Characterization and detection of PPM-encoded servo signals in tape drives

Timing-based servo signals, which are read back from dedicated servo patterns on tape to generate estimates for the operation of reel-to-reel and track-follow servomechanisms, are characterized by a first-order position jitter noise and pulse-width variation noise model. A method for the identification of servo signal parameters and the evaluation of the relative contributions of additive noise and medium noise components is presented. The performance of matched-filter detection of binary symbols that are embedded in recorded servo patterns using pulse-position modulation is investigated, and an analytical expression for the symbol-error probability in the presence of additive noise and medium noise is obtained. Finally, the performance of a near-optimum detector approximating the matched filter is evaluated by simulations and compared with matched-filter detection performance.