Carrier tracking method, system and equipment of second-order frequency-locked loop assisted third-order phase-locked loop, and medium

Abstract

The invention discloses a carrier tracking method, system, equipment and medium for a second-order frequency-locked loop assisted third-order phase-locked loop, and the method comprises the steps: receiving an in-phase integral value and a quadrature integral value outputted by a correlator, and carrying out the second-order frequency-locked loop tracking and the third-order phase-locked loop tracking based on the in-phase integral value and the quadrature integral value, the control quantity of the frequency-locked loop and the phase-locked loop is obtained; estimating a carrier-to-noise ratio and a carrier wave attitude of the received signal corresponding to the in-phase integral value and the orthogonal integral value in real time, and determining a first gain coefficient and a second gain coefficient according to the carrier-to-noise ratio and the carrier wave attitude; and generating a final control quantity of the carrier numerical control oscillator based on the control quantities of the frequency-locked loop and the phase-locked loop, the first gain coefficient and the second gain coefficient. By introducing a real-time sensing and dynamic gain control mechanism based on the carrier-to-noise ratio and the carrier wave fluctuation attitude, weighted fusion of contribution of the frequency-locked loop and the phase-locked loop is realized, and the robustness, the precision and the adaptive capacity of the carrier tracking loop under all working conditions can be improved.

Description

Technical Field

[0001] This invention relates to the technical field of satellite navigation and communication, and in particular to a carrier tracking method, system, device, and medium using a second-order frequency-locked loop assisted by a third-order phase-locked loop. Background Technology

[0002] In global navigation satellite system receivers, the carrier tracking loop (CLL) is one of the core modules of baseband signal processing. Its main task is to accurately track the carrier phase and frequency of the received satellite signal in order to demodulate the navigation message and provide high-precision observations for pseudorange and carrier phase measurements. To balance the dynamic performance and noise performance of tracking, various carrier tracking loop architectures have been proposed. Among them, the frequency-locked loop (FLL) assisted phase-locked loop (PLL) is a common combination loop. Because the FLL can quickly pull the frequency error after acquisition and has a wide dynamic response range, while the PLL has high tracking phase accuracy and strong noise suppression capability, the in-phase (I) and quadrature (Q) branch signals generated after correlation despreading of the intermediate frequency digital signal in existing receivers are sent to a frequency discriminator. The frequency error output by this discriminator is passed through a second-order loop filter to generate the FLL control input. The I and Q signals are simultaneously sent to a phase discriminator, and the phase error output by this discriminator is passed through a third-order loop filter to generate the PLL control input. Finally, the FLL control input and PLL control input are added together to jointly control the carrier digitally controlled oscillator, forming a feedback closed loop.

[0003] However, the parameters of the FLL and PLL loop filters are fixed, and their contribution to the control of the carrier numerically controlled oscillator is static. This fixed-parameter design represents a trade-off between high dynamic response and weak signal noise suppression. In high-dynamic environments, the Doppler frequency change rate of the carrier is high, requiring a sufficiently wide bandwidth for the carrier loop to respond quickly to frequency changes and prevent loop lock-up. In weak-signal environments, the carrier-to-noise ratio of the received signal is low, requiring a sufficiently narrow bandwidth for the carrier loop to effectively suppress thermal noise, improve tracking sensitivity and accuracy, and prevent noise-induced lock-up. The fixed loop cannot simultaneously meet these two conflicting requirements. In harsh environments with weak signals and high dynamics, this static compromise loop will fail simultaneously: its bandwidth is too wide for suppressing strong noise, causing noise to overwhelm the signal; while it is too narrow for tracking high dynamics, leading to excessive dynamic tracking errors and lock-up. Existing mathematical modeling and performance analysis of the 2-FLL+3-PLL structure are also based on fixed loop parameters and do not propose how to adjust the loop characteristics according to real-time changing signal conditions and dynamic environments. Therefore, there is an urgent need for a method that can overcome the static limitations of the 2-FLL+3-PLL loop, enabling it to adaptively adjust the contributions of the FLL and PLL to maintain optimal tracking performance in dynamically changing environments. Summary of the Invention

[0004] In view of the aforementioned existing problems, this invention is proposed. Therefore, this invention provides a carrier tracking method, system, device, and medium using a second-order frequency-locked loop assisted by a third-order phase-locked loop to solve the problems mentioned in the background art.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: In a first aspect, embodiments of the present invention provide a carrier tracking method for a second-order frequency-locked loop assisted third-order phase-locked loop, comprising: receiving in-phase integral values ​​and quadrature integral values ​​output by a correlator, performing second-order frequency-locked loop tracking and third-order phase-locked loop tracking based on the in-phase integral values ​​and quadrature integral values ​​respectively, and obtaining control quantities of the frequency-locked loop and the phase-locked loop; The carrier-to-noise ratio and carrier dynamics of the received signals corresponding to the in-phase integral value and the quadrature integral value are estimated in real time, and the first gain coefficient and the second gain coefficient are determined based on the carrier-to-noise ratio and the carrier dynamics. Based on the control quantities of the frequency-locked loop and the phase-locked loop, as well as the first gain coefficient and the second gain coefficient, the final control quantity of the carrier numerically controlled oscillator is generated.

