JP2011169829A - Meteorological radar signal processing apparatus and ground clutter removing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To automatically find an effective parameter for MTI and speed width filter. <P>SOLUTION: The meteorological radar signal processing apparatus includes an MTI processor A1 that computes ground clutter elements from the reception signals of a target-reflected wave, on the basis of the predetermined MTI parameters and removes them; a speed width filter A2, that compares signals wherein the ground clutter is removed by the MTI processing with thresholds based on the predetermined speed width parameters and extracts meteorological echo elements included in the signals processed by the MTI processing; and a meteorological information computing section A3, that obtains meteorological information from the output of the speed width filter. Observation data and simulated weather echo at the radar installation point are used to automatically search the optimal values of the MTI parameter and the speed width parameter, and the automatically searched MTI parameter and speed width parameter are set in the MTI processing apparatus A1 and the speed width filter A2, in advance, so that parameters can be automatically adjusted by simulation in an off-line mode. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a weather radar signal processing apparatus and method for accurately detecting a weather echo by removing a ground clutter (terrain echo) component from a radar reception signal in a weather radar.

  As is well known, weather radars observe precipitation amounts by region by receiving radio waves reflected by clouds and rain and analyzing their power values. In addition, wind power is also observed by analyzing the Doppler frequency of received radio waves using the Doppler effect of radio waves.

  However, the radio wave reception signal includes not only a weather echo that is a reflected wave from a weather object but also a ground clutter component (terrain echo) that is a reflected wave from a mountain or a building. Since the ground clutter hinders weather observation, a moving target indicator (Moving Target Indicator: MTI) is used for the signal processing device of the weather radar in order to remove the ground clutter component.

  However, if the MTI parameters are set improperly, a problem arises that the ground clutter component remains and the weather echoes are excessively deleted. On the other hand, a threshold value process called a speed width filter is used to determine whether the data after MTI processing includes a ground clutter component. This speed width filter, when the threshold value is set inappropriately, has a large speed range. Echo is removed.

  Regarding the parameter design of these MTI and velocity width filter, an efficient design method has not yet been established, and it is necessary to manually adjust the observation site where the radar is installed. Therefore, a great deal of labor and time must be taken to obtain the optimum parameters.

Masahito Ishihara, Principle and Basics of Doppler Weather Radar, Meteorological Research Note No.200, Japan Meteorological Association, pp.1-38, 2001

  As described above, in the conventional weather radar signal processing apparatus, an efficient design method for the parameters of the MTI and the speed width filter has not yet been established. I had to go to the ground and adjust it manually.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a meteorological radar signal processing apparatus and a ground clutter removal method capable of automatically obtaining effective parameters for the MTI and the speed width filter. .

  In order to achieve the above object, a weather radar signal processing apparatus according to the present invention is configured as follows.

  (1) An MTI processor that calculates and removes a ground clutter component from a received signal of a target reflected wave based on a preset MTI (moving target instruction device) processing parameter, and after the MTI processing in which the ground clutter is removed A speed range filter that extracts a meteorological echo component included in the signal after MTI processing, and weather information that obtains weather information from the output of the speed range filter A calculation unit, parameter automatic search means for automatically searching for optimum values of the MTI processing parameter and the velocity width parameter using observation data and simulated weather echo at the radar installation point, the automatically searched MTI processing parameter, And a control means for setting a speed width parameter in the MTI processor and the speed width filter in advance. And aspects.

  (2) In the configuration of (1), the parameter automatic search means calculates and evaluates a ground clutter removal rate from a signal after the MTI processing for a plurality of MTI processing parameter candidates prepared in advance. The one having a high removal rate is selected, and the simulated weather echo is used to evaluate the retention of the weather echo, and the MTI processing parameter that minimizes the intensity difference between the weather echoes before and after the MTI processing is selected as the optimum parameter. Let it be an aspect.

