30000002103440'

UNIVERSITI TUN HUSSEIN ONN MALAYSIA

PENGESAHAN STATUS LAPORAN PROJEK SARJANA

MODELING OF ELECTROMAGNETIC WAVE PENETRATION IN A HUMAN HEAD DUE TO EMISSIONS

FROM CELLULAR PHONE

SESI PENGAJIAN : 2006/2007

Saya NURULHUDA BINTI ISMAIL mengaku membenarkan laporan projek sarjana ini disimpan di Perpustakaan dengan syarat-syarat kegunaan seperti berikut:

1. Tesis adalah hak milik Universiti Tun Hussein Onn Malaysia (UTHM). 2. Perpustakaan dibenarkan membuat salinan untuk tujuan pengajian sahaja. 3. Perpustakaan dibenarkan membuat salinan tesis ini sebagai bahan pertukaran antara institusi

pengajian tinggi. 4. **Sila tandakan ( V )

(Mengandungi maklumat yang berdarjah keselamatan SULIT atau kepentingan Malaysia seperti yang termaktub

di dalam AKTA RAHSIA RASMI 1972)

TERHAD (Mengandungi maklumat TERHAD yang telah ditentukan oleh organisasi/badan di mana penyelidikan dijalankan)

TIDAK TERHAD

Disahkan oleh:

4 (TANDATANGAN PENULIS)

Alamat Tetap:

NO.38, KG. PT. LAPIS SEMARANG, 86400, PT. RAJA, BATU PAHAT, JOHOR.

PROF. DR MOHD. ZARAR BIN MOHD. JENU

(Nama Penyelia)

Tarikh: 23 MEI 2007 Tarikh: 23 MEI 2007

CATATAN: ** Jika tesis ini SULIT atau TERHAD, sila lampirkan surat daripada pihak

berkuasa/organisasi berkenaan dengan menyatakan sekali tempoh tesis ini perlu dikelaskan sebagai SULIT atau TERHAD.

rZMN

"I hereby declare that I have read this report and in my opinion it fulfills the partial

requirements for the award of Master of Electrical Engineering (Communication)."

Signature

Name of Supervisor

Date

PROF. DR. MOHD. ZARAR BIN MOHD. JENU

23 M A Y 2007

MODELING OF ELECTROMAGNETIC WAVE PENETRATION IN A

HUMAN HEAD DUE TO EMISSIONS FROM CELLULAR PHONE

NURULHUDA BINTI ISMAIL

A project report submitted in partial fulfillment of the requirements for the

award of Master of Electrical Engineering

Faculty of Electrical and Electronic Engineering

Universiti Tun Hussein Onn Malaysia

MAY 2007

i i

I declare that this report on "Modeling of Electromagnetic Wave Penetration in a

Human Head Due to Emissions from Cellular Phone" is the result of my own

research except for works which have been cited in the references. The report has

not been accepted any degree and not concurrently submitted in candidature of any

other degree.

Signature

Name of Author : N U R U L H U D A BINTI ISMAIL

Date : 23 M A Y 2007

i i i

For my dearest father Hj. Ismail bin Kamari,

My lovely mother Hjh. Saodah binti Nawawi & my family for their encouragement

and blessing

iv

ACKNOWLEDGMENT

First of all, I am greatly indebted to Allah SWT on His blessing to make this

project successful.

I would like to express my gratitude to honourable Prof. Dr. Mohd Zarar bin

Mohd. Jenu, my project supervisor for his guidance and help rendered throughout

this project.

To Dr. R. Kandasamy, Mr. Zulkarnain and others whose name could not be

mentioned here one by one. Your encouragement, help and concern is greatly

appreciated.

Finally, I wish to thank everyone who has helped in one way or another

towards the successful implementation of this project.

XI

A B S T R A C T

Nowadays, cellular phone becomes a necessity for human being due to its

mobility, small size and useful applications provided in the chip. In a long term use,

the user will be exposed to the high frequency E M radiation that possibly causes

serious illnesses such as alzheimer and brain cancer. Increasing exposure f rom this

radiation is a growing concern for the community to investigate the effects of the

emissions to human health. While cellular phone is in used, the energy is transferred

f rom the applied electric field to the human head in the form of kinetic energy of

charged particles. The rate of change of the energy transferred is called the absorbed

power or Specific Absorption Rate (SAR). SAR values are of key importance when

validating possible health hazard and these values are compared with a safety limit

set by International Commission on Non-Ionizing Radiation Protection, ICNIRP to

ensure that the phone is safe to use. In this study, Finite Difference Frequency

Domain (FDFD) technique was used to evaluate the electric field and SAR

distribution in a human head due to the emissions f rom cellular phone that operates

