A method for locating a radio emission source

Abstract

This invention discloses a method for locating radio transmitters, relating to the field of unmanned aerial vehicle (UAV) technology. The method includes deploying a UAV swarm, comprising a first, second, third, fourth, and fifth UAV; the first and second UAVs forming a first baseline pair, and the third and fourth UAVs forming a second baseline pair; controlling the first baseline pair to fly along the outer edge of a first edge, and the second baseline pair to fly along the outer edge of a second edge; performing time and frequency synchronization on the first and second baseline pairs respectively, and calculating their real-time positions; controlling the baseline pairs to synchronously acquire radio signals, obtaining first, second, third, and fourth signals; performing signal-level collaborative processing to obtain first and second confidence distributions; transmitting the first and second confidence distributions to the fifth UAV, calculating a joint confidence score; detecting transmitters based on the joint confidence score and aggregating adjacent detection results to obtain the location results of all radio transmitters within the task area.

Description

Technical Field

[0001] This invention relates to a method for locating radio transmitters, belonging to the field of unmanned aerial vehicle (UAV) technology. Background Technology

[0002] Radio monitoring in urban environments is a crucial responsibility of radio management departments. This involves the precise location, statistics, and control of illegal or unregistered radio sources within their jurisdiction, and, when necessary, dispatching personnel for intervention. Applications of radio monitoring in urban environments include routine, 24 / 7 surveillance and targeted, stringent monitoring during critical events.

[0003] Radio monitoring primarily targets transmitters of various types of radio stations, which, based on broadcast frequency bands, include:

[0004] (1) Shortwave (SW): 3MHz-30MHz;

[0005] (2) Frequency modulation (FM): 88MHz-108MHz;

[0006] (3) Very High Frequency (VHF): 48.5MHz-72.5 MHz, 76MHz-92 MHz, 167~223 MHz;

[0007] (4) Ultra-high frequency (UHF): 470~700 MHz;

[0008] In urban environments, the task of radio monitoring is to accurately locate the transmitters in the aforementioned frequency bands, down to the specific building, in order to carry out subsequent control work. The positioning accuracy is mainly determined by the direction finding accuracy of the transmitter.

[0009] Traditional radio monitoring methods are implemented through ground monitoring vehicles, such as the vehicle-mounted radio monitoring system disclosed in patent application number CN202320658175.6. However, due to limitations such as road passability, this method is not suitable for scenarios with many obstacles and requires a lot of manpower, such as vehicle drivers.

[0010] Using drones for radio source monitoring can, to some extent, avoid the influence of obstacles in urban areas and improve the coverage of radio monitoring systems. Several related technologies already exist, such as patent application CN202511758567.X, which discloses a drone target tracking method and system; patent application CN202511037930.9, which discloses a radio aerial monitoring system and method for drones; patent application CN202520541351.7, which discloses a drone-based real-time electromagnetic spectrum monitoring system; patent application CN202111653178.2, which discloses a drone-based airborne radio monitoring and direction-finding device; and patent application CN202111218533.3, which discloses a monitoring device for locating illegal radio broadcasts. However, the direction-finding accuracy of existing technologies is insufficient. They all use a single drone for direct radio direction finding, and while some technologies use multiple drones, they do not utilize signal-level coordination between these drones. Because individual UAVs have limited carrying capacity and can only carry small signal receiving antennas, their direction-finding accuracy is low due to the Rayleigh criterion, making it difficult to reach or surpass the direction-finding accuracy of vehicle-mounted antennas. Even when using the direction-finding results of multiple UAVs simultaneously, the overall direction-finding accuracy is unlikely to see a significant improvement of orders of magnitude. Summary of the Invention

[0011] The purpose of this invention is to provide a method for locating radio transmitters. By deploying five UAVs to form two baseline pairs and placing them on opposite sides of the mission area, the method collects signals synchronously and performs signal-level collaborative processing to obtain relative phase information and calculates the confidence level of the presence of transmitters in each grid. Then, the two sets of confidence levels are combined for detection and aggregation, which solves the problem of insufficient direction finding accuracy of a single UAV and achieves building-level positioning accuracy.

[0012] To achieve the above objectives, the present invention is implemented using the following technical solution.

[0013] This invention provides a method for locating radio transmitters, comprising:

[0014] A drone swarm is deployed, comprising a first drone, a second drone, a third drone, a fourth drone, and a fifth drone; the first drone and the second drone form a first baseline pair, and the third drone and the fourth drone form a second baseline pair; both the first baseline pair and the second baseline pair are equipped with radio signal acquisition devices.

