CN119471738A - Time service signal protection method and time service protection system using electric wave clock - Google Patents

本发明提出一种使用电波钟的授时信号保护方法及授时保护系统，监测GNSS接收机接收的时间信号是否受到干扰；若受到干扰，则通过GNSS接收机获取卫星的星历数据，再通过电波钟驯服修正晶振获得基准时钟信号；基于所述星历数据和所述基准时钟信号，生成模拟卫星信号；将模拟卫星信号输出至卫星授时时钟设备。本发明提出的授时保护设备在受到干扰时，依靠自身生成的模拟卫星信号完成准确的卫星信号输出，用电波钟完成正确的卫星信号输出具有更高的精度、稳定性和抗干扰性。

The present invention proposes a timing signal protection method and timing protection system using a radio-wave clock, which monitors whether the time signal received by a GNSS receiver is interfered with; if interfered with, the satellite's ephemeris data is obtained through the GNSS receiver, and then the reference clock signal is obtained by taming and correcting the crystal oscillator through the radio-wave clock; based on the ephemeris data and the reference clock signal, a simulated satellite signal is generated; and the simulated satellite signal is output to a satellite timing clock device. When the timing protection device proposed by the present invention is interfered with, it relies on the simulated satellite signal generated by itself to complete accurate satellite signal output, and the correct satellite signal output using a radio-wave clock has higher accuracy, stability and anti-interference.

Time service signal protection method and time service protection system using electric wave clock

Technical Field

The invention belongs to the field of radio signals, and particularly relates to a time service signal protection method and a time service protection system using an electric wave clock.

Background

The global navigation satellite system GNSS is an air-based radio navigation positioning system which can provide all-weather three-dimensional coordinates and speed and time information for a user at any place on the earth surface or near-earth space, and the user receives satellite signals through satellite time service clock equipment to realize GNSS time service. GNSS timing has the characteristics of high accuracy, high cost efficiency, easy installation and global availability, and is usually the preferred scheme of timing technology.

However, in the process of satellite signal transmission, each link of the transmission link may have interference signals due to environmental factors, equipment or human factors, and the interference signals may affect accuracy and synchronism of time information provided by the satellite signals, so that potential safety hazards exist.

In the prior art, although an anti-interference scheme exists, the satellite signals are subjected to self-adaptive anti-interference processing and the like, and the interference signals with stronger fraud cannot really play an anti-interference role.

Disclosure of Invention

The invention provides a time service signal protection method and a time service protection system using an electric wave clock, which can provide accurate and synchronous time information no matter whether satellite signals are interfered or not by using the electric wave clock to replace a crystal oscillator through mechanisms such as monitoring, comparison, self-correction and the like.

In order to achieve the above purpose, the technical scheme of the invention is realized as follows:

a time service signal protection method using an electric wave clock, comprising:

S1, monitoring whether satellite signals received by a Global Navigation Satellite System (GNSS) receiver are interfered;

S2, if the satellite is interfered, acquiring ephemeris data of the satellite through a GNSS receiver, and acquiring a reference clock signal through the electric wave clock taming and correcting the crystal oscillator;

s3, generating an analog satellite signal based on the ephemeris data and the reference clock signal;

s4, outputting the analog satellite signals to satellite time service clock equipment to realize satellite time service.

Further, in step S1, the method for monitoring whether the satellite signal is interfered includes:

and comparing the carrier-to-noise ratio of the signal received by the GNSS receiver with a set carrier-to-noise ratio threshold, wherein a carrier-to-noise ratio lower than the threshold indicates that the signal is interfered.

Further, in step S2, the ephemeris data includes orbit information, position, velocity, and reference time of each satellite.

Further, in step S2, the method for obtaining the reference clock signal by the electric wave clock taming correction crystal oscillator includes:

S201, receiving a time signal by the electric wave clock, wherein the electric wave clock receives a low-frequency radio time code signal from a national standard time station;

s202, extracting a 1PPS signal, namely extracting the 1PPS signal from a received low-frequency radio time code signal by the electric wave clock;

S203, generating a local crystal oscillator signal, wherein the local crystal oscillator continuously generates a clock signal;

s204, comparing the 1PPS signal extracted by the electric wave 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, namely converting the error into binary numbers and then converting the binary numbers into analog voltage signals;

S206, applying correction voltage to the local crystal oscillator, wherein the analog voltage signal is applied to a control pin of the local crystal oscillator, and finely adjusting the frequency of the crystal oscillator to reduce errors;

and S207, frequency and phase locking, namely continuously monitoring and adjusting until the 1PPS signal generated by the local crystal oscillator is gradually locked to be consistent with the 1PPS signal of the electric wave clock, so that the synchronization of the frequency and the phase is realized.

