Method and device for predicting and capturing Doppler frequency shift of low-orbit satellite by high-speed equipment

Abstract

The invention relates to the technical field of satellite communication, in particular to a Doppler frequency shift prediction capturing method and device for a low-orbit satellite by high-speed equipment, and the method comprises the steps: calculating Doppler frequency shift prediction values of the high-speed equipment and the low-orbit satellite; judging whether the Doppler frequency shift predicted value exceeds a Doppler frequency shift estimation range or not, and if so, correcting the received signal by using the Doppler frequency shift predicted value; performing decimal-integer Doppler frequency shift estimation and compensation on the corrected receiving signal; and synchronously demodulating the received signal according to the decimal-integer Doppler frequency shift estimation and compensation result. According to the scheme of the embodiment of the invention, the frequency shift capture range of the radio frequency signal is greatly reduced, and the consumption of system resources by frequency shift capture is reduced; the frequency shift capturing precision is improved, and the residual error after capturing and tracking is reduced; the rapidity of frequency shift capturing and tracking is improved, and the frequency shift capturing and tracking lock losing probability is reduced.

Description

Technical Field

[0001] The present invention relates to the field of satellite communication technology, and in particular to a method and device for predicting and capturing Doppler frequency shift of low-orbit satellites using high-speed equipment. Background Art

[0002] Low-orbit communication satellite technology has developed rapidly in recent years, greatly improving the accessibility and throughput of the network. The rapid relative displacement between high-speed equipment (such as high-speed aircraft) and satellites leads to a large Doppler shift in the carrier frequency of the received signal. When high-speed equipment is maneuvering at high speed or when the satellite passes overhead, the received signal frequency changes rapidly, that is, there is a Doppler shift rate. The Doppler shift and frequency shift rate cause the signal synchronization capture performance to deteriorate, and at the same time affect the performance of the received signal demodulation. In the past, solving this kind of problem mostly relied on the RF end to perform Doppler shift compensation after receiving the signal sent by the satellite. However, due to the rapid relative speed change between the high-speed equipment and the satellite and the large dynamic range of the frequency shift, it is necessary to preset multiple parallel capture branches to perform them simultaneously, which consumes a lot of computing and solution resources.

[0003] How to solve the problem that the low-orbit satellite capture algorithm in the existing technology is highly complex, difficult to implement, has low reliability, is easy to lose capture, and is not conducive to continuous tracking is an urgent problem that needs to be solved. Summary of the invention

[0004] To solve the problems in the prior art, the embodiments of this specification provide a method and apparatus for predicting and capturing Doppler frequency shift of low-orbit satellites using a high-speed device, which solves the problems in the prior art of large frequency shift range of received RF signals, consuming a large amount of on-chip resources; low frequency shift capture accuracy, and large residual errors after capture and tracking; and slow frequency shift capture and tracking speed, and a high probability of capture and tracking loss of lock.

[0005] The embodiment of this specification provides a method for predicting and capturing Doppler frequency shift of a low-orbit satellite using a high-speed device, comprising:

[0006] Calculate Doppler shift predictions for high-speed equipment and low-orbit satellites;

[0007] Determining whether the Doppler frequency shift prediction value exceeds the Doppler frequency shift estimation range;

[0008] When it exceeds the limit, the Doppler frequency shift prediction value is used to correct the received signal from the low-orbit satellite;

[0009] Performing fractional-integer Doppler frequency shift estimation and compensation on the corrected received signal;

[0010] The received signal is synchronously demodulated according to the result of the fractional-integer Doppler frequency shift estimation and compensation.

[0011] As a further aspect of the present specification, calculating the Doppler shift prediction value of the high-speed device and the low-orbit satellite further includes,

[0012] Performing geometric modeling for the high-speed equipment and the low-orbit satellite;

[0013] Calculating the relative motion characteristics of the high-speed device and the low-orbit satellite based on the geometric modeling;

[0014] According to the relative motion characteristics, the Doppler frequency shift prediction values ​​of the high-speed device and the low-orbit satellite are calculated.

[0015] As another further aspect of the present specification, according to the geometric modeling, calculating the relative motion characteristics of the high-speed device and the low-orbit satellite further includes:

[0016] Calculating the relative position vector, relative velocity vector and relative acceleration of the high-speed device and the low-orbit satellite according to the geometric modeling;

[0017] Calculating according to the relative position vector, obtaining a unit vector;

[0018] Obtaining a line of sight velocity according to the relative velocity vector and the unit vector;

[0019] The line of sight acceleration is obtained according to the relative acceleration and the unit vector.

[0020] As another further aspect of the present specification, determining whether the Doppler frequency shift prediction value exceeds the Doppler frequency shift estimation range further includes:

[0021] When the Doppler frequency shift prediction value is within the Doppler frequency shift estimation range, fractional-integer Doppler frequency shift estimation and compensation are directly performed on the received signal.

[0022] As another further aspect of the present specification, performing fractional-integer Doppler shift estimation and compensation on the received signal further includes:

[0023] performing fractional Doppler shift estimation and compensation on the received signal;

[0024] Integer Doppler frequency shift estimation and compensation are performed on the received signal after the fractional Doppler frequency shift estimation and compensation.

[0025] As another further aspect of the present specification, estimating the fractional Doppler shift of the received signal further comprises:

[0026] Performing sampling point phase differential correlation calculation according to two unique words UW with a preset frequency shift estimation interval in the same signal frame of the received signal to complete fractional Doppler frequency shift estimation and compensation; or,

[0027] The UW word in the signal frame of the received signal is matched with the local UW word, and then FFT is performed to complete fractional Doppler frequency shift estimation and compensation.

[0028] As another further aspect of the present specification, performing sampling point phase differential correlation calculation based on two unique words UW with a preset frequency shift estimation interval in the same signal frame of the received signal to complete fractional Doppler frequency shift estimation and compensation further includes,

[0029] For the two UW1 and UW2 with an interval of L in the signal frame, the conjugate of UW1 and UW2 are phase-differentiated at each sampling point, and then accumulated to obtain the fractional Doppler frequency shift estimate UW d , UW d =sum(UW1 * ☉UW2), where ☉ is the element-by-element multiplication symbol, * represents conjugation, and sum is the summation symbol;

[0030] The fractional Doppler frequency shift estimation value is used to perform fractional Doppler frequency shift compensation on the received signal.

[0031] As another further aspect of the present specification, performing integer Doppler shift estimation and compensation on the received signal after the fractional Doppler shift compensation further includes:

[0032] Dividing the Doppler frequency shift estimation range of the received signal after the fractional Doppler frequency shift compensation into K intervals, where K is a preset natural number;

[0033] Each interval is compensated according to the preset frequency shift value, and then the UW word of each interval is autocorrelated with the local UW word, and integer Doppler frequency shift estimation and compensation are performed according to the autocorrelation peak value, wherein the preset frequency shift value is obtained according to the Doppler frequency shift estimation range and the number of intervals K.

