The oscillating, or repeating, signal that is the basis for constructing all signals is a voltage that exactly follows simple periodic sine and cosine functions of time. The synthesis of such signals, using an oscillator coupled with a "frequency synthesizer" can never be perfectly realized because the voltages from these devices are perturbed by random noise from real electronic components.

Frequency synthesis plays a role in virtually all present-day commercial, industrial, and military technologies. State-of-the-art low-noise frequency synthesis is a particularly important technical asset to high-speed telecommunications, efficient management of the wireless spectrum, and high-resolution imaging. It is worth noting that overall performance of various technologies depends on, and is often limited by, phase and amplitude noise fluctuations in oscillators and frequency synthesizers.

NIST’s Time and Frequency Metrology Group has the world's most advanced measurement and calibration facilities for characterizing noise components in oscillators and frequency synthesizers. It engages in many activities to determine the cause of various kinds of noise for the purpose of isolating and reducing it, leading to improved components, instruments and techniques that are often necessary in new applications.

Activities include:
    1) measurements of oscillator phase noise (equivalently, relative time-fluctuation noise), and associated amplifiers and passive-devices, for government, commercial, industrial, and military users,
    2) technical training, mentoring, and consulting through seminars, workshops, and on-site visitations and facility inspections,
    3) certification of phase and time-fluctuation noise measurements of national metrology laboratories,
    4) technology transfer, primarily with respect to oscillators, measurement systems, and analysis techniques, to insure best performance, consistency, and accuracy in specifications.

As steady state phase noise becomes lower and lower, temperature fluctuations, acceleration, and other environmental effects, cause various phase instabilities. To augment the Group's phase noise metrology program, we have expanded characterization of oscillator and other-device environmental sensitivity to include vibration and acceleration sensitivity. A fast-growing concern in future electronics systems is that acceleration sensitivity causes vibration-induced noise that coincides with a critical range of offset frequencies relative to an oscillator's carrier frequency.

The Time and Frequency Metrology Group has a responsibility for: