TEC-Test Procedure EMF Measurement of Base Station

Issue-SEP 2009

Test Procedure for

Measurement of Electromagnetic Fields

from Base Station Antenna

(For Telecommunication Sector)'

No: TEC/TP/EMF/OOl/Ol.SEP 2009

©TEC

TELECOMMUNICATION ENGINEERING CENTRE

KHURSHID LAL BHAVAN, JANPATH

NEW DELHI-IIOOOI

INDIA

l rights reserved and no part of this publication may be reproduced, stored in a retrIeval:tem or transmitted, in any form or by any means, electronic, mechanical,Jtocopying, recording, scanning or otherwise without written permission from thelecommunication Engineering Centre New Delhi.

Contents

CI. No.TopicPage

No.1Scope 1

2

References 13

Compliance Requirement 1

4EMF exposure zones. 3

5Exposure Level Assessment 3

6

The installation classification scheme 4

7Procedure for determining installation class 4

8EMF evaluation techniques 5

9

Calculation Methods 7

9.1

Prediction of RF Fields 7

9.1.1Equations for Predicting RF fields 7

9.1.2

Field regions 8

9.1.3

Computation for Compliance with Exposure9Limits

9.1.4Calculation of Exclusion Zone Distance 11

9.2Determination of E1RPth 12

9.2.1Accessibility categories 12

9.2.2Antenna directivity categories 15

9.2.3

The exclusion area 17

10Field Measurement Approaches 18

10.1Test Instruments Required 20

10.2

Calibration of instruments 21

10.3Check points before Measurement 21

10.4Functional tests for measuring instruments 23

10.5

Measurement Results 23

Appendix 'A'

EMF MEASUREMENTS 24-- Appendix 'B' Examples of EIRP th calculation 29

,Appendix 'e' TERMS AND DEFINITIONS 37

Test Procedure for Measurement of Electromagnetic Field Strengthfrom Base station Antennas

1. Scope

The document describes the test procedure for the measurement of electromagnetic fieldsfrom telecom base stations in GSM, CDMA, W-CDMA, 3 G and Wi-Max etc.environment. The main aim of the measurement is to confirm the compliance of basestation installation as per ICNIRP guidelines limits. Hence the measuring instrumentsshall have the capability to average the measurements over any period of six minutes andalso other conditions as per the ICNIRP guidelines. This document aims to help withcompliance of telecommunication installations with safety limits for human exposure toelectromagnetic fields (EMFs) produced by telecommunication equipment.

The test procedure will comply with ITU-T Recommendations K.52 (2004): "Guidance

on complying with limits for human exposure to electromagnetic fields" and K.61 (2003),

"Guidance to measurement and numerical prediction of electromagnetic fields for

compliance with human exposure limits for telecommunication installations". Each

service provider will establish necessary infrastructure for self- monitoring, self-testing

and for auditing of EMF measurement for complying with emission limits as per

ICNIRP guidelines.

2. References

The following ITU-T Recommendations:

ITU-T Recommendation K.52 (2004), Guidance on complying with limits forhuman exposure to electromagnetic fields.

ITU-T Recommendation K.61 (2003), Guidance to measurement and numericalprediction of electromagnetic fields for compliance with human exposure limitsfor telecommunication installations.

3.. Compliance Requirement

The Government has adopted ICNIRP guidelines for limiting exposure to time varyingelectric, magnetic and electromagnetic fields in telecom sector in India. The values ofEMF exposure limits to be complied with are provided in Table. 1

Table 1 - ICNIRP reference levels (unperturbed rms values)

Type of FrequencyElectric fieldMagnetic fieldEquivalent Planeexposure

rangeStrengthStrength (Aim)Wave power(Vim)

Density Seq(W1m2)

Up to 1 Hz

-2xl0:l -1-8 Hz

200002x105 If' -Occupational

8-25 Hz200002x104 If-exposure

0.025-0.82 kHz500/f20/f -0.82-65 kHz

61024.4 -0.065-1 MHz

6101.6/f -1-10 MHz

610/f1.6/f -10-400 MHz

610.16 10400-2000 MHz

3f y,0.008f Ylf/402-300 GHz

1370.36 50General

Up to 1 Hz-2x104 -public

1-8 Hz100002xl04 If -8-25 Hz

100005000/f -0.025-0.8 kHz

250/f4/f -0.8-3 kHz

250/f5 -3-150 kHz

875 -0.15-1 MHz

870.73/f -1-10 MHz

87/f y,0.73/f -10-400 MHz

280.073 2400-2000 MHz

1.375f y.0.0037(/·f/2002-300 GHz

610.16 10

NOTE 1 - f is as indicated in the frequency range column. NOTE 2- For frequencies between 100 kHz and 10GHz, the averaging time is 6 minutes.NOTE 3- For frequencies up to 100 kHz, the peak values can be obtained by multiplyingthe rms value by..J2 (=1.414). For pulses of duration tp, the equivalent frequency to applyshould be calculated as f = 1/(2 tp).NOTE 4 -Between 100 kHz and 10 MHz, peak values for the field strengths are obtainedby interpolation from the 1.5-fold peak at 100 MHz to the 32-fold peak at 10 MHz. Forfrequencies exceeding 10 MHz, it is suggested that the peak equivalent plane-wave powerdensity, as averaged over the pulse width, does not exceed 1000 times the Seq limits, orthat the field strength does not exceed the field strength exposure levels given in thetable.NOTE 5- For frequencies exceeding 10 GHz, the averaging time is 68/f 1.05 minutes (f inGHz).

2

4. EMF exposure zones.EMF exposure assessment is made if the intentional emitters are present, and conducted

for all locations where people might be exposed to EMF in course of their normal

activities. All such exposures to EMF pertain to one of these three zones (See Figure

below):

I) Compliance zone: In the compliance zone, potential exposure to EMF isbelow the applicable limits for both controlled/occupational exposure anduncontrolled/general public exposure.

2) Occupational zone: In the occupational zone, potential exposure to EMF isbelow the applicable limits for controlled/occupational exposure but exceedsthe applicable limits for uncontrolled/general public exposure.

3) Exceedance zone: In the exceedance zone, potential exposure to EMFexceeds the applicable limits for both controlled/occupational exposure anduncontrolled/general public exposure ..

Compliance zone

Figure 1 - Figurative illustration of exposure zones

5. Exposure level assessment

The assessment of the exposure level shall consider:• the worst emission conditions;

• the simultaneous presence of several EMF sources, even at different frequencies.The following parameters should be considered:

• the maximum EIRP of the antenna system (see definition: Equivalent IsotropicRadiated Power (EIRP));

NOTE - Maximum EIRP should be calculated for mean transmitter power. Forthe majority of sources, the mean transmitter power is the nominal (rated)transmitter power.

