Time service method and device of low earth orbit satellite, electronic equipment and storage medium

Abstract

The invention relates to the technical field of computers, and particularly provides a time service method and device of a low-orbit satellite, electronic equipment and a storage medium. The method comprises the following steps: acquiring a digital navigation signal, and suppressing an interference spectral line of the digital navigation signal to obtain a suppressed digital navigation signal; performing amplitude-frequency compensation on the suppressed digital navigation signal to obtain a target navigation signal; correcting the pseudo-range observation model and the carrier phase observation model of the low-orbit satellite based on an error model of precise point positioning to obtain a corrected pseudo-range observation model and a corrected carrier phase observation model; and carrying out precise point positioning calculation on the corrected pseudo-range observation model, the corrected carrier phase observation model and the navigation message of the target navigation signal to obtain clock error data of the target navigation signal, and carrying out time service on a local clock according to the clock error data.

Description

Technical Field

[0001] The present disclosure relates to the technical field of computers, and particularly to a time synchronization method, device, electronic device, and storage medium for low-earth orbit satellites. Background Art

[0002] Time synchronization of low-earth orbit satellites is a process of using low-earth orbit satellites as a time reference source or a forwarding intermediary to restore the original time of the local clock by receiving satellite signals of low-earth orbit satellites and performing time delay compensation.

[0003] In related technologies, the time synchronization methods for low-earth orbit satellites are mainly divided into two categories. One is to achieve time synchronization through the space-ground time synchronization link of the ground measurement and control station; the other is to achieve on-board time maintenance through the on-board GNSS time synchronization method. The space-ground time synchronization link is difficult to undertake the space-ground measurement and control requirements of a large number of satellites. Moreover, the on-board GNSS time synchronization method may be affected by interference, resulting in limited ranging accuracy and difficulty in providing sub-nanosecond precision time synchronization services. Summary of the Invention

[0004] In view of the above problems, the present disclosure is proposed. The present disclosure provides a time synchronization method, device, electronic device, and storage medium for low-earth orbit satellites.

[0005] According to one aspect of the present disclosure, a time synchronization method for low-earth orbit satellites is provided, including:

[0006] Obtaining a digital navigation signal, and suppressing interference spectral lines of the digital navigation signal to obtain a suppressed digital navigation signal;

[0007] Performing amplitude-frequency compensation on the suppressed digital navigation signal to obtain a target navigation signal;

[0008] Based on the error model of precise point positioning, correcting the pseudorange observation model and the carrier phase observation model of the low-earth orbit satellite to obtain a corrected pseudorange observation model and a corrected carrier phase observation model;

[0009] Performing precise point positioning calculation on the corrected pseudorange observation model, the corrected carrier phase observation model, and the navigation message of the target navigation signal to obtain clock offset data of the target navigation signal, and performing time synchronization on the local clock according to the clock offset data.

[0010] In addition, according to one aspect of the present disclosure, it further includes: the obtaining the digital navigation signal includes:

[0011] Receiving a satellite navigation signal, and filtering the satellite navigation signal to obtain a filtered satellite navigation signal;

[0012] Processing the filtered satellite navigation signal to obtain an analog intermediate frequency signal;

[0013] Perform analog-to-digital conversion on the analog intermediate frequency signal to obtain the digital navigation signal.

[0014] In addition, according to one aspect of the present disclosure, it further includes: The amplitude-frequency compensation for the suppressed digital navigation signal to obtain the target navigation signal includes:

[0015] Determine the narrowband interference in the digital navigation signal;

[0016] Based on the anti-interference filter, determine the measured zero value corresponding to the narrowband interference;

[0017] Determine the measured zero value to be compensated among the measured zero values; wherein, the measured zero value to be compensated is the measured zero value that has changed after passing through the anti-interference filter;

[0018] Perform amplitude-frequency compensation on the measured zero value to be compensated to obtain the target navigation signal.

[0019] In addition, according to one aspect of the present disclosure, it further includes: Before performing precise point positioning calculation on the corrected observation model and the navigation message of the target navigation signal, the method further includes:

[0020] Determine the code phase and Doppler information of the target navigation signal;

[0021] Based on the code phase and the Doppler information, perform fine tracking on the target navigation signal to obtain the navigation message of the target navigation signal.

[0022] In addition, according to one aspect of the present disclosure, it further includes: The precise point positioning calculation for the corrected pseudorange observation model, the corrected carrier phase observation model, and the navigation message of the target navigation signal to obtain the clock offset data of the target navigation signal includes:

[0023] Determine the parameters to be measured in the precise point positioning calculation; wherein, the parameters to be measured include but are not limited to: the clock offset data to be measured, the position data to be measured, and the tropospheric error to be measured;

[0024] Based on the parameters to be measured, perform precise point positioning calculation on the corrected pseudorange observation model and the corrected carrier phase observation model to obtain the clock offset data of the target navigation signal.

[0025] In addition, according to one aspect of the present disclosure, it further includes: The precise point positioning calculation for the corrected pseudorange observation model and the corrected carrier phase observation model based on the parameters to be measured to obtain the clock offset data of the target navigation signal includes:

[0026] Based on the parameters to be measured, establish the observation equation and the state equation;

[0027] The observation equation and the state equation are solved by the Kalman filtering algorithm to obtain the floating-point solution corresponding to the parameter to be measured;

[0028] The clock error data of the target navigation signal is determined from the floating-point solution corresponding to the parameter to be measured.

[0029] According to another aspect of the present disclosure, a timing device for a low-Earth orbit satellite is provided, including:

[0030] An interference suppression unit configured to obtain a digital navigation signal and suppress the interference spectral lines of the digital navigation signal to obtain a suppressed digital navigation signal;

[0031] An amplitude-frequency compensation unit configured to perform amplitude-frequency compensation on the suppressed digital navigation signal to obtain a target navigation signal;

[0032] A correction unit configured to correct the pseudorange observation model and the carrier phase observation model of the low-Earth orbit satellite based on the error model of precise point positioning to obtain a corrected pseudorange observation model and a corrected carrier phase observation model;

[0033] A timing unit configured to perform precise point positioning calculation on the corrected pseudorange observation model, the corrected carrier phase observation model, and the navigation message of the target navigation signal to obtain the clock error data of the target navigation signal, and perform timing on the local clock according to the clock error data.

