Regulation no. 86/2007, published on 22 of May

ICP - Autoridade Nacional de Comunicações, I. P. (ICP - National Communications Authority, I. P.)

Regulation

Procedures for monitoring and measuring intensity levels of electromagnetic fields produced by radiocommunication stations

It is incumbent upon ICP-ANACOM, pursuant to paragraph 2 of article 11 of Decree-Law no. 11/2003, of 18 January, to establish procedures for monitoring and measuring intensity levels of electromagnetic fields produced by radiocommunication stations.

Therefore, under point a) of article 9 of the Statutes of ICP-National Communications Authority (ICP-ANACOM), approved by Decree-Law no. 309/2001, of 7 December, and paragraph 2 of article 11 of Decree-Law no. 11/2003, of 18 January, the Board of Directors of ICP-ANACOM, having heard the Ministries for National Defence, for Economy, for Science and Higher Education, for Health and for Cities, Territorial Planning and Environment, hereby approves the following regulation:

Article 1

1 – The present regulation specifies in-situ measurement procedures for non-ionising electromagnetic radiation (9 kHz-300 GHz), in order to evaluate electromagnetic fields for the sake of comparison with reference levels set out in Administrative Rule no. 1421/2004, of 23 November, published under paragraph 1 of article 11 of Decree-Law no. 11/2003 of 18 January.

2 – The provisions in this Regulation are based on Recommendation ECC «Measuring non-ionising electromagnetic radiation (9 kHz – 300 GHz)», adopted by the Working Group “Frequency Management” (FM), of the Electronic Communications Committee (ECC) within the European Conference of Postal and Telecommunications Administrations (CEPT).

3 – Procedures referred to in paragraph 1 are comprised in Annexes 1 to 6 hereto, which are deemed to be an integral part hereof.

Article 2

For the purpose of application and use of procedures referred to herein, it is hereby established that:

a) General information contained in Annex 1 forms the basis for non-ionising radiation measurements;
b) Non-ionising radiation measurement methods should be applied according to the Annexes 2, 3, 4 and 5;
c) Such measurements should be reported in accordance with Annex 6;
d) The level of decision, defined in paragraph 4.10 of Annex 1, shall be 17dB lower that the reference level, that applies to each situation under analysis;
e) The duration of measurements shall comply with Administrative Rule no. 1421/2004, of 23 November, published pursuant to paragraph 1 of article 11 of

Decree-Law no. 11/2003, of 18 January, which is mentioned in Annexes as the reference document.

Article 3

This regulation shall be reviewed whenever necessary, as appropriate in the light of changing technologies and legal or regulatory requirements, namely where an international or Community rule is provided on procedures for monitoring and measuring intensity levels of electromagnetic fields produced by radiocommunication stations.

26 March 2007. - The Chairman of the Board of Directors, José Manuel Amado da Silva.

 Annex 1
General information
 

1- Scope

This document describes a measurement method that should be used to assess electromagnetic radiation against the appropriate reference levels for exposure of human beings to electromagnetic fields (9 kHz – 300 GHz). The measuring method is based on 3 cases which are described in Annex 2:

 - Case 1 - Quick overview;
 - Case 2 - Variable frequency band scan;
 - Case 3 - Detailed investigation.

The present recommendation is based on the application of the three methods indicated above, the rigour and complexity of which increases gradually.

Only the execution of Case 3 can determine if the limits are exceeded, thus guaranteeing a confidence in the results.

This method is not suitable for situations where the critical exposure is strongly localised, e.g., with cellular phone handsets. Licence exempt equipment like microwave ovens, or cellular phone handsets should be ignored for the measurement process, and if it is not the case, the test report should mention this fact.

2 - Normative references

IEC, Guide to the expression of uncertainty in measurement, Ed. 1, 1995.

IPQ, International Vocabulary of Terms in Metrology, Ed. 2, 1996.

3 - Physical quantities and units

SI-units are used throughout the present recommendation:

4 -Terms and definitions
 

Quantity	Symbol	Unit	Symbol
Frequency	f	Hertz	Hz
Wavelength	l	metre	m
Electric field strength	E	Volt per metre	V/m
Magnetic field strength	H	Ampere per metre	A/m
Magnetic flux density	B	Tesla	T
Power density or EM power flux density	S	Watt per square metre	W/m²
Intrinsic impedance	Z	Ohm	W
Largest dimension of the antenna	D	metre	m

4.1 - Electric field strength. - Electric field strength is a vector quantity (E) that corresponds to the force exerted on a charged particle regardless of its motion in space.

4.2 - Magnetic field strength. - Magnetic field strength is a vector quantity (H), which, together with the magnetic flux density, specifies a magnetic field at any point in space.

