ETSI ETR 273-2 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 2: Anechoic chamber
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
DTR/ERM-RP01-018-2
Elektromagnetna združljivost (EMC) in zadeve v zvezi z radijskim spektrom (ERM) - Izboljšanje zvezdastih merilnih metod (z uporabo merilnih mest) in ovrednotenje ustreznih merilnih negotovosti - 2. del: Neodmevna komora
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
01-april-1999
Elektromagnetna združljivost (EMC) in zadeve v zvezi z radijskim spektrom (ERM) -
Izboljšanje zvezdastih merilnih metod (z uporabo merilnih mest) in ovrednotenje
ustreznih merilnih negotovosti - 2. del: Neodmevna komora
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
Ta slovenski standard je istoveten z: ETR 273-2 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 273-2
TECHNICAL February 1998
REPORT
Source: ERM Reference: DTR/ERM-RP01-018-2
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 2: Anechoic chamber
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.
Page 2
ETR 273-2: 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.
Page 3
ETR 273-2: February 1998
Contents
Foreword .7
1 Scope.9
2 References .9
3 Definitions, symbols and abbreviations .10
3.1 Definitions.10
3.2 Symbols .14
3.3 Abbreviations .17
4 Introduction.18
5 Uncertainty contributions specific to an anechoic chamber.19
5.1 Effects of the metal shielding.19
5.1.1 Resonances.19
5.1.2 Imaging of antennas (or an EUT) .19
5.2 Effects of the radio absorbing materials .20
5.2.1 Introduction.20
5.2.2 Pyramidal absorbers.21
5.2.3 Wedge absorbers.22
5.2.4 Ferrite tiles.23
5.2.5 Ferrite grids .24
5.2.6 Urethane/ferrite hybrids.24
5.2.7 Floor absorbers.24
5.2.8 Performance comparison .25
5.2.9 Reflection in an anechoic chamber .26
5.2.10 Mutual coupling due to imaging in the absorbing material .28
5.3 Other effects.29
5.3.1 Extraneous reflections.29
5.3.2 Mutual coupling between antennas (or antenna and EUT) .29
5.3.3 Turntable and antenna mounting fixtures.31
5.3.4 Antenna cabling.32
5.3.5 Positioning of the EUT and antennas .32
5.3.6 Equipment cabling.33
6 Verification procedure for an anechoic chamber.33
6.1 Introduction.33
6.2 Normalized site attenuation.34
6.2.1 NSA for the ideal anechoic chamber.34
6.2.2 Mutual coupling.36
6.3 Overview of the verification procedure.37
6.3.1 Apparatus required.37
6.3.2 Site preparation.38
6.3.3 Measurement configuration.39
6.3.4 What to record .41
6.4 Verification procedure.41
6.4.1 Procedure 1: 30 MHz to 1 000 MHz .41
6.4.2 Alternative Procedure 1: 30 MHz to 1 000 MHz.47
6.4.3 Procedure 2: 1 GHz to 12,75 GHz .47
6.5 Processing the results of the verification procedure.52
6.5.1 Introduction.52
6.5.2 Procedure 1: 30 MHz to 1 000 MHz .52
6.5.3 Procedure 2 (1 GHz to 12,75 GHz).55
Page 4
ETR 273-2: February 1998
6.5.4 Report format.58
6.6 Calculation of measurement uncertainty (Procedure 1) .58
6.6.1 Uncertainty contribution, direct attenuation measurement .58
6.6.2 Uncertainty contribution, NSA measurement.59
6.6.3 Expanded uncertainty of the verification procedure .61
6.7 Calculation of measurement uncertainty (Procedure 2) .61
6.7.1 Uncertainty contribution, direct attenuation measurement .61
6.7.2 Uncertainty contribution, NSA measurement.62
6.7.3 Expanded uncertainty of the verification procedure .63
6.8 Summary .64
7 Test methods .64
7.1 Introduction.64
7.1.1 Site preparation.65
7.1.2 Preparation of the EUT.66
7.1.3 Standard antennas.66
7.1.4 Mutual coupling and mismatch loss correction factors.67
7.1.5 Power supplies to the EUT .67
7.1.6 Restrictions.67
7.2 Transmitter tests .68
