A PPS signal preprocessing method and system based on satellite clock synchronization

Abstract

The present invention discloses a PPS signal preprocessing method and system based on satellite clock synchronization, the method comprising: acquiring a satellite PPS signal and performing signal preprocessing to obtain a preprocessed satellite PPS signal; setting a standard gate signal, performing error frequency measurement processing on the preprocessed satellite PPS signal based on a multi-source time synchronization mechanism to obtain a satellite PPS signal clock frequency error; performing frequency measurement correction processing on the preprocessed satellite PPS signal according to the satellite PPS signal clock frequency error to obtain a corrected satellite PPS signal. By using the present invention, the degree of dependence on satellite signals can be reduced, thereby improving the reception stability and accuracy of system signals. As a PPS signal preprocessing method and system based on satellite clock synchronization, the present invention can be widely used in the field of electronic information real-time transmission technology.

Description

Technical Field

[0001] The present invention relates to the technical field of real-time transmission of electronic information, and in particular to a PPS signal preprocessing method and system based on satellite clock synchronization. Background Art

[0002] In distributed data acquisition systems, time synchronization is a key factor in ensuring data accuracy and real-time performance. Traditional clock synchronization methods include the Network Time Protocol (NTP) and the Precision Time Protocol (PTP, also known as IEEE1588). However, with the expansion of application scenarios and the improvement of real-time requirements, these traditional methods may not be able to meet the needs of high-precision time synchronization in some cases. For example, the existing satellite clock synchronization technology provides a high-precision time reference for ground receiving equipment by broadcasting PPS (pulses per second) signals containing precise time information. However, relying solely on satellite signals may be affected by environmental factors (such as building obstruction, electromagnetic interference) and weather conditions (such as cloud obstruction), resulting in unstable signal reception or reduced accuracy. In addition, there are problems such as difficulty in synchronizing distributed systems and poor restoration of satellite PPS nanosecond synchronization accuracy in marine environments. Summary of the invention

[0003] In order to solve the above technical problems, the purpose of the present invention is to provide a PPS signal preprocessing method and system based on satellite clock synchronization, which can reduce the dependence on satellite signals and thus improve the reception stability and accuracy of system signals.

[0004] The first technical solution adopted by the present invention is: a PPS signal preprocessing method based on satellite clock synchronization, comprising the following steps:

[0005] Acquire the satellite PPS signal and perform signal preprocessing to obtain the preprocessed satellite PPS signal;

[0006] Set a standard gate signal, perform error frequency measurement on the pre-processed satellite PPS signal based on a multi-source time synchronization mechanism, and obtain the satellite PPS signal clock frequency error;

[0007] According to the satellite PPS signal clock frequency error, the pre-processed satellite PPS signal is subjected to frequency measurement correction processing to obtain a corrected satellite PPS signal.

[0008] Further, the step of acquiring the satellite PPS signal and performing signal preprocessing to obtain the preprocessed satellite PPS signal specifically includes:

[0009] Acquire satellite PPS signals and perform frequency measurement processing to obtain satellite PPS signal frequency information;

[0010] Set the frequency screening range to screen the satellite PPS signal frequency information to obtain the screened satellite PPS signal;

[0011] The screened satellite PPS signals are saved and signal variance is calculated to obtain the satellite PPS signal variance value;

[0012] The satellite PPS signal variance values ​​are screened, and the satellite PPS signal corresponding to the preset variance threshold is selected as the preprocessed satellite PPS signal.

[0013] Further, the step of setting a standard gate signal and performing error frequency measurement processing on the pre-processed satellite PPS signal based on a multi-source time synchronization mechanism to obtain a satellite PPS signal clock frequency error specifically includes:

[0014] Set standard gate signal;

[0015] According to the frequency of the standard gate signal, the number of inversions of the standard gate signal clock number within a preset time is obtained to obtain the standard inversion number;

[0016] According to the frequency of the preprocessed satellite PPS signal, the number of reversals of the preprocessed satellite PPS signal clock number within the same preset time is obtained to obtain the number of satellite PPS signal reversals;

[0017] The satellite PPS signal clock frequency error is determined based on the ratio of the standard inversion number to the satellite PPS signal inversion number.

[0018] Furthermore, the standard gate signal is a satellite 1pps time synchronization signal.

[0019] Further, the frequency of the preprocessed satellite PPS signal is obtained by the following expression:

[0020]

[0021] In the above formula, f x Represents the frequency of the preprocessed satellite PPS signal, N x It represents the number of cycles of the preprocessed satellite PPS signal, and T represents the time of the standard gate signal.

[0022] Further, the step of performing frequency measurement and correction processing on the preprocessed satellite PPS signal according to the satellite PPS signal clock frequency error to obtain a corrected satellite PPS signal specifically includes:

[0023] According to the satellite PPS signal clock frequency error, the pre-processed satellite PPS signal is subjected to OCXO clock correction processing through the DA chip to obtain a corrected satellite PPS signal;

[0024] or;

[0025] According to the satellite PPS signal clock frequency error, the pre-processed satellite PPS signal is subjected to OCXO clock correction processing according to the preset correction time interval threshold through the clock chip configuration register to obtain the corrected satellite PPS signal.

[0026] The second technical solution adopted by the present invention is: a PPS signal preprocessing system based on satellite clock synchronization, comprising:

[0027] A preprocessing module is used to acquire the satellite PPS signal and perform signal preprocessing to obtain the preprocessed satellite PPS signal;

[0028] The error frequency measurement module is used to set the standard gate signal, perform error frequency measurement on the pre-processed satellite PPS signal based on the multi-source time synchronization mechanism, and obtain the satellite PPS signal clock frequency error;

[0029] The error correction module is used to perform frequency measurement correction processing on the pre-processed satellite PPS signal according to the satellite PPS signal clock frequency error to obtain a corrected satellite PPS signal.

[0030] The beneficial effects of the method and system of the present invention are as follows: the present invention improves the stability of the received signal by performing signal preprocessing on the satellite PPS signal, further sets a standard gate signal, performs error frequency measurement processing on the preprocessed satellite PPS signal based on a multi-source time synchronization mechanism, introduces a multi-source time synchronization mechanism, reduces the degree of dependence on the satellite signal, and improves the reliability and stability of the system; finally, the preprocessed satellite PPS signal is subjected to frequency measurement correction processing, a relatively stable standard gate signal is selected for error estimation, and then calculation and correction are performed, thereby improving the reception stability and accuracy of the signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a flow chart of the steps of a PPS signal preprocessing method based on satellite clock synchronization of the present invention;

[0032] Figure 2 It is a structural block diagram of a PPS signal preprocessing system based on satellite clock synchronization of the present invention;

[0033] Figure 3 is a schematic diagram of frequency comparison between an acquired PPS signal and a standard gate signal provided by a specific embodiment of the present invention;

[0034] Figure 4 is a schematic diagram of frequency error correction through a DA chip provided by a specific embodiment of the present invention;

[0035] Figure 5is a schematic diagram of frequency error correction through an RTC chip provided by a specific embodiment of the present invention;

[0036] Figure 6 It is a schematic diagram of the RTC chip supporting the configuration of sampling PPS signal counting provided by a specific embodiment of the present invention. DETAILED DESCRIPTION

[0037] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. The step numbers in the following embodiments are only provided for the convenience of explanation and description, and the order between the steps is not limited in any way. The execution order of each step in the embodiment can be adaptively adjusted according to the understanding of those skilled in the art.

[0038] Before describing the embodiments of the present application in detail, some nouns and terms involved in the embodiments of the present application are first described. The nouns and terms involved in the embodiments of the present application are subject to the following explanations.

[0039] In the past, there were problems with distributed system synchronization difficulties and poor restoration of satellite PPS nanosecond synchronization accuracy in marine environments. High-precision time synchronization is achieved in distributed data acquisition systems, especially in multi-scene and long-distance application scenarios to ensure the accuracy and real-time performance of time synchronization. The embodiments of the present invention belong to the field of electronic information, particularly to the field of distributed data acquisition and real-time transmission technology.

[0040] As the performance of distributed data acquisition systems continues to improve, the requirements for synchronization accuracy have also been upgraded accordingly. The accuracy requirements have gradually changed from milliseconds and microseconds to nanoseconds, and the corresponding clock synchronization solutions have also been iteratively upgraded. Currently, there are three commonly used synchronization technologies at home and abroad, which are introduced as follows:

[0041] 1) IRIG-B code time synchronization technology;

[0042] IRIG-B (Inter-Range Instrumentation Group-B) code is a time signal expressed in digital form, which contains time information such as year, day, hour, minute, second, and other time-related symbols. First, the IRIG-B signal is embedded into the electrical signal by using special hardware equipment, and then transmitted to other devices through cables. The receiving end completes the decoding and obtains the real-time time. This method can achieve microsecond clock synchronization.

[0043] 2) GNSS timing synchronization technology;

[0044] GNSS (Global Navigation Satellite System) timing synchronization technology first uses the high-precision characteristics of the atomic clock, cesium clock or rubidium clock carried by the GNSS, and then sends the precise time edge and total seconds per second through satellite messages. The ground receiver then performs delay compensation to generate a deviation of only nanoseconds of PPS (Pulse per Second) signal and UTC (Coordinated Universal Time). Finally, the system compares and adjusts the local clock with the PPS signal and UTC time to achieve synchronization. The biggest advantage of this synchronization method is that it can provide wireless timing. According to the characteristics of the receiver, it is divided into position-keeping timing and positioning timing, which means that when the user's position remains unchanged, only 1 to 2 satellites are needed to maintain the timing of a given accuracy; and the position is settled by positioning, and then the ground time is solved by delay compensation. This method can achieve sub-microsecond clock synchronization.

[0045] 3) Network time protocol synchronization technology;

[0046] Traditional NTP (Network Time Protocol) is based on TCP / IP (Transmission Control Protocol / Internet Protocol) to achieve time synchronization between the host and the slave. The clock source of the host is generally an atomic clock, a time station, a satellite or Ethernet. The NTP protocol measures the delay of data packets between nodes and estimates the time drift between computers to achieve time synchronization on the node network. The accuracy is between 0.1ms and 10ms in the local area network and tens of milliseconds in the wide area network, but the millisecond-level synchronization accuracy is difficult to meet most industrial requirements. In order to improve the time accuracy of the network time protocol, the IEEE Standards Committee passed the IEEE1588 protocol, also known as PTP (Precise Time Protocol), which can achieve sub-microsecond time synchronization accuracy.

[0047] However, the prior art has the following disadvantages:

[0048] 1) Unstable signal reception: Due to environmental factors and weather conditions, satellite signals may not be stably received, resulting in reduced time synchronization accuracy.

[0049] 2) Limited accuracy: Even if the satellite signal can be stably received, the delay in signal transmission and the processing time of ground equipment will limit the final time synchronization accuracy.

[0050] Based on this, the embodiments of the present invention improve the time synchronization accuracy and stability of the system by optimizing the signal reception and processing algorithm and combining other auxiliary synchronization means, while reducing the dependence on satellite signals.

[0051] Reference Figure 1 The present invention provides a PPS signal preprocessing method based on satellite clock synchronization, the method comprising the following steps:

[0052] S1. Acquire the satellite PPS signal and perform signal preprocessing to obtain the preprocessed satellite PPS signal;

[0053] Specifically, the satellite PPS signal is acquired and frequency measurement processing is performed to obtain the satellite PPS signal frequency information; a frequency screening range is set to screen the satellite PPS signal frequency information to obtain a screened satellite PPS signal; the screened satellite PPS signal is saved and the signal variance is calculated to obtain a satellite PPS signal variance value; the satellite PPS signal variance value is screened, and the satellite PPS signal corresponding to the preset variance threshold is selected as the preprocessed satellite PPS signal.

[0054] In this embodiment, in order to solve the problem of unstable satellite signal reception, the embodiment of the present invention adopts optimized signal reception, that is, the satellite PPS signal is effectively screened through software. When the satellite signal is good, 10 consecutive PPS signals are saved and the time length is extracted to calculate the variance, so as to select a stable and high-precision PPS signal.

[0055] S2. Set a standard gate signal, perform error frequency measurement on the pre-processed satellite PPS signal based on a multi-source time synchronization mechanism, and obtain the satellite PPS signal clock frequency error;

[0056] Specifically, a standard gate signal is set; based on the frequency of the standard gate signal, the number of inversions of the standard gate signal clock number within a preset time is obtained to obtain a standard inversion number; based on the frequency of the preprocessed satellite PPS signal, the number of inversions of the preprocessed satellite PPS signal clock number within the same preset time is obtained to obtain a satellite PPS signal inversion number; based on the ratio of the standard inversion number to the satellite PPS signal inversion number, the satellite PPS signal clock frequency error is determined.

[0057] In this embodiment, if Figure 3 As shown in the figure, a high-precision and stable satellite 1pps time synchronization signal is selected as the standard gate signal, the OCXO output is 10MHz, and the clock after FPGA digital PLL frequency multiplication is used as the measured signal. The standard gate time is T, and the measured signal cycle number is N x , then the measured signal frequency is f xSatisfy the following formula:

[0058]

[0059] In the above formula, f x Represents the frequency of the preprocessed satellite PPS signal, N x It represents the number of cycles of the preprocessed satellite PPS signal, and T represents the time of the standard gate signal.

[0060] By comparing with a precise clock with a fixed frequency such as 1Hz pps, the number of reversals of its own clock within 1s is obtained. If it is assumed that there is no error within the 1s interval of pps, the number of occurrences of its own clock is calculated and compared with the calculated value of the theoretical frequency to obtain the error size of the existing clock frequency.

[0061] It should be noted that the multi-source time synchronization mechanism means that in addition to relying on satellite signals, other auxiliary synchronization means are introduced to form a multi-source time synchronization mechanism. When satellite signals are unavailable, the self-corrected clock can still use other synchronization sources for time synchronization, such as constant temperature crystal oscillators or RTC clock chips.

[0062] Multi-source refers to satellite clock sources such as constant temperature crystal oscillators or RTC chips. When the satellite signal is good, the satellite clock source provided by the satellite signal can be used to calibrate the clock source, such as constant temperature crystal oscillators and RTC clock chips. When the satellite signal is poor, the clock source can also maintain a synchronization state that is not much different from the previous one.

[0063] S3. Perform frequency measurement and correction processing on the preprocessed satellite PPS signal according to the satellite PPS signal clock frequency error to obtain a corrected satellite PPS signal.

[0064] Specifically, according to the satellite PPS signal clock frequency error, the preprocessed satellite PPS signal is subjected to OCXO clock correction processing through the DA chip to obtain a corrected satellite PPS signal; or; according to the satellite PPS signal clock frequency error, the preprocessed satellite PPS signal is subjected to OCXO clock correction processing according to a preset correction time interval threshold through the clock chip configuration register to obtain a corrected satellite PPS signal.

[0065] In this embodiment, if Figure 4 and Figure 5 As shown, use a precision DA chip to adjust the OCXO constant temperature crystal oscillator output clock to quickly complete the correction, which can greatly improve the satellite timing synchronization accuracy, or choose a high-performance clock chip configuration register such as a chip with RTC clock deviation correction. After obtaining the deviated clock frequency ppm, it can be automatically completed by setting a fixed register (correction once every 4 minutes / correction once every 2 hours), sacrificing accuracy to reduce power consumption.

[0066] That is, the system monitors the time synchronization status of each node in real time and makes real-time adjustments as needed. For example, when a node's time synchronization deviates greatly, the system can actively send a time correction instruction to the node to quickly restore time synchronization, such as Figure 6 shown.

[0067] It should be noted that the method of DA directly correcting high-performance clock sources such as constant temperature crystal oscillators or atomic clocks is better and can reach microseconds or even nanoseconds, but their cost and power consumption are relatively high. For example, the power consumption of constant temperature crystal oscillators is about 3W on average, and atomic clocks are even higher. The above-mentioned method of configuring RTC chips can select chips with different performances to reach milliseconds to microseconds, which is suitable for marine applications with low accuracy requirements and high power consumption requirements, and the power consumption is on the order of 100mW.

[0068] In summary, the technical effects of the embodiments of the present invention are:

[0069] 1) Improve signal reception stability: Improve satellite signal reception stability and anti-interference capability by optimizing the antenna design and signal processing algorithm of the receiving device.

[0070] 2) Improve time synchronization accuracy: Combined with GNSS satellite synchronization technology, high-performance processors such as FPGA and ARM are used to accurately process PPS signals, reduce delays in signal transmission and processing, and improve time synchronization accuracy.

[0071] 3) Reduce system cost: By optimizing hardware design and software algorithms, unnecessary hardware support and complexity can be reduced, thereby reducing the overall cost of the system.

[0072] Reference Figure 2 , a PPS signal preprocessing system based on satellite clock synchronization, comprising:

[0073] A preprocessing module is used to acquire the satellite PPS signal and perform signal preprocessing to obtain the preprocessed satellite PPS signal;

[0074] The error frequency measurement module is used to set the standard gate signal, perform error frequency measurement on the pre-processed satellite PPS signal based on the multi-source time synchronization mechanism, and obtain the satellite PPS signal clock frequency error;

[0075] The error correction module is used to perform frequency measurement correction processing on the pre-processed satellite PPS signal according to the satellite PPS signal clock frequency error to obtain a corrected satellite PPS signal.

