High-sensitivity acquisition method for pilot branch and data branch

Abstract

This invention belongs to the field of satellite systems and relates to a high-sensitivity acquisition method for pilot and data branches. The method includes: constructing multiple search units; acquiring the pilot and data branches of a satellite signal based on the current search unit, obtaining the coherent integrals of the pilot and data branches; performing a first merging of the coherent integrals of the pilot and data branches to obtain a merged result; making an acquisition decision on the merged result; if successful, stopping the process; performing a second merging of the coherent integrals of the pilot and data branches to obtain a merged result; making an acquisition decision on the merged result; if successful, stopping the process; determining whether the current search unit is the last search unit; if so, failing; otherwise, proceeding to the next acquisition. This invention selects the primary and secondary peak values ​​in the magnitude of the merged result and makes an acquisition decision by comparing the ratio of the primary and secondary peak values ​​with a threshold value, thus solving the data branch flipping problem and improving acquisition sensitivity.

Description

Technical Field

[0001] This invention belongs to the field of satellite systems and relates to a high-sensitivity acquisition method for pilot and data branches. Background Technology

[0002] With the completion and operation of my country's BeiDou system and the rapid development of other GNSS (global navigation satellite system) systems (US GPS, Russian GLONASS, European Galileo), the availability of these systems has greatly increased. Among these, the proportion of dual-branch signal systems that include both pilot and data signals is gradually increasing. Since traditional acquisition circuits can generally only acquire a single-branch signal, for new signal systems that include pilots and messages, how to maximize acquisition sensitivity while maintaining the same data length is a crucial problem that needs to be solved in engineering applications. Summary of the Invention

[0003] To address the aforementioned problems in the prior art, this invention employs a high-sensitivity acquisition method using a pilot branch and a data branch, comprising:

[0004] S1. Receive satellite signals, construct multiple search units, and use the first search unit as the current search unit; each search unit includes multiple data points;

[0005] S2. Based on the current search unit, the pilot branch and data branch of the satellite signal are captured respectively, and the coherent integral of the pilot branch and data branch at each data point in the current search unit is obtained;

[0006] S3. Perform the first merging of the coherent integrals of the pilot branch and the data branch at each data point in the current search unit to obtain the first merging result of the pilot branch and the data branch at each data point in the current search unit.

[0007] S4. Make a capture decision on the first merged result of each data point in the current search unit for the pilot branch and the data branch. If the capture is successful, stop processing; otherwise, proceed to step S5.

[0008] S5. Perform a second merging of the coherent integrals of the pilot branch and the data branch at each data point in the current search unit to obtain the second merging result of the pilot branch and the data branch at each data point in the current search unit.

[0009] S6. Make a capture decision on the second merged result of each data point in the current search unit for the pilot branch and the data branch. If the capture is successful, stop processing; otherwise, proceed to step S7.

[0010] S7. Determine if the current search unit is the last search unit. If so, the capture fails. Otherwise, take the next search unit as the current search unit and return to step S2 for the next capture.

[0011] Beneficial effects:

[0012] 1. This invention utilizes the power allocation coefficients of the Pilot and Data branches to weightedly combine the coherent integrals of the Pilot and Data branches, thereby improving the merging effect of the coherent integrals and increasing the acquisition sensitivity. 2. This invention utilizes the phase relationship between the Pilot and Data branches to merge the coherent integrals of the Pilot and Data branches, increasing the gain of the coherent integral and thus improving the acquisition sensitivity. 3. This invention selects the primary and secondary peak values ​​in the magnitude of the merged results of each data point in the search unit and makes an acquisition decision by comparing the ratio of the primary and secondary peak values ​​with a preset threshold value, solving the flipping problem of the Data branch and thus improving the acquisition sensitivity. Attached Figure Description

[0013] Figure 1 This is a flowchart of a high-sensitivity acquisition method for a pilot branch and a data branch provided in an embodiment of the present invention. Detailed Implementation

[0014] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0015] like Figure 1 As shown, the present invention employs a high-sensitivity acquisition method using a pilot branch and a data branch, comprising:

[0016] S1. Receive satellite signals, construct multiple search units, and use the first search unit as the current search unit; each search unit includes multiple data points;

[0017] Constructing multiple search units includes:

[0018] The search range for pseudocode phase and frequency offset is predefined, and the search range for pseudocode phase and frequency offset is divided into multiple search units on an average basis; wherein, each data point includes: code phase offset and frequency offset.

[0019] The search range for the pseudocode phase offset is typically based on an integer multiple of the pseudocode period, for example, set to... Where N is the multiple of the maximum possible phase deviation covered. This refers to the pseudocode period. The search range for frequency offset is based on the subcarrier spacing, superimposed with dynamic factors such as Doppler frequency shift and oscillator tolerance, and combined with the characteristics of the acquisition algorithm to achieve a balance between coverage and computational complexity. For example, the ±10kHz range for GPS receivers and the ±10kHz range for LTE.

