High-precision time synchronization system and method and application thereof

Abstract

The invention discloses a high-precision time synchronization system and method and application thereof, and belongs to the technical field of time synchronization. In the application, based on a communication result with a first device, at least one path of pseudo-range ranging signal and at least one downlink signal are acquired; determining a pseudo-range ranging value based on the pseudo-range ranging signal; a forwarding ranging value is determined based on forwarding ranging signals and represented by a forwarding ranging expression, and the forwarding ranging signals comprise at least one uplink signal broadcasted to the first device and at least one downlink signal forwarded by the first device; and determining a clock difference between the first device and the second device based on the forwarding ranging value, the pseudo-range ranging value and a preset carrier frequency relationship.

Description

[0001] Cross-references

[0002] This disclosure claims the application number 202411070053.0 filed on August 6, 2024 and is entitled "A High Precision The priority of the Chinese patent application for "Time synchronization system and time synchronization method" is claimed. The entire contents of the Chinese patent application are All are incorporated herein by reference. Technical Field

[0003] The present application relates to the field of space technology, and in particular to a high-precision time synchronization system, method and application thereof. Background Art

[0004] The GNSS system (Global Navigation Satellite Sytem) is the current mainstream satellite navigation system. Internationally, there are China's Beidou system, the United States' GPS system, Europe's Galileo system, and Russia's Glonass system. The satellite navigation system is a very large and complex system, involving three major parts: operation and control, satellites, and users. It involves the satellite-ground time synchronization between the operation and control station and the satellite, the time synchronization between the operation and control stations, satellite orbit determination technology, and user positioning and timing applications. The operation and control part monitors the satellite atomic clock time to ensure that the satellite time is accurate and reliable. At the same time, it also determines the satellite orbit and provides ephemeris for users to use; the satellite is the carrier that directly provides services to users, broadcasting three pseudo-range signals, which contain satellite ephemeris messages; users obtain pseudo-range values ​​by measuring pseudo-range ranging signals, and realize user positioning and timing based on pseudo-range values ​​and satellite ephemeris.

[0005] The operation and control part of the satellite navigation system monitors the satellite orbit and satellite time to ensure the long-term reliable operation of the satellite. The synchronization of the navigation satellite time and the operation and control system time is the key. In addition to navigation satellites, aerospace systems such as communication satellites and remote sensing satellites also require high-precision satellite-ground time synchronization requirements. The key to the positioning accuracy of the navigation satellite system lies in determining the clock error of the onboard atomic clock and its changes. At present, there are mainly the following methods to determine the satellite clock error:

[0006] 1. One-way ranging method: This method uses the measured pseudo-range measurement value and the distance between the satellite and the synchronous station obtained by orbit positioning to obtain the difference between the two to obtain the satellite clock error. This method requires the exact satellite-to-ground space distance, ionospheric delay, tropospheric delay and other parameters.

[0007] 2. GPS inverse positioning method. The basic principle of this method is as follows: 4 time-synchronized ground stations simultaneously receive the pseudo-range signal of a certain satellite to obtain 4 pseudo-range observation values, and calculate the position coordinates of the satellite and the clock difference of the satellite relative to the system time according to the GPS positioning equation. The time synchronization accuracy obtained by this method is closely related to the time synchronization accuracy between each station.

[0008] 3. Two-way pseudo-range measurement method. The working principle of two-way pseudo-range time synchronization is based on the fact that the signal propagation path between the satellite and the ground is exactly the same, with the same satellite-ground space distance and tropospheric delay, but different ionospheric delay. Therefore, the clock difference between the satellite and the ground station is the difference in the measured pseudo-range divided by the speed of light c or the difference in the time when the satellite and the ground station detect the corresponding time scale. The process is that both the satellite and the ground station transmit signals at their own independent clock face time under the control of the local clock. After the satellite and the ground station receiver receive the signals transmitted by each other, they complete the pseudo-range measurement with the local clock. By comparing the two pseudo-code ranging values, the satellite clock difference can be obtained, and the obtained clock difference contains the ionospheric delay residual.

[0009] In order to achieve satellite-ground time synchronization, laser methods can also be used. Laser can be regarded as a very high-frequency radio signal. When the laser signal passes through the ionosphere, the time delay is very small and can be ignored. Both satellites and ground stations use laser devices instead of radio transmitters or receivers, which have the disadvantages of high cost and limited application. When using lasers, there is a disadvantage of being greatly affected by the weather. The laser method cannot be used under weather conditions such as rainy days, snowy days, and cloudy days. It can only be used in clear weather. Therefore, although the laser method can achieve excellent time synchronization performance, it is restricted by the disadvantages of high cost and being greatly affected by the weather, making it difficult to be widely used.

[0010] All of the above methods require satellites or ground receivers to receive signals and make measurements. When the signals are transmitted between the satellite and the ground, for the receiver, it involves the influence of the ionosphere and troposphere of the atmosphere at the far end, and the multipath effect and electromagnetic environment at the near end. The far end and the near end are collectively referred to as environmental segment influences. Among them, the atmospheric influence is comprehensive and fundamental, and it is a global problem. In addition to the environmental segment influence, the above methods have the disadvantages of a large number of observation devices, the time synchronization error is affected by the satellite orbit determination accuracy and the user coordinate accuracy, and the time synchronization accuracy is poor.

[0011] The above contents are only used to assist in understanding the technical solution of the present application and do not constitute an admission that the above contents are prior art. Summary of the invention

[0012] The present application combines the characteristics of a satellite transponder with the carrier frequency multiplexing technology and multiple access characteristics of a spread spectrum signal, and utilizes the characteristic that a satellite transponder can forward one signal into at least one signal, and the characteristic that at least two spread spectrum signals can use carrier frequency multiplexing, and at the same time constrains the carrier frequency of a pseudorange ranging signal and the carrier frequency of a forwarded ranging signal to satisfy a certain relationship, and creatively proposes a system and method for determining a clock error using the relationship between a pseudorange ranging value, a forwarded ranging value, and a preset carrier frequency.

[0013] To achieve the above-mentioned purpose, the present application provides a high-precision time synchronization system, comprising a first device and a second device connected in communication, and a computing device connected in communication with the first device and the second device respectively; there are m pseudo-range ranging signals and h forwarding ranging signals between the first device and the second device, and the pseudo-range ranging signals and the forwarding ranging signals have at least two different carrier frequencies; the carrier frequencies of the m pseudo-range ranging signals and the carrier frequencies of the h forwarding ranging signals satisfy a preset carrier frequency relationship; wherein m and h are both positive integers greater than or equal to 1; the pseudo-range ranging signal is broadcast by the first device and received by the second device, or broadcast by the second device and received by the first device; the forwarding ranging signal is composed of an uplink signal and a downlink signal, the second device broadcasts the uplink signal and receives the downlink signal, and the first device receives the uplink signal and forwards it to form the downlink signal.

[0014] In addition, to achieve the above, the present application also provides a pseudorange value determination method, which is applied to the high-precision time synchronization system described in any embodiment of the present application, and the method is executed by a first device, and the method includes: receiving m pseudorange ranging signals broadcast by a second device; synchronously measuring each of the pseudorange ranging signals to obtain m pseudorange ranging values; wherein m is a positive integer.

[0015] In addition, to achieve the above, the present application also provides a ranging value determination method, which is applied to the high-precision time synchronization system described in any embodiment of the present application, and the method is executed by a second device, and the method includes: when the pseudo-range ranging signal is broadcast by the first device, broadcasting at least one uplink signal to the first device; obtaining at least one downlink signal forwarded by the first device based on the at least one uplink signal, wherein the at least one uplink signal and the at least one downlink signal constitute an h-path forwarding ranging signal; obtaining m-path pseudo-range ranging signals broadcast by the first device; synchronizing Measuring each of the pseudorange ranging signals and each of the forwarding ranging signals to obtain m pseudorange ranging values ​​and h forwarding ranging values; when the pseudorange ranging signal is broadcast by the second device and received by the first device, broadcasting at least one uplink signal to the first device; obtaining at least one downlink signal forwarded by the first device based on the at least one uplink signal, wherein the at least one uplink signal and the at least one downlink signal constitute h forwarding ranging signals; synchronously measuring each of the forwarding ranging signals to obtain h forwarding ranging values; wherein m+h≥2, and m and h are both positive integers.

[0016] In addition, to achieve the above-mentioned purpose, the present application also provides a high-precision time synchronization method, which is applied to the high-precision time synchronization system described in any embodiment of the present application, and the method is executed by a computing device, and the method includes: when the pseudorange ranging signal is broadcast by the second device and received by the first device, obtaining m pseudorange ranging values ​​measured by the first device based on communication with the first device, and obtaining h forwarding ranging values ​​measured by the second device based on communication with the second device; when the pseudorange ranging signal is broadcast by the first device and received by the second device, obtaining the first pseudorange ranging value based on communication with the second device. m pseudorange measurement values ​​and h forwarding ranging values ​​measured by two devices; wherein the carrier frequencies corresponding to the h forwarding ranging values ​​and the carrier frequencies corresponding to the m pseudorange measurement values ​​satisfy a preset carrier frequency relationship; m+h≥2, and m and h are both positive integers; each of the pseudorange measurement values ​​is represented by a pseudorange measurement expression and each of the forwarding ranging values ​​is represented by a forwarding ranging expression; the clock difference between the first device and the second device is determined based on the m pseudorange measurement values ​​represented by the pseudorange measurement expression, the h forwarding ranging values ​​represented by the forwarding ranging expression and the preset carrier frequency relationship.

[0017] In addition, to achieve the above-mentioned purpose, the present application also provides a method for determining the satellite-to-ground space distance, which is applied to the high-precision time synchronization system described in any embodiment of the present application, and the method is executed by a computing device, and the method includes: determining the tropospheric delay on the ranging signal path between the first device and the second device based on a preset tropospheric model; determining the ionospheric delay on the ranging signal path between the first device and the second device based on an ionospheric model or a known total number of ionospheric electrons, wherein when the pseudorange ranging value and the forwarding ranging value are both one, the ionospheric delay is determined by the ionospheric model; when the number of pseudorange ranging values ​​and / or forwarding ranging values ​​is greater than or equal to 2, the ionospheric delay is determined by the ionospheric model. The tropospheric delay is determined by any two pseudorange measurement values ​​or any two forwarding ranging values; based on the determined tropospheric delay, the ionospheric delay and any one forwarding ranging value, the satellite-to-ground space distance between the second device and the first device is determined; or, based on the determined tropospheric delay, the ionospheric delay, the clock difference between the first device and the second device and any one pseudorange measurement value, the satellite-to-ground space distance between the first device and the second device is determined, wherein the clock difference between the first device and the second device, the pseudorange measurement value, and the forwarding ranging value are determined according to the high-precision time synchronization method described in any embodiment of the present application.

[0018] In addition, to achieve the above-mentioned purpose, the present application also provides a satellite navigation system, including: a high-precision time synchronization system as described in any embodiment of the present application, wherein the first device is a satellite, the second device is a user station, and the number of the satellites is greater than or equal to 2; multiple third devices, all of which are communicatively connected to the satellite; wherein the user station obtains the orbital parameters of the corresponding satellite based on the data transmission results with each satellite, and determines the coordinate information of the user station based on the orbital parameters of each satellite and the space distance between the user station and the satellite; some of the third devices constitute a satellite orbit determination system, which is used to monitor and process the orbit of the satellite to obtain satellite orbit parameters; some of the third devices constitute a satellite-to-ground time synchronization system, which is used to monitor the time of each satellite.

[0019] In addition, to achieve the above-mentioned purpose, the present application also provides an inter-station time synchronization system, including: the satellite navigation system described in any embodiment of the present application; wherein, when there are at least two user stations, at least two of the user stations achieve time synchronization with each other by exchanging data through communication.

[0020] In addition, to achieve the above-mentioned purpose, the present application also provides an inter-station time synchronization system, including: the high-precision time synchronization system described in any embodiment of the present application; wherein, when the second device or the first device is at least two, at least two of the second devices or the first devices achieve time synchronization with each other by exchanging data through communication.

[0021] In addition, to achieve the above-mentioned purpose, the present application also provides a satellite positioning method, which is applied to the satellite navigation system described in any embodiment of the present application, and the method is executed by a user station, and the method includes: obtaining the orbital parameters of each satellite; determining the coordinate information of the corresponding satellite based on the orbital parameters; determining the star-to-earth space distance between each satellite according to the star-to-earth space distance determination method described in any embodiment of the present application; determining the coordinate information of the user station based on the orbital parameters of each satellite and the star-to-earth space distance between each satellite.

[0022] In the high-precision time synchronization system provided by the present application, the second device can not only determine the clock difference between the first device and the second device, but also determine the satellite-to-ground space distance, etc. When the time synchronization system is applied to the field of satellite navigation, compared with the prior art, it overcomes the error influence of ionospheric delay and tropospheric delay, can improve the accuracy of the determined clock difference, improve navigation accuracy and has the advantage of strong real-time performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A schematic diagram of the structure of a high-precision time synchronization system according to an implementation mode of the present application;

[0024] Figure 2A structural block diagram of a first device and a second device according to an implementation manner of the present application;

[0025] Figure 3 A flowchart of a time synchronization method according to an implementation of the present application;

[0026] Figure 4-Figure 7 A schematic diagram of a modified structure of a high-precision time synchronization system provided in an embodiment of the present application;

[0027] Figure 8 The present invention is a flowchart of a method for determining the satellite-to-earth space distance according to one embodiment of the present application.