[0034] According to still another aspect of the present disclosure, an electronic device is provided, including: a processor, a memory, and a bus, where the memory stores machine-readable instructions executable by the processor. When the electronic device runs, the processor communicates with the memory through the bus, and when the machine-readable instructions are executed by the processor, the steps in the first aspect, or any possible implementation manner in the first aspect, are executed.

[0035] According to still another aspect of the present disclosure, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is run by a processor, the steps in the first aspect, or any possible implementation manner in the first aspect, are executed.

[0036] According to still another aspect of the present disclosure, a computer program product is provided, including a computer program / instructions, and when the computer program / instructions are executed by a processor, the steps of a timing method for a low-Earth orbit satellite are implemented.

[0037] As will be described in detail below, a time synchronization method, apparatus, electronic device, and storage medium for a low-Earth orbit satellite according to an embodiment of the present disclosure. By suppressing interference spectral lines and compensating amplitude-frequency characteristics of digital navigation signals, interference is reduced and signal characteristics are optimized, providing a high-quality signal basis for subsequent operations. Based on a precise point positioning error model, the pseudorange and carrier phase observation models are corrected, measurement errors are reduced, positioning accuracy is improved, and clock offset data can be accurately obtained, enabling sub-nanosecond-level precise time synchronization. At the same time, this method does not rely on the space-ground time synchronization link of a ground measurement and control station, reducing the ground burden and enhancing the autonomy and flexibility of the time synchronization system.

[0038] It is to be understood that both the foregoing general description and the following detailed description are exemplary and are intended to provide further explanation of the claimed technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] By describing the embodiments of the present disclosure in more detail in conjunction with the accompanying drawings, the above and other objects, features, and advantages of the present disclosure will become more apparent. The accompanying drawings are used to provide a further understanding of the embodiments of the present disclosure, and constitute a part of the specification, and are used to explain the present disclosure together with the embodiments of the present disclosure, and do not constitute a limitation to the present disclosure. In the drawings, the same reference numerals generally represent the same components or steps.

[0040] Figure 1 It is a flowchart of the time synchronization method for a low-Earth orbit satellite provided by an embodiment of the present disclosure.

[0041] Figure 2 It is a schematic diagram of the amplitude-frequency response before compensation of the time synchronization method for a low-Earth orbit satellite provided by an embodiment of the present disclosure.

[0042] Figure 3 It is a schematic diagram of the amplitude-frequency response after compensation of the time synchronization method for a low-Earth orbit satellite provided by an embodiment of the present disclosure.

[0043] Figure 4 It is an architecture diagram of the time synchronization system for a low-Earth orbit satellite provided by an embodiment of the present disclosure.

[0044] Figure 5 It is an architecture diagram of the interference suppression module of the time synchronization system for a low-Earth orbit satellite provided by an embodiment of the present disclosure.

[0045] Figure 6 It is a schematic diagram of the time synchronization apparatus for a low-Earth orbit satellite provided by an embodiment of the present disclosure.

[0046] Figure 7 It is a schematic diagram of an electronic device provided by an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0047] To make the objectives, technical solutions, and advantages of the present disclosure more apparent, the exemplary embodiments according to the present disclosure will be described in detail below with reference to the accompanying drawings. Apparently, the described embodiments are only a part rather than all of the embodiments of the present disclosure. It should be understood that the present disclosure is not limited by the exemplary embodiments described herein.

[0048] Therefore, the following detailed description of the embodiments of the present disclosure provided in the drawings is not intended to limit the scope of the claimed present disclosure, but merely represents selected embodiments of the present disclosure. Based on the embodiments of the present disclosure, all other embodiments obtained by those skilled in the art without creative efforts shall fall within the scope of protection of the present disclosure.

[0049] It should be noted that similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not require further definition and explanation in subsequent drawings.

[0050] As used herein, the term "and / or" merely describes an association relationship and indicates that three relationships may exist. For example, A and / or B may represent: A alone, both A and B present simultaneously, or B alone. Additionally, the term "at least one" as used herein represents any one of multiple items or any combination of at least two of multiple items. For example, including at least one of A, B, and C may represent including any one or more elements selected from the set composed of A, B, and C.

[0051] Through research, it has been found that the time synchronization of low-orbit satellites is a process of restoring the original time of the local clock by using low-orbit satellites as a time reference source or a relay medium and receiving satellite signals from low-orbit satellites and performing time delay compensation.

[0052] In related technologies, the time synchronization methods of low-orbit satellites are mainly divided into two categories. One is to achieve time synchronization through the space-ground time synchronization link of ground measurement and control stations; the other is to achieve on-board time maintenance through the on-board GNSS time synchronization method. The space-ground time synchronization link is difficult to undertake the space-ground measurement and control requirements of a large number of satellites. Moreover, the on-board GNSS time synchronization method may be affected by interference, resulting in limited ranging accuracy and difficulty in providing sub-nanosecond-level precise time synchronization services.

[0053] In view of the many problems of the above-mentioned existing solutions, this solution proposes a new timing method and device for low-earth orbit satellites. By suppressing the interference spectral lines and compensating the amplitude-frequency of digital navigation signals, interference is reduced and signal characteristics are optimized, providing a high-quality signal basis for subsequent operations. Based on the precise point positioning error model, the pseudorange and carrier phase observation models are corrected to reduce measurement errors and improve positioning accuracy. Furthermore, clock offset data can be accurately obtained, enabling sub-nanosecond-level precise timing. At the same time, this method does not rely on the space-ground time synchronization link of ground measurement and control stations, reducing the ground burden and enhancing the autonomy and flexibility of the timing system.

[0054] To facilitate the understanding of this embodiment, first, a detailed introduction to a timing method for low-earth orbit satellites disclosed in this embodiment of the present disclosure is provided. The execution subject of the timing method for low-earth orbit satellites provided in this embodiment of the present disclosure is generally an electronic device with certain computing capabilities. In some possible implementation manners, this timing method for low-earth orbit satellites can be implemented by a processor invoking computer-readable instructions stored in a memory.

