A doppler frequency offset compensation method, apparatus and device

Abstract

The application provides a Doppler frequency offset compensation method, device and equipment, and relates to the technical field of satellite communication. The method comprises the following steps: predicting state information of a satellite at a target moment according to state information of the satellite at a first moment and a two-body orbit model; predicting state information of a terminal on a flying object at the target moment according to navigation data of the flying object at the first moment; and determining a downlink Doppler frequency offset between the satellite and the terminal at the target moment according to the state information of the satellite at the target moment and the state information of the terminal on the flying object at the target moment. The method of the application effectively solves the key technical problems of low frequency offset prediction accuracy, large compensation lag and poor link coordination of the traditional Doppler compensation method in the communication process between a high-speed flying object and a low-orbit satellite in a high dynamic environment, and improves the frequency offset prediction accuracy.

Description

Technical Field

[0001] This invention relates to the field of satellite communication technology, and in particular to a Doppler frequency offset compensation method, apparatus, and device. Background Technology

[0002] With the rapid development of the low-altitude economy, new flight platforms such as drone logistics, urban air traffic, emergency rescue, and missile aircraft are growing rapidly in both number and type, placing higher demands on the real-time performance, reliability, and anti-interference capabilities of integrated space-ground communication networks. Low-Earth orbit (LEO) satellites, with their advantages of low orbit, low latency, strong signal, and dense deployment, are becoming the ideal infrastructure for supporting communication in low-altitude, high-dynamic scenarios.

[0003] Among related technologies, compared with traditional terrestrial base station communication, low-Earth orbit (LEO) satellite communication can achieve stable all-weather coverage across regions and seas, making it particularly suitable for high-speed aircraft communication. However, LEO satellites themselves operate at high speeds, and the relative speed between the flight platform and the satellite changes drastically, causing frequency offset to change rapidly over time. This results in significant Doppler frequency offset problems in the communication link. If not accurately compensated, this can lead to problems such as frequency deviation from the local oscillator center, carrier lock failure, code tracking instability, and demodulation performance degradation, which in severe cases can cause communication link interruption. Summary of the Invention

[0004] This invention provides a Doppler frequency offset compensation method, apparatus, and device, which effectively solves the key technical problems of traditional Doppler compensation methods in high dynamic environments, such as low frequency offset prediction accuracy, large compensation lag, and poor link coordination, in the communication process between high-speed flying objects and low-orbit satellites, and improves the frequency offset prediction accuracy.

[0005] This invention provides a Doppler frequency offset compensation method, comprising the following steps.

[0006] Based on the satellite's state information at the first moment and the two-body orbit model, predict the satellite's state information at the target moment;

[0007] Based on the navigation data of the flying object at the first moment, predict the status information of the terminal on the flying object at the target moment;

[0008] Based on the satellite's status information and the terminal's status information on the aircraft at the target time, the downlink Doppler frequency offset between the satellite and the terminal at the target time is determined.

[0009] According to a Doppler frequency offset compensation method provided by the present invention, determining the downlink Doppler frequency offset between the satellite and the terminal at the target time based on the satellite's state information and the terminal's state information on the spacecraft at the target time includes:

[0010] The downlink Doppler frequency offset between the satellite and the terminal at the target time is determined based on the following method:

[0011] ;

[0012] in, Indicates downlink Doppler frequency offset; Indicates the communication carrier frequency; Represents the speed of light; The location information of the terminal on the aircraft at the target time; Indicates the satellite's position information at the target time; The speed information of the terminal on the aircraft at the target time; This indicates the satellite's velocity information at the target time.

[0013] According to a Doppler frequency offset compensation method provided by the present invention, after determining the downlink Doppler frequency offset between the satellite and the terminal at the target time based on the satellite's state information and the terminal's state information on the spacecraft at the target time, the method further includes:

[0014] The downlink code phase offset at the target time is determined based on the downlink Doppler frequency offset at the target time.

[0015] According to a Doppler frequency offset compensation method provided by the present invention, after determining the downlink Doppler frequency offset between the satellite and the terminal at the target time based on the satellite's state information and the terminal's state information on the spacecraft at the target time, the method further includes:

[0016] Obtain the downlink residual frequency offset;

[0017] Based on the downlink residual frequency offset, determine the clock offset between the satellite and the terminal;

[0018] The uplink Doppler frequency offset is determined based on the clock offset between the satellite and the terminal, the satellite's status information at the first moment, and the navigation data of the flying object at the first moment.

[0019] According to a Doppler frequency offset compensation method provided by the present invention, determining the uplink Doppler frequency offset based on the clock offset between the satellite and the terminal, the satellite's state information at the first moment, and the navigation data of the flying object at the first moment includes:

[0020] The uplink Doppler frequency offset is determined based on the following method:

[0021] ;

[0022] in, Indicates upward Doppler frequency offset; Indicates the communication carrier frequency; Indicates the clock offset between the satellite and the terminal; The Doppler coefficient is represented by the Doppler coefficient, which is determined based on the satellite's state information and the navigation data of the flying object at the first moment.