Further, in step S3, the method for generating an analog satellite signal includes:

s301, receiving a reference clock signal, namely receiving a 1PPS signal generated by the local crystal oscillator through a signal simulation device, and taking the 1PPS signal as a reference clock of a phase locking loop PLL in the signal simulation device;

S302, generating an internal clock, wherein the signal simulation device generates a stable high-frequency clock signal based on the received 1PPS signal through an internal phase locking loop PLL;

S303, signal modulation and coding, wherein a signal simulation device uses the high-frequency clock signal as a reference and generates a simulation satellite signal according to GNSS standards provided by ephemeris data;

s304, frequency conversion and output, wherein the signal simulation device outputs a final simulation satellite signal of the target frequency band through frequency conversion.

The invention also provides a time service protection system using the electric wave clock, which comprises a GNSS receiver, an electric wave clock receiver, a control center, a signal simulation device and a signal output switch, wherein the GNSS receiver is respectively connected with the signal output switch, the signal simulation device and the control center;

The GNSS receiver receives satellite signals through a satellite signal receiving antenna and sends the satellite signals to the control center and the signal output switch, the electric wave clock receiver comprises an electric wave clock and a local crystal oscillator connected with the electric wave clock signals, the electric wave clock receives national standard time station signals through the electric wave clock signal receiving antenna and disciplines and corrects the local crystal oscillator to obtain reference clock signals, the control center monitors whether satellite signals received by the GNSS receiver are interfered, if the satellite signals are not interfered, the signal output switch outputs satellite signals to satellite time service clock equipment, if the satellite signals are interfered, the reference clock signals of the electric wave clock receiver are received and sent to the signal simulation device, the signal simulation device simultaneously receives satellite ephemeris data acquired by the GNSS receiver, generates simulated satellite signals based on the satellite ephemeris data and the reference clock signals and sends the simulated satellite signals to the signal output switch, and the control center controls the signal output switch to output the simulated satellite signals to the satellite time service clock equipment.

Further, the control center includes:

The monitoring module is used for judging whether satellite signals of the GNSS receiver are interfered or not through signal carrier-to-noise ratio parameters;

The signal flow direction control module is used for controlling the signal output switch to perform signal switching selection so as to control satellite signals sent to the satellite time service clock equipment and generated by a GNSS receiver or an analog satellite signal generated by a signal analog device;

and the reference clock signal module is used for receiving a reference clock signal of the electric wave clock receiver and transmitting the reference clock signal to the signal simulation device.

The electric wave clock receiver comprises an electric wave clock, a radio wave clock signal receiving antenna, a frequency conversion circuit and a frequency conversion circuit, wherein the electric wave clock receives a low-frequency radio time code signal from a national standard time station through the electric wave 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 binary numbers, then converts the binary numbers into analog voltage signals, applies the analog voltage signals to a control pin of the local crystal oscillator, finely adjusts the frequency of the crystal oscillator to reduce errors, and continuously adjusts the frequency until the 1PPS signal generated by the local crystal oscillator is gradually locked to be consistent with the 1PPS signal of the electric wave clock, so that the frequency and the phase synchronization is realized.

Further, the signal simulation device includes:

The reference clock signal receiving unit is used for receiving the 1PPS signal generated by the local crystal oscillator through the signal simulation device and taking the 1PPS signal as a reference clock of a phase locking loop PLL in the signal simulation device;

An internal clock generation unit for generating a stable high frequency clock signal based on the received 1PPS signal by the signal simulation device through the internal phase locked loop PLL;

The signal simulation device uses the high-frequency clock signal as a reference and generates a simulation satellite signal according to GNSS standards provided by ephemeris data;

and the frequency conversion and output unit is used for outputting the final analog satellite signal of the target frequency band through frequency conversion by the signal analog device.

Further, the signal simulation device comprises an Analog DEVICES AD9361 chip or ational Instruments USRP device or a combination of a NVIDIA Jetson AGX Xavier processor and a Ettus Research B210 platform.

