A low small single-photon radar based on a probe array

Abstract

The application belongs to the technical field of laser radar, and discloses a low, slow and small single-photon radar based on a detection array, which comprises a laser, a beam splitter, an acousto-optic modulator, an optical amplification module, a transceiving light path, a rotary table, a fiber array, a heterodyne detection array module and a data acquisition and processing module; the data acquisition and processing module extracts the body vibration characteristic parameters of the unmanned aerial vehicle through a vibration characteristic extraction algorithm, and identifies the unmanned aerial vehicle target by using a target identification algorithm. Compared with the prior art, the application generates high-coherence laser, realizes laser projection and vibration signal reception in a large range of space through the fiber array, and then combines the heterodyne detection array to suppress environmental noise and extract the body vibration characteristics of the unmanned aerial vehicle, so that the precise detection and identification of the unmanned aerial vehicle are finally completed through a signal processing and identification module, and the application has the advantages of a large field of view, strong anti-interference capability, high vibration signal extraction precision and the like, and can realize the detection of the low, slow and small unmanned aerial vehicle at a long distance, high sensitivity and low misjudgment rate.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of laser radar detection, in particular to a low, small and single-photon radar based on a detection array. BACKGROUND

[0002] With the rapid development of low, small and slow unmanned aerial vehicles and other technologies, the number of consumer and industrial unmanned aerial vehicles has increased dramatically. Currently, unmanned aerial vehicle detection technologies mainly include radio detection, radar detection, optical / infrared detection, acoustic detection, etc., but all have obvious defects: radio detection cannot identify silent flying unmanned aerial vehicles; radar detection has low identification accuracy for "low, slow and small" targets and is easily disturbed by birds, balloons and other objects; optical / infrared detection is greatly affected by light and weather, and its detection performance significantly decreases at night or in bad weather; acoustic detection has a short detection distance and is easily disturbed by environmental noise.

[0003] Laser vibration measurement technology is based on laser interference or Doppler effect, and can realize non-contact high-precision vibration measurement, providing a new technical path for unmanned aerial vehicle detection. However, traditional laser vibration meters are mostly in "point measurement" mode, with a narrow field of view and unable to realize large-scale airspace unmanned aerial vehicle search; at the same time, environmental light, atmospheric turbulence, laser intensity fluctuation and other factors will seriously interfere with the extraction of vibration signals, resulting in high false and missed detection rates of unmanned aerial vehicle identification. In addition, existing laser radar systems mostly rely on spatial profile to identify unmanned aerial vehicles, and it is difficult to distinguish similar unmanned aerial vehicles and interference targets (such as birds), while unmanned aerial vehicle body vibration characteristics (such as motor vibration frequency and propeller disturbance frequency) are unique and can be used as a key basis for accurate identification. SUMMARY

[0004] In view of the above defects of the prior art, the present application provides a low, small and single-photon radar based on a detection array.

[0005] The technical solution of the present application is as follows:

[0006] A low, small and single-photon radar based on a detection array, comprising:

[0007] a laser for generating a narrow linewidth optical signal;

[0008] a beam splitter for splitting the optical signal output by the laser into a first component and a second component;

[0009] an acousto-optic modulator for pulse modulation and frequency shift of the first component;

[0010] an optical amplification module for amplifying the first component to a required power;

[0011] A transceiver light path is used for collimating and expanding the amplified first component, and for collecting the echo signal reflected from the target UAV and transmitting to the fiber array;

[0012] The fiber array is used for transmitting the echo signal to the heterodyne detection array module, and includes N×M fibers, N and M being positive integers, the end faces of the fibers being arrayed closely at one end, and the plane being located at the focal plane of the transceiver light path; the other ends of the fibers are connected to the signal light input interfaces of the pixels of the heterodyne detection array module respectively;

[0013] The second component is used as the local oscillator light of the heterodyne detection array module;

[0014] The heterodyne detection array module includes a plurality of heterodyne detection units for detecting single-photon-level optical signals, and is used for detecting the echo signal transmitted by the fiber array; each unit uses one local oscillator light component to perform heterodyne detection with one optical signal of the fiber array, outputs an electrical signal containing the UAV body vibration information, and amplifies and filters the electrical signal;

[0015] The data acquisition and processing module is used for analog-to-digital conversion of the electrical signal output by each detection unit of the heterodyne detection array module, extraction of the UAV body vibration characteristic parameters through a vibration characteristic extraction algorithm, and UAV target identification through a target identification algorithm;

[0016] The turntable is used for directing the transceiver light path to scan the target area, judging the target position according to the electrical signal response distribution of each heterodyne detection unit of the heterodyne detection array module, and generating a control instruction to adjust the attitude or position of the transceiver light path so that the echo signal reflected by the target falls into the central region of the fiber array.

