Method for improving tracking performance of GNSS receiving chip

Abstract

The invention relates to the field of GNSS (Global Navigation Satellite System), in particular to a method for improving the tracking performance of a GNSS receiving chip, which comprises the following steps of: capturing a GNSS satellite signal sent by a GNSS satellite, and calculating the peak-to-average ratio of the captured GNSS satellite signal; judging whether the peak-to-average ratio is not less than a preset peak-to-average ratio threshold, if so, configuring a large tracking integral interception value to perform interception processing on the integral operation result of the GNSS satellite signal sent by the GNSS satellite, and if not, configuring a small tracking integral interception value to perform interception processing on the integral operation result of the GNSS satellite signal sent by the GNSS satellite; gNSS satellite signals sent by a GNSS satellite are continuously tracked, and the GNSS satellite signal intensity is calculated in real time; performing dynamic scheduling processing according to the GNSS satellite signal intensity calculated each time; the signal strength calculation accuracy and the navigation message decoding success rate are improved.

Description

Technical Field

[0001] The present invention relates to the field of GNSS, and in particular to a method for improving the tracking performance of a GNSS receiving chip. Background Art

[0002] The Satellite Navigation and Positioning System (GNSS) is a satellite-based radio navigation system that provides all-weather, uninterrupted, high-precision, real-time navigation and positioning services for all types of vehicles on land, sea, and air. It has been applied in various areas of the national economy and daily life, such as ground traffic control, aircraft and ship navigation, precision timing, and geodetic surveying. GNSS primarily consists of three segments: the space segment, the ground segment, and the user segment. From a device perspective, the various devices in the user segment are similar to "receiving devices." Devices such as mobile phones, car navigation systems, ship positioning devices, and surveying instruments receive satellite signals through built-in GNSS receiver chips. These chips then process and calculate the signals to determine their position, velocity, and time. Specifically, after the antenna of the GNSS receiving device receives the GNSS satellite signal, the GNSS satellite signal is processed by the RF component and converted into a digital intermediate frequency signal; the GNSS receiving chip first uses the digital intermediate frequency signal to complete signal capture; then the captured GNSS satellite signal is continuously tracked and the navigation message is parsed from it to obtain satellite navigation information; finally, the position, speed, and time information of the GNSS receiving device (hereinafter referred to as PVT information) are 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 signals. Currently, the following problems exist in GNSS signal tracking:

[0004] 1) GNSS receiver chips are expensive;

[0005] 2) The SNR calculation accuracy for weak signals is low: The signal strengths sent by different GNSS satellites vary, and GNSS receiver chips typically select GNSS satellites with high signal strength for PVT calculations. Therefore, during tracking, the satellite signal carrier-to-noise ratio (SNR) must be calculated in real time. The signal strength is then calculated based on the SNR value, which necessitates improving the accuracy of SNR calculations for weak signals.

[0006] 3) Low success rate of navigation message parsing: New GNSS satellite signals use encoding for navigation messages. For example, the BeiDou-3 B1C signal uses hexadecimal LDPC encoding, and the GPS L5 signal uses Viterbi encoding. These encodings cannot be effectively decoded during tracking.

[0007] 4) Due to factors such as obstruction and GNSS satellite orbit, the GNSS satellite signal strength varies randomly. Summary of the Invention

[0008] To solve the above problems, the present invention provides a method for improving the tracking performance of a GNSS receiving chip, which dynamically changes the truncation of the tracking integral operation result to improve the tracking performance of the GNSS receiving chip.

[0009] The specific plan includes the following steps:

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

[0011] S2. Determine whether the peak-to-average ratio is not less than a preset peak-to-average ratio threshold. If so, configure a large tracking integral cutoff value to perform a truncation process on the integral calculation result of the GNSS satellite signal sent by the GNSS satellite. If not, configure a small tracking integral cutoff value to perform a truncation process on the integral calculation result of the GNSS satellite signal sent by the GNSS satellite.

[0012] S3. Continuously track the GNSS satellite signals sent by the GNSS satellites and calculate the GNSS satellite signal strength in real time; dynamically adjust the truncation processing method based on the GNSS satellite signal strength calculated each time.

