Data link terminal heaven and earth fusion method

Abstract

The invention discloses a data link terminal space-ground fusion method, which belongs to the technical field of satellite communication, and comprises the following steps: selecting an equivalent position of a data link satellite-borne terminal as a Doppler center position of a data link service area; obtaining orbit parameters according to the solved ephemeris, calculating position coordinates of a satellite earth fixed coordinate system, and then calculating position coordinates of a geometric center of a data link service area; calculating the Doppler center position of the data link service area according to the satellite earth fixed coordinate system position coordinate and the position coordinate of the geometric center of the data link service area; calculating a time delay value and a Doppler value at the Doppler center according to the Doppler center position of the data link service area and the position coordinates of the satellite earth fixed coordinate system; and correcting the time delay based on the time delay value, and pre-compensating the Doppler value on the signal sending frequency of the data link terminal, thereby solving the problem of incompatibility of the data link terminal caused by long time delay and high Doppler frequency shift in a satellite-ground communication high dynamic environment in the prior art.

Description

Technical Field

[0001] The invention relates to a data link terminal ground-to-earth fusion method, belonging to the technical field of satellite communications. Background Art

[0002] With the rapid development of science and technology, low-orbit satellite communication systems have occupied an increasingly important position in the field of modern communications. Low-orbit satellite communications have significant advantages such as wide coverage, low transmission delay, and low path loss. They can break through the limitations of geographical conditions and achieve seamless communication coverage around the world. In the field of military and national defense, low-orbit satellite communication systems are key infrastructure to ensure the stable operation of remote combat command, intelligence transmission, and military communication networks. They play an irreplaceable role in improving the combat effectiveness, strategic deployment capabilities, and emergency response speed of the military. In the civilian field, they are widely used in remote area communications, aviation and navigation communications, emergency rescue communications, and Internet of Things data transmission. They have greatly promoted the interconnection of global information, promoted social and economic development and progress, and improved human quality of life and production efficiency. Therefore, the importance of low-orbit satellite communication scenarios is self-evident.

[0003] Carrying data link terminals on low-orbit satellites for network relay can extend the communication distance of data links, expand the scope of tactical information protection, and increase the situational awareness distance of data links. Satellite data links have the characteristics of wide coverage, rapid deployment, large communication capacity, and stable transmission channels. The unique broadcast characteristics of satellites have unparalleled advantages in the broadcast distribution of intelligence and battlefield situations. Satellite data links can connect geographically dispersed troops, various detectors and weapon systems, grasp the battlefield situation in real time, shorten decision-making time, improve command speed and coordinated combat capabilities, so as to carry out rapid, accurate and continuous strikes on the enemy. It is an important guarantee for the effective implementation of cross-sea and large-scale joint operations. Compared with ground platforms, low-orbit satellites have the characteristics of long communication distance and fast movement speed. How to adapt the data link technology system to satellite-to-ground communication and the long delay and high Doppler frequency shift caused by the high dynamic environment under satellite-to-ground transmission have become urgent problems to be solved. Summary of the invention

[0004] The purpose of the present invention is to provide a data link terminal space-ground fusion method, which calculates the Doppler value at the Doppler center and pre-compensates the data link terminal sending signal frequency to solve the problem of data link terminal incompatibility caused by long delay and high Doppler frequency shift in the high dynamic environment of satellite-to-ground communication in the prior art.

[0005] In order to solve the above technical problems, the present invention is implemented by adopting the following technical solutions:

[0006] The present invention provides a data link terminal ground-to-earth fusion method, comprising:

[0007] Select the equivalent position of the data link satellite terminal as the Doppler center position of the data link service area;

[0008] Obtaining ephemeris data, solving it to obtain orbital parameters, and calculating the satellite's position coordinates in an earth-fixed coordinate system based on the orbital parameters;

[0009] Calculate the position coordinates of the geometric center of the data link service area based on the satellite's earth-fixed coordinate system position coordinates;

[0010] Calculate the Doppler center position of the data link service area based on the satellite's earth fixed coordinate system position coordinates and the position coordinates of the geometric center of the data link service area;

[0011] According to the Doppler center position of the data link service area and the satellite earth fixed coordinate system position coordinates, calculate the delay value and Doppler value at the Doppler center;

[0012] The delay is corrected based on the delay value, and the message is sent in advance using the delay value at the Doppler center so that the message is at a typical time of the time slot when it arrives at the ground node, and the message is received with a delay using the delay value at the Doppler center so that the message is at a typical time of the time slot when it arrives at the satellite node;

[0013] The Doppler value is pre-compensated on the frequency of the signal transmitted by the data link terminal.

