Ayobami Babatunde Iji- Vector Antenna for UltraHigh Energy Cosmic Neutrino Detection in the Antarctic Ice

8/3/2019 Ayobami Babatunde Iji- Vector Antenna for UltraHigh Energy Cosmic Neutrino Detection in the Antarctic Ice

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DIPLOMA THESIS

VECTOR ANTENNA FOR

ULTRAHIGH ENERGY COSMIC

NEUTRINO DETECTION IN THE

ANTARCTIC ICE

AYOBAMI BABATUNDE IJI

Uppsala School of Engineering

and

Department of Astronomy and Space Physics, Uppsala University, Sweden

DECEMBER 19, 2007


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This thesis work is Dedicated to:

THE MOST HIGH GOD.


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CONTENTS

Contents iii

List of Figures v

1 Introduction 1

2 Introduction to Antennas 5

2.1 Wire antennas 5

2.2 Dipole antennas 6

2.3 Half-wavelenght Dipole 8

2.4 Radiation Pattern of a Dipole Antenna 8

2.5 Antenna Polarization 10

3 Design Considerations for the Vector Antenna 11

3.1 Vector Antenna 11

3.2 Determining the Wavelength () for the Vector Antenna 11

3.3 Efficiency Analysis. 12

3.4 Radiation Efficiency of Antenna 12

3.5 Antenna Loss Resistance 14

3.6 Determining the Operation Frequency for the Vector Antenna 16

3.7 Design Considerations 17

3.8 Ultra HighEnergy Cosmic Neutrino (UHEC) Antanna 17

4 Mechanical Construction 19

4.1 Mechanical Considerations for Design 19

4.2 The Cover of the Antenna 19

4.3 The material for the Antennas 20

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CONTENTS

4.4 Mechanical Model And Drawings of the Vector Antenna 20

4.5 Geometry alignment for a 3D object 21

5 Vector Antenna performance 35

5.1 Electrical Properties of the Antenna Medium or Environment 35

5.1.1 Electromagnetic Wave in Ice 35

5.2 UHEC Antenna Amplification 35

5.3 Vector Measurements 36

5.3.1 The 3D E-field antennas 36

5.4 Vector Pulse Post-Processing 36

6 Electrical Simulation of Antenna 41

7 Conclusion 51

Bibliography 55

Bibliography 55

iv


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LIST OF FIGURES

2.1 Current Distribution of a Vertical Electric Dipole. 6

2.2 Current Distribution of a 3D orthogonal dipole 7

3.1 Thevenin equivalent transmitting mode of antenna 13

4.1 Top model made of peek 20

4.2 Machine drawing of the top model 22

4.3 Angle formed by the orthogonal antennas with centre 23

4.4 Bottom model 24

4.5 Bottom model machine drawing 25

4.6 Vee band 26

4.7 Vee band machine drawing 27

4.8 Antenna with fittings 28

4.9 Antenna with fitting 29

4.10 Electronics circuit board. 30

4.11 complete model 31

4.12 Internal structure of complete model 32

4.13 Finished tripole antenna. Photo by T. Thrnlund 33

5.1 Circuitry of the orthogonal dipole antenna 37

5.2 Simulation of vector pulse processing. The pulse record is 64 samples

long. At 1 Gsamp/s corresponding to 64 ns. 39

6.1 Orthogonal Vector antennas total gain 42

6.2 Orthogonal vector antennas total gain 43

6.3 vector antennas total gain 44

6.4 Vertical gain 45

6.5 vertical gain orthogonal dipole 46

v


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LIST OF FIGURES

6.6 Horizontal gain 47

6.7 horizontal gain orthogonal dipole 48

6.8 horizontal axis total gain 3D orthogonal dipole 49

6.9 vertical axis total gain 3D orthogonal dipole 50

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1

INTRODUCTION

This project describes the design of a vector antenna for ultrahigh energy cosmic

neutrino (UHEC) detection in the Antarctic ice. Neutrinos are elementary parti-

cles that travel close to the speed of light, lack an electric charge, are able to pass

through ordinary matter almost undisturbed and are thus extremely difficult to de-

tect. Neutrinos have a minuscule, but non-zero, mass too small to be measured as

of 2007. They are usually denoted by the Greek letter (nu). Neutrinos are cre-

ated as a result of certain types of radioactive decay or nuclear reactions such as

those that take place in the sun, in nuclear reactors, or when cosmic rays hit atoms.

Neutrino was postulated in 1930 by Wolfgang Pauli,[2] 1945 Nobel Laureate in

Physics, in order to solve an energy crisis in nuclear physics. There are three types

of neutrinos: the electron neutrino e, the muon neutrino and the tau neutrino

t. These neutrinos are related with three electrically charged particles, the elec-

tron, the muon and the tau. When a neutrino interacts with matter, it can either

continue as a neutrino after the interaction (neutral current interaction) or create

the corresponding charged particle (charge current interaction). The electron neu-

trino creates an electron, the muon neutrino a muon, and the tau neutrino a tau

lepton.

