On coding and decoding for high-order partial response systems

High-data-rate signal processing for hard disk drives is discussed. A recording channel is equalized as a partial response (PR) (1+D)(1-D³), where D is a delay operator. Furthermore, 1/(1+D) pre-coding scheme is used, and the resulting response is given as (1-D³), which achieves three-bit interleaving. The working speed of each Viterbi detector in interleaving PR channels is reduced to one third of the original bit-frequency. The performance of the reduced two-state Viterbi detector in the interleaving PR channel is compared with the conventional two-state Viterbi detector of the PR4 system. As a result, the proposed system improves the signal-to-noise ratio by about 3.0 db compared with the baseline PR4 maximum system. Finally, it is shown that the Error Coding (ECC) scheme for the interleaving needs a reversed hierarchy of ECC and channel coding