CEPT
ECC
Electronic Communications Committee
FM(13)020
Working Group FM
76th Meeting
Warsaw, 04 - 08 February 2013
Date issued:
14 January 2013
Source:
FM 22
Subject:
Draft CEPT/ECC Recommendation (12)03 on Determination of the
radiated power through field strength measurements in the frequency
range from 400 MHz to 6000 MHz
Group membership required to read? (Y/N)
N
Summary:
The last meeting of WG FM finally adopted the Draft New Recommendation for public
consultation. The pages overleaf contain the comments received during the public consultation
as well as responses and proposals of FM PT 22 for resolution.
Proposal:
WG FM is invited to consider the comments and responses and to adopt the Recommendation
finally and to task ECO to publish it.
Background:
FM 22 work program
Comments on ECC Deliverable REC(12)03
“Draft CEPT/ECC Recommendation (12)03 on Determination of the radiated power through field strength measurements in the
frequency range from 400 MHz to 6000 MHz”
Comments received from
France (32 comments – 20 editorial and 12 general/technical)
ETSI ERM (1 comment
2
Proposals related to the ECC Deliverables
Comment
number
Section
number/
Clause
Paragraph
Figure/
Table
Type of comment
(General/
Technical/Editorial)
FR/1
Introduction
General / Technical
FR/2
Considering
d)
Editorial
COMMENTS
Proposed change
“…in the frequency range from 400 MHz to 6000 MHz
The
objective
of
this
from field strength measurements by reducing as much as
recommendation is not limited
to reducing the uncertainty of possible the error and the uncertainty of the measurement.”
the measurement but also
reducing the error of the
measurement by identifying
most of influence factors.
“ that radiated power determination through measurements
at the transmitter output are often impossible due to access
problems or lacking test output,”
2
FM22 Comment Resolution
Not accepted. The only parameter that can
be limited is the measurement uncertainty.
The reduction of the measurement error is
just a possible consequence.
Furthermore, the word “by” in the old text
must be deleted. The following text is
proposed:
“...in the frequency range from 400 MHz
to 6000 MHz from field strength
measurements reducing as much as
possible the uncertainty of the
measurement.”
Accepted.
FR/3
Recommends
Editorial
“that the measurement method described in Annex 1
Proposal to align the title of the
should be used to determine the radiated power of a
recommendation, the
transmitter based on field strength measurements in the
introduction and the
frequency range from 400 MHz to 6000 MHz by reducing
recommends part.
as much as possible the error and the uncertainty of the
measurement.”
FR/4
Annex 1
Editorial
A.1.1
Introduction
FR/5
Annex1
A.1.2 Scope
of
application
and
limitations
1st paragraph
General/technical
“Field strength measurements are one of the basic tasks of
all radio monitoring services. It is feasible to measure the
field strength at a single location in the electromagnetic
field but due to reflections and other propagation effects,
the measured values may change extremely from one
measurement location to the next. The following
measurement method describes how these effects can be
handled in order to retrieve reliable field strength values
which may be used for the determination of the radiated
power of a transmitter.”
“The measurement method emphasises many precautions to
The scope of this draft
take into account in order to reduce external influence
recommendation is not
factors which may lead to errors in the measurement
restricted to the correction of
process. In particular, this method describes how to handle
the influence of possible
the influence of possible ground reflections from
ground reflection.
information gained through a height scan of the field
The basic principle of the draft
strength at the location of reception which allows
recommendation is to
estimating the effective reflection coefficient. This method
emphasize a large number of
is basically frequency independent. However, in practice
possible influence factors in
order to minimize the error and there are limitations.”
the uncertainty of the
measurement.
The proposal aims to reflect
this.
3
Proposals in this line accepted.
This part of the proposal is not accepted
because measurements are not done “by
reducing the error”. A specific
measurement method is recommended.
There is no need to recommend the
reduction of the measurement uncertainty.
