Satellite mcsk signal acquisition method and related apparatus

Abstract

The application discloses a satellite MCSK signal acquisition method and a related device, and belongs to the technical field of satellite navigation. The improved parallel code phase search algorithm is used to perform coarse search on the MCSK signal. In the local code generation process, the data component local code is phase-rotated to generate the local code of various data component code phases, so that the coarse estimation value of the Doppler frequency shift and the main code phase are calculated. Then, the PMF-FFT search method of double-layer matching filtering is used to realize the secondary code phase search and the fine estimation of the Doppler frequency shift. Further, a dynamic search factor is introduced into the signal search in the further embodiment, so that the problem of correlation peak attenuation in the high dynamic Doppler scene is effectively solved. The signal acquisition state judgment mechanism based on the acquisition results of multiple search rounds is further proposed in the further embodiment. Through comparison and screening of the acquisition results at multiple moments, the accuracy and stability of the algorithm for signal acquisition in the low-orbit high dynamic scene are enhanced, and the misjudgment probability is effectively reduced.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of satellite navigation, and particularly relates to a satellite MCSK signal acquisition method and a related device. BACKGROUND

[0002] With the rapid development of global navigation satellite system (GNSS) and low-orbit satellite communication technology, signal systems based on multi-carrier modulation mode have become an important development direction for future high-dynamic and high-precision positioning scenarios. Among them, multiplexed code shift keying (MCSK) as a composite modulation technology that combines carrier phase and code domain state, has shown broad application prospects in integrated satellite-terrestrial communication and navigation systems due to its spectrum efficiency and anti-interference ability.

[0003] MCSK is a hybrid signal modulation scheme with high information transmission rate, which multiplexes ranging components based on binary phase shift keying (BPSK) modulation and data components based on code shift keying (CSK) modulation in the time domain, simultaneously carrying high-precision navigation information and high-speed data broadcast in one signal structure, and realizing the unification of ranging and data transmission. Its structure often also includes hierarchical codes (such as primary codes and secondary codes) to enhance anti-interference and tracking performance.

[0004] For MCSK signal acquisition, the current two-dimensional search method is mainly used to complete the coarse estimation and alignment of carrier frequency and code phase, and the zero-return code (RZC) acquisition is often used, i.e. the ranging component code is zero-padded, only the ranging component code is used for correlation operation with the input intermediate frequency signal to obtain the acquisition result, and the data component correlation is ignored. Low energy utilization leads to reduced acquisition sensitivity. When the local code generation strategy based on the ranging component code and the cyclic shift data component code (CSC) is used, although the acquisition sensitivity is improved, multiple cyclic shifts and FFT calculations are required, and the FFT calculation amount increases exponentially.

[0005] Secondly, the existing acquisition method only focuses on two-dimensional parameters of primary code phase search and Doppler frequency shift estimation, while in the MCSK hierarchical code modulation signal, the secondary code symbol jump causes serious attenuation of the correlation peak, resulting in a significant decrease in acquisition sensitivity. In addition, low-orbit satellites have a large Doppler frequency offset and high-order change rate due to low orbit height and high running speed, which causes the signal correlation peak to shift and widen in long-time coherent integration in traditional acquisition algorithms, seriously reducing detection accuracy and acquisition efficiency. SUMMARY

[0006] Based on this, the application aims to provide a satellite MCSK signal acquisition method and related device, through an improved parallel code phase search algorithm and double-layer matching filter, to realize three-dimensional acquisition of Doppler frequency shift, primary code phase and secondary code phase in a low-orbit high-dynamic scene.

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

[0008] A Doppler frequency shift coarse estimation step:

[0009] Parallel code phase search is performed on the baseband signal to obtain a Doppler frequency shift coarse estimation value and a primary code phase, and the data component local code is phase-rotated during the parallel code phase search;

[0010] A Doppler frequency shift fine estimation step:

[0011] A mixing frequency is determined according to the Doppler frequency shift coarse estimation value, a carrier is stripped from the baseband signal based on the mixing frequency to obtain an intermediate frequency signal, and the local primary code and the intermediate frequency signal are code phase-aligned using the primary code phase;

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

[0013] The local secondary code and the first-level short integration result are subjected to second-level matching filtering to obtain a second-level short integration result;

[0014] The second-level short integration result is converted in the frequency domain to obtain an acquisition result, and the acquisition result is used to obtain a Doppler frequency shift fine estimation value and a secondary code phase.