[0014] Furthermore, the equivalent position of the data link satellite terminal is selected as the Doppler center position of the data link service area, wherein, under the coverage of the low-orbit satellite, the Doppler center of the data link service area is the position where the average value of the minimum Doppler value and the maximum Doppler value of the terminal in the data link service area is located.

[0015] Furthermore, the orbital parameters include orbital inclination, right ascension of ascending node, argument of perigee, mean anomaly, eccentricity and mean motion.

[0016] Further, calculating the position coordinates of the satellite in an earth-fixed coordinate system according to the orbital parameters includes:

[0017] Calculate the mean anomaly angle based on the mean motion;

[0018] Solve the eccentric anomaly according to the calculation formula of the mean anomaly angle;

[0019] Calculating a true anomaly angle according to the eccentric anomaly and the eccentricity;

[0020] Calculate the orbit radius according to the orbit semi-major axis, the true anomaly and the eccentricity;

[0021] Calculating the position of the satellite in the orbital plane according to the orbital radius and the true anomaly;

[0022] According to the position coordinates of the satellite in the orbital plane and the orbital parameters, the coordinates of the satellite in the orbital plane are converted into the geocentric inertial coordinate system ECI to obtain the position coordinates of the satellite in the geocentric inertial coordinate system ECI;

[0023] According to the angular velocity of the earth's rotation and the definition of the earth-fixed coordinate system, the geocentric inertial coordinate system ECI and the earth-fixed coordinate system are transformed to obtain the satellite's earth-fixed coordinate system position coordinates.

[0024] Further, the position coordinates of the geometric center of the data link service area are the projection point of the ground center point covered by the beam below the satellite orbit, that is, the ground meridian point of the satellite, wherein the position coordinates of the geometric center of the data link service area are calculated according to the position coordinates of the satellite earth fixed coordinate system, including:

[0025] Calculate the longitude and latitude of the meridian point based on the satellite's position coordinates in the satellite earth-fixed coordinate system and the distance between the satellite and the center of the earth;

[0026] Based on the longitude and latitude of the meridian point and the radius of the earth, the earth-fixed coordinates of the meridian point, that is, the position coordinates of the geometric center of the data link service area, are calculated.

[0027] Further, the Doppler center position of the data link service area is calculated according to the position coordinates of the satellite earth fixed coordinate system and the position coordinates of the geometric center of the data link service area, wherein:

[0028] The center position of the satellite's position coordinates in the satellite's earth-fixed coordinate system and the position coordinates of the geometric center of the data link service area is usually located in the middle between the beam center point and the beam edge point, that is, the Doppler center position of the data link service area.

[0029] Further, the abscissa, ordinate and vertical coordinate of the Doppler center position of the data link service area are respectively expressed as:

[0030] ;

[0031] In the formula, , and The horizontal, vertical and vertical coordinates represent the coordinates of the Doppler center position of the data link service area, respectively. Indicates the Doppler center of the data link service area.

[0032] Further, according to the Doppler center position of the data link service area and the position coordinates of the satellite in the satellite earth fixed coordinate system, the delay value and the Doppler value at the Doppler center are calculated, including:

[0033] According to the Doppler center position of the data link service area and the position coordinates of the satellite in the satellite earth fixed coordinate system, the vector between the satellite and the Doppler center position of the data link service area and the geometric distance between the satellite and the Doppler center position of the data link service area are calculated;

[0034] Calculate the radial velocity, i.e., the velocity component in the projection direction, based on the vector between the satellite and the Doppler center position of the data link service area of ​​the Doppler center point and the radial velocity of the satellite;

[0035] According to the geometric distance and light speed between the satellite and the Doppler center of the data link service area, the delay value at the Doppler center is calculated;

[0036] The Doppler value at the Doppler center is calculated based on the radial velocity, the speed of light, and the signal frequency.

[0037] Further, the delay is corrected based on the delay value, the message is sent in advance using the delay value at the Doppler center so that the message is at a typical time of the time slot when arriving at the ground node, and the message is received with a delay using the delay value at the Doppler center so that the message is at a typical time of the time slot when arriving at the satellite node, including:

[0038] For the uplink, the satellite receives the ground data link terminal sending time slot start time reference ground transmission time slot adaptive delay ; For the downlink, the satellite data link terminal sends the time slot start time with reference to the ground transmission time slot adaptive advance ,in, Indicates the delay value at the Doppler center.