Most neutrinos passing through the Earth emanate from the sun, and more than 50

trillion solar electron neutrinos pass through the human body every second. The

sun emits vast numbers of neutrinos which can pass through the earth with little

or no interaction. This leads to the statement Solar neutrinos shine down on us

during the day and shine up on us during the night". Neutrinos are produced by

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CHAPTER 1. INTRODUCTION

the decay of radioactive elements and elementary particles such as pions (pi me-

son). Unlike other particles, neutrinos are antisocial, difficult to trap in a detector.

It is the feeble interaction of neutrinos with matter that makes them uniquely valu-

able as astronomical messengers. Unlike photons or charged particles, neutrinos

can emerge from deep inside their sources and travel across the universe without

interference. They are not deflected by interstellar magnetic fields and are not

absorbed by intervening matter.

However, this same trait makes cosmic neutrinos extremely difficult to detect;

immense instruments are required to find them in sufficient numbers to trace theirorigin. There are large volumes of ice below the South Pole to watch for the

rare neutrino that crashes into an atom of ice. This collision produces a particle

dubbed a muon that emerges from the wreckage. In the ultra-transparent ice, the

muon radiates blue light that is detected by IceCubes optical sensors. The muon

preserves the direction of the original neutrino, thus pointing back to its cosmic

source. The IceCube is located at the South Pole, which is actually near the middle

of Antarctic. Antarctic is from the Greek word antarktikos which means opposite

the Arctic is generally defined as one of the coldest, windiest, highest, and driest

locations in the world. Its also one of the most fascinating.

Antarctic is the fifth largest continent at 13,720,000 km2 but has the highest av-

erage elevation because of its thick layer of ice. Centered around the South Pole,almost the entire continent is located south of the Antarctic circle.

The IceCube Neutrino Detector is a neutrino telescope currently under construc-

tion at the South Pole. Like its predecessor, the Antarctic Muon and Neutrino

Detector Array (AMANDA), IceCube is being constructed in deep Antarctic ice

by deploying thousands of spherical optical sensors (photomultiplier tubes, or

PMTs) at depths between 1,450 and 2,450 meters. The sensors are deployed on

strings of sixty modules each, into holes melted in the ice using a hot water drill.

Another of the Icecube project is the Radio Ice Cherenkov Experiment (RICE),

which consists of 18 radio receivers deployed in the ice at a depth of 100 - 300 m;presently another project known as Askaryan Underice Radio Array (AURA), has

been proposed for the next-generation radio neutrino detector for south pole. The

AURA consists of new digital radio module (DRM) which incorporate triggering

and data handling electronics.

We are developing a broadband vector antennas made of three orthogonal dipole

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antennas that will be compatible with the AURA triggering electronics and capa-

ble of obtaining full polarization coverage for detection of neutrinos in the Ice-

Cube. [1]

The main goal of the experiment is to detect neutrino in the high energy range,

spanning from 1011 eV to about 1021 eV.

The neutrinos are not detected themselves. Instead, the rare instance of a collision

between a neutrino and an atom within the ice is used to deduce the kinematical

parameters of the incoming neutrino. Current estimates predict the detection of

about one thousand such events per day in the fully constructed IceCube detector.

Due to the high density of the ice, almost all detected products of the initial colli-sion will be muons.

The experiment is most sensitive to the flux of muon neutrinos through its vol-

ume. Most of these neutrinos will come from cascades in Earths atmosphere

caused by cosmic rays, but some unknown fraction may come from astronomical

sources.

To distinguish these two sources statistically, the direction and angle of the in-

coming neutrino is estimated from its collision by-products. One can generally

say, that a neutrino coming from above down into the detector is most likely stem-

ming from an atmospheric shower, and a neutrino traveling up from below is more

likely from a different source.

The sources of those neutrinos coming up from below could be black holes,

gamma ray bursters, or supernova remnants. The data that IceCube will collect

will also contribute to our understanding of cosmic rays, supersymmetry, weakly

interacting massive particles (WIMPS), and other aspects of nuclear and particle

physics. [2]

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2

INTRODUCTION TO

ANTENNAS

An antenna is a conducting device or transducer designed to transmit or receive

radio waves which are a class of electromagnetic waves. Hence, antennas converts

radio frequency electrical currents into electromagnetic waves and vise versa. An-

tennas are used in systems such as radio and television broadcasting, point to point

radio communication, wireless lan, radar and space exploration. Antennas usually

work in air or outer space and can also be operated under water, in ice and in other

dielectric media. An ideal antenna is one that will radiate all the power deliveredto it from the transmitter in a desired direction or directions. However, In prac-

tice such ideal performances cannot be achieved but may be closely approached.

