Time service signal protection method and time service protection system using radio controlled clock

Abstract

The invention provides a time service signal protection method and a time service protection system using a radio controlled clock. The method comprises the following steps: monitoring whether a time signal received by a GNSS (Global Navigation Satellite System) receiver is interfered or not; if interference occurs, ephemeris data of a satellite are obtained through a GNSS receiver, and a reference clock signal is obtained through a radio controlled clock tame correction crystal oscillator; generating an analog satellite signal based on the ephemeris data and the reference clock signal; and outputting the simulated satellite signal to satellite time service clock equipment. When the time service protection equipment provided by the invention is interfered, accurate satellite signal output is completed by means of the self-generated simulation satellite signal, and the accurate satellite signal output is completed by using the wave clock, so that higher precision, stability and anti-interference performance are achieved.

Description

Technical Field

[0001] The invention belongs to the field of radio signals, and in particular relates to a timing signal protection method and a timing protection system using a radio-wave clock. Background Art

[0002] The Global Navigation Satellite System (GNSS) is an air-based radio navigation and positioning system that can provide users with all-weather three-dimensional coordinates, speed and time information at any location on the Earth's surface or in near-Earth space. Users receive satellite signals through satellite timing clock equipment to achieve GNSS timing. GNSS timing is characterized by high accuracy, high cost-effectiveness, easy installation, and global availability, and is usually the preferred timing technology.

[0003] However, during the transmission of satellite signals, interference signals may be generated in various links of the transmission link due to environmental factors, equipment or human factors. Interference signals will affect the accuracy and synchronization of the time information provided by the satellite signals, posing a safety hazard.

[0004] Although there are anti-interference solutions in the prior art, most of them are adaptive anti-interference processing of satellite signals, etc., which may not really play an anti-interference role when encountering highly deceptive interference signals. Summary of the invention

[0005] The present invention proposes a timing signal protection method and a timing protection system using a radio-wave clock, which uses a radio-wave clock to replace a crystal oscillator and can provide accurate and synchronous time information through monitoring, comparison and self-correction mechanisms regardless of whether the satellite signal is interfered with.

[0006] To achieve the above object, the technical solution of the present invention is achieved as follows: A method for protecting a timing signal using a radio-controlled clock, comprising: S1. Monitor whether the satellite signals received by the Global Navigation Satellite System (GNSS) receiver are interfered with; S2. If interference occurs, the satellite's ephemeris data is obtained through the GNSS receiver, and then the reference clock signal is obtained by correcting the crystal oscillator through the radio-controlled clock. S3, generating a simulated satellite signal based on the ephemeris data and the reference clock signal; S4. Output the simulated satellite signal to the satellite timing clock device to realize satellite timing.

[0007] Furthermore, in step S1, the method for monitoring whether the satellite signal is interfered includes: The carrier-to-noise ratio of the signal received by the GNSS receiver is compared with the set carrier-to-noise ratio threshold. A carrier-to-noise ratio lower than the threshold indicates that the signal is interfered.

[0008] Furthermore, in step S2, the ephemeris data includes orbit information, position, speed, and reference time of each satellite.

[0009] Furthermore, in step S2, the method of obtaining a reference clock signal by taming and correcting a crystal oscillator through a radio-controlled clock includes: S201, radio-controlled clock receives time signal: the radio-controlled clock receives low-frequency radio time code signal from the national standard time station; S202, extracting 1PPS signal: the radio-controlled clock extracts 1PPS signal from the received low-frequency radio time code signal; S203, generating a local crystal oscillator signal; the local crystal oscillator continuously generates a clock signal; S204, comparison and error detection: comparing the 1PPS signal extracted by the radio-controlled clock with the 1PPS signal generated by the local crystal oscillator, and detecting the frequency deviation of the local crystal oscillator; S205, converting the error into a control signal: the error is converted into a binary number and then converted into an analog voltage signal; S206, applying a correction voltage to a local crystal oscillator: the analog voltage signal is applied to a control pin of the local crystal oscillator to fine-tune the frequency of the crystal oscillator to reduce errors; S207, frequency and phase locking: Continuously monitor and adjust until the 1PPS signal generated by the local crystal oscillator is gradually locked to the same as the 1PPS signal of the radio-controlled clock, thereby achieving frequency and phase synchronization.

