SIST EN 61079-5:1999
(Main)Methods of measurement on receivers for satellite broadcast transmissions in the 12 GHz band -- Part 5: Electrical measurements on decoder units for MAC/Packet systems
Methods of measurement on receivers for satellite broadcast transmissions in the 12 GHz band -- Part 5: Electrical measurements on decoder units for MAC/Packet systems
Defines the conditions and methods of measurement to be applied to MAC/packet decoder units.
Meßverfahren für Empfänger für Satelliten-Rundfunkübertragung im 12-GHz-Bereich -- Teil 5: Elektrische Messungen an Dekodern für MAC/Paket-Systeme
Méthodes de mesure sur les récepteurs d'émissions de radiodiffusion par satellite dans la bande de 12 GHz -- Partie 5: Mesures électriques sur les décodeurs pour les systèmes MAC/Paquet
S'applique aux décodeurs pour les systèmes MAC/paquet. Définit les conditions et les méthodes de mesure à appliquer à ces décodeurs.
Methods of measurement on receivers for satellite broadcast transmissions in the 12 GHz band -- Part 5: Electrical measurements on decoder units for MAC/Packet systems (IEC 61079-5:1993)
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN 61079-5:1999
01-april-1999
Methods of measurement on receivers for satellite broadcast transmissions in the
12 GHz band -- Part 5: Electrical measurements on decoder units for MAC/Packet
systems (IEC 61079-5:1993)
Methods of measurement on receivers for satellite broadcast transmissions in the 12
GHz band -- Part 5: Electrical measurements on decoder units for MAC/Packet systems
Meßverfahren für Empfänger für Satelliten-Rundfunkübertragung im 12-GHz-Bereich --
Teil 5: Elektrische Messungen an Dekodern für MAC/Paket-Systeme
Méthodes de mesure sur les récepteurs d'émissions de radiodiffusion par satellite dans
la bande de 12 GHz -- Partie 5: Mesures électriques sur les décodeurs pour les
systèmes MAC/Paquet
Ta slovenski standard je istoveten z: EN 61079-5:1993
ICS:
33.060.20 Sprejemna in oddajna Receiving and transmitting
oprema equipment
SIST EN 61079-5:1999 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
---------------------- Page: 1 ----------------------
NORME CEI
INTERNATIONALE IEC
61079-5
INTERNATIONAL
Première édition
STANDARD
First edition
1993-07
Méthodes de mesure sur les récepteurs
d'émissions de radiodiffusion par satellite
dans la bande 12 GHz
Partie 5:
Mesures électriques sur les décodeurs pour
les systèmes MAC/paquet
Methods of measurement on receivers for
satellite broadcast transmissions in
the 12 GHz band
Part 5:
Electrical measurements on decoder units
for MAC/packet
systems
© IEC 1993 Droits de reproduction réservés — Copyright - all rights reserved
Aucune partie de cette publication ne peut être reproduite ni No part of this publication may be reproduced or utilized in
utilisée sous quelque forme que ce soit et par aucun any form or by any means, electronic or mechanical,
procédé, électronique ou mécanique, y compris la photo- including photocopying and microfilm, without permission in
copie et les microfilms, sans l'accord écrit de l'éditeur.
writing from the publisher.
International Electrotechnical Commission 3, rue de Varembé Geneva, Switzerland
Telefax: +41 22 919 0300 e-mail: inmail@iec.ch IEC web site http: //www.iec.ch
CODE PRIX ^/ B
Commission Electrotechnique Internationale
PRICE CODE /^
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Pour prix, voir catalogue en vigueur
• • For price, see current catalogue
---------------------- Page: 2 ----------------------
1079-5 ©I EC – 3 –
CONTENTS
Page
FOREWORD 7
Clause
SECTION 1: GENERAL
1.1 Scope and object 11
1.2 Normative references 11
SECTION 2: GENERAL EXPLANATION OF TERMS
2.1 MAC/packet decoder unit 13
SECTION 3: GENERAL NOTES ON MEASUREMENTS
3.1 General conditions 15
3.2 Setting of the decoder 15
3.3 Video, audio and digital test signals 17
3.4 Reference signals 21
3.5 Standard measuring conditions 21
3.6 Measuring instruments 21
SECTION 4: VIDEO SIGNAL MEASUREMENTS
4.1 Video signal distortion 25
4.1.1 Amplitude versus frequency response 25
4.1.2 Group delay characteristics 27
4.1.3 Automatic amplitude and phase measurements within the video band 27
4.1.4 Pulse response 31
4.1.5 Bar signal response 33
4.1.6 Low-frequency distortion 35
4.1.7 Linearity 35
4.1.8 Response to a ramp signal in the case of scrambled/descrambled
signals 39
4.2 Unwanted signals 39
4.2.1 Signal-to-noise in nominal conditions 39
4.2.2 Suppression of energy dispersal signal 41
4.2.3 Spectrum aliasing 43
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1079-5 ©I EC – 5
Clause Page
4.3 Time domain demultiplexing 45
4.3.1 Accuracy of colour decoding 45
4.3.2 Delay between luminance and chrominance
channels 45
4.3.3 Relative delays of R,G,B signals 47
4.4 Noise sensitivity 49
4.4.1 Video output signal-to-noise ratio versus input signal-to-noise ratio 49
4.4.2 Clamp efficiency in the presence of noise 51
4.5 Conformity of composite synchronization signal 53
4.6 Miscellaneous video measurements 55
SECTION 5: DATA RECOVERY
5.1 Clock recovery in the presence of noise 55
5.2 Bit error rate due to random noise 57
5.3 Audio-click perceptibility in the presence of noise 57
SECTION 6: AUDIO MEASUREMENTS
6.1 Audio-frequency characteristics 59
6.2 Harmonic distortion of audio channels 61
6.3 Dynamic range of audio channels 63
6.4 Audio crosstalk 63
6.5 Phase difference between left and right channels 65
6.6 Audio signal-to-noise ratio 67
Figures 69
Annexes
A Analytical description 135
B Bibliography 149
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1079-5©IEC – 7 --
INTERNATIONAL ELECTROTECHNICAL COMMISSION
METHODS OF MEASUREMENT ON RECEIVERS FOR
SATELLITE BROADCAST TRANSMISSIONS IN
THE 12 BAND
GHz
Part 5: Electrical measurements on decoder units for
MAC/packet systems
FOREWORD
1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization
comprising all national electrotechnical committees (IEC National Committees). The object of the IEC is to
promote international cooperation on all questions concerning standardization in the electrical and
electronic fields. To this end and in addition to other activities, the IEC publishes International Standards.
Their preparation is entrusted to technical committees; any IEC National Committee interested in
the subject dealt with may participate in this preparatory work. International, governmental and
non-governmental organizations liaising with the IEC also participate in this preparation. The IEC
collaborates closely with the International Organization for Standardization (ISO) in accordance with
conditions determined by agreement between the two organizations.
2) The formal decisions or agreements of the IEC on technical matters, prepared by technical committees on
which all the National Committees having a special interest therein are represented, express, as nearly as
possible, an international consensus of opinion on the subjects dealt with.
3) They have the form of recommendations for international use published in the form of standards, technical
reports or guides and they are accepted by the National Committees in that sense.
4) In order to promote international unification, IEC National Committees undertake to apply IEC International
Standards transparently to the maximum extent possible in their national and regional standards. Any
divergence between the IEC Standard and the corresponding national or regional standard shall be clearly
indicated in the latter.
International Standard IEC 1079-5 has been prepared by IEC by sub-committee 12A:
Receiving equipment, of IEC technical committee 12: Radiocommunications.
The text of this standard is based on the following documents:
DIS Report on Voting
12A(CO)169 12A(CO)172
Full information on the voting for the approval of this standard can be found in the repo rt
on voting indicated in the above table.
---------------------- Page: 5 ----------------------
1079-5 ©I EC - 9 -
IEC 1079 consists of the following parts, under the general title: Methods of measurement
GHz
on receivers for satellite broadcast transmission in the 12 band.
- Part 1: 1992, Radio-frequency measurements on outdoor units.
- Part 2: 1992, Electrical measurements on DBS tuner units.
