A quality frequency source (oscillator) is often required for the loca
l oscillator (LO), in a wireless handset, the frequency reference in a
phase-locked LO, or the master clock source in a microprocessor or da
ta-acquisition (DAQ) system, The important signal-source parameters ar
e frequency accuracy and frequency stability, Accuracy pertains to the
initial value of frequency while stability refers to the frequency's
phase-noise (short-term) and drift (long-term) components, which are a
ffected by temperature and aging of the crystal.