Method and device for extracting GPS M code authorized sequence based on C / A code assistance

Abstract

The application discloses a kind of based on C / A code auxiliary GPS M code authorization sequence extraction method and device, method includes: through C / A code signal stable tracking after obtaining the carrier frequency and initial phase of CASM modulated signal, according to carrier frequency and initial phase, the carrier of CASM modulated signal is stripped and is divided into I, Q road signal;Through low-pass filter, BOC (10,5) Signal and high frequency signal in I road signal are filtered out, to extract P (Y) code signal;Through low-pass filter, high frequency signal in Q road signal is filtered out, to extract including BOC (10,5) Signal, P (Y) code signal, C / A code signal Q road signal;Simplified signal is obtained by using C / A code signal to the extracted Q road signal and simplified processing;Direct current signal is obtained by direct current operation to simplified signal;BOC (10,5) Signal is obtained by using P (Y) code signal to direct current signal and simplified processing;Subcarrier of BOC (10,5) Signal is removed, to extract GPS M code authorization sequence.The application can quickly extract correct M code authorization sequence.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of satellite navigation signal processing, and particularly relates to a GPS M code authorization sequence extraction method and device based on C / A code assistance. BACKGROUND

[0002] The "navigation war" capability of the global satellite navigation positioning system (GPS) has become an important guarantee for modern satellite navigation positioning and timing services. In the process of GPS modernization, the United States has added an M code signal to the L1 frequency band on the Block IIR-M satellite and the Block IIF satellite. The signal is an authorized signal, and compared with the traditional authorized signal P(Y) code signal, the M code signal has faster acquisition rate, stronger anti-interference ability and higher security. However, since the M code signal is an authorized signal, its signal pseudo code sequence is unknown, so how to extract the M code authorization sequence is a big difficulty. The existing M code authorization sequence extraction method is mainly based on the correlation of the signal, and uses the combination of high and low levels to extract the authorization sequence of the M code signal with the maximum correlation as the evaluation standard.

[0003] However, when the signal-to-noise ratio of the signal is low, the correlation of different high and low level combinations is not much different from the correlation of the M code authorization sequence alone, so using correlation as the evaluation standard may cause the extracted M code authorization sequence to be incorrect. Moreover, extracting the M code authorization sequence by combining high and low levels has a huge amount of calculation in the process of trying these combinations one by one, and the extraction efficiency is not high. SUMMARY

[0004] In order to solve the above problems existing in the prior art, the present application provides a GPS M code authorization sequence extraction method and device based on C / A code assistance. The technical problems to be solved by the present application are realized by the following technical solutions:

[0005] In the first aspect, the present application embodiment provides a GPS M code authorization sequence extraction method based on C / A code assistance, applied to a scenario including GPS L1 frequency band, and the method comprises:

[0006] The CASM modulated signal is acquired, and the carrier frequency and initial phase of the CASM modulated signal are acquired after the CASM modulated signal is stably tracked through the C / A code signal; the carrier of the CASM modulated signal is stripped and divided into I channel signal and Q channel signal according to the carrier frequency and the initial phase; wherein, the I channel signal comprises BOC(10, 5) signal, P(Y) code signal and first high frequency signal; the Q channel signal comprises the BOC(10, 5) signal, the P(Y) code signal, C / A code signal and second high frequency signal; the C / A code signal is a known signal; the P(Y) code signal and the C / A code signal are both BPSK modulated signals;

[0007] The BOC(10, 5) signal and the first high frequency signal in the I channel signal are filtered through a first low pass filter to extract the P(Y) code signal;

[0008] The second high frequency signal in the Q channel signal is filtered through a second low pass filter to extract the Q channel signal comprising the BOC(10, 5) signal, the P(Y) code signal and the C / A code signal;

[0009] Based on the characteristics of the BPSK modulated signal, the extracted Q channel signal is processed by the C / A code signal to obtain a simplified signal;

[0010] The simplified signal is subjected to a direct current removal operation to obtain a direct current removed signal;

[0011] Based on the characteristics of the BPSK modulated signal, the direct current removed signal is processed by the P(Y) code signal to obtain the BOC(10, 5) signal;

[0012] The subcarriers of the BOC(10, 5) signal are removed to extract the GPS M code authorization sequence.

