Microwave-optical wave cooperative detection system based on Fourier domain mode-locked photoelectric oscillator

Abstract

This invention discloses a microwave-optical wave cooperative detection system based on a Fourier domain mode-locked optoelectronic oscillator, belonging to the field of microwave photonics technology. The system includes: a linear frequency modulated (LFM) signal generation module based on a Fourier domain mode-locked optoelectronic oscillator, a microwave photonic radar transceiver module, and a lidar transceiver module. The LFM optical signal used by the lidar is directly generated by the LFM signal generation module based on the Fourier domain mode-locked optoelectronic oscillator, while the LFM microwave signal used by the microwave photonic radar is generated by converting the optical signal generated by the module into a 20GHz high-speed photodetector. By replacing the discrete notch filter with a microdisk optical filter in microwave photonics technology, a large-bandwidth LFM signal is generated for simultaneous use by both lidar and microwave radar, achieving system miniaturization. Furthermore, the system can be adjusted to different processing modes to cope with different environments, fully leveraging the advantages of microwave-optical wave cooperative detection and using a radar detection system more suitable for the current environment.

Description

Technical Field

[0001] This invention relates to the field of microwave photonics technology, specifically to a microwave optical wave cooperative detection system based on a Fourier domain mode-locked optoelectronic oscillator. Background Technology

[0002] With the increasing complexity of today's detection environments and the diversification and miniaturization of detection targets, traditional radar systems are no longer sufficient to meet the demands of modern complex battlefield environments. Microwave-optical wave cooperative detection radar systems, characterized by high survivability, high versatility, and strong resistance to complex electromagnetic interference, have become a key technology supporting composite radar systems for overall perception in complex environments. On the one hand, commonly used lidar possesses advantages such as fast measurement speed, large bandwidth, high range resolution, strong anti-interference and anti-monitoring capabilities, and the ability to operate at ultra-low elevation angles for easy concealment, making it widely used in high-precision target detection. However, its detection performance is highly susceptible to atmospheric influences, and the narrow beamwidth severely limits its search radius. On the other hand, microwave radar offers all-weather, all-day operation with a large sensing angle and wide measurement range. However, its large system size hinders concealment and results in weaker resistance to electromagnetic interference. Therefore, combining lidar and microwave radar systems to form a complementary microwave-optical wave cooperative detection radar system is crucial for achieving strong adaptability of radar systems in complex environments.

[0003] Currently, radar detection is mainly divided into two methods: lidar detection and microwave radar detection. Lidar detection can obtain deskewing information about the target by processing the echo signal, achieving high-precision range detection. This method uses laser as a carrier to emit high-frequency, highly directional, and monochromatic electromagnetic waves, enabling high-resolution detection. However, the accuracy and range of lidar detection are easily affected by the refraction and scattering of laser light in the atmosphere caused by complex environments. Compared to lidar detection, microwave radar detection is similar, but traditional microwave radar is limited by electronic bandwidth bottlenecks, making it difficult to generate, control, and process high-frequency broadband signals. In recent years, the emergence of microwave photonics technology has made it possible to generate wide-bandwidth, tunable linear frequency modulated microwave signals and detect targets over a wide area with high precision, becoming a key technology to overcome the radar bandwidth bottleneck and "illuminate the future of radar."

[0004] Currently, lidar systems are highly susceptible to environmental influences, and microwave photonic radar has slightly insufficient detection accuracy; both struggle to achieve high-precision detection of complex environments and diverse targets. In recent years, with the rapid development of both microwave photonic radar and lidar technologies, integrating these two technologies to achieve microwave-optical wave coordinated detection has become an inevitable trend in radar technology development. By employing a Fourier-domain mode-locked optoelectronic oscillator-based method to simultaneously generate linear frequency-modulated signals for both lidar and microwave photonic radar, the high-resolution, rapid measurement capabilities of lidar are combined with the miniaturization and all-weather, wide-area spatial search characteristics of microwave photonic radar. This enables coordinated optical and microwave wave detection, miniaturized, all-weather, rapid, high-precision, and diverse target detection capabilities.

