A PMF_FFT spread spectrum signal acquisition method with multi-threshold fusion decision

Abstract

The application relates to a PMF_FFT spread spectrum signal capturing method based on multi-threshold fusion decision. The method comprises the following steps: according to the correlation point number of a partial matching filter, storing serial time domain I / Q data and two groups of spread spectrum code sequences into a BRAM respectively as a group to obtain a plurality of groups of signal search pairs; taking code phase search precision as a step to search all code phases of the I / Q data in the BRAM, performing partial matching filter operation on the signal search pairs corresponding to the local target pseudo code sequence and the noise pseudo code sequence respectively to obtain corresponding operation results; performing FFT transformation processing on the operation results to obtain search results; performing multi-threshold fusion decision on the search results; and capturing the spread spectrum signal according to the decision result. The method can effectively reduce the false alarm probability of a low-sensitivity receiver in a strong signal or interference signal environment, and improve the satellite signal capturing performance of the receiver.

Description

Technical Field

[0001] This invention relates to the field of satellite signal acquisition technology, and in particular to a PMF_FFT spread spectrum signal acquisition method based on multi-threshold fusion decision. Background Technology

[0002] Telemetry, tracking, and command (TT&C) signals may simultaneously cover and point to multiple satellites. To ensure that the acquisition capability of small signals meets sensitivity specifications, the acquisition module of the transponder is typically designed with a large integral gain, resulting in a significant peak value when the signal is integrated. Therefore, even if each satellite uses a different spreading code, a high received signal level can still lead to a high number of false alarms in the TT&C transponder, causing satellite tracking loop lock-off bias and mislocking.

[0003] Existing false alarm reduction technologies primarily focus on acquisition performance when a signal is present or absent, or when interference is present. The main methods employed include noise thresholding, multiple acquisition result verification, and adaptive thresholding. These methods mostly address scenarios where noisy signals are received (i.e., no signal input) or an interference signal with a different information rate at the same frequency is input. Even when faced with signals of the same frequency, information rate, and coding (same system), differing only in spreading code, the probability of false alarms remains relatively high. For satellites in space, previously a ground station signal rarely continuously pointed at a non-target satellite. However, due to current multi-satellite launches and multi-satellite orbits, satellites continuously receive telemetry and control signals from other satellites during orbit insertion. These signals are typically at the same frequency but with different spreading codes. However, since the signal strength received in orbit is generally much higher than the receiver's sensitivity specifications, traditional acquisition sensitivity is poor. Summary of the Invention

[0004] Therefore, it is necessary to provide a PMF_FFT spread spectrum signal acquisition method with multi-threshold fusion decision that can reduce the false alarm probability of acquisition and improve the receiver's performance in acquiring satellite signals, in order to address the above-mentioned technical problems.

[0005] A PMF_FFT spread spectrum signal acquisition method with multi-threshold fusion decision, the method comprising: The sampled data is multiplied by the local intermediate frequency carrier to obtain the I / Q data at zero intermediate frequency.

[0006] After filtering, the zero-IF I / Q data is decimated to an integer multiple of the spreading code rate so that the filtered zero-IF I / Q data can be bit-width quantized and FFT transformed. Spectral components in the frequency domain that exceed the threshold are assigned values ​​and removed. Then, an IFFT transform is performed on the frequency domain data to obtain the time-domain I / Q data.

[0007] Based on the correlation points of the partially matched filter, the serial time-domain I / Q data and two sets of spreading code sequences are stored as a pair in the BRAM, resulting in several signal search pairs. The two sets of spreading code sequences are the local target pseudocode sequence and the noise pseudocode sequence.

[0008] The code phase search is performed on all code phases of the I / Q data in the BRAM in increments of code phase search accuracy. Partial matched filtering is performed on the signal search pairs of each local target pseudocode sequence and the signal search pairs of each noisy pseudocode sequence to obtain the first operation result and the second operation result.

[0009] The results of the first and second operations are processed by FFT transformation respectively until the search of all code phases is completed, and the search results are obtained.

[0010] Perform multi-threshold fusion decision on the search results and capture the spread spectrum signal based on the decision result.

[0011] A PMF_FFT spread spectrum signal acquisition device with multi-threshold fusion decision, the device comprising: The data sampling module is used to multiply the sampled data with the local intermediate frequency carrier to obtain zero-IF I / Q data.

