SIST EN 60835-1-2:2002

SLOVENSKI STANDARD
01-oktober-2002
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 60835-1-
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
Meßverfahren für Geräte in digitalen Mikrowellen-Funkübertragungssystemen -- Teil 1:
Messungen an terrestrischen Richtfunksystemen und Satelliten-Erdfunkstellen --
Hauptabschnitt 2: Grundlegende Eigenschaften
Méthodes de mesure applicables au matériel utilisé pour les systèmes de transmission
numérique en hyperfréquence -- Partie 1: Mesures communes aux faisceaux hertziens
terrestres et aux stations terriennes de télécommunications par satellite -- Section 2:
Caractéristiques de base
Ta slovenski standard je istoveten z: EN 60835-1-2:1993
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
60835-1-2
INTERNATIONAL
Première édition
STANDARD
First edition
1992-04
Méthodes de mesure applicables au matériel
utilisé pour les systèmes de transmission
numérique en hyperfréquence
Partie 1:
Mesures communes aux faisceaux hertziens
terrestres et aux stations terriennes de
télécommunications par satellite
Section 2: Caractéristiques de base
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
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835-1-2 ©IEC – 3 –
CONTENTS
Page
FOREWORD
INTRODUCTION
Clause
1 Scope
2 Carrier frequency
3 Spectrum
4 Impedance (admittance) 17
Level (voltage/power level, gain) 5
Figures
Annex A – Bibliography 37
835-1-2 ©IEC — 5 —
INTERNATIONAL ELECTROTECHNICAL COMMISSION
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
FOREWORD
1)
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.
2)
They have the form of recommendations for international use and they are accepted by the National
Committees in that sense.
3)
In order to promote international unification, the IEC expresses the wish that all National Committees
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 section of International Standard IEC 835-1 has been prepared by Sub-
Committee 12E: Radio relay and fixed satellite communications systems, of IEC Technical
Committee No. 12: Radiocommunications.
The text of this section is based on the following documents:
DIS Report on Voting
12E(CO)132
12E(CO)138
Full information on the voting for the approval of this section can be found in the Voting
Repo rt
indicated in the above table.
Annex A is for information only.

835-1-2 ©IEC — 7 —
INTRODUCTION
Modern test sets often combine a number of different measurement functions under the
control of a microprocessor. In this way generally more than one parameter is checked
and analysed step-by-step in accordance with specific software programmes.
The results of the measurements are printed or plotted automatically and the programme
description and tolerance analysis form part of the presentation of results. An example of
such specialized equipment is a network analyser which combines two and four-port
measurement facilities in one microprocessor-controlled unit.

835-1-2 ©I EC – 9 –
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
1 Scope
This section of IEC 835-1 deals with the measurement of basic characteristics common to
terrestrial radio-relay systems and satellite earth stations. These basic characteristics
apply to all of the frequency ranges employed in the radio systems, i.e:
- radio frequency;
intermediate frequency;
-
baseband (e.g. clock frequency of the digital baseband signal).
The method of measurement for each parameter (e.g. return loss) is presented, wherever
possible, as a single clause which is applicable to any of the above frequency ranges.
Where exceptions occur, they will be given in the relevant clauses.
2 Carrier frequency
2.1
Definition and general consideration
The carrier frequency is that frequency in the r.f. signal spectrum which is modulated by
the information, or baseband, signal. The carrier frequency is normally measured without
modulation. If energy dispersal is employed, it should be rendered inoperative, if possible,
before making measurements.
2.2 Methods of measurement
The arrangement for measuring frequency using a counter or digital frequency-meter is
shown in figure 1. The band-pass filter is required only if spurious signals are present. The
amplifier and/or attenuator are required only if the input range of the frequency-meter does
not cover the range of levels concerned.
Both the equipment under test and the test equipment itself should be allowed to attain
thermal stability before making any measurements.
The digital frequency-meter indications are then read during an interval of, for example,
one second, depending upon the integrating time of the instrument used.
Alternatively, a recorder may be used to record the indications of the digital frequency-
meter for a number of counts. The number of counts will depend upon whether noise is
present or not, and whether this modulates the signal or is superimposed upon it.

835-1-2 ©IEC - 11 -
Generally, the analysis of a statistical series averaged over several measuring intervals
will provide evidence of the repeatability of the results.
NOTE - The above method may also be used when the r.f. carrier is modulated by a zero mean baseband
signal, provided that the digital frequency-meter does not introduce errors which depend upon the
modulating signal. The averaging interval of the digital frequency-meter should exceed 100 cycles of the
modulating signal. Alternatively, e.g. when performing frequency measurements on baseband signals,
where a long time is required (10 s or more), several counter readings with a short averaging time can be
taken and the average of these readings calculated.
There are also other methods applicable for carrier frequency measurement with
modulation. For example, the substitution or interference method using a spectrum
analyser as an indicator in conjunction with a synthesizer as a reference frequency
source.
Presentation of results
2.3
The readings of the digital frequency-meter should be recorded manually or automatically
as a function of time. The integrating time and the accuracy of the digital frequency-meter
should be stated. When several counter readings are taken they should be tabulated,
together with the calculated average value.
The measured accuracy can be expressed as an absolute value, e.g. 50 kHz, or as a
. The nominal carrier frequency should also be
fractional value, e.g. one part in 10-5
stated.
2.4 Details to be specified
The following items should be included, as required, in the detailed equipment
specification:
nominal value of frequency and required accuracy;
a)
the part of the equipment to be measured and the port at which the measurement is
b)
to be made;
c) permitted frequency tolerance.
3 Spectrum
It is necessary to evaluate the spectrum which is to be transmitted by the radio-relay or
satellite earth station in terms of wanted or unwanted signals. Wanted signals within the
necessary bandwidth are treated under "signal spectrum", and unwanted signals which
appear outside the necessary bandwidth are treated under "spurious emissions".
Signal spectrum
3.1
3.1.1 Definitions and general considerations
In accordance with reference 1 the spectrum of a modulated signal is defined by the
following characteristics:
- necessary bandwidth;
- occupied bandwidth;
out-of-band signal;
- unwanted spectrum components.

835-1-2 ©IEC — 13 —
The
necessary bandwidth
is a theoretical value which ensures that the information will be
transmitted with the required quality, whereas the
occupied bandwidth is a measurable
value within which a specified percentage of the total power of a given signal should lie
(e.g. 99 %).
The out-of-band signal
is that part of the signal which is outside the necessary bandwidth
and results from the modulation process and/or caused by spectral restoration or spectral
spreading.
Unwanted spectrum components
within the necessary bandwidth are also measured.
NOTE - Unwanted components with an inadmissibly high level in the transmitted signal usually adversely
affect the error ratio. These components therefore have a different significance in digital systems than in
analogue systems.
3.1.2
Methods of measurement
A suitable measuring arrangement is shown in figure 2.
To measure the spectrum of the modulated signal, a random bit sequence modulation may
be applied. This bit sequence is usually generated by a pseudo-random generator (e.g. a
sequence of 2 23 —
1 bits for 140 Mbit/s systems). The resolution bandwidth of the analyser
should be greater than the bit rate of the pseudo-random bit sequence by a factor of 50
to 100 (e.g. for a bit rate of 34 Mbit/s and a sequence of 2
15 — 1 bits, the resolution
bandwidth is (50:100) x 34 • 10
6/(2 15 — 1), approximately 50:100 kHz).
To measure the level of the unwanted components within the necessary bandwidth it is
necessary to operate the equipment under test without modulation.
3.2 Spectrum of spurious components
3.2.1
Definition and general considerations
According to the Radio Regulations, a spurious emission is an emission on a frequency or
frequencies which are outside the necessary bandwidth and the level of which may be
reduced without affecting the corresponding transmission of information. Spurious
emissions include harmonic emissions, parasitic emissions, intermodulation products and
frequency conversion products,
but exclude out-of-band emissions.
Unwanted signal components may be divided into two categories:
i)
Spurious components excluding intermodulation products but including:
-
harmonic signals;
parasitic signals;
—
frequency conversion products.
ii) Intermodulation products
835-1-2 ©IEC — 15 —
Harmonics are components having a frequency n times that of the wanted signal, where n
is an integer greater than 1.
Intermodulation products are generated when two or more signals pass through a non-
linear network. They are identified by their order, e.g. third order (2 x f1 ) — f2 or (2 x f2 ) — f1
etc.
3.2.2 Method of measurement
For measuring spurious emissions, excluding intermodulation products, the arrangement
of figure 2 can again be used. A selective level-meter may be used instead of the
spectrum analyser. The dynamic range of the measuring instrument should be approxi-
mately 10 dB more than the measured spurious signal ratio, e.g. 70 dB for 60 dB
specification, and any non-uniformity of its amplitude/frequency characteristic should be
taken into account.
NOTE - For measuring harmonics, the input impedance of the measuring instrument (spectrum analyser
or selective level-meter) at harmonic frequencies should be nominally the same as the output impedance of
the equipment under test. If the output circuit of the equipment under test is a waveguide, suitable mode
transducers will be required.
In cases where the fundamental signal tends to overload the spectrum analyser, the high-pass filter should
be used.
For measuring intermodulation products, the measuring arrangement shown in figure 3 is
suitable. Additional attenuators or isolators may be inserted at the output of generators 1
and 2 if the 3 dB coupler and the internal attenuators of the signal generators do not
provide sufficient isolation to prevent mutual interaction between the two generators. It is
sometimes desirable to inse rt an isolator or an attenuator at the input of the spectrum
analyser. The spectrum analyser (or selective level-meter) should have a dynamic range
appropriate to the intermodulation ratio to be measured.
The reference signal generator is used to examine the frequencies of the intermodulation
products shown by the spectrum analyser. If necessary, it can also be used to examine
the levels of the intermodulation products. The calibration accuracy of the signal
generator, both in frequency and level, needs to be compatible with the required accuracy
of the measurements.
NOTES
1 The reference generator is not needed when the spectrum analyser has adequate frequency and level
measurement accuracy.
2 If the gain of the equipment under test is not uniform over the specified frequency band, the
measurement procedure described above requires the input signal levels to be unequal.
If the output levels at the frequencies of the applied signals are not equal, the lower signal is used as
the reference.
3.3 Presentation of results
The results of the measurement should be presented preferably as a photograph, print-out
or copy of the calibrated spectrum analyser display with appropriate ve rtical and horizontal
calibration.
If a selective level-meter is used the frequencies, frequency combinations and levels of
the spurious emissions should be given.

835-1-2 ©IEC — 17 —
The results of the measurement should be expressed in decibels as the ratio of the
individual spurious emissions to the corresponding wanted signals.
NOTES
1 The occupied bandwidth within which a specified percentage of the total signal power is contained may
also be presented.
2 When harmonics are measured via mode transducers, the characteristics of the transducer should be
stated.
3.4 Details to be specified
The following items should be included, as required, in the detailed equipment speci-
fication:
a) displayed frequency range, dynamic range and resolution bandwidth of the
spectrum analyser or selective level-meter;
b) range of in-band and out-of-band frequencies within which specified signals are to
be measured;
c) permitted level of unwanted signal components and/or intermodulation products;
d)
frequencies and levels of applied input signals, if applicable, to which intermodula-
tion products and/or unwanted signals are referred;
e)
permitted limits of modulated signal power distribution (e.g. necessary bandwidth),
if applicable;
f) bit-rate and sequence length of modulating input signal, if applicable;
g) part of the equipment under test and designation of connected port or ports.
4 Impedance (admittance)
4.1 Definitions and general considerations
The input or output impedance (admittance) of equipment used in microwave transmission
systems is usually expressed either in terms of return loss relative to the nominal value of
the impedance of the equipment under test or as a voltage standing-wave ratio (v.s.w.r.).
The return loss (L)
of an impedance (Z) relative to its nominal value (Z0) is given by:
Z + Zo
L = 20 log10
(dB)
(5-1)
Z — Zo
or alternatively by:
L = 20 log10 (dB)
(5-2)
p
where p is the voltage reflection coefficient of the impedance
(Z) relative to Z0 , i.e.
Z — ZO
(5-3)
P
Z + Z0
835-1-2 ©IEC — 19 —
Return loss, L,
is related to voltage standing-wave ratio, v.s.w.r., as follows:
+ 1
L = 20 log.10 dB
(5-4)
v.s.w.r. — 1 ( )
g10
The voltage reflection coefficient, and the characteristic impedance (Z 0) of the measuring
system, may be used to determine the actual value of the unknown impedance (Z), since
we may solve equation (5-3) for Z:
Z = Zo (1 + p) / (1 — p) (5-5)
4.2
Methods of measurement
The following methods of measurement are valid for linear devices for measuring thei
...