A carrier synchronization method, device and equipment for a continuous phase modulation signal

Abstract

The application discloses a kind of carrier synchronization method, device and equipment of continuous phase modulation signal, belong to satellite communication field, first the time domain correlation value of target satellite signal and its local reference sequence is carried out spectrum analysis, determine the first frequency offset estimation value of target satellite signal and carry out first phase offset compensation, realize the coarse range acquisition to target satellite signal, then target satellite signal is linearized processing, then the target satellite signal after linearization processing is carried out second frequency offset compensation, finally the target satellite signal after second frequency offset compensation is carried out phase offset compensation, coarse range acquisition and the combination of high-precision frequency offset compensation and phase offset compensation, the compensation of frequency offset and phase offset can be efficiently and accurately realized, improve the reception efficiency and precision of target satellite signal, and linearization processing can avoid phase deviation, further improve the reception accuracy of target satellite signal.

Description

Technical Field

[0001] This invention relates to the field of satellite communications, and in particular to a carrier synchronization method, apparatus, and device for continuous phase modulation signals. Background Technology

[0002] Satellites may communicate with the ground via continuous phase modulation (CPM) signals, which requires the ground to accurately receive CPM signals. However, there is a lack of mature carrier synchronization methods for CPM signals in related technologies, making it difficult to accurately receive satellite signals when performing carrier synchronization for CPM signals.

[0003] Therefore, how to provide a solution to the above-mentioned technical problems is a problem that needs to be solved by those skilled in the art. Summary of the Invention

[0004] The purpose of this invention is to provide a carrier synchronization method, apparatus, and device for continuous phase modulation signals. This invention first performs spectral analysis on the time-domain correlation values ​​of the target satellite signal and its local reference sequence to determine the first frequency offset estimate of the target satellite signal and perform a first phase offset compensation, achieving coarse-range acquisition of the target satellite signal. Then, the target satellite signal is linearized, followed by a second frequency offset compensation, and finally, phase offset compensation. This combination of coarse-range acquisition and high-precision frequency and phase offset compensation efficiently and accurately achieves frequency and phase offset compensation, improving the reception efficiency and accuracy of the target satellite signal. Furthermore, the linearization process avoids phase detection bias, further enhancing the reception accuracy of the target satellite signal.

[0005] To solve the above-mentioned technical problems, the present invention provides a carrier synchronization method for continuous phase modulation signals, comprising: Spectral analysis is performed on the temporal correlation values ​​of the target satellite signal and its local reference sequence to determine the first frequency offset estimate of the target satellite signal; wherein, the target satellite signal is a continuous phase modulated signal; The first frequency offset compensation is performed on the target satellite signal based on the first frequency offset estimate; Linearization processing is performed on the target satellite signal after the first frequency offset compensation; A second frequency offset compensation is performed on the linearized target satellite signal; Phase offset compensation is performed on the target satellite signal after the second frequency offset compensation.

[0006] On the other hand, the step of performing spectral analysis on the time-domain correlation values ​​of the target satellite signal and its local reference sequence to determine the first frequency offset estimate of the target satellite signal includes: The complex correlation values ​​of the target satellite signal with the local reference sequence are calculated synchronously in multiple non-overlapping time domain sub-windows to obtain a complex correlation value sequence; Spectral analysis is performed on the complex correlation value sequence to determine the first frequency offset estimate of the target satellite signal.

[0007] On the other hand, the step of performing spectral analysis on the complex correlation value sequence to determine the first frequency offset estimate of the target satellite signal includes: The N-point Fast Fourier Transform is performed on the complex correlation value sequence to obtain the spectrum sequence; N is a positive integer greater than 1. The first frequency offset estimate of the target satellite signal is determined based on the position of the maximum peak in the spectral sequence.

[0008] On the other hand, the linearization process for the target satellite signal after the first frequency offset compensation includes: The target satellite signal after the first frequency offset compensation is decomposed into a linear superposition of multiple pulse amplitude modulation components, and the main pulse amplitude modulation component with the largest energy proportion is selected as the target satellite signal. The target satellite signal is subjected to phase despinning to remove the inherent nonlinear phase of the continuous phase modulation signal and obtain an equivalent linear modulation signal.

[0009] On the other hand, the second frequency offset compensation for the linearized target satellite signal includes: The linearized target satellite signal is orthogonally decomposed to obtain in-phase branch signals and quadrature branch signals; For any in-phase branch signal, the in-phase branch signal and its preceding and following signals are... l w The average value of the in-phase branch signals of each symbol is used as the in-phase branch signal; l w It is a positive integer greater than 2; For any orthogonal branch signal, the orthogonal branch signal and its preceding and following branches are considered together. l w The average of the quadrature branch signals of each symbol is used as the quadrature branch signal; the in-phase branch signal and the quadrature branch signal constitute the first complex signal; Frequency error discrimination is performed on the smoothed first complex signal to obtain the second frequency offset estimate; The target satellite signal is compensated for a second frequency offset based on the second frequency offset estimate.

[0010] On the other hand, the phase offset compensation for the target satellite signal after the second frequency offset compensation includes: The target satellite signal after the second frequency offset compensation is orthogonally decomposed to obtain the in-phase branch signal and the quadrature branch signal; For any in-phase branch signal, the in-phase branch signal and its preceding and following signals are... l w The average value of the in-phase branch signals of each symbol is used as the in-phase branch signal; l w It is a positive integer greater than 2; For any orthogonal branch signal, the orthogonal branch signal and its preceding and following branches are considered together. l w The average of the quadrature branch signals of each symbol is used as the quadrature branch signal; the in-phase branch signal and the quadrature branch signal constitute the second complex signal; Phase error identification is performed on the smoothed second complex signal to obtain the phase offset estimate; Phase offset compensation is performed on the target satellite signal based on the phase offset estimate.

