A polarization tracking and switching method and system, device, and medium for low earth orbit satellite communications

Abstract

The application relates to the technical field of satellite communication, in particular to a polarization tracking and switching method and system for low-orbit satellite communication, equipment and a medium. The method provided by the application mainly comprises the following steps: if a current polarization mismatch factor is less than a lower threshold, a digital polarization tracking weighting matrix is generated; after a double-channel signal is directionally rotated and compensated, a received signal is returned; if the current polarization mismatch factor is greater than or equal to the lower threshold, a deflection angle change rate is calculated, and a switching condition is set; when the polarization mismatch factor and the deflection angle change rate both satisfy the switching condition, polarization channel interchanging is performed. Through the construction of a polarization rotation compensation matrix in a digital baseband domain, geometric rotation and Faraday rotation can be accurately compensated in real time without mechanical inertia, and the defect that a traditional mechanical polarization adjustment is slow in response is overcome.

Description

Technical Field

[0001] This invention relates to the field of satellite communication technology, and more specifically, to a polarization tracking and switching method, system, device, and medium for low-Earth orbit satellite communication. Background Technology

[0002] Low Earth orbit (LEO) satellite communication offers advantages such as low transmission latency, low link loss, and global coverage, making it a crucial component of future integrated space-ground networks. To improve spectrum utilization, orthogonal dual-polarization multiplexing techniques (such as left-hand / right-hand circular polarization or horizontal / vertical linear polarization) are commonly employed in LEO satellite communication.

[0003] However, the high-speed motion of low-Earth orbit satellites relative to ground stations presents the following severe challenges in terms of polarization for communication links: 1. Large dynamic range of polarization deflection: The relative attitude between the satellite and the ground station is constantly changing, causing geometric rotation; at the same time, electromagnetic waves are affected by the Earth's magnetic field when passing through the ionosphere, resulting in Faraday rotation. The superposition effect of these two factors causes the polarization surface of the signal reaching the ground station to undergo rapid and large-amplitude rotational deflection.

[0004] 2. Polarization mismatch and cross-polarization interference: When the polarization direction of the receiving antenna is not aligned with the polarization direction of the incoming wave, polarization mismatch loss will occur. More seriously, the deflection will cause cross-leakage of the orthogonal polarization components, greatly reducing the cross-polarization discrimination rate and causing serious cross-polarization interference in dual-polarization multiplexing systems, resulting in a decrease in system throughput or even communication interruption.

[0005] Existing polarization compensation methods mainly include mechanical adjustment and digital polarization tracking. Mechanical adjustment has a slow response speed and cannot adapt to the high dynamic changes of low-Earth orbit satellites; traditional digital polarization tracking is usually only effective at small-angle deflections. When the polarization deflection angle approaches or exceeds 45°, the amplitudes of the two orthogonal polarization components tend to be consistent, the polarization state becomes ambiguous, and the tracking algorithm is prone to polarization state jumps or locking errors. In addition, existing polarization switching methods lack effective anti-jitter mechanisms. Under the influence of channel fading or estimation errors, frequent switching of polarization modes is easily triggered, leading to unstable baseband demodulation. Summary of the Invention

[0006] The purpose of this invention is to provide a polarization tracking and switching method, system, device, and medium for low-Earth orbit satellite communication to solve the above-mentioned problems in the prior art.

[0007] This invention is achieved through the following technical solution: In a first aspect, the present invention provides a polarization tracking and switching method for low-Earth orbit satellite communication, comprising: The signal is received and the pilot sequence is extracted. The current polarization deflection angle is obtained by maximum likelihood estimation based on the pilot sequence. The polarization mismatch factor is calculated based on the polarization deflection angle, and a lower threshold is set. If the current polarization mismatch factor is less than the lower threshold, a digital polarization tracking weighting matrix is ​​generated, and after directional rotation compensation is performed on the dual-channel signal, the received signal is returned. If the current polarization mismatch factor is greater than or equal to the lower threshold, calculate the deflection angle change rate and set the switching conditions. When both the polarization mismatch factor and the deflection angle change rate meet the switching conditions, perform polarization channel swapping, update the reference, and return the received signal. If the switching conditions are not met, return the received signal.

