Method and apparatus for predicting and capturing Doppler frequency shift of low-Earth orbit satellites using high-speed equipment

Abstract

This specification relates to the field of satellite communication technology, and in particular to a method and apparatus for predicting and acquiring Doppler frequency shift of a low-Earth orbit (LEO) satellite using a high-speed device. The method includes calculating the predicted Doppler frequency shift values ​​for the high-speed device and the LEO satellite; determining whether the predicted Doppler frequency shift values ​​exceed the Doppler frequency shift estimation range; if so, correcting the received signal using the predicted Doppler frequency shift values; performing fractional-integer Doppler frequency shift estimation and compensation on the corrected received signal; and performing synchronous demodulation on the received signal based on the result of the fractional-integer Doppler frequency shift estimation and compensation. The scheme implemented in this specification significantly reduces the frequency shift acquisition range of radio frequency signals, reduces the consumption of system resources by frequency shift acquisition, improves frequency shift acquisition accuracy, reduces residual errors after acquisition and tracking, improves the speed of frequency shift acquisition and tracking, and reduces the probability of frequency shift acquisition and tracking loss.

Description

Technical Field

[0001] This specification relates to the field of satellite communication technology, and in particular to a method and apparatus for predicting and capturing the Doppler frequency shift of low-orbit satellites using high-speed equipment. Background Technology

[0002] Low-Earth orbit (LEO) communication satellite technology has developed rapidly in recent years, greatly improving network reachability and throughput. The rapid relative displacement between high-speed devices (such as high-speed aircraft) and satellites results in a significant Doppler frequency shift in the received signal carrier frequency. Furthermore, during high-speed maneuvers and satellite overhead maneuvers, the received signal frequency changes rapidly, exhibiting a Doppler frequency shift rate. This Doppler frequency shift and its rate of change degrade signal synchronization acquisition performance and affect demodulation performance. Previously, solutions relied on Doppler frequency shift compensation at the radio frequency (RF) end after receiving the satellite signal. However, due to the rapid changes in relative speed between high-speed devices and satellites and the large range of frequency shift states, multiple parallel acquisition branches need to be pre-programmed, consuming substantial computational and decoding resources.

[0003] The urgent problem to be solved is how to address the high complexity, implementation difficulty, low reliability, and tendency to lose capture of low-Earth orbit satellites in existing technologies, which are not conducive to continuous tracking. Summary of the Invention

[0004] To address the problems in the prior art, this specification provides a method and apparatus for predicting and capturing Doppler frequency shifts of low-orbit satellites using a high-speed device. This method solves the problems in the prior art, such as large frequency shift range of received radio frequency signals, consumption of large amounts of on-chip resources, low frequency shift capture accuracy, large residual error after capture and tracking, slow frequency shift capture and tracking speed, and high probability of capture and tracking loss.

[0005] This specification provides an embodiment of a method for predicting and capturing the Doppler frequency shift of low-Earth orbit satellites using high-speed equipment, including:

[0006] Calculate the predicted Doppler shift values ​​for high-speed equipment and low-Earth orbit satellites;

[0007] Determine whether the predicted Doppler frequency shift value exceeds the Doppler frequency shift estimation range;

[0008] If the value exceeds the limit, the received signal from the low-Earth orbit satellite is corrected using the Doppler frequency shift prediction value.

[0009] The corrected received signal is then subjected to fractional-integer Doppler frequency shift estimation and compensation.

[0010] The received signal is synchronously demodulated based on the fractional-integer Doppler frequency shift estimation and compensation results.

[0011] As a further aspect of this specification, the calculation of Doppler shift predictions for high-speed devices and low-Earth orbit satellites further includes,

[0012] Geometric modeling is performed for the aforementioned high-speed equipment and low-orbit satellite;

[0013] Based on the geometric modeling, the relative motion characteristics of the high-speed equipment and the low-orbit satellite are calculated;

[0014] Based on the relative motion characteristics, the predicted Doppler shift values ​​for the high-speed equipment and the low-orbit satellite are calculated.

[0015] As a further aspect of this specification, the calculation of the relative motion characteristics between the high-speed device and the low-orbit satellite based on the described geometric modeling further includes,

[0016] Based on the geometric modeling, calculate the relative position vector, relative velocity vector, and relative acceleration of the high-speed device and the low-orbit satellite;

[0017] The unit vector is calculated based on the relative position vector.

[0018] The line-of-sight velocity is obtained based on the relative velocity vector and the unit vector;

[0019] The line-of-sight acceleration is obtained based on the relative acceleration and the unit vector.

[0020] As a further aspect of this specification, determining whether the predicted Doppler frequency shift value exceeds the Doppler frequency shift estimation range further includes,

[0021] If the predicted Doppler frequency shift value is within the range of the Doppler frequency shift estimation, then the received signal is directly subjected to fractional-integer Doppler frequency shift estimation and compensation.

[0022] As a further aspect of this specification, fractional-integer Doppler frequency shift estimation and compensation of the received signal further includes,

[0023] The received signal is subjected to fractional Doppler frequency shift estimation and compensation;

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

[0025] As a further aspect of this specification, fractional Doppler frequency shift estimation of the received signal further includes,

[0026] Based on two unique words (UW words) with a preset frequency shift estimation interval in the same signal frame of the received signal, phase differential correlation calculation is performed at the sampling points 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 the fractional Doppler frequency shift estimation and compensation.

[0028] As another further aspect of this specification, the fractional Doppler frequency shift estimation and compensation is further achieved by performing phase differential correlation calculation on two unique words (UW words) with a preset frequency shift estimation interval in the same signal frame of the received signal, which includes the following:

[0029] For two UW1 and UW2 signals spaced L apart in a signal frame, the conjugate of UW1 and UW2 are sampled point by point and their phase differences are calculated. These are then accumulated to obtain the fractional Doppler frequency shift estimate, UW. d UW d =sum(UW1) * ☉UW2), where ☉ is the element-wise multiplication symbol, * represents conjugate, and sum is the summation symbol;

[0030] The fractional Doppler frequency shift estimate is used to compensate for the fractional Doppler frequency shift of the received signal.

