A method and system for acquiring weak signals in BeiDou based on a two-stage integration and detection process.

Abstract

This invention provides a BeiDou weak signal acquisition method and system based on a two-stage integration and detection process, comprising: establishing a differential coherent integration accumulation model without bit jumps, reflecting the influence of integration time and delay time on differential coherent integration; establishing a zero-padding FFT model unaffected by NH code jumps, which avoids the influence of NH code jumps by padding 1ms of zero values ​​after 1ms of local carrier, obtaining a 1ms coherent integration result; setting a differential coherent integration with a 20ms delay, accumulating multiple consecutive 10ms differential coherent integration results to eliminate the influence of NH code and data bit jumps; and detecting the presence of a signal and its code phase using the maximum and second-largest value ratio detection method, without needing to obtain noise characteristics in advance. This invention uses the maximum and second-largest value ratio detection method to detect signals, thereby determining the presence of a signal when noise characteristics are unknown.

Description

Technical Field

[0001] This invention relates to the field of satellite signal detection technology, and in particular to a BeiDou weak signal acquisition method and system based on a two-stage integration and detection process. Background Technology

[0002] In today's global satellite navigation field, the BeiDou system has become an indispensable core infrastructure due to its widespread application and reliable performance. From transportation to precision agriculture, from surveying and mapping to smart city management, BeiDou technology is profoundly reshaping the operating models of various industries. However, with the increasing complexity of application scenarios, especially in urban canyons with towering buildings and crisscrossing highways, satellite signals are easily blocked and significantly attenuated. Traditional receiver designs often struggle to guarantee the continuity of high-precision positioning in such weak signal environments. Therefore, how to achieve high-sensitivity reception in scenarios with severe signal attenuation has become a key research direction in current navigation technology.

[0003] One common method to improve receiver sensitivity is to extend the coherent integration time to enhance the signal-to-noise ratio. However, the NH code (secondary coding, 1 kbps rate) embedded in the BeiDou navigation signal, while improving anti-interference capability, introduces frequent data symbol transitions—phase flips can occur within every 1-millisecond sampling segment. This characteristic fundamentally restricts acquisition modules based on coherent integration, making it impossible to simply extend the time using traditional integration methods.

[0004] To address the impact of NH code transitions on acquisition performance, the academic and engineering communities have proposed various improvement strategies, which can be mainly summarized into the following three technical approaches: The time-slot-based selection method utilizes the NH code encoding rules to ensure that there is at least one 1-millisecond clean interval without transitions within a continuous 6-millisecond data window. By collecting multiple 1-millisecond coherent integration results and filtering those unaffected by transitions, sign-flipping interference can be avoided. However, this method can only utilize a single 1-millisecond data segment for coherent integration, resulting in limited gain and making it difficult to meet the acquisition sensitivity requirements in scenarios with very weak signals.

[0005] Correlation search based on combined long codes: NH codes and ranging codes (PRNs) are combined to construct long sequences with a period of 20 milliseconds. Matching these long-period code sequences effectively extends the coherent integration time. While this scheme effectively improves the integration gain, the narrowing of the frequency search bandwidth due to the long codes leads to a sharp increase in search dimensions and an exponential rise in computational complexity, making it prone to real-time bottlenecks on practical hardware platforms.

[0006] The strategy based on nonlinear accumulation involves performing modulo or squaring operations on the coherent integration results over consecutive 1-millisecond intervals, and then summing them to synthesize an equivalent 20-millisecond incoherent integration result. Compared to the combined code scheme, the computational cost is significantly reduced. However, while the nonlinear processing preserves signal energy, it also amplifies background noise, resulting in a lower signal-to-noise ratio improvement compared to pure coherent integration, thus incurring performance degradation.

[0007] Besides the integration phase itself, the signal confirmation phase after acquisition also presents unresolved issues. Most existing studies default to a fixed threshold detection strategy, setting the decision threshold based on prior noise statistics. This approach heavily relies on accurate estimation of environmental noise; when the receiving device or application scenario changes, the original threshold often becomes invalid, requiring manual recalibration. This limitation, rarely discussed in detail in previous literature, severely restricts the versatility and adaptability of acquisition algorithms.