[0039] Furthermore, the Doppler value is pre-compensated on the frequency of the signal sent by the data link terminal, which is expressed as:

[0040] ;

[0041] In the formula, Indicates the frequency of the data link terminal sending signal after compensation. Indicates the frequency of the data link terminal sending signal before compensation. Indicates the Doppler value at the Doppler center.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] 1. The present invention selects the equivalent position of the data link satellite terminal as the Doppler center position of the data link service area, and based on the ephemeris solution and orbit parameter calculation, can accurately determine the geometric center position of the satellite and the data link service area, and then accurately calculate the Doppler center position and its corresponding delay value and Doppler value, thereby ensuring the time synchronization and frequency accuracy of data in the process of ground-to-earth transmission.

[0044] 2. At the same time, the present invention also uses the delay value at the Doppler center to implement a correction strategy for early sending and delayed receiving messages, effectively ensuring that the messages are at the typical time of the time slot when they arrive at the ground node and the satellite node, thereby significantly reducing the data transmission error caused by delay and Doppler effect, and improving the real-time and reliability of data transmission.

[0045] 3. In addition, the present invention also pre-compensates the Doppler value on the signal transmission frequency of the data link terminal, further compensating for the frequency offset caused by relative motion, ensuring the stability and quality of signal transmission. The present invention significantly improves the overall performance and communication efficiency of the space-ground data link system, and solves the problem of data link terminal incompatibility caused by long delay and high Doppler frequency shift in the high dynamic environment of satellite-to-ground communication in the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a flow chart of a data link terminal ground-to-earth integration method provided by an embodiment of the present invention;

[0047] Figure 2 is a schematic diagram of a process for correcting delay provided by an embodiment of the present invention;

[0048] Figure 3 1 is a schematic diagram of the delay of a satellite data link before compensation when the elevation angle is 20° provided by an embodiment of the present invention;

[0049] Figure 4 1 is a schematic diagram of the delay of a satellite data link before compensation when the elevation angle is 40° provided by an embodiment of the present invention;

[0050] Figure 5 1 is a schematic diagram of the delay of a satellite data link before compensation when the elevation angle is 60° provided by an embodiment of the present invention;

[0051] Figure 6 1 is a schematic diagram of the time delay after compensation of the satellite data link provided by an embodiment of the present invention when the elevation angle is 20°;

[0052] Figure 7 1 is a schematic diagram of the time delay after compensation of the satellite data link provided by an embodiment of the present invention when the elevation angle is 40°;

[0053] Figure 8 1 is a schematic diagram of the time delay after compensation of the satellite data link provided by an embodiment of the present invention when the elevation angle is 60°;

[0054] Fig. 9 Schematic diagram of Doppler frequency shift before compensation of a satellite data link at an elevation angle of 20° provided by an embodiment of the present invention;

[0055] Fig.10Schematic diagram of Doppler frequency shift before compensation of a satellite data link at an elevation angle of 40° provided by an embodiment of the present invention;

[0056] Fig.11 Schematic diagram of Doppler frequency shift before compensation of a satellite data link at an elevation angle of 60° provided by an embodiment of the present invention;

[0057] Fig.12 Schematic diagram of Doppler frequency shift after compensation of a satellite data link provided by an embodiment of the present invention when the elevation angle is 20°;

[0058] Fig.13 Schematic diagram of Doppler frequency shift after compensation of a satellite data link provided by an embodiment of the present invention when the elevation angle is 40°;

[0059] Fig.14 It is a schematic diagram of the Doppler frequency shift after compensation of the satellite data link provided by an embodiment of the present invention when the elevation angle is 60°. DETAILED DESCRIPTION

[0060] The technical solution of the present invention is described in detail below through the accompanying drawings and specific embodiments. It should be understood that the embodiments of the present invention and the specific features in the embodiments are detailed descriptions of the technical solution of the present invention, rather than limitations on the technical solution of the present invention. The embodiments of the present invention and the technical features in the embodiments may be combined with each other unless there is a conflict.

[0061] The term "and / or" is only a description of the association relationship between related objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " generally indicates that the related objects are in an "or" relationship.

[0062] Example 1

[0063] like Figure 1 As shown, this embodiment introduces a data link terminal ground-ground integration method, including:

[0064] Step 1: Select the equivalent position of the data link satellite terminal as the Doppler center position of the data link service area.