  (3) In the configuration of (1), the parameter automatic search means sequentially calculates and evaluates the ground clutter removal rate from the signal after the MTI processing for the MTI processing parameters continuously variable within a predetermined range prepared in advance. , Selecting a parameter at the time when the ground clutter removal rate becomes the highest, and further evaluating the holding of the weather echo using the simulated weather echo, and the MTI when the intensity difference of the weather echo before and after the MTI processing is minimized The processing parameter is selected as the optimum parameter.

  (4) In the configuration of (2), the automatic parameter search means further obtains a speed width parameter for obtaining a predetermined ground clutter removal rate.

  The ground clutter removal method according to the present invention is configured as follows.

  (5) A ground clutter component is calculated from the received signal of the target reflected wave based on a preset MTI (moving target instruction device) processing parameter, and the signal after the MTI processing from which the ground clutter has been removed A meteorological radar ground clutter removal method for extracting a meteorological echo component included in a signal after MTI processing by comparing with a threshold value based on a set speed width parameter, the observation data and a simulated meteorological echo at a radar installation point Is used to automatically search for optimum values of the MTI processing parameter and velocity width parameter, and to set the automatically searched MTI processing parameter and velocity bandwidth parameter in advance to extract the MTI processing and the weather echo component. It is set as the aspect to perform.

  (6) In the configuration of (5), the automatic parameter search is performed by calculating and evaluating a ground clutter removal rate from a signal after the MTI processing for a plurality of MTI processing parameter candidates prepared in advance. The one having a high removal rate is selected, and the simulated weather echo is used to evaluate the retention of the weather echo, and the MTI processing parameter that minimizes the intensity difference between the weather echoes before and after the MTI processing is selected as the optimum parameter. Let it be an aspect.

  (7) In the configuration of (5), the automatic search for the parameter is performed by sequentially calculating a ground clutter removal rate from a signal after the MTI processing for a variable continuous MTI processing parameter prepared in a predetermined range. Further, the holding of the weather echo is evaluated using the simulated weather echo, and the MTI processing parameter that minimizes the difference in the intensity of the weather echo before and after the MTI processing is selected as the optimum parameter.

  (8) In the configuration of (6) or (7), the automatic search for the parameter is a mode in which a speed width parameter that further obtains a predetermined ground clutter removal rate is obtained.

  ADVANTAGE OF THE INVENTION According to this invention, the weather radar signal processing apparatus which can obtain | require automatically the parameter effective about MTI and a speed-width filter, and its ground clutter removal method can be provided.

The block diagram which shows the structure of one Embodiment of the weather radar signal processing apparatus with which this invention is applied. The block diagram which shows the structure of an MTI processor in the apparatus shown in FIG. The block diagram which shows the structure of the process which calculates | requires the MTI parameter and speed range filter which are used for the MTI processor shown in FIG. FIG. 4 is a flowchart showing a process flow of a ground clutter removal evaluation unit shown in FIG. 3. FIG. The flowchart which shows the process sequence of the weather echo maintenance evaluation part shown in FIG. The flowchart which shows the process sequence of the speed width threshold value update part shown in FIG.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram showing a configuration of a weather radar signal processing apparatus according to the present invention as an embodiment of the present invention. In FIG. 1, the radar pulse signal generated by the pulse signal generator 11 is frequency-converted by the transmission device 12, power amplified, and radiated from the antenna 14 toward the space via the circulator 13.

  The reflected signal from the target received by the antenna 14 is sent to the receiving device 15 via the circulator 13. The receiving device 15 amplifies the signal received by the antenna 14 and converts the frequency to baseband, and the output is sent to the signal processing device 16.

  The signal processing device 16 converts an input received signal into digital data by an A / D converter 161, converts it to IQ data in a complex format by an IQ detector 162, and removes a ground clutter component by an MTI processor 163. To obtain observation data by meteorological echo.

  The IQ data obtained by the IQ detector 162 is sent to the offline computer 17 as necessary. The off-line computer 17 takes in IQ data of an arbitrary period from the IQ detector 162, and calculates MTI parameters and speed width parameters optimal for MTI processing. The parameters obtained here are sent to the parameter control device 18. The parameter control device 18 sets the MTI parameter and the speed width parameter calculated by the off-line computer 17 in the MTI processor 163, and causes the MTI processor 163 to execute optimum processing.

