Unmanned aerial vehicle detection method, system and equipment based on multifunctional radar and medium

Abstract

The invention discloses an unmanned aerial vehicle detection method, system and device based on a multifunctional radar and a medium, and relates to the technical field of unmanned aerial vehicle target detection, and the method comprises the steps: obtaining the detection position of an unmanned aerial vehicle target when a search result is that the unmanned aerial vehicle target exists; judging the area of the unmanned aerial vehicle target according to the detection position; when the judgment result is the early warning area, obtaining positioning information of the unmanned aerial vehicle target through radar equipment in a continuous wave radar working mode; when the judgment result is that the unmanned aerial vehicle is in the other area, obtaining the positioning information of the unmanned aerial vehicle target through the radar equipment in the phased array working mode; when the judgment result is a critical area, performing joint positioning according to the target information in the phased array working mode and the target information in the continuous wave radar working mode to determine the positioning information of the unmanned aerial vehicle target; the method solves the problems that a traditional anti-no phased array radar has a distance blind area and is poor in positioning precision, and can flexibly adapt to the positioning requirements of illegal unmanned aerial vehicles in different scenes.

Description

Technical Field

[0001] The present invention relates to the technical field of unmanned aerial vehicle (UAV) target detection, and more specifically, to a UAV detection method, system, device and medium based on a multi-functional radar. Background Art

[0002] With the development of industrial technology and the popularization of consumer UAVs, relevant departments urgently need a method that can supervise the low-altitude area and has a low cost; traditional methods often use optoelectronic cameras and acoustic sensors to realize the perception and positioning of consumer UAVs. However, optoelectronic cameras are costly and have problems such as slow focusing, being easily interfered with, and high cost, which limits their maximum effect. Secondly, although acoustic arrays can better perceive and locate UAVs in some scenarios, they do not work well in urban environments and have a limited detection range (usually less than 500 meters). Therefore, in practical applications, both optoelectronic cameras and acoustic sensors are greatly restricted.

[0003] Radar instruments are not restricted by the above. Traditionally, radars can be divided into two categories: one is a passive radar that does not actively emit electromagnetic waves and only realizes electronic reconnaissance by passively receiving electromagnetic waves emitted by UAVs or other signal sources; the other is an active radar that can actively emit specific modulated signals and electromagnetic waves of specific frequencies and receive and process the electromagnetic waves reflected by the target to realize positioning. Compared with passive radars, active radars not only have the ability to work all-weather and can detect fully autonomous UAVs (i.e., UAVs that do not radiate electromagnetic waves outward), but also can realize functions such as classification and recognition by analyzing the micro-Doppler characteristics of the echo reflected by the target. Therefore, in actual "key area protection scenarios", it is usually necessary to cooperate with active radars to realize large-scale UAV search and tracking.

[0004] In the field of traditional technical methods, although there are a large number of related UAV detection radar products, they mainly adopt the "pulse Doppler radar" system and the "phased array"-"mechanical scanning" system; these UAV detection radars of these systems not only have a considerable distance blind area (usually several hundred meters), making illegal flights take advantage of this range and making key areas vulnerable to such UAVs, but also their range resolution, angle resolution, and velocity resolution are limited, making it difficult to adapt to different application scenarios. Summary of the Invention

[0005] The purpose of the present invention is to provide a UAV detection method, system, device and medium based on a multi-functional radar. By switching between the phased array working mode and the continuous wave radar working mode, the problems of the traditional "anti-UAV" phased array radar having a distance blind area and poor positioning accuracy are solved, and it can also flexibly adapt to the positioning requirements for illegal UAVs in different scenarios.

[0006] The above technical object of the present invention is achieved by the following technical solutions: In the first aspect, the present application provides a method for detecting unmanned aerial vehicles based on a multifunctional radar, including the following specific steps: Search for targets in the surrounding area. When the search result indicates the presence of an unmanned aerial vehicle target, obtain the detection position of the unmanned aerial vehicle target through the radar device in the phased array operating mode. Judge the area where the unmanned aerial vehicle target is located according to the detection position. The areas include a warning area, a critical area, and other areas. When the judgment result is the warning area, obtain the positioning information of the unmanned aerial vehicle target through the radar device in the continuous wave radar operating mode until there is no unmanned aerial vehicle target in the warning area. When the judgment result is other areas, obtain the positioning information of the unmanned aerial vehicle target through the radar device in the phased array operating mode until there is no unmanned aerial vehicle target in the other areas. When the judgment result is the critical area, the radar device switches between the phased array operating mode and the continuous wave radar operating mode, and performs joint positioning based on the target information in the phased array operating mode and the target information in the continuous wave radar operating mode to determine the positioning information of the unmanned aerial vehicle target until there is no unmanned aerial vehicle target in the critical area.

[0007] Based on the above technical solutions, the present invention can be further improved as follows.

