Adaptive crystal oscillator specification speed measurement method, GNSS receiver and storage medium

Abstract

An adaptive crystal oscillator specification velocity measurement method, a GNSS receiver, and a storage medium are disclosed. The method includes: acquiring quality characteristic data of signals from N satellites; determining clock drift estimation characteristic data based on the current satellite signals, assuming the current signal quality meets set quality requirements based on the quality characteristic data; determining an additional clock drift constraint equation based on the clock drift estimation characteristic data, including a first velocity and clock drift solution equation set of N+1 equations, and solving for the receiver velocity and clock drift values; wherein the weights of the clock drift constraint equations in the first velocity and clock drift solution equation set are negatively correlated with the estimated jitter variance of the clock drift. This disclosed scheme, with its adaptive crystal oscillator specification, employs a first velocity and clock drift solution equation set with an added clock drift constraint equation for velocity calculation, enhancing the compatibility of the GNSS receiver / chip calculation method with various crystal oscillator specifications and performance variations caused by usage conditions, and improving the accuracy of receiver velocity calculation.

Description

Technical Field

[0001] This article relates to, but is not limited to, the field of satellite positioning technology, particularly a velocity measurement method with adaptive crystal oscillator specifications, a GNSS receiver, and a storage medium. Background Technology

[0002] The Global Navigation Satellite System (GNSS) provides global users with three-dimensional, all-weather, high-quality positioning, navigation, and timing (PNT) services, making it a crucial positioning method for industries such as transportation, communication, and surveying. In particular, the development of autonomous systems such as autonomous driving and low-altitude aircraft has placed higher demands on the accuracy and reliability of GNSS-based rapid positioning. GNSS modules typically use temperature-compensated crystal oscillators (TCXOs) as the master clock source. Their characteristics directly affect baseband signal processing performance (acquisition, tracking, and anti-interference performance, etc.) as well as positioning and velocity measurement performance, making them a core component of GNSS modules. Crystal oscillators are typically available in multiple specifications based on frequency deviation, clock drift characteristics, vibration resistance, and temperature characteristics. GNSS receivers are used in various fields (consumer, industrial, automotive, etc.), and using different specifications of crystal oscillators can achieve good product goals (cost-effectiveness, quality-price ratio, etc.). GNSS chips are compatible with multiple crystal oscillator specifications, further expanding their applicability. Summary of the Invention

[0003] This application provides an adaptive crystal oscillator specification-based velocity measurement method, a GNSS receiver, and a storage medium. Based on clock drift estimation characteristic data indicating the current crystal oscillator performance specification, it adaptively employs a first velocity with added clock drift constraint equations and a set of clock drift solution equations to calculate the velocity. This enhances the compatibility of the GNSS receiver / chip's calculation method with various crystal oscillator specifications and performance variations caused by usage conditions, thereby improving the accuracy of the receiver's velocity calculation.

[0004] This application provides a velocity measurement method with adaptive crystal oscillator specifications, applied to a GNSS receiver, including: Acquire quality characteristic data of N satellite signals, wherein the quality characteristic data includes at least one of the following: signal strength, carrier-to-noise ratio, and satellite geometric distribution quality assessment index; If the current signal quality meets the set quality requirements based on the quality characteristic data, clock drift estimation characteristic data is determined based on the current satellite signal. The clock drift estimation characteristic data includes: clock drift estimation jitter variance. Based on the clock drift estimation characteristic data, the first velocity and clock drift solution equation set including N+1 equations are determined, and the receiver velocity and clock drift value are calculated. The N+1 equation set includes: solution equations corresponding to N satellites and a clock drift constraint equation; the weight of the clock drift constraint equation in the first velocity and clock drift solution equation set is negatively correlated with the estimated jitter variance of the clock drift, and N is an integer greater than 1.

[0005] This application also provides a GNSS receiver for a global satellite navigation system, including a processor configured to implement a velocity measurement method with adaptive crystal oscillator specifications as described in any embodiment of this application.

[0006] This application also provides a computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements a speed measurement method for adaptive crystal oscillator specifications as described in any embodiment of this application.

