Three-dimensional wind field inversion method of coherent wind lidar

Abstract

The invention provides a three-dimensional wind field inversion method of a coherent wind lidar, and relates to the technical field of lidar wind measurement, and the method comprises the steps: building a mathematical model of a coherent wind lidar receiving echo signal, and determining an optimal target detection distance; under the optimal target detection distance, emitting a modulated laser detection signal to a target wind field, and processing echo signals which are received by a laser radar and are mixed at different frequencies to obtain an echo signal light field distribution condition; calculating the radial velocity of the wind in the wind field of the target based on the light field distribution condition of the echo signal; the elevation angle of the laser radar is fixed, the four orientations are scanned, radial wind speeds corresponding to the four orientations are obtained, the atmospheric three-dimensional wind field is inverted, and real-time atmospheric wind field three-dimensional detection with high temporal-spatial resolution and high wind measurement precision can be realized.

Description

Technical Field

[0001] The invention proposes a three-dimensional wind field inversion method of a coherent wind measurement laser radar, and relates to the technical field of wind field detection. Background Art

[0002] With the development of science and technology, LiDAR has been widely used in meteorological monitoring, environmental science and other fields due to its advantages such as high precision and fast response. Especially in wind speed measurement, LiDAR measures the speed of particles in the atmosphere by emitting light pulses and detecting the returned light signals. However, in actual application, due to the influence of environmental factors and the multiple frequency components that may exist in the echo signal, how to accurately determine the target detection distance and accurately process the echo signal has become an urgent problem to be solved.

[0003] Coherent wind laser radar has wide application value in many fields. For example, in meteorological observation, laser radar can provide accurate and reliable wind observation data to support meteorological forecasting and climate change research. In terms of aviation meteorological support, laser radar can monitor the changes in atmospheric wind field in real time, providing important guarantee for flight safety. In addition, laser radar can also be used in the fields of atmospheric pollution source tracing and diffusion forecasting, wind power system management and deployment. Coherent wind laser radar has the characteristics of high precision and high resolution, and can realize the observation of atmospheric parameters without blind spots from the ground to the height of the troposphere. This high precision and high resolution give laser radar a significant advantage in three-dimensional wind field observation. The detection range of laser radar is wide, covering the vertical wind profile of the atmosphere from the ground to about 10 kilometers. Coherent wind laser radar system usually adopts an integrated design, which is stable and reliable. At the same time, the built-in positioning module can automatically calibrate the wind direction to realize real-time and automatic wind field data processing and display. This makes laser radar have wide application value in meteorological observation, aviation meteorological support and other fields. It is particularly important to develop efficient and accurate atmospheric wind field detection technology, especially to improve the performance of wind measuring lidar, which is of great significance for deepening our understanding of atmospheric dynamics and effectively responding to climate change. Summary of the invention

[0004] The present invention proposes a three-dimensional wind field inversion method of a coherent wind laser radar, comprising the following steps:

[0005] S1. Establish a mathematical model for receiving echo signals of coherent wind laser radar to determine the optimal target detection distance;

[0006] S2. At the optimal target detection distance, the modulated laser detection signal is transmitted to the target wind field, and the echo signals mixed with different frequencies received by the laser radar are processed to obtain the light field distribution of the echo signal;

[0007] S3. Calculate the radial velocity of the wind in the target wind field based on the light field distribution of the echo signal;

[0008] S4. Fix the elevation angle of the laser radar, scan four directions, obtain the radial wind speeds corresponding to the four directions, and invert the three-dimensional wind field of the atmosphere.

[0009] Furthermore, in step S1: the mathematical model of the received echo signal is constructed as follows:

[0010] ;

[0011] Among them, P S (R) is the received echo signal power, is the laser radar transmitting signal power, Ar is the laser radar effective receiving area, is the laser radar receiving efficiency, E T is the pulse energy of the laser radar signal, β is the wind field scattering coefficient, c is the speed of light, R is the detection distance, and T(R) is the wind field attenuation function.