Various types of antennas are available and each type can take different forms

to achieve the desired radiation characteristics for the particular application. The

vector antenna designed used in this thesis consists of three mutually orthogonal

wire antennas oriented along the x, y, and z -axes.

2.1 Wire antennas

These are common type of antenna that are familiar to layman because they are

mostly seen every where on building automobile ships and aircrafts etc. There are

various shapes of wire antennas such as a straight wire (dipole), loop and helix

antenna. The vector antenna is a dipole antenna in 3D, orthogonally aligned in its

axes.

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CHAPTER 2. INTRODUCTION TO ANTENNAS

2.2 Dipole antennas

A dipole antenna is a linear wire positioned symmetrically at the origin of its co-

ordinate system and oriented in its axes; the dipole antenna is small with its length

and cross-sectional area very small or negligible. The antenna is centre-fed with

current and the current vanishes at the end points. [5]

Figure 2.1: Current Distribution of a Vertical Electric Dipole.

Vertical electric dipole: an antenna oriented along the z-axes above the ground

is referred to as the vertical dipole.Horizontal electric dipole: an antenna oriented along the y-axes above the ground

is referred to as the horizontal dipole.

The vector antenna as a 3D orthogonal dipole, consists of three mutually orthog-

onal dipoles and can be oriented so that one of the dipole is vertical and the other

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2.2. DIPOLE ANTENNAS

two horizontal.

Figure 2.2: Current Distribution of a 3D orthogonal dipole

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2.3 Half-wavelenght Dipole

The often used antenna is the half wavelength dipole which has a radiation resis-

tance of 73 which is very close to the 5075 characteristics impedances of

the most common transmission lines. This makes the matching to the transmis-

sion line is simple, especially at resonance.

The electric far-field and magnetic field components of a half wavelength dipole

are shown in the equation below:

E jIoe

jKr

2r

cos

2cos

sin

(2.1)

H jIoejKr

2r

cos

2cos

sin

(2.2)

Also the time average radiation density and radiation intensity can be written re-

spectively as follows [5]

Wav = |Io|282r2

cos

2cos

sin

2 |Io|

2

82r2sin3 (2.3)

and

U= r2Wav = |Io|282

cos

2cos

sin

2 |Io|

2

82sin3 (2.4)

2.4 Radiation Pattern of a Dipole Antenna

The radiation pattern describes the radiation parameters as a function of space

coordinates for an antenna but usually, the power pattern is meant. It could be in

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2.4. RADIATION PATTERN OF A DIPOLE ANTENNA

the fraunhofer region (Far Field Pattern) or the Fresnel region (Near Field Pattern).

A finite length dipole antenna is subdivided into a number of infinitesimal dipoles

of length z. As the number of the subdivisions is increased each infinitesimal

dipole approaches a length dz. An infinitesimal dipole of length dz

positioned

along the z -axis at z

the electric and magnetic field components in the far field

are given as, [5]

dE j KIe(xyzejkR)4R

sindz

(2.5a)

dEr dE = dHr= dH= 0 (2.5b)

dH jKIe(x

y

zejkR)

4Rsindz

(2.5c)

where:

R rz cos for phase termsR r for amplitude

Then the Far field approximation is given by:

dE j KIe(x

y

zejkr)

4rsinejkz

cosdz

(2.6)

E=

+l/2

l/2dE= j

kejkr

4rsin

+l/2

l/2Ie

x

,y

,z

ejkzcosdz

(2.7)

where the factor outside the brackets represents the elements factor and that withthe brackets is the space factor. The elements factor depends on the type of cur-

rents and its direction of flow while the space factor is a function of the current

distribution along the source. The total field of the antenna is equal to the product

of the element and space factors.

Total field = (Element factor Space factor).

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2.5 Antenna Polarization

All electromagnetic, EM, waves, traveling in free space, have an electric field

component, E, and a magnetic field component, H, which are perpendicular to

each other and both components are perpendicular to the direction of propaga-

tion. The orientation of the E vector is used to define the polarization of the wave;

if the E field is orientated vertically the wave is said to be vertically polarized.

Sometimes the E field rotates with time and it is said to be circularly polarized.

Polarization of the wave radiating from an antenna is an important concept when

one is concerned with the coupling between two antennas or the propagation of aradio wave.

A closely related parameter is the impedance of a wave; this is the ratio of E/H

= and for free space is close to 377 ohms. This is not to be confused with the

radiation resistance of an antenna; its just that they have the same units. If a

propagating radio wave encounters a medium of a different impedance, part of

the wave is reflected, much like the reflections at a discontinuity in a transmission

line. The remaining energy of the wave that passes through the discontinuity is

refracted in a different direction of propagation, just like the distortion one sees as

a light beam passes through water. The reflection and refraction properties often

depend upon the polarization of the EM wave.

