A solid-state dual-polarization weather radar distance sidelobe identification and suppression method

Abstract

The application discloses a solid-state dual-polarization weather radar distance sidelobe identification and suppression method, comprising the following steps: calculating the correlation coefficients of the current distance bin and the adjacent distance bin of the horizontal channel and the vertical channel data respectively; calculating the standard deviations of the correlation coefficients of the horizontal channel and the vertical channel respectively; if the correlation coefficients of the current bin are all greater than a specified threshold, and the standard deviations of the correlation coefficients of the current bin are all less than a specified threshold, it is determined that the echo of the current distance bin is affected by the distance sidelobe. Otherwise, it is determined that the current distance bin is not affected by the distance sidelobe; if it is determined that the current bin is affected by the distance sidelobe, the echo power of the horizontal channel and the vertical channel is respectively corrected according to the correlation coefficients of the current bin. Otherwise, the original I / Q data is directly output. The method reduces the adverse effects of the distance sidelobe on the solid-state dual-polarization weather radar, and helps to improve the detection effect of the solid-state dual-polarization radar on disaster weather.

Description

Technical Field

[0001] This invention relates to the field of radar signal processing research, and in particular to a method for identifying and suppressing range sidelobes in solid-state dual-polarization weather radar. Background Technology

[0002] Pulse compression is a widely used technique in solid-state weather radar, typically employing linear frequency modulation (LFM) or nonlinear frequency modulation (NLFM) pulse compression signals. LFM signals have an inherent drawback: high range sidelobes in the matched filter output waveform. To reduce these range sidelobes, a weighting factor is introduced into the compression filter, which inevitably introduces loss into the pulse compression output main lobe, reducing system sensitivity. NLFM, on the other hand, avoids the mismatch loss caused by weighting and achieves lower sidelobe levels. The key to pulse compression signal waveform design is ensuring good autocorrelation performance. Since there is a one-to-one correspondence between the signal's autocorrelation function and power spectrum, LFM / NLFM signal design boils down to designing the signal according to the required power spectrum, generally achieved through window functions.

[0003] Regarding range sidelobe suppression, Jian Fusheng et al. (2001) proposed a method for combining and optimizing window functions, which can quickly and flexibly design the required signal; however, designing the optimal waveform remains a challenge. Tao Guangyuan et al. (2003) studied a phase-coded pulse compression method, using an iterative weighted least squares algorithm to design and optimize the sidelobe suppression filter, thereby achieving a high practical level of main lobe-to-sidelobe ratio (main-to-side lobe ratio) in the pulse compression output. This method also focuses on waveform design. Kurdzo et al. (2014) designed an optimized nonlinear frequency-modulated waveform based on a genetic algorithm. Compared to window function filters, this technique can reduce signal-to-noise ratio loss while ensuring range sidelobe suppression; however, it requires a larger bandwidth.

[0004] In current solid-state weather radars, the LFM pulse compression method is still widely used. Coupled with the specific needs of weather observation, this can lead to a significant number of range sidelobes in the radar echo. These false echoes degrade data quality and affect the understanding of weather phenomena. Therefore, identifying and suppressing range sidelobes from the perspective of radar echoes, based on waveform design, is particularly important. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to address the shortcomings of the prior art by providing a method for identifying and suppressing range sidelobes in solid-state dual-polarization weather radar. This method can identify and suppress range sidelobes from the radar echo angle, and can solve the technical problem that the range sidelobes of current solid-state weather radar are greatly affected by pulse compression, resulting in false echoes during weather observation and thus causing a decline in data quality.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0007] A method for identifying and suppressing range sidelobes in a solid-state dual-polarization weather radar includes the following steps.