[0028] Fig. 9 A satellite navigation system according to an embodiment of the present application;

[0029] Fig.10 This is a flowchart of a satellite positioning method according to an implementation mode of the present application;

[0030] Figure 11 to Figure 13 A schematic diagram of the structure of a high-precision time synchronization system according to an implementation mode of the present application;

[0031] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solutions and advantages of the present application clearer, the technical solutions in the present application will be clearly and completely described below in conjunction with the drawings in the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0033] The meanings of various parameters involved in the embodiments of the present application are first explained as follows:

[0034] ρ mean1 (n) represents the corrected average pseudo-range measurement value at the nth moment, in meters; ρ z1,a (n) represents the first corrected pseudorange measurement value at the nth moment, in meters; ρ z1 (n) represents the first pseudo-range measurement value at the nth moment, in meters; R true,z1 (n) represents the real space distance that the first pseudo-range measurement signal at the nth moment has passed, in meters; z1 (n) represents the ionospheric delay of the first pseudo-range measurement signal at the nth moment, in meters; T duiliu,z1(n) represents the tropospheric delay of the first pseudo-range measurement signal at the nth moment, in meters; c represents the speed of light, in meters per second; δt s (n) represents the clock difference between the first device and the system time at the nth moment, in seconds; δt z (n) represents the clock difference between the second device and the system time at the nth moment, in seconds; sagnac zz (n) represents the Sagnac effect delay of the pseudo-range measurement signal at the nth moment, in meters; X z1 (n) represents the hardware device delay of the first pseudo-range measurement signal at the nth moment, in meters, wherein the hardware device delay of the pseudo-range measurement signal includes the transmission delay of the first pseudo-range measurement signal and the reception delay of the first pseudo-range measurement signal;

[0035] L mean1 (n) represents the corrected average forwarding ranging value at the nth moment, in meters; L 1,a (n) represents the first corrected forward ranging value at the nth moment, in meters; L1(n) represents the first forward ranging value at the nth moment, in meters; R true,u1 (n) represents the real spatial distance that the uplink signal of the first forwarded ranging signal at the nth moment has passed, in meters; R true,d1 (n) represents the real spatial distance that the downlink signal of the first forwarded ranging signal at the nth moment has passed, in meters; u1 (n) represents the ionospheric delay of the uplink signal of the first forwarded ranging signal at the nth moment, in meters; d1 (n) represents the ionospheric delay of the downlink signal of the first forwarding ranging signal at time n, in meters; T duiliu,u1 (n) represents the tropospheric delay of the uplink signal of the first forwarded ranging signal at time n, in meters; T duiliu,d1 (n) represents the tropospheric delay of the downlink signal of the first forwarding ranging signal at the nth moment, in meters; Y1(n) represents the hardware device delay of the first forwarding ranging signal at the nth moment, in meters, and the hardware device delay of the forwarding ranging signal includes the transmission delay of the uplink signal of the first forwarding ranging signal, the forwarding delay of the downlink signal of the first forwarding ranging signal, and the receiving delay of the downlink signal of the first forwarding ranging signal;

[0036] dT represents the value of the first pseudo-range ranging signal and the first forwarded ranging signal multiplied by the ionospheric delay coefficient and the total number of ionospheric electrons according to formula (f1), unit: second, where dT≥0;

[0037] Q ion represents the ionospheric delay coefficient, TEC(n) represents the total number of ionospheric electrons on the ranging signal path between the first device and the second device at the nth moment; f u1(n) represents the carrier frequency of the first forwarded ranging signal uplink signal at the nth moment, in Hertz; f d1 (n) represents the carrier frequency of the first forwarded ranging signal downlink signal at the nth moment, in Hertz; f z1 (n) represents the carrier frequency of the first pseudo-range measurement signal at the nth moment, in Hertz.

[0038] Special mention: Q ion is the ionospheric delay coefficient, which is published by some international organizations. With the in-depth study of ionospheric delay, the ionospheric delay coefficient is becoming more and more accurate. The ionospheric delay coefficient used to be 40.28, 40.30, and is currently 40.309. There may be more accurate ionospheric delay coefficients in the future. This application does not specifically limit the ionospheric delay coefficient, and takes the latest published value. In this embodiment, Q ion The value is 40.309.

[0039] The present application proposes a system and method for obtaining a high-precision clock error by creatively applying the carrier frequency of a forwarded ranging signal and a pseudo-ranging signal.

[0040] At the same time, based on the high-precision time synchronization system and its method, a satellite navigation system is proposed through combination. Compared with the existing Beidou satellite navigation system, the biggest feature of this satellite navigation is that it first obtains high-precision user clock errors, and then uses the spatial geometric distance between the user station and the satellite to calculate the three-dimensional coordinates of the user station, instead of calculating the three-dimensional coordinates and user clock errors as in the Beidou satellite navigation system. The satellite navigation system provided by this application requires only two satellites at a minimum to achieve high-precision timing and positioning services, and has the characteristics of low investment and excellent performance.

[0041] The system time described in this application refers to the time generated and maintained by a certain system, such as the system composed of the first device and the second device of this application. In practical applications, my country's Beidou time is often used as the reference time and system time, and the clock difference of different devices is the clock difference of different devices relative to this Beidou reference time.

[0042] The computing device of the present application can communicate with the first device and the second device respectively to obtain a pseudorange measurement value and a forwarding range measurement value.

[0043] When the first device broadcasts a pseudo-range measurement signal, the second device receives the pseudo-range measurement signal and measures to obtain a pseudo-range measurement value, and the second device sends and receives a forwarding ranging signal to obtain a forwarding ranging value. At this time, the computing device communicates with the second device to obtain the pseudo-range measurement value and the forwarding ranging value;

[0044] When the second device broadcasts a pseudorange ranging signal, the first device receives the pseudorange ranging signal and measures to obtain a pseudorange ranging value, and the second device spontaneously sends and receives a forwarding ranging signal to obtain a forwarding ranging value. At this time, the computing device communicates with the second device to obtain the forwarding ranging value, and communicates with the first device to obtain the pseudorange ranging value.

[0045] After the computing device obtains the pseudorange measurement value and the forwarded range measurement value, it executes the method of the present application to calculate the clock difference between the first device and the second device.

[0046] It is worth noting that in the embodiments of the present application, the computing device may be integrated into the first device; or integrated into the second device; or may be independent of the first device and the second device, that is, an independent device.

[0047] The core function of the present application is that the sum of the number of ways of forwarding ranging signals and pseudo-ranging signals between the first device and the second device is greater than or equal to 2, and the corresponding pseudo-range ranging value and forwarding ranging value are obtained, and the sum of their numbers is greater than or equal to 2, and the clock difference between the first device and the second device is calculated according to the relationship between the pseudo-range ranging value, the forwarding ranging value and the corresponding preset carrier frequency.

[0048] Therefore, this application focuses on explaining the first device, the second device and the signal structure therebetween, as well as a method for calculating the clock difference between the first device and the second device and a method for calculating the satellite-to-earth space distance.

[0049] This application first describes the high-precision time synchronization system and then describes the satellite navigation system.

[0050] In the present application, there are pseudo-range measurement signals and forwarded ranging signals between the first device and the second device, and the sum of the number of pseudo-range measurement signals and the number of forwarded ranging signals is greater than or equal to 2;

[0051] The forwarded ranging signal is composed of an uplink signal and a downlink signal, the second device broadcasts the uplink signal, the first device receives the uplink signal and forwards it to form the downlink signal, and the second device receives the downlink signal; the pseudo-range ranging signal is broadcast by the first device and received by the second device, or broadcast by the second device and received by the first device.

[0052] Among them, both the pseudo-range ranging signal and the forwarding ranging signal are spread spectrum signals.

[0053] As described above, in the embodiment of the present application, the pseudorange ranging signal may be broadcast by the first device and received by the second device, or may also be broadcast by the second device and received by the first device.

[0054] When the pseudorange ranging signal is broadcast by the second device, the uplink signal broadcast by the forwarding ranging device in the second device can be used as the pseudorange ranging signal. After the uplink signal reaches the first device, it is divided into multiple signals, one of which is used as the pseudorange ranging signal, and the remaining signals are forwarded by the repeater as signals; or, the uplink signal broadcast by the forwarding ranging device in the second device is directly received by the first pseudorange ranging device of the satellite, and is not forwarded as a downlink signal by the repeater.

[0055] When the pseudo-range measurement signal is broadcast by the first device and received by the second device, the forwarded ranging signal is automatically sent and received by the second device, and both the forwarded ranging signal and the pseudo-range measurement signal are received and measured by the second device, and the pseudo-range measurement value and the forwarded ranging value can be synchronously measured;

[0056] It should be noted that when the pseudorange ranging signal is broadcast by the second device and received by the first device, the forwarded ranging signal is spontaneously sent and received by the second device, and the forwarded ranging signal and the pseudorange ranging signal are received and measured by the second device and measured by the first device respectively. Strictly speaking, synchronous measurement cannot be achieved, and the first device and the second device need to have rough time synchronization conditions (the same is true for the two-way pseudorange measurement method. The satellite and the ground station each measure the pseudorange ranging signal sent by the other party, and the satellite and the ground station need to have rough time synchronization requirements). At this time, the pseudorange value measured by the first device and the forwarded ranging value obtained by the second measuring device can be regarded as synchronous measurement, and the clock difference is calculated using the method of the present application.

[0057] In addition, the pseudo-range measurement signal is measured by the second device or the first device, corresponding to two different types of systems. These two different types of systems have the same signal structure, system composition, and processing method except for the pseudo-range measurement signal transmission direction and pseudo-range measurement device. Therefore, for the sake of simplicity and clarity, the following only describes the case where the first device broadcasts the pseudo-range measurement signal.

[0058] There are m-path pseudo-range ranging signals and h-path forwarding ranging signals between the first device and the second device; wherein the pseudo-range ranging signal is broadcast by the first device and received by the second device; the forwarding ranging signal includes an uplink signal broadcast by the second device and a received downlink signal, and the downlink signal is obtained by forwarding the uplink signal by the first device; a carrier frequency of the m-path pseudo-range ranging signal and a carrier frequency of the h-path forwarding ranging signal satisfy a preset carrier frequency relationship; m and h are both positive integers greater than or equal to 1.

[0059] The high-precision time synchronization system provided in the embodiments of the present application can be applied to aerospace systems, typically a high-precision time synchronization system composed of a user station and a satellite, that is, a satellite-to-ground high-precision time synchronization system, in which the user station monitors the clock difference between the satellite and the user station. Specific applications of the satellite-to-ground high-precision time synchronization system may include, for example, satellite navigation, satellite communications, satellite remote sensing, satellite reconnaissance, and meteorological satellites.

[0060] It is worth noting that in the embodiment of the present application, if the telemetry signal is a spread spectrum system, the telemetry signal sent by the telemetry unit in the satellite can be used as a pseudo-range measurement signal.

[0061] Figure 1 This is a schematic diagram of the structure of a high-precision time synchronization system according to an implementation method of the present application, a system when a pseudorange ranging signal is broadcast by a first device, and the system includes a first device 100 and a second device 200 that are communicatively connected.

[0062] In the high-precision time synchronization system provided by the embodiment of the present application, the satellite 100 sends a pseudo-range ranging signal to the user station 200, and the user station 200 sends an uplink signal to the satellite 100. After acquiring the uplink signal, the satellite 100 forwards the uplink signal to obtain a downlink signal and sends the downlink signal to the user station 200. There is a preset carrier frequency relationship between the carrier frequency of the uplink signal, the carrier frequency of the downlink signal, and the carrier frequency of the pseudo-range ranging signal. In this way, the user station 200 can determine the clock error of the satellite 100 relative to the user station 200 through the preset carrier frequency relationship between the pseudo-range ranging signal and the carrier frequency of the forwarded ranging signal without knowing the exact atmospheric delay error caused by the influence of the atmosphere. When the high-precision time synchronization system is applied to satellite navigation, compared with the prior art, the high-precision time synchronization system of the present application overcomes the error influence of ionospheric delay and tropospheric delay, eliminates the satellite-to-ground space distance, can improve the accuracy of the determined clock error, and has the advantages of simplifying satellite payload and reducing satellite cost.

[0063] In an embodiment of the present application, the first device 100 may be, for example, a satellite, and the second device 200 may be, for example, a user station. When the computing device is integrated in the user station, the user station determines the clock difference between the satellite and the user station and the satellite-to-ground space distance, so that the satellite can be synchronized with the clock of the user station. Of course, in other embodiments, the first device 100 may also be a user station, and the second device 200 may be a satellite. Furthermore, the first device described in the embodiment of the present application may also be a high-orbit device, and the second device may be a low-orbit device, or both the first device and the second device may be low-orbit devices, as long as the two devices are located on both sides of the ionosphere, or one device is located in the ionosphere and the other device is located outside the ionosphere, or both devices are located in the ionosphere.

[0064] Of course, in other embodiments, the first device and the second device may also be located on the same side of the ionosphere, for example, both are located on the ground, or both are located in space. In this case, the ionospheric delay is 0, and the clock difference between the first device and the second device can also be determined by the time synchronization method described in the embodiment of the present application.

[0065] Unless otherwise specified, the following description will be given by taking the first device 100 as a satellite and the second device 200 as a user station as an example.

[0066] In order to explain the working principle of the present system more clearly and generally, the present application uses a signal structure in which one forwarding ranging signal and one pseudo-ranging ranging signal, and the carrier frequencies of all signals are different from each other, as an example. At this time, m=1, h=1, such as Figure 1 As shown, the synchronous measurement obtains a forwarding ranging value and a pseudo-range ranging value, so as to illustrate the specific implementation of the method of the present application.

[0067] Due to the preciousness of radio spectrum resources, when m=1, h=1, one forwarding ranging signal and one pseudo-ranging signal are very representative, and the least radio frequency resources can be used to achieve high-precision time synchronization with excellent cost-effectiveness. This example is used for illustration.

[0068] When the present application has multiple forwarded ranging signals or multiple pseudo-range ranging signals, the clock difference between the first device and the second device can also be obtained by setting the carrier frequencies of the multiple forwarded ranging signals and the carrier frequencies of the multiple pseudo-range ranging signals to satisfy a preset carrier frequency relationship using the method of the present application.

