ETSI TS 103 051 V1.1.1 (2011-08)

Electromagnetic compatibility and Radio spectrum Matters (ERM); Expanded measurement uncertainty for the measurement of radiated electromagnetic fields

DTS/ERM-TG27-012

General Information

• Status: Published
• Publication Date: 04-Aug-2011
• Technical Committee: ERM TG27 - ERM Radio Site Engineering
• Current Stage: 12 - Completion
• Due Date: 12-Aug-2011
• Completion Date: 05-Aug-2011

Standards Content (Sample)

Technical Specification
Electromagnetic compatibility
and Radio spectrum Matters (ERM);
Expanded measurement uncertainty
for the measurement of radiated electromagnetic fields

2 ETSI TS 103 051 V1.1.1 (2011-08)

Reference
DTS/ERM-TG27-012
Keywords
measurement uncertainty, radio, testing
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3 ETSI TS 103 051 V1.1.1 (2011-08)
Contents
Intellectual Property Rights . 6
Foreword . 6
Introduction . 6
1 Scope . 8
2 References . 8
2.1 Normative references . 8
2.2 Informative references . 10
3 Definitions, symbols and abbreviations . 11
3.1 Definitions . 11
3.2 Symbols . 13
3.3 Abbreviations . 14
4 Measurement uncertainty . 14
4.1 Introduction . 14
4.2 Measurement uncertainty . 15
5 Application of expanded measurement uncertainty to specification limits . 15
5.1 Introduction . 15
5.2 Development of the "shared risk" concept . 15
5.3 Shared risk, the new approach . 16
5.3.1 Maximum acceptable expanded measurement uncertainty . 16
5.3.2 Guidance on compliance assessment when expanded measurement uncertainty is equal to or less
than maximum acceptable expanded uncertainty . 17
5.3.3 Strength and weaknesses of the "shared risk" approach . 18
5.4 Assessment for market surveillance and enforcement . 18
5.4.1 Market surveillance. 18
5.4.2 Enforcement . 18
5.5 Interpretation of EMF test results in CENELEC standards . 18
6 Void . 18
7 The role of calibration in measurement uncertainty . 18
7.1 Introduction to calibration . 18
7.2 Test site calibration . 19
7.2.1 Calibration of OATS . 19
7.2.2 Calibration of semi-anechoic rooms . 19
7.2.3 Calibration of fully lined anechoic rooms . 20
7.2.4 Calibration and minimum requirements for test sites for measurements above 18 GHz . 20
7.3 Antenna calibration . 21
7.4 Test equipment calibration . 21
7.5 Automated test system calibration . 22
8 Recommended maximum expanded measurement uncertainties for RF electromagnetic field
measurements . 22
8.1 Introduction . 22
8.2 Substitution measurement methods . 22
8.2.1 Frequency Error and Frequency Drift . 22
8.2.2 Effective radiated power (e.r.p.) and equivalent isotropically radiated power (e.i.r.p.) . 23
8.2.2.1 Measurements in the frequency range above 66 GHz (e.i.r.p.) . 23
8.2.2.2 Conversion loss data and expanded measurement uncertainty for measurements above 66 GHz
(e.i.r.p.) . 25
8.2.3 Radiated unwanted emissions in the spurious domain . 26
8.2.3.1 Measurements in the frequency range between 30 MHz and 1 GHz (radiated) . 26
8.2.3.2 Measurements in the frequency range between 1 GHz and 66 GHz (radiated) . 26
8.2.3.3 Measurements in the frequency range above 66 GHz (radiated) . 27
8.2.4 Low power radio wanted emission measurements (radiated) . 27
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4 ETSI TS 103 051 V1.1.1 (2011-08)
8.2.5 Radiated transient power . 28
8.2.6 Receiver sensitivity (radio) . 28
8.2.7 Receiver 2-signal or multiple signal measurements (radiated) . 29
8.3 Single measurement methods . 30
8.3.1 Radiated emissions (EMC) . 30
8.3.2 Radiated immunity (EMC) . 30
9 Controlling measurement uncertainty . 30
9.1 Introduction . 30
9.2 Void . 30
9.3 Void . 30
9.4 Void . 30
9.5 Design and validation of appropriate test sites . 31
9.6 Void . 31
9.7 Validation of test methods . 31
9.8 Test instrumentation . 32
9.9 Documentation . 32
Annex A (informative): History of the "shared risk" concept . 33
A.1 Reporting and interpretation of the measurement results . 33
Annex B (informative): Examples of measurement uncertainty calculations. 36
B.1 Equivalent isotropically radiated power (e.i.r.p.) (Substitution method) anechoic room . 37
B.2 Equivalent isotropically radiated power (e.i.r.p.) (Substitution method) OATS . 39
B.3 Equivalent isotropically radiated power (e.i.r.p.) (Pre-Substitution method above 1 GHz),