[0006] As a preferred embodiment of the carrier tracking method of the second-order frequency-locked loop assisted by the third-order phase-locked loop described in this invention, wherein: second-order frequency-locked loop tracking and third-order phase-locked loop tracking are performed based on the in-phase integral value and the quadrature integral value, respectively, and the control quantities of the frequency-locked loop and the phase-locked loop are obtained, including: The in-phase integral value and the quadrature integral value are processed by the frequency-locked loop discriminator to obtain the frequency error, and the frequency error is input into the second-order frequency-locked loop filter to obtain the frequency-locked loop control quantity. The phase error is obtained by processing the in-phase integral value and the quadrature integral value using a phase-locked loop phase detector, and the phase error is then input into a third-order phase-locked loop loop filter to obtain the phase-locked loop control quantity.

[0007] As a preferred embodiment of the carrier tracking method of the second-order frequency-locked loop assisted by the third-order phase-locked loop described in this invention, the real-time estimation of the carrier-to-noise ratio and carrier dynamics of the received signal corresponding to the in-phase integral value and the quadrature integral value includes: using the narrowband and wideband power ratio method to calculate the estimated value of the carrier-to-noise ratio of the received signal based on the in-phase integral value and the quadrature integral value, wherein the narrowband power is obtained from the signal power of the instantaneous correlation branch, and the wideband power is jointly estimated from the signal power of the leading and lagging correlation branches; A Kalman filter is constructed, wherein the state vector of the Kalman filter includes at least phase error, frequency error and frequency change rate error, and the phase error output by the phase-locked loop phase detector and the frequency error output by the frequency-locked loop frequency detector are used as measurement inputs; Based on the carrier-to-noise ratio estimate, the measurement variance of the phase detector and the frequency detector are calculated in real time, and the measurement noise covariance matrix of the Kalman filter is dynamically updated. The Kalman filter is run to output the updated state estimate, and the absolute value of the frequency change rate error component in the state vector is used as the carrier dynamics estimate.

[0008] As a preferred embodiment of the carrier tracking method of the second-order frequency-locked loop assisted by the third-order phase-locked loop described in this invention, the real-time calculation of the phase detector measurement variance and the frequency detector measurement variance includes: the phase detector measurement variance and the frequency detector measurement variance are determined based on the estimated carrier-to-noise ratio and the loop update period in the following manner: in, To measure the variance of the phase detector, To measure the variance of the frequency discriminator, For loop noise bandwidth, For the loop update cycle, This is a linear value of the carrier-to-noise ratio estimate.

[0009] As a preferred embodiment of the carrier tracking method of the second-order frequency-locked loop assisted by the third-order phase-locked loop described in this invention, the determination of the first gain coefficient and the second gain coefficient based on the carrier-to-noise ratio and carrier dynamics includes: using the carrier-to-noise ratio and carrier dynamics as indexes, and determining the first gain coefficient and the second gain coefficient by querying a two-dimensional lookup table.

[0010] As a preferred embodiment of the carrier tracking method of the second-order frequency-locked loop assisted by the third-order phase-locked loop described in this invention, the determination of the first gain coefficient and the second gain coefficient further includes: When the carrier-to-noise ratio is lower than the first threshold and the carrier dynamics is higher than the second threshold, the first gain coefficient is greater than the second gain coefficient. When the carrier-to-noise ratio is not lower than the first threshold and the carrier dynamics is not higher than the second threshold, the second gain coefficient is greater than the first gain coefficient.

[0011] As a preferred embodiment of the carrier tracking method of the second-order frequency-locked loop assisted by the third-order phase-locked loop described in this invention, wherein: based on the control quantities of the frequency-locked loop and the phase-locked loop, as well as the first gain coefficient and the second gain coefficient, the final control quantity of the carrier numerically controlled oscillator is generated, including: the final control quantity of the carrier numerically controlled oscillator is expressed as: in, This is the frequency lock loop control quantity. This is the control quantity for the phase-locked loop. The first gain coefficient, This is the second gain coefficient.

