Double-system laser wind finding radar based on frequency reuse

Abstract

The invention discloses a double-system laser wind finding radar system based on frequency reuse. The device comprises a narrow linewidth seed light source (1), a continuous optical amplifier pre-amplification module (2), a first 1 * 2 coupler (3), a second 1 * 2 coupler (4), a first acoustic optical modulator (5), a pulsed optical amplifier multistage amplification module (6), a second acoustic optical modulator (7), a continuous optical amplifier multistage amplification module (8), a third 1 * 2 coupler (9), a circulator (10), an optical antenna (11), a 2 * 2 coupler (12), a balance detector (13) and a signal processing module (14). According to the invention, a double-system composite optical path structure based on frequency multiplexing is adopted, the near blind area characteristic of continuous coherent detection can be obtained, and the characteristics of long measurement range and high precision of pulse coherent detection can also be obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of laser wind measurement, and relates to a dual-system laser wind measurement radar based on frequency multiplexing. Background Art

[0002] Atmospheric wind fields are closely related to our daily lives. For example, they are of great significance in civil meteorological observations, civil aviation, the utilization and optimization of wind energy, and the study of atmospheric dynamics. Especially in terms of civil aviation safety, it has important application value for airport wind shear monitoring, aircraft wake vortex measurement, and civil aircraft takeoff and landing. Specifically, during the takeoff and landing phase of aircraft near the ground, the height position will be significantly affected by dynamic and thermal forces, and turbulence and wind shear are prone to occur. Since this height is mainly in the takeoff and landing phase of the aircraft, the speed of the aircraft is relatively low, so it is more susceptible to interference from wind field changes, resulting in unstable state and shaking of the aircraft. In order to ensure flight safety, the need for high-precision real-time measurement of the wind field within this altitude range is urgent. However, due to the limitations of resolution and radar detection blind spots, the existing wind measurement technology cannot simultaneously meet the requirements of high resolution and large range of wind measurement.

[0003] Compared with traditional wind field characterization methods such as wind speed sensors, laser wind radar has the advantages of large measurement range, high measurement accuracy and a wide range of applications. After years of development, laser wind radar can be mainly divided into coherent detection system and incoherent detection system. The two technical systems use different frequency discrimination technologies to obtain the Doppler frequency shift, and then invert the wind speed. Among them, the incoherent detection method uses a discriminator to convert the frequency change of light into the change of optical power that can be directly measured; while the coherent detection method is to mix the received backscattered signal with the reference signal, and further process the mixed signal to obtain the Doppler frequency shift caused by the wind speed. However, since the incoherent detection system is easily affected by interference such as solar and ground background radiation, its performance is limited. Therefore, the current laser wind radar is mainly based on the coherent detection system. The coherent detection system can be mainly divided into two types according to its output light: pulse coherent detection system and continuous coherent detection system. Among them, the pulse coherent detection system has the advantages of small size, low power consumption and large measurement range, and has been applied in many scenarios. However, due to the limitation of detection mechanism (pulse width), pulse coherent detection system has a large detection blind area (30m-50m) and low resolution (greater than 30m), which makes the laser wind radar based on this system not suitable for wind field detection at short distance (near ground height) and high range resolution; in contrast, although the laser wind radar based on continuous coherent detection system is only suitable for high-resolution measurement at near ground height (<150m), its range is greatly limited compared with the laser wind radar based on pulse coherent detection system because the long range requires higher output power. At present, most of the laser wind radars are mainly based on a single coherent technology system, which cannot take into account the actual requirements of large range, low blind area, high range resolution, small size, high integration, etc. Therefore, it is crucial to realize a laser wind radar with the performance advantages of pulse coherent detection system and continuous coherent detection system, and avoid the real-time limitation problem faced by the current laser radar based on the composite system (channel switching is required to realize near-field and far-field measurement respectively), which is crucial for the function expansion of laser wind radar and its overall performance improvement. Summary of the invention

[0004] (I) Purpose of the invention

[0005] The purpose of the present invention is to provide a dual-system laser wind measuring radar based on frequency reuse with good real-time performance, narrow blind area and long measuring range, in order to solve the problem that the current laser wind measuring radar is difficult to simultaneously take into account large measuring range and small-scale space for real-time wind field measurement.