[0023] According to a Doppler frequency offset compensation method provided by the present invention, after determining the uplink Doppler frequency offset, the method further includes:

[0024] The uplink code phase offset is determined based on the uplink Doppler frequency offset.

[0025] The Doppler frequency offset compensation method provided by the present invention further includes:

[0026] Obtain open-source two-line orbit TLE data from the satellite;

[0027] Based on the TLE data, the satellite's status information at the first moment is determined.

[0028] The present invention also provides a Doppler frequency offset compensation device, comprising the following modules:

[0029] The first prediction module is used to predict the satellite's state information at the target time based on the satellite's state information at the first moment and the two-body orbit model;

[0030] The second prediction module predicts the status information of the terminal on the flying object at the target time based on the navigation data of the flying object at the first moment.

[0031] The determination module is used to determine the downlink Doppler frequency offset between the satellite and the terminal at the target time based on the satellite's status information and the terminal's status information on the flying object at the target time.

[0032] The present invention also provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the Doppler frequency offset compensation method as described above.

[0033] The present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the Doppler frequency offset compensation method as described above.

[0034] The present invention also provides a computer program product, including a computer program that, when executed by a processor, implements the Doppler frequency offset compensation method as described above.

[0035] The Doppler frequency offset compensation method, apparatus, and device provided by this invention integrate satellite orbit extrapolation and object navigation state extrapolation at the terminal side to construct a frequency offset prediction and pre-compensation process. This enables Doppler prediction and compensation between high-speed objects and satellites based on navigation information, effectively solving key technical problems of traditional Doppler compensation methods in high-dynamic environments, such as low frequency offset prediction accuracy, large compensation lag, and poor link coordination, during communication between high-speed objects and low-orbit satellites. Moreover, by completing frequency offset prediction and compensation control at the terminal side, the compensation response delay can be effectively reduced, the processing bottleneck under limited onboard resources can be avoided, the real-time performance of link frequency synchronization can be significantly improved, and the frequency offset prediction accuracy can be increased. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0037] Figure 1 This is a schematic diagram of a high-speed aircraft communicating with a satellite, as provided by the present invention.

[0038] Figure 2 This is one of the flowcharts of the Doppler frequency offset compensation method provided by the present invention.

[0039] Figure 3 This is the second flowchart of the Doppler frequency offset compensation method provided by the present invention.

[0040] Figure 4 This is a flowchart of satellite orbit prediction provided by the present invention.

[0041] Figure 5 This is a schematic diagram of terminal frequency offset and code offset pre-compensation provided by the present invention.

[0042] Figure 6 This is a schematic diagram of the Doppler frequency offset compensation device provided by the present invention.

[0043] Figure 7 This is a schematic diagram of the structure of the electronic device provided by the present invention. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0045] The following is combined with Figures 1-7 The present invention describes a Doppler frequency offset compensation method, apparatus, and device.

[0046] To facilitate a clearer understanding of the technical solutions of the various embodiments of this application, some technical content related to the various embodiments of this application will be introduced first.

[0047] Typical application scenarios in high-speed aircraft and satellite communication include: Figure 1 As shown, high-speed aircraft can be high-speed cruise missiles, drones, aerospace vehicles, etc., equipped with terminals that provide real-time communication support. Low-Earth orbit (LEO) satellites act as communication relay nodes, and ground stations act as data hubs, responsible for two-way communication with the satellites. The terminals need to maintain stable uplink and downlink communication with the LEO satellites under highly dynamic conditions.

[0048] Current traditional Doppler compensation strategies still face significant technical bottlenecks in high-speed, high-dynamic environments, mainly including:

[0049] ① Satellite-side frequency offset pre-compensation strategy: The satellite estimates the link frequency offset and adjusts the frequency accordingly. This requires high-precision time synchronization between the two communicating parties. However, the onboard processing resources are limited, making it difficult to continuously support high-frequency, full-link frequency offset estimation and compensation operations.

[0050] ② The problem of terminal state prediction error accumulation: Traditional methods often use "current position and current speed" to roughly extrapolate future frequency deviation, without considering the nonlinear changes in the motion state of the flight platform, resulting in the gradual accumulation of compensation error.

[0051] ③ Time synchronization and interface delay issues: There are often interface delays or asynchrony issues between the terminal navigation module and the communication module, which cause navigation status to lag and affect the accuracy of frequency offset estimation.

[0052] ④ The contradiction between algorithm complexity and deployment capability: Some numerical prediction algorithms have high requirements for terminal computing power, making it difficult to deploy on small flight platforms such as drones or missile-borne platforms with limited resources.

[0053] In summary, existing technologies struggle to achieve high-precision, low-complexity Doppler compensation under real-world conditions of limited terminal computing resources, highly dynamic states, and incomplete satellite orbit information. Therefore, there is an urgent need to propose a Doppler compensation method that combines orbit prediction with navigation state extrapolation to compress the frequency offset dynamic range and improve synchronization success rate and communication reliability.