[0012] The filtering and quantization module is used to filter the zero-IF I / Q data and extract the data to an integer multiple of the spreading code rate so that the filtered zero-IF I / Q data can be bit-width quantized and FFT transformed. The spectral components in the frequency domain that exceed the threshold are assigned values ​​and removed. Then, the frequency domain data is transformed by IFFT to obtain the time domain I / Q data.

[0013] The serial-to-parallel storage module is used to store the serial time-domain I / Q data and two sets of spreading code sequences as a single pair in the BRAM according to the correlation points of the partially matched filter, thus obtaining several signal search pairs. The two sets of spreading code sequences are the local target pseudocode sequence and the noise pseudocode sequence.

[0014] The PMF module is used to search for all code phases of the I / Q data in the BRAM in increments of code phase search accuracy. It performs partial matched filtering operations on the signal search pairs of each local target pseudocode sequence and the signal search pairs of each noisy pseudocode sequence to obtain a first operation result and a second operation result.

[0015] The search and analysis module is used to perform FFT transformation on the results of the first operation and the second operation respectively, until the search results are obtained after the complete code phase search is completed.

[0016] The capture module is used to perform multi-threshold fusion decision on the search results and capture the spread spectrum signal based on the decision result.

[0017] A computer device includes a memory and a processor, the memory storing a computer program, and the processor executing the computer program performing the following steps: The sampled data is multiplied by the local intermediate frequency carrier to obtain the I / Q data at zero intermediate frequency.

[0018] After filtering, the zero-IF I / Q data is decimated to an integer multiple of the spreading code rate so that the filtered zero-IF I / Q data can be bit-width quantized and FFT transformed. Spectral components in the frequency domain that exceed the threshold are assigned values ​​and removed. Then, an IFFT transform is performed on the frequency domain data to obtain the time-domain I / Q data.

[0019] Based on the correlation points of the partially matched filter, the serial time-domain I / Q data and two sets of spreading code sequences are stored as a pair in the BRAM, resulting in several signal search pairs. The two sets of spreading code sequences are the local target pseudocode sequence and the noise pseudocode sequence.

[0020] The code phase search is performed on all code phases of the I / Q data in the BRAM in increments of code phase search accuracy. Partial matched filtering is performed on the signal search pairs of each local target pseudocode sequence and the signal search pairs of each noisy pseudocode sequence to obtain the first operation result and the second operation result.

[0021] The results of the first and second operations are processed by FFT transformation respectively until the search of all code phases is completed, and the search results are obtained.

[0022] Perform multi-threshold fusion decision on the search results and capture the spread spectrum signal based on the decision result.

[0023] The aforementioned PMF_FFT spread spectrum signal acquisition method with multi-threshold fusion decision firstly eliminates narrowband interference components directly in the frequency domain through data preprocessing including FFT transform, over-threshold spectrum removal, and inverse IFFT transform, thus avoiding the formation of false peaks in the interference signal. This significantly reduces the possibility of false alarms caused by interference. Secondly, a noise pseudocode sequence unrelated to the target pseudocode and other satellite pseudocodes is introduced, and the noise peak value and noise floor mean are simultaneously statistically analyzed to construct a more accurate noise benchmark. The noise pseudocode is independent of the signal sequence and can truly reflect the environmental noise level, providing a reliable reference for threshold decision. Finally, the noise threshold (a dual comparison of peak value and noise peak value / noise floor mean) is combined with the bi-peak spacing threshold for cross-validation from two dimensions: energy intensity and signal characteristics. The spacing between the main and secondary peaks of a real spread spectrum signal must match parameters such as information rate and sampling rate, while spurious peaks caused by noise do not have this characteristic. This multi-dimensional decision based on the inherent properties of the signal breaks through the limitations of a single energy threshold, significantly improves the robustness of the decision, effectively reduces the probability of false alarms in low-sensitivity scenarios, reduces the risk of tracking loop mis-locking and false locking, and enables the receiver to work stably in complex electromagnetic environments. Attached Figure Description

[0024] Figure 1 This is a flowchart illustrating a PMF_FFT spread spectrum signal acquisition method with multi-threshold fusion decision in one embodiment; Figure 2 This is a schematic diagram of the receiver data preprocessing process in one embodiment; Figure 3 This is a flowchart illustrating a complete PMF_FFT capture method in one embodiment; Figure 4 This is a schematic diagram of the phase control process in one embodiment; Figure 5 This is a structural block diagram of a PMF_FFT spread spectrum signal acquisition device with multi-threshold fusion decision in one embodiment; Figure 6 This is an internal structural diagram of a computer device in one embodiment. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0026] In one embodiment, such as Figure 1 As shown, a PMF_FFT spread spectrum signal acquisition method with multi-threshold fusion decision is provided, including the following steps: Step 102: Multiply the sampled data with the local intermediate frequency carrier to obtain the zero intermediate frequency I / Q data.