4.3 - Power density (S) or electromagnetic power flux density. - Power per unit area perpendicular to the direction of propagation:

For a plane wave in the far field, power density (S), electric field strength (E) and magnetic field strength (H) are related by the impedance of free space, i.e. Z0=377 Ohms. In particular,

 

or

or

 

4.4 - Far-field. - The far-field region, (also called the Fraunhofer region), is the field region of an antenna in which angular field distribution is independent of distance from the antenna. In this region, the field has a predominantly plane wave character, i.e., local, very uniform distribution of electric and magnetic field strength in planes that are transverse to the propagation direction.

4.5 - Near-Field. - The near-field region is the region in the field of an antenna, located near the antenna, in which electric and magnetic fields do not have a substantial plane-wave character, but vary considerably from point to point. The term «near-field region» does not have a very precise definition, with different meanings for large and small antennas. The near-field region is further subdivided into the radiating near-field region and the reactive near-field region – that is closest to the antenna and contains most/almost all stored energy associated with the antenna’s field. In the event that the maximum overall dimension of the antenna is small compared to the wavelength, the radiating near-field region may not exist. For antennas that have a large wavelength, the radiating near-field region is sometimes referred to as the Fresnel region – by way of analogy to optical terminology.

4.6 - Root-mean-square value or effective value. - Certain electrical effects are proportional to the square root of the mean of the square of a periodic function (over one period). This value is known as the effective value or root-mean-square value, since it is derived by first squaring the function, determining the mean value of the squared amounts obtained, and then taking the square root of that mean value. It is mathematically defined as the root mean square of the squares of the instantaneous values of the signal:

where x(t) is time variant signal and T the signal period.

4.7 - Peak value. - It corresponds to the maximum absolute value of the function.

4.8 - Mean value. - Mathematically, the mean value can be defined as:

The mean value, by itself, does not provide sufficient information in order to differentiate the phenomenon that can be completely different in terms of time variation, even though it has the same mean value.

4.9 - Reference level. - The reference levels are derived from the basic limits of exposure of human beings to electromagnetic fields for comparison against measured electromagnetic fields. Measurements below the reference level guarantee that the requirement that basic limits of exposure are not exceeded is satisfied.

4.10 - Decision level. - The decision levels are the thresholds which are set to allow for measurement uncertainties, taking into account the measurement equipment used, the environment and spectrum characteristics, allowing:

 - to make the bridge between the different cases (Case 1 to Case 2 and Case 2 to Case 3); and

 - to decide whether a spatial average according to point 6.2 has to be established.

4.11 - Exposure quotient. - The exposure quotient is the ratio of the measured maximum electromagnetic power density to the appropriate reference level at a given frequency. A value greater than 1 signifies that reference levels have been exceeded. Several exposure quotients may be applicable for one frequency, according to the reference levels considered (for example, E and H-field), and different quotients may apply across the frequency band of interest.

4.12 - Total exposure quotient. - The total exposure quotient is a summation of all the individual frequency exposure quotients in the measured frequency band at a single location. The calculation of this value from the individual frequency quotients is defined in the exposure limits. Several total exposure quotients may be applicable (for example, for E and H).

5 - Examples of emissions in the frequency band from 9 kHz to 300 GHz
 

Symbol	Frequency range (lower limit exclusive, upper limit inclusive)	Services
VLF(*https://www.anacom.pt/render.jsp?contentId=55129)	9 kHz to 30 kHz	Induction heating.
LF	30 kHz to 300 kHz	Industrial induction heating, broadcasting.
MF	300 kHz to 3 000 kHz	Broadcasting, industrial induction heating.
HF	3 MHz to 30 MHz	Broadcasting, radio-amateurs, Armed Forces.
VHF	30 MHz to 300 MHz	PMR, TV, Armed Forces, radio-amateurs, broadcasting, aeronautical services.
UHF	300 MHz to 3 000 MHz	TV, GSM, DECT, UMTS, bluetooth, earth stations, radars.
SHF	3 GHz to 30 GHz	Radars, earth stations, microwave links.
EHF	30 GHz to 300 GHz	Radars, microwave links.

(*) By definition, the frequency range for VLF is 3 to 30 kHz.

6 - General considerations for measurement operation

6.1 - Electric and magnetic fields. - Electromagnetic fields can be sub-divided into two components: the electric field (E) and the magnetic field (H). The E-field and the H-field are mathematically interdependent in the far-field, that means only one component has to be measured. For example, if free space of the magnetic field (H) is measured in this region, it can be used to calculate the magnitude of the electric field (E) and power density (S):

knowing Z₀ = 377 Ω.

In contrast, the H-field and E-field must be measured separately in the reactive near-field region.

