Frequency awarding method based on GEO communication satellite beacon signals

Abstract

This invention provides a frequency assignment method based on GEO communication satellite beacon signals. The standard time-frequency signal output from the NTSC clock array is used as the time-frequency reference signal for the ground control station. The ground control station transmits control signals modulated with the standard time-frequency signal to the GEO satellite in a self-transmitting and self-receiving mode. The GEO satellite receives the control signals from the ground control station, mixes them with an onboard high-stability crystal oscillator, and then feeds them back to the ground control station, while also sending beacon signals to the user terminal. The ground control station obtains the satellite clock offset based on the signal fed back from the GEO satellite and sends it to the user terminal. The user terminal obtains its standard frequency based on the satellite clock offset sent by the ground control station, the beacon signal sent by the GEO satellite, and the satellite orbit sent by the passive orbit determination system. This invention can not only provide a basis for satellite ground control stations to search for, measure, and track satellites, but also provide precise frequency assignment services to ground users with known locations.

Description

Technical Field

[0001] This invention belongs to the field of satellite frequency awarding technology, specifically relating to a frequency awarding method based on GEO communication satellite beacon signals. Background Technology

[0002] High-precision time and frequency information is a crucial strategic infrastructure resource for the nation, playing an irreplaceable fundamental role in national security and the national economy. It is also a vital technology for enhancing national scientific and technological strength and defense capabilities. With the national economy showing a clear trend of steady improvement, the demand for high-precision time and frequency information is gradually increasing across various industries, such as satellite communication, smart cities, deep space exploration, and basic scientific research, all of which require high-precision time and frequency information for support and assurance. In recent years, my country has proposed building a national integrated positioning, navigation, and timing (PNT) system to achieve higher precision and more stable and reliable time and space benchmarks. This system comprehensively utilizes various navigation technologies and methods for positioning, navigation, and time synchronization. By integrating multiple navigation satellite systems, ground reference stations, inertial navigation systems, wireless communication, and clock synchronization technologies, it aims to provide more accurate and reliable PNT services to meet the needs of various application fields for precise positioning, navigation, and time synchronization. It can be said that the level of PNT technology has become an important strategic indicator of comprehensive national strength. Meanwhile, the PNT (Portable Targeting and Navigation) system, with the BeiDou system at its core, has been elevated to a national strategy. It is expected that a comprehensive national PNT system will be established around 2035, providing higher-quality services to global users. The development and construction of a comprehensive PNT system has become a future trend in global satellite navigation systems.

[0003] Time and frequency are closely related, but they are also distinct. A time-frequency system provides users with standard time and frequency signals and information to ensure the entire operating system uses a unified time and frequency standard. Period, a physical quantity closely linked to time, refers to the time required for a process to repeat once. The corresponding frequency can be obtained from the period, and the two are reciprocals of each other. To meet the diverse frequency requirements of different ground users, especially within the context of my country's integrated PNT (Planetary Network Technology) architecture, further research into wide-area, omnidirectional, and high-precision satellite frequency distribution methods is essential. Clearly, satellite frequency distribution offers advantages such as wide coverage, independence from the number of ground users, and high accuracy and stability, and will remain the most widely used frequency distribution technology for a considerable period.

[0004] A satellite beacon signal is a fixed-frequency and fixed-amplitude signal emitted by the satellite. It is primarily used for antenna alignment and automatic tracking by the satellite's uplink earth station. It is a special signal characterizing the satellite's presence and features, providing a basis for ground control stations to search for, measure, and track the satellite. All satellites have inherent beacon signals, which operate continuously from launch until the satellite's decommissioning. Standard frequency and time signals can be transmitted via electromagnetic waves, directly serving various applications. In satellite navigation systems, navigation and positioning technology is based on time measurement; a highly stable and accurate time-frequency reference is crucial for ensuring the system's correct functionality. Although the high-stability crystal oscillators used by satellites have high stability and accuracy, they still exhibit some frequency offset. Building upon previous research, this invention uses ground control stations to achieve high-precision frequency distribution for geostationary orbit satellites. It focuses on breakthroughs in beacon signal-based GEO communication satellite frequency distribution technology, aiming to develop a beacon signal-based satellite frequency distribution method independent of the BeiDou satellite navigation system, becoming an auxiliary frequency distribution technology for the BeiDou system, possessing both scientific significance and application value.

