Low, small and slow single photon radar based on detection array

Abstract

The invention belongs to the technical field of laser radars, and discloses a low, small and slow single photon radar based on a detection array, which comprises a laser, a beam splitter, an acousto-optic modulator, a light amplification module, a receiving and transmitting light path, a turntable, an optical fiber array, a heterodyne detection array module and a data acquisition and processing module, and the data acquisition and processing module extracts fuselage vibration characteristic parameters of the unmanned aerial vehicle through a vibration characteristic extraction algorithm, and performs unmanned aerial vehicle target identification by using a target identification algorithm. Compared with the prior art, high-coherence laser is generated, large-range airspace laser projection and vibration signal receiving are achieved through the optical fiber array, the heterodyne detection array is combined to suppress environment noise and extract unmanned aerial vehicle fuselage vibration characteristics, and finally accurate detection and recognition of the unmanned aerial vehicle are completed through the signal processing and recognition module. The system has the advantages of being large in view field range, high in anti-interference capability, high in vibration signal extraction precision and the like, and remote, high-sensitivity and low-misjudgment-rate detection of the low-slow-small unmanned aerial vehicle can be achieved.

Description

Technical Field

[0001] This invention relates to the field of lidar detection technology, and in particular to a low-profile, slow-moving single-photon radar based on a detection array. Background Technology

[0002] With the rapid development of technologies such as low-altitude, small, and slow-moving drones, the number of consumer and industrial drones has increased dramatically. Currently, drone detection technologies mainly include radio detection, radar detection, optical / infrared detection, and acoustic detection, but all have significant drawbacks: radio detection cannot identify drones flying silently; radar detection has low accuracy in identifying "low, slow, and small" targets and is easily interfered with by birds, balloons, etc.; optical / infrared detection is greatly affected by lighting and weather, and its detection performance drops significantly at night or in inclement weather; acoustic detection has a short detection range and is easily interfered with by environmental noise. Laser vibrometrics, based on laser interferometry or the Doppler effect, enables non-contact, high-precision vibration measurement, providing a new technological approach for UAV detection. However, traditional laser vibrometers are mostly "point measurement" devices with narrow fields of view, making it impossible to search for UAVs over large airspaces. Furthermore, factors such as ambient light, atmospheric turbulence, and laser intensity fluctuations can severely interfere with vibration signal extraction, leading to high false positive and false negative rates in UAV identification. In addition, existing lidar systems largely rely on spatial contour recognition of UAVs, making it difficult to distinguish similarly shaped UAVs from interfering targets (such as birds). In contrast, the unique vibration characteristics of a UAV's fuselage (such as motor vibration frequency and propeller disturbance frequency) can serve as a crucial basis for accurate identification. Summary of the Invention

[0003] In view of the above-mentioned defects in the existing technology, the present invention proposes a low-cost, slow-speed single-photon radar based on a detector array.

[0004] The technical solution of this invention is implemented as follows: A small, slow single-photon radar based on a detector array, comprising: 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 optic array, used to transmit the echo signal to the heterodyne detection array module, includes N×M optical fibers, where N and M are positive integers. The end faces of each fiber are closely arranged in an array at one end, and the plane where they are located is located at the focal plane of the light receiving path. At the other end, each fiber 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, and to determine the target position based on the electrical signal response distribution of each heterodyne detection unit in the heterodyne detection array module. It then generates control commands to adjust the attitude or position of the receiving and transmitting optical paths so that the echo signal reflected by the target falls into the central area of ​​the fiber optic array.

[0005] 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 SPAD, and N×M signal processing modules SP. The directional coupler array chip DCA contains N×M 2×2 directional couplers DC; Each output port fiber of the PLC is coupled to an input port of each directional coupler of the DCA via a mode converter MSC. Another input port of each directional coupler of the DCA is coupled to a polarization-maintaining fiber PMF through a mode converter MSC. Each directional coupler of the DCA has two output ports coupled to a single-photon avalanche diode (SPAD), and the differential electrical signals of the two SPADs are output to a signal processing module (SP).

[0006] Preferably, the heterodyne detection array module includes a multimode interferometer array chip, a photoelectric detection array chip, and N×M signal processing modules SP. 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 PMF through a mode spot converter (MSC); 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 PMF via a mode spot converter (MSC). The photoelectric detection array chip contains 2N×M single-photon avalanche diodes (SPADs). Two adjacent SPADs 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 (SP).