[0013] In an embodiment of the present application, the carrier of the CASM modulated signal is stripped and divided into I channel signal and Q channel signal according to the carrier frequency and the initial phase, comprising:

[0014] The carrier of the CASM modulated signal is stripped according to the carrier frequency and the initial phase, and the CASM modulated signal is re-expressed without considering the power and modulation index of the CASM modulated signal;

[0015] The part of the re-expressed CASM modulated signal containing the C / A code signal is taken as the Q channel signal, and the part of the re-expressed CASM modulated signal not containing the C / A code signal is taken as the I channel signal.

[0016] In an embodiment of the present application, the I channel signal is expressed as:

[0017] BOC(10,5)+P(Y)+fh1;

[0018] Wherein, BOC(10,5) represents BOC(10,5) signal, P(Y) represents P(Y) code signal, fh1 represents first high frequency signal.

[0019] The Q channel signal formula is represented as:

[0020] C / A+C / A*BOC(10,5)*P(Y)+fh2;

[0021] Wherein, C / A represents C / A code signal, fh2 represents second high frequency signal.

[0022] In one embodiment of the present application, the characteristic of the BPSK modulated signal is 1 when the same signals are multiplied.

[0023] In one embodiment of the present application, based on the characteristic of the BPSK modulated signal, the simplified signal obtained by simplifying the extracted Q channel signal using the C / A code signal, the formula is represented as:

[0024]

[0025] Wherein, C / A*C / A=1, C / A+C / A*BOC(10,5)*P(Y) represents the extracted Q channel signal.

[0026] In one embodiment of the present application, the direct current operation is performed on the simplified signal to obtain a direct current signal, and the formula is represented as:

[0027] BOC(10,5)*P(Y).

[0028] In one embodiment of the present application, based on the characteristic of the BPSK modulated signal, the BOC(10,5) signal is obtained by simplifying the direct current signal using the P(Y) code signal, and the formula is represented as:

[0029]

[0030] Wherein, P(Y)*P(Y)=1.

[0031] In one embodiment of the present application, after the BOC(10,5) signal and the first high frequency signal in the I channel signal are filtered out through the first low pass filter, the present application further comprises:

[0032] The signal filtered out through the first low pass filter is aligned to extract the P(Y) code signal.

[0033] In one embodiment of the present application, after the second high frequency signal in the Q-path signal is filtered out by the second low-pass filter, the method further comprises:

[0034] The signal filtered out by the second low-pass filter is aligned to extract the Q-path signal comprising the BOC(10,5) signal, the P(Y) code signal and the C / A code signal.

[0035] In a second aspect, an embodiment of the present application provides a GPS M code authorization sequence extraction device based on C / A code assistance, which is applied to a scenario comprising a GPS L1 frequency band, and the device comprises:

[0036] A preprocessing module is configured to acquire a CASM modulated signal, acquire a carrier frequency and an initial phase of the CASM modulated signal after stable tracking of a C / A code signal, and strip the carrier of the CASM modulated signal and divide it into an I-path signal and a Q-path signal according to the carrier frequency and the initial phase; wherein the I-path signal comprises a BOC(10,5) signal, a P(Y) code signal and a first high frequency signal; the Q-path signal comprises the BOC(10,5) signal, the P(Y) code signal, a C / A code signal and a second high frequency signal; the C / A code signal is a known signal; the P(Y) code signal and the C / A code signal are both BPSK modulated signals.

[0037] A first extraction module is configured to filter out the BOC(10,5) signal and the first high frequency signal in the I-path signal by a first low-pass filter to extract the P(Y) code signal.

[0038] A second extraction module is configured to filter out the second high frequency signal in the Q-path signal by a second low-pass filter to extract the Q-path signal comprising the BOC(10,5) signal, the P(Y) code signal and the C / A code signal.

[0039] A first simplification module is configured to simplify the extracted Q-path signal by using the C / A code signal based on the characteristics of the BPSK modulated signal to obtain a simplified signal.

[0040] A direct current removal module is configured to perform a direct current removal operation on the simplified signal to obtain a direct current removed signal.

[0041] A second simplification module is configured to simplify the direct current removed signal by using the P(Y) code signal based on the characteristics of the BPSK modulated signal to obtain the BOC(10,5) signal.