  FIG. 2 is a block diagram showing a specific configuration of the MTI processor 163. In FIG. 2, the MTI processing unit A1 based on the PPP method (Pulse Pair Processing) captures IQ data obtained by the IQ detector 162, and performs terrain echo based on the MTI parameter preset by the parameter control device 18. The weather echo component is extracted by calculating and removing the ground clutter component, and the IQ data after MTI processing obtained here is sent to the speed width filter A2.

  The speed width filter A2 performs threshold processing for determining whether IQ data after MTI processing includes weather echo based on a speed width parameter set in advance by the parameter control device 18, and here, The selected IQ data is sent to the weather information calculation unit A3. The weather information calculation unit A3 performs noise removal, threshold processing of power values corresponding to radio wave reception intensity, and isolated point removal on the IQ data obtained by the speed width filter 12, and outputs the speed, Get weather information of speed range and power value.

  In the above configuration, calculation of optimum parameters obtained by the offline computer 17 will be described below.

  First, when the MTI parameters are set improperly, there are problems that the ground clutter remains unerased or weather echoes are excessively deleted. Also, if the speed width parameter (threshold value) of the speed width filter is set inappropriately, weather echoes with a large speed width will be removed.

  Therefore, the offline computer 17 searches for an optimum parameter using a plurality of scan data and simulated weather echoes observed at the radar installation point. Here, the optimum parameters shall satisfy the conditions of 1) almost no disappearance of ground clutter, and 2) keeping weather echo as much as possible.

  For the first condition, the evaluation of holding the ground clutter uses scan data actually observed at the radar installation point. At this time, since the observation data is data including only the ground clutter, the observation data is limited to that observed during clear weather. The second condition, the evaluation of weather echo retention, uses simulated weather echoes and adjusts the parameters so that the weather echoes can be retained as much as possible.

  FIG. 3 shows the flow of the parameter calculation processing in the offline computer 17, and basically the processing of the data conversion unit S1, the ground clutter removal evaluation unit S2, the weather echo retention evaluation unit S3, and the speed width threshold update unit S4. included.

  The data converter S1 converts IQ data into a single PRF (Pulse Repeat Frequency) and sector mode, and corrects data in advance in order to apply the present invention to observation data. In order to convert a plurality of PRFs into a single PRF, IQ data adjacent in a time series is used.

  The ground clutter removal evaluation unit S2 calculates and evaluates the ground clutter removal rate from the IQ data after the MTI processing. A candidate having a high ground clutter removal rate is selected from MTI parameter candidates prepared in advance.

  The weather echo retention evaluation unit S3 evaluates the retention of the weather echo using the simulated weather echo. The processing target is the MTI parameter selected by the ground clutter removal evaluation unit S2. The intensity difference between the weather echoes before and after the MTI processing is calculated, and the MTI parameter that minimizes it is optimized.

  The speed width threshold value updating unit S4 adjusts the speed width parameter so as to realize a desired ground clutter removal rate and obtains the threshold value.

  Here, with reference to the flowchart shown in FIG. 4, a specific processing flow of the ground clutter removal evaluating unit S2 will be described.

  First, X different MTI parameters are prepared, and IQ data is input (step S21).

Next, a ground clutter removal rate is calculated (step S22). Here, in order to calculate the MTI parameter, the speed width threshold is fixed. The calculation is performed by applying MTI processing to IQ data and calculating the ground clutter removal rate I.
I = (1−M / N) × 100 [%]
Obtained according to the following equation. Here, M is the number of remaining meshes, and N is the total number of meshes. The remaining M disappearance determination is based on the condition that the power value of the target mesh is equal to or higher than the noise level, or the speed width of the target mesh is less than the speed width threshold value 4 [m / s]. Further, in the determination of N, the nearest distance 2 range and azimuth blanking are not targeted for calculation.