effective radiated power (e.r.p.) (Pre-Substitution method below 1 GHz) anechoic room . 41
B.4 Equivalent isotropically radiated power (e.i.r.p.) (Pre-Substitution method above 1 GHz),
effective radiated power (e.r.p.) (Pre-Substitution method below 1 GHz) OATS . 43
B.5 Radiated field strength (EMC) . 45
Annex C (informative): Void . 48
Annex D (informative): Measurement Uncertainty contributions . 49
D.1 Reflectivity . 50
D.2 Mutual coupling . 51
D.3 Range length . 55
D.4 Corrections . 57
D.5 Radio frequency cables . 58
D.6 Phase centre positioning . 59
D.7 Ambient signals . 61
D.8 Mismatch . 62
D.9 Signal generator . 64
D.10 Insertion losses . 64
D.11 Antennas . 65
D.12 Receiving device . 66
D.13 Random uncertainty . 67
D.14 Summary, tables and figures . 68
Annex E (informative): Broadband Systems (BW > 10 MHz) . 72
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5 ETSI TS 103 051 V1.1.1 (2011-08)
Annex F (informative): Overview of new standards at EHF frequencies using radiated
measurements . 73
Annex G (informative): Bibliography . 74
History . 75

ETSI
6 ETSI TS 103 051 V1.1.1 (2011-08)
Intellectual Property Rights
IPRs essential or potentially essential to the present document may have been declared to ETSI. The information
pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found
in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in
respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web
server (http://ipr.etsi.org).
Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee
can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web
server) which are, or may be, or may become, essential to the present document.
Foreword
This Technical Specification (TS) has been produced by ETSI Technical Committee Electromagnetic compatibility and
Radio spectrum Matters (ERM).
Introduction
The present document has been produced in response to the need for expanded measurement uncertainty information,
and to determine practical maximum frequency of measurement which is also cost effective for manufacturers self
declaration as well as for test laboratories offering certification testing.
In metrology the term "measurement uncertainty" is nearly always associated with the simple standard deviation (σ). In
the case that a different confidence interval is used, the term "Expanded Measurement Uncertainty" is used, stating the
associated expansion factor, see EA-4/02 [19].
Considerable work on radio test methods and expanded measurement uncertainty up to 1 GHz has previously been
undertaken by ETSI to determine the contributions to the calculation of measurement uncertainty and these have been
published in TR 100 028 [1] and [2] and TR 102 273 [3] to [10]. However, more and more ETSI standards and norms
are generated for radio devices operating at higher frequencies as far as 100 GHz or even higher.
The expanded measurement uncertainty values have been included based on new information on state-of-the-art
measurements for expanded measurement uncertainty for measurements at higher frequencies, also taking into account
new work in ERM for radio applications at EHF frequencies.
The changing role of regulation due to the implementation of the Radio and Telecommunications Terminal Equipment
(R&TTE) Directive [11] within the European Union has meant that there is a need to review and if necessary revise the
previously agreed methods for the comparison of measurement values with limits to determine conformance with
standards and specifications.
As a result of discussions with manufacturers, test laboratories, and regulators it is clear that some test methods need to
be reviewed and more clearly defined as the frequency of measurement increases above 1 GHz. The re-defining of test
methods is not within the scope of the present document, but may result in a more extensive evaluation of the test
methods, bearing in mind the globalization of radio products, and the implementation of Mutual Recognition
Agreements (MRA) for this purpose.
The present document contains the results of many discussions held with test equipment manufacturers, test
laboratories, administrations, trade associations, societies, and members of the GRSC, all who have an interest in
expanded measurement uncertainty above 1 GHz.
