The rotating-target algorithm for jointly detecting asynchronous tracks

Two-dimensional magnetic recording promises to increase areal density through the joint detection of multiple tracks of interest. This paper concerns the problem of joint detection of multiple tracks that are written asynchronously, meaning that neither the bit boundaries (phase) nor the bit rate (frequency) are aligned between neighboring tracks. We propose the rotating-target (ROTAR) algorithm for jointly detecting multiple asynchronous tracks from one or more readback waveforms. The proposed approach is based on the joint Viterbi algorithm and a time-varying target that results when the asynchrony of the tracks is absorbed into the underlying target. Timing estimation for the tracks being detected is embedded inside the joint Viterbi detector using per-survivor processing. Performance results show that the proposed algorithm closely matches the performance of a fictitious system in which neighboring tracks are synchronous, and further that it significantly outperforms a previously reported detector that separately detects the two tracks.