ETSI ETR 273-6 ed.1 (1998-02)
ElectroMagnetic Compatibility and Radio Spectrum Matters (ERM); Improvement of radiated methods of measurement (using test sites) and evaluation of the corresponding measurement uncertainties; Part 6: Test fixtures
ElectroMagnetic Compatibility and Radio Spectrum Matters (ERM); Improvement of radiated methods of measurement (using test sites) and evaluation of the corresponding measurement uncertainties; Part 6: Test fixtures
DTR/ERM-RP01-018-6
Elektromagnetna združljivost (EMC) in zadeve v zvezi z radijskim spektrom (ERM) - Izboljšanje zvezdastih merilnih naprav (z uporabo merilnih mest) in ovrednotenje ustreznih merilnih negotovosti 6. del: Pravila preskušanj
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
01-april-1999
Elektromagnetna združljivost (EMC) in zadeve v zvezi z radijskim spektrom (ERM) -
Izboljšanje zvezdastih merilnih naprav (z uporabo merilnih mest) in ovrednotenje
ustreznih merilnih negotovosti 6. del: Pravila preskušanj
ElectroMagnetic Compatibility and Radio Spectrum Matters (ERM); Improvement of
radiated methods of measurement (using test sites) and evaluation of the corresponding
measurement uncertainties; Part 6: Test fixtures
Ta slovenski standard je istoveten z: ETR 273-6 Edition 1
ICS:
33.060.01 Radijske komunikacije na Radiocommunications in
splošno general
33.100.01 Elektromagnetna združljivost Electromagnetic compatibility
na splošno in general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
ETSI ETR 273-6
TECHNICAL February 1998
REPORT
Source: ERM Reference: DTR/ERM-RP01-018-6
ICS: 33.020
Key words: Analogue, data, measurement uncertainty, mobile, radio, testing
Electromagnetic compatibility
and Radio spectrum Matters (ERM);
Improvement of radiated methods of
measurement (using test sites) and
evaluation of the corresponding
measurement uncertainties;
Part 6: Test fixtures
ETSI
European Telecommunications Standards Institute
ETSI Secretariat
Postal address: F-06921 Sophia-Antipolis CEDEX - FRANCE
Office address: 650 Route des Lucioles - Sophia Antipolis - Valbonne - FRANCE
X.400: c=fr, a=atlas, p=etsi, s=secretariat - Internet: secretariat@etsi.fr
Tel.: +33 4 92 94 42 00 - Fax: +33 4 93 65 47 16
Copyright Notification: No part may be reproduced except as authorized by written permission. The copyright and the
foregoing restriction extend to reproduction in all media.
© European Telecommunications Standards Institute 1998. All rights reserved.
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ETR 273-6: February 1998
Whilst every care has been taken in the preparation and publication of this document, errors in content,
typographical or otherwise, may occur. If you have comments concerning its accuracy, please write to
"ETSI Editing and Committee Support Dept." at the address shown on the title page.