7.2.1 Frequency error (30 MHz to 1 000 MHz).68
7.2.1.1 Apparatus required.68
7.2.1.2 Method of measurement.68
7.2.1.3 Procedure for completion of the results sheets.69
7.2.1.4 Log book entries .70
7.2.1.5 Statement of results .70
7.2.2 Expanded uncertainty for frequency error test.71
7.2.3 Effective radiated power (30 MHz to 1 000 MHz) .71
7.2.3.1 Apparatus required.71
7.2.3.2 Method of measurement.72
7.2.3.3 Procedure for the completion of the results sheets.75
7.2.3.4 Log book entries .76
7.2.3.5 Statement of results .77
7.2.4 Measurement uncertainty for effective radiated power.77
7.2.4.1 Uncertainty contributions: Stage 1: EUT measurement .77
7.2.4.2 Uncertainty contributions: Stage two: Substitution
measurement.78
7.2.4.3 Expanded uncertainty of the ERP measurement .80
7.2.5 Spurious emissions (30 MHz to 4 GHz or 12,75 GHz).80
7.2.5.1 Apparatus required.81
7.2.5.2 Method of measurement.81
7.2.5.3 Procedure for completion of the results sheets.86
7.2.5.4 Log book entries .88
7.2.5.5 Statement of results .89
7.2.6 Measurement uncertainty for Spurious emissions .89
7.2.6.1 Uncertainty contributions: Stage 1: EUT measurement .90
7.2.6.2 Uncertainty contributions: Stage 2: Substitution
measurement.91
7.2.6.3 Expanded uncertainty of the spurious emission.92
7.2.7 Adjacent channel power .93
7.3 Receiver tests.93
7.3.1 Sensitivity tests (30 MHz to 1 000 MHz) .93
7.3.1.1 Apparatus required.94
7.3.1.2 Method of measurement.94
7.3.1.3 Procedure for completion of the results sheets.100
7.3.1.4 Log book entries .101
7.3.1.5 Statement of results .103
7.3.2 Measurement uncertainty for Receiver sensitivity.104
7.3.2.1 Uncertainty contributions: Stage 1: Determination of
Transform Factor.104
Page 5
ETR 273-2: February 1998
7.3.2.2 Uncertainty contributions: Stage 2: EUT measurement.105
7.3.2.3 Expanded uncertainty of the receiver sensitivity
measurement.107
7.3.3 Co-channel rejection .107
7.3.4 Adjacent channel selectivity .107
7.3.5 Intermodulation immunity.107
7.3.6 Blocking immunity or desensitization.107
7.3.7 Spurious response immunity to radiated fields (30 MHz to 4 GHz) .107
7.3.7.1 Apparatus required .108
7.3.7.2 Method of measurement.108
7.3.7.3 Procedure for completion of the results sheets.114
7.3.7.4 Log book entries.115
7.3.7.5 Statement of results.117
7.3.8 Measurement uncertainty for Spurious response immunity .118
7.3.8.1 Uncertainty contributions: Stage 1: Transform factor.118
7.3.8.2 Uncertainty contributions: Stage 2: EUT measurement.120
7.3.8.3 Expanded uncertainty of the spurious response immunity
measurement.121
Annex A (informative): Bibliography.122
History .124
Page 6
ETR 273-2: February 1998
Blank page
Page 7
ETR 273-2: 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 2 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".
Page 8
ETR 273-2: February 1998
Blank page
Page 9
ETR 273-2: February 1998
1 Scope
This ETR covers the methods of radiated measurements on mobile radio equipment in anechoic chambers
and applies to the assessment of the associated measurement uncertainties.
This ETR also 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] "ANSI C63.5-(1988): "Electromagnetic Compatibility-Radiated Emission
Measurements in Electromagnetic Interference (EMI) Control - Calibration of
Antennas".
[2] "Antenna theory", C. Balanis, J. E. Wiley 1982.
[3] "Calculation of site attenuation from antenna factors" A. A. Smith Jr, RF German
and J B Pate. IEEE transactions EMC. Vol. EMC 24 pp 301-316 Aug 1982.
[4] CCITT Recommendation O.153: "Basic parameters for the measurement of
error performance at bit rates below the primary rate".
