Innovations in OCXO production

Friday 3rd of August 2012

Each piece of quartz crystal used by HCD is unique; small variations and imperfections in the crystal structure mean that each piece will oscillate differently at different temperatures and if they all went into identical circuits, a consistent output frequency and a good thermal stability range would not be achievable.  Each crystal oscillator has what we refer to as a ‘turnover’ temperature, this relates to the ability of the crystal to resonate at a given temperature.  By changing some of the resistance values in the oven control circuit, we can vary the oven operating temperature and produce a graph of deviation from specified frequency. By finding the resistance that produces a 0⁰ gradient (indicated with the red line below) on the frequency/resistance graph HCD can setup the initial operating temperature of the oven housing the crystal specifically for each piece of quartz used.

The consequence of this is that each HCD oscillator will react less to environmental temperature change compared to other OCXOs that may not take into account the turnover temperature of each individual crystal.