[0007] Preferably, the laser outputs an optical signal with a wavelength of 1550nm and a linewidth of less than 1kHz.

[0008] Preferably, the acousto-optic modulator modulates the optical signal into a 50ns pulse of light and shifts the frequency by 100MHz.

[0009] Preferably, 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 dominant vibration frequency, frequency stability, and amplitude.

[0010] Preferably, the vibration feature extraction module also has a spectrum accumulation analysis function, continuously collecting and superimposing the vibration spectrum within 100-500ms to improve the signal-to-noise ratio of weak vibration signals by a factor of ≥10; 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.

[0011] Preferably, 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 (accuracy ≤ 10m), vibration features, and confidence level.

[0012] Preferably, the data acquisition and processing module has a time measurement function to obtain the position and angle information of the UAV target based on the response distribution of the detection units included in the heterodyne detection array module.

[0013] Compared with the prior art, the present invention has the following beneficial effects: This invention proposes a low-profile, slow-moving single-photon radar based on a detector array. It generates highly coherent laser light through a narrow-linewidth laser, which is then projected over a wide airspace and receives vibration signals via a fiber optic array. Combined with a heterodyne detector array, it suppresses environmental noise and extracts the vibration characteristics of the UAV's fuselage. Finally, a signal processing and recognition module completes the accurate detection and recognition of the UAV. It has advantages such as a large field of view, strong anti-interference ability, and high accuracy in vibration signal extraction, enabling long-range, high-sensitivity, and low-false-error detection of "low-profile, slow-moving, and small" UAVs. Attached Figure Description

[0014] Figure 1 This is a block diagram illustrating the principle of the low-profile, slow-speed single-photon radar based on a detector array according to the present invention. Figure 2 This is a schematic diagram of the principle of a first embodiment of the low-profile, slow-speed single-photon radar based on a detector array according to the present invention; Figure 3 This is a schematic diagram of the second embodiment of the low-speed single-photon radar based on a detector array according to the present invention. Detailed Implementation

[0015] The present invention will now be clearly and completely described with reference to the accompanying drawings in the embodiments of the present invention.

[0016] like Figure 1 As shown, a low-power, slow single-photon radar based on a detector array includes a laser, a beam splitter, an acousto-optic modulator, an optical amplifier module, a light-receiving and receiving path, a turntable, an optical fiber array, a heterodyne detector array module, and a data acquisition and processing module. The laser is used to generate narrow linewidth optical signals; The beam splitter is used to split the optical signal output by the laser into a first component and a second component. The acousto-optic modulator is used to pulse modulate and frequency shift the first component; The optical amplification module is used to amplify the first component to the required power; The light-receiving 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 array. The fiber array is used to transmit the echo signal to the heterodyne detection array module. It includes N×M optical fibers, with the end faces of each fiber closely arranged in an array at one end, and the plane where they are located is located at the focal plane of the light receiving path; the other end of each fiber interface is connected to the signal light input interface of each unit 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 consists of multiple heterodyne detection units for detecting single-photon-level optical signals, used to detect the 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 a vibration feature extraction algorithm, and perform UAV target identification using a target recognition algorithm. The turntable is used to make the receiving and transmitting optical paths point to the target area for scanning, and to determine the target position based on the electrical signal response distribution of each detection unit of the heterodyne detection array module, and generate control commands to adjust the attitude or position of the receiving and transmitting optical paths so that the echo signal reflected by the target falls into the central area of ​​the fiber array.

[0017] The specific work process is as follows: 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 undergoes pulse modulation and frequency shifting by an acousto-optic modulator, resulting in a center frequency of [value missing]. ,in , This represents the frequency shift of the acousto-optic modulator. It is then amplified to the required power by an optical amplification module. The second component, as the local oscillator light, enters the heterodyne detector array module. The amplified first component, after being collimated and expanded by the light-receiving path, illuminates the target area and is then scanned by a turntable.