[0013] Beneficial effects of the present invention:

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

[0015] The present invention uses the integral operation result to calculate the satellite signal strength in real time during the tracking process, and then dynamically changes the integral result cutoff value according to the signal strength, thereby improving the weak signal tracking integral operation result, thereby improving the signal strength calculation accuracy and the navigation message decoding success rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Flow chart of the method of the present invention;

[0017] Figure 2 This is a schematic diagram of multi-level truncation of the integration result of the present invention;

[0018] Figure 3 Schematic diagram of the signal-to-noise ratio calculation process of GNSS satellite signals according to the present invention. DETAILED DESCRIPTION

[0019] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0020] Tracking GNSS satellite signals involves integrating digital intermediate frequency signals using digital signal processing methods. The stronger the GNSS satellite signal, the larger the integral result; the longer the continuous integration time, the larger the integral result. Regarding the problems mentioned in the background technology, further considering the relationship with the integral result, we can conclude that:

[0021] 1) To control the cost of GNSS receiver chips, it is necessary to reduce hardware storage resources. Therefore, the tracking integral calculation results need to be truncated to retain only the high-significant bits to avoid result overflow.

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

[0023] 3) During the tracking process, the GNSS receiver chip uses the integral calculation results to decode the navigation message. To improve the success rate of navigation message parsing, the tracking integral calculation results should be as large as possible, according to the requirements of decoding algorithms such as LDPC and Viterbi.

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

[0025] S1. After capturing the GNSS satellite signal sent by the GNSS satellite, calculate the peak-to-average ratio of the captured GNSS satellite signal. Since the carrier-to-noise ratio of the signal cannot be calculated immediately after the GNSS satellite signal is captured, the peak-to-average ratio can be used to determine the signal strength.

[0026] S2. Determine whether the peak-to-average ratio is not less than a preset peak-to-average ratio threshold. If so, it indicates that the current GNSS satellite signal is strong. In this case, a large tracking integral cutoff value is configured to perform truncation processing on the integral calculation result of the GNSS satellite signal sent by the GNSS satellite. If not, it indicates that the current GNSS satellite signal is weak. In this case, a small tracking integral cutoff value is configured to perform truncation processing on the integral calculation result of the GNSS satellite signal sent by the GNSS satellite.

[0027] The truncation process in this invention converts the integral result into a binary value and truncates it from the lowest bit to the highest bit, retaining only the high bits of the binary value that are above the tracking integral truncation value. A larger tracking integral truncation value is used to ensure that the integral result of a strong signal does not overflow, while a smaller tracking integral truncation value is used to ensure that the integral result of a weak signal is not too small and is not overwhelmed by noise.

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

[0029] Specifically, the preset peak-to-average ratio threshold is 3. To obtain the peak-to-average ratio threshold, the embodiment of the present invention sets the output signal strength on the GNSS simulator to -130dBm (this signal strength belongs to a strong signal) and -135dBm (this signal strength belongs to a weak signal), respectively. After counting the peak-to-average ratio results of successful captures, it is determined that the threshold for distinguishing between strong and weak signals is 3.

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

[0031] S3. Continuously track the GNSS satellite signals sent by GNSS satellites and calculate the GNSS satellite signal strength in real time; perform dynamic scheduling based on the calculated GNSS satellite signal strength each time.

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

[0033] The tracking channel uses Figure 3 The narrowband power ratio method (NWPR) shown here calculates the signal-to-noise ratio (SNR) of the tracked GNSS satellite signal using the following formula:

[0034]

[0035]

[0036]

[0037] Where SL represents the signal value of the GNSS satellite signal, NL represents the noise value of the GNSS satellite signal, and I i represents the tracking integral value of the I-channel GNSS satellite signal at time i=1,2,…,M, Qi This represents the integrated value of Q-channel GNSS satellite signal tracking at time i, where M represents the total time. The tracking channel calculates SL and NL and outputs them to the software, which then calculates SL / NL as the SNR.

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

[0039] After calculating the SNR value, the receiver uses the SNR-signal strength comparison table to find the corresponding signal strength value based on the calculated signal-to-noise ratio as the GNSS satellite signal strength. The signal strength value is expressed in dBm.

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

[0041] Specifically, dynamic scheduling is performed based on the calculated GNSS satellite signal strength each time, including:

[0042] S31 determines whether the GNSS satellite signal strength is not less than a preset strength threshold. If so, 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 configured cutoff value of the integral calculation result of the GNSS satellite signal sent by the GNSS satellite is a large tracking integral cutoff value. If so, it remains unchanged. If not, configure the large tracking integral cutoff value to perform a cutoff processing on the integral calculation result of the GNSS satellite signal sent by the GNSS satellite;

[0044] S33. Determine whether the truncation value currently configured for the integral calculation result of the GNSS satellite signal sent by the GNSS satellite is a small tracking integral truncation value. If so, keep it unchanged; if not, configure the small tracking integral truncation value to truncate the integral calculation result of the GNSS satellite signal sent by the GNSS satellite.

