How Signal Generator Spectral Purity Affects Measurements
Application Notes
What is spectral purity?
Spectral purity is the inherent stability of a signal. Does it change in frequency? Stabilities can either be short or long term. Drift or long-term stability is usually defined over a period of time greater than a second. Does the signal drift off frequency in minutes, hours, days, or months? Current signal generator technology generally offers good long-term stability.
The greater concern is for short-term stability or changes in frequency in less than one second. These fluctuations come from non-deterministic signals like noise, shot noise and 1/f flicker noise that modulates the carrier. These affect both phase and amplitude.