[0042] A third extraction module is configured to remove the subcarriers of the BOC(10,5) signal to extract a GPS M code authorization sequence.

[0043] The present application has the following beneficial effects:

[0044] The present invention proposes a GPS M-code license sequence extraction method based on C / A code assistance. This method addresses the problem of difficulty in obtaining GPS M-code license sequences by providing a simple, feasible, and fast way to obtain the correct M-code license sequence. This method does not depend on the correlation of the M-code license sequence and can still correctly extract the M-code license sequence even under low signal-to-noise ratio conditions. Furthermore, it does not require trying different combinations and has high extraction efficiency.

[0045] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0046] Figure 1 This is a flowchart illustrating a GPS M-code authorization sequence extraction method based on C / A code assistance provided in an embodiment of the present invention;

[0047] Figure 2 This is a schematic diagram of the GPS L1 band signal spectrum distribution provided in an embodiment of the present invention;

[0048] Figure 3 This is a schematic diagram of the spectrum distribution of the I-channel signal provided in an embodiment of the present invention;

[0049] Figure 4 This is a schematic diagram of the Q-channel signal spectrum distribution provided in an embodiment of the present invention;

[0050] Figure 5 This is a schematic diagram of the GPS M code license sequence extraction device based on C / A code assistance provided in an embodiment of the present invention. Detailed Implementation

[0051] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto.

[0052] For information regarding the characteristics of GPS L1 band signals using Coherent Adaptive Subcarrier Modulation (CASM) multiplexing, please refer to [link to relevant documentation]. Figure 1 This invention provides a method for extracting GPS M code license sequences based on C / A code assistance, applicable to scenarios including the GPS L1 frequency band. The method includes:

[0053] S10. Obtain the CASM modulated signal, and after stabilizing the C / A code signal, obtain the carrier frequency and initial phase of the CASM modulated signal. Based on the carrier frequency and initial phase, strip the carrier of the CASM modulated signal and divide it into I-channel signals and Q-channel signals. The I-channel signals include the BOC(10,5) signal, the P(Y) code signal, and the first high-frequency signal. The Q-channel signals include the BOC(10,5) signal, the P(Y) code signal, the C / A code signal, and the second high-frequency signal. The C / A code signal is a known signal. The P(Y) code signal and the C / A code signal are both BPSK modulated signals.

[0054] This embodiment of the invention first acquires a CASM modulated signal, in which every 1 millisecond of data contains a complete BOC(10,5) signal. The CASM modulated signal is a three-channel CASM modulation, and its general expression is:

[0055]

[0056] Among them, P I P represents the power of the I-channel signal. Q Let represent the Q-channel signal power, s1(t), s2(t), and s3(t) represent the three signals. In the GPS L1 band, s1(t) represents the C / A code signal, s2(t) represents the P(Y) code signal, and s3(t) represents the BOC(10,5) signal, i.e., the M-code signal. m3 represents the modulation index, f c This indicates the carrier frequency of the CASM modulated signal. This indicates the initial phase when the CASM modulated signal is split into I and Q channels. The pseudocode sequence of the C / A code signal is known. Visual satellites are acquired and tracked using the C / A code signal. Once stable tracking is achieved, the stable tracking frequency is the carrier frequency f of the CASM modulated signal. c Then, by utilizing the correlation of the C / A code signals, the initial phase of the CASM modulated signal is obtained when the correlation is at its maximum. More specifically:

[0057] C / A code signals, P(Y) code signals, and BOC(10,5) signals are all pseudo-random codes. The characteristic of pseudo-random codes is that they exhibit maximum correlation with the same code sequence, and zero correlation with different code sequences. Calculate the initial phase. This correlation is mainly utilized. The carrier frequency f has already been obtained based on stable tracking. c Next, the initial phase is calculated. Note the combination of CASM modulated signals; only the Q-channel signal contains the C / A code signal. This is if the initial phase is not equal to... A portion of the energy of the C / A code signal leaks into the I-channel signal. At this point, a cross-correlation value can be obtained using the cross-correlation of the C / A code signals. However, due to signal energy leakage, the obtained cross-correlation value is certainly not the maximum. In this embodiment of the invention, the phase is calculated by searching from 0 to 360 degrees if and only if the searched phase is equal to... At this point, the cross-correlation value of the C / A code signal is at its maximum; therefore, the phase at which the cross-correlation value is maximum is taken as the initial phase.

