CN115308715A - Method and system for sparse modulation wind-measuring radar - Google Patents

Method and system for sparse modulation wind-measuring radar Download PDF

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CN115308715A
CN115308715A CN202211066865.9A CN202211066865A CN115308715A CN 115308715 A CN115308715 A CN 115308715A CN 202211066865 A CN202211066865 A CN 202211066865A CN 115308715 A CN115308715 A CN 115308715A
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light
frequency
modulation
signal
wind
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罗道斌
胡广东
李方明
郭晓凡
吴圣博
洪鹏程
侯瑞宁
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Shaanxi University of Science and Technology
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Shaanxi University of Science and Technology
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
    • G01S7/481—Constructional features, e.g. arrangements of optical elements
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
    • G01S17/88—Lidar systems specially adapted for specific applications
    • G01S17/95—Lidar systems specially adapted for specific applications for meteorological use
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
    • G01S7/483—Details of pulse systems
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A90/00—Technologies having an indirect contribution to adaptation to climate change
    • Y02A90/10—Information and communication technologies [ICT] supporting adaptation to climate change, e.g. for weather forecasting or climate simulation

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  • Physics & Mathematics (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • General Physics & Mathematics (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Electromagnetism (AREA)
  • Optical Radar Systems And Details Thereof (AREA)

Abstract

The invention provides a method and a system for sparsely modulating a wind measuring radar, wherein a laser device modulates a good signal and then emits a light beam, the light velocity passes through a light splitter, the light splitter divides one light beam into two light beams, one light beam is a detection light, and the other light beam is an intrinsic light; the detection light is modulated by an acousto-optic modulator to modulate a good signal, the power amplifier amplifies the light intensity and transmits the amplified light to the telescope through the circulator, the telescope transmits the detection light, the detection light is transmitted by aerosol in the air and then returns to signal light, the telescope receives the signal light, and the signal light is transmitted to the coupler through the circulator; the intrinsic light is attenuated by the attenuator and coupled with the signal light; the coupled light beams are sent to a balance detector for adjustment, then processed by a data processor, and the speed and direction of wind are obtained by modulating the light source inside and outside, so that the influence of system echo interference can be eliminated, and near-distance blind areas are effectively reduced or eliminated; the detection bandwidth is reduced, and the signal-to-noise ratio is improved.

Description

Method and system for sparse modulation wind-measuring radar
Technical Field
The invention belongs to the technical field of wind-measuring radars, and particularly relates to a method and a system for sparsely modulating a wind-measuring radar.
Background
The laser radar emits high-purity spectrum light beams to a detection airspace, a radar system receives backscattering from aerosol particles, and the aerosol has a very low backscattering coefficient, so that a one-stage or multi-stage optical amplifier is generally adopted to obtain high emission power; in order to identify the wind direction, a frequency shifter is generally required to be arranged; the coherent mixing optical signal is changed into an alternating current signal through balanced detection, and the wind field information is obtained through the Doppler frequency generated by the identification of the processing unit after the analog/digital conversion.
The wind measuring radar generally has a pulse system and a continuous system, and the type of the receiving and transmitting of radar signals can be divided into a receiving and transmitting co-location and a receiving and transmitting separate location; the receiving and transmitting have the interference of the system; for example, after the echoes on the end surfaces of the lens and the optical fiber are mixed with the eigen frequency, a fixed interference frequency is formed in an intermediate frequency spectrum (the influence of the interference frequency is mainly reflected in two aspects of (1) influencing the lower limit of the measured wind speed, and (2) reducing the signal to noise ratio of effective signals, so that the pulse system radar generally filters the interference through a range gate and generates a measured distance blind area, while the continuous system radar adopts a phase-locked loop circuit and the like to inhibit the interference but influences the lower limit of the wind speed measurement, and therefore, the sparse modulation wind measuring radar is urgently needed to be provided.
The indices of frequency modulated continuous wave lidar are mainly limited by the performance parameters of the light source: coherent detection methods at a receiving end are relatively mature; due to the rapid development of technologies such as high-speed analog-to-digital converters, digital signal processing and the like, the acquisition and processing of back-end data are not bottlenecks of overall indexes at present; therefore, how to generate an optical frequency modulation signal with excellent performance becomes a major concern of researchers of the FMCW lidar.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a method and a system for sparsely modulating a wind finding radar, which can improve the stability and reliability of detection.
The invention is realized by the following technical scheme:
a method of sparsely modulating a wind lidar comprising the steps of:
s1, modulating a linearly-changed signal by a laser device, then emitting a light beam, wherein the light speed passes through a light splitter, the light splitter divides a beam into two beams, one beam is detection light, and the other beam is intrinsic light;
s2: the detection light is modulated by an acousto-optic modulator to modulate a signal with linear change, the light intensity is amplified by a power amplifier and is transmitted to a telescope by a circulator, the telescope transmits the detection light, the detection light is transmitted by aerosol in the air and then returns to signal light, the telescope receives the signal light, and the signal light is transmitted to a coupler by the circulator;
s3: the intrinsic light attenuates the light intensity through the attenuator, is transmitted to the coupler through the light path and is coupled with the return signal light;
s4: the coupled light beams are sent to a balance detector for adjustment and then processed by a data processor to obtain the speed and direction of wind.
Further, the modulation of the good signal in the step S2 includes sparse inner modulation and sparse outer modulation;
the sparse internal modulation is modulation of a laser signal at a laser source;
the sparse external modulation is to modulate laser emitted by a laser by a frequency shifter.
Furthermore, the sparse internal modulation drives the cavity length negative feedback coarse adjustment of the external cavity type semiconductor laser through piezoelectric ceramics, and simultaneously injects current into the external cavity type semiconductor laser to change the refractive index of the gain medium in the wall, so that the sparse internal modulation is used for the feedback fine adjustment of the optical length in the cavity.
Further, the calculation process of the anemometry of the sparse inner modulation and the sparse outer modulation is as follows:
the frequency of the emission signal is periodically changed linearly up and down along with the time, the rising time is the same as the falling time, the average value of the frequency is fc, the transmission delay used for emitting light from the circulator to irradiate the measured target and then scattering the light back to the receiving end is tau, and the change range of the signal frequency is the bandwidth B;
the frequency difference generated between the frequencies of the received echo signals and the local oscillation signals is df;
frequency difference resulting from frequency variation f introduced by distance delay tau R And Doppler shift f d The frequency difference Δ f1 generated at the rising edge of the frequency and the frequency differences Δ f2 and f generated at the falling edge of the frequency are formed R Each phase difference therebetween f d ；
Difference frequency quantity f introduced by distance R And Doppler shift f d fd can be calculated from Δ f1 and Δ f2 by means of coherent demodulation:
R＝2CT*fd/(4B)；
v＝fd*c/(2fc cosθ)；
in the formula: gamma represents the frequency change rate of the emission signal, R represents the distance between the laser radar and the measured target, c represents the light velocity, v represents the projection of the target velocity on the connecting line of the laser radar and the measured target, fc represents the central frequency of the optical carrier of the emission signal, and theta is the included angle between the emission laser and the movement direction of the particles to be measured.
Further, the wind direction calculation process of the sparse inner modulation is as follows:
at t 1 Time linear frequency modulation at t 2 Not frequency modulation; then at t 1 Time, intermediate frequency f IF ＝f L +f d In which
Figure BDA0003828714390000031
B is the modulation bandwidth, R is the detection range, T fm Is the time of the chirp, c represents the speed of light;
using a focus-adjusting lens, the detection distance is the distance between the focal position of the lens and the radar, so f L Is a known quantity, if IF ＞f L If the wind direction is positive, otherwise, the wind direction is negative, and sparse inner modulation wind is completedAnd (4) judging the direction.
Further, the wind direction meter process of the sparse external modulation is as follows:
when at t 2 Time, the intermediate frequency spectrum can generate interference frequency and wind speed signals generated by a frequency shifter, only the frequency of the wind signals and the interference frequency are judged to obtain the wind direction, and the frequency shifter is f N Judging the wind signal frequency and f N If the size of (b) is larger than f N The radial wind is positive and vice versa.
Further, the sparse external modulation adopts a tuning mode based on an electro-optical modulator, and comprises the following steps:
transmitting laser emitted by a laser to an electro-optical modulator, applying voltage to an electro-optical crystal, changing the refractive index of the electro-optical crystal, and modulating the phase, amplitude, intensity and polarization state of an optical signal through the change of the laser characteristics of the crystal; a linear optical frequency signal is output.
Further, the sparse external modulation adopts a tuning mode based on a cyclic frequency shift structure, and comprises the following steps:
and the circulating frequency shift loop and the scanning tuning device modulate the received laser to obtain a linear optical frequency signal.
A system of a sparse modulation wind-measuring radar comprises a seed source, and a beam splitter and an attenuator which are respectively connected with the seed source;
the output end of the beam splitter is sequentially connected with an AOM, an EDFA and a circulator, and the circulator is also connected with a telescope; the output end of the attenuator and the output end of the circulator are respectively connected to the coupler, and the output end of the coupler is sequentially connected to the balance detector and the oscilloscope.
Compared with the prior art, the invention has the following beneficial technical effects:
the invention provides a method and a system for sparsely modulating a wind measuring radar, wherein a laser modulates a linearly-changed signal and then emits a light beam, the light velocity passes through a light splitter, the light splitter divides one beam into two beams, one beam is a probe light, and the other beam is an intrinsic light; the detection light is modulated by an acousto-optic modulator to modulate a signal with linear change, the light intensity is amplified by a power amplifier and is transmitted to a telescope by a circulator, the telescope transmits the detection light, the detection light is transmitted by aerosol in the air and then returns to the signal light, the telescope receives the signal light, and the signal light is transmitted to a coupler by the circulator; the intrinsic light attenuates the light intensity through the attenuator, and is transmitted to the coupler through the light path to be coupled with the signal light; the coupled light beams are sent to a balance detector for adjustment and then processed by a data processor to obtain the speed and direction of wind; the method and the device can eliminate the influence of system echo interference, and effectively reduce or eliminate short-distance blind areas; meanwhile, the detection bandwidth can be reduced, and the signal-to-noise ratio is improved; the wind direction identification can be realized without using a frequency shifter in the internal frequency modulation mode under continuous wave modulation, and the system cost can be reduced.
Drawings
FIG. 1 is a flow chart of a method of sparsely modulating a wind radar of the present invention;
FIG. 2 is a schematic diagram of a system of a sparse modulation wind radar of the present invention;
FIG. 3 is a schematic diagram of the relationship between the time domain and the frequency domain of the transmitted signal and the received echo signal under triangular waveform frequency modulation according to the present invention;
FIG. 4 is a time-frequency relationship diagram of beat signals obtained by coherent detection according to the present invention;
FIG. 5 is a sparse inner modulation system architecture of the present invention;
FIG. 6 shows a modulation signal applied to a light source by a controller according to the present invention;
FIG. 7 is a sparse outer modulation system architecture of the present invention;
FIG. 8 is a flow chart of the wind signal frequency and frequency shifter determination of the present invention.
Detailed Description
The present invention will now be described in further detail with reference to specific examples, which are intended to be illustrative, but not limiting, of the invention.
In order to make those skilled in the art better understand the technical solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, shall fall within the protection scope of the present invention.
