Method, system and storage medium for capturing CDMA signals

Abstract

The present application discloses a capture method, system and storage medium for CDMA signals, and relates to the field of signal processing technology. The above method includes: respectively delaying the conjugate multiplication to process the signal to be processed and the local code to obtain the conjugated signal and the conjugated local code; based on the sliding window algorithm, coherently integrating the signal segment of the conjugated signal selected by the integration window and the conjugated local code in the conjugated signal to obtain multiple integration results; determining the peak-to-average ratio of the corresponding signal segments of the multiple integration results in the signal to be processed, and when the peak-to-average ratio is greater than the first preset peak-to-average ratio threshold, selecting the position of the maximum integration result in the signal to be processed from the multiple integration results as the secondary processing data position; traversing and searching the secondary processing data segment according to the preset frequency search window to capture the peak signal of the secondary processing data segment. The above method can reduce the resource consumption of low-orbit satellite CDMA signal capture while ensuring the capture effect.

Description

Technical Field

[0001] The present application relates to the field of signal processing technology, and in particular to a method and system for capturing CDMA signals and a storage medium thereof. Background Art

[0002] With the advent of the era of integrated low-orbit satellite communications and navigation, the integrated navigation and communication signals broadcast by LEO satellites present new challenges for baseband signal processing. Satellite communication signals often utilize signal schemes such as TDMA or OFDM, while navigation signals, due to ranging requirements, generally employ code division multiple access (CDMA) spread spectrum. When the navigation signal reaches the ground receiver, for example, the Beidou B3I satellite, the signal level is around -127dBm, drowning in noise and significantly lower in power than the communication signal. The navigation and ranging CDMA signals used in integrated communication and navigation, which utilize covert bursts, are likely to be interfered with or impacted by communication signals during ground signal detection. Furthermore, LEO satellites, located only a few hundred kilometers above the ground, experience high relative motion and short visibility times. The signals they broadcast are highly dynamic, bursty, and short-lived for users. Due to the low signal-to-noise ratio of navigation signals and interference from communication signals, direct capture using methods similar to communication signal power detection is difficult. Furthermore, traditional signal acquisition methods typically require continuous storage of multiple full cycles of data until the target signal is detected, which consumes significant resources. Therefore, how to achieve effective CDMA signal capture while reducing resource consumption in the capture process is a technical problem that needs to be solved at present. Summary of the Invention

[0003] The purpose of the embodiments of the present application is to provide a method for capturing CDMA signals, so as to solve the technical problem in the prior art of how to achieve effective CDMA signal capture while reducing resource consumption in the capture process.

[0004] In order to achieve the above-mentioned object, the present application provides a first aspect of a method for capturing a CDMA signal, comprising:

[0005] Get the signal to be processed and the local code;

[0006] Delaying the conjugate multiplication of the signal to be processed and the local code respectively to obtain a conjugated signal and a conjugated local code;

[0007] An integration window is slid within the conjugated signal based on a sliding window algorithm, and a signal segment of the conjugated signal selected by the integration window is coherently integrated with the conjugated local code to obtain multiple integration results;

[0008] determining peak-to-average ratios of corresponding signal segments of the plurality of integration results in the signal to be processed, and selecting, when the peak-to-average ratio is greater than a first preset peak-to-average ratio threshold, a position of a maximum integration result among the plurality of integration results in the signal to be processed as a secondary processing data position;

[0009] The secondary processed data segment of the signal to be processed is determined according to the secondary processed data position, and the secondary processed data segment is traversed and searched according to a preset frequency search window to capture the peak signal of the secondary processed data segment.

[0010] In an embodiment of the present application, a sliding integration window is performed within the conjugated signal based on a sliding window algorithm, and a signal segment of the conjugated signal selected by the integration window is coherently integrated with the conjugated local code to obtain multiple integration results, including:

[0011] Determine the signal segment selected by the integration window within the conjugated signal;

[0012] Coherently integrating the signal segments and the conjugated local code to obtain an integration result;

[0013] An integration window is slid within the conjugated signal based on a preset step size of a sliding window algorithm to determine the signal segment selected after each sliding of the integration window, and the signal segment selected after sliding and the conjugated local code are coherently integrated to obtain multiple sliding integration results, wherein the number of sliding times of the integration window in the process of obtaining multiple sliding integration results is greater than or equal to the code period length of the signal to be processed.

[0014] In the embodiment of the present application, when the CDMA signal is a continuous signal, the number of sliding times of the integration window is equal to the code period length of the signal to be processed.

[0015] In the embodiment of the present application, when the CDMA signal is a burst CDMA signal, the number of sliding times of the integration window is greater than or equal to the sum of the code period length of the signal to be processed and the burst signal frame interval length.

[0016] In an embodiment of the present application, the length of the integration window is greater than or equal to the code period length of the signal to be processed.

[0017] In the embodiment of the present application, the length of the integration window is an integer multiple of the code period length.

[0018] In an embodiment of the present application, determining peak-to-average ratios of corresponding signal segments of a plurality of integration results in a signal to be processed, and selecting a position of a maximum integration result in the signal to be processed as a secondary processing data position among the plurality of integration results when the peak-to-average ratio is greater than a first preset peak-to-average ratio threshold includes:

[0019] Determining the signal segment to be processed in the signal to be processed according to the position of the signal segment corresponding to the integration result in the conjugated signal;

[0020] determining a signal mean value based on the signal segments to be processed of the plurality of integration results;

[0021] Determine a signal peak value of the signal segment to be processed corresponding to the maximum integration result among the multiple integration results;

[0022] The peak-to-average ratio of the corresponding signal segment is determined according to the signal peak value and the signal mean value, and when the peak-to-average ratio is greater than the first preset peak-to-average ratio threshold, the position of the maximum integration result among multiple integration results in the signal to be processed is selected as the secondary processing data position.

[0023] In an embodiment of the present application, determining a secondary processed data segment of a signal to be processed according to a position of the secondary processed data, and performing a traversal search on the secondary processed data segment according to a preset frequency search window to capture a peak signal of the secondary processed data segment includes:

[0024] Determine the secondary processing data center segment of the signal to be processed according to the secondary processing data position;

[0025] Determine the signal protection segment before and after the secondary processing data center segment of the signal to be processed according to the preset signal protection segment length;

[0026] Determine the secondary processing data segment according to the signal protection segment and the secondary processing data segment;

[0027] The secondary processed data segment is traversed and searched according to a preset frequency search window to capture the peak signal of the secondary processed data segment.

[0028] In the embodiment of the present application, the magnitude of the preset frequency search window is greater than 10 to the first power.

[0029] In an embodiment of the present application, determining a secondary processed data segment of a signal to be processed according to a position of the secondary processed data, and performing a traversal search on the secondary processed data segment according to a preset frequency search window to capture a peak signal of the secondary processed data segment includes:

[0030] Determine the secondary processing data segment of the signal to be processed according to the secondary processing data position, and perform a traversal search on the secondary processing data segment according to a preset frequency search window to obtain a peak signal of the secondary processing data segment;

[0031] When the peak-to-average ratio of the peak signal is greater than a second preset peak-to-average ratio threshold, the peak signal is captured.

[0032] A second aspect of the present application provides a system for capturing CDMA signals, the system including a processor configured to call instructions from a memory and implement the method for capturing CDMA signals provided in the first aspect of the present application when executing the instructions.

[0033] A third aspect of the present application provides a machine-readable storage medium having instructions stored thereon, the instructions being used to enable a machine to execute the method for capturing a CDMA signal provided in accordance with the first aspect of the present application.

[0034] The above technical solution uses a sliding window algorithm to perform sliding window on the conjugated signal obtained by delayed conjugation processing, and performs coherent integration processing on the signal segment and the conjugated local code within the window, so as to determine the position of the secondary processed data in the signal to be processed according to the maximum integration result among multiple integration results to obtain the secondary processed data segment, and use the position and code phase of the secondary processed data segment as the more accurate CDMA signal broadcast position and code phase, and then perform a time-frequency parallel two-dimensional search on the secondary processed data segment through traversal search, so as to achieve low-latency, low computational complexity and low resource consumption capture of low-orbit satellite CDMA signals while ensuring the capture effect.

[0035] Other features and advantages of the embodiments of the present application will be described in detail in the subsequent detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The accompanying drawings are used to provide a further understanding of the embodiments of the present application and constitute a part of the specification. Together with the following detailed description, they are used to explain the embodiments of the present application but do not constitute a limitation on the embodiments of the present application. In the accompanying drawings:

[0037] Figure 1 The following schematically shows a flow chart of a method for capturing a CDMA signal according to an embodiment of the present application;

[0038] Figure 2 The following schematically shows a flow chart of another method for capturing a CDMA signal according to an embodiment of the present application;

[0039] Figure 3 The schematic diagram schematically shows a principle diagram of a system for capturing CDMA signals according to an embodiment of the present application. DETAILED DESCRIPTION

[0040] To make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. It should be understood that the specific implementation methods described herein are only used to illustrate and explain the embodiments of the present application and are not used to limit the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0041] It should be noted that the acquisition, transmission, storage, use, and processing of data in the technical solution of this application are in compliance with the relevant provisions of laws and regulations. In the embodiments of this application, certain software, components, models, and other existing solutions in the industry may be mentioned. These should be considered as exemplary. Their purpose is only to illustrate the feasibility of implementing the technical solution of this application, but it does not mean that the applicant has or will necessarily use such solutions.

[0042] It should be noted that if there are descriptions involving "first", "second", etc. in the embodiments of this application, the descriptions of "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of such features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in this field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by this application.

[0043] Signals broadcast by low-orbit satellites have a short visible time and very large Doppler dynamics, often requiring a frequency search range of ±100 kHz. Traditional CDMA signal capture methods are time-consuming when the signal's appearance time is unknown (burst) or the code rate is high. Therefore, embodiments of the present application provide a method for capturing CDMA signals. This method uses delayed differencing to perform a phase search to reduce CDMA code phase ambiguity, even when the CDMA signal has large Doppler dynamics, the start position of the signal burst is unknown, and there is significant background noise and interference. A phase and frequency traversal search is then performed, significantly reducing the overall computational complexity required to capture CDMA signals with large frequency ambiguity while ensuring capture effectiveness.

[0044] Figure 1 The following schematically shows a flow chart of a method for capturing a CDMA signal according to an embodiment of the present application. Figure 1 As shown, an embodiment of the present application provides a method for capturing a CDMA signal, which may include the following steps:

[0045] S102, obtaining a signal to be processed and a local code;

[0046] S104, performing delayed conjugate multiplication on the signal to be processed and the local code to obtain a conjugated signal and a conjugated local code;

[0047] S106, sliding an integration window within the conjugated signal based on a sliding window algorithm, and coherently integrating a signal segment of the conjugated signal selected by the integration window with the conjugated local code to obtain a plurality of integration results;

[0048] S108, determining peak-to-average ratios of corresponding signal segments of the plurality of integration results in the signal to be processed, and if the peak-to-average ratio is greater than a first preset peak-to-average ratio threshold, selecting a position of a maximum integration result among the plurality of integration results in the signal to be processed as a secondary processing data position;

[0049] S110 , determining a secondary processed data segment of the signal to be processed according to the secondary processed data position, and performing a traversal search on the secondary processed data segment according to a preset frequency search window to capture a peak signal of the secondary processed data segment.

[0050] The capture method for CMDA signals provided in an embodiment of the present application performs sliding window on the conjugated signal obtained by delayed conjugation processing through a sliding window algorithm, and performs coherent integration processing on the signal segment and the conjugated local code within the window. Since the integration results of the signal segment and the conjugated local code after delayed conjugation processing are insensitive to Doppler and are only affected by the local code phase, and the detection gain of the integration result is high, it can resist noise and possible interference signals. Therefore, the position of the secondary processed data in the signal to be processed is determined according to the maximum integration result among multiple integration results to obtain the secondary processed data segment, and the position and code phase of the secondary processed data segment are used as the more accurate CDMA signal broadcast position and code phase. Then, a time-frequency parallel two-dimensional search is performed on the secondary processed data segment through traversal search, so as to achieve low-latency, low-computational, and low-resource-consuming capture of low-orbit satellite CDMA signals while ensuring the capture effect.

[0051] It can be understood that the signal to be processed in step S102 may be, for example, an intermediate frequency signal, and the local code may be, for example, a locally generated pseudo-random code.

[0052] Specifically, obtaining the signal to be processed in step S102 may include:

[0053] Obtain intermediate frequency signal data;

[0054] The signal to be processed is obtained through clock domain conversion and downsampling processing.

[0055] Specifically, step S104 may include:

[0056] Determine the number of delayed chips;

[0057] Determining the delayed conjugate terms of the signal to be processed and the local code according to the number of delayed code chips;

[0058] Determining a conjugated signal according to the signal to be processed and its delayed conjugate term;

[0059] The conjugated local code is determined according to the local code and its delayed conjugate term.

[0060] It can be understood that the optimal value of the number of delayed chips can be determined through simulation based on signal characteristics.

[0061] As an example, step S104 may include:

[0062] Determine whether the number of delayed chips is 0.5 chip or 1 chip;

[0063] Determining a delayed conjugate term conj[X(n+d)] of the signal to be processed X(n) and a delayed conjugate term conj[C(n+d)] of the local code C(n) according to the number of delayed chips;

[0064] According to the signal to be processed X(n) and its delayed conjugate term conj[X(n+d)], the conjugated signal is determined to be X1(n) = X(n)*conj[X(n+d)];

[0065] According to the local code C(n) and its delayed conjugate term conj[C(n+d)], the conjugated local code is determined to be C1(n)=C(n)*conj[C(n+d)], where d is the number of delayed code chips.

[0066] like Figure 2 As shown, in some embodiments of the present application, step S106 may include:

[0067] S202, determining a signal segment selected by the integration window in the conjugated signal;

[0068] S204, coherently integrating the signal segment and the conjugated local code to obtain an integration result;

[0069] S206. Slide the integration window within the conjugated signal based on the preset step size of the sliding window algorithm to determine the signal segment selected after each sliding of the integration window, and coherently integrate the selected signal segment and the conjugated local code to obtain multiple sliding integration results, wherein the number of sliding times of the integration window in the process of obtaining the multiple sliding integration results is greater than or equal to the code period length of the signal to be processed.

[0070] Based on the above steps, multiple integration results can be obtained, and the number of sliding times of the integration window is greater than or equal to the code period length of the signal to be processed, so that the number of multiple integration results is greater than or equal to the number of code bits included in a code period, and the signal segments of multiple integration results can cover a complete code period, thereby ensuring that among the multiple integration results, there is at least one integration result whose signal segment can correspond to a signal peak value including a code period.

[0071] It is understood that the signal segment and the conjugated local code may be discrete quantities, for example. The coherent integration processing of the signal segment and the conjugated local code may be, for example, the sum of each sampling point of the signal segment and each sampling point of the local code. The code period length may be, for example, the number of chips within one code period.

[0072] Specifically, coherently integrating the signal segments and the conjugated local code to obtain an integration result may include:

[0073] Coherently integrate the M sampling points of the signal segment and the M sampling points of the conjugated local code to obtain the integration result Rxc= , where M is the integration window length, and the number of sampling points corresponds to the integration window length setting.

[0074] In some embodiments of the present application, when the CDMA signal is a continuous signal, the number of sliding times of the integration window is equal to the code period length of the signal to be processed.

[0075] When the CDMA signal is a continuous signal, the CDMA signal to be captured appears continuously in the signal to be processed. Therefore, setting the sliding times of the integration window to the code period length of the signal to be processed can make multiple integration results include a signal peak.

[0076] In other embodiments of the present application, when the CDMA signal is a burst CDMA signal, the number of sliding times of the integration window is greater than or equal to the sum of the code period length of the signal to be processed and the burst signal frame interval length.

[0077] In the case of a burst CDMA signal, the CDMA signals that need to be captured in the signal to be processed do not appear continuously, and there may be a certain burst signal frame interval between two adjacent CDMA signals. Therefore, the number of sliding times of the integration window is set to be greater than or equal to the sum of the code period of the signal to be processed and the burst signal frame interval, so that the process of executing the sliding window algorithm in step S106 to obtain multiple integration results can ensure that the multiple integrated signal segments can cover the signal peak.

[0078] In some embodiments of the present application, the length of the integration window is greater than or equal to the length of the code period of the signal to be processed.