[0017] Preferably, the heterodyne detection array module includes a 1×(N×M) optical splitter PLC, a directional coupler array chip DCA, 2N×M single-photon avalanche diodes SPADs, and N×M signal processing modules SP,

[0018] The directional coupler array chip DCA includes N×M 2×2 directional couplers DC;

[0019] Each output port fiber of the PLC is coupled to one input port of each directional coupler of the DCA through a mode spot converter MSC;

[0020] The other input port of each directional coupler of the DCA is coupled to a polarization maintaining fiber PMF through a mode spot converter MSC;

[0021] The two output ports of each directional coupler of the DCA are coupled to a single-photon avalanche diode SPAD respectively, and the differential electrical signal output of the corresponding two SPADs is output to a signal processing module SP.

[0022] Preferably, the heterodyne detection array module comprises a multimode interferometer array chip, a photodetector array chip and NXM signal processing modules SP,

[0023] The multimode interferometer array chip comprises a 1x(NXM) multimode interferometer MMl, NXM 2x2 multimode interferometers,

[0024] The input port of the 1x(NXM) multimode interferometer is coupled to a polarization maintaining optical fiber PMF through a mode spot converter MSC; each output port is connected to an input port of a 2x2 multimode interferometer;

[0025] The other input port of each 2x2 multimode interferometer is coupled to a polarization maintaining optical fiber PMF through a mode spot converter MSC;

[0026] The photodetector array chip comprises 2NXM single photon avalanche diodes SPADs, adjacent two SPADs are coupled and aligned with two output ports of a 2x2 multimode interferometer, and the differential electrical signals of the two are output to a signal processing module SP.

[0027] Preferably, the wavelength of the laser output optical signal is 1550nm band, and the line width is less than 1kHz.

[0028] Preferably, the acousto-optic modulator modulates the optical signal into pulsed light with a pulse width of 50ns and shifts the frequency by 100MHz.

[0029] Preferably, the data acquisition and processing module adopts an adaptive Kalman filtering algorithm to pre-process the electrical signals output by the heterodyne detection array module, and suppresses the interference caused by atmospheric turbulence and ambient light.

[0030] The vibration feature extraction algorithm is based on the pre-processed electrical signals, calculates the vibration frequency spectrum through fast Fourier transform (FFT), extracts the characteristic parameters, and the characteristic parameters include the main frequency, frequency stability and amplitude.

[0031] Preferably, the vibration feature extraction module also has a spectrum accumulation analysis function, continuously collects and superimposes the vibration frequency spectrum within 100-500ms, improves the signal-to-noise ratio of weak vibration signals, and the signal-to-noise ratio is improved by ≥10 times; when the main frequency of the vibration signal is continuously stable for ≥50ms, the feature extraction process is triggered, and false triggering caused by instantaneous noise is avoided.

[0032] Preferably, the target recognition algorithm is built-in with the unmanned aerial vehicle vibration feature library and the interference target vibration feature library, a "feature matching + weight voting" algorithm is adopted, the extracted vibration features are compared with the feature library, when the unmanned aerial vehicle feature matching degree is a first set threshold value, and the interference target feature matching degree is less than or equal to a second set threshold value, the unmanned aerial vehicle is determined and the detection result is output, the detection result includes the unmanned aerial vehicle position (accuracy ≤ 10m), vibration feature and confidence.

[0033] Preferably, the data acquisition and processing module has a time measurement function, and the position and angle information of the unmanned aerial vehicle target is obtained according to the response distribution of the detection unit included in the heterodyne detection array module.

[0034] Compared with the prior art, the present application has the following beneficial effects:

[0035] The present application provides a low small single photon radar based on a detection array, which generates high coherence laser through a narrow linewidth laser, realizes laser projection and vibration signal reception in a large range of space through a fiber array, and finally realizes accurate detection and identification of the unmanned aerial vehicle through a signal processing and identification module, has the advantages of large field of view, strong anti-interference ability, high vibration signal extraction precision, and can realize remote, high sensitivity and low false alarm rate detection of the "low, slow and small" unmanned aerial vehicle. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 The present application provides a low small single photon radar based on a detection array, which generates high coherence laser through a narrow linewidth laser, realizes laser projection and vibration signal reception in a large range of space through a fiber array, and finally realizes accurate detection and identification of the unmanned aerial vehicle through a signal processing and identification module, has the advantages of large field of view, strong anti-interference ability, high vibration signal extraction precision, and can realize remote, high sensitivity and low false alarm rate detection of the "low, slow and small" unmanned aerial vehicle.

[0037] Figure 2 The present application provides a low small single photon radar based on a detection array, which generates high coherence laser through a narrow linewidth laser, realizes laser projection and vibration signal reception in a large range of space through a fiber array, and finally realizes accurate detection and identification of the unmanned aerial vehicle through a signal processing and identification module, has the advantages of large field of view, strong anti-interference ability, high vibration signal extraction precision, and can realize remote, high sensitivity and low false alarm rate detection of the "low, slow and small" unmanned aerial vehicle.

[0038] Figure 3 The present application provides a low small single photon radar based on a detection array, which generates high coherence laser through a narrow linewidth laser, realizes laser projection and vibration signal reception in a large range of space through a fiber array, and finally realizes accurate detection and identification of the unmanned aerial vehicle through a signal processing and identification module, has the advantages of large field of view, strong anti-interference ability, high vibration signal extraction precision, and can realize remote, high sensitivity and low false alarm rate detection of the "low, slow and small" unmanned aerial vehicle. DETAILED DESCRIPTION

[0039] The present application will be described clearly and completely below in combination with the drawings in the embodiments of the present application.

[0040] As shown in the drawings, Figure 1 A low small single photon radar based on a detection array, comprising a laser, a beam splitter, an acousto-optic modulator, an optical amplification module, a transceiver optical path, a turntable, a fiber array, a heterodyne detection array module and a data acquisition and processing module;

[0041] The laser is used to generate a narrow linewidth optical signal;

[0042] The beam splitter is used to split the optical signal output by the laser into a first component and a second component;

[0043] The acousto-optic modulator is used for pulse modulation and frequency shift of the first component;

[0044] The optical amplification module is used for amplifying the first component to the required power;

[0045] The transceiving light path is used for collimating and expanding the amplified first component, and for collecting the echo signal reflected from the target unmanned aerial vehicle and transmitting to the optical fiber array;

[0046] The optical fiber array is used for transmitting the echo signal to the heterodyne detection array module, including N×M optical fibers, the end faces of each optical fiber are closely arrayed at one end, and the plane is located at the focal plane of the transceiving light path; the other end of each optical fiber is connected with the signal light input interface of each unit of the heterodyne detection array module;

[0047] The second component is used as the local oscillator light of the heterodyne detection array module;

[0048] The heterodyne detection array module is composed of a plurality of heterodyne detection units for detecting single-photon-level optical signals, and is used for detecting the echo signal transmitted by the optical fiber array; wherein each unit uses one local oscillator light component to heterodyne detect one optical signal of the optical fiber array, outputs an electrical signal containing the unmanned aerial vehicle body vibration information, and amplifies and filters the electrical signal;

[0049] The data acquisition and processing module is used for analog-to-digital conversion of the electrical signal output by each detection unit of the heterodyne detection array module, extraction of the unmanned aerial vehicle body vibration characteristic parameters through a vibration characteristic extraction algorithm, and unmanned aerial vehicle target identification through a target identification algorithm;

[0050] The turntable is used for directing the transceiving light path to scan the target area, and judging the target position according to the electrical signal response distribution of each detection unit of the heterodyne detection array module, generating a control instruction to adjust the attitude or position of the transceiving light path, so that the echo signal reflected by the target falls into the central region of the optical fiber array.

[0051] The specific working process is as follows:

[0052] The laser generates a narrow linewidth optical signal with a center frequency of After being split by a beam splitter, a first component and a second component are generated. The first component is pulse-modulated and frequency-shifted by an acousto-optic modulator, and the center frequency becomes , wherein , is the frequency shift amount of the acousto-optic modulator. Then, the first component is amplified to the required power by an optical amplification module. The second component enters the heterodyne detection array module as the local oscillator light. The amplified first component is collimated and expanded by the transceiving light path and irradiates the target area, and the transceiving light path is scanned by the turntable.

[0053] After the echo signal is reflected by the target, it is collected by the transceiver optical path and then transmitted to the fiber array. The fiber array transmits the echo signal to the heterodyne detection array module, which includes N x M fibers. The end faces of each fiber are closely arrayed in a plane located at the focal plane of the transceiver optical path. The other end of each fiber is connected to the signal light input interface of each unit of the heterodyne detection array module. The local oscillator light entering the heterodyne detection array module is split into the same number of local oscillator light components as the detection units. Each local oscillator light component and each echo signal component input to the heterodyne detection array module are heterodyne detected in a detection unit.

