A wind-measuring laser radar

Abstract

The present invention provides a wind laser radar, which is characterized by comprising: a transmitting part for generating a continuous modulated wave and adjusting the modulation frequency of the modulated wave; a transceiver system for transmitting a light source to a target and receiving an echo signal of the target; and a detection and processing part for obtaining wind field information according to the received echo signal and the transmitted continuous modulated light, and determining the adjustment amount of the modulation frequency of the Nth frame according to the intermediate frequency of at least the previous frame. The resolution can be improved, a better resolution can be obtained, the bandwidth of the receiving unit can be reduced, and the amount of data can be reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of wind measurement radars, and more particularly, to a method for adaptively adjusting the frequency of a wind measurement lidar. Background Art

[0002] Currently, the basic working mode of a wind measurement radar is to track a rising and drifting balloon by transmitting a pulsed wave and receiving the pulsed wave returned from the target, and thereby measure the movement trajectory of the balloon in space to determine the wind direction and horizontal wind speed of the free atmosphere at various altitudes.

[0003] A reflector target, which is an object that can effectively reflect radio waves, is suspended under the balloon. The distance of the balloon is determined according to the time when the radar receives the echo signal. A radar working in this way is called a primary radar. When a transponder is suspended under the balloon, after receiving the radio pulse emitted by the radar, it immediately emits a response pulse, and the radar determines the distance of the balloon according to the time when it receives the response pulse. A radar working in this way is called a secondary radar.

[0004] A wind measurement radar can automatically track a radiosonde balloon, measure the wind speed and wind direction as a function of the atmospheric altitude, and receive and process meteorological element information such as temperature, humidity, and air pressure detected by a radiosonde.

[0005] A semiconductor laser wind measurement radar is a new type of atmospheric remote sensing device and the only effective tool for realizing three-dimensional atmospheric wind field remote sensing observation. Its working principle is to collect the scattered echo information of particles in the air by using a laser transceiver system, and then directly obtain high-resolution and high-precision real-time three-dimensional wind field data by analyzing and calculating these measurement data. It solves the problem of detecting low-altitude wind shear in the aviation field, which seriously affects aviation safety, and can be widely used in the fields of meteorology, environmental protection, national defense, airports, etc.

[0006] A coherent wind measurement lidar is based on heterodyne detection technology. It uses the signal light scattered by aerosols moving with the wind in the atmosphere to perform heterodyne coherence with the eigenlight, and inversely calculates the wind field information by detecting and demodulating the Doppler frequency shift.

[0007] Doppler lidar is a brand-new and emerging means for detecting the atmospheric wind field.

[0008] However, what a lidar directly measures is the frequency shift of the laser reflected light in the line-of-sight direction (line-of-sight wind speed). On this basis, the lidar must also be able to obtain wind speed data in multiple directions in order to invert the wind field. This requires a corresponding optical scanning system, which, on the premise of ensuring the overlap of the transmitting and receiving fields of view, controls the laser beam to be projected in a specified direction so that the lidar can obtain wind speed data at different line-of-sight angles.

[0009] Commercial wind power generation devices mainly include windmill towers, rotating devices, electronic control systems, and windmill blades. Among them, the electronic control system adjusts the rotating device according to the local wind field information, so that the direction of the windmill blades is adjusted towards the direction of high power generation efficiency, thereby obtaining higher wind energy utilization and power generation efficiency. Therefore, in a wind power generation plant area, high-precision real-time wind field information guarantees the power generation efficiency of the wind power generation device and is necessary for improving the power generation efficiency. Therefore, it is necessary to provide a wind measurement radar system with a simple optical path and algorithm, less calculation amount, and capable of providing real-time wind field information. Summary of the Invention

[0010] The object of the present invention is to provide a wind measurement lidar to solve a series of problems in the existing wind measurement radar, such as too large intermediate frequency range resulting in too large calculation amount.

[0011] To achieve the above object, the technical solutions adopted in the embodiments of the present invention are as follows:

[0012] The embodiments of the present invention provide a wind measurement lidar, which is characterized by including:

[0013] A transmitting part, which is used to generate a continuous modulated wave and adjust the modulation frequency of the modulated wave;

[0014] A transceiver system, which is used to transmit a light source to a target and receive the echo signal of the target;

[0015] A detection and processing part, which is used to obtain wind field information according to the received echo signal and the transmitted continuous modulated light, and determine the adjustment amount of the modulation frequency of the Nth frame according to at least the intermediate frequency of the previous frame.