[0065] The Doppler effect is a common phenomenon in wireless communication. Due to the relative motion between the transmitting end and the receiving end, the received signal frequency will change. The present invention selects the equivalent position of the satellite terminal as the Doppler center to simplify the subsequent Doppler effect calculation and compensation. It provides a reference point for the subsequent steps to facilitate the unified processing of the Doppler effect.

[0066] Step 2: Obtain ephemeris data, solve to obtain orbital parameters, and calculate the satellite's position coordinates in the Earth-fixed coordinate system based on the orbital parameters.

[0067] The ephemeris is data describing the trajectory of the satellite, and the orbital parameters of the satellite can be obtained by solving the ephemeris. The present invention uses the orbital parameters to calculate the position coordinates of the satellite in the earth's fixed coordinate system.

[0068] Step 3: Calculate the position coordinates of the geometric center of the data link service area based on the satellite's earth-fixed coordinate system position coordinates.

[0069] The data link service area refers to the area that can be covered by the communication between the satellite and the ground node. The present invention can further simplify the calculation of the Doppler effect by calculating the geometric center position of the service area, determine the center point of the service area, and provide a basis for the subsequent Doppler center position calculation.

[0070] Step 4: Calculate the Doppler center position of the data link service area based on the position coordinates of the satellite's earth-fixed coordinate system and the position coordinates of the geometric center of the data link service area.

[0071] The present invention combines the satellite position and the geometric center position of the service area to more accurately determine the Doppler center position, providing a basis for subsequent Doppler effect compensation.

[0072] Step 5: Calculate the delay value and Doppler value at the Doppler center based on the Doppler center position of the data link service area and the satellite's earth fixed coordinate system position coordinates.

[0073] Time delay and Doppler value are key parameters in wireless communication, which directly affect the communication quality. The present invention calculates the time delay and Doppler value at the Doppler center to supplement and compensate for the signal transmission frequency of the data link terminal.

[0074] Step six: correct the delay based on the delay value, use the delay value at the Doppler center to send the message in advance so that the message is at the typical time of the time slot when it arrives at the ground node, and use the delay value at the Doppler center to delay the reception of the message so that the message is at the typical time of the time slot when it arrives at the satellite node.

[0075] Delay correction is to compensate for the delay difference caused by the propagation distance and speed change. The present invention can ensure that the message arrives within a specific time slot by sending / receiving the message in advance or lag, thereby improving the synchronization and reliability of communication, realizing accurate correction of delay, and ensuring the synchronous arrival of the message.

[0076] Step 7: Pre-compensate the Doppler value on the frequency of the signal sent by the data link terminal.

[0077] Doppler compensation is to eliminate the frequency deviation caused by the Doppler effect. The present invention can ensure that the frequency of the signal received by the receiving end is consistent with that of the transmitting end by pre-compensating the frequency of the transmitted signal, eliminate the influence of the Doppler effect on the signal frequency, and ensure the accuracy and stability of the communication.

[0078] In summary, this embodiment achieves efficient and accurate data communication between the ground and the sky through precise calculation and compensation, and provides an effective ground-sky integration method for the field of wireless communications.

[0079] Example 2

[0080] Based on the same inventive concept as Example 1, this example introduces specific implementation steps of a data link terminal ground-ground integration method, including:

[0081] Step 1: Select the equivalent position of the data link satellite terminal as the Doppler center position of the data link service area.

[0082] In some embodiments, under the coverage of a low-orbit satellite, the Doppler center of the data link service area is the location where the average value of the minimum Doppler value and the maximum Doppler value of the terminal in the data link service area is located.

[0083] Step 2: Calculate the satellite's Earth-fixed coordinate system position coordinates based on the orbital parameters.

[0084] In some embodiments, the orbital parameters include orbital inclination, right ascension of ascending node, argument of perigee, mean anomaly, eccentricity, and mean motion.

