ETSI TR 102 457 V2.1.0 (2018-09)

TECHNICAL REPORT
Fixed Radio Systems;
Evaluation of the ElectroMagnetic Field (EMF) radiated
by Line-of-Sight (LoS) fixed radio stations using
parabolic dish directional antennas

2 ETSI TR 102 457 V2.1.0 (2018-09)

Reference
RTR/ATTM-0444
Keywords
antenna, DFRS, DRRS, EMF, FWS, radio
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3 ETSI TR 102 457 V2.1.0 (2018-09)
Contents
Intellectual Property Rights . 5
Foreword . 5
Modal verbs terminology . 5
Introduction . 5
1 Scope . 7
2 References . 7
2.1 Normative references . 7
2.2 Informative references . 8
3 Definitions, symbols and abbreviations . 9
3.1 Definitions . 9
3.2 Symbols . 10
3.3 Abbreviations . 11
4 Some properties of fixed radio systems. 12
4.1 General . 12
4.1.1 Frequency bands . 12
4.1.2 Transmit power levels . 12
4.1.3 Antennas . 12
4.1.3.1 Directive antennas . 12
4.1.3.2 Sectorial and omni-directional antennas . 12
4.2 Point-to-point fixed radio stations . 12
4.3 Multipoint fixed radio stations . 13
5 Antenna properties . 13
5.1 Near-field and Far-field concept . 13
5.2 Emission parameters. 14
5.3 Parameter description . 14
5.4 Relationship between parameters (localised SAR, S, E) . 14
5.5 Variation with distance and power . 15
6 EMF exposure limits . 15
6.1 Introduction . 15
6.1.1 Applicability of limits . 15
6.1.2 Applicable frequency bands . 15
6.2 General public exposure . 16
6.3 Occupational exposure . 16
7 Calculations and measurements of power density . 16
7.1 General . 16
7.2 Far-field power density . 17
7.3 Near-field power density . 17
7.4 Power density/electric field upper bound . 18
8 Assessment of compliance to limits . 19
8.1 General . 19
8.2 Compliance boundaries evaluation . 19
8.3 Tabulated values . 22
8.4 Examples for equipment with different antenna size. 23
Annex A: Power density calculations . 27
A.1 Near-field calculations using the Fresnel transform . 27
A.1.0 Introduction . 27
A.1.1 Region of validity . 27
A.1.2 Scaling factors . 27
A.1.3 Electric field calculation . 28
A.1.4 Results . 28
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4 ETSI TR 102 457 V2.1.0 (2018-09)
A.1.4.0 General trend . 28
A.1.4.1 High frequency approximation . 29
A.1.4.2 Results using realistic tapers . 29
Annex B: Simulations and measurements . 32
B.1 Simulations and measurements of a 0,24 m 38 GHz antenna . 32
B.1.1 FEKO™ simulations of a 0,24 m 38 GHz antenna . 32
B.1.1.1 Physical layout of the antenna . 32
B.1.1.2 On-axis results . 33
B.1.1.3 Off-axis results . 33
B.1.2 Measurements . 34
B.1.2.1 Test setup . 34
B.1.2.2 On-axis results . 35
B.1.2.3 Off-axis results . 35
B.1.3 Conclusions . 36
B.2 Simulations and measurements of a 0,6 m 8,1 GHz antenna . 36
B.2.1 Simulation model and test device . 36
B.2.2 Measurement setup . 36
B.2.3 Measurement results . 38
B.2.3.1 Measurement result with absorber . 38
B.2.3.2 Measurement result without absorber . 38
B.2.4 Comparison of measurement and simulation . 39
B.2.5 Conclusions . 40
B.3 Investigation on antennas from 5 to 38 GHz . 40
B.3.1 Detailed analysis of a 7 GHz antenna (2 feet) and a 19 GHz antenna (1 foot) . 40
B.3.1.1 Description of test cases . 40
B.3.1.2 Simulations . 41
B.3.1.3 Simulation results . 42
B.3.1.4 Measurement setup . 43
B.3.1.5 Measurement results . 44
B.3.1.6 Evaluation of the factor F . 45
B.3.1.7 Conclusions. 45
B.3.2 Power density measurement on the axis . 45
B.3.2.0 Introduction. 45
B.3.2.1 Description test cases . 46
B.3.2.2 Description of the envelope template. 46
B.3.2.3 Measurement and calculation results on the axis using inner diameter . 47
B.3.2.4 Proposal of envelope template using outer diameter . 47
B.3.3 Conclusions . 48
B.4 Simulations using SRSR tool on 8 GHz and 13 GHz antennas. 48
