Recent results on quartz crystal LD-cuts operating in oscillators

These last few years, a new doubly rotated cut of quartz crystal resonator has been thought up at the LCEP (Laboratoire de Chronometrie Electronique et Piezoelectricite). This cut, named LD-cut for "low isochronism defect" cut, exhibits an amplitude-frequency effect one hundred times lower than the SC-cut one, that is to say a relative frequency change of about 1·10^-11. This paper deals with the behavior of such a crystal cut working in an oscillator. It is based on results from a batch of 10 MHz LD-cuts recently manufactured in a BVA process. Properties, advantages and drawbacks of the LD-cut are first reviewed. They have been tested in terms of noise and then built in oscillators. Experiments with various resonator drive levels have been performed. Measurements of their power spectral density of phase fluctuations are given and discussed.