[0005] The high-precision distance measurement capabilities of lidar systems and the superior all-weather, wide-area detection performance of microwave photonic radar have been confirmed, making microwave-optical wave coordinated detection possible. However, high-precision detection in complex environments using microwave-optical wave coordinated detection has not yet been reported. Summary of the Invention

[0006] In view of this, the present invention provides a microwave optical wave cooperative detection system based on a Fourier domain mode-locked optoelectronic oscillator, which can control the operation of different radars and obtain high-precision detection for different complex environments.

[0007] To achieve the above objectives, the technical solution of the present invention includes: a linear frequency modulation signal generation module based on a Fourier domain mode-locked optoelectronic oscillator, a microwave photonic radar transceiver module, and a lidar transceiver module.

[0008] The linear frequency modulation signal generation module includes a laser source, a phase modulator, a micro-disk optical filter, an erbium-doped fiber amplifier, and a high-speed photodetector.

[0009] The laser source is used to provide an optical carrier, which is incident on the optical input port of the phase modulator.

[0010] The phase modulator is used to generate a double-sideband modulated signal, which is incident on the microdisk optical filter.

[0011] The micro-disk optical filter is used to separate the first-order sidebands of the double-sideband modulated signal, so that part of the first-order sidebands are output from the download end as the linear frequency modulated optical signal used by the lidar and sent to the lidar transceiver module; the other part of the first-order sidebands are output from the pass-through end, amplified by the erbium-doped fiber amplifier, and then converted by the high-speed photodetector to generate the linear frequency modulated microwave signal used by the microwave photonic radar and sent to the microwave photonic radar transceiver module.

[0012] Furthermore, the micro-disk optical filter uses a sawtooth wave electrical signal to adjust the resonant wavelength, which linearly increases the frequency of the sidebands, ultimately making the signals input to the two different radar transceiver modules linear frequency modulated signals.

[0013] Furthermore, the microdisk optical filter has four ports: port a is the input port for optical signals; port b is the Through port, which outputs optical signals that do not meet the resonant wavelength; port c is the Drop port, which outputs optical signals that meet the resonant wavelength; and port d is the Add port.

[0014] The double-sideband modulated signal generated by the phase modulator contains positive and negative first-order sidebands f0 and f1 respectively. c +f m and f c -f m f c f is the frequency of the optical carrier generated by the laser source. m The center frequency of the modulated signal.

[0015] The double-sideband modulated signal is incident on the microdisk optical filter from port a.

[0016] The resonant wavelength of the microdisk optical filter is Where R and n eff Here, denoted by and , respectively, the radius and effective refractive index of the microdisk optical filter, where m is a positive integer. The microdisk optical filter incorporates metal micro / nano heating electrodes, and the resonant wavelength of the microdisk optical filter is adjusted using the thermo-optical effect, thereby enabling the positive first-order sideband f... c +f m The output from port C is input to the LiDAR transceiver module, while the negative first-order sideband and the optical carrier f... c -f m The signal is output from port b and amplified by an erbium-doped fiber amplifier. After passing through a 20GHz high-speed photodetector (2-5), the linear frequency modulated microwave signal used by the microwave photonic radar is obtained. The signal is then split into two paths by an RF power divider. One path is input to the microwave photonic radar transceiver module, and the other path is input to the phase modulator to serve as the signal for the next phase modulation.

[0017] Furthermore, the lidar transceiver module includes a Mach-Zehnder interferometer (MZI), a circulator, a collimator, an optical bandpass filter, a first high-speed photodetector, a first analog-to-digital converter (ADC), and a first digital signal processor (DSP).

[0018] The circulator has three ports, a, b, and c, arranged in a ring. When a signal is input from port a, it is output from port b only; when a signal is input from port b, it is output from port c only.

[0019] The linear frequency modulated optical signal used by the lidar enters the Mach-Zehnder interferometer (MZI). The upper arm optical signal enters port a of the circulator and exits from port b, enters the collimator, detects the target, and receives the echo. The echo enters port b of the circulator and exits from port c into the MZI. The lower arm optical signal of the MZI serves as a reference signal and, together with the echo from the upper arm, enters the first 20GHz high-speed photodetector to obtain a de-chirp signal. This signal is then sampled by the first analog-to-digital converter (ADC) and processed by the first digital signal processor (DSP) to obtain information about the target's distance.

