The Design and Implementation of a Pierce Low Phase Noise Crystal Oscillator

The importance of loaded quality factor Q_L was analyzed and the method of reducing phase noise on the basis of improving Q_L was performed. The formula of Q_L was derived from analysis of the Pierce oscillator circuit, and calculated by MATLAB. According to the results, we can draw a conclusion that Q_L is explicitly related to circuit parameters. Based on this conclusion, the prototype 120MHz crystal oscillator was designed and the experiments were carried out. The crystal resonator we use is AT-cut 5th overtone crystal resonator with UM- 1 resistance welding package, its unloaded quality factor Q₀ is about 1.06 × 10⁵. The measurement results of near carrier frequency phase noise are -103dBc/Hz@10Hz and -134dBc/Hz@100Hz. Experimental results show that it is feasible to design low phase noise crystal oscillators based on improving Q_L.