[0054] Figure 2 This is one of the flowcharts of the Doppler frequency offset compensation method provided by the present invention, which includes the following:

[0055] Step 201: Based on the satellite's state information at the first moment and the two-body orbit model, predict the satellite's state information at the target moment.

[0056] Specifically, in this embodiment, the satellite's state information at a target time is first predicted based on the satellite's state information at a first moment and the two-body orbit model. Optionally, the first moment can be the moment when the terminal on the spacecraft is powered on, or it can be any other moment; the target time is a moment after the first moment. The satellite's state information includes its position and velocity information. Optionally, the satellite's state information at the first moment can be determined based on the satellite's open-source two-line orbit TLE data, and then the two-body orbit model is used to perform short-time, high-frequency extrapolation calculations on the satellite's state at several future moments, thereby achieving the prediction of the satellite's trajectory.

[0057] Step 202: Based on the navigation data of the flying object at the first moment, predict the status information of the terminal on the flying object at the target moment.

[0058] Specifically, in this embodiment, the state information of the terminal on the aircraft at the target time is predicted based on the navigation data of the aircraft at the first moment. In other words, this application predicts the state of the terminal on the aircraft by introducing the aircraft's navigation information.

[0059] For example, the navigation system of an aircraft is periodic (in terms of periodicity). Provides current location and velocity information, taking into account time delays in information transmission and processing. This application assumes that the flying object is moving with uniform acceleration for a short period of time, based on Navigation data at any given moment for future moments Extrapolate the state of the flying object to obtain the predicted position. and prediction speed .

[0060] Step 203: Determine the downlink Doppler frequency offset between the satellite and the terminal at the target time based on the satellite status information and the terminal status information on the flying object at the target time.

[0061] Specifically, in this embodiment, after predicting the satellite's state information at the target time based on the satellite's state information at the first moment and the two-body orbit model, and predicting the terminal's state information on the flying object at the target time based on the flying object's navigation data at the first moment, the downlink Doppler frequency offset between the satellite and the terminal at the target time can be determined based on the satellite's state information at the target time and the terminal's state information on the flying object at the target time. Optionally, based on the predicted states of the satellite and the flying object, the projection of the relative velocity in the line-of-sight direction can be calculated at any time t to obtain the radial velocity, and the downlink Doppler frequency offset between the satellite and the terminal can be determined accordingly. That is, by fusing orbit extrapolation and navigation state extrapolation at the terminal side, the motion state of the high-speed flying object and the relative velocity of the satellite are estimated, a frequency offset prediction and pre-compensation process is constructed, and the downlink frequency offset is compensated in advance, thereby significantly improving the Doppler compensation accuracy and link synchronization performance when the high-speed flying object communicates with the satellite under high dynamic conditions, reducing the frequency range that the terminal needs to search when receiving, and reducing the time complexity and hardware resource consumption of frequency offset acquisition.

[0062] The method described in the above embodiments, by fusing satellite orbit extrapolation and object navigation state extrapolation at the terminal side, constructs a frequency offset prediction and pre-compensation process, realizing Doppler prediction and compensation between high-speed objects and satellites based on navigation information. This effectively solves key technical problems such as low frequency offset prediction accuracy, large compensation lag, and poor link coordination in the communication process between high-speed objects and low-orbit satellites under high dynamic environments, which are inherent to traditional Doppler compensation methods. Moreover, by completing frequency offset prediction and compensation control at the terminal side, the compensation response delay can be effectively reduced, the processing bottleneck under limited onboard resources can be avoided, the real-time performance of link frequency synchronization can be significantly improved, and the frequency offset prediction accuracy can be increased.

[0063] In some embodiments, determining the downlink Doppler frequency offset between the satellite and the terminal at the target time based on the satellite's state information at the target time and the terminal's state information on the aircraft at the target time includes:

[0064] The downlink Doppler frequency offset between the satellite and the terminal at the target time is determined based on the following method:

[0065] ;

[0066] in, Indicates downlink Doppler frequency offset; Indicates the communication carrier frequency; Represents the speed of light; This indicates the position information of the terminal on the target aircraft at that moment; Indicates the satellite's position information at the target time; This indicates the speed information of the terminal on the target aircraft at that moment; This indicates the satellite's velocity information at the target time.

[0067] Specifically, in this embodiment, based on the predicted state of the satellite and the flying object, the projection of the relative velocity in the line-of-sight direction is calculated at any time t to obtain the radial velocity, and the downlink Doppler frequency offset between the satellite and the terminal is determined accordingly. Optionally, the calculation formula is as follows:

[0068] ;

[0069] in, Indicates downlink Doppler frequency offset; Indicates the communication carrier frequency; Represents the speed of light; This indicates the position information of the terminal on the target aircraft at that moment; Indicates the satellite's position information at the target time; This indicates the speed information of the terminal on the target aircraft at that moment; This indicates the satellite's velocity information at the target time.

[0070] Optionally, to achieve frequency domain compensation, the terminal receiving module uses a direct digital synthesizer (DDS) to generate and estimate the frequency offset. A sinusoidal signal of opposite frequency is used, and point-by-point multiplication is performed with the received signal to achieve frequency offset cancellation. This is predicted based on the downlink Doppler frequency offset and code phase offset calculation steps. Then, calculate the Doppler coefficients. , recorded as .