[0058] BOC(10,5) is the M-code signal. The BOC(10,5) signal is modulated using a binary offset carrier (BOC). The BOC(10,5) signal represents a data code frequency of f. b =5*f0, the carrier frequency of the subcarrier is f s =10*f0, where f0 represents the frequency reference, f0=1.023MHz, the subcarrier is a square wave, that is, the BOC(10,5) signal indicates that the data code frequency of its license sequence is 5.115MHz, the carrier frequency of the subcarrier is 10.23MHz, and the M code license sequence is the sequence of the BOC(10,5) signal after removing the subcarrier.

[0059] As can be seen from the above analysis, the extraction of the M-code authorization sequence can be converted into the extraction of the BOC(10,5) signal. The key is how to extract the BOC(10,5) signal from the CASM modulated signal shown in formula (1). Currently, there is a lack of a practical method for quickly and accurately extracting the BOC(10,5) signal from the CASM modulated signal. Therefore, based on the inventor's research on formula (1), a scheme is provided to divide the CASM modulated signal into I-channel and Q-channel signals. After the C / A code signal is stably tracked, the carrier frequency and initial phase of the CASM modulated signal are obtained. Based on the carrier frequency and initial phase, the carrier of the CASM modulated signal is stripped and divided into I-channel and Q-channel signals. The BOC(10,5) signal is extracted by analyzing the signal characteristics of the I-channel and Q-channel signals. The embodiment of this invention involves stripping the carrier of the CASM modulated signal and dividing it into I-channel and Q-channel signals based on the carrier frequency and initial phase, including:

[0060] The carrier of the CASM modulated signal is stripped based on the carrier frequency and initial phase, and the power and modulation index of the CASM modulated signal are ignored to re-represent the CASM modulated signal. The portion of the re-represented CASM modulated signal containing the C / A code signal is taken as the Q-path signal, and the portion of the re-represented CASM modulated signal not containing the C / A code signal is taken as the I-path signal. Therefore, in this embodiment of the invention, the first half of formula (1) is taken as the I-path signal, and the second half as the Q-path signal, without considering the power and modulation index of the CASM modulated signal, i.e., without considering P in formula (1). I P Q The influence of m3 on signal amplitude, and the removal of the carrier frequency f from the CASM modulated signal after stable tracking of the C / A code signal. c and initial phase The affected signal components, i.e. The influence of the two signal components ultimately divides the CASM modulated signal into an I-channel signal and a Q-channel signal.

[0061] To more intuitively express the relationship between the three signals in the I-channel and Q-channel signals, this embodiment of the invention denotes s1(t), s2(t), and s3(t) as C / A, P(Y), and BOC(10,5), respectively. After the CASM modulated signal is re-represented, the high-frequency signal in the I-channel signal is denoted as the first high-frequency signal fh1, and the high-frequency signal in the Q-channel signal is denoted as the second high-frequency signal fh2. Finally:

[0062] In this embodiment of the invention, the formula for the I-channel signal is expressed as:

[0063] BOC(10,5)+P(Y)+fh1(2);

[0064] Wherein, BOC(10,5) represents the BOC(10,5) signal, P(Y) represents the P(Y) code signal, and fh1 represents the first high-frequency signal;

[0065] In this embodiment of the invention, the Q-channel signal formula is expressed as:

[0066] C / A+C / A*BOC(10,5)*P(Y)+fh2(3);

[0067] Where C / A represents the C / A code signal, and fh2 represents the second high-frequency signal.

[0068] Based on such Figure 2 Based on the spectral distribution characteristics of the GPS L1 band signal shown, and formulas (2) and (3), this embodiment of the invention proposes a feasible process for extracting the M code authorization sequence, including S20 to S70.

[0069] It should be noted that formulas (2) and (3) only illustrate the signal combination forms of the I-channel signal and the Q-channel signal. The I-channel signal mainly includes two types of signals: BOC(10,5) and P(Y). The Q-channel signal mainly includes three types of signals: BOC(10,5), P(Y), and C / A. The specific signal composition forms are related to the actual CASM modulation signal forms. The plus sign in the formulas representing the signal composition forms only indicates that the signal exists in the signal and does not strictly represent the actual addition or subtraction relationship of the signal.

[0070] S20. The BOC(10,5) signal and the first high-frequency signal in the I-channel signal are filtered out by the first low-pass filter in order to extract the P(Y) code signal.

[0071] Depend on Figure 3 As can be seen from the spectral distribution characteristics of the I-channel signal, the P(Y) code signal can be extracted by using a low-pass filter. Specifically, in this embodiment of the invention, the BOC(10,5) signal and the first high-frequency signal in the I-channel signal are filtered out by a first low-pass filter to extract the P(Y) code signal. Figure 3 The cutoff frequency of the first low-pass filter shown is 10.23MHz. The specific cutoff frequency of the first low-pass filter depends on the P(Y) code signal. Figure 3 The first high-frequency signal fh1 is not shown in the diagram. The first low-pass filter will simultaneously filter out the first high-frequency signal fh1 and most of the BOC(10,5) signal. The small amount of BOC(10,5) signal has little impact on the P(Y) code signal. The extracted P(Y) code signal is not a standard ±1 sequence. It can be converted into a standard ±1 sequence by signal decision. The decision process is as follows: determine whether the current signal amplitude is greater than 0. If it is greater than 0, it is a high level and is determined as 1; if it is less than or equal to 0, it is a low level and is determined as -1.

[0072] During the experiment, the inventors also discovered that aligning the signal after it has been filtered out by the first low-pass filter is also crucial for extracting the P(Y) code signal, because the lack of alignment processing will affect the accuracy of P(Y) code signal extraction.

[0073] S30. The second high-frequency signal in the Q-channel signal is filtered out by the second low-pass filter in order to extract the Q-channel signal including the BOC(10,5) signal, the P(Y) code signal and the C / A code signal.

[0074] Depend on Figure 4As shown in the spectral distribution characteristics of the Q-channel signal, the Q-channel signal, including the BOC(10,5) signal, the P(Y) code signal, and the C / A code signal, can be extracted using a low-pass filter, i.e., C / A + C / A * BOC(10,5) * P(Y). Specifically, in this embodiment of the invention, a second low-pass filter is used to filter out the second high-frequency signal fh2 in the Q-channel signal to extract C / A + C / A * BOC(10,5) * P(Y), as shown. Figure 4 The cutoff frequency of the second low-pass filter shown can contain the C / A*BOC(10,5)*P(Y) signal. Figure 4 The second high-frequency signal fh2 is not shown.

[0075] Similar to S20, during the experiment, the inventors found that aligning the signal after it has been filtered by the second low-pass filter is crucial for extracting C / A+C / A*BOC(10,5)*P(Y), because the lack of alignment will affect the accuracy of C / A+C / A*BOC(10,5)*P(Y) extraction.

[0076] S40. Based on the characteristics of the BPSK modulation signal, the extracted Q-channel signal is simplified by using the C / A code signal to obtain a simplified signal.

[0077] In this embodiment of the invention, the C / A code signal is a known BPSK modulated signal. A characteristic of BPSK modulated signals is that the product of identical signals equals 1, i.e., C / A*C / A = 1. Utilizing this characteristic, the C / A code signal is multiplied by the extracted Q-channel signal C / A + C / A*BOC(10,5)*P(Y) to achieve a simplified signal obtained by simplifying the extracted Q-channel signal. The formula is expressed as:

[0078]

[0079] S50. Perform DC removal operation on the simplified signal to obtain the DC removed signal.

[0080] As can be seen from formula (4), the simplified signal contains a DC signal "1". A DC removal operation is performed on the simplified signal, i.e., 1+BOC(10,5)*P(Y), to obtain the de-DC signal, expressed by the formula:

[0081] BOC(10,5)*P(Y)(5);

[0082] Specifically, the DC removal operation involves subtracting the mean value of the signal from the signal.

[0083] S60. Based on the characteristics of the BPSK modulated signal, the DC signal is simplified by using the P(Y) code signal to obtain the BOC(10,5) signal.