It should be noted that the terms "first," "second," and the like in the description and claims of the present invention and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the invention described herein are capable of operation in sequences other than those illustrated or described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
The invention provides a method for sparsely modulating a wind-measuring radar, which comprises the following steps as shown in figure 1:
s1, modulating a linearly-changed signal by a laser device, then emitting a light beam, wherein the light speed passes through a light splitter, the light splitter divides a beam into two beams, one beam is detection light, and the other beam is intrinsic light;
s2: the detection light is modulated by an acousto-optic modulator to modulate a signal with linear change, the light intensity is amplified by a power amplifier and is transmitted to a telescope by a circulator, the telescope transmits the detection light, the detection light is transmitted by aerosol in the air and then returns to signal light, the telescope receives the signal light, and the signal light is transmitted to a coupler by the circulator;
s3: the intrinsic light attenuates the light intensity through the attenuator, is transmitted to the coupler through the light path and is coupled with the return signal light;
s4: and the coupled light beams are sent to a balance detector for adjustment and then processed by a data processor to obtain the speed and direction of wind.
Preferably, the modulation of the good signal in step S2 includes sparse inner modulation and sparse outer modulation;
the sparse internal modulation is modulation of a laser signal at a laser source;
the sparse external modulation is to modulate laser emitted by a laser by a frequency shifter.
Furthermore, the sparse internal modulation drives the cavity length negative feedback coarse adjustment of the external cavity type semiconductor laser through piezoelectric ceramics, and simultaneously injects current into the external cavity type semiconductor laser to change the refractive index of the gain medium in the wall, so that the sparse internal modulation is used for the feedback fine adjustment of the optical length in the cavity.
Preferably, the calculation process of the anemometry of the sparse inner modulation and the sparse outer modulation is as follows: as shown in fig. 3, the frequency of the emission signal periodically changes linearly up and down with time, the rising time is the same as the falling time, the average value of the frequency is fc, the transmission delay used by the emission from the circulator, the emission of the emission irradiates the measured target and then scatters back to the receiving end is recorded as τ, and the change range of the signal frequency is recorded as bandwidth B; due to the linear change of the signal frequency along with the time and the doppler effect generated by the relative displacement of the target to be measured, a frequency difference df is generated between the frequencies of the received echo signal and the local oscillator signal, as shown in fig. 4, and the frequency difference is the frequency variation f introduced by the distance delay τ R And Doppler shift f d The frequency difference Δ f1 generated at the rising edge of the frequency and the frequency differences Δ f2 and f generated at the falling edge of the frequency are formed R Each phase difference therebetween f d Then the difference frequency quantity f introduced by the distance R And Doppler shift f d It can be calculated from Δ f1 and Δ f2 by means of coherent demodulation:
R＝2CT*f d /(4B)；
v＝f d *c/(2λcosθ)；
in the formula: lambda represents the wavelength of the emission signal, R represents the distance between the laser radar and the measured target, c represents the light velocity, v represents the projection of the target velocity on the connecting line of the laser radar and the measured target, and theta is the included angle between the emission laser and the movement direction of the particles to be measured; therefore, the distance R and the relative speed v of the measured target can be demodulated.
And installing the sparse modulation device at a seed source, transmitting continuous laser by the seed source, and finally selecting the most appropriate modulation laser device according to the measurement effect.
Preferably, a sparse frequency modulation mode is adopted for the wind-measuring radar of the continuum system, the system structure is shown in fig. 5, the frequency modulation light emitted by the laser is divided into two paths through the beam splitter, and one path is used as the intrinsic light E L And the other path is used as detection light E S The aerosol particles are output and detected by a circulator transmitted by an amplifier and a lens, and the backward scattering of the circulator is received by the lens, passes through the circulator and is mixed with the light at a coupler; the mixed frequency optical signal passes through a balance detector and transmits the alternating current component of the mixed frequency optical signal to a processing unit, so that the detection of a wind signal is obtained; the echoes of the circulator or lens end-face will also be coherent with the intrinsic light.
The controller gives the light source a modulation signal, as shown in fig. 6, i.e. at t 1 Time linear frequency modulation at t 2 Not frequency modulation; then at t 1 Time, intermediate frequency f IF ＝f L +f d In which
Figure BDA0003828714390000071
B is modulation bandwidth, R is detection distance, T fm Is the time of linear frequency modulation, c represents the light speed, and fL represents the local oscillator light frequency; using a focus-adjusting lens, the detection distance is the distance between the focal position of the lens and the radar, so f L Is a known quantity, so as to obtain the wind speed, but the wind speed result is coupled by the distance to influence the wind measuring precision, so that only the direction of the wind, namely f, is seen in the linear frequency modulation stage IF ＞f L The wind direction is positive, otherwise, the wind direction is negative, and the judgment of the wind direction is realized; and detecting the frequency of the wind signal in a non-frequency-modulation time period to obtain the wind speed, thereby realizing the measurement of the wind speed and the wind direction.
Under the frequency modulation system, because the distance of the system echo is far less than the detection distance, the interference of the system echo is low frequency, and the influence can be effectively eliminated by adopting a high-pass filter.
Preferably, as shown in fig. 7, the single-mode laser emitted from the laser is divided into two paths by the beam splitter, and one path is used as the intrinsic light E L And the other path is used as detection light E S The probe light is passed through an optical switch controlled by a controller, the optical switch is periodically modulated, i.e. at t 1 The light diameter passes through the beam combiner in time t 2 In time, light passes through the frequency shifter and then the beam combiner; then the light passes through a circulator transmitted by an amplifier and is output by a lens to detect aerosol particles, and the backscattered light of the circulator is received by the lens and is mixed with the light at a coupler; the mixed frequency optical signal passes through a balance detector and transmits the alternating current component of the mixed frequency optical signal to a processing unit, so that the detection of a wind signal is obtained; of course, the echo of the circulator or lens end will be coherent with the intrinsic light, and the controller outputs the synchronous signal for controlling the optical switch when at t 2 In time, the intermediate frequency spectrum can generate interference frequency and wind speed signals generated by the frequency shifter; when at t 1 Time due to E S And E L Zero beat frequency, the intermediate frequency spectrum only has wind signals; thus at t 2 The time is only judged according to the frequency of the wind signal and the interference frequency to obtain the wind direction, if the frequency shifter is f N Judging the wind signal frequency and f N If the size of (b) is larger than f N The radial wind is positive, otherwise, the radial wind is negative; further, at t 1 Obtaining the frequency value of the wind signal according to the relation
Figure BDA0003828714390000081
Obtaining a radial wind velocity, wherein f d Indicating the doppler frequency and lambda the wavelength of the emitted light.
To determine the frequency and f of the wind signal N Using a processing unit as shown in FIG. 8, the filtering range is set to B < f N If the frequency is less than f N Then there is a wind signal in the intermediate frequency spectrum and conversely there is no in the spectrum, so at t 2 Time, only need to detect whether there is a signal in the bandwidth, if there is a signal, the wind direction is negative, if there is no wind direction is positive; further at t 1 The wind element is detected in time, so that the wind speed and the wind direction are measured, the influence of interference frequency is inhibited, and the same index is obtainedThe bandwidth is reduced, a high signal-to-noise ratio is obtained, and the close-range blind area is effectively reduced or eliminated.
Preferably, the sparse external modulation adopts a tuning mode based on an electro-optical modulator, and comprises the following steps:
the laser emitted by the laser is transmitted to the electro-optical modulator, voltage is applied to the electro-optical crystal, the refractive index of the electro-optical crystal changes, and the phase, the amplitude, the intensity and the polarization state of an optical signal are modulated through the change of the laser characteristics of the crystal to obtain a linear optical frequency signal.
Preferably, the sparse external modulation adopts a tuning mode based on a cyclic frequency shift structure, and comprises the following steps:
and the circulating frequency shift loop and the scanning tuning device modulate the received laser to obtain a linear optical frequency signal.
The invention provides a system for sparsely modulating a wind measuring radar, which comprises a seed source, and a beam splitter and an attenuator which are respectively connected with the seed source, as shown in figure 2;
the output end of the beam splitter is sequentially connected with an AOM, an EDFA and a circulator, and the circulator is also connected with a telescope; the output end of the attenuator and the output end of the circulator are respectively connected to the coupler, and the output end of the coupler is sequentially connected to the balance detector and the oscilloscope.
The AOM is an acousto-optic modulator, and the EDFA is a power amplifier;
furthermore, the continuous coherent radar system consists of a laser transmitting module and a signal receiving module. The laser emission module comprises a laser, a beam splitter, an acousto-optic modulator (AOM), a power amplifier (EDFA), a circulator and a telescope; the signal receiving module comprises a coupler, a balance detector, an acquisition card and a data processor.
When the continuous coherent Doppler laser wind measuring radar works, a seed source generates continuous laser with the center frequency of f0, the continuous laser is divided into two parts of light by a beam splitter, and one part of light is used as local oscillation light and is input into a coupler through an attenuator for beat frequency; the other part firstly performs frequency modulation on continuous light through an AOM (automatic optical modulator) to generate fm modulation frequency, then the frequency-shifted light is subjected to power amplification after passing through an EDFA (erbium-doped fiber amplifier), is subjected to beam expansion and is diffused into the atmosphere through a circulator and generates backscattering with aerosol particles in the atmosphere, the backscattering is received by the same telescope, a frequency shift quantity fd is generated on a scattered echo signal through an optical Doppler effect, and finally, the scattered echo signal and local oscillator light are subjected to coherent beat frequency at a coupler, converted into an electric signal through a balanced detector, converted into a digital signal through analog-digital acquisition, and the Doppler frequency shift is calculated through a signal processing unit. From the time of flight of the laser pulses, the wind speed at different distance resolution units can be calculated.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.

Claims (9)

1. A method of sparsely modulating a wind lidar comprising the steps of:
s1, modulating a linearly-changed signal by a laser device, then emitting a light beam, wherein the light speed passes through a light splitter, the light splitter divides a beam into two beams, one beam is detection light, and the other beam is intrinsic light;
s2: the detection light is modulated by an acousto-optic modulator to modulate a signal with linear change, the light intensity is amplified by a power amplifier and is transmitted to a telescope by a circulator, the telescope transmits the detection light, the detection light is transmitted by aerosol in the air and then returns to signal light, the telescope receives the signal light, and the signal light is transmitted to a coupler by the circulator;
s3: the intrinsic light attenuates the light intensity through the attenuator, is transmitted to the coupler through the light path and is coupled with the return signal light;
s4: and the coupled light beams are sent to a balance detector for adjustment and then processed by a data processor to obtain the speed and direction of wind.
2. The method of sparse modulation wind radar according to claim 1, wherein the modulation of the good signal in step S2 comprises sparse inner modulation and sparse outer modulation;
the sparse internal modulation is modulation of a laser signal at a laser source;
the sparse external modulation is to modulate laser emitted by a laser by a frequency shifter.
3. The method of claim 2, wherein the sparse inner modulation drives a coarse cavity length negative feedback adjustment of the external cavity semiconductor laser through piezoelectric ceramics, and simultaneously injects current into the external cavity semiconductor laser to change the refractive index of a gain medium in a wall, so as to be used for the fine feedback adjustment of the optical length in the cavity.
