Externally compensated crystal oscillator (ECXO) study

The primary objective of this contract was an investigation and exploratory development of an externally compensated crystal oscillator (EXCO) in which frequency-temperature compensation of the C-mode frequency of an SC-cut quartz crystal is achieved by utilizing the concurrent B-mode frequency as a highly sensitive digital temperature sensor. The digitized B-mode output, used in conjunction with a microcomputer and a stored frequency/temperature look-up table or a suitable compensation algorithm, is able to provide precise and accurate clock corrections over a much wider range than that possible with a conventional TCXO oscillator (a temperature compensated oscillator which employs a voltage-variable capacitor for direct oscillator frequency control).