High-precision time synchronization system and method

Abstract

The present application belongs to the technical field of time synchronization. Disclosed are a high-precision time synchronization system and method. The present application comprises: on the basis of a result of communication with a first device, acquiring at least one pseudo-range measurement signal and at least one downlink signal; determining a pseudo-range measurement value on the basis of the pseudo-range measurement signal; determining a forward range measurement value on the basis of a forward range measurement signal and representing same using a forward range measurement expression, the forward range measurement signal comprising at least one uplink signal broadcast to the first device and at least one downlink signal forwarded by the first device; and, on the basis of the forward range measurement value, the pseudo-range measurement value and a preset carrier frequency relationship, determining a clock difference between the first device and a second device.

Description

A high-precision time synchronization system and method

[0001] Cross-references

[0002] This disclosure claims priority to Chinese Patent Application No. 202411070053.0, filed on August 6, 2024, entitled “A High-Precision Time Synchronization System and Time Synchronization Method,” the entire contents of which are incorporated herein by reference. Technical Field

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

[0004] GNSS (Global Navigation Satellite System) is currently the 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. A satellite navigation system is a very large and complex system, involving three main parts: operation and control, satellites, and users. It involves time synchronization between operation and control stations and satellites, time synchronization between operation and control stations, satellite orbit determination technology, and user positioning and timing applications. The operation and control part monitors the satellite's atomic clock time to ensure accuracy and reliability, and also determines the satellite's orbit and provides ephemeris for user use. Satellites are the carriers that directly provide services to users, broadcasting three pseudorange signals containing satellite ephemeris messages. Users obtain pseudorange values ​​by measuring the pseudorange signals, and use these pseudorange values ​​and satellite ephemeris to achieve positioning and timing.

[0005] The operation and control unit of a satellite navigation system monitors satellite orbits and time to ensure long-term reliable operation. Synchronization between the navigation satellite's time and the operation and control system's time is crucial. Besides navigation satellites, other aerospace systems such as communication satellites and remote sensing satellites also require high-precision space-to-ground time synchronization. The key to the positioning accuracy of a navigation satellite system lies in determining the clock bias and its variations in the onboard atomic clock. Currently, the main methods for determining satellite clock bias include:

[0006] 1. One-way ranging method: This method uses the pseudorange measurement value and the distance between the satellite and the geostationary station obtained from orbital positioning. The difference between the two values ​​yields the satellite clock error. This method requires knowledge of parameters such as the exact satellite-to-ground spatial distance, ionospheric delay, and tropospheric delay.

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

[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 paths between the satellite and the ground station are completely the same, have the same space distance between the satellite and the ground station and the troposphere time delay, but the ionosphere time delay is different, so the clock error between the satellite and the ground station is the difference between the measured pseudo-range divided by the speed of light c or the difference between the time of detecting the corresponding time scale by the satellite and the ground station. The process is that the satellite and the ground station both transmit signals under the control of the local clock with their own independent clock faces, and after the satellite and the ground station receivers receive the signals transmitted by the other party, the pseudo-range measurement between the local clock is completed, and by comparing the two pseudo-code ranging values, the satellite clock error can be obtained. The obtained clock error contains the residual error of the ionosphere time delay.

[0009] In order to realize the time synchronization between the satellite and the ground station, laser method can also be used. Laser can be regarded as a radio signal with very high frequency. When laser signal passes through the ionosphere, the time delay it receives is very small and can be ignored. Both the satellite and the ground station use laser devices instead of radio transmitters or receivers, which has the disadvantages of high cost and limited application. When using laser, there is the disadvantage of being greatly affected by weather. In rainy, snowy, cloudy and other weather conditions, laser method cannot be used, and can only be used in sunny weather. Therefore, although laser method can achieve very good time synchronization performance, it is difficult to popularize due to the disadvantages of high cost and great influence of weather.

[0010] All the above methods require the satellite or ground receiver to receive signals and make measurements. When the signals are transmitted between the satellite and the ground station, for the receiving party, it involves the ionosphere and the 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 effects. Among them, the atmospheric effect is comprehensive and fundamental, and it is a worldwide problem. In addition to the environmental segment effects, the above methods have the disadvantages of large number of observation devices, poor time synchronization accuracy affected by satellite orbit determination accuracy and user coordinate accuracy, and poor time synchronization accuracy.

[0011] The above content is only used to assist in understanding the technical solutions of the present application and does not represent the acknowledgement of the above content as prior art. SUMMARY

[0012] The application combines the characteristics of a satellite transponder and the carrier frequency multiplexing technology and multi-address characteristics of a spread spectrum signal, uses the characteristics that a satellite transponder can convert one signal into at least one signal, and at least two spread spectrum signals can be carrier frequency multiplexed, and at the same time, the carrier frequencies of the pseudo-range measurement signal and the carrier frequencies of the converted measurement signal are constrained to satisfy a certain relationship, and creatively proposes a system and method for determining the clock difference using the pseudo-range measurement value, the converted measurement value and the preset carrier frequency relationship.

[0013] To achieve the above-mentioned purpose, the 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 measurement signals and h converted measurement signals between the first device and the second device, and the pseudo-range measurement signals and the converted measurement signals have at least two different carrier frequencies; the carrier frequencies of the m pseudo-range measurement signals and the carrier frequencies of the h converted measurement signals satisfy a preset carrier frequency relationship; wherein m and h are positive integers greater than or equal to 1; the pseudo-range measurement signals are broadcast by the first device and received by the second device, or broadcast by the second device and received by the first device; the converted measurement signals are composed of uplink signals and downlink signals, the second device broadcasts the uplink signals and receives the downlink signals, and the first device receives the uplink signals and converts them to form the downlink signals.

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

[0015] Further, to achieve the above, the application further provides a ranging value determination method, applied to the high-precision time synchronization system in any of the embodiments of the application, the method is executed by the second device, and the method comprises: 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 h pieces of forwarding ranging signals; obtaining m pieces of pseudo-range ranging signals broadcast by the first device; synchronously measuring each of the pseudo-range ranging signals and each of the forwarding ranging signals to obtain m pieces of pseudo-range ranging values and h pieces of forwarding ranging values; when the pseudo-range 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 pieces of forwarding ranging signals; and synchronously measuring each of the forwarding ranging signals to obtain h pieces of forwarding ranging values; wherein m+h≥2, and m and h are positive integers.

[0016] Further, to achieve the above, the application further provides a high-precision time synchronization method, applied to the high-precision time synchronization system in any of the embodiments of the application, the method is executed by the computing device, and the method comprises: when the pseudo-range ranging signal is broadcast by the second device and received by the first device, obtaining m pieces of pseudo-range ranging values measured by the first device based on the communication with the first device, and obtaining h pieces of forwarding ranging values measured by the second device based on the communication with the second device; when the pseudo-range ranging signal is broadcast by the first device and received by the second device, obtaining m pieces of pseudo-range ranging values and h pieces of forwarding ranging values measured by the second device based on the communication with the second device; wherein the preset carrier frequency relationship is satisfied between the carrier frequencies corresponding to the h pieces of forwarding ranging values and the carrier frequencies corresponding to the m pieces of pseudo-range ranging values; m+h≥2, and m and h are positive integers; each of the pseudo-range ranging values is represented by a pseudo-range ranging expression, and each of the forwarding ranging values is represented by a forwarding ranging expression; and the clock difference between the first device and the second device is determined based on the m pieces of pseudo-range ranging values represented by the pseudo-range ranging expression, the h pieces of forwarding ranging values represented by the forwarding ranging expression, and the preset carrier frequency relationship.

[0017] The high-precision time synchronization system provided by the application can determine the clock difference between the first device and the second device. When the time synchronization system is applied to the field of satellite navigation, compared with the prior art, the error influence of ionospheric delay and tropospheric delay is overcome, the accuracy of the determined clock difference is improved, the navigation accuracy is improved, and the real-time performance is strong. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is a schematic diagram of a high-precision time synchronization system according to an embodiment of this application;

[0019] Figure 2 is a structural block diagram of a first device and a second device according to one embodiment of this application;

[0020] Figures 3-5 are schematic diagrams of the deformed structure of the high-precision time synchronization system provided in the embodiments of this application.

[0021] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application. It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit this application.

[0023] The meanings of the various parameters involved in the embodiments of this application are explained below:

[0024] ρ mean1 (n) represents the corrected average pseudorange value at time n, in meters; ρ z1,a (n) represents the first corrected pseudorange measurement value at time n, in meters; ρ z1 (n) represents the first pseudorange measurement value at time n, in meters; R true,z1 (n) represents the actual spatial distance traversed by the first pseudorange ranging signal at time n, in meters; z1 (n) represents the ionospheric delay of the first pseudorange ranging signal at time n, in meters (T). duiliu,z1 (n) represents the tropospheric delay of the first pseudorange ranging signal at time n, in meters; c represents the speed of light, in meters per second; δt s (n) represents the clock difference of the first device relative to the system time at time n, in seconds; δt z (n) represents the clock difference of the second device relative to the system time at time n, in seconds; sagnac zz (n) represents the Sagnac effect delay of the pseudorange ranging signal at time n, in meters; X z1(n) represents the first pseudo-range measurement signal hardware device delay at the nth moment, unit: meter, the pseudo-range measurement signal hardware device delay includes the first pseudo-range measurement signal transmission delay, the first pseudo-range measurement signal receiving delay;