[0008] Preferably, obtaining the current polarization deflection angle based on the pilot sequence through maximum likelihood estimation includes:

[0009]

[0010]

[0011] In the formula, For dual-polarization signal vectors, For horizontal polarization components, For vertical polarization components, For transpose, This is the signal vector received by the ground station. This is the polarization rotation compensation matrix. It is an additive white Gaussian noise vector. This is the polarization deflection angle.

[0012] Preferably, the calculation of the polarization mismatch factor based on the polarization deflection angle includes:

[0013] In the formula, Polarization mismatch factor The value range is from 0 to 1, when hour, No mismatch; when hour, Orthogonal polarization complete crosstalk; when hour, The main polarization is completely transformed into cross polarization.

[0014] Preferably, the generation of the digital polarization tracking weighted matrix includes:

[0015] In the formula, For digital polarization tracking weighting matrix; Direction rotation compensation for dual-channel signals includes:

[0016] In the formula, This is the compensated signal.

[0017] Preferably, the calculation of the deflection angle change rate and the setting of switching conditions include:

[0018] In the formula, The rate of change of deflection angle. The current moment; Set the polarization blur region when , When the upper threshold is set, the rate of change of the deflection angle is crossing the polarization ambiguity region, and the current signal-to-noise ratio of the received signal is lower than the dynamic threshold, polarization channel swapping is performed.

[0019] Preferably, the polarization channel interchange includes: Set a polarization interchange matrix, and based on this matrix, interchange the primary and secondary relationships of the dual polarization channels. Reset to , This is the polarization deflection angle after reset; The weighted matrix after the switch is:

[0020] In the formula, This is the weighted matrix after the switch. This is the polarization interchange matrix.

[0021] Preferably, the returned received signal includes: Once the handover is complete, the logic to trigger a new tracking or reverse handover is only allowed to be executed if the next polarization mismatch factor is less than the lower threshold and the duration exceeds the stabilization time window.

[0022] Secondly, the present invention also provides a polarization tracking and switching system for low-Earth orbit satellite communication, for performing the aforementioned polarization tracking and switching method for low-Earth orbit satellite communication, comprising: The polarization parameter estimation unit, based on maximum likelihood estimation, calculates the amplitude ratio and phase difference between the two channels, and estimates the current polarization deflection angle in real time. Simultaneously, it performs a difference operation on the polarization deflection angle to calculate the rate of change of the deflection angle. The polarization mismatch calculation unit is configured to obtain the polarization deflection angle and calculate the current polarization mismatch factor based on the electromagnetic field polarization mismatch physical model. The channel quality monitoring unit is configured to acquire the synchronized baseband signal, calculate the signal-to-noise ratio of the received signal in real time, and provide a channel quality benchmark for polarization switching.

[0023] The mode decision and hysteresis control unit is configured to output a mode switching command to the execution unit to perform channel swapping if the switching conditions are met, update the internal polarization reference, and start the hysteresis debounce timer to block subsequent switching requests.

[0024] Thirdly, the present invention also provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the above-described polarization tracking and switching method for low-Earth orbit satellite communication.

[0025] Fourthly, the present invention also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the above-described polarization tracking and switching method for low-Earth orbit satellite communication.

[0026] The technical solution of the present invention has at least the following advantages and beneficial effects: The method provided by this invention mainly includes: if the current polarization mismatch factor is less than a lower threshold, generating a digital polarization tracking weighted matrix, performing directional rotation compensation on the dual-channel signals, and then returning the received signal; if the current polarization mismatch factor is greater than or equal to the lower threshold, calculating the deflection angle change rate and setting switching conditions; and performing polarization channel swapping when both the polarization mismatch factor and the deflection angle change rate simultaneously meet the switching conditions. By constructing a polarization rotation compensation matrix in the digital baseband domain, it is possible to accurately compensate for geometric rotation and Faraday rotation in real time without mechanical inertia, overcoming the slow response of traditional mechanical polarization adjustment.