[0018] After being reflected by the target, the echo signal is collected by the receiving optical path and transmitted to the fiber optic array. The fiber optic array transmits the echo signal to the heterodyne detection array module, which consists of N×M optical fibers. At one end, the fiber end faces are closely arranged in an array, with the plane of the array located at the focal plane of the receiving optical path. At the other end, each fiber interface is connected to the signal input interface of each unit in 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, along with each echo signal component input from the fiber optic array to the heterodyne detection array module, undergoes heterodyne detection on a detection unit.

[0019] Because the target drone vibrates, it will cause a Doppler frequency shift in the light signal shining on it. The center frequency of the echo signal then becomes Assume that each local oscillator component and each echo signal component can be written as... , in, denoted as the amplitudes of the local oscillator light component and the echo signal component, respectively, and t is the time interval.

[0020] After heterodyne detection, the electrical signal output by each detection unit can be written as: , in, The frequency difference between the echo signal component and the local oscillator component is denoted by , and k is the detection and amplification correlation coefficient. The Doppler frequency can be accurately measured through the data acquisition and processing module. The vibration velocity of the target can be calculated as follows: , Where v(t) is the vibration velocity and λ is the wavelength of the laser.

[0021] Integrating v(t), we can obtain the displacement X of the target in the vibration direction: , The vibration amplitude A of the target object can be obtained by taking its extreme value; the vibration amplitude curve is fitted with a sine curve, and the time interval t between adjacent zeros of the fitted curve is calculated. The vibration frequency of the object is 1 / (2t). Differentiating v(t) yields the acceleration of the object under test in the direction of vibration. , The vibration equation of the target can be obtained based on the above parameters, and vibration features can be extracted by analyzing the vibration parameters. A target recognition algorithm is then used for UAV target recognition.

[0022] The turntable is used to point the receiving and transmitting optical paths towards the target area for scanning, and to determine the target position based on the electrical signal response distribution of each detection unit of the heterodyne detection array module. It then generates control commands to adjust the attitude or position of the receiving and transmitting optical paths so that the echo signal reflected by the target falls into the central area of ​​the fiber array.

[0023] like Figure 2 As shown, Example 1: 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 SPAD, and N×M signal processing modules SP. The directional coupler array chip DCA contains N×M 2×2 directional couplers DC; Each output port fiber of the PLC is coupled to an input port of each directional coupler of the DCA via a mode converter MSC. Another input port of each directional coupler of the DCA is coupled to a polarization-maintaining fiber PMF through a mode converter MSC. Each of the two output ports of the DCA directional coupler is coupled to a single-photon avalanche diode (SPAD), and the differential electrical signals of the two SPADs are output to a signal processing module (SP).

[0024] 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 dominant vibration frequency, frequency stability, and amplitude.

[0025] The specific principle is as follows: 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 undergoes pulse modulation and frequency shifting by an acousto-optic modulator, resulting in a center frequency of [value missing]. ,in , This represents the frequency shift of the acousto-optic modulator. It is then amplified to the required power by an optical amplification module. The second component, as the local oscillator light, enters the heterodyne detector array module. The amplified first component, after being collimated and expanded by the light-receiving path, illuminates the target area and is then scanned by a turntable.

[0026] After being reflected by the target, the echo signal is collected by the optical transmission path and transmitted to the fiber optic array. The fiber optic array transmits the echo signal to the heterodyne detection array module, which consists of N×M fibers, with the end faces of each fiber closely arranged in an array at one end, and the plane of the array located at the focal plane of the optical transmission path. One input port of each directional coupler of the DCA is coupled to a polarization-maintaining fiber PMF through a mode converter (MSC), and connected to the respective fiber optic interfaces at the other end of the fiber optic array.

[0027] The local oscillator light enters the heterodyne detection array module and is first split into N×M local oscillator light components by a 1×(N×M) optical splitter PLC. The optical fiber at each output port of the PLC is coupled to an input port of each directional coupler of the DCA through a mode-spot converter (MSC). It interferes with each echo signal transmitted by the fiber array on the DC, generating two interference results, which are then fed into the SPAD for detection. The differential signal is processed by the SP to become the output signal of the heterodyne detection unit.

[0028] Because the target drone vibrates, it will cause a Doppler frequency shift in the light signal shining on it. The center frequency of the echo signal then becomes Assume that each local oscillator component and each echo signal component can be written as... , in, denoted as the amplitudes of the local oscillator light component and the echo signal component, respectively, and t is the time interval.