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ETR 273-6: February 1998
Contents
Foreword .7
1 Scope.9
2 References .9
3 Definitions, symbols and abbreviations .9
3.1 Definitions.9
3.2 Symbols .13
3.3 Abbreviations .16
4 Introduction.17
4.1 Performance limitations.18
4.2 Summary.18
5 Uncertainty contributions specific to test fixtures.19
5.1 Test fixture effect .19
5.2 Climatic facility effect.19
5.2.1 Resonances within a climatic facility.19
5.2.2 Internal reflections using a climatic facility.20
5.2.3 Mutual coupling effects using a climatic facility .20
5.2.4 Waveguide-type modes within a climatic facility.21
5.2.5 Summary .21
6 Verification procedure for a test fixture.21
6.1 Definition.21
6.2 Overview of the verification procedure.21
6.2.1 Apparatus required.22
6.2.2 Site preparation.22
6.2.3 Measurement configuration.22
6.2.4 What to record .23
6.3 Verification procedure.23
6.4 Processing the results of the verification procedure.27
6.5 Calculation of measurement uncertainty.27
7 Test methods.27
7.1 Introduction.27
7.1.1 Site preparation.27
7.1.2 Preparation of the EUT .28
7.1.3 Power supplies to the EUT.28
7.2 Transmitter tests.29
7.2.1 Frequency error (30 MHz to 1 000 MHz) .29
7.2.1.1 Apparatus required .29
7.2.1.2 Method of measurement.29
7.2.1.3 Procedure for completion of the results sheets.31
7.2.1.4 Log book entries.31
7.2.1.5 Statement of results.31
7.2.2 Expanded uncertainty for frequency error test.32
7.2.3 Effective radiated power (30 MHz to 1 000 MHz).32
7.2.3.1 Apparatus required .32
7.2.3.2 Method of measurement.33
7.2.3.3 Procedure for the completion of the results sheets .35
7.2.3.4 Log book entries.36
7.2.3.5 Statement of results.37
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ETR 273-6: February 1998
7.2.4 Uncertainty for effective radiated power measurement.37
7.2.4.1 Expanded uncertainty for Effective radiated power
measurement.37
7.2.5 Spurious emissions (30 MHz to 4 GHz or 12,75 GHz).37
7.2.6 Adjacent channel power (30 MHz to 1 000 MHz) .38
7.2.6.1 Apparatus required.38
7.2.6.2 Method of measurement.38
7.2.6.3 Procedure for completion of the results sheets.41
7.2.6.4 Log book entries .42
7.2.6.5 Statement of results .43
7.2.7 Measurement uncertainty for Adjacent channel power.43
7.2.7.1 Expanded uncertainty of the Adjacent channel power
measurement.44
7.3 Receiver tests.44
7.3.1 Maximum usable sensitivity (30 MHz to 1 000 MHz).44
7.3.1.1 Apparatus required.45
7.3.1.2 Method of measurement.46
7.3.1.3 Procedure for the completion of the results sheets.49
7.3.1.4 Log book entries .50
7.3.1.5 Statement of results .52
7.3.2 Measurement uncertainty for Maximum usable sensitivity.52
7.3.2.1 Expanded uncertainty of the maximum usable sensitivity
measurement.52
7.3.3 Average usable sensitivity.52
7.3.4 Co-channel rejection.53
7.3.4.1 Apparatus required.53
7.3.4.2 Method of measurement.54
7.3.4.3 Procedure for completion of the results sheets.58
7.3.4.4 Log book entries .59
7.3.4.5 Overall results sheet.62
7.3.5 Measurement uncertainty for Co-channel rejection.63
7.3.5.1 Expanded uncertainty of the co-channel rejection
measurement.63
7.3.6 Adjacent channel selectivity .63
7.3.6.1 Apparatus required.64
7.3.6.2 Method of measurement.64
7.3.6.3 Procedure for completion of the results sheets.68
7.3.6.4 Log book entries .70
7.3.6.5 Overall results sheet.73
7.3.7 Measurement uncertainty for adjacent channel selectivity.73
7.3.7.1 Expanded uncertainty of the adjacent channel selectivity
measurement.73
7.3.8 Intermodulation immunity .73
7.3.8.1 Apparatus required.74
7.3.8.2 Method of measurement.74
7.3.8.3 Procedure for completion of the results sheets.79
7.3.8.4 Log book entries .81
7.3.8.5 Overall results sheet.84
7.3.9 Measurement uncertainty for Intermodulation immunity .84
7.3.9.1 Expanded uncertainty of the Intermodulation immunity
measurement.84
7.3.10 Blocking immunity (or desensitization).84
7.3.10.1 Apparatus required.85
7.3.10.2 Method of measurement.86
7.3.10.3 Procedure for completion of the results sheets.90
7.3.10.4 Log book entries .91
7.3.10.5 Overall results sheet.96
7.3.11 Measurement uncertainty for blocking immunity (or desensitization) .96
7.3.11.1 Expanded uncertainty of the blocking immunity (or
desensitization) measurement .97
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ETR 273-6: February 1998
7.3.12 Spurious response rejection.97
Annex A (informative): Bibliography.98
History .100
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ETR 273-6: February 1998
Foreword
This ETSI Technical Report (ETR) has been produced by the Electromagnetic compatibility and Radio
spectrum Matters (ERM) Technical Committee of the European Telecommunications Standards Institute
(ETSI).
