Digital intermediate-frequency coherent Doppler wind-finding radar system

Abstract

The invention discloses a digital intermediate-frequency coherent Doppler wind-finding radar system, and relates to the field of wind-finding radars, in particular to a compact laser wind-finding radar system based on optical fiber optics design, which comprises a transmitting unit, a digital intermediate-frequency coherent receiving module and an upper computer unit, the digital intermediate-frequency coherent receiving module receives backward echo signals scattered by aerosol particles in the atmosphere in a digital intermediate-frequency coherent receiving mode and performs preliminary signal conditioning, and the upper computer unit accurately extracts Doppler frequency shift information by applying a digital signal processing algorithm, so that the wind speed and the wind direction are calculated; and the system is responsible for coordinating the work of each unit and realizing the automatic operation of the system. By optimizing the optical module, the digital intermediate frequency coherent receiving mode and the signal processing algorithm, the wind measurement precision and reliability are improved, the system complexity is reduced, and the wide application prospect is achieved.

Description

Technical Field

[0001] This invention relates to the field of wind measurement radar technology, and more specifically to a digital intermediate frequency coherent Doppler wind measurement radar system. Background Technology

[0002] With the development of meteorological monitoring, aerospace, wind power generation and other fields, the demand for accurate measurement of atmospheric wind fields is increasing. Doppler wind radar, as an important wind measurement device, measures wind speed and direction by emitting electromagnetic waves and receiving echo signals scattered by aerosol particles in the atmosphere, using the Doppler effect.

[0003] Traditional Doppler wind radar has several problems. Firstly, its transmitted signal stability and frequency accuracy are limited, resulting in poor echo signal quality and affecting wind measurement accuracy. Secondly, due to the incoherence of lidar pulse signals, the initial phases of each pulse carrier cannot remain consistent, exhibiting randomness. This randomness is caused by internal switching time jitter during the pulse output process of the radar laser source. This randomness has the following characteristics: the initial phase of each pulse carrier changes randomly, and the initial phase of a transmitted pulse carrier is the same as the initial phase of the echo pulse corresponding to that transmitted pulse.

[0004] Therefore, how to eliminate randomness and improve the wind measurement accuracy of Doppler wind radar is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] In view of the above problems, the present invention is proposed to provide a digital intermediate frequency coherent Doppler wind measurement radar system that overcomes or at least partially solves the above problems, eliminates the incoherence of each pulse, that is, eliminates the random initial phase of each pulse carrier, so as to improve wind measurement accuracy, reduce system cost, enhance system reliability and anti-interference capability.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, embodiments of the present invention provide a digital intermediate frequency coherent Doppler wind measurement radar system, including a transmitting unit, a digital intermediate frequency coherent receiving module, and a host computer unit; The transmitting unit generates and transmits radio frequency signals; the digital intermediate frequency coherent receiving module receives the echo signal and the synchronization signal and local oscillator light sent by the transmitting unit, performs digital coherent reception processing to generate digital signals; the host computer unit analyzes and processes the digital signals to obtain wind speed and wind direction. The digital intermediate frequency (IF) coherent receiver module includes a digitally controlled oscillator (NCO), an optical heterodyne detector, an IF amplifier, an analog-to-digital converter (ADC), and a digital phase subtractor. The optical heterodyne detector receives the echo signal and the local oscillator light, and performs photoelectric signal conversion to generate an analog electrical signal. The IF amplifier amplifies the analog electrical signal to obtain the IF signal. The ADC digitally samples the IF signal to obtain a sampled signal. The NCO receives the synchronization signal to generate an IF local oscillator signal for detection. The digital phase subtractor receives the sampled signal and the IF local oscillator signal, performs phase difference processing to remove random phase from the sampled signal, and obtains a digital signal.

