A method for calibrating two-axis errors of a phased array weather radar based on a solar apparent motion trajectory

Abstract

This invention discloses a dual-axis error calibration method for phased array weather radar based on the apparent motion trajectory of the sun, comprising the following steps: Step 1, calculation of the sun pointing angle; Step 2, selection of azimuth scanning parameters based on calibration error and azimuth deviation estimation; Step 3, evaluation of elevation angle calibration accuracy based on azimuth scanning time and apparent solar motion; Step 4, sampling of solar radiation signals; Step 5, extraction of peak values ​​in pulse-by-pulse repetition cycles and acquisition of dual-axis calibration coefficients. The method disclosed in this invention can generate dual-axis error calibration coefficients for X-band phased array weather radar that simultaneously meet high timeliness and high accuracy requirements. This is of great significance for effectively improving the detection capabilities of X-band phased array weather radar in mobile and unattended field applications.

Description

Technical Field

[0001] This invention belongs to the field of X-band phased array weather radar technology, and specifically relates to a dual-axis error calibration method for phased array weather radar based on the apparent motion trajectory of the sun. Background Technology

[0002] X-band phased array weather radar is a new type of meteorological detection equipment that utilizes X-band electromagnetic waves and phased array technology to achieve high-precision and rapid scanning. Compared with traditional mechanically scanned weather radar, it has significant advantages in detection accuracy, data update rate, and adaptive observation, and is particularly suitable for monitoring and early warning of severe convective weather (such as tornadoes, hail, and short-duration heavy rain). Dual-axis error calibration of radar azimuth and elevation is a prerequisite for high-precision weather radar detection. Traditionally, the metal ball method is used for radar pointing calibration. However, this method requires UAVs to suspend metal balls over a long line for flight calibration, which has high requirements for site conditions, a long calibration cycle, high cost, and is greatly affected by weather conditions such as strong winds. It also cannot meet the near-real-time calibration requirements of X-band phased array weather radar in mobile application scenarios. Using the solar method for calibration, by scanning the radar elevation and azimuth angles, can achieve low-cost, robust, and relatively high-timeliness dual-axis error calibration. However, because the radar takes a long time to scan the elevation and azimuth matrix, there is a conflict between near-real-time calibration and calibration accuracy. Therefore, how to make full use of the physical laws of apparent solar motion to obtain a low-cost dual-axis error calibration method that simultaneously satisfies timeliness and calibration accuracy is an urgent problem to be solved in order to efficiently utilize X-band phased array weather radar in mobile application scenarios. Summary of the Invention

[0003] The technical problem to be solved by this invention is to provide a dual-axis error calibration method for phased array weather radar based on the apparent motion trajectory of the sun.

[0004] The present invention adopts the following technical solution:

[0005] An improved method for dual-axis error calibration of phased array weather radar based on the apparent motion trajectory of the sun includes the following steps:

[0006] Step 1, Calculate the sun's pointing angle:

[0007] Based on the radar station's geographical longitude, latitude, and time, calculate the theoretical solar elevation angle and azimuth angle;

[0008] Step 2, selection of azimuth scanning parameters based on calibration error and azimuth deviation estimation:

[0009] The azimuth scanning speed is calculated based on the calibration error, and the azimuth scanning range is calculated based on the azimuth deviation estimation.

[0010] Step 3, Evaluation of elevation angle calibration accuracy based on azimuth scanning time and apparent solar motion:

[0011] The elevation angle calibration accuracy of the solar method based on the apparent solar motion is evaluated by calculating the elevation angle difference of the apparent solar motion with the azimuth scan time as the time interval.

[0012] Step 4, solar radiation signal sampling:

[0013] Based on the azimuth scanning speed, azimuth scanning range, pulse repetition frequency, pulse accumulation count, and operating frequency, solar radiation signals are sampled to obtain raw IQ data and calculate the radiation power distribution of different sectors.

[0014] Step 5, peak value extraction and biaxial calibration coefficient acquisition for each pulse repetition period:

[0015] The IQ data of each pulse repetition period in a set of pulse accumulation times are extracted, the mean is calculated along the range direction, and the peak value is calculated in the pulse repetition period dimension to obtain the radar apparent solar azimuth angle.

