
3-16
Operation
KJM6335
3.7
Symmetry and Slice Level
The CD (EFM) modulation systems provide a time ratio of 50:50
between "1" and "0" when bit strings are averaged. In other words,
DSV (Digital Sum Value) is "0," indicating that the signal does not
contain a DC value. However, when signals are recorded to disc,
the pit length on the disc changes, due to various conditions such as
optical power at mastering, the developing time of the original
disc, and other factors. When a pickup reads the disc, the RF signal
will have a DC value. This phenomenon is called "asymmetry."
Slicing the RF signal at the center of the full amplitude of the RF
signal when binary-coding the signal gives a DC value to the signal
obtained after slicing. In slicing the RF signal, a certain slice level
will prevent the signal from taking a DC value after slicing. This
level is known as the symmetry level of the RF signal.
Operations When SYMMETRY mode is set to AUTO
(AUTO: lit)
The KJM6765 has a feature that allows the slice level to follow up
the symmetry level of an RF signal automatically to correct the
asymmetry of the RF signal. This is done by feeding back the slice
level so that the DC value of a signal obtained after slicing the RF
signal becomes 0.
Signal after slicing is
integrated and compared
with 0.
Slice level is controlled
so that the DC value of
the output signal becomes 0.
Output signal
Fig. 3-7
Fig. 3-7 shows a typical automatic symmetry level follow-up
circuit. Changing the slice level of an input signal in this way varies
the DC value of the signal obtained after the slicer. This allows for
feedback control.
Содержание KJM6335
Страница 1: ...KJM 6335 Part No Z1 002 622 IA002856 Jul 2009 KJM6335 OPERATION MANUAL CD TIME INTERVAL JITTER METER...
Страница 10: ...VIII Contents KJM6335...
Страница 12: ...P 2 Preface KJM6335...
Страница 41: ...KJM6335 Operation 3 7...
Страница 47: ...KJM6335 Operation 3 13...
Страница 104: ...4 46 GPIB Operation KJM6335...
Страница 112: ...5 8 Control Using EXT I O KJM6335...
Страница 126: ...A 2 Appendix KJM6335...