[0071] The downlink frequency offset pre-compensation amount is:

[0072]

[0073] The corresponding DDS frequency control word is represented as follows:

[0074]

[0075] in, The terminal signal sampling rate, This is the bit width of the phase accumulator in the DDS. Indicates the storage depth of the DDS lookup table.

[0076] The method described in the above embodiments introduces a Doppler pre-compensation mechanism based on navigation information, which uses satellite orbit prediction and object state estimation results to pre-correct downlink frequency offset. This significantly reduces the frequency range that the terminal needs to search during reception, reduces the time complexity and hardware resource consumption of frequency offset acquisition, and improves the initial synchronization efficiency of the receiving link.

[0077] In some embodiments, after determining the downlink Doppler frequency offset between the satellite and the terminal at the target time based on the satellite's state information at the target time and the terminal's state information on the aircraft at the target time, the method further includes:

[0078] The downlink code phase offset at the target time is determined based on the downlink Doppler frequency offset at the target time.

[0079] Specifically, based on downlink Doppler frequency offset compensation, this application employs resampling compensation technology to adjust the code phase of the received signal in order to further eliminate sampling time base drift caused by the Doppler effect. Optionally, the code phase offset... The calculation formula is expressed as follows:

[0080]

[0081] in, Represents the symbol period, This represents the chip rate.

[0082] Based on the downlink frequency offset prediction results, the sampling rate after resampling is set as follows:

[0083]

[0084] The method described in the above embodiments comprehensively considers Doppler frequency offset and code phase drift, and proposes a joint frequency offset and code offset compensation method based on DDS compensation and resampling adjustment. This effectively realizes integrated processing of frequency and time synchronization, and greatly improves the communication quality between satellites and high-speed flying objects.

[0085] In some embodiments, after determining the downlink Doppler frequency offset between the satellite and the terminal at the target time based on the satellite's state information at the target time and the terminal's state information on the aircraft at the target time, the method further includes:

[0086] Obtain the downlink residual frequency offset;

[0087] Based on the downlink residual frequency offset, determine the clock offset between the satellite and the terminal;

[0088] The uplink Doppler frequency offset is determined based on the clock offset between the satellite and the terminal, the satellite status information at the first moment, and the navigation data of the flying object at the first moment.

[0089] Specifically, for highly dynamic flying objects, without pre-compensation, the uplink signal frequency offset changes rapidly and over a wide range, easily exceeding the acquisition window of the satellite receiving channel, leading to communication failure. Furthermore, since terminals have more resources than satellites, and satellite resources are more limited, clock offset can have a more severe impact on the uplink. Therefore, this application addresses the clock offset problem between the terminal and the satellite in the uplink by introducing clock bias feedback and clock offset compensation mechanisms. Compared to compensating only for Doppler frequency offset, this further eliminates systematic errors caused by clock bias and improves the accuracy of uplink pre-compensation.

[0090] Optionally, this application proposes a method for clock bias estimation based on downlink residual frequency offset sequences, and feeds the estimation results back to uplink frequency offset correction. Optionally, the downlink residual frequency offset estimation result, i.e., the residual frequency offset estimate, can be obtained after downlink receiver acquisition and tracking. The residual frequency offset includes the following components:

[0091]

[0092] Among them, the Doppler frequency offset estimation error The prediction error is caused by the accumulation of satellite orbit prediction errors over time. With random platform motion prediction error composition, , Assuming a short period of time , Both are constant terms, and their sum is denoted as the estimator. .conduct The residual frequency offset observations then yield:

[0093]

[0094] Observation noise Based on this, the following least squares estimation model is constructed:

[0095]

[0096]

[0097] Optionally, the least squares estimation result is as follows, thus achieving an accurate estimation of clock offset based on the downlink residual frequency offset sequence:

[0098]

[0099] Optionally, when clock offset is determined, this embodiment of the application feeds back the downlink clock offset estimation result to the uplink signal transmitter for Doppler prediction compensation. The uplink is mainly affected by the Doppler frequency offset between satellite terminals and the clock offset between satellite terminals, and the Doppler coefficient... It was estimated in the downlink Doppler frequency offset calculation step. This is estimated during the downlink code offset pre-compensation step. Optionally, the carrier frequency received on-board is considered by the satellite to be... Then the actual receiving frequency on the satellite should be , Represents the satellite's clock offset. Uplink frequency compensation. With terminal clock offset carrier frequency The Doppler coefficients satisfy the following relationship:

[0100]

[0101] Therefore, the uplink frequency offset compensation amount satisfy:

[0102]

[0103] Due to the Doppler coefficient Generally satisfies To facilitate implementation, it can be Approximately Simplified uplink frequency offset compensation amount:

[0104]

[0105] Corresponding DDS frequency control word It is expressed as follows:

[0106]

[0107] The method described in the above embodiments, by predicting the motion state of the high-speed flying object and its relative velocity with the satellite, compensates for the uplink frequency offset in advance, significantly suppressing the dynamic range of frequency offset changes, improving the on-board acquireability of the uplink signal, and effectively ensuring the communication capability of the uplink under high dynamic conditions. Furthermore, in this embodiment, clock bias estimation is performed based on the downlink residual frequency offset sequence, and the estimation result is fed back to correct the uplink frequency offset. Compared to compensating only for the Doppler frequency offset, this further eliminates systematic errors caused by clock bias and improves the accuracy of uplink pre-compensation.