[0079] The length of the integration window directly determines the number of sampling points in the coherent integration, that is, the size of the coherent integration points. Furthermore, a larger integration window increases the detection confidence of the secondary processing data segment, while a smaller integration window increases the signal acquisition speed. Therefore, by setting the integration window length to be greater than or equal to the code period length of the signal to be processed, the signal segment selected by the integration window can be guaranteed to include the signal peak and detection confidence, while maintaining a reasonable signal acquisition speed.

[0080] In some embodiments of the present application, the length of the integration window is an integer multiple of the length of the code period.

[0081] Since the code period length can be, for example, D = (sampling rate / code rate) * number of codes in one period, the code rate and number of codes in one period can be considered predetermined properties of the CDMA signal to be captured, and the code period length varies positively with the sampling rate. The sampling rate is generally an integer multiple of the code rate, so the integration window length is set to an integer multiple of the code period length. This improves detection confidence while coherently integrating the chips within a complete code period.

[0082] In some embodiments of the present application, step S108 may include:

[0083] Determining the signal segment to be processed in the signal to be processed according to the position of the signal segment corresponding to the integration result in the conjugated signal;

[0084] determining a signal mean value based on the signal segments to be processed of the plurality of integration results;

[0085] Determine a signal peak value of the signal segment to be processed corresponding to the maximum integration result among the multiple integration results;

[0086] The peak-to-average ratio of the corresponding signal segment is determined according to the signal peak value and the signal mean value, and when the peak-to-average ratio is greater than the first preset peak-to-average ratio threshold, the position of the maximum integration result among multiple integration results in the signal to be processed is selected as the secondary processing data position.

[0087] In some embodiments of the present application, if the peak-to-average ratio of the corresponding signal segment is greater than a first preset peak-to-average ratio threshold, step S106 may be stopped to reduce power consumption.

[0088] In some embodiments of the present application, step S110 may include:

[0089] Determine the secondary processing data center segment of the signal to be processed according to the secondary processing data position;

[0090] Determine the signal protection segment before and after the secondary processing data center segment of the signal to be processed according to the preset signal protection segment length;

[0091] Determine the secondary processing data segment according to the signal protection segment and the secondary processing data segment;

[0092] The secondary processed data segment is traversed and searched according to a preset frequency search window to capture the peak signal of the secondary processed data segment.

[0093] The signal protection segment setting can deal with the problem that the peak signal slides out of the sliding window search range due to signal Doppler or crystal oscillator frequency offset during long-term search.

[0094] In some embodiments of the present application, the order of magnitude of the preset frequency search window is greater than 10 to the first power.

[0095] For CDMA signals broadcast by low-orbit satellites, the Doppler frequency deviation often reaches ±50 to ±100 kHz, requiring 10 to 20 frequency search windows. In this case, the computational complexity of the CDMA signal capture method provided in the embodiments of the present application is (multiple coherent integrations of the sliding integration window) + (coherent integrations equal to the number of chips in the preset signal protection segment length) * (number of frequency search windows), while the computational complexity required by existing capture methods is (coherent integrations equal to the number of chips in a code period) * (number of frequency search windows). This shows that as the Doppler frequency deviation increases and the number of frequency search windows increases, the computational complexity reduction advantage of the CDMA signal capture method provided in the embodiments of the present application becomes more pronounced, significantly improving CDMA signal capture efficiency.

[0096] In some embodiments of the present application, step S110 may include:

[0097] Determine the secondary processing data segment of the signal to be processed according to the secondary processing data position, and perform a traversal search on the secondary processing data segment according to a preset frequency search window to obtain a peak signal of the secondary processing data segment;

[0098] When the peak-to-average ratio of the peak signal is greater than a second preset peak-to-average ratio threshold, the peak signal is captured.

[0099] It can be understood that the traversal search performed on the secondary processed data segment may be, for example, time domain mixing and sliding correlation traversal search, or matched filtering and fast Fourier transform traversal search, etc.

[0100] In other embodiments of the present application, when the peak-to-average ratio of the corresponding signal segment is greater than the first preset peak-to-average ratio threshold, step S106 can be continued to find the next target phase that can pass the first preset peak-to-average ratio threshold, so that when the peak-to-average ratio of the peak signal is less than or equal to the second preset peak-to-average ratio threshold, step S108 can be quickly entered to start a new time-frequency traversal search, thereby speeding up the search speed under weak signals.