[0069] In this exemplary embodiment, the user station sends an uplink signal to the satellite based on its own clock system, that is, based on the local time. After acquiring the uplink signal, the satellite forwards the uplink signal to obtain a downlink signal, and forwards the frequency-converted downlink signal to the user station. It can be seen that the carrier frequencies of the uplink signal and the downlink signal in this exemplary embodiment are different.

[0070] The uplink signal and the downlink signal forwarded by the satellite constitute a forwarding ranging signal, and the user station can determine the forwarding ranging value based on the forwarding ranging signal. In addition, the satellite also sends a pseudo-range ranging signal to the user station based on its own clock system, that is, the local time. The user station receives and demodulates the pseudo-range ranging signal to obtain the pseudo-range ranging value, so that the user station can calculate the clock difference between the satellite and the user station, as well as the satellite-to-ground space distance based on the determined forwarding ranging value and pseudo-range ranging value and the preset frequency relationship.

[0071] The forwarded ranging signal and the pseudo-ranging signal are both spread spectrum signals, and are processed accordingly using spread spectrum technology, carrier frequency multiplexing technology and code division multiple access technology in signal transmission, forwarding and receiving processing.

[0072] It should be noted that the pseudo-range ranging signal and forwarding ranging signal described in the embodiments of the present application refer to the modulated signal obtained after modulating the ranging code signal in the carrier signal. The ranging codes used in the pseudo-range ranging signal and the forwarding ranging signal may be the same or different, and the ranging code of the uplink signal in the forwarding ranging signal is the same as the ranging code of the downlink signal. In some specific embodiments, the ranging code can be obtained by loading protocol data such as pseudo-code, weil code, M code, etc., and this application does not make any special restrictions on the specific selection of the ranging code. It can also be understood that the forwarding ranging signal and pseudo-range ranging signal described in the embodiments of the present application are both spread spectrum signals. When multiple spread spectrum signals are transmitted and received, the relationship between the carrier frequency and the ranging code is processed according to the spread spectrum communication technology, the carrier frequency multiplexing technology and the code division multiple access communication technology, which will not be repeated here.

[0073] The specific process of the user station determining the clock difference between the satellite and the user station can be found in the introduction of the subsequent method embodiments, which will not be expanded here.

[0074] Figure 2 is a structural block diagram of a satellite and a user station according to an implementation mode of the present application. Figure 2 FIG. 4 shows the internal structure of the system when the pseudo-range measurement signal is broadcast by the first device. Figure 2 As shown, in an exemplary embodiment, the satellite 100 may include a communication-connected repeater 101, a pseudorange generating device 102, and a first time-frequency device 103. The pseudorange generating device 102 generates and broadcasts a pseudorange ranging signal; the repeater 101 receives an uplink signal, and after forwarding the uplink signal (including frequency conversion processing and power amplification), forwards a downlink signal to the user station 200; the first time-frequency device 103 provides a time-frequency signal for the repeater 101 and the pseudorange generating device 102.

[0075] It should be understood that the repeater 101 and the pseudorange generating device 102 described in the embodiment of the present application can be set independently, or can also be integrated in one hardware device, that is, the functions of the repeater and the pseudorange generating device are realized by an integrated hardware device, or the repeater 101, the pseudorange generating device 102 and the first time-frequency device 103 are integrated, all of which belong to the protection scope of the present application.

[0076] It should be noted that in the embodiment of the present application, the pseudorange generating device 102 and the repeater 101 are communicatively connected, that is, the two can realize communication interaction. They can communicate with each other directly, or they can be connected to a third-party device to realize communication interaction. All of the above belong to the protection scope of the present application.

[0077] Because the computing device is only used to implement the computing function, its independent setting or integration into the first device or the second device does not affect the implementation of the solution of the present application. Therefore, this exemplary embodiment takes the computing device integrated into the second device as an example for illustrative description. Based on this, the user station 200 may include a forwarding ranging device 201, a second pseudo-range ranging device 202, a second time-frequency device 203 and a computing device 204. The second time-frequency device 203 provides a time-frequency signal for the forwarding ranging device 201 and the second pseudo-range ranging device 202.

[0078] The second pseudo-range measuring device 202 processes the received pseudo-range measuring signal to obtain a pseudo-range measuring value; the forwarding ranging device 201 generates and broadcasts an uplink signal, and receives a downlink signal and determines a forwarding ranging value based on the downlink signal. The calculation device 204 receives the pseudo-range measuring value and the forwarding ranging value, and determines the clock difference of the satellite 100 relative to the user station 200 based on the relationship between the pseudo-range measuring value, the forwarding ranging value, and the preset carrier frequency; the second time-frequency device 203 provides a time-frequency signal for the forwarding ranging device 201 and the second pseudo-range ranging device 202.

[0079] In addition, it should be noted that the second pseudo-range ranging device 202 and the forwarding ranging device 201 in the embodiment of the present application can be set independently, or can also be integrated in one hardware device, that is, the functions of the second pseudo-range ranging device 202 and the forwarding ranging device 201 are realized by one hardware device, or the second pseudo-range ranging device 202, the forwarding ranging device 201 and the second time-frequency device 203 are integrated, all of which belong to the protection scope of the present application.

[0080] As described above, the pseudorange ranging signal can also be broadcast by the second device and received by the first device. In this case, the first device includes a first time-frequency device, a repeater and a first pseudorange ranging device; the first time-frequency device is used to provide a time-frequency signal to the repeater and the first pseudorange ranging device; the repeater is used to receive the uplink signal, perform frequency conversion processing and power amplification on the uplink signal, and then forward the downlink signal to the second device; the first pseudorange ranging device is communicatively connected to the repeater, and the first pseudorange ranging device is used to receive and measure the pseudorange ranging signal; the second device includes a second time-frequency device and a forwarding ranging device; the second time-frequency device is at least used to provide a time-frequency signal to the forwarding ranging device; the forwarding ranging device is used to generate and broadcast the uplink signal, and receive the downlink signal, and based on the forwarding ranging device The forwarding ranging value is determined by the ranging signal; wherein the uplink signal broadcast by the forwarding ranging device is used as the pseudorange ranging signal; the computing device is communicatively connected with the first device and the second device, the computing device receives the pseudorange ranging value and the forwarding ranging value, and determines the satellite-to-ground space distance between the first device and the second device, the total number of ionospheric electrons on the ranging signal path between the first device and the second device, and the clock difference between the first device and the second device based on the forwarding ranging value and the pseudorange ranging value; wherein, when determining the clock difference, the sum of the number of the forwarding ranging value and the pseudorange ranging value is greater than or equal to 2; wherein, the first pseudorange ranging device is integrated or separately arranged with the first time-frequency device and the repeater, and the second pseudorange ranging device is integrated or separately arranged with the second time-frequency device and the forwarding ranging device.

[0081] In this case, the transmission delay of the forwarding ranging device can be measured in advance, so that the delay can be pre-set into the computing device, and the computing device directly uses the delay in subsequent calculations. Because the first device and the second device in this working condition have corresponding differences in system structure only due to the different broadcasting methods of the pseudo-range ranging signal, the specific functions of each functional component are different. Figure 2 The structure shown is similar. Figure 2 The system structure shown is taken as an example to further introduce the specific structures of the first device and the second device.

[0082] In an exemplary embodiment, the forwarding ranging device 201 may include a modulator, a mixer, a demodulator, an antenna, a data collector, etc. The modulator generates an intermediate frequency spread spectrum signal; the mixer mixes the intermediate frequency spread spectrum signal into a radio frequency signal, the antenna sends the radio frequency signal to the satellite, and receives the radio frequency signal forwarded by the satellite, the antenna receives the radio frequency signal and is mixed into an intermediate frequency signal by the mixer; the demodulator demodulates the intermediate frequency signal and obtains the forwarding ranging value through ranging code correlation operation; the data collector records and stores the forwarding ranging value. The second pseudo-range ranging device 202 may include a demodulator, a receiving antenna, a data collector, etc. The receiving antenna receives the pseudo-range ranging signal of the satellite and the second pseudo-range ranging device 202 generates a pseudo-range ranging value.

[0083] In the embodiment of the present application, a zero baseline is set between the second pseudo-range measuring device 202 and the forwarding ranging device 201 .

[0084] It is worth pointing out that the zero baseline setting mentioned in the present application does not mean that the distance between the second pseudo-range ranging device 202 and the forwarding ranging device 201 is 0, but that the distance setting between them must satisfy that the spatial paths experienced by the forwarding ranging signal and the pseudo-range ranging signal are approximately the same. When the distance between the second pseudo-range ranging device 202 and the forwarding ranging device 201 becomes smaller and smaller, and becomes one device or one chip, the approximately same gradually becomes the same, with the same satellite-to-ground space distance, the same tropospheric delay, and the same total number of ionospheric electrons.

[0085] At this time, the pseudorange ranging signal and the forwarded ranging signal have the same transmission path, so the atmosphere has the same influence on the forwarded ranging signal and the pseudorange ranging signal, that is, the forwarded ranging signal and the pseudorange ranging signal have the same ionospheric path and tropospheric path. Therefore, the preset carrier frequency relationship between the carrier frequencies of the forwarded ranging signal and the pseudorange ranging signal can be used to eliminate the influence of the atmospheric error and accurately calculate the clock difference between the satellite and the user station.

[0086] In an exemplary embodiment, the second device is a user station of the present embodiment, and the user station uses at least one second time-frequency device 203. Specifically, the second pseudo-range measuring device 202 and the forwarding ranging device 201 of the user station use at least one second time-frequency device 203. It is worth noting that the at least one second time-frequency device 203 in the embodiment of the present application may include multiple clocks (crystal oscillators or atomic clocks) or one clock (crystal oscillator or atomic clock). When the second time-frequency device 203 includes multiple clocks (crystal oscillators or atomic clocks), one clock provides a clock signal for the second pseudo-range measuring device 202, and the remaining clocks provide clock signals for the forwarding ranging device 201. In actual use, the preset time interval can be set as needed, and here, for example, it can be set to 1s, and the second pseudo-range measuring device 202 and the forwarding ranging device 201 are measured at the rising edge or falling edge of their respective 1PPS (1Pulse PerSecond, second pulse) signals. As a preference, it is generally recommended to use one clock to perform synchronous measurement of pseudo-range ranging signals and forwarding ranging signals at the rising edge or falling edge of the same 1PPS signal.

[0087] The first device is similar, there is at least one first time-frequency device 103. When there are multiple time-frequency devices, one time-frequency device provides a time-frequency signal for the repeater 101, and another time-frequency device provides a time-frequency signal for the pseudorange generating device 102 or the pseudorange generating device 102.

[0088] In this exemplary embodiment, the repeater 101 has a forwarding delay, and the pseudorange generating device 102 has a transmission delay; the second pseudorange ranging device 202 has a receiving delay, and the forwarding ranging device 201 has a transmission delay and a receiving delay;

[0089] The pseudorange ranging signal carries the forwarding delay of the repeater and the transmission delay of the pseudorange generating device, or the forwarding delay of the repeater 101 and the transmission delay of the pseudorange generating device 102 are preset in the computing device 204 .

[0090] The forwarding delay of the repeater 101 refers to the delay generated when the satellite forwards the uplink signal to obtain the downlink signal after receiving the uplink signal sent by the user station.

[0091] The transmission delay of the pseudorange generating device 102 refers to the delay generated by the pseudorange generating device 102 of the satellite in the process of generating and transmitting the pseudorange ranging signal, which is recorded as the pseudorange ranging signal transmission delay.

[0092] Specifically, the repeater 101 is connected in communication with the pseudorange generating device 102, so that the forwarding delay can be sent to the pseudorange generating device 102. The pseudorange generating device 102 can load the acquired forwarding delay and pseudorange ranging signal transmission delay into the pseudorange ranging signal, so that after sending the pseudorange ranging signal to the user station, the second pseudorange ranging device 202 in the user station can obtain the forwarding delay of the repeater and the pseudorange ranging signal transmission delay after demodulating the pseudorange ranging signal. Alternatively, because the change amount of the forwarding delay and the pseudorange ranging signal transmission delay is very small or known, the forwarding delay and the pseudorange ranging signal transmission delay can be regarded as known quantities, so that in actual use, the forwarding delay and the pseudorange ranging signal transmission delay can also be preset in the computing device.

[0093] By loading the forwarding delay and the pseudorange measurement signal transmission delay into the pseudorange measurement signal and transmitting it to the user station, the existing signals between the satellite and the user station are fully utilized to transmit the forwarding delay and the pseudorange measurement signal transmission delay. There is no need to set up additional communication links, so no additional communication resources are occupied, which can greatly reduce communication costs and save frequency resources.

[0094] It is worth noting that the above embodiment is described only by taking the user station and the satellite's own signal (the pseudo-range measurement signal broadcast by the pseudo-range generation device 102) to transmit the forwarding delay and the pseudo-range measurement signal transmission delay as an example.

[0095] The second pseudo-range measuring device 202 of the user station has a receiving delay, which refers to the delay generated in the process of the second pseudo-range measuring device 202 receiving the pseudo-range measuring signal sent by the satellite and generating the pseudo-range measuring value.

[0096] The forwarding ranging device 201 of the user station has a transmission delay and a receiving delay. The transmission delay refers to the delay from the generation of the uplink signal to the transmission of the antenna; the receiving delay refers to the delay from receiving the downlink signal to generating the forwarding ranging value.

[0097] In some embodiments of the present application, additional communication signals may be used between the user station and the satellite to transmit the forwarding delay and the pseudo-range measurement signal transmission delay. For example, a remote control telemetry unit may be provided in the satellite, and the forwarding delay and the pseudo-range measurement signal transmission delay may be transmitted by the telemetry signal broadcast by the remote control telemetry unit, or the forwarding delay and the pseudo-range measurement signal transmission delay may be transmitted to the user station by other user-defined communication link signals. The present application does not specifically limit the specific signal used to transmit the forwarding delay and the pseudo-range measurement signal transmission delay.

