ETSI ETR 273-4 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 4: Open area test site
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
DTR/ERM-RP01-018-4
Elektromagnetna združljivost (EMC) in zadeve v zvezi z radijskim spektrom (ERM) - Izboljšanje zvezdastih merilnih metod (z uporabo merilnih mest) in ovrednotenje ustreznih merilnih negotovosti - 4. del: Merilno mesto v odprtem prostoru
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 - 4. del: Merilno mesto v odprtem prostoru
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
Ta slovenski standard je istoveten z: ETR 273-4 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 273-4
TECHNICAL February 1998
REPORT
Source: ERM Reference: DTR/ERM-RP01-018-4
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 4: Open area test site
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 273-4: 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 273-4: 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 .16
4 Introduction.17
5 Uncertainty contributions specific to an open area test site.18
5.1 Introduction.18
5.2 Ground plane .18
5.2.1 Coatings .19
5.2.2 Reflections from the ground plane.19
5.2.3 Mutual coupling between antennas and in the ground plane.21
5.3 Other effects.24
5.3.1 Range length and measurement distance.24
5.3.2 Antenna mast, turntable and mounting fixtures.26
5.3.3 Test antenna height limitations.27
5.3.4 Test antenna cabling.28
5.3.5 EUT supply and control cabling.28
5.3.6 Positioning of the EUT and antennas .29
5.3.7 Electromagnetic environment.29
5.3.8 Extraneous reflections.30
6 Verification procedure for an open area test site.32
6.1 Introduction.32
6.2 Normalized site attenuation.33
6.2.1 Anechoic chamber .33
6.2.2 Open area test site.35
max max
6.2.3 Improvements to the formulae for E and E .38
DH DV
6.2.4 Mutual coupling.39
6.3 Overview of the verification procedure.40
6.3.1 Apparatus required.42
6.3.2 Site preparation.42
6.3.3 Measurement configuration.43
6.3.4 What to record .45
6.4 Verification procedure.46
6.4.1 Procedure 1: 30 MHz to 1 000 MHz .46
6.4.2 Alternative Procedure 1: 30 MHz to 1 000 MHz.51
6.4.3 Procedure 2: 1 GHz to 12,75 GHz .52
6.5 Processing the results of the verification procedure.56
6.5.1 Introduction.56
6.5.2 Procedure 1: 30 MHz to 1 000 MHz .56
6.5.3 Procedure 2: 1 GHz to 12,75 GHz .60
6.5.4 Report format.63
6.6 Calculation of measurement uncertainty (Procedure 1) .63
6.6.1 Uncertainty contribution, direct attenuation measurement.64
6.6.2 Uncertainty contribution, NSA measurement.65
6.6.3 Expanded uncertainty of the verification procedure.67
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ETR 273-4: February 1998
6.7 Calculation of measurement uncertainty (Procedure 2) .67
6.7.1 Uncertainty contribution, direct attenuation measurement .67
6.7.2 Uncertainty contribution, NSA measurement.68
6.7.3 Expanded uncertainty of the verification procedure .69
6.8 Summary .70
7 Test methods .70
7.1 Introduction.70
7.1.1 Site preparation.70
7.1.2 Preparation of the EUT.71
7.1.3 Standard antennas.72
7.1.4 Mutual coupling and mismatch loss correction factors.72
7.1.5 Power supplies to EUT.73
7.1.6 Restrictions.73
7.2 Transmitter tests .73
7.2.1 Frequency error (30 MHz to 1 000 MHz).73
7.2.1.1 Apparatus required.73
7.2.1.2 Method of measurement.73
7.2.1.3 Procedure for completion of the results sheets.75
7.2.1.4 Log book entries .75
7.2.1.5 Statement of results .75
7.2.2 Expanded uncertainty for Frequency error test.76
7.2.3 Effective radiated power (30 MHz to 1 000 MHz) .76
7.2.3.1 Apparatus required.76
7.2.3.2 Method of measurement.77
7.2.3.3 Procedure for completion of the results sheets.79
7.2.3.4 Log book entries .81
7.2.3.5 Statement of results .82
7.2.4 Measurement uncertainty for Effective radiated power.83
7.2.4.1 Uncertainty contributions: Stage 1: EUT measurement .83
7.2.4.2 Uncertainty contributions: Stage 2: Substitution
measurement.84
7.2.4.3 Expanded uncertainty of the ERP measurement .85
7.2.5 Spurious Emissions (30 MHz - 4 GHz or 12,75 GHz) .86
7.2.5.1 Apparatus required.86
7.2.5.2 Method of measurement.87
7.2.5.3 Procedure for completion of the results sheets.92
7.2.5.4 Log book entries .95
7.2.5.5 Statement of results .97
7.2.6 Measurement uncertainty for Spurious emissions .97
7.2.6.1 Uncertainty contributions: Stage 1: EUT measurement .97
7.2.6.2 Uncertainty contributions: Stage 2: Substitution
measurement.98
7.2.6.3 Expanded uncertainty of the Spurious emission.99
7.2.7 Adjacent channel power .100
7.3 Receiver tests.100
7.3.1 Sensitivity tests (30 MHz to 1 000 MHz) .100
7.3.1.1 Apparatus required.101
7.3.1.2 Method of measurement.101
7.3.1.3 Procedure for completion of the results sheets.106
7.3.1.4 Log book entries .107
7.3.1.5 Statement of results .110
7.3.2 Measurement uncertainty for maximum or average usable sensitivity .110
7.3.2.1 Uncertainty contributions: Stage one: Transform Factor .110
7.3.2.2 Uncertainty contributions: Stage 2: EUT measurement .111
7.3.2.3 Expanded uncertainty of the receiver sensitivity
measurement.113
7.3.3 Co-channel rejection.113
7.3.4 Adjacent channel selectivity .113
7.3.5 Intermodulation immunity .113
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ETR 273-4: February 1998
7.3.6 Spurious response rejection. 113
Annex A (informative): Bibliography. 114
History . 116
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ETR 273-4: February 1998