[0008] In summary, the current technical system still faces two major bottlenecks: First, in the integration processing stage, it is still impossible to completely overcome the limitation of coherent accumulation caused by NH code symbol transitions while effectively suppressing noise; second, in the absence of prior noise information, there is no reliable method to automatically and accurately determine the presence of signals. These shortcomings make it difficult for existing solutions to achieve the ideal acquisition performance and universality requirements when dealing with complex and ever-changing real-world environments. Summary of the Invention

[0009] This invention provides a BeiDou weak signal acquisition method and system based on a two-stage integration and detection approach, addressing the shortcomings of existing technologies. It incorporates a maximum and second-largest value ratio detection method after half-bit matched differential coherent integration, fully covering both the integration and detection stages. Furthermore, compared to the most commonly used threshold detection method, the maximum and second-largest value ratio detection method does not require prior acquisition of noise characteristics.

[0010] In a first aspect, the present invention provides a BeiDou weak signal acquisition method based on a two-stage integration and detection process, comprising: A differential coherent integral accumulation model is established based on intermediate frequency signal and local carrier. The differential coherent integral accumulation model does not consider data bit jump interference and outputs a differential coherent integral value that is affected by both integration time and delay time. A Fast Fourier Transform (FFT) model is established by adding zero values ​​of a preset duration after the local carrier. The FFT is multiplied in the frequency domain, which is equivalent to time domain correlation containing zero values. This suppresses the influence of NH code jumps and outputs the coherent integral result corresponding to the preset duration. The differential coherent integrals with the first preset delay time are accumulated in segments to obtain multiple consecutive differential coherent integral results with the second preset delay time. To avoid interference from NH code and data bit transitions, the differential coherent integral results are divided into two groups, and different combination addition methods are determined. Based on the maximum and second-largest value ratio detection method, the presence of a signal and the code phase of the signal can be detected without prior knowledge of noise characteristics.

[0011] According to the present invention, a BeiDou weak signal acquisition method based on a two-stage integration and detection process is provided, wherein the intermediate frequency signal includes:

[0012] in, For sampling points, It is the time interval between sampling points. This is the moment when sampling points begin. It is the signal amplitude, which can be considered constant in the short term. It is the carrier frequency. It is the carrier phase.

[0013] According to the present invention, a BeiDou weak signal acquisition method based on a two-stage integration and detection process is provided, wherein the local carrier includes:

[0014] in, It is the local carrier frequency. It is the local carrier phase.

[0015] According to the present invention, a BeiDou weak signal acquisition method based on a two-stage integration and detection process is provided. The differential coherent integral accumulation model does not consider data bit-jump interference and outputs a differential coherent integral value affected by both the integration duration and the delay duration, including: The intermediate frequency signal is mixed with the local carrier to obtain:

[0016] Disassembling the summation symbol yields: Based on the properties of trigonometric functions, we obtain:

[0017] Substituting the fractional term, we get:

[0018] Substitution get:

[0019] The integral accumulation term is:

[0020] The differential coherent integral is derived as follows:

[0021] in, It's time to start accumulating points. It's time to finish the points. It is the delay time of the differential coherent integral.

[0022] According to the present invention, a BeiDou weak signal acquisition method based on a two-stage integration and detection process is provided. The method involves segmented accumulation of differential coherent integrals with a first preset delay duration to obtain multiple consecutive differential coherent integral results with a second preset delay duration. To avoid interference from NH code and data bit transitions, the differential coherent integral results are divided into two groups, and different combination and addition methods are determined, including: The sequence of four consecutive differential coherent integral results with a second preset delay time is determined as follows: , , and By taking the modulus and the maximum value of each of the four sequences, the peak value of each sequence can be obtained:

[0023] Take the minimum value among the peaks of the four sequences. :

[0024] It is determined that there are at most two bit transitions in four consecutive second preset delay durations, corresponding to the first and third second preset delay durations, and the second and fourth second preset delay durations, with a minimum value set. If the corresponding sequence is one of the transitions, then determine the value of the other transition and the values ​​of the other two non-transitions; The other two non-jumping values ​​are represented as and :

[0025]

[0026] when and If the sign values ​​are the same, add them directly and take the modulo; otherwise, invert any one of them and add them together and take the modulo. Calculate the maximum value of the integral sequence obtained by the two addition methods respectively:

[0027] Obtain the integral result of the first preset delay duration. :

[0028] Will A matrix is ​​formed by column vectors. :

[0029] make If the correct way to add the above column vectors yields the maximum value of the sequence, then... The integral result is expressed as: .