- Part 3: 1992, Electrical measurements of the overall performance of receiver
systems comprising an outdoor unit and a tuner unit for direct DBS reception.
Part 4: 1993, Electrical measurements on sound/data decoder units for the digital
-
subcarrier/NTSC system.
- Part 5: 1993, Electrical measurements on decoder units for MAC/packet systems.
Annex A forms an integral part of this standard.
Annex B is for information only.
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1079-5 © IEC - 11 -
METHODS OF MEASUREMENT ON RECEIVERS FOR
SATELLITE BROADCAST TRANSMISSIONS IN
THE 12 GHz BAND
Part 5: Electrical measurements on decoder units for
MAC/packet systems
Section 1: General
1.1 Scope and object
The object of this part of IEC 1079 is to define the conditions and methods of measure-
ment to be applied to MAC/packet decoder units.
The specifications of the limit values of the various parameters of the decoder are outside
the scope of this pa rt .
This unit can either be connected to the output of a DBS tuner unit or be a pa
rt of it.
The methods of measurement concerning the DBS tuner pa rt are described in pa rt 2
of IEC 1079.
The input signal is a baseband video signal encoded according to one of the following
MAC standards:
- D-MAC/packet;
- D2 MAC/packet.
The output signals are:
-
red, green, blue colour signals (R,G,B);
- one or more audio signal(s);
- the composite synchronization signal.
NOTE - The methods of measurement can also be used for MAC/packet receivers with built-in MAC
decoder units if R,G,B output signals are available.
1.2 Normative references
The following normative documents contain provisions which, through reference in this
text, constitute provisions of this part of IEC 1079. At the time of publication of
this standard, the editions indicated were valid. All normative documents are subject to
revision, and pa rties to agreements based on this pa rt
of IEC 1079 are encouraged
to investigate the possibility of applying the most recent editions of the normative
documents indicated below. Members of IEC and ISO maintain registers of currently valid
International Standards.
IEC 107-1: 1977, Recommended methods of measurement on receivers for television
broadcast transmissions - Part 1: General considerations. Electrical measurements other
than those at audio frequencies
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1079-5 ©IEC - 13 -
IEC 107-2: 1980, Recommended methods of measurement on receivers for television broad-
cast transmissions - Part 2: Electrical and acoustic measurements at audio frequencies
IEC 107-3: 1988, Recommended methods of measurement on receivers for television
broadcast transmissions - Part 3: Electrical measurements on multichannel sound tele-
vision receivers using subcarrier systems
IEC 107-4: 1988, Recommended methods of measurement on receivers for television
broadcast transmissions - Part 4: Electrical measurements on multichannel sound tele-
vision receivers using the two-carrier FM system
IEC 107-5: 1992, Recommended methods of measurement on receivers for television
broadcast transmissions - Part 5: Electrical measurements on multichannel sound televi-
sion receivers using the NICAM two-channel digital sound system
IEC 107-6: 1989, Recommended methods of measurement on receivers for television
broadcast transmissions - Pa rt 6: Measurement under conditions different from broadcast
signal standards
IEC 933-1: 1988,
Audio, video and audiovisual systems - Interconnections and matching
values. Part 1: 21-pin connector for video systems - Application No.1.
Section 2: General explanation of terms
For the purpose of this part of IEC 1079, the following general definitions apply.
2.1 MAC/packet decoder unit
The function of this unit is to process an incoming baseband video MAC signal issued from
a DBS tuner unit and to decode it in order to provide R,G,B colour, audio and composite
synchronization signals which can be applied to a monitor or a TV set having an appro-
priate audiovideo connector such as the one defined by IEC 933-1.
The exact configuration of the unit depends on overall product design and the related type
of MAC/packet system that the equipment is designed to process.
In the description of the measurement methods, it is assumed that the arrangement of the
units is similar to the notional block diagram shown in figure 1.
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1079-5 ©I EC - 15 -
Section 3: General notes on measurements
3.1
General conditions
3.1.1 '
Introduction
Measurements should be carried out in accordance with the following conditions to ensure
measurement reliability.