[0015] Further, the above method further comprises:

[0016] A dynamic search factor is constructed according to the correlation peak value of the baseband signal, and the above Doppler frequency shift fine estimation step is repeated according to the dynamic search factor in a single search round to obtain a plurality of acquisition results;

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

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

[0019] ,

[0020] Wherein, The correlation peak value of the baseband signal is represented by, The rounding operation is represented by.

[0021] Further, the above method further comprises:

[0022] The baseband signal is searched in successive rounds based on the above Doppler shift fine estimation step, and acquisition results corresponding to each search round are obtained, each search round including a plurality of acquisition results;

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

[0024] A round Doppler shift fine estimation value is calculated according to the Doppler shift fine estimation values corresponding to the acquisition results in the same search round, and a round secondary code phase is calculated according to the secondary code phases corresponding to the acquisition results in the same search round.

[0025] The signal acquisition state is determined according to the secondary code phases of each search round.

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

[0027] Each search round includes an acquisition result, a dynamic search factor of the jthsearch round;

[0028] Let the Doppler shift fine estimation values corresponding to the acquisition results form a first array, a first reference value is determined in the first array, a second array is formed according to the first reference value, the elements in the second array satisfying the first screening condition, and the secondary code phases corresponding to the elements in the second array form a third array;

[0029] A element in the third array is determined as a second reference value, the number of elements in the third array satisfying the second screening condition is determined according to the second reference value, and is recorded as the round secondary code phase effective number;

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

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

[0032] The state indication value is calculated according to the round secondary code phase effective numbers of each search round, and the signal acquisition is considered successful when the state indication value meets the preset acquisition condition.

[0033] Further, the phase rotation of the local code data component during the parallel code phase search includes:

[0034] The data component local code is subjected to fast Fourier transform to obtain a data component frequency domain representation;

[0035] The data component frequency domain representation is subjected to phase rotation by using a phase rotation factor to generate the data component local code corresponding to each code phase.

[0036] Further, the local primary code and the intermediate frequency signal are subjected to one-stage matching filtering to obtain one-stage short integration results including:

[0037] The intermediate frequency signal and the local primary code are subjected to matching filtering operation in P first-stage matching filters to obtain one-stage short integration results :

[0038]

[0039] wherein, represents the intermediate frequency signal, represents the local primary code, , represents the length of the first-stage matching filter, represents the number of sampling points;

[0040] The one-stage short integration operation results obtained by a single two-stage code period are represented as the following one-stage short integration result matrix:

[0041] ,

[0042] wherein, represents the two-stage code period, , represents the signal period processed by the first-stage matching filter.

[0043] Further, the local two-stage code and the one-stage short integration results are subjected to two-stage matching filtering to obtain two-stage short integration results including:

[0044] The one-stage short integration result matrix is subjected to the following accumulation operation to obtain an accumulation matrix :

[0045] ,

[0046] wherein, the elements of the matrix represent the K adjacent element accumulation values of each element in the matrix , is a P / K-order unit matrix, represents Kronecker product, represents a K-dimensional all-1 row vector;

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

[0048] ,

[0049] wherein, represents the local two-stage code matrix, and Z satisfies​ and , denotes Hadamard product, vec denotes vectorization operation, .

[0050] In a second aspect, the present application 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 performs each step of the satellite MCSK signal acquisition method provided in the first aspect.

[0051] In a third aspect, the present application provides a readable storage medium, storing a computer executable program, when the program is executed, each step of the satellite MCSK signal acquisition method provided in the first aspect can be realized.

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

[0053] The present application provides a satellite MCSK signal acquisition method, first, the improved parallel code phase search algorithm is used to perform coarse search on the MCSK signal, the local code of the data component is rotated to generate a variety of data component code phase local codes, instead of the traditional time domain cyclic shift, which significantly improves the energy utilization rate and acquisition sensitivity of the data component, and greatly reduces the FFT calculation amount and calculation complexity in the acquisition algorithm, so as to calculate the coarse estimation value of the Doppler shift and the main code phase; Then, the double-layer PMF-FFT search method is used to realize the secondary code phase search and the fine estimation of the Doppler shift, and the further embodiment introduces a dynamic search factor into the signal search, which effectively solves the problem of correlation peak attenuation in the high dynamic Doppler scene, and significantly improves the secondary code phase estimation accuracy and the Doppler estimation precision; The further embodiment also proposes a signal acquisition state judgment mechanism based on the acquisition results of multiple search rounds, which compares and filters the acquisition results at multiple times, enhances the accuracy and stability of the algorithm in the low-orbit high-dynamic scene, and effectively reduces the false judgment probability. BRIEF DESCRIPTION OF DRAWINGS

[0054] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or prior art description. Obviously, the drawings in the following description are only embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of the provided drawings.