[0011] On the other hand, the target satellite signal is a continuous phase-modulated signal that has undergone spread spectrum processing; The orthogonal decomposition of the linearized target satellite signal to obtain in-phase and orthogonal branch signals includes: Despreading is performed on the linearized target satellite signal; The target satellite signal after despreading is orthogonally decomposed to obtain in-phase branch signal and orthogonal branch signal; The orthogonal decomposition of the target satellite signal after the second frequency offset compensation to obtain the in-phase branch signal and the orthogonal branch signal includes: Despreading is performed on the target satellite signal after the second frequency offset compensation. The target satellite signal after despreading is orthogonally decomposed to obtain in-phase branch signal and orthogonal branch signal.

[0012] On the other hand, after performing frequency error identification on the smoothed first complex signal to obtain a second frequency offset estimate, and before performing a second frequency offset compensation on the target satellite signal based on the second frequency offset estimate, the carrier synchronization method for the continuous phase modulation signal further includes: Interpolation compensation is performed on the symbol-level second frequency offset estimate sequence to obtain the chip-level second frequency offset estimate sequence; the second frequency offset estimate sequence includes multiple second spectrum estimates.

[0013] To address the aforementioned technical problems, the present invention also provides a carrier synchronization device for a continuous phase modulation signal, comprising: The acquisition module is used to perform spectral analysis on the time-domain correlation values ​​of the target satellite signal and its local reference sequence to determine the first frequency offset estimate of the target satellite signal; wherein, the target satellite signal is a continuous phase modulation signal; The first compensation module is used to perform the first frequency offset compensation on the target satellite signal based on the first frequency offset estimate. The linearization module is used to linearize the target satellite signal after the first frequency offset compensation. The second compensation module is used to perform a second frequency offset compensation on the target satellite signal that has undergone linearization processing. The third compensation module is used to perform phase offset compensation on the target satellite signal after the second frequency offset compensation.

[0014] To address the aforementioned technical problems, the present invention also provides a carrier synchronization device for a continuous phase modulation signal, comprising: Memory, used to store computer programs; A processor is configured to implement the carrier synchronization method for the continuous phase modulation signal as described above when executing the computer program.

[0015] Beneficial Effects: This invention provides a carrier synchronization method for continuous phase modulation signals. Considering that coarse-range acquisition followed by high-precision frequency offset and phase offset compensation can efficiently and accurately receive target satellite signals, and that linearization processing can improve the estimation accuracy of the phase detection process, this invention first performs spectral analysis on the time-domain correlation values ​​of the target satellite signal and its local reference sequence to determine the first frequency offset estimate of the target satellite signal and perform the first phase offset compensation, thus achieving coarse-range acquisition of the target satellite signal. Then, the target satellite signal is linearized, followed by a second frequency offset compensation, and finally, phase offset compensation is performed on the target satellite signal after the second frequency offset compensation. The combination of coarse-range acquisition and high-precision frequency offset and phase offset compensation can efficiently and accurately achieve frequency offset and phase offset compensation, improving the reception efficiency and accuracy of the target satellite signal. Furthermore, linearization processing can avoid phase detection bias, further improving the reception accuracy of the target satellite signal.

[0016] The present invention also provides a carrier synchronization device and apparatus for continuous phase modulation signals, which has the same beneficial effects as the carrier synchronization method for continuous phase modulation signals described above. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention, the relevant technologies and the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A schematic diagram of the first process of the carrier synchronization method for continuous phase modulation signals provided by the present invention; Figure 2 This is a schematic diagram of the capture module provided by the present invention; Figure 3 This is a schematic diagram of the structure of the second compensation module and the third compensation module provided by the present invention; Figure 4 A first structural schematic diagram of the carrier synchronization device for continuous phase modulation signals provided by the present invention; Figure 5 A schematic diagram of the second structure of the carrier synchronization device for continuous phase modulation signals provided by the present invention; Figure 6 A schematic diagram of the structure of the carrier synchronization device for continuous phase modulation signals provided by the present invention. Detailed Implementation

[0019] The core of this invention is to provide a carrier synchronization method, apparatus, and device for continuous phase modulation signals. This invention first performs spectral analysis on the time-domain correlation values ​​of the target satellite signal and its local reference sequence to determine the first frequency offset estimate of the target satellite signal and perform a first phase offset compensation, achieving coarse-range acquisition of the target satellite signal. Then, the target satellite signal is linearized, followed by a second frequency offset compensation, and finally, phase offset compensation. This combination of coarse-range acquisition and high-precision frequency and phase offset compensation efficiently and accurately achieves frequency and phase offset compensation, improving the reception efficiency and accuracy of the target satellite signal. Furthermore, the linearization process avoids phase detection bias, further enhancing the reception accuracy of the target satellite signal.

[0020] 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, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Please refer to Figure 1 , Figure 1 This is a first flowchart illustrating the carrier synchronization method for a continuously phase modulated signal provided by the present invention. The carrier synchronization method for the continuously phase modulated signal includes: S101: Perform spectral analysis on the time-domain correlation values ​​of the target satellite signal and its local reference sequence to determine the first frequency offset estimate of the target satellite signal; wherein, the target satellite signal is a continuous phase modulation signal; Specifically, considering the technical problems of Doppler frequency offset and limited signal acquisition time that may be caused by the high-speed movement of certain satellites (such as satellites in low-Earth orbit constellation communication), this embodiment of the present invention includes this step. This step performs spectral analysis on the time-domain correlation values ​​of the target satellite signal and its local reference sequence, which can complete a coarse estimate of a large range of frequency offsets in a short time (that is, determine the first frequency offset estimate of the target satellite signal) while maintaining high estimation accuracy. This significantly shortens the signal acquisition time, expands the range of acquireable frequency offsets, provides an initial frequency reference for subsequent high-precision tracking, and ensures that the system can quickly lock onto the target signal in a highly dynamic environment.