[0007] Other features and advantages of this application will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the application. Other advantages of this application can be realized and obtained by means of the embodiments described in the description and the accompanying drawings. Attached Figure Description

[0008] The accompanying drawings are used to provide an understanding of the technical solutions of this application and constitute a part of the specification. They are used together with the embodiments of this application to explain the technical solutions of this application and do not constitute a limitation on the technical solutions of this application.

[0009] Figure 1 A flowchart of a speed measurement method for adaptive crystal oscillator specifications provided in this embodiment of the disclosure; Figure 2 A flowchart of a speed measurement method for another adaptive crystal oscillator specification provided in an embodiment of this disclosure; Figure 3 A flowchart of another adaptive crystal oscillator specification speed measurement method provided in an embodiment of this disclosure. Detailed Implementation

[0010] This application describes several embodiments, but these descriptions are exemplary and not limiting, and it will be apparent to those skilled in the art that many more embodiments and implementations are possible within the scope of the embodiments described herein. Although many possible combinations of features are shown in the drawings and discussed in the detailed description, many other combinations of the disclosed features are also possible. Unless specifically limited, any feature or element of any embodiment may be used in combination with, or may replace, any feature or element of any other embodiment.

[0011] This application includes and contemplates combinations of features and elements known to those skilled in the art. The embodiments, features, and elements disclosed in this application can also be combined with any conventional features or elements to form unique inventive solutions. Any feature or element of any embodiment can also be combined with features or elements from other inventive solutions to form another unique inventive solution. Therefore, it should be understood that any feature shown and / or discussed in this application can be implemented individually or in any suitable combination. Therefore, the embodiments are not limited except by the limitations imposed by the appended claims and their equivalents. Furthermore, various modifications and changes can be made within the scope of the appended claims.

[0012] Furthermore, in describing representative embodiments, the specification may have presented methods and / or processes as a specific sequence of steps. However, the method or process should not be limited to the specific order of steps described herein, to the extent that it does not depend on such a specific order. As will be understood by those skilled in the art, other sequences of steps are also possible. Therefore, the specific order of steps set forth in the specification should not be construed as a limitation of the claims. Moreover, the claims concerning the method and / or process should not be limited to the steps performed in the written order, and those skilled in the art will readily understand that these orders can be varied and still remain within the spirit and scope of the embodiments of this application.

[0013] Among some feasible velocity measurement algorithms, GNSS Doppler measurements caused by relative motion can be used to solve for the receiver's velocity and the clock drift of the receiver's crystal oscillator. Velocity and clock drift are calculated epoch-by-epoch using either the least squares algorithm or the Kalman algorithm by tracking the Doppler observations from the satellite.

[0014] In complex signal or high-mobility motion modes, the Doppler accuracy of the receiver may decrease, which in turn leads to a decrease in velocity measurement accuracy. Traditional algorithms generally use receiver autonomous uprightness detection (RAIM) to detect gross errors and perform star-kicking operations, ultimately obtaining an internal coincidence result, but with poor accuracy and reliability.

[0015] Unlike high-specification crystal oscillators, ordinary crystal oscillators generally have lower performance and stability. At room temperature, clock drift can reach 5-15Hz at the typical GNSS frequency of 1575.42MHz. Under conditions of significant temperature variation, the clock drift becomes even greater and more irregular. The inherent instability of crystal oscillators makes it difficult to set key parameters based on empirical values ​​during the algorithm design phase. Furthermore, GNSS modules typically use multiple crystal oscillators of various specifications for different industry applications, which complicates the maintenance of GNSS algorithm software and hardware / software compatibility. This application's solution monitors clock drift estimation characteristic data indicating crystal oscillator performance and adaptively adjusts speed and clock drift calculation algorithm parameters, effectively improving speed calculation performance and accuracy.

