R&S FSL Cable TV Measurements (Option K20)
1300.2519.12 2.47 E-11
Analog TV Basics
This section gives an introduction into the fundamentals of analog modulated TV signals. A special
focus is laid on the parameters that the Cable TV Measurements option (K20) uses to characterize
signals.
For analog modulated TV signals based on PAL, SECAM, and NTSC, Fig. 2-32 shows the situation in
principle: the components of the signal, and both frequency and level at the output of a TV transmitter
(RF range).
Fig. 2-32 Analog modulated signals in the RF range
The gray area marks the TV channel. Inside this area, all components of a TV signal are located. A TV
signal consists of the following:
• The vision carrier, indicated in Fig. 2-32 with "vision", is located 1.25 MHz above the channel
start. The vision carrier has the highest level and mainly assesses the total power of the
channel. It transmits the luminance information and is amplitude modulated. The amplitude
modulation is mostly negative (the smaller the luminance signal the larger the vision carrier
level), apart from SECAM/L (large vision carrier level combined with a large luminance signal).
Only a part (around 0.75 MHz) of the lower sidebands of the vision carrier is transmitted.
Therefore it is called "residual sideband modulation". The video bandwidth BW
video
amounts to,
depending on the standard, approx. 5 MHz (e.g. PAL B/G) or approx. 4 MHz (e.g. M/NTSC).
• The color carrier, indicated in Fig. 2-32 with "color", is shifted by f
color
to a higher frequency
value in respect to the vision carrier. The magnitude of f
color
depends on the standard. The level
of the color carrier is by far smaller than that of the vision carrier. Depending on the standard,
the signal is analog quadrature amplitude modulated (e.g. PAL B/G) or frequency modulated
(SECAM).
The color carrier is not considered in the measurements of the Cable TV Measurements option.
• One or two sound carriers, indicated in Fig. 2-32 with "sound 1" and "sound 2", are shifted by
f
sound1
or f
sound2
to a higher frequency value in respect to the vision carrier. The magnitude of
f
sound1
or f
sound2
depends on the standard. The level of the sound carriers is by far smaller than
that of the vision carrier. Depending on the standard, the sound carriers are frequency,
amplitude, or NICAM (digitally) modulated. The sound carriers do not need to possess the
same modulation. For example, a combination of a frequency modulated carrier with a NICAM
modulated carrier is possible.
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