ETRs are informative documents resulting from ETSI studies which are not appropriate for European
Telecommunication Standard (ETS) or Interim European Telecommunication Standard (I-ETS) status. An
ETR may be used to publish material which is either of an informative nature, relating to the use or the
application of ETSs or I-ETSs, or which is immature and not yet suitable for formal adoption as an ETS or
an I-ETS.
The present document is part 6 of a multi-part Technical Report (ETR) covering Electromagnetic
compatibility and Radio spectrum Matters (ERM); Improvement of radiated methods of measurement
(using test sites) and evaluation of the corresponding measurement uncertainties, as identified below:
Part 1-1: "Uncertainties in the measurement of mobile radio equipment characteristics; Sub-part 1:
Introduction";
Part 1-2: "Uncertainties in the measurement of mobile radio equipment characteristics; Sub-part 2:
Examples and annexes";
Part 2: "Anechoic chamber";
Part 3: "Anechoic chamber with a ground plane";
Part 4: "Open area test site";
Part 5: "Striplines";
Part 6: "Test fixtures";
Part 7: "Artificial human beings".
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ETR 273-6: February 1998
1 Scope
This ETR covers the methods of radiated measurements on mobile radio equipment using test fixtures and
applies to the assessment of the associated measurement uncertainties.
This ETR provides the methods for evaluation and calculation of the measurement uncertainties for each of
the measured parameters and the required corrections for measurement conditions and results.
2 References
Within this ETR the following references apply:
[1] CCITT Recommendation O.41: "Psophometer for use on telephone-type
circuits".
[2] CCITT Recommendation O.153:"Basic parameters for the measurement of error
performance at bit rates below the primary rate".
[3] ETR 027 1991: "Radio Equipment and Systems (RES); Methods of
measurement for private mobile radio equipment".
[4] ETR 273-1-1: "Electromagnetic compatibility and Radio spectrum Matters
(ERM); Improvement of radiated methods of measurement (using test sites) and
evaluation of the corresponding measurement uncertainties; Part 1: Uncertainties
in the measurement of mobile radio equipment characteristics; Sub-part 1:
Introduction".
[5] ETR 273-2: "Electromagnetic compatibility and Radio spectrum Matters (ERM);
Improvement of radiated methods of measurement (using test sites) and
evaluation of the corresponding measurement uncertainties; Part 2: Anechoic
chamber".
[6] ETR 273-3: "Electromagnetic compatibility and Radio spectrum Matters (ERM);
Improvement of radiated methods of measurement (using test sites) and
evaluation of the corresponding measurement uncertainties; Part 3: Anechoic
chamber with a ground plane".
[7] ETR 273-4: "Electromagnetic compatibility and Radio spectrum Matters (ERM);
Improvement of radiated methods of measurement (using test sites) and
evaluation of the corresponding measurement uncertainties; Part 4: Open area
test site".
3 Definitions, symbols and abbreviations
3.1 Definitions
For the purposes of this ETR, the following definitions apply:
Audio Frequency (AF) load: Normally a resistor of sufficient power rating to accept the maximum audio
output power from the EUT. The value of the resistor is normally that stated by the manufacturer and is
normally the impedance of the audio transducer at 1 000 Hz.
NOTE 1: In some cases it may be necessary to place an isolating transformer between the
output terminals of the receiver under test and the load.
AF termination: Any connection other than the audio frequency load which may be required for the
purpose of testing the receiver. (i.e. in a case where it is required that the bit stream be measured, the
connection may be made, via a suitable interface, to the discriminator of the receiver under test).
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ETR 273-6: February 1998
NOTE 2: The termination device is normally agreed between the manufacturer and the testing
authority and details included in the test report. If special equipment is required then it
is normally provided by the manufacturer.
antenna: That 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. 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: The 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.
bit error ratio: The ratio of the number of bits in error to the total number of bits.
combining network: A multipole network allowing the addition of two or more test signals produced by
different sources for connection to a receiver input.