Only electric field strength is normally measured, since measurements are typically made in the far field. The magnetic field level can then be calculated using the intrinsic impedance of free space (Z0= 377Ω). If both the electric field and magnetic field values are lower than the more stringent reference value, the power flux density must also be lower.

The table below indicates the method at different distances from stations antennas:

	Reactive near-field region	Radiating near-field region	Far-field region
Lateral edge of the region, measured from antenna	0 to l	l to l+2D2/l	l to l+2D2/l
E ^ H
Z = E / H	¹ Z0	» Z0	= Z0
Component to be measured	E and H	E or H	E or H

Measurements are usually made further than the distance of the reactive near-field region, thus the measurement of one component E field (or H field) is sufficient in the following situations:

 - LF broadcast at a approximate distance of 2000 m (λ for 150 kHz), it can be lower (for example some hectometres for a quarter wavelength antenna) depending on the type of antenna;

 - Radio broadcasting at a distance of 3 m (l for 100 MHz);

 - TV broadcasting at a distance of 6 m (l for band I), 1,5 m (l for band III ), and 50 cm (l for IV-V);

 - GSM base station at a distance of 30 cm (l for 935 MHz) and 15 cm (l for 1800 MHz);

 - Radar station with parabolic antenna (D=1,5m and f=1367 MHz) at a distance of 21 m.

Examples described above are merely indicative, thus in practise the emission frequency and the constitution of the antenna must be taken into account.

6.2 Measurement point(s):

Location of measurement points - Measurement point(s) should be chosen to represent the highest levels of exposure to which a person might be subjected, considering the positions of neighbouring antennas. These locations can either be found by a quick check by calculation based on the theoretical propagation from neighbouring antennas or by using measuring equipment (see case 1 and case 2).

Number of measurement point(s) - the measurement shall be made for a single point, 1.5m above ground level.

In case 1 and 3, if the measurement result reaches the decision level, a spatial average of 3 points to match the dimensions of the human body shall be performed. Other measurement points shall be 1.1m and 1.7m above ground level, according to the following picture:

 The field strength value to be used in further calculations is the averaged value of the three values, obtained for each spatial point:

 ANNEX 2
Applicability of non-ionising radiation measurement methods
 

Case 1 - Quick overview

The quick overview method should be applied when just the global level of non-ionising radiation is required.

The quick overview method has some restrictions. This method should not be applied:

a) If it is necessary to know the non-ionising radiation levels by frequency;

b) If the value given by this method exceeds the lowest reference for the frequency band covered by the equipment;

c) If the value given by this method or the spatial average according to Annex 1, point 6.2 (where appropriate) exceeds the decision level defined in Annex 1, point 4.10.

In these situations, case 2 should be applied.

Case 2 - Variable frequency band scan

The variable frequency band scan method should be applied when non-ionising radiation levels are required by frequency within the scanned band.

The variable frequency band scan method has some restrictions. This method should not be applied:

a) Where near-field measurements are required;

b) Where measurements of strong electric or magnetic field are required;

c) If pulsed, discontinuous, or wide-band emissions have to be measured;

d) If the resulting values exceed the decision level.

In these situations, case 3 should be applied.

Case 3 - Detailed investigation

The detailed investigation method should be applied where Case 1 and 2 are not applicable.

The detailed investigation should be applied in the following cases:

a) Where near-field measurements are required,

b) Where measurements of strong electric or magnetic fields are required,

c) To the measurement of non-classic services (for example: pulsed, discontinuous or wide-band emissions, …).

 ANNEX 3
Measurement method applicable to case 1
 

1 - Scope and specific requirements

The quick overview method should be applied when the summation of non-ionising radiation level is required. The present method should be applied to a far field situation.

2 - Measurement equipment

RF radiation meters with isotropic field probes should be used for these measurements. The idea of such equipment is to assess general radiation value in a specific location. The radiation meter and the probe measure the effective value of field strength, also known as the root mean square value (RF radiation meters generally use «peak» detectors, which will give an artificially high result for elliptically polarised signals).

3 - Measurement procedure

The procedure should follow these steps:

3.1 - Choosing the most suitable probe(s) for the frequency emissions to be studied. - Probes should be selected to cover frequency emissions of interest. In certain cases two or more probes would be required to survey the full band. In this case, the final result will be calculated using the values given by each probe (processed as if individually obtained) by using the following formula:

where n is the number of probes covering the frequency band in study and E_i or H_i are the value obtained individually by each probe.

The obtained value may be over-evaluated, since sometimes the probe frequency bands overlap each other, and the formula does not correct this.

3.2 - Measurement. - The choice of measurement point (location and number of points) should be in accordance with the general considerations (Annex 1, point 6.2).

