VILNIUS GEDIMINAS TECHNICAL UNIVERSITY

Raimondas BUCKUS

ELECTROMAGNETIC RADIATION OF MOBILE COMMUNICATION INVESTIGATION AND SPREAD REDUCTION INSTRUMENTALITIES

SUMMARY OF DOCTORAL DISSERTATION

TECHNOLOGICAL SCIENCES, ENVIRONMENTAL ENGINEERING (04T)

Vilnius 2013

Doctoral dissertation was prepared at Vilnius Gediminas Technical University in 2009–2013. Scientific Supervisor

Prof Dr Habil Pranas BALTRĖNAS (Vilnius Gediminas Technical University, Technological Sciences, Environmental Engineering – 04T).

The dissertation is being defended at the Council of Scientific Field of Environmental Engineering at Vilnius Gediminas Technical University: Chairman

Prof Dr Habil Donatas BUTKUS (Vilnius Gediminas Technical University, Technological Sciences, Environmental Engineering – 04T).

Members: Assoc Prof Dr Eglė JOTAUTIENĖ (Aleksandras Stulginskis University, Technological Sciences, Environmental Engineering – 04T), Prof Dr Habil Algirdas JUOZULYNAS (Vilnius University, Environmental Engineering – 04T), Prof Dr Habil Algimantas KAJACKAS (Vilnius Gediminas Technical University, Technological Sciences, Electrical and Electronic Engineering – 01T), Prof Dr Egidijus Rytas VAIDOGAS (Vilnius Gediminas Technical University, Technological Sciences, Civil Engineering – 02T).

Opponents: Assoc Prof Dr Diana ADLIENĖ (Kaunas University of Technology, Physical Sciences, Physics – 02P), Prof Dr Aloyzas GIRGŽDYS (Vilnius Gediminas Technical University, Technological Sciences, Environmental Engineering – 04T).

The dissertation will be defended at the public meeting of the Council of Scientific Field of Environmental Engineering in the Senate Hall of Vilnius Gediminas Technical University at 1 p. m. on 7 June 2013. Address: Saulėtekio al. 11, LT-10223 Vilnius, Lithuania. Tel.: +370 5 274 4952, +370 5 274 4956; fax +370 5 270 0112; e-mail: doktor@vgtu.lt The summary of the doctoral dissertation was distributed on 6 May 2013. A copy of the doctoral dissertation is available for review at the Library of Vilnius Gediminas Technical University (Saulėtekio al. 14, LT-10223 Vilnius, Lithuania).

© Raimondas Buckus, 2013

VILNIAUS GEDIMINO TECHNIKOS UNIVERSITETAS

Raimondas BUCKUS

MOBILIOJO RYŠIO ELEKTROMAGNETINĖS SPINDULIUOTĖS TYRIMAI IR SKLAIDOS MAŽINIMO PRIEMONĖS

DAKTARO DISERTACIJOS SANTRAUKA

TECHNOLOGIJOS MOKSLAI, APLINKOS INŽINERIJA (04T)

Vilnius 2013

Disertacija rengta 2009–2013 metais Vilniaus Gedimino technikos universitete. Mokslinis vadovas

prof. habil. dr. Pranas BALTRĖNAS (Vilniaus Gedimino technikos universitetas, technologijos mokslai, aplinkos inžinerija – 04T).

Disertacija ginama Vilniaus Gedimino technikos universiteto Aplinkos inžinerijos mokslo krypties taryboje: Pirmininkas

prof. habil. dr. Donatas BUTKUS (Vilniaus Gedimino technikos universitetas, technologijos mokslai, aplinkos inžinerija – 04T).

Nariai: doc. dr. Eglė JOTAUTIENĖ (Aleksandro Stulginskio universitetas, technologijos mokslai, aplinkos inžinerija – 04T), prof. habil. dr. Algirdas JUOZULYNAS (Vilniaus universitetas, technologijos mokslai, aplinkos inžinerija – 04T), prof. habil. dr. Algimantas KAJACKAS (Vilniaus Gedimino technikos universitetas, technologijos mokslai, elektros ir elektronikos inžinerija – 01T), prof. dr. Egidijus Rytas VAIDOGAS (Vilniaus Gedimino technikos universitetas, technologijos mokslai, statybos inžinerija – 02T).

Oponentai: doc. dr. Diana ADLIENĖ (Kauno technologijos universitetas, fiziniai mokslai, fizika – 02P), prof. dr. Aloyzas GIRGŽDYS (Vilniaus Gedimino technikos universitetas, technologijos mokslai, aplinkos inžinerija – 04T).

Disertacija bus ginama viešame Aplinkos inžinerijos mokslo krypties tarybos posėdyje 2013 m. birželio 7 d. 13 val. Vilniaus Gedimino technikos universiteto senato posėdžių salėje. Adresas: Saulėtekio al. 11, LT-10223 Vilnius, Lietuva. Tel.: (8 5) 274 4952, (8 5) 274 4956; faksas (8 5) 270 0112; el. paštas doktor@vgtu.lt Disertacijos santrauka išsiuntinėta 2013 m. gegužės 6 d. Disertaciją galima peržiūrėti Vilniaus Gedimino technikos universiteto bibliotekoje (Saulėtekio al. 14, LT-10223 Vilnius, Lietuva). VGTU leidyklos „Technika“ 2137-M mokslo literatūros knyga.

© Raimondas Buckus, 2013

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Introduction

Topicality of the problem The world we live in is constantly modernizing and the electromagnetic

radiation emitted by electronic devices, electric-power transmissions, television and radio stations, computers, radars, mobile phone antennas and, especially, by mobile phones constantly affect people and can cause various health problems. Electromagnetic waves surround us, however, we are not capable to smell, see or feel them.

In the twenty-first century, with the spread of mobile phone networks and introduction of GSM-900, GSM-1800, UMTS-2100 systems, the number of sources of electromagnetic radiation increased. A lot of people use mobile connection without concerning its operating principles: something that is not seen can cause harm. Active use of mobile phones and their level temporal dynamics allow perceiving the component of electromagnetic background as one of the most important physical agents that actively affect live organisms and environment.