3

• the antenna gain G (see definition: antenna gain) or the relative numeric gain F(see definition: relative numeric gain), including maximum gain and beam width;

• the frequency of operation; and

• various characteristics of the installation, such as the antenna location, antennaheight, beam direction, beam tilt and the assessment of the probability that aperson could be exposed to the EMF.

To manage the procedure and these parameters, the following classification scheme isintroduced.

6. The installation classification scheme

Each emitter installation should be classified into the following three classes:

1) Inherently compliant: Inherently safe sources produce fields that comply withrelevant exposure limits a few centimetres away from the source. Particularprecautions are not necessary.

2) Normally compliant: Normally compliant installations contain sources thatproduce EMF that can exceed relevant exposure limits. However, as a result ofnormal installation practices and the typical use of these sources forcommunication purposes, the exceedance zone of these sources is not accessibleto people under ordinary conditions. Examples include antennas mounted onsufficiently tall towers or narrow-beam earth stations pointed at the satellite.Precaution may need to be exercised by maintenance personnel who come intothe close vicinity of emitters in certain normally compliant installations.

3) Provisionally compliant: These installations require special measures to achievecompliance.

7. Procedure for determining installation class

It is expected that operators providing a particular telecommunication service use alimited set of antennas and associated equipment with well-defined characteristics.

Furthermore, installation and exposure conditions for many emitter sites are likely to besimilar. Therefore, it is possible to defme a set of reference configurations, referenceexposure conditions and corresponding critical parameters that will enable convenientclassification of sites.

A useful procedure is as follows:

I) Define a set of reference antenna parameters or antenna types. These categoriescan be customized to the types of emitters used for the particular application.

2) Define a set oLaccessibility conditions. These categories depend on theaccessibility of various areas in the proximity of the emitter to people. Thesecategories can be customized to the most commonly occurring installationenvironment for the particular service or application.

4

3) For each combination of reference antenna parameters and accessibilitycondition, detennine the threshold EIRP. This threshold EIRP, which will bedenoted as EIRPth, is the value that corresponds to the exposure limit for thepower density or field from the reference antenna for the accessibility condition.The determination may be performed by calculation or measurements.

4) An installation source belongs to the inherently compliant class if the emitter isinherently compliant (as defined above). There is no need to consider otherinstallation aspects.

NOTE - An inherently compliant source for ICNIRP limits has EIRP less than 2W.

5) For each site, an installation belongs to the normally compliant class, if thefollowing criterion is fulfilled:

L EIRP; ~l. EIRP.th iI ,

where EIRPj is the temporal averaged radiated power of the antenna at aparticular frequency i, and EIRPth,iis the EIRP threshold relevant to the particularantenna parameters and accessibility conditions. For a multiple-antennainstallation, the following two conditions need to be distinguished:

• If the sources have overlapping radiation patterns as determined byconsidering the half-power beam width, the respective maximum timeaveraged EIRP should satisfy the criterion.

• If there is no overlap of the multiple sources, they shall be consideredindependently.

6) Sites that do not meet the conditions for normally compliant classification areconsidered provisionally compliant.

For sites where the application of these categories is ambiguous, additional calculations

or measurements will need to be performed.

8. EMF evaluation techniques

Evaluation of EMF for telecommunication installations can·be done by following

techniques:

(i) Calculation MethodFollowing two methods are being prescribed. Either of which could be used

for predicting compliance to the radiation limits.

(a) Prediction ofRF Fields.(b) Calculation Method for determination of EIRPth

(ii) Field Measurement Approach.

A flow chart of the exposure assessment for single EMF source of a telecommunication

installation is given in Figure 2.

5

Exposure MeasurementProcedure

InherentlyComoliant

Assessment

procedure not

required

Determine the appropriateEMF limits.

Determine

EIRPth

ProvisionallyCompliant

Determine exposure zone.

No further precautions areneeded

Normally

Compliant

Yes

Freauencv

Accessibilitv

Directivitv

Protection measures or

further measurement

not required

Analytical Methods,

Numerical Methods,Field Measurements

Mitigation

Techniques

Figure 2 : Flowchart of assessment of EMF exposure

as per ITU- T K.526

,r

9. Calculation MethodsThe material in this section is designed to provide assistance in determining whether agiven facility would be in compliance with ICNRlP guidelines for human exposure to RFradiation. The calculation methods discussed below should be helpful in evaluating aparticular exposure situation. '

9.1 Prediction ofR.F. Fields

9.1.1 Equations for Predicting RF fields. ,The geometry for calculating exposure at the ground level due to an elevated antenna is shown inFigure 3.

2m

Figure 3: Sample configuration for calculating exposure at ground level

An antenna is installed so that the centre of radiation is at the height habove the ground.The goal of the calculation is to evaluate the power density at a pOInt 2 m above theground (approximate head level) at a distance x from the tower. In this example the mainbeam is parallel to the ground and the antenna gain is axially symmetrical(omnidirecti anal).

t13 simplify the foregoing, define h' = h - 2 [mJ. Using trigonometry,

, 'R2 = h,2 +x2

e=tan-t~)Taking into account reflections from the ground, the power density becomes:

S = 2.56 F(B) ElRP41l' x2+h'2

The factor of 2.56 may be replaced by 4 considering 100 % reflection. F(e) is relative gain ofantenna at a given angle. This parameter should be obtained from Antenna Data Sheet, In theabsence of this parameter value, it may be taken as 1. The equation is thus modified as below:

7

9.1.2 Field regions

The properties of EM Fields need to be taken into consideration for their measurementand evaluation. For example:

.• measurement of both the electric and magnetic components may be necessary inthe non-radiating near field region;

• for numerical prediction: the far-field model usually leads to an overestimation ofthe field if applied in near field regions.

Therefore, it is important to be aware of the boundaries of each field region beforestarting a compliance procedure..

9.1.2.1 Near Field Regioni) Reactive near-field zone: It is immediately surrounding the antenna wherereactive field predominates and typically extends to a distance of one wavelengthfrom the antenna. For compliance with the safe exposure limits, measurement ofboth E & H components, or evaluation of SAR is required in this region.

ii) Reactive - radiating near-field region' .The transitional.region wherein the radiating field is beginning to be importantcompared with the reactive component. This outer region extends to a few (e.g.,

3A.) wavelengths from the electromagnetic source. For compliance with the safeexposure limits, measurement of both E & H components or evaluation of SAR isrequired in this region.

iii) Radiating near-tield (Fresnel) zoneThe region of the field of an antenna between the reactive near-field and the far-field region and wherein the radiation field predominates. Here, the electric andmagnetic components can be considered locally normal; moreover the ratio E(Hcan be assumed constant (and almost equal to 20, the intrinsic impedance of free

space). This region exists only if the maximum dimension D of the antenna islarge compared with the wavelength A.. For compliance with the safe exposurelimits, measurement of only E component is required in this region.