[0007] Preferably, the transmitting unit includes a seed laser, an optical fiber beam splitter, an acousto-optic modulator, a synchronization signal transmitter, a driver, an optical fiber main amplifier, a circulator, and an optical antenna. The synchronization signal generator generates a stable initial frequency signal, which is sent to the driver as a synchronization trigger signal and to the digitally controlled oscillator of the digital intermediate frequency coherent receiver module as a synchronization signal. The driver modulates the acousto-optic modulator according to the synchronization trigger signal. The seed laser outputs a steady-state laser, which passes through the optical fiber beam splitter. Part of the steady-state laser is sent to the modulated acousto-optic modulator to be converted into a pulsed light signal, and the remaining steady-state laser is sent as the local oscillator light to the optical heterodyne detector of the digital intermediate frequency coherent receiver module. The optical fiber main amplifier amplifies the power of the pulsed light signal to obtain a radio frequency (RF) signal. The RF signal is transmitted by the optical antenna through the circulator, and simultaneously, the RF signal is transmitted as the first set of echo signals to the optical heterodyne detector of the digital intermediate frequency coherent receiver module.

[0008] The technical effects of the above-mentioned technical solution are as follows: the synchronous signal transmitter generates a highly stable and high-precision initial frequency signal, which meets the frequency stability requirements of the transmitted signal; the acousto-optic modulator modulates the initial frequency signal to make the signal have a specific frequency change pattern, so as to improve the distance resolution; the fiber optic main amplifier amplifies the power of the modulated signal to ensure that the transmitted signal has sufficient strength to propagate to the target area and obtain an effective echo signal.

[0009] Preferably, the digital intermediate frequency coherent receiving module shares an optical antenna with the transmitting unit, or has an independent optical antenna. The second set of echo signals is received through the optical antenna and transmitted to the optical heterodyne detector through the circulator of the transmitting unit.

[0010] Preferably, the digital intermediate frequency (IF) coherent receiver module includes two sets of optical heterodyne detectors, two sets of IF amplifiers, two sets of analog-to-digital converters, a digitally controlled oscillator, and a digital phase subtractor. The first set of optical heterodyne detectors receives a first set of echo signals and local oscillator light, performs photoelectric signal conversion to generate a first set of analog electrical signals, and the second set of optical heterodyne detectors receives a second set of echo signals and local oscillator light, performs photoelectric signal conversion to generate a second set of analog electrical signals. The first set of IF amplifiers amplifies the first set of analog electrical signals to obtain the first set of IF signals, and the second set of IF amplifiers amplifies the second set of analog electrical signals to obtain the second set of IF signals. The system generates a frequency signal; the first set of analog-to-digital converters digitally samples the first set of intermediate frequency signals to obtain a reference sample signal, and the second set of analog-to-digital converters digitally samples the second set of intermediate frequency signals to obtain an echo sample signal; the digitally controlled oscillator receives the synchronization signal to generate an I-channel intermediate frequency local oscillator signal and a Q-channel intermediate frequency local oscillator signal; the digital phase subtractor performs digital down-conversion on the reference sample signal and the I-channel intermediate frequency local oscillator signal, the reference sample signal and the Q-channel intermediate frequency local oscillator signal, the echo sample signal and the I-channel intermediate frequency local oscillator signal, and the echo sample signal and the Q-channel intermediate frequency local oscillator signal respectively, and then performs phase difference interaction to output a digital signal.

[0011] Preferably, the host computer unit includes a signal processing unit, a microcontroller, and a communication interface. The signal processing unit receives and analyzes digital signals to obtain wind speed and direction. The microcontroller connects the signal processing unit, the seed laser of the transmitting unit, the acousto-optic modulator, the synchronization signal transmitter, the intermediate frequency amplifier of the digital intermediate frequency coherent receiver module, and the signal processing unit. It is used to control the frequency, power, and modulation method of the transmitted signal, the gain and filter bandwidth of the digital intermediate frequency coherent receiver module, and the processing algorithm parameters of the signal processing unit. The communication interface connects the signal processing unit, the microcontroller, and external devices. It is used to transmit wind speed and direction to external devices and to receive control commands from external devices and transmit them to the microcontroller. The microcontroller and the communication interface are used to control the working status of each unit. The microcontroller is also responsible for coordinating the workflow of each unit to ensure the normal operation of the system. The communication interface realizes remote control of the system by receiving control commands from external devices.

