Specification for radio disturbance and immunity measuring apparatus and methods - Part 4-5: Uncertainties, statistics and limit modelling - Conditions for the use of alternative test methods

This Technical Report specifies a method to enable product committees to develop limits for alternative test methods, using conversions from established limits. This method is generally applicable for all kinds of disturbance measurements, but focuses on radiated disturbance measurements (i.e. field strength), for which several alternative methods are presently specified. These limits development methods are intended for use by product committees and other groups responsible for defining emissions limits in situations where it is decided to use alternative test methods and the associated limits in product standards.

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TECHNICAL CISPR
REPORT 16-4-5
First edition
2006-10
INTERNATIONAL SPECIAL COMMITTEE ON RADIO INTERFERENCE
Specification for radio disturbance and
immunity measuring apparatus and methods –
Part 4-5:
Uncertainties, statistics and limit modelling –
Conditions for the use of alternative test methods
Reference number
CISPR 16-4-5/TR:2006(E)
---------------------- Page: 1 ----------------------
Publication numbering
As from 1 January 1997 all IEC publications are issued with a designation in the
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---------------------- Page: 2 ----------------------
TECHNICAL CISPR
REPORT 16-4-5
First edition
2006-10
INTERNATIONAL SPECIAL COMMITTEE ON RADIO INTERFERENCE
Specification for radio disturbance and
immunity measuring apparatus and methods –
Part 4-5:
Uncertainties, statistics and limit modelling –
Conditions for the use of alternative test methods
© IEC 2006 ⎯ Copyright - all rights reserved

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 the publisher.

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Telephone: +41 22 919 02 11 Telefax: +41 22 919 03 00 E-mail: inmail@iec.ch Web: www.iec.ch

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For price, see current catalogue
---------------------- Page: 3 ----------------------
– 2 – TR CISPR 16-4-5 © IEC:2006(E)
CONTENTS

FOREWORD...........................................................................................................................4

1 Scope...............................................................................................................................6

2 Normative references .......................................................................................................6

3 Terms and definitions .......................................................................................................6

4 Symbols and abbreviated terms........................................................................................7

5 Introduction ......................................................................................................................8

6 Procedure to derive limits for an alternative test method...................................................9

6.1 Overview .................................................................................................................9

6.2 Select the reference quantity X..............................................................................12

6.3 Describe the test methods and measurands ..........................................................12

6.4 Determine the deviations of the measured quantities from the reference

quantity .................................................................................................................13

6.5 Determine the average values of the deviations ....................................................13

6.6 Estimate the standard uncertainties of the test methods ........................................14

6.7 Estimate the expanded uncertainties of the test methods ......................................15

6.8 Calculate the average conversion factor................................................................16

6.9 Verify the calculated values...................................................................................17

6.10 Apply the conversion .............................................................................................17

Annex A (informative) Remarks on EUT modelling ...............................................................18

Annex B (informative) Examples of application of the test method comparison

procedure .............................................................................................................................19

Bibliography..........................................................................................................................49

Figure 1 – Overview of quantities to estimate for use in conversion procedure......................10

Figure 2 – Overview of limit conversion procedure using estimated quantities.......................11

Figure B.1 – Example reference quantity ..............................................................................19

Figure B.2 – EUT and antenna set-up for fully anechoic room emission measurement ..........20

Figure B.3 – EUT and antenna set-up for open-area test site measurement..........................20

Figure B.4 – Radiation characteristics of elementary radiator (left), and scheme of

EUT-model (right) .................................................................................................................21

Figure B.5 – Maximum average deviations for 3 m FAR (top) and 10 m OATS (bottom) ........24

Figure B.6 – Sample cumulative distribution function ............................................................26

Figure B.7 – Uncertainties due to the unknown EUT characteristic for 3 m FAR (top)

and 10 m OATS (bottom) ......................................................................................................28

Figure B.8 – Expanded uncertainties (k = 2) of alternative (3 m FAR, top) and

established (10 m OATS, bottom) test methods ....................................................................32

Figure B.9 – Maximum average conversion factors for different volumes ..............................33

Figure B.10 – Photo (left) and cut-view of simulation model (right) of the specimen EUT ......35

Figure B.11 – Deviations of the specimen EUT: 3 m fully anechoic room (top) and 10 m

open area test site (bottom) ..................................................................................................36

Figure B.12 – Sample FAR measurement .............................................................................37

Figure B.13 – OATS 10 m limit line converted to FAR 3 m conditions....................................37

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TR CISPR 16-4-5 © IEC:2006(E) – 3 –

Figure B.14 – Expanded uncertainties...................................................................................37

Figure B.15 – Comparison of the measured values with the corrected converted limit ...........38

Figure B.16 – EUT and antenna set-up of 3 m open area test site measurement...................39