[0101] For the purpose of ease of understanding, the following Figure 3 The following is an exemplary description of the method for capturing CDMA signals provided in an embodiment of the present application:

[0102] In this design and application example of a capture accelerator in the baseband of a low-orbit communication and navigation prototype, the code rate of the target burst CDMA signal is fc = 1.023 MHz, the code period length L is 1023, and the phase search length, i.e., the number of sliding windows, is set to N = L, traversing all phases. The coherent integration length, i.e., the sliding window length, is 2 code periods, and the non-coherent integration length is 1. Based on a sampling point accuracy of 0.5 code chips, the number of integration points per time is M = 2 * L / 0.5 = 4092 points. The receiver frequency search range is not less than ± 60 kHz, and the accelerator FPGA operating clock clk = 100 MHz. The specific design and implementation process is as follows:

[0103] (1) Preprocessing: The real-time burst communication integrated intermediate frequency signal data is input into the receiver capture engine. After preprocessing such as clock domain conversion and downsampling, the real-time original signal to be captured X(n) with a 0.5 chip accuracy is obtained, and the signal rate is 2*fc=2.046MHz;

[0104] (2) In step S1, X(n) and C(n) are delayed by one chip and then conjugate-multiplied with the pre-delayed X(n) and C(n). X(n) then enters the data synchronization unit in step S5.

[0105] (3) Step S2, in this example, is implemented using RAM. The receiver software writes the CDMA spread spectrum PRN Gold code of the current target satellite signal into RAM via the AXI bus.

[0106] (4) Step S3: The sampling point slides into the integrator. After sliding into M = 4092 points continuously, the integration result of the first phase point is sent out. , where since the coherent integration length is 2 code periods, the integrator reads C1 in RAM twice in a loop; a complete phase search process ends after the integration result Rxc(2046) at the N=2046th phase point comes out;

[0107] (5) Step S3: In a specific embodiment, considering that there are N phases to be searched, the hardware design can use a 16-way parallel correlator corr_16 to accelerate the calculation. Alternatively, the most suitable number of parallel correlators can be selected based on the system's requirements for capture speed, hardware operating frequency, code rate, integration length, etc.

[0108] (6) Step S4 calculates the approximate mean value of each Rxc obtained in step S3 by cumulative averaging, which is used as the noise floor NOISE_A of the coherent integration; at the same time, the peak value Peak of the maximum integration result is retained, and the phase index position peakPhase is recorded. After N=2046 Rxc are accumulated in step S3, the peak-to-average ratio PAR=Peak / NOISE_A is obtained, and the PAR is compared with the threshold A of the decision device 1. The threshold A is verified by simulation and is set to 8. Here, as one of the preferred solutions, the PAR calculation can be started in advance to judge the peak-to-average ratio to speed up the search process, and it is not necessary to wait until all 2046 phases are calculated;

[0109] (7) Step S5: In a specific embodiment, the data synchronization unit stores the signal to be processed X(n) in real time, with a storage depth of 1.5*L / 0.5=3069 points, ensuring that the buffered data contains the peakPhase phase, and peakPhase is a value in the range of 0 to N-1;

[0110] (8) Step S6. In a specific embodiment, the integral controller processes the results of the decision maker 1 and the decision maker 2 to control the integration process. Only when the decision maker 1 detects successfully does the process proceed to step S7; otherwise, steps S1 to S6 are repeated. If the decision maker 1 detects successfully, the data synchronization unit in step S5 is controlled to read X(n) from a specific location in the storage buffer and pass it to step S7. If the decision maker 2 detects successfully, the capture is terminated. Otherwise, if the decision maker 1 detects unsuccessfully, steps S1 to S6 are repeated.

[0111] (9) Step S6: In a specific embodiment, after the decision maker 1 successfully detects, the integral controller reads the X(n) signal from the peakPhase position in the data synchronization unit cache, advances it by 4 phases, and sends it to S7. A protection segment of 4 phases is reserved before and after the peakPhase to cope with the code phase slip caused by the large Doppler of the low-orbit satellite.

[0112] (10) Step S7: In a specific embodiment, after the decision maker 1 detects successfully, the sliding integral calculation process is stopped, thereby reducing system power consumption; thus, the 16-way parallel correlator in S3 can be reused in S7;

[0113] (11) Step S7: In a specific embodiment, the data X(n) extracted from the data synchronization unit is subjected to a time-frequency traversal search using a typical partial matched filter and fast Fourier transform (PMF-FFT) algorithm. However, in the present invention, since the phase ambiguity of the signal has been significantly reduced, only four phases need to be traversed, and 20 frequency windows need to be searched simultaneously. Compared with directly implementing the PMF-FFT algorithm, the amount of computation is significantly reduced from L*F, i.e., 1023*20 PMF-FFT calculations, to 2*4*20 PMF-FFT calculations.

[0114] (12) Step S8. In a specific embodiment, the decision maker 2 decides the peak-to-average ratio (PAR) of the search result of step S7. The threshold B is set to 3.0. When PAR ≥ B, the detection is considered successful, and the controller of step S6 is notified to stop the search. If PAR is less than the preset threshold B, the detection is considered failed, and the controller of step S6 is notified to continue the phase search process of steps S1 to S6.

[0115] In summary, the CDMA signal capture method provided in the embodiments of the present application employs a sliding search of up to 1023 code phases, followed by a search of 20 frequency windows based on four phase ambiguities. This reduces the computational complexity of the entire capture from a maximum of (1023 4092-point coherent integrations) * (20 frequency window traversals) to a maximum of (1023 4092-point coherent integrations) + (2*4 4092-point coherent integrations) * (20 frequency window traversals), reducing the computational complexity for a single satellite by more than tenfold. For CDMA signals broadcast by low-orbit satellites, the Doppler often reaches ±50 to ±100 kHz, requiring 10 to 20 frequency search windows. The CDMA signal capture method provided in this application is particularly advantageous in reducing resource consumption during the capture process while achieving effective CDMA signal capture.

[0116] An embodiment of the present application further provides a system for capturing CDMA signals, the system including a processor configured to call instructions from a memory and implement the method for capturing CDMA signals provided in the embodiment of the present application when executing the instructions.

[0117] An embodiment of the present application further provides a machine-readable storage medium having instructions stored thereon, the instructions being used to enable a machine to execute the method for capturing a CDMA signal provided in accordance with an embodiment of the present application.

[0118] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware. Furthermore, the present application may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0119] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes 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 a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0120] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0121] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0122] In a typical configuration, a computing device includes one or more processors (CPUs), input / output interfaces, network interfaces, and memory.

[0123] The memory may include non-permanent memory in a computer-readable medium, random access memory (RAM) and / or non-volatile memory in the form of read-only memory (ROM) or flash RAM. The memory is an example of a computer-readable medium.

[0124] Computer-readable media includes both permanent and non-permanent, removable and non-removable media that can be implemented using any method or technology for information storage. Information can be computer-readable instructions, data structures, program modules, or other data. Examples of computer storage media include, but are not limited to, phase-change RAM (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, compact disc read-only memory (CD-ROM), digital versatile disc (DVD) or other optical storage, magnetic cassettes, magnetic disk storage or other magnetic storage devices, or any other non-transmission media that can be used to store information that can be accessed by a computing device. As defined herein, computer-readable media does not include transitory computer-readable media, such as modulated data signals and carrier waves.

[0125] It should also be noted that the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, commodity, or apparatus that includes a series of elements includes not only those elements but also other elements not explicitly listed, or includes elements inherent to such process, method, commodity, or apparatus. In the absence of further limitations, an element defined by the phrase "comprises a ..." does not exclude the presence of other identical elements in the process, method, commodity, or apparatus that includes the element.

[0126] The above are merely embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application should all be included within the scope of the claims of the present application.

Claims

1. A method for capturing a CDMA signal, characterized in that: include: Get the signal to be processed and the local code; respectively delaying and conjugating the signal to be processed and the local code and multiplying them to obtain a conjugated signal and a conjugated local code; Sliding an integration window within the conjugated signal based on a sliding window algorithm, and coherently integrating a signal segment of the conjugated signal selected by the integration window with the conjugated local code to obtain a plurality of integration results; determining peak-to-average ratios of corresponding signal segments of the plurality of integration results in the signal to be processed, and, if the peak-to-average ratio is greater than a first preset peak-to-average ratio threshold, selecting a position of a maximum integration result among the plurality of integration results in the signal to be processed as a secondary processing data position; The secondary processed data segment of the signal to be processed is determined according to the secondary processed data position, and the secondary processed data segment is traversed and searched according to a preset frequency search window to capture the peak signal of the secondary processed data segment.

2. The capture method according to claim 1, characterized in that The sliding integration window within the conjugated signal based on the sliding window algorithm, and coherently integrating the signal segment of the conjugated signal selected by the integration window with the conjugated local code to obtain a plurality of integration results includes: determining a signal segment selected by the integration window within the conjugated signal; Coherently integrating the signal segment and the conjugated local code to obtain an integration result; An integration window is slid within the conjugated signal based on a preset step size of a sliding window algorithm to determine a signal segment selected after each sliding of the integration window, and the signal segment selected after sliding and the conjugated local code are coherently integrated to obtain a plurality of sliding integration results, wherein the number of sliding times of the integration window in the process of obtaining the plurality of sliding integration results is greater than or equal to the code period length of the signal to be processed.

3. The capture method according to claim 2, characterized in that In the case that the CDMA signal is a continuous signal, the number of sliding times of the integration window is equal to the code period length of the signal to be processed.

4. The capture method according to claim 2, characterized in that In the case that the CDMA signal is a burst CDMA signal, the number of sliding times of the integration window is greater than or equal to the sum of the code period length of the signal to be processed and the burst signal frame interval length.

5. The capture method according to any one of claims 1 to 4, characterized in that: The length of the integration window is greater than or equal to the code period length of the signal to be processed.

6. The capture method according to claim 5, characterized in that The length of the integration window is an integer multiple of the length of the code period.

7. The capture method according to claim 1, characterized in that Determining the peak-to-average ratios of corresponding signal segments of the multiple integration results in the signal to be processed, and selecting, when the peak-to-average ratios are greater than a first preset peak-to-average ratio threshold, a position of a maximum integration result among the multiple integration results in the signal to be processed as the secondary processing data position includes: determining a signal segment to be processed in the signal to be processed according to a position of the signal segment corresponding to the integration result in the conjugated signal; determining a signal mean value according to the signal segments to be processed of the plurality of integration results; determining a signal peak value of the signal segment to be processed corresponding to a maximum integration result among the multiple integration results; The peak-to-average ratio of the corresponding signal segment is determined based on the signal peak value and the signal mean value, and when the peak-to-average ratio is greater than a first preset peak-to-average ratio threshold, the position of the maximum integration result among the multiple integration results in the signal to be processed is selected as the secondary processing data position.

8. The capture method according to claim 1, characterized in that The step of determining the secondary processed data segment of the signal to be processed according to the secondary processed data position, and performing a traversal search on the secondary processed data segment according to a preset frequency search window to capture a peak signal of the secondary processed data segment includes: Determining a secondary processing data center segment of the signal to be processed according to the secondary processing data position; Determining a signal protection segment before and after the secondary processing data center segment of the signal to be processed according to a preset signal protection segment length; Determining the secondary processing data segment according to the signal protection segment and the secondary processing data segment; The secondary processed data segment is traversed and searched according to a preset frequency search window to capture the peak signal of the secondary processed data segment.

9. The capture method according to claim 1, characterized in that: The order of magnitude of the preset frequency search window is greater than 10 to the first power.

10. The capture method according to claim 1, characterized in that: The step of determining the secondary processed data segment of the signal to be processed according to the secondary processed data position, and performing a traversal search on the secondary processed data segment according to a preset frequency search window to capture a peak signal of the secondary processed data segment includes: Determining a secondary processed data segment of the signal to be processed according to the secondary processed data position, and performing a traversal search on the secondary processed data segment according to a preset frequency search window to obtain a peak signal of the secondary processed data segment; When the peak-to-average ratio of the peak signal is greater than a second preset peak-to-average ratio threshold, the peak signal is captured.

11. A capture system for CDMA signals, characterized in that: The system includes a processor configured to call instructions from a memory and implement the method for acquiring a CDMA signal according to any one of claims 1 to 10 when executing the instructions.

12. A machine-readable storage medium, characterized in that The machine-readable storage medium stores instructions, which are used to enable a machine to execute the method for acquiring a CDMA signal according to any one of claims 1 to 10.

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