[0006] (II) Technical solution

[0007] In order to solve the above technical problems, the present invention provides a dual-system laser wind measurement radar system based on frequency multiplexing, comprising: a narrow linewidth seed light source 1, a continuous light amplifier preamplifier module 2, a first 1x2 coupler 3, a second 1x2 coupler 4, a first acousto-optic modulator 5, a pulse light amplifier multi-stage amplification module 6, a second acousto-optic modulator 7, a continuous light amplifier multi-stage amplification module 8, a third 1x2 coupler 9, a circulator 10, an optical antenna 11, a 2x2 coupler 12, a balanced detector 13 and a signal processing module 14; the narrow linewidth seed light source 1 is connected to the input end of the continuous light amplifier preamplifier module 2, the output end of the continuous light amplifier preamplifier module 2 is connected to the 1 port of the first 1x2 coupler 3, and the output end of the first 1x2 coupler 3 is connected to the 1 port of the first 1x2 coupler 3. The 2nd port is connected to the 1st port of the second 1x2 coupler 4, the 3rd port of the first 1x2 coupler 3 is connected to the 1st port of the 2x2 coupler 12, the 2nd port of the second 1x2 coupler 4 is connected to the input end of the first acousto-optic modulator 5, the 3rd port of the second 1x2 coupler 4 is connected to the input end of the second acousto-optic modulator 7, the output end of the first acousto-optic modulator 5 is connected to the input end of the pulse light amplifier multistage amplification module 6, the output end of the pulse light amplifier multistage amplification module 6 is connected to the 1st port of the third 1x2 coupler 9, the output end of the second acousto-optic modulator 7 is connected to the input end of the continuous light amplifier multistage amplification module 8, the output end of the continuous light amplifier multistage amplification module 8 is connected to the 2nd port of the third 1x2 coupler 9, and the output end of the third 1x2 coupler 9 is connected to the 2nd port of the third 1x2 coupler 9. Port 3 of the coupler 9 is connected to port 1 of the circulator 10, port 2 of the circulator 10 is connected to the optical antenna 11, port 3 of the circulator 10 is connected to port 2 of the 2x2 coupler 12, the other ports of the 2x2 coupler 12 are connected to the input end of the balanced detector 13, and the output end of the balanced detector 13 is connected to the input end of the signal processing module 14; the narrow linewidth seed light source 1 outputs continuous light and is connected to the continuous light amplifier preamplifier module 2, and the continuous light after preamplification is connected to the first 1x2 coupler 3, and the port 3 after being split by the first 1x2 coupler 3 outputs one continuous light as the local oscillator light, and the port 2 outputs another continuous signal light and is connected to the input end of the second 1x2 coupler 4; the port 2 outputs light after being split by the second 1x2 coupler 4 The input end of the first acousto-optic modulator 5 is connected to the pulse light modulated to the intermediate frequency f1, and the output end of the first acousto-optic modulator 5 is connected to the input end of the pulse light amplifier multistage amplification module 6 for amplification; at the same time, the 3-port output light after the second 1x2 coupler 4 is connected to the input end of the second acousto-optic modulator 7 for frequency shifting with the intermediate frequency f2, and the output end of the second acousto-optic modulator 7 is connected to the continuous light amplifier multistage amplification module 8 for amplification, and the pulse signal light and the continuous signal light respectively amplified by the pulse light amplifier multistage amplification module 6 and the continuous light amplifier multistage amplification module 8 are connected to the input end of the coupler 9, and the output end of the coupler 9 enters from the 1 port and exits from the 2 port of the circulator 10, and the 2 port of the circulator 10 is connected to the optical antenna 11;The target echo signal returns to the 3-port output of the circulator 10 through the optical antenna 11, and is connected to the input end of the 2x2 coupler 12 with the local oscillator light split by the first 1x2 coupler 3 for coherent signal beat frequency; the optical signal after the beat frequency is transmitted to the signal processing module 14 for signal processing after photoelectric conversion to obtain the corresponding wind field information. ;

[0008] (III) Beneficial effects

[0009] The dual-system laser wind measurement radar based on frequency multiplexing provided by the above technical solution has the following beneficial effects:

[0010] (1) The present invention combines the advantages of continuous coherent detection and pulse coherent detection, and adopts a dual-system composite optical path structure based on frequency multiplexing, which can obtain the near-blind zone characteristics of continuous coherent detection and the long-range and high-precision characteristics of pulse coherent detection;

[0011] (2) The present invention uses frequency multiplexing technology to perform different frequency modulation on the optical signals of the pulse coherent detection channel and the optical signals of the continuous coherent detection channel, so that their respective echo signals can be processed synchronously, thereby improving the real-time performance of the system measurement. At the same time, since the optical signal frequencies of the two channels are different, the two signals can share a set of transceiver antennas and photoelectric detectors, simplifying the system structure of the dual-system laser wind measurement radar;

[0012] (3) The present invention coats all ports of all optical fiber devices with a 1550nm anti-reflection film, thereby increasing the transmittance of the optical fiber, improving the transceiver efficiency of the system, and reducing the adverse effects of the end face reflection of the output light on coherent detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 The schematic diagram of the optical system of a dual-system laser wind measurement radar based on frequency multiplexing according to an embodiment of the present invention.

[0014] In the figure: 1 narrow linewidth seed light source, 2 continuous optical amplifier pre-amplifier module, 3 1x2 coupler, 4 1x2 coupler, 5 first acousto-optic modulator, 6 pulse optical amplifier multi-stage amplification module, 7 second acousto-optic modulator, 8 continuous optical amplifier multi-stage amplification module, 9 1x2 coupler, 10 circulator, 11 optical antenna, 12 2x2 coupler, 13 balanced detector, 14 signal processing module. DETAILED DESCRIPTION

[0015] In order to make the purpose, content and advantages of the present invention more clear, the specific implementation methods of the present invention are further described in detail below in conjunction with the drawings and examples.

[0016] Reference Figure 1As shown, the dual-system laser wind measurement radar system based on frequency multiplexing in this embodiment includes: a narrow linewidth seed light source 1, a continuous optical amplifier preamplifier module 2, a first 1x2 coupler 3, a second 1x2 coupler 4, a first acousto-optic modulator 5, a pulse optical amplifier multistage amplification module 6, a second acousto-optic modulator 7, a continuous optical amplifier multistage amplification module 8, a third 1x2 coupler 9, a circulator 10, an optical antenna 11, a coupler 12, a balanced detector 13 and a signal processing module 14; the narrow linewidth seed light source 1 is connected to the input end of the continuous optical amplifier preamplifier module 2, the output end of the continuous optical amplifier preamplifier module 2 is connected to the 1 port of the first 1x2 coupler 3, the 2 port of the first 1x2 coupler 3 is connected to the 1 port of the second 1x2 coupler 4, the 3 port of the first 1x2 coupler 3 is connected to the 1 port of the 2x2 coupler 12, and the 2 port of the second 1x2 coupler 4 is connected to the first acousto-optic The input end of the modulator 5 is connected, the 3-port of the second 1x2 coupler 4 is connected to the input end of the second acousto-optic modulator 7, the output end of the first acousto-optic modulator 5 is connected to the input end of the pulse light amplifier multistage amplification module 6, the output end of the pulse light amplifier multistage amplification module 6 is connected to the 1-port of the third 1x2 coupler 9, the output end of the second acousto-optic modulator 7 is connected to the input end of the continuous light amplifier multistage amplification module 8, the output end of the continuous light amplifier multistage amplification module 8 is connected to the 2-port of the third 1x2 coupler 9, the 3-port of the third 1x2 coupler 9 is connected to the 1-port of the circulator 10, the 2-port of the circulator 10 is connected to the optical antenna 11, the 3-port of the circulator 10 is connected to the 2-port of the 2x2 coupler 12, the other ports of the 2x2 coupler 12 are connected to the input end of the balanced detector 13, and the output end of the balanced detector 13 is connected to the input end of the signal processing module 14. The narrow linewidth seed light source 1 outputs continuous light and connects to the continuous light amplifier pre-amplifier module 2. The continuous light after pre-amplification connects to the input end of the coupler 3. After being split by the coupler 3, one of the continuous lights (3-port output light) is used as the local oscillator light. Another continuous signal light (2-port output light) after being split by the coupler 3 connects to the input end of the coupler 4. After being split by the coupler 4, one of the lights (2-port output light) connects to the input end of the acousto-optic modulator 5 and is modulated into a pulse light (intermediate frequency is f1). The output end of the first acousto-optic modulator 5 connects to the input end of the pulse light amplifier multi-stage amplification module 6 for amplification; at the same time, after being split by the coupler 4, another light (3-port output light) connects to the input end of the second acousto-optic modulator 7 for frequency shifting (intermediate frequency is f2). The output end of the second acousto-optic modulator 7 connects to the continuous light amplifier multi-stage amplification module 8 for amplification. The amplified pulse signal light (input light at port 1) and continuous signal light (input light at port 2) are connected to the input end of the coupler 9. The output end (port 3) of the coupler 9 enters from port 1 and exits from port 2 of the circulator 10. Port 2 of the circulator 10 is connected to the optical antenna 11.The target echo signal returns to the 3-port output of the circulator 10 through the optical antenna 11, and is connected to the input end of the coupler 12 with the local oscillator light split by the coupler 3 for coherent signal beat. The output end of the coupler 12 is connected to the balanced detector 13, and the balanced detector 13 is connected to the signal processing module 14, so that the optical signal after the beat is transmitted to the signal processing module for signal processing after photoelectric conversion to obtain the corresponding wind field information.

