Spurious-Free Dynamic Range

Formula

Description

Spurious-free dynamic range is the ratio of the wanted signal to the largest unwanted spur (harmonic or spurious tone) in the spectrum. It defines the usable dynamic range of a converter or receiver: a small signal can only be detected if it sits above the worst spur. SFDR is critical in communications and instrumentation where weak signals must be found near strong ones.

Variables

• SFDR — Spurious-free dynamic range (dB)
• Vsignal — Amplitude of the fundamental (V)
• Vspur — Amplitude of the worst spurious tone (V)

Practical Notes

SFDR is often specified separately from SNR because a single spur, not the broadband noise, limits the ability to resolve small signals. Dithering can trade SFDR against noise floor.