[0012] Secondly, the present invention provides a carrier tracking system with a second-order frequency-locked loop assisted by a third-order phase-locked loop, comprising: a correlator, a second-order frequency-locked loop, a third-order phase-locked loop, a carrier-to-noise ratio estimation module, a dynamic state estimation module, a loop gain control module, a weighting unit, and a carrier digitally controlled oscillator; the second-order frequency-locked loop includes a frequency-locked loop discriminator and a second-order frequency-locked loop filter, and the third-order phase-locked loop includes a phase-locked loop phase discriminator and a third-order phase-locked loop filter; The correlator receives the intermediate frequency digital signal output from the radio frequency front-end of the global navigation satellite system, and performs correlation despreading processing using the local carrier and local pseudocode from the carrier numerically controlled oscillator, outputting instantaneous, leading and lagging in-phase integral values ​​and quadrature integral values. The frequency-locked loop discriminator calculates the frequency error based on the instantaneous in-phase integral value and instantaneous quadrature integral value generated by the correlator, and sends the frequency error to the second-order frequency-locked loop loop filter to obtain the frequency-locked loop control quantity; the phase-locked loop phase discriminator calculates the phase error based on the instantaneous in-phase integral value and instantaneous quadrature integral value generated by the correlator, and sends the phase error to the third-order phase-locked loop loop filter to obtain the phase-locked loop control quantity. The carrier-to-noise ratio estimation module receives all in-phase and quadrature integral values ​​output by the correlator and estimates the carrier-to-noise ratio of the received signal in real time. The dynamic state estimation module receives the frequency error of the frequency-locked loop discriminator, the phase error of the phase-locked loop phase discriminator, and the carrier-to-noise ratio estimation value from the carrier-to-noise ratio estimation module, and outputs the carrier dynamics. The loop gain control module receives the estimated carrier-to-noise ratio and the carrier dynamics, and determines the first gain coefficient and the second gain coefficient by querying a two-dimensional lookup table. The weighting unit receives the frequency-locked loop control quantity, the phase-locked loop control quantity, the first gain coefficient, and the second gain coefficient, and calculates the final carrier numerically controlled oscillator control quantity. The carrier numerically controlled oscillator generates the local carrier signal for the next moment based on the final carrier numerically controlled oscillator control quantity, and feeds it back to the correlator.

[0013] Thirdly, the present invention provides an electronic device, comprising: Memory and processor; The memory is used to store computer-executable instructions, and the processor is used to execute the computer-executable instructions. When the computer-executable instructions are executed by the processor, they implement the steps of the carrier tracking method of the second-order frequency-locked loop assisted by the third-order phase-locked loop.

[0014] Fourthly, the present invention provides a computer-readable storage medium storing computer-executable instructions that, when executed by a processor, implement the steps of the carrier tracking method of the second-order frequency-locked loop assisted by the third-order phase-locked loop.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: By introducing a real-time sensing and dynamic gain control mechanism based on carrier-to-noise ratio and carrier dynamics, the present invention realizes the weighted fusion of the contributions of frequency-locked loop and phase-locked loop, which can improve the robustness, accuracy and adaptability of carrier tracking loop under all operating conditions. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein: Figure 1 This is a schematic flowchart of a carrier tracking method using a second-order frequency-locked loop assisted by a third-order phase-locked loop, according to an embodiment of the present invention. Figure 2 This is a framework diagram of a carrier tracking method for a second-order frequency-locked loop assisted by a third-order phase-locked loop, according to an embodiment of the present invention, for parallel acquisition of BeiDou dual-frequency signals. Figure 3This is a hardware radio frequency front-end block diagram of a carrier tracking method using a second-order frequency-locked loop assisted by a third-order phase-locked loop, according to an embodiment of the present invention. Figure 4 The diagram shows a single BeiDou fast pseudocode acquisition algorithm for a carrier tracking method assisted by a second-order frequency-locked loop and a third-order phase-locked loop, according to an embodiment of the present invention. Figure 5 This is a flowchart illustrating the signal evaluation process of a carrier tracking method using a second-order frequency-locked loop assisted by a third-order phase-locked loop, as described in one embodiment of the present invention. Detailed Implementation

[0017] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0018] Example 1, referring to Figure 1 As one embodiment of the present invention, this embodiment provides a carrier tracking method for a second-order frequency-locked loop assisted by a third-order phase-locked loop, comprising: S100: Receives the in-phase integral value and quadrature integral value output by the correlator, and performs second-order frequency-locked loop tracking and third-order phase-locked loop tracking based on the in-phase integral value and quadrature integral value respectively, to obtain the control quantities of the frequency-locked loop and phase-locked loop; S200: Estimate the carrier-to-noise ratio and carrier dynamics of the received signal corresponding to the in-phase integral value and the quadrature integral value in real time, and determine the first gain coefficient and the second gain coefficient based on the carrier-to-noise ratio and the carrier dynamics. S300: Based on the control quantities of the frequency-locked loop and phase-locked loop, as well as the first and second gain coefficients, the final control quantity of the carrier numerically controlled oscillator is generated.