[5] CCITT Recommendation O.41: "Psophometer for use on telephone-type
circuits".
[6] CISPR 16-1: "Specification for radio disturbance and immunity measuring
apparatus and methods - Part 1: Radio disturbance and immunity measuring
apparatus".
[7] EN 50147-2 (1996): "Anechoic chambers -- Part 2: Alternative test site suitability
with respect to site attenuation".
[8] 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".
[9] ETR 273-1-2: "Electromagnetic compatibility and Radio spectrum Matters
(ERM); Improvement of radiated methods of measurement (using test sites) and
evaluation of the corresponding measurement uncertainties; Part 1: Uncertainties
in the measurement of mobile radio equipment characteristics; Sub-part 2:
Examples and annexes".
[10] "The gain resistance product of the half-wave dipole", W. Scott Bennet
Proceedings of IEEE vol. 72 No. 2 Dec 1984 pp 1824-1826.
[11] The new IEEE standard dictionary of electrical and electronic terms. Fifth
edition, IEEE Piscataway, NJ USA 1993.
Page 10
ETR 273-2: February 1998
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.
A-M1: 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: 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: 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.
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).
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).
Page 11
ETR 273-2: February 1998
DM-0: A test modulation consisting of a signal representing an infinite series of "0" bits.
DM-1: A test modulation consisting of a signal representing an infinite series of "1" bits.
DM-2: A test modulation consisting of a signal representing a pseudorandom bit sequence of at least
511 bits in accordance with CCITT Recommendation O.153 [4].
DM-3: A test signal 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 4: The agreed test signal may be formatted and may contain error detection and
correction. Details of the test signal are be supplied in the test report.
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.
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.
Page 12
ETR 273-2: February 1998
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 5: 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.
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 [5].
Page 13
ETR 273-2: February 1998
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.
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 6: 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 7: This combination is carried out by applying the Root Sum of Squares (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.
Page 14
ETR 273-2: February 1998
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 8: 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
calculated on the basis of given and measured data
c
cross correlation coefficient
C
cross
derived from a measuring equipment specification
d
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
max
calculated maximum electric field strength in the receiving antenna height scan
E
DH
from a half wavelength dipole with 1 pW of radiated power (for horizontal
polarisation) (mV/m)
max
calculated maximum electric field strength in the receiving antenna height scan
E
DV
from a half wavelength dipole with 1 pW of radiated power (for vertical
polarization) (mV/m)
antenna efficiency factor
e
ff
fangle (°)
Dbandwidth (Hz)
f
frequency (Hz)
f
fgain of the source (which is the source directivity multiplied by the antenna
G(q, )
efficiency factor)
magnetic field intensity (A/m)
H
the (assumed constant) current (A)
I
the maximum current amplitude
I
m
2p/lk
a factor from Student's t distribution
k
Boltzmann's constant (1,38 x 10-23 Joules/° Kelvin)
k
K relative dielectric constant
the length of the infinitesimal dipole (m)
l
L the overall length of the dipole (m)
the point on the dipole being considered (m)
l
m measured
lwavelength (m)
Page 15
ETR 273-2: February 1998
p power level value
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
r indicates rectangular distribution
SNR Signal to noise ratio at a specific BER
b*
SNR Signal to noise ratio per bit
b
T antenna temperature (° Kelvin)
A
u indicates U-distribution
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
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
Page 16
ETR 273-2: February 1998
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 )
Page 17
ETR 273-2: February 1998
3.3 Abbreviations
For the purposes of this ETR, the following abbreviations apply:
AF Audio Frequency
BER Bit Error Ratio
CD Citizen's Band
DELT
DM-0 A test modulation consisting of a signal representing an infinite series of "0" bits
DM-1 A test modulation consisting of a signal representing an infinite series of "1" bits
DM-2 A test modulation consisting of a signal representing a pseudorandom bit
sequence of at least 511 bits in accordance with
CCITT Recommendation O.153 [4]
DM-3 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 are be supplied in the test report.
emf Electromotive force
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
LPDA Log Periodic Dipole Antenna
m measured
NaCl Sodium chloride
NSA Normalized Site Attenuation
r indicates rectangular distribution
RF Radio Frequency
rms root mean square
RSS Root-Sum-of-the-Squares
TEM Transverse Electro-Magnetic
u indicates U-distribution
VSWR Voltage Standing Wave Ratio
Page 18
ETR 273-2: February 1998
4 Introduction
An anechoic chamber is an enclosure whose internal walls, floor and ceiling are covered with radio
absorbing material, normally of the pyramidal urethane foam type. It is normally shielded against local
ambients. The chamber contains an antenna support at one end and a turntable at the other. A typical
anechoic chamber is shown in figure 1 with dipole antennas at both ends.