[0020] Furthermore, the microwave photonic radar transceiver module includes a power amplifier, an RF power divider, a radar transmitter, a radar receiver, a low-noise amplifier, a dual-drive Mach-Zehnder modulator, an optical bandpass filter, a second high-speed photodetector, a second analog-to-digital converter (ADC), and a second digital signal processor (DSP).

[0021] The linear frequency modulated microwave signal is amplified and then split into two paths by an RF power divider. One path is emitted from the microwave photonic radar transmitter, and the other path is used as a reference signal to enter one arm of the dual-drive Mach-Zehnder modulator (DDMZM).

[0022] After the signal emitted by the microwave photonic radar transmitter detects the target, the receiver receives the echo signal and amplifies it through a low-noise amplifier (LNA). The echo signal enters another arm of the DDMZM and is then filtered out by an optical bandpass filter to remove frequency components other than the first-order sideband. After passing through a 20GHz high-speed photodetector (3-8), the de-slanted microwave signal is obtained. Subsequently, the signal is processed by a second analog-to-digital converter (ADC) and a second digital signal processor (DSP) to obtain the distance information of the target.

[0023] Beneficial effects:

[0024] This invention proposes a microwave-optical wave cooperative detection system based on a Fourier domain mode-locked optoelectronic oscillator. By replacing discrete notch filters with microdisk optical filters in microwave photonics technology, a wide-bandwidth linear frequency-modulated signal is generated for simultaneous use by lidar and microwave radar, achieving system miniaturization. Furthermore, the system can be adjusted to different processing modes to cope with different environments, fully leveraging the advantages of microwave-optical wave cooperative detection. It utilizes a radar detection system more suitable for the current environment, achieving self-adaptive adjustment and high-precision measurement under different conditions. It possesses significant advantages such as miniaturization, low cost, strong adaptability, and high-precision measurement. Attached Figure Description

[0025] Figure 1 A block diagram of the overall structure of a microwave optical wave cooperative detection system based on a Fourier domain mode-locked optoelectronic oscillator provided by the present invention;

[0026] Figure 2This is a schematic diagram of the linear frequency modulation signal module;

[0027] Figure 3 This is a schematic diagram of the structure of a microwave photonic radar transceiver module.

[0028] Figure 4 This is a schematic diagram of the structure of a lidar transceiver module. Detailed Implementation

[0029] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0030] Figure 1 This invention provides a novel microwave optical wave cooperative detection system based on a Fourier domain mode-locked optoelectronic oscillator, and presents an overall structural block diagram. The system includes: a linear frequency modulated signal generation module based on a Fourier domain mode-locked optoelectronic oscillator, a microwave photonic radar transceiver module, and a lidar transceiver module.

[0031] The linear frequency modulation signal generation module includes a laser source 2-1, a phase modulator 2-2, a micro disk optical filter 2-3, an erbium-doped fiber amplifier 2-4, and a high-speed photodetector 2-5;

[0032] Laser source 2-1 is used to provide optical carrier, which is incident on the optical input port of phase modulator 2-2.

[0033] Phase modulator 2-2 is used to generate a double-sideband modulated signal, which is incident on the microdisk optical filter 2-3.

[0034] Microdisk optical filter 2-3 is used to separate the first-order sideband of the double-sideband modulated signal, so that part of the first-order sideband is output from the download end as the linear frequency modulated optical signal used by the lidar and sent to the lidar transceiver module; the other part of the first-order sideband is output from the pass-through end, amplified by erbium-doped fiber amplifier 2-4, and then converted by high-speed photodetector 2-5 to generate the linear frequency modulated microwave signal used by microwave photonic radar and sent to microwave photonic radar transceiver module.

[0035] The linear frequency modulated optical signal used in lidar is directly generated by a linear frequency modulated signal generation module based on a Fourier domain mode-locked photoelectric oscillator, while the linear frequency modulated microwave signal used in microwave photonic radar is generated by converting the optical signal generated by the module into a 20GHz high-speed photodetector.

