CN110426690B - Automatic calibration method for airborne weather radar beam pointing - Google Patents
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
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- G01S7/4004—Means for monitoring or calibrating of parts of a radar system
- G01S7/4026—Antenna boresight
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Abstract
The invention discloses a method for calibrating beam pointing of an airborne weather radar, which is characterized in that a digital elevation map is used, the difference between a beam irradiation area and a theoretical irradiation area is calculated in the scanning process, and azimuth and pitching beam pointing errors are automatically estimated to realize calibration. The invention utilizes the digital elevation map information to calculate the difference between the beam irradiation area and the theoretical irradiation area in the scanning process, automatically estimates the azimuth and pitch beam pointing errors and realizes the calibration function. The method greatly simplifies the measurement mode of the airborne weather radar beam pointing error method, and effectively improves the weather detection performance. The method can be applied to the field of military and civil airborne forward-looking radars. The method has the advantages of simple principle, accurate calculation, automatic estimation of the beam pointing angle error of the radar antenna and good market application prospect.
Description
Technical Field
The invention belongs to the technical field of airborne weather radars, and relates to an airborne weather radar beam pointing automatic calibration method.
Background
The airborne weather radar can detect and display weather targets in front of the flight route, and a pilot makes evasive measures in advance according to information such as strength, distance and direction of the weather targets on the displayer, so that flight safety is guaranteed. For ease of viewing and decision making, it is desirable that the radar provide an accurate weather display free of clutter interference.
The radar beam pointing deviation can influence the antenna beam coverage, as shown in fig. 1, certain pointing errors exist in the azimuth direction and the elevation direction of the antenna beam, so that the beam irradiation area and the designated area deviate, the meteorological target strength and position marking detected by the radar are inaccurate, clutter influence can be brought even, and the loss of radar detection performance is caused. In order to ensure that the radar can accurately acquire meteorological information in front of the airplane and eliminate clutter interference, the radar needs to be calibrated in beam pointing after being re-installed every time.
The beam pointing error is an angle difference between the actual pointing direction and the required pointing direction of the radar antenna, and is a result of interaction of various errors, the main error sources are antenna installation error and random amplitude-phase error, and if an active phased array antenna is adopted, beam pointing deviation can be caused by mutual coupling among units, inconsistency of an antenna directional diagram, influence of an antenna housing and the like.
At present, the wave beam calibration of the airborne weather radar focuses on the calibration of the antenna installation error, a machine head needs to be jacked up, the horizontal reference surface of an airplane needs to be adjusted to be in an absolute horizontal state, and special instrument equipment is used for calibrating the installed antenna; and the requirements on test sites and conditions are strict, the operation is inconvenient, and meanwhile, each installed radar needs to carry out special measurement, and the accuracy requirements required by the system are difficult to meet for some radars which cannot meet the measurement conditions, so that a simple and effective means for realizing the measurement and calibration of the antenna beam pointing error is urgently needed.
The patent provides a method for assisting automatic calibration of beam pointing by using a digital elevation map, aiming at the practical problems of large difficulty in manually measuring antenna beam pointing errors, limited test field and the like. According to the method, in the flying process, an antenna automatic calibration button is selected, the radar emits electromagnetic waves to scan a certain area, radar beam pointing errors are obtained by comparing and correlating a scanning image obtained by the radar with an actually corresponding digital elevation image, the errors are stored in a processor, and the errors can be called to calibrate the beam pointing errors in the later radar using process. The method has the advantages of simple principle, convenient operation, no extra requirements on measurement conditions, places and measurement personnel, realization in the flight process, convenience, rapidness and great cost saving.
Objects of the invention
The patent provides a method for utilizing a digital elevation map to assist an airborne weather radar to perform automatic beam pointing calibration, aiming at the practical problems of high difficulty in manually measuring antenna beam pointing errors, limited test field and the like. By means of radar scanning data and digital elevation data in the flight process, beam pointing errors of the airborne weather radar are automatically estimated, antenna pointing accuracy is improved, accurate detection and display of weather targets are achieved, and detection performance of the weather radar is improved.
Disclosure of Invention
A method for calibrating the beam pointing direction of airborne weather radar is characterized in that a digital elevation map is used, the difference between a beam irradiation area and a theoretical irradiation area is calculated in the scanning process, and the azimuth and elevation beam pointing errors are automatically estimated to achieve calibration.