[0020] The received satellite signal is an intermediate frequency (IF) signal, represented as: Where k represents the discrete time index, For navigation messages, For satellite codes, The carrier wave of the received satellite signal. The carrier frequency of the received satellite signal. The initial phase offset of the received satellite signal. It is additive white Gaussian noise (AWGN).

[0021] S2. Based on the current search unit m, capture the Pilot and Data branches of the satellite signal respectively, and obtain the coherent integrals of the Pilot and Data branches at each data point n within the current search unit m. , ;in, , For the I-path coherent integral of the pilot branch, For the Q-path coherent integral of the pilot branch, , For the I-path coherent integral of the data branch, For the Q-path coherent integral of the data branch;

[0022] The acquisition process of the pilot branch is as follows:

[0023] S21. Generate pseudocode for each data point n of the pilot branch to be reproduced locally within the current search unit m. and carrier ;in, The carrier of the I-path is the data point n locally reproduced by the pilot branch within the current search unit m. The carrier of the Q path is the local reproduction of the pilot branch at data point n within the current search unit m;

[0024] The pseudocode of the pilot branch is reproduced locally at each data point n within the current search unit m. include:

[0025] Select a specific initial state (seed value) for the pilot branch and a specific pseudocode generation algorithm for the pilot branch; generate a pseudocode sequence based on the selected initial state and pseudocode generation algorithm; appropriately shift the generated pseudocode sequence according to the pseudocode phase offset of each data point n within the current search unit m to obtain the pseudocode locally reproduced by the pilot branch at each data point n within the current search unit m. .

[0026] The carriers locally reproduced at each data point n within the current search unit m for generating the pilot branch include:

[0027] Calculate the total carrier frequency: based on the known carrier frequency By adding the frequency offset of each data point n within the current search unit m, the total carrier frequency of each data point n is obtained. That is, the carrier frequency reproduced locally;

[0028] Generate carrier signal: based on the total carrier frequency of data point n Generate carrier signals in the form of in-phase (I) and quadrature (Q) components for data point n, respectively. , .

[0029] S22. Calculate the I-path coherent integral and Q-path coherent integral of each data point n in the current search unit m based on the satellite signal, the locally reproduced pseudocode, and the locally reproduced carrier.

[0030] The coherent integral of the I-branch of data point n within the current search unit m is calculated as follows:

[0031]

[0032]

[0033] Where N is the time length.

[0034] Branch Q is similar to branch I:

[0035]

[0036] The capture operation process of the Data branch is similar to that of the Pilot branch, except that the pseudocode PN reproduced locally is different. The Data branch is calculated using the code of Data, while the Pilot branch is calculated using the code of Pilot.

[0037] S3. Based on the phase relationship between the Pilot branch and the Data branch, perform coherent integration of the Pilot branch and the Data branch for each data point n within the current search unit m. , Perform the first merge to obtain the first merge result of each data point n in the current search unit m of the Pilot branch and the Data branch. ;

[0038] The merging of the coherent integrals of the Pilot branch and the Data branch for each data point n within the current search unit m includes:

[0039] S31. Obtain the power allocation coefficients of the pilot branch and the data branch. , To obtain the phase difference between the pilot branch and the data branch;

[0040] Power allocation factor for Pilot and Data branches , Both the phase difference and power distribution factor are defined by the Interface Control Document (ICD) to guide receiver designers on how to process the received signal; , satisfy Currently, the phase difference between the Pilot and Data branches is defined in only two ways: 0 degrees and 90 degrees. At the communication transmitter, this is determined by the power allocation coefficient pre-defined in the ICD. , The signal is transmitted based on phase difference. The Interface Control Document (ICD) details key information such as signal format, data structure, and communication protocol to ensure correct interaction between different devices and systems. For example, for GPS L5, the power allocation coefficient... , Both are defined as 1 / 2.

[0041] S32. When the phase difference between the Pilot branch and the Data branch is 0, according to the power allocation coefficient... , The coherent integrals of the Pilot and Data branches over each data point n within the current search unit m. , A weighted combination is performed to obtain the first merged result for each data point n within the current search unit m; when the phase difference between the Pilot branch and the Data branch is 90 degrees, the coherent integral of the Pilot branch and the Data branch for each data point n within the current search unit m is then calculated. , Perform phase alignment based on power allocation factor , The coherent integrals of the Pilot branch and the Data branch after phase alignment of each data point n in the current search unit m are weighted and combined to obtain the first merged result of each data point n in the current search unit m.

[0042] According to the power allocation coefficient , The formula for weighted combining the coherent integrals of the pilot branch and the data branch for each data point n within the current search unit m is as follows: The first merge result was obtained. .

