System for detecting the presence of a digital signal carrier wave, and a receiver including such a system

摘要

The invention relates to a system for detecting the presence of a carrier wave in a digital signal that is available at a given frequency. The system delivers at least two baseband samples of the digital signal at each symbol time. The system comprises a timing estimator responsive to the baseband samples to deliver an error signal (epsi) corresponding to the phase error between the clock frequency that is to be recovered and a local clock frequency, and a detector that generates a detection signal indicating that a carrier wave has been detected whenever a level representative of the variance of the error signal (epsi) reaches a threshold value. The invention is particularly applicable to receivers of signals transmitted in DTMA mode.