Intermediate frequency self-calibration method and device of wind measurement laser radar and storage medium

Abstract

The invention discloses an intermediate frequency self-calibration method and device for a wind measurement laser radar and a storage medium, and the method comprises the following steps: S1, a data collection system of a pulse laser wind measurement radar collects atmosphere return light signals, and forms a plurality of pulse signal sequences xi = {a0, a1,... am}, and the atmosphere return light signals comprise a signal sampling rate of mHz and a pulse repetition frequency of n; s2, according to the return light signals, a blind area segment in a pulse signal sequence xi = {a0, a1,... am} is searched, and am represents m return light signal data; compared with the prior art, the method uses the return light signal of the pulse laser radar to find the return light signal of the blind area section of the radar; the signals in the blind area are used for power spectrum estimation to obtain the intermediate frequency of the laser radar, so that the function of intermediate frequency self-calibration is achieved, and the fixed intermediate frequency after one-time calibration before delivery is avoided.

Description

Technical Field

[0001] The present invention relates to the field of radar speed measurement, and in particular to a medium frequency self-calibration method, a device and a storage medium for a wind measuring laser radar. Background Art

[0002] Pulse laser wind radar is a device that uses laser technology to measure wind speed and direction. Its core principle is based on the Doppler effect. When a laser light source emits light waves to a moving target (such as aerosol particles in the atmosphere), the frequency of the returning light waves will change due to the movement of the target. By measuring this frequency change, the size and direction of the wind speed can be accurately calculated. It has the characteristics of high time and space resolution. Therefore, laser wind radar is widely used in weather forecast research and wind energy evaluation.

[0003] Since pulsed laser radar uses Doppler frequency shift to calculate wind speed, in order to distinguish the direction of wind speed, in the actual laser radar design process, it is necessary to use an acousto-optic frequency shifter to make the local oscillator laser and the emitted pulse laser have a fixed frequency shift, namely the intermediate frequency, which is used to eliminate the ambiguity of the frequency shift direction of the return signal, thereby determining the direction of wind speed.

[0004] Since the wind speed frequency detected by the laser wind radar is the result of the return light beating the local oscillator laser frequency minus the intermediate frequency, whether the intermediate frequency of the pulse laser radar is correct will affect the accuracy of the wind speed measurement. At present, the method for determining the intermediate frequency of the pulse laser radar is to use a spectrum analyzer to measure the frequency of the acousto-optic modulator before leaving the factory.

[0005] As optical devices age and decay over time, and environmental changes can cause frequency deviation in the optical devices, the radar intermediate frequency will shift, thus affecting the measurement accuracy of wind speed. Summary of the invention

[0006] The purpose of the present invention is to propose a self-calibration method, device and storage medium for the intermediate frequency of a wind measuring laser radar to address the problem that the intermediate frequency of the existing radar will shift after long-term use, thereby affecting the measurement accuracy of the wind speed.

[0007] In order to achieve the above object, the present invention adopts the following technical solution:

[0008] A medium frequency self-calibration method for a wind laser radar comprises the following steps:

[0009] S1. The data acquisition system of the pulsed laser wind radar collects atmospheric echo signals to form several pulse signal sequences x i ={a0,a1,…a m}, the atmospheric echo signal includes: a signal sampling rate of mHz, a pulse repetition frequency of n;

[0010] S2. Find the pulse signal sequence x according to the echo signal i ={a0,a1,…a m} in the blind section, a m Indicates the mth return light signal data;

[0011] S3, calculating the blind spot frequency based on the sliding Fourier transform power spectrum;

[0012] S4. According to

[0013] where f d is the Doppler shift, λ is the wavelength, f is the frequency detected by the pulse laser radar through the spectrum, and the center frequency of the radar

[0014] As a further preferred embodiment of the present invention, S2 includes:

[0015] S21, according to y i =abs(x i ), calculate the absolute value y of each pulse return signal i ;

[0016] S22, take the absolute value of the pulse signal sequence x i Perform sliding average to obtain the smoothed signal s i ; The sliding average window is the pulse width N;

[0017] S23. According to The smoothed signal of n pulse signals is averaged s avg ;

[0018] S24. Find the mean s avg The position index of the maximum amplitude of the sequence, the middle point j of the blind zone signal, then the signal of the blind zone is The pulse return signal selects the blind section

[0019] As a further preferred embodiment of the present invention, S3 includes:

[0020] S31, performing sliding windowing processing on the signal of the blind section based on the Hanning window function; obtaining the blind section signal H after sliding windowing t ;

[0021] S32, based on sliding window Fourier transform, the signal H of the blind section after windowing t Calculate the power spectrum to get the center frequency of the radar

[0022] A medium frequency self-calibration device for a wind laser radar, the device comprising one or more processors and a memory, the memory being used to store one or more programs; when the one or more programs are executed by the processor, the processor is enabled to implement the medium frequency self-calibration method for a wind laser radar.