[0008] Step 1: Calculate the correlation coefficients CC_Gate_H and CC_Gate_V: The solid-state dual-polarization weather radar has horizontal channel echo and vertical channel echo, and both the horizontal and vertical channel echoes have N range databases along the ray direction; where N≥500; calculate the correlation coefficients CC_Gate_H and CC_Gate_V for each range database; where CC_Gate_H is the correlation coefficient between the horizontal channel echo in the current i-th range database and the horizontal channel echo in the adjacent j-th range database; CC_Gate_V is the correlation coefficient between the vertical channel echo in the current i-th range database and the vertical channel echo in the adjacent j-th range database; where i≠j.

[0009] Step 2: Calculate the standard deviations CC_Gate_Std_H and CC_Gate_Std_V: Calculate the standard deviations CC_Gate_Std_H and CC_Gate_Std_V for each distance library; where CC_Gate_Std_H is the standard deviation of the horizontal channel echo correlation coefficient between the current distance library and the left and right adjacent a distance libraries; where 2≤a≤8; CC_Gate_Std_V is the standard deviation of the vertical channel echo correlation coefficient between the current distance library and the adjacent a distance libraries.

[0010] Step 3, determining the impact of distance to the sidelobe, specifically includes the following steps:

[0011] Step 3-1: Set the correlation coefficient threshold CC_Thr and the standard deviation threshold CC_Std_Thr.

[0012] Step 3-2: Determine if the current range library's CC_Gate_H and CC_Gate_V are both greater than the correlation coefficient threshold CC_Thr, and the current range library's CC_Gate_Std_H and CC_Gate_Std_V are both less than the standard deviation threshold CC_Std_Thr, then the current range library echo is determined to be affected by range sidelobes; otherwise, the current range library is determined to be unaffected by range sidelobes.

[0013] Step 4, Range Sidelobe Suppression: When it is determined in Step 3 that the current range library echo is affected by range sidelobes, the echo power or signal-to-noise ratio of the horizontal and vertical channels needs to be corrected according to the correlation coefficients CC_Gate_H and CC_Gate_V of the current library, so as to reduce or eliminate the influence of range sidelobes on the current range library echo.

[0014] In step 1, the correlation coefficients CC_Gate_H and CC_Gate_V are calculated based on the ratio of the pulse voltage and signal power values ​​of the current i-th distance library and the adjacent j-th distance library.

[0015] The formulas for calculating the correlation coefficients CC_Gate_H and CC_Gate_V are as follows:

[0016]

[0017]

[0018] In the formula, M represents the total number of times the horizontal channel echo or vertical channel echo pulse voltage is collected in each distance library.

[0019] m represents the acquisition sequence number of the horizontal or vertical channel echo pulse voltage in each distance library, where 1 ≤ m ≤ M.

[0020] It represents the conjugate of the echo pulse voltage acquired m times in the horizontal channel of the current i-th distance library.

[0021] V j_H (m) represents the echo pulse voltage acquired for the mth time in the horizontal channel of the adjacent j-th distance library.

[0022] This represents the estimated power of the horizontal channel echo signal in the current i-th distance library.

[0023] This represents the estimated power of the horizontal channel echo signal in the j-th adjacent distance library.

[0024] It represents the conjugate of the echo pulse voltage acquired m times by the vertical channel in the current i-th distance library.

[0025] V j_V (m) represents the echo pulse voltage acquired for the mth time in the vertical channel of the j-th adjacent distance library.

[0026] This represents the estimated power of the vertical channel echo signal in the current i-th distance library.

[0027] This represents the estimated power of the vertical channel echo signal in the j-th adjacent distance library.

[0028] The value of j needs to be determined based on the relative distance between the main lobe and the side lobe after pulse compression of the signal waveform actually used by the radar, as well as the range library sampling rate.

[0029] j = i + 1 or j = i + 2 or j = i + 3; the interval between the j-th range database and the i-th range database must be greater than or equal to the radar range resolution.

[0030] In step 2, a = 6. When calculating the standard deviations CC_Gate_Std_H and CC_Gate_Std_V for each group, the correlation coefficients of the current distance database, the three distance databases adjacent to the current distance database, and the three distance databases adjacent to the current distance database, for a total of 7 distance databases, are used to calculate the standard deviation.