[0085] In this embodiment, calculating the position coordinates of the satellite earth-fixed coordinate system according to the orbital parameters includes:

[0086] The mean anomaly angle is calculated based on the average motion, where the calculation formula of the mean anomaly angle is expressed as:

[0087] ;

[0088] Where n represents the average motion, is the average angular velocity of the satellite, t represents the current time, Indicates the reference time when the satellite passes the perigee;

[0089] The eccentric anomaly is solved according to the calculation formula of the mean anomaly angle, where the calculation formula of the mean anomaly angle is expressed as:

[0090] ;

[0091] In the formula, represents the mean anomaly angle, E represents the eccentric anomaly, represents the eccentricity, represents the sine function;

[0092] The true anomaly angle is calculated according to the eccentric near point and the eccentricity, wherein the calculation formula of the true anomaly angle is expressed as:

[0093] ;

[0094] In the formula, represents the true anomaly angle, represents the tangent function, represents the inverse tangent function;

[0095] Calculate the orbital radius based on the orbital semi-major axis, the true anomaly, and the eccentricity:

[0096] ;

[0097] In the formula, r represents the orbit radius, and a represents the semi-major axis of the orbit;

[0098] The position of the satellite in the orbital plane is calculated according to the orbital radius and the true anomaly, wherein the abscissa, ordinate and vertical coordinate of the position of the satellite in the orbital plane are respectively expressed as:

[0099] ;

[0100] ;

[0101] ;

[0102] In the formula, The abscissa representing the satellite's position in the orbital plane, The ordinate representing the satellite's position in the orbital plane, The vertical coordinate representing the satellite's position in the orbital plane, represents the cosine function, represents the sine function;

[0103] According to the position coordinates of the satellite in the orbital plane and the orbital parameters, the coordinates of the satellite in the orbital plane are converted to the geocentric inertial coordinate system ECI to obtain the position coordinates of the satellite in the geocentric inertial coordinate system ECI, wherein the abscissa, ordinate and ordinate of the position coordinates of the satellite in the geocentric inertial coordinate system ECI are respectively expressed as:

[0104] ;

[0105] In the formula, The horizontal coordinate of the satellite's position in the Earth-centered inertial coordinate system ECI, The ordinate represents the position coordinate of the satellite in the Earth-centered inertial coordinate system ECI. The vertical coordinate of the satellite's position in the Earth-centered inertial coordinate system ECI represents the right ascension of the ascending node, represents the argument of perigee, represents the orbital inclination;

[0106] According to the angular velocity of the earth's rotation and the definition of the earth-fixed coordinate system, the geocentric inertial coordinate system ECI and the earth-fixed coordinate system are transformed to obtain the satellite's earth-fixed coordinate system position coordinates, where the horizontal coordinate, vertical coordinate and vertical coordinate of the satellite's position in the earth-fixed coordinate system are expressed as:

[0107] ;

[0108] In the formula, The horizontal coordinate representing the satellite's position in the Earth-fixed coordinate system, The ordinate of the satellite's position in the Earth-fixed coordinate system, The vertical coordinate representing the satellite's position in the Earth-fixed coordinate system, It is the rotation angle of the Earth G relative to the fixed celestial body, obtained by Greenwich Mean Time GMT or Universal Time UT.

[0109] Step 3: Calculate the position coordinates of the geometric center of the data link service area based on the satellite's earth-fixed coordinate system position coordinates.

[0110] In some embodiments, the position coordinates of the geometric center of the data link service area are the projection point of the ground center point covered by the beam below the satellite orbit, that is, the ground meridian point of the satellite.

[0111] In this embodiment, the position coordinates of the geometric center of the data link service area are calculated according to the position coordinates of the satellite earth fixed coordinate system, including:

[0112] The longitude and latitude of the meridian point are calculated based on the satellite's position coordinates in the satellite's earth-fixed coordinate system and the distance between the satellite and the center of the earth.

[0113] In this embodiment, the longitude and latitude of the meridian point are respectively expressed as:

[0114] ;

[0115] ;

[0116] In the formula, Indicates the meridian point The longitude, Indicates satellite The ordinate of the position coordinate in the satellite's earth-fixed coordinate system, Indicates satellite The abscissa of the position coordinate in the satellite's earth-fixed coordinate system, Indicates the meridian point The latitude, represents the inverse sine function, Indicates satellite The vertical coordinate of the position coordinate in the satellite earth fixed coordinate system, Indicates satellite Distance from the center of the Earth, where , represents the radius of the Earth, For satellite orbital altitude;

[0117] Based on the longitude and latitude of the meridian point and the radius of the earth, the earth-fixed coordinates of the meridian point, that is, the position coordinates of the geometric center of the data link service area, are calculated.

[0118] In this embodiment, the abscissa, ordinate and ordinate of the earth-fixed coordinates of the meridian point are respectively expressed as:

[0119]

[0120]

[0121]

[0122] In the formula, , and Meridian The horizontal, vertical and vertical coordinates of the Earth-fixed coordinates.

