A code tracking method for direct sequence spread spectrum signals based on symbol search

Abstract

The application discloses a direct sequence spread spectrum signal pseudo code tracking method based on symbol search and relates to the technical field of pseudo code synchronization and tracking, which comprises the following steps: receiving a direct sequence spread spectrum signal, and performing carrier stripping on the direct sequence spread spectrum signal by using a carrier Doppler estimation result output by a carrier tracking loop to obtain a Doppler demodulation result; generating three local pseudo codes of early, instant and lag by using a carrier auxiliary technology according to the carrier Doppler estimation result and a pseudo code delay estimation value provided by acquisition; performing despread processing on the Doppler demodulation result by using the three local pseudo codes of early, instant and lag respectively to obtain three despread results of early, instant and lag; and starting to segmentally integrate and clear the three despread results of early, instant and lag by using a set segmentation time from the moment when it is detected that the transient code phase of the instant branch jumps to zero to obtain segmented integration and clearing results of each branch.

Description

Technical Field

[0001] This invention relates to the field of pseudocode synchronization and tracking technology, and in particular to a method for tracking pseudocodes of direct sequence spread spectrum signals based on symbol search. Background Technology

[0002] Pseudocode synchronization and tracking technology refers to the process in direct sequence spread spectrum communication or navigation systems where the receiver locally generates a pseudo-random noise code identical to that of the transmitter and continuously adjusts its phase and frequency to precisely align it with the pseudocode in the received spread spectrum signal in time. This process is divided into two stages: acquisition and tracking. The tracking loop continuously monitors the phase deviation between the local pseudocode and the received pseudocode through three correlators: lead, instant, and lag. It also uses a discriminator and loop filter to dynamically correct the parameters of the local pseudocode numerically controlled oscillator to maintain high-precision code phase locking, thereby achieving despreading and subsequent data demodulation. This is a key technological foundation for the normal operation of a spread spectrum system.

[0003] In traditional pseudocode tracking loops, when the integration time exceeds the width of one data symbol, unknown data symbol transitions can cause phase reversal in the coherent integration result, resulting in energy cancellation. This severely limits the effective coherent integration time, making it impossible to achieve stable tracking under extremely low carrier-to-noise ratio conditions. Furthermore, in high-speed relative motion scenarios, the pseudocode frequency is shifted by carrier Doppler modulation. If not effectively compensated, this will lead to a mismatch between the local pseudocode and the received pseudocode, causing tracking loss. Moreover, traditional code loops have limited bandwidth and cannot independently cope with high dynamic stress. Summary of the Invention

[0004] In view of the aforementioned existing problems, the present invention is proposed.

[0005] Therefore, this invention provides a direct sequence spread spectrum signal pseudocode tracking method based on symbol search to solve the problem that in traditional pseudocode tracking loops, when the integration time exceeds the width of one data symbol, unknown data symbol transitions can cause phase reversal in the coherent integration result, resulting in energy cancellation and severely limiting the effective coherent integration time. This makes it impossible to achieve stable tracking under extremely low carrier-to-noise ratio conditions. Furthermore, in high-speed relative motion scenarios, the pseudocode frequency is offset by carrier Doppler modulation. If not effectively compensated, this will lead to a mismatch between the local pseudocode and the received pseudocode, causing tracking loss. In addition, traditional code loops have limited bandwidth and cannot independently cope with the problem of high dynamic stress.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: In a first aspect, the present invention provides a method for tracking pseudocodes of direct sequence spread spectrum signals based on symbol search, comprising: The direct sequence spread spectrum signal is received, and the carrier Doppler estimation result output by the carrier tracking loop is used to perform carrier stripping on the direct sequence spread spectrum signal to obtain the Doppler demodulation result; Based on the carrier Doppler estimation results and the pseudocode delay estimation values ​​provided by the acquisition, carrier-assisted techniques are used to generate three local pseudocodes: lead, instant, and lag. The Doppler demodulation results are despread using the three local pseudo-codes (lead, instant, and lag) to obtain the three despread results (lead, instant, and lag). Starting at the moment when the transient code phase of the instantaneous branch is detected to jump to zero, the despreading results of the three paths (leading, instantaneous, and lagging) are segmented and integrated to clear them, and the segmented integration clearing results of each path are obtained. Based on the data symbol width, segment time, and loop control interval, a symbol search matrix is ​​constructed, and the symbol search matrix is ​​multiplied by the segmented integral clearing results of the lead, instant, and lag paths respectively to obtain the secondary search accumulation results of each path. Calculate the square of the modulus of the accumulated result of the instantaneous branch secondary search, and select the symbol search pattern corresponding to the maximum value of the square of the modulus as the matching symbol search pattern; Based on the matching symbol search pattern, the corresponding accumulation result is selected from the secondary search accumulation results of the three paths of advance, instant, and lag to obtain the final long-term secondary accumulation result; Using the final long-term quadratic accumulation result, a pseudocode phase discrimination result is generated through a normalized dot product power discriminator; The pseudocode phase discrimination result is subjected to median filtering to obtain the median filtered result; The median filtering result is input into the loop filter to generate the loop filter output, and the frequency word of the local pseudocode numerically controlled oscillator is corrected based on the loop filter output.

