A method for improving GNSS receiving chip tracking performance

Abstract

The present application relates to the field of GNSS, and particularly relates to a method for improving tracking performance of a GNSS receiving chip, comprising capturing GNSS satellite signals sent by GNSS satellites, calculating a peak-to-average ratio of the captured GNSS satellite signals; judging whether the peak-to-average ratio is not less than a preset peak-to-average ratio threshold, if yes, configuring a large tracking integral truncation value to perform truncation processing on an integral operation result of the GNSS satellite signals sent by the GNSS satellites, if not, configuring a small tracking integral truncation value to perform truncation processing on the integral operation result of the GNSS satellite signals sent by the GNSS satellites; continuously tracking the GNSS satellite signals sent by the GNSS satellites, and calculating GNSS satellite signal strength in real time; performing dynamic scheduling processing according to the GNSS satellite signal strength calculated each time; the present application improves signal strength calculation accuracy and navigation message decoding success rate.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of GNSS, in particular to a method for improving the tracking performance of a GNSS receiving chip. BACKGROUND

[0002] The satellite navigation positioning system (GNSS) is a satellite-based radio navigation system that can provide all-weather, uninterrupted, high-precision, real-time navigation and positioning services for various types of land, sea and air carriers, and has been applied in various fields of national economy and daily life, such as ground transportation supervision, aircraft and ship navigation, precise time reception, and geodetic surveying. GNSS is mainly composed of space segment, ground segment and user segment. From the perspective of equipment, the various devices of the user segment are similar to "receiving devices". For example, mobile phones, vehicle navigation systems, ship positioning devices, and measuring instruments, etc. They receive satellite signals through the built-in GNSS receiving chip, then process and calculate the signals to obtain their own position, speed and time information. Specifically, after the antenna of the GNSS receiving device receives the GNSS satellite signal, the GNSS satellite signal is processed by the radio frequency component to change into a digital intermediate frequency signal; the GNSS receiving chip uses the digital intermediate frequency signal to first complete the signal acquisition; then continuously tracks the acquired GNSS satellite signal and parses the navigation message from it to obtain satellite navigation information; finally, the position, speed and time information (hereinafter referred to as PVT information) of the GNSS receiving device is calculated.

[0003] To continuously and accurately calculate the PVT information of the GNSS receiving device, the GNSS receiving chip needs to continuously track the GNSS satellite signal. However, there are the following problems in the current GNSS signal tracking:

[0004] 1) High cost of GNSS receiving chip;

[0005] 2) Low accuracy of SNR value calculation for weak signals: the signals transmitted by different GNSS satellites have different strengths, and the GNSS receiving chip usually selects GNSS satellites with high signal strength for PVT calculation; therefore, it is necessary to calculate the satellite signal carrier-to-noise ratio (hereinafter referred to as SNR) in real time during the tracking process, and then obtain the signal strength according to the SNR value, so as to improve the accuracy of SNR value calculation for weak signals;

[0006] 3) Low success rate of navigation message parsing: the signals of new system GNSS satellites are encoded, for example, the B1C signal of the third generation of Beidou is encoded by hexadecimal LDPC, and the L5 signal of GPS is encoded by Viterbi; the decoding process cannot be well performed during tracking;

[0007] 4) Due to the reasons of shielding, GNSS satellite orbit operation, etc., the GNSS satellite signal strength is randomly changed. SUMMARY

[0008] To solve the above problems, the application provides a method for improving the tracking performance of a GNSS receiving chip, dynamically changing the tracking integral operation result truncation, and improving the tracking performance of the GNSS receiving chip.

[0009] The specific scheme comprises the following steps:

[0010] S1. After capturing the GNSS satellite signal sent by the GNSS satellite, the peak-to-average ratio of the captured GNSS satellite signal is calculated;

[0011] S2. It is judged whether the peak-to-average ratio is not less than a preset peak-to-average ratio threshold value, if yes, a large tracking integral truncation value is configured to perform truncation processing on the integral operation result of the GNSS satellite signal sent by the GNSS satellite, and if not, a small tracking integral truncation value is configured to perform truncation processing on the integral operation result of the GNSS satellite signal sent by the GNSS satellite;

[0012] S3. The GNSS satellite signal sent by the GNSS satellite is continuously tracked, and the GNSS satellite signal strength is calculated in real time; the truncation processing mode is dynamically adjusted according to the GNSS satellite signal strength calculated each time.