Hence the following text is proposed:
“that the measurement method described
in Annex 1 should be used to determine
the radiated power of a transmitter based
on field strength measurements in the
frequency range from 400 MHz to 6000
MHz.”
All proposals accepted.
The main purpose is to describe how the
measurement is done and not to emphasise
the problems and the limitations of the
method. Therefore the following text is
proposed.
“The measurement method relies on the
correction of the influence of possible
ground reflections from information
gained through a height scan of the field
strength at the location of reception which
allows estimating the effective reflection
coefficient. This method is basically
frequency independent. However, there
are many cautions to take into account in
order to reduce external influence factors
which may lead to errors in the
measurement process. “
FR/6
Annex1
4th paragraph
Editorial
A.1.2 Scope
of
application
and
limitations
FR/7
Annex1
A.1.2 Scope
of
application
and
limitations
5th paragraph
Editorial
There are, however, even more constraints with regard to
the applicability of the method. Field strength
measurements have to be performed in the far field. The far
field condition is usually defined as the range from 2D2/λ
to ∞ with D being the largest dimension of the transmitting
antenna. If D=1 m (typical base station antenna) and λ=0.1
m (3 GHz) the measurement distance between the
transmitter and the receiving antenna has to be at least 20
m.
The first proposal is not accepted because
the far field is defined (in which far field
conditions are assumed).
The second proposal is accepted.
It has further to be taken into account that the actual
All proposals are accepted.
location where the effective ground reflection occurs is
different for different heights of the measurement antenna.
A valid estimate of the reflection coefficient from a field
strength height scan can thus be obtained under the
provision only that the locations of reflection for the
“maximum” and the “minimum” reflection nearly coincide.
This condition is more easily achieved with higher
frequencies and closer measurement distances. In contrast,
in the case of typical high power broadcast transmitters,
large transmitting antenna heights are prevailing. In
addition, the radiation is confined to a vertically narrow
lobe which meets the ground at distances of several
kilometres from the transmitter only. This forces the
measurements to be done at large distances from the
transmitter and the locations of reflections may be 50 or
100 metres apart under these circumstances.
4
ETSI
ERM/1
A.1.2 far
field
Technical
ETSI TC ERM would like to
stress that it is important that
the measurement is made in
the far field regions of both the
transmit and receive antennas,
unless the gain of the receive
antenna in the particular point
in the near field lobe is known
(Ref. 1). This follows from the
reciprocity principle (Ref. 2).
It proposed to add, into the draft Recommendation, words
explaining the situation (i.e. words similar to those in the
explanation above), and to include the following equations:
Where Dt and Dr are the values for the parameter “D”
considered above, respectively for the transmit and for the
receive antennas, we have :
The proposal of ETSI is not accepted for
the following reasons.
In an antenna's far field, the magnetic and
electric field components are
perpendicular to each other. It is only here
2
2
that calculations between the two
2 Dt
2 Dr
components are possible by means of the
measurement dis tan ce 


 or free-space wave impedance. It suffices to
measure just one component, usually the
2
2
2 Dt  Dr
electric one. The formula for open air
Obviously, there may be
measurement dis tan ce 
conditions – in particular in
attenuation then also applies to this range.

view of the choice of the
.
receive antenna – where the
As a result, if the receive and transmit antennas are of the
In the case of antennas of large dimension
dominant factor may be the
same type, with the same parameters as above, the
in relation to the wavelength, a condition
transmit antenna. However, in measurement distance has to be at least 40 m.
which normally applies to array antennas
order to better control the
(mobile radio sector antennas comprise
reflections that may occur in
rd edition, John D.
Ref
1.