[0016] The mean value of the difference between the apparent solar azimuth angle of the radar in different scanning sectors and the actual solar azimuth angle at the current moment is calculated and used as the calibration coefficient of the azimuth angle in the dual-axis parameters.

[0017] The maximum solar radiation intensity of the scanned sector at different azimuth angles is obtained, and the difference between the radar elevation angle and the actual solar elevation angle at this moment is used as the calibration coefficient of the elevation angle in the dual-axis parameters.

[0018] Furthermore, step 1 specifically includes:

[0019] Let the Confucian scholars live ,from The starting number of days is:

[0020]

[0021] Average orbital parameters and They are respectively:

[0022]

[0023]

[0024] In the above formula, A function for finding the remainder;

[0025] Yellow Classic for:

[0026]

[0027] obliquity of the ecliptic for:

[0028]

[0029] Right Ascension and declination They are respectively:

[0030]

[0031]

[0032] In the above formula, It is the arctangent function in the fourth quadrant. It is the arcsine function;

[0033] Greenwich Sidereal Time for:

[0034]

[0035] Local sidereal time for:

[0036]

[0037] In the above formula, Longitude of the radar station;

[0038] Hour angle for:

[0039]

[0040] Sun elevation angle for:

[0041]

[0042] In the above formula, Latitude of the radar station;

[0043] Sun azimuth for:

[0044] .

[0045] Furthermore, step 2 specifically includes:

[0046] Calculate azimuth scan rate :

[0047]

[0048] In the above formula, Let n be the expected calibration error, and n be the number of pulse accumulations. The radar pulse repetition frequency;

[0049] Set azimuth angle The scanning range is:

[0050]

[0051] In the above formula, The azimuth of the sun. This is the antenna pointing deviation angle. This is the lower limit of the scanning range. This represents the upper limit of the scan range.

[0052] Furthermore, in step 3, the azimuth scan period T scan Calculated using the following formula:

[0053]

[0054] In the above formula, For the maximum scanning azimuth angle, For the minimum scanning azimuth angle, This refers to the azimuth scanning speed. This refers to the braking time.

[0055] Furthermore, step 6, azimuth calibration accuracy detection, is also included.

[0056] The root mean square value of the difference between the radar apparent solar azimuth angle and the actual solar azimuth angle for different scanning sectors is calculated and used as an indicator parameter to evaluate the calibration accuracy.

[0057] The beneficial effects of this invention are:

[0058] The method disclosed in this invention can generate dual-axis error calibration coefficients for X-band phased array weather radar that simultaneously meet the requirements of high timeliness and high precision. This is of great significance for effectively improving the detection capability of X-band phased array weather radar in mobile and unattended field application scenarios.

[0059] The method disclosed in this invention can achieve radar azimuth and pitch dual-axis error calibration without using a drone to suspend a metal ball for flight. This avoids the problems of the metal ball method, such as high requirements for site conditions, long calibration cycle, high cost, and great influence from strong winds and other weather conditions.

[0060] The method disclosed in this invention can make full use of the physical laws of apparent solar motion and achieve radar azimuth and elevation dual-axis error calibration by scanning only the azimuth angle. It solves the problem that the solar method cannot achieve near real-time calibration and high precision at the same time, and is of great significance for the efficient use of X-band phased array weather radar in mobile application scenarios.

[0061] The method disclosed in this invention can be naturally extended to other meteorological detection equipment that requires azimuth or elevation dual-axis error calibration. By making full use of the physical laws of apparent solar motion, the calibration efficiency and accuracy can be improved, which is of great significance for the efficient use of meteorological detection equipment. Attached Figure Description

[0062] Figure 1 This is a schematic flowchart of the method of the present invention;

[0063] Figure 2 A graph showing the changes in the sun's azimuth at different times;

[0064] Figure 3 A graph showing the change in the sun's elevation angle at different times;

[0065] Figure 4 A graph showing the variation in the calibration accuracy of the solar elevation angle at different times;

[0066] Figure 5 This is a diagram showing the azimuth scan results of solar radiation radar for sector 1.

[0067] Figure 6 This is a diagram showing the azimuth scan results of the solar radiation radar for sector 2.

[0068] Figure 7 This is a diagram showing the azimuth scan results of solar radiation radar in sector 3.

[0069] Figure 8 This is a diagram showing the azimuth scan results of the solar radiation radar in sector 4.

[0070] Figure 9 This is a diagram showing the azimuth scan results of solar radiation radar for sector 5.

[0071] Figure 10 This is a diagram showing the azimuth scan results of the solar radiation radar in sector 6.

[0072] Figure 11 This is a diagram showing the azimuth scan results of the solar radiation radar for sector 7.

[0073] Figure 12 This is a diagram showing the azimuth scan results of the solar radiation radar for sector 8.

[0074] Figure 13 This is a diagram showing the azimuth scan results of the solar radiation radar for sector 9.

[0075] Figure 14 The graph shows the average radar received power results on different radial directions. Detailed Implementation

[0076] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0077] Example 1 discloses a dual-axis error calibration method for phased array weather radar based on the apparent motion trajectory of the sun, such as... Figure 1 As shown, it includes the following steps:

[0078] Step 1, Calculate the sun's pointing angle:

[0079] Based on the radar station's geographical longitude, latitude, and time, calculate the theoretical solar elevation angle and azimuth angle;

[0080] Let the Confucian scholars live ,from The starting number of days is:

[0081]

[0082] Average orbital parameters and They are respectively:

[0083]

[0084]

[0085] In the above formula, A function for finding the remainder;

[0086] Yellow Classic for:

[0087]

[0088] obliquity of the ecliptic for:

[0089]

[0090] Right Ascension and declination They are respectively:

[0091]

[0092]

[0093] In the above formula, It is the arctangent function in the fourth quadrant. It is the arcsine function;

[0094] Greenwich Sidereal Time for:

[0095]

[0096] Local sidereal time for:

[0097]

[0098] In the above formula, Longitude of the radar station;

[0099] Hour angle for:

[0100]

[0101] Sun elevation angle for:

[0102]

[0103] In the above formula, Latitude of the radar station;

[0104] Sun azimuth for:

[0105]

[0106] Based on the above formula, the solar elevation angle at 16:20:30 on February 1, 2026 is calculated to be 15.68° and the solar azimuth angle is 235.08° (clockwise from north). This angle will be used as the reference for subsequent radar scanning parameter configuration.

[0107] Step 2, selection of azimuth scanning parameters based on calibration error and azimuth deviation estimation:

[0108] The azimuth scanning speed is calculated based on the calibration error, and the azimuth scanning range is calculated based on the azimuth deviation estimation.

[0109] Calculate azimuth scan rate :

[0110]

[0111] In the above formula, Let n be the expected calibration error, and n be the number of pulse accumulations. The radar pulse repetition frequency;

[0112] Set azimuth angle The scanning range is:

[0113]

[0114] In the above formula, The azimuth of the sun. This is the antenna pointing deviation angle. This is the lower limit of the scanning range. This represents the upper limit of the scan range.

[0115] In this embodiment, the expected calibration error is... Take 0.1°, radar pulse repetition frequency If the Hz frequency is 1000 and the pulse accumulation count n is 32, then the scanning speed is... The azimuth scanning speed is set to 3.125° / s to allow for some margin.

[0116] Because a waveguide slot antenna is used, there is a horizontal beam pointing deviation angle. In this embodiment, the radar is set to operate at a frequency of 9300MHz, and the anechoic chamber measurement results show that the deviation angle is 5.63°. Centered on the solar azimuth angle corrected for the deviation angle, the azimuth angle scanning range is set to 237.5°~247.5°.

[0117] Step 3, Evaluation of elevation angle calibration accuracy based on azimuth scanning time and apparent solar motion:

[0118] Since completing one azimuth scan requires a certain period, the magnitude of the change in elevation angle due to the apparent motion of the sun within that period determines the accuracy of the elevation angle calibration. Therefore, this embodiment evaluates the accuracy of the elevation angle calibration based on the apparent motion of the sun by calculating the difference in elevation angle due to the apparent motion of the sun over time intervals equal to the azimuth scan time.

[0119] Azimuth scan period T scan Calculated using the following formula:

[0120]

[0121] In the above formula, For the maximum scanning azimuth angle, For the minimum scanning azimuth angle, This refers to the azimuth scanning speed. This refers to the braking time.

[0122] In this embodiment, the azimuth scanning period is approximately 12 seconds. The azimuth angle is calculated at different time intervals. Figure 2 ), Sun elevation angle ( Figure 3 ), and the accuracy of solar elevation angle calibration during the scanning cycle ( Figure 4 As can be seen from the figure, the accuracy of the elevation angle calibration is between 0.028 and 0.037 degrees.