[0055] Refer to Figure 1 As shown in the figure, it is a flowchart of the timing method for low-earth orbit satellites provided in this embodiment of the present disclosure. The method includes steps S101 to S104, where:

[0056] S101. Obtain a digital navigation signal, and suppress the interference spectral lines of the digital navigation signal to obtain a suppressed digital navigation signal.

[0057] In the embodiment of the present disclosure, first, the interference spectral lines of the digital navigation signal can be detected to determine the narrowband interference of the digital navigation signal. Secondly, based on the frequency of the narrowband interference, the digital navigation signal can be interference-suppressed to obtain a suppressed digital navigation signal.

[0058] Here, the ranging before and after the suppressed digital navigation signal and the digital navigation signal will not change.

[0059] Among them, while determining the narrowband interference of the digital navigation signal, the interference characteristics corresponding to the narrowband interference are determined, that is, the narrowband interference frequency and the narrowband interference intensity.

[0060] S102. Perform amplitude-frequency compensation on the suppressed digital navigation signal to obtain a target navigation signal.

[0061] In the embodiment of the present disclosure, amplitude-frequency compensation for non-bandstop frequency points can be performed on the suppressed digital navigation signal to ensure that the measurement zero value of the target navigation signal is consistent with the measurement zero value of the digital navigation signal.

[0062] S103. Modify the pseudorange observation model and the carrier phase observation model of the low-earth orbit satellite based on the error model of precise point positioning to obtain the modified pseudorange observation model and the modified carrier phase observation model.

[0063] In the embodiments of the present disclosure, first, a pseudorange observation model and a carrier phase observation model can be established. Second, the error model of the Precise Point Positioning (PPP) algorithm can be determined.

[0064] Here, the error model includes but is not limited to: the earth solid tide correction model, the ocean loading correction model, and the tropospheric error model.

[0065] Finally, the above error model can be used to modify the pseudorange observation model and the carrier phase observation model.

[0066] Among them, the displacements in the horizontal and vertical directions of the station caused by the earth solid tide can be represented by spherical harmonic functions of n dimensions and m orders containing Love numbers and Shida numbers. The ocean tide correction model is determined by the convolution integral of the instantaneous tide height of seawater provided by the global ocean tide model and the Green's function (the load function of the earth on a unit mass point).

[0067] S104. Perform precise point positioning calculations on the modified pseudorange observation model, the modified carrier phase observation model, and the navigation message of the target navigation signal to obtain the clock offset data of the target navigation signal, and perform time synchronization on the local clock according to the clock offset data.

[0068] In the embodiments of the present disclosure, the modified pseudorange observation values, the carrier phase observation values, and the processed navigation message data can be input into the precise point positioning algorithm.

[0069] Among them, the above precise point positioning algorithm can be based on the least squares principle or other advanced mathematical optimization methods, and at the same time consider multiple observation equations and unknown parameters, and gradually solve the clock offset data of the target navigation signal through iterative calculations.

[0070] Here, after obtaining the clock offset data of the target navigation signal, the local clock can be synchronized according to the clock offset data.

[0071] In an embodiment of the present disclosure, first, a digital navigation signal is acquired, and interference spectral lines of the digital navigation signal are suppressed to obtain a suppressed digital navigation signal; second, amplitude-frequency compensation is performed on the suppressed digital navigation signal to obtain a target navigation signal; second, based on the error model of precise point positioning, the pseudorange observation model and the carrier phase observation model of the low-earth orbit satellite are corrected to obtain a corrected pseudorange observation model and a corrected carrier phase observation model; finally, precise point positioning calculations are performed on the navigation messages of the corrected pseudorange observation model, the corrected carrier phase observation model, and the target navigation signal to obtain the clock offset data of the target navigation signal, and the local clock is timed according to the clock offset data.

[0072] In the above embodiment, by suppressing interference spectral lines and performing amplitude-frequency compensation on the digital navigation signal, interference is reduced and signal characteristics are optimized, providing a high-quality signal basis for subsequent operations. Based on the precise point positioning error model, the pseudorange and carrier phase observation models are corrected to reduce measurement errors and improve positioning accuracy. Furthermore, the clock offset data can be accurately obtained, enabling sub-nanosecond-level precise timing. At the same time, this method does not rely on the space-ground time synchronization link of the ground measurement and control station, reducing the ground burden and enhancing the autonomy and flexibility of the timing system.

[0073] In an alternative embodiment, acquiring the digital navigation signal specifically includes the following steps:

[0074] First, a satellite navigation signal is received, and the satellite navigation signal is filtered to obtain a filtered satellite navigation signal;

[0075] Second, the filtered satellite navigation signal is processed to obtain an analog intermediate-frequency signal;

[0076] Finally, the analog intermediate-frequency signal is subjected to analog-to-digital conversion to obtain a digital navigation signal.

[0077] In an embodiment of the present disclosure, the satellite navigation signal can be received through a BDS antenna. Here, after receiving the satellite navigation signal, pre-filtering can be performed on the satellite navigation signal to obtain a filtered satellite navigation signal.

[0078] After that, the filtered satellite navigation signal can be input into a band-pass filter, and then the filtered satellite navigation signal after passing through the band-pass filter is subjected to down-conversion processing to obtain an analog intermediate-frequency signal.

[0079] Here, the frequency bands set by the above band-pass filter are the B1 band (about 1561.098 MHz), the B2 band (about 1207.14 MHz), and the B3 band (about 1268.52 MHz).

[0080] Here, the analog intermediate frequency signal can be sampled by an ADC (Analog-to-Digital Converter) to obtain a digital navigation signal.

[0081] In an optional embodiment, amplitude-frequency compensation is performed on the suppressed digital navigation signal to obtain a target navigation signal, which specifically includes the following steps:

[0082] First, determine the narrowband interference in the digital navigation signal;

[0083] Second, based on the anti-interference filter, determine the measured zero value corresponding to the narrowband interference;

[0084] Second, determine the measured zero value to be compensated among the measured zero values; where the measured zero value to be compensated is the measured zero value that has changed after passing through the anti-interference filter;

[0085] Finally, perform amplitude-frequency compensation on the measured zero value to be compensated to obtain a target navigation signal.