[0034] As another further aspect of the present specification, compensating each interval according to a preset frequency shift value, then autocorrelating the UW word of each interval with the local UW word, and performing integer Doppler frequency shift estimation and compensation according to the autocorrelation peak further includes:

[0035] An integer Doppler frequency shift estimation value is obtained according to the segment sequence number corresponding to the maximum value of the autocorrelation peak value, and the integer Doppler frequency shift estimation value is used to perform integer Doppler frequency shift compensation on the received signal after fractional Doppler estimation and compensation.

[0036] As another further aspect of the present specification, compensating each interval according to a preset frequency shift value, then autocorrelating the UW word of each interval with the local UW word, and performing integer Doppler frequency shift estimation and compensation according to the autocorrelation peak further includes:

[0037] K parallel capture branches are set, each parallel capture branch corresponds to a section, compensation is performed according to a preset frequency shift value, and then the UW word of each section is autocorrelated with the local UW word to determine the autocorrelation peak.

[0038] As another further aspect of the present specification, before synchronously demodulating the received signal, the method further includes:

[0039] Obtaining a residual Doppler frequency shift of the received signal after the fractional-integer Doppler frequency shift estimation and compensation;

[0040] It is determined whether the residual Doppler frequency shift meets a preset condition, and if so, the received signal is synchronously demodulated.

[0041] As another further aspect of the present specification, obtaining the residual Doppler shift of the received signal after the fractional-integer Doppler shift estimation and compensation further includes:

[0042] The residual Doppler shift of the received signal includes the residual shift caused by fractional-integer Doppler shift estimation and compensation, and the residual shift caused by the Doppler shift change rate caused by the relative acceleration between the high-speed device and the low-orbit satellite.

[0043] As another further aspect of this specification, determining whether the residual Doppler frequency shift meets a preset condition further includes:

[0044] Determining whether the received signal can be correctly demodulated;

[0045] When signal synchronization and correct demodulation are not possible, the frequency shift estimation interval is reduced to re-estimate and compensate the fractional-integer Doppler frequency shift of the received signal;

[0046] If the demodulation is correct, the received signal is synchronously demodulated.

[0047] As another further aspect of the present specification, when signal synchronization and correct demodulation are not possible, reducing the frequency shift estimation interval to re-estimate and compensate the fractional-integer Doppler frequency shift of the received signal further includes:

[0048] In re-estimating and compensating the fractional-integer Doppler frequency shift of the received signal, sampling point phase differential correlation calculation is performed on two UW words after reducing the frequency shift estimation interval in the same signal frame of the received signal to complete the fractional Doppler frequency shift estimation.

[0049] The embodiment of this specification also provides a device for predicting and capturing Doppler frequency shift of a low-orbit satellite using a high-speed device, comprising:

[0050] A prediction unit, used to calculate the Doppler shift prediction value of high-speed equipment and low-orbit satellites;

[0051] A comparison unit, used to determine whether the Doppler frequency shift prediction value exceeds the Doppler frequency shift estimation range;

[0052] a correction unit, configured to correct a received signal from a low-orbit satellite using the Doppler frequency shift prediction value when the Doppler frequency shift exceeds the value;

[0053] A frequency shift estimation and compensation unit, used for performing fractional-integer Doppler frequency shift estimation and compensation on the corrected received signal;

[0054] A processing unit is used to synchronously demodulate the received signal according to the result of the fractional-integer Doppler frequency shift estimation and compensation.

[0055] The embodiments of the present specification also provide a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the above method when executing the computer program.

[0056] The embodiments of this specification also provide a computer-readable storage medium on which computer instructions are stored. When the computer instructions are executed by a processor, the above method is implemented.

[0057] By using the embodiments of this specification, the frequency shift capture range of the RF signal is greatly reduced, and the consumption of system resources by frequency shift capture is reduced; the frequency shift capture accuracy is improved, and the residual error after capture and tracking is reduced; the rapidity of frequency shift capture and tracking is improved, and the probability of frequency shift capture and tracking losing lock is reduced; the capture range is reduced, the capture accuracy is improved, and excellent performance is guaranteed, which is very suitable for eliminating frequency shift deviations and ensuring communication quality when communicating between low-orbit satellites and high-speed equipment. In addition, it can be widely used in current and future low-orbit satellite communication terminals and 5G, 6G air interface protocol systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] In order to more clearly illustrate the embodiments of this specification or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this specification. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0059] Figure 1 It is a schematic diagram of the structure of the high-speed device and the low-orbit satellite communication system according to the embodiment of this specification;

[0060] Figure 2 It is a flow chart of a method for predicting and capturing Doppler frequency shift of a low-orbit satellite using a high-speed device according to an embodiment of this specification;

[0061] Figure 3 The figure shows a schematic diagram of the structure of a device for predicting and capturing Doppler frequency shift of a low-orbit satellite using a high-speed device according to an embodiment of the present specification;

[0062] Figure 4 This is an overall flow chart of a method for predicting and capturing Doppler frequency shift of a low-orbit satellite using a high-speed device according to an embodiment of this specification;

[0063] Figure 5 The figure shows a schematic diagram of the signal frame format of an embodiment of this specification;

[0064] Figure 6 It is a schematic diagram showing the frequency shift range of the received signal being segmented in the embodiment of this specification;

[0065] Figure 7 The figure shows a computer device provided by an embodiment of this specification.

[0066] [Description of Reference Numerals]

[0067] 301. prediction unit;

[0068] 302. Comparison unit;

[0069] 303, Correction Unit;

[0070] 304, frequency shift estimation and compensation unit;

[0071] 305. Processing unit;

[0072] 702. Computer equipment;

[0073] 704, processor;

[0074] 706. Memory;

[0075] 708, driving mechanism;

[0076] 710, input / output module;

[0077] 712. Input devices;

[0078] 714. Network interface;

[0079] 716. Communication link;

[0080] 718. Communication bus. DETAILED DESCRIPTION

[0081] The following will be combined with the drawings in the embodiments of this specification to clearly and completely describe the technical solutions in the embodiments of this specification. Obviously, the described embodiments are only part of the embodiments of this specification, not all of the embodiments. Based on the embodiments in this specification, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this specification.

[0082] In the case of low-orbit satellites with large Doppler shift and dynamics, only giving the initial estimate of the carrier frequency is not enough to assist the subsequent tracking module to work properly. Therefore, the carrier frequency capture module in the high-dynamic communication link of low-orbit satellites needs to expand the dimension of the parameters to be estimated, and take the carrier frequency and its derivatives into consideration. The traditional Doppler shift estimation methods mainly include the following categories: ① Using the maximum likelihood estimation (MLE) algorithm to estimate the Doppler shift, this algorithm is similar to the periodogram method, suitable for high-dynamic communication environments, and has the characteristics of high precision and large frequency shift range, but the algorithm complexity is high, requires more hardware resources and has a large delay, and is less applicable to scenarios with limited hardware resources and power consumption; ② Using the Kalman filter (EKF) estimation algorithm, the minimum linear mean square error can be achieved, and real-time calculations can be performed, ensuring real-time and accuracy, but this algorithm requires high computational complexity and has poor tracking performance for the dynamic characteristics of frequency shift. In addition, the MLE algorithm and the ELK algorithm have a limited range for estimating Doppler shift and rate of change, and the algorithm complexity increases sharply as the Doppler shift range increases. Therefore, they are suitable for estimating Doppler shift in communication links between low-orbit satellites and ground fixed targets or targets with small speed and dynamics, but are less suitable for high-speed and high-dynamic targets. For terminals mounted on platforms such as high-dynamic aircraft, the hardware weight, volume, power consumption and processing resources are limited, and high-performance, low-complexity Doppler shift estimation and processing methods are important conditions for algorithm implementation and engineering realization.

