A method for finding and locating interference sources in a satellite navigation system

Abstract

The present invention belongs to the technical field of interference source search and positioning methods. In order to solve the technical problem that when a satellite navigation system is currently facing electromagnetic interference during operation, it is difficult to obtain the specific location of the interference source, and a single electromagnetic interference search device method is used, which has technical limitations, time and space limitations and environmental limitations. A satellite navigation system interference source search and positioning method is provided, which uses a maximum signal method to monitor and analyze the interference source, uses a correlation interferometer to find the direction of the interference source, and obtains the initial incoming wave direction. According to the initial incoming wave direction, a maximum signal method combined with a correlation interferometer direction finding method is used to obtain an accurate interference wave direction, arranges three monitoring stations, judges whether the interference signals monitored by the three monitoring stations are the same signal, obtains positioning area information through direction finding cross positioning, and obtains the interference source position.

Description

Technical Field

[0001] The present invention belongs to the technical field of interference source searching and positioning methods, and in particular relates to an interference source searching and positioning method for a satellite navigation system. Background Art

[0002] The Beidou satellite navigation system has become an important infrastructure for all-weather, all-day, high-precision positioning, navigation and timing services, with great economic and technological significance.

[0003] However, satellite navigation systems face severe electromagnetic interference problems during operation. In actual propagation environments, satellite navigation systems cannot predict the type and characteristics of interference. Therefore, how to monitor and identify satellite navigation interference signals and obtain the specific location of the interference source has gradually become a research hotspot in the field of satellite navigation security applications. At present, most of them use a single electromagnetic interference search device to monitor and identify interference signals, but the use of a single electromagnetic interference search device method has technical limitations, time and space limitations, and environmental limitations. Summary of the invention

[0004] The present invention aims to solve the technical problem that when a satellite navigation system is currently facing electromagnetic interference during operation, it is difficult to obtain the specific location of the interference source, and a single electromagnetic interference search device method has technical limitations, time and space limitations and environmental limitations. A method for finding and locating the interference source of a satellite navigation system is provided to solve the technical problem that when a satellite navigation system is currently facing electromagnetic interference during operation, it is difficult to obtain the specific location of the interference source, and a single electromagnetic interference search device method is used, which has technical limitations, time and space limitations and environmental limitations.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A method for finding and locating interference sources of a satellite navigation system, which is special in that it includes the following steps:

[0007] S1, interference source search

[0008] Monitor and analyze the interference source using the maximum signal method; if it is greater than the preset sensitivity of the maximum signal method direction finding device, execute step S2; otherwise, use the current position as the reference point, move the maximum signal method direction finding device, and use the maximum signal method to find the interference source until the detected interference source signal is greater than the preset sensitivity of the maximum signal method direction finding device, and execute step S2;

[0009] S2, interference source direction finding

[0010] Use the correlation interferometer to find the direction of the interference source. If the sensitivity requirement of the correlation interferometer direction finding is met, the correlation interferometer direction finding is used to obtain the initial wave direction. Otherwise, the maximum signal method is used to obtain the rough angle of the interference source, and this direction is used as the initial wave direction.

[0011] S3, interference source location

[0012] S3.1, according to the initial wave direction, the maximum signal method and the correlation interferometer direction finding method are combined to obtain the accurate interference wave direction, and according to the accurate interference wave direction, the first monitoring station is arranged at the position where the correlation interferometer is located at this time;

[0013] S3.2, on two straight lines with an angle of 30° with the reference direction, respectively arrange a second monitoring station and a third monitoring station, and determine whether the interference signals monitored by the three monitoring stations are the same signal by using the signal feature comprehensive identification direction finding technology. If so, execute step S3.3; otherwise, find the same interference signal by using the in-band power, amplitude value, modulation mode, frequency information, azimuth information, and interference occurrence time information, and then execute step S3.3;

[0014] S3.3, move the first monitoring station toward the reference direction, use the relevant interferometer to measure the direction, and the second and third monitoring stations move toward the reference direction along two straight lines with an angle of 30° with the reference direction respectively, and obtain the positioning area information through direction finding cross-positioning, until the positioning area is at the inner center of the triangle formed by the three monitoring stations as vertices. The positioning area is the location of the interference source.

