Data retrieval

Details Data retrieval Data retrieval

2005-11-29

2005-11-29

Le, Amanda T. (Department: 2634)

Pulse or digital communications

Receivers

Particular pulse demodulator or detector

C375S288000, C714S794000, C369S275300

Reexamination Certificate

active

06970522

ABSTRACT:
A digital data storage (DDS) system for reading DDS tapes employs a partial response maximum likelihood detection system which utilises redundancy in the 8-10 DC free modulation encoding to reduce low frequency noise. The system incorporates a time-varying trellis decoder which embodies some of the PR1 rules together with the rules regarding the charge state or the digital sum variation (DSV) implicit in 8-10 modulation coding. The decoder operates to reject low frequency noise such as that caused by crosstalk noise between adjacent tracks on the tape. The trellis topography has been considerably simplified by adopting a two step six state trellis which operates on bit pairs and in which the states relate to the current DSV value, and sign of the previous bit.

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