Ionized layer time delay monitoring and time synchronization system, method and application

Abstract

The invention discloses an ionosphere time delay monitoring and time synchronization system, method and application, and relates to the technical field of space. The method comprises the following steps: a second device broadcasts at least one path of uplink signal to a first device, and the first device forwards at least two paths of downlink signals based on the at least one path of uplink signal; the second equipment acquires at least one path of pseudo-range ranging signal broadcasted by the first equipment, and synchronously measures to obtain at least one pseudo-range ranging value and at least two forwarding ranging values; representing a pseudo-range ranging value by using a pseudo-range ranging expression and representing a forwarding ranging value by using a forwarding ranging expression; and based on the pseudo-range ranging value represented by the pseudo-range ranging expression and the forwarding ranging value represented by the forwarding ranging expression, determining the total electron number of the ionized layer on the ranging signal path between the first device and the second device, determining the clock difference between the first device and the second device, and determining the spatial distance value between the first device and the second device.

Description

[0001] Cross-references

[0002] This disclosure claims the application number 202411068715.0 filed on August 6, 2024 and entitled "AN IONOSPHERE 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 system (Global Navigation Satellite Sytem) is the current mainstream satellite navigation system. Internationally, there are China's Beidou system, the United States' GPS system, Europe's Galileo system, and Russia's Glonass system. The satellite navigation system is a very large and complex system, involving three major parts: operation and control, satellites, and users. It involves the satellite-ground time synchronization between the operation and control station and the satellite, the time synchronization between the operation and control stations, satellite orbit determination technology, and user positioning and timing applications. The operation and control part monitors the satellite atomic clock time to ensure that the satellite time is accurate and reliable. At the same time, it also determines the satellite orbit and provides ephemeris for users to use; the satellite part is the carrier that directly provides services to users, broadcasting three pseudo-range signals, which contain satellite ephemeris messages; users obtain pseudo-range values ​​by measuring pseudo-range ranging signals, and realize user positioning and timing based on pseudo-range values ​​and satellite ephemeris.

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

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

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

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

[0009] All of the above methods require satellites or ground receivers to receive signals and perform measurements. When the signals are transmitted between the satellite and the ground, for the receiver, the ionosphere and troposphere of the atmosphere at the far end are affected, and the multipath effect and electromagnetic environment at the near end are affected. The far end and the near end are collectively referred to as environmental segment effects. Among them, the atmospheric tropospheric delay has the same delay for RF signals of different carrier frequencies, which can be estimated using a model, while the atmospheric ionospheric delay changes with the change of carrier frequency. It is a very common error influencing factor, which is comprehensive and basic, and is 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 contents are only used to assist in understanding the technical solution of the present application and do not constitute an admission that the above contents are prior art. Summary of the invention

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

[0012] To achieve the above-mentioned purpose, the present application provides an ionospheric delay monitoring and time synchronization system, comprising a first device and a second device connected in communication, and a computing device connected in communication with the first device and the second device respectively; there are m pseudo-range ranging signals and h forwarding ranging signals between the first device and the second device, and the pseudo-range ranging signal and the forwarding ranging signal have at least three different carrier frequencies; wherein m+h≥3, m, h are both positive integers greater than or equal to 1; and the pseudo-range ranging signal and the forwarding ranging signal have at least three different carrier frequencies; wherein the pseudo-range ranging signal is broadcast by the first device and received by the second device, or broadcast by the second device and received by the first device; the forwarding ranging signal is composed of an uplink signal and a downlink signal, the second device broadcasts the uplink signal, 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 method for determining a pseudorange measurement value, 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 measurement signals broadcast by a second device; synchronously measuring each pseudorange measurement signal to obtain m pseudorange measurement 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 executed by a second device, and the method includes: when the pseudo-range ranging signal is broadcast by the first device, broadcasting at least one uplink signal to the first device; obtaining at least one downlink signal forwarded by the first device based on the at least one uplink signal, wherein the at least one uplink signal and the at least one downlink signal constitute an h-path forwarding ranging signal; obtaining m-path pseudo-range ranging signals broadcast by the first device. ; 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, and the method includes: when the pseudorange ranging signal is broadcast by the second device and received by the first device, m pseudorange ranging values ​​measured by the first device are obtained based on the communication result with the first device, and h forwarding ranging values ​​measured by the second device are obtained 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, h forwarding ranging values ​​and m pseudorange ranging values ​​measured by the second device are obtained based on the communication result with the second device; wherein m+h≥3, and m and h are both positive integers; each of the pseudorange ranging values ​​is represented by a pseudorange ranging expression and each of the forwarding ranging values ​​is represented by a forwarding ranging expression; based on the m pseudorange ranging values ​​and the h forwarding ranging values, 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.

[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 forwarding ranging signal, and the carrier frequency of at least one pseudo-range ranging signal, respectively determine the ionospheric delay of the at least one forwarding ranging signal and the ionospheric delay of the at least one pseudo-range 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 forwarding ranging signal and the corresponding forwarding ranging signal, the ionospheric delay of the at least one pseudo-range ranging signal is determined. The method comprises the following steps: determining the sum of the satellite-to-earth 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-earth 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; determining the satellite-to-earth space distance between the first device and the second device based on the sum of the satellite-to-earth 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 connected to the satellite communication; wherein the user station obtains the orbital parameters of the corresponding satellite based on the data transmission results with each satellite, and determines the coordinate information of the user station based on the orbital parameters of each satellite and the space distance between the user station and the satellite; some of the third devices constitute a satellite orbit determination system, which is used to monitor and process the orbit of the satellite to obtain satellite orbit parameters; some of the third devices constitute a satellite-to-ground time synchronization system, which is used to monitor the time of each satellite.

[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 by exchanging data through communication.

[0019] In addition, to achieve the above-mentioned purpose, a time synchronization system between stations includes: the ionospheric delay monitoring and time synchronization system described in any embodiment of the present application; wherein, when the second device or the first device is at least two, at least two of the second devices or the first devices achieve time synchronization with each other by exchanging data through communication.

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

[0022] Figure 1It is a structural schematic diagram of an ionospheric delay monitoring and time synchronization system according to an implementation mode of the present application;

[0023] Figure 2 A structural block diagram of a satellite and a user station according to an implementation manner of the present application;

[0024] Figures 3 to 10 It is a schematic diagram of the composition of the forwarding ranging signal and the pseudo-ranging signal of the satellite and the user station according to other embodiments of the present application;

[0025] Fig.11 It is a flow chart of an ionospheric delay monitoring and time synchronization method according to an embodiment of the present application;

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

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

[0028] Fig.14 A flowchart of a method for time synchronization between stations according to an implementation of the present application;

[0029] Fig.15 This is a flowchart of a satellite positioning method according to an implementation mode of the present application;

[0030] Figure 16 to Figure 18 A schematic diagram of the structure 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 described 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 used to limit the present application.