[0012] Furthermore, in step S1, the detection distance corresponding to when the echo signal power is the minimum detection power of the coherent wind laser radar is selected as the optimal target detection distance.

[0013] Furthermore, in step S2, the expression of the light field u0 of the baseband signal emitted by the laser radar is:

[0014] ;

[0015] Among them, E0 is the amplitude of the baseband signal, f0 is the center frequency of the baseband signal, is the initial phase of the baseband signal, and t is the time.

[0016] Furthermore, the baseband signal of the signal emitted by the laser radar is modulated by a modulator into an intermediate frequency pulse light signal output, and the pulse frequency of the output intermediate frequency pulse light signal is f0+f m , where f m is the modulated offset frequency, and the light field u of the intermediate frequency pulse light signal output after modulation is m The expression is:

[0017] ;

[0018] Among them, E m is the amplitude of the intermediate frequency pulse optical signal, is the phase of the intermediate frequency pulse optical signal.

[0019] Furthermore, the frequency deviation of the optical signal caused by the wind field is f d , get the echo signal light field u rThe expression is:

[0020] ;

[0021] Among them, E r is the amplitude of the echo signal, is the phase of the echo signal.

[0022] Furthermore, in step S3, the frequency deviation f of the optical signal caused by the wind field d The radial velocity v of the wind in the wind field of the target r The relationship is:

[0023] ;

[0024] Where, λ is the wavelength of the optical signal;

[0025] Substitute the above formula into the echo signal light field u r The expression of the echo signal light field u is obtained r The radial velocity v of the wind in the wind field r The relationship is:

[0026] ;

[0027] According to the echo signal light field u r The peak value of the distribution, the amplitude and phase of the echo signal, and the pulse frequency f0+f of the intermediate frequency pulse light signal m , the radial velocity of the wind in the target wind field is calculated.

[0028] Further, in step S3, the coherent wind laser radar is used at the zenith angle , azimuth angle θ, scan in four directions to obtain radial wind speeds in four directions, and synthesize and invert horizontal wind speed, horizontal wind direction and vertical airflow. Let V A 、V B 、V C 、V D are four radial wind speeds, u and v represent the components of the horizontal wind speed on the x-axis and y-axis respectively, and w represents the wind speed in the vertical direction. The relationship between the three-dimensional atmospheric wind field and the measured radial wind speeds in the four directions is:

[0029] .

[0030] Furthermore, the echo signal is correlated with the baseband signal:

[0031] According to the echo signal light field u r The peak value E1 of the distribution is input into the photoelectric filter, and the output filtered current intensity I0 is obtained, which is expressed as:

[0032]

[0033] Among them, R1 represents the filter responsivity, E s represents the amplitude of the baseband signal, δ represents the modulation phase of the signal light, γ represents the line width of the laser, and μ represents the phase noise caused by the frequency offset. The signal corresponding to the current intensity I0 is digitized to obtain the signal amplitude E0.

[0034] Furthermore, the signal amplitude E0 is substituted for E in the following formula: r :

[0035]

[0036] get:

[0037]

[0038] The radial velocity of the wind in the wind field at the target position is measured according to the peak value, signal amplitude E0 and phase of the distribution of the filtered echo signal light field u0 and the pulse frequency of the intermediate frequency pulse light signal.

[0039] Compared with the prior art, the present invention has the following beneficial technical effects:

[0040] Improve data inversion accuracy: By establishing a mathematical model for the coherent wind lidar to receive echo signals, the optimal target detection distance can be determined more accurately, thereby improving the measurement accuracy of wind speed and direction, and improving the data inversion accuracy under low signal-to-noise ratio conditions.

[0041] Enhanced detection capability: Emitting modulated laser detection signals at the optimal target detection distance can more effectively process the mixed echo signals of different frequencies received by the lidar, thereby obtaining a more accurate distribution of the light field of the echo signals.