[0015] The first baseline is controlled to fly along the outer edge of a first edge of the mission area, and the second baseline is controlled to fly along the outer edge of a second edge of the mission area; wherein the outer edges of the first and second edges are arranged opposite to each other;

[0016] Time synchronization and frequency synchronization are performed on the first baseline pair and the second baseline pair respectively, and the real-time position of each UAV in the first baseline pair and the second baseline pair is calculated.

[0017] Control the first baseline to synchronously acquire radio signals to obtain a first signal and a second signal; control the second baseline to synchronously acquire radio signals to obtain a third signal and a fourth signal;

[0018] The first and second signals are processed at the signal level to obtain a first confidence distribution; the third and fourth signals are processed at the signal level to obtain a second confidence distribution; the signal level collaborative processing includes: acquiring the relative phase information between the two signals, and calculating the confidence that there is a transmission source in each grid within the task area based on the relative phase information and the real-time position of the corresponding UAV.

[0019] The first confidence distribution and the second confidence distribution are transmitted to the fifth UAV, and the fifth UAV calculates the joint confidence based on the first confidence distribution and the second confidence distribution;

[0020] Based on the joint confidence level detection of the transmitting source and the aggregation of adjacent detection results, the location results of all radio transmitting sources within the mission area are obtained.

[0021] Furthermore, obtaining the relative phase information between the two signals includes:

[0022] Based on the pre-registered working frequency band information, the two signals are divided into multiple frequency bands in the frequency domain, and the signals in each frequency band are divided into multiple time slices in the time domain to form a two-dimensional time-frequency division unit.

[0023] Calculate the cross-correlation coefficient between two signals within each time-frequency two-dimensional partition unit;

[0024] The phase of the cross-correlation coefficient is extracted as the relative phase information.

[0025] Furthermore, the expression for the cross-correlation coefficient between the two signals within each time-frequency two-dimensional division unit is as follows:

[0026] (1),

[0027] In the formula, Indicates the first The first frequency band The cross-correlation coefficient between two signals within a two-dimensional time-frequency partition defined by a time slice. Indicates the index of the frequency band set. , Indicates the total number of frequency bands. Indicates the index of the time slice set. , Indicates the total number of time slices; Indicates the first The center time of each time slice Indicates the initial time. Indicates the set time slice length; Indicates time The first drone collected only frequency band components. The time-domain signal, Indicates time The first drone collected only frequency band components. time domain signal .

[0028] Furthermore, the process of determining the confidence level of the existence of emission sources in each grid within the computation task area specifically includes:

[0029] Divide the task area into multiple grids;

[0030] The expression for the confidence level of the emission source in each grid cell is as follows:

[0031] (2),

[0032] In the formula, Indicates the first Each frequency band, grid center coordinates are The confidence level of the existence of an emission source within the grid; Indicates the first The first frequency band The phase of the cross-correlation coefficient of each time slice, ;

[0033] Indicates the first The signal wavelength corresponding to each frequency band , This represents the speed of light in a vacuum.

[0034] i represents the imaginary unit; Indicates the first Grid center within a time slice The distance difference between the two drones , express The location of the first drone, express The location of the second drone.

[0035] Furthermore, the step of detecting the emission source based on the joint confidence level specifically includes:

[0036] An adaptive threshold is set, and each grid within the task area is traversed. The grid coordinates where the joint confidence score is greater than the adaptive threshold are detected and used as the detection results.

[0037] Furthermore, the agglomeration neighbor detection results specifically include:

[0038] Traverse all detection results. When there are two or more detection results with the same frequency band, the same first direction coordinate, the same second direction coordinate, and any two of the three parameters being the same and the third parameter being adjacent, merge them into one detection result, retain the detection result with the highest confidence value, and delete the rest of the detection results.

[0039] Furthermore, it also includes:

[0040] The positioning results are matched with the location information and operating frequency band information of the legally registered transmitters provided by the user;

[0041] A position error tolerance is set, and when the position difference between the positioning result and a legally registered transmitter is less than the position error tolerance, the position is determined to be successfully matched.

[0042] Set a frequency band error tolerance; when the frequency band difference is less than the frequency band error tolerance, the frequency band matching is considered successful.

[0043] For transmitters whose location matching fails, mark them as illegally registered transmitters and output their location and operating frequency band;

[0044] For transmitters that successfully match the location but fail to match the frequency band, mark them as frequency band abnormal transmitters and output their registration number and actual operating frequency band.

