IEC 62037-6:2013
(Main)Passive RF and microwave devices, intermodulation level measurement - Part 6: Measurement of passive intermodulation in antennas
Passive RF and microwave devices, intermodulation level measurement - Part 6: Measurement of passive intermodulation in antennas
IEC 62037-6:2013 defines test fixtures and procedures recommended for measuring levels of passive intermodulation generated by antennas, typically used in wireless communication systems. The purpose is to define qualification and acceptance test methods for antennas for use in low intermodulation (low IM) applications.
Dispositifs RF et à micro-ondes passifs, mesure du niveau d'intermodulation - Partie 6: Mesure de l'intermodulation passive dans les antennes
La CEI 62037-6:2013 définit les dispositifs et les procédures d'essai recommandés pour mesurer les niveaux d'intermodulation passive générés par les antennes, généralement utilisées dans les systèmes de communication sans fil. L'objectif est de définir des méthodes d'essai de qualification et d'acceptation pour les antennes destinées à être utilisées dans des applications d'intermodulation basse (IM basse).
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Standards Content (Sample)
IEC 62037-6 ®
Edition 1.0 2013-01
INTERNATIONAL
STANDARD
Passive RF and microwave devices, intermodulation level measurement –
Part 6: Measurement of passive intermodulation in antennas
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
either IEC or IEC's member National Committee in the country of the requester.
If you have any questions about IEC copyright or have an enquiry about obtaining additional rights to this publication,
please contact the address below or your local IEC member National Committee for further information.
IEC Central Office Tel.: +41 22 919 02 11
3, rue de Varembé Fax: +41 22 919 03 00
CH-1211 Geneva 20 info@iec.ch
Switzerland www.iec.ch
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.
About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigenda or an amendment might have been published.
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IEC 62037-6 ®
Edition 1.0 2013-01
INTERNATIONAL
STANDARD
Passive RF and microwave devices, intermodulation level measurement –
Part 6: Measurement of passive intermodulation in antennas
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
M
ICS 33.040.20 ISBN 978-2-83220-581-5
– 2 – 62037-6 © IEC:2013(E)
CONTENTS
FOREWORD . 3
1 Scope . 5
2 Normative references . 5
3 Abbreviations . 5
4 Antenna definitions as it pertains to PIM . 5
4.1 Antenna . 5
4.2 Antenna under test . 6
4.3 Active antenna . 6
4.4 Antenna PIM . 6
5 Antenna design and field installation considerations . 6
5.1 Environmental effects on PIM performance . 6
5.2 Antenna interface connection . 6
5.3 Mounting considerations to avoid PIM generation . 6
5.4 Neighbouring sources of interference . 7
5.5 Standard practices and guidelines for material selection . 7
6 PIM measurement considerations . 7
6.1 Quality assurance process and handling procedures . 7
6.2 Measurement accuracy . 7
6.3 Test environment. 8
6.4 Safety . 8
6.5 Test set-up . 8
6.5.1 Coaxial test cable assemblies . 8
6.5.2 Defining a good low PIM reference load . 8
6.5.3 Test set-up and test site baseline PIM verification . 8
6.6 PIM test configurations . 9
6.7 Combined environmental and PIM testing . 10
6.7.1 General . 10
6.7.2 Mechanical considerations . 10
6.7.3 Test system cables and connectors . 11
6.8 PIM test chamber design . 11
6.8.1 General . 11
6.8.2 RF absorber materials . 11
6.8.3 Supporting structures and walls . 12
6.8.4 RF shielding . 12
Figure 1 – Antenna reverse PIM test set-up . 9
Figure 2 – Antenna forward PIM test set-up . 10
62037-6 © IEC:2013(E) – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
PASSIVE RF AND MICROWAVE DEVICES,
INTERMODULATION LEVEL MEASUREMENT –
Part 6: Measurement of passive intermodulation in antennas
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). 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. 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 IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 62037-6 has been prepared by technical committee 46: Cables,
wires, waveguides, r.f. connectors, r.f. and microwave passive components and accessories.
The text of this standard is based on the following documents:
FDIS Report on voting
46/410/FDIS 46/422/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all the parts in the IEC 62037 series, published under the general title Passive RF
and microwave devices, Intermodulation level measurement can be found on the IEC website.
