The Algorithm And Realization Of Digital Circuit Part In Cpt Frequency Standard

Passive coherent population trapping (CPT) Rubidium frequency standard based on CPT is a new atomic frequency standard, and theoretically the only one that can be realized as a chip-scale size atomic frequency standard. Its volume and power consumption are considerable less than those of an optical pumped Rubidium atomic clock. The smallest CPT frequency standard is expected to be of watch size and supported with a Button battery. Because of these advantages, it is believed that CPT frequency standards are promiseful in long-term application in military and civilian area, such as long-distance communication systems timing, large-area network synchronization and the portability of weapons and equipment. To realize a prototype of CPT frequency standard, it is necessary to design its physical package and corresponding electronics. The subject of this thesis is mainly the study on electronic of CPT frequency standards, both the relevant principles and the electrical circuit studies.In this thesis, chapter I is devoted to the history of the development of time standards, the appearance and the development of atomic frequency standards, the classification of atomic frequency standards and the current situation of CPT frequency standards study. In Chapter II it is described in detail that the working principle of physical package of CPT frequency standard and the overall scheme of recently developed CPT frequency standard prototype of our team. In Chapter III, the simulation works on two circuit loops are presented. By means of MATLAB, the loop of laser frequency stabilization and the loop of microwave frequency stabilization have been simulated from which the parameters for the electric circuit were chosen and a new loop feedback algorithm was obtained. In Chapter IV, it is firstly described that the basic principles of software-defined radio, such as the principle of digital phase-sensitive detector and digital quadrature demodulation, and then it is presented in detail that the realization of the digital quadrature demodulation method and the simulation which proves the feasibility of the scheme. The experimental results of applying the scheme to CPT atomic frequency standard are also presented which are consists with those from simulation. In chapter V, on principle the polarization characteristics of the VCSEL output laser and its impact on CPT atomic frequency are briefly analyzed, the study on laser polarization behavior of the VCSEL which we used is present, and the study results prove the effectiveness of our new scheme of physical package.