Hilbert filter for double-layer perpendicular recording media

Readback waveforms from GMR heads in perpendicular magnetic recording are completely different from the regular longitudinal recording waveforms. Proper signal equalization is therefore critical. For this purpose a Hilbert filter is discussed. This filter is known to transform the dipulse response from a single layer perpendicular media into a longitudinal signal, however, for double layer perpendicular media with a soft magnetic underlayer its properties have not been reported yet. In this paper the authors discuss the performance of the Hilbert filter for double-layer perpendicular recording media.