[0016] Optionally, the detection and processing part feeds back the determined adjustment amount of the modulation frequency of the Nth frame to the transmitting part.

[0017] Optionally, the transmitting part sets the modulation frequency when starting up, and the set modulation frequency meets the measurement requirements of the farthest measurement distance and the maximum wind speed.

[0018] Optionally, the detection and processing part sets the upper and lower limits of the intermediate frequency.

[0019] Optionally, the adjustment amount of the modulation frequency is determined according to the relationship between the intermediate frequency obtained according to the set modulation frequency and the upper and lower limits of the set intermediate frequency, and is fed back to the transmitting system.

[0020] Optionally, when the intermediate frequency obtained according to the set modulation frequency is within the range of the set intermediate frequency, the detection and processing part outputs the intermediate frequency.

[0021] Optionally, when the intermediate frequency frequency difference between the previous two frames is greater than or equal to 0, the transmitting part reduces the modulation frequency of the Nth frame.

[0022] Optionally, when the intermediate frequency frequency difference between the previous two frames is less than 0, the transmitting part increases the modulation frequency of the Nth frame.

[0023] Optionally, the detection and processing part obtains the wind speed according to the intermediate frequency.

[0024] Optionally, the increased or decreased frequency value is related to the bandwidth, the measurement distance, the speed of light, at least the intermediate frequency of the previous frame, and the upper and lower limit values of the set intermediate frequency.

[0025] The beneficial effect of the present invention is: The present invention provides a wind measurement lidar, which is characterized by including: a transmitting part for generating a continuous modulation wave and adjusting the modulation frequency of the modulation wave;

[0026] a transceiver system for transmitting a light source to a target and receiving an echo signal of the target;

[0027] a detection and processing part for obtaining wind field information according to the received echo signal and the transmitted continuous modulation light, and determining the adjustment amount of the modulation frequency of the Nth frame according to at least the intermediate frequency of the previous frame. It can improve the resolution, obtain better resolution, reduce the bandwidth of the receiving unit, and reduce the data volume. Description of the Drawings

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0029] Figure 1 It is a schematic diagram of a continuous modulation wave wind measurement radar provided by an embodiment of the present application;

[0030] Figure 2 It is the relationship between the distance and the intermediate frequency signal bandwidth in the continuous modulation wave lidar provided by an embodiment of the present application;

[0031] Figure 3 It is a schematic diagram of a method for measuring distance provided by the prior art;

[0032] Figures 4(a)-4(b) are schematic diagrams of the effect of reducing the intermediate frequency bandwidth provided by an embodiment of the present application;

[0033] Figure 5A schematic diagram of an adaptive process provided by an embodiment of the present application;

[0034] Figure 6 Another schematic diagram of an adaptive process provided by an embodiment of the present application;

[0035] Figure 7 A schematic diagram of the intermediate frequency adaptive adjustment process provided by an embodiment of the present application. Detailed implementation manners

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention.

[0037] Figure 1 A schematic diagram of a continuous wave modulation wind lidar provided by an embodiment of the present application; including a light source system for providing light that meets the detection requirements and outputting a modulated carrier light signal; a beam splitter for splitting the light into two paths, the first path being used as local light and input into a coupler, and the second path being signal light for detection; a circulator, as Figure 1 shown, the light input from channel 1 can only be input through channel 2, and the light entering from channel 2 can only be output from channel 3; a transceiver system, the transceiver system is as Figure 1 shown, for receiving the target echo signal at a distance of L, the coupler is used to mix the intrinsic light and the signal light and output it at a ratio of 50:50. A balanced detector for detecting the coherent light signal and converting it into an electrical signal; a processing unit with functions such as amplifying, storing, calculating, data transmitting, wind field inversion, and result display for the electrical signal.