B.4.1 SRSR . 48
B.4.2 Factor F, peak to average ratio . 48
B.4.3 Antenna data . 49
B.4.4 Simulation results 8 GHz . 50
B.4.5 Simulation results 13 GHz . 53
B.4.6 Modified FCC model. 55
B.4.7 SRSR results versus the new envelope template . 55
B.4.7.1 8 GHz and 13 GHz antennas . 55
B.4.7.2 New 8 GHz 1,2 m diameter antennas . 56
B.4.7.3 Focal distance parametric analysis with new 8 and 13 GHz 1,2 m diameter antennas . 57
Annex C: Rationale for equivalence of SAR (BR/ELV) to E or S (RL/AL) between 1,3 GHz
and 10 GHz . 59
Annex D: Bibliography . 60
History . 61

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5 ETSI TR 102 457 V2.1.0 (2018-09)
Intellectual Property Rights
Essential patents
IPRs essential or potentially essential to normative deliverables may have been declared to ETSI. The information
pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found
in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in
respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web
server (https://ipr.etsi.org/).
Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee
can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web
server) which are, or may be, or may become, essential to the present document.
Trademarks
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ETSI claims no ownership of these except for any which are indicated as being the property of ETSI, and conveys no
right to use or reproduce any trademark and/or tradename. Mention of those trademarks in the present document does
not constitute an endorsement by ETSI of products, services or organizations associated with those trademarks.
Foreword
This Technical Report (TR) has been produced by ETSI Technical Committee Access, Terminals, Transmission and
Multiplexing (ATTM).
Modal verbs terminology
In the present document "should", "should not", "may", "need not", "will", "will not", "can" and "cannot" are to be
interpreted as described in clause 3.2 of the ETSI Drafting Rules (Verbal forms for the expression of provisions).
"must" and "must not" are NOT allowed in ETSI deliverables except when used in direct citation.
Introduction
The protection of the general public and workers from Electromagnetic Fields (EMF) is subject of EU and national
regulations.
Basic information is generally taken from ICNIRP guidelines [i.6], while EU regulations setting harmonised exposure
limits are provided in Council Recommendation 1999/519/EC [i.2] for general public and 2013/35/EU Directive [i.3]
for workers.
EU member states may set more restrictive national limits for the general public, which will prevail on the EU ones;
information on such national limits may be found in a European Commission implementation report [i.5].
EU RF exposure limits are expressed in terms of Basic Restrictions (BR, for general public) or Exposure Limitation
Values (ELV, for workers); the entity placing the EMF transmitting equipment on the market and the entity putting it
into in the affected environment (either with specific field tests or other specific protection measures) are assessing
compliance of RF exposure with the limits defined in the above mentioned EU Recommendation and Directive.
However, RF exposure assessment based on BR/ELV may be complex, for example when Specific Absorption Rate
(SAR) needs to be measured below 10 GHz (for general public) or 6 GHz (for workers); therefore, both EU
Recommendation [i.2] and Directive [i.6] have defined limits in terms of Reference Levels (RL, for general public) or
Action Levels (AL, for workers) which are more easily tested/calculated Electric field (E) and/or Power density (S);
they indicate that, whenever they are satisfied, also the BR/ELV are fulfilled.