[0030] The present invention provides a BeiDou weak signal acquisition method based on a two-stage integration and detection process. Based on the maximum and second-largest value ratio detection method, it detects the presence of a signal and its code phase without prior acquisition of noise characteristics. The method includes: The maximum peak of the sequence is obtained, and when the satellite signal is present, the maximum peak is regarded as the corresponding signal value; Exclude the code phase of one pseudo-code length around the largest peak, obtain the second largest peak, and regard the second largest peak as the noise peak. If the ratio of the corresponding signal value to the noise peak value is greater than the preset threshold, then the signal is determined to have been successfully captured. After successful or unsuccessful signal acquisition, the satellite number or frequency is switched to return to the acquisition integration phase to obtain a new sequence.

[0031] Secondly, the present invention also provides a BeiDou weak signal acquisition system based on a two-stage integration and detection process, comprising: The first establishment module is used to establish a differential coherent integral accumulation model derived based on intermediate frequency signal and local carrier. The differential coherent integral accumulation model does not consider data bit jump interference and outputs a differential coherent integral value that is affected by both integration time and delay time. The second establishment module is used to establish a fast Fourier transform model with zero values ​​padded after the local carrier for a preset duration. The fast Fourier transform performs frequency domain multiplication, which is equivalent to time domain correlation containing zero values, suppressing the influence of NH code jumps, and outputting the coherent integral result corresponding to the preset duration. The calculation module is used to accumulate the differential coherent integral for the first preset delay time in segments to obtain multiple consecutive differential coherent integral results for the second preset delay time. In order to avoid interference from NH code and data bit switching, the differential coherent integral results are divided into two groups, and different combination addition methods are determined. The detection module is used to detect the presence of a signal and the code phase of the signal based on the ratio of the maximum and second-largest values, without needing to obtain the noise characteristics in advance.

[0032] Thirdly, the present invention also provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the BeiDou weak signal acquisition method based on integration and detection as described above.

[0033] Fourthly, the present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the BeiDou weak signal acquisition method based on integration and detection as described above.

[0034] The present invention provides a BeiDou weak signal acquisition method and system based on a two-stage integration and detection approach. By using zero-padded FFT, differential coherent integration with a delay of 20ms, and half-bit grouping, a coherent integration result of more than 20ms is obtained. The maximum value to second maximum value ratio detection method is used to detect the signal, thereby determining the presence of the signal when the noise characteristics are unknown. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0036] Figure 1 This is a flowchart illustrating the BeiDou weak signal acquisition method based on a two-stage integration and detection process provided by the present invention. Figure 2 This is a schematic diagram illustrating the principle of the half-bit group differential coherent integral acquisition method provided by the present invention; Figure 3 This is a schematic diagram illustrating the impact of BeiDou NH code secondary encoding on the signal provided by this invention; Figure 4 This is a schematic diagram illustrating the relationship between the zero-padding local code and the received signal provided by the present invention; Figure 5 This is a flowchart illustrating the maximum and second-largest value ratio detection method provided by the present invention. Figure 6 This is a schematic diagram of the structure of the BeiDou weak signal acquisition system based on a dual-stage integration and detection provided by the present invention; Figure 7 This is a schematic diagram of the structure of the electronic device provided by the present invention. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0038] Figure 1 This is a flowchart illustrating the BeiDou weak signal acquisition method based on a two-stage integration and detection approach provided in this embodiment of the invention. Figure 1 As shown, it includes: Step 100: Establish a differential coherent integral accumulation model based on the intermediate frequency signal and the local carrier. The differential coherent integral accumulation model does not consider data bit jump interference and outputs a differential coherent integral value that is affected by both the integration time and the delay time. Step 200: Establish a Fast Fourier Transform model with zero values ​​padded after the local carrier for a preset duration. Perform frequency domain multiplication using the Fast Fourier Transform, which is equivalent to time domain correlation containing zero values. Suppress the influence of NH code jumps and output the coherent integral result corresponding to the preset duration. Step 300: Segmentally accumulate the differential coherent integral for the first preset delay time to obtain multiple consecutive differential coherent integral results for the second preset delay time. To avoid interference from NH code and data bit transitions, the differential coherent integral results are divided into two groups, and different combination addition methods are determined. Step 400: Based on the maximum and second-largest value ratio detection method, the presence of the signal and the code phase of the signal are detected without prior acquisition of noise characteristics.