[0038] The emission optical carrier frequency generated by the light source system changes continuously and periodically. After being split into two paths by the beam splitter, the first path is used as the intrinsic light and transmitted to the coupler; the second path is used as the signal light and transmitted to port 1 of the circulator, and emitted from port 2 to the transceiver telescope. The transceiver telescope emits the carrier signal light into the atmosphere, and at the same time receives the echo scattered by the aerosol and transmits it to port 2 of the circulator, and is emitted from port 3 of the circulator and input into the coupler to be mixed with the intrinsic light. The mixed signal is converted into an electrical signal by the balanced detector, and the electrical signal enters the processing unit, and then the wind speed, wind direction, and distance information are obtained by inversion.

[0039] The above continuous carrier light source can adopt sawtooth wave modulation, including rising sawtooth wave and falling sawtooth wave. Assuming the laser wavelength is λ, then the optical frequency f c = c / λ (c is the speed of light),, using f M to represent the modulation frequency, then the intrinsic optical frequency f l = f c + f M , taking the rising sawtooth wave as an example:

[0040]

[0041] Let \(B\) denote the frequency modulation bandwidth. Then, the frequency of the aerosol-scattered echo is:

[0042]

[0043] where \(\tau = 2L / c\) represents the flight time of the laser at a position with a distance of \(L\), and \(f\) L represents the frequency generated by the target distance echo. \(f\) d represents the frequency generated by the movement of aerosol particles with the wind, and \(f\) d is expressed as \(v\) r represents the radial wind speed, and the positive and negative signs represent the wind direction. Then, the intermediate frequency signal \(f\) after mixing and superposition is IF \(= |f\) s \(- f\) L \(| = |f\) L \(+ f\) d \(|\)

[0044] When \(f\) L \(> f\) d , the radial wind speed is expressed as:

[0045]

[0046] where \(v\) r being positive means that the direction of the radial wind speed is the same as the direction of the emitted laser, and \(v\) r being negative means that the direction of the radial wind speed is opposite to the direction of the emitted laser.

[0047] From the above process, it can be seen that as long as the distance is known before determining the wind speed. The distance information can be preset, for example, it is required to measure the wind speed at a distance of 100 m. It can also be the distance measured according to the existing technology.

[0048] The above continuous carrier light source can be modulated with a triangular wave. Usually, a symmetric triangular wave is used to frequency-modulate the laser light source. The laser light source usually uses a narrow linewidth laser, and the relationship between its linewidth and the ranging distance can usually be expressed as: \(2L = c / \Delta f\), where \(c\) is the speed of light, \(\Delta f\) is the linewidth of the laser, and \(L\) is the ranging distance. When ranging, at least half of a complete frequency modulation period is required to complete a single ranging / velocity measurement, that is:

[0049]

[0050] where \(t\) min is the time required to complete a single ranging, and \(T\) is the period of frequency modulation.

[0051] During this period, the frequencies of the local oscillator light and the signal light reflected from the moving target are respectively expressed as: f L , f S . The two of them interfere on the photosensitive surface, and the generated intermediate frequency is: f mid = |f L - f S |, where the frequency of the signal light includes the frequency change caused by the distance and the Doppler shift caused by the relative velocity of the target. The frequency of the signal light can be expressed as:

[0052]

[0053] Among them, B is the frequency modulation bandwidth or frequency modulation range, that is, the maximum frequency change generated by one-time frequency modulation; L is the ranging distance; is the frequency to complete the triangular wave frequency modulation. Then when at the rising and falling edges respectively, the frequencies of the intermediate frequency signals are:

[0054]

[0055] Or:

[0056]

[0057] At this time, we need to obtain the intermediate frequency frequencies generated when the frequency is at the rising and falling edges of the frequency modulation period: f mid+ and f mid- , then we can completely calculate the distance and speed of the target at the current moment. That is:

[0058]

[0059] If the distance and wind speed information can be directly obtained through the triangular modulation wave.

[0060] Whether it is sawtooth wave modulation or triangular wave modulation, it is necessary to satisfy that the line width of the emitted laser needs to be less than or equal to the optical limit coherence length corresponding to the distance, that is, the line width Δω ≤ c / 2L max (Δω is the laser line width, c is the speed of light, L max is the preset maximum ranging range). In this embodiment, the light source generated by the light source system can meet the measurement requirements in terms of power.