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

[0034] ρ 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 pseudo-range measurement value and the second pseudo-range measurement value at the nth moment, in meters; R true,z,1 (n), R true,z,2(n) represents the real space distance that the first pseudo-range measurement signal and the second pseudo-range measurement signal have passed 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 the nth moment, 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 the nth moment, 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 the nth moment, in seconds; δt z (n) represents the clock difference between the second device and the system time at the nth moment, in seconds; sagnac zz (n) represents the Sagnac effect delay of the pseudo-range measurement signal at the nth moment, in meters;

[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, in meters; L z,1 (n), L z,2 (n) respectively represent 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 distances traveled by the uplink signals of the first forwarding ranging signal and the second forwarding ranging signal at the nth moment, in meters; R true,zd,1 (n), R true,zd,2 (n) represents the real spatial distances traveled by the downlink signals of the first forwarding ranging signal and the second forwarding ranging signal at the nth moment, in meters; zu,1 (n), I zu,1 (n) respectively represent 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 the nth moment, in meters; T duiliu,zu,1 (n), T duiliu,zu,2(n) represents the tropospheric delay of the uplink signal of the first forwarded ranging signal and the second forwarded ranging signal at the nth moment, 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 the nth moment, 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 the nth moment, 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 the nth moment, unit: electron / 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) respectively represent the carrier frequencies of the uplink signals 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) respectively represent the carrier frequencies of the downlink signals of the first forwarding ranging signal and the second forwarding ranging signal at the nth moment, in Hertz.

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

[0039] The present application creatively proposes an ionospheric delay monitoring and time synchronization system and method thereof that can obtain both the total number of ionospheric electrons and high-precision clock errors by organically integrating the forwarding ranging signal and the pseudo-range ranging signal.

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

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

[0042] The 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 range measurement value.

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

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

[0046] After the computing device obtains the pseudorange measurement value and the forwarding range measurement value, the method of the present application is executed 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 the present application is that the sum of the number of ways of forwarding ranging signals and pseudo-range 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, and the sum of their numbers is greater than or equal to 3. 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, and then describes the satellite navigation system.

[0051] In the present application, there are pseudo-range measurement signals and forwarding ranging signals between the first device and the second device, the sum of the number of pseudo-range measurement signals and the number of forwarding ranging signals is greater than or equal to 3, and the pseudo-range measurement signals and the forwarding 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 pseudo-range ranging signal is broadcast by the first device and received by the second device, or broadcast by the second device and received by the first device.

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

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

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

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

[0058] In addition, the pseudo-range measurement signal is measured by the second device or the first device, corresponding to two different types of systems. These two different types of systems have the same signal structure, system composition, and processing method except for the pseudo-range measurement signal transmission direction and pseudo-range measurement device. Therefore, for the sake of simplicity and clarity, the following only describes the case where the first device broadcasts the pseudo-range measurement signal.

[0059] When the first device broadcasts a pseudorange ranging signal, the number of pseudorange ranging signals is set to m, the number of forwarding ranging signals is set to h, and m+h≥3. There are two simplest systems that meet this condition, which are respectively 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 and the carrier frequency of the pseudo-range ranging signal can be multiplexed or not.

[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, and then the clock difference between the first device and the second device, the satellite-to-earth space distance, etc. can be obtained by using the method provided in the present application.

[0062] The first simplest system adds one forwarding ranging signal, and the second system adds one pseudo-range ranging signal. The two simplest systems become systems with the same two pseudo-range ranging signals and two forwarding ranging signals. When the number of pseudo-range ranging signals and forwarding ranging signals of the two simplest systems is two, the two systems are exactly the same, and the corresponding calculation methods are also the same. Even more, when there are more pseudo-range ranging signals and forwarding ranging signals, they become one system.

[0063] In addition, in the first simplest system, the process of calculating the total number of ionosphere electrons using two pseudorange measurement values ​​has been introduced in the relevant technology, and the process of calculating the clock error and the satellite-to-earth space distance after obtaining the total number of ionosphere electrons is similar to the process of the second simplest system. Therefore, in order to explain the method provided by the present application more clearly and generally, the process of calculating the total number of ionosphere electrons for the first simplest system is no longer repeated in the present application, and only the second simplest system is used as an example for illustrative explanation, and 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, so as to illustrate the specific implementation of the method of the present 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, the least carrier frequency resources can be used to achieve time synchronization, which is cost-effective, so this case is used for illustration.

[0066] For the convenience of explanation, the uplink signals of the two-way forwarding ranging signals 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 lines are respectively referred to as the first downlink signal and the second downlink signal, the pseudorange ranging signal is referred to as the first pseudorange ranging signal, and an example is given in which the computing device is integrated into the second device. Because the computing device is integrated into the second device, that is, the computing device is a 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 explanation.

[0067] Figure 1 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, such as Figure 1 As shown, the system includes a first device 100 and a second device 200 which 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 the first pseudorange ranging signal to the second device 200; wherein the first uplink signal and the first downlink signal constitute a first forwarding ranging signal, and the second uplink signal and the second downlink signal constitute a second forwarding ranging signal; the second device 200 is used 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 forwarding ranging signal, the second forwarding ranging signal, and the first pseudorange ranging signal to obtain a first forwarding ranging value, a second forwarding ranging value, and a first pseudorange ranging value, and determine the total number of ionospheric electrons on the ranging signal path between the first device 100 and the second device 200 and the clock difference between the first device 100 and the second device 200 based on the first pseudorange ranging value, the first forwarding ranging value, and the second forwarding ranging value.

[0069] Figure 1 The fu and fd shown are satellite-to-ground communication links added between the user station and the satellite, and 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 in 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 clock of the user station. Of course, in other embodiments, the first device 100 may also be a user station, and the second device 200 may be a satellite. Furthermore, the first device 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 embodiment of the present application can be applied to aerospace systems, typically a satellite-to-ground system composed of a user station and a satellite, where the user station monitors the clock difference between the satellite and the user station, the ionospheric delay on the ranging signal path, and determines the satellite-to-ground space distance between the satellite and the user station. Specific applications of the satellite-to-ground time synchronization system may 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 the local time. After acquiring the uplink signal, the satellite forwards 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 after forwarding by the satellite constitute a forwarding ranging signal, and the user station can determine the forwarding ranging value based on the forwarding ranging signal. For example, the first uplink signal and the first downlink signal constitute the first forwarding ranging signal, and the second uplink signal and the second downlink signal constitute the second forwarding ranging signal. The user station can determine the first forwarding ranging value based on the first forwarding ranging signal, and can determine the second forwarding ranging value based on the second forwarding ranging signal. In addition, the satellite also sends a pseudorange ranging signal to the user station based on its own clock system, that is, the local time. The user station receives and demodulates the pseudorange ranging signal to obtain the pseudorange ranging value, so that the user station can calculate the clock difference between the satellite and the user station, and the total number of ionospheric electrons on the path of the user station and the satellite ranging signal based on the determined forwarding 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 forwarding ranging signal described in the embodiments of the present application refer to the signals obtained after modulating the ranging code signal in the carrier signal. In some specific embodiments, the ranging code can be selected from pseudo-code, weil code, M code, etc., and this application does not specifically limit the specific selection of the ranging code. And it can be understood that the forwarding ranging signal and pseudo-range ranging signal described in the embodiments of the present application are both spread spectrum signals. When multiple spread spectrum signals are sent and received, the relationship between the carrier frequency and the ranging code is processed according to the spread spectrum communication technology, carrier frequency multiplexing technology and code division multiple access communication technology, which will not be repeated 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 principle of determining the clock difference between the satellite and the user station by the user station can be found in the introduction of the subsequent method embodiment, which will not be expanded here. In addition, because the user station can determine the clock difference between the satellite and the user station and the total number of ionospheric electrons between the satellite and the user station through one pseudo-range ranging signal and two forwarding ranging signals, the working principle of more pseudo-range ranging signals and forwarding ranging signals is similar to that of one pseudo-range ranging signal and two forwarding ranging signals, and this application will not elaborate on it.

