Satellite selection method of satellite signal forwarding system

Abstract

The invention provides a satellite selection method for a satellite signal forwarding system, and the method comprises the following steps at preset time intervals: carrying out the coordinate system conversion of the spatial positions of all visible satellites, and obtaining the angles of all visible satellites relative to a directional receiving antenna array; equally dividing the 360-degree azimuth angle to all directional receiving antennas to obtain an airspace range; for each directional receiving antenna, dividing visible satellites for the directional receiving antenna based on the airspace range of the directional receiving antenna and the azimuth angles of all the visible satellites; calculating DOP values of all visible satellites obtained through division, and selecting the visible satellite with the minimum DOP value as an alternative satellite; and calculating the sparseness of all the alternative satellites based on the directional receiving antenna array, and selecting at least four alternative satellites as optimal satellites according to the sequence of the sparseness from small to large. The invention provides a satellite selection method of a satellite signal forwarding system. The satellite selection method is used for solving the problem that when the number of satellites is large, a directional receiving antenna cannot be stripped, and target satellite signals cannot be purified, so that the quality of synthetic signals is affected.

Description

Technical Field

[0001] The present invention relates to the technical field of satellite navigation signal processing, and in particular to a satellite selection method for a satellite signal forwarding system. Background Art

[0002] Navigation satellite signals are very weak after being transmitted from satellites to the ground, and receivers are easily affected by suppression interference and spoofing signals. Among them, navigation spoofing technology is divided into generative spoofing and forwarding spoofing. Civilian navigation signals are public signals, and receivers can be deceived by regenerating signals. The technology is relatively mature and can be implemented at a low cost. However, military navigation signals can only be deceived by signal forwarding because the pseudo-random code has a long period and the generation method is not public. The forwarded signal is exactly the same as the original signal, but the time delay is different. Compared with generative spoofing, the forwarding spoofing system does not need to know any content of the satellite signal and does not require time synchronization.

[0003] The signal receiving device of the currently commonly used forwarding deception system uses multiple parabolic antennas (a directional antenna) pointing to different navigation satellites or phased array antennas to generate beams to track different satellite signals. Among them, the phased array antenna has poor consistency in receiving signals and is extremely expensive, so it is currently less used. The parabolic antenna has a higher gain and better consistency in receiving signals, which better meets the needs of the forwarding system. When the antenna receives the signal pointing to the satellite, the signal received by each channel is processed with different delays, and finally mixed and sent to the target receiver, which can achieve the position deception of the target receiver. The satellite selection strategy directly affects the quality of the received signal and the deception effect of the final synthesized signal.

[0004] The commonly used satellite selection strategy is to calibrate the selected satellites by calculating the DOP (Dilution of Precision) value, and then combine it with the delay control theory to achieve arbitrary position deception. In practical applications, the directivity of the receiving antenna is biased, especially when pointing to a navigation system with a large number of satellites (such as the Beidou navigation system). Some satellites may be received by multiple directional receiving antennas at the same time, or the directional receiving antenna may receive the satellite signals that are screened out, and the signal cannot be purified or stripped during the signal processing process, which affects the quality of the synthesized signal, and further affects the positioning accuracy and positioning time of the target receiver. Summary of the invention

[0005] The present invention provides a satellite selection method for a satellite signal forwarding system, which is used to solve the problem that when there are many satellites, a directional receiving antenna cannot strip off and purify target satellite signals, thereby affecting the quality of the synthesized signal.

[0006] The present invention provides a satellite selection method for a satellite signal forwarding system, which performs the following steps at preset time intervals:

[0007] Receive navigation satellite ephemeris based on an omnidirectional receiving antenna, and determine the spatial positions of all visible satellites according to the navigation satellite ephemeris;

[0008] Performing coordinate system conversion on the spatial positions of all the visible satellites to obtain angles of all the visible satellites relative to a directional receiving antenna array, where the directional receiving antenna array is composed of a plurality of directional receiving antennas, and the angles include azimuth and elevation;

[0009] Divide the 360° azimuth angle equally among all directional receiving antennas to obtain the airspace range of each directional receiving antenna;

[0010] For each directional receiving antenna, the visible satellites are divided based on the airspace range and the azimuth angles of all visible satellites;

[0011] For each directional receiving antenna, the DOP values ​​of all the visible satellites divided by the antenna are calculated, and the visible satellite with the smallest DOP value is selected as the candidate satellite;

[0012] The sparsity of all candidate satellites is calculated based on the directional receiving antenna array, and at least four candidate satellites are selected as preferred satellites in order of sparsity from small to large.

