A Study of Three-Dimensional Equalization for Reproducing a Double-Layer Magnetic Recording Medium

To increase the recording density of hard disk drives (HDD), three-dimensional (3-D) magnetic recording with multiple recording layers is attracting much attention as a next-generation recording method. We have reported that the two-dimensional (2-D) partial response maximum likelihood (PRML) can achieve a good BER performance using the PR channel obtained from the differential-phase bit response in the 3-D magnetic recording system with a double recording layer. In this study, we realize the 3-D equalization by the 2-D finite impulse response (FIR) (2-D FIR) filter and 2-D PRML system over two layers and evaluate the 3-D equalization to further increase the recording density. The transfer function of the 2-D PR channels is determined by the response for the in-phase or differential-phase bits in a double-layer magnetic recording medium. The results show that the 2-D PRML channels with 3-D equalization based on the differential-phase transfer function achieve a good bit error rate (BER) performance for system noise.