阅读说明：本技术 一种高耦合gnss接收机跟踪环路系统 (High-coupling GNSS receiver tracking loop system ) 是由 汤新华 孟骞 祝雪芬 于 2019-10-23 设计创作，主要内容包括：本发明公开了一种高耦合GNSS接收机跟踪环路系统,本发明主要融合了传统载波频率跟踪环路,载波相位跟踪环路和码相位跟踪环路,采用了一个新型环路结构将传统独立的跟踪环路融为一体,以达到观测信息的最大合理应用。在该环路结构方案中,主要包括了2个输入,4个输出。在环路参数设计中,采用了自适应算法参数配置。主要包含过渡参数与稳态参数配置,其中过渡参数采用LUT预先参数存储技术来实现大参数误差前提下的快速正确收敛,最后稳态参数配置是基于载体动态应力预期,参数稳态误差预期,接收机时钟误差等要求来完成。实现了单结构多功能目标,解决了传统跟踪环路中的带宽与精度不可兼得的矛盾问题。(The invention discloses a tracking loop system of a high-coupling GNSS receiver, which mainly integrates a traditional carrier frequency tracking loop, a carrier phase tracking loop and a code phase tracking loop, and adopts a novel loop structure to integrate the traditional independent tracking loops into a whole so as to achieve the maximum reasonable application of observation information. In the loop structure scheme, 2 inputs and 4 outputs are mainly included. In the design of loop parameters, adaptive algorithm parameter configuration is adopted. The method mainly comprises the configuration of transition parameters and steady-state parameters, wherein the transition parameters adopt an LUT pre-parameter storage technology to realize the rapid and correct convergence on the premise of large parameter errors, and the final steady-state parameter configuration is completed based on the requirements of carrier dynamic stress expectation, parameter steady-state error expectation, receiver clock errors and the like. The method realizes a single-structure multifunctional target and solves the problem that the bandwidth and the precision in the traditional tracking loop cannot be compatible.)

1. A high-coupling GNSS receiver tracking loop system is characterized by comprising a correlator, a code phase detector, a carrier phase detector, a first proportional gain, a first summator, a second proportional gain, a first integrator, a third proportional gain, a second summer, a second integrator, a fourth proportional gain, a fifth proportional gain, a third summer, a sixth proportional gain, a third integrator, a carrier NCO, a fourth integrator and a code NCO, wherein,

a correlator for correlating the satellite received signal with local carrier and local pseudo-random code and outputting the correlation integral value I of the same-directional branch and the correlation integral value Q of the orthogonal branch, which are ahead of the correlation integral value I of the same-directional branch_EIntegral value Q of related branch of leading quadrature branch_EIntegral value I associated with the lagging dipleg_LIntegral value Q of the associated branch of the lagging quadrature branch_L(ii) a Wherein, I_E,I_L,Q_E,Q_LThe input is to a code phase discriminator, and the I and Q are input to a carrier phase discriminator;

a code phase discriminator for pair I_E,I_L,Q_E,Q_LPerform calculation

a first proportional gain for multiplying Δ τ by a first proportional coefficient K₀Rear output K₀Δ τ to the first summer;

a carrier phase discriminator for carrying out delta theta tan on I and Q^-1(Q/I) calculating and then outputting the carrier phase difference delta theta to a second proportional gain, a third proportional gain and a fifth proportional gain;

a second proportional gain for multiplying Δ θ by a second proportional coefficient K₃Rear output K₃Δ θ to the first integrator;

a first integrator for pair K₃Δ θ performs an integration operation and outputs the integration value to the second summer;

a third proportional gain for multiplying Δ θ by a third proportional coefficient K₂Back transfusionGo out K₂Δ θ to a second summer;

a second summer for summing the received integrated values and K₂The sum is output to a second integrator after the sum is carried out on the delta theta;

a second integrator for integrating the received sum to obtain a carrier frequency error Δ f_carrierOutput carrier frequency error Δ f_carrierTo a fourth proportional gain, a sixth proportional gain, and a carrier NCO;