[0016] This disclosure provides a speed measurement method applied to a GNSS receiver, such as... Figure 1 As shown, it includes: Step 110: Obtain quality characteristic data of N satellite signals, wherein the quality characteristic data includes at least one of the following: signal strength, carrier-to-noise ratio, and satellite geometric distribution quality assessment index; Step 120: If the current signal quality meets the set quality requirements based on the quality characteristic data, determine the clock drift estimation characteristic data based on the current satellite signal. The clock drift estimation characteristic data includes: clock drift estimation jitter variance. Step 130: Based on the clock drift estimation feature data, determine the first velocity and clock drift solution equation set including N+1 equations, and solve them to obtain the receiver velocity and clock drift value. The N+1 equation set includes: solution equations corresponding to N satellites and a clock drift constraint equation; the weight of the clock drift constraint equation in the first velocity and clock drift solution equation set is negatively correlated with the estimated jitter variance of the clock drift, and N is an integer greater than 1.

[0017] It should be noted that the first velocity and clock drift calculation equation set and the second velocity and clock drift calculation equation set in this embodiment are different equation sets used for numerical calculation of velocity and clock drift, and can also be referred to as different algorithms for velocity and clock drift calculation. The N satellites are all or some of the satellites selected from all satellites observable by the receiver, and N is determined according to the calculation algorithm; for example, N = 4, 5, 6, or other values. In some exemplary embodiments, the N satellites are the N satellites among all observable satellites whose carrier-to-noise ratio (CNR) CN0 is greater than a first CNR threshold. For example, if the first CNR threshold is 5 dB·Hz, then the N satellites are the N satellites among all observable satellites whose CNR CN0 is greater than 5 dB·Hz, meaning that satellites whose signal quality meets the threshold requirement are selected from all observable satellites.

[0018] In some feasible solutions, the GNSS satellite Doppler velocity equations are as follows: (1); in, The crystal oscillator drift to be solved; The satellite clock drift of satellite n can be obtained by fitting the satellite clock parameters in the ephemeris. Let n be the pseudorange change rate of satellite n, which is the Doppler observation. For the geometric change rate of the receiver and the satellite; The residuals of the Doppler observations.

[0019] =( ) (2); The orbital velocity of satellite n can be calculated using ephemeris parameters; The receiver speed to be calculated; Let n be the unit observation vector of satellite n at the receiver.

[0020] Substituting equation (2) into equation (1) and rearranging, we get: (3); Each epoch has observations of N stars, and each star can generate an equation. The N equations can be combined into the following matrix equation, denoted as the second velocity and clock drift solution equation set: (4); G is N 4. Design matrix; Here is the Doppler residual vector; according to the least squares solution principle, we can obtain: (5); Where W is the weighting matrix for each satellite, and the weighting can be determined based on information such as the elevation angle and carrier-to-noise ratio CN0 of each satellite; the weighting coefficient matrix H is... (6); The velocity variance for that epoch can be calculated using the weighting matrix. and the variance of the clock : (7); (8); As can be seen, the second velocity and clock drift solution equation set, which includes N equations, can be established based on the observations of N satellites, and the clock drift value and clock drift variance can be calculated. Among them, the GNSS Doppler observation equation is established according to formula (1), and formula (1) and formula (2) are combined to obtain formula (3); N formulas (3) can be established for each epoch tracking N satellites, thus obtaining the equation set formula (4); formula (5) can be used to calculate the receiver velocity and clock drift value of the current epoch based on the least squares solution principle; based on the weight coefficient matrix H of formula (6) and formulas (7) and (8), the velocity and clock drift variance of the epoch can be calculated, which is used to evaluate the accuracy of the velocity and clock drift calculation.

[0021] To improve the velocity measurement performance of GNSS receivers, the velocity measurement algorithm based on adaptive crystal oscillator specifications provided in this disclosure adds a clock drift constraint equation to assist the GNSS velocity measurement algorithm, in addition to the N solution equations established based on N satellites. This constructs a first velocity and clock drift solution equation set comprising N+1 equations. Based on the different clock drift estimation characteristic data indicating the current specifications of the crystal oscillator, the weights of the clock drift constraint equations are determined accordingly. In other words, the depth of use of clock drift assistance is determined by the clock drift estimation characteristic data, thereby improving velocity measurement performance in highly maneuverable and complex environments.

[0022] As can be seen, the adaptive crystal oscillator specification speed measurement method provided in this embodiment of the present disclosure, under the condition that the signal quality meets the set quality requirements, that is, under the condition that the signal meets the reliable clock drift assessment requirements, uses a first velocity and a set of clock drift solution equations with added clock drift constraint equations to calculate the velocity.

[0023] The quality characteristic data includes one or more of the following: signal strength, carrier-to-noise ratio (CNR), and satellite geometric distribution quality assessment indicators. Correspondingly, the set quality requirements also include one or more. For example, if the quality characteristic data includes signal strength, then the quality requirements include a signal strength threshold; if the current signal strength is greater than the signal strength threshold, the quality requirements are met. If the quality characteristic data includes carrier-to-noise ratio (CNR), then the quality requirements include a second CNR threshold; if the current CNR is greater than the second CNR threshold, the quality requirements are met. If the quality characteristic data includes satellite geometric distribution quality assessment indicators, then the quality requirements include an indicator threshold; if the current ratio of the satellite geometric distribution quality assessment indicator is greater than the indicator threshold, the quality requirements are met. As another example, if the quality characteristic data includes both CNR and satellite geometric distribution quality assessment indicators, then the quality requirements include a second CNR threshold and an indicator threshold; if the current CNR is greater than the second CNR threshold and the ratio of the satellite geometric distribution quality assessment indicator is greater than the indicator threshold, the quality requirements are met. More examples are not listed here.

[0024] In some exemplary embodiments, the carrier-to-noise ratio is the average carrier-to-noise ratio of the signals from N satellites. (9); in, The average carrier-to-noise ratio, ,…, The carrier-to-noise ratio is 1 to N satellites.

[0025] The satellite geometric distribution quality assessment index is used to indicate the satellite status that the receiver can currently effectively observe, reflecting the reliability of the satellite distribution status for accurate clock drift estimation. In some exemplary embodiments, the satellite geometric distribution quality assessment index is calculated according to the following method: (10); in, The satellite geometric distribution quality assessment index is defined as follows: ValidADRCnt is the number of phase-locked and carrier-enabled satellites among the N satellites; ValidAzelCnt is the number of azimuth sectors where the number of satellites exceeds a first threshold; AzelCnt is the total number of azimuth sectors; ValidElCnt is the number of elevation sectors where the number of satellites exceeds a second threshold; and ElCnt is the total number of elevation sectors.

[0026] In some exemplary embodiments, the first quantity thresholds corresponding to different azimuth sectors may be the same or different; the second quantity thresholds corresponding to different elevation sectors may be the same or different.

[0027] For example, the total number of azimuth sectors, AzelCnt, is 8, and the first threshold is 2. This means dividing the azimuth into 8 groups with a 45° bandwidth, calculating the number of satellites within each bandwidth, and considering 2 or more satellites within a bandwidth as normal, then calculating ValidAzelCnt. The total number of elevation sectors, ElCnt, is 4, and the second threshold is 3 or 4. This means dividing the elevation into 4 groups with a 20° bandwidth starting at 10°, calculating the number of satellites within each bandwidth, and considering 4 or more satellites within a bandwidth as normal (3 satellites in the zenith direction), then calculating ValidElCnt. The corresponding formula is: (10-1); In some exemplary embodiments, the estimated clock drift values ​​are obtained by statistical analysis of clock drift calculation values ​​across multiple epochs; The clock drift calculation values ​​are obtained by solving the second velocity and clock drift calculation equations, which include the calculation equations corresponding to the N satellites. Each epoch corresponds to an observation time point, and t epochs correspond to t time points. It should be noted that in this embodiment, the multiple epochs are multiple epochs close to the current time. In some exemplary embodiments, the multiple epochs are consecutive epochs close to the current time.