[0027] Step 104: After filtering, the zero-IF I / Q data is decimated to an integer multiple of the spreading code rate so that the filtered zero-IF I / Q data can be bit-width quantized and FFT transformed. Spectral components in the frequency domain that exceed the threshold are assigned values ​​and removed. Then, an IFFT transform is performed on the frequency domain data to obtain the time-domain I / Q data.

[0028] Step 106: Based on the correlation points of the partially matched filter, the serial time-domain I / Q data and the two sets of spreading code sequences are stored as a pair in the BRAM, resulting in several signal search pairs. The two sets of spreading code sequences are the local target pseudocode sequence and the noise pseudocode sequence.

[0029] Step 108: Search all code phases of the I / Q data in the BRAM with the code phase search accuracy as the step, and perform partial matched filtering operation on the signal search pairs of each local target pseudocode sequence and the signal search pairs of each noisy pseudocode sequence to obtain the first operation result and the second operation result.

[0030] Step 110: Perform FFT transformation on the first operation result and the second operation result respectively until the entire code phase search is completed, and obtain the search result.

[0031] Step 112: Perform multi-threshold fusion decision on the search results and capture the spread spectrum signal based on the decision result.

[0032] In the aforementioned PMF_FFT spread spectrum signal acquisition method with multi-threshold fusion decision, firstly, narrowband interference components are directly eliminated in the frequency domain through data preprocessing including FFT transform, over-threshold spectrum removal, and inverse IFFT transform, avoiding the formation of false peaks in the interference signal. This significantly reduces the possibility of false alarms caused by interference. Secondly, a noise pseudocode sequence unrelated to the target pseudocode and other satellite pseudocodes is introduced, and the noise peak value and noise floor mean are simultaneously statistically analyzed to construct a more accurate noise benchmark. The noise pseudocode is independent of the signal sequence and can truly reflect the environmental noise level, providing a reliable reference for threshold decision. Finally, the noise threshold (a dual comparison of peak value and noise peak value / noise floor mean) is combined with the bi-peak spacing threshold for cross-validation from two dimensions: energy intensity and signal characteristics. The spacing between the main and secondary peaks of a real spread spectrum signal must match parameters such as information rate and sampling rate, while spurious peaks caused by noise do not have this characteristic. This multi-dimensional decision based on the inherent properties of the signal breaks through the limitations of a single energy threshold, significantly improves the robustness of the decision, effectively reduces the probability of false alarms in low-sensitivity scenarios, reduces the risk of tracking loop mis-locking and false locking, and enables the receiver to work stably in complex electromagnetic environments.

[0033] In one embodiment, the zero-IF I / Q data is filtered, and the data is decimated to an integer multiple of the spreading code rate. The filtered zero-IF I / Q data is then quantized to a smaller bit width, and an FFT is performed. The energy at each point in the frequency domain is counted to obtain the average power value. After the threshold value in the frequency domain that exceeds the product of the average power value and a preset power coefficient is assigned a value and removed, the frequency domain data is then subjected to an FFT to obtain the time domain I / Q data.

[0034] In one embodiment, the serial time-domain I / Q data and two sets of spreading code sequences are stored as a group in the BRAM according to the correlation points of the partially matched filter. The storage depth of the code phase in the BRAM is set to be equal to the spreading code length divided by the search precision of the code phase. Each time data is stored in the BRAM, M time-domain I / Q data are grouped together, corresponding to a set of pseudo-code sequence segments of the same length, until N groups of data are stored, resulting in several signal search pairs. N is the number of points of the FFT transform. The signal search pairs are divided into two categories: the first category is time-domain I / Q data and local target pseudo-code sequence segments, and the second category is time-domain I / Q data and noise pseudo-code sequence segments.

[0035] It is worth noting that the local or noisy code sequence only needs to store M bits of data at a storage depth equal to the code phase, while the length of the I / Q data is N times the number of correlation points of the partially matched filter.

[0036] In one embodiment, the sampling rate of the time-domain I / Q data is an integer multiple of the spreading code rate.