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

[0046] Specifically, if truncation is performed only once during truncation processing, based on the truncation value (either the large tracking integral truncation value or the small tracking integral truncation value), the resulting truncation result may be too large for certain signal processing applications, resulting in poor processing results. To accommodate different signal processing applications, the present invention classifies signal processing applications into N types, analyzes the optimal truncation result required for each signal processing application, and sets a series for each signal processing application, for a total of N different series. During truncation processing, multiple truncation operations are performed according to the series corresponding to the signal processing application.

[0047] For example, Figure 2 As shown in the figure, signal processing usage is divided into three types: hardware storage, bit demodulation, and carrier-to-noise ratio calculation. Hardware storage corresponds to a level of 1, bit demodulation corresponds to a level of 2, and carrier-to-noise ratio calculation corresponds to a level of 3. If bit demodulation is required, the integral result is truncated twice, each time based on the currently assigned truncation value (large tracking integral truncation value or small tracking integral truncation value).

[0048] In the present invention, unless otherwise clearly stipulated and limited, the terms "installation", "setting", "connection", "fixation", "rotation" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be the internal connection of two elements or the interaction relationship between two elements. Unless otherwise clearly defined, ordinary technicians in this field can understand the specific meanings of the above terms in the present invention according to the specific circumstances.

[0049] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for improving the tracking performance of a GNSS receiving chip, characterized in that: The following steps are involved: S1. After capturing the GNSS satellite signal sent by the GNSS satellite, calculate the peak-to-average ratio of the captured GNSS satellite signal; S2. Determine whether the peak-to-average ratio is not less than a preset peak-to-average ratio threshold. If so, configure a large tracking integral cutoff value to perform a truncation process on the integral calculation result of the GNSS satellite signal sent by the GNSS satellite. If not, configure a small tracking integral cutoff value to perform a truncation process on the integral calculation result of the GNSS satellite signal sent by the GNSS satellite. S3. Continuously track the GNSS satellite signals sent by the GNSS satellites and calculate the GNSS satellite signal strength in real time; Dynamically adjust the truncation processing method based on the GNSS satellite signal strength calculated each time; The calculation of GNSS satellite signal strength includes: Calculate the signal-to-noise ratio of the GNSS satellite signal using the following formula: ， ， ， in, Indicates the signal-to-noise ratio of the GNSS satellite signal, SL indicates the signal value of the GNSS satellite signal, NL indicates the noise value of the GNSS satellite signal, and I i represents the tracking integral value of the I-channel GNSS satellite signal at time i=1,2,…,M, Q i represents the Q-channel signal tracking integral value of the GNSS satellite signal at time i, and M represents the total time; Based on the receiver's SNR-signal strength comparison table, the corresponding signal strength value is found according to the calculated signal-to-noise ratio as the GNSS satellite signal strength; Dynamically adjust based on the calculated GNSS satellite signal strength each time, including: S31 determines whether the GNSS satellite signal strength is not less than a preset strength threshold, if so, proceed to step S32, if not, proceed to step S33; S32. Determine whether the current configured cutoff value of the integral calculation result of the GNSS satellite signal sent by the GNSS satellite is a large tracking integral cutoff value. If so, it remains unchanged. If not, configure the large tracking integral cutoff value to perform a cutoff processing on the integral calculation result of the GNSS satellite signal sent by the GNSS satellite; S33. Determine whether the truncation value currently configured for the integral calculation result of the GNSS satellite signal sent by the GNSS satellite is a small tracking integral truncation value. If so, keep it unchanged; if not, configure the small tracking integral truncation value to truncate the integral calculation result of the GNSS satellite signal sent by the GNSS satellite.

2. The method for improving the tracking performance of a GNSS receiving chip according to claim 1, characterized in that: The default peak-to-average ratio threshold is 3.

3. The method for improving the tracking performance of a GNSS receiving chip according to claim 1, characterized in that: During tracking, the GNSS satellite signal strength is calculated every 100ms.

4. The method for improving the tracking performance of a GNSS receiving chip according to claim 1, wherein: The preset intensity threshold is 39dbHz.

5. The method for improving the tracking performance of a GNSS receiving chip according to claim 1, wherein: The integration operation result of the GNSS satellite signal sent by the GNSS satellite is truncated to retain only the high-significant bits.

6. The method for improving the tracking performance of a GNSS receiving chip according to claim 1, characterized in that: After capturing the GNSS satellite signal sent by the GNSS satellite, the peak value and 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.

7. The method for improving the tracking performance of a GNSS receiving chip according to claim 1, characterized in that: Signal processing purposes are divided into N types, and a level is set for each signal processing purpose; during truncation processing, multiple truncation is performed according to the level corresponding to the signal processing purpose.

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