A Research On Technology Exploring Of TCXO Based On Stress Process

With the continually development of science and technology,the applications of TCXO significantly increase in communication and national defense domains.The market brings requirements of TCXO in cost,size and some other key performance indexes with greater strictness.Traditional analog compensation and digital compensation generate compensation control voltage respectively from components like thermistor network and temperature sensor to output the feedback control voltage,and then realize the compensation of crystal frequency shift.The composition and debugging process of these components is rather complicated,and the cost,size and power consumption of the product is comparatively high.Therefore,seeking for new compensation approach that is more effective becomes important.In order to make breakthrough upon the traditional compensation method,further improve the performance index of the resonator,it is essential to enhance the fundamental research of quartz crystal resonator,understand the vibration mode of crystal oscillator and make purposeful research about how its frequency been affected by various factors.In this context,the finite element method is applied to the vibration mode simulation of crystal resonator in this paper.In addition,according to the two physical properties of crystal itself,namely the temperature frequency characteristic and the force frequency characteristic,we propose the design process and implementation plan based on the stress frequency stabilized compensation method.This project derives from the basic research of force frequency sensing characteristic based high performance TCXO with overtone crystal funded by the National Natural Science Foundation of China.The main contributions of the paper are as follows:1.With the help of ANSYS,we explore the application of vibration mode analysis in the design of quartz crystal resonator.In this paper,we first construct an AT-cut quartz crystal resonator model base on the piezoelectric coupling finite element equation and kinetic equation,calculate the model's vibration mode under different boundary conditions,and fully understand the distribution patterns of resonator's thickness shear vibration and various parasitic vibration.We simulate and analyze how size affects the vibration mode of the resonator,the result provides a significant reference for finding the optimal size range of quartz crystal in practical production process.Next,we simulate and obtain the change of resonator's vibration mode and vibration displacement when prestress applied on the quartz plate from different angles.Frequency is affected by vibration,so with this simulation result,we then see that the optimum compensation result of force compensation film coating should be along the X-axis of crystal,and the crystal holder fixing angle should be along the Y-axis.By this means,the influence of process design on crystal performance can be minimized.2.On the basis of simulation,we propose the design idea and implementation plan base on the stress frequency stabilization compensation method which combine the force characteristic and frequency characteristic of the crystal itself,and use the stress generated with temperature change to compensate the frequency effected by temperature.Then we simulate the corresponding crystal resonators under different stress treatments by ANSYS,compare the size of the internal equivalent stress.Then the most obvious effect of the stress frequency stabilization method which is plate a strip metallic film along the direction of X-axis on the crystal's surface is obtained.At last,we prove the feasibility of this stress compensation approach by experimental results,it shows that this approach not only can make frequency stability reach 10^-7 magnitude in a wide temperature range of-50?⁸5?,but also have strong maneuverability compare to traditional compensation method,while avoiding the increase of power consumption and cost.Our work provide a significant reference for researching,designing and developing TCXO with high frequency stability.