[0008] Further, the radar device in the continuous wave radar operating mode obtains the positioning information of the unmanned aerial vehicle target, specifically: , ; where:

[0009]

[0010]

[0011] In the formula, represents the background noise, represents the set of reference units on both sides of the current test unit, represents the two-dimensional range-Doppler spectrum, represents the range image in the slow time dimension, represents the test unit, represents a given threshold factor, represents the autocorrelation matrix, represents the total number of indices of the area where the target exists, represents the azimuth angle, represents the pitch angle, represents the steering vector, represents the coordinates of the UAV target, represents the radial velocity of the UAV target, is the number of FFT points in the Doppler direction, is the Doppler cell, represents the speed of light, represents the carrier frequency, represents the pulse width, is the frequency modulation slope.

[0012] Furthermore, the above-mentioned joint positioning based on the target information in the phased array working mode and the target information in the continuous wave radar working mode is specifically as follows: Based on the radar equipment in the continuous wave radar working mode to obtain the positioning information of the UAV target, and the radar equipment in the phased array working mode to obtain the positioning information of the UAV target, fuse the existing observations to obtain the initial track observation, and determine the stable track; Use the calculated Mahalanobis distance of the stable track to update the track of the stable track at the next moment, and obtain the positioning information of the determined UAV target based on the track update result.

[0013] Furthermore, the above-mentioned stable track is obtained through the following method: When is less than the set threshold, , ,

[0014] In the formula, is the stable track, represents the Mahalanobis distance of the initial track, represents the positioning information of the UAV target obtained by the radar equipment in the continuous wave radar working mode, represents the positioning information of the UAV target obtained by the radar equipment in the phased array working mode.

[0015] Furthermore, the above-mentioned track update of the stable track at the next moment is specifically as follows: ,

[0016] Among them:

[0017]

[0018]

[0019]

[0020]

[0021] In the formula, represents the track information at time represents time the updated track information, represents the Kalman gain, represents the track covariance at time represents time the updated track covariance, represents the track information covariance, represents the measurement matrix, represents the state transition matrix, represents the process noise matrix, represents a stable track, represents the track information in the continuous wave radar working mode, represents the track information in the phased array working mode.

[0022] Furthermore, the above track update for the stable track at the next moment further includes: Calculating the Mahalanobis distance of the stable track. If the Mahalanobis distance of the stable track satisfies the association relationship with other tracks, the track of the stable track at the next moment is updated.

[0023] Furthermore, the above Mahalanobis distance of the stable track is specifically:

[0024] Where:

[0025] In the formula, represents the Mahalanobis distance of the stable track, represents the stable track, represents the track information in the continuous wave radar working mode, represents the track information in the phased array working mode.

[0026] In a second aspect, the present application provides a UAV detection system based on a multi-functional radar, which is applied to the multi-functional radar-based UAV detection method in any one of the first aspects, and includes: A target search module, configured to search for targets in the surrounding area. When the search result is that there is a UAV target, the detection position of the UAV target is obtained through the radar device in the phased array working mode; A position judgment module, configured to judge the area where the UAV target is located according to the detection position. The area where it is located includes a warning area, a critical area, and other areas; The first-mode positioning module is used to obtain the positioning information of the UAV target through the radar device in the continuous-wave radar working mode when the judgment result is the warning area until there is no UAV target in the warning area; The second-mode positioning module is used to obtain the positioning information of the UAV target through the radar device in the phased-array working mode when the judgment result is other areas until there is no UAV target in other areas; The third-mode positioning module is used to switch the radar device between the phased-array working mode and the continuous-wave radar working mode when the judgment result is the critical area, and perform joint positioning based on the target information in the phased-array working mode and the target information in the continuous-wave radar working mode to determine the positioning information of the UAV target until there is no UAV target in the critical area.

[0027] In a third aspect, the present application provides an electronic device, including a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the computer program, the method according to any one of the first aspect is implemented.

[0028] In a fourth aspect, the present application provides a non-transitory computer-readable storage medium. The non-transitory computer-readable storage medium stores computer instructions, and the computer instructions cause the computer to execute the method according to any one of the first aspect.

[0029] Compared with the prior art, the present invention has at least the following beneficial effects: The present invention provides a design and implementation method for a multi-functional UAV detection radar, which can realize the search and warning of long-distance illegal UAV targets, and switch to the MIMO continuous-wave radar working mode when the illegal UAV target approaches the "key area protection" target, which can provide a larger virtual array to achieve high-precision positioning of the UAV target. At the same time, because the present invention adopts multiple working modes, in the actual application environment, it not only solves the problems of distance blind area and poor positioning accuracy existing in traditional "anti-UAV" phased-array radars, but also can flexibly adapt to the positioning requirements for illegal UAVs in different scenarios, switch to the MIMO continuous-wave radar working mode in scenarios requiring high precision, and can be switched to the "phased-array" working mode in tasks requiring long-distance reconnaissance of UAVs. Therefore, the multi-functional radar solution proposed by the present invention has a wider application range, can provide more choices to adapt to different application environments, and can also cooperate with existing electronic reconnaissance equipment for joint positioning of illegal UAVs. Description of the Drawings

