Also known as: clock recovery, symbol timing

Clock recovery determines a digital signal’s symbol timing from the signal itself, since the transmitter’s clock is not shared.¹ It lets the receiver sample each symbol at its centre, where the eye is widest.

Clock recovery finds the symbol rhythm from the signal itself so each symbol is sampled at its centre.

How it works

A timing-recovery loop watches where transitions fall and nudges the sampling instant to stay centred, tracking small clock drift. Common algorithms are Gardner and Mueller–Müller.

Relevance to SDR

Loss of symbol lock — from low SNR or multipath — closes the eye and breaks the decode, a key thing the scopes reveal.

Sources

1. Clock recovery — Wikipedia, on recovering symbol timing from a received signal. ↩

See also

• Gardner timing recovery
• Mueller–Müller timing recovery
• Symbol rate (baud)
• Eye diagram
• Demodulation

Learn it step by step

• Clock recovery & symbol timing

From the blog

• SDR Internals, Part 7: Symbol timing & sync recovery