Figure B.17 – Maximum average deviations for 3 m OATS....................................................40

Figure B.18 – Uncertainties due to the unknown EUT characteristic for 3 m OATS................41

Figure B.19 – Expanded uncertainties (k = 2) of alternative test method [OATS (3 m)]..........43

Figure B.20 – Maximum average conversion factors .............................................................44

Figure B.21 – Deviations of the specimen EUT: Open area test site (3 m).............................46

Figure B.22 – Sample OATS (3 m) measurement..................................................................47

Figure B.23 – OATS (10 m) limit line converted to OATS (3 m) conditions ............................47

Figure B.24 – Expanded uncertainties...................................................................................48

Figure B.25 – Comparison of the corrected values with the converted limit ...........................48

Table 1 – Summary of steps in conversion procedure .............................................................9

Table 2 – Overview of quantities and defining equations for conversion process...................12

Table B.1 – Instrumentation uncertainty of the 3 m fully anechoic chamber test method .......25

Table B.2 – Uncertainties in dB due to the unknown EUT characteristic for 3 m FAR ............30

Table B.3 – Uncertainties in dB due to the unknown EUT characteristic for 10 m OATS........31

Table B.4 – Maximum average conversion factors in dB between 10 m OATS and

3 m FAR ...............................................................................................................................34

Table B.5 – Uncertainties in dB due to the unknown EUT characteristic for 3 m OATS..........42

Table B.6 – Maximum average conversion factors in dB between 10 m and 3 m OATS .........45

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– 4 – TR CISPR 16-4-5 © IEC:2006(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
SPECIFICATION FOR RADIO DISTURBANCE
AND IMMUNITY MEASURING APPARATUS AND METHODS –
Part 4-5: Uncertainties, statistics and limit modelling –
Conditions for the use of alternative test methods
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 provides no marking procedure to indicate its approval and cannot be rendered responsible for any

equipment declared to be in conformity with an IEC Publication.

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.

The main task of IEC technical committees is to prepare International Standards. However, a

technical committee may propose the publication of a technical report when it has collected

data of a different kind from that which is normally published as an International Standard, for

example "state of the art".

CISPR 16-4-5, which is a technical report, has been prepared by CISPR subcommittee A:

Radio-interference measurements and statistical methods.
The text of this technical report is based on the following documents:
Enquiry draft Report on voting
CISPR/A/665/DTR CISPR/A/685/RVC

Full information on the voting for the approval of this technical report can be found in the

report on voting indicated in the above table.
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TR CISPR 16-4-5 © IEC:2006(E) – 5 –

This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

A list of all parts of the CISPR 16-4 series, published under the general title Specification for

radio disturbance and immunity measuring apparatus and methods – Part 4: Uncertainties,

statistics and limit modelling, can be found on the IEC website.

The committee has decided that the contents of this publication will remain unchanged until

the maintenance result 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.
---------------------- Page: 7 ----------------------
– 6 – TR CISPR 16-4-5 © IEC:2006(E)
SPECIFICATION FOR RADIO DISTURBANCE
AND IMMUNITY MEASURING APPARATUS AND METHODS –
Part 4-5: Uncertainties, statistics and limit modelling –
Conditions for the use of alternative test methods
1 Scope

This part of CISPR 16-4 specifies a method to enable product committees to develop limits for

alternative test methods, using conversions from established limits. This method is generally

applicable for all kinds of disturbance measurements, but focuses on radiated disturbance

measurements (i.e. field strength), for which several alternative methods are presently

specified. These limits development methods are intended for use by product committees and

other groups responsible for defining emissions limits in situations where it is decided to use

alternative test methods and the associated limits in product standards.
2 Normative references
IEC 60050-161, International Electrotechnical Vocabulary (IEV) – Chapter 161:
Electromagnetic compatibility

CISPR 16-4-1:2003, Specification for radio disturbance and immunity measuring apparatus

and methods – Part 4-1: Uncertainties, statistics and limit modelling – Uncertainty in

standardized EMC tests

CISPR 16-4-2:2003, Specification for radio disturbance and immunity measuring apparatus

and methods – Part 4-2: Uncertainties, statistics and limit modelling – Uncertainty in EMC

measurements
3 Terms and definitions

For the purposes of this document, the terms and definitions given in IEC 60050-161 and the

following apply.
3.1
established test method

test method described in a basic standard with established emissions limits defined in

corresponding product or generic standards. An established test method consists of a specific

test procedure, a specific test set-up, a specific test facility or site, and an established

emissions limit

NOTE The following test methods have been considered to be established test methods in CISPR:

– conducted disturbance measurements: test method defined in CISPR 16-2-1:2003, Clause 7;

– radiated disturbance measurements up to 1 GHz: the test method defined in CISPR 16-2-3, 7.2.1;

– radiated disturbance measurements up to 18 GHz: the test method defined in CISPR 16-2-3, 7.3.

3.2
alternative test method

test method described in a basic standard without established emissions limits. The

alternative test method is designed for the same purpose as the established test method. An

alternative test method consists of a specific test procedure, a specific test set-up, a specific

test facility or site, and a derived emissions limit that was determined by the application of the

proposed method stated in this document
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TR CISPR 16-4-5 © IEC:2006(E) – 7 –
3.3
established limit
limit having “many years” of good protection of radio services.

NOTE An example is radiated field strength measured on OATS, developed to protect radio services as described

in CISPR 16-3.
3.4
derived limit

limit applicable for the alternative test method, derived by appropriate conversion from the

established limit and expressed in terms of the misbrands
3.5
conversion factor K

for a given EUT or type of EUT, the relation of the measured value of the established test

method to the measured value of the alternative test method

NOTE The terms measured and calculated are used interchangeably at various places in this document to

describe actual laboratory tests and computer simulations.
3.6
reference quantity X

the basic parameter which determines the interference potential to radio reception. It may be

independent of the parameters presently used in established standards

NOTE The goal for both the established and alternative test methods is to determine the reference quantity (X) for

all frequencies of interest. For both established and alternative test methods, the test results may deviate from the

reference quantity values. The specification of the reference quantity when applying methods of this document

should include applicable procedures and conditions to calculate (or measure) this quantity

3.7
inherent uncertainty
inherent

uncertainty caused solely by the difference in EUT characteristics and the ability of the

measurement procedure to cope with them. It is specific to each test method and remains,

even if the measurement is performed perfectly, i.e., the standards compliance uncertainty is

zero and the measurement instrumentations uncertainty is zero
3.8
intrinsic uncertainty of the measurand
intrinsic

minimum uncertainty that can be assigned in the description of a measured quantity. In

theory, the intrinsic uncertainty of the measurand would be obtained if the measurand was

measured using a measurement system having negligible measurement instrumentation

uncertainty.
[CISPR 16-4-1, definition 3.6]
3.9
EUT type

grouping of products with sufficient similarity in electromagnetic characteristics to allow

testing with the same test installation and the same test protocol.
4 Symbols and abbreviated terms
The following abbreviations are used in this technical report:
ATM alternative test method (e.g. subscript in D )
ATM
D deviation
ETM established test method (e.g. subscript in D )
ETM
i index of one individual (e.g., of a number of EUTs)
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K conversion factor
k coverage factor
L limit
M measurement (or calculation) result
N number of EUTs
s standard deviation
U expanded uncertainty
u standard uncertainty
v volume
X reference quantity
Δ difference of two values or quantities
x mean value of a set of values x (e.g., D )
5 Introduction

Over the years, several test procedures and test set-ups for radiated emissions testing have

been described in basic standards. One particular combination of test method and test set-up

also having defined emissions limits is the open area test site (OATS) method, which has

proven to be successful for the protection of radio services. In general limits have not been

defined for the other, alternative test methods, e.g., fully anechoic room, TEM waveguide,

reverberation chamber.

Each alternative method can be used to get measurement results related to emission of the

EUT. Although each method gives an emission level from the EUT, the different methods may

capture the EUT emission differently. For example, considering radiated emission

measurements, different methods may capture different EUT radiation pattern lobes, differing

numbers of lobes, or the test facility may alter the EUT radiation pattern producing a different

apparent emission level. Therefore the limits defined for the established test method cannot

be applied directly to the alternative test methods. Consequently, a procedure is needed for

how to derive limits to use for the results of alternative test methods.

The specification for such a procedure should consider the general goal of disturbance

measurements. The aim of the disturbance measurement is to verify whether the EUT

satisfies or violates certain compliance criteria. Past experience has shown that using the

present system of the established test method and the associated limits yields a situation

without many cases of interference due to conducted or radiated emissions. Applying the

established test method with the associated limits will fulfill the protection requirement with a

high probability. To preserve this situation, the most important requirement for the use of

alternative test methods is as follows.

– Use of an alternative test method in a normative standard shall provide the same

protection of radio services as the established test method.