[0037] In one embodiment, the I / Q data in the BRAM is searched for all code phases in increments of code phase search precision. The spread spectrum code length is set to the maximum search value K of the code phase, divided by the code phase search precision. Based on the maximum search value K, a partial matched filtering operation is performed on the signal search pairs of each group of local target pseudocode sequences to obtain a first operation result and a second operation result.

[0038]

[0039] in, For the first The first result of the partial matched filtering operation. For the first The second operation result of partial matched filtering. This is a local pseudocode. For code phase difference The pseudocode corresponding to the time-domain I / Q data, To account for the Doppler frequency offset of the received signal, This represents the phase difference between the local intermediate frequency carrier and the received signal carrier. Local pseudocode includes local target pseudocode and noise pseudocode.

[0040] In one embodiment, the first operation result is processed by FFT transformation, specifically as follows: peak detection is performed on the N-point frequency domain data of each code phase to identify the maximum and second-largest peak values ​​and their corresponding frequency indexes in a single search; after traversing K code phase searches, the maximum value among all maximum peak values ​​is taken as the target maximum peak value, and the second-largest peak value is taken as the target second-largest peak value, and the frequency index pair of the target maximum peak value and the target second-largest peak value is recorded. The second operation result is processed by FFT transformation, specifically as follows: peak detection is performed on the N-point frequency domain data of each code phase, and the maximum value in a single search is taken as the single noise peak value; after traversing K code phase searches, the maximum value among all single noise peak values ​​is taken as the target noise peak value; simultaneously, the energy of the N-point frequency domain data of each code phase is summed and divided by N to obtain the single noise floor value; after traversing K code phase searches, the average value of all single noise floor values ​​is taken as the target noise floor mean value. The target maximum peak value, the target second-largest peak value, the frequency index pair, the target noise peak value, and the target noise floor mean value are integrated as the search result.

[0041] In one embodiment, if the target maximum peak value meets the noise threshold condition, and the frequency index pair of the target maximum peak value and the target second maximum peak value meets the double-peak interval threshold condition, then the spread spectrum signal acquisition is determined to be successful, and the spread spectrum signal acquisition is completed; otherwise, the spread spectrum signal acquisition is determined to be unsuccessful, and the spread spectrum signal acquisition is re-executed.

[0042] In one embodiment, the noise threshold condition includes a peak value decision condition and a peak-to-average power ratio (PAPR) decision condition; The peak value determination condition is:

[0043] in, To achieve the target maximum peak value, This is the preset noise peak threshold coefficient. The target noise peak value; The peak-to-average ratio (PAR) determination criteria are as follows:

[0044] in, To achieve the target maximum peak value, This is the preset noise floor threshold coefficient. The target noise floor mean is defined as follows: The bimodal interval threshold condition is:

[0045] in, Index of the frequency point where the target maximum peak value is located. For the frequency index of the target second largest peak value, This is a preset information rate threshold coefficient. The information rate of the received signal. The sampling rate of the extracted I / Q data is , The number of points in the FFT transform. This represents the number of correlation points in a partially matched filter. This represents the frequency resolution of the FFT transform.

[0046] In one embodiment, such as Figure 2 As shown, a receiver data preprocessing flow is provided, and the specific steps are as follows: (1) Direct acquisition of intermediate frequency signals requires a large acquisition range and a long acquisition time. Therefore, the received sampled data is first multiplied with the local intermediate frequency carrier to obtain the I / Q data of zero intermediate frequency.

[0047] (2) The purpose of filtering and decimation is to reduce the sampling rate so that the acquisition operation's I / Q data sampling rate is consistent with the pseudocode rate. The received sampled data is directly decimated to an integer multiple of the spreading code rate, typically 2 or 4 times (the multiple is equal to the reciprocal of the acquisition code interval; the multiple is 2 for half-chip phase search accuracy and 4 for 1 / 4-chip search accuracy). Therefore, the received signal needs to be filtered first to prevent spectral aliasing before the data is decimated to an integer multiple of the spreading code rate.

[0048] (3) Quantization refers to quantizing large-bit-width I / Q data to small-bit-width I / Q data.

[0049] Reducing the BRAM resources required for subsequent data storage can be achieved by reducing the BRAM resource usage by more than 40% through analysis of reducing the bit width by 4 bits. Simultaneously, the quantized data requires fewer resources during computation, and it has been verified that quantization has no impact on capture performance.

