A code loop phase detection method for high-precision GPS signal tracking
By using the method of multiplication and summing the adjacent amplitudes of I and Q signals in the GPS signal receiver, the square loss is reduced and the phase identification method is selected according to the tracking state, the problems of low accuracy and slow tracking speed in the prior art are solved, and high-precision code ring tracking and phase identification processing are realized.
Patent Information
- Application Number
- CN202411730840.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-29
- Publication Date
- 2025-04-08
AI Technical Summary
In the code ring tracking and phase identification processing, existing GPS signal receivers have an impact on square loss due to the signal-to-noise ratio, resulting in low accuracy and poor tracking speed and steady-state error.
A high-precision code ring phase identification method is adopted, and the traditional signal mode square calculation is replaced by multiplication and sum of adjacent amplitudes of the I and Q signals, square loss is reduced, and different phase identification error detection methods are selected according to the current tracking state, and the phase identification error is corrected by adjusting the coefficient.
The overall data phase detection accuracy of the GPS signal receiver is improved, the impact of signal-to-noise ratio on square loss is reduced, and the tracking speed and steady-state error performance is enhanced.
Smart Images
Figure CN119780974A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the fields of GPS signal reception and code loop tracking technology of a navigation system, and in particular to a code loop phase discrimination method for high-precision GPS signal tracking. Background Art
[0002] Code loop tracking technology is a key technology in the design of GPS signal receivers. The code loop identifier uses the peak symmetry of the pseudocode correlation function to identify the phase difference between the received code and the local replica code, and then adjusts the circuit to make the local replica code consistent with the received code phase, further obtaining the code phase of the received signal and the pseudorange measurement value between the nodes.
[0003] Commonly used code loop phase detection methods include the incoherent advance minus lag amplitude method, the incoherent advance minus lag power method, the quasi-coherent dot product power method, and the coherent dot product power method. However, the incoherent advance minus lag power method has the fastest tracking speed, but the tracking steady-state error is high; the coherent dot product power method has the highest phase detection accuracy, but is affected by the stable state of the carrier loop, the tracking completion time is longer and the tracking speed is slower. Therefore, it is of great significance to study high-precision GPS signal reception, code loop tracking, phase detection processing and other technologies. Summary of the invention
[0004] To solve the above problems, the present invention proposes a code loop phase detection method for high-precision GPS signal tracking, which can reduce the influence of the received signal noise ratio on the square loss and improve the phase detection accuracy of the overall data.
[0005] The technical solution adopted by the present invention is as follows:
[0006] A code loop phase detection method for high-precision GPS signal tracking comprises the following steps:
[0007] Step 1: After the GPS satellite signal is processed by the receiver RF front end, a digital intermediate frequency signal is obtained. After completing signal capture and carrier loop tracking and carrier stripping, the signal enters the code loop, and the intermediate frequency carrier is stripped from the I and Q signals of the received signal. After that, the I and Q signals are correlated with the locally copied advanced, immediate, and delayed pseudo codes, respectively, and the correlation results are integrated to obtain the input signal I of the phase detector. E , Q E ,I P , Q P ,I L , Q L , where I E is the integral value after correlation between I-channel signal and advance pseudo code, Q E is the integral value after correlation between Q-path signal and leading pseudo code, I P Q is the integral value after correlation between I-channel signal and instantaneous pseudo code, Pis the integral value after correlation between Q-path signal and instantaneous pseudo code, I L is the integral value after correlation between I-channel signal and delayed pseudo code, Q L is the integral value after correlation between the Q-path signal and the delayed pseudo code;
[0008] Step 2: I E , Q E The sampling points of the two signals are denoted as I E (n), Q E (n), multiply the product of the leading code I adjacent signals by I E (n)I E (n+1) and the product of Q adjacent signals Q E (n)Q E (n+1) is added to obtain the approximate value of the signal amplitude modulus square. According to the non-correlation of the signal modulus square approximation, the leading code non-coherent integration result y is obtained. E (k):
[0009]
[0010] Where k = 2, 3, ...;
[0011] Will I L , Q L The sampling points of the two signals are denoted as I L (n), Q L (n), multiply the adjacent signals of the lagged code I by I L (n)I L (n+1) and the product of Q adjacent signals Q L (n)Q L (n+1) is added to obtain the approximate value of the signal amplitude modulus square. According to the non-correlation of the signal modulus square approximation, the lag code incoherent integration result y is obtained. L (k):
[0012]
[0013] Where k = 2, 3, ...;
[0014] Step 3, determine the current tracking state, use t to represent the current tracking time, T0 to represent the time when the pull-in state switches to the stable tracking state, that is, the time when the tracking process is completed and enters the stable tracking state, and compare t with T0;
[0015] Step 4: If t￡T0, it means that the tracking is still adjusting and has not yet entered the stable stage. In this state, the non-coherent leading minus lagging power method is used to obtain the code phase error δ of the phase detection:
[0016]
[0017] Where a and b are adjustment coefficients;
[0018] Step 5: If t>T0, it indicates that the tracking has entered a stable state. In this state, the code phase error δ of the phase detection is obtained by using the coherent dot product power method:
[0019]
[0020] Among them, a, b, and c are adjustment coefficients;
[0021] Step 6: Send the code phase error δ to the loop filter for filtering to achieve phase detection.
[0022] The beneficial effects of the present invention are:
[0023] 1. In order to obtain the amplitude modulus square of the coherent integral value signal of the input phase detector, the existing non-correlated amplitude modulus square calculation method introduces square loss because of the use of square operation. The present invention improves the signal amplitude modulus square calculation method, and uses the multiplication and summation of adjacent amplitudes of I and Q signals to replace the traditional signal modulus square calculation, thereby avoiding the influence of the received signal noise ratio on the square loss.
[0024] 2. Aiming at the algorithm shortcomings of the existing commonly used code loop phase-locking methods, the incoherent leading minus lagging power method and the coherent dot product power method, the present invention selects different phase-locking error detection methods according to the current tracking state, and corrects the phase-locking error formula by adding an adjustable coefficient, which can further improve the phase-locking accuracy of the overall data. BRIEF DESCRIPTION OF THE DRAWINGS
[0025] Figure 1 It is a flow chart of a code loop phase discrimination method for high-precision GPS signal tracking in an embodiment of the present invention;
[0026] Figure 2 It is a schematic diagram of the structure of the code loop tracking loop used in the method of the present invention. DETAILED DESCRIPTION
[0027] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in combination with specific implementation examples and with reference to the accompanying drawings.
[0028] A code loop phase detection method for high-precision GPS signal tracking is applied to the phase detector part of the GPS receiver code loop to identify the phase difference between the local pseudo code phase and the received signal pseudo code, and to strip the pseudo code from the received signal through the code loop. This method is based on the data after the correlation integration of the GPS received signal and the local pseudo code of the code loop, and uses the multiplication and accumulation of adjacent sample values of each I and Q channel to obtain the non-coherent integration result. When detecting the phase error, the corresponding phase detection method is used according to the current tracking state, and the result is corrected by adjusting the coefficient. The phase detection result with high precision is subjected to the next step of loop filtering and phase adjustment.
[0029] like Figure 1 As shown, the specific steps of the method are as follows:
[0030] Step 1: After the GPS satellite signal is processed by the receiver RF front end, a digital intermediate frequency signal is obtained. After completing signal capture and carrier loop tracking and carrier stripping, the signal enters the code loop, and the intermediate frequency carrier is stripped from the I and Q signals of the received signal. After that, the I and Q signals are correlated with the locally copied advanced, immediate, and delayed pseudo codes, respectively, and the correlation results are integrated to obtain the input signal I of the phase detector. E , Q E ,I P , Q P ,I L , Q L , where I E is the integral value after correlation between I-channel signal and advance pseudo code, Q E is the integral value after correlation between Q-path signal and leading pseudo code, I P Q is the integral value after correlation between I-channel signal and instantaneous pseudo code, P is the integral value after correlation between Q-path signal and instantaneous pseudo code, I L is the integral value after correlation between I-channel signal and delayed pseudo code, Q L is the integral value after correlation between the Q-path signal and the delayed pseudo code. The phase difference between the leading and immediate, and the immediate and delayed pseudo codes is half a chip length.
[0031] Step 2: I E , Q E The two signals are oversampled by a large factor, and the sampling point is recorded as I E (n), Q E (n), compared with the sampling signal itself squared and then integrated, when the signal-to-noise ratio of the signal coherent integration value is lower than 7.1dB, the method of multiplying two adjacent values of each I and Q signal and then integrating them will significantly reduce the influence of the noise energy superposition caused by the square calculation. E (n)I E (n+1) and the product of Q adjacent signals Q E(n)Q E (n+1) is added to get the approximate value of the signal amplitude modulus square. According to the non-correlation of the signal modulus square approximation, the incoherent integration result y E (k) can be expressed as
[0032]
[0033] Among them, k=2,3,...
[0034] to I L , Q L The same signal processing flow as above can be used to calculate the integral value y of the non-correlated amplitude of the lag code. L (k).
[0035] Step 3, determine the current tracking state, use t to represent the current tracking time, T0 represents the time when the pull-in state switches to the stable tracking state, that is, the time when the tracking process is completed and enters the stable tracking state, and compare the relationship between t and T0.
[0036] Step 4, if t￡T0, it means that the tracking is still adjusting and has not yet entered the stable stage. In this state, the non-coherent advance-minus-lag power method is used to obtain the code phase error δ of the phase detection. Since this method uses the received data of the in-phase I branch and the orthogonal Q branch for phase detection processing at the same time, it can get rid of the dependence on the performance of the carrier loop. The formula of the non-coherent advance-minus-lag power method is as follows
[0037]
[0038] Where a and b are adjustment coefficients.
[0039] Step 5: If t>T0, it indicates that the tracking enters a stable state. In this state, the coherent dot product power method is used to obtain the code phase error δ of the phase detection. Since the received signal power in the stable tracking state is concentrated on the I branch, only noise is left on the Q branch. This method only involves the coherent integral value I of the I branch. E ,I P ,I L Compared with the I and Q data processing in the adjustment stage, the interference caused by noise is reduced and the phase accuracy of the phase detection is improved. The coherent dot product power method formula used is as follows
[0040]
[0041] Where a, b, and c are adjustment coefficients.
[0042] Step 6, after obtaining the incoherent integral value not affected by the square loss, the phase error is obtained by judging different tracking states and selecting the corresponding modified phase detection method. The phase error δ is then sent to the loop filter for filtering to achieve phase detection.
[0043] The above phase detection method is implemented by software, which has higher configuration flexibility. The schematic diagram of the code ring structure used is as follows: Figure 2 shown. Figure 2 In the process, the code ring identifier module loads the algorithm of the present invention.
[0044] The present invention is based on the data after correlation integration of GPS receiving signals and local pseudo-codes of code loops, multiplies adjacent sample values of I and Q paths and then accumulates them to obtain non-coherent integration results, uses corresponding phase detection methods according to the current tracking state during phase error detection, and corrects the results by adjusting coefficients, and performs the next step of loop filtering and phase adjustment on the obtained phase detection results with higher precision.
[0045] In summary, the present invention uses the multiplication and summation of adjacent amplitudes of I and Q signals to replace the traditional signal modulus square calculation, which reduces the influence of the received signal noise ratio on the square loss. In addition, different phase-lock error detection methods are selected according to the current tracking state, and the phase-lock error formula is corrected by adding an adjustable coefficient, which further improves the phase-lock accuracy of the overall data.
[0046] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.
Claims
1. A code loop phase detection method for high-precision GPS signal tracking, characterized in that: The following steps are involved: Step 1: After the GPS satellite signal is processed by the receiver RF front end, a digital intermediate frequency signal is obtained. After completing signal capture and carrier loop tracking and carrier stripping, the signal enters the code loop, and the intermediate frequency carrier is stripped from the I and Q signals of the received signal. After that, the I and Q signals are correlated with the locally copied advanced, immediate, and delayed pseudo codes, respectively, and the correlation results are integrated to obtain the input signal I of the phase detector. E , Q E ,I P , Q P ,I L , Q L , where I E is the integral value after correlation between I-channel signal and advance pseudo code, Q E is the integral value after correlation between Q-path signal and leading pseudo code, I P Q is the integral value after correlation between I-channel signal and instantaneous pseudo code, P is the integral value after correlation between Q-path signal and instantaneous pseudo code, I L is the integral value after correlation between I-channel signal and delayed pseudo code, Q L is the integral value after correlation between the Q-path signal and the delayed pseudo code; Step 2: I E , Q E The sampling points of the two signals are denoted as I E (n), Q E (n), multiply the product of the leading code I adjacent signals by I E (n)I E (n+1) and the product of Q adjacent signals Q E (n)Q E (n+1) is added to obtain the approximate value of the signal amplitude modulus square. According to the non-correlation of the signal modulus square approximation, the leading code non-coherent integration result y is obtained. E (k): Where k = 2, 3, ...; Will I L , Q L The sampling points of the two signals are denoted as I L (n), Q L (n), multiply the adjacent signals of the lagged code I by I L (n)I L (n+1) and the product of Q adjacent signals Q L (n)Q L (n+1) is added to obtain the approximate value of the signal amplitude modulus square. According to the non-correlation of the signal modulus square approximation, the lag code incoherent integration result y is obtained. L (k): Where k = 2, 3, ...; Step 3, determine the current tracking state, use t to represent the current tracking time, T0 represents the time when the pull-in state switches to the stable tracking state, that is, the time when the tracking process is completed and enters the stable tracking state, and compare t with T0; Step 4: If t￡T0, it means that the tracking is still adjusting and has not yet entered the stable stage. In this state, the non-coherent leading minus lagging power method is used to obtain the code phase error δ of the phase detection: Where a and b are adjustment coefficients; Step 5: If t>T0, it indicates that the tracking has entered a stable state. In this state, the code phase error δ of the phase detection is obtained by using the coherent dot product power method: Among them, a, b, and c are adjustment coefficients; Step 6: Send the code phase error δ to the loop filter for filtering to achieve phase detection.