An electromagnetic interference localization method applicable to medium and high Earth orbit satellites

Abstract

The present application discloses an electromagnetic interference positioning method applicable to medium and high-orbit satellites. The positioning method includes: Step 1, determining the satellite under interference according to the electromagnetic monitoring results in the satellite system; Step 2, calculating the global map coverage matrix according to the coverage range of the satellite under interference, summing up the global map coverage matrix, and selecting the region corresponding to the largest element in the global map coverage matrix after summation as the initial positioning region; Step 3, in a traversing manner, sequentially determining whether there are three or more satellites in co-visibility within the selected initial positioning region. If so, execute Step 4. Otherwise, re-obtain the electromagnetic monitoring results in the satellite system and execute Step 1; Step 4, performing multi-satellite time difference positioning according to the electromagnetic monitoring results of the co-visible satellites and calculating the positioning coordinates of the interference source. Through the technical solution in the present application, the monitoring and positioning of high-power interference sources on the ground are realized, thereby improving the security of the uplink of the satellite system.

Description

Technical Field

[0001] This application relates to the technical field of electronic reconnaissance and countermeasure. Specifically, it relates to an electromagnetic interference localization method applicable to medium and high earth orbit satellites. Background Art

[0002] The medium and high earth orbit multi-station electronic system is used to receive and measure the parameters of signals emitted by long-term existing and high-power threat interference sources on the ground, form monitoring data and intermediate frequency data, and then perform processing such as localization and interference source identification to provide support for eliminating the influence of interference.

[0003] Interference source localization is an important link in the processing of this system. The success rate and accuracy of localization are directly related to the processing effect of interference source localization. An effective and high-success-rate localization processing method is one of the core technologies of this system.

[0004] Modern advanced electronic radiation sources have the characteristics of multi-attribute parameter agility. However, no matter how the parameters change, once radiated, if they can be received by a multi-station localization electronic reconnaissance system, the sequence and structure of the pulse stream remain unchanged. That is to say, the sequence and structure of the pulse stream of the same electronic radiation source received by the electronic reconnaissance equipment at each station are exactly the same, only offset in time. Within a small observation window time, the offset value can be approximately regarded as a fixed value. Therefore, since the electronic radiation source cannot generate position or azimuth agility within a small observation window time, the time difference of arrival (TDOA) of the same pulse reaching each station cannot change.

[0005] Due to this characteristic, the multi-station localization electronic reconnaissance system can effectively separate the pulse signals of different radiation sources from the pulse signals, and then realize further interference source localization processing such as localization and radiation source identification.

[0006] In the prior art, the objects of interference source localization are limited to high-power interference sources that exist on the ground surface for a long time, and the constraints in aspects such as constellation configuration, on-board resources, and data transmission are not considered, resulting in limited localization duration and localization accuracy of current interference source localization. Summary of the Invention

[0007] The purpose of this application is to solve the problem of limited interference source localization duration and localization accuracy in the medium and high earth orbit multi-station electronic system, and adopt a localization system mainly based on multi-satellite beam coverage localization and supplemented by time difference localization. First, use multi-satellite beam coverage localization to determine the interference source frequency band and approximate location; then, select three satellites with co-visibility conditions, conduct constellation mission planning, collect intermediate frequency data, and use the time difference system for precise localization.

[0008] The technical solution of this application is: A method for electromagnetic interference positioning applicable to medium and high orbit satellites is provided. The electromagnetic interference positioning method includes: Step 1, determining the satellite under interference according to the electromagnetic monitoring results in the satellite system; Step 2, calculating the global map coverage matrix according to the coverage range of the satellite under interference, summing the global map coverage matrix, and selecting the area corresponding to the largest element in the global map coverage matrix after summation as the initial positioning area; Step 3, in a traversing manner, sequentially determining whether there are three or more satellites in co - view within the selected initial positioning area. If so, execute Step 4; otherwise, re - obtain the electromagnetic monitoring results in the satellite system and execute Step 1; Step 4, performing multi - satellite time - difference positioning according to the electromagnetic monitoring results of the co - view satellites, and calculating the interference source positioning coordinates, where the co - view satellites are the satellites in co - view within the initial positioning area.

