Ionospheric delay monitoring and time synchronization system, method and application

Abstract

The present application discloses an ionospheric delay monitoring and time synchronization system, method, and application, and the present invention relates to the field of space technology. The method includes: a second device broadcasts at least one uplink signal to a first device, and the first device forwards at least two downlink signals based on the at least one uplink signal; the second device obtains at least one pseudorange ranging signal broadcast by the first device, and synchronously measures to obtain at least one pseudorange ranging value and at least two forwarded ranging values; the pseudorange ranging value is represented using a pseudorange ranging expression, and the forwarded ranging value is represented using a forwarded ranging expression; based on the pseudorange ranging value represented by the pseudorange ranging expression and the forwarded ranging value represented by the forwarded ranging expression, the total number of ionospheric electrons on the ranging signal path between the first and second devices is determined, the clock difference between the first and second devices is determined, and the spatial distance value between the first and second devices is determined.

Description

[0001] Cross-references

[0002] This disclosure claims the application number 202411068715.0 filed on August 6, 2024, entitled "A IONOSPHERIC The priority of the Chinese patent application for "Time Delay Monitoring and Time Synchronization System and Method", the entire content of the Chinese patent application Incorporated herein by reference in its entirety. Technical Field

[0003] The present application relates to the field of space technology, and in particular to an ionospheric delay monitoring and time synchronization system, method and application. Background Art

[0004] The GNSS (Global Navigation Satellite System) is the current mainstream satellite navigation system. Internationally, there are China's Beidou system, the United States' GPS system, Europe's Galileo system, and Russia's Glonass system. Satellite navigation systems are extremely large and complex, involving three major components: operations and control, satellites, and users. These components involve ground-to-space time synchronization between the operations and control stations and satellites, time synchronization between operations and control stations, satellite orbit determination technology, and user positioning and timing applications. The operations and control component monitors the satellite's atomic clock time to ensure accurate and reliable satellite time, determines its orbit, and provides ephemeris for users. The satellite component directly provides services to users, broadcasting three pseudorange signals containing satellite ephemeris messages. Users measure the pseudorange signals to obtain pseudorange values, and use these values ​​and satellite ephemeris to achieve user positioning and timing.

[0005] The operations and control section of a satellite navigation system monitors satellite orbits and satellite time to ensure the long-term reliability of satellite operation. Synchronizing navigation satellite time with the operations and control system is crucial. In addition to navigation satellites, aerospace systems such as communications satellites and remote sensing satellites also require high-precision satellite-to-ground time synchronization. The key to the positioning accuracy of a navigation satellite system lies in determining the clock error of the onboard atomic clock and its variations. Currently, there are several main methods for determining satellite clock errors:

[0006] 1. One-way ranging: This method uses the measured pseudorange value and the distance between the satellite and the synchronous station obtained from orbital positioning. The satellite clock error is obtained by subtracting the distance value from the pseudorange value. This method requires the exact distance between the satellite and the ground, the ionospheric delay, the tropospheric delay, and other parameters.

[0007] 2. GPS inverse positioning. This method works as follows: Four time-synchronized ground stations simultaneously receive pseudorange signals from a satellite, obtaining four pseudorange observations. The satellite's position coordinates and the clock error between the satellite and the ground station are then calculated using the GPS positioning equation. The accuracy of this method is highly dependent on the geometric distribution of the stations and the accuracy of inter-station time synchronization. It also requires overcoming tropospheric signal delay.

[0008] 3. Two-way pseudorange measurement. The principle of pseudorange two-way time synchronization is based on the fact that the signal propagation paths between the satellite and the ground are identical, with the same spatial distance and tropospheric delay, but different ionospheric delays. Therefore, the clock error is the difference in the measured pseudoranges divided by the speed of light, c, or the difference in the corresponding time scales detected by the satellite and the ground. The process involves both the satellite and the ground station transmitting signals at their own independent clock times under the control of local clocks. Upon receiving each other's signals, the satellite and ground station receivers perform pseudorange measurements with their local clocks. By comparing these two pseudorange measurements, the clock error between the satellite and the ground station can be calculated, which includes the residual ionospheric delay.

[0009] All of the above methods require satellite or ground receivers to receive and measure signals. When signals are transmitted between the satellite and the ground, the receiver is affected by the ionosphere and troposphere of the atmosphere at the far end, and the multipath effect and electromagnetic environment at the near end. The far and near ends are collectively referred to as environmental segment influences. Among them, the atmospheric tropospheric delay has the same delay for RF signals of different carrier frequencies and can be estimated using a model, while the atmospheric ionospheric delay varies with the carrier frequency. It is a very common error factor, comprehensive and fundamental, and a global problem. In addition to the environmental segment influence, the above methods have the disadvantages of a large number of observation devices, time synchronization errors affected by satellite orbit determination accuracy and user coordinate accuracy, and poor time synchronization accuracy.

[0010] The above content is only used to assist in understanding the technical solution of this application and does not constitute an admission that the above content is prior art. Summary of the Invention

[0011] The present application combines the characteristics of satellite transponders and spread spectrum signals, and at the same time utilizes the zero baseline relationship between the transponder ranging device and the second pseudo-range ranging device or the zero baseline relationship between the transponder and the first pseudo-range ranging device, and utilizes the clock-free characteristic of the transponder ranging signal and the clock-bias characteristic of the pseudo-range ranging signal, and creatively proposes a system and method that can obtain both the total electron count in the ionosphere and the high-precision clock error, aiming to solve the problem in the prior art that time synchronization is affected by ionospheric delay errors.

[0012] To achieve the above objectives, the present application provides an ionospheric delay monitoring and time synchronization system, comprising a first device and a second device in communication connection, and a computing device in communication connection with the first device and the second device, respectively. m pseudorange ranging signals and h forwarding ranging signals are provided between the first device and the second device, and the pseudorange ranging signals and the forwarding ranging signals have at least three different carrier frequencies. m + h ≥ 3, and m and h are both positive integers greater than or equal to 1. The pseudorange ranging signals and the forwarding ranging signals have at least three different carrier frequencies. The pseudorange ranging 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 forwarding ranging signals are composed of an uplink signal and a downlink signal. The second device broadcasts the uplink signal, the first device receives the uplink signal and forwards it to form the downlink signal, and the second device receives the downlink signal.

[0013] In addition, to achieve the above-mentioned purpose, the present application also provides a pseudorange ranging value determination method, which is applied to the ionospheric delay monitoring and time synchronization system described in any embodiment of the present application. The method is executed by a first device, and the method includes: receiving m pseudorange ranging signals broadcast by a second device; synchronously measuring each pseudorange ranging signal to obtain m pseudorange ranging values, where m is a positive integer.

[0014] In addition, to achieve the above-mentioned purpose, the present application also provides a ranging value determination method, which is applied to the ionospheric delay monitoring and time synchronization system described in any embodiment of the present application, and the method is performed by a second device, and the method includes: 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 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-path forwarding ranging signals; obtaining m-path pseudorange ranging signals broadcast by the first device. ; synchronously measuring each of the pseudorange ranging signals and each of the forwarding ranging signals to obtain m pseudorange ranging values ​​and h forwarding ranging values; when the pseudorange ranging signal is broadcast by the second device and received by the first device, broadcasting at least one uplink signal to the first device; obtaining at least one downlink signal forwarded by the first device based on the at least one uplink signal, wherein the at least one uplink signal and the at least one downlink signal constitute h forwarding ranging signals; synchronously measuring each of the forwarding ranging signals to obtain h forwarding ranging values, wherein m+h≥3, and m and h are both positive integers.

[0015] In addition, to achieve the above-mentioned purpose, the present application also provides an ionospheric delay monitoring and time synchronization method, which is applied to the ionospheric delay monitoring and time synchronization system described in any embodiment of the present application, and the method is executed by a computing device. The method includes: when the pseudorange ranging signal is broadcast by the second device and received by the first device, obtaining m pseudorange ranging values ​​measured by the first device based on the communication result with the first device, and obtaining h forwarding ranging values ​​measured by the second device based on the communication result with the second device; when the pseudorange ranging signal is broadcast by the first device and received by the second device, obtaining h forwarding ranging values ​​and m pseudorange ranging values ​​measured by the second device based on the communication result with the second device; wherein m+h≥3, and m and h are both positive integers; representing each pseudorange ranging value using a pseudorange ranging expression and representing each forwarding ranging value using a forwarding ranging expression; and determining the total number of ionospheric electrons on the ranging signal path between the first device and the second device and the clock difference between the first device and the second device based on the m pseudorange ranging values ​​and the h forwarding ranging values.

[0016] In addition, to achieve the above-mentioned purpose, the present application also provides a method for determining the satellite-to-ground space distance, which is applied to the ionospheric delay monitoring and time synchronization system described in any embodiment of the present application, and the method is executed by a computing device, and the method includes: based on the total number of ionospheric electrons on the ranging signal path between the first device and the second device, a preset ionospheric delay coefficient, the carrier frequency of at least one forwarded ranging signal, and the carrier frequency of at least one pseudorange ranging signal, respectively determining the ionospheric delay of the at least one forwarded ranging signal and the ionospheric delay of the at least one pseudorange ranging signal; wherein the total number of ionospheric electrons is determined according to the ionospheric delay monitoring and time synchronization method described in any embodiment of the present application; based on the ionospheric delay of at least one forwarded ranging signal and the corresponding forwarded ranging signal, the ionospheric delay of the at least one pseudorange ranging signal is determined. The method further comprises determining the sum of the satellite-to-ground space distance and the tropospheric delay between the first device and the second device based on the forwarded ranging value of the ranging signal; or determining the sum of the satellite-to-ground space distance and the tropospheric delay between the first device and the second device based on the ionospheric delay of at least one pseudorange ranging signal, the pseudorange ranging value of the corresponding pseudorange ranging signal, and the determined clock difference between the first device and the second device; determining the tropospheric delay on the ranging signal path between the first device and the second device based on a preset tropospheric model; and determining the satellite-to-ground space distance between the first device and the second device based on the sum of the satellite-to-ground space distance and the tropospheric delay between the first device and the second device and the tropospheric delay on the ranging signal path between the first device and the second device.

[0017] In addition, to achieve the above-mentioned purpose, the present application also provides a satellite navigation system, including: the ionospheric delay monitoring and time synchronization system described in any embodiment of the present application, wherein the first device is a satellite, the second device is a user station, and the number of the satellites is greater than or equal to 2; multiple third devices are all communicatively connected to the satellite; wherein the user station obtains the orbital parameters of the corresponding satellite based on the data transmission results with each satellite, and determines the coordinate information of the user station based on the orbital parameters of each satellite and the satellite-to-ground space distance between the user station and the satellite; part of the third devices constitutes a satellite orbit determination system, which is used to perform orbit monitoring and processing on the satellite to obtain satellite orbit parameters; part of the third devices constitutes a satellite-to-ground time synchronization system, which is used to perform time monitoring on each of the satellites.

[0018] In addition, to achieve the above-mentioned purpose, the present application also provides an inter-station time synchronization system, including: the satellite navigation system described in any embodiment of the present application; wherein, when there are at least two user stations, at least two of the user stations achieve time synchronization with each other through communication and data exchange.

[0019] In addition, to achieve the above-mentioned purpose, an inter-station time synchronization system includes: the ionospheric delay monitoring and time synchronization system described in any embodiment of the present application; wherein, when there are at least two second devices or the first devices, at least two of the second devices or the first devices achieve time synchronization with each other through communication and data exchange.

[0020] In addition, to achieve the above-mentioned purpose, a satellite positioning method is applied to the satellite navigation system described in any embodiment of the present application, and the method is executed by a user station, and the method includes: obtaining the orbital parameters of each satellite; determining the coordinate information of the corresponding satellite based on the orbital parameters; determining the star-to-earth space distance between the user station and each satellite according to the star-to-earth space distance determination method described in any embodiment of the present application; and determining the coordinate information of the user station based on the orbital parameters of each satellite and the star-to-earth space distance between the user station and each satellite.

[0021] In the ionospheric delay monitoring and time synchronization system provided herein, a second device can not only determine the clock difference between the first and second devices, but also the ionospheric delay along the ranging signal path between the first and second devices, the satellite-to-ground distance, and other parameters. When applied to satellite navigation, this time synchronization system overcomes the influence of ionospheric and tropospheric delays compared to existing technologies, improving the accuracy of the determined clock difference and navigation precision while also offering the advantages of strong real-time performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1Schematic diagram of the structure of an ionospheric delay monitoring and time synchronization system according to one embodiment of the present application;

[0023] Figure 2 is a structural block diagram of a satellite and a user station according to one embodiment of the present application;

[0024] Figures 3 to 10 Schematic diagram of the composition of the forwarded ranging signal and the pseudo-ranging signal between the satellite and the user station according to other embodiments of the present application;

[0025] Figure 11 Flowchart of a method for ionospheric delay monitoring and time synchronization according to one embodiment of the present application;

[0026] Figure 12 This is a flow chart of a method for determining the satellite-to-earth space distance according to one embodiment of the present application;

[0027] Figure 13 A schematic structural diagram of a satellite navigation system according to an embodiment of the present application;

[0028] Figure 14 This is a flowchart of a method for inter-station time synchronization according to an embodiment of the present application;

[0029] Figure 15 This is a flowchart of a satellite positioning method according to one embodiment of the present application;

[0030] Figures 16 to 18 A schematic structural diagram of the ionospheric delay monitoring and time synchronization system provided in other embodiments of the present application.

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

[0032] It should be understood that the specific embodiments described herein are only used to explain the present application and are not intended to limit the present application.

