CN-121978693-A - Time-frequency domain dual-polarized radar detection variable estimation method for staggered pulse repetition interval

CN121978693ACN 121978693 ACN121978693 ACN 121978693ACN-121978693-A

Abstract

The invention relates to the technical field of radar signal processing, in particular to a method for estimating detection variables of a staggered pulse repetition interval time-frequency domain dual-polarized radar, which comprises the steps of estimating echo signal-to-noise ratio, reflectivity factors and differential reflectivity based on horizontal/vertical polarization of power spectral density in a frequency domain; and in the time domain, after the ground clutter based on the odd-even pulse is filtered, the odd-even pulse cross-correlation parameter estimation is respectively carried out, so that two detection variables of the dual-polarized radar correlation coefficient and the differential propagation phase shift of the odd-even pulse are respectively obtained, and then the estimation results of the accurate correlation coefficient and the accurate differential propagation phase shift can be obtained by odd-even combination. The method realizes accurate estimation of multiple detection variables of the dual-polarized radar, ensures that an estimation result is not interfered by ground clutter, simultaneously adapts to two working modes of single pulse repetition interval and staggered pulse repetition interval, and improves the reliability and applicability of radar detection.

Inventors

YAO LIREN
YAO ZHENDONG
Zong An
HU SHIHONG

Assignees

成都亘波雷达科技有限公司

Dates

Publication Date: 20260505
Application Date: 20260407

Claims (10)

