Signalling for peak power limited magnetic channels

The magnetic channel is peak power limited if the head is subject to saturation when reading flux transitions. This is the case, for example, when a magnetoresistive sensor is in contact with the magnetic tape medium. The authors describe two different approaches to peak amplitude reduction: (1) insert additional transition blocks between existing transitions (write equalization). The resulting transition response is DC free, therefore conventionally used equalization targets are not suitable. Read equalization transfer functions for both peak position and sampled detection are determined; (2) eliminate the binary input combinations causing high amplitude peaks. The authors describe a rate 4/5 code to reduce the peak amplitude of a read signal by 3 dB through the elimination of the 010 combination (NRZI coding), and provide a 20% density enhancement for EPR4 signaling in white noise