[0033] The following first provides a unified explanation of the meanings of the various parameters involved in the embodiments of this application:

[0034] ρ z,1,a (n),ρ z,2,a (n) represents the first corrected pseudorange measurement value and the second corrected pseudorange measurement value at the nth moment, in meters; ρ z,1 (n),ρ z,2 (n) represents the first pseudorange measurement value and the second pseudorange measurement value at the nth moment, in meters; R true,z,1 (n), R true,z,2(n) represents the real space distance traveled by the first pseudo-range ranging signal and the second pseudo-range ranging signal at the nth moment, in meters; z,1 (n), I z,2 (n) represents the ionospheric delay of the first pseudorange ranging signal and the second pseudorange ranging signal at time n, in meters; T duiliu,z,1 (n), T duiliu,z,2 (n) represents the tropospheric delay of the first pseudorange ranging signal and the second pseudorange ranging signal at time n, in meters; X z,1 (n), X z,2 (n) represents the hardware delay of the first pseudo-range measurement signal and the second pseudo-range measurement signal at the nth moment, in meters. The hardware delay of the pseudo-range measurement signal includes the transmission delay of the first pseudo-range measurement signal and the second pseudo-range measurement signal, and the reception delay of the first pseudo-range measurement signal and the second pseudo-range measurement signal; c represents the speed of light, in meters per second; δt s (n) represents the clock difference between the first device and the system time at time n, in seconds; δt z (n) represents the clock difference between the second device and the system time at time n, in seconds; sagnac zz (n) represents the Sagnac effect delay of the pseudorange measurement signal at time n, in meters;

[0035] L z,1,a (n), L z,2,a (n) represents the first corrected forward ranging value and the second corrected forward ranging value at the nth moment, respectively, in meters; L z,1 (n), L z,2 (n) represents the first forwarding ranging value and the second forwarding ranging value at the nth moment, in meters; R true,zu,1 (n), R true,zu,2 (n) represents the real spatial distance traveled by the uplink signals of the first forwarded ranging signal and the second forwarded ranging signal at time n, in meters; R true,zd,1 (n), R true,zd,2 (n) represents the real spatial distance traveled by the downlink signals of the first forwarding ranging signal and the second forwarding ranging signal at time n, in meters; zu,1 (n), I zu,1 (n) represents the ionospheric delay of the uplink signal of the first forwarding ranging signal and the second forwarding ranging signal at the nth moment, in meters; I zd,1 (n), I zd,1 (n) represents the ionospheric delay of the downlink signal of the first forwarding ranging signal and the second forwarding ranging signal at time n, in meters; T duiliu,zu,1 (n), T duiliu,zu,2(n) represents the tropospheric delay of the uplink signals of the first forwarded ranging signal and the second forwarded ranging signal at time n, in meters; T duiliu,zd,1 (n), T duiliu,zd,2 (n) represents the tropospheric delay of the downlink signal of the first forwarding ranging signal and the second forwarding ranging signal at time n, in meters; Y z,1 (n), Y z,2 (n) represents the hardware device delay of the first forwarding ranging signal and the second forwarding ranging signal at time n, respectively, in meters. The hardware device delay of the forwarding ranging signal includes the transmission delay of the uplink signal of the first forwarding ranging signal and the second forwarding ranging signal, the forwarding delay of the downlink signal of the first forwarding ranging signal and the second forwarding ranging signal, and the reception delay of the downlink signal of the first forwarding ranging signal and the second forwarding ranging signal;

[0036] dL m2 (n) represents the forwarding ranging difference at the nth moment, in meters;

[0037] Q ion represents the ionospheric delay coefficient, TEC(n) represents the total number of ionospheric electrons on the ranging signal path between the first device and the second device at time n, in electrons / square meter; f z,1 (n), f z,2 (n) represents the carrier frequency of the first pseudo-range measurement signal and the second pseudo-range measurement signal at the nth moment, in Hertz; f zu,1 (n), f zu,2 (n) represents the carrier frequency of the uplink signal of the first forwarded ranging signal and the second forwarded ranging signal at the nth moment, in Hertz; f zd,1 (n), f zd,2 (n) represents the carrier frequency of the downlink signals of the first forwarded ranging signal and the second forwarded ranging signal at the nth moment, in Hertz.

[0038] Special note: Q ion The ionospheric delay coefficient is published by some international organizations. As people deepen their research on ionospheric delay, the ionospheric delay coefficient is becoming more and more accurate. The ionospheric delay coefficient used to be 40.28, 40.30, and is currently 40.309. There may be more accurate ionospheric delay coefficients in the future. This application does not specifically limit the ionospheric delay coefficient and takes the latest published value. In this embodiment, Q ion The value is 40.309.

[0039] This application organically integrates the forwarding ranging signal and the pseudo-ranging signal, and creatively proposes an ionospheric delay monitoring and time synchronization system and method that can obtain both the total number of ionospheric electrons and high-precision clock errors.

[0040] A satellite navigation system is proposed based on this ionospheric delay monitoring and time synchronization system and method. Compared to the existing Beidou satellite navigation system, this satellite navigation system's most significant feature is that it first obtains a high-precision user station clock error, then calculates the user station's three-dimensional coordinates using the spatial geometric distance between the user station and the satellite. Unlike the Beidou satellite navigation system, which requires only three-dimensional coordinates and user clock errors, the system requires only two satellites to provide high-precision timing and positioning services, offering low investment and excellent performance.

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

[0042] The ionospheric delay monitoring and time synchronization system provided in the present application includes a first device and a second device that are communicatively connected, and a computing device that is communicatively connected to the first device and the second device respectively.

[0043] The computing device may communicate with the first device and the second device respectively to obtain a pseudo-range measurement value and a forwarded ranging value.

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

[0045] When the second device broadcasts a pseudorange ranging signal, the first device receives the pseudorange ranging signal and measures to obtain a pseudorange ranging value. The second device autonomously transmits and receives a forwarding ranging signal to obtain a forwarding ranging value. At this time, the computing device communicates with the second device to obtain the forwarding ranging value, and communicates with the first device to obtain the pseudorange ranging value.

[0046] After the computing device obtains the pseudorange measurement value and the forwarding ranging value, it executes the method of the present application to calculate the total number of ionospheric electrons between the first device and the second device and the clock difference between the first device and the second device.

[0047] It is worth noting that in the embodiments of the present application, the computing device may be integrated into the first device; or integrated into the second device; or may be independent of the first device and the second device, that is, an independent device.

[0048] The core function of this application is that the sum of the number of ways of forwarding ranging signals and pseudo-ranging signals between the first device and the second device is greater than or equal to 3, and the corresponding pseudo-range ranging value and forwarding ranging value are obtained, the sum of which is greater than or equal to 3, and the total number of ionospheric electrons between the first device and the second device and the clock difference between the first device and the second device are calculated based on the pseudo-range ranging value and the forwarding ranging value.

[0049] Therefore, this application focuses on explaining the first device, the second device and the signal structure between the two, as well as the calculation method of the total ionospheric electron number and clock error, and the spatial distance calculation method.

[0050] The following first describes the ionospheric delay monitoring and time synchronization system, followed by an explanation of the satellite navigation system.

[0051] In the present application, there are pseudo-range measurement signals and forwarded ranging signals between the first device and the second device, the sum of the number of pseudo-range measurement signals and the number of forwarded ranging signals is greater than or equal to 3, and the pseudo-range measurement signals and the forwarded ranging signals have at least three different carrier frequencies;

[0052] The forwarded ranging signal is composed of an uplink signal and a downlink signal. The second device broadcasts the uplink signal, the first device receives the uplink signal and forwards it to form the downlink signal, and the second device receives the downlink signal. The pseudorange ranging signal is broadcast by the first device and received by the second device, or broadcast by the second device and received by the first device.

[0053] Among them, the pseudo-range ranging signal and the forwarding ranging signal are both spread spectrum signals.

[0054] As described above, in the embodiment of the present application, the pseudorange measurement signal may be broadcast by the first device and received by the second device, or may be broadcast by the second device and received by the first device.

[0055] When the pseudorange ranging signal is broadcast by the second device, the uplink signal broadcast by the forwarding ranging device in the second device can be used as the pseudorange ranging signal. After the uplink signal reaches the first device, it is split into multiple signals, one of which is used as the pseudorange ranging signal, and the remaining signals are forwarded by the repeater as signals; alternatively, the uplink signal broadcast by the forwarding ranging device in the second device is directly received by the first pseudorange ranging device of the satellite without being forwarded as a downlink signal by the repeater.

[0056] When the pseudorange ranging signal is broadcast by the first device and received by the second device, the forwarded ranging signal is automatically sent and received by the second device. Both the forwarded ranging signal and the pseudorange ranging signal are received and measured by the second device, and the pseudorange ranging value and the forwarded ranging value can be synchronously measured.

[0057] It should be noted that when the pseudorange ranging signal is broadcast by the second device and received by the first device, the forwarded ranging signal is spontaneously transmitted and received by the second device, and the forwarded ranging signal and the pseudorange ranging signal are received and measured by the second device and measured by the first device, respectively. Strictly speaking, synchronous measurement cannot be achieved, and the first device and the second device need to have rough time synchronization conditions (the same is true for the two-way pseudorange measurement method. The satellite and the ground station each measure the pseudorange ranging signal sent by the other party, and the satellite and the ground station need to have rough time synchronization requirements). At this time, the pseudorange value measured by the first device and the forwarded ranging value obtained by the second measuring device can be regarded as synchronous measurement and calculated using the method of the present application.

[0058] Furthermore, two different types of systems are generated depending on whether the pseudorange measurement signal is measured by the second device or the first device. These two different types of systems differ in terms of the pseudorange measurement signal transmission direction and the pseudorange measurement device. Their signal structure, system composition, and processing methods are the same. Therefore, for the sake of brevity and clarity, the following description focuses solely on the case where the first device broadcasts the pseudorange measurement signal.

[0059] When the first device broadcasts a pseudorange ranging signal, the number of pseudorange ranging signal paths is set to m, the number of ranging signal forwarding paths is set to h, and m+h≥3. There are two simplest systems that meet this condition, which are called the first simplest system and the second simplest system.

[0060] The first simplest system is that the first device broadcasts two pseudo-range ranging signals to the second device, and there is a forwarding ranging signal between the first device and the second device, wherein the downlink signal of the forwarding ranging signal can be carrier frequency multiplexed or not with any pseudo-range ranging signal; the second simplest system is that the first device broadcasts one pseudo-range ranging signal to the second device, and there are two forwarding ranging signals between the first device and the second device, wherein the carrier frequency of the pseudo-range ranging signal can be multiplexed or not with the carrier frequency of any downlink signal of the two forwarding ranging signals, and even the carrier frequency of the two downlink signals of the two forwarding ranging signals can be multiplexed or not with the carrier frequency of the pseudo-range ranging signal.

[0061] The two simplest systems mentioned above, the first simplest system obtains two pseudorange measurement values, and the second simplest system obtains two forwarding ranging values. The characteristics of the total number of ionospheric electrons between the first device and the second device can be obtained by using the two pseudorange measurement values ​​or the two forwarding ranging values. Then, the clock difference between the first device and the second device, the satellite-to-ground space distance, etc. can be obtained using the method provided in this application.

[0062] The first simplest system adds one forward ranging signal, and the second system adds one pseudorange ranging signal. These two simplest systems then become systems with the same two pseudorange ranging signals and two forward ranging signals. When the two simplest systems have two pseudorange ranging signals and two forward ranging signals, the two systems are identical, and the corresponding calculation methods are also the same. Furthermore, when there are more pseudorange ranging signals and forward ranging signals, they become one system.

[0063] In addition, in the first simplest system, the process of calculating the total number of ionospheric electrons using two pseudorange ranging values ​​has been introduced in the relevant technology, and the process of calculating the clock error and the satellite-to-ground space distance after obtaining the total number of ionospheric electrons is similar to the process of the second simplest system. Therefore, in order to explain the method provided by this application more clearly and generally, this application will not go into details about the process of calculating the total number of ionospheric electrons for the first simplest system, and will only use the second simplest system as an example for exemplary explanation. The carrier frequencies of the signals of the second simplest system are different from each other, and two forwarding ranging values ​​and one pseudorange ranging value are obtained by synchronous measurement to illustrate the specific implementation of the method of this application.

[0064] At this time, m=1, h=2.

[0065] Due to the preciousness of radio spectrum resources, when m=1, h=2, or m=2, h=1, time synchronization can be achieved with minimal carrier frequency resources, which is cost-effective. Therefore, this case is used for illustration.

[0066] For convenience of explanation, the uplink signals of the two-way forwarding ranging signal of the second simplest system are respectively referred to as the first uplink signal and the second uplink signal, the downlink signals of the two-way forwarding ranging signal are respectively referred to as the first downlink signal and the second downlink signal, and the pseudorange ranging signal is referred to as the first pseudorange ranging signal. An example in which the computing device is integrated into the second device is used for illustrative explanation. Because the computing device is integrated into the second device, that is, the computing device is part of the second device, therefore, unless otherwise specified, the functions implemented by the computing device are described as part of the functions of the second device for subsequent explanation.

[0067] Figure 1 This is a schematic diagram of the structure of an ionospheric delay monitoring and time synchronization system according to an embodiment of the present application. When the pseudo-range ranging signal is broadcast by the first device, the system Figure 1 As shown, the system includes a first device 100 and a second device 200 that are communicatively connected;

[0068] The first device 100 forwards the first downlink signal and the second downlink signal to the second device 200 based on the received first uplink signal and the second uplink signal, and broadcasts a first pseudorange ranging signal to the second device 200; wherein the first uplink signal and the first downlink signal constitute a first forward ranging signal, and the second uplink signal and the second downlink signal constitute a second forward ranging signal; the second device 200 is configured to broadcast the first uplink signal and the second uplink signal to the first device 100, receive the first pseudorange ranging signal and the first downlink signal and the second downlink signal, and synchronously measure the first forward ranging signal, the second forward ranging signal, and the first pseudorange ranging signal to obtain a first forward ranging value, a second forward ranging value, and a first pseudorange ranging value respectively; and determine a total ionospheric electron number on a ranging signal path between the first device 100 and the second device 200 and a clock difference between the first device 100 and the second device 200 based on the first pseudorange ranging value, the first forward ranging value, and the second forward ranging value.

[0069] Figure 1 The fu and fd shown are satellite-to-ground communication links added between the user station and the satellite, which can be remote control and telemetry signals.

[0070] In an embodiment of the present application, the first device 100 may be, for example, a satellite, and the second device 200 may be, for example, a user station. When the computing device is integrated into the user station, the user station determines the clock difference between the satellite and the user station, the total number of ionospheric electrons on the ranging signal path between the satellite and the user station, and the satellite-to-ground space distance, so that the satellite can be synchronized with the user station clock. Of course, in other embodiments, the first device 100 may also be a user station, and the second device 200 may be a satellite. Furthermore, the first device 100 described in the embodiment of the present application may also be a high-orbit device, and the second device 200 may be a low-orbit device, or both the first device 100 and the second device 200 may be low-orbit devices, as long as the two devices are located on both sides of the ionosphere, or one device is located in the ionosphere and the other device is located outside the ionosphere, or both devices are located in the ionosphere.

[0071] Of course, in other embodiments, the first device 100 and the second device 200 may also be located on the same side of the ionosphere, for example, both are located on the ground, or both are located in space. In this case, the ionospheric delay is 0, and the clock difference between the first device 100 and the second device 200 can also be determined by the time synchronization method described in the embodiment of the present application.

[0072] The embodiment of the present application is only illustrated by taking the first device 100 as a satellite and the second device 200 as a user station as an example.

[0073] The time synchronization system provided in the embodiments of the present application can be applied to aerospace systems, typically a satellite-to-ground system consisting of a user station and a satellite. The user station monitors the clock difference between the satellite and the user station, the ionospheric delay along the ranging signal path, and determines the distance between the satellite and the user station. Specific applications of the satellite-to-ground time synchronization system include, for example, satellite navigation, satellite communications, satellite remote sensing, satellite reconnaissance, and meteorological satellites.

[0074] In this exemplary embodiment, the user station sends an uplink signal (including a first uplink signal and a second uplink signal) to the satellite based on its own clock system, that is, based on local time. After obtaining the uplink signal, the satellite forwards and processes the uplink signal to obtain a downlink signal (i.e., a first downlink signal and a second downlink signal), and forwards the downlink signal obtained after frequency conversion to the user station.