The polarization of an antenna is the polarization of the wave radiated by the an-

tenna. At a given position, the polarization describes the orientation of the electric

field. The energy radiated by any antenna is contained in a transverse electromag-

netic wave that is comprised of an electric and a magnetic field. These fields are

always orthogonal to one another and orthogonal to the direction of propagation.

The electric field of the electromagnetic wave is used to describe its polarization

and hence, the polarization of the antenna. In general, all electromagnetic waves

are elliptically polarized. In this general case, the total electric field of the wave is

comprised of two linear components, which are orthogonal to one another. Each

of these components has a different magnitude and phase. At any fixed point along

the direction of propagation, the total electric field would trace out an ellipse as afunction of time. [5]

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3

DESIGN

CONSIDERATIONS FOR THE

VECTOR ANTENNA

3.1 Vector Antenna

The design of a vector antenna to be used for detection of cosmic neutrino in the

Antarctic came as a result of undetected genetic particles originating beyond the

Earth that impinge on the Earths atmosphere and the interstellar medium.

The antenna is able to recieve cosmic ray signals from all directions. Antennasare capable of detecting signals depending on the orientation of the antenna. If

an antenna is oriented along the x -axis, only the x -component of the electric

field can drive through the antenna. Hence, to be able to detect signals from all

directions we have chosen to have three dipole antennas oriented along the x, y, z

-axes. This antenna is to be deposited in ice at about 1500 meters depth.

3.2 Determining the Wavelength () for the Vector Antenna

The wavelength of a dipole antenna can be determined in relative to the antennalength and the method is as follows. = /2 for dipole, = /4 for quarter pole

antenna, and = for monopole antenna.

Therefore, in this case we use = /2 for the antenna length = 250 cm = 0.25 m.

Hence, = 2 = 0.5 m. Also considering the Electrical length of the vectorantenna which is different from the physical length, then the wavelength is ap-

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CHAPTER 3. DESIGN CONSIDERATIONS FOR THE VECTOR ANTENNA

proximately [5] = 0.95/2 with = 0.25 m, obtaining the free-space wavelength

= 20.95

= 0.526 m.

3.3 Efficiency Analysis.

From the schematic diagram, the antenna is capable of reception in x, y, z -axes

and part of an incident wave would be reflected back at the junction because of

impedance mismatch. The use of broadband matching transformer to distributethe input signal, This is an advantage to the antenna though the antenna become

more complex.

The far-field directivity can be obtain in respect to the dipole antenna on each axis

respectively since each dipole antenna is fed with different voltages. The gain

also varies from one axis to another.

3.4 Radiation Efficiency of Antenna

The radiation efficiency ecd of an antenna is the ratio of the total power radiated

by the antenna and the total supplied power. The supplied power consists of the

radiated power and power dissipated by ohmic losses in the antenna

ecd =Prad

Pin=

Prad

Prad+Pohmic(3.1)

By viewing the antenna in transmitting mode, it can be represented by a Thevenin

equivalent according to the Fig. 3.1

The antenna is represented by an impedance ZA and is given by:

ZA =RL+Rr + jXA (3.2)

where Rr is the radiation resistance and XA the antenna reactance. RL represents

both the conduction and dielectric losses of the antenna. The source of the an-

tenna is represented by an ideal generator Vg having its own internal complex

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3.4. RADIATION EFFICIENCY OF ANTENNA

Rg

Xa

RL

Rr

Xg

Vg

Ig

Source

Antenna

Figure 3.1: Thevenin equivalent transmitting mode of antenna

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impedance Rg + Xg. The radiated power can be expressed as:

Pr =

Vg22

Rr

4(Rr+RL)2

=

Vg28

Rr

(Rr +RL)2

(3.3)

and the power dissipated in the antenna as:

POhmic = PL =

Vg2

8 RL

(Rr +RL)2

(3.4)

Now, the radiation efficiency becomes:

ecd=Rr

Rr+RL(3.5)

Hence, RL should be very low compared toRr and it should not be chosen too large

because, the antenna impedance should be conjugately matched to the generator

impedance.

3.5 Antenna Loss ResistanceThe antenna loss resistance consists of the conductor and dielectric losses, which

for many antenna it is difficult to calculate. But for a wire antenna it can be cal-

culated accurately from the conductor length and cross-sectional area A which

carries a uniform current density. The DC resistance is;

RDC =

A(3.6)

Where is the conductivity of the conductor material. At high frequencies the

current tends to concentrate to the outer surface of the conductor. This phenom-ena is called the skin effect.

The high frequency resistance can be define in terms of the skin depth

skin dept [7]

=1

f(3.7)

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3.5. ANTENNA LOSS RESISTANCE

Where is the permeability of the material and f is the frequency in Hz for in-

stance the skin dept for copper.

= 5.8107/m, =o = 4107H/m

skin depth can be written as;

= 0.0661f frequency in Hertz

As the frequency increases, the current begins to move from an equal distribution

through the conductor cross-section towards the surface depending on the con-

ductor bulk resistivity. At surficiently high frequencies all the current are flowing

within a very thin layer close to the surface.

However, the current concentrates nearest to the surface that is about the highest

relative dielectric constant. Lower bulk resistivity result in shallower skin depths.

For a solid wire the current concentrates on the outer surface for this reason, when

skin depth is shallow the solid conductor can be replaced with a hollow tube with

no perceivable losses of performance. The choice of a plating material can de-

grade performance (increase attenuation) if its bulk resistivity is greater than thatof the copper.

Hence skin depth can be calculated as follows; [7]

s =

2

..=

P

2(3.8)

RHF =l

2bRs (3.9)

Rs = surface resistance. In analogue with equation (3.6), we obtain

Rs =1

=

.f.(3.10)

The high-frequency resistance becomes;

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RHF =l

2b

2(3.11)

The loss resistance is RL = RHF but for a half-wavelength dipole RL =12RHF

3.6 Determining the Operation Frequency for the Vector An-

tenna

The actual operating frequency is determined by considering the refractive index

of the environment or the region where the antenna is to be used, for this design

we are considering ice. Hence, the refractive index of ice at microwave frequency

is = 1.78 [3]. Following the calculation below,

= kc (3.12)

while c =

=kc

= 1 for free space (3.13)

=kc

= 1.78 for Ice (3.14)

where c = 3108m/s

k = 2

= 2

from the expression of a dipole above = 0.25 m.

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3.7. DESIGN CONSIDERATIONS

and = 2

then = 0.526 m.

=c

(3.15)

= 3108

0.5261.78 = 320 MHz.

3.7 Design Considerations

The UHEC antenna is designed to be installed in the ice at a depth of 1500 m

in a hot water drill-hole in the Antarctic, The antenna comprises of three dipole

antenna aligned in the x, y, z -axes with frequencies of 320 MHz. The dipole

antennas are enclosed in a spherical plastic capable of withstanding a pressure of

about 1000 Bar.

Simulations have been done to ensure that the antenna enclosure are properly

chosen and selected to withstand future deterioration or environmental effect on

the antenna enclosure, and various effects were observed to improve the simula-

tion results. Also simulations are run for the dipole antenna itself to ensure better

performance, Part of an incident wave would be reflected back at the junction

because of impedance mismatch. The use of broadband matching transformers

to distribute the input signal is an advantage to the antenna though the antenna

become more complex.

The far-field gain can be obtain in respect to the dipole antenna on each axes re-

spectively since each dipole antenna is fed with differently. The gain also varies

from one axis to another.

3.8 Ultra HighEnergy Cosmic Neutrino (UHEC) Antanna

The frequency of operation of the UHEC antenna is at 320 MHz according to

design specification.

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Broadband antennas have been studied for short pulse applications typically trad-

ing phase linearity with gain. The UHEC antenna can easily reach a low standing

wave ratio over several octaves due to its asymmetrical structure.

However the electrical size of ground axis increases at high frequencies and the

radiation pattern is reflected away from azimuthal axis.

The radiation is made broadsided so that all frequency components are transmitted

and received simultaneously.

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4

MECHANICAL

CONSTRUCTION

4.1 Mechanical Considerations for Design

Certain measures have been considered for the mechanical construction and de-

sign of the UHEC antenna to make sure that it is strong enough to withstand

stress and pressure during and after the installation of the antenna. Such measures

include selecting a proper cable for communication between the antenna and the

surface, three double-shielded coaxal cables supported by integrated steel wires

and is capable of operating in the ice under high pressure without squeezing or

rupturing. The cable is connected to the antenna via an underwater pressure tight

connector strong enough to withstand a pressure at about 1000 Bar in ice. The

central part made of plastic has been constructed sufficiently strong to make sure

that it cannot be broken. In order words, proper considerations and measures have

been taken to make sure that the cable is suitable for the demanding environment.

4.2 The Cover of the Antenna

The material used for the antenna cover is plastic peek, the chemical propertiesfor peek is polyetheretherketones or polyketones obtained from aromatic dihaldes

and bisphenolate salt by uncleophilic substitution. Peek is a thermoplastic with

extraordinary mechanical properties, its tensile strength is 170 MPa and melt at

temperature 3500C. The raw material is manufactured in Kiruna in the north of

Sweden.