3.1.2
Test site
Measurement shall be carried out at a location that is not subject to external radio fre-
quency interference. If interference cannot be avoided, the tests shall be carried out in a
screened room.
3.1.3 Environmental conditions
Sections three, four and five of IEC 107-1 shall be applied.
3.1.4 Power supply
A power supply equivalent to the rated voltage and rated frequency of the unit shall be
used. The fluctuation of the power supply voltage and frequency during the tests shall not
exceed ±2 % and harmonic components of the power supply shall not exceed 5 %.
3.1.5 Accuracy of measuring instruments
The accuracy of the measuring instruments used, if known, shall either be stated as a
percentage or in decibels, as appropriate.
Alternatively, the precision class may be quoted as stated in the relevant publications.
3.1.6 Stabilization period
Unless otherwise specified, measurements should be started at the time that stabilization
of the characteristics is obtained.
3.2 Setting of the decoder
Unless otherwise specified, all adjustments of the decoder should be set to nominal (for
video and audio parts).
Special care should be taken concerning saturation and contrast settings. They can be
checked using the colour-bar test signal and observing that R,G,B output colour signals
are as close as possible to those shown in figure 17.
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1079-5 ©IEC –17 –
3.3 Video, audio and digital test signals
3.3.1 Video test signals
Most video measurements are performed on one of the outgoing R,G,B colour signals
which are derived from both luminance and chrominance components. In order to easily
determine the characteristics of each processing channel, the video test signals exist in
two forms:
–
one for the luminance channel testing (referred to as "L") where the test signal is
included in the luminance part of the line;
– one for the chrominance
(referred to as "Ch") where the test signal is included in
the chrominance
part of the video line.
a) Multiburst L and Ch signals.
b) Complex wobbulation L and Ch signals (real part).
c) Complex wobbulation L and Ch signals (imaginary part).
d)
Modulated pulses signal L and Ch signals.
e) Pulse and bar L and Ch signals.
f) Rising ramp L and Ch signals.
g) Eight-riser staircase L and Ch signals.
h) 50 % grey level signal.
i) 75 % colour-bar signal.
j) Bow-tie signal (even line), bow-tie signal (odd line).
k)
Low frequency black to white transition signal
Examples are shown in figure 2, but complete signal description is provided in the
annex A.
NOTES
1 The nominal dynamic range of the MAC video is 1 V. In this text, signals will be described as ranging
from —0,5 V to +0,5 V as follows:
Chrominance Luminance
Nominal dynamic range —0,5 V to +0,5 V —0,5 V to +0,5 V
Offset (relative to standardized
0 V — 0,5 V
signal descriptions)
Relative gain (relative to 0,733 for Eu'
standardized signal descriptions) 0,927 for Ev'
Black signal
0V —0,5 V
50 % grey signal 0V 0V
White signal 0V +0,5 V
2 In the figures showing the colour output signals, a gain is arbitrarily applied in order to set the range
between 0 and +0,7 V.
3 The test signals are usually defined on one or two successive lines. It is always assumed that field and
frame structures comply with the relevant MAC system. Normalized reference signal on line 624 should
also be present.
4 The time interval T used in the text is equal to the reference sampling period
64
µs = 49,38 µs
20125 1 296
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1079-5 40 I EC - 19 -
3.3.2 Audio test signals
Due to the form of audio transmission used in the MAC system, it is necessary either to use
an audio-frequency signal generator incorporating the relevant encoding and formatting
device or a test signal generator with data sequences in a memory that provides pure sine
waves at discrete frequencies.
The audio test signals necessary to perform the tests described in this standard are
defined as follows:
Frequencies:
From 40 Hz to 15 kHz. If the test generator only provides a given number of
discrete frequencies, they should be:
40 Hz, 100 Hz, 200 Hz, 500 Hz, 1 kHz, 2 kHz,
5 kHz, 7,5 kHz, 10 kHz, 12 kHz, 15 kHz.
Amplitude:
Full-scale amplitude is defined for a digital signal as maximum signal with respect
to the encoding system specifications. Full-scale amplitude is defined
after pre-emphasis
and is thus the same for all frequencies
after encoding. As a consequence, at the output
of the decoder, full-scale amplitude is different according to the frequency of the signal.
