False Lock Performance in Polarity-Type Costas Receivers in the Presence of Periodic Data Patterns

This paper addresses the false lock performance of receivers which use polarity-type Costas loops for the carrier recovery of unbalanced QPSK, asynchronous QPSK or BPSK signals in the presence of periodic data patterns. The potential false lock frequencies are first identified. Expressions for both true lock and false lock components are also derived, thereby allowing numerical evaluation of various key parameters for cases of practical interest.