[0023] A computer storage medium stores at least one program instruction, and the at least one program instruction is used to be loaded and executed by a processor to implement the intermediate frequency self-calibration method of a wind laser radar.

[0024] The intermediate frequency self-calibration method, device and storage medium of a wind laser radar proposed in the present invention have the following beneficial effects compared with the prior art:

[0025] 1. Use the return light signal of the pulse laser radar itself to find the return light signal of the blind area of ​​the radar; use the signal in the blind area to perform power spectrum estimation to obtain the intermediate frequency of the laser radar, thereby obtaining the function of intermediate frequency self-calibration, avoiding the fixed intermediate frequency after a one-time calibration before leaving the factory;

[0026] 2. In order to avoid the influence of wind measurement signal on intermediate frequency signal, sliding Fourier transform is used to obtain power spectrum, and Gaussian fitting method is used to obtain intermediate frequency, which improves the accuracy of intermediate frequency signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the process of the present invention;

[0028] Figure 2 This is the pulse laser radar echo signal diagram. DETAILED DESCRIPTION

[0029] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0030] The present invention uses the laser radar's own return light signal to calibrate the intermediate frequency of the laser wind radar in real time, and secondly, there is no need to use a spectrum analyzer to measure the radar frequency, thereby simplifying the production process. The present invention collects the laser radar's pulse signal for analysis, so as to calibrate the intermediate frequency of the pulse laser radar in real time.

[0031] Pulse laser radar uses the continuous laser signal generated by the laser seed light source to split the optical signal into two paths through a beam splitter. One path is passed through an acousto-optic modulator and an amplifier to produce a pulse signal with an intermediate frequency; the other path is a high-coherence continuous intrinsic laser, which is used to mix with the pulse laser and the return light signal to produce a heterodyne signal.

[0032] Embodiment 1: Combination Figure 1-Figure 2Since the pulse wind laser radar has a fixed pulse width, the receiving system has a certain detection blind spot, and the frequency signal in the blind spot is the intermediate frequency signal of the pulse laser radar. The present invention achieves the effect of intermediate frequency self-calibration of the wind laser radar by analyzing the frequency information in the blind spot.

[0033] The specific steps include:

[0034] S1. The data acquisition system of the pulsed laser wind radar collects atmospheric echo signals to form several pulse signal sequences x i ={a0,a1,…a m}, the atmospheric echo signal includes: the signal sampling rate is mHz, and the pulse repetition frequency is n.

[0035] S2. Find the pulse signal sequence x according to the echo signal i ={a0,a1,…a m} in the blind section, a m Indicates the mth return light signal data.

[0036] S21, according to y i =abs(x i ), calculate the absolute value y of each pulse return signal i ;y i =|x i |={|a0|,|a1|,…|a m |}.

[0037] S22, take the absolute value of the pulse signal sequence x i Perform sliding average to obtain the smoothed signal s i ; The sliding average window is the pulse width N.

[0038] S23. According to The smoothed signal of n pulse signals is averaged s avg .

[0039] S24. Find the mean s avg The position index of the maximum amplitude of the sequence, that is, to find s avg The maximum value is the number of the pulse signal sequence, and the middle point j of the blind zone signal, then the signal of the blind zone is The pulse return signal selects the blind section

[0040] S3. Calculate the blind zone frequency based on the sliding Fourier transform power spectrum.

[0041] During the actual wind measurement process, the wind speed will bring Doppler frequency shift along with the aerosol. For the pulse echo signal, the Doppler frequency shift brought by the wind speed will leak into the blind area signal. Therefore, when using the power spectrum to calculate the blind area frequency, it is necessary to shield the leaked Doppler frequency shift. The main method is to use sliding Fourier transform to calculate the frequency in the blind area.