[0028] It can be known that the clock drift calculated in each epoch is obtained based on the second velocity and the clock drift equations. This is called the clock drift solution value. Clock drift estimation is one of the characteristic data indicating crystal oscillator performance. Based on the calculated values ​​of clock drift over multiple consecutive epochs Statistical results. This could be the calculated values ​​of clock drift across multiple epochs. The average value can be the median or the mode.

[0029] In some exemplary embodiments, the clock drift estimation feature data further includes: a clock drift estimation value; the clock drift estimation value is calculated according to the following method: (11); in, Let be the estimated clock drift values ​​for t epochs, where k represents k consecutive time windows, each containing t epochs; This represents the clock drift calculation value at the i-th epoch within the k-th time window.

[0030] In some exemplary embodiments, the estimated jitter variance of the clock drift is obtained by statistical analysis of the calculated values ​​of the clock drift variance in multiple epochs; wherein, the calculated values ​​of the clock drift variance are obtained by calculation based on the weight coefficient matrix corresponding to the second velocity and the clock drift calculation equation set.

[0031] It can be known that the clock drift variance calculated in each epoch based on the weight coefficient matrix H corresponding to the second velocity and the clock drift solution equations is... Also known as the numerical solution of clock drift variance. One of the characteristic data indicating crystal oscillator performance is the clock drift estimate jitter variance, which is calculated from the clock drift variance over multiple epochs. Statistical results. This could be the variance of clock drift across multiple epochs. The average value can be the median or the mode.

[0032] In some exemplary embodiments, the clock drift estimation feature data further includes: satellite geometric distribution quality assessment indicators; The first velocity and clock drift calculation equations are as follows: (12); The equations for solving the second velocity and clock drift are as follows: (5); in, , , , ; (13); (14); G is the design matrix corresponding to the N equations for N satellites, and G1 is the design matrix corresponding to the N+1 equations with added clock drift constraint equations. Let W be the Doppler residual vector corresponding to N satellites, W be the weighting matrix corresponding to N satellites, and W1 be the weighting matrix with added weights for the clock drift constraint equation. The weights of the clock drift constraint equation are... Estimate residuals for clock drift; Estimated values ​​for clock drift. Estimate the jitter variance for clock drift. As an indicator for assessing the quality of satellite geometric distribution; The velocity is along the x-axis. The velocity is along the y-axis. The velocity along the z-axis. For clock drift, i.e., the velocity and clock drift to be solved; in formula (14), the clock drift solution value is obtained by solving the equation set based on the second velocity and clock drift. Among them, G1 is an additional row based on G, and G1 is also called the augmented design matrix.

[0033] As can be seen, based on the second velocity and the N equations included in the clock drift solution equation set, the estimated clock drift value is... As known observations are added to the solution equations, i.e., formula (4) adds a one-dimensional clock drift constraint equation to the N satellites, resulting in N+1 equations, thus obtaining the first velocity and clock drift solution equation set. This is formula (12) obtained based on this least squares solution principle. Wherein, G is The design matrix, also denoted as G1 is The matrix is ​​also denoted as According to formula (12), the clock drift value matching the current crystal oscillator specification of the epoch to be solved can be obtained. and carrier speed .

[0034] In some exemplary embodiments, the method further includes: determining the crystal oscillator performance level, i.e., the crystal oscillator performance specification, in the receiver based on the jitter variance estimated by clock drift. Multiple levels are determined according to a threshold for classifying multiple specifications. (Clock drift estimation jitter variance) In some exemplary embodiments, the method further includes: determining the crystal oscillator performance level, i.e., crystal oscillator specification, in the receiver based on the estimated jitter variance of the clock drift. Multiple levels are determined according to multiple threshold values. The smaller the estimated jitter variance of the clock drift, the higher the level, meaning higher crystal oscillator performance. For example, taking a frequency of 1575.42MHz as an example, a crystal oscillator with an estimated jitter variance of less than 1Hz is considered a high-performance crystal oscillator, one with an estimated jitter variance between 1Hz and 10Hz is considered a medium-performance crystal oscillator, and one with an estimated jitter variance exceeding 10Hz is considered a low-performance crystal oscillator. It should be noted that the crystal oscillator performance / specification in the embodiments of this disclosure is related to the specifications of the crystal oscillator itself and also to the operating conditions. As the receiver is used, the scheme provided in the embodiments of this disclosure is used to dynamically detect and determine the latest performance / specification.