[0086] In the embodiments of the present disclosure, the compensation for the interference band notch is divided into two parts: interference suppression and amplitude-frequency compensation of non-notch frequency points. Among them, the amplitude-frequency compensation part of non-notch frequency points is the selection of compensation frequency points and the determination of compensation weights.

[0087] Here, first, based on the frequencies of the narrowband interferences, the frequency responses of the narrowband interferences can be determined. Among them, the frequency response f of the i-th narrowband interference i meets the following conditions:

[0088]

[0089] where i ranges from 1 to K, and K is the number of narrowband interferences in the digital navigation signal, is the lower frequency limit of the i-th narrowband interference, is the upper frequency limit of the i-th narrowband interference, and f is the normalized frequency of the chip width.

[0090] Among them, f meets the following conditions: f = 1 / T c , T c is the chip width.

[0091] After that, based on the frequency response, the measured zero values of the narrowband interferences can be determined. Among them, the measured zero value ε of the i-th narrowband interference i , meets the following conditions:

[0092]

[0093] where τ g (f i) is the normalization function of Tc (chip width), -b is the lower frequency limit of the frequency response of the ideal anti-interference filter, and b is the upper frequency limit of the frequency response of the ideal anti-interference filter.

[0094] Here, since the amplitude-frequency response of the anti-interference filter at the band-stop frequency band is zero, it causes changes in the numerator and denominator in the above formula, and further causes the measured zero value to change before and after interference.

[0095] Here, the changes in the numerator and denominator in the above formula can be compensated to ensure that the measured zero value remains unchanged before and after anti-interference after compensation.

[0096] Among them, the measured zero value after compensation for the i-th narrowband interference meets the following conditions:

[0097]

[0098] Among them, Δ1 is the first compensation amount, and Δ2 is the second compensation amount.

[0099] Here, as Figure 2 shown, it is the schematic diagram of the amplitude-frequency response before compensation of the time synchronization method for low-earth orbit satellites provided by the embodiment of the present disclosure, where: the abscissa is the frequency, and the ordinate is the amplitude-frequency response.

[0100] As Figure 3 shown, it is the schematic diagram of the amplitude-frequency response after compensation of the time synchronization method for low-earth orbit satellites provided by the embodiment of the present disclosure, where: the abscissa is the frequency, and the ordinate is the amplitude-frequency response.

[0101] In the above embodiment, the additional compensation amounts Δ1 and Δ2 that need to be added can be solved by changing the amplitude-frequency response of the non-band-stop frequency points. If the frequency interval of the non-band-stop frequency points is used for compensation.

[0102] In an optional embodiment, before performing precise point positioning calculation on the corrected observation model and the navigation message of the target navigation signal, the following steps are further included:

[0103] Determine the code phase and Doppler information of the target navigation signal;

[0104] Based on the code phase and Doppler information, perform fine tracking on the target navigation signal to obtain the navigation message of the target navigation signal.

[0105] In the embodiment of the present disclosure, perform acquisition calculation on the target navigation signal to determine the code phase and Doppler information of the target navigation signal.

[0106] Here, techniques such as a phase-locked loop (PLL) and a frequency-locked loop (FLL) can be adopted to input the code phase and Doppler frequency of the target navigation signal as initial parameters into the tracking loop. The PLL is responsible for precisely tracking the code phase, enabling it to follow the changes in the code phase of the target navigation signal in real time; the FLL focuses on the stable tracking of the Doppler frequency, ensuring that the signal frequency can still be accurately locked in the presence of dynamic changes in the signal. By continuously adjusting the phase and frequency of the local carrier and code sequence, they are made to match the target navigation signal as closely as possible. During the continuous tracking process, the navigation message is successfully demodulated from the target navigation signal.

[0107] In an alternative embodiment, precise point positioning calculations are performed on the corrected pseudorange observation model, the corrected carrier phase observation model, and the navigation message of the target navigation signal to obtain the clock offset data of the target navigation signal, which specifically includes the following steps:

[0108] Determine the parameters to be measured in the precise point positioning calculation; among them, the parameters to be measured include but are not limited to: the clock offset data to be measured, the position data to be measured, and the tropospheric error to be measured;

[0109] Based on the parameters to be measured, precise point positioning calculations are performed on the corrected pseudorange observation model and the corrected carrier phase observation model to obtain the clock offset data of the target navigation signal.

[0110] In the embodiments of the present disclosure, first, a pseudorange observation model and a carrier phase observation model can be established. Among them, the initial pseudorange observation model and the initial carrier phase observation model meet the following conditions:

[0111]

[0112] Among them, represents several distances between the satellite side and the receiving side, c is the speed of light, dt r is the receiver clock offset, dT s is the satellite clock offset, is the tropospheric delay, is the ionospheric delay, λ i represents the wavelength of the i frequency, b r,i 、 respectively represent the hardware delays of the carrier phase observation values at the receiver side and the satellite side at the i frequency, in cycles, represents the cycle ambiguity at the i frequency, is the carrier phase measurement noise, d r,i 、 respectively represent the hardware delays at the receiver side and the satellite side at the i frequency, in seconds, is the pseudorange measurement noise.

[0113] After that, the above observation models can be linearly combined for the observation data at different frequencies to obtain a virtual combined observation model. Among them, the linear combination of the observation values of the initial carrier phase observation model and the initial pseudorange observation model is as follows:

[0114]

[0115] Among them, the first parameter α1 and the second parameter α2 meet the following conditions:

[0116]

[0117] Then,

[0118]

[0119] Among them, the estimable receiver clock error parameter not only includes the receiver clock error itself, but also contains the influence of the ranging code hardware delay at the receiver end. Δt r is the ranging code and phase hardware delay deviation at the receiver end, and this parameter will be absorbed by the ambiguity parameter, and the ambiguity parameter is

[0120] Finally, based on the above conditions, the initial pseudorange observation model and the initial carrier phase observation model can be simplified to obtain a pseudorange observation model and a carrier phase observation model:

[0121]

[0122] After that, an error model can be established, and the pseudorange observation model and the carrier phase observation model can be corrected by using the above error model to obtain a corrected pseudorange observation model and a corrected carrier phase observation model.