[0045] Furthermore, the task area is a rectangular area;

[0046] If the monitoring area specified by the user is not a rectangular area, then the smallest rectangular area that can cover the monitoring area shall be used as the task area.

[0047] Further, the step of calculating the joint confidence level based on the first confidence distribution and the second confidence distribution specifically includes:

[0048] The joint confidence score is obtained by multiplying the first confidence distribution and the second confidence distribution grid by grid.

[0049] Furthermore, the fifth UAV is deployed at any location outside the edge of the mission area.

[0050] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0051] 1. This invention deploys a swarm of unmanned aerial vehicles (UAVs), with the first and second UAVs forming a first baseline pair, and the third and fourth UAVs forming a second baseline pair. The first baseline pair is controlled to fly along the outer edge of the first edge of the mission area, and the second baseline pair is controlled to fly along the outer edge of the second edge of the mission area, thus forming two long baselines in space. Compared to the maximum antenna aperture of approximately 1 meter that a single UAV can carry, the effective aperture between the two baseline pairs can reach hundreds of meters, fundamentally breaking through the physical limitations of single-UAV antenna size on direction-finding accuracy.

[0052] 2. This invention performs time and frequency synchronization on two UAVs within the same baseline and controls them to synchronously acquire radio signals, enabling the two signals to have the basic conditions for coherent processing. Based on this, signal-level collaborative processing is performed on the two signals to obtain their relative phase information. Then, based on this relative phase information and the UAV's real-time position, the confidence level of the presence of a transmitting source in each grid within the task area is calculated, mapping the phase difference information of the two signals onto the spatial grid. The grid confidence level essentially converts the phase difference information into a probability distribution of spatial position; the higher the confidence level, the closer the grid's position is to the actual transmitting source position. Compared to traditional direct direction finding methods, this signal-level collaborative processing utilizes the large phase difference information provided by the long baseline, thus achieving angle measurement accuracy far exceeding that of single-UAV direct direction finding.

[0053] 3. This invention transmits the confidence distributions obtained from the first baseline pair and the second baseline pair to the fifth UAV, which calculates the joint confidence and detects the emission source and aggregates adjacent detection results based on the joint confidence. The joint confidence integrates the two sets of independent observation results, enhancing the confidence response at the actual emission source location. Finally, the positioning result is accurate to the building level, solving the technical problem of insufficient direction finding accuracy of existing single UAVs. Attached Figure Description

[0054] Figure 1 The diagram shown is a flowchart of a radio transmitter location method provided by the present invention.

[0055] Figure 2 The diagram shows a UAV swarm deployment method and flight path setting for a radio transmitter location method provided by the present invention.

[0056] Figure 3 The diagram shown is a schematic flowchart of the signal-level collaborative processing of a radio transmitter location method provided by the present invention. Detailed Implementation

[0057] It should be noted that the technical solution of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the embodiments of the present invention and the specific features in the embodiments are detailed descriptions of the technical solution of the present invention, rather than limitations on the technical solution of the present invention. In the absence of conflict, the embodiments of the present invention and the technical features in the embodiments can be combined with each other.

[0058] The term "and / or" simply describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone. Additionally, the character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0059] Example 1:

[0060] See Figure 1 This embodiment provides a method for locating radio transmitters. Based on UAV signal-level collaborative implementation, this invention aims to achieve precise location and frequency band measurement of all radio transmitters within a designated task area in an urban environment through UAV swarms. Based on this, the location of the radio transmitters is matched with buildings on a map to establish and maintain a database of transmitter location coordinates, frequency bands, and other information. Combined with user-provided data, it supports the confirmation of registered legal transmitters and the marking of illegal or unregistered transmitters, providing guidance for users in handling these transmitters.

[0061] The specific tasks of this embodiment are as follows:

[0062] 1. Input:

[0063] (1) The scope of the task requiring radio monitoring in an urban environment ;

[0064] (2) Used to provide task area Total Coordinates of the deployment locations of each legally registered radio transmitter: , ,......, And the corresponding list of registered working frequency bands: , ,......, .

[0065] 2. Output:

[0066] (1) Mission area scope The total number of unregistered entities Location coordinates of the radio transmitters: , ,......, And a list of corresponding operating frequency band information: , ,......, ;

[0067] (2) Scope of the mission area The internal frequency band is legally registered, but the actual operating frequency band does not match the registered operating frequency band. Registration number of each launch source: , ,......, And a list of the corresponding actual operating frequency bands: , ,......, .