[0012] Preferably, the signal processing unit includes a filter, a fast Fourier transform module, and a wind speed and direction calculation module; the filter is a bandpass filter to remove noise and interference signals, allowing only signals within a specific frequency range to pass; the fast Fourier transform module uses the phase unwrapping algorithm of fast Fourier transform to perform spectral analysis on the down-converted digital signal to obtain the signal's spectral distribution; the wind speed and direction calculation module calculates wind speed and direction based on the signal's spectral distribution using a Doppler frequency shift algorithm.

[0013] Preferably, the wind speed and direction calculation module calculates the radial velocity of the target based on the Doppler frequency shift formula combined with the radar's operating frequency and the wavelength of the transmitted signal, and then obtains the wind speed and direction through multi-beam measurement and geometric relationship calculation.

[0014] Preferably, the signal processing process of the digital intermediate frequency coherent receiver module is as follows: Step 1: The optical heterodyne detector processes the received local oscillator light and echo signal to obtain an analog electrical signal; Step 2: After the analog electrical signal is amplified by the intermediate frequency amplifier, the intermediate frequency signal is obtained, and its expression is:

[0015]

[0016] in, This refers to the intermediate frequency (IF) signal frequency of the radar. For Doppler frequency, For each pulse carrier, there is a random phase; A r Indicates the first group of analog electrical signals; A e This represents the second group of analog electrical signals; This is the first group of intermediate frequency signals; This is the second group of intermediate frequency signals; Step 3: The intermediate frequency signal is sampled by the analog-to-digital converter to generate a sampled signal, the expression of which is:

[0017]

[0018] In the formula, The digital angular frequency of the intermediate frequency. , The sampling frequency; The digital angular frequency of the Doppler frequency. ; Indicates the reference sampled signal; This represents the echo sampled signal; n represents the sampling point number during the conversion from the continuous time domain to the discrete time domain. Step 4: The synchronization signal is used by a digitally controlled oscillator to generate an intermediate frequency (IF) local oscillator signal, and the IF local oscillator signal is then decomposed into IQ values, as follows:

[0019] in, This represents the I-channel component of the intermediate frequency local oscillator signal; A0 represents the Q-channel component of the intermediate frequency local oscillator signal; A0 represents the synchronization signal. Digital down-conversion is achieved by performing IQ decomposition on the sampled signal, as shown below:

[0020]

[0021] in, and These represent the I-channel and Q-channel components of the reference sampled signal, respectively. and These represent the I-channel and Q-channel components of the echo sampling signal, respectively. Step 5: The I and Q components of the intermediate frequency local oscillator signal, the I and Q components of the reference sampling signal, and the I and Q components of the echo sampling signal undergo phase difference interaction in a digital phase subtractor, outputting a digital signal with the following expression:

[0022] The digital signal is the result of combining the I / Q component outputs of the reference signal and the echo signal, including... and , representing the I-channel component and the Q-channel component of the digital signal, respectively.

[0023] As can be seen from the above technical solution, compared with the prior art, the present invention discloses a digital intermediate frequency coherent Doppler wind radar system for high-precision measurement of atmospheric wind fields. By optimizing the frequency source and modulation technology of the transmitting unit, the quality of the transmitted signal is improved; advanced digital intermediate frequency coherent receiving method and signal processing technology are adopted to enhance the processing capability and wind measurement accuracy of the echo signal; and automatic control of the system is realized through the host computer unit, which improves the reliability and anti-interference capability of the system. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0025] Figure 1 A schematic diagram of a digital intermediate frequency coherent Doppler wind measurement radar system provided by the present invention; Figure 2 This is a schematic diagram of the structure of the digital intermediate frequency coherent receiver module provided by the present invention. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] This invention discloses a digital intermediate frequency coherent Doppler wind measurement radar system, including a transmitting unit, a digital intermediate frequency coherent receiving module, and a host computer unit; The transmitting unit generates and transmits radio frequency signals; the digital intermediate frequency coherent receiving module receives the echo signal and the synchronization signal and local oscillator light sent by the transmitting unit, performs digital coherent reception processing to generate digital signals; the host computer unit analyzes and processes the digital signals to obtain wind speed and wind direction. The digital intermediate frequency (IF) coherent receiver module includes a digitally controlled oscillator (NCO), an optical heterodyne detector, an IF amplifier, an analog-to-digital converter (ADC), and a digital phase subtractor. The optical heterodyne detector receives the echo signal and the local oscillator light, and performs photoelectric signal conversion to generate an analog electrical signal. The IF amplifier amplifies the analog electrical signal to obtain the IF signal. The ADC digitally samples the IF signal to obtain a sampled signal. The NCO receives the synchronization signal to generate an IF local oscillator signal for detection. The digital phase subtractor receives the sampled signal and the IF local oscillator signal, performs phase difference processing to remove random phase from the sampled signal, and obtains a digital signal.