[0010] Furthermore, in step S3, the method for generating a simulated satellite signal includes: S301, receiving a reference clock signal: receiving a 1PPS signal generated by the local crystal oscillator through a signal simulation device as a reference clock of a phase-locked loop PLL inside the signal simulation device; S302, internal clock generation: the signal simulation device generates a stable high-frequency clock signal based on the received 1PPS signal through an internal phase-locked loop PLL; S303, signal modulation and coding: the signal simulation device uses the high-frequency clock signal as a reference to generate a simulated satellite signal according to the GNSS standard provided by the ephemeris data; S304, frequency conversion and output: the signal simulation device undergoes frequency conversion and outputs the final simulated satellite signal of the target frequency band.

[0011] On the other hand, the present invention also proposes a timing protection system using a radio-wave clock, comprising: a GNSS receiver, a radio-wave clock receiver, a control center, a signal simulation device, and a signal output switch; the GNSS receiver is respectively connected to the signal output switch, the signal simulation device, and the control center; the radio-wave clock receiver is connected to the control center, the control center is also connected to the signal simulation device and the signal output switch, the signal simulation device is also connected to the signal output switch, and the signal output switch is connected to a satellite timing clock device; The GNSS receiver receives satellite signals through a satellite signal receiving antenna and sends them to the control center and the signal output switch; the radio-controlled clock receiver includes a radio-controlled clock and a local crystal oscillator connected to the radio-controlled clock signal. The radio-controlled clock receives national standard time station signals through the radio-controlled clock signal receiving antenna and tames and corrects the local crystal oscillator to obtain a reference clock signal; the control center monitors whether the satellite signals received by the GNSS receiver are interfered with. If no interference is received, the control center controls the signal output switch to output satellite signals to the satellite timing clock device. If interference is received, the control center receives the reference clock signal of the radio-controlled clock receiver and sends it to the signal simulation device. The signal simulation device simultaneously receives satellite ephemeris data acquired by the GNSS receiver, and generates a simulated satellite signal based on the ephemeris data and the reference clock signal, and sends it to the signal output switch. The control center controls the signal output switch to output the simulated satellite signal to the satellite timing clock device.

[0012] Furthermore, the control center includes: Monitoring module: determines whether the satellite signal of the GNSS receiver is interfered by the signal-to-noise ratio parameter; Signal flow control module: controls the signal output switch to perform signal switching selection, thereby controlling whether the satellite signal sent to the satellite timing clock device is the satellite signal of the GNSS receiver or the simulated satellite signal generated by the signal simulation device; Reference clock signal module: receives the reference clock signal of the radio-controlled clock receiver and sends it to the signal simulation device.

[0013] Furthermore, the radio-controlled clock receiver specifically includes: the radio-controlled clock receives a low-frequency radio time code signal from a national standard time station through a radio-controlled clock signal receiving antenna, and extracts a 1PPS signal from the received low-frequency radio time code signal, compares the extracted 1PPS signal with the 1PPS signal generated by a local crystal oscillator, detects the frequency deviation of the local crystal oscillator, converts the frequency deviation into a binary number, and then converts it into an analog voltage signal, applies the analog voltage signal to a control pin of the local crystal oscillator, and fine-tunes the frequency of the crystal oscillator to reduce the error; and continues to adjust until the 1PPS signal generated by the local crystal oscillator is gradually locked to be consistent with the 1PPS signal of the radio-controlled clock, thereby achieving frequency and phase synchronization.

