Satellite selection forecasting method for spatial multi-antenna receiver

Abstract

The invention discloses a satellite selection forecasting method for a space multi-antenna receiver, and the method comprises the steps: considering the shielding performance of the earth for the sight line from a target navigation star to the receiver and whether the receiver is within the beam width of a satellite signal, and discriminating the geometric visibility of the target navigation star from a space high-orbit orbit and a space low-orbit orbit; for a multi-antenna receiver, antenna coordinate systems are respectively established according to different antenna directions, the maximum receiving gain is obtained by comparing the receiving gains under the antenna coordinate systems, the receiving signal power is calculated, and the antenna number corresponding to the maximum receiving gain is obtained at the same time, so that the signal intensity of a navigation signal reaching a target receiver antenna is judged. According to the method, the availability of navigation signals is comprehensively considered from the two aspects of geometric visibility and received signal strength, capturing parameters of a receiver can be effectively adjusted, coherent integration time is shortened, and by abandoning navigational stars which are geometrically invisible and low in signal strength, invalid navigational stars can be prevented from occupying a capturing channel, and the capturing speed is further increased.

Description

Technical Field

[0001] The present invention relates to the field of satellite navigation and positioning, and particularly to a satellite selection and prediction method for a space multi-antenna receiver. Background Art

[0002] Whether it is ground equipment or high, medium, and low-orbit spacecraft, to achieve tasks such as positioning and navigation, the primary condition is to be able to receive navigation signals, and the visibility of the target navigation star relative to the receiver is the key to whether it can communicate with the receiver. However, in the high-orbit part of space, since the target navigation star antenna points to the center of the earth, the high-orbit receiver can only receive navigation signals from the other side of the earth. At the same time, the main lobe beam width of the target navigation star is limited, and some of the navigation signals are blocked by the earth. The high-orbit receiver can only receive some main lobe signals and side lobe signals, which will cause problems such as weak space signals and poor visibility. The main disadvantages and deficiencies of the existing satellite selection and prediction methods are as follows:

[0003] (1) Only simply describes the calculation strategy of satellite visibility, without jointly considering the different situations of high and low orbits, and classifying and discussing the geometric visibility;

[0004] (2) Does not consider the application scenario of the multi-antenna receiver, and discriminates the availability of signals from the perspectives of multiple receiving antennas. Summary of the Invention

[0005] The technical problem solved by the present invention is: overcoming the deficiencies of the prior art, providing a satellite selection and prediction method for a space multi-antenna receiver, and realizing the signal availability evaluation in the application scenarios of high and low orbits and multi-antennas.

[0006] The technical solution of the present invention is: a satellite selection and prediction method for a space multi-antenna receiver, including:

[0007] S1. For a time point within a specified time period, determine whether the target navigation star is within the geometric visible range of the target receiver; the determination method is: considering the occlusion of the earth on the line of sight from the target navigation star to the target receiver and whether the target receiver is within the beam width of the target navigation star signal, based on the position of the target receiver, judge the geometric visibility of the target navigation star from two situations of high-orbit and low-orbit in space;

[0008] S2. When the target navigation star is geometrically visible, continue to determine whether the received signal power of the target navigation star signal reaching the target receiver antenna meets the preset conditions. For multiple antennas of the target receiver, establish antenna coordinate systems with different antenna pointings respectively, compare the receiving gains under multiple antenna coordinate systems, obtain the maximum receiving gain, and obtain the received signal power, so as to determine whether the target navigation star signal is finally available.

[0009] Further, step S1 specifically includes:

[0010] Denote the center of the earth as O, the position of the target navigation star as S, and the position of the target receiver as P, where the position of the high-orbit receiver is denoted as P1 and the position of the low-orbit receiver is denoted as P2. Then the line connecting P and S is denoted as L SP , the line connecting P1 and S is denoted as the line connecting P2 and S is denoted as The tangent of the target navigation star to the earth's surface is denoted as L SR , the ground antenna of the target navigation star to the earth is denoted as L S , the tangent of the low-orbit receiver to the earth's surface is denoted as the line connecting the low-orbit receiver and the center of the earth is denoted as α1 is the beam divergence angle of the target navigation star, α is the angle between L S and L SR , β is the angle between L SP and L S , α3 is and the angle between, α4 is and the angle between, the distance of P relative to the center of the earth is r PO , the distance of S relative to the center of the earth is r SO ;