a fifth proportional gain for multiplying Δ θ by a fifth proportional coefficient K₁Rear output K₁Δ θ to a third summer;

a sixth proportional gain for the carrier frequency error Δ f_carrieMultiplying by a sixth gain coefficient 2 pi to output 2 pi · Δ f_carrierTo a third summer;

a third summer for receiving K₁Δ θ and 2 π Δ f_carrierThe summed output K₁·Δθ+2π·Δf_carrierTo a third integrator;

a third integrator for pair K₁·Δθ+2π·Δf_carrierOutput phase error estimate delta theta after integration₀To carrier NCO;

carrier NCO for calculating Delta theta₀Carrier frequency error Δ f_carrierUpdating the carrier phase and the carrier frequency at the same time, and outputting a local carrier to a correlator, wherein the updating mode of the code/carrier NCO is a frequency/phase dual-drive mode;

a fourth proportional gain for the carrier frequency error Δ f_carrierMultiplying by a fourth scaling factor β to output a code frequency error estimate Δ f_codeTo a first summer, code NCO;

a first summer for receiving K₀Δ τ and Δ f_codeAdding and summing to output K₀·Δτ+Δf_codeTo a fourth integrator;

a fourth integrator for pair K₀·Δτ+Δf_codeOutputting the code phase error estimate Deltatau after integration₀To code NCO;

code NCO for pair receptionΔ τ of₀And Δ f_codeAnd outputting a local pseudo-random code signal to a correlator after phase and frequency updating, wherein the code/carrier NCO updating mode is a frequency/phase dual-driving mode.

2. The highly coupled GNSS receiver tracking loop system of claim 1, wherein the first proportional gain, the fifth proportional gain, the third proportional gain, and the second proportional gain are configured in two processes: a transition process and a stabilization process, wherein the LUT query method is adopted to complete K under the condition that the initial error of the carrier frequency error is larger than the preset difference value of the tracking loop₀、K₁、K₂、K₃Configuring; equal tracking loop transitions to steady state process, K₀、K₁、K₂、K₃Selecting the following formula for configuration;

wherein Q₁，Q₂，Q₃，Q₄Error covariance, R, of code phase, carrier frequency, rate of change of carrier frequency, respectively₁，R₂Error covariance of code phase and carrier phase of observed quantity, q, p, E_sAre all intermediate variables.

3. The highly coupled GNSS receiver tracking loop system of claim 2, wherein R is₁，R₂The calculation formula is as follows:

where T is the loop period, d_oIs the chip distance between the delayed code and the advanced code, (C/N)₀|_*) Is the signal-to-noise ratio; r₁R₂The value of β is converted into the proportionality coefficient of unit chip for unit cycle.

4. The highly coupled GNSS receiver tracking loop system of claim 2, wherein Q is₁＝10^-10，Q₂＝10^-4，Q₃＝10^-2，Q₄＝1。

5. The highly coupled GNSS receiver tracking loop system of claim 1,

6. The highly coupled GNSS receiver tracking loop system of claim 1Characterised by a code phase error estimate Δ τ₀Code frequency error estimate Δ f_codeSimultaneously, the method is used for updating the code NCO; carrier phase delta theta₀Error Δ f from carrier frequency_carrierAnd at the same time for updating the carrier NCO.

7. The highly coupled GNSS receiver tracking loop system of claim 2, wherein during steady state, the covariance of the state quantities error is configured as follows, Q₁＝10^-10，Q₂Q₃For a VCTCXO oscillator, the setting of Q depends on the Allan variance h parameter in the receiver clock model₂＝10^-4,Q₃＝10^-2，Q₄The value range is 0 to 10 depending on the terminal dynamic stress condition³Low dynamic Q removal₄＝1。

8. The highly coupled GNSS receiver tracking loop system of claim 1, wherein the carrier frequency error, carrier phase error, code frequency error are updated for code NCO and carrier NCO respectively, and in NCO updating process, the frequency and phase are updated simultaneously.