[0028] In one specific embodiment, such as Figure 1 As shown, a digital intermediate frequency coherent Doppler wind radar system includes a transmitting unit, a digital intermediate frequency coherent receiving module 9, and a host computer unit 10. The transmitting unit includes a seed laser 1, an optical fiber beam splitter 2, an acousto-optic modulator 3, a synchronization signal transmitter 4, a driver 5, an optical fiber main amplifier 6, a circulator 7, and an optical antenna 8. The synchronization signal transmitter 4 generates a stable initial frequency signal, which is sent to the driver as a synchronization trigger signal and to the digitally controlled oscillator of the digital intermediate frequency coherent receiving module as a synchronization signal, such as an 80MHz microwave signal. The driver 5 modulates the acousto-optic modulator 3 according to the synchronous trigger signal; the seed laser 1 outputs a steady-state laser and passes through the fiber beam splitter 2, sending part of the steady-state laser to the modulated acousto-optic modulator 3 to be converted into a pulsed light signal, and the remaining steady-state laser is sent as the local oscillator light to the optical heterodyne detector of the digital intermediate frequency coherent receiver module 9; the fiber main amplifier 6 amplifies the power of the pulsed light signal to obtain the radio frequency signal; the radio frequency signal is transmitted by the optical antenna 8 through the circulator 7, and at the same time, the radio frequency signal is transmitted as the first set of echo signals to the optical heterodyne detector of the digital intermediate frequency coherent receiver module 9.

[0029] In one specific embodiment, the structure of the digital intermediate frequency coherent receiver module is as follows: Figure 2 As shown, the system includes a first set of optical heterodyne detectors 11 and a second set of optical heterodyne detectors 12, a first set of intermediate frequency amplifiers 13 and a second set of intermediate frequency amplifiers 14, a first set of analog-to-digital converters (ADCs) 15 and a second set of analog-to-digital converters 16, a digitally controlled oscillator (NCO) 17, and a digital phase subtractor 18. The first set of optical heterodyne detectors 11 receives a first set of echo signals 1 and local oscillator light 1, and performs photoelectric signal conversion to generate a first set of analog electrical signals. The second set of optical heterodyne detectors 12 receives a second set of echo signals 2 and local oscillator light 2, and performs photoelectric signal conversion to generate a second set of analog electrical signals. The first set of intermediate frequency amplifiers 13 amplifies the first set of analog electrical signals to obtain the first set of intermediate frequency signals, and the second set of intermediate frequency amplifiers 14 amplifies the second set of analog electrical signals to obtain the second set of intermediate frequency signals. The first set of analog-to-digital converters 15 digitally samples the first set of intermediate frequency signals. The second set of analog-to-digital converters 16 obtains a reference sampling signal, and the second set of intermediate frequency signals 16 performs digital sampling on the second set of intermediate frequency signals to obtain an echo sampling signal; the digitally controlled oscillator 17 receives a synchronization signal to generate an I-channel intermediate frequency local oscillator signal and a Q-channel intermediate frequency local oscillator signal; the digital phase subtractor 18 performs digital down-conversion on the reference sampling signal and the I-channel intermediate frequency local oscillator signal, the reference sampling signal and the Q-channel intermediate frequency local oscillator signal, the echo sampling signal and the I-channel intermediate frequency local oscillator signal, and the echo sampling signal and the Q-channel intermediate frequency local oscillator signal respectively, and then performs phase difference interaction to output a digital signal.

[0030] A digital intermediate frequency (IF) coherent receiver module based on software-defined radio (SDR) principles is a multi-band, multi-mode, and multi-functional receiver with strong signal processing capabilities. In the application of coherent laser wind measurement radar, digital IF technology is used to achieve coherent reception of radar signals, eliminating random initial phase of each pulse carrier. Applying digital IF technology to coherent laser wind measurement radar systems offers numerous advantages, including wide linear range, low drift, low distortion, good I / Q channel orthogonality, and good amplitude consistency. This invention combines digital IF technology with coherent reception and applies it to a coherent laser wind measurement radar receiving system to achieve digital IF coherent reception of laser radar meteorological echo signals.

[0031] Furthermore, the digital intermediate frequency coherent receiving module shares the optical antenna 8 with the transmitting unit, or has an independent optical antenna. The second set of echo signals is received through the optical antenna and transmitted to the optical heterodyne detector through the circulator 7 of the transmitting unit.

[0032] In one specific embodiment, the host computer unit includes a signal processing unit, a microcontroller, and a communication interface. The signal processing unit receives and analyzes digital signals to obtain wind speed and direction. The microcontroller connects to the signal processing unit, the seed laser of the transmitting unit, the acousto-optic modulator, the synchronization signal transmitter, the intermediate frequency amplifier of the digital intermediate frequency coherent receiver module, and the signal processing unit. It is used to control the frequency, power, and modulation method of the transmitted signal, the gain and filter bandwidth of the digital intermediate frequency coherent receiver module, and the processing algorithm parameters of the signal processing unit. The communication interface connects the signal processing unit, the microcontroller, and external devices. It is used to transmit wind speed and direction to external devices and to receive control commands from external devices and transmit them to the microcontroller. The microcontroller and the communication interface are used to control the working status of each unit. The microcontroller is also responsible for coordinating the workflow of each unit to ensure the normal operation of the system. The communication interface enables remote control of the system by receiving control commands from external devices.

[0033] In one specific embodiment, the signal processing unit includes a filter, a fast Fourier transform module, and a wind speed and direction calculation module; the filter is a bandpass filter to remove noise and interference signals, allowing only signals within a specific frequency range to pass; the fast Fourier transform module uses the phase unwrapping algorithm of fast Fourier transform to perform spectral analysis on the down-converted digital signal to obtain the signal's spectral distribution; the wind speed and direction calculation module calculates the wind speed and direction based on the signal's spectral distribution using a Doppler frequency shift algorithm.

[0034] Furthermore, the wind speed and direction calculation module calculates the target's radial velocity based on the Doppler frequency shift formula combined with the radar's operating frequency and the wavelength of the transmitted signal. Then, through multi-beam measurement and geometric relationship calculation, the wind speed and direction are obtained.

[0035] In one specific embodiment, the process by which the digital intermediate frequency (IF) coherent receiving module implements digital IF coherent reception is as follows: S1: The expressions for the intermediate frequency signals output by the first group of optical heterodyne detectors 11 and the second group of optical heterodyne detectors 12 are shown in formulas (1) and (2). (1) (2) In the formula, This refers to the intermediate frequency (IF) signal frequency of the radar. For Doppler frequency, Each pulse carrier has a random phase; S2: Perform passband sampling on the two intermediate frequency signals shown in formulas (1) and (2) respectively to obtain the expressions shown in formulas (3) and (4) respectively.

[0036] (3) (4) In the formula, The digital angular frequency of the intermediate frequency. ; The digital angular frequency of the Doppler frequency. ; S3: When the acousto-optic modulator shifts the seed laser frequency by 80MHz, the optical heterodyne detector outputs an intermediate frequency (IF) signal centered at 80MHz, with a Doppler bandwidth of 40MHz. This means the IF signal is a bandpass signal (40MHz, 120MHz). In this embodiment, the IF sampling rate... Set to 250MHz; The signals shown in formulas (3) and (4) are quantized into digital signals and then interacted with the NCO to achieve digital downconversion. The expression of the NCO acting on the quadrature dual channel is shown in formula (5), where the frequency of the NCO should be set to 30MHz according to the intermediate frequency on the baseband. (5) S4: The NCO shown in formula (5) is digitally downconverted with the reference signal shown in formula (3) and the echo signal shown in formula (4). The results of the digital downconversion of the reference signal and the echo signal are shown in formula (6) and (7), respectively. (6) (7) in, and These represent the I-channel and Q-channel components of the reference sampled signal, respectively. and These represent the I-channel and Q-channel components of the echo sampling signal, respectively. S5: The echo signal shown in formula (7) interacts with the reference signal shown in formula (6) to achieve the purpose of eliminating random initial phase. The two signals need to be input into the digital phase subtractor 22. Using the trigonometric identity shown in formula (8), we can obtain the expression of the interaction between formulas (6) and (7) to eliminate the random initial phase of each pulse carrier in the echo, as shown in formula (9). (8) (9) and , representing the I-channel component and Q-channel component of the digital signal, respectively; Formula (9) is the principle of a digital phase subtractor. By combining the two I / Q outputs of the reference signal and the echo signal, two I / Q outputs with eliminated random phase are obtained, which require four multiplication operations and two addition operations respectively. Digital coherent reception is realized through a digital phase subtractor.