[0055] Figure 1 is a satellite MCSK signal acquisition method implementation flowchart provided by an embodiment of the present application;

[0056] Figure 2 is a schematic diagram of an existing parallel code phase search algorithm implementation;

[0057] Figure 3 is a schematic diagram of an improved parallel code phase search algorithm implementation provided by an embodiment of the present application;

[0058] Figure 4 is a schematic diagram of an existing PMF-FFT algorithm implementation;

[0059] Figure 5 is a schematic diagram of an improved PMF-FFT algorithm implementation provided by an embodiment of the present application;

[0060] Figure 6 is a schematic diagram of a satellite MCSK signal acquisition method implementation architecture provided by another embodiment of the present application;

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

[0062] Figure 8 is a data component complement bit zero padding code sequence as illustrated by an embodiment of the present application;

[0063] Figure 9 is a performance index change of an improved parallel code phase search algorithm provided by the present application compared with an existing technology CSC strategy in generating a local code of a data component, the performance index including a local code utilization reduction ratio, an FFT calculation amount reduction ratio and a power loss theoretical value;

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

[0065] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0066] GNSS refers to a satellite navigation system composed of a group of satellites, ground control stations and user receiving devices, which can provide positioning, navigation and timing services for global users. Common GNSS systems include GPS of the United States, BDS of China, Galileo of Europe, GLONASS of Russia, etc.

[0067] Low Earth Orbit (LEO) enhanced Global Navigation Satellite System (GNSS) is a new navigation enhancement system that introduces LEO satellites as enhancement sources into GNSS system. Due to low orbit height and fast relative ground motion, LEO satellites have the advantages of small signal transmission delay, fast visible geometry change and strong signal power, and can work with traditional GNSS satellites to improve positioning accuracy, shorten convergence time and enhance system robustness.

[0068] Compared with the medium-high orbit satellites in GNSS, LEO satellites have the advantages of short delay and low power consumption due to lower orbit height and faster running speed. LEO satellite signals can be broadcast as enhanced navigation signals to provide high-precision ranging signals, and the rapid change of signal geometry to the observation station can effectively shorten the convergence time of precise point positioning, thereby jointly positioning with GNSS to provide more efficient positioning services for users.

[0069] The following embodiments of the application will focus on providing a capture method for LeGNSS multi-path composite code shift keying (MCSK) hierarchical code modulation signals, which realizes the estimation of Doppler frequency, main code phase and secondary code phase in a low-orbit high-dynamic scene, significantly improves the accuracy and stability of LeGNSS-MCSK signal capture, prolongs the coherent integration time of the tracking loop of the low-orbit navigation receiver, and lays a good foundation for enhancing the tracking performance of the signal and the overall navigation accuracy of the system.

[0070] Generally, satellite navigation signal capture is essentially a maximum likelihood estimation process. The receiver realizes Doppler frequency shift estimation and pseudo-code phase alignment by generating a local carrier and a local pseudo-code. The capture method proposed in the application improves two kinds of capture algorithms based on fast Fourier transform (FFT) and realizes three-dimensional search of Doppler frequency shift, main code phase and secondary code phase by combining the two algorithms.

[0071] Referring to Figure 1 One embodiment of the application provides a satellite MCSK signal capture method, comprising the following steps:

[0072] Doppler frequency coarse estimation step:

[0073] Step S110. Parallel code phase search is performed on the baseband signal to calculate the Doppler frequency coarse estimation value and the main code phase. The data component local code is phase-rotated during the parallel code phase search.

[0074] The step improves the conventional parallel code phase search algorithm (PCS), and phase rotation factors are used to rotate the local code data components generated by a local code generator to generate local code data components corresponding to code phases.

[0075] Specifically, as shown in Figure 2 , the conventional PCS algorithm uses the property that FFT time domain correlation is equivalent to frequency domain multiplication to perform FFT transformation on the received signal after stripping the carrier, to obtain a frequency domain transformed signal; the local code is transformed by FFT to obtain a conjugate value, the frequency domain transformed signal and the conjugate value are sent to a multiplier for multiplication operation, and the IFFT is performed on the multiplication result, and the modulus of the output value is the correlation value of the received signal and the local code.

[0076] The improved algorithm (PRC-PCS) of the PCS algorithm is shown in Figure 3 , based on the property of FFT frequency domain phase rotation, the data component local code is transformed by FFT to generate local codes corresponding to each code phase through a phase rotation factor, and the remaining operation process is similar to the conventional PCS algorithm, which will not be described here. Finally, the coherent result obtained by IFFT is taken as a modulus, and the main code phase and the Doppler shift coarse estimation value are obtained by coherent integration and incoherent accumulation.

