Research And Design Of The Microwave Cavity In Rubidium Atomic Frequency Standard For Miniaturization

The atomic frequency standard(or atomic clock)not only has a wide range of applications in technical fields such as navigation and positioning,digital communication,but also a necessary tool for precise experiments to measure physical data and verify physical theories.In order to meet the current needs for small portability in navigation,communication,measurement,etc.,atomic frequency standards with small size,light weight,and high stability have become an important research direction and have broad application prospects.First of all,this thesis studies and summarizes the existing atomic frequency standards and their most suitable resonant cavities.Starting from the principle of atomic clocks and the shape of microwave cavity with consideration the characteristics of low consumption,simple structure and good stability that the most widely used rubidium atomic frequency standard has,the optically pumped vapor-chamber rubidium atomic frequency standard was finally selected as the design object to miniaturize.The microwave resonant cavity,an important part of the atomic frequency standard,is to store the microwave radiation energy fed into it and provide the electromagnetic field required for the atomic energy level transition.Also it loads with rubidium atom bubbles,detectors,coupling excitation and other important components.Since the microwave cavity occupies the main volume of the entire atomic frequency standard,the design of a small-volume,light-weight microwave resonator is the key to miniaturize the rubidium atomic clock.Based on a comprehensive analysis of the existing loop-gap resonant cavity,this thesis studies the influence of the size of each part on the performance of the resonant cavity by numerical simulation,and prepares for the subsequent adjustment of structural parameters and performance optimization.On the basis of previous work,this thesis has carried out in-depth research and optimized design for the microwave resonant cavity of the quantum part of the rubidium atomic frequency standard,aiming to further reduce the volume,the weight,and to optimize the structure and facilitate mass production.The coating method to flatten the loop-gap resonant cavity and multiple layers stacking to form a stacked loop-gap resonator has been proposed.With the premise of ensuring the performance parameters such as the electromagnetic field distribution,resonance frequency,quality factor,fill factor and field orientation factor,meet the design requirements,the coating processing method can reduce the high processing level in manufacture the traditional loop-gap resonant cavity and the difficulty of mass production,simultaneously compressed the volume of the loop-gap resonant cavity greatly.In this paper,a four-plated resonant cavity was processed and mounted to verify the design idea.The test results are consistent with the theoretical analysis.In addition,a series of optimization and improvement measures has been performed,which can also improve the performance of the resonator to a certain extent.Moreover,based on electric wall symmetry,a new type of loop-gap resonant cavity is proposed and analyzed by simulation.Its performance meets all the requirements of the microwave cavity for atomic frequency standard,also the volume can be reduced by 50% compared with the existing loop-gap resonant cavity,which is laid a theoretical foundation for further miniaturization.