9.1.2.2 Far Field Zone-RadiatingThe region of the field where the angular field distribution in essentially independent ofthe distance from the antenna and the radiated power density [W1m2} is constant. The

inner boundary of the radiating far-field region is defined by the larger between 31.. and.2rYrA in most of the technicalliterature(i.e., the limit is 2IY/A if the maximum dimension

8

D of the antenna is large compared with the wavelength A). In the far-field region, the E

and H field components are transverse and propagate as a plane wave.

For compliance with the safe exposure limits, measurement ofE or Power (S) is requiredin this region.

The above regions are shown in Figure 4 given below (where D is supposed to be large

compared with the wavelength A).

K.61]Ol

Reactive

! near-field

rEM ~

sourc:J [,1

Reactive

radiating

i near-field

I;: 'A.

Radiating(Fresnel)

! near-field

r1in

Radiating far-field•. c •.

Distance from the source

2D2/)..

Figure 4 - Field regions around an EM source(the antenna maximum dimension D is supposed to

be large compared with the wavelength A)

In the case of EMF exposure assessment, however, a large phase difference and thus a

shorter distance marking the beginning of the far-field zone is acceptable. A realistic

practical distance from a large antenna, where the far-field begins is:

?1.3 Computation for Compliance with Exposure Limits-Example 1:After time spatially averaged measurements, the electric fields to which general publicare exposed are found to be 10 Vim, 20 Vim and 15 Vim at 20 MHz, 90 MHz and 150MHz, respectively.

Where Rf=D=A=

distance which marks the beginning of the far-field regionthe maximum dimension of the antenna

wavelength, in metres (m)

For general public exposure, taking the ICNIRP reference levels of electric field = 28V1m in the 10-400 MHz frequency range, the relative values with respect to the exposurelimits in the frequency bands of concern are given as follows: / .

• R1= (10/28i = 0.13 for 20 MHz ( in the frequency band 10-400 MHz)• R2 = (20/28i = 0.51 for 90 MHz ( in the frequency band 1O-400MHz)• R3 = (15/28)2 = 0.15 for 150 MHz (in the frequency band 10-400 MHz)

9

From above Rl+ R2 + R3 = 0.79, which is less than unity and therefore the combined filedstrength confOffilS to the Safe Limit.

Example 2:Assume that a worker is exposed to RF fields at three different frequencies. Exposuremeasurements were performed, which were time and spatially averaged, producing thefollowing condition:

• 0.1 AIm at 27 MHz• 70 Vim at 915 MHz• 25 W/m2 at 10000 MHz

For occupational exposure, taking the ICNIRP reference levels of magnetic field = 0.16Nm for the 10-400 MHz, electric field = 3f \I, = 3x (915) \/, = 90.75 AJm for 400-2000MHz and power density =50 W/m2 for 2-300 GHz frequency range, the relative valueswith respect to the exposure limits in the frequency bands of concern are given asfollows;

• Rl = (0. 110.16i = 0.39 for 27 MHz (in the frequency band 10-400 MHz)• R2 = (70/90.75i = 0.59 for 915 MHz (in the frequency band 400-2000 MHz)• R3 = (25/50) = 0.5 for 10000 MHz (in the frequency band 2.;300 GHz)

From above Rl + R2+ R3 = 1.48, which is more than unity and therefore the combinedfield strengths and power density does not conform to the Safe limit.

Example 3: Far field (FF) Power density calculation for compliance with limits

(I) A realistic practical distance from a large antenna, where the far-field begins is givenby:

Rf = 0.5D2/,}"

Where

Rf = distance which marks the beginning of the far-field regionD = the maximum dimension of the antenna

A. = is the wavelength in meters (m) (A. = 300/f, where f is in Megahertz.

The far-field (FF) formula is used to check that the safe distance calculated is valid. Thevalidity is dependent on the maximum dimension of the antenna being greater than thewavelength being analysed.

(II) Calculations can be made to predict RF field strength and power density levelsaround typical RF sources. For example, in the case of a single radiating antenna aprediction for power density in the far-field of the antenna can be made by using equationat page 7. This equation is generally accurate in the far-field of an antenna but will overpredict power density in the near field, where they could be used for making a "worstcase" or conservative prediction.

10

9.1.4 Calculation of Exclusion Zone Distance

An illustrative example of calculating the exclusion zone is given below:

An antenna measuring at (0.25 x 0.25 x 0.22) metres, operating at 2000 MHz with anEIRP of 50 W is to be installed. What is the minimum distance from the antenna where

the exposure does not exceed the limits for the general public?

i) Calculate the maximum power density exposure limit for the general public (as perICNIRP Limits).

Slimit == f 1200 = 2000/200 == 10 W/m2

ii) Calculate the minimum safe distance by rearranging the equation,

S = EIRPI (n R2)

= PTG 1 ( n R2)

For the distance from the antenna, Rmin:

Rmin= " [EIRP/(n SlimiD}

=...j (50.0/(3.14 x 10]= 1.26 m

iii) Check to make sure that the minimum distance calculated above is in the far-fieldzone where equation Slimit is valid):

First calculate the wavelength:= 300/f (f in MHz)=300/2000=0.15 m

As this antenna's maximum dimension (i.e. 0.25 m) is greater than the wavelength (0.15m), it may be considered a large antenna. Now calculate the realistic practical distance forthis antenna, where the far-field begins i.e.;

Rf= O.SlY/A

Rf = 0.5 (0.25)2/ (0.15)Rf= O.21m

Since the minimum distance calculated above, is in the far-field zone of the antenna, thebasis for the calculation is valid and the exclusion zone is to be marked at 1.26 m.

Note:

The above illustration for reference purpose is based on exposure at the same level as theantenna on the main beam direction e.g. on a roof top or in a building directly acrossfrom and at the same height as the ante1ll1a.For directions other than the main beamrelative gain with respect to the main beam may be taken.

11

9.2 Determination of ElRPth

The procedure is the following:

1) Determine the field or the power density for each point 0, where exposure canoccur, for the particular antenna

2) Find the maximum power density Smax within the exposure area from this set.3) The condition Smax = Slim gives the EIRPth where Slim is the relevant limit given by

the EMF exposure standard at the relevant frequency.

This procedure may be performed by calculations methods or by measurements. If

measurements are used, it is necessary to perform them at a number of representative

locations for each accessibility configuration and anteD?a type.

9.2.1 Accessibility categories

These categories, which depend on the installation circumstances, assess the likelihood

that a person can access the exceedance zone of the emitter are given in Table 2 below:

Table 2 - Accessibility categories

AccessibilityRelevant installation circumstances

Figure

category

referenceAntenna is installed on an inaccessible tower - the centre of radiation is at a height h above ground -level. There is a constrainth>3m.

