CN111045040A - Satellite navigation signal tracking system and method suitable for dynamic weak signals - Google Patents

Satellite navigation signal tracking system and method suitable for dynamic weak signals Download PDF

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CN111045040A
CN111045040A CN201911248587.7A CN201911248587A CN111045040A CN 111045040 A CN111045040 A CN 111045040A CN 201911248587 A CN201911248587 A CN 201911248587A CN 111045040 A CN111045040 A CN 111045040A
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tracking
carrier
module
loop
pseudo code
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吴雨航
毕波
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Beijing Microelectronic Technology Institute
Mxtronics Corp
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Beijing Microelectronic Technology Institute
Mxtronics Corp
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
    • G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
    • G01S19/13—Receivers
    • G01S19/24—Acquisition or tracking or demodulation of signals transmitted by the system
    • G01S19/29—Acquisition or tracking or demodulation of signals transmitted by the system carrier including Doppler, related
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
    • G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
    • G01S19/13—Receivers
    • G01S19/24—Acquisition or tracking or demodulation of signals transmitted by the system
    • G01S19/30—Acquisition or tracking or demodulation of signals transmitted by the system code related

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  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Computer Networks & Wireless Communication (AREA)
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Abstract

The invention relates to a satellite navigation signal tracking system and method of dynamic weak signals, and belongs to the technical field of satellite navigation signal processing. In order to realize stable tracking of satellite navigation signals under dynamic weak signals and improve the dynamic property and tracking precision, the UKF algorithm is used in loop tracking to realize carrier tracking under high dynamic, and for tracking of code phase, the correlation of code phase shift and Doppler frequency shift is utilized to adopt a carrier auxiliary code loop technology, so that the dynamic stress borne by the code loop is basically eliminated, and the high dynamic code tracking is realized. Meanwhile, a self-adaptive text removal method is provided, under the condition that the text is not collected, the influence of the text is eliminated by adopting a symbol judgment and phase inversion mode, under the condition that the text is collected, the influence of the text is eliminated by adopting the known satellite navigation text, the long-time coherent integration is realized, and the carrier tracking and the code tracking under the weak signal environment are further realized.

Description

Satellite navigation signal tracking system and method suitable for dynamic weak signals
Technical Field
The invention relates to a satellite navigation signal tracking system and method of dynamic weak signals, and belongs to the technical field of satellite navigation signal processing.
Background
At present, along with the expansion of the application field of satellite navigation, the traditional receiver can not meet the navigation and positioning requirements under severe environments such as dynamic environment, shielding environment and the like. Therefore, receivers under high dynamic conditions are developed in China, and the receivers are developed and suitable for being used in sheltered environments. Under a severe environment with high dynamic state, the receiver has certain speed or acceleration or jerk, so that the Doppler change of signals is increased, and the receiver is difficult to track satellite navigation signals. Under the condition of shielding, satellite signals are weak, the tracking accuracy of a traditional tracking loop is low, and the lock is easy to lose.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: the invention overcomes the defects of the prior art, provides a system and a method suitable for stably tracking carrier waves and pseudo codes in a navigation receiver in a dynamic weak signal environment, and solves the problems of poor dynamic property, lower tracking precision, easy unlocking and the like of a tracking loop in the prior art. Meanwhile, a self-adaptive text removal method is provided, under the condition that the text is not collected, the influence of the text is eliminated by adopting a symbol judgment and phase inversion mode, under the condition that the text is collected, the influence of the text is eliminated by adopting the known satellite navigation text, the long-time coherent integration is realized, and the carrier tracking and the code tracking under the weak signal environment are further realized.