[0108] In some embodiments, after determining the uplink Doppler frequency offset, the method further includes:

[0109] The uplink code phase offset is determined based on the uplink Doppler frequency offset.

[0110] Specifically, based on uplink Doppler frequency offset compensation, this application employs resampling compensation technology to adjust the received signal code phase in order to further eliminate sampling time base drift caused by the Doppler effect. Optionally, based on the uplink frequency offset prediction result, the sampling rate after resampling is set as follows:

[0111]

[0112] The method described in the above embodiments comprehensively considers Doppler frequency offset and code phase drift, and proposes a joint frequency offset and code offset compensation method based on DDS compensation and resampling adjustment. This effectively realizes integrated processing of frequency and time synchronization, and greatly improves the communication quality between satellites and high-speed flying objects.

[0113] In some embodiments, the Doppler frequency offset compensation method further includes:

[0114] Obtain open-source two-line orbit TLE data from the satellite;

[0115] Based on TLE data, determine the satellite's status information at the first moment.

[0116] Specifically, in this embodiment, the satellite's status information is determined based on the open-source two-line element (TLE) orbit data of the satellite. For example, after powering on, the communication terminal reads the open-source two-line element (TLE) orbit data set of all satellites, extracts the orbital six elements of each satellite, including mean angular velocity, orbital inclination, eccentricity, argument of perigee, right ascension of the ascending node, and mean perigee. Based on the SGP4 orbit extrapolation algorithm, the orbital six elements are perturbated and corrected to calculate the satellite's three-dimensional position vector. and velocity vector This allows for the accurate determination of the satellite's initial state information, which in turn effectively improves the accuracy of satellite trajectory prediction and Doppler offset estimation, thereby enhancing communication capabilities under high dynamic conditions.

[0117] The method described above, based on open-source two-line orbit TLE data of the satellite, enables accurate determination of the initial state information of the satellite, thereby effectively improving the accuracy of satellite trajectory prediction and Doppler offset estimation results, and enhancing communication capabilities under high dynamic conditions.

[0118] For example, such as Figure 3 As shown in the figure, this application provides a Doppler frequency offset compensation method, the specific process of which is as follows:

[0119] ① Satellite status initialization.

[0120] After powering on, the communication terminal reads the open-source two-line element (TLE) data set of all satellites, extracts the six orbital elements for each satellite, including mean angular velocity, orbital inclination, eccentricity, argument of perigee, right ascension of the ascending node, and mean perigee. Based on the SGP4 orbital extrapolation algorithm, the six orbital elements are perturbed and corrected to calculate the satellite's position at the current moment. 3D position vector and velocity vector Among them, the SGP4 model is an analytical method whose orbit prediction accuracy is independent of the step size selection. It can quickly calculate the satellite state directly from the TLE epoch, making it suitable for satellite state recovery and rapid screening in the early stages of terminal startup.

[0121] Subsequently, the system determines the location of the communication terminal. Based on satellite status, calculate the line-of-sight vector between the satellite and the terminal. And based on the line-of-sight vector and the zenith vector at the communication terminal. Calculate elevation angle .

[0122]

[0123] If the elevation angle of a satellite is higher than the threshold ,Right now If it is within the visible range, it is added to the visible set. Finally, the target satellite is selected from the visible set according to the satellite selection strategy, and its SGP4 output state is used as the basis for the selection. As initial values ​​for orbit extrapolation:

[0124]

[0125] ② Dual-model fusion orbital state prediction

[0126] Within each prediction window, the satellite state is first obtained from the satellite state initialization step. As initial conditions, a two-body orbit model is used to perform short-term, high-frequency extrapolation calculations of the satellite's state at several future moments to meet the need for frequently acquiring the target satellite's state during communication to support frequency offset prediction.

[0127] Assuming the Earth is a standard ellipse and its mass is concentrated at the origin of the coordinate system, then the acceleration of a satellite caused by Earth's gravity is:

[0128]

[0129] in, It is the vector from the Earth's center to the satellite; It is the gravitational constant; The mass of the Earth determines the velocity vector of the satellite. , This represents the first derivative of the satellite's position with respect to time. The equation is transformed into two first-order differential equations.

[0130]

[0131] in, This represents the first derivative of the satellite's velocity with respect to time, i.e., the acceleration vector. Numerical methods are used to solve for this vector to obtain the predicted position at any given time. and speed .