[0025] L mean1 (n) represents the first pseudo-range measurement signal hardware device delay at the nth moment, unit: meter, the pseudo-range measurement signal hardware device delay includes the first pseudo-range measurement signal transmission delay, the first pseudo-range measurement signal receiving delay; 1,a (n) represents the first pseudo-range measurement signal hardware device delay at the nth moment, unit: meter, the pseudo-range measurement signal hardware device delay includes the first pseudo-range measurement signal transmission delay, the first pseudo-range measurement signal receiving delay; true,u1 (n) represents the first pseudo-range measurement signal hardware device delay at the nth moment, unit: meter, the pseudo-range measurement signal hardware device delay includes the first pseudo-range measurement signal transmission delay, the first pseudo-range measurement signal receiving delay; true,d1 (n) represents the first pseudo-range measurement signal hardware device delay at the nth moment, unit: meter, the pseudo-range measurement signal hardware device delay includes the first pseudo-range measurement signal transmission delay, the first pseudo-range measurement signal receiving delay; u1 (n) represents the first pseudo-range measurement signal hardware device delay at the nth moment, unit: meter, the pseudo-range measurement signal hardware device delay includes the first pseudo-range measurement signal transmission delay, the first pseudo-range measurement signal receiving delay; d1 (n) represents the first pseudo-range measurement signal hardware device delay at the nth moment, unit: meter, the pseudo-range measurement signal hardware device delay includes the first pseudo-range measurement signal transmission delay, the first pseudo-range measurement signal receiving delay; duiliu,u1 (n) represents the first pseudo-range measurement signal hardware device delay at the nth moment, unit: meter, the pseudo-range measurement signal hardware device delay includes the first pseudo-range measurement signal transmission delay, the first pseudo-range measurement signal receiving delay; duiliu,d1 (n) represents the first pseudo-range measurement signal hardware device delay at the nth moment, unit: meter, the pseudo-range measurement signal hardware device delay includes the first pseudo-range measurement signal transmission delay, the first pseudo-range measurement signal receiving delay;

[0026] dT, represents the value of the first pseudo-range measurement signal, the first retransmission ranging signal according to formula (f1) multiplied by the ionospheric delay coefficient and the total electron content of the ionosphere, unit: second, wherein dT≥0;

[0027] Q ion represents the ionospheric delay coefficient, TEC(n) represents the total electron content of the ionosphere 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 retransmission ranging signal uplink signal at the nth moment, unit: hertz; d1 (n) represents the carrier frequency of the first retransmission ranging signal downlink signal at the nth moment, unit: hertz; z1 (n) represents the carrier frequency of the first pseudo-range measurement signal at the nth moment, unit: hertz.

[0028] It is particularly pointed out that Q ionThe ionospheric delay coefficient is a coefficient published by some international organizations. With the deepening of the research on ionospheric delay, the ionospheric delay coefficient is more and more accurate. The ionospheric delay coefficient was 40.28, 40.30, and is currently 40.309. In the future, there may be more accurate ionospheric delay coefficients. The ionospheric delay coefficient is not particularly limited in the application, and the latest published value is taken. In the embodiment, Q ion The value is 40.309.

[0029] The application creatively applies the carrier frequencies of the relay ranging signal and the pseudo-range ranging signal, and proposes a system and method capable of obtaining high-precision clock difference.

[0030] The system time described in the application refers to the time generated and maintained by a system, such as the system composed of the first device and the second device in the application. In actual application, the Beidou time of China is often taken as the reference time and system time, and the clock difference of different devices is the clock difference of different devices relative to the Beidou reference time.

[0031] The computing device of the application can communicate with the first device and the second device respectively to obtain the pseudo-range ranging value and the relay ranging value. When the first device broadcasts the pseudo-range ranging signal, the second device receives the pseudo-range ranging signal and measures the pseudo-range ranging value, and the second device transmits the relay ranging signal by itself to obtain the relay ranging value. At this time, the computing device communicates with the second device to obtain the pseudo-range ranging value and the relay ranging value. When the second device broadcasts the pseudo-range ranging signal, the first device receives the pseudo-range ranging signal and measures the pseudo-range ranging value, and the second device transmits the relay ranging signal by itself to obtain the relay ranging value. At this time, the computing device communicates with the second device to obtain the relay ranging value, and communicates with the first device to obtain the pseudo-range ranging value.

[0032] After the computing device obtains the pseudo-range ranging value and the relay ranging value, the method of the application is executed to calculate the clock difference between the first device and the second device.

[0033] It is worth noting that in the embodiment of the application, the computing device can be integrated into the first device, or integrated into the second device, or independent of the first device and the second device, that is, an independent device.

[0034] The core function of the application is that the sum of the number of relay ranging signals and pseudo-range ranging signals between the first device and the second device is greater than or equal to 2, and the sum of the number of pseudo-range ranging values and relay ranging values obtained is greater than or equal to 2. The clock difference between the first device and the second device is calculated according to the relationship between the pseudo-range ranging value, the relay ranging value, and the corresponding preset carrier frequency.

[0035] Therefore, the application focuses on the signal structure of the first device, the second device, and the signal between the two devices, as well as the calculation method for obtaining the clock difference between the first device and the second device.

[0036] The first device and the second device described in the application have pseudo-range measurement signals and relay measurement signals, and the sum of the number of pseudo-range measurement signals and the number of relay measurement signals is greater than or equal to 2; wherein the relay measurement 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 relays to form the downlink signal, and the second device receives the downlink signal; the pseudo-range measurement 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. Wherein the pseudo-range measurement signal and the relay measurement signal are spread spectrum signals.

[0037] As described above, in the embodiments of the application, the pseudo-range measurement signal can be broadcast by the first device and received by the second device, or it can also be broadcast by the second device and received by the first device.

[0038] When the pseudo-range measurement signal is broadcast by the second device, the uplink signal broadcast by the relay measurement device in the second device can be used as the pseudo-range measurement signal. After the uplink signal reaches the first device, it is divided into multiple signals, one of which is used as the pseudo-range measurement signal, and the remaining signal is forwarded by the repeater; or the uplink signal broadcast by the relay measurement device in the second device is directly received by the first pseudo-range measurement device of the satellite without being forwarded to the downlink signal by the repeater.

[0039] When the pseudo-range measurement signal is broadcast by the first device and received by the second device, the relay measurement signal is self-generated and self-received by the second device, and the relay measurement signal and the pseudo-range measurement signal are both received and measured by the second device, so that the pseudo-range measurement value and the relay measurement value can be measured synchronously;

[0040] It should be noted that when the pseudo-range measurement signal is broadcast by the second device and received by the first device, the relay measurement signal is self-generated and self-received by the second device, and the relay measurement signal and the pseudo-range measurement signal are respectively received and measured by the second device and the first device, so that the first device and the second device have a rough time synchronization condition (the same is true for the two-way pseudo-range measurement method, the satellite and the ground station each measure the pseudo-range measurement signal sent by the other, and the satellite and the ground station need to have a rough time synchronization requirement), at this time, the pseudo-range value measured by the first device and the relay measurement value measured by the second measurement device can be regarded as synchronous measurement, and the clock difference is calculated using the method of the application.

[0041] In addition, whether the pseudo-range measurement signal is measured by the second device or the first device corresponds to two different types of systems, which are the same in signal structure, system composition and processing method except for the direction of pseudo-range measurement signal transmission and the difference between the devices. Therefore, for the sake of simplicity, the following will only be described in the case of the first device broadcasting the pseudo-range measurement signal.

[0042] The first device and the second device have m pseudo-range measurement signals and h forwarding measurement signals; wherein the pseudo-range measurement signals are broadcast by the first device and received by the second device; the forwarding measurement signals include uplink signals broadcast by the second device and downlink signals received by the second device, and the downlink signals are obtained by the first device forwarding the uplink signals; the carrier frequencies of the m pseudo-range measurement signals and the h forwarding measurement signals satisfy a preset carrier frequency relationship; m and h are positive integers greater than or equal to 1.

[0043] The high-precision time synchronization system provided by the embodiments of the present application can be applied to a space system, and typically can be a high-precision time synchronization system composed of a user station and a satellite, i.e., a satellite-ground high-precision time synchronization system, in which the clock difference between the satellite and the user station is monitored by the user station. The specific application of the satellite-ground high-precision time synchronization system can include satellite navigation, satellite communication, satellite remote sensing, satellite reconnaissance, and meteorological satellites, etc.

[0044] It is worth noting that in the embodiments 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 the pseudo-range measurement signal.

[0045] FIG. 1 is a schematic diagram of the structure of a high-precision time synchronization system according to an embodiment of the present application, in which the pseudo-range measurement signal is broadcast by the first device, and the system includes a first device 100 and a second device 200 connected in communication.

[0046] The high-precision time synchronization system provided in the embodiments of the present application is characterized in that the satellite 100 sends a pseudo-range measurement signal to the user station 200, the user station 200 sends an uplink signal to the satellite 100, the satellite 100 forwards the uplink signal to obtain a downlink signal after obtaining the uplink signal and sends the downlink signal to the user station 200, and the carrier frequency of the uplink signal, the carrier frequency of the downlink signal and the carrier frequency of the pseudo-range measurement signal have a preset carrier frequency relationship. In this way, the user station 200 can determine the clock difference between the satellite 100 and the user station 200 according to the preset carrier frequency relationship between the carrier frequencies of the pseudo-range measurement signal and the forwarded measurement signal without knowing the exact atmospheric delay error caused by 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 space distance between the satellite and the user station, can improve the accuracy of the determined clock difference, has the advantages of simplifying the satellite load and reducing the cost of the satellite.

[0047] In the embodiments of the present application, the first device 100 can be a satellite, and the second device 200 can be a user station. When the computing device is integrated into the user station, the clock difference between the satellite and the user station is determined by the user station, so that the satellite can be synchronized with the clock of the user station. Of course, in other embodiments, the first device 100 can be a user station, and the second device 200 can be a satellite. Further, the first device in the embodiments of the present application can also be a high-orbit device, and the second device can be a low-orbit device, or the first device and the second device can both be low-orbit devices, as long as the two devices are located on the two 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.

[0048] Of course, in other embodiments, the first device and the second device can also be located on the same side of the ionosphere, for example, both on the ground or both in space, at this time, 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 embodiments of the present application.

