An over-the-air calibration system for radar testing and a method of radar testing

Abstract

The application discloses an aerial calibration system and a radar testing method for radar testing, which utilizes a UAV to carry a calibration body, realizes quick arrangement of the calibration body at any height and position, designs a special customized metal shell of a persimmon body to realize rapid attenuation of electromagnetic waves, utilizes a test UAV to carry a radar to realize aerial flight along any flight path, and comprehensively utilizes small UAV technology to realize quick arrangement of the aerial calibration body and calibration testing of radar scattering. The calibration body and the radar to be tested are respectively small UAVs, which can be quickly arranged and are not limited by a site; the calibration body adopts the shape design of the persimmon body, reduces high requirements of a traditional method on target alignment, and reduces the design difficulty of the radar testing system; the whole testing is carried out in the air, interference is reduced, and signal quality is higher.

Description

Technical Field

[0001] This invention relates to the field of radar testing, specifically to an airborne calibration system and radar method for radar testing, which can meet the needs of flexible and rapid deployment of small platforms and achieve high-precision scattering measurement, thereby ensuring the reliability and accuracy of test data. Background Technology

[0002] In recent years, Synthetic Aperture Radar (SAR) has become one of the most versatile and powerful tools in remote sensing technology. Unlike traditional optical imaging systems that rely on infrared or visible light, SAR uses received electromagnetic waves for imaging. This unique capability allows SAR to penetrate clouds, smoke, and darkness, enabling continuous, all-weather, 24 / 7 Earth observation. Traditional SAR systems are mainly deployed on satellites or large aircraft platforms, which are insufficient for responding to the rapid testing needs of small-scale scenarios. Therefore, SAR testing systems based on small unmanned aerial vehicles (UAVs) have emerged.

[0003] In some testing scenarios, accurate calibration is crucial for precisely measuring and acquiring the scattering characteristics of targets. Traditional spaceborne and airborne SAR systems typically rely on large corner reflectors deployed at fixed sites as reference standards. While effective, this method is complex to deploy due to the need for large equipment and fixed locations, and it is difficult to apply in flexible and varied testing environments.

[0004] With the widespread application of small unmanned aerial vehicle (UAV) technology, including rotary-wing UAVs, aerial flight and applications are becoming increasingly common, enabling relatively simple aerial positioning of objects and flight along arbitrary paths. Therefore, how to combine small UAV technology to simplify SAR radar calibration and achieve high-precision measurements has become a pressing technical problem that needs to be solved. Summary of the Invention

[0005] The purpose of this invention is to propose an airborne calibration system and radar testing method for radar testing. This device enables rapid and high-precision calibration. The experimental device is small and portable, reducing the requirements for the test site and eliminating the influence of ground clutter and other interference on the calibration results, thereby achieving high-precision scattering measurement.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] An airborne calibration system for radar testing, characterized in that it includes a calibration body, a test drone, and a ground control station;

[0008] The calibration body includes a peach-shaped metal shell, a drone, and a positioning module.

[0009] The hollow interior of the peach-shaped metal shell is used to fix and install the drone. The upper and lower surfaces each have multiple honeycomb-shaped openings to provide airflow for the drone inside. The honeycomb-shaped openings can be regarded as waveguides, in which incident electromagnetic waves will be rapidly attenuated. The peach-shaped metal shell is CNC machined and the surface is uniformly coated to make its scattering characteristics isotropic.

[0010] The drone is installed inside the metal shell of the peach body, enabling the metal shell of the peach body to hover or fly in the air for aerial calibration.

[0011] The positioning module is installed on the drone and is used to provide accurate altitude and position information;

[0012] The test drone is used to carry a test radar and can fly along a designated route to perform radar calibration tests on the calibration body.

[0013] The ground control station is used to communicate with the calibration body and the test drone, receive working information, and control the working status of the calibration body and the test drone.

