Solving the interaction problem of timing synchronization and equalization

In a digital receiver the adaptation processes of the adaptive equalizer and the decision-directed timing synchronizer are coupled. As a consequence these circuits interact and the sampling phase and the equalizer coefficients are drifting slowly. This interaction can give rise to a performance degradation of the receiver. In this paper the adaptive circuits of the equalizer and of the synchronizer are described as control loops and the coupling mechanisms are explained by means of loop-equivalent models. We propose a new solution to the interaction problem that can be implemented as a simple circuit. Timing-phase information that is contained in the equalizer coefficients is fed into the timing-control circuit. In this way the synchronization and the equalization processes can be coordinated.