[0036] Figure 2 A schematic diagram of the linear frequency modulation signal generation module based on a Fourier domain mode-locked optoelectronic oscillator in this invention is provided. The frequency generated by laser 2-1 is f. c A single-frequency optical signal is incident on the optical input port of phase modulator 2-2. The phase modulator generates a double-sideband modulation signal, with the carrier and positive and negative first-order sidebands fi and fi respectively.c and f c ±f m , where f m The center frequency of the modulated signal is used. The microdisk optical filter 2-3 has four ports: port a is the input port for the optical signal; port b is the Through port, which outputs an optical signal that does not meet the resonant wavelength; port c is the Drop port, which outputs an optical signal that meets the resonant wavelength; and port d is the Add port, which is not used in this patent. The double-sideband signal generated by the phase modulator 2-2 is incident into the microdisk optical filter 2-3 through port a. The resonant wavelength of the microdisk optical filter 2-3 can be expressed as...

[0037]

[0038] Where R and n eff Here, λ represents the radius and effective refractive index of the microdisk optical filter 2-3, respectively, where m is a positive integer. The microdisk optical filter 2-3 incorporates metal micro / nano heating electrodes. By utilizing the thermo-optical effect, the resonant wavelength of the microdisk optical filter 2-3 is adjusted, thereby enabling the positive first-order sideband f... c +f m The output from port C is input to the LiDAR transceiver module, while the negative first-order sideband and the optical carrier f... c -f m The signal output from port b is first amplified by an erbium-doped fiber amplifier 2-4, and then passed through a 20GHz high-speed photodetector 2-5 to obtain the final linearly frequency-modulated microwave signal. This signal is then split into two paths by an RF power divider 2-6. One path is input to the microwave photonic radar transceiver module, and the other is input to the phase modulator 2-2, serving as the signal for the next phase modulation. By applying a sawtooth wave electrical signal to adjust the resonant wavelength of the microdisk optical filter 2-3, the sideband frequency increases linearly, ultimately ensuring that the signals input to both radar transceiver modules are linearly frequency-modulated signals.

[0039] The microwave photonic radar transceiver module includes a power amplifier 3-1, an RF power divider 3-2, a radar transmitter 3-3, a radar receiver 3-4, a low-noise amplifier 3-5, a dual-drive Mach-Zehnder modulator 3-6, an optical bandpass filter 3-7, a second high-speed photodetector 3-8, a second analog-to-digital converter (ADC) 3-9, a second digital signal processor (DSP), and 3-10. The linear frequency modulated microwave signal, after passing through the power amplifier 3-1, is split into two paths by the RF power divider 3-2. One path is emitted from the microwave photonic radar transmitter 3-3, and the other path serves as a reference signal entering the dual-drive Mach-Zehnder modulator. One arm of the DDMZM3-6 modulator; after the signal emitted from the microwave photonic radar transmitter 3-3 detects the target, the receiver 3-4 receives the echo signal, and the echo signal is amplified by the low noise amplifier LNA3-5 and enters the other arm of the DDMZM3-6. Then, the frequency components other than the first-order sideband are filtered out by the optical bandpass filter 3-7, and then the de-slanted microwave signal is obtained after passing through the 20GHz high-speed photodetector 3-8. Subsequently, the second analog-to-digital converter ADC3-9 and the second digital signal processor DSP are used to process the signal to obtain the distance information of the target.

[0040] Figure 3 This is a schematic diagram of the microwave radar transceiver module. The wideband linear frequency modulated signal is amplified by power amplifier 3-1 and then transmitted from the microwave photonic radar transmitter 3-3 via RF power divider 3-2. Another portion serves as a reference signal, entering one arm of the dual-drive Mach-Zehnder modulator (DDMZM) 3-6. After target detection, the echo signal is received by transmitter 3-4 and amplified by low-noise amplifier LNA 3-5 before entering the other arm of DDMZM 3-6. Then, the signal passes through optical bandpass filter 3-7 to remove frequency components other than the first-order sidebands, and finally through a 20GHz high-speed photodetector 3-8 to obtain a de-slanted microwave signal. Subsequently, ADC sampling 3-9 and DSP processing 3-10 can be used to obtain information such as the target's distance.

