement range of the range gate. The line segment is determined by the following formula:

[0018]

[0019] Wherein, S is the length of the line segment, A is the length of the front end, L is the length of the test target, α is the rubbing angle, and C is the thickness of the test target.

[0020] In one possible design, determining the length and thickness of the test target includes:

[0021] The length and thickness of the test target are measured using an indoor cross laser marking point.

[0022] In one possible design, determining the lengths of the front end and the back end of the test target includes:

[0023] The lengths of the front and rear ends of the test object are measured using an indoor cross laser marking point.

[0024] In a possible design, before collecting circular SAR data, the method further includes:

[0025] Turn on the system and warm it up until the system is stable, then set the frequency band, polarization, and vehicle load.

[0026] In one possible design, after collecting circular SAR data, the method further includes:

[0027] Perform two-dimensional imaging processing on the collected data to observe whether the target outline is complete.

[0028] Compared with the prior art, the present invention has at least the following beneficial effects:

[0029] In this embodiment, the range of electromagnetic wave scattering generated by the test target includes the projection of the test target in the radial direction of the transmitting device antenna (the axial direction of the antenna is collinear with the connecting line). When the ground-grabbing angle is 0°, the radial projection is the length of the test target. In order for the receiving device to receive all electromagnetic wave scattering data from the test target, the range length of the range gate needs to be greater than or equal to the length of the test target, preferably equal to. As the ground-grabbing angle begins to increase, the length of the radial projection of the test target continuously shortens, and the length of the adjusted range gate is reduced accordingly. As the length decreases, the portion of the foam support within the range of the range gate is reduced, and the data within the range is the collected data. Therefore, reducing the portion of the foam support within the range of the range gate improves the accuracy of the collected data. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0031] Figure 1 1 is a structural diagram of a circular SAR data acquisition system provided by an embodiment of the present invention.

[0032] In the picture:

[0033] α-ground rubbing angle;

[0034] I-center point;

[0035] T-radial projection;

[0036] A-front end length;

[0037] B- rear end length;

[0038] C-Thickness. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0040] In the description of the embodiments of the present invention, unless otherwise expressly specified or limited, the terms "first" and "second" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance; unless otherwise specified or explained, the term "plurality" refers to two or more; the terms "connected" and "fixed" should be understood in a broad sense. For example, "connected" can mean a fixed connection, a detachable connection, an integral connection, or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0041] In the description of this specification, it should be understood that the directional terms such as "upper" and "lower" described in the embodiments of the present invention are described from the perspectives shown in the accompanying drawings and should not be understood as limiting the embodiments of the present invention. In addition, in the context, it should be understood that when it is mentioned that an element is connected "upper" or "lower" of another element, it can not only be directly connected "upper" or "lower" of the other element, but also indirectly connected "upper" or "lower" of the other element through an intermediate element.

[0042] like Figure 1 As shown, an embodiment of the present invention provides a dynamic background suppression method for circular SAR, including:

[0043] Place the test target on the foam support;

[0044] Place the foam support within the arc-shaped track so that the center of the test target coincides with the center of the arc-shaped track. A radar transmitter and receiver are installed on the arc-shaped track. The electromagnetic waves emitted by the transmitter are always directed toward the center of the arc-shaped track. The angle between the line connecting the transmitter and the center of the arc-shaped track and the horizontal plane is recorded as the ground contact angle.

[0045] Set the measurement range of the distance gate. The range of the distance gate is determined by the ground grazing angle.

[0046] Perform circular SAR data collection.

[0047] In this embodiment, the range of electromagnetic wave scattering generated by the test target includes the projection of the test target in the radial direction of the transmitting device antenna (the axial direction of the antenna is collinear with the connecting line). When the ground-grabbing angle is 0°, the radial projection is the length of the test target. In order for the receiving device to receive all electromagnetic wave scattering data from the test target, the range length of the range gate needs to be greater than or equal to the length of the test target, preferably equal to. As the ground-grabbing angle begins to increase, the length of the radial projection of the test target continuously shortens, and the length of the adjusted range gate is reduced accordingly. As the length decreases, the portion of the foam support within the range of the range gate is reduced, and the data within the range is the collected data. Therefore, reducing the portion of the foam support within the range of the range gate improves the accuracy of the collected data.

[0048] In some embodiments of the present invention, the range of the range gate is determined based on the grazing angle, including:

[0049] Determine the length and thickness of the test target;

[0050] The receiving range of the distance gate is determined based on the length, thickness and ground scraping angle.

[0051] In this embodiment, the receiving range of the radial projection is mainly related to the length, thickness and grazing angle of the test target. By determining the data of the length, thickness and grazing angle of the test target, the receiving range of the range gate can be accurately calculated.

[0052] In some embodiments of the present invention, determining the range of the range gate receiving range based on the length, thickness, and ground grazing angle includes:

[0053] Determine the lengths of the front and rear ends of the test target. The test target is divided into two parts of equal length along the length direction, wherein the part close to the launch device is the front end, and the part away from the launch device is the rear end.