[0123] Step 4: Calculate the Doppler center position of the data link service area based on the satellite's earth-fixed coordinate system position coordinates and the position coordinates of the geometric center of the data link service area.

[0124] In some embodiments, the center position of the satellite's position coordinates in the satellite's earth-fixed coordinate system and the position coordinates of the geometric center of the data link service area is usually located in the middle between the beam center point and the beam edge point, that is, the Doppler center position of the data link service area.

[0125] In this embodiment, the horizontal coordinate, vertical coordinate and vertical coordinate of the Doppler center position of the data link service area are respectively expressed as:

[0126] ;

[0127] In the formula, , and The horizontal, vertical and vertical coordinates represent the coordinates of the Doppler center position of the data link service area, respectively. Indicates the Doppler center of the data link service area.

[0128] Step 5: Calculate the delay value and Doppler value at the Doppler center based on the Doppler center position of the data link service area and the satellite's earth fixed coordinate system position coordinates.

[0129] In this embodiment, the delay value and the Doppler value at the Doppler center are calculated according to the Doppler center position of the data link service area and the position coordinates of the satellite in the satellite earth fixed coordinate system, including:

[0130] According to the Doppler center position of the data link service area and the position coordinates of the satellite in the satellite earth fixed coordinate system, the vector between the satellite and the Doppler center position of the data link service area and the geometric distance between the satellite and the Doppler center position of the data link service area are calculated;

[0131] The vector representation of the Doppler center position of the satellite and the Doppler center point data link service area is:

[0132] ;

[0133] In the formula, The vector representing the Doppler center position of the data link service area between the satellite and the Doppler center point;

[0134] The geometric distance between the satellite and the Doppler center position of the data link service area is expressed as:

[0135] ;

[0136] In the formula, Indicates the geometric distance between the satellite and the Doppler center position of the data link service area;

[0137] According to the vector of the Doppler center position of the satellite and the Doppler center point data link service area and the satellite radial velocity, the radial velocity, that is, the velocity component in the projection direction, is calculated. The radial velocity is expressed as:

[0138] ;

[0139] In the formula, represents the radial velocity, The vector representing the Doppler center position of the satellite and the Doppler center point data link service area, represents the satellite radial velocity;

[0140] According to the geometric distance and light speed between the satellite and the Doppler center position of the data link service area, the delay value at the Doppler center is calculated. The delay value at the Doppler center is expressed as:

[0141] ;

[0142] In the formula, represents the delay value at the Doppler center, represents the speed of light;

[0143] The Doppler value at the Doppler center is calculated according to the radial velocity, the speed of light and the signal frequency. The Doppler value at the Doppler center is expressed as:

[0144] ;

[0145] In the formula, represents the Doppler value at the Doppler center, represents the signal frequency, represents the maximum Doppler shift, represents the minimum Doppler shift, where , .

[0146] Step 6: Correct the delay based on the delay value, use the delay value at the Doppler center to send the message in advance so that the message is at the typical time of the time slot when it arrives at the ground node, and use the delay value at the Doppler center to delay the reception of the message so that the message is at the typical time of the time slot when it arrives at the satellite node.

[0147] In some embodiments, for the uplink, the satellite receives the ground data link terminal to send the time slot start time reference ground transmission time slot adaptive delay ; For the downlink, the satellite data link terminal sends the time slot start time with reference to the ground transmission time slot adaptive advance ,in, Indicates the delay value at the Doppler center, such as Figure 2 shown.

[0148] Step 7: Pre-compensate the Doppler value on the data link terminal sending signal frequency.

[0149] In this embodiment, the Pulser value is pre-compensated on the frequency of the signal sent by the data link terminal, which is expressed as:

[0150]

[0151] In the formula, Indicates the frequency of the data link terminal sending signal after compensation. Indicates the frequency of the data link terminal sending signal before compensation. Indicates the Doppler value at the Doppler center.