[0007] As a preferred embodiment of the direct sequence spread spectrum signal pseudocode tracking method based on symbol search described in this invention, the step of performing segmented integration and clearing of the lead, instantaneous, and lag despreading results at the moment when the transient code phase of the instantaneous branch is detected to jump to zero, with a set segmented time interval, specifically includes the following steps: Calculate data symbol width With pseudocode period Greatest common divisor Then the data symbol width and pseudocode period are both Multiples of positive integers; Select the segmented integration clearing time as ,in It is a positive integer, and the data symbol width and pseudocode period are also... Multiples of positive integers are denoted as ,in It is a positive integer.

[0008] When a direct sequence spread spectrum signal is generated, the data symbols and the spreading pseudocode are synchronously fixed, and spatial transmission delay does not affect this relationship. Any... The data symbol transition times are: ; Any number The start time of each pseudocode cycle is: ; in, That is, the transient code phase of the spread spectrum signal from The moment it jumps to 0.

[0009] A pseudocode period contains a total of indivual Time interval segmentation, any number of segments Within the pseudocode period, the first The range of each time segment is If the data sign changes within a segment, then there exists... This makes the data symbol transition time satisfy: ; Equivalent to: ; because All are integers. Since the integer is also an integer, the above statement is invalid. Therefore, the transient code phase of the instantaneous branch is detected in real time. When it first came from Starting from the moment of transition to 0, utilize The generation interval is The timing pulse can guarantee that, at any time... The data symbols in the despreading results do not change within the time period.

[0010] As a preferred embodiment of the direct sequence spread spectrum signal pseudocode tracking method based on symbol search described in this invention, the specific steps for constructing the symbol search matrix according to the data symbol width, segmentation time, and loop control interval are as follows: Let the loop control interval be The loop control interval contains Data symbols, namely ; Taking the local integration start time as a reference, there are ββ possible data symbol transition positions, corresponding to the transition occurring at the th... indivual Segment endpoints; For the Possible jump positions Crossing within the loop control interval A data symbol interval; The value of the first data symbol is used as the reference, and the rest... The values ​​of each data symbol are either the same sign as the reference or have a different sign than the reference, totaling [number missing]. Combinations; Represent each combination as a binary sequence. ,in =0 indicates a reference symbol; Convert binary sequence to symbol sequence ; The total number of segments within the loop control interval Divided into Section, No. The segment contains indivual Segmented, including: ; For each transition position Combined with each symbol, construct a length of Symbol search style , among which the former The elements are Next The elements are And so on; All symbol search patterns are arranged in rows to form a symbol search matrix. ,in But when hour, and Since the symbols are the same, only one is retained. time A unique style; The final symbol search matrix has 10 rows. .

[0011] As a preferred embodiment of the direct sequence spread spectrum signal pseudocode tracking method based on symbol search described in this invention, the specific steps of performing matrix multiplication operations between the symbol search matrix and the piecewise integral clearing results of the lead, instant, and lag paths to obtain the secondary search accumulation results of each path are as follows: The piecewise integral clearing result of the leading branch is represented as a complex vector. ,in For the first indivual Piecewise complex correlation values; The piecewise integral clearing result of the instantaneous branch is represented as a complex vector. ; The piecewise integral clearing result of the lagging branch is represented as a complex vector. ; Search matrix for symbols each line Calculate the accumulated results of the second-order search of the lead branch: ; Calculate the accumulated results of the instantaneous branch quadratic search: ; Calculate the accumulated results of the second-order search for the lagging branch: ; All , , These are respectively used to form the vector of accumulated results from the secondary search.

