A novel AGC scheme for DFE read channels

The problem of automatic gain control (AGC) for DFE (decision feedback equa lization) read channels is addressed. We analyze an existing AGC algorithm that uses slicer input for deriving the gain error signal and show that it suffers from ambiguity in the control direction of AGC loop due to the pres ence of feedback equalizer. This could result in slow convergence and possi ble instability problems. A new AGC scheme has been proposed to overcome th is ambiguity and it uses the sign of the forward equalizer output instead o f slicer input to control the AGC loop direction. Simulation results show g ood acquisition and tracking performances of the new scheme under noisy cir cumstances.