-I Antenna is installed on a publicly accessible structure (such as aFigure 5

rooftop) - the centre of radiation is at a height h above thestructure.Antenna is installed at ground level- the centre of radiation is ata height h above ground level. There is an adjacent building or2

structure accessible to the general public and of approximatelyFigure 6height h located a distance d from the antenna along the direction of propagation. There is a constraint h > 3 m.Antenna is installed at ground level- the centre of radiation is ata height h (h > 3 m) above ground level. There is an adjacent3

building or structure accessible to the general public and ofFigure 7approximately height h' located at a distance d from the antenna along the direction of propagation.Antenna is installed on a structure at a height h (h> 3 m). Thereis an exclusion area associated with the antenna. Two geometries4

for the exclusion area are defined:

-A circular area with radius a surrounding the antenna; or Figure 8-A rectangular area of size a x b in front of the antenna. Figure 9

12

h

Figure 5 - Illustration of the accessibility category 1


13


h

Figure 8 - Illustration of the accessibility category 4, circular exclusion area

14

II

Figure 9 - Illustration of the accessibility category 4, rectangular exclusion area

9.2.2 Antenna directivity categoriesAntenna directivity is important because it determines the pattern of potential exposure.

High directivity means that most of the radiated power is concentrated in a narrow beam

which may allow good control of the location of the exposure zones.

The antenna pattern is a major determinant and a frequently varying factor in determining

the field. Table 3 presents a description to facilitate classification of antennas into generic

categories. The most important parameter for determining the exposure due to elevated

; antennas is the vertical (elevation) antenna pattern. The horizontal (azimuth) pattern is

•not relevant because the exposure assessment assumes exposure along the direction of, maximum radiation in the horizontal plane.

Note, however, that the vertical and horizontal patterns determine the antenna gain, and

that horizontal pattern determines the exclusion area for accessibility category 4.

15

Table3-A direct" . t~

Directivity Antenna descriptionRelevant parameterscategory

1

Half-wave dipole None See Figure 10

2

Broad coverage antenna (omnidirectional or·Vertical half-power beamwidth: 8bw

sectional), such as those used for wireless·Maximum side-lobe amplitude with

communication or broadcastingrespect to the maximum: Asl· Beam tilt: a

See Figure 11.3High-gain antenna producing a "pencil" ·Vertical half-power beamwidth: 8bw

(circularly symmetrical beam), such as those

·Maximum side-lobe amplitude with

used for point-to-point communication or earth,respect to the maximum: ASI

stations•Beam tilt: a

See Figure 11.

'90·

Figure 10 - Verticalpattern for a half-wave dipole in vertical polarization

16

\.-\ \

\\\

-90"

OdB

-3 dB

Constant

sideband

envelope

Beamtilt

Half-powerbeamwidth

90· Constantsideband

envelope

Figure 11 - Illustration of terms relating to antenna patterns

9.2.3 The exclusion area

This clause describes the exclusion areas for accessibility category 4. The exclusion area

depends on the horizontal pattern of the antenna. The relevant parameter is the horizontal

coverage of the antenna. Table 4 presents the exclusion areas for a few typical values of

the horizontal coverage of onmidirectional, sectional or narrow-beam antennas.

Table 4 - Exclusion area as function of horizontal coverage

Horizontal Exclusion area

coverage OmnidirectionalCircular area (Figure 4)

120°

Rectangular area (Figure 5)b= 0.866a

90°Rectangular area (Figure 5)b= 0.707a

60°

Rectangular area (Figure 5)b = 0.5a

30°

Rectangular area (Figure 5)b = 0.259a

Less than SO

Rectangular area (Figure 5)b= O.09a

17

10. Field Measurement Approach.

As per ITU-T rec. K.52, a series offield-strength measurements shall be made throughout a height of

2.0 m, corresponding to the position of interest to be occupied by the body, but with the body absent. In

the presentation of the results, the average value shall be stated together with the maximum valuemeasured.

Before beginning a measurement it is important to characterize the exposure situation asmuch as possible. An attempt should be made to determine:

(i) The frequency and maximum power of the RF source(s) in question, as well asany nearby sources.

(ii) Areas those are accessible to either workersor the general public.

(iii) The location of any nearby reflecting surfaces or conductive objects that couldproduce regions offield intensification ("hot spots").

(iv) If appropriate, antenna gain and vertical and horizontal radiation patterns.

(v) Type of modulation of the source(s).

(vi) Polarization of the antenna(s).

(vii) Whether measurements are to be made in the near-field, in close proximity to aleakage source, or under plane-wave conditions. The type of measurementneeded can influence the type of survey probe, calibration conditions andtechniques used.

(viii) If possible, one should estimate the maximum expected field levels, in order tofacilitate the selection of an appropriate survey instrument. For safety purposes,the electric field (or the far-field equivalent power density derived from the Efield) should be measured first because the body absorbs more energy from theelectric field. In many cases it may be best to begin by using a broadbandinstrument capable of accurately measuring the total field from all sources in alldirections. If the total field does not exceed the relevant exposure guideline inaccessible areas, and if the measurement technique employed is sufficientlyaccurate, such a determination would constitute a showing of compliance withthat particular guideline, and further measurements would be unnecessary.

(ix) When using a broadband measuring instrument, spatially-averaged exposurelevels may be determined by slowly moving the probe while scanning over anarea approximately equivalent to the vertical cross-section (projected area) ofthe human body. An average can be estimated by observing the meter readingduring this scanning process or be read directly on those meters that providespatial averaging.

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(x) In many situations there may be several RF sources. For example, a broadcastantenna farm or multiple-use tower could have several types of RF sourcesincluding GSM, COMA, W-CDMA, 3 G and Wi-Max etc and microwaveantennas. Also, at rooftop sites many different types of cellular base stationantennas are commonly present. In such situations it is generally useful to useboth broadband and narrowband instrumentation to fully characterize theelectromagnetic environment. Broadband instrumentation could be used todetermine what the overall field levels appeared to be, while narrowbandinstrumentation would be required to determine the relat~ve contributions ofeach signal to the total field.

(xi) In many situations a relatively large sampling of data will be necessary tospatially resolve areas of field intensification that may be caused by reflectionand multipath interference. Areas that are normally occupied by personnel orare accessible to the public should be examined in detail to determine exposurepotential. If narrowband instrumentation and a linear antenna are used, fieldintensities at three mutually orthogonal orientations of the antenna must beobtained at each measurement point. The values of E2 or H2 will then be equalto the sum of the squares of the corresponding, orthogonal field components. Ifan aperture antenna is used, unless the test antenna responds uniformly to allpolarizations in a plane, e.g., a conical log-spiral antenna, it should be rotated inboth azimuth and elevation until a maximum is obtained. The antenna shouldthen be rotated about its longitudinal axis and the measurement repeated so thatboth horizontally and vertically polarized field components are measured. Itshould be noted that when using aperture antennas in reflective or near-fieldenvironments, significant negativeerrors may be obtained.