[0098] In this exemplary embodiment, the preset carrier frequency relationship refers to the frequency relationship satisfied between the carrier frequency of the uplink signal of the forwarding ranging signal, the carrier frequency of the downlink signal of the forwarding ranging signal, and the carrier frequency of the pseudo-range ranging signal. In a specific embodiment, the carrier frequencies of the h uplink signals, the carrier frequencies of the h downlink signals, and the carrier frequencies of the m pseudo-range ranging signals satisfy the preset carrier frequency relationship shown in the following formula (f1):

[0099]

[0100] Wherein: V represents a real constant, and for example, V=1e-12.

[0101] Some special cases of the carrier frequency of the forward ranging signal and the carrier frequency of the pseudo-range ranging signal are described below.

[0102] When m=1 and h=1, there is only one forwarding ranging signal and one pseudo-ranging signal.

[0103] When the pseudo-range ranging signal is broadcast by the first device, and when the carrier frequency of the pseudo-range ranging signal is the same as the carrier frequency of the downlink signal of the forwarded ranging signal, that is, f z1 (n) = f d1 (n), at this time, there is a preset carrier frequency relationship as shown in formula (f1-1), and only two carrier frequency resources are used to achieve satellite-ground time synchronization;

[0104]

[0105] When the pseudo-range measurement signal is broadcast by the second device, the carrier frequency of the pseudo-range measurement signal is the same as the carrier frequency of the uplink signal of the forwarded ranging signal, that is, f z1 (n) = f u1 (n), at this time, there is a preset carrier frequency relationship as shown in formula (f1-2), and only two carrier frequency resources are used to achieve satellite-ground time synchronization;

[0106]

[0107] At this point, the system evolves into a satellite-ground time synchronization system with two carrier frequencies, in which the carrier frequency of the pseudo-range measurement signal is the same as the carrier frequency of the downlink signal of the forwarded ranging signal. In this case, two carrier frequencies can be used to achieve better satellite-ground time synchronization accuracy.

[0108] The specific impact of the relationship between the carrier frequencies in formula (f1-1) can be further explained by a specific example. When the carrier frequency of the uplink signal of the forwarding ranging signal and the carrier frequency of the pseudo-ranging signal use the L frequency band, such as f z1 =1330MHz, f u1=1575MHz, the frequency relationship is:

[0109]

[0110] When TEC = 50e16 electrons / square meter, the ionospheric residual is:

[0111] 0.5(I z1 -I u1 )=1.63m, which is 5.45ns when converted into time. The ionospheric residual is quite large.

[0112] When the carrier frequency of the uplink signal of the forwarding ranging signal and the carrier frequency of the pseudo-ranging signal use the Cn frequency band (5010 MHz-5030 MHz), this frequency band is a new frequency band allocated by the International Telecommunication Union for satellite navigation.

[0113] Such as z1 =5010MHz, f u1 =5030MHz, the frequency relationship is:

[0114]

[0115] When TEC=50e16, the ionospheric residual is:

[0116] 0.5(I z1 -I u1 )=0.0032m, which is converted to time as 0.0106ns;

[0117] It can be seen that when using the Cn frequency band, the ionospheric residual is very small; when using the Ku, Ka, Q, V frequency bands, the ionospheric residual is still very small. Therefore, when using the Cn, Ku, Ka, Q, V and other frequency bands, considering other factors such as random errors, it is entirely possible to achieve sub-nanosecond time synchronization accuracy.

[0118] Furthermore, in some embodiments, the carrier frequency of the forwarded ranging signal and the carrier frequency of the pseudo-range ranging signal are frequency-hopped according to a preset frequency-hopping pattern on the time axis, that is, the uplink signal, the downlink signal and the pseudo-range ranging signal at different times do not use the same fixed frequency, but use signals of different frequencies at different times. Frequency hopping the signal in this way can improve the signal's anti-interference ability and enhance the signal's anti-interception ability.

[0119] It is worth noting that no matter how the frequency hopping is performed, the carrier frequencies of the pseudo-range measurement signal, the uplink signal, and the downlink signal still need to satisfy the preset carrier frequency relationship shown in the relationship (f1).

[0120] Of course, the carrier frequency of the forwarded ranging signal and the carrier frequency of the pseudo-ranging signal may also remain unchanged for a long time, that is, the time interval between two adjacent frequency hops is infinite.

[0121] In an exemplary embodiment, the high-precision time synchronization system provided by the embodiment of the present application also has a communication function, and the first device uses any uplink signal of the forwarding ranging signal and any pseudo-range ranging signal to transmit data with the second device, or uses an additional communication signal to transmit data with the second device. Specifically, after receiving the uplink signal of the forwarding ranging signal, the satellite is divided into two, one is forwarded downlink to the user station, and the other is received by the satellite to realize communication, or an additional communication signal is added to realize data transmission between the satellite and the user station.

[0122] In an exemplary embodiment, if Figure 1 As shown, the satellite can also send the forwarding delay and the pseudo-range measurement signal transmission delay to the user station by adding a communication signal, that is, in addition to the uplink signal link, the downlink signal link and the pseudo-range measurement signal link, there is an additional communication link (including the communication link uplink signal fu and the communication link downlink signal fd) between the satellite and the user station. The satellite transmits the forwarding delay and the pseudo-range measurement signal transmission delay to the user station through the additional communication link, wherein the additional communication signal can be a remote control and telemetry signal.

[0123] It can be seen that the satellite can transmit the forwarding delay and the pseudo-range measurement signal transmission delay to the user station in a variety of ways. The present application does not specifically limit the specific transmission method of the forwarding delay and the pseudo-range measurement signal transmission delay.

[0124] Based on the above embodiments, the embodiments of the present application also provide a high-precision time synchronization method, which can be applied to the high-precision time synchronization system described in any of the above embodiments. The method can be executed by a computing device. When the computing device is integrated in a user station, the method is executed by the user station.

[0125] In the pseudorange measurement value, it is necessary to obtain the Sagnac effect delay of the satellite, and the Sagnac effect delay requires the coordinates of the user station and the satellite. The coordinates of the satellite can be obtained through the known satellite ephemeris, and the coordinates of the user station can be obtained through the existing positioning method. In this way, the coordinate information required by the method of the embodiment of the present application is obtained, and then the Sagnac effect delay is obtained.

[0126] There is no relativistic delay effect term in the pseudo-range measurement value. This is because in reality, satellites in space have a time-frequency system to provide time and frequency. According to the knowledge of relativity, it is easy to know that the clock on the satellite will produce a corresponding relativistic effect delay due to relativity. The relativistic effect delay of the satellite clock can be solved using existing methods. For example, the satellite clock has been adjusted before going into space. After adjustment, the satellite clock has no relativistic effect delay like the clock on the ground. For details, please refer to the Beidou navigation satellite clock's approach to relativity.

[0127] When the forwarding ranging expression is used to characterize the forwarding ranging value, there is no Sagnac effect delay in the forwarding ranging expression because the Sagnac effect delay of the uplink signal is opposite to the Sagnac effect delay of the downlink signal, and the absolute value difference between the two is very small, so the two Sagnac effect delays can be approximately offset, so that the Sagnac effect delay term is not reflected in the forwarding ranging expression. Of course, in some other embodiments of the present application, the Sagnac effect delay can also be considered, that is, the Sagnac effect delay of the uplink signal and the Sagnac effect delay of the downlink signal are added to the forwarding ranging expression, so as to obtain better measurement accuracy of the forwarding ranging value, which all belong to the protection scope of the present application.

[0128] In addition, for the device delay and its acquisition method used in the embodiment of the present method, reference can be made to the introduction of the above-mentioned system embodiment, which will not be repeated here.

[0129] The ionosphere is a diffuse medium, that is, the time delay caused by the ionosphere to radio frequency signals of different carrier frequencies is different due to the different carrier frequencies, while the troposphere is a non-dispersive medium, that is, the troposphere produces the same time delay for radio frequency signals of different carrier frequencies.

[0130] Because a zero baseline is set between the second pseudo-range ranging device 202 and the forwarding ranging device 201, the pseudo-range ranging signal and the downlink signal traverse the same space path, but the time when the uplink signal crosses the ionosphere is different from the time when the downlink signal crosses the ionosphere after being forwarded by the satellite, and there is a certain time difference. In a relatively short period of time (such as a few seconds), the ionosphere is stable and the total number of electrons in the ionosphere is almost unchanged. It can be calculated that the round-trip time of the radio frequency signal between almost all spacecraft and ground stations will not exceed a few seconds, which fully meets the conditions. Combined with the spatial relationship of the zero baseline setting and the time relationship with a very short time difference, the spatial paths traversed by the forwarding ranging signal and the pseudo-range ranging signal are exactly the same. Because a zero baseline is set between the second pseudo-range ranging device 202 and the forwarding ranging device 201, the space paths traversed by the m-way pseudo-range ranging signal and the h-way forwarding ranging signal are exactly the same, the spatial distances of the pseudo-range ranging signal and the forwarding ranging signal are equal, and the tropospheric delays of the pseudo-range ranging signal and the forwarding ranging signal are equal. In this embodiment, there are equations (19) and (20):

[0131] R true,z1 (n) = R true,u1 (n) = R true,d1 (n) (19);

[0132] T duiliu,z1 (n) = T duiliu,u1 (n) = T duiliu,d1 (n) (20);

[0133] When the pseudo-range measurement signal is broadcast by the second device, the pseudo-range measurement signal and the uplink signal of the forwarded ranging signal traverse the same spatial path, and the forwarder and the first pseudo-range measurement device also have the above formula for setting the zero baseline.

[0134] The method for calculating the clock difference between a satellite and a user station provided in the present application involves h forwarding ranging values ​​and m pseudorange ranging values ​​in the calculation, wherein the minimum value of h is 1 and the minimum value of m is 1. The calculation device first processes the m pseudorange ranging values ​​to obtain a corrected average pseudorange ranging value and processes the h forwarding ranging values ​​to obtain a corrected average forwarding ranging value, and then determines the clock difference using the relationship between the corrected average forwarding ranging value, the corrected average pseudorange ranging value and the preset carrier frequency.

[0135] To illustrate the use of this method, m=1, h=1, that is, there is one corrected average forward ranging value and one corrected average pseudorange ranging value, and the clock difference between the satellite and the user station is calculated based on these two values.

[0136] When the pseudo-range measurement signal is broadcast by the second device and received by the first device, the first device obtains the pseudo-range measurement value by performing the following process:

[0137] Receiving m-channel pseudo-range measurement signals broadcasted by the second device;

[0138] The pseudo-range measurement signals are synchronously measured to obtain m pseudo-range measurement values, wherein m is a positive integer.

[0139] In addition, when the pseudo-range measurement signal is broadcast by the first device and received by the second device, the second device obtains the forwarded ranging value and the pseudo-range measurement value by performing the following process:

[0140] broadcasting at least one uplink signal to the first device;

[0141] Acquire at least one downlink signal forwarded by the first device based on the at least one uplink signal, wherein the at least one uplink signal and the at least one downlink signal constitute an h-path forwarding ranging signal;

[0142] Acquire m-channel pseudo-range measurement signals broadcasted by the first device;

[0143] Synchronously measuring each of the forwarded ranging signals and each of the pseudorange ranging signals to obtain m pseudorange ranging values ​​and h forwarded ranging values;

[0144] Wherein, m+h≥2, and m and h are both positive integers;

[0145] It is particularly worth noting that when the pseudorange ranging signal is broadcast by the second device and received by the first device, or when the pseudorange ranging signal is broadcast by the first device and received by the second device, the h forwarded ranging values ​​all need to be measured by the second device and all need to satisfy m+h≥2.

[0146] Figure 3 is a flowchart of a time synchronization method according to an embodiment of the present application, wherein the method is executed by a computing device, such as Figure 3 As shown, the time synchronization method may include the following steps:

[0147] S100, when the pseudorange ranging signal is broadcast by the second device and received by the first device, obtaining m pseudorange ranging values ​​measured by the first device based on communication with the first device, and obtaining h forwarding ranging values ​​measured by the second device based on communication with the second device;

[0148] When the pseudorange ranging signal is broadcast by the first device and received by the second device, acquiring m pseudorange ranging values ​​and h forwarded ranging values ​​measured by the second device based on communication with the second device;

[0149] The carrier frequencies corresponding to the h forwarded ranging values ​​and the carrier frequencies corresponding to the m pseudorange ranging values ​​satisfy a preset carrier frequency relationship; m+h≥2, and m and h are both positive integers;

[0150] S110, using a pseudorange measurement expression to represent each of the pseudorange measurement values ​​and using a forwarding measurement expression to represent each of the forwarding measurement values;

[0151] S120. Determine a clock difference between the first device and the second device based on the m pseudorange ranging values ​​represented by the pseudorange ranging expression, the h forwarding ranging values ​​represented by the forwarding ranging expression, and the preset carrier frequency relationship.

[0152] The method will be described in detail below by taking the first device being a satellite and the second device being a user station as an example.

[0153] Among them, during the communication process with the satellite, the user station can obtain the pseudo-range measurement signal, demodulate the pseudo-range measurement signal to obtain the forwarding delay and the pseudo-range measurement signal transmission delay. The pseudo-range measurement signal is sent by the satellite to the user station, and the user station receives and demodulates the pseudo-range measurement signal to determine the pseudo-range measurement value.

[0154] During the communication process between the user station and the satellite, it can also send and receive forwarding ranging signals and obtain forwarding ranging values.

[0155] It should be noted that the Sagnac effect delay in the pseudo-range measurement expression and the forwarding ranging expression of the present application has been explained in the previous text and can be used as a known value, while the satellite-to-ground space distance, tropospheric delay, ionospheric delay, satellite clock error relative to system time, and user station clock error relative to system time are unknown. The present application calculates the clock error between the satellite and the user station based on the pseudo-range measurement value and the forwarding ranging value obtained by measurement, as well as the method described.