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6 ETSI TR 102 457 V2.1.0 (2018-09)
One possible approach to the problem, according the EC Non-binding guide [i.4], is to test or calculate a conservative
volume (compliance boundary) around the EMF source where the RL/AL limits are certainly respected; therefore, the
need for EMF assessment of BR/ELV is limited only inside that volume, if accessible by general public or by workers.
Radio equipment are subject to 2014/53/EU Directive [i.1], which article 3.1a) requires self declared assessment also
the "health" of persons; this might include considerations about the evaluation of the impact of the EMF radiated
through the connected antenna based on the above RL or AL limits.
Assessment to article 3.1a of the 2014/53/EU Directive [i.1] of equipment in the scope of the present document may be
carried on based on harmonised standards CENELEC EN 50385 [i.9] for placing equipment on the market and
CENELEC EN 50401 [i.8] for putting them into service. Both harmonised standards rely on CENELEC EN 62232 [i.7]
basic standard that provides the appropriate RF exposure assessment methods.
In case the radio equipment is supplied also with the antenna (or the manufacturer specifies the antenna characteristics
to be connected to the equipment, as it is often the case for fixed service radio systems) the manufacturer might consider
to calculate the above described compliance boundary within the technical documentation in support of the DoC to
2014/53/EU Directive [i.1] as support for the customer's further RF exposure assessment.
The present document describes one methodology for assessing that compliance boundary when the antenna of the
fixed service radio system uses conventional passive directional antennas (parabolic dish).

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7 ETSI TR 102 457 V2.1.0 (2018-09)
1 Scope
The present document provides guidelines for assessing the compliance of human exposure to established RF exposure
limits based on the evaluation of the electromagnetic fields in the main beam emission of fixed service radio (base)
stations when operating in line-of-sight (LoS) using directional parabolic (dish) antennas (e.g. in Point to Point
applications). The methodology may be applicable also to other fixed radio stations provided that they use similar
directional parabolic antenna type (e.g. for some terminals in Point to Multipoint and Multipoint to Multipoint systems).
Fixed radio stations using sector and omni-directional antennas are not in the scope of the present document.
Fixed service radio stations in the scope of the present document may use integral/integrated antennas or dedicated
antennas, supplied by the same manufacturer, or stand-alone antennas from different manufacturer, but compliant to
radio equipment manufacturer specifications; detailed definition of those antenna types are found in ETSI
EN 302 217-1 [i.10].
Article 3.1a of the 2014/53/EU Directive [i.1], provides essential requirement for health and safety. Council
Recommendation 1999/519/EC [i.2] (for general public) and Directive 2013/35/EU (for workers) gives recommended
limits for exposure to electromagnetic fields based on the ICNIRP guidelines [i.6]. Assessment of compliance to
article 3.1a of the 2014/53/EU Directive [i.1] of equipment in the scope of the present document and to the requirements
defined in the Directive 2013/35/EU [i.3] (for workers) and Council Recommendation 1999/519/EC [i.2] (for general
public) may be carried on based on harmonised standards CENELEC EN 50385 [i.9] for placing equipment on the
market and CENELEC EN 50401 [i.8] for putting them into service.
The present document considers these exposure limits for comparison; calculations and measurements are reported. The
guidelines presented may be used for calculation of the compliance boundaries as required by CENELEC
EN 50385 [i.9] and CENELEC EN 50401 [i.8].
The simplified assessment method described is derived from measurement and calculation techniques defined in
clause 8 of CENELEC EN 62232 [i.7] (see note) and may help in the compliance assessment of the above mentioned
fixed service radio stations.
Definitions from the above mentioned EN standards are used in the present document where appropriate.
NOTE: CENELEC EN 62232 [i.7] considers a very broad types of radio antennas used in Base Stations
(including Fixed Radio Stations) and is presently limited to 100 GHz; however, in specific case of
parabolic (dish) antennas, the electromagnetic field generation is dominated by purely geometrical factors
(related to the D/λ ratio); therefore, the methodology in the present document is considered applicable
also to fixed service stations operating at higher frequency up to 300 GHz.