[0084] In this embodiment of the invention, the P(Y) code signal is a BPSK modulated signal, i.e., P(Y)*P(Y) = 1. Utilizing this characteristic, the P(Y) code signal is multiplied by the simplified signal BOC(10,5)*P(Y) to simplify the de-DC signal and obtain the BOC(10,5) signal. The formula is expressed as:

[0085]

[0086] S70. Remove the subcarrier of the BOC(10,5) signal to extract the GPS M code license sequence.

[0087] As can be seen from S60, the embodiment of the present invention has extracted the BOC(10,5) signal. The subcarrier removal operation is performed on the BOC(10,5) signal. Specifically, a square wave with a frequency of 10.23MHz is generated first, and the square wave is multiplied in. The product of the square wave is 1, so a signal containing only the M code license sequence can be obtained. Then, the final M code license sequence can be obtained through signal decision.

[0088] In summary, the GPS M-code license sequence extraction method based on C / A code assistance proposed in this invention addresses the problem of difficulty in obtaining GPS M-code license sequences by providing a simple, feasible, and fast method for acquiring correct M-code license sequences. This method does not depend on the correlation of the M-code license sequence and can still correctly extract the M-code license sequence even under low signal-to-noise ratio conditions. Furthermore, it does not require trying different combinations and has high extraction efficiency.

[0089] Secondly, please see Figure 5 This invention provides a GPS M code license sequence extraction device based on C / A code assistance, applicable to scenarios including the GPS L1 frequency band. The device includes:

[0090] The preprocessing module acquires the CASM modulated signal and obtains its carrier frequency and initial phase after stabilizing it with the C / A code signal. Based on the carrier frequency and initial phase, the carrier of the CASM modulated signal is stripped and divided into I-channel and Q-channel signals. The I-channel signal includes the BOC(10,5) signal, the P(Y) code signal, and the first high-frequency signal. The Q-channel signal includes the BOC(10,5) signal, the P(Y) code signal, the C / A code signal, and the second high-frequency signal. The C / A code signal is a known signal. The P(Y) code signal and the C / A code signal are both BPSK modulated signals.

[0091] The first extraction module is used to filter out the BOC(10,5) signal and the first high-frequency signal in the I-channel signal through the first low-pass filter in order to extract the P(Y) code signal.

[0092] The second extraction module is used to filter out the second high-frequency signal in the Q-channel signal through the second low-pass filter in order to extract the Q-channel signal including the BOC(10,5) signal, the P(Y) code signal, and the C / A code signal.

[0093] The first simplification module is used to simplify the extracted Q-channel signal by using C / A code signals based on the characteristics of the BPSK modulated signal to obtain a simplified signal.

[0094] The DC removal module is used to remove DC from the simplified signal to obtain a DC-removed signal.

[0095] The second simplification module is used to simplify the DC signal by using the P(Y) code signal to obtain the BOC(10,5) signal based on the characteristics of the BPSK modulated signal.

[0096] The third extraction module is used to remove the subcarrier of the BOC(10,5) signal in order to extract the GPS M code authorization sequence.

[0097] Furthermore, in the preprocessing module of this embodiment of the invention, the carrier of the CASM modulated signal is stripped and divided into I-channel signals and Q-channel signals according to the carrier frequency and initial phase, including:

[0098] The carrier of the CASM modulated signal is stripped off based on the carrier frequency and initial phase, while the power and modulation index of the CASM modulated signal are ignored in order to re-represent the CASM modulated signal.

[0099] The portion of the re-represented CASM modulated signal containing the C / A code signal is taken as the Q-path signal, and the portion of the re-represented CASM modulated signal not containing the C / A code signal is taken as the I-path signal.

[0100] Furthermore, the formula for the I-channel signal in the preprocessing module of this embodiment is expressed as follows:

[0101] BOC(10,5)+P(Y)+fh1;

[0102] Wherein, BOC(10,5) represents the BOC(10,5) signal, P(Y) represents the P(Y) code signal, and fh1 represents the first high-frequency signal;

[0103] The formula for the Q-channel signal is expressed as follows:

[0104] C / A+C / A*BOC(10,5)*P(Y)+fh2;

[0105] Where C / A represents the C / A code signal, and fh2 represents the second high-frequency signal.

[0106] Furthermore, in the first and second simplified modules of this embodiment, the BPSK modulated signal has the characteristic that the product of the same signals is 1.