[0054] Due to the vibration of the target unmanned aerial vehicle, the light signal irradiated thereon will have a Doppler shift , the center frequency of the echo signal becomes . Assuming that each local oscillator light component and each echo signal component can be written as

[0055] ,

[0056] wherein, are the amplitudes of the local oscillator light component and the echo signal component, respectively, and t is the interval time.

[0057] After heterodyne detection, the electrical signal output by each detection unit can be written as

[0058] ,

[0059] wherein, is the frequency difference between the echo signal component and the local oscillator light component, and k is the detection and amplification correlation coefficient. The Doppler frequency can be accurately measured by the data acquisition and processing module.

[0060] ,

[0061] wherein, v(t) is the vibration speed, and λ is the wavelength of the laser.

[0062] Integrating v(t) gives the displacement X of the target in the vibration direction:

[0063] ,

[0064] Taking the extreme value gives the vibration amplitude A of the target object. The vibration amplitude curve is fitted with a sine curve, and the interval time t of the adjacent zero points of the fitted curve is calculated. The vibration frequency of the object is 1 / (2t);

[0065] Differentiating v(t) gives the acceleration a(t) of the object in the vibration direction:

[0066] ,

[0067] According to the above parameters, the vibration equation of the target can be obtained, and the vibration characteristic extraction is performed by analyzing the vibration parameters. The target recognition algorithm is used for unmanned aerial vehicle target recognition.

[0068] The turntable is used for directing the transmitting and receiving light path to the target area for scanning, and judging the target position according to the electrical signal response distribution of each detection unit of the heterodyne detection array module, generating a control instruction to adjust the posture or position of the transmitting and receiving light path, so that the echo signal reflected by the target falls into the central region of the optical fiber array.

[0069] As shown in Figure 2 , embodiment one:

[0070] The heterodyne detection array module includes a 1×(N×M) optical splitter PLC, a directional coupler array chip DCA, 2N×M single photon avalanche diodes SPADs and N×M signal processing modules SP,

[0071] The directional coupler array chip DCA includes N×M 2×2 directional couplers DC;

[0072] Each output port optical fiber of the PLC is coupled to one input port of each directional coupler of the DCA through a mode spot converter MSC;

[0073] The other input port of each directional coupler of the DCA is coupled to a polarization maintaining optical fiber PMF through a mode spot converter MSC;

[0074] The two output ports of each directional coupler of the DCA are coupled to a single photon avalanche diode SPAD respectively, and the differential electrical signal of the corresponding two SPADs is output to a signal processing module SP.

[0075] The data acquisition and processing module adopts an adaptive Kalman filter algorithm to pre-process the electrical signal output by the heterodyne detection array module, and suppresses the interference caused by atmospheric turbulence and ambient light;

[0076] The vibration characteristic extraction algorithm is based on the pre-processed electrical signal, calculates the vibration frequency spectrum through fast Fourier transform (FFT), extracts characteristic parameters, and the characteristic parameters include the vibration main frequency, the frequency stability and the amplitude.

[0077] The specific principle is as follows:

[0078] The laser generates a narrow linewidth optical signal, and the center frequency is , which is split into a first component and a second component by a beam splitter. The first component is pulse-modulated and frequency-shifted by an acousto-optic modulator, and the center frequency becomes , wherein , is the frequency shift of the acousto-optic modulator. Then it is amplified to the required power by the optical amplifier module. The second component enters the heterodyne detection array module as the local light. The amplified first component is collimated and expanded by the transmitting and receiving optical path, and then irradiates the target area and is scanned by the rotating platform.

[0079] After the echo signal is reflected by the target, it is collected by the transmitting and receiving optical path and then transmitted to the optical fiber array. The optical fiber array transmits the echo signal to the heterodyne detection array module, which includes N×M optical fibers, the end faces of which are arrayed closely, and the plane is located at the focal plane of the transmitting and receiving optical path. One input port of each directional coupler of the DCA is coupled to a polarization maintaining fiber PMF through a mode spot converter MSC, which is connected to the interface of each optical fiber at the other end of the optical fiber array.

[0080] The local light enters the heterodyne detection array module, and is first split into N×M local light components by a 1×(N×M) optical splitter PLC. The optical fiber at each output port of the PLC is coupled to one input port of each directional coupler of the DCA through a mode spot converter MSC, and interferes with each echo signal transmitted by the optical fiber array on the DC to produce two interference results, which are detected by the SPAD, and the differential signal after SP processing is the output signal of the heterodyne detection unit.

[0081] Due to the vibration of the target UAV, it will cause Doppler shift to the light signal irradiated on it , then the center frequency of the echo signal becomes . Assuming that each local light component and each echo signal component can be written as

[0082] ,

[0083] wherein, are the amplitudes of the local light component and the echo signal component respectively, and t is the interval time.

[0084] After heterodyne detection, the electrical signal output by each detection unit can be written as

[0085] ,

[0086] wherein, is the frequency difference between the echo signal component and the local light component, and k is the detection and amplification correlation coefficient. The Doppler frequency can be accurately measured by the data acquisition and processing module.

[0087] ,

[0088] wherein, v(t) is the vibration speed, and λ is the wavelength of the laser.

[0089] Integrating v(t) can obtain the displacement X of the target in the vibration direction:

[0090] ,

[0091] Taking the extreme value can obtain the vibration amplitude A of the target object; performing sine curve fitting on the vibration amplitude curve to obtain the interval time t of adjacent zero points of the fitting curve, and the vibration frequency of the object is 1 / (2t);

[0092] Differentiating v(t) can obtain the acceleration a of the object to be measured in the vibration direction

[0093] ,

[0094] According to the above parameters, the vibration equation of the target can be obtained, and the vibration characteristics are extracted by analyzing the vibration parameters. The target recognition algorithm is used for unmanned aerial vehicle target recognition.

[0095] The vibration characteristic extraction algorithm calculates the vibration frequency spectrum by fast Fourier transform (FFT), extracts characteristic parameters, and the characteristic parameters include the main frequency, frequency stability, and amplitude. The vibration characteristic extraction module also has a spectrum accumulation analysis function, which continuously collects and superimposes the vibration frequency spectrum within 100-500 ms, improves the signal-to-noise ratio of weak vibration signals, and the signal-to-noise ratio is improved by ≥10 times; when the main frequency of the vibration signal is detected to be continuously stable for ≥50 ms, the characteristic extraction process is triggered, and false triggering caused by instantaneous noise is avoided.

[0096] The target recognition algorithm has an unmanned aerial vehicle vibration characteristic library and an interference target (bird, insect, balloon) vibration characteristic library, adopts a “feature matching + weight voting” algorithm, compares the extracted vibration characteristics with the characteristic library, when the unmanned aerial vehicle feature matching degree is a first set threshold, and the interference target feature matching degree is less than or equal to a second set threshold, the unmanned aerial vehicle is determined and the detection result is output, the detection result includes the unmanned aerial vehicle position (accuracy ≤10 m), vibration characteristics, and confidence.

[0097] The turntable is used for directing the transmitting and receiving light path to the target area for scanning, and judging the target position according to the electrical signal response distribution of each detection unit of the heterodyne detection array module, generating a control instruction to adjust the posture or position of the transmitting and receiving light path, so that the echo signal reflected by the target falls into the central region of the optical fiber array.

[0098] As shown in FIG. 2, Figure 3 Embodiment two:

[0099] The heterodyne detection array module includes a multimode interferometer array chip, a photodetection array chip, and N×M signal processing modules SP,

[0100] The multi-mode interferometer array chip comprises 1 1x(NxM) multi-mode interferometer MMIs, N x M 2x2 multi-mode interferometers,

[0101] The input port of the 1x(NxM) multi-mode interferometer is coupled with a polarization maintaining optical fiber PMF through a mode spot converter MSC; each output port is connected with an input port of a 2x2 multi-mode interferometer;

[0102] The other input port of each 2x2 multi-mode interferometer is coupled with a polarization maintaining optical fiber PMF through a mode spot converter MSC;

[0103] The photoelectric detection array chip comprises 2N x M single photon avalanche diodes SPADs, adjacent two SPADs are coupled and aligned with two output ports of a 2x2 multi-mode interferometer respectively, and the differential electrical signals of the two are output to a signal processing module SP.

[0104] The data acquisition and processing module adopts an adaptive Kalman filtering algorithm to pre-process the electrical signals output by the heterodyne detection array module, so as to suppress the interference caused by atmospheric turbulence and ambient light;

[0105] The vibration feature extraction algorithm is based on the pre-processed electrical signals, and calculates the vibration frequency spectrum through fast Fourier transform (FFT), and extracts feature parameters, including the vibration main frequency, frequency stability and amplitude.