[0037] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0038] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A digital intermediate frequency coherent Doppler wind measurement radar system, characterized in that, It includes a transmitting unit, a digital intermediate frequency coherent receiving module, and a host computer unit; The transmitting unit generates and transmits radio frequency signals; the digital intermediate frequency coherent receiving module receives the echo signal and the synchronization signal and local oscillator light sent by the transmitting unit, performs digital coherent reception processing to generate digital signals; the host computer unit analyzes and processes the digital signals to obtain wind speed and wind direction. The digital intermediate frequency coherent receiver module includes a digitally controlled oscillator, an optical heterodyne detector, an intermediate frequency amplifier, an analog-to-digital converter, and a digital phase subtractor. The optical heterodyne detector receives the echo signal and the local oscillator light, and performs photoelectric signal conversion to generate an analog electrical signal. The intermediate frequency amplifier amplifies the analog electrical signal to obtain the intermediate frequency signal. The analog-to-digital converter digitally samples the intermediate frequency signal to obtain the sampled signal. A digitally controlled oscillator receives a synchronization signal to generate an intermediate frequency local oscillator signal; a digital phase subtractor receives a sampled signal and an intermediate frequency local oscillator signal, performs phase difference processing, and obtains a digital signal.

2. The digital intermediate frequency coherent Doppler wind measurement radar system according to claim 1, characterized in that, The transmitting unit includes a seed laser, an optical fiber beam splitter, an acousto-optic modulator, a synchronization signal transmitter, a driver, an optical fiber main amplifier, a circulator, and an optical antenna; the synchronization signal generator generates a stable initial frequency signal, which is sent to the driver as a synchronization trigger signal and to the digitally controlled oscillator as a synchronization signal; the driver modulates the acousto-optic modulator according to the synchronization trigger signal; The seed laser outputs a steady-state laser beam, which is then split by an optical fiber beam splitter. Part of the steady-state laser beam is sent to a modulated acousto-optic modulator to be converted into a pulsed light signal. The remaining steady-state laser beam is sent as the local oscillator beam to an optical heterodyne detector. The optical fiber main amplifier amplifies the power of the pulsed light signal to obtain an radio frequency signal. The radio frequency signal is transmitted by the optical antenna through the circulator, and at the same time, the radio frequency signal is transmitted to the optical heterodyne detector as the first set of echo signals.

3. The digital intermediate frequency coherent Doppler wind measurement radar system according to claim 2, characterized in that, The digital intermediate frequency coherent receiving module shares an optical antenna with the transmitting unit, or has an independent optical antenna; the digital intermediate frequency coherent receiving module receives the second set of echo signals through the optical antenna, and transmits them to the optical heterodyne detector through a circulator.