[0075] The uplink signal and the downlink signal forwarded by the satellite constitute a forward ranging signal, from which the user station can determine the forward ranging value. For example, the first uplink signal and the first downlink signal constitute the first forward ranging signal, and the second uplink signal and the second downlink signal constitute the second forward ranging signal. The user station can determine the first forward ranging value based on the first forward ranging signal and the second forward ranging value based on the second forward ranging signal. In addition, the satellite also transmits a pseudorange ranging signal to the user station based on its own clock system, namely local time. The user station receives and demodulates the pseudorange ranging signal to obtain the pseudorange ranging value. The user station can then calculate the clock difference between the satellite and the user station and the total number of ionospheric electrons in the path between the user station and the satellite ranging signal based on the determined forward ranging value and pseudorange ranging value.

[0076] In addition, in this exemplary embodiment, the second device 200 synchronously measures one pseudorange ranging signal and two forwarding ranging signals at a preset time interval to obtain one pseudorange ranging value and two forwarding ranging values.

[0077] It should be noted that the pseudo-range ranging signal and forwarded ranging signal described in the embodiments of the present application refer to signals obtained by modulating a ranging code signal into a carrier signal. In some specific embodiments, the ranging code may be a pseudo-code, a Weil code, an M code, etc., and this application does not specifically limit the specific ranging code selected. It is also understandable that the forwarded ranging signal and pseudo-range ranging signal described in the embodiments of the present application are both spread spectrum signals. When multiple spread spectrum signals are transmitted and received, the relationship between the carrier frequency and the ranging code is processed according to spread spectrum communication technology, carrier frequency multiplexing technology, and code division multiple access communication technology, and will not be further described here.

[0078] Because both the forwarding ranging signal and the pseudo-range ranging signal are spread spectrum signals, for the sake of brevity and convenience, the forwarding ranging signal and the pseudo-range ranging signal are collectively referred to as ranging signals.

[0079] The specific principles for determining the clock difference between the satellite and the user station by the user station can be found in the description of the subsequent method embodiments and will not be elaborated here. Furthermore, because the user station can determine the clock difference between the satellite and the user station and the total ionospheric electron count between the satellite and the user station using one pseudorange ranging signal and two forwarding ranging signals, the operating principles for more pseudorange ranging signals and forwarding ranging signals are similar to those for one pseudorange ranging signal and two forwarding ranging signals, and will not be elaborated on in this application.

[0080] The specific structures of the satellite and user station in the embodiments of the present application are further described below.

[0081] Figure 2 is a structural block diagram of a satellite and a user station according to one embodiment of the present application. Figure 2 FIG. 4 shows the internal structure of the system when the pseudo-range measurement signal is broadcast by the first device. Figure 2 As shown, in an exemplary embodiment, the satellite may include a communicatively connected transponder 101, a pseudorange generating device 102, and a first time-frequency device 103, wherein the transponder 101 is used to receive a first uplink signal and a second uplink signal, perform frequency conversion processing on the first uplink signal, power amplify the first uplink signal, and forward the first downlink signal to the user station, and perform frequency conversion processing on the second uplink signal, power amplify the second downlink signal to the user station; the pseudorange generating device 102 is communicatively connected to the transponder 101, and the pseudorange generating device 102 is used to generate and broadcast a first pseudorange ranging signal; the first time-frequency device 103 provides time-frequency signals for the transponder 101 and the pseudorange generating device 102.

[0082] It should be understood that the repeater 101 and the pseudorange generating device 102 described in the embodiment of the present application can be set independently, or can be integrated into one hardware device, that is, the functions of the repeater 101 and the pseudorange generating device 102 are realized by an integrated hardware device, or the repeater 101, the pseudorange generating device 102 and the first time-frequency device 103 are integrated, all of which fall within the scope of protection of the present application.

[0083] It should be noted that in the embodiment of the present application, the pseudorange generating device 102 and the repeater 101 are communicatively connected, that is, the two can realize communication interaction. They can communicate with each other directly, or they can be connected to a third-party device to realize communication interaction. The above all fall within the scope of protection of the present application.

[0084] like Figure 2 As shown, the user station may include a second pseudorange ranging device 202, a forwarding ranging device 201, a second time-frequency device 203, and a computing device 204. The second time-frequency device 203 provides a time-frequency signal to the forwarding ranging device 201 and the second pseudorange ranging device 202.

[0085] The second pseudorange ranging device 202 processes the received first pseudorange ranging signal to obtain a first pseudorange ranging value; the forwarding ranging device 201 is used to generate and broadcast a first uplink signal and a second uplink signal, and receive a first downlink signal and a second downlink signal, and determine a first forwarding ranging value based on the first forwarding ranging signal and a second forwarding ranging value based on the second forwarding ranging signal; the computing device 204 receives the first pseudorange ranging value, the first forwarding ranging value, and the second forwarding ranging value through communication, and performs corrections thereon to obtain a first corrected pseudorange ranging value, a first corrected forwarding ranging value, and a second corrected forwarding ranging value. value, and using the first corrected forward ranging value and the second corrected forward ranging value to determine the total number of ionospheric electrons on the ranging signal path; and determining the clock difference between the first device 100 and the second device 200 based on the total number of ionospheric electrons, any corrected forward ranging value, and any corrected pseudorange ranging value; or, determining the total number of ionospheric electrons on the ranging signal path between the first device 100 and the second device 200 and determining the clock difference between the first device 100 and the second device 200 based on the first corrected forward ranging value, the second corrected forward ranging value, and the first corrected pseudorange ranging value.

[0086] In addition, it should be noted that the second pseudorange ranging device 202 and the forwarding ranging device 201 in the embodiment of the present application can be set independently, or can also be integrated into one hardware device, that is, the functions of the second pseudorange ranging device 202 and the forwarding ranging device 201 are realized by one hardware device, or the second pseudorange ranging device 202, the forwarding ranging device 201 and the second time-frequency device 203 are integrated, all of which fall within the scope of protection of the present application.

[0087] As described above, the pseudorange ranging signal can also be broadcast by the second device and received by the first device. In this case, the first device includes a first time-frequency device, a repeater, and a first pseudorange ranging device; the first time-frequency device is used to provide a time-frequency signal to the repeater and the first pseudorange ranging device; the repeater is used to receive the uplink signal, perform frequency conversion processing and power amplification on the uplink signal, and then forward the downlink signal to the second device; the first pseudorange ranging device is communicatively connected to the repeater, and the first pseudorange ranging device is used to receive and measure the pseudorange ranging signal; the second device includes a second time-frequency device and a forwarding ranging device; the second time-frequency device is used to provide a time-frequency signal to the forwarding ranging device; the forwarding ranging device is used to generate and broadcast the uplink signal, receive the downlink signal, and determine a forwarding ranging value based on the forwarding ranging signal, wherein part of the uplink signal broadcast by the forwarding ranging device is used as the pseudorange ranging signal. Furthermore, the first time-frequency device, the repeater and the first pseudo-range measuring device are integrated or separately provided, and / or the second time-frequency device and the repeater ranging device are integrated or separately provided.

[0088] In this case, the transmission delay of the forwarding ranging device can be measured in advance, so that the delay can be pre-set into the calculation device, and the calculation device can directly use the delay in subsequent calculations. Because the first device and the second device in this working condition have corresponding differences in system structure only due to the different broadcasting methods of the pseudo-range ranging signal, the specific functions of each functional component are different. Figure 2 The structure shown is similar, and the following continues Figure 2 The system structure shown is taken as an example to further introduce the specific structures of the first device and the second device.

[0089] In an exemplary embodiment, the forwarding ranging device 201 may include a modulator, a mixer, a demodulator, an antenna, a data collector, etc. The modulator generates an intermediate frequency (IF) spread spectrum signal; the mixer mixes the IF spread spectrum signal into an RF signal; the antenna transmits the RF signal to the satellite and receives the RF signal forwarded by the satellite. The antenna receives the RF signal and mixes it into an IF signal via the mixer; the demodulator demodulates the IF signal and obtains a forwarding ranging value through ranging code correlation calculation; the data collector records and stores the forwarding ranging value. The second pseudorange ranging device 202 may include a demodulator, a receiving antenna, a data collector, etc. The receiving antenna receives the pseudorange ranging signal from the satellite and generates a pseudorange ranging value by the second pseudorange ranging device 202.

[0090] It is worth noting that, in the embodiment of the present application, a zero baseline is set between the second pseudo-range measuring device 202 and the forwarding ranging device 201 .

[0091] It is worth noting that the zero baseline setting referred to in this application does not mean that the distance between the second pseudorange ranging device 202 and the forwarding ranging device 201 is zero. Instead, the distance setting between them must ensure that the spatial paths traversed by the forwarding ranging signal and the pseudorange ranging signal are approximately the same. As the distance between the second pseudorange ranging device 202 and the forwarding ranging device 201 decreases and they can be integrated into one device, the "approximately the same" gradually becomes "identical," with the same satellite-to-ground spatial distance, the same tropospheric delay, and the same total ionospheric electron count.

[0092] At this time, the first pseudorange ranging signal and the first and second forwarding ranging signals have the same transmission path. Thus, the atmosphere has the same path influence on the first pseudorange ranging signal, the first and second forwarding ranging signals. That is, the first pseudorange ranging signal and the first and second forwarding ranging signals have the same ionospheric path and tropospheric path. This allows the satellite-to-ground space distance and tropospheric time delay in one pseudorange ranging signal and two forwarding ranging signals to be eliminated. The total number of ionospheric electrons between the satellite and the user station can then be specifically calculated using the ionospheric time delay.

[0093] In an exemplary embodiment, the second device is a user station of this embodiment, and the user station uses at least one second time-frequency device 203. Specifically, the second pseudo-range measuring device 202 and the forwarding ranging device 201 of the user station use at least one second time-frequency device 203. It is worth noting that the at least one time-frequency system described in the embodiment of the present application may include multiple clocks (crystal oscillators or atomic clocks) or one clock (crystal oscillator or atomic clock). When multiple clocks are included, one clock provides a clock signal for the second pseudo-range measuring device 202, and the remaining clocks provide clock signals for the forwarding ranging device 201. In actual use, the preset time interval can be set to 1s, for example, and the second pseudo-range measuring device 202 and the forwarding ranging device 201 perform measurements on the rising edge or falling edge of their respective 1PPS (1 Pulse Per Second) signals. Preferably, it is generally recommended to use one clock to perform synchronous measurements of the pseudo-range ranging signal and the forwarding ranging signal on the rising edge or falling edge of the same 1PPS signal.

[0094] The first device is similar, with at least one first time-frequency device 103. When there are multiple time-frequency devices, one time-frequency device provides a time-frequency signal for the repeater 101, and another time-frequency device provides a time-frequency signal for the pseudorange generating device 102 or the pseudorange measuring device.

[0095] The repeater 101 has a forwarding delay, and the pseudorange generating device 102 has a transmission delay; the second pseudorange ranging device 202 has a receiving delay, and the forwarding ranging device 201 has a transmission delay and a receiving delay;

[0096] The first pseudorange ranging signal carries the forwarding delay of the repeater 101 and the transmission delay of the pseudorange generating device 102 , or the forwarding delay of the repeater 101 and the transmission delay of the pseudorange generating device 102 are preset in the computing device 204 .

[0097] The forwarding delay of the transponder 101 refers to the delay incurred when the satellite receives the first uplink signal and the second uplink signal from the user station and then forwards and processes them to produce the first downlink signal and the second downlink signal. The transmission delay of the satellite's pseudorange generator 102 refers to the delay incurred when the pseudorange generator 102 generates and transmits the first pseudorange ranging signal.

[0098] The second pseudo-range measuring device 202 of the user station has a reception delay, which refers to the delay generated in the process of the second pseudo-range measuring device 202 receiving the pseudo-range measuring signal sent by the satellite and generating a pseudo-range measuring value.

[0099] The forwarding ranging device 201 of the user station has a transmission delay and a reception delay. The transmission delay refers to the delay from the generation of the uplink signal to the transmission of the antenna; the reception delay refers to the delay from receiving the downlink signal to generating the forwarding ranging value.

[0100] It is worth noting that in this exemplary embodiment, the satellite can transmit the forwarding delay of the ranging signal and the transmission delay of the pseudo-range ranging signal to the user station through any pseudo-range ranging signal, or the user station and the satellite can also use additional communication signals to transmit the signal forwarding delay of the repeater 101 and the transmission delay of the pseudo-range ranging signal. For example, the satellite can be provided with a telemetry unit, and the signal forwarding delay of the repeater 101 and the transmission delay of the pseudo-range ranging signal can be transmitted through the telemetry signal broadcast by the telemetry unit, or the signal forwarding delay of the repeater 101 and the transmission delay of the pseudo-range ranging signal can be transmitted to the user station through other user-defined communication signals. This application does not specifically limit the specific signal used to transmit the signal forwarding delay and the transmission delay of the pseudo-range ranging signal of the repeater 101.

[0101] Alternatively, because the variation of the signal forwarding delay of the repeater 101 and the pseudo-range measurement signal transmission delay is very small or known, the signal forwarding delay of the repeater 101 and the pseudo-range measurement signal transmission delay can be regarded as known quantities. Therefore, in actual use, the signal forwarding delay of the repeater 101 and the pseudo-range measurement signal transmission delay can also be preset in the computing device 204.

[0102] By loading the forwarding delay and the pseudo-range measurement signal transmission delay into any pseudo-range measurement signal and transmitting it to the user station, the existing signal between the satellite and the user station is fully utilized to transmit the forwarding delay and the pseudo-range measurement signal transmission delay. There is no need to set up additional communication signals, so no additional communication resources are occupied, which can greatly reduce communication costs and save frequency resources.

[0103] It is worth noting that the above Figure 1 The signal structure of one pseudo-range measurement signal and two forwarding measurement signals is shown. Figures 3 to 10 Schematic diagram of the composition of the forwarded ranging signal and the pseudo-ranging signal between the satellite and the user station according to other embodiments of the present application.

[0104] like Figure 3 As shown, there may be only one forwarding ranging signal and two pseudo-ranging signals between the user station and the satellite;

[0105] Or, as Figure 4 As shown, there can be two forwarding ranging signals and one pseudo-range ranging signal between the user station and the satellite;

[0106] Or, as Figure 5 As shown, there can be one forwarding ranging signal and three pseudo-range ranging signals between the user station and the satellite.

[0107] Or, as Figure 6 As shown, there can be three forwarding ranging signals and one pseudo-range ranging signal between the user station and the satellite.

[0108] Furthermore, in the embodiment of the present application, the signal structure can be further simplified by multiplexing the carrier frequency of the signal. Continuing with the signal structure between the user station and the satellite as an example, the following is an illustrative description.

[0109] Or, as Figure 7 As shown in FIG, when there are two forwarding ranging signals and one pseudo-ranging signal between the user station and the satellite, the first downlink signal, the second downlink signal and the pseudo-ranging signal can be carrier frequency multiplexed. This is the carrier frequency multiplexing mode of the second simplest system.