[0042] Achieve fast inversion: Based on the light field distribution of the echo signal, the radial velocity in the target wind field can be quickly calculated, which is particularly important for application scenarios that require real-time or near-real-time wind field data.

[0043] Provide comprehensive wind field information: By fixing the elevation angle of the lidar and scanning in four directions, the radial wind speeds corresponding to the four directions can be obtained, thereby inverting the three-dimensional wind field of the atmosphere, providing more comprehensive wind field information, including the size and direction of the wind speed, as well as the spatial structure of the wind field.

[0044] It improves the stability and reliability of wind field detection, improves the real-time performance of wind field inversion, and enables rapid response to weather forecasts. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative labor.

[0046] Figure 1 This is an exemplary schematic diagram of a coherent wind laser radar carrying platform.

[0047] Figure 2 This is a flow chart of the three-dimensional wind field inversion method of the coherent wind laser radar of the present invention.

[0048] Figure 3 This is a curve showing the relationship between the received echo signal power and the detection distance of the present invention.

[0049] Figure 4 It is a schematic diagram of the inverted wind speed in the atmospheric wind field according to the present invention.

[0050] Figure 5 It is a schematic diagram of wind profile distribution of the present invention. DETAILED DESCRIPTION

[0051] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0052] In the drawings of the specific embodiments of the present invention, in order to better and more clearly describe the working principles of the various components in the system, the connection relationship of the various parts in the device is shown, which only clearly distinguishes the relative position relationship between the various components, and cannot constitute a limitation on the signal transmission direction, connection sequence and size, dimensions and shape of the components or structures.

[0053] Wind LiDAR is a device that uses Light Detection And Ranging (LiDAR) technology to measure wind speed and direction. It is often used in meteorology to obtain accurate atmospheric wind field data. The core of the working principle of wind LiDAR is to use coherent detection technology to analyze the laser signal returned from atmospheric scattered particles.

[0054] A coherent wind measurement lidar carrying platform is established, which includes: pulse laser, optical system, laser transceiver, transmission scanning mirror, electrical signal detector, and A / D converter.

[0055] The pulsed laser is the core component of the platform, which is used to emit high-energy laser pulses. Preferably, the Q-switched laser is a laser that obtains high peak power and narrow pulse width laser pulses. It suppresses the generation of laser oscillation by reducing the Q value of the resonant cavity at the beginning of optical pumping, and then suddenly increases the Q value to release the accumulated energy, thereby obtaining a laser pulse output with extremely high peak power. This laser can be used in coherent wind laser radar to achieve high-precision wind speed and wind direction measurement.

[0056] The optical system is responsible for focusing the emitted laser beam and receiving the laser signal scattered back by the wind field. It includes components such as lenses, narrow-band filters and beam splitters. The narrow-band filter is used to control the scattered laser signal received, filter out stray light, and ensure that the laser signal received by the sensor is accurate.

[0057] Laser transceiver: responsible for the emission and reception of laser beams, with stable tracking and pointing capabilities, including laser modulators and beam controllers to control the direction and number of lines of emitted lasers. Preferably, a telescope is used to receive echo signals.

[0058] Transmission type scanning mirror is used to adjust the emission direction of the laser beam to achieve multi-directional wind speed measurement. This scanning mirror can quickly change the direction of the laser beam to cover different spatial areas and measure wind speed and direction.

[0059] Detector: Converts the reflected signal into an analog electrical signal to improve the measurement sensitivity. The detector is usually very sensitive and can detect very weak light signals and convert them into electrical signals.

[0060] A / D converter is used to convert analog electrical signals into digital signals for subsequent processing. A / D converter is a circuit that converts analog signals that are continuous in time and amplitude into digital signals that are discrete in time and amplitude. It usually includes the steps of sampling, quantization and encoding.

[0061] Data processor: processes and analyzes the digital signal output by the A / D converter and calculates parameters such as wind speed and direction.

[0062] like Figure 1 Shown is an exemplary schematic diagram of a coherent wind measurement lidar carrying platform.