[0027] Breaking the Tracking Limits in the Polarization Ambiguity Region: When the polarization deflection angle approaches the 45° polarization ambiguity region, traditional tracking algorithms are prone to failure and locking errors. This invention sets an upper threshold for the mismatch factor and actively triggers polarization switching before approaching the ambiguity region. By using a channel swap matrix to offset the polarization reference by 90°, the system returns to a stable operating range with high cross-polarization discrimination rate.

[0028] Effective suppression of the ping-pong effect: This invention introduces a dual hysteresis decision mechanism based on the rate of change of deflection angle, SNR evaluation, and time window jitter prevention, which avoids frequent switching of polarization modes caused by ionospheric scintillation, multipath fading, or jitter of estimation algorithms, and greatly enhances the robustness of low-Earth orbit satellite communication links. Attached Figure Description

[0029] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a schematic diagram of the process of the present invention; Figure 2 This is a schematic diagram of the system structure of the present invention. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0032] The module division in this application is a logical division. In actual application, there may be other division methods. For example, multiple modules may be combined into or integrated into another system, or some features may be ignored or not executed.

[0033] In addition, the connection, coupling or communication in this application can be a direct connection, coupling or communication between related objects, or an indirect connection, coupling or communication through other devices. Furthermore, the connection, coupling or communication between objects can be electrical or other similar forms, and no limitation is made in this application.

[0034] The independently described modules or sub-modules may or may not be physically separated; they may be implemented in software or hardware, and some modules or sub-modules may be implemented in software, with the processor calling the software to implement the function of these modules or sub-modules, while other modules or sub-modules may be implemented in hardware, such as through hardware circuits. Furthermore, some or all of the modules can be selected to achieve the purpose of this application's solution according to actual needs.

[0035] Please refer to Figures 1-2 This invention provides a polarization tracking and switching method for low-Earth orbit satellite communication, comprising: S1: Receive the signal and extract the pilot sequence. Based on the pilot sequence, obtain the current polarization deflection angle through maximum likelihood estimation. Calculate the polarization mismatch factor based on the polarization deflection angle and set the lower threshold. Let the dual-polarization signal vector of the low-orbit satellite be... ,in and These are the horizontal and vertical polarization components, respectively. Due to geometric and Faraday rotations during transmission, the signal vector received by the ground station... It can be represented as:

[0036] in, It is an additive white Gaussian noise vector; This is the total polarization deflection angle; The polarization rotation compensation matrix is ​​defined as follows:

[0037] In baseband processing, the current polarization deflection angle is estimated using the known pilot sequence in the received signal and maximum likelihood estimation. .

[0038] Additive white Gaussian noise (AWGN) vectors are used to simulate random interference generated by various devices, channels, and sensors in reality. They are the most standard noise model in engineering, communications, AI, and control fields. Simulating wireless channel interference when mobile phone, WiFi, satellite, and radar signals are transmitted through the air involves the superposition of circuit thermal noise and cosmic background noise, all modeled using AWGN vectors.

[0039] In one embodiment, a polarization mismatch factor is defined to quantify the impact of polarization deflection on signal reception. Under ideal matching conditions, the power proportion of the dominant polarization component is 1; after deflection, the dominant polarization power leaks to the cross-polarization, and the dominant polarization power proportion becomes... Therefore, the polarization mismatch factor is defined as the cross-polarization leakage power ratio:

[0040] The value range is [0, 1]. When When =0, No mismatch; when hour, Orthogonal polarization complete crosstalk; when hour, The main polarization is completely transformed into cross polarization.