Due to the growing number and scope of sources of electromagnetic radiation from mobile phones, their effect became significant not only for specialist but for all the inhabitants of surrounding areas. In some countries mobile-free zones are demanded. In such zones it is forbidden to install mobile communication base stations, it is also required to reduce the highest levels of allowed electromagnetic radiation or other restrictions are imposed.

When the mobile phone is used, it is put to the ear, and when not – it usually stays in the pocket, near the body, in this way the electromagnetic radiation emitted by (ringing) mobile phone directly interacts with human body. Common mobile phone cases do not provide protection from electromagnetic radiation. Therefore, cases that would protect from electromagnetic radiation, when using mobile phones, and that would not have negative effect on the quality of connection, are necessary.

Measurements and evaluation of electromagnetic radiation level, reduction of the highest allowed level of electromagnetic radiation and establishment of other regulations – are issues of world-wide importance. At the moment, the most important concern is the contradictory information about mobile phones and mobile communication base stations, and their declared effects on human health.

The Ministry of Health informs that on 31st May 2011 the World Health Organisation’s International Agency for Research on Cancer announced that, when the mobile phone is used for a long time – 30 or more minutes per day, the radiofrequency electromagnetic fields can increase risks of the brain

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tumour. World Health Organisation stresses that when mobile phone is used properly and following all safety measures the negative effects on health caused by electromagnetic radiation can be minimised or avoided.

Due to the lack of scientific researches on electromagnetic radiation from mobile phones and public concern, the tendencies of EMF insensitivity parameters in the environment are discussed in this thesis. The contemporary opinion on the negative effect of mobile phone antennas and electromagnetic radiation from mobile phones does not allow making assumptions about future consequences. Thus, on the basis of conducted scientific research, not only practical but also engineering – technical safety measures from electromagnetic radiation have been provided in this thesis.

A rapid increase in the level of electromagnetic radiation (many times exceeding original background) that can damage ecological balance of the environment has been observed; therefore, it should be researched and evaluated by theoretical and experimental methods.

Object of the work – the electromagnetic radiation emitted by mobile

connection antennas and mobile phones.

Aim and tasks of the work The aim of this thesis is to research and evaluate the spread of

electromagnetic radiation emitted by mobile connection antennas and mobile phones.

To reach the aim set in the thesis, it is necessary to tackle the following tasks:

1. To evaluate the spread of electromagnetic radiation, created by the antennas with different overall effective radiated power in the environment.

2. To research the strength of electric field created by the various mobile phone models.

3. To create the strength spread of electric fields of mobile phones around head; and provide the evaluation of electromagnetic radiation strength of mobile phone antennas by applying theoretical research.

4. To investigate materials that screen electromagnetic radiation, and to create mobile phone case that reduces the electromagnetic radiation.

Methodology of research. In this thesis the methodologies of researches

on electromagnetic radiation emitted by the mobile connection antennas and mobile phones are applied according to the requirements of hygiene norms and ISO standards. The researches on the materials that screen electromagnetic radiation are conducted according to research conducting methodologies

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provided in the IEEE standards. The empirical formulas have been used for the model investigations of electromagnetic radiation level of mobile phone antennas. “COMSOL Multiphysics” software was used to establish spread of electric fields strength created by mobile phones around head.

Scientific novelty of the work. Complex experimental studies of mobile

connection antennas (of low, medium and high effective radiation power) and mobile phones (GSM second generation (2G) and UMTS third generation (3G)). Simulations carried out by employing two different modelling methodologies (“COMSOL Multiphysics” applied for mobile phone electromagnetic field strength modelling, and simulation researches – for assessment and visualization of mobile connection antennas’ electromagnetic radiation according to the acquired results). Scientific novelty of the work in scientific field of Environmental engineering is created mobile phone case that protects from electromagnetic radiation.

Practical value. According to the results of the research, it is possible to

renew the legal regulatory framework of electromagnetic expertise, that regulates the allowed intensity level of the electromagnetic fields, and to improve evaluation methods and methodologies for electromagnetic radiation. Considering the gathered results in the analysis of electromagnetic radiation of mobile phones it is possible to provide recommendations for mobile phone safety. The mobile phone case that reduces the electromagnetic radiation of mobile phone, for which the patent application has been filed, has been created. The field research methodology can be further used for the evaluation of the epidemiologic state of a certain area.

Defended propositions

1. Mobile connection antennas’ electromagnetic field energy flux density values in ground-level air increase further from the antenna, highest values can be observed at the point where main antenna radiation zone reaches earth surface, further on, it declines.

2. The strength of electric field is directly proportional to the transmission power of a mobile phone and is inversely proportional to frequency and depends on the space, whether it is closed or open.

3. Strength of a mobile phone electric field on the head decreases exponentially while moving sideward from the epicentre of the effect zone, and depends on density of constituent parts of the head.

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The scope of the scientific work. The thesis consists of introduction, three body chapters, discussion of results, general conclusions and recommendations.

Scope of the thesis is 155 pages, 22 numbered formulas, 85 figures and 14 tables. The list of references consists of 107 sources. 1. Mobile telecommunication electromagnetic radiation analysis

During the last two decades the number of mobile phone antennas that emit electromagnetic radiation in the living areas increased significantly, therefore much more attention is paid to the electromagnetic radiation and its effects on human body. The irradiance of electromagnetic radiation is not as dangerous as ionizing radiation, but its effects on live organism are different and effect more people, therefore, the effects of electromagnetic radiation on human beings is becoming more relevant.

The distribution of electromagnetic radiation of mobile phone antennas largely depends on the electrical and mechanic tilt angles in antenna directional diagrams. When the antenna directional diagrams are chosen precisely in the vertical and horizontal planes, with different electrical tilt angles, it assures that measured real parameter values of electromagnetic insensitivity created by antennas at any point in the plane will not be higher than forecasted and will correspond to the requirements of hygiene norms that regulate sources of nonionizing radiation.

One of the most actively used sources of electromagnetic radiation is the mobile phone. Mobile phone is a small compact transmitter and receiver in a single casing. The owner always carries mobile phone nearby; therefore it has effects on the owner. While talking on the phone, the electromagnetic field is directly pointed towards the brain. During the conversation each mobile phone emits different strengths of electric field.