This requirement can be met by developing a procedure for deriving emission limits for the

alternative test method from the existing limits of the established test method. Such a

procedure shall relate the results of the alternative test method to those of the established

test method. Using this relation the limits of the established test method can be converted into

limits for the alternative test method. The measured values of the alternative test method can

then easily be evaluated against the converted limits. Such a procedure will provide a similar

amount of protection, even though an alternative test method is used.
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TR CISPR 16-4-5 © IEC:2006(E) – 9 –

The limits conversion procedure should consider the goal of emissions measurements as

described above. The results of standard emissions tests can be considered as an

approximation of the interference potential of an EUT. Depending on the characteristics of the

EUT (e.g., radiation pattern characteristics for radiated disturbance test methods), and on the

measurement set-up, the measured value differs from the actual interference potential of the

EUT. This deviation can be divided into two parts: a systematic deviation, which can be

interpreted as a bias of the test method, and a random deviation depending on the

characteristics of different EUTs, which can be interpreted as an uncertainty of the test

method. Each emissions test method contains both quantities, and consequently the

established test method does too. In the following clauses, a procedure based on these two

quantities for comparing an alternative test method with the established test method is

described. To determine these quantities, the abstract term “interference potential” needs to

be expressed in terms of a physical quantity. For the purposes of this report, this quantity is

called the “reference quantity,” X. More details about correlation of test methods using a

reference quantity can be found in [1] .
6 Procedure to derive limits for an alternative test method
6.1 Overview

A procedure to derive limits for an alternative test method based on the limits of an

established test method is described in the following paragraphs. Figure 1 shows a summary

of the estimated quantities needed for the correlation process. Figure 2 shows a flowchart for

the correlation process using these quantities. The nine-step conversion process below can

be accomplished using numerical simulations, measurements, or a combination of simulations

and measurements. Calculable or reference EUTs are invaluable for this conversion

procedure. In the following subclauses, as part of the conversion process the quantities

shown in Figure 1 and Figure 2 are combined into several equations. A summary of the

equations is given in Table 2. A summary of the steps in the conversion procedure is shown in

Table 1.
Table 1 – Summary of steps in conversion procedure
1 Select the reference quantity
2 Describe the test methods and measurands

3 Determine the deviations of the measured quantities from the reference quantity

4 Determine the average values of the deviations
5 Determine the standard uncertainties of the test methods
6 Verify the calculated values
7 Apply the conversion
———————
Figures in square brackets refer to the Bibliography.
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– 10 – TR CISPR 16-4-5 © IEC:2006(E)
Statistical consideration
set of N EUTs
Alternative test Reference Established test
method
quantity method
definition
Measurement result Reference quantity Measurement result
M M
ATM ETM
– –
+ +
Set of deviations Set of deviations
D D
ATM ETM
Average deviation
Average deviation
ATM
ETM
Standard deviation Standard deviation
inherent uncertainty inherent uncertainty
∼ ∼
s(D ) D , s(D ) D ,
ATM ATM inherent ETM ETM inherent
Comparison
Average
of expanded
conversion
measurement
factor k
uncertainties
IEC 1694/06
Figure 1 – Overview of quantities to estimate for use in conversion procedure
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TR CISPR 16-4-5 © IEC:2006(E) – 11 –
Limit for established
Average
conversion test method L
ETM
factor k
Limit for alternative
Limitf oralternative
test method L
ATM
Uncertainties of Uncertainties of
alternative test method established test method
Inherent uncertainty Inherent uncertainty
U U
ATM, inherent ETM, inherent
Instrumentation uncertainty Instrumentation uncertainty
U U
ATM, instrumentation ETM, instrumentation
Intrinsic uncertainty Intrinsic uncertainty
U U
ATM, intrinsic ETM, intrinsic
Alternative test method + Established test method
expanded uncertainty expanded uncertainty
U U
ATM ETM
Difference of
uncertainties
Corrected limit for alternative test method L
ATM,U
IEC 1695/06
Figure 2 – Overview of limit conversion procedure using estimated quantities
---------------------- Page: 13 ----------------------
– 12 – TR CISPR 16-4-5 © IEC:2006(E)
Table 2 – Overview of quantities and defining equations for conversion process
Quantity Meaning Equation no.
the deviation from the reference quantity of the measurement result of EUT i (1)
D (f )
ATMi
as produced by the alternative test method
the deviation from the reference quantity of the measurement result of EUT i (2)
D (f )
ETMi
as produced by the established test method
the average deviation of the alternative test method (3)
ATM
the average deviation of the established test method (4)
ETM
the inherent uncertainty of the alternative test method (5)
ATM,inherent
the inherent uncertainty of the established test method (6)
ETM,inherent
combined standard uncertainty of the alternative test method (7)
ATM
the expanded uncertainty of the alternative test method (8)
ATM
combined standard uncertainty of the established test method (9)
ETM
the expanded uncertainty of the established test method (10)
ETM
frequency dependent conversion factor for EUT i (11)
K (f )
the average of the conversion factors (12), (13), (14)
K (f )

the limit line of the alternative test method equivalent to the limit of the (15)

L (f )
ATM
established test method, without consideration of the uncertainties
difference of expanded uncertainties (16)
the limit to be used for alternative measurements (17)
ATM,U
6.2 Select the reference quantity X

The first step is to select the reference quantity X. It should be selected on the basis of a

quantity that can possibly cause interference to a radio service, and selection of a reference

quantity also depends on the type of EUT.
For
...

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