Research On Improving Frequency-Temperature Characteristics Of Voltage Controlled Crystal Oscillator Based On Active Compensation Method

With the advent of intelligent life and the rapid development of communication technology,crystal oscillators,as a small-volume,low-cost frequency source,are used more and more widely.The continuous advancement of electronic technology and the rapid change of electronic products have also led to a rapid increase in the industry’s demand for crystal oscillators.Whether it is in communication equipment or in the military field,the crystal oscillator,as the frequency reference of the system,will be affected by the external temperature and the aging of the equipment itself,resulting in a serious shift in the output frequency,which will greatly affect the performance of the equipment.For a long time,researchers never stop studying crystal oscillator compensation technology,However,a miniaturized high-frequency stable crystal oscillator capable of industrial mass production has not been developed until now.Based on the purpose of improving the stability of the crystal oscillator frequency while reducing the size of the crystal oscillator,The thesis conducts a technical study on a microcomputer compensated crystal oscillator(MCXO)of low power consumption which can be applied to small mobile device.Starting from the characteristics of the crystal oscillator,the thesis discusses two key factors of temperature and aging influencing the crystal oscillator output frequency,According to the temperature-frequency characteristics and aging-frequency characteristics of crystal oscillator,It build the temperature compensation model and the aging compensation model of the crystal oscillator.In order to improve the short-term frequency stability of crystal oscillator,PID algorithm is introduced to realize step output of voltage.Then,this thesis describes the overall design scheme of system and introduces the design of hardware circuit and software in details including microprocessor circuit,power circuit,main oscillation circuit based on Colpitts oscillation circuit,filter circuit,fine tuning circuit,temperature sensor,etc.The system uses the MSP430G2230 chip as the core and carries out fitting for temperature curve and aging curve through MATLAB.Schematic diagram and PCB design are completed with software Altium Designer.Tektronix FCA3000 frequency counter and UTP3702 DC stabilized power supply are used in process of data measurement and system board debugging.According to test results,the frequency stability of MCXO reaches up to0.9 PPM.which improves the frequency stability of the crystal oscillator and verifies the accuracy of the compensation method.Both volume and power consumption achieve expected goals.Finally,in consideration of compensation efficiency of crystal oscillator in practical application,multichannel crystal oscillator compensation scheme is introduced to compensate crystal oscillator frequency.