[0012] As a preferred embodiment of the direct sequence spread spectrum signal pseudocode tracking method based on symbol search described in this invention, the specific steps for calculating the square of the modulus of the instantaneous branch secondary search accumulation result and selecting the symbol search pattern corresponding to the maximum value of the square of the modulus as the matching symbol search pattern are as follows: Search for the style number for each symbol Calculate the squared modulus of the accumulated result of the instantaneous branch quadratic search: ; Compare all Select to make Largest serial number ,Right now: ; serial number Corresponding symbol search style The search style is set to match symbols; The matching symbol search style can correct the sign of the piecewise integral clearing result even when the position of the data symbol jump is unknown, so that the secondary accumulation of the piecewise integral clearing result is not affected by the data symbol jump.

[0013] As a preferred embodiment of the direct sequence spread spectrum signal pseudocode tracking method based on symbol search described in this invention, the specific steps for generating pseudocode phase discrimination results using the final long-term secondary accumulation result through a normalized dot product power discriminator are as follows: Select the sequence number from the vector of accumulated results of the secondary search of the advanced branch. corresponding value ; Select the sequence number from the vector of accumulated results of the secondary search of the lagging branch. corresponding value ; Will and Substitute the values ​​into the normalized dot product power discriminator to calculate the pseudocode phase discrimination result. Its expression is: ; Pseudocode phase identification results The unit is a chip, which reflects the direction and magnitude of the phase deviation between the local pseudocode and the received signal pseudocode.

[0014] As a preferred embodiment of the direct sequence spread spectrum signal pseudocode tracking method based on symbol search described in this invention, the specific steps for performing median filtering on the pseudocode phase discrimination result to obtain the median filtering result are as follows: Cache contiguous The pseudocode phase identification results of each loop control time slot form a sequence. ; Sort the sequence according to its numerical value; like For odd numbers, the value at the middle position after sorting is taken as the median filter result. ; like If the number is even, take the arithmetic mean of the two middle values ​​after sorting as the median filtering result. ; The median filtering result Used to remove outliers in the pseudocode phase identification results and eliminate the disturbance effect of outliers on the loop.

[0015] As a preferred embodiment of the direct sequence spread spectrum signal pseudocode tracking method based on symbol search described in this invention, the specific steps of inputting the median filtering result into a loop filter to generate a loop filter output, and correcting the frequency word of the local pseudocode numerically controlled oscillator according to the loop filter output are as follows: Median filtering results were obtained by using a first-order loop filter. For filtering, the difference equation of the loop filter is: ; in, For the first The loop filter output of each loop control time slot, To normalize the gain of the dot product power discriminator, For loop control interval; Loop filter output As the frequency control word increment, it corrects the frequency word of the local pseudocode numerically controlled oscillator. Its update formula is: ; Driven by the sampling clock, the local pseudo-code numerically controlled oscillator continuously generates three local pseudo-codes—leading, instantaneous, and lagging—based on the updated frequency word, achieving closed-loop tracking of the pseudo-code phase.

[0016] In a second aspect, the present invention provides a computer device including a memory and a processor, wherein the memory stores a computer program, wherein when the computer program is executed by the processor, it implements any step of the symbol-search-based direct sequence spread spectrum signal pseudocode tracking method as described in the first aspect of the present invention.

[0017] Thirdly, the present invention provides a computer-readable storage medium having a computer program stored thereon, wherein: when the computer program is executed by a processor, it implements any step of the direct sequence spread spectrum signal pseudocode tracking method based on symbol search as described in the first aspect of the present invention.