[0011] For the geometric visibility judgment of the high-orbit receiver to the target navigation star:

[0012] When r PO > r SO , it is determined that the target receiver is in the high orbit. At this time, if α2 < β < α1, it is considered that the target navigation star is not blocked by the earth, and the high-orbit receiver is within the emission beam width range of the target navigation star. At this time, the target navigation star is geometrically visible;

[0013] For the geometric visibility judgment of the low-orbit receiver to the target navigation star:

[0014] When r PO ≤ r SO , it is determined that the target receiver is in the low orbit. At this time, if β < α1 and α3 > α4, it is considered that the target navigation star is within the visible range of the low-orbit receiver, and at the same time the target receiver is also within the emission beam width range of the target navigation star. At this time, the target navigation star is geometrically visible.

[0015] Further, in step S2, to calculate the received signal power of the target navigation star signal reaching the target receiver antenna, the specific method is:

[0016] S21. Determine the transmit power P of the target navigation star signal T ;

[0017] S22. Calculate the transmission gain G under the transmitting antenna of the target navigation star T ; including: converting the coordinates (X S , Y S , Z S ) of the target navigation star in the Earth-Centered Earth-Fixed coordinate system to the coordinates (L S , B S , H S ) in the geodetic coordinate system, using (L S , B S , H S ) to calculate the coordinates (X S , Y S , Z S ) of the target receiver in the Northeast-East coordinate system established with the coordinates (X S-P , Y S-p , Z S-P ) of the target navigation star as the origin, and then converting (X S-P , Y S-p , Z S-P ) to the coordinates (X NEDT , Y NEDT , Z NEDT ) in the North-East-Earth coordinate system. At this time, the pointing direction of the target navigation star's antenna to the ground coincides with the Z-axis of the North-East-Earth coordinate system, and the included angle between the antenna pointing vector of the target navigation star and the direction vector connecting the target receiver and the target navigation star is the pitch angle θ S , The included angle between the projection of S on the XOY plane of the North-East-Earth coordinate system and the positive direction of the X-axis is the azimuth angle α S ; According to the azimuth angle θ S and the pitch angle α T , obtain the transmission gain G

[0018] S23. Calculate the reception gain G under the receiving antenna of the target receiver R ; including: calculating the coordinates (X P , Y P , Z P ) of the target navigation star in the Northeast-East coordinate system established with the coordinates (X P-S , Y P-S , Z P-S ) of the target receiver as the origin, converting (X P-S , Y P-S , Z P-S ) to the coordinates (X NEDR , Y NEDR , Z NEDR ) in the North-East-Earth coordinate system, and then converting (X NEDR, Y NEDR , Z NEDR ) Convert to the coordinates in each antenna coordinate system. At this time, the Z-axis of the antenna coordinate system coincides with the pointing direction of different antennas, and the observation vector of the connection line between the target receiver and the target navigation star and the antenna pointing vector of the target receiver The included angle is the pitch angle α P , The included angle between the projection of the antenna coordinate system XOY plane and the antenna Z-axis is the azimuth angle θ P , According to the azimuth angle θ P and the pitch angle α P , the receiving gain G is obtained R ;

[0019] S24. Calculate the free space propagation loss L of the navigation star signal during propagation P ;

[0020] According to the results of S21~S24, the received signal power is obtained.

[0021] Furthermore, in S23, calculate the receiving gain G under the target receiver antenna R , The specific method is as follows:

[0022] S231. The antenna of the target receiver is named N i , i = 1, 2, 3...;

[0023] S232. First, rotate the north-east-earth coordinate system to the antenna coordinate system with the pointing of the N1 antenna as the Z-axis, and calculate the pitch angle α P1 and the azimuth angle θ P1 in the N1 antenna coordinate system, and obtain the receiving gain G R1 ;

[0024] S233. Refer to step S232, and successively obtain the receiving gains G R2 , G R3 …G Ri . By comparing the receiving gains under different antennas, the maximum receiving gain is obtained, and at the same time, the antenna number corresponding to the maximum receiving gain is obtained;

[0025] S234. Take the maximum receiving gain value as G R for calculating the received power;

[0026] Each target navigation star at the selected time point goes through the steps of S231, S232, S233, and S234.

