Arbitrary polarized antenna test method for unmanned aerial vehicle

Abstract

The invention relates to an arbitrary polarized antenna test method for an unmanned aerial vehicle, and belongs to the field of radio, and the test method comprises the steps: enabling the unmanned aerial vehicle carrying a measurement load to fly according to a planned path, and synchronously recording dual-channel receiving data, unmanned aerial vehicle position data, load attitude data and a timestamp in real time in the flight process; preprocessing of coordinate conversion, attitude compensation and calibration correction is sequentially carried out on data collected by the unmanned aerial vehicle, then polarization parameter calculation is carried out to judge the polarization type, and the inclination angle, the maximum amplitude of long and short axes, the axial ratio and the rotation direction are calculated; and associating the calculated polarization parameters in each direction with the corresponding azimuth angle and pitch angle to generate index data of the tested antenna. The unmanned aerial vehicle can automatically fly according to the preset path and collect data, the test time is greatly shortened, the test efficiency is improved, and the method is particularly suitable for three-dimensional directional diagram tests needing a large number of sampling points.

Description

Technical Field

[0001] The present invention relates to the field of antennas, and in particular, to a method for testing arbitrary polarization antennas for unmanned aerial vehicles (UAVs). Background Art

[0002] With the rapid development of wireless communication technologies, especially applications such as 5G and satellite communication, the requirements for antenna performance are getting higher and higher; the polarization characteristics of antennas are one of the important indicators to measure their performance, including linear polarization, circular polarization, and elliptical polarization, etc. Accurately testing parameters such as the polarization pattern, axial ratio, and cross-polarization discrimination ratio of antennas is crucial for antenna design, optimization, and verification.

[0003] Traditional antenna testing methods are usually carried out in an anechoic chamber or an open test field. The anechoic chamber testing is costly and has limited space, making it difficult to simulate complex actual application scenarios; the open test field testing is easily affected by ground reflections and surrounding environmental interference, which affects the testing accuracy, and for far-field testing, a large testing distance and movable transmitting / receiving devices are required, making the operation inconvenient. Especially for large antennas or scenarios that need to be tested at specific heights and specific angles, traditional methods face many challenges.

[0004] In recent years, UAV technology has developed rapidly. Its advantages such as high flexibility, relatively low cost, and strong accessibility have enabled it to be widely used in various fields. Applying UAVs to the field of antenna testing is expected to overcome the deficiencies of traditional testing methods. However, when a UAV is flying, polarization testing errors will be caused by vibrations, especially in the accurate evaluation of arbitrary polarization characteristics, and there is still a lack of accurate and efficient testing methods. Summary of the Invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for testing arbitrary polarization antennas for UAVs, which solves the deficiencies existing in the prior art.

[0006] The purpose of the present invention is achieved through the following technical solutions: A method for testing arbitrary polarization antennas for UAVs, the testing method includes: Data synchronous acquisition step: Flying the UAV carrying the measurement payload according to the planned path, and synchronously recording dual-channel received data, UAV position data, payload attitude data, and timestamps in real time during the flight; Data processing and polarization characteristic analysis step: Sequentially performing preprocessing of coordinate transformation, attitude compensation, and calibration correction on the data collected by the UAV, and then calculating polarization parameters to determine the polarization type, calculate the inclination angle, maximum amplitudes of the major and minor axes, axial ratio, and rotation direction; Pattern generation and visualization step: Associating the calculated polarization parameters in each direction with the corresponding azimuth angle and elevation angle to generate the index data of the antenna under test.

[0007] The dual-channel received data includes: the amplitude A of the horizontally polarized component signal received by the horizontal polarization port H , the amplitude A of the vertically polarized component signal received by the vertical polarization port V and the relative phase difference , represents the phase of the vertically polarized component, represents the phase of the horizontally polarized component; The UAV position data includes: longitude, latitude and altitude; The payload attitude data includes: pitch angle, roll angle and yaw angle.

[0008] The preprocessing of sequentially performing coordinate transformation, attitude compensation and calibration correction on the data collected by the UAV includes: Coordinate transformation: Combining the position data and attitude data of the UAV with the position and orientation of the antenna under test, and transforming them into a spherical coordinate system with the antenna under test as the origin to obtain the azimuth angle θ and elevation angle Φ corresponding to each data sampling point; Attitude compensation: According to the attitude data of the UAV, perform attitude compensation on the signals received by the dual-polarization receiving antenna to correct the rotation between the receiving antenna coordinate system and the global coordinate system caused by the UAV attitude change; Calibration correction: Correct the amplitude and phase of the received signal through the obtained calibration parameters.

[0009] The subsequent calculation of polarization parameters to determine the polarization type, calculate the inclination angle, the maximum amplitudes of the major and minor axes, the axial ratio and the sense of rotation includes: For each measurement point, calculate the polarization characteristic parameters of the antenna under test in this direction using the amplitude and relative phase difference of the preprocessed dual-channel received signals; For an electromagnetic wave propagating in a certain direction, its electric field vector is expressed as , where and respectively represent the unit vectors in the vertical and horizontal directions, and A V , A H and , represent and ; When or , it is linear polarization. When A V =A H and , it is circular polarization. In other cases, it is elliptical polarization; When A V ≠A H , the inclination angle Ψ is , when A V =AH When the inclination angle Ψ = ±45°, the maximum amplitude of the major axis is , and the maximum amplitude of the minor axis is . The axis ratio is AR = a / b, where sqr represents the square root; When , the rotation direction is left-handed, and when , the rotation direction is right-handed.

[0010] The flight path planning of the drone includes: Horizontal plane circular flight: The drone moves in a circular motion around the antenna under test at a set distance and height for testing the horizontal plane pattern; Vertical plane arc flight: The drone makes arc motions with different pitch angles at a set azimuth angle in front of the antenna under test for testing the vertical plane pattern; Spherical scanning flight: The drone flies along a predetermined trajectory on a virtual sphere centered on the antenna under test for obtaining three-dimensional pattern data.

[0011] The test method further includes the steps of test system preparation and calibration; specifically including the following: Preparation of the antenna under test: Set the multi-polarization antenna to be tested to the transmit mode so that it transmits test signals with known frequencies and powers; Preparation of the drone test platform: Select a drone with high-precision positioning and attitude sensing, and mount a measurement payload on the drone. The measurement payload includes a three-axis gimbal, a dual-polarization receiving antenna, a dual-channel coherent receiver, and a data recording and control unit; System calibration: Before testing, calibrate the amplitude and phase consistency of the two channels of the dual-polarization receiving antenna on the drone and the isolation between ports to obtain calibration parameters, evaluate or measure the free space path loss model, and ensure the accuracy of the attitude sensor readings at the same time.

[0012] The three-axis gimbal is used to mount other structures and adjust and test azimuth, pitch, and roll; The dual-polarization receiving antenna is a calibrated dual-polarization receiving antenna with known polarization characteristics and a working frequency covering the test frequency of the antenna under test; The dual-channel coherent receiver is connected to the two ports of the dual-polarization receiving antenna, can synchronously receive two signals, and record the amplitude and relative phase information; The data recording and control unit is used to record the output data of the dual-channel receiver, the real-time position coordinates of the drone, the attitude data of the measurement payload, and the timestamp information, and to control the flight path of the drone and the start and stop of the receiver.

[0013] The present invention has the following advantages: 1. High flexibility and wide range of test scenarios: UAVs can easily reach various heights and positions, and can test antennas installed in complex environments (such as urban rooftops, wild mountainous areas) or at high altitudes, simulating more realistic far-field application scenarios.

[0014] 2. High test efficiency: The drone can automatically fly and collect data along a preset path, which greatly shortens the test time and improves the test efficiency. It is especially suitable for three-dimensional directional pattern testing that requires a large number of sampling points.

[0015] 3. Relatively low cost: Compared with building large darkrooms or complex ground mobile test systems, using drones for testing can significantly reduce equipment and site costs, probably from tens of millions to millions.

[0016] 4. Rich data latitude and comprehensive polarization characteristics: Through dual-polarization receiving antennas and dual-channel coherent receivers, the amplitude and phase information of two orthogonal polarization components can be obtained synchronously, so as to comprehensively analyze various polarization characteristics of the antenna under test (linear polarization, circular polarization, elliptical polarization, axial ratio, tilt angle, rotation direction, XPD, etc.), rather than just the power pattern of a single polarization.

[0017] 5. High test accuracy: This method carries out amplitude and phase tests simultaneously by carrying out dual-polarization orthogonal receiving antennas on the drone, combines real-time and accurate attitude and position information, and compensates for attitude influences through data processing algorithms, so as to achieve efficient and accurate measurement of the radiation characteristics of arbitrary polarization of the antenna under test in three-dimensional space. Compared with time-sharing rotation for acquisition, this method can avoid the non-orthogonality problem caused by the vibration of the drone in time-sharing, and achieve more accurate measurement.

[0018] 6. Little interference to the antenna under test: The UAV platform is relatively small and has little impact on the electromagnetic environment around the antenna under test. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the process of the present invention. DETAILED DESCRIPTION

[0020] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are only some of the embodiments of this application, rather than all of them. The components of the embodiments of this application usually described and illustrated in the accompanying drawings here can be arranged and designed in various different configurations. Therefore, the detailed description of the embodiments of this application provided below with reference to the accompanying drawings is not intended to limit the protection scope of the claimed application, but merely represents the selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative efforts belong to the protection scope of this application. The following further describes the present invention with reference to the accompanying drawings.

[0021] The present invention specifically relates to a method for testing an arbitrary polarization antenna for an unmanned aerial vehicle (UAV) to solve the problems existing in the existing antenna testing methods, such as high cost, inconvenient operation, limited testing scenarios, and difficulty in accurately evaluating the arbitrary polarization characteristics. This method realizes the efficient and accurate measurement of the arbitrary polarization radiation characteristics of the antenna under test in three-dimensional space by carrying a dual-polarization orthogonal receiving antenna on the UAV to simultaneously perform amplitude-phase testing and through a polarization analysis algorithm, combined with real-time and accurate attitude and position information. Compared with the method of rotating for polarization matching and then testing, this method can avoid polarization errors caused by the vibration of the UAV.

[0022] As Figure 1 shown, it specifically includes the following content: Step 1: Preparation and calibration of the test system; 1. Preparation of the antenna under test: Set the multi-polarization antenna to be tested (for example, a base station antenna fixedly installed on the ground, a satellite ground station antenna, etc.) to the transmit mode so that it transmits a test signal with a known frequency and power. This test signal can be a continuous wave signal or a specific modulation signal.

[0023] 2. Preparation of the UAV test platform: Select a UAV system with high-precision positioning and attitude perception capabilities. The UAV also needs to carry a measurement payload, which includes the following functional structures: Three-axis gimbal: Used to mount other structures and adjust and test azimuth, pitch, and roll.

[0024] Dual-polarization receiving antenna: Install a calibrated dual-polarization receiving antenna on the UAV. This dual-polarization antenna should have known and good polarization characteristics (for example, two orthogonal linear polarization ports), and its operating frequency covers the test frequency of the antenna under test.

[0025] Dual-channel coherent receiver: Connected to the two ports of the dual-polarization receiving antenna, it can synchronously receive two signals and record their amplitude (power) and relative phase information.

[0026] Data recording and control unit: It is used to record the output data of the dual-channel receiver, the real-time position coordinates (latitude, longitude, and altitude) of the UAV, the attitude data of the measurement payload (pitch angle, roll angle, yaw angle), and the timestamp information. This unit can also be used to control the flight path of the UAV and the start and stop of the receiver.

[0027] 3. System calibration: Dual-polarization receiving antenna calibration: Before testing, it is necessary to calibrate the amplitude, phase consistency of the two channels of the dual-polarization receiving antenna on the UAV, and the isolation between ports to obtain calibration parameters.

[0028] Path loss calibration: Evaluate or measure the free-space path loss model for compensation in subsequent data processing.

[0029] Attitude calibration: Ensure the accuracy of the attitude sensor readings.

[0030] Step 2: UAV flight path planning and data acquisition; 1. UAV path planning: According to the expected radiation characteristics of the antenna under test and the test requirements (e.g., main lobe direction, specific cross-section, etc.), plan the flight path of the UAV; the flight path can be a preset sequence of waypoints or a dynamically adjusted path, including: Horizontal plane circular flight: The UAV makes a circular motion around the antenna under test at a specific distance and altitude for testing the horizontal plane pattern.

[0031] Vertical plane arc flight: The UAV makes an arc motion with different pitch angles at a specific azimuth angle in front of the antenna under test for testing the vertical plane pattern.

[0032] Spherical scanning flight: The UAV flies along a predetermined trajectory on a virtual sphere centered on the antenna under test to obtain three-dimensional pattern data.

[0033] During the flight, ensure that the dual-polarization receiving antenna on the UAV always faces the antenna under test. This can be achieved through the gimbal control or flight attitude adjustment of the UAV.

[0034] 2. Data synchronous acquisition: The UAV flies according to the planned path, and during the flight, the data recording and control unit synchronously records the following associated data: Dual-channel received data: The amplitude A of the horizontally polarized component signal received by the horizontal polarization port H and the amplitude A of the vertically polarized component signal received by the vertical polarization port V and the relative phase difference , where represents the phase of the vertically polarized component, Represents the phase of the horizontal polarization component; UAV position data: longitude, latitude, and altitude; Payload attitude data: pitch angle, roll angle, and yaw angle; Timestamp: The timestamp corresponding to the above data.

[0035] Step 3: Data processing and polarization characteristic analysis; 1. Data preprocessing: Coordinate transformation: Combine the position data and attitude data of the UAV with the position and orientation of the antenna under test, and transform them into a spherical coordinate system with the antenna under test as the origin to obtain the azimuth angle (θ) and elevation angle (Φ) corresponding to each data sampling point.

[0036] Attitude compensation: According to the attitude data of the UAV, perform attitude compensation on the signals received by the dual-polarization receiving antenna to correct the rotation between the receiving antenna coordinate system and the global coordinate system caused by the UAV attitude change. This step is crucial for accurately analyzing the polarization direction. For example, if the UAV measures that the payload is tilted, the signals actually received by its horizontal and vertical ports will be the projections of the incident wave on the tilted plane.

[0037] Calibration data application: Apply the obtained calibration parameters to correct the amplitude and phase of the received signal.

[0038] Path loss compensation: According to the distance between the UAV and the antenna under test, perform path loss compensation on the amplitude of the received signal.

[0039] 2. Polarization parameter calculation: Overall calculation objective: For each measurement point (i.e., specific θ, direction Φ), use the amplitude and relative phase difference of the preprocessed dual-channel received signals to calculate the polarization characteristic parameters of the antenna under test in this direction.

[0040] Polarization analysis algorithm: Since the TEM electromagnetic wave is transmitted in space during the test, only the test results in the direction of the electric field need to be considered. The total vector of the electric field is the vector synthesis of the vertical component and the horizontal component in space. For an electromagnetic wave propagating in a certain direction, its electric field vector can be expressed as , where, and respectively represent the unit vectors in the vertical and horizontal directions, and let A V , A H and , represent and , represents the electric field vector, E V ( t ) represents the electric field vector in the vertical direction,E H ( t ) represents the electric field vector in the horizontal direction, ω represents the angular frequency of the carrier frequency, and t represents the time when the electromagnetic wave starts from the initial position; Polarization type judgment: When or , it is linear polarization. When A V =A H and , it is circular polarization. In other cases, it is elliptical polarization; Calculation of the tilt angle (linear polarization and elliptical polarization): When A V ≠A H , the tilt angle Ψ is . When A V =A H , the tilt angle Ψ = ±45°; The maximum amplitude of the major axis is , and the maximum amplitude of the minor axis is ; Axial ratio (circular polarization and elliptical polarization): The axial ratio is AR = a / b, where sqr represents the square root; Sense of rotation (circular polarization and elliptical polarization): When , the sense of rotation is left-handed. When , the sense of rotation is right-handed.

[0041] 3. Pattern generation and visualization: Associate the calculated polarization parameters in each direction (such as power, axial ratio, tilt angle, etc. under specific polarization) with the corresponding azimuth angle and elevation angle to generate the index data of the antenna under test.

[0042] Among them, the index data includes: Specific polarization pattern: For example, co-polarization pattern, cross-polarization pattern; Axial ratio pattern: Displays the axial ratio values in different directions; Tilt angle pattern: Displays the polarization tilt angles in different directions.

[0043] The above is only the preferred embodiment of the present invention. It should be understood that the present invention is not limited to the form disclosed herein, should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications, and improvements, and can be changed within the scope of the concept described herein through the above teachings or the technology or knowledge in related fields. And the changes and modifications made by those skilled in the art that do not depart from the spirit and scope of the present invention should all be within the protection scope of the appended claims of the present invention.

Claims

1. A method for testing an arbitrarily polarized antenna for a drone, characterized in that: The described test method includes: Data synchronous acquisition step: Flying the unmanned aerial vehicle (UAV) equipped with measurement payloads along the planned path, and synchronously recording the dual-channel received data, UAV position data, payload attitude data, and timestamps in real time during the flight; Data processing and polarization characteristic analysis step: Preprocessing the data collected by the UAV successively through coordinate transformation, attitude compensation, and calibration correction, and then calculating polarization parameters to determine the polarization type, calculate the inclination angle, maximum amplitudes of the major and minor axes, axial ratio, and rotation direction; Pattern generation and visualization step: Associating the calculated polarization parameters in each direction with the corresponding azimuth angle and elevation angle to generate the index data of the antenna under test.

