Based On Software Simulation Of The Low Phase Noise Crystal Oscillator Design And Realization

Crystal oscillator can produce oscillation steady signal. It's widely used in those fields which highly require the frequency such as timekeeper, war industry, and communication and so on. With the development of electronic communication, radar technology and frequency synthesis, there are more and more demands on crystal oscillator, which is considered as the benchmark frequency source. So fabricating high stability crystal oscillator and improving phase noise index have become a trend.This paper narrates the current international level and development trend of crystal oscillators and introduces the performance, classification and some basal crystal oscillator circuit as well. Meanwhile, this paper gives time-domainand and frequency-domain presentation ways of phase noise, reason of forming phase noise and a few contributors to influence on it. Then the phase noise of Colpitts oscillator circuit is analysed on the basis of phase noise equation of Leeson model in feedback oscillator and we can draw a conclusion that QL is a monotone increasing function of C 2 by MATLAB and VC++. And the design of the oscillator is given on the basis of loaded Q. The phase noise of the circuit is simulated by the software-based method of harmonic balance. Based on the simulation result, a design of the prototype 50MHz low noise crystal oscillator is presented and the experiments are carried out. The frequency–temperature stability of the experimental oscillator achieves <±2.8×10-7 in the temperature -40℃～+75℃, the measurement results of phase noise are above -120dBc/Hz@100Hz,-150dBc/Hz@1KHz. These results meet the engineering requirements.