Real-time Detection and Location Method for Airport GNSS Interference by Fusing Multiple Single-antenna Receiver Direction Finding

Abstract

The present invention provides a real-time detection and positioning method for airport GNSS interference by fusing the direction finding of multiple single-antenna receivers, belonging to the field of satellite navigation technology. The interference source determination method includes: obtaining the detection data transmitted by each reference station in the airport to be detected; for each reference station, when the detection data transmitted by the reference station does not contain the carrier-to-noise ratio data, judging whether there is an interference source in the airport to be detected according to the received signal power; when the detection data transmitted by the reference station contains the carrier-to-noise ratio data, judging whether there is an interference source in the airport to be detected according to the carrier-to-noise ratio data; if there is an interference source in the airport to be detected, generating a direction finding control instruction and sending it to the reference station; obtaining the angle information of the interference source transmitted by the reference station determined to have an interference source, and determining the position of the interference source according to the angle information. It can be applied to the detection of interference sources in the case where the receiver cannot capture and track, improving the detection efficiency and accuracy of airport interference sources.

Description

Technical Field

[0001] The present invention relates to the field of satellite navigation, and particularly to a method for real-time detection and positioning of GNSS interference in an airport by fusing direction finding of multiple single-antenna receivers. Background Art

[0002] GNSS (Global Navigation Satellite System) is the main navigation source for PBN (Performance Based Navigation) in aviation navigation and is widely used in PBN operations in en-route and terminal areas globally, being an important part of aviation navigation. However, since the GNSS signals reaching the ground are very weak and the format of civilian satellite signals is public, GNSS receivers are vulnerable to radio frequency interference. Especially in recent years, GNSS interference incidents have occurred frequently in airport areas globally, seriously affecting aviation safety.

[0003] The existing research on GNSS interference source detection and positioning technologies can be classified into real-time processing and post-processing according to timeliness. Post-processing technologies require a large amount of data during interference, and trace back the overall interference area when the interference event occurs. In airport areas, data from the automatic dependent surveillance - broadcast system is generally collected for analysis to roughly determine the location of the interference source, and then personnel are dispatched for search and investigation, with low efficiency and inaccurate interference source detection accuracy.

[0004] Most real-time processing technologies are based on data such as carrier-to-noise ratio calculated during the GNSS receiver data processing process to perform real-time positioning of the interference source. Classified by observable quantities, it can be divided into two types: pre-despreading and post-despreading according to the receiver data processing flow. The pre-despreading method detects the signal and describes its characteristics before the received signal enters the correlator branch. Since it processes the original signal, and the characteristics of the original signal are not as obvious as the post-despread data, the detection efficiency is low and inaccurate. The post-despreading method is based on the degradation of the receiver performance caused by the interference signal. Usually, it analyzes the change in the carrier-to-noise ratio (C / N0) of the received signal after the receiver tracks. This method can only be used in cases where the receiver can normally track and capture. For cases where the interference power is too large for the receiver to capture and track, interference source positioning cannot be achieved.

[0005] In addition, in order to improve the interference detection and positioning performance, most research uses array antennas, with high system complexity and manufacturing cost, and great limitations in practical applications.

[0006] Therefore, in combination with the actual needs of the airport, there is an urgent need for an interference source detection method that can ensure the detection ability and is not affected by whether the receiver can successfully capture and track satellite signals. Summary of the Invention

[0007] The object of the present invention is to provide a real-time detection and positioning method for airport GNSS interference by fusing the direction finding of multiple single-antenna receivers, which is not affected by whether the receivers of the reference stations can successfully capture and track satellite signals, and improves the detection efficiency and accuracy of airport interference sources.

[0008] To achieve the above object, the present invention provides the following solution:

[0009] A reference station is provided, which is set in the airport to be detected and connected to the control center. The reference station includes:

[0010] An antenna for capturing and tracking the carrier-to-noise ratio data of each satellite signal;

[0011] An antenna rotating component, on which the antenna is arranged, for driving the antenna to rotate uniformly and detecting the antenna angle in real time; at different antenna angles, the received signal power of the satellite signal by the antenna is different;

[0012] A receiver is connected to the control center, the antenna and the antenna rotating component, and is used for receiving each pair of antenna angles and the corresponding received signal power; sending the detection data to the control center, and receiving the direction finding control instruction transmitted by the control center and sending it to the antenna rotating component; the direction finding control instruction is a start signal for controlling the antenna rotating component to rotate uniformly; the detection data includes carrier-to-noise ratio data, or carrier-to-noise ratio data and received signal power;

[0013] A control component is respectively connected to the receiver and the antenna rotating component, and is used for executing the following program according to each pair of antenna angles and the corresponding received signal power in each rotation:

[0014] For the first rotation, according to the antenna angle corresponding to the maximum received signal power within one week of the antenna rotation, determine the center point and narrow the rotation range;

[0015] For the nth rotation, control the antenna rotating component to make the antenna rotate within the current rotation range of the current center point, and update the center point according to the antenna angle corresponding to the maximum received signal power within the current rotation range, and narrow the rotation range; until the rotation range is less than the range threshold or the maximum rotation number is reached, the rotation ends; 2≤n≤N, where N is the maximum rotation number;

[0016] According to the antenna angle corresponding to the maximum received signal power within the last rotation range, determine the angle information of the interference source.

[0017] Optionally, the antenna rotating component includes:

[0018] The transmission rod is connected to the antenna and is used to drive the antenna to rotate at a constant speed;

[0019] The speed reducer is connected to the transmission rod and is used to drive the transmission rod to rotate at a constant speed;

[0020] The angle sensor is respectively connected to the antenna and the control component and is used to detect the antenna angle;

[0021] The motor drive module is respectively connected to the speed reducer, the receiver and the control component and is used to control the start and operation of the speed reducer according to the direction finding control instruction, and adjust the rotation angle and speed of the speed reducer under the control of the control component.