[0027] Furthermore, when calculating the received signal power of the target navigation star signal reaching the target receiver antenna, it also includes calculating the atmospheric loss L of the target navigation star signal during propagationA , the atmospheric loss L A is also used for calculating the received signal power of the target receiver antenna.

[0028] Further, according to the azimuth and elevation angles, through the transmitting antenna pattern and the receiving antenna pattern, the transmitting gain G T and the receiving gain G R are obtained.

[0029] Further, it is determined whether the received signal power of the target navigation star signal reaching the target receiver antenna meets a preset condition: if the received signal power of the target receiver antenna is not less than the set minimum received power threshold, it is determined that the target navigation star signal is available, otherwise the signal is unavailable.

[0030] The present invention also provides a star selection and prediction system for a space multi-antenna receiver, including:

[0031] The first module is used to determine whether the target navigation star is within the geometric visibility range of the HEO orbit target receiver at a time point within a specified time period; the determination method is to consider the occlusion of the earth on the line of sight from the target navigation star to the target receiver and whether the target receiver is within the beam width of the target navigation star signal, and based on the position of the target receiver, judge the geometric visibility of the target navigation star from two cases of high-orbit and low-orbit orbits in space;

[0032] The second module is used to continue to determine whether the received signal power of the target navigation star signal reaching the target receiver antenna meets a preset condition to determine whether the target navigation star signal is available when the geometric visibility of the target navigation star is satisfied; for multiple antennas of the receiver, antenna coordinate systems are established respectively with different antenna pointings, the received gains in multiple antenna coordinate systems are compared, the maximum received gain is obtained, and then the received signal power is calculated.

[0033] The present invention also provides an on-board computing terminal deployed on a navigation satellite, including a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the computer program, the steps of the method described above are implemented.

[0034] The present invention also provides a computer program product, and when the computer program product is executed by a processor, the steps of the method described above are implemented.

[0035] The advantages of the present invention compared with the prior art are as follows:

[0036] The present invention starts from two perspectives of high and low orbits, and discusses the signal availability of a multi-antenna receiver respectively. The geometric visibility is judged by whether the target navigation star is blocked by the earth and whether the receiver is within the beam width range of the target navigation star; through the mutual conversion between coordinate systems, the reception gain of the navigation signal in different antenna coordinate systems is obtained, so as to calculate the received power. By combining the above two points to judge the availability of the navigation signal at a certain time point, the receiver can capture the target navigation star targeted, reduce the capture time, and improve the speed of going into orbit. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a flowchart of the star selection and prediction method in the specific implementation manner;

[0038] Figure 2 It is a schematic diagram of the approximate geometric positions of the target navigation star and the receiver in the high-orbit region in the specific implementation manner;

[0039] Figure 3 It is a schematic diagram of the approximate geometric positions of the target navigation star and the receiver in the low-orbit region in the specific implementation manner;

[0040] Figure 4 It is a schematic diagram of the satellite signal propagation link in the specific implementation manner. SPECIFIC IMPLEMENTATION MANNER

[0041] In order to better understand the technical solution of the present invention, the specific implementation manner of the present invention will be described below.

[0042] As Figure 1 shown, the star selection and prediction method for a space multi-antenna receiver provided in this embodiment includes the following steps:

[0043] Step 1: For a certain target time point within a specified time period, judge whether the target navigation star is within the geometric visible range of the target receiver at this time point. If the target receiver is within the beam divergence angle range of the target navigation star and the target navigation star is not blocked by the earth, it is determined that the target navigation star is geometrically visible at this time point, otherwise it is invisible;

[0044] Step 2: Under the condition that the geometric visibility of the target navigation star is satisfied, continue to judge the signal strength of the navigation signal reaching the target receiver antenna. By determining the signal transmission power, transmission gain, reception gain, free space propagation loss, atmospheric loss, etc. of the target navigation star, calculate the received signal power of the target navigation star. If the signal power is higher than the set minimum power threshold, it is judged that the signal of the target navigation star is available, otherwise it is unavailable. For the application scenario of a multi-antenna receiver, a strategy of establishing antenna coordinate systems with different antenna pointings is adopted. By comparing the reception gains in multiple antenna coordinate systems, the maximum reception gain is obtained, and then the received signal power is calculated, and at the same time, the antenna number corresponding to the maximum reception gain is obtained.