The technical scheme adopted by the invention is as follows:
a tracking system of dynamic weak signal satellite navigation signals comprises a sign removing module, an integration module, a dimension expansion Unscented Kalman Filtering (UKF) module, a traditional second-order auxiliary third-order tracking loop module, a carrier NCO module, a code phase discriminator module, a loop filter module and a pseudo code NCO module;
the sign removing module is used for removing the sign influence of the I branch signal early-late code and instant pseudo code coherent integration value and the Q branch signal early-late code and instant pseudo code coherent integration value;
the integration module performs coherent integration of self-adaptive time length after removing the influence of navigation message symbols to obtain an instantaneous, an advance and a lag three-way coherent integration value;
the dimension expansion Unscented Kalman Filtering (UKF) module is used for removing I branch signals influenced by navigation message symbols and instantaneous pseudo code coherent integration values IPSum Q branch signal and instantaneous pseudo code coherent integral value QPAs a measured value of an extended dimension Unscented Kalman Filter (UKF) module, carrier tracking is carried out to output a state quantity xk＝[xp；xw；xa；xj]kThe best estimate of (c); using carrier phase difference estimate xpkCorrecting angular frequency value w of local carrier NCO in real timeNCOk+1；
The traditional second-order auxiliary third-order tracking loop module is used for carrying out carrier loop tracking before coherent integration is not completed, so that the stable tracking of a loop before the UKF module is started is realized;
carrier NCO module according to angular frequency value wNCOk+1Finishing the copying work of sine carrier waves and cosine carrier waves;
the code phase discriminator module receives I branch signals and an overtime pseudo code coherent integral value IEI branch signal and lag pseudo code coherent integral value ILCoherent integration value Q of sum Q branch signal and overtime pseudo codeEQ branch signal and lag pseudo code coherent integral value QLDifference of output code phase deltacp；
The loop filter module is used for receiving the code phase difference deltacpFiltered output, angular frequency value w of local carrier NCONCOk+1Passing through a proportioner kappacAdding the results, and outputting the added sum M as the control input quantity of the pseudo code NCO module;
pseudo code NCO module real-time output frequency fcoFrequency fcoThe drive pseudocode generator generates local timeout, prompt and lag pseudocodes.
Specifically, the tracking method for the dynamic weak signal satellite navigation signal comprises the following steps:
s1, sending the navigation signal of completing pseudo code and carrier stripping to a tracking channel, and simultaneously storing the captured maximum energy value, the captured carrier Doppler and the captured code phase;
s2, judging whether the navigation message is collected, if not, removing the influence of the navigation message sign through sign judgment or phase inversion and the like, entering step S3, if the message collection is finished, multiplying the navigation message with the navigation message to finish the navigation message stripping on the navigation signal which finishes the pseudo code and carrier stripping, and entering step S3;
the navigation message symbol removal is completed by the navigation message influence removal module and the text removal module.
S3, when the carrier-to-noise ratio calculation is not finished, setting the coherent integration time length according to the maximum energy value obtained by capturing; and when the carrier-to-noise ratio calculation is finished, setting the coherent integration time length according to the carrier-to-noise ratio.
S4, coherent accumulation of the corresponding coherent integration time length is carried out according to the coherent integration time length obtained in the step S3, and a coherent accumulation result is stored, wherein the coherent accumulation result comprises an I branch immediate pseudo code coherent integration value IpQ branch real-time pseudo code coherent integral value QPI branch overtime pseudo code coherent integral value IEI branch lag pseudo code coherent integral value ILQ branch overtime pseudo code coherent integral value QEQ branch lag pseudo code coherent integral value QL；
And S5, comparing the loop tracking time with the coherent integration time length, and if the loop tracking time is less than the coherent integration time length, starting a traditional second-order auxiliary third-order tracking loop module to realize carrier tracking. If the loop tracking time is not less than the coherent integration time length, a dimension expansion Unscented Kalman Filtering (UKF) module is started to realize carrier tracking.
The traditional second-order auxiliary third-order tracking loop module is a carrier tracking loop adopting a second-order frequency-locked loop auxiliary third-order phase-locked loop. Specifically, frequency discrimination is performed first, the PLL discriminator does not operate, the phase error input value of the loop filter is 0, which is equivalent to performing pure FLL, the FLL is used to eliminate carrier dynamics, the PLL is started after the FLL is closed, the FLL assists the PLL to operate (i.e., there is both a frequency error input and a phase error input), the frequency error is controlled within a range in which the PLL can operate, after phase locking, the frequency-locked loop is closed, then the PLL is converted into the pure PLL, and the PLL is closed in the pure PLL operation mode, so as to meet the requirement of accuracy. Under the dynamic environment, the frequency locking ring is not closed, and the frequency locking ring is adopted to assist the working mode of the phase-locked loop.