[0106] The vibration feature extraction module also has a spectrum accumulation analysis function, which continuously collects and superimposes the vibration frequency spectrum within 100-500 ms, improves the signal-to-noise ratio of the weak vibration signal, and the signal-to-noise ratio is improved by ≥10 times; when the main frequency of the vibration signal is continuously stable for ≥50 ms, the feature extraction process is triggered, so as to avoid false triggering caused by instantaneous noise.

[0107] The target recognition algorithm has an unmanned aerial vehicle vibration feature library and an interference target (bird, insect, balloon) vibration feature library built in, adopts a "feature matching + weight voting" algorithm, compares the extracted vibration features with the feature library, when the unmanned aerial vehicle feature matching degree is a first set threshold, and the interference target feature matching degree is less than or equal to a second set threshold, the unmanned aerial vehicle is determined and the detection result is output, the detection result includes the unmanned aerial vehicle position (accuracy ≤10 m), vibration feature and confidence.

[0108] The data acquisition and processing module acquires the position and angle information of the unmanned aerial vehicle target according to the response distribution of the detection unit of the heterodyne detection array module.

[0109] The specific principle is as follows:

[0110] The laser generates a narrow linewidth optical signal, and the center frequency is , after the beam splitter, the first component and the second component are generated. Wherein, the first component passes through the acousto-optic modulator for pulse modulation and frequency shift, and the center frequency becomes , wherein , is the frequency shift of the acousto-optic modulator. Subsequently, it is amplified to the required power through the optical amplification module. The second component enters the heterodyne detection array module as the local oscillator light. After collimation and expansion of the transceiver optical path, the amplified first component is irradiated to the target area and is transmitted through the rotating table scanning.

[0111] After the echo signal is reflected by the target, it is collected by the transceiver optical path and then transmitted to the optical fiber array. The optical fiber array transmits the echo signal to the heterodyne detection array module, which includes N×M optical fibers, the end faces of which are closely arrayed on a plane located at the focal plane of the transceiver optical path. One input port of each directional coupler of the DCA is coupled to a polarization maintaining fiber PMF through a mode spot converter MSC, and is connected to the interface of each optical fiber at the other end of the optical fiber array.

[0112] The local oscillator light enters the heterodyne detection array module, is first split into N×M local oscillator light components by the 1×(N×M) multimode interferometer, and each output port is connected to one input port of a 2×2 multimode interferometer. Each local oscillator light component and each echo signal transmitted by the optical fiber array interfere with each other on the 2×2 multimode interferometer, generating two interference results which are detected by two single photon avalanche diodes SPADs of the photodetection array chip, and the differential signal after SP processing is the output signal of the heterodyne detection unit.

[0113] Due to the vibration of the target unmanned aerial vehicle, a Doppler frequency shift is generated on the light signal irradiated thereon . Assuming that each local oscillator light component and each echo signal component can be written as

[0114] ,

[0115] wherein, are the amplitudes of the local oscillator light component and the echo signal component respectively, and t is the interval time.

[0116] After heterodyne detection, the electrical signal output by each detection unit can be written as

[0117] ,

[0118] wherein, is the frequency difference between the echo signal component and the local oscillator light component, and k is the detection and amplification correlation coefficient. The Doppler frequency can be accurately measured through the data acquisition and processing module , and the vibration speed of the target can be calculated as:

[0119] ,

[0120] wherein v(t) is the vibration velocity, and λ is the wavelength of the laser.

[0121] Integrating v(t) can obtain the displacement X of the target in the vibration direction:

[0122] ,

[0123] Taking the extreme value can obtain the vibration amplitude A of the target object; performing sine curve fitting on the vibration amplitude curve, and obtaining the interval time t of adjacent zero points of the fitting curve, the vibration frequency of the object is 1 / (2t);

[0124] Differentiating v(t) can obtain the acceleration a(t) of the object to be measured in the vibration direction:

[0125] ,

[0126] According to the above parameters, the vibration equation of the target can be obtained, and the vibration characteristics are extracted by analyzing the vibration parameters. The target recognition algorithm is used for unmanned aerial vehicle target recognition.

[0127] The vibration characteristic extraction algorithm calculates the vibration frequency spectrum by fast Fourier transform (FFT), extracts characteristic parameters, and the characteristic parameters include the vibration main frequency, the frequency stability, and the amplitude. The vibration characteristic extraction module also has a spectrum accumulation analysis function, continuously collects the vibration frequency spectrum within 100-500 ms and superimposes, improves the signal-to-noise ratio of the weak vibration signal, and the signal-to-noise ratio improvement multiple is ≥10 times; when the main frequency of the vibration signal is detected to be continuously stable for ≥50 ms, the characteristic extraction process is triggered, and false triggering caused by instantaneous noise is avoided.