The maximum electric field or power density evaluation is based on calculations and measurements performed with the
most common configurations and the values are tabulated. The measurement and calculation results on real systems that
have been used to establish the method are also provided to give an estimation on the accuracy of the method adopted.
2 References
2.1 Normative references
Normative references are not applicable in the present document.
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8 ETSI TR 102 457 V2.1.0 (2018-09)
2.2 Informative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are not necessary for the application of the present document but they assist the
user with regard to a particular subject area.
[i.1] Directive 2014/53/EU of the European Parliament and of the Council of 16 April 2014 on the
harmonisation of the laws of the Member States relating to the making available on the market of
radio equipment and repealing Directive 1999/5/EC.
[i.2] Council Recommendation 1999/519/EC of 12 July 1999 on the limitation of exposure of the
general public to electromagnetic fields (0 Hz to 300 GHz).
[i.3] Directive 2013/35/EU of the European Parliament and of the Council of 26 June 2013on the
minimum health and safety requirements regarding the exposure of workers to the risks arising
from physical agents (electromagnetic fields) (20th individual Directive within the meaning of
Article 16(1) of Directive 89/391/EEC) and repealing Directive 2004/40/EC.
[i.4] Non-binding guide to good practice for implementing Directive 2013/35/EU Electromagnetic
Fields: Volume 1 - Practical guide.
NOTE: Available at http://ec.europa.eu/social/main.jsp?catId=738&langId=en&pubId=7845.
[i.5] Report from the Commission on the application of Council Recommendation of 12 July 1999
(1999/519/EC) on the limitation of the exposure of the general public to electromagnetic fields
(0 Hz to 300 GHz) - Second Implementation report 2002-2007.
NOTE: Available at http://eur-lex.europa.eu/legal-content/EN/TXT/?uri=celex%3A52008DC0532.
[i.6] ICNIRP Guidelines for Limiting Exposure to Time-Varying Electric, Magnetic and
Electromagnetic Fields (up to 300 GHz), Health Physics April 1998, Volume 74,
Number 4:494-522.
[i.7] CENELEC EN 62232 (2017): "Determination of RF field strength, power density and SAR in the
vicinity of radiocommunication base stations for the purpose of evaluating human exposure".
[i.8] CENELEC EN 50401 (2017): "Product standard to demonstrate the compliance of base station
equipment with radiofrequency electromagnetic field exposure limits (110 MHz - 100 GHz), when
put into service".
[i.9] CENELEC EN 50385 (2017): "Product standard to demonstrate the compliance of base station
equipment with radiofrequency electromagnetic field exposure limits (110 MHz - 100 GHz), when
placed on the market".
[i.10] ETSI EN 302 217-1: "Fixed Radio Systems; Characteristics and requirements for point-to-point
equipment and antennas; Part 1: Overview, common characteristics and system-independent
requirements".
[i.11] ETSI EN 302 326-2: "Fixed Radio Systems; Multipoint Equipment and Antennas; Part 2:
Harmonised Standard for access to radio spectrum".
[i.12] ETSI TR 102 243-1: "Fixed Radio Systems; Representative values for transmitter power and
antenna gain to support inter- and intra-compatibility and sharing analysis; Part 1: Digital
point-to-point systems".
[i.13] R. C. Hansen; L. F. Libelo: "Rapid Calculation of Near-field Fluence of High Power Microwave
Antennas". IEEE Transact. EMC Year: 1992, Volume: 34, Issue: 3.
[i.14] C. Balanis: "Advanced engineering electromagnetics", ISBN: 978-0-470-58948-9.
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9 ETSI TR 102 457 V2.1.0 (2018-09)
[i.15] E.V. Jull: "Aperture Antennas and Diffraction Theory". IEEE Electromagnetic Waves Series
ISBN: 978-0906048528.
[i.16] R. C. Hansen: "Circular-Aperture Axial Power Density". Microwave Journal (vol. 19, pp. 50-52,
February 1976).