Technical Field

The invention relates to the technical field of GNSS satellite navigation terminals, in particular to a high-coupling GNSS receiver tracking loop system.

Background

The global satellite navigation system is an important wireless positioning technology in the field of navigation at present, and provides all-weather reliable positioning service for military use and civil use. Position services with different accuracies such as meter level, sub-meter level, centimeter level and the like can be obtained through different terminal technologies. In a conventional GNSS receiver, the processing procedure of the satellite signal can be simply divided into: signal acquisition, tracking and PVT calculation. Of course, the acquisition and tracking modules are often not strictly distinct in hardware. The acquisition mainly includes acquiring visible star numbers and estimating Doppler frequency shift of visible star signals and rough values of code phase parameters. The tracking loop is responsible for continuous and accurate estimation of the Doppler frequency shift, the code phase and the carrier phase of each visible star signal, is an important link of a receiver terminal technology, and is an important basis of a subsequent PVT module. Meanwhile, in high-precision positioning service, the tracking loop provides important observation information for the three parameter estimation technologies such as RTK and the like, and the final positioning service quality is directly influenced.

The tracking loop is an important link in the GNSS receiver technology, the traditional scalar tracking loop is always used up to now, the design of the traditional scalar tracking loop focuses on single-dimensional parameter estimation control, such as a carrier frequency control loop (FLL), a carrier phase control loop (PLL), and a code phase control loop (DLL) are respectively and independently responsible for the estimation of three parameters of carrier frequency, carrier phase, and code phase, wherein the FLL, the PLL, and the DLL all share one control loop design scheme. Due to the limitations of the tracking loop design, a Kalman filter is usually needed to further improve the positioning accuracy in the position, velocity, time calculation module (PVT module). In an actual application platform, in order to further improve the comprehensive performance of the system, such as the dynamic performance of the system, various combined loop schemes are correspondingly proposed and adopted, so as to further make up for the limitations of the conventional tracking loop. In order to improve the overall performance of the receiver in the tracking loop stage, further improvement and innovation are required in the conventional loop design.

Disclosure of Invention

The invention aims to solve the technical problem of overcoming the defects of the prior art and provides a tracking loop system of a high-coupling GNSS receiver, which greatly improves the estimation precision and the dynamic adaptation range of parameters and provides accurate observation information for subsequent PVT modules, RTK and other technologies.

The invention adopts the following technical scheme for solving the technical problems:

the high-coupling GNSS receiver tracking loop system provided by the invention comprises a correlator, a code phase detector, a carrier phase detector, a first proportional gain, a first summator, a second proportional gain, a first integrator, a third proportional gain, a second summator, a second integrator, a fourth proportional gain, a fifth proportional gain, a third summer, a sixth proportional gain, a third integrator, a carrier NCO, a fourth integrator and a code NCO, wherein,

a correlator for correlating the satellite received signal with local carrier and local pseudo-random code and outputting the correlation integral value I of the same-directional branch and the correlation integral value Q of the orthogonal branch, which are ahead of the correlation integral value I of the same-directional branch_EIntegral value Q of related branch of leading quadrature branch_EIntegral value I associated with the lagging dipleg_LIntegral value Q of the associated branch of the lagging quadrature branch_L(ii) a Wherein, I_E,I_L,Q_E,Q_LThe input is to a code phase discriminator, and the I and Q are input to a carrier phase discriminator;

a code phase discriminator for pair I_E,I_L,Q_E,Q_LPerform calculation

Outputting the code phase error delta tau to a first proportional gain;

a first proportional gain for multiplying Δ τ by a first proportional coefficient K₀Rear output K₀Δ τ to the first summer;

a carrier phase discriminator for carrying out delta theta tan on I and Q^-1(Q/I) calculating and then outputting the carrier phase difference delta theta to a second proportional gain, a third proportional gain and a fifth proportional gain;

a second proportional gain for multiplying Δ θ by a second proportional coefficient K₃Rear output K₃Δ θ to the first integrator;