[0110] Or, as Figure 8 As shown in FIG, when there are two forwarding ranging signals and one pseudo-range ranging signal between the user station and the satellite, the first downlink signal or the second downlink signal is carrier frequency multiplexed with the pseudo-range ranging signal. Here, the second downlink signal is carrier frequency multiplexed with the pseudo-range ranging signal. This is another carrier frequency multiplexing mode of the second simplest system.

[0111] Or, as Figure 9As shown, when there are two forwarding ranging signals and two pseudo-range ranging signals between the user station and the satellite, the first pseudo-range ranging signal is carrier frequency multiplexed with the first downlink signal, and the second pseudo-range ranging signal is carrier frequency multiplexed with the second downlink signal.

[0112] Or, as Figure 10 As shown, when there are three-way forwarding ranging signals and three-way pseudorange ranging signals between the user station and the satellite, the first downlink signal is carrier-frequency multiplexed with the first pseudorange ranging signal, the second downlink signal is carrier-frequency multiplexed with the second pseudorange ranging signal, and the third downlink signal is carrier-frequency multiplexed with the third pseudorange ranging signal.

[0113] It should be understood that the above Figures 3 to 10 This is only an example of the signal structure between the user station and the satellite. In actual use, there may be other forms of signal structures and signal carrier frequency multiplexing, which will not be described in detail here.

[0114] Furthermore, in some embodiments, the carrier frequency of the forwarded ranging signal and the carrier frequency of the pseudo-ranging signal are both frequency-hopped according to a preset frequency hopping pattern. Frequency hopping the signal in this way can improve the signal's anti-interference ability and enhance the signal's anti-interception ability.

[0115] Of course, the carrier frequencies of all forwarded ranging signals and the carrier frequencies of all pseudo-range ranging signals may also remain unchanged for a long time, that is, the time interval between two frequency hops is infinite.

[0116] In an exemplary embodiment, the ionospheric delay monitoring and time synchronization system provided in the embodiment of the present application also has a communication function, and the satellite uses the first uplink signal or the second uplink signal, and the first pseudo-range ranging signal to transmit data with the user station, or uses an additional communication signal to transmit data with the user station. Specifically, after receiving an uplink signal of any one forwarding ranging signal, the satellite is divided into two, one forwarding signal is sent downlink to the user station, and the other satellite receives data uploaded by the user station, and the satellite uses any pseudo-range ranging signal to transmit the data downlink to the user station, thereby realizing the satellite-to-ground communication function. Alternatively, an additional communication signal is added to realize data transmission between the satellite and the user station.

[0117] In an exemplary embodiment, as Figure 1 As shown in FIG, the satellite can also send the forwarding delay and the pseudo-range measurement signal transmission delay to the user station through the additional communication link. That is, in addition to the uplink signal link, the downlink signal link and the pseudo-range measurement signal link, there is an additional communication link (including the communication link uplink signal fu and the communication link downlink signal fd) between the satellite and the user station. The satellite transmits the forwarding delay and the pseudo-range measurement signal transmission delay to the user station through the additional communication link.

[0118] It can be seen that the satellite can transmit the forwarding delay and the pseudo-range measurement signal transmission delay to the user station in a variety of ways. This application does not specifically limit the specific transmission method of the forwarding delay and the pseudo-range measurement signal transmission delay.

[0119] In the pseudorange measurement value, it is necessary to obtain the Sagnac effect delay of the satellite, and the Sagnac effect delay requires the coordinates of the user station and the satellite. The coordinates of the satellite can be obtained through the known satellite ephemeris, and the coordinates of the user station can be obtained through the existing positioning method. In this way, the coordinate information required by the embodiment method of the present application is obtained, and then the Sagnac effect delay is obtained.

[0120] The relativistic delay effect is absent from pseudorange measurements. This is because satellites in space are equipped with time and frequency systems to provide time and frequency. Based on the theory of relativity, it's easy to see that satellite clocks experience relativistic delays due to relativity. This relativistic delay can be addressed using established methods, such as pre-launch adjustment of satellite clocks. After adjustment, the satellite clocks, like ground-based clocks, are free of relativistic delays. For more information, see Beidou Navigation Satellite Clocks: Relativistic Methods.

[0121] When using a forward ranging expression to represent the forward ranging value, the Sagnac effect delay is not included in the forward ranging expression. This is because the Sagnac effect delay of the uplink signal and the Sagnac effect delay of the downlink signal have opposite signs, and the difference in their absolute values ​​is very small. Therefore, the two Sagnac effect delays can be approximately offset, and thus the Sagnac effect delay term is not reflected in the forward ranging expression. Of course, in other embodiments of the present application, the Sagnac effect delay may also be considered, that is, the Sagnac effect delay of the uplink signal and the Sagnac effect delay of the downlink signal may be added to the forward ranging expression to achieve better measurement accuracy of the forward ranging value. All of these fall within the scope of protection of the present application.

[0122] When a pseudorange measurement signal is broadcast by a second device and received by a first device, based on the above embodiments, an embodiment of the present application further provides a method for determining a pseudorange measurement value, which is applied to the ionospheric delay monitoring and time synchronization system described in any of the above embodiments. The method for determining a pseudorange measurement value is performed by the first device. The method for determining a pseudorange measurement value is as follows:

[0123] receiving m-path pseudo-range measurement signals broadcast by a second device;

[0124] Each pseudorange ranging signal is synchronously measured to obtain m pseudorange ranging values, where m is a positive integer.

[0125] When a pseudorange ranging signal is broadcast by a first device and received by a second device, based on the above embodiments, an embodiment of the present application further provides a method for determining a ranging value, which is applied to the ionospheric delay monitoring and time synchronization system described in any of the above embodiments, and the method for determining a ranging value is performed by the second device. The method for determining a pseudorange ranging value is as follows:

[0126] broadcasting at least one uplink signal to the first device;

[0127] Acquire at least one downlink signal forwarded by the first device based on the at least one uplink signal, wherein the at least one uplink signal and the at least one downlink signal constitute an h-path forwarding ranging signal;

[0128] Acquire m-path pseudo-range measurement signals broadcast by the first device;

[0129] Synchronously measuring each of the forwarded ranging signals and each of the pseudorange ranging signals to obtain h forwarded ranging values ​​and m pseudorange ranging values;

[0130] Wherein, m+h≥3, and m and h are both positive integers.

[0131] It is particularly worth noting that when the pseudorange ranging signal is broadcast by the second device and received by the first device, or when the pseudorange ranging signal is broadcast by the first device and received by the second device, the h forwarded ranging values ​​all need to be measured by the second device and all need to satisfy m+h≥3.

[0132] The above describes the specific process by which the system determines the pseudorange measurement value and the forwarded ranging value under two different pseudorange ranging signal transmission methods. Regardless of the method, after obtaining the pseudorange measurement value and the forwarded ranging value, the computing device communicates with the first device and the second device to obtain the pseudorange measurement value and the forwarded ranging value, and further calculates the total ionospheric electron count and clock error.

[0133] Based on the above embodiments, embodiments of the present application also provide an ionospheric delay monitoring and time synchronization method. This ionospheric delay monitoring and time synchronization method can be applied to the ionospheric delay monitoring and time synchronization system described in any of the above embodiments. For details on the device delays used in this method embodiment and how to obtain them, refer to the description of the above system embodiments and will not be repeated here. The method is described in detail below.

[0134] Figure 11 Flowchart of a method for ionospheric delay monitoring and time synchronization according to an embodiment of the present application, which is executed by a computing device, such as Figure 11 As shown, the ionospheric delay monitoring and time synchronization method may include the following steps:

[0135] S110: When the pseudorange ranging signal is broadcast by the second device and received by the first device, obtain m pseudorange ranging values ​​measured by the first device based on a communication result with the first device, and obtain h forwarding ranging values ​​measured by the second device based on a communication result with the second device;

[0136] When the pseudorange ranging signal is broadcast by the first device and received by the second device, obtaining, based on a communication result with the second device, h forwarded ranging values ​​and m pseudorange ranging values ​​measured by the second device; where m+h≥3, and m and h are both positive integers;

[0137] S120, using a pseudorange measurement expression to represent each pseudorange measurement value and using a forwarding ranging expression to represent each forwarding ranging value;

[0138] S130. Determine a total number of ionospheric electrons on a ranging signal path between the first device and the first device and a clock difference between the first device and the first device based on the m pseudorange ranging values ​​and the h forwarded ranging values.

[0139] Among them, step S130 can specifically be: selecting ɑ (2≤ɑ≤m) from the m pseudorange ranging values, selecting β (1≤β≤h) from the h forwarded ranging values, and determining the total number of ionospheric electrons on the ranging signal path between the first device and the first device; or selecting λ (1≤λ≤m) from the m pseudorange ranging values, selecting θ (2≤θ≤h) from the h forwarded ranging values, and determining the total number of ionospheric electrons on the ranging signal path between the first device and the first device and the clock difference between the first device.

[0140] Because the present application includes two simplest systems and corresponding methods, the first simplest system has two pseudorange measurement values ​​and one forwarding measurement value, and the total number of ionospheric electrons can be calculated based on the two common pseudorange measurement values, and then the clock error can be calculated based on any one of the pseudorange values ​​and any one of the forwarding measurement values; the second simplest system has one pseudorange measurement value and two forwarding measurement values, and the total number of ionospheric electrons can be calculated based on the two forwarding measurement values, and then the clock error can be calculated based on any one of the pseudorange values ​​and any one of the forwarding measurement values;

[0141] Because there are only two unknowns, the total number of electrons in the ionosphere and the clock error between the satellite and the user station, the two simplest systems can both be composed of a 2×2 matrix when calculated according to the matrix method, and the matrix is ​​reversible, so the two unknowns can be obtained, and the calculation method is similar.

[0142] Therefore, in order to concisely and clearly illustrate the method of the present application, only the calculation method corresponding to the second simplest system is used as an example for explanation. In the second simplest system, the pseudorange ranging signal can be specifically defined as the first pseudorange ranging signal, the uplink signal can be specifically defined as the first uplink signal and the second uplink signal, and the downlink signal can be specifically defined as the first downlink signal and the second downlink signal. Correspondingly, the forwarding ranging signal can be specifically defined as the first forwarding ranging signal and the second forwarding ranging signal.

[0143] At this time, m = 1, h = 2; for this specific case, λ = 1, θ = 2;

[0144] The above method can be specifically divided into the following steps:

[0145] S110: When the pseudorange ranging signal is broadcast by the second device and received by the first device, obtain one pseudorange ranging value measured by the first device based on a communication result with the first device, and obtain two forwarding ranging values ​​measured by the second device based on a communication result with the second device;

[0146] When the pseudorange ranging signal is broadcast by the first device and received by the second device, obtaining one pseudorange ranging value and two forwarded ranging values ​​measured by the second device based on a communication result with the second device;

[0147] S120: Use a pseudorange ranging expression to represent the first pseudorange ranging value, and use a forward ranging expression to represent the first forward ranging value and the second forward ranging value;

[0148] S130: Determine a total number of ionospheric electrons on a ranging signal path between the first device and the second device, and a clock difference between the first device and the second device based on the first pseudorange ranging value represented by the pseudorange ranging expression, the first forwarding ranging value represented by the forwarding ranging expression, and the second forwarding ranging value.

[0149] The method will be described in detail below by taking the first device as a satellite and the second device as a user station as an example.

[0150] It should be noted that the Sagnac effect delay in the pseudorange and forward ranging expressions of this application has been explained above and can be used as a known value, while the satellite-to-ground distance, tropospheric delay, ionospheric delay, and the clock error of the satellite relative to the system time or the clock error of the user station relative to the system time are unknown. This application uses the above method to calculate the clock error between the satellite and the user station and the total number of ionospheric electrons in the ranging signal path based on the measured pseudorange and forward ranging values.

[0151] It should be noted that the ionospheric monitoring and time synchronization system and method proposed in this application can not only solve the clock difference of the satellite relative to the system time when the clock difference of the user station relative to the system time is known, but also solve the clock difference of the user station relative to the system time when the clock difference of the satellite relative to the system time is known.

[0152] Both pseudorange and relay ranging signals travel through the atmosphere, which consists of the troposphere and ionosphere. The ionosphere is a diffuse medium, and the time delay it produces for RF signals of different carrier frequencies varies depending on the carrier frequency. The troposphere, on the other hand, is a non-dispersive medium, and the time delay it produces for RF signals of different carrier frequencies is the same.

[0153] Because a zero baseline is set between the second pseudo-range ranging device 202 and the forwarding ranging device 201, the pseudo-range ranging signal and the forwarding ranging signal traverse exactly the same atmospheric path, and the total number of ionospheric electrons experienced by the ranging signal is exactly the same. The pseudo-range ranging signal and the downlink signal traverse the same spatial path, but the time when the uplink signal passes through the ionosphere is different from the time when the downlink signal passes through the ionosphere after being forwarded by the satellite, and there is a certain time difference. In a relatively short period of time (such as a few seconds), the ionosphere is stable and the total number of ionospheric electrons remains almost unchanged. It can be calculated that the round-trip time of the radio frequency signal between almost all spacecraft and user stations will not exceed a few seconds, which fully meets the conditions. Combined with the spatial relationship of the zero baseline setting and the time relationship of the very short time difference, the spatial paths traversed by the forwarding ranging signal and the pseudo-range ranging signal are exactly the same, so the following equations (56) and (57) are obtained:

[0154] R true,z,1 (n) = R true,z,2 (n) = R true,zu,1 (n) = R true,zd,1 (n) = R true,zu,2 (n) = R true,zd,2 (n)(56);

[0155] T duiliu,z,1 (n) = T duiliu,z,2 (n) = T duiliu,zu,1 (n) = T duiliu,zd,1 (n) = T duiliu,zu,2 (n) = T duiliu,zd,2 (n)(57);

[0156] When the pseudo-range measurement signal is broadcast by the second device, the pseudo-range measurement signal and the uplink signal of the forwarded ranging signal traverse the same spatial path, and also have the above formula for setting the zero baseline.

[0157] In some embodiments, after step S120, the ionospheric delay monitoring and time synchronization method may further include the following step: using a pseudorange smoothing algorithm to correct the first forwarding ranging value, the second forwarding ranging value, and the first pseudorange ranging value. Specifically, using the pseudorange smoothing algorithm to correct the pseudorange ranging value and the forwarding ranging value can reduce noise in the pseudorange ranging value and the forwarding ranging value, thereby improving the accuracy of the ultimately determined clock error. The specific details of the pseudorange smoothing algorithm are not further described here.

[0158] Before introducing the specific method, it is specially noted that ±c·(δt z (n)-δt s (n)), when taking +c·(δt z (n)-δt s (n)), the first device broadcasts the pseudo-range measurement signal, and the second device receives and measures it; when -c·(δt z (n)-δt s (n)), the corresponding second device broadcasts a pseudo-range measurement signal, and the first device receives and measures it;

[0159] ±sagnca in the pseudorange measurement formula (z1) zz (n), when taking +sagnca zz (n) corresponds to the Sagnac effect when the first device broadcasts the pseudo-range ranging signal. When -sagnac zz (n) corresponds to the Sagnac effect of the pseudorange measurement signal broadcast by the second device. It can be seen that when the pseudorange measurement signals are in opposite directions, the absolute value of the Sagnac effect is the same but the sign is opposite.

