Asynchronous Inter-Track Interference Cancellation (A-ITIC) for Interlaced Magnetic Recording (IMR)

Abstract

In this study, a novel inter-track interference (ITI) cancelling scheme is proposed for the interlaced magnetic recording (IMR). Recently proposed IMR shows an areal density capability (ADC) gain by recording tracks in an interlaced manner with separately optimized linear densities, while the severe ITI at the double-sided squeezed tracks limits the extra ADC growth. Due to the inherent frequency offsets between the target and side tracks in IMR, ITI in the squeezed track read-back signal cannot be suppressed effectively by conventional schemes. In order to account for the frequency mismatch effect, the proposed asynchronous ITI cancellation (A-ITIC) scheme estimates and subtracts the ITI contributions from its side tracks in the higher and lower frequency domains respectively, which enables efficient ITI mitigation for extra ADC growth. To estimate ITI responses from the side track data asynchronously, the interpolation filter based timing adjustment scheme is employed for the oversampled read-back signal. Then, the ITI signal is reconstructed jointly with two side track data in the oversampled domain, and realigned to the baud rate read samples by another set of interpolation filters. By subtracting the ITI estimate from the baud rate read samples, A-ITIC provides improved bit error rate (BER) performance, particularly for off-track read, and enables additional track density push for extra ADC gain. The proposed A-ITIC performance is numerically evaluated by the grain-level magnetic recording channel simulator near 1 Tb/inch square scenario. BER off-track performance can be improved by the proposed A-ITIC, and the track density can be pushed by a factor of 1.077, which corresponds to 7.7% extra ADC gain on top of the legacy IMR gain.