GNSS-based high-stability crystal oscillator taming and maintaining system and method

Abstract

The invention discloses a GNSS-based high-stability crystal oscillator taming and maintaining system and method, and the system comprises a GNSS receiver board card and an OCXO crystal oscillator FPGA, the second pulse signal output ends of the GNSS receiver board card and the FPGA are connected to a phase difference measurement module, the output end of the phase difference measurement module is connected to a processor, the output end of the processor is connected to a D / A conversion module, and the D / A conversion module is connected to a digital-to-analog conversion module. The output end of the D / A conversion module is connected to an OCXO crystal oscillator through a signal conditioning circuit, second pulse signals of the OCXO crystal oscillator are output after being subjected to FPGA frequency division, and the OCXO crystal oscillator is connected with a temperature sensor. The frequency of the crystal oscillator can be automatically kept.

Description

technical field [0001] The invention belongs to the technical field of Beidou timing, and in particular relates to a GNSS-based high-stable crystal oscillator taming and maintaining system and method, which are used for Beidou products to tame fast crystal oscillators to obtain high-precision timing, and improve the taming and maintaining accuracy of Beidou products' crystal oscillators. Background technique [0002] Yang Shaochen (2016) of the Rocket Force Engineering University established an aging model of crystal oscillators and introduced the temperature as an accelerating stress into the model parameters. He used historical data to estimate the diffusion parameters of the model through the maximum likelihood estimation method, and used Kalman filtering to estimate the drift. The parameter predicts the frequency drift of the crystal oscillator that loses the GPS signal, so as to complete the compensation of the system frequency. However, the model cannot distinguish the...

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Problems solved by technology

However, the frequency accuracy of the system shows a monotonous downward trend when maintaining, indicating that the algorithm has limited compensation for crystal oscillator aging.

[0004] Tan Songrong (2014) of South China University of Technology implemented the OCXO-based LTE base station clock system hold algorithm, using the recursive least square method with forgetting factor to obtain the estimated value of the crystal oscillator parameters. When the GPS receiver is in the hold state, the system uses the linear model Obtain the voltage control data of the constant temperature crystal oscillator, and continue to calibrate the constant temperature crystal oscillator. After 12 hours of training, the even-second error of the system is 600ns, but it does not consider the aging rate-frequency characteristics of the crystal oscillator, and has not been established. predictive model

[0005] Primary frequency standards such as hydrogen clocks and cesium clocks have high frequency accuracy and stability, but due to their large size, high price, and high environmental requirements; on the contrary, secondary frequency standards are cheap and have high environmental requirements. Generally, the short-term stability is also good, but the frequency accuracy and long-term frequency stability are poor

Therefore, it is necessary to combine the advantages of the two to improve the frequency accuracy and long-term stability of the secondary frequency standard with the least impact on the short-term frequency stability of the secondary frequency standard; The output standard 1PPS signal is used to lock the local crystal oscillator. If the satellite signal is lost, the crystal oscillator is in an uncalibrated state. At this time, the frequency accuracy of the crystal oscillator cannot be maintained, and the frequency accuracy error will gradually increase due to aging

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