[0054] On the connecting line, a point that is 1 / 2 the length of the test target away from the center point of the test target is determined as the first endpoint of the receiving range of the gate;

[0055] Starting from the first endpoint, draw a line segment through the center point of the test target. The end point of the line segment is the second endpoint. The range between the first endpoint and the second endpoint is the measurement range of the distance gate. The line segment is determined by the following formula:

[0056]

[0057] Where S is the length of the line segment, A is the length of the front end, L is the length of the test target, α is the ground scraping angle, and C is the thickness of the test target.

[0058] In this embodiment, the radial projection of the front portion falls above the front portion. There is no foam support above the front portion, resulting in an atmospheric environment that does not affect the accuracy of data acquisition. The maximum radial projection of the front portion is the length of the front portion. Because this does not affect data acquisition accuracy, the length of the front portion of the range gate's reception range is the length A of the front portion, with the first endpoint located on an arc with the test target's center as its center and A as its radius. The radial projection of the rear portion falls on the bottom of the test target, where it lands on the foam support. In the prior art, the range of the rear portion is the length of the rear portion. However, as the scrubbing angle increases, the radial projection of the rear portion shortens, but the data acquisition range remains unchanged. The foam support outside the radial projection still causes errors. In this application, the range gate's reception range is shortened as the rear portion's projection shortens, effectively avoiding errors caused by the foam support outside the radial projection. Specifically, the length of the rear portion's radial projection is 1 / 2 × cosα, making the rear range of the range gate equal to the length of the radial projection. However, the test target has thickness. As the radial projection becomes shorter, when the radial projection is less than half of the thickness, if the receiving range of the rear range gate is still equal to the radial projection, some test target data will be missing. Therefore, when the length of the radial projection is less than half of the thickness, the receiving range of the rear range gate is set to 1 / 2C. In summary, the length of the test target's range gate is:

[0059]

[0060] It should be noted that L=2A=2B.

[0061] In some embodiments of the present invention, determining the length and thickness of a test target includes:

[0062] Use the indoor cross laser marking point to measure the length and thickness of the test target.

[0063] In this embodiment, the length and thickness of the test target can be accurately measured using the indoor cross laser marking point, reducing errors.

[0064] In some embodiments of the present invention, determining the lengths of the front end and the back end of the test target includes:

[0065] Use the indoor cross laser marking point to measure the length of the front and rear ends of the test target.

[0066] In this embodiment, the lengths of the front and rear ends of the test target can be accurately measured using the indoor cross laser marking point, thereby reducing errors.

[0067] In some embodiments of the present invention, before collecting circular SAR data, the method further includes:

[0068] Turn on the system and warm it up until the system is stable, then set the frequency band, polarization, and vehicle load.

[0069] In this embodiment, before collecting circular SAR data, it is necessary to start the system and warm it up until the system is stable, and then set the frequency band, polarization, and vehicle.

[0070] In some embodiments of the present invention, after collecting circular SAR data, the method further includes:

[0071] Perform two-dimensional imaging processing on the collected data to observe whether the target outline is complete.

[0072] In this embodiment, after the circular SAR data is collected, two-dimensional imaging processing is further performed on the collected data to observe whether the target contour is complete. If it is complete, the next set of tests is performed. Otherwise, the software gate setting is widened according to the two-dimensional imaging image.

[0073] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A dynamic background suppression method for circular SAR, characterized in that: include: Place the test target on the foam support; The foam support is placed in a circular track so that the center point of the test target coincides with the center of the circular track. The circular track is provided with a radar transmitter and a receiver. The electromagnetic waves emitted by the transmitter are always directed toward the center of the circular track. The angle between the line connecting the transmitter and the center of the circular track and the horizontal plane is recorded as the ground contact angle. Setting a measurement range of a distance gate, wherein the range of the distance gate is determined according to the ground scraping angle; Conduct circular SAR data collection; The range of the distance gate is determined according to the grazing angle, including: Determining the length and thickness of the test object; Determine the receiving range of the range gate according to the length, the thickness and the ground scraping angle; Determining the receiving range of the range gate according to the length, the thickness, and the ground-grabbing angle includes: Determining the lengths of the front and rear ends of the test target, wherein the test target is divided into two parts of equal length along the length direction, wherein the part close to the launch device is the front end, and the part away from the launch device is the rear end; On the connecting line, a point that is 1 / 2 the length of the test target away from the center point of the test target is determined as the first endpoint of the receiving range of the range gate; A line segment is drawn from the first endpoint through the center point of the test target, with the end point of the line segment being the second endpoint. The range between the first endpoint and the second endpoint is the measurement range of the range gate. The line segment is determined by the following formula: S=A+ L ,S≥A+ C, Wherein, S is the length of the line segment, A is the length of the front end, L is the length of the test target, α is the rubbing angle, and C is the thickness of the test target.

2. The suppression method according to claim 1, characterized in that Determining the length and thickness of the test target includes: The length and thickness of the test target are measured using an indoor cross laser marking point.

3. The suppression method according to claim 1, characterized in that Determining the length of the front end and the back end of the test target includes: The lengths of the front and rear ends of the test object are measured using an indoor cross laser marking point.

4. The suppression method according to claim 1, characterized in that Before collecting circular SAR data, the method further includes: Turn on the system and warm it up until the system is stable, then set the frequency band, polarization, and vehicle load.

5. The suppression method according to claim 1, characterized in that: After the circular SAR data collection, the method further includes: Perform two-dimensional imaging processing on the collected data to observe whether the target outline is complete.

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