The measurement problem typically approachesone of the following cases1. The source of the EMF and at least some of its characteristics are known. The

EMF from other sources is negligible for compliance considerations. Theobjective is to determine the compliancezones for this known source.

2. The sources of the EMF are not known. The objective is to determine compliancein a particular location, or to survey the EM fields in the out-band region toconfirm that other EM sources can be neglected.

3. The objective is to determine compliance in a particular location, and if noncompliance is found, to determine the relative contribution of the sources to thenon-compliance.

In Case 1, the transmitting frequency band should be known precisely. Thetransmitted power, polarization and the antenna pattern may be known approximately.

.Thus, the measurements can focus onto the frequency range of interest. ITU-T Rec.K.52 should be used to obtain an estimate of the field strength in order to determineappropriate instrumentation.

19

In Case 2, a survey of the entire frequency spectrum may be required. An alternativeis measurements with wideband probe that integrates various frequencies.

In Case 3, is an extension of Case 2. If the initial measurement indicates noncompliance, frequency selective measurements, using an antenna and spectrumanalyzer for example, are needed.

To make meaningful near-field measurements, the following conditions shall be met.

a) The probe shall respond to particular parameter and not have significant spuriousresponses (e.g. respond to an E-field without any spurious H-field response).

b) The dimensions of the probe sensor shall preferably be less than IJIO in itssurrounding medium at its highest operating frequency.

c) The probe shall not produce significant scattering.d) The probe response shall be isotropic (i.e. non-directional and non-polarized).e) Any leads from the sensor to the meter shall not significantly perturb the field at

he sensor or couple energy from the field.

10.1 Test Instruments Required

Instruments used for measuring radiofrequency fields may be either broadband ornarrowband devices. A typical broadband instrument responds essentially uniformly andinstantaneously over a wide frequency range and requires no tuning. A narrowbandinstrument may also operate over a wide frequency range, but the instantaneousbandwidth may be limited to only a few kilohertz, and the device must be tuned to thefrequency of interest. The choice of instrument depends on the situation wheremeasurements are being made.

All instruments used for measuring RF fields have the following basic componentscovering the frequency range of interest.

i) Field Strength Meter or Spectrum Analyzerii) H-field measuring instrumentiii) an antenna or probe to sample the field. Isotropic, shaped isotropic and directional

both.iv) Laptop to process the measured results.

The antennas most commonly used with broadband instruments are either dipoles thatrespond to the electric field (E) or loops that respond to the magnetic field (R). Surfacearea or displacement-current sensors that respond to the E-field are also used. In order toachieve a uniform response over the indicated frequency range, the size of the dipole orloop must be small compared to the wavelength of the highest frequency to be measured.Isotropic broadband probes contain three mutually orthogonal dipoles or loops whoseoutputs are summed so that the response is independent of orientation of the probe.

All measuring instruments as required to be available for the measurements and displayof results.

20

The instruments and accessories shall have the capability to measure in the frequencyrange of interest.

Field Strength Meter of required capabilities to measure• E-field• H-field

• Power density

in the specified frequency range in V1M,NM, W/square meter as p~ ICNIRP guidelineslimits. The instrument should preferably be portable and battery operated for carrying toroof-top and various accessible places easily.

Field strength measuring instruments shall have facility to display spectrum and presentresults in anyone unit.

(i) Field Strength Meter of specified frequencies.

(ii) Isotropic Probe for E-field and H-field measurement with facility for directconnecting to the meter. Shaped probe weighted as per ICNIRP guidelines limitsshall also be available.

(iii)Directional Antennas of various frequencies to identify the source of emission.The directional may be of various types.

(iv)Connecting cable (CXL/Optical).

(v) Lap-top PC to perform necessary measurements and display results in case fieldstrength meter is not integrated with calculating the results and displaying indesired units.

10.2 Calibration of instruments

It is outside the scope of this standard to detail methods of calibration for the various

measuring instruments described above but, for safety reasons, it is important that they be

recalibrated at regular intervals by an accredited calibration laboratory .

.A list of simple routine functional checks to be carried out before and after undertaking a

measurement survey.

10.3 Check points before Measurement

Before making a survey of potentially hazardous electromagnetic fields, it is important to

determine as many characteristics of the source of these fields as possible and their likely

propagation characteristics.

21

This knowledge will facilitate better estimation of expected field strengths and a moreappropriate selection of test instruments and test procedures.

(a) A check-list of source and characteristics may include the following:(i) type of generator and generated power;(ii) carrier frequency or frequencies;(iii) modulation characteristics;(iv) polarization;(v) duty factor, pulse width and repetition frequency, if relevant;(vi) type of antenna (unless a leakage source) and such properties as gain, physical

dimensions and radiation pattern, etc.

(vii) number of sources, including any out-of-band signals that might affect themeasurements.

(b) A check-list on propagation characteristics may include:(i) distance from source to test site or measuring point;(ii) existence of absorbing, scattering or reflecting objects likely to influence the

strength at the measuring point.

Measurement procedures may differ, depending on the source and propagationinformation that is available. If the information is well-defined, then the surveyor, aftermaking estimates of expected field strengths and selecting a suitable instrument, mayproceed with the survey using a high-power probe, to avoid inadvertent burnout.

On the other hand, if the information is not well-defined, then it may be necessary tomake a number of exploratory measurements around the test site, scanning a broadfrequency spectrum until some positive response is found.

The test procedures will differ depending on whether the radiation source is anintentional radiator or a leakage source. If an intentional radiator, the surveyor canproceed progressively and knowingly toward the main beam and the antenna. In the case

of a leakage source, the surveyor shall start first with low-level probe and range settingsas the approach is made cautiously towards the likely sources of leakage, i.e. , first at adistance along the exterior surface of the equipment. The instrument is then switched to

higher range settings after the location of the leakage is confirmed and a closer approachmade. For leakage measurements, a non-directional and non-polarized sensor is desirable

because of its ability to respond to signals of arbitrary direction and. polarization.However, in cases of strong fields where the source of leakage is uncertain, initially adirectional probe may be found helpful in locating the actual source.

22

10.4 Functional tests for measuring instruments

Before commencing a measurement survey it is strongly recommended that some simple

functional tests be made on the measuring instruments to confirm that they function correctly.

