Kikusui KJM6310, Operation Manual

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3-8 Operation KJM6310
3.4 Symmetry and Slice Level
In the DVD modulation (8-16 Modulation) or CD modulation (EFM),
the time ratio of 1s and 0s are 50:50 when the bit sequence is aver-
aged. This is expressed as DSV (Digital Sum Value) being 0. It signi-
fi es that the signal contains no DC component. However, when
signals are recorded to the disk, various conditions such as the optical
power during mastering and the developing time cause the pit lengths
of the disk to vary. Consequently, when the pits are read by the
pickup, the RF signal will contain a DC component. This phenome-
non is referred to as asymmetry. If the RF signal is sliced at the center
of all amplitudes of the RF signal when the RF signal is binary-coded,
the signal after slicing will have a DC component. The RF signal
symmetry level refers to the level at which the signal after slicing will
not have a DC component when the RF signal is sliced.
Operation when SYMMETRY mode is set to AUTO
The KJM6310 is equipped with a function that automatically controls
the slice level to follow the symmetry level of the RF signal to correct
the RF signal asymmetry. This function is achieved through feedback
control so that the DC component of the sliced RF signal will be 0.
Fig.3-7
Fig. 3-7 shows a typical symmetry level follow-up circuit. By chang-
ing the level at which the input signal is sliced, the DC component of
the sliced signal is changed and allows feedback control.
Integrate the sliced signal
and compare with 0
Control the slice level
so that the DC value of
the output signal is 0
Output signal