Hitachi, Ltd.

Hitachi Video and Information System, Inc.

Noritaka Narita

Takuya Mizokami

Masahiro Takasago

Toru Kawashima

Masanori Matsuzaki

Makoto Asari

Takahiro Sunada

Toshiharu Kon

Naoto Kawakubo

Akira Takagishi

A PLL circuit produces a synchronous signal by utilizing a regenerative clock signal in a VFO portion in a regenerative signal which was read out from a recording medium in sections. When a defective portion is present in a regenerative clock signal, the same sector is read out again from the recording medium to obtain the regenerative signal. A loop gain of the PLL circuit is made to be low in the defective portion of the regenerative signal which was read out again, thereby to prevent the synchronous fault of the PLL circuit due to the defective portion.

Apparatus for reproducing data from a regenerative signal using a PLH

An information recording method and apparatus records information signals having data signals and synchronizing signal patterns inserted at predetermined intervals of the data signals on a recording medium with a binary level by using a coding rule without a DC free property. The synchronizing signal patterns are inserted into the data at intervals of a fixed block length and are supplied to a recording apparatus as a mark/space pattern (record signal pattern). The data are converted into the same pattern as the mark/space pattern and an accumulated value (corresponding to the average DC value) for each block length is counted. The sum and the difference of an output of a memory which stores the accumulated values from the head of the sector to the (N-1)-st block, and the accumulated value of the N-th block, are compared with each other in absolute value. When the difference is smaller than the sum, a pattern inversion circuit is operated at the head of the N-th block of the record code string to invert the polarity of the record signal pattern, and when the sum is smaller than the difference, the pattern inversion circuit is not operated and the polarity of the record signal pattern is not inverted.

Information recording and reproducing apparatus for reducing average DC

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Fujisawa, Japan

Noritaka Narita