KOLEJ UNIVERSITI TEKNOLOGI TUN HUSSEIN ONN

BORANG PENGESAHAN STATUS TESIS·

JUDUL:

Saya

CHARACTERIZA TION OF ELECTRIC FIELD DISTRIBUTION IN A GTEM CELL

SESI PENGA.IIAN: 2003/2004

AIZAN BIN UBIN

(HURUF BESAR)

mcngaku mcmbcnarkan tcsis (Sarjana-MUElafSarjana /&elaer-Falsafilh)* ini disimpan di Pcrpustakaan dcngan syarat-syarat kcgunaan scpcrti bcrikut:

I. Tcsis adalah hakmilik Kolcj Univcrsiti Tcknologi Tun Husscin ann. 2. Pcrpustakaan dibcnarkan mcmbuat salinan untuk tujuan pcngajian sahaja. 3. Pcrpustakaan dibcnarkan mcmbuat salinan tcsis ini scbagai bahan pcrtukamn antam institusi

pcngajian tinggi.

4. **Sila tandakan (" )

o o ~

SULIT

TERHAD

(Mcngandungi maklumat yang bcrdarjah kcsclamatan atau kcpcntingan Malaysia scpcrti yang tcmlaktub di dalalll AKTA RAHSIA RASMI1972)

(Mcngandungi Illaklulllat TERHAD yang tclah ditcntukan olch organisasilbadan di mana pcnyclidikan dijalankan)

TIDAK TERHAD

Disahkan olch:

(TANDATANGAN PENULlS)

Alamat Tctap:

17 .IALAN TIONG 3, 83500 PARIT SULONG, BATU PAHAT, .I0HOR.

PROF. DR. l\IOHD ZARAR BIN l\IOHD .IENU ( Nama Pcnyclia )

Tarikh: __ 2_7_A_I_'R_I_L_20_0_4 __ _ Tarikh: 27 APRIL 2004

CATATAN: * **

•

Po tong yang tidak bcrkcnaan. Jika tcsis ini SULIT at au TERHAD, sila lalllpirkan sura! daripada pihak bcrkuasa/organisasi bcrkcnaan dcngan mcnyatakan sckali tcmpoh tcsis ini perlu dikclaskan scbagai SULIT atau TERHAD. Tcsis dimaksudkan scbagai tcsis bagi Ijazah Doktor Falsafah dan Sarjana sccara pcnyclidikan. atau discrtasi bagi pcngajian sccam kcrja kursus dan pcnyclidikan. at au Laporan Projck Sarjana ivluda (PS;\I).

"I hereby acknowledge that the scope and quality of this thesis is qualified for the

award of the Master Degree of Electrical Engineering"

Signature

Name PROF. DR. MOHD ZARAR BIN MOHD JENU

Date 27 APRIL 2004

CHARACTERIZATION OF ELECTRIC FIELD

DISTRIBUTION IN A GTEM CELL

AIZAN BIN UBIN

A project report is submitted as partial fulfillment of the requirements for the award

of the Master Degree of Electrical Engineering

Department of Electrical Enginecring

Faculty of Enginccring

Ko\cj Univcrsiti Tcknologi Tun Husscin Onn

APRIL. 2004

11

"All the trademark and copyrights use herein are property of their respective owner.

References of infonnation from other sources are quoted accordingly; otherwise the

information presented in this report is solely work of the author."

Signature

Author AIZAN BIN UBIN

Date 27 APRlL 2004

Par 11Iy 'Wife 1(fiairaty CJ3inti CJ3acfrol1,

:My SOIlS,

:Mu fia 111 111 a a Parfial1 ana :Mufiammaa Zaf(]vall,

:My aaugfitel~

jl11lirafi Parzana.

111

IV

ACKNOWLEDGEMENT

The author wishes to extend his sincere appreciation to the project supervisor

Professor Dr Mohd Zarar Bin Mohd Jenu for his guidance, help and advice

throughout this project.

The author wishes to express his thanks to Mr. Azwan, Shahrul, Mohd

Shamian, Nazri, Xavier, Erdi and others whose name could not be mentioned here

one by one. Your encouragement and concem is greatly appreciated by author.

In particular, my most appreciation is for my wife and family members for

their support during this project.

The author wishes to thank everyone who has helped in one way or another

towards the successful implementation of this project.

Finally, I would like to praise and thank God for giving me patience,

perseverance and strength to complete this project.