[0107] Furthermore, in the first simplification module of this embodiment, based on the characteristics of the BPSK modulation signal, the simplified signal obtained by simplifying the extracted Q-channel signal using the C / A code signal is expressed by the following formula:

[0108]

[0109] Where C / A*C / A=1, C / A+C / A*BOC(10,5)*P(Y) represents the extracted Q-channel signal.

[0110] Furthermore, in the DC removal module of this embodiment, a DC removal operation is performed on the simplified signal to obtain a DC-removed signal, expressed by the formula:

[0111] BOC(10,5)*P(Y).

[0112] Furthermore, in the second simplification module of this embodiment, based on the characteristics of the BPSK modulated signal, the P(Y) code signal is used to simplify the DC signal to obtain the BOC(10,5) signal, as expressed by the formula:

[0113]

[0114] Where, P(Y)*P(Y)=1.

[0115] Furthermore, in the first extraction module of this embodiment of the invention, after filtering out the BOC(10,5) signal and the first high-frequency signal from the I-channel signal using a first low-pass filter, the module further includes:

[0116] The signal filtered out by the first low-pass filter is aligned to extract the P(Y) code signal.

[0117] Furthermore, in the second extraction module of this embodiment of the invention, after filtering out the second high-frequency signal in the Q-channel signal using a second low-pass filter, it further includes:

[0118] The signal filtered by the second low-pass filter is aligned to extract the Q-channel signal, which includes the BOC(10,5) signal, the P(Y) code signal, and the C / A code signal.

[0119] As the apparatus embodiment of the second aspect is basically similar to the method embodiment of the first aspect, the description is relatively simple, and relevant details can be found in the description of the method embodiment of the first aspect.

[0120] In the description of this invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0121] Although the invention has been described herein in conjunction with various embodiments, those skilled in the art, by reviewing the specification and accompanying drawings, will understand and implement other variations of the disclosed embodiments in carrying out the claimed invention. In the specification, the word "comprising" does not exclude other components or steps, and "a" or "an" does not exclude a plurality. While certain measures are described in different embodiments, this does not mean that these measures cannot be combined to produce good results.

[0122] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A method for extracting GPS M code license sequences based on C / A code assistance, characterized in that, Applied to scenarios including the GPS L1 frequency band, the method includes: A CASM modulated signal is acquired, and its carrier frequency and initial phase are obtained after stable tracking using a C / A code signal. Based on the carrier frequency and initial phase, the carrier of the CASM modulated signal is stripped and divided into I-channel and Q-channel signals. The I-channel signal includes a BOC(10,5) signal, a P(Y) code signal, and a first high-frequency signal. The Q-channel signal includes the BOC(10,5) signal, the P(Y) code signal, the C / A code signal, and a second high-frequency signal. The C / A code signal is a known signal. Both the P(Y) code signal and the C / A code signal are BPSK modulated signals. The BOC(10,5) signal and the first high-frequency signal in the I-channel signal are filtered out by the first low-pass filter in order to extract the P(Y) code signal. The second high-frequency signal in the Q-channel signal is filtered out by the second low-pass filter to extract the Q-channel signal including the BOC(10,5) signal, the P(Y) code signal, and the C / A code signal; Based on the characteristics of BPSK modulated signals, the extracted Q-channel signals are simplified using the C / A code signals to obtain simplified signals. The simplified signal is subjected to a DC removal operation to obtain a DC-removed signal; Based on the characteristics of the BPSK modulated signal, the DC-demodulated signal is simplified using the P(Y) code signal to obtain the BOC(10,5) signal. Remove the subcarrier of the BOC(10,5) signal to extract the GPS M code license sequence; The process of stripping the carrier of the CASM modulated signal and dividing it into I-channel and Q-channel signals according to the carrier frequency and the initial phase includes: stripping the carrier of the CASM modulated signal according to the carrier frequency and the initial phase, while re-representing the CASM modulated signal without considering the power and modulation index; using the portion of the re-represented CASM modulated signal containing C / A code signals as the Q-channel signal, and using the portion of the re-represented CASM modulated signal not containing C / A code signals as the I-channel signal; The formula for the I-channel signal is expressed as follows: ； in, This represents the BOC(10,5) signal. This represents the P(Y) code signal. Indicates the first high-frequency signal; The formula for the Q-channel signal is expressed as follows: ； in, Indicates C / A code signal, This indicates the second high-frequency signal.