[0160] Because the directions of the pseudorange signals are different, except for the opposite signs of the clock error and the Sagnac effect between the first and second devices, everything else is the same. Therefore, when the first device broadcasts the pseudorange signal, the pseudorange measurement formula is as follows (fz1); when the second device broadcasts the pseudorange signal, the pseudorange measurement formula is as follows (sz1):

[0161]

[0162] The corresponding corrected pseudorange measurement formulas are (fz1') and (sz1'):

[0163]

[0164] The method of the present application is described below using the example of the first device broadcasting a pseudorange ranging signal, that is, the pseudorange ranging formula (fz1) and the corrected pseudorange ranging formula (fz1') corresponding to the pseudorange ranging signal broadcast by the first device are used for description.

[0165] In an exemplary embodiment, in step S120, the computing device may specifically use the pseudorange measurement expression shown in the following formula (fz1) to represent the pseudorange measurement value numbered i:

[0166] ρ z,i (n) = R true,z,i (n)+I z,i (n)+T duiliu,z,i (n)+c·(δt z (n)-δt s (n))+sagnac zz (n)+X z,i (n)(fz1);

[0167] Wherein, i=1, 2, ..., m, i is a positive integer;

[0168] The first pseudo-range measurement value obtained is specifically shown in the following formula (fz1-1):

[0169] ρ z,1 (n) = R true,z,1 (n)+I z,1 (n)+T duiliu,z,1 (n)+c·(δt z (n)-δt s (n))+sagnac zz (n)+X z,1 (n)(fz1-1);

[0170] The forwarding ranging value numbered j is represented by the forwarding ranging expression shown in the following formula (z2):

[0171] L z,j (n) = R true,zu,j (n)+R true,zd,j (n)+I zu,j (n)+I zd,j (n)+T duiliu,zu,j (n)+T duiliu,zd,j (n)+Y z,j (n)(z2);

[0172] Wherein, j=1, 2, ..., h, j is a positive integer;

[0173] The obtained first forwarding ranging value and second forwarding ranging value are specifically shown in the following formula (z2-1) and formula (z2-2):

[0174] L z,1 (n) = R true,zu,1 (n)+R true,zd,1 (n)+I zu,1 (n)+Izd,1 (n)+T duiliu,zu,1 (n)+T duiliu,zd,1 (n)+Y z,1 (n)(z2-1);

[0175] L z,2 (n) = R true,zu,2 (n)+R true,zd,2 (n)+I zu,2 (n)+I zd,2 (n)+T duiliu,zu,2 (n)+T duiliu,zd,2 (n)+Y z,2 (n)(z2-2);

[0176] In an exemplary embodiment, in step S130, the computing device may first correct the forwarded ranging value and the pseudorange ranging value to obtain a corrected forwarded ranging value and a corrected pseudorange ranging value, and then use the corrected forwarded ranging value and the corrected pseudorange ranging value to determine the total ionospheric electron count and the clock error between the satellite and the user station. Specifically, the process of correcting the forwarded ranging value and the pseudorange ranging value may include the following steps:

[0177] S1301: Correct the first forward ranging value to obtain a first corrected forward ranging value, and correct the second forward ranging value to obtain a second corrected forward ranging value;

[0178] S1302: Correct the first pseudorange measurement value to obtain a first corrected pseudorange measurement value;

[0179] S1303: Determine a forwarding ranging difference by using the first corrected forwarding ranging value and the second corrected forwarding ranging value.

[0180] In step S1301, the computing device may correct the pseudorange measurement value numbered i represented by the pseudorange measurement expression shown in formula (fz1) according to formula (fz1') to obtain a corrected pseudorange measurement value numbered i (fz1'-1):

[0181]

[0182] Wherein, i=1, 2, ..., m, i is a positive integer;

[0183] The specific first corrected pseudorange measurement value is obtained as shown in formula (fz1'-1):

[0184]

[0185] The computing device corrects the forwarding ranging value numbered j represented by the forwarding ranging expression shown in formula (z2) to obtain a corrected forwarding ranging value numbered j:

[0186]

[0187] Wherein, j=1, 2, ..., h, j is a positive integer;

[0188] The obtained first corrected forward ranging value and second corrected forward ranging value are specifically shown in the following formulas (z2'-1) and (z2'-2):

[0189]

[0190] Then in step S1303, the computing device determines a forwarding ranging difference using the first corrected forwarding ranging value and the second corrected forwarding ranging value.

[0191] Specifically, the computing device may perform a difference calculation on the first corrected forward ranging value shown in formula (z2'-1) and the second corrected forward ranging value shown in formula (z2'-2) to obtain a forward ranging difference value shown in the following formula (u7-1);

[0192]

[0193] Furthermore, the computing device may specifically perform the following steps to determine the total number of ionospheric electrons on the ranging signal path between the satellite and the user station:

[0194] S1304: Determine a total number of ionospheric electrons on a ranging signal path between the first device and the second device based on the forwarded ranging difference.

[0195] The computing device may use the forwarded ranging difference, the carrier frequency of each signal in the forwarded ranging signal, and the preset ionospheric delay coefficient to determine the total number of ionospheric electrons on the ranging signal path between the satellite and the user station as shown in the following formula (u9-1):

[0196]

[0197] Then, the computing device may determine the ionospheric delay of the pseudorange ranging signal and the forwarded ranging signal by using the following formulas (u60) to (u64):

[0198]

[0199] As described above, the computing device can use the pseudorange smoothing algorithm to correct the pseudorange measurement value and the forwarding ranging value. Therefore, in this step, the computing device can correct the forwarding ranging value corrected by the pseudorange smoothing algorithm and the pseudorange measurement value corrected by the pseudorange smoothing algorithm, and then use the corrected forwarding ranging value and the corrected pseudorange ranging value to determine the clock difference between the satellite and the user station.

[0200] After obtaining the ionospheric delay of each signal, in step S130, the computing device can determine the clock difference between the satellite and the user station based on any forwarding ranging value and any pseudorange ranging value.

[0201] In one embodiment of the present application, a computing device may determine a clock difference between the first device and the second device based on the total ionospheric electron count, any corrected forward ranging value, and any corrected pseudorange ranging value. This process may include the following steps:

[0202] S1311. Perform mathematical processing on any corrected pseudorange measurement value and any corrected forward ranging value to obtain an expression including the clock difference between the first device and the second device;

[0203] S1312. Determine the clock difference between the satellite and the user station using an expression including the clock difference.

[0204] After obtaining the above-mentioned corrected pseudorange measurement value and corrected forward ranging value, an expression representing the first corrected pseudorange measurement value and an expression representing the first corrected forward ranging value are mathematically processed to obtain an expression containing the clock difference between the satellite and the user station; or an expression representing the first corrected pseudorange measurement value and an expression representing the second corrected forward ranging value are mathematically processed to obtain an expression containing the clock difference between the satellite and the user station. That is, the computing device can use any corrected pseudorange measurement value and any corrected forward ranging value to perform calculations to obtain the clock difference between the satellite and the user station.

[0205] Specifically, in step S1311, the computing device may perform a difference calculation using the first corrected pseudorange measurement value shown in formula (fz1′-1) and the first corrected forwarding ranging value and the second corrected forwarding ranging value shown in formulas (z2′-1) and (z2′-2), and utilize the zero baseline setting relationship between the forwarding ranging device and the second pseudorange ranging device, as shown in formulas (56) and (57), and obtain the following expressions containing the clock difference between the first device and the second device, as shown in formulas (u10-1) and (u10-2), according to formula (u10):

[0206]

[0207]

[0208] According to the clock difference expressions shown in formula (u10-1) to formula (u10-2), the clock difference between the first device and the second device shown in the following formula (z3-1) to formula (z3-2) is obtained:

[0209]

[0210] Of course, in other embodiments, the computing device may also use the above formulas (z3-1) to (z3-2) to perform averaging to obtain the averaged clock difference between the satellite and the user station:

[0211] Obviously, after weighted averaging, a clock difference between the satellite and the user station with a smaller error can be obtained, which will not be described in detail here.

[0212] In another optional embodiment of the present application, the total number of ionospheric electrons on the ranging signal path between the satellite and the user station and the clock difference between the satellite and the user station as described in step S130 can also be achieved by executing a set of simultaneous equations and solving matrix equations.

[0213] At this time, m=1, h=2; λ=1; θ=2;

[0214] The computing device determines the total number of ionospheric electrons on the ranging signal path between the first device and the second device and determines the clock difference between the first device and the second device based on the first corrected forwarding ranging value, the second corrected forwarding ranging value, and the first corrected pseudorange ranging value.

[0215] Specifically, as described above, according to formula (u10-1) to formula (u10-2), formula (u20) to formula (u21) are obtained:

[0216]

[0217] In general, each of the λ corrected pseudorange values ​​is subtracted from the θ corrected forwarded range values, so that λ·θ difference formulas are obtained, and the (λ·θ)×2 matrix G is obtained. u , where the first column is all 1; (λ·θ)×1 matrix b u .

[0218] In this way, the computing device can use the formulas shown in formulas (u20) to (u21) to construct the following matrix equation (u18-1), where the unknowns are the clock difference between the satellite and the user station and the total number of ionospheric electrons on the ranging signal path between the satellite and the user station:

[0219]

[0220] Among them, in the matrix equation (u18-1),

[0221]

[0222] Special note here: Matrix G u1 The elements and matrix b u1 The elements of must correspond one to one according to the corrected pseudorange ranging value, the corrected forward ranging value and its corresponding carrier frequency.

[0223] Then the solution of the above matrix equation (u18-1) is the expression (u19-1)

[0224]

[0225] When c·(δt z (n)-δt s (n)) and then divided by the speed of light c to get the clock difference δt between the satellite and the user station z (n)-δt s (n).

[0226] In the above formula (u19-1), the matrix is the matrix G u1 The transpose of column vector b u1 It is known that, in this way, the computing device can calculate the clock difference between the satellite and the user station and the total ionospheric electron number TEC(n) according to formula (u19-1).

[0227] It is worth noting that formula (u19-1) shows the expression for determining the clock difference between the satellite and the user station in the case of one pseudo-range ranging signal and two forwarding ranging signals. When the carrier frequencies of the signals are the same, the matrix G u , column vector b u It also changes accordingly, so formula (u19) is universal.

[0228] In addition, because the value of TEC(n) is relatively large, in the actual calculation process, we can set TEC(n) = x(n) × TECU, TECU = 10 16 , unit: electron / square meter (el / m 2 ), at this time, the matrix G u1 Change to G u1m :

[0229]

[0230] Solving matrix equations The result is as follows:

[0231]

[0232] It should be understood that when the system is the first simplest system, ɑ=2,β=1,the matrix G z ,b z Specifically, the matrix G is as follows z1 ,b z1 :

[0233]

[0234] According to formula (z19), the total number of ionospheric electrons on the ranging signal path between the first device and the second device and the clock difference between the first device and the second device are solved. The specific process can refer to the solution process of the second simplest system mentioned above, which will not be repeated here.

[0235] When the first minimalist system adds a forward ranging signal and the second system adds a pseudorange ranging signal, the two minimalist systems become systems with the same two pseudorange ranging signals and two forward ranging signals. When the two minimalist systems have two pseudorange ranging signals and two forward ranging signals, the two systems are identical. In this case, the carrier frequencies are different, and the corresponding calculation methods are also the same. In this case, the total ionospheric electron count can be obtained using either the two forward ranging values ​​or the two pseudorange ranging values. Then, using any corrected forward ranging value and any corrected pseudorange ranging value, along with the known total ionospheric electron count, the clock difference between the first and second devices can be obtained.

[0236] When using simultaneous equations to solve, the corresponding matrices Gu and bu are Gu2 and bu2 respectively:

[0237]

[0238] Then use formula (u19-2) to solve the total number of ionospheric electrons between the ranging signals and the clock difference between the first device and the second device.

[0239]

[0240] Of course, you can also select one pseudorange measurement value and two forwarding ranging values, or select two pseudorange measurement values ​​and one forwarding ranging value to implement the above method to obtain the total number of ionospheric electrons between the ranging signals and the clock difference between the first device and the second device.

[0241] When two pseudo-range measurement signals and two forwarding ranging signal systems perform carrier frequency multiplexing, such as Figure 9 As shown in the multiplexing, matrices Gu and ub become Gu3 and bu3 respectively:

[0242]

[0243] When c·(δtz (n)-δt s (n)) and then divided by the speed of light c to get the clock difference δt between the satellite and the user station z (n)-δt s (n).

[0244] After obtaining the clock difference between the satellite and the user station, the satellite further uses the clock difference to synchronize its own clock with the system clock.

[0245] After calculating the clock difference between the satellite and the user station, when the clock difference δt of the user station relative to the system time is z When (n) is a known quantity, the clock error δt of the satellite relative to the system time can be easily obtained s (n) If the time of the ground control station of the BeiDou satellite navigation system is known, the method of the present application is used to calculate the clock difference between the control station and the satellite, and then obtain the satellite clock difference;

[0246] On the contrary, when the clock difference δt between the satellite and the system time is s When (n) is a known quantity, the clock difference δt of the user station relative to the system time can be easily obtained z (n), at this time the satellite can provide time services to the user station;

[0247] When 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 both unknown, the clock difference between the satellite and the user station is obtained.

[0248] In an exemplary embodiment, after determining the clock difference between the satellite and the user station, the computing device may communicate with the first device and the second device, transmitting the determined clock difference between the first device and the second device to the first device and / or the second device, thereby achieving time synchronization between the first device and the second device. Exemplarily, the computing device transmits data to the satellite, and the satellite obtains the clock difference between the satellite and the user station based on the data transmission result, and synchronizes its own clock with the time of the user station based on the clock difference between the satellite and the user station.

[0249] Alternatively, the user station does not exchange clock error data with the satellite.

[0250] Based on the above embodiments, the present application also provides a method for determining the satellite-to-ground distance, which is applied to the ionospheric delay monitoring and time synchronization system described in any of the above embodiments. Figure 12 This is a flow chart of a method for determining the distance between the satellite and the earth according to one embodiment of the present application. The method can be executed by a computing device, such as Figure 12 As shown, the method may include the following steps:

[0251] S210: Determine, based on a total number of ionospheric electrons on a ranging signal path between the first device and the second device, a preset ionospheric delay coefficient, a carrier frequency of at least one forwarded ranging signal, and a carrier frequency of at least one pseudorange ranging signal, an ionospheric delay of the at least one forwarded ranging signal and an ionospheric delay of the at least one pseudorange ranging signal;

[0252] S220: Determine the sum of the satellite-to-ground distance and the tropospheric delay between the first device and the second device based on the ionospheric delay of at least one forwarded ranging signal and the forwarded ranging value of the corresponding forwarded ranging signal; or determine the sum of the satellite-to-ground distance and the tropospheric delay between the first device and the second device based on the ionospheric delay of at least one pseudorange ranging signal, the pseudorange ranging value of the corresponding pseudorange ranging signal, and the clock difference between the first device and the second device.