[0030] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, form a part of this application, and do not constitute a limitation to the embodiments of the present invention. In the drawings: Figure 1The FPGA board after assembling the housing in the embodiment of the present invention; Figure 2 The RF board after assembling the housing in the embodiment of the present invention; Figure 3 The schematic diagram of the digital phase shifter in the embodiment of the present invention; Figure 4 The schematic diagram of the microstrip array antenna in the embodiment of the present invention; Figure 5 The schematic diagram of some instruments after assembly in the embodiment of the present invention; Figure 6 The schematic diagram of a virtual scene in the embodiment of the present invention; Figure 7 The schematic diagram of the phased array radar working mode scene in the embodiment of the present invention; Figure 8 The schematic diagram of the continuous wave radar working mode scene in the embodiment of the present invention; Figure 9 The processing flow chart of the phased array radar working mode in the embodiment of the present invention; Figure 10 The processing flow chart of the continuous wave radar working mode in the embodiment of the present invention; Figure 11 The processing flow chart of the mutual switching and mutual associated data processing between the phased array radar working mode and the MIMO continuous wave radar working mode in the embodiment of the present invention; Figure 12 The estimated two-dimensional angle spectrum and range-Doppler spectrum diagram in the continuous wave radar working mode in the embodiment of the present invention; Figure 13 The estimated one-dimensional angle spectrum and the moving target detection results of multiple targets in the phased array radar working mode in the embodiment of the present invention; Figure 14 The schematic diagram of the combined data association and the finally estimated track in the embodiment of the present invention; Figure 15 The method flow chart of the detection method in the embodiment of the present invention; Figure 16 The connection schematic diagram of the detection system in the embodiment of the present invention; Figure 17 The connection schematic diagram of the electronic device in the embodiment of the present invention. Detailed implementation manners

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and illustrated herein can generally be arranged and designed in various different configurations.

[0032] Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0033] It should be noted that like reference numerals and letters denote like items in the following drawings. Therefore, once an item is defined in one drawing, it does not require further definition and explanation in subsequent drawings.

[0034] In the description of the embodiments of the present invention, "a plurality of" represents at least two.

[0035] Embodiment 1: To solve the problems of range blind spots and poor positioning accuracy existing in traditional "anti-null" phased array radars, this embodiment provides a method for detecting unmanned aerial vehicles (UAVs) based on a multi-functional radar. By switching between the phased array operating mode and the continuous wave radar operating mode, it can also flexibly adapt to the positioning requirements for dealing with illegal UAVs in different scenarios, such as Figure 15 shown, including the following specific steps: S1. Search for targets in the surrounding area. When the search result indicates the presence of a UAV target, obtain the detection position of the UAV target through the radar device in the phased array operating mode.

[0036] S2. Determine the area where the UAV target is located based on the detection position. The areas include a warning area, a critical area, and other areas.

[0037] S3. When the judgment result is the warning area, obtain the positioning information of the UAV target through the radar device in the continuous wave radar operating mode until there is no UAV target in the warning area.

[0038] Optionally, the radar device in the continuous wave radar operating mode obtains the positioning information of the UAV target specifically as follows: , ; where:

[0039]

[0040]

[0041] In the formula, represents the background noise, represents the set of reference units on both sides of the current test unit, represents the two-dimensional range-Doppler spectrum, represents the range image in the slow-time dimension, represents the test unit, represents a given threshold factor, represents the autocorrelation matrix, represents the total index number of the region where the target exists, represents the azimuth angle, represents the elevation angle, represents the steering vector, represents the coordinates of the UAV target, represents the radial velocity of the UAV target, is the number of FFT points in the Doppler direction, is the Doppler cell, represents the speed of light, represents the carrier frequency, represents the pulse width, is the frequency modulation slope.

[0042] S4. When the judgment result is other regions, the radar device in the phased array working mode is used to obtain the positioning information of the UAV target until there is no UAV target in other regions.

[0043] S5. When the judgment result is the critical region, the radar device switches between the phased array working mode and the continuous wave radar working mode, and performs joint positioning based on the target information in the phased array working mode and the target information in the continuous wave radar working mode to determine the positioning information of the UAV target until there is no UAV target in the critical region.

[0044] Optionally, the above-mentioned joint positioning based on the target information in the phased array working mode and the target information in the continuous wave radar working mode is specifically as follows: S51. Based on the positioning information of the UAV target obtained by the radar device in the continuous wave radar working mode and the positioning information of the UAV target obtained by the radar device in the phased array working mode, the existing observations are fused to obtain the initial track observation, and a stable track is determined.

[0045] Among them, the above-mentioned stable track is obtained through the following method: When is less than the set threshold, , ,

[0046] In the formula, is the stable trajectory, represents the Mahalanobis distance of the initial trajectory, represents the positioning information of the UAV target obtained by the radar device in the continuous wave radar working mode, represents the positioning information of the UAV target obtained by the radar device in the phased array working mode.

