Carrier frequency recovery for a fully digital direct-sequence spread-spectrum receiver: A comparison

A family of different structures for carrier frequency estimation and correction in fully digital direct-sequence spread-spectrum (DS/SS) receivers for M-ary phase shift keying (MPSK)-modulated signals is presented. The performance of the proposed structures is compared analytically as well as by computer simulation. Among the different estimators, feedforward structures are shown to yield near-optimum bit-error performance at moderately large carrier frequency offsets. Furthermore, the use of feedforward estimators allows the design of digital DS/SS modems showing superior acquisition behavior. The simplicity of the involved operations makes the presented structures attractive for VLSI implementation