30000002103440' - UTHM Institutional...
Transcript of 30000002103440' - UTHM Institutional...
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
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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
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For my dearest father Hj. Ismail bin Kamari,
My lovely mother Hjh. Saodah binti Nawawi & my family for their encouragement
and blessing
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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.
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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.
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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
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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.
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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
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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
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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
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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
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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
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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].
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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.