Timing-based servo (TBS), a technology developed in the mid-1990s for linear tape drives, has been adopted as the Linear-Tape-Open (LTO) standard. In TBS systems, recorded patterns to aid track-following servo consist of transitions with two different azimuthal slopes, as shown in Figure 1.
The lateral position is derived from the relative timing of pulses generated by a narrow head reading the pattern. TBS patterns also enable the encoding of additional longitudinal position (LPOS) information by properly shifting transitions from their nominal pattern position using pulse-position modulation. To improve the resolution of the position and velocity information, we are investigating advances in the servo-channel architecture which include:
- optimum matched-filter detection of servo bursts,
- optimum demodulation of LPOS symbols, and
- generation of a fixed number of signal samples per unit tape length, irrespective of tape velocity.