[0019] In this embodiment of the invention, step S100 involves performing second-order frequency-locked loop (LLL) tracking and third-order phase-locked loop (PLL) tracking based on the in-phase integral value and the quadrature integral value, respectively, to obtain the control quantities of the LLL and PLL, including: The frequency error is obtained by processing the in-phase integral value and the quadrature integral value using a frequency-locked loop discriminator, and the frequency error is input into the second-order frequency-locked loop filter to obtain the frequency-locked loop control quantity. The phase error is obtained by processing the in-phase integral value and the quadrature integral value using a phase-locked loop phase detector, and then inputting the phase error into a third-order phase-locked loop loop filter to obtain the phase-locked loop control quantity.

[0020] In this embodiment of the invention, the real-time estimation of the carrier-to-noise ratio and carrier dynamics of the received signal corresponding to the in-phase integral value and the quadrature integral value in step S200 includes: using the narrowband and wideband power ratio method to calculate the estimated value of the carrier-to-noise ratio of the received signal based on the in-phase integral value and the quadrature integral value, wherein the narrowband power is obtained from the signal power of the instantaneous correlation branch, and the wideband power is jointly estimated from the signal power of the leading and lagging correlation branches. Construct a Kalman filter whose state vector includes at least phase error, frequency error, and frequency change rate error, and use the phase error output by the phase-locked loop phase detector and the frequency error output by the frequency-locked loop frequency detector as measurement inputs; Based on the carrier-to-noise ratio estimate, the measurement variance of the phase detector and the frequency detector are calculated in real time, and the measurement noise covariance matrix of the Kalman filter is dynamically updated. Run the Kalman filter, output the updated state estimate, and use the absolute value of the frequency change rate error component in the state vector as the carrier dynamics estimate.

[0021] In this embodiment of the invention, the real-time calculation of the phase detector measurement variance and the frequency detector measurement variance in step S200 includes: the phase detector measurement variance and the frequency detector measurement variance are determined based on the carrier-to-noise ratio estimate and the loop update cycle in the following manner: in, To measure the variance of the phase detector, To measure the variance of the frequency discriminator, For loop noise bandwidth, For the loop update cycle, This is a linear value of the carrier-to-noise ratio estimate.

[0022] In this embodiment of the invention, step S200, which determines the first gain coefficient and the second gain coefficient based on the carrier-to-noise ratio and carrier dynamics, includes: using the carrier-to-noise ratio and carrier dynamics as indexes, and determining the first gain coefficient and the second gain coefficient by querying a two-dimensional lookup table.

[0023] In this embodiment of the invention, the determination of the first gain coefficient and the second gain coefficient in step S200 further includes: When the carrier-to-noise ratio is lower than the first threshold and the carrier dynamics is higher than the second threshold, the first gain coefficient is greater than the second gain coefficient. When the carrier-to-noise ratio is not lower than the first threshold and the carrier dynamics is not higher than the second threshold, the second gain coefficient is greater than the first gain coefficient.

[0024] It should be noted that in this embodiment, the first threshold can be set to 35dB-Hz and the second threshold can be set to 500rad / s².

[0025] In this embodiment of the invention, step S300, based on the control quantities of the frequency-locked loop and the phase-locked loop, as well as the first gain coefficient and the second gain coefficient, generates the final control quantity of the carrier numerically controlled oscillator, which is expressed as follows: in, This is the frequency lock loop control quantity. This is the control quantity for the phase-locked loop. The first gain coefficient, This is the second gain coefficient.

[0026] Example 2, refer to Figures 2-5 This embodiment of the present invention provides a carrier tracking method using a second-order frequency-locked loop assisted by a third-order phase-locked loop, comprising: a correlator, a second-order frequency-locked loop, a third-order phase-locked loop, a carrier-to-noise ratio estimation module, a dynamic state estimation module, a loop gain control module, a weighting unit, and a carrier numerically controlled oscillator; the second-order frequency-locked loop includes a frequency-locked loop discriminator and a second-order frequency-locked loop filter, and the third-order phase-locked loop includes a phase-locked loop phase discriminator and a third-order phase-locked loop filter; The correlator receives the intermediate frequency digital signal output from the radio frequency front end of the global navigation satellite system, and performs correlation despreading processing using the local carrier and local pseudocode from the carrier numerically controlled oscillator, outputting the instantaneous, leading and lagging in-phase integral value and quadrature integral value; The frequency-locked loop discriminator calculates the frequency error based on the instantaneous in-phase integral value and instantaneous quadrature integral value generated by the correlator, and sends the frequency error to the second-order frequency-locked loop loop filter to obtain the frequency-locked loop control quantity; the phase-locked loop phase discriminator calculates the phase error based on the instantaneous in-phase integral value and instantaneous quadrature integral value generated by the correlator, and sends the phase error to the third-order phase-locked loop loop filter to obtain the phase-locked loop control quantity. The carrier-to-noise ratio estimation module receives all in-phase and quadrature integral values ​​output by the correlator and estimates the carrier-to-noise ratio of the received signal in real time. The dynamic state estimation module receives the frequency error of the frequency-locked loop discriminator, the phase error of the phase-locked loop phase discriminator, and the carrier-to-noise ratio estimate from the carrier-to-noise ratio estimation module, and outputs the carrier dynamics. The loop gain control module receives the estimated carrier-to-noise ratio and carrier dynamics, and determines the first gain coefficient and the second gain coefficient by querying a two-dimensional lookup table. The weighting unit receives the frequency-locked loop control quantity, the phase-locked loop control quantity, the first gain coefficient, and the second gain coefficient, and calculates the final carrier numerically controlled oscillator control quantity. The carrier numerically controlled oscillator generates the local carrier signal for the next moment based on the final carrier numerically controlled oscillator control quantity, and feeds it back to the correlator.