The extended dimension Unscented Kalman Filtering (UKF) module comprises a carrier dynamic model and a measurement model;
the state transition equation of the carrier dynamic model is as follows:
Figure BDA0002308384490000041
wherein x isk＝[xp；xw；xa；xj]kThe state vector at the current k moment is obtained;
xpis the phase difference between the received carrier and the local carrier of the receiver; x is the number ofwA doppler shift for the received carrier; x is the number ofaIs the Doppler shift x of the received carrierwFirst order rate of change of; x is the number ofjIs the Doppler shift x of the received carrierwA second order rate of change of; delta TkIs the coherent integration length; w is akThe process noise matrix is 4 multiplied by 1, the process noise is Gaussian white noise, the mean value is 0, and k is the current moment;
the actual observed quantity matrix of the measurement model is zk。
Figure BDA0002308384490000042
Expanding the process noise matrix and the measurement noise matrix into a state vector to obtain an expanded state vector:
Figure BDA0002308384490000043
wherein upsilon iskA white gaussian noise measurement noise matrix with zero mean of 2 × 1;
obtaining x of current k timepThe label being xpkAnd using x in combinationpkCorrecting the angular frequency value of the local carrier NCO in real time;
s6, converting the I obtained in the step S4E、IL、QE、QLAfter passing through the code phase discriminator, the code phase difference delta is outputcp，δcpAfter passing through a loop filter, the angular frequency value of the local carrier NCO passes through a proportioner kappacThe latter results are added, the added sum M is used as the control input quantity of a pseudo code NCO module, and the pseudo code NCO outputs the frequency f in real timecoFrequency fcoThe drive pseudocode generator generates local timeout, prompt and lag pseudocodes.
Advantageous effects
In order to realize stable tracking of satellite navigation signals under dynamic weak signals and improve the dynamic property and tracking precision, the UKF algorithm is used in loop tracking to realize carrier tracking under high dynamic, and for tracking of code phase, the correlation of code phase shift and Doppler frequency shift is utilized to adopt a carrier auxiliary code loop technology, so that the dynamic stress borne by the code loop is basically eliminated, and the high dynamic code tracking is realized. Meanwhile, a self-adaptive text removal method is provided, under the condition that the text is not collected, the influence of the text is eliminated by adopting a symbol judgment and phase inversion mode, under the condition that the text is collected, the influence of the text is eliminated by adopting the known satellite navigation text, the long-time coherent integration is realized, and the carrier tracking and the code tracking under the weak signal environment are further realized.
Drawings
FIG. 1 is a flow chart of the present invention for tracking satellite navigation signals;
FIG. 2 is a flowchart illustrating a text removal process according to the present invention;
FIG. 3 is a block diagram of a conventional tracking loop of the present invention;
fig. 4 is a diagram of the tracking loop based on the UKF of the present invention.
Detailed Description
The invention will be further described with reference to the drawings and the principles of the method. The invention provides a tracking method of dynamic weak signal satellite navigation signals.
As shown in fig. 1 to 4, a method for tracking a dynamic weak signal satellite navigation signal includes the following steps:
step 1: maximum energy value and Doppler frequency shift f obtained by capturingdacqAnd a code phase offset pacqStoring the signals and sending the satellite navigation signals after completing the pseudocode and carrier stripping to a tracking channel, wherein the signals after the frequency mixing result is related to the copied pseudocode can be expressed as follows:
IP(t)＝aD(t)cos(ωet+θe) (1)
QP(t)＝aD(t)sin(ωet+θe) (2)
wherein, ω iseIs the carrier angular frequency, thetaeIs the initial phase.
Step 2: judging whether the messages are collected, if so, multiplying the navigation messages by sine and cosine carriers generated by the voltage-controlled oscillator to remove the influence of the navigation messages, wherein the result is shown as the following formula; under the condition of no collecting telegraph text, in order to eliminate the influence of navigation data, two paths of signals, namely an I branch signal and an instantaneous pseudo code coherent integral value IPSum Q branch signal and instantaneous pseudo code coherent integral value QPAnd (4) carrying out symbol judgment or twice phase inversion to remove the influence of the symbol.
