CN113253316A

CN113253316A - Universal navigation signal capturing and processing method

Info

Publication number: CN113253316A
Application number: CN202110368127.9A
Authority: CN
Inventors: 杨燕姣; 陈静; 刘坤; 连猛; 刘飞; 王君帅; 薛志芹
Original assignee: Space Star Technology Co Ltd
Current assignee: Space Star Technology Co Ltd
Priority date: 2021-04-06
Filing date: 2021-04-06
Publication date: 2021-08-13
Anticipated expiration: 2041-04-06
Also published as: CN113253316B

Abstract

The invention discloses a general navigation signal capturing and processing method, which relates to a rapid and efficient signal capturing method for various civil signals of the conventional and modern frequency point signals of the existing mainstream navigation system, including GPS L1CA/L5/L1C, BDSB1I/B2I/B3I/B1C/B2a/B2B/S2C, Galileo E1/E5a/E5B, GLONASS L1f/L2f and the like. The method generates a corresponding local code according to the configuration of software, adaptively samples the local code and signal data, and performs capturing processing based on a PMF-FFT algorithm. The method has the advantages that the length and the number of the segments in the PMF-FFT algorithm parameters are flexibly configured, the effect of flexibly configuring various PMF-FFT algorithm parameters and flexibly designing the search processing parallelism of the time-frequency unit is achieved by designing the effective combination of two FFT length conversion functions, the flexible switching function of various capturing speeds, capturing sensitivities and Doppler coverage ranges is achieved, and the characteristics of strong signal compatibility, high capturing speed and high capturing sensitivity are achieved.

Description

Universal navigation signal capturing and processing method

Technical Field

The invention belongs to the field of satellite application, and relates to a general navigation signal capturing and processing method which can be used for rapid and high-sensitivity capturing of various civil navigation signals such as GPS L1CA/L5/L1C, BDS B1I/B2I/B3I/B1C/B2a/B2B/S2C, Galileo E1/E5a/E5B, GLONASS L1f/L2f and the like.

Background

The Global Navigation Satellite System (GNSS) can provide all-weather and high-precision position, speed and time information for various fields of the world, such as sea, land, air and sky, and the application of the GNSS is permeated into various fields of national economy, thereby playing an important promoting role in the development process of human beings all the time.

The GNSS is continuously developed and perfected, the satellite navigation signals are improved and changed in the aspects of a modulation system, a spread spectrum mechanism, new frequency band addition and the like, the navigation signals are greatly increased in number, the modulation mode is diversified, and the ranging code has the development trend of long-period complexity. These new changes require receiver acquisition techniques with multi-frequency and multi-mode signal processing in macro-functionality and can be adapted to the requirements of different application scenarios. Under the background, the strong flexibility, the high compatibility, the wide application scene, the fast processing speed and the high sensitivity are urgent requirements of the new generation of receiver capturing technology.

The currently disclosed navigation signal processing capturing method only supports one or two navigation constellation navigation signals, or has the single advantage of capturing speed or capturing sensitivity, and has the disadvantages of low universality, poor flexibility, single application scene and certain limitation.

Disclosure of Invention

The technical problems solved by the invention are as follows: the method overcomes the defects of the prior art, provides a general navigation signal capturing and processing method, is suitable for capturing of various navigation signal systems, meets scene requirements of different Doppler dynamics and different capturing speeds and sensitivities, and has the characteristics of high flexibility, strong compatibility, high processing speed, high sensitivity and strong practicability.