NOTE 3: Sources of test signals are normally connected in such a way that the impedance
presented to the receiver is 50 W. The combining networks are designed so that effects
of any intermodulation products and noise produced in the signal generators are
negligible.
correction factor: The numerical factor by which the uncorrected result of a measurement is multiplied to
compensate for an assumed systematic error.
confidence level: The probability of the accumulated error of a measurement being within the stated
range of uncertainty of measurement.
directivity: The ratio of the maximum radiation intensity in a given direction from the antenna to the
radiation intensity averaged over all directions (i.e. directivity = antenna gain + losses).
duplex filter: A device fitted internally or externally to a transmitter/receiver combination to allow
simultaneous transmission and reception with a single antenna connection.
error of measurement (absolute): The result of a measurement minus the true value of the measurand.
error (relative): The 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 =
s=
n-1
th
x being the i result of measurement (i = 1,2,3, .,n) and x the arithmetic mean of the n results
i
considered.
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ETR 273-6: February 1998
A practical form of this formula is:
X
Y-
n
s=
n-1
Where X is the sum of the measured values and Y is the sum of the squares of the measured values.
extreme test conditions: Conditions defined in terms of temperature and supply voltage. Tests are
normally made with the extremes of temperature and voltage applied simultaneously. The upper and lower
temperature limits are specified in the relevant testing standard. The test report states the actual
temperatures measured.
error (of a measuring instrument): The indication of a measuring instrument minus the (conventional)
true value.
free field: A field (wave or potential) which has a constant ratio between the electric and magnetic field
intensities.
free Space: A region free of obstructions and characterized by the constitutive parameters of a vacuum.
impedance: A measure of the complex resistive and reactive attributes of a component in an alternating
current circuit.
impedance (wave): The 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: A 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.
intermittent operation: Operation where manufacturer states the maximum time that the equipment is
intended to transmit and the necessary standby period before repeating a transmit period.
isotropic radiator: A hypothetical, lossless antenna having equal radiation intensity in all directions.
limited Frequency Range: The limited frequency range is a specified smaller frequency range within the
full frequency range over which the measurement is made.
NOTE 4: The details of the calculation of the limited frequency range are normally given in the
relevant testing standard.
maximum permissible frequency deviation: The maximum value of frequency deviation stated for the
relevant channel separation in the relevant testing standard.
measuring system: A complete set of measuring instruments and other equipment assembled to carry
out a specified measurement task.
measurement repeatability: The 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.
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ETR 273-6: February 1998
measurement reproducibility: The 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.
measurand: A quantity subjected to measurement.
noise gradient of EUT: A function characterizing the relationship between the RF input signal level and the
performance of the EUT, e.g., the SINAD of the AF output signal.
nominal frequency: One of the channel frequencies on which the equipment is designed to operate.
nominal mains voltage: The declared voltage or any of the declared voltages for which the equipment
was designed.
normal test conditions: The conditions defined in terms of temperature, humidity and supply voltage
stated in the relevant testing standard.
normal deviation: The frequency deviation for analogue signals which is equal to 12 % of the channel
separation.
psophometric weighting network: As described in CCITT Recommendation O.41 [1].
polarization: For an electromagnetic wave, the figure traced as a function of time by the extremity of the
electric vector at a fixed point in space.
quantity (measurable): An attribute of a phenomenon or a body which may be distinguished qualitatively
and determined quantitatively.
rated audio output power: The maximum audio output power under normal test conditions, and at
standard test modulations, as declared by the manufacturer.
rated radio frequency output power: The maximum carrier power under normal test conditions, as
declared by the manufacturer.
shielded enclosure: A 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.