Antennas
for
all
Applications,
3
many phase-coupled dipoles), another
the measurement considered, it
factor needs to be considered. In "visual"
may be tempting to use, as the Kraus & Ronald J. Marhefka, McGraw Hill, ISBN 0-07232103-2, sect 24-2b, p 830 et seq.
terms, the individual fields of the antennas
receive antenna, an antenna
with considerable gain, in
in the near-field have not yet merged
which case the far field, for
Ref 2. Ibid, Sect 24-2a, p 829 et seq.
completely. As the distance increases, the
that antenna, may also start
angle between the fields diminishes so
quite far away.
that at a certain distance the field may be
deemed to have been generated by a single
source.
 

 

 

A generally acknowledged rule of thumb
for flat wave fronts is the formula d >
2D²/λ. At the time, this formula had been
presented in FM22 by Denmark in
connection with the WiMAX document
and had subsequently been accepted by
FM22 as well. In addition, the Russian
Federation provided this formula for draft
ECC/REC(12)03 for the FM22 meeting in
September 2012 (document 06 of that
meeting).
The following should be considered when
discussing the proposal to double the
minimum measurement distance as
suggested by ETSI ERM.
5
ETSI
ERM/1
A.1.2 far
field
1) For the measurement, a measuring
antenna constituting a single antenna, e.g.
a horn antenna, is used rather than a base
station antenna (antenna array). Using
such an antenna means that the condition
is met which stipulates that the radiator, in
this instance the receiving antenna, is of
small dimension in relation to the
wavelength. Hence the additional far-field
condition should not be used and d >> 10
λ applies.
Technical
Cont.
2) Even if a base station antenna was used
as receiving antenna, there are doubts as
to whether the distance should be
doubled. If the distance to the transmitting
antenna is so large that flat wave fronts
may be assumed (d > 2D²/λ), then all
antennas within the receiving antenna
array will "see" the same field. The inphase addition in the receiving antennas
yields the antenna gain.
FR/8
Annex1
A.1.3 Terms,
Definitions,
abbreviations
and symbols
FR/9
Annex 1
Table 1 :
General
Abbreviations
1st paragraph
Editorial
A.1.4
FR/10
Annex 1
A.1.4
Legend of the Editorial
2nd formula
E in upper case is the common
designation for the field
strength. Moreover, “e” is used
just one time in the
Recommendation though “E”
is used several time.
E Field strength
Accepted.
The field strength E is generally calculated from RF level
Accepted.
measurements. The subsequent sections assume that field
strengths are measured in the far field region under free
space conditions using receiving antennas with known
antenna factors, cables with known losses, with adequate
receiver bandwidth and sufficient signal to noise ratio. The
formulas further assume an antenna load resistance of 50
Ω.
e.i.r.p. = effective radiated power in dBW relative to an
isotropic antenna
eE = field strength in dBV/m
R = distance in m
6
Accepted.
FR/11
Annex 1
A.1.5
FR/12
Annex 1
A.1.5
FR/13
Annex 1
A.1.6
Figure 1
(Title)
Editorial
Below Figure Editorial
2
“1. inspect
the
installation”
General
Example of the dependency of the measured field strength
on measurement antenna height
Accepted.
The free space attenuation field strength value E is
determined by the following formula:
The proposal is not accepted. The formula
calculates field strength and not
attenuation.
The field strength measurement requires that the
Accepted.
The proposed part to be deleted
monitoring antenna can be positioned in the main lobe of
is too specific (“base station”)
the transmitter and that the area between transmitter and
and doesn’t bring any
monitoring antenna is unobstructed. Height, directivity and
information
down tilt of the transmitter antenna have to be determined.
FR/14
Annex 1
A.1.6
FR/15
Annex 1
A.1.6
“2. Calculate
at which
distance…”
Editorial
“3. Search a
suitable
measurement
...…”
Editorial
This is usually done with the help of an electronic map that Accepted.
includes terrain height or field strength prognosis tools.
Alternatively, the measurement car can search the area in
question until maximum field strength is reached. This is
one of the key elements which allow defining the minimum
distance between the transmitter and the measurement
location.
Search a suitable measurement location
Accepted.
The measurement location within the area determined in
step 2 must have a line of sight to the transmitter. The
measurement conditions applicable for field strength
measurements as outlined in the relevant documents
mentioned in section A.1.4 have also to be fulfilled. If
directional transmit antennas are used, the monitoring
antenna has to be placed in the direction of the main lobe.
The distance will usually be in the range of one to several
hundred meters so that far field conditions apply.
7
FR/16
Annex 1
A.1.6
“3. Search a
suitable
measurement
...…”
Measure the field strength at the predetermined location
Editorial
Ensure that there are no other transmitters that are in close
proximity or close in frequency that can impact the
measurement. Using a directional measurement antenna
mounted on a retractable mast on the measurement vehicle,
first at roof height, to measure the field strength of the
transmitter.
Usually the measurement has to be done with an RMS
detector. For continuous emissions, the…
2nd paragraph
FR/17
Annex 1
A.1.6
“3. Search a
suitable
measurement
...…”
General/Technical
3rd paragraph
FR/18
Annex 1
A.1.6
“3. Search a
suitable
measurement
...…”
4th paragraph
All proposals accepted.
General/Technical
The sentence is too specific
and this is not directly
related to determine the
radiated power from a field
strength measurement. In
addition, this is only
applicable for GSM system
and not all multiple
channels signal (Frequency
hopping system for
example)
It’s difficult to address in
this procedure the case of
cross-polarised emission
without any clear
knowledge on the nature of
the emission itself. Some
equipment use the cross
polarized emission
alternatively and some new
system use both
polarization to transmit two
signals.
.
Accepted.
The measurement bandwidth should be equal to or higher
than the occupied bandwidth of the signal under
investigation. The polarisation of the measurement antenna
should be the same as used by the transmitter. In case of
cross-polarized transmitter antennas the polarisation of the
measurement antenna is not relevant. In this case, a special
care should be taken as in some situation the cross
polarisation is used to transmit two different signals and in
this case, both polarisation have to be addressed separately.
In the case of cross polarised emission, the nature of the
signal has to be known. Further details regarding field
strength measurements may be found in section 4.4 of the
ITU Handbook Spectrum Monitoring [2].
There is no benefit in addressing the
nature of polarised signals without
providing additional information. Hence,
with editorial corrections the paragraph
should read:
“The measurement bandwidth should be
equal to or higher than the occupied
bandwidth of the signal under
investigation. The polarisation of the
measurement antenna should be the same
as used by the transmitter. In case of
cross-polarised transmitter antennas the
polarisation of the measurement antenna is
not relevant. In this case, special care
should be taken as in some situations the
cross polarisation is used to transmit two
different signals and in this case, both
polarisations have to be addressed
separately. Further details regarding field
strength measurements may be found in
section 4.4 of the ITU Handbook
Spectrum Monitoring [2].
8
FR/19
Annex 1
A.1.6
FR/20
Annex 1
A.1.6
“5. Determine Editorial
the minimum
height of the
receiving
antenna”
“5. Determine Editorial
the minimum
height of the
receiving
antenna”
To ensure the validity of the formula in section A1.4
According to Recommendation ITU-R R.526 [5] line-ofsight (LoS) propagation is assumed, i.e. diffraction is
negligible, if there is no obstacle within the first Fresnel
ellipsoid. In order to ensure the validity of the formula in
section A.1.4., the clearance of the first Fresnel ellipsoid
should be ensured If you reduce the height of the receiving
antenna even the Earth's surface may become an obstacle
(see Figure 3).
f
= center measuring frequency in MHz;
Htrans = height of the transmitting antenna in meter;
Hrec = height of the measurement antenna in meter;
R
= separation distance between the transmitter and
the receiver in meter.
The proposal is basically accepted.