[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 an implementation mode of the present application. Figure 2 FIG. 4 shows the internal structure of the system when the pseudo-range measurement signal is broadcast by the first device. Figure 2 As shown, in an exemplary embodiment, the satellite may include a communication-connected repeater 101, a pseudorange generating device 102, and a first time-frequency device 103, wherein the repeater 101 is used to receive a first uplink signal and a second uplink signal, perform frequency conversion processing on the first uplink signal, and power amplify the first uplink signal before forwarding the first downlink signal to the user station, and perform frequency conversion processing on the second uplink signal, and power amplify the second uplink signal before forwarding the second downlink signal to the user station; the pseudorange generating device 102 is communication-connected to the repeater 101, and the pseudorange generating device 102 is used to generate and broadcast a first pseudorange ranging signal; and the first time-frequency device 103 provides time-frequency signals for the repeater 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 also be integrated in 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 belong to the protection scope 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. All of the above belong to the protection scope of the present application.

[0084] like Figure 2 As shown, the user station may include a second pseudo-range measuring 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 pseudo-range measuring 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 determine 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 corrects and obtains a first corrected pseudorange ranging value, a first corrected forwarding ranging value, and a second corrected forwarding ranging value. value, and determine the total number of ionospheric electrons on the ranging signal path by using the first corrected forwarding ranging value and the second corrected forwarding ranging value; and determine the clock difference between the first device 100 and the second device 200 based on the total number of ionospheric electrons, any corrected forwarding ranging value and any corrected pseudorange ranging value; or, determine the total number of ionospheric electrons on the ranging signal path between the first device 100 and the second device 200 and determine the clock difference between the first device 100 and the second device 200 based on the first corrected forwarding ranging value, the second corrected forwarding ranging value and the first corrected pseudorange ranging value.

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

[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 the 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 arranged, and / or the second time-frequency device and the repeater ranging device are integrated or separately arranged.

[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 computing device, and the computing device directly uses the delay in subsequent calculations. Because the first device and the second device in this working condition have corresponding differences in system structure only due to the different broadcasting methods of the pseudo-range ranging signal, the specific functions of each functional component are different. Figure 2 The structure shown is similar. Figure 2 The system structure shown is taken as an example to further introduce the specific structures of the first device and the second device.

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

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

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

[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 are measured at the rising edge or falling edge of their respective 1PPS (1Pulse Per Second) signals. As a preference, it is generally recommended to use one clock to perform synchronous measurement of pseudo-range ranging signals and forwarding ranging signals at the rising edge or falling edge of the same 1PPS signal.

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

[0095] The repeater 101 has a forwarding delay, and the pseudo-range generating device 102 has a transmission delay; the second pseudo-range 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 repeater 101 refers to the delay generated in the process of the satellite forwarding the first uplink signal and the second uplink signal to obtain the first downlink signal and the second downlink signal after receiving the first uplink signal and the second uplink signal sent by the user station. The transmission delay of the pseudorange generating device 102 of the satellite refers to the delay generated in the process of the pseudorange generating device 102 generating and transmitting the first pseudorange ranging signal.

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

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

[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-ranging signal to the user station through any pseudo-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-ranging signal. For example, a telemetry unit can be provided in the satellite, and the signal forwarding delay of the repeater 101 and the transmission delay of the pseudo-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-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 of the repeater 101 and the transmission delay of the pseudo-ranging signal.

[0101] Alternatively, because the changes in the signal forwarding delay of the repeater 101 and the pseudo-range measurement signal transmission delay are 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 pseudorange measurement signal transmission delay into any pseudorange measurement signal for transmission to the user station, the existing signals between the satellite and the user station are fully utilized to transmit the forwarding delay and the pseudorange measurement signal transmission delay. There is no need to set up additional communication 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 range measurement signals is shown. Figures 3 to 10 It is a schematic diagram of the composition of the forwarded ranging signal and the pseudo-ranging signal of the satellite and the user station according to other implementation methods 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, if Figure 4 As shown, there can be two forwarding ranging signals and one pseudo-ranging signal between the user station and the satellite;

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

[0107] Or, if Figure 6 As shown, there may 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. The signal structure between the user station and the satellite is further described as an example.

[0109] Or, if Figure 7 As shown, 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, if Figure 8 As shown, 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, if Fig. 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, if Fig.10 As shown, when there are three forwarding ranging signals and three pseudo-range ranging signals between the user station and the satellite, the first downlink signal is carrier frequency multiplexed with the first pseudo-range ranging signal, the second downlink signal is carrier frequency multiplexed with the second pseudo-range ranging signal, and the third downlink signal is carrier frequency multiplexed with the third pseudo-range 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 structure 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 downlink to the user station, and one satellite receiving is used to receive 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. Or an additional communication signal is added to realize data transmission between the satellite and the user station.

[0117] In an exemplary embodiment, if Figure 1 As shown, the satellite can also send the forwarding delay and 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, and 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. The present 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 method of the embodiment of the present application is obtained, and then the Sagnac effect delay is obtained.

[0120] There is no relativistic delay effect term in the pseudo-range measurement value. This is because in reality, satellites in space have a time-frequency system to provide time and frequency. According to the knowledge of relativity, it is easy to know that the clock on the satellite will produce a corresponding relativistic effect delay due to relativity. The relativistic effect delay of the satellite clock can be solved using existing methods. For example, the satellite clock has been adjusted before going into space. After adjustment, the satellite clock has no relativistic effect delay like the clock on the ground. For details, please refer to the Beidou navigation satellite clock's approach to relativity.

[0121] When the forwarding ranging expression is used to characterize the forwarding ranging value, there is no Sagnac effect delay in the forwarding ranging expression because the Sagnac effect delay of the uplink signal is opposite to the Sagnac effect delay of the downlink signal, and the absolute value difference between the two is very small, so the two Sagnac effect delays can be approximately offset, so that the Sagnac effect delay term is not reflected in the forwarding ranging expression. Of course, in some other embodiments of the present application, the Sagnac effect delay can also be considered, that is, the Sagnac effect delay of the uplink signal and the Sagnac effect delay of the downlink signal are added to the forwarding ranging expression, so as to obtain better measurement accuracy of the forwarding ranging value, which all belong to the protection scope of the present application.

[0122] When the pseudo-range measurement signal is broadcast by the second device and received by the first device, based on the above embodiments, the embodiment of the present application further provides a method for determining a pseudo-range measurement 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 the pseudo-range measurement value is executed by the first device. The method for determining the pseudo-range measurement value is as follows:

[0123] Receiving m-channel pseudo-range measurement signals broadcasted by the second device;

[0124] Each pseudo-range measurement signal is synchronously measured to obtain m pseudo-range measurement values, where m is a positive integer.

[0125] When the pseudo-range ranging signal is broadcast by the first device and received by the second device, based on the above embodiments, the 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 the pseudo-range 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-channel pseudo-range measurement signals broadcasted by the first device;

[0129] Synchronously measuring each of the forwarding ranging signals and each of the pseudo-range ranging signals to obtain h forwarding ranging values ​​and m pseudo-range ranging values;

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

[0131] It is particularly worth pointing out 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 of the system determining the pseudorange measurement value and the forwarding measurement value under two different pseudorange measurement signal transmission modes. Regardless of the mode, after obtaining the pseudorange measurement value and the forwarding measurement value, the computing device acquires the pseudorange measurement value and the forwarding measurement value by communicating with the first device and the second device, and further calculates the total number of ionospheric electrons and the clock error.