[0156] In some embodiments, after step S110, the time synchronization method may further include the following steps: using a pseudorange smoothing algorithm to correct the forwarding ranging value and the pseudorange ranging value. Specifically, the pseudorange ranging value and the forwarding ranging value are corrected using the pseudorange smoothing algorithm, so that the noise of the pseudorange ranging value and the forwarding ranging value can be reduced, which is conducive to improving the accuracy of the clock difference finally determined. The specific content of the pseudorange smoothing algorithm is not repeated here.

[0157] Before introducing the specific method, it is specially noted that ±c·(δt z (n)-δt s (n)), when taking +c·(δt z (n)-δt s (n)), the corresponding satellite broadcasts the pseudo-range measurement signal, and the user station receives and measures it; when -c·(δt z (n)-δt s (n)), the corresponding user station broadcasts a pseudo-range measurement signal, and the satellite receives and measures;

[0158] ±sagnca in pseudorange measurement formula (3) zz (n), when taking + sagnca zz (n) corresponds to the Sagnac effect when the satellite broadcasts the pseudo-range measurement signal. When -sagnac zz (n), corresponds to the Sagnac effect of the pseudorange ranging signal broadcast by the user station. It can be seen that when the pseudorange ranging signals are in opposite directions, the absolute value of the Sagnac effect is the same, but the sign is opposite.

[0159] Because the directions of pseudo-range measurement signals are different, except for the opposite signs of the clock difference between the satellite and the user station and the opposite signs of the Sagnac effect, the rest are the same. Therefore, when the satellite broadcasts a pseudo-range measurement signal, the pseudo-range measurement formula is as follows (f3); when the user station broadcasts a pseudo-range measurement signal, the pseudo-range measurement formula is as follows (s3):

[0160] ρ zi (n) = R true,zi (n)+I zi (n)+T duiliu,zi (n)+c·(δt z (n)-δt s (n))+sagnac zz (n)+X zi (n)(f3);

[0161] ρ zi (n) = R true,zi (n)+I zi (n)+T duiliu,zi (n)-c·(δt z (n)-δt s (n))-sagnac zz (n)+X zi (n)(s3);

[0162] The corresponding corrected pseudorange measurement value formulas are (f3') and (s3'):

[0163]

[0164] The method of the present application is described below by taking the pseudo-range ranging signal broadcast by the satellite as an example, that is, the pseudo-range ranging formula (f3) and the corrected pseudo-range ranging formula (f3') corresponding to the pseudo-range ranging signal broadcast by the satellite are used for description.

[0165] In some embodiments, the pseudo-range measurement expression includes preset delay parameter items, and the preset delay parameter items include at least tropospheric delay, ionospheric delay, Sagnac effect delay, real space distance between the satellite and the user station, and clock error. In some other embodiments, the preset delay parameter items may also include hardware device delay.

[0166] After the pseudorange measurement value and the forwarding ranging value are obtained by measurement, in step S110, the corresponding ranging expressions are further used for characterization, that is, the mathematical expressions of the pseudorange measurement value and the forwarding ranging value are obtained, so that the mathematical expressions are used for mathematical processing in subsequent steps to eliminate the common error terms of the two, and finally the clock difference between the satellite and the user station is obtained.

[0167] Specifically, the user station may use the pseudo-range measurement value numbered i including the satellite-to-ground spatial distance and the preset delay parameter item as shown in the following formula (f3):

[0168] ρ zi (n) = R true,zi (n)+I zi (n)+T duiliu,zi (n)+c·(δt z (n)-δt s (n))+sagnac zz (n)+X zi (n)(f3);

[0169] Exemplarily, when i=1, the user station obtains the first pseudorange measurement value shown in the following formula (f3-1):

[0170] ρ z1 (n) = R true,z1 (n)+I z1 (n)+T duiliu,z1 (n)+c·(δt z (n)-δt s (n))+sagnac zz (n)+X z1 (n)(f3-1);

[0171] The user station can use the forwarding ranging value numbered j as shown in the following formula (4): L j (n) = R true,uj (n)+R true,dj (n)+I uj (n)+I dj (n)+T duiliu,uj (n)+T duiliu,dj (n)+Y j (n)(4);

[0172] Exemplarily, when j=1, the user station may use the first forwarding ranging value shown in the following formula (4-1):

[0173] L1(n)=R true,u1 (n)+R true,d1 (n)+I u1 (n)+I d1 (n)+T duiliu,u1 (n)+T duiliu,d1 (n)+Y1(n)(4-1);

[0174] As described above, the pseudorange ranging signal includes an ionospheric delay term, and the forwarded ranging signal also includes an ionospheric delay term. In the present application, the user station can eliminate or reduce the linear combination of the ionospheric delay between the uplink signal, the downlink signal, and the ionospheric delay of the pseudorange ranging signal based on a preset carrier frequency relationship, so as to ultimately eliminate the ionospheric delay error in the process of calculating the clock difference between the satellite and the user station.

[0175] In detail, when the carrier frequency of the signal between the user station and the satellite satisfies the preset carrier frequency relationship, the specific process of step S120 is as follows:

[0176] Because of the zero baseline setting of the user station forwarding ranging device and the user station second pseudo-range ranging device, the ionospheric path traversed by the forwarding ranging signal and the pseudo-range ranging signal is the same, but the total ionospheric electron number TEC(n) is unknown.

[0177] Based on the preset carrier frequency relationship between the carrier frequency of h=1 uplink signal, the carrier frequency of h=1 downlink signal and the carrier frequency of m=1 pseudo-range ranging signal, the ionospheric delay parameters are respectively associated in the corresponding carrier frequency items to obtain the ionospheric delay correspondence between the ionospheric delay of h=1 uplink signal, the ionospheric delay of h=1 downlink signal and the ionospheric delay of m=1 pseudo-range ranging signal, wherein the ionospheric delay parameters include the ionospheric total electron number TEC(n) and the ionospheric delay coefficient on the ranging signal path of the satellite and the user station, so the following formula (1-1) is obtained:

[0178]

[0179] According to the formula (1-1), the corresponding relationship between the ionospheric delay of the uplink signal, the ionospheric delay of the downlink signal and the ionospheric delay of the pseudo-range measurement signal is obtained as shown in formula (1-2):

[0180]

[0181] Thus, in subsequent steps, the user station can determine the clock difference between the satellite and the user station based on the obtained ionospheric time delay correspondence.

[0182] In some embodiments, step S120 may specifically include the following process:

[0183] S121, correcting the m pseudorange measurement values ​​represented by the pseudorange measurement expression to obtain m corrected pseudorange measurement values, and averaging the m corrected pseudorange measurement values ​​to obtain a corrected average pseudorange measurement value;

[0184] S122, correcting the h forwarding ranging values ​​represented by the forwarding ranging expression to obtain h corrected forwarding ranging values, and averaging the h corrected forwarding ranging values ​​to obtain a corrected average forwarding ranging value;

[0185] S123: Determine a clock difference between the first device and the second device based on the corrected average pseudorange ranging value, the corrected average forward ranging value, and the preset carrier frequency relationship.

[0186] Specifically, step S121 is to correct the m pseudorange ranging values ​​shown in formula (f3) obtained in the above step respectively to obtain m corrected pseudorange ranging values, and step S122 is to correct the h forwarding ranging values ​​shown in formula (4) obtained in the above step to obtain h corrected forwarding ranging values.

[0187] Exemplarily, taking m=1, h=1, i.e., one pseudorange ranging value and one forwarding ranging value as an example, in step S121, the user station corrects the above formula (f3-1) according to formula (f3') to obtain the corrected pseudorange ranging value numbered 1 as shown in the following formula (f3'-1):

[0188]

[0189] In step S122, the user station transforms the forwarding ranging value numbered 1 shown in the above formula (4-1) to obtain a modified forwarding ranging value numbered 1 shown in the following formula (4'-1):

[0190]

[0191] When there are multiple pseudorange measurement values ​​and forwarding measurement values ​​(for example, both are greater than or equal to two), the user station further calculates the average of the multiple corrected pseudorange measurement values ​​and the multiple corrected forwarding measurement values, and obtains the corrected average pseudorange measurement value and the corrected average forwarding measurement value respectively, and then in step S123, the clock difference between the satellite and the user station is obtained by using the relationship between the corrected average pseudorange measurement value, the corrected average forwarding measurement value and the preset carrier frequency.

[0192] In this exemplary embodiment, the user station can calculate the corrected average pseudorange measurement value according to the following formula (5):

[0193]

[0194] Exemplarily, when m=1, that is, there is only one pseudorange measurement value, based on the above formula (5), combined with formula (f3'), the corrected average pseudorange measurement value of the following formula (5-1) is determined: ρ mean1 (n) = ρ z1,a (n) = R true,z1 (n)+I z1 (n)+T duiliu,z1 (n)+c·(δt z (n)-δt s (n))(5-1);

[0195] The user station can calculate the corrected average forwarding ranging value according to formula (6): The corrected average forwarding ranging value calculation method shown in formula (6-1) is obtained:

[0196]

[0197] Exemplarily, when h=1, that is, there is only one forwarding ranging value, the corrected average forwarding ranging value of the following formula (6-1) is determined based on the above formula (6):

[0198] L mean1 (n) = L 1,a (n)=(R true,u1 (n)+R true,d1 (n)) / 2+(I u1 (n)+I d1 (n)) / 2+(T duiliu,u1 (n)+T duiliu,d1 (n)) / 2(6-1);

[0199] In an exemplary embodiment, step S123 may specifically include the following steps:

[0200] S1231, mathematically processing an expression representing the corrected average pseudorange measurement value and an expression representing the corrected average forwarding measurement value to obtain an expression including a clock difference between a satellite and a user station;

[0201] S1232. Determine the clock difference between the satellite and the user station using an expression containing the clock difference and a linear combination result of the ionospheric delay.

[0202] Specifically, the corrected average pseudorange value represented by formula (5-1) and the corrected average forwarding range value represented by formula (6-1) are further processed to obtain the clock difference between the satellite and the user station, as shown in formula (7-1);

[0203] (δt z (n)-δt s (n)) c =(ρ mean1 (n)-L mean1 (n)) / c(7-1);

[0204] ±(δt z (n)-δt s (n)) c =(ρ mean (n)-L mean (n)) / c(7);

[0205] It should be noted that the reason why formula (7-1) or formula (7) can be used to calculate the clock error between the satellite and the user station is because the pseudorange measurement value contains the clock error, while the forwarding measurement value does not contain the clock error. The corrected average pseudorange measurement value and the corrected average forwarding measurement value are expanded to obtain the following formula (8-1):

[0206]

[0207] On this basis, because the second pseudo-range measurement value device and the forwarding ranging value in the user station are set to zero baseline, the user station can substitute equations (19) and (20) into formula (8-1) to obtain the clock difference between the satellite and the user station as shown in the following formula (9-1):

[0208]

[0209] The relationship between the ionospheric delay of the forwarding ranging signal and the ionospheric delay of the pseudo-range ranging signal in this embodiment generated according to the preset carrier frequency relationship is shown in formula (1-2). Because the total number of ionospheric electrons between the satellite and the user station is an unknown number, the linear combination result of the ionospheric delay of the forwarding ranging signal and the ionospheric delay of the pseudo-range ranging signal is a numerical range, which is also an unknown number.

[0210] The actual clock difference between the user station and the satellite is shown in formula (10-1):

[0211] (ρ mean1 (n)-L mean1 (n)) / c-dT≤(δt z (n)-δt s (n))≤(ρ mean1 (n)-L mean1(n)) / c+dT (10-1);

[0212] This unknown number is taken as the error of the clock difference between the user station and the satellite, and the result shown in formula (7-1) is obtained.

[0213] As described above, the forwarding ranging value and the pseudorange ranging value can be corrected using a pseudorange smoothing algorithm. Accordingly, in step S120, the forwarding ranging value and the pseudorange ranging value corrected by the pseudorange smoothing algorithm can be used to calculate the clock difference between the satellite and the user station. It can be understood that the use of a pseudorange smoothing algorithm to correct the pseudorange ranging value and the forwarding ranging value can reduce the noise of the pseudorange ranging value and the forwarding ranging value, which is conducive to improving the accuracy of the clock difference finally determined. The specific content of the pseudorange smoothing algorithm will not be repeated here.

[0214] It should be noted that the high-precision time synchronization system and method proposed in the present application can not only solve the clock difference of the satellite relative to the system time when the clock difference of the user station relative to the system time is known, but also solve the clock difference of the user station relative to the system time when the clock difference of the satellite relative to the system time is known.

[0215] According to formula (7-1), when the clock difference δt between the user station and the system time is z When the satellite clock error δt relative to the system time is known, it is easy to obtain s (n), then Indicates the actual calculated clock difference of the satellite relative to the system time. At this time, the user station can monitor the satellite clock difference. For example, the time of the ground control station of the Beidou satellite navigation system is known. The method of this application is used to calculate the clock difference between the control station and the satellite, and then obtain the satellite clock difference;

[0216] On the contrary, when the satellite clock difference δt relative to the system time is s When (n) is a known quantity, the clock difference δt of the user station relative to the system time can be easily obtained: z (n), then It indicates the actual calculated clock difference of the user station relative to the system time. At this time, the satellite can provide time services for the user station.

[0217] When the clock error of the user station relative to the system time and the clock error of the satellite relative to the system time are both unknown, the clock error (δt z (n)-δt s (n)) c .

[0218] The user station determines the clock difference (δt z (n)-δt s (n)) cAfter that, data can be transmitted with the satellite based on the uplink signal and the pseudo-range measurement signal, or based on the additional communication signal. The additional communication signal can be a satellite remote control signal or a telemetry signal. The satellite obtains the clock difference between the satellite and the user station based on the data transmission result. After obtaining the clock difference between the satellite and the user station, the satellite further uses the clock difference to synchronize its own time with the time of the user station. All of these belong to the protection scope of this application.

[0219] Alternatively, the user station does not exchange clock error data with the satellite.