[0083] like Figure 1The structure diagram of the high-speed device and low-orbit satellite communication system of the embodiment of this specification is shown in this figure. In this figure, it is described that when the high-speed device communicates with the low-orbit satellite, the PVT information of the low-orbit satellite (including the position, speed and time of the low-orbit satellite) is obtained by pre-processing according to the ephemeris information of the low-orbit satellite, and the Doppler shift is predicted by using the geometric analysis method according to the PVT information of the low-orbit satellite and the PVT information of the high-speed device. A low-complexity fractional-integer Doppler shift estimation algorithm is designed for the signal frame structure to estimate and process the high-dynamic Doppler shift. When the maximum Doppler shift range generated by the relative motion between the low-orbit satellite and the high-dynamic aircraft exceeds the Doppler shift estimation range of the fractional-integer estimation algorithm, the Doppler shift prediction frequency shift value is used to compensate the received signal received from the low-orbit satellite, and the Doppler shift range is reduced to the estimation range of the fractional-integer algorithm, and then the fractional-integer Doppler shift estimation and compensation algorithm is applied to obtain the Doppler shift value, so as to synchronize and demodulate the received signal received by the high-speed aircraft, which can reduce the complexity of the algorithm implementation and the difficulty of engineering implementation. Among them, high-speed equipment may include high-speed aircraft or other mobile equipment, such as aerospace vehicles, high-speed trains, etc.

[0084] like Figure 2 The flowchart of a method for predicting and capturing Doppler shift of a low-orbit satellite by a high-speed device in an embodiment of the present specification is shown. In this figure, it is described that after compensating the Doppler shift prediction value of the received signal whose Doppler shift exceeds the range, the received signal within the estimation range is estimated and compensated by using the fractional-integer Doppler shift estimation and compensation algorithm, so that the received signal can be correctly decoded and the received signal is captured. The method specifically includes:

[0085] Step 201, calculating the Doppler shift prediction value of the high-speed equipment and the low-orbit satellite.

[0086] Step 202, determining whether the Doppler frequency shift prediction value exceeds the Doppler frequency shift estimation range;

[0087] Step 203, when it exceeds, the Doppler frequency shift prediction value is used to correct the received signal received from the low-orbit satellite;

[0088] Step 204, performing fractional-integer Doppler shift estimation and compensation on the corrected received signal;

[0089] Step 205: synchronously demodulate the received signal according to the result of the fractional-integer Doppler shift estimation and compensation.

[0090] Through the method of the above-mentioned embodiment of this specification, for the communication scenario between high-speed equipment and low-orbit satellites (especially the communication scenario between high-speed aircraft and low-orbit satellites), the received signal that exceeds the Doppler frequency shift estimation range is compensated by calculating the Doppler frequency shift prediction value, which can reduce the resource consumption of subsequent Doppler frequency shift estimation and compensation. The fractional-integer Doppler frequency shift estimation and compensation algorithm can reduce the complexity of the low-orbit satellite acquisition algorithm, reduce energy consumption, and improve the performance and reliability of communication between high-speed equipment and low-orbit satellites.

[0091] As an embodiment of the present specification, calculating the Doppler frequency shift prediction value of the high-speed device and the low-orbit satellite further includes:

[0092] Performing geometric modeling for the high-speed equipment and the low-orbit satellite;

[0093] Calculating the relative motion characteristics of the high-speed device and the low-orbit satellite based on the geometric modeling;

[0094] According to the relative motion characteristics, the Doppler frequency shift prediction values ​​of the high-speed device and the low-orbit satellite are calculated.

[0095] In this embodiment, the high-speed device obtains the PVT information of the low-orbit satellite (including the position, speed and time of the low-orbit satellite) through ephemeris information, obtains the PVT information of the high-speed device itself (including the position, speed and time of the high-speed device) according to the data or sensor of the high-speed device itself, geometrically models the PVT information of the low-orbit satellite and the PVT information of the high-speed device itself, calculates the relative motion characteristics of the low-orbit satellite and the high-speed device in the geocentric inertial system through parameters such as the position and speed of the low-orbit satellite and the high-speed device, and calculates the Doppler frequency shift prediction value of the high-speed device and the low-orbit satellite based on the relative motion characteristics.

[0096] As an embodiment of the present specification, according to the geometric modeling, calculating the relative motion characteristics of the high-speed device and the low-orbit satellite further includes:

[0097] According to the geometric modeling, the relative position vector of the high-speed device and the low-orbit satellite is calculated Relative velocity vector and relative acceleration

[0098] According to the relative position vector calculation Get the unit vector

[0099] According to the relative velocity vector and the unit vector Get the line of sight speed v rad ;

[0100] According to the relative acceleration and the unit vector Get the line of sight acceleration a rad .

[0101] In this embodiment, the position vector of the high-speed device is obtained by using the position, speed and other parameters of the low-orbit satellite and the high-speed device in the geocentric inertial system. Position vector of low-orbit satellite High-speed equipment speed vector Velocity vector of low-orbit satellite LEO satellite acceleration vector High-speed equipment acceleration vector According to the position vector of the high-speed device and the position vector of the low-orbit satellite Calculate the relative position vector According to the high-speed device speed vector and the LEO satellite velocity vector Calculate the relative velocity vector According to the low-orbit satellite acceleration vector High-speed equipment acceleration vector Calculate the relative acceleration According to the relative position vector Calculate the unit vector According to the relative velocity vector and the unit vector Calculate the line of sight velocity v rad According to the relative acceleration and the unit vector Get the line of sight acceleration a rad .

[0102] As an embodiment of the present specification, determining whether the Doppler frequency shift prediction value exceeds the Doppler frequency shift estimation range further includes:

[0103] When the Doppler frequency shift prediction value is within the Doppler frequency shift estimation range, fractional-integer Doppler frequency shift estimation and compensation are directly performed on the received signal.

