INVESTIGATIONS IN LOW DRIVE LEVEL SENSITIVITY OF QUARTZ RESONATORS AFFECTING THEIR MOTIONAL PARAMETERS

Usually, starting of oscillation in a quartz crystal oscillator requires a resonator’s input power in the range of – 20 dBm, but under storage a phenomenon known as Drive Level Dependency (DLD) or Drive Level Sensitivity (DLS) may appear that prevents the starting of oscillation. Several studies performed in the past have shown that at low drive level some quartz resonators may exhibit a large increase of their series resistance preventing the starting of oscillation. This work reviews the studies and results obtained for nearly fifty years on very low drive level sensitivity of quartz. The various mechanisms and models based on the hypothesis of moving particles and surface defects in the resonator inducing resistance increase and its relation with noise mechanism are reviewed as well. Also, the paper describes several experimental set-ups, and measurement procedures used to obtain very low drive level motional parameters. This work is a contribution to understand the problem of starting quartz after a long storage period. Some preliminary results of the series resistance measured at very low drive level are also presented.