MBOC signal correlator joint reception combination coefficient calculation method

Abstract

The present application relates to a kind of MBOC signal correlator joint receiving combination coefficient calculation method, constructs the overall structure of MBOC signal data / pilot correlator joint tracking positioning.By establishing joint tracking accuracy mathematical model, determine optimal combination coefficient.Model predicts that amplitude ratio combination scheme is the best combination coefficient of MBOC correlator joint reception, second is power ratio combination scheme, last is 1:1 combination scheme.The experimental results of measured satellite data show that, B1C signal amplitude ratio combination positioning accuracy is improved by 2% relative to traditional 1:1 combination, is improved by 1.3% relative to power ratio combination;L1C signal amplitude ratio combination positioning accuracy is improved by 2.37% relative to traditional 1:1 combination, is improved by 1.6% relative to power ratio combination.Because E1OS data and pilot component special 1:1 ratio scheme design, so the positioning accuracy of three kinds of combination schemes is same.It is suggested that user selects amplitude ratio combination mode in MBOC signal correlator joint reception, can maximize the combination tracking accuracy.

Description

Technical Field

[0001] This invention belongs to the field of signal reception technology, specifically relating to a method for calculating the combined reception coefficients of an MBOC signal correlator. Background Technology

[0002] The design of modern GNSS signal systems has received significant attention from military and civilian sectors worldwide over the past few decades. To ensure compatibility and interoperability between systems, the United States, the European Union, and China have designed a special signal, the MBOC signal, for their new generation satellites in the L1 band. The flexible design of the data and pilot components of the MBOC signal improves the accuracy of navigation signal ranging and message demodulation. However, developing the signal's characteristics and potential to better utilize its advantages is appealing to users. Many scholars have proposed joint reception methods to improve the positioning accuracy of MBOC signals, including correlator joint reception, phase detector joint reception, and filter joint reception. Each method has its advantages and disadvantages, with correlator joint reception being the most resource-efficient. However, traditional correlator joint reception directly superimposes the integral results of data and pilot components, which is not the optimal combination. Considering that the combination coefficients affect reception performance, this invention constructs an overall structure for MBOC signal data / pilot correlator joint tracking positioning, establishes a mathematical model for joint tracking accuracy, and determines the optimal combination coefficients. Finally, an experimental platform is designed to verify the proposed method. The method and test results provided by this invention offer technical support for high-precision GNSS user receivers. Summary of the Invention

[0003] The purpose of this invention is to solve the above-mentioned problems and provide a method for calculating the combined coefficients of the MBOC signal correlator joint reception, and to construct an overall structure for joint tracking and positioning of the MBOC signal data / pilot correlator. A mathematical model for joint tracking accuracy is established to determine the optimal combined coefficients.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] A method for calculating the combined reception coefficients of an MBOC signal correlator, where the MBOC signal is represented as MBOC(6,1,1 / 11). and The power spectra are weighted and mixed with a weighting factor of 1 / 11. The characteristic is that, according to the definition of the MBOC signal, the normalized PSD can be obtained as follows:

[0006]

[0007] Its normalized autocorrelation function is derived from the following formula:

[0008] in, The trigonometric function is represented by the following mathematical expression:

[0009]

[0010] in Representing the pseudocode period, the MBOC modulated signal is achieved by adding high-frequency (6MHz) power to BOC (1,1).

[0011] MBOC(6,1,1 / 11) is defined in the frequency domain, while the BOC(n, n) and BOC(m, n) components can be arbitrarily multiplexed and combined in the time domain. GPS / QZSS, GALILEO, and BDS have designed three different allocation schemes. Based on these three MBOC designs, their time-domain model can be written as:

[0012] ;

[0013] ;

[0014] .