[0220] In the present application, the carrier frequency of the h-path forwarding ranging signal and the carrier frequency of the m-path pseudo-ranging signal need to satisfy the relationship shown in formula (f1):

[0221]

[0222] Among them, the V value is equal to 1e-12, and m and h are both positive integers.

[0223] When formula (f1) is a special preset carrier frequency relationship as shown in formula (f2):

[0224]

[0225] Formula (f2) shows that the function value composed of the carrier frequency of the m-path pseudo-range measurement signal and the carrier frequency of the h-path forwarding ranging signal is equal to 0, and the corresponding ionospheric delay linear combination result is 0. At this time, when the clock difference between the satellite and the user station is calculated using the method provided by the present application, the ionospheric delay is completely eliminated. The clock difference between the satellite and the user station obtained according to formula (7) eliminates the ionospheric delay and obtains an accurate clock difference.

[0226] Several schematic diagrams of preset carrier frequency relationships satisfying formula (f2) are given below.

[0227] The pseudo-range measurement signal and the downlink signal of the forwarded ranging signal are carrier frequency multiplexed.

[0228] For example, when the carrier frequency of the signal between the user station and the satellite has Figure 4 When , it can be obtained that the carrier frequency of the signal satisfies the relationship of formula (21):

[0229]

[0230] For example, when the carrier frequency of the signal between the user station and the satellite has Figure 5 When , it can be obtained that the carrier frequency of the signal satisfies the relationship of formula (22):

[0231]

[0232] For example, when the carrier frequency of the signal between the user station and the satellite has Figure 6 When , it can be obtained that the carrier frequency of the signal satisfies the relationship of formula (23):

[0233]

[0234] For example, when the carrier frequency of the signal between the user station and the satellite has Figure 7 When , it can be obtained that the carrier frequency of the signal satisfies the relationship of formula (24):

[0235]

[0236] Therefore, in actual use, in order to obtain better results, the carrier frequency of the forwarded ranging signal and the carrier frequency of the pseudorange ranging signal should be made to satisfy the relationship shown in formula (f2). Then, when the forwarded ranging value and the pseudorange ranging value are used to calculate the clock difference between the satellite and the user station, accurate results can be obtained.

[0237] In addition, based on the above embodiment, the embodiment of the present application further provides a method for determining the space distance between the satellite and the earth. The method for determining the space distance between the satellite and the earth can be executed by a computing device. Figure 8 FIG. 1 is a flow chart of a method for determining the satellite-to-earth space distance according to an embodiment of the present application. Figure 8 As shown, the method may specifically include the following steps:

[0238] S210, determining a tropospheric delay on a ranging signal path between the first device and the second device based on a preset tropospheric model;

[0239] S220, determining an ionospheric delay on a ranging signal path between the first device and the second device based on an ionospheric model or a known total number of ionospheric electrons;

[0240] S230, determining a satellite-to-earth space distance between the first device and the second device based on the determined tropospheric delay, the ionospheric delay, the clock difference between the first device and the second device, and any pseudorange measurement value;

[0241] Alternatively, based on the determined tropospheric delay, the ionospheric delay and any forwarding ranging value, the satellite-to-earth space distance between the first device and the second device is determined.

[0242] In step S210, the tropospheric delay T between the user station and the satellite can be corrected using a preset model. The tropospheric delay calculation requires the use of meteorological parameters. In the absence of real-time meteorological parameters, a simple model related only to the satellite elevation angle can be used for calculation, as shown in formula (T1):

[0243] T=2.47 / (sinθ+0.0121) (T1);

[0244] Where: T is the tropospheric delay, unit: meter; θ is the satellite elevation angle, unit: radian.

[0245] There are relatively many models for calculating tropospheric delay based on meteorological parameters. The differences between them decrease with the satellite elevation angle by about a few millimeters to a few centimeters, which is more accurate than that calculated by this simple model.

[0246] Common models for determining tropospheric delay correction include the Saastamoinen model and the Hopfield model. Studies have shown that when the altitude angle is greater than or equal to 15°, the results obtained by different models are in good agreement, and the model can be selected arbitrarily. However, when the value of the station elevation is large, the tropospheric delay in the zenith direction calculated by the two models can differ by tens of centimeters. After comparison with the measured meteorological data, it is recommended to use the Saastamoinen model.

[0247] In step S220, when the pseudorange measurement value and the forwarding ranging value are both one, the computing device can calculate the ionospheric delay through the ionosphere model; when the number of pseudorange measurement values ​​and / or forwarding ranging values ​​is greater than or equal to 2, the computing device can calculate the total number of ionospheric electrons on the ranging signal path between the user station and the satellite through any two pseudorange measurement values ​​or any two forwarding ranging values, and then the calculated total number of ionospheric electrons can be used to further calculate the ionospheric delay.

[0248] In detail, the ionospheric delay can be obtained using the 8-parameter Klobuchar model, or using the 14-parameter Klobuchar model, or the ionospheric total electron number TEC value can be obtained by other means. Then, the computing device can calculate the ionospheric delay of each signal based on the following formulas (15), (16), and (17).

[0249] The ionospheric total electron count TEC obtained by other means may be obtained through a third party such as the IGS organization, or when there are at least two forwarding ranging signals or at least two pseudo-range ranging signals, the ionospheric total electron count TEC may be calculated.

[0250]

[0251] In step S230, the clock difference, pseudorange measurement value, and forwarding ranging value between the first device (satellite) and the second device (user station) may be determined according to the high-precision time synchronization method described in any of the above embodiments.

[0252] In addition, in this exemplary embodiment, the computing device can also specifically correct the pseudorange measurement value and the forwarding measurement value to obtain a corrected pseudorange measurement value and a corrected forwarding measurement value, and then use the corrected pseudorange measurement value and the corrected forwarding measurement value to calculate the satellite-to-earth space distance.

[0253] The computing device is based on the determined tropospheric delay, the ionospheric delay, the clock difference between the satellite and the user station, and any corrected pseudorange measurement value. Exemplarily, when m=1, that is, there is only one corrected pseudorange measurement value, according to formula (11), and combined with (f3'), the satellite-to-ground space distance shown in the following formula (11-1) is obtained:

[0254] R true,z1 (n) = ρ z1,a (n)-I z1a (n)-T duiliu,z1 (n)-c·(δt z (n)-δt s (n)) c (11-1);

[0255] Alternatively, the computing device is based on the determined tropospheric delay, the ionospheric delay, and any one of the corrected forwarding ranging values ​​between the satellite and the user station. Exemplarily, when h=1, that is, there is only one corrected forwarding ranging value, according to formula (12), the satellite-to-ground space distance shown in the following formula (12-1) is obtained:

[0256] R true,u1 (n) = L 1,a (n)-T duiliu,u1 (n)-(I u1 (n)+I d1 (n)) / 2(12-1);

[0257] The computing device can specifically determine the satellite-to-earth space distance between the satellite and the computing device through the above formula (11-1) or formula (12-1), or the computing device performs weighted averaging of the formula (11-1) and the formula (12-1) to obtain the weighted average satellite-to-earth space distance between the satellite and the user station, where the sum of the weighted coefficients is equal to 1.

[0258] In addition, when the carrier frequency of the pseudo-range ranging signal and the carrier frequency of the forwarded ranging signal perform frequency hopping according to the frequency hopping pattern, the frequency after frequency hopping still meets the requirements of formula (f1), and the above-mentioned satellite-ground time synchronization method is still used to calculate the satellite-ground clock difference, and the calculated clock difference is transmitted to the satellite, and the specific calculation steps are not repeated.

[0259] Based on the above embodiments, the present application also provides a satellite navigation system, which is based on the above high-precision time synchronization system and method, adds an operation and control system, and increases the number of satellites to form a complete and simplest satellite navigation system.

[0260] Specifically, the satellite navigation system includes the high-precision time synchronization system described in any of the above embodiments, and in the high-precision time synchronization system, the first device is specifically a satellite, the second device is specifically a user station, and the number of satellites is greater than or equal to 2. The user station obtains the orbital parameters of the corresponding satellite based on the data transmission results with each satellite, and determines the coordinate information of the user station based on the orbital parameters of each satellite and the satellite-to-earth space distance between the user station and the satellite.

[0261] The satellite navigation system also includes a plurality of third devices, which are connected to the satellite for communication. Some of the third devices constitute a satellite orbit determination system, which is used to monitor and process the orbit of the satellite to obtain satellite orbit parameters; some of the third devices constitute a satellite-to-ground time synchronization system, which is used to monitor the time of each satellite and keep the time of each satellite synchronized with the operation and control system. The operation and control system mentioned here refers to a system composed of a satellite orbit determination system and a satellite-to-ground time synchronization system.

[0262] The satellite navigation system Fig. 9 As shown, in the satellite navigation system, there are at least two satellites. In the satellite navigation system, the orbit determination system can adopt the existing Beidou orbit determination method.

[0263] The third device in the satellite-to-ground time synchronization system has the hardware composition and signal structure of the high-precision time synchronization system with the satellite. The computing device can be integrated into the third device to execute the high-precision time synchronization method. At this time, the time of the third device in the satellite-to-ground time synchronization system is used as the system time, and the satellite relative to the system time is used as an unknown number. The clock difference of the satellite relative to the system time is obtained through the method of this application, and the time synchronization of the satellite and the operation and control system is realized. The satellite then broadcasts a pseudo-range measurement signal with a known time to the outside. At this time, the time of the satellite relative to the system is known, and the time of the user station relative to the system is unknown. Through the high-precision time synchronization system and method of this application, the clock difference of the user station relative to the system time is obtained, and the satellite timing function is realized. At this time, after the user station obtains its own clock difference relative to the system time, it does not interact with the satellite for clock difference data.

[0264] Of course, the satellite-ground time synchronization system can also use other existing satellite-ground time synchronization technologies, such as a two-way pseudo-range measurement method, etc. Satellite-ground time synchronization can be achieved using these methods.

[0265] After the user station obtains high-precision time synchronization, the space distance between the user station and the satellite is obtained. According to the satellite ephemeris and the space distance between the user station and the satellite, if the satellite navigation system has only two satellites, the user needs to configure an altimeter to obtain the user elevation, and then refer to the Beidou dual-star positioning principle to obtain the user station coordinates; when there are three or more satellites, the user station does not need to be configured with an altimeter, and the user station coordinate information can be obtained through the space distance between the user station and the satellite ephemeris and the three satellites.

[0266] Based on the above embodiments, the embodiments of the present application further provide a method for time synchronization between stations, which can be applied to the high-precision time synchronization system described in the above embodiments or to the satellite navigation system described in the above embodiments. The embodiments of the present application provide a method for time synchronization between stations, which can be performed by a user station. The method may include:

[0267] S510, directly communicating with a target user station to perform data interaction and obtain a clock difference of the target user station;

[0268] S520: Calculate the time difference between the user station and the target user station based on the user station's own clock difference and determine the time difference between the two.

[0269] Among them, after determining the clock difference of the user station relative to the system time, the user station can transmit data with the target user station based on the communication link. Multiple user stations exchange the clock differences of each user station relative to the system time through communication, thereby realizing time synchronization between multiple user stations, which is similar to the common view method and will not be repeated here.

[0270] On the basis of the above embodiments, the present application also provides a satellite positioning method, which can be applied to the above satellite navigation system. Fig.10 FIG. 1 is a flow chart of a satellite positioning method according to an embodiment of the present application. The method may be executed by a user station that needs to perform positioning, such as Fig.10 As shown, the satellite positioning method may include the following steps:

[0271] S610, obtaining orbital parameters of each satellite;

[0272] S620, determining the coordinates of the corresponding satellite based on the orbital parameters;

[0273] S630, determining the space distance between the satellite and the ground;

[0274] S640: Determine the coordinate information of the satellite based on the coordinates of each satellite and the space distance between the satellite and the ground.

[0275] Among them, in step S610, the orbital parameters of the satellite are satellite ephemeris, and the orbital parameters of the satellite are determined according to existing satellite orbit determination methods, such as the orbit determination method of Beidou navigation satellites, etc. Therefore, the user station obtains the orbital parameters of the corresponding satellite based on the data transmission results with each satellite (for example, by receiving pseudorange measurement signals).

[0276] In step S620, the user station calculates the satellite coordinates at the current ranging time according to the acquired orbital parameters of the satellite.

[0277] In step S630, the user station may determine the satellite-to-earth space distance between itself and each satellite by using any of the satellite-to-earth space distance determination methods executed by the user station.

[0278] In step S640, the user station calculates its own coordinate information based on the coordinate information of each satellite and the satellite-to-ground space distance between itself and each satellite, that is, realizes satellite positioning for itself.

[0279] It is worth noting that in this exemplary embodiment, the number of satellites needs to be greater than or equal to 2. Specifically, when the number of satellites is greater than or equal to 2, the user station can select at least two satellites from all satellites and calculate its own coordinate information with reference to the existing Beidou dual-star positioning method.

[0280] As described above, in the high-precision time synchronization system provided by the embodiment of the present application, the pseudo-range ranging signal can also be broadcast by the second device and received by the first device. In this case, the uplink signal broadcast by the second device is used as the pseudo-range ranging signal, and the first pseudo-range ranging device of the first device receives and measures. The present application provides the following embodiments:

[0281] like Fig.11 As shown, when the second device broadcasts an uplink signal of a forwarding ranging signal, an uplink signal reaches the satellite and is received by the first pseudo-range ranging device of the satellite to obtain a pseudo-range ranging value. The uplink signal is forwarded by the satellite transponder into two downlink signals with different carrier frequencies, forming two forwarding ranging signals, and obtaining two forwarding ranging values.

[0282] Or, if Fig.12 As shown, when the second device broadcasts an uplink signal for forwarding ranging signals, the uplink signal reaches the satellite and is received by the first pseudo-range ranging device of the satellite to obtain a pseudo-range ranging value, and is not forwarded by the transponder at the same time; when the second device broadcasts another uplink signal for forwarding ranging signals, the uplink signal is forwarded by the satellite transponder as two downlink signals with different carrier frequencies, forming two forwarding ranging signals, and obtaining two forwarding ranging values;

[0283] Or, if Fig.13As shown, when the second device broadcasts two uplink signals of forwarding ranging signals with different carrier frequencies, they are respectively received by the first pseudo-range ranging device of the satellite to obtain two pseudo-range ranging values. The two uplink signals are further forwarded by the satellite transponder as two downlink signals with the same carrier frequency, forming two forwarding ranging signals, and obtaining two forwarding ranging values.