Dipole antennas
Radio
absorbin g
material
Antenna support
Ante nna su pp ort
Turntable
Figure 1: A typical anechoic chamber
The chamber shielding and radio absorbing material work together to provide a controlled environment for
testing purposes. This type of test chamber attempts to simulate free space conditions. The shielding
provides a test space, with reduced levels of interference from ambient signals and other outside effects,
whilst the radio absorbing material minimizes unwanted reflections from the walls, floor and ceiling which
could influence the measurements.
In practice whilst it is relatively easy for the shielding to provide high levels (80 dB to 140 dB) of ambient
interference rejection (normally making ambient interference negligible), no design of radio absorbing
material satisfies the requirement of complete absorption of all the incident power. For example it cannot
be perfectly manufactured and installed and its return loss (a measure of its efficiency) varies with
frequency, angle of incidence and in some cases, is influenced by high power levels of incident radio
energy. To improve the return loss over a broader frequency range, ferrite tiles, ferrite grids and hybrids of
urethane foam and ferrite tiles are used with varying degrees of success.
The anechoic chamber generally has several advantages over other test facilities. There is minimal ambient
interference, minimal floor, ceiling and wall reflections and it is independent of the weather. It does
however have some disadvantages which include limited measuring distance (due to available room size,
cost, etc.) and limited lower frequency usage due to the size of the room and the pyramidal absorbers.
Both absolute and relative measurements can be performed in an anechoic chamber. Where absolute
measurements are to be carried out, or where the test facility is to be used for accredited measurements,
the chamber should be verified. Verification involves comparison of the measured performance to that of
an ideal theoretical chamber, with acceptability being decided on the basis of the maximum difference
between the two.
R ange leng th 3 m or 10 m
Page 19
ETR 273-2: February 1998
5 Uncertainty contributions specific to an anechoic chamber
A typical anechoic chamber comprises two main components:
- a metallic shield;
- radio absorbing material.
Whilst each component is included to improve the quality of the testing environment within the chamber,
each has negative effects as well. Below, some positive effects are mentioned as a brief introduction to a
discussion of the negative effects and their impact on measurement uncertainty.
5.1 Effects of the metal shielding
The benefits of shielding a testing area can be seen by considering the situation on a typical open area test
site where ambient RF interference can add considerable uncertainty to the measurements. Such RF
ambient signals can be continuous sources e.g. commercial radio and television, link services, navigation
etc. or intermittent ones e.g. CB, emergency services, DECT, GSM, paging systems, machinery and a
variety of others. The interference can be either narrowband or broadband.
The anechoic chamber overcomes these problems by the provision of a shielded enclosure. A shielded
enclosure is defined as any structure that protects its interior from the effects of an exterior electric or
magnetic field, or conversely, protects the surrounding environment from the effects of an interior field. The
shielding is normally provided by metal panels with continuous electrical contact between them and any
opening provided in the shield (e.g. doors and breakout panels).
Further advantages of the shield are protection from the weather and the general degradation effects it
can have.
5.1.1 Resonances
Any metal shield will act as a reflecting surface and grouping six of them together to form a metal box
makes it possible for the chamber to act like a resonant waveguide cavity. Whilst these resonance effects
tend to be narrowband, their peak magnitudes can be high, resulting in a significant disruption of the
desired field distribution.
A resonant waveguide cavity mode can, in theory, be excited at any frequency which satisfies the following
formula:
22 2
x y z
f = 150 + + MHz
ŁlłŁbłŁhł
where l, b and h are respectively the length, breadth and height of the chamber in metres and x, y and z
are mode numbers of which only one is allowed to be zero at any time. As
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.
Loading comments...