Significant scientific researches on electromagnetic radiation have been conducted by a number of scholars: S. Allen, H. Bassen, G. D´Inzeo, A. Hirata, K. Jokela, J. Lin, S. Mann, R. Matthes, C. Roy, M. Taki, J. Wang, S. Watanabe. They researched the electromagnetic radiation effects on health and relation between electromagnetic radiation and oncological illnesses. Such scholars as U. Bergqvist, G. Friedrich, Y. Hamnerius, L. Martens, G. Neubauer, G. Thuroczy, E. Vogel, J. Wiart conducted researches on electromagnetic radiation of mobile communication base stations in Switzerland. The researches were conducted in inhabitant areas by identifying the sources of electromagnetic radiation. K. Y. Nikolaevich, A. V. Nikolaevich, K. V. Anatolievich, W. P. Thompson, O. H. Peter invented protective screen from electromagnetic radiation. The scholars from VGTU Department of Telecommunication

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Engineering R. Pocius, A. Anskaitis, D. Guršnys, K. Mikėnas and G. Montvilas are conducting model investigations on electromagnetic radiation intensivity parameters in the base station environment.

2. Mobile telecommunication electromagnetic radiation research methodology

While conducting field researches on electromagnetic radiation it is very

important to foresee and evaluate the areas of research. One of the most important parts is to evaluate where values of electromagnetic radiation will be highest i.e. to determine the most intense radiation direction of each antenna. This is done in two steps: by analysing technical characteristics of mobile phone antennas and conducting control researches in the researched environment. In order to evaluate the most intense radiation direction, all of the antenna directional diagrams in vertical and horizontal planes are used. All mobile phone antenna manufacturers provide antenna radiation diagrams with technical characteristics in catalogues.

The most important criteria for the choice of researches on electromagnetic radiation of mobile phone antennas: overall effective radiated power (ERP), height of antenna and specific research points (the researches are conducted in living areas, towards the most intensive direction of mobile connection antenna, on the roofs with mobile phone connection and in the areas, towards the most intensive direction of mobile phone antenna, where people have free access).

Models of mobile connection antennas used in Lithuania have been chosen for the research. The mobile phone antennas are divided into 3 groups according to the different effective radiated power of mobile connection antennas: antennas of low (i. e. 193 W, 281 W and 305 W), medium – (i. e. 484 W, 707 W and 966 W) and high – (i. e. 1329 W, 1428 W and 1739 W) effective radiated strength. In each group 3 mobile connection antennas of different height are chosen for the research: short antennas (i. e. 14 m, 21.5 m and 25 m), medium – (i. e. 30 m and 50 m) and high (75 m). Three antennas have been put on top of the building and 4 on special towers. According to the radiated frequency mobile connection antennas are divided into 3 technologies: GSM 900, GSM 1800 and UMTS 2100. GSM standard for mobile connection is the second generation (2G) European standard for mobile connection, in which frequency range is 900 MHz (GSM-900) and 1800 MHz (GSM-1800). UMTS standard for mobile connection is the third generation (3G) mobile connection technology, in which frequency range 2100 MHz (UMTS-2100) is used.

In the close distance area i. e. closer than 30 m from the antenna (in both horizontal and vertical planes) the strengths of electric and magnetic fields are

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measured. In the far distance areas i.e. further than 30 m (in both horizontal and vertical planes) energy flux density of electromagnetic field is measured from the antenna. If the mobile connection antenna is mounted on the building or mast that is higher than 30 m, the energy flux density of electromagnetic field is measured on the ground.

Electric and magnetic field strengths are measured in the distance of – 1 m, 5 m, 10 m, 15 m, 20 m, 25 m and 30 m in the close distance area (closer than 30 m), on the roof, towards the most intensive direction of mobile phone antenna. The researches are conducted 1.5 m above the roof of the building with mounted antenna. The energy flux density of electromagnetic field is measured in 10 m distance from mobile connection antenna. The radius of the research is 500 m. The result of the research is the arithmetic average of 3 values. The duration of one measurement is 6 minutes.

The researches on electric field strength of mobile phones are conducted: in open space, when sending and receiving antennas are in the zone of direct visibility; in closed space when sending and receiving antennas are not in the zone of direct visibility and have obstacles (building walls); in non-stationary space (when driving a car). The aim is to investigate the electric field strength created by various mobile phones models under different conditions. The researches are conducted by using GSM second generation (2G) mobile phones that operate within frequency range from 900 MHz to 1800 MHz and by UMTS third generation (3G) smart mobile phones that operate in 2100 MHz frequency range. The main criteria in the choice of mobile phones were differences in SAR and power. The most popular GSM 900 mobile phones consume two types of power: high maximum power transfer i. e. up to 2 W and medium – up to 0.8 W. GSM 1800 consumes medium – up to 1 W and low – up to 0.25 W power. Mobile phones UMTS consumes 4 types of power: high which is up to – 2 W, medium – up to 0.5 W, 0.25 W and low – up to 0.125 W. The electromagnetic measuring device is put in front of the mobile phone; the electric field strength is measured during conversation.

The “COMSOL Multiphysics” software allows to model the spread of electromagnetic fields in head, when the mobile phone is used . The aim of modelling is to evaluate distribution of electric field strength created by different mobile phones on the surface of head.

The theoretical modelling of energy flux density spread of electromagnetic field is done by applying physical peculiarities of electromagnetic waves radiation. The aim of modelling is to evaluate the energy flux density distribution of electromagnetic field from mobile phone antennas. After the evaluation of modelling researches, the visual representation of electromagnetic

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radiation spread is carried out according to the results by using AutoCad program package.

The methodology of researches on materials that screen electromagnetic radiation is provided. Electromagnetic field measuring device NBM 550 is put in 30 cm distance from the material that is being researched. On the opposite side in 30 cm distance from the material that is being researched the antenna of electromagnetic field generator is set. The antenna of electromagnetic field generator is constantly emitting electromagnetic field energy density of 10 µW/cm².

In order to reduce the electromagnetic radiation, the following materials are investigated: metal netting, aluminized foil, tin, brass sheet, steel sheet, aluminium sheet, concrete, rubber, plasterboard, wooden sheet. Various types of glass have been used as well.