[0027] In an optional embodiment, the workflow of the wave tracking system during a loop update cycle (epoch k) includes steps A through H: Step A: The correlator utilizes a carrier digitally controlled oscillator in The local carrier output at the epoch, for the current Integrate the intermediate frequency signal of 1 second and output the result. .in, The instantaneous in-phase integral value, The instantaneous orthogonal integral value; This is the leading in-phase integral value. The value is the advanced orthogonal integral; This is the value of the in-phase integral with lag. The values ​​are lagging orthogonal integrals. In this invention, the in-phase integral (I) and the orthogonal integral (Q) mainly refer to... and However, it is also used in some specific implementations (such as C / N0 estimation). .

[0028] Step B: The carrier-to-noise ratio estimation module receives the output from step A and calculates the power ratio using the narrowband and broadband power ratio method. .

[0029] Step C: The frequency-locked loop (LLL) discriminator and the phase-locked loop (PLL) phase discriminator receive the output from step A. and the previous moment ), calculate the measurement error for the current period [rad] and [Hz] forms the measurement vector: Step D: The dynamic state estimation module performs the following sub-steps: SD1: Obtained from step B Dynamically calculate the measurement noise covariance matrix ; SD2: Dynamic State Estimation Prediction: SD3: Utilizing step C and SD1 and the definition Matrix, calculate Kalman gain and update the status: and .

[0030] SD4: Extracting Dynamics: .

[0031] Step E: Loop gain module execution: With step B and SD4 Use the index to query the two-dimensional LUT and obtain the gain coefficient. and .

[0032] Step F: Loop Filtering SF1: FLL loop filter receiving step C Calculate according to the difference equation .

[0033] SF2: PLL loop filter receiving step C Calculate according to the difference equation .

[0034] Step G: Weighted unit calculates the final NCO control word: Step H: It is fed into the NCO, which updates its internal frequency and phase accumulators to generate the data for use in generating the data. The local carrier signal of the epoch.

[0035] Return to step A to begin the next tracking cycle.

[0036] Example 3: This example details the specific implementation of the basic components in the system.

[0037] The PLL phase detector uses a Costas phase-locked loop phase detector, preferably a two-quadrant arctangent phase detector, to be compatible with data bit flipping. Although it is mentioned that a two-quadrant arctangent phase detector is used in a third-order loop, for the sake of generality, a standard Costas phase detector can be used here.

[0038] in, and It is the instantaneous correlation value of the k-th coherent integral period. It reflects the phase error (unit: rad).

[0039] The FLL discriminator employs a two-quadrant arctangent discriminator that is insensitive to data bit flipping, also known as a cross-product discriminator.

[0040] in, It is the coherent integration time (loop update cycle). It reflects the frequency error (in Hz). For cross product, It is the dot product.

[0041] The third-order PLL loop filter uses a standard digital third-order loop filter. Its Z-domain transfer function... From the loop coefficient Determine (coefficients based on required noise bandwidth) Damping ratio The derivation (standard design details omitted here) is as follows: Its difference equation (an example implementation) is: in, These are the internal state variables of the filter.

[0042] The second-order FLL loop filter uses a standard digital second-order loop filter. Its Z-domain transfer function... From the loop coefficient Confirmed. Its difference equation (an example implementation) is: in, These are the internal state variables of the filter.

[0043] Example 4 provides a specific implementation of the carrier-to-noise ratio estimation module, namely the narrowband to wideband power ratio (NWPR) method. This method utilizes the principle that signal power is concentrated on the correlation value of the instantaneous branch, while noise power is uniformly distributed in the outputs of the instantaneous, leading, and lagging correlators.

[0044] The calculation steps include: Calculate instantaneous branch power (signal + noise): Calculate noise power (broadband power): Use the lead (E) and lag (L) correlation values ​​(which are outside the correlation peak and mainly contain noise) to estimate the noise power.

[0045] Smoothing filtering: To reduce estimation jitter, a low-pass filter (such as an N-point moving average or an IIR filter) is used. and Perform smoothing to obtain the smoothed mean. and .

