Robust Modulation of PWM-Based Multi-Level Perpendicular Magnetic Recording for Conventional Media

In this letter, we propose a robust 3-ary modulation for a pulse width modulation (PWM)-based multi-level perpendicular magnetic recording. In the proposed 3-ary modulation, narrow-width pulses are restrained in PWM signal corresponding to resolution of magnetic media. We evaluate a user bit density (UBD) gain in our proposal using a low-density parity-check (LDPC) coded frame error rate performance. A low-resolution media is assumed as read/write (R/W) channel in the evaluation. Our simulation results show the proposed modulation has robust UBD gain compared with the conventional binary R/W systems in the low-resolution media. In addition, our proposed 7B6T modulation with non-binary LDPC codes over GF(128) has more than 6% density gain from the practical binary systems.