[0133] On the basis of the above embodiments, the embodiments of the present application also provide an ionospheric delay monitoring and time synchronization method, which can be applied to the ionospheric delay monitoring and time synchronization system described in any of the above embodiments. For the device delay used in the embodiment of this method and its acquisition method, please refer to the introduction of the above system embodiment, which will not be repeated here. The method is described in detail below.

[0134] Fig.11 Flow chart of an ionospheric delay monitoring and time synchronization method according to an embodiment of the present application, the method is executed by a computing device, such as Fig.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 the communication result with the first device, and obtain h forwarding ranging values ​​measured by the second device based on the communication result with the second device;

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

[0137] S120, using a pseudorange measurement expression to represent each of the pseudorange measurement values ​​and using a forwarding measurement expression to represent each of the forwarding measurement values;

[0138] S130. Determine the total number of ionospheric electrons on the ranging signal path 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 ionosphere electrons can be calculated according to the two common pseudorange measurement values, and then the clock error can be calculated according to any pseudorange value and any forwarding measurement value; the second simplest system has one pseudorange measurement value and two forwarding measurement values, and the total number of ionosphere electrons can be calculated according to the two forwarding measurement values, and then the clock error can be calculated according to any pseudorange value and any forwarding measurement value;

[0141] Because there are only two unknowns, namely the total number of electrons in the ionosphere and the clock difference between the satellite and the user station, the two simplest systems can form 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 defined as the following steps:

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

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

[0148] S130. Determine 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 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 being a satellite and the second device being a user station as an example.

[0150] It should be noted that the Sagnac effect delay in the pseudo-range ranging expression and the forwarding ranging expression of the present application has been explained in the previous text and can be used as a known value, while the satellite-to-ground space distance, tropospheric delay, ionospheric delay, the clock difference of the satellite relative to the system time or the clock difference of the user station relative to the system time are unknown. The present application uses the above method to calculate the clock difference between the satellite and the user station and the total number of ionospheric electrons on the ranging signal path based on the measured pseudo-range ranging value and forwarding ranging value.

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

[0152] Both pseudo-range measurement signals and forwarding range measurement signals pass through the atmosphere, which includes the troposphere and ionosphere. The ionosphere is a diffuse medium, and the time delays caused by the ionosphere to RF signals of different carrier frequencies vary depending on the carrier frequency, while the troposphere is a non-dispersive medium, and the troposphere causes the same time delays to RF signals of different carrier frequencies.

[0153] Because of the zero baseline setting 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 space path, but the time when the uplink signal crosses the ionosphere is different from the time when the downlink signal crosses the ionosphere after being forwarded by the satellite. 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 RF 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 with a very short time difference, the spatial paths traversed by the forwarding ranging signal and the pseudo-range ranging signal are exactly the same, 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 steps: using a pseudorange smoothing algorithm to correct the first forwarding ranging value, the second forwarding ranging value, and the first pseudorange ranging value. Specifically, the pseudorange ranging value and the forwarding ranging value are corrected using a pseudorange smoothing algorithm, so that the noise of the pseudorange ranging value and the forwarding ranging value can be reduced, which is conducive to improving the accuracy of the clock error finally determined. The specific content of the pseudorange smoothing algorithm is not repeated here.

[0158] Before introducing the specific method, it is specially noted that ±c·(δt z (n)-δt s (n)), when +c·(δt z (n)-δt s (n)), the first device broadcasts a pseudo-range measurement signal, and the second device receives and measures; 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 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 values ​​of the Sagnac effect are the same, but the signs are opposite.

[0160] Because the directions of the pseudo-range measurement signals are different, except for the opposite signs of the clock difference and the Sagnac effect between the first device and the second device, the rest are the same. Therefore, when the first device broadcasts the pseudo-range measurement signal, the pseudo-range measurement formula is the following formula (fz1); when the second device broadcasts the pseudo-range measurement signal, the pseudo-range measurement formula is the following formula (sz1):

[0161]

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

[0163]

[0164] The method of the present application is described below by taking the pseudorange ranging signal broadcast by the first device as an example, 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 forwarding ranging value and the pseudo-range ranging value to obtain a corrected forwarding ranging value and a corrected pseudo-range ranging value, and then use the corrected forwarding ranging value and the corrected pseudo-range ranging value to determine the total number of ionospheric electrons and the clock difference between the satellite and the user station. Specifically, the process of correcting the forwarding ranging value and the pseudo-range ranging value may include the following steps:

[0177] S1301: Correct the first forwarding ranging value to obtain a first corrected forwarding ranging value, and correct the second forwarding ranging value to obtain a second corrected forwarding 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 forwarding ranging value and second corrected forwarding 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 by 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 forwarding ranging value shown in formula (z2'-1) and the second corrected forwarding ranging value shown in formula (z2'-2) to obtain a forwarding ranging difference value shown in the following formula (u7-1);

[0192]

[0193] Further, 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 pseudo-range ranging signal and the forwarded ranging signal by the following formula (u60) to formula (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, correct the pseudorange measurement value corrected by the pseudorange smoothing algorithm, and then use the corrected forwarding ranging value and the corrected pseudorange measurement 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 pseudo-range ranging value.

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

[0202] S1311. Perform mathematical processing on any corrected pseudorange measurement value and any corrected forwarding ranging value to obtain an expression including a 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] Among them, after obtaining the above-mentioned corrected pseudorange measurement value and corrected forwarding ranging value, mathematical processing is performed on the expression representing the first corrected pseudorange measurement value and the expression representing the first corrected forwarding ranging value to obtain an expression containing the clock difference between the satellite and the user station; or, mathematical processing is performed on the expression representing the first corrected pseudorange measurement value and the expression representing the second corrected forwarding ranging value 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 forwarding 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 use 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) to perform difference calculation, and use 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 including 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] 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:

[0208]

[0209] Of course, in other embodiments, the computing device may also use the above formula (z3-1) to formula (z3-2) to average and obtain the averaged clock difference between the satellite and the user station:

[0210] 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.

[0211] In another optional implementation 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 described in step S130 can also be achieved by executing a set of simultaneous equations and solving matrix equations.

[0212] At this time, m = 1, h = 2; λ = 1; θ = 2;

[0213] 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.

[0214] Specifically, as described above, according to formula (u10-1) to formula (u10-2), formula (u20) to formula (u21) are obtained:

[0215]

[0216] In general, each of the λ corrected pseudorange values ​​is subtracted from the θ corrected forwarded range values, thus obtaining λ·θ subtraction formulas, thus obtaining the (λ·θ)×2 matrix G u , where the first column is all 1; (λ·θ)×1 matrix b u .

[0217] In this way, the computing device can use the formulas shown in the formulas (u20) to (u21) to construct the following matrix equation (u18-1) in which 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:

[0218]

[0219] Among them, in the matrix equation (u18-1),

[0220]

[0221] 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.

[0222] Then the solution of the above matrix equation (u18-1) is the expression (u19-1)

[0223]

[0224] In order to obtain 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).

[0225] 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 electron number TEC(n) in the ionosphere according to formula (u19-1).

[0226] 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.

[0227] 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 :

[0228]

[0229] Solving Matrix Equations The result is as follows:

[0230]

[0231] It should be understood that when the system is the first simplest system, α = 2, β = 1, and the matrix G z ,b z Specifically, the matrix G is as follows z1 ,b z1 :

[0232]

[0233] 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.