From an international perspective, measurements for radio testing, both radio parameters and EMC are already required
above 1 GHz, notably in US FCC regulations (40 GHz), ITU-R spurious emissions (300 GHz), and CISPR EMC testing
(6 GHz). These extensions to the measurement frequency range necessitate a review and some level of co-ordination to
ensure that a common approach to test methods and the associated measurement uncertainty calculations are agreed.
ETSI
7 ETSI TS 103 051 V1.1.1 (2011-08)
Contrary to the requirement of performing measurements at higher frequencies up to 100 GHz or even more, the
descriptions on traceable validation or calibration of test sites lacks considerable information leading to another source
of uncertainties in the measurement results. The source descriptions for open area test sites, semi-anechoic rooms and
anechoic test chambers at/in which radiated measurements can be performed are lacking information regarding
frequencies above 40 GHz.
Measurement receivers are also limited regarding their capabilities in terms of fundamental frequency measurements
and measurement bandwidth. At the time of writing, an investigation has shown that spectrum analyzers were only
available for frequency measurements up to 63 MHz. Non-continuous, impulsive radio technologies could also be
measured with a measurement bandwidth of up to 25 MHz. In the case of EHF frequency measurements above 60 GHz,
it has therefore been considered to make use of external mixers (either ground wave or harmonic wave) to measure
emissions. However, this comes at the expense of great additional measurement uncertainty contributions. The present
document does not attempt to repeat the detailed statistical methods to calculate the expanded measurement uncertainty
that has already been extensively prepared in other ETSI deliverables. However, to assist test engineers to calculate
their own expanded measurement uncertainties associated with their particular test equipment configurations, a series of
spread sheets are identified in the present document (see annex B).
The present document captures the state of the art regarding measurement techniques, their capabilities and associated
expanded measurement uncertainties. It is offered as an assistive document to ETSI standard makers. Whilst it remains
the responsibility of the individual Technical Bodies to define their own test methodologies, the present document
should be considered as a source of what is possible, practical and therefore recommended.
ETSI
8 ETSI TS 103 051 V1.1.1 (2011-08)
1 Scope
The present document presents an evaluation of maximum acceptable measurement uncertainty for Radio Frequency
(RF) electromagnetic field (emf) measurements for the frequency range from 30 MHz to 100 GHz for inclusion within
ETSI documents on radio products used for compliance testing.
The maximum acceptable expanded measurement uncertainty is given for the following measurement parameters:
• radiated RF power;
• radiated unwanted emissions in the spurious domain; and
• EMC radiated emissions.
The maximum frequency specifications are based upon current capabilities of measurement equipment at April 2011
and the ability to calculate expanded measurement uncertainty from traceable calibration certificates. Frequencies above
the specified maximum frequency for each method of measurement are for further study.
A specification is given on how to apply the laboratory calculated expanded measurement uncertainty to a measured
parameter and to assess the quality of the measurement against a defined limit given in a standard.
In determining the maximum acceptable expanded measurement uncertainty, particular account has been taken of
current methods of measurement already identified in ETSI standards. However where there is an inconsistency, or
uncertainties that have not previously been taken into account in the uncertainty budgets, these are clearly identified in
the relevant clauses.
Fixed link microwave methods of measurement do not use radiated measurements except for EMC and antennae
characteristics testing. All other measurements are performed using conducted measurements. Therefore they are
considered not to be covered by the present document. However, as new technologies with integral antennas are being
developed, this may be reviewed in a future edition.
Satellite equipment is not covered by the present document; however, this may be reviewed in a future edition.
The expanded measurement uncertainty for conducted measurements is not covered by the present document.
The use of a test jig for radiated RF measurements of integral antenna radio equipment is not covered by the present
document.
2 References
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
reference document (including any amendments) applies.
Referenced documents which are not found to be publicly available in the expected location might be found at
http://docbox.etsi.org/Reference.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
2.1 Normative references
The following referenced documents are necessary for the application of the present document.
NOTE: Specifications to provide policy on the evaluation and reporting of expanded measurement uncertainty for
testing and calibration laboratories are laid down in several reference documents, some examples of them
being listed in annex H of the present document.
