Multi-Level Read/Write Signaling Using Pulse Width Modulation for High Density Perpendicular Magnetic Recording

In this letter, we propose a novel read/write (R/W) signal processing method by 3-ary amplitude shift keying for high density perpendicular magnetic recording. We also provide a 3B2T modulation to generate 3-ary signal, which will be converted to a pulse width modulation (PWM) signal, and then recorded on magnetic media. The PWM signal can be simply demodulated to derive the 3-ary signal through a low-pass filter at readback side. The demodulated signal in the presence of intersymbol interference is detected by the Viterbi algorithm as partial response signal. Nonbinary low-density parity-check codes over GF(8) are applied as error correcting codes in our evaluation. Our simulation result shows the proposed R/W method has +4% more user bit density gain than conventional binary recording.