In some case full-scale minus X dB amplitude is used (X = 60 dB, .) (see figure 4).
In order to perform most audio tests, and especially amplitude response tests, it is more
convenient to dispose of a signal whose amplitude is the same for all frequencies within
the audio-frequency band. In order to avoid overloading of the analogue to digital converter
after the pre-emphasis filter, the reference amplitude is defined as being the full-scale
amplitude minus 20 dB for a 1 kHz audio-frequency signal at the input of the audio encoder
(see figure 4).
Modes:
- mono/stereo
- high quality (HQ), medium quality (MQ);
-
Lin 1, Lin 2, Comp 1, Comp 2 encoding laws;
where "Lin" stands for linearly coded audio mode and "Comp" stands for companded
audio mode.
NOTES
1 An analogue audio signal entering the MAC/packet encoder should be corrected with an audio
pre-emphasis law according to Recommendation J.17 of CCITT (see figure 3).
2 Sine waves in medium-quality encoding are limited to 7,5 kHz in frequency.
3.3.3 Data signal content
The data component content shall comply with the line and frame structure of the relevant
MAC/packet specification; i.e. line and frame synchronization words plus all additional
data necessary to make the decoder work properly should be present.
However, the packets which are not used for transmitting an audio signal should be filled
with pseudo-random sequences properly encoded and formatted. These packets shall
have the dummy packet address (1023).
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1079-5 ©I EC - 21 -
3.4 Reference signals
3.4.1 Reference video signal
The reference video signal is the colour-bar test signal as defined in 3.3.1.
3.4.2 Reference audio signal
The reference audio signal is the 1 kHz sine wave signal, in Lin 1 mode, with the
reference amplitude as defined in 3.3.2.
3.5 Standard measuring conditions
Unless otherwise specified, the following conditions apply:
1) Data burst content: pseudo-random sequence with synchronization words.
2) Energy dispersal: none.
3)
Reference video signal: a 75 % colour-bar signal as defined in A.3.7.
4)
Reference data burst: a pseudo-random binary sequence properly encoded and
formatted.
Whatever the test arrangement is, the decoder outputs shall be checked to see that they
are properly loaded with 75 SI
3.6 Measuring instruments
3.6.1 Test signal generator
The test signal generator shall be capable of providing:
-
baseband video test signals as specified in 3.3.1 with the reference data burst
specified in 3.3.3;
- the reference baseband video signal specified in 3.4 with the audio test sequences
specified in 3.3.2.
The undefined pa rt of the data burst shall be pseudo-random sequences with appropriate
synchronization words.
The output baseband composite signal amplitude is 1 V ± 5 % when loaded with 75 O.
3.6.2 Line inserter
The line inserter, if used, shall be capable of inserting into a MAC signal any type of signal
in the frequency range 0 MHz to 20 MHz. The inserted signal can take place either in
chrominance
or luminance parts as the operator chooses.
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1079-5 ©IEC – 23 –
3.6.3 Spectrum analyzer
The spectrum analyzer shall have a minimum frequency range of 20 MHz or more.
3.6.4
Automatic data acquisition system
It may be a simple digital oscilloscope with a convenient data transmission link which can
be connected to a calculator. Its minimum bandwidth shall be 20 MHz.
3.6.5 Video analyzer
For timing measurements on the composite synchronization signal a classical 625-line
video analyzer can be used.
It may include features of the video noise meter mentioned in 3.6.8.
3.6.6 Oscilloscope
The oscilloscope used shall be a dual trace model, and its frequency range shall exceed
20 MHz.
3.6.7 Low-pass filter
When performing noise measurements, a low-pass filter shall be connected at the signal
output (R or G or B). Unless a specific filter is standardized, it is recommended that the
filter specified in CCIR Recommendation 567-3 be used.
3.6.8 Video noise meter
If a video noise meter is used, it shall be capable of measuring the noise component on a
steady-level signal when externally synchronized. Internal noise measuring and weighting
filters shall be by-passed, if they do not comply with the MAC system specifications.