[0123] Step 4, solar radiation signal sampling:

[0124] Solar radiation signals are sampled based on parameters such as azimuth scanning speed, azimuth scanning range, pulse repetition frequency, pulse accumulation count, and operating frequency to obtain raw IQ data and calculate the radiation power distribution of different sectors.

[0125] In this embodiment, the specific radar operating mode parameters are as follows:

[0126] Operating frequency: 9300MHz;

[0127] Fill-in mode: No fill-in;

[0128] Pulse repetition frequency: 1000Hz;

[0129] Pulse accumulation count: 10 times;

[0130] Elevation angle: 15.68°;

[0131] Azimuth scanning speed: 3° / s;

[0132] Azimuth scanning range: 237.5°~247.5°.

[0133] A total of 9 sectors were scanned, and the scan echo results are as follows: Figures 5-13 As shown in the figure, there is an echo enhancement characteristic with a full-range gate in the direction of solar radiation. Based on this, radar elevation and azimuth angles are calibrated.

[0134] Step 5, Pulse-by-pulse repetition period (PRT) peak extraction and biaxial calibration coefficient acquisition:

[0135] To further improve calibration accuracy, the IQ data of each pulse repetition cycle in a set of pulse accumulation times are extracted, the mean is calculated along the range direction, and the peak value is calculated in the pulse repetition cycle dimension to obtain the radar apparent solar azimuth angle.

[0136] The mean value of the difference between the apparent solar azimuth angle of the radar in different scanning sectors and the actual solar azimuth angle at the current moment is calculated and used as the calibration coefficient of the azimuth angle in the dual-axis parameters.

[0137] The moment when the maximum solar radiation intensity of the scanning sector is obtained at different azimuth angles is used as the calibration coefficient of the elevation angle in the dual-axis parameters.

[0138] In this embodiment, the duration of a single PRT is 1ms, while the actual time resolution of servo feedback elevation and azimuth information is 10ms. Therefore, the IQ data from 10 PRTs are averaged before subsequent analysis. For radar systems where the servo time resolution meets the requirements, single PRT analysis can be used. The average of the processed IQ data along the range direction is calculated to obtain the radar received power results at different radial directions (number of PRT groups). Figure 14).from Figure 14 As can be seen, significant solar radiation peak structures are observed in all nine sectors scanned by the radar. The azimuth angle corresponding to the peak is the radar's apparent solar azimuth angle. Therefore, the calibration coefficient for the azimuth angle in the dual-axis parameters is:

[0139]

[0140] In the above formula, is the radar apparent solar azimuth, and is the actual solar azimuth at the current moment. In this embodiment, the radar apparent solar azimuth, actual solar azimuth, and azimuth difference values ​​for the nine sectors are shown in the table below.

[0141] The calibration factor for the azimuth angle is 6.2553°.

[0142] Serial Number time Radar apparent solar azimuth angle ° Actual azimuth angle of the sun (°) Azimuth difference (°) 1. 16:20:28 241.39 235.08 6.31 2. 16:20:41 241.43 235.12 6.31 3. 16:20:54 241.42 235.16 6.26 4. 16:21:06 241.47 235.19 6.28 5. 16:21:18 241.55 235.23 6.32 6. 16:21:30 241.50 235.27 6.23 7. 16:21:42 241.51 235.30 6.21 8. 16:21:54 241.55 235.34 6.21 9. 16:22:07 241.54 235.37 6.17

[0143] from Figure 14 The data also shows that the peak structure initially increases and then decreases. This is mainly because the radar scans the azimuth at a fixed elevation angle, and over time, the apparent motion trajectory of the sun crosses the radar's scanning sector. When the radar elevation angle is not aligned with the sun, the peak value of the sector scan is smaller. When the radar is aligned with the sun, the peak structure is at its maximum, and then gradually weakens over time.

[0144] The calibration factor for the elevation angle in the dual-axis parameters is:

[0145]

[0146] In the above formula, Radar elevation angle, The times when the solar radiation intensity of the scanned sector reaches its maximum value at different azimuth angles. This represents the actual azimuth angle of the sun at that moment. In this embodiment, the peak intensity of the second sector is the strongest, corresponding to the time 16:20:41. At this moment, the radar elevation angle is 15.68°, and the actual elevation angle of the sun is 15.69°, therefore the calibration coefficient is -0.01°.

