Patent 7127665 was granted and assigned to Sony on October, 2006 by the United States Patent and Trademark Office.
The present invention is to reduce the maximum magnetization reversal interval of a trellis code. A trellis diagram for the trellis code takes into consideration a constraint condition on the DSV of a code and an inter-symbol-interference for three bits. The minimum squared Euclidean distance is 4. When a non-interleaving encoder and a non-de-interleaving code detector are constructed using the trellis diagram, the maximum magnetization reversal interval of a trellis code to be used is reduced to half of that in a known case while having the error rate and circuit size approximately equal to those in the known case. The trellis diagram has a basic repeating unit for two bits. In the actual apparatus, the trellis diagram is repeatedly used. The present invention is applicable to a read/write apparatus.