Jitter measurement method for the PRML signal processing

Abstract

The Blu-ray Disc (BD), which achieves approximately five times the recording density as that of a DVD, employs 1-7PP encoding, a more efficient encoding method than EFM+ modulation (8-16) of DVD. The shortest mark length recorded by this method is 2T (approximately one-third of the length) as compared to 3T of a DVD (where T is the channel clock period). Because it is difficult to reproduce such high-density signal using binarized decoding, Partial Response Maximum Likelihood (PRML) is often used in its place. Jitter, which has been used as a reference in the evaluation of the reproducing signal of DVDs, does not necessarily match the bit error that results from PRML decoding. Consequently, BD which heavily uses PRML decoding requires a new evaluation method that replaces the conventional method using jitter evaluation. Because the correlation between the jitter and bit error is worse when the jitter of the 2T mark is predominant among all mark jitters, we focused our attention to jitters that exclude the jitter of the 2T mark as a reference for evaluating the S/N ratio of the system directly through the use of the inter-symbol interference analysis function of the time interval analyzer. This paper describes the analysis of the correlation between jitters that exclude the jitter of the 2T mark and the bit error rate.