[0104] In this embodiment, a boundary value close to 0 can be set for engineering needs, and the Doppler shift estimation range is subtracted from the Doppler shift prediction value. If the result is less than the above boundary value (it can also be less than or equal to the boundary value), it is considered that the Doppler shift between the high-speed equipment and the low-orbit satellite is suitable for fractional-integer Doppler shift estimation and compensation, and fractional-integer Doppler shift estimation and compensation can be performed directly, thereby further reducing the algorithm complexity of fractional-integer Doppler shift estimation and compensation, and reducing the frequency shift estimation and compensation time; if the result exceeds the above boundary value (it can also be greater than the boundary value), then at the center frequency of the received signal On the basis of the Doppler frequency shift prediction value, correction is performed. For example, the Doppler frequency shift estimation range is ±20kHz. At this time, if the Doppler frequency shift prediction value is within the range of positive and negative 20kHz, the received signal directly enters the next step of decimal-integer Doppler frequency shift estimation and compensation. If the Doppler frequency shift prediction value is outside the range of positive and negative 20kHz, the Doppler frequency shift prediction value is added to the received signal, and then the next step of decimal-integer Doppler frequency shift estimation and compensation is entered, so as to correct the received signal, and then the subsequent decimal-integer Doppler frequency shift estimation and compensation are performed on the corrected received signal.

[0105] As an embodiment of the present specification, performing fractional-integer Doppler shift estimation and compensation on the received signal further includes:

[0106] performing fractional Doppler shift estimation and compensation on the received signal;

[0107] Integer Doppler frequency shift estimation and compensation are performed on the received signal after the fractional Doppler frequency shift estimation and compensation.

[0108] In this embodiment, in performing fractional Doppler shift estimation and compensation on the received signal, the received signal may include, when the Doppler shift prediction value exceeds the Doppler shift estimation range, the corrected received signal, or when the Doppler shift prediction value is within the Doppler shift estimation range, the received signal that has not undergone the aforementioned correction processing.

[0109] As an embodiment of this specification, estimating the fractional Doppler shift of the received signal further includes:

[0110] Performing sampling point phase differential correlation calculation according to two unique words (UW words) with a preset frequency shift estimation interval in the same signal frame of the received signal to complete fractional Doppler frequency shift estimation and compensation; or,

[0111] The UW word in the signal frame of the received signal is matched with the local UW word, and then FFT is performed to complete fractional Doppler frequency shift estimation and compensation.

[0112] In this embodiment, according to the frame structure of the received signal, there are two UW words with a preset frequency shift estimation interval in the signal frame, and the fractional Doppler frequency shift estimation can be obtained according to the phase differential correlation calculation of the sampling points of the two UW words. For example, if the symbol rate of the received signal is Mksps, the Doppler frequency shift estimation range is ±Mksps / (2L) (L is the preset frequency shift estimation interval between the two UW words); or, another method is selected to perform fractional Doppler frequency shift estimation, and the UW word in the signal frame of the received signal is dot-multiplied with the local UW word, and then an FFT transformation is performed, and the Doppler frequency shift is estimated according to the FFT spectrum line peak, thereby completing the fractional Doppler frequency shift estimation, and then the fractional Doppler frequency shift estimation value is used to perform fractional Doppler frequency shift compensation on the received signal transmitted from the previous step.

[0113] Furthermore, the two fractional Doppler shift estimation methods can be selected according to the needs of the project and the scene. After the fractional Doppler shift estimation is performed, the received signal is compensated using the fractional Doppler shift estimation value.

[0114] Specifically, performing sampling point phase differential correlation calculation based on two unique words UW with a preset frequency shift estimation interval in the same signal frame of the received signal to complete fractional Doppler frequency shift estimation and compensation further includes:

[0115] For the two UW1 and UW2 with an interval of L in the signal frame, the conjugate of UW1 and UW2 are phase-differentiated at each sampling point, and then accumulated to obtain the fractional Doppler frequency shift estimate UW d , UW d =sum(UW1 * ☉UW2), where ☉ is the element-by-element multiplication symbol, * represents conjugation, and sum is the summation symbol;

[0116] The fractional Doppler frequency shift estimation value is used to perform fractional Doppler frequency shift compensation on the received signal.

[0117] As an embodiment of the present specification, performing integer Doppler shift estimation and compensation on the received signal after the fractional Doppler shift compensation further includes:

[0118] Dividing the Doppler frequency shift range of the received signal after the fractional Doppler frequency shift compensation into K intervals, where K is a preset natural number;

[0119] Each interval is compensated according to the preset frequency shift value, and then the UW word of each interval is autocorrelated with the local UW word, and integer Doppler frequency shift estimation and compensation are performed according to the autocorrelation peak value, wherein the preset frequency shift value is obtained according to the Doppler frequency shift estimation range and the number of intervals K.

[0120] In this embodiment, an integer Doppler shift estimate is obtained according to the segment number corresponding to the maximum value of the autocorrelation peak value, and the integer Doppler shift estimate is used to perform integer Doppler shift compensation on the received signal after fractional Doppler estimation and compensation.

[0121] As an embodiment of the present specification, for each interval, each interval is compensated according to a preset frequency shift value, and then the UW word of each interval is autocorrelated with the local UW word, and integer Doppler frequency shift estimation and compensation are performed according to the autocorrelation peak value, further including:

[0122] Set K parallel capture branches, each parallel capture branch corresponds to a section, and perform compensation for each section according to the preset frequency shift value. Then autocorrelate the UW word of each section with the local UW word, and determine the autocorrelation peak to estimate and compensate for the integer Doppler frequency shift.

[0123] In this embodiment, since the Doppler frequency shift range of the received signal obtained after the Doppler frequency shift prediction value and the fractional Doppler frequency shift estimation and compensation is significantly reduced, the number of interval segments is reduced and the corresponding number of parallel capture branches is also reduced, thereby greatly reducing the requirements for on-chip resources of high-speed devices and capturing received signals.

[0124] As an embodiment of the present specification, before synchronously demodulating the received signal, the method further includes:

[0125] Obtaining a residual Doppler frequency shift of the received signal after the fractional-integer Doppler frequency shift estimation and compensation;

[0126] It is determined whether the residual Doppler frequency shift meets a preset condition, and if so, the received signal is synchronously demodulated.

[0127] In this embodiment, the preset conditions may include, for example, whether the received signal with the current residual Doppler frequency shift can be correctly synchronized or demodulated. If it can be correctly synchronized or demodulated, it means that the capture of the received signal based on the Doppler frequency shift is completed; if it cannot be correctly synchronized or demodulated, it means that the current residual Doppler frequency shift does not meet the preset conditions.

[0128] As an embodiment of the present specification, the residual Doppler frequency shift of the received signal includes the residual frequency shift caused by the fractional-integer Doppler frequency shift estimation and compensation, and the residual frequency shift caused by the Doppler frequency shift change rate caused by the relative acceleration of the high-speed device and the low-orbit satellite.

[0129] In this embodiment, the Doppler shift change rate is obtained according to the line of sight acceleration and the nominal signal frequency.

[0130] As an embodiment of this specification, determining whether the residual Doppler frequency shift meets a preset condition further includes:

[0131] Determining whether the received signal can be correctly demodulated;

[0132] When correct demodulation is not possible, the frequency shift estimation interval is reduced to re-estimate and compensate the fractional-integer Doppler frequency shift of the received signal;

[0133] If the demodulation is correct, the received signal is synchronously demodulated.