[0022] To achieve the above object, the present invention also provides the following solution:

[0023] A control center, the control center includes:

[0024] The communication unit is connected to a plurality of the above-mentioned reference stations and is used to receive the detection data and the angle information of the interference source transmitted by each reference station; a plurality of reference stations are arranged at different positions of the airport to be detected;

[0025] The first interference source determination unit is connected to the communication unit and is used to, for any reference station, when the detection data transmitted by the reference station does not include the carrier-to-noise ratio data, judge whether there is an interference source in the airport to be detected according to the received signal power transmitted by the reference station;

[0026] The second interference source determination unit is connected to the communication unit and is used to, for any reference station, when the detection data transmitted by the reference station includes the carrier-to-noise ratio data, judge whether there is an interference source in the airport to be detected according to the carrier-to-noise ratio data;

[0027] The control unit is respectively connected to the first interference source determination unit, the second interference source determination unit and the reference station and is used to generate a direction finding control instruction and send it to the reference station when there is an interference source in the airport to be detected;

[0028] The interference source position determination unit is connected to each reference station and is used to determine the position of the interference source according to the position coordinates of the reference station where the interference source is determined to exist and the angle information of the interference source.

[0029] To achieve the above object, the present invention also provides the following solution:

[0030] An interference source determination method, the interference source determination method includes:

[0031] Obtain the detection data transmitted by each reference station in the airport to be detected;

[0032] For each reference station, when the detection data transmitted by the reference station does not include carrier-to-noise ratio data, determine whether there is an interference source at the airport to be measured according to the received signal power transmitted by the reference station;

[0033] When the detection data transmitted by the reference station includes carrier-to-noise ratio data, determine whether there is an interference source at the airport to be measured according to the carrier-to-noise ratio data;

[0034] If there is an interference source at the airport to be measured, generate a direction finding control instruction and send it to the reference station;

[0035] Determine the position of the interference source according to the position coordinates of the reference station where the interference source is determined to exist and the angle information of the interference source.

[0036] Optionally, when the detection data transmitted by the reference station does not include carrier-to-noise ratio data, determining whether there is an interference source at the airport to be measured according to the received signal power transmitted by the reference station specifically includes:

[0037] Obtain the frequency at which the received signal power transmitted by the reference station exceeds the power threshold within a continuous time period; if the frequency is greater than the frequency threshold, determine that there is an interference source at the airport to be measured, otherwise determine that there is no interference source at the airport to be measured.

[0038] Optionally, when the detection data transmitted by the reference station includes carrier-to-noise ratio data, determining whether there is an interference source at the airport to be measured according to the carrier-to-noise ratio data specifically includes:

[0039] For any satellite signal, obtain the number of carrier-to-noise ratio data greater than the carrier-to-noise ratio threshold within n sliding windows; if the number of carrier-to-noise ratio data is greater than the first quantity threshold, determine that the satellite signal is interfered;

[0040] If the number of satellite signals with interference is greater than the second quantity threshold, and the number of satellite signals with carrier-to-noise ratio data greater than the carrier-to-noise ratio threshold in the most recent sliding window is greater than the third quantity threshold, determine that there is an interference source at the airport to be measured.

[0041] Optionally, obtaining the angle information of the interference source transmitted by the reference station where the interference source is determined to exist and determining the position of the interference source according to the angle information specifically includes:

[0042] For any reference station where the interference source is determined to exist, determine a ray according to the position coordinates of the reference station and the angle information of the interference source transmitted by the reference station;

[0043] Using the least squares method, based on the objective function, determine the position of the interference source according to the rays corresponding to each reference station where the interference source is determined to exist.

[0044] Optionally, according to the following formula, determine the ray corresponding to the reference station i:

[0045]

[0046] where (x i , y i ) is the position coordinate of the reference station i, α i is the angle information transmitted by the reference station i, and (x, y) is the point on the ray.

[0047] To achieve the above object, the present invention also provides the following solution:

[0048] An interference source detection system, the interference source detection system includes a plurality of the above-mentioned reference stations and a control center;

[0049] Each reference station is set at different positions of the airport to be detected, and each reference station is connected to the control center.

[0050] To achieve the above object, the present invention also provides the following solution:

[0051] An interference source detection method, applied to the above-mentioned interference source detection system, the interference source detection method includes:

[0052] Capture and track the carrier-to-noise ratio data of each satellite signal through a plurality of reference stations respectively;

[0053] Through the control center for any reference station, when the detection data transmitted by the reference station does not include the carrier-to-noise ratio data, judge whether there is an interference source in the airport to be detected according to the received signal power transmitted by the reference station; when the detection data transmitted by the reference station includes the carrier-to-noise ratio data, judge whether there is an interference source in the airport to be detected according to the carrier-to-noise ratio data;

[0054] When there is an interference source in the airport to be detected, generate a direction finding control instruction and send it to the reference station;

[0055] Start the rotation of the antenna of the reference station according to the direction finding control instruction through the antenna rotation component of the reference station to drive the antenna of the reference station to rotate;

[0056] Through the control component of the reference station for the first rotation of the antenna, determine the center point according to the antenna angle corresponding to the maximum received signal power within one rotation of the antenna, and narrow the rotation range;

[0057] For the nth rotation, control the antenna rotating component to rotate the antenna within the current rotation range of the current center point. Update the center point according to the antenna angle corresponding to the maximum received signal power within the current rotation range, and reduce the rotation range; stop rotating until the rotation range is less than the range threshold or the maximum number of rotations is reached; 2 ≤ n ≤ N, where N is the maximum number of rotations.

[0058] Determine the angle information of the interference source according to the antenna angle corresponding to the maximum received signal power within the last rotation range.

[0059] Based on the position coordinates of the reference station determined to have an interference source and the angle information of the interference source by the control center, determine the position of the interference source.

[0060] According to the specific embodiments provided by the present invention, the following technical effects are disclosed by the present invention:

[0061] The present invention combines the advantages of the received signal power of the data before despreading and the carrier-to-noise ratio of the data after despreading, selects two observables to comprehensively judge whether there is an interference source in the airport to be measured. When there is an interference source in the airport to be measured, direction finding of the interference source is performed by the reference station, and based on the positions of each reference station and the angle information of the interference source obtained, positioning of the interference source is performed. It can be applied to the detection of interference sources in the case where the receiver of the reference station cannot capture and track, improving the detection efficiency and accuracy of airport interference sources. Description of the Drawings

[0062] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0063] Figure 1 It is a schematic structural diagram of the reference station of the present invention;

[0064] Figure 2 It is a schematic structural diagram of the antenna rotating component;

[0065] Figure 3 It is a schematic module structure diagram of the control center of the present invention;

[0066] Figure 4 It is a flowchart of the method for determining the interference source of the present invention;

[0067] Figure 5 It is a flowchart of the interference source detection algorithm;

[0068] Figure 6 It is a flowchart of the interference source positioning algorithm.