[0049] In the following, the first device 100 is taken as a satellite, and the second device 200 is taken as a user station for example without special instructions.

[0050] In order to more clearly and more generally illustrate the working principle of the system, the present application uses a signal structure of one forwarded measurement signal and one pseudo-range measurement signal, and the carrier frequencies of all signals are different, at this time, m = 1 and h = 1, as shown in FIG. 1, a forwarded measurement value and a pseudo-range measurement value are obtained by synchronous measurement, and the specific implementation of the method of the present application is illustrated.

[0051] Because of the preciousness of radio spectrum resource, when m = 1, h = 1, one way of the retransmission ranging signal and one way of the pseudo-range ranging signal are very representative, and the least radio frequency resource can be applied to realize high-precision time synchronization, and the cost-effectiveness is optimal. The application is described by using the example.

[0052] When there are multiple retransmission ranging signals or multiple pseudo-range ranging signals in the application, the clock difference between the first device and the second device can also be obtained by setting the preset carrier frequency relationship between the carrier frequencies of the multiple retransmission ranging signals and the carrier frequencies of the multiple pseudo-range ranging signals using the method of the application.

[0053] In the example embodiment, the user station sends an uplink signal to the satellite based on its own clock system, i.e., taking the local time as the reference. After obtaining the uplink signal, the satellite performs retransmission processing on the uplink signal to obtain a downlink signal, and retransmits 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 the example embodiment are different.

[0054] The uplink signal and the downlink signal retransmitted through the satellite constitute a retransmission ranging signal. The user station can determine a retransmission ranging value according to the retransmission ranging signal. In addition, the satellite also sends a pseudo-range ranging signal to the user station based on its own clock system, i.e., taking the local time as the reference. The user station receives and demodulates the pseudo-range ranging signal to obtain a pseudo-range ranging value. Thus, the user station can calculate the clock difference between the satellite and the user station according to the determined retransmission ranging value and the pseudo-range ranging value and the preset frequency relationship.

[0055] Both the retransmission ranging signal and the pseudo-range ranging signal are spread spectrum signals, and spread spectrum technology, carrier frequency multiplexing technology and code division multiple access technology are used for corresponding processing in signal transmission, retransmission and reception processing.

[0056] It should be noted that the pseudo-range ranging signal and the retransmission ranging signal in the embodiments of the application refer to modulated signals obtained after modulating a ranging code signal in a carrier signal. The ranging codes used by the pseudo-range ranging signal and the retransmission ranging signal can be the same or different, and the ranging code of the uplink signal in the retransmission ranging signal is the same as that of the downlink signal. In some specific embodiments, the ranging code can be obtained by loading protocol data through a pseudo code, a weil code, an M code, etc. The application does not make special limitations on the specific selection of the ranging code. It can be understood that the retransmission ranging signal and the pseudo-range ranging signal in the embodiments of the application are 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 spread spectrum communication technology, carrier frequency multiplexing technology and code division multiple access communication technology, which will not be described here.

[0057] The specific process of determining the clock difference between the satellite and the user station by the user station can be referred to the introduction of the subsequent method embodiments, which will not be expanded here.

[0058] Figure 2 is a structural block diagram of a satellite and a user station according to an embodiment of the present application, which shows the internal structure of the system when the pseudo-range ranging signal is broadcast by the first device. As shown in Figure 2, in the exemplary embodiment, the satellite 100 can include a transponder 101, a pseudo-range generating device 102 and a first time-frequency device 103 which are communicatively connected. The pseudo-range generating device 102 generates and broadcasts the pseudo-range ranging signal; the transponder 101 receives the uplink signal, and after performing the transponding (including frequency conversion processing and power amplification) on the uplink signal, transponds the downlink signal to the user station 200; and the first time-frequency device 103 provides time-frequency signals for the transponder 101 and the pseudo-range generating device 102.

[0059] It should be understood that the transponder 101 and the pseudo-range generating device 102 described in the embodiments of the present application can be independently provided, or can be integrated in one hardware device, i.e., the functions of the transponder and the pseudo-range generating device are realized by one integrated hardware device, or the transponder 101, the pseudo-range generating device 102 and the first time-frequency device 103 are integrally provided, which all belong to the protection scope of the present application.

[0060] It should be noted that in the embodiments of the present application, the pseudo-range generating device 102 and the transponder 101 are communicatively connected, i.e., they can realize communication interaction, which can be that they directly perform communication interaction, or that they are both connected to a third party device to realize communication interaction, which all belong to the protection scope of the present application.

[0061] Because the computing device is only used to realize the computing function, it can be independently provided or integrated in the first device or the second device, which does not affect the realization of the scheme of the present application, therefore, the exemplary embodiment takes the computing device integrated in the second device as an example for exemplary description, based on which, the user station 200 can include a transponding ranging device 201, a second pseudo-range ranging device 202, a second time-frequency device 203 and a computing device 204, and the second time-frequency device 203 provides time-frequency signals for the transponding ranging device 201 and the second pseudo-range ranging device 202.

[0062] The second pseudo-range ranging device 202 processes the received pseudo-range ranging signal to obtain a pseudo-range ranging value; the transponding ranging device 201 generates and broadcasts the uplink signal, and receives the downlink signal and determines a transponding ranging value based on the downlink signal. The computing device 204 receives the pseudo-range ranging value and the transponding ranging value, and determines the clock difference of the satellite 100 relative to the user station 200 based on the pseudo-range ranging value, the transponding ranging value and a preset carrier frequency relationship; and the second time-frequency device 203 provides time-frequency signals for the transponding ranging device 201 and the second pseudo-range ranging device 202.

[0063] In addition, it should be noted that the second pseudo-range measuring device 202 and the forwarding range measuring device 201 in the embodiments of the present application can be independently arranged or integrated in one hardware device, that is, one hardware device implements the functions of the second pseudo-range measuring device 202 and the forwarding range measuring device 201, or the second pseudo-range measuring device 202, the forwarding range measuring device 201 and the second time-frequency device 203 are integrated, which all belong to the protection scope of the present application.

[0064] As described above, the pseudo-range measuring signal can also be broadcasted by the second device and received by the first device, in which case, the first device comprises a first time-frequency device, a forwarder and a first pseudo-range measuring device; the first time-frequency device is configured to provide a time-frequency signal to the forwarder and the first pseudo-range measuring device; the forwarder is configured 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 pseudo-range measuring device is in communication connection with the forwarder, and the first pseudo-range measuring device is configured to receive and measure the pseudo-range measuring signal; the second device comprises a second time-frequency device and a forwarding range measuring device; the second time-frequency device is configured to provide a time-frequency signal to the forwarding range measuring device at least; the forwarding range measuring device is configured to generate and broadcast the uplink signal, and receive the downlink signal, and determine a forwarding range value based on the forwarding range measuring signal; wherein the uplink signal broadcasted by the forwarding range measuring device is the pseudo-range measuring signal; the computing device is in communication connection with the first device and the second device, and the computing device receives the pseudo-range measuring value and the forwarding range value, and determines a clock difference between the first device and the second device based on the forwarding range value, the pseudo-range measuring value and a preset carrier frequency relationship; wherein when the clock difference is determined, the sum of the number of the forwarding range value and the pseudo-range measuring value is greater than or equal to 2; wherein the first pseudo-range measuring device is integrated with or independently arranged from the first time-frequency device and the forwarder, and the second pseudo-range measuring device is integrated with or independently arranged from the second time-frequency device and the forwarding range measuring device.

[0065] In this case, the transmission delay of the forwarding range measuring device can be measured in advance, so that the delay is pre-set in the computing device, and the computing device directly uses the delay in subsequent calculation. Because in this working condition, the first device and the second device only differ in the broadcasting mode of the pseudo-range measuring signal, and the specific functions of the functional components are similar to those of the structure shown in FIG. 2, the specific structure of the first device and the second device will be further introduced below taking the system structure shown in FIG. 2 as an example.

[0066] In the example embodiment, the retransmission ranging device 201 can 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 to a radio frequency signal. The antenna transmits the radio frequency signal to the satellite and receives the radio frequency signal retransmitted by the satellite. The antenna receives the radio frequency signal and mixes the radio frequency signal to an intermediate frequency signal by the mixer. The demodulator demodulates the intermediate frequency signal to obtain the retransmission ranging value by ranging code correlation operation. The data collector records and stores the retransmission ranging value. The second pseudorange ranging device 202 can include a demodulator, a receiving antenna, a data collector, etc. The receiving antenna receives the pseudorange ranging signal of the satellite and generates the pseudorange ranging value by the second pseudorange ranging device 202.

[0067] In the embodiment of the present application, the zero baseline is set between the second pseudorange ranging device 202 and the retransmission ranging device 201.

[0068] It should be noted that the zero baseline set in the present application is not that the distance between the second pseudorange ranging device 202 and the retransmission ranging device 201 is 0, but the distance between them is set to meet the condition that the space paths experienced by the retransmission ranging signal and the pseudorange ranging signal are approximately the same. When the distance between the second pseudorange ranging device 202 and the retransmission ranging device 201 becomes smaller and smaller, becomes one device or becomes one chip, the approximately the same gradually becomes the same, has the same space distance between the satellite and the user station, has the same troposphere delay, and has the same ionosphere total electron content.

[0069] At this time, the two signals of the pseudorange ranging signal and the retransmission ranging signal have the same transmission path, so the atmosphere has the same effect on the retransmission ranging signal and the pseudorange ranging signal, i.e. the retransmission ranging signal and the pseudorange ranging signal have the same ionosphere path and troposphere path. Therefore, the preset carrier frequency relationship between the carrier frequencies of the retransmission ranging signal and the pseudorange ranging signal can be used to eliminate the influence of the atmosphere error and accurately calculate the clock difference between the satellite and the user station.