[0046] in, It is the smoothing coefficient, for example .

[0047] Calculate C / N0: in, It is the coherent integration time. Carrier-to-noise ratio The linear value.

[0048] this The value is output to the dynamic state estimation module and the loop gain control module. Example 4 provides the complete mathematical derivation and implementation details of the adaptive Kalman filter module.

[0049] The purpose of this adaptive Kalman filter is to robustly estimate the dynamic state of the loop, especially the rate of frequency change, under strong noise. ).

[0050] State vector Choose a three-dimensional state vector to match the dynamic characteristics of a third-order PLL (which can track constant acceleration, i.e., a linear frequency ramp): in, The phase error is in rad. Frequency error (rad / s), The error is the rate of change of frequency (rad / s²).

[0051] The state transition model (prediction phase) assumes a loop update period. Within, rate of change of frequency It is constant (driven by Jerk process noise).

[0052] in, This is the predicted state value. To predict the covariance matrix, This is the state estimate from the previous time step. This is the estimated covariance matrix from the previous time step. The state transition matrix is ​​also shown. for: Process noise covariance matrix (by Jerk) drive): in, It is a design parameter (tuning value) that represents the expectation of Jerk (dynamic model uncertainty).

[0053] Measurement model (update phase) KF measurement values ​​( Output from the phase detector (unit: rad) and the output of the frequency discriminator (Unit: Hz), used as KF for fusion of FLL and PLL measurements.

[0054] Measurement Matrix The state vector ( Mapping to measurement vector ( Due to the state The unit is rad / s, while the measurement The unit is Hz, measurement matrix One is needed The conversion factor.

[0055] Adaptive measurement noise covariance Must be based on Updated in real time. The matrix must be related to the measurement vector. The units match.

[0056] (Assuming the noise of the phase detector and the frequency detector are uncorrelated) Among them, the measurement variance of the phase detector (Costas) (unit )for: in,( for The linear value; The bandwidth of the front-end loop noise can be approximated as: ); Measurement variance of frequency discriminator (unit )for: In each loop update cycle k, the KF module first obtains the value from the C / N0 estimation module. Convert to linear value Then use the above formula to calculate and To build dynamically matrix.

[0057] KF Update Equation (Standard Formula 5) a) Measurement Residuals: b) Residual covariance: c) Kalman gain: d) Update state estimate: e) Update the covariance estimate: in, It is an identity matrix. To measure the residual, For residual covariance, For Kalman gain, This is the updated estimated covariance.

[0058] Module output KF module output dynamic degree That is, the updated state vector. The third component (estimated value of the rate of change of frequency) The absolute value of ) in, Representing vectors The third element.

[0059] this The value is output to the LGC module.

[0060] Example 5: This example provides an efficient implementation of the loop gain control module: a two-dimensional lookup table.

[0061] This embodiment maps "state" (C / N0, dynamic degree) to "control" ( ).enter: Output: and .

[0062] The loop gain control module internally stores a two-dimensional array (lookup table), which is pre-calculated based on offline simulation and optimization. and After quantization, it is used as the index of this table, as shown in Table 1.

[0063] Table 1. Two-dimensional lookup table for loop gain control (LGC) (example values)

[0064] As can be seen from Table 1, the bottom left corner (strong signal / low dynamics) is: ( =0.1, =1.0). At this time, the loop switches to high-precision PLL mode. The contribution of FLL is suppressed to prevent FLL discriminator noise ( Affects the loop. Top right corner (weak signal / high dynamic range): ( =1.0, =0.1). This is the worst-case scenario. At this point, the loop switches to highly robust FLL mode. The contribution of the PLL is greatly suppressed because the PLL phase detector ( under weak signals) The noise is extremely high and sensitive to data flips, making it highly susceptible to loss of lock. The loop relies on a frequency lock-up (FLL) that is insensitive to phase flips to maintain frequency lock and ensure the loop's "survival." In other areas, the contributions of the FLL and PLL are smoothly weighted to achieve a dynamic balance between dynamic response and noise suppression.