[0015] Further, in step S3.1, the moving maximum signal method direction finding device and using the maximum signal method to find the interference source are specifically:

[0016] Move the maximum signal method direction finding device in eight directions: up, down, left, right, upper right, upper left, lower right and lower left respectively, and simultaneously observe the spectrum characteristic information and power information of the interference source signal, and use the maximum signal method to find the interference source.

[0017] Furthermore, the step S3.1 is specifically as follows:

[0018] Move the correlation interferometer to gradually approach the initial incoming wave direction. At the same time, use the correlation interferometer to perform direction finding, and use the maximum signal method to calibrate the direction finding until the output direction finding angle information fluctuation remains within a preset error range, thereby obtaining an accurate interference wave direction. Using the accurate interference wave direction as the reference direction, arrange the first monitoring station at the location of the correlation interferometer.

[0019] Furthermore, the direction finding technology is used to comprehensively identify signal characteristics to determine whether the interference signals monitored by the three monitoring stations are the same signal, specifically:

[0020] At the three monitoring stations, the in-band power, amplitude value, modulation mode, frequency information and azimuth information of the interference source signal are identified through the signal feature comprehensive identification and direction finding technology. If they are the same, the three monitoring stations monitor the same signal; otherwise, the three monitoring stations monitor different signals.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. Based on the existing spectrum monitoring means and direction-finding algorithms, combined with the complexity of the causes of electromagnetic interference in satellite navigation and the application limitations of electromagnetic interference search equipment (including technical limitations, time and space limitations, and environmental limitations, etc.), the present invention proposes a method for searching and locating interference sources, which can quickly monitor, identify, search, and locate satellite navigation interference.

[0023] 2. The present invention adopts a method combining the maximum signal method with the correlation interferometer direction finding. Since the maximum signal method uses a high-gain antenna, the system sensitivity is high and can meet the monitoring and direction finding of weak signals, but the direction finding accuracy is low. Since the correlation interferometer direction finding uses an omnidirectional antenna unit, the system sensitivity is low, but the direction finding accuracy is high and the direction finding speed is fast. Therefore, the combined method can avoid the shortcomings of using any one method alone and can realize rapid monitoring and direction finding of weak interference signals.

[0024] 3. In the present invention, when confirming the accurate direction of the interference signal, the signal feature comprehensive identification direction finding technology is first used to confirm whether the three monitoring stations are monitoring the same signal, thereby avoiding initial errors in the monitoring process and affecting subsequent monitoring judgments.

[0025] 4. The present invention adopts a method of co-positioning three monitoring sites, which makes the monitoring accuracy higher and avoids misjudgment caused by single monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A schematic diagram of a flow chart of an embodiment of the present invention;

[0027] Figure 2 Schematic diagram of the coordinated positioning of three stations in a Y-shaped arrangement in an embodiment of the present invention;

[0028] Figure 3 Schematic diagram of multiple cross-positioning coordinated by three stations in an embodiment of the present invention. DETAILED DESCRIPTION

[0029] The technical solution of the present invention will be clearly and completely described below in combination with the embodiments of the present invention and the accompanying drawings. Obviously, the described embodiments are not limitations of the present invention.

[0030] The present invention proposes a method for finding and locating interference sources of a satellite navigation system. In order to improve the direction-finding capability of weak signals, the maximum signal method direction-finding and the correlation interferometer direction-finding are combined. When the device finds interference, the approximation method is used to confirm the accurate direction of the interference source. When it is confirmed that there is no problem with the signal direction, a device is fixed at this point to perform interference source direction-finding. The other two sets of equipment perform direction-finding forward along the two forks of the Y. When the intersection formed by the direction-finding of the three sets of equipment is near the inner center of the triangle with the three sets of equipment as vertices, the direction-finding result is relatively accurate, and the direction-finding positioning is completed. To ensure that the three monitoring stations are cross-positioning the direction finding for the same interference source during the direction finding and positioning process, the direction finding technology based on the maximum signal method and the correlation interferometer direction finding is combined. The maximum signal method is to control the antenna to rotate and measure 360° at a certain degree interval, and compare the direction at which the amplitude of the signal is the largest. This direction is the direction of the interference source obtained by the maximum signal method. In this process, the spectral characteristics of the interference signal of the interference source can be obtained. Although the correlation interferometer direction finding has high direction finding accuracy, its principle is to use the phase relationship generated by the time difference between the interference source signal reaching different antenna array elements in the antenna array with a fixed spacing to determine the direction of the radio signal, and it is impossible to obtain spectral characteristic information. The signal feature comprehensive recognition algorithm is used to identify and compare the characteristic parameters of the interference signal such as the in-band power, amplitude value, modulation mode, etc., to determine whether the direction finding cross-positioning is performed for the same interference source.

