Patent ID: 8144415

Claim:
A magnetic recording/reproducing apparatus, comprising a perpendicular magnetic recording medium and a reproducing head, wherein a reproduced signal outputted from said reproducing head is processed through a partial response equalization circuit having a function of a noise-whitening matched filter, and 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 having said noise-whitening matched filter function, wherein said reproduced signal outputted from said partial response equalization circuit having said noise-whitening matched filter function 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 having said noise-whitening matched filter function, or as a dipulse waveform having asymmetrical amplitudes with opposite polarities through said partial response equalization circuit having said noise-whitening matched filter function, and wherein said outputted waveforms are supplied to said maximum-likelihood decoder so as to be data-reproduced.