[0039] Specifically, embodiments of the present invention include: establishing a bit-transition-free differential coherent integration accumulation model, which, starting from the intermediate frequency signal and local carrier modeling, reflects the influence of integration time and delay time on differential coherent integration; establishing a zero-padding FFT model unaffected by NH code transitions, which avoids the influence of NH code transitions by padding 1ms of zero values ​​after 1ms of local carrier and performing FFT to obtain a 1ms coherent integration result; setting a 20ms delay for differential coherent integration, accumulating multiple consecutive 10ms differential coherent integration results, dividing them into two groups, discussing the addition method, and eliminating the influence of NH code and data bit transitions; and using the maximum and second-largest value ratio detection method to detect the presence of a signal and its code phase without prior acquisition of noise characteristics. The present invention utilizes zero-padding FFT, a 20ms delay for differential coherent integration, and half-bit grouping to obtain coherent integration results longer than 20ms, and uses the maximum and second-largest value ratio detection method to detect the signal, thereby determining the presence of a signal when noise characteristics are unknown.

[0040] Figure 2 This is a schematic diagram illustrating the principle of the half-bit grouped differential coherent integration acquisition method provided by the present invention. Specifically, the embodiments of the present invention first establish a differential coherent integration accumulation model without bit jumps. This model starts from the modeling of intermediate frequency signals and local carriers, reflecting the influence of integration time and delay time on differential coherent integration. Then, a zero-padding FFT model unaffected by NH code jumps is established. This model avoids the influence of NH code jumps by padding 1ms of zero values ​​after 1ms of local carrier and performing FFT, obtaining a 1ms coherent integration result. A differential coherent integration with a delay of 20ms is set, and multiple consecutive 10ms differential coherent integration results are accumulated and divided into two groups. The addition method is discussed to eliminate the influence of NH code and data bit jumps. Finally, the presence of a signal and its code phase are detected by the ratio of the maximum and second largest values ​​without prior acquisition of noise characteristics.

[0041] A bit-transition-free differential coherent integral accumulation model is established. This model starts from the intermediate frequency signal and local carrier modeling and reflects the influence of integration time and delay time on differential coherent integration.

[0042] The intermediate frequency signal can be modeled as: (1) in, For sampling points, It is the time interval between sampling points. This is the moment when sampling points begin. It is the signal amplitude, which can be considered constant in the short term. It is the carrier frequency. It is the carrier phase.

[0043] The local carrier is modeled as: (2) in, It is the local carrier frequency. It is the local carrier phase.

[0044] The result of the mixing is: (3) By breaking down the accumulation symbol, we can obtain: (4) According to the properties of trigonometric functions, we have: (5) Substituting the fractional term, we get: (6) Substitution We can obtain: (7) The term for cumulative integration is: (8) The differential coherent integral is derived as follows: (9) Among them, It's time to start accumulating points. It's time to finish the points. It is the delay time of the differential coherent integral.

[0045] Therefore, in the absence of bit transitions, the direction of each accumulated term in the differential coherent integral is consistent. and The larger the difference, the larger the integral result; and since the noise accumulation terms are not in the same direction, they will cancel each other out during accumulation. Therefore, differential coherent integration can improve the signal-to-noise ratio and has a better integration gain.