The measurement duration should be referenced to the exposure time limits determined in the adopted reference document.

The RF radiation sensors should be mounted on a non conductive tripod, in order not to perturb electromagnetic field, and will derive the effective or root-mean-square value of E (or H). Personnel should be retreat from the antenna during measurements.

4 - Post-processing

4.1 - According to the value obtained:

 - If the value is below the sensitivity level of the probe, the value must be ignored;

 - A probe specific correction factor may be applied according to the probe manufacturer’s instructions.

4.2 - Calculation of electric field (E)/magnetic field (H)/power density (S). - Under far field conditions, unmeasured quantities can be calculated using the following formulae:

4.3 - Exposure to single/multiple frequency fields. - Exposure to a single frequency field is the ideal situation. Nevertheless, in practice a single frequency field situation may be assumed, where there is a predominant one. Considering simultaneous exposure to multiple frequency fields, it is easy to prove mathematically that if the value given by the RF meter does not exceed the more stringent value of the frequency band covered by the probes, then the contributions of all individual frequencies will also fall below that value, since:

where Esum is the display value of the RF meter (probe) and n, the number of emissions considered.

If the exposure level given by the equipment exceeds any decision levels (or limits) within the frequency band of interest, the method of Case 2 should be applied.

5 - Uncertainty estimation

The measurement uncertainty should be evaluated taking into account, at the least, the sources of uncertainty indicated in the table below. The standard uncertainty and the sensitivity coefficient ci shall be evaluated for the estimate xi of each quantity. The combined standard uncertainty uc(y) of the estimate y of the measurand is calculated as a weighted root sum square:

The expanded measurement uncertainty ue is calculated as:

u_e = 1,96 u_c¹

and should be stated in the measurement report.

Sources of uncertainty	Uncertainty of xi		u(xi)	ci	(ci u(xi))2 (percentage)
	Value %	Probability distribution; divisor k
Isotropy		Uniform2; √3		1
Linearity		Uniform; √3		1
Flatness		Normal; k=1		1
Temperature		Uniform; √3		1
...................	...	...	...	...	...
Combined standard uncertainty
Expanded uncertainty (confidence interval of 95%)		ue = 1,96 uc

In most of cases, figures above are given for a confidence interval of 95%. Values for RF radiation meters with isotropic field probes are as follows:

Sources of uncertainty	Expanded uncertainty (dB) (confidence interval of 95%)	Expanded uncertainty (num.) (confidence interval of 95%)	Standard uncertainty (num.) (confidence interval of 66%)
Isotropy	1.50	0.19	0.10
Linearity	1	0.12	0.06
Flatness	1	0.12	0.06

 6 - Measurement report

The measurement results shall be submitted in the form of a table (graphic form is optional) for each location to be measured, given the recommended levels.

The measurement report shall follow the structure defined in Annex 6. For case 1 the following particularities have to be taken into account:

Measured component E (or H):

Probe (type and reference)	Value	Used correction factor	Final result	Unit	Start time	Stop time	Date
				V/m	hh:mm:ss	hh:mm:ss	dd- mm- yyyy
				A/m

Calculated component(s). - H (or E) and S can be calculated taking into account the remarks in point 4.2.

Application of the adopted reference document. - Measured and calculated quantities must be compared with the lowest reference level that applies to the case under consideration, set out in the legislation in force. If the quantities of measured and/or calculated values are higher than this level of decision (or limit), the method of case 2 should be applied.

 ANNEX 4
Measurement method applicable to case 2
 

1 - Scope and specific requirements

The variable frequency band scan method should be applied when non-ionising radiation levels are required by frequency within the scanned band or case 1 is inappropriate. This method is applicable under far field conditions.

2 - Measurement equipment

This type of survey is best carried out using a battery powered receiver or spectrum analyser (SA). The receiver or spectrum analyser should be capable of software control. Software control is essential due to the vast amount of data (frequency and amplitude) to be collected during the survey and to maintain consistent results over several sets of survey equipment being operated by several different survey officers. This software should also make provision for the programming of antenna factors and feeder cable insertion loss. This will allow the survey system to use a variety of antennas and cables, allowing for a degree of customisation for specific band surveys. In this way, probabilities of error can be kept to a minimum. Survey receivers or spectrum analysers will occasionally be required to operate in hostile RF environments, and thus should be prepared.

Good dynamic range and inter-modulation performance will be essential to achieve reliable results.

Survey antennas and cables shall be metrologically characterized. Preferred types of antennas (which must be robust) to be used are:

 - Magnetic loop for HF;

 - Broadband dipole antenna or (encapsulated) log periodic antenna;

 - Bi-conical antenna;

 - Directional antenna when there is a main contribution (and other contributions are negligible);

 - Three axis antenna.