[0063] Embodiment 1:

[0064] The wind laser radar of this embodiment uses coherent detection technology to detect the echo signal light field u rThe peak value of the distribution, the amplitude and phase of the echo signal, and the pulse frequency of the intermediate frequency pulse light signal are measured to measure the radial velocity of the wind in the wind field at the target location. Laser pulses are emitted toward the atmosphere in different directions in turn to calculate the three-dimensional wind field motion information of the atmosphere and perform three-dimensional wind field inversion.

[0065] like Figure 2 The flowchart of the three-dimensional wind field inversion method of the coherent wind laser radar according to the first embodiment of the present invention is shown. The three-dimensional wind field inversion method comprises:

[0066] S1. Establish a mathematical model for the coherent wind laser radar to receive echo signals and determine the optimal target detection distance.

[0067] According to the working principle of coherent wind laser radar, a mathematical model for receiving echo signals is established. The mathematical model for receiving echo signals takes into account parameters such as laser detection distance, signal pulse energy, wind field attenuation function, and wind field scattering coefficient, and is used to describe the relationship between the power of the laser signal reflected from the target wind field and the change of the laser detection distance.

[0068] The mathematical model of the received echo signal is constructed as follows:

[0069] ;

[0070] Among them, P S (R) is the received echo signal power, is the laser radar transmitting signal power, Ar is the laser radar effective receiving area, is the laser radar receiving efficiency, E T is the pulse energy of the laser radar signal, β is the wind field scattering coefficient, c is the speed of light, and R is the detection distance.

[0071] T(R) is the wind field attenuation function. Since the laser beam will attenuate when propagating in the wind field, the wind field attenuation function T(R) describes the degree to which the power of the laser beam decreases with increasing distance. The wind field attenuation function obeys the exponential law.

[0072] like Figure 3 The figure shows the relationship between the received echo signal power and the detection distance. It can be seen that the relationship between the echo signal power and the detection distance is usually inversely proportional, because as the distance increases, the signal energy will gradually weaken due to scattering and absorption in the air. Therefore, the shorter the detection distance, the stronger the echo signal power. In order to achieve a long detection distance, it is preferred to select the detection distance corresponding to the minimum detection power of the coherent wind laser radar as the optimal target detection distance for the subsequent steps.

[0073] S2. At the optimal target detection distance, the modulated laser detection signal is emitted to the target wind field, and the echo signals mixed with different frequencies received by the laser radar are processed to obtain the light field distribution of the echo signal.

[0074] The laser radar transmits a baseband signal and receives an echo signal. The emitted baseband signal is modulated to obtain an intermediate frequency pulse light signal. The intermediate frequency pulse light signal is introduced with a modulation offset frequency and then emitted into the atmosphere. The wind speed will cause a frequency deviation of the light signal, so the received echo signal includes the center frequency of the baseband signal, the modulation offset frequency and the deviation frequency.

[0075] The expression of the light field u0 of the baseband signal emitted by the laser radar is:

[0076] ;

[0077] Among them, E0 is the amplitude of the baseband signal, f0 is the center frequency of the baseband signal, is the initial phase of the baseband signal, and t is the time.

[0078] The baseband signal of the laser radar is modulated into an intermediate frequency pulse light signal through a modulator. The pulse frequency of the output intermediate frequency pulse light signal is f0+f m , where f m is the modulated offset frequency, and the light field u of the intermediate frequency pulse light signal output after modulation is m The expression is:

[0079] ;

[0080] Among them, E m is the amplitude of the intermediate frequency pulse optical signal, is the phase of the intermediate frequency pulse optical signal.

[0081] Frequency deviation f of optical signal caused by wind field d , we can get the echo signal light field u r The expression is:

[0082] ;

[0083] Among them, E r is the amplitude of the echo signal, is the phase of the echo signal.

[0084] In practical applications, the following aspects should also be noted:

[0085] Phase unwrapping: In some cases, the phase variation may exceed the range of 2π, leading to the problem of phase unwrapping, which needs to be resolved.

[0086] Signal Processing: The signal processing algorithm needs to be able to accurately extract the frequency offset from the received signal.

[0087] System Calibration: Regularly calibrate the system to ensure the accuracy of the baseband signal and modulation offset frequency.

[0088] Environmental influence: Considering the influence of atmospheric conditions (such as temperature, humidity, air pressure, etc.) on the propagation of optical signals, appropriate compensation is required.

[0089] S3. Calculate the radial velocity of the wind in the target wind field based on the light field distribution of the echo signal.

[0090] Assuming that the radial velocity of the wind in the wind field remains unchanged, when the wind field moves toward the lidar, the frequency of the received echo signal increases; conversely, when the wind field moves away from the lidar, the frequency of the echo signal decreases.

[0091] Frequency deviation f of the optical signal caused by the wind field d The relationship between the radial velocity of the wind in the target wind field is:

[0092] ;

[0093] λ is the wavelength of the optical signal. Substitute the above formula into the echo signal light field u r The expression of the echo signal light field u can be obtained r The relationship with the radial velocity of the wind in the wind field is:

[0094] ;

[0095] Therefore, according to the echo signal light field u r The peak value of the distribution, the amplitude and phase of the echo signal, and the pulse frequency f0+f of the intermediate frequency pulse light signal m , the radial velocity of the wind in the wind field at the target location can be measured, that is, the speed at which the wind in the wind field at the target location moves away from or approaches the direction of the lidar.

[0096] S4. Fix the elevation angle of the laser radar, scan four directions, obtain the radial wind speeds corresponding to the four directions, and invert the three-dimensional wind field of the atmosphere.

[0097] The process of scanning four different azimuths by fixing the elevation angle of the lidar to obtain radial wind speeds at different azimuths is called three-dimensional wind field inversion.

[0098] like Figure 4 As shown, the coherent wind lidar uses the zenith angle , azimuth angle θ to scan in four directions, obtain radial wind speed in four directions, and synthesize and invert horizontal wind speed, horizontal wind direction and vertical airflow. A 、V B、V C 、V D They are Figure 4 The four radial wind speeds measured along the directions of OA, OB, OC, and OD, u and v represent the components of the horizontal wind speed on the x-axis and y-axis respectively, and w represents the wind speed in the vertical direction. The relationship between the three-dimensional atmospheric wind field and the radial wind speeds in the four directions is:

[0099] ;

[0100] .

[0101] The atmospheric wind field is a three-dimensional vector field with the characteristics of time and space. In order to fully describe the instantaneous wind field at a certain location, in the specific application process, it is necessary to measure the three vector components of the wind field, namely u (east wind speed), v (north wind speed) and w (vertical wind speed).

[0102] By using a lidar system and scanning at different azimuth angles, radial wind speed data in different directions is obtained, and the three-dimensional wind field is inverted and reconstructed.

[0103] Setting the elevation angle of the lidar to remain constant means that the laser beam will be emitted along a fixed tilt angle. Four different azimuth angles (e.g., 0°, 90°, 180°, 270°) are scanned to cover different horizontal directions.

[0104] At each set azimuth, the lidar emits laser pulses and receives echo signals. The radial wind speed in each direction is calculated through the echo signals. For each scanning direction, the corresponding radial wind speed, elevation angle and azimuth angle in each direction are recorded to reconstruct the three-dimensional wind field.

[0105] Embodiment 2:

[0106] By calculating the corresponding radial wind speed in each direction and combining the radial wind speed in different scanning directions, a three-dimensional vector wind field is synthesized to obtain the corresponding wind profile distribution.

[0107] The radial wind speed v in each direction i ri Converted into three components in the Cartesian coordinate system (v x ,v y ,v z ), assuming that the laser radar is located at the origin of the coordinate system, the following conversion formula can be used:

[0108]

[0109]

[0110]

[0111] in: is the pitch angle in direction i, is the azimuth in direction i.

