Method and apparatus for obtaining calibration parameters of a radar system

Abstract

The application provides a method and device for obtaining calibration parameters of a radar system, and relates to the technical field of radars, and solves the problem that after low-altitude target detection radars are arranged at different locations, the target detection accuracy of the radars cannot be ensured when the radars are working. The method comprises the following steps: obtaining a target measurement point trail result of a flight trail of a UAV in a flight process; obtaining a target detection point trail result obtained by target detection processing of a radar according to echo signals reflected by the UAV; determining a target detection point according to the target measurement point trail result and the target detection point trail result; and determining calibration parameters of the radar according to the target detection point, wherein the calibration parameters comprise an amplitude and phase correction coefficient, an azimuth angle deviation, a pitch angle deviation, and a distance deviation. The scheme of the application achieves optimal calibration parameters, and improves the target detection accuracy of the radar when the radar is working.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of radar technology, and particularly relates to a method and device for obtaining calibration parameters of a radar system. BACKGROUND

[0002] Low-altitude target detection radar can effectively detect low-altitude, slow-flying and small-sized targets such as unmanned aerial vehicles, and can obtain real-time information such as the position and speed of the targets and has tracking capability, and is a powerful tool for preventing illegal low-altitude flight and safeguarding low-altitude safety.

[0003] Low-altitude target detection radar has high requirements for the accuracy of obtaining the position of a target when detecting a low-altitude target, which requires calibration of the parameters of the radar system and use of the obtained calibration parameters in signal processing when the radar system is in operation.

[0004] A common system calibration scheme uses an internal calibration method, which forms an internal calibration loop in the radar system, obtains internal calibration parameters, and keeps the internal calibration parameters unchanged after the radar system is integrated. However, low-altitude target detection radar is often used in multiple locations. When the low-altitude target detection radar is deployed in different locations, there are deviations in the installation direction and angle of the radar antenna array, and differences in the replacement and installation of cables connecting the radar antenna and the radio frequency, which can cause differences in the amplitude and phase characteristics of each receiving channel, resulting in changes in the radar calibration parameters used for subsequent signal processing, and thus cannot guarantee the target detection accuracy of the radar in operation. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a method and device for obtaining calibration parameters of a radar system. The obtained calibration parameters can be optimized, and the target detection accuracy of the radar in operation can be improved.

[0006] To solve the above technical problems, the technical solutions of the present application are as follows:

[0007] A method for obtaining calibration parameters of a radar system, comprising the following steps:

[0008] Obtaining a target measurement track result of the flight track of an unmanned aerial vehicle in the flight process;

[0009] Obtaining a target detection track result obtained by target detection processing of the radar according to the echo signal reflected by the unmanned aerial vehicle;

[0010] Determining a target detection point according to the target measurement track result and the target detection track result;

[0011] The calibration parameters of the radar are determined according to the target detection point, and the calibration parameters include: amplitude and phase correction coefficients, azimuth deviation, pitch angle deviation, and range deviation.

[0012] Optionally, obtain the target measurement point results of the UAV's flight track during flight, including:

[0013] Obtaining the position information of each sampling point in the flight trajectory of the UAV during flight;

[0014] According to the position information of the sampling points and the position information of the center of the radar antenna array, the distance between each sampling point and the radar and the azimuth and elevation angle of each sampling point relative to the normal direction of the radar antenna array are calculated to obtain the target measurement point trace result.

[0015] Optionally, obtaining a target detection point trace result obtained by the radar performing target detection processing based on the echo signal reflected by the drone includes:

[0016] Acquire four echo signals reflected by the UAV and received by the radar, wherein one echo signal corresponds to one antenna array of the radar;

[0017] Apply amplitude and phase correction coefficients to the echo signals reflected by the 4 drones respectively Perform target detection processing to obtain 4 groups of target detection point trace results;

[0018] The distance information D of the target detection points detected in the four groups of target detection point trace results is j , and each channel amplitude information and phase information As the target detection point trace result;

[0019] Among them, j is the serial number of the target detection point, ranging from 1 to N, and N is the number of target detection points;

[0020] i is the channel number, i=1, 2, 3, 4, indicating the number of 4 channels, and the superscript (0) indicates the amplitude and phase information and the initial value of the amplitude and phase correction coefficient.

[0021] Optionally, determining a target detection point according to the target measurement point trace result and the target detection point trace result includes:

[0022] The target measurement point trace result and the target detection point trace result are feature matched through the flight trajectory of the UAV to determine multiple matched target detection points; the parameter information of each matched target detection point includes the distance information D inherited from the target measurement point trace result. j , each channel amplitude information Channel phase information And the GPS measurement azimuth angle matched by the corresponding target measurement point trace result And the GPS measurement elevation angle θ j .

[0023] Optionally, according to the target detection point, the scaling parameter of the radar is determined, including:

[0024] The distance deviation of the target detection point in each channel is obtained;

[0025] The amplitude and phase coefficients of the target detection point in each channel are corrected to obtain the amplitude and phase correction coefficient result and the fitting slope of the phase correction coefficient of each channel;

[0026] According to the amplitude and phase correction coefficient of the target detection point with the distance information being the distance average value of all target detection points, the target detection processing is performed on the original echo signal to obtain a detection result;

[0027] The azimuth deviation and the elevation deviation of the target detection point in the detection result are obtained;

[0028] It is judged whether the fitting slope of the phase correction coefficient is less than or equal to a preset threshold value, and whether the azimuth deviation and the elevation deviation of each target detection point are consistent, and whether the iteration number of the method makes the azimuth deviation converge to the azimuth threshold value range and makes the elevation deviation converge to the elevation threshold value range. If one or more of the above determination results is no, then the step is repeated according to the updated parameter for iteration processing; if all the above determination results are yes, then the iteration processing of the step is stopped, and the scaling parameter is output, including: the amplitude and phase correction coefficient, the azimuth deviation, the elevation deviation and the distance deviation.