[0134] In this embodiment, taking demodulation as an example, if the maximum phase deviation of a single symbol that can be tolerated by normal demodulation is T e / T (where T is the symbol time length, T e is the relative error), that is, the maximum phase deviation is ±(T e / T)*2π, then the maximum Doppler residual allowed for normal demodulation is (±(T e / T)*2π) / T L / 2π, where T L is the duration of the signal frame, in seconds. When the residual error of demodulating the received signal according to the current residual Doppler frequency shift exceeds the above-mentioned maximum allowed Doppler residual error, it is considered that the demodulation cannot be correct, otherwise, it is considered that the demodulation can be correct. Reduce the frequency shift estimation interval, for example, reduce the interval between two UW words in the sampling point phase differential correlation calculation.

[0135] As an embodiment of the present specification, when correct demodulation is not possible, the frequency shift estimation interval is reduced to re-estimate and compensate the fractional-integer Doppler frequency shift of the received signal, and a sampling point phase differential correlation calculation is performed on the two unique words UW words after the frequency shift estimation interval is reduced in the same signal frame of the received signal to complete the fractional Doppler frequency shift estimation.

[0136] Through the method of the above-mentioned embodiment of this specification, the resource consumption of subsequent Doppler frequency shift estimation and compensation can be reduced. The fractional-integer Doppler frequency shift estimation and compensation algorithm can reduce the complexity of the low-orbit satellite acquisition algorithm, reduce energy consumption, and improve the performance and reliability of communication between high-speed equipment and low-orbit satellites.

[0137] like Figure 3The structure diagram of a Doppler frequency shift prediction and capture device for a low-orbit satellite in a high-speed device according to an embodiment of this specification is shown. The device in this embodiment can be integrated into a high-speed device or can be independent of a device other than a high-speed device. The order of steps implemented by the system listed in the embodiment described in this figure is only one of many execution orders of steps and does not represent the only execution order. When the actual system or device product is executed, it can be executed in sequence or in parallel according to the method shown in the embodiment or the accompanying drawings:

[0138] It includes a prediction unit 301, a comparison unit 302, a correction unit 303, a frequency shift estimation and compensation unit 304, and a processing unit 305;

[0139] The prediction unit 301 is used to calculate the Doppler frequency shift prediction value of the high-speed equipment and the low-orbit satellite;

[0140] The comparison unit 302 is used to determine whether the Doppler frequency shift prediction value exceeds the Doppler frequency shift estimation range;

[0141] The correction unit 303 is used to correct the received signal received from the low-orbit satellite using the Doppler frequency shift prediction value when it exceeds;

[0142] The frequency shift estimation and compensation unit 304 is used to perform fractional-integer Doppler frequency shift estimation and compensation on the corrected received signal;

[0143] The processing unit 305 is configured to synchronously demodulate the received signal according to the result of the fractional-integer Doppler shift estimation and compensation.

[0144] The functions of the devices, units, parts, components, etc. in the embodiments of this specification can be implemented by a dedicated chip or a general-purpose chip running specific software, or by a programmable logic device such as an FPGA, and one or more functional modules therein can be implemented by one chip or device respectively, or one or several functional modules can be implemented by multiple chips or devices.

[0145] Figure 4 This is an overall flow chart of a method for predicting and capturing Doppler shift of a low-orbit satellite by a high-speed device according to an embodiment of the present specification. In this figure, an overall flow chart of the prediction and capture method is described. The Doppler shift prediction value is calculated by the geometric modeling relationship between the high-speed device and the low-orbit satellite, and then the fractional-integer Doppler shift estimation and compensation calculation are performed according to the frame format of the signal frame. The frequency shift estimation interval in the fractional-integer Doppler shift estimation and compensation calculation is adjusted by evaluating the residual Doppler shift, so that the signal capture of the high-speed device and the low-orbit satellite can be completed with a relatively small computational cost and hardware resources. The method specifically includes:

[0146] Step 401: geometrically model the low-orbit satellite and high-speed equipment according to ephemeris information.

[0147] In this step, satellite internet system communication services need to calculate the satellite position and speed based on satellite ephemeris data to determine beam pointing and Doppler shift compensation. The high-speed device can calculate the position coordinates and speed of the corresponding low-orbit satellite in the earth-fixed coordinate system based on the received model ephemeris.

[0148] In three-dimensional space, six parameters are needed to uniquely determine the trajectory of an object, such as the position vector and the velocity vector (both three-dimensional), which can jointly determine the trajectory of the object. In addition, it can also be described by six orbital elements. The six common orbital elements refer to: semi-major axis a, eccentricity e, orbital inclination i, pericentric angle ω, ascending node longitude Ω and true anomaly φ. After trigonometric calculations, they can represent the specific position and velocity of the low-orbit satellite.

[0149] 1) Direction cosine matrix

[0150]

[0151] Where φ, θ, ψ are the three Euler angles of coordinate transformation.

[0152] 2) Calculate the satellite semi-path p

[0153] p=a(1-e 2 );

[0154] 3) Calculate the distance r between the satellite and the center of the earth

[0155] in, is the true anomaly angle mentioned above.

[0156] 4) Calculate the position vector of the low-orbit satellite orbital coordinate system

[0157]

[0158] 5) Calculate the position vector of the low-orbit satellite in the geocentric inertial system

[0159] The orbital coordinate system can be transformed into the geocentric inertial system after three direction cosine matrix transformations. In the first transformation, the orbital plane (i.e., the equatorial plane) rotates around the reference coordinate system z-axis by -Ω, and the ascending node coincides with the reference coordinate system x-axis; in the second transformation, the orbital plane rotates around the reference coordinate system x-axis by -i, and the positive normal of the orbital plane coincides with the reference coordinate system z-axis; in the third transformation, the orbital plane rotates around the reference coordinate system z-axis by -ω, and the eccentricity vector coincides with the reference coordinate system x-axis; the whole process is the Euler angle sequence 3-1-3, of course, it can also be other Euler angle sequences.

[0160]

[0161] Finally, we have:

[0162]

[0163]

[0164] 6) Calculate the differential of the satellite's true anomaly

[0165]

[0166] Where μ is the gravitational constant of the central body and p is the semi-diameter of the satellite.

[0167] 7) Calculate the velocity vector of the low-orbit satellite in the geocentric inertial system

[0168] Since the orbital elements remain unchanged except φ during motion, and the six orbital elements can uniquely determine the velocity vector, the velocity vector is a function of φ. Thus:

[0169]

[0170] in, is the vector of the distance between the satellite and the center of the earth; finally, we have:

[0171]

[0172] Step 402, the relative line-of-sight velocity and line-of-sight acceleration between the low-orbit satellite and the high-speed device are calculated by using the position velocity of the low-orbit satellite and the high-speed device in the geocentric inertial system.

[0173] In this step, the low-orbit satellite position vector is obtained through the above steps High-speed equipment position vector Velocity vector of low-orbit satellite where v xsat 、v ysat 、v zsat is the speed of the low-orbit satellite in space; the acceleration vector of the low-orbit satellite where a xsat 、a ysat 、a zsat is the acceleration of the low-orbit satellite in space; the velocity vector of the high-speed device where v xf 、v yf 、v zf is the speed of the high-speed device in space; the acceleration vector of the high-speed device Among them, a xf 、a yf 、a zfis the acceleration of the high-speed device in space.

