Spectral Density
Frequency fluctuations in precision oscillators often exhibit a spectral density that varies inversely with the frequency. Natural flicker frequency noise typically dominates the short-term stability of quartz crystals and atomic clocks. It arises from physical processes within the resonator and its supporting electronics that are not fully modeled by classical physics.
Stability Floor
The presence of this noise creates a flat region in the Allan deviation plot where the frequency stability no longer improves with longer averaging times. This flicker frequency noise floor sets the fundamental limit for the precision of time-keeping instruments. It prevents the infinite averaging of errors that would be possible if only white noise were present in the system.
Long-term performance is hindered by this stationary stochastic process.
Material Influence
Environmental factors like temperature and pressure can influence the magnitude of these fluctuations. External conditions can change the slope of flicker frequency noise in sensitive oscillators.
Component Selection
High-quality resonators are selected based on their specific stability coefficients. Selecting components with low flicker frequency noise ensures long-term reliability for timing applications. Calibration cycles are often dictated by the rate at which these internal instabilities cause the frequency to drift away from the reference.