And step 3: when the carrier-to-noise ratio calculation is not finished, setting coherent integration duration according to a captured energy value; and after the carrier-to-noise ratio is calculated, setting coherent integration time length according to the size of the carrier-to-noise ratio, wherein the coherent integration time length is set to nms. Then, performing nms coherent integration on the I branch signal and the Q branch signal to obtain a coherent integration value IP、QP、IE、IL、QE、QL。
IP(n)＝aD(n)R(τP)cos(ωe(n)t(n)+θe) (3)
QP(n)＝aD(n)R(τP)sin(ωe(n)t(n)+θe) (4)
IE(n)＝aD(n)R(τE)cos(ωe(n)t(n)+θe) (5)
QE(n)＝aD(n)R(τE)sin(ωe(n)t(n)+θe) (6)
IL(n)＝aD(n)R(τL)cos(ωe(n)t(n)+θe) (7)
QL(n)＝aD(n)R(τL)sin(ωe(n)t(n)+θe) (8)
And 4, step 4: and (5) judging the loop tracking time length, if the loop tracking time length is less than the coherent integration time length, turning to the step 5, and otherwise, turning to the step 6.
And 5: in a traditional second-order auxiliary third-order tracking loop, a second-order frequency-locked loop is adopted to assist a third-order phase-locked loop, so that carrier tracking is realized. The working process of the tracking loop comprises the following steps of firstly carrying out frequency discrimination, enabling a PLL discriminator not to work, enabling a phase error input value of a loop filter to be 0, equivalently carrying out pure FLL at the moment, utilizing the FLL to eliminate carrier dynamics, starting the PLL after the FLL is closed, working in a mode of assisting the PLL by the FLL (namely, both frequency error input and phase error input), controlling the frequency error within a range in which the PLL can work, closing a frequency locking loop after phase locking, then switching to the pure PLL, and closing in a working mode of the pure PLL to meet the requirement of precision. Under the dynamic environment, the frequency locking ring is not closed, and the frequency locking ring is adopted to assist the working mode of the phase-locked loop.
Step 6: setting the update period of dimension expansion UKF, here 1ms, and then integrating the coherent integration value I obtained in step 3PAnd QPAnd sending the data to an extended dimension Unscented Kalman Filter (UKF) module. And the UKF tracking module is divided into a carrier dynamic model and a measurement model.
A carrier dynamic model:
considering stable tracking of satellite navigation signals in high dynamic state, the following 4 state quantities x should be included in the state vectork＝[xp；xw；xa；xj]kThe state transition equation is:
Figure BDA0002308384490000071
wherein xpThe phase difference between the real carrier and the local carrier of the receiver is obtained; x is the number ofwTrue carrier doppler shift; x is the number ofaIs the first order rate of change of the carrier doppler shift; x is the number ofjIs the second order rate of change of the carrier doppler shift; delta TkIs the cumulative time interval, here Δ TkIs determined by step 3. w is akIs a 4 x 1 process noise matrix, the noise is white Gaussian noise with a mean of 0 and the covariance matrix is Qk。
Measurement model:
coherent integration value I in step 3PAnd QPForm the actual observation matrix z in the expanded dimension UKFk。
Figure BDA0002308384490000072
The measurement equation is as follows:
Figure BDA0002308384490000073
wherein N is1kIs the number of sample points in the cumulative time interval, upsilonkIs a 2 x 1 zero mean Gaussian white noise measurement noise matrix with a covariance matrix of Rk。
Carrying out dimension expansion UKF algorithm operation, which comprises the following steps:
(1) state vector and its covariance initialisation:
considering that the process and metrology equations may be non-linear with respect to the corresponding noise, the process and measurement noise is extended into the state vector, i.e.:
Figure BDA0002308384490000081
initializing the dimension expansion UKF by using the capture Doppler frequency shift obtained in the step 1, wherein the initial value of the state vector and the initial value of the covariance thereof are as follows:
Figure BDA0002308384490000082
wherein Q0Is the covariance of the process noise, R0To measure the covariance of the noise.
