Crystal Oscillator Low Phase Noise Design And Simulation

Crystal oscillator,as a high precision and high stability frequency source,is still in the core position in the high-end frequency source.With the rapid development of electronic information technology,the demand for crystal oscillators in the fields of civil production and defense industry is increasing,and the requirements for its performance index are getting higher and higher.The phase noise performance of the crystal oscillator directly determines the performance index of the electronic system,and has become an important factor limiting the performance of the system.In this thesis,we consider the oscillation circuit design of crystal oscillator itself,deeply study the working mechanism and phase noise characteristics of crystal oscillator,find out the effective method to reduce the phase noise of crystal oscillator,and carry out the simulation verification by combining the calculation-aided design means,so as to provide guidance for the practical oscillation circuit design,which has important theoretical significance and practical value.The specific research contents of this thesis are as follows:（1）Research on the design of crystal oscillators with low phase noise.Firstly,the working principle of crystal resonator and crystal oscillator is analyzed in depth,and three kinds of oscillation circuits are analyzed and compared to determine the circuit type used in this topic.Then,the noise characteristics of the crystal oscillator are studied in depth,and the phase noise spectral structure characteristics and its influencing factors are analyzed from the Leeson phase noise model,and the conclusion that improving the loaded quality factor Q_L can reduce the phase noise performance is obtained.Then,the circuit design and simulation of the low-phase noise crystal oscillator are carried out.First,the transistor parameters _FA and _KA,which have significant effects on the phase noise performance of the crystal oscillator,are analyzed,and methods to reduce the effects of these two parameters on its phase noise performance are proposed.Second,the loaded quality factor Q_L of the crystal oscillator circuit is calculated and derived,and the quantitative relationship betweenQ_L and the circuit parameters is derived,i.e.,the phase noise decreases with the increase of C₂.Finally,the crystal oscillator circuit is designed,and these two methods of phase noise reduction are simulated separately using ADS computer-aided design,and the simulation results are analyzed to verify that the methods studied in this thesis of increasing the feedback resistor to optimize the effect of flicker noise and reducing the phase noise of the crystal oscillator based on increasing the value of the loaded quality factor _LQ are correct and effective,and the phase noise performance of the circuit after improvement compared with the previous one,has been improved significantly,thus improving the phase noise performance of the oscillator.（2）Research on wide temperature and stable frequency high precision temperature control technology.The effect of temperature on crystal oscillators cannot be ignored,and keeping the temperature constant can improve their phase noise to some extent.The advanced PID control technology is used to improve the temperature control accuracy.The complete transfer function of the temperature control system is analyzed and derived in detail,and the step response of the system under different parameters is simulated and compared.Then the temperature control circuit was designed and simulated to verify that the temperature control accuracy of the designed temperature control circuit is 0.1℃,which verifies the feasibility of the temperature control circuit and theoretically the frequency-temperature stability is up to1×10^-9/℃,which is a better indicator.（3）Research on the low-noise design of phase-locked crystal oscillator.Aiming at the practical application problems of some complex electronic systems that require the simultaneous existence of multiple frequency reference signals at high and low frequencies,the low phase noise design of the phase-locked crystal oscillator and the design of each link are thoroughly analyzed and designed.After simulation and verification,the phase noise of the final output signal of the phase-locked crystal oscillator is-115.8d Bc/Hz@1Hz,-125.3d Bc/Hz@10Hz-155.3d Bc/Hz@100Hz,-162.3d Bc/Hz@1k Hz,-163.8d Bc/Hz@10k Hz,which basically meets the requirements of the index.