ABSTRACT
This thesis reports the result of an assessment of the impact of harmattan particles on
microwave signals in the savannah region. Emphasis was placed on the spatial harmattan
particle density, the specific particle attenuation variation, the atmospheric attenuation
and the dominant propagation mechanism during the harmattan period which is peculiar
to the savannah region. The report studied scattering mechanism, absorption mechanism
and specifically described how to determine the specific particle attenuation, atmospheric
losses and spatial harmattan particles density. The attenuation of wavelengths in the
900MHz and 1800MHz band during harmattan period in the savannah region was studied
and path loss curves are presented. The significant results obtained are also discussed and
interpreted. Finally the comparative statistical analysis of the results has been done. It is
established that the particle density is responsible for the scattering of electromagnetic
energy which leads to attenuation in its signal strength. For the year 2004, the
atmospheric losses range between 3.7dB and 12.55dB, for 2005, the atmospheric losses
range between 3.3dB and 18.94dB for 2006, the atmospheric losses range between
1.71dB and 13.03dB. From the statistical analysis, the highest path loss occurs on Farcha
road while the lowest occurs on Moursal road.
TABLE OF CONTENTS
Title page …. ….. ….. …. …. … …. i
Declaration …. …. …. …. …. …. …. ii
Certification …. ….. ….. …. ….. ….. ….. iii
Dedication …… ….. …. …. ….. …. ….. iv
Acknowledgement …. ….. ….. …. ….. ….. v
Abstract …. ….. …. …. …. …. …. vii
Table of contents …. ….. …. …. …. …. viii
List of Figures … ….. …. …. … …. ix
List of Tables …. …. …. …. …. …. xiii
List of Abbreviations/Symbols … …. …. …. xx
CHAPTER ONE-GENERAL INTRODUCTION
1.1 Introduction … …. …. …. .. 1
1.2 Thesis Motivation …. …. …. …. … 2
1.3 Statement of Problem … …. …. … 3
1.4 Thesis Outline …. …. …. … … 4
CHAPTER TWO- LITERATURE REVIEW
2.0 Introduction … … …. … … … 5
2.1 Literature Review .. … … 5
2.2 Dielectric Materials … …. …. …. …. 8
2.3 Absorption Mechanism … …. …. .. 9
2.4 Scattering Mechanism … …. …. ….. 12
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2.5 Harmattan Particle density … … …. … … 14
2.6 Electrodynamics … …. … … …. … 19
2.6.1 Coulomb’s Law … …. …. …. … … 19
2.6.2 Electric Field …. …. …. …. ….. …. … 20
CHAPTER THREE- METHODOLOGY
3.1 Methodology and Data Collection … …. …. …. 22
3.2 Data Collection … …. …. … … … … 22
3.3 Discussion on data ……… …….. ………. ……. 28
3.4 Mathematical Analysis … …. …. …. …. …. 28
CHAPTER FOUR-ANALYSIS AND RESULTS
4.0 INTRODUCTION …. …. …. …. …. 31
4.1 Results obtained using spatial harmattan particle density model 31
4.2 Results obtained using specific attenuation due to hamattan dust
Particles ….. …. ……… ………… ….. …. … …. 36
4.3 Path loss analysis from field data … … ….. …. 79
4.3.1 Free space path loss Model (Analytical)… … ….. …. 79
4.3.2 Analysis of the cost-231 Hata Model… … …. …. 81
4.4 Analysis of visibility effects of signal wavelength …. … 86
4.5 Discussion of Results. …. …. …. …. …. …. 98
4.6 Statistical analysis of results.. …….. ……… …….. .. 99
CHAPTER FIVE-CONCLUSIONS AND RECOMMENDATIONS
5.0 INTRODUCTION … …. .. …. …. 101
5.1 Summary of results …. …. …. … …. 101
x
5.2 Significance of Results and Applications … … …. 102
5.3 Limitations. Problems Encountered and Solutions Proffered … 103
5.4 Conclusions …. ….. …. …. …. …. …. 103
5.5 Recommendations for Further Work …. …. …. …. 104
REFERENCES 105
APPENDIX A 108
APPENDIX B 109
APPENDIX C 110
APPENDIX D 111
APPENDIX E 112
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LIST OF FIGURES
FIGURE PAGE
2.1: Plane in the space 9
2.2: Illustration of instantaneous and ray diagram of scattering 13
4.1 Specific particle Attenuation Variation for 2004 (Minimum temperature) 70
4.2: Specific particle Attenuation Variation for 2004(Average temperature) 71
4.3: Specific particle Attenuation Variation for 2004(Maximum temperature). 72
4.4: Specific particle Attenuation Variation for 2005(Minimum temperature) 73
4.5: Specific particle Attenuation Variation for 2004(Average temperature). 74
4.6: Specific particle Attenuation Variation for 2005(Maximum temperature) 75
4.7: Specific particle Attenuation Variation for 2006(Minimum temperature) 76
4.8: Specific particle Attenuation Variation for 2006(Average temperature) 77
4.9: Specific particle Attenuation Variation for 2006(Maximum temperature) 78
4.10 Path loss on Diguel Road for March 2006 82
4.11 Path loss on Moursal Road for March 2006 83
4.12 Path loss on Diguel Road for February 2006 84
4.13 Path loss on Farcha Road for February 2006 84
4.14 Path loss on Moursal Road for January 2006 85
4.15 Path loss on Chagoua Road for November 2005 85
4.16: Atmospheric losses for 2004. 92
4.17: Atmpospheric losses for 2005 93
4.18: Atmospheric losses for 2006 94
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4.19: Atmospheric losses for 2004 95
4.20: Atmospheric losses for 2005 96
4.21: Atmospheric losses for 2006 97
CHAPTER ONE
GENERAL INTRODUCTION
1.1 INTRODUCTION
It has been established that the impact of harmattan particles can lead to
Ssssssatmospheric attenuation, signal fading, obstructions in the signal path and
multipath effects leading to a drop in the signal power.[ 1 ] This thesis is aimed at the
assessment of the impact of harmattan particles on microwave propagation in the
savannah region with N’Djamena, Chad as a case study.