[0041] S2: If the current polarization mismatch factor is less than the lower threshold, a digital polarization tracking weighting matrix is ​​generated, and after directional rotation compensation is performed on the dual-channel signal, the received signal is returned. When the polarization mismatch factor η is small, the system operates in polarization tracking mode. A lower threshold is set. If η < This indicates that the deflection angle is small and the cross-polarization interference is controllable.

[0042] In one embodiment, the baseband processing unit generates a digital polarization tracking weighting matrix. Reverse rotation compensation is applied to the dual-channel signals:

[0043] For the digital polarization tracking weighting matrix, the compensated signal This eliminates the mismatch and interference caused by polarization deflection. This is the compensated signal.

[0044] S3: If the current polarization mismatch factor is greater than or equal to the lower threshold, calculate the deflection angle change rate and set the switching conditions. When both the polarization mismatch factor and the deflection angle change rate meet the switching conditions, perform polarization channel swapping, update the reference, and return the received signal. If the switching conditions are not met, return the received signal.

[0045] In one embodiment, when the high-speed motion of a low-Earth orbit satellite causes the polarization deflection angle to continuously increase, approaching or exceeding 45°, Approaching 0.5, It also approaches 0.5, and the amplitudes of the two polarization channels are almost identical, relying solely on Digital tracking is prone to polarization state jumps due to estimation errors (such as locking the original H polarization to V polarization).

[0046] Set upper threshold (A value around 0.5 is recommended), when At that time, a polarization switching decision is triggered.

[0047] In one embodiment, the deflection angle change rate is calculated, and switching conditions are set, including:

[0048] In the formula, The rate of change of deflection angle. The current moment; Set the polarization blur region when , When the upper threshold is set, the rate of change of the deflection angle is crossing the polarization ambiguity region, and the current signal-to-noise ratio of the received signal is lower than the dynamic threshold, polarization channel swapping is performed.

[0049] The polarization ambiguity region can be monotonically varied from 0° to 90°.

[0050] Secondly, polarization channel interchange includes: Set a polarization interchange matrix, and based on this matrix, interchange the primary and secondary relationships of the dual polarization channels. Reset to (or (depending on the image) This is the polarization deflection angle after reset; The weighted matrix after the switch is:

[0051] In the formula, This is the weighted matrix after the switch. This is the polarization interchange matrix.

[0052] In one embodiment, the returned received signal includes: Once the handover is complete, the logic to trigger a new tracking or reverse handover is only allowed to be executed if the next polarization mismatch factor is less than the lower threshold and the duration exceeds the stabilization time window.

[0053] A polarization tracking and switching system for low-Earth orbit (LEO) satellite communication, used to execute the aforementioned polarization tracking and switching method for LEO satellite communication, comprising: The radio frequency receiver layer includes: Antenna unit: Employs an orthogonal dual-polarized antenna (such as a ±45° tilted polarized antenna or a horizontal / vertical orthogonal dipole) to receive two orthogonal polarized radio frequency signals transmitted from low-Earth orbit satellites. and .

[0054] Dual-channel RF front-end: Includes a low-noise amplifier (LNA), a bandpass filter (BPF), and a downconverter (DNC). Two orthogonal signals undergo low-noise amplification, filtering, and downconversion via independent RF channels, converting them into two analog intermediate frequency (IF) signals. High amplitude and phase consistency between the two channels is required.

[0055] The analog-to-digital conversion layer includes: Dual-channel ADC unit: synchronously samples and quantizes the two analog intermediate frequency signals output from the RF front-end, converting them into a digital discrete signal sequence. and It is then fed into the subsequent baseband signal processing layer.

[0056] The baseband signal processing layer includes: Digital downconversion and synchronization unit: performs digital downconversion, matched filtering, carrier synchronization and timing synchronization on the digital signal output by the ADC, and outputs the synchronized baseband complex signal sampling sequence.

[0057] Pilot extraction unit: Based on the frame structure defined in the low-orbit satellite communication protocol, it separates the pilot sequence or reference signal for polarization estimation from the synchronized baseband signal and filters out interference from the effective data payload.