[0014] Furthermore, the signal simulation device comprises: A reference clock signal receiving unit: receiving a 1PPS signal generated by the local crystal oscillator through a signal simulation device as a reference clock of a phase-locked loop PLL inside the signal simulation device; Internal clock generation unit: The signal simulation device generates a stable high-frequency clock signal based on the received 1PPS signal through the internal phase-locked loop PLL; Signal modulation and coding unit: The signal simulation device uses the high frequency clock signal as a reference to generate a simulated satellite signal according to the GNSS standard provided by the ephemeris data; Frequency conversion and output unit: The signal simulation device undergoes frequency conversion and outputs the final simulated satellite signal in the target frequency band.

[0015] Furthermore, the signal simulation device includes: an Analog Devices AD9361 chip or an Analog Instruments USRP device or a combination of an NVIDIA Jetson AGX Xavier processor and an Ettus Research B210 platform.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. When the satellite signal is interfered with, the timing protection device proposed by the present invention relies on the simulated satellite signal generated by itself to complete the accurate timing signal (simulated satellite signal) output. The simulated satellite signal output completed by the radio wave clock has higher accuracy, stability and anti-interference.

[0017] 2. The present invention can provide accurate and synchronous satellite timing information regardless of interference through monitoring, comparison and self-correction mechanisms. When interference occurs, measures can be taken to maintain time synchronization to ensure the normal operation of the system and the accuracy of the data. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a flow chart of a timing signal protection method according to an embodiment of the present invention.

[0019] Figure 2 The structure and working process diagram of the timing protection system of the embodiment of the present invention.

[0020] Figure 3 It is a schematic diagram of the process of taming and correcting the local crystal oscillator according to an embodiment of the present invention.

[0021] Figure 4 Schematic diagram of the working process of the signal simulation device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0022] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0023] In order to make the purpose and features of the present invention more obvious and understandable, the specific implementation methods of the present invention are further described below in conjunction with the accompanying drawings.

[0024] The present invention proposes a method for protecting the timing signal using a radio-controlled clock, such as Figure 1 As shown, including: S1. Monitor whether the satellite signals received by the Global Navigation Satellite System (GNSS) receiver are interfered with; S2. If interference occurs, the satellite's ephemeris data is obtained through the GNSS receiver, and then the reference clock signal is obtained by correcting the crystal oscillator through the radio-controlled clock. S3, generating a simulated satellite signal based on the ephemeris data and the reference clock signal; S4. Output the simulated satellite signal to the satellite timing clock device to realize satellite timing.

[0025] Based on the above method, a timing protection system is proposed. Figure 2 As shown, including: A satellite signal receiving antenna and a GNSS receiver connected thereto, and a radio-wave clock signal receiving antenna and a radio-wave clock receiver connected thereto; the GNSS receiver receives satellite signals via the satellite signal receiving antenna, and the radio-wave clock receiver receives national standard time station signals via the radio-wave clock signal receiving antenna; The GNSS receiver is connected to one of the signal output switches, and sends the received satellite time signal to the satellite timing clock device through the signal output switch to complete satellite timing.

[0026] The other way of the signal output switch is connected to the signal simulation device, which can generate a simulated satellite signal and send the received satellite time signal to the satellite timing clock device through the signal output switch to complete the satellite timing.

[0027] The signal output switch is connected to the control center, and the control center controls the signal output switch to switch, so as to control whether the signal output switch sends a satellite signal or a simulated satellite signal to the satellite timing clock device.

[0028] The signal simulation device is connected to the GNSS receiver to receive the ephemeris data required to generate the simulated satellite signal; the signal simulation device is also connected to the control center to receive the reference clock signal from the radio clock receiver through the control center.

[0029] In addition, the control center of the present invention is connected to the GNSS receiver, the radio clock receiver, and the signal output switch. The control center implements the following functions through its microcontroller or FPGA: (1) Monitor the status of satellite signals, especially whether the GNSS timing signal is interfered with, mainly through parameters such as signal carrier-to-noise ratio. The control center sets a carrier-to-noise ratio threshold for the GNSS signal, which is usually adjusted according to system requirements and environmental conditions. Compare the actual carrier-to-noise ratio of the GNSS signal with the set threshold. If the carrier-to-noise ratio is lower than the threshold, it indicates that the GNSS signal may be interfered with.

[0030] (2) Control the switching of the signal output switch to control the direction of the signal to ensure that the timing signal is switched to the simulated satellite signal generated by the signal simulation device according to the predefined logic.

[0031] (3) Observe the error between GNSS timing and radio-controlled clock to evaluate the error and calibrate the time signal. Receive the time reference clock signal from the radio-controlled clock receiver and provide it to the signal simulation device.

[0032] In this embodiment, the radio-controlled clock receiver includes a radio-controlled clock and a local crystal oscillator connected to the radio-controlled clock signal. The radio-controlled clock receives the national standard time station signal through the radio-controlled clock signal receiving antenna and trains and corrects the local crystal oscillator to obtain a reference clock signal. The specific process of training and correcting the local crystal oscillator is as follows: Figure 3 As shown, the description is as follows: 1. Radio-controlled clocks receive time signals: Radio-controlled clocks receive low-frequency radio time code signals from standard time stations through built-in radio-controlled clock signal receiving antennas. The low-frequency radio time code signals are usually at 60kHz or other low-frequency bands and contain accurate time information and frequency information.

[0033] 2. Extract 1PPS signal: The radio-controlled clock decodes the signal and extracts one pulse per second (1PPS signal) as a reference signal.

[0034] 3. Local crystal oscillator signal generation: The local crystal oscillator (OCXO is used in this embodiment) generates a stable clock signal, but its frequency may drift slightly due to environmental factors (such as temperature changes, power supply fluctuations, etc.).

[0035] 4. Comparison and error detection: Compare the 1PPS signal of the radio-controlled clock with the 1PPS signal of the local crystal oscillator through a counter or comparator. Detect the difference between the two signals to determine the frequency deviation of the crystal oscillator.

[0036] 5. Error conversion to control signal: The detected frequency error is converted into a binary number and converted into an analog voltage signal through a digital-to-analog converter (DAC). This process usually uses a digital phase-locked loop (DPLL) or other digital control technology.

[0037] 6. Correction voltage applied to local crystal oscillator: The generated analog voltage signal is applied to the control pin of the local crystal oscillator, usually by adjusting the control voltage of the OCXO. This adjustment voltage will fine-tune the frequency of the crystal oscillator to reduce the detected error.

[0038] 7. Frequency and phase lock: Through continuous monitoring and adjustment, the 1PPS signal of the local crystal oscillator gradually synchronizes with the 1PPS signal of the radio-controlled clock. Finally, the frequency and phase are locked to ensure that the frequency signal output by the local crystal oscillator is consistent with the standard frequency.

[0039] The signal simulation device is described as follows: 1. The Analog Devices AD9361 chip can be used. This is a high-performance RF transceiver that supports a wide frequency range and modulation modes. It can be used to generate and receive high-precision radio signals and is suitable for GNSS signal simulation.

[0040] 2. You can use the National Instruments USRP (Universal Software RadioPeripheral), which can generate and receive various radio signals, including GNSS signals, through software-defined radio (SDR) technology. USRP devices usually have built-in high-performance RF front-end chips, such as Analog Devices' AD9361 or similar chips.

[0041] 3. You can use a combination of the NVIDIA Jetson AGX Xavier processor and the Ettus Research B210 platform. This combination takes advantage of a high-performance embedded processor (Jetson AGX Xavier) and a high-performance SDR platform (B210) to generate and process complex GNSS signals through software.

[0042] In this embodiment, Analog Devices AD9361 chip is used as the signal simulation device. Figure 4 The workflow is briefly described as follows: 1. Receive the reference clock signal: AD9361 receives the 1PPS signal of the local crystal oscillator (the corrected reference clock signal from the radio clock receiver) as the reference clock of the internal high-precision phase-locked loop (PLL).

[0043] 2. Internal clock generation: PLL generates a stable high-frequency clock signal (e.g. 10MHz) based on the 1PPS signal.