[0022] S102: Perform the first frequency offset compensation on the target satellite signal based on the first frequency offset estimate; Specifically, considering that Doppler frequency offset can cause severe shifts in the signal spectrum, exceeding the traction range of subsequent tracking loops and even causing signal distortion, the first frequency offset compensation is performed based on the first frequency offset estimate from the previous step in this embodiment of the invention. This can limit the residual frequency offset to the frequency operating range of subsequent compensation steps, prevent signal loss of lock, and provide a relatively stable input signal for linearization processing.

[0023] S103: Linearize the target satellite signal after the first frequency offset compensation; Specifically, considering the inherent nonlinear phase characteristics of continuous phase modulated signals, which make it difficult to directly apply traditional carrier synchronization techniques, traditional linear modulation-based carrier synchronization algorithms, when directly applied to continuous phase modulated signals, will suffer from phase detection bias due to the additional phase jitter introduced by the modulation information, thus reducing estimation accuracy. Therefore, this embodiment of the invention includes a linearization processing step. This step can convert the nonlinear continuous phase modulated signal into a linear equivalent representation, decoupling the modulation phase from the carrier phase, simplifying the complexity of subsequent carrier tracking, improving tracking accuracy and stability, while maintaining the spectral efficiency advantage of continuous phase modulated signals, thus creating conditions for reliable synchronization in low signal-to-noise ratio environments.

[0024] S104: Perform a second frequency offset compensation on the linearized target satellite signal; Specifically, since the residual frequency offset can be limited to a certain frequency range after the first frequency offset compensation, this step can perform a second frequency offset compensation for the target satellite signal with a small residual frequency offset, thereby efficiently and accurately performing a second frequency offset compensation for the residual frequency offset of the target satellite signal, thus correcting the frequency of the target satellite signal.

[0025] S105: Perform phase offset compensation on the target satellite signal after the second frequency offset compensation.

[0026] Specifically, considering that precise frequency offset compensation of the target satellite signal is beneficial to improving the accuracy of phase offset compensation, phase offset compensation can be performed on the target satellite signal after the second frequency offset compensation in this step. This allows for precise phase offset compensation of the target satellite signal and improves the accuracy of carrier synchronization.

[0027] Specifically, this invention employs a hierarchical processing architecture. It achieves rapid acquisition of Doppler frequency offset through spectral analysis, removes the nonlinear phase characteristics of the CPM signal through linearization processing, and finally achieves high-precision tracking of residual frequency and phase offsets through a hierarchical compensation mechanism. This solves the carrier synchronization problem of CPM signals in high-dynamic environments, improves synchronization accuracy and tracking range, and reduces system complexity.

[0028] This invention provides a carrier synchronization method for continuously phase modulated signals. Considering that coarse-range acquisition followed by high-precision frequency offset and phase offset compensation can efficiently and accurately receive target satellite signals, and that linearization processing can improve the estimation accuracy of the phase detection process, this invention first performs spectral analysis on the time-domain correlation values ​​of the target satellite signal and its local reference sequence to determine the first frequency offset estimate of the target satellite signal and perform the first phase offset compensation, thus achieving coarse-range acquisition of the target satellite signal. Then, the target satellite signal is linearized, followed by a second frequency offset compensation, and finally, phase offset compensation is performed on the target satellite signal after the second frequency offset compensation. The combination of coarse-range acquisition and high-precision frequency offset and phase offset compensation can efficiently and accurately achieve frequency offset and phase offset compensation, improving the reception efficiency and accuracy of the target satellite signal. Furthermore, linearization processing can avoid phase detection bias, further improving the reception accuracy of the target satellite signal.

[0029] Based on the above embodiments: As an optional embodiment, spectral analysis is performed on the time-domain correlation values ​​of the target satellite signal and its local reference sequence to determine the first frequency offset estimate of the target satellite signal, including: The complex correlation values ​​of the target satellite signal with the local reference sequence are calculated synchronously in multiple non-overlapping time domain sub-windows to obtain a complex correlation value sequence; Spectral analysis of the complex correlation value sequence was performed to determine the first frequency offset estimate of the target satellite signal.

[0030] Specifically, traditional frequency offset estimation methods suffer from slow acquisition speed and high computational complexity in Doppler extended scenarios. This invention addresses these issues by employing a scheme that simultaneously calculates the complex correlation values ​​between the target satellite signal and the local reference sequence within multiple non-overlapping time-domain sub-windows, obtaining a complex correlation value sequence. Then, spectral analysis is performed on this sequence to determine the first estimated frequency offset value of the target satellite signal. This scheme utilizes a strategy of time-domain sub-window partitioning and simultaneous calculation, improving processing speed while maintaining acquisition accuracy, shortening frequency offset acquisition time, expanding the acquireable frequency offset range, and reducing algorithm complexity, thus laying the foundation for subsequent high-precision tracking.

[0031] Among these steps, the complex correlation values ​​between the target satellite signal and the local reference sequence are calculated synchronously within multiple non-overlapping time-domain sub-windows, resulting in a complex correlation value sequence including: The complex correlation values ​​of the target satellite signal with the local reference sequence are calculated synchronously in multiple non-overlapping time-domain sub-windows by using multiple partially matched filters in parallel, thus obtaining a sequence of complex correlation values; each partially matched filter corresponds one-to-one with a time-domain sub-window.

