A high-precision wireless time comparison method on the surface

Abstract

The present invention provides a high-precision surface wireless time comparison method that integrates pseudocode and carrier phase ranging technology, along with the principle of two-way time comparison, using pseudocode observations to resolve the problem of carrier integer ambiguity. This method does not require the individual determination of the integer ambiguity for each time comparison terminal; instead, it simply calculates the relative integer ambiguity of the carrier observations during the two-way time comparison process. This method requires fewer input conditions than traditional navigation receiver carrier integer ambiguity determination methods, is computationally inefficient, and is simple and feasible. The present invention effectively avoids the calculation of integer ambiguity during the relative calibration of the hardware delay of the carrier channel at the transceiver terminal, further improving the accuracy of time comparison. Furthermore, both the time comparison signal and the two-way comparison data are transmitted using the same wireless channel, eliminating the need for an additional data transmission link. This facilitates the miniaturization of the time comparison system and increases its application flexibility.

Description

Technical Field

[0001] The present invention relates to a wireless time comparison method, which is applicable to application scenarios on the ground or within 10 km from the ground and without obstruction. Background Art

[0002] High-precision time standards play a vital role in the development of a nation's science, technology, economy, and military sectors. Their applications extend across fundamental fields such as astronomy, geodynamics, and physics, as well as engineering and technical fields such as information transmission, power transmission and distribution, deep space exploration, navigation and positioning, weapons testing, earthquake monitoring, and metrology and testing. The transmission of high-precision time standards requires the technical support of high-precision time comparison methods. These methods are crucial for disseminating high-precision time standards to users and realizing their practical value.

[0003] Wired time comparison technology, due to the need to lay cables, suffers from poor mobility and limited application scenarios. Commonly used high-precision wireless time comparison technologies with accuracy on the order of tens of nanoseconds and above include satellite two-way time comparison and navigation satellite common view technology. However, satellite two-way time comparison technology requires leasing satellites and pre-establishing a two-way data transmission link, which is costly. Navigation satellite common view technology also requires establishing a data exchange link, relying on a wired network or other wireless communication equipment, which reduces system flexibility or increases complexity. Some research institutions have also used microwave links to establish ground-based wireless time comparison systems, achieving time comparisons on the order of several nanoseconds. However, due to the accuracy of the pseudo-code observations themselves, the time comparison results fluctuate significantly, with peak-to-peak values ​​approaching tens of nanoseconds. This method has certain shortcomings for users with high stability requirements. Summary of the Invention

[0004] In order to overcome the shortcomings of the existing technology, the time comparison method provided by the present invention utilizes a wireless network to transmit and receive time comparison signals and data, offsets the influence of spatial link delay through the principle of two-way time comparison, uses pseudo-code observations to resolve the carrier integer ambiguity, and finally uses carrier phase observations to calculate the clock difference between the two locations. The stability of the time comparison reaches the order of ten picoseconds, and the accuracy is at the nanosecond level.

[0005] The technical solution adopted by the present invention to solve the technical problem includes the following steps:

[0006] 1) Perform relative zero-baseline transmit / receive channel hardware delay calibration on the wireless time comparison terminals of time comparison master station A and time comparison slave station B. Generate four phase-aligned time-frequency reference signals, two of which are connected to the time comparison terminals of stations A and B, and the other two are connected to the time interval counter to measure the time difference. Collect pseudo-code, carrier observation, and time interval counter measurement data from the two terminals according to the set duration.

[0007] 2) Calculate the relative hardware delay of the pseudo code channel using the pseudo code observations and time interval counter data of the two terminals and its average value

[0008] 3) Calculate the relative hardware delay of the carrier channel using the carrier observation data and time interval counter data of the two terminals and its average value

[0009] 4) Two wireless time comparison terminals are installed at stations A and B respectively, and each receives the time-frequency reference signals of stations A and B. Under the control of their own time-frequency references, the wireless time comparison terminals of the two stations send time comparison signals to each other. After receiving the signals from each other, the wireless time comparison terminals of the two stations generate pseudo-code and carrier observation values, and send the locally generated observation data along with the time comparison signal to the other station. The terminal at station B collects the pseudo-code observation value P generated by the station. B And the pseudo code observation quantity P sent by station A A , and collect the carrier observation quantity φ generated by this station B and the carrier observation value φ sent by station A A ;