[0123] Here, in the case where the error model is the earth tide correction model, the displacements of the station in the horizontal and vertical directions caused by the earth solid tide can be expressed by spherical harmonic functions of n latitude and m order containing Love numbers and Shida numbers. Therefore, the correction vector of the station position in the celestial coordinate system can be expressed by the following formula:

[0124]

[0125] Among them, is the second-order Love number, is the nominal value of the second-order Shida number, h3 = 0.292 is the third-order Love number, l3 = 0.015 is the nominal value of the third-order Shida number, GM j is the gravitational constant of the moon or the sun, GMΘ is the gravitational constant of the Earth, R e is the radius of the Earth, is the unit vector from the centroid of the moon or the sun to the center of the Earth, R j is its corresponding amplitude, is the unit vector from the center of the Earth to the measuring station, λ is the longitude of the measuring station, is the latitude of the measuring station, θ g is the Greenwich sidereal time difference.

[0126] Here, in the case where the error model is the ocean loading correction model, the ocean loading correction model can be obtained by the convolution integral of the instantaneous tide height of seawater provided by the global ocean tide model and the Green's function (the loading function of the Earth on a unit mass point). Among them, the Earth's solid tide correction model L meets the following conditions:

[0127]

[0128] Among them, N is the total number of tidal components. The ocean tide model considers the influence of 11 tidal waves on the displacement correction of the measuring station (i.e., M2, S2, N2, K1, K2, O1, P1, Q1, M f , M m , S sa ), including 4 semi-diurnal tidal waves (subscript 2), 4 diurnal tidal waves (subscript 1), and three long-period tidal waves (M f , M m , S sa ), L P径向 (θ,λ), L P东西 (θ,λ), L P南北 (θ,λ) and δ P径向 , δ P东西 , δ P南北 are the amplitudes and phases corresponding to the vertical, east-west, and north-south directions of each tidal wave (p) at the measuring station, respectively.

[0129] After that, navigation parameters can be extracted from the navigation message. Among them, the navigation parameters include but are not limited to: ephemeris parameters, clock bias parameters, and ionospheric parameters.

[0130] After that, precise point positioning calculations can be performed based on the navigation parameters and the corrected pseudo-range observation model and the corrected carrier phase observation model to obtain the parameter values of the parameters to be measured. Finally, the clock bias data of the target navigation signal can be determined from the parameter values of the parameters to be measured.

[0131] In an alternative embodiment, precise point positioning calculations are performed based on the parameters to be measured on the corrected pseudo-range observation model and the corrected carrier phase observation model to obtain the clock bias data of the target navigation signal, specifically including the following steps:

[0132] First, establish the observation equation and state equation based on the parameter to be measured;

[0133] Secondly, solve the observation equation and state equation through the Kalman filtering algorithm to obtain the floating-point solution corresponding to the parameter to be measured;

[0134] Finally, determine the clock error data of the target navigation signal in the floating-point solution corresponding to the parameter to be measured.

[0135] In the embodiments of the present disclosure, first, a mathematical equation can be established based on the observable quantities related to the satellite signals that can be received and the state quantities to be estimated. The observable quantities include satellite position information, signal propagation time, carrier phase, etc., and the state quantities to be estimated are clearly defined as the receiver antenna motion state parameters, receiver clock error, tropospheric parameters, and ambiguity parameters. In this way, the unknown quantities to be solved are theoretically defined, providing an overall framework for subsequent calculations.

[0136] Here, due to the non-linearity of satellite signal propagation and positioning calculations, the extended Kalman filtering algorithm can perform iterative updates based on the estimated value at the previous moment and the observed value at the current moment by linearizing and approximating the state quantities.

[0137] In this process, the state quantities to be estimated including the receiver antenna motion state parameters, receiver clock error, tropospheric parameters, and ambiguity parameters can be initially solved to obtain their floating-point solutions.

[0138] Among them, the floating-point solution is a preliminary estimate of each state quantity to be estimated and is the starting point for subsequent further optimization and accurate determination.

[0139] Here, for the position parameters, clock error parameters, and tropospheric error parameters to be estimated, considering the actual change characteristics of them have a certain degree of randomness.

[0140] For example, the movement of the receiver antenna is affected by various complex factors and its position changes irregularly, the receiver clock error will randomly drift due to clock instability, and the tropospheric parameters are affected by atmospheric changes and have uncertainty. Therefore, a random walk model is adopted. This model assumes that the parameter value at each moment is added with a random change amount based on the previous moment, which can effectively simulate the dynamic characteristics of these parameters and provide a more reasonable model basis for accurately determining these state quantities to be estimated.

[0141] Here, for the ambiguity parameters, different models are selected according to their states. When they are not fixed or cycle slips occur, their values are unstable and random, and a Gaussian white noise model is adopted. This model assumes that the error conforms to a Gaussian distribution and can reasonably describe its random fluctuation situation.

[0142] When it is fixed and there is no cycle slip, a constant model is adopted to simplify the calculation while ensuring the accuracy of the positioning calculation. Through this targeted model selection, the determination of the ambiguity, which is the state quantity to be estimated, is further optimized to obtain the clock offset data of the target navigation signal.

[0143] In the above embodiment, the observation equation is established to define the unknown quantity, providing a framework for the solution; the extended Kalman filter algorithm is used to obtain the floating-point solution of the state quantity to be estimated, laying the computational foundation; the random walk model is adopted for parameters such as position to fit its dynamic characteristics; different models are selected according to the state for the ambiguity parameter to optimize the processing method. Each step collaboratively realizes the solution of the state quantity to be estimated in precise point positioning, making the output clock offset data more accurate.

[0144] Based on the same inventive concept, the present disclosure also provides a time synchronization system for a low-Earth orbit satellite corresponding to the time synchronization method for a low-Earth orbit satellite. Since the principle of solving problems in the system of the present disclosure embodiment is similar to that of the above time synchronization method for a low-Earth orbit satellite of the present disclosure embodiment, the implementation of the system can refer to the implementation of the method, and the repeated parts will not be elaborated.

