Read Channel for Multilevel Run-Length-Limited Read-Only Disc

A novel multilevel run-length-limited read channel which employs an interpolating timing recovery system and an adaptive partial-response maximum-likelihood (PRML) detector is developed. In proposed adaptive PRML detection system, we adopt a 112-levels adaptive Viterbi detector which uses every RF sample to adjust the reference levels for the calculation of branch metrics. The reference levels of adaptive Viterbi detector are also used to regenerate RF signals for phase error calculation. The usage of adaptive PRML detector makes the performance more robust, and the combination of Viterbi reference levels and RF generator makes the calculated phase errors more accurate.