The technical scheme adopted by the invention is as follows: a general navigation signal capturing processing method comprises the following steps:

(1) generating a pseudo code modulated by the constellation to which the input navigation signal belongs according to the information of the constellation to which the input navigation signal belongs and the initial phase information of the input navigation signal, modulating and sampling the pseudo code to obtain a local code data stream prn _ local, and outputting and caching the local code data stream prn _ local to a storage unit mem 0;

inputting information of a constellation to which a navigation signal belongs, including: type, frequency point, satellite number;

(2) obtaining a carrier intermediate frequency control word FCW1 according to the carrier intermediate frequency of the input navigation signal, and generating a numerically controlled oscillator NCO1 by using the carrier intermediate frequency control word FCW 1; performing table lookup by using a periodic signal 1 output by a numerically controlled oscillator NCO1 to obtain a local sine intermediate frequency carrier and a local cosine intermediate frequency carrier, wherein sin and cos are used for representing the carriers;

respectively mixing a local sine intermediate frequency carrier and a local cosine intermediate frequency carrier with an external input intermediate frequency signal IF to obtain an in-phase branch mixing signal tmp _ i and an orthogonal branch mixing signal tmp _ q; generating a numerically controlled oscillator NCO2 by using a down-sampling frequency control word FCW2, and generating a down-sampling clock samp _ down by using a periodic signal 2 output by the numerically controlled oscillator NCO 2;

sampling the in-phase branch frequency mixing signal tmp _ i and the orthogonal branch frequency mixing signal tmp _ q respectively by using a down-sampling clock samp _ down to generate an in-phase branch down-sampling data stream mix _ i and an orthogonal branch down-sampling data stream mix _ q, and caching the in-phase branch down-sampling data stream mix _ i and the orthogonal branch down-sampling data stream mix _ q into a storage unit mem1_ i and a storage unit mem1_ q respectively; (3) reading the local code data stream prn _ local in the step (1) by using the initial address addr _ coh, wherein the total number of read data is L; simultaneously reading the in-phase branch down-sampled data stream mix _ i and the orthogonal branch down-sampled data stream mix _ q in the step (2) by using an initial address addr _ init + addr _ coh, wherein the total number of the read data is L; l local code data prn _ local and L same-phase branch down-sampling data streams mix _ i are multiplied in a one-to-one correspondence mode, then every K multiplied data are accumulated to form a piece of data to form L/K point subsection related data, and the subsection related data are arranged in a row-first mode to form a real part branch cross-correlation matrix corr _ i with N rows and P columns; l local code data prn _ local and L orthogonal branch down-sampling data streams mix _ q are multiplied in a one-to-one correspondence mode, and then every K multiplied data are accumulated to form data to form L/K point segmentation related data; preferentially arranging the segment-related data according to rows to form imaginary part branch cross-correlation moments corr _ q of N rows and P columns; addr _ init is a positive integer and takes a value from 0; addr _ coh is a positive integer and takes a value from 0; l, K, N, P is a positive integer, and L can be divided by K, L/K is N P;

(4) performing FFT processing on the cross-correlation values in the matrix form, including real part branch cross-correlation values corr _ i and imaginary part branch cross-correlation values corr _ q, to obtain a frequency spectrum matrix of N rows and P columns of cross-correlation values; taking a modulus for each matrix element; judging whether incoherent accumulation of multiple lines is needed or not according to the difference of FFT processing lengths, if so, adding corresponding elements at the positions of each column of each line to obtain incoherent data, storing the incoherent data to the first line, and assigning zero to each element of other lines to be used as a currently obtained total N x P incoherent data matrix; otherwise, directly obtaining a total N x P incoherent data matrix from the modulus values; adding the N x P incoherent data matrix and the incoherent data matrix stored in the memory cell mem3 last time, and storing the added incoherent data matrix in mem 3; the values of the elements of the incoherent data matrix initially stored in mem3 are 0;

the FFT processing length comprises P and N P, wherein after the FFT processing with the length of N, noncoherent accumulation processing of multiple lines is needed, and after the FFT processing with the length of N, noncoherent accumulation processing of multiple lines is not needed;