[0253] S230: Determine a tropospheric delay on a ranging signal path between the first device and the second device based on a preset tropospheric model;

[0254] S240: Determine a satellite-to-ground distance between the first device and the second device based on the sum of the satellite-to-ground distance and the tropospheric delay between the first device and the second device, and the tropospheric delay on a ranging signal path between the first device and the second device.

[0255] In step S210, the total number of ionospheric electrons can be determined according to the ionospheric delay monitoring and time synchronization method described in the above embodiment.

[0256] In addition, as described above, the computing device can correct the pseudorange ranging value and the forwarding ranging value to obtain a corrected pseudorange ranging value and a corrected forwarding ranging value accordingly. Therefore, in the method of the present application, the computing device can specifically use the corrected pseudorange ranging value and the corrected forwarding ranging value to calculate the sum of the satellite-to-ground space distance and the tropospheric delay between the first device and the second device.

[0257] In step S220, the computing device may use the formula (z2′-1) to obtain the sum of the satellite-to-ground distance and the tropospheric delay between the satellite and the user station as shown in the following formula (z14-1):

[0258]

[0259] Among them, I zu,1 (n) is the ionospheric delay of the uplink signal in the first forwarded ranging signal, I zd,1 (n) is the ionospheric delay of the downlink signal in the first forwarded ranging signal, and its value is determined according to formulas (u60) and (u61);

[0260] Alternatively, the computing device may use the following formula (fz1′-1) to obtain the sum of the satellite-to-ground distance and the tropospheric delay between the satellite and the user station as shown in the following formula (z15-1): R true,z,1 (n)+T duiliu,z,1 (n) = ρ z,1,a (n)-I z,1 (n)-c·(δt z (n)-δt s (n))(z15-1);

[0261] Among them, I z,1 (n) Determined according to formula (u64);

[0262] In step S230, the tropospheric delay T between the user station and the satellite can be corrected using a preset model. The tropospheric delay calculation requires the help of meteorological parameters. In the absence of real-time meteorological parameters, a simple model related only to the satellite elevation angle can be used for calculation, as shown in formula (T1):

[0263] T=2.47 / (sinθ+0.0121)(T1)

[0264] Where: T is the tropospheric delay, unit: meter; θ is the satellite elevation angle, unit: radian.

[0265] Currently, there are relatively many models for calculating tropospheric delay based on meteorological parameters. The differences between them decrease with the satellite elevation angle, ranging from a few millimeters to a few centimeters, which is more accurate than that calculated by this simple model.

[0266] Common models for determining tropospheric delay corrections include the Saastamoinen model and the Hopfield model. Research has shown that when the elevation angle is greater than or equal to 15°, the results obtained by different models agree well with each other, and any model can be selected. However, when the station elevation is large, the zenithal tropospheric delay calculated by the two models can differ by tens of centimeters. Comparison with measured meteorological data suggests that the Saastamoinen model is recommended.

[0267] In this way, after obtaining the tropospheric delay, in step S240, the computing device can use the known tropospheric delay to eliminate the tropospheric delay in formula (z14-1) and formula (z15-1), thereby obtaining the satellite-to-ground space distance between the user station and the satellite. The relevant calculation process will not be repeated here.

[0268] When there are multiple forwarded ranging values ​​or multiple pseudorange ranging values, multiple satellite-to-ground space distances can be obtained based on the above method, and then the multiple satellite-to-ground space distances are averaged to obtain an average result of the multiple satellite-to-ground space distances.

[0269] When the carrier frequency of the pseudo-range ranging signal and the carrier frequency of the forwarded ranging signal perform frequency hopping according to the frequency hopping pattern, the above-mentioned satellite-ground time synchronization method is still used to calculate the clock difference between the satellite and the user station, the total number of ionospheric electrons, and the calculated clock difference is transmitted to the satellite. The specific calculation steps are not repeated here.

[0270] Based on the above embodiments, the present application also provides a satellite navigation system, which is based on the above ionospheric delay monitoring and time synchronization system and method, adds an operation and control system, and increases the number of satellites to form a complete and simplest satellite navigation system.

[0271] Specifically, the satellite navigation system includes the ionospheric delay monitoring and time synchronization system described in any of the above embodiments, and in the ionospheric delay monitoring and time synchronization system, the first device is specifically a satellite, the second device is specifically a user station, and the number of satellites is greater than or equal to 2. The user station obtains orbital parameters of the corresponding satellite based on data transmission results with each satellite, and determines its own coordinate information based on the orbital parameters of each satellite and the space-to-ground distance between itself and the satellite.

[0272] The satellite navigation system also includes multiple third devices that are communicatively connected to the satellites. Some of these third devices constitute a satellite orbit determination system, used to monitor and process the orbits of the satellites and obtain satellite orbit parameters. Some of these third devices constitute a satellite-to-ground time synchronization system, used to monitor the time of each satellite and maintain time synchronization between each satellite and the operation and control system. The operation and control system referred to here refers to a system consisting of a satellite orbit determination system and a satellite-to-ground time synchronization system.

[0273] The satellite navigation system Figure 13 As shown, there are at least two satellites in the satellite navigation system. In the satellite navigation system, the orbit determination system can adopt the existing Beidou orbit determination method.

[0274] The third device in the satellite-to-ground time synchronization system has the hardware composition and signal structure of the ionospheric delay monitoring and time synchronization system with the satellite, and executes the ionospheric delay monitoring and time synchronization method. At this time, the time of the third device in the satellite-to-ground time synchronization system is used as the system time, and the satellite relative to the system time is used as an unknown number. The clock difference of the satellite relative to the system time is obtained through the method of this application, thereby achieving time synchronization between the satellite and the operation and control system. The satellite then broadcasts a pseudo-range measurement signal with a known time. At this time, the time of the satellite relative to the system is known, and the time of the user station relative to the system is unknown. The ionospheric delay monitoring and time synchronization system and method of this application are used to obtain the clock difference of the user station relative to the system time, thereby achieving the satellite timing function. At this time, after the user station obtains its own clock difference relative to the system time, it can stop exchanging clock difference data with the satellite.

[0275] Of course, the satellite-ground time synchronization system can also use other existing satellite-ground time synchronization technologies, such as two-way pseudo-range measurement method, etc. Satellite-ground time synchronization can be achieved using these methods.

[0276] After the user station obtains high-precision time synchronization, the space distance between the user station and the satellite is obtained. Based on the satellite ephemeris and the space distance, if the satellite navigation system has only two satellites, the user needs to configure an altimeter to obtain the user elevation, and then refer to the Beidou dual-star positioning principle to obtain the user station coordinates; when there are three or more satellites, the user station does not need to be configured with an altimeter, and the user station coordinate information can be obtained through the space distance between the user station and the satellite ephemeris and the three satellites.

[0277] Based on the above embodiments, the present application also provides an inter-station time synchronization system, which may include the satellite navigation system described in any of the above embodiments; wherein, when there are at least two user stations, at least two of the user stations achieve time synchronization with each other through communication and data exchange.

[0278] Alternatively, the inter-station time synchronization system includes the ionospheric delay monitoring and time synchronization system described in any of the above embodiments; wherein, when there are at least two second devices, at least two second devices achieve time synchronization with each other by exchanging data through communication.

[0279] Based on the above embodiments, an embodiment of the present application also provides an inter-station time synchronization method, which can be applied to the ionospheric delay monitoring and time synchronization system described in the above embodiments or can also be applied to the satellite navigation system described in the above embodiments. Figure 14 This is a flowchart of a method for inter-station time synchronization according to an embodiment of the present application. The method may be performed by a user station. The method may include:

[0280] S510, directly communicating with the target user station to perform data exchange and obtain the clock difference of the target user station;

[0281] S520: Calculate the time difference between the user station and the target user station based on their own clock difference and determine the time difference between them.

[0282] Among them, after determining the clock difference of the user station relative to the system time, the user station can transmit data with the target user station based on the communication link. Multiple user stations exchange the clock differences relative to each other's system time through communication, thereby achieving time synchronization between multiple user stations, which is similar to the common view method and will not be repeated here.

[0283] On the basis of the above embodiments, the present application also provides a satellite positioning method, which can be applied to the above satellite navigation system. Figure 15This is a flow chart of a satellite positioning method according to an embodiment of the present application. The method can be executed by a user station that needs to be positioned. In this case, the user station has the computing function of a computing device, such as Figure 15 As shown, the satellite positioning method may include the following steps:

[0284] S610, obtaining orbital parameters of each satellite;

[0285] S620, determining the coordinates of the corresponding satellite based on the orbital parameters;

[0286] S630, determining the space distance between the satellite and the ground;

[0287] S640: Determine the coordinate information of the satellite based on the coordinates of each satellite and the space distance between the satellite and the ground.

[0288] In step S610, the orbital parameters of the satellite are the satellite ephemeris, which can be determined according to existing satellite orbit determination methods, such as the orbit determination method of Beidou navigation satellites. Thus, the user station obtains the orbital parameters of the corresponding satellite based on the data transmission results with each satellite (for example, by receiving pseudorange measurement signals).

[0289] In step S620, the user station calculates the satellite coordinates at the current ranging time based on the acquired satellite orbit parameters.

[0290] In step S630, the user station may determine the satellite-to-earth space distance between itself and each satellite by using any of the above-mentioned satellite-to-earth space distance determination methods executed by the user station.

[0291] In step S640, the user station calculates its own coordinate information based on the coordinate information of each satellite and the satellite-to-ground space distance between itself and each satellite, thereby achieving satellite positioning for itself.

[0292] It is worth noting that in this exemplary embodiment, the number of satellites needs to be greater than or equal to 2. Specifically, when the number of satellites is greater than or equal to 2, the user station can select at least two satellites from all satellites and calculate its own coordinate information with reference to the existing Beidou dual-star positioning method.

[0293] As described above, in the ionospheric delay monitoring and time synchronization system provided in the embodiment of the present application, the pseudorange ranging signal can also be broadcast by the second device and received by the first device. In this case, the uplink signal broadcast by the second device is used as the pseudorange ranging signal, and the first pseudorange ranging device of the first device receives and measures it. The present application provides the following embodiments:

[0294] like Figure 16As shown, when the second device broadcasts an uplink signal for forwarding the ranging signal, the uplink signal reaches the satellite and is received by the first pseudo-range measuring device of the satellite to obtain a pseudo-range ranging value. The uplink signal is then forwarded by the satellite transponder into two downlink signals with different carrier frequencies, forming two forwarding ranging signals, and obtaining two forwarding ranging values.

[0295] Or, as Figure 17 As shown, when the second device broadcasts an uplink signal for forwarding ranging signals, one uplink signal reaches the satellite and is received by the satellite's first pseudorange ranging device to obtain a pseudorange measurement value, while not being forwarded by the transponder. When the second device broadcasts another uplink signal for forwarding ranging signals, this uplink signal reaches the satellite and is received by the satellite's first pseudorange ranging device to obtain a pseudorange measurement value. It is also forwarded by the transponder as a downlink signal, forming one forwarding ranging signal. The first device obtains two pseudorange measurement values, and the second device obtains one forwarding ranging value.

[0296] Or, as Figure 18 As shown, when the second device broadcasts two uplink signals of forwarding ranging signals with different carrier frequencies, they are respectively received by the first pseudo-range ranging device of the satellite to obtain two pseudo-range ranging values. The two uplink signals are then forwarded by the satellite transponder as two downlink signals with the same carrier frequency, forming two forwarding ranging signals and obtaining two forwarding ranging values.

[0297] Figures 16 to 18 The signal structure and the obtained pseudorange ranging value and forwarding ranging value can still be calculated using the method proposed in this application to obtain the clock difference between the first device and the second device, as well as the satellite-to-ground space distance between them. The specific calculation instructions will not be repeated here.

[0298] In summary, it can be seen that the ionospheric delay monitoring and time synchronization system, method, and application provided in the embodiments of the present application creatively integrate at least one pseudorange ranging signal and at least two forwarding ranging signals, achieving both high satellite-to-ground time synchronization performance and accurate ionospheric total electron count. Simultaneously, utilizing the ionospheric delay monitoring and time synchronization system and method, a satellite navigation system is also provided. The ionospheric delay monitoring and time synchronization system, satellite navigation system, and related methods provided in the embodiments of the present application have the following features:

[0299] 1. This application can independently obtain the total ionospheric electron count on the ranging signal path without the need for ionospheric electron count data provided by a third party. At the same time, it can also provide ionospheric electron count data to other users for use;

[0300] 2. Compared with the two-way pseudorange measurement method, this method does not require coarse satellite-ground synchronization, which reduces system requirements;

[0301] 3. Compared with the two-way pseudorange measurement method, this method completely overcomes the influence of atmospheric delay, including tropospheric delay and ionospheric delay, thereby achieving higher satellite-ground time synchronization accuracy, reaching sub-nanosecond level;

[0302] 4. Compared with the existing two-way pseudo-range measurement method, the present invention can reduce the complexity of satellite payloads and the cost of satellites.

[0303] 5. Because the user station only needs to receive signals from one satellite, it can use a directional antenna to reduce multipath effects and achieve better ranging accuracy;

[0304] 6. This method not only overcomes the influence of atmospheric delay, but also overcomes the influence of multipath effect and the influence of the near-end and far-end environmental segments between the satellite and the user station.

[0305] 7. This application can obtain accurate satellite-to-ground distance, providing support for subsequent satellite orbit determination and user positioning.

[0306] 8. The satellite navigation system of this application requires time synchronization before user positioning, which is significantly different from existing satellite navigation systems and has the advantages of low investment and high efficiency.

[0307] The above are only preferred embodiments of the present application and do not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. An ionospheric delay monitoring and time synchronization system, characterized in that: comprising a first device and a second device in communication with each other, and a computing device in communication with each of the first device and the second device; There are m pseudo-range measurement signals and h forwarded ranging signals between the first device and the second device, and the pseudo-range measurement signals and the forwarded ranging signals have at least three different carrier frequencies; Wherein, m+h≥3, m and h are both positive integers greater than or equal to 1; The pseudorange 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, and the second device or the first device measures the received m pseudorange measurement signals to obtain m pseudorange measurement values; The forward ranging signal is composed of an uplink signal and a downlink signal. The second device broadcasts the uplink signal and receives the downlink signal. The first device receives the uplink signal and forwards it to form the downlink signal. The second device measures h received downlink signals to obtain h forward ranging values. The computing device receives the pseudorange measurement value and the forwarding ranging value, determines a total number of ionospheric electrons on a ranging signal path using at least two pseudorange measurement values ​​or at least two forwarding ranging values, and determines a clock difference between the first device and the second device using the total number of ionospheric electrons, any forwarding ranging value, and any pseudorange measurement value; or determines a total number of ionospheric electrons on a ranging signal path between the first device and the second device and a clock difference between the first device and the second device using at least two forwarding ranging values ​​and at least one pseudorange measurement value or using at least one forwarding ranging value and at least two pseudorange measurement values; wherein, when determining the total number of ionospheric electrons and the clock difference, a sum of the forwarding ranging values ​​and the pseudorange ranging values ​​is greater than or equal to 3.