[0005] Currently, commonly used time and frequency transmission technologies include shortwave time synchronization, longwave time synchronization, satellite time and frequency transmission, fiber optic time and frequency transmission, and space laser time and frequency transmission. Different time and frequency transmission systems are suitable for different application scenarios. Shortwave time synchronization is characterized by low accuracy and weak anti-interference capability, and is often used as a backup in certain application fields. Longwave time synchronization is suitable for scenarios with general accuracy requirements, such as power and transportation. The Loland C system's strong resilience and long-range propagation over water make it an important supplement to satellite synchronous time synchronization. Satellite time and frequency transmission features high accuracy and wide coverage, making it the most widely used time synchronization technology, and its importance is increasing daily. Fiber optic time and frequency transmission benefits from the shielding effect of fiber optics and extensive related research, achieving the highest transmission accuracy. Time and frequency transmission based on optical frequency combs has the advantages of high transmission accuracy and good flexibility, and is expected to replace traditional microwave-based transmission methods in high-precision inter-satellite and satellite-to-ground time and frequency transmission.

[0006] Shortwave time synchronization suffers from low accuracy and weak anti-interference capability. The Loland C system's receiving antenna is relatively large, and its transmission accuracy fluctuates due to variations in climate and weather. Fiber optic time-frequency transmission requires pre-installed fiber optic cables, making it only suitable for fixed-target time-frequency networks on the ground, lacking flexibility. Time-frequency transmission based on optical frequency combs is significantly affected by the environment, has short transmission distances, and is complex and costly. Summary of the Invention

[0007] To address the aforementioned problems in the existing technology, this invention provides a frequency awarding method based on GEO communication satellite beacon signals. The technical problem to be solved by this invention is achieved through the following technical solution:

[0008] A frequency awarding method based on GEO communication satellite beacon signals includes:

[0009] S100, the ground control station transmits a telemetry and control signal modulated with a standard time and frequency signal to the GEO satellite in self-transmitting and self-receiving mode; wherein, the ground control station uses the standard time and frequency signal output from the NTSC clock room as its own time and frequency reference signal;

[0010] S200: The GEO satellite receives telemetry and control signals from the ground telemetry and control station, mixes them with an onboard high-stability crystal oscillator, and then feeds them back to the ground telemetry and control station; it also sends beacon signals to the user terminal.

[0011] In S300, the ground control station obtains the satellite clock frequency offset based on the signal fed back by the GEO satellite and sends it to the user terminal.

[0012] S400, the user terminal obtains the standard frequency of the user terminal based on the star clock offset frequency sent by the ground telemetry and control station, the beacon signal sent by the GEO satellite, and the satellite orbit sent by the passive orbit determination system.

[0013] Beneficial effects:

[0014] This invention uses the standard time and frequency signal output by the NTSC clock array as the time and frequency reference signal for the ground control station. The ground control station transmits a control signal modulated with the standard time and frequency signal to the GEO satellite in self-transmitting and self-receiving mode. The GEO satellite receives the control signal from the ground control station, mixes it with an onboard high-stability crystal oscillator, and then feeds it back to the ground control station, while also sending a beacon signal to the user terminal. The ground control station obtains the satellite clock offset based on the signal fed back from the GEO satellite and sends it to the user terminal. The user terminal obtains its standard frequency based on the satellite clock offset sent by the ground control station, the beacon signal sent by the GEO satellite, and the satellite orbit sent by the passive orbit determination system. This invention uses the satellite's beacon signal to transmit a signal with a fixed frequency and amplitude. Besides providing a basis for searching, measuring, and tracking satellites for the satellite ground control station, it can also provide precise frequency instruction services to ground users with known locations.