[0010] 5) After the tracking loops of the two terminals of the wireless time comparison link are stable, the pseudo-code observation data at the next second t0 is used to calculate the clock difference σ(t0) between the two stations at that time;

[0011] 6) Determine the relative integer ambiguity NN of the two-way time comparison carrier observations between the two stations;

[0012] AB

[0013] 7) Under the premise that the time comparison terminals of stations A and B do not lose lock, use the relative integer ambiguity calculation results of step 6) and the carrier observation data collected in step 4) to calculate the clock difference σt of the real-time two-way time comparison between the two stations. B-A .

[0014] The step 1) places the wireless time comparison terminals of the time comparison master station A and the time comparison slave station B in the same location to perform relative calibration of the zero-baseline transceiver channel hardware delay; uses a distribution amplifier to generate four phase-consistent time-frequency reference signals, two of which are connected to the time comparison terminals of stations A and B through cables of equal length, and the other two are connected to time interval counters through cables of equal length to measure the time difference.

[0015] The step 1) collects the pseudo codes, carrier observation values ​​and time interval counter measurement data of the two terminals, and the measurement time is ten minutes or more.

[0016] The step 2) uses the pseudo code observations and time interval counter data of the two terminals to calculate the relative hardware delay of the pseudo code channel Among them, P A and P B are the pseudo-code observation quantities generated by terminals A and B respectively, σ is the measurement result of the time interval counter at the same moment, and c is the speed of light.

[0017] Step 3) uses the carrier observations and time interval counter data of the two terminals to calculate the relative hardware delay of the carrier channel where φ A and φ B The carrier observations generated by terminals A and B, respectively, and the relative hardware delay of the carrier channel Contains the difference in carrier phase ambiguity between terminals A and B

[0018] Step 5) uses the pseudo-code observation data at the next second t0 to calculate the clock difference between the two stations at that time

[0019] Step 6) determines the relative integer ambiguity of the two-way time comparison carrier observations of the two stations

[0020] Step 7) calculates the clock difference of the two stations in real-time two-way time comparison

[0021] If the time comparison terminal tracking loop of at least one station is unlocked in step 7), the process returns to step 5) after all the time comparison terminal tracking loops are stabilized again.

[0022] The present invention can be extended to a master station A and multiple first-level slave stations B for time comparison, and can also be extended to treating the first-level slave station B as a master station and comparing it with the second-level slave station, thereby realizing time comparison between multiple cascade nodes.

[0023] The beneficial effects of the present invention are as follows: the present invention comprehensively applies pseudo-code and carrier phase ranging technology, and the principle of two-way time comparison, and uses pseudo-code observations to solve the problem of carrier integer ambiguity. This method does not need to determine the integer ambiguity of each time comparison terminal separately. It only needs to calculate the relative integer ambiguity of the carrier observation in the two-way time comparison process. It requires fewer input conditions than the traditional navigation receiver carrier integer ambiguity determination method, and has a small amount of calculation, which is simple and feasible. Secondly, the present invention effectively avoids the calculation of integer ambiguity in the relative calibration process of the hardware delay of the carrier channel of the transceiver terminal, and further improves the accuracy of time comparison. Combining the above technical means, the time comparison stability achieved by the present invention reaches the order of ten picoseconds, and the accuracy is in the order of nanoseconds, which is better than the performance of time comparison using pseudo-code alone. In addition, the time comparison signal and the two-way comparison data are both transmitted using the same wireless channel, without the need to build an additional data transmission link, which is conducive to the miniaturization of the time comparison system and increases the application flexibility of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a structural diagram of the wireless time comparison terminal;

[0025] Figure 2 It is the relative delay calibration diagram of the two terminal receiving and transmitting channels;

[0026] Figure 3 This is the principle diagram of one-way wireless time comparison and clock error measurement;

[0027] Figure 4 This is the wireless two-way time comparison result after the pseudo code assisted carrier. DETAILED DESCRIPTION

[0028] The present invention will be further described below with reference to the accompanying drawings and examples. The present invention includes but is not limited to the following examples.