[0009] In any of the above - mentioned technical solutions, further, calculating the global map coverage matrix in Step 2 specifically includes: Step 21, expanding the global map into a two - dimensional map according to longitude, latitude and a preset interval, and performing grid - division. According to the grid - divided two - dimensional map, generating an initial global map coverage matrix, where the elements in the initial global map coverage matrix take the value of 0; Step 22, calculating the distances between the satellite under interference and the central positions of each grid in the grid - divided two - dimensional map according to the coverage range of the satellite under interference; Step 23, when it is determined that the distance is less than or equal to the satellite - to - ground limit distance, assigning the value of 1 to the element in the corresponding initial global map coverage matrix to calculate the global map coverage matrix.

[0010] In any of the above - mentioned technical solutions, further, the calculation formula for multi - satellite time - difference positioning in Step 4 is:

[0011]

[0012] In the formula, Δt i is the time - difference between the interference source signal reaching the main satellite and the i - th secondary satellite of the interference source. The main satellite is any one of the co - view satellites, and the secondary satellites are the remaining co - view satellites except the main satellite. X = [x y z] T is the interference source positioning coordinate, X0 = [x0 y0 z0] T is the position of the main satellite, X i = [x i y i z i T is the position of the i - th secondary satellite, P is the number of secondary satellites, c is the electromagnetic wave propagation speed, and ||·|| is the norm function.

[0013] In any of the above - mentioned technical solutions, further, Step 4 further includes:

[0014] ​Step 41: Perform discrete Fourier transform on the interference signals received by the master satellite and the slave satellite, and calculate the cross-spectrum parameters of the interference signals received by the master satellite and the slave satellite after discrete Fourier transform. The calculation formula for the cross-spectrum parameters is as follows:

[0015]

[0016] In the formula, k is the discrete point, [·] is the integer function, and N is the total number of discrete points;

[0017] Step 42: Perform inverse Fourier transform on the cross-spectrum parameters to calculate R 12 (τ), and the corresponding calculation formula is:

[0018]

[0019] In the formula, R 12 (τ) is the inverse Fourier transform parameter of the cross-spectrum parameter, f k is the radio frequency corresponding to the digital frequency of the kth discrete point after DFT discrete Fourier transform, and τ is the reference time difference;

[0020] Step 43: Select the reference time difference corresponding to the maximum value of R 12 (τ), and record it as the time difference between the interference source signal reaching the master satellite and the slave satellite.

[0021] In any of the above technical solutions, further, calculating the time difference between the interference source signal reaching the master satellite and the slave satellite specifically further includes:

[0022] When it is determined that the signal-to-noise ratio is less than the preset threshold, according to the preset power threshold, select the discrete points with cross-spectrum parameters greater than the preset power threshold to form a set of stronger frequency points K I , and the corresponding calculation formula is:

[0023]

[0024] In the formula, γ0 is the preset power threshold;

[0025] According to the set of stronger frequency points K I , calculate the inverse Fourier transform parameter R 12 (τ) of the cross-spectrum parameter, and the corresponding calculation formula is:

[0026]

[0027] In any of the above technical solutions, further, the electromagnetic interference localization method further includes: Step 5: According to a preset distance error, compare the calculated interference source localization coordinates with the known interference source position coordinates in the interference knowledge base. When it is determined that the distance error between the calculated interference source localization coordinates and the known interference source position coordinates in the interference knowledge base is less than or equal to the preset distance error, use the known interference source position coordinates as the matching result; otherwise, use the calculated interference source localization coordinates as the matching result, and use the calculated interference source localization coordinates as the new known interference source position coordinates to update the interference knowledge base.

[0028] The beneficial effects of this application are as follows:

[0029] In the technical solution of this application, under the condition of satisfying the co-visibility of three or more satellites, based on the electromagnetic monitoring results transmitted by multiple satellites, multi-satellite beam analysis is carried out. The time difference is obtained by using the correlation method for the intermediate frequency data transmitted back by the co-visible satellites, and the interference source position is calculated based on the time difference, thereby realizing the monitoring and localization of high-power interference sources on the ground surface, and further enhancing the security of the uplink of the satellite system.

[0030] The technical solution in this application is based on the existing satellite resources, without major changes to the current satellite positioning system state, does not affect the normal operation of the core functions and services of the satellite, can efficiently locate the interference sources in the satellite system, reasonably utilizes resources, improves the positioning accuracy, and shortens the positioning duration.

[0031] In the preferred implementation manner of this application, in order to improve the positioning accuracy of multi-station in medium and high orbits, using the broadband characteristics of the signal, according to the relative phase relationship of two signals at different frequency components, through comprehensive processing, an estimated value of the time difference is obtained to be used as the time difference between the interference signal of the interference source reaching the main satellite and the i-th sub-satellite during the multi-satellite time difference positioning process.