(2) 2n +1 sigma points are selected
Figure BDA0002308384490000083
From xkBest estimate of the mean and covariance of
Figure BDA0002308384490000084
And
Figure BDA0002308384490000085
with appropriate modifications thereto.
Figure BDA0002308384490000086
Figure BDA0002308384490000087
Figure BDA0002308384490000088
I.e. the total sigma point number is: 2n +1(n is after expansion)
Figure BDA0002308384490000089
Dimension of) wherein
Figure BDA00023083844900000810
Represents (n + λ) PxColumn i of the square root matrix of (1), scale factor λ α2(n + κ) -n, where α denotes the degree of scattering, was determined
Figure BDA00023083844900000814
The distribution of surrounding sigma points is adjusted α to minimize the effect of higher order terms, which range from 1e-4 ≦ α ≦ 1, and κ is an auxiliary scale factor for n + κ ≠ 0And 0 as a default.
(3) Calculating a weighting coefficient:
Figure BDA00023083844900000811
Figure BDA00023083844900000812
Figure BDA00023083844900000813
β reflects the state vector prior information quantity, and adjusting it can improve the precision of variance, and when 2 is taken, it corresponds to the optimal value of Gaussian distribution.
Figure BDA0002308384490000091
Is a weighting coefficient when first-order statistical characteristics (mean) are calculated;
Figure BDA0002308384490000092
the weighting coefficients are used for the second-order statistical characteristics (covariance matrix).
(4) The time update equation:
(a) and carrying out state transfer on the selected sigma point at the k-1 moment through a nonlinear equation f (-) to obtain the state quantity at the k moment:
Figure BDA0002308384490000093
(b) will be provided with
Figure BDA0002308384490000094
Obtaining a prior state estimated value at the k moment through weighted summation:
Figure BDA0002308384490000095
(c) the covariance of the a priori estimation error is also found by weighted summation, and since the noise is already extended into the state quantity, there is no need to add process noise:
Figure BDA0002308384490000096
(5) and measurement updating is realized:
(a) to reduce the amount of computation, the sigma point generated in the time update will be used directly here
Figure BDA0002308384490000097
Converting the sigma points into measurement predicted values through a nonlinear measurement equation h (-)
Figure BDA0002308384490000098
Figure BDA0002308384490000099
(b) Predict the measurement
Figure BDA00023083844900000910
Merging vectors to obtain measurement prediction of k time:
Figure BDA00023083844900000911
(c) the measured predicted covariance is:
Figure BDA00023083844900000912
(d) state quantity estimation value
Figure BDA00023083844900000913
And observed quantity prediction value
Figure BDA00023083844900000914
The cross-covariance between is:
Figure BDA0002308384490000101
(6) updating process of state quantity and covariance thereof:
Kk＝Pxz/Pz(23)
Figure BDA0002308384490000102
Figure BDA0002308384490000103
Kkkalman gain at time k, zkIs the observed information at time k. Pxz/PzThe weighted sum of the measured prediction errors can be reduced, and the ratio of the weighted sum of the prior estimation errors to the weighted sum of the measured prediction errors is left, namely the Kalman gain.
Figure BDA0002308384490000104
The error between the actual observed value and the estimated measured value is the residual error. And multiplying the residual error by Kalman gain to obtain the error of the estimated state quantity, and adding the error of the estimated state quantity to the prior state estimation to obtain an updated state estimation value. The kalman gain may minimize the root mean square error of the updated state estimate, such that the updated estimate is closest to the true value.
Reconstructing local carrier to obtain updated carrier phase difference estimated value x after each iteration is completedpk(x at time k)p) The method is used for correcting the local carrier NCO and tracking the next moment.
wNCOk+1＝wNCOk+xpk/ΔTk(26)
Wherein wNCOk+1The angular frequency of the local carrier NCO at time k + 1.
And 7: tracking the code loop by carrier auxiliary technology, coherent integral value I in step 4E、IL、QE、QLOutputting the code phase difference delta after passing through the code phase discriminatorcpAnd filtered by a loop filter and then passes through a proportioner kappa with a carrier tracking resultc(e.g. 1/1540 for GPS) and adding the results together, the sum of which is used as the control input of the pseudo-code NCO, and finally the pseudo-code NCO adjusts the output frequency f in real timeco。

Claims (10)

1. A system for tracking dynamic weak signal satellite navigation signals, comprising: the tracking system comprises a sign removing module, an integral module, an extended dimensional unscented Kalman filtering module, a traditional second-order auxiliary third-order tracking loop module, a carrier NCO module, a code phase discriminator module, a loop filter module and a pseudo code NCO module;
the sign removing module is used for removing the sign influence of the I branch signal early-late code and instant pseudo code coherent integration value and the Q branch signal early-late code and instant pseudo code coherent integration value;
the integration module performs coherent integration of self-adaptive time length after removing the influence of navigation message symbols to obtain an instantaneous, an advance and a lag three-way coherent integration value;
the dimension expansion unscented Kalman filtering module is used for removing the I branch signal affected by navigation message symbols and the instantaneous pseudo code coherent integration value IPSum Q branch signal and instantaneous pseudo code coherent integral value QPAs the measured value of the extended dimension unscented Kalman filtering module, the carrier tracking is carried out to output the state quantity xk＝[xp；xw；xa；xj]kThe best estimate of (c); using carrier phase difference estimate xpkCorrecting angular frequency value w of local carrier NCO in real timeNCOk+1；
The traditional second-order auxiliary third-order tracking loop module is used for carrying out carrier loop tracking before coherent integration is not completed, so that the stable tracking of a loop before the UKF module is started is realized;
carrier NCO module according to angular frequency value wNCOk+1Finishing the copying work of sine carrier waves and cosine carrier waves;
the code phase discriminator module receives I branch signals and an overtime pseudo code coherent integral value IEI branch signal and lag pseudo code coherent integral value ILCoherent integration value Q of sum Q branch signal and overtime pseudo codeEQ branch signalCoherent integration value Q with late pseudo codeLDifference of output code phase deltacp；
The loop filter module is used for receiving the code phase difference deltacpFiltered output, angular frequency value w of local carrier NCONCOk+1Passing through a proportioner kappacAdding the results, and outputting the added sum M as the control input quantity of the pseudo code NCO module;
pseudo code NCO module real-time output frequency fcoFrequency fcoThe drive pseudocode generator generates local timeout, prompt and lag pseudocodes.
2. A method for tracking dynamic weak signal satellite navigation signals, the method comprising the steps of:
s1, sending the navigation signal of completing pseudo code and carrier stripping to a tracking channel, and simultaneously storing the captured maximum energy value, the captured carrier Doppler and the captured code phase;
s2, judging whether the navigation message is collected, if not, removing the influence of the navigation message sign through sign judgment or phase inversion and the like, entering step S3, if the message collection is finished, multiplying the navigation message with the navigation message to finish the navigation message stripping on the navigation signal which finishes the pseudo code and carrier stripping, and entering step S3;
s3, when the carrier-to-noise ratio calculation is not finished, setting the coherent integration time length according to the maximum energy value obtained by capturing; when the carrier-to-noise ratio calculation is finished, setting the coherent integration time length according to the carrier-to-noise ratio;
s4, coherent accumulation of the corresponding coherent integration time length is carried out according to the coherent integration time length obtained in the step S3, and a coherent accumulation result is stored, wherein the coherent accumulation result comprises an I branch immediate pseudo code coherent integration value IpQ branch real-time pseudo code coherent integral value QPI branch overtime pseudo code coherent integral value IEI branch lag pseudo code coherent integral value ILQ branch overtime pseudo code coherent integral value QEQ branch lag pseudo code coherent integral value QL；
S5, comparing the loop tracking time with the coherent integration time length, if the loop tracking time is less than the coherent integration time length, starting a traditional second-order auxiliary third-order tracking loop module to realize carrier tracking; if the loop tracking time is not less than the coherent integration time length, starting the extended-dimension unscented Kalman filtering module to realize carrier tracking;
s6, converting the I obtained in the step S4E、IL、QE、QLAfter passing through the code phase discriminator, the code phase difference delta is outputcp，δcpAfter passing through a loop filter, the angular frequency value of the local carrier NCO passes through a proportioner kappacThe latter results are added, the added sum M is used as the control input quantity of a pseudo code NCO module, and the pseudo code NCO outputs the frequency f in real timecoFrequency fcoThe drive pseudocode generator generates local timeout, prompt and lag pseudocodes.