[0234] When the first simplest system adds one forwarding ranging signal and the second system adds one pseudo-range ranging signal, the two simplest systems become systems with the same two pseudo-range ranging signals and two forwarding ranging signals. When the number of pseudo-range ranging signals of the two simplest systems is two and the number of forwarding ranging signals is two, the two systems are exactly the same. At this time, the carrier frequencies are different and the corresponding calculation methods are also the same. At this time, the total number of electrons in the ionosphere can be obtained by using two forwarding ranging values ​​or two pseudo-range ranging values, and then the clock difference between the first device and the second device can be obtained by using any corrected forwarding ranging value and any corrected pseudo-range ranging value and the known total number of electrons in the ionosphere.

[0235] When using simultaneous equations to solve, the corresponding matrices Gu and bu are Gu2 and bu2 respectively:

[0236]

[0237] 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.

[0238]

[0239] 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.

[0240] When two pseudo-range measurement signals and two forwarding ranging signal systems use carrier frequency multiplexing, such as Fig. 9 The multiplexing shown in the figure, matrices Gu and ub become Gu3 and bu3 respectively:

[0241]

[0242] In order to obtain c·(δt z (n)-δts (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).

[0243] 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.

[0244] 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 the satellite clock error δt relative to the system time is known, it is easy to obtain s 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;

[0245] On the contrary, when the satellite clock difference δt relative to the system time is s When t is a known quantity, the clock difference δt of the user station relative to the system time can be easily obtained. z ,At this time, the satellite can provide time services to the user station;

[0246] 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.

[0247] 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, and transmit 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 performs data transmission with 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.

[0248] Alternatively, the user station does not exchange clock error data with the satellite.

[0249] Based on the above embodiments, 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 of the above embodiments. Fig.12 FIG. 1 is a flow chart of a method for determining the distance between a satellite and the earth according to an embodiment of the present application. The method may be executed by a computing device, such as Fig.12 As shown, the method may include the following steps:

[0250] S210, 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, a carrier frequency of at least one forwarded ranging signal, and a carrier frequency of at least one pseudorange ranging signal, respectively determine the ionospheric delay of the at least one forwarded ranging signal and the ionospheric delay of the at least one pseudorange ranging signal;

[0251] S220, determining 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 forwarding ranging signal and the forwarding ranging value of the corresponding forwarding ranging signal; or determining 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;

[0252] S230. Determine a tropospheric delay on a ranging signal path between the first device and the second device based on a preset tropospheric model;

[0253] S240: Determine the satellite-to-earth space distance between the first device and the second device based on the sum of the satellite-to-earth 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.

[0254] Among them, 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.

[0255] In addition, as described above, the computing device can correct the pseudorange measurement value and the forwarding ranging value to obtain the corresponding corrected pseudorange measurement value and the corrected forwarding ranging value. Therefore, in the method of the present application, the computing device can specifically use the corrected pseudorange measurement 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.

[0256] In step S220, the computing device may use the formula (z2'-1) to obtain the sum of the satellite-to-ground space distance and the tropospheric delay between the satellite and the user station as shown in the following formula (z14-1):

[0257]

[0258] 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);

[0259] Alternatively, the computing device may use the following formula (fz1'-1) to obtain the sum of the satellite-to-ground space 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);

[0260] Among them, I z,1 (n) Determined according to formula (u64);

[0261] 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):

[0262] T=2.47 / (sinθ+0.0121)(T1)

[0263] Where: T is the tropospheric delay, unit: meter; θ is the satellite elevation angle, unit: radian.

[0264] There are relatively many models for calculating tropospheric delay based on meteorological parameters. The differences between them decrease with the satellite elevation angle by about a few millimeters to a few centimeters, which is more accurate than that calculated by this simple model.

[0265] Common models for determining tropospheric delay correction include the Saastamoinen model and the Hopfield model. Studies have shown that when the altitude angle is greater than or equal to 15°, the results obtained by different models are in good agreement, and the model can be selected arbitrarily. However, when the value of the station elevation is large, the tropospheric delay in the zenith direction calculated by the two models can differ by tens of centimeters. After comparison with the measured meteorological data, it is recommended to use the Saastamoinen model.

[0266] 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-earth space distance between the user station and the satellite. The relevant calculation process will not be repeated here.

[0267] 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 the average result of the multiple satellite-to-ground space distances.

[0268] 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-to-ground time synchronization method is still used to calculate the clock difference between the satellite and the user station, the total number of electrons in the ionosphere, and the calculated clock difference is transmitted to the satellite. The specific calculation steps are not repeated here.

[0269] 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.

[0270] 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 the orbital parameters of the corresponding satellite based on the data transmission results with each satellite, and determines its own coordinate information based on the orbital parameters of each satellite and the satellite-to-earth space distance between itself and the satellite.

[0271] The satellite navigation system also includes a plurality of third devices, which are connected to the satellite for communication. Some of the third devices constitute a satellite orbit determination system, which is used to monitor and process the orbit of the satellite to obtain satellite orbit parameters; some of the third devices constitute a satellite-to-ground time synchronization system, which is used to monitor the time of each satellite and keep the time of each satellite synchronized with the operation and control system. The operation and control system mentioned here refers to a system composed of a satellite orbit determination system and a satellite-to-ground time synchronization system.

[0272] The satellite navigation system Fig.13 As shown, in the satellite navigation system, there are at least two satellites. In the satellite navigation system, the orbit determination system can adopt the existing Beidou orbit determination method.

[0273] 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 system time is used as an unknown number. The clock difference of the satellite relative to the system time is obtained through the method of this application, and the time synchronization of the satellite and the operation and control system is realized. The satellite then broadcasts a pseudo-range measurement signal with a known time to the outside. At this time, the time of the satellite relative to the system is known, and the time of the user station relative to the system is unknown. Through the ionospheric delay monitoring and time synchronization system and method of this application, the clock difference of the user station relative to the system time is obtained, and the satellite timing function is realized. At this time, after the user station obtains its own clock difference relative to the system time, it does not need to interact with the satellite for clock difference data.

[0274] Of course, the satellite-ground time synchronization system can also use other existing satellite-ground time synchronization technologies, such as a two-way pseudo-range measurement method, etc. Satellite-ground time synchronization can be achieved using these methods.

[0275] After the user station obtains high-precision time synchronization, the space distance between the user station and the satellite is obtained. According to the satellite ephemeris and the space distance between the user station and the satellite, if the satellite navigation system has only two satellites, the user needs to configure an altimeter to obtain the user elevation, and then refer to the Beidou dual-star positioning principle to obtain the user station coordinates; when there are three or more satellites, the user station does not need to be configured with an altimeter, and the user station coordinate information can be obtained through the space distance between the user station and the satellite ephemeris and the three satellites.

[0276] 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 by exchanging data through communication.

[0277] 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 of the second devices achieve time synchronization with each other by exchanging data through communication.

[0278] Based on the above embodiments, the embodiments of the present application also provide 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. Fig.14 The flowchart of the inter-station time synchronization method according to one embodiment of the present application, the method may be executed by a user station, and the method may include:

[0279] S510, directly communicating with a target user station to perform data interaction and obtain a clock difference of the target user station;

[0280] S520: Calculate the time difference between the user station and the target user station based on the user station's own clock difference and determine the time difference between the two.

[0281] 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 the system time with each other through communication, thereby achieving time synchronization between multiple user stations, which is similar to the common view method and will not be repeated here.