[0128] The target recognition algorithm has an unmanned aerial vehicle vibration characteristic library and an interference target (bird, insect, balloon) vibration characteristic library, adopts a “feature matching + weight voting” algorithm, compares the extracted vibration characteristics with the characteristic library, when the unmanned aerial vehicle feature matching degree is a first set threshold, and the interference target feature matching degree is less than or equal to a second set threshold, the unmanned aerial vehicle is determined and the detection result is output, the detection result includes the unmanned aerial vehicle position (accuracy ≤10 m), the vibration characteristics, and the confidence.

[0129] The turntable is used for directing the transmitting and receiving light path to the target area for scanning, and judging the target position according to the electrical signal response distribution of each detection unit of the heterodyne detection array module, generating a control instruction to adjust the posture or position of the transmitting and receiving light path, so that the echo signal reflected by the target falls into the central region of the optical fiber array.

[0130] According to various embodiments of the present application, a low, slow and small unmanned aerial vehicle radar based on a detection array is provided, high coherence laser is generated by a narrow linewidth laser, laser projection and vibration signal reception in a large range of space are realized through a fiber array, and then a heterodyne detection array is combined to suppress environmental noise and extract unmanned aerial vehicle body vibration characteristics, and finally, precise detection and identification of unmanned aerial vehicles are completed through a signal processing and identification module, which has the advantages of large field of view, strong anti-interference ability, high vibration signal extraction precision, and can realize long-distance, high-sensitivity and low-misjudgment rate detection of the "low, slow and small" unmanned aerial vehicle.

Claims

1. A low small single-photon radar based on a probe array, characterized in that, include: Lasers are used to generate optical signals with narrow linewidths. A beam splitter is used to split the optical signal output by a laser into a first component and a second component. An acousto-optic modulator is used for pulse modulation and frequency shifting of the first component; An optical amplifier module is used to amplify the first component to the required power; The light and sound path is used to collimate and expand the amplified first component, and to collect the echo signal reflected from the target UAV and transmit it to the fiber optic array. The fiber array is used to transmit the echo signal to the heterodyne detection array module. It includes N×M optical fibers, where N and M are positive integers. The end faces of each fiber are arranged in an array, and the plane is located at the focal plane of the light receiving path. At the other end, each fiber optic interface is connected to the signal light input interface of each pixel of the heterodyne detection array module. The second component serves as the local oscillator light of the heterodyne detection array module; The heterodyne detection array module includes multiple heterodyne detection units for detecting single-photon-level optical signals, used to detect echo signals transmitted by the fiber optic array; each unit uses one local oscillator component and one optical signal from the fiber optic array for heterodyne detection, outputting an electrical signal containing the vibration information of the UAV fuselage, and amplifying and filtering the electrical signal. The data acquisition and processing module is used to perform analog-to-digital conversion on the electrical signals output by each detection unit of the heterodyne detection array module, extract the fuselage vibration characteristic parameters of the UAV through the vibration feature extraction algorithm, and perform UAV target identification using the target recognition algorithm. The turntable is used to point the receiving and transmitting optical paths towards the target area for scanning. Based on the electrical signal response distribution of each heterodyne detection unit in the heterodyne detection array module, it determines the target position, generates control commands to adjust the attitude or position of the receiving and transmitting optical paths, so that the echo signal reflected from the target falls into the central region of the fiber optic array. The heterodyne detection array module includes a 1×(N×M) optical splitter, a directional coupler array chip, 2N×M single-photon avalanche diodes, and an N×M signal processing module. The directional coupler array chip contains N×M 2×2 directional couplers; Each output port fiber of the 1×(N×M) optical splitter is coupled to one input port of each directional coupler via a mode converter. Each directional coupler in the directional coupler array chip has another input port coupled to a polarization-maintaining fiber via a mode converter. In the directional coupler array chip, the two output ports of each directional coupler are coupled to a single-photon avalanche diode, and the differential electrical signals of the two corresponding single-photon avalanche diodes are output to a signal processing module.