[0041] Distance D can be expressed as

[0042]

[0043] Where c is the speed of light, Tp is the duration of the emitted pulse, B is the bandwidth of the emitted signal, and f de-chirp This is the frequency after deskewing.

[0044] The lidar transceiver module includes a Mach-Zehnder interferometer MZI4-1, a circulator 4-2, a collimator 4-3, an optical bandpass filter 4-5, a first high-speed photodetector 4-6, a first analog-to-digital converter (ADC) 4-7, and a first digital signal processor (DSP) 4-8. The circulator 4-2 has three ports (a, b, and c) arranged in a ring. When a signal is input from port a, it is output only from port b; when a signal is input from port b, it is output only from port c. The linear frequency modulated optical signal used by the lidar enters the Mach-Zehnder interferometer MZI4-1. The upper arm optical signal enters port 4-2a of the circulator and exits from port b, entering collimator 4-3 to detect target 4 and receive the echo. The echo enters port 4-2b of the circulator and exits from port c to enter the MZI. The lower arm optical signal of the MZI serves as a reference signal and, together with the upper arm echo, enters the first 20GHz high-speed photodetector 4-5 to obtain the de-chirp signal. Subsequently, it is sampled by the first analog-to-digital converter ADC 4-7 and processed by the first digital signal processor DSP 4-8 to obtain information about the distance to the target.

[0045] Figure 4 This is a schematic diagram of the lidar transceiver module. The modulated optical signal output from the drop end of the microdisk optical filter enters the Mach-Zehnder interferometer (MZI4-1). The upper arm optical signal enters port a of circulator 4-2 and exits from port b, entering collimator 4-3 to detect the target 4-4 and receive the echo. Circulator 4-2 has three ports; when the signal is input from port a, it is output only from port b; when the signal is input from port b, it is output only from port c. The echo enters port b of circulator 4-2 and exits from port c into the MZI. The optical signal from the lower arm of the MZI serves as a reference signal, and together with the echo from the upper arm, it enters the 20GHz high-speed photodetector 4-5 to obtain the de-chirp signal. Subsequently, it can be sampled by ADC 4-6 and processed by DSP 4-7 to obtain information such as the target's distance.

[0046] In summary, the above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A microwave optical wave cooperative detection method based on a Fourier domain mode-locked optoelectronic oscillator, characterized in that, include: A linear frequency modulation signal generation module based on a Fourier domain mode-locked optoelectronic oscillator, a microwave photonic radar transceiver module, and a lidar transceiver module; The linear frequency modulation signal generation module includes a laser source (2-1), a phase modulator (2-2), a micro disk optical filter (2-3), an erbium-doped fiber amplifier (2-4), and a high-speed photodetector (2-5). The laser source (2-1) is used to provide an optical carrier, which is incident on the optical input port of the phase modulator (2-2); The phase modulator (2-2) is used to generate a double-sideband modulated signal, which is incident on the microdisk optical filter (2-3); The micro-disk optical filter (2-3) is used to separate the first-order sideband of the double-sideband modulated signal, so that part of the first-order sideband is output from the download end as the linear frequency modulated optical signal used by the lidar and sent to the lidar transceiver module; the other part of the first-order sideband is output from the pass-through end, amplified by the erbium-doped fiber amplifier (2-4), and then converted by the high-speed photodetector (2-5) to generate the linear frequency modulated microwave signal used by the microwave photonic radar and sent to the microwave photonic radar transceiver module. The micro-disk optical filter (2-3) uses a sawtooth wave electrical signal to adjust the resonant wavelength, which linearly increases the frequency of the sideband, ultimately making the signals input to the two different radar transceiver modules linear frequency modulated signals. The microdisk optical filter (2-3) has four ports: port a is the input port for optical signals; port b is the through port, which outputs optical signals that do not meet the resonant wavelength; port c is the drop port, which outputs optical signals that meet the resonant wavelength; and port d is the add port. The double-sideband modulated signal generated by the phase modulator (2-2) contains positive and negative first-order sidebands f, respectively. c +f m and f c -f m f c f is the frequency of the optical carrier generated by the laser source (2-1). m The center frequency of the modulated signal; The double-sideband modulated signal is incident from port a into the microdisk optical filter (2-3); The resonant wavelength of the microdisk optical filter (2-3) is ;in, R and n eff Here, λ represents the radius and effective refractive index of the microdisk optical filter (2-3), respectively, where m is a positive integer. The microdisk optical filter (2-3) is equipped with metal micro / nano heating electrodes. By utilizing the thermo-optical effect to adjust the resonant wavelength of the microdisk optical filter (2-3), the positive first-order sideband... f c +f m The output from port C is input to the LiDAR transceiver module, while the negative first-order sideband and optical carrier... f c - f m The signal is output from port b and amplified by an erbium-doped fiber amplifier (2-4). After passing through a 20GHz high-speed photodetector (2-5), it obtains the linear frequency modulated microwave signal used by the microwave photonic radar. The signal is then split into two paths by an RF power divider (2-6). One path is input to the microwave photonic radar transceiver module, and the other path is input to the phase modulator (2-2) to serve as the signal for the next phase modulation.