SINAD sensitivity: The minimum standard modulated carrier-signal input required to produce a specified
SINAD ratio at the receiver output.
stochastic (random) variable: A 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 measurand and the
related measurement uncertainty).
test load: The test load is a 50 W substantially non-reactive, non-radiating power attenuator which is
capable of safely dissipating the power from the transmitter.
test modulation: The test modulating signal is a baseband signal which modulates a carrier and is
dependent upon the type of EUT and also the measurement to be performed.
trigger device: A circuit or mechanism to trigger the oscilloscope timebase at the required instant. It may
control the transmit function or inversely receive an appropriate command from the transmitter.
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ETR 273-6: February 1998
uncertainty (random): A component of the uncertainty of measurement which, in the course of a number
of measurements of the same measurand, varies in an unpredictable way.
uncertainty (systematic): A 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 (limits of uncertainty of a measuring instrument): The extreme values of uncertainty
permitted by specifications, regulations etc. for a given measuring instrument.
NOTE 5: This term is also known as "tolerance".
uncertainty (standard): The representation of each individual uncertainty component that contributes to
the overall measurement uncertainty by an estimated standard deviation is termed the standard
uncertainty.
uncertainty (combined standard): The combined standard uncertainty of a measurement is calculated by
combining the standard uncertainties for each of the individual contributions identified.
NOTE 6: This combination is carried out by applying the Root of the Sum of the Squares (the
RSS) method under the assumption that all contributions are stochastic i.e. independent
of each other.
uncertainty (expanded): The combined standard uncertainty is multiplied by a constant to give the
expanded uncertainty limits.
upper specified AF limit: The maximum audio frequency of the audio pass-band. It is dependent on the
channel separation.
wanted signal level: For conducted measurements Pa level of +6 dBmV emf referred to the receiver input
under normal test conditions. Under extreme test conditions the value is +12 dBmV emf.
NOTE 7: For analogue measurements the wanted signal level has been chosen to be equal to
the limit value of the measured usable sensitivity. For bit stream and message
measurements the wanted signal has been chosen to be +3 dB above the limit value of
measured usable sensitivity.
3.2 Symbols
For the purposes of this ETR, the following symbols apply:
b2p/l (radians/m);
gincidence angle with ground plane (°)
lwavelength (m)
fphase angle of reflection coefficient (°)
H
h120p Ohms - the intrinsic impedance of free space (W)
mpermeability (H/m)
antenna factor of the receive antenna (dB/m)
AF
R
antenna factor of the transmit antenna (dB/m)
AF
T
mutual coupling correction factor (dB)
AF
TOT
cross correlation coefficient
C
cross
fdirectivity of the source
D(q, )
distance between dipoles (m)
d
dskin depth (m)
an antenna or EUT aperture size (m)
d
an antenna or EUT aperture size (m)
d
path length of the direct signal (m)
d
dir
path length of the reflected signal (m)
d
refl
electric field intensity (V/m)
E
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ETR 273-6: February 1998
max
E calculated maximum electric field strength in the receiving antenna height scan
DH
from a half wavelength dipole with 1 pW of radiated power (for horizontal
polarization) (mV/m)
max
E calculated maximum electric field strength in the receiving antenna height scan
DV
from a half wavelength dipole with 1 pW of radiated power (for vertical
polarization) (mV/m)
e antenna efficiency factor
ff
fangle (°)
Df bandwidth (Hz)
f frequency (Hz)
G(q,f) gain of the source (which is the source directivity multiplied by the antenna
efficiency factor)
H magnetic field intensity (A/m)
I the (assumed constant) current (A)
I the maximum current amplitude
m
k 2p/l
k a factor from Student's t distribution
k Boltzmann's constant (1,38 x 10-23 Joules/° Kelvin)
K relative dielectric constant
l the length of the infinitesimal dipole (m)
L the overall length of the dipole (m)
l the point on the dipole being considered (m)
lwavelength (m)
Pe probability of error n
(n)
Pp probability of position n
(n)
P antenna noise power (W)
r
P power received (W)
rec
P power transmitted (W)
t
qangle (°)
