SIST EN 61079-1:1999
(Main)Methods of measurement on receivers for satellite broadcast transmissions in the 12 GHz band -- Part 1: Radiofrequency measurements on outdoor units
Methods of measurement on receivers for satellite broadcast transmissions in the 12 GHz band -- Part 1: Radiofrequency measurements on outdoor units
Applies to the outdoor unit of a receiver for the direct reception of satellite broadcast transmissions in the 12 GHz band. Defines the conditions and methods of measurement to be applied.
Meßverfahren für Empfänger für Satellitenrundfunk-Übertragungen im 12-GHz-Bereich -- Teil 1: Radiofrequenz-Messungen an der Außeneinheit
Méthodes de mesure sur les récepteurs d'émissions de radiodiffusion par satellite dans la bande 12 GHz -- Partie 1: Mesures en radiofréquence sur le matériel extérieur
S'applique à l'unité extérieure d'un récepteur d'émission de radiodiffusion directe par satellite dans la bande 12 GHz. Définit les conditions et méthodes de mesure qui doivent être appliquées.
Methods of measurement on receivers for satellite broadcast transmissions in the 12 GHz band -- Part 1: Radiofrequency measurements on outdoor units (IEC 61079-1:1992) (IEC 61079-1:1992)
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN 61079-1:1999
01-april-1999
Methods of measurement on receivers for satellite broadcast transmissions in the
12 GHz band -- Part 1: Radiofrequency measurements on outdoor units (IEC 61079
-1:1992) (IEC 61079-1:1992)
Methods of measurement on receivers for satellite broadcast transmissions in the 12
GHz band -- Part 1: Radiofrequency measurements on outdoor units
Meßverfahren für Empfänger für Satellitenrundfunk-Übertragungen im 12-GHz-Bereich --
Teil 1: Radiofrequenz-Messungen an der Außeneinheit
Méthodes de mesure sur les récepteurs d'émissions de radiodiffusion par satellite dans
la bande 12 GHz -- Partie 1: Mesures en radiofréquence sur le matériel extérieur
Ta slovenski standard je istoveten z: EN 61079-1:1993
ICS:
33.060.20 Sprejemna in oddajna Receiving and transmitting
oprema equipment
SIST EN 61079-1:1999 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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NORME
CEI
INTERNATIONALE
IEC
61079-1
INTERNATIONAL
Première édition
STAN
DARD
First edition
1992-06
Méthodes de mesure sur les récepteurs
d'émissions de radiodiffusion par satellite
dans la bande 12 GHz
Partie 1:
Mesures en radiofréquence sur le matériel extérieur
Methods of measurement on receivers for
satellite broadcast transmissions in
the 12 GHz band
Part 1:
Radio-frequency measurements on outdoor units
© IEC 1992 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
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Pour prix, voir catalogue en vigueur
• • For price, see current catalogue
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1079-1 ©IEC - 3 -
CONTENTS
Page
FOREWORD 9
SECTION 1 - GENERAL
Clause
11
1.1 Scope
1.2 Normative references 11
1.3 Definitions 13
SECTION 2 - GENERAL NOTES ON MEASUREMENT
13
2.1 General conditions
2.1.1 Introduction 13
2.1.2 Test site 13
2.1.3 Environmental conditions 13
2.1.4 Power supply 13
2.1.5 Other conditions 15
2.2 Radio-frequency input signals 15
2.2.1 Introduction 15
2.2.2 Test signals 15
2.2.3 Test frequencies 15
2.2.4 Radio-frequency input arrangement 15
2.2.5 17 Input signal level
SECTION 3 - MEASURING METHODS
3.1 Polarization isolation 19
3.1.1 Introduction 19
3.1.2 Method of measurement 19
3.1.3 Presentation of the results 21
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1079-1 ©IEC - 5 -
Clause Page
3.2 Impedance matching at the input terminal 21
32.1 Introduction 21
3.2.2 Method of measurement 21
3.2.3 Presentation of the results 23
3.3 Impedance matching at the output terminal 23
