Adaptive nonlinear decision feedback equalization with channelestimation and timing recovery in digital magnetic recordingsystems

摘要

In high density digital magnetic recording systems, the nonlinearneffects in the write process appear in the readback waveform as shiftsnin the peak positions and changes in the amplitude. The pulse shiftncauses a nonlinear intersymbol interference (ISI) on the readbacknsignal. In this paper, a Volterra-DFE, in which a Volterra filter isnused in the feedback section of decision feedback structure, is proposednto equalize the nonlinear ISI. By theoretical analysis, the minimum meannsquared error (MSE) of the Volterra-DFE is found to be a function ofnsampling phase. This will affect the output signal-to-noise ratio (SNR)nof the playback system. A baud-rate timing recovery system innconjunction with a channel estimator is used to operate the samplingnclock on the optimum phase. By computer simulation, Volterra-DFE isnfound to outperform conventional DFE in both output SNR and BER in anhigh density magnetic recording system