A fixed circular array radar omnidirectional array accuracy verification system and method

Abstract

The present invention provides a system and method for verifying the accuracy of a circular array radar's omnidirectional array by using a single-direction flight of an unmanned aerial vehicle (UAV). By using an automatic control turntable and a data acquisition and analysis system, the accuracy of the circular array radar's omnidirectional array is verified by flying the UAV in a fixed direction. This reduces restrictions on the radar's installation environment, avoids problems and difficulties associated with multi-directional flight inspections of UAVs, improves test efficiency, and shortens the test cycle.

Description

Technical Field

[0001] The present invention belongs to the field of radar technology, and in particular relates to a radar verification system and method. Background Art

[0002] Circular array radar is a type of phased array radar. Its array consists of antenna elements evenly distributed around a circle, making it omnidirectional and capable of 360° scanning. Currently, the most widely used S-band circular array radar is a two-dimensional phased array fixed radar with omnidirectional multi-beam capabilities. It primarily targets close-range, low-altitude targets and has been gradually adopted in low-altitude surveillance, key location security, and other fields.

[0003] The performance of a radar antenna directly impacts its detection effectiveness. To verify the radar's high-precision detection of "low, slow, and small" moving targets, such as ultra-small UAVs and light helicopters, radar detection accuracy must be analyzed and verified during the manufacturing process to ensure performance. Currently, radar detection accuracy testing is primarily conducted through flight testing. The detection accuracy requirements for two-dimensional phase-scanned circular array radars primarily include azimuth and elevation detection errors—the difference between the target's true position and the radar's detected position. For S-band low-altitude surveillance radars, small civilian UAVs are often used as targets for flight testing. Compared to planar arrays, flight testing of fixed circular array low-altitude surveillance radars using this method is relatively difficult. This is primarily due to the fact that the circular array radar array is distributed along a circumference. To ensure the performance of all arrays is verified, multiple flights at different angles and in all directions are required to cover the entire array's range. This method not only requires a long test cycle but also requires clear obstructions within the radar's detection range. Under field test conditions that do not fully meet these requirements, it is virtually impossible to verify the detection accuracy of the entire antenna array. Summary of the Invention

[0004] In order to solve the problems and shortcomings of the existing methods, the present invention provides a system and method for realizing the accuracy verification of the omnidirectional array of circular array radar by using the single-direction flight of an unmanned aerial vehicle. The equipment and system used include a radar turntable, a radar echo data acquisition and analysis system, a micro-sized civilian unmanned aerial vehicle, a signal transmission line and other necessary accessories.

[0005] The present invention overcomes the difficulties in conducting precision testing of fixed circular array radar antennas based on omnidirectional flight of UAVs, and provides a method that combines an automatic control turntable and a data acquisition and analysis system to realize single-direction UAV flight to complete precision verification of the entire circular array, effectively avoiding the limitations of traditional testing methods on test environment conditions and the shortcomings of long test cycles.

[0006] A fixed circular array radar omnidirectional array accuracy verification system includes a servo turntable, a servo control system, a multi-channel data acquisition and analysis system, a miniature civilian drone, and other supporting equipment. The circular array radar is mounted and fastened to the turntable, which is connected to the servo control system. The multi-channel data acquisition and analysis system receives radar echo data.

[0007] according to Figure 1 A circular array radar accuracy verification test system was built. The radar weighed 180 kg, had a diameter of 1100 mm, and a height of 1000 mm. The antenna consisted of 48 column feeds evenly distributed around the circumference and was powered by 28 V DC. The servo turntable and control system provided one-dimensional azimuth rotation, with a minimum step of ≤0.5° / s, a maximum rotation speed of ≥6° / s, a payload of ≥180 kg, emergency stop capability, and a fixed array fixture. The multi-channel data acquisition and analysis system processed the downlink data recorded by the recorder, including intra-frame amplitude and phase unpacking and display, inter-frame amplitude and phase unpacking and display, and received sum and difference pattern data unpacking and display. The drone was a DJI Phantom 4 (RCS = 0.02 m 2 ); Other supporting equipment includes power supply cables, optical fibers, network cables, Gigabit network switches, DC regulated power supplies, debugging computers, screws and other fasteners.

[0008] A method for verifying the accuracy of a fixed circular array radar omnidirectional array is described in detail below:

[0009] Step (1), install and fasten the circular array radar on the turntable, connect the cables required for the test, and adjust all equipment to the ready-to-work state;

[0010] Step (2), turn on the radar, and complete the radar true north calibration and azimuth parameter correction through the UAV test flight;

[0011] Step (3), setting the radar to a receiving state, and using a multi-channel signal acquisition and analysis system to record the echo data of each array channel of the radar over a period of time;

[0012] Step (4): Analyze the data of all corresponding channels of the array using the echo data analysis algorithm, find the channel with the lowest echo noise floor, and calculate the direction it points to, which is recorded as direction A;

[0013] Step (5), setting the flight direction of the UAV to direction A;

[0014] Step (6): Keep the turntable stationary, keep the UAV in radial flight at a certain height along the A direction, start the launch to perform target detection and tracking, and record the target data at the same time;

[0015] Step (7), calculating the error between the recorded target data and the actual flight track data of the UAV, and obtaining the pitch and azimuth detection accuracy of the radar array at this position;

[0016] Step (8), controlling the turntable to rotate the radar antenna to an angle M and then stop, repeating steps 6 to 7 to obtain the pitch and azimuth detection accuracy of the radar array at the corresponding position;

[0017] Step (9): Repeat step 8 until the radar returns to its initial position, and the test ends.