[0029] Optionally, the distance deviation of the target detection point in each channel is obtained, including:

[0030] The target measurement point trace result and the target detection point trace result are respectively drawn into a distance-sampling time two-dimensional graph of the point trace according to the respective distance coordinates and time coordinates;

[0031] When the point traces on the two-dimensional graph are superimposed, the distance of the target detection point trace along the distance axis is determined as the distance deviation of the target detection point.

[0032] Optionally, the amplitude and phase coefficients of the target detection point in each channel are corrected to obtain the amplitude and phase correction coefficient result and the fitting slope of the phase correction coefficient of each channel, including:

[0033] Through the following formula:

[0034]

[0035]

[0036]

[0037] The amplitude and phase coefficients of the target detection points in each channel are corrected to obtain amplitude and phase correction coefficient results

[0038] Wherein, d x is the azimuth antenna phase center spacing, d z is the elevation antenna phase center spacing, N is the amplitude correction coefficient calculated by each target detection point in the kth iteration, N is the phase correction coefficient calculated by each target detection point in the kth iteration, is the GPS measured azimuth angle in the parameter information of the target detection points, θ j is the elevation angle, and λ is a predetermined constant representing the radar operating wavelength;

[0039] All phase correction coefficient results calculated according to the target detection points in each channel are obtained One-dimensional phase unwrapping and linear fitting are performed on the distance Dj in the parameter information of the target detection points as the independent variable to obtain a fitting slope as the fitting slope of the phase correction coefficient of each channel.

[0040] Optionally, the amplitude and phase correction coefficients of the target detection point at the distance average of all target detection points are used to perform target detection processing on the original echo signal to obtain a detection result, including:

[0041] The distance information D j in the parameter information of the target detection points is selected;

[0042] The amplitude and phase correction coefficients calculated using the parameter information of the selected target detection point The original echo data of 4 channels is processed to obtain a detection result, and the detection result is the parameter information of each target detection point after one iteration, including the distance information D j of the target detection point, the channel amplitude information the channel phase information and the radar measured azimuth angle and the radar measured elevation angle

[0043] Optionally, the azimuth angle deviation and the elevation angle deviation of the target detection point in the detection result are obtained, including:

[0044] the radar measurement azimuth angle of each target detection point in the detection result and the radar measurement elevation angle the GPS measurement azimuth angle and the GPS measurement elevation angle j comparison, the azimuth angle deviation and the elevation angle deviation

[0045] The embodiment of the application further provides an acquisition device of a scaling parameter of a radar system, comprising:

[0046] a first acquisition module, used for acquiring a target measurement point track result of a flight track of a UAV in a flight process;

[0047] a second acquisition module, used for acquiring a target detection point track result obtained by target detection processing of a radar according to echo signals reflected by the UAV;

[0048] a processing module, used for determining a target detection point according to the target measurement point track result and the target detection point track result, and acquiring a scaling parameter of each target detection point, wherein the scaling parameter comprises an amplitude-phase correction coefficient, an azimuth angle deviation, an elevation angle deviation and a distance deviation.

[0049] The above scheme of the application has at least the following beneficial effects:

[0050] The above scheme of the application can realize the fast calibration of the scaling parameter of the radar system in a new place after the radar moves, and improve the target detection precision of the radar in the working state. BRIEF DESCRIPTION OF DRAWINGS

[0051] Figure 1 is a flow chart of a scaling parameter acquisition method of a radar system of an embodiment of the application;

[0052] Figure 2 is a schematic diagram of a two-dimensional graph matching result of a flight track of a UAV in an embodiment of the application;

[0053] Figure 3is a schematic diagram of the phase correction coefficient and its linear fitting result obtained by each target detection point after 4 times of iteration processing in the embodiment of the present application;

[0054] Figure 4 is a comparison diagram of the target detection angle result obtained by processing echo data by using the scaling parameter and the true value result of the target GPS measurement in the embodiment of the present application;

[0055] Figure 5 is a specific implementation flowchart of the method for obtaining the scaling parameter of the radar system in the embodiment of the present application;

[0056] Figure 6 is a module schematic diagram of the device for obtaining the scaling parameter of the radar system in the embodiment of the present application. DETAILED DESCRIPTION

[0057] Exemplary embodiments of the present disclosure will be described more fully hereinafter with reference to the accompanying drawings; however, they are not limited to the embodiments set forth herein but can be implemented in various forms. The embodiments are provided so that this disclosure will be thorough, and will fully convey the scope of the disclosure to those skilled in the art.

[0058] As shown in Figure 1 , the embodiment of the present application proposes a method for obtaining the scaling parameter of a radar system, comprising the following steps:

[0059] Step 11, obtaining a target measurement point trail result of a flight path of a UAV in a flight process, the target measurement point trail result comprising: a distance between each sampling point on the flight path and a center of a radar antenna array surface, and an azimuth angle and an elevation angle of each sampling point position relative to a normal direction of the radar antenna array surface;

[0060] Step 12, obtaining a target detection point trail result obtained by target detection processing of the radar according to echo signals reflected by the UAV, the target detection point trail result comprising: distance information of a target detection point, channel amplitude information and phase information;

[0061] Step 13, determining a target detection point according to the target measurement point trail result and the target detection point trail result;

[0062] Step 14, determining a scaling parameter of the radar according to the target detection point, the scaling parameter comprising: an amplitude and phase correction coefficient, an azimuth angle deviation, an elevation angle deviation, and a distance deviation.

[0063] This embodiment of the present invention uses the drone's built-in GPS (Global Positioning System) to obtain the drone's flight trajectory location information. Based on the flight trajectory location information, sampling points are extracted and the distance, azimuth, and pitch angle between each target sampling point and the center of the radar antenna array are calculated to form a target measurement point trace result. Simultaneously, the radar illuminates the drone's flight process to obtain an echo signal. Target detection processing is performed on the echo signal to obtain a radar target detection point trace result. Feature matching is performed between the target measurement point trace result and the target detection point trace result based on the drone's flight trajectory to determine multiple target detection points. These target detection points are then processed and compared to obtain calibration parameters for the radar system. This method can calibrate a low-altitude target detection radar deployed at a working location. By collecting target echo information from a cooperating drone with a real-time GPS location, calibration parameters are obtained through multiple iterative processes and used in target detection processing, thereby improving the accuracy of target detection results and ensuring the accuracy of low-altitude target detection results.

[0064] In an optional embodiment of the present invention, in step 11, obtaining the target measurement point track results of the flight track of the UAV during the flight process includes:

[0065] 111 obtains the position information of each sampling point in the flight trajectory of the UAV during flight;

[0066] 112 calculates the distance between each sampling point and the radar, and the azimuth and elevation angles of each sampling point relative to the normal direction of the radar antenna array based on the position information of the sampling points and the position information of the center of the radar antenna array, to obtain the target measurement point trace result.

[0067] In this embodiment, a UAV cooperative target is flown in a specific manner in the normal direction of the antenna illumination of the low-altitude target detection radar. During the flight, the GPS module on the UAV records the location information of its flight trajectory. Based on the GPS data recorded during the flight of the UAV, each sampling point qm of the UAV in the flight track is extracted, where m = 1, 2, ..., M, where M is the number of UAV target sampling points in the track. Each target sampling point q m Contains the location information of the point, i.e., longitude, latitude and altitude information. The target sampling points q are calculated based on the measured radar array center position information and its nominal normal direction. m Distance D from the radar m , azimuth and pitch angle θ m , forming the target measurement point trace result;

[0068] The unmanned aerial vehicle cooperates with the target in a specific way, specifically, the unmanned aerial vehicle flies from near to far along the normal direction of the antenna, and then flies from far to near, and swings left and right along the azimuth direction and swings up and down along the pitch direction in the radar antenna beam irradiation range during the flight.

[0069] In an optional embodiment of the present application, in step 12, the target detection point track result obtained by the radar according to the echo signal reflected by the unmanned aerial vehicle is acquired, including:

[0070] In step 121, the four paths of echo signals reflected by the unmanned aerial vehicle received by the radar are acquired, and one path of echo signals corresponds to one antenna array surface of the radar.

[0071] In step 122, the four paths of echo signals reflected by the unmanned aerial vehicle are respectively subjected to target detection processing using amplitude and phase correction coefficients to obtain four groups of target detection point track results.

[0072] In step 123, the distance information D j of the target detection point detected in the four groups of target detection point track results and the channel amplitude information and the phase information are taken as the target detection point track result; wherein j is the serial number of the target detection point, and takes a value of 1 to N, and N is the number of target detection points.

[0073] i is the channel serial number, i=1, 2, 3, 4, indicating the serial number of the four channels, and the superscript (0) indicates the initial value of the amplitude and phase information and the amplitude and phase correction coefficient.

[0074] In this embodiment, the four paths of unmanned aerial vehicle target echo data collected and recorded by the radar are subjected to target detection processing, wherein each path of echo data corresponds to one antenna array surface, and the amplitude and phase correction coefficient of each path of echo data is set to the initial value 0 during the target detection processing, and one group of target detection point track results is obtained after processing; the target detection points detected in the four groups of target detection point track results are extracted as the final acquired target detection point track results, and the extracted target detection points are denoted as p j , wherein j is the serial number of the target detection point, and takes a value of 1 to N, and N is the number of target detection points; each target detection point p j contains the distance information D j of the target detection point, and the channel amplitude information and the phase information , wherein i is the channel serial number, and takes a value of 1 to 4, indicating the serial number of the four channels, and the superscript (0) indicates the initial value of the amplitude and phase information and the amplitude and phase correction coefficient.

[0075] The radar has four antenna arrays, and four receiving channels correspond to the four antenna arrays.

[0076] The target detection processing in the embodiment includes amplitude and phase correction of the radar echo data, pulse compression processing, multi-pulse cancellation processing, Doppler sharpening processing, CFAR detection processing, and difference beam angle measurement processing, so as to obtain the detected target detection points and the distance, azimuth angle, elevation angle, radial velocity, channel amplitude and phase information of the points, and the amplitude and phase information after channel and difference beam synthesis.

[0077] In another optional embodiment of the present application, in step 13, the target detection points are determined according to the target measurement point trail results and the target detection point trail results, and the determination includes:

[0078] The target measurement point trail results and the target detection point trail results are matched through the flight trajectory of the unmanned aerial vehicle, then the two groups of point trail results are matched point by point to determine the matched target detection points; the parameter information of each matched target detection point p j includes the distance information D j , channel amplitude information , channel phase information , GPS measurement azimuth angle and GPS measurement elevation angle θ j inherited by the target detection point from the target measurement point trail results.