[0031] As a further aspect of this specification, the integer Doppler frequency shift estimation and compensation of the received signal after fractional Doppler frequency shift compensation further includes,

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

[0033] Each interval is compensated according to a preset frequency shift value. Then, the UW word of each interval is autocorrelated with the local UW word. Integer Doppler frequency shift estimation and compensation are performed based on the autocorrelation peak value. The preset frequency shift value is obtained based on the Doppler frequency shift estimation range and the number of interval segments K.

[0034] As another further aspect of this specification, 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. Integer Doppler frequency shift estimation and compensation are further included based on the autocorrelation peak value.

[0035] The integer Doppler frequency shift estimate is obtained based on the segment number corresponding to the maximum value of the autocorrelation peak. This integer Doppler frequency shift estimate is then used to perform integer Doppler frequency shift compensation on the received signal after fractional Doppler estimation and compensation.

[0036] As another further aspect of this specification, 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. Integer Doppler frequency shift estimation and compensation based on the autocorrelation peak value is further included.

[0037] Set up K parallel capture branches, each corresponding to a segment of the interval. Perform compensation according to the preset frequency shift value, and then perform autocorrelation between the UW word of each segment and the local UW word to determine the autocorrelation peak value.

[0038] As another further aspect of this specification, prior to synchronous demodulation of the received signal, the method further includes,

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

[0040] Determine whether the residual Doppler frequency shift meets the preset conditions. If it does, then perform synchronous demodulation on the received signal.

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

[0042] The residual Doppler frequency shift of the received signal includes the residual frequency shift resulting from fractional-integer Doppler frequency shift estimation and compensation, as well as the residual frequency shift resulting from calculating the rate of change of Doppler frequency shift caused by the relative acceleration of high-speed equipment and low-orbit satellites.

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

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

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

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

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

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

[0049] This specification also provides an embodiment of a high-speed device for predicting and capturing the Doppler frequency shift of low-Earth orbit satellites, including,

[0050] The prediction unit is used to calculate the predicted Doppler shift values ​​for high-speed equipment and low-Earth orbit satellites;

[0051] The comparison unit is used to determine whether the predicted Doppler frequency shift value exceeds the Doppler frequency shift estimation range;

[0052] A correction unit is used to correct the received signal from the low-Earth orbit satellite using the Doppler frequency shift prediction value when the error exceeds the limit.

[0053] A frequency shift estimation and compensation unit is used to perform fractional-integer Doppler frequency shift estimation and compensation on the corrected received signal;

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

[0055] This specification also provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the method described above.

[0056] This specification also provides a computer-readable storage medium storing computer instructions that, when executed by a processor, implement the above-described method.

[0057] The embodiments described in this specification significantly reduce the frequency shift acquisition range of radio frequency signals, thereby reducing the consumption of system resources by frequency shift acquisition; improve frequency shift acquisition accuracy, reducing residual errors after acquisition and tracking; and enhance the speed of frequency shift acquisition and tracking, reducing the probability of frequency shift acquisition and tracking loss. By reducing the acquisition range and improving acquisition accuracy while ensuring excellent performance, it is highly suitable for eliminating frequency shift deviations and ensuring communication quality in communication between low-Earth orbit satellites and high-speed equipment. Furthermore, it can be widely used in current and future low-Earth orbit satellite communication terminals and 5G and 6G air interface protocol systems. Attached Figure Description

[0058] To more clearly illustrate the technical solutions in the embodiments or prior art of this specification, the drawings used in the description of the embodiments or prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this specification. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0059] Figure 1 The diagram shown is a structural schematic of a high-speed device and a low-orbit satellite communication system according to an embodiment of this specification.

[0060] Figure 2 The diagram shown is a flowchart of a Doppler shift prediction and acquisition method for low-Earth orbit satellites using a high-speed device, according to an embodiment of this specification.

[0061] Figure 3 The diagram shown is a schematic representation of a Doppler shift prediction and acquisition device for low-Earth orbit satellites, according to an embodiment of this specification.

[0062] Figure 4 This is an overall flowchart of a Doppler shift prediction and acquisition method for low-Earth orbit satellites using a high-speed device, as described in this specification.

[0063] Figure 5 The diagram shown is a schematic representation of the signal frame format in an embodiment of this specification.

[0064] Figure 6 The diagram shown is a schematic representation of how the frequency shift range of the received signal is segmented according to an embodiment of this specification.

[0065] Figure 7 The image shown is a computer device provided in an embodiment of this specification.

[0066] [Explanation of Labels in the Attached Image]

[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. Drive mechanism;

[0076] 710. Input / Output Module;

[0077] 712. Input devices;

[0078] 714. Network interface;

[0079] 716. Communication link;

[0080] 718. Communication bus. Detailed Implementation

[0081] The technical solutions in the embodiments of this specification will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this specification, and not all embodiments. Based on the embodiments in this specification, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this specification.

[0082] For low-Earth orbit (LEO) satellites with large Doppler frequency shifts and dynamic ranges, simply providing an initial estimate of the carrier frequency is insufficient to assist the subsequent tracking module in functioning properly. Therefore, the carrier frequency acquisition module in the high-dynamic communication link of LEO satellites needs to expand the dimension of the parameters to be estimated, incorporating the carrier frequency and its derivatives. Traditional Doppler frequency shift estimation methods mainly include the following: ① Using the maximum likelihood estimation (MLE) algorithm to estimate the Doppler frequency shift. This algorithm is similar to the periodogram method, suitable for high-dynamic communication environments, and features high accuracy and a large frequency shift range. However, it has high algorithm complexity, requires significant hardware resources, and has a large time delay, making it less suitable for scenarios with limited hardware resources and power consumption; ② Using the Kalman filter (EKF) estimation algorithm, which can achieve the minimum linear mean square error and can perform calculations in real time, ensuring real-time performance and accuracy. However, this algorithm requires high computational complexity and has poor tracking performance for frequency shift dynamic characteristics. In addition, the MLE and ELK algorithms have limited ranges for estimating Doppler frequency shift and rate of change, and their complexity increases dramatically with the range of Doppler frequency shift. Therefore, they are suitable for Doppler frequency shift estimation in communication links between low-Earth orbit satellites and fixed ground targets or targets with low speed and dynamics, but have poor applicability to high-speed, high-dynamic targets. For terminals mounted on platforms such as high-dynamic aircraft, hardware weight, size, power consumption, and processing resources are limited, making high-performance, low-complexity Doppler frequency shift estimation and processing methods crucial for algorithm implementation and engineering realization.

