Oscillator AM-to-FM noise conversion due to the dynamic frequency-drive sensitivity of the crystal resonator

An analysis has been made of the potential effects of AM-to-FM noise conversion in quartz crystal oscillators as a result of the dynamic frequency-drive sensitivity of the crystal resonator. The analysis indicates that it is quite possible for the FM noise resulting from AM-to-FM conversion in the crystal resonator to equal or exceed that due to the conversion of oscillator open loop phase noise to closed loop frequency noise. This is especially true in oscillators designed to exhibit low white phase noise (floor) levels by operating the crystal resonator at relatively high drive level. In addition, the analysis indicates that, for the same drive sensitivity, the relative degradation in FM noise level due to this effect is more severe at lower relative oscillator operating frequencies.

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