[0152] In summary, under the condition that the orbital altitude of the satellite is 550km and the radius of the beam coverage service area is 550km, Figure 3-Figure 5As shown in Figure 2, the propagation delay of different data link terminals changes with the elevation angle of the ground data link terminal and the satellite. At an elevation angle of 20°, the average propagation delay is 7.7 Around, the minimum propagation delay is 5.7 The maximum propagation delay is about 8.8ms. When the elevation angle is 40°, the average propagation delay is about 5 Around, the minimum propagation delay is 2.9 Around, the maximum propagation delay is 6.1 At an elevation angle of 60°, the average propagation delay is 3.9 Around, the minimum propagation delay is 2.3 The maximum propagation delay is about 5 The maximum protection period of general data link time slot transmission is 4.4 Therefore, it is impossible to support normal communication of existing satellite data links. However, the propagation delay after the delay correction method of the present invention can meet the demand, such as Figure 6-Figure 8 As shown in Figure 2, after delay correction, the maximum propagation delay at different elevation angles is 2.375 to 2.528 , fully meeting the requirements of the existing data link time slot propagation protection period and enabling normal satellite-to-ground communications.

[0153] The satellite orbit altitude is 550km, the radius of the beam coverage service area is 550km, and the satellite speed is 7.5 , the data link terminal signal transmission frequency is 1GHz, such as Figure 9-11 As shown in the figure, the Doppler frequency shift of different data link terminals changes with the satellite elevation angle. At an elevation angle of 20°, the Doppler mean is 11.758 , the maximum Doppler shift is 23.309 , the minimum Doppler shift is 0.306 ; At an elevation angle of 40°, the Doppler mean is 9.587 , the maximum Doppler shift is 18.758 , the minimum Doppler shift is 0.08 ; At an elevation angle of 60°, the Doppler mean is 6.261 , the maximum Doppler shift is 12.102 , the minimum Doppler shift is 0.053 The maximum frequency deviation tolerance range of existing general data link terminals is Therefore, the signal cannot be received normally, affecting signal demodulation. However, after the Doppler compensation method of the present invention, the Doppler frequency shift after compensation at different elevation angles is less than 10 , can meet the data link terminal receiving signal requirements. Figure 12-14As shown, the maximum Doppler frequency shift after compensation is 5.144 , the minimum is -5.286 , meeting the frequency deviation tolerance of existing data link terminals and not affecting the normal reception and demodulation of signals.

[0154] In summary, in actual work, the present invention has successfully calculated the satellite position coordinates, the position coordinates of the geometric center of the data link service area, and the position coordinates of the Doppler center of the data link service area under the existing foreign low-orbit satellite scenarios, and calculated the delay value and the Doppler value of the Doppler center. The present invention also provides ideas and breakthroughs for the delay compensation scheme and the Doppler frequency shift compensation scheme. The present invention successfully solves the influence of excessive delay and excessive Doppler frequency deviation in low-orbit satellite data link communications. The compensated delay and Doppler can fully realize the integrated access of the existing data link terminal and the satellite-borne terminal, which has practical significance in the data link terminal ground-to-earth fusion technology.

[0155] It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0156] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0157] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0158] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0159] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the enlightenment of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the purpose of the present invention and the claims, which all fall within the protection of the present invention.

Claims

1. A data link terminal ground-to-earth fusion method, characterized in that: include: Select the equivalent position of the data link satellite terminal as the Doppler center position of the data link service area; Obtaining ephemeris data, solving it to obtain orbital parameters, and calculating the satellite's position coordinates in an earth-fixed coordinate system based on the orbital parameters; Calculate the position coordinates of the geometric center of the data link service area based on the satellite's earth-fixed coordinate system position coordinates; Calculate the Doppler center position of the data link service area based on the satellite's earth fixed coordinate system position coordinates and the position coordinates of the geometric center of the data link service area; According to the Doppler center position of the data link service area and the satellite earth fixed coordinate system position coordinates, calculate the delay value and Doppler value at the Doppler center; The delay is corrected based on the delay value, the message is sent in advance using the delay value at the Doppler center so that the message is at a typical time of the time slot when it arrives at the ground node, and the message is received with a delay using the delay value at the Doppler center so that the message is at a typical time of the time slot when it arrives at the satellite node; The Doppler value is pre-compensated on the frequency of the signal transmitted by the data link terminal.

2. The data link terminal ground-to-air fusion method according to claim 1, characterized in that: The equivalent position of the data link satellite terminal is selected as the Doppler center position of the data link service area, wherein, under the coverage of the low-orbit satellite, the Doppler center of the data link service area is the position where the average value of the minimum Doppler value and the maximum Doppler value of the terminal in the data link service area is located.

3. The data link terminal ground-to-air fusion method according to claim 1, characterized in that: The orbital parameters include orbital inclination, right ascension of ascending node, argument of perigee, mean anomaly, eccentricity and mean motion.