1. A method for estimating detection variable of a spread pulse repetition interval time-frequency domain dual-polarized radar is characterized by comprising the following steps: Acquiring a horizontal polarization complex baseband signal and a vertical polarization complex baseband signal output by a radar digital receiver, and performing discrete Fourier transform on the horizontal polarization complex baseband signal and the vertical polarization complex baseband signal respectively to acquire a horizontal polarization power spectral density and a vertical polarization power spectral density; Determining horizontal polarization noise power and vertical polarization noise power based on the horizontal polarization power spectral density and the vertical polarization power spectral density, and further calculating a horizontal polarization noise power estimated value and a vertical polarization noise power estimated value; respectively calculating echo average power of horizontal polarization and vertical polarization on each distance gate by using the horizontal polarization power spectral density and the vertical polarization power spectral density, and combining a horizontal polarization noise power estimated value and a vertical polarization noise power estimated value to obtain a horizontal polarization echo signal-to-noise ratio and a vertical polarization echo signal-to-noise ratio; calculating radar reflectivity factors and differential reflectivity based on echo average power, horizontal polarization echo signal-to-noise ratio and vertical polarization echo signal-to-noise ratio of horizontal polarization and vertical polarization on each range gate, and estimating average Doppler velocity and velocity spectrum width based on horizontal polarization power spectrum density and vertical polarization power spectrum density; Respectively carrying out odd-even pulse high-pass filtering on the horizontal polarization complex baseband signal and the vertical polarization complex baseband signal to remove ground clutter interference and obtain odd-even pulse after filtering; Respectively carrying out cross-correlation estimation and self-correlation estimation on the filtered odd-even pulses to obtain a cross-correlation result and an self-correlation result corresponding to the odd-even pulses; the cross-correlation results of the odd-even pulse are respectively normalized by the corresponding autocorrelation results and averaged to obtain the correlation coefficient; performing continuous processing on the initial differential propagation phase shift to obtain a corrected differential propagation phase shift; And carrying out sliding average smoothing on the radar reflectivity factor, the differential reflectivity, the average Doppler speed and the velocity spectrum width, and carrying out sliding median filtering smoothing on the correlation coefficient and the corrected differential propagation phase shift to finally obtain the estimation results of all radar detection variables.
2. The method for estimating the detection variable of the spread pulse repetition interval time-frequency domain dual-polarized radar according to claim 1, wherein the odd-even pulse high-pass filtering is implemented in one of the following two ways: The DC removing process is to calculate the average value of the signals of the odd pulse group and even pulse group in the horizontal polarized complex baseband signal and the vertical polarized complex baseband signal respectively, take the average value as the DC component of the corresponding pulse group, then deduct the DC component of the pulse group from each signal sample, and keep the AC component to remove the main component of the ground clutter; And IIR high-pass filtering, namely adopting a 6-order elliptic filter, wherein the stop band speed of the filter is set to be 0.7m/s, the pass band speed is set to be 1m/s, constructing a differential equation through a preset autoregressive coefficient and a sliding average coefficient, and respectively filtering the odd-even pulse group to thoroughly inhibit ground clutter.
3. The method for estimating the detection variable of the spread pulse repetition interval time-frequency domain dual polarized radar according to claim 1, wherein the specific process of determining the horizontal polarization noise power and the vertical polarization noise power is as follows: The horizontal polarization power spectrum density and the vertical polarization power spectrum density of each distance gate are respectively sequenced from low to high to obtain a corresponding power spectrum density sequence; Calculating the accumulated power sum of each sequence point in each sequenced power spectrum density sequence to form a power sum distribution diagram; Identifying a starting point of power jump exceeding a preset threshold value in a power sum distribution diagram according to an empirical rule that the noise power is distributed in a power sum interval of 5-40%, wherein the accumulated power sum corresponding to the starting point is the horizontal polarization noise power or the vertical polarization noise power of a corresponding range gate; And counting a plurality of distance gates and horizontal polarization noise power average values and vertical polarization noise power average values in different radial directions, and respectively taking the average value as a horizontal polarization noise power estimated value and a vertical polarization noise power estimated value.
4. The method for estimating a detection variable of a spread pulse repetition interval time-frequency domain dual-polarized radar according to claim 1, further comprising the step of, after performing discrete fourier transform on the horizontal polarization complex baseband signal and the vertical polarization complex baseband signal: determining the power spectrum density of a target echo signal adjacent to a low-frequency end and a high-frequency end of the ground clutter; Calculating a signal power spectral density change rate based on the target echo signal power spectral density; And replacing the numerical value of the part interfered by the ground clutter in the power spectrum density by adopting a linear interpolation result corresponding to the change rate to obtain the horizontal polarization power spectrum density and the vertical polarization power spectrum density after clutter removal.
5. The method for estimating the detection variable of the dual-polarized radar in the time-frequency domain of the staggered pulse repetition interval according to claim 1, wherein the cross-correlation estimation is respectively carried out in a grouping mode of an odd pulse short interval and an even pulse long interval; And taking an absolute value after the normalization processing, wherein the absolute value is a real number range of limiting the phase relation number to 0-1, so that tiny imaginary components generated by complex number calculation are prevented from influencing an estimation result.
6. The method for estimating the detection variable of the spread pulse repetition interval time-frequency domain dual-polarized radar according to claim 1, wherein the continuously processing the initial differential propagation phase shift specifically comprises: The transient jump is eliminated, namely the jump amplitude of the initial differential propagation phase shift between adjacent distance gates is detected, and if the jump amplitude exceeds the phase jump perturbation threshold and is smaller than the maximum range threshold of the phase jump, the initial differential propagation phase shift of the current distance gate is corrected to be the value of the last distance gate; Eliminating the over-range jump, namely if the jump amplitude exceeds the phase forward folding threshold or the phase backward folding threshold, the jump amplitude is recalculated by adjusting the initial differential propagation phase shift of the next distance gate, and the effective measured value of the adjacent distance gate is used for replacing the abnormal measured value; And (3) carrying out numerical range normalization processing, namely subtracting 360 degrees if the initial differential propagation phase shift is larger than 180 degrees, and adding 360 degrees if the initial differential propagation phase shift is smaller than-180 degrees, so as to ensure that the corrected differential propagation phase shift is within a range of +/-180 degrees.
7. The method for estimating the detection variable of the spread pulse repetition interval time-frequency domain dual-polarized radar according to claim 1, wherein the number of moving average times of the moving average smoothing process is set to be 10 distance gate numbers, and the processing length of the sliding median filtering smoothing process corresponds to the number of distance gate numbers corresponding to a distance range of 300m to 500m so as to eliminate tiny fluctuation generated in the processing process and ensure that the estimation result is smooth and undistorted.
8. The method for estimating the detection variable of the spread pulse repetition interval time-frequency domain dual-polarized radar according to claim 1, wherein the discrete fourier transform is adapted to two working modes of a single pulse repetition interval and a spread pulse repetition interval: when the radar works in a single pulse repetition interval mode, a horizontal polarization complex baseband signal and a vertical polarization complex baseband signal are processed by adopting fast Fourier transform, and the horizontal polarization power spectral density and the vertical polarization power spectral density are directly obtained; when the radar works in a staggered pulse repetition interval mode, a staggered discrete Fourier transform technology is adopted, and an odd pulse group and an even pulse group are respectively processed to ensure sampling interval uniformity, so that horizontal polarization power spectral density and vertical polarization power spectral density are obtained.
9. The method for estimating the detection variable of the spread pulse repetition interval time-frequency domain dual-polarized radar according to claim 8, further comprising the step of removing the image frequency component when the spread discrete fourier transform technique is adopted: For each distance gate, finding out the position of the strongest power spectral density in the horizontal polarization power spectral density and the vertical polarization power spectral density; Based on the characteristic that the amplitude of the main frequency region is larger than that of the image frequency component, the effective frequency domain range is determined by taking the position of the strongest power spectrum density as a reference, and the image frequency component generated by interpolation of the complementary 0 is removed, so that the pure power spectrum density is obtained.
10. The method for estimating a detection variable of a spread pulse repetition interval time-frequency domain dual polarized radar according to claim 1, further comprising attenuation correction, channel error correction, and observation error correction when calculating the differential reflectivity: The attenuation correction is performed based on the attenuation coefficient determined by fitting after actual observation; The channel error correction describes the power measurement difference of horizontal polarization and vertical polarization in the normal linear dynamic range of the radar through a quadratic fit curve determined when the station is out of the factory standard; the observation error correction is performed based on the observation error value determined by the external field calibration, so that the estimation accuracy of the differential reflectivity is improved.