[0068] The method provided in this embodiment uses the transmission source in the frequency modulation (FM) band (88MHz-108MHz) as the monitoring target, and the mission area... The monitoring area is a rectangular area within the city, measuring 5000m in length and width. If the user-specified monitoring area is not rectangular, the smallest rectangular area that can cover the monitored area will be used as the task area.

[0069] The method specifically includes the following steps:

[0070] Step S1: Deploy the drone swarm. The drone swarm includes a first drone, a second drone, a third drone, a fourth drone, and a fifth drone; the first and second drones form a first baseline pair, and the third and fourth drones form a second baseline pair. Both the first and second baseline pairs are equipped with radio signal acquisition devices.

[0071] Specifically, all drones in the deployed drone swarm are rotary-wing drones. Among them, the first, second, third, and fourth drones are equipped with omnidirectional antennas, responsible for collecting radio signals from the transmitting source. The fifth drone is responsible for summarizing the radio source location results and reporting them to the user via remote communication.

[0072] In one specific implementation, the first and second drones are deployed outside the bottom edge of the rectangle, the third and fourth drones are deployed outside the top edge of the rectangle, and the fifth drone can be deployed at any location. In this embodiment, the fifth drone is preferably deployed outside the right side of the rectangle. This embodiment establishes a coordinate system with the lower left corner of the rectangular task area as the origin, and the coordinate unit is meters. The initial deployment coordinates at the specific initial moment are as follows:

[0073] Initial coordinates of the first UAV: ;

[0074] Initial coordinates of the second UAV: ;

[0075] Initial coordinates of the third UAV: ;

[0076] Initial coordinates of the fourth UAV: ;

[0077] Initial coordinates of the fifth UAV: .

[0078] This indicates the initial time of the deployment of the first baseline pair and the fifth drone. This indicates the initial time when the second baseline pair is deployed; the deployment of the first and second baseline pairs can be performed sequentially. It can also be executed in parallel. .

[0079] During the execution of subsequent tasks, the fifth UAV remained hovering; the flight altitude of all UAVs in the UAV swarm was set to 100m and remained unchanged throughout the mission.

[0080] Step S2: Control the first baseline pair to fly along the outer edge of the first edge of the mission area, and the second baseline pair to fly along the outer edge of the second edge of the mission area; wherein the outer edge of the first edge and the outer edge of the second edge are set opposite to each other.

[0081] From an overhead view, the deployment of the five drones is as follows: Figure 2 As shown.

[0082] The outer edge of the first boundary is the mission area. Outside the base of the rectangle, a first baseline pair consisting of the first UAV and the second UAV is initially deployed outside the base of the rectangle and flies along the base of the rectangle. Apart from this, the invention does not impose strict requirements on the flight path, but a preferred flight path should satisfy the following constraints.

[0083] Let the initial position of the first UAV be... The initial position of the second drone is At the end of the mission, the position of the first drone was... The location of the second drone is The expression that determines the positioning accuracy of the transmitter is as follows:

[0084] (3),

[0085] In the formula, The effective aperture length of the first baseline pair determines the positioning accuracy of the transmitter. The larger the value, the better the route of the first baseline pair.

[0086] As a specific implementation method, considering the limited flight speed of the UAV and in order to save time for each mission, the flight path setting method adopted in this embodiment is as follows: Figure 2 As shown: During the first mission, the first UAV hovers, while the second UAV flies 200 meters at a constant speed along the positive x-axis from the starting point to the endpoint. Upon reaching the endpoint, it performs the mission. After completing the mission, the second UAV returns to the starting point. The endpoint coordinates of the second UAV are... ,at this time During the second mission, the first UAV remained hovering, while the second UAV flew 200 meters at a constant speed along the negative x-axis from the starting point to the endpoint to complete the mission before returning to the starting point. Subsequent missions followed the same pattern. The second UAV's flight speed was set to 10 m / s, and each mission lasted 20 seconds.

[0087] Similarly, the second baseline, composed of the third and fourth UAVs, flies along the outer edge of the second edge of the mission area. As one specific implementation, such as... Figure 2 As shown, in this embodiment, the outer side of the second edge is the outer side of the top edge of the rectangle, and the second baseline flies along the outer side of the top edge of the rectangle. Apart from this, the present invention does not impose strict requirements on the flight path.

[0088] Let the initial position of the third UAV be... The initial position of the fourth UAV is At the end of the mission, the location of the third drone was... The location of the fourth drone is The expression that determines the positioning accuracy of the transmitter is as follows:

[0089] (4),

[0090] In the formula, The effective aperture length of the second baseline pair determines the positioning accuracy of the transmitter. The larger the value, the better the route of the first baseline pair.

