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State of the Art in Crystal Oscillators, Present and Future

The state of the art of stable crystal oscillators for frequency control and timekeeping is discussed. The results of an oscillator evaluation program show that temperature compensated crystal oscillators (TCXO's) in the 5 ppm stability class are available from several sources. The availability of higher stability TCXO's (1 ppm or less) is limited. System designers planning to use high stability TCXO's are cautioned to specify carefully, plan on a thorough incoming inspection program and plan on a backup position using less stable oscillators. The limitations on the performance and availability of oven controlled crystal oscillators (OCXO's) are also discussed. A summary of recent developments which promise to result in order of magnitude improvements in the stability of both TCXO's and OCXO's is presented. A comparison is made between the best performance that is available today and what is likely to be available by 1990.