| 摘要 |
PROBLEM TO BE SOLVED: To perform simply and accurately evaluation of signal quality performed by obtaining the standard deviation of frequency distribution for the path metric difference of two lines in a correct solution state of trellis diagram in a PRML decoding process. SOLUTION: In PRML decoding process of a reproduced signal from a magneto-optical disk 1, path metric difference is obtained with a path metric calculating circuit 6, a viterbi decoding circuit 7 and a threshold value register 8. The relative frequencies of one side part in which the frequency distribution of the path metric difference is sectioned by using the prescribed threshold value is obtained with a comparator 9, counters 10, 11 and a dividing device 12. The quality of a reproduced signal is evaluated with a controller 13 on the basis of this relative frequencies. |