[0050] (4) When the information rate is high, the spreading ratio (the ratio of the spreading pseudocode rate to the information rate) will also decrease, and its resistance to narrowband interference will also decrease. Therefore, it is necessary to eliminate the interference signal during acquisition to obtain better acquisition performance. The process is as follows: ① First, perform an FFT transformation on the quantized I / Q data to transform the signal from the time domain to the frequency domain; ②Statistically analyze the energy at each point in the frequency domain to obtain an average power value, and continuously update and smooth this average power value. ③ Remove any values ​​in the frequency spectrum that exceed the average power value multiplied by the power coefficient (by assigning a value of 0 or the average power value). ④ Then perform an IFFT transform on the frequency domain data to obtain the I / Q data in the time domain.

[0051] It is worth noting that IFFT data is preprocessed I / Q data that can be used for capture.

[0052] In one embodiment, PMF_FFT is a parallel frequency, serial code phase capture. Therefore, when storing a segment of I / Q data for capture, all phases need to be searched step by step with chip phase search accuracy. Each phase search requires one FFT calculation. Figure 3 The diagram shows the complete flow of a PMF_FFT capture method, with the following specific steps: (1) Store the serial I / Q data into the BRAM in groups of M (the number of relevant points of the matched filter) until N (the number of FFT points) groups are stored.

[0053] (2) The pseudo-random sequence generated by the local pseudo-code with the same code phase search precision as the received signal is also stored in the BRAM in groups of M (the number of relevant points of the matched filter). The depth of code phase storage is equal to the code length divided by the chip phase search precision.

[0054] (3) The pseudo-random sequence generated by the noise pseudo-code that is different from the received signal in terms of code phase search accuracy is also stored in the BRAM in groups of M (the number of relevant points of the matched filter). The depth of code phase storage is equal to the code length divided by the chip phase search accuracy.

[0055] (4) Phase control process as follows Figure 5 As shown in the diagram. Here, K is the maximum value of the code phase search, equal to the spreading code length / code phase search accuracy. M is the number of correlation points in the matched filter.

[0056] It is worth noting that the sampling rate of the I / Q data is equal to the chip rate of the pseudocode. The main purpose of this operation is to ensure the continuity of phase during calculation by maintaining the continuity of I / Q and pseudocode data acquisition when the two rates are consistent. The calculation clock can use a clock frequency much higher than the sampling clock, reducing time overhead. In addition, the PMF operation only calculates the sum of the cross-correlation values ​​of the M chip and I / Q data points. The result of the m-th partially matched filter can be expressed as:

[0057] in, This is local pseudocode. For code phase difference The pseudocode of I / Q data, To account for the Doppler frequency offset of the received signal, This represents the phase difference between the local intermediate frequency carrier and the received signal carrier.

[0058] (5) After the calculation results of N PMFs are all output, the N*M point data capture result with phase i as the initial address can be obtained by N-point FFT calculation.

[0059] (6) Perform K phase searches on the local pseudocode.

[0060] (7) For the largest and second largest peaks in the N-point FFT results of the initial phase i of the local pseudocode statistics, record their frequency indexes. and The set with the largest peak among all K phase capture results is taken as the final result of the phase search, and is considered as the captured maximum peak. Second peak and frequency index and .

[0061] (8) Perform K phase searches on the noise code group.

[0062] (9) Noise peak statistics: For the noise pseudocode, the maximum value among the N-point FFT results of the initial phase i is taken as the maximum value of a single search, and the maximum value among all phase search maximum values ​​is taken as the noise peak. .

[0063] (10) Noise floor statistics: The sum of the N-point FFT results of the initial phase i is divided by N to obtain the single noise floor value. The average of the noise floor values ​​of K phase searches is taken as the final noise floor value. .

[0064] (11) The noise threshold decision includes peak value decision and peak-to-average power ratio decision, and the decision conditions are as follows: a) The captured maximum peak Greater than the peak sound threshold, ,in is the configurable noise peak threshold coefficient.

[0065] b) The captured maximum peak Greater than the noise floor threshold, ,in is the configurable noise floor threshold coefficient.

[0066] (12) Double-peak interval threshold decision: the interval between the two peaks should be less than the information rate interval threshold.

[0067] in, This is the configurable information rate threshold coefficient. For information rate, The sampling rate of the extracted I / Q data. This represents the frequency resolution of the FFT transform.

[0068] (13) If the capture result satisfies the judgments of both steps (11) and (12), the capture is considered successful.