3. Mobile telecommunication electromagnetic radiation experimental research results

The researches on directional mobile connection antenna (ERP = 1739 W)

conducted in 14 m height above ground revealed that electric and magnetic fields’ strength quickly diminishes when the distance from antenna increases. Evident decrease in electric field strength is noticed in 15 metres distance from mobile connection antenna, then its values are reduced twice, from 20 V/m to 11.4 V/m. When the distance from antenna increases, 20 meters or more, the electric field strength is not so evident and changes are within the range of 10.5 V/m to 7.5 V/m. The changing mobile phone electric field creates magnetic field, therefore, the magnetic field strength tendencies to diminish are similar to the electric field’s. In the distance from 1 meter to 15 meters the magnetic field strength is reduced by 0.6 time and changed within the range of 0.05 A/m to 0.03 A/m. When the distance from mobile phone antenna increases, the magnetic field strength diminished evenly and changed within the range of 0.028 A/m to 0.02 A/m.

In the far distance area (more than 20 m distance) the electromagnetic field has formed into electromagnetic wave: the spread directions of electric and magnetic field strengths are perpendicular to each other; the ratio of electric and magnetic field strengths is constant and equal to 377. In the far distance area the energy flux density of electromagnetic field is measured.

The mobile connection antenna (ERP = 1739 W, height 14 m) EMF energy flux density dependence on the distance of 1.5 m above the ground is shown in the Figure 1.

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0,01

0,1

1

10

30 40 50 60 70 80 90 100 200 300 400 500

Distance, m

Ene

rgy

flux

den

sity

, µW

/cm

²...

The mobile antenna EMFradiation

Total EMF radiation

Fig. 1. Dependence of mobile connection antenna (ERP = 1739 W, height 14 m) EMF energy flux density distribution from distance, if the height is 1,5 m above the ground

level

From Figure 1, reveals that directional mobile connection antenna (ERP = 1739 W, height 14 m) towards the most intensive direction of radiation, 1.5 m above ground in 50 m distance, creates the local maximum of EMF energy flux density (0.98 µW/cm²). In greater than 50 m distance, EMF energy flux density starts to decrease: in 60 metres distance reaches 0.74 µW/cm², in 70 m – 0.15 µW/cm², in 80 m – 0.13 µW/cm², in 90 – 0.11 µW/cm², in 100 m – 0.1 µW/cm². In greater than 100 m distance energy flux density of electromagnetic field changes marginally and is scattered within the range of 0.05 µW/cm² to 0.1 µW/cm². The investigations of the research revealed that antenna diagram in the vertical plane has a narrow radiation lobe of 6.8º radiation width which is directed downwards with the help of mechanical and electrical tilt. Therefore, the highest energy flux density is registered where the main antenna diagram lobe reaches ground level (in this case in 50 m distance from antenna). It is obvious that the maximum created by mobile phone antenna depends on the ERP of the antenna and height above the ground level of the antenna. The mobile connection antenna in the maximum radiation direction creates one maximum. Mobile connection antennas electromagnetic field energy flux density values in ground-level air increase further from the antenna, highest values can be observed at the point where main antenna radiation zone reaches earth surface, further on, it declines.

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Different SAR of mobile phones (GSM-900) generated electric field strength distribution (in active mode) in open, closed, and moving space is shown in Figure 2.

0

2

4

6

8

10

12

14

16

0.37 0.44 0.6 0.78 0.82 0.99 1.01 1.16 1.31 1.4

Specific absorption rate (SAR), W/kg

Ele

ctri

c fi

eld

stre

nght

, V/m

...

open space

closed space

moving space

Fig. 2. Different SAR of mobile phones (GSM-900) generated electric field strength

distribution (in active mode) in open, closed, and moving space

Figure 2 shows that mobile phones (GSM-900) in the closed space emit electric field strength, which is up to 3 times higher compared to the open or non-stationary space. In the open space the electric field strength values of mobile phones change within the range of 1 V/m to 7 V/m, in the closed space within the range of 4 V/m to 11 V/m; in the non-stationary space within the range of 5 V/m to 14 V/m. In the analysis of factors that could influence such uneven distribution of the electric field strength, it should be taken in consideration that power classes of mobile phones (GSM-900) differ: the maximum transmission power of the first 5 mobile phones is 0.8 watts and these phones belong to class 5, for the rest – 2 watts and they belong to class 4. Moreover, electric field strength values emitted by mobile phones directly depend on the electromagnetic signal in the environment. The closer mobile phone is to the mobile phone antenna, the lower electric field values it emits during the conversation. The mobile phone emits such power to provide quality connection, as the level of electromagnetic signal in the open space is very strong (from –60 to –80 dBm), thus mobile phones emit about 2–3 times smaller values, in comparison to the close or moving space, where the level of electromagnetic signal is low (from –80 to –95 dBm).

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Smart mobile phone (power – 0.125 W, SAR 0.57 W/kg, frequency – 2100 MHz) electric field intensity distribution in active mode is shown in Figure 3.

Fig. 3. Smart mobile phone (power – 0.125 W, SAR 0.57 W/kg, frequency – 2100 MHz) electric field intensity distribution in active mode

Fig. 4. The mobile antenna KATHREIN 742241 electromagnetic radiation dispersion in Rugių g. 5 (Vilnius, Lithuania) territory

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The Figure 3 displays the distribution of mobile phone electric field strength during the conversation over a mobile phone, which SAR is 0.57 W/kg, maximum power 0.125 W, used frequency 2100 MHz, the level of electromagnetic signal in the environment (–70 dBm). The received results (Figure 3) reveal that the electric field strength created by mobile phone (colour red) reaches 1 V/m around the ear (i. e. the place to which mobile phone is put) in 1 cm radius. Since the mobile phone emits very low electric field strength, thus, its radiation area is very small, only 3 cm. In this area the prevailing electric field strength is 0.1–0.9 V/m. When the distance from mobile phone is more than 3 cm, the electric field strength is not detected in the upper and lower parts of the head, in both sides of the head or on top of the head. The electric field strength of the mobile phone takes about 1% of the whole artificial head.