rreflection coefficient
r the distance to the field point (m)
rreflection coefficient of the generator part of a connection
g
rreflection coefficient of the load part of the connection
l
R equivalent surface resistance (W)
s
sconductivity (S/m)
sstandard deviation
SNR Signal to noise ratio at a specific BER
b*
SNR Signal to noise ratio per bit
b
T antenna temperature (° Kelvin)
A
U the expanded uncertainty corresponding to a confidence level of x %: U = k · u
c
u the combined standard uncertainty
c
u general type A standard uncertainty
i
u random uncertainty
i
u general type B uncertainty
j
u reflectivity of absorbing material: EUT to the test antenna
j
u reflectivity of absorbing material: substitution or measuring antenna to the test
j
antenna
u reflectivity of absorbing material: transmitting antenna to the receiving antenna
j
u mutual coupling: EUT to its images in the absorbing material
j
u mutual coupling: de-tuning effect of the absorbing material on the EUT
j
u mutual coupling: substitution, measuring or test antenna to its image in the
j
absorbing material
u mutual coupling: transmitting or receiving antenna to its image in the absorbing
j
material
u mutual coupling: amplitude effect of the test antenna on the EUT
j
u mutual coupling: de-tuning effect of the test antenna on the EUT
j
u mutual coupling: transmitting antenna to the receiving antenna
j
u mutual coupling: substitution or measuring antenna to the test antenna
j
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ETR 273-6: February 1998
u mutual coupling: interpolation of mutual coupling and mismatch loss correction
j
factors
u mutual coupling: EUT to its image in the ground plane
j
u mutual coupling: substitution, measuring or test antenna to its image in the
j
ground plane
u mutual coupling: transmitting or receiving antenna to its image in the ground
j
plane
u range length
j
u correction: off boresight angle in the elevation plane
j
u correction: measurement distance
j
u cable factor
j
u position of the phase centre: within the EUT volume
j
u positioning of the phase centre: within the EUT over the axis of rotation of the
j
turntable
u position of the phase centre: measuring, substitution, receiving, transmitting or
j
test antenna
u position of the phase centre: LPDA
j
u Stripline: mutual coupling of the EUT to its images in the plates
j
u Stripline: mutual coupling of the 3-axis probe to its image in the plates
j
u Stripline: characteristic impedance
j
u Stripline: non-planar nature of the field distribution
j
u Stripline: field strength measurement as determined by the 3-axis probe
j
u Stripline: Transform Factor
j
u Stripline: interpolation of values for the Transform Factor
j
u Stripline: antenna factor of the monopole
j
u Stripline: correction factor for the size of the EUT
j
u Stripline: influence of site effects
j
u ambient effect
j
u mismatch: direct attenuation measurement
j
u mismatch: transmitting part
j
u mismatch: receiving part
j
u signal generator: absolute output level
j
u signal generator: output level stability
j
u insertion loss: attenuator
j
u insertion loss: cable
j
u insertion loss: adapter
j
u insertion loss: antenna balun
j
u antenna: antenna factor of the transmitting, receiving or measuring antenna
j
u antenna: gain of the test or substitution antenna
j
u antenna: tuning
j
u receiving device: absolute level
j
u receiving device: linearity
j
u receiving device: power measuring receiver
j
u EUT: influence of the ambient temperature on the ERP of the carrier
j
u EUT: influence of the ambient temperature on the spurious emission level
j
u EUT: degradation measurement
j
u EUT: influence of setting the power supply on the ERP of the carrier
j
u EUT: influence of setting the power supply on the spurious emission level
j
u EUT: mutual coupling to the power leads
j
u frequency counter: absolute reading
j
u frequency counter: estimating the average reading
j
u Salty man/Salty-lite: human simulation
j
u Salty man/Salty-lite: field enhancement and de-tuning of the EUT
j
u test fixture: effect on the EUT
j
u test fixture: climatic facility effect on the EUT
j
V received voltage for cables connected via an adapter (dBmV/m)
direct
V received voltage for cables connected to the antennas (dBmV/m)
site
W radiated power density (W/m )
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ETR 273-6: February 1998
3.3 Abbreviations
For the purposes of this ETR, the following abbreviations apply:
AF Audio Frequency
A-M1 is a test modulation consisting of a 1 000 Hz tone at a level which produces a
deviation of 12 % of the channel separation