[0035] In some exemplary embodiments, the weights of the first velocity and the clock drift constraint equations in the clock drift solution equation set are adaptively adjusted according to the different crystal oscillator performance. For crystal oscillators with higher performance, the clock drift auxiliary weights are relaxed, and the real-time update status is more reliable. For crystal oscillators with lower performance, the weights of the clock drift auxiliary weights need to be increased in complex environments, thereby constraining the unstable changes in clock drift.

[0036] In some exemplary embodiments, the method further includes generating an alarm message when the estimated clock drift value is greater than a set upper limit for clock drift and / or the estimated clock drift jitter variance is greater than a set upper limit for jitter variance. This means that when the clock drift value and / or jitter exceed the baseband's tolerance for signal acquisition and tracking, GNSS observations cannot track stably, and the clock drift is no longer usable, thus triggering an alarm.

[0037] Some exemplary embodiments also include: Step 140: If the current signal quality meets the set quality requirements based on the quality characteristic data, the clock drift estimation characteristic data is saved to the receiver's local memory. Step 150: If the current signal quality does not meet the set quality requirements based on the quality characteristic data, determine the first velocity and clock drift solution equation set including N+1 equations based on the clock drift estimation characteristic data in the memory, and solve the receiver velocity and clock drift value.

[0038] When the current signal quality does not meet the set quality requirements, it means that it is impossible to accurately determine the first velocity and the newly added observations in the clock drift solution equations in real time. Weights of the clock drift equation Therefore, the clock drift estimation feature data acquired at historical time and stored in the local memory of the receiver / chip are used to determine the first velocity and the clock drift solution equations and solve them.

[0039] In some exemplary embodiments, such as Figure 2 As shown, it also includes: Step 160: If the current signal quality does not meet the set quality requirements based on the quality characteristic data, and the historical clock drift estimation characteristic data in the memory is empty, the second velocity and clock drift solution equation set is used to solve the receiver velocity and clock drift value.

[0040] During the epoch calculation process, when the signal quality does not meet the quality requirements of real-time clock drift estimation and there is no available historical data, the second velocity without clock drift constraint equations and the clock drift solution equation set are used for velocity calculation.

[0041] In some exemplary embodiments, steps 110-140 are executed periodically according to a set time interval, and the method further includes: Step 210: If the time interval has not been reached, obtain the clock drift estimation feature data stored in the local memory, and determine the first velocity and clock drift solution equation set including N+1 equations based on the clock drift estimation feature data, and solve the receiver velocity and clock drift value.

[0042] In other words, the latest clock drift estimation feature data is periodically updated. In epochs not currently being updated, historically acquired clock drift estimation feature data is used to perform calculations based on the first velocity and the clock drift solution equations. The time interval can be flexibly set as needed.

[0043] In some exemplary embodiments, the method further includes: calculating at least one of the following from a plurality of clock drift values ​​obtained within the current evaluation time window: maximum value, minimum value, m The corresponding value determines whether the receiver's clock drift meets a preset standard. If it does not, an alarm is triggered. m = 1, 2, or 3. This represents the standard deviation. For example, if m=3, 3 The corresponding value is the average ± 3 times the standard deviation. The preset standard receiver's accuracy or specification requirements are based on the maximum value, minimum value, and m. One or more of the corresponding values ​​can be flexibly determined, and are not limited to specific numerical values.

[0044] This disclosure also provides a speed measurement method that adapts to crystal oscillator specifications, such as... Figure 3 As shown, it includes: Step 310, receiver starts; Step 320: Obtain the locally configured (stored) clock drift estimation feature data and perform the calculation; that is, determine the first velocity and clock drift solution equation set including N+1 equations based on the locally configured clock drift estimation feature data, and calculate the receiver velocity and clock drift value. Step 330: Obtain solution data from multiple epochs and calculate the current clock drift estimation feature data; Step 340: Update the locally stored clock drift estimation feature data.

[0045] The locally configured clock drift estimation feature data comes from other applications within the host computer or receiver device.

[0046] Therefore, when the receiver has just started up and the real-time clock drift estimation feature data has not been obtained in time, the configuration data from the outside can be used first, which can balance startup efficiency and solution accuracy.

[0047] In some exemplary embodiments, step 340 further includes: issuing an alarm when the difference between the real-time calculated clock drift estimation feature data and the locally initially configured clock drift estimation feature data is greater than a set threshold. The clock drift estimation feature data used for data comparison may include one or more of the following: clock drift estimation values, clock drift estimation jitter variance, and satellite geometric distribution quality assessment indicators. For example, it may include clock drift estimation jitter variance, i.e., comparing the real-time calculated clock drift estimation jitter variance with the initially configured clock drift estimation jitter variance.

[0048] This disclosure provides a GNSS receiver including a processor configured to implement a speed measurement method with adaptive crystal oscillator specifications as described in any embodiment of this disclosure.

[0049] In some exemplary embodiments, the GNSS receiver includes a BeiDou satellite navigation receiver or a GPS satellite navigation receiver.

[0050] This disclosure provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements a speed measurement method for adaptive crystal oscillator specifications as described in any embodiment of this disclosure.

[0051] The adaptive crystal oscillator specification-based velocity measurement scheme provided in this disclosure can quickly and accurately evaluate the clock drift characteristics of different hardware crystal oscillators, accurately reflect the frequency offset performance of the crystal oscillator, and provide accurate feedback of the crystal oscillator clock drift jitter level to the baseband, thereby assisting in satellite signal acquisition and tracking. A GNSS velocity measurement algorithm is integrated based on crystal oscillators of different specifications / performance, reducing software maintenance costs. Clock drift constraint assistance ensures the stability of clock drift updates. In high and low temperature environments or when clock jitter occurs, it ensures that the clock drift change trend is a continuous and smooth curve, avoiding steep drops, steep rises, and abrupt changes. Since clock drift has a significant impact on baseband signal tracking, large clock drift jitter can easily cause signal tracking lock-up and a decrease in Doppler observation quality. Stable clock drift changes offer significant benefits for velocity measurement performance in highly maneuverable and complex environments.

[0052] It will be understood by those skilled in the art that all or some of the steps, systems, or apparatuses disclosed above, and their functional modules / units, can be implemented as software, firmware, hardware, or suitable combinations thereof. In hardware implementations, the division between functional modules / units mentioned above does not necessarily correspond to the division of physical components; for example, a physical component may have multiple functions, or a function or step may be performed collaboratively by several physical components. Some or all components may be implemented as software executed by a processor, such as a digital signal processor or microprocessor, or as hardware, or as an integrated circuit, such as an application-specific integrated circuit (ASIC). Such software may be distributed on a computer-readable medium, which may include computer storage media (or non-transitory media) and communication media (or transient media). As is known to those skilled in the art, the term "computer storage medium" includes volatile and non-volatile, removable and non-removable media implemented in any method or technology for storing information (such as computer-readable instructions, data structures, program modules, or other data). Computer storage media include, but are not limited to, RAM, ROM, EEPROM, flash memory or other memory technologies, disk storage or other magnetic storage devices, or any other medium that can be used to store desired information and can be accessed by a computer. Furthermore, it is well known to those skilled in the art that communication media typically contain computer-readable instructions, data structures, program modules, or other data in modulated data signals such as carrier waves or other transmission mechanisms, and may include any information delivery medium.