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

3. The ionospheric delay monitoring and time synchronization system according to claim 1, characterized in that: The carrier frequency of the forwarded ranging signal and the carrier frequency of the pseudo-ranging signal are frequency-hopped according to a preset frequency hopping pattern on the time axis.

4. The ionospheric delay monitoring and time synchronization system according to claim 1, characterized in that: The first device includes a first time-frequency device, a repeater, and a pseudorange generating device, and the second device includes a second time-frequency device, a repeater ranging device, and a second pseudorange ranging device; The first time-frequency device is used to provide a time-frequency signal to the repeater and the pseudorange generating device; The repeater is 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 pseudorange generating device is communicatively connected to the repeater, and the pseudorange generating device is used to generate and broadcast the pseudorange ranging signal; The second time-frequency device is used to provide a time-frequency signal to the forwarding ranging device and the second pseudo-range ranging device; The second pseudorange measuring device is used to receive the pseudorange measuring signal and process it to obtain a pseudorange measuring value; The forwarding ranging device is used to generate and broadcast the uplink signal, receive the downlink signal, and determine a forwarding ranging value based on the forwarding ranging signal; The first time-frequency device, the repeater and the pseudo-range generating device are integrated or separately arranged, and / or the second time-frequency device, the repeater ranging device and the second pseudo-range ranging device are integrated or separately arranged; or, The first device includes a first time-frequency device, a repeater, and a first pseudo-range ranging device, and the second device includes a second time-frequency device and a repeater ranging device; The first time-frequency device is used to provide a time-frequency signal to the repeater and the first pseudo-range measuring device; The repeater is 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 pseudorange ranging device is communicatively connected to the repeater, and is configured to receive and measure the pseudorange ranging signal; The second time-frequency device is used to provide a time-frequency signal 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 based on the forwarding ranging signal, wherein a portion of the uplink signal broadcast by the forwarding ranging device serves as the pseudorange ranging signal; The first time-frequency device, the repeater and the first pseudo-range measuring device are integrated or separately arranged, and / or the second time-frequency device and the repeater ranging device are integrated or separately arranged.

5. The ionospheric delay monitoring and time synchronization system according to claim 4, characterized in that: The second pseudo-range measuring device and the repeater ranging device are set to a zero baseline; the first pseudo-range measuring device or the pseudo-range generating device and the repeater are set to a zero baseline.

6. The ionospheric delay monitoring and time synchronization system according to claim 4, characterized in that: The first device uses at least one of the first time-frequency devices, and the second device uses at least one of the second time-frequency devices.

7. The ionospheric delay monitoring and time synchronization system according to claim 1, characterized in that: The computing device is provided in the first device or in the second device, or exists independently; When the computing device is provided on the first device or the second device, the first device performs data transmission with the second device using an additional communication signal; or When the computing device is independently provided, the computing device communicates with the first device and the second device.

8. The ionospheric delay monitoring and time synchronization system according to claim 4, characterized in that: The repeater has a forwarding delay, and the pseudorange generating device has a transmission delay; the first pseudorange ranging device and the second pseudorange ranging device both have a receiving delay, and the forwarding ranging device has a transmission delay and a receiving delay; The computing device obtains the forwarding delay of the repeater, the transmission delay of the pseudorange generating device, the reception delay of the first pseudorange ranging device and the second pseudorange ranging device, and the transmission delay and reception delay of the forwarding ranging device.

9. A method for determining a pseudorange measurement value, characterized in that: The ionospheric delay monitoring and time synchronization system according to any one of claims 1 to 8 is applied thereto, wherein the method is performed by a first device and comprises: receiving m-path pseudo-range measurement signals broadcast by a second device; Synchronously measure each pseudorange ranging signal to obtain m pseudorange ranging values; Wherein, m is a positive integer.

10. A method for determining a distance measurement value, characterized in that: The ionospheric delay monitoring and time synchronization system according to any one of claims 1 to 8 is applied, wherein the method is performed by a second device, and the method includes: When the pseudorange measurement signal is broadcast by the first device, broadcast at least one uplink signal to the first device; Acquire at least one downlink signal forwarded by the first device based on the at least one uplink signal, wherein the at least one uplink signal and the at least one downlink signal constitute an h-path forwarding ranging signal; Acquire m-path pseudo-range measurement signals broadcast by the first device; Synchronously measuring each of the pseudorange ranging signals and each of the forwarded ranging signals to obtain m pseudorange ranging values ​​and h forwarded ranging values; or, When the pseudorange measurement signal is broadcast by the second device and received by the first device, broadcast at least one uplink signal to the first device; Acquire at least one downlink signal forwarded by the first device based on the at least one uplink signal, wherein the at least one uplink signal and the at least one downlink signal constitute an h-path forwarding ranging signal; Synchronously measuring each of the forwarding ranging signals to obtain h forwarding ranging values; Wherein, m+h≥3, and m and h are both positive integers.

11. A method for ionospheric delay monitoring and time synchronization, characterized in that: The ionospheric delay monitoring and time synchronization system according to any one of claims 1 to 8 is applied thereto, wherein the method is executed by a computing device, and the method comprises: When the pseudorange ranging signal is broadcast by the second device and received by the first device, obtain m pseudorange ranging values ​​measured by the first device based on a communication result with the first device, and obtain h forwarded ranging values ​​measured by the second device based on a communication result with the second device; When the pseudorange ranging signal is broadcast by the first device and received by the second device, obtaining m pseudorange ranging values ​​and h forwarded ranging values ​​measured by the second device based on a communication result with the second device; where m+h≥3, and m and h are both positive integers; Respectively using a pseudorange measurement expression to represent each of the pseudorange measurement values ​​and using a forwarding ranging expression to represent each of the forwarding ranging values; Determine a total number of ionospheric electrons on a ranging signal path using pseudorange ranging values ​​represented by at least two pseudorange ranging expressions or forward ranging values ​​represented by at least two forward ranging expressions, and determine a clock difference between the first device and the second device using the total number of ionospheric electrons, any forward ranging value, and any pseudorange ranging value; Alternatively, the total number of ionospheric electrons on the ranging signal path between the first device and the second device and the clock difference between the first device and the second device are determined using forwarding ranging values ​​represented by at least two forwarding ranging expressions and a pseudorange ranging value represented by at least one pseudorange ranging expression, or using a forwarding ranging value represented by at least one forwarding ranging expression and a pseudorange ranging value represented by at least two pseudorange ranging expressions.

12. The ionospheric delay monitoring and time synchronization method according to claim 11, characterized in that: Respectively using a pseudorange ranging expression to represent each of the pseudorange ranging values ​​and using a forward ranging expression to represent each of the forward ranging values, including: The pseudorange measurement value numbered i is represented by the pseudorange measurement expression shown in the following formula (z1): z,i (n) = R true,z,i (n)+I z,i (n)+T duiliu,z,i (n)±c·(δt z (n)-δt s (n))+X z,i (n)±sagnac zz (n)(z1); Wherein, i=1, 2, ..., m, i is a positive integer; The forwarding ranging expression shown in the following formula (z2) represents the forwarding ranging value numbered j: L z,j (n) = R true,zu,j (n)+R true,zd,j (n)+I zu,j (n)+I zd,j (n)+T duiliu,zu,j (n)+T duiliu,zd,j (n)+Y z,j (n)(z2); Wherein, j=1, 2, ..., h, j is a positive integer; Where: ρ z,i (n) represents the pseudo-range value of the number i at the nth moment, in meters; R true,z,i (n) represents the real space distance that the pseudo-range measurement signal numbered i has traveled at the nth moment, in meters; I z,i (n) represents the ionospheric delay of the pseudorange ranging signal numbered i at time n, in meters; T duiliu,z,i (n) represents the tropospheric delay of the pseudorange ranging signal numbered i at time n, in meters; X z,i (n) represents the hardware device delay of the pseudo-range measurement signal numbered i at the nth moment, in meters. The hardware device delay of the pseudo-range measurement signal includes the transmission delay of the pseudo-range measurement signal numbered i and the reception delay of the pseudo-range measurement signal numbered i; c represents the speed of light, in meters per second; δt s (n) represents the clock difference between the first device and the system time at time n, in seconds; δt z (n) represents the clock difference between the second device and the system time at time n, in seconds; sagnac zz (n) represents the Sagnac effect delay of the pseudorange measurement signal at time n, in meters; L z,j (n) represents the forwarding ranging value of j at the nth moment, in meters; R true,zu,j (n) represents the real spatial distance traveled by the uplink signal of the forwarding ranging signal numbered j at the nth moment, in meters; R true,zd,j (n) represents the real spatial distance traveled by the downlink signal of the forwarding ranging signal numbered j at the nth moment, in meters; zu,j (n) represents the ionospheric delay of the uplink signal of the forwarding ranging signal numbered j at time n, in meters; I zd,j (n) represents the ionospheric delay of the downlink signal of the forwarding ranging signal numbered j at time n, in meters; T duiliu,zu,j (n) represents the tropospheric delay of the uplink signal of the forwarding ranging signal numbered j at time n, in meters; T duiliu,zd,j (n) represents the tropospheric delay of the downlink signal of the forwarding ranging signal numbered j at time n, in meters; Y z,j (n) represents the hardware device delay of the forwarding ranging signal numbered j at the nth moment, in meters. The hardware device delay of the forwarding ranging signal includes the transmission delay of the uplink signal of the forwarding ranging signal numbered j, the forwarding delay of the downlink signal of the forwarding ranging signal numbered j, and the reception delay of the downlink signal of the forwarding ranging signal numbered j.

13. The ionospheric delay monitoring and time synchronization method according to claim 11, characterized in that: After respectively using a pseudorange ranging expression to represent each of the pseudorange ranging values ​​and using a forward ranging expression to represent each of the forward ranging values, the method further includes: Correcting the m pseudorange measurement values ​​and the h forwarding ranging values ​​to obtain m corrected pseudorange measurement values ​​and h corrected forwarding ranging values; Accordingly, determining the total number of ionospheric electrons on the ranging signal path using the pseudorange ranging values ​​represented by at least two pseudorange ranging expressions or the forward ranging values ​​represented by at least two forward ranging expressions, and determining the clock difference between the first device and the second device using the total number of ionospheric electrons, any forward ranging value, and any pseudorange ranging value includes: determining a total ionospheric electron number on a ranging signal path using at least two of the corrected pseudorange ranging values ​​or at least two of the corrected forward ranging values, and determining a clock difference between the first device and the second device using the total ionospheric electron number, any one of the corrected forward ranging values, and any one of the corrected pseudorange ranging values; The determining, using the forwarding ranging values ​​represented by at least two forwarding ranging expressions and the pseudorange ranging value represented by at least one pseudorange ranging expression, or using the forwarding ranging value represented by at least one forwarding ranging expression and the pseudorange ranging values ​​represented by at least two pseudorange ranging expressions, of the total number of ionospheric electrons on the ranging signal path between the first device and the second device and the clock difference between the first device and the second device, includes: Determine a total number of ionospheric electrons on a ranging signal path between the first device and the second device and a clock difference between the first device and the second device using at least two of the corrected forwarded ranging values ​​and at least one of the corrected pseudorange ranging values ​​or using at least one of the corrected forwarded ranging value and at least two of the corrected pseudorange ranging values; The sum of the corrected pseudorange values ​​and the corrected forward ranging values ​​is greater than or equal to 3.

14. The ionospheric delay monitoring and time synchronization method according to claim 13, characterized in that: The respectively correcting the m pseudorange ranging values ​​and the h forwarding ranging values ​​to obtain m corrected pseudorange ranging values ​​and h corrected forwarding ranging values ​​includes: The pseudorange measurement value numbered i represented by the pseudorange measurement expression shown in the following formula (z1) is corrected to obtain the corrected pseudorange measurement value numbered i shown in the following formula (z1'): ρ z,i (n)=R true,z,i (n)+I z,i (n)+T duiliu,z,i (n)±c·(δt z (n)-δt s (n))+X z,i (n)±sagnac zz (n)(z1); Wherein, i=1, 2, ..., m, i is a positive integer; The forwarding ranging value numbered j represented by the forwarding ranging expression shown in the following formula (z2) is corrected to obtain the corrected forwarding ranging value numbered j shown in the following formula (z2'): L z,j (n)=R true,zu,j (n)+R true,zd,j (n)+I zu,j (n)+I zd,j (n)+T duiliu,zu,j (n)+T duiliu,zd,j (n)+Y z,j (n)(z2); Wherein, j=1, 2, ..., h, j is a positive integer; Where: ρ z,i,a (n) represents the corrected pseudorange value of the number i at the nth moment, in meters; ρ z,i (n) represents the pseudo-range value of the number i at the nth moment, in meters; R true,z,i (n) represents the real space distance that the pseudo-range measurement signal numbered i has traveled at the nth moment, in meters; I z,i (n) represents the ionospheric delay of the pseudorange ranging signal numbered i at time n, in meters; T duiliu,z,i (n) represents the tropospheric delay of the pseudorange ranging signal numbered i at time n, in meters; X z,i (n) represents the hardware device delay of the pseudo-range measurement signal numbered i at the nth moment, in meters. The hardware device delay of the pseudo-range measurement signal includes the transmission delay of the pseudo-range measurement signal numbered i and the reception delay of the pseudo-range measurement signal numbered i; c represents the speed of light, in meters per second; δt s (n) represents the clock difference between the first device and the system time at time n, in seconds; δt z (n) represents the clock difference between the second device and the system time at time n, in seconds; sagnac zz (n) represents the Sagnac effect delay of the pseudorange measurement signal at time n, in meters; L z,j,a (n) represents the corrected forwarding ranging value of the number j at the nth moment, in meters; L z,j (n) represents the forwarding ranging value of j at the nth moment, in meters; R true,zu,j (n) represents the real spatial distance traveled by the uplink signal of the forwarding ranging signal numbered j at the nth moment, in meters; R true,zd,j (n) represents the real spatial distance traveled by the downlink signal of the forwarding ranging signal numbered j at the nth moment, in meters; zu,j (n) represents the ionospheric delay of the uplink signal of the forwarding ranging signal numbered j at time n, in meters; I zd,j (n) represents the ionospheric delay of the downlink signal of the forwarding ranging signal numbered j at time n, in meters; T duiliu,zu,j (n) represents the tropospheric delay of the uplink signal of the forwarding ranging signal numbered j at time n, in meters; T duiliu,zd,j (n) represents the tropospheric delay of the downlink signal of the forwarding ranging signal numbered j at time n, in meters; Y z,j (n) represents the hardware device delay of the forwarding ranging signal numbered j at the nth moment, in meters. The hardware device delay of the forwarding ranging signal includes the transmission delay of the uplink signal of the forwarding ranging signal numbered j, the forwarding delay of the downlink signal of the forwarding ranging signal numbered j, and the reception delay of the downlink signal of the forwarding ranging signal numbered j.