[0044] 3. Signal modulation and coding: Using the high-frequency clock signal as a reference, AD9361 generates a GNSS simulation signal, i.e., a simulated satellite signal, according to the GNSS standard in the ephemeris data. This step includes BPSK / QPSK modulation of the signal and adding navigation message coding.

[0045] 4. Frequency conversion and output: The generated analog satellite signal is frequency converted and output to the target frequency band (e.g. 1575.42MHz in the L1 band) as the analog satellite signal that is ultimately sent to the satellite timing clock device.

[0046] The use process of the timing protection system of the present invention is as follows: 1. Uninterrupted state: Figure 2 As shown by the solid arrow, when the control center continuously detects that the satellite signal is not interfered, the control center controls the signal output switch to stably output the satellite signal transmitted by the GNSS receiver to the timing clock device; 2. Interference state: After the control center determines that the satellite signal is interfered, the control center controls the signal output switch to output the simulated satellite signal. The simulated satellite signal is simulated and generated by the signal simulation device based on the ephemeris data and the reference clock signal of the radio clock, so that the simulated satellite signal is highly synchronized with the standard time. (As indicated by the dotted arrow in the figure).

[0047] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for protecting a timing signal using a radio-controlled clock, characterized in that: include: S1. Monitor whether the satellite signals received by the Global Navigation Satellite System (GNSS) receiver are interfered with; S2. If interference occurs, the satellite's ephemeris data is obtained through the GNSS receiver, and then the reference clock signal is obtained by correcting the crystal oscillator through the radio-controlled clock. S3, generating a simulated satellite signal based on the ephemeris data and the reference clock signal; S4. Output the simulated satellite signal to the satellite timing clock device to realize satellite timing.

2. The method for protecting the timing signal using a radio-controlled clock according to claim 1, characterized in that: In step S1, the method for monitoring whether the satellite signal is interfered includes: The carrier-to-noise ratio of the signal received by the GNSS receiver is compared with the set carrier-to-noise ratio threshold. A carrier-to-noise ratio lower than the threshold indicates that the signal is interfered.

3. The timing signal protection method using a radio-controlled clock according to claim 1, characterized in that: In step S2, the ephemeris data includes orbit information, position, speed, and reference time of each satellite.

4. The timing signal protection method using a radio-controlled clock according to claim 1, characterized in that: In step S2, the method of obtaining a reference clock signal by taming and correcting a crystal oscillator through a radio-controlled clock includes: S201, radio-controlled clock receives time signal: the radio-controlled clock receives low-frequency radio time code signal from the national standard time station; S202, extracting 1PPS signal: the radio-controlled clock extracts 1PPS signal from the received low-frequency radio time code signal; S203, generating a local crystal oscillator signal; the local crystal oscillator continuously generates a clock signal; S204, comparison and error detection: comparing the 1PPS signal extracted by the radio-controlled clock with the 1PPS signal generated by the local crystal oscillator, and detecting the frequency deviation of the local crystal oscillator; S205, converting the error into a control signal: the error is converted into a binary number and then converted into an analog voltage signal; S206, applying a correction voltage to a local crystal oscillator: the analog voltage signal is applied to a control pin of the local crystal oscillator to fine-tune the frequency of the crystal oscillator to reduce errors; S207, frequency and phase locking: Continuously monitor and adjust until the 1PPS signal generated by the local crystal oscillator is gradually locked to the same as the 1PPS signal of the radio-controlled clock, thereby achieving frequency and phase synchronization.

5. The method for protecting the timing signal using a radio-controlled clock according to claim 4, characterized in that: In step S3, the method for generating a simulated satellite signal includes: S301, receiving a reference clock signal: receiving a 1PPS signal generated by the local crystal oscillator through a signal simulation device as a reference clock of a phase-locked loop PLL inside the signal simulation device; S302, internal clock generation: the signal simulation device generates a stable high-frequency clock signal based on the received 1PPS signal through an internal phase-locked loop PLL; S303, signal modulation and coding: the signal simulation device uses the high-frequency clock signal as a reference to generate a simulated satellite signal according to the GNSS standard provided by the ephemeris data; S304, frequency conversion and output: the signal simulation device undergoes frequency conversion and outputs the final simulated satellite signal of the target frequency band.

