Evaluation of oven controlled crystal oscillator performance under non-continuous stressed operating conditions

The frequency stability of a set of six oven controlled crystal oscillators has been measured under noncontinuous and other stressed operating conditions. The oscillators were subjected to a range of environmental conditions which would be experienced in an airborne communications terminal. A database, corresponding to those measurements, was generated for support of a Kalman Filter/Neural Network modeling and training effort. The tests were performed at a MITRE environmental control laboratory utilizing a vibration table which was enclosed within a heating chamber. An automated measurement system was used for control and data logging. Initial observations of the test results indicate that non-continuous operation in a benign environment has no noticeable impact on the aging characteristics, while aging under stress is harder to discern from frequency measurements made under composite environmental stress conditions. More elusive are the infrequent but sudden and permanent changes in frequency that appear to occur at random. The magnitude of those frequency jumps was often significant, and justifies further investigation