4. The method of the sparse modulation wind radar according to claim 2, wherein the anemometry calculation process of the sparse inner modulation and the sparse outer modulation is as follows:
the frequency of the emission signal is periodically changed linearly up and down along with the time, the rising time is the same as the falling time, the average value of the frequency is fc, the transmission delay used for emitting light from the circulator to irradiate the measured target and then scattering the light back to the receiving end is tau, and the change range of the signal frequency is the bandwidth B;
the frequency difference generated between the frequencies of the received echo signals and the local oscillation signals is df;
frequency difference resulting from frequency variation f introduced by distance delay tau R And Doppler shift f d The frequency difference Δ f1 generated at the rising edge of the frequency and the frequency differences Δ f2 and f generated at the falling edge of the frequency are formed R Each phase difference therebetween f d ；
Difference frequency quantity f introduced by distance R And Doppler shiftf d fd can be calculated from Δ f1 and Δ f2 by means of coherent demodulation:
R＝2CT*fd/(4B)；
v＝fd*c/(2fccosθ)；
in the formula: gamma represents the frequency change rate of the emission signal, R represents the distance between the laser radar and the measured target, c represents the light velocity, v represents the projection of the target velocity on the connecting line of the laser radar and the measured target, fc represents the central frequency of the optical carrier of the emission signal, and theta is the included angle between the emission laser and the movement direction of the particles to be measured.
5. The method of the sparse modulation wind radar according to claim 1, wherein the wind direction calculation process of the sparse inner modulation is as follows:
at t 1 Time chirp at t 2 Frequency modulation is not carried out; then at t 1 Time, intermediate frequency f IF ＝f L +f d Wherein
Figure FDA0003828714380000021
B is modulation bandwidth, R is detection distance, T fm Is the time of the chirp, c represents the speed of light;
using a focus-adjusting lens, the detection distance is the distance between the focal position of the lens and the radar, so f L Is a known quantity, if IF ＞f L If the wind direction is positive, otherwise, the wind direction is negative, and the judgment of the sparse internal modulation wind direction is completed.
6. The method of sparse modulation wind radar according to claim 2, wherein the wind direction measurement process of sparse outer modulation is:
when at t 2 Time and intermediate frequency spectrum can generate interference frequency and wind speed signals generated by a frequency shifter, only the frequency of the wind signals and the interference frequency are judged to obtain the wind direction, and the frequency shifter is f N Judging the wind signal frequency and f N If the size of (b) is larger than f N The radial wind is positive and vice versa.
7. The method of the sparse modulation wind radar according to claim 2, wherein the sparse outer modulation adopts an electro-optical modulator-based tuning mode, and comprises the following steps:
transmitting laser emitted by a laser into an electro-optical modulator, applying voltage to an electro-optical crystal, changing the refractive index of the electro-optical crystal, and modulating the phase, amplitude, intensity and polarization state of an optical signal through the change of the laser characteristic of the crystal; a linear optical frequency signal is output.
8. The method of the sparse modulation wind radar according to claim 2, wherein the sparse outer modulation adopts a tuning mode based on a cyclic frequency shift structure, and comprises the following steps:
and the circulating frequency shift loop and the scanning tuning device modulate the received laser to obtain a linear optical frequency signal.
9. A system of a sparse modulation wind radar is characterized in that the method of the sparse modulation wind radar based on any one of claims 1 to 7 comprises a seed source and a beam splitter and an attenuator which are respectively connected with the seed source;
the output end of the beam splitter is sequentially connected with an AOM, an EDFA and a circulator, and the circulator is also connected with a telescope; the output end of the attenuator and the output end of the circulator are respectively connected with a coupler, and the output end of the coupler is sequentially connected with the balance detector and the oscilloscope.
CN202211066865.9A 2022-09-01 2022-09-01 Method and system for sparse modulation wind-measuring radar Pending CN115308715A (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115656983A (en) * 2022-12-08 2023-01-31 武汉聚合光子技术有限公司 Continuous laser for coherent laser radar
CN118566943A (en) * 2024-08-01 2024-08-30 山东省科学院激光研究所 Non-blind area coherent wind lidar system

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115656983A (en) * 2022-12-08 2023-01-31 武汉聚合光子技术有限公司 Continuous laser for coherent laser radar
CN118566943A (en) * 2024-08-01 2024-08-30 山东省科学院激光研究所 Non-blind area coherent wind lidar system

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