[0032] Especially when the signal-to-noise ratio is small, a preset power threshold is introduced, the cross-spectrum parameters are selected to form a stronger frequency point set, and then the time difference between the interference signal of the interference source reaching the main satellite and the sub-satellite is estimated according to the selected stronger frequency point set to ensure the reliability and positioning accuracy of the interference source localization. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The above and / or additional advantages of this application will become obvious and easy to understand when combined with the description of the embodiments with the following drawings, where:

[0034] Figure 1 is a schematic flowchart of an electromagnetic interference localization method applicable to medium and high orbit satellites according to an embodiment of this application;

[0035] Figure 2 is a schematic diagram of the positioning principle according to an embodiment of this application;

[0036] Figure 3 Schematic diagram of the space - ground limit distance according to an embodiment of the present application;

[0037] Figure 4 Schematic diagram of multi - satellite time difference positioning according to an embodiment of the present application. Detailed implementation manners

[0038] In order to more clearly understand the above - mentioned objects, features and advantages of the present application, the present application will be further described in detail below in conjunction with the accompanying drawings and specific implementation manners. It should be noted that, without conflict, the embodiments of the present application and the features in the embodiments can be combined with each other.

[0039] In the following description, many specific details are set forth to fully understand the present application. However, the present application can also be implemented in other ways different from those described herein. Therefore, the protection scope of the present application is not limited by the specific embodiments disclosed below.

[0040] As Figure 1 and Figure 2 shown, this embodiment provides an electromagnetic interference positioning method applicable to medium - and high - orbit satellites. This electromagnetic interference positioning method performs joint processing based on multi - satellite beam coverage and time difference positioning, realizing the monitoring and positioning of high - power electromagnetic interference sources on the ground.

[0041] Assume that the satellites can monitor the same interference source at times t0, t1, t2, …. (such as Figure 2 indicated by the asterisk). At time t0, the beam coverage range of satellite A is area 101, and the beam coverage range of satellite B is area 103; at time t1, the beam coverage range of satellite A becomes area 102, and the beam coverage range of satellite B becomes area 104. Therefore, through the change of the satellite beam coverage range, the possible area of this interference source ( Figure 2 the shaded part in) will gradually shrink to achieve the positioning effect.

[0042] The positioning method in this embodiment is simple to implement. Multiple satellites respectively transmit their electromagnetic environment monitoring data back to the ground, and the ground performs comprehensive processing. Through accumulation over a period of time, the position of the interference source is found. This method includes:

[0043] Step 1, determine the interfered satellite according to the electromagnetic monitoring results in the satellite system;

[0044] Specifically, assume that within a certain time period T of the satellite system, interference occurs at frequency f. According to the frequency and pattern of the satellite signal, retrieve the electromagnetic monitoring results of multiple satellites in the satellite system from the data archive library, and find the satellite i that detects the interference signal and the interference time t, where i = 1, …, S and t = 1, …, T.

[0045] In this embodiment, the electromagnetic monitoring results include monitoring result data, intermediate frequency data of interference samples, and satellite broadcast ephemeris information. When determining the interfered satellite, according to the set polling period, regularly poll to detect whether there are new data files in the data archive library, and parse the new data files classified according to the formats of the monitoring result data and the intermediate frequency data of interference samples to remove duplicate and invalid data; at the same time, calculate the satellite ephemeris data according to the satellite orbital elements with a time resolution.

[0046] Step 2: Conduct multi-satellite beam coverage positioning processing. According to the coverage range of the interfered satellite, calculate the global map coverage matrix, sum the global map coverage matrix, perform multi-satellite beam coverage positioning, and select the area corresponding to the largest element in the global map coverage matrix after summation as the initial positioning area to determine the approximate location of the interference source.

[0047] Further, the calculation of the global map coverage matrix in step 2 specifically includes:

[0048] Step 21: Expand the global map into a two-dimensional map according to the longitude and latitude and a preset interval, and perform grid division. Generate an initial global map coverage matrix based on the grid-divided two-dimensional map, where the values of the elements in the initial global map coverage matrix are 0.

[0049] Step 22: Calculate the distances between the interfered satellite and the center positions of each grid in the grid-divided two-dimensional map according to the coverage range of the interfered satellite.