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CHAPTER 4. MECHANICAL CONSTRUCTION

4.3 The material for the Antennas

Different materials, such as brass, aluminium, titanium, copper, and stainless

steel, have been considered for the antennas. Among these materials, stainless

steel was chosen because it does not corrode easily and it is heavy to be sus-

pendend in a hot water-drilled hole.

4.4 Mechanical Model And Drawings of the Vector AntennaThe drawing tools used for this project design is the 3D cad program Solid works

office premium 2006 developed in the United States of America. The program

allowed pressure simulations to be made on the model, as well as making 2D

drawings.

Figure 4.1: Top model made of peek

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4.5. GEOMETRY ALIGNMENT FOR A 3D OBJECT

4.5 Geometry alignment for a 3D object

Proper Calculation of the mid point of the model has been made for the 3D an-

tenna to ensure that the antenna is properly positioned, figure 4.3 show more detail

about the angle formed by the antennas to the centre. considering the geometry:

ca1

= cos

ba/2

= tan 6

= 13

c2 = a2

4+ b2 = a

2

4+ 1

3a2

4= a

2

3 c =

a3

c/a = 13

= cos

= arccos 13

= 54.730.

Hence the angle between the center of the model to the antennas is measured to

be 54.730, for a proper geometrical positioning of the antennas in 3D.

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54.74

15.

50

A

A

24

44

26.

50

48.36

39.76

4.20

DO NO T SCALE DRAWING

FINISH

MATERIAL Peek

REV.

APPLICATION

USED O NNEXTASSY

0.001

. ANYREPRODUCTION IN PARTOR AS A WHOLE

THP

PROPRIETARY AND CON FIDENTIAL

THEINFORMATION CONTAINED IN THIS

ISPROHIBITED.

DWG. NO.SIZE

0.01

CO MMENTS:

SHEET1O F1

Q.A.

MFG APPR.

WITHOUTTHE WRITTEN PERMISSION O F

ENG APPR.

WEIGHT:

NAME

0.01

CHECKED

DRAWN Ayobam i IJI

A

DATE

DRAWING ISTHESOLE PROPERTY OF

DIMENSIONSA REIN MM

TOLERANC ES:0.01FRACTIONAL 0.01ANGULAR: MACH 0.01degBEND 0.01TWO PLACEDECIMAL 0.01THREEPLACE DECIMAL

SCALE:1:1

SECTION A -A

21.

60

27.

60

6.

20

4.57

31.

60

3.12

Figure 4.2: Machine drawing of the top model

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T

h

c

a1

a2

a/2

a3

b

O

S

Considering the triangle OST we can calculate thevalue of angle

From the figure a1 = a2 = a3and line ST = a/2 this is mid point along line a1

The line h is the height and the point O is the centre of thefigure

Figure 4.3: Angle formed by the orthogonal antennas with centre

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Figure 4.4: Bottom model

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SIZE

WEIGHT:

newMODL12

PROPRIETARY AND CO NFIDENTIAL

DWG. NO.

AREV.

MATERIAL

FINISH

DO NO T SCALE DRAWINGPROHIBITED.

CO MMENTS:

SHEET1O F1

Q.A.

ISWITHOUTTHE WRITTEN PERMISSION O F

REPRODUCTION IN PARTOR AS A WHOLE

0.01

ENG APPR.

CHECKED

DRAWN Ayob ami IJI

DATENAME

-

+

USED O N

MFG APPR.

. ANY

0.001



NEXTASSY

APPLICATION

DIMENSIONSA REIN MMTOLERANC ES: 0.01FRACTIONAL 0.1ANGULAR: MACH 0.01deg.BEND 0.01

TWO PLACEDECIMAL 0.01THREEPLACE DECIMAL

SCALE:1:1

38

4.6

2

4.57

30

343

1.6

0

3

54.74

1.2

02

13

44

39.76

49

M24

2 x-DEPTH> 3

A

A

Figure 4.5: Bottom model machine drawing

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The Vee band are used to fasten the top and bottom models together by

providing adequate support for the models from falling apart or leakage

of its content, through its grooves that key into the top and bottom mod-

els. The pair of Vee band is then fasten together with screw at both ends.

Figure 4.6: Vee band

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M

5.5

0

9.2

06.8

0

2.7

0

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0

M2.50

ADWG. NO.SIZE

WEIGHT:

REV.

MATERIAL

FINISH

DO NO T SCALE DRAWINGAPPLICATION

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CO MMENTS:

PROPRIETARY AND CO NFIDENTIAL+

NAME


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SHEET1O F1

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MFG APPR.

