Perpendicular magnetic recording of analog signals by means of pulse width modulation

A pulse width modulation (PWM) recording, which effectively utilizes the perpendicular recording feature, is proposed to record analog signals on perpendicular media. Experimentally obtained PWM recording results showed a good linearity in a wide signal frequency range, even at high modulation levels. Frequency response curve for a double-layer (Co-Cr/Fe-Ni) medium differs from that for a single-layer (Co-Cr) medium. This difference is explained by the backlayer (Fe-Ni) flux-sink effect in the double-layer medium.