Spectral Purity
Short-term phase fluctuations in periodic signals manifest as unwanted energy spread around carrier frequencies in oscillator outputs. Spectrum analyzers and dedicated phase noise test sets quantify phase noise in decibels relative to carrier power per hertz bandwidth. Measurements evaluate power spectral density across offset frequencies ranging from hertz to megahertz from nominal carrier lines.
Frequency Stability
Thermal agitation and semiconductor shot noise within active oscillator circuits generate random phase fluctuations. Close-in offset noise reflects flicker frequency variations, while far-out offset noise defines the broadband noise floor of signal generation equipment. Low phase noise maintains clock stability in high-resolution analog-to-digital converters and radar sensing systems.
Quartz crystals or acoustic wave resonators minimize internal phase jitter by concentrating RF power into narrow resonant modes.
Sensor Degradation
Radar and ultrasonic sensing receivers convert phase fluctuations directly into range measurement uncertainty and target velocity errors. Phase jitter spreads strong clutter signals into adjacent frequency bins, obscuring weak target returns in Doppler signal processing. Specifying low noise floor performance prevents sensitivity loss in coherent detection front-ends.
Measurement Protocol
Phase noise verification requires cross-correlation test systems to eliminate internal analyzer noise floors. Calibration procedures verify reference oscillator stability and carrier suppression levels before recording spectral power density curves. Quality certificates list phase noise density values at specific standard offset frequencies.