[0083] like Figure 1The diagram illustrates the structure of a high-speed device communicating with a low-Earth orbit (LEO) satellite according to an embodiment of this specification. The diagram describes how, when the high-speed device communicates with the LEO satellite, it preprocesses the LEO satellite's ephemeris information to obtain the LEO satellite's PVT information (including its position, velocity, and time). Based on the LEO satellite's PVT information and the high-speed device's PVT information, a geometric analysis method is used to predict the Doppler frequency shift. A low-complexity fractional-integer Doppler frequency shift estimation algorithm is designed for the signal frame structure to perform high-dynamic Doppler frequency shift estimation and processing. When the maximum Doppler frequency shift range generated by the relative motion between the LEO satellite and the high-dynamic spacecraft exceeds the Doppler frequency shift estimation range of the fractional-integer algorithm, the predicted Doppler frequency shift value is used to compensate for the received signal from the LEO satellite, narrowing the Doppler frequency shift range to within the fractional-integer algorithm's estimation range. Then, the fractional-integer Doppler frequency shift estimation and compensation algorithm is applied to obtain the Doppler frequency shift value, thereby synchronizing and demodulating the received signal from the high-speed spacecraft. This reduces the algorithm's implementation complexity and engineering difficulty. High-speed equipment can include high-speed aircraft or other mobile devices, such as aerospace vehicles and high-speed trains.

[0084] like Figure 2 The diagram shows a flowchart of a Doppler shift prediction and acquisition method for low-Earth orbit satellites using a high-speed device, as described in this specification. The diagram illustrates how, after compensating for Doppler shift prediction values ​​in received signals whose Doppler shift exceeds a certain range, a fractional-integer Doppler shift estimation and compensation algorithm is used to estimate and compensate for received signals within the estimation range. This allows for correct decoding of the received signal, thus completing the acquisition of the received signal. Specifically, the method includes:

[0085] Step 201: Calculate the predicted Doppler shift values ​​for high-speed equipment and low-orbit satellites.

[0086] Step 202: Determine whether the predicted Doppler frequency shift value exceeds the Doppler frequency shift estimation range;

[0087] Step 203: If the value exceeds the limit, the received signal from the low-Earth orbit satellite is corrected using the Doppler frequency shift prediction value.

[0088] Step 204: Perform fractional-integer Doppler frequency shift estimation and compensation on the corrected received signal;

[0089] Step 205: Synchronize and demodulate the received signal based on the results of the fractional-integer Doppler frequency shift estimation and compensation.

[0090] The methods described in the embodiments of this specification are applicable to communication scenarios between high-speed devices and low-Earth orbit satellites (especially communication scenarios between high-speed aircraft and low-Earth orbit satellites). By calculating the predicted Doppler frequency shift value to compensate for received signals exceeding the Doppler frequency shift estimation range, 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 low-Earth orbit satellite acquisition algorithms, reduce energy consumption, and improve the performance and reliability of communication between high-speed devices and low-Earth orbit satellites.

[0091] As one embodiment of this specification, calculating the predicted Doppler frequency shift for high-speed devices and low-Earth orbit satellites further includes...

[0092] Geometric modeling is performed for the aforementioned high-speed equipment and low-orbit satellite;

[0093] Based on the geometric modeling, the relative motion characteristics of the high-speed equipment and the low-orbit satellite are calculated;

[0094] Based on the relative motion characteristics, the predicted Doppler shift values ​​for the high-speed equipment and the low-orbit satellite are calculated.

[0095] In this embodiment, the high-speed device obtains the PVT information (including the position, velocity, and time of the low-Earth orbit satellite) of the low-Earth orbit satellite through ephemeris information, and obtains its own PVT information (including the position, velocity, and time of the high-speed device) based on its own data or sensors. The PVT information of the low-Earth orbit satellite and the PVT information of the high-speed device are used to perform geometric modeling. The relative motion characteristics of the low-Earth orbit satellite and the high-speed device in the geocentric inertial frame are calculated using parameters such as the position and velocity of the low-Earth orbit satellite and the high-speed device. Based on the relative motion characteristics, the predicted Doppler frequency shift values ​​of the high-speed device and the low-Earth orbit satellite are calculated.

[0096] As one embodiment of this specification, the calculation of the relative motion characteristics between the high-speed device and the low-orbit satellite based on the described geometric modeling further includes,

[0097] Based on the geometric modeling, calculate the relative position vectors of the high-speed equipment and the low-orbit satellite. Relative velocity vector and relative acceleration

[0098] Calculated based on the relative position vector Obtain the unit vector

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

[0100] According to the relative acceleration and the unit vector The line-of-sight acceleration a is obtained rad .

[0101] In this embodiment, the position vector of the high-speed equipment is obtained by using parameters such as the position and velocity of the low-orbit satellite and the high-speed equipment in the geocentric inertial frame. Position vector of low-Earth orbit satellites High-speed equipment velocity vector Low Earth Orbit Satellite Velocity Vector Low Earth Orbit Satellite Acceleration Vector High-speed equipment acceleration vector Based on the position vector of the high-speed equipment and the position vector of low-Earth orbit satellites Calculate the relative position vector Based on the velocity vector of high-speed equipment and low-Earth orbit satellite velocity vector Calculate the relative velocity vector Based on the acceleration vector of low-orbit satellites 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 speed v rad According to the relative acceleration and the unit vector The line-of-sight acceleration a is obtained rad .

[0102] As an embodiment of this specification, determining whether the predicted Doppler frequency shift value exceeds the Doppler frequency shift estimation range further includes...

[0103] If the predicted Doppler frequency shift value is within the range of the Doppler frequency shift estimation, then the received signal is directly subjected to fractional-integer Doppler frequency shift estimation and compensation.