4. The data link terminal ground-to-air fusion method according to claim 3, characterized in that: Calculating the satellite's earth-fixed coordinate system position coordinates according to the orbital parameters includes: Calculate the mean anomaly angle based on the mean motion; Solve the eccentric anomaly according to the calculation formula of the mean anomaly angle; Calculating a true anomaly angle according to the eccentric anomaly and the eccentricity; Calculate the orbit radius according to the orbit semi-major axis, the true anomaly and the eccentricity; Calculating the position of the satellite in the orbital plane according to the orbital radius and the true anomaly; According to the position coordinates of the satellite in the orbital plane and the orbital parameters, the coordinates of the satellite in the orbital plane are converted into the geocentric inertial coordinate system ECI to obtain the position coordinates of the satellite in the geocentric inertial coordinate system ECI; According to the angular velocity of the earth's rotation and the definition of the earth-fixed coordinate system, the geocentric inertial coordinate system ECI and the earth-fixed coordinate system are transformed to obtain the satellite's earth-fixed coordinate system position coordinates.

5. The data link terminal ground-to-earth fusion method according to claim 4, characterized in that: The position coordinates of the geometric center of the data link service area are the projection point of the ground center point covered by the beam below the satellite orbit, that is, the ground meridian point of the satellite, wherein the position coordinates of the geometric center of the data link service area are calculated according to the position coordinates of the satellite earth fixed coordinate system, including: Calculate the longitude and latitude of the meridian point based on the satellite's position coordinates in the satellite earth-fixed coordinate system and the distance between the satellite and the center of the earth; Based on the longitude and latitude of the meridian point and the radius of the earth, the earth-fixed coordinates of the meridian point, that is, the position coordinates of the geometric center of the data link service area, are calculated.

6. The data link terminal ground-to-air fusion method according to claim 5, characterized in that: The Doppler center position of the data link service area is calculated based on the satellite's earth fixed coordinate system position coordinates and the position coordinates of the geometric center of the data link service area, where: The center position of the satellite's position coordinates in the satellite's earth-fixed coordinate system and the position coordinates of the geometric center of the data link service area is usually located in the middle between the beam center point and the beam edge point, that is, the Doppler center position of the data link service area.

7. The data link terminal ground-to-air fusion method according to claim 6, characterized in that: The abscissa, ordinate and vertical coordinate of the Doppler center position of the data link service area are respectively expressed as: ； In the formula, , and The horizontal, vertical and vertical coordinates represent the coordinates of the Doppler center position of the data link service area, respectively. Indicates the Doppler center of the data link service area.

8. The data link terminal ground-to-air fusion method according to claim 6, characterized in that: According to the Doppler center position of the data link service area and the satellite position coordinates in the satellite earth fixed coordinate system, the delay value and Doppler value at the Doppler center are calculated, including: According to the Doppler center position of the data link service area and the position coordinates of the satellite in the satellite earth fixed coordinate system, the vector between the satellite and the Doppler center position of the data link service area and the geometric distance between the satellite and the Doppler center position of the data link service area are calculated; Calculate the radial velocity, i.e., the velocity component in the projection direction, based on the vector between the satellite and the Doppler center position of the data link service area of ​​the Doppler center point and the radial velocity of the satellite; According to the geometric distance and light speed between the satellite and the Doppler center of the data link service area, the delay value at the Doppler center is calculated; The Doppler value at the Doppler center is calculated based on the radial velocity, the speed of light, and the signal frequency.

9. The data link terminal ground-to-earth fusion method according to claim 1, characterized in that: The method of correcting the delay based on the delay value, sending a message in advance by using the delay value at the Doppler center so that the message is at a typical time of the time slot when arriving at the ground node, and receiving the message with a delay by using the delay value at the Doppler center so that the message is at a typical time of the time slot when arriving at the satellite node, comprises: For the uplink, the satellite receives the ground data link terminal sending time slot start time reference ground transmission time slot adaptive delay ; For the downlink, the satellite data link terminal sends the time slot start time with reference to the ground transmission time slot adaptive advance ,in, Indicates the delay value at the Doppler center.

10. The data link terminal ground-to-earth fusion method according to claim 1, characterized in that: The Doppler value is pre-compensated on the data link terminal sending signal frequency, which is expressed as: ； In the formula, Indicates the frequency of the data link terminal sending signal after compensation. Indicates the frequency of the data link terminal sending signal before compensation. Indicates the Doppler value at the Doppler center.

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