3.3.1 Introduction 23
3.3.2 Method of measurement 23
3.3.3 Presentation of the results 25
3.4 Gain frequency characteristics 25
3.4.1 Introduction 25
3.4.2 Method of measurement 25
3.4.3 Presentation of the results 27
3.5 Output signal level versus input signal level 27
3.5.1 Introduction 27
27
3.5.2 Method of measurement
3.5.3 Presentation of the results 29
3.6 Intermodulation 29
3.6.1 Introduction 29
3.6.2 Method of measurement 29
3.6.3 Presentation of the results 31
3.7 Noise figure and noise temperature 31
3.7.1 Introduction 31
3.7.2 Method of measurement 31
3.7.3 Presentation of the results 35
3.8 G/T 35
3.8.1 Introduction 35
3.8.2 Method of measurement 35
3.8.3 Presentation of the results 37
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1079-1 ©I EC - 7
Clause Page
3.9 Alternative method for G/T 37
3.9.1 Introduction 37
3.9.2 Method of measurement 39
3.9.3 Presentation of the results 43
3.10 Image suppression ratio 43
3.10.1 Introduction 43
3.10.2 Method of measurement 43
3.10.3 Presentation of the results 45
3.11 Spurious responses 45
3.11.1 Introduction 45
3.11.2 Method of measurement 45
3.11.3 Presentation of the results 47
3.12 Intermediate frequency beat suppression ratio 49
3.12.1 Introduction 49
3.12.2 Method of measurement 49
3.12.3 Presentation of the results 49
3.13 Local oscillator frequency stability 51
3.13.1 Introduction 51
3.13.2 Method of measurement 51
3.13.3 Presentation of the results 51
FIGURES 53
ANNEX A (informative) - Bibliography 85
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- 9 -
1079-1 40 IEC
INTERNATIONAL ELECTROTECHNICAL COMMISSION
METHODS OF MEASUREMENT ON RECEIVERS FOR
SATELLITE BROADCAST TRANSMISSIONS
BAND
IN THE 12 GHz
Part 1: Radio-frequency measurements on outdoor units
FOREWORD
The formal decisions or agreements of the IEC on technical matters, prepared by Technical Committees on
1)
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.
They have the form of recommendations for international use and they are accepted by the National
2)
Committees in that sense.
In order to promote international unification, the IEC expresses the wish that all National Committees
3)
should adopt the text of the IEC recommendation for their national rules in so far as national conditions will
permit. Any divergence between the IEC recommendation and the corresponding national rules should, as
far as possible, be clearly indicated in the latter.
This standard has been prepared by Sub-Committee 12A: Receiving equipment, of IEC
Technical Committee No. 12: Radiocommunications.
The text of this standard is based on the following documents:
Report on Voting
Report on Voting Two Months' Procedure
Six Months' Rule / DIS
12A(CO)164
12A(CO)135 12A(CO)149
12A(CO)131
Full information on the voting for the approval of this standard can be found in the Voting
Reports indicated in the above table.
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1079-1 © IEC - 11 -
METHODS OF MEASUREMENT ON RECEIVERS FOR
SATELLITE BROADCAST TRANSMISSIONS
IN THE 12 GHz BAND
Part 1: Radio-frequency measurements on outdoor units
SECTION 1 - GENERAL
1.1 Scope
This International Standard applies to the outdoor unit of a receiver for the direct reception
of satellite broadcast transmissions in the 12 GHz band. The channels are those defined
by WARC BS-77 and RARC SAT-83 and the systems are those defined in CCIR
Recommendation 650.
The object of this standard is to define the conditions and methods of measurement to be
applied. The standard does not specify pe rformance requirements.
An outdoor unit normally comprises three main pa
rts, the antenna, the depolarizer and
optional orthomode transducer (OMT), and the SHF converter as defined in clause 1.3.
The methods of measuring the electrical properties described in this pa rt of the standard
apply particularly to the outdoor unit or the SHF converter.
Methods of measurement on the associated DBS tuner unit are described in Part 2 of this
standard.
1.2 Normative references
The following normative documents contain provisions which, through reference in
this text, constitute provisions of this International Standard. 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 International Standard are
encouraged to investigate the possibility of applying the most recent editions of the
standards 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.
IEC 1079-2: 1992, Methods of measurement on receivers for satellite broadcast trans-
missions in the 12 GHz
band - Part 2: Electrical measurements on DBS tuner units.
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1079-1 © IEC –13 –
1.3 Definitions
For the purpose of this International Standard, the following definitions apply.
The outdoor unit is a part
of the receiver for satellite broadcast transmissions in the
12 GHz
band, and comprises three main pa rts:
a)
the antenna including the feed horn which receives the signals broadcast by
satellites;
b)
the depolarizer that converts circular polarization to linear polarization and an op-
tional orthomode transducer, OMT, which separates two incoming differently polarized
signals into two independent SHF outputs;
c)
the SHF converter (also called low noise converter (LNC) or low noise block
converter (LNB)), which is a device to convert the received signals in the 12 GHz band
to intermediate frequencies (often called the first i.f.) usually in the range of
approximately 1 GHz to 2 GHz, for application to one or more DBS tuner units, where
demodulation and decoding of the received signals are performed.
SECTION 2 - GENERAL NOTES ON MEASUREMENT
2.1 General conditions
2.1.1 Introduction
Measurements shall be made in accordance with the following conditions to ensure
reproducible results. The methods described here assume the use of the following trans-
mission systems: digital sub-carrier/NTSC, B-MAC, C-MAC/packet, D-MAC/packet and
D2 MAC/packet. Information pertaining to these systems may be found in the references
listed in the bibliography given in annex A.
2.1.2
Test site
Measurements shall be carried out at a location that is not subject to external interference
from radio frequency energy. If interference cannot be avoided, the measurements shall
be carried out in a screened room.
2.1.3
Environmental conditions
Sections Three, Four and Five of IEC 107-1 shall be applied.
2.1.4 Power supply
2.1.4.1
Bias network
When measuring the characteristics of an outdoor unit, it is necessary to supply d.c. or
a.c. power to it without influencing the output signal. For this purpose, a bias network such
as that shown in figure 1 can be used.
NOTE - Reverse connection of the bias network (see figure 2) is likely to cause damage.
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1079-1 ©IEC – 15 –
2.1.4.2 Nominal voltage
The d.c. or a.c. voltage to be applied to the unit during the test shall be within ±2 % of the
nominal operating voltage, unless otherwise specified.
Where only a range of voltages is specified, the nominal voltage shall be taken as the
mean value of this range. Measurements shall be repeated at the limits of the specified
range, as indicated in the following clauses.
2.1.5 Other conditions
2.1.5.1
Accuracy of the 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 accuracy class may be quoted
as laid down in the relevant publications (under consideration).
2.1.5.2 Stabilization period
The characteristics of an outdoor unit may change for some period after the application of
supply voltage. Unless otherwise specified, measurements should be started after the
stabilization of the characteristics is obtained.
2.2 Radio-frequency input signals
2.2.1 Introduction
The following input signals shall be used.
2.2.2
Test signals
Unless otherwise specified, continuous wave (c.w.) radio-frequency (r.f.) signals shall be
used.
2.2.3 Test frequencies
Unless otherwise specified, test frequencies shall be selected near the nominal carrier
frequency of each broadcast channel, as specified by the standards of the count ry or
countries in which the equipment is intended for use.
2.2.4
Radio-frequency input arrangement
Depending on the input facilities of the equipment under test, the radio-frequency input
signal can be applied in three different ways:
a)
by means of a waveguide, having a flange and a cross-section compatible with the
input of the unit;
b)
by means of a coaxial cable and a connector compatible with the input of the unit;
c) by means of a transmitting antenna generating a field of wanted level at the
receiving antenna which provides the electrical input signal for the unit.
