Also known as: Gardner timing recovery, Gardner

Gardner timing recovery is a feedback algorithm that estimates symbol-timing error using samples at the symbol and half-symbol instants.¹ A useful property is that it works independently of carrier phase.

Gardner timing recovery uses two samples per symbol (midpoint and peak) to track symbol timing.

How it works

Its timing-error detector drives a loop that nudges the sampling instant toward the centre of each symbol, where the eye is widest, tracking small clock drift.

Relevance to SDR

Gardner recovery is a common choice in SDR demodulators for locking symbol timing on PSK and QAM signals.

Sources

1. Symbol synchronization — Wikipedia, for symbol-timing recovery including the Gardner timing-error detector. ↩

See also

• Clock recovery
• Mueller–Müller timing recovery
• Symbol rate (baud)
• Demodulation

Learn it step by step

• Clock recovery & symbol timing

From the blog

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