[Paper] A Study on Timing Recovery for High-Recording-Density Tape Systems

Abstract

Tape systems experience large speed variations compared to disk systems, and therefore, it is necessary to design a stable timing recovery scheme that can operate under a low signal-to-noise ratio (SNR) condition. In such low SNR scenarios, the decision error made by the detector often results in a phase-locked loop circuit losing track of the correct signal. This phenomenon is often called the loss-of-lock (LOL) phenomenon. In order to mitigate the LOL issue, soft information from the soft output Viterbi algorithm decoder is used to control the feedback in the timing recovery loop. Therefore, a timing recovery method for high-density tape storage system is studied in this paper. By applying this new method to the read back signal from the actual tape drive, it is verified that the negative effect of misdetection due to unreliable decisions from the detector can be compensated, with only a minor increase in implementation complexity.