Compared with the prior art, the invention has the following beneficial effects:

1. When the satellite signal is interfered, the time service protection device provided by the invention completes accurate time service signal (analog satellite signal) output by means of the analog satellite signal generated by the time service protection device, and the analog satellite signal output completed by the wave clock has higher precision, stability and anti-interference performance.

2. The invention can provide accurate and synchronous satellite time service information through mechanisms such as monitoring, comparison, self-correction and the like no matter whether the satellite time service information is interfered or not. When being interfered, measures can be taken to maintain time synchronization so as to ensure normal operation of the system and accuracy of data.

Drawings

Fig. 1 is a flow chart of a time service signal protection method according to an embodiment of the invention.

Fig. 2 is a schematic diagram of the structure and workflow of the time service protection system according to the embodiment of the present invention.

FIG. 3 is a schematic flow chart of the method for domesticating and correcting local crystal oscillator according to the embodiment of the invention.

Fig. 4 is a schematic workflow diagram of a signal simulation device according to an embodiment of the invention.

Detailed Description

It should be noted that, without conflict, the embodiments of the present invention and features of the embodiments may be combined with each other.

For the purpose of making the objects and features of the present invention more comprehensible, embodiments accompanied with figures are described in detail below.

The time service signal protection method using the electric wave clock provided by the invention, as shown in figure 1, comprises the following steps:

S1, monitoring whether satellite signals received by a Global Navigation Satellite System (GNSS) receiver are interfered;

S2, if the satellite is interfered, acquiring ephemeris data of the satellite through a GNSS receiver, and acquiring a reference clock signal through the electric wave clock taming and correcting the crystal oscillator;

s3, generating an analog satellite signal based on the ephemeris data and the reference clock signal;

s4, outputting the analog satellite signals to satellite time service clock equipment to realize satellite time service.

Based on the above method, a time service protection system is provided, as shown in fig. 2, including:

The system comprises a satellite signal receiving antenna, a GNSS receiver connected with the satellite signal receiving antenna, an electric wave clock signal receiving antenna and an electric wave clock receiver connected with the electric wave clock signal receiving antenna, wherein the GNSS receiver receives satellite signals through the satellite signal receiving antenna, and the electric wave clock receiver receives national standard time station signals through the electric wave clock signal receiving antenna;

The GNSS receiver is connected with one path of the signal output switch, and the received satellite time signals are sent to the satellite time service clock equipment through the signal output switch to finish satellite time service.

The other path of the signal output switch is connected with the signal simulation device, the signal simulation device can generate a simulation satellite signal, and the received satellite time signal is sent to the satellite time service clock equipment through the signal output switch to finish satellite time service.

The signal output switch is connected with the control center, and the control center controls the signal output switch to switch and is used for controlling whether the signal output switch sends satellite signals or analog satellite signals to the satellite time service clock equipment.

The signal simulation device is connected with the GNSS receiver and used for receiving ephemeris data required by generating simulated satellite signals, and the signal simulation device is also connected with the control center and used for receiving reference clock signals from the electric wave clock receiver through the control center.

In addition, the control center is connected with the GNSS receiver, the radio controlled clock receiver and the signal output switch, and the control center realizes the following functions through a microcontroller or an FPGA thereof:

(1) The method for monitoring the satellite signal state, particularly whether the GNSS time service signal is interfered or not is mainly judged through parameters such as signal carrier-to-noise ratio and the like, and comprises the steps that a control center sets a carrier-to-noise ratio threshold value for the GNSS signal, and the threshold value is usually adjusted according to system requirements and environmental conditions. Comparing the actual carrier-to-noise ratio of the GNSS signal with a set threshold, and if the carrier-to-noise ratio is lower than the threshold, indicating that the GNSS signal may be interfered.

(2) The switching of the signal output switch is controlled to control the flow direction of the signal to ensure that the time service signal is switched to the analog satellite signal generated by the signal analog device according to predefined logic.

(3) GNSS timing and wave clock error observations are performed to evaluate the error and calibrate the time signal. A reference clock signal of a radio-controlled clock receiver is received and supplied to a signal simulator.

In this embodiment, the electric wave clock receiver includes an electric wave clock and a local crystal oscillator connected to an electric wave clock signal, where the electric wave clock receives a national standard time station signal through an electric wave clock signal receiving antenna and obtains a reference clock signal by disciplining and correcting the local crystal oscillator. The specific process of taming and correcting the local crystal oscillator is shown in fig. 3, and is described as follows:

1. The radio controlled clock receives a time signal, and the radio controlled clock receives a low frequency radio time code signal from a standard time station through a built-in radio controlled clock signal receiving antenna. The low frequency radio time code signal typically contains accurate time information and frequency information at 60kHz or other low frequency band.

2. The 1PPS signal is extracted, the electric wave Zhong Jiema signal, and one pulse per second (1 PPS signal) is extracted as a reference signal.

3. The local crystal oscillator signal is generated, namely the local crystal oscillator (OCXO is adopted in the embodiment) generates a stable clock signal, but the frequency of the local crystal oscillator may drift slightly due to environmental factors (such as temperature change and power supply fluctuation).

4. And comparing and error detecting, namely comparing the 1PPS signal of the electric wave clock with the 1PPS signal of the local crystal oscillator through a counter or a comparator. The difference between the two signals is detected to determine the frequency deviation of the crystal oscillator.

5. The error is converted to a control signal by converting the detected frequency error to a binary number and converting it to an analog voltage signal by a digital-to-analog converter (DAC). This process typically uses a Digital Phase Locked Loop (DPLL) or other digital control technique.

6. The correction voltage is applied to the local crystal and the generated analog voltage signal is applied to the control pins of the local crystal, typically by adjusting the control voltage of the OCXO. This regulated voltage will fine tune the frequency of the crystal to reduce the detected error.

7. Frequency and phase locking, namely gradually synchronizing the 1PPS signal of the local crystal oscillator with the 1PPS signal of the electric wave clock through continuous monitoring and adjustment. Finally, locking of frequency and phase is achieved, and the fact that the frequency signal output by the local crystal oscillator is consistent with the standard frequency is guaranteed.

The signal simulation device is described as follows:

1. An Analog DEVICES AD9361 chip, which is a high-performance RF transceiver, can be used to support a wide frequency range and modulation mode, and can be used to generate and receive high-precision radio signals, suitable for the simulation of GNSS signals.

2. National Instruments USRP (Universal Software Radio Peripheral) may be employed and such devices may generate and receive various radio signals, including GNSS signals, through Software Defined Radio (SDR) technology. USRP Devices typically incorporate a high performance RF front-end chip, such as the AD9361 of Analog Devices or similar chips.

3. A combination of NVIDIA Jetson AGX Xavier processors and Ettus Research B210 platforms may be employed, which utilizes a high-performance embedded processor (Jetson AGX Xavier) and a high-performance SDR platform (B210), which may generate and process complex GNSS signals through software.

In this embodiment, an Analog DEVICES AD9361 chip is used as the signal simulation device. As shown in fig. 4, the workflow is briefly described as follows:

1. The received reference clock signal AD9361 receives the 1PPS signal of the local crystal oscillator (corrected reference clock signal from the radio-controlled clock receiver) as a reference clock for an internal high-precision Phase Locked Loop (PLL).

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

3. Signal modulation and coding using the high frequency clock signal as a reference, AD9361 generates GNSS analog signals, i.e. analog satellite signals, according to the GNSS standards in the ephemeris data. The method comprises the steps of performing BPSK/QPSK modulation on the signal and adding navigation message coding.

4. And frequency conversion and output, namely outputting the generated analog satellite signal into a target frequency band (such as 1575.42MHz of L1 frequency band) through frequency conversion, and taking the target frequency band as the analog satellite signal finally transmitted to the satellite time service clock equipment.

The use process of the time service protection system is as follows:

1. In the undisturbed state, as shown by the solid arrow in fig. 2, when the control center continuously detects that the satellite signals are undisturbed, the control center controls the signal output switch to stably output the satellite signals transmitted by the GNSS receiver to the time service clock equipment;

2. And in the interfered state, after the control center judges that the satellite signal is interfered, the control center controls the signal output switch to output the analog satellite signal, and the analog satellite signal is generated by the signal simulation device in a simulation mode according to ephemeris data and a reference clock signal of the electric wave clock, so that the analog satellite signal is kept highly synchronous with the standard time. (as indicated by the dashed arrow).

The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, alternatives, and improvements that fall within the spirit and scope of the invention.