For lower frequencies, taking into account the significant wavelength, electrically small antennas should be chosen. Using passive electric antennas, the minimum distance between the antenna and any obstacle (wall or ground for example) must be at least 1. Measurements of frequencies lower than 600 MHz with a 50 cm height above ground-level should use broadband, electr ically small magnetic or electric antennas rather than a half-wave dipole. Antennas should be mounted on non conductive tripods in order not to perturb the electromagnetic field. Personnel should retreat from the antenna during measurements.

3 - Pre-processing

Equipment checks. - All measurement equipment should be calibrated (according to the manufacturer’s recommendations or quality management procedures of the competent body) to traceable standards. RF cables, waveguides and connectors should be individually marked and checked prior to use for mechanical damage. They should also be checked regularly for electrical characteristics (return loss and insertion). Any changes in antenna and cable parameters should be reprogrammed into the measurement receiver.

A check should be made to verify that the correct cable and antenna parameters are loaded and activated in the receiver. It is the responsibility of the survey team to confirm the calibration factors are correct and updated prior to each measurement. Records of the survey should show that the check/update has been made.

4 - Measurement procedure

The procedure should be conducted according to the following steps:

1 - Measurement point - the choice of measurement point (location and number of points) will be in accordance with the general considerations (Annex 1 - point 6.2).

2 - Frequency band - The method is appropriate to frequencies between 9 kHz and 3 GHz. Within this frequency range, this measurement process provides confident results. For frequencies above 3 GHz (for example, radar, microwave links), either case 1 or recommendations of case 3 (and especially Annex 5, point 4) must be applied.

3 - Settings of receiver or spectrum analyser:

Bandwidth, stepping and time limits - the measurement bandwidth will be a compromise for the various RF sources in the radio spectrum. Throughout the spectrum there is a mixture of wide/narrow, analogue/digital and continuous/discontinuous sources. In addition, although there are many single-service bands, there are also many shared bands where services exist with widely different signal characteristics.

For receivers, it is recommended that the dwell time is at least 0.1 seconds and that the following parameters are used according to the bandwidth under consideration:

 - 9 kHz - 30 MHz => BW = 9 or 10kHz - step size of 10 kHz;

 - 30 MHz - 3GHz => BW = 100 kHz - step size of 100 kHz.

For spectrum analysers, it is recommended that the following parameters are used according to the bandwidth under consideration:

 - 9 kHz - 30 MHz - BW = 10 kHz - with a sweep time of 50 - 100 ms;

 - 30 MHz - 300 MHz - BW = 100 kHz - with a sweep time of 100 ms;

 - 300 MHz - 3 GHz - BW = 100 kHz - with a sweep time of 700 ms - 1 sec.

Threshold level - The threshold level is established at 40 dB below the reference level, as from which emissions are taken into consideration. If no emission exceed the threshold level within a frequency band, the two highest emissions may be reported.

Antenna polarisation - measurements shall be made with the measurement antenna in both horizontal and vertical planes.

Mode - Max-hold techniques and peak mode detector should be used.

5 - Post-processing

Calculation of magnetic field (H)/power density (S) - under far field conditions, unmeasured quantities can be calculated using the following formulae:

6 - Uncertainty estimation

The measurement uncertainty should be evaluated taking into account, at the least, the sources of uncertainty indicated in the table below. The standard uncertainty u(_xi) and the sensitivity coefficient c(_i) shall be evaluated for the estimate xi of each quantity. The combined standard uncertainty uc(_y) of the estimate y of the measurand is calculated as a weighted root sum square:

The expanded measurement uncertainty ue is calculated as:

u_e = 1,96 u_c*

* The coverage factor of 1.96 yields a 95% level of confidence for the near-normal distribution typical of most measurement results.

and should be stated in the measurement report.

Sources of uncertainty	Uncertainty of xi		u(xi)	ci	(ci u(xi))2 (percentage)
	Value (percentage)	Probability distribution; divisor k
Measurement device (receiver, spectrum analyser) including cable loss		Normal; k=1		1
Antenna factor		Normal; k=1		1
...................	...	...	...	...	...
Combined standard uncertainty
Expanded uncertainty (confidence interval of 95%)		ue = 1,96 uc

In most cases, figures above are given for a level of confidence of 95%.

Typically values for a spectrum analyser associated with a calibrated antenna are as follows:

Sources of uncertainty	Expanded uncertainty (dB) (confidence interval of 95%)	Expanded uncertainty (num.) (confidence interval of 95%)	Standard uncertainty (num) (confidence interval of 66%)
Antenna factor	1	0.12	0.06
Cable	0.20	0.02	0.01
Receiver	2	0.26	0.13

 7 - Report

The measurement results shall be submitted in the form of a table (graphic form is optional) for each location to be measured, given the levels recommended.