[0045] In a preferred embodiment, step 1 of this embodiment includes:

[0046] Step 1.1: Denote the center of the earth as O, the position of the target navigation star as S, and the position of the target receiver as P. Among them, the position of the high-orbit receiver is denoted as P1, and the position of the low-orbit receiver is denoted as P2. Then the line connecting P and S is denoted as L SP , the line connecting P1 and S is denoted as the line connecting P2 and S is denoted as The tangent of the target navigation star to the earth's surface is denoted as L SR , the ground antenna of the target navigation star to the earth is denoted as L S , the tangent of the low-orbit receiver to the earth's surface is denoted as the line connecting the low-orbit receiver and the center of the earth is denoted as α1 is the beam divergence angle of the target navigation star, α2 is the angle between L S and L SR , β is the angle between L SP and L S , α3 is and the angle between, α4 is and the angle between, the distance of P relative to the center of the earth is r PO , the distance of S relative to the center of the earth is r SO ;

[0047] Step 1.2: Geometric visibility of the high-orbit receiver to the target navigation star

[0048] As Figure 2 shown, when r PO > r SO , it is determined that the target receiver is in the high orbit. At this time, if α2 < β < α1, it is considered that the target navigation star is not blocked by the earth, and the high-orbit receiver is within the emission beam width range of the target navigation star. At this time, the target navigation star is geometrically visible;

[0049] Step 1.3: Geometric visibility of the low-orbit receiver to the target navigation star

[0050] As Figure 3 shown, when r PO ≤ r SO , it is determined that the target receiver is in the low orbit. At this time, if β < α1 and α3 > α4, it is considered that the target navigation star is within the visible range of the low-orbit receiver, and at the same time the target receiver is also within the emission beam width range of the target navigation star. At this time, the target navigation star is geometrically visible;

[0051] Step 1.4. According to the descriptions in Step 1.2 and Step 1.3, the degree of α1 should be determined according to the beam divergence angle of the specific target navigation star, and the calculation formulas of the remaining relevant angles are as follows.

[0052]

[0053]

[0054] As Figure 4 shown, in the satellite signal propagation link, the whole process can be divided into three parts: the GNSS constellation, signal propagation, and receiving terminal. Among them, the satellite transmission part has signal transmission power and transmission gain; the space propagation part involves path loss and atmospheric loss; and finally, the terminal receiving part has receiving gain. The present invention solves the problem separately from the above-mentioned parts. In this embodiment, Step 2 includes:

[0055] Step 2.1. Determine the transmission power P of the target navigation star signal T ;

[0056] Step 2.2. Calculate the transmission gain G under the transmitting antenna of the target navigation star T

[0057] Assume that the coordinates of the target navigation star in the Earth-Centered Earth-Fixed coordinate system (abbreviated as ECEF coordinate system) are (X S , Y S , Z S ), and the coordinates of the target receiver are (X P , Y p , Z P ). Establish a North-East-Up coordinate system (abbreviated as ENU coordinate system) with the position of the target navigation star as the coordinate origin. Then, first convert the ECEF coordinates (X S , Y S , Z S ) into the corresponding geodetic coordinate system (L S , B S , H S ). The calculation formula is as follows:

[0058]

[0059] Where: a is the semi-major axis of the reference ellipsoid, b is the semi-minor axis of the reference ellipsoid, e is the first eccentricity of the reference ellipsoid, and N is the prime meridian of the prime vertical. Here, B S and H S are solved by iteration. The initial value B0 of B S is as shown in (10). Then, use this initial value to calculate the value of B S again using Equation (6). Continue the iteration until the calculated B S , H S converge.

[0060]

[0061] Next, calculate the coordinates (X S-P , Y S-p , Z S-P ) of the target receiver in the northeast celestial coordinate system established with the position of the target navigation star. The specific formula is as follows:

[0062]

[0063] Where: S1 is the rotation matrix for conversion. Since the antenna of the target navigation star is directed towards the ground, for the convenience of calculation, the present invention rotates and converts the coordinates of the target receiver in the northeast celestial coordinate system again to obtain the coordinates in the north-east-down coordinate system (abbreviated as NED coordinate system). The conversion matrix S2 is shown as follows:

[0064]

[0065] Then the coordinate conversion formula is:

[0066]

[0067] Where: Roll is the roll angle, Pitch is the pitch angle, and Yaw is the yaw angle. At this time, the direction of the ground-facing antenna of the target navigation star coincides exactly with the Z-axis of the north-east-down coordinate system. The angle between the direction vector of the target navigation star antenna and the direction vector SP on the straight line L is the launch angle, that is, the pitch angle θ S , The angle between the projection of S in the XOY plane and the positive direction of the X-axis is the azimuth angle α

[0068]

[0069] According to the azimuth angle and the pitch angle, the transmission gain G T is obtained by looking up the transmitting antenna pattern.

[0070] Step 2.3: Calculate the receiving gain G under the receiver antenna R

[0071] Calculate the coordinates (X P , Y P , Z P ) of the target navigation star in the northeast celestial coordinate system with the coordinates (X P-S , Y P-S , Z P-S ) of the target receiver as the origin. Then, through the rotation matrix, (X P-S , YP-S , Z P-S ) The coordinates (X NEDR , Y NEDR , Z NEDR ) converted to the North-East-Earth coordinate system. The specific process is similar to the process of calculating the transmission gain. Then, based on the application scenario of the multi-antenna receiver, the present invention further converts the target navigation star coordinates (X NEDR , Y NEDR , Z NEDR ) in the North-East-Earth coordinate system into the coordinates in different antenna coordinate systems. At this time, the Z-axis of the antenna coordinate system coincides with the pointing direction of different antennas. The transformation matrix S3 is as follows:

[0072]

[0073] Then the coordinate transformation formula is:

[0074]

[0075] Let the target receiver antenna pointing vector The observation vector of the connection line between the receiver and the target navigation star is Then and The included angle between them is the reception angle, that is, the elevation angle. The included angle between the projection of

[0076]

[0077] in the XOY plane and the antenna Z-axis is the azimuth angle. The calculation formulas are as shown in (19) and (20).

[0078]

[0079] First, rotate the North-East-Earth coordinate system to an antenna coordinate system with the pointing direction of the N1 antenna as the Z-axis. Calculate the elevation angle and azimuth angle in the N1 antenna coordinate system to obtain the reception gain G R1 ; Then, obtain the reception gains G R2 , G R3 etc. in the same steps in sequence. By comparing the reception gains under different antennas, finally obtain the maximum reception gain, and at the same time obtain the antenna number corresponding to the maximum reception gain. Use the maximum reception gain value in the formula calculation for obtaining the reception power.

[0080] Step 2.4. Calculate the free space propagation loss L of the target navigation star signal during propagation P

[0081] The straight-line distance d between the target receiver and the target navigation star position is obtained, the wavelength of the transmitted navigation signal is input, and the free-space propagation loss is obtained using formula (21).

[0082]

[0083] Step 2.5: Calculate the atmospheric loss L during the propagation of the target navigation star signal A

[0084] For general ground or near-earth users, the atmospheric loss is about 2 dB. In the high-orbit space, the atmosphere is thin and the atmospheric loss can be almost negligible.

[0085] Step 2.6: Calculate the signal power intensity received by the receiver antenna according to the parameters obtained in the processes of Step 2.1, Step 2.2, Step 2.3, Step 2.4, and Step 2.5. If the received power intensity is not less than the set minimum received power threshold, it is determined that the target navigation star signal is available; otherwise, the signal is unavailable. The formula for calculating the received power is as follows.

[0086] P R =P T +G T +G R -L P -L A (22)

[0087] This embodiment also provides a star selection and prediction system for a space multi-antenna receiver, including:

[0088] The first module is used to determine whether the target navigation star is within the geometric visibility range of the target receiver at a time point within a specified time period; the determination method is to consider the occlusion of the earth on the line of sight from the target navigation star to the target receiver and whether the target receiver is within the beam width of the target navigation star signal, and based on the target receiver position, judge the geometric visibility of the target navigation star from two situations of high-orbit and low-orbit orbits in space;

[0089] The second module is used to continue to determine whether the received signal power of the target navigation star signal reaching the target receiver antenna meets the preset conditions when the target navigation star is geometrically visible, and finally determine whether the target navigation star signal is available; for multiple antennas of the receiver, antenna coordinate systems are established with different antenna pointings respectively, the received gains in multiple antenna coordinate systems are compared to obtain the maximum received gain, and then the received signal power is calculated.

[0090] The specific functions of the modules are implemented according to the methods described above.

[0091] It will be understood that the present invention is described by way of examples, and those skilled in the art will appreciate that various changes or equivalent substitutions can be made to these features and examples without departing from the spirit and scope of the present invention. Additionally, under the teachings of the present invention, these features and examples can be modified to suit specific circumstances without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and embodiments that can fall within the scope of the claims of this application all belong to the scope protected by the present invention.

[0092] Contents not detailedly described in the specification of the present invention are well-known technologies to those skilled in the art.

Claims

1. A star selection prediction method for a space multi-antenna receiver, characterized in that Including: S1. For a time point within a specified time period, determine whether the target navigation star is within the geometric visibility range of the target receiver at this time point. The determination method is as follows: Considering the occlusion of the Earth on the line of sight from the target navigation star to the target receiver and whether the target receiver is within the beam width of the target navigation star signal, based on the position of the target receiver, judge the geometric visibility of the target navigation star from two cases of high-orbit and low-orbit in space; S2. When the target navigation star is geometrically visible, continue to determine whether the received signal power of the target navigation star signal reaching the target receiver antenna meets the preset conditions. For multiple antennas of the target receiver, establish antenna coordinate systems with different antenna pointings respectively, compare the received gains in multiple antenna coordinate systems, obtain the maximum received gain, and obtain the received signal power, so as to determine whether the target navigation star signal is finally available.

2. The star selection and prediction method for a space-oriented multi-antenna receiver according to claim 1, characterized in that: The step S1 specifically includes: Denote the center of the earth as O, the position of the target navigation star as S, and the position of the target receiver as P. Among them, the position of the high-orbit receiver is denoted as P1, and the position of the low-orbit receiver is denoted as P2. Then the line connecting P and S is denoted as L SP , the line connecting P1 and S is denoted as , the line connecting P2 and S is denoted as The tangent line of the target navigation star to the earth's surface is denoted as L SR , the ground antenna of the target navigation star to the earth is denoted as L S , the tangent line of the low-orbit receiver to the earth's surface is denoted as , the line connecting the low-orbit receiver and the center of the earth is denoted as α1 is the beam angle of the target navigation star, α2 is the angle between L S and L SR , β is the angle between L SP and L S , α3 is the angle between and , α4 is the angle between and , the distance of P relative to the center of the earth is r PO , the distance of S relative to the center of the earth is r SO ; Judgment of the geometric visibility of the target navigation star by the high-orbit receiver: When r PO > r SO it is determined that the target receiver is in a high-orbit. At this time, if α2 < β < α1, it is considered that the target navigation star is not blocked by the earth and the high-orbit receiver is within the transmitting beam width range of the target navigation star. At this time, the target navigation star is geometrically visible; Judgment of the geometric visibility of the target navigation star by the low-orbit receiver: When r PO ≤ r SO , it is determined that the target receiver is in a low-earth orbit. At this time, if β < α1 and α3 > α4, it is considered that the target navigation star is within the visible range of the receiver in the low-earth orbit, and at the same time, the target receiver is also within the transmitting beam width range of the target navigation star. At this time, the target navigation star is geometrically visible.

3. The star selection prediction method for a space-oriented multi-antenna receiver according to claim 1, characterized in that: In the step S2, the calculation of the received signal power of the target navigation star signal reaching the target receiver antenna is specifically as follows: S21. Determine the transmission power P of the target navigation star signal T ; S22. Calculate the transmission gain G under the transmitting antenna of the target navigation star. T ; It includes: converting the coordinates (X S , Y S , Z S ) of the target navigation star in the Earth-centered Earth-fixed coordinate system to the coordinates (L S , B S , H S ) in the geodetic coordinate system, and using (L S , B S , H S ) to calculate the coordinates (X S , Y S , Z S ) of the target receiver in the northeast-down coordinate system established with the coordinates (X S-P , Y S-p , Z S-P ) of the target navigation star as the origin, and then converting (X S-P , Y S-p , Z S-P ) to the coordinates (X NEDT , Y NEDT , Z NEDT ) in the north-east-down coordinate system. At this time, the pointing direction of the ground antenna of the target navigation star coincides with the Z-axis of the north-east-down coordinate system, and the included angle between the antenna pointing vector of the target navigation star and the direction vector connecting the target receiver and the target navigation star is the elevation angle θ S , The included angle between the projection of S on the XOY plane of the north-east-down coordinate system and the positive direction of the X-axis is the azimuth angle α S ; According to the azimuth angle θ S and the elevation angle α T , obtain the transmission gain G. S23. Calculate the receiving gain G under the target receiver antenna R ; including: calculating the coordinates (X P , Y P , Z P ) of the target navigation star in the northeast celestial coordinate system established with the coordinates (X P-S , Y P-S , Z P-S ) of the target receiver as the origin, converting (X P-S , Y P-S , Z P-S ) to the coordinates (X NEDR , Y NEDR , Z NEDR ) in the north-east-earth coordinate system, and then converting (X NEDR , Y NEDR , Z NEDR ) into the coordinates in each antenna coordinate system. At this time, the Z-axis of the antenna coordinate system coincides with the pointing direction of different antennas. The included angle between the observation vector of the connection line between the target receiver and the target navigation star and the antenna pointing vector of the target receiver antenna is the pitch angle α P , The included angle between the projection of in the XOY plane of the antenna coordinate system and the antenna Z-axis is the azimuth angle θ P . According to the azimuth angle θ P and the pitch angle α P , the receiving gain G R is obtained; S24. Calculate the free space propagation loss L of the navigation star signal during propagation P ; According to the results of S21 - S24, obtain the received signal power.

