COMPENSATION OF NONLINEARITIES IN HIGH-DENSITY MAGNETIC RECORDING CHANNELS

Volterra-series models of magnetic-saturation recording channels are u sed to derive readback structures that compensate for channel nonlinea rities. These structures are based on a canceler of linear and nonline ar channel distortions, and can achieve significant;improvement in ter ms of mean-square error and error probability. Proper operation of the canceler requires reliable preliminary decisions to be taken on the i nformation symbols. These decisions are obtained by passing the receiv ed signal through a linear equalizer, then processing the equalized si gnal through a symbol-by-symbol detector or a Viterbi detector. By usi ng the data obtained in [4] for magneto-resistive heads, it was found that symbol-by-symbol preliminary detection performs adequately. A Vol terra model was also obtained experimentally for the recording channel generated by magneto-inductive heads. that exhibit higher-order nonli near effects. In order to recover data from this highly distorted chan nel the preliminary detection scheme needs a 4-state Viterbi detector.