– 4 – 62037-6 © IEC:2013(E)
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.
62037-6 © IEC:2013(E) – 5 –
PASSIVE RF AND MICROWAVE DEVICES,
INTERMODULATION LEVEL MEASUREMENT –
Part 6: Measurement of passive intermodulation in antennas
1 Scope
This part of IEC 62037 defines test fixtures and procedures recommended for measuring
levels of passive intermodulation generated by antennas, typically used in wireless
communication systems. The purpose is to define qualification and acceptance test methods
for antennas for use in low intermodulation (low IM) applications.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and
are indispensable for its application. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 62037-1:2012, Passive r.f. and microwave devices, intermodulation level measurement –
Part 1: General requirements and measuring methods
IEC 62037-3, Passive r.f. and microwave devices, intermodulation level measurement –
Part 3: Measurement of passive intermodulation in coaxial connectors
3 Abbreviations
AIM Active intermodulation
AUT Antenna under test
ESD Electrostatic discharge
HPA High power amplifier
IM Intermodulation
LNA Low noise amplifier
PIM Passive intermodulation
RF Radio frequency
4 Antenna definitions as it pertains to PIM
4.1 Antenna
An antenna is that part of a radio transmitting or receiving system which is designed to
provide the required coupling between a transmitter or a receiver and the medium in which the
radio wave propagates.
The antenna consists of a number of parts or components. These components include, but
are not limited to, one or many radiating elements, one or many RF interfaces, a distribution
or combining feed network, internal support structures, devices which control or adjust the
amplitude/phase response and distribution to the radiating element(s), filters, diplexers,
orthomode transducers, polarizers, waveguides, coaxial cables or printed circuits. In addition,
peripheral components could also influence the PIM performance of the antenna. These
– 6 – 62037-6 © IEC:2013(E)
components may include, but are not limited to, mounting brackets, mounting hardware,
radome, radome fasteners, thermal insulation and grounding hardware.
4.2 Antenna under test
The antenna hardware can have an effect on the overall antenna PIM performance.
Therefore, it is necessary to specify the hardware which is to be part of the antenna under
test (AUT).
4.3 Active antenna
An active antenna incorporates active devices such as low noise amplifiers (LNAs), high
power amplifiers (HPAs), phase shifters, etc. An active antenna has the additional concern of
active intermodulation (AIM) which is typically at a much higher level than PIM. The
measurement of PIM in the presence of AIM is not within the scope of this standard. If
required, the PIM measurement of an active antenna shall be performed on the passive
portion of the antenna only.
4.4 Antenna PIM
The antenna PIM is defined as the PIM that is generated by the antenna assembly itself at a
reference plane or RF interface. The PIM can be measured in a radiated or conducted
(transmissive or reflective) mode.
5 Antenna design and field installation considerations
5.1 Environmental effects on PIM performance
Any hardware located in the near-by environment can significantly influence the PIM
performance of an antenna or antenna system. The effect of ferromagnetic materials,
dissimilar metallic junctions which are part of neighbouring hardware, such as other antennas,
towers structures, aircraft fuselage components, spacecraft thermal control hardware, d.c.
and ESD grounding hardware, non-high pressure mechanical connections etc., can potentially
have a detrimental effect on the PIM performance of the communication system.
5.2 Antenna interface connection
Any interface that is exposed to RF is a potential PIM source and shall be designed to be low
PIM. Care shall be taken to ensure that all the mating surfaces are clean. The connections,
whether coaxial or waveguide, should be inspected for dirt, metallic filings, sharp protruding
material, and other potential contaminates. Any coaxial connections shall be torqued to the
manufacturer’s specifications to assure proper metal-to-metal contact pressure is achieved. If
waveguide is used, then the flange bolts shall be torqued to the recommended manufacturer’s
specifications. Careful attention shall be paid to the alignment of the mating coaxial
connectors or waveguide flanges.
The materials and combination of materials used in the connectors, including plating, are
important for the PIM performance. The use of a soft plating material (e.g. gold, silver, etc.) of
sufficient thickness (several skin depths) over a hard base material (brass, BeCu, etc.) is
usually preferable. The number of interfaces (coaxial connectors and adapters) should be
minimized. This will reduce the number of metal-to-metal junctions and, thus, the possibility of
PIM generation. More information about coaxial connectors can be found in IEC 62037-3.