In the Figure 4 it can be observed that the highest energy flux density values of electromagnetic field are formed when the radiation direction of the mobile connection antenna is the most intensive (colour red). When the distance is up to 20 m the energy flux density values of electromagnetic field are scattered within the range of 50 µW/cm² to 10000 µW/cm². When the distance is greater the energy flux density values of electromagnetic field evidently decrease and in front of the living (yellow colour) reaches values of 7 µW/cm². The modelling of energy flux density spread of electromagnetic field, as well as the conducted investigations, revealed that the highest values were registered in 13.5–22.5 m height above ground level. Further on, when the distance is 100 m (colour green) energy flux density values of electromagnetic field are scattered within the range of 0.5 µW/cm² to 0.1 µW/cm².

a) b) Fig. 5. Mobile phone case axonometric image with incision: a) front wall image, b) rear

wall image: 1 – aluminized foil; 2 – rubber; 3 – cover; 4 – plastic screen; 5 – sticky tape; 6 – holes

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Mobile phone case (Figure 5) is composed of two-layer material: inside aluminized foil of eleven µm, outside – rubber of two mm thickness. Front part of the mobile phone is made of the lid in the bottom, eight holes at the top and bottom of the case, one third of the front part is used for the plastic transparent screen for the keyboard. The back part of the mobile phone case is composed of the Velcro tape which is on the back of the lid, and another Velcro tape in the bottom part. When mobile phone is ringing inside the case, the electromagnetic radiation, the reflected electromagnetic radiation, the absorbed electromagnetic radiation, the electromagnetic radiation which reaches outside are formed. The created mobile phone case effectively minimises electromagnetic radiation emitted by mobile phone, does not disturb duty cycle or reduce quality of the connection.

The electromagnetic radiation of mobile connection is best screened by the materials with high conductivity and magnetic conductivity of the material i.e. aluminized foil, tin, bras, steal, and aluminium. Rubber, plasterboard, wood sheet cannot be characterised as highly screening materials. These materials absorb only small part of electromagnetic radiation, whereas all the rest is emitted outside.

Glass packets made of two or three glasses, from which one or two glasses are selective, screen electromagnetic radiation up to 10 times. The electromagnetic radiation is screened by the selective glass, with a thin metal and metal oxide layer, which is characterised by the ability to reflect electromagnetic rays outside.

General conclusions

1. The analysis of scientific literature revealed that the number of directional comprehensive researches on electromagnetic radiation of mobile phone antennas and mobile phones and researches providing recommendations and measures for reducing the effect of electromagnetic radiation is not sufficient.

2. The research on electric field strength of mobile phone antennas showed that in the close distance area the intensity parameters of electromagnetic radiation exceed the allowed norms from 1.5 to 100 times.

3. The research results of three different mobile connection antennas’ groups revealed that EMF energy flux density values of low effective power mobile phone antennas are twice lower compared to medium effective radiation power antennas, and 10 times lower compared to high effective radiation power mobile connection antennas. This has to be considered while reducing electromagnetic radiation in the environment.

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4. The highest electromagnetic field energy flux density values of low, medium and high effective radiation power mobile connection antennas in the ground level air form in the points, where main antenna radiation zone reaches earth surface, further on, it starts to decline.

5. The biggest electric field strength values are emitted by the second generation (2G) GSM mobile phones that operate in the frequency band of 900 MHz. This is determined by the maximum transmission power of mobile phones, which under the weak level of electromagnetic signal (from –80 to –95 dBm) reaches 2 W.

6. The second generation (2G) GSM mobile phones that operate in the frequency band of 1800 MHz, emit electric field strength values from 1 V/m to 10 V/m during conversation. The smaller electric field strength values are determined by the higher frequency (1800 MHz) used by mobile phones and smaller maximum power, the maximum of which reaches up to 1 W.

7. Third generation (3G) UMTS smart phones that operate in the frequency bond of 2100 MHz, emit smallest electric field strength values during the conversation. This is determined by the effective usage (smart phones use communication types of extended spectrum) of the radio frequency (2100 MHz).

8. Strength of a mobile phone electric field on the phantom head decreases exponentially while moving sideward from the epicentre of the effect zone, and constitutes 1–12% of the artificial head’s surface and depends on density of constituent parts of the head.

9. The effectiveness of materials that suppress electromagnetic radiation depends on the conductivity and magnetic conductivity of the material. The electromagnetic radiation of mobile connection is best screened by the materials with high conductivity (from 1,45 · 106 S/m to 5,96 · 107 S/m) and magnetic conductivity (from 1,25 · 10−6 H/m to 8,75 · 10−4 H/m) of the material i.e. aluminized foil, tin, bras, steal, and aluminium.

Recommendations 1. In order to avoid and reduce possible mobile phone radiation effects on

health, it is advisable to use created two-layer mobile phone case, which reduces electromagnetic radiation by 10 times during conversation and thus allows to maintain a quality conversation.

2. Glass packets made of two or three glasses, from which one or two glasses are selective, should be used in buildings. The electromagnetic radiation is screened by the selective glass, with a thin metal and metal oxide layer, which is characterised by the ability to reflect electromagnetic rays outside.

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List of published works on the topic of the dissertation In the reviewed scientific journals

Baltrėnas, P.; Buckus, R.; Vasarevičius, S. 2012. Research and evaluation of the intensity parameters of electromagnetic fields produced by mobile communication antennas. Journal of environmental engineering and landscape management. Vilnius: Technika. ISSN 1648-6897 (print), ISSN 1822-4199 (online). 20(4): 273–284 (Thomson ISI Web of Science). IF = 1,958 (2011).

Baltrėnas, P.; Buckus, R. 2012. Mobiliųjų telefonų elektromagnetinio lauko energijos srauto tankio tyrimai ir įvertinimas. Mokslas – Lietuvos ateitis = Science – future of

Lithuania: Aplinkos apsaugos inžinerija. Vilnius: Technika. ISSN 2029-2341(print), ISSN 2029-7106 (online). 4(5): 462–467 (Index Copernicus).

