Design Of Vibration Isolation Structure For Crystal Oscillator In Airborne Electronic Equipments

As the core components for precisely measuring time and frequency, crystal oscillator modules are decisive to the reliability and stability of the electronic equipments. However, crystal oscillator is very sensitive to vibration and prone to producing frequency drift and phase noise under vibration environment. It’s necessary to design isolation structure for crystal oscillator to improve its working performance. This thesis gives information about vibration isolation scheme that meet the project specifications and to minimize the influence of vibration on the crystal properties with crystal oscillator in airborne electronic equipments as the study subject.Firstly, this thesis starts from the working principle of the crystal oscillator, gives the calculation method of the phase noise of crystal oscillator under different vibration environment and analyses the influence on the phase noise of crystal oscillator caused by the vibration environment. A theory model of single degree of freedom system for isolation system of crystal oscillator is established, and its response under simple harmonic vibration and random vibration is analyzed and all as the oretical foundation for designing, calculating and simulating of crystal oscillator vibration isolation structure.Secondly, by analyzing the project requirements, three kinds of vibration isolation structures are designed, and the simulation and prototype experiments are carried out.Then, a new structure scheme is proposed based on the lessons of failure.Then the mechanical model and finite element model of the vibration isolation structure are calculated and simulated under the condition of simple harmonic vibration to verify whether the vibration isolation rate of the vibration isolation structure meets the requirements of the project index.Finally, the simple harmonic vibration and random vibration experiments on vibration isolation structure are carried on, according to the experimental results, the phase noise has improved over 10 d Bc/Hz than the original scheme. The vibration isolation structure of crystal oscillator can effectively reduce the effect on the phase noise of crystal oscillator at 20~2000Hz frequency under random vibration, and has a favorable vibration isolation effect under the vibration which frequency is above 10 Hz.