2. The arbitrary polarization antenna test method for a drone according to claim 1, wherein: The dual-channel received data includes: the amplitude A of the horizontally polarized component signal received by the horizontal polarization port H , the amplitude A of the vertically polarized component signal received by the vertical polarization port V and the relative phase difference , denotes the phase of the vertically polarized component, denotes the phase of the horizontally polarized component; The UAV position data includes: longitude, latitude, and altitude; The payload attitude data includes: pitch angle, roll angle, and yaw angle.

3. The arbitrary polarization antenna test method for an unmanned aerial vehicle according to claim 1, characterized in that: The preprocessing of successively performing coordinate transformation, attitude compensation, and calibration correction on the data collected by the UAV includes: Coordinate transformation: Combining the position data and attitude data of the UAV with the position and orientation of the antenna under test, and transforming them into a spherical coordinate system with the antenna under test as the origin to obtain the corresponding azimuth angle θ and elevation angle Φ for each data sampling point; Attitude compensation: According to the attitude data of the UAV, performing attitude compensation on the signals received by the dual-polarization receiving antenna to correct the rotation between the receiving antenna coordinate system and the global coordinate system caused by the attitude change of the UAV; Calibration correction: Correcting the amplitude and phase of the received signal through the obtained calibration parameters.

4. The method for testing an arbitrary polarization antenna for a drone according to claim 2, wherein: The further calculation of polarization parameters to determine the polarization type, calculate the inclination angle, maximum amplitudes of the major and minor axes, axial ratio, and rotation direction includes: For each measurement point, calculating the polarization characteristic parameters of the antenna under test in this direction by using the amplitude and relative phase difference of the preprocessed dual-channel received signals; For an electromagnetic wave propagating in a certain direction, its electric field vector is expressed as , where and represent the unit vectors in the vertical and horizontal directions respectively, and A V , A H and , represent and , represents the electric field vector, E V ( t ) represents the electric field vector in the vertical direction, E H ( t ) represents the electric field vector in the horizontal direction, ω represents the angular frequency of the carrier frequency, and t represents the time elapsed since the electromagnetic wave started from its initial position; When or it is linear polarization. When A V = A H and it is circular polarization; in other cases, it is elliptical polarization. When A V ≠ A H , the inclination angle Ψ is , when A V = A H , the inclination angle Ψ = ±45°; then the maximum amplitude of the major axis is , the maximum amplitude of the minor axis is , the axial ratio is AR = a / b, where, sqr represents the square root and AR represents the axial ratio; When , the helix direction is left-handed. When , the helix direction is right-handed.

5. The method for testing an arbitrary polarization antenna for a drone according to claim 2, characterized in that: The flight path planning of the UAV includes: Horizontal plane circular flight: The UAV makes a circular motion around the antenna under test at a set distance and height for testing the horizontal plane pattern; Vertical plane arc flight: The UAV makes arc motions with different elevation angles at a set azimuth angle in front of the antenna under test for testing the vertical plane pattern; Spherical surface scanning flight: The UAV flies along a predetermined trajectory on a virtual spherical surface centered on the antenna under test for obtaining three-dimensional pattern data.

6. A method for testing an arbitrary polarization antenna for an unmanned aerial vehicle according to any one of claims 1-5, characterized in that: The test method further includes the test system preparation and calibration steps; specifically including the following contents: Antenna under test preparation: Setting the multi-polarization antenna to be tested to the transmit mode so that it transmits test signals with known frequency and power; UAV test platform preparation: Selecting a UAV with high-precision positioning and attitude perception, and mounting measurement payloads on the UAV. The measurement payloads include a three-axis gimbal, a dual-polarization receiving antenna, a dual-channel coherent receiver, and a data recording and control unit; System calibration: Before the test, calibrating the amplitude and phase consistency of the two channels of the dual-polarization receiving antenna on the UAV and the isolation between ports to obtain calibration parameters, evaluating or measuring the free space path loss model, and ensuring the accuracy of the attitude sensor readings at the same time.

7. The method for testing an arbitrary polarization antenna for a drone according to claim 6, wherein: The three-axis gimbal is used to mount other structures and adjust and test azimuth, elevation, and roll; The dual-polarization receiving antenna is a calibrated dual-polarization receiving antenna, which has known polarization characteristics and a working frequency covering the test frequency of the antenna under test; The dual-channel coherent receiver is connected to two ports of the dual-polarization receiving antenna, and can synchronously receive two signals, and record the amplitude and relative phase information; The data recording and control unit is used to record the output data of the dual-channel receiver, the real-time position coordinates of the UAV, the attitude data of the measurement payload, and the timestamp information, and to control the flight path of the UAV and the start and stop of the receiver.

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