3.6.9 Video monitor
This monitor is used to perform subjective evaluation. It shall have an appropriate R,G,B
synchronization input connector.
3.6.10 Quasi-peak voltmeter
For audio signal-to-noise measurements a quasi-peak voltmeter shall be used as in
IEC 107-2 and IEC 107-4. This equipment is in conformity with CCIR Report 468-4.
3.6.11 Reference matrix circuit
Measurements on the video part are usually done using one of the three colour signals.
To be able to use video component measuring equipment which already exists, it is
necessary to recompose the R,G,B colour signals in order to obtain the three component
signals, luminance Y and chrominance Eu' and Ev'. The performances of this matrix circuit
shall comply with the tolerances required for the measurements.
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1079-5 ©I EC – 25 –
Section 4: Video signal measurements
4.1 Video signal distortion
This section deals with both linear and non-linear video signal distortions. Due to the
fact that within the decoders the chrominance and luminance signals are processed
through different channels and are only available in the mixed R,G,B form at the output, it
is necessary, in most cases, to define a specific test signal for each channel.
The video measurements are usually done using the outgoing R,G,B colour signals, but, if
preferred, it is also possible in some cases to use a matrix circuit as described in 3.6.11 to
obtain conventional Y, Eu', Ev' signals. It is then possible to use video measuring equip-
ment which is not specific to the MAC systems.
The reference audio signal specified in 3.4.2 shall be used for all video signal measure-
ments unless otherwise specified.
4.1.1
Amplitude versus frequency response
4.1.1.1 Introduction
The test measures the amplitude/frequency response of
chrominance and luminance
channels of the decoder.
4.1.1.2
Method of measurement
The measurement is performed using a multiburst type test signal, defined for each
channel according to its theoretical bandwidth.
The test arrangement is shown in figure 5.
4.1.1.2.1
Measuring conditions
a) For luminance channel testing: multiburst L test signal.
b) For
chrominance channel testing: multiburst Ch test signal.
4.1.1.2.2 Measurement procedure
a)
Apply the test signal to the decoder video input.
b)
For luminance testing, display one of the R,G,B colour signals on an oscilloscope.
In the case of chrominance testing, display an R or B signal.
c)
Use the two-step portion of the test signal as amplitude reference and measure
the amplitude of each burst in its steady part so as to avoid the transient response
distortion.
4.1.1.2.3 Presentation of results
The results shall be listed in a table or plotted graphically in linear relative scale or
decibels.
The frequency scale shall show the frequency of each burst before and after decom-
pression (i.e. in 3:2 ratio for luminance and 3:1 for
chrominance).
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1079-5 ©I EC - 27 -
4.1.1.3 Alternative method of measurement
If a MAC video inserter is available, the measurement can be conducted using a pure sine
wave restricted to the luminance or chrominance
part of the signal according to the
channel tested. A very-low frequency square signal is used for amplitude reference (see
figure 6).
4.1.2
Group delay characteristics
4.1.2.1 Introduction
The test emphasizes the group delay characteristics versus frequency for both luminance
and chrominance channels.
4.1.2.2 Method of measurement
The measurement is performed using a train of modulated pulses quite similar to the 20 T
test signal used for the PAL /SECAM standards.
The resulting signal allows the comparison of the propagation delay of the frequency of
modulation with that of the low-frequency envelope.
The test arrangement is shown in figure 5.
4.1.2.2.1 Measuring conditions
a) For luminance channel testing: modulated pulses L test signal.
b) For chrominance channel testing: modulated pulses Ch test signal.
4.1.2.2.2
Measurement procedure
a) Apply the test signal to the decoder input and collect one of the R,G,B output
chrominance testing.
signals for luminance and an R or B signal for
b) Display the output signal on an oscilloscope with a 64 ps time window.
c) Obtain the amplitude and group delay for each modulated pulse (thus for each
7.
modulating frequency) using the nomogram shown in figure Due to time decom-
pression, the values indicated by the nomogram shall be multiplied by a factor 3/2 and
a factor 3 for luminance and chrominance channels, respectively.