[0070] In the example embodiment, the second device is a user station of the embodiment, and the user station uses at least one second time-frequency device 203, specifically, the second pseudo-range measuring device 202 and the retransmission measuring 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 application can 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 retransmission measuring device 201. In actual use, the preset time interval can be set as needed, for example, it can be set to 1s, and the second pseudo-range measuring device 202 and the retransmission measuring device 201 measure at the rising edge or falling edge of the respective 1PPS (1 Pulse Per Second, second pulse) signal. As a preferred, it is generally recommended to use one clock to perform synchronous measurement of the pseudo-range measuring signal and the retransmission measuring signal at the rising edge or falling edge of the same 1PPS signal.

[0071] The first device is also similar, and at least one first time-frequency device 103 is provided, when there are multiple time-frequency devices, one time-frequency device provides a time-frequency signal for the retransmitter 101, and another time-frequency device provides a time-frequency signal for the pseudo-range generating device 102 or the pseudo-range generating device 102.

[0072] In the example embodiment, the retransmitter 101 has a retransmission delay, and the pseudo-range generating device 102 has a transmission delay; the second pseudo-range measuring device 202 has a receiving delay, and the retransmission measuring device 201 has a transmission delay and a receiving delay; wherein the pseudo-range measuring signal carries the retransmission delay of the retransmitter and the transmission delay of the pseudo-range generating device, or the computing device 204 is preset with the retransmission delay of the retransmitter 101 and the transmission delay of the pseudo-range generating device 102.

[0073] The retransmission delay of the retransmitter 101 refers to the delay generated in the process of the satellite receiving the uplink signal sent by the user station, processing the uplink signal to obtain the downlink signal.

[0074] The transmission delay of the pseudo-range generating device 102 refers to the delay generated in the process of the pseudo-range generating device 102 of the satellite generating and transmitting the pseudo-range measuring signal, which is denoted as the pseudo-range measuring signal transmission delay.

[0075] Specifically, the repeater 101 is in communication connection with the pseudo-range generating device 102, so that the repeater delay can be sent to the pseudo-range generating device 102. The pseudo-range generating device 102 can load the obtained repeater delay and pseudo-range ranging signal transmission delay into the pseudo-range ranging signal, so that after the pseudo-range ranging signal is sent to the user station, the repeater delay and the pseudo-range ranging signal transmission delay can be obtained after the second pseudo-range ranging device 202 in the user station demodulates the pseudo-range ranging signal. Alternatively, because the repeater delay and the pseudo-range ranging signal transmission delay have a small change or are known, the repeater delay and the pseudo-range ranging signal transmission delay can be regarded as known quantities, so that in actual use, the repeater delay and the pseudo-range ranging signal transmission delay can also be preset in the computing device.

[0076] By loading the repeater delay and the pseudo-range ranging signal transmission delay into the pseudo-range ranging signal for transmission to the user station, the repeater delay and the pseudo-range ranging signal transmission delay are completely transmitted by using the existing signals between the satellite and the user station, without the need for additional communication links, so that no additional communication resources are occupied, and the communication cost can be greatly reduced, and the frequency resources can be saved.

[0077] It is worth noting that the above embodiment is only described by taking the user station and the signals owned by the satellite (the pseudo-range ranging signal broadcast by the pseudo-range generating device 102) as an example.

[0078] The second pseudo-range ranging device 202 of the user station has a receiving delay, which refers to the delay generated by the second pseudo-range ranging device 202 in the process of receiving the pseudo-range ranging signal sent by the satellite and generating the pseudo-range ranging value. The repeater 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 emission of the uplink signal from the antenna; and the receiving delay refers to the delay of receiving the downlink signal and generating the repeater ranging value.

[0079] In some embodiments of the present application, the repeater delay and the pseudo-range ranging signal transmission delay can also be transmitted between the user station and the satellite by using additional communication signals, for example, a remote control and telemetry unit can be arranged in the satellite, and the repeater delay and the pseudo-range ranging signal transmission delay can be transmitted by the telemetry signal broadcast by the remote control and telemetry unit, or the repeater delay and the pseudo-range ranging signal transmission delay can be transmitted to the user station by other communication link signals defined by the user. The present application does not specially limit the specific signals used to transmit the repeater delay and the pseudo-range ranging signal transmission delay.

[0080] In the example embodiment, the preset carrier frequency relationship refers to the frequency relationship satisfied among the carrier frequencies of the uplink signals of the relay ranging signals, the carrier frequencies of the downlink signals of the relay ranging signals, and the carrier frequencies of the pseudorange ranging signals. In a specific embodiment, the preset carrier frequency relationship satisfied among the carrier frequencies of the h uplink signals, the carrier frequencies of the h downlink signals, and the carrier frequencies of the m pseudorange ranging signals is shown in the following formula (fl):

[0081] In the formula, V represents a real constant, and in an example, V = le-12.

[0082] Some special cases of the carrier frequencies of the relay ranging signals and the carrier frequencies of the pseudorange ranging signals are described below.

[0083] When m = 1 and h = 1, there is only one relay ranging signal and one pseudorange ranging signal.

[0084] When the pseudorange ranging signal is broadcast by the first device, and when the carrier frequency of the pseudorange ranging signal is the same as the carrier frequency of the downlink signal of the relay ranging signal, i.e., f z1 (n) = f d1 (n), the preset carrier frequency relationship is shown in the following formula (fl-1), and only two carrier frequency resources are used to achieve the satellite-ground time synchronization.

[0085] When the pseudorange ranging signal is broadcast by the second device, the carrier frequency of the pseudorange ranging signal is the same as the carrier frequency of the uplink signal of the relay ranging signal, i.e., f z1 (n) = f u1 (n), the preset carrier frequency relationship is shown in the following formula (fl-2), and only two carrier frequency resources are used to achieve the satellite-ground time synchronization.

[0086] In this case, the system evolves into a satellite-ground time synchronization system with two carrier frequencies, in which the carrier frequency of the pseudorange ranging signal is the same as the carrier frequency of the downlink signal of the relay ranging signal. In this case, two carrier frequencies can be used to achieve better satellite-ground time synchronization accuracy.

[0087] The specific influence of the relationship among the carrier frequencies in the formula (fl-1) can be further illustrated by a specific example. When the carrier frequency of the uplink signal of the relay ranging signal and the carrier frequency of the pseudorange ranging signal use the L frequency band, such as f z1 = 1330 MHz and f u1 = 1575 MHz, the frequency relationship is:

[0088] When TEC = 50e16 electrons / m2, then the ionospheric residual is: 0.5(I z1 -I u1 ) = 1.63m, converted into time, it is 5.45ns, the ionospheric residual obtained is still relatively large.

[0089] When the carrier frequency of the uplink signal forwarding the ranging signal and the carrier frequency of the pseudorange ranging signal use the Cn frequency band (5010MHz-5030MHz), the frequency band is a new frequency band allocated to satellite navigation by the International Telecommunication Union. For example, f z1 = 5010MHz, f u1 = 5030MHz, the frequency relationship is:

[0090] When TEC = 50e16, then the ionospheric residual is: 0.5(I z1 -I u1 ) = 0.0032m, converted into time, it is 0.0106ns; it can be seen that when the Cn frequency band is used, the ionospheric residual is very small; when the Ku, Ka, Q, and V frequency bands are used, the ionospheric residual is still very small. Therefore, when the Cn, Ku, Ka, Q, and V frequency bands are used, considering other random errors and other factors, sub-nanosecond level time synchronization accuracy can be completely achieved.

[0091] Further, in some embodiments, the carrier frequency of the ranging signal forwarding signal and the carrier frequency of the pseudorange ranging signal perform frequency hopping according to a preset frequency hopping pattern on the time axis, that is, the uplink signal, the downlink signal, and the pseudorange ranging signal at different moments do not use the same fixed frequency, but use different frequency signals at different moments. In this way, the signal is frequency-hopped, which can improve the anti-interference performance of the signal and improve the anti-interception performance of the signal.

[0092] It is worth noting that no matter how the frequency hopping is performed, the carrier frequencies of the pseudorange ranging signal, the uplink signal, and the downlink signal still need to satisfy the preset carrier frequency relationship shown in the relationship (f1).

[0093] Of course, the carrier frequency of the ranging signal forwarding signal and the carrier frequency of the pseudorange ranging signal can also remain unchanged for a long time, that is, the time interval between adjacent two frequency hopping is infinite.

[0094] In the example embodiment, the high-precision time synchronization system provided by the embodiment of the application also has a communication function, the first device uses the uplink signal of any one of the relay ranging signals and any one of the pseudo-range ranging signals to perform data transmission with the second device, or uses an added communication signal to perform data transmission with the second device. Specifically, the satellite divides the uplink signal of the relay ranging signal into two parts, one part is relayed downward to the user station, and the other part 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.

[0095] In the example embodiment, as shown in FIG. 1, the satellite can also send the relay delay and the pseudo-range ranging signal transmission delay to the user station through an added communication signal, that is, in addition to the uplink signal link, the downlink signal link and the pseudo-range ranging signal link between the satellite and the user station, the satellite also has an added communication link (including the communication link uplink signal fu and the communication link downlink signal fd), and the satellite transmits the relay delay and the pseudo-range ranging signal transmission delay to the user station through the added communication link. The added communication signal can be a remote control and telemetry signal.

[0096] As can be seen, the satellite can transmit the relay delay and the pseudo-range ranging signal transmission delay to the user station in various ways, and the specific transmission mode of the relay delay and the pseudo-range ranging signal transmission delay is not specially limited in the application.

[0097] On the basis of the above-mentioned embodiments, the embodiment of the application also provides a high-precision time synchronization method, which can be applied to the high-precision time synchronization system of any of the above-mentioned embodiments, and the method can be executed by a computing device. When the computing device is integrated into a user station, the method is executed by the user station.

