Also known as: eye diagram, eye pattern

An eye diagram overlays many short segments of a demodulated signal, each one symbol period long, so they stack into characteristic “eye” shapes between the symbol levels.¹

An eye diagram overlays symbol periods; a wide-open eye means good timing and noise margin.

How it works

The wider and taller the eye opening, the more margin the decoder has to sample each symbol correctly. Noise and timing jitter close the eye. A 4-level signal like C4FM shows three stacked eyes.

Relevance to SDR

GopherTrunk’s eye-diagram panel shows timing and noise margin at a glance, complementing the constellation for diagnosing a marginal signal.

Sources

1. Eye pattern — Wikipedia, for the overlaid-symbol-period display and what an open eye indicates. ↩

See also

• Constellation diagram
• Clock recovery
• Symbol rate (baud)
• C4FM

Learn it step by step

• Digital modulation & constellations
• Tuning for a clean lock