[0174] The relative motion characteristics of the low-orbit satellite and the high-speed device are calculated based on the parameters of the above geometric modeling, including the relative position vector of the high-speed device and the low-orbit satellite. Relative velocity vector and relative acceleration According to the relative position vector calculation Get the unit vector According to the relative velocity vector and the unit vector Get the line of sight speed v rad According to the relative acceleration and the unit vector Get the line of sight acceleration a rad .

[0175] Where: Calculate the relative position vector

[0176] Calculate the relative velocity vector

[0177] Calculating relative acceleration

[0178] Calculate the unit vector of the relative position vector where |r ref | is the relative position vector r ref Model:

[0179]

[0180] Calculate the line of sight speed v rad : The line of sight velocity is the projection of the relative velocity vector in the direction of the relative position vector:

[0181] where the dot product represents the scalar product of two vectors:

[0182]

[0183] Calculate the line of sight acceleration a rad : The line of sight acceleration is the projection of the relative acceleration vector in the direction of the relative position vector:

[0184] where the dot product represents the scalar product of two vectors:

[0185]

[0186] Step 403, calculating the Doppler shift prediction value and Doppler shift change rate of the high-speed device and the low-orbit satellite according to the line-of-sight velocity and line-of-sight acceleration.

[0187] In this step, during the relative motion process, the Doppler frequency shift prediction value is calculated as follows:

[0188]

[0189] where F preshift is the Doppler frequency shift prediction value, v rad is the line of sight velocity calculated in the previous step, F std is the nominal signal frequency, C is the speed of light; this calculation can obtain the predicted value of the Doppler frequency shift caused by the relative motion of the low-orbit satellite and the high-speed equipment.

[0190] Similarly, the Doppler frequency shift rate for:

[0191]

[0192] Step 404, determining whether the Doppler frequency shift prediction value exceeds the Doppler frequency shift estimation range, if so, proceeding to step 405, otherwise, proceeding to step 406.

[0193] In this step, the Doppler frequency shift prediction value F obtained in the previous step is preshift , the range of Doppler frequency shift estimation is ±f dest , where the range of Doppler frequency shift estimation calculated based on the symbol rate Mksps of the received signal is ±f dest The Doppler frequency shift estimation range is ±Mksps / (2L) (L is the preset frequency shift estimation interval between two UW words). According to the engineering reliability requirements, considering a certain frequency shift estimation range margin, f dmargin Under the condition (f dmargin Close to 0, for example 10 -5 ), if f dest -|F preshitf |≥f dmargin , then proceed to step 406 to directly estimate the fractional-integer Doppler frequency shift of the received signal; if f dest -|F preshitf |<f dmargin , then go to step 405 to correct the received signal and then go to step 406.

[0194] Step 405: using the Doppler frequency shift prediction value F preshift Correct the received signal.

[0195] In this step, the center frequency of the received signal is combined with the Doppler frequency shift prediction value Fpreshift A correction is performed, with the result that when the Doppler frequency shift prediction value is a positive value, the center frequency is added with the Doppler frequency shift prediction value, and when the Doppler frequency shift prediction value is a negative value, the center frequency is subtracted with the Doppler frequency shift prediction value.

[0196] Step 406: perform fractional Doppler shift estimation and compensation on the received signal.

[0197] In this step, the frame format of the signal frame in the received signal (such as Figure 5 As shown is a schematic diagram of the signal frame format of an embodiment of the present specification, at least two methods can be used to perform fractional Doppler frequency shift estimation, for example, based on the phase differential correlation calculation of the sampling points of two UW words with a predetermined frequency shift estimation interval in the same signal frame of the received signal to complete the fractional Doppler frequency shift estimation; or, based on matching the UW word in the signal frame of the received signal with the local UW word, and then performing FFT to complete the fractional Doppler frequency shift estimation.

[0198] Among them, the sampling point phase difference correlation is to first perform phase difference on the two UW words with an interval of L in the signal frame, that is, to perform phase difference between the conjugate of UW1 and UW2 for each sampling point, and then accumulate them, as follows:

[0199] UW d =sum(UW1 * ⊙UW2);

[0200] Where ⊙ is the element-by-element multiplication symbol, * represents conjugation, and sum is the summation symbol.

[0201] Get the sampling point phase difference UW d That is, corresponding to the fractional Doppler frequency shift estimation value, the fractional Doppler frequency shift estimation value is used to perform fractional Doppler frequency shift compensation on the received signal obtained in this step.

[0202] Step 407: perform integer Doppler shift estimation and compensation on the received signal after the fractional Doppler shift compensation.

[0203] In this step, refer to Figure 6 FIG. 1 is a schematic diagram showing segmenting of the frequency shift range of a received signal according to an embodiment of the present specification, wherein the Doppler frequency shift range of the received signal after the fractional Doppler frequency shift compensation is divided into K segments, wherein K is a preset natural number;

[0204] For each interval, after compensation according to the preset frequency shift value, the UW word of each interval is autocorrelated with the local UW word, and integer Doppler frequency shift estimation is performed according to the peak value of the autocorrelation to determine the integer Doppler frequency shift estimation value, and the integer Doppler frequency shift estimation value is used to compensate the received signal after fractional Doppler compensation, wherein the preset frequency shift value is obtained according to the Doppler frequency shift estimation range and the number of interval segments K.

[0205] Among them, for K-segment intervals, K parallel capture branches are set. Corresponding to each interval, each parallel capture branch is responsible for compensating the corresponding interval according to the preset frequency shift value, and then the UW word of the interval is autocorrelated with the locally stored UW word to determine the autocorrelation peak value, and the integer Doppler frequency shift estimation value is obtained according to the segment sequence number corresponding to the maximum value of the autocorrelation peak value, and the integer Doppler frequency shift estimation value is used to perform integer Doppler frequency shift compensation. Among them, the preset frequency shift value is m is the segment number.

[0206] By reducing the number of parallel capture branches, the computational complexity and the demand for on-chip resources of high-speed devices can be greatly reduced.

[0207] Step 408: Obtain the residual Doppler frequency shift in the received signal after the fractional-integer Doppler frequency shift estimation and compensation.

[0208] In this step, the residual Doppler frequency shift F rest It consists of two parts: one is the residual frequency shift F caused by fractional-integer Doppler frequency shift estimation and compensation. rest1 (t), where t is the signal sampling interval, and the residual frequency shift is related to the sampling interval and sampling method; the other part is to calculate the Doppler frequency shift change rate caused by the relative acceleration of high-speed equipment and low-orbit satellites. The residual frequency shift Where t is the signal sampling interval. Thus, the residual Doppler frequency shift F rest for:

[0209] Step 409, determining whether the received signal can be correctly demodulated based on the residual Doppler frequency shift, if not, reducing the frequency shift estimation interval and returning to step 406, if it can be correctly demodulated, proceeding to step 410.