[0043] Phase alignment of the coherent integrals of the Pilot branch and the Data branch within the current search unit m includes: multiplying the coherent integral of the Data branch within the current search unit m of the data point n by the imaginary unit j, to obtain... The coherent integral of the Pilot branch for data point n within the current search unit m is not processed, and the phase-aligned coherent integral of the Pilot branch and the Data branch for data point n within the current search unit m is obtained.

[0044] According to the power allocation coefficient , The formula for weighted combining the coherent integrals of the pilot branch and the data branch after phase alignment of each data point n within the current search unit m is as follows:

[0045]

[0046] Will Representing this as a tuple, we obtain the first merge result. ; where j is the imaginary unit.

[0047] S4. The first merged result of the Pilot branch and the Data branch for each data point n within the current search unit m. Perform a capture decision; if the capture is successful, stop processing; otherwise, proceed to step S5.

[0048] The first merged result of each data point n within the current search unit m for the Pilot branch and the Data branch. The capture decision includes: since the merged result is a complex number, calculating the first merged result of the Pilot branch and the Data branch for each data point n within the current search unit m. The modulus (i.e., absolute value) in the first merged result Select the maximum value from the modulus. That is, the main peak value; select the maximum value. The corresponding data points of the first merge result Acquire data points The corresponding pseudocode reproduced locally by the pilot branch phase Remove the pseudocode that is locally reproduced in the pilot branch from all data points within the current search unit m. The phase in the interval For the data points within the range, select the maximum value from the modulus of the first merged result of the remaining data points. That is, the second highest peak value; calculate the highest peak value. , If the ratio is greater than a preset threshold, the capture is considered successful; otherwise, the capture is considered unsuccessful.

[0049] Pseudocodes reproduced locally in the pilot branch were removed. The phase in the interval The first merge result corresponding to the data points within is to remove the normal small peaks near the main peak, find the secondary peaks outside the normal peaks, and then calculate the ratio of the main peak to the secondary peak. The ratio of the main peak to the secondary peak can determine the capture result, which solves the flipping problem of the data branch and thus improves the capture sensitivity.

[0050] Where Q is the phase threshold, typically 0.5 chips.

[0051] The preset threshold is set based on the test results and is related to the expected sensitivity and RF circuitry, generally ranging from 1.1 to 4.0.

[0052] S5. Based on the phase relationship between the Pilot branch and the Data branch, perform a second merging of the coherent integrals of the Pilot branch and the Data branch for each data point n in the current search unit m to obtain the second merging result of the Pilot branch and the Data branch for each data point n in the current search unit m.

[0053] The process of performing the second merging of the coherent integrals of the pilot and data branches at each data point within the current search unit is the same as the first merging process, except that the difference in the navigation message on the Data branch will result in equivalent coefficients. The sign before "" indicates that the second merged result is obtained when the phase difference between the Pilot and Data branches is 0. When the phase difference between the Pilot and Data branches is 90 degrees, the second merged result is obtained. .

[0054] S6. Make a capture decision on the second merged result of each data point n in the current search unit m for the Pilot branch and the Data branch. If the capture is successful, stop processing; otherwise, proceed to step S7.

[0055] The capture and decision process in this step is the same as in step S4.

[0056] S7. Determine if the current search unit is the last search unit. If so, the capture fails. Otherwise, take the next search unit m+1 as the current search unit and return to step S2 for the next capture.