4.1.2.2.3 Presentation of results
The results of group delay characteristics as a function of frequency shall be listed in a
table indicating the frequencies after decoding (i.e. by applying a 2/3 ratio for luminance
and a 1/3 ratio for chrominance). A photographic record or graphical plot shall be given.
4.1.3 Automatic amplitude and phase measurements within the video band
4.1.3.1 Introduction
This test allows both amplitude and phase response to be obtained over the video fre-
quency band provided that an automatic data acquisition system is available. In this case,
it replaces the two preceding tests and provides more complete results.
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OO
1079-5 IEC - 29 -
4.1.3.2 Method of measurement
The test signal is a complex wobbulation transmitted on two successive frames. The test
arrangement is shown in figure 8.
4.1.3.2.1 Measuring conditions
a) For luminance channel testing: the two complex wobbulation L signals (real and
imaginary) on two successive frames.
b) For chrominance channel testing: the two complex wobbulation Ch signals (real and
imaginary) on two successive frames.
4.1.3.2.2 Measurement procedure
Apply the test signal to the decoder input and connect the data acquisition system
a)
to one of the R,G,B outputs.
b) Trigger an acquisition procedure during two lines separated in time by a frame.
c) The computing device should have a discrete Fourier transform (DFT) algorithm in
order to provide the following information:
fr(k)-> FR (p)
i
=
F(p) FR (p) + (p)
JF
fi (k)-^ F^ (p)
where
fr (k) and f. (k) are the resulting output signals to real and imaginary parts of the
complex wobbulation test signal respectively
F(p) is the complex discrete Fourier transform of the channel response
where
1=VT
k is the number of the time sample
p is the number of the frequency sample
The transfer function H(p) of the channel is thus:
Jp27c
l
512 )
^
e
(p)
- F
H (p)
512
This complex transfer function can be decomposed in module response A(co) and phase
versus frequency.
response 40)
it
p2
^
A(w) - F(p)
C o)) =Arg (F(p)) +
512
5 1 2
where
2nAfxp and Af= 1
=
512 T
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1079-5 © IEC - 31 -
4.1.3.2.3 Presentation of results
The results shall be presented as two plots for each channel. One is the module
expressed in relative amplitude or decibels, the other is phase in degrees or radians as a
function of frequency at the output.
4.1.4 Pulse response
4.1.4.1 Introduction
This test permits the determination of the pulse response capabilities of each channel.
Because of the sampling at
20,25 MHz performed inside a MAC decoder, it is preferable to
define a pulse which would have very little power outside of the
10,125 MHz frequency
band in order to avoid aliasing problems.
4.1.4.2 Method of measurement
The measurement is carried out using a 6 T and
12 T pulse test signal and the test arran-
gement as shown in figure
5.
4.1.4.2.1 Measuring conditions
a) For luminance channel testing:
- chrominance: null level;
- luminance:
6 T pulse followed by a bar signal for amplitude reference. Overall
amplitude is limited to 70 % of maximum.
b) For chrominance channel testing:
- chrominance: 12 T
pulse followed by a bar signal for amplitude reference. Overall
amplitude is limited to
70 % of maximum;
-
luminance: null level (0 V).
4.1.4.2.2 Measurement procedure
a) Apply the test signal to the decoder input and display one of the R,G,B output
signals on an oscilloscope with a
64 .is time window.
b) Measure the departure of peak level of the pulse signal from the amplitude refer-
ence at the steady part (B) of the bar signal shown in figure 9.
c)
Measure the amplitude of the pulse signal relative to the peak amplitude at each
time period on a Tm
±15 time interval.
Tm
is equal to 3 T for luminance testing and Tm
/2 is equal to 3 T for chrominance testing,
Tm
where = 0 at the peak of the pulse.
4.1.4.2.3 Presentation of results
The results shall be presented in a table with the amplitude in per cent of peak level for
each sample between ±15
Tm. A photographic record or graphical plot can also be given.
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1079-5 ©IEC - 33 -
4.1.5 Bar signal response
4.1.5.1 Introduction
This test examines both step response and bar tilt distortions. The bar signal used as test
signal has its transition defined so as to have very little power over 10,125 MHz.
4.1.5.2
...
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