[0079] The initial values of the antenna center azimuth angle deviation and the antenna center elevation angle deviation θ corr are both 0°, that is

[0080] The specific implementation method of the flight trajectory feature matching of the unmanned aerial vehicle in the embodiment is as follows: the target detection point trail results of the radar in step S23 and the target measurement point trail results in step 112 are drawn into a two-dimensional graph of "distance-sampling time" according to their respective distance coordinates and time coordinates, the point trail shapes of the two graphs are compared, the two point trails are translated on the two-dimensional plane to make the point trails on the two graphs coincide, and the flight trajectory feature matching of the unmanned aerial vehicle is realized.

[0081] In another optional embodiment of the present invention, in step 14, determining the calibration parameters of the radar according to the target detection point includes:

[0082] Step 141, obtaining the distance deviation of the target detection point in each channel;

[0083] Step 142, performing correction processing on the amplitude and phase coefficients of the target detection point in each channel, obtaining amplitude and phase correction coefficient results and fitting slopes of the phase correction coefficients of each channel;

[0084] Step 143 , performing target detection processing on the original echo signal according to the amplitude and phase correction coefficient of the target detection point whose distance information is the average distance of all target detection points, to obtain a detection result;

[0085] Step 144, obtaining the azimuth deviation and pitch angle deviation of the target detection point in the detection result;

[0086] Step 145: Determine whether the fitting slope of the phase correction coefficient is less than or equal to a preset threshold, whether the azimuth deviation and the pitch angle deviation of each target detection point are consistent, and whether the number of iterations of the method makes the azimuth deviation converge to the azimuth threshold. The pitch angle deviation converges to the pitch angle threshold θ th If one or more of the above judgment results are negative, repeat this step for iterative processing according to the updated parameters; if all of the above judgment results are positive, stop the iterative processing of this step and output the calibration parameters, which include: amplitude and phase correction coefficient, azimuth deviation, pitch angle deviation and range deviation.

[0087] In this embodiment, step 141 may specifically include:

[0088] Step 1411 , plotting the target measurement trace result and the target detection trace result into a distance-sampling time two-dimensional graph according to their respective distance coordinates and time coordinates;

[0089] Step 1412: When the points on the two-dimensional graph are overlapped, the distance of the target detection point trace translated along the distance axis is determined as the distance deviation of the target detection point.

[0090] like Figure 2 As shown, the target measurement point trace result in step 112 and the target detection point trace result in step 123 are respectively plotted as a "distance-sampling time" two-dimensional graph according to their respective distance coordinates and time coordinates; when the points on the two-dimensional graph overlap, the distance that the target detection point trace is translated along the distance axis is determined as the distance deviation of the target detection point, thereby obtaining the distance calibration result of the target detection point, that is, the distance deviation D corrFor example, the target detection point trace translates along the distance axis by a distance of 1.3 m, that is, the distance deviation D of the target detection point is 1.3 m corr 1.3 m.

[0091] Further, the step 142 can specifically include:

[0092] By the following formula:

[0093]

[0094]

[0095]

[0096] The amplitude and phase coefficients of the target detection points in each channel are corrected to obtain amplitude and phase correction coefficient results;

[0097] Where d x is the azimuth antenna phase center spacing, d z is the elevation antenna phase center spacing, N is the amplitude correction coefficient calculated by each target detection point in the kth iteration, N is the phase correction coefficient calculated by each target detection point in the kth iteration, is the GPS measured azimuth angle in the parameter information of the target detection point, θ j is the GPS measured elevation angle in the parameter information of the target detection point, and λ is a preset constant representing the radar operating wavelength.

[0098] Then all the phase correction coefficient results calculated according to the target detection points in each channel are obtained with the distance D j of the target detection point as the independent variable to perform one-dimensional phase unwrapping and linear fitting to obtain the fitting slope of the phase correction coefficient of each channel and the fitting phase offset

[0099] Further, the step 143 can specifically include:

[0100] Step 1431, selecting each target detection point p ij with the distance information D j in the parameter information as the point p iJ at the distance average value, and taking the point p iJ as the selected target detection point;

[0101] Step 1432, using the amplitude and phase correction coefficients calculated from the parameter information of p iJ ​Perform target detection processing on the 4-channel original echo data to obtain the target detection point p j The parameter information after one iteration includes the distance information D of the target detection point j , each channel amplitude information Phase information of each channel And the radar measurement azimuth obtained by the 4-channel sum difference beam measurement method Measuring pitch angle with radar

[0102] When this embodiment is implemented, the target detection point p is selected. ij Distance information D of the midpoint j is the point p at the distance from the mean iJ , use p iJ The amplitude and phase correction coefficients are calculated based on the information Expressed as:

[0103]

[0104] Using the Amplitude and Phase Correction Factors Perform target detection processing on the 4-channel original echo data to obtain the target detection point p j The parameter information after one iteration includes the distance information D of the target detection point j , each channel amplitude information Phase information of each channel where exp(·) represents the exponential function with the natural logarithm e as the base; and the radar measurement azimuth obtained by the 4-channel sum and difference beam measurement method. Measuring pitch angle with radar

[0105] Step 144 may specifically include: and pitch angle With GPS measurement results and θ j Compare and obtain the azimuth deviation of each point Deviation from pitch angle

[0106] Specifically, the azimuth angle measured by the radar and pitch angle Results and GPS measurements and θ j Make the corresponding difference to obtain the azimuth deviation of each target detection point Deviation from pitch angle

[0107] Wherein, i is the channel number, i = 1, 2, 3, 4, representing the channel number of 4 paths, j is the target detection point number, taking value 1 ~ N, N is the target detection point number.

[0108] In step 145, it is judged whether the phase correction coefficient slope is less than the threshold value K th , whether the azimuth angle deviation and the pitch angle deviation are consistent, and whether they converge to and θ th respectively with the increase of the iteration number, if not, repeat step 14 to enter the next iteration processing; if yes, end the iteration, and output the calibration parameters, including: amplitude and phase correction coefficient azimuth angle deviation pitch angle deviation and distance deviation D corr , wherein n is the iteration number when the iteration ends.

[0109] Figure 3 The phase correction coefficient of each channel and its linear fitting result after 4 iterations are shown. It can be seen that after 4 iterations, the slope of the phase correction coefficient is relatively flat, and its value is less than 0.1° / m. After 4 iterations, the calibration parameters obtained in this embodiment are:

[0110] The amplitude and phase correction coefficient of each channel:

[0111] η1 = 1, η2 = -0.55 + 0.60j, η3 = -0.42 - 0.82j, η4 = -0.29 - 0.82j.

[0112] Distance deviation: D corr = 1.3m;

[0113] Azimuth and pitch deviation: θ corr = -7.15°;

[0114] Figure 4 The target detection result obtained by processing the echo data using the calibration parameters obtained after 4 iterations is compared with the true value of the target GPS measurement in the pitch angle measurement result. It can be seen that the target positioning result obtained by processing has high precision.

[0115] As Figure 5 shown, it is a specific implementation flowchart of the above embodiment, and the process includes:

[0116] Step 51: Fly a cooperative UAV in a specific manner in the normal direction of the low-altitude target detection radar's antenna illumination. During the flight, the UAV's built-in GPS module records the location information of its flight trajectory. At the same time, the low-altitude target detection radar illuminates the UAV throughout its flight, and the radar's four receiving channels collect and record echo data.

[0117] Step 52: Extract the sampling points q of the drone in the flight track according to the GPS data recorded during the flight of the drone. m , where m = 1, 2, ..., M, where M is the number of target sampling points of the UAV in the track. Each target sampling point q m Contains the location information of the point, i.e., longitude, latitude and altitude information. The target sampling points q are calculated based on the measured radar array center position information and its nominal normal direction. m Distance D from the radar m , azimuth and pitch angle θ m , forming the GPS measurement point trace results of the target.

[0118] Step 53: Target detection is performed on the four channels of UAV target echo data collected and recorded by the radar. Each channel of echo data corresponds to one antenna array. When performing target detection, the amplitude and phase correction coefficient η of each channel of echo data is used. i , i=1, 2, 3, 4 are all set to the initial value 0, and after processing, a set of target detection point trace results is obtained. Among the four sets of target detection point trace results, the target detection points detected in all four sets of results are extracted as the final target detection point trace results, and the extracted target detection points are recorded as p j , where j is the target detection point number, ranging from 1 to N, and N is the number of target detection points. Each target detection point p j The distance information D of the target detection point is included j , and each channel amplitude information and phase information Where i is the channel number, ranging from 1 to 4, indicating the number of the four channels, and the superscript (0) indicates the initial value of the amplitude and phase information.

[0119] Step 54: Match the target detection point trace result measured by the radar in step 53 with the target GPS measurement point trace result in step 52 through the UAV flight trajectory feature to obtain the distance calibration result D of the target detection point. corr Then the two sets of point traces are matched point by point so that each target detection point p j Contains the distance information D of the target detection point j , each channel amplitude information Phase information of each channel GPS measurement azimuth θ is measured by GPS j θ is measured by GPS θ is measured by GPS corr θ is measured by GPS

[0120] Step 55, the matching target detection point p obtained by matching the GPS measurement point trace and the radar measurement point trace ij The amplitude and phase correction coefficient results are obtained by performing amplitude and phase correction processing on each point, and are represented as:

[0121]

[0122]

[0123]

[0124]

[0125] wherein d x is the azimuth antenna phase center distance, d z is the elevation antenna phase center distance, N is the amplitude correction coefficient calculated for each point in the kth iteration, N is the phase correction coefficient calculated for each point in the kth iteration.

[0126] All phase correction coefficient results calculated according to the target detection point in each channel One-dimensional phase unwrapping and linear fitting are performed with the distance Dj of the target detection point as the independent variable, to obtain the fitting slope of the phase correction coefficient of each channel and the fitting phase offset

[0127] Step 56, selecting the target detection point p ij The distance information D j of the midpoint iJ , the amplitude and phase correction coefficients calculated using the p iJ detection point information are represented as:

[0128]

[0129] The amplitude and phase correction coefficients are used to perform target detection processing on the 4-way original echo data, to obtain the target detection point p j , the target detection point distance information D j contained in the point, the channel amplitude information , and the channel phase information And the radar measurement azimuth obtained by the 4-channel sum difference beam measurement method Measuring pitch angle with radar

[0130] Step 57: The azimuth angle measured by the radar and pitch angle Results and GPS measurements and θ j Compare and obtain the azimuth deviation of each point Deviation from pitch angle

[0131] Step 58: Determine the slope of the phase correction coefficient in step 55. Is the value less than the threshold K? th , azimuth deviation of each point Deviation from pitch angle Are they consistent, and as the number of iterations increases, they converge to and θ th If not, repeat step S5 to enter the next iteration process; if so, end the iteration and obtain the calibration result: amplitude and phase correction coefficient Azimuth deviation Pitch angle deviation and the distance deviation D corr , where n is the number of iterations at the end of the iteration.