[i.17] R. W. Bickmore and R. C. Hansen: "Antenna Power Densities in the Fresnel Region". Proceedings
IRE, vol. 47, pp. 2119-2120, 1959.
[i.18] ETSI EG 202 373: "Electromagnetic compatibility and Radio spectrum Matters (ERM); Guide to
the methods of measurement of Radio Frequency (RF) fields".
3 Definitions, symbols and abbreviations
3.1 Definitions
For the purposes of the present document, the following terms and definitions apply:
action level (AL): action levels are provided for practical exposure-assessment purposes to establish boundaries, within
which the Exposure Limits Values (ELV) are satisfied
NOTE: AL notation used is used in Directive 2013/35/EU [i.3], while "reference level" (RL) notation is used with
similar meaning in Recommendation 1999/519/EC [i.2].
antenna: device that serves as a transducer between a guided wave (e.g. coaxial cable) and a free space wave, or vice
versa
antenna gain: ratio of the maximum radiation intensity from an (assumed lossless) antenna to the radiation intensity
that would be obtained if the same power were radiated isotropically by a similarly lossless antenna
Base Station (BS): fixed equipment including the radio transmitter and associated antenna(s) as used in wireless
telecommunications networks (CENELEC EN 50385 [i.9])
basic restrictions (BR): lawful limit for general public exposure to time-varying electric, magnetic, and
electromagnetic fields (EMF) that are based directly on established health effects and biological considerations
NOTE: Basic restriction (BR) notation is used in Recommendation 1999/519/EC [i.2], while "Exposure Limits
Values" (ELV) notation is used in Directive 2013/35/EU [i.3] with similar meaning.
compliance boundary: volume outside which any point of investigation is deemed to be compliant with the RL or AL
exposure limits
NOTE: Outside the compliance boundary, the exposure levels do not exceed the basic restrictions (BR) or
exposure limit values (ELV) irrespective of the time of exposure.
dish antenna: parabolic antenna usually used for radio-relays or point-to-point communications
Electric field strength (E): magnitude of a field vector at a point that represents the force (F) on a positive small
charge (q) divided by the charge
NOTE 1: Electric field strength is expressed in units of volt per metre (V/m).
NOTE 2: RL (for general public) and AL (for workers) are defined in term of E limits. Above 10 MHz (for general
public) and above 6 GHz (for workers), alternative equivalent S limits are also defined.
Equipment Under Test (EUT): device (such as transmitter, base station or antenna as appropriate) that is the subject
of the specific test investigation being described
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10 ETSI TR 102 457 V2.1.0 (2018-09)
Equivalent Isotropically Radiated Power (EIRP): product of the power supplied to the antenna and the maximum
antenna gain relative to an isotropic antenna
NOTE: EIRP = G * P
where:
P is the emitted power;
G is the maximum gain of the antenna relative to an isotropic antenna.
Exposure Limit Values (ELV): lawful limit for workers exposure to EMF, established on the basis of biophysical and
biological considerations
NOTE 1: ELV notation is used in Directive 2013/35/EU [i.3], while "basic restriction" (BR) notation is used in
Recommendation 1999/519/EC [i.2] with similar meaning.
NOTE 2: Same as note 2 to the definition of basic restriction (BR) above.
fixed radio station: radio station used for systems in the Fixed Service; typically for PP or Multipoint systems and
included in the broader term "Base Station" in CENELEC EN 50385 [i.9]
parabolic antenna: See dish antenna.
Point Of Investigation: location in space at which the value of E-field, H-field, Power flux density or SAR is evaluated
NOTE: This location is defined in cartesian, cylindrical or spherical co-ordinates relative to the reference point on
the EUT.
Power flux density (S): power per unit area normal to the direction of electromagnetic wave propagation
NOTE 1: Lawful limits are expressed in S values above 10 GHz (for general public) or above 6 GHz (for workers).
NOTE 2: AL (for workers above 6 GHz) and RL (for general public) are defined in term of S limits. Alternative
equivalent E limits are also defined.