Description

Time-frequency domain dual-polarized radar detection variable estimation method for staggered pulse repetition interval Technical Field The invention relates to the technical field of radar signal processing, in particular to a method for estimating detection variables of a staggered pulse repetition interval time-frequency domain dual-polarized radar. Background The traditional radar signal processing only adopts a single method of time domain correlation moment or frequency domain power spectral density, and has a plurality of technical bottlenecks: Time domain processing defects that an IIR filter can consume a meteorological signal and has no compensation basis, the performance is reduced due to the fact that the filter order is limited by a low sampling rate at a staggered pulse repetition interval, and blind quick response exists (useful meteorological signals are misjudged to be ground clutter); the frequency domain processing limitation is that under the staggered pulse repetition interval, the low sampling rate does not meet the sampling theorem, so that the sampling sample is wrong, and effective parameter statistics cannot be carried out; The core contradiction is that the single pulse repetition interval can not simultaneously give consideration to the 'no-blurring distance' and the 'no-blurring speed', but can be selected from two to one, and the actual detection requirement is difficult to meet. Disclosure of Invention The invention provides a method for estimating detection variables of a staggered pulse repetition interval time-frequency domain dual-polarized radar, which overcomes the principle contradictions of ground clutter interference, blind speed effect, insufficient sampling rate, non-fuzzy distance and speed in the traditional radar signal processing, realizes accurate estimation of multiple detection variables of the dual-polarized radar, ensures that an estimation result is not interfered by the ground clutter, adapts to two working modes of a single pulse repetition interval and a staggered pulse repetition interval, and improves the reliability and applicability of radar detection. In order to achieve the above purpose, the invention adopts the following technical scheme: A method for estimating detection variable of a spread pulse repetition interval time-frequency domain dual-polarized radar comprises the following steps: Acquiring a horizontal polarization complex baseband signal and a vertical polarization complex baseband signal output by a radar digital receiver, and performing discrete Fourier transform on the horizontal polarization complex baseband signal and the vertical polarization complex baseband signal respectively to acquire a horizontal polarization power spectral density and a vertical polarization power spectral density; Determining horizontal polarization noise power and vertical polarization noise power based on the horizontal polarization power spectral density and the vertical polarization power spectral density, and further calculating a horizontal polarization noise power estimated value and a vertical polarization noise power estimated value; respectively calculating echo average power of horizontal polarization and vertical polarization on each distance gate by using the horizontal polarization power spectral density and the vertical polarization power spectral density, and combining a horizontal polarization noise power estimated value and a vertical polarization noise power estimated value to obtain a horizontal polarization echo signal-to-noise ratio and a vertical polarization echo signal-to-noise ratio; calculating radar reflectivity factors and differential reflectivity based on echo average power, horizontal polarization echo signal-to-noise ratio and vertical polarization echo signal-to-noise ratio of horizontal polarization and vertical polarization on each range gate, and estimating average Doppler velocity and velocity spectrum width based on horizontal polarization power spectrum density and vertical polarization power spectrum density; Performing odd-even pulse high-pass filtering on the horizontal polarization complex baseband signal and the vertical polarization complex baseband signal respectively to remove ground clutter interference to obtain filtered odd-even pulses; carrying out normalization processing on the cross-correlation results of the odd-even pulses by using corresponding autocorrelation results, taking absolute values and then averaging to obtain correlation coefficients; Calculating the argument of the odd-even pulse cross-correlation result and averaging to obtain an initial differential propagation phase shift; performing continuous processing on the initial differential propagation phase shift to obtain a corrected differential propagation phase shift; And carrying out sliding average smoothing on the radar reflectivity factor, the differential reflectivity, the average Doppler speed and the velocity spectrum width, an