[0069] It should be understood that although the steps in flowcharts 1-4 are shown sequentially as indicated by the arrows, these steps are not necessarily executed in the exact order indicated by the arrows. Unless explicitly stated herein, there is no strict order requirement for the execution of these steps, and they can be performed in other orders. Furthermore, Figure 1-4 At least some of the steps in the process may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but can be executed in turn or alternately with other steps or at least some of the sub-steps or stages of other steps.

[0070] In one embodiment, such as Figure 5 As shown, a PMF_FFT spread spectrum signal acquisition device with multi-threshold fusion decision is provided, including: a data sampling module 502, a filtering and quantization module 504, a serial-to-parallel storage module 506, a PMF module 508, a search and analysis module 510, and an acquisition module 512, wherein: The data sampling module 502 is used to multiply the sampled data with the local intermediate frequency carrier to obtain zero intermediate frequency I / Q data.

[0071] The filtering and quantization module 504 is used to filter the zero-IF I / Q data and extract the data to an integer multiple of the spreading code rate so that the filtered zero-IF I / Q data can be bit-width quantized and FFT transformed. The spectral components in the frequency domain that exceed the threshold are assigned values ​​and removed. Then, the frequency domain data is transformed by IFFT to obtain the time domain I / Q data.

[0072] The serial-to-parallel storage module 506 is used to store the serial time-domain I / Q data and two sets of spreading code sequences as a group into the BRAM according to the correlation points of the partially matched filter, thus obtaining several sets of signal search pairs. The two sets of spreading code sequences are the local target pseudocode sequence and the noise pseudocode sequence.

[0073] The PMF module 508 is used to search for all code phases of the I / Q data in the BRAM in increments of code phase search accuracy. It performs partial matched filtering operations on the signal search pairs of each local target pseudocode sequence and the signal search pairs of each noisy pseudocode sequence to obtain the first operation result and the second operation result.

[0074] The search analysis module 510 is used to perform FFT transformation on the first operation result and the second operation result respectively until the search results are obtained after the complete code phase search is completed.

[0075] The capture module 512 is used to perform multi-threshold fusion decision on the search results and capture the spread spectrum signal based on the decision result.

[0076] Specific limitations regarding the PMF_FFT spread spectrum signal acquisition device with multi-threshold fusion decision can be found in the above-described limitations of the PMF_FFT spread spectrum signal acquisition method with multi-threshold fusion decision, and will not be repeated here. Each module in the aforementioned PMF_FFT spread spectrum signal acquisition device with multi-threshold fusion decision can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in hardware or independently of the processor in a computer device, or stored in software in the memory of a computer device, so that the processor can call and execute the operations corresponding to each module.

[0077] In one embodiment, a computer device is provided, which may be a terminal, and its internal structure diagram may be as follows: Figure 6 As shown, the computer device includes a processor, memory, network interface, display screen, and input devices connected via a system bus. The processor provides computing and control capabilities. The memory includes non-volatile storage media and internal memory. The non-volatile storage media stores the operating system and computer programs. The internal memory provides an environment for the operation of the operating system and computer programs stored in the non-volatile storage media. The network interface is used to communicate with external terminals via a network connection. When executed by the processor, the computer program implements a PMF_FFT spread spectrum signal acquisition method with multi-threshold fusion decision. The display screen can be a liquid crystal display (LCD) or an e-ink display. The input devices can be a touch layer covering the display screen, buttons, a trackball, or a touchpad mounted on the computer device casing, or an external keyboard, touchpad, or mouse.

[0078] Those skilled in the art will understand that the structures shown in Figures 5-6 are merely block diagrams of some structures related to the present invention and do not constitute a limitation on the computer device to which the present invention is applied. Specific computer devices may include more or fewer components than shown in the figures, or combine certain components, or have different component arrangements.

[0079] In one embodiment, a computer device is provided, including a memory and a processor, the memory storing a computer program, the processor executing the computer program to perform the following steps: The sampled data is multiplied by the local intermediate frequency carrier to obtain the I / Q data at zero intermediate frequency.

[0080] After filtering, the zero-IF I / Q data is decimated to an integer multiple of the spreading code rate so that the filtered zero-IF I / Q data can be bit-width quantized and FFT transformed. Spectral components in the frequency domain that exceed the threshold are assigned values ​​and removed. Then, an IFFT transform is performed on the frequency domain data to obtain the time-domain I / Q data.

[0081] Based on the correlation points of the partially matched filter, the serial time-domain I / Q data and two sets of spreading code sequences are stored as a pair in the BRAM, resulting in several signal search pairs. The two sets of spreading code sequences are the local target pseudocode sequence and the noise pseudocode sequence.