[0013] Optionally, the preset duration does not exceed the update period of the navigation satellite ephemeris.

[0014] Optionally, the directional receiving antenna array includes a distributed directional receiving antenna array and a phased array antenna.

[0015] Optionally, the calculation formula of the azimuth angle is as follows:

[0016]

[0017] Among them, θ i is the azimuth of the i-th visible satellite, and They are respectively the three components of the vector from the ith visible satellite to the directional receiving antenna array in the station center geostationary coordinate system.

[0018] Optionally, the pitch angle is calculated as follows:

[0019]

[0020] in, is the elevation angle of the i-th visible satellite.

[0021] Optionally, for each directional receiving antenna, dividing the visible satellites for it based on its airspace range and the azimuth angles of all visible satellites includes:

[0022] For each directional receiving antenna, visible satellites within the azimuth range of the directional receiving antenna are divided.

[0023] Optionally, the DOP is any one of GDOP, PDOP, HDOP, VDOP and TDOP.

[0024] Optionally, the calculating the sparsity of all candidate satellites based on the directional receiving antenna array includes:

[0025] Taking the directional receiving antenna array as the vertex of a cone;

[0026] For each candidate satellite, the beam width of the directional receiving antenna to which it belongs is taken as the cone angle, the candidate satellite is placed at the height of the cone, and the sparsity within the cone coverage area is calculated.

[0027] Optionally, the calculating the sparsity within the cone coverage area includes:

[0028] Calculate the difference between the spatial position of each visible satellite in the conical coverage area and the spatial position of the directional receiving antenna array to obtain an observation vector of each visible satellite in the conical coverage area;

[0029] Calculating the angle between the observation vector of each visible satellite in the conical coverage area and the observation vector of the candidate satellite;

[0030] The number of visible satellites whose included angle is less than half of the cone angle is counted to obtain the sparsity.

[0031] Optionally, selecting at least four candidate satellites as preferred satellites in ascending order of sparsity includes:

[0032] Sort the sparsity of all candidate satellites in ascending order;

[0033] Based on all the sorted candidate satellites, at least the first four candidate satellites are selected as the preferred satellites.

[0034] The present invention further screens the candidate satellites by sparsity to obtain the preferred satellite, thereby avoiding the reception of non-candidate satellite signals due to the pointing deviation of the directional receiving antenna or the wide beam, effectively improving the purity of the signal received by the directional receiving antenna, and avoiding the influence of the non-candidate satellite signals on the quality of the synthetic signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0036] Figure 1 A schematic diagram of a flow chart of a satellite selection method for a satellite signal forwarding system provided by an embodiment of the present invention;

[0037] Figure 2 A schematic diagram of a cone coverage area provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only 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 ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] Figure 1 The flow of a satellite selection method of a satellite signal forwarding system provided by an embodiment of the present invention is shown in detail, and the following steps are performed at preset time intervals:

[0040] S101, receiving navigation satellite ephemeris based on an omnidirectional receiving antenna, and determining the spatial positions of all visible satellites according to the navigation satellite ephemeris;

[0041] In an example, the preset duration does not exceed the update period of the navigation satellite ephemeris, so it can be ensured that the navigation satellite ephemeris received each time is the latest navigation satellite ephemeris.

[0042] By regularly reselecting satellites at preset intervals, the forwarding system is able to track the optimal satellite in real time around the clock.

[0043] In one example, the navigation satellite belongs to the Beidou navigation system or other navigation systems with a large number of satellites.

[0044] The Beidou navigation satellite ephemeris is received by an omnidirectional receiving antenna. Assuming the number of visible satellites is m, the set of spatial positions of the visible satellites in the Earth-centered Earth-fixed coordinate system is calculated according to the ephemeris:

[0045] P = {X 1 ,X 2 ,...,X m}

[0046] Among them, X i (1≤i≤m) represents the spatial position of the i-th satellite.

[0047] S102: Perform coordinate system conversion on the spatial positions of all visible satellites to obtain angles of all visible satellites relative to the directional receiving antenna array.

[0048] Specifically, the directional receiving antenna array is composed of multiple directional receiving antennas, and the angles include azimuth and elevation.

[0049] It should be noted that the coordinate system conversion is from the Earth-centered Earth-fixed coordinate system to the Station-centered Earth-fixed (ENU) coordinate system.

[0050] In one example, the directional receive antenna array includes a distributed directional receive antenna array and a phased array antenna.

