Also known as: John Costas, John P. Costas

John P. Costas was an American engineer best known for the Costas loop, a phase-locked carrier-recovery circuit he devised in the 1950s.¹ It made coherent reception of suppressed-carrier signals (such as SSB and later PSK) practical.

Costas's carrier-recovery loop feeds a phase-error estimate back to a controlled oscillator.

Contribution

The Costas loop remains a standard building block in digital receivers, including the carrier recovery used when demodulating phase-modulated digital-voice systems.

Sources

1. John P. Costas (engineer) — Wikipedia, for biography and his invention of the Costas loop. ↩

See also

• Costas loop
• Phase-shift keying (PSK)
• Single sideband (SSB)
• Demodulation

Learn it step by step

• Clock recovery & symbol timing