Chad is a continental country located in the northern hemisphere. The coordinates
of Chad are: 80 latitude and 240 latitude (tropic of cancer for latitude North, 14
and 24 degree of longitude East). Its area is 1,284 million sqkm. Chad is a land locked
country located in North Central Africa. It shares boundary with, Libya to the North,
Sudan to the East, the Central African Republic to the South, Cameroon and Nigeria to
the South West and Niger to the West. The country is mostly an arid, semi –desert
plateau on the edge of the sahara desert. Its prominent feature is the broad shallow basin
of Lake Chad in the South and South West part of the country, from there the land rises
gradually to plateau in the South while to the North of the Basin the land rises to the
Ennedi Plateau and the volcanic Tibesti Ranges. For the most part the country vegetation
is generally desert scrub or steppe [2].
Chad is placed under the influence of the anticyclone of Libya (continental air:
harmattan monsoon). These anticyclones provoke the motion of masses of air that push
each other either in South-East direction or according to reverse direction. The Interxxiii
Topical Convergence zone (ITC) or the Inter-Topical Font (ITF) moves between 40 and
200 Latitude North according to the apparent motion of the sun.
Chad has three climatic zones:
(1) A Subtropical Zone within the equatorial rain belt to the South with a wet
season from May to November and a dry season from September to April.
(2) A Sahelian Zone in the Central region which has a longer dry season and a
brief wet season between June and September.
(3) The Saharan Zone in the Northern region which has a true desert climate
with hot and arid conditions and is almost entirely rainless. Average annual
precipitation in N’Djamena is 744mm (29 inches) and the average
temperature ranges are from 14 to 35 degrees Celsius (57 to 91 degrees
Fahrenheit) in December to 23 to 42 degrees Celsius (73 to 108 degrees
Fahrenheit) in August. [2]
In Chad the harmattan season occurs between December and March.
1.2 THESIS MOTIVATION
Communication systems: such as radar system, radio navigation, heating, energy
transfer, mobile communication, remote sensing, control and recording use microwave
frequencies as a fundamental transmission medium for their operations.
The need for assessing the effect of harmattan on microwave propagation is for
monitoring of the radio signals and measurements of their field strength and fading
characteristics and analyses.
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This investigation can also lead the radio planner to a thorough understanding of
microwave propagation in the savannah region for designing point- to- point links among
other things.
1.3 STATEMENT OF PROBLEM
It has been previously investigated and found that harmattan disturbs propagation
of radio signals at frequencies generally above 30MHz. It is well known that radio
reception in general and microwave signals in particular, are affected by the phenomenon
of fading. The result is that, the incoming radio signal which enters the receiver circuitry
varies in magnitude. These variations are attributed to changes in propagation conditions.
In extreme cases it can even lead to complete cancellation of a signal at the receiving
point. These signal variations can occur fast or slow and the speed at which they take
place is known as “rate of fading” the reception of microwaves depends on their
propagation between a transmitter and a receiver [3].
In the savannah region and hence also in N’Djamena capital of Chad, the
atmosphere is seasonally affected by: “harmattan”; a weather condition during which dust
is blown southwards from the sahara desert by a North East wind. Dust particles of about
a micron size are finally deposited when the North East wind loses its speed on meeting a
warm and opposite wind from the Gulf of Guinea. The intensity of the harmattan may be
so great that the visibility at ground level is reduced to less than a hundred meters.
The main objective of this thesis is, therefore, to find out whether, and how, the
harmattan is influencing microwave propagation in the region in general and N’Djamena
in particular. To carry out this investigation, the records of ground level visibility during
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harmattan will be analyzed with respect to the actual particle rate (or density) of
harmattan dust in the air. On the strength of these analyses, specific attenuation during
harmattan will be analysed and computed. After field strength measurements, the
pathlosses in a typical case will be discussed.
1.4 THESIS OUTLINE
This thesis report begins with a general introduction of an assessment of the
impact of harmattan particles on signals and the climate of Chad as contained in chapter
one. This chapter also contains the basis for this research. In chapter two, literature
review related to the theory of dielectrics and electrodynamics are discussed, and in
chapter three, the methodology and data collection used in this work is presented.
Chapter four contains the results obtained and the analysis. Interpretation of the results is
also discussed in this chapter. Finally, chapter five rounds off with limitations, problems
encountered and the solution proffered. It also contains conclusions and
recommendations for further work.
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