[0053] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A velocity measurement method with adaptive crystal oscillator specifications, applied to a GNSS receiver, characterized in that, include: Acquire quality characteristic data of N satellite signals, wherein the quality characteristic data includes at least one of the following: signal strength, carrier-to-noise ratio, and satellite geometric distribution quality assessment index; If the current signal quality meets the set quality requirements based on the quality characteristic data, clock drift estimation characteristic data is determined based on the current satellite signal. The clock drift estimation characteristic data includes: clock drift estimation jitter variance. Based on the clock drift estimation characteristic data, the first velocity and clock drift solution equation set including N+1 equations are determined, and the receiver velocity and clock drift value are calculated. The N+1 equation set includes: solution equations corresponding to N satellites and a clock drift constraint equation; the weight of the clock drift constraint equation in the first velocity and clock drift solution equation set is negatively correlated with the estimated jitter variance of the clock drift, and N is an integer greater than 1.

2. The method according to claim 1, characterized in that, The satellite geometric distribution quality assessment index is calculated according to the following method: ; in, The satellite geometric distribution quality assessment index is defined as follows: ValidADRCnt is the number of phase-locked and carrier-enabled satellites among the N satellites; ValidAzelCnt is the number of azimuth sectors where the number of satellites exceeds a first threshold; AzelCnt is the total number of azimuth sectors; ValidElCnt is the number of elevation sectors where the number of satellites exceeds a second threshold; and ElCnt is the total number of elevation sectors.

3. The method according to claim 1, characterized in that, The clock drift estimation feature data also includes: clock drift estimation values; The estimated values ​​of clock drift are obtained by statistical analysis of clock drift calculation values ​​in multiple epochs; The clock drift calculation values ​​are obtained by solving the second velocity and the clock drift calculation equation set, which includes the calculation equations corresponding to the N satellites.

4. The method according to claim 3, characterized in that, The estimated value of the clock drift is calculated according to the following method: ； in, Let be the estimated clock drift values ​​for t epochs, where k represents k consecutive time windows, each containing t epochs; This represents the clock drift calculation value at the i-th epoch within the k-th time window.

5. The method according to claim 3, characterized in that, The estimated jitter variance of the clock drift is obtained by statistical analysis of the clock drift variance solution values ​​in multiple epochs; The calculated value of the clock drift variance is obtained by solving the weight coefficient matrix corresponding to the second velocity and the clock drift calculation equation set.

6. The method according to claim 3, characterized in that, The clock drift estimation feature data also includes: satellite geometric distribution quality assessment indicators; The first velocity and clock drift calculation equations are as follows: ; The second velocity and clock drift solution equations are as follows: ; in, , , ， ； ； ； G is the design matrix corresponding to the N equations for N satellites, and G1 is the design matrix corresponding to the N+1 equations with added clock drift constraint equations. Let W be the Doppler residual vector corresponding to N satellites, W be the weighting matrix corresponding to N satellites, and W1 be the weighting matrix with added weights for the clock drift constraint equation. The weights of the clock drift constraint equation are... Estimate residuals for clock drift; Estimate the value for the clock drift. Estimate the jitter variance for clock drift. As an indicator for assessing the quality of satellite geometric distribution; The velocity is along the x-axis. The velocity is along the y-axis. The velocity along the z-axis. For Zhong Piao.

7. The method according to any one of claims 1-6, characterized in that, The method further includes: when it is determined from the quality characteristic data that the current signal quality meets the set quality requirements, saving the clock drift estimation characteristic data to the receiver's local memory; If the current signal quality does not meet the set quality requirements based on the quality characteristic data, the first velocity and clock drift solution equation set including N+1 equations are determined based on the clock drift estimation characteristic data in the memory, and the receiver velocity and clock drift value are calculated.

8. The method according to claim 7, characterized in that, The method further includes: when it is determined from the quality characteristic data that the current signal quality does not meet the set quality requirements, and the historical clock drift estimation characteristic data in the memory is empty, a second speed and clock drift solution equation set is used to solve for the receiver speed and clock drift value. The second velocity and clock drift calculation equation set includes the calculation equations corresponding to the N satellites.

9. A GNSS receiver for a global satellite navigation system, characterized in that, Includes a processor configured to implement a speed measurement method for adaptive crystal oscillator specifications as described in any one of claims 1-8.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When executed by the processor, the program implements the speed measurement method for adaptive crystal oscillator specifications as described in any one of claims 1-8.

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