[0069] Symbol description:

[0070] Reference station - 1, antenna - 11, receiver - 12, antenna rotating component - 13, transmission rod - 131, reduction gear - 132, angle sensor - 133, motor drive module - 134, control component - 14, control center - 2, communication unit - 21, first interference source determination unit - 22, second interference source determination unit - 23, control unit - 24, interference source position determination unit - 25. Specific implementation manners

[0071] 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 only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0072] The object of the present invention is to provide a method for real - time detection and positioning of airport GNSS interference by combining multiple single - antenna receiver direction - finding. By combining the advantages of received signal power and carrier - to - noise ratio data, it comprehensively determines whether there is an interference source in the airport to be measured. When there is an interference source in the airport to be measured, the reference station is used to measure the direction of the interference source, and based on the position of the reference station and the angle information of the interference source obtained, the interference source is positioned. It is applicable to the detection of interference sources in the case where the receiver cannot capture and track, improving the detection efficiency and accuracy of airport interference sources.

[0073] To make the above - mentioned objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific implementation manners.

[0074] As Figure 1 shown, the reference station 1 of the present invention is set in the airport to be detected and is connected to the control center 2. The reference station 1 includes: an antenna 11, a receiver 12, an antenna rotating component 13, and a control component 14.

[0075] Among them, the antenna 11 is used to capture and track the carrier - to - noise ratio data of each satellite signal.

[0076] The antenna 11 is arranged on the antenna rotating component 13. The antenna rotating component 13 is used to drive the antenna to rotate uniformly and detect the antenna angle in real - time. At different antenna angles, the received signal power of the satellite signal by the antenna is different.

[0077] The receiver 12 is connected to the control center 2, the antenna 11, and the antenna rotation component 13. The receiver 12 is configured to receive the angles of each pair of antennas and the corresponding received signal powers; send the detection data to the control center 2, and receive the direction finding control instructions transmitted by the control center 2 and send them to the antenna rotation component 13; the direction finding control instruction is a start signal for controlling the antenna rotation component 13 to rotate at a constant speed. A data interface is designed on the receiver 12, enabling the receiver 12 to output the detection data in real time.

[0078] The control component 14 is respectively connected to the receiver 12 and the antenna rotation component 13. The control component 14 is configured to execute the following procedures according to the angles of each pair of antennas and the corresponding received signal powers in each rotation:

[0079] For the first rotation, determine the center point according to the antenna angle corresponding to the maximum received signal power within one rotation of the antenna, and narrow the rotation range.

[0080] For the nth rotation, control the antenna rotation component to make the antenna rotate within the current rotation range of the current center point. According to the antenna angle corresponding to the maximum received signal power within the current rotation range, update the center point and narrow the rotation range; until the rotation range is less than the range threshold or the maximum rotation times is reached, the rotation ends; 2 ≤ n ≤ N, where N is the maximum rotation times.

[0081] Determine the angle information of the interference source according to the antenna angle corresponding to the maximum received signal power within the last rotation range.

[0082] Specifically, during the first rotation, the antenna rotates at a constant speed of 360°. During the rotation, the angle of the antenna and the received signal power are detected in real time. According to the angle of the antenna and the received signal power, the direction of the interference source relative to the antenna is judged by using the directivity of the antenna. After the antenna rotates one week, the angle corresponding to the moment of the maximum received signal power is used as the new center point. Make the antenna rotate within the range of ±60° from the center point, determine the direction with the maximum received power, and narrow the rotation angle until the rotation range is controlled within ±0.88°. The angle with the maximum received signal power is used as the direction of the incoming wave, that is, the angle information of the interference source. The standard rotation speed of the antenna is 6 rpm. The pitch angle of the antenna can be adjusted by turning the screw to adapt to the situation where the reference station is placed at different heights.

[0083] Further, the receiver 12 is a single-antenna receiver. According to the directivity of the antenna, the direction of the interference source relative to the antenna 11 is measured by rotating the antenna 11, and then the position of the interference source is calculated based on the positions of multiple receivers 12 and the direction-finding results. The direction finding of the interference source is realized based on a single-antenna software receiver, and the positioning of the interference source is realized by the direction-finding results of multiple single-antenna software receivers, avoiding the use of array antennas which leads to high-cost and high-complexity equipment and improving flexibility.

[0084] Further, as Figure 2 shown, the antenna rotation component 13 includes: a transmission rod 131, a speed reducer 132, an angle sensor 133, and a motor drive module 134.

[0085] Among them, the transmission rod 131 is connected to the antenna 11, and the transmission rod 131 is used to drive the antenna 11 to rotate at a constant speed.

[0086] The speed reducer 132 is connected to the transmission rod 131, and the speed reducer 132 is used to drive the transmission rod 131 to rotate at a constant speed.

[0087] The angle sensor 133 is respectively connected to the antenna 11 and the control component 14, and the angle sensor 133 is used to detect the antenna angle and send it to the control component 14. In this embodiment, an angle sensor 133 is provided in each of the horizontal and pitch directions of the antenna 11.

[0088] The motor drive module 134 is respectively connected to the speed reducer 132, the receiver 12, and the control component 14. The motor drive module 134 is used to control the start and operation of the speed reducer 132 according to the direction-finding control instruction, and adjust the rotation angle and speed of the speed reducer 132 under the control of the control component 14.

[0089] Further, the reference station 1 further includes a radio frequency front end. The radio frequency front end uses HackRF One.

[0090] As Figure 3 shown, the present invention also provides a control center 2, including: a communication unit 21, a first interference source determination unit 22, a second interference source determination unit 23, a control unit 24, and an interference source position determination unit 25.

[0091] Among them, the communication unit 21 is connected to multiple reference stations 1 as described above. The communication unit 21 is used to receive the detection data and the angle information of the interference source transmitted by each reference station 1; multiple reference stations 1 are arranged at different positions of the airport to be detected.

