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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Publication Date
15-Jan-2013
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23-Nov-2021
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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
IEC 62037-6:2013-01(EN-FR)
---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
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

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 – 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

---------------------- Page: 4 ----------------------
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

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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.
---------------------- Page: 5 ----------------------
– 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.
---------------------- Page: 6 ----------------------
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

---------------------- Page: 7 ----------------------
– 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)

---------------------- Page: 8 ----------------------
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.
---------------------- Page: 9 ----------------------
– 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.
---------------------- Page: 10 ----------------------
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 f
...

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