[0091] As a specific implementation method, considering the limited flight speed of the drone and in order to save time for each mission, the route setting method adopted in this embodiment is as follows: Figure 2 As shown: During the first mission, the third UAV hovers, while the fourth UAV flies 200 meters at a constant speed along the positive x-axis from the starting point to the endpoint. After reaching the endpoint, it performs the mission. Upon completion of the mission, the fourth UAV returns to the starting point. The endpoint coordinates of the fourth UAV are... ,at this time During the second mission, the third UAV remained hovering. The fourth UAV flew 200 meters at a constant speed along the negative x-axis from the starting point to the endpoint to complete its mission, then returned to the starting point. Subsequent missions followed the same pattern. The fourth UAV's flight speed was set to 10 m / s, and each mission lasted 20 seconds.

[0092] Step S3: Perform time synchronization and frequency synchronization on the first baseline pair and the second baseline pair respectively, and calculate the real-time position of each UAV in the first baseline pair and the second baseline pair.

[0093] Specifically, time and frequency synchronization is performed on the first and second UAVs. Specific synchronization methods include satellite navigation synchronization systems, atomic clock synchronization, and local oscillator distribution synchronization. This embodiment preferably employs the synchronization method proposed in another Chinese patent application (application number: CN202610784172.5) disclosed by the applicant. This method utilizes three auxiliary UAVs to transmit single-frequency and dual-frequency signals, which are received and sampled by the UAV to be calibrated. Signal processing is then performed to obtain coarse measurements of the clock speed difference, frequency difference, and clock error between the two UAVs. Through iterative calculation and phase compensation, frequency, time, and phase synchronization between the two UAVs are completed in one step. This method achieves time and frequency synchronization between the first and second UAVs without relying on external equipment.

[0094] The position of the first UAV during the measurement mission The location of the second drone , The position measurement method is not innovative in this invention; existing methods such as satellite navigation or the positioning method proposed in another published Chinese patent application (application number: CN202610784172.5) can be used. This method utilizes three auxiliary UAVs to transmit single-frequency and dual-frequency signals, which are received and sampled by the UAV to be calibrated. Signal processing is then performed, and the precise value of the frequency difference and the coarse coordinate measurement value are iteratively calculated. Finally, the coordinate residual is calculated based on the phase difference, resulting in the precise coordinates between the UAVs to be calibrated. This method allows for high-precision relative positioning of the first and second UAVs without relying on external equipment (such as satellite navigation).

[0095] Similarly, the same method was used to synchronize the time and frequency of the third and fourth UAVs, and their real-time positions were calculated. and , .

[0096] Step S4: Control the first baseline to synchronously acquire radio signals to obtain the first signal and the second signal; control the second baseline to synchronously acquire radio signals to obtain the third signal and the fourth signal.

[0097] After synchronizing the time and frequency of the first, second, third, and fourth UAVs in step S3, the first, second, third, and fourth UAVs are controlled to collect radio signals from the transmitting source and store the signals collected during the mission, which are respectively denoted as the first signal, the second signal, the third signal, and the fourth signal.

[0098] The first signal collected by the first drone is denoted as... The second signal collected by the second drone is denoted as and will The signal is transmitted to the first drone for subsequent signal-level collaborative processing.

[0099] Similarly, the third signal collected by the third drone is denoted as... The fourth signal collected by the fourth UAV is denoted as and will The signal is transmitted to the third drone for further signal-level collaborative processing in the next step.

[0100] Step S5: Perform signal-level co-processing on the first and second signals to obtain the first confidence distribution; perform signal-level co-processing on the third and fourth signals to obtain the second confidence distribution.

[0101] For example, to obtain the first confidence level distribution, please refer to Figure 3 Signal-level collaborative processing includes:

[0102] Step S5A1: Divide the two signals into multiple frequency bands in the frequency domain according to the pre-registered operating frequency band information. (Based on the user-provided list of registered operating frequency bands.) , ,......, The receiving frequency bands of the first and second UAVs are divided into two groups with the same or finer granularity. Each frequency band, after division The center frequencies of each frequency band are denoted as follows: , ,......, .

[0103] In this specific implementation, the mission objective is to locate the transmitter in the FM band (88MHz-108MHz) within the designated area. Therefore, the band is evenly divided into 20 segments, N=20, with each segment having a width of 1MHz. Segment 1 represents 88MHz~89MHz, segment 2 represents 89MHz~90MHz, segment 3 represents 90MHz~91MHz, and so on, with segment 20 representing 107MHz~108MHz. The center frequencies of the 20 segmented bands are denoted as follows: , ,......, .

[0104] Step S5A2: Divide the signal in each frequency band into multiple time slices in the time domain to form a two-dimensional time-frequency partitioning unit.

[0105] As a specific implementation method, the preferred time slice length in this embodiment is... .

[0106] Through Fourier transform, and Transforming to the frequency domain, we obtain the following results: and For the p-th frequency band, perform the following operations:

[0107] right and Perform frequency domain filtering to obtain only those containing The frequency domain signal of the frequency band component is then subjected to inverse Fourier transform to obtain a signal containing only the frequency band component. Time-domain signal of frequency band components and .

[0108] Will and Divided into time domain There are several time slices, and the center time of each time slice is denoted as . ,in .

[0109] Step S5A3: Calculate the cross-correlation coefficient between the two signals within each time-frequency two-dimensional division unit.

[0110] Cross-correlation coefficient of the partition unit defined by the p-th frequency band and the q-th time slice The calculation formula is as follows:

[0111] (1),

[0112] In the formula, Indicates the first The first frequency band The cross-correlation coefficient between two signals within a two-dimensional time-frequency partition defined by a time slice. Indicates the index of the frequency band set. , Indicates the total number of frequency bands. Indicates the index of the time slice set. , Indicates the total number of time slices; Indicates the first The center time of each time slice Indicates the initial time. Indicates the set time slice length; Indicates time The first drone collected only frequency band components. The time-domain signal, Indicates time The first drone collected only frequency band components. time domain signal .

[0113] Step S5A4: Extract the phase of the cross-correlation coefficient as relative phase information.

[0114] Cross-correlation coefficient of the partition unit defined by the p-th frequency band and the q-th time slice phase The calculation expression is as follows:

[0115] (5).

[0116] Step S5A5: Based on the relative phase information and the real-time position of the corresponding UAV, calculate the confidence level of the existence of a transmission source in each grid within the mission area.

[0117] The task area is divided into a rectangular grid. The granularity of the grid can be set as needed, and can be set to the size of a normal building, such as a square with a length and width of 10 meters. As a specific implementation, in this embodiment, the task area (5000m×5000m) is divided into a grid of size 10m×10m, for a total of 500×500=250000 grids.

[0118] For each grid cell, let the coordinates of the grid center be denoted as . For the first Each frequency band, grid center coordinates are The expression for calculating the confidence level of the presence of an emission source within the grid is as follows:

[0119] (2),

[0120] In the formula, Indicates the first Each frequency band, grid center coordinates are The confidence level of the existence of an emission source within the grid;

[0121] Indicates the first The signal wavelength corresponding to each frequency band , This represents the speed of light in a vacuum.

[0122] i represents the imaginary unit; Indicates the first Grid center within a time slice The distance difference between the two drones , express The location of the first drone, express The location of the second drone.

[0123] Similarly, except for the different UAV numbers, the signal-level collaborative processing steps from S5A1 to S5A5 for the third and fourth signals are completely identical, resulting in the second confidence distribution. .

[0124] Step S6: Transmit the first confidence distribution and the second confidence distribution to the fifth UAV, and the fifth UAV calculates the joint confidence based on the first confidence distribution and the second confidence distribution.

[0125] The first confidence distribution obtained in step S5 Second confidence distribution The data is transmitted to the fifth UAV for frequency measurement and location of all radio transmitters within the mission area. Specifically, this includes:

[0126] Establish a collection of all radio transmitters within the mission area. ,Include Each subset is denoted as . subset The element inside represents the element belonging to the first element. Transmission sources in each frequency band. For To conduct emission source detection and joint confidence level The calculation expression is as follows:

[0127] (6),

[0128] That is, each grid within the task area The confidence scores obtained from the first baseline pair and the second baseline pair are multiplied together to obtain the joint confidence score.

[0129] Step S7: Based on the joint confidence level, detect the transmitting sources and aggregate the results of adjacent detections to obtain the location results of all radio transmitting sources within the mission area.

[0130] Set adaptive threshold As a specific implementation method, in this embodiment, an adaptive threshold is set according to the technical solution of Constant False Alarm Rate Radar (CFAR). The expression is as follows:

[0131] (7),

[0132] In the formula, Indicates that the matrix is ​​performed first. sum matrix A 2D convolution is performed, and then the values ​​located at the exact center, size, and matrix of the convolution result are taken. The same portion of data is used as the final output. The matrix is ​​not fixed; in this embodiment, it is preferably... .

[0133] Iterate through the grid coordinates divided in step S6 and check all that satisfy the conditions. The grid coordinates are combined to form a quadruple. and add it to the set as a set element. .

[0134] Traversal All elements in the frequency band. Similar to the point clustering method in radar signal processing: when there exists a frequency band... When any two of the three parameters (same x-coordinate, same y-coordinate) are the same, and the third parameter is adjacent, two or more elements are grouped into one element and retained. Delete the element with the largest value and the remaining elements. Specifically:

[0135] If two elements Same, same x, and adjacent y (i.e.) If ), then they will coalesce into one;

[0136] If two elements The same, the same y, and adjacent x (i.e.) If ), then they will coalesce into one;

[0137] If two elements Those that are identical, adjacent in x and adjacent in y (diagonally adjacent) also converge into one.

[0138] After agglomeration, the element with the highest confidence value is retained, and the rest are deleted, finally yielding the set of all radio sources in the agglomerated region. .

[0139] Step S8: Match the positioning results with the location information and operating frequency band information of the legally registered transmitters provided by the user.

[0140] Step S8A1: Collect all radio sources within the agglomerated area obtained in step S7. Chinese elements and user-provided Coordinates of the deployment location of a legally registered radio transmitter , Operating frequency band information Perform matching. Set a certain position error tolerance. When the position difference is less than This indicates a successful location match; a certain frequency band error tolerance is set. When the frequency band difference is less than This indicates that the frequency band match was successful.

[0141] In one specific implementation, K is preferably 10, representing the set of all radio transmitters within the region. Chinese elements and user-provided The location coordinates and operating frequency band information of each legally registered radio transmitter are matched. A location error tolerance is set. The frequency band error tolerance is set to 30m. It is 2MHz.

[0142] Step S8A2: For transmitters whose location matching fails, mark them as illegally registered transmitters and output their location and operating frequency band;

[0143] For sets Elements whose inner position matching failed Count their total number Radio sources that are not legally registered within the area are marked with their location parameters as follows: , The operating frequency band is denoted as The output is then given to the user.

[0144] As a specific implementation method, let's assume a set There are a total of 5 elements whose positions failed to match. Count the number of such elements. , place its position , Operating frequency band Output to the user.

[0145] Step S8A3: For a transmitter that successfully matches the location but fails to match the frequency band, mark it as a transmitter with abnormal frequency band and output its registration number and actual operating frequency band.

[0146] For sets Elements with successful internal location matching but failed frequency band matching. Count their total number Record their registration numbers as The actual operating frequency band is denoted as The output is then given to the user.

[0147] As a specific implementation method, for the set If there are 3 elements whose internal location matches successfully but whose frequency band matches, and their locations match the 3rd, 5th, and 7th legally registered transmitters provided by the user, then count the number of such elements. their registration numbers Actual operating frequency band Output to the user.

[0148] Compared to vehicle-mounted and drone-tethered radio detection systems, this embodiment does not require any ground facilities, is not limited by ground mobility in urban environments, has a wider monitoring range, and drones have the advantage of replacing human labor for all-weather work.

[0149] This embodiment presents a method for signal-level coordination between drones, applicable to shortwave, FM broadcast, and VHF wavelengths. For radio transmitters with a range of approximately 1m to 10m, the angle measurement and positioning accuracy can be improved by more than two orders of magnitude compared to existing radio monitoring technologies. For example, current technologies use a single small UAV for direct direction finding; the maximum antenna aperture that a UAV can carry is approximately 1m. The angular measurement accuracy of a 1m transmitter is 57.3°; using the method proposed in this invention, two UAVs can perform signal-level coordination with an effective synthetic aperture of 200m. The angular measurement accuracy of a 1m transmitter reaches 0.25°, which is 200 times better than existing technologies. It can locate the transmitter at the level of a single building from 5km away (with an error of less than 25m), and the positioning accuracy exceeds that of existing methods.

[0150] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0151] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0152] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A method for locating a radio transmitter, characterized in that, include: Deploy a drone swarm, the drone swarm including a first drone, a second drone, a third drone, a fourth drone, and a fifth drone; The first and second UAVs form a first baseline pair, and the third and fourth UAVs form a second baseline pair. Both the first and second baseline pairs are equipped with radio signal acquisition devices. The first baseline is controlled to fly along the outer edge of a first edge of the mission area, and the second baseline is controlled to fly along the outer edge of a second edge of the mission area; wherein the outer edges of the first and second edges are arranged opposite to each other; Time synchronization and frequency synchronization are performed on the first baseline pair and the second baseline pair respectively, and the real-time position of each UAV in the first baseline pair and the second baseline pair is calculated. Control the first baseline to synchronously acquire radio signals to obtain a first signal and a second signal; control the second baseline to synchronously acquire radio signals to obtain a third signal and a fourth signal; The first and second signals are processed at the signal level to obtain a first confidence distribution; the third and fourth signals are processed at the signal level to obtain a second confidence distribution; the signal level collaborative processing includes: acquiring the relative phase information between the two signals, and calculating the confidence that there is a transmission source in each grid within the task area based on the relative phase information and the real-time position of the corresponding UAV. The process of obtaining the relative phase information between the two signals includes: dividing the two signals into multiple frequency bands in the frequency domain according to the pre-registered working frequency band information, and dividing the signal in each frequency band into multiple time slices in the time domain to form a two-dimensional time-frequency division unit; calculating the cross-correlation coefficient between the two signals in each two-dimensional time-frequency division unit; and extracting the phase of the cross-correlation coefficient as the relative phase information. The process of calculating the confidence level of the existence of an emission source in each grid within the task area specifically includes: dividing the task area into multiple grids; the expression for the confidence level of the existence of an emission source in each grid is as follows: （2）， In the formula, Indicates the first Each frequency band, grid center coordinates are The confidence level of the existence of an emission source within the grid; Indicates the first The first frequency band The phase of the cross-correlation coefficient of each time slice, , Indicates the first The first frequency band The cross-correlation coefficient between two signals within a time-frequency two-dimensional partition unit defined by a time slice; Indicates the first The signal wavelength corresponding to each frequency band , This represents the speed of light in a vacuum. i represents the imaginary unit; Indicates the first Grid center within a time slice The distance difference between the two drones , express The location of the first drone, express The location of the second drone; The first confidence distribution and the second confidence distribution are transmitted to the fifth UAV, which then multiplies the first confidence distribution and the second confidence distribution grid by grid to obtain the joint confidence. Based on the joint confidence level detection of the transmitting source and the aggregation of adjacent detection results, the location results of all radio transmitting sources within the mission area are obtained.

2. The radio transmitter localization method according to claim 1, characterized in that, The expression for the cross-correlation coefficient between the two signals within each time-frequency two-dimensional division unit is as follows: （1）， In the formula, Indicates the index of the frequency band set. , Indicates the total number of frequency bands. Indicates the index of the time slice set. , Indicates the total number of time slices; Indicates the first The center time of each time slice Indicates the initial time. Indicates the set time slice length; Indicates time The first drone collected only frequency band components. The time-domain signal, Indicates time The first drone collected only frequency band components. time domain signal .

3. The radio transmitter localization method according to claim 1, characterized in that, The detection of the emission source based on the joint confidence level specifically includes: An adaptive threshold is set, and each grid within the task area is traversed. The grid coordinates where the joint confidence score is greater than the adaptive threshold are detected and used as the detection results.

4. The radio transmitter localization method according to claim 3, characterized in that, The agglomeration adjacent detection results specifically include: Traverse all detection results. When there are two or more detection results with the same frequency band, the same first direction coordinate, the same second direction coordinate, and any two of the three parameters being the same and the third parameter being adjacent, merge them into one detection result, retain the detection result with the highest confidence value, and delete the rest of the detection results.

5. The radio transmitter localization method according to claim 1, characterized in that, Also includes: The positioning results are matched with the location information and operating frequency band information of the legally registered transmitters provided by the user; A position error tolerance is set, and when the position difference between the positioning result and a legally registered transmitter is less than the position error tolerance, the position is determined to be successfully matched. Set a frequency band error tolerance; when the frequency band difference is less than the frequency band error tolerance, the frequency band matching is considered successful. For transmitters whose location matching fails, mark them as illegally registered transmitters and output their location and operating frequency band; For transmitters that successfully match the location but fail to match the frequency band, mark them as frequency band abnormal transmitters and output their registration number and actual operating frequency band.

6. The radio transmitter localization method according to claim 1, characterized in that, The task area is a rectangular area; If the monitoring area specified by the user is not a rectangular area, then the smallest rectangular area that can cover the monitoring area shall be used as the task area.

7. The radio transmitter localization method according to claim 1, characterized in that, The fifth UAV is deployed at any location outside the edge of the mission area.

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