[0092] The first interference source determination unit 22 is connected to the communication unit 21. The first interference source determination unit 22 is configured to, for any reference station 1, when the detection data transmitted by the reference station 1 does not include carrier-to-noise ratio data, determine whether there is an interference source at the airport to be measured according to the received signal power transmitted by the reference station 1.

[0093] The second interference source determination unit 23 is connected to the communication unit 21. The second interference source determination unit 23 is configured to, for any reference station 1, when the detection data transmitted by the reference station 1 includes carrier-to-noise ratio data, determine whether there is an interference source at the airport to be measured according to the carrier-to-noise ratio data.

[0094] The control unit 24 is respectively connected to the first interference source determination unit 22, the second interference source determination unit 23, and the reference station 1. The control unit 24 is configured to generate a direction finding control instruction and send it to the reference station 1 when there is an interference source at the airport to be measured.

[0095] The interference source position determination unit 25 is connected to each reference station 1. The interference source position determination unit 25 is configured to determine the position of the interference source according to the position coordinates of the reference station 1 where the interference source is determined to exist and the angle information of the interference source.

[0096] Further, the first interference source determination unit 22 includes: a frequency acquisition module and a determination module.

[0097] Among them, the frequency acquisition module is connected to the communication unit 21. The frequency acquisition module is configured to acquire the frequency at which the received signal power transmitted by the reference station exceeds the power threshold within a continuous time period.

[0098] The first determination module is connected to the frequency acquisition module. The first determination module is configured to determine that there is an interference source at the airport to be measured when the frequency is greater than the frequency threshold, otherwise determine that there is no interference source at the airport to be measured.

[0099] Even further, the second interference source determination unit 23 includes: a carrier-to-noise ratio quantity determination module, a second determination module, and a third determination module.

[0100] Among them, the carrier-to-noise ratio quantity determination module is connected to the communication unit 21. The carrier-to-noise ratio quantity determination module is configured to, for any satellite signal, acquire the quantity of carrier-to-noise ratio data whose carrier-to-noise ratio data is greater than the carrier-to-noise ratio threshold within n sliding windows.

[0101] The second determination module is connected to the carrier-to-noise ratio quantity determination module. The second determination module is configured to determine that the satellite signal is interfered when the quantity of carrier-to-noise ratio data is greater than the first quantity threshold.

[0102] The third determination module is connected to the second determination module, and is used to determine that there is an interference source at the airport to be tested when the number of satellite signals with interference is greater than a second number threshold, and the number of satellite signals whose carrier-to-noise ratio data of each satellite signal in a most recent sliding window is greater than the carrier-to-noise ratio threshold is greater than a third number threshold.

[0103] Furthermore, the interference source position determination unit 25 includes: a ray determination module and a position determination module.

[0104] The ray determination module is connected to each reference station 1 and is used to determine a ray for any reference station determined to have an interference source according to the position coordinates of the reference station and the angle information of the interference source transmitted by the reference station.

[0105] The position determination module is connected to the ray determination module, and the position determination module is used to determine the position of the interference source by adopting the least square method based on the objective function and according to the rays corresponding to each reference station where the interference source is determined to exist.

[0106] The present invention combines the advantages of data before despreading (received signal power) and data after despreading (carrier-to-noise ratio data), solves the problem that the detection rate and application scope of the existing algorithm cannot be taken into account at the same time, and on the basis of ensuring the detection capability, the interference detection algorithm is no longer affected by the state of the GNSS receiver, thereby improving the availability of the interference detection algorithm.

[0107] like Figure 4 As shown, the present invention also provides a method for determining an interference source, the method for determining an interference source comprising:

[0108] S1: Acquire the detection data transmitted by each reference station in the airport to be detected.

[0109] S2: for each reference station, when the detection data transmitted by the reference station does not include carrier-to-noise ratio data, judging whether there is an interference source at the airport to be detected according to the received signal power transmitted by the reference station.

[0110] Specifically, the frequency at which the power of the received signal transmitted by the reference station exceeds the power threshold within a continuous period is obtained; if the frequency is greater than the frequency threshold, it is determined that there is an interference source at the airport to be tested, otherwise it is determined that there is no interference source at the airport to be tested. In this embodiment, the threshold value of the received signal power is determined by analyzing the distribution of the data actually received by the receiver, and the distribution of the received signal power value is fitted using a Gaussian distribution to obtain the mathematical characteristics of the received power, and its mean and variance correspond to the tolerable interference power specified by the International Civil Aviation Organization (ICAO) to determine the detection threshold (power threshold).

[0111] S3: When the detection data transmitted by the reference station includes carrier-to-noise ratio data, determine whether there is an interference source at the airport to be measured according to the carrier-to-noise ratio data.

[0112] Specifically, for any satellite signal, obtain the number of carrier-to-noise ratio data whose carrier-to-noise ratio is greater than the carrier-to-noise ratio threshold within n sliding windows; if the number of carrier-to-noise ratio data is greater than the first quantity threshold, it is determined that the satellite signal is interfered. In this embodiment, the first quantity threshold is 7.

[0113] If the number of satellite signals with interference is greater than the second quantity threshold, and the number of satellite signals whose carrier-to-noise ratio data in the most recent sliding window is greater than the carrier-to-noise ratio threshold is greater than the third quantity threshold, it is determined that there is an interference source at the airport to be measured. In this embodiment, the second quantity threshold is 2. The third quantity threshold is 6.

[0114] S4: If there is an interference source at the airport to be measured, generate a direction finding control instruction and send it to the reference station.

[0115] S5: Obtain the angle information of the interference source transmitted by the reference station determined to have an interference source, and determine the position of the interference source according to the angle information.

[0116] Specifically, for any reference station determined to have an interference source, determine a ray according to the position coordinates of the reference station and the angle information of the interference source transmitted by the reference station. In this embodiment, according to the following formula, determine the ray corresponding to reference station i:

[0117]

[0118] where, (x i ,y i ) are the position coordinates of reference station i, α i is the angle information transmitted by reference station i, and (x, y) are the points on the ray.

[0119] Adopt the least squares method, based on the objective function, and determine the position of the interference source according to the rays corresponding to each reference station determined to have an interference source. In this embodiment, obtain the optimal solution of the intersection of multiple rays through the least squares method, and this optimal solution is the position of the interference source.