A-M2 is a test modulation consisting of a 1 250 Hz tone at a level which produces a
deviation of 12 % of the channel separation
A-M3 is a test modulation consisting of a 400 Hz tone at a level which produces a
deviation of 12 % of the channel separation. This signal is used as an unwanted
signal for analogue and digital measurements
BER Bit Error Ratio
BIPM the International Bureau of Weights and Measures (Bureau International des
Poids et Mesures)
c calculated on the basis of given and measured data
d derived from a measuring equipment specification
DM-0 is a test modulation consisting of a signal representing an infinite series of "0"
bits
DM-1 is a test modulation consisting of a signal representing an infinite series of "1"
bits
DM-2 is a test modulation consisting of a signal representing a pseudorandom bit
sequence of at least 511 bits in accordance with CCITT
Recommendation O.153 [2]
D-M3 a test signal should be agreed between the testing authority and the
manufacturer in the cases where it is not possible to measure a bit stream or if
selective messages are used and are generated or decoded within an equipment
NOTE: The agreed test signal may be formatted and may contain error detection and
correction. Details of the test signal should be supplied in the test report.
emf Electromotive force
ETS European Telecommunication Standard
EUT Equipment Under Test
FSK Frequency Shift Keying
GMSK Gaussian Minimum Shift Keying
GSM Global System for Mobile telecommunication (Pan European digital
telecommunication system)
IF Intermediate frequency
m measured
NaCl Sodium chloride
NSA Normalized Site Attenuation
p power level value
r indicates rectangular distribution
RF Radio Frequency
rms Root mean square
RSS Root-Sum-of-the-Squares
u indicates U-distribution
VSWR Voltage Standing Wave Ratio
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ETR 273-6: February 1998
4 Introduction
A test fixture is usually constructed for testing a specific EUT. It consists of a 50 W RF connector and a
device for electromagnetically coupling to the EUT. It should also incorporate a means for repeatable
positioning of the EUT. Figure 1 illustrates a typical test fixture.
Electromagnetic
coupling "Probe"
W 50
RF connector
Low dielectric constant material
Figure 1: Basic, typical test fixture
The coupling device usually comprises a small antenna that is placed, physically and electrically, close to
the EUT. This antenna/coupling device is used for sampling or generating the test fields when the EUT is
undergoing testing, usually at extreme conditions of temperature and/or voltage.
Test fixtures should be constructed in such a way that measurements are repeatable. This requires some
specific mounting arrangements to be incorporated within the test fixture to secure the EUT in a fixed,
repeatable position. Such mounting arrangements would additionally help to maintain the relative
polarization between the EUT and the coupling device. A typical scheme is shown in figure 2.
EUT
Pow er/signal leads
plus ferrite beads
Figure 2: EUT mounted in a typical test fixture
A test fixture should enable adequate access to the EUT for interfacing with the test equipment. In
particular, it should provide, where relevant, access to:
- the "press to talk" button for a transmitter;
- the modulator input for a transmitter;
- the audio output for a receiver;
- the power terminals for connection to an external power supply.
The entire assembly of test fixture plus EUT is generally extremely compact and it can be regarded as a
miniature test site. Its compactness enables the whole assembly to be accommodated within a test
chamber (usually a climatic facility) that completely encloses the extreme condition.
The circuitry associated with the RF coupling device should contain no active or non-linear components and
should present a VSWR of better than 1,5:1 to a 50 W line.
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ETR 273-6: February 1998
4.1 Performance limitations
The coupling mechanism between the EUT and the test fixture is extremely complex since the two are
placed physically and electrically very close together. This complexity makes any attempt at theoretically
modelling a test fixture's performance not only very difficult but also time consuming and costly. In practice,
therefore, modelling is seldom attempted. The direct consequence of this is that absolute measurements
cannot be made in a test fixture and any measurement results have to be related, in some way, to results
taken on a verified free field test site.