[0013] The application has the following beneficial effects:

[0014] The application performs truncation processing on the tracking integral operation result, only retains the high effective bits, thereby reducing the hardware storage resources and controlling the cost of the GNSS receiving chip.

[0015] In the tracking process, the application uses the integral operation result to calculate the satellite signal strength in real time, and dynamically changes the integral result intercept value according to the signal strength, improves the weak signal tracking integral operation result, and thereby improves the signal strength calculation accuracy and the navigation text decoding success rate. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 The application is a method flowchart;

[0017] Figure 2 The application is an integral result multi-level truncation schematic diagram;

[0018] Figure 3 The application is a signal-to-noise ratio calculation flowchart of the GNSS satellite signal. DETAILED DESCRIPTION

[0019] With reference to the drawings and embodiments of the present application, the technical solutions in the embodiments of the present application will be described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of the present application.

[0020] Tracking GNSS satellite signals is to perform integral operation on digital intermediate frequency signals by using digital signal processing methods. The stronger the GNSS satellite signals are, the larger the integral operation result is. The longer the continuous integral time of integral operation is, the larger the integral operation result is. In view of the problems mentioned in the background art, further consideration is given to the relationship with the integral operation result, and then:

[0021] 1) In order to control the cost of GNSS receiving chips, the hardware storage resources need to be reduced, so the tracking integral operation result needs to be truncated, only the high significant bits are reserved, so as to avoid result overflow.

[0022] 2) The calculation of the SNR value of the GNSS satellite signal is related to the integral operation result. In order to improve the SNR calculation accuracy of the weak signal, the larger the tracking integral operation result is, the better.

[0023] 3) In the tracking process of the GNSS receiving chip, the integral operation result needs to be used for decoding processing to parse the navigation message. According to the requirements of LDPC, Viterbi and other decoding algorithms, in order to improve the success rate of navigation message parsing, the larger the tracking integral operation result is, the better.

[0024] Based on the above analysis, the present application provides a method for improving the tracking performance of GNSS receiving chips, so that the GNSS chip hardware tracking module can dynamically configure the truncation of the integral operation result. As shown in Figure 1 the following steps are included:

[0025] S1. After capturing the GNSS satellite signal sent by the GNSS satellite, the peak-to-average ratio of the captured GNSS satellite signal is calculated. Since the carrier-to-noise ratio of the signal cannot be calculated in time when the GNSS satellite signal is captured, the peak-to-average ratio can reflect the signal strength, so the signal strength can be judged by the peak-to-average ratio.

[0026] S2. It is judged whether the peak-to-average ratio is not less than a preset peak-to-average ratio threshold. If yes, it indicates that the current GNSS satellite signal is strong, and a large tracking integral truncation value is configured to perform truncation processing on the integral operation result of the GNSS satellite signal sent by the GNSS satellite. If not, it indicates that the current GNSS satellite signal is weak, and a small tracking integral truncation value is configured to perform truncation processing on the integral operation result of the GNSS satellite signal sent by the GNSS satellite.

[0027] The present application mainly converts the integral operation result into a binary value, performs the truncation processing from low bit to high bit, and only keeps the high bit above the tracking integral truncation value in the binary value. The larger tracking integral truncation value is to ensure that the integral operation result of the strong signal does not overflow, and the smaller tracking integral truncation value is to ensure that the integral operation result of the weak signal is not too small and is not submerged by noise.

[0028] Specifically, for the GNSS satellite signal with a peak-to-average ratio not less than a preset peak-to-average ratio threshold, in order to ensure that the integral result does not overflow, the large tracking integral truncation value is set to be greater than 3; for the GNSS satellite signal with a peak-to-average ratio less than a preset peak-to-average ratio threshold, in order to ensure that the signal part in the integral result is greater than the noise part, the small tracking integral truncation value is set to be less than or equal to 1.