[0050] Step 23: When it is determined that the distance is less than or equal to the satellite-earth limit distance, assign the value of 1 to the element in the corresponding initial global map coverage matrix of the distance to calculate the global map coverage matrix.

[0051] Specifically, as Figure 3 shown, expand the global map into a two-dimensional map according to the longitude and latitude and a preset interval, and perform grid division. The X-axis is the longitude and the Y-axis is the latitude, then the earth's surface is divided into K×K uniform grids, and each grid (n, m) represents the corresponding position on the earth's surface.

[0052] Therefore, at the interference time t, based on the above-selected interfered satellite i, i = 1, …, S, the global map coverage matrix of the i-th satellite can be calculated The definition of its elements is:

[0053]

[0054]

[0055] Wherein, d(n,m) is the distance between the center position of the grid (n,m) and the satellite i at time t, d max is the satellite-earth limit distance, R e is the radius of the earth, and H is the vertical distance between the satellite and the earth's surface.

[0056] Furthermore, by using the method of cumulative summation, the global map coverage matrix within the time period T is statistically calculated for multi-satellite beam coverage positioning, and the corresponding calculation formula is:

[0057]

[0058] Wherein, C Ts is the global map coverage matrix after summation, C TS ∈R K×K .

[0059] In this embodiment, by calculating the global map coverage matrix of the satellite i at the interference time t, the beam coverage range matrix of the interference signal received by the satellite i can be matrixed. Then, through matrix summation, for the matrix sum value C TS search can be carried out to find out the maximum element c TS in the global map coverage matrix C max after summation, that is, the area with the highest coincidence degree of the beam coverage range. This area is the possible location of the interference source, denoted as the initial positioning area.

[0060] It should be noted that because the beam coverage range of the satellite is large, and the number of satellites in the satellite system is large and their operating parameters are inconsistent, therefore, there can be multiple such initial positioning areas.

[0061] Step 3: In a traversing manner, sequentially determine whether three or more satellites are in co-visibility within the selected initial positioning area. If so, execute Step 4; otherwise, re-obtain the electromagnetic monitoring result in the satellite system and execute Step 1;

[0062] In this embodiment, satellite co-visibility means that a certain area is the overlapping area of the beam coverage ranges of two or more satellites. Assuming that the position of the ground interference source is P(x,y,z), the earth model adopts the average ellipsoid model, and the three satellites participating in the interference positioning are A, B, and C respectively. At the interference source positioning moment, the positions of the three satellites are:

[0063] P A (x a ,y a ,z a ),PB (x b ,y b ,z b ),P C (x c ,y c ,z c )

[0064] The positioning model of the Samsung time difference positioning system is as follows:

[0065]

[0066] Where τ ab is the time difference of arrival measured by satellites A and B for the interference source, τ ac is the time difference measured by satellites A and C for the interference source, c is the speed of light, a is the semi-major axis of the earth, and b is the semi-minor axis of the earth.

[0067] Therefore, as long as the positions of satellites A, B, and C and the two time difference values are known, and the positioning model is solved, the position of the interference source on the ground surface can be estimated. The positioning model can be solved by methods such as Newton descent, and the specific process will not be elaborated here. Therefore, at least three satellites are required for time difference positioning of high-power interference sources on the ground surface.

[0068] Step 4: According to the electromagnetic monitoring results of the common-view satellites, perform multi-satellite time difference positioning and calculate the positioning coordinates of the interference source, where the common-view satellites are the satellites that are in common view within the initial positioning area.

[0069] Specifically, according to the positioning results of the initial positioning area, analyze the satellite status of the monitoring data to determine whether the condition of three or more satellites in common view is satisfied. If the condition is satisfied, carry out multi-satellite time difference positioning processing, use the correlation method to calculate the time difference for the intermediate frequency data transmitted back by the common-view satellites, and determine the precise position of the interference source based on the time difference.

[0070] Since the path lengths from a ground target to different satellites are different, the arrival times of the target interference signals received by the satellites are different, resulting in a time difference of arrival TDOA (Time Difference of Arrival). This time difference TDOA is related to the target position and the satellite's own position. When the satellite's own position is known, the target (interference source) position can be solved by measuring the time difference.