[0120] The objective function is:

[0121]

[0122] where, J(x, y) is the objective function value, n is the total number of reference stations determined to have an interference source, α i is the angle information transmitted by reference station i, (x i ,y i) is the position coordinate of reference station i, and (x, y) are the points on the ray.

[0123] As a specific implementation, when the detection data transmitted by the reference station includes carrier-to-noise ratio data, the Serial Multiple Detection (SMD) algorithm and the Parallel Multiple Detection (PMD) algorithm are combined to determine whether there is an interference source. Select Ω = 2, N = 7, M = 6. Ω is the number of satellite signals with interference signals detected by the PMD algorithm, N is the number of carrier-to-noise ratio time periods observed by the SMD algorithm, and M is the number of time periods exceeding the carrier-to-noise ratio threshold in the SMD algorithm. For the signal of a single satellite, if there are no less than 6 carrier-to-noise ratio data exceeding the set threshold within the nearest 7 sliding windows, it is determined that there is an interference source for the satellite signal; if there are no less than 2 satellite signals with interference for all received satellite signals, the SMD algorithm determines that there is interference.

[0124] For all received satellite signals, if there are no less than 2 satellite signals with carrier-to-noise ratio data exceeding the threshold within the nearest sliding window, the PMD algorithm determines that there is interference.

[0125] If both the SMD algorithm and the PMD algorithm determine that there is interference, it is considered that there is an interference signal affecting navigation.

[0126] The present invention integrates the Serial Multiple Detection (SMD) algorithm and the Parallel Multiple Detection (PMD) algorithm, and respectively detects the interference situation of a single satellite within a period of time and the interference situation of multiple satellites at the nearest moment. On the premise of ensuring the optimal detection rate and a relatively low false alarm rate, the false alarm rate is reduced as much as possible to meet the requirements of the airport area for interference detection.

[0127] In addition, in order to test the interference source determination method, before step S1, interference sources can be generated to simulate the test conditions. Specifically, baseband signals of three common interference signals, namely Gaussian white noise, narrowband continuous wave, and swept-frequency wave, and binary messages of GPS spoofing signals are generated. Among them, the sampling rate of Gaussian white noise is 21 MHz, and after passing through an 8th-order Butterworth low-pass filter of 10 MHz, narrowband Gaussian white noise with a bandwidth of 10 MHz is generated; the frequency of the narrowband continuous wave is 1000 Hz, and the sampling rate is 2.6 MHz; the baseband signal of the sine swept-frequency wave ranges from 20 Hz to 20 KHz, and the sampling rate is 2.6 MHz; the sampling rate of the spoofing interference source is 2.6 MHz. The sampling rates and bandwidths of various interference sources are all matched with the RF front-end of the reference station, and the interference sources are modulated to the GPS L1 band (1575.42 MHz) by the RF front-end and transmitted to simulate GNSS jamming sources and spoofing sources.

[0128] The present invention also provides an interference source detection system, which includes a plurality of reference stations 1 and a control center 2. Each reference station 1 is set at different positions of the airport to be detected, and each reference station 1 is connected to the control center 2.

[0129] Specifically, when an interference source is detected, each interfered reference station measures the direction of the interference source respectively, and transmits the direction finding result to the control center. The control center determines the location of the interference source according to the coordinates of different reference stations and the direction of the interference source relative to each station.

[0130] Corresponding to the above interference source detection system, the present invention also provides an interference source detection method to realize the interaction between a plurality of reference stations and the control center. The interference source detection method includes:

[0131] Capturing and tracking the carrier-to-noise ratio data of each satellite signal by a plurality of reference stations respectively.

[0132] For any reference station through the control center, when the detection data transmitted by the reference station does not contain carrier-to-noise ratio data, it is judged whether there is an interference source in the airport to be detected according to the received signal power transmitted by the reference station; when the detection data transmitted by the reference station contains carrier-to-noise ratio data, it is judged whether there is an interference source in the airport to be detected according to the carrier-to-noise ratio data.

[0133] When there is an interference source in the airport to be detected, a direction finding control instruction is generated and sent to the reference station.

[0134] The antenna rotation component of the reference station is started to rotate according to the direction finding control instruction, so as to drive the antenna of the reference station to rotate.

[0135] For the first rotation of the antenna through the control component of the reference station, the center point is determined according to the antenna angle corresponding to the maximum received signal power within one rotation of the antenna, and the rotation range is reduced.

[0136] For the nth rotation, control the antenna rotation component to make the antenna rotate within the current rotation range of the current center point. According to the antenna angle corresponding to the maximum received signal power within the current rotation range, update the center point and reduce the rotation range; until the rotation range is less than the range threshold or the maximum rotation times is reached, the rotation ends; 2 ≤ n ≤ N, and N is the maximum rotation times.

[0137] Determine the angle information of the interference source according to the antenna angle corresponding to the maximum received signal power within the last rotation range.

[0138] The control center determines the location of the interference source according to the position coordinates of the reference station determined to have an interference source and the angle information of the interference source.

[0139] To better understand the solution of the present invention, the following further elaborates with specific application scenarios.

[0140] (1) Set up multiple reference stations at the airport to be detected. The interference source detection method is encapsulated in the Raspberry Pi.

[0141] (2) Use tools such as MATLAB and Python to generate baseband signals corresponding to three types of interference: Gaussian white noise, narrowband continuous wave (CW), and swept-frequency wave. Modulate them to the GPS L1 band (1575.42 MHz) through the HackRF One RF front-end and transmit, so as to realize the simulated suppression interference source in the test.

[0142] Generate the binary message of the GPS spoofing signal based on the open-source project GPS-SDR-SIM, and modulate it to 1575.42 MHz through the hackrf_transfer command of the HackRF One RF front-end for transmission, so as to realize the simulated spoofing interference source in the test.

[0143] (3) Set the received power threshold: Measure the received power distribution when the receiver is working normally for a period of time, fit it with a Gaussian distribution to obtain the mathematical characteristics of the received signal power, and correspond its mean and variance to the tolerable interference power specified by the International Civil Aviation Organization (ICAO) to determine the detection threshold (power threshold).

[0144] (4) Determine the carrier-to-noise ratio threshold: Since the true carrier-to-noise ratio is greatly affected by factors such as satellite altitude, directly setting a threshold for the carrier-to-noise ratio data has poor performance. To unify the setting standard, the present invention uses the normalized carrier-to-noise ratio data as a characteristic quantity.

