Miniature portable ground object broadband scattering characteristic measurement method

Abstract

The invention provides a miniature portable ground feature broadband scattering characteristic measurement method, which comprises the steps of S1, constructing a ground feature characteristic measurement device, S2, networking the ground feature characteristic measurement device and a control computer through a wireless network bridge, S3, measuring the distance of a test site and confirming the starting position and the ending position of an unmanned aerial vehicle, and S4, measuring the scattering characteristic of the unmanned aerial vehicle. S4, the ground feature characteristic measuring device measures echo data of the target and the metal ball calibration body along the flight path, and the echo data are processed into an SAR image through a distance Doppler imaging algorithm. S5, performing calibration processing on the SAR image by using a metal ball calibration body to obtain an RCS distribution image in the ground object imaging area; and S6, obtaining a ground object backscattering coefficient according to the RCS distribution image. The method has the advantages that the method is not restricted by experimental sites and measurement conditions, and all ground features and landforms can be flexibly and conveniently measured.

Description

Technical Field

[0001] The invention belongs to the technical field of radar measurement, and in particular relates to a method for measuring broadband scattering characteristics of a miniature portable ground object. Background Art

[0002] In the field of radar detection and information confrontation, the object scattering characteristic is a physical quantity that measures the reflection or scattering intensity of the target object to the radar signal. However, the interference of ground clutter on the target echo may reduce the accuracy of target detection. If we want to better eliminate the influence of ground clutter on the target echo, we must conduct in-depth research and analysis on the ground scattering characteristics, so as to establish a more accurate ground scattering model and further reduce the influence of ground clutter on the target. At the same time, for the military, in-depth understanding and research on the ground scattering characteristics can help our military equipment to carry out stealth design and reduce the possibility of being identified by radars of other countries.

[0003] In addition, the measurement of ground object scattering characteristics is an important branch of remote sensing technology, which can help us gain a deeper understanding of the characteristics of the earth's surface, including surface cover types, land use, vegetation cover, meteorological changes, etc. In short, the measurement of ground object scattering characteristics can provide important scientific basis for environmental protection, agricultural production, urban planning, natural resource management, etc., and therefore has important practical application value.

[0004] The simplest way to study the scattering characteristics of ground objects is to conduct field measurement experiments directly. The measured data can directly indicate the scattering characteristics of ground objects. At present, traditional field measurement experiments are mainly based on radar scatterometer systems. Traditional scatterometer measurement systems not only have high construction costs but also take a long time to complete. Although the data obtained are reliable and effective, they are restricted by experimental sites and measurement conditions and cannot measure all ground objects and landforms flexibly and conveniently. Therefore, in response to the above problems, a miniature portable ground object scattering characteristic measurement method is proposed, which provides a new way to study the scattering characteristics of ground objects. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a miniature portable method for measuring broadband scattering characteristics of land objects, which has the advantages of not being restricted by experimental sites and measurement conditions and can flexibly and conveniently measure all land objects and landforms.

[0006] As one wishes Figure 1 As shown, the present invention proposes a miniature portable method for measuring broadband scattering characteristics of ground objects, comprising the following steps:

[0007] Step S1, installing a radar module on a drone to construct a ground feature measurement device;

[0008] Step S2, networking the ground feature characteristic measuring device with the control computer via a wireless bridge;

[0009] Step S3, determining the starting position and the ending position of the UAV on the test site, setting the flight trajectory of the ground feature characteristic measuring device according to the starting position and the ending position of the UAV, and placing a metal ball calibration body in the test site;

[0010] Step S4, the ground feature characteristic measurement device sends a radar signal to the metal ball calibration body along the flight trajectory and receives echo data. After removing the metal ball calibration body from the scene, the ground feature characteristic measurement device sends a radar signal to the target to be measured along the same flight trajectory and receives echo data, and performs imaging processing on the echo data through a range Doppler imaging algorithm to obtain a SAR image;

[0011] Step S5, calibrating the SAR image using a metal ball calibration body to obtain a radar scattering interface RCS distribution image within the imaging area of ​​the ground object;

[0012] Step S6, obtaining the ground object backscattering coefficient according to the RCS distribution image.

[0013] Furthermore, in step S4, the imaging processing process of the range Doppler imaging algorithm is as follows: the echo data is subjected to range compression, range motion correction, azimuth compression, and projection to the ground plane to obtain a SAR image. The pixel matrix after imaging is as shown in Formula 1:

[0014]

[0015] Among them, A0 is a constant, p r , p a are the inverse Fourier transforms of the window function, τ is the fast time in the distance direction, η is the slow time in the azimuth direction, and η c is the middle deviation time of the beam, R0 is η c The slant distance between the radar and the target at the moment, c is the speed of light, f0 is the center frequency of the carrier, f ηc is the Doppler center frequency, exp represents the exponential function with the natural constant e as the base, and j represents the imaginary unit.

[0016] Furthermore, in step S4, the terrain feature measurement device performs multiple flights along the starting position and the ending position of the UAV to confirm the real motion trajectory and the real starting position and the real ending position of the flight, and uses a measuring tool to measure the real straight-line distance of the starting position and the ending position: wherein the echo data recorded after multiple flights form multiple groups of samples of the imaging area, and these sample data are processed by the range Doppler imaging algorithm to obtain a SAR image.

[0017] Furthermore, after the SAR image of the metal ball calibration body is obtained in step S5, pixel points of the image are extracted according to the actual size of the metal ball calibration body and accumulated and summed to obtain the scattering intensity of the metal ball calibration body in the SAR image, and the scattering intensity is compared with the precise solution of theoretical calculation to obtain the calibration coefficient of RCS in the test process; wherein, the SAR image is calibrated using the calibration coefficient obtained by metal ball imaging to obtain the RCS distribution image in the imaging area.

[0018] In addition, the present invention proposes a miniature portable computer device for measuring broadband scattering characteristics of ground objects, comprising a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps of any one of the methods when executing the computer program.

[0019] In addition, the present invention provides a storage medium having a computer program stored thereon, wherein the computer program implements the steps of any one of the methods when executed by a processor.

[0020] Beneficial effects: Compared with the prior art, the technical solution of the present invention has the following beneficial technical effects:

[0021] The present invention has the advantage of forming a ground feature characteristic measurement device by using an unmanned aerial vehicle and a radar module, so that the device is not restricted by the experimental site and measurement conditions during measurement, and can flexibly and conveniently measure all ground features and landforms. It can make up for the shortcomings of the traditional scatterometer measurement system, which is high in cost and time-consuming to build, to a certain extent, and provides a new way for ground feature scattering research. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a flow chart of the present invention;

[0023] Figure 2 It is a schematic diagram of an application scenario of the present invention;

[0024] Figure 3 A schematic diagram of the correction of the starting position and the ending position of the flight trajectory of the present invention;

[0025] Figure 4 It is a schematic diagram of the imaging processing process of the range Doppler imaging algorithm of the present invention. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] like Figure 1 As shown, the present invention proposes a miniature portable method for measuring broadband scattering characteristics of ground objects, and the specific steps of the method include:

[0028] Step S1: installing a radar module on a drone to construct a ground feature characteristic measurement device, wherein the drone may be a DJI DJM drone, and the radar module may be a radar P440 module, wherein the DJI DJM drone is used to carry the radar P440 module and fly along a specified trajectory, and the radar P440 module is used to transmit radar signals and receive radar echo data;

[0029] Step S2: Networking the ground feature measurement device with the control computer via a wireless bridge;

[0030] Among them, the radar module and the control computer are networked through a wireless bridge, and the wireless LAN configuration is completed to achieve communication and data transmission between the radar module and the control computer; in order to make the wireless bridge work normally, it is first necessary to connect the wireless bridge to the control computer for initialization configuration, set the working mode of the wireless bridge to bridge mode, and then set the IP static addresses of the wireless bridge, the control computer and the radar module, so that the IP static addresses of the wireless bridge, the control computer and the radar module are in the same network segment;

[0031] The steps to set static IP addresses for the wireless bridge, control computer, and radar module include:

[0032] Connect the radar module to the control computer through the USB interface and set the static IP address of the radar module to 192.168.1.100. Then connect the wireless bridge 1 and wireless bridge 2 to the control computer through the network port and set the working frequency band and working mode of the wireless bridge to 5G band and bridge working mode respectively, and set their static IP addresses to 192.168.1.1 and 192.168.1.2 respectively. Finally, set the static IP address of the control computer to 192.168.1.68;

[0033] Connecting the wireless bridge to the control computer and radar module can realize wireless communication between the control computer and the radar module. To avoid the communication between the drone and the remote controller interfering with the communication between the wireless bridges, the working frequency band of the wireless bridge is set to the 5G band, and the communication working frequency band of the drone is set to 2.4G.

[0034] Step S3: Use a measuring tool such as a ruler to measure the distance on the test site, then place the drone at the start and end positions of the ruler, hover the drone at the start and end positions, use the DJI Pilot flight control software developed by DJI to mark waypoints, set the flight trajectory of the ground feature measurement device according to the measurement data, the start and end positions of the drone, and place a metal ball calibration body in the test site; Among them, the P440 radar module and the wireless bridge module need to be powered separately, so two independent power supplies are selected to power the two modules separately.

[0035] Step S4: The ground feature measurement device sends radar signals to the metal ball calibration body along the flight trajectory and receives echo data. After removing the metal ball calibration body from the scene, the ground feature measurement device sends radar signals to the target to be measured along the same flight trajectory and receives echo data. The echo data is imaged and processed by the range Doppler imaging algorithm to obtain a SAR image. The imaging processing process is as follows: Figure 4 As shown;

[0036] The imaging process of the range Doppler imaging algorithm is as follows: the echo data is subjected to range compression, range motion correction, azimuth compression, and projection to the ground plane to obtain a SAR image. The pixel matrix after imaging is as shown in Formula 1:

[0037]

[0038] Among them, A0 is a constant, p r , p a are the inverse Fourier transforms of the window function, τ is the fast time in the distance direction, η is the slow time in the azimuth direction, and η c is the middle deviation time of the beam, R0 is η c The slant distance between the radar and the target at the moment, c is the speed of light, f0 is the center frequency of the carrier, f ηc is the Doppler center frequency, exp represents the exponential function with the natural constant e as the base, and j represents the imaginary unit.

[0039] Among them, when the drone is manually operated, there will be a certain error in the flight trajectory. In order to ensure the accuracy and consistency of the route trajectory, the ground feature measurement device needs to fly multiple times along the starting and ending positions of the drone to confirm the true motion trajectory and the true starting and ending positions of the flight, and use a ruler to reconnect the two points with a straight line. Figure 3 As shown, the line between the rulers is the actual motion trajectory of the route and the distance between the rulers represents the actual distance of the route mission: the echo data recorded after multiple flights form multiple groups of samples of the imaging area, and these sample data are processed by the range Doppler imaging algorithm to obtain SAR images.

[0040] Step S5: Calibrate the SAR image using a metal ball calibration body to obtain an RCS distribution image within the imaging area of ​​the ground object; wherein the relationship between the RCS of the target to be determined and the RCS of the metal ball calibration body is as shown in Formula 2:

[0041]

[0042] Among them, σ dBsm is the RCS of the target to be determined, E s is the scattered electric field intensity of the target, E s0 is the electric field intensity of the scattering field of the calibration body in the actual measurement process, RCS0 represents the RCS theoretical value of the metal ball calibration body, dBsm represents decibels per square meter, and dB represents decibels; after obtaining the SAR image of the metal ball calibration body, the pixel points of the image are extracted according to the actual size of the metal ball calibration body and the scattering intensity of the metal ball calibration body in the SAR image is obtained by cumulative summation, and the scattering intensity is compared with the exact solution of theoretical calculation to obtain the calibration coefficient of RCS in the test process; wherein, the SAR image is calibrated using the calibration coefficient obtained by metal ball imaging to obtain the RCS distribution image in the imaging area.

[0043] Step S6: Obtaining the ground object backscattering coefficient according to the RCS distribution image.

[0044] Among them, the RCS distribution image is divided into several sub-band areas of equal length according to the ground distance. At this time, different sub-band areas represent the RCS distribution of the ground object at different incident angles. The RCS of all pixel values ​​in the sub-band area is accumulated and summed and divided by the area of ​​the sub-band area to obtain the backscattering coefficient of the ground object at the corresponding incident angle.

[0045] In addition, the present invention proposes a miniature portable computer device for measuring broadband scattering characteristics of ground objects, comprising a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps of any one of the methods when executing the computer program.

[0046] In addition, the present invention provides a storage medium having a computer program stored thereon, wherein the computer program implements the steps of any one of the methods when executed by a processor.

[0047] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A miniature portable method for measuring broadband scattering characteristics of ground objects, characterized in that: The method comprises the following steps: Step S1, installing a radar module on a drone to construct a ground feature measurement device; Step S2, networking the ground feature characteristic measuring device with the control computer via a wireless bridge; Step S3, determining the starting position and the ending position of the UAV on the test site, setting the flight trajectory of the ground feature characteristic measuring device according to the starting position and the ending position of the UAV, and placing a metal ball calibration body in the test site; Step S4, the ground feature characteristic measurement device sends a radar signal to the metal ball calibration body along the flight trajectory and receives echo data. After removing the metal ball calibration body from the scene, the ground feature characteristic measurement device sends a radar signal to the target to be measured along the same flight trajectory and receives echo data, and performs imaging processing on the echo data through a range Doppler imaging algorithm to obtain a SAR image; Step S5, calibrating the SAR image using a metal ball calibration body to obtain a radar scattering interface RCS distribution image within the imaging area of ​​the ground object; Step S6, obtaining the ground object backscattering coefficient according to the RCS distribution image.

2. A method for measuring broadband scattering characteristics of a miniature portable ground object according to claim 1, characterized in that: In step S4, the imaging processing process of the range Doppler imaging algorithm is: the echo data is subjected to range compression, range motion correction, azimuth compression, and projection to the ground plane to obtain a SAR image. The pixel matrix after imaging is as follows: Among them, A0 is a constant, p r , p a are the inverse Fourier transforms of the window function, τ is the fast time in the distance direction, η is the slow time in the azimuth direction, and η c is the middle deviation time of the beam, R0 is η c The slant distance between the radar and the target at the moment, c is the speed of light, f0 is the center frequency of the carrier, f ηc is the Doppler center frequency, exp represents the exponential function with the natural constant e as the base, and j represents the imaginary unit.

3. A miniature portable method for measuring broadband scattering characteristics of ground objects according to claim 2, characterized in that: In step S4, the ground feature measurement device performs multiple flights along the starting position and the ending position of the UAV to confirm the real motion trajectory and the real starting position and the real ending position of the flight, and uses a measuring tool to measure the real straight-line distance of the starting position and the ending position; The echo data recorded after multiple flights form multiple groups of samples of the imaging area, and these sample data are processed by the range Doppler imaging algorithm to obtain SAR images.

4. A miniature portable method for measuring broadband scattering characteristics of ground objects according to claim 1, characterized in that: In step S5, after obtaining the SAR image of the metal ball calibration body, the pixel points of the image are extracted according to the actual size of the metal ball calibration body and the scattering intensity of the metal ball calibration body in the SAR image is obtained by cumulative summation. The scattering intensity is compared with the RCS analytical solution of the metal ball calibration body to obtain the calibration coefficient of RCS in the test process; the SAR image is calibrated using the calibration coefficient obtained by metal ball imaging to obtain the RCS distribution image in the imaging area.

5. The method for measuring broadband scattering characteristics of a micro portable ground object according to claim 1, characterized in that: In step S5, the relationship between the RCS of the target to be determined and the RCS of the metal ball calibration body is as follows: Among them, σ dBsm is the RCS of the target to be determined, E s is the scattered electric field intensity of the target, E s0 It is the electric field strength of the scattered field of the calibration body in the actual measurement process, RCS0 represents the RCS theoretical value of the metal ball calibration body, dBsm represents decibel per square meter, and dB represents decibel.

6. A miniature portable computer device for measuring broadband scattering characteristics of ground objects, comprising a memory and a processor, wherein the memory stores a computer program, characterized in that: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 5 are implemented.

7. A storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 5 are implemented.

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