[0098] In the pseudo-range ranging value, the Sagnac effect delay of the satellite needs to be obtained, and the Sagnac effect delay needs the coordinates of the user station and the satellite. The coordinates of the satellite can be obtained by known satellite ephemeris, and the coordinates of the user station can be obtained by existing positioning methods. Thus, the coordinate information required by the method of the embodiment of the application is obtained, and the Sagnac effect delay is further obtained.

[0099] In the pseudo-range ranging value, there is no relativistic delay effect term. This is because in practice, the satellite in space has 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 the relativistic effect. For the relativistic effect delay of the satellite clock, existing methods can be used to solve it, such as the satellite clock has been adjusted before being launched into space. The adjusted satellite clock is the same as the clock on the ground and has no relativistic effect delay. For details, reference can be made to the practice of the Beidou navigation satellite clock in terms of relativity.

[0100] When using the forwarding ranging expression to characterize the forwarding ranging value, the Sagnac effect delay is not included in the expression because the Sagnac effect delay of the uplink signal and the downlink signal have opposite signs, and their absolute values ​​differ very little. Therefore, these two Sagnac effect delays can be approximately canceled out, and thus the Sagnac effect delay term is not reflected in the forwarding ranging expression. Of course, in other embodiments of this application, the Sagnac effect delay can also be considered, that is, the Sagnac effect delay of the uplink signal and the downlink signal can be added to the forwarding ranging expression to achieve better measurement accuracy of the forwarding ranging value. These are all within the scope of protection of this application.

[0101] Furthermore, the device latency and its acquisition method used in this method embodiment can be found in the description of the above system embodiment, and will not be repeated here.

[0102] The ionosphere is a diffuse medium, meaning that the time delay produced by the ionosphere for radio frequency signals with different carrier frequencies varies depending on the carrier frequency. In contrast, the troposphere is a non-diffuse medium, meaning that the troposphere produces the same time delay for radio frequency signals with different carrier frequencies.

[0103] Because the second pseudorange ranging device 202 and the relay ranging device 201 are set with a zero baseline, the pseudorange ranging signal and the downlink signal traverse the same spatial path. However, the time when the uplink signal crosses the ionosphere is different from the time when the downlink signal after being relayed by the satellite crosses the ionosphere, resulting in a certain time difference. Within a relatively short period of time (e.g., a few seconds), the ionosphere is stable, and the total number of electrons in the ionosphere remains almost unchanged. It can be calculated that the round-trip time of radio frequency signals between almost all spacecraft and ground stations will not exceed a few seconds, which fully meets the conditions. Combining the spatial relationship of the zero baseline setting and the time relationship of the very short time difference, the spatial paths traversed by the relay ranging signal and the pseudorange ranging signal are exactly the same. Because the second pseudorange ranging device 202 and the relay ranging device 201 are set with a zero baseline, the spatial paths traversed by the m-path pseudorange ranging signal and the h-path relay ranging signal are exactly the same. The spatial distance between the pseudorange ranging signal and the relay ranging signal is equal, and the tropospheric delay of the pseudorange ranging signal and the relay ranging signal is equal. In this embodiment, there are equations (19) and (20): R true,z1 (n)=R true,u1 (n)=R true,d1 (n) (19); T duiliu,z1 (n)=T duiliu,u1 (n)=T duiliu,d1 (n) (20);

[0104] When the pseudo-range measurement signal is broadcast by the second device, the pseudo-range measurement signal and the uplink signal of the retransmission measurement signal traverse the same spatial path, and the retransmitter and the first pseudo-range measurement device also have the formula of the above-mentioned zero baseline setting relationship.

[0105] The method for calculating the clock difference between the satellite and the user station provided in the present application involves h retransmission measurement values and m pseudo-range measurement values, where h is at least 1 and m is at least 1. The calculation device first processes the m pseudo-range measurement values to obtain a corrected average pseudo-range measurement value and processes the h retransmission measurement values to obtain a corrected average retransmission measurement value, and then determines the clock difference by using the corrected average retransmission measurement value, the corrected average pseudo-range measurement value, and a preset carrier frequency relationship.

[0106] In order to illustrate the use of the present method, m = 1 and h = 1 here, i.e., there is one corrected average retransmission measurement value and one corrected average pseudo-range measurement value, and the clock difference between the satellite and the user station is calculated according to the two values.

[0107] When the pseudo-range measurement signal is broadcast by the second device and received by the first device, the first device measures the pseudo-range measurement value by performing the following process:

[0108] The second device receives the m pseudo-range measurement signals broadcast by the first device, synchronously measures each of the pseudo-range measurement signals to obtain m pseudo-range measurement values, and m is a positive integer. 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 retransmission measurement value and the pseudo-range measurement value by performing the following process: broadcasting at least one uplink signal to the first device; obtaining at least one downlink signal retransmitted by the first device based on the at least one uplink signal, where the at least one uplink signal and the at least one downlink signal constitute h retransmission measurement signals; obtaining m pseudo-range measurement signals broadcast by the first device; synchronously measuring each of the retransmission measurement signals and each of the pseudo-range measurement signals to obtain m pseudo-range measurement values and h retransmission measurement values; where m + h ≥ 2, and m and h are both positive integers; it is particularly worth pointing out that when the pseudo-range measurement signal is broadcast by the second device and received by the first device, or when the pseudo-range measurement signal is broadcast by the first device and received by the second device, the second device needs to measure the h retransmission measurement values, and m + h ≥ 2 needs to be met.

[0109] The time synchronization method of the present application is executed by the calculation device, and the time synchronization method can include the following steps:

[0110] S100, when the pseudo-range measurement signal is broadcast by the second device and received by the first device, obtaining the m pseudo-range measurement values measured by the first device based on the communication with the first device, and obtaining the h retransmission range values measured by the second device based on the communication with the second device; when the pseudo-range measurement signal is broadcast by the first device and received by the second device, obtaining the m pseudo-range measurement values and the h retransmission range values measured by the second device based on the communication with the second device; wherein the preset carrier frequency relationship is satisfied between the carrier frequencies corresponding to the h retransmission range values and the carrier frequencies corresponding to the m pseudo-range measurement values; m+h≥2, and m and h are positive integers;

[0111] S110, respectively using a pseudo-range measurement expression to represent each of the pseudo-range measurement values and using a retransmission range expression to represent each of the retransmission range values;

[0112] S120, determining the clock difference between the first device and the second device based on the m pseudo-range measurement values represented by the pseudo-range measurement expression, the h retransmission range values represented by the retransmission range expression, and the preset carrier frequency relationship.

[0113] The following will continue to take the first device as a satellite and the second device as a user station as an example to specifically describe the method.

[0114] In the communication process between the user station and the satellite, the user station can obtain a pseudo-range measurement signal, demodulate the pseudo-range measurement signal to obtain a retransmission delay and a pseudo-range measurement signal transmission delay, the pseudo-range measurement signal is transmitted by the satellite to the user station, and the user station receives and demodulates the pseudo-range measurement signal to determine a pseudo-range measurement value.

[0115] In the communication process between the user station and the satellite, the user station can also obtain a retransmission range signal by self-transmission and self-reception, and further obtain a retransmission range value.

[0116] It should be noted that the Sagnac effect delay in the pseudo-range measurement expression and the retransmission range expression in the present application has been explained in the foregoing and can be taken as a known value, and the satellite-ground space distance, the troposphere delay, the ionosphere delay, the clock difference of the satellite relative to the system time, and the clock difference of the user station relative to the system time are unknowns. The present application calculates the clock difference between the satellite and the user station according to the measured pseudo-range measurement values and retransmission range values.

[0117] In some embodiments, after step S110, the time synchronization method may further include the following step: correcting the forwarding ranging value and the pseudorange ranging value using a pseudorange smoothing algorithm. Specifically, correcting the pseudorange ranging value and the forwarding ranging value using a pseudorange smoothing algorithm can reduce the noise in the pseudorange ranging value and the forwarding ranging value, which is beneficial to improving the accuracy of the finally determined clock difference. The specific details of the pseudorange smoothing algorithm will not be elaborated here.

[0118] Before introducing the specific method, it is important to note that in the pseudorange measurement formula (3), ±c·(δt) z (n)-δt s (n)), when +c·(δt) z (n)-δt s When (n)), the corresponding satellite broadcasts a pseudorange ranging signal, and the user station receives the measurement; when -c·(δt) is taken... z (n)-δt s When (n) is reached, the corresponding user station broadcasts a pseudorange ranging signal, which is then received and measured by the satellite.

[0119] ±sagnca in pseudorange measurement formula (3) zz (n), when taking +sagnca zz When (n), it corresponds to the Sagnac effect when the satellite broadcasts pseudorange ranging signals. When -sagnac is taken... zz When (n), this 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 values ​​of the Sagnac effect are the same, but the signs are opposite.

[0120] Because the directions of the pseudorange 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, everything else is the same. Therefore, when the satellite broadcasts the pseudorange signal, the pseudorange formula is as follows (f3); when the user station broadcasts the pseudorange signal, the pseudorange formula is as follows (s3): 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); ρ zi (n)=R true,zi (n)+I zi (n)+T duiliu,zi (n)-c·(δt z (n)-δt s (n))-sagnaczz (n) + X zi (n) (s3);

[0121] The corresponding modified pseudo-range measurement value formula is (f3') and (s3'):

[0122] The method of the present application is described below using the satellite broadcast pseudo-range measurement signal as an example, i.e. using the pseudo-range measurement formula (f3) and the modified pseudo-range measurement formula (f3') corresponding to the satellite broadcast pseudo-range measurement signal for expansion.