[0061] Figure 2 is the relationship between the distance and the intermediate frequency signal bandwidth in the continuous modulation wave laser Doppler wind lidar provided by the embodiment of the present application. The coherent Doppler wind lidar is based on the heterodyne detection technology, using the signal light scattered by the aerosol moving with the wind in the atmosphere to perform heterodyne coherence with the eigenlight, and inversely retrieving the wind field information by detecting and demodulating the Doppler shift.

[0062] According to the different working modes of the laser emission source, coherent wind lidar can be divided into two working systems: continuous and pulsed. Among them, for the radar system with the pulsed working system, the optical path and heterodyne algorithm technology are complex, the system cost is relatively high, and there is a near-range blind area. It is generally used for long-distance detection; the pulsed working system generally judges the distance through range gates.

[0063] For the radar system modulated by continuous wave, the optical path structure and algorithm are relatively simple; the continuous working system generally judges the measurement distance through a zoom system.

[0064] To achieve wind direction recognition, a frequency shifter (such as an acousto-optic modulator, an electro-optic modulator, etc.) also needs to be set in the above optical system. In addition, the laser wind measurement technology based on continuous wave modulation can use frequency-modulated continuous wave to identify the wind direction. As can be seen from Figure 2 it that when the measurement distance reaches 400m, the bandwidth is as high as over 1GHz.

[0065] Figure 3 FIG. 12 is a schematic diagram of a method for measuring distance provided for the prior art in the embodiments of the present application. As Figure 3 shown, the light coming out of the transmission optical fiber is focused on a certain wind layer area in the air through a zoom system controlled by a stepping motor. After being scattered by the atmospheric aerosol particles drifting with the wind within the focused range, the frequency of its backscattered light will change, and the change amount is the Doppler frequency f related to the moving speed of the atmospheric particles at this point along the direction of the laser beam. d . The scattered light is collected and focused by the receiving antenna and then coupled into the receiving / transmitting unit port 2 through the transmission optical fiber and output from port 3, and is heterodyne coherently mixed with the local oscillator light, and finally focused on the photodetector, and the main heterodyne coherent intermediate frequency electrical signal is output by the detector. As Figure 3 shown, the system focuses the emitted laser beam on the measurement space layer position, and collects the backscattering of aerosol particles at the beam waist of the focus through the same antenna system. By using a zoom system, a low-power laser can be focused in the air, and the aerosol particles at the focus are irradiated with high brightness, so the power density of the backscattering is increased, which is convenient for realizing long-distance detection. The measurement distance is realized according to the distance from the end face of the optical fiber to the telescope, that is, the change of the focus point is realized by controlling the distance between the optical fiber head and the telescope through a stepping motor.

[0066] FIGS. 4(a)-4(b) are schematic diagrams of an effect of reducing the intermediate frequency bandwidth provided for the embodiments of the present application. As Figure 2 shown, as the measurement distance increases, the bandwidth of the intermediate frequency signal becomes very large, which requires a large effective bandwidth of the detector, resulting in a large pressure on the A / D sampling module (for example, if the bandwidth is 1G, the required sampling rate is 2G). To solve this problem, it is necessary to reduce the bandwidth of the intermediate frequency signal and reduce the pressure on the A / D sampling module. In FIGS. 4(a) and 4(b),Figure 3 The ranging method shown, of course, other existing technologies can also be used for ranging. Here, Figure 3 the method shown is taken as an illustrative example, and other methods will not be elaborated.

[0067] In Figure 1 the system shown, the light source can adopt triangular wave modulation. Assuming the laser wavelength is λ, then the optical frequency f c = c / λ (c is the speed of light). Using f M to represent the modulation frequency, then the intrinsic optical frequency f l = f c + f M , taking the rising sawtooth wave as an example:

[0068]

[0069] B represents the frequency modulation bandwidth. Then, the frequency of the aerosol scattered echo is:

[0070]

[0071] where τ = 2L / c represents the flight time of the laser at a position with a distance of L, f L represents the frequency generated by the target distance echo, f d represents the frequency generated by the aerosol particles moving with the wind, and f d is expressed as v r represents the radial wind speed, and the positive and negative signs represent the wind direction. Then, the intermediate frequency signal after mixing and superposition is fIF = f s - fL = fL + fd

[0072] When f L > f d , the radial wind speed is expressed as:

[0073]

[0074] where v r being positive means that the direction of the radial wind velocity is the same as the direction of the emitted laser, and v r being negative means that the direction of the radial wind velocity is opposite to the direction of the emitted laser.

[0075]

[0076] In the formula

[0077] k = f M B (5)

[0078] Then

[0079]

[0080] As shown above Figure 2 As can be seen, f L represents the frequency shift caused by distance. It can be seen from formula (4) that if the laser (i.e., the light source) is not frequency modulated, then for a laser, there is a fixed bandwidth B and modulation frequency f M , that is, in formula (4), B and f M are fixed values. Then, it can be seen from formula (4) that different distances correspond to different frequency shifts, which will cause the bandwidth of the detector receiving end to increase with the increase of the measurement distance. To solve this problem, it is necessary to ensure that the bandwidth of the detector receiving end does not change due to distance. The specific implementation method is as follows:

[0081] 1. Given an f L value, this f L is limited by the upper limit of the wind speed. The relationship between f L and fd is f L >|fd|. As shown in Figure 4(a), when the upper limit of the wind speed is 30 m / s, the Doppler frequency shift caused by 30 m / s is 38.7 MHz, then f L is 50 MHz.

[0082] 2. From step 1, it can be seen that f L is 50 MHz. Then, it can be seen from formula (6) that for a fixed f L , measuring different distances L can only change k. Different k values can be calculated by combining the distance to be measured with formula (6).

[0083] 3. After calculating the k value corresponding to the distance to be measured, adjust the modulation frequency f M of the laser through formula (5) to adjust the k value.

[0084] The distance L can be obtained by using Figure 3 the method shown, or preset, or obtained through existing technologies, which will not be elaborated here. When the modulation waveform is a triangular wave, k can be defined as the slope of the triangular wave. Here, this is for illustrative purposes only and is not limited to the modulation wave being a triangular wave form.

[0085] It should be noted that in the k adjustment technology, f L is a fixed value.

[0086] Figures 4(a) and 4(b) show wind speeds of 30 m / s and 5 m / s respectively. It can be seen from the figures that to meet a wind speed of ±30 m / s, the detector bandwidth needs to be at least 90 MHz and the sampling frequency needs to be at least 180 MHz. As shown in Figure 4(a), if the actual wind speed remains low for a long time, such as ±5 m / s, the corresponding frequency change caused by the speed is ±6.5 MHz. Still, a detector bandwidth of at least 90 MHz and a sampling frequency of at least 180 MHz are required as shown in Figure 4(b), which will cause waste and increase the computational load. Therefore, this problem needs to be solved.

[0087] In Figure 1 the system shown, the light source can adopt triangular wave modulation. Assuming the laser wavelength is λ, then the optical frequency f c = c / λ (c is the speed of light). Using f M to represent the modulation frequency, the intrinsic optical frequency f l = f c + f M . Taking the rising sawtooth wave as an example:

[0088]

[0089] B represents the frequency modulation bandwidth. Then, after passing through the aerosol scattered echo frequency:

[0090]

[0091] where τ = 2L / c represents the laser flight time at a position with a distance of L, f L represents the frequency generated by the target distance echo, f d represents the frequency generated by the aerosol particles moving with the wind, and f d is expressed as v r represents the radial wind speed, and the positive and negative signs represent the wind direction. Then, the intermediate frequency signal f IF = |f s - f L | = |f L + f d . Set the adaptive range of the intermediate frequency to [f min , f max . Adaptive adjustment of the intermediate frequency to the specified range [f m i n , f max can reduce the computational load.

[0092] Take Δf ∈ (f min , f max ). The subscript j represents the parameters of the jth frame.

[0093]

[0094] Define δ IF,j = f IF,j-1 - f IF,j-2 .

[0095] m can take a fixed constant so that the intermediate frequency adjusted each time is equal, or it can change in real time according to the previous intermediate frequency. For example: In this way, the more the previous frame changes, the more it is adjusted.