[0018] Furthermore, in step (2), each time the radar is re-installed, the system parameters need to be corrected, including the system errors of range, azimuth, and elevation. The system parameters are corrected based on the data from the first flight test, and the system errors are corrected in the display and control interface.

[0019] Furthermore, in step (4), the echo noise floor refers to the echo noise floor of the low elevation wave position; the calculation of the azimuth A is deduced from the relationship between the due north azimuth and the channel number. The azimuth A is the azimuth with the lowest echo noise floor, that is, the azimuth with the least influence of ground interference.

[0020] Furthermore, in step (6), the flight altitude of the UAV is generally set at 100m to 300m, and the altitude should remain fixed during a sortie.

[0021] Furthermore, in step (6), the target data recorded by the radar refers to the detected UAV track data.

[0022] Furthermore, in step (7), when calculating the pitch error, the high-precision GPS return value installed on the drone is used as the true height value, and the height value recorded in step (6) is used as the detection value. Figure 2 Based on the relationship between distance, altitude, and elevation, the elevation detection value at each distance point is deduced from the true value, and the root mean square difference between the two is calculated to obtain the elevation error. The azimuth error is directly calculated from the root mean square difference of the detection value. When there is no clear reason to explain some excessively large or small data in the observation data sample, if the number of observations is greater than 20, the data with a difference greater than 3 times the standard deviation are eliminated. After eliminating the abnormal data, the first difference data is processed as follows:

[0023] Calculate the mean of the first difference

[0024]

[0025] Calculate the standard deviation S of a single difference j

[0026]

[0027] Calculate the root mean square value U of the first difference j

[0028]

[0029] Where: △X ji is the first difference of the i-th inspection flight; N' j is the number of observation points within the sampling interval of the jth inspection flight.

[0030] Furthermore, in step (8), the radar rotation angle M is determined according to the number of radar array quadrants or the number of column feeds.

[0031] The beneficial effects of the present invention are:

[0032] This invention uses an automatic control turntable and a data acquisition and analysis system to verify the omnidirectional array accuracy of the circular array radar by flying a drone in a fixed heading, reducing the restrictions on the radar installation environment, avoiding the problems and difficulties of multi-directional flight inspections of drones, improving test efficiency, and shortening the test cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Schematic diagram of drone flight inspection

[0034] Figure 2 Schematic diagram of elevation angle calculation method

[0035] Figure 3 System flow chart

[0036] Figure 4 Channel 1-10 echo data analysis DETAILED DESCRIPTION

[0037] The technical solutions provided by the present invention will be described in detail below with reference to specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0038] A fixed circular array radar omnidirectional array accuracy verification system includes a servo turntable, a servo control system, a multi-channel data acquisition and analysis system, a miniature civilian drone, and other supporting equipment. The circular array radar is mounted and fastened to the turntable, which is connected to the servo control system. The multi-channel data acquisition and analysis system receives radar echo data.

[0039] according to Figure 1A circular array radar accuracy verification test system was built. The radar weighed 180 kg, had a diameter of 1100 mm, and a height of 1000 mm. The antenna consisted of 48 column feeds evenly distributed around the circumference and was powered by 28 V DC. The servo turntable and control system provided one-dimensional azimuth rotation, with a minimum step of ≤0.5° / s, a maximum rotation speed of ≥6° / s, a payload of ≥180 kg, emergency stop capability, and a fixed array fixture. The multi-channel data acquisition and analysis system processed the downlink data recorded by the recorder, including intra-frame amplitude and phase unpacking and display, inter-frame amplitude and phase unpacking and display, and received sum and difference pattern data unpacking and display. The drone was a DJI Phantom 4 (RCS = 0.02 m 2 ); Other supporting equipment includes power supply cables, optical fibers, network cables, Gigabit network switches, DC regulated power supplies, debugging computers, screws and other fasteners.

[0040] A method for verifying the accuracy of a fixed circular array radar omnidirectional array, the specific steps are as follows:

[0041] Step 1: Install and fix the radar on the servo turntable according to Figure 1 Schematic diagram, connect all supporting equipment and build the test system.

[0042] Step 2: Turn on the radar power and set it to work. Set the north heading to release the drone and recall it after reaching a distance of 5km. The radar tracks the drone target and records data. Based on the flight data, it corrects the system parameters such as direction and altitude. The system error is corrected on the display and control interface, and the north calibration is completed.

