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.
NISTís 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.
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:
-- PM and AM Noise
-- Clock Jitter
-- Frequency and Time Stability
-- Allan and Total frequency variances
-- Jitter Histogram
-- Fourier Transform
-- Kalman Filter
-- Tunable Noise and SSB-Tone Standards
-- Frequency (Atomic Frequency Reference)
-- Beat Frequency (Heterodyne and Dual Heterodyne)
-- Digital Clocks and Logic Devices
-- Frequency Standards
-- 1 kHz to 110 GHz
-- 1 x 10-15 frequency stability
-- Clock Jitter down to 10 femtoseconds
-- L(f) down to -177 dBc/Hz for 0 dBm signal at room temperature