Optical fiber ground-based time service system and time frequency synchronization method

Abstract

The invention discloses an optical fiber ground-based time service system and a time frequency synchronization method, the system comprises a power supply conversion unit, an antenna unit, a radio frequency unit, a time service unit, a local clock unit and a display control unit, the time service unit comprises a signal processing module, a data processing module and a time service time scale synthesis module, the time service unit is used for receiving an optical fiber limiting number and carrying out time synchronization, and the radio frequency unit is used for carrying out down-conversion and amplification on an RNSS signal which is subjected to low-noise amplification and comes from the antenna unit. And meanwhile, the reliability of the time service system is improved, the problem of signal interruption does not exist, a long-term high-precision time reference is ensured, the precision of pulse per second of time service is improved, and time synchronization is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of optical fiber ground-based timing service, and in particular to an optical fiber ground-based timing service system and a method for time and frequency synchronization. Background Art

[0002] With the continuous development of science and technology, various equipment and technologies need to be based on high-precision time and frequency. For example, the establishment of intelligent transportation systems and the realization of the digital earth need to be based on high-precision time and frequency. Various monitoring and weapon launches in modern warfare also need to be based on high-precision time and frequency. At present, the most widely used timing systems are based on satellite navigation systems, that is, wireless networks are used to transmit signals, which are easily affected by external interference and cannot be used (such as man-made electromagnetic wave interference), and are also easily affected by weather or climate. In addition, signals can only be used in open places. If the satellite signal is blocked by obstacles, it cannot be used. Obviously, the high-precision timing systems based on satellites in the prior art have the problems of being susceptible to interference, susceptible to weather or climate, and only being able to use signals in open places. Therefore, a fiber-optic ground-based timing system and a method for time and frequency synchronization are provided to solve the above problems. Summary of the invention

[0003] The technical solution adopted by the present invention to solve the technical problem is: an optical fiber ground-based timing system, which system includes: a power conversion unit, an antenna unit, a radio frequency unit, a timing unit, a local clock unit and a display control unit. The timing unit includes a signal processing module, a data processing module and a timing time mark synthesis module. The timing unit is used to receive optical fiber restrictions and perform time synchronization. The radio frequency unit down-converts and amplifies the RNSS signal amplified by low noise from the antenna unit, and after AGC control, provides the signal processing module with an intermediate frequency signal that meets certain signal-to-noise ratio and amplitude requirements.

[0004] As a preferred technical solution of the present invention, the power conversion unit is used to provide power for the system. The system adopts 220V AC input externally, and the power used internally includes 12V and 5V DC power supplies.

[0005] As a preferred technical solution of the present invention, the antenna unit is used to receive the configured satellite signal, which is then low-noise amplified in the radio frequency unit and then enters the corresponding receiving radio frequency channel through the optical fiber cable to complete the signal down-conversion and intermediate frequency amplification processing.

[0006] As a preferred technical solution of the present invention, the local clock unit has a clock selection circuit, and uses an internal clock or an external reference clock input, thereby ensuring a high-precision and stable local time reference.

[0007] As a preferred technical solution of the present invention, the signal processing module is responsible for baseband signal processing and completes the tasks of sampling, capturing, tracking, demodulating navigation messages, and calculating original observation quantities of navigation signals.

[0008] As a preferred technical solution of the present invention, the data processing module is responsible for reading the original observation quantity and telegram information from the signal processing module, completing navigation telegram analysis, satellite orbit data smoothing filtering, satellite position calculation, pseudorange calculation, positioning solution, various clock error compensation, time information serial port output, and responding to user control command functions.

[0009] As a preferred technical solution of the present invention, the time scale synthesis module is used to calculate the clock difference between the local time and the system time. After adding digital filtering and fault-tolerant design, accurate synchronous time scale generation is achieved. It can output second pulses with a synchronization accuracy better than 50ns with the Coordinated Universal Time (UTC) and output the time information through the serial port in a certain format.

[0010] As a preferred technical solution of the present invention, the data processing module includes a navigation message parsing module, an original observation quantity extraction module, a positioning solution module and a timing module. The navigation message parsing module stores the demodulated navigation message in a register through a signal processing module, triggers a navigation message reading interrupt when a subframe data is received, and analyzes the message data in the navigation message parsing processing function.

[0011] As a preferred technical solution of the present invention, the original observation quantity extraction module receives satellite signals. When the observation quantity in the FPGA is ready, the DSP external interrupt is triggered, and the original observation quantity extraction function is triggered. The positioning solution module can call the relevant error compensation processing module according to the ephemeris information analyzed in the navigation message analysis data, perform corresponding calculations on various errors in the ionosphere, troposphere, and earth rotation, compensate for the pseudo-range, and then use the least squares method or Kalman filtering method to perform positioning solution. The timing module is used to realize the reception of satellite signals according to the stored configuration or the control configuration instructions analyzed by the receiving serial port data processing module according to the configuration instructions, and configure the timing working mode according to whether the local position is known.

[0012] A method for time and frequency synchronization of an optical fiber ground-based timing system comprises the following steps:

[0013] Step 1: First, the time information and position information are displayed through the display and control unit, and the synchronous time stamp signal is output at the same time, and the time message data is transmitted to the main control machine through the external data interface, and the working parameters of the timing receiver are configured through the display and control unit or through the data interface;

[0014] Step 2: The system can complete the self-check of each functional module. If an abnormality occurs, the corresponding status prompt will be given. If all modules are detected normally, the clock unit will normally output the reference second pulse, and the signal receiving unit will start searching and capturing satellite signals.

[0015] Step 3: The antenna of the timing receiver receives the RF signal broadcast by the navigation satellite, sends the received weak satellite signal to the pre-filter for filtering, and then amplifies the signal through the low-noise amplifier. The RF unit converts the signal into an intermediate frequency signal through secondary down-conversion and sends it to the signal processing module for signal demodulation;

[0016] Step 3: The A / D converter in the signal processing module samples and quantizes the intermediate frequency signal sent by the radio frequency unit, converts it into a digital intermediate frequency, completes the pseudo code capture and tracking of the satellite signal and the data despreading and demodulation operations, and then sends the decoded navigation message and the calculated observation value to the data processing module;

[0017] Step 4: After completing the relevant pseudo-range calculation, positioning solution, and various time error compensations through the data processing module, the local clock difference measurement value is obtained, the unadjusted second pulse deviation is obtained, and the time information is output through the serial port. The time scale synthesis module synchronizes the second pulse through the second pulse deviation and the local clock unit to achieve time synchronization.

[0018] The present invention has the following advantages: the timing system of the present invention, the accuracy of the time-frequency signal and the reference frequency signal of the time synchronization meet the index requirements of the pseudo-satellite subsystem, and at the same time improves the reliability of the timing system, and there is no signal interruption problem, which ensures a long-term high-precision time reference, improves the accuracy of the timing second pulse, realizes time synchronization, has good practicality, and can provide technical reserves for subsequent formal promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a schematic diagram of a timing system according to a preferred embodiment of the present invention;

[0020] Figure 2 It is a schematic diagram of the operation flow of the data processing module of the preferred embodiment of the present invention;

[0021] Figure 3 It is a schematic diagram of the operating principle of the timing unit of the preferred embodiment of the present invention. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present invention are described clearly and completely below. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Many specific details are explained in the following description to facilitate a full understanding of the present invention. However, the present invention can also be implemented in other ways different from those described herein. Therefore, the scope of protection of the present invention is not limited by the specific embodiments disclosed below.

[0023] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0024] Please refer to Figure 1-Figure 3 The present invention discloses an optical fiber ground-based timing system, which includes: a power conversion unit, an antenna unit, a radio frequency unit, a timing unit, a local clock unit and a display control unit. The timing unit includes a signal processing module, a data processing module and a timing time mark synthesis module. The timing unit is used to receive optical fiber number limits and perform time synchronization. The radio frequency unit down-converts and amplifies the RNSS signal amplified by low noise from the antenna unit, and after AGC control, provides the signal processing module with an intermediate frequency signal that meets certain signal-to-noise ratio (S / N) and amplitude requirements.

[0025] Among them, the power conversion unit is used to provide power for the system. The system uses 220V AC input externally, and the internal power supplies include 12V and 5V DC power supplies. The antenna unit is used to receive the configured satellite signal. After low-noise amplification in the RF unit, it enters the corresponding receiving RF channel through the optical fiber cable to complete the signal down-conversion and intermediate-frequency processing. The local clock unit has a clock selection circuit and uses an internal clock or an external reference clock input to ensure a high-precision and stable local time reference. The signal processing module is responsible for baseband signal processing and completes the sampling, capture, tracking, navigation message demodulation, and original The data processing module is responsible for reading the original observation and message information from the signal processing module, completing navigation message analysis, satellite orbit data smoothing and filtering, satellite position calculation, pseudo-range calculation, positioning solution, various clock error compensation, time information serial port output, and responding to user control instructions. The time scale synthesis module is used to calculate the clock difference between local time and system time. After adding digital filtering and fault-tolerant design, accurate synchronous time scale generation can be achieved. It can output second pulses (1PPS) with a synchronization accuracy better than 50ns with the coordinated universal time UTC time, and output the time information through the serial port in a certain format. For the second pulse output port, photoelectric isolation processing is added to improve the anti-interference and reliability, ensure the accuracy and stability of the time scale, and meet various time synchronization application requirements.

[0026] Among them, the data processing module also includes the following units:

[0027] Original observation extraction unit: responsible for corresponding timing interruption, collecting original observations, and completing pseudo-range measurement calculation;

[0028] Navigation message analysis unit: completes navigation message analysis, extracts satellite ephemeris information, time information and corresponding error parameter information;

[0029] Satellite orbit calculation unit: calculates satellite position and speed based on time information and ephemeris data;

[0030] Error model calculation unit: Based on time information and ephemeris data, it calculates the errors of ionosphere, troposphere and earth rotation;

[0031] System integrity detection unit: detects the health status and availability of satellite data based on the obtained ephemeris data to ensure the correctness of the information;

[0032] Positioning and speed calculation unit: According to time information and satellite orbit information, it calculates pseudo-range and uses Kalman filtering method to complete the receiver position and speed calculation function;

[0033] Satellite geometric precision factor calculation unit: Calculates the satellite geometric precision factor based on the coefficient matrix in the positioning solution process to evaluate the positioning accuracy.

[0034] Among them, the signal processing module can set the satellite number, frequency, Doppler frequency search interval, precision ranging code phase search interval and other parameters to be captured under the control of the data processing module; the loop parameters of various tracking loops (including frequency-locked loop, phase-locked loop, code loop) of the tracking channel can be programmed; the frequency of extraction of original observations can be configured; the signal processing module has 24 channels, which can track 12 B1 frequency points and 12 B2 frequency points satellite signals at the same time. After successfully capturing the specified navigation signal, the tracking channel can automatically complete the tracking and processing of the navigation signal. The signal processing module is a baseband signal processing module that is used for navigation and navigation. The baseband ...

[0035] Among them, the data processing module includes a navigation message parsing module, an original observation extraction module, a positioning solution module and a timing module. The navigation message parsing module stores the demodulated navigation message in a register through the signal processing module. When a subframe data is received, the navigation message reading interrupt is triggered, and the message data is analyzed in the navigation message parsing processing function. The original observation extraction module receives the satellite signal. When the observation quantity is ready in the FPGA, the DSP external interrupt is triggered to trigger the original observation extraction function. This function reads the register values ​​such as the channel state, random code phase, carrier phase, and carrier Doppler of each receiving channel, and calculates the pseudorange according to the extracted observation quantity. If the ephemeris information has been obtained at this time, the positioning solution can be started. The positioning solution module can first call the relevant error compensation processing module according to the ephemeris information parsed in the navigation message parsing data, and after performing corresponding calculations on various errors such as the ionosphere, troposphere, and the earth's rotation, the pseudorange is compensated, and then the least squares method or Kalman filtering method is used for positioning solution. The timing module is used to receive satellite signals according to the stored configuration or the control configuration instructions parsed by the receiving serial port data processing module, and configure the timing working mode according to whether the local position is known.

[0036] A method for time and frequency synchronization of an optical fiber ground-based timing system comprises the following steps:

[0037] Step 1: First, the time information and position information are displayed through the display and control unit, and the synchronous time stamp signal is output at the same time, and the time message data is transmitted to the main control machine through the external data interface, and the working parameters of the timing receiver are configured through the display and control unit or through the data interface;

[0038] Step 2: The system can complete the self-test of each functional module. If an abnormality occurs, the corresponding status prompt will be given. If all modules are detected normally, the clock unit will normally output the reference second pulse (1PPS), and the signal receiving unit will start searching and capturing satellite signals.

[0039] Step 3: The antenna of the timing receiver receives the RF signal broadcast by the navigation satellite, sends the received weak satellite signal to the pre-filter for filtering, and then amplifies the signal through the low-noise amplifier. The RF unit converts the signal into an intermediate frequency signal through secondary down-conversion and sends it to the signal processing module for signal demodulation;

[0040] Step 3: The A / D converter in the signal processing module samples and quantizes the intermediate frequency signal sent by the radio frequency unit, converts it into a digital intermediate frequency, completes the pseudo code capture and tracking of the satellite signal and the data despreading and demodulation operations, and then sends the decoded navigation message and the calculated observation value to the data processing module;

[0041] Step 4: After completing the relevant pseudo-range calculation, positioning solution, and various time error compensations through the data processing module, the local clock difference measurement value is obtained, the unadjusted second pulse deviation is obtained, and the time information is output through the serial port. The time scale synthesis module synchronizes the second pulse through the second pulse deviation and the local clock unit to achieve time synchronization.

[0042] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the attached claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention. Any figure mark in the claims should not be regarded as limiting the claims involved.

[0043] Other parts of the present invention not described in detail belong to the prior art and will not be described in detail here.