[1] ETSI TR 100 028-1: "Electromagnetic compatibility and Radio spectrum Matters (ERM);
Uncertainties in the measurement of mobile radio equipment characteristics; Part 1".
ETSI
9 ETSI TS 103 051 V1.1.1 (2011-08)
[2] ETSI TR 100 028-2: "Electromagnetic compatibility and Radio spectrum Matters (ERM);
Uncertainties in the measurement of mobile radio equipment characteristics; Part 2".
[3] ETSI TR 102 273-1-1 (V1.2.1): "Electromagnetic compatibility and Radio spectrum Matters
(ERM); Improvement on Radiated Methods of Measurement (using test site) and evaluation of the
corresponding measurement uncertainties Part 1: Uncertainties in the measurement of mobile radio
equipment characteristics; Sub-part 1: Introduction".
[4] ETSI TR 102 273-1-2 (V1.2.1): "Electromagnetic compatibility and Radio spectrum Matters
(ERM); Improvement on Radiated Methods of Measurement (using test site) and evaluation of the
corresponding measurement uncertainties; Part 1: Uncertainties in the measurement of mobile
radio equipment characteristics; Sub-part 2: Examples and annexes".
[5] ETSI TR 102 273-2 (V1.2.1): "Electromagnetic compatibility and Radio spectrum Matters (ERM);
Improvement on Radiated Methods of Measurement (using test site) and evaluation of the
corresponding measurement uncertainties; Part 2: Anechoic chamber".
[6] ETSI TR 102 273-3 (V1.2.1): "Electromagnetic compatibility and Radio spectrum Matters (ERM);
Improvement on Radiated Methods of Measurement (using test site) and evaluation of the
corresponding measurement uncertainties; Part 3: Anechoic chamber with a ground plane".
[7] ETSI TR 102 273-4 (V1.2.1): "Electromagnetic compatibility and Radio spectrum Matters (ERM);
Improvement on Radiated Methods of Measurement (using test site) and evaluation of the
corresponding measurement uncertainties; Part 4: Open area test site".
[8] ETSI TR 102 273-5 (V1.2.1): "Electromagnetic compatibility and Radio spectrum Matters (ERM);
Improvement on Radiated Methods of Measurement (using test site) and evaluation of the
corresponding measurement uncertainties; Part 5: Striplines".
[9] ETSI TR 102 273-6 (V1.2.1): "Electromagnetic compatibility and Radio spectrum Matters (ERM);
Improvement on Radiated Methods of Measurement (using test site) and evaluation of the
corresponding measurement uncertainties; Part 6: Test fixtures".
[10] ETSI TR 102 273-7 (V1.2.1): "Electromagnetic compatibility and Radio spectrum Matters (ERM);
Improvement on Radiated Methods of Measurement (using test site) and evaluation of the
corresponding measurement uncertainties; Part 7: Artificial human beings".
[11] Directive 1999/5/EC of the European Parliament and of the Council of 9 March 1999 on radio
equipment and telecommunications terminal equipment and the mutual recognition of their
conformity (R&TTE Directive).
[12] United Kingdom Accreditation Service LAB34 Edition 1 (2002): "The Expression of Uncertainty
in EMC Testing".
[13] CISPR 16-4: "Specification for radio disturbance and immunity measuring apparatus and methods
- Part 4: Uncertainties, statistics and limit modelling".
[14] CISPR 16-1: "Specification for radio disturbance and immunity measuring apparatus and methods
- Part 1: Radio disturbance and immunity measuring apparatus".
[15] ISO/IEC 17025:2005: "General requirements for the competence of testing and calibration
laboratories".
[16] CENELEC EN 62311:2008: "Assessment of electronic and electrical equipment related to human
exposure restrictions for electromagnetic fields (0 Hz - 300 GHz)".
[17] ETSI TS 102 321: "Electromagnetic compatibility and Radio spectrum Matters (ERM);
Normalized Site Attenuation (NSA) and validation of a fully lined anechoic chamber up to
40 GHz".
[18] ETSI EN 301 489-1: "Electromagnetic compatibility and Radio spectrum Matters (ERM);
ElectroMagnetic Compatibility (EMC) standard for radio equipment and services; Part 1:
Common technical requirements".
ETSI
10 ETSI TS 103 051 V1.1.1 (2011-08)
[19] EA-4/02: "Expression of the Uncertainty of Measurement in Calibration", European co-operation
for Accreditation, December 1999 (previously EAL-R2).
[20] ETSI TS 103 052: "Electromagnetic compatibility and Radio spectrum Matters (ERM); Radiated
measurement methods and general arrangements for test sites up to 100 GHz".
[21] JCGM 100:2008: "Evaluation of measurement data - Guide to the expression of uncertainty in
measurement".
[22] Draft Technical Report - IEC/TR 61000-1-6 Ed. 1.0: "Electromagnetic Compatibility (EMC) -
Part 1-6: General - Guide to the assessment of measurement uncertainty".
[23] "Measurement Instrumentation Uncertainty of Radiated Disturbances Due to Antenna - Receiver
Transmission" elaborated by the test engineer Jan Sroka of EMC-Testcenter Zürich AG,
Switzerland for the 19th International Wroclaw Symposium and Exhibition on Electromagnetic
Compatibility, Wroclaw, 11 - 13 June, 2008.
[24] EA-4/16: "EA guidelines on the expression of uncertainty in quantitative testing", European
co-operation for Accreditation, December 2003.
[25] ETSI EN 301 091 (Parts 1 and 2): "Electromagnetic compatibility and Radio spectrum Matters
(ERM); Short Range Devices; Road Transport and Traffic Telematics (RTTT); Radar equipment
operating in the 76 GHz to 77 GHz range".
[26] ETSI EN 302 264 (Parts 1 and 2): "Electromagnetic compatibility and Radio spectrum Matters
(ERM); Short Range Devices; Road Transport and Traffic Telematics (RTTT); Short Range Radar
equipment operating in the 77 GHz to 81 GHz band".
[27] ETSI EN 305 550 (Parts 1 and 2): "Electromagnetic compatibility and Radio spectrum Matters
(ERM); Short Range Devices (SRD); Radio equipment to be used in the 40 GHz to 246 GHz
frequency range".
[28] ETSI EN 302 372 (Parts 1 and 2): "Electromagnetic compatibility and Radio spectrum Matters
(ERM); Short Range Devices (SRD); Equipment for Detection and Movement; Tanks Level
Probing Radar (TLPR) operating in the frequency bands 5,8 GHz, 10 GHz, 25 GHz, 61 GHz and
77 GHz".
[29] ETSI EN 302 729 (Parts 1 and 2): "Electromagnetic compatibility and Radio spectrum Matters
(ERM); Short Range Devices (SRD); Level Probing Radar (LPR) equipment operating in the
frequency ranges 6 GHz to 8,5 GHz, 24,05 GHz to 26,5 GHz, 57 GHz to 64 GHz, 75 GHz to
85 GHz".
[30] ETSI EN 302 686: "Intelligent Transport Systems (ITS); Radiocommunications equipment
operating in the 63 GHz to 64 GHz frequency band; Harmonized EN covering the essential
requirements of article 3.2 of the R&TTE Directive".
[31] ETSI EN 302 567: "Broadband Radio Access Networks (BRAN); 60 GHz Multiple-Gigabit
WAS/RLAN Systems; Harmonized EN covering the essential requirements of article 3.2 of the
R&TTE Directive".
2.2 Informative references
The following referenced documents are not necessary for the application of the present document but they assist the
user with regard to a particular subject area.
Not applicable.
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11 ETSI TS 103 051 V1.1.1 (2011-08)
3 Definitions, symbols and abbreviations
3.1 Definitions
For the purposes of the present document, the following terms and definitions apply:
antenna: part of a transmitting or receiving system that is designed to radiate or to receive electromagnetic waves
antenna factor: quantity relating the strength of the field in which the antenna is immersed to the output voltage across
the load connected to the antenna
NOTE: When properly applied to the meter reading of the measuring instrument, yields the electric field strength
in V/m or the magnetic field strength in A/m.
antenna gain: ratio of the maximum radiation intensity from an (assumed lossless) antenna to the radiation intensity
that would be obtained if the same power were radiated isotropically by a similarly lossless antenna
confidence level: probability of the accumulated error of a measurement being within the stated range of uncertainty of
measurement
NOTE: The confidence level is usually not below 95 %.