The measurement report shall follow the structure defined in Annex 6. For case 2 the following particularities have to be taken into account.

Measured component E. - The table below is used for reporting the significant emissions:

Frequency	Recommended Value	Results	Unit	Equipment

Calculated component(s). – H or S can be calculated taking into account the remarks in point 5.

Application of the adopted reference document. - Measured and calculated quantities shall be used to check the compliance of RF exposure with the legislation in force. This is done in the following two steps:

 - E, H and S shall be compared to reference levels;

 - E, H and S are used to calculate the eventual total exposure quotients.

Some examples for the calculation of the total exposure quotients can be found below:

Total exposure quotient based on power flux density:

Total exposure quotient referred to electrical stimulation effects (a=87 V/m, b=5 A/m; E_L,_i and H_L,_j are frequency depended limits):

     

(Source : European Recommendation 1999/519/EC of 12 July 1999)

Total exposure quotient referred to thermal effect circumstances (c=87/f ^1/2 V/m, d=0.73/f A/m ; E _L,i and H _L,j are frequency depended limits):

              

(Source : European Recommendation 1999/519/EC of 12 July 1999)

Taking into account the measured and calculated values and their uncertainty, the case 3 method should be applied if the results reach or exceed the decision level (or the limits).
 

 ANNEX 5
Measurement method applicable to case 3 
 

 1 - Scope and specific requirements

The present method should be applied where case 1 and 2 are not suitable and especially:

 - Where near-field measurements are required;

 - Where strong electric or magnetic field measurements are required;

To non classic services measurement (for example, pulsed, discontinuous or wide-band emissions).

2 - Measurement equipment

The equipment used is the same as used for cases 1 and 2. Additionally, it should be noted that for a near-field situation, both electric and magnetic measurement are required (use of E and H sensors). And, for some types of signals, especially pulsed or UWB³, the use of a time domain receiver/analyser is strongly recommended to pre-analyse signals (for example detection and characterisation of bursts), ensuring that measurement settings are adapted accordingly.

3 – Pre-processing

Pre-processing operation is identical to case 2. Additionally, it could be helpful to ask the operators for more details concerning the station (number of transmitters, temporal operation mode and antenna system/pattern).

4 - Measurement procedure

The procedure should be according to the following steps:

1) Measurement point - the choice of measurement points (location and number of points) will be done according to the general considerations (Annex 1 - point 6.2). Antennas should be mounted on non conductive tripods in order not to perturb electromagnetic field. Personnel should retreat from the antenna during measurements;

2) Frequency band – this measurement operation is appropriate for frequencies between 9 kHz and 3 GHz. If in a measurement location, there are emissions at frequencies above 3 GHz (for example: radar, microwave links), they have to be measured considering the remarks below (point 4, “Specific configurations”).

3) Settings of the equipment - they have to be identical to case 2 except for the emissions reaching the adopted reference levels as well as pulsed, discontinuous and wide-band emissions. For these types of emissions, point 4 shall be taken into account (“Specific configurations”).

4) Specific configurations:

4.1) Reactive near-field measurement - in contrast to the radiating near-field and the far-field region, in the reactive near-field region, the H-field and E-field must be measured separately, by using distinct sensors. The electric component (E) of the field can be easily measured using suitable antennas, for example dipole, bi-conical, log-periodic, etc, and the magnetic component (H) of the electromagnetic field is usually measured with loop sensors;

4.2) Strong electric or magnetic field measurement - immunity of equipment, especially for receivers or spectrum analysers, has to be checked. If necessary, probes should be used, having better immunity against strong signals.
If receivers or spectrum analysers are necessary, it is necessary to:

 - Use passive antennas and protected equipment;

 - Reduce one or several transmitter’s power and simultaneously record the reduction factor(s).

For these types of equipment, the measurement procedure should be according to the following steps:

 - Setting the centre frequency on each emission with a resolution equal or larger than the bandwidth of the channel;

 - Selecting “average mode” during adequate time referred to in the adopted reference document;

 - Selecting "rms" detector;

 - If a single dipole or single loop is used, three measurements should be performed in 3 orthogonal directions to obtain the different components of the field.

The total field is given by the following formula:

 

Precautions for measurement staff - when strong electromagnetic fields have to be measured, safety measures against radiation exposure of the staff have to be taken. The use of radiation protection gauges and field strength predictions are recommended and safe working conditions must be ensured;

4.3) Signals above 3 GHz - in these frequency bands there are only a few omni-directional antennas available. Therefore, directive survey antennas (horn, dish, lens, log-periodic, …) should be used.