[0132] In certain embodiments of the present invention, in step 51, the low-altitude target detection radar has four antenna arrays, corresponding to four receiving channels. The centers of the four antenna arrays are arranged in a 2×2 pattern in azimuth and elevation. Based on the direction facing the antenna array, the centers of the antenna arrays corresponding to receiving channels 1, 2, 3, and 4 are located in the upper left corner, upper right corner, lower left corner, and lower right corner, respectively.

[0133] In certain embodiments of the present invention, in step 51, the specific implementation method of flying a drone cooperation target in a specific manner is: let the drone fly roughly along the normal direction of the antenna from near to far (or from far to near), and then from far to near (or from near to far). During the flight, the drone can be swung left and right in azimuth and up and down in pitch within the illumination range of the radar antenna beam.

[0134] In the embodiment of the present application, in step 53, the target detection processing includes amplitude and phase correction of radar echo data, pulse compression processing, multi-pulse cancellation processing, Doppler sharpening processing, CFAR detection processing, and difference beam angle measurement processing, to obtain the detected target points and the distance, azimuth angle, elevation angle, radial velocity, amplitude and phase information of each channel, and amplitude and phase information after channel and difference beam synthesis. The amplitude and phase correction of radar echo data is to multiply the radar echo data of each channel with the amplitude and phase correction coefficient of the corresponding channel respectively to obtain the processing result.

[0135] In the embodiment of the present application, in step 54, the UAV flight trajectory feature matching is to draw the target detection point trail results measured by the radar in step 53 and the target GPS measurement point trail results in step 52 respectively according to the respective distance coordinates and time coordinates to draw the point trail of the “distance-sampling time” two-dimensional graph, compare the point trail shapes of the two graphs, and realize the feature matching of the UAV flight trajectory by translating the two point trails on the two-dimensional plane to make the point trails on the two graphs coincide. At this time, the distance of the target detection point trail along the distance axis is calculated, that is, the distance calibration result D of the target detection point. corr .

[0136] The present application provides a field system calibration method for low-altitude target detection radar. The method only needs to use a small unmanned aerial vehicle with GPS positioning function to fly in the radar irradiation area once, obtain target echo data and process, and then obtain the calibration parameters of the radar arranged in the working scene. The calibration method provided by the present application adopts an iterative processing mode, so that the obtained calibration parameters are optimal, and the target detection accuracy of the radar in working is improved.

[0137] As shown in Figure 6 , the embodiment of the present application further provides an acquisition device 60 of calibration parameters of a radar system, comprising:

[0138] A first acquisition module 61 is configured to acquire target measurement point trail results of a flight path of an unmanned aerial vehicle in a flight process.

[0139] A second acquisition module 62 is configured to acquire target detection point trail results obtained by target detection processing of the radar according to echo signals reflected by the unmanned aerial vehicle.

[0140] A processing module 63 is configured to determine target detection points according to the target measurement point trail results and the target detection point trail results, and acquire calibration parameters of each target detection point, wherein the calibration parameters include amplitude and phase correction coefficients, azimuth angle deviations, elevation angle deviations, and distance deviations.

[0141] Optionally, the target measurement point trail results of the flight path of the unmanned aerial vehicle in the flight process comprise:

[0142] acquire position information of each sampling point in a flight trajectory during the flight of the unmanned aerial vehicle;

[0143] According to the position information of the sampling points and the position information of the center of the antenna array of the radar, the distance between each sampling point and the radar, and the azimuth angle and the elevation angle of each sampling point position relative to the normal direction of the radar antenna array are calculated to obtain the target measurement point track result.

[0144] Optionally, the target detection point track result obtained by the radar according to the echo signal reflected by the unmanned aerial vehicle is acquired, including:

[0145] The 4 paths of the echo signal reflected by the unmanned aerial vehicle received by the radar are acquired, wherein 1 path of the echo signal corresponds to 1 antenna array of the radar;

[0146] The amplitude and phase correction coefficients are used for the 4 paths of the echo signal reflected by the unmanned aerial vehicle respectively to perform target detection processing to obtain 4 groups of target detection point track results;

[0147] The distance information D j of the target detection point detected in the 4 groups of target detection point track results and the channel amplitude information and the phase information are taken as the target detection point track result;

[0148] wherein j is the serial number of the target detection point, and takes a value of 1 to N, and N is the number of target detection points;

[0149] i is the serial number of the channel, i=1, 2, 3, 4, indicating the serial number of the 4 paths of the channel, and the superscript (0) indicates the initial value of the amplitude and phase information and the amplitude and phase correction coefficient.

[0150] Optionally, according to the target measurement point track result and the target detection point track result, the target detection point is determined, including:

[0151] The target measurement point track result and the target detection point track result are matched through the flight trajectory of the unmanned aerial vehicle to determine a plurality of matched target detection points; the parameter information of each matched target detection point includes the distance information D of the target detection point inherited from the target measurement point track result, the channel amplitude information the channel phase information , the GPS measurement azimuth angle j , and the GPS measurement elevation angle θ

[0152] Optionally, according to the target detection point, the calibration parameter of the radar is determined, including:

[0153] obtaining a distance deviation of the target detection point in each channel;

[0154] correcting the amplitude and phase coefficients of the target detection point in each channel to obtain an amplitude and phase correction coefficient result and a fitting slope of the phase correction coefficient of each channel;

[0155] performing target detection processing on the original echo signal according to the amplitude and phase correction coefficient of the target detection point whose distance information is the average distance of all target detection points to obtain a detection result;

[0156] obtaining an azimuth deviation and a pitch deviation of the target detection point in the detection result;

[0157] determining whether the fitting slope of the phase correction coefficient is less than or equal to a preset threshold value, and whether the azimuth deviation and the pitch deviation of each target detection point are consistent, and whether the iteration number of the method makes the azimuth deviation converge within an azimuth threshold range and makes the pitch deviation converge within a pitch threshold range, if one or more of the above determination results is false, then repeating the iteration processing according to the updated parameters; if all the above determination results are true, then stopping the iteration processing of the step and outputting a calibration parameter, the calibration parameter including: the amplitude and phase correction coefficient, the azimuth deviation, the pitch deviation and the distance deviation.