[0032] As an optional embodiment, spectral analysis of the complex correlation value sequence to determine the first frequency offset estimate of the target satellite signal includes: Perform an N-point Fast Fourier Transform on the complex correlation value sequence to obtain the spectrum sequence; N is a positive integer greater than 1. The first frequency offset estimate of the target satellite signal is determined based on the position of the maximum peak in the spectral sequence.

[0033] Specifically, for a better explanation of the embodiments of the present invention, please refer to... Figure 2 , Figure 2 This is a schematic diagram of the acquisition module provided by the present invention. Considering that the N-point Fast Fourier Transform has the advantages of high efficiency and accuracy, and that the position of the maximum peak in the spectrum sequence obtained by the N-point Fast Fourier Transform can accurately reflect the frequency offset, in this embodiment of the present invention, the complex correlation value sequence can be subjected to the N-point Fast Fourier Transform to obtain the spectrum sequence; and the first frequency offset estimate of the target satellite signal can be determined according to the position of the maximum peak in the spectrum sequence.

[0034] Specifically, Figure 2The buffer in the code can buffer the target satellite signal, and then multiple parallel partially matched filters (PMFs) can synchronously calculate the complex correlation values ​​between the target satellite signal and the local reference sequence in multiple non-overlapping time-domain sub-windows based on the local PN (pseudo-noise) code (i.e., the local reference sequence), obtaining a complex correlation value sequence, where the PMFs... m This represents the m-th partially matched filter; then, an N-point Fast Fourier Transform can be performed on the complex correlation value sequence to obtain the spectrum sequence, and based on the position of the maximum peak in the spectrum sequence, the first frequency offset estimate of the target satellite signal (i.e., ...) can be determined. Figure 2 (Related peak judgment in the data).

[0035] Additionally, as an optional embodiment, determining the first frequency offset estimate of the target satellite signal based on the position of the maximum peak in the spectral sequence includes: The frequency offset estimation accuracy of the first frequency offset estimate is determined based on the number of partially matched filters, the sampling period, the number of FFT points N, and the length L of the local reference sequence. When the position of the maximum peak in the spectrum sequence is located in the first half of the peak of the FFT output, the product of the difference between the position of the maximum peak in the spectrum sequence and 1 and the frequency offset estimation accuracy is used as the first frequency offset estimate. When the maximum peak in the spectral sequence is located in the latter half of the peak in the FFT output, the first frequency offset estimate can be obtained from... Find it; Where N is the number of points in the FFT. k max This is the index corresponding to the maximum peak in the spectral sequence, that is, the position of the maximum peak in the spectral sequence. f △ This is for the accuracy of frequency offset estimation.

[0036] Specifically, this embodiment of the invention uses GMSK (Gaussian Minimum Shift Keying) spread spectrum signal as an example to introduce the GMSK spread spectrum signal model and the high dynamic range received signal (target satellite signal) model: (1) GMSK spread spectrum signal model: At the transmitting end, the expression for the GMSK signal is: (1); In the formula, For GMSK signal, s (·) represents the function name of the GMSK signal. t For time, It is the power of the transmitted signal. j The imaginary unit, For the transmitted sequence The spread binary chip sequence, i The index of the original information bit sequence. For a continuous phase carrying information, its expression is: (2); in, h This is the modulation index of the GMSK, typically taken as 0.5; It is the chip cycle. The phase pulse function is expressed as follows: (3); It is a frequency pulse shaped by a Gaussian pre-modulation filter. Its shape is determined by the normalized 3dB bandwidth (e.g., 0.3). Its tail causes phase correlation between adjacent chips, i.e., phase memory.

[0037] (2) High dynamic range received signal model: Considering the low-Earth orbit satellite communication scenario, the received signal is affected by the high-dynamic Doppler effect. Assuming the Doppler frequency offset varies linearly with time, the received signal after passing through a channel considering additive white Gaussian noise (AWGN) can be modeled as follows: (4); in, To delay the transmission time, The GMSK signal after propagation delay. It is the initial Doppler frequency shift. It is the initial phase bias. The rate of change of Doppler frequency deviation, It is additive white Gaussian noise with a two-sided power spectral density of N 0 One-half of, N 0 This represents the noise power per unit bandwidth.

[0038] The instantaneous phase of the received signal can be expressed as: (5); As can be seen from equation (5), The received signal's instantaneous phase at time t is composed of three coupled parts: the inherent nonlinear phase of GMSK modulation. Time-varying carrier phase caused by high dynamics and noise phase .

[0039] In a specific example, there are P partially matched filters of length X, and the local reference sequence length is L = PX. When the target satellite signal is aligned with the local reference sequence, the output of the m-th (index of the partially matched filter) partially matched filter can be expressed as: (6); in, For the first m The output of a partially matched filter, where k in Equation 6 is the sampling point index. The phase of the received signal, A The signal amplitude, The sampling period is obtained by performing an N-point FFT on the output of the matched filter. (7); in, for Y ( m The discrete Fourier transform result of ), where N is the number of FFT points, in Equation 7 k For the frequency domain index of an N-point FFT, search The peak value, and its corresponding index A coarse estimate of the Doppler frequency offset is given. Considering the correlation loss caused by partial matched filtering, the one-sided analysis bandwidth is usually taken as 1 / 4 of the FFT analysis bandwidth. Then, the frequency offset estimation accuracy, frequency offset estimate, and frequency offset estimation range in the acquisition stage can be given by the following equations (8), (9), and (10), respectively: (8); (9); (10); in, f △ It refers to the frequency offset estimation accuracy during the acquisition phase. This is the frequency offset estimate during the acquisition phase. This is the range for frequency offset estimation during the acquisition phase.

[0040] PMF-FFT enables rapid coarse estimation of frequency offset parameters, keeping residual frequency offset within the traction range of subsequent tracking loops.

[0041] As an optional embodiment, linearization processing of the target satellite signal after the first frequency offset compensation includes: The target satellite signal after the first frequency offset compensation is decomposed into a linear superposition of multiple pulse amplitude modulation components, and the main pulse amplitude modulation component with the largest energy proportion is selected as the target satellite signal. A phase despinning operation is performed on the target satellite signal to remove the inherent nonlinear phase of the continuous phase modulated signal and obtain an equivalent linear modulated signal.

[0042] Specifically, considering that the inherent nonlinear phase characteristics of continuous phase modulation (CPM) signals hinder the direct application of traditional linear carrier synchronization (LCS) techniques, this embodiment of the invention proposes a scheme that decomposes the target satellite signal after the first frequency offset compensation into a linear superposition of multiple pulse amplitude modulation (CPM) components, selecting the main pulse amplitude modulation component with the largest energy proportion as the target satellite signal. A phase despinning operation is then performed on the target satellite signal to remove the inherent nonlinear phase of the CPM signal, resulting in an equivalent linear modulation signal. This scheme, based on Laurent decomposition theory, transforms the nonlinear CPM signal into an approximately linear equivalent representation, decoupling the modulation phase from the carrier phase, simplifying the complexity of subsequent carrier tracking, improving tracking accuracy and stability, while maintaining the spectral efficiency advantage of the CPM signal, thus creating conditions for reliable synchronization in low signal-to-noise ratio (SNR) environments.

[0043] Specifically, in a concrete example, for a CPM signal processed by GMSK, in order to remove the nonlinear modulation phase of GMSK, this paper uses Laurent decomposition to approximate the GMSK signal as a linear superposition of multiple pulse amplitude modulation signals. For a GMSK spread spectrum signal with a normalized 3dB bandwidth of 0.3, its main energy is concentrated in the first PAM (Pulse Amplitude Modulation) component, therefore, the following approximation can be made: (11); in, It is an approximate representation of the GMSK signal after Laurent decomposition. k For summation index; For equivalent complex pseudocode symbols, n For summation index; The main pulse function is used. This approximation converts the nonlinear phase modulation of GMSK into a linear complex pseudocode sequence pair of main pulses. Amplitude modulation. Due to ,but ,make At this point, equation (11) can be expressed as: (12); Furthermore, a phase derotation operation is performed on the approximate signal, multiplying it by a rotation factor associated with the symbol index within each symbol interval. We can obtain: (13); At this point, the despinned equivalent symbol sequence degenerates into a real-valued binary sequence without frequency offset. The residual frequency offset and phase offset then manifest as linear phase rotation of the baseband pulse. Therefore, the received signal can be modeled as a linear modulation form: (14); in, The received signal after linear processing. The residual frequency offset after capture compensation. This represents the noise term after despinning. This linearization process lays the foundation for the subsequent linear carrier tracking loop.

[0044] As an optional embodiment, performing a second frequency offset compensation on the linearized target satellite signal includes: The linearized target satellite signal is orthogonally decomposed to obtain in-phase branch signals and quadrature branch signals; For any in-phase branch signal, the in-phase branch signal and its preceding and following signals are... l w The average value of the in-phase branch signals of each symbol is used as the in-phase branch signal; l w It is a positive integer greater than 2; For any orthogonal branch signal, the orthogonal branch signal and its preceding and following branches are considered together. l w The average of the quadrature branch signals of each symbol is used as the quadrature branch signal; the in-phase branch signal and the quadrature branch signal constitute the first complex signal; Frequency error discrimination is performed on the smoothed first complex signal to obtain the second frequency offset estimate; The target satellite signal is compensated for a second frequency offset based on the second frequency offset estimate.

[0045] Specifically, considering that sliding coherent integration can improve the input signal-to-noise ratio of the discriminator without increasing the loop bandwidth, this embodiment of the invention designs the following scheme: The linearized target satellite signal is orthogonally decomposed to obtain in-phase and quadrature branch signals; sliding coherent integration is performed on the in-phase and quadrature branch signals to obtain a smoothed first complex signal; frequency error discrimination is performed on the smoothed first complex signal to obtain a second frequency offset estimate; and a second frequency offset compensation is performed on the target satellite signal based on the second frequency offset estimate. This can improve the input signal-to-noise ratio of the discriminator without increasing the loop bandwidth.

[0046] Of course, in addition to this specific form, the second frequency offset compensation for the linearized target satellite signal can also take other forms, which are not limited in this embodiment of the invention.

[0047] Specifically, for a better explanation of the embodiments of the present invention, please refer to... Figure 3 and Figure 4 , Figure 3 This is a schematic diagram of the structure of the second compensation module and the third compensation module provided by the present invention; Figure 3 The target satellite signal is a satellite signal spread by GMSK. The frequency discriminator, loop filter and FLL NCO (Frequency-Locked Loop Numerically Controlled Oscillator) form a frequency-locked loop, and the phase discriminator, loop filter and PLL NCO (Phase-Locked Loop Numerically Controlled Oscillator) form a phase-locked loop. Figure 4 In the process, the target satellite signal emitted by the signal generator is processed by the mapping spread spectrum and GMSK modulation module, and then enters the acquisition module after being subjected to noise interference. Figure 4 The first compensation module is omitted. The linearization module includes the Laurent module and the despinning module. The tracking module, which consists of the second compensation module and the third compensation module, is composed of a despreading module (used to perform phase despreading) and an improved second-order frequency-locked loop assisted third-order phase-locked loop module (performs sliding coherent integration, determines the second spectrum estimate, and determines the phase offset estimate). Finally, the target satellite signal, which has undergone two frequency offset compensations and one phase offset compensation, is jointly despreaded and decoded.

[0048] As an optional embodiment, phase offset compensation for the target satellite signal after the second frequency offset compensation includes: The target satellite signal after the second frequency offset compensation is orthogonally decomposed to obtain the in-phase branch signal and the quadrature branch signal; For any in-phase branch signal, the in-phase branch signal and its preceding and following signals are... l w The average value of the in-phase branch signals of each symbol is used as the in-phase branch signal; l w It is a positive integer greater than 2; For any orthogonal branch signal, the orthogonal branch signal and its preceding and following branches are considered together. l w The average of the quadrature branch signals of each symbol is used as the quadrature branch signal; the in-phase branch signal and the quadrature branch signal constitute the second complex signal; Phase error identification is performed on the smoothed second complex signal to obtain the phase offset estimate; Phase offset compensation is performed on the target satellite signal based on the phase offset estimate.

[0049] Specifically, considering that traditional phase-locked loops (PLLs) suffer from insufficient phase tracking accuracy and are prone to cycle slips in high-dynamic environments, this embodiment of the invention provides a phase offset compensation scheme. This scheme employs a third-order PLL structure combined with sliding coherent integration technology, improving phase tracking accuracy and dynamic response capability. While maintaining high tracking accuracy, it enhances adaptability to high-dynamic phase changes, reduces the bit error rate in low signal-to-noise ratio environments, and provides a reliable phase reference for coherent demodulation of CPM signals.

[0050] Of course, in addition to this specific form, phase offset compensation for the target satellite signal after the second frequency offset compensation can also take other forms, and the embodiments of the present invention are not limited here.

[0051] As an optional embodiment, the target satellite signal is a continuously phase-modulated signal that has undergone spread spectrum processing; Orthogonal decomposition is performed on the linearized target satellite signal to obtain in-phase and quadrature branch signals, including: Despreading is performed on the linearized target satellite signal; The target satellite signal after despreading is orthogonally decomposed to obtain in-phase branch signal and orthogonal branch signal; The target satellite signal after the second frequency offset compensation is orthogonally decomposed to obtain the in-phase branch signal and the quadrature branch signal, including: Despreading is performed on the target satellite signal after the second frequency offset compensation. The target satellite signal after despreading is orthogonally decomposed to obtain in-phase branch signal and orthogonal branch signal.

[0052] Specifically, considering that in low-Earth orbit (LEO) constellation communication systems, after spread spectrum processing, the noise power of the undespread signal is much greater than the useful signal power, making it difficult for the carrier synchronization loop to operate stably and prone to loss of lock-in, this embodiment of the invention can perform despreading processing on the linearized target satellite signal; then, orthogonal decomposition is performed on the despread target satellite signal to obtain in-phase and quadrature branch signals. Furthermore, despreading processing is performed on the target satellite signal after a second frequency offset compensation; then, orthogonal decomposition is performed on the despread target satellite signal to obtain in-phase and quadrature branch signals. This can suppress broadband noise and provide high-quality signal input for subsequent carrier synchronization.

[0053] As an optional embodiment, after frequency error identification is performed on the smoothed first complex signal to obtain a second frequency offset estimate, and before a second frequency offset compensation is performed on the target satellite signal based on the second frequency offset estimate, the carrier synchronization method for the continuous phase modulation signal further includes: Interpolation compensation is performed on the symbol-level second frequency offset estimate sequence to obtain the chip-level second frequency offset estimate sequence; the second frequency offset estimate sequence includes multiple second spectrum estimates.

[0054] Specifically, considering that traditional methods typically use zero-order hold for chip-level phase compensation of symbol-level frequency offset estimates, which can lead to phase jumps and accumulated errors when the frequency changes rapidly; therefore, in this embodiment of the invention, the symbol-level second frequency offset estimate sequence can be interpolated to obtain the chip-level second frequency offset estimate sequence, and then the target satellite signal can be compensated for a second time using the chip-level second frequency offset estimate sequence, followed by phase compensation, which can avoid phase jumps and accumulated errors when the frequency changes rapidly.

[0055] The specific interpolation compensation method can be various, such as third-order spline interpolation technology, etc., and the embodiments of the present invention are not limited here.

[0056] Specifically, in one particular example, this embodiment of the invention introduces, on the one hand, the sliding coherent integration technique to improve the input signal-to-noise ratio of the discriminator without increasing the loop bandwidth; on the other hand, it uses third-order spline interpolation compensation at the chip level to correct timing deviations caused by dynamic frequency offsets. The specific signal processing flow is as follows.

[0057] (1) First despread then tracking and sliding coherent integral: To improve the equivalent input signal-to-noise ratio of the loop, a strategy of first despreading and then tracking is adopted for the linearized signal. First, despreading is performed using a local complex pseudocode sequence, thus providing approximately [missing information - likely a data structure or feature] for the subsequent carrier tracking loop. The signal-to-noise ratio is improved. Spreading factor.

[0058] The despread in-phase branch signal and quadrature branch signal can be represented as: (15); (16); in, For the first n The in-phase branch signal of each symbol, For the first n Orthogonal branch signals of each symbol, For signal amplitude, For the first The residual carrier phase error at each symbol time, For the first n The noise component of the in-phase branch of each symbol, For the first n The noise components of the orthogonal branches of each symbol.

[0059] To extend the linear range of the frequency discriminator and further suppress noise while avoiding excessive loop bandwidth, a sliding coherent integration technique is introduced to continuously... A moving average is performed on each symbol: (17); (18); In the formula, The in-phase branch signal after moving average. The orthogonal branch signal after moving average. This indicates the current symbol number being processed. After moving average, the noise variance is reduced to half of its original value. While the signal amplitude remains unchanged, this effectively increases the input signal-to-noise ratio of the discriminator. In the context of traditional systems being forced to increase loop noise bandwidth to adapt to highly dynamic environments, this technology enhances the dynamic tracking range and discrimination accuracy under low signal-to-noise ratio conditions.

[0060] (2) Grading error identification and filtering: A graded error discrimination strategy is employed to balance dynamic response and steady-state accuracy. The smoothed first complex signal is first fed into a second-order FLL for coarse tracking. The FLL uses a four-quadrant arctangent frequency discriminator. (19); in, This is the FLL frequency discrimination error signal. It refers to the symbol period. This frequency discriminator has the advantages of a wide linear range and strong noise immunity. The frequency discrimination error, after being filtered by a second-order loop filter, is used to quickly pull and stabilize the residual large dynamic frequency offset.

[0061] After the FLL traction stabilizes, the signal is sent to a third-order PLL for precise tracking. The PLL uses a dot-matrix phase detector. (20); in, The signal is the PLL phase detection error signal. This phase detector exhibits near-linear phase detection characteristics at low signal-to-noise ratios. After being filtered by a third-order loop filter, the phase detection error is used to accurately track residual phase bias and frequency change rate, providing good matching for high-dynamic scenarios.

[0062] (3) Chip-level timing compensation based on third-order spline interpolation: Traditional methods typically use zero-order hold for chip-level phase compensation by estimating the frequency at the symbol level, which can lead to phase jumps and accumulated errors when the frequency changes rapidly. This invention employs third-order spline interpolation to reconstruct a continuous frequency trajectory at the chip level using the symbol-level discrete frequency estimation sequence output by the frequency-locked loop.

[0063] Let the symbol time be The corresponding frequency estimate is In each sub-interval Construct a cubic polynomial above: (twenty one); By solving the corresponding tridiagonal linear equations, we can achieve the following: The function exhibits continuous first and second derivatives at the nodes, allowing for the acquisition of instantaneous frequency estimates at any given time. For time points exceeding the symbol time range, constant extrapolation is employed to ensure stability. Finally, the continuous frequency function is applied to chip-level phase rotation, achieving precise dynamic compensation point-by-sampling.

[0064] (twenty two); in, This is the received signal after dynamic phase compensation. For the received signal after moving average processing, third-order spline interpolation ensures the smoothness of the frequency trajectory and phase continuity, suppresses the error accumulation introduced by traditional zero-order hold, and significantly improves the synchronization accuracy in high dynamic scenarios.

[0065] Please refer to Figure 5 , Figure 5 This is a second structural schematic diagram of the carrier synchronization device for a continuous phase modulation signal provided by the present invention. The carrier synchronization device for the continuous phase modulation signal includes: The acquisition module 51 is used to perform spectral analysis on the time-domain correlation values ​​of the target satellite signal and its local reference sequence to determine the first frequency offset estimate of the target satellite signal; wherein, the target satellite signal is a continuous phase modulation signal; The first compensation module 52 is used to perform the first frequency offset compensation on the target satellite signal based on the first frequency offset estimate; Linearization module 53 is used to linearize the target satellite signal after the first frequency offset compensation. The second compensation module 54 is used to perform a second frequency offset compensation on the target satellite signal after linearization processing; The third compensation module 55 is used to perform phase offset compensation on the target satellite signal after the second frequency offset compensation.

[0066] For a description of the carrier synchronization device for continuous phase modulation signals provided in the embodiments of the present invention, please refer to the aforementioned embodiments of the carrier synchronization method for continuous phase modulation signals. The embodiments of the present invention will not be repeated here.

[0067] Please refer to Figure 6 , Figure 6This is a schematic diagram of the structure of the carrier synchronization device for continuous phase modulation signals provided by the present invention. The carrier synchronization device for continuous phase modulation signals includes: Memory 61 is used to store computer programs; The processor 62 is used to implement the steps of the carrier synchronization method for the continuous phase modulation signal as described in the foregoing embodiments when executing a computer program.

[0068] For a description of the carrier synchronization device for the continuous phase modulation signal provided in the embodiments of the present invention, please refer to the aforementioned embodiments of the carrier synchronization method for the continuous phase modulation signal. The embodiments of the present invention will not be repeated here.

[0069] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section. It should also be noted that in this specification, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising a..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0070] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A carrier synchronization method for a continuous phase modulation signal, characterized in that, include: Spectral analysis is performed on the temporal correlation values ​​of the target satellite signal and its local reference sequence to determine the first frequency offset estimate of the target satellite signal; wherein, the target satellite signal is a continuous phase modulated signal; The first frequency offset compensation is performed on the target satellite signal based on the first frequency offset estimate; Linearization processing is performed on the target satellite signal after the first frequency offset compensation; A second frequency offset compensation is performed on the linearized target satellite signal; Phase offset compensation is performed on the target satellite signal after the second frequency offset compensation; The linearization process for the target satellite signal after the first frequency offset compensation includes: The target satellite signal after the first frequency offset compensation is decomposed into a linear superposition of multiple pulse amplitude modulation components, and the main pulse amplitude modulation component with the largest energy proportion is selected as the target satellite signal. The target satellite signal is subjected to phase despinning to remove the inherent nonlinear phase of the continuous phase modulation signal and obtain an equivalent linear modulation signal.

2. The carrier synchronization method for a continuous phase modulated signal according to claim 1, characterized in that, The step of performing spectral analysis on the time-domain correlation values ​​of the target satellite signal and its local reference sequence to determine the first frequency offset estimate of the target satellite signal includes: The complex correlation values ​​of the target satellite signal with the local reference sequence are calculated synchronously in multiple non-overlapping time domain sub-windows to obtain a complex correlation value sequence; Spectral analysis is performed on the complex correlation value sequence to determine the first frequency offset estimate of the target satellite signal.

3. The carrier synchronization method for a continuous phase modulation signal according to claim 2, characterized in that, The step of performing spectral analysis on the complex correlation value sequence to determine the first frequency offset estimate of the target satellite signal includes: The N-point Fast Fourier Transform is performed on the complex correlation value sequence to obtain the spectrum sequence; N is a positive integer greater than 1. The first frequency offset estimate of the target satellite signal is determined based on the position of the maximum peak in the spectral sequence.

4. The carrier synchronization method for a continuous phase modulated signal according to any one of claims 1 to 3, characterized in that, The second frequency offset compensation for the linearized target satellite signal includes: The linearized target satellite signal is orthogonally decomposed to obtain in-phase branch signals and quadrature branch signals; For any in-phase branch signal, the in-phase branch signal and its preceding and following branches are considered as l w The average value of the in-phase branch signals of each symbol is used as the in-phase branch signal; w It is a positive integer greater than 2; For any orthogonal branch signal, the orthogonal branch signal and its preceding and following branches are combined into a single line. w The average of the quadrature branch signals of each symbol is used as the quadrature branch signal; the in-phase branch signal and the quadrature branch signal constitute the first complex signal; Frequency error discrimination is performed on the smoothed first complex signal to obtain the second frequency offset estimate; The target satellite signal is compensated for a second frequency offset based on the second frequency offset estimate.

5. The carrier synchronization method for a continuous phase modulated signal according to claim 4, characterized in that, The phase offset compensation for the target satellite signal after the second frequency offset compensation includes: The target satellite signal after the second frequency offset compensation is orthogonally decomposed to obtain the in-phase branch signal and the quadrature branch signal; For any in-phase branch signal, the in-phase branch signal and its preceding and following branches are considered as l w The average value of the in-phase branch signals of each symbol is used as the in-phase branch signal; w It is a positive integer greater than 2; For any orthogonal branch signal, the orthogonal branch signal and its preceding and following branches are combined into a single line. w The average of the quadrature branch signals of each symbol is used as the quadrature branch signal; the in-phase branch signal and the quadrature branch signal constitute the second complex signal; Phase error identification is performed on the smoothed second complex signal to obtain the phase offset estimate; Phase offset compensation is performed on the target satellite signal based on the phase offset estimate.

6. The carrier synchronization method for a continuous phase modulated signal according to claim 5, characterized in that, The target satellite signal is a continuous phase-modulated signal that has undergone spread spectrum processing; The orthogonal decomposition of the linearized target satellite signal to obtain in-phase and orthogonal branch signals includes: Despreading is performed on the linearized target satellite signal; The target satellite signal after despreading is orthogonally decomposed to obtain in-phase branch signal and orthogonal branch signal; The orthogonal decomposition of the target satellite signal after the second frequency offset compensation to obtain the in-phase branch signal and the orthogonal branch signal includes: Despreading is performed on the target satellite signal after the second frequency offset compensation. The target satellite signal after despreading is orthogonally decomposed to obtain in-phase branch signal and orthogonal branch signal.

7. The carrier synchronization method for a continuous phase modulation signal according to claim 6, characterized in that, After performing frequency error identification on the smoothed first complex signal to obtain a second frequency offset estimate, and before performing a second frequency offset compensation on the target satellite signal based on the second frequency offset estimate, the carrier synchronization method for the continuous phase modulation signal further includes: Interpolation compensation is performed on the symbol-level second frequency offset estimate sequence to obtain the chip-level second frequency offset estimate sequence; the second frequency offset estimate sequence includes multiple second spectrum estimates.

8. A carrier synchronization device for a continuous phase modulation signal, characterized in that, include: The acquisition module is used to perform spectral analysis on the time-domain correlation values ​​of the target satellite signal and its local reference sequence to determine the first frequency offset estimate of the target satellite signal; wherein, the target satellite signal is a continuous phase modulation signal; The first compensation module is used to perform the first frequency offset compensation on the target satellite signal based on the first frequency offset estimate. The linearization module is used to linearize the target satellite signal after the first frequency offset compensation. The second compensation module is used to perform a second frequency offset compensation on the target satellite signal that has undergone linearization processing. The third compensation module is used to perform phase offset compensation on the target satellite signal that has undergone the second frequency offset compensation. The linearization process for the target satellite signal after the first frequency offset compensation includes: The target satellite signal after the first frequency offset compensation is decomposed into a linear superposition of multiple pulse amplitude modulation components, and the main pulse amplitude modulation component with the largest energy proportion is selected as the target satellite signal. The target satellite signal is subjected to phase despinning to remove the inherent nonlinear phase of the continuous phase modulation signal and obtain an equivalent linear modulation signal.

9. A carrier synchronization device for a continuous phase modulation signal, characterized in that, include: Memory, used to store computer programs; A processor, configured to implement the steps of the carrier synchronization method for a continuous phase modulated signal as described in any one of claims 1-7 when executing the computer program.

Images