Crystal-Controlled Oscillators

Crystal-controlled oscillators are commonly used to provide the stable frequencies required for electronic communications, navigation, and data processing systems. Depending upon the frequency of operation, ambient conditions, and specific oscillator design, crystal-controlled oscillators are capable of providing frequency stability varying from about 1 × 10-4 to 1 × 10-11 over time periods ranging from milliseconds to years. The specification and/or description of the performance characteristics of crystal-controlled oscillators has remained a source of misunderstanding and dissatisfaction for both supplier and user, due largely to a lack of standard nomenclature and definitions as applied to crystal-controlled oscillators. It is the objective of this paper to summarize some of the performance characteristics of crystal-controlled oscillators, to propose a suitable terminology for their description, and to suggest the important parameters that should be included in any crystal-oscillator specification.