[0018] The beneficial effects of this invention are as follows: By utilizing the synchronous fixed relationship between data symbols and pseudocode periods to determine the non-jumping segmented integration time, and combining the symbol search matrix to perform full combination symbol correction and secondary coherent accumulation on the segmented integration results within multiple symbol periods, the destruction of long-term coherent accumulation by unknown data symbol jumps is effectively eliminated. True coherent accumulation of multiple symbol periods is achieved without the need for known symbol edges. At the same time, by combining carrier-assisted, normalized dot product power discrimination, median filtering and first-order loop filtering and other techniques, the pseudocode tracking accuracy, stability and weak signal acquisition capability of the system in high dynamic and extremely low carrier-to-noise ratio environments are improved, overcoming the square loss and signal-to-noise ratio loss problems caused by traditional incoherent or differential coherent accumulation. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a flowchart of the direct sequence spread spectrum signal pseudocode tracking method based on symbol search in Example 1. Detailed Implementation

[0021] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0022] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0023] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0024] Example 1, referring to Figure 1 This is one embodiment of the present invention, which provides a method for tracking the pseudocode of a direct sequence spread spectrum signal based on symbol search, comprising the following steps: S1. Receive the direct sequence spread spectrum signal and use the carrier Doppler estimation result output by the carrier tracking loop to perform carrier stripping on the direct sequence spread spectrum signal to obtain the Doppler demodulation result; based on the carrier Doppler estimation result and the pseudocode delay estimation value provided by the acquisition, use carrier-assisted technology to generate three local pseudocodes: lead, instant, and lag; use the three local pseudocodes to despread the Doppler demodulation result respectively to obtain the three despreading results: lead, instant, and lag.

[0025] It should be noted that the input signal is quadraturely demodulated using the Doppler estimation provided by the carrier tracking loop, and combined with the coarse estimation of pseudocode delay during the acquisition stage, three local pseudocodes—lead, instant, and lag—are generated using carrier-assisted technology. This effectively compensates for the pseudocode Doppler frequency offset caused by high dynamics, reduces the dynamic stress that the code loop itself needs to withstand, and enables the low-order code loop to work stably in high-dynamic scenarios, thereby improving the tracking robustness of the system under high-speed relative motion.

[0026] S2. Starting from the moment when the transient code phase of the instantaneous branch is detected to jump to zero, the despreading results of the leading, instantaneous, and lagging channels are segmented and integrated to clear them, and the segmented integration clearing results of each channel are obtained.

[0027] Furthermore, calculate the width of the data symbol. With pseudocode period Greatest common divisor Then the data symbol width and pseudocode period are both Multiples of positive integers; Select the segmented integration clearing time as ,in It is a positive integer, and the data symbol width and pseudocode period are also... Multiples of positive integers are denoted as ,in It is a positive integer.

[0028] When a direct sequence spread spectrum signal is generated, the data symbols and the spreading pseudocode are synchronously fixed, and spatial transmission delay does not affect this relationship. Any... The data symbol transition times are: ; Any number The start time of each pseudocode cycle is: ; in, That is, the transient code phase of the spread spectrum signal from The moment it jumps to 0.

[0029] A pseudocode period contains a total of indivual Time interval segmentation, any number of segments Within the pseudocode period, the first The range of each time segment is If the data sign changes within a segment, then there exists... This makes the data symbol transition time satisfy: ; Equivalent to: ; because All are integers. Since the integer is also an integer, the above statement is invalid. Therefore, the transient code phase of the instantaneous branch is detected in real time. When it first came from Starting from the moment of transition to 0, utilize The generation interval is The timing pulse can guarantee that, at any time... The data symbols in the despreading results do not change within the time period.

[0030] It should be noted that by calculating the greatest common divisor of the data symbol width and the pseudocode period and setting the segmented integration clearing time accordingly, the inherent synchronization and fixed relationship between the two is used to mathematically guarantee that there are no data symbol jumps within any segmented integration interval. This method can achieve coherent segmented integration without symbol jump interference without relying on external symbol synchronization information, laying a pure data foundation for subsequent long-term coherent accumulation.

[0031] S3. Based on the data symbol width, segment time, and loop control interval, construct a symbol search matrix, and perform matrix multiplication operations with the segmented integral clearing results of the lead, instant, and lag paths respectively to obtain the secondary search accumulation results of each path.