at 900 MHz. The numerical results were compared with the CST Microwave Studio

software which is based on FDTD method. The results demonstrated that FDFD is

not an efficient method to evaluate E field and SAR due to its limitation and

imperfect boundary condition. On the other hand, the CST Microwave Studio results

show that magnitude of E M field decreases exponentially with the penetration

distance at a rate specified by the attenuation constant, a. Besides, the SAR is

affected by operational frequency of the phone and the electrical properties of

human head. Since FDFD technique can work only for 2D models, it is

recommended that a fast and efficient numerical technique need to be studied for 3D

human head model and an experimental technique on SAR distribution needs to be

done to validate the results from simulation technique.

vi

ABSTRAK

Dewasa ini, telefon selular merupakan keperluan dalam kehidupan seharian

memandangkan kepada faktor mobilitinya, saiz yang kecil dan pelbagai aplikasi

yang dimuatkan di dalam cipnya. Untuk penggunaan yang lama, pengguna telefon

ini akan terdedah kepada radiasi elektomagnetik yang berfrekuensi tinggi dan

berkemungkinan mengundang kepada penyakit serius seperti alzheimer dan barah

otak. Peningkatan kepada pendedahan terhadap radiasi ini telah meningkatkan

kesedaran di kalangan masyarakat untuk mengkaji kesan radiasi ini kepada

kesihatan manusia. Semasa telefon selular sedang digunakan, sejumlah tenaga akan

dipindahkan daripada medan elektrik kenaan ke dalam kepala manusia dalam bentuk

tenaga kinetik yang terhasil daripada zarah-zarah bercas. Kadar perubahan terhadap

tenaga yang dipindahkan ini dinamakan sebagai kuasa terserap atau Specific

Absorption Rate (SAR). Nilai SAR begitu penting untuk mengesahkan simptom

penyakit dan nilai ini kemudianna akan dibandingkan dengan had keselamatan yang

telah ditentukan oleh International Commission on Non-Ionizing Radiation

Protection (ICNIRP) bagi memastikan bahawa telefon tersebut selamat digunakan.

Dalam kajian ini, teknik Finite Difference Frequency Domain (FDFD) telah

digunakan untuk menilai medan elektrik dan taburan SAR di dalam kepala manusia

berdasarkan kepada pancaran telefon selular yang beroperasi pada frekuensi 900

MHz. Hasil daripada teknik ini akan dibandingkan pula dengan perisian CST

Microwave Studio yang berasaskan kepada teknik Finite Difference Time Domain

(FDTD). Keputusan yang terhasil menunjukkan bahawa kaedah FDFD tidak efisien

untuk digunakan dalam kajian ini disebabkan oleh aplikasi yang agak terhad dan

keadaan sempadan yang tidak tepat. Namun begitu, hasil daripada CST Microwave

Studio menunjukkan bahawa magnitud medan elektromagnetik berkurangan secara

eksponen melawan jarak penembusan pada kadar yang ditetapkan oleh pemalar

pelemahan, a. Di samping itu, taburan SAR pula dipengaruhi oleh frekuensi

kendalian telefon tersebut dan ciri-ciri elektrik kepala manusia. Oleh kerana teknik

vii

FDFD hanya relevan untuk model 2 dimensi, kajian yang melibatkan model 3

dimensi dengan menggunakan teknik berangka yang lebih cepat dan efisien perlu

dijalankan dan kaedah eksperimen tentang taburan SAR perlu dibuat bagi

mengesahkan keputusan yang terhasil daripada kaedah simulasi.

V l l l

TABLE OF CONTENTS

CHAPTER CONTENTS PAGE

THESIS STATUS CONFIRMATION

SUPERVISOR'S CONFIRMATION

TITLE i

TESTIMONY ii

DEDICATION iii

A C K N O W L E D G E M E N T iv

ABSTRACT v

ABSTRAK vi

TABLE OF CONTENTS viii

LIST OF FIGURES xi

LIST OF TABLES xiii

LIST OF SYMBOLS / ABBREVIATIONS xiv

CHAPTER 1 INTRODUCTION 1

1.1 General 1

1.2 Problem Statement 4

1.3 Aim of the study 6

1.4 Objectives of the study 6

1.5 Research Scopes 7

1.6 Report Outline 7

XI

CHAPTER 2 REVIEW OF THE EM WAVE 9

PENETRATION DUE TO CELLULAR

PHONE

2.1 Cellular Phone and its Emission 10

2.2 Bioelectromagnetics 11

2.2.1 Biological Model 12

2.2.2 Macroscopic Model 12

2.2.3 Absorption in Biological Materials 15

2.3 Specific Absorption Rate (SAR) 16

2.4 ICNIRP Standard 18

2.5 Review of Important Research Works on 20

Electromagnetic Absorption and SAR

Distribution

2.6 Numerical Method used in this project 23

CHAPTER 3 METHODOLOGY 26

3.1 Research Flow 26

3.2 Derivation of Maxwell ' s Equations 28

3.3 Numerical analysis Using Finite Difference 32

Frequency Domain (FDFD)