[0014] Optionally, the metal outer shell of the peach body is a structure of a metal cylinder and a sphere superimposed, wherein the middle part is a metal cylinder with radius a and height h, and a spherical structure with radius h / 2 is superimposed on the side of the metal cylinder; there are four honeycomb openings on each of the upper and lower surfaces.

[0015] Optionally, the theoretical radar cross-section of the calibration body is

[0016] Optionally, the drone is a rotary-wing drone, installed inside the metal shell of the peach body, and connected to the metal shell of the peach body using a bracket.

[0017] Optionally, the drone also has a communication module for transmitting the flight status of the drone and the altitude and position information measured by the positioning module to the ground control station in real time.

[0018] Optionally, the positioning module uses real-time dynamic carrier phase differential technology;

[0019] The communication module uses a different frequency than the radar test.

[0020] The metal outer shell of the calibration body is also equipped with a parachute or floats.

[0021] This invention further discloses a radar testing method utilizing the above-mentioned airborne calibration system, comprising the following steps:

[0022] Step S110 for determining the distance R between the calibration body and the test radar:

[0023] Based on the radar equations, and utilizing the calibration volume theory, the radar cross section σ t Calculate the upper limit R of the distance R between the calibrator and the radar to ensure a sufficient signal-to-noise ratio (SNR). max Based on the design of the head-up alignment test, considering the radar antenna elevation angle control error and the maximum elevation deviation between the radar and the calibration object, to ensure that the calibration object is uniformly illuminated by the radar beam, the lower limit R of the distance R between the calibration object and the radar is determined. min ;

[0024] Step S120 for determining the flight altitude and radar flight path of the calibration body:

[0025] Based on the actual site environment, determine the hovering position of the calibration body, the radar flight path, and the flight altitude H of the test drone carrying the radar and the calibration body during calibration;

[0026] Antenna beam illumination range adjustment step S130:

[0027] Based on the hovering position information of the calibration body, the test drone adjusts its own orientation or controls the gimbal to adjust the orientation of the test antenna so that the antenna beam evenly illuminates the calibration body 10.

[0028] Calibration test step S140:

[0029] The radar module is activated, and the test drone flies along the flight path determined in step S3 to acquire calibration data and complete the calibration process.

[0030] Optionally, in step S110,

[0031]

[0032] In the formula, P t Let G be the transmit power, G be the antenna gain, λ be the radar signal wavelength, N0 be the noise power, SNR be the required signal-to-noise ratio, and the theoretical radar cross section be... where 'a' is the radius of the basic cylinder and 'h' is the height of the basic cylinder.

[0033]

[0034] In the formula, H is the height of the calibration body, ΔH is the elevation control error of the test UAV and the calibration body, and θ is the radar antenna beamwidth.

[0035] Optionally, in step S120, the flight altitude H is calculated as follows:

[0036]

[0037] In the formula, c is the speed of light, B is the radar bandwidth, d is the distance between the test drone and the calibration object, and θ is the radar beam incident angle.

[0038] Optionally, in step S120, the calibrator 20 is hovering in the air without any trees or other objects obstructing its view.

[0039] In step S140, during calibration, the flight altitude of the test drone and the calibration body are kept consistent through the measurement of the positioning module;

[0040] The flight path of the test drone equipped with radar is controlled via a ground control station.

[0041] In summary, the present invention has the following advantages:

[0042] 1. Both the calibration target and the radar under test are small UAVs, which can be deployed quickly, are not limited by the site, and accurately control the position of the calibration target, which is suitable for the needs of small UAV SAR systems to quickly and accurately perform calibration.

[0043] 2. The calibration body adopts a peach-shaped design, which makes its scattering characteristics unchanged along the azimuth within a certain elevation angle range. This reduces the high requirements for target alignment in traditional methods and reduces the design difficulty of the radar test system.