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1079-1 © I EC – 17 –
When two or more signals are to be applied (two or multi-signal measuring methods),
suitable combining networks, such as hybrid networks or directional couplers with the
specified characteristic impedance shall be used to connect the various signal generators.
All unused terminals shall be terminated with matched loads.
When input arrangement indicated in c) is used, the signals of the various generators are
combined before application to the transmitting antenna.
NOTE - Any type of hybrid such as magic tee, rat-race or hybrid-ring can be used.
2.2.5 Input signal level
The input signal level to an outdoor unit shall be expressed according to the input arrange-
ment used (see 2.2.4).
2.2.5.1 Available power
With the input arrangement a) or b) of 2.2.4, the input signal level is expressed in terms of
available power at the output of the signal generator, including its associated network.
The available power is the power delivered by the signal generator to a matched load. It is
expressed in milliwatts and can be calculated by the following formula:
2
_ (mW)
P
R
9
where
P = available power (mW);
9 = electromotive force at the output terminal of the signal generator (V);
Rg = output resistance of the signal generator (S2).
2.2.5.2 Power flux density
With input arrangement c) of 2.2.4, the input signal level is expressed in terms of power
flux density (PFD) at the aperture plane of the receiving antenna, calculated as follows:
PAG
PFD= (W/m2)
4nd 2
where
power delivered by the signal generator to the input of the transmitting antenna (W);
PA =
G = gain of the transmitting antenna in the direction towards the receiving antenna;
d = distance between the transmitting antenna and the receiving antenna (m), measured
between the electrical centres.
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1079-1 ©IEC - 19
2.2.5.3 Siting of the antennas
The antennas shall be placed at least 4 m above ground level to lessen the interference
by the reflected wave from the ground. When a slant antenna range* setting (see figure 3)
is used, the transmitting antenna can be placed on the ground while the receiving antenna
is placed at the top of a tower.
To avoid measurement errors caused by a non-uniform distribution of spherically propa-
gated electromagnetic waves, the distance between the transmitting and the receiving
antennas should be larger than 2 D 1 2
/A, and D1 D2 / 0,32 X, where D 1 and D2 are the
maximum diameters of the antenna under test and the transmitting antenna respectively,
and X is the free space wavelength at the test frequency. If the electric field strength at
the receiving point deviates more than ±0,5 dB in the ape
rture plane, the height and the
distance shall be rearranged to obtain a deviation smaller than ±0,5 dB. The method of
measuring the electric field strength at the receiving point is mentioned in clause 3.8.
SECTION 3 - MEASURING METHODS
3.1 Polarization isolation
3.1.1 Introduction
This method of measurement determines the isolation between the two independent and
differently polarized signals entering the outdoor unit measured at the output of the
complete outdoor unit.
NOTE - According to CCIR recommendations, the polarization of the signals is right hand or left hand
circular.
3.1.2 Method of measurement
A test signal is applied to the input terminal of the outdoor unit and the resulting output,
from one of the SHF converters, is measured at specified frequencies. The polarization of
the input signal is reversed by appropriate means and the resulting new output level is
recorded. The polarization isolation is determined from the level difference between the
two measurements. The arrangement of the test equipment is shown in figure 4. Only
input arrangement c) (see 2.2.4) can be used to perform this measurement which should
be made according to the following conditions and procedure.
3.1.2.1 Measuring conditions
a) Test frequency: the centre frequency of the lowest (L), the mid (M) and the highest
(H) channels in the 12 GHz
broadcasting band.
b) Test signal level at the input (12 GHz band): -94 dB(W/m2).
For a slant antenna range, the following paper can be referred to: P.W. Arnold,
The slant antenna range,
IEEE Trans. Antennas & Propag., AP-14, 5 pp. 658-659 (1966).
