Research On The Time-keeping Technology Of Constant Temperature Crystal Oscillator Based On Beidou Time Service

Accurate time information is of great significance in aerospace,military,communications and other fields.As the progress of science and technology,one by one realms higher and higher needs for the stability and accuracy of clock sources.The traditional taming and punctuality system uses the US GPS1 PPS signal as the reference source,which has problems such as strategic security.The Beidou satellite navigation system was independently researched and invented by China,which is providing time standard signals with high reliability and strong security for various fields.The 1PPS signal that it broadcasts has the advantages of good long-term stability and high accuracy.Using it as a standard source for training the OCXO can effectively improve the problem of unsatisfactory long-term stability of the constant temperature crystal oscillator.Based on this,this paper designs a constant-temperature crystal oscillator taming and punctual system based on Beidou 1PPS signal.Based on the analysis of the relevant theories of the taming and punctual system,the paper focuses on the factors that affect the frequency stability of the constant-temperature crystal oscillator,and completes the design of the taming and punctuality algorithm;for the hardware implementation part of the system,ARM is used as the core processor to design the constant-temperature crystal oscillator Circuits,power supply and conditioning circuits and other hardware circuits have achieved the goal of low power consumption of the system;in the software design part,based on the analysis of the tame and punctual algorithm,the software design adopts the modular design idea,and the states of the system are designed in detail.The realization of the algorithm realizes the purpose of high-precision time service and punctuality.In the implementation process,the constant temperature crystal oscillator is used as the local clock source to provide the working clock for the system.When the Beidou1 PPS signal is valid,the time measurement technology is used to measure the phase difference between the local 1PPS and the Beidou 1PPS signal,and the phase difference value is adjusted by the PID controller.The adjusted digital control quantity is converted through D/A,and the analog voltage is acquired and then input to the voltage control terminal of the OCXO to make it output a stable and accurate frequency.During the entire signal transmission process,a series of filtering processing is performed on the signal.Eliminate occasional random errors and avoid affecting the timing and punctuality accuracy.The system forms a closed loop state in the process of taming the constant temperature crystal oscillator.At the same time,in the process of taming the crystal oscillator,collect clock error data,crystal aging data and data affected by temperature changes and store them in the external FLASH,so that when the reference signal is lost,the crystal oscillator frequency deviation can be predicted and processed based on historical data to achieve punctuality Effect.In the punctual state,two Kalman filters are used to predict the aging model and temperature model of the constant temperature crystal oscillator.In order to eliminate the delay caused by the signal in the transmission process,the aging model and temperature model are tested and tested.After processing,a delay compensation module is added to ensure that the constant temperature crystal oscillator can output a frequency within a certain accuracy range during the punctuality process.Finally,the performance of the system test is indicated that the system's timing accuracy can achieve 14 ns,and the timing accuracy required by the design index is less than 20 ns,achieving high-precision timing;the timing accuracy can reach 97us/24 h,meeting the punctuality requirements of the index The accuracy is <100us/24 h,achieving high-precision punctuality;in addition,the system power consumption has been significantly reduced to only 185 m W,which is far lower than the 800 m W of the traditional tame and punctual system,while achieving the goal of low cost.