15. The ionospheric delay monitoring and time synchronization method according to claim 13, characterized in that: The determining the clock difference between the first device and the second device by using the total number of ionospheric electrons, any one of the corrected forward ranging values, and any one of the corrected pseudorange ranging values ​​includes: Using the zero baseline setting relationship between the forwarding ranging device and the second pseudorange ranging device, or using the zero baseline setting relationship between the forwarder and the first pseudorange ranging device, based on the total number of ionospheric electrons, any one of the corrected pseudorange ranging values, and any one of the corrected forwarding ranging values, a clock difference between the first device and the second device is obtained as shown in formula (z3): Alternatively, averaging multiple clock differences between the first device and the second device determined based on the total number of ionospheric electrons, multiple corrected pseudorange ranging values, and multiple corrected forward ranging values ​​to obtain an averaged clock difference between the first device and the second device; Where: ρ z,i,a (n) represents the corrected pseudorange value of the number i at the nth moment, in meters; L z,j,a (n) represents the corrected forwarding distance value of the number j at the nth moment, in meters; c represents the speed of light, in meters per second; δt s (n) represents the clock difference between the first device and the system time at time n, in seconds; δt z (n) represents the clock difference between the second device and the system time at time n, in seconds; Q ion represents the ionospheric delay coefficient, TEC(n) represents the total number of ionospheric electrons on the ranging signal path between the first device and the second device at time n, unit: electrons / square meter; f z,i (n) represents the carrier frequency of the pseudo-range measurement signal numbered i at the nth moment, in Hertz; f zu,j (n), f zd,j (n) represents the carrier frequency of the uplink signal and the downlink signal of the forwarded ranging signal numbered j at the nth moment, respectively, in Hertz.

16. The ionospheric delay monitoring and time synchronization method according to claim 13, characterized in that: The determining, using at least two of the corrected forwarded ranging values ​​and at least one of the corrected pseudorange ranging values ​​or using at least one of the corrected forwarded ranging values ​​and at least two of the corrected pseudorange ranging values, of a total number of ionospheric electrons on a ranging signal path between the first device and the second device and a clock difference between the first device and the second device, comprises: When there are at least two corrected pseudorange values ​​and at least one corrected forward ranging value, select ɑ from the m corrected pseudorange values ​​and select β from the h corrected forward ranging values, where 2≤ɑ≤m, 1≤β≤h; Subtract the α corrected pseudorange values ​​shown in formula (z1') and the β corrected forward ranging values ​​shown in formula (z2') from each other to obtain the difference formula shown in formula (z10): Where: i = 1, 2, ..., ɑ, i and ɑ are positive integers; j = 1, 2, ..., β, j and β are positive integers; According to formula (z10) and the zero baseline setting relationship between the forwarding ranging device and the second pseudo-range ranging device, or using the zero baseline setting relationship between the forwarder and the first pseudo-range ranging device, the matrix equation shown in formula (z18) is obtained: Solving the matrix equation (z18) yields the total number of ionospheric electrons on the ranging signal path between the first device and the second device and the clock difference between the first device and the second device, as shown in the following formula (z19): Among them: G z It is a (ɑ·β)×2 matrix with all 1s in the first column; b z is a (ɑ·β)×1 matrix; When the corrected pseudorange measurement value is at least one and the corrected forward ranging values ​​are at least two, selecting λ from the m corrected pseudorange measurement values ​​and selecting θ from the h corrected forward ranging values, where 1≤λ≤m, 2≤θ≤h; Subtract the λ corrected pseudorange values ​​from the θ corrected forwarded range values ​​to obtain the difference formula shown in the following formula (u10): Where: i = 1, 2, ..., λ, j = 1, 2, ..., θ, i, λ, j, θ are all positive integers; According to formula (u10) and the zero baseline setting relationship between the forwarding ranging device and the second pseudo-range ranging device, or the zero baseline setting relationship between the forwarder and the first pseudo-range ranging device, the matrix equation shown in formula (u18) is obtained: Solving the matrix equation (u18) yields the total number of ionospheric electrons on the ranging signal path between the first device and the second device and the clock difference between the first device and the second device, as shown in the following formula (u19): Among them: G u is a (λ·θ)×2 matrix with the first column all 1; b u is a (λ·θ)×1 matrix; Where: ρ z,i,a (n) represents the corrected pseudorange value of the number i at the nth moment, in meters; ρ z,i (n) represents the pseudo-range value of the number i at the nth moment, in meters; R true,z,i (n) represents the real space distance that the pseudo-range measurement signal numbered i has traveled at the nth moment, in meters; I z,i (n) represents the ionospheric delay of the pseudorange ranging signal numbered i at time n, in meters; T duiliu,z,i (n) represents the tropospheric delay of the pseudorange ranging signal numbered i at time n, in meters; X z,i (n) represents the hardware device delay of the pseudo-range measurement signal numbered i at the nth moment, in meters. The hardware device delay of the pseudo-range measurement signal includes the transmission delay of the pseudo-range measurement signal numbered i and the reception delay of the pseudo-range measurement signal numbered i; c represents the speed of light, in meters per second; δt s (n) represents the clock difference between the first device and the system time at time n, in seconds; δt z (n) represents the clock difference between the second device and the system time at time n, in seconds; sagnac zz (n) represents the Sagnac effect delay of the pseudorange measurement signal at time n, in meters; L z,j,a (n) represents the corrected forwarding ranging value of the number j at the nth moment, in meters; L z,j (n) represents the forwarding ranging value of j at the nth moment, in meters; R true,zu,j (n) represents the real spatial distance traveled by the uplink signal of the forwarding ranging signal numbered j at the nth moment, in meters; R true,zd,j (n) represents the real spatial distance traveled by the downlink signal of the forwarding ranging signal numbered j at the nth moment, in meters; zu,j (n) represents the ionospheric delay of the uplink signal of the forwarding ranging signal numbered j at time n, in meters; I zd,j (n) represents the ionospheric delay of the downlink signal of the forwarding ranging signal numbered j at time n, in meters; T duiliu,zu,j (n) represents the tropospheric delay of the uplink signal of the forwarding ranging signal numbered j at time n, in meters; T duiliu,zd,j (n) represents the tropospheric delay of the downlink signal of the forwarding ranging signal numbered j at time n, in meters; Y z,j (n) represents the hardware device delay of the ranging signal forwarding numbered j at the nth moment, in meters. The hardware device delay of the ranging signal forwarding numbered j includes the transmission delay of the uplink signal of the ranging signal forwarding numbered j, the forwarding delay of the downlink signal of the ranging signal forwarding numbered j, and the reception delay of the downlink signal of the ranging signal forwarding numbered j; Q ion represents the ionospheric delay coefficient, TEC(n) represents the total number of ionospheric electrons on the ranging signal path between the first device and the second device at time n, unit: electrons / square meter; f z,1 (n), f z,2 (n), f z,α (n), f z,λ (n) represents the carrier frequency of the pseudo-range measurement signal numbered 1, 2, α, and λ at the nth moment, in Hertz; f zu,1 (n), f zu,2 (n), f zu,β (n), f zu,θ (n) represents the carrier frequency of the uplink signal of the forwarded ranging signal numbered 1, 2, β, and θ at the nth moment, in Hertz; f zd,1 (n), f zd,2 (n), f zd,β (n), f zd,θ (n) represents the carrier frequency of the downlink signal of the forwarded ranging signal numbered 1, 2, β, and θ at the n-th moment, respectively, in Hertz.

17. The ionospheric delay monitoring and time synchronization method according to claim 11, characterized in that: After determining the clock difference between the first device and the second device, the method further includes: 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, thereby achieving 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 own clock difference relative to the system time based on the clock difference between the first device and the second device; When the clock difference of the second device relative to the system time is known, the first device determines its own clock difference relative to the system time based on the clock difference between the first device and the second device.

18. A method for determining the distance between satellite and earth, characterized in that: The ionospheric delay monitoring and time synchronization system according to any one of claims 1 to 8 is applied thereto, wherein the method is executed by a computing device, and the method comprises: Determine, based on a total number of ionospheric electrons on a ranging signal path between the first device and the second device, a preset ionospheric delay coefficient, a carrier frequency of at least one forwarded ranging signal, and a carrier frequency of at least one pseudorange ranging signal, an ionospheric delay of the at least one forwarded ranging signal and an ionospheric delay of the at least one pseudorange ranging signal; Determine the sum of the satellite-to-ground space distance and the tropospheric time delay between the first device and the second device based on the ionospheric time delay of at least one forwarded ranging signal and the forwarded ranging value of the corresponding forwarded ranging signal; or determine the sum of the satellite-to-ground space distance and the tropospheric time delay between the first device and the second device based on the ionospheric time delay of at least one pseudorange ranging signal, the pseudorange ranging value of the corresponding pseudorange ranging signal, and the clock difference between the first device and the second device; determining, based on a preset tropospheric model, a tropospheric delay on a ranging signal path between the first device and the second device; Determine the satellite-to-ground distance between the first device and the second device based on the sum of the satellite-to-ground distance and the tropospheric delay between the first device and the second device, and the tropospheric delay on the ranging signal path between the first device and the second device; The total number of ionospheric electrons, the pseudorange measurement value and the forwarding ranging value are determined according to the ionospheric delay monitoring and time synchronization method according to any one of claims 11 to 17.

19. The method for determining the satellite-to-ground distance according to claim 18, wherein: The determining the sum of the satellite-to-ground space distance and the tropospheric delay between the first device and the second device based on the ionospheric delay of at least one forwarding ranging signal and the forwarding ranging value of the corresponding forwarding ranging signal includes: The sum of the satellite-to-ground space distance and the tropospheric delay between the first device and the second device as shown in the following formula (z14) is obtained using the corrected forwarding ranging value numbered j as shown in the following formula (z2'): Wherein, j=1, 2, ..., h, j is a positive integer; Alternatively, averaging the sum of the satellite-to-ground space distance and the tropospheric delay between the first device and the second device, determined based on the multiple corrected forward ranging values; and obtaining the average sum of the satellite-to-ground space distance and the tropospheric delay between the first device and the second device. The determining, based on the ionospheric delay of at least one pseudorange ranging signal, the pseudorange ranging value corresponding to the pseudorange ranging signal, and the clock difference between the first device and the second device, a sum of the satellite-to-ground space distance and the tropospheric delay between the first device and the second device, includes: The sum of the satellite-to-ground space distance and the tropospheric delay between the first device and the second device is obtained by using the corrected pseudorange measurement value numbered i as shown in the following formula (z1′): Wherein, i=1, 2, ..., m, i is a positive integer; Alternatively, the sum of the satellite-to-ground space distances and the tropospheric time delays between the plurality of first devices and the second device determined based on the plurality of corrected pseudorange measurement values ​​is averaged to obtain the sum of the satellite-to-ground space distances and the tropospheric time delays between the first device and the second device; Where: ρ z,i,a (n) represents the corrected pseudorange value of the number i at the nth moment, in meters; ρ z,i (n) represents the pseudo-range value of the number i at the nth moment, in meters; R true,z,i (n) represents the real space distance that the pseudo-range measurement signal numbered i has traveled at the nth moment, in meters; I z,i (n) represents the ionospheric delay of the pseudorange ranging signal numbered i at time n, in meters; T duiliu,z,i (n) represents the tropospheric delay of the pseudorange ranging signal numbered i at time n, in meters; X z,i (n) represents the hardware device delay of the pseudo-range measurement signal numbered i at the nth moment, in meters. The hardware device delay of the pseudo-range measurement signal includes the transmission delay of the pseudo-range measurement signal numbered i and the reception delay of the pseudo-range measurement signal numbered i; c represents the speed of light, in meters per second; δt s (n) represents the clock difference between the first device and the system time at time n, in seconds; δt z (n) represents the clock difference between the second device and the system time at time n, in seconds; sagnac zz (n) represents the Sagnac effect delay of the pseudorange measurement signal at time n, in meters; L z,j,a (n) represents the corrected forwarding ranging value of the number j at the nth moment, in meters; L z,j (n) represents the forwarding ranging value of j at the nth moment, in meters; R true,zu,j (n) represents the real spatial distance traveled by the uplink signal of the forwarding ranging signal numbered j at the nth moment, in meters; R true,zd,j (n) represents the real spatial distance traveled by the downlink signal of the forwarding ranging signal numbered j at the nth moment, in meters; zu,j (n) represents the ionospheric delay of the uplink signal of the forwarding ranging signal numbered j at time n, in meters; I zd,j (n) represents the ionospheric delay of the downlink signal of the forwarding ranging signal numbered j at time n, in meters; T duiliu,zu,j (n) represents the tropospheric delay of the uplink signal of the forwarding ranging signal numbered j at time n, in meters; T duiliu,zd,j (n) represents the tropospheric delay of the downlink signal of the forwarding ranging signal numbered j at time n, in meters; Y z,j (n) represents the hardware device delay of the forwarding ranging signal numbered j at the nth moment, in meters. The hardware device delay of the forwarding ranging signal includes the transmission delay of the uplink signal of the forwarding ranging signal numbered j, the forwarding delay of the downlink signal of the forwarding ranging signal numbered j, and the reception delay of the downlink signal of the forwarding ranging signal numbered j.

20. A satellite navigation system, characterized in that: include: The ionospheric delay monitoring and time synchronization system according to any one of claims 1 to 8, wherein the first device is a satellite, the second device is a user station, and the number of the satellites is greater than or equal to 2; a plurality of third devices, each of which is communicatively connected to the satellite; The user station obtains the orbital parameters of the corresponding satellite based on the data transmission results with each satellite, and determines the coordinate information of the user station based on the orbital parameters of each satellite and the space distance between the user station and the satellite; Part of the third device constitutes a satellite orbit determination system for performing orbit monitoring and processing on the satellite to obtain satellite orbit parameters; Part of the third devices constitutes a satellite-ground time synchronization system for performing time monitoring on each of the satellites.

21. The satellite navigation system according to claim 20, wherein: The signal structure between the third device in the satellite-to-ground time synchronization system and the satellite is the same as the signal structure in the ionospheric delay monitoring and time synchronization system.

22. An inter-station time synchronization system, characterized in that: include: The satellite navigation system according to claim 20 or 21; When there are at least two user stations, the at least two user stations achieve time synchronization with each other by exchanging data through communication.

23. An inter-station time synchronization system, characterized in that: include: The ionospheric delay monitoring and time synchronization system according to any one of claims 1 to 8; When there are at least two first devices or at least two second devices, the at least two first devices or the at least two second devices achieve time synchronization with each other by exchanging data through communication.

24. A satellite positioning method, characterized in that: Applied to the satellite navigation system of claim 20 or 21, the method is performed by a user station, and the method comprises: Get the orbital parameters of each satellite; Determining coordinate information of a corresponding satellite based on the orbital parameters; Determine the satellite-to-ground distance between the user station and each satellite according to the satellite-to-ground distance determination method according to any one of claims 18-19; The coordinate information of the user station is determined based on the orbital parameters of each satellite and the space-to-ground distance between the user station and each satellite.

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