3. The method for tracking a dynamic weak signal satellite navigation signal as claimed in claim 2, wherein: in step S2, the removing of the navigation message symbol is completed by the navigation message influence removing module and the incoming message removing module.
4. The method for tracking a dynamic weak signal satellite navigation signal as claimed in claim 2, wherein: in step S5, the conventional second-order auxiliary third-order tracking loop module is a carrier tracking loop that uses a second-order frequency-locked loop to assist a third-order phase-locked loop.
5. The method for tracking dynamic weak signal satellite navigation signals as claimed in claim 4, wherein: the method for realizing carrier tracking by adopting the carrier tracking loop of the second-order frequency-locked loop-assisted third-order phase-locked loop comprises the following steps: firstly, frequency discrimination is carried out, a PLL discriminator does not work, the input value of the phase error of a loop filter is 0, at the moment, pure FLL is equivalently carried out, carrier dynamics is eliminated by utilizing the FLL, the PLL is started after the FLL is closed, the FLL works in a mode of assisting the PLL, the frequency error is controlled in the working range of the PLL, a frequency locking loop is closed after phase locking, then the pure PLL is converted into the pure PLL, the PLL is closed in a working mode of the pure PLL, and under the dynamic environment, the frequency locking loop is not closed, and the working mode of assisting the phase locking loop by the frequency locking loop is adopted.
6. The method for tracking a dynamic weak signal satellite navigation signal as claimed in claim 5, wherein: operating in the FLL assisted PLL mode means that there is both a frequency error input and a phase error input.
7. The method for tracking a dynamic weak signal satellite navigation signal as claimed in claim 2, wherein: in step S5, the extended-dimension unscented kalman filter module includes a carrier dynamic model and a measurement model.
8. The method of claim 7, wherein the method further comprises the following steps: the state transition equation of the carrier dynamic model is as follows:
Figure FDA0002308384480000031
wherein x isk＝[xp；xw；xa；xj]kThe state vector at the current k moment is obtained;
xpis the phase difference between the received carrier and the local carrier of the receiver; x is the number ofwA doppler shift for the received carrier; x is the number ofaIs the Doppler shift x of the received carrierwFirst order rate of change of; x is the number ofjIs the Doppler shift x of the received carrierwA second order rate of change of; delta TkIs the coherent integration length; w is akIs a 4 × 1 process noise matrix, the process noise is white gaussian noise, the mean is 0, and k is the current time.
9. The method of claim 8, wherein the method further comprises the following steps: the actual observed quantity matrix of the measurement model is zk；
Figure FDA0002308384480000041
10. The method of claim 9, wherein the method further comprises the following steps: expanding the process noise matrix and the measurement noise matrix into a state vector to obtain an expanded state vector:
Figure FDA0002308384480000042
wherein upsilon iskA white gaussian noise measurement noise matrix with zero mean of 2 × 1;
obtaining x of current k timepThe label being xpkAnd using x in combinationpkAnd correcting the angular frequency value of the local carrier NCO in real time.
CN201911248587.7A 2019-12-09 2019-12-09 Satellite navigation signal tracking system and method suitable for dynamic weak signals Pending CN111045040A (en)

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CN112083452A (en) * 2020-08-28 2020-12-15 中国人民解放军63921部队 Loop tracking system and method for satellite navigation receiver
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CN114786240A (en) * 2022-03-02 2022-07-22 厦门大学 5G downlink signal discontinuity tracking method
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CN114609652A (en) * 2022-03-11 2022-06-10 北京航空航天大学 Multi-frequency open-loop receiver tracking method and system under extreme ionosphere anomaly
CN114609652B (en) * 2022-03-11 2024-06-07 北京航空航天大学 Multi-frequency open-loop receiver tracking method and system under extreme ionosphere abnormality
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CN116482724B (en) * 2023-03-09 2024-05-03 北京理工大学 High-precision observed quantity calculation method of navigation receiver

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Application publication date: 20200421