[0015] Furthermore, the MBOC correlator joint receiver design includes a tracking module and a positioning module. The tracking module incorporates a Costas loop in the data component carrier and a pure phase-locked loop in the pilot component carrier. After the digital intermediate frequency signal is stripped from the carrier, it is coherently integrated with the early, immediate, and delayed local copy codes to obtain the correlation integration result. The correlation integration results of the data component and the pilot component are then combined. The positioning module uses a data stream for message decoding, which is a linear combination of the pilot component correlator output according to the symbol of the data component and the data component correlator output. The positioning module also uses a data stream for frame synchronization, which is a linear combination of the pilot component message symbol and the pilot component correlator output. The positioning module calculates the observed values ​​for pseudorange: carrier frequency, carrier phase, code frequency, and code phase are the output values ​​of the combined signal loop phase detector.

[0016] Furthermore: The lead, instantaneous, and lag integral results after the MBOC correlators are combined are as follows, where the combination coefficients are... and

[0017]

[0018]

[0019]

[0020] A code tracking accuracy model is established by combining three MBOC correlators: B1C, L1C, and E1OS. The model formula for B1C / L1C is as follows:

[0021] ;

[0022] The digital model formula for E1OS is:

[0023] .

[0024] The combination coefficients of the data components, These are the combination coefficients of the pilot components. Their optimal values ​​are those corresponding to the minimum tracking accuracy of the joint code.

[0025]

[0026] Numerical analysis can determine that the joint optimal coefficient of the correlator is the amplitude ratio of the data and the pilot signals.

[0027] .

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] Measured satellite data and simulation results show that the amplitude ratio combination scheme is the optimal combination for joint reception of MBOC correlators, followed by the power ratio combination scheme, and lastly the 1:1 combination scheme. The positioning accuracy of the B1C signal amplitude ratio combination scheme is 2% higher than the traditional 1:1 combination and 1.3% higher than the power ratio combination. The positioning accuracy of the L1C signal amplitude ratio combination scheme is 2.37% higher than the traditional 1:1 combination and 1.6% higher than the power ratio combination. Due to the special 1:1 ratio design of E1OS data and pilot components, the positioning accuracy of the three combination schemes is the same. It is recommended that users choose the amplitude ratio combination method for joint reception of MBOC signal correlators to maximize the combined tracking accuracy. Attached Figure Description

[0030] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only for more clearly illustrating the technical solutions in the embodiments of the present invention or the prior art. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a schematic diagram of the MBOC power spectrum of the present invention;

[0032] Figure 2This is a structural diagram of the MBOC correlator joint receiving framework of the present invention;

[0033] Figure 3 This is a schematic diagram illustrating the theoretical phase detection standard deviation of the code ring under different correlator intervals in this invention.

[0034] Figure 4 This is a schematic diagram illustrating the standard deviation difference of the DLL theory for simulating amplitude ratio combination and power ratio combination under common receiver parameters. Detailed Implementation

[0035] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention will be further described below with reference to specific embodiments. However, the embodiments are only for illustration and are not intended to limit the present invention.

[0036] Mathematical model and characteristics of MBOC signals:

[0037] The MBOC signal modulated on a GNSS system is denoted as MBOC(6,1,1 / 11), defined by its power spectral density (PSD), which is a representation of the signal modulated on a GNSS system. and The power spectrum is weighted and mixed with a weighting factor of 1 / 11. According to the definition of MBOC signal, the normalized PSD (pilot and data channel) can be obtained as Equation (1):

[0038] (1)

[0039] Its normalized autocorrelation function is derived as formula (2).

[0040] (2)

[0041] in, The trigonometric function is represented by the following mathematical expression:

[0042] (3)

[0043] in Representing the pseudocode period, the MBOC modulated signal adds power at a higher frequency (6MHz) to BOC (1,1), and its power spectrum is as follows. Figure 1 As shown.

[0044] MBOC(6,1,1 / 11) is defined in the frequency domain, while the BOC(n, n) and BOC(m, n) components can be arbitrarily multiplexed and combined in the time domain, as long as the final PSD satisfies the constraint of equation (1). GPS / QZSS, GALILEO and BDS have designed three different allocation schemes.

[0045] The L1C, E1OS, and B1C design schemes are shown in Table 1.

[0046] Table 1 L1C, E1OS, B1C Design Schemes

[0047]

[0048] Based on the three MBOC designs in Table 1, their time-domain models can be written as equations (4) to (6).

