Satellite MCSK signal capturing method and related device

Abstract

The invention discloses a satellite MCSK signal capturing method and a related device, and belongs to the technical field of satellite navigation. Firstly, an improved parallel code phase search algorithm provided by the invention is used for carrying out coarse search on an MCSK signal; wherein in the local code generation process, phase rotation is carried out on a data component local code to generate local codes of various data component code phases, so that a Doppler frequency shift coarse estimation value and a main code phase are calculated; second-level code phase search and Doppler frequency shift fine estimation are realized by using a PMF-FFT search method of double-layer matched filtering, and a dynamic search factor is introduced into signal search in a further embodiment, so that the problem of related peak attenuation in a high-dynamic Doppler scene is effectively solved. Further, the embodiment also provides a signal capture state judgment mechanism based on multi-search round capture results, and by comparing and screening the multi-moment capture results, the accuracy and stability of the algorithm on signal capture in a low-orbit and high-dynamic scene are enhanced, and the misjudgment probability is effectively reduced.

Description

Technical Field

[0001] The present invention belongs to satellite navigation technology, and in particular relates to a satellite MCSK signal capture method and related devices. Background Art

[0002] With the rapid development of global navigation satellite systems (GNSS) and low-orbit satellite communication technologies, signal systems based on multi-carrier modulation have become an important development direction for future high-dynamic, high-precision positioning scenarios. Multiplexed Code Shift Keying (MCSK), a composite modulation technique that integrates carrier phase and code domain states, demonstrates broad application prospects in integrated satellite-ground communication and navigation systems due to its spectral efficiency and anti-interference capabilities.

[0003] MCSK is a hybrid signal modulation scheme with high information transmission rates. It multiplexes the ranging component, based on binary phase shift keying (BPSK), with the data component, based on code shift keying (CSK), in the time domain. This allows a single signal structure to carry both high-precision navigation information and high-speed data broadcast, unifying ranging and data transmission. This structure often includes hierarchical codes (such as a primary code and a secondary code) to enhance anti-interference and tracking performance.

[0004] Currently, the capture of MCSK signals primarily relies on a two-dimensional search method to achieve a coarse estimation and alignment of the carrier frequency and code phase. This often involves using a return-to-zero code (RZC) capture method, which pads the ranging component code with zeros. Only the ranging component code is correlated with the input intermediate frequency signal to obtain the capture result, ignoring the correlation of the data component. This results in low energy efficiency and reduced capture sensitivity. While a local code generation strategy based on the ranging component code and a cyclically shifted data component code (CSC) improves capture sensitivity, it requires multiple cyclic shifts and FFT calculations, exponentially increasing the amount of FFT computation required.

[0005] Second, existing acquisition methods focus solely on the two-dimensional parameters of primary code phase search and Doppler frequency shift estimation. However, in MCSK hierarchically modulated signals, secondary code symbol transitions cause severe attenuation of the correlation peak, significantly reducing acquisition sensitivity. Furthermore, due to their low orbital altitude and high speed, low-Earth orbit satellites exhibit large Doppler frequency offsets and their high-order rate of change. This causes the signal correlation peak to shift and broaden during the long coherent integration phase of traditional acquisition algorithms, severely reducing detection accuracy and acquisition efficiency. Summary of the Invention

[0006] Based on this, the present invention aims to propose a satellite MCSK signal capture method and related devices, which realizes the three-dimensional capture of Doppler frequency shift, primary code phase and secondary code phase in low-orbit and high-dynamic scenarios through an improved parallel code phase search algorithm and a double-layer matched filter.

[0007] In a first aspect, the present invention provides a satellite MCSK signal acquisition method, comprising:

[0008] Doppler shift rough estimation steps:

[0009] Perform a parallel code phase search on the baseband signal to calculate a rough estimate of the Doppler frequency shift and the main code phase. During the parallel code phase search, phase rotation is performed on the local code of the data component.

[0010] Doppler shift precise estimation steps:

[0011] The mixing frequency is determined based on the rough Doppler shift estimate. The baseband signal carrier is stripped based on the mixing frequency to obtain the intermediate frequency signal. The main code phase is used to align the code phase of the local main code and the intermediate frequency signal.

[0012] The local master code and the intermediate frequency signal are subjected to a first-level matched filtering to obtain a first-level short integration result;

[0013] Perform secondary matched filtering on the local secondary code and the primary short integration result to obtain the secondary short integration result;

[0014] The second-level short integration result is converted into the frequency domain to obtain the capture result, which is used to obtain the precise estimation value of Doppler frequency shift and the second-level code phase.

[0015] Furthermore, the above method also includes:

[0016] A dynamic search factor is constructed based on the correlation peak of the baseband signal. In a single search round, the above Doppler shift precise estimation steps are repeated based on the dynamic search factor to obtain several capture results.

[0017] The local master code is determined according to the dynamic search factor and the master code phase, and the mixing frequency is determined according to the dynamic search factor and the Doppler shift coarse estimation value.