5.3 Mounting considerations to avoid PIM generation
The antenna shall be properly secured to its mounting bracket. All bolts and holding
harnesses used t
...
IEC 62037-6 ®
Edition 1.0 2013-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Passive RF and microwave devices, intermodulation level measurement –
Part 6: Measurement of passive intermodulation in antennas
Dispositifs RF et à micro-ondes passifs, mesure du niveau d’intermodulation –
Partie 6: Mesure de l’intermodulation passive dans les antennes
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
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About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.
About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigenda or an amendment might have been published.
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IEC 62037-6 ®
Edition 1.0 2013-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Passive RF and microwave devices, intermodulation level measurement –
Part 6: Measurement of passive intermodulation in antennas
Dispositifs RF et à micro-ondes passifs, mesure du niveau d’intermodulation –
Partie 6: Mesure de l’intermodulation passive dans les antennes
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX M
ICS 33.040.20 ISBN 978-2-8322-1345-2
– 2 – 62037-6 © IEC:2013
CONTENTS
FOREWORD . 3
1 Scope . 5
2 Normative references . 5
3 Abbreviations . 5
4 Antenna definitions as it pertains to PIM . 5
4.1 Antenna . 5
4.2 Antenna under test . 6
4.3 Active antenna . 6
4.4 Antenna PIM . 6
5 Antenna design and field installation considerations . 6
5.1 Environmental effects on PIM performance . 6
5.2 Antenna interface connection . 6
5.3 Mounting considerations to avoid PIM generation . 6
5.4 Neighbouring sources of interference . 7
5.5 Standard practices and guidelines for material selection . 7
6 PIM measurement considerations . 7
6.1 Quality assurance process and handling procedures . 7
6.2 Measurement accuracy . 7
6.3 Test environment. 8
6.4 Safety . 8
6.5 Test set-up . 8
6.5.1 Coaxial test cable assemblies . 8
6.5.2 Defining a good low PIM reference load . 8
6.5.3 Test set-up and test site baseline PIM verification . 8
6.6 PIM test configurations . 9
6.7 Combined environmental and PIM testing . 10
6.7.1 General . 10
6.7.2 Mechanical considerations . 10
6.7.3 Test system cables and connectors . 11
6.8 PIM test chamber design . 11
6.8.1 General . 11
6.8.2 RF absorber materials . 11
6.8.3 Supporting structures and walls . 12
6.8.4 RF shielding . 12
Figure 1 – Antenna reverse PIM test set-up . 9
Figure 2 – Antenna forward PIM test set-up . 10
62037-6 © IEC:2013 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
PASSIVE RF AND MICROWAVE DEVICES,
INTERMODULATION LEVEL MEASUREMENT –
Part 6: Measurement of passive intermodulation in antennas
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). 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. 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 IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 62037-6 has been prepared by technical committee 46: Cables,
wires, waveguides, r.f. connectors, r.f. and microwave passive components and accessories.
This bilingual version (2014-01) corresponds to the monolingual English version, published in
2013-01.
The text of this standard is based on the following documents:
FDIS Report on voting
46/410/FDIS 46/422/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
The French version of this standard has not been voted upon.
– 4 – 62037-6 © IEC:2013
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all the parts in the IEC 62037 series, published under the general title Passive RF
and microwave devices, Intermodulation level measurement can be found on the IEC website.
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
62037-6 © IEC:2013 – 5 –
PASSIVE RF AND MICROWAVE DEVICES,
INTERMODULATION LEVEL MEASUREMENT –
Part 6: Measurement of passive intermodulation in antennas
1 Scope
This part of IEC 62037 defines test fixtures and procedures recommended for measuring
levels of passive intermodulation generated by antennas, typically used in wireless
communication systems. The purpose is to define qualification and acceptance test methods
for antennas for use in low intermodulation (low IM) applications.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and
are indispensable for its application. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 62037-1:2012, Passive r.f. and microwave devices, intermodulation level measurement –
Part 1: General requirements and measuring methods
IEC 62037-3, Passive r.f. and microwave devices, intermodulation level measurement –
Part 3: Measurement of passive intermodulation in coaxial connectors
3 Abbreviations
AIM Active intermodulation
AUT Antenna under test
ESD Electrostatic discharge
HPA High power amplifier
IM Intermodulation
LNA Low noise amplifier
PIM Passive intermodulation
RF Radio frequency
4 Antenna definitions as it pertains to PIM
4.1 Antenna
An antenna is that part of a radio transmitting or receiving system which is designed to
provide the required coupling between a transmitter or a receiver and the medium in which the
radio wave propagates.
The antenna consists of a number of parts or components. These components include, but
are not limited to, one or many radiating elements, one or many RF interfaces, a distribution
or combining feed network, internal support structures, devices which control or adjust the
amplitude/phase response and distribution to the radiating element(s), filters, diplexers,
orthomode transducers, polarizers, waveguides, coaxial cables or printed circuits. In addition,
peripheral components could also influence the PIM performance of the antenna. These
– 6 – 62037-6 © IEC:2013
components may include, but are not limited to, mounting brackets, mounting hardware,
radome, radome fasteners, thermal insulation and grounding hardware.
4.2 Antenna under test
The antenna hardware can have an effect on the overall antenna PIM performance.
Therefore, it is necessary to specify the hardware which is to be part of the antenna under
test (AUT).
4.3 Active antenna
An active antenna incorporates active devices such as low noise amplifiers (LNAs), high
power amplifiers (HPAs), phase shifters, etc. An active antenna has the additional concern of
active intermodulation (AIM) which is typically at a much higher level than PIM. The
measurement of PIM in the presence of AIM is not within the scope of this standard. If
required, the PIM measurement of an active antenna shall be performed on the passive
portion of the antenna only.
4.4 Antenna PIM
The antenna PIM is defined as the PIM that is generated by the antenna assembly itself at a
reference plane or RF interface. The PIM can be measured in a radiated or conducted
(transmissive or reflective) mode.
5 Antenna design and field installation considerations
5.1 Environmental effects on PIM performance
Any hardware located in the near-by environment can significantly influence the PIM
performance of an antenna or antenna system. The effect of ferromagnetic materials,
dissimilar metallic junctions which are part of neighbouring hardware, such as other antennas,
towers structures, aircraft fuselage components, spacecraft thermal control hardware, d.c.
and ESD grounding hardware, non-high pressure mechanical connections etc., can potentially
have a detrimental effect on the PIM performance of the communication system.
5.2 Antenna interface connection
Any interface that is exposed to RF is a potential PIM source and shall be designed to be low
PIM. Care shall be taken to ensure that all the mating surfaces are clean. The connections,
whether coaxial or waveguide, should be inspected for dirt, metallic filings, sharp protruding
material, and other potential contaminates. Any coaxial connections shall be torqued to the
manufacturer’s specifications to assure proper metal-to-metal contact pressure is achieved. If
waveguide is used, then the flange bolts shall be torqued to the recommended manufacturer’s
specifications. Careful attention shall be paid to the alignment of the mating coaxial
connectors or waveguide flanges.
The materials and combination of materials used in the connectors, including plating, are
important for the PIM performance. The use of a soft plating material (e.g. gold, silver, etc.) of
sufficient thickness (several skin depths) over a hard base material (brass, BeCu, etc.) is
usually preferable. The number of interfaces (coaxial connectors and adapters) should be
minimized. This will reduce the number of metal-to-metal junctions and, thus, the possibility of
PIM generation. More information about coaxial connectors can be found in IEC 62037-3.
5.3 Mounting considerations to avoid PIM generation
The antenna shall be properly secured to its mounting bracket. All bolts and holding
harnesses used to secure the antenna to its support structure shall be tightened and torqued
according to the manufacturer’s specifications. The coaxial or waveguide transmission line(s)
62037-6 © IEC:2013 – 7 –
leading to the antenna input port(s) shall also be well-secured and prohibited from rubbing or
moving.
Care should be taken in the antenna placement by pointing it towards a clear sky view and to
isolate it from all possible neighbouring sources of interference such as tower structures,
near-by antennas, buildings, walls, aircraft fuselage, spacecraft platform, etc.
5.4 Neighbouring sources of interference
Knowledge of the RF environment in which the antenna is to be installed is important. Care
should be taken in the antenna placement to isolate it from all possible neighbouring sources
of interference. For instance, structures having low contact pressure or corroding parts should
be avoided. Additionally, other antennas radiating in a similar band or in bands whose
harmonics could fall within the receive frequency band of the antenna being installed also
requires consideration. Other electric or electronic devices may emit interfering RF signals
that fall into the receive frequency band of the antenna.
5.5 Standard practices and guidelines for material selection
Clause 6 of IEC 62037-1:2012 serves as a guide for the design, selection of materials, and
handling of components that may be susceptible to PIM generation. It is very important to
consider the application of the antenna, as there are large differences in acceptable PIM
levels between space applications and terrestrial applications.
6 PIM measurement considerations
6.1 Quality assurance process and handling procedures
The purpose of Clause 6 is to provide guidance in the areas of quality control as it pertains to
the performance of PIM testing of antenna products. Procedures are included to enhance the
accuracy and ensure safety when performing PIM measurements on antenna products. The
following guidelines will help minimize errors induced within the test system.
6.2 Measurement accuracy
The accuracy of PIM tests performed on antenna products may be severely affected by a
multitude of sources that may be either external or internal to the test system. Some of the
sources which can affect the results of PIM tests performed on antenna products include, but
are not limited to, the following:
a) objects comprising parts made of electrically conductive materials that are exposed to the
electromagnetic fields radiated by the AUT;
b) loose, damaged or corroded mounting hardware attached to the AUT;
c) loose or corroded hardware exposed to the radiated RF fields from the AUT;
d) radio frequency signals generated by external sources;
e) faulty or poorly performing coaxial interface cables;
f) dirty/contaminated/worn interface connections;
g) improperly mated interface connections;
h) poorly shielded RF interface connections;
i) inadequately filtered AIM from the test set-up;
j) consideration should be given to input transmission line losses;
k) contaminated absorbers.
– 8 – 62037-6 © IEC:2013
6.3 Test environment
When applicable, PIM measurements may be accomplished outdoors. In performing such a
test, it is important to ensure that government regulations pertaining to the maximum
authorized RF radiation levels are met. Also, the RF energy radiated from the AUT may
generate PIM in surrounding structures that may couple back into the antenna resulting in
invalid PIM test results. Additionally, external sources of RF radiation may interfere with the
test measurements. A survey of the frequencies locally in use is recommended prior to
testing. Many of the external sources of PIM may be minimized or eliminated by performing
the PIM testing of antennas within an anechoic test chamber providing a low PIM test
environment. More information on the construction of anechoic test chambers suitable for PIM
testing is provided in 6.8.
6.4 Safety
Performing PIM tests on antenna products can be dangerous. Potentially high voltages and
high levels of RF energy may be present both within the AUT and within the test environment.
The AUT should be positioned such that personnel will not be exposed to electromagnetic
fields exceeding the acceptable levels specified by government agencies.
6.5 Test set-up
6.5.1 Coaxial test cable assemblies
A problem with PIM test set-ups using coaxial cable interfaces is the need to repeatedly
connect/disconnect coaxial connectors. The following are some recommendations on test set-
up procedures.
a) Sealing O-rings at connector interfaces should be thoroughly cleaned or should preferably
be avoided if possible. These O-rings accumulate metal filings, which can become a
source of PIM.
b) Inspect connectors, dielectric and interface mating surfaces or flanges for contamination,
especially metallic debris, just prior to mating the interface. Also inspect connector mating
surfaces for burrs, scratches, dents, and loss of plating. Proper installation and torquing of
the hardware will minimize the generation of PIM within interface connections.
c) Clean compressed air should be used to blow potential metal particles from the connector
interfaces after each connect-disconnect cycle.
d) Great care shall be taken to ensure that the cables have not been stressed or fatigued to
the point of cracking. The inner and outer conductors can crack under the insulating cable
jacket and not be detectable by visual inspection. This will cause intermittent PIM signals
to be generated. One way to test for this is to flex or tap on the cable while performing a
baseline test. If there are fluctuations in the PIM signal, the cable may be damaged and
should be replaced.
6.5.2 Defining a good low PIM reference load
A good low PIM load can be made using a long section of high quality coaxial cable
terminated with a high quality (low PIM) connector. This connector should be soldered to the
coaxial cable on both the inner and outer conductors. The length of cable should be held in a
fixture so that no fatigue is placed on the connector or cable.
6.5.3 Test set-up and test site baseline PIM verification
Prior to the testing of the antenna, perform a baseline PIM test set-up noise floor verification.
To verify the test set-up itself, a low PIM termination may be used. Check the cables and
connections for sensitivity to flexure, mechanical stress and configuration during the baseline
test.
62037-6 © IEC:2013 – 9 –
The test site should also be evaluated to ensure that it does not generate unacceptable levels
of PIM or to identify any potential extraneous interfering RF sources. The test site could be an
anechoic test enclosure or a chosen outdoor site. If an anechoic chamber is used, special
design considerations are needed as outlined in 6.8. During the site verification, if possible,
use a low PIM reference antenna having a radiation pattern and gain comparable to that of
the AUT in order to ensure that the test environment is exposed to representative flux
densities as for the AUT test.
The actual antenna PIM test should be performed using the same set-up as for the baseline
test: minimize movements of components, do not add components, minimize changes in the
environment, etc. After the antenna PIM test is completed or as required during the test,
compare the baseline test results with previous set-up verification results for any sign of
degradation in the test system.
6.6 PIM test configurations
A typical test set-up for antenna reverse (reflected) PIM testing is shown in Figure 1 and one
for antenna forward (transmitted) PIM is shown in Figure 2. It should be noted that dynamic
range between the two test configurations should be examined to assess the appropriate
choices to use. In both cases, the test should take place in either a well-designed low PIM
anechoic chamber or outdoors, which would allow full range of antenna movement. For the
antenna forward (transmitted) PIM test, a low PIM antenna on the receiver side of the test set-
up is required. Also for this test, the environment may be first verified by using two low PIM
antennas.
Whenever possible, the diplexer (Figure 1) and the filter (Figure 2), both of which should be
low PIM, shall be placed as close as possible to the AUT input port to minimize PIM
generated by the test set-up. The overall cable or waveguide lengths should be minimized to
deliver maximum power to the AUT. Also, coaxial and waveguide adapters should be avoided
as much as possible.
Test chamber
f
Amplifier Transmit filter
AUT
Diplexer
Σ
f
Amplifier Transmit filter
Receive filter
Receiver Low noise
IEC 001/13
amplifier
Figure 1 – Antenna reverse PIM test set-up
– 10 – 62037-6 © IEC:2013
Each set-up has two synthesized sources, amplified separately to avoid AIM (active
intermodulation). The two-tone-test results in discrete intermodulation products, whose levels
are to be measured. These PIM-products are typically first amplified by one or two stages of
LNAs before detection by the spectrum analyser or digital receiver. This is in order to increase
the sensitivity of the set-up.
f
1 Test chamber
Amplifier Transmit filter
Transmit filter AUT Receive antenna
Σ
Transmit
f
2 Amplifier
filter
Load
Diplexer
Low noise Receive filter
Receiver
amplifier
IEC 002/13
Figure 2 – Antenna forward PIM test set-up
6.7 Combined environmental and PIM testing
6.7.1 General
Whenever possible and practical, each AUT should be measured for PIM while being exposed
to representative environmental operating conditions. If it is not possible, the AUT may be
measured for PIM before and after exposure to representative environmental conditions.
6.7.2 Mechanical considerations
A loose mechanical joint is likely to cause PIM. Materials expand and contract due to
temperature changes. Different materials expand and contract at different rates. This
difference can cause varying amounts of stress to be induced in any mechanical joint of the
antenna components. The differences in expansion and contraction can even cause the parts
to move so much as to loosen a mechanical joint. A bolted joint that was torqued to its
specified value can loosen to the point where the required clamping force is no longer being
produced. Evaluation of mechanical connections may be accomplished by performing PIM
testing during thermal cycling.
Vibrations can produce detrimental effects similar to those from thermal environments.
62037-6 © IEC:2013 – 11 –
For terrestrial applications, extreme temperature cycling occurs only in specific geographical
areas and is more applicable to aeronautical and space applications. Wind-induced vibrations
occur in most terrestrial and aeronautical applications but never for space applications.
However, vibrations are induced on space-borne antennas during platform manoeuvres. For
space and aeronautical applications, it is recommended that PIM testing be performed during
thermal cycling before and after vibration testing.
6.7.3 Test system cables and connectors
The test cables connected to the antenna under test are exposed to the same test
environments as the antenna itself. Therefore, great care shall be taken in selecting cables
suitable for PIM testing in the specific test environment. The entire test set-up, including the
cables, shall be verified under the same test conditions as for the AUT testing.
6.8 PIM test chamber design
6.8.1 General
The purpose of 6.8 is to provide guidance for the construction of test chambers suitable for
the performance of PIM testing on antennas.
Evaluation of antenna products for PIM presents additional challenges not found with other
non-radiating components. The antenna will be connected to an RF source and will radiate RF
energy during the PIM test. This energy shall not be allowed to excite potential PIM sources in
the test environment. It is also sometimes not practical to perform these tests in an outdoor
environment since the radiated RF energy should preferably be contained. To successfully
perform PIM testing on antennas, it may be desirable to construct an RF anechoic chamber
specially designed for PIM testing.
The main components of an RF anechoic test chamber are:
a) RF absorber materials;
b) supporting structures and walls;
c) RF shielding.
Each of these components will be discussed in the following subclauses.
6.8.2 RF absorber materials
RF absorber materials are commonly manufactured from a carbon impregnated foam. This
material offers attenuation to radio frequency signals as they pass through it. This attenuation
of the signal (absorption of energy) serves in essence as a “load” to the antenna.
RF absorber materials are available in many styles and sizes. The selection of style and size
is dependent on the frequency of operation and the placement within the test chamber. Proper
selection of the RF absorbers may be the most critical factor in the construction of a PIM test
chamber. Recommendations that may help in the selection process are as follows.
a) Select an absorber with an incident RF attenuation greater than 30 dB.
b) For good results, place pyramidal absorber panels in the field of the antenna radiation
pattern, preferably with normal incidence to the beam peak. However, best results can be
achieved when the interior of the test chamber is completely covered with RF absorber
material.
c) As a minimum, ensure there are enough panels to avoid back reflections.
For safety purposes, select an absorber that contains fire retardant materials and is rated for
the anticipated maximum power dissipation required.
– 12 – 62037-6 © IEC:2013
6.8.3 Supporting structures and walls
The supporting structure and walls for the PIM test chamber shall provide a suitable inner
surface for attachment of the RF absorber material. In some applications, the supporting
structure and walls may also be required to assist in the control of the temperature, the
pressure, the humidity level, or other environmental conditions for the test.
The materials and methods of construction will vary greatly depending on the specific
application. For many applications, simple lumber and plywood provide very good results.
Cement block construction also provides excellent support but at a much greater expense.
Some general considerations in designing the support structure and walls are as follows.
a) The use of metal shielding in the outer structure improves the isolation of the anechoic
chamber and is recommended when RF shielding needs to be high (see 6.8.4). However,
it is critical to ensure that the design does not include metal-to-metal junctions that
themselves have poor PIM performance. Examples of this would include overlapping metal
plates or the use of metal hardware going through sheet metal parts that are exposed.
b) Wood supports can be successfully joined using screws. Screws are stronger than nails
and it is easier to control their final location. Do not allow metal fasteners to contact each
other, even within the framework.
c) Make sure that the actual dimensions of absorber panels are known before completing the
design of the structure as they do not usually have the exact size advertised.
d) The size of the test chamber should be large enough to allow the test antenna to be
sufficiently far from any RF absorber to avoid mutual coupling between the radiating
antenna and the absorber material.
e) Hinges, fasteners, light fixtures, fire sprinklers, mounting hardware, etc. should all be
evaluated for potential PIM generation.
6.8.4 RF shielding
RF shielding may or may not be required, depending on the particular application. The
purpose of RF shielding may be for security, to maintain a low RF noise floor in the test
facility, or may be required to ensure personnel safety. A method of identifying the need for
RF shielding is based on the calculated power densities. From such calculations, it may be
found that RF levels behind the RF absorber are extremely low and therefore safe. It is
always recommended that an RF survey of the area surrounding the chamber be performed
prior to the approval of the final test plan or procedure.
Methods of RF shielding also vary depending on the application. One method providing good
results for most applications is to apply thin aluminium sheets or panels to the exterior surface
of the test chamber structure. The sheets can be securely attached using adhesive products.
Placing a plastic insulating material on the edge of each panel will prevent any direct contact
between panels. A small gap between the panels will not pass RF energy except at extremely
small wavelengths compared to the gap size. Although RF power levels may be extremely low
at the RF shield, it would still be advisable to avoid materials which may generate PIM such
as wire mesh fabrics.
___________
– 14 – 62037-6 © CEI:2013
SOMMAIRE
AVANT-PROPOS . 15
1 Domaine d’application . 17
2 Références normatives . 17
3 Abréviations . 17
4 Définitions de l’antenne relatives à l’intermodulation passive . 17
4.1 Antenne . 17
4.2 Antenne en essai . 18
4.3 Antenne active . 18
4.4 Intermodulation passive dans l’antenne . 18
5 Considérations relatives à la conception de l’antenne et à son installation sur le
terrain . 18
5.1 Effets environnementaux sur les performances d’intermodulation passive . 18
5.2 Connexion d’interface de l’antenne . 18
5.3 Considérations relatives au montage pour éviter la génération
d’intermodulation passive. 19
5.4 Sources de perturbations dans le voisinage . 19
5.5 Pratiques et lignes directrices normalisées relatives au choix des
matériaux . 19
6 Considérations relatives à la mesure de l’intermodulation passive . 19
6.1 Processus d’assurance qualité et procédures de manipulation . 19
6.2 Précision de la mesure. 19
6.3 Environnement d’essai . 20
6.4 Sécurité . 20
6.5 Montage d'essai . 20
6.5.1 Cordons d’essais coaxiaux . 20
6.5.2 Définition d’une bonne charge de référence d’intermodulation
passive basse . 21
6.5.3 Vérification de l’intermodulation passive ambiante dans le
montage d’essai et sur le site d’essai . 21
6.6 Configurations d’essais d’intermodulation passive . 21
6.7 Essais environnementaux et d’intermodulation passive combinés . 23
6.7.1 Généralités . 23
6.7.2 Considérations mécaniques . 23
6.7.3 Câbles et connecteurs du système d’essai. 24
6.8 Conception de la chambre d’essai d’intermodulation passive . 24
6.8.1 Généralités . 24
6.8.2 Matériaux d’absorption RF . 24
6.8.3 Structures de support et parois . 25
6.8.4 Ecrantage RF . 25
Figure 1 – Montage d’essai d’intermodulation passive inverse (réfléchie) de l’antenne. 22
Figure 2 – Montage d’essai d’intermodulation passive directe (émise) de l’antenne . 23
62037-6 © CEI:2013 – 15 –
COMMISSION ÉLECTROTECHNIQUE INTERNATIONALE
____________
DISPOSITIFS RF ET À MICRO-ONDES PASSIFS,
MESURE DU NIVEAU D’INTERMODULATION –
Partie 6: Mesure de l’intermodulation passive dans les antennes
AVANT-PROPOS
1) La Commission Electrotechnique Internationale (CEI) est une organisation mondiale de normalisation
composée de l'ensemble des comités électrotechniques nationaux (Comités nationaux de la CEI). La CEI a
pour objet de favoriser la coopération internationale pour toutes les questions de normalisation dans les
domaines de l'électricité et de l'électronique. A cet effet, la CEI – entre autres activités – publie des Normes
internationales, des Spécifications techniques, des Rapports techniques, des Spécifications accessibles au
public (PAS) et des Guides (ci-après dénommés "Publication(s) de la CEI"). Leur élaboration est confiée à des
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également aux travaux. La CEI collabore étroitement avec l'Organisation Internationale de Normalisation (ISO),
selon des conditions fixées par accord entre les deux organisations.
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du possible, un accord international sur les sujets étudiés, étant donné que les Comités nationaux de la CEI
intéressés sont représentés dans chaque comité d’études.
3) Les Publication
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