Reference Level (RL): reference levels are provided for practical exposure-assessment purposes to establish
boundaries, within which the relevant basic restriction (BR) are satisfied
NOTE: reference level (RL) notation is used in Recommendation 1999/519/EC [i.2], while Action Level (AL)
notation is used, with similar meaning, in Directive 2013/35/EU [i.3].
Specific Absorption Rate (SAR): time derivative of the incremental energy (dW) absorbed by (dissipated in) an
incremental mass (dm) contained in a volume element (dV) of given mass density (ρ)

d dW d dW 


 
NOTE 1: SAR = =
 
dt dm dt  ρdV
SAR is expressed in units of watt per kilogram (W/kg).
NOTE 2: SAR can be calculated by:
σ E
i
SAR =
ρ
where:
E is rms value of the electric field strength in the tissue in V/m
i
σ is conductivity of body tissue in S/m (e.g. ICNIRP [i.6] assumes a typical value of 0,2 S/m)
3 3
ρ is density of body tissue in kg/m (typically about 1 000 kg/m ).
NOTE 3: Lawful limits are expressed in SAR values up to 10 GHz (for general public) or up to 6 GHz (for
workers).
3.2 Symbols
For the purposes of the present document, the following symbols apply:
ξ Normalized variable for the antenna radius ξ ∈ (0,1)
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11 ETSI TR 102 457 V2.1.0 (2018-09)
γ Factor for spatial averaging
λ Wavelength (m)
η Antenna aperture efficiency (see annex A, equation A.5)
Α
a Radius of the antenna (m), a=D/2
A Geometric antenna aperture (m )
A Equivalent antenna aperture (m )
e
A Reference area 20 cm for spatial averaging
CD Compliance distance (to the AL or in the line of sight
los
Din Inner diameter of the antenna (m)
Dout Outer diameter of the antenna (m)
E Electromagnetic field (V/m)
E Electromagnetic field limit value (V/m) of AL (for general public) or RL (for workers)
lim
F Peak to average factor of the power density (S)
G Antenna gain
m Reference mass 10 g for spatial averaging (expressed in kg)
P Power transmitted by the antenna
r Distance between the point of investigation and the antenna
NOTE: Some figures in the annexes the notation "z" is alternatively used and in some phormulas the alternatively
notation ρ is alternatively used.
R Far-field distance
ff
NOTE: Some figures in the annexes the notation r is alternatively used.
FAR
R Extension of compliance boundary
lim
rms root mean square
S Power density (W/m ) at distance r (m) from the antenna
NOTE: Not to be confused with "S" abbreviation of the unit "Siemens" used as S/m in conductivity (σ).
S Power density at a distance R from the antenna
ff ff
S Power flux density limit value (W/m ) of AL (for general public) or RL (for workers)
lim
S Maximum power density (W/m ) spatially averaged over 20 cm
max
S Power density normalized to P/D
n
SAR Specific Absorption Rate (W/kg) on 10g contiguous tissue; lawful limit value
lim10g
x Normalised distance (Ratio of distance to the antenna (r) and Rff)
z See r
3.3 Abbreviations
For the purposes of the present document, the abbreviations apply:
AL Action Level
BR Basic Restriction
BS Base Station
CAD Computer Aided Design
EIRP Equivalent Isotropically Radiated Power
ELV Exposure Limit Value
EMC ElectroMagnetic Compatibility
EMF ElectroMagnetic Field
EUT Equipment Under Test
FCC Federal Communications Commission
MMF Mobile Manufacturers Forum (MMF)
st
NOTE: From Jan 1 2017 changed into Mobile & Wireless Forum (MWF).
MoM Method of Moments
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12 ETSI TR 102 457 V2.1.0 (2018-09)
RF Radio Frequency
RL Reference Level
SAR Specific Absorption Rate
4 Some properties of fixed radio systems
4.1 General
4.1.1 Frequency bands
Frequency bands for the fixed radio systems range from about 1,3 GHz up to 86 GHz and beyond. Details are given in
ETSI EN 302 217-1 [i.10] and ETSI EN 302 326-2 [i.11].