[0210] In this step, whether the received signal can be correctly demodulated based on the residual Doppler frequency shift can be judged by, for example, using a sensitivity drop of ≤1 dB as a judgment standard. It can also be judged by estimating the impact of the residual Doppler frequency shift on demodulation within the signal frame transmission time range: Taking demodulation as an example, if the maximum single symbol phase deviation that can be tolerated by normal demodulation is T of the symbol, e / T (where T is the symbol time length, T e is the relative error), that is, the maximum phase deviation is ±(T e / T)×2π, so the maximum Doppler residual allowed for normal demodulation is (±(T e / T)×2π) / T L / 2π, where T L is the signal frame duration length, with the unit of s. When the residual of demodulating the received signal based on the current residual Doppler frequency shift exceeds the maximum Doppler residual allowed above, it is considered that correct demodulation cannot be performed. On the contrary, it is considered that correct demodulation can be performed.

[0211] In this step, the frequency shift estimation interval before and after the UW word is reduced (for example, from L to L1, L1 < L) to perform the UW word differential correlation calculation to complete the fractional Doppler frequency shift estimation.

[0212] In this step, if correct demodulation cannot be performed, the frequency shift estimation interval is reduced, and after returning to step 406, when performing the fractional Doppler frequency shift estimation and compensation on the received signal again, it is necessary to perform the sampling point phase differential correlation processing on two UW words in the same signal frame of the received signal using the reduced frequency shift estimation interval to complete the fractional Doppler frequency shift estimation, where the reduced frequency shift estimation interval is used when performing the sampling point phase differential correlation processing. When performing the integer Doppler frequency shift estimation and compensation, the reduced frequency shift estimation interval is used to obtain a new Doppler frequency shift estimation range, so as to obtain a new offset value and interval for the integer Doppler frequency shift estimation and compensation.

[0213] Step 410, synchronously demodulate the received signal that has undergone fractional-integer Doppler frequency shift estimation and compensation.

[0214] Through the method of the embodiments of this specification, an FFT of N points is performed at ±w Hz near the predicted Doppler frequency shift value F preshift (the more points, the more accurate the frequency shift estimation. For example, N can be 1024 points) to perform fractional-integer Doppler frequency shift estimation and compensation. The Doppler residual does not exceed ±X Hz (±X Hz = ±w Hz / N), thereby greatly reducing the radio frequency signal frequency shift capture range and reducing the consumption of system resources by the frequency shift capture. It can make the signal-to-noise ratio of the received signal above 15 dB, and the maximum error of the Doppler frequency shift can reach below 5 Hz. It not only reduces the capture range and improves the capture accuracy but also ensures excellent performance, and is very suitable for eliminating the frequency shift difference during the communication between low-orbit satellites and high-speed devices to ensure the communication quality. It can be widely used in current and future low-orbit satellite communication terminals and 5G and 6G air interface protocol systems.

[0215] Such as Figure 7A computer device provided in an embodiment of this specification is shown. The method in the embodiment of this specification can be run on the computer device in this embodiment to execute the above method of this specification. The computer device 702 may include one or more processors 704, such as one or more central processing units (CPUs), and each processing unit may implement one or more hardware threads. The computer device 702 may also include any memory 706, which is used to store any kind of information such as code, settings, data, etc. Non-restrictive, for example, the memory 706 may include any one or more combinations of the following: any type of RAM, any type of ROM, flash memory device, hard disk, optical disk, etc. More generally, any memory can use any technology to store information. Further, any memory can provide volatile or non-volatile retention of information. Further, any memory can represent a fixed or removable component of the computer device 702. In one case, when the processor 704 executes an associated instruction stored in any memory or a combination of memories, the computer device 702 can perform any operation of the associated instruction. The computer device 702 also includes one or more drive mechanisms 708 for interacting with any memory, such as a hard disk drive mechanism, an optical disk drive mechanism, etc.

[0216] The computer device 702 may also include an input / output module 710 (I / O) for receiving various inputs (via an input device 712). In other embodiments, the input / output module 710 (I / O) and the input device 712 may not be included, and the computer device 702 may only be a computer device in the network. The computer device 702 may also include one or more network interfaces 714 for exchanging data with other devices via one or more communication links 716. One or more communication buses 718 couple the components described above together.

[0217] The communication link 716 may be implemented in any manner, for example, through a local area network, a wide area network (e.g., the Internet), a point-to-point connection, etc., or any combination thereof. The communication link 716 may include any combination of hardwired links, wireless links, routers, gateway functions, name servers, etc. governed by any protocol or combination of protocols.

[0218] The embodiment of the present specification also provides a computer-readable instruction, wherein when a processor executes the instruction, the program therein causes the processor to execute the method as described above.

[0219] It should be understood that in the various embodiments of this specification, the size of the serial numbers of the above-mentioned processes does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this specification.

[0220] It should also be understood that in the embodiments of this specification, the term "and / or" is only a description of the association relationship of the associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this specification generally indicates that the associated objects before and after are in an "or" relationship.

[0221] Those of ordinary skill in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed in this specification can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described in the above description according to function. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of this specification.

[0222] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0223] In the several embodiments provided in this specification, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interfaces, devices or units, or it can be an electrical, mechanical or other form of connection.

[0224] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the embodiments of this specification.

[0225] In addition, each functional unit in each embodiment of this specification may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0226] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this specification is essentially or the part that contributes to the prior art, or all or part of the technical solution can be embodied in the form of a software product, and the computer software product is stored in a storage medium, including a number of instructions to enable a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of this specification. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk and other media that can store program codes.

[0227] Specific embodiments are used in this specification to illustrate the principles and implementation methods of this specification. The description of the above embodiments is only used to help understand the methods and core ideas of this specification. At the same time, for those skilled in the art, according to the ideas of this specification, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on this specification.

Claims

1. A method for predicting and capturing Doppler frequency shift of a low-orbit satellite using a high-speed device, characterized in that include, Calculate Doppler shift predictions for high-speed equipment and low-orbit satellites; Determining whether the Doppler frequency shift prediction value exceeds the Doppler frequency shift estimation range; When it exceeds the limit, the Doppler frequency shift prediction value is used to correct the received signal from the low-orbit satellite; Performing fractional-integer Doppler frequency shift estimation and compensation on the corrected received signal; The received signal is synchronously demodulated according to the result of the fractional-integer Doppler frequency shift estimation and compensation.

2. The method for predicting and capturing Doppler frequency shift of a low-orbit satellite using a high-speed device according to claim 1, characterized in that: Calculating the Doppler shift prediction values ​​for high-speed equipment and low-orbit satellites further includes, Performing geometric modeling for the high-speed equipment and the low-orbit satellite; Calculating the relative motion characteristics of the high-speed device and the low-orbit satellite based on the geometric modeling; According to the relative motion characteristics, the Doppler frequency shift prediction values ​​of the high-speed device and the low-orbit satellite are calculated.

3. The method for predicting and capturing Doppler frequency shift of a low-orbit satellite using a high-speed device according to claim 2, characterized in that: According to the geometric modeling, calculating the relative motion characteristics of the high-speed device and the low-orbit satellite further includes: Calculating the relative position vector, relative velocity vector and relative acceleration of the high-speed device and the low-orbit satellite according to the geometric modeling; Calculating according to the relative position vector, obtaining a unit vector; Obtaining a line of sight velocity according to the relative velocity vector and the unit vector; The line of sight acceleration is obtained according to the relative acceleration and the unit vector.