[0282] On the basis of the above embodiments, the present application also provides a satellite positioning method, which can be applied to the above satellite navigation system. Fig.15is 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 a computing function of a computing device, such as Fig.15 As shown, the satellite positioning method may include the following steps:

[0283] S610, obtaining orbital parameters of each satellite;

[0284] S620, determining the coordinates of the corresponding satellite based on the orbital parameters;

[0285] S630, determining the space distance between the satellite and the ground;

[0286] 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.

[0287] Among them, in step S610, the orbital parameters of the satellite are satellite ephemeris, and the orbital parameters of the satellite can be determined according to existing satellite orbit determination methods, such as the orbit determination method of Beidou navigation satellites, etc., so that 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).

[0288] In step S620, the user station calculates the satellite coordinates at the current ranging time according to the acquired orbital parameters of the satellite.

[0289] In step S630, the user station may determine the satellite-to-earth space distance between itself and each satellite by using any of the satellite-to-earth space distance determination methods executed by the user station.

[0290] In step S640, the user station calculates its own coordinate information based on the coordinate information of each satellite and the satellite-to-ground space distance between itself and each satellite, that is, realizes satellite positioning for itself.

[0291] 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.

[0292] 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. The present application provides the following embodiments:

[0293] like Fig.16As shown, when the second device broadcasts an uplink signal of a forwarding ranging signal, an uplink signal reaches the satellite and is received by the first pseudo-range ranging device of the satellite to obtain a pseudo-range ranging value. The uplink signal is forwarded by the satellite transponder into two downlink signals with different carrier frequencies, forming two forwarding ranging signals, and obtaining two forwarding ranging values.

[0294] Or, if Fig.17 As shown, when the second device broadcasts an uplink signal of a forwarding ranging signal, one uplink signal reaches the satellite and is received by the first pseudo-range ranging device of the satellite to obtain a pseudo-range ranging value, and is not forwarded by the repeater; when the second device broadcasts another uplink signal of a forwarding ranging signal, the uplink signal reaches the satellite and is received by the first pseudo-range ranging device of the satellite to obtain a pseudo-range ranging value, and is forwarded by the repeater as a downlink signal, forming a forwarding ranging signal. The first device obtains two pseudo-range ranging values, and the second device obtains one forwarding ranging value;

[0295] Or, if Fig.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 further forwarded by the satellite transponder as two downlink signals with the same carrier frequency, forming two forwarding ranging signals, and obtaining two forwarding ranging values.

[0296] Figure 16 to Figure 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, and the specific calculation instructions will not be repeated here.

[0297] In summary, it can be seen that the ionospheric delay monitoring and time synchronization system, method and application provided in the embodiment of the present application creatively integrate at least one pseudo-range ranging signal and at least two forwarding ranging signals, which can not only obtain high satellite-ground time synchronization performance, but also obtain accurate total ionospheric electron count. At the same time, using 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 embodiment of the present application have the following characteristics:

[0298] 1. This application can independently obtain the total number of ionospheric electrons on the ranging signal path without the need for the total number of ionospheric electrons data provided by a third party. At the same time, it can also provide the total number of ionospheric electrons data to other users for use;

[0299] 2. Compared with the two-way pseudo-range measurement method, this method does not require satellite-ground coarse synchronization, which reduces system requirements;

[0300] 3. Compared with the two-way pseudo-range measurement method, this method completely overcomes the influence of atmospheric delay, including tropospheric delay and ionospheric delay, thereby achieving higher satellite-ground time synchronization accuracy, up to sub-nanosecond level;

[0301] 4. By applying this method, compared with the existing two-way pseudo-range measurement method, the satellite in the embodiment of the present application does not need pseudo-range measurement equipment, which can reduce the complexity of satellite payload and reduce satellite cost;

[0302] 5. Because the user station only needs to receive the signal from one satellite, the user station can use a directional antenna to reduce the multipath effect, thereby achieving better ranging accuracy;

[0303] 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.

[0304] 7. This application can obtain accurate satellite-to-ground space distance, providing support for subsequent satellite orbit determination and user positioning.

[0305] 8. The satellite navigation system of the present application requires time synchronization before user positioning, which is significantly different from the existing satellite navigation system and has the advantages of low investment and high efficiency.

[0306] The above are only preferred embodiments of the present application, and are not intended to limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. An ionospheric delay monitoring and time synchronization system, characterized in that: comprising a first device and a second device in communication connection, and a computing device in communication connection with the first device and the second device respectively; There are m pseudo-range measurement signals and h forwarding ranging signals between the first device and the second device, and the pseudo-range measurement signals and the forwarding 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 broadcasted by the first device and received by the second device, or is broadcasted by the second device and received by the first device; The forwarded ranging signal is composed of an uplink signal and a downlink signal. The second device broadcasts the uplink signal and receives the downlink signal. The first device receives the uplink signal and forwards it to form the downlink signal.

2. The 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 processing.

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

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 with a zero baseline; the first pseudo-range measuring device or the pseudo-range generating device and the repeater are set with 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 arranged in the first device or in the second device, or exists independently; When the computing device is set in the first device or the second device, the first device performs data transmission with the second device by 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 pseudo-range generating device has a transmission delay; the first pseudo-range measuring device and the second pseudo-range measuring device both have a receiving delay, and the forwarding ranging device has a transmission delay and a receiving delay; The computing device obtains the forwarding delay of the repeater, the transmission delay of the pseudorange generating device, the receiving delay of the first pseudorange measuring device and the second pseudorange measuring device, and the transmission delay and the receiving delay of the forwarding ranging device.

9. The ionospheric delay monitoring and time synchronization system according to claim 1, characterized in that: The computing device is communicatively connected to the first device and the second device respectively, receives the pseudorange measurement value and the forwarding ranging value, and determines the satellite-to-ground space distance between the first device and the second device, the total number of ionospheric electrons on the ranging signal path between the first device and the second device, and the clock difference between the first device and the second device based on the forwarding ranging value and the pseudorange measurement value; wherein, when determining the total number of ionospheric electrons and the clock difference, the sum of the forwarding ranging values ​​and the pseudorange measurement values ​​is greater than or equal to 3.

10. A method for determining a pseudorange measurement value, characterized in that: Applied to the ionospheric delay monitoring and time synchronization system according to any one of claims 1 to 9, the method is performed by a first device, and the method includes: Receiving m-channel pseudo-range measurement signals broadcasted by the second device; Synchronously measure each pseudo-range measurement signal to obtain m pseudo-range measurement values; Wherein, m is a positive integer.

11. A method for determining a distance measurement value, characterized in that: Applied to the ionospheric delay monitoring and time synchronization system according to any one of claims 1 to 9, the method is performed by a second device, and the method includes: When the pseudo-range measurement signal is broadcast by the first device, broadcast at least one uplink signal to the first device; Acquire at least one downlink signal forwarded by the first device based on the at least one uplink signal, wherein the at least one uplink signal and the at least one downlink signal constitute an h-path forwarding ranging signal; Acquire m-channel pseudo-range measurement signals broadcasted by the first device; Synchronously measuring each of the pseudorange ranging signals and each of the forwarded ranging signals to obtain m pseudorange ranging values ​​and h forwarded ranging values; or, When the pseudorange measurement signal is broadcast by the second device and received by the first device, broadcast at least one uplink signal to the first device; Acquire at least one downlink signal forwarded by the first device based on the at least one uplink signal, wherein the at least one uplink signal and the at least one downlink signal constitute an h-path forwarding ranging signal; Synchronously measuring each of the forwarding ranging signals to obtain h forwarding ranging values; Among them, m+h≥3, and m and h are both positive integers.