[0047] Furthermore, the above-mentioned trajectory update of the stable trajectory at the next moment is specifically as follows: ,

[0048] Among them:

[0049]

[0050]

[0051]

[0052]

[0053] In the formula, represents the trajectory information at time represents time the updated trajectory information, represents the Kalman gain, represents the trajectory covariance at time represents time the updated trajectory covariance, represents the trajectory information covariance, represents the measurement matrix, represents the state transition matrix, represents the process noise matrix, represents the stable trajectory, represents the trajectory information in the continuous wave radar working mode, represents the trajectory information in the phased array working mode.

[0054] S52. Use the calculated Mahalanobis distance of the stable trajectory to update the trajectory of the stable trajectory at the next moment, and obtain the positioning information of the determined UAV target based on the trajectory update result.

[0055] Among them, the above-mentioned trajectory update of the stable trajectory at the next moment also includes: Calculate the Mahalanobis distance of the stable track. If the Mahalanobis distance of the stable track satisfies the association relationship with other tracks, the stable track at the next moment is updated.

[0056] Specifically, the Mahalanobis distance of the above-mentioned stable track is specifically:

[0057] Where:

[0058] In the formula, represents the Mahalanobis distance of the stable track, represents the stable track, represents the track information in the continuous wave radar working mode, represents the track information in the phased array working mode.

[0059] Embodiment 2: To solve the problems of distance blind area and poor positioning accuracy existing in traditional "anti-drone" phased array radars, the present invention proposes a multi-functional UAV detection radar and implementation method, which uses a communication software radio frequency board (ADRV9025A) and a digital phase shifter to realize an integrated "continuous wave" - "phased array" radar. By adjusting the board on the field programmable gate array (FPGA) board and flexibly adjusting the radar system according to the current position of the target, finally, when no UAV target is detected or the target is at a "safe distance", it will switch to the "phased array" working mode and perform beamforming to ensure that the energy is used for searching / detecting UAVs to prevent the loss of the target. At the same time, when the UAV approaches the "sensitive area", the device can switch to the continuous wave radar working mode. At this time, the device will transmit multiple pulses at different transmitting antennas in time division and form a larger virtual array to ensure that the radar has high resolution in both the azimuth and elevation directions.

[0060] Furthermore, the implemented detection system includes: a communication software radio frequency board, a digital phase shifter, an FPGA board, and a multi-functional antenna. Among them, the radio frequency board is connected to the FPGA board, the digital phase shifter is directly connected to the radio frequency board and then to the multi-functional antenna, and the digital phase shifter is directly controlled by the FPGA board. The detection method includes the following steps: S1. Turn on the phased array antenna and the digital phase shifter, and move the beam to search the surrounding area to estimate the position of the target.

[0061] S2. Adjust according to the detection result obtained in step S1. If a target appears in the detection area, adjust the radar to the track-while-search (TWS) mode as needed.

[0062] S3. Continuously track the UAV targets. If a UAV target intrudes into the designated "key area", turn on the continuous wave antenna simultaneously and enter the Multiple Input Multiple Output (MIMO) radar working mode.

[0063] S4. Time-division multiplex the "continuous wave" - "phased array" working modes, and perform radar signal processing separately to obtain the locations of different UAV targets.

[0064] S5. Filter and associate the locations of different UAV targets obtained in step S4, and continuously update the locations of the UAV targets.

[0065] S6. Continuously monitor the UAV targets in step S1. When a UAV target is about to enter the detection blind area of the "phased array" (i.e., the critical area) or leave the detectable area, the FPGA board will automatically turn on the "continuous wave" working mode and perform data processing in step S5, so as to ensure that when the UAV target enters the detection blind area of the "phased array" or enters the current beam blind area of the "phased array", the system can still locate the UAV target.

[0066] To facilitate those skilled in the art to understand the technical content of the present invention, the following further explains the content of the present invention in conjunction with the accompanying drawings.

[0067] As Figure 1 shown, it is an FPGA board equipped with an X CZU9EG chip. This board has signal processing capabilities and data processing capabilities. As Figure 2 shown, it is a radio frequency board that can transmit any radio signal with an intermediate frequency of 650 MHz to 6 GHz, so it can work on different frequency bands and can be applied in different scenarios; Figure 3 shows a highly reliable digital phase shifter with channels, whose operating frequency is between 5.0 GHz - 6.0 GHz, and can realize the function of beamforming at the transmitting end; Figure 4 is the schematic diagram of the antenna array proposed by the present invention. This array can be used by both the "phased array" radar and the continuous wave radar at the same time, and respectively form a linear array of and a virtual planar array of the size of ; Figure 5 is the schematic diagram of some instruments after all parts are assembled.

[0068] This embodiment takes the scenario of multiple UAVs at a long distance as an example. First, enter the "phased array" working mode. After the FPGA board enters the "phased array" working mode, it will automatically calculate the optimal wave position . As Figure 7 shown, in combination with the above optimal wave position, the radar equipment will follow Execute the Search Mode. By adjusting the Figure 3 shown digital phase shifter, the signal of TX1 (Transmitting Antenna 1) can be shifted according to the specified wave position to achieve the search function.