correction factor: numerical factor by which the uncorrected result of a measurement is multiplied to compensate for
an assumed systematic error
directivity: ratio of the maximum radiation intensity in a given direction from the antenna to the radiation intensity
averaged over all directions (i.e. antenna gain = directivity - losses)
error (of a measuring instrument): indication of a measuring instrument minus the true value
NOTE: See clause 4.2.
error of measurement (absolute): result of a measurement minus the true value of the measurand
NOTE: See clause 4.2.
error (relative): ratio of an error to the true value
estimated standard deviation: from a sample of n results of a measurement the estimated standard deviation is given
by the formula:
n
(x − x)
∑
i
i=1
σ =
n
th
x being the i result of measurement (i = 1, 2, 3, ., n) and x the arithmetic mean of the n results considered.
i
A practical form of this formula is:
X
Y −
n
σ =
n
where X is the sum of the measured values and Y is the sum of the squares of the measured values.
NOTE: The term standard deviation has also been used in the present document to characterize a particular
probability density. Under such conditions, the term standard deviation may relate to situations where
there is only one result for a measurement.
expansion factor: multiplicative factor used to change the confidence level associated with a particular value of a
measurement uncertainty
ETSI
12 ETSI TS 103 051 V1.1.1 (2011-08)
free field: field (wave or potential) that has a constant ratio between the electric and magnetic field intensities, i.e. a
plane wave outside of the Fresnel zone)
free space: region free of obstructions and characterized by the constitutive parameters of a vacuum
impedance: measure of the complex resistive and reactive attributes of a component in an alternating current circuit
impedance (wave): complex factor relating the transverse component of the electric field to the transverse component
of the magnetic field at every point in any specified plane, for a given mode
influence quantity: quantity which is not the subject of the measurement but which influences the value of the quantity
to be measured or the indications of the measuring instrument
isotropic radiator: hypothetical, lossless antenna having equal radiation intensity in all directions
measurand: quantity subjected to measurement
measurement repeatability: closeness of the agreement between the results of successive measurements of the same
measurand carried out subject to all the following conditions:
• the same method of measurement;
• the same observer;
• the same measuring instrument;
• the same location;
• the same conditions of use;
• repetition over a short period of time.
measurement reproducibility: closeness of agreement between the results of measurements of the same measurand,
where the individual measurements are carried out changing conditions such as:
• method of measurement;
• observer;
• measuring instrument;
• location;
• conditions of use;
• time.
measurement uncertainty: describes a region about an observed value of a physical quantity which is likely to enclose
the true value
measuring system: complete set of measuring instruments and other equipment assembled to carry out a specified
measurement task
polarization (for an electromagnetic wave): figure traced as a function of time by the extremity of the electric vector
at a fixed point in space
probability density function (PDF): derivative, when it exists, of the distribution function
quantity (measurable): attribute of a phenomenon or a body that may be distinguished qualitatively and determined
quantitatively
quiet zone: region within an anechoic chamber that complies with the Normalized Site Attenuation (NSA)
requirements of being reflection free
NOTE: The term "quiet zone" does not imply that the physical dimensions of equipment under test can equal the
same dimensions. The maximum size of the equipment is determined in accordance with
TR 102 273-1-1 [3], clause 8.3.4 when related to range length and frequency of measurement.
ETSI
13 ETSI TS 103 051 V1.1.1 (2011-08)
shielded enclosure: structure that protects its interior from the effects of an exterior electric or magnetic field, or
conversely, protects the surrounding environment from the effect of an interior electric or magnetic field
stochastic (random) variable: variable whose value is not exactly known, but is characterized by a distribution or
probability function, or a mean value and a standard deviation (e.g. a measured value and the related measurement
uncertainty)
uncertainty (combined standard): uncertainty characterizing the complete measurement or part thereof
NOTE: It is calculated by combining appropriately the standard uncertainties for each of the individual
contributions identified in the measurement considered or in the part of it that has been considered.
