Tektronix 77807-1, Руководство пользователя

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Glossary
Glossary–2
DS1000 Series User Manual
CW
Continuous Wave. A separate subcarrier sine wave used for
synchronization of chrominance information.
dB (Decibel)
A logarithmic unit used to describe signal ratios. For voltages,
dB = 20 Log
10
(V
1
/V
2
).
Demodulator
In general, any device that recovers the original signal after it has
modulated a high frequency carrier. In television, it refers to one of
the following descriptions:
1. An instrument, such as the Tektronix DS1001, which takes
video in its transmitted form (modulated onto the picture
carrier) and converts it to baseband.
2. The circuits that recover R-Y and B-Y from the composite
signal.
Field
Half of the video lines required to produce a full video frame. In
interlaced scan systems, such as NTSC and PAL, the information
for one video frame is divided into two fields. Two vertical scans
overlay the two fields to produce the complete frame. In the
complete frame, adjacent video lines in the picture are from
alternate fields.
FM
Frequency Modulation. The process by which the frequency of a
carrier signal is varied in proportion to the modulating signal, such
as an audio signal. In the NTSC and PAL television systems, audio
information is transmitted using FM.
Frame
Contains all the information required for a complete picture. For
interlaced scan systems, there are two fields in a frame.
Harmonic Distortion
Signal distortion caused by non-linearities in a system. System
non-linearities produce multiples of a single frequency signal
applied to the the system. Harmonic distortion is evident when a
pure sine wave applied to a system produces harmonic content at
multiples of the sine wave frequency at the output.
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