[0123] In some embodiments, the preset time delay parameter term included in the pseudo-range measurement expression includes at least the tropospheric time delay, the ionospheric time delay, the Sagnac effect time delay, the real space distance between the satellite and the user station, and the clock difference. In other embodiments, the preset time delay parameter term can also include the hardware device time delay.

[0124] After the pseudo-range measurement value and the retransmission measurement value are measured, in step S110, the corresponding measurement expression is further used for characterization, i.e. the mathematical expression of the pseudo-range measurement value and the mathematical expression of the retransmission measurement value are obtained, so that the common error term is eliminated by using the mathematical expression for mathematical processing in the subsequent steps, and finally the clock difference between the satellite and the user station is obtained.

[0125] Specifically, the user station can use the pseudo-range measurement value of number i containing the space distance between the satellite and the ground and the preset time delay parameter term as shown in the following formula (f3): 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);

[0126] Exemplarily, when i = 1, the user station obtains the first pseudo-range measurement value as shown in the following formula (f3-1): 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);

[0127] The user station can utilize a retransmission ranging value numbered j shown in equation (4) as follows: 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).

[0128] Exemplarily, when j = 1, the user station can use a first retransmission ranging value shown in equation (4-1) as follows: 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).

[0129] As described above, the ionospheric delay term is included in the pseudorange ranging signal, and the ionospheric delay term is also included in the retransmission ranging signal. In the present application, the user station can eliminate or reduce the linear combination result of the ionospheric delay of the uplink signal, the ionospheric delay of the downlink signal, and the ionospheric delay of the pseudorange ranging signal based on the 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.

[0130] In detail, when the carrier frequencies of the signals between the user station and the satellite satisfy the preset carrier frequency relationship, the specific process of step S120 is as follows:

[0131] Because of the zero baseline relationship between the user station retransmission ranging device and the user station second pseudorange ranging device, the ionospheric paths traversed by the retransmission ranging signal and the pseudorange ranging signal are the same, but the total electron content TEC(n) of the ionosphere is unknown.

[0132] Based on the preset carrier frequency relationship between the carrier frequency of the h = 1 uplink signal and the carrier frequency of the h = 1 downlink signal and the carrier frequency of the m = 1 pseudorange ranging signal, the ionospheric delay parameters are associated in the corresponding carrier frequency terms, respectively, to obtain the ionospheric delay corresponding relationship between the ionospheric delay of the h = 1 uplink signal, the ionospheric delay of the h = 1 downlink signal, and the ionospheric delay of the m = 1 pseudorange ranging signal, wherein the ionospheric delay parameters include the total electron content TEC(n) and the ionospheric delay coefficient of the ranging signal path between the satellite and the user station, and the following equation (1-1) is obtained:

[0133] According to the formula (1-1), the ionospheric delay of the uplink signal, the ionospheric delay of the downlink signal and the ionospheric delay of the pseudo-range measurement signal are obtained as shown in formula (1-2):

[0134] Thus, in the subsequent step, the user station can determine the clock difference between the satellite and the user station based on the obtained ionospheric delay correspondence.

[0135] In some embodiments, the step S120 can specifically include the following process:

[0136] S121, correcting the m pseudo-range measurement values represented by the pseudo-range measurement expression to obtain m corrected pseudo-range measurement values, and averaging the m corrected pseudo-range measurement values to obtain a corrected average pseudo-range measurement value;

[0137] S122, correcting the h retransmission range values represented by the retransmission range expression to obtain h corrected retransmission range values, and averaging the h corrected retransmission range values to obtain a corrected average retransmission range value;

[0138] S123, determining the clock difference between the first device and the second device based on the corrected average pseudo-range measurement value, the corrected average retransmission range value and the preset carrier frequency relationship.

[0139] Specifically, step S121 is to correct the m pseudo-range measurement values represented by formula (f3) obtained in the above steps to obtain m corrected pseudo-range measurement values, and step S122 is to correct the h retransmission range values represented by formula (4) obtained in the above steps to obtain h corrected retransmission range values.

[0140] For example, taking m=1 and h=1, i.e. one pseudo-range measurement value and one retransmission range value, as an example, in step S121, the user station corrects the above formula (f3-1) according to formula (f3') to obtain the corrected pseudo-range measurement value No. 1 as shown in the following formula (f3'-1):

[0141] In step S122, the user station transforms the retransmission range value No. 1 represented by the above formula (4-1) to obtain the corrected retransmission range value No. 1 as shown in the following formula (4'-1):

[0142] When both the pseudo-range measurement value and the retransmission measurement value are multiple (for example, both are greater than or equal to two), the user station further performs mean value calculation on the multiple corrected pseudo-range measurement values and the multiple corrected retransmission measurement values respectively, and correspondingly obtains a corrected average pseudo-range measurement value and a corrected average retransmission measurement value, and then utilizes the corrected average pseudo-range measurement value, the corrected average retransmission measurement value and a preset carrier frequency relationship to obtain the clock difference between the satellite and the user station in step S123.

[0143] In the present exemplary embodiment, the user station can calculate the corrected average pseudo-range measurement value according to the following formula (5):

[0144] Exemplarily, when m = 1, i.e., there is only one pseudo-range measurement value, then based on the above formula (5), and in combination with formula (f3'), the corrected average pseudo-range measurement value of formula (5-1) is determined as follows:

[0145] 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);

[0146] The user station can calculate the corrected average retransmission measurement value according to formula (6): the corrected average retransmission measurement value calculation method shown in the figure obtains the corrected average retransmission measurement value of formula (6-1) as follows:

[0147] Exemplarily, when h = 1, i.e., there is only one retransmission measurement value, then based on the above formula (6), the corrected average retransmission measurement value of formula (6-1) is determined as follows: 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);

[0148] In the exemplary embodiment, step S123 can specifically include the following steps:

[0149] S1231, performing mathematical processing on the expression representing the corrected average pseudo-range measurement value and the expression representing the corrected average retransmission measurement value to obtain an expression containing the clock difference between the satellite and the user station;

[0150] S1232, determining the clock difference between the satellite and the user station by using the linear combination result of the ionospheric delay and the expression containing the clock difference.

[0151] Specifically, the modified average pseudo-range measurement value represented by formula (5-1) and the modified average retransmission measurement 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); (δt z (n)-δt s (n)) c =(ρ mean1 (n)-L mean1 (n)) / c (7-1); ±(δt z (n)-δt s (n)) c =(ρ mean (n)-L mean (n)) / c (7);

[0152] It should be noted that the clock difference between the satellite and the user station can be calculated by using formula (7-1) or formula (7) because the pseudo-range measurement value contains the clock difference, and the retransmission measurement value does not contain the clock difference. The modified average pseudo-range measurement value and the modified average retransmission measurement value are expanded to obtain the following formula (8-1):

[0153] On this basis, because the second pseudo-range measurement value device in the user station and the retransmission measurement value are zero baseline settings, 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):

[0154] The relationship between the ionospheric delay of the retransmission measurement signal and the ionospheric delay of the pseudo-range measurement signal in the present embodiment according to the preset carrier frequency relationship is shown in formula (1-2). Because the total electron content of the ionosphere between the satellite and the user station is an unknown quantity, the linear combination result of the ionospheric delay of the retransmission measurement signal and the ionospheric delay of the pseudo-range measurement signal is a numerical range, which is also an unknown quantity.

[0155] The actual clock difference between the user station and the satellite is shown in formula (10-1): (ρ mean1 (n)-L mean1 (n)) / c-dT≤(δt z (n)-δt s (n))≤(ρ mean1 (n)-L mean1 (n)) / c+dT (10-1);

[0156] The unknown is taken as the clock error between the user station and the satellite, thus the result shown in formula (7-1) is obtained.

[0157] As mentioned above, a pseudorange smoothing algorithm can be used to correct the transponder ranging values ​​and pseudorange ranging values. Accordingly, in step S120, the corrected transponder ranging values ​​and pseudorange ranging values ​​can be used to calculate the clock difference between the satellite and the user station. It is understandable that using a pseudorange smoothing algorithm to correct the pseudorange ranging values ​​and transponder ranging values ​​can reduce the noise in the pseudorange ranging values ​​and transponder ranging values, which is beneficial to improving the accuracy of the finally determined clock difference. The specific details of the pseudorange smoothing algorithm will not be elaborated here.

[0158] It should be noted that the high-precision time synchronization system and method proposed in this application can solve for 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, and can also solve for 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.

[0159] According to formula (7-1), when the clock difference δt between the user station and the system time is used... z When the time difference is known, the clock difference δt between the satellite and the system time can be easily obtained. s (n), then δt s c(n)=(δt z (n)-δt s (n)) c -δt z (n), This represents the clock difference between the satellite and the system time as actually calculated. At this time, the user station can monitor the satellite clock difference. For example, if the time of the ground control station of the Beidou satellite navigation system is known, the clock difference between the control station and the satellite can be calculated using the method of this application, and then the satellite clock difference can be obtained.

[0160] Conversely, when the clock difference δt between the satellite and the system time is used... s When (n) is a known quantity, the clock difference δ between the user station and the system time can be easily obtained. tz ( n ),but This represents the clock difference between the user station and the system time as calculated, at which point the satellite can provide time services to the user station.

[0161] When both the clock difference of the user station relative to the system time and the clock difference of the satellite relative to the system time are unknown, the clock difference (δt) between the satellite and the user station is obtained. z (n)-δt s (n)) c .

[0162] The user station determines the clock difference (δt) between the satellite and the user station.z (n)-δt s (n)) c After that, data transmission can be carried out with the satellite based on the uplink signal and the pseudo-range measurement signal, or data transmission can be carried out with the satellite based on an additional communication signal, which 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 synchronizes the time of the satellite with the time of the user station. These all belong to the protection scope of the present application.

[0163] Alternatively, the user station does not exchange clock difference data with the satellite.