The usual way to relate the results is by a process, sometimes referred to as field equalization, in which
the relevant parameter (effective radiated power, receiver sensitivity, etc.) is initially measured on a free
field test site under normal conditions and then subsequently re-measured using only the test fixture (with
the EUT installed) also under normal conditions. The difference (in dB) of the two results (received signal
level for an effective radiated power test, output power from a signal generator for a sensitivity test) is
termed the coupling factor of the test fixture and provides the link between all the results of EUT tests
carried out in the test fixture and its performance on a verified free field test site. As a general rule, the
coupling factor should not be greater than 20 dB.
To reiterate, this key limitation for a test fixture can be stated in two ways:
- only relative measurements can be made;
- absolute measurements cannot be made.
A further limitation to the use of a test fixture results from the unknown variation of the coupling factor with
frequency. This variation cannot be relied upon to be linear over large bandwidths and this puts a limit on
those tests which can be accurately carried out. As a result, emission tests are generally limited to the
nominal frequencies (for which the performance of the test fixture has been verified) of low power devices
for effective radiated power and frequency error tests. Occasionally, however, adjacent channel power is
measured.
Similarly, receiver tests are normally limited to receiver sensitivity although, occasionally, co-channel
rejection, adjacent channel selectivity, inter-modulation immunity and blocking are tested.
Ideally, all test fixtures should be verified and where EUT testing will be required over a frequency band,
the verification procedure should be extended to include the frequencies at the band edges. In any case,
routine verification, perhaps every six months, should be carried out as a means of detecting any
deterioration or change in performance.
Local ambient signals can be problematic to measurements carried out in a test fixture, although very little
uncertainty is introduced into transmitter tests, since EUT power levels will dominate. However, for receiver
tests (i.e. sensitivity and various types of immunity testing) shielding from ambient signals may be required.
Adequate shielding can be achieved by either using the test fixture within a metalized test chamber (e.g.
climatic facility) or by enclosing it within a shielded room. In either case, one needs to be aware of the
possible frequencies of resonance for these structures.
Only integral antenna devices are tested in a test fixture. For devices possessing either permanent or
temporary external RF connectors, all testing is carried out using conducted methods.
4.2 Summary
Test fixtures are tools that allow the measurement of certain radio parameters of an EUT whilst it is
subjected to extremes of either voltage or temperature or both. They only allow relative measurements to
be carried out since its coupling mechanism to the EUT is extremely complex, making it virtually impossible
to calculate an absolute coupling factor.
Only after it has been verified that the test fixture does not affect performance can the EUT be confidently
tested under extreme conditions. As a result of verifying the test fixture and equating the performance of
the EUT in the test fixture under normal conditions to results taken on a free field test site, the EUTs
performance at an extreme condition can be directly related to the free-field measurements.
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ETR 273-6: February 1998
5 Uncertainty contributions specific to test fixtures
There are essentially two main sources of error that contribute to tests involving a test fixture. Firstly, the
effect that the close physical presence of the test fixture has on the EUT and secondly the overall effect
produced by the climatic facility. Both these sources are quite complex and are discussed below.
5.1 Test fixture effect
This effect is a result of the close proximity of the test fixture to the EUT. It is a combination of a detuning
effect on the EUT produced by the dielectric constant of the materials from which the test fixture is
constructed and various mutual coupling and reflection effects arising from the interaction between the EUT
and components within the test fixture e.g. the coupling probe, RF connector, etc. The overall magnitude of
this effect is determined during the verification procedure and is used to decide if the test fixture degrades
EUT performance unacceptably.
u is used for the uncertainty contribution associated with the test fixture effect on the EUT as
j
determined during the verification procedure.
5.2 Climatic facility effect
This effect can be broken down into several constituent parts. These parts include resonances due to the
dimensions of the climatic facility itself, internal reflections from the metallic walls, mutual coupling effects
and the possible propagation of waveguide type modes. All of these effects cause disruption to the field
distribution within the facility.
5.2.1 Resonances within a climatic facility
To fully contain and control the extreme conditions in which the EUT is tested, the test fixture is usually
placed within a clim
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