[0284] Figure 11 to Figure 13 The signal structure and the obtained pseudorange ranging value and forwarding ranging value can still be calculated using the method proposed in this application to obtain the clock difference between the first device and the second device, and the specific calculation instructions will not be repeated.

[0285] In summary, it can be seen that the high-precision time synchronization system and method provided in the embodiment of the present application creatively integrates the pseudo-range measurement signal and the forwarding range measurement signal, and utilizes the relationship between the carrier frequencies to obtain both high-precision satellite-to-ground time synchronization performance and relatively accurate satellite-to-ground spatial distance; at the same time, the high-precision time synchronization system and method are also used to provide a satellite navigation system. The high-precision time synchronization system, satellite navigation system and method provided in the embodiment of the present application have the following characteristics:

[0286] 1. Compared with the two-way pseudo-range measurement method, this method completely overcomes the influence of atmospheric delay, including tropospheric delay and ionospheric delay, thereby achieving higher satellite-ground time synchronization accuracy, up to sub-nanosecond level;

[0287] 2. Compared with the two-way pseudo-range measurement method, this method does not require satellite-ground coarse synchronization, reduces system requirements, and brings convenience in operation;

[0288] 3. This method completely overcomes the influence of ionospheric delay and no longer relies on ionospheric data provided by third parties such as the IGS organization, making this system completely independent, safe and reliable;

[0289] 4. By applying this method, compared with the existing two-way pseudo-range measurement method, the satellite in the embodiment of the present application does not need pseudo-range measurement equipment, which can reduce the complexity of satellite payload and reduce satellite cost;

[0290] 5. High flexibility in use. When users need time synchronization, they can achieve time synchronization through the self-transmitting and self-receiving signals mastered by the users themselves, which has the flexibility to be used anytime and anywhere;

[0291] 6. Because the user station only needs to receive signals from one satellite, the user station can use a directional antenna to reduce the multipath effect, thereby achieving better ranging accuracy and better time synchronization accuracy;

[0292] 7. This method not only overcomes the influence of atmospheric delay, but also overcomes the influence of multipath effect and the influence of the near-end and far-end environmental segments between the satellite and the user station.

[0293] 8. This application can obtain a relatively accurate space distance between the satellite and the earth, providing support for subsequent satellite orbit determination and user positioning.

[0294] 9. The satellite navigation system of the present application requires time synchronization before user positioning, which is significantly different from the existing satellite navigation system and has the advantages of low investment and high efficiency.

[0295] The above are only preferred embodiments of the present application, and are not intended to limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A high-precision time synchronization system, characterized in that: comprising a first device and a second device in communication connection, and a computing device in communication connection with the first device and the second device respectively; There are m pseudo-range measurement signals and h forwarding measurement signals between the first device and the second device, and the pseudo-range measurement signals and the forwarding measurement signals have at least two different carrier frequencies; The carrier frequency of the m-path pseudo-range measurement signal and the carrier frequency of the h-path forwarded ranging signal satisfy a preset carrier frequency relationship; Wherein, m and h are both positive integers greater than or equal to 1; The pseudorange ranging signal is broadcasted by the first device and received by the second device, or is broadcasted by the second device and received by the first device; The forwarded ranging signal is composed of an uplink signal and a downlink signal. The second device broadcasts the uplink signal and receives the downlink signal. The first device receives the uplink signal and forwards it to form the downlink signal.

2. The high-precision time synchronization system according to claim 1, characterized in that: The forwarded ranging signal and the pseudo-ranging signal are both spread spectrum signals, and the first device and / or the second device use spread spectrum technology, carrier frequency multiplexing technology and code division multiple access technology to perform corresponding processing in signal transmission, forwarding and reception processing.

3. The high-precision time synchronization system according to claim 1, characterized in that: The carrier frequency of the m-path pseudo-range measurement signal and the carrier frequency of the h-path forwarding ranging signal satisfy the preset carrier frequency relationship shown in formula (f1): Where: V represents a real constant, V = 1e-12; m represents the number of pseudo-range ranging signals; i represents the number of pseudo-range ranging signals; h represents the number of forwarded ranging signals; j represents the number of forwarded ranging signals; f uj (n) represents the carrier frequency of the uplink signal of the forwarding ranging signal numbered j at the nth moment, in Hertz; f dj (n) represents the carrier frequency of the downlink signal of the forwarding ranging signal numbered j at the nth moment, in Hertz; f zi (n) represents the carrier frequency of the pseudo-range measurement signal numbered i at the nth moment, in Hertz.

4. The high-precision time synchronization system according to claim 1, characterized in that: The carrier frequency of the forwarded ranging signal and the carrier frequency of the pseudo-range ranging signal are frequency-hopped according to a preset frequency-hopping pattern on the time axis and satisfy the preset carrier frequency relationship.

5. The high-precision time synchronization system according to claim 1, characterized in that: The first device includes a first time-frequency device, a repeater, and a pseudo-range generating device, and the second device includes a second time-frequency device, a repeater ranging device, and a second pseudo-range ranging device; The first time-frequency device is used to provide a time-frequency signal to the repeater and the pseudorange generating device; The repeater is used to receive the uplink signal, perform frequency conversion and power amplification on the uplink signal, and then forward the downlink signal to the second device; The pseudorange generating device is communicatively connected with the repeater, and the pseudorange generating device is used to generate and broadcast the pseudorange ranging signal; The second time-frequency device is used to provide a time-frequency signal to the forwarding ranging device and the second pseudo-range ranging device; The second pseudo-range measuring device is used to receive the pseudo-range measuring signal and process it to obtain a pseudo-range measuring value; The forwarding ranging device is used to generate and broadcast the uplink signal, receive the downlink signal, and determine the forwarding ranging value; Wherein, the first time-frequency device, the repeater and the pseudo-range generating device are integrated or separately arranged, and / or the second time-frequency device, the repeater ranging device and the second pseudo-range ranging device are integrated or separately arranged; or, The first device includes a first time-frequency device, a repeater, and a first pseudo-range measuring device, and the second device includes a second time-frequency device and a repeater ranging device; The first time-frequency device is used to provide a time-frequency signal to the repeater and the first pseudo-range measuring device; The repeater is used to receive the uplink signal, perform frequency conversion and power amplification on the uplink signal, and then forward the downlink signal to the second device; The first pseudorange measuring device is communicatively connected to the repeater, and is used to receive and measure the pseudorange measuring signal; The second time-frequency device is used to provide a time-frequency signal to the forwarding ranging device; The forwarding ranging device is used to generate and broadcast the uplink signal, receive the downlink signal, and determine the forwarding ranging value, wherein part of the uplink signal broadcast by the forwarding ranging device is used as the pseudo-range ranging signal; The first time-frequency device, the repeater and the first pseudo-range measuring device are integrated or separately arranged, and / or the second time-frequency device and the repeater ranging device are integrated or separately arranged.

6. The high-precision time synchronization system according to claim 5, characterized in that: Zero baseline setting of the second pseudo-range measuring device and the forwarding ranging device; The first pseudorange measuring device or the pseudorange generating device is set with a zero baseline of the repeater.

7. The high-precision time synchronization system according to claim 5, characterized in that: The first device uses at least one of the first time-frequency devices, and the second device uses at least one of the second time-frequency devices.

8. The high-precision time synchronization system according to claim 1, characterized in that: The computing device is arranged in the first device or in the second device, or exists independently; When the computing device is arranged on the first device or the second device, the first device performs data transmission with the second device by using an additional communication signal; When the computing device is independently provided, the computing device communicates with the first device and the second device.

9. The high-precision time synchronization system according to claim 5, characterized in that: The repeater has a forwarding delay, and the pseudo-range generating device has a transmission delay; the first pseudo-range measuring device and the second pseudo-range measuring device both have a receiving delay, and the forwarding ranging device has a transmission delay and a receiving delay; The computing device obtains the forwarding delay of the repeater, the transmission delay of the pseudorange generating device, the receiving delay of the first pseudorange measuring device or the second pseudorange measuring device, and the transmission delay and the receiving delay of the forwarding ranging device.

10. The high-precision time synchronization system according to claim 1, characterized in that: The computing device is communicatively connected to the first device and the second device respectively, receives the pseudorange measurement value and the forwarding ranging value, and determines the satellite-to-ground space distance between the first device and the second device based on the forwarding ranging value and / or the pseudorange measurement value, and determines the clock difference between the first device and the second device based on the relationship between the pseudorange measurement value, the forwarding ranging value and a preset carrier frequency; wherein, when determining the clock difference between the first device and the second device, the sum of the forwarding ranging values ​​and the pseudorange measurement values ​​is greater than or equal to 2.

11. A method for determining a pseudorange value, characterized in that: Applied to the high-precision time synchronization system according to any one of claims 1 to 10, the method is performed by a first device, and the method includes: Receiving m-channel pseudo-range measurement signals broadcasted by the second device; The pseudo-range measurement signals are synchronously measured to obtain m pseudo-range measurement values, wherein m is a positive integer.

12. A method for determining a distance measurement value, characterized in that: Applied to the high-precision time synchronization system according to any one of claims 1 to 10, the method is performed by a second device, and the method includes: When the pseudo-range measurement signal is broadcast by the first device, broadcast at least one uplink signal to the first device; Acquire at least one downlink signal forwarded by the first device based on the at least one uplink signal, wherein the at least one uplink signal and the at least one downlink signal constitute an h-path forwarding ranging signal; Acquire m-channel pseudo-range measurement signals broadcasted by the first device; Synchronously measuring each of the pseudorange ranging signals and each of the forwarded ranging signals to obtain m pseudorange ranging values ​​and h forwarded ranging values; or, When the pseudorange measurement signal is broadcast by the second device and received by the first device, broadcast at least one uplink signal to the first device; Acquire at least one downlink signal forwarded by the first device based on the at least one uplink signal, wherein the at least one uplink signal and the at least one downlink signal constitute an h-path forwarding ranging signal; Synchronously measuring each of the forwarding ranging signals to obtain h forwarding ranging values; Among them, m+h≥2, and m and h are both positive integers.

13. A high-precision time synchronization method, characterized in that: Applied to the high-precision time synchronization system according to any one of claims 1 to 10, the method is executed by a computing device, and the method comprises: When the pseudorange ranging signal is broadcast by the second device and received by the first device, acquiring m pseudorange ranging values ​​measured by the first device based on communication with the first device, and acquiring h forwarding ranging values ​​measured by the second device based on communication with the second device; When the pseudorange ranging signal is broadcast by the first device and received by the second device, m pseudorange ranging values ​​and h forwarding ranging values ​​measured by the second device are obtained based on communication with the second device; wherein the carrier frequencies corresponding to the h forwarding ranging values ​​and the carrier frequencies corresponding to the m pseudorange ranging values ​​satisfy a preset carrier frequency relationship; m+h≥2, and m and h are both positive integers; Using a pseudorange measurement expression to represent each of the pseudorange measurement values ​​and using a forwarding measurement expression to represent each of the forwarding measurement values; The clock difference between the first device and the second device is determined based on the m pseudorange ranging values ​​represented by the pseudorange ranging expression, the h forwarding ranging values ​​represented by the forwarding ranging expression, and the preset carrier frequency relationship.

14. The high-precision time synchronization method according to claim 13, characterized in that: The method of using a pseudorange ranging expression to represent each of the pseudorange ranging values ​​and using a forward ranging expression to represent each of the forward ranging values ​​comprises: The pseudo-range measurement expression shown in the following formula (3) is used to represent the pseudo-range measurement value numbered i: zi (n) = R true,zi (n)+I zi (n)+T duiliu,zi (n)±c·(δt z (n)-δt s (n))±sagnac zz (n)+X zi (n) (3); Wherein, i=1, 2, ..., m, i is a positive integer; The forwarding range value numbered j is represented by the forwarding range expression shown in the following formula (4): j (n) = R true,uj (n)+R true,dj (n)+I uj (n)+I dj (n)+T duiliu,uj (n)+T duiliu,dj (n)+Y j (n) (4); Wherein, j = 1, 2, ..., h, j is a positive integer; Where: zi (n) represents the pseudo-range measurement value numbered i at the nth moment, in meters; R true,zi (n) represents the real space distance traversed by the pseudo-range measurement signal numbered i at the nth moment, in meters; I zi (n) represents the ionospheric delay of the pseudo-range signal numbered i at the nth time, in meters; T duiliu,zi (n) represents the tropospheric delay of the pseudo-range measurement signal numbered i at the nth moment, in meters; c represents the speed of light, in meters per second; δt s (n) represents the clock difference between the first device and the system time at the nth moment, in seconds; δt z (n) represents the clock difference between the second device and the system time at the nth moment, in seconds; sagnac zz (n) represents the Sagnac effect delay of the pseudo-range measurement signal at the nth moment, in meters; X zi (n) represents the hardware device delay of the pseudo-range measurement signal numbered i at the nth moment, in meters, and the hardware device delay of the pseudo-range measurement signal includes the transmission delay of the pseudo-range measurement signal numbered i and the reception delay of the pseudo-range measurement signal numbered i; L j (n) represents the forwarding ranging value of j at the nth time, in meters; R true,uj (n) represents the real spatial distance traveled by the uplink signal of the forwarding ranging signal numbered j at the nth moment, in meters; R true,dj (n) represents the real spatial distance traveled by the downlink signal of the forwarding ranging signal numbered j at the nth moment, in meters; uj (n) represents the ionospheric delay of the uplink signal of the forwarding ranging signal numbered j at the nth time, in meters; I dj (n) represents the ionospheric delay of the downlink signal of the forwarding ranging signal numbered j at the nth time, in meters; T duiliu,uj (n) represents the tropospheric delay of the uplink signal of the forwarding ranging signal numbered j at the nth time, in meters; T duiliu,dj (n) represents the tropospheric delay of the downlink signal of the forwarding ranging signal numbered j at the nth time, in meters; Y j (n) represents the hardware device delay of the forwarding ranging signal numbered j at the nth moment, in meters. The hardware device delay of the forwarding ranging signal includes the transmission delay of the uplink signal of the forwarding ranging signal numbered j, the forwarding delay of the downlink signal of the forwarding ranging signal numbered j, and the receiving delay of the downlink signal of the forwarding ranging signal numbered j.