  Subsequently, in the filter selection process, a parameter with a ground clutter removal rate of 90% or more is selected (step S23). That is, a parameter for which ground clutter removal is 90% or more is primarily retained as a filter candidate (step S24), and is excluded when ground clutter removal is less than 90% (step S25). The above process is executed for all X MTI parameters (step S26), and the series of processes is terminated.

  Next, with reference to the flowchart shown in FIG. 5, a specific processing flow of the weather echo retention evaluation unit S3 will be described.

  First, the MTI parameters selected in the process of FIG. 4 (Y here) are taken in, and IQ data and simulated weather echoes are input (step S33).

Next, an evaluation function is calculated (step S34). This evaluation function (H) is calculated by the following equation.
H = | Pmti−Pwe |
Here, Pwe represents the power value of the simulated weather echo to be superimposed, and Pmti represents the power value of the superimposed data after MTI processing.

  The evaluation function H is calculated for each mesh, and the average value is used as the evaluation value. However, the presence / absence determination of the weather echo is based on when the power value of the target mesh is less than the noise level or when the speed width of the target mesh is equal to or greater than the speed width threshold value 4 m / s. If it is determined that there is no weather echo, Pmti is replaced with a noise level as a penalty for canceling the weather echo. As a comprehensive evaluation, the above-described evaluation function is calculated from a plurality of weather echoes, and the average value is used as an evaluation regarding the weather echo retention of the filter.

  The above processing is performed for all Y MTI parameters (step S35), and when all Y are completed, the filter with the smallest overall filter evaluation value is selected as the optimum filter (step S36).

  Finally, with reference to the flowchart shown in FIG. 6, a specific processing flow of the speed width threshold update unit S4 will be described.

  First, IQ data is input, and the optimum filter selected in the process of FIG. 5 is fetched (step S41), and the ground clutter removal rate is calculated (step S42).

  In the calculation of the ground clutter removal rate in step S42, since the MTI parameter has already been selected by the preprocessing, only the speed width threshold value is adjusted. In order to apply MTI processing to IQ data, a plurality of filters are prepared for subsequent filter selection.

The calculation formula for the ground clutter removal rate (I) is as follows, similarly to step S22 in FIG.
I = (1−M / N) × 100 [%]
Here, M is the number of remaining meshes, and N is the total number of meshes. However, the remaining disappearance determination of M is based on the condition that the power value of the target mesh is equal to or higher than the noise level, or the speed width of the target mesh is less than the speed width threshold value 4 [m / s]. Further, isolated point removal is performed on the binary data representing the presence or absence of the remaining disappearance. Further, in the determination of N, the nearest distance 2 range and azimuth blanking are not targeted for calculation.

  Finally, as the speed width threshold update process, the maximum speed width threshold that can realize a desired ground clutter removal rate is selected (step S43).

  By executing the series of processes described above, it is possible to automatically adjust the parameters of the MTI and the speed width filter that are effective at each radar installation point. As a result, parameter adjustment by off-line simulation can be automated, so that no personnel are required for adjustment, which can contribute to cost reduction.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage.

  For example, in the above embodiment, as a parameter automatic search method, a plurality of MTI processing parameter candidates prepared in advance are evaluated by calculating the ground clutter removal rate from the signal after MTI processing, and the ground clutter removal rate is high. Further, the meteorological echoes were evaluated using a simulated meteorological echo, and the meteorological echo retention was evaluated, and the MTI processing parameter that minimizes the intensity difference between the meteorological echoes before and after the MTI processing was selected as the optimum parameter. For this, for the MTI processing parameters that are continuously variable within a certain range prepared in advance, the ground clutter removal rate is calculated and evaluated sequentially from the signal after the MTI processing. It is also possible to evaluate the holding of weather echoes using simulated weather echoes, and to select the MTI processing parameters when the intensity difference between weather echoes before and after the MTI processing is minimized as the optimum parameters.