[0145] For a given elevation angle and a given satellite distribution, first normalize the carrier-to-noise ratio data C / N0 of the reference station to obtain the normalized value

[0146]

[0147] where θ k represents different satellite elevation angles, N θ represents the observation sliding window length, represents the total number of satellites receiving signals at the satellite elevation angle of θ k case, represents at θ k the carrier-to-noise ratio value of satellite k received at the elevation angle, which is a directly measured quantity, and PRN represents the "pseudo-random noise code" of the satellite.

[0148] Normalize for different elevation angles and satellites to obtain the characteristic quantity

[0149] Among them, is the root mean square, representing the degree of deviation from the average level, M is the number of ground reference receivers, m is the m-th receiver, and θ k,m is the elevation angle corresponding to the m-th receiver, and a0, a1, a2, and θ0 are pre-selected parameters as shown in Table 1. Take the maximum value of RMS and substitute it into the characteristic quantity calculation formula to determine the characteristic quantity.

[0150] According to the characteristic quantity distribution and the 3σ principle, determine the carrier-to-noise ratio threshold. Specifically, use Gaussian distribution to fit the distribution of the characteristic quantity According to the mean value, variance of the characteristic quantity and the 3σ principle, set the larger one of the critical points with a confidence probability less than 99.74% as the carrier-to-noise ratio threshold.

[0151] Table 1

[0152]

[0153] (5) Perform interference detection based on the received signal power and carrier-to-noise ratio data: Considering that it is necessary to detect whether there is interference when the receiver cannot capture and track, it is necessary to select the data before the receiver despreads as the observable. However, the data that has not been tracked usually has unclear characteristics, and the detection ability is not as good as the scheme that selects the tracked data as the observable. In order to improve the interference detection ability most of the time and meet the requirements of interference detection under different working conditions of the receiver, the present invention selects two observables, the received signal power and the carrier-to-noise ratio data, to cover the two situations where the receiver can and cannot track. As Figure 5 shown is the flowchart of the interference source detection algorithm.

[0154] When the receiver cannot capture and track, since the GNSS frequency band is strictly regulated, the received signal power will not change significantly without interference. Therefore, it can be considered that when this data changes significantly, the receiver is interfered.

[0155] When the receiver can capture and track normally, if there is an interference signal, the carrier-to-noise ratio of the receiver intermediate frequency data will increase significantly. If the carrier-to-noise ratios of multiple satellite signals exceed the threshold at the same time, or the carrier-to-noise ratio of a single satellite signal stably exceeds the threshold for a period of time, it can be considered that there is interference. According to this change characteristic of the carrier-to-noise ratio, multi-satellite single detection is used as the main criterion, and single-satellite multiple detection is used as the auxiliary criterion for interference detection at this time.

[0156] For the case where the receiver can normally capture and track the carrier-to-noise ratio data, the following conclusions can be drawn: The PMD algorithm has a greater impact on the false alarm rate than the SMD algorithm. When the SMD algorithm is not used, taking the detection of interference by three satellites simultaneously as the detection criterion of PMD can meet the false alarm rate requirements of users. When the PMD judgment criterion is lowered and the detection of interference by two satellites simultaneously is used as the criterion, the use of SMD for assistance can also meet the requirements. Increasing the number of detections of a single satellite in the SMD algorithm and the total number of detections with interference will both increase the false alarm rate.

[0157] To obtain better detection capabilities and a lower false alarm rate, a PMD and SMD fusion algorithm with Ω = 2, N = 7, and M = 6 is selected. Among them, Ω represents the number of satellites that detect the interference signal in the PMD algorithm, and N and M represent the number of observed carrier-to-noise ratios and the number of thresholds in the SMD algorithm, respectively. The possible situations and judgment results of the interference source detection are shown in Table 2.

[0158] Table 2

[0159]

[0160] (6) Interference source location: The main existing methods for interference location are the interference signal direction finding method (AOA), the time difference of arrival method (TDOA), and the received signal strength measurement method (RSS). The infrastructure of the AOA and TDOA methods is complex and has great limitations in practical applications. Therefore, the widely used method is the RSS method. The RSS method is divided into two types: based on the radio frequency front end (RFFE) and based on the carrier-to-noise ratio (CNR). In the method based on the radio frequency front end, the main observables are the automatic gain control (AGC) and the jammer-to-noise ratio (JNR). In the method based on the carrier-to-noise ratio, there are mainly three methods: single receiver synthesis (SRS), multi-source geometric center (CC), and multi-source carrier-to-noise ratio data fusion (CC / N0F). Similarly, due to the more stable data after despreading, the currently most commonly used GNSS interference location observable is also the carrier-to-noise ratio.

[0161] Considering the actual needs of the airport: Regardless of the working state of the receiver, it is necessary to locate the interference source in order to quickly investigate and expel it. Therefore, the positioning algorithm must select the data before despreading of the receiver as the observable. At the same time, it is necessary to be convenient to deploy and control the cost within a reasonable range.

[0162] During the positioning process of a single receiver, the required antenna structure is relatively complex, and the observation points are single, resulting in limited positioning accuracy and range. Based on the requirements of simplicity, low cost, and high flexibility, instead of using an array antenna with a relatively complex structure, the present invention selects a single-antenna receiver as the main device. Multiple single-antenna receivers respectively perform direction finding on the interference source, and then fuse the direction-finding results to increase the data sources, improve the positioning accuracy, and at the same time reduce the complexity of each receiver antenna. By deploying multiple receivers at different locations, the regional range of interference source positioning is improved.

[0163] Different from directly using the detection observables for positioning after existing interference detection, the present invention will only call the interference positioning algorithm after detecting interference, and the interference positioning observables can be different from the interference detection observables. The system modularizes the interference detection algorithm and the interference positioning algorithm. When interference is detected, the interference positioning module is called. At the same time, since it is known that there is jamming interference when starting the interference positioning algorithm, it can be directly considered that the direction with the strongest antenna received power is the direction of the interference source relative to the receiver, reducing the complexity of the algorithm. As Figure 6 shown in the flowchart of the interference source positioning algorithm.

[0164] Interference source direction finding based on antenna directivity: The characteristics of the airport environment are open terrain and relatively easy to lock the target. Therefore, only the approximate position needs to be determined on the two-dimensional plane to lock the interference source.

