Airborne meteorological radar adaptive clutter suppression method

Abstract

The invention provides an airborne meteorological radar adaptive clutter suppression method, and belongs to the technical field of airborne meteorological radars, and the method specifically comprises the steps: calculating a reference angle iAngT between each distance unit and an airplane; calculating a first radar echo angle iAngR of each distance unit; calculating the error of the radar echo angle of each distance unit, and removing the error to obtain a corrected second radar echo angle; and performing ground clutter suppression on the radar data of the current antenna row, comparing the second radar echo angle of each distance unit with the reference angle, when the angle difference between the second radar echo angle and the reference angle is smaller than a preset value, considering that the current radar echo is a ground echo, and deducting the current radar echo to complete ground clutter suppression. Through the processing scheme provided by the invention, more accurate ground clutter suppression can be realized, the detection capability of low-altitude weather is improved, and the detection performance of the weather radar is effectively improved.

Description

Technical Field

[0001] The present application relates to the field of airborne weather radar, and in particular to an airborne weather radar adaptive clutter suppression method. Background Art

[0002] In the process of detecting weather, the beam of airborne weather radar is very easy to hit the ground. The actual echo includes both weather echo and ground echo. The aliasing of weather and ground clutter will seriously affect the display performance of weather radar. Airborne weather radar usually identifies ground clutter based on the difference in the spatial distribution of weather and ground clutter, and then deducts the ground echo. This method requires the weather radar to have a more accurate angle measurement capability. The angle measurement error of airborne weather radar mainly includes antenna installation error, inertial navigation error, aircraft deformation error, radar beam pointing error, radar angle measurement algorithm error, etc. The conventional error measurement procedure is complicated and the conditions are relatively harsh. For example, after the aircraft is leveled on the ground, special test equipment is used to measure the installation angle, or a special calibration procedure is developed to select flat terrain during flight and the operator follows fixed steps to measure the error. Usually, the installation error is only tested once, and the calibration data is written into the radar and no changes are made. Conventional methods only measure the installation error, and lack accurate measurement and evaluation methods for other more complex error sets, resulting in the inability to accurately measure the angle of the target relative to the airborne meteorological radar, which in turn affects the ground clutter suppression effect. Summary of the invention

[0003] In view of this, the present application provides an adaptive clutter suppression method for airborne weather radar, which can evaluate in real time the antenna beam pointing error caused by the superposition of multiple factors during the flight of the aircraft, improve the angle measurement accuracy of the airborne weather radar, and further achieve more accurate ground clutter suppression, enhance the detection capability of low-altitude weather, and effectively improve the detection performance of the weather radar.

[0004] The present application provides an airborne weather radar adaptive clutter suppression method using the following technical solutions:

[0005] An airborne weather radar adaptive clutter suppression method comprises the following steps:

[0006] Calculate the reference angle iAng_T between each distance unit and the aircraft;

[0007] Calculate the first radar echo angle iAng_R of each range unit;

[0008] Calculate the error of the radar echo angle of each distance unit, and obtain the corrected second radar echo angle after removing the error;

[0009] Ground clutter suppression is performed on the radar data of the current antenna row. The second radar echo angle of each distance unit is compared with the reference angle. When the angle difference between the two is less than the preset value, the current radar echo is considered to be a ground echo. The current radar echo is deducted to complete ground clutter suppression.

[0010] Optionally, the method of calculating the error of the radar echo angle of each distance unit and obtaining the corrected second radar echo angle after removing the error includes:

[0011] Calculate the average value of the difference between the reference angle of all effective range units and the first radar echo angle iAng_E=mean(iAng_R-iAng_T);

[0012] After completing an antenna scanning line, the average angle difference data {Az,iAng_E} corresponding to each azimuth in the scanning line is obtained;

[0013] Fit the orientation-angle error data to form an error quadratic curve Angeline=f(Az), calculate the mean value of the fitting error, and take the fitting result whose mean value of the fitting error is less than the preset value Th_E as a valid error curve for a scanning line;

[0014] The second radar echo angle is equal to the first radar echo angle minus the angle error value, and the angle error value is obtained from the error curve.

[0015] Optionally, when fitting the azimuth-angle error data, ground markers are used to remove known meteorological target angles;

[0016] The ground mark is determined by the error of the fitting result of the previous antenna scan line. The ground mark is valid by default. The ground mark whose angle corresponds to the curve fitting error greater than the preset threshold is invalid.