[0071] Assume that the target position is fixed, and its position to be located is X = [x y z] T , which is the positioning coordinate of the interference source, and the position of the main satellite is X0 = [x0 y0 z0] T , and the position of the i-th secondary satellite is X i = [x i y i zi T (i = 1, …, P), where P is the number of slave satellites among the co-visible satellites, and the time difference between the arrival of the target interference signal at the master satellite and the slave satellites is Δt i , then the calculation formula for multi-satellite time difference positioning, that is, the relationship between the time difference and the target position and satellite position is:

[0072]

[0073] In the formula, Δt i is the time difference between the arrival of the interference signal at the master satellite and the i-th slave satellite. The master satellite is any one of the co-visible satellites, and the slave satellites are the remaining co-visible satellites except the master satellite. X = [x y z] T is the positioning coordinate of the interference source, X0 = [x0 y0 z0] T is the position of the master satellite, X i = [x i y i z i T is the position of the i-th slave satellite, P is the number of slave satellites, c is the propagation speed of electromagnetic waves, that is, the speed of light; ||·|| is the norm function, which is used to calculate the time when the interference source signal arrives at the satellite (master satellite or slave satellite). Subtracting the two norms gives the time difference between the signal arriving at the two satellites.

[0074] It should be noted that the master satellite is any one of the above co-visible satellites, and the slave satellites are the remaining co-visible satellites except the master satellite.

[0075] Assume that the Earth is approximately an ellipsoid with a semi-major axis radius of R e , satisfying: Solving the above equations can obtain the position of the ground interference source.

[0076] It can be seen from the above formula that the i-th time difference equation determines an equi-time difference hyperboloid in space, and the target is located on this surface. If the target is located on the Earth's surface, then the target is located on the intersection line of this surface and the Earth's surface, and this intersection line is called the time difference position line. The intersection point of multiple position lines is the position where the interference source is located. Theoretically, only two position lines are required to achieve positioning, that is, at least two groups of time differences need to be measured.

[0077] As Figure 4 shown, the curves in the figure are the position lines corresponding to two groups of time differences respectively. The hyperbola shown by the dashed line is the position line corresponding to one group of time differences, and the hyperbola shown by the solid line is the position line corresponding to the other group of time differences. There are two intersection points between the two time difference position lines, one is the position of the target interference source (the position where the asterisk is located), and the other is a false point.

[0078] ​​On the basis of the above embodiments, in order to improve the positioning accuracy of multi-station in medium and high orbits, this embodiment also shows a method for estimating the time difference of the interference signal of the interference source arriving at the main satellite and the deputy satellite. By mainly using the broadband characteristics of the signal and according to the relative phase relationship of the two signals at different frequency components, an estimated value of the time difference is obtained through comprehensive processing, so as to be used as the time difference Δt of the interference signal of the interference source arriving at the main satellite and the i-th deputy satellite during the multi-satellite time difference positioning process. i . The time difference estimation method specifically includes:

[0079] Step 41: Perform discrete Fourier transform on the interference signal received by the main satellite and the interference signal received by the deputy satellite, and calculate the cross-spectrum parameter of the interference signals received by the main satellite and the deputy satellite after discrete Fourier transform. The calculation formula of the cross-spectrum parameter is:

[0080]

[0081] In the formula, k is the discrete point, [·] is the rounding function, and N is the total number of discrete points;

[0082] Step 42: Perform inverse Fourier transform on the cross-spectrum parameter X 12 (k), and calculate the inverse Fourier transform parameter R 12 (τ). The corresponding calculation formula is:

[0083]

[0084] In the formula, R 12 (τ) is the inverse Fourier transform parameter of the cross-spectrum parameter, f k is the radio frequency corresponding to the digital frequency of the k-th discrete point after DFT discrete Fourier transform, and τ is the reference time difference;

[0085] Step 43: Select the reference time difference corresponding to the maximum value of R 12 (τ), and record it as the time difference of the interference signal arriving at the main satellite and the deputy satellite.

[0086] Specifically, for any deputy satellite, the signal received by the main satellite is denoted as s1(t), and the signal received by the deputy satellite is denoted as s2(t) = p·s1(t + τ0), where p is the amplitude difference of the signal arriving at the main satellite and the deputy satellite. τ0 is the time difference between the signal arriving at the main satellite and the deputy satellite, that is, the time difference Δt i .

[0087] Performing Fourier transform on the two signals respectively, we can obtain:

[0088]

[0089]

[0090] Wherein, p is the amplitude difference between the signals arriving at the main satellite and the secondary satellite, and τ0 is the time difference between the signals arriving at the main satellite and the secondary satellite.