[0058] Polarization Weighting and Reconstruction Execution Unit: This is the physical execution mechanism for polarization compensation. This unit receives the weighting coefficient matrix from the decision layer and processes the dual-channel baseband data. and It performs linear transformations. Internally, it contains two core sub-modules: Polarization tracking weighter: Execution Matrix multiplication enables continuous and precise compensation for small-angle deflections; Polarization channel switcher: Execution Matrix multiplication (i.e., swapping the data streams of the two channels) enables the reference polarization to be reversed during large-angle deflections.

[0059] The execution order is as follows: First, determine whether to perform channel swapping based on the control instructions. Then perform tracking weighted compensation ( Output the compensated signal. and It is then sent to the subsequent demodulation and decoding module.

[0060] Polarization control and decision-making layer, including: This layer is responsible for extracting polarization features, assessing the degree of mismatch, and issuing control commands. It contains the following four core functional units: Polarization parameter estimation unit: Input: Dual-channel orthogonal pilot signals output by the pilot extraction unit.

[0061] Function: Based on maximum likelihood estimation, calculate the amplitude ratio and phase difference between two channels, and estimate the current polarization deflection angle in real time. At the same time, for Perform a difference operation to calculate the rate of change of the deflection angle. .

[0062] Output: Polarization deflection angle estimate Deflection angle change rate .

[0063] Polarization mismatch calculation unit: Input: Polarization deflection angle estimate .

[0064] Function: Calculates the current polarization mismatch factor based on a rigorous physical model of electromagnetic field polarization mismatch. .

[0065] Output: Polarization mismatch factor .

[0066] Channel quality monitoring unit: Input: Synchronized baseband signal.

[0067] Function: Calculates the signal-to-noise ratio (SNR) of the received signal in real time, provides a channel quality benchmark for polarization switching, and prevents accidental handover during deep fading.

[0068] Output: Current signal-to-noise ratio (SNR).

[0069] Mode decision and hysteresis control unit: Input: Mismatch factor Deflection angle change rate Current signal-to-noise ratio (SNR).

[0070] Function: This is the brain of the system, executing the debouncing logic.

[0071] like If the system is in the polarization tracking region, it will output the tracking mode command and deflection angle. Give to the execution unit; like , combined Direction and SNR determine whether the region has entered the polarization ambiguity or deterioration zone; If the switching conditions are met, a switching mode instruction is output to the execution unit to perform channel swapping, and the internal polarization reference is updated. At the same time, a hysteresis debouncing timer is started to block subsequent switching requests.

[0072] Output: Mode control command (tracking or switching), and real-time updated deflection angle compensation value.

[0073] The signal enters from the antenna, and after being digitized by RF and ADC, the main path signal enters the polarization weighting and reconstruction execution unit for processing; the bypass pilot signal enters the polarization parameter estimation unit for extraction. And w. Subsequently, the polarization mismatch calculation unit calculates η. The mode decision and hysteresis control unit, combining η, w, and SNR, determines whether to adopt fine tracking or channel switching, and sends the final weighted matrix coefficients to the execution unit. The execution unit performs matrix multiplication on the main path signal and outputs a polarization-aligned clean signal for baseband demodulation. This process runs continuously in a closed loop at the symbol rate, achieving real-time and precise countermeasures against the high dynamic polarization deflection of low-Earth orbit satellites.

[0074] Furthermore, the functional units in the various embodiments of the present invention 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.

[0075] 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. This computer software product, stored in a storage medium, 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 of the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0076] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A polarization tracking and switching method for low-Earth orbit satellite communication, characterized in that, include: The signal is received and the pilot sequence is extracted. The current polarization deflection angle is obtained by maximum likelihood estimation based on the pilot sequence. The polarization mismatch factor is calculated based on the polarization deflection angle, and a lower threshold is set. If the current polarization mismatch factor is less than the lower threshold, a digital polarization tracking weighting matrix is ​​generated, and after directional rotation compensation is performed on the dual-channel signal, the received signal is returned. If the current polarization mismatch factor is greater than or equal to the lower threshold, calculate the deflection angle change rate and set the switching conditions. When both the polarization mismatch factor and the deflection angle change rate meet the switching conditions, perform polarization channel swapping, update the reference, and return the received signal. If the switching conditions are not met, return the received signal.