[0069] As Figure 6 shown, when a potential UAV target is found, the search mode is turned off, and the TWS mode is executed to continue searching for and locating known UAV targets; among them, when and only when there is a UAV target entering Figure 6 the specified critical area, TX2 to TX4 will be turned on to execute the MIMO continuous wave radar working mode, and the Figure 8 formed equivalent planar array of such size; thereby, this device will simultaneously obtain higher-precision elevation and azimuth measurement results.

[0070] The following takes the scenario in Figure 6 as an example to introduce the specific implementation steps: Step 1: "Phased array" radar signal generation, optimal wave position estimation and signal processing, as Figure 9 shown, the specific processing process is: Step 1-1: Radar signal generation: The "phased array" radar usually generates pulse linear frequency modulation (LFM, Linear Frequency Modulated) signals, and performs signal processing and data processing on the FPGA side. Assume that the carrier frequency of the radar is , transmits pulses, the bandwidth is , the pulse width is , the pulse repetition interval is , the sampling rate is , the total time length is , then the sampling time points are defined as:

[0071] Then the single LFM pulse signal can be written as:

[0072] Among them, represents a complex number, is the frequency modulation slope, which can be denoted as: ; Based on the single LFM pulse signal, a multi-pulse LFM waveform can be constructed, that is: ; Discretize , there is:

[0073] Among them, is a discretized signal, is defined as:

[0074] Step 1-2: Optimal wave position determination: Based on the radar signal described in Step 1-1, it is necessary to pre-determine the optimal wave position to implement the subsequent search pattern. Existing research indicates that the half-power point of the antenna beam width is:

[0075] Among them, is the wavelength, is the number of array elements, is the array element spacing, is the current pointing direction of the antenna. It can be directly found from the above formula that among different antenna pointing angles, the half-power point width is continuously broadening. In order to save the scanning time resources of the "phased array" radar, improve the radar search efficiency, and increase the detection rate of UAV targets, it is necessary to find the optimal scanning wave position .

[0076] It can be assumed that the pointing angle of the antenna beam at the th wave position is , then the relationship between adjacent wave positions is as follows: Among them, has: .

[0077] By traversing the above formula, the optimal scanning wave position set can be obtained. However, considering that the above formula is a transcendental equation and is difficult to directly solve in actual radar equipment, therefore, in practical applications, the present invention will directly write the calculation results into the equipment and input them into the phase shifter in sequence.

[0078] Step 1-3: "Phased array" radar signal processing: After completing the above steps, the "phased array" radar will search the surrounding environment. Assume that the two-dimensional echo data after reception is , here, is the pulse index, is the sampling sequence number of the analog-to-digital converter (ADC). Then, through matched filtering, the estimation of the target distance can be achieved. First, construct a matched filter :

[0079] Among them, represents the conjugate inversion of the single-pulse emission signal Then, convolution is performed on the pulse dimension of each echo data, that is:

[0080] Among them, is the echo data after pulse compression, represents the convolution operation. Next, perform Moving Target Detection (MTD). Through the echo data of multiple pulses, the "phased array" radar can obtain the relative radial velocity of the target. Thus, the range-Doppler spectrum obtained after MTD is:

[0081] Among them, represents the velocity dimension index here, represents performing a Fast-Fourier Transform (FFT) in the direction of the pulse dimension. Finally, through 1D Cell-Averaging Constant False Alarm Rate (1D CA-CFAR), the range and radial velocity of the target can be extracted. To calculate the target coordinates, it is necessary to use the Minimum Variance Distortionless Response (MVDR) angle measurement method to calculate the azimuth angle where the target is located. The specific steps will be elaborated later.

[0082] Steps 1 - 4: Working mode switching: When the target enters the critical area, due to the range blind area of the "phased array" radar, it cannot effectively detect and locate the UAV in a relatively close area. Therefore, the present invention sets a critical area to time-division multiplex the working modes of the "phased array" radar and the MIMO continuous wave radar, which can not only ensure the stable tracking of high-speed UAVs, but also continue to search for other UAV targets while accurately positioning the UAVs in the critical area, enabling the present invention to timely warn the users.

[0083] Step 2: MIMO continuous wave signal processing and target position estimation, as Figure 10 shown, specifically as follows: Step 2 - 1: Frequency-Modulated Continuous Waveform (FMCW) radar signal generation: Similar to Step 1-1, when initializing the MIMO continuous wave radar in the present invention, it is necessary to initialize according to the LFM signal model. Considering that the range resolution and velocity resolution of the FMCW radar are directly related to the bandwidth , pulse width , and number of pulses , a larger bandwidth , a longer pulse width , and more pulses will be adopted in the MIMO radar mode. Denote the FMCW transmitted signal as , and there is:

[0084] Among them, represents the frequency modulation slope of the FMCW radar. Assume the distance of the target is , then the delay from the target to this device can be calculated as:

[0085] Among them, represents the speed of light. The echo signal can be expressed as:

[0086] Among them, is the reflection coefficient. Further, mixing is performed at the FPGA end, and the beat frequency signal can be obtained as:

[0087] Among them, is the received signal after conjugation. Further analyzing the beat frequency signal , there is:

[0088] Ignoring the other two terms, it can be found that the beat frequency has the following relationship:

[0089] Thus, the FPGA board can directly obtain the beat frequency signal that is proportional to the target distance.

