阅读说明：本技术 一种高动态扩频信号捕获装置及捕获方法 (High-dynamic spread spectrum signal capturing device and capturing method ) 是由 李晓 王竹刚 于 2020-11-24 设计创作，主要内容包括：本发明属于扩频信号接收处理的技术领域,具体地说,涉及一种高动态扩频信号捕获装置,包括：FPGA芯片和设置在FPGA芯片上的频率搜索控制器、PRN码发生器、本地振荡器产生模块、第一FFT模块,第二FFT模块、第一复数乘法器、第二复数乘法器、第三复数乘法器、IFFT模块、峰值检测模块、数据处理模块和计数器；所述数据处理模块,用于根据判决结果,获取当前捕获的码相位；并结合下一次捕获得到的码相位,得到捕获时的码相位,完成对高动态扩频信号的捕获。(The invention belongs to the technical field of spread spectrum signal receiving and processing, and particularly relates to a high dynamic spread spectrum signal capturing device, which comprises: the system comprises an FPGA chip, and a frequency search controller, a PRN code generator, a local oscillator generation module, a first FFT module, a second FFT module, a first complex multiplier, a second complex multiplier, a third complex multiplier, an IFFT module, a peak detection module, a data processing module and a counter which are arranged on the FPGA chip; the data processing module is used for acquiring the currently captured code phase according to the judgment result; and combining the code phase obtained by the next acquisition to obtain the code phase during acquisition, and completing the acquisition of the high dynamic spread spectrum signal.)

1. A high dynamic spread spectrum signal acquisition apparatus, comprising: the system comprises an FPGA chip, and a frequency search controller, a PRN code generator, a local oscillator generation module, a first FFT module, a second FFT module, a first complex multiplier, a second complex multiplier, a third complex multiplier, an IFFT module, a peak detection module, a data processing module and a counter which are arranged on the FPGA chip;

the frequency search controller is used for generating a search frequency value in real time and outputting the search frequency value to the PRN code generator;

the PRN code generator is used for changing the frequency value of the local pseudo code according to the search frequency value, outputting the local pseudo code with the changed frequency value and outputting the local pseudo code to the first FFT module; the local pseudo code after the frequency value is changed is a pseudo code sequence which comprises a plurality of pseudo codes;

the first FFT module is used for carrying out FFT transformation on the local pseudo code with the changed frequency value, transforming the local pseudo code with the changed frequency value to a frequency domain to obtain frequency domain data, taking the complex conjugate of the frequency domain data, outputting first input data and outputting the first input data to a third complex multiplier;

the local oscillator generating module is used for generating sin data and cos data and outputting the sin data to the first complex multiplier; outputting cos data to a second complex multiplier;

the first complex multiplier is used for performing complex multiplication operation on the first input pseudo code and the sin data to obtain first input pseudo code data and outputting the first input pseudo code data to the second FFT module;

the second complex multiplier is used for carrying out complex multiplication operation on the first input pseudo code and cos data to obtain second input pseudo code data and outputting the second input pseudo code data to the second FFT module;

the second FFT module is used for integrating the first input pseudo code data and the second input pseudo code data to obtain integrated input pseudo code data, and carrying out FFT operation on the integrated input pseudo code data to obtain a second input data frequency domain and outputting the second input data frequency domain to a third complex multiplier;

the third complex multiplier is used for performing complex multiplication operation on the frequency domains of the first input data and the second input data to obtain third input data and outputting the third input data to the IFFT module;

the IFFT module is used for carrying out IFFT transformation on the third input data to obtain time domain data, carrying out absolute value solving processing on each data in the time domain data to obtain a plurality of time domain values, and further obtaining a plurality of moduli and outputting the moduli to the peak value detection module;

the peak detection module is used for selecting the maximum value from the plurality of moduli, carrying out peak detection judgment on the maximum value and outputting the judgment result to the data processing module;

the data processing module is used for acquiring the currently captured code phase according to the judgment result; combining the code phase obtained by the next acquisition to obtain the code phase during acquisition, and completing the acquisition of the high dynamic spread spectrum signal;

the counter is used for counting the times of the capturing process; wherein the number of capture processes is greater than or equal to 2.

2. The apparatus according to claim 1, wherein the local oscillator generation module is a carrier generator.

3. The apparatus according to claim 1, wherein the specific decision process of the peak detection module is:

if the maximum value is greater than or equal to the preset threshold value, the acquisition is successful, and the maximum value is taken as the code phase P of the current acquisition₁And the currently captured code phase P is compared₁Sending the data to a data processing module;

if the maximum value is less than the preset threshold value, the capture fails.

4. The apparatus according to claim 3, wherein the data processing module comprises:

according to the currently captured code phase P₁(ii) a And combining the code phase P obtained by the next acquisition₂Calculating the code phase difference P obtained by two adjacent captures₂-P₁The code phase P at the time of acquisition is obtained as the acquisition time for acquiring a highly dynamic spread spectrum signal_initial＝P₁-(P₂-P₁) And as an initial phase value during acquisition, the acquisition of the high dynamic spread spectrum signal is completed.

5. A highly dynamic spread spectrum signal acquisition method, which is implemented based on the highly dynamic spread spectrum signal acquisition apparatus of any one of claims 1 to 5, the method comprising:

acquiring a captured first captured pseudo code phase through first capturing;

acquiring a captured second captured pseudo code phase through second capturing;

calculating the code phase difference of a first acquisition pseudo code phase and a second acquisition pseudo code phase obtained by two times of acquisition;

and acquiring a code phase during acquisition according to the code phase difference, and realizing acquisition of the high-dynamic spread spectrum signal.

6. The method according to claim 5, wherein the first acquisition is performed to obtain a first acquired pseudo code phase; the specific process comprises the following steps:

the PRN code generator changes the frequency value of the local pseudo code according to the search frequency value, outputs the local pseudo code with the changed frequency value and outputs the local pseudo code to the first FFT module;

the first FFT module is used for carrying out FFT transformation on the local pseudo code with the changed frequency value, transforming the local pseudo code with the changed frequency value into a frequency domain to obtain frequency domain data, and taking complex conjugate of the frequency domain data to output first input data;

the second FFT module integrates the first input pseudo code data and the second input pseudo code data to obtain integrated input pseudo code data, and carries out FFT operation on the integrated input pseudo code data to obtain a first input data frequency domain;

the third complex multiplier performs complex multiplication operation on the first input data and the first input data in frequency domain to obtain second input data;

the IFFT module performs IFFT transformation on the second input data to obtain first time domain data, and performs absolute value solving processing on each data in the first time domain data to obtain a plurality of first time domain values and further obtain a plurality of moduli;

the peak detection module selects the maximum value from the obtained multiple moduli and carries out peak detection judgment on the maximum value;

if the maximum value is greater than or equal to a preset threshold value, the acquisition is successful, and the maximum value is used as a first acquisition code phase;

if the maximum value is less than the preset threshold value, the capture fails.

7. The method for acquiring a high dynamic spread spectrum signal according to claim 6, wherein the obtaining of the second input data frequency domain specifically comprises:

a local oscillator generating module generates sin data and cos data;

the first complex multiplier performs complex multiplication operation on the input pseudo code and sin data to obtain first input pseudo code data;

the second complex multiplier performs complex multiplication operation on the input pseudo code and cos data to obtain second input pseudo code data;

and the second FFT module integrates the first input pseudo code data and the second input pseudo code data to obtain integrated input pseudo code data, and performs FFT operation on the integrated input pseudo code data to obtain a first input data frequency domain.

8. The method according to claim 5, wherein the second acquisition is performed to obtain a second acquired pseudo code phase; the specific process comprises the following steps:

the PRN code generator changes the frequency value of the local pseudo code according to the search frequency value, outputs the local pseudo code with the changed frequency value and outputs the local pseudo code to the first FFT module;

the first FFT module is used for carrying out FFT transformation on the local pseudo code with the changed frequency value, transforming the local pseudo code with the changed frequency value into frequency domain data, taking the complex conjugate of the frequency domain data and outputting first input data;

the second FFT module integrates the third input pseudo code data and the fourth input pseudo code data to obtain integrated input pseudo code data, and carries out FFT operation on the integrated input pseudo code data to obtain a second input data frequency domain;

the third complex multiplier performs complex multiplication operation on the first input data and the second input data in frequency domain to obtain third input data;

the IFFT module performs IFFT conversion on the third input data to obtain second time domain data, and performs absolute value solving processing on each data in the second time domain data to obtain a plurality of second time domain values so as to obtain a plurality of moduli;

the peak detection module selects the maximum value from the obtained multiple moduli and carries out peak detection judgment on the maximum value;

if the maximum value is greater than or equal to a preset threshold value, the acquisition is successful, and the maximum value is used as a second acquisition code phase;

if the maximum value is less than the preset threshold value, the capture fails.

9. The method for capturing highly dynamic spread spectrum signal according to claim 5, wherein the code phase at the time of capturing is obtained according to the code phase difference, thereby capturing the highly dynamic spread spectrum signal; the specific process comprises the following steps:

the data processing module acquires a first capture code phase P according to a judgment result₁(ii) a And combining the second acquisition code phase P₂Calculating the code phase difference P obtained by two adjacent captures₂-P₁The code phase P at the time of acquisition is obtained as the acquisition time for acquiring a highly dynamic spread spectrum signal_initial＝P₁-(P₂-P₁) And as an initial phase value during acquisition, the acquisition of the high dynamic spread signal is completed.

Technical Field

The invention belongs to the technical field of high-dynamic spread spectrum signal capture of equipment on a spacecraft, and particularly relates to a high-dynamic spread spectrum signal capture device and a capture method.

Background

Due to the high-speed movement of the flight carrier, the navigation signal received by the navigation receiver on the spacecraft usually has a large doppler shift, and the large doppler shift causes the following problems for the high dynamic spread spectrum signal acquisition:

the first problem is that: a large doppler shift increases the doppler search range in spread spectrum signal acquisition, increasing acquisition time. The longer acquisition time causes code phase drift of the acquired code phase, and the acquired pseudo code phase time is not the same as the pseudo code phase output time.

The code phase drift means that, in the acquisition process, the acquired time and the result output time are time-difference, and a large doppler needs to consume more time in the search, while in the acquisition process, the acquisition code phase is always searched backwards, that is, the code phase is always changed, and we approximate the result output time to the acquisition time under the condition of low dynamic. In the case of high dynamics, the acquisition time is long and cannot be approximated to be equal, and therefore, the code phase of the acquired time and the code phase of the resultant output time are different.

The second problem is that: the doppler shift also causes a change in the pseudo code rate of the received signal. In the acquisition process of the navigation signal, the speed difference between the local pseudo code and the input pseudo code is large, and the acquisition result is influenced.

In the acquisition process, due to the influence of large Doppler, the input pseudo code has large Doppler, so that the code element carried by the input pseudo code is elongated or compressed, the length of the code element is changed, and the width of the code element of the local pseudo code is unchanged. The optimal acquisition scheme is that the rates of the input pseudo code and the local pseudo code are consistent, and the code element widths are equal. Therefore, if the input pseudo code rate and the local pseudo code rate have a large difference due to a large doppler effect, it is difficult to obtain an accurate acquisition result.

The existing method for solving the problem of high dynamic spread spectrum signal capture mainly comprises a PMF-FFT (Partial Matched Filters-Fast Fourier Transform) method, but the method has the problems of more consumed resources and long capture time.

Disclosure of Invention

In order to solve the defects in the prior art, the invention provides a high dynamic spread spectrum signal capturing device, which solves the problems of pseudo code phase drift and inconsistent speed of local pseudo codes and input pseudo codes in high dynamic spread spectrum signal capturing; the device includes: the system comprises an FPGA chip, and a frequency search controller, a PRN code generator, a local oscillator generation module, a first FFT module, a second FFT module, a first complex multiplier, a second complex multiplier, a third complex multiplier, an IFFT module, a peak detection module, a data processing module and a counter which are arranged on the FPGA chip;

the frequency search controller is used for generating a search frequency value in real time and outputting the search frequency value to the PRN code generator;

the PRN code generator is used for changing the frequency value of the local pseudo code according to the search frequency value, outputting the local pseudo code with the changed frequency value and outputting the local pseudo code to the first FFT module; the local pseudo code after the frequency value is changed is a pseudo code sequence which comprises a plurality of pseudo codes;

the first FFT module is used for carrying out FFT transformation on the local pseudo code with the changed frequency value, transforming the local pseudo code with the changed frequency value to a frequency domain to obtain frequency domain data, taking the complex conjugate of the frequency domain data, outputting first input data and outputting the first input data to a third complex multiplier;

the local oscillator generating module is used for generating sin data and cos data and outputting the sin data to the first complex multiplier; outputting cos data to a second complex multiplier;

the first complex multiplier is used for performing complex multiplication operation on the first input pseudo code and the sin data to obtain first input pseudo code data and outputting the first input pseudo code data to the second FFT module;

the second complex multiplier is used for carrying out complex multiplication operation on the first input pseudo code and cos data to obtain second input pseudo code data and outputting the second input pseudo code data to the second FFT module;

the second FFT module is used for integrating the first input pseudo code data and the second input pseudo code data to obtain integrated input pseudo code data, and carrying out FFT operation on the integrated input pseudo code data to obtain a second input data frequency domain and outputting the second input data frequency domain to a third complex multiplier;

the third complex multiplier is used for performing complex multiplication operation on the frequency domains of the first input data and the second input data to obtain third input data and outputting the third input data to the IFFT module;

the IFFT module is used for carrying out IFFT transformation on the third input data to obtain time domain data, carrying out absolute value solving processing on each data in the time domain data to obtain a plurality of time domain values, and further obtaining a plurality of moduli and outputting the moduli to the peak value detection module;

the peak detection module is used for selecting the maximum value from the plurality of moduli, carrying out peak detection judgment on the maximum value and outputting the judgment result to the data processing module;

the data processing module is used for acquiring the currently captured code phase according to the judgment result; combining the code phase obtained by the next acquisition to obtain the code phase during acquisition, and completing the acquisition of the high dynamic spread spectrum signal;

the counter is used for counting the times of the capturing process; wherein the number of capture processes is greater than or equal to 2.

As an improvement of the above technical solution, the local oscillator generation module is a carrier generator.

As an improvement of the above technical solution, a specific decision process of the peak detection module is as follows:

if the maximum value is greater than or equal to the preset threshold value, the acquisition is successful, and the maximum value is taken as the code phase P of the current acquisition₁And the currently captured code phase P is compared₁Sending the data to a data processing module;

if the maximum value is less than the preset threshold value, the capture fails.

As one improvement of the above technical solution, the specific process of the data processing module is as follows:

according to the currently captured code phase P₁(ii) a And combining the code phase P obtained by the next acquisition₂Calculating the code phase difference P obtained by two adjacent captures₂-P₁To doTo capture the acquisition time of a highly dynamic spread spectrum signal, the code phase P at the time of acquisition is obtained_initial＝P₁-(P₂-P₁) And as an initial phase value during acquisition, the acquisition of the high dynamic spread spectrum signal is completed.

The invention also provides a high dynamic spread spectrum signal capturing method, which comprises the following steps:

acquiring a captured first captured pseudo code phase through first capturing;

acquiring a captured second captured pseudo code phase through second capturing;

calculating the code phase difference of a first acquisition pseudo code phase and a second acquisition pseudo code phase obtained by two times of acquisition;

and acquiring a code phase during acquisition according to the code phase difference, and realizing acquisition of the high-dynamic spread spectrum signal.

As an improvement of the above technical solution, the first captured pseudo code phase is obtained by first capturing; the specific process comprises the following steps:

the PRN code generator changes the frequency value of the local pseudo code according to the search frequency value, outputs the local pseudo code with the changed frequency value and outputs the local pseudo code to the first FFT module;

the first FFT module is used for carrying out FFT transformation on the local pseudo code with the changed frequency value, transforming the local pseudo code with the changed frequency value into a frequency domain to obtain frequency domain data, and taking complex conjugate of the frequency domain data to output first input data;

the second FFT module integrates the first input pseudo code data and the second input pseudo code data to obtain integrated input pseudo code data, and carries out FFT operation on the integrated input pseudo code data to obtain a first input data frequency domain;

the third complex multiplier performs complex multiplication operation on the first input data and the first input data in frequency domain to obtain second input data;

the IFFT module performs IFFT transformation on the second input data to obtain first time domain data, and performs absolute value solving processing on each data in the first time domain data to obtain a plurality of first time domain values and further obtain a plurality of moduli;

the peak detection module selects the maximum value from the obtained multiple moduli and carries out detection judgment on the maximum value;

if the maximum value is greater than or equal to a preset threshold value, the acquisition is successful, and the maximum value is used as a first acquisition code phase;

if the maximum value is less than the preset threshold value, the capture fails.