[0029] Taking the time comparison between stations A and B as an example, station A is the time comparison master station and station B is the time comparison slave station. Both stations A and B are equipped with wireless time comparison terminal devices that can transmit and receive wireless signals. The present invention includes the following steps 1 to 8:

[0030] Step 1. Place the wireless time comparison terminals of stations A and B at the master station A, use a pulse distribution amplifier to generate four phase-matched 1PPS pulse signals, and use a frequency distribution amplifier to generate four phase-matched 10MHz signals. Two 1PPS pulse signals are connected to the time comparison terminals of stations A and B through cables of equal length, and the other two 1PPS pulse signals are connected to the time interval counter through cables of equal length for time difference measurement. The four 10MHz signals are respectively sent to the time comparison terminal and the time interval counter through cables of equal length. The two terminals remain stationary, and the two sets of transmitting and receiving antennas are about 1 meter apart. Collect about 10 minutes of pseudo code, carrier observation and time interval counter measurement data;

[0031] Step 2. Calculate the relative hardware delay of the pseudo code channel The physical meaning is the pseudo code transmission channel delay of the A station terminal + the pseudo code receiving channel delay of the B station terminal - the pseudo code transmission channel delay of the B station terminal - the pseudo code receiving channel delay of the A station terminal. The calculation formula is And calculate the statistical mean

[0032] Step 3. Calculate the relative hardware delay of the carrier channel The physical meaning of is the carrier transmission channel delay of the terminal A + the carrier receiving channel delay of the terminal B - the carrier transmission channel delay of the terminal B - the carrier receiving channel delay of the terminal A. The calculation formula is: And calculate the statistical mean

[0033] Step 4. Install two wireless time comparison terminals at stations A and B, with the distance between them no more than 1 km. The two terminals receive the time reference signals from stations A and B, including 10 MHz and 1PPS pulse signals. Place the two transceiver antennas in an open area to ensure there is no obstruction between them.

[0034] Step 5. The B-station terminal collects the pseudo-code observation quantity P generated by the station B And the pseudo code observation quantity P sent by station A A , and collect the carrier observation quantity φ generated by this station B and the carrier observation value φ sent by station A A , the data frequency is 1 second;

[0035] Step 6. Observe the wireless time comparison monitoring software at station B. After the tracking loop indicators of the two terminals show stable tracking, extract the pseudo-code observation data at time t0 and calculate the clock difference between the two stations at that time. The calculation formula is:

[0036] Step 7. Using the calculation results of steps 3) and 6) and the carrier observation data at time t0, calculate the relative integer ambiguity of the two-way time comparison carrier observations of the two stations. The calculation formula is:

[0037] Step 8. Extract the tracking loop status data of the two terminals and determine whether the loop has lost lock from time t0 to the calculation time. If not, use the relative integer ambiguity calculation result of step 7), the carrier observation data collected in step 5), and the carrier channel relative hardware delay data calculated in step 3 to calculate the clock difference of the real-time two-way time comparison between the two stations. The calculation formula is: If the tracking loop of at least one terminal loses lock, repeat steps 6 to 8 after all loops are stable again.

[0038] As can be seen from the above implementation steps, the implementation process of the proposed high-precision surface wireless time comparison method primarily includes four steps: relative delay calibration of the transceiver channels between two terminals, data acquisition, carrier-to-carrier ambiguity calculation, and real-time clock difference calculation. Relative delay calibration of the transceiver channels is a preliminary step in high-precision time comparison, and the calibration results serve as input for subsequent time comparison calculations. If the tracking loop remains locked, the carrier-to-carrier ambiguity only needs to be calculated once, but recalculation is required if the loop loses lock.

[0039] As can be seen from the above embodiments, the main feature of the present invention is that it utilizes the surface environment, where wireless signals do not pass through the ionosphere during transmission. Except for the hardware delay, the delay components of the pseudo-code and carrier observation equations are equal. Under the premise of calibrating the hardware delay, the pseudo-code observation can be used to assist the carrier observation to determine the integer ambiguity, thereby improving the stability of time comparison.