[0090] Step 2-2: FMCW continuous wave radar signal processing: can directly perform FFT on to obtain the distance of the UAV target. At this time, the after FFT is called the range image. Denote as the two-dimensional echo data after discrete sampling and arrangement. Among them, is the slow time dimension index, is the ADC sampling serial number. Then the corresponding range profile in the slow time dimension can be calculated as:

[0091] where, denotes performing FFT in the fast time dimension (i.e., ADC sampling). Similarly, after obtaining the range profile performing FFT in the slow time dimension can obtain the two-dimensional range-Doppler spectrum , which is denoted here as:

[0092] Based on , candidate targets can be obtained by the 1D CA-CFAR method. The processing method of 1D CA-CFAR is as follows. For the test cell with index , its background noise is calculated as follows:

[0093] where, denotes the number of reference cells, is the set of reference cells on both sides of the current test cell. Assuming is the number of guard cells, then the index of the left reference cell is from to , and the index of the right reference cell is from to . For the test cell , based on the above background noise and the given threshold factor , there is:

[0094] Finally, based on the above detected targets, angle estimation is performed. In the present invention, in order to obtain a relatively accurate angle value, the MVDR angle measurement method is used to achieve the three-dimensional positioning of the UAV. Specifically, first calculate the autocorrelation matrix obtained from the range cells with targets, and there is:

[0095] where, denotes the total index number of the area with targets, denotes the current index, denotes the current index set. Assuming the steering vector finally formed by the MIMO radar is , where is the azimuth angle, is the elevation angle, then finally MVDR at the test cell The obtained result is as follows:

[0096] By traversing and selecting the peaks that reach the specified threshold, the relative angle of the UAV target can be obtained; to obtain the position of the target , combining the angle values obtained above , the distance index, and the radial velocity index, the coordinates of the current target , coordinates, and radial velocity can be estimated respectively. Based on the azimuth angle and the distance to the current target , there is: ; where represents the distance conversion function, which can be simply calculated as:

[0097] where is the number of distance FFT points. For the "phased array" radar mode, a similar method can also be adopted, that is, calculating the time delay and the relative angle of the target to obtain the target position. Further, by querying the corresponding distance-Doppler distance cell and Doppler cell , the radial velocity of the current target can be obtained; that is:

[0098] where is the number of Doppler-to-FFT points.

[0099] Step 2-3: Working mode switching: When all targets are far from the critical area, to save time resources, this device will no longer execute the MIMO continuous wave radar working mode, but directly execute the "phased array" radar working mode (as shown in Figure 7 the scene). If there is at least one target still within the critical area, allocate at least one complete coherent processing interval (CPI) time to TX2, TX3, and TX4 for this device to continuously track the threatening UAV targets (as shown in Figure 6 the scene).

[0100] Step 3: Joint target positioning and working mode switching between MIMO continuous wave radar and "phased array" radar, as shown in Figure 11 as follows: Step 3-1: Joint target positioning: As shown in Figure 6As shown, when the device detects that there is a drone in the critical area, it will switch between different time slots for operation. Assume that the target information obtained by the current "phased array" radar is , and the target information obtained by the MIMO continuous wave radar is , where respectively represent coordinates and radial velocity. At initialization, the existing observations are first fused, that is, when the following conditions are met, the observation is fused into the initial track observation:

[0101] where, is the Mahalanobis distance of the initial track, and , when is less than the specified value, the observation is fused, that is: , is the identity matrix; at the same time, after the above steps are completed, the covariance of each track is . After multiple-frame observations, a stable track can be obtained. Based on the above information, the corresponding Mahalanobis distance can be calculated as: , where takes values as:

[0102] At the same time, is the covariance of the track information. If does not meet the association with any track, it is considered that the target point is a new target, otherwise the subsequent track update work continues. Assume that the target state transition matrix is , the process noise matrix is , and the measurement matrix is , then the update equations of the track at time are respectively: ,

[0103] where, is the track information updated at time , represents the track information at time , is the track covariance matrix at time , is the updated track covariance matrix at time . Thus, the Mahalanobis distance track information covariance can be updated to:

[0104] where, is zero-mean, white Gaussian noise. Further, the Kalman gain is as follows:

[0105] The last updated track information and the track covariance are as follows: ,

[0106] By repeatedly traversing and iterating the above formula, the joint UAV target association and positioning can be achieved while the MIMO continuous-wave radar and the "phased array" radar are observing in the critical area, and the optimal estimation result can be obtained.

[0107] Step 3-2: Working mode switching: The present invention will continue to determine whether to switch the working mode in the centralized target association, which is mainly divided into: 1. When all UAV targets are detected / no UAV targets exist, directly adopt the "phased array" radar working mode (as Figure 7 shown).

[0108] 2. When at least one UAV target is detected approaching the target area, directly adopt the MIMO continuous-wave radar working mode (as Figure 8 shown).