[0104] In this embodiment, for engineering purposes, a boundary value close to 0 can be set, such that the difference between the Doppler frequency shift estimation range and the Doppler frequency shift prediction value is calculated. If the result is less than the boundary value (or less than or equal to the boundary value), it is considered that the Doppler frequency shift of the high-speed equipment and the low-orbit satellite is suitable for fractional-integer Doppler frequency shift estimation and compensation, and fractional-integer Doppler frequency shift estimation and compensation can be performed directly, thereby further reducing the algorithm complexity of fractional-integer Doppler frequency shift estimation and compensation and reducing the frequency shift estimation and compensation time. If the result exceeds the boundary value (or is greater than the boundary value), then at the center frequency of the received signal... Based on the Doppler frequency shift prediction value, correction is performed. For example, if the Doppler frequency shift estimation range is ±20kHz, and the Doppler frequency shift prediction value is within ±20kHz, the received signal will directly proceed to the next step of fractional-integer Doppler frequency shift estimation and compensation. If the Doppler frequency shift prediction value is outside the ±20kHz range, the received signal will be added to the Doppler frequency shift prediction value, and then proceed to the next step of fractional-integer Doppler frequency shift estimation and compensation, thereby correcting the received signal. Then, the corrected received signal will be subjected to subsequent fractional-integer Doppler frequency shift estimation and compensation.

[0105] As one embodiment of this specification, the fractional-integer Doppler frequency shift estimation and compensation of the received signal further includes...

[0106] The received signal is subjected to fractional Doppler frequency shift estimation and compensation;

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

[0108] In this embodiment, during the fractional Doppler frequency shift estimation and compensation of the received signal, the received signal may include, when the predicted Doppler frequency shift value exceeds the Doppler frequency shift estimation range, the corrected received signal, or when the predicted Doppler frequency shift value is within the Doppler frequency shift estimation range, the received signal that has not undergone the aforementioned correction process.

[0109] As one embodiment of this specification, the fractional Doppler frequency shift estimation of the received signal further includes...

[0110] Based on two unique words (UW words) with a preset frequency shift estimation interval in the same signal frame of the received signal, phase differential correlation calculation is performed at the sampling points 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 the fractional Doppler frequency shift estimation and compensation.

[0112] In this embodiment, based on the frame structure of the received signal, two UW words with a preset frequency shift estimation interval are in the signal frame. The fractional Doppler frequency shift estimate can be obtained by calculating the phase differential correlation of the sampling points of these 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). Alternatively, another method can be selected for fractional Doppler frequency shift estimation. The UW words in the signal frame of the received signal are multiplied by the local UW word, and then an FFT transformation is performed. The Doppler frequency shift is estimated based on the peak value of the FFT spectrum, thereby completing the fractional Doppler frequency shift estimation. Then, the fractional Doppler frequency shift estimate is used to compensate for the fractional Doppler frequency shift of the received signal transmitted from the previous step.

[0113] Furthermore, the two fractional Doppler frequency shift estimation methods mentioned above can be selected according to the needs of the project and the scenario. After fractional Doppler frequency shift estimation, the received signal is compensated using the fractional Doppler frequency shift estimate.

[0114] Specifically, based on two unique words (UW words) with a preset frequency shift estimation interval in the same signal frame of the received signal, phase differential correlation calculation is performed at the sampling points to complete the fractional Doppler frequency shift estimation and compensation. This further includes...

[0115] For two UW1 and UW2 signals spaced L apart in a signal frame, the conjugate of UW1 and UW2 are sampled point by point and their phase differences are calculated. These are then accumulated to obtain the fractional Doppler frequency shift estimate, UW. d UW d =sum(UW1) * ☉UW2), where ☉ is the element-wise multiplication symbol, * represents conjugate, and sum is the summation symbol;

[0116] The fractional Doppler frequency shift estimate is used to compensate for the fractional Doppler frequency shift of the received signal.

[0117] As one embodiment of this specification, the integer Doppler frequency shift estimation and compensation of the received signal after fractional Doppler frequency shift compensation further includes...

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

[0119] Each interval is compensated according to a preset frequency shift value. Then, the UW word of each interval is autocorrelated with the local UW word. Integer Doppler frequency shift estimation and compensation are performed based on the autocorrelation peak value. The preset frequency shift value is obtained based on the Doppler frequency shift estimation range and the number of interval segments K.

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

[0121] As one embodiment of this specification, for each interval, compensation is performed according to a preset frequency shift value. Then, the UW word of each interval is autocorrelated with the local UW word. Further steps include integer Doppler frequency shift estimation and compensation based on the autocorrelation peak value.

[0122] Set up K parallel acquisition branches, each corresponding to a segment. Perform compensation for each segment according to the preset frequency shift value, and then perform autocorrelation between the UW word of each segment and the local UW word to determine the autocorrelation peak value for integer Doppler frequency shift estimation and compensation.

[0123] In this embodiment, since the Doppler frequency shift range of the received signal obtained after Doppler frequency shift prediction and fractional Doppler frequency shift estimation and compensation is significantly reduced, the number of interval segments is reduced, and the number of parallel acquisition branches is also reduced accordingly. This can greatly reduce the requirements for on-chip resources of high-speed equipment, and thus enable the acquisition of the received signal.

[0124] As one embodiment of this specification, the method further includes, before synchronous demodulating the received signal, the following steps:

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

[0126] Determine whether the residual Doppler frequency shift meets the preset conditions. If it does, then perform synchronous demodulation on the received signal.

[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 received signal based on the Doppler frequency shift has been successfully acquired; if it cannot be correctly synchronized or demodulated, it means that the current residual Doppler frequency shift does not yet meet the preset conditions.

[0128] As one embodiment of this specification, the residual Doppler frequency shift of the received signal includes the residual frequency shift resulting from fractional-integer Doppler frequency shift estimation and compensation, as well as the residual frequency shift resulting from calculating the rate of change of Doppler frequency shift caused by the relative acceleration between the high-speed device and the low-orbit satellite.

[0129] In this embodiment, the Doppler frequency shift rate is obtained based on the line-of-sight acceleration and the nominal signal frequency.

[0130] As one embodiment of this specification, determining whether the residual Doppler frequency shift meets preset conditions further includes...