[0031] In step 4, during distance sidelobe suppression, the same corrected correlation coefficient is used for both the horizontal and vertical channels. The corrected correlation coefficient is the mean of the correlation coefficients CC_Gate_H and CC_Gate_V calculated from the current distance library.

[0032] In step 4, during range sidelobe suppression, the signal-to-noise ratios (SNRs) of the horizontal and vertical channels are corrected according to the correlation coefficients CC_Gate_H and CC_Gate_V of the current library, in order to reduce or eliminate the influence of range sidelobes on the current range library echo. The SNR correction method is: the current library SNR minus the product of the square of the current library correction correlation coefficient and the SNR.

[0033] In step 3, the correlation coefficient threshold CC_Thr is 0.5 and the standard deviation threshold CC_Std_Thr is 0.1.

[0034] The present invention has the following beneficial effects:

[0035] 1. It can identify and suppress range sidelobes from the radar echo angle, which can solve the technical problem that the range sidelobes of current solid-state weather radar are greatly affected by pulse compression, resulting in false echoes during weather observation and thus causing a decline in data quality.

[0036] 2. Based on radar echo signal I / Q data, it boasts a high degree of automation and is convenient to implement. Compared to existing technologies, it reduces the adverse effects of range sidelobes on solid-state dual-polarization weather radar, thus helping to improve the detection performance of solid-state dual-polarization radar against severe weather. Attached Figure Description

[0037] Figure 1 This is a flowchart of a method for identifying and suppressing range sidelobes in a solid-state dual-polarization weather radar according to the present invention.

[0038] Figure 2 This is the result of the identification and processing of range sidelobes of solid-state dual-polarization radar according to the present invention. Detailed Implementation

[0039] The present invention will now be described in further detail with reference to the accompanying drawings and specific preferred embodiments.

[0040] Existing research has shown that meteorological echoes vary between different pulses (Marshall and Hitschfeld 1953; Wallace 1953). This variation is caused by the relative motion between particles, with a scale approximately one-quarter of the wavelength, which increases or decreases the electromagnetic wave energy reaching the radar antenna. Compared to the radar range library, the scale of the inter-particle motion is extremely small, resulting in variations in echo sampling between each range library and other range libraries. In other words, each time series is unique. Therefore, theoretically, the correlation coefficient between different range libraries should be 0. However, this is conditional: the sampling time between range libraries must be greater than the correlation time of the meteorological echoes; otherwise, the correlation coefficient between different range libraries will not be 0. Even so, the correlation coefficient between different range libraries for meteorological echoes remains very small. When range sidelobes exist, information from a stronger echo range library leaks into a nearby weaker echo range library, significantly increasing the correlation between these two range libraries. Based on this principle, range sidelobes can be identified and suppressed by analyzing the correlation between adjacent range libraries.

[0041] like Figure 1 As shown, a method for identifying and suppressing range sidelobes in a solid-state dual-polarization weather radar includes the following steps.

[0042] Step 1: Calculate the correlation coefficients CC_Gate_H and CC_Gate_V: The solid-state dual-polarization weather radar has horizontal channel echo and vertical channel echo, and both the horizontal and vertical channel echoes have N range databases along the ray direction; where N≥500; calculate the correlation coefficients CC_Gate_H and CC_Gate_V for each range database; where CC_Gate_H is the correlation coefficient between the horizontal channel echo in the current i-th range database and the horizontal channel echo in the adjacent j-th range database; CC_Gate_V is the correlation coefficient between the vertical channel echo in the current i-th range database and the vertical channel echo in the adjacent j-th range database; where i≠j.

[0043] The value of j needs to be determined based on the relative distance between the main lobe and sidelobe after pulse compression of the signal waveform actually used by the radar, as well as the range library sampling rate. The usual values ​​of j are: j = i + 1, j = i + 2, or j = i + 3, etc. It is necessary to ensure that the interval between the j-th range library and the i-th range library is greater than or equal to the radar range resolution.