[0132] To overcome the error accumulation problem of numerical methods in long-term extrapolation, this application sets the SGP4 update cycle. Each time at the current moment satisfy Then, the SGP4 method is used again to calculate the current satellite motion state:

[0133]

[0134] And assign the value to the current predicted state as the initial value for extrapolation, let Restart the two-body model extrapolation process based on this state, ensuring that the error is controlled and the computational complexity is lower than using the SGP4 algorithm alone. For example, Figure 4 The study demonstrates the "dual-model fusion extrapolation" strategy used in the orbital state prediction section: during the initialization phase, the SGP4 model is used to quickly recover the satellite state, followed by short-term high-frequency prediction based on the two-body model, and periodic SGP4 corrections are combined to achieve a balance between error control and complexity.

[0135] This application's embodiment combines the SGP4 analytical model with a two-body numerical model for orbit state prediction, balancing the rapid initialization capability of the SGP4 model with the accuracy advantages of the numerical model in short-term, high-frequency state updates, thus adapting to communication satellite systems with limited orbit broadcasting capabilities. Optionally, when navigation ephemeris data or third-party high-precision orbit products are available, the SGP4 model can be replaced with a higher-precision numerical integral orbit model (such as HPOP) to improve orbit prediction accuracy.

[0136] ③ Predicting the state of flying objects based on navigation-aided information

[0137] The navigation system of the flying object is periodic (in terms of periodicity) Provides current location and velocity information, taking into account time delays in information transmission and processing. This application assumes that the flying object is moving with uniform acceleration for a short period of time, based on Navigation data at any given moment for future moments Extrapolate the state of the flying object to obtain the predicted position. and prediction speed as follows:

[0138]

[0139]

[0140] in, , and (t) represent the input position, velocity, and acceleration information provided by the navigation assistance information, respectively. Optionally, Kalman filtering or extended Kalman filtering methods can be introduced to filter and smooth the navigation system output, improving the robustness of state prediction, which is particularly suitable for platforms with large fluctuations in navigation data quality. Optionally, for terminal platforms that asynchronously update navigation states using multiple sensors, timestamp alignment and state interpolation algorithms can be used to improve data fusion efficiency and temporal consistency.

[0141] ④ Calculation of downlink Doppler frequency offset and code phase offset

[0142] Based on the satellite and platform prediction status, at any given time Calculate the projection of the relative velocity onto the line of sight to obtain the radial velocity, and then calculate the Doppler frequency shift based on this. and code phase offset The calculation formula is expressed as follows, where Represents the symbol period, This represents the chip rate.

[0143]

[0144]

[0145] ⑤ Downlink frequency offset pre-compensation

[0146] To achieve frequency domain compensation, the terminal receiving module uses a direct digital synthesizer (DDS) to generate and estimate the frequency offset. A sinusoidal signal of opposite frequency is used, and point-by-point multiplication is performed with the received signal to achieve frequency offset cancellation. This is predicted based on the downlink Doppler frequency offset and code phase offset calculation steps. Then, calculate the Doppler coefficients. , recorded as .

[0147] The downlink frequency offset pre-compensation amount is:

[0148]

[0149] The corresponding DDS frequency control word is represented as follows:

[0150]

[0151] in, The terminal signal sampling rate, This is the bit width of the phase accumulator in the DDS. Indicates the storage depth of the DDS lookup table.

[0152] ⑥ Downlink code offset pre-compensation

[0153] After frequency compensation, to further eliminate sampling time base drift caused by the Doppler effect, this invention employs resampling compensation technology to adjust the code phase of the received signal. Based on the downlink frequency offset prediction results, the sampling rate after resampling is set as follows:

[0154]

[0155] In other words, this application considers both Doppler frequency offset and code phase drift, and proposes a joint frequency offset and code offset compensation method based on DDS compensation and resampling adjustment to achieve integrated processing of frequency and time synchronization.

[0156] ⑦ Satellite-Terminal Clock Offset Extraction

[0157] After downlink reception acquisition and tracking, the residual frequency offset estimation result of the downlink is obtained, i.e., the residual frequency offset estimate. The residual frequency offset includes the following components:

[0158]

[0159] Among them, the Doppler frequency offset estimation error The prediction error is caused by the accumulation of satellite orbit prediction errors over time. With random platform motion prediction error composition, , Assuming a short period of time , Both are constant terms, and their sum is denoted as the estimator. .conduct The residual frequency offset observations then yield:

[0160]

[0161] Observation noise Based on this, the following least squares estimation model is constructed:

[0162]

[0163]

[0164] Least squares estimation results:

[0165]

[0166] In other words, this application proposes a least-squares estimation strategy based on downlink residual frequency offset, extracts the inter-satellite clock offset and feeds it back for uplink compensation, thus establishing a cooperative path between uplink and downlink and effectively reducing the uplink acquisition failure rate. Optionally, a closed-loop learning mechanism can be constructed by combining the frequency offset residuals extracted from the actual reception results to achieve dynamic adaptive updates of the prediction parameters and further suppress the accumulation of model bias.