4. The satellite selection prediction method for a space-oriented multi-antenna receiver according to claim 3, wherein: In S23, calculate the receiving gain G under the target receiver antenna R , and the specific method is as follows: The antenna of the target receiver is named N i , where i = 1, 2, 3...; S232. First, rotate the north-east local coordinate system to convert it into an antenna coordinate system with the pointing direction of the N1 antenna as the Z-axis. Calculate the elevation angle α and the azimuth angle θ in the N1 antenna coordinate system, and obtain the receiving gain G; P1 and azimuth angle θ P1 , obtaining the receiving gain G R1 ; S233. Referring to step S232, the receiving gains G R2 , G R3 …G Ri are obtained in sequence. By comparing the receiving gains under different antennas, the maximum receiving gain is obtained, and at the same time, the antenna number corresponding to the maximum receiving gain is obtained; S234. Use the maximum received gain value as G R For calculating the received power Each target navigation star at the selected time point goes through the steps of S231, S232, S233, and S234.

5. The star selection and prediction method for a space-oriented multi-antenna receiver according to claim 3, characterized in that: When calculating the received signal power of the target navigation star signal arriving at the target receiver antenna, it also includes calculating the atmospheric loss L of the target navigation star signal during the propagation process A , and the atmospheric loss L A is also used for calculating the received signal power of the target receiver antenna.

6. The star selection prediction method for a space-oriented multi-antenna receiver according to claim 3, characterized in that: According to the azimuth angle and elevation angle, the transmission gain G is obtained through the transmission antenna pattern and the reception antenna pattern T and the reception gain G R .

7. The star selection prediction method for a space-oriented multi-antenna receiver according to claim 3, characterized in that: Judge whether the received signal power of the target navigation star signal reaching the target receiver antenna meets the preset conditions: If the received signal power of the target receiver antenna is not less than the set minimum received power threshold, it is judged that the target navigation star signal is available; otherwise, the signal is unavailable.

8. A satellite selection and prediction system for a spatial multi-antenna receiver, characterized in that, Including: The first module is used to judge whether the target navigation star is within the geometric visibility range of the HEO orbit target receiver for a time point within a specified time period; The judgment method is to consider the occlusion of the Earth on the line of sight from the target navigation star to the target receiver and whether the target receiver is within the beam width of the target navigation star signal, and judge the geometric visibility of the target navigation star from two cases of high-orbit and low-orbit in space based on the position of the target receiver; The second module is used to continue to judge whether the received signal power of the target navigation star signal reaching the target receiver antenna meets the preset conditions when the target navigation star is geometrically visible, and determine whether the target navigation star signal is available; for multiple antennas of the receiver, establish antenna coordinate systems with different antenna pointings respectively, compare the received gains in multiple antenna coordinate systems, obtain the maximum received gain, and then calculate the received signal power.

9. A on-board computing terminal is deployed on a navigation satellite, characterized in that: Including a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the computer program, the steps of the method according to any one of claims 1 - 7 are implemented.

10. A computer program product, characterized in that: When the computer program product is executed by the processor, the steps of the method according to any one of claims 1 - 7 are implemented.

Images