[0017] Optionally, the method of calculating the error of the radar echo angle of each distance unit and obtaining the corrected second radar echo angle after removing the error also includes:

[0018] The effective error curve Angeline=f(Az) is discretized to form an angle error table and sent to the beam control unit. In the next antenna scanning line, the beam control unit performs adaptive correction of beam pointing according to the angle error table data.

[0019] Optionally, the angle error curve is updated and iterated once after each antenna scan line is completed.

[0020] Optionally, the step of calculating an average value iAng_E of the angle differences between all effective range unit reference angles and the first radar echo includes:

[0021] Calculate the ground coverage range of the antenna beam {Rs:Re}, where Rs is the starting distance unit and Re is the ending distance unit;

[0022] Extract the effective echo distance unit {Rt1 Rt2....Rtn} with signal-to-noise ratio greater than TSNR in {Rs:Re};

[0023] The first radar echo angle value and the reference angle value of the effective echo unit are extracted, and the average value of the angle difference between the first radar echo angle value and the reference angle value is calculated.

[0024] Optionally, the step of calculating the error of the radar echo angle of each distance unit and obtaining a corrected second radar echo angle after removing the error further includes:

[0025] The mean of abs(iAng_E) is calculated. If the mean meets the angle measurement accuracy requirement, the angle error is 0.

[0026] Optionally, the method for calculating the reference angle iAng_T between each distance unit and the aircraft includes:

[0027] According to the aircraft platform height H, heading, distance iR, and beam pointing (iAZ, iEL), calculate the longitude and latitude (iLat, iLon) corresponding to the distance iR;

[0028] Extract the terrain height iH from the terrain database according to the longitude and latitude (iLat, iLon);

[0029] According to the aircraft height H and the terrain height iH, calculate the angle iAng_T corresponding to the distance iR;

[0030] Where Re is the radius of the Earth.

[0031] Optionally, in step 2, the first radar echo angle iAng_R of each distance unit is calculated by measuring angle by amplitude or phase.

[0032] In summary, this application includes the following beneficial technical effects:

[0033] The present application provides an airborne weather radar adaptive clutter suppression method, which does not require special installation error correction, performs adaptive clutter suppression in real time during flight, and automatically compensates for angle errors caused by various factors. Compared with traditional methods, in addition to being fast, efficient and repeatable, it can also more comprehensively estimate the impact of various errors, thereby improving the detection performance of the airborne weather radar.

[0034] The method of the present application can improve the radar's target angle measurement capability through adaptive adjustment, and can be promoted to different aircraft platforms and multiple-system weather radars. At the same time, the method can also be used to improve target tracking accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0036] Figure 1 This is a block diagram of the hardware structure involved in the method of this application;

[0037] Figure 2 A flow chart of the adaptive clutter suppression method for airborne weather radar in this application;

[0038] Figure 3 Schematic diagram of an angle error table in an embodiment of the present application. DETAILED DESCRIPTION

[0039] The embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0040] The following describes the implementation methods of the present application through specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The present application can also be implemented or applied through other different specific implementation methods, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that, in the absence of conflict, the following embodiments and the features in the embodiments can be combined with each other. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work belong to the scope of protection of the present application.

[0041] It should be noted that various aspects of the embodiments within the scope of the appended claims are described below. It should be apparent that the aspects described herein can be embodied in a wide variety of forms, and any specific structure and / or function described herein is merely illustrative. Based on the present application, it should be understood by those skilled in the art that an aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects described herein can be used to implement the device and / or practice the method. In addition, other structures and / or functionalities other than one or more of the aspects described herein can be used to implement this device and / or practice this method.

[0042] It should also be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present application. The illustrations only show the components related to the present application rather than being drawn according to the number, shape and size of the components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed at will, and the component layout may also be more complicated.

[0043] Additionally, in the following description, specific details are provided to facilitate a thorough understanding of the examples. However, it will be understood by those skilled in the art that the aspects described may be practiced without these specific details.

[0044] An embodiment of the present application provides an adaptive clutter suppression method for an airborne weather radar.

[0045] An airborne weather radar adaptive clutter suppression method comprises the following steps:

[0046] Calculate the reference angle iAng_T of each distance unit to the aircraft.

[0047] Calculate the first radar echo angle iAng_R for each range cell.

[0048] The error of the radar echo angle of each distance unit is calculated, and the corrected second radar echo angle is obtained after removing the error.

[0049] Ground clutter suppression is performed on the radar data of the current antenna row. The second radar echo angle of each distance unit is compared with the reference angle. When the angle difference between the two is less than the preset value, the current radar echo is considered to be a ground echo. The current radar echo is deducted to complete ground clutter suppression.