12. An ionospheric delay monitoring and time synchronization method, characterized in that: The ionospheric delay monitoring and time synchronization system according to any one of claims 1 to 9 is applied, 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, acquiring m pseudorange ranging values ​​measured by the first device based on the communication result with the first device, and acquiring 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, m pseudorange ranging values ​​and h forwarding ranging values ​​measured by the second device are obtained based on the communication result with the second device; wherein m+h≥3, and m and h are both positive integers; Using a pseudorange measurement expression to represent each of the pseudorange measurement values ​​and using a forwarding measurement expression to represent each of the forwarding measurement values; The 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 based on the m pseudorange ranging values ​​represented by the pseudorange ranging expression and the h forwarding ranging values ​​represented by the forwarding ranging expression.

13. The ionospheric delay monitoring and time synchronization method according to claim 12, characterized in that: Respectively using a pseudorange ranging expression to characterize each of the pseudorange ranging values ​​and using a forward ranging expression to characterize 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) is used to represent 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: z,i (n) represents the pseudo-range measurement value numbered i at the nth moment, in meters; R true,z,i (n) represents the real space distance traversed by the pseudo-range measurement signal numbered i at the nth moment, in meters; I z,i (n) represents the ionospheric delay of the pseudo-range signal numbered i at the nth time, in meters; T duiliu,z,i (n) represents the tropospheric delay of the pseudo-range signal numbered i at the nth moment, 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, and the hardware device delay of the pseudo-range measurement signal includes the transmission delay of the pseudo-range measurement signal numbered i and the reception delay of the pseudo-range measurement signal numbered i; c represents the speed of light, in meters per second; δt s (n) represents the clock difference between the first device and the system time at the nth moment, in seconds; δt z (n) represents the clock difference between the second device and the system time at the nth moment, in seconds; sagnac zz (n) represents the Sagnac effect delay of the pseudo-range measurement signal at the nth moment, in meters; L z,j (n) represents the forwarding ranging value of j at the nth time, 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 the nth time, in meters; I zd,j (n) represents the ionospheric delay of the downlink signal of the forwarding ranging signal numbered j at the nth time, in meters; T duiliu,zu,j (n) represents the tropospheric delay of the uplink signal of the forwarding ranging signal numbered j at the nth time, in meters; T duiliu,zd,j (n) represents the tropospheric delay of the downlink signal of the forwarding ranging signal numbered j at the nth time, 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 receiving delay of the downlink signal of the forwarding ranging signal numbered j.

14. The ionospheric delay monitoring and time synchronization method according to claim 12, characterized in that: The determining, based on the m pseudorange ranging values ​​and the h forwarded ranging values, 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 comprises: Correcting the m pseudorange measurement values ​​and the h forwarding measurement values ​​respectively to obtain m corrected pseudorange measurement values ​​and h corrected forwarding measurement values; Determine the total number of ionospheric electrons 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 determine the clock difference between the first device and the second device using the total number of ionospheric electrons, any of the corrected forward ranging values, and any of the corrected pseudorange ranging values; Alternatively, using at least two of the corrected forwarding ranging values ​​and at least one of the corrected pseudorange ranging values ​​or using at least one of the corrected forwarding ranging values ​​and at least two of the corrected pseudorange ranging values, determine 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; The sum of the corrected pseudorange values ​​and the corrected forward ranging values ​​is greater than or equal to 3.

15. The ionospheric delay monitoring and time synchronization method according to claim 14, characterized in that: The method of respectively 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 ​​comprises: 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: 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 measurement value numbered i at the nth moment, in meters; R true,z,i (n) represents the real space distance traversed by the pseudo-range measurement signal numbered i at the nth moment, in meters; I z,i (n) represents the ionospheric delay of the pseudo-range signal numbered i at the nth time, in meters; T duiliu,z,i (n) represents the tropospheric delay of the pseudo-range signal numbered i at the nth moment, 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, and the hardware device delay of the pseudo-range measurement signal includes the transmission delay of the pseudo-range measurement signal numbered i and the reception delay of the pseudo-range measurement signal numbered i; c represents the speed of light, in meters per second; δt s (n) represents the clock difference between the first device and the system time at the nth moment, in seconds; δt z (n) represents the clock difference between the second device and the system time at the nth moment, in seconds; sagnac zz (n) represents the Sagnac effect delay of the pseudo-range measurement signal at the nth moment, in meters; L z,j,a (n) represents the corrected forwarding ranging value of the number j at the nth time, in meters; L z,j (n) represents the forwarding ranging value of j at the nth time, 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 the nth time, in meters; I zd,j (n) represents the ionospheric delay of the downlink signal of the forwarding ranging signal numbered j at the nth time, in meters; T duiliu,zu,j (n) represents the tropospheric delay of the uplink signal of the forwarding ranging signal numbered j at the nth time, in meters; T duiliu,zd,j (n) represents the tropospheric delay of the downlink signal of the forwarding ranging signal numbered j at the nth time, 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 receiving delay of the downlink signal of the forwarding ranging signal numbered j.

16. The ionospheric delay monitoring and time synchronization method according to claim 14, 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 of the corrected forward ranging values, and any of the corrected pseudorange ranging values ​​comprises: By using the zero baseline setting relationship between the forwarding ranging device and the second pseudo-range ranging device, or by using the zero baseline setting relationship between the forwarder and the first pseudo-range ranging device, based on the total number of ionospheric electrons, any one of the corrected pseudo-range ranging values ​​and any one of the corrected forwarding ranging values, the clock difference between the first device and the second device as shown in formula (z3) is obtained: Alternatively, the clock difference 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 forwarding ranging values ​​is averaged to obtain the averaged clock difference between the first device and the second device; Where: z,i,a (n) represents the corrected pseudorange measurement value of the number i at the nth moment, in meters; L z,j,a (n) represents the corrected forwarding distance measurement value of the number j at the nth time, in meters; c represents the speed of light, in meters per second; δt s (n) represents the clock difference between the first device and the system time at the nth moment, in seconds; δt z (n) represents the clock difference between the second device and the system time at the nth moment, in seconds; Q ion represents the ionospheric delay coefficient, TEC(n) represents the total number of ionospheric electrons on the ranging signal path between the first device and the second device at the nth moment, unit: electron / square meter; f z,i (n) represents the carrier frequency of the pseudo-range measurement signal numbered i at the nth time, in Hertz; f zu,j (n), f zd,j (n) respectively denotes the carrier frequencies of the uplink signal and the downlink signal of the forwarded ranging signal numbered j at the nth moment, in Hertz.