[0017] The narrow linewidth seed light source 1 outputs continuous linearly polarized light with a wavelength of 1550nm and a linewidth of less than 5kHz, and an output power of not less than 10mW.

[0018] The coupler 3 is a 1x2 coupler with a splitting ratio of 99:1.

[0019] The coupler 4 is a 1x2 coupler with a splitting ratio of 50:50.

[0020] The coupler 9 is a 1x2 coupler with a splitting ratio of 50:50.

[0021] The coupler 12 is a 2x2 coupler.

[0022] The frequency shifting frequency of the first AOM 5 and the frequency shifting frequency of the second AOM 7 are higher than 200 MHz, and the frequency difference between the frequency shifting frequencies of the two AOMs is greater than 50 MHz.

[0023] The diameter of the optical antenna 11 is greater than 130 mm, and can be quickly and continuously focused according to actual needs.

[0024] The first AOM 5 and the second AOM 7 are connected to the signal processing module 14 via a radio frequency line, and the signal processing module 14 provides modulation signals to the first AOM 5 and the second AOM 7 respectively.

[0025] The optical fiber device includes a narrow linewidth seed light source 1, a continuous light amplifier pre-amplifier module 2, a coupler 3, a coupler 4, a first acousto-optic modulator 5, a pulse light amplifier multi-stage amplification module 6, a second acousto-optic modulator 7, a continuous light amplifier multi-stage amplification module 8, a coupler 9, a circulator 10, and a coupler 12, all of which are polarization-maintaining devices, and each port is coated with a 1550nm anti-reflection film.

[0026] Since the frequency difference between the frequency shift of the first acousto-optic modulator 5 and the second acousto-optic modulator 7 is greater than 50MHz, the collected beat frequency signal is transmitted to the signal processing module for signal processing after photoelectric conversion, and the test results of the two systems can be demodulated separately by frequency division multiplexing to obtain the corresponding wind field information. Specifically, the collected beat frequency signal is filtered (center frequency f1), range gate divided, and short-time Fourier transform processed, and the Doppler frequency shift is calculated by accumulating multiple spectrum signals, and the radial wind speed and wind direction on the measurement range of the corresponding pulse coherent detection system can be obtained; and the Doppler frequency shift signal can be obtained by filtering the collected data (center frequency f2), fast Fourier transform and spectrum accumulation, and then the wind speed and wind direction on the measurement range of the continuous coherent detection system can be obtained.

