Research On The Vibration Modal Analysis And The Environment Electromagnetic Field Influence Of Quartz Crystal Resonators

Quartz crystal resonators are the key components for frequency standard in modern telecommunication system. With the development of the correlation technique about the aviation, spaceflight, electron, communication and machinery field, the accuracy requirement of quartz crystal resonator is higher and higher. Enhancing the frequency stability of quartz crystal resonator has also become an important problem.This article will start with theory and experiment to research the stability of quartz crystal resonator. On one hand, use the finite element method to research the vibration mode of quartz crystal resonator, on the other hand, research the mechanism of quartz crystal resonator under the magnetic field through experiment. The main work of this paper is as follows:To search the application of the finite element method in the high precision quartz crystal resonator. Use the finite element method to analysis disc type AT-cut quartz crystal resonator’s three-dimensional vibration mode under free boundary conditions. The simulation result generally coincides with the experiment result of document report using X-ray, so that proved the reliability of this method. This method can not only acquire the surface vibration displacement distributed information but also observe the marginal vibration mode, thereby, contribute to comprehend the existence condition of spurious coupling modal. With this character of the method, it found that the thickness shear vibration mode playing an important role in the quartz crystal resonator. But at the same time, it accompanied with a strong parasitic vibrate including face shear vibratation, flexural vibration and so on. In allusion to the parasitic vibration effect on the properties of quartz crystal resonator, this article will optimal design the size of quartz crystal wafer through modal analytical method. Through analyzing the vibration displacement distribution of quartz crystal resonator in different size to find an optimum size to control obstruct of parasitic vibration, and then optimize its temperature frequency and impedance characteristic. This method has been tested in the research of actual product and achieved a good application effect. 2. To research the mode of quartz crystal resonator under prestress conditions through finite element method. Use finite element method to simulate the eight steps vibration mode of AT-cut quartz crystal resonator in free state and proved the reliability by comparing with the experimental result of document report. On this basis, simulating calculated the vibration mode of AT-cut quartz crystal resonator in different azimuth angle constraint conditions and found the main vibration direction of quartz crystal resonator changing with different constraint angle. Furthermore, this article researched the vibration mode of AT cut quartz crystal resonator by inflicting diameter force on different azimuth angle, and found that not only the main vibration direct but also the main vibration center change with the inflicting diameter force. According to the simulation result, the thickness shear vibration and parasitic vibration will be stronger when inflicting the inflicting diameter force on00or1800azimuth angle, on the contrary, when inflicting the inflicting diameter force on600or1200, the vibration displacement of all the directions won’t change obviously compared with free boundary condition. The frequency vibration variation acquired by this method is general the same with experiment result of quartz crystal resonator’s force and frequency effect reported by the document. The analysis above has an important reference value to select the dispense position and research the mechanics sensor for example the acceleration of quartz crystal.3. To discuss the frequency drifting mechanism when quartz crystal resonator in the static magnetic field. To break up complex construction quartz crystal resonator into simple structure, separately research their frequency change in static magnetic field to clarify the frequency drifting mechanism when quartz crystal resonator in the static magnetic field, combine with finite element method to construct a physical model based on magneto elastic coupling theory, analyze the stress distribution which in the static magnetic field to definite the magnetic field’s influence action mode to the frequency.4. To research the effects of the alternating electromagnetic field of quartz crystal resonator. Inflict alternating electromagnetic field in different intensity and direction to observe the change law of frequency under this condition, analyze the change of equivalent circuit parameter (including static capacity, dynamic capacity, dynamic resistance and so on) in the alternating electromagnetic field to clarify the frequency change mechanism in alternating electromagnetic field.