[0082] The code phase search is performed on all code phases of the I / Q data in the BRAM in increments of code phase search accuracy. Partial matched filtering is performed on the signal search pairs of each local target pseudocode sequence and the signal search pairs of each noisy pseudocode sequence to obtain the first operation result and the second operation result.

[0083] The results of the first and second operations are processed by FFT transformation respectively until the search of all code phases is completed, and the search results are obtained.

[0084] Perform multi-threshold fusion decision on the search results and capture the spread spectrum signal based on the decision result.

[0085] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium. When executed, the computer program can include the processes of the embodiments of the above methods. Any references to memory, storage, databases, or other media used in the embodiments provided by this invention can include non-volatile and / or volatile memory. Non-volatile memory can include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), or flash memory. Volatile memory can include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in various forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), dual data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link DRAM (SLDRAM), Rambus direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM), etc.

[0086] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0087] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A PMF_FFT spread spectrum signal acquisition method with multi-threshold fusion decision, characterized in that, The method includes: After multiplying the sampled data with the local intermediate frequency carrier, the zero-IF I / Q data is obtained; After filtering, the zero-IF I / Q data is decimated to an integer multiple of the spreading code rate so that the filtered zero-IF I / Q data can be bit-width quantized and FFT transformed. Spectral components in the frequency domain that exceed the threshold are assigned values ​​and removed. Then, IFFT transform is performed on the frequency domain data to obtain the time-domain I / Q data. Based on the correlation points of the partially matched filter, the serial time-domain I / Q data and two sets of spreading code sequences are stored in the BRAM as a group to obtain several signal search pairs; the two sets of spreading code sequences are the local target pseudocode sequence and the noise pseudocode sequence. The code phase search is performed on all code phases of the I / Q data in the BRAM in increments of code phase search precision. Partial matched filtering is performed on the signal search pairs of each set of local target pseudocode sequences and the signal search pairs of each set of noise pseudocode sequences to obtain the first operation result and the second operation result. The results of the first operation and the second operation are processed by FFT transformation respectively until the search of all code phases is completed, and the search results are obtained. Perform multi-threshold fusion decision on the search results, and capture the spread spectrum signal based on the decision result; If the target maximum peak value meets the noise threshold condition, and the frequency index pair of the target maximum peak value and the target second largest peak value meets the double-peak interval threshold condition, then the spread spectrum signal acquisition is determined to be successful and the spread spectrum signal acquisition is completed; otherwise, the spread spectrum signal acquisition is determined to be unsuccessful and the spread spectrum signal acquisition is re-executed.

2. The method according to claim 1, characterized in that, After filtering, the zero-IF I / Q data is decimated to an integer multiple of the spreading code rate to enable bit-width quantization and FFT transformation of the filtered zero-IF I / Q data. Spectral components exceeding a threshold in the frequency domain are then removed by assignment. Finally, an IFFT transformation is performed on the frequency domain data to obtain the time-domain I / Q data, including: After filtering, the zero-IF I / Q data is decimated to an integer multiple of the spreading code rate. The filtered zero-IF I / Q data is then quantized to a smaller bit width, and an FFT is performed. The energy at each point in the frequency domain is calculated to obtain the average power value. After removing data in the frequency domain that exceed the product of the average power value and a preset power coefficient, an FFT is performed on the frequency domain data to obtain the time-domain I / Q data.

3. The method according to claim 1, characterized in that, Based on the correlation points of the partially matched filter, the serial time-domain I / Q data and the two sets of spreading code sequences are stored as a group in the BRAM, resulting in several signal search pairs, including: Based on the correlation points of the partially matched filter, the serial time-domain I / Q data and two sets of spreading code sequences are stored in the BRAM as a group. The storage depth of the code phase in the BRAM is set to be equal to the code length of the spreading code divided by the search precision of the code phase. Each time the data is stored in the BRAM, M time-domain I / Q data are used as a group, corresponding to a group of pseudo-code sequence segments of the same length, until N groups of data are stored, resulting in several signal search pairs. N is the number of points in the FFT transform; The signal search pairs are divided into a first category consisting of time-domain I / Q data and local target pseudocode sequence segments, and a second category consisting of time-domain I / Q data and noise pseudocode sequence segments.

4. The method according to any one of claims 1 to 3, characterized in that, The sampling rate of the time-domain I / Q data is an integer multiple of the spreading code rate.

