Time and frequency stability of oscillators: models

Time and frequency are the physical quantities measured and generated with the greatest precision, far from it, which has led to the definition of several other physical quantities being linked to the definition of the second.

The first consequence of this extreme precision is the ever-increasing number of systems using frequency standards, whether quartz oscillators or atomic clocks. In addition to metrology applications, the various sectors concerned include telecommunications, positioning (GPS, Galileo) and all domestic applications using the stability of an oscillator either directly (hi-fi systems, micro-computers, etc.) or indirectly (quartz thermometers, electronic scales, etc.).

The second consequence concerns time-frequency metrology, which is extremely demanding in terms of rigor in the choice of relevant quantities to characterize oscillator stability, and in the definition of analysis methods. This is why we felt it necessary to devote two dossiers to the scientific background underlying all "time-frequency" metrology. The first is devoted to the presentation of , the second to analysis tools . As a result, these are rather theoretical texts, even though we were keen to illustrate the estimation of oscillator stability with concrete examples. This is where all the concepts are defined that will enable the reading of the other, more experimental texts that follow: "Time and frequency generation" [R 1 780] and "Time-frequency instrumentation" [R 1 785] .