The procedure should be according to the following steps:

 - Setting the centre frequency on each emission with a resolution equal or larger than the bandwidth of the channel;

 - Selecting “average mode” during adequate time referred to in the adopted reference document;

 - Selecting “rms" detector;

 - The antenna should be used in a maximum signal position of the antenna (with the appropriate polarisation and direction).In that measurement procedure, the reflections are negligible.

4.4) Pulsed/radar emission measurements - for this type of signals, the energy is carried in "short bursts". The pulse is usually short compared to the interval between pulses. There is a great diversity of radars, in particular for aeronautical applications, but also in other fields such as, for example, monitoring and control activities. These applications have very varied characteristics, typically in frequency between 100 MHz and 95 GHz and in peak power between 1 W and 50 MW. The values to be assessed (for the electric and magnetic field) are the peak value and the effective value (“rms” value) of the pulsed field.

For the assessment of the peak value, the procedure should be in accordance with the following steps:

 - Selecting a filter, centred on the emission frequency, of a sufficiently large broadband, given characteristics of the signal to be measured, namely the width of the impulse (in the case of an unmodulated impulse, a filter of width 4/t, with t being the duration of the impulse, it is possible to obtain 99% of the power of the signal);

 - Selecting “max hold” mode for one or several rotations of the radar (until stabilisation of the signal);

 - Selecting “positive peak detection mode";

 - Selecting a span = 0.

The peak power should not exceed the reference level by a factor of:

 - 1000, where the power density is concerned;

 - 32, where the field strength is concerned.

The figures above have to be in accordance with the adopted reference document, and do not directly relate to the pulse characteristics of the radar.

For the assessment of the effective value “rms” of the field-strength, it is necessary:

 - To know the temporal characteristics of the signal in order to determine the average value, knowing the peak value, or

 - To carry out the average of the instantaneous signal in effective “rms” mode.

The effective “rms” value averaged should not exceed the reference level. Many radar antennas have a narrow beam with agility in direction obtained by mechanical or electronic means. In general in these cases it is not useful to assess the average value. However, the question of the decomposition of this agility or the cumulative effect with other emissions may be raised.

4.5) Discontinuous signals - for this type of signal, two different cases should be considered:

1) The technical parameters of the signal are known ("duty cycle", modulation, …); the measurement procedure should be in accordance with the following steps:

 - Setting the centre frequency of each emission with a resolution equal or larger than the bandwidth of the channel;

 - Selecting “max hold" mode;

 - Selecting a “peak detector";

 - The “rms” value is then assessed by calculation. If a single dipole or single loop is used, three measurements should be performed in three orthogonal directions to obtain the different components of the field. The total field would be given by the following formula:

2) The technical parameters of the signal are unknown; the measurement procedure should be in accordance with the following steps:

 - Setting the centre frequency of each emission with a resolution equal or larger than the bandwidth of the channel;

 - Selecting “average mode” during adequate time referred to in the adopted reference document (for example 6 minutes in   Recommendation EU 1999/519/EC);

 - Selecting “rms” detector;

 - If a single dipole or single loop is used, three measurements should be performed in three orthogonal directions to obtain the different components of the field. The total field would be given by the following formula:

The station should be activated only as long as is strictly necessary to perform the measurement, so as to avoid a long period of exposure.

4.6) Trunked Systems (GSM, TETRA,…) - transmissions by these systems consist of a permanent control channel and additional traffic channels. In this context, a base station could be regarded as n transmitters, being:

 - One transmitter (for example, in GSM, the BCCH channel) with a constant power level PControl_channel;

 - (n-1) transmitters of a power level equal to PControl_channel (where n corresponds to the total number of transmitters of the base station).

In order to take into account the maximum possible traffic, the measurement procedure should be in accordance with the following steps:

 - Identifying the permanent control channel, which can be done using a spectrum analyser (the permanent control channel is identified by its permanence and its stable level);

 - Setting the centre frequency on the permanent control channel with a resolution equal or larger than the bandwidth of the channel;

 - Selecting “max hold mode”;

 - Selecting a “peak” detector;

 - If a single dipole or single loop is used, three measurements should be performed in three orthogonal directions to obtain the different components of the field. The total field would be given by the following formula:

E_{Control_channel} / H_{Control_channel}  is then assessed.

 - Investigating the number of transmitters of the base station (traffic channels and control channel), using a spectrum analyser, in order to note the numbers of channels (except in some cases of frequency hopping).