5. The method according to claim 4, characterized in that, The code phase search is performed on all code phases of the I / Q data in the BRAM in increments of code phase search precision. Partial matched filtering is then performed on the signal search pairs of each set of local target pseudocode sequences and each set of noisy pseudocode sequences to obtain a first operation result and a second operation result, including: The code phase search is performed on all code phases of the I / Q data in the BRAM in increments of code phase search precision. The maximum search value K of the code phase is set by dividing the spreading code length by the code phase search precision. Based on the maximum search value K, a partial matched filtering operation is performed on the signal search pairs of each group of the local target pseudocode sequences to obtain the first operation result and the second operation result. in, For the first The first result of the partial matched filtering operation. For the first The second operation result of partial matched filtering. This is a local pseudocode. For code phase difference The pseudocode corresponding to the time-domain I / Q data, To account for the Doppler frequency offset of the received signal, This represents the phase difference between the local intermediate frequency carrier and the received signal carrier. The local pseudocode includes the local target pseudocode and the noise pseudocode.

6. The method according to claim 5, characterized in that, Perform FFT transformations on the results of the first and second operations respectively until the entire code phase search is completed, and obtain the search results, including: The first operation result is processed by FFT transformation. The specific steps are as follows: peak detection is performed on the N-point frequency domain data of each code phase to identify the maximum peak and the second largest peak and the corresponding frequency index of a single search; after traversing K code phase searches, the maximum value among all the maximum peaks is taken as the target maximum peak and the second largest peak is taken as the target second largest peak, and the frequency index pair of the target maximum peak and the target second largest peak is recorded. The result of the second operation is processed by FFT transformation. The specific steps are as follows: peak detection is performed on the N-point frequency domain data of each code phase, and the maximum value of a single search is taken as the single noise peak value; after traversing K code phase searches, the maximum value among all single noise peak values ​​is taken as the target noise peak value; at the same time, the energy of the N-point frequency domain data of each code phase is summed and divided by N to obtain the single noise floor value; after traversing K code phase searches, the average value of all single noise floor values ​​is taken as the target noise floor mean value. The search results are obtained by integrating the target maximum peak value, the target second maximum peak value, the frequency point index pair, the target noise peak value, and the target noise floor mean value.

7. The method according to claim 6, characterized in that, The noise threshold conditions include the peak value decision condition and the peak-to-average power ratio decision condition; The peak value determination condition is: in, To achieve the target maximum peak value, This is the preset noise peak threshold coefficient. The target noise peak value; The peak-to-average ratio (PAR) determination criteria are as follows: in, To achieve the target maximum peak value, This is the preset noise floor threshold coefficient. The target noise floor mean; The bimodal interval threshold condition is: in, Index of the frequency point where the target maximum peak value is located. For the frequency index of the target second largest peak value, This is a preset information rate threshold coefficient. The information rate of the received signal. The sampling rate of the extracted I / Q data. The number of points in the FFT transform. This represents the number of correlation points in a partially matched filter. This represents the frequency resolution of the FFT transform.

8. A PMF_FFT spread spectrum signal acquisition device with multi-threshold fusion decision, characterized in that, The apparatus for implementing the steps of the method according to any one of claims 1 to 7, comprising: The data sampling module is used to multiply the sampled data with the local intermediate frequency carrier to obtain zero-IF I / Q data; The filtering and quantization module is used to filter the zero-IF I / Q data and extract the data to an integer multiple of the spreading code rate so that the filtered zero-IF I / Q data can be bit-width quantized and FFT transformed to remove spectral components in the frequency domain that exceed the threshold. Then, IFFT transformation is performed on the frequency domain data to obtain the time domain I / Q data. The serial-to-parallel storage module is used to store the serial time-domain I / Q data and two sets of spreading code sequences as a group into the BRAM according to the correlation points of the partially matched filter, thereby obtaining several sets of signal search pairs; the two sets of spreading code sequences are the local target pseudocode sequence and the noise pseudocode sequence. The PMF module is used to search all code phases of the I / Q data in the BRAM in increments of code phase search precision, and to perform partial matched filtering operations on the signal search pairs of each set of local target pseudocode sequences and the signal search pairs of each set of noise pseudocode sequences to obtain a first operation result and a second operation result. The search and analysis module is used to perform FFT transformation on the first operation result and the second operation result respectively until the search of all code phases is completed and the search results are obtained. The capture module is used to perform multi-threshold fusion decision on the search results and capture the spread spectrum signal based on the decision result.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1 to 7.

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