Patent ID: 7817367

Claim:
A magnetic recording/reproducing apparatus, comprising a perpendicular magnetic recording double-layer medium with a soft magnetic underlayer and a reproducing head constituted by a magneto resistive effect type head with a shield film, wherein a reproduced signal outputted from said reproducing head is processed through a partial response equalization circuit having a frequency characteristic so that a low-frequency component of said reproduced signal including a direct current component is partially suppressed but not completely cut off through said partial response equalization circuit, wherein said reproduced signal outputted from said partial response equalization circuit is supplied to a maximum-likelihood decoder so as to be data-reproduced, wherein reproduced waveforms responding to a pair of the two closest recording transitions recorded on said recording medium at a shortest bit length interval are outputted as a waveform having intersymbol interference with intersymbol interference values A 1 , A 2 , A 3 , . . . , A k , . . . , A N wherein k is an integer indicating bit time, A 1 , A 2 , A 3 , . . . , A k , . . . , A N are real or integer numbers, and A 1 and A N are non-zero numbers with opposite signs or polarities: A 1 +A 2 +A 3 . . . +A k . . . +A N ≠0 and N>2 at each bit time through said partial response equalization circuit, or as a dipulse waveform having asymmetrical amplitudes with opposite polarities through said partial response equalization circuit, and wherein said outputted waveforms are supplied to said maximum-likelihood decoder so as to be data-reproduced.