[0065] In weak signal conditions, the Costas phase detector of the PLL is extremely sensitive to 180° data bit flips (phase jumps), making it prone to loss of lock. In contrast, the frequency detector of the FLL is not sensitive to phase flips. This invention employs a "sacrifice the PLL, preserve the FLL" strategy, actively sacrificing phase accuracy and switching to a highly robust FLL mode to ensure the loop can lock at least the frequency, greatly improving its survivability in this extremely harsh environment. It can operate effectively in four typical operating quadrants: Operating Condition 1: Strong signal, low dynamics ( high, (Low). The LGC module will set it automatically. , The loop switches to high-precision PLL mode, suppressing the noise contribution of the FLL, narrowing the loop, and achieving extremely high phase tracking accuracy. Operating Condition 2: Strong signal, high dynamic range (…) high, (High). The LGC module will set... , Strong signal, noise is not a problem. The FLL and PLL work in full-speed coordination, widening the loop bandwidth and closely tracking high dynamics. Operating condition 3: Weak signal, low dynamics ( Low, (Low). The LGC module will simultaneously reduce... and (For example, all set to 0.5). The overall equivalent bandwidth of the loop is narrowed, strongly suppressing thermal noise and improving tracking sensitivity. Operating condition 4: Weak signal, high dynamic range ( Low, (High). This is the "death zone" of the fixed loop. The LGC module of this invention will make a critical decision: setting... , This perfectly resolves the technical contradiction between "high dynamics" and "weak signals." Loop characteristics are no longer a fixed compromise, but are dynamically optimized based on real-time operating conditions.

[0066] Example 6: This example provides an electronic device applicable to a carrier tracking method using a second-order frequency-locked loop assisted by a third-order phase-locked loop, including: The system includes a memory and a processor. The memory stores computer-executable instructions, and the processor executes these instructions to implement the carrier tracking method for implementing a second-order frequency-locked loop assisted by a third-order phase-locked loop, as proposed in the above embodiments.

[0067] This embodiment also provides a storage medium storing a computer program that, when executed by a processor, implements the carrier tracking method for implementing a second-order frequency-locked loop assisted by a third-order phase-locked loop as proposed in the above embodiments.

[0068] The storage medium proposed in this embodiment and the carrier tracking method for implementing a second-order frequency-locked loop assisted by a third-order phase-locked loop proposed in the above embodiments belong to the same inventive concept. Technical details not described in detail in this embodiment can be found in the above embodiments, and this embodiment has the same beneficial effects as the above embodiments.

[0069] Based on the above description of the implementation methods, those skilled in the art can clearly understand that the present invention can be implemented using software and necessary general-purpose hardware, and of course, it can also be implemented using hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as a computer floppy disk, read-only memory (ROM), random access memory (RAM), flash memory, hard disk, or optical disk, etc., including several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods of the various embodiments of the present invention.

[0070] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A carrier tracking method using a second-order frequency-locked loop assisted by a third-order phase-locked loop, characterized in that, include: Receive the in-phase integral value and quadrature integral value output by the correlator, and perform second-order frequency-locked loop tracking and third-order phase-locked loop tracking based on the in-phase integral value and quadrature integral value respectively to obtain the control quantities of the frequency-locked loop and phase-locked loop; The carrier-to-noise ratio and carrier dynamics of the received signals corresponding to the in-phase integral value and the quadrature integral value are estimated in real time, and the first gain coefficient and the second gain coefficient are determined based on the carrier-to-noise ratio and the carrier dynamics. Based on the control quantities of the frequency-locked loop and the phase-locked loop, as well as the first gain coefficient and the second gain coefficient, the final control quantity of the carrier numerically controlled oscillator is generated.

2. The carrier tracking method of a second-order frequency-locked loop assisted by a third-order phase-locked loop as described in claim 1, characterized in that, Based on the in-phase integral value and the quadrature integral value, second-order frequency-locked loop (FLL) tracking and third-order phase-locked loop (PLL) tracking are performed respectively, and the control quantities of the FLL and PLL are obtained as follows: The in-phase integral value and the quadrature integral value are processed by the frequency-locked loop discriminator to obtain the frequency error, and the frequency error is input into the second-order frequency-locked loop filter to obtain the frequency-locked loop control quantity. The phase error is obtained by processing the in-phase integral value and the quadrature integral value using a phase-locked loop phase detector, and the phase error is then input into a third-order phase-locked loop loop filter to obtain the phase-locked loop control quantity.

3. The carrier tracking method of a second-order frequency-locked loop assisted by a third-order phase-locked loop as described in claim 2, characterized in that, Real-time estimation of the carrier-to-noise ratio and carrier dynamics of the received signal corresponding to the in-phase integral value and the quadrature integral value includes: using the narrowband and wideband power ratio method to calculate the estimated carrier-to-noise ratio of the received signal based on the in-phase integral value and the quadrature integral value, wherein the narrowband power is obtained from the signal power of the instantaneous correlation branch, and the wideband power is jointly estimated from the signal power of the leading and lagging correlation branches; A Kalman filter is constructed, wherein the state vector of the Kalman filter includes at least phase error, frequency error and frequency change rate error, and the phase error output by the phase-locked loop phase detector and the frequency error output by the frequency-locked loop frequency detector are used as measurement inputs; Based on the carrier-to-noise ratio estimate, the measurement variance of the phase detector and the frequency detector are calculated in real time, and the measurement noise covariance matrix of the Kalman filter is dynamically updated. The Kalman filter is run to output the updated state estimate, and the absolute value of the frequency change rate error component in the state vector is used as the carrier dynamics estimate.