As an improvement of the above technical solution, the process of acquiring the frequency domain of the second input data specifically includes:

a local oscillator generating module generates sin data and cos data;

the first complex multiplier performs complex multiplication operation on the input pseudo code and sin data to obtain first input pseudo code data;

the second complex multiplier performs complex multiplication operation on the input pseudo code and cos data to obtain second input pseudo code data;

and the second FFT module integrates the first input pseudo code data and the second input pseudo code data to obtain integrated input pseudo code data, and performs FFT operation on the integrated input pseudo code data to obtain a first input data frequency domain.

As an improvement of the above technical solution, the second captured pseudo code phase is obtained by the second capturing; the specific process comprises the following steps:

the PRN code generator changes the frequency value of the local pseudo code according to the search frequency value, outputs the local pseudo code with the changed frequency value and outputs the local pseudo code to the first FFT module;

the first FFT module is used for carrying out FFT transformation on the local pseudo code with the changed frequency value, transforming the local pseudo code with the changed frequency value into frequency domain data, taking the complex conjugate of the frequency domain data and outputting first input data;

the second FFT module integrates the third input pseudo code data and the fourth input pseudo code data to obtain integrated input pseudo code data, and carries out FFT operation on the integrated input pseudo code data to obtain a second input data frequency domain;

the third complex multiplier performs complex multiplication operation on the first input data and the second input data in frequency domain to obtain third input data;

the IFFT module performs IFFT conversion on the third input data to obtain second time domain data, and performs absolute value solving processing on each data in the second time domain data to obtain a plurality of second time domain values so as to obtain a plurality of moduli;

the peak detection module selects the maximum value from the obtained multiple moduli and carries out peak detection judgment on the maximum value;

if the maximum value is greater than or equal to a preset threshold value, the acquisition is successful, and the maximum value is used as a second acquisition code phase;

if the maximum value is less than the preset threshold value, the capture fails.

As an improvement of the above technical solution, the code phase at the time of acquisition is obtained according to the code phase difference, so as to realize acquisition of a high dynamic spread spectrum signal; the specific process comprises the following steps:

the data processing module acquires a first capture code phase P according to a judgment result₁(ii) a And combining the second acquisition code phase P₂Calculating the code phase difference P obtained by two adjacent captures₂-P₁The code phase P at the time of acquisition is obtained as the acquisition time for acquiring a highly dynamic spread spectrum signal_initial＝P₁-(P₂-P₁) And as an initial phase value during acquisition, the acquisition of the high dynamic spread signal is completed.

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

1. the invention solves the problems that the Doppler search range in the spread spectrum signal capture is enlarged by the large Doppler shift in the spread spectrum signal capture under the high dynamic condition, the capture time is prolonged, the pseudo code rate of the received signal is changed by the Doppler shift, the rate difference between the local pseudo code and the input pseudo code is large in the capture process of the navigation signal, and the capture result is influenced, and the capture of the high dynamic signal is realized by only adopting a secondary capture method on the premise of hardly increasing resources;

2. the method can quickly capture the high-dynamic spread spectrum signal and has short capture time.

Drawings

Fig. 1 is a schematic structural diagram of a high dynamic spread spectrum signal acquisition apparatus of the present invention;

FIG. 2 is a flow chart of modifying a frequency value of local pseudo-codes;

fig. 3 is a two-dimensional search schematic composed of the code phase values and doppler values of fig. 2.

Detailed Description

The invention will now be further described with reference to the accompanying drawings.

As shown in fig. 1, the present invention provides a high dynamic spread spectrum signal acquisition apparatus, which includes: the system comprises an FPGA chip, and a frequency search controller, a PRN code generator, a local oscillator generation module, a first FFT module, a second FFT module, a first complex multiplier, a second complex multiplier, a third complex multiplier, an IFFT module, a peak detection module, a data processing module and a counter which are arranged on the FPGA chip;

the PRN (pseudo random noise) code generator changes the frequency value of the local pseudo code according to the search frequency value, outputs the local pseudo code with the changed frequency value and outputs the local pseudo code to the first FFT module; the local pseudo code after the frequency value is changed is a pseudo code sequence which comprises a plurality of pseudo codes;

the frequency search controller is used for generating a search frequency value in real time and outputting the search frequency value to the PRN code generator; wherein the search frequency value is a frequency range searched in a two-dimensional search process, as shown in fig. 1, generated by a frequency search controller.

The first FFT module is used for carrying out FFT transformation on the local pseudo code x (n) with the frequency value changed and output by the PRN code generator, transforming the local pseudo code x (n) with the frequency value changed to a frequency domain to obtain frequency domain data X (k), taking the complex conjugate of the frequency domain data X (k), and outputting first input data X (k)^*And output to the third complex multiplier;

the local oscillator generating module is a carrier wave generator and is used for generating sin data and cos data and outputting the sin data to the first complex multiplier; outputting cos data to a second complex multiplier;

wherein, the sin data are sine waves with different frequencies; cos data is cosine waves with different frequencies; the sin and cos data are generated using a DDS (direct Digital synthesizer) generator; the DDS generator may be implemented by a program or an IP core.

The first complex multiplier is used for performing complex multiplication operation on the first input pseudo code r (n) and sin data output by the carrier wave generator to obtain first input pseudo code data Q and outputting the first input pseudo code data Q to the second FFT module;

the second complex multiplier is used for carrying out complex multiplication operation on the first input pseudo code r (n) and cos data output by the carrier wave generator to obtain second input pseudo code data I and outputting the second input pseudo code data I to the second FFT module;

the second FFT module is configured to integrate the first input pseudo code data Q and the second input pseudo code data I to obtain integrated input pseudo code data S, and perform FFT operation on the integrated input pseudo code data S to obtain a first input data frequency domain r (k);

the third complex multiplier is used for converting the first input data X (k)^*Performing complex multiplication operation on the first input data frequency domain R (k) to obtain second input data L (k);

the IFFT module is configured to perform IFFT transformation on the second input data l (k) to obtain first time domain data l (n), perform absolute value calculation on each of data l (1), l (2), l (3) … l (n) in the first time domain data l (n), to obtain a plurality of first time domain values | l (1) |, | l (2) |, | l (3) |, … | l (n) |, and further obtain a plurality of moduli | l (1) |²，|l(2)|²，|l(3)|²，…|l(n)|²；

The peak detection module is used for counting a plurality of obtained moduli | l (n)²Selecting the maximum value, and carrying out peak detection judgment on the maximum value;

if the maximum value is greater than or equal to the preset threshold value, the acquisition is successful, and the maximum value is taken as the code phase P of the current acquisition₁；

If the maximum value is smaller than a preset threshold value, the capture fails;

the data processing module is used for acquiring the currently captured code phase P according to the judgment result₁(ii) a And combining the code phase P obtained by the next acquisition₂Calculating the code phase difference P obtained by two adjacent captures₂-P₁The code phase P at the time of acquisition is obtained as the acquisition time for acquiring a highly dynamic spread spectrum signal_initial＝P₁-(P₂-P₁) The initial phase value is used for capturing, and the high dynamic spread spectrum signal is captured;

the counter is used for counting the times of the capturing process; wherein the number of capture processes is greater than or equal to 2.

The invention provides a high dynamic spread spectrum signal capturing method, which comprises the following steps:

obtaining a first captured pseudo code phase P through first capturing₁；

Specifically, the PRN code generator changes the frequency value of the local pseudo code generated by the PRN code generator according to the search frequency value generated in real time, and outputs the local pseudo code x (n) after the frequency value is changed; the local pseudo code x (n) after the frequency value is changed is a pseudo code sequence which comprises a plurality of pseudo codes;

the first FFT module carries out FFT transformation on the local pseudo code x (n) with the frequency value changed and output by the PRN code generator, the local pseudo code x (n) with the frequency value changed is transformed to the frequency domain to obtain frequency domain data X (k), the complex conjugate of the frequency domain data X (k) is taken, and first input data X (k) is output^*；

The second FFT module integrates the first input pseudo code data Q and the second input pseudo code data I to obtain integrated input pseudo code data S, and FFT operation is carried out on the integrated input pseudo code data S to obtain a first input data frequency domain R (k);

specifically, the local oscillator generation module generates sin data and cos data; wherein, the sin data are sine waves with different frequencies; cos data is cosine waves with different frequencies;

the first complex multiplier performs complex multiplication operation on the first input pseudo code r (n) and the sin data to obtain first input pseudo code data Q;

the second complex multiplier performs complex multiplication operation on the first input pseudo code r (n) and cos data to obtain second input pseudo code data I;

and the second FFT module integrates the first input pseudo code data Q and the second input pseudo code data I to obtain integrated input pseudo code data S, and FFT operation is carried out on the integrated input pseudo code data S to obtain a first input data frequency domain R (k).

Said third complex multiplier converts first input data X (k)^*Performing complex multiplication operation on the first input data frequency domain R (k) to obtain second input data L (k);

the IFFT module performs IFFT transformation on the second input data l (k) to obtain first time domain data l (n), and performs absolute value calculation on each of data l (1), l (2), l (3) … l (n) in the first time domain data l (n) to obtain a plurality of first time domain values | l (1) |, | l (2) |, | l (3) |, … | l (n) |, and further obtain a plurality of moduli | l (1) |²，|l(2)|²，|l(3)|²，…|l(n)|²；

The peak detection module performs calculation on the obtained plurality of module squares | l (n) & gtY²Selecting the maximum value, and carrying out peak detection judgment on the maximum value;

if the maximum value is greater than or equal to the preset threshold value, the acquisition is successful, and the maximum value is taken as the first acquisition code phase P₁；

If the maximum value is less than the preset threshold value, the capture fails.

If the first capture is successful, performing a second capture; obtaining a second captured pseudo code phase P through second capturing₂；

Specifically, the PRN code generator changes the frequency value of the local pseudo code generated by the PRN code generator according to the search frequency value generated in real time, and outputs the local pseudo code x (n) after the frequency value is changed; the local pseudo code x (n) after the frequency value is changed is a pseudo code sequence which comprises a plurality of pseudo codes;

the first FFT module modifies the frequency of the PRN code generator outputFFT transform is carried out on the local pseudo code x (n) after the value is changed, the local pseudo code x (n) after the frequency value is changed is transformed to a frequency domain to obtain frequency domain data X (k), the complex conjugate of the frequency domain data X (k) is taken, and first input data X (k) are output^*；

The second FFT module integrates the third input pseudo code data Q 'and the fourth input pseudo code data I' to obtain integrated input pseudo code data S ', and FFT operation is carried out on the integrated input pseudo code data S' to obtain a second input data frequency domain R (k)¹；

Specifically, the local oscillator generation module generates sin data and cos data;

the first complex multiplier inputs the second pseudo code r (n)₁Performing complex multiplication operation with the sin data to obtain first input pseudo code data Q';

the second complex multiplier inputs a second pseudo code r (n)₁Performing complex multiplication operation with cos data to obtain second input pseudo code data I';

the second FFT module integrates the first input pseudo code data Q 'and the second input pseudo code data I' to obtain integrated input pseudo code data S ', and FFT operation is carried out on the integrated input pseudo code data S' to obtain a second input data frequency domain R (k)¹。

The third complex multiplier is used for converting the first input data X (k)^*And a second input data frequency domain R (k)¹Performing complex multiplication to obtain third input data L (k)₁；

The IFFT module is used for inputting third input data L (k)₁IFFT conversion is carried out to obtain a second time domain l (n)₁For the second time domain data, l (n)₁Each data l (1)₁，l(2)₁，l(3)₁…l(n)₁Performing absolute value calculation to obtain multiple second time domain values | l (1) & gtY₁，|l(2)|₁，|l(3)|₁…|l(n)|₁Further, a plurality of module | l (1) & ltY & gt luminance calculation results are obtained₁ ²，|l(2)|₁ ²，|l(3)|₁ ²…|l(n)|₁ ²；

The peak detection module obtains a plurality of module squares l (n)₁|²Selecting from amongThe maximum value is detected and judged;

if the maximum value is greater than or equal to the preset threshold value, the acquisition is successful, and the maximum value is taken as the second acquisition code phase P₂；

If the maximum value is less than the preset threshold value, the capture fails.

Calculating the code phase difference P of the first acquisition pseudo code phase and the second acquisition pseudo code phase obtained by two times of acquisition₂-P₁The code phase difference is code phase drift caused by acquisition time and Doppler frequency offset;

obtaining the code phase P at the time of acquisition according to the code phase difference_initial＝P₁-(P₂-P₁) And the acquisition of a high-dynamic spread spectrum signal is realized.

Specifically, the data processing module obtains a first capture code phase P according to a decision result₁(ii) a And combining the second acquisition code phase P₂Calculating the code phase difference P obtained by two adjacent captures₂-P₁The code phase P at the time of acquisition is obtained as the acquisition time for acquiring a highly dynamic spread spectrum signal_initial＝P₁-(P₂-P₁) And as an initial phase value during acquisition, the acquisition of the high dynamic spread signal is completed.

The method adopts a secondary capture method, can estimate the phase of the captured code, and solves the problem of pseudo code phase drift under the high dynamic condition. The method for updating the local pseudo code according to the search frequency point reduces the speed difference between the local pseudo code and the input pseudo code, as shown in fig. 2, the search controller receives the search frequency value corresponding to the current frequency search unit from the doppler search control, updates the pseudo code frequency word in real time according to the search frequency value, searches the corresponding code table after passing through the phase accumulator, and outputs the local pseudo code with the changed frequency value, so that the pseudo code speed difference between the local pseudo code of the captured signal frequency point and the input pseudo code is not more than 1/2 search steps.

As shown in fig. 2, the frequency value of the local pseudo code generated by the PRN code generator is updated according to the search frequency value corresponding to the search frequency point generated in real time, the difference between the rate of inputting the pseudo code and the rate of the local pseudo code is reduced, and the code phase at the time of accurate capturing is obtained, thereby improving the accuracy of the captured result. The search controller receives a Doppler value corresponding to a current frequency search unit from Doppler control, and the PRN code generator receives a local pseudo code with a changed frequency value sent by the frequency search controller and outputs the local pseudo code with the changed frequency value; and the frequency value corresponding to the changed local pseudo code is the Doppler value corresponding to the current frequency searching unit, the pseudo code frequency word is updated according to the searching frequency point, the corresponding code table is searched after the searching frequency word passes through the phase accumulator, and the local pseudo code of which the frequency value is changed corresponding to the current frequency searching unit is output.

FIG. 3 is a schematic diagram of an overall two-dimensional search process, which is the capture process; the abscissa value is a code phase search range and the ordinate value is a doppler search range, since the code phase and doppler of the input pseudo code are unknown, but it is certain that the input code phase and doppler are within this range. The acquisition process of the spread spectrum signal belongs to two-dimensional search, as shown in fig. 3, when the doppler is the one-dimensional search, a search range-D to + D is set, and the frequency is stepped by D, then the search sequence is 0- + D, -D-0, + D- +2D, -2D-D, and. In each search interval, the frequency of the local pseudo code is set to be the middle value of the search interval. For example: and if the search interval is +3d- +4d, setting the local pseudo code frequency to be +3.5 d. Therefore, when the Doppler interval in which the input pseudo code is located is searched, the Doppler difference between the local pseudo code and the input pseudo code is smaller than 1/2d, and therefore the speed difference between the local pseudo code and the input pseudo code is reduced. The grey squares shown in figure 3 represent the initial position of the capture process; starting from the initial position, searching each Doppler value and the corresponding code phase one by one so as to acquire the code phase during acquisition.

Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and are not limited. Although the present invention has been described in detail with reference to the embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the spirit and scope of the invention as defined in the appended claims.