The extrapolation to the maximum traffic is then calculated by the following formula:

If the transmitting channels belonging to the same cell are using different power levels, the following formula should be used:

where P _total is the maximum possible power;

4.7) Analog /digital wide-band emissions (TV, T-DAB, DVB-T, …) - for these types of emissions, it could be difficult to get a resolution equal to the bandwidth of the emissions. The procedure should thus be according to the following steps:

 - Selecting a lower resolution filter and carry out a cumulative calculation taking into account the shape of the filter. This type of process is known as the «channel power» mode;

 - The measurement duration should be referenced to adopted reference document;

 - If a single dipole or single loop is used, three measurements should be performed in three orthogonal directions to obtain the different components of the field. The total field would be given by the following formula:

5 - Uncertainty estimation

The measurement uncertainty should be evaluated taking into account, at the least, the sources of uncertainty indicated in the table below. The standard uncertainty u(_xi) and the sensitivity coefficient c_i shall be evaluated for the estimate xi of each quantity. The combined standard uncertainty uc(_y) of the estimate y of the measurand is calculated as a weighted root sum square:

 The expanded measurement uncertainty ue is calculated as:

u_e = 1,96 u_c⁴

and should be stated in the measurement report.

For RF radiation meters with isotropic field probes:

Sources of uncertainty	Uncertainty of xi		u(xi)	ci	(ci u(xi))2 (percentage)
	Value (percentage)	Probability distribution; divisor k
Isotropy		Uniform5; √3		1
Linearity		Uniform; √3		1
Flatness		Normal; k=1		1
Temperature		Uniform; √3		1
...................	...	...	...	...	...
Standard combined uncertainty
Expanded uncertainty (confidence interval of 95%)		ue = 1,96 uc

For a receiver or spectrum analyser (associated with a calibrated antenna):

Sources of uncertainty	Uncertainty of xi		u(xi)	ci	(ci u(xi))2 (percentage)
	Value (percentage)	Probability distribution; divisor k
Measurement device (receiver, spectrum analyser) including cable loss		normal; k=1		1
Antenna factor		normal; k=1		1
...................	...	...	...	...	...
Standard combined uncertainty
Expanded uncertainty (confidence interval of 95%)		ue = 1,96 uc

 
  6 - Report

The measurement results shall be submitted in the form of a table (graphic form is optional) for each location to be measured, given the levels recommended.

The measurement report shall follow the structure defined in Annex 6. For case 3 the following particularities have to be taken into account:
Measured component E (or H):

Frequency	Recommended Value	Results	Unit	Equipment

Application of the adopted reference document - measured and calculated quantities have to be used to check the compliance of RF exposure with the legislation in force. This assessment should be in accordance with the two following steps:

 - E, H and S have to be compared to reference levels;

 - E, H and S are used to calculate the eventual quotients (see case 2 for examples).

 ANNEX 6
Report

The main elements of the report structure are as follows:

1 - Objectives and limitations

The objectives and the operation should be described (site of measurement, choice of the points of measurement).

2 - Description of the site of measurement

Information below should be provided:

 - Date, start and stop time;

 - Geographic co-ordinates (based on WGS84: latitude – longitude);

 - Address;

 - Photographs that illustrate the situation;

 - Description and particular characteristics of the site of measurement (in the case of an operation in a complex area - in an urban area for example - the exact site of measurement has to be described);

 - List of identified transmitters;

 - Temperature in °C.

3 - Description of equipment

The used equipment and its relevant characteristics will be noted in the report. Examples for some categories of equipment categories are described below.

For an antenna:

Antenna no. ...
Manufacturer	Gain (f min and f max - gain in the axis)
Type	Antenna factor uncertainty
Frequency band	Check/update date

For a spectrum analyser or receiver:

Equipment no.
Manufacturer	Frequency Band
Type	Check/update date
Measurement Uncertainty

For a probe:

Equipment no.
Frequency Band	Dynamic range
Measurement Uncertainty	Check/update date

 
4 - Uncertainty

In order to be complete, each measurement should be accompanied by a statement of uncertainty in accordance with the specifications introduced in case 1, case 2 or case 3. However, due to the in-situ nature of the measurement site, it may not be practical to include all the uncertainties associated with the measurement location.

5 - Report of measurements

The report of measurements should be in accordance with the specifications introduced in case 1, case 2 or case 3.

6 - Applied limits and formulas for total exposure quotients

The value of limits in the observed frequency band and the method to obtain the total exposure quotients should be described. Alternatively the method could be referred to.

7 - Conclusion

A conclusion on the conformity of the RF exposure with respect to the reference document must be specified.

 
¹ The coverage factor of 1.96 yields a 95% level of confidence for the near-normal distribution typical of most measurement results.
² Also known as rectangular distribution.
³ UWB, ultra wide band.
⁴ The coverage factor of 1.96 yields a 95% level of confidence for the near-normal distribution typical of most measurement results
⁵ Also known as rectangular distribution.

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