[0077] Further, the Doppler shift estimation value obtained by coherent integration and incoherent accumulation is used to further calculate the Doppler shift coarse estimation value :

[0078]

[0079] , wherein, represents the intermediate frequency frequency in the receiver, represents the maximum search range of the Doppler shift, represents the search step of the Doppler shift.

[0080] Doppler shift fine estimation step:

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

[0082] Step S130. Perform one-stage matched filtering on the local main code and the intermediate frequency signal to obtain one-stage short integration result.

[0083] Step S140. Perform two-stage matched filtering on the local two-stage code and the one-stage short integration result to obtain two-stage short integration result.

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

[0085] The embodiment of the present application improves the conventional PMF-FFT search algorithm, proposes a double-layer matching filter, and uses double-layer matching filter short integration and FFT to realize fine estimation of the secondary code phase and the Doppler frequency shift.

[0086] The PMF-FFT search algorithm is a signal capture technology combining partial matching filter (PMF) and fast Fourier transform (FFT), and is widely used in high dynamic environments. As shown in the figure, the conventional PMF-FFT algorithm uses a matching filter to realize frequency domain parallel fast capture. The baseband signal enters the matching filter after carrier stripping and down-sampling, and is correlated with a segmented local code. Code phase alignment is realized through sliding matching. The matching filter in the correlator has P in total, and each matching filter has a length of S. The original L-point long data becomes P short data, i.e. P = L / S. The P correlation values are subjected to FFT operation, the maximum value in the FFT result is taken as the operation result of the current code phase. Figure 4

[0087] As shown in the figure, the fine estimation step of the present application uses the main code phase to align the code phase of the baseband signal and the local main code. The frequency of the local mixer is set as the coarse estimation value of the Doppler frequency shift obtained in the foregoing step. The intermediate frequency signal is correlated with the local main code in the first-level matching filter to obtain P first-level short integration results. The first-level short integration results corresponding to all secondary code periods are combined to form a first-level short integration result matrix. The adjacent K columns of each row in the matrix are added to obtain a K-time short integration accumulation matrix. The accumulation matrix and the local secondary code are used as the input of the second-level matching filter to perform correlation operation, and the second-level short integration result is obtained. Finally, frequency domain parallel fine search is realized through FFT to obtain a capture result. According to the capture result, the fine estimation value of the Doppler frequency shift and the secondary code phase can be calculated. Figure 5 Further, in order to improve the accuracy of the fine estimation step in estimating the Doppler frequency shift and the secondary code phase, a dynamic search factor is constructed according to the correlation peak value of the baseband signal. When the correlation peak value of the signal capture satisfies a preset condition, dynamic search is performed during signal search, otherwise, dynamic search is not needed. Finally, a plurality of capture results and their corresponding fine estimation values of the Doppler frequency shift and secondary code phases are obtained in each round of search.

[0088]

[0089] ​​Further, considering that in a high dynamic scene, the longer the coherent integration time of a general capture algorithm, the greater the chip offset caused by Doppler, which will lead to a correlation peak shift and attenuation, therefore, the coherent integration time of the capture in a low-orbit satellite high dynamic scene should not be too long, in order to further improve the detection performance and capture probability, the further embodiment of the present application further proposes a multi-round search joint judgment mechanism, by searching the signal at multiple continuous time points, comparing the Dopplers and secondary code phases of the multi-round search capture results, combining the joint decision mechanism of the capture results at multiple continuous time points, by comparing and screening the multi-time capture results, the accuracy and stability of the algorithm for signal capture in a low-orbit high dynamic scene are enhanced.

[0090] Specifically, the joint decision mechanism comprises:

[0091] Based on the fine estimation step, the baseband signal is searched in continuous rounds to obtain capture results corresponding to each search round, and each search round includes a plurality of capture results;

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

[0093] The round Doppler frequency shift fine estimation value is calculated according to the Doppler frequency shift fine estimation values corresponding to each capture result under the same search round, and the round secondary code phase is calculated according to the secondary code phases corresponding to each capture result under the same search round;

[0094] The signal capture state is determined according to the secondary code phases of each search round.

[0095] In order to further illustrate the signal capture method proposed by the present application, the following will be described through a specific embodiment.

[0096] Referring to Figure 6 , which illustrates a satellite MCSK signal capture method proposed by an embodiment of the present application, comprising coarse estimation based on an improved parallel code phase search algorithm and fine estimation based on PMF-FFT double-layer matching filter, finally through a multi-round search joint judgment mechanism, three-dimensional search of Doppler frequency shift, primary code phase and secondary code phase is realized, and the capture accuracy of MCSK signal of a low-orbit satellite in a high dynamic scene is improved.

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

[0098] The input signal of this embodiment is modulated and captured by sliding window energy detection, and the energy feature is used to obtain the coarse primary code phase, and the data reading pointer is adjusted to ensure that the signal data in the unit integration period is of the RT type.

[0099] Doppler shift rough estimation step:

[0100] Referring to the foregoing Figure 3 , the input signal is carrier-stripped by the carrier NCO to obtain an intermediate frequency signal, and the signal obtained by multiplying the intermediate frequency signal by the local carrier is defined as:

[0101]

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

[0103] The ranging component local code is defined as , and the data component local code is , and the data component local code with M phase is generated by time domain cyclic shift, and the signal is correlated with the local code in the time domain, and the time domain cyclic correlation can be expressed as:

[0104]

[0105]

[0106] wherein, the coherence value is represented, and N represents the number of data points.

[0107] Based on the property of FFT frequency domain phase rotation, the data component local code is subjected to FFT, and M kinds of code phases are generated by a phase rotation factor , the correlation operation is completed in the frequency domain, and the following correlation result is obtained by IFFT:

[0108]

[0109]

[0110] wherein, is the local RZC sequence of the ranging component, is the local complement zero code sequence of the data component, is defined as the last bit of the data component local code in one code period length is supplemented with code chips, and the remaining part is supplemented with zero to form a data component local code with two code period lengths, as shown in Figure 8 .

[0111] The MCSK signal is usually denoted as wherein U represents the number of bits per CSK code phase mapping of the data component, U bits of information can be mapped to B represents the number of code periods in a time division symbol period, represents the number of code periods occupied by the ranging component in each time division symbol period, The MCSK modulation fuses the ranging component of the BPSK modulation and the data component of the CSK modulation through time division multiplexing technology, and the ranging component and the data component have corresponding Pseudo-Random Noise (PRN) generators, wherein in the data component branch, the code sequence of each period is represented by different initial phases of the base PRN code to represent different precise message information symbols.

[0112] Taking the MCSK(U, 2, 1) as an example, if the code length of the ranging component and the data component is 2046 (chip), when U takes different values, the change of the data component local code generated by the local code generation strategy based on phase rotation (PRC) proposed by the application compared with the local code generation strategy based on the cyclic shift data component code (CSC) in terms of local code utilization rate reduction ratio, FFT calculation amount reduction ratio and power loss theoretical value is as shown in Figure 9 .

[0113] According to Figure 9 It can be known that when the data component code phase mapping bit number U≤8, the PRC compared with the CSC data component local code utilization rate reduction ratio is less than 6.24%, the energy loss is not more than 0.28dB, and when the data component code phase mapping bit number U≥4, the reduction ratio of the FFT calculation amount of the PRC compared with the CSC is greater than 87.5%, therefore when the value of U is between 4-8, the local code adopts the PRC strategy proposed by the embodiment of the application, which can greatly improve the algorithm calculation efficiency while abandoning a small amount of local code correlation, and the energy loss compared with the CSC strategy is very small.

[0114] The Doppler band estimation result obtained by coherent integration and incoherent accumulation on the above-mentioned correlation result and the main code phase estimation result .

[0115] The relationship between the Doppler shift coarse estimation value and is as follows:

[0116]

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

[0118] Furthermore, the phase normalization estimation result of the primary code is defined. This is the main code phase when the search step size is 0.1 chips. Phase estimation results of the primary code The relationship is as follows:

[0119]

[0120] Among them, f s Indicates the signal sampling rate; This indicates the PRN code length for both the ranging component and the data component, which is 2046 (chip) by default.

[0121] Doppler frequency shift precise estimation steps:

[0122] See the above. Figure 5 Using the primary code phase Align the input signal with the local master code. The intermediate frequency signal is obtained by stripping the carrier frequency from the local mixer.

[0123] The first-stage matched filter short integral processing signal period is... The baseband signal is downsampled to After the first-level matched filter is input, the local master code is upsampled to point L through interpolation, where L represents the PRN code rate (default value is 2.046 Mcps). 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 key They are represented as follows:

[0124]

[0125]

[0126]

[0127]

[0128] in, After performing correlation operations between the intermediate frequency signal and the local master code within the first-stage matched filter, P short integral results can be obtained, as shown below:

[0129]

[0130] A second-level code period T sc It can be obtained The following short integral result matrix is ​​obtained by considering several short integral results. :

[0131]

[0132] Let the sum of the K adjacent short integral results of each element of the above matrix be (T) sc / 2T c The P / K short integral sums are input to the second-stage matched filter, meaning there are P / K second-stage matched filters, and each second-stage matched filter corresponds to 2T. c K / P ms data.

[0133] matrix The summation of the elements in each of the K adjacent columns of each row yields a summation matrix of K times the short integral. :

[0134]

[0135] in, It is a P / K order identity matrix. Represents the Kronecker product. Let K represent a K-dimensional all-1 row vector.

[0136] Construct a local second-level code matrix containing Z phases Z must satisfy and .Will After performing correlation operations with the local second-order code, P / K short second-order integral results can be obtained. Finally, a parallel fine search in the frequency domain is performed using FFT to obtain the acquisition results. :

[0137]

[0138] in, This represents the Hadamard product, and vec represents the vectorized operation. .

[0139] according to The maximum correlation peak V1, the secondary correlation peak V2, and the precise estimate of the Doppler frequency shift can be obtained. Phase of the second code .

[0140] To improve the accuracy of signal Doppler shift and second-level code phase estimation, a dynamic search factor parameter is defined. In capturing relevant peak values hour ,and Real-time detection offers high reliability and eliminates the need for dynamic searching.

[0141]

[0142]

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

[0144]

[0145]

[0146] The is taken as the local primary code starting index, is taken as the frequency stripping carrier of the local mixer, and the above fine estimation steps are repeated to finally obtain capture results and the corresponding Doppler shift fine estimation value and secondary code phase.

[0147] In the multi-round search joint judgment mechanism, the signal is searched in consecutive rounds to obtain capture results corresponding to each search round, and each search round includes a plurality of capture results.

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

[0149] The round Doppler shift fine estimation value is calculated according to the Doppler shift fine estimation values corresponding to the capture results under the same search round, and the round secondary code phase is calculated according to the secondary code phases corresponding to the capture results under the same search round.

[0150] The signal capture state is determined according to the secondary code phases of each search round.

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

[0152] Each search round includes capture results, denotes the dynamic search factor of the jth search round.

[0153] Let the Doppler shift fine estimation values corresponding to the capture results form a first array, determine a element in the first array as a first reference value, and determine the elements in the first array that satisfy a first screening condition according to the first reference value to form a second array, 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, determine the number of elements in the third array that satisfy a second screening condition according to the second reference value, and record it as the number of valid secondary code phases in the round.

[0155] Record the average value of the elements in the second array as the round Doppler shift fine estimation value, and the second reference value as the round secondary code phase.

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

[0157] The status indication value is calculated based on the number of valid phases of the second-order code in each search round. The signal is considered to be successfully captured when the status indication value meets the preset capture conditions.

[0158] The multi-round search joint judgment mechanism is as follows: Figure 9 As shown, J rounds of acquisition and search are performed on the same signal data, with the data start times for each round of search being respectively... Each round of search includes One correlation peak, a precise estimate of the Doppler frequency shift, and the phase of the second-level code.

[0159] After each precise estimation step, the data for that round is... The relevant peak values ​​are sorted from largest to smallest to form an array. Corresponding An array is formed from the Doppler frequency shift precise estimates. .

[0160] array The first value in As a reference value, filter the array middle and reference value The absolute error is less than The elements form an array , The corresponding second-level code phase constitutes an array , denote array Average value of each element This serves as the final precise estimate of the Doppler shift in this search round.

[0161] array The element with the most repetitions As a reference value, select the array. Zhongyu For elements whose difference is less than 2, record the number of elements that satisfy the condition. , This serves as the final second-level code phase in this round.

[0162] Finally, the number of valid phase elements of the second-level code in each round is summed, i.e. If satisfied If the capture is successful, then the capture is considered successful.

[0163] The device provided in this application embodiment has the same implementation principle and technical effect as the aforementioned method embodiment. For the sake of brevity, any parts not mentioned in the device embodiment can be referred to the corresponding content in the aforementioned method embodiment.

[0164] The methods and related apparatuses mentioned in the above embodiments are described with reference to the method flowcharts and / or structural schematic diagrams provided by the embodiments of the present application. Each flow and / or block in the method flowchart and / or structural schematic diagram, and the combination of the flows and / or blocks in the flowchart and / or block diagram can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices produce a device that implements the functions specified in the flowchart Figure 1 one flow or multiple flows and / or structural schematic Figure 1 one block or multiple blocks. These computer program instructions can also be stored in a computer-readable memory that can cause the computer or other programmable data processing devices to work in a specific manner, so that the instructions stored in the computer-readable memory produce a manufactured product including instruction devices that implement the functions specified in the flowchart Figure 1 one flow or multiple flows and / or structural schematic Figure 1 one block or multiple blocks. These computer program instructions can also be loaded into a computer or other programmable data processing device, so that a series of operation steps are performed on the computer or other programmable device to produce a computer-implemented process, so that the instructions executed on the computer or other programmable device provide a process for implementing the functions specified in the flowchart Figure 1 one flow or multiple flows and / or structural schematic

[0165] The following embodiments take the computer device to which the method is applied as an example for illustration. It can be understood that the computer device can be any device with operation and processing functions, which can be but is not limited to a server or a personal notebook computer, etc. In one of the embodiments, the computer device can be an application server, which can be a server for running an application to be tested.

[0166] Referring to Figure 10 , which shows a hardware structural block diagram of a satellite MCSK signal receiving device. The electronic device is intended to represent various forms of digital computers, such as laptops, desktops, workstations, personal digital assistants, servers, blade servers, mainframes, and other appropriate computers. The electronic device can also represent various forms of mobile devices, such as personal digital assistants, cellular telephones, smartphones, wearable devices, and other similar computing devices. The components shown here, their connections, and their functions, as described above, are meant to be examples only, and are not intended to limit the implementations of the present application described and / or claimed in this document.

[0167] As Figure 10As shown, the satellite MCSK signal receiving device comprises 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 embodiments 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 complete the communication with each other through the communication bus 4;

[0169] The processor 1 can 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 application, etc.

[0170] The memory 3 can include a high-speed RAM memory, and can also include a non-volatile memory, etc., for example, 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 various processing procedures described above.

[0172] The embodiments of the present application also provide a readable storage medium having a computer program stored thereon, and the computer program is executed by the processor to implement the various processing procedures of the above-mentioned embodiments and / or the schemes provided by any one of the possible implementation manners in combination with the embodiments.

[0173] The above-mentioned embodiments have described the present application in detail with respect to possible cases, and those skilled in the art will recognize that the present application can be practiced by other embodiments. The specific naming of the components, the capitalization of terms, the attributes, data structures or any other programming or structural aspects of the system described in the specification is not mandatory or important, and the mechanisms of the present application can have different names, formats or procedures that implement the same or similar functions. The system can be implemented by a combination of hardware and software (as described), entirely by hardware elements, or entirely by software elements. The specific division of functions between various system components described in the specification is only exemplary and not mandatory; on the contrary, a single system component can perform the functions of multiple system components, or multiple system components can perform the functions of a single system component.

[0174] Those skilled in the art will appreciate that the various steps of the methods disclosed above can be implemented by general computing devices, which can be centralized on a single computing device or distributed across a network of multiple computing devices, and optionally can be implemented by program code executable by a computing device, which can be stored in a storage device and executed by a computing device, or can be implemented by individual integrated circuit modules, or by multiple modules or steps implemented by a single integrated circuit module. Thus, the embodiments of the present application are not limited to any particular combination of hardware and software.

[0175] The computing device executable programs (also referred to as programs, software, software applications, or code) include machine instructions for a programmable processor, 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., magnetic discs, optical disks, memory, Programmable Logic Devices (PLDs)) used to provide 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 that can be used to provide machine instructions and / or data to a programmable processor.

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

[0177] Those skilled in the art can understand that the structures shown in the various figures are only block diagrams of the partial structures related to the schemes of the present application, and do not constitute a limitation on the terminal device to which the schemes of the present application are applied. The specific terminal device can include more or less components than those shown in the figures, or combine certain components, or have a different arrangement of components.

[0178] In the description of the specification, the description of the terms "one embodiment", "some embodiments", "example", "specific example", or "possible design" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are contained in at least one embodiment or example of the application. In the description of the specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in one or more embodiments or examples. In addition, the person skilled in the art can combine and combine the different embodiments or examples described in the specification and the features of the different embodiments or examples without contradiction and combination.

[0179] Finally, it should also be noted that, in this paper, the relationship terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between the entities or operations. Moreover, the terms "include", "contain" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or equipment. Without more limitations, the element defined by the statement "including a" does not exclude the presence of other identical elements in the process, method, article or equipment including the element.

[0180] The above embodiments are only used to illustrate the technical solutions of the present application, but not to limit it; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that the technical solutions recorded in the foregoing embodiments can be modified, or some technical features can be replaced by equivalent; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for acquisition of a satellite MCSK signal, characterized by, The method comprises: a Doppler frequency coarse estimation step: performing a parallel code phase search on the baseband signal to calculate a Doppler frequency coarse estimation value and a main code phase, wherein the data component local code is phase-rotated during the parallel code phase search; a Doppler frequency fine estimation step: determining a mixing frequency according to the Doppler frequency coarse estimation value, stripping the baseband signal carrier based on the mixing frequency to obtain an intermediate frequency signal, and aligning the local main code and the intermediate frequency signal in code phase using the main code phase; performing first-stage matched filtering on the local main code and the intermediate frequency signal to obtain a first-stage short integration result; performing second-stage matched filtering on the local secondary code and the first-stage short integration result to obtain a second-stage short integration result; performing frequency domain conversion on the second-stage short integration result to obtain an acquisition result, wherein the acquisition result is used to obtain a Doppler frequency fine estimation value and a secondary code phase.

2. The method of claim 1, wherein, The method further comprises: constructing a dynamic search factor according to the correlation peak value of the baseband signal, and repeating the Doppler frequency fine estimation step according to the dynamic search factor in a single search round to obtain a plurality of acquisition results; wherein the local main code is determined according to the dynamic search factor and the main code phase, and the mixing frequency is determined according to the dynamic search factor and the Doppler frequency coarse estimation value.

3. The method of claim 1, wherein, The method further comprises: performing continuous round searches on the baseband signal based on the Doppler frequency fine estimation step to obtain acquisition results corresponding to each search round, wherein each search round comprises a plurality of acquisition results; performing the following round parameter calculation process for each search round: calculating a round Doppler frequency fine estimation value according to the Doppler frequency fine estimation values corresponding to the acquisition results in the same search round, and calculating a round secondary code phase according to the secondary code phases corresponding to the acquisition results in the same search round; determining a signal acquisition state according to the secondary code phases of each search round.

4. The method of claim 3, wherein, The round parameter calculation process specifically comprises: Each search round comprises a capture result, a dynamic search factor representing the jth search round; Let a first array be composed of the Doppler shift fine estimation values corresponding to the capture results, determine an element in the first array to be a first reference value, determine a second array composed of the elements in the first array satisfying a first screening condition according to the first reference value, and compose a third array of the secondary code phases corresponding to the elements in the second array. determining an element in the third array as a second reference value, determining the number of elements in the third array that satisfy a second screening condition according to the second reference value, and recording the number as a round secondary code phase effective number; recording the average value of the elements of the second array as a round Doppler frequency fine estimation value, and recording the second reference value as a round secondary code phase.

5. The method of claim 4, wherein, Determining a signal acquisition state according to the secondary code phases of each search round comprises: calculating a state indication value according to the round secondary code phase effective numbers of each search round, and considering that the signal acquisition is successful when the state indication value satisfies a preset acquisition condition.

6. The method of claim 1, wherein, The phase rotation of the data component local code during the parallel code phase search comprises: performing fast Fourier transform on the data component local code to obtain a data component frequency domain representation; performing phase rotation on the data component frequency domain representation using a phase rotation factor to generate a data component local code corresponding to each code phase.

7. The method of claim 1, wherein, The first-stage matched filtering of the local main code and the intermediate frequency signal to obtain a first-stage short integration result comprises: The intermediate frequency signal and the local main code are matched and filtered in P first-stage matched filters to obtain first-stage short integration results : wherein represents an intermediate frequency signal, represents a local primary code, , represents a length of the first stage matched filter, represents a number of sampling points; The short integration result of each single secondary code period is represented as a primary short integration result matrix as follows: The short integration result of each single secondary code period is represented as a primary short integration result matrix as follows: ， wherein, denotes a second stage code period, , denotes a first stage matched filter processed signal period.

8. The method of claim 7, wherein, The second-stage matched filtering of the local secondary code and the first-stage short integration result to obtain a second-stage short integration result comprises: The first short integral result matrix is accumulated to obtain an accumulated matrix as follows : ， where the elements of the matrix represent the K adjacent element accumulated values of the elements in the matrix , is a P / K order unit matrix, denotes the Kronecker product, denotes a K-dimensional all-1 row vector; The first-level short integration result matrix and the local secondary code are subjected to a matched filtering operation in P / K second-level matched filters to obtain a secondary short integration result as follows : ， wherein denotes a local secondary code matrix, Z satisfies and , denotes a Hadamard product, vec denotes a vectorization operation, .

9. A satellite MCSK signal receiving device, characterized in that, An apparatus comprising a memory storing computer executable instructions and a processor, the computer executable instructions, when executed by the processor, cause the apparatus to perform the method of any of claims 1-8.

10. A readable storage medium, characterized by, A computer program product comprising computer executable instructions, the computer executable instructions, when executed by a processor, cause the processor to perform the method of any of claims 1-8.

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