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

[0132] If demodulation fails, the frequency shift estimation interval is reduced to re-estimate and compensate for the fractional-integer Doppler frequency shift of the received signal;

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

[0134] In this embodiment, taking demodulation as an example, if the maximum tolerable phase deviation of a single symbol under normal demodulation is T of the symbol... e / T (where T is the symbol time length, T e (This is a relative error), meaning the maximum phase deviation is ±(T). e / T)*2π, then the maximum allowable Doppler residual for normal demodulation is (±(T) e / T)*2π) / T L / 2π, where T L This refers to the duration of the signal frame, measured in seconds. If the residual after demodulating the received signal based on the current residual Doppler frequency shift exceeds the maximum allowable Doppler residual, demodulation is considered incorrect; otherwise, it is considered correct. Reducing the frequency shift estimation interval can be achieved, for example, by reducing the interval between two UW words in the phase differential correlation calculation at the sampling points.

[0135] As an embodiment of this specification, when demodulation cannot be performed correctly, the frequency shift estimation interval is reduced to re-estimate and compensate the fractional-integer Doppler frequency shift of the received signal. In this case, the sampling point phase differential correlation is calculated for the two unique words (UW words) in the same signal frame of the received signal after reducing the frequency shift estimation interval, so as to complete the fractional Doppler frequency shift estimation.

[0136] The methods described in the embodiments of this specification can reduce the resource consumption of subsequent Doppler shift estimation and compensation. The fractional-integer Doppler shift estimation and compensation algorithm can reduce the complexity of the low-Earth orbit satellite acquisition algorithm, reduce energy consumption, and improve the performance and reliability of communication between high-speed equipment and low-Earth orbit satellites.

[0137] like Figure 3The diagram shown is a structural schematic of a Doppler shift prediction and acquisition device for low-Earth orbit satellites using a high-speed device according to an embodiment of this specification. The device in this embodiment can be integrated into the high-speed device or exist independently in a device other than the high-speed device. The sequence of system implementation steps listed in this embodiment is merely one possible execution order among many and does not represent the only possible execution order. In actual system or device products, the methods shown in the embodiments or accompanying drawings can be executed sequentially or in parallel.

[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 predicted Doppler frequency shift values ​​for high-speed equipment and low-orbit satellites;

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

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

[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 used to synchronously demodulate the received signal based on the result of the fractional-integer Doppler frequency shift estimation and compensation.

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

[0145] Figure 4 This document presents an overall flowchart of a high-speed device's Doppler frequency shift prediction and acquisition method for low-Earth orbit (LEO) satellites, as described in this embodiment. The flowchart illustrates the overall process: Based on the geometric modeling relationship between the high-speed device and the LEO satellite, the predicted Doppler frequency shift value is calculated. Then, fractional-integer Doppler frequency shift estimation and compensation calculations are performed according to the signal frame format. The frequency shift estimation interval in the fractional-integer Doppler frequency shift estimation and compensation calculations is adjusted by evaluating the residual Doppler frequency shift. This allows for signal acquisition of high-speed devices and LEO satellites with relatively low computational cost and hardware resources. The method specifically includes:

[0146] Step 401: Perform geometric modeling of the low-orbit satellite and high-speed equipment based on ephemeris information.

[0147] In this step, satellite internet system communication services require the calculation of satellite positions and velocities based on satellite ephemeris data to determine beam pointing and Doppler shift compensation. High-speed equipment can calculate the position coordinates and velocities of the corresponding low-Earth orbit satellites in the Earth-fixed coordinate system based on the received model ephemeris.

[0148] In three-dimensional space, six parameters are needed to uniquely determine an object's trajectory. These include the position vector and velocity vector (both three-dimensional), which together define the trajectory. Additionally, it can be described using six orbital elements. The six orbital elements are typically: semi-major axis (a), eccentricity (e), orbital inclination (i), pericentric argument (ω), ascending node longitude (Ω), and true anomaly (φ). Through trigonometric function operations, these elements can represent the specific position and velocity of a low-Earth orbit satellite.

[0149] 1) Direction cosine matrix

[0150]

[0151] Where φ, θ, and ψ are the three Euler angles for 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 Earth's center.

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

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

[0157]

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

[0159] The orbital coordinate system can be transformed into a geocentric inertial frame through three direction cosine matrix transformations. In the first transformation, the orbital plane (i.e., the equatorial plane) rotates through -Ω around the z-axis of the reference coordinate system, and the ascending intersection coincides with the x-axis of the reference coordinate system. In the second transformation, the orbital plane rotates through -i around the x-axis of the reference coordinate system, and the positive normal of the orbital plane coincides with the z-axis of the reference coordinate system. In the third transformation, the orbital plane rotates through -ω around the z-axis of the reference coordinate system, and the eccentricity vector coincides with the x-axis of the reference coordinate system. The entire process follows the Euler angle sequence 3-1-3; however, other Euler angle sequences are also possible.

[0160]

[0161] Ultimately, we have:

[0162]

[0163]

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

[0165]

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

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

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

[0169]

[0170] in, It is the vector distance between the satellite and the Earth's center; finally, we have:

[0171]

[0172] Step 402: Calculate the relative line-of-sight velocity and line-of-sight acceleration between the low-orbit satellite and the high-speed equipment in the geocentric inertial frame by using their positions and velocities.

[0173] In this step, the low-Earth orbit satellite position vector is obtained through the above steps. High-speed equipment position vector Low Earth Orbit Satellite Velocity Vector Where v xsat v ysat v zsat The velocity of the low-Earth orbit satellite in space; the acceleration vector of the low-Earth orbit satellite. Where a xsat a ysat a zsat The acceleration of low-Earth orbit satellites in space; the velocity vector of high-speed equipment. Where v xf v yf v zf The velocity of the high-speed device in space; the acceleration vector of the high-speed device. Among them, a xf a yf a zfThis refers to the acceleration of high-speed equipment in space.

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

[0175] Where: Calculate the relative position vector

[0176] Calculate the relative velocity vector

[0177] Calculate relative acceleration

[0178] The unit vector for calculating relative position vectors Where |r ref | is the relative position vector r ref The model:

[0179]

[0180] Calculate the line-of-sight speed v rad Line-of-sight velocity is the projection of the relative velocity vector onto the direction of the relative position vector.