[0042] S31, performing sliding windowing processing on the signal of the blind section based on the Hanning window function; obtaining the blind section signal H after sliding windowing t ;

[0043] H t (r) = h t (r)*W(r),

[0044] in, The window function used is the Hanning window function, and its formula is Where W(r) is the value of the window function at r, r is the sample point index in the window, starting from 0, and Windows is the length of the window. In this implementation case, the length of the window function Windows = Nt, and the blind area signal after windowing is H t (r)=d(r)*W(r), t is the tth blind section, r is the rth data point in the blind section,

[0045] S32, based on sliding window Fourier transform, the signal H of the blind section after windowing t Calculate the power spectrum to get the center frequency of the radar

[0046] Perform sliding window Fourier transform on the blind area signal after windowing. The Fourier transform formula is: in You can use F m (k) Calculate the power spectrum. The calculation formula for the power spectrum is spec m =|F m (k)| 2 , the power spectra of t signals {spec1,spec m ,…spec t} Calculate the mean spec avg , look for spec avg The frequency with the maximum amplitude is the intermediate frequency of the radar itself. avg Maximum amplitude amp max The frequency is taken as the center frequency f0, and it is widened to the left and right by p Hz to obtain a frequency band near the center frequency of x hz =[f0-p,f0+p], and obtain the amplitude y of its frequency band amp, x hz With y amp Perform Gaussian fitting, the Gaussian fitting formula is Where a is the amplitude point, b is the center frequency, and c is the pulse width. By using x hz The corresponding amplitude point y amp The amplitude y′ after Gaussian fitting amp , the maximum amplitude point max(y′ amp ) corresponds to the frequency This is the center frequency of the radar we require. The wind speed sampling of each telescope channel of the wind laser radar is zHz, so the final The frequency of change is also consistent with the sampling rate of each channel, which is zHz.

[0047] S4. According to where f d is the Doppler shift, λ is the wavelength, f is the frequency detected by the pulse laser radar through the spectrum; this frequency includes the intermediate frequency of the radar, so when the present invention is used to calculate the wind speed, the intermediate frequency of the radar will be self-calibrated in real time. This ensures the accuracy of the calculated wind speed.

[0048] Embodiment 2: A medium-frequency self-calibration device for a wind-measuring laser radar, the device comprising one or more processors and a memory, the memory being used to store one or more programs; when the one or more programs are executed by the processor, the processor is enabled to implement the medium-frequency self-calibration method for a wind-measuring laser radar.

[0049] Embodiment 3: A computer storage medium, wherein at least one program instruction is stored in the computer storage medium, and the at least one program instruction is used to be loaded and executed by a processor to implement the intermediate frequency self-calibration method of a wind laser radar.

[0050] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the above embodiments do not limit the present invention in any form, and any technical solution obtained by equivalent replacement or equivalent transformation falls within the protection scope of the present invention.

Claims

1. A medium frequency self-calibration method for a wind laser radar, characterized in that: The following steps are involved: S1. The data acquisition system of the pulsed laser wind radar collects atmospheric echo signals to form several pulse signal sequences x i ={a0,a1,…a m }, the atmospheric echo signal includes: a signal sampling rate of mHz, a pulse repetition frequency of n; S2. Find the pulse signal sequence x according to the echo signal i ={a0,a1,…a m } in the blind section, a m Indicates the mth return light signal data; S3, calculating the blind spot frequency based on the sliding Fourier transform power spectrum; S4. According to where f d is the Doppler shift, λ is the wavelength, f is the frequency detected by the pulse laser radar through the spectrum, and the center frequency of the radar 2. The intermediate frequency self-calibration method of a wind laser radar according to claim 1, characterized in that: The S2 includes: S21, according to y i =abs(x i ), calculate the absolute value y of each pulse return signal i ; S22, take the absolute value of the pulse signal sequence x i Perform sliding average to obtain the smoothed signal s i ; The sliding average window is the pulse width N; S23. According to The smoothed signal of n pulse signals is averaged s avg ; S24. Find the mean s avg The position index of the maximum amplitude of the sequence, the middle point j of the blind zone signal, then the signal of the blind zone is The pulse return signal selects the blind section 3. The intermediate frequency self-calibration method of a wind laser radar according to claim 1, characterized in that: The S3 includes: S31, performing sliding windowing processing on the signal of the blind section based on the Hanning window function; obtaining the blind section signal H after sliding windowing t ; S32, based on sliding window Fourier transform, the signal H of the blind section after windowing t Calculate the power spectrum to get the center frequency of the radar 4. A medium frequency self-calibration device for a wind laser radar, characterized in that: The device includes one or more processors and a memory, wherein the memory is used to store one or more programs; when the one or more programs are executed by the processor, the processor is enabled to implement the intermediate frequency self-calibration method for a wind measuring laser radar as described in any one of claims 1 to 3.

5. A computer storage medium, characterized in that: The computer storage medium stores at least one program instruction, and the at least one program instruction is used to be loaded and executed by the processor to implement the intermediate frequency self-calibration method of a wind measuring laser radar as described in any one of claims 1 to 3.

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