Baltrėnas, P.; Buckus, R. 2011a. Research and assessment of safety distance of TV electromagnetic fields. International Journal of Occupational Safety and Ergonomics

(JOSE). Warszawa : Central Institute for Labour Protection – National Research Institute. ISSN 1080-3548. 17(1): 33–39 (Thomson ISI Web of Science). IF = 0,407 (2010).

In the other editions

Buckus, R.; Baltrėnas, P. 2012. Research and analysis of electromagnetic radiation from mobile telephone base station antenas inresidential environment. The 19th International

Conference on Microwaves, Radar and Wireless Communications: Conference Proceedings, May 21–23, 2012 Warsaw, Poland. Warsaw: Technika. ISSN 978-1-61284-1438-2/12. 1: 175–175.

Baltrėnas, P.; Buckus, R. 2011b. Indoor measurements of the power density close to mobile station antenna. The 8th International conference “Environmental engineering“

selected papers, May 19–20, 2011 Vilnius, Lithuania. Vilnius: Technika. ISBN 978-9955-28-826-8. 1: 16–21 (ISI Proceedings).

Prepared application of patent

Baltrėnas, P.; Buckus, R. 2012. Mobiliojo telefono dėklas. Nr. 2012 029 LR Valstybinis patentų biuras. About the author

Raimondas Buckus was born in Joniškis district on 14 of September 1983. In 2006, he acquired bachelor's degree in applied ecology Faculty of Nature Sciences at Šiauliai University. In 2009, he received a master's degree in technologies of environmental radiation safety at the Faculty of Environmental engineering at Vilnius Gediminas Technical University. Since 2009 – he is a graduate student at Vilnius Gediminas Technical University. Currently, he is working as senior technician at the Department of Environmental Protection.

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MOBILIOJO RYŠIO ELEKTROMAGNETINĖS SPINDULIUOTĖS TYRIMAI IR SKLAIDOS MAŽINIMO PRIEMONĖS

Mokslo problemos aktualumas

Gyvename kasdien vis labiau modernėjančiame pasaulyje, kuriame elektromagnetinė spinduliuotė, sklindanti iš buitinių elektros prietaisų, elektros perdavimo linijų, radijo ir televizijos stočių, kompiuterių, radarų, mobiliojo ryšio antenų ir ypač iš mobiliųjų telefonų, nuolat veikia žmogų ir gali sukelti įvairių sveikatos sutrikimų. Elektromagnetinės bangos tvyro aplink mus, tačiau mes jų negalime nei užuosti, nei pamatyti, nei apčiuopti.

Dvidešimt pirmajame amžiuje išsiplėtus mobiliojo ryšio tinklui ir ypač atsiradus GSM-900, GSM-1800 ir UMTS-2100 sistemoms, žymiai padaugėjo elektromagnetinės spinduliuotės šaltinių. Žmonės masiškai ėmė naudoti mobilųjį ryšį, nesusimąstydami nei dėl jo veikimo principų, nei dėl galimo kenksmingo poveikio. Aktyvus mobiliųjų telefonų naudojimas leidžia šią elektromagnetinio fono komponentę laikyti viena svarbiausių fizikinių veiksnių, aktyviai veikiančių visus gyvuosius organizmus ir aplinką.

Elektromagnetinės spinduliuotės poveikis tapo reikšmingas ne tik specialistams, dirbantiems toje aplinkoje, bet ir visiems aplinkinių vietovių gyventojams. Kai kuriose šalyse pradėta reikalauti zonų be mobiliųjų telefonų, kuriose būtų draudžiama įrengti bazines mobiliojo ryšio stotis, taip pat gerokai sumažinti maksimalius leistinus elektromagnetinės spinduliuotės lygius ar įvesti kitokius apribojimus.

Kai kalbama mobiliuoju telefonu, dažniausiai jis glaudžiamas prie ausies, o kai juo nesinaudojama, jis laikomas kišenėje prie kūno, tad iš mobiliojo telefono sklindanti elektromagnetinė spinduliuotė tiesiogiai veikia žmogaus kūną. Įprasti mobiliųjų telefonų dėklai nuo elektromagnetinės spinduliuotės neapsaugo, todėl reikia tokių dėklų, kurie veikiant mobiliesiems telefonams galėtų apsaugoti nuo elektromagnetinės spinduliuotės, nepablogindami mobiliojo ryšio kokybės.

Elektromagnetinės spinduliuotės lygio matavimai, jų vertinimas ir maksimalių leistinųjų elektromagnetinės spinduliuotės lygių mažinimas ar kitokių apribojimų įvedimas – aktuali problema visame pasaulyje. Pastaruoju metu ypač daug nerimo kelia apie mobiliuosius telefonus ir mobiliojo ryšio bazines stotis ir jų poveikį gyventojų sveikatai skelbiama prieštaringa informacija.

Sveikatos apsaugos ministerija išplatino informaciją, kad Pasaulio sveikatos organizacijos Tarptautinė vėžio tyrimų agentūra 2011 m. gegužės

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31 d. žiniasklaidai pateikė pranešimą, kad elektromagnetiniai radijo dažnio laukai gali padidinti riziką susirgti smegenų vėžiu ilgą laiką (30 minučių ir ilgiau per dieną) naudojantis mobiliuoju telefonu. Pasaulio sveikatos organizacija atkreipė dėmesį į tai, kad tinkamai naudojantis mobiliuoju telefonu ir imantis atsargumo priemonių galima sumažinti ir išvengti spinduliuotės poveikio sveikatai.

Įvertinant patikimų mokslinių duomenų apie žalingos mobiliojo ryšio elek-tromagnetinės spinduliuotės įtakos stoką ir atsižvelgiant į pagrįstą visuomenės susirūpinimą, šiame darbe nagrinėjamos elektromagnetinio lauko intensyvumo parametrų tendencijos aplinkoje. Šiuolaikinė samprata apie neigiamą mobiliojo ryšio antenų ir mobiliųjų telefonų elektromagnetinės spinduliuotės poveikį neleidžia prognozuoti visų pasekmių ateityje, todėl darbe pagal atliktus mokslinius tyrimus pristatytos ne tik praktinės, bet ir inžinerinės-techninės apsaugos nuo elektromagnetinės spinduliuotės priemonės.

Akivaizdu, kad pastaruoju metu agresyviai besireiškiantis spartus elektromagnetinės spinduliuotės (daug kartų viršijančios natūralųjį foną) lygio didėjimas gali pažeisti ekologinę aplinkos pusiausvyrą, todėl šis procesas turi būti ne tik tiriamas, bet ir vertinamas tiek teoriniais, tiek eksperimentiniais metodais.

Darbo tyrimų objektas – mobiliojo ryšio antenų ir mobiliųjų telefonų skleidžiama elektromagnetinė spinduliuotė.

Darbo tikslas ir uždaviniai

Darbo tikslas – ištirti ir įvertinti mobiliojo ryšio antenų ir mobiliųjų telefonų skleidžiamos elektromagnetinės spinduliuotės sklaidą.

Darbo tikslui pasiekti reikia išspręsti šiuos uždavinius: 1. Įvertinti skirtingos efektyviosios spinduliuotės galios antenų sukuriamą

elektromagnetinės spinduliuotės sklaidą aplinkoje. 2. Ištirti įvairių modelių mobiliųjų telefonų sukurtą elektrinio lauko stiprį. 3. Naudojantis programine įranga, sumodeliuoti mobiliųjų telefonų elektrinio

lauko stiprio sklidimą aplink galvą, taip pat remiantis teoriniais tyrimais atlikti modelinį mobiliojo ryšio antenų elektromagnetinės spinduliuotės sklaidos įvertinimą.

4. Ištirti elektromagnetinę spinduliuotę ekranuojančiąsias medžiagas ir sukurti mobiliojo telefono dėklą, apsaugantį nuo elektromagnetinės spinduliuotės.

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Tyrimų metodika

Darbe naudojama mobiliojo ryšio antenų ir mobiliųjų telefonų skleidžiamos elektromagnetinės spinduliuotės tyrimų metodika pagal higienos normose ir ISO standartuose nustatytus reikalavimus. Elektromagnetinę spinduliuotę ekranuojančiųjų medžiagų tyrimai atlikti pagal IEEE standarte pateiktą bandymų atlikimo metodiką. Mobiliojo ryšio antenų elektromagnetinio lauko energijos srauto tankio sklidimas nagrinėjamojoje teritorijoje paremtas atliktais teoriniais tyrimais bei sklaidos vizualizavimu pagal gautus rezultatus, panaudojant programinį AutoCad paketą. Mobiliųjų telefonų sukurto elektrinio lauko stiprio sklaidai aplink galvą naudota „COMSOL Multiphysics“ modeliavimo programa.

Mokslinis darbo naujumas

Atlikti kompleksiniai eksperimentiniai elektromagnetinės spinduliuotės tyrimai apima mažos, vidutinės bei didelės efektyviosios spinduliuotės galios mobiliojo ryšio antenas ir GSM antros kartos (2G), UMTS trečios kartos (3G) mobiliuosius telefonus. Mobiliojo ryšio antenų elektromagnetinės spinduliuotės sklaidos modeliavimas atliekamas taikant fizikinius elektromagnetinių bangų sklidimo teorinius ypatumus, o vizualizavimas – naudojant programinį AutoCad paketą. Mobiliojo telefono sukuriamo elektrinio lauko stiprio pasiskirstymas galvoje atliekamas „COMSOL Multiphysics“ programa. Darbo naujumas, Aplinkos inžinerijos mokslo kryptyje, pasireiškia mobiliojo telefono dėklo, apsaugančio nuo elektromagnetinės spinduliuotės, sukūrimu bei pritaikymu.

Praktinė reikšmė

Remiantis tyrimų rezultatais gali būti atnaujinama teisinė norminė elektromagnetinės ekspertizės bazė, reglamentuojanti leidžiamus elektromagnetinės spinduliuotės intensyvumo lygius, tobulinami elektromagnetinės spinduliuotės įvertinimo metodai ir metodika. Atsižvelgus į gautus rezultatus tiriant mobiliųjų telefonų elektromagnetinę spinduliuotę, disertacijoje pateiktos saugaus naudojimosi mobiliaisiais telefonais rekomendacijos. Sukurtas mobiliojo telefono skleidžiamą elektromagnetinę spinduliuotę mažinantis mobiliojo telefono dėklas ir Valstybiniam patentų biurui pateikta paraiška patentui gauti. Natūrinių tyrimų metodikas galima naudoti tam tikros teritorijos epidemiologinei būklei vertinti.

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Ginamieji teiginiai

1. Mobiliojo ryšio antenų elektromagnetinio lauko energijos srauto tankio vertės pažemio ore tolstant nuo antenos didėja, didžiausios vertės susidaro ten, kur pagrindinė antenos spinduliavimo zona pasiekia žemės paviršių, o toliau pradeda mažėti.

2. Mobiliojo telefono elektrinio lauko stipris tiesiogiai proporcingas mobiliojo telefono perdavimo galiai, atvirkščiai proporcingas dažniui ir priklauso nuo to, ar erdvė yra uždara ar atvira.

3. Mobiliojo telefono elektrinio lauko stipris galvos paviršiuje tolstant nuo poveikio zonos epicentro į kraštus eksponentiškai mažėja ir priklauso nuo galvos sudėtinių dalių tankio. Darbo apimtis. Disertaciją sudaro įvadas, trys skyriai ir rezultatų

apibendrinimas, bendrosios išvados ir rekomendacijos. Įvadiniame skyriuje aptarta tiriamoji problema ir darbo aktualumas,

aprašytas tyrimų objektas, suformuluotas darbo tikslas bei iškelti uždaviniai, aprašyta tyrimų metodika, atskleistas mokslinis darbo naujumas, pagrįsta praktinė darbo rezultatų reikšmė ir pateikti ginamieji teiginiai. Taip pat pristatytos disertacijos tema paskelbtos autoriaus publikacijos bei pranešimai konferencijose ir detalizuota disertacijos struktūra.