3.4 Electrical properties of a human head 37

3.5 2D Human Head Model 38

3.6 Commercial Software 39

XI

CHAPTER 4 RESULTS AND DISCUSSIONS 40

4.1 Numerical Analysis Results 41

4.2 Human Head Model 46

4.3 CST Results 47

CHAPTER 5 CONCLUSION AND FUTURE WORK 53

5.1 Conclusion 53

5.2 Future Work 54

REFERENCES

APPENDIX A

APPENDIX B

MATLAB SIMULATION RESULTS

CST RESULTS

55

57

66

XI

LIST OF FIGURES

FIGURE NUMBER TITLE PAGE

1.1 Electromagnetic wave propagation 2

1.2 Electromagnetic spectrum 3

1.3 The illustration of electromagnetic fields penetration 6

in a human head

2.1 The variation of electrical properties of muscle 15

and fat with frequency

3.1 Flowchart of research work 29

3.2 A biological body under EM radiation 30

3.3 2D rectangular region 35

3.4 A grid system 36

3.5 3D human head model in CST Microwave Studio 41

3.6 2D human head model in CST Microwave Studio 41

4.1 Six interior grid points 43

4.2 Contour of E-field intensity before iteration process 45

4.3 Contour of E-field intensity after iteration process 45

4.4 Electric field propagation in a lossless medium 46

4.5 Electric field propagation in a lossy medium 46

4.6 2D Human Head Model 48

4.7 FDTD model of human head (xy-plane) 49

4.8 & 4.9 Distribution of E-field in xz-plane 50

4.10 & 4.11 Distribution of H-field in xz-plane 50

4.12 Propagation of EM wave in a lossy medium 51

xii

4.13 SAR (lg) at 900 MHz 52

4.14 SAR (lOg) at 900MHz 52

4.15 SAR (lg) at 1800 MHz 52

4.16 SAR (lOg) at 1800 MHz 52

xni

LIST OF TABLES

TABLE TITLE PAGE

2.1 Current reference standards and limits (status January 2001) 19

2.2 ICNIRP Protection Guidelines 20

3.1 Densities and electrical properties of the simulated tissues 40

4.1 E-field at each unknown point 44

4.2 E-field at each unknown point before iteration 44

4.3 E-field at each unknown point after iteration 45

4.4 SAJRmaxfor different averaging mass 53

x i v

LIST O F S Y M B O L S / A B B R E V I A T I O N S

E - Electric Field Intensity (V/m)

H - Magnetic Field Intensity (A/m)

f - Frequency (Hz)

a - Attenuation Constant ( N p / m )

p - Phase Constant (rad /m)

y - Propagation Constant (m'!)

S - Skin Depth (/?:)

Dp - Depth of Penetration (m)

e - Relative Permittivity (F/m)

e0 - Relative Permittivity of Free Space

(e0 = 8.854 x 10~12 F/m)

e r - Relative Permittivity of Material (dimensionless)

// - Relative Permeability (H/m)

jU0 - Relative Permeability of Free Space

(ju0 = 4tix 10'7 H/m)

y.r - Relative Permeability of Material (dimensionless)

cr - Conductivity (S/m)

>1 - Intrinsic Impedance (Q.)

}]0 ~ Impedance of Free Space (r)0 = 3HQ.)

X - Wavelength (m)

v - Velocity (m/s)

co - Angle Frequency (rad / s )

c - Speed of Light in Free Space (2.998 x 108 m/s)

h - Step size

EM - Electromagnetic

FDTD - Finite Difference Time Domain

XV

FDFD - Finite Difference Frequency Domain

FEM - Finite Element Method

SAR - Specific Absorption Rate

RFR - Radio Frequency Radiation

ICNIRP - International Commission on Non-Ionizing Radiation

Protection

ANSI - American National Standards Institute

IEEE - Electrical and Electronic Engineer

FCC - Federal Communication Commission

ACGIH - American Conference of Governmental Industrial

Hygienists

CHAPTER 1

INTRODUCTION

1.1 General

Electromagnetic wave consists of electric and magnetic field that are

perpendicular to each other as illustrated in Figure 1.1. Electric fields are created by

differences in voltage: the higher the voltage, the stronger will be the resultant field.