[0031] In general, the indicators for measuring the quality of the received signal of the satellite navigation terminal include the signal-to-noise ratio SNR and the carrier-to-noise ratio CNR. The indicators for measuring the interference intensity of the satellite navigation terminal include the interference-to-noise ratio JNR, the interference-to-signal ratio JSR and the interference-to-signal-to-noise ratio JSNR. In practical applications, it is generally judged by the above indicators whether the satellite navigation terminal is interfered by the electromagnetic interference signal. Some basic concepts involved in the present invention are explained as follows:

[0032] 1. The working principle of the interference detection receiver

[0033] Suppression interference increases the noise power of the tracking loop by transmitting high-power signals, which will cause the power spectrum density curve of the intermediate frequency signal to be distorted. Since the intermediate frequency signal is more sensitive to such high-power signals, and since the intermediate frequency signal has not yet been despread and processed, the characteristics of the interference signal can be estimated more accurately. Therefore, at the intermediate frequency signal stage, a suppression interference detection receiver is used in combination with a suppression interference identification algorithm, and frequency domain and time-frequency analysis methods are used to identify the interference signal and estimate its characteristic parameters, including frequency, power, bandwidth, modulation mode, period, duty cycle, etc.

[0034] 2. Working principle of deception interference detection receiver

[0035] There are certain differences between spoofed signals and real signals in certain specific attributes, including signal arrival angle, position information, time information, pseudorange, signal-to-noise ratio, signal power, navigation message, Doppler frequency shift, etc. Since the influence of spoofing interference on the intermediate frequency signal is not obvious, but the spoofing delay will cause the characteristic phenomenon of correlation curve distortion and navigation solution anomaly, the spoofing interference detection receiver is combined with the spoofing interference identification algorithm to identify the interference signal and estimate the characteristic parameters.

[0036] 3. Working principle of maximum signal method and correlation interferometer direction finding receiver

[0037] In order to improve the direction finding capability of weak signals, the maximum signal method and the correlation interferometer direction finding are used to find the direction of interference signals. The maximum signal method uses a high-gain antenna, so the system sensitivity is high and can meet the monitoring and direction finding of weak signals, but the direction finding accuracy is low; the correlation interferometer direction finding uses an omnidirectional antenna unit, so the system sensitivity is low, but the direction finding accuracy is high and the direction finding speed is fast. The combination of the two can realize the rapid monitoring and direction finding of weak interference signals.

[0038] 4. Principle of distributed multi-station collaborative cross-positioning method

[0039] By measuring the incident angle of the signal from the interference source to each monitoring station, ideally, three rays starting from the monitoring station and with the arrival angle as the direction intersect in a limited area, which is the area where the interference source target is located.

[0040] It is suitable for locating interference sources of various bandwidth systems, but its defect is that after the wave direction of each monitoring station is determined, the positioning error increases with the distance from the interference source. Therefore, in practical applications, the Y-shaped station layout is often used to cross-locate the interference source to reduce the influence of the distance factor from the interference source on the positioning error.

[0041] In order to realize the positioning method of the present invention, relevant equipment can be first built, including a deception interference detection receiver, a suppression interference detection receiver, a correlation interferometer detection direction finding receiver and a maximum signal method monitoring direction finding receiver. The deception interference detection receiver and the suppression interference detection receiver respectively perform detection through their own receiving antennas. The deception interference detection receiver and the suppression interference detection receiver are both installed nearby on the corresponding mobile carrier platform. The related interferometer detection direction finding receiver is connected to the related interferometer direction finding antenna array. The maximum signal method monitoring direction finding receiver is connected to a high-gain antenna. The deception interference detection receiver, the suppression interference detection receiver, the correlation interferometer detection direction finding receiver and the maximum signal method monitoring direction finding receiver are each installed on a mobile carrier platform. The four devices are independent of each other. During the positioning process, the detected data is fused and processed at the back end.