[0109] 3. When no UAV is approaching the target area, but there are UAVs in the critical area, search for distant targets using the "phased array" radar mode at fixed time slots while positioning close targets using the MIMO continuous-wave radar working mode (as Figure 6 shown), and centrally associate the positioning results in sequence.

[0110] Based on the above logic, the present invention will automatically adjust the working mode of the radar device to achieve large-range and dead-angle-free UAV target positioning and tracking.

[0111] Step 4: UAV target positioning and warning Based on the track of each UAV obtained by this device, specific warning areas and critical areas are set. When a UAV target enters the above areas, a warning is given to the operator, and the position information of the UAV is indicated . At the same time, in different scenarios, this device will perform different search behaviors and working modes to achieve obtaining the rough position of the UAV in advance at a long distance and achieving high-precision three-dimensional UAV target positioning at a short distance.

[0112] The following experimental verification is further described: As Figure 12 and Figure 13As shown, they are respectively the spatial spectrum and the range-Doppler spectrogram obtained by the present invention under the MIMO continuous wave radar mode and the "phased array" radar mode at the current moment; in this experiment, the carrier frequency of the "phased array" radar mode is , the bandwidth , the number of pulses , the pulse width , the pulse repetition time , the sampling rate ; while in the MIMO continuous wave radar mode, the same carrier frequency is maintained, the bandwidth is increased to , the same number of pulses is maintained, and the pulse width is increased . Based on the above parameters, the results in Figures 12 - 14 are obtained.

[0113] Among them, in combination with Figures 12 - 14 of the experimental results, the present invention mainly shows the situation where multiple UAV targets are detected by the "phased array" radar under the condition that the detection range of the MIMO radar is limited; thus, as Figure 14 shows, the present invention will preferentially fuse the targets simultaneously detected by the MIMO continuous wave radar and the "phased array" radar at the FPGA end and execute the joint positioning method in step 3-1. At the same time, for the targets that cannot be measured simultaneously, the present invention will establish a temporary track and confirm it after multiple observations; if it cannot be confirmed after multiple observations, the FPGA end will eliminate such tracks to reduce resource consumption.

[0114] Finally, when there is a target entering the Figure 14 shown warning area, the present invention will no longer allocate time slots to the "phased array" radar mode, but will allocate all time resources to the MIMO radar mode to ensure high-precision UAV target tracking.

[0115] Embodiment 3: The embodiment of the present application provides a UAV detection system based on a multifunctional radar, which is applied to the UAV detection method based on a multifunctional radar in Embodiment 1. As Figure 16 shows, it includes: A target search module, which is used to search for targets in the surrounding area. When the search result is that there is a UAV target, the detection position of the UAV target is obtained through the radar device in the phased array working mode; A position judgment module, which is used to judge the area where the UAV target is located according to the detection position. The areas include a warning area, a critical area, and other areas; A first mode positioning module, which is used to obtain the positioning information of the UAV target through the radar device in the continuous wave radar working mode when the judgment result is the warning area until there is no UAV target in the warning area; A second-mode positioning module, configured to, when the judgment result is other areas, obtain the positioning information of the UAV target through the radar device in the phased array working mode until there is no UAV target in the other areas; A third-mode positioning module, configured to, when the judgment result is a critical area, switch the radar device between the phased array working mode and the continuous wave radar working mode, and perform joint positioning based on the target information in the phased array working mode and the target information in the continuous wave radar working mode to determine the positioning information of the UAV target until there is no UAV target in the critical area.

[0116] Embodiment 4: The embodiment of the present application provides an electronic device, such as Figure 17 shown, including a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the computer program, the method of Embodiment 1 is implemented.

[0117] Embodiment 5: The embodiment of the present application provides a non-transitory computer-readable storage medium. The non-transitory computer-readable storage medium stores computer instructions, and the computer instructions cause the computer to execute the method of Embodiment 1.

[0118] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system, or a computer program product. Therefore, the present application can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk memories, CD-ROMs, optical memories, etc.) containing computer-usable program codes.

[0119] The present application is described with reference to the flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or block in the flowchart and / or block diagram, and the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices generate a device for implementing the functions specified in Figure 1 one process or multiple processes and / or blocks Figure 1 one block or multiple blocks.

[0120] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, such that the instructions stored in the computer-readable memory produce a manufacture including an instruction device that implements the functions specified in one or more processes and / or blocks Figure 1 in one or more processes and / or blocks Figure 1 specified in the function of the block or blocks.

[0121] These computer program instructions can also be loaded onto a computer or other programmable data processing device, such that a series of operational steps are performed on the computer or other programmable device to produce a computer-implemented process, so that the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in one or more processes and / or blocks Figure 1 in one or more processes and / or blocks Figure 1 specified in the function of the block or blocks.

[0122] Those of ordinary skill in the art can understand that all or part of the steps in implementing the above facts and methods can be completed by instructing relevant hardware through a program. The involved program or the program described above can be stored in a computer-readable storage medium. When the program is executed, it includes the following steps: At this time, the corresponding method steps are introduced. The storage medium can be ROM / RAM, magnetic disk, optical disc, etc.