[0015] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0016] Figure 1 This is a flowchart illustrating a frequency awarding method based on GEO communication satellite beacon signals provided by the present invention;

[0017] Figure 2 This is a schematic diagram of the frequency awarding process of the frequency awarding method based on GEO communication satellite beacon signals provided by the present invention;

[0018] Figure 3This is a schematic diagram of the satellite frequency transmission principle provided by the present invention;

[0019] Figure 4 This is a schematic diagram of the satellite's velocity relative to the ground station in the line-of-sight direction, provided by the present invention. Detailed Implementation

[0020] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto.

[0021] To provide high-precision frequency transmission services to users using satellite beacon transmitters, the inability to accurately monitor and correct the impact of satellite local oscillator signal frequency offset will prevent users from obtaining accurate reference frequency signals. This is the technical problem this invention aims to solve. By utilizing the Doppler model of the signal link in self-transmitting and self-receiving mode at the ground control station, the frequency variation of the satellite local oscillator is calculated, and a function model is established. This model is then transmitted to the user via satellite, thereby correcting the influence of the satellite local oscillator on the user's receiving frequency and further improving the frequency transmission accuracy.

[0022] Most satellites transmit both satellite status information and telemetry signals to earth stations via beacons, and some satellites can also transmit transponder time information. With the support of the NTSC's existing passive orbit determination system, high-precision predicted orbits (meter-level accuracy) for GEO satellites can be obtained. Users can be categorized into static and dynamic users based on their location. For static users, a single satellite is sufficient for frequency assignment; however, for dynamic users, four satellites with known positions are required. This invention primarily focuses on research for static users with known positions, and the proposed technical solution is as follows: First, the atomic clock at the satellite control center needs to be synchronized with the standard time and frequency signal output from the clock room of the National Time Service Center. The standard time and frequency signal is modulated onto a subcarrier, and then modulated together with the remote control signal onto an uplink carrier. This signal is then transmitted to the satellite via the control antenna of the ground control station. After receiving the signal, the satellite mixes it with a high-stability crystal oscillator carried on board before transmitting it to the ground control station along with the downlink beacon signal. Based on the satellite's high-precision orbit, the projection of the satellite's velocity onto the direction of the ground control station can be calculated. Using the Doppler effect calculation method, the deviation of the standard time and frequency signal in the satellite's downlink beacon signal can be obtained after reduction. After compensation, the standard frequency signal at the user end can be obtained, thus completing satellite frequency assignment.

[0023] Combination Figure 1 and Figure 2 This invention provides a frequency awarding method based on GEO communication satellite beacon signals, comprising:

[0024] S100, the ground control station transmits a telemetry and control signal modulated with a standard time and frequency signal to the GEO satellite in self-transmitting and self-receiving mode; wherein, the ground control station uses the standard time and frequency signal output from the NTSC clock room as its own time and frequency reference signal;

[0025] refer to Figure 2 In this step, the standard time and frequency signal output from the NTSC clock room is used as the time and frequency reference signal of the ground telemetry and control station, and it is modulated onto the uplink remote control carrier of the unified carrier system. The telemetry and control signal modulated with the standard time and frequency signal, i.e. the uplink carrier signal, is transmitted to the satellite through the telemetry and control antenna of the ground telemetry and control station.

[0026] refer to Figure 3 and Figure 4 Figure 3 is a schematic diagram of the satellite frequency distribution principle described in this invention. It is assumed that the direction of the line connecting the satellite to the ground tracking and control station is positive. Figure 4 Showing the satellite's velocity vector The projection along the line connecting the satellite and the ground tracking station, i.e. .Depend on Figure 4 It can be known that:

[0027] (1);

[0028] Therefore, the basic expression for the Doppler frequency shift caused by the Doppler effect, that is, the basic expression for the Doppler frequency shift that this invention needs to determine, is expressed as:

[0029] (2);

[0030] In the formula, The frequency of the uplink measurement and control signal. The carrier frequency of the measurement and control signal. This represents the projection of the satellite's velocity onto the line-of-sight directions of both the satellite and the ground control station. At the speed of light, The wavelength of the signal. The angle between the satellite's velocity and the direction of the telemetry and control signal propagation. It is the vector from the satellite to the ground tracking station. Let be the satellite's velocity vector, ( , , ) are the coordinates of the GEO satellite, ( , , () are the coordinates of the ground control station.