[0158] Optionally, the distance deviation of the target detection point in each channel is obtained, including:

[0159] drawing a distance-sampling time two-dimensional graph of the point trace according to the respective distance coordinates and time coordinates of the target measurement point trace result and the target detection point trace result respectively;

[0160] when the point traces on the two-dimensional graph are superimposed, the distance of the target detection point trace along the distance axis is determined as the distance deviation of the target detection point.

[0161] Optionally, the amplitude and phase coefficients of the target detection point in each channel are corrected to obtain the amplitude and phase correction coefficient result and the fitting slope of the phase correction coefficient of each channel, including:

[0162] by the following formula:

[0163]

[0164]

[0165]

[0166] correcting the amplitude and phase coefficients of the target detection point in each channel to obtain the amplitude and phase correction coefficient result;

[0167] wherein d x is the azimuth antenna phase center separation, d z is the elevation antenna phase center separation, N is the amplitude correction coefficient calculated by each target detection point in the kth iteration, N is the phase correction coefficient calculated by each target detection point in the kth iteration, is the GPS measured azimuth angle in the parameter information of the target detection point, θ j is the elevation angle, and λ is a preset constant representing the wavelength of the radar;

[0168] all the phase correction coefficient results calculated by each channel according to the target detection point are with the distance D j in the parameter information of the target detection point as the independent variable to perform one-dimensional phase unwrapping and linear fitting to obtain the fitting slope as the fitting slope of the phase correction coefficient of each channel.

[0169] Optionally, the amplitude and phase correction coefficients of the target detection point at the distance average of all target detection points are used to perform target detection processing on the original echo signal to obtain a detection result, including:

[0170] the distance information D j in the parameter information of each target detection point is selected as the selected target detection point;

[0171] the amplitude and phase correction coefficients calculated by using the parameter information of the selected target detection point are The original echo data of 4 channels are processed to obtain a detection result, and the detection result is the parameter information of each target detection point after one iteration, including the distance information D j of the target detection point, the channel amplitude information the channel phase information and the radar measured azimuth angle and the radar measured elevation angle

[0172] Optionally, the azimuth angle deviation and the elevation angle deviation of the target detection point in the detection result are obtained, including:

[0173] the radar measured azimuth angle and the radar measured elevation angle of each target detection point in the detection result are compared with the GPS measured azimuth angle and the GPS measures the pitch angle θ j Comparing, the azimuth angle deviation of each target detection point is obtained and the pitch angle deviation

[0174] It should be noted that the device is the device corresponding to the above method, all the implementation manners in the above method embodiment are suitable for the embodiment of the device, and the same technical effects can also be achieved.

[0175] The radar system calibration parameter acquisition method and device in the above embodiment of the application can calibrate the low-altitude target detection radar arranged at the working position, the calibration parameters obtained through the multiple iteration processing of the cooperative unmanned aerial vehicle target echo information with the real-time GPS position are used for target detection processing, the target detection result precision is improved, and the accuracy of the low-altitude flight target detection result is ensured.

[0176] The above is the preferred embodiment of the application, and it should be noted that for ordinary skilled persons in the art, without departing from the principles of the application, a number of improvements and refinements can be made, and these improvements and refinements should also be considered as the protection scope of the application.

Claims

1. A method of obtaining calibration parameters of a radar system, characterized in that, The method comprises the following steps: Obtain a target measurement point trail result of a flight path of a UAV in a flight process; Obtain a target detection point trail result obtained by target detection processing of a radar on a return signal reflected by the UAV; Determine a target detection point according to the target measurement point trail result and the target detection point trail result; Determine a calibration parameter of the radar according to the target detection point, wherein the calibration parameter comprises an amplitude and phase correction coefficient, an azimuth angle deviation, an elevation angle deviation, and a distance deviation; The method comprises the following steps: Obtain a distance deviation of the target detection point in each channel; Correct the amplitude and phase coefficient of the target detection point in each channel to obtain an amplitude and phase correction coefficient result and a fitting slope of a phase correction coefficient of each channel; Perform target detection processing on the original return signal according to the amplitude and phase correction coefficient of the target detection point at a position where distance information of the target detection point is an average distance of all target detection points to obtain a detection result; Obtain an azimuth angle deviation and an elevation angle deviation of the target detection point in the detection result; Determine whether the fitting slope of the phase correction coefficient is less than or equal to a preset threshold value, whether the azimuth angle deviation and the elevation angle deviation of each target detection point are consistent, and whether the iteration number makes the azimuth angle deviation converge within an azimuth angle threshold range and makes the elevation angle deviation converge within an elevation angle threshold range, and if one or more of the above determination results is false, repeat the iteration processing according to the updated parameter; if all the above determination results are true, stop the iteration processing of the step, and output the calibration parameter, wherein the calibration parameter comprises the amplitude and phase correction coefficient, the azimuth angle deviation, the elevation angle deviation, and the distance deviation.

2. The method of claim 1, wherein Obtain a target measurement point trail result of a flight path of a UAV in a flight process, comprising: Obtain position information of each sampling point in a flight path of the UAV in the flight process; Calculate a distance between each sampling point and the radar, and an azimuth angle and an elevation angle of the position of each sampling point relative to a normal direction of an antenna array surface of the radar according to the position information of the sampling point and position information of a center of the antenna array surface of the radar to obtain the target measurement point trail result.