[0091] Performing cross-spectrum processing on the two signals gives:

[0092]

[0093] Combining the above cross-spectrum and performing inverse Fourier transform gives:

[0094]

[0095] Therefore, when the reference time difference τ = τ0, the inverse Fourier transform parameter R 12 (τ) of the cross-spectrum parameter reaches the maximum value.

[0096] Based on the above theoretical analysis, and considering that there is noise in general signals and its accuracy will be affected during actual processing, therefore, the outputs after A / D conversion of the above two signals are set as:

[0097]

[0098] Wherein, v1(n) is the noise of the signal s1(n), and v2(n) is the noise of the signal s2(n).

[0099] Performing N-point DFT (Discrete Fourier Transform) on the two digital signals respectively, we can obtain:

[0100]

[0101] Wherein, X1(k) is the discrete signal of the interference signal x1(n) received by the main satellite containing the noise v1(n), X2(k) is the discrete signal of the interference signal x2(n) received by the secondary satellite containing the noise v2(n), S1(k) is the discrete signal of the signal s1(n) received by the main satellite, S2(k) is the discrete signal of the signal s2(n) received by the secondary satellite, V1(k) is the discrete signal of the noise v1(n) received by the main satellite, and V2(k) is the discrete signal of the noise v2(n) received by the secondary satellite.

[0102] Through analysis, it can be seen that since the positive-frequency part spectrum and the negative-frequency part spectrum in the signal spectrum are the same after DFT (Discrete Fourier Transform), therefore, only the positive-frequency part spectrum after DFT (Discrete Fourier Transform) needs to be considered for time difference estimation, and the cross-spectrum parameter X 12 (k) can be obtained as:

[0103]

[0104] Wherein, k is the discrete point, [·] is the integer function, and N is the total number of discrete points.

[0105] The inverse Fourier transform is performed on the cross-spectrum parameters of the two signals, and the calculation formula for the corresponding inverse Fourier transform parameters is as follows:

[0106]

[0107] where f k is the RF frequency corresponding to the digital frequency of the k-th discrete point after the DFT discrete Fourier transform, and τ is the reference time difference.

[0108] Therefore, when R 12 (τ) reaches the maximum value, it is the time difference between the signals arriving at the two satellites, thereby realizing the estimation of the time difference for use as the time difference Δt i of the interference signal from the interference source arriving at the main satellite and the i-th secondary satellite during the multi-satellite time difference positioning.

[0109] Through analysis, it can be seen that the above high-precision time difference estimation method for broadband signals based on cross-spectrum can obtain a relatively accurate time difference estimation value when the signal-to-noise ratio is relatively high, thereby improving the measurement accuracy of interference positioning. However, for the case where the signal-to-noise ratio is not too high, the measurement accuracy will be affected.

[0110] Furthermore, by studying the phase distribution of the cross-spectrum, it is found that in the frequency spectrum segment with a stronger signal, the phase relationship is very stable and less affected by noise perturbations, while in the frequency spectrum segment with a weaker signal, the phase relationship is very unstable and more affected by noise perturbations.

[0111] Therefore, on the basis of the above embodiments, in the process of calculating the time difference between the interference signal arriving at the main satellite and the secondary satellite, it further includes: when it is determined that the signal-to-noise ratio is less than the preset threshold, according to the preset power threshold, discrete points with a cross-spectrum greater than the preset power threshold in the two signals are selected to form a set of stronger frequency points, and the corresponding calculation formula is:

[0112]

[0113] where γ0 is the preset power threshold, generally taken as 1.5 to 10 times the average power. When the signal bandwidth is relatively wide, the value of the preset power threshold γ0 should be taken as a smaller value.

[0114] According to the set of stronger frequency points, calculate the inverse Fourier transform parameter R 12 (τ) of the cross-spectrum parameter, and the corresponding calculation formula is:

[0115]

[0116] And select the reference time difference corresponding to the maximum value of R 12 (τ) and record it as the time difference between the interference source signal arriving at the main satellite and the secondary satellite. The specific process will not be elaborated here.

