Schneider Electric Analog & digital TV processing User Guide

Application Note
Analog & Digital
TV processing with Delta 8
07
Application Note
Analog & Digital
TV processing with Delta 8
Presentation
The Delta 8 core unit for home network is fitted
with a TV path processor compliant
with International TV rules.
The design of a TV distribution system in home,
involves the respect of severals rules.
The main requirements of the TV standardisation committees
are summed up below. This document covers:
b Signal levels for analogue and digital signals
b Signal quality for analogue and digital signals
b Bit Error Rates for digital signals
b TV signal attenuation in the air and through a cable
b Amplification constraints due to the number of channels to be processed
b Consequences of misprocessing the TV signal.
Then, a special focus will cover the TV processor
built-into the Delta 8 core unit.
b Equalisation
b Gain control
b Tilt adjustment.
Notice: the target values indicated were decided by CENELEC, the European standardisation
committee and described in the EN50083-x standard. However, some target values may vary
according to specific country rules and installation habits.
Delta 8 in Home Networks
TV
LAN
Telephone
Data switching
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Presentation
2
Signal levels for analogue and digital signals
4
Signal quality for analogue and digital signals
5
Bit Error Rate for digital signals (BER)
6
TV signal attenuation
through a cable
7
Consequences of TV system
misprocessing for the end user
8
Delta 8 TV adjustment functions
with Delta 8 test kit
9
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3
Signal levels for analogue
and digital signals
Application Note
Analog & Digital
TV processing with Delta 8
The minimum and maximum values change depending on whether the signal is
analogue or digital. There are the values in the frequency range from 47 to 860 MHz
at the telecommunication outlet.
Both a minimum and maximum signal level are set out by European TV standards
EN500083-x. The aim is to design a TV distribution system that is compliant with
tuners fit in devices like TV sets, Set Top Boxes or VCRs.
Signal level
CATV & Terrestrial Transmission
Minimum
Maximum
Analogue Signal (Video carrier)
57 dBµV
74 dBµV
Digital Signal
35 dBµV
70 dBµV
Signal level dBµV
Max.
70
dBµV
Signal level
for digital
transmission
Min.
35
dBµV
Frequency in MHz
8 MHz
Signal level dBµV
Max.
74
dBµV
Video
carrier
Min.
57
dBµV
Audio
carrier
Signal level
for analogue
transmission
Frequency in MHz
8 MHz
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Signal quality for analogue
and digital signals
The quality of a TV signal processed by a TV system is mainly measured
by the Carrier To Noise Ratio (CNR).
The CNR is the difference between the "useful" signal and the noise level.
All active devices in a TV system contribute more or less greatly to the system
noise level.
The higher the CNR, the higher the quality level will be.
Requirement according to EN50083-x
Terrestrial Transmission
CNR(dB)
Analogue Signal
>45.5 dB
Digital Signal
>26 dB
Signal level dBµV
CNR
for a digital
signal in dB
Noise
level
Frequency in MHz
8 MHz
Signal level dBµV
Video
carrier
Noise
level
Audio
carrier
CNR for an
analogue
signal in dB
Frequency in MHz
8 MHz
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5
Application Note
Analog & Digital
TV processing with Delta 8
Bit Error Rate for digital signals
(BER)
The Bit Error Rate indicates the amount of wrong information detected in a Digital TV
signal. The higher the BER, the lower the quality of the Digital TV signal.
This error level can vary considerably depending on the TV processing in
the building and in the home. For example if CNR worsens, the Bit Error Rate
will also worsen.
The BER normaly expected for a digital channel is 10e-6
Max. Bit Error Rate (BER)*
Digital Signal
10e-4
* The rate is expressed as 10 to the negative power.
For example a BER equals to 10e-4 would indicate that 1 digital info is in error
out of 10.000 transmitted.
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TV signal attenuation
through a cable
Transmitting a TV signal through a cable based TV system causes signal level
attenuation. The degree of attenuation varies according to the frequency used for
transmitting the signal and the distance covered.
The higher the TV signal frequency, the greater the attenuation.
Consequently, the signal level received on the TV system input to a building or a
home is not flat. The signal in the low frequency can be acceptable, but the high
frequency signal cannot be received properly.
Signal level dBµV
Max.
74
dBµV
Signal tilted
Flatness
Signal level received
at the input of TV system
Signal flat
Min.
57
dBµV
Frequencies in MHz
It is mandatory to equalise the TV level at the output of each wall outlet.
The European standard gives the maximum value as:
Terrestrial Transmission Maximum Flatness of a TV signal
TV Signal
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Signal 60 MHz bandwidth
Within the range 47 to 860 MHz
6 dB
12 dB
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Application Note
Analog & Digital
TV processing with Delta 8
Consequences of TV system
misprocessing for the end user
Compliance with TV standards brings the end user the right picture quality
on their TV set.
