Research On Clock Frequency Calibration And Synchronization Technology

With the development of social economy,science and technology, high precision time frequency has become an important parameter in the fields of national science, technology, economy, military and social life. It has been applied from basic research field to the engineering technology and it affects many aspects of the country and the people's livelihood,and national economy. The contents of this dissertation are from the subitem—"Research on the Time Transmission Technology Between Aircrafts"of Knowledge Innovation Important Direction Project of Chinese Academy of Sciences. As an elementary project, this thesis has mainly completed the calibration and local clock synchronization work,providing accurate clock benchmarks for the system and many intermediate frequency needed, to ensure the relativity of kinds of frequencies . The concrete contents are as follows.Firstly, the calibration and synchronous technology of clock frequency has been studied according to the requirements of the system. It has applied the PLL and DDS scheme to realize the frequency comprehension. And it uses the output of DDS as the reference input of PLL,to solve the contradiction of frequency resolution and phase noise.In addition,it has designed a spacecraft time delivery system frequency comprehensive device,which can produce clock signals with 70MHz, 140MHz and 240MHz as the frequencies needed by the system.Secondly, a voltage control stability frequency algorithm has been put forward after the advantages and disadvantages of the Least-square method and the PID algorithm have been analysed. This algorithm has the characteristics of low cost,high efficiency,high reliability and easy to engineering realization. It has been shown that the algorithm can satisfy the accuracy requirement of the system. Thirdly, it has also completed the clock calibration module design and implementation based on AVR series microcontroller. In the light of the requirements of the system, it has simulated the needed signal conditioning circuit and other circuits in the Multisim circuit simulation environment. Then the hardware circuit has been structured according to the simulation results. Eventually, it has finished the design of the circuit and has it implemented.Lastly, an A/D sampling method has been proposed based on external 1pps signal control, which has replaced traditional time interval counter, and has realized the control and calibrated of quartz crystal oscillator's output frequency. At the same time, the clock signal generated is purified and regulated by using the phase-locked loop.