The Phase-Locked Loop and Costas Loop

Abstract

In this study, the classical phase-locked loop (PLL) and Costas loop are investigated together. How the synchronization is obtained by the carrier recovery from the sinusoidal reference signal is mathematically shown with some assumptions and presented. It is concluded from this paper that Costas loop produces about half of the error signal produced by the PLL in the locked-stateoperation. This result may affect the decision whether the Costas loop will be used more frequently in the phase coherent communication systems in the future.