[0112] Through the above conversion, the three components of the radial wind speed in each direction i can be obtained. Then, these components are combined to form a three-dimensional vector wind field. Furthermore, the three components of the radial wind speed in each direction i can be put into a three-dimensional grid to obtain a three-dimensional vector wind field, and the wind profile distribution can be extracted from it. The wind profile refers to the change of wind speed with height, usually expressed as the average wind speed distribution in the vertical direction, which can be achieved by calculating the average wind speed at different height layers. Figure 5 The figure shows the wind profile distribution diagram. The horizontal and vertical coordinates represent longitude and latitude, and the color represents the wind speed.

[0113] Embodiment 3:

[0114] The echo signal is correlated with the baseband signal, and the noise elimination performance of the system is improved by summing up multiple measurement results.

[0115] Specifically, according to the echo signal light field u r The peak value E1 of the distribution is input into the photoelectric filter, and the output filtered current intensity I0 is obtained, which is expressed as:

[0116]

[0117] Among them, R1 represents the filter responsivity, E s represents the amplitude of the fundamental frequency signal, δ represents the modulation phase of the signal light, γ represents the line width of the laser, and μ represents the phase noise caused by the frequency offset.

[0118] After digitizing the signal corresponding to the current intensity I0, a clearer signal amplitude E0 is obtained, and the signal amplitude is displayed in a graphical manner, such as a waveform diagram, a spectrum diagram, etc., for easy observation and analysis.

[0119] Furthermore, the signal amplitude E0 is substituted for E in the following formula: r :

[0120]

[0121] get:

[0122]

[0123] Therefore, according to the peak value, signal amplitude E0 and phase of the distribution of the filtered echo signal light field u0 and the pulse frequency f0+f m, the radial velocity of the wind in the wind field at the target location can be measured, that is, the speed at which the wind in the wind field at the target location moves away from or approaches the direction of the lidar.

[0124] In one embodiment, a computer device is further provided, including a memory and a processor, wherein a computer program is stored in the memory, and the processor implements the steps in the above method embodiments when executing the computer program.

[0125] In one embodiment, a computer-readable storage medium is provided, storing a computer program, which implements the steps in the above method embodiments when executed by a processor.

[0126] In one embodiment, a computer program product or computer program is provided, the computer program product or computer program includes computer instructions, the computer instructions are stored in a computer-readable storage medium. A processor of a computer device reads the computer instructions from the computer-readable storage medium, and the processor executes the computer instructions, so that the computer device performs the steps in the above-mentioned method embodiments.

[0127] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to the memory, database or other medium used in the embodiments provided in this application may include at least one of non-volatile and volatile memory. The database involved in the embodiments provided in this application may include at least one of a relational database and a non-relational database. Non-relational databases may include distributed databases based on blockchains, etc., but are not limited thereto. The processors involved in the embodiments provided in this application may be general-purpose processors, central processing units, graphics processors, digital signal processors, programmable logic devices, data processing logic devices based on quantum computing, etc., but are not limited thereto.

[0128] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0129] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be construed as limiting the scope of the present application. It should be noted that, for a person of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A three-dimensional wind field inversion method using a coherent wind laser radar, characterized in that: The steps include: S1. Establish a mathematical model for receiving echo signals of coherent wind laser radar to determine the optimal target detection distance; S2. At the optimal target detection distance, the modulated laser detection signal is transmitted to the target wind field, and the echo signals mixed with different frequencies received by the laser radar are processed to obtain the light field distribution of the echo signal; S3. Calculate the radial velocity of the wind in the target wind field based on the light field distribution of the echo signal; S4. Fix the elevation angle of the laser radar, scan four directions, obtain the radial wind speeds corresponding to the four directions, and invert the three-dimensional wind field of the atmosphere.

2. The three-dimensional wind field inversion method of the coherent wind laser radar according to claim 1 is characterized in that: In step S1: the mathematical model of the received echo signal is constructed as follows: ； Among them, P S (R) is the received echo signal power, is the laser radar transmitting signal power, Ar is the laser radar effective receiving area, is the laser radar receiving efficiency, E T is the pulse energy of the laser radar signal, β is the wind field scattering coefficient, c is the speed of light, R is the detection distance, and T(R) is the wind field attenuation function.

3. The three-dimensional wind field inversion method of the coherent wind laser radar according to claim 2 is characterized in that: In step S1, the detection distance corresponding to the minimum detection power of the coherent wind laser radar when the echo signal power is selected as the optimal target detection distance.

4. The three-dimensional wind field inversion method of the coherent wind laser radar according to claim 3, characterized in that: In step S2, the expression of the light field u0 of the baseband signal emitted by the laser radar is: ； Among them, E0 is the amplitude of the baseband signal, f0 is the center frequency of the baseband signal, is the initial phase of the baseband signal, and t is the time.

5. The three-dimensional wind field inversion method of the coherent wind laser radar according to claim 4, characterized in that: The baseband signal of the laser radar is modulated into an intermediate frequency pulse light signal through a modulator. The pulse frequency of the output intermediate frequency pulse light signal is f0+f m , where f m is the modulated offset frequency, and the light field u of the intermediate frequency pulse light signal output after modulation is m The expression is: ； Among them, E m is the amplitude of the intermediate frequency pulse optical signal, is the phase of the intermediate frequency pulse optical signal.

6. The three-dimensional wind field inversion method of the coherent wind laser radar according to claim 5, characterized in that: The frequency deviation of the optical signal caused by the wind field is f d , get the echo signal light field u r The expression is: ； Among them, E r is the amplitude of the echo signal, is the phase of the echo signal.

7. The three-dimensional wind field inversion method of the coherent wind laser radar according to claim 6, characterized in that: In step S3, the frequency deviation f of the optical signal caused by the wind field d The radial velocity v of the wind in the wind field of the target r The relationship is: ； Where, λ is the wavelength of the optical signal; Substitute the above formula into the echo signal light field u r The expression of the echo signal light field u is obtained r The radial velocity v of the wind in the wind field r The relationship is: ； According to the echo signal light field u r The peak value of the distribution, the amplitude and phase of the echo signal, and the pulse frequency f0+f of the intermediate frequency pulse light signal m , the radial velocity of the wind in the target wind field is calculated.

8. The three-dimensional wind field inversion method of the coherent wind laser radar according to claim 7, characterized in that: In step S3, the coherent wind laser radar is used at the zenith angle , azimuth angle θ, scan in four directions to obtain radial wind speeds in four directions, and synthesize and invert horizontal wind speed, horizontal wind direction and vertical airflow. Let V A 、V B 、V C 、V D are four radial wind speeds, u and v represent the components of the horizontal wind speed on the x-axis and y-axis respectively, and w represents the wind speed in the vertical direction. The relationship between the three-dimensional atmospheric wind field and the measured radial wind speeds in the four directions is: 。 9. The three-dimensional wind field inversion method of the coherent wind laser radar according to claim 7, characterized in that: Perform correlation operation on the echo signal and the baseband signal: According to the echo signal light field u r The peak value E1 of the distribution is input into the photoelectric filter, and the output filtered current intensity I0 is obtained, which is expressed as: ； Among them, R1 represents the filter responsivity, E s represents the amplitude of the baseband signal, δ represents the modulation phase of the signal light, γ represents the line width of the laser, and μ represents the phase noise caused by the frequency offset. The signal corresponding to the current intensity I0 is digitized to obtain the signal amplitude E0.

10. The three-dimensional wind field inversion method of the coherent wind laser radar according to claim 9, characterized in that: Replace the signal amplitude E0 with E in the following formula r : ； get: ； The radial velocity of the wind in the wind field at the target position is measured according to the peak value, signal amplitude E0 and phase of the distribution of the filtered echo signal light field u0 and the pulse frequency of the intermediate frequency pulse light signal.

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