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ETR 273-4: 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 ETR is part 4 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 273-4: February 1998
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ETR 273-4: February 1998
1 Scope
This ETR covers the methods of radiated measurements on mobile radio equipment on an open area test
site 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.41: "Psophometer for use on telephone-type
circuits".
[5] CCITT Recommendation O.153: "Basic parameters for the measurement of
error performance at bit rates below the primary rate".
[6] CISPR 16-1: "Specification for radio disturbance and immunity measuring
apparatus and methods - Part 1: Radio disturbance and immunity measuring
apparatus".
[7] "Control of errors on Open Area Test Sites", A. A. Smith Jnr. EMC technology
October 1982 page 50-58.
[8] EN 50147-2: "Anechoic chambers -- Part 2: Alternative test site suitability with
respect to site attenuation".
[9] 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".
[10] 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".
[11] "The gain resistance product of the half-wave dipole", W. Scott Bennet
Proceedings of IEEE vol. 72 No. 2 Dec 1984 pp 1824-1826.
[12] "The new IEEE standard dictionary of electrical and electronic terms". Fifth
edition, IEEE Piscataway, NJ USA 1993.
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ETR 273-4: 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.
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.
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.
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. Combining networks are so designed that 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).
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ETR 273-4: February 1998
duplex filter: A device fitted internally or externally to a transmitter/receiver combination to allow
simultaneous transmission and reception with a single antenna connection.
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 [5].
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 should be supplied in the test report.
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.
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ETR 273-4: February 1998
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 the 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: 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.
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ETR 273-4: February 1998
psophometric weighting network: As described in CCITT Recommendation O.41 [4].
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 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.
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ETR 273-4: February 1998
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, a 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 purpose 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
polarization) (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 273-4: February 1998
p power
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 rectangular distribution
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 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
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 three-axis probe to its image in the plates
j
u Stripline: characteristic impedance
j
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ETR 273-4: February 1998
u Stripline: non-planar nature of the field distribution
j
u Stripline: field strength measurement as determined by the three-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 )
3.3 Abbreviations
For the purpose of this ETR, the following abbreviations apply:
AF Audio Frequency
BER Bit Error Ratio
dB decibel
emf Electromotive force
ERP Effective Radiated Power
EUT Equipment Under Test
FSK Frequency Shift Keying
GMSK Gaussian Minimum Shift Keying
GSM Global System for Mobile telecommunication (Pan European digital
telecommunication system)
LPDA Log Periodic Dipole Antenna
IF Intermediate Frequency
NaCl Sodium chloride
NSA Normalised Site Attenuation
RF Radio Frequency
RMS Root Mean Square
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ETR 273-4: February 1998
RSS Root-Sum-of Squares
SINAD Signal Noise And Distortion
TEM Transverse ElectroMagnetic
VSWR Voltage Standing Wave Ratio
4 Introduction
An open area test site comprises a turntable at one end and an antenna mast of variable height at the
other set above a ground plane which, in the ideal case, is perfectly conducting and of infinite extent. In
practice, whilst good conductivity can be achieved, the ground plane size has to be limited. A typical open
area test site is shown in figure 1.
Dipole antennas
An te nna m ast
Turntable
Ground plane
Figure 1: A typical open area test site
The ground plane creates a wanted reflection path, such that the signal received by the receiving antenna
is the sum of the signals received from the direct and reflected transmission paths. The phasing of these
two signals creates a unique received level for each height of the transmitting antenna (or EUT) and the
receiving antenna above the ground plane.
In practice, the antenna mast provides a variable height facility so that the elevation of the test antenna can
be optimized for maximum coupled signal in conjunction with the turntable for azimuth angle.