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CHECKED

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ISWITHOUTTHE WRITTEN PERMISSION O F

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0.01

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SCALE:1:1

SECTION A-A

3.5

0

39.758.63

47.51

R22

A

A

Figure 4.7: Vee band machine drawing

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Figure 4.8: Antenna with fittings

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NEXTASSY USED O N

APPLICATION DO NO T SCALE DRAWING

0.001

. ANYREPRODUCTION IN PARTOR AS A WHOLE

DRAWING IS THESOLE PROPERTY OF

NAME DATE

ADWG. NO.SIZE

WEIGHT:

fitting + a ntenna

PROPRIETARY AND CON FIDENTIAL


ISWITHOUTTHEW RITTEN PERMISSION O F

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MATERIAL: Stainlesssteel and Co pp er.

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CHECKED

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SCALE:1:2

SECTION A -A

7

4.

20

1585 25

5

A

A

125

Figure 4.9: Antenna with fitting

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The printed circuit board has a diameter of 31.6 mm and a thickness of 1.4 mm

also on it are holes to allow free flow of transformer oil called Flourine in

swedish inside the model. The flourine oil will provide cooling for the electron-

ics and prevent the lectronics from damage or deterioration in ice over years.

Figure 4.10: Electronics circuit board.

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Figure 4.11: complete model

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Vee band

Top m odel (pe ek)

Bottom model (peek)

Plug

Printed c ircuit b oard

with a mplifiers

O ring

Oil drain hole

Antenna rod)

Vee band

Top m odel (pe ek)

Bottom model (peek)

Plug

Printed c ircuit b oard

with a mplifiers

O ring

Oil drain hole

Antenna rod)

Figure 4.12: Internal structure of complete model

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Figure 4.13: Finished tripole antenna. Photo by T. Thrnlund

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5

VECTOR

ANTENNA PERFORMANCE

5.1 Electrical Properties of the Antenna Medium or Environ-

ment

The medium or environment of the 3D antenna is Ice at about 450C to 700Cat a depth of 1500 meters and pressure of 1000 Bar. Ice is transparent to visible

light. It has the lowest index of sodium D line of any known crystalline material.

It is double refracting, uniaxial, optically positive with very small birefringence.The proton disordered phases have a broad infrared absorbtion band for the fun-

damental intramolecular bending and stretching vibrations.

5.1.1 Electromagnetic Wave in Ice

At frequencies from 5 to 300 MHz the loss of energy by absorption in Ice is suffi-

ciently small that they can penetrate large Ice masses great distances. Radio waves

are reflected by inhomogeneities in the ice and at material boundaries, especially

at the ice - water and ice - rock interfaces.

5.2 UHEC Antenna Amplification

We use (LTC6400-20) a product of Linear technology corporation, 1.8 GHz Low

Noise, Low distortion differential ADC driver for 300 MHz IF, for the amplifica-

tion of the UHEC antenna.

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CHAPTER 5. VECTOR ANTENNA PERFORMANCE

The LTC6400-20 is a high-speed differential amplifier targeted at processing sig-

nals from DC to 300 MHz. The part has been specifically designed to drive 12,

14 and 16-bitADCs with low noise and low distortion, but can also be used as a

general-purpose broadband gain block. It is easy to use, with minimal support

circuitry required. The output common mode voltage is set using an external

pin, independent of the inputs, which eliminates the need for transformers or AC-

coupling capacitors. The gain is internally fixed at 20dB(10V/V). The LTC6400-

20 saves space and power compared to alternative solutions using IF gain blocks

and Transformers. The Amplifier is packaged in a compact 16-lead 3 mm

3mm

QFN package and operates over the 400C to 850C temperature range, Storagetemperature range is 650C to 1500C, Maximum Junction Temperature is 1500Cand Lead Temperature (soldering, 10 second) is 3000C. [6] The supply voltage

peak to peak is 3.6volt and input current 10mA. Figure 5.1 is the electronicscircuitry of the vector antenna.

5.3 Vector Measurements

5.3.1 The 3D E-field antennas

The vector antenna has full Polarization Coverage and the antenna Intensity |E|2is a scalar with three times higher detection probability.

5.4 Vector Pulse Post-Processing

The amplifier coupled to the antennas improves the signal to noise ratio com-

pletely and the pulse shape will also improve making the antenna to perform bet-

ter without causing noise to other equipment in its environ.

Using the Hilbert transform to obtain analytic complex signal [4]

H [s(t)] = s(t) =1

s(t

)

t t dt

(5.1)

Evaluating the integral as the Cauchy principal value, it can be written

s(t) =1

t s(t). (5.2)

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CHAPTER 5. VECTOR ANTENNA PERFORMANCE

The Hilbert transform can be considered as a filter that shift phases of all fre-

quency components of its input signal. Let us consider an analytic (complex)

time signal, E(t). It can be constructed from a real valued input signal Re{E(t)}as shown in Eq. (5.3),

E(t) Re {E(t)}+ iIm {E(t)} , (5.3)

where, E(t) is the analytic signal constructed from Re {E(t)} and its Hilbert trans-form, iIm {E(t)}.

