Design And Implementation Of The 80MHz Low Phase Noise Crystal Oscillator

In this paper, from a practical point of view, chose how to design low phase noise crystal oscillator as the research subject, we analyzed the generation mechanism of the phase noise and explored a new simulation method. Then we designed an 80 MHz low phase noise crystal oscillator using this simulation method and get rather good indicator.The main work of this paper is:1) Described the basic working principle of the feedback oscillator, get the amplitude stability conditions and phase stability conditions of the oscillator, then, from the perspective of complex oscillation equation, the paper focus on the analysis of the structure and working principle of the Butler common-based series oscillation circuit. Selects the SC-cut resonator to design the oscillator in this subject and choose the Butler common-based series oscillation circuit as oscillator circuit. Then based on the classical Leeson model, the paper analyzed the phase noise of Butler oscillator and derived a formula of LQ by using a passive network and obtain the relation curve between LQ and 2C by MATLAB, then we get the theory that make a compromise between those two parameters can reduce the phase noise,which lays the theoretical foundation for the design in the following passage.2) The ADS simulation software and the harmonic balance simulation were introduced in the forth chapter of this paper. Firstly, it showed the oscillator phase noise simulation curve using ADS ideal model, after comparing with the phase noise spectrum structure in the theory, it got the conclusion that the simulation goes wrong is because the effect of nonlinear devices was not considered. Then it explored a new simulation method, i.e. establishing a nonlinear model of the transistor, then did simulation again, it obtained the phase noise simulation curve after considering the effect of nonlinear devices, through the comparison between those two curves, it confirmed the validity of the proposed method, which provided guidance for the oscillator design in following part. 3) During the last chapter, it analyzed the noise sources of the oscillation circuit, gave out the design principle of the low phase noise crystal oscillator, and then we designed an 80 MHz low phase noise crystal oscillator. Based on all the conclusions of this paper, an 80 MHz low phase noise crystal oscillator sample was made at the last of this paper. Then, made the actual testing using the Agilent E5052 B signal analyzer and obtained the measured phase noise level:-140dBc/Hz@100Hz, which meets with the design requirements. Then, after comparing with the phase noise of oscillators internationally in similar frequency, we demonstrated the value of this method and then completed the design of this subject.