In the case of additive components (linearly combined components where all the corresponding
coefficients are equal to one) and when all these contributions are independent of each other (stochastic),
this combination is calculated by using the Root of the Sum of the Squares (the RSS method). A more
complete methodology for the calculation of the combined standard uncertainty is given in
TR 100 028-2 [2], clause D.3.12.
uncertainty (expanded): uncertainty value corresponding to a specific confidence level different from that inherent to
the calculations made in order to find the combined standard uncertainty
NOTE: The combined standard uncertainty is multiplied by a constant to obtain the expanded uncertainty limits
(see TR 100 028-2 [2], clause D.5.6.2).
uncertainty (limits of uncertainty of a measuring instrument): extreme values of uncertainty permitted by
specifications, regulations etc. for a given measuring instrument
uncertainty (random): component of the uncertainty of measurement, which, in the course of a number of
measurements of the same measurand, varies in an unpredictable way (and has not being considered otherwise)
uncertainty (standard): expression characterizing the uncertainty of each individual uncertainty component
NOTE: It is the standard deviation of the corresponding distribution.
uncertainty (systematic): component of the uncertainty of measurement, which, in the course of a number of
measurements of the same measurand remains constant or varies in a predictable way
uncertainty (type A): uncertainties evaluated using the statistical analysis of a series of observations
uncertainty (type B): uncertainties evaluated using other means than the statistical analysis of a series of observations
3.2 Symbols
For the purposes of the present document, the following symbols apply:
+
a Upper bound of quantity X
-
a Lower bound of quantity X
°C degrees Centigrade
cm centimetres
dB deciBel
GHz GigaHertz
MHz MegaHertz
mV milliVolt
u(xi) Standard uncertainty of the best estimate of the influence quantity X
i
X Generic quantity
X Influence quantity to a mathematical measurement model
i
x Best estimate of the influence quantity to a mathematical measurement model
i
ETSI
14 ETSI TS 103 051 V1.1.1 (2011-08)
3.3 Abbreviations
For the purposes of the present document, the following abbreviations apply:
AFC Automatic Frequency Control
ANSI American National Standards Institute
EHF Extremely High Frequency
e.i.r.p. equivalent isotropically radiated power
EMC ElectroMagnetic Compatibility
emf electromagnetic fields
EMU Expanded Measurement Uncertainty
e.r.p. effective radiated power
EUT Equipment Under Test
FCC Federal Communications Commission
FH Frequency Hopping
FMCW Frequency Modulated Continuous Wave
FSL Free Space Loss
GRSC Global Radiocommunication Standardization Collaboration
IF Intermediate Frequency
LNA Low Noise Amplifier
LPDA Log Periodic Dipole Antenna
MRA Mutual Recognition Agreement
NRA National Regulatory Authority
NSA Normalized Site Attenuation
OATS Open Area Test Site
PDF Probability Density Function
R&TTE Radio and Telecommunications Terminal Equipment (Directive)
RBW Resolution BandWidth
RF Radio Frequency
RSS Root of the Sum of the Squares
TCXO Temperature Compensated Crystal Oscillators
UKAS United Kingdom Accreditation Service
VBW Video BandWidth
VSWR Voltage Standing Wave Radio
WGSE Working Group on Spectrum Engineering
4 Measurement uncertainty
4.1 Introduction
The terms "accuracy" and "uncertainty" are frequently misused and interchanged when applied to measurement
equipment and to a measured value. The following clauses define the meaning of each of the phrases and how they are
used in measurement equipment literature. The difference in their meanings can be significant and in many
measurement applications it is vital to understand the difference.
The use of the term "accuracy" plays a significant role in measurement equipment sales literature often to compete
against similar equipment from other manufacturers and this should be regarded with caution. It has been known for
competing manufacturers to quote performance values that exceed the finest metrology laboratory values for calibration
and this of course is impossible. Realistic values are derived from traceable standards where the term "accuracy" is
never used; only the term "uncertainty" is used. The true value of a measurand is never known, as it is impossible to
define or make perfect measurements.
When a measured value with its measurement uncertainty bounds is compared with a specification (standard) limit
interpretation of the result is not always clear. Clause 5 gives guidance on how to make this assessment, which is
dependant upon the testing regime that is being followed.
Consequently, the present document only uses the term "uncertainty" and avoids completely the usage of the term
"accuracy".
ETSI
15 ETSI TS 103 051 V1.1.1 (2011-08)
4.2 Measurement uncertainty
The definition of measurement uncertainty as described in clause 3.1 makes no attempt to define the true value, nor
does it rely upon it. It is a statis
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