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

[0182]

[0183] Calculate the line-of-sight acceleration a rad Line-of-sight acceleration is the projection of the relative acceleration vector onto the direction of the relative position vector.

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

[0185]

[0186] Step 403: Calculate the predicted Doppler frequency shift and the Doppler frequency shift rate of the high-speed device and the low-orbit satellite based on the line-of-sight velocity and line-of-sight acceleration.

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

[0188]

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

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

[0191]

[0192] Step 404: Determine whether the predicted Doppler frequency shift value exceeds the Doppler frequency shift estimation range. If it does, proceed to step 405; otherwise, proceed to step 406.

[0193] In this step, the Doppler frequency shift prediction value F obtained in the preceding steps is... preshift The range of Doppler frequency shift estimation is ±f dest The range of the Doppler frequency shift estimate calculated based on the symbol rate Mksps of the received signal is ±f. dest The Doppler frequency shift estimation range is ±Mksps / (2L) (where L is the preset frequency shift estimation interval between two UW words). Based on engineering reliability requirements, considering a certain margin in the frequency shift estimation range, f... dmargin Under the condition (f) dmargin Approaching 0, for example, 10 -5 If f dest -|F preshitf |≥f dmargin Then proceed to step 406 to directly perform fractional-integer Doppler frequency shift estimation on the received signal; if f dest -|F preshitf |<f dmargin If the received signal is not corrected, proceed to step 405 and then proceed 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 F.preshift The correction is performed such that when the predicted Doppler frequency shift value is positive, the center frequency is added to the predicted Doppler frequency shift value; when the predicted Doppler frequency shift value is negative, the center frequency is subtracted from the predicted Doppler frequency shift value.

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

[0197] In this step, the frame format of the signal frame in the received signal (e.g., Figure 5 The diagram shown is a schematic of the signal frame format in an embodiment of this specification. Few-Doppler frequency shift estimation can be performed in at least two ways. For example, the phase differential correlation of the sampling points of two UW words with a predetermined frequency shift estimation interval in the same signal frame of the received signal can be used to complete the small-Doppler frequency shift estimation; or, the UW words in the signal frame of the received signal can be matched with the local UW words, and then FFT can be performed to complete the small-Doppler frequency shift estimation.

[0198] The sampling point phase differential correlation involves first performing phase differential on two UW words spaced L apart in the signal frame. This means performing phase differential on the conjugate of UW1 and UW2 at each sampling point, and then accumulating the results, as detailed below:

[0199] UW d =sum(UW1) * ⊙UW2);

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

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

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

[0203] In this step, refer to Figure 6 The diagram shown is a schematic diagram of the segmentation of the received signal frequency shift range in an embodiment of this specification. The Doppler frequency shift range of the received signal after fractional Doppler frequency shift compensation is divided into K segments, where 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. Integer Doppler frequency shift estimation is performed based on the peak value of the autocorrelation, and the integer Doppler frequency shift estimation value is determined. The received signal after fractional Doppler compensation is compensated using the integer Doppler frequency shift estimation value. The preset frequency shift value is obtained based on the Doppler frequency shift estimation range and the number of interval segments K.

[0205] Specifically, for each K-segment interval, K parallel acquisition branches are set up. For each interval, each parallel acquisition branch is responsible for compensating the corresponding interval according to a preset frequency shift value. Then, the UW words of that interval are autocorrelated with the locally stored UW words to determine the autocorrelation peak value. Based on the segment number corresponding to the maximum value of the autocorrelation peak, an integer Doppler frequency shift estimate is obtained, and this integer Doppler frequency shift estimate is used for integer Doppler frequency shift compensation. The preset frequency shift value is... m is the segment number.

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

[0207] Step 408: Obtain the residual Doppler frequency shift in the received signal after 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 part is the residual frequency shift F resulting from 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 the rate of change of Doppler frequency shift caused by the relative acceleration between high-speed equipment and low-orbit satellites. The resulting residual frequency shift Where t is the signal sampling interval. Therefore, the residual Doppler frequency shift F... rest for:

[0209] Step 409: Determine whether the received signal can be correctly demodulated based on the residual Doppler frequency shift. If it cannot be correctly demodulated, reduce the frequency shift estimation interval and return to step 406. If it can be correctly demodulated, proceed to step 410.

[0210] In this step, determining whether the received signal can be correctly demodulated based on the residual Doppler frequency shift can be done, for example, by using a sensitivity decrease of ≤1dB as the criterion. Alternatively, the impact of the residual Doppler frequency shift on demodulation can be estimated within the signal frame transmission time range. Taking demodulation as an example, if the maximum tolerable phase deviation of a single symbol under 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, then 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 according to 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, reduce the frequency shift estimation interval before and after the UW word (for example, reduce from L to L1, L1 < L) to perform UW word differential correlation calculation to complete the fractional Doppler frequency shift estimation.

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

[0213] Step 4:10, perform synchronous demodulation on the received signal that has undergone fractional-integer Doppler frequency shift estimation and compensation.

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

[0215] Such as Figure 7The illustration shows a computer device provided in an embodiment of this specification. The methods described in this embodiment can be run on the computer device described in this specification to perform the methods described above. The computer device 702 may include one or more processors 704, such as one or more central processing units (CPUs), each of which can implement one or more hardware threads. The computer device 702 may also include any memory 706 for storing information of any kind, such as code, settings, data, etc. Without limitation, for example, the memory 706 may include any type of RAM, any type of ROM, flash memory, 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 may represent a fixed or removable component of the computer device 702. In one case, when the processor 704 executes associated instructions stored in any memory or combination of memories, the computer device 702 can perform any operation of the associated instructions. The computer device 702 also includes one or more drive mechanisms 708 for interacting with any memory, such as hard disk drive mechanisms, optical disk drive mechanisms, etc.

[0216] Computer device 702 may also include an input / output module 710 (I / O) for receiving various inputs (via input device 712). In other embodiments, the input / output module 710 (I / O) and input device 712 may be omitted, and the device may function solely as a computer device within a network. 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] Communication link 716 can be implemented in any way, such as via a local area network (LAN), a wide area network (e.g., the Internet), a point-to-point connection, or any combination thereof. 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] This specification also provides computer-readable instructions, wherein when a processor executes the instructions, the program therein causes the processor to perform the methods described above.

[0219] It should be understood that in the various embodiments of this specification, the sequence number of each process does not imply 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 merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this specification generally indicates that the preceding and following related objects have an "or" relationship.

[0221] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed in this specification can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of each example have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this specification.

[0222] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing 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, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the couplings or direct couplings or communication connections shown or discussed may be indirect couplings or communication connections through some interfaces, devices, or units, or they may be electrical, mechanical, or other forms of connection.

[0224] 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 units can be selected to achieve the purpose of the embodiments described in this specification, depending on actual needs.

[0225] Furthermore, the functional units in the various embodiments of this specification can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0226] If the integrated unit is implemented as 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, in essence, 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. 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 this specification. 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.

[0227] This specification uses specific embodiments to illustrate the principles and implementation methods of this specification. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this specification. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this specification. Therefore, the content of this specification should not be construed as a limitation of this specification.

Claims

1. A method for predicting and capturing the Doppler frequency shift of low-orbit satellites using high-speed equipment, characterized in that... include, Based on the relative motion characteristics of the high-speed equipment and the low-Earth orbit satellite, the predicted Doppler frequency shift values ​​of the high-speed equipment and the low-Earth orbit satellite are calculated; wherein, the relative motion characteristics include at least the line-of-sight velocity and line-of-sight acceleration of the high-speed equipment and the low-Earth orbit satellite. Determine whether the predicted Doppler frequency shift value exceeds the Doppler frequency shift estimation range; If the value exceeds the limit, the received signal from the low-Earth orbit satellite is corrected using the Doppler frequency shift prediction value. The corrected received signal is then subjected to fractional-integer Doppler frequency shift estimation and compensation. The received signal is synchronously demodulated based on the fractional-integer Doppler frequency shift estimation and compensation results. The Doppler frequency shift prediction value is obtained by dividing the product of the line-of-sight velocity and the nominal signal frequency by the speed of light. The Doppler frequency shift estimation range is: Where ±Mksps is the positive and negative symbol rate of the received signal, and L is the preset frequency shift estimation interval between two UW words; If the error exceeds the limit, the Doppler frequency shift prediction value is used to correct the received signal from the low-Earth orbit satellite. This further includes: when the Doppler frequency shift prediction value is positive, the center frequency of the received signal is added to the Doppler frequency shift prediction value; when the Doppler frequency shift prediction value is negative, the center frequency is subtracted from the Doppler frequency shift prediction value. Determining whether the predicted Doppler frequency shift value exceeds the Doppler frequency shift estimation range further includes, When the predicted Doppler frequency shift value is within the range of the Doppler frequency shift estimation, the received signal is directly subjected to fractional-integer Doppler frequency shift estimation and compensation. The fractional-integer Doppler frequency shift estimation and compensation of the received signal further includes, The received signal is subjected to fractional Doppler frequency shift estimation and compensation; Integer Doppler frequency shift estimation and compensation are performed on the received signal after fractional Doppler frequency shift estimation and compensation. The fractional Doppler frequency shift estimation and compensation of the received signal further includes, Based on two unique words (UW words) with a preset frequency shift estimation interval in the same signal frame of the received signal, the phase differential correlation of the sampling points is calculated to complete the fractional Doppler frequency shift estimation and compensation; The integer Doppler frequency shift estimation and compensation of the received signal after fractional Doppler frequency shift compensation further includes, The Doppler frequency shift estimation range of the received signal after fractional Doppler frequency shift compensation is divided into K segments, where K is a preset natural number; Each interval is compensated according to a preset frequency shift value. Then, the UW word of each interval is autocorrelated with the local UW word. Integer Doppler frequency shift estimation and compensation are performed based on the autocorrelation peak value. The preset frequency shift value is obtained based on the Doppler frequency shift estimation range and the number of intervals K.

2. The method for predicting and capturing the Doppler frequency shift of a low-orbit satellite using a high-speed device according to claim 1, characterized in that, The calculation of Doppler shift predictions for high-speed equipment and low-Earth orbit satellites further includes, Geometric modeling is performed for the aforementioned high-speed equipment and low-orbit satellite; Based on the geometric modeling, the relative motion characteristics of the high-speed equipment and the low-orbit satellite are calculated; Based on the relative motion characteristics, the predicted Doppler shift values ​​for the high-speed equipment and the low-orbit satellite are calculated.

3. The Doppler frequency shift prediction and acquisition method for low-orbit satellites using high-speed equipment according to claim 2, characterized in that, Based on the aforementioned geometric modeling, the calculation of the relative motion characteristics between the high-speed device and the low-orbit satellite further includes, Based on the geometric modeling, calculate the relative position vector, relative velocity vector, and relative acceleration of the high-speed device and the low-orbit satellite; The unit vector is calculated based on the relative position vector. The line-of-sight velocity is obtained based on the relative velocity vector and the unit vector; The line-of-sight acceleration is obtained based on the relative acceleration and the unit vector.

4. The Doppler frequency shift prediction and acquisition method for low-orbit satellites using high-speed equipment according to claim 1, characterized in that, The fractional Doppler frequency shift estimation and compensation of the received signal further includes, 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 the fractional Doppler frequency shift estimation and compensation.

5. A method for predicting and capturing the Doppler frequency shift of a low-orbit satellite using a high-speed device according to claim 4, characterized in that, Based on two unique words (UW words) with a preset frequency shift estimation interval in the same signal frame of the received signal, phase differential correlation calculation is performed at the sampling points to complete the fractional Doppler frequency shift estimation and compensation. This further includes... For two UW1 and UW2 signals spaced L apart in a signal frame, the conjugate of UW1 and UW2 are sampled point by point and their phase differences are calculated. These are then accumulated to obtain the fractional Doppler frequency shift estimate, UW. d UW d =sum(UW1 * ☉UW2), where ☉ is the element-wise multiplication symbol, * represents conjugate, and sum is the summation symbol; The fractional Doppler frequency shift estimate is used to compensate for the fractional Doppler frequency shift of the received signal.