[0145] Refer to Figure 4 As shown, it is the architecture diagram of the time synchronization system for a low-Earth orbit satellite provided by the present disclosure embodiment, which includes:

[0146] An antenna receiving module 401, a first filtering module 402, a low-noise amplification module 403, a power splitting module 451, a second filtering module 452, a down-conversion module 453, an AD acquisition module 454, an interference suppression module 455, a capture module 456, a tracking module 457, a measurement module 458, a ppp calculation module 459, and a time-frequency synthesis module 460;

[0147] Among them, the antenna receiving module 401, the first filtering module 402, and the low-noise amplification module 403 all belong to the BDC antenna unit 400.

[0148] The antenna receiving module is used to receive satellite navigation signals.

[0149] The first filtering module is used to perform pre-filtering on the satellite navigation signal to obtain the filtered satellite navigation signal.

[0150] The low-noise amplification module is used to amplify the low noise of the filtered satellite navigation signal.

[0151] Among them, the power splitting module 451, the second filtering module 452, the down-conversion module 453, the AD acquisition module 454, the interference suppression module 455, the capture module 456, the tracking module 457, the measurement module 458, and the ppp calculation module 459 all belong to the receiver unit 450.

[0152] Among them, the power splitting module 451, the second filtering module 452, and the down-conversion module 453 all belong to the radio frequency unit 420.

[0153] The power splitting module is used to perform power splitting on the signal output by the low-noise amplification module.

[0154] The down-conversion module is used to perform down-conversion on the signal output by the power splitting module.

[0155] The second filtering module is used to perform filtering on the signal output by the down-conversion module to obtain an analog intermediate frequency signal.

[0156] Among them, the AD acquisition module 454, the interference suppression module 455, the acquisition module 456, the tracking module 457, the measurement module 458, and the ppp calculation module 459 all belong to the signal processing unit 430.

[0157] The AD acquisition module is used to perform analog-to-digital conversion on the analog signal to obtain a digital navigation signal.

[0158] The interference suppression module is used to suppress the interference of the digital navigation signal to obtain a target navigation signal.

[0159] Refer to Figure 5 As shown, it is the architecture diagram of the interference suppression module of the time synchronization system of the low-earth orbit satellite provided by the embodiment of the present disclosure, which includes:

[0160] The Fourier transform module 501, the interference spectrum line detection module 502, the interference spectrum line suppression module 503, the compensation point selection module 504, the amplitude-frequency compensation module 505, and the inverse Fourier transform module 506;

[0161] The Fourier transform module is used to receive the digital navigation signal of the AD acquisition module and perform Fourier transform processing on the digital navigation signal;

[0162] The interference spectrum line detection module is used to detect the interference spectrum line of the signal output by the Fourier transform module;

[0163] The interference spectrum line suppression module is used to suppress the interference of the signal output by the Fourier transform module.

[0164] The compensation point selection module is used to determine the compensation point of the signal output by the interference spectrum line suppression module, that is, the narrowband interference point with an amplitude-frequency response of 0.

[0165] The amplitude-frequency compensation module is used to perform amplitude-frequency compensation on the signal output by the interference spectrum line suppression module based on the compensation point determined by the compensation point selection module to obtain a target navigation signal.

[0166] A capture module for performing capture calculations on the target navigation signal, obtaining the code phase and Doppler of the target navigation signal, and completing rough detection.

[0167] A tracking module for finely tracking the signal output by the capture module to obtain the navigation message.

[0168] A measurement module for extracting the navigation message to obtain navigation parameters.

[0169] A PPP calculation module for performing precise point positioning calculations based on the navigation parameters to obtain the clock offset data of the target navigation signal.

[0170] A time-frequency synthesis module, including a time maintenance module, a time synchronization module, and a time output module, for timing the local clock based on the clock offset data.

[0171] Among them, the time maintenance module is jointly maintained by an FPGA (Field Programmable Gate Array) and a DSP (Digital Signal Processing technology).

[0172] A time synchronization module for adjusting the time of the local clock according to the clock offset information input by the information processing module.

[0173] A time output module for outputting a 1PPS signal to complete timing.

[0174] In the actual operation of this solution, the following technical effects can be achieved:

[0175] (1) Complete signal interference suppression under the constraint of high-precision measurement, and keep the ranging unchanged before and after interference suppression; solve the additional compensation amount by changing the amplitude-frequency response of non-notch frequency points.

[0176] (2) By linearly combining the pseudorange and carrier phase observation models, absorb the code hardware delay and phase hardware delay into the receiver clock offset and ambiguity parameters respectively to obtain an ionosphere-free combined observation model; use a random walk model for the position parameters, clock offset parameters, and tropospheric error, and use a Gaussian white noise or constant model for the ambiguity parameters to establish a state equation, and perform PPP positioning and timing solution to accurately and reasonably handle various errors and accuracy influencing factors, and achieve sub-nanosecond timing accuracy.

[0177] Based on the same inventive concept, the embodiments of the present disclosure also provide a timing system for low-earth orbit satellites corresponding to the timing method for low-earth orbit satellites. Since the principle of solving problems in the system in the embodiments of the present disclosure is similar to the above-mentioned timing method for low-earth orbit satellites in the embodiments of the present disclosure, the implementation of the system can refer to the implementation of the method, and the repeated parts will not be described again.

[0178] Refer to Figure 6 As shown, it is a schematic diagram of the timing device for low-earth orbit satellites provided by the embodiments of the present disclosure. The device includes: an interference suppression unit 11, an amplitude-frequency compensation unit 12, a correction unit 13, and a timing unit 14; where:

[0179] The interference suppression unit 11 is configured to obtain a digital navigation signal and suppress the interference spectral lines of the digital navigation signal to obtain a suppressed digital navigation signal;

[0180] The amplitude-frequency compensation unit 12 is configured to perform amplitude-frequency compensation on the suppressed digital navigation signal to obtain a target navigation signal;

[0181] The correction unit 13 is configured to correct the pseudo-range observation model and the carrier phase observation model of the low-earth orbit satellite based on the error model of precise point positioning to obtain a corrected pseudo-range observation model and a corrected carrier phase observation model;

[0182] The timing unit 14 is configured to perform precise point positioning calculations on the corrected pseudo-range observation model, the corrected carrier phase observation model, and the navigation message of the target navigation signal to obtain the clock offset data of the target navigation signal, and perform timing on the local clock according to the clock offset data.