a first integrator for pair K₃Δ θ performs an integration operation and outputs the integration value to the second summer;

a third proportional gain for multiplying Δ θ by a third proportional coefficient K₂Rear output K₂Δ θ to a second summer;

the second summing device is used for summing the signals,for the received integral value and K₂The sum is output to a second integrator after the sum is carried out on the delta theta;

a second integrator for integrating the received sum to obtain a carrier frequency error Δ f_carrierOutput carrier frequency error Δ f_carrierTo a fourth proportional gain, a sixth proportional gain, and a carrier NCO;

a fifth proportional gain for multiplying Δ θ by a fifth proportional coefficient K₁Rear output K₁Δ θ to a third summer;

a sixth proportional gain for the carrier frequency error Δ f_carrieMultiplying by a sixth gain coefficient 2 pi to output 2 pi · Δ f_carrierTo a third summer;

a third summer for receiving K₁Δ θ and 2 π Δ f_carrierThe summed output K₁·Δθ+2π·Δf_carrierTo a third integrator;

a third integrator for pair K₁·Δθ+2π·Δf_carrierOutput phase error estimate delta theta after integration₀To carrier NCO;

carrier NCO for calculating Delta theta₀Carrier frequency error Δ f_carrierUpdating the carrier phase and the carrier frequency at the same time, and outputting a local carrier to a correlator, wherein the updating mode of the code/carrier NCO is a frequency/phase dual-drive mode;

a fourth proportional gain for the carrier frequency error Δ f_carrierMultiplying by a fourth scaling factor β to output a code frequency error estimate Δ f_codeTo a first summer, code NCO;

a first summer for receiving K₀Δ τ and Δ f_codeAdding and summing to output K₀·Δτ+Δf_codeTo a fourth integrator;

a fourth integrator for pair K₀·Δτ+Δf_codeOutputting the code phase error estimate Deltatau after integration₀To code NCO;

code NCO, for received Delta tau₀And Δ f_codeAfter phase and frequency updatingAnd outputting the local pseudo-random code signal to a correlator, wherein the code/carrier NCO updating mode is a frequency/phase dual driving mode.

As a further optimization scheme of the tracking loop system of the high-coupling GNSS receiver, the configuration of a first proportional gain, a fifth proportional gain, a third proportional gain and a second proportional gain is divided into two processes: a transition process and a stabilization process, wherein the LUT query method is adopted to complete K under the condition that the initial error of the carrier frequency error is larger than the preset difference value of the tracking loop₀、K₁、K₂、K₃Configuring; equal tracking loop transitions to steady state process, K₀、K₁、K₂、K₃Selecting the following formula for configuration;

wherein Q₁，Q₂，Q₃，Q₄Error covariance, R, of code phase, carrier frequency, rate of change of carrier frequency, respectively₁，R₂Error covariance of code phase and carrier phase of observed quantity, q, p, E_sAre all intermediate variables.

As a further optimization scheme of the high-coupling GNSS receiver tracking loop system, R₁，R₂The calculation formula is as follows:

where T is the loop period, d_oThe chip distance between the delayed code and the advanced code,

is the signal-to-noise ratio; r₁R₂The value of β is converted into the proportionality coefficient of unit chip for unit cycle.

As a further optimization scheme for the high coupling GNSS receiver tracking loop system, Q₁＝10^-10，Q₂＝10^-4，Q₃＝10^-2，Q₄＝1。

As a further optimization scheme of the tracking loop system of the high-coupling GNSS receiver according to the present invention,

wherein I is the current co-branch correlation integral value, Q is the current quadrature branch correlation integral value, subscript E indicates the advance, L indicates the lag, I is the current quadrature branch correlation integral value_EFor the leading cocurrent branch, Q_EFor the associated branch integral value of the leading quadrature branch, I_LIntegral value, Q, associated with the lagging dipleg_LThe integral value of the relevant branch of the lagging orthogonal branch.