[0018] Furthermore, the dynamic search factor is expressed as:

[0019] ,

[0020] in, represents the correlation peak of the baseband signal, Indicates rounding operation.

[0021] Furthermore, the above method also includes:

[0022] Performing continuous rounds of searches on the baseband signal based on the above-mentioned Doppler frequency shift precise estimation step to obtain capture results corresponding to each search round, each search round including a plurality of capture results;

[0023] The following round parameter calculation process is performed for each search round:

[0024] Calculating a round Doppler shift precise estimate value based on the Doppler shift precise estimate values ​​corresponding to each capture result in the same search round, and calculating a round secondary code phase based on the secondary code phase corresponding to each capture result in the same search round;

[0025] The signal acquisition state is determined based on the secondary code phase of each search round.

[0026] Furthermore, the round parameter calculation process specifically includes:

[0027] Each search round includes Capture results, represents the dynamic search factor of the j-th search round;

[0028] make The Doppler frequency shift precise estimation values ​​corresponding to the capture results form a first array, an element in the first array is determined as a first reference value, elements in the first array that meet a first screening condition are determined according to the first reference value to form a second array, and the secondary code phases corresponding to the elements in the second array form a third array;

[0029] Determine an element in the third array as a second reference value, and determine the number of elements in the third array that meet the second screening condition based on the second reference value, and record it as the effective number of the round-two code phase;

[0030] The average value of the elements of the second array is recorded as the precise estimation value of the round Doppler frequency shift, and the second reference value is recorded as the round secondary code phase.

[0031] Furthermore, the signal acquisition state is determined according to the secondary code phase of each search round:

[0032] The state indicator value is calculated according to the effective number of the round-two code phase of each search round. When the state indicator value meets the preset capture condition, it is considered that the signal capture is successful.

[0033] Furthermore, performing phase rotation on the local code data component during the parallel code phase search includes:

[0034] Performing fast Fourier transform on the local code of the data component to obtain a frequency domain representation of the data component;

[0035] The phase rotation factor is used to perform phase rotation on the frequency domain representation of the data component to generate a local code of the data component corresponding to each code phase.

[0036] Furthermore, the local master code and the intermediate frequency signal are subjected to a first-level matched filtering, and the first-level short integration results obtained include:

[0037] Perform matched filtering operations on the intermediate frequency signal and the local main code in P first-stage matched filters to obtain the first-stage short integration result. :

[0038]

[0039] in, represents the intermediate frequency signal, Indicates the local master code, , represents the length of the first stage matched filter, Indicates the number of sampling points;

[0040] The single secondary code cycle is obtained The result of a short integral operation is expressed as the following first-level short integral result matrix:

[0041] ,

[0042] in, Represents the secondary code period, , Indicates the signal processing period of the first-stage matched filter.

[0043] Furthermore, the local secondary code and the primary short integration result are subjected to secondary matched filtering, and the secondary short integration result obtained includes:

[0044] Perform the following accumulation operation on the first-level short integral result matrix to obtain the accumulation matrix :

[0045] ,

[0046] Among them, the matrix The elements of the matrix The accumulated values ​​of the K adjacent elements of each element in , is the P / K order unit matrix, represents the Kronecker product, represents a K-dimensional all-one row vector;

[0047] The first-level short integration result matrix and the local second-level code are subjected to matched filtering operation in P / K second-level matched filters to obtain the following second-level short integration results: :

[0048] ,

[0049] in, Represents the local secondary code matrix, Z satisfies and , Represents Hadamard product, vec represents vectorized operation, .

[0050] In a second aspect, the present invention provides a satellite MCSK signal receiving device, comprising a memory storing computer-executable instructions and a processor. When the computer-executable instructions are executed by the processor, the device executes the various steps of the satellite MCSK signal acquisition method provided in the first aspect.

[0051] In a third aspect, the present invention provides a readable storage medium storing a computer executable program, which, when executed, can implement the various steps of the satellite MCSK signal acquisition method provided in the first aspect.

[0052] Compared with the existing signal acquisition technology, the present invention has the following beneficial effects:

[0053] The present invention proposes a satellite MCSK signal acquisition method. The method first uses the improved parallel code phase search algorithm proposed in the present invention to perform a coarse search on the MCSK signal, performs phase rotation on the local code of the data component, and generates local codes with multiple data component code phases. This replaces the traditional time-domain cyclic shift, significantly improving the energy utilization and acquisition sensitivity of the data component, while greatly reducing the FFT calculation amount and computational complexity in the acquisition algorithm, thereby calculating a coarse estimate of the Doppler shift and the main code phase. A two-layer PMF-FFT search method is then used to implement secondary code phase search and precise Doppler shift estimation. A further embodiment introduces a dynamic search factor into the signal search, effectively solving the problem of correlation peak attenuation in high-dynamic Doppler scenarios and significantly improving the accuracy of secondary code phase estimation and Doppler estimation precision. A further embodiment also proposes a signal acquisition status judgment mechanism based on the acquisition results of multiple search rounds. By comparing and screening the acquisition results at multiple times, the algorithm enhances the accuracy and stability of signal acquisition in low-orbit and high-dynamic scenarios, effectively reducing the probability of misjudgment. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0055] Figure 1 This is a flow chart of a method for capturing satellite MCSK signals according to an embodiment of the present invention;

[0056] Figure 2 It is a schematic diagram of the implementation of the parallel code phase search algorithm in the prior art;

[0057] Figure 3 1 is a schematic diagram of an improved parallel code phase search algorithm according to an embodiment of the present invention;

[0058] Figure 4 It is a schematic diagram of the PMF-FFT algorithm implementation in the prior art;

[0059] Figure 5 Schematic diagram of an improved PMF-FFT algorithm implementation provided by an embodiment of the present invention;

[0060] Figure 6 This is a diagram illustrating an implementation architecture of a satellite MCSK signal acquisition method provided by another embodiment of the present invention;

[0061] Figure 7 1 is a schematic diagram of intermediate frequency signal classification provided by an embodiment of the present invention;

[0062] Figure 8 is a data component bit-padded return-to-zero code sequence illustrated in an embodiment of the present invention;

[0063] Figure 9 The performance indicators of the improved parallel code phase search algorithm proposed in the present invention compared with the CSC strategy in the prior art in generating local codes for data components include the local code utilization reduction ratio, the FFT calculation reduction ratio, and the theoretical power loss value.

[0064] Figure 10 This is a diagram of the architecture of a satellite MCSK signal receiving device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0065] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0066] GNSS refers to a satellite navigation system consisting of a constellation of satellites, ground control stations, and user receiving devices. It provides positioning, navigation, and timing services to users worldwide. Common GNSS systems include the US's GPS, China's BeiDou (BDS), Europe's Galileo, and Russia's GLONASS.

[0067] The Low Earth Orbit (LEO) enhanced GNSS (LeGNSS) system is a new navigation augmentation system that uses Low Earth Orbit (LEO) satellites as augmentation sources within the GNSS system. Due to their low orbital altitude and rapid motion relative to the ground, LEO satellites offer advantages such as low signal transmission latency, rapid changes in visible geometry, and high signal power. These satellites can work in conjunction with traditional GNSS satellites to improve positioning accuracy, shorten convergence time, and enhance system robustness.

[0068] Compared with medium- and high-orbit satellites in GNSS, low-orbit satellites have the advantages of short latency and low power consumption due to their lower orbital altitude and faster operating speed. Low-orbit satellite signals can be used as an enhanced source of navigation signals to broadcast high-precision ranging signals, and the rapid change of the signal to the geometric structure of the observation station can effectively shorten the convergence time of precise single-point positioning, thereby performing joint positioning with GNSS and providing users with more efficient positioning services.

[0069] The following embodiments of the present invention will focus on providing a method for capturing multi-channel composite code shift keying (MCSK) hierarchical code modulation signals in LeGNSS. This method estimates the Doppler frequency, primary code phase, and secondary code phase in low-orbit, high-dynamic scenarios, significantly improving the accuracy and stability of LeGNSS-MCSK signal capture. This method lays a good foundation for extending the coherent integration time of the tracking loop of low-orbit communication and navigation receivers, enhancing signal tracking performance and the overall navigation accuracy of the system.

[0070] General satellite navigation signal acquisition is essentially a maximum likelihood estimation process. The receiver generates a local carrier and a local pseudo-code to achieve Doppler frequency shift estimation and pseudo-code phase alignment. The acquisition method proposed in this paper improves two fast Fourier transform (FFT)-based acquisition algorithms and combines the two algorithms to achieve three-dimensional search of Doppler frequency shift, primary code phase, and secondary code phase.

[0071] See Figure 1 One embodiment of the present invention provides a method for acquiring a satellite MCSK signal, comprising the following steps:

[0072] Doppler shift rough estimation steps:

[0073] Step S110: Perform a parallel code phase search on the baseband signal to calculate a rough Doppler shift estimate and a main code phase. During the parallel code phase search, phase rotation is performed on the local code of the data component.

[0074] This step improves the conventional parallel code phase search algorithm (PCS). By utilizing the property that FFT frequency-domain phase rotation is equivalent to time-domain cyclic shift, the local code data components generated by the local code generator are phase rotated by the phase rotation factor to generate local code data components corresponding to each code phase.

[0075] Specifically, if Figure 2 As shown in the figure, the conventional PCS algorithm uses the property that FFT time-domain correlation is equivalent to frequency-domain multiplication. It performs an FFT on the received signal after stripping the carrier to obtain a frequency-domain transformed signal. After the local code is FFT-transformed, the complex conjugate is taken to obtain the conjugate value. The frequency-domain transformed signal and the conjugate value are fed into a multiplier for multiplication. The multiplication result is subjected to an inverse FFT (IFFT), and the modulus of the output value is the correlation value between the received signal and the local code.

[0076] This step improves the PCS algorithm (PRC-PCS) as follows Figure 3 As shown in the figure, based on the FFT frequency-domain phase rotation property, the local codes of the data components are subjected to an FFT and then the phase rotation factors are used to generate the local codes corresponding to the code phases. The remaining operations are similar to those of the conventional PCS algorithm and are not further described here. Finally, the coherent result obtained by the IFFT is modulo-ed, and a coarse estimate of the main code phase and Doppler shift is obtained through coherent integration and non-coherent accumulation.

[0077] Furthermore, the Doppler shift estimate is obtained through coherent integration and incoherent accumulation. , the following relationship is used to further calculate the rough estimate of Doppler frequency shift :

[0078]

[0079] in, Indicates the receiver intermediate frequency, Indicates the maximum search range of Doppler frequency shift, Indicates the search step size for Doppler shift.

[0080] Doppler shift precise estimation steps:

[0081] Step S120: Determine the mixing frequency according to the rough estimation value of the Doppler frequency shift, strip the baseband signal carrier based on the mixing frequency to obtain an intermediate frequency signal, and align the code phase of the local main code and the intermediate frequency signal using the main code phase.

[0082] Step S130: Perform first-level matched filtering on the local master code and the intermediate frequency signal to obtain a first-level short integration result.

[0083] Step S140: Perform secondary matched filtering on the local secondary code and the primary short integration result to obtain a secondary short integration result.

[0084] Step S150: Convert the secondary short integration result into the frequency domain to obtain a capture result, which is used to obtain a precise estimation value of the Doppler frequency shift and the secondary code phase.

[0085] The embodiment of the present invention improves the conventional PMF-FFT search algorithm, proposes a double-layer matched filter, and utilizes the double-layer matched filter short integration and FFT to achieve secondary code phase search and precise estimation of Doppler frequency shift.

[0086] The PMF-FFT search algorithm is a signal capture technique that combines partial matched filtering (PMF) and fast Fourier transform (FFT), and is widely used in high dynamic environments. Figure 4 As shown in the figure, the conventional PMF-FFT algorithm uses matched filters to achieve parallel fast acquisition in the frequency domain. After carrier stripping and downsampling, the baseband signal enters the matched filter, where it is correlated with the segmented local code. Code phase alignment is achieved through sliding matching. The correlator contains P matched filters, each of length S. The original L points of long data are converted into P segments of short data, i.e., P = L / S. An FFT is performed on the P correlation values, and the modulo of the FFT result is used to calculate the maximum value as the current code phase.

[0087] like Figure 5 As shown, the Doppler shift precise estimation step proposed by the present invention utilizes the main code phase to align the baseband signal and the local main code, and sets the local mixer frequency to the Doppler shift coarse estimation value obtained in the aforementioned step. The intermediate frequency signal and the local main code are re-correlated in a first-stage matched filter to obtain P first-stage short integration results; the first-stage short integration results corresponding to all second-stage code periods are combined into a first-stage short integration result matrix, and the elements of each row and K adjacent columns in the matrix are accumulated to obtain a K-fold short integration accumulation matrix. The accumulation matrix and the local second-stage code are used as inputs of the second-stage matched filter to perform correlation operations to obtain the second-stage short integration results. Finally, the frequency domain parallel precise search is implemented through FFT to obtain the capture result. The Doppler shift precise estimation value and the second-stage code phase can be calculated based on the capture result.

[0088] Furthermore, in order to improve the accuracy of the Doppler frequency shift and secondary code phase estimation in the precise estimation step, a dynamic search factor is constructed according to the correlation peak of the baseband signal. During the signal search, a dynamic search is performed when the correlation peak of the signal capture meets the preset conditions. Otherwise, no dynamic search is required. Ultimately, each round of search obtains several capture results and their corresponding precise Doppler frequency shift estimation values ​​and secondary code phase.

[0089] Furthermore, considering that in high-dynamic scenarios, the longer the coherent integration time of a general capture algorithm is, the greater the code chip offset caused by Doppler, which will lead to correlation peak offset and attenuation. Therefore, the capture coherent integration time in low-orbit satellite high-dynamic scenarios should not be too long. In order to further improve the detection performance and capture probability, a further embodiment of the present invention also proposes a multi-round search joint judgment mechanism. By searching the signal at multiple consecutive moments, comparing the Doppler and secondary code phase of the multi-round search capture results, and combining the joint judgment mechanism of the capture results at multiple consecutive moments, the algorithm is enhanced in signal capture accuracy and stability in low-orbit high-dynamic scenarios by comparing and screening the capture results at multiple moments.

[0090] Specifically, the joint judgment mechanism includes:

[0091] Performing continuous rounds of searching on the baseband signal based on the precise estimation step to obtain capture results corresponding to each search round, each search round including a plurality of capture results;

[0092] The following round parameter calculation process is performed for each search round:

[0093] Calculating a round Doppler shift precise estimate value based on the Doppler shift precise estimate values ​​corresponding to each capture result in the same search round, and calculating a round secondary code phase based on the secondary code phase corresponding to each capture result in the same search round;

[0094] The signal acquisition state is determined based on the secondary code phase of each search round.

[0095] In order to further illustrate the signal capture method proposed by the present invention, a specific embodiment is provided below.

[0096] See Figure 6 , which illustrates a satellite MCSK signal capture method proposed in one embodiment of the present invention, including coarse estimation based on an improved parallel code phase search algorithm and fine estimation based on a two-layer matched filter using PMF-FFT. Finally, through a multi-round search and joint judgment mechanism, a three-dimensional search of Doppler frequency shift, primary code phase, and secondary code phase is achieved, thereby improving the capture accuracy of low-orbit satellite MCSK signals in high-dynamic scenarios.

[0097] Specifically, the captured MCSK signal is in the unit integration period The signal includes the ranging component and the data component period, so the signal is divided into the data component truncation event (DT) and the ranging component truncation event (RT) according to the starting pointer position, such as Figure 7 shown.

[0098] In this embodiment, the signal input for modulation capture has passed the sliding window energy detection, and the rough main code phase is obtained using the energy characteristics, and the data reading pointer is adjusted to ensure that the signal data is of RT type within the unit integration period.

[0099] Doppler shift rough estimation steps:

[0100] See the aforementioned Figure 3 , input signal The carrier NCO performs carrier stripping to obtain the intermediate frequency signal. The signal after the intermediate frequency signal is multiplied by the local carrier is defined as:

[0101]

[0102] in is the Doppler shift to be estimated.

[0103] Define the local code of the ranging component as , the local code of the data component is , in the time domain, cyclic shift generates M phases of data component local code, signal With local code The time domain cyclic correlation can be expressed as follows:

[0104]

[0105]

[0106] in, represents the coherence value, and N represents the number of data points.

[0107] Based on the property of FFT frequency domain phase rotation, the local code of the data component is FFTed and the phase rotation factor is used. Generate local codes with M code phases, perform correlation operations in the frequency domain, and obtain the following correlation results through IFFT:

[0108]

[0109]

[0110] in is the local RZC sequence of the ranging component, is the local return-to-zero code sequence of the data component, Defined as the data component with a code period length, the local code is supplemented by the last bit. chips, and the rest is padded with zeros to form a data component local code with a length of two code periods, such as Figure 8 shown.

[0111] The MCSK signal is usually recorded as , where U represents the number of bits mapped to each CSK code phase of the data component, and the U bit information can be mapped to CSK symbols, B represents the number of code periods in the time division symbol period, Indicates the number of code periods occupied by the ranging component in each time division symbol period, MCSK modulation uses time-division multiplexing technology to combine the ranging component of BPSK modulation and the data component of CSK modulation. The ranging component and the data component each have a corresponding pseudo-random noise (PRN) generator. In the data component branch, the code sequence of each cycle uses different initial phases of the basic PRN code to represent different precision telegram information symbols.

[0112] Taking MCSK (U, 2, 1) as an example, if the code length of the ranging component and the data component is both 2046 (chips), when U takes different values, the local code generation strategy based on phase rotation (PRC) proposed in this invention is compared with the local code generation strategy based on cyclic shift data component code (CSC). The changes in the local code utilization reduction ratio, FFT calculation reduction ratio and power loss theoretical value of the generated data component local code are as follows: Figure 9 shown.

[0113] according to Figure 9 It can be seen that when the number of data component code phase mapping bits U≤8, the reduction in local code utilization of PRC data components compared to CSC is less than 6.24%, and the energy loss does not exceed 0.28dB. When the number of data component code phase mapping bits U≥4, the reduction in FFT calculation amount of PRC compared to CSC is greater than 87.5%. Therefore, when the value of U is between 4-8, the local code adopts the PRC strategy proposed in the embodiment of the present invention. It can greatly improve the algorithm calculation efficiency while discarding a small amount of local code correlation, and the energy loss is very small compared to the CSC strategy.

[0114] The Doppler band estimation result obtained by coherent integration and incoherent accumulation of the above correlation results is And the main code phase estimation result .

[0115] Coarse Doppler shift estimate and The relationship is as follows:

[0116]

[0117] Among them, in the receiver is the intermediate frequency, is the maximum search range of Doppler frequency shift, is the Doppler shift search step size.

[0118] Furthermore, the main code phase normalized estimation result is defined as is the main code phase when the search step is 0.1 chip, And the main code phase estimation result The relationship is as follows:

[0119]

[0120] Among them, f s Indicates the signal sampling rate; Indicates the PRN code length of the ranging component and the data component. The default value is 2046 (chip).

[0121] Doppler shift precise estimation steps:

[0122] See the aforementioned Figure 5 , using the main code phase Align the input signal with the local master code, The frequency of the local mixer is used to strip off the carrier to obtain the intermediate frequency signal.

[0123] The first stage matched filter short integration processing signal period is , the baseband signal is downsampled to After the point, the first-stage matched filter is input, and the local main code is upsampled to point L through interpolation, where it represents the PRN code rate (the default value is 2.046Mcps). When the number of matched filters is P, the length of each matched filter is S=L / P, corresponding to 2T c / P ms data, intermediate frequency signal and local master code Respectively expressed as:

[0124]

[0125]

[0126]

[0127]

[0128] in, After the correlation operation between the intermediate frequency signal and the local master code in the first stage matched filter, P short integration results can be obtained, which are expressed as follows:

[0129]

[0130] A secondary code period T sc Can get Short integral results, the following short integral result matrix is ​​obtained :

[0131]

[0132] Suppose the K adjacent short integration results of each element of the above matrix are accumulated to obtain (T sc / 2T c )×(P / K) short integral accumulation values ​​are input into the second-stage matched filter, that is, the number of second-stage matched filters is P / K, and each second-stage matched filter corresponds to 2T c K / P ms data.

[0133] matrix The elements of the adjacent K columns of each row are accumulated to obtain the K times short integral accumulation matrix :

[0134]

[0135] in, is the P / K order unit matrix, represents the Kronecker product, represents a K-dimensional all-one row vector.

[0136] Construct a local secondary code matrix containing Z phases , where Z must satisfy and .Will After correlation operation with the local secondary code, P / K secondary short integration results can be obtained. Finally, the frequency domain parallel fine search is realized through FFT, and the capture result is obtained. :

[0137]

[0138] in, Represents Hadamard product, vec represents vectorized operation, .

[0139] according to The maximum correlation peak V1, secondary correlation peak V2, and Doppler frequency shift estimation value can be obtained. and secondary code phase .

[0140] In order to improve the accuracy of signal Doppler frequency shift and secondary code phase estimation, the dynamic search factor parameter is defined , capturing the correlation peak hour ,and High reliability of real-time detection without the need for dynamic search:

[0141]

[0142]

[0143] The carrier Doppler frequency and main code phase of the dynamic search input are:

[0144]

[0145]

[0146] Will As the local master code starting index, As the frequency stripping carrier of the local mixer, repeat the above precise estimation steps and finally get Capture results and its corresponding Doppler frequency shift precise estimate and secondary code phase.

[0147] In the multi-round search joint judgment mechanism, the signal is searched in successive rounds to obtain capture results corresponding to each search round, and each search round includes several capture results;

[0148] The following round parameter calculation process is performed for each search round:

[0149] Calculating a round Doppler shift precise estimate value based on the Doppler shift precise estimate values ​​corresponding to each capture result in the same search round, and calculating a round secondary code phase based on the secondary code phase corresponding to each capture result in the same search round;

[0150] The signal acquisition state is determined based on the secondary code phase of each search round.

[0151] The aforementioned round parameter calculation process specifically includes:

[0152] Each search round includes Capture results, represents the dynamic search factor of the j-th search round;

[0153] make The Doppler frequency shift precise estimation values ​​corresponding to the capture results form a first array, an element in the first array is determined as a first reference value, elements in the first array that meet a first screening condition are determined according to the first reference value to form a second array, and the secondary code phases corresponding to the elements in the second array form a third array;

[0154] Determine an element in the third array as a second reference value, and determine the number of elements in the third array that meet the second screening condition based on the second reference value, and record it as the effective number of the round-two code phase;

[0155] The average value of the elements of the second array is recorded as the precise estimation value of the round Doppler frequency shift, and the second reference value is recorded as the round secondary code phase.

[0156] Furthermore, the process of determining the signal capture state includes:

[0157] The state indicator value is calculated according to the effective number of the round-two code phase of each search round. When the state indicator value meets the preset capture condition, it is considered that the signal capture is successful.

[0158] The specific multi-round search joint judgment mechanism is as follows: Figure 9 As shown, the same signal data is captured and searched for J rounds, and the starting time of each round of search data is , each round of search includes correlation peaks, precise Doppler shift estimates, and secondary code phase.

[0159] After each accurate estimation step is completed, The correlation peaks are sorted from large to small to form an array , corresponding to Doppler frequency shift precise estimation values ​​form an array .

[0160] The array The first value in As a reference value, filter out the array Medium and reference value The absolute error is less than The elements of the array , The corresponding secondary code phases form an array , remember the array The average value of each element As the final Doppler frequency shift estimate of this search round.

[0161] Array The most repeated element in As a reference value, select the array Zhongyu For elements with a difference less than 2, record the number of elements that meet the conditions , As the final secondary code phase of this round.

[0162] Finally, the number of valid elements of the secondary code phase of each round is summed up, that is, , if satisfied , the capture is considered successful.

[0163] The device provided in the embodiment of the present application has the same implementation principle and technical effects as those in the aforementioned method embodiment. For the sake of brief description, for matters not mentioned in the device embodiment, reference can be made to the corresponding content in the aforementioned method embodiment.

[0164] The methods and related devices mentioned in the above embodiments are described with reference to the method flow charts and / or structural diagrams provided in the embodiments of the present application. Specifically, each process and / or block in the method flow charts and / or structural diagrams, as well as the combination of processes and / or blocks in the flow charts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the steps in the process. Figure 1 Schematic diagram of one or more processes and / or structures Figure 1 These computer program instructions can also be stored in a computer-readable memory that can guide a computer or other programmable data processing device to work in a specific way, so that the instructions stored in the computer-readable memory produce a product including the instruction device, which implements the function specified in the process. Figure 1 Schematic diagram of one or more processes and / or structures Figure 1 These computer program instructions can also be loaded onto a computer or other programmable data processing device, so that a series of operation steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process in the process. Figure 1 The flow or flows and / or structures illustrate the steps of the functions specified in one block or multiple blocks.

[0165] The following embodiments illustrate this method using a computer device as an example. It is understood that the computer device may be any device with computing and processing capabilities, including, but not limited to, a server or a personal laptop. In one embodiment, the computer device may be an application server, which may be a server for running the application under test.

[0166] See Figure 10 , which shows a hardware block diagram of a satellite MCSK signal receiving device. The electronic device is intended to represent various forms of digital computers, such as laptop computers, desktop computers, workstations, personal digital assistants, servers, blade servers, mainframe computers, and other suitable computers. The electronic device can also represent various forms of mobile devices, such as personal digital assistants, cellular phones, smart phones, wearable devices, and other similar computing devices. The components shown herein, their connections and relationships, and their functions are merely examples and are not intended to limit the implementation of the present application described and / or claimed herein.

[0167] like Figure 10As shown, the satellite MCSK signal receiving device includes: at least one processor 1, at least one communication interface 2, at least one memory 3 and at least one communication bus 4;

[0168] In the embodiment of the present application, the number of the processor 1, the communication interface 2, the memory 3, and the communication bus 4 is at least one, and the processor 1, the communication interface 2, and the memory 3 communicate with each other through the communication bus 4;

[0169] The processor 1 may be a central processing unit (CPU), or an application-specific integrated circuit (ASIC), or one or more integrated circuits configured to implement the embodiments of the present invention;

[0170] The memory 3 may include a high-speed RAM memory, and may also include a non-volatile memory (non-volatile memory), such as at least one disk memory;

[0171] The memory stores a program, and the processor can call the program stored in the memory, and the program is used to implement the aforementioned various processing flows.

[0172] An embodiment of the present invention further provides a readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the processing flow of the solution provided in the above embodiment and / or any possible implementation method in combination with the embodiment is implemented.

[0173] The above embodiments have described the invention in particular detail with respect to possible scenarios, and those skilled in the art will recognize that the invention can be practiced through other embodiments. The specific naming of components, capitalization of terms, attributes, data structures, or any other programming or structural aspects are not mandatory or important, and the mechanisms or features of the invention may have different names, forms, or procedures. The system may be implemented through a combination of hardware and software (as described), entirely through hardware elements, or entirely through software elements. The specific division of functions between the various system components described herein is exemplary only and not mandatory; rather, the functions performed by a single system component may be performed by multiple components, or the functions performed by multiple components may be performed by a single component.

[0174] Those skilled in the art will appreciate that the various steps of the method disclosed above can be implemented by a general-purpose computing device. They can be centralized on a single computing device or distributed across a network of multiple computing devices. Alternatively, they can be implemented using program code executable by a computing device, so that they can be stored in a storage device and executed by the computing device, or they can be fabricated into separate integrated circuit modules, or multiple modules or steps can be fabricated into a single integrated circuit module for implementation. Thus, the embodiments disclosed herein are not limited to any specific combination of hardware and software.

[0175] The programs executable by these computing devices (also referred to as programs, software, software applications, or code) include machine instructions for programmable processors and can be implemented using high-level procedural and / or object-oriented programming languages, and / or assembly / machine languages. As used herein, the terms "machine-readable medium" and "computer-readable medium" refer to any computer program product, apparatus, and / or device (e.g., a magnetic disk, an optical disk, a memory, a programmable logic device (PLD)) for providing machine instructions and / or data to a programmable processor, including a machine-readable medium that receives machine instructions as a machine-readable signal. The term "machine-readable signal" refers to any signal for providing machine instructions and / or data to a programmable processor.

[0176] Certain aspects of the present invention include the process steps and instructions described herein in the form of algorithms. It should be noted that the process steps and instructions of the present invention can be implemented in software, firmware and / or hardware, and when implemented in software, they can be downloaded, stored on different platforms used by various operating systems, and operated from the platforms.

[0177] Those skilled in the art will understand that the structures shown in the accompanying drawings are merely block diagrams of partial structures related to the scheme of the present application, and do not constitute a limitation on the terminal device to which the scheme of the present application is applied. The specific terminal device may include more or fewer components than shown in the figure, or combine certain components, or have a different arrangement of components.

[0178] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "possible design" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine different embodiments or examples described in this specification and features of different embodiments or examples, unless they are mutually inconsistent.

[0179] Finally, it should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article, or device comprising the element.

[0180] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments can still be modified, or some of the technical features thereof can be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A satellite MCSK signal acquisition method, characterized in that: include: Doppler shift rough estimation steps: Performing a parallel code phase search on the baseband signal to calculate a rough Doppler shift estimate and a main code phase, wherein the local code of the data component is phase rotated during the parallel code phase search; Doppler shift precise estimation steps: determining a mixing frequency according to the coarse Doppler shift estimate, stripping a baseband signal carrier based on the mixing frequency to obtain an intermediate frequency signal, and performing code phase alignment on a local master code and the intermediate frequency signal using the master code phase; The local master code and the intermediate frequency signal are subjected to a first-level matched filtering to obtain a first-level short integration result; Performing secondary matched filtering on the local secondary code and the primary short integration result to obtain a secondary short integration result; The secondary short integration result is converted into a frequency domain to obtain a capture result, and the capture result is used to obtain a Doppler frequency shift precise estimation value and a secondary code phase.

2. The method according to claim 1, characterized in that The method further comprises: Constructing a dynamic search factor according to a correlation peak value of the baseband signal, and repeating the Doppler shift precise estimation step according to the dynamic search factor in a single search round to obtain a plurality of capture results; The local master code is determined according to a dynamic search factor and a master code phase, and the mixing frequency is determined according to the dynamic search factor and a coarse estimation value of Doppler frequency shift.

3. The method according to claim 1, characterized in that The method further comprises: Performing continuous rounds of searches on the baseband signal based on the Doppler shift precise estimation step to obtain capture results corresponding to each search round, each search round including a plurality of capture results; The following round parameter calculation process is performed for each search round: Calculating a round Doppler shift precise estimate value based on the Doppler shift precise estimate values ​​corresponding to each capture result in the same search round, and calculating a round secondary code phase based on the secondary code phase corresponding to each capture result in the same search round; The signal acquisition state is determined based on the secondary code phase of each search round.

4. The method according to claim 3, characterized in that The round parameter calculation process specifically includes: Each search round includes Capture results, represents the dynamic search factor of the j-th search round; make The Doppler shift precise estimation values ​​corresponding to the capture results form a first array, an element in the first array is determined as a first reference value, elements in the first array that meet a first screening condition are determined according to the first reference value to form a second array, and the secondary code phases corresponding to the elements in the second array form a third array; Determining an element in the third array as a second reference value, and determining the number of elements in the third array that meet a second screening condition based on the second reference value, and recording the number as a round-two code phase valid number; The average value of the elements of the second array is recorded as the round Doppler frequency shift precise estimation value, and the second reference value is recorded as the round secondary code phase.

5. The method according to claim 4, characterized in that Determining the signal acquisition state based on the secondary code phase of each search round includes: A state indicator value is calculated according to the effective number of the round-two code phases of each search round. When the state indicator value satisfies a preset capture condition, it is considered that the signal capture is successful.

6. The method according to claim 1, characterized in that The phase rotation of the local code of the data component during the parallel code phase search includes: Performing a fast Fourier transform on the local code of the data component to obtain a frequency domain representation of the data component; The frequency domain representation of the data component is phase rotated using a phase rotation factor to generate a local code of the data component corresponding to each code phase.

7. The method according to claim 1, characterized in that The local master code and the intermediate frequency signal are subjected to a first-level matched filtering to obtain a first-level short integration result including: Perform matched filtering operations on the intermediate frequency signal and the local main code in P first-stage matched filters to obtain the first-stage short integration result. : in, represents the intermediate frequency signal, Indicates the local master code, , represents the length of the first stage matched filter, Indicates the number of sampling points; The single secondary code cycle is obtained The result of a short integral operation is expressed as the following first-level short integral result matrix: ， in, Represents the secondary code period, , Indicates the signal processing period of the first-stage matched filter.

8. The method according to claim 7, characterized in that The local secondary code and the primary short integration result are subjected to secondary matched filtering to obtain a secondary short integration result including: Perform accumulation operation on the first-level short integral result matrix to obtain the following accumulation matrix : ， Among them, the matrix The elements of the matrix The accumulated values ​​of the K adjacent elements of each element in , is the P / K order unit matrix, represents the Kronecker product, represents a K-dimensional all-one row vector; The first-level short integration result matrix and the local second-level code are subjected to matched filtering operation in P / K second-level matched filters to obtain the following second-level short integration result: : ， in, Represents the local secondary code matrix, Z satisfies and , Represents Hadamard product, vec represents vectorized operation, .

9. A satellite MCSK signal receiving device, characterized in that: The device comprises a memory storing computer-executable instructions and a processor, and when the computer-executable instructions are executed by the processor, the device executes the satellite MCSK signal acquisition method according to any one of claims 1 to 8.

10. A readable storage medium, characterized in that: A computer executable program is stored, and when the program is executed, the satellite MCSK signal acquisition method according to any one of claims 1 to 8 can be implemented.

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