\'

ABSTRACT

Two of the most important measurements related to electromagnetic

compatibility (EMC) are radiated emission and radiated immunity. These measurements

must be performed in a facility which provides reliability and reproducibility. The

Gigahertz Transverse Electromagnetic Mode (GTEM) cell is one of the facilities for

EMC measurement due to its well defined electric and magnetic field distribution in

addition to being cost effective. The research undertaken in this project is to determine

the field distribution in the GTEM by using Finite Difference Time Domain (FDTD).

The results from the modeling are then compared with actual measurements and any

differences will be noted and explained. The field strength inside a GTEM cell is a

fl.lI1ction of the input power as well as location along the longitudinal axis or septum

height. Radiated immunity measurements require field uniformity (+6 dB according to

IEC 61000-4-3 standard) which depends on the design aspects of the GTEM such as

size, material and absorbing condition. The capability of the GTEM cell to provide the

unifo1111 field can be tested theoretically and experimentally. FDTD is a numerical

method that can be used to predict the electric field distribution in a GTEM cell. The

electric field distribution for frequencies at 100 MHz, 200 MHz, and 400 MHz were

calculated using the EZ-FDTD software. In this report, theoretical study on the field

strength and distribution in a GTEM cell is described. It is followed by making

measurements of the field based on the radiated immunity test setup. It is found that at

septum height 63 cm for frequency 100 MHz, the measured and simulated results are

very close. This is the location recommended by the manufacturer for the placement of

equipment under test (EUT) in radiated emission and radiated immunity test. The

difference varies from 0.01 dB to 4.91 dB. The difference between modeling and actual

measurement can be attributed to the input field distribution, inhomogeneous

characteristics of the septum and existence of standing wave. In the future, it is

recommended that other numerical methods such as Finite Element Method (FEM) and

Transmission Lines Method (TLM) be used and more accurate model and absorbing

boundary condition parameters be implemented.

VI

ABSTRAK

Dua daripada pengukuran paling penting berhubung keserasian elektromagnet

(EMC) adalah panearan radiasi dan ketahanan radiasi. Pengukuran ini mestilah

dilakukan di dalam kemudahan yang menyediakan kebolehharapan dan

kebolehulangan. Sel Mod Elektromagnet Melintang Gigahertz (GTEM) adalah satu

daripada kemudahan untuk pengukuran EMC hasil daripada medan elektrik dan

medan magnetnya yang tertakrif dengan baik disamping kosnya yang efektif.

Penyelidikan yang dijalankan di dalam projek ini adalah untuk menentukan taburan

medan di dalam GTEM menggunakan Bezaan Terhingga Domain Masa (FDTD).

Keputusan daripada permodelan kemudian dibandingkan dengan pengukuran sebenar

dan sebarang perbezaan diantaranya akan dieatat dan dihuraikan. Kekuatan medan di

dalam sel GTEM adalah fungsi bagi kuasa masukan dan juga lokasi sepanjang paksi

membujur atau ketinggian septum (pengalir dalam). Pengukuran ketahanan radiasi

memerlukan keseragaman medan (+ 6 dB menurut piawaian IEC 61000-4-3) yang

bersandar kepada aspek rekabentuk sel GTEM seperti saiz, bahan dan keadaan

serapan. Kemampuan sel GTEM menyediakan medan yang seragam boleh diuji

seeara teori dan ujikaji. FDTD adalah satu kaedah berangka yang boleh digunakan

untuk meramal taburan medan elektrik di dalam sel GTEM. Taburan medan elektrik

pada frekuensi 100 MHz, 200 MHz dan 400 MHz telah dikira menggunakan perisian

EZ-FDTD. Di dalam laporan ini, kajian teori ke atas kekuatan medan dan taburannya

di dalam sel GTEM diterangkan. Ianya diikuti dengan melakukan penguh.'uran medan

berdasarkan pengujian ketahanan radiasi. Didapati bahawa pada ketinggian septum

63 em untuk frekuensi 100 MHz, keputusan pengukuran dan simulasi adalah paling

hampir. Lokasi ini adalah yang dieadangkan oleh pengeluar untuk perletakan

peralatan dibawah ujian (EUT) dalam ujian panearan radiasi dan ketahanan radiasi.

Perbezaan berubah dari 0.01 dB hingga 4.91 dB. Perbezaan diantara permodelan dan

pengukuran sebenar boleh disifatkan kepada masukan taburan medan, eiri-eiri

ketakhomogenan bagi septum dan kewujudan gelombang pegun. Di masa hadapan,

adalah dieadangkan kaedah berangka yang lain seperti Kaedah Elemen Terhingga

(FEM) dan Kaedah Penghantaran Talian (TLM) digunakan dan model dan

parameter keadaan serapan sempadan yang lebih tepat dilaksanakan.

