Research On Chip-scale Atomic Clock And Multi-channel Data Acquisition Synchronization System

With the rapid development of quantum physics,microwave spectroscopy,and radio electronics,people realized the undisturbed internal motion of atoms and molecules is very stable,so they made efforts to define time and frequency metrology standard on the stability of the periodic signal of microscopic quantum state.In 1967,at the international conference of measurement,a new definition of seconds was made: the second was defined as the duration of 9192631770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium-133 atom.From then on,people entered the era of atomic time.Due to the advantages of high precision and good stability,traditional atomic clocks are widely used in precision navigation,precise time synchronization and military fields.But the high price,high power consumption and large volume make the traditional atomic clocks not suitable for portable equipment.Therefore,the miniaturization of atomic clocks has attracted more and more attention due to the advantages of small size,low power consumption,medium precision and stability.The chip-scale atomic clock(CSAC)is a kind of miniaturization atomic clock,which mainly includes the RF signal source module,the physical package and other modules.In this paper,on the one hand,we set a solid foundation for the realization of the chip scale atomic clock prototype through the study of RF signal source,peripheral control circuit module and physical package;On the other hand,this paper proposes a multi-channel data acquisition synchronization system based on CSAC for surface electromagnetic prospecting system,for case without GPS signal.The main achievements and innovations of this paper are summarized as follows:(1)In order to improve the stability of CSAC,a phase-locked loop circuit is used as RF signal source.The phase-locked loop circuit mainly includes a voltage-controlled oscillator(VCO),a frequency synthesizer and a loop filter.The designed VCOs were tested at high and low temperature.The results showed that the performance of high and low temperature was good and the average phase noise was about-60.83 d Bc/Hz@1k Hz with 1000 samples.The designed PLL circuit was simulated and tested.The results showed that the phase noise was-83.57 d Bc/Hz@300Hz,which was far better than specification of CSAC claimed by Romisch S and Lutwak R.(2)In order to meet the requirement that the temperature control accuracy of the alkali metal vapor and VCSEL should be in ±0.05?.In this paper,the PID algorithm was proposed to control constant current source to realize the stable temperature of the alkali metal vapor and VCSEL balance.The control circuit was designed for the request,and the test results met the requirement of CSAC.(3)The physics package is the most important part of CSAC.The vertical assembly structure was used to build the physics package,and the function and performance of every part of the physics package was described respectively.Before testing the physics package,the thermal simulation was carried out to optimize the structure.With optimized design,the heating power consumption was reduced to 450 m W.With the test of the perspective of atomic physics,a good absorption peak of Gaussian appeared.The RF signal source was then fed into the circuit,producing the desired phenomenon of absorption.Finally,the CPT formant was realized with the line width of about 2k Hz.(4)In order to meet requirements of the surface electromagnetic prospecting(SEP)system,this paper puts forward a kind of time synchronization system based on CSAC with the advantages of high stability,low consumption and small size.The synchronous system includes the base station equipment,interface equipment and clock timing modules.With full consideration for the field application of reliability and portability,the time drift of the system in 24 hours is less than 1us,the power consumption is about 326 m W and the battery life lasts more than 24 hours.The synchronous system was tested with the SEP system in laboratory site,Gu'an and Caosiyao molybdenum mine.Results showed that the designed synchronous system could meet all the requirements of the time synchronization of the SEP system.