[0043] Step 3: Set the radar to receive mode, start the multi-channel signal acquisition and analysis system, and record 3 minutes of data;

[0044] Step 4: Download the recorded data to the debugging machine, process the received data through the Matlab test data processing program to form the low elevation echo data of each channel, corresponding to the low elevation echo data of each column feed, Figure 4 Analyzing the echo data for channels 1-10 reveals that, with the exception of channel 2, the echo signals received by all other channels are strongly cluttered by ground objects. Therefore, the azimuth corresponding to channel 2 is used as the optimal azimuth A for target detection. In this case, the azimuth corresponding to the first channel, obtained in step 2, is 20 degrees. Therefore, the optimal azimuth A = 20 + (360 / 48) = 27.5 degrees.

[0045] Step 5: Set the drone's flight heading to 27.5 degrees north-east, the flight altitude to 150 meters, the flight distance to 5 kilometers, and return home on its own.

[0046] Step 6: Set the radar to working state and fly the drone according to the settings in step 5. The radar will track the drone target and record data.

[0047] Step 7: Extract the flight altitude, azimuth, and distance information from the track data corresponding to the target batch number, and calculate the detection errors of the pitch and azimuth angles of the sortie using the Matlab data processing program.

[0048] Step 8: Control the turntable to rotate by an angle M. In this embodiment, angle M is determined by the number of radar quadrants. This radar has 48 antenna array feeds. During normal operation, the array array selects 12 adjacent array feeds to operate simultaneously in azimuth. Therefore, at least four rotations of M = 90 degrees are required to ensure that all arrays can be inspected and verified in their working state. After the array antenna rotates to the target position, the servo rotation is stopped, and the pitch and azimuth detection accuracy of the array array is verified according to the methods in Steps 6 and 7.

[0049] Step 9: Repeat step 8 until all array quadrants are verified and the test ends.

[0050] The above description is only the best specific implementation method of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or replacements that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed by the present invention should be covered by the scope of protection of the present invention.

[0051] The contents not described in detail in the specification of the present invention belong to the common knowledge of professionals in this field.

Claims

1. A method for verifying the accuracy of a fixed circular array radar omnidirectional array, characterized in that: The steps of this method are as follows: Step (1), install and fasten the circular array radar on the turntable, connect the cables required for the test, and adjust all equipment to the ready-to-work state; Step (2), turn on the radar, and complete the radar true north calibration and azimuth parameter correction through the UAV test flight; Step (3), setting the radar to a receiving state, and using a multi-channel signal acquisition and analysis system to record the echo data of each array channel of the radar over a period of time; Step (4): Analyze the data of all corresponding channels of the array using the echo data analysis algorithm, find the channel with the lowest echo noise floor, and calculate the direction it points to, which is recorded as direction A; Step (5), setting the flight direction of the UAV to direction A; Step (6): Keep the turntable stationary, keep the UAV in radial flight at a certain height along the A direction, start the launch to perform target detection and tracking, and record the target data at the same time; Step (7), calculating the error between the recorded target data and the actual flight track data of the UAV, and obtaining the pitch and azimuth detection accuracy of the radar array at this position; Step (8), control the turntable to rotate the radar antenna to an angle M and then stop, repeat steps (6) to (7), and obtain the pitch and azimuth detection accuracy of the radar array at the corresponding position; Step (9): Repeat step (8) until the radar returns to its initial position, and the test ends.

2. The method according to claim 1, characterized in that In step (2), the system parameters need to be corrected each time the radar is re-installed, including the system errors of distance, azimuth and elevation; the system parameters are corrected based on the data of the first flight test, and the system errors are corrected in the display and control interface.

3. The method according to claim 1, characterized in that In step (4), the echo noise floor refers to the echo noise floor of the low elevation wave position; the calculation of the azimuth A is deduced from the relationship between the true north azimuth and the channel number. The azimuth A is the azimuth with the lowest echo noise floor, that is, the azimuth with the least influence of ground interference.

4. The method according to claim 1, wherein In step (6), the flight altitude of the UAV is generally set at 100m to 300m, and the altitude should remain fixed during a sortie.

5. The method according to claim 4, characterized in that In step (6), the target data recorded by the radar refers to the detected UAV track data.

6. The method according to claim 1, characterized in that In step (7), when calculating the pitch error, the return value of the high-precision GPS installed on the UAV is used as the true height value, and the height value recorded in step (6) is used as the detection value. According to the relationship between distance, height and elevation angle, the elevation detection value and the true value at each distance point are deduced, and the root mean square difference between the two is calculated to obtain the elevation error; the azimuth error is directly calculated from the root mean square difference of the detection value; when there is no clear reason to explain some excessively large or too small data in the observation data sample, when the number of observations is greater than 20, the data with a difference greater than 3 times the standard deviation are eliminated, and the first difference data after eliminating the abnormal data are processed as follows: Calculate the mean of the first difference Calculate the standard deviation S of a single difference j Calculate the root mean square value U of the first difference j Where: △X ji is the first difference of the i-th inspection flight; N' j is the number of observation points within the sampling interval of the jth inspection flight.

7. The method according to claim 1, characterized in that In step (8), the radar rotation angle M is determined according to the number of radar array quadrants or the number of column feeds.

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