Both absolute and relative measurements can be performed on an open area test site. Where absolute
measurements are to be carried out, or where the test site is to be used for accredited measurements, the
open area test site should be verified. Verification involves comparison of the measured performance to
that of an ideal theoretical site, with acceptability being decided on the basis of the differences not
exceeding some pre-determined limits.
The open area test site has been, historically, the reference site upon which the majority, if not all, of the
specification limits have been set. The ground plane was originally introduced to provide uniformity of
ground conditions, between test sites, during testing.
Ra nge length 3 m or 10 m
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ETR 273-4: February 1998
5 Uncertainty contributions specific to an open area test site
5.1 Introduction
open area test site performance is dependant on many factors such as the size and shape of the ground
plane, its surface material and roughness, edge termination, dielectric coverings, environmental conditions,
weather protection, the size of the EUT, the type of test being carried out, the required frequency range,
etc.
These are some of the factors that have to be evaluated to ensure optimum use of the open area test site.
In this case "optimum use" refers to minimization of the uncertainty contributions.
5.2 Ground plane
A conducting ground plane should be made from metals preferably of a non ferrous nature such as copper
or aluminium. It does not have to be constructed of solid sheet but can be perforated metal, welded mesh,
metal gratings, etc., but wherever a gap or a void occurs within the screen, it should not measure more
than l/10 at the highest frequency of operation in any dimension. This maximum dimension applies equally
to joints and seams between metal sheets/panels where these have been used to make the ground plane.
The main reflection comes from the ray which makes equal incident and reflected angles on the ground
plane surface, although other areas within the plane contribute to the overall interference signal level
coming from the ground. This is a result of diffraction. The resulting size of the ground plane for reliable
measurements is subject to both calculation and practical experience and can vary depending on the profile
of ground plane chosen i.e. there are different recommendations for elliptical and rectangular planes.
The size of the ground plane needs to be large enough to cover the entire area from which reflections will
arise. ANSI use Fresnel ellipses on the reflecting surface (see figure 63) as a basis for determining the
size, where the ellipse is defined by the locus of equal reflected path lengths from the EUT to the test
antenna.
Test
antenna
z
EUT
y
x
Fresnel ellipses
Figure 2: Fresnel ellipses drawn on the reflecting surface
The ellipse corresponding to the first Fresnel zone i.e. the one which gives a path length change of half a
wavelength at the lowest frequency of operation, is the minimum size of ground plane they recommend.
This is dependent on the test site geometry (i.e. measurement distance, source height, receive antenna
height variation) and the wavelength of the lowest frequency.
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ETR 273-4: February 1998
It has been reported "Control of errors on Open Area Test Sites" [7] that simply increasing the ground
plane size, in an attempt to improve its approximation to an infinite plane, may not always be beneficial.
When the edge of the ground plane is not well terminated, the edge effects (i.e. the difference between
theoretical and measured results for vertical polarization) can actually increase as the ground plane gets
larger.
The smoothness of the reflecting surface is of importance and as a general rule of thumb, the surface
roughness is taken to be less than l/10 at the shortest wavelength of usage. For all tests under
consideration here (where 12,75 GHz is the uppermost frequency of interest), this implies that the surface
should smoother than 2,35 mm.
5.2.1 Coatings
Where thick dielectric coatings have been applied to a metal ground plane e.g. asphalt, gravel, concrete,
etc.; or where a layer of snow has fallen, the nature of the reflection can be significantly changed,
particularly for vertical polarization. This effect is illustrated in figure 3 where the patterns above ground of
a vertical dipole are presented. The solid line represents the performance above a perfectly reflecting
surface, whereas the dashed line is for the same antenna above a dielectric covered, reasonably
conductive ground plane. The received signal levels consequently can show an enormous variation in level
depending on the state of the reflecting surface when vertically polarized tests are being performed. The
change in reflectivity for horizontal polarization is relatively minor in comparison.
G round Ground
2-
=¥s10 Sm/, 5,freq 1GH z
se== =
r
Figure 3: Patterns for vertical dipole above different ground planes
When comparing results from different sites, the reflection coefficient variations from one ground plane
medium to another, even when measurement geometry remains the same, can produce significant
differences in the measured results.
To minimize these uncertainties, the ground plane should be a highly conductive, relatively non ferrous
metal with no dielectric coating.
5.2.2 Reflections from the ground plane
Far from a perfectly conducting ground plane, at a distance sufficient to make the difference between the
direct and reflected path lengths negligible and the direct and reflected waves appear parallel to each
other, the amplitude of the reflected wave is equal to the amplitude of the direct wave. When these two
waves add "in phase" the electric field strength doubles (6 dB gain) whereas, at another point the two
waves are "out of phase" and cancel entirely resulting in no net electric field. Therefore, over a perfectly
conducting ground plane at infinite distance it is possible to obtain field strengt
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