4. The carrier tracking method of a second-order frequency-locked loop assisted by a third-order phase-locked loop as described in claim 3, characterized in that, The real-time calculation of the phase detector measurement variance and the frequency detector measurement variance includes: the phase detector measurement variance and the frequency detector measurement variance are determined based on the carrier-to-noise ratio estimate and the loop update cycle in the following manner: in, To measure the variance of the phase detector, To measure the variance of the frequency discriminator, For loop noise bandwidth, For the loop update cycle, This is a linear value of the carrier-to-noise ratio estimate.

5. The carrier tracking method of a second-order frequency-locked loop assisted by a third-order phase-locked loop as described in claim 4, characterized in that, Determining the first gain coefficient and the second gain coefficient based on the carrier-to-noise ratio and carrier dynamics includes: using the carrier-to-noise ratio and carrier dynamics as indexes, and determining the first gain coefficient and the second gain coefficient by querying a two-dimensional lookup table.

6. The carrier tracking method of a second-order frequency-locked loop assisted by a third-order phase-locked loop as described in claim 5, characterized in that, The determination of the first gain coefficient and the second gain coefficient also includes: When the carrier-to-noise ratio is lower than the first threshold and the carrier dynamics is higher than the second threshold, the first gain coefficient is greater than the second gain coefficient. When the carrier-to-noise ratio is not lower than the first threshold and the carrier dynamics is not higher than the second threshold, the second gain coefficient is greater than the first gain coefficient.

7. The carrier tracking method of a second-order frequency-locked loop assisted by a third-order phase-locked loop as described in claim 6, characterized in that, Based on the control quantities of the frequency-locked loop and the phase-locked loop, as well as the first gain coefficient and the second gain coefficient, the final control quantity of the carrier numerically controlled oscillator is generated, which is expressed as follows: in, This is the frequency lock loop control quantity. This is the control quantity for the phase-locked loop. The first gain coefficient, This is the second gain coefficient.

8. A carrier tracking system with a second-order frequency-locked loop assisting a third-order phase-locked loop, characterized in that, include: Correlator, second-order frequency-locked loop, third-order phase-locked loop, carrier-to-noise ratio estimation module, dynamic state estimation module, loop gain control module, weighting unit, and carrier numerically controlled oscillator; The second-order frequency-locked loop includes a frequency-locked loop discriminator and a second-order frequency-locked loop filter, and the third-order phase-locked loop includes a phase-locked loop phase discriminator and a third-order phase-locked loop filter. The correlator receives the intermediate frequency digital signal output from the radio frequency front-end of the global navigation satellite system, and performs correlation despreading processing using the local carrier and local pseudocode from the carrier numerically controlled oscillator, outputting instantaneous, leading and lagging in-phase integral values ​​and quadrature integral values. The frequency-locked loop discriminator calculates the frequency error based on the instantaneous in-phase integral value and instantaneous quadrature integral value generated by the correlator, and sends the frequency error to the second-order frequency-locked loop loop filter to obtain the frequency-locked loop control quantity; the phase-locked loop phase discriminator calculates the phase error based on the instantaneous in-phase integral value and instantaneous quadrature integral value generated by the correlator, and sends the phase error to the third-order phase-locked loop loop filter to obtain the phase-locked loop control quantity. The carrier-to-noise ratio estimation module receives all in-phase and quadrature integral values ​​output by the correlator and estimates the carrier-to-noise ratio of the received signal in real time. The dynamic state estimation module receives the frequency error of the frequency-locked loop discriminator, the phase error of the phase-locked loop phase discriminator, and the carrier-to-noise ratio estimation value from the carrier-to-noise ratio estimation module, and outputs the carrier dynamics. The loop gain control module receives the estimated carrier-to-noise ratio and the carrier dynamics, and determines the first gain coefficient and the second gain coefficient by querying a two-dimensional lookup table. The weighting unit receives the frequency-locked loop control quantity, the phase-locked loop control quantity, the first gain coefficient, and the second gain coefficient, and calculates the final carrier numerically controlled oscillator control quantity. The carrier numerically controlled oscillator generates the local carrier signal for the next moment based on the final carrier numerically controlled oscillator control quantity, and feeds it back to the correlator.

9. An electronic device, comprising: Memory and processor; The memory is used to store computer-executable instructions, and the processor is used to execute the computer-executable instructions. When the computer-executable instructions are executed by the processor, they implement the steps of the carrier tracking method of the second-order frequency-locked loop assisted by the third-order phase-locked loop as described in any one of claims 1 to 7.

10. A computer-readable storage medium storing computer-executable instructions that, when executed by a processor, implement the steps of the carrier tracking method of the second-order frequency-locked loop assisted by the third-order phase-locked loop as described in any one of claims 1 to 7.

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