[0044] 3. The entire test was conducted in the air, which reduced interference, resulting in more stable calibration signal acquisition and higher signal quality. Attached Figure Description

[0045] Figure 1 This is a schematic diagram of a calibration body according to a specific embodiment of the present invention;

[0046] Figure 2 This is a block diagram of an air calibration system according to a specific embodiment of the present invention;

[0047] Figure 3 This is a flowchart of an air calibration method according to a specific embodiment of the present invention;

[0048] Figure 4 This is a one-dimensional distance imaging method for an aerial calibration system operating in a scenario where there are interfering objects, according to a specific embodiment of the present invention.

[0049] The technical features referred to by the reference numerals in the figure are as follows:

[0050] 10. Calibration body; 20. Test drone; 30. Ground control station; 1. Peach shell; 2. Positioning module; 3. Drone mounted on the drone; 4. Communication module. Detailed Implementation

[0051] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0052] The main features of this invention are: using a drone to carry a calibration target to achieve rapid deployment of the calibration target at any altitude and position; designing a specially customized peach-shaped metal shell to achieve rapid attenuation of electromagnetic waves; and using a test drone to carry radar to achieve aerial flight on any trajectory, thereby comprehensively utilizing small drone technology to achieve rapid deployment of aerial calibration targets and calibration testing of radar scattering.

[0053] For details, see Figure 1 and Figure 2 An aerial calibration system for radar testing according to a specific embodiment of the present invention is shown, including a calibration body 10, a test drone 20 and a ground control station 30;

[0054] The calibration body 10 includes a peach-shaped metal shell 1, a drone 3, and a positioning module 2.

[0055] The hollow interior of the peach-shaped metal shell 1 is used to fix and install the drone 3. The upper and lower surfaces each have multiple honeycomb-shaped openings to provide air ducts for the drone 3 inside. The honeycomb-shaped openings can be regarded as waveguides, in which incident electromagnetic waves will be rapidly attenuated. The peach-shaped metal shell is CNC machined and the surface is uniformly coated to make its scattering characteristics isotropic.

[0056] The drone 3 is installed inside the metal shell 1 of the peach body, enabling the metal shell 1 of the peach body to hover or fly in the air for aerial calibration.

[0057] The positioning module 2 is installed on the drone 3 and is used to provide accurate altitude and position information.

[0058] The test drone 20 is used to carry a test radar and can fly along a designated route to perform radar calibration tests on the calibration body 10.

[0059] The ground control station 30 is used to communicate with the calibration body 10 and the test drone 20, receive working information, and control the working status of the calibration body 10 and the test drone 20.

[0060] Further, see Figure 1The metal outer shell 1 of the peach body is a structure of superimposed metal cylinder and sphere, wherein the middle part is a metal cylinder with radius a and height h, and a spherical structure with radius h / 2 is superimposed on the side of the metal cylinder; there are 4 honeycomb openings on each of the upper and lower surfaces.

[0061] Under this structure, the theoretical radar cross-section of the calibration body 10 is

[0062] The drone 3 is a rotary-wing drone, installed inside the metal shell 1 of the peach body, and connected to the metal shell 1 of the peach body using a bracket.

[0063] Furthermore, the drone 3 also has a communication module 4, which is used to transmit the flight status of the drone 3 and the altitude and position information measured by the positioning module 2 to the ground control station 30 in real time.

[0064] The positioning module 2 uses real-time dynamic carrier phase differential technology to achieve more precise position control;

[0065] Furthermore, the frequency used by the communication module 4 is different from the frequency used for radar testing, to avoid interference with the testing.

[0066] Furthermore, the metal outer shell 1 of the calibration body 10 is also equipped with safety protection equipment such as parachutes or floats to improve operational safety.