[0027] In the actual test, the parameters of the acousto-optic modulator 5 are set to an intermediate frequency of 220 MHz, a pulse width of 100 ns, and a repetition rate of 10 kHz. According to the principle of pulse coherent detection mechanism, the distance resolution ΔL and the blind area L of the radar system can be calculated by the following formulas:

[0028]

[0029] Where τ is the pulse width and c is the speed of light.

[0030] The distance resolution and detection blind area calculated according to the above parameters are 15m and 22.5m respectively. The parameters cannot fully meet the demand for accurate detection of wind fields near the ground. In addition, due to the influence of pulse power and the blind area of ​​the antenna itself under narrow pulse width conditions, it is difficult to achieve wind field detection within the theoretical blind area. Therefore, this scheme combines the pulse coherent detection system and the continuous coherent detection system by frequency division multiplexing, avoiding the real-time limitation problem currently faced by the laser radar based on the composite system (channel switching is required to achieve near-field and far-field measurements respectively). Specifically, the parameters of the acousto-optic modulator 7 are set to an intermediate frequency of 320MHz and continuous output. The continuous coherent detection technology based on this scheme can perform high-performance detection of wind fields within the blind area of ​​pulse coherent detection, and then can realize the integration of the two detection systems on a set of systems by frequency division multiplexing, and can take into account both large-range and small-scale space for real-time measurement of wind fields.

[0031] The signal processing module synchronously collects and processes the beat frequency signal, and extracts the signal of the corresponding channel through frequency division multiplexing in data processing. By processing the signals of two different intermediate frequencies separately, the corresponding near-field and far-field wind speed and wind direction information are obtained, and the processing results are combined together to complete a complete measurement of the wind field detection.

[0032] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A dual-system laser wind measurement radar system based on frequency multiplexing, characterized in that: include: A narrow linewidth seed light source (1), a continuous light amplifier preamplifier module (2), a first 1x2 coupler (3), a second 1x2 coupler (4), a first acousto-optic modulator (5), a pulse light amplifier multistage amplification module (6), a second acousto-optic modulator (7), a continuous light amplifier multistage amplification module (8), a third 1x2 coupler (9), a circulator (10), an optical antenna (11), a 2x2 coupler (12), a balanced detector (13) and a signal processing module (14); the narrow linewidth seed light source (1) is connected to the input end of the continuous light amplifier preamplifier module (2), and the output end of the continuous light amplifier preamplifier module (2) is connected to the first 1 The first 1x2 coupler (3) is connected to port 1 of the first 1x2 coupler (3), the second port of the first 1x2 coupler (3) is connected to port 1 of the second 1x2 coupler (4), the third port of the first 1x2 coupler (3) is connected to port 1 of the 2x2 coupler (12), the second port of the second 1x2 coupler (4) is connected to the input end of the first acousto-optic modulator (5), the third port of the second 1x2 coupler (4) is connected to the input end of the second acousto-optic modulator (7), the output end of the first acousto-optic modulator (5) is connected to the input end of the pulse light amplifier multistage amplification module (6), and the output end of the pulse light amplifier multistage amplification module (6) is connected to port 1 of the third 1x2 coupler (9). The output end of the second acousto-optic modulator (7) is connected to the input end of the continuous optical amplifier multi-stage amplification module (8), the output end of the continuous optical amplifier multi-stage amplification module (8) is connected to the 2nd port of the third 1x2 coupler (9), the 3rd port of the third 1x2 coupler (9) is connected to the 1st port of the circulator (10), the 2nd port of the circulator (10) is connected to the optical antenna (11), the 3rd port of the circulator (10) is connected to the 2nd port of the 2x2 coupler (12), the other ports of the 2x2 coupler (12) are connected to the input end of the balanced detector (13), and the output end of the balanced detector (13) is connected to the signal processing module (14). The input end of the optical amplifier is connected; the narrow line width seed light source (1) outputs continuous light and is connected to the continuous light amplifier pre-amplifier module (2); the continuous light after pre-amplification is connected to the first 1x2 coupler (3); the 3-port outputs one continuous light as the local oscillator light after the first 1x2 coupler (3) splits the light, and the 2-port outputs another continuous signal light and is connected to the input end of the second 1x2 coupler (4); the 2-port output light after the second 1x2 coupler (4) splits the light and is connected to the input end of the first acousto-optic modulator (5) to be modulated into a pulse light with an intermediate frequency of f1; the output end of the first acousto-optic modulator (5) is connected to the input end of the pulse light amplifier multi-stage amplification module (6) for amplification;At the same time, the 3-port output light after beam splitting by the second 1x2 coupler (4) is connected to the input end of the second acousto-optic modulator (7) for frequency shifting to an intermediate frequency of f2, the output end of the second acousto-optic modulator (7) is connected to the continuous optical amplifier multi-stage amplification module (8) for amplification, the pulse signal light and the continuous signal light after being respectively amplified by the pulse optical amplifier multi-stage amplification module (6) and the continuous optical amplifier multi-stage amplification module (8) are connected to the input end of the coupler (9), the output end of the coupler (9) enters from the 1 port and exits from the 2 port of the circulator (10), and the 2 port of the circulator (10) is connected to the optical antenna (11); the target echo signal returns to the 3-port output of the circulator (10) through the original path of the optical antenna (11), and is connected to the input end of the 2x2 coupler (12) for coherent signal beat frequency with the local oscillator light beam split by the first 1x2 coupler (3); the optical signal after the beat frequency is transmitted to the signal processing module (14) for signal processing after photoelectric conversion, and the corresponding wind field information is obtained. ; 2. The dual-system laser wind measurement radar system based on frequency reuse as claimed in claim 1, characterized in that: The narrow linewidth seed light source (1) outputs continuous linearly polarized light with a wavelength of 1550nm and a linewidth of less than 5kHz, and an output power of not less than 10mW.