CHAPTER

CHAPTER I

TABLE OF CONTENTS

TITLE

DECLARA TION

DEDICATION

ACKNOWLEDGEi\IENT

ABSTRACT

ABSTRAK

TABLE OF CONTENTS

LIST OF TABLES

LIST OF FIGURES

GLOSSARY OF ABBREVI:\ TIONS

LIST OF SYi\1BOLS

LIST OF APPENDICES

INTRODUCTION

1.1 Introduction to Project

1.2

1.3

IA

Objecti\'es

Scopes or Work

Importancc or Projcct

\ II

PACE

i\U:\IBER

II

III

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V III

CHAPTER II LITERA TURE REVIEW 4

2.1 Introduction 4

2.2 EMC Measurement Facilities 5

2.2.1 Open Area Test Site (OATS) 5

2.2.2 Anechoic Room 6

2.2.3 TEM Cell 6

2.2.4 GTEM Cell 7

2.3 Radiated Immunity Overview 8

2.4 GTEM Cell Concept 8

2.4.1 Testing Volume 9

2.5 GTEM Parameters 9

2.5.1 Characteristic Impedance 10

2.5.2 Unifonnity of Electric Field 10

2.6 Electric Field Strength 11

2.7 GTEM Tem1ination 13

2.7.1 Current Tem1ination 13

2.7.2 Field Termination 14

2.8 Wave Propagation 15

2.9 Finite Difference Time Domain Method 16

2.9.1 Basic FDTD and

Maxwell's Equations 17

2.9.1.1 One Dimensional FDTD 17

2.9.1.2 Two Dimensional FDTD 18

2.9.1.3 Three Dimensional FDTD 20

2.10 Stability Condition 24

2.11 Boundary Condition 25

2.12 Electric Field Distribution Work 28

CHAPTER III

CHAPTER IV

CHAPTER V

METHODOLOGY

3.1

3.2

3.3

3.4

Introduction

FDTD GTEM Model

Measurement Procedure

Radiated Immunity Measurement System

SIMULA TION MODEL AND MEASUREMENTS

4.1 Model Definition

4.2 Computational Domain

4.3 Absorbing Boundary Condition

4.4 Plate

4.5 Source Parameter

4.6 Monitor Point (Observation Points)

4.7 Lumped Element

4.8 Instrumentation for Measurement

4.8.1 Electric Field Probe

4.8.2 Directional Coupler

4.8.3 Signal Generator

4.8.4 Power Amplifier

4.8.5 Control Software

RESULTS AND ANALYSIS

5.1

5.2

5.3

Introduction

Result

Analysis

IX

29

29

29

31

32

34

34

34

35

36

37

37

38

38

39

40

41

41

42

43

43

44

46

x

CHAPTER VI CONCLUSIONS AND RECOMMENDATIONS 51

REFERENCES

APPENDIX A

APPENDIX B

APPENDIX C

APPENDIX D

APPENDIX E

6.1 Conclusion

6.2 Recommendations for Future Work

51

52

53

56

61

66

76

78

\\

LIST OF TABLES

TABLE NO. TITLE PAGE

5.1 The cutoff frequencies for higher modes related to

cross sectional dimension ofGTEM cell 47

5.2 The cOITelation coefficients of the measured

electric field to calculated electric field 49

5.3 The minimum and maximum ratio of the measured

electric field to calculated electric field 50

Xli

LIST OF FIGURES

FIGURE NO. TITLE PAGE

2.1 EMC Structure 5

2.2 Typical TEM cell 7

2.3 Diagram of GTEM cell 9

2.4 Field strength at the testing volume II

2.5 The electric field strength related to the height of septum

for different values of power with characteristic

line impedance son 12

2.6 The broadband pyramidal RF absorbers 14

2.7 TEM waves IS

2.8 One Dimensional FDTD Grid 18

2.9 Two Dimensional FDTD Grid 19

2.10 Three dimensional FDTD grid (Yee cell) 23

2.11 Reflectionless transmission of a plane wave at PML

and free space interface 27

3.1 Typical Setup for RF Immunity 32

3.2 Methodology Flowchart 33

4.1 FDTD GTEM Model 36

4.2 Schaffner GTEM 750 38

4.3 The Side View of GTEM Cell 39

4.4 The Top View of GTEM Cell 39

4.5 HI-4422 Electric field probe 40

4.6 Dual directional coupler 41

X 111

5.1 The measured and calculated of electric field distribution

below septum height, h = 63cm for 100 MHz. 44

5.2 The measured and calculated of electric field distribution

below septum height, h = 63cm for 200 MHz 45

5.3 The measured and calculated of electric field distribution

below septum height, h = 63cm for 400 MHz 45

5.4 The electric field strength at 100 MHz at y = 20 cm

from the floor of outer conductor. a) Septum height 54 cm

b) Septum height 63 cm c) Septum height 70 cm 48

ABC

CW

DC

EMC

EMI

EMS

EUT

FDTD

FEM

GPIB

GTEM

OATS

PEC

PML

RAM

RF

TEM

TUvl

GLOSSARY OF ABBREVIA nONS

Absorbing Boundary Conditions

Continuous Wave

Direct Current

Electromagnetic Compatibility

Electromagnetic Interference

Electromagnetic Susceptibility

Equipment Under Test