6. A time protection system using a radio-controlled clock, characterized in that: include: GNSS receiver, radio-controlled clock receiver, control center, signal simulation device, signal output switch; The GNSS receiver is respectively connected to a signal output switch, a signal simulation device, and a control center; the radio clock receiver is connected to the control center, the control center is also connected to the signal simulation device and the signal output switch, the signal simulation device is also connected to the signal output switch, and the signal output switch is connected to a satellite timing clock device; The GNSS receiver receives satellite signals through a satellite signal receiving antenna and sends them to the control center and the signal output switch; the radio-controlled clock receiver includes a radio-controlled clock and a local crystal oscillator connected to the radio-controlled clock signal. The radio-controlled clock receives national standard time station signals through the radio-controlled clock signal receiving antenna and tames and corrects the local crystal oscillator to obtain a reference clock signal; the control center monitors whether the satellite signals received by the GNSS receiver are interfered with. If no interference is received, the control center controls the signal output switch to output satellite signals to the satellite timing clock device. If interference is received, the control center receives the reference clock signal of the radio-controlled clock receiver and sends it to the signal simulation device. The signal simulation device simultaneously receives satellite ephemeris data acquired by the GNSS receiver, and generates a simulated satellite signal based on the ephemeris data and the reference clock signal, and sends it to the signal output switch. The control center controls the signal output switch to output the simulated satellite signal to the satellite timing clock device.

7. The timing protection system using a radio-controlled clock according to claim 6, characterized in that: The control center includes: Monitoring module: determines whether the satellite signal of the GNSS receiver is interfered by the signal-to-noise ratio parameter; Signal flow control module: controls the signal output switch to perform signal switching selection, thereby controlling whether the satellite signal sent to the satellite timing clock device is the satellite signal of the GNSS receiver or the simulated satellite signal generated by the signal simulation device; Reference clock signal module: receives the reference clock signal of the radio-controlled clock receiver and sends it to the signal simulation device.

8. The timing protection system using a radio-controlled clock according to claim 6, characterized in that: The radio-controlled clock receiver specifically includes: the radio-controlled clock receives a low-frequency radio time code signal from a national standard time station through a radio-controlled clock signal receiving antenna, extracts a 1PPS signal from the received low-frequency radio time code signal, compares the extracted 1PPS signal with the 1PPS signal generated by a local crystal oscillator, detects the frequency deviation of the local crystal oscillator, converts the frequency deviation into a binary number, and then converts it into an analog voltage signal, applies the analog voltage signal to a control pin of the local crystal oscillator, and fine-tunes the frequency of the crystal oscillator to reduce the error; and continues to adjust until the 1PPS signal generated by the local crystal oscillator is gradually locked to be consistent with the 1PPS signal of the radio-controlled clock, thereby achieving frequency and phase synchronization.

9. The timing protection system using a radio-controlled clock according to claim 6, characterized in that: The signal simulation device comprises: A reference clock signal receiving unit: receiving a 1PPS signal generated by the local crystal oscillator through a signal simulation device as a reference clock of a phase-locked loop PLL inside the signal simulation device; Internal clock generation unit: The signal simulation device generates a stable high-frequency clock signal based on the received 1PPS signal through the internal phase-locked loop PLL; Signal modulation and coding unit: The signal simulation device uses the high frequency clock signal as a reference to generate a simulated satellite signal according to the GNSS standard provided by the ephemeris data; Frequency conversion and output unit: The signal simulation device undergoes frequency conversion and outputs the final simulated satellite signal in the target frequency band.

10. The timing protection system using a radio-controlled clock according to claim 6, characterized in that: The signal simulation device includes: an Analog Devices AD9361 chip or a National Instruments USRP device or a combination of an NVIDIA JetsonAGX Xavier processor and an Ettus Research B210 platform.

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