[0029] Specifically, the preset peak-to-average ratio threshold is 3. In order to obtain the peak-to-average ratio threshold, the output signal strength is set to be-130dBm (the signal strength belongs to a strong signal) and-135dBm (the signal strength belongs to a weak signal) on a GNSS simulator respectively, and the peak-to-average ratio threshold for distinguishing the strong and weak signals is obtained as 3 after the peak-to-average ratio results of successful capture are counted.

[0030] Specifically, after the GNSS satellite signal sent by the GNSS satellite is captured, the peak value and the average noise value of the captured GNSS satellite signal are recorded, and the peak-to-average ratio is obtained by dividing the peak value by the average noise value.

[0031] S3. Continuously tracking the GNSS satellite signal sent by the GNSS satellite, and calculating the GNSS satellite signal strength in real time; and performing dynamic scheduling processing according to the GNSS satellite signal strength calculated each time.

[0032] Specifically, in the continuous tracking process, the calculation of the GNSS satellite signal strength includes:

[0033] The tracking channel adopts a narrow bandwidth power ratio method (NWPR) shown in Figure 3 to calculate the signal noise ratio (SNR) of the tracked GNSS satellite signal, and the formula is as follows:

[0034]

[0035]

[0036]

[0037] wherein, SL represents the signal value of the GNSS satellite signal, NL represents the noise value of the GNSS satellite signal, I i represents the I-channel signal tracking integral value of the GNSS satellite signal at time i=1, 2, …, M, and Qi represents the Q-path signal tracking integral value of the GNSS satellite signal at time i, and M represents the total number of times.

[0038] The size of the SNR directly reflects the signal strength of the GNSS satellite signal, and the greater the SNR value of the GNSS satellite signal, the stronger the signal strength.

[0039] After the SNR value is calculated, based on the SNR-signal strength table of the receiver, the corresponding signal strength value is searched according to the calculated signal noise ratio as the GNSS satellite signal strength, and the signal strength value is in dBm.

[0040] Specifically, the embodiment of the present application calculates the GNSS satellite signal strength once every 100 ms in the tracking process, that is, the SNR value of the GNSS satellite signal is calculated once every 100 ms, that is, M = 100 ms; wherein the I-path signal tracking integral value and the Q-path signal tracking integral value of the GNSS satellite signal are calculated once every 1 ms.

[0041] Specifically, the GNSS satellite signal strength calculated each time is dynamically scheduled, including:

[0042] S31. Determine whether the GNSS satellite signal strength is not less than a preset strength threshold, if yes, it indicates that the current GNSS satellite signal is strong, then execute step S32, if not, it indicates that the current GNSS satellite signal is weak, then execute step S33;

[0043] S32. Determine whether the current GNSS satellite signal sent by the GNSS satellite is configured with a large tracking integral bit value, if yes, it remains unchanged, if not, configure the large tracking integral bit value to the integral operation result of the GNSS satellite signal sent by the GNSS satellite;

[0044] S33. Determine whether the current GNSS satellite signal sent by the GNSS satellite is configured with a small tracking integral bit value, if yes, it remains unchanged, if not, configure the small tracking integral bit value to the integral operation result of the GNSS satellite signal sent by the GNSS satellite.

[0045] Specifically, the preset strength threshold is 39dbHz.

[0046] Specifically, if only one truncation is performed according to the truncation value (the large tracking integration truncation value or the small tracking integration truncation value) during the truncation processing, the obtained truncation result can be too large for some signal processing purposes, so that the processing result is not good. In order to adapt to different signal processing purposes, the present application divides the signal processing purposes into N kinds, analyzes the best truncation result required by each kind of signal processing purpose, sets a rank for each kind of signal processing purpose, and there are N different ranks in total; during the truncation processing, multiple truncations are performed according to the rank corresponding to the signal processing purpose.

[0047] For example, as shown in Figure 2 the signal processing purposes are divided into three kinds of hardware storage result, bit demodulation use and carrier-to-noise ratio calculation use, wherein the rank corresponding to the hardware storage result is 1, the rank corresponding to the bit demodulation use is 2, and the rank corresponding to the carrier-to-noise ratio calculation use is 3. If the bit demodulation use is required, the integration operation result is truncated twice, and each truncation is performed according to the currently allocated truncation value (the large tracking integration truncation value or the small tracking integration truncation value).