However, the words “should be” should
be replaced by “has to be”. The paragraph
would read:
“According to Recommendation ITU-R
R.526 [5] line-of-sight (LoS) propagation
is assumed, i.e. diffraction is negligible, if
there is no obstacle within the first Fresnel
ellipsoid. In order to ensure the validity of
the formula in section A.1.4., the
clearance of the first Fresnel ellipsoid has
to be ensured If you reduce the height of
the receiving antenna even the Earth's
surface may become an obstacle (see
Figure 3).“
All proposals accepted.
Legend of the
formula
below Figure
3
FR/21
Annex 1
A.1.6
“6. Perform a
height scan”
Editorial
This is done by permanently recording the receive field
All proposals accepted.
strength while the mast rises from minimum height defined
in item 5 (or from car roof level) to 10 m above ground.
The path difference of the direct and the reflected signals
varies if the height of the receiving antenna is changed. The
height difference between two adjacent peaks of the signal
is approximately given by:
Δh = ( * R) / (2 * Htrans).

= wavelength in meter;
Htrans = height of the transmitting antenna in meter;
Δh
= height difference between two adjacent peaks in
meter;
R
= separation distance between the transmitter and
the receiver in meter.
9
FR/22
Annex 1
A.1.6
FR/23
Annex 1
A.1.6
FR/24
Annex 1
A.1.6
FR/25
Annex 1
A.1.6
FR/26
FR/27
“7. Determine Editorial
the maximum
field
strength…”
“8. Determine Editorial
the field
strength…”
Determine the minimum field strength adjacent to the
maximum field strength identified in Step 7
This local minimum is hereafter designated Emin. It is not
the overall minimum of the complete height scan, but the
minimum just next to the predetermined Emax. See also
figure 1.
All proposals accepted.
All proposals accepted.
The step 9 contributes to
cancel out the ground effect
and not any other
reflection.
The final magnitude of E is determined according to
section A.1.5. This cancels out the effect of the ground
reflections that may have influenced the measurement
result.
“10.
Calculate the
e.i.r.p”
The purpose of the
Recommendation is the
radiated power and not only
e.i.r.p.
Calculate the radiated power.
All proposals accepted.
The radiated power is calculated by using the free space
propagation formula according to section A.1.4 from the
measured field strength E and the measurement distance R.
General
A.1.6
Annex 1
2nd paragraph General/Technical
A.1.7
Accepted.
“9. Calculate General/Technical
the final
magnitude…”
“11.
Editorial
Calculate and
report the
measurement
uncertainty”
Annex 1
The maximum field strength is designated as Emax.
Depending on reflections, especially from the ground,
Emax must not necessarily be at the maximum antenna
height.
Methods used to calculate the uncertainty from the
experimental observation and input data should be clearly
described. All the uncertainty components and their
assessment should be listed and documented.
The sentence including PN
Scanner is not relevant as
the purpose of the
recommendation is to
deduce a power level of a
signal from a field strength
measurement. The use of a
UMTS PN scanner
provides directly a power
level.
All proposals accepted.
Accepted.
10
FR/28
Annex 1
1st paragraph
Editorial
A.1.8
FR/29
Annex 1
A.1.8
2nd paragraph General
The described method assumes that the main contributor to Accepted.
the measurement uncertainty is caused by reflections, this
is usually the case. Reflections from distant objects may be
minimised by using a measurement antenna with high
directivity or determining a horizontal field strength profile
in addition to the vertical height scan as given in section
A1.6.
The consideration on the
The accuracy of this method depends mainly on the local
First proposal accepted.
expected measurement
circumstances in between the transmitter to be tested and
uncertainty is not relevant
the measurement location.