(5) adding non to the value of an incoherent counting variable Z, then assigning the value to Z, judging whether the current value of Z is equal to the set incoherent total times Z, if not, adding L to the value of addr _ coh in the step (3), then assigning the value to addr _ coh, keeping the value of addr _ init unchanged, and returning to the step (3); if yes, performing the step (6); z is a positive integer and the initial value is 0; non is a positive integer, and the value of non is N (the FFT processing length is P) or 1 (the FFT processing length is N x P) according to the difference of the FFT processing lengths; z is a positive integer;

(6) p is the phase value searched currently, the maximum element in the incoherent data matrix accumulated for multiple times in mem3 is found out and recorded as the maximum element max (p) of the pth group, and the corresponding row and column are recorded; adding 1 to the value of p, then assigning p, judging whether the current value of p is equal to the set phase search total PH or not, if not, adding 1 to the value of addr _ init in the step (3), then assigning addr _ init, meanwhile initializing addr _ coh to be 0, and returning to the step (3); if yes, performing the step (7); p is a positive integer and the initial value is 0; PH is a positive integer;

(7) finding out the maximum value in PH (PH) max (p) data, recording the maximum value as the S-th value in PH max (p) data, recording the line number of the maximum value as max _ row and the column number as max _ column; s, max _ row and max _ column values are calculated differently according to different lengths of FFT processing, so that a captured phase value and a Doppler frequency value can be obtained, and the whole capturing search is completed; s, max _ row and max _ column are positive integers, starting from 0.

Preferably, in the step (1), local pseudo codes of BPSK/QPSK modulated signals of four navigational constellations, GPS, BDS, Galileo and GLONASS can be generated by a conventional shift register set manner, where the pseudo codes include pseudo codes of frequency points L1CA, L5I, L5Q, B1I, B2I, B3I, B2a, B2B, S2C, E5a, E5B, L1f and L2 f; and generating local pseudo codes of the BOC modulation signals in a table look-up mode, wherein the pseudo codes comprise pseudo codes of L1C, B1C and E1 frequency points.

Preferably, the native code data prn _ local generated in step (1) is obtained by modulating original pseudo codes and symbols and performing 1, 2, 3 … 20 times of pseudo code frequency integral multiple sampling processing; the symbol includes NH code/subcode, the modulation is exclusive-or processing, the modulation period includes, but is not limited to, time lengths of 1ms, 2ms, 5ms, 10ms, 1/16ms, and the number of NH code/subcode that can be modulated is 32 bits.

Preferably, the down-sampling rate samp _ down in step (2) is flexibly configured, and is configured to include, but not limited to, 2.046MHz, 4.092MHz, 8.16MHz, and 20.46 MHz.

Preferably, the input data and the output data required by the FFT processing technique in step (4) are in the form of a matrix N × P, and N independent FFT conversions with a length of P points or one FFT conversion with a length of N × P may be formed by configuration.

Preferably, the calculation of the capture result in the step (7) may have different calculation processing methods according to the processing length of the FFT, specifically as follows:

the FFT length is P:

1) the captured phase value is S;

2) the captured Doppler frequency grid is max _ column;

3) the captured Doppler frequency step fbin is samp _ down/K/P;

4) the captured doppler frequency is max _ column × fbin;

FFT length N × P:

1) the captured phase value is S;

2) the captured doppler bin is max _ column + max _ row 32;

3) the captured Doppler frequency step fbin is samp _ down/K/P/N;

4) the captured doppler frequency is max _ column × fbin.

Compared with the prior art, the invention has the beneficial effects that:

(1) the invention is compatible with the capture of various navigation modulation signals. The rapid acquisition of frequency point satellite signals such as GPS L1CA/L5/L1C, BD 2B 1I/B2I/B3I/B1C/B2a/B2B/S2C, Galileo E1/E5a/E5B, GLONASS L1f/L2f and the like can be completed by configuring different parameters through software.

(2) The invention is based on PMF-FFT algorithm, can configure a plurality of corresponding parameters, has larger flexibility, and meets the requirements of different Doppler dynamic ranges and capture sensitivity.

(3) The present invention has configurable FFT computation processing. The method has two types of FFT conversion selection with different lengths, the FFT conversion with large selection length can realize higher sensitivity or larger Doppler search range, the FFT conversion with small selection length has more search calculation parallelism, and the capture speed is accelerated.

(4) The invention realizes balanced switching between the capture speed and the capture sensitivity, and has the characteristics of high capture speed and high sensitivity.

(5) The invention is suitable for capturing various navigation signal systems by designing a configurable local code generation design and a data down-sampling method; the effective combination of two FFT length conversion functions is designed, data is processed in a matrix form, various PMF-FFT algorithm parameters can be configured and applied, and the method is suitable for the scene requirements of different Doppler dynamics, different capture speeds and different sensitivities. The invention has the characteristics of high flexibility, strong compatibility, high processing speed, high sensitivity and strong practicability.

Drawings

FIG. 1 is a system diagram of a generic navigation signal acquisition processing method;

FIG. 2 is a schematic diagram of a generic code generation module according to the principle and structure thereof;

FIG. 3 is a schematic view of a read control process;

fig. 4 is a schematic diagram of the FFT processing method.

Detailed Description

The present invention will be further described with reference to the accompanying drawings and examples, which are only a part of the examples of the present invention and are not intended to be exhaustive.

The general navigation signal capturing and processing method provided by the invention can be used for rapidly capturing and highly sensitively capturing various navigation signals. The invention can generate various system signal local codes by configuration, supports the application of various PMF-FFT algorithm parameters, processes data in a matrix form, and effectively combines two FFT length conversions to adapt to the requirements of various capture speeds and capture sensitivities. The device can support the rapid and high-sensitivity acquisition operation of various navigation signals such as GPS L1CA/L5/L1C, BD 2B 1I/B2I/B3I/B2a/B2B/S2C, Galileo E1/E5a/E5B, GLONASS L1f/L2f and the like. The method for capturing and processing the universal navigation signal comprises the aspects of local code stream generation and storage, mixing data generation and storage, reading control processing, FFT processing, non-coherent processing and maximum value detection, and is shown in figure 1. The method comprises the following specific steps:

(1) the local code stream is generated and stored, and fig. 2 shows a principle and a schematic diagram of generating the local universal code. And generating a local code of a corresponding satellite by configuring signal parameters including the frequency point type and the satellite number. According to the signal characteristics, the local code is subjected to secondary modulation, namely exclusive-or operation, of NH code or subcode or other known symbols to generate a modulation code _ m. Performing a kronecker product operation on code _ m and a constant 2 to complete 2-time code rate sampling processing on the code _ m to form a code stream prn _ local, wherein the bit width of each prn _ local data is 1 bit, and the code stream prn _ local is stored in mem0 with the depth of 40920.

In this embodiment, the signal type of the configuration is GPS L1 CA. For the gold code type pseudo code GPS L1CA, the pseudo code corresponding to the satellite number can be generated according to the initial phase values of G1 and G2 which are specific to different satellite numbers by the exclusive OR addition of the outputs of two m-sequence shift registers G1 and G2. In this embodiment, the data secondarily modulated with the local code is 0.

(2) Mixing data is generated and stored. Obtaining a carrier intermediate frequency control word FCW1 according to the carrier intermediate frequency of the input navigation signal, and generating a 32-bit-width digital control oscillator NCO1 by using the carrier intermediate frequency control word FCW 1; performing table lookup by using high 4-bit data output by a numerically controlled oscillator NCO1 to obtain a local sine intermediate frequency carrier sin and a local cosine intermediate frequency carrier cos; and respectively mixing the local sine intermediate frequency carrier and the local cosine intermediate frequency carrier with an external input intermediate frequency signal IF to obtain an in-phase branch mixing signal tmp _ i and a quadrature branch mixing signal tmp _ q.

Generating a 32-bit-width numerically controlled oscillator NCO2 by using a down-sampling frequency control word FCW2, and taking the rising edge of the highest bit change of a periodic signal output by the numerically controlled oscillator NCO2 as a down-sampling clock samp _ down; in this embodiment, the down-sampling clock frequency samp _ down is 2.046 MHz.

Respectively performing down-sampling treatment on the in-phase branch frequency mixing signal tmp _ i and the orthogonal branch frequency mixing signal tmp _ q by using a down-sampling clock samp _ down by adopting an average value sampling method, namely respectively accumulating the sampled signals tmp _ i and tmp _ q before the samp _ down effective pulse, and then respectively using the average value calculated by accumulating and dividing the sampling times as effective data to obtain down-sampled in-phase branch frequency mixing data mix _ i and orthogonal branch frequency mixing data mix _ q; the bit width of each mix _ i or mix _ q data is 4 bits, and the data is respectively cached to a storage unit mem1_ i and a storage unit mem1_ q; the storage depth of mem1_ i or mem1_ q is 81840.

(3) Read controls and generate a correlation data matrix. Reading local code data prn _ local from mem0 by using an initial address addr _ coh, wherein if the read address depth is 32768, the total read data volume is 32768; using addr _ init + addr _ coh (addr _ init is 0,1 …, addr _ coh is 0, L,2 × L …) as an initial address, a reading depth is L32768, and the total data amount of the mixed data mix _ i, mix _ q, mix _ i, or mix _ q is 32768 from mem1_ i and mem1_ q, respectively, and the reading control process is as shown in fig. 3; the prn _ local is respectively multiplied by the mix _ i and mix _ q at corresponding points to obtain 32768 pieces of correlation data corr _ i _ tmp and corr _ q _ tmp, and each 128 pieces of corr _ i _ tmp and corr _ q _ tmp are respectively accumulated to obtain 32768/128 pieces of 256 pieces of real part segment correlation data and 256 pieces of virtual part segment correlation data. The 256 pieces of real part segment related data are arranged according to row priority to obtain a real part branch cross-correlation matrix corr _ i with 8 rows and 32 columns; 256 imaginary part related data are arranged according to row priority, and an imaginary part branch cross-correlation matrix corr _ q with 8 rows and 32 columns is obtained.

(4) And (5) frequency domain conversion processing. And (3) performing FFT conversion on the real part branch cross-correlation matrix corr _ i and the imaginary part branch cross-correlation matrix corr _ q obtained in the step (3) in the embodiment. The FFT processing technique requires that the input data and the output data have the same form, are in a matrix form of N rows and P columns, and have configurability of two lengths, P and N × P, and a schematic structural diagram thereof is shown in fig. 4. The two length configurations are characterized as follows:

and the FFT length is P, and independent P-point frequency domain conversion processing of N channels is carried out on the input N rows and P columns of data. In the embodiment, N is 8, P is 32;

taking the input N rows and P columns of data as a complete sequence, and carrying out N P dot frequency domain conversion processing of 1 channel. In the embodiment, N is 8, P is 32;

and (5) carrying out non-coherent accumulation processing. Performing modulus processing on the N rows and P columns of data output after the FFT processing, and respectively performing different processing according to the subsequent length configuration of the FFT, specifically as follows:

and the FFT length is P, 8 x 32 data matrixes are output by the FFT, each column of data of 8 rows of data is accumulated to obtain one piece of data, 32 columns of data are obtained in total, the data are used as elements of a first row, elements of other rows are assigned to be 0 to form an 8-row 32-column incoherent data matrix, the incoherent data matrix is added with the 8-row 32-column incoherent data matrix read from the storage unit mem3 in the last time, and the addition result is stored in mem 3. The initial value of each element of the incoherent data matrix of 8 rows and 32 columns read last time in the memory cell mem3 is 0.

And the FFT output 8 x 32 data matrix directly forms an 8-row 32-column incoherent data matrix after modulus processing, and is added with the 8-row 32-column incoherent data matrix read from the memory cell mem3, and the addition result is stored in mem 3. The initial value of each element of the incoherent data matrix of 8 rows and 32 columns read last time in the memory cell mem3 is 0.

(5) Non-coherent treatment. Adding non to the value of an incoherent counting variable Z, then giving Z, judging whether the current value of Z is equal to the incoherent total times Z, taking Z as 8, and according to different processing lengths of FFT, carrying out the following different processing:

the FFT length is P, non is 8, and the step (6) is carried out;

FFT length N × P: and (3) adding L to the value of addr _ coh in the step (3) to obtain the value of addr _ coh as 512, then adding the value of addr _ init to the addr _ coh, keeping the value of addr _ init unchanged, and returning to the step (3).

(6) p is the phase value searched currently, the maximum element in 8 rows and 32 columns of incoherent data matrix accumulated for multiple times in mem3 is found out and recorded as the maximum element max (p) of the p-th group, and the corresponding row number and column are recorded; adding 1 to the value of p, then assigning p, judging whether the current value of p is equal to the set phase search total PH (PH is 2046), if not, adding 1 to the value of addr _ init in the step (3), then assigning addr _ init, meanwhile initializing addr _ coh to 0, and returning to the step (3); if yes, performing the step (7); the initial value of p is 0;

(7) finding out the maximum value of 2046 max (p) data, wherein the maximum value is the S-th data in 2046 max (p), the maximum value is max (S), the row number of the maximum value is max _ row, and the column number is max _ column; the captured phase value and Doppler frequency value can be obtained according to the input mode and S, max _ row and max _ column values, and the whole capturing search is completed. According to the difference of the FFT processing length, the specific capture result processing is as follows:

FFT length 32:

1) the captured phase value is S;

2) the captured Doppler frequency grid is max _ column;

3) the doppler frequency step for acquisition was 2.046MHz/128/32 ═ 499.5 Hz;

4) the captured doppler frequency is max _ column × 499.5 Hz;

FFT length 8 × 32:

1) the captured phase value is S;

2) the captured doppler bin is max _ column + max _ row 32;

3) the doppler frequency step for acquisition was 2.046MHz/128/32 ═ 62.4 Hz;

4) the captured doppler frequency is max _ column × 62.4 Hz;

the characteristics of the two different FFT processing lengths in this example are summarized in table 1:

TABLE 1 summary of two different FFT processing lengths

The invention is compatible with the capture of various navigation modulation signals. The rapid acquisition of frequency point satellite signals such as GPS L1CA/L5/L1C, BD 2B 1I/B2I/B3I/B1C/B2a/B2B/S2C, Galileo E1/E5a/E5B, GLONASS L1f/L2f and the like can be completed by configuring different parameters through software; the invention is based on PMF-FFT algorithm, can configure a plurality of corresponding parameters, has larger flexibility, and meets the requirements of different Doppler dynamic ranges and capture sensitivity.

The present invention has configurable FFT computation processing. The method has the advantages that two FFT conversion selections with different lengths are provided, the selection of the FFT conversion with a large length can realize a Doppler search range with higher sensitivity or a larger Doppler search range, the selection of the FFT conversion with a small length has more search calculation parallelism, and the capture speed is accelerated; the invention realizes balanced switching between the capture speed and the capture sensitivity, and has the characteristics of high capture speed and high sensitivity.

The invention is suitable for capturing various navigation signal systems by designing a configurable local code generation design and a data down-sampling method; the effective combination of two FFT length conversion functions is designed, data is processed in a matrix form, various PMF-FFT algorithm parameters can be configured and applied, and the method is suitable for the scene requirements of different Doppler dynamics, different capture speeds and different sensitivities. The invention has the characteristics of high flexibility, strong compatibility, high processing speed, high sensitivity and strong practicability.

Claims

1. A general navigation signal capturing processing method is characterized by comprising the following steps:

sampling the in-phase branch frequency mixing signal tmp _ i and the orthogonal branch frequency mixing signal tmp _ q respectively by using a down-sampling clock samp _ down to generate an in-phase branch down-sampling data stream mix _ i and an orthogonal branch down-sampling data stream mix _ q, and caching the in-phase branch down-sampling data stream mix _ i and the orthogonal branch down-sampling data stream mix _ q into a storage unit mem1_ i and a storage unit mem1_ q respectively;

(3) reading out the local code data stream prn _ local in the step (1) by using the initial address addr _ coh, wherein the total read data number is L; simultaneously reading the in-phase branch down-sampled data stream mix _ i and the orthogonal branch down-sampled data stream mix _ q in the step (2) by using an initial address addr _ init + addr _ coh, wherein the total number of the read data is L; l local code data prn _ local and L same-phase branch down-sampling data streams mix _ i are multiplied in a one-to-one correspondence mode, then every K multiplied data are accumulated to form a piece of data to form L/K point subsection related data, and the subsection related data are arranged in a row-first mode to form a real part branch cross-correlation matrix corr _ i with N rows and P columns; l local code data prn _ local and L orthogonal branch down-sampling data streams mix _ q are multiplied in a one-to-one correspondence mode, and then every K multiplied data are accumulated to form data to form L/K point segmentation related data; preferentially arranging the segment-related data according to rows to form imaginary part branch cross-correlation moments corr _ q of N rows and P columns; addr _ init is a positive integer and takes a value from 0; addr _ coh is a positive integer and takes a value from 0; l, K, N, P is a positive integer, and L can be divided by K, L/K is N P;

2. The method of claim 1, wherein the method further comprises: in the step (1), local pseudo codes of BPSK/QPSK modulation signals of four navigational constellations, GPS, BDS, Galileo and GLONASS, including pseudo codes of frequency points L1CA, L5I, L5Q, B1I, B2I, B3I, B2a, B2B, S2C, E5a, E5B, L1f and L2f, may be generated in a conventional shift register set manner; and generating local pseudo codes of the BOC modulation signals in a table look-up mode, wherein the pseudo codes comprise pseudo codes of L1C, B1C and E1 frequency points.

3. The method of claim 1, wherein the method further comprises: the native code data prn _ local generated in the step (1) is obtained by modulating original pseudo codes and symbols and performing 1, 2 and 3 … 20 times of pseudo code frequency integral multiple sampling processing; the symbol includes NH code/subcode, the modulation is exclusive-or processing, the modulation period includes, but is not limited to, time lengths of 1ms, 2ms, 5ms, 10ms, 1/16ms, and the number of NH code/subcode that can be modulated is 32 bits.

4. The method of claim 1, wherein the method further comprises: the down-sampling rate samp _ down in step (2) is flexibly configured, and is configured to include, but not limited to, 2.046MHz, 4.092MHz, 8.16MHz, and 20.46 MHz.

5. The method of claim 1, wherein the method further comprises: the input data and the output data required by the FFT processing technique in step (4) are both in the form of a matrix N × P, and N independent FFT conversions with a length of P points or one FFT conversion with a length of N × P may be formed by configuration.

6. The method of claim 1, wherein the method further comprises: the calculation of the capture result in the step (7) may have different calculation processing methods according to the processing length of the FFT, which is specifically as follows:

the FFT length is P:

1) the captured phase value is S;

2) the captured Doppler frequency grid is max _ column;

3) the captured Doppler frequency step fbin is samp _ down/K/P;

4) the captured doppler frequency is max _ column × fbin;

FFT length N × P:

1) the captured phase value is S;

2) the captured doppler bin is max _ column + max _ row 32;

3) the captured Doppler frequency step fbin is samp _ down/K/P/N;

4) the captured doppler frequency is max _ column × fbin.