[0032] Furthermore, let the loop control interval be... The loop control interval contains Data symbols, namely ; Taking the local integration start time as a reference, there are ββ possible data symbol transition positions, corresponding to the transition occurring at the th... indivual Segment endpoints; For the Possible jump positions Crossing within the loop control interval A data symbol interval; The value of the first data symbol is used as the reference, and the rest... The values ​​of each data symbol are either the same sign as the reference or have a different sign than the reference, totaling [number missing]. Combinations; Represent each combination as a binary sequence. ,in =0 indicates a reference symbol; Convert binary sequence to symbol sequence ; The total number of segments within the loop control interval Divided into Section, No. The segment contains indivual Segmented, including: ; For each transition position Combined with each symbol, construct a length of Symbol search style , among which the former The elements are Next The elements are And so on; All symbol search patterns are arranged in rows to form a symbol search matrix. ,in But when hour, and Since the symbols are the same, only one is retained. time A unique style; The final symbol search matrix has 10 rows. ; The piecewise integral clearing result of the leading branch is represented as a complex vector. ,in For the first indivual Piecewise complex correlation values; The piecewise integral clearing result of the instantaneous branch is represented as a complex vector. ; The piecewise integral clearing result of the lagging branch is represented as a complex vector. ; Search matrix for symbols each line Calculate the accumulated results of the second-order search of the lead branch: ; Calculate the accumulated results of the instantaneous branch quadratic search: ; Calculate the accumulated results of the second-order search for the lagging branch: ; All , , These are respectively used to form the vector of accumulated results from the secondary search.

[0033] It should be noted that by constructing a symbol search matrix covering all possible symbol transition positions and symbol combinations, and by performing full combination symbol correction and secondary accumulation on the piecewise integration results, the single-symbol period coherent accumulation, which was originally limited by unknown symbol transitions, is extended to multiple symbol periods. This mechanism achieves true long-term coherent accumulation without relying on bit synchronization, fundamentally avoiding the signal-to-noise ratio loss caused by incoherent or differential coherent accumulation.

[0034] S4. Calculate the square of the modulus of the second-order search accumulation result of the immediate branch, select the symbol search pattern corresponding to the maximum value of the modulus as the matching symbol search pattern, and select the corresponding accumulation result from the second-order search accumulation results of the leading, immediate and lagging paths according to the matching symbol search pattern to obtain the final long-term second-order accumulation result.

[0035] Furthermore, search for the style number for each symbol. Calculate the squared modulus of the accumulated result of the instantaneous branch quadratic search: ; Compare all Select to make Largest serial number ,Right now: ; serial number Corresponding symbol search style The search style is set to match symbols; The matching symbol search style can correct the sign of the piecewise integral clearing result even when the position of the data symbol jump is unknown, so that the secondary accumulation of the piecewise integral clearing result is not affected by the data symbol jump.

[0036] It should be noted that by selecting the symbol search pattern corresponding to the quadratic accumulation result with the largest modulus square as the matching pattern, the optimal estimation and symbol correction of the real data symbol sequence are automatically completed. This maximum likelihood criterion ensures the maximization of accumulated energy, effectively suppresses the influence of noise, and improves the accuracy and reliability of pseudocode phase estimation under extremely low carrier-to-noise ratio conditions.

[0037] S5. Using the final long-term secondary accumulation result, a pseudo-code phase discrimination result is generated through a normalized dot product power discriminator.

[0038] Furthermore, the index is selected from the accumulated result vector of the secondary search of the advanced branch. corresponding value ; Select the sequence number from the vector of accumulated results of the secondary search of the lagging branch. corresponding value ; Will and Substitute the values ​​into the normalized dot product power discriminator to calculate the pseudocode phase discrimination result. Its expression is: ; Pseudocode phase identification results The unit is a chip, which reflects the direction and magnitude of the phase deviation between the local pseudocode and the received signal pseudocode.

[0039] It should be noted that the normalized dot product power discriminator is used to process the accumulation results of the lead and lag branches under the matching pattern. Its output has good linearity and resistance to amplitude fluctuations. It can accurately reflect the phase deviation between the local pseudocode and the received pseudocode, and provide a high-precision error driving signal for the loop, thereby ensuring the steady-state accuracy of pseudocode tracking.

[0040] S6. Perform median filtering on the pseudocode phase discrimination result to obtain the median filtering result.

