EN 60835-3-7:1995
(Main)Methods of measurement for equipment used in digital microwave radio transmission systems - Part 3: Measurements on satellite earth stations - Section 7: Figure-of-merit of receiving system
Methods of measurement for equipment used in digital microwave radio transmission systems - Part 3: Measurements on satellite earth stations - Section 7: Figure-of-merit of receiving system
Describes several methods of measuring the figure-of-merit (G/T) of the receiving systems of earth stations.
Meßverfahren für Geräte in digitalen Mikrowellen-Funkübertragungssystemen - Teil 3: Messungen an Satelliten-Erdfunkstellen - Hauptabschnitt 7: Gütezahl des Empfangssystems
Méthodes de mesure applicables au matériel utilisé pour les systèmes de transmission numérique en hyperfréquence - Partie 3: Mesures applicables aux stations terriennes de télécommunications par satellite - Section 7: Facteur de qualité du système de réception
Décrit plusieurs méthodes de mesure du facteur de qualité (G/T) des systèmes de réception des stations terriennes.
Methods of measurement for equipment used in digital microwave radio transmission systems - Part 3: Measurements on satellite earth stations - Section 7: Figure-of-merit of receiving system (IEC 60835-3-7:1995)
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
01-oktober-2002
Methods of measurement for equipment used in digital microwave radio
transmission systems - Part 3: Measurements on satellite earth stations - Section
7: Figure-of-merit of receiving system (IEC 60835-3-7:1995)
Methods of measurement for equipment used in digital microwave radio transmission
systems -- Part 3: Measurements on satellite earth stations -- Section 7: Figure-of-merit
of receiving system
Meßverfahren für Geräte in digitalen Mikrowellen-Funkübertragungssystemen -- Teil 3:
Messungen an Satelliten-Erdfunkstellen -- Hauptabschnitt 7: Gütezahl des
Empfangssystems
Méthodes de mesure applicables au matériel utilisé pour les systèmes de transmission
numérique en hyperfréquence -- Partie 3: Mesures applicables aux stations terriennes de
télécommunications par satellite -- Section 7: Facteur de qualité du système de réception
Ta slovenski standard je istoveten z: EN 60835-3-7:1995
ICS:
33.060.30 Radiorelejni in fiksni satelitski Radio relay and fixed satellite
komunikacijski sistemi communications systems
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
NORME CEI
INTERNATIONALE IEC
60835-3-7
INTERNATIONAL
Première édition
STAN DARD
First edition
1995-03
Méthodes de mesure applicables au matériel
utilisé pour les systèmes de transmission
numérique en hyperfréquence
Partie 3:
Mesures applicables aux stations terriennes
de télécommunications par satellite
Section 7: Facteur de qualité du système
de réception
Methods of measurement for equipment used in
digital microwave radio transmission systems
Part 3:
Measurements on satellite earth stations
Section 7: Figure-of-merit of receiving system
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835-3-7 © IEC:1995
CONTENTS
Page
FOREWORD 7
INTRODUCTION
Clause
1 Scope
2 Normative references
3 Definition and general considerations
4 Indirect method of measurement
5 Direct method of measurement using a radio star
5.1 General considerations 13
5.2 Method of measurement 15
5.3 Correction factors
17 Correction for atmospheric attenuation (C 1 ) 5.3.1
2) 17
5.3.2 Correction for the angular extension of the radio star (C
Correction for the change of radio-star flux density
5.3.3
with time (C3)
5.3.4 Correction for frequency dependence of flux density of
the radio star (C4)
5.3.5 Correction for the polarization of radio-star flux
5.4 Presentation of results
5.5 Details to be specified
5.6 Error analysis 21
6 Direct method of measurement using a remote source
6.1 General considerations
6.2 Method of measurement
6.2.1 Measurement procedures
6.2.2 Calculation of G/T 25
6.3 Presentation of results
6.4 Details to be specified
Figures
1 Typical G/T measurement arrangement using i.f. precision variable attenuator 27
2 Typical G/T measurement arrangement using r.f. precision variable attenuator 29
835-3-7 © IEC:1995 — 5 —
Figures Page
3 Typical G/T measurement arrangement using a test down-converter 31
4 Simplified arrangement for direct G/T measurement 33
5 Linearity and signal ratio 35
A.1 Correction factor for the angular extension of radio stars 39
Annexes
A Radio star and atmospheric loss data 37
B Bibliography 41
835-3-7 © IEC:1995 - 7 -
INTERNATIONAL ELECTROTECHNICAL COMMISSION
METHODS OF MEASUREMENT FOR EQUIPMENT
USED IN DIGITAL MICROWAVE RADIO
TRANSMISSION SYSTEMS -
Part 3: Measurements on satellite earth stations -
Section 7: Figure-of-merit of receiving system
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 835-3-7 has been prepared by sub-committee 12E: Radio relay
and satellite communication systems, of IEC technical committee 12: Radiocommunications.
The text of this standard is based on the following documents:
DIS Report on voting
12E(CO)169 12E/253/RVD
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.
835-3-7 © IEC:1995 - 9 -
INTRODUCTION
The quantity G/T represents the figure-of-merit of an earth station for satellite communication
applications.
Two measurement principles may be used in the measurement of the G/T of an earth
station, using both direct and indirect measurement methods.
The direct method measures the combined characteristics of the antenna and the receiver
and can be carried out using a radio star or other remote transmitter as a suitable signal
source.
In the indirect method, the antenna gain and receiver equivalent noise temperature are
measured separately and the G/T is calculated from the two measurements.
The choice between the indirect method, which is of low accuracy, and of the higher
accuracy, but more complex, direct method, mainly depends on the type of satellite earth
station under test.
835-3-7 © IEC:1995 - 11 -
METHODS OF MEASUREMENT FOR EQUIPMENT
USED IN DIGITAL MICROWAVE RADIO
TRANSMISSION SYSTEMS -
Part 3: Measurements on satellite earth stations -
Section 7: Figure-of-merit of receiving system
1 Scope
This section of IEC 835-3 describes several methods of measuring the figure-of-merit
(G/T) of the receiving systems of earth stations.
2 Normative references
The following normative documents contain provisions which, through reference in this
text, constitute provisions of this section of IEC 835-3. At the time of publication, the
editions indicated were valid. All normative documents are subject to revision, and pa rties
to agreements based on this section of IEC 835-3 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 835-1-2: 1992, Methods of measurement for equipment used in digital microwave
radio transmission systems - Part 1: Measurements common to terrestrial radio-relay
systems and satellite earth stations - Section 2: Basic characteristics
IEC 835-3-2, Methods of measurement for equipment used in digital microwave radio
transmission systems - Part 3: Measurements on satellite earth stations - Section 2:
Antenna (under consideration)
ITU-R Recommendation 574-3: 1990, Use of the decibel and the neper in telecom-
munications
3 Definition and general considerations
The figure-of-merit (G/T) of a satellite earth station is a logarithmic quantity which is
related to the antenna power gain G, given in decibels, and the absolute temperature T,
given in kelvins, by the following expression:
G/T = G - 10 log 10 (T/1 K) [dB/K] (1)
This definition is in accordance with that given in Recommendation ITU-R 574-3.
835-3-7 © IEC:1995 - 13 -
The indirect method (see clause 4) is generally usable with all receiving systems, taking
into account the lower measurement accuracy of the method, and is the most feasible
method for receiving systems with small and medium-size antennas. In these cases, the
expected G/T of the receiving systems does not result in a sufficiently large Y-factor to
enable the direct method to be used. The indirect method may also be used for earth
stations with large antenna systems, either when the tracking capability of the antenna is
limited or a suitable remote source does not exist.
The direct method using a radio star (see clause 5) is the preferred method, with
maximum accuracy for large antenna systems.
NOTE - If the higher accuracy, more complex, direct method is preferred, specialized knowledge and
experience is necessary to carry out the measurement.
The direct method using a remote source and reference antenna is also possible for
relatively small antennas (see clause 6).
The measurement should always be carried out with clear sky conditions so as to
eliminate the effects of rain, snow, cloud, fog, etc.
4 Indirect method of measurement
The indirect measurement uses separate measurements of antenna gain G and system
noise temperature T to calculate G/T.
For measurement of G, refer to IEC 835-3-2.
For measurement of T, refer to IEC 835-1-2 (future amendment 1).
5 Direct method of measurement using a radio star
5.1 General considerations
When the direct method of measurement using a radio star is carried out, the determination of
the figure-of-merit is based on the measurement of the Y-factor, using the following
calculation:
G/T = 10 log o S) (Y - 1) [dB/K] (2)
(8 nk / X2
where
k is the Boltzmann constant, 1,38 x 10 -23 [Ws/K];
X is the wavelength;
S is the spectral power flux density of the radiation from the radio star at the
frequency at the time of the measurement (Wm -2 Hz-1);
Y is the measured Y-f actor.
The Y-factor is defined as the ratio of the measured noise power when the antenna is
pointed towards the radio star to that measured when the antenna is pointed towards the
background sky at the same elevation angle.
835-3-7 © IEC:1995 -
15 -
5.2 Method of measurement
Three different test arrangements can be used depending on which equipment contributions
to the figure-of-merit have to be determined, as detailed in the following table:
Test arrangement Contributions
Figure 1, using i.f. attenuator Antenna feed, LNA, down-converter,
i.f. amplifier
Figure 2, using r.f. attenuator Antenna feed, LNA
Figure 3, using test down-converter Antenna feed, LNA
According to the test arrangements of figures 1 and 2, the measurement is carried out by
pointing the antenna first to the background sky at an elevation angle corresponding to
that of the chosen radio star and noting the reading of the power meter connected to the
i.f. output. The antenna is then pointed, at the same elevation angle, to the chosen radio
star, thereby causing the noise power to increase. The output noise power is reduced to
its original value by adjusting the r.f. or i.f. attenuator. The Y-factor is then given by the
difference in decibels between the two attenuator settings. The measurement can also be
accomplished using a scanning technique, which is capable of indicating the maximum
noise power by sweeping the antenna over the position of the radio star. When using the
scanning technique, the Y-factor is normally measured by reading two power levels with
the same attenuator setting.
According to the test arrangement of figure 3, the down-converter normally used in the earth
station, i.e. the operational down-converter, may be replaced by a test down-converter
which has a much improved gain stability. This will eliminate the effects of gain variations
during the antenna pointing or scanning procedure. The two noise powers are read from
the power meter connected to the i.f. output of the test down-converter.
The minimum elevation angles for the G/T measurement should be limited because of the
effect of refraction and atmospheric absorption at low elevation angles.
Following the above measurement, the G/T is calculated by substituting into equation (2)
the measured Y-factor, the wavelength corresponding to the receiving frequency and the
flux density of the chosen radio star as given in table A.1.
The calculated G/T value has to be corrected by applying the appropriate correction
factors as given in the following subclause.
835-3-7 © IEC:1995 - 17 -
5.3 Correction factors
The following correction
...
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