6. The Doppler frequency shift prediction and acquisition method for low-orbit satellites using high-speed equipment according to claim 1, characterized in that, Each interval is compensated according to a preset frequency shift value. Then, the UW word of each interval is autocorrelated with the local UW word. Based on the autocorrelation peak value, integer Doppler frequency shift estimation and compensation are further performed. The integer Doppler frequency shift estimate is obtained based on the segment number corresponding to the maximum value of the autocorrelation peak. This integer Doppler frequency shift estimate is then used to perform integer Doppler frequency shift compensation on the received signal after fractional Doppler estimation and compensation.

7. A method for predicting and capturing the Doppler frequency shift of a low-orbit satellite using a high-speed device according to claim 1, characterized in that, Each interval is compensated according to a preset frequency shift value. Then, the UW word of each interval is autocorrelated with the local UW word. The integer Doppler frequency shift estimation and compensation based on the autocorrelation peak value further includes... Set up K parallel capture branches, each corresponding to a segment of the interval. Perform compensation according to the preset frequency shift value, and then perform autocorrelation between the UW word of each segment and the local UW word to determine the autocorrelation peak value.

8. A method for predicting and capturing the Doppler frequency shift of a low-orbit satellite using a high-speed device according to claim 1, characterized in that, The process includes, before synchronous demodulating the received signal, the following: Obtain the residual Doppler frequency shift of the received signal after fractional-integer Doppler frequency shift estimation and compensation; Determine whether the residual Doppler frequency shift meets the preset conditions. If it does, then perform synchronous demodulation on the received signal.

9. A method for predicting and capturing the Doppler frequency shift of a low-orbit satellite using a high-speed device according to claim 8, characterized in that, Obtaining the residual Doppler frequency shift of the received signal after the fractional-integer Doppler frequency shift estimation and compensation further includes, The residual Doppler frequency shift of the received signal includes the residual frequency shift resulting from fractional-integer Doppler frequency shift estimation and compensation, as well as the residual frequency shift resulting from calculating the rate of change of Doppler frequency shift caused by the relative acceleration of high-speed equipment and low-orbit satellites.

10. A method for predicting and capturing the Doppler frequency shift of a low-orbit satellite using a high-speed device according to claim 9, characterized in that, Determining whether the residual Doppler frequency shift meets the preset conditions further includes, Determine whether the received signal can be correctly demodulated; If signal synchronization and proper demodulation are not possible, the frequency shift estimation interval is reduced to re-estimate and compensate for the fractional-integer Doppler frequency shift of the received signal; If the demodulation is successful, the received signal is then synchronously demodulated.

11. A method for predicting and capturing the Doppler frequency shift of a low-orbit satellite using a high-speed device according to claim 10, characterized in that, When signal synchronization and proper demodulation are not possible, the process of reducing the frequency shift estimation interval to re-estimate and compensate for the fractional-integer Doppler frequency shift of the received signal further includes, In the process of re-estimating and compensating the fractional-integer Doppler frequency shift of the received signal, the sampling point phase differential correlation is calculated for two UW words in the same signal frame of the received signal after reducing the frequency shift estimation interval, so as to complete the fractional Doppler frequency shift estimation.

12. A high-speed device for predicting and capturing the Doppler frequency shift of low-orbit satellites, characterized in that... include, The prediction unit is used to calculate the predicted Doppler frequency shift of the high-speed device and the low-Earth orbit satellite based on the relative motion characteristics of the high-speed device and the low-Earth orbit satellite; wherein the relative motion characteristics include at least the line-of-sight velocity and line-of-sight acceleration of the high-speed device and the low-Earth orbit satellite; the predicted Doppler frequency shift value is obtained by dividing the product of the line-of-sight velocity and the nominal signal frequency by the speed of light; A comparison unit is used to determine whether the predicted Doppler frequency shift value exceeds the Doppler frequency shift estimation range; the Doppler frequency shift estimation range is... Where ±Mksps is the positive and negative symbol rate of the received signal, and L is the preset frequency shift estimation interval between two UW words; The correction unit is used to correct the received signal from the low-Earth orbit satellite by using the Doppler frequency shift prediction value when the value exceeds the limit; when the Doppler frequency shift prediction value is positive, the center frequency of the received signal is added to the Doppler frequency shift prediction value, and when the Doppler frequency shift prediction value is negative, the center frequency is subtracted from the Doppler frequency shift prediction value. A frequency shift estimation and compensation unit is used to perform fractional-integer Doppler frequency shift estimation and compensation on the corrected received signal; The processing unit is used to synchronously demodulate the received signal based on the result of the fractional-integer Doppler frequency shift estimation and compensation. The frequency shift estimation and compensation unit is further configured to, when determining whether the predicted Doppler frequency shift value exceeds the Doppler frequency shift estimation range, further include... When the predicted Doppler frequency shift value is within the range of the Doppler frequency shift estimation, the received signal is directly subjected to fractional-integer Doppler frequency shift estimation and compensation. The fractional-integer Doppler frequency shift estimation and compensation of the received signal further includes, The received signal is subjected to fractional Doppler frequency shift estimation and compensation; Integer Doppler frequency shift estimation and compensation are performed on the received signal after fractional Doppler frequency shift estimation and compensation. The fractional Doppler frequency shift estimation and compensation of the received signal further includes, Based on two unique words (UW words) with a preset frequency shift estimation interval in the same signal frame of the received signal, the phase differential correlation of the sampling points is calculated to complete the fractional Doppler frequency shift estimation and compensation; The integer Doppler frequency shift estimation and compensation of the received signal after fractional Doppler frequency shift compensation further includes, The Doppler frequency shift estimation range of the received signal after fractional Doppler frequency shift compensation is divided into K segments, where K is a preset natural number; Each interval is compensated according to a preset frequency shift value. Then, the UW word of each interval is autocorrelated with the local UW word. Integer Doppler frequency shift estimation and compensation are performed based on the autocorrelation peak value. The preset frequency shift value is obtained based on the Doppler frequency shift estimation range and the number of intervals K.

13. 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, it implements the method of any one of claims 1-11.

14. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed by a processor, performs the method of any one of claims 1-11.

15. A computer program product, characterized in that, The computer program product includes a computer program that, when run by the processor of a computer device, executes instructions according to any one of claims 1-11.

Images