[0147] Step 6, Azimuth calibration accuracy check:

[0148] The root mean square value of the difference between the radar apparent solar azimuth angle and the actual solar azimuth angle for different scanning sectors is calculated and used as an indicator parameter to evaluate the calibration accuracy.

[0149]

[0150] In the above formula, m is the number of scan sectors, and in this embodiment, m=9. The azimuth calibration accuracy calculated using the above formula is 0.0532°.

Claims

1. A dual-axis error calibration method for phased array weather radar based on the apparent motion trajectory of the sun, characterized in that, Includes the following steps: Step 1, Calculate the sun's pointing angle: Based on the radar station's geographical longitude, latitude, and time, calculate the theoretical solar elevation angle and azimuth angle; Step 2, selection of azimuth scanning parameters based on calibration error and azimuth deviation estimation: The azimuth scanning speed is calculated based on the calibration error, and the azimuth scanning range is calculated based on the azimuth deviation estimation. Step 3, Evaluation of elevation angle calibration accuracy based on azimuth scanning time and apparent solar motion: The elevation angle calibration accuracy of the solar method based on the apparent solar motion is evaluated by calculating the elevation angle difference of the apparent solar motion with the azimuth scan time as the time interval. Step 4, solar radiation signal sampling: Based on the azimuth scanning speed, azimuth scanning range, pulse repetition frequency, pulse accumulation count, and operating frequency, solar radiation signals are sampled to obtain raw IQ data and calculate the radiation power distribution of different sectors. Step 5, peak value extraction and biaxial calibration coefficient acquisition for each pulse repetition period: The IQ data of each pulse repetition period in a set of pulse accumulation times are extracted, the mean is calculated along the range direction, and the peak value is calculated in the pulse repetition period dimension to obtain the radar apparent solar azimuth angle. The mean value of the difference between the apparent solar azimuth angle of the radar in different scanning sectors and the actual solar azimuth angle at the current moment is calculated and used as the calibration coefficient of the azimuth angle in the dual-axis parameters. The maximum solar radiation intensity of the scanned sector at different azimuth angles is obtained, and the difference between the radar elevation angle and the actual solar elevation angle at this moment is used as the calibration coefficient of the elevation angle in the dual-axis parameters.

2. The dual-axis error calibration method for phased array weather radar based on the apparent motion trajectory of the sun according to claim 1, characterized in that, Step 1 specifically includes: Let the Confucian scholars live ,from The starting number of days is: Average orbital parameters and They are respectively: In the above formula, A function for finding the remainder; Yellow Classic for: obliquity of the ecliptic for: Right Ascension and declination They are respectively: In the above formula, It is the arctangent function in the fourth quadrant. It is the arcsine function; Greenwich Sidereal Time for: Local sidereal time for: In the above formula, Longitude of the radar station; Hour angle for: Sun elevation angle for: In the above formula, Latitude of the radar station; Sun azimuth for: 。 3. The dual-axis error calibration method for phased array weather radar based on the apparent motion trajectory of the sun according to claim 1, characterized in that, Step 2 specifically includes: Calculate azimuth scan rate : In the above formula, Let n be the expected calibration error, and n be the number of pulse accumulations. The radar pulse repetition frequency; Set azimuth angle The scanning range is: In the above formula, The azimuth of the sun. This is the antenna pointing deviation angle. This is the lower limit of the scanning range. This represents the upper limit of the scan range.

4. The dual-axis error calibration method for phased array weather radar based on the apparent motion trajectory of the sun according to claim 1, characterized in that, In step 3, the azimuth scan period T scan Calculated using the following formula: In the above formula, For the maximum scanning azimuth angle, For the minimum scanning azimuth angle, This refers to the azimuth scanning speed. This refers to the braking time.

5. The dual-axis error calibration method for phased array weather radar based on the apparent motion trajectory of the sun according to claim 1, characterized in that, It also includes step 6, azimuth calibration accuracy detection: The root mean square value of the difference between the radar apparent solar azimuth angle and the actual solar azimuth angle for different scanning sectors is calculated and used as an indicator parameter to evaluate the calibration accuracy.

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