[0051] In one example, the azimuth angle is calculated as follows:

[0052]

[0053] Among them, θ i is the azimuth of the i-th visible satellite, and They are the three components of the vector from the i-th visible satellite to the directional receiving antenna array in the station center geocentric coordinate system.

[0054] Furthermore, the pitch angle is calculated as follows:

[0055]

[0056] in, is the elevation angle of the i-th visible satellite.

[0057] The angle set of all visible satellites relative to the directional receiving antenna array obtained by coordinate system transformation is:

[0058]

[0059] S103: Evenly distribute the 360° azimuth angle to all directional receiving antennas to obtain the airspace range of each directional receiving antenna.

[0060] The spatial range of each directional receiving antenna is actually the azimuth range. It should be noted that all directional antennas should be placed in a way that the beams do not cross.

[0061] S104. For each directional receiving antenna, divide the visible satellites for it based on its airspace range and the azimuth angles of all visible satellites.

[0062] In one example, for each directional receiving antenna, dividing the visible satellites for it based on its airspace range and the azimuth angles of all visible satellites includes:

[0063] For each directional receiving antenna, the visible satellites within its airspace are divided into azimuths.

[0064] Assuming that the number of directional receiving antennas is n, based on the airspace range of each directional receiving antenna and the azimuth angles of all visible satellites, the angle set of all visible satellites is divided to the directional receiving antenna, for example:

[0065]

[0066] It can be seen from the above that within the airspace of the directional receiving antenna 2 there are visible satellites 4 and m.

[0067] S105. For each directional receiving antenna, calculate the DOP values ​​of all the visible satellites divided by it, and select the visible satellite with the smallest DOP value as its candidate satellite.

[0068] In one example, the DOP is any one of GDOP (Geometric Dilution of Precision), PDOP (Three-Dimensional Dilution of Precision), HDOP (Horizontal Dilution of Precision), VDOP (Vertical Dilution of Precision), and TDOP (Temporal Dilution of Precision).

[0069] It should be noted that each directional receiving antenna has a backup satellite.

[0070] For example, the DOP set obtained by directional receiving antenna n is {σ 2 ,σ 12 ,...}, since the smallest DOP value is the best, the visible satellite with the smallest DOP value is selected from the DOP set as the candidate satellite for the directional receiving antenna n.

[0071] S106. Calculate the sparsity of all candidate satellites based on the directional receiving antenna array, and select at least four candidate satellites as preferred satellites in ascending order of sparsity.

[0072] In one example, calculating the sparsity of all candidate satellites based on a directional receiving antenna array includes:

[0073] The directional receiving antenna array is taken as the vertex of the cone;

[0074] For each candidate satellite, the beam width of the directional receiving antenna to which it belongs is taken as the cone angle, which is placed on the height of the cone, and the sparsity within the cone coverage area is calculated.

[0075] It should be noted that the cone coverage area refers to the space within the entire cone.

[0076] Furthermore, calculating the sparsity within the cone coverage area includes:

[0077] Calculate the difference between the spatial position of each visible satellite in the conical coverage area and the spatial position of the directional receiving antenna array to obtain the observation vector of each visible satellite in the conical coverage area;

[0078] Calculate the angle between the observation vector of each visible satellite in the conical coverage area and the observation vector of the candidate satellite;

[0079] The number of visible satellites with an angle less than half of the cone angle is counted to obtain the sparsity.

[0080] It should be noted that the visible satellites within the cone coverage area include the candidate satellites, and the candidate satellites themselves are taken into account when calculating the sparsity.

[0081] Assume that the spatial position of the directional receiving antenna array is X′, and the spatial position set of all visible satellites in the conical coverage area is P′={X′ 1 ,X′ 2 ,…,X′ a ,…}, where X′ a is the spatial position of the candidate satellite in the conical coverage area, then the set of observation vectors of all visible satellites calculated is:

[0082] ΔX′={ΔX′ 1 ,ΔX′ 2 ,…,ΔX′ a ,…}={X′ 1 -X′,X′ 2 -X′,…,ΔX′ α -X′,…}

[0083] The angle β between the observation vector of the jth visible satellite in the conical coverage area and the observation vector of the candidate satellite is calculated according to the following formula: j :

[0084]

[0085] Get the set of angles {β 1 ,β 2 ,…,β a ,…}, the number of angles in the angle set that are less than half of the cone angle is counted, which is the sparsity.

[0086] Figure 2 The cone coverage area is shown, where ψ is the cone angle.