[0048] In the present application, unless otherwise specifically specified and limited, the terms "mounting", "setting", "connecting", "fixing", "rotating" and the like should be understood in a broad sense, for example, can be fixedly connected, can be detachably connected, or can be integrated; can be mechanically connected, or can be electrically connected; can be directly connected, or can be indirectly connected through an intermediate medium; can be the internal communication of two elements or the interaction relationship between two elements, unless otherwise specifically limited, the above-mentioned terms in the present application can be understood according to the specific meaning of the above-mentioned terms in the present application by those skilled in the art.

[0049] Although the embodiments of the present application have been shown and described, those skilled in the art can understand that various changes, modifications, replacements and variations can be made to the embodiments without departing from the principles and spirits of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A method for improving GNSS receiving chip tracking performance, characterized in that, The method comprises the following steps: S1. After capturing a GNSS satellite signal sent by a GNSS satellite, calculating a peak-to-average ratio of the captured GNSS satellite signal; After capturing a GNSS satellite signal sent by a GNSS satellite, recording a peak value and an average noise value of the captured GNSS satellite signal, and obtaining a peak-to-average ratio by dividing the peak value by the average noise value; S2. Judging whether the peak-to-average ratio is not less than a preset peak-to-average ratio threshold, if yes, configuring a large tracking integral clipping value to clip the integral operation result of the GNSS satellite signal sent by the GNSS satellite, and if not, configuring a small tracking integral clipping value to clip the integral operation result of the GNSS satellite signal sent by the GNSS satellite; S3. Continuously tracking the GNSS satellite signal sent by the GNSS satellite and calculating the GNSS satellite signal strength in real time; According to the GNSS satellite signal strength calculated each time, dynamically adjusting the clipping processing mode; The calculation of the GNSS satellite signal strength comprises: Calculating the signal-to-noise ratio of the GNSS satellite signal, and the formula is as follows: ， ， ， wherein represents a signal-to-noise ratio of a GNSS satellite signal, SL represents a signal value of the GNSS satellite signal, NL represents a noise value of the GNSS satellite signal, I i represents an I-path signal tracking integration value of a GNSS satellite signal at time i = 1, 2, …, M, Q i represents a Q-path signal tracking integration value of a GNSS satellite signal at time i, M represents a total number of times; According to the calculated signal-to-noise ratio, looking up the corresponding signal strength value as the GNSS satellite signal strength based on the SNR-signal strength reference table of the receiver; According to the GNSS satellite signal strength calculated each time, dynamically adjusting, comprising: S31. Judging whether the GNSS satellite signal strength is not less than a preset strength threshold, if yes, executing step S32, and if not, executing step S33; S32. Judging whether the clipping value currently configured for the integral operation result of the GNSS satellite signal sent by the GNSS satellite is the large tracking integral clipping value, if yes, keeping unchanged, and if not, configuring the large tracking integral clipping value to clip the integral operation result of the GNSS satellite signal sent by the GNSS satellite; S33. Judging whether the clipping value currently configured for the integral operation result of the GNSS satellite signal sent by the GNSS satellite is the small tracking integral clipping value, if yes, keeping unchanged, and if not, configuring the small tracking integral clipping value to clip the integral operation result of the GNSS satellite signal sent by the GNSS satellite; Dividing the signal processing purposes into N kinds, setting a rank for each kind of signal processing purpose; and clipping multiple times according to the rank corresponding to the signal processing purpose during the clipping processing.

2. The method of claim 1, wherein, The preset peak-to-average ratio threshold is 3.

3. The method of claim 1, wherein, During the tracking process, the GNSS satellite signal strength is calculated once every 100 ms.

4. The method of claim 1, wherein, The preset strength threshold is 39 dbHz.

5. The method of claim 1, wherein, The integral operation result of the GNSS satellite signal sent by the GNSS satellite is clipped, and only the high significant bits are kept.

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