Magnetic fields are created when electric current flows: the greater the current, the

stronger the magnetic field. An electric field will exist even when there is no current

flowing. If current does flow, the strength of the magnetic field will vary with power

consumption but the electric field strength will be constant.

Figure 1.1: Electromagnetic wave propagation

Besides that, electric field, E and magnetic field, H are coupled for time-

varying, but they become independent in the limit of unchanging fields [1 ].

Practically, from 20-30 kHz and above, E and H cannot be seen separately; they

merge to form EM waves. EM waves at low frequencies are referred to as EM fields

and at very high frequencies are called EM radiation. As the frequency goes up, the

wavelength becomes shorter, and more energy is transferred to objects similar in

size to the wavelength. The term EM radiation applies to the dispersal of EM

energy. Once generated, EM fields radiate in all directions, depending on how they

have been converged. As the field opens, the power spreads, and the energy could be

reflected, transmitted, or absorbed as it comes into contact with different types of

material.

Moreover, the evolution of the electromagnetic frequency spectrum as shown

in Figure 1.2 started from the discoveries of Maxwell, Hertz, and Marconi. The EM

spectrum under which devices and systems are working extended from extremely

low-frequency (ELF) fields and very low-frequency (VLF) fields to radio frequency

radiation (RFR), infrared (IR) radiation, visible light, ultraviolet (UV). X-rays and

gamma-ray frequencies exceeding 1024 Hz.

J

Radio frequency radiation (RFR) is a general term applying to the use of EM

waves for radio and television, radar, and other RF/microwave communication

applications. RFR is composed of moving waves, which lie in the frequency range

of 3 kHz to 300 GHz. Interesting bands of frequency with wide applications

especially in wireless, mobile, cellular, and satellite communications are the VHF

and UHF (30 MHz-3 GHz). Propagation above 30 MHz is basically a straight line

(line of sight) with probability of scattering. Frequencies of special interest for

cellular communications are in the range of 800-900 MHz, while personal

communications band extends from 1700-2200 MHz.

Figure 1.2: Electromagnetic spectrum [1]

4

Therefore, the interest of this research work presented in this report is to

model the EM wave penetration in a human head due to cellular phone.

1.2 Problem statement

The revolution in communication technology in recent years has seen

widespread use of cellular phone. It becomes a necessity for human being due to its

mobility, small size and useful applications provided in the chip. Widespread use of

cell phone and other types of hand-held transceivers has led to increased concerns

about possible health hazards, particularly concerns about brain cancer, as the

antennas for these phones lie along the head during use [2],

Frequently reported symptoms to physicians and cellular phone

manufacturers include headaches, vision and hearing difficulties, increased ear and

facial temperatures, nausea, dizziness, tingling sensations on the skin, and numbness

or irritation to the face and neck. Some studies have presented evidence that blood

pressure increases when using a cellular phone, and there has been litigation over

cancer and brain tumors allegedly caused by cellular phone radiation.

Furthermore, with the enormous increase of electromagnetic and radio wave

radiation emitted by cellular phones, increasing numbers of illnesses such as

allergies, fatigue, asthma, heart disease, brain cancer, depression, sleep disorders and

ill temper are on the rise. These various biological effects depend upon the amount

of energy absorbed from the EMF [1].

5

While the cellular phone is working, it uses electric power to receive and

transmit signals through a base station tower that is linked with other transmission

towers. Increasing exposure from the use of devices such as cellular phones and base

stations are a growing concern for the community. This is because cellular phone, at

distances within a wavelength f rom a RF transmitter is a region known as the near

field. Since cellular phone radiation has a wavelength of 30 cm at 900 MHz (GSM

phone) the users head will be within this near field region. The head disturbs the

field and alters the manner in which RFR interacts with tissue.

This interaction complicates the absorption of RF energy within the head

and makes calculations difficult. This increases the temperature of the brain and

surrounding tissue and equally as significant, also affects protective biological

mechanisms far below what can be measured at the thermal level using current

Specific Absorption Rate (SAR) test procedures and standards. SAR standards are

used as the basis for determining cell phone safety worldwide.

Therefore, it is important to model the behavior of the electromagnetic waves

as they interact with the complex tissues of the human due to GSM frequency (900

MHz). Thus, this research is performed to calculate the propagation of the

electromagnetic fields in a human head due to the emissions from cellular phone and

to study the effects of SAR due to the operational frequency of the cellular phone

and the electrical properties of a human head. Numerical technique has been used in

this report as one of the computational methods for analyzing electromagnetic

problems.