[0123] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for detecting unmanned aerial vehicles based on a multi-functional radar, characterized in that It includes the following specific steps: Perform target search on the surrounding area. When the search result shows the existence of a drone target, obtain the detection position of the drone target through the radar device in phased array working mode; Judge the area where the drone target is located according to the detection position. The area where it is located includes a warning area, a critical area, and other areas; When the judgment result is the warning area, obtain the positioning information of the drone target through the radar device in continuous wave radar working mode until there is no drone target in the warning area; When the judgment result is the other area, obtain the positioning information of the drone target through the radar device in phased array working mode until there is no drone target in the other area; When the judgment result is the critical area, the radar device switches between the phased array working mode and the continuous wave radar working mode, and performs joint positioning according to the target information in the phased array working mode and the target information in the continuous wave radar working mode to determine the positioning information of the drone target until there is no drone target in the critical area.

2. The method for detecting an unmanned aerial vehicle based on a multi-functional radar according to claim 1, wherein The radar device in continuous wave radar working mode obtains the positioning information of the drone target, specifically: , ; wherein: Wherein, represents the background noise, represents the set of reference units on both sides of the current test unit, represents the two-dimensional range-Doppler spectrum, represents the range image in the slow time dimension, represents the test unit, represents a given threshold factor, represents the autocorrelation matrix, represents the total number of indices of the region where the target exists, represents the azimuth angle, represents the elevation angle, represents the steering vector, represents the coordinates of the UAV target, represents the radial velocity of the UAV target, is the number of FFT points in the Doppler direction, is the Doppler cell, represents the speed of light, represents the carrier frequency, represents the pulse width, is the frequency modulation slope.

3. The method for detecting an unmanned aerial vehicle based on a multi-functional radar according to claim 1, wherein, The joint positioning according to the target information in phased array working mode and the target information in continuous wave radar working mode, specifically: Based on the positioning information of the drone target obtained by the radar device in continuous wave radar working mode and the positioning information of the drone target obtained by the radar device in phased array working mode, fuse the existing observations to obtain the initial track observations and determine the stable track; Calculate the Mahalanobis distance using the stable track, update the track of the stable track at the next moment, and obtain the positioning information of the determined drone target based on the track update result.

4. The method for detecting drones based on a multi-functional radar according to claim 3, wherein The stable track is obtained through the following method: When is less than the set threshold value, , , In the formula, is the stable track, represents the Mahalanobis distance of the initial track, represents the positioning information of the UAV target obtained by the radar device in the continuous wave radar working mode, represents the positioning information of the UAV target obtained by the radar device in the phased array working mode.

5. The method for detecting drones based on a multi-functional radar according to claim 3, characterized in that The track update of the stable track at the next moment, specifically: ， Wherein: Wherein, represents the track information at time represents time the updated track information, represents the Kalman gain, represents the track covariance at time represents time the updated track covariance, represents the track information covariance, represents the measurement matrix, represents the state transition matrix, represents the process noise matrix, represents the stable track, represents the track information in the continuous wave radar working mode, represents the track information in the phased array working mode.

6. The method for detecting an unmanned aerial vehicle based on a multifunctional radar according to claim 4, characterized in that The track update of the stable track at the next moment further includes: Calculate the Mahalanobis distance of the stable track. If the Mahalanobis distance of the stable track satisfies the correlation relationship with other tracks, update the track of the stable track at the next moment.

7. The method for detecting an unmanned aerial vehicle based on a multi-functional radar according to claim 6, characterized in that, The Mahalanobis distance of the stable track, specifically: Where: Wherein, represents the Mahalanobis distance of the stable track, represents the stable track, represents the track information in the continuous wave radar operating mode, represents the track information in the phased array operating mode.

8. The UAV detection system based on a multi-functional radar is characterized in that, It includes: A target search module for performing target search on the surrounding area. When the search result shows the existence of a drone target, obtain the detection position of the drone target through the radar device in phased array working mode; A position judgment module for judging the area where the drone target is located according to the detection position. The area where it is located includes a warning area, a critical area, and other areas; A first mode positioning module for obtaining the positioning information of the drone target through the radar device in continuous wave radar working mode when the judgment result is the warning area until there is no drone target in the warning area; A second mode positioning module for obtaining the positioning information of the drone target through the radar device in phased array working mode when the judgment result is the other area until there is no drone target in the other area; The third-mode positioning module is used to, when the judgment result is the critical area, cause the radar device to switch between the phased array operating mode and the continuous wave radar operating mode, and perform joint positioning based on the target information in the phased array operating mode and the target information in the continuous wave radar operating mode to determine the positioning information of the UAV target until there is no UAV target in the critical area.

9. An electronic device, characterized in that, It includes a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the computer program, the method described in any one of claims 1-7 is implemented.

10. A non-transitory computer-readable storage medium, characterized in that, The non-transitory computer-readable storage medium stores computer instructions that cause the computer to execute the method described in any one of claims 1-7.

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