[0076] The contents of the above method embodiments are all applicable to the present system embodiments. The functions specifically implemented by the present system embodiments are the same as those of the above method embodiments, and the beneficial effects achieved are also the same as those achieved by the above method embodiments.

[0077] The above is a specific description of the preferred implementation of the present invention, but the invention is not limited to the embodiments. Those skilled in the art may make various equivalent modifications or substitutions without violating the spirit of the present invention. These equivalent modifications or substitutions are all included in the scope defined by the claims of this application.

Claims

1. A PPS signal preprocessing method based on satellite clock synchronization, characterized in that: The following steps are involved: Acquire the satellite PPS signal and perform signal preprocessing to obtain the preprocessed satellite PPS signal; Set standard gate signal; According to the frequency of the standard gate signal, the number of inversions of the standard gate signal clock number within a preset time is obtained to obtain the standard inversion number; According to the frequency of the preprocessed satellite PPS signal, the number of reversals of the preprocessed satellite PPS signal clock number within the same preset time is obtained to obtain the number of satellite PPS signal reversals; Determine the satellite PPS signal clock frequency error based on the ratio of the standard inversion times to the satellite PPS signal inversion times; According to the satellite PPS signal clock frequency error, the pre-processed satellite PPS signal is subjected to frequency measurement correction processing to obtain a corrected satellite PPS signal.

2. A PPS signal preprocessing method based on satellite clock synchronization according to claim 1, characterized in that: The step of acquiring the satellite PPS signal and performing signal preprocessing to obtain the preprocessed satellite PPS signal specifically includes: Acquire satellite PPS signals and perform frequency measurement processing to obtain satellite PPS signal frequency information; Set the frequency screening range to screen the satellite PPS signal frequency information to obtain the screened satellite PPS signal; The screened satellite PPS signals are saved and signal variance is calculated to obtain the satellite PPS signal variance value; The satellite PPS signal variance values ​​are screened, and the satellite PPS signal corresponding to the preset variance threshold is selected as the preprocessed satellite PPS signal.

3. A PPS signal preprocessing method based on satellite clock synchronization according to claim 2, characterized in that: The standard gate signal is a satellite 1pps time synchronization signal.

4. The PPS signal preprocessing method based on satellite clock synchronization according to claim 3, characterized in that: The acquisition expression of the frequency of the pre-processed satellite PPS signal is specifically as follows: ； In the above formula, represents the frequency of the preprocessed satellite PPS signal, Indicates the number of cycles of the preprocessed satellite PPS signal, Indicates the time of the standard gate signal.

5. A PPS signal preprocessing method based on satellite clock synchronization according to claim 4, characterized in that: The step of performing frequency measurement and correction processing on the preprocessed satellite PPS signal according to the satellite PPS signal clock frequency error to obtain a corrected satellite PPS signal specifically includes: According to the satellite PPS signal clock frequency error, the pre-processed satellite PPS signal is subjected to OCXO clock correction processing through the DA chip to obtain a corrected satellite PPS signal; or; According to the satellite PPS signal clock frequency error, the pre-processed satellite PPS signal is subjected to OCXO clock correction processing according to the preset correction time interval threshold through the clock chip configuration register to obtain the corrected satellite PPS signal.

6. A PPS signal preprocessing system based on satellite clock synchronization, characterized in that: Includes the following modules: A preprocessing module is used to acquire the satellite PPS signal and perform signal preprocessing to obtain the preprocessed satellite PPS signal; Error frequency measurement module, used to set the standard gate signal; According to the frequency of the standard gate signal, the number of inversions of the standard gate signal clock number within a preset time is obtained to obtain the standard inversion number; According to the frequency of the preprocessed satellite PPS signal, the number of reversals of the preprocessed satellite PPS signal clock number within the same preset time is obtained to obtain the number of satellite PPS signal reversals; Determine the satellite PPS signal clock frequency error based on the ratio of the standard inversion times to the satellite PPS signal inversion times; The error correction module is used to perform frequency measurement correction processing on the pre-processed satellite PPS signal according to the satellite PPS signal clock frequency error to obtain a corrected satellite PPS signal.

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