[0046] Based on the above embodiments, step 200 includes: A zero-padding FFT model unaffected by NH code transitions is established. This model avoids the influence of NH code transitions by padding 1ms of zero values ​​after a 1ms local carrier and performing FFT, thus obtaining a 1ms coherent integral result.

[0047] like Figure 3 The diagram illustrating the impact of BeiDou NH code secondary encoding on the signal shows that, taking BeiDou D1 navigation message as an example, the bit length is 20 ms. The original encoded symbol value can change once every 20 ms. After adding NH code modulation with a period of 20 ms, the symbol value can change once every 1 ms.

[0048] like Figure 4 In the diagram illustrating the correlation between the zero-padded local code and the received signal, the signal symbol value can change once every 1 ms. If a local code without zero padding is used for 2 ms, the correlation values ​​will cancel out; if a zero-padded local code is used, the correlation values ​​will not cancel out.

[0049] Therefore, in BeiDou B1I signals modulated with NH code, zero-padded FFT needs to be used instead of ordinary FFT to obtain a 1ms coherent integration result. After obtaining several such short coherent integration results, it is possible to obtain a long coherent integration result by accumulating them.

[0050] Based on the above embodiments, step 300 includes: A differential coherent integral with a delay of 20ms is set, and multiple consecutive differential coherent integral results of 10ms are obtained by summing them. The results are divided into two groups, and the summing method is discussed to eliminate the influence of NH code and data bit transitions.

[0051] The NH code has a code width of 1ms and a code period of 20ms. This means that the NH code at 1ms has the same sign value as the NH code at 21ms, the NH code at 2ms has the same sign value as the NH code at 22ms, and so on. Therefore, when the coherent integral result at any 1ms delay is multiplied conjugately with the coherent integral result delayed by 20ms, the sign value of the NH code will either both be +1 or both be -1, thus canceling out the influence of the NH code.

[0052] Let the sequence of four consecutive 10ms differential coherent integral results be... , , , Taking the modulus of each of the four sequences and finding the maximum value yields the peak value for each sequence: (10) Take the minimum value among the peak values ​​of these four sequences. ,Right now (11) Since there can be at most two bit transitions in four consecutive 10ms intervals, assuming there are two bit transitions, they would either occur between the first and third 10ms intervals, or between the second and fourth 10ms intervals. The presence of bit transitions within the sequence would significantly reduce the sequence's peak value. The corresponding sequence must be one of the transitions, thus determining the other transitioning value and the other two non-transitioning values. The other two non-transitioning values ​​are required and are represented as follows: and Then we have: (12) (13) However, two non-transitional values ​​can only guarantee that the sign values ​​of the data bits are consistent within their respective 10ms. It is possible that the sign values ​​of one 10ms are all -1 and the sign values ​​of the other 10ms are all +1, so further discussion is needed. When the sign values ​​of the two are consistent, they should be added directly and the modulus taken; when the signs of the two are inconsistent, one of them should be inverted and then added and the modulus taken.

[0053] Calculate the maximum value of the integral sequence obtained by each of the two addition methods: (14) The correct addition method produces the largest integral result, thus yielding an integral result in 20ms. It is represented as: (15) Similarly, when it is necessary to obtain a length of When calculating the integral result, you need to use... An integral result with a duration of 10ms. A matrix is ​​formed by column vectors. : (16) By multiplying by a sign vector This allows for free addition and subtraction of the above column vectors. Let... If the above column vectors are added in the correct way, then the maximum value of the sequence can be obtained. The integral result can be expressed as: (17) For example, when , hour, (18) Using the above methods, we can obtain correlation sequences with an integration length of more than 20ms.

[0054] Based on the above embodiments, step 400 includes: The presence of a signal and its code phase can be detected by the ratio of the maximum and second-largest values, without the need to obtain noise characteristics in advance.

[0055] After obtaining the relevant sequence of the acquisition integral, a acquisition discriminator is needed to determine whether a satellite signal has been acquired. Existing similar studies have not focused on the acquisition discriminator because threshold detection methods are very common in acquisition discriminators; exceeding a threshold indicates signal acquisition. The advantage of this method is its simplicity.