[0049] (4)

[0050] (5)

[0051] (6)

[0052] In the satellite payload design, the pseudocodes of the MBOC signal data components and pilot components are completely synchronized, with both components having the same frequency and a fixed carrier phase relationship. Traditional single-component tracking methods would waste useful power. Based on the fixed relationship between the data and pilot signals, the receiver employs a correlator for joint reception, increasing the total signal power to achieve higher tracking accuracy. The design framework for joint MBOC signal reception is as follows: Figure 2 As shown, it includes a tracking module and a positioning module.

[0053] The tracking module is as follows Figure 2 As shown in the upper part of the structure, the data component carrier tracking loop adopts "Costas," and a higher-performance pure phase-locked loop is designed in the pilot component carrier loop. After the digital intermediate frequency signal is stripped from the carrier, it is coherently integrated with the early, immediate, and delayed local copy codes, and the correlation integration results of the data component and the pilot component are combined.

[0054] The positioning module is as follows Figure 2 As shown in the lower part of the structure, the data stream used for message processing is a linear combination of the pilot component correlator output and the data component correlator output according to the symbols of the data components; while the data stream used for frame synchronization is a linear combination of the data component correlator output and the pilot component message symbols according to the pilot component correlator output. The observations used to calculate the pseudorange—carrier frequency, carrier phase, code frequency, and code phase—are the output values ​​of the combined signal loop phase detector. Finally, the satellite position and pseudorange are combined using the least squares method to obtain the combined positioning result.

[0055] The lead, instantaneous, and lag integral results after correlators are combined are as follows, where the combination coefficients are... and .

[0056] (7)

[0057] (8)

[0058] (9)

[0059] The code tracking accuracy model for correlators is established as follows, where equation (10) is the B1C / L1C model and equation (11) is the E1OS mathematical model:

[0060] (10)

[0061] (11)

[0062] The combination coefficients of the data components, These are the combination coefficients of the pilot components. Their optimal values ​​are those corresponding to the minimum tracking accuracy of the joint code.

[0063]

[0064] Numerical analysis can determine that the joint optimal coefficient of the correlator is the amplitude ratio of the data and the pilot signals.

[0065]

[0066] Traditional correlator combination directly superimposes the integral results of the data components and the pilot components, i.e., a 1:1 combination scheme. Alternatively, a power ratio combination scheme may be used. The optimal combination coefficients calculated in this invention are amplitude ratio combinations. Table 2 lists the coefficient allocations for the three combination schemes:

[0067] Table 2 L1C, E1OS, B1C Signal Combination Coefficients

[0068]

[0069] Based on the correlator joint code tracking accuracy models (10) and (11), the theoretical phase detection standard deviation of the code ring under different correlator intervals was simulated as follows: Figure 3 As shown, simulation results indicate that for both B1C and L1C, the amplitude ratio combination tracking method achieves the highest accuracy within the main lobe bandwidth (32MHz), followed by the power ratio combination, and finally the direct superposition combination (1:1 combination). When d = 0.01 chips, the E1OS combination tracking accuracy is equivalent to the B1C / E1C signal amplitude ratio combination; when d = 0.05, 0.1, and 0.15, the E1OS combination tracking accuracy is equivalent to the B1C / E1C signal power ratio combination.

[0070] To further determine the accuracy of joint reception of L1C and B1C signals, Figure 4The standard deviation differences of the theoretical DLL for amplitude ratio and power ratio combinations were simulated under common receiver parameters. The C / N0 range of typical user GNSS ground received signals is 25dB to 60dB. Because the platform area of ​​MBOC signal design is prone to receiver deadlock, users select phase detector spacing within 0.15 chips. The differences in the DLL standard deviations of B1C (L1C) power ratio and amplitude ratio combinations were simulated at commonly used user receiver bandwidths, including main lobe bandwidth (16MHz), transmit bandwidth (32MHz), and wideband reception (40MHz).