As a further optimization scheme of the tracking loop system of the high-coupling GNSS receiver, the code phase error is estimated to be delta tau₀Code frequency error estimate Δ f_codeSimultaneously, the method is used for updating the code NCO; carrier phase delta theta₀Error Δ f from carrier frequency_carrierAnd at the same time for updating the carrier NCO.

The invention relates to a high-coupling GNSS receiver tracking loop systemIn a further optimization scheme, in a steady-state process, the error covariance of the state quantities is configured as follows, Q₁＝10^-10，Q₂Q₃For a VCTCXO oscillator, the setting of Q depends on the Allan variance h parameter in the receiver clock model₂＝10^-4,Q₃＝10^-2，Q₄The value range is 0 to 10 depending on the terminal dynamic stress condition³Low dynamic Q removal₄＝1。

As a further optimization scheme of the tracking loop system of the high-coupling GNSS receiver, the carrier frequency error, the carrier phase error, the code phase error and the code frequency error are used for respectively updating the code NCO and the carrier NCO, and the frequency and the phase are simultaneously updated in the NCO updating process.

Compared with the prior art, the invention adopting the technical scheme has the following technical effects:

(1) the method has the advantages that the estimation objects required by the traditional FLL \ DLL \ PLL are subjected to coupling estimation through a system equation, so that the estimation value precision can be improved, and meanwhile, the traditional distributed independent tracking mode is replaced by a single composite structure;

(2) the tracking coefficient configuration in the transition process adopts an LUT mode, so that the traction range of the tracking loop is expanded, and the convergence rate of the tracking loop is improved;

(3) the tracking loop coefficient configuration in the steady-state process adopts a self-adaptive configuration method, replaces a bandwidth/damping ratio double-parameter configuration scheme in the traditional tracking loop, and associates specific motion indexes of the carrier in a new loop coefficient. The adaptability and robustness of parameters are improved to a greater extent;

(4) the novel tracking loop provides parameters such as high-precision carrier phase, carrier frequency, code phase, code frequency and the like, directly simplifies the complexity of a PVT module, and can abandon a traditional Kalman filter in PVT; meanwhile, in high-precision application technologies such as RTK (real time kinematic), the precision of observation information is also ensured, and the service quality is improved.

Drawings

FIG. 1 is a block diagram of the system of the present invention.

FIG. 2 shows the loop coefficient K₀、K₁、K₂、K₃And (5) configuration diagrams.

FIG. 3 shows the loop coefficient K of the transition process₀、K₁、K₂、K₃The configuration is schematic.

FIG. 4 shows three Z changes corresponding to S in the system discretization; wherein, (a) is a forward difference approximation, (b) is a reverse difference approximation, and (c) is a trapezoidal approximation.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in detail with reference to the accompanying drawings and specific embodiments.

The core idea of the invention is to provide a high-coupling tracking loop model based on a traditional FLL \ DLL \ PLL model, and carry out system programming according to the thought from the bottom layer to the upper layer from simple to complex and according to a theoretical framework, wherein the specific implementation method comprises the following steps:

1, the basic principle of the traditional tracking loop FLL \ DLL \ PLL is firstly familiar, and the basic principle comprises a signal correlation module, a code phase discriminator module, a carrier phase discriminator module and the like. And is familiar with the novel high-coupling tracking loop of the present invention shown in fig. 1, the structure of the new tracking loop is understood in comparison with the conventional tracking loop.

2 Loop factor K according to the invention₀、K₁、K₂、K₃And the configuration scheme is respectively configured according to a transition process and a stabilization process, and the configuration of the loop coefficient is mainly realized by adopting an LUT (look-up table) mode in the transition process.

4 during the stabilization process, the loop coefficients are updated in real time in the manner shown in fig. 4. Wherein includes S₁、S₂、S₃、S₄And the associated values of the code phase accuracy requirement, the physical characteristics of the receiver clock module and the carrier dynamic condition, R₁、R₂Taking values related to the input signal characteristics, and finally completing K₀、K₁、K₂、K₃And (5) configuration calculation.

