Ultra-stable OCXO using dual-mode crystal oscillator

A high-stability oven controlled crystal oscillator (OCXO) (frequency stability; /spl plusmn/0.5 ppb from -10 to +50/spl deg/C) has been developed using a dual-mode SC-cut quartz crystal oscillator. The OCXO described here uses a conventional oven control system for coarse compensation and a digital correction system, which uses B-mode signals as a temperature sensor, for fine compensation. These compensations combine to greatly improve the C-mode frequency stability when the ambient temperature changes. The experimental results indicated that the proposed OCXO had a frequency-temperature stability 60 times better than that of a free-running mode oscillator.