4. The method for predicting and capturing Doppler frequency shift of a low-orbit satellite using a high-speed device according to claim 1, characterized in that: The step of judging whether the Doppler frequency shift prediction value exceeds the Doppler frequency shift estimation range further includes: When the Doppler frequency shift prediction value is within the Doppler frequency shift estimation range, fractional-integer Doppler frequency shift estimation and compensation are directly performed on the received signal.

5. The method for predicting and capturing Doppler frequency shift of a low-orbit satellite using a high-speed device according to claim 4, characterized in that: Performing fractional-integer Doppler shift estimation and compensation on the received signal further comprises: performing fractional Doppler shift estimation and compensation on the received signal; Integer Doppler frequency shift estimation and compensation are performed on the received signal after the fractional Doppler frequency shift estimation and compensation.

6. The method for predicting and capturing Doppler frequency shift of a low-orbit satellite using a high-speed device according to claim 5, characterized in that: Estimating and compensating the fractional Doppler shift of the received signal further comprises: Performing sampling point phase differential correlation calculation according to two unique words UW with a preset frequency shift estimation interval in the same signal frame of the received signal to complete fractional Doppler frequency shift estimation and compensation; or, The UW word in the signal frame of the received signal is matched with the local UW word, and then FFT is performed to complete fractional Doppler frequency shift estimation and compensation.

7. The method for predicting and capturing Doppler frequency shift of a low-orbit satellite using a high-speed device according to claim 6, characterized in that: Performing sampling point phase differential correlation calculation based on two unique words UW with a preset frequency shift estimation interval in the same signal frame of the received signal to complete fractional Doppler frequency shift estimation and compensation further includes: For the two UW1 and UW2 with an interval of L in the signal frame, the conjugate of UW1 and UW2 are phase-differentiated at each sampling point, and then accumulated to obtain the fractional Doppler frequency shift estimate UW d , UW d =sum(UW1 * ☉UW2), where ☉ is the element-by-element multiplication symbol, * represents conjugation, and sum is the summation symbol; The fractional Doppler frequency shift estimation value is used to perform fractional Doppler frequency shift compensation on the received signal.

8. The method for predicting and capturing Doppler frequency shift of a low-orbit satellite using a high-speed device according to claim 5, characterized in that: Estimating and compensating integer Doppler shift of the received signal after the fractional Doppler shift compensation further includes: Dividing the Doppler frequency shift estimation range of the received signal after the fractional Doppler frequency shift compensation into K intervals, where K is a preset natural number; Each interval is compensated according to the preset frequency shift value, and then the UW word of each interval is autocorrelated with the local UW word, and integer Doppler frequency shift estimation and compensation are performed according to the autocorrelation peak value, wherein the preset frequency shift value is obtained according to the Doppler frequency shift estimation range and the number of intervals K.

9. The method for predicting and capturing Doppler frequency shift of a low-orbit satellite using a high-speed device according to claim 8, characterized in that: Compensating each interval according to a preset frequency shift value, then autocorrelating the UW word of each interval with the local UW word, and performing integer Doppler frequency shift estimation and compensation according to the autocorrelation peak value further includes, An integer Doppler frequency shift estimation value is obtained according to the segment sequence number corresponding to the maximum value of the autocorrelation peak value, and the integer Doppler frequency shift estimation value is used to perform integer Doppler frequency shift compensation on the received signal after fractional Doppler estimation and compensation.

10. The method for predicting and capturing Doppler frequency shift of a low-orbit satellite using a high-speed device according to claim 8, characterized in that: Compensating each interval according to a preset frequency shift value, then autocorrelating the UW word of each interval with the local UW word, and performing integer Doppler frequency shift estimation and compensation according to the autocorrelation peak value further includes: K parallel capture branches are set, each parallel capture branch corresponds to a section, compensation is performed according to a preset frequency shift value, and then the UW word of each section is autocorrelated with the local UW word to determine the autocorrelation peak.

11. The method for predicting and capturing Doppler frequency shift of a low-orbit satellite using a high-speed device according to claim 1, characterized in that: Before synchronously demodulating the received signal, the method further includes: Obtaining a residual Doppler frequency shift of the received signal after the fractional-integer Doppler frequency shift estimation and compensation; It is determined whether the residual Doppler frequency shift meets a preset condition, and if so, the received signal is synchronously demodulated.

12. The method for predicting and capturing Doppler frequency shift of a low-orbit satellite using a high-speed device according to claim 11, characterized in that: Obtaining the residual Doppler shift of the received signal after the fractional-integer Doppler shift estimation and compensation further includes, The residual Doppler shift of the received signal includes the residual shift caused by fractional-integer Doppler shift estimation and compensation, and the residual shift caused by the Doppler shift change rate caused by the relative acceleration between the high-speed device and the low-orbit satellite.

13. A method for predicting and capturing Doppler frequency shift of a low-orbit satellite using a high-speed device according to claim 12, characterized in that: Determining whether the residual Doppler frequency shift meets a preset condition further includes: Determining whether the received signal can be correctly demodulated; When signal synchronization and correct demodulation are not possible, the frequency shift estimation interval is reduced to re-estimate and compensate the fractional-integer Doppler frequency shift of the received signal; If the demodulation is correct, the received signal is synchronously demodulated.

14. The method for predicting and capturing Doppler frequency shift of a low-orbit satellite using a high-speed device according to claim 13, characterized in that: When signal synchronization and correct demodulation are not possible, the frequency shift estimation interval is reduced to re-estimate and compensate the fractional-integer Doppler frequency shift of the received signal, which further includes: In re-estimating and compensating the fractional-integer Doppler frequency shift of the received signal, sampling point phase differential correlation calculation is performed on two UW words after reducing the frequency shift estimation interval in the same signal frame of the received signal to complete the fractional Doppler frequency shift estimation.

15. A high-speed device predicts and captures the Doppler frequency shift of a low-orbit satellite, characterized in that include, A prediction unit, used to calculate the Doppler shift prediction value of high-speed equipment and low-orbit satellites; A comparison unit, used to determine whether the Doppler frequency shift prediction value exceeds the Doppler frequency shift estimation range; a correction unit, configured to correct a received signal from a low-orbit satellite using the Doppler frequency shift prediction value when the Doppler frequency shift exceeds the value; A frequency shift estimation and compensation unit, used for performing fractional-integer Doppler frequency shift estimation and compensation on the corrected received signal; A processing unit is used to synchronously demodulate the received signal according to the result of the fractional-integer Doppler frequency shift estimation and compensation.

16. A computer 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, the method according to any one of claims 1 to 14 is implemented.

17. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the method of any one of claims 1 to 14 is executed.

18. A computer program product, characterized in that The computer program product comprises a computer program, and when the computer program is executed by a processor of a computer device, the computer program executes instructions of the method according to any one of claims 1 to 14.

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