2. The microwave optical wave cooperative detection method based on a Fourier domain mode-locked optoelectronic oscillator as described in claim 1, characterized in that, The lidar transceiver module includes a Mach-Zehnder interferometer (MZI) (4-1), a circulator (4-2), a collimator (4-3), an optical bandpass filter (4-5), a first high-speed photodetector (4-6), a first analog-to-digital converter (ADC) (4-7), and a first digital signal processor (DSP) (4-8). The circulator (4-2) has three ports a, b, and c arranged in a ring. When a signal is input from port a, it is output only from port b; when a signal is input from port b, it is output only from port c. The linear frequency modulated optical signal used by the lidar enters the Mach-Zehnder interferometer MZI (4-1). The upper arm optical signal enters port a of the circulator (4-2) and exits from port b, entering the collimator (4-3) to detect the target (4) and receive the echo. The echo enters port b of the circulator (4-2) and exits from port c into the MZI. The lower arm optical signal of the MZI serves as a reference signal and, together with the echo from the upper arm, enters the first high-speed photodetector (4-5) at 20 GHz to obtain the de-chirp signal. Subsequently, it is sampled by the first analog-to-digital converter (ADC) (4-7) and processed by the first digital signal processor (DSP) (4-8) to obtain information about the distance to the target.

3. The microwave optical wave cooperative detection method based on a Fourier domain mode-locked optoelectronic oscillator as described in claim 2, characterized in that, The microwave photonic radar transceiver module includes a power amplifier (3-1), an RF power divider (3-2), a radar transmitter (3-3), a radar receiver (3-4), a low-noise amplifier (3-5), a dual-drive Mach-Zehnder modulator (3-6), an optical bandpass filter (3-7), a second high-speed photodetector (3-8), a second analog-to-digital converter (ADC) (3-9), and a second digital signal processor (DSP) (3-10). The linear frequency modulated microwave signal is amplified by a power amplifier (3-1) and then split into two paths by a radio frequency power divider (3-2). One path is emitted from the microwave photonic radar transmitter (3-3), and the other path is used as a reference signal to enter one arm of the dual-drive Mach-Zehnder modulator (DDMZM) (3-6). After the signal emitted by the microwave photonic radar transmitter (3-3) detects the target, the echo signal is received by the receiver (3-4) and amplified by the low noise amplifier LNA (3-5). The echo signal enters another arm of the DDMZM (3-6), and then the frequency components other than the first-order sideband are filtered out by the optical bandpass filter (3-7). After passing through the 20GHz high-speed photodetector (3-8), the de-slanted microwave signal is obtained. Then, the second analog-to-digital converter ADC (3-9) and the second digital signal processor DSP (3-10) are used to process the signal to obtain the distance information of the target.

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