[0056] However, this method has a drawback: it requires prior acquisition of noise characteristics, and the threshold may need to be reset when the environment or signal processing equipment changes, because it detects the absolute strength of the signal. To be unaffected by changes in the environment or signal processing equipment, it is necessary to detect the relative strength of the signal, which is the maximum to second-largest value ratio detection method.

[0057] Figure 5 This is a flowchart illustrating the maximum and second-largest value ratio detection method provided by the present invention, as shown below. Figure 5 As shown, the maximum peak of the search-related sequence is denoted as... When satellite signals are present, This is considered the corresponding value of the signal. After excluding the code phase of one pseudo-code length around the maximum peak, the second largest peak is found. This is considered the peak value of the noise. If the ratio of the corresponding signal value to the peak noise value is... Greater than the set threshold If the signal strength is significantly greater than the noise strength, the signal is present and acquisition is successful. After successful or failed acquisition, depending on the specific situation, the satellite number or frequency is switched, returning to the acquisition integration stage described in the previous section to obtain a new correlation sequence. This method, together with the aforementioned half-bit grouped differential coherent integration method, constitutes a complete two-stage BeiDou weak signal acquisition algorithm combining integration and detection.

[0058] The following describes the BeiDou weak signal acquisition system based on a two-stage integration and detection method provided by the present invention. The BeiDou weak signal acquisition system based on a two-stage integration and detection method described below can be referred to in correspondence with each other.

[0059] Figure 6 This is a schematic diagram of the structure of the BeiDou weak signal acquisition system based on a two-stage integration and detection method provided in an embodiment of the present invention, as shown below. Figure 6 As shown, it includes: a first establishment module 61, a second establishment module 62, a calculation module 63, and a detection module 64, wherein: The first establishment module 61 is used to establish a differential coherent integral accumulation model derived based on the intermediate frequency signal and the local carrier. The differential coherent integral accumulation model does not consider data bit jump interference and outputs a differential coherent integral value affected by both the integration duration and the delay duration. The second establishment module 62 is used to establish a fast Fourier transform model with zero values ​​padded after the local carrier for a preset duration. The fast Fourier transform performs frequency domain multiplication, which is equivalent to time domain correlation containing zero values, suppressing the influence of NH code jumps, and outputting a coherent integral result corresponding to the preset duration. The calculation module 63 is used to accumulate the differential coherent integral for the first preset delay duration in segments to obtain multiple consecutive differential coherent integral results for the second preset delay duration. To avoid NH code and data bit jump interference, the differential coherent integral results are divided into two groups, and different combination addition methods are determined. The detection module 64 is used to detect the presence of a signal and the code phase of the signal based on the maximum value to the second largest value ratio detection method, without needing to obtain the noise characteristics in advance.

[0060] Figure 7 An example is a schematic diagram of the physical structure of an electronic device, such as... Figure 7As shown, the electronic device may include: a processor 710, a communication interface 720, a memory 730, and a communication bus 740, wherein the processor 710, the communication interface 720, and the memory 730 communicate with each other through the communication bus 740. The processor 710 can call logic instructions in the memory 730 to execute a BeiDou weak signal acquisition method based on a two-stage integration and detection process. This method includes: establishing a differential coherent integral accumulation model derived from an intermediate frequency signal and a local carrier, wherein the differential coherent integral accumulation model does not consider data bit jump interference and outputs a differential coherent integral value affected by both the integration duration and the delay duration; establishing a fast Fourier transform model with zero values ​​padded after the local carrier for a preset duration, where the fast Fourier transform performs frequency domain multiplication, equivalent to time domain correlation containing zero values, suppressing the influence of NH code jumps, and outputting a coherent integral result corresponding to the preset duration; segmentally accumulating the differential coherent integral for a first preset delay duration to obtain multiple consecutive differential coherent integral results for a second preset delay duration; to avoid NH code and data bit jump interference, the differential coherent integral results are divided into two groups, determining different combination addition methods; and detecting the presence of a signal and its code phase based on the ratio of the maximum and second-largest values, without needing to obtain noise characteristics in advance.