[0164] In the present application, the carrier frequency of the h-path retransmission ranging signal and the carrier frequency of the m-path pseudo-range measurement signal need to satisfy the relationship shown in formula (f1):

[0165] wherein V is equal to 1e-12, and m and h are positive integers.

[0166] When formula (f1) is a special preset carrier frequency relationship shown in formula (f2) as follows:

[0167] 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 retransmission 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 in the present application, the ionospheric delay is completely eliminated, and 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.

[0168] The following will give several schematic diagrams of the preset carrier frequency relationship shown in formula (f2).

[0169] The downlink signals of the pseudo-range measurement signal and the retransmission ranging signal are carrier frequency multiplexed.

[0170] For example, when the carrier frequency of the signal between the user station and the satellite has that shown in FIG. 3, it can be obtained that the carrier frequency of the signal satisfies the relationship of formula (21):

[0171] For example, when the carrier frequency of the signal between the user station and the satellite has that shown in FIG. 4, it can be obtained that the carrier frequency of the signal satisfies the relationship of formula (22):

[0172] For example, when the carrier frequency of the signal between the user station and the satellite has that shown in FIG. 5, it can be obtained that the carrier frequency of the signal satisfies the relationship of formula (23):

[0173] For example, when the carrier frequency of the signal between the user station and the satellite has the relationship as shown in Fig. 6, it can be obtained that the carrier frequency of the signal satisfies the relationship of formula (24):

[0174] Therefore, in actual use, in order to obtain better results, the carrier frequency of the retransmission ranging signal and the carrier frequency of the pseudo-range ranging signal should be made to satisfy the relationship shown in formula (f2) as much as possible, and then when the clock difference between the satellite and the user station is calculated using the retransmission ranging value and the pseudo-range ranging value, accurate results can be obtained.

[0175] As described above, in the high-precision time synchronization system provided by the embodiments 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 the pseudo-range ranging signal, which is received and measured by the first pseudo-range ranging device of the first device. The present application gives the following several embodiments:

[0176] When the second device broadcasts the uplink signal of the retransmission ranging signal, one of the uplink signals 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 also retransmitted by the satellite transponder into two downlink signals with different carrier frequencies, forming two retransmission ranging signals and obtaining two retransmission ranging values.

[0177] Alternatively, when the second device broadcasts the uplink signal of the retransmission ranging signal, one of the uplink signals reaches the satellite and is received by the first pseudo-range ranging device of the satellite to obtain a pseudo-range ranging value, while the other uplink signal is not retransmitted by the transponder. When the second device broadcasts another uplink signal of the retransmission ranging signal, the uplink signal is also retransmitted by the satellite transponder into two downlink signals with different carrier frequencies, forming two retransmission ranging signals and obtaining two retransmission ranging values.

[0178] Alternatively, when the second device broadcasts two uplink signals of the retransmission ranging signal with different carrier frequencies, the two uplink signals 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 also retransmitted by the satellite transponder into two downlink signals with the same carrier frequency, forming two retransmission ranging signals and obtaining two retransmission ranging values.

[0179] The signal structure and the obtained pseudo-range ranging value and retransmission ranging value described above can still be calculated to obtain the clock difference between the first device and the second device using the method proposed in the present application, and specific calculation descriptions will not be repeated.

[0180] In summary, the high-precision time synchronization system and method provided by the embodiments of the present application creatively integrates the pseudo-range measurement signal and the retransmission measurement signal, and uses the relationship between the carrier frequencies to obtain high-precision satellite-ground time synchronization performance. The high-precision time synchronization system and method provided by the embodiments of the present application have the following characteristics:

[0181] 1. Compared with the two-way pseudo-range measurement method, the present application completely overcomes the influence of the atmospheric time delay, including the tropospheric time delay and the ionospheric time delay, thereby achieving higher satellite-ground time synchronization accuracy, which can reach sub-nanosecond level.

[0182] 2. Compared with the two-way pseudo-range measurement method, the present application does not require satellite-ground coarse synchronization, thereby reducing the system requirements and bringing convenience in operation.

[0183] 3. The present application completely overcomes the influence of the ionospheric time delay, and no longer depends on the ionospheric data provided by the third party such as the IGS organization, so that the present system has the characteristics of complete independence and safety and reliability.

[0184] 4. For the satellite, compared with the existing two-way pseudo-range measurement method, the satellite in the embodiments of the present application does not need a pseudo-range measurement device, so that the satellite load complexity and the satellite cost can be reduced.

[0185] 5. The present application has high flexibility. When the user needs time synchronization, the time synchronization is realized by the self-transmitting and self-receiving signals mastered by the user, and the present application has the flexible advantage of being used anytime and anywhere.

[0186] 6. Because the user station only needs to receive a satellite signal, the user station can use a directional antenna to reduce the multipath effect, thereby achieving better ranging accuracy and better time synchronization accuracy.

[0187] 7. The present application not only overcomes the influence of the atmospheric time delay, but also overcomes the influence of the multipath effect, and overcomes the influence of the near-end and far-end environment sections between the satellite and the user station.

[0188] The above is only the preferred embodiment of the present application, and does not limit the patent scope of the present application. Any equivalent structure or equivalent flow transformation using the content of the specification and drawings of the present application, or direct or indirect application in other related technical fields, is also included in the patent protection scope of the present application.

Claims

1. A high precision time synchronization system, characterized by, The first device and the second device are connected in communication, and a computing device is 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 positive integers greater than or equal to 1; The pseudo-range ranging signals are broadcasted by the first device and received by the second device, or broadcasted 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 to form the downlink signal.

2. The high precision time synchronization system of claim 1, wherein, The carrier frequency of the m-way pseudo-range measurement signal and the carrier frequency of the h-way retransmission measurement signal satisfy a preset carrier frequency relationship shown in formula (f1): In the formula, V represents a real constant value, V=1e-12; m represents the number of pseudorange ranging signals; i represents the number of pseudorange ranging signals; h represents the number of relay ranging signals; j represents the number of relay ranging signals; f uj (n) represents the carrier frequency of the uplink signal of the relay ranging signal numbered j at the nth moment, unit: hertz; f dj (n) denotes the carrier frequency of the downlink signal of the jth forwarding ranging signal at the nth time, unit: hertz; f zi (n) denotes the carrier frequency of the pseudo-range measurement signal numbered i at the n-th moment, unit: hertz.

3. The high-precision time synchronization system according to claim 1, wherein The first device comprises a first time-frequency device, a forwarder and a pseudo-range generating device, and the second device comprises a second time-frequency device, a forwarding ranging device and a second pseudo-range ranging device; The first time-frequency device is configured to provide time-frequency signals to the forwarder and the pseudo-range generating device; The forwarder is configured 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 pseudo-range generating device is connected in communication with the forwarder, and is configured to generate and broadcast the pseudo-range ranging signal; The second time-frequency device is configured to provide time-frequency signals to the forwarding ranging device and the second pseudo-range ranging device; The second pseudo-range ranging device is configured to receive the pseudo-range ranging signal and process to obtain a pseudo-range ranging value; The forwarding ranging device is configured to generate and broadcast the uplink signal, receive the downlink signal, and determine a forwarding ranging value; Wherein, the first time-frequency device, the forwarder and the pseudo-range generating device are integrated or separately arranged, and / or the second time-frequency device, the forwarding ranging device and the second pseudo-range ranging device are integrated or separately arranged; Alternatively, The first device comprises a first time-frequency device, a forwarder and a first pseudo-range ranging device, and the second device comprises a second time-frequency device and a forwarding ranging device; The first time-frequency device is configured to provide time-frequency signals to the forwarder and the first pseudo-range ranging device; The forwarder is configured 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 pseudo-range ranging device is connected in communication with the forwarder, and is configured to receive and measure the pseudo-range ranging signal; The second time-frequency device is configured to provide time-frequency signals to the forwarding ranging device; The forwarding ranging device is configured to generate and broadcast the uplink signal, receive the downlink signal, and determine a forwarding ranging value, wherein part of the uplink signal broadcasted by the forwarding ranging device serves as the pseudo-range ranging signal; The first time-frequency device, the repeater, and the first pseudorange ranging device are integrated or separately arranged, and / or the second time-frequency device and the repeater ranging device are integrated or separately arranged.

4. The high precision time synchronization system of claim 3, wherein, The second pseudorange ranging device and the repeater ranging device are zero baseline arranged. The first pseudorange ranging device or the pseudorange generating device is zero baseline arranged with the repeater.

5. The high precision time synchronization system of claim 3, wherein, The first device uses at least one first time-frequency device, and the second device uses at least one second time-frequency device.

6. The high precision time synchronization system of claim 1, wherein, The computing device is communicatively connected with the first device and the second device respectively, receives the pseudorange ranging value and the repeater ranging value, determines the space distance between the first device and the second device based on the repeater ranging value and / or the pseudorange ranging value, and determines the clock difference between the first device and the second device based on the pseudorange ranging value, the repeater ranging value, and the preset carrier frequency relationship; wherein, when the clock difference between the first device and the second device is determined, the sum of the number of the repeater ranging value and the pseudorange ranging value is greater than or equal to 2.

7. A method of determining a pseudorange value, the method comprising: The method is applied to the high-precision time synchronization system of any one of claims 1-6, and the method is executed by the first device, and the method comprises: receiving m pieces of pseudorange ranging signals broadcast by the second device; synchronously measuring each of the pseudorange ranging signals to obtain m pieces of pseudorange ranging values; wherein, m is a positive integer.

8. A method of determining a range value, characterized by The method is applied to the high-precision time synchronization system of any one of claims 1-6, and the method is executed by the second device, and the method comprises: when the pseudorange ranging signal is broadcast by the first device, broadcasting at least one uplink signal to the first device; obtaining at least one downlink signal which is 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 pieces of repeater ranging signals; obtaining m pieces of pseudorange ranging signals broadcast by the first device; synchronously measuring each of the pseudorange ranging signals and each of the repeater ranging signals to obtain m pieces of pseudorange ranging values and h pieces of repeater ranging values; or, 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 which is 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 pieces of repeater ranging signals; synchronously measuring each of the repeater ranging signals to obtain h pieces of repeater ranging values; wherein, m+h≥2, and m and h are positive integers.