[0057] The above-described embodiments further illustrate the purpose, technical solution, and advantages of the present invention. It should be understood that the above-described embodiments are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made to the present invention within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-sensitivity acquisition method for pilot and data branches, characterized in that, include: S1. Receive satellite signals, construct multiple search units, and use the first search unit as the current search unit; each search unit includes multiple data points; S2. Based on the current search unit, the pilot branch and data branch of the satellite signal are captured respectively, and the coherent integral of the pilot branch and data branch at each data point in the current search unit is obtained; S3. Perform the first merging of the coherent integrals of the pilot branch and the data branch at each data point in the current search unit to obtain the first merging result of the pilot branch and the data branch at each data point in the current search unit. S4. Make a capture decision on the first merged result of each data point in the current search unit for the pilot branch and the data branch. If the capture is successful, stop processing; otherwise, proceed to step S5. S5. Perform a second merging of the coherent integrals of the pilot branch and the data branch at each data point in the current search unit to obtain the second merging result of the pilot branch and the data branch at each data point in the current search unit. S6. Make a capture decision on the second merged result of each data point in the current search unit for the pilot branch and the data branch. If the capture is successful, stop processing; otherwise, proceed to step S7. S7. Determine if the current search unit is the last search unit. If so, the capture fails. Otherwise, take the next search unit as the current search unit and return to step S2 for the next capture. The first merging of the coherent integrals of the pilot and data branches at each data point within the current search unit includes: obtaining the power allocation coefficients of the pilot and data branches. , The phase difference between the pilot branch and the data branch is obtained. When the phase difference between the pilot branch and the data branch is 0, the power allocation coefficient is used to determine the phase difference. , The coherent integrals of the pilot branch and the data branch at each data point n within the current search unit m are weighted and combined to obtain the first combined result for each data point n within the current search unit m. When the phase difference between the pilot branch and the data branch is 90 degrees, the coherent integrals of the pilot branch and the data branch at each data point n within the current search unit m are phase aligned, based on the power allocation coefficient. , The coherent integrals of the pilot branch and the data branch after phase alignment of each data point n in the current search unit m are weighted and combined to obtain the first combined result of each data point n in the current search unit m. The capture decision for the first merged result of the pilot branch and data branch for each data point within the current search unit includes: calculating the magnitude of the first merged result of the pilot branch and data branch for each data point n within the current search unit m, and selecting the maximum value among the magnitudes of the first merged results of all data points within the current search unit m. Select the maximum value The corresponding data points of the first merge result Acquire data points The phase of the pseudocode reproduced locally in the corresponding pilot branch In the current search unit m, remove the phase of the pseudocode locally reproduced by the pilot branch from all data points. For the data points within the range, select the maximum value from the modulus of the first merged result of the remaining data points. ; Calculate the maximum value , The ratio of Q to Q is used to determine whether the capture is successful or not. If the ratio is greater than a preset threshold, the capture is considered successful; otherwise, the capture is considered unsuccessful. Here, Q is a preset phase threshold. The second merging process is the same as the first merging process, except that the power allocation coefficient of the data branch is [missing information]. ; The process of making a capture decision on the second merge result is the same as the process of making a capture decision on the first merge result.

2. The high-sensitivity acquisition method for pilot and data branches according to claim 1, characterized in that, Constructing multiple search units includes: predefining the search range of pseudocode phase and frequency offset, and dividing the search range of pseudocode phase and frequency offset into multiple search units; wherein, each data point of the search unit includes: code phase offset and frequency offset.

3. The high-sensitivity acquisition method for pilot and data branches according to claim 1, characterized in that, The acquisition of the pilot and data branches of the satellite signal includes: generating pseudocodes and carriers that are locally reproduced for each data point in the current search unit; and calculating the I-path coherent integral and Q-path coherent integral for each data point in the current search unit based on the satellite signal, the locally reproduced pseudocodes, and the locally reproduced carriers.

4. The high-sensitivity acquisition method for pilot and data branches according to claim 3, characterized in that, Calculating the I-path coherent integral and Q-path coherent integral of the pilot branch at each data point within the current search unit includes: ； ； in, , Let I and Q be the coherent integrals of the pilot branch for data point n within the current search unit m, respectively, and k represent the discrete time index. For the received satellite signals, The pseudocode for the local reproduction of data point n within the current search unit m by the pilot branch. The carrier of the I-path is the data point n locally reproduced by the pilot branch within the current search unit m. The carrier of the Q-path is the local reproduction of the data point n of the pilot branch within the current search unit m.

5. The high-sensitivity acquisition method for pilot and data branches according to claim 1, characterized in that, The preset phase threshold Q is 0.

5.

6. The high-sensitivity acquisition method for pilot and data branches according to claim 1, characterized in that, The preset threshold value ranges from 1.1 to 4.

0.

7. The high-sensitivity acquisition method for pilot and data branches according to claim 1, characterized in that, Phase alignment of the coherent integrals of the pilot branch and the data branch within the current search unit m includes: multiplying the coherent integral of the data branch within the current search unit m by the imaginary unit j, and leaving the coherent integral of the pilot branch within the current search unit m unprocessed, to obtain the phase-aligned coherent integrals of the pilot branch and the data branch within the current search unit m.

8. The high-sensitivity acquisition method for pilot and data branches according to claim 1, characterized in that, The second merging of the coherent integrals of the pilot and data branches at each data point within the current search unit includes: obtaining the power allocation coefficients of the pilot and data branches. , The phase difference between the pilot branch and the data branch is obtained; when the phase difference between the pilot branch and the data branch is 0, the power allocation coefficient is used. , The coherent integrals of the pilot branch and the data branch at each data point n within the current search unit m are weighted and combined to obtain the second combined result for each data point n within the current search unit m. When the phase difference between the pilot branch and the data branch is 90 degrees, the coherent integrals of the pilot branch and the data branch at each data point n within the current search unit m are phase aligned, based on the power allocation coefficient. , The coherent integrals of the pilot branch and the data branch after phase alignment of each data point n in the current search unit m are weighted and combined to obtain the second merged result of each data point n in the current search unit m.

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