[0029] After heterodyne detection, the electrical signal output by each detection unit can be written as: , in, The frequency difference between the echo signal component and the local oscillator component is denoted by , and k is the detection and amplification correlation coefficient. The Doppler frequency can be accurately measured through the data acquisition and processing module. The vibration velocity of the target can be calculated as follows: , Where v(t) is the vibration velocity and λ is the wavelength of the laser.

[0030] Integrating v(t), we can obtain the displacement X of the target in the vibration direction: , The vibration amplitude A of the target object can be obtained by taking its extreme value; the vibration amplitude curve is fitted with a sine curve, and the time interval t between adjacent zeros of the fitted curve is calculated. The vibration frequency of the object is 1 / (2t). Differentiating v(t) yields the acceleration of the object under test in the direction of vibration. , The vibration equation of the target can be obtained based on the above parameters, and vibration features can be extracted by analyzing the vibration parameters. A target recognition algorithm is then used for UAV target recognition.

[0031] The vibration feature extraction algorithm calculates the vibration frequency spectrum using Fast Fourier Transform (FFT) and extracts feature parameters, including the dominant vibration frequency, frequency stability, and amplitude. The vibration feature extraction module also features a spectrum accumulation analysis function, continuously acquiring and superimposing vibration spectra within 100-500ms to improve the signal-to-noise ratio of weak vibration signals by ≥10 times. When the dominant frequency of the vibration signal is detected to be consistently stable for ≥50ms, the feature extraction process is triggered to avoid false triggering caused by transient noise.

[0032] The target recognition algorithm has a built-in UAV vibration feature library and a vibration feature library of interfering targets (birds, insects, balloons). 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 interfering 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 (accuracy ≤10m), vibration features, and confidence level.

[0033] The turntable is used to point the receiving and transmitting optical paths towards the target area for scanning, and to determine the target position based on the electrical signal response distribution of each detection unit of the heterodyne detection array module. It then generates control commands to adjust the attitude or position of the receiving and transmitting optical paths so that the echo signal reflected by the target falls into the central area of ​​the fiber array.

[0034] like Figure 3 As shown, Example 2: The heterodyne detection array module includes a multimode interferometer array chip, a photoelectric detection array chip, and N×M signal processing modules SP. 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 PMF through a mode spot converter (MSC); 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 PMF via a mode spot converter (MSC). The photoelectric detection array chip contains 2N×M single-photon avalanche diodes (SPADs). Two adjacent SPADs 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 (SP).

[0035] 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 dominant vibration frequency, frequency stability, and amplitude.

[0036] 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.

[0037] The target recognition algorithm has a built-in UAV vibration feature library and an interference target (bird, insect, balloon) 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 (accuracy ≤ 10m), vibration features, and confidence level.

[0038] The data acquisition and processing module obtains the position and angle information of the UAV target based on the response distribution of the detection units of the heterodyne detection array module.

[0039] The specific principle is as follows: 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 undergoes pulse modulation and frequency shifting by an acousto-optic modulator, resulting in a center frequency of [value missing]. ,in , This represents the frequency shift of the acousto-optic modulator. It is then amplified to the required power by an optical amplification module. The second component, as the local oscillator light, enters the heterodyne detector array module. The amplified first component, after being collimated and expanded by the light-receiving path, illuminates the target area and is then scanned by a turntable.

[0040] After being reflected by the target, the echo signal is collected by the optical transmission path and transmitted to the fiber optic array. The fiber optic array transmits the echo signal to the heterodyne detection array module, which consists of N×M fibers, with the end faces of each fiber closely arranged in an array at one end, and the plane of the array located at the focal plane of the optical transmission path. One input port of each directional coupler of the DCA is coupled to a polarization-maintaining fiber PMF through a mode converter (MSC), and connected to the respective fiber optic interfaces at the other end of the fiber optic array.

[0041] The local oscillator light enters the heterodyne detector array module and is first split into N×M local oscillator components by a 1×(N×M) multimode interferometer. Each local oscillator component is connected to an input port of a 2×2 multimode interferometer. Each local oscillator component interferes with each echo signal transmitted from the fiber array on the 2×2 multimode interferometer, producing two interference results. These two results are then detected by two single-photon avalanche diodes (SPADs) on the photodetector array chip. The differential signal is processed by the SPs to become the output signal of the heterodyne detector unit.