4. The digital intermediate frequency coherent Doppler wind measurement radar system according to claim 3, characterized in that, The digital intermediate frequency (IF) coherent receiver module includes two sets of optical heterodyne detectors, two sets of IF amplifiers, two sets of analog-to-digital converters, a digitally controlled oscillator, and a digital phase subtractor. The first set of optical heterodyne detectors receives the first set of echo signals and the local oscillator light, performing photoelectric signal conversion to generate the first set of analog electrical signals. The second set of optical heterodyne detectors receives the second set of echo signals and the local oscillator light, performing photoelectric signal conversion to generate the second set of analog electrical signals. The first set of IF amplifiers amplifies the first set of analog electrical signals to obtain the first set of IF signals, and the second set of IF amplifiers amplifies the second set of analog electrical signals to obtain the second set of IF signals. The first set of analog-to-digital converters (ADCs) digitally samples the first set of intermediate frequency (IF) signals to obtain a reference sample signal; the second set of ADCs digitally samples the second set of IF signals to obtain an echo sample signal; the digitally controlled oscillator receives the synchronization signal to generate an I-channel IF local oscillator signal and a Q-channel IF local oscillator signal; the digital phase subtractor performs digital down-conversion on the reference sample signal and the I-channel IF local oscillator signal, the reference sample signal and the Q-channel IF local oscillator signal, the echo sample signal and the I-channel IF local oscillator signal, and the echo sample signal and the Q-channel IF local oscillator signal respectively, and then performs phase difference interaction to output a digital signal.

5. A digital intermediate frequency coherent Doppler wind measurement radar system according to claim 1, characterized in that, The host computer unit includes a signal processing unit, a microcontroller, and a communication interface; the signal processing unit receives digital signals, analyzes and processes them to obtain wind speed and wind direction; the microcontroller connects to the transmitting unit, the digital intermediate frequency coherent receiving module, and the signal processing unit; the communication interface connects the signal processing unit, the microcontroller, and external devices.

6. A digital intermediate frequency coherent Doppler wind measurement radar system according to claim 5, characterized in that, The signal processing unit includes a filter, a fast Fourier transform module, and a wind speed and direction calculation module. The filter uses a bandpass filter to remove noise and interference signals. The fast Fourier transform module uses the phase unwrapping algorithm of fast Fourier transform to perform spectral analysis on the down-converted digital signal to obtain the signal's spectral distribution. The wind speed and direction calculation module calculates wind speed and direction based on the signal's spectral distribution using a Doppler frequency shift algorithm.

7. A digital intermediate frequency coherent Doppler wind measurement radar system according to claim 6, characterized in that, The wind speed and direction calculation module calculates the radial velocity of the target based on the Doppler frequency shift formula, combined with the radar's operating frequency and the wavelength of the transmitted signal. Then, through multi-beam measurement and geometric relationship calculation, the wind speed and direction are obtained.

8. A digital intermediate frequency coherent Doppler wind measurement radar system according to claim 4, characterized in that, The process of signal processing by the digital intermediate frequency coherent receiver module is as follows: Step 1: The optical heterodyne detector processes the received local oscillator light and echo signal to obtain an analog electrical signal; Step 2: After the analog electrical signal is amplified by the intermediate frequency amplifier, the intermediate frequency signal is obtained, and its expression is: in, This refers to the intermediate frequency (IF) signal frequency of the radar. For Doppler frequency, For each pulse carrier, there is a random phase; A r Indicates the first group of analog electrical signals; A e This represents the second group of analog electrical signals; This is the first group of intermediate frequency signals; This is the second group of intermediate frequency signals; Step 3: The intermediate frequency signal is sampled by the analog-to-digital converter to generate a sampled signal, the expression of which is: In the formula, The digital angular frequency of the intermediate frequency. , The sampling frequency; The digital angular frequency of the Doppler frequency. ; Indicates the reference sampled signal; This represents the echo sampling signal; n represents the sampling point number; Step 4: The synchronization signal is used by a digitally controlled oscillator to generate an intermediate frequency (IF) local oscillator signal, and the IF local oscillator signal is then decomposed into IQ values, as follows: in, This represents the intermediate frequency local oscillator signal of channel I; A0 represents the intermediate frequency local oscillator signal of the Q-channel; A0 represents the synchronization signal. Digital down-conversion is achieved by performing IQ decomposition on the sampled signal, as shown below: in, and These represent the I-channel and Q-channel components of the reference sampled signal, respectively. and These represent the I-channel and Q-channel components of the echo sampling signal, respectively. Step 5: The I and Q components of the intermediate frequency local oscillator signal, the I and Q components of the reference sampling signal, and the I and Q components of the echo sampling signal undergo phase difference interaction in a digital phase subtractor, outputting a digital signal with the following expression: in, and These represent the I-channel component and the Q-channel component of the digital signal, respectively.

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