Finite Difference Time Domain

Finite Element Method

General Purpose Interface Bus

Gigahertz Transverse Electromagnetic Mode

Open Area Test Site

Perfect Electric Conductor

Perfectly Matched Layer

Radio Frequency Absorbing Material

Radio Frequency

Transverse Electromagnetic Mode

Transmission Lines fvlcthod

XI\'

B

C

c

D

E

J H

h

J

n

P

P"

v

Voutcr

v

Z

b.(

b..x,b.y,b.z

LIST OF SYMBOLS

Magnetic flux density (T or Wb/m2)

Capacitance (F)

Speed of light in free space (m/s)

Electric flux density (C/nl)

Electric field strength (Vim)

Frequency (Hz)

Magnetic field strength (Aim)

Distance between center conductor and

outer floor conductor (m)

Current density (Alm 2)

Number of step

Input power (W)

Volume charge density (C/m3)

Time (s)

Input voltage (V)

Voltage at center conductor (V)

Voltage at outer conductor (V)

Phase velocity (m/s)

Characteristic impedance (Q)

Time step (s)

Space increment or cell size (m)

Conductivity of material (S/m)

Pem1ittivity of free space (F/m)

Pem1ittivity of material (F/m)

xv

f.1

['

'7

A

Permeability of material (Him)

Amount of reflection

Intrinsic impedance (n)

Wavelength (01)

XVI

LIST OF APPENDICES

APPENDIX NO. TITLE

A

B

C

D

E

GTEM EZ-FDTD Model and Model Definition Tab

Electric Field Distribution

Simulation and Measurement Data

Sample MA TLAB Code for Graph Plotting

Observation Points

xvii

PAGE

56

61

66

76

78

CHAPTER I

INTRODUCTION

1.1 Introduction to Project

The measurement method for radiated emission and radiated susceptibility

requires a method, which is reliable and reproducible. This is important to ensure the

measurements fl.dfill the electromagnetic compatibility (EMC) standard. The

Gigahertz Transverse Electromagnetic Mode (GTEM) cell as a new measurement

facility in electromagnetic compatibility need to be evaluated especially its electric

field distributions.

It is important to determine the field strength and distribution in a GTEM cell

for EMC and calibration measurements. The field strength inside a GTEM Cell is a

function of the input power as well as location along the longitudinal axis or septum

height. Immunity measurements require field uniformity (+6 dB according to IEC

61000-4-3 standard) over certain test area and calibration can only be carried out if

the precise field strength at a particular location is known.

2

Finite Difference Time Domain (FDTD) is a numerical method that can be

used to predict the electric field distribution in a GTEM cell. FDTD is a tool to

calculate the electric field in a defined test volume in a GTEM cell. The electric field

distribution at certain frequency was calculated using EZ-FDTD software based on

FDTD method.

In this report, theoretical study on the field strength and distribution in a

GTEM cell is described. It is followed by making measurements of the field. The

results from both works will be compared and the differences will be noted and

explained. The differences of the theoretical and measurements denotes the sources

of field problems and recommended solution will be mentioned.

1.2 Objectives

i) To perfonTI numerical modeling of field strength in GTEM cell using

Finite Difference Time Domain, (FDTD).

ii) To conduct measurements of field strength in GTEM cell based on

immunity measurement setllp.

iii) To analyze, compare, and conclude the results obtained from the

modeling and measurements.

1.3 Scopes of Work

i) Measurement and calculation of electric field distribution was done at

frequency 100MHz, 200M Hz and 400MHz.

ii) Simulation model using three-dimensional FDTD method.

iii) Measurement GTEM facility is GTEM 750 model by Schaffner.

iv) Electric field distribution for an unloaded GTEM cell.

v) Measurement and calculation was done at three different planes where

septum height, h was 54cm, 63cm, and 70cm.

1.4 Importance of Project

i) To determine the capability of a GTEM cell as a measurement facility in

electromagnetic compatibility.

ii) To provide an input to GTEM manufacturer to improve their GTEM cell.

3