Pirmajame skyriuje pateikiama mokslo darbų disertacijos temos apžvalga, kurioje aptariamos mobiliojo ryšio elektromagnetinės spinduliuotės savybės, atskleidžiami modeliavimo ir matavimo metodikos bei ekranavimo principai. Antrajame skyriuje detalizuojama antenų elektromagnetinio lauko intensyvumo parametrų ir mobiliųjų telefonų elektrinio lauko stiprio, taip pat elektromagnetinės spinduliuotės modeliavimo ir elektromagnetinę spinduliuotę ekranuojančiųjų medžiagų tyrimų metodika. Trečiajame skyriuje pateikiama antenų elektromagnetinės spinduliuotės sklaidos ypatumų analizė ir nagrinėjami skirtingų mobiliųjų telefonų sukurto elektrinio lauko stiprio eksperimentinių tyrimų duomenys bei gautieji elektromagnetinės spinduliuotės modeliavimo rezultatai. Skyriuje atskleidžiami elektromagnetinę spinduliuotę mažinančių ekranuojančiųjų medžiagų tyrimai, pristatomas gautų tyrimų pagrindu sukurtas mobiliojo telefono dėklas.

Darbo apimtis 155 puslapiai, panaudota 22 numeruotos formulės, 85 paveikslai ir 14 lentelių. Rašant disertaciją buvo panaudoti 107 literatūros šaltiniai.

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Bendrosios išvados

1. Išanalizavus mokslinę literatūrą, nustatyta, kad kryptingų ir išsamių, apimančių mobiliojo ryšio antenų, mobiliųjų telefonų elektromagnetinę spinduliuotę bei sklaidos mažinimo priemonių tyrimų pasaulyje atlikta nedaug.

2. Mobiliojo ryšio antenų išspinduliuojamos elektrinio lauko stiprio ir magnetinio lauko stiprio vertės artimojoje zonoje (iki 30 m atstumo) viršija leidžiamas normas nuo 1,5 iki 100 kartų.

3. Trijų skirtingų grupių mobiliojo ryšio antenų tyrimų rezultatai parodė, kad mažos efektyviosios galios mobiliojo ryšio antenų EML energijos srauto tankio vertės yra dvigubai mažesnės, palyginti su vidutinės efektyviosios spinduliuotės galios antenomis ir 10 kartų mažesnės, palyginti su didelės efektyviosios spinduliuotės galios mobiliojo ryšio antenomis. Mažinant elektromagnetinę spinduliuotę aplinkoje reikia tai įvertinti.

4. Mažų, vidutinių ir didelių efektyviosios spinduliuotės galios mobiliojo ryšio antenų didžiausios elektromagnetinio lauko energijos srauto tankio vertės pažemio ore susidaro ten, kur pagrindinė antenos spinduliavimo zona pasiekia žemės paviršių, o toliau pradeda mažėti.

5. Didžiausias elektrinio lauko stiprio vertes iki 14 V/m pokalbio metu išspinduliuoja antrosios kartos (2G) GSM mobilieji telefonai, kurie veikia 900 MHz dažnių juostose. Tai lemia mobiliųjų telefonų maksimali perdavimo galia, kuri esant silpnam elektromagnetinio signalo lygiui (nuo –80 iki –95 dBm) siekia 2 W.

6. Antrosios kartos (2G) GSM mobilieji telefonai, kurie veikia 1800 MHz dažnių juostose, kalbėjimo metu išspinduliuoja elektrinio lauko stiprio vertes nuo 1 V/m iki 10 V/m. Mažesnes elektrinio lauko stiprio vertes lemia mobiliųjų telefonų naudojamas dažnis (1800 MHz) bei mažesnė naudojama maksimali galia (1 W).

7. Trečiosios kartos (3G) UMTS išmanieji telefonai, kurie veikia 2100 MHz dažnių juostoje, kalbėjimo metu išspinduliuoja mažiausias (iki 8 V/m) elektrinio lauko stiprio vertes, nes jie efektyviau naudoja radijo dažnį.

8. Modeliuojant nustatyta, kad mobiliojo telefono elektrinio lauko stipris galvos paviršiuje tolstant nuo poveikio zonos epicentro į kraštus eksponentiškai mažėja, užima nuo 1 % iki 12 % galvos paviršiaus ploto ir priklauso nuo galvos sudėtinių dalių tankio.

9. Elektromagnetinę spinduliuotę slopinančių medžiagų efektyvumas priklauso nuo savitojo medžiagos laidžio ir magnetinės skvarbos. Geriausiai mobiliojo ryšio elektromagnetinę spinduliuotę ekranuoja medžiagos, turinčios didelį savitąjį laidį (nuo 1,45 · 106 S/m iki 5,96 · 107 S/m) ir didelę magnetinę

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skvarbą (nuo 1,25 · 10−6 H/m iki 8,75 · 10−4 H/m), pvz., aliuminizuota folija, skarda, žalvaris, plienas, aliuminis.

Rekomendacijos

1. Kad išvengtume ir sumažintume galimą mobiliojo telefono spinduliuotės

poveikį sveikatai, galingiems mobiliesiems telefonams (nuo 1 W iki 2 W), patariama naudoti sukurtą dvisluoksnį mobiliojo telefono dėklą, kuris pokalbio metu iki 10 kartų sumažina elektromagnetinę spinduliuotę ir kartu leidžia palaikyti kokybišką pokalbį.

2. Pastatuose patariama naudoti stiklo paketus, sudarytus iš dviejų arba trijų stiklų, kurių vienas arba du stiklai yra selektyviniai. Elektromagnetinę spinduliuotę ekranuoja selektyvinis stiklas, ant kurio yra plonas metalų ir metalų oksidų sluoksnis, turintis savybę atspindėti elektromagnetinius spindulius atgal į išorę.

Trumpos žinios apie autorių

Raimondas Buckus gimė 1983 m. rugsėjo 14 d. Joniškio rajone. 2006 m. įgijo taikomosios ekologijos bakalauro laipsnį Šiaulių universiteto Gamtos mokslų fakultete. 2009 m. įgijo aplinkos radiacinės saugos technologijų magistro laipsnį Vilniaus Gedimino technikos universiteto Aplinkos inžinerijos fakultete. Nuo 2009 m. – Vilniaus Gedimino technikos universiteto doktorantas. Šiuo metu dirba vyresniuoju laborantu Vilniaus Gedimino technikos universiteto Aplinkos apsaugos katedroje.