[0183] In the embodiments of the present disclosure, by suppressing the interference spectral lines and performing amplitude-frequency compensation on the digital navigation signal, interference is reduced and the signal characteristics are optimized, providing a high-quality signal basis for subsequent operations. Based on the precise point positioning error model, the pseudo-range and carrier phase observation models are corrected to reduce measurement errors and improve positioning accuracy. Furthermore, the clock offset data can be accurately obtained, enabling sub-nanosecond-level precise timing. At the same time, this method does not rely on the space-ground time synchronization link of the ground measurement and control station, reducing the ground burden and enhancing the autonomy and flexibility of the timing system.

[0184] In a possible implementation, the interference suppression unit is further configured to receive a satellite navigation signal, filter the satellite navigation signal to obtain a filtered satellite navigation signal;

[0185] Process the filtered satellite navigation signal to obtain an analog intermediate frequency signal;

[0186] Perform analog-to-digital conversion on the analog intermediate frequency signal to obtain the digital navigation signal.

[0187] In a possible implementation, the amplitude-frequency compensation unit is further configured to determine the narrowband interference in the digital navigation signal;

[0188] Based on an anti-interference filter, determine the measurement zero value corresponding to the narrowband interference;

[0189] Determine the measurement zero value to be compensated among the said measurement zero values; wherein, the measurement zero value to be compensated is the measurement zero value that has changed after passing through the anti-interference filter;

[0190] Perform amplitude-frequency compensation on the measurement zero value to be compensated to obtain the target navigation signal.

[0191] In a possible implementation manner, the correction unit is further configured to determine the code phase and Doppler information of the target navigation signal;

[0192] Perform fine tracking on the target navigation signal based on the code phase and the Doppler information to obtain the navigation message of the target navigation signal.

[0193] In a possible implementation manner, the timing unit is further configured to determine the parameters to be measured for the precise point positioning calculation; wherein, the parameters to be measured include but are not limited to: the clock error data to be measured, the position data to be measured, and the tropospheric error to be measured;

[0194] Perform precise point positioning calculation on the corrected pseudorange observation model and the corrected carrier phase observation model based on the parameters to be measured to obtain the clock error data of the target navigation signal.

[0195] In a possible implementation manner, the timing unit is specifically configured to establish an observation equation and a state equation based on the parameters to be measured;

[0196] Solve the observation equation and the state equation through the Kalman filtering algorithm to obtain the floating-point solution corresponding to the parameters to be measured;

[0197] Determine the clock error data of the target navigation signal in the floating-point solution corresponding to the parameters to be measured.

[0198] The description of the processing flow of each module in the device and the interaction flow between each module can refer to the relevant description in the above method embodiment and will not be elaborated here.

[0199] Corresponding to Figure 1 the timing method for low-earth orbit satellites in Figure 7 shown in, the present disclosure embodiment further provides an electronic device 700, as

[0200] A processor 71, a memory 72, and a bus 73; the memory 72 is used to store execution instructions, including an internal memory 721 and an external memory 722; here, the internal memory 721 is also called the main memory, which is used to temporarily store the operation data in the processor 71 and the data exchanged with the external memory 722 such as a hard disk. The processor 71 exchanges data with the external memory 722 through the internal memory 721. When the electronic device 700 runs, the processor 71 communicates with the memory 72 through the bus 73, so that the processor 71 executes the following instructions:

[0201] Obtain a digital navigation signal, and suppress the interference spectral lines of the digital navigation signal to obtain a suppressed digital navigation signal;

[0202] Perform amplitude-frequency compensation on the suppressed digital navigation signal to obtain a target navigation signal;

[0203] Based on the error model of precise point positioning, correct the pseudorange observation model and the carrier phase observation model of the low-earth orbit satellite to obtain a corrected pseudorange observation model and a corrected carrier phase observation model;

[0204] Perform precise point positioning calculation on the corrected pseudorange observation model, the corrected carrier phase observation model, and the navigation message of the target navigation signal to obtain the clock offset data of the target navigation signal, and perform time synchronization on the local clock according to the clock offset data.

[0205] The embodiments of the present disclosure also provide a computer-readable storage medium, on which a computer program is stored. When the computer program is run by a processor, it executes the steps of the time synchronization method of the low-earth orbit satellite described in the above method embodiments. Wherein, the storage medium can be a volatile or non-volatile computer-readable storage medium.

[0206] The embodiments of the present disclosure also provide a computer program product, which carries program codes. The instructions included in the program codes can be used to execute the steps of the time synchronization method of the low-earth orbit satellite described in the above method embodiments. For details, please refer to the above method embodiments and will not be elaborated here.

[0207] Wherein, the above computer program product can be specifically implemented in a way of hardware, software, or a combination thereof. In an optional embodiment, the computer program product is specifically embodied as a computer storage medium. In another optional embodiment, the computer program product is specifically embodied as a software product, such as a Software Development Kit (SDK), etc.

[0208] The basic principles of the present disclosure have been described above in connection with specific embodiments. However, it should be noted that the advantages, benefits, effects, etc. mentioned in the present disclosure are merely examples and not limitations, and it cannot be considered that these advantages, benefits, effects, etc. are essential for each embodiment of the present disclosure. Additionally, the specific details disclosed above are only for illustrative and facilitating understanding purposes, rather than limitations, and these details do not limit the present disclosure to necessarily adopt such specific details for implementation.

[0209] The block diagrams of the devices, apparatuses, equipment, and systems involved in the present disclosure are only illustrative examples and do not intend to require or imply that they must be connected, arranged, and configured in the manner shown in the block diagrams. As those skilled in the art will recognize, these devices, apparatuses, equipment, and systems can be connected, arranged, and configured in any manner. Words such as "including", "comprising", "having", etc. are open-ended terms, meaning "including but not limited to", and can be used interchangeably with each other. The word "or" and "and" used herein refer to the word "and / or" and can be used interchangeably with it, unless the context clearly indicates otherwise. The word "such as" used herein refers to the phrase "such as but not limited to" and can be used interchangeably with it.