[0117] Furthermore, in order to uniformly manage the identified interference sources, an interference knowledge base is set up. The interference knowledge base stores the information of the identified known interference sources and their location coordinates. Therefore, after calculating the location coordinates of the interference sources, the coordinates are compared with the interference knowledge base. The electromagnetic interference location method further includes:

[0118] Step 5: Compare the location coordinates of the interference sources with the location coordinates of the known interference sources in the interference knowledge base according to a certain preset distance error. When it is determined that the distance error between the calculated location coordinates of the interference sources and the location coordinates of the known interference sources in the interference knowledge base is less than or equal to the preset distance error, the location coordinates of the known interference sources are used as the matching result. Otherwise, the calculated location coordinates of the interference sources are used as the matching result, and the calculated location coordinates of the interference sources are used as the new location coordinates of the known interference sources to update the interference knowledge base.

[0119] Through the simulation analysis of the electromagnetic interference location method in this embodiment, the earth's surface is divided into 18×9 grids, and three constellation configurations are adopted, namely: 3 geostationary orbits, 6 medium orbits, and 6 medium orbits + 3 geostationary orbits. The positioning interval time of the simulation analysis is 10 minutes / time, that is, within the visible area, the satellite can see the interference source once every ten minutes. The distribution data of the positioning errors for 8 hours, 12 hours, and 24 hours are respectively counted, and the positioning accuracy is shown in Table 1.

[0120] Table 1

[0121]

[0122] It can be seen from Table 1 that under the configuration of 6 medium orbits + 3 geostationary orbits, the average global positioning accuracies of the interference sources for 12 hours and 24 hours are 79.42 km and 35.29 km respectively, and with the extension of the positioning time, the positioning accuracy can be further improved.

[0123] In this embodiment, through the multi-satellite beam coverage positioning method, multiple satellites respectively transmit their monitoring data back to the ground, and the ground conducts comprehensive processing. Through the accumulation over a period of time, the location of the interference source is found. The positioning accuracy of the multi-satellite beam coverage positioning system is related to the constellation configuration, positioning duration, and the location of the interference source. Generally speaking, the more satellites equipped with interference monitoring payloads, the longer the positioning time, and the higher the latitude of the interference source, the higher the achievable positioning accuracy. The positioning of the interference source mainly relies on the medium-orbit constellation, and it is basically impossible to achieve positioning only relying on the geostationary orbit constellation.

[0124] On this basis, a multi-satellite time difference positioning method is also set up. The left and right sides of the equation set are fully differentiated to derive the positioning error equation. Combining with the time difference estimation accuracy, it can be known through simulation analysis that this positioning method can perform positioning more accurately and can be widely used.

[0125] The above two interference source localization methods cooperate with each other, which can quickly and accurately locate when the medium and high orbit satellite link is interfered, reduce the difficulty of troubleshooting and cost, and will play an important role in the safe and effective operation of the medium and high orbit satellite link.

[0126] Therefore, the electromagnetic interference localization method applicable to medium and high orbit satellites in this embodiment can solve the problems of limited localization time and accuracy of interference sources in medium and high orbit multi-station electronic systems, and helps to improve the accuracy of interference source localization.

[0127] The technical solution of the present application has been described in detail above with reference to the accompanying drawings. The present application proposes an electromagnetic interference localization method applicable to medium and high orbit satellites. The electromagnetic interference localization method includes: Step 1, determine the interfered satellite according to the electromagnetic monitoring results in the satellite system; Step 2, calculate the global map coverage matrix according to the coverage range of the interfered satellite, sum the global map coverage matrix, and select the area corresponding to the largest element in the global map coverage matrix after summation as the initial localization area; Step 3, in a traversal manner, sequentially determine whether three or more satellites are in mutual visibility within the selected initial localization area. If so, execute Step 4; otherwise, re-obtain the electromagnetic monitoring results in the satellite system and execute Step 1; Step 4, perform multi-satellite time difference localization according to the electromagnetic monitoring results of the mutually visible satellites, and calculate the interference source localization coordinates, where the mutually visible satellites are the satellites in mutual visibility within the initial localization area. Through the technical solution in the present application, the monitoring and localization of high-power interference sources on the ground are realized, thereby improving the security of the uplink of the satellite system.

[0128] The steps in the present application can be adjusted, combined, and deleted according to actual needs.

[0129] The units in the device of the present application can be combined, divided, and deleted according to actual needs.

[0130] Although the present application has been disclosed in detail with reference to the accompanying drawings, it should be understood that these descriptions are merely exemplary and are not used to limit the application of the present application. The protection scope of the present application is defined by the appended claims and may include various modifications, improvements, and equivalent solutions made to the invention without departing from the protection scope and spirit of the present application.

