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Signal Processing for Dedicated Servo Recording System

Perpendicular magnetic recording (PMR) in the hard disk drive is approaching its physical limits. In an earlier work, the dedicated servo recording system has been proposed to provide continuous position error signal (PES) for servo, enable higher servo sampling rate and improve the overall servo performance. A further benefit is that the dedicated servo layer results in surface area savings at the data layer. However, it was also reported that the embedded servo layer introduces baseline variation and non-linear transition shifts to the readback signal of the data layer.

In this work, we propose novelsignal processing techniques to improve the bit error rate (BER) in dedicated servo recording. The synchronous averaging technique is proposed to improve the BER in the presence of baseline variation distortions. Further, the servo and data-dependent noise prediction (SDDNP) method is proposed to mitigate the effect of the non-linear transition shift. Through the use of these techniques the linear density loss from conventional PMR media is reduced.