[0044] The correlation coefficients CC_Gate_H and CC_Gate_V are calculated based on the ratio of the pulse voltage and signal power values ​​of the current i-th distance library and the adjacent j-th distance library.

[0045] The preferred formulas for calculating the correlation coefficients CC_Gate_H and CC_Gate_V are:

[0046]

[0047]

[0048] In the formula, M represents the total number of times the horizontal channel echo or vertical channel echo pulse voltage is collected in each distance library.

[0049] m represents the acquisition sequence number of the horizontal or vertical channel echo pulse voltage in each distance library, where 1 ≤ m ≤ M.

[0050] It represents the conjugate of the echo pulse voltage acquired m times in the horizontal channel of the current i-th distance library.

[0051] V j_H (m) represents the echo pulse voltage acquired for the mth time in the horizontal channel of the adjacent j-th distance library.

[0052] This represents the estimated power of the horizontal channel echo signal in the current i-th distance library.

[0053] This represents the estimated power of the horizontal channel echo signal in the j-th adjacent distance library.

[0054] It represents the conjugate of the echo pulse voltage acquired m times by the vertical channel in the current i-th distance library.

[0055] V j_V (m) represents the echo pulse voltage acquired for the mth time in the vertical channel of the j-th adjacent distance library.

[0056] This represents the estimated power of the vertical channel echo signal in the current i-th distance library.

[0057] This represents the estimated power of the vertical channel echo signal in the j-th adjacent distance library.

[0058] Step 2: Calculate the standard deviations CC_Gate_Std_H and CC_Gate_Std_V: Calculate the standard deviations CC_Gate_Std_H and CC_Gate_Std_V for each distance library; where CC_Gate_Std_H is the standard deviation of the horizontal channel echo correlation coefficient between the current distance library and the left and right adjacent a distance libraries; where 2≤a≤8; CC_Gate_Std_V is the standard deviation of the vertical channel echo correlation coefficient between the current distance library and the adjacent a distance libraries.

[0059] In this embodiment, a=6 is preferred. That is, when calculating the standard deviations CC_Gate_Std_H and CC_Gate_Std_V, the correlation coefficients of the current distance library, the three distance libraries adjacent to the current distance library, and the three distance libraries adjacent to the current distance library are used to calculate the standard deviation. Distance libraries that do not meet the number of libraries are not included in the calculation, so that the number of distance libraries involved in the calculation can better represent the data characteristics.

[0060] Step 3, determining the impact of distance to the sidelobe, specifically includes the following steps:

[0061] Step 3-1: Set the correlation coefficient threshold CC_Thr and the standard deviation threshold CC_Std_Thr.

[0062] Step 3-2: Determine if the current range library's CC_Gate_H and CC_Gate_V are both greater than the correlation coefficient threshold CC_Thr, and the current range library's CC_Gate_Std_H and CC_Gate_Std_V are both less than the standard deviation threshold CC_Std_Thr, then the current range library echo is determined to be affected by range sidelobes; otherwise, the current range library is determined to be unaffected by range sidelobes.

[0063] The correlation coefficient threshold CC_Thr mentioned above needs to be calculated based on the radar data results, with a typical value of 0.5. Using the standard deviation as an auxiliary judgment can effectively reduce misjudgments caused by outliers. Similarly, the standard deviation threshold also needs to be calculated based on the radar data results, with a typical value of 0.1.

[0064] Step 4, Range Sidelobe Suppression: If Step 3 determines that the current range library echo is affected by range sidelobes, then the echo power or signal-to-noise ratio of the horizontal and vertical channels needs to be corrected according to the correlation coefficients CC_Gate_H and CC_Gate_V of the current library to reduce or eliminate the influence of range sidelobes on the current range library echo. Otherwise, the original I / Q data is output directly.