[0167] ⑧ Uplink frequency offset pre-compensation

[0168] The downlink clock offset estimation results are fed back to the uplink signal transmitter for Doppler prediction compensation. The uplink is mainly affected by the Doppler frequency offset between satellite terminals and the clock offset between satellite and terminal. The Doppler coefficient... It is estimated in the downlink Doppler frequency offset and code phase offset calculation steps. It is estimated in the downlink code offset pre-compensation step.

[0169] The carrier frequency received by the satellite must still be recognized by the satellite as [a specific frequency]. Then the actual receiving frequency on the satellite should be , Represents the satellite's clock offset. Uplink frequency compensation. With terminal clock offset carrier frequency The Doppler coefficients satisfy the following relationship:

[0170] 1+ )

[0171] Therefore, the uplink frequency offset compensation amount satisfy:

[0172]

[0173] Due to the Doppler coefficient Generally satisfies To facilitate implementation, it can be Approximately Simplified uplink frequency offset compensation amount:

[0174]

[0175] Corresponding DDS frequency control word It is expressed as follows:

[0176]

[0177] 9. Uplink code offset pre-compensation

[0178] After frequency compensation, to further eliminate sampling time base drift caused by the Doppler effect, this invention employs resampling compensation technology to adjust the code phase of the received signal. Based on the uplink frequency offset prediction results, the sampling rate after resampling is set as follows:

[0179]

[0180] For example, such as Figure 5 The diagram illustrates the terminal compensation path for frequency and code offset, including frequency control word generation, resampling processing, and a frequency offset management mechanism that coordinates uplink and downlink operations. By controlling computational complexity through model design and algorithm selection, this compensation strategy is feasible for deployment on terminal platforms such as missile-borne and UAVs, meeting the needs of practical engineering environments. Optionally, this application can also be extended to multi-channel architectures to support simultaneous communication with multiple satellites or multi-target tracking communication, adapting to complex application requirements such as UAV swarm and cluster operations.

[0181] It should be noted that the Doppler compensation strategy between high-speed flying objects and satellites based on navigation assistance information in this application embodiment can effectively achieve the following technical objectives: (1) Improve frequency offset prediction accuracy: By introducing terminal navigation assistance information and satellite orbit dynamics modeling, a dynamic frequency offset prediction mechanism for future time periods is established to solve the problems of navigation information update delay and state extrapolation error accumulation. (2) Reduce compensation response delay: Frequency offset prediction and compensation control are completed on the terminal side to avoid the processing bottleneck under limited onboard resources and significantly improve the real-time performance of link frequency synchronization. (3) Adapt to non-broadcast orbital status scenarios: For communication constellations that do not have high-precision ephemeris broadcasting capabilities, TLE simplifies orbital parameters and extrapolates orbital dynamics models to improve the orbital status acquisition capability. (4) Establish an uplink and downlink frequency offset information feedback mechanism: In the design, an uplink and downlink frequency offset residual collaborative modeling and dynamic adjustment mechanism is introduced to improve the overall link acquisition success rate and frequency utilization efficiency. (5) Controlling algorithm complexity and adapting to terminal computing power limitations: A lightweight frequency offset prediction and compensation method is adopted to adapt to the deployment requirements of resource-constrained terminals such as embedded UAVs and missile platforms.

[0182] The Doppler frequency offset compensation device provided by the present invention is described below. The Doppler frequency offset compensation device described below can be referred to in correspondence with the Doppler frequency offset compensation method described above. The Doppler frequency offset compensation device of the embodiments of this application is as follows: Figure 6 As shown, it includes:

[0183] The first prediction module 610 is used to predict the satellite's state information at the target time based on the satellite's state information at the first moment and the two-body orbit model;

[0184] The second prediction module 620 predicts the status information of the terminal on the flying object at the target time based on the navigation data of the flying object at the first moment.

[0185] The determination module 630 is used to determine the downlink Doppler frequency offset between the satellite and the terminal at the target time based on the satellite's status information and the terminal's status information on the flying object at the target time.

[0186] Figure 7 A schematic diagram of the physical structure of an electronic device is provided. This electronic device may include a processor 710, a communications interface 720, a memory 730, and a communication bus 740. The processor 710, communications interface 720, and memory 730 communicate with each other via the communication bus 740. The processor 710 can call logical instructions in the memory 730 to execute a Doppler frequency offset compensation method. This method includes: predicting the satellite's state information at a target time based on the satellite's state information at a first moment and a two-body orbit model; predicting the terminal's state information on the flying object at the target time based on the flying object's navigation data at the first moment; and determining the downlink Doppler frequency offset between the satellite and the terminal at the target time based on the satellite's state information and the terminal's state information at the target time.

[0187] Furthermore, the logical instructions in the aforementioned memory 730 can be implemented as software functional units and, when sold or used as independent products, can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, essentially, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0188] On the other hand, the present invention also provides a computer program product, which includes a computer program that can be stored on a non-transitory computer-readable storage medium. When the computer program is executed by a processor, the computer can execute the Doppler frequency offset compensation method provided by the above methods. The method includes: predicting the satellite's state information at a target time based on the satellite's state information at a first time and a two-body orbit model; predicting the terminal's state information on the flying object at the target time based on the flying object's navigation data at the first time; and determining the downlink Doppler frequency offset between the satellite and the terminal at the target time based on the satellite's state information at the target time and the terminal's state information on the flying object at the target time.