Claims

1. A high-precision wireless time comparison method for the surface, characterized in that: The following steps are involved: 1) Perform relative zero-baseline transmit / receive channel hardware delay calibration on the wireless time comparison terminals of time comparison master station A and time comparison slave station B. Generate four phase-aligned time-frequency reference signals, two of which are connected to the time comparison terminals of stations A and B, and the other two are connected to the time interval counter to measure the time difference. Collect pseudo-code, carrier observation, and time interval counter measurement data from the two terminals according to the set duration. 2) Calculate the relative hardware delay of the pseudo code channel using the pseudo code observations and time interval counter data of the two terminals and its average value 3) Calculate the relative hardware delay of the carrier channel using the carrier observation data and time interval counter data of the two terminals and its average value 4) Two wireless time comparison terminals are installed at stations A and B respectively, and each receives the time-frequency reference signals of stations A and B. Under the control of their own time-frequency references, the wireless time comparison terminals of the two stations send time comparison signals to each other. After receiving the signals from each other, the wireless time comparison terminals of the two stations generate pseudo-code and carrier observation values, and send the locally generated observation data along with the time comparison signal to the other station. The terminal at station B collects the pseudo-code observation value P generated by the station. B And the pseudo code observation quantity P sent by station A A , and collect the carrier observation quantity φ generated by this station B and the carrier observation value φ sent by station A A ; 5) After the tracking loops of the two terminals of the wireless time comparison link are stable, the pseudo-code observation data at the next second t0 is used to calculate the clock difference σ(t0) between the two stations at that time; 6) Determine the relative integer ambiguity N of the two-way time comparison carrier observations between the two stations A -N B ; 7) Under the premise that the time comparison terminals of stations A and B do not lose lock, use the relative integer ambiguity calculation results of step 6) and the carrier observation data collected in step 4) to calculate the clock difference σt of the real-time two-way time comparison between the two stations. B-A .

2. The surface high-precision wireless time comparison method according to claim 1, characterized in that: The step 1) places the wireless time comparison terminals of the time comparison master station A and the time comparison slave station B in the same location to perform a relative calibration of the zero-baseline transceiver channel hardware delay; A distribution amplifier is used to generate four phase-coherent time-frequency reference signals. Two of them are connected to the time comparison terminals of stations A and B through cables of equal length, and the other two are connected to the time interval counter through cables of equal length for time difference measurement.

3. The surface high-precision wireless time comparison method according to claim 1, characterized in that: The step 1) collects the pseudo codes, carrier observation values ​​and time interval counter measurement data of the two terminals, and the measurement time is ten minutes or more.

4. The surface high-precision wireless time comparison method according to claim 1, characterized in that: The step 2) uses the pseudo code observations and time interval counter data of the two terminals to calculate the relative hardware delay of the pseudo code channel Among them, P A and P B are the pseudo-code observation quantities generated by terminals A and B respectively, σ is the measurement result of the time interval counter at the same moment, and c is the speed of light.

5. The surface high-precision wireless time comparison method according to claim 1, characterized in that: Step 3) uses the carrier observations and time interval counter data of the two terminals to calculate the relative hardware delay of the carrier channel where φ A and φ B The carrier observations generated by terminals A and B, respectively, and the relative hardware delay of the carrier channel Contains the difference in carrier phase ambiguity between terminals A and B 6. The surface high-precision wireless time comparison method according to claim 1, characterized in that: Step 5) uses the pseudo-code observation data at the next second t0 to calculate the clock difference between the two stations at that time 7. The surface high-precision wireless time comparison method according to claim 1, characterized in that: Step 6) determines the relative integer ambiguity of the two-way time comparison carrier observations of the two stations 8. The high-precision wireless time comparison method for the surface of the Earth according to claim 1, characterized in that: Step 7) calculates the clock difference of the two stations in real-time two-way time comparison 9. The surface high-precision wireless time comparison method according to claim 1, characterized in that: If the time comparison terminal tracking loop of at least one station is unlocked in step 7), the process returns to step 5) after all the time comparison terminal tracking loops are stabilized again.

10. The surface high-precision wireless time comparison method according to claim 1, characterized in that: It can be expanded to a master station A and multiple first-level slave stations B for time comparison, and can also be expanded to treat the first-level slave station B as the master station and compare it with the second-level slave station, thereby realizing time comparison between multiple cascade nodes.

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