2. A low small single-photon radar based on a probe array, characterized in that, include: Lasers are used to generate optical signals with narrow linewidths. A beam splitter is used to split the optical signal output by a laser into a first component and a second component. An acousto-optic modulator is used for pulse modulation and frequency shifting of the first component; An optical amplifier module is used to amplify the first component to the required power; The light and sound path is used to collimate and expand the amplified first component, and to collect the echo signal reflected from the target UAV and transmit it to the fiber optic array. The fiber array is used to transmit the echo signal to the heterodyne detection array module. It includes N×M optical fibers, where N and M are positive integers. The end faces of each fiber are arranged in an array, and the plane is located at the focal plane of the light receiving path. At the other end, each fiber optic interface is connected to the signal light input interface of each pixel of the heterodyne detection array module. The second component serves as the local oscillator light of the heterodyne detection array module; The heterodyne detection array module includes multiple heterodyne detection units for detecting single-photon-level optical signals, used to detect echo signals transmitted by the fiber optic array; each unit uses one local oscillator component and one optical signal from the fiber optic array for heterodyne detection, outputting an electrical signal containing the vibration information of the UAV fuselage, and amplifying and filtering the electrical signal. The data acquisition and processing module is used to perform analog-to-digital conversion on the electrical signals output by each detection unit of the heterodyne detection array module, extract the fuselage vibration characteristic parameters of the UAV through the vibration feature extraction algorithm, and perform UAV target identification using the target recognition algorithm. The turntable is used to point the receiving and transmitting optical paths towards the target area for scanning. Based on the electrical signal response distribution of each heterodyne detection unit in the heterodyne detection array module, it determines the target position, generates control commands to adjust the attitude or position of the receiving and transmitting optical paths, so that the echo signal reflected from the target falls into the central region of the fiber optic array. The heterodyne detection array module includes a multimode interferometer array chip, a photoelectric detection array chip, and N×M signal processing modules. The multimode interferometer array chip includes one 1×(N×M) multimode interferometer MMI and N×M 2×2 multimode interferometers. The input port of the 1×(N×M) multimode interferometer is coupled to a polarization-maintaining fiber through a mode pattern converter; each of its output ports is connected to an input port of a 2×2 multimode interferometer. Another input port of each 2×2 multimode interferometer is coupled to a polarization-maintaining fiber via a mode converter; The photoelectric detection array chip contains 2N×M single-photon avalanche diodes. Two adjacent single-photon avalanche diodes are coupled and aligned with the two output ports of a 2×2 multimode interferometer, and their differential electrical signals are output to a signal processing module.

3. The low, small and single-photon radar based on a probe array according to claim 2, characterized in that, The laser outputs an optical signal with a wavelength of 1550nm and a linewidth of less than 1kHz.

4. The low, small, all-optical-photon-radar based on a probe array according to claim 2, characterized in that, The acousto-optic modulator modulates the optical signal into a 50ns pulse of light and shifts the frequency by 100MHz.

5. The low, small, all-optical, photon radar based on an array of probes according to claim 2, characterized in that, The data acquisition and processing module uses an adaptive Kalman filter algorithm to preprocess the electrical signal output by the heterodyne detection array module to suppress interference from atmospheric turbulence and ambient light. The vibration feature extraction algorithm is based on the preprocessed electrical signal. It calculates the vibration frequency spectrum through Fast Fourier Transform (FFT) and extracts feature parameters, including the vibration dominant frequency, frequency stability, and amplitude.

6. The low-power, slow-moving single-photon radar based on a detector array according to any one of claims 2-5, characterized in that, The vibration feature extraction module also has a spectrum accumulation analysis function, which continuously collects and superimposes vibration spectrum within 100-500ms to improve the signal-to-noise ratio of weak vibration signals by ≥10 times; when the main frequency of the vibration signal is detected to be stable for ≥50ms, the feature extraction process is triggered to avoid false triggering caused by instantaneous noise.

7. The low-power, slow-moving single-photon radar based on a detector array according to any one of claims 2-5, characterized in that, The target recognition algorithm has a built-in UAV vibration feature library and an interference target vibration feature library. It adopts a "feature matching + weighted voting" algorithm to compare the extracted vibration features with the feature library. When the UAV feature matching degree is at a first set threshold and the interference target feature matching degree is less than or equal to a second set threshold, it is determined to be a UAV and the detection result is output. The detection result includes the UAV position, vibration features, and confidence level.

8. The low-power, slow-moving single-photon radar based on a detector array according to any one of claims 2-5, characterized in that, The data acquisition and processing module uses time measurement to obtain the position and angle information of the UAV target based on the response distribution of the detection units contained in the heterodyne detection array module.

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