The main problems that may be faced by a TV system, when TV rules are not
complied with, are detailed below.
A signal level that is not equalised and is either too high or too low through
the TV system, will dramatically disrupt the TV service.
This table shows some TV problems that can occur.
CNR too low
Signal not equalised,
amplifier not adjusted
White or black "snow"
on-screen
Picture in sound or sound
in picture phenomena
Blocks, picture freezing, black
screen (BER goes too high)
Blocks, picture freezing, black
screen (BER goes too high)
(TV signal too low or
noise level too high)
Analogue Signal
Digital Signal
In order to always ensure the right picture and sound quality to every user and
whatever their location in the house.
The Delta 8 is fitted with a wide range of set-up and amplification that makes Delta 8
compliant with international standard as EN50083-x.
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Delta 8 TV adjustment functions
with Delta 8 test kit
Delta 8 is fitted with three dedicated TV functions: Equalisation, Gain control and Tilt.
Equalisation function (Tilt at input stage)
The equalisation function equalises the incoming signal. The target is to prepare
the signal for proper amplification by the Delta 8 core unit amplifier.
Incoming Signal
Signal after equalisation
Signal level dBµV
Signal level dBµV
Incoming signal
Signal after the equalisation
Frequency in MHz
47 MHz
860 MHz
Frequency in MHz
47 MHz
860 MHz
Gain control
The gain control is aimed at amplifying the TV signal and to provide the right output
level to the wall outlet.
The gain control has to be adjusted regarding the incoming signal level.
Signal before amplification
TV Signal after amplification
Signal level dBµV
Signal level dBµV
Max output level: 110 dBµV
Delta 8
amplifier gain
Signal after equalisation
47 MHz
Frequency in MHz
860 MHz
47 MHz
Frequency in MHz
Max. output level
dBµV
Accoding to Din B 3 carriers method
110 dBµV
Accoding to Cenelec CSO / CTB 42 carriers method
93 dBµV
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860 MHz
9
Delta 8 TV adjustment functions
with Delta 8 test kit (continued)
Application Note
Analog & Digital
TV processing with Delta 8
Tilt Control for each link
As it is explained in page 7, the TV signal is attenuated according to
the distance and the frequencies.
The tilt adjustement makes a pre accentation at the highest frequencies
of the TV signal.
The Delta 8 is fitted with a tilt adjustement for each drop cable (up to 8 wall outlets
are handled by the Delta 8 system). This makes the Delta 8 core unit match with
the TV standard whatever the drop cable length up to 50 m.
Amplifier without tilt control
Signal level dBµV
47 MHz
Frequency in MHz
860
860 MHz
Amplifier without tilt adjustment
C The output level response is flat at the output
of the amplifier.
Signal level dBµV
Signal attenuation
through the cable
d Min. level
according to
the standard
57
dBµV
47 MHz
Frequency in MHz
860 MHz
The signal response at the outlet is not flat and
can be outside of the standard.
1
2
Delta 8 with tilt control
Signal level dBµV
Delta 8 tilt
adjustement
Frequency in MHz
47 MHz
860 MHz
Amplifier with tilt adjustment
C The output level is tilted to compensate
for cable losses at the output of the Delta 8.
Signal level dBµV
TV signal equalized at the wall outlet
47 MHz
Frequency in MHz
860 MHz
At the Wall Outlet, the TV signal is flat.
The signal is OK in relation to the standard.
Delta 8 and Delta 8 Test Kit
All of these TV functions can be adjusted accurately using the Schneider Electric
Test Kit.
The test kit can emulate a TV signal at 100 MHz and 900 MHz.
The two TV signals are used as a reference for adjusting equalisation gain
and the tilt for each drop cable.
Using the Delta 8 Test Kit, it is possible to adjust the Delta 8 core unit without
the need for any TV reception on-site.
The delta 8 test Kit is recommended to meet the TV specifications required
by international standards.
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Delta 8 TV adjustment functions
with Delta 8 test kit (continued)
Conclusion
In order to bring the right picture quality to the customers, a home network TV
processing must be fitted with such a range of set-up as Delta 8.
On top of that, the Delta 8 TV processing features make the TV system
compliant with International TV standards.
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11
DRAFT © Schneider Electric Industries SAS All rights reserved
Schneider Electric Industries SAS
VDI Offer Management Department
89, boulevard Franklin Roosevelt
F-92506 Rueil-Malmaison Cedex
Tel: +33 (0)1 41 29 82 00
http://www.schneider-electric.com
As standards, specifications and designs change from time to time, please ask for confirmation
of the information given in this publication.
This document has been printing
on a ecological paper
Publishing: Schneider Electric Industries SAS
Design: SEDOC (38)
Printing:
UT00631_01-2007_EN
01-2007

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