Improvements in OCXO performance by the use of an on-board microprocessor

This paper demonstrates advances made in correcting the effects of ambient temperature and supply voltage on an oven controlled crystal oscillator (OCXO) by means of a microprocessor. In one implementation, the controller is programmed to read ambient temperature and/ or operating supply voltage; and then calculate a correction voltage that is applied to a varactor diode in series with the resonator. In another method, the oven controller itself is steered as a function of ambient temperature or supply voltage to achieve desired compensation. A single-board OCXO housed within an industry standard CO-08 enclosure has been utilized for this investigation. The uncompensated design exhibits a typical thermal gain of 75 degC/degC and an inherent temperature coefficient (TempCo) averaging about 10 ppb.