[0067] The present invention further discloses a radar testing method utilizing the above-described airborne calibration system, comprising the following steps:

[0068] Step S110 for determining the distance R between the calibration body and the test radar:

[0069] Based on the radar equations, and utilizing the calibration volume theory, the radar cross section σ t Calculate the upper limit R of the distance R between the calibrator and the radar to ensure a sufficient signal-to-noise ratio (SNR). max Based on the design of the head-up alignment test, considering the radar antenna elevation angle control error and the maximum elevation deviation between the radar and the calibration object, to ensure that the calibration object is uniformly illuminated by the radar beam, the lower limit R of the distance R between the calibration object and the radar is determined. min .

[0070] Step S120 for determining the flight altitude and radar flight path of the calibration body:

[0071] Based on the actual site environment, determine the hovering position of the calibration body, the radar flight path, and the flight altitude H of the test UAV 20 carrying the radar and the calibration body 10 during calibration.

[0072] Antenna beam illumination range adjustment step S130:

[0073] Based on the hovering position information of the calibration body 10, the test drone 20 adjusts its own orientation or controls the gimbal to adjust the orientation of the test antenna so that the antenna beam evenly illuminates the calibration body 10.

[0074] Calibration test step S140:

[0075] The radar module is activated, and the test drone flies along the flight path determined in step S3 to acquire calibration data and complete the calibration process.

[0076] Specifically, in step S110,

[0077]

[0078] In the formula, P t Let G be the transmit power, G be the antenna gain, λ be the radar signal wavelength, N0 be the noise power, SNR be the required signal-to-noise ratio, and the theoretical radar cross section be... where 'a' is the radius of the basic cylinder and 'h' is the height of the basic cylinder.

[0079]

[0080] In the formula, H is the height of the calibration body, ΔH is the elevation control error of the test UAV and the calibration body, and θ is the radar antenna beamwidth.

[0081] Furthermore, in step S120, see... Figure 4 When the test drone and calibration target are at too low an altitude, interfering objects in the test scenario, such as trees and buildings, can easily generate radar echoes, affecting the radar echo image of the calibration target. Therefore, the flight altitude H is calculated as follows:

[0082]

[0083] In the formula, c is the speed of light, B is the radar bandwidth, d is the distance between the test drone and the calibration object, and θ is the radar beam incident angle.

[0084] Furthermore, in step S120, the calibrator 20 is hovering in the air without any trees or other objects obstructing its view.

[0085] Furthermore, the flight path of the test drone 20, which is equipped with radar, is controlled by the ground control station 30.

[0086] In step S140, during calibration, the flight altitudes of the test drone 20 and the calibration body 10 are kept consistent through the measurement of the positioning module 2.

[0087] In summary, the present invention has the following advantages:

[0088] 1. Both the calibration target and the radar under test are small UAVs, which can be deployed quickly, are not limited by the site, and accurately control the position of the calibration target, which is suitable for the needs of small UAV SAR systems to quickly and accurately perform calibration.

[0089] 2. The calibration body adopts a peach-shaped design, which makes its scattering characteristics unchanged along the azimuth within a certain elevation angle range. This reduces the high requirements for target alignment in traditional methods and reduces the design difficulty of the radar test system.

[0090] 3. The entire test was conducted in the air, which reduced interference, resulting in more stable calibration signal acquisition and higher signal quality.

[0091] The above description is a further detailed explanation of the present invention in conjunction with specific preferred embodiments. It should not be considered that the specific embodiments of the present invention are limited to this. For those skilled in the art, several simple deductions or substitutions can be made without departing from the concept of the present invention, and all such deductions or substitutions should be considered to fall within the scope of protection of the present invention as defined by the submitted claims.