[0065] When suppressing the sidelobe at the distance mentioned above, the same corrected correlation coefficient is used for both the horizontal and vertical channels. The corrected correlation coefficient is preferably the mean of the correlation coefficients CC_Gate_H and CC_Gate_V calculated from the current distance library.

[0066] In this embodiment, when suppressing range sidelobes, it is preferable to correct the signal-to-noise ratios (SNRs) of the horizontal and vertical channels respectively based on the correlation coefficients CC_Gate_H and CC_Gate_V of the current library, so as to reduce or eliminate the influence of range sidelobes on the current range library echo; wherein, the preferred SNR correction method is: the current library SNR minus the product of the square of the current library correction correlation coefficient and the SNR.

[0067] Figure 2 This image shows the processing effect of range sidelobe echoes in the rainfall data from a single rainfall event detected by the solid-state dual-polarization weather radar of this invention. Figure 2 'a' represents the original intensity estimate from radar detection. Figure 2 b、 Figure 2 c represents the intensity echo processed by the method of this invention and the identification result of the range sidelobe echo by the method of this invention, respectively. As can be seen from the figure, the original intensity echo, due to the presence of range sidelobe echoes, is prone to tailing at the echo edges, such as... Figure 2 The area shown in the black box in section a can lead to misidentification of weather phenomena (as it resembles the characteristics of three-body scattering echoes). After processing, as shown... Figure 2 As shown in the black box (b), the range sidelobe echo was effectively suppressed, thus preventing it from being misidentified as other types of precipitation echoes. The figure also shows that other locations identified as range sidelobe echoes were processed, resulting in an overall echo pattern more consistent with weather characteristics. Therefore, the range sidelobe identification and suppression method for solid-state dual-polarization weather radar proposed in this invention can effectively reduce the impact of range sidelobes on precipitation observations by solid-state weather radar, improving the data quality of solid-state radar.

[0068] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various equivalent transformations can be made to the technical solutions of the present invention, and these equivalent transformations all fall within the protection scope of the present invention.

Claims

1. A method for identifying and suppressing range sidelobes in a solid-state dual-polarization weather radar, characterized in that: Includes the following steps: Step 1: Calculate the correlation coefficients CC_Gate_H and CC_Gate_V: The solid-state dual-polarization weather radar has horizontal channel echo and vertical channel echo, and both the horizontal and vertical channel echoes have N range databases along the ray direction; where N≥500; calculate the correlation coefficients CC_Gate_H and CC_Gate_V for each range database; where CC_Gate_H is the correlation coefficient between the horizontal channel echo in the current i-th range database and the horizontal channel echo in the adjacent j-th range database; CC_Gate_V is the correlation coefficient between the vertical channel echo in the current i-th range database and the vertical channel echo in the adjacent j-th range database; where i≠j; Step 2: Calculate the standard deviations CC_Gate_Std_H and CC_Gate_Std_V: Calculate the standard deviations CC_Gate_Std_H and CC_Gate_Std_V for each distance library; where CC_Gate_Std_H is the standard deviation of the horizontal channel echo correlation coefficient between the current distance library and the next a adjacent distance libraries; where 2≤a≤8; CC_Gate_Std_V is the standard deviation of the vertical channel echo correlation coefficient between the current distance library and the next a adjacent distance libraries. Step 3, determining the impact of distance to the sidelobe, specifically includes the following steps: Step 3-1: Set the correlation coefficient threshold CC_Thr and the standard deviation threshold CC_Std_Thr; Step 3-2: Determine if the current range library's CC_Gate_H and CC_Gate_V are both greater than the correlation coefficient threshold CC_Thr, and the current range library's CC_Gate_Std_H and CC_Gate_Std_V are both less than the standard deviation threshold CC_Std_Thr, then the current range library echo is determined to be affected by range sidelobes; otherwise, the current range library is determined to be unaffected by range sidelobes. Step 4, Range Sidelobe Suppression: When it is determined in Step 3 that the current range library echo is affected by range sidelobes, the echo power or signal-to-noise ratio of the horizontal and vertical channels needs to be corrected according to the correlation coefficients CC_Gate_H and CC_Gate_V of the current library, so as to reduce or eliminate the influence of range sidelobes on the current range library echo.

