Viterbi detector and information reproducing apparatus
AssigneeNEC Corporation
InventorHiromi Honma
Life of this patent
Estimating the term…
Abstract
A Viterbi detector includes an ACS circuit that performs addition of a path metric and branch metrics, comparison of the path metric values and path selection based on the result of comparison. The ACS circuit performs a path decision based on the path metric values and the reproduced signal supplied to the Viterbi detector at the time instant that is a specified number of channel clocks earlier during the path selection. The ACS circuit selects a mark-continuing path if the reproduced signal at the time instant that is the specified number of channel clocks earlier has an amplitude corresponding to any mark, and performs path decision based on the path metric values if the reproduced signal does not have the amplitude corresponding to any mark.
Claims21
A Viterbi detector for identifying recorded data in a reproduced signal from an information recording medium, comprising:
- a branch-metric calculation unit that calculates branch metric values corresponding to the reproduced signal and a plurality of possible paths;
- a path metric calculator that includes an adder that adds a path metric value currently retained and the branch metric values corresponding to the reproduced signals of a plurality of possible paths, a comparator that compares results of addition by the adder corresponding to the plurality of possible paths with one other, a path selection circuit that refers to a result of comparison by the comparator and selects a single path out of the plurality of possible paths, and an update unit that updates the retained path metric value by the result of addition corresponding to the single path;
- and
- a decision circuit that performs a path decision based on the path metric value currently retained by the path metric calculator and the reproduced signal at a specific time instant that is a specified number of channel clocks earlier, wherein:
- the selection circuit selects the single path based on the result of comparison by the comparison circuit and the result of decision by the decision circuit.
A Viterbi detection method for identifying recorded data in a reproduced signal from an information recording medium, the method comprising:
- a path decision that selects a single path out of a plurality of paths based on a path metric value calculated from the reproduced signal and the reproduced signal at a specific time instant that is a specified number of channel clocks earlier.
An information reproducing apparatus comprising:
- a signal reproduction unit that generates a reproduced signal from an information recording medium;
- a branch-metric calculation unit that calculates branch metric values corresponding to the reproduced signal and a plurality of possible paths;
- a path metric calculator that includes an adder that adds a path metric value currently retained and the branch metric values corresponding to the reproduced signals of a plurality of possible paths, a comparator that compares results of addition by the adder corresponding to the plurality of possible paths with one other, a selection circuit that refers to the result of comparison by the comparator and selects a single path out of the plurality of possible paths, and an update unit that updates the currently retained path metric value by the result of addition corresponding to the single path;
- and
- a decision circuit that performs a path decision based on the path metric value currently retained by the path metric calculator and the reproduced signal at a time instant that is a specified number of channel clocks earlier, wherein:
- the selection circuit selects the single path based on the result of comparison by the comparison circuit and the result of decision by the decision circuit.
Dependencies are inferred from the claim text.