[0096] Figure 5 This is a schematic diagram of an adaptive process provided by an embodiment of the present application. The following will be combined with Figure 5 to detail how to perform intermediate frequency adaptive adjustment. As Figure 5 shown, first when starting up, the transmitting part sets the modulation frequency to a preset value. For example, Figure 5 in S102, set f M = f M0 , where f M0 is a parameter that satisfies the preset maximum intermediate frequency (such as the value of the maximum radial wind speed for preset measurement of the maximum distance); according to formulas (1)-(2), and f IF = |f s - f L | = |f L + f d |, the intermediate frequency f IF can be calculated. For example, in S103 of Figure 5 , when in S104 of Figure 5 , the detection and processing part determines whether the intermediate frequency f IF is within the set range. If it is within the set range, S105 can be executed to output the intermediate frequency f IF , and the wind speed can be calculated according to formula (9). If the intermediate frequency f IF obtained in S103 is not within the set adjustment range, then S106 is executed to determine whether the intermediate frequency f IF exceeds the upper limit f max of the set intermediate frequency range. If it exceeds the upper limit of the set range, the modulation frequency f M needs to be subtracted by a value. As shown in S107 of Figure 5 , and then the value to be adjusted is fed back to the transmitting part, and the entire system executes the adjustment process again until the obtained intermediate frequency signal is within the specified range. If in Figure 5 of S106, the detection and processing part determines that the intermediate frequency f IF does not exceed the upper limit f max of the set intermediate frequency range, it means that the obtained f IF is less than the lower limit f min of the set intermediate frequency range. Then S108 is executed, and the modulation frequency fM Add a value, and the detection processing part feeds this value back to the transmitting part, and then the entire system executes the adjustment process again until the intermediate frequency signal obtained by the detection processing part is within the specified range.

[0097] Figure 6 Another schematic diagram of the adaptive process provided for this application example. As Figure 6 shown, during the measurement process, when performing the measurement of the j-th frame, first determine the modulation frequencies of the (j - 1)-th frame and the (j - 2)-th frame, and the detection processing part calculates the intermediate frequency difference δ IF,j = f IF,j-1 - f IF,j-2 As Figure 6 shown in S203; then determine whether the intermediate frequency difference between the (j - 1)-th frame and the (j - 2)-th frame is greater than or equal to 0, as Figure 6 shown in S204. If the intermediate frequency difference is greater than or equal to zero, then subtract a value from the modulation frequency of the j-th frame, as Figure 6 shown in S206, and feed this value back to the transmitting part; if the intermediate frequency difference is less than zero, then add a value to the modulation frequency of the j-th frame, as Figure 6 shown in S205; then execute Figure 6 in S207 to determine the modulation frequency of the j-th frame; the intermediate frequency of the j-th frame can be obtained according to the modulation frequency, as Figure 6 shown in S208; then the wind speed of the j-th frame can be obtained according to the intermediate frequency of the j-th frame, as Figure 6 shown in S209; thus, the adaptive adjustment process of the intermediate frequency of the j-th frame is completed. Then execute Figure 6 in S210 to perform the adaptive adjustment process of the intermediate frequency for the next frame. Through Figure 6 the adjustment process shown, it can be ensured that the intermediate frequency is always within the set intermediate frequency range during the measurement of each frame to reduce the calculation amount. During the adaptive adjustment process, the adjustment for the next frame can be determined according to the previous intermediate frequency change trend, as Figure 6 shown, the adjustment amount can be determined by taking the intermediate frequencies of the first and second previous frames. It can also be determined according to δ IF,j = f IF,j-1 - f IF,j-3 the first previous frame and the third previous frame, or δ IF,j = f IF,j-1 - f IF,-j4 the first previous frame and the fourth previous frame, and it can also be determined according to δ IF,j = f IF,j-2 - f IF,j-3 the second and third previous frames, δ IF,j = f IF,j-2 - f IF,j-4determined by the second previous frame and the fourth previous frame; additionally, the adjustment amount can also be determined according to the first previous frame and a fixed value; here, it is only for illustrative purposes and there is no specific limitation. The adjustment amount is determined by the first previous frame and a fixed value; here, it is only for illustrative purposes and there is no specific limitation.

[0098] Figure 7 This is a schematic diagram of the intermediate frequency adaptive adjustment process provided by the embodiment of the present application. As Figure 7 shown, f min is the lower limit of the set intermediate frequency range, and f max is the upper limit of the set intermediate frequency range. Through the adaptive adjustment process shown in Figure 5 and Figure 6 , during the measurement process of each frame, the intermediate frequency is always within the specified frequency range. The specific adjustment process is shown in Figure 5 and Figure 6 , and will not be elaborated here.

[0099] The following advantages are achieved through the technical solution of the present invention:

[0100] 1. Improve resolution: For the same number of points, better resolution is obtained. When the maximum wind speed is 30 m / s, if the frequency shift is 50 MHz, according to the sampling theorem f s = 180 MHz, by controlling the intermediate frequency between 4 - 10 MHz, 20 MHz sampling can be used, and the corresponding spectral resolution distributions are 175 kHz and 19 kHz, and the spectral resolution is improved by about an order of magnitude.

[0101] 2. Reduce the bandwidth of the receiving unit, reduce the data volume, and reduce the calculation amount.

[0102] It should be noted that in this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non - exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not explicitly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising one..." does not exclude the existence of additional identical elements in the process, method, article or device comprising the said element.

[0103] The above are only the preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, various modifications and variations can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the protection scope of the present application. It should be noted that similar reference numerals and letters indicate similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings. The above are only the preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, various modifications and variations can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the protection scope of the present application.

Claims

1. A wind laser radar, characterized in that: include: The transmitting part is used to generate a continuous modulation wave and adjust the modulation frequency of the modulation wave; A transceiver system, used to transmit a light source to a target and receive an echo signal from the target; The detection processing part is used to detect the received echo signal and the emitted continuous modulated light. The wind field information is obtained, and the adjustment amount of the modulation frequency of the Nth frame is determined according to the intermediate frequency of at least the previous frame, as follows: Calculating an intermediate frequency, and the detection processing part determines whether the intermediate frequency is within a set range; If yes, output the intermediate frequency, and calculate the wind speed according to the intermediate frequency; If not, determining whether the intermediate frequency exceeds an upper limit of a set intermediate frequency range; If yes, the modulation frequency is subtracted by a value, and then the value to be adjusted is fed back to the transmitting part, and the entire system performs the adjustment process again until the intermediate frequency signal obtained is within the specified range; If not, a value is added to the modulation frequency, and the detection processing part feeds this value back to the transmitting part, and then the entire system performs the adjustment process again until the intermediate frequency signal obtained by the detection processing part is within the specified range.

2. The wind laser radar according to claim 1, characterized in that: The detection processing section feeds back the determined adjustment amount of the modulation frequency of the Nth frame to the transmitting section.

3. The wind laser radar according to claim 2, characterized in that: The transmitting part sets a modulation frequency when it is turned on, and the modulation frequency meets the measurement requirements of the farthest measurement distance and the maximum wind speed.

4. The wind laser radar according to claim 3, characterized in that: The detection processing section sets the upper and lower limits of the intermediate frequency.

5. The wind laser radar according to claim 4, characterized in that: The adjustment amount of the modulation frequency is determined according to the relationship between the intermediate frequency obtained from the modulation frequency and the upper limit and the lower limit of the set intermediate frequency and is fed back to the transmitting part.

6. The wind laser radar according to claim 4, characterized in that: When the intermediate frequency obtained by the detection processing part according to the modulation frequency is within the range of the set intermediate frequency, the intermediate frequency is output.

7. The wind laser radar according to claim 1, characterized in that: When the intermediate frequency difference between the two frames preceding the Nth frame is greater than or equal to 0, the transmitting part reduces the modulation frequency of the Nth frame.

8. The wind laser radar according to claim 1, characterized in that: When the intermediate frequency difference between the two frames preceding the Nth frame is less than 0, the transmitting part increases the modulation frequency of the Nth frame.

9. The wind laser radar according to claim 1, characterized in that: The detection processing part obtains the wind speed according to the intermediate frequency.

10. The wind laser radar according to any one of claims 7 or 8, characterized in that: The frequency value by which the modulation frequency of the Nth frame is increased or decreased is related to the bandwidth, the measurement distance, the speed of light, the intermediate frequency of at least one frame before the Nth frame, and the upper and lower limits of the intermediate frequency.

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