2. The method for identifying and suppressing range sidelobes in solid-state dual-polarization weather radar according to claim 1, characterized in that: In step 1, the correlation coefficients CC_Gate_H and CC_Gate_V are calculated based on the ratio of the pulse voltage and signal power values ​​of the current i-th distance library and the adjacent j-th distance library.

3. The method for identifying and suppressing range sidelobes of solid-state dual-polarization weather radar according to claim 2, characterized in that: The formulas for calculating the correlation coefficients CC_Gate_H and CC_Gate_V are as follows: In the formula, M represents the total number of times the horizontal channel echo or vertical channel echo pulse voltage is collected in each distance library; m represents the acquisition sequence number of the horizontal channel echo or vertical channel echo pulse voltage in each distance library, 1≤m≤M; It represents the conjugate of the echo pulse voltage acquired m times by the horizontal channel in the current i-th distance library; V j_H (m) represents the echo pulse voltage acquired for the mth time in the horizontal channel of the j-th adjacent distance library; This represents the estimated power of the horizontal channel echo signal in the current i-th distance library; This represents an estimated value of the horizontal channel echo signal power in the j-th adjacent distance library; It represents the conjugate of the echo pulse voltage acquired m times by the vertical channel in the current i-th distance library; V j_V (m) represents the echo pulse voltage acquired for the mth time in the vertical channel of the j-th adjacent distance library; This represents the estimated power of the vertical channel echo signal in the current i-th distance library; This represents the estimated power of the vertical channel echo signal in the j-th adjacent distance library.

4. The method for identifying and suppressing range sidelobes of solid-state dual-polarization weather radar according to claim 1, characterized in that: The value of j needs to be determined based on the relative distance between the main lobe and the side lobe after pulse compression of the signal waveform actually used by the radar, as well as the range library sampling rate.

5. The method for identifying and suppressing range sidelobes of a solid-state dual-polarization weather radar according to claim 1 or 4, characterized in that: j = i + 1 or j = i + 2 or j = i + 3; the interval between the j-th range database and the i-th range database must be greater than or equal to the radar range resolution.

6. The method for identifying and suppressing range sidelobes of solid-state dual-polarization weather radar according to claim 1, characterized in that: In step 2, a = 6. When calculating the standard deviations CC_Gate_Std_H and CC_Gate_Std_V for each group, the correlation coefficients of the current distance database, the three distance databases adjacent to the current distance database, and the three distance databases adjacent to the current distance database, for a total of 7 distance databases, are used to calculate the standard deviation.

7. The method for identifying and suppressing range sidelobes of solid-state dual-polarization weather radar according to claim 1, characterized in that: In step 4, during distance sidelobe suppression, the same corrected correlation coefficient is used for both the horizontal and vertical channels. The corrected correlation coefficient is the mean of the correlation coefficients CC_Gate_H and CC_Gate_V calculated from the current distance library.

8. The method for identifying and suppressing range sidelobes of solid-state dual-polarization weather radar according to claim 7, characterized in that: In step 4, during range sidelobe suppression, the signal-to-noise ratios (SNRs) of the horizontal and vertical channels are corrected according to the correlation coefficients CC_Gate_H and CC_Gate_V of the current library, in order to reduce or eliminate the influence of range sidelobes on the current range library echo. The SNR correction method is: the current library SNR minus the product of the square of the current library correction correlation coefficient and the SNR.

9. The method for identifying and suppressing range sidelobes of a solid-state dual-polarization weather radar according to claim 1, characterized in that: In step 3, the correlation coefficient threshold CC_Thr is 0.5 and the standard deviation threshold CC_Std_Thr is 0.1.

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