[0210] In addition, as used herein, the "or" used in the listing of items starting with "at least one" indicates a separate listing, so that for example, the listing of "at least one of A, B, or C" means A or B or C, or AB or AC or BC, or ABC (i.e., A and B and C). Furthermore, the term "exemplary" does not mean that the described examples are preferred or better than other examples.

[0211] It should also be noted that in the systems and methods of the present disclosure, each component or each step can be decomposed and / or recombined. These decompositions and / or recombinations should be regarded as equivalent solutions of the present disclosure.

[0212] Various changes, substitutions, and alterations to the technologies described herein can be made without departing from the teachings defined by the appended claims. In addition, the scope of the claims of the present disclosure is not limited to the specific aspects of the processes, machines, manufactures, compositions of events, means, methods, and acts described above. Current or later-developed processes, machines, manufactures, compositions of events, means, methods, or acts that perform substantially the same function or achieve substantially the same result as the corresponding aspects described herein can be utilized. Thus, the appended claims include such processes, machines, manufactures, compositions of events, means, methods, or acts within their scope.

[0213] The foregoing description of the disclosed aspects is provided to enable any person skilled in the art to make or use the present disclosure. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other aspects without departing from the scope of the present disclosure. Accordingly, the present disclosure is not intended to be limited to the aspects shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0214] The foregoing description has been presented for purposes of illustration and description. In addition, the description is not intended to limit embodiments of the present disclosure to the form disclosed herein. Although several example aspects and embodiments have been discussed above, those skilled in the art will recognize some variations, modifications, alterations, additions, and subcombinations thereof.

Claims

1. A time synchronization method for low-earth orbit satellites, characterized in that, Including: Obtain a digital navigation signal, suppress interference spectral lines of the digital navigation signal, and obtain a suppressed digital navigation signal; Perform amplitude-frequency compensation on the suppressed digital navigation signal to obtain a target navigation signal; Based on the error model of precise point positioning, correct the pseudorange observation model and carrier phase observation model of the low-earth orbit satellite to obtain a corrected pseudorange observation model and a corrected carrier phase observation model; Perform precise point positioning calculation on the corrected pseudorange observation model, the corrected carrier phase observation model, and the navigation message of the target navigation signal to obtain the clock offset data of the target navigation signal, and perform time service on the local clock according to the clock offset data.

2. The method according to claim 1, wherein The obtaining of the digital navigation signal includes: Receive a satellite navigation signal, filter the satellite navigation signal, and obtain a filtered satellite navigation signal; Process the filtered satellite navigation signal to obtain an analog intermediate frequency signal; Perform analog-to-digital conversion on the analog intermediate frequency signal to obtain the digital navigation signal.

3. The method according to claim 1, characterized in that The performing of amplitude-frequency compensation on the suppressed digital navigation signal to obtain a target navigation signal includes: Determine narrowband interference in the digital navigation signal; Based on an anti-interference filter, determine a measurement zero value corresponding to the narrowband interference; Determine a measurement zero value to be compensated among the measurement zero values; wherein, the measurement zero value to be compensated is a measurement zero value that has changed after passing through the anti-interference filter; Perform amplitude-frequency compensation on the measurement zero value to be compensated to obtain the target navigation signal.

4. The method according to claim 1, wherein Before performing precise point positioning calculation on the corrected observation model and the navigation message of the target navigation signal, the method further includes: Determine the code phase and Doppler information of the target navigation signal; Based on the code phase and the Doppler information, perform fine tracking on the target navigation signal to obtain the navigation message of the target navigation signal.

5. The method according to claim 1, characterized in that, The performing of precise point positioning calculation on the corrected pseudorange observation model, the corrected carrier phase observation model, and the navigation message of the target navigation signal to obtain the clock offset data of the target navigation signal includes: Determine the parameters to be measured for the precise point positioning calculation; wherein, the parameters to be measured include but are not limited to: to-be-measured clock offset data, to-be-measured position data, and to-be-measured tropospheric error; Based on the parameters to be measured, perform precise point positioning calculation on the corrected pseudorange observation model and the corrected carrier phase observation model to obtain the clock offset data of the target navigation signal.

6. The method according to claim 5, characterized in that, The performing of precise point positioning calculation on the corrected pseudorange observation model and the corrected carrier phase observation model based on the parameters to be measured to obtain the clock offset data of the target navigation signal includes: Establish an observation equation and a state equation based on the parameters to be measured; Solve the observation equation and the state equation through a Kalman filtering algorithm to obtain a floating-point solution corresponding to the parameters to be measured; Determine the clock offset data of the target navigation signal in the floating-point solution corresponding to the parameters to be measured.

7. A time synchronization device for a low-earth orbit satellite, characterized in that, Including: An interference suppression unit, configured to obtain a digital navigation signal, suppress interference spectral lines of the digital navigation signal, and obtain a suppressed digital navigation signal; An amplitude-frequency compensation unit for performing amplitude-frequency compensation on the suppressed digital navigation signal to obtain a target navigation signal; A correction unit for correcting the pseudorange observation model and the carrier phase observation model of the low-earth orbit satellite based on the error model of precise point positioning to obtain a corrected pseudorange observation model and a corrected carrier phase observation model; A timing unit for performing precise point positioning calculation on the corrected pseudorange observation model, the corrected carrier phase observation model, and the navigation message of the target navigation signal to obtain the clock error data of the target navigation signal, and timing the local clock according to the clock error data.

8. An electronic device, characterized in that, Comprising: A processor, a memory, and a bus. The memory stores machine-readable instructions executable by the processor. When the electronic device is running, the processor communicates with the memory through the bus. When the machine-readable instructions are executed by the processor, the steps of the timing method for a low-earth orbit satellite according to any one of claims 1 to 6 are executed.

9. A computer-readable storage medium, characterized in that, A computer program is stored on the computer-readable storage medium. When the computer program is run by a processor, the steps of the timing method for a low-earth orbit satellite according to any one of claims 1 to 6 are executed.

10. A computer program product, comprising a computer program / instructions, characterized in that, When the computer program / instructions are executed by a processor, the steps of the timing method for a low-earth orbit satellite according to any one of claims 1 to 6 are implemented.

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