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1079-1 ©IEC - 21 -
3.1.2.2
Measurement procedure
a) A c.w. signal at the specified test signal level is applied to the input terminal of the
outdoor unit.
b) The output signal level of the outdoor unit (at the bias network output terminal) is
measured: LP1 dB(mW).
c)
The polarization of the input signal is reversed by appropriate means.
d) The new output signal level of the outdoor unit is measured: LP2 dB(mW).
e) Polarization isolation is:
(LPisol)
LP2 (dB)
LPisol = L P1 —
f) The test signal frequency is changed and steps a) to e) are repeated.
g)
The other output terminal is taken into consideration by connecting the bias network
and spectrum analyzer to it while terminating the previous output terminal with a
matched load.
h) Steps a) to f) are repeated with this new output terminal.
3.1.3
Presentation of the results
The results shall be listed in a table and/or presented graphically.
3.2 Impedance matching at the input terminal
3.2.1 Introduction
This method of measurement determines the impedance matching at the input terminal of
the SHF converter. It is applicable only to input arrangement a) or b) (see 2.2.4).
3.2.2 Method of measurement
A test signal is applied to the input terminal of the outdoor unit and the levels of the direct
signal and reflected signal at the terminal are measured using a directional coupler.
The return loss is the level difference between these two signals. The arrangement of the
test equipment is shown in figure 5. The measurement should be made according to
the following conditions and procedure.
3.2.2.1 Measuring conditions
a)
Test frequency: the centre frequency of each channel in the reception band
(12 GHz).
b) Test signal level: -70 dB(mW).
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1079-1 ©IEC - 23 -
3.2.2.2 Measurement procedure
a)
A c.w. signal is applied and the variable attenuator adjusted to obtain the
recommended signal level at the output terminal of the directional coupler.
b)
With a short-circuit termination placed at the output terminal of the directional
coupler, the output signal level of the amplifier
LPo [dB(mW)] is measured.
c)
The SHF converter input terminal is connected to the directional coupler output
terminal and the amplifier output signal level Lp [dB(mW)] is measured.
d)
The return loss is expressed as the difference:
LPo -
LP (dB)
e)
The test signal frequency is changed and steps a), b), c) and d) are repeated.
NOTE - The amplifier shall be sufficiently linear not to influence the results within the range of the signal
levels used.
3.2.3 Presentation of the results
The results shall be listed in a table and/or presented graphically.
3.3 Impedance matching at the output terminal
3.3.1 Introduction
This method of measurement determines the impedance matching at the output terminal of
the outdoor unit.
3.3.2 Method of measurement
A test signal is applied to the output terminal of the outdoor unit and the levels of the
direct signal and reflected signal at the terminal are measured using a SWR bridge.
The return loss is the level difference between these two signals. The arrangement of
the test equipment is shown in figure 6. The measurement shall be made according to the
following conditions and procedure.
3.3.2.1 Measuring conditions
a) Test frequency: the centre frequency of each channel in the i.f. band.
b) Test signal level:
-30 dB(mW).
3.3.2.2 Measurement procedure
a) The input terminal is terminated with a matched load when input arrangement a)
2.2.4) is
or b) (see used. Otherwise, when input arrangement c) (see 2.2.4) is
used,
the outdoor unit antenna shall be oriented towards the sky, avoiding any satellite
reception.
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1079-1 © IEC - 25 -
b) A c.w. signal is applied and the variable attenuator is adjusted to obtain the recom-
mended signal level at the output terminal of the SWR bridge.
c)
A short-circuit termination is placed at the test terminal of the SWR bridge and the
output signal level of the SWR bridge Lp0 [dB(mW)] is measured.
d)
The output terminal of the outdoor unit is connected to the SWR bridge test terminal
and the output signal level of the SWR bridge Lp [dB(mW)] is measured.
e) The return loss is expressed as the difference: Lp0 - Lp (dB).
The insertion loss and SWR of the bias network shall be known and taken into account
in the measurement result.
f)
The test signal frequency is changed and steps b), c), d) and e) are repeated.
3.3.3
Presentation of the results
The results shall be listed in a table and/or presented graphically.
3.4 Gain frequency characteristics
3.4.1 Introduction
This method of measurement determines the gain variation within a channel and between
channels in the reception band.
3.4.2 Method of measurement
A constant level of test signal is applied to the input terminal and the corresponding output
signal level is measured at specified frequencies. The arrangement of the test equipment
is shown in figure 7 when input arrangement a) or b) (see 2.2.4) is used, and in figure 8
when input arrangement c) (see 2.2.4) is used. The measurement shall be made according
to the following conditions and procedure.
3.4.2.1 Measuring conditions
a) Test frequency: the centre frequency of each allocated channel in the 12 GHz
broadcasting band.
b) Test signal level: -70 dB(mW) when input arrangement a) or b) is used, or
-94 dB(W/m2) when input arrangement c) is used.
c) Seven points are measured every 5 MHz within ±15 MHz of the centre frequency in
each channel.
3.4.2.2 Measurement procedure
a) A c.w. signal at the specified test signal level is applied to the input terminal of the
outdoor unit.
b) The signal level L p0 [dB(mW)] at the branch port of the directional coupler, and the
signal level Lp [dB(mW)] at the bias network output terminal are measured.
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1079-1 ©IEC - 27 -
c) When input arrangement a) or b) is used, the gain (G) is calculated using the follow-
ing equation:
G= Lp - LPo + Lr – Ls + Lb (dB)
where
Lr = attenuation of the second variable attenuator (dB);
L s =
coupling factor of the directional coupler (dB);
Lb = insertion loss of the bias network (dB).
When input arrangement c) is used, the gain (G') is calculated using the following equation:
G' = L p - PFD - 30 (dB(m2))
where
PFD
(see 2.2.5.2) is measured according to the procedure mentioned in clause 3.8.
The factor 30 is included because Lp is expressed in dB(mW) and PFD in dB(W/m2).
d) The test frequency is changed and steps a), b) and c) are repeated.
NOTE - The attenuation of the second variable attenuator should be such as to minimize the difference
between the signal level at the coupling terminal of the directional coupler and the output signal level of the
SHF converter.
3.4.3 Presentation of the results
The results shall be presented graphically, using plotted curves showing the gain
frequency characteristic, with the channel tested (or the frequency variation with respect
to the nominal centre frequency of the channel) as the abscissa and the gain as the
ordinate. Examples are shown in figures 9 and 10.
3.5 Output signal level versus input signal level
3.5.1 Introduction
This method of measurement determines the amplitude linearity of an outdoor unit.
3.5.2 Method of measurement
To obtain the linearity curve, the output signal level is measured at several input signal
levels. The arrangement of the test equipment is shown in figure 7 when input arrange-
ment a) or b) (see 2.2.4) is used and in figure 8 when input arrangement c) (see 2.2.4)
is used. The measurement shall be made according to the following conditions and
procedure.
3.5.2.1 Measuring conditions
a) Test frequency: the centre frequencies of the lowest (L), the mid (M) and the highest
GHz
(H) channels in the frequency band specified to be covered by the outdoor unit (12
band at the input and i.f. band at the output).
b) Test signal level at the input (12 GHz band): from -80 dB(mW) to -40 dB(mW)
2
(5 dB steps), when input arrangement a) or b) is used; from -104 dB(W/m ) to
-64 dB(W/m2) (5 dB steps), when input arrangement c) is used.
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1079-1 ©IEC - 29 -
3.5.2.2 Measurement procedure
a) A c.w. signal is applied and the first variable attenuator is adjusted to obtain a
convenient signal level [e.g. -35 dB(mW)] at the directional coupler output terminal.
b) The second variable attenuator is adjusted to obtain the minimum test signal level
specified in 3.5.2.1, according to the input arrangement used.
c) The output signal level of the outdoor unit is measured.
The test signal level is increased by adjusting the second variable attenuator and
d)
the output signal level of the outdoor unit is measured.
e) The test signal frequency is changed and steps a), b), c) and d) are repeated.
the maximum power specified for the
NOTE - The output signal level of the outdoor unit may exceed
spectrum analyzer input terminal.
3.5.3 Presentation of the results
The results are presented graphically, using a plotted curve with the input signal level as
the abscissa and the output signal level as the ordinate. An example is shown in figure 11.
3.6 Intermodulation
3.6.1
Introduction
This method of measurement determines the level of the interference components caused
by the intermodulation of two signals received outside the desired channel.
3.6.2 Method of measurement
Two test signals are applied to the input of the outdoor unit and the intermodulation
product level is measured at the output in the desired channel. The arrangement of the
test equipment is shown in figure 12 when input arrangement a) or b) (see 2.2.4) is used,
and in figure 13 when input arrangement c) (see 2.2.4) is used. The measurement shall be
made according to the following conditions and procedure.
3.6.2.1 Measuring conditions
Desired signal frequency: the centre frequencies of the lowest (L), the mid (M) and
a)
the highest (H) channels in the reception band.
b) Desired signal level: from -80 dB(mW) to -40 dB(mW) (5 dB steps) when input
arrangement a) or b) is used, from -104 dB(W/m 2) to -64 dB(W/m2) (5 dB steps) when
input arrangement c) is used.
c) Interference signal frequencies; for systems now planned or in service, suitable
frequencies are:
- centre frequencies of channels (L+2) and (L+4) for the L channel;
- centre frequencies of channels (M-2) and (M-4), or (M+2) and (M+4) for the
M channel;
- centre frequencies of channels (H-2) and (H-4) for the H channel.
(See ITU Radio Regulations, appendix 30*.)
d) Interference signal level: same as the desired signal level.
See also CCIR Reports 473-4 and 811-2 (annex A).
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1079-1 ©IEC - 31 -
3.6.2.2
Measurement procedure
a) A c.w. signal at the desired frequency at the test signal level is applied.
b) The variable band-pass filter is adjusted to obtain the maximum i.f. signal level.
The i.f. signal level Lp0
[dB(mW)] is measured at the output terminal.
c) The two c.w. interference signals are applied simultaneously, as indicated for
p [dB(mW)] is measured
each case, with the same level as a). The i.f. signal level L
at the output terminal. The intermodulation interference ratio is given by the value
Lp) (dB).
-
(Lp0
d) The desired signal level is changed and steps a), b) and c) are repeated.
e) The desired signal frequency is changed and steps a), b), c) and d) are repeated.
NOTE - The variable band-pass filter is used to prevent the spectrum analyzer from generating
intermodulation. Although it may be unnecessary to use the band-pass filter for a spectrum analyzer having
a large dynamic range, confirmation shall be made that intermodulation does not occur within it.
3.6.3 Presentation of the results
The results shall be listed in a table and/or presented graphically. Curves showing the
intermodulation interference ratio are plotted with the input signal level as the abscissa
and the intermodulation ratio as the ordinate. A graphical example is shown in figure 14.
3.7 Noise figure and noise temperature
3.7.1 Introduction
This method of measurement determines the noise generated in the SHF converter. It is
applicable only if input arrangement a) or b) (see 2.2.4) is possible. The test site should
comply with the conditions indicated in 2.1.2.
3.7.2 Method of measurement
A noise source is connected to the input terminal of the SHF converter and the noise
level appearing at the output terminal is measured with and without the input noise.
The noise figure and noise temperature are obtained from these data by calculation. The
arrangement of the test equipment is shown in figure 15. The measurement shall be made
according to the following conditions and procedure.
NOTE - An isolator or an attenuator should be inserted between the noise s
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