2. The GPS M-code license sequence extraction method based on C / A code assistance according to claim 1, characterized in that, The characteristic of the BPSK modulated signal is that the product of the same signals is 1.

3. The GPS M-code license sequence extraction method based on C / A code assistance according to claim 2, characterized in that, Based on the characteristics of BPSK modulated signals, the simplified signal obtained by simplifying the extracted Q-channel signal using the C / A code signal is expressed by the following formula: ； in, , This indicates the extracted Q-channel signal.

4. The GPS M-code license sequence extraction method based on C / A code assistance according to claim 3, characterized in that, The simplified signal is subjected to a DC removal operation to obtain a DC-removed signal, expressed by the formula: 。 5. The GPS M-code license sequence extraction method based on C / A code assistance according to claim 4, characterized in that, Based on the characteristics of the BPSK modulated signal, the DC-demodulated signal is simplified using the P(Y) code signal to obtain the BOC(10,5) signal, expressed by the following formula: ； in, .

6. The GPS M-code license sequence extraction method based on C / A code assistance according to claim 1, characterized in that, After filtering out the BOC(10,5) signal and the first high-frequency signal from the I-channel signal using the first low-pass filter, the signal further includes: The signal filtered out by the first low-pass filter is aligned to extract the P(Y) code signal.

7. The GPS M-code license sequence extraction method based on C / A code assistance according to claim 1, characterized in that, After filtering out the second high-frequency signal from the Q-channel signal using a second low-pass filter, the method further includes: The signal filtered by the second low-pass filter is aligned to extract the Q-channel signal, which includes the BOC(10,5) signal, the P(Y) code signal, and the C / A code signal.

8. A GPS M-code license sequence extraction device based on C / A code assistance, characterized in that, For applications including GPS L1 bands, the device includes: A preprocessing module is used to acquire the CASM modulated signal, and after stabilizing and tracking the C / A code signal, acquire the carrier frequency and initial phase of the CASM modulated signal. Based on the carrier frequency and initial phase, the carrier of the CASM modulated signal is stripped and divided into I-channel signals and Q-channel signals. The I-channel signals include a BOC(10,5) signal, a P(Y) code signal, and a first high-frequency signal. The Q-channel signals include the BOC(10,5) signal, the P(Y) code signal, the C / A code signal, and a second high-frequency signal. The C / A code signal is a known signal. Both the P(Y) code signal and the C / A code signal are BPSK modulated signals. The process of stripping the carrier of the CASM modulated signal and dividing it into I-channel and Q-channel signals according to the carrier frequency and the initial phase includes: stripping the carrier of the CASM modulated signal according to the carrier frequency and the initial phase, while re-representing the CASM modulated signal without considering the power and modulation index; using the portion of the re-represented CASM modulated signal containing C / A code signals as the Q-channel signal, and using the portion of the re-represented CASM modulated signal not containing C / A code signals as the I-channel signal; The formula for the I-channel signal is expressed as follows: ； in, This represents the BOC(10,5) signal. This represents the P(Y) code signal. Indicates the first high-frequency signal; The formula for the Q-channel signal is expressed as follows: ； in, Indicates C / A code signal, Indicates the second high-frequency signal; The first extraction module is used to filter out the BOC(10,5) signal and the first high-frequency signal from the I-channel signal through a first low-pass filter in order to extract the P(Y) code signal. The second extraction module is used to filter out the second high-frequency signal in the Q-channel signal through the second low-pass filter in order to extract the Q-channel signal including the BOC(10,5) signal, the P(Y) code signal and the C / A code signal; The first simplification module is used to simplify the extracted Q-channel signal by using the C / A code signal based on the characteristics of the BPSK modulated signal to obtain a simplified signal. A DC removal module is used to perform a DC removal operation on the simplified signal to obtain a DC-removed signal. The second simplification module is used to simplify the DC-de-DC signal using the P(Y) code signal based on the characteristics of the BPSK modulated signal to obtain the BOC(10,5) signal. The third extraction module is used to remove the subcarrier of the BOC(10,5) signal in order to extract the GPS M code authorization sequence.

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