[0042] Because the target drone vibrates, it will cause a Doppler frequency shift in the light signal shining on it. The center frequency of the echo signal then becomes Assume that each local oscillator component and each echo signal component can be written as... , in, denoted as the amplitudes of the local oscillator light component and the echo signal component, respectively, and t is the time interval.

[0043] After heterodyne detection, the electrical signal output by each detection unit can be written as: , in, The frequency difference between the echo signal component and the local oscillator component is denoted by , and k is the detection and amplification correlation coefficient. The Doppler frequency can be accurately measured through the data acquisition and processing module. The vibration velocity of the target can be calculated as follows: , Where v(t) is the vibration velocity and λ is the wavelength of the laser.

[0044] Integrating v(t), we can obtain the displacement X of the target in the vibration direction: , The vibration amplitude A of the target object can be obtained by taking its extreme value; the vibration amplitude curve is fitted with a sine curve, and the time interval t between adjacent zeros of the fitted curve is calculated. The vibration frequency of the object is 1 / (2t). Differentiating v(t) yields the acceleration of the object under test in the direction of vibration. , The vibration equation of the target can be obtained based on the above parameters, and vibration features can be extracted by analyzing the vibration parameters. A target recognition algorithm is then used for UAV target recognition.

[0045] The vibration feature extraction algorithm calculates the vibration frequency spectrum using Fast Fourier Transform (FFT) and extracts feature parameters, including the dominant vibration frequency, frequency stability, and amplitude. The vibration feature extraction module also features a spectrum accumulation analysis function, continuously acquiring and superimposing vibration spectra within 100-500ms to improve the signal-to-noise ratio of weak vibration signals by ≥10 times. When the dominant frequency of the vibration signal is detected to be consistently stable for ≥50ms, the feature extraction process is triggered to avoid false triggering caused by transient noise.

[0046] The target recognition algorithm has a built-in UAV vibration feature library and a vibration feature library of interfering targets (birds, insects, balloons). 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 interfering 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 (accuracy ≤10m), vibration features, and confidence level.

[0047] The turntable is used to point the receiving and transmitting optical paths towards the target area for scanning, and to determine the target position based on the electrical signal response distribution of each detection unit of the heterodyne detection array module. It then generates control commands to adjust the attitude or position of the receiving and transmitting optical paths so that the echo signal reflected by the target falls into the central area of ​​the fiber array.

[0048] As can be seen from the various embodiments of the present invention, the present invention proposes a low-profile, slow-moving single-photon radar based on a detection array. It generates highly coherent laser light through a narrow-linewidth laser, and achieves laser projection and vibration signal reception over a large airspace through a fiber optic array. Combined with a heterodyne detection array to suppress environmental noise and extract the vibration characteristics of the UAV fuselage, the radar finally completes the accurate detection and identification of the UAV through a signal processing and recognition module. It has advantages such as a large field of view, strong anti-interference ability, and high vibration signal extraction accuracy, and can achieve long-range, high-sensitivity, and low-false-rate detection of "low-profile, slow-moving, and small" UAVs.

Claims

1. A low-profile, slow-moving single-photon radar based on a detector 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, and to determine the target position based on the electrical signal response distribution of each heterodyne detection unit in the heterodyne detection array module. It then generates control commands to adjust the attitude or position of the receiving and transmitting optical paths so that the echo signal reflected by the target falls into the central area of ​​the fiber optic array.

2. The low-power, slow-moving single-photon radar based on a detector array according to claim 1, characterized in that, 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 an 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.

3. The low-power, slow-moving single-photon radar based on a detector array according to claim 1, characterized in that, 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.

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

5. The low-power, slow-moving single-photon radar based on a detector array according to claim 1, characterized in that, The acousto-optic modulator modulates the optical signal into a 50ns pulse of light and shifts the frequency by 100MHz.

6. The low-power, slow-moving single-photon radar based on a detector array according to claim 5, 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.

7. The low-power, slow-moving single-photon radar based on a detector array according to any one of claims 1-6, 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.

8. The low-power, slow-moving single-photon radar based on a detector array according to any one of claims 1-6, 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.

9. The low-power, slow-moving single-photon radar based on a detector array according to any one of claims 1-6, 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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