The complete deletion of the sentence is
since this result has been
not accepted. The uncertainty calculation
achieved on only one type
in section A.1.9 is based on parameters
of equipment (base station)
that are sometimes unknown in practice.
while the described
In these cases the calculations cannot be
methodology may be
accomplished according to this section
applied in a more general
and the reader needs an estimate of the
way.
achievable accuracy. At least an example
should be given. The following text is
proposed:
"The accuracy of this method depends
mainly on the local circumstances in
between the transmitter to be tested and
the measurement location. The following
example may give an impression. Several
1000 measurements at base stations of
mobile phone operators and verifications
using test transmitters with known
parameters have shown a maximum
measurement uncertainty of 3 dB."
11
FR/30
Annex 1
A.1.8
3rd paragraph General
The described method to
check the validity of the
measurement doesn’t allow
to check the accuracy of the
measurement method but
may be used to assess and
to minimize the error in the
measurement due to the
impact of the environment
It is possible to verify the contribution of the spectrum
environment (like the impact of reflexions) on the error of
the measurement. If the location of the transmitter antenna
(roof, mast) is accessible, the general principle outlined as
follows may be applied : a test transmitter with known
parameters (power, antenna gain) is installed close to the
antenna, operating on a free frequency close to the
frequency of the transmitter to be measured. A height scan
of the test transmitter at the predetermined measurement
location is performed and its radiated power is calculated
Moreover, at the end of this using the method described in this document. By
paragraph, it is proposed to comparing the result with the known true radiated power of
draw the attention of the
the test transmitter the additional measurement error for the
reader that additional
particular radio path can be determined. The calculated
uncertainties should be
power of the transmitter to be measured can then be
taken into account due to
corrected by the magnitude of the error. Environmental
uncertainties induced by the effects may be assumed to be “zeroed out” this way. It
test chain.
should be noted that this method may introduce additional
uncertainties in the measurement result as far as the test
transmitter and especially, the used antenna may not be
identical and the frequency is slightly different than those
of the transmitter to be measured. The more such
parameters are close to those of the transmitter to be
measured, the more the uncertainty is negligible.
12
The first proposals are accepted with one
editorial correction.
The last proposal might give the reader the
impression that additional errors are
introduced rather than eliminated. Hence
slight modifications are necessary. The
paragraph should read:
“It is possible to verify the contribution of
the spectrum environment (like the impact
of reflexions) on the error of the
measurement. If the location of the
transmitter antenna (roof, mast) is
accessible, the general principle outlined
as follows may be applied: A test
transmitter with known parameters
(power, antenna gain) is installed close to
the antenna, operating on a free frequency
close to the frequency of the transmitter to
be measured. A height scan of the test
transmitter at the predetermined
measurement location is performed and its
radiated power is calculated using the
method described in this document. By
comparing the result with the known true
radiated power of the test transmitter the
additional measurement error for the
particular radio path can be determined.
The calculated power of the transmitter to
be measured can then be corrected by the
magnitude of the error. Environmental
effects may be assumed to be “zeroed out”
this way. It should be noted that also this
method may introduce uncertainties in the
measurement result. For example, the used
antenna may not be identical and the
frequency is slightly different from those
of the transmitter to be measured. The
more such parameters are close to those of
the transmitter to be measured, the more
the uncertainty is negligible.”
FR/31
Annex 1
1st paragraph
General
“Typical
measurement
uncertainty”
Editorial
A.1.9
FR/32
Annex 1
A.1.9
The legal value of a
measurement is not only
ensured by uncertainty
assessment.
To ensure the reliability of the measurement, the
uncertainty should be calculated. Keeping the previous
chapter in mind a single calculation for the specific test set
used is sufficient in many cases. This is called the typical
measurement uncertainty of the test set.
The “concept” of “average
measurement situation” is
not defined [Which
environment? Which type
of signal? Which frequency
bands...]
A typical measurement uncertainty between 1.5 dB and
2.5 dB for a 95% confident interval can be considered a
good achievement for a field strength measurement system
but can only be achieved when all main contributing error
sources are minimized and when the measurement is
conducted very precisely.
Accepted.
Deletion accepted
Proposal accepted but must read
“confidence”.
13