[0031] Applying equation (2) to this invention requires calculating the Doppler frequency shift for both the uplink and downlink carrier signals. First, when a ground-based telemetry and control station transmits an uplink carrier signal to a satellite in space, the Doppler offset of the telemetry and control signal during uplink is calculated using the basic expression for the Doppler frequency shift, expressed as:

[0032] (3);

[0033] S200: The GEO satellite receives telemetry and control signals from the ground telemetry and control station, mixes them with the onboard high-stability crystal oscillator, and then feeds them back to the ground telemetry and control station, and sends beacon signals to the user terminal;

[0034] The GEO satellite receives a telemetry signal from the ground control station, and the frequency received at this time is represented as:

[0035] (4).

[0036] The GEO satellite receives telemetry and control signals from ground control stations, amplifies them, mixes the amplified signals using its own high-stability crystal oscillator, and then transmits the mixed signal back to the ground control stations via the downlink. The transmission frequency for transmitting the downlink signal is represented as follows:

[0037] (5)

[0038] In the formula, The local oscillator frequency of the GEO satellite transponder. This is due to the frequency deviation of the star clock.

[0039] In S300, the ground control station obtains the satellite clock frequency offset based on the signal fed back by the GEO satellite and sends it to the user terminal.

[0040] When the downlink signal transmitted by the satellite transmitting antenna reaches the ground control station, the Doppler frequency shift of the downlink signal is:

[0041] (6)

[0042] Substituting equations (1) to (5) into (6), the Doppler frequency shift of the downlink signal can be further expressed as follows:

[0043] (7)

[0044] At this time, the carrier frequency received by the ground telemetry and control station is:

[0045] (8)

[0046] In summary, by substituting equations (3) to (7) into equation (8), the carrier frequency received by the ground telemetry and control station can be re-expressed as follows:

[0047] (9)

[0048] According to equation (9), the satellite clock frequency offset can be obtained from the ground control station in the self-transmitting and self-receiving mode, as follows:

[0049] (10).

[0050] S400, the user terminal obtains the standard frequency of the user terminal based on the star clock offset frequency sent by the ground telemetry and control station, the beacon signal sent by the GEO satellite, and the satellite orbit sent by the passive orbit determination system.

[0051] The beacon on the GEO satellite continuously transmits beacon signals to the user terminal. Given that the location of the ground user is known, the standard frequency received by the user terminal can be obtained according to equation (8), as follows:

[0052] (11)

[0053] In the formula, The frequency carried by the beacon signal. These are the coordinates on the user's end.

[0054] After the Doppler frequency shift of the downlink is known, the receiver or baseband at the user end extracts the standard signal and combines it with the satellite orbit to obtain the standard frequency signal provided by the NTSC and transmitted by the ground control station, thus completing the satellite frequency assignment.

[0055] In satellite navigation systems, navigation and positioning technology is based on time measurement. A highly stable and accurate time-frequency reference is crucial to ensuring the correctness of system function. Traditional frequency transmission methods suffer from significant environmental influences, limited transmission distance, and complex and costly systems. This invention utilizes satellite beacon signals, transmitting a signal with a fixed frequency and amplitude. Besides providing a basis for ground control stations to search, measure, and track satellites, it can also provide frequency transmission services to ground users with known locations.