[0165] For a single reference station, according to the characteristics of antenna directivity, determine the direction with the strongest antenna reception ability and take it as the "positive direction". Rotate the antenna. When the "positive direction" is facing the direction of the interference incoming wave, the antenna received signal power is the largest. Thus, the direction of the interference source relative to the reference station can be determined.

[0166] After receiving the start signal from the control center, perform time synchronization detection and start interference source positioning. The antenna rotates 360°, and at the same time, the current angle and the antenna received signal power are output in real time. After rotating one week, rotate ±60° with the angle corresponding to the moment of the maximum received signal power as the center point to further lock the incoming wave direction, and further reduce the rotation angle, and so on, until the incoming wave direction range is controlled within ±0.88°. After obtaining the incoming wave direction, transmit the reference station coordinates and the incoming wave direction angle to the control center.

[0167] Interference source positioning based on the direction-finding results: After each reference station returns the site coordinates and the incoming wave direction, the optimal solution of the interference source coordinates and the 95% confidence probability interval (uncertainty) are obtained through the least squares method.

[0168] The interference source location is solved by the least squares method: when the coordinates of multiple reference stations are known, and the direction of the interfering incoming wave measured at each station is known, four rays can be obtained. The optimal solution of the intersection of the four rays can be obtained by the least squares method, and the coordinates of this optimal solution are the most probable interference source location on the two-dimensional plane. At the same time, the uncertainties in the two directions of the interference source location can be obtained.

[0169] Let the two-dimensional position coordinates of reference station i be (x i , y i ), and the angle information transmitted by this reference station is α i . Then, the ray equation can be obtained from this fixed point position and direction. Since the straight line and the ray do not affect the intersection solution, for the convenience of representation, the straight line equation is used to represent this ray:

[0170]

[0171] Among them, α i is the angle information transmitted by reference station i, (x i , y i ) is the position coordinates of reference station i, and x - x i can be transformed into:

[0172] x - x i = tanα i (y - y i )

[0173] When the total number of reference stations where the interference source is determined to exist is n, the following system of equations can be listed:

[0174]

[0175] Among them, the optimal solution (x, y) of the system of equations is the optimal solution of the interference source location. The above system of equations can be transformed into matrix form:

[0176]

[0177] Let be the coordinates of the intersection point to be found; It can be obtained that:

[0178]

[0179] It can be deduced that:

[0180]

[0181] However, (x, y) (or ) is mostly unsolvable in most cases. Therefore, the optimal solution needs to be obtained by the least squares method. Set the objective function:

[0182]

[0183] Iteratively obtain the optimal solution of the interference source position coordinates (x p , y p ).

[0184] (7) Determine the positioning error of the interference source: The positioning error of the interference source is represented by uncertainty. The uncertainty of the interference source position is only related to the angle measurement uncertainty. When the uncertainty Δθ i of the direction finding result θ i of each reference station is known, let k i = tanα i , b i = y i - x i ·tanα i , then the uncertainties of x i and y i can be obtained from the uncertainty Δα p of α p :

[0185]

[0186] Among them, Δx is the uncertainty of the interference source position on the x-axis, and Δy is the uncertainty of the interference source position on the y-axis. σ represents uncertainty, k = tanα, b = y - x·tanα, and α is the angle information transmitted by the reference station.

[0187] If the uncertainty is represented by a matrix, let Then the covariance matrix (matrix representation of uncertainty) can be obtained. This matrix is the expression of the interference source position uncertainty in matrix form:

[0188]

[0189] X is is the mathematical expectation of, is the mathematical expectation of, and the C matrix is the covariance matrix of X, where c ij = Cov(x i , y j ), i, j = 1, 2,..., n.

[0190] Uncertainty represents a rough range, that is, an ellipse centered on the positioning result with Δx and Δy on the horizontal and vertical axes respectively. The positioning result has a 95% probability of falling within this range.

[0191] The present invention conducts GNSS interference detection and interference source localization on an airport-by-airport basis, focusing on high-interference areas. Compared with the existing method of interference detection on a route-by-route basis, it significantly reduces the amount of data required and improves the timeliness of detection and localization. Compared with the existing methods for interference source localization in the aviation field, it significantly narrows down the search scope, improves the localization accuracy, and greatly reduces the work intensity of the staff for investigation.

[0192] In this specification, each embodiment is described in a progressive manner. The key point of each embodiment is to illustrate the differences from other embodiments. For the same or similar parts among the embodiments, reference can be made to each other. For the system disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple. For the relevant parts, reference can be made to the description in the method section.

[0193] In this article, specific examples are used to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A reference station, which is set in the airport to be detected and is connected to a control center, characterized in that, The reference station includes: An antenna for capturing and tracking the carrier-to-noise ratio data of each satellite signal; An antenna rotating component, on which the antenna is arranged, for driving the antenna to rotate uniformly and detecting the antenna angle in real time; at different antenna angles, the received signal power of the satellite signal by the antenna is different; A receiver, connected to the control center, the antenna and the antenna rotating component, for receiving each pair of antenna angles and the corresponding received signal power; sending the detection data to the control center, and receiving the direction finding control instruction transmitted by the control center and sending it to the antenna rotating component; the direction finding control instruction is a start signal for controlling the antenna rotating component to rotate uniformly; the detection data includes carrier-to-noise ratio data, or carrier-to-noise ratio data and received signal power; The receiver is a single-antenna receiver. According to the directivity of the antenna, the direction of the interference source relative to the antenna is measured by rotating the antenna, and then the position of the interference source is calculated based on the positions of multiple receivers and the direction finding results. The direction finding of the interference source is realized based on a single-antenna software receiver, and the positioning of the interference source is realized by the direction finding results of multiple single-antenna software receivers; A control component, respectively connected to the receiver and the antenna rotating component, for executing the following program according to each pair of antenna angles and the corresponding received signal power in each rotation: For the first rotation, determine the center point according to the antenna angle corresponding to the maximum received signal power within one week of antenna rotation, and narrow the rotation range; For the nth rotation, control the antenna rotating component to make the antenna rotate within the current rotation range of the current center point. According to the antenna angle corresponding to the maximum received signal power within the current rotation range, update the center point and narrow the rotation range; until the rotation range is less than the range threshold or the maximum rotation times is reached, the rotation ends; 2 ≤ n ≤ N, and N is the maximum rotation times; Determine the angle information of the interference source according to the antenna angle corresponding to the maximum received signal power within the last rotation range.