[0050] The airborne weather radar adaptive clutter suppression method of the present application embeds digital elevation data into a weather radar processor to provide a reference angle for the radar, designs an airborne weather radar angle measurement method, compares the radar angle measurement result with the reference angle, and performs angle error measurement and fitting in real time during flight, which can effectively reduce the estimation error of the angle error under the condition of weather clutter aliasing, automatically compensate for the angle error caused by various factors, realize adaptive clutter suppression, and improve the detection performance of the airborne weather radar.

[0051] In one embodiment, Figures 1 to 3 As shown, the airborne weather radar adaptive clutter suppression method specifically includes the following steps:

[0052] Step 1, calculate the reference angle iAng_T between each distance unit and the aircraft:

[0053] For the iNAzth frame of radar data, the theoretical angle Ang_T(iNr) of each distance unit iNr relative to the aircraft is calculated. It is necessary to predict the terrain height and aircraft height, aircraft attitude, and radar beam pointing. For any distance unit iNr, the angle is calculated as follows:

[0054] According to the aircraft platform height H, heading, distance iR, beam pointing (iAZ, iEL), calculate the longitude and latitude (iLat, iLon) corresponding to the distance iR; extract the terrain height iH from the terrain database according to the longitude and latitude (iLat, iLon); according to the aircraft height H and the terrain height iH, calculate the angle iAng_T corresponding to the distance iR:

[0055] Re is the radius of the earth.

[0056] Step 2, calculate the first radar echo angle iAng_R of each range unit:

[0057] The first radar echo angle iAng_R of each distance unit is calculated by comparing the amplitude angle or the phase angle, as follows:

[0058] For the iNAzth frame radar data, the dual-beam amplitude ratio angle measurement method is used to calculate the radar echo angle. The iNAzth frame radar data includes the pitch angle echo data of the upper and lower antennas. According to the power ratio of the echo data of the two, the echo angle value iAng_R is obtained by looking up the table.

[0059] Step 3, calculate the error of the radar echo angle of each distance unit, and obtain the corrected second radar echo angle after removing the error:

[0060] Calculate the average value iAng_E=mean(iAng_R-iAng_T) of the angle difference between the reference angle of all valid distance units and the first radar echo; calculate the ground coverage range of the antenna beam {Rs:Re}, where Rs is the starting distance unit and Re is the ending distance unit; extract the valid echo distance units {Rt1 Rt2....Rtn} with a signal-to-noise ratio greater than TSNR within {Rs:Re}; extract the first radar echo angle value and the reference angle value of the valid echo unit, calculate the average angle difference between the first radar echo angle value and the reference angle value, and obtain the angle difference mean iAng_E(iNAz) of each frame, iAng_E=mean(iAng_R(RTn)-iAng_T(RTn)), mean(g) means taking the average value.

[0061] After completing an antenna scanning line, the average angle difference data {Az, iAng_E} corresponding to each azimuth in the scanning line is obtained, where Az is the azimuth angle and iAng_E is the corresponding error angle.

[0062] The mean of abs(iAng_E) is calculated. If the mean meets the angle measurement accuracy requirement, the angle error is 0. The abs in abs(iAng_E) represents the absolute value.

[0063] The azimuth-angle error data are fitted, and the fitting method includes but is not limited to the least squares method, to form an error quadratic curve Angeline=f(Az), calculate the mean of the fitting absolute error Fitting_E(Az), and use the fitting result with the fitting error mean less than the preset value Th_E as an effective error curve for a scanning line, the second radar echo angle is equal to the first radar echo angle minus the angle error value, and the angle error value is obtained from the error curve; and the radar processor discretizes the effective error curve Angeline=f(Az) to form an angle error table and sends it to the beam control unit, and in the next antenna scanning line, the beam control unit performs adaptive correction of the beam pointing according to the angle error table data; wherein, the angle error curve is updated and iterated once after each antenna scanning line is completed, and if the fitting result of this antenna line is invalid, the angle error table is not updated.

[0064] When fitting the azimuth-angle error data, the ground mark is used to remove the known meteorological target angles to prevent meteorological data from participating in the angle error fitting; the ground mark is determined by the error of the fitting result of the previous antenna scan line. The ground mark is valid by default, and the ground mark corresponding to the angle where the curve fitting error is greater than the preset threshold is invalid. Specifically, if the mean value of the fitting error Fitting_E(Az) is not greater than the preset fitting threshold Th_G, the fitting result is marked as valid, and the ground mark of all azimuths of this antenna line is set to valid. Otherwise, the azimuth greater than the preset fitting threshold Th_WX is extracted, and its ground mark is set to invalid, indicating that there is meteorology in this direction.

[0065] Step 4, perform ground clutter suppression on the radar data of the current antenna row, compare the second radar echo angle of each distance unit with the reference angle, and when the angle difference between the two is less than a preset value, the current radar echo is considered to be a ground echo, and the current radar echo is deducted to complete ground clutter suppression.

[0066] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. An adaptive clutter suppression method for airborne weather radar, characterized in that: The steps include: Calculate the reference angle iAng_T between each distance unit and the aircraft; Calculate the first radar echo angle iAng_R of each range unit; Calculate the error of the radar echo angle of each distance unit, and obtain the corrected second radar echo angle after removing the error; Ground clutter suppression is performed on the radar data of the current antenna row. The second radar echo angle of each distance unit is compared with the reference angle. When the angle difference between the two is less than the preset value, the current radar echo is considered to be a ground echo. The current radar echo is deducted to complete ground clutter suppression.

2. The airborne weather radar adaptive clutter suppression method according to claim 1, characterized in that: The method of calculating the error of the radar echo angle of each range unit and obtaining the corrected second radar echo angle after removing the error includes: Calculate the average value of the difference between the reference angle of all effective range units and the first radar echo angle iAng_E=mean(iAng_R-iAng_T); After completing an antenna scanning line, the average angle difference data {Az,iAng_E} corresponding to each azimuth in the scanning line is obtained; Fit the orientation-angle error data to form an error quadratic curve Angeline=f(Az), calculate the mean value of the fitting error, and take the fitting result whose mean value of the fitting error is less than the preset value Th_E as a valid error curve for a scanning line; The second radar echo angle is equal to the first radar echo angle minus the angle error value, and the angle error value is obtained from the error curve.

3. The airborne weather radar adaptive clutter suppression method according to claim 2, characterized in that: When fitting the azimuth-angle error data, ground markers are used to remove known meteorological target angles; The ground mark is determined by the error of the fitting result of the previous antenna scan line. The ground mark is valid by default. The ground mark whose angle corresponds to the curve fitting error greater than the preset threshold is invalid.

4. The airborne weather radar adaptive clutter suppression method according to claim 2, characterized in that: The method of calculating the error of the radar echo angle of each range unit and obtaining the corrected second radar echo angle after removing the error also includes: The effective error curve Angeline=f(Az) is discretized to form an angle error table and sent to the beam control unit. In the next antenna scanning line, the beam control unit performs adaptive correction of beam pointing according to the angle error table data.

5. The airborne weather radar adaptive clutter suppression method according to claim 2, characterized in that: The angle error curve is updated once after each antenna scan line is completed.

6. The airborne weather radar adaptive clutter suppression method according to claim 2, characterized in that: The step of calculating the average value iAng_E of the angle difference between all effective range unit reference angles and the first radar echo includes: Calculate the ground coverage range of the antenna beam {Rs:Re}, where Rs is the starting distance unit and Re is the ending distance unit; Extract the effective echo distance unit {Rt1 Rt2....Rtn} with signal-to-noise ratio greater than TSNR in {Rs:Re}; The first radar echo angle value and the reference angle value of the effective echo unit are extracted, and the average value of the angle difference between the first radar echo angle value and the reference angle value is calculated.

7. The airborne weather radar adaptive clutter suppression method according to claim 2, characterized in that: The step of calculating the error of the radar echo angle of each distance unit and obtaining the corrected second radar echo angle after removing the error also includes: The mean of abs(iAng_E) is calculated. If the mean meets the angle measurement accuracy requirement, the angle error is 0.

8. The airborne weather radar adaptive clutter suppression method according to claim 1, characterized in that: The method for calculating the reference angle iAng_T between each distance unit and the aircraft includes: According to the aircraft platform height H, heading, distance iR, and beam pointing (iAZ, iEL), calculate the longitude and latitude (iLat, iLon) corresponding to the distance iR; Extract the terrain height iH from the terrain database according to the longitude and latitude (iLat, iLon); According to the aircraft height H and the terrain height iH, calculate the angle iAng_T corresponding to the distance iR; Where Re is the radius of the Earth.

9. The airborne weather radar adaptive clutter suppression method according to claim 1, characterized in that: In step 2, the first radar echo angle iAng_R of each distance unit is calculated by measuring angle by amplitude or phase.

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