A study on the measured correlation of drive level dependency and phase noise of quartz crystal resonators

One of the largest problems affecting crystal manufacturers today is the mass production and testing of low noise crystals. It has been reported in these proceedings that an effective way to predict the phase noise of a crystal in production is to use the Drive Level Dependence (DLD) phenomena that many crystals exhibit. It has been shown that there is a positive correlation between the slope of the crystal resistance over increasing drive level and the noise that the crystal exhibits. This leads us to believe that by reducing the DLD of a crystal resonator, we could reduce the resulting phase noise. One of the causes of the DLD phenomenon is thought to be contaminants on the surface of the crystal. This paper provides data from a large sample size of 100,000 MHz crystals examining the correlation between DID and phase noise. A variety of crystal packages and frequencies are examined for the effect of known contaminants on DLD and phase noise performance. Additionally, the correlation of DLD measurements using other measurement techniques is examined. The research shows that DLD may not be the most effective method of screening for short-term stability in a variety of crystal packages.