Such a check-list could include the following:

a) Take a suitable far-field reading on a known radiation source.b) If the probe is isotropic, check that the reading is largely independent of probe

orientation.

c) Change the direction of the sensor leads whilst keeping the probe stationery to checkfor undue pickup on the leads.

d) If a second instrument is available, compare their readings.e) If possible, compare the reading with the expected (or calculated) field strength.

Repeat the above tests after the survey has been completed, in order to check there has been no

inadvertent damage to the measuring instrument during use.

10.5 Measurement Results

The measurement at site shall be performed based on the following procedures:

(i) Digital map of the area indicating the BTS site for the measurement to beavailable for the purpose of identification.

(ii) All the necessary tools with valid calibration to be made available for thenecessary measurement.

(iii) All measurement data shall be collected using automatic test setup. Wherever itis not possible to carry the instruments, GPS enabled walk test kit or hand helddevice to be used. The total field strength will be recorded for particular BISlocation. There may be multiple antennas. Cumulative strength will be seen andrecorded.

(iv) The electromagnetic fields being measured shall use isotropic probes becausethe EMF are usually from multiple sources and from various directions.

(v) The duration of the readings taken shall be averaged over 6 minutes per locationor as per actual requirements.

(vi) All radio channels should be occupied during the measurement. In case themeasurements with all channels occupied are not possible, then theextrapolation procedure as per ITU-T Rec. K.61 to be used.

(vii) Due consideration be taken of other effects such as reflection, scattering,

standin& waves, grounding while taking measurements.(viii) The measurement should be performed from near the base of the tower and at

various distances going around the tower (360 degree). The maximum readingswill be recorded. In case· it is not possible to go around the tower, take thepossible movement and record the maximum level received as given in the tableas per Appendix-'A'

23

Appendix- 'A'EMF MEASUREMENTS

In the far field anyone parameter i.e. E-field or H-field or Power density can bemeasured whereas in near field both E-field and H-field will be measured.

S.No. Distance from theAzimuthElectric Field! MagneticCompliancebase of tower in

AngleField! Power Densitywith limitshorizontal direction at 2.0 Meter height1

2.0 Meters2

3.0 Meters3

4.0 Meters4

5.0 Meters5

7 Meters6

10 Meters7

15 Meters8

20 Meters

9

30 Meters10

Any maximumfield strengthlocation11

Nearbyaccessibleareas l.2.3.4.5.12

Worst scenario

(Max. fieldstrength) inhorizontal orvertical direction

Note: Measurement for 10 meters beyond the distance at which the ICNIRP limitsare met can be dispensed.

24

The measurement shall also be recorded in vertical direction going to the variousnearby buildings in aU the directions wherever possible and the places exposed forthe movement of general public.

S.No. DistancefromtheElectric Field!Compliance with limitsbase

oftowerInMagnetic Field/vertical direction

Power Density

I 23456789

Any maximum fieldstrength location

12

Worst scenario (Max.field

strength)Inhorizontal or verticaldirection

NOTE:

(a) Maximum possible readings will be taken to record the maximum signal coveringall possible accessible points.

(b) All measured data will be recorded in CD and submitted with hard copy of theresults.

(c) The readings should be taken at the site's busiest period of the day, which isdefined as the site's busy hour. A site's busy hour can be determine from dailytraffic recordings commonly obtainable from the operator's mobile switch.

(d) Annex B gives about the exclusion zone and accessibility criterion.(e) Due consideration be taken of other effects such as reflection, scattering, standing

waves, grounding etc. while making measurements.

25

SAFETY SIGNS:

The warning sign indicates that restricted occupancy is allowed for RF and microwaveexposed workers within its boundaries. This zone indicates an area where the RF field orpower density exceeds the limits prescribed for the general public but is less than thelimit for workers/ occupancy exposure. A warning sign should be placed at the entranceof such zone, wherein the survey has shown that RF levels are within the aforesaid valuesspecified in Annex A.

A Danger sign indicates a denied access zone where the field or power density is evenmore than the maximum limit for RF workers/occupancy exposure.A radio site's exclusion zone is determined based on theoretical calculations. However

actual site measurements using field strength and power density meters could be used toverify the accuracy ofthe theoretical calculations.

The sign board should be clearly visible and identifiable and may contain the followingor other similar text:

1) Danger! RF radiations, Do' not enter!2) Restricted Area

The colour code may be as follows;

Symbol and text - red, against white background

In certain places such as where mobile antennas are installed inside the building, signageis not necessc;rry as RF safe level distance does not normally exceed 10s of centimetresfrom the antenna and is moreover installed at ceiling height.

In summary the signage placement rules shall be as follows;a) At the boundary of the exclusion zone.

b) If signage is placed on an ante~a mounting structure, the signage needs to beclearly readable at the boundary of the exclusion zone.

c) The operators can, at their own discretion, implement additional measures asnecessary for the safely of workers and public at the site.

26

SUMMARY REPORT FOR EMF MEASUREMENT

Measurement of Electro-magnetic Fields from Base Station Antennas

Name of the Service Provider:

Address of the Service Provider:

l. Date of the measurement

2.

Test instruments used

Name ofInstrumentimake/calibration date.3.

Location of BTS

4.

Address of BTS

5

Technology Type ofBTS (GSM, CDMA,

W-CDMA,3 G and Wi-Max etc)6

Measurement Particulars Antenna 1Antenna 2-------

i) Frequencies ofBTS / BTSs

.'

ii) Tx Poweriii) Whether single or Multiple antennaiv)Longitude of BTSv)Latitude ofBTSvi) Whether Roof top antenna or groundbased antennavii) Roof top Heightviii)Antenna height above RoofTopix) Antenna height for ground based antenna

27

7. I Maximum Field Strength measured at

different horizontal distance and height

A) E-Field (VIm)

B) H Field( AIm)

C) Power density (W/m2)

Anyone of the above can be measured

preferably and recorded for Far Fieldmeasurement.

8. I Whether fencing provided for restricted area.

Whether

Danger!

RF radiations Do not enter!

sign for safety displayed

9 I Any other remarks

10. I Conclusion

28

Appendix -'B'Example of EIRPth calculation

The EIRP th valuesTables B.1 to B.3 show the expressions for EJRP'h values based on the ICNIRP limits for

various frequency ranges, accessibility conditions and antenna directivity categories.

It is necessary to point out that the radiated density power can be used only in far-field

conditions, when it is representative of the electric and magnetic fields. This represents

the limit of validity of the proposed assessment procedure for normally compliant

installations. Where the procedure is not applicable (e.g., low frequencies or exposure in

near-field conditions), then the installation shall be considered provisionally compliant.

The ICNIRP guidelines define three frequency ranges to which correspond different limit

values of equivalent plane wave power density. For frequencies. above 100 MHz thelimits are:

/ (MHz)S/im(f) (W1m2)

General public

Occupational100-400

210400-2000

1/2001/402 '1Oj -300 . lOJ

1050

The E1RPth values are given as functions of antenna height and other relevant parameters

such as accessibility, directivity and frequency.