Calculating the eigenvalues and eigenvectors, using for instance a SingularValue Decomposition (SVD),

Exx+Eyy+Ezz E1e1+E2e2+E3e3. (5.4)

The eigenvector en corresponding to the largest eigenvalue En contain the sig-

nal, and the eigenvector corresponding to the smallest eigenvalue contains the

noise signal. The post-processed signals for the input and output signal are shown

below:

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5.4. VECTOR PULSE POST-PROCESSING

The antenna input signal

The processed signal from the antenna

Figure 5.2: Simulation of vector pulse processing. The pulse record is

64 samples long. At 1 Gsamp/s corresponding to 64 ns.

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6

ELECTRICAL

SIMULATION OF

ANTENNA

The method of simulation used in this project is the Numerical Electromagnetic

code (NEC) is a method of moments (MOM) for wire antennas developed by

Lawrence Livermore National Laboratory in the early 1980s. Since then it has

been widely used in antenna simulations and design. In this project the second

version (4NEC2X) is used for simulating the radiation pattern of the vector an-

tenna.As earlier discursed the Electric dipole antenna is one of the oldest, simplest, and

most common type of antennas. In this case it is observed as a straight linear

wire of high Electrical conductivity. The Electric dipoles can be divided into dif-

ferent categories depending on their length and the wavelength of the dipole, for

infinitesimal dipole antennas the length is less than /50 for small electric dipole

antennas the length is greater than /50 and less than /10 and for finite electric

dipoles where the length is greater than /10 also for half wave electric dipole the

length is equal to /2. Hence the antenna frequency is determined to be 320 MHZ

that is been used for the electrical simulations, figures below shows the electric

dipole antenna simulations for an ideal situation.

During the simulations it is assumed that the vector antennas are in phase and theyhave thesame amplitude.

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CHAPTER 6. ELECTRICAL SIMULATION OF ANTENNA

Figure 6.1: Orthogonal Vector antennas total gain

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Figure 6.2: Orthogonal vector antennas total gain

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Figure 6.3: vector antennas total gain

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Figure 6.4: Vertical gain

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Figure 6.5: vertical gain orthogonal dipole

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Figure 6.6: Horizontal gain

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Figure 6.7: horizontal gain orthogonal dipole

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Figure 6.8: horizontal axis total gain 3D orthogonal dipole

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Figure 6.9: vertical axis total gain 3D orthogonal dipole

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7

CONCLUSION

The vector antenna is a quite an interesting project for research work. Very low

mutual coupling between the axially placed dipoles was maintained. The concept

of the vector antenna is to receive signal in x, y, z -axes in the antarctic Ice where

the antenna cannot rotated but remain in a fixed position, the structure is stronge

enough to withstand high pressure in ice and in underwater applications.

Vector antenna for ultrahigh energy cosmic neutrino detection with three orthog-

onal dipoles, in the frequency of 320 MHz, all at an angle of 90 degree to one

another. I was able to observe, the total gain in all direction, we have used pre-amplifiers to boost the signal and to improve SNR of the vector antenna.

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ACKNOWLEDGEMENT

My profound gratitude goes to my supervisor, Dr Jan Bergman, at the Swedish

Institute of Space Physics, who has immensely contributed to this Master thesis

with motivations and advice.

Special thanks goes to people who has contributed mentally, materially, and oth-

erwise to the success of this project; such include Dr Roger Karlsson, my subject-

examiner, Mr Walter Puccio and Mr Kiran Kumar Kovi who designed the elec-

tronics circuit board, Mr Bertil Segerstrom, Dr Thomas Leyser, Mr Lennart Ahlen,

Prof. Bo Thide, and all other staff of Swedish Institute of Space Physics.

I give thanks to the following groups for their advice and collaborations: Prof.

Lars Stenmark at Uppsala University, who came up with the original idea to the

antenna design, Mr Sone Sdergren, Maintenance superintendent of the mechani-

cal workshop at the

Angstrom laboratory, Dr Hugo Nguyen and Dr Henrik Kratz atAngstrom Space Technology Centre, Dr Leif Gustafsson and Dr Allan Hallgren

at the Department of Nuclear and Particle Physics, Dr Fredrik Bruhn and Miss

Jenny Davidsson at the Angstrom Aerospace Corporation, who provided software

and support for drawing the model, the Department of underwater research at the

Swedish Defence Research Agency (FOI) for their advice and hospitality during

my visit there, and to Ericsson Cable in Hudiksvall for their advice.

I would like to thank the PI of IceCube, Prof. Francis Halzen at the University of

Wisconsin, as the originator of this project, as well as the PI of RICE, Prof. David

Besson at the University of Kansas for his kind support.

I also use this opportunity to say thank you to my colