An experimental study of long term aging of quartz oscillators

The relation between the integrating drive level and the drive level-frequency dependence (DLD) of the nearby mode was examined for AT-cut quartz resonators used in high stability OCXOs. The authors had previously developed a precise measurement system for DLD characteristics. We have also pointed out that the frequency jump appears to depend on the resonator drive level. We used some quartz resonators which exhibited DLD frequency jumps. These are caused by the nearby mode. The experimental investigation included: (1) the resonator was vibrated by a constant driving current at regular intervals; (2) after one interval, the frequency-jump (current) was searched by DLD characteristic measurements. By continuing this sequence, we specified a relation between the drive level integration (or elapsed time) vs. the “frequency jump current”. The results clearly indicated that the “frequency jump current” level increases as a function of drive current integration. We concluded that the drive level characteristics of nearby modes varied with the total (integrated) power provided to the resonator. The oscillation frequency then jumps suddenly