[0087] Since a general receiver needs at least four satellites for stable positioning, it is preferred that there are at least four satellites.

[0088] In one example, selecting at least four candidate satellites as preferred satellites in ascending order of sparsity includes:

[0089] Sort the sparsity of all candidate satellites in ascending order;

[0090] Based on all the sorted candidate satellites, at least the first four candidate satellites are selected as preferred satellites.

[0091] The above scheme further screens the candidate satellites by sparsity to obtain the preferred satellite, avoiding the reception of non-candidate satellite signals due to the pointing deviation of the directional receiving antenna or the wide beam, effectively improving the purity of the received signal of the directional receiving antenna, and avoiding the influence of the non-candidate satellite signals on the control accuracy of the synthetic signal.

[0092] After the satellite selection is completed through the above scheme, the beam pointing of the corresponding directional receiving antenna is adjusted according to the azimuth and elevation angle of the preferred satellite, so that the corresponding directional receiving antenna points to and tracks the preferred satellite, and the remaining directional receiving antennas do not work. For parabolic antennas, the turntable can be controlled to point to the corresponding preferred satellite. For phased array antennas, the beam can be formed to point to the corresponding preferred satellite by controlling the phase of multi-unit signals.

[0093] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0094] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims

1. A satellite selection method for a satellite signal forwarding system, characterized in that: Perform the following steps at preset intervals: Receive navigation satellite ephemeris based on an omnidirectional receiving antenna, and determine the spatial positions of all visible satellites according to the navigation satellite ephemeris; Performing coordinate system conversion on the spatial positions of all the visible satellites to obtain angles of all the visible satellites relative to a directional receiving antenna array, where the directional receiving antenna array is composed of a plurality of directional receiving antennas, and the angles include azimuth and elevation; Divide the 360° azimuth angle equally among all directional receiving antennas to obtain the airspace range of each directional receiving antenna; For each directional receiving antenna, the visible satellites are divided based on the airspace range and the azimuth angles of all visible satellites; For each directional receiving antenna, the DOP values ​​of all the visible satellites divided by the antenna are calculated, and the visible satellite with the smallest DOP value is selected as the candidate satellite; The sparsity of all candidate satellites is calculated based on the directional receiving antenna array, and at least four candidate satellites are selected as preferred satellites in order of sparsity from small to large.

2. The method according to claim 1, characterized in that: The preset duration does not exceed the update period of the navigation satellite ephemeris.

3. The method according to claim 1, characterized in that: The directional receiving antenna array includes a distributed directional receiving antenna array and a phased array antenna.

4. The method according to claim 1, characterized in that: The calculation formula of the azimuth angle is as follows: Among them, θ i is the azimuth of the i-th visible satellite, and They are respectively the three components of the vector from the ith visible satellite to the directional receiving antenna array in the station center geostationary coordinate system.

5. The method according to claim 4, characterized in that: The calculation formula of the pitch angle is as follows: in, is the elevation angle of the i-th visible satellite.

6. The method according to claim 1, characterized in that: For each directional receiving antenna, dividing the visible satellites for it based on its airspace range and the azimuth angles of all visible satellites includes: For each directional receiving antenna, visible satellites within the azimuth range of the directional receiving antenna are divided.

7. The method according to claim 1, characterized in that: The DOP is any one of GDOP, PDOP, HDOP, VDOP and TDOP.

8. The method according to claim 1, characterized in that: The calculating the sparsity of all candidate satellites based on the directional receiving antenna array comprises: Taking the directional receiving antenna array as the vertex of a cone; For each candidate satellite, the beam width of the directional receiving antenna to which it belongs is taken as the cone angle, the candidate satellite is placed at the height of the cone, and the sparsity within the cone coverage area is calculated.

9. The method according to claim 8, characterized in that: The calculation of the sparsity within the cone coverage area includes: Calculate the difference between the spatial position of each visible satellite in the conical coverage area and the spatial position of the directional receiving antenna array to obtain an observation vector of each visible satellite in the conical coverage area; Calculating the angle between the observation vector of each visible satellite in the conical coverage area and the observation vector of the candidate satellite; The number of visible satellites whose included angle is less than half of the cone angle is counted to obtain the sparsity.

10. The method according to claim 1, characterized in that: The selecting at least four candidate satellites as preferred satellites in ascending order of sparsity comprises: Sort the sparsity of all candidate satellites in ascending order; Based on all the sorted candidate satellites, at least the first four candidate satellites are selected as the preferred satellites.

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