[0042] like Figure 1 The specific steps of the positioning method of the present invention are as follows:

[0043] First, the received interference signal is detected for interference existence. When it is determined that the satellite navigation terminal is interfered with, a deception interference detection receiver and a suppression interference detection receiver are used in combination with a deception interference detection algorithm and a suppression interference detection algorithm to determine whether the interference source is deception interference or suppression interference.

[0044] After determining whether the interference to the satellite navigation receiver is deception interference or suppression interference, if it is deception interference, the type, power, arrival angle and other information of the deception interference are analyzed; if it is suppression interference, the interference signal format, power, center frequency, bandwidth and other information are analyzed.

[0045] Then, the maximum signal method is used to monitor and analyze the interference signal. If an obvious interference source signal can be found, the maximum signal method and the related interferometer direction finding method are used to find the direction of the interference source to obtain the accurate azimuth information of the interference source. The obvious interference source signal here depends on the detection sensitivity of the equipment used, for example, 20dB higher than the equipment detection sensitivity. If no obvious interference signal can be found using the maximum signal method, the interference source search stage is entered. Taking the current position as the reference point, according to the actual situation, the maximum signal method direction finding device is moved in eight directions, namely up, down, left, right, upper right, upper left, lower right, and lower left. During the movement, the spectral characteristic information and power and other information of the interference signal are continuously observed, and the interference source is searched using the maximum signal method until the obvious interference source signal can be successfully found using the maximum signal method. Then, the maximum signal method direction finding and the related interferometer direction finding combined direction finding process is entered to obtain the accurate azimuth information of the interference source. In an actual environment, due to factors such as the local terrain, it may not be possible to move in the eight directions of up, down, left, right, upper right, upper left, lower right, and lower left. In this case, you can move to search for signals according to the actual site conditions.

[0046] The maximum signal method uses a high-gain antenna, so the system sensitivity is high and can meet the monitoring and direction finding of weak signals, but the direction finding accuracy is low; the correlation interferometer direction finding uses an omnidirectional antenna unit, so the system sensitivity is low, but the direction finding accuracy is high and the direction finding speed is fast. The combination of the two can realize the rapid monitoring and direction finding of weak interference signals.

[0047] The interference signal is directed using a correlation interferometer. If the requirements for direction finding of the correlation interferometer are met, the initial wave direction is obtained using the correlation interferometer direction finding, and the initial wave direction is gradually approached. The correlation interferometer is continuously used for direction finding until the output direction finding angle information is stable. The stability here can be adjusted according to the specific situation. The evaluation standard for stability, for example, the equipment direction finding sensitivity is ≤2° (RMS), the results of multiple direction finding should fluctuate within -2 to +2°, and accurate interference wave direction information is output; if the requirements for direction finding of the correlation interferometer are not met at the beginning, the maximum signal method is used to obtain the rough angle of the interference signal, and this direction is used as the initial direction. The method of stepwise approximation is used to gradually move the correlation interferometer direction finding device toward the initial direction, and the correlation interferometer is continuously used for direction finding. At the same time, the maximum signal method direction finding is used for auxiliary calibration. The calibration here refers to the comparison of the interference signal wave directions given by the two devices to ensure that the approximate directions are consistent and mutually verified until the output direction finding angle information is stable and accurate interference wave direction information is output.

[0048] While performing joint direction finding using the maximum signal method and the correlation interferometer direction finding, the signal feature comprehensive identification direction finding technology is used to ensure that the same interference source is being targeted during the direction finding and positioning process.

[0049] At multiple monitoring sites, the maximum signal method direction finding and the correlation interferometer direction finding are used together with the direction finding equipment to obtain relevant information such as the spectral characteristics of the interference source. The signal feature comprehensive recognition algorithm is used to automatically identify and compare the signal's in-band power, amplitude value, modulation mode, frequency information, azimuth information and other characteristic parameters to determine whether the direction finding and positioning is for the same interference source. If the information monitored by each monitoring site is basically the same, it is considered to be the same signal.

[0050] like Figure 2 and Figure 3 When the device finds interference, first, the maximum signal method is used to perform rough direction finding on the interference source position, and the direction of the interference source obtained by the maximum signal method is gradually approached. The direction finding is gradually carried out by using the correlation interferometer direction finding. The process of approaching confirmation is the vertical line of the letter Y in the Y-shaped station arrangement. The judgment principle of the approximation method is that the closer the distance to the signal source, the greater the signal reception strength, and the more accurate the direction finding accuracy. When it is confirmed that there is no problem with the signal direction, it is equivalent to reaching the middle point of the letter Y in the Y-shaped station arrangement. The direction finding angle of the interference source obtained at this time is used as the reference direction. At this time, the monitoring station at this position is named the first monitoring station. The layout movement routes of the other two second monitoring stations and the third monitoring station are arranged according to the principle of 30° angles with the reference direction, and the direction finding is cross-positioned to obtain the positioning area information. The angle is set to 30° so that the three monitoring stations can form an equilateral triangle during the cross positioning process.

[0051] Then move the first monitoring station toward the reference direction, and use the relevant interferometer to measure the direction again. The movement routes of the second and third monitoring stations are arranged at an angle of 30° to the direction of the current monitoring station 1, and cross-positioning is performed to obtain the positioning area information.

[0052] Move the position several times and repeat the above process until the positioning area is relatively stable, and then a more accurate interference source location can be obtained. When the intersection area formed by the three sets of equipment is near the inner center of the triangle with the three sets of equipment as vertices (i.e. Figure 3 The direction finding result is relatively accurate.

[0053] After the initial positioning of multi-station collaborative cross-positioning, the position of the first monitoring station is moved towards the reference direction, and the direction is repeatedly measured using the relevant interferometer. As the distance to the interference source approaches, the positioning becomes more accurate.

[0054] The above descriptions are merely embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings, or directly or indirectly applied in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A method for finding and locating interference sources in a satellite navigation system, characterized in that: The steps include: S1, interference source search Monitor and analyze the interference source using the maximum signal method; if it is greater than the preset sensitivity of the maximum signal method direction finding device, execute step S2; otherwise, use the current position as the reference point, move the maximum signal method direction finding device, and use the maximum signal method to find the interference source until the detected interference source signal is greater than the preset sensitivity of the maximum signal method direction finding device, and execute step S2; S2, interference source direction finding Use the correlation interferometer to find the direction of the interference source. If the sensitivity requirement of the correlation interferometer direction finding is met, the correlation interferometer direction finding is used to obtain the initial wave direction. Otherwise, the maximum signal method is used to obtain the rough angle of the interference source, and this direction is used as the initial wave direction. S3, interference source location S3.1, move the correlation interferometer to gradually approach the initial incoming wave direction, and at the same time, use the correlation interferometer to perform direction finding, and use the maximum signal method to calibrate the direction finding, until the output direction finding angle information fluctuation is maintained within a preset error range, and the accurate interference wave direction is obtained, and the first monitoring station is arranged at the location of the correlation interferometer with the accurate interference wave direction as the reference direction; S3.2, on two straight lines with an angle of 30° with the reference direction, respectively arrange a second monitoring station and a third monitoring station, and determine whether the interference signals monitored by the three monitoring stations are the same signal by using the signal feature comprehensive identification direction finding technology. If so, execute step S3.3; otherwise, find the same interference signal by using the in-band power, amplitude value, modulation mode, frequency information, azimuth information, and interference occurrence time information, and then execute step S3.3; S3.3, move the first monitoring station toward the reference direction, use the relevant interferometer to measure the direction, and the second and third monitoring stations move toward the reference direction along two straight lines with an angle of 30° with the reference direction respectively, and obtain the positioning area information through direction finding cross-positioning, until the positioning area is at the inner center of the triangle formed by the three monitoring stations as vertices. The positioning area is the location of the interference source.

2. A method for finding and locating interference sources in a satellite navigation system as claimed in claim 1, characterized in that: In step S1, the device for finding the direction using the maximum signal method is moved to find the interference source using the maximum signal method, specifically: Move the maximum signal method direction finding device in eight directions: up, down, left, right, upper right, upper left, lower right and lower left respectively, and simultaneously observe the spectrum characteristic information and power information of the interference source signal, and use the maximum signal method to find the interference source.

3. A method for finding and locating interference sources in a satellite navigation system as claimed in claim 1, characterized in that: In step S3.2, the signal feature comprehensive identification direction finding technology is used to determine whether the interference signals monitored by the three monitoring stations are the same signal, specifically: At the three monitoring stations, the in-band power, amplitude value, modulation mode, frequency information and azimuth information of the interference source signal are identified through the signal feature comprehensive identification and direction finding technology. If they are the same, the three monitoring stations monitor the same signal; otherwise, the three monitoring stations monitor different signals.

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