The calibration method comprises the following specific implementation steps:
(1) In the process of the stable flight of the carrier, selecting a beam calibration mode: the radar beam completely irradiates the ground, the echo zone distinguishes the miscellaneous wave band, the radar scans and simultaneously records data, and after a scanning period is completed, the terrain echo data received by the radar is obtained;
(2) Radar data preprocessing: calculating a module value of radar echo data, estimating noise power on the basis, and setting a noise threshold;
(3) Pitch pointing error estimation: comparing the radar echo ground position with the calculated theoretical ground position, and estimating a beam pointing error through the position deviation;
(4) Azimuth error estimation: performing binarization processing on radar echo data of a scanning line, extracting digital elevation map data in a radar scanning range after compensating pitching pointing errors, performing binarization processing at the same time, and calculating the correlation between the radar echo data and the digital elevation map data by using a data partitioning method to realize the estimation of azimuth pointing errors;
(5) And (4) calibrating beam pointing errors. And storing the calculated pitching and azimuth beam pointing error values, and calling the values to calibrate the beam pointing error in the radar use process.
In the step (3), the estimation of the pitching pointing error specifically comprises the following steps:
1) For each azimuth echo data, extracting a beam coverage area, and calculating the nearest ground-lapping distance of each azimuth echo data;
2) Extracting terrain height information of a beam irradiation direction from the digital high-range map according to longitude, latitude, altitude, course angle, azimuth angle and pitch angle information of the carrier; calculating a theoretical nearest ground-building distance according to the terrain height, the carrier height and the beam pointing information;
3) Estimating a pitching wave beam pointing error according to the difference between the actual ground-overlapping distance and the theoretical ground-overlapping distance of the echo;
4) Repeating the steps 1) to 3), and estimating the pointing errors of the pitching beams of all the directions;
5) And filtering the pitching error data, and taking the obtained result as the pitching beam pointing error.
In the step (4), the azimuth pointing error estimation is specifically implemented by the following steps:
1) Carrying out binarization processing on radar echo data, partitioning the data into blocks, and recording a central azimuth angle corresponding to each block of data;
2) Eliminating the influence of the pitch angle error of the radar, extracting topographic information without pitch error from the digital elevation map, and considering beam coverage and shielding;
3) Performing binarization processing on the extracted digital elevation map topographic data, performing sliding window partitioning, wherein the size of each partition is consistent with that of radar data, and recording a central azimuth corresponding to each block of data;
4) Calculating a correlation coefficient, performing correlation calculation on each radar echo data block and all data blocks of the digital elevation map data, finding out data corresponding to the maximum value of the correlation coefficient, and calculating the error of the center azimuth angle of the two data blocks;
5) Repeating the step 4) to obtain the center azimuth error data of each radar echo data block;
6) And filtering the central azimuth error data, and taking the obtained result as an azimuth beam pointing error.
The filtering in step 5) is specifically median processing.
Advantageous effects
(1) The invention utilizes the digital elevation map information to calculate the difference between the beam irradiation area and the theoretical irradiation area in the scanning process, automatically estimates the azimuth and the pitching beam pointing error and realizes the calibration function. The method greatly simplifies the measurement mode of the airborne weather radar beam pointing error method, and effectively improves the weather detection performance.
(2) The method can be applied to the field of military and civil airborne forward-looking radars. The method has the advantages of simple principle, accurate calculation, automatic estimation of the beam pointing angle error of the radar antenna and good market application prospect.
Drawings
FIG. 1 is a schematic view of a pitch pointing error estimation;
FIG. 2 is a schematic diagram of the algorithm flow of the present invention.
Detailed Description
The invention is described in further detail below with reference to the drawings of the specification:
(1) And in the process of the stable flight of the carrier, selecting a beam calibration mode. The radar automatically selects proper pitching beam direction and azimuth scanning range according to parameters such as current carrier height, terrain height, beam width and the like, so that radar beams completely irradiate the ground, echoes can be obviously distinguished from miscellaneous wave bands, data are recorded while radar scanning is carried out, and terrain echo data X received by the radar is obtained after a scanning period is completed Radar [N r ][N az ]In which N is r 、N az Respectively representing the number of units of a distance dimension and an orientation dimension, and a current pitching direction value f EL And azimuth data f Az [N az ]。
(2) And (4) preprocessing radar data. Calculating the module value of the radar echo data and recording the module value as Y Radar [N r ][N az ]And estimating the noise power based on the estimated noise power, and setting a noise threshold P n_Threshold 。
(3) Pitch pointing error estimation
The corresponding relation (shown in figure 1) exists between the beam ground-lapping position and the pitch angle, the ground-lapping position calculated according to the radar echo ground-lapping position and a theoretical value is compared, and the beam pointing error can be estimated through the deviation of the position, and the specific steps are as follows:
1) For each orientation n az (n az ＝1，2，3，...，N az ) Extracting the coverage area of the wave beam, calculating the nearest ground contact distance of each azimuth echo data, and recording as R min (na)；
2) According to the longitude, latitude, course angle, azimuth and other information of the carrier, the terrain height information of the beam irradiation direction is extracted from a Digital Elevation Map (DEM)And storing the information according to the radar sampling rate, wherein the DEM information of the current direction is stored as Tmp DEM [N r ]；
3) Calculating the theoretical nearest ground-carrying distance R according to the information of terrain height, aircraft height, beam pointing and the like DEM_min (na)；
4) Estimating the pointing error of the pitching wave beam according to the difference between the actual ground-overlapping distance and the theoretical ground-overlapping distance of the echo, and recording the error as Err el (na)；
5) Repeating the steps 1) to 4), and estimating the pitching wave beam pointing errors Err of all the azimuths el [N az ]；
6) For pitch error data Err el [N az ]Performing median processing, and taking the obtained result as a pitching wave beam pointing error, and recording the error as the pitching wave beam pointing error
(4) Azimuth pointing error estimation
Performing binarization processing on radar echo data of a scanning line, extracting terrain data after compensating pitching pointing errors from a DEM, performing binarization processing simultaneously, and estimating azimuth pointing errors by using a data block correlation method, wherein the specific steps are as follows:
1) Performing binarization processing on radar echo data, setting the echo position larger than a noise threshold to be 1, otherwise setting the echo position to be 0, partitioning the echo position into blocks, and recording a data set as Y Radar { N }, N is the number of blocks, each block contains K frames of echo data Y Radar { N }. Data, N =1,2,..., N, and the corresponding azimuth center angle Y for each block of Data Radar {n}.f Az ；
2) Eliminating the influence of pitch angle error, extracting topographic information without pitch error from the digital elevation map DEM, taking beam coverage and shielding into consideration, and recording the extracted DEM data as X DEM [N r ][N az ]；
3) Performing binary processing on DEM (digital elevation model) terrain data, and performing sliding window partitioning, wherein the size of the partition is consistent with that of radar data and is recorded as Y DEM { M }, where M is the number of blocks, each block containing K frames of echo data Y DEM { M }. Data, M =1,2,.. M, and the corresponding attitude of center Y for each block of Data DEM {m}.f Az ；
4) Calculating a correlation coefficient for the data block Y Radar Data is associated with Y, respectively DEM The M data blocks are subjected to correlation calculation, data corresponding to the maximum value of the correlation coefficient are found out, and the azimuth angle error is calculated and recorded as Err az (n)；
[～，j]＝max(R)
Err az (n)＝Y Radar {n}.f Az -Y DEM {j}.f Az
5) Repeating the step 4) to obtain N azimuth error data Err az [N]；
6) For azimuth error data Err az [N]The median processing is carried out, and the obtained result is taken as the azimuth beam pointing error and is recorded as the azimuth beam pointing error
(5) And calibrating the beam pointing error. Storing the calculated pitching and azimuth beam pointing error values, and calling the values to calibrate the beam pointing error in the radar use process:
Claims (4)
1. a method for calibrating beam pointing of airborne weather radar is characterized in that a digital elevation map is used, the difference between a beam irradiation area and a theoretical irradiation area is calculated in the scanning process, azimuth and pitching beam pointing errors are automatically estimated, and calibration is achieved, wherein the specific implementation steps of the calibration comprise:
(1) In the process of the stable flight of the carrier, selecting a beam calibration mode: the radar beam completely irradiates the ground, the echo zone distinguishes the miscellaneous wave band, the radar scans and simultaneously records data, and after a scanning period is completed, the terrain echo data received by the radar is obtained;
(2) Radar data preprocessing: calculating a module value of radar echo data, estimating noise power on the basis, and setting a noise threshold;
(3) Pitch pointing error estimation: comparing the radar echo ground position with the calculated theoretical ground position, and estimating a beam pointing error through the position deviation;
(4) Azimuth error estimation: performing binarization processing on radar echo data of one scanning line, extracting digital elevation map data in a radar scanning range after compensation of pitching pointing errors, performing binarization processing simultaneously, and calculating the correlation between the radar echo data and the digital elevation map data by using a data partitioning method to realize estimation of azimuth pointing errors;
(5) And (3) calibrating beam pointing errors: and storing the calculated pitching and azimuth beam pointing error values, and calling the values to calibrate the beam pointing error in the radar use process.