2. The reference station according to claim 1, characterized in that, The antenna rotating component includes: A transmission rod, connected to the antenna, for driving the antenna to rotate uniformly; A speed reducer, connected to the transmission rod, for driving the transmission rod to rotate uniformly; An angle sensor, respectively connected to the antenna and the control component, for detecting the antenna angle; A motor drive module, respectively connected to the speed reducer, the receiver and the control component, for controlling the speed reducer to start running according to the direction finding control instruction, and adjusting the rotation angle and speed of the speed reducer under the control of the control component.

3. A control center, characterized in that, The control center includes: A communication unit, connected to multiple reference stations as claimed in claim 1 or 2, for receiving the detection data and the angle information of the interference source transmitted by each reference station; multiple reference stations are arranged at different positions of the airport to be detected; A first interference source determination unit, connected to the communication unit, for, for any reference station, when the detection data transmitted by the reference station does not include carrier-to-noise ratio data, judging whether there is an interference source in the airport to be detected according to the received signal power transmitted by the reference station; The second interference source determination unit, connected to the communication unit, is configured to, for any reference station, when the detection data transmitted by the reference station includes carrier-to-noise ratio data, determine whether there is an interference source at the airport to be measured according to the carrier-to-noise ratio data; The control unit, connected to the first interference source determination unit, the second interference source determination unit, and the reference station respectively, is configured to generate a direction finding control instruction and send it to the reference station when there is an interference source at the airport to be measured; The interference source position determination unit, connected to each reference station, is configured to determine the position of the interference source according to the position coordinates of the reference station determined to have an interference source and the angle information of the interference source.

4. A method for determining an interference source, which is applied to the control center described in claim 3, and is characterized in that, The interference source determination method includes: Obtain the detection data transmitted by each reference station in the airport to be detected; For each reference station, when the detection data transmitted by the reference station does not include carrier-to-noise ratio data, determine whether there is an interference source at the airport to be measured according to the received signal power transmitted by the reference station; When the detection data transmitted by the reference station includes carrier-to-noise ratio data, determine whether there is an interference source at the airport to be measured according to the carrier-to-noise ratio data; If there is an interference source at the airport to be measured, generate a direction finding control instruction and send it to the reference station; Determine the position of the interference source according to the position coordinates of the reference station determined to have an interference source and the angle information of the interference source.

5. The interference source determination method according to claim 4, characterized in that, When the detection data transmitted by the reference station does not include carrier-to-noise ratio data, determining whether there is an interference source at the airport to be measured according to the received signal power transmitted by the reference station specifically includes: Obtain the frequency at which the received signal power transmitted by the reference station exceeds the power threshold within a continuous time period; if the frequency is greater than the frequency threshold, it is determined that there is an interference source at the airport to be measured, otherwise it is determined that there is no interference source at the airport to be measured.

6. The interference source determination method according to claim 4, wherein When the detection data transmitted by the reference station includes carrier-to-noise ratio data, determining whether there is an interference source at the airport to be measured according to the carrier-to-noise ratio data specifically includes: For any satellite signal, obtain the number of carrier-to-noise ratio data whose carrier-to-noise ratio data in n sliding windows is greater than the carrier-to-noise ratio threshold; if the number of carrier-to-noise ratio data is greater than the first quantity threshold, it is determined that the satellite signal is interfered; If the number of satellite signals with interference is greater than the second quantity threshold, and the number of satellite signals whose carrier-to-noise ratio data in the last sliding window is greater than the carrier-to-noise ratio threshold is greater than the third quantity threshold, it is determined that there is an interference source at the airport to be measured.

7. The interference source determination method according to claim 5, wherein Determining the position of the interference source according to the position coordinates of the reference station determined to have an interference source and the angle information of the interference source specifically includes: For any reference station determined to have an interference source, determine a ray according to the position coordinates of the reference station and the angle information of the interference source transmitted by the reference station; Using the least squares method, based on the objective function, determine the position of the interference source according to the rays corresponding to each reference station determined to have an interference source.

8. The interference source determination method according to claim 7, characterized in that According to the following formula, determine the ray corresponding to reference station i: Among them, (x i , y i ) is the position coordinate of the reference station i, α i is the angle information transmitted by the reference station i, and (x, y) is the point on the ray.

9. An interference source detection system, characterized in that, The interference source detection system includes a plurality of reference stations according to any one of claims 1-2 and the control center according to claim 3; Each reference station is set at different positions of the airport to be detected, and each reference station is connected to the control center.

10. A method for detecting an interference source, applied to the interference source detection system described in claim 9, characterized in that, The interference source detection method includes: Capturing and tracking the carrier-to-noise ratio data of each satellite signal by multiple reference stations respectively; For any reference station through the control center, when the detection data transmitted by the reference station does not contain carrier-to-noise ratio data, judging whether there is an interference source in the airport to be detected according to the received signal power transmitted by the reference station; when the detection data transmitted by the reference station contains carrier-to-noise ratio data, judging whether there is an interference source in the airport to be detected according to the carrier-to-noise ratio data; When there is an interference source in the airport to be detected, generating a direction finding control instruction and sending it to the reference station; Starting the rotation of the antenna of the reference station according to the direction finding control instruction through the antenna rotation component of the reference station to drive the antenna of the reference station to rotate; For the first rotation of the antenna through the control component of the reference station, determining the center point according to the antenna angle corresponding to the maximum received signal power within one rotation of the antenna, and narrowing the rotation range; For the nth rotation, controlling the antenna rotation component to make the antenna rotate within the current rotation range of the current center point, updating the center point according to the antenna angle corresponding to the maximum received signal power within the current rotation range, and narrowing the rotation range; ending the rotation until the rotation range is less than the range threshold or the maximum rotation times is reached; 2≤n≤N, N is the maximum rotation times; Determining the angle information of the interference source according to the antenna angle corresponding to the maximum received signal power within the last rotation range; Determining the position of the interference source through the control center according to the position coordinates of the reference station where the interference source is determined to exist and the angle information of the interference source.

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