[0041] Furthermore, cache contiguous The pseudocode phase identification results of each loop control time slot form a sequence. ; Sort the sequence by numerical value; like For odd numbers, the value at the middle position after sorting is taken as the median filter result. ; like If the number is even, take the arithmetic mean of the two middle values ​​after sorting as the median filtering result. ; Median filtering results Used to remove outliers in the pseudocode phase identification results and eliminate the disturbance effect of outliers on the loop.

[0042] It should be noted that by applying median filtering to the pseudocode phase discrimination results, outliers caused by noise bursts or accumulation anomalies are effectively eliminated, thus avoiding the disturbance of the loop state by erroneous error signals. This nonlinear filtering method enhances the stability and anti-interference capability of the system in a strong noise environment while preserving the loop's dynamic response capability.

[0043] S7. Input the median filtering result into the loop filter to generate the loop filter output, and correct the frequency word of the local pseudocode numerically controlled oscillator based on the loop filter output.

[0044] Furthermore, a first-order loop filter is used to filter the median filtering result. For filtering, the difference equation of the loop filter is: ; in, For the first The loop filter output of each loop control time slot, To normalize the gain of the dot product power discriminator, For loop control interval; Loop filter output As the frequency control word increment, it corrects the frequency word of the local pseudocode numerically controlled oscillator. Its update formula is: ; Driven by the sampling clock, the local pseudo-code numerically controlled oscillator continuously generates three local pseudo-codes—leading, instantaneous, and lagging—based on the updated frequency word, thereby achieving closed-loop tracking of the pseudo-code phase.

[0045] It should be noted that a first-order loop filter is used to process the error signal after median filtering, and the frequency word of the local pseudocode numerically controlled oscillator is dynamically adjusted accordingly. The structure is simple and convergent. Combined with the aforementioned carrier-assisted and symbol search accumulation, the entire loop can still maintain closed-loop tracking under extremely low carrier-to-noise ratio and high dynamic conditions, achieving high-precision and high-robust pseudocode synchronization for weak spread spectrum signals.

[0046] This embodiment also provides a computer device applicable to the symbol-search-based direct sequence spread spectrum signal pseudocode tracking method, comprising: a memory and a processor; the memory is used to store computer-executable instructions, and the processor is used to execute the computer-executable instructions to implement the symbol-search-based direct sequence spread spectrum signal pseudocode tracking method proposed in the above embodiment.

[0047] The computer device can be a terminal, comprising a processor, memory, communication 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 communication interface is used for wired or wireless communication with external terminals; wireless communication can be achieved through Wi-Fi, carrier networks, NFC (Near Field Communication), or other technologies. The display screen can be an LCD screen or an e-ink screen. The input devices can be a touch layer covering the display screen, buttons, a trackball, or a touchpad on the computer device's casing, or an external keyboard, touchpad, or mouse.

[0048] This embodiment also provides a storage medium storing a computer program that, when executed by a processor, implements the direct sequence spread spectrum signal pseudocode tracking method based on symbol search as proposed in the above embodiments. The storage medium can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as Static Random Access Memory (SRAM), Electrically Erasable Programmable Read-Only Memory (EEPROM), Erasable Programmable Read Only Memory (EPROM), Programmable Red-Only Memory (PROM), Read-Only Memory (ROM), magnetic storage, flash memory, magnetic disk, or optical disk.

[0049] In summary, this invention determines the transition-free segmented integration time by utilizing the synchronous fixed relationship between data symbols and pseudocode periods. It then combines this with a symbol search matrix to perform full combination symbol correction and secondary coherent accumulation on the segmented integration results across multiple symbol periods. This effectively eliminates the disruption to long-term coherent accumulation caused by unknown data symbol transitions, achieving true coherent accumulation across multiple symbol periods without requiring known symbol edges. Furthermore, by incorporating carrier-assisted input, normalized dot product power discrimination, median filtering, and first-order loop filtering techniques, the invention improves the pseudocode tracking accuracy, stability, and weak signal acquisition capability of the system in high-dynamic, extremely low carrier-to-noise ratio environments. This overcomes the squared loss and signal-to-noise ratio loss problems caused by traditional incoherent or differential coherent accumulation.

[0050] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for tracking pseudocodes of direct sequence spread spectrum signals based on symbol search, characterized in that: include: The direct sequence spread spectrum signal is received, and the carrier Doppler estimation result output by the carrier tracking loop is used to perform carrier stripping on the direct sequence spread spectrum signal to obtain the Doppler demodulation result; Based on the carrier Doppler estimation results and the pseudocode delay estimation values ​​provided by the acquisition, carrier-assisted techniques are used to generate three local pseudocodes: lead, instant, and lag. The Doppler demodulation results are despread using the three local pseudo-codes (lead, instant, and lag) to obtain the three despread results (lead, instant, and lag). Starting at the moment when the transient code phase of the instantaneous branch is detected to jump to zero, the despreading results of the three paths (leading, instantaneous, and lagging) are segmented and integrated to clear them, and the segmented integration clearing results of each path are obtained. Based on the data symbol width, segment time, and loop control interval, a symbol search matrix is ​​constructed, and the symbol search matrix is ​​multiplied by the segmented integral clearing results of the lead, instant, and lag paths respectively to obtain the secondary search accumulation results of each path. Calculate the square of the modulus of the accumulated result of the instantaneous branch secondary search, and select the symbol search pattern corresponding to the maximum value of the square of the modulus as the matching symbol search pattern; Based on the matching symbol search pattern, the corresponding accumulation result is selected from the secondary search accumulation results of the three paths of advance, instant, and lag to obtain the final long-term secondary accumulation result; Using the final long-term quadratic accumulation result, a pseudocode phase discrimination result is generated through a normalized dot product power discriminator; The pseudocode phase discrimination result is subjected to median filtering to obtain the median filtered result; The median filtering result is input into the loop filter to generate the loop filter output, and the frequency word of the local pseudocode numerically controlled oscillator is corrected based on the loop filter output.

2. The direct sequence spread spectrum signal pseudocode tracking method based on symbol search as described in claim 1, characterized in that: The step of performing segmented integration and clearing of the lead, instantaneous, and lag despreading results, starting from the moment the transient code phase of the instantaneous branch is detected to jump to zero, is as follows: Calculate data symbol width With pseudocode period Greatest common divisor Then the data symbol width and pseudocode period are both Multiples of positive integers; Select the segmented integration clearing time as ,in It is a positive integer, and the data symbol width and pseudocode period are also... Multiples of positive integers are denoted as ,in It is a positive integer; When a direct sequence spread spectrum signal is generated, the data symbols and the spreading pseudocode are synchronously fixed, and spatial transmission delay does not affect this relationship. Any... The data symbol transition times are: ; Any number The start time of each pseudocode cycle is: ； in, That is, the transient code phase of the spread spectrum signal from The moment when it jumps to 0; A pseudocode period contains a total of indivual Time interval segmentation, any number of segments Within the pseudocode period, the first The range of each time segment is If the data sign changes within a segment, then there exists... This makes the data symbol transition time satisfy: ; Equivalent to: ; because All are integers. Since the integer is also an integer, the above statement is invalid. Therefore, the transient code phase of the instantaneous branch is detected in real time. When it first came from Starting from the moment of transition to 0, utilize The generation interval is The timing pulse can guarantee that, at any time... The data symbols in the despreading results do not change within the time period.

3. The direct sequence spread spectrum signal pseudocode tracking method based on symbol search as described in claim 2, characterized in that: The specific steps for constructing the symbol search matrix based on the data symbol width, segmentation time, and loop control interval are as follows: Let the loop control interval be The loop control interval contains Data symbols, namely ; Taking the local integration start time as a reference, there are ββ possible data symbol transition positions, corresponding to the transition occurring at the th, th, and th... indivual Segment endpoints; For the Possible jump positions Crossing within the loop control interval A data symbol interval; The value of the first data symbol is used as the reference, and the rest... The values ​​of each data symbol are either the same sign as the reference or have a different sign than the reference, totaling [number missing]. Combinations; Represent each combination as a binary sequence. ,in =0 indicates a reference symbol; Convert binary sequence to symbol sequence ; The total number of segments within the loop control interval Divided into Section, No. The segment contains indivual Segmented, including: ; For each transition position Combined with each symbol, construct a length of Symbol search style , among which the former The elements are Next The elements are And so on; All symbol search patterns are arranged in rows to form a symbol search matrix. ,in But when hour, and Since the symbols are the same, only one is retained. time A unique style; The final symbol search matrix has 10 rows. .

4. The direct sequence spread spectrum signal pseudocode tracking method based on symbol search as described in claim 3, characterized in that: The step of performing matrix multiplication operations between the symbol search matrix and the piecewise integral clearing results of the lead-instantaneous, lag-instantaneous, and semi-lag-instantaneous paths to obtain the quadratic search accumulation results for each path is as follows: The piecewise integral clearing result of the leading branch is represented as a complex vector. ,in For the first indivual Piecewise complex correlation values; The piecewise integral clearing result of the instantaneous branch is represented as a complex vector. ; The piecewise integral clearing result of the lagging branch is represented as a complex vector. ; Search matrix for symbols each line Calculate the accumulated results of the second-order search of the lead branch: ; Calculate the accumulated results of the instantaneous branch quadratic search: ; Calculate the accumulated results of the second-order search for the lagging branch: ; All , , These are respectively used to form the vector of accumulated results from the secondary search.

5. The direct sequence spread spectrum signal pseudocode tracking method based on symbol search as described in claim 4, characterized in that: The specific steps for calculating the squared modulus of the accumulated result of the instantaneous branch quadratic search, and selecting the symbol search pattern corresponding to the maximum value of the squared modulus as the matching symbol search pattern are as follows: Search for the style number for each symbol Calculate the squared modulus of the accumulated result of the instantaneous branch quadratic search: ; Compare all Select to make Largest serial number ,Right now: ； serial number Corresponding symbol search style The search style is set to match symbols; The matching symbol search style can correct the sign of the piecewise integral clearing result even when the position of the data symbol jump is unknown, so that the secondary accumulation of the piecewise integral clearing result is not affected by the data symbol jump.

6. The direct sequence spread spectrum signal pseudocode tracking method based on symbol search as described in claim 5, characterized in that: The specific steps for generating pseudocode phase discrimination results using the final long-term secondary accumulation result through a normalized dot product power discriminator are as follows: Select the sequence number from the vector of accumulated results of the secondary search of the advanced branch. corresponding value ; Select the sequence number from the vector of accumulated results of the secondary search of the lagging branch. corresponding value ; Will and Substitute the values ​​into the normalized dot product power discriminator to calculate the pseudocode phase discrimination result. Its expression is: ; Pseudocode phase identification results The unit is a chip, which reflects the direction and magnitude of the phase deviation between the local pseudocode and the received signal pseudocode.

7. The direct sequence spread spectrum signal pseudocode tracking method based on symbol search as described in claim 6, characterized in that: The specific steps for performing median filtering on the pseudocode phase discrimination result to obtain the median filtering result are as follows: Cache contiguous The pseudocode phase identification results of each loop control time slot form a sequence. ; Sort the sequence according to its numerical value; like For odd numbers, the value at the middle position after sorting is taken as the median filter result. ; like If the number is even, take the arithmetic mean of the two middle values ​​after sorting as the median filtering result. ; The median filtering result Used to remove outliers in the pseudocode phase identification results and eliminate the disturbance effect of outliers on the loop.

8. The direct sequence spread spectrum signal pseudocode tracking method based on symbol search as described in claim 7, characterized in that: The specific steps are as follows: inputting the median filtering result into the loop filter to generate the loop filter output, and correcting the frequency word of the local pseudo-code numerically controlled oscillator based on the loop filter output. Median filtering results were obtained by using a first-order loop filter. For filtering, the difference equation of the loop filter is: ; in, For the first The loop filter output of each loop control time slot, To normalize the gain of the dot product power discriminator, For loop control interval; Loop filter output As the frequency control word increment, it corrects the frequency word of the local pseudocode numerically controlled oscillator. Its update formula is: ; Driven by the sampling clock, the local pseudo-code numerically controlled oscillator continuously generates three local pseudo-codes—leading, instantaneous, and lagging—based on the updated frequency word, achieving closed-loop tracking of the pseudo-code phase.

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 direct sequence spread spectrum signal pseudocode tracking method based on symbol search as described in any one of claims 1 to 8.

10. A 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 steps of the direct sequence spread spectrum signal pseudocode tracking method based on symbol search as described in any one of claims 1 to 8.

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