2. The airborne weather radar beam pointing calibration method according to claim 1, wherein in said step (3), the pitch pointing error estimation is implemented by the steps of:
1) For each azimuth echo data, extracting a beam coverage area, and calculating the nearest ground-lapping distance of each azimuth echo data;
2) Extracting terrain height information of a beam irradiation direction from the digital high-range map according to longitude, latitude, altitude, course angle, azimuth angle and pitch angle information of the carrier; calculating a theoretical nearest ground-building distance according to the terrain height, the carrier height and the beam pointing information;
3) Estimating a pitching wave beam pointing error according to the difference between the actual ground-overlapping distance and the theoretical ground-overlapping distance of the echo;
4) Repeating the steps 1) to 3), and estimating the pointing errors of the pitching beams of all the directions;
5) And filtering the pitching error data, and taking the obtained result as the pitching beam pointing error.
3. The airborne weather radar beam pointing calibration method according to claim 1, wherein in the step (4), the azimuth pointing error estimation is implemented by the following steps:
1) Carrying out binarization processing on radar echo data, partitioning the data into blocks, and recording a central azimuth angle corresponding to each block of data;
2) Eliminating the influence of the pitch angle error of the radar, extracting topographic information without pitch error from the digital elevation map, and considering beam coverage and shielding;
3) Performing binarization processing on the extracted digital elevation map topographic data, performing sliding window partitioning, wherein the size of each partition is consistent with that of radar data, and recording a central azimuth corresponding to each block of data;
4) Calculating a correlation coefficient, performing correlation calculation on each radar echo data block and all data blocks of the digital elevation map data, finding out data corresponding to the maximum value of the correlation coefficient, and calculating the error of the center azimuth angle of the two data blocks;
5) Repeating the step 4) to obtain the center azimuth error data of each radar echo data block;
6) And filtering the central azimuth error data, and taking the obtained result as an azimuth beam pointing error.
4. A method for airborne weather radar beam pointing calibration according to claim 2, characterized in that said filtering process in step 5), in particular a median process.
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| CN111366913A (en) * | 2020-03-24 | 2020-07-03 | 上海卫星工程研究所 | Calibration method for optical axis pointing measurement error of satellite-borne laser radar |
| CN111521882B (en) * | 2020-05-07 | 2021-03-19 | 清华大学 | On-orbit calibration method and device for beam pointing error of deep space probe antenna |
| CN111796246A (en) * | 2020-06-12 | 2020-10-20 | 中国船舶重工集团公司第七二四研究所 | Azimuth multi-parameter combined correction method for wave beam offset of waveguide slot antenna |
| CN111859255B (en) * | 2020-07-17 | 2021-02-09 | 中国人民解放军78125部队 | Radar detection range calculation method under influence of terrain shielding |
| CN112098958B (en) * | 2020-10-22 | 2022-04-26 | 中国电波传播研究所（中国电子科技集团公司第二十二研究所） | Radar clutter prediction method based on digital map and meteorological hydrological information |
| CN113702402B (en) * | 2021-09-01 | 2023-08-01 | 中国电波传播研究所（中国电子科技集团公司第二十二研究所） | Automatic calibration method for azimuth elevation angle of water vapor radiometer |
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| CN115267711B (en) * | 2022-09-27 | 2023-02-28 | 成都信息工程大学 | An antenna directivity gross error calibration method, device, equipment and storage medium |
| CN116108703B (en) * | 2023-04-12 | 2023-07-14 | 中国人民解放军63921部队 | Correction method and device applied to beam pointing value of non-planar radome |
| CN116879857B (en) * | 2023-09-07 | 2023-11-17 | 成都远望科技有限责任公司 | Far-field target and radar central beam alignment method |
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| CN103576702B (en) * | 2013-11-22 | 2016-02-24 | 北京无线电测量研究所 | A kind of MMW Weather Radar aerial angle Calibration Method |
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