[0071] Simulation results show that for weak signals (less than 40dB), the amplitude ratio combination is significantly better than the power ratio combination; for stronger signals (greater than 40dB), when the user selects a phase detector interval of less than 0.1 chips, the amplitude ratio combination is slightly better than the power ratio combination. Otherwise, when the receiver selects an interval between 0.1 and 0.15 chips, the power ratio combination will be slightly better than the amplitude ratio combination (this value is very small and can be ignored).

[0072] The above analysis shows that MBOC amplitude ratio combined tracking can improve combined tracking accuracy, especially for weak signals where the improvement is significant. We recommend that users choose the amplitude ratio combined method in MBOC signal correlator joint reception to maximize combined tracking accuracy. Example

[0073] Satellite signal verification

[0074] At 23:31 on January 25, 2021, static testing was conducted in Luonan, Shaanxi Province, using a dual-channel acquisition card developed by NI, with a sampling rate of 250MHz and an intermediate frequency of 62.5MHz. Users are most concerned about the improvement effect of combined positioning compared to pilot component positioning. Experimental results show that, in amplitude ratio combined positioning, the E1OS combined signal has the highest improvement effect compared to pilot component positioning, at 16%, followed by the L1C signal at 14%, and finally the B1C signal at 11%.

[0075] The B1C signal amplitude ratio combination improves the positioning accuracy by 2% compared to the traditional 1:1 combination and by 1.3% compared to the power ratio combination. The L1C signal amplitude ratio combination improves the positioning accuracy by 2.37% compared to the traditional 1:1 combination and by 1.6% compared to the power ratio combination. The above analysis shows that the method of the present invention significantly improves the accuracy of traditional correlator joint positioning.

[0076] All content not described in detail in this invention is prior art.

[0077] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for calculating the combined coefficients of a joint reception of a MBOC signal correlator, the MBOC signal being represented as MBOC (6, 1, 1 / 11), the power spectrum of and being mixed with a weighting factor of 1 / 11, characterized in that, The normalized PSD can be obtained according to the definition of the MBOC signal as ; ​​​​​ The normalized autocorrelation function thereof derives a formula: ； wherein represents a trigonometric function, the mathematical expression of which is as follows: ； wherein represents a pseudo-code period, the MBOC modulated signal being a BOC (1,1) with an additional 6 MHz of power; MBOC(6,1,1 / 11) is defined in the frequency domain, while the BOC(n, n) component and the BOC(m, n) component can be arbitrarily multiplexed and combined in the time domain, GPS / QZSS, GALILEO and BDS design three different allocation schemes, according to the three designs of MBOC, the time domain model can be written as: ； ； ； The code tracking accuracy model of the joint of B1C, L1C and E1OS three MBOC correlators is divided into the model of B1C / L1C and the digital model of E1OS, the formula of the model of B1C / L1C is: ； The formula of the digital model of E1OS is: ； a combination coefficient for the data components, a combination coefficient for the pilot components, the optimal value of which corresponds to the value at which the joint code tracking accuracy is minimal: ； Through numerical analysis, it can be determined that the optimal coefficient of the correlator joint is the amplitude ratio of data and pilot: 。 2. The method of claim 1, wherein the method further comprises: The MBOC correlator joint receiving design includes a tracking module and a positioning module, the tracking module is provided with a Costas loop in the data component carrier and a pure phase-locked loop in the pilot component carrier, after the digital intermediate frequency signal is stripped from the carrier, the correlation integration result is obtained after the early, instant and lag local copy codes are integrated, and the data component correlation integration result and the pilot component correlation integration result are combined; The data stream for the positioning module to solve the message is linearly combined according to the symbol of the data component and the data component correlator output according to the pilot component correlator output, the data stream for the positioning module to synchronize the frame is linearly combined according to the pilot component message symbol and the pilot component correlator output according to the data component correlator output; The positioning module is used for calculating the observation value of the pseudo-range: the carrier frequency, the carrier phase, the code frequency and the code phase are the output values of the combined signal loop phase detector.

3. The method for calculating the combined reception coefficients of an MBOC signal correlator according to claim 1, characterized in that, The early, prompt, and late integration results of the MBOC correlator after combination are as follows, where the combination coefficient is and , ； ； 。

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