And 5, discretizing the loop tracking in the figure 1, wherein the discretization mainly comprises discretization of an integral link 1/S and frequency and phase updating of carrier NCO and code NCO.

And 6, finally, the Doppler frequency shift estimation, the carrier phase estimation and the code phase estimation of each period are completed and transmitted to a subsequent PVT calculation module or other high-precision application modules such as RTK and the like.

The specific scheme is as follows:

referring to fig. 1, the design and implementation of a tracking loop of a novel high-coupling GNSS receiver of the present invention mainly includes four parts, i.e., input signal calculation, tracking loop parameter design calculation, error parameter estimation, and NCO update. The input signal mainly includes calculation of carrier phase and code phase error, and adopts traditional phase discriminator, and after double input, it respectively passes through K₀、K₁、K₂、K₃And 4 feedback signals delta tau are obtained by calculating through a plurality of integration links₀、Δθ₀、Δf_code、Δf_carrierThe feedback signal obtained in the above way is used for updating carrier NCO and code NCO, so as to generate a new local signal for the signal correlation operation of the next period.

The method comprises the following steps:

(1)2 calculation of input signals

Referring to FIG. 1, the inputs are carrier phase error and code phase error, respectivelyAnd

to complete the calculation, wherein I Q is the correlation result, I, of the current branch_EQ_EFor the correlation result of the leading branch, I_LQ_LIs the correlation result of the delay branch.

(2) Loop coefficient K₀、K₁、K₂、K₃And β calculation

Loop coefficient K₀、K₁、K₂、K₃The configuration is mainly divided into two processes, and the initial error of the carrier frequency error is largeUnder the condition of the loop coefficient K, the loop coefficient K needs to be completed through a transition process₀、K₁、K₂、K₃The configuration mainly adopts the LUT query method shown in figure 2, such as the transition period shown in figure 3, wherein one period corresponds to one step length in the LUT, and the loop coefficient K is used for the transition to the steady-state process₀、K₁、K₂、K₃The configuration is completed by the following formula

In steady state process calculations, Q is primarily involved₁，Q₂，Q₃，Q₄Configuration and R₁R₂Arrangement of (1), wherein Q₁Depending on the requirement for code phase accuracy, Q may be set₁＝10^-10，Q₁＝10^-10，Q₂Q₃For a VCTCXO oscillator, the setting of Q depends on the Allan variance h parameter in the receiver clock model₂＝10^-4,Q₃＝10^-2，Q₄The value range is 0 to 10 depending on the terminal dynamic stress condition³Taking Q under low dynamic conditions₄＝1；R₁R₂The configuration of (2) is as follows:

where T is the loop period, d_oThe chip distance between the delayed code and the advanced code,

is the signal-to-noise ratio; r₁R₂The value of β is a proportionality coefficient that changes unit cycle to unit chip (β is 1/1540 under GPS L1).

(3) Discretization of integral link and NCO updating

In the actual implementation of the system, the discrete signal processing platform is required to be based, so that the integration link 1/S is subjected to discrete processing, and three conditions shown in FIG. 4 can be adopted; FIG. 4 shows three Z changes corresponding to S in the system discretization; in fig. 4, (a) is a forward difference approximation, (b) is a reverse difference approximation, and (c) is a trapezoidal approximation. In the NCO updating process, the method is mainly in a frequency/phase dual-driving mode, and is different from the traditional frequency mode.

The principle of the invention is as follows: a high-coupling tracking loop is designed through the interconnection relation of the carrier phase, the carrier frequency, the code phase and the code frequency, and meanwhile, the effects of high precision of tracking parameter estimation and adaptation to different dynamic stresses are achieved by matching with a flexible loop coefficient configuration scheme. In the loop coefficient configuration scheme, the estimation of the carrier frequency can be quickly converged in the transition process, and the tracking estimation of the parameters can be finished in a high-precision and self-adaptive manner in the steady-state process, so that good observation information is provided for subsequent PVT, RTK and other modules.

The above description is only for the specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention.