Passive RF and microwave devices, intermodulation level measurement - Part 6: Measurement of passive intermodulation in antennas

IEC 62037-6:2021 is available as IEC 62037-6:2021 RLV which contains the International Standard and its Redline version, showing all changes of the technical content compared to the previous edition.IEC 62037-6:2021 defines the 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. This second edition cancels and replaces the first edition published in 2013. This edition includes the following significant technical changes with respect to the previous edition:
a. dynamic testing requirements updated to define impact energy and locations to apply impacts to devices under test

Dispositifs RF et à micro-ondes passifs, mesure du niveau d'intermodulation - Partie 6: Mesure de l'intermodulation passive dans les antennes

IEC 62037-6:2021 est disponible sous forme de IEC 62037-6:2021 RLV qui contient la Norme internationale et sa version Redline, illustrant les modifications du contenu technique depuis l'édition précédente.L'IEC 62037-6:2021 définit les dispositifs et les procédures d’essai recommandés pour mesurer les niveaux d’intermodulation passive générés par des antennes, généralement utilisées dans des systèmes de communication sans fil. L’objectif est de définir des méthodes d’essai de qualification et d’acceptation pour des antennes destinées à être utilisées dans des applications de faible intermodulation (faible IM). Cette seconde édition annule et remplace la première édition parue en 2013. Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente:
a. mise à jour des exigences relatives aux essais dynamiques afin de définir l’énergie des chocs et la position où ils sont appliqués sur les dispositifs soumis à essai.

General Information

Status
Published
Publication Date
22-Nov-2021
Current Stage
PPUB - Publication issued
Completion Date
23-Nov-2021
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IEC 62037-6
Edition 2.0 2021-11
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
IEC 62037-6:2021-11(en-fr)
---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
IEC 62037-6
Edition 2.0 2021-11
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
INTERNATIONALE
ICS 33.040.20 ISBN 978-2-8322-1049-3

Warning! Make sure that you obtained this publication from an authorized distributor.

Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.

® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
---------------------- Page: 3 ----------------------
– 2 – IEC 62037-6:2021 © IEC 2021
CONTENTS

FOREWORD ........................................................................................................................... 3

1 Scope .............................................................................................................................. 5

2 Normative references ....................................................................................................... 5

3 Terms, definitions and abbreviated terms ........................................................................ 5

3.1 Terms and definitions .............................................................................................. 5

3.2 Abbreviated terms ................................................................................................... 5

4 Definitions of antenna 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 .................................................... 7

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 ............................................................... 10

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 ..................................................................... 11

6.8.4 RF shielding .................................................................................................. 12

7 Dynamic PIM measurement considerations .................................................................... 12

7.1 General ................................................................................................................. 12

7.2 Dynamic testing methodology ............................................................................... 13

7.3 Shocks test ........................................................................................................... 13

Bibliography .......................................................................................................................... 14

Figure 1 – Antenna reverse PIM test set-up ............................................................................ 9

Figure 2 – Antenna forward PIM test set-up .......................................................................... 10

Figure 3 – Hammer description ............................................................................................. 13

---------------------- Page: 4 ----------------------
IEC 62037-6:2021 © IEC 2021 – 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

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any IEC Publication and the corresponding national or regional publication shall be clearly indicated in the latter.

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6) All users should ensure that they have the latest edition of this publication.

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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.

IEC 62037-6 has been prepared by IEC technical committee 46: Cables, wires, waveguides, RF

connectors, RF and microwave passive components and accessories. It is an International

Standard.

This second edition cancels and replaces the first edition published in 2013. This edition

constitutes a technical revision.

This edition includes the following significant technical changes with respect to the previous

edition:

a) dynamic testing requirements updated to define impact energy and locations to apply

impacts to devices under test;
---------------------- Page: 5 ----------------------
– 4 – IEC 62037-6:2021 © IEC 2021
The text of this International Standard is based on the following documents:
Draft Report on voting
46/838/FDIS 46/859/RVD

Full information on the voting for its approval can be found in the report on voting indicated in

the above table.
The language used for the development of this International Standard is English.

This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in

accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available

at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are

described in greater detail at www.iec.ch/standardsdev/publications.

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 document will remain unchanged until the

stability date indicated on the IEC website under webstore.iec.ch in the data related to the

specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
---------------------- Page: 6 ----------------------
IEC 62037-6:2021 © IEC 2021 – 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 the 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
There are no normative references in this document.
3 Terms, definitions and abbreviated terms
3.1 Terms and definitions
No terms and definitions are listed in this document.

ISO and IEC maintain terminological databases for use in standardization at the following

addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.2 Abbreviated terms
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 Definitions of antenna 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.
---------------------- Page: 7 ----------------------
– 6 – IEC 62037-6:2021 © IEC 2021

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

components can 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 document. 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 nearby 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, tower

structures, aircraft fuselage components, spacecraft thermal control hardware, DC 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 ensure 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.

---------------------- Page: 8 ----------------------
IEC 62037-6:2021 © IEC 2021 – 7 –
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) 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 require

consideration. Other electric or electronic devices can emit interfering RF signals that fall into

the receive frequency band of the antenna.
5.5 Standard practices and guidelines for material selection

IEC 62037-1:2021, Clause 6 serves as a guide for the design, selection of materials, and

handling of components that can 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 can be severely affected by a

multitude of sources that can 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 of input transmission line losses;
k) contaminated absorbers.
---------------------- Page: 9 ----------------------
– 8 – IEC 62037-6:2021 © IEC 2021
6.3 Test environment

When applicable, PIM measurements can 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 can generate PIM in

surrounding structures that may couple back into the antenna resulting in invalid PIM test results.

Additionally, external sources of RF radiation can 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 can 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 can 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 can 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. When soldering coaxial cables, it should be done

very carefully to avoid melting or deforming the insulation, which can cause impedance changes.

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.
---------------------- Page: 10 ----------------------
IEC 62037-6:2021 © IEC 2021 – 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 an
...

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