Claims

1. An electromagnetic interference positioning method applicable to medium and high orbit satellites, characterized in that, The electromagnetic interference positioning method includes: Step 1: Determine the interfered satellite according to the electromagnetic monitoring results in the satellite system; Step 2: Calculate the global map coverage matrix according to the coverage range of the interfered satellite, sum the global map coverage matrix, and select the area corresponding to the largest element in the global map coverage matrix after summation as the initial positioning area; Step 3: In a traversal manner, sequentially determine whether three or more satellites are in mutual visibility within the selected initial positioning area. If so, execute Step 4; otherwise, re-obtain the electromagnetic monitoring results in the satellite system and execute Step 1; Step 4: Perform multi-satellite time difference positioning according to the electromagnetic monitoring results of the mutually visible satellites, and calculate the positioning coordinates of the interference source, where the mutually visible satellites are the satellites in mutual visibility within the initial positioning area; The calculation formula for multi-satellite time difference positioning in Step 4 is: where Δt i is the time difference between the interference source signal of the interference source arriving at the main satellite and the i-th deputy satellite. The main satellite is any one of the co-viewing satellites, and the deputy satellite is the remaining co-viewing satellites except the main satellite. X = [x y z] T is the positioning coordinate of the interference source, X0 = [x0 y0 z0] T is the position of the main satellite, X i = [x i y i z i T is the position of the i-th deputy satellite, P is the number of the deputy satellites, c is the electromagnetic wave propagation speed, and ||·|| is the norm function;​ Step 4 further includes: calculating the time difference between the interference source signal arriving at the main satellite and the secondary satellite, specifically including: Step 41: Perform discrete Fourier transform on the interference signal received by the main satellite and the interference signal received by the secondary satellite, and calculate the cross-spectrum parameter of the interference signals received by the main satellite and the secondary satellite after discrete Fourier transform. The calculation formula for the cross-spectrum parameter is: In the formula, k is the discrete point, [·] is the rounding function, and N is the total number of discrete points; Step 42: Perform an inverse Fourier transform on the cross-spectrum parameters to calculate R 12 (τ), and the corresponding calculation formula is: where R 12 (τ) is the Fourier inverse transform parameter of the cross-spectrum parameter, f k is the RF frequency corresponding to the digital frequency of the k-th discrete point after the DFT discrete Fourier transform, and τ is the reference time difference; Step 43, select the reference time difference corresponding to the maximum value of R 12 (τ), and denote it as the time difference for the interference source signal to reach the main satellite and the secondary satellite; The calculation of the time difference between the interference source signal arriving at the main satellite and the secondary satellite specifically further includes: When it is determined that the signal-to-noise ratio is less than the preset threshold, according to the preset power threshold, discrete points with cross-spectrum parameters greater than the preset power threshold are selected to form a set K of strong frequency points I , and the corresponding calculation formula is: In the formula, γ0 is the preset power threshold; According to the set K of stronger frequency points I , calculate the Fourier inverse transform parameter R 12 (τ) of the cross-spectrum parameter, and the corresponding calculation formula is:

2. The electromagnetic interference positioning method applicable to medium and high orbit satellites according to claim 1, wherein The calculation of the global map coverage matrix in Step 2 specifically includes: Step 21: Expand the global map into a two-dimensional map according to the longitude, latitude and preset interval, and perform grid division. Generate the initial global map coverage matrix according to the grid-divided two-dimensional map, where the element value in the initial global map coverage matrix is 0; Step 22: Calculate the distance between the interfered satellite and the center position of each grid in the grid-divided two-dimensional map according to the coverage range of the interfered satellite; Step 23: When it is determined that the distance is less than or equal to the satellite-earth limit distance, assign the element value in the corresponding initial global map coverage matrix of the distance to 1 to calculate the global map coverage matrix.

3. The electromagnetic interference localization method applicable to medium and high orbit satellites according to claim 1, characterized in that, The electromagnetic interference positioning method further includes: Step 5: Compare the calculated positioning coordinates of the interference source with the known interference source position coordinates in the interference knowledge base according to the preset distance error. When it is determined that the distance error between the calculated positioning coordinates of the interference source and the known interference source position coordinates in the interference knowledge base is less than or equal to the preset distance error, use the known interference source position coordinates as the matching result. Otherwise, use the calculated positioning coordinates of the interference source as the matching result, and use the calculated positioning coordinates of the interference source as the new known interference source position coordinates to update the interference knowledge base.

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