Claims

1. An airborne calibration system for radar testing, characterized in that, This includes a calibration body, a test drone, and a ground control station; The calibration body includes a peach-shaped metal shell, a drone, and a positioning module. The hollow interior of the peach-shaped metal shell is used to fix and install the drone. The upper and lower surfaces each have multiple honeycomb-shaped openings to provide airflow for the drone inside. The honeycomb-shaped openings can be regarded as waveguides, in which incident electromagnetic waves will be rapidly attenuated. The peach-shaped metal shell is CNC machined and the surface is uniformly coated to make its scattering characteristics isotropic. The drone is installed inside the metal shell of the peach body, enabling the metal shell of the peach body to hover or fly in the air for aerial calibration. The positioning module is installed on the drone and is used to provide accurate altitude and position information; The test drone is used to carry a test radar and can fly along a designated route to perform radar calibration tests on the calibration body. The ground control station is used to communicate with the calibration body and the test drone, receive working information, and control the working status of the calibration body and the test drone.

2. The aerial calibration system according to claim 1, characterized in that: The metal outer shell of the peach-shaped body is a structure of superimposed metal cylinder and sphere, wherein the middle part is a metal cylinder with radius a and height h, and a spherical structure with radius h / 2 is superimposed on the side of the metal cylinder; there are four honeycomb-shaped openings on each of the upper and lower surfaces.

3. The aerial calibration system according to claim 2, characterized in that: The theoretical radar cross-section of the calibration body is:

4. The aerial calibration system according to claim 2, characterized in that: The drone being carried is a rotary-wing drone, installed inside the metal shell of the peach body, and connected to the metal shell of the peach body using a bracket.

5. The airborne calibration system according to claim 2, characterized in that: The drone is also equipped with a communication module, which is used to transmit the flight status of the drone and the altitude and position information measured by the positioning module to the ground control station in real time.

6. The air calibration system according to claim 2, characterized in that: The positioning module uses real-time dynamic carrier phase differential technology; The communication module uses a different frequency than the radar test. The metal outer shell of the calibration body is also equipped with a parachute or floats.

7. A radar testing method using the airborne calibration system according to any one of claims 1-6, comprising the following steps: Step S110 for determining the distance between the calibration body and the test radar: Based on the radar equations, and utilizing the calibration volume theory, the radar cross section σ t Calculate the upper limit R of the distance R between the calibrator and the radar to ensure a sufficient signal-to-noise ratio (SNR). max Based on the design of the head-up alignment test, considering the radar antenna elevation angle control error and the maximum elevation deviation between the radar and the calibration object, to ensure that the calibration object is uniformly illuminated by the radar beam, the lower limit R of the distance R between the calibration object and the radar is determined. min ; Step S120 for determining the flight altitude and radar flight path of the calibration body: Based on the actual site environment, determine the hovering position of the calibration body, the radar flight path, and the flight altitude H of the test drone carrying the radar and the calibration body during calibration; Antenna beam illumination range adjustment step S130: Based on the hovering position information of the calibration body, the test drone adjusts its own orientation or controls the gimbal to adjust the orientation of the test antenna so that the antenna beam evenly illuminates the calibration body 10. Calibration test step S140: The radar module is activated, and the test drone flies along the flight path determined in step S3 to acquire calibration data and complete the calibration process.

8. The radar testing method according to claim 7, characterized in that: In step S110, In the formula, P t Let G be the transmit power, G be the antenna gain, λ be the radar signal wavelength, N0 be the noise power, SNR be the required signal-to-noise ratio, and the theoretical radar cross section be... where 'a' is the radius of the basic cylinder and 'h' is the height of the basic cylinder. In the formula, H is the height of the calibration body, ΔH is the elevation control error of the test UAV and the calibration body, and θ is the radar antenna beamwidth.

9. The radar testing method according to claim 7, characterized in that: In step S120, the flight altitude H is calculated as follows: In the formula, c is the speed of light, B is the radar bandwidth, d is the distance between the test UAV and the calibration object, and θ is the radar beam incident angle.

10. The radar testing method according to claim 7, characterized in that: In step S120, the calibrator 20 is hovering in the air without any trees or other objects obstructing its view. In step S140, during calibration, the flight altitude of the test drone and the calibration body are kept consistent through the measurement of the positioning module; The flight path of the test drone equipped with radar is controlled via a ground control station.

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