9. A high precision time synchronization method, characterized by, The method is applied to the high-precision time synchronization system of any one of claims 1-6, and the method is executed by the computing device, and the method comprises: when the pseudorange ranging signal is broadcast by the second device and received by the first device, obtaining m pieces of pseudorange ranging values measured by the first device based on the communication with the first device, and obtaining h pieces of repeater ranging values measured by the second device based on the communication with the second device; When the pseudo-range measurement signal is broadcast by the first device and received by the second device, m pseudo-range measurement values and h retransmission range values measured by the second device are obtained based on the communication with the second device; wherein the preset carrier frequency relationship is satisfied between the carrier frequencies corresponding to the h retransmission range values and the carrier frequencies corresponding to the m pseudo-range measurement values; m+h≥2, and m and h are positive integers; Each of the pseudo-range measurement values is represented by a pseudo-range measurement expression, and each of the retransmission range values is represented by a retransmission range expression; The clock difference between the first device and the second device is determined based on the m pseudo-range measurement values represented by the pseudo-range measurement expression, the h retransmission range values represented by the retransmission range expression, and the preset carrier frequency relationship.

10. The high precision time synchronization method of claim 9, wherein, The m pseudo-range measurement values are represented by a pseudo-range measurement expression, and the h retransmission range values are represented by a retransmission range expression, respectively. The pseudorange measurement value numbered i is represented using a pseudorange measurement expression shown in Equation (3) below: p 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 forward ranging value numbered j is characterized using a forward ranging expression shown in Equation (4) as follows: 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; wherein: p zi (n) represents the pseudo-range measurement value of the i-th at the n-th moment, unit: meter; R true,zi (n) represents the real space distance of the i-th pseudo-range measurement signal at the n-th moment, unit: meter; I zi (n) represents the ionospheric delay of the i-th pseudo-range measurement signal at the n-th moment, unit: meter; T duiliu,zi (n) represents the tropospheric delay of the i-th pseudo-range measurement signal at the n-th moment, unit: meter; c represents the speed of light, unit: meter / second; δt s (n) represents the clock difference of the first device relative to the system time at the n-th moment, unit: second; δt z (n) represents the clock difference of the second device relative to the system time at the n-th moment, unit: second; sagnac zz (n) represents the Sagnac effect delay of the pseudo-range measurement signal at the n-th moment, unit: meter; X zi (n) represents the i-th pseudo-range measurement signal hardware device delay at the n-th moment, unit: meter, which includes the transmission delay of the i-th pseudo-range measurement signal, the receiving delay of the i-th pseudo-range measurement signal; L j (n) represents the real space distance of the uplink signal of the numbered j forward ranging signal at the nth moment, unit: meter; R true,uj (n) represents the real space distance of the uplink signal of the numbered j forward ranging signal at the nth moment, unit: meter; R true,dj (n) represents the real space distance of the downlink signal of the numbered j forward ranging signal at the nth moment, unit: meter; I uj (n) represents the ionospheric delay of the uplink signal of the numbered j forward ranging signal at the nth moment, unit: meter; I dj (n) represents the ionospheric delay of the downlink signal of the numbered j forward ranging signal at the nth moment, unit: meter; T duiliu,uj (n) represents the tropospheric delay of the uplink signal of the numbered j forward ranging signal at the nth moment, unit: meter; T duiliu,dj (n) represents the tropospheric delay of the downlink signal of the numbered j forward ranging signal at the nth moment, unit: meter; Y j (n) represents the hardware device delay of the numbered j forward ranging signal at the nth moment, unit: meter, the hardware device delay of the numbered j forward ranging signal includes the transmission delay of the uplink signal of the numbered j forward ranging signal, the forwarding delay of the downlink signal of the numbered j forward ranging signal, the receiving delay of the downlink signal of the numbered j forward ranging signal.

11. The high precision time synchronization method of claim 9, wherein, The clock difference between the first device and the second device is determined based on the m pseudo-range measurement values represented by the pseudo-range measurement expression, the h retransmission range values represented by the retransmission range expression, and the preset carrier frequency relationship. The m pseudo-range measurement values represented by the pseudo-range measurement expression are corrected to obtain m corrected pseudo-range measurement values, and the m corrected pseudo-range measurement values are averaged to obtain a corrected average pseudo-range measurement value; The h retransmission range values represented by the retransmission range expression are corrected to obtain h corrected retransmission range values, and the h corrected retransmission range values are averaged to obtain a corrected average retransmission range value; The clock difference between the first device and the second device is determined based on the m pseudo-range measurement values represented by the pseudo-range measurement expression, the h retransmission range values represented by the retransmission range expression, and the preset carrier frequency relationship.

12. The high precision time synchronization method of claim 11, wherein, The m pseudo-range measurement values represented by the pseudo-range measurement expression are corrected to obtain m corrected pseudo-range measurement values, including: 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 the formula (3’): p 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; The m corrected pseudo-range measurement values are averaged to obtain a corrected average pseudo-range measurement value, including: The m corrected pseudo-range measurements are averaged to obtain a corrected average pseudo-range measurement as shown in equation (5): The h retransmission range values represented by the retransmission range expression are corrected to obtain h corrected retransmission range values, including: The retransmission range value numbered j shown in the following formula (4) is transformed to obtain the corrected retransmission range value numbered j shown in the 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) ; Wherein, j=1, 2, …, h; The h corrected retransmission range values are averaged to obtain a corrected average retransmission range value, including: The h modified round-trip ranging values are averaged to obtain a modified average round-trip ranging value as shown in equation (6): wherein: p mean (n) represents the corrected average pseudo-range measurement value at the nth moment, unit: meter; p zi,a (n) represents the corrected pseudo-range measurement value of the i-th at the nth moment, unit: meter; p zi (n) represents the pseudo-range measurement value of the i-th at the nth moment, unit: meter; R true,zi (n) represents the real space distance of the i-th pseudo-range measurement signal at the nth moment, unit: meter; I zi (n) represents the ionospheric delay of the i-th pseudo-range measurement signal at the nth moment, unit: meter; T duiliu,zi (n) represents the tropospheric delay of the i-th pseudo-range measurement signal at the nth moment, unit: meter; c represents the speed of light, unit: meter / second; δt s (n) represents the clock difference of the first device relative to the system time at the nth moment, unit: second; δt z (n) represents the clock difference of the second device relative to the system time at the nth moment, unit: second; sagnac zz (n) represents the Sagnac effect delay of the pseudo-range measurement signal at the nth moment, unit: meter; X zi (n) represents the i-th pseudo-range measurement signal hardware device delay at the nth moment, unit: meter, which includes the transmission delay of the i-th pseudo-range measurement signal, the reception delay of the i-th pseudo-range measurement signal; L mean (n) represents the corrected average round trip ranging value at the nth moment, unit: meter; L j,a (n) represents the corrected round trip ranging value of the jth at the nth moment, unit: meter; L j (n) represents the round trip ranging value of the jth at the nth moment, unit: meter; R true,uj (n) represents the real space distance of the uplink signal of the jth round trip ranging signal at the nth moment, unit: meter; R true,dj (n) represents the real space distance of the downlink signal of the jth round trip ranging signal at the nth moment, unit: meter; I uj (n) represents the ionospheric delay of the uplink signal of the jth round trip ranging signal at the nth moment, unit: meter; I dj (n) represents the ionospheric delay of the downlink signal of the jth round trip ranging signal at the nth moment, unit: meter; T duiliu,uj (n) represents the tropospheric delay of the uplink signal of the jth round trip ranging signal at the nth moment, unit: meter; T duiliu,dj (n) represents the tropospheric delay of the downlink signal of the jth round trip ranging signal at the nth moment, unit: meter; Y j (n) represents the hardware device delay of the jth round trip ranging signal at the nth moment, unit: meter, the hardware device delay of the jth round trip ranging signal includes the transmission delay of the uplink signal of the jth round trip ranging signal, the forwarding delay of the downlink signal of the jth round trip ranging signal, the receiving delay of the downlink signal of the jth round trip ranging signal.

13. The high precision time synchronization method of claim 12, wherein, The clock difference between the first device and the second device is determined based on the m pseudo-range measurement values represented by the pseudo-range measurement expression, the h retransmission range values represented by the retransmission range expression, and the preset carrier frequency relationship. The clock difference between the first device and the second device is determined according to the modified average pseudo-range measurement value, the modified average retransmission range measurement value and the preset carrier frequency relationship based on a zero baseline setting relationship between the retransmission ranging device and the second pseudo-range ranging device or a zero baseline setting relationship between the retransmitter and the first pseudo-range ranging device. ± (δt z (n)-δt s (n)) c = (ρ mean (n)-L mean (n)) / c(7); wherein: ± (δt z (n) - δt s (n) c denotes the clock difference between the first device and the second device calculated according to the corrected average pseudo-range measurement value and the corrected average retransmission measurement value, in seconds; c denotes the speed of light, in meters / second; p mean (n) denotes the corrected average pseudo-range measurement value at the n-th moment, in meters; L mean (n) denotes the corrected average retransmission measurement value at the n-th moment, in meters.

14. The high precision time synchronization method of claim 9, wherein, After the clock difference between the first device and the second device is determined, the method further comprises: communicating with the first device or the second device, transmitting the determined clock difference between the first device and the second device to the first device or the second device, and realizing time synchronization between the first device and the second device; When the clock difference of the first device relative to the system time is known, the second device determines its 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 clock difference relative to the system time according to the clock difference between the first device and the second device.

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