  Further, according to the present invention, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

  DESCRIPTION OF SYMBOLS 11 ... Pulse signal generation part, 12 ... Transmitter, 13 ... Circulator, 14 ... Antenna, 15 ... Receiver, 16 ... Signal processor, 161 ... A / D converter, 162 ... IQ detector, 163 ... MTI processor , 17 ... Offline computer, 18 ... Parameter control device, A1 ... MTI processing unit, A2 ... Speed width filter, A3 ... Weather information calculation unit, S1 ... Data conversion unit, S2 ... Grand clutter removal evaluation unit, S3 ... Weather echo holding Evaluation part, S4 ... Speed width threshold value update part.

Claims (8)

An MTI processor that calculates and removes a ground clutter component from the received signal of the target reflected wave based on a preset MTI (moving target indicating device) processing parameter;
A speed width filter that extracts a weather echo component included in the signal after MTI processing by comparing the signal after MTI processing from which the ground clutter has been removed with a threshold based on a preset speed width parameter;
A weather information computing unit for obtaining weather information from the output of the speed width filter;
Parameter automatic search means for automatically searching for the optimum values of the MTI processing parameter and the speed width parameter using observation data at the radar installation point and simulated weather echo;
A weather radar signal processing apparatus comprising: control means for setting the automatically searched MTI processing parameter and speed width parameter in the MTI processor and the speed width filter in advance. The parameter automatic search means calculates and evaluates a ground clutter removal rate from a signal after the MTI processing for a plurality of MTI processing parameter candidates prepared in advance, selects one having a high ground clutter removal rate, and 2. The MTI processing parameter that minimizes the difference in the intensity of the weather echo before and after the MTI processing is selected as the optimum parameter by evaluating the holding of the weather echo using the simulated weather echo. Weather radar signal processing device. The parameter automatic search means sequentially calculates and evaluates a ground clutter removal rate from a signal after the MTI processing for a continuously variable MTI processing parameter prepared in advance, and the ground clutter removal rate becomes the highest. Are further selected, and the simulated weather echo is used to evaluate the retention of the weather echo, and the MTI processing parameter when the intensity difference between the weather echoes before and after the MTI processing is minimized is selected as the optimum parameter. The meteorological radar signal processing apparatus according to claim 1. 4. The meteorological radar signal processing apparatus according to claim 2, wherein the parameter automatic search means further obtains a speed width parameter for obtaining a predetermined ground clutter removal rate. A ground clutter component is calculated and removed from the received signal of the target reflected wave based on preset MTI (moving target indicating device) processing parameters, and the signal after the MTI processing from which the ground clutter has been removed is set in advance. A method of removing ground clutter of a weather radar that extracts a weather echo component included in a signal after MTI processing in comparison with a threshold based on a speed width parameter,
The optimum values of the MTI processing parameter and the speed width parameter are automatically searched using the observation data at the radar installation point and the simulated weather echo, and the automatically searched MTI processing parameter and the speed width parameter are set in advance. A ground clutter removal method for a weather radar, wherein the MTI processing and the extraction of the weather echo component are executed. In the automatic parameter search, a plurality of MTI processing parameter candidates prepared in advance are evaluated by calculating a ground clutter removal rate from the signal after the MTI processing, and a candidate having a high ground clutter removal rate is selected. 6. The MTI processing parameter that minimizes the difference in intensity of weather echoes before and after the MTI processing is selected as the optimal parameter by evaluating the weather echo holding using the simulated weather echo. Ground clutter removal method for weather radar. The automatic search for the parameter is performed by sequentially calculating and evaluating a ground clutter removal rate from the signal after the MTI processing for a variable continuous MTI processing parameter in a predetermined range prepared in advance, and further using the simulated weather echo 6. The method for removing ground clutter of a weather radar according to claim 5, wherein the holding of the weather echo is evaluated, and an MTI processing parameter that minimizes the difference in intensity of the weather echo before and after the MTI processing is selected as an optimum parameter. 8. The method for removing ground clutter of a weather radar according to claim 6, wherein the automatic search for the parameter further determines a speed width parameter for obtaining a predetermined ground clutter removal rate.

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