3. The method of claim 1, wherein Obtain a target detection point trail result obtained by target detection processing of a radar on a return signal reflected by the UAV, comprising: Obtain four paths of the return signal reflected by the UAV received by the radar, wherein one path of the return signal corresponds to one antenna array surface of the radar; Respective four said unmanned aerial vehicle reflected echo signal using amplitude and phase correction coefficient Target detection processing is performed to obtain four groups of target detection point results; distance information of the target detection points detected in all of the 4 groups of target detection point trace results and channel amplitude information and phase information as the target detection point trace results; wherein, is the serial number of the target detection point, taking a value of 1~N, N being the number of target detection points; is the channel number, , indicates the channel number of the 4-way channel, the upper index indicates the initial value of the amplitude and phase information and the amplitude and phase correction coefficient.

4. The method of claim 1, wherein Determine a target detection point according to the target measurement point trail result and the target detection point trail result, comprising: The target measurement point trail result and the target detection point trail result are matched by a flight track of the unmanned aerial vehicle to determine a plurality of matched target detection points, and parameter information of each matched target detection point includes distance information inherited from the target detection point trail result , channel amplitude information , channel phase information , and a GPS measurement azimuth angle matched from the corresponding target measurement point trail result , and a GPS measurement elevation angle .

5. The method of claim 1, wherein Obtain a distance deviation of the target detection point in each channel, comprising: Draw a distance-sampling time two-dimensional graph of the point trail according to the distance coordinates and the time coordinates of the target measurement point trail result and the target detection point trail result respectively; When the point trails on the two-dimensional graph are superimposed, a distance of a translation of the target detection point trail along the distance axis is determined as the distance deviation of the target detection point.

6. The method of claim 1, wherein Correct the amplitude and phase coefficient of the target detection point in each channel to obtain an amplitude and phase correction coefficient result and a fitting slope of a phase correction coefficient of each channel, comprising: Through the following formula: The amplitude and phase correction coefficients of the target detection points in each channel are corrected to obtain amplitude and phase correction coefficient results. in, is the azimuth antenna phase center spacing, is the phase center distance of the antennas in elevation, For the The amplitude correction coefficient calculated for each target detection point in the iteration, For the The phase correction coefficient calculated for each target detection point in the iteration, is the GPS measurement azimuth in the parameter information of each target detection point, The GPS measured pitch angle in the parameter information of each target detection point, is a preset constant, representing the radar operating wavelength; all the phase correction coefficient results calculated according to the target detection point in each channel one-dimensional phase unwrapping with the distance in the target detection point parameter information as the independent variable and linear fitting to obtain a fitting slope the fitting slope of the obtained phase correction coefficient of each channel.​ 7. The method of claim 1, wherein According to the amplitude and phase correction coefficient of the target detection point in which the distance information is the distance average value of all target detection points, the original echo signal is subjected to target detection processing to obtain a detection result, including: selecting distance information in the parameter information of each target detection point a point at the distance average value as the selected target detection point Amplitude and phase correction coefficients calculated using the parameter information of the selected target detection points Target detection processing is performed on the 4-path raw echo data to obtain a detection result, which is the parameter information of each target detection point after one iteration, including the distance information of the target detection point , the amplitude information of each channel , the phase information of each channel , and the radar measurement azimuth angle obtained by the 4-channel and difference beam measurement method , and the radar measurement elevation angle .

8. The method of claim 1, wherein, Obtaining the azimuth deviation and the elevation deviation of the target detection point in the detection result, including: comparing the radar measurement azimuth angle of each target detection point in the detection result and the radar measurement elevation angle with the GPS measurement azimuth angle in the corresponding target detection point parameter information and the GPS measurement elevation angle to obtain the azimuth angle deviation and the elevation angle deviation of each target detection point.

9. An acquisition device for scaling parameters of a radar system, characterized in that, Including: The first acquisition module is configured to acquire a target measurement point trail result of a flight path of the UAV in a flight process. The second acquisition module is configured to acquire a target detection point trail result obtained by performing target detection processing on the echo signal reflected by the UAV. The processing module is configured to determine a target detection point according to the target measurement point trail result and the target detection point trail result. The calibration parameters of each target detection point include: an amplitude and phase correction coefficient, an azimuth deviation, an elevation deviation, and a distance deviation. The calibration parameters of the radar are determined according to the target detection point, including: Obtaining the distance deviation of the target detection point in each channel. The amplitude and phase coefficients of the target detection point in each channel are corrected to obtain an amplitude and phase correction coefficient result and a fitting slope of the phase correction coefficient of each channel. According to the amplitude and phase correction coefficient of the target detection point in which the distance information is the distance average value of all target detection points, the original echo signal is subjected to target detection processing to obtain a detection result. Obtaining the azimuth deviation and the elevation deviation of the target detection point in the detection result. Determining whether the fitting slope of the phase correction coefficient is less than or equal to a preset threshold value, and whether the azimuth deviation and the elevation deviation of each target detection point are consistent, and whether the iteration number makes the azimuth deviation converge within the azimuth threshold value range and makes the elevation deviation converge within the elevation threshold value range. If one or more of the above determination results is false, the step is repeated for iteration processing according to the updated parameters; if all the above determination results are true, the iteration processing of the step is stopped, and the calibration parameters are output, including: the amplitude and phase correction coefficient, the azimuth deviation, the elevation deviation, and the distance deviation.

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