17. The ionospheric delay monitoring and time synchronization method according to claim 14, characterized in that: The method of 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 by using at least two of the corrected forwarding ranging values ​​and at least one of the corrected pseudorange ranging values ​​or by using at least one of the corrected forwarding ranging value and at least two of the corrected pseudorange ranging values ​​comprises: When the number of the corrected pseudorange values ​​is at least two and the number of the corrected forwarding ranging value is at least one, select ɑ from the m corrected pseudorange values ​​and select β from the h corrected forwarding ranging values, wherein 2≤ɑ≤m, 1≤β≤h; Subtract the α corrected pseudorange values ​​shown in formula (z1') from the β corrected forwarding range values ​​shown in formula (z2') to obtain the difference formula shown in the following formula (z10): Wherein: 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), 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 obtained as shown in the following formula (z19): Where: G z is a (ɑ·β)×2 matrix, with the first column containing all 1s; b z is a (ɑ·β)×1 matrix; When the corrected pseudorange measurement value is at least one and the corrected forwarding ranging values ​​are at least two, select λ from the m corrected pseudorange measurement values ​​and select θ from the h corrected forwarding ranging values, wherein 1≤λ≤m, 2≤θ≤h; Subtract the λ corrected pseudorange values ​​from the θ corrected forwarding range values ​​to obtain the difference formula shown in the following formula (u10): Wherein: 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 using 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), 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 obtained as shown in the following formula (u19): Where: G u is a (λ·θ)×2 matrix, with the first column all 1; b u is a (λ·θ)×1 matrix; Where: 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 measurement value numbered i at the nth moment, in meters; R true,z,i (n) represents the real space distance traversed by the pseudo-range measurement signal numbered i at the nth moment, in meters; I z,i (n) represents the ionospheric delay of the pseudo-range signal numbered i at the nth time, in meters; T duiliu,z,i (n) represents the tropospheric delay of the pseudo-range signal numbered i at the nth moment, 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, and the hardware device delay of the pseudo-range measurement signal includes the transmission delay of the pseudo-range measurement signal numbered i and the reception delay of the pseudo-range measurement signal numbered i; c represents the speed of light, in meters per second; δt s (n) represents the clock difference between the first device and the system time at the nth moment, in seconds; δt z (n) represents the clock difference between the second device and the system time at the nth moment, in seconds; sagnac zz (n) represents the Sagnac effect delay of the pseudo-range measurement signal at the nth moment, in meters; L z,j,a (n) represents the corrected forwarding ranging value of the number j at the nth time, in meters; L z,j (n) represents the forwarding ranging value of j at the nth time, 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 the nth time, in meters; I zd,j (n) represents the ionospheric delay of the downlink signal of the forwarding ranging signal numbered j at the nth time, in meters; T duiliu,zu,j (n) represents the tropospheric delay of the uplink signal of the forwarding ranging signal numbered j at the nth time, in meters; T duiliu,zd,j (n) represents the tropospheric delay of the downlink signal of the forwarding ranging signal numbered j at the nth time, in meters; Y z,j (n) represents the hardware device delay of the forwarding ranging signal numbered j at the nth moment, in meters, wherein the hardware device delay of the forwarding ranging signal includes the transmission delay of the uplink signal of the forwarding ranging signal numbered j, the forwarding delay of the downlink signal of the forwarding ranging signal numbered j, and the receiving delay of the downlink signal of the forwarding ranging signal numbered j; Q ion represents the ionospheric delay coefficient, TEC(n) represents the total number of ionospheric electrons on the ranging signal path between the first device and the second device at the nth moment, unit: electron / 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 signals numbered 1, 2, ɑ, 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 forwarding ranging signal numbered 1, 2, β, 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 nth moment, respectively, in Hertz.

18. The ionospheric delay monitoring and time synchronization method according to claim 12, characterized in that: After determining the clock difference between the first device and the second device, the method further includes: Communicate with the first device or the second device, and transmit the determined clock difference between the first device and the second device to the first device or the second device, so as to achieve time synchronization between the first device and the second device; Wherein, when the clock difference of the first device relative to the system time is known, the second device determines its own clock difference relative to the system time according to the clock difference between the first device and the second device; When the clock difference of the second device relative to the system time is known, the first device determines its own clock difference relative to the system time according to the clock difference between the first device and the second device.

19. A method for determining the distance between satellite and earth, characterized in that: The ionospheric delay monitoring and time synchronization system according to any one of claims 1 to 9 is applied, wherein the method is executed by a computing device, and the method comprises: 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, a carrier frequency of at least one forwarded ranging signal, and a carrier frequency of at least one pseudorange ranging signal, respectively determine the ionospheric delay of the at least one forwarded ranging signal and the 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 forwarding ranging signal and the forwarding ranging value of the corresponding forwarding 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; Determine, based on a preset tropospheric model, a tropospheric delay on a ranging signal path between the first device and the second device; Determine the 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; Wherein, the total number of ionospheric electrons, pseudorange measurement value and forwarding ranging value are determined according to the ionospheric delay monitoring and time synchronization method according to any one of claims 12-18.

20. The method for determining the satellite-to-earth space distance according to claim 19, characterized in that: 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 by 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, 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 forwarding ranging values ​​is averaged to obtain the average sum of the satellite-to-ground space distance and the tropospheric delay between the first device and the second device; The determining 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 comprises: 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 (z15) 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 distance and the tropospheric time delay between the first device and the second device determined based on the multiple corrected pseudorange measurement values ​​is averaged to obtain the averaged sum of the satellite-to-ground space distance and the tropospheric time delay between the first device and the second device; Where: 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 measurement value numbered i at the nth moment, in meters; R true,z,i (n) represents the real space distance traversed by the pseudo-range measurement signal numbered i at the nth moment, in meters; I z,i (n) represents the ionospheric delay of the pseudo-range signal numbered i at the nth time, in meters; T duiliu,z,i (n) represents the tropospheric delay of the pseudo-range signal numbered i at the nth moment, 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, and the hardware device delay of the pseudo-range measurement signal includes the transmission delay of the pseudo-range measurement signal numbered i and the reception delay of the pseudo-range measurement signal numbered i; c represents the speed of light, in meters per second; δt s (n) represents the clock difference between the first device and the system time at the nth moment, in seconds; δt z (n) represents the clock difference between the second device and the system time at the nth moment, in seconds; sagnac zz (n) represents the Sagnac effect delay of the pseudo-range measurement signal at the nth moment, in meters; L z,j,a (n) represents the corrected forwarding ranging value of the number j at the nth time, in meters; L z,j (n) represents the forwarding ranging value of j at the nth time, 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 the nth time, in meters; I zd,j (n) represents the ionospheric delay of the downlink signal of the forwarding ranging signal numbered j at the nth time, in meters; T duiliu,zu,j (n) represents the tropospheric delay of the uplink signal of the forwarding ranging signal numbered j at the nth time, in meters; T duiliu,zd,j (n) represents the tropospheric delay of the downlink signal of the forwarding ranging signal numbered j at the nth time, 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 receiving delay of the downlink signal of the forwarding ranging signal numbered j.

21. A satellite navigation system, characterized in that: include: The ionospheric delay monitoring and time synchronization system according to any one of claims 1 to 9, wherein the first device is a satellite, the second device is a user station, and the number of the satellites is greater than or equal to 2; a plurality of third devices, all of which are communicatively connected to the satellite; The user station obtains the orbital parameters of the corresponding satellite based on the data transmission results with each satellite, and determines the coordinate information of the user station based on the orbital parameters of each satellite and the satellite-to-ground space distance between the user station and the satellite; Part of the third device constitutes a satellite orbit determination system, which is used to monitor and process the orbit of the satellite to obtain satellite orbit parameters; Part of the third devices constitutes a satellite-ground time synchronization system for performing time monitoring on each of the satellites.

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

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

24. An inter-station time synchronization system, characterized in that: include: The ionospheric delay monitoring and time synchronization system according to any one of claims 1 to 9; When there are at least two first devices or at least two second devices, at least two first devices or at least two second devices achieve time synchronization with each other by exchanging data through communication.

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

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