[0189] In another aspect, the present invention also provides a non-transitory computer-readable storage medium storing a computer program thereon, which, when executed by a processor, is implemented to perform the Doppler frequency offset compensation method provided by the above methods. The method includes: predicting the satellite's state information at a target time based on the satellite's state information at a first time and a two-body orbit model; predicting the state information of a terminal on the flying object at the target time based on the flying object's navigation data at the first time; and determining the downlink Doppler frequency offset between the satellite and the terminal at the target time based on the satellite's state information at the target time and the terminal's state information on the flying object at the target time.

[0190] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without any creative effort.

[0191] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus necessary general-purpose hardware platforms, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solutions, in essence or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in the various embodiments or some parts of the embodiments.

[0192] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A Doppler frequency offset compensation method, characterized in that, Terminals used on flying objects include: Based on the satellite's state information at the first moment and the two-body orbit model, predict the satellite's state information at the target moment; Based on the navigation data of the flying object at the first moment, predict the status information of the terminal on the flying object at the target moment; Based on the satellite's status information at the target time and the terminal's status information on the flying object at the target time, the downlink Doppler frequency offset between the satellite and the terminal at the target time is determined; After determining the downlink Doppler frequency offset between the satellite and the terminal at the target time based on the satellite's status information and the terminal's status information on the spacecraft at the target time, the method further includes: Obtain the downlink residual frequency offset; Based on the downlink residual frequency offset, determine the clock offset between the satellite and the terminal; Based on the clock offset between the satellite and the terminal, the satellite's status information at the first moment, and the navigation data of the flying object at the first moment, the uplink Doppler frequency offset is determined; The step of determining the uplink Doppler frequency offset based on the clock offset between the satellite and the terminal, the satellite's state information at the first moment, and the navigation data of the flying object at the first moment includes: The uplink Doppler frequency offset is determined based on the following method: ； in, Indicates upward Doppler frequency offset; Indicates the communication carrier frequency; Indicates the clock offset between the satellite and the terminal; The Doppler coefficient is represented by the Doppler coefficient, which is determined based on the satellite's state information and the navigation data of the flying object at the first moment.

2. The Doppler frequency offset compensation method according to claim 1, characterized in that, The step of determining the downlink Doppler frequency offset between the satellite and the terminal at the target time based on the satellite's status information and the terminal's status information on the spacecraft at the target time includes: The downlink Doppler frequency offset between the satellite and the terminal at the target time is determined based on the following method: ； in, Indicates downlink Doppler frequency offset; Indicates the communication carrier frequency; Represents the speed of light; The location information of the terminal on the aircraft at the target time; Indicates the satellite's position information at the target time; The speed information of the terminal on the aircraft at the target time; This indicates the satellite's velocity information at the target time.

3. The Doppler frequency offset compensation method according to claim 1, characterized in that, After determining the downlink Doppler frequency offset between the satellite and the terminal at the target time based on the satellite's status information and the terminal's status information on the spacecraft at the target time, the method further includes: The downlink code phase offset at the target time is determined based on the downlink Doppler frequency offset at the target time.

4. The Doppler frequency offset compensation method according to claim 1, characterized in that, After determining the uplink Doppler frequency offset, the method further includes: The uplink code phase offset is determined based on the uplink Doppler frequency offset.

5. The Doppler frequency offset compensation method according to any one of claims 1-3, characterized in that, The method further includes: Obtain open-source two-line orbit TLE data from the satellite; Based on the TLE data, the satellite's status information at the first moment is determined.

6. A Doppler frequency offset compensation device, characterized in that, include: The first prediction module is used to predict the satellite's state information at the target time based on the satellite's state information at the first moment and the two-body orbit model; The second prediction module predicts the status information of the terminal on the flying object at the target time based on the navigation data of the flying object at the first moment. The determination module is used to determine the downlink Doppler frequency offset between the satellite and the terminal at the target time based on the satellite's status information and the terminal's status information on the flying object at the target time. The determining module is also used for: Obtain the downlink residual frequency offset; Based on the downlink residual frequency offset, determine the clock offset between the satellite and the terminal; Based on the clock offset between the satellite and the terminal, the satellite's status information at the first moment, and the navigation data of the flying object at the first moment, the uplink Doppler frequency offset is determined; The step of determining the uplink Doppler frequency offset based on the clock offset between the satellite and the terminal, the satellite's state information at the first moment, and the navigation data of the flying object at the first moment includes: The uplink Doppler frequency offset is determined based on the following method: ； in, Indicates upward Doppler frequency offset; Indicates the communication carrier frequency; Indicates the clock offset between the satellite and the terminal; The Doppler coefficient is represented by the Doppler coefficient, which is determined based on the satellite's state information and the navigation data of the flying object at the first moment.

7. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the Doppler frequency offset compensation method as described in any one of claims 1 to 5.

8. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the Doppler frequency offset compensation method as described in any one of claims 1 to 5.

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