NOTE - In the following Tables a, d, h and hI are in metres.

Table B.l - Conditions for normal compliance of installations basedon ICNIRP limits for frequency range 100-400 MHz

Directivity Accessibility EIRPt/,(W)

category

categoryGeneral publicOccupational

I

8n(h _2)240n(h-2)2

Lesser of:

Lesserof:

2

8n(h _2)2 -40n(h- 2)2

or

or

21td2lOnd2

1 Lesser of:Lesser of:

8n(h-2)2

40n(h-2)2

3

oror

21d' +(~-h')'r [d' + (h-h')' rIOn .d

29·

Table B.1 - Conditions for normal compliance of installations basedon ICNIRP limits for frequency range 100-400 MHz

Directivity Accessi bility EIRPth (W)

category


Lesser of:

Lesser of:

811:(h- 2)2 {If a < (h - 2)}

4011:(h- 2)2 {If a < (h - 2)}

1

4 oror

2{ a' +<;-2)'J10,[ a' +(;_2)' J

Lesser of:

Lesser of:

211:(h-2)2

1011:(h _ 2)2 .As!

As!I oror

[ ]' [ ]'11-2 1011: h-2

211:sin(a + 1.1290bw)sin(a + 1.1290bw)

Lesser of:

Lesser of:

2211:(h _ 2)21011:(h-2)2

(determined by: h' >As! .As!

h - d tan( CY. + 1. 1290bw»oror

21td2101td2

2

Lesser of:Lesser of:

3

21t (h-2)2

1011:(h_2)2As!

As!(determined by: h' <

oror

h-d tan(a+1.1290bw»

2. [d' +(h-h')' J10'[ d' +(h- h')' J. As! d

As! d

Lesser of:

Lesser of:

~[a' +(h-2)'J10,[a'+(h-2)'J4

As! aAs! a

or

or

[ ]' [ ]'11-2 1011: h-2

21t sin(a + 1.1290bw)sin(a + 1.1290bw)

30


Directivity Accessibility EIRPth (W)

category


Lesser of:

Lesser of:

2n (h _ 2)2

IOn (h-2)2As!

As!3

1 or or

[ h-2 ]'[ rIOn h-2

27t sinea +1.1298 bw). sin(a + l.I298bw)

N/A

N/A2

(Line of sight is usually(Line of sight is usuallyrequired)

required)

Lesser of:

Lesser of:

3

2n (h _ 2)2lOn(h_2)2

As!

As!(determined by: h' <

oror

h-d tan(a+1.l296bw»

--,,--[a' +(h- Hi r2.5"[d' + (h-h')' r32As! d

-As! d

Lesser of:

Lesser of:

3':[a'+(h-2)']'10"[a' +(h-2)']'4

As! aAs! a

or

or

[ ]' [ rh-2 IOn h-2

27t sin(a + l.I296bw)sin(a + I.I298bw)

Table B.2 - Conditions for normal compliance of installations basedon ICNIRP limits for frequency range 400-2000 MHz'


category

categoryGeneral public

Occupational

1

I fit (h-2)2fit (h-2)2

50

10

31


Directivity Accessibility E1RPth (W)

category


Lesser of:

Lesser of:

fit (h _ 2)2

fir. (h _ 2)22

50 10or

or

fir. d2fie d2

200

40

Lesser of:

Lesser of:

fit (h _2)2

fie (h-2)250

103

or or

ft [d' +(h-h')2 r Jit[ d2 +(h-h')2J200 d

40 d

Lesser of:

Lesser of:

fir. (h-2)2 {If a < (h - 2)}

fie (h-2)2 {If a < (h- 2)}50 .

10-

1 4 or or

A[ a2+(h-Z)2 r Jit[ a2+(h-z)'J200 a

40 a

Lesser of:

Lesser of:

fit (h _ 2)2

~(h-2)2200As1

40As12

1 oror

[ ]2

[ ]2

fie h-2fit h-2

200 sin(a + 1.1298bw)

40 sin(a + 1. 1298bw)

Lesser of:

Lesser of:

2

fit (h _ 2)2~(h-2)2

(determined by: h' >

200As140As1

h - d tan(a. + 1.1298bw»

oror

fie d2fie d2

200

40

32



category


Lesser of:

Lesser of:

3

Ire (h _2)2~(h-2)2

200Asl

40Asl(determined by: h' <

oror

h -d tan(a + 1.1298bw))

fi< [d' +(h-h')']'. ~[d' + (h-h')' ]'200Asl d

40Asl d

Lesser of:

Lesser of:

fi< [a' +(h-Zl']'~[ a'+(h-Zl']'4

200Asl a40Asl a

or

or

[ r [ Jfit h-2 fir h-2

200 sin(a+1.1298bw)

40 sin(a + 1.1298bw)

Lesser of:

Lesser of:-

Ire (h-2l ~(h-2)2200Asl

40Asl3

1 oror

:00 [sin(" + ,hI29G,,,Jfi<[ h r40 sm(a + 1.1298bw)

,N/AN/A

32(Line of sight is usually(Line of sight is usually

required)required)

Lesser of:

Lesser of:

3

fn (h-2)2~(h-2)2

200As1

40Asl(determined by: h' <

oror

h-d tan(a+ 1.1298bw»

A[d' +(h-h')']'~[d' +(h-h')']'SOAsl d

lOAsl d

33


Directivity Accessibility EIRPtll (W)

category


Lesser of:

Lesser of:

.fit [a' +(h-2)']'~[ a'+(h-2)']'4

200Asl a40Asl a

or

or

[ ]' [ rfie h-2 ' fir h-2

200 sin(a+1.1298bw)

40 sine a + 1.1298 bw)

Table B.3 - Conditions for normal compliance of installations based on ICNIRP limits forfrequency range 2000-300 000 MHz


category


1

401t(h- 2)22001t(h - 2)2

Lesser of:

Lesser of:

2

401t(h-2/2001t(h-2)2

or

or

101td2501td2

1 Lesser of:Lesser of:

401t(h - 2)2

200n(h - 2)2

3

or or

[d' +(h-h')' J [ d' +(h-h')' JIOn

SOnd

d

Lesser of:

Lesser of:

40n(h - 2)2 {If a < (h - 2)}

200n(h - 2)2 {If a < (h - 2)}

1

4 or or

10_[a' +(~-2)'J 50{h(~-2)'J

34


Dil'ectivitycategory

Accessibilitycategory

E1RPtll (W)

General public I Occupational

2

3

3

2

(determined by: h' >h-d tan(a + 1.1298bw»

3(determined by: h' <

h--d tan(a + 1.1298bw»

4

I

2

Lesser of:

IOn (h _ 2)2As!

or

[ ]2

IOn h-2sin(a + 1.1298bw)

Lesser of:

or

107td2

Lesser of:

IOn (h-2)2As!