[0061] Furthermore, the logical instructions in the aforementioned memory 730 can be implemented as software functional units and, when sold or used as independent products, can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, essentially, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0062] On the other hand, the present invention also provides a computer program product, which includes a computer program that can be stored on a non-transitory computer-readable storage medium. When the computer program is executed by a processor, the computer can execute the BeiDou weak signal acquisition method based on integration and detection provided by the above methods. This method includes: establishing a differential coherent integral accumulation model derived based on intermediate frequency signals and local carriers, wherein the differential coherent integral accumulation model does not consider data bit jump interference and outputs a differential coherent integral value affected by both integration duration and delay duration; establishing a fast Fourier transform model with zero values ​​padded after the local carrier for a preset duration, wherein the fast Fourier transform performs frequency domain multiplication, which is equivalent to time domain correlation containing zero values, suppressing the influence of NH code jumps, and outputting a coherent integral result corresponding to the preset duration; and accumulating the differential coherent integral for a first preset delay duration in segments to obtain multiple consecutive differential coherent integral results for a second preset delay duration, in order to avoid NH... Code and data bit transition interference is used to divide the differential coherent integration results into two groups and determine different combination addition methods; based on the maximum and second largest value ratio detection method, the presence of the signal and the code phase of the signal can be detected without prior acquisition of noise characteristics.

[0063] On another front, the present invention also provides a non-transitory computer-readable storage medium storing a computer program thereon. When executed by a processor, this computer program implements the BeiDou weak signal acquisition method based on a two-stage integration and detection approach provided by the above methods. This method includes: establishing a differential coherent integral accumulation model derived based on an intermediate frequency signal and a local carrier, wherein the differential coherent integral accumulation model does not consider data bit jump interference and outputs a differential coherent integral value affected by both the integration duration and the delay duration; establishing a fast Fourier transform model with zero values ​​padded after the local carrier for a preset duration, wherein the fast Fourier transform performs frequency domain multiplication, which is equivalent to time domain correlation containing zero values, suppressing the influence of NH code jumps, and outputting a coherent integral result corresponding to the preset duration; and accumulating the differential coherent integral for a first preset delay duration in segments to obtain multiple consecutive differential coherent integral results for a second preset delay duration, to avoid NH... Code and data bit transition interference is used to divide the differential coherent integration results into two groups and determine different combination addition methods; based on the maximum and second largest value ratio detection method, the presence of the signal and the code phase of the signal can be detected without prior acquisition of noise characteristics.

[0064] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without any creative effort.

[0065] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus necessary general-purpose hardware platforms, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solutions, in essence or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in the various embodiments or some parts of the embodiments.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for acquiring weak BeiDou signals based on a two-stage integration and detection process, characterized in that, include: A differential coherent integral accumulation model is established based on intermediate frequency signal and local carrier. The differential coherent integral accumulation model does not consider data bit jump interference and outputs a differential coherent integral value that is affected by both integration time and delay time. A Fast Fourier Transform (FFT) model is established by adding zero values ​​of a preset duration after the local carrier. The FFT is multiplied in the frequency domain, which is equivalent to time domain correlation containing zero values. This suppresses the influence of NH code jumps and outputs the coherent integral result corresponding to the preset duration. The differential coherent integrals with the first preset delay time are accumulated in segments to obtain multiple consecutive differential coherent integral results with the second preset delay time. To avoid interference from NH code and data bit transitions, the differential coherent integral results are divided into two groups, and different combination addition methods are determined. Based on the maximum and second-largest value ratio detection method, the presence of a signal and the code phase of the signal can be detected without prior knowledge of noise characteristics.

2. The BeiDou weak signal acquisition method based on a two-stage integration and detection process according to claim 1, characterized in that, The intermediate frequency signal includes: in, For sampling points, It is the time interval between sampling points. This is the moment when sampling points begin. It is the signal amplitude, which can be considered constant in the short term. It is the carrier frequency. It is the carrier phase.

3. The BeiDou weak signal acquisition method based on a two-stage integration and detection process according to claim 2, characterized in that, The local carrier includes: in, It is the local carrier frequency. It is the local carrier phase.