[0044] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An optical fiber ground-based timing system, characterized in that: The system includes: A power conversion unit, an antenna unit, a radio frequency unit, a timing unit, a local clock unit and a display control unit. The timing unit includes a signal processing module, a data processing module and a timing time mark synthesis module. The timing unit is used to receive optical fiber restrictions and perform time synchronization. The radio frequency unit down-converts and amplifies the RNSS signal from the antenna unit after low-noise amplification, and after AGC control, provides the signal processing module with an intermediate frequency signal that meets certain signal-to-noise ratio and amplitude requirements.

2. The optical fiber ground-based timing system according to claim 1, characterized in that: The power conversion unit is used to provide power for the system. The system uses 220V AC input externally, and the power used internally includes 12V and 5V DC power.

3. The optical fiber ground-based timing system according to claim 1, characterized in that: The antenna unit is used to receive the configured satellite signal. After low-noise amplification in the radio frequency unit, the signal enters the corresponding receiving radio frequency channel through the optical fiber cable to complete the signal down-conversion and intermediate frequency amplification processing.

4. The optical fiber ground-based timing system according to claim 1, characterized in that: The local clock unit is provided with a clock selection circuit, and uses an internal clock or an external reference clock input, thereby ensuring a high-precision and stable local time reference.

5. The optical fiber ground-based timing system according to claim 1, characterized in that: The signal processing module is responsible for baseband signal processing and completes the tasks of sampling, capturing, tracking, demodulating navigation messages, and calculating original observation quantities of navigation signals.

6. The optical fiber ground-based timing system according to claim 1, characterized in that: The data processing module is responsible for reading the original observation quantity and telegram information from the signal processing module, completing navigation telegram analysis, satellite orbit data smoothing filtering, satellite position calculation, pseudorange calculation, positioning solution, various clock error compensation, time information serial port output, and responding to user control command functions.

7. The optical fiber ground-based timing system according to claim 1, characterized in that: The time-scale synthesis module is used to calculate the clock difference between the local time and the system time. After adding digital filtering and fault-tolerant design, accurate synchronous time-scale generation is achieved. It can output second pulses with a synchronization accuracy better than 50ns with the Coordinated Universal Time (UTC) and output the time information through the serial port in a certain format.

8. The optical fiber ground-based timing system according to claim 1, characterized in that: The data processing module includes a navigation message parsing module, an original observation quantity extraction module, a positioning solution module and a timing module. The navigation message parsing module stores the demodulated navigation message in a register through a signal processing module, triggers a navigation message reading interrupt when a subframe data is received, and analyzes the message data in the navigation message parsing processing function.

9. The optical fiber ground-based timing system according to claim 1, characterized in that: The original observation quantity extraction module receives satellite signals. When the observation quantity is ready in the FPGA, the DSP external interrupt is triggered to trigger the original observation quantity extraction function. The positioning solution module can call the relevant error compensation processing module according to the ephemeris information analyzed in the navigation message analysis data, calculate the various errors of the ionosphere, troposphere, and earth rotation accordingly, compensate the pseudo-range, and then use the least squares method or Kalman filtering method to perform positioning solution. The timing module is used to receive satellite signals according to the stored configuration or the control configuration instructions analyzed by the receiving serial port data processing module according to the configuration instructions, and configure the timing working mode according to whether the local position is known.

10. A method for time and frequency synchronization of an optical fiber ground-based timing system, characterized in that: Applied to the system according to any one of claims 1 to 9 above, the method comprises the following steps: Step 1: First, the time information and position information are displayed through the display and control unit, and the synchronous time stamp signal is output at the same time, and the time message data is transmitted to the main control machine through the external data interface, and the working parameters of the timing receiver are configured through the display and control unit or through the data interface; Step 2: The system can complete the self-check of each functional module. If an abnormality occurs, the corresponding status prompt will be given. If all modules are detected normally, the clock unit will normally output the reference second pulse, and the signal receiving unit will start searching and capturing satellite signals. Step 3: The antenna of the timing receiver receives the RF signal broadcast by the navigation satellite, sends the received weak satellite signal to the pre-filter for filtering, and then amplifies the signal through the low-noise amplifier. The RF unit converts the signal into an intermediate frequency signal through secondary down-conversion and sends it to the signal processing module for signal demodulation; Step 3: The A / D converter in the signal processing module samples and quantizes the intermediate frequency signal sent by the radio frequency unit, converts it into a digital intermediate frequency, completes the pseudo code capture and tracking of the satellite signal and the data despreading and demodulation operations, and then sends the decoded navigation message and the calculated observation value to the data processing module; Step 4: After completing the relevant pseudo-range calculation, positioning solution, and various time error compensations through the data processing module, the local clock difference measurement value is obtained, the unadjusted second pulse deviation is obtained, and the time information is output through the serial port. The time scale synthesis module synchronizes the second pulse through the second pulse deviation and the local clock unit to achieve time synchronization.

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