15. The high-precision time synchronization method according to claim 13, characterized in that: The determining the clock difference between the first device and the second device based on the m pseudorange ranging values ​​represented by the pseudorange ranging expression, the h forwarding ranging values ​​represented by the forwarding ranging expression, and the preset carrier frequency relationship includes: The m pseudorange measurement values ​​represented by the pseudorange measurement expression are corrected to obtain m corrected pseudorange measurement values, and the m corrected pseudorange measurement values ​​are averaged to obtain a corrected average pseudorange measurement value; The h forwarding ranging values ​​represented by the forwarding ranging expression are corrected to obtain h corrected forwarding ranging values, and the h corrected forwarding ranging values ​​are averaged to obtain a corrected average forwarding ranging value; A clock difference between the first device and the second device is determined based on the corrected average pseudorange ranging value, the corrected average forward ranging value, and the preset carrier frequency relationship.

16. The high-precision time synchronization method according to claim 15, characterized in that: The step of correcting the m pseudorange measurement values ​​represented by the pseudorange measurement expression to obtain m corrected pseudorange measurement values ​​includes: The pseudo-range measurement value numbered i shown in the following formula (3) is corrected to obtain the corrected pseudo-range measurement value numbered i shown in formula (3'): ρ zi (n)=R true,zi (n)+I zi (n)+T duiliu,zi (n)±c·(δt z (n)-δt s (n))±sagnac zz (n)+X zi (n)(3); Where, i = 1, 2, ..., m; The step of averaging the m corrected pseudorange measurement values ​​to obtain a corrected average pseudorange measurement value comprises: The m corrected pseudorange values ​​are averaged to obtain the corrected average pseudorange value as shown in formula (5): The step of correcting the h forwarding ranging values ​​represented by the forwarding ranging expression to obtain h corrected forwarding ranging values ​​includes: The forwarding ranging value numbered j shown in the following formula (4) is transformed to obtain the corrected forwarding ranging value numbered j shown in formula (4'): L j (n)=R true,uj (n)+R true,dj (n)+I uj (n)+I dj (n)+T duiliu,uj (n)+T duiliu,dj (n)+Y j (n) (4); Where, j = 1, 2, ..., h; The step of averaging the h corrected forwarding ranging values ​​to obtain a corrected average forwarding ranging value includes: The h corrected forwarding ranging values ​​are averaged to obtain the corrected average forwarding ranging value shown in formula (6): Where: mean (n) represents the corrected average pseudo-range measurement value at the nth moment, in meters; ρ zi,a (n) represents the corrected pseudorange value of the number i at the nth moment, in meters; ρ zi (n) represents the pseudo-range measurement value numbered i at the nth moment, in meters; R true,zi (n) represents the real space distance traversed by the pseudo-range measurement signal numbered i at the nth moment, in meters; I zi (n) represents the ionospheric delay of the pseudo-range signal numbered i at the nth time, in meters; T duiliu,zi (n) represents the tropospheric delay of the pseudo-range measurement signal numbered i at the nth moment, in meters; c represents the speed of light, in meters per second; δt s (n) represents the clock difference between the first device and the system time at the nth moment, in seconds; δt z (n) represents the clock difference between the second device and the system time at the nth moment, in seconds; sagnac zz (n) represents the Sagnac effect delay of the pseudo-range measurement signal at the nth moment, in meters; X zi (n) represents the hardware device delay of the pseudo-range measurement signal numbered i at the nth moment, in meters, and the hardware device delay of the pseudo-range measurement signal includes the transmission delay of the pseudo-range measurement signal numbered i and the reception delay of the pseudo-range measurement signal numbered i; L mean (n) represents the corrected average forwarding ranging value at the nth moment, in meters; L j,a (n) represents the corrected forwarding ranging value of the number j at the nth time, in meters; L j (n) represents the forwarding ranging value of j at the nth time, in meters; R true,uj (n) represents the real spatial distance traveled by the uplink signal of the forwarding ranging signal numbered j at the nth moment, in meters; R true,dj (n) represents the real spatial distance traveled by the downlink signal of the forwarding ranging signal numbered j at the nth moment, in meters; uj (n) represents the ionospheric delay of the uplink signal of the forwarding ranging signal numbered j at the nth time, in meters; I dj (n) represents the ionospheric delay of the downlink signal of the forwarding ranging signal numbered j at the nth time, in meters; T duiliu,uj (n) represents the tropospheric delay of the uplink signal of the forwarding ranging signal numbered j at the nth time, in meters; T duiliu,dj (n) represents the tropospheric delay of the downlink signal of the forwarding ranging signal numbered j at the nth time, in meters; Y j (n) represents the hardware device delay of the forwarding ranging signal numbered j at the nth moment, in meters. The hardware device delay of the forwarding ranging signal includes the transmission delay of the uplink signal of the forwarding ranging signal numbered j, the forwarding delay of the downlink signal of the forwarding ranging signal numbered j, and the receiving delay of the downlink signal of the forwarding ranging signal numbered j.

17. The high-precision time synchronization method according to claim 16, characterized in that: The determining the clock difference between the first device and the second device based on the corrected average pseudorange ranging value, the corrected average forward ranging value and the preset carrier frequency relationship includes: By using the zero baseline setting relationship between the forwarding ranging device and the second pseudo-range ranging device, or by using the zero baseline setting relationship between the forwarder and the first pseudo-range ranging device, the clock difference between the first device and the second device as shown in the following formula (7) is determined based on the relationship between the corrected average pseudo-range ranging value, the corrected average forwarding ranging value and the preset carrier frequency: ±(δt z (n)-δt s (n)) c =(ρ mean (n)-L mean (n)) / c(7); Where: ±(δt z (n)-δt s (n)) c represents the clock difference between the first device and the second device calculated based on the corrected average pseudorange measurement value and the corrected average forwarding measurement value, in seconds; c represents the speed of light, in meters per second; ρ mean (n) represents the corrected average pseudo-range measurement value at the nth moment, in meters; L mean (n) represents the corrected average forwarding ranging value at the nth moment, in meters.

18. The high-precision time synchronization method according to claim 13, characterized in that: After determining the clock difference between the first device and the second device, the method further includes: Communicate with the first device or the second device, and transmit the determined clock difference between the first device and the second device to the first device or the second device, so as to achieve time synchronization between the first device and the second device; Wherein, when the clock difference of the first device relative to the system time is known, the second device determines its own clock difference relative to the system time according to the clock difference between the first device and the second device; When the clock difference of the second device relative to the system time is known, the first device determines its own clock difference relative to the system time based on the clock difference between the first device and the second device.

19. A method for determining the distance between satellite and earth, characterized in that: Applied to the high-precision time synchronization system according to any one of claims 1 to 10, the method is executed by a computing device, and the method comprises: Determine, based on a preset tropospheric model, a tropospheric delay on a ranging signal path between the first device and the second device; Determine the ionospheric delay on the ranging signal path between the first device and the second device based on the ionospheric model or the known total number of ionospheric electrons, wherein when the pseudorange measurement value and the forwarding ranging value are both one, the ionospheric delay is determined by the ionospheric model; when the number of pseudorange measurement values ​​and / or forwarding ranging values ​​is greater than or equal to 2, the ionospheric delay is determined by any two pseudorange measurement values ​​or any two forwarding ranging values; Determine a satellite-to-earth space distance between the first device and the second device based on the determined tropospheric delay, the ionospheric delay, and any forwarding ranging value; Alternatively, based on the determined tropospheric delay, the ionospheric delay, the clock difference between the first device and the second device, and any one pseudorange measurement value, the satellite-to-earth space distance between the first device and the second device is determined, wherein the clock difference between the first device and the second device, the pseudorange measurement value, and the forwarding ranging value are determined according to the high-precision time synchronization method according to any one of claims 13-18.

20. The method for determining the satellite-to-earth space distance according to claim 19, characterized in that: The determining, based on the determined tropospheric delay, the ionospheric delay, the clock difference between the first device and the second device, and any pseudorange measurement value, a satellite-to-ground space distance between the first device and the second device, comprises: Based on the determined tropospheric delay, the ionospheric delay, the clock difference between the first device and the second device, and any one of the corrected pseudorange measurement values ​​shown in the following formula (3'), the satellite-to-ground space distance between the first device and the second device as shown in formula (11) is determined: Where, i = 1, 2, ..., m; Alternatively, the satellite-to-ground space distance between the first device and the second device as shown in formula (12) is determined based on the determined tropospheric delay, the ionospheric delay and any one of the corrected forwarding ranging values ​​shown in the following formula (4'): R true,uj (n)=L j,a (n)-T duiliu,uj (n)-(I uj (n)+I dj (n)) / 2 (12); Where, j = 1, 2, ..., h; Alternatively, performing weighted averaging on the formula (11) and the formula (12) to obtain a weighted average satellite-to-ground space distance between the first device and the second device, wherein the sum of the weighted coefficients is equal to 1; Where: zi,a (n) represents the corrected pseudorange value of the number i at the nth moment, in meters; ρ zi (n) represents the pseudo-range measurement value numbered i at the nth moment, in meters; R true,zi (n) represents the real space distance traversed by the pseudo-range measurement signal numbered i at the nth moment, in meters; I zi (n) represents the ionospheric delay of the pseudo-range signal numbered i at the nth time, in meters; T duiliu,zi (n) represents the tropospheric delay of the pseudo-range measurement signal numbered i at the nth moment, in meters; c represents the speed of light, in meters per second; δt s (n) represents the clock difference between the first device and the system time at the nth moment, in seconds; δt z (n) represents the clock difference between the second device and the system time at the nth moment, in seconds; sagnac zz (n) represents the Sagnac effect delay of the pseudo-range measurement signal at the nth moment, in meters; X zi (n) represents the hardware device delay of the pseudo-range measurement signal numbered i at the nth moment, in meters, and the hardware device delay of the pseudo-range measurement signal includes the transmission delay of the pseudo-range measurement signal numbered i and the reception delay of the pseudo-range measurement signal numbered i; (δt z (n)-δt s (n)) c represents the clock difference between the first device and the second device calculated at the nth moment; L j,a (n) represents the corrected forwarding ranging value of the number j at the nth time, in meters; L j,a (n) represents the corrected forwarding ranging value of the number j at the nth time, in meters; L j (n) represents the forwarding ranging value of j at the nth time, in meters; R true,uj (n) represents the real spatial distance traveled by the uplink signal of the forwarding ranging signal numbered j at the nth moment, in meters; R true,dj (n) represents the real spatial distance traveled by the downlink signal of the forwarding ranging signal numbered j at the nth moment, in meters; uj (n) represents the ionospheric delay of the uplink signal of the forwarding ranging signal numbered j at the nth time, in meters; I dj (n) represents the ionospheric delay of the downlink signal of the forwarding ranging signal numbered j at the nth time, in meters; T duiliu,uj (n) represents the tropospheric delay of the uplink signal of the forwarding ranging signal numbered j at the nth time, in meters; T duiliu,dj (n) represents the tropospheric delay of the downlink signal of the forwarding ranging signal numbered j at the nth time, in meters; Y j (n) represents the hardware device delay of the forwarding ranging signal numbered j at the nth moment, in meters. The hardware device delay of the forwarding ranging signal includes the transmission delay of the uplink signal of the forwarding ranging signal numbered j, the forwarding delay of the downlink signal of the forwarding ranging signal numbered j, and the receiving delay of the downlink signal of the forwarding ranging signal numbered j.

21. A satellite navigation system, characterized in that: include: The high-precision time synchronization system according to any one of claims 1 to 10, wherein the first device is a satellite, the second device is a user station, and the number of the satellites is greater than or equal to 2; a plurality of third devices, all of which are communicatively connected to the satellite; The user station obtains the orbital parameters of the corresponding satellite based on the data transmission results with each satellite, and determines the coordinate information of the user station based on the orbital parameters of each satellite and the satellite-to-ground space distance between the user station and the satellite; Part of the third device constitutes a satellite orbit determination system, which is used to monitor and process the orbit of the satellite to obtain satellite orbit parameters; Part of the third devices constitutes a satellite-ground time synchronization system for performing time monitoring on each of the satellites.

22. The satellite navigation system according to claim 21, characterized in that: The signal structure between the third device in the satellite-to-ground time synchronization system and the satellite is the same as the signal structure in the high-precision time synchronization system.

23. An inter-station time synchronization system, characterized in that: include: The satellite navigation system according to claim 21 or 22; Wherein, when there are at least two user stations, at least two of the user stations achieve time synchronization with each other by exchanging data through communication.

24. An inter-station time synchronization system, characterized in that: include: The high-precision time synchronization system according to any one of claims 1 to 10; When there are at least two first devices or second devices, at least two first devices or second devices achieve time synchronization with each other by exchanging data through communication.

25. A satellite positioning method, characterized in that: Applied to the satellite navigation system of claim 21 or 22, the method is performed by a user station, and the method comprises: Get the orbital parameters of each satellite; Determining coordinate information of a corresponding satellite based on the orbital parameters; Determine the satellite-to-earth space distance between each satellite according to the satellite-to-earth space distance determination method according to any one of claims 19-20; Based on the orbital parameters of each of the satellites and the space distance between each of the satellites and the ground, the coordinate information of the user station is determined.

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