Lesser of:

lon[a2 +(h_2)2]2As! aor

[ ]2


Lesser of:

. IOn (h-2)2As!

or

[ ]2


N/A

(Line of sight is usuallyrequired)

35

Lesser of:

50n (h _ 2)2As!

or

[ ]2

50n h- 2sin(a + 1.12gebw)

Lesser of:

Lesser of:

50n (h _2)2As!

or

50n[d2 +(h_h')2]2Asl d

Lesser of:

50n[a2 +(h_2)2]2As! aor

[ ]2

SOn. h-2sin(a + 1.12gebw)

Lesser of:

50n (h-2)2As!

or

[ ]2

SOn h-2sin(a+1.1298bw)

N/A

(Line of sight is usuallyrequired)


Directivity Accessibility EIRPt/l (W)

category


Lesser of:

Lesser of:

3

101C(h_2)2

SOn (h _ 2)2ASl

As/(determined by: h' <

oror

h-d tan(a + 1. I 298bw))

2.5"[ d' +(h-h'J'r12.5,,[d' +(h- h')' rAs/ d

As/ d

Lesser of:

Lesser of:

10"[ a' +(h-2)' r5Ox[ a' +(h- 2)2 r4

As/ aAs/ a

or

or

[ r 1[ ]2IOn h-2 50 h-2

sin(a + 1.12gebw)

sin(a + 1.1298bw)

NOTE I - fis in MHz. NOTE 2 - All angles should be expressed in radians.NOTE 3 - Asl should be expressed as a numerical factor. However, usually, it is given in dB with respect. A [dB]1l0to the maximum. To convert: As/ = 10 sf •

36

Appendix-'C'

TERMS AND DEFINITIONS

1. antenna gain: The antenna gain G (8, ~) is the ratio of power radiated per unit

solid angle multiplied by 41t to the total input power. Gain is frequently expressed in

decibels with respect to an isotropic antenna (dBi). The equation defining gain is:

where:

8, ~ are the angles in a polar coordinate system

Pr is the radiated power along the (8, ~) direction

Pin is the total input power

Q elementary solid angle along the direction of observation2. average (temporal) power (Pavg): The time-averaged rate of energy transfer

defined by:

I rt2Pavg = -- Ji P(t)dt/2 -/} t1

where /1 and /2 are the start and stop time of the exposure. The period /1 - t2 is the

exposure duration time.

3. averaging time (Tavg): The averaging time is the appropriate time period over

which exposure is averaged for purposes of determining compliance with the limits.

4. continuous exposure: Continuous exposure is defined as exposure for duration

exceeding the corresponding averaging time. Exposure for less than the averaging time is

called short-term exposure.

5. contact current: Contact current is the current flowing into the body by touching

a conductive object in an electromagnetic field.

6. controlled/occupational exposure: Controlled/occupational exposure applies to

situations where persons are exposed as a consequence of their employment and in which

those persons who are exposed have been made fully aware of the potential for exposure

and can exercise control over their exposure. Occupational/controlled exposure also

applies where the exposure is of transient nature as a result of incidental passage through

a location where the exposure limits may be above the general population/uncontrolled

limits, as long as the exposed person has been made fully aware of the potential for

37

exposure and can exercise control over his or her exposure by leaving the area or by some

other appropriate means.

7. directivity: Directivity is the ratio of the power radiated per unit solid angle over

the average power radiated per unit solid angle.

8. Equivalent Isotropically Radiated Power (EIRP): The EIRP is the product of

the power supplied to the antenna and the maximum antenna gain relative to an isotropicantenna.

9. exposure: Exposure occurs wherever a person is subjected to electric, magnetic or

electromagnetic fields, or to contact currents other than those originating from

physiological processes in the body or other natural phenomena.

10. exposure level: Exposure level is the value of the quantity used when a person is

exposed to electromagnetic fields or contact currents.

11. exposure, non-uniform/partial body: Non-uniform or partial-body exposure

levels result when fields are non-uniform over volumes comparable to the whole human

body. This may occur due to highly directional sources, standing waves, scatteredradiation or in the near field.

12. far-field region: That region of the field of an antenna where the angular fielddistribution is essentially independent of the 'distance from the antenna. In the far-field

region, the field has a predominantly plane-wave character, i.e., locally uniform

distribution of electric field strength and magnetic field strength in planes transverse to

the direction of propagation.

13. general public: All non-workers (see definition of workers in 3.27) are defined as

the general public.

14. induced current: Induced current is the current induced inside the body as a

result of direct exposure to electric, magnetic or electromagnetic fields.

15. intentional emitter: Intentional emitter is a device that intentionally generates

and emits electromagnetic energy by radiation or induction.

16. near-field region: The near-field region exists in proximity to an antenna or other

radiating structure in which the electric and magnetic fields do not have a substantially

plane-wave character but vary considerably from point-to-point. The near..;field region is

further subdivided into the reactive near-field region, which is closest to the radiating

structure and that contains most or nearly all of the stored energy, and the radiating near

field region where the radiation field predominates over the reactive field, but lacks

substantial plane-wave character and is complicated in structure.

38

NOTE - For many antennas, the outer boundary of the reactive near-field is taken to existat a distance of one-half wavelength from the antenna surface.17. power density (S): Power flux-density is the power per unit area nOffi1alto the

direction of electromagnetic wave propagation, usually expressed in units of Watts per

square metre (W/m2).

NOTE - For plane waves, power flux-density, electric field strength (E), and magneticfield strength (ll) are related by the intrinsic impedance of free space, TJo = 377 Q. Inparticular,

E2 2S=-=TJoH =EH

T)o

where EandHare expressed in units ofV/m and Aim, respectively, and S in units of

W/m2 . Although many survey instruments indicate power density units, the actual

quantlti~§iJ:l'lcrfl-Spredare E or H.

18... :i~~"~"~lllopulation/uncontrolled exposure: General population/uncontrolled

expo~ll?~'~I:ipliesto situations in which the general public may be exposed, or in which

persR~:~~~tCll"eexposed as a consequence of their employment may not be made fullyawareo.ftliepotential for exposure, or cannot exercise control over their exposure.

19. Workers: Employed and self-employed persons are tenned workers, whilst

followIng their employment.

20.. unintentional emitter: An unintentional emitter is a device that intentionally

generates electromagnetic energy for use within the device, or that sends electromagnetic

energy by conduction to other equipment, but which is not intended to emit or radiate

electromagnetic energy by radiation or induction.

39

Documents

TEC-Test Procedure EMF Measurement of Base Station