2. The polarization tracking and switching method for low-Earth orbit satellite communication according to claim 1, characterized in that, The process of obtaining the current polarization deflection angle based on the pilot sequence through maximum likelihood estimation includes: In the formula, For dual-polarization signal vectors, For horizontal polarization components, For vertical polarization components, For transpose, This is the signal vector received by the ground station. This is the polarization rotation compensation matrix. It is an additive white Gaussian noise vector. This is the polarization deflection angle.

3. The polarization tracking and switching method for low-Earth orbit satellite communication according to claim 2, characterized in that, The calculation of the polarization mismatch factor based on the polarization deflection angle includes: In the formula, Polarization mismatch factor The value range is from 0 to 1, when hour, No mismatch; when hour, Orthogonal polarization complete crosstalk; when hour, The main polarization is completely transformed into cross polarization.

4. The polarization tracking and switching method for low-Earth orbit satellite communication according to claim 3, characterized in that, The generated digital polarization tracking weighted matrix includes: In the formula, For digital polarization tracking weighting matrix; Direction rotation compensation for dual-channel signals includes: In the formula, This is the compensated signal.

5. A polarization tracking and switching method for low-Earth orbit satellite communication according to claim 4, characterized in that, The calculation of the rate of change of deflection angle and the setting of switching conditions include: In the formula, The rate of change of deflection angle. The current moment; Set the polarization blur region when , When the upper threshold is set, the rate of change of the deflection angle is crossing the polarization ambiguity region, and the current signal-to-noise ratio of the received signal is lower than the dynamic threshold, polarization channel swapping is performed.

6. The polarization tracking and switching method for low-Earth orbit satellite communication according to claim 5, characterized in that, The polarization channel interchange includes: Set a polarization interchange matrix, and based on this matrix, interchange the primary and secondary relationships of the dual polarization channels. Reset to , This is the polarization deflection angle after reset; The weighted matrix after the switch is: In the formula, This is the combined weighted matrix after the switch. This is the polarization interchange matrix.

7. A polarization tracking and switching method for low-Earth orbit satellite communication according to claim 6, characterized in that, The returned received signal includes: Once the handover is complete, the logic to trigger a new tracking or reverse handover is only allowed to be executed if the next polarization mismatch factor is less than the lower threshold and the duration exceeds the stabilization time window.

8. A polarization tracking and switching system for low-Earth orbit satellite communication, characterized in that, A polarization tracking and switching method for low-Earth orbit satellite communication as described in any one of claims 1-7, comprising: The polarization parameter estimation unit calculates the amplitude ratio and phase difference between the two channels based on maximum likelihood estimation, and estimates the current polarization deflection angle in real time. At the same time, it performs differential operations on the polarization deflection angle to calculate the rate of change of the deflection angle. The polarization mismatch calculation unit is configured to obtain the polarization deflection angle and calculate the current polarization mismatch factor based on the electromagnetic field polarization mismatch physical model. The channel quality monitoring unit is configured to acquire the synchronized baseband signal, calculate the signal-to-noise ratio of the received signal in real time, and provide a channel quality benchmark for polarization switching. The mode decision and hysteresis control unit is configured to output a mode switching command to the execution unit to perform channel swapping if the switching conditions are met, update the internal polarization reference, and start the hysteresis debounce timer to block subsequent switching requests.

9. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the polarization tracking and switching method for low-orbit satellite communication as described in any one of claims 1-7.

10. A computer-readable storage medium, characterized in that, A computer program is stored on the computer-readable storage medium, and when executed by a processor, the computer program implements a polarization tracking and switching method for low-Earth orbit satellite communication as described in any one of claims 1-7.

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