3. The dual-system laser wind measurement radar system based on frequency reuse as claimed in claim 2, characterized in that: The coupler (3) is a 1x2 coupler with a splitting ratio of 99:

1.

4. The dual-system laser wind measurement radar system based on frequency reuse as claimed in claim 3, characterized in that: The coupler (4) is a 1x2 coupler with a splitting ratio of 50:

50.

5. The dual-system laser wind measurement radar system based on frequency reuse as claimed in claim 4, characterized in that: The coupler (9) is a 1x2 coupler with a splitting ratio of 50:

50.

6. The dual-system laser wind measurement radar system based on frequency reuse as claimed in claim 5, characterized in that: The coupler (12) is a 2x2 coupler.

7. The dual-system laser wind measurement radar system based on frequency reuse as claimed in claim 6, characterized in that: The frequency shift frequency of the first acousto-optic modulator (5) and the frequency shift frequency of the second acousto-optic modulator (7) are both higher than 200 MHz, and the frequency difference between the frequency shift frequencies of the two acousto-optic modulators is greater than 50 MHz.

8. The dual-system laser wind measurement radar system based on frequency reuse as claimed in claim 7, characterized in that: The diameter of the optical antenna (11) is greater than 130 mm.

9. The dual-system laser wind measurement radar system based on frequency reuse as claimed in claim 8, characterized in that: The first acousto-optic modulator (5) and the second acousto-optic modulator (7) are connected to a signal processing module (14) via a radio frequency line, and the signal processing module (14) provides modulation signals to the first acousto-optic modulator (5) and the second acousto-optic modulator (7), respectively.

10. The dual-system laser wind measurement radar system based on frequency reuse according to claim 9, characterized in that: The narrow linewidth seed light source (1), the continuous light amplifier preamplifier module (2), the coupler (3), the coupler (4), the first acousto-optic modulator (5), the pulse light amplifier multi-stage amplification module (6), the second acousto-optic modulator (7), the continuous light amplifier multi-stage amplification module (8), the coupler (9), the circulator (10), and the coupler (12) are optical fiber devices, all of which are polarization-maintaining devices, and each port is plated with a 1550 nm anti-reflection film.

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