4.1.2 Transmit power levels
Transmit power levels are in general determined by EIRP restrictions or power flux density restrictions. Thus the
restrictions are placed for a combination of both transmit power and antenna gain. Representative values can be found
in ETSI TR 102 243-1 [i.12].
Licensed EIRP is generally regulated on link-by-link basis through Remote Transmit Power Control (RTPC)
functionality; however, when generic equipment assessment for article 3.1a of the 2014/53/EU Directive [i.1] is
concerned (i.e. for placing equipment on the market through application of CENELEC EN 50385 [i.9]) the maximum
EIRP delivered by the equipment through the highest foreseen antenna gain may be used for defining the safeguard
boundaries valid for all stations.
When put into service (i.e. through application of CENELEC EN 50401 [i.8]) the actual licensed EIRP (including any
positive tolerance, if any) could be used; however, the real field conditions should also be considered (e.g. presence of
more than one systems in the same location).
4.1.3 Antennas
4.1.3.1 Directive antennas
This class of antennas are generally used to send and/or receive a signal from a single location.
The most common antenna type is a parabolic dish antenna. Prominent characteristics are high directivity and low
radiation outside the main beam direction.
For the purpose to calculate the maximum power flux density from these antennas only a few parameters are needed
like transmitted power, frequency, antenna diameter, aperture efficiency and antenna gain.
4.1.3.2 Sectorial and omni-directional antennas
Sectorial and omni-directional antennas are not in the scope of the present document.
4.2 Point-to-point fixed radio stations
Point-to-point fixed radio stations , similarly to macro-cells base stations in mobile systems, are installed in towers,
masts, on rooftops or in similar locations. The main design criteria consists in having the two corresponding locations in
line of sight, so there is no possibility that some building be "crossed" by the radio signal, since, in such case, an
attenuation would be produced and the connection would not work properly.
Outdoor units and antennas are normally required to be inaccessible by the general public to prevent intentional or
unintentional damage to the equipment or to the radio link.
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13 ETSI TR 102 457 V2.1.0 (2018-09)
The above situation establishes a special condition for these systems: unavailability of the radio path for the general
public. Nevertheless, care should be taken (see note) when very short links are deployed at street level (i.e. buildings
might be immediately beyond the receiver station).
NOTE: In literature, some systems (e.g. high power radars) have an obstruction avoidance mechanism which will
immediately (i.e. within less than 1 s) stop the transmission if a person is staying in the main lobe of the
antenna. Such mechanism, might also be taken into account when appropriate.
4.3 Multipoint fixed radio stations
Multipoint communication systems are communication systems between multiple (source) terminal stations access
points and a single (destination) base station access point for bi-directional asymmetric, bi-directional symmetric, or
unidirectional communication.
Base stations for multipoint fixed radio systems, not in the scope of the present document, are installed in towers, masts,
on rooftops or in similar locations.
Terminal stations, in the scope of the present document when using directional parabolic-like antennas, are considered
similar to point-to-point stations and can be deployed in similar conditions.
5 Antenna properties
5.1 Near-field and Far-field concept
A very common subdivision of the space surrounding an antenna consists in defining two regions of space, called
"near-field" and "far-field".
Although there are not sharp boundaries between these regions, the near-field is the region of space nearest to the
antenna, where the wave is still nearly plane, like in the aperture. The "far-field" region is assumed to start in a location
of the space, where the wave can be considered as a spherical wave and free space conditions can be adopted.
For the parabolic reflector, a common shape of reflector that is frequently met on microwave antennas, the lower
boundary of near-field region is situated at a distance R from the antenna given by the formula R = D²/2λ (called
nf nf
Rayleigh distance), where D, R and λ are respectively the antenna diameter, the near-field distance and the
nf
wavelength. At this distance the degradation of the main beam is moderate low, but the gain is reduced.
), is assumed at a distance equal to
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