4. The BeiDou weak signal acquisition method based on a two-stage integration and detection process according to claim 3, characterized in that, The differential coherent integral accumulation model does not consider data bit transition interference and outputs a differential coherent integral value that is affected by both the integration duration and the delay duration, including: The intermediate frequency signal is mixed with the local carrier to obtain: Disassembling the summation symbol yields: Based on the properties of trigonometric functions, we obtain: Substituting the fractional term, we get: Substitution get: The integral accumulation term is: The differential coherent integral is derived as follows: in, It's time to start accumulating points. It's time to finish the points. It is the delay time of the differential coherent integral.

5. The BeiDou weak signal acquisition method based on a two-stage integration and detection process according to claim 1, characterized in that, The differential coherent integrals with a first preset delay are accumulated in segments to obtain multiple consecutive differential coherent integral results with a second preset delay. To avoid interference from NH code and data bit transitions, the differential coherent integral results are divided into two groups, and different combination and addition methods are determined, including: The sequence of four consecutive differential coherent integral results with a second preset delay time is determined as follows: , , and By taking the modulus and the maximum value of each of the four sequences, the peak value of each sequence can be obtained: Take the minimum value among the peaks of the four sequences. : It is determined that there are at most two bit transitions in four consecutive second preset delay durations, corresponding to the first and third second preset delay durations, and the second and fourth second preset delay durations, with a minimum value set. If the corresponding sequence is one of the transitions, then determine the value of the other transition and the values ​​of the other two non-transitions; The other two non-jumping values ​​are represented as and : when and If the sign values ​​are the same, add them directly and take the modulo; otherwise, invert any one of them and add them together and take the modulo. Calculate the maximum value of the integral sequence obtained by the two addition methods respectively: Obtain the integral result of the first preset delay duration. : Will A matrix is ​​formed from column vectors. : make If the correct way to add the above column vectors yields the maximum value of the sequence, then... The integral result is expressed as: 。 6. The BeiDou weak signal acquisition method based on a two-stage integration and detection process according to claim 1, characterized in that, Based on the maximum and second-largest value ratio detection method, the presence of a signal and its code phase can be detected without prior knowledge of noise characteristics, including: The maximum peak of the sequence is obtained, and when the satellite signal is present, the maximum peak is regarded as the corresponding signal value; Exclude the code phase of one pseudo-code length around the largest peak, obtain the second largest peak, and regard the second largest peak as the noise peak. If the ratio of the corresponding signal value to the noise peak value is greater than the preset threshold, then the signal is determined to have been successfully captured. After successful or unsuccessful signal acquisition, the satellite number or frequency is switched to return to the acquisition integration phase to obtain a new sequence.

7. A BeiDou weak signal acquisition system based on a two-stage integration and detection process, characterized in that, include: The first establishment module is used to establish a differential coherent integral accumulation model derived based on intermediate frequency signal and local carrier. The differential coherent integral accumulation model does not consider data bit jump interference and outputs a differential coherent integral value that is affected by both integration time and delay time. The second establishment module is used to establish a fast Fourier transform model with zero values ​​padded after the local carrier for a preset duration. The fast Fourier transform performs frequency domain multiplication, which is equivalent to time domain correlation containing zero values, suppressing the influence of NH code jumps, and outputting the coherent integral result corresponding to the preset duration. The calculation module is used to accumulate the differential coherent integral for the first preset delay time in segments to obtain multiple consecutive differential coherent integral results for the second preset delay time. In order to avoid interference from NH code and data bit switching, the differential coherent integral results are divided into two groups, and different combination addition methods are determined. The detection module is used to detect the presence of a signal and the code phase of the signal based on the ratio of the maximum and second-largest values, without needing to obtain the noise characteristics in advance.

8. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the BeiDou weak signal acquisition method based on integration and detection as described in any one of claims 1 to 6.

9. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the BeiDou weak signal acquisition method based on integration and detection as described in any one of claims 1 to 6.

10. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by the processor, it implements the BeiDou weak signal acquisition method based on integration and detection as described in any one of claims 1 to 6.

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