[0056] This invention utilizes beacon signals from GEO communication satellites to achieve satellite frequency assignment. It studies a high-precision, low-cost frequency assignment scheme using telemetry and control signals from ground control centers. This research aligns with the overall architecture of my country's future integrated PNT (Planetary Telemetry and Control System). Currently, no research institutions or scholars, domestically or internationally, have provided a solution to this problem, which is also the main innovation of this invention: researching a frequency assignment method based on GEO communication satellite beacon signals. This invention meets the current construction needs of my country's integrated PNT system, which aims to achieve higher precision and more stable and reliable spatiotemporal references by fusing multiple information sources based on different principles. It can endow satellite telemetry and control systems with new functions without increasing additional costs, namely, achieving high-precision satellite frequency assignment based on telemetry and control signals.

[0057] Although this application has been described herein in conjunction with various embodiments, those skilled in the art will understand and implement other variations of the disclosed embodiments by reviewing the accompanying drawings, the disclosure, and the appended claims in carrying out the claimed application. In the claims, the word "comprising" does not exclude other components or steps, and "a" or "an" does not exclude a plurality.

[0058] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A frequency awarding method based on GEO communication satellite beacon signals, characterized in that, include: S100, the ground control station transmits a control signal modulated with a standard time and frequency signal to the GEO satellite in self-transmitting and self-receiving mode; wherein, the ground control station uses the standard time and frequency signal output from the NTSC clock room as its own time and frequency reference signal; S200: The GEO satellite receives telemetry and control signals from the ground telemetry and control station, mixes them with an onboard high-stability crystal oscillator, and then feeds them back to the ground telemetry and control station; it also sends beacon signals to the user terminal. In S300, the ground control station obtains the satellite clock frequency offset based on the signal fed back by the GEO satellite and sends it to the user terminal. S400, the user terminal obtains the standard frequency of the user terminal based on the star clock offset frequency sent by the ground telemetry and control station, the beacon signal sent by the GEO satellite, and the satellite orbit sent by the passive orbit determination system.

2. The frequency transmission method based on GEO communication satellite beacon signals according to claim 1, characterized in that, In S100, the ground tracking and control station sends tracking and control signals to the GEO satellite via the uplink. The Doppler offset of the uplink tracking and control signals is expressed as follows: ； ； In the formula, The frequency of the uplink measurement and control signal. The carrier frequency of the measurement and control signal. This represents the projection of the satellite's velocity onto the line-of-sight directions of both the satellite and the ground control station. At the speed of light, The wavelength of the signal. The angle between the satellite's velocity and the direction of the telemetry and control signal propagation. It is the vector from the satellite to the ground tracking station. Let be the satellite's velocity vector, ( , , ) are the coordinates of the GEO satellite, ( , , () are the coordinates of the ground control station.

3. The frequency transmission method based on GEO communication satellite beacon signals according to claim 2, characterized in that, In S200, the GEO satellite receives telemetry and control signals from the ground control station, amplifies and mixes them to obtain downlink signals, and then transmits them to the ground control station; the frequency received by the GEO satellite from the ground control station is represented as: 。 4. The frequency transmission method based on GEO communication satellite beacon signals according to claim 3, characterized in that, In S200, the transmission frequency at which the GEO satellite sends downlink signals to the ground control station via the downlink is represented as follows: ； In the formula, The local oscillator frequency of the GEO satellite transponder. This is due to the frequency deviation of the star clock.

5. The frequency transmission method based on GEO communication satellite beacon signals according to claim 4, characterized in that, In S200, when the downlink signal transmitted by the GEO satellite arrives at the ground control station, the Doppler shift of the downlink is expressed as: 。 6. The frequency transmission method based on GEO communication satellite beacon signals according to claim 5, characterized in that, In S300, when the ground control station receives the signal fed back by the GEO satellite, the received carrier frequency is represented as follows: 。 7. The frequency transmission method based on GEO communication satellite beacon signals according to claim 6, characterized in that, The satellite clock offset frequency obtained by the ground control station in the self-transmitting and self-receiving mode is expressed as follows: 。 8. The frequency awarding method based on GEO communication satellite beacon signals according to claim 7, characterized in that, In S400, the user terminal receives beacon signals transmitted from the GEO satellite, and the frequency received by the user terminal is represented as: ； In the formula, The frequency of the beacon signal. For user-side coordinates.

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