SIST EN 60835-1-2:2002/A1:2002

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 -
Amendment A1 (IEC 60835-1-2:1992/A1:1995
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/A1:1995
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
INTERNATIONAL
60835-1-2
STANDARD
AMENDEMENT 1
AMENDMENT 1
1995-02
Amendement 1
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
Amendment 1
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 Amend. 1 © IEC:1995 - 3 -
FOREWORD
This amendment has been prepared by sub-committee 12E: Radio relay and satellite
communication systems, of IEC technical committee 12: Radiocommunications.
The text of this amendment is based on the following documents:
DIS
Report on voting
12E(CO)164 12E/250/RVD
Full information on the voting for the approval of this amendment can be found in the
report on voting indicated in the above table.
Page 3
CONTENTS
Add the title of clause 6 as follows:
6 Noise temperature and noise figure
Page 29
Add, after 5.2.5, the following new clause:
6 Noise temperature and noise figure
Introduction
6.1
This clause concentrates on the methods of measurement to be used in order to evaluate
the noise figure of sub-systems and/or combinations of sub-systems under linear
conditions where appropriate ports are available.
Noise temperature is an important parameter in satellite systems and is a convenient
indication of the noise power produced by a system or sub-system. It is usually expressed
in terms of an "equivalent" temperature rather than an "actual" temperature, since it is a
measure of the effects of all the thermal and non-thermal noise sources.
6.2 Definitions
The performance of a receiver is generally characterized by its noise figure NF, expressed
in decibels. For a two-port device it is defined as the ratio of the signal-to-noise ratio at
the input to the signal-to-noise ratio at the output under matched conditions. The noise
figure therefore indicates how much the signal-to-noise ratio at the output is lower than at
the input. NF
is therefore always greater than 0 dB.

- 5 -
835-1-2 Amend. 1 © IEC:1995
The equivalent noise temperature, TE, is related to the noise figure F, expressed in linear
numerals, by the expression:
(7-1)
TE = 290 (F-1)
The noise figure NF, expressed in decibels, is defined as:
T
NF= 10 log o (7-2)
(1 + 290 )
6.2.1
Equivalent noise temperature of a two-port device
The equivalent noise temperature T E of a two-port device is a fictitious noise temperature
which, when added to that of the input source connected to a theoretically ideal noise-free,
two-po rt device having the same input impedance and gain as the actual device, will
produce the same output noise power density as the actual device.
o of a two-po rt device with an equivalent noise tempera-
The output noise power density N
ture TE when connected to a noise source of temperature T is given by:
SOURCE
(7-3)
TE ) kG (W/Hz)
No = (TSOURCE +
where
k is the Boltzmann's constant, 1,38 x 10-23 Ws/K;
G is the gain of the two-po rt device.
input noise temperature over a given bandwidth B, the
If TE is the equivalent average
output noise power Pm:, of a two-port device is then:

+ TE ) k GB (7-4)
Pno = (TSOURCE
where B is the noise bandwidth in hertz.
is assumed constant over the noise bandwidth B.
TSOURCE
Unless otherwise specified, the term "equivalent noise temperature" will be taken to mean
the average input noise temperature over a given bandwidth.
6.2.2
Average noise figure
The average noise figure F of a two-port device is the ratio of the total noise power P0
delivered by the device into a matched load, when the noise temperature of its input
termination is 290 K, to the noise power PS available under the same conditions at the
output port of an ideal noise-free device.
(7-5)
F. = Po - Po
PS kTGB
where T is equal to 290 K.
835-1-2 Amend. 1 © IEC:1995 -
7 -
For equipment having gain in more than one frequency band, such as an image frequency
in a heterodyne system, the denominator P S includes only the noise power from the input
termination which lies in the same frequency band as the modulated signal. This case is
applicable to satellite communication systems and is known as the "single-sideband noise
figure".
F and the average equivalent input
The relationship between the average noise figure
noise temperature TE can be obtained as follows:
Po = kGB • 290 + k TE GB = kGB (290 + TE ) (7-6)
From the above equations:
F kGB (290 + TE)
E
T
-
1 + (7-7)
kGB • 290
where
TE = 290 (F-1) (7-8)
Unless otherwise specified, the term "noise figure" will be taken to mean the average
noise figure over a given bandwidth.
6.3 General considerations
F are divided into two groups: broad-
The methods employed to measure the noise figure
band and narrowband techniques. Broadband techniques typically use noise generators as
measurement signals, whereas narrowband techniques employ continuous wave (c.w.)
signal generators.
The most widely used methods for broadband measurements are:
a) the Y-factor method;
b) the 3 dB loss method.
As a narrowband technique the c.w. method using an unmodulated signal is the most
widely used single-sideband measurement. This method is applicable from very low
frequencies to tens of GHz.
Automatic noise figure measuring equipment is available which uses the above
measurement techniques. Such equipment usually switches the noise generator (or signal
generator) periodically between two known output levels and measures the receiver output
noise levels. The noise figure is then computed automatically and is displayed directly on
an indicator.
The choice of method for a given situation will depend upon many factors including:
a) desired accuracy;
b) instrumentation required;
835-1-2 Amend. 1 © IEC:1995 - 9 -
c) frequency range;
d) type of equipment under test;
e) convenience;
f)
speed of measurement.
These methods are described in 6.4 together with their advantages and disadvantages,
with the intention of providing a general understanding of the basic procedures involved
for each method. The "equipment under test" can therefore be either a single sub-system,
for example a low-noise amplifier, or a combination of sub-systems, for example a low-
noise amplifier followed by a down-converter.
6.4 Method of measurement
Methods for measuring the noise figure are presented in the following subclauses. If
required, the equivalent noise temperature can then be calculated by equation (7-1) given
in 6.2.
All measurements are based on methods where either a broadband noise or sinusoidal
c.w. signal is applied to the input of the equipment under test and the increase in output
power due to the applied signal is recorded. The noise figure is then obtained either by
calculation or by directly reading a display, depending on the specific method used, as
given in the following.
6.4.1
Y-factor method
A pair of random noise generators and a power-meter are connected to the equipment
under test as shown in figure 7. One of the noise generators, designated "hot", has a
higher noise temperature, Th , than that of the other generator, designated "cold", which
has a noise temperature, Tc.
NOTE 1 — "Hot" or "cold" noise generator means the relative difference in noise temperatures between the
generators. The noise generator may be a simple matched load of ambient temperature.
Examples of cold and hot noise generator are as follows:
cold: a matched load cooled in the liquid nitrogen;
hot: a matched load heated in the oven, a current-saturated diode or a gas discharge
tube.
The hot and the cold noise generators provide known available noise powers to the equip-
ment under test. The output noise power levels of the equipment under test are measured
by the power meter. The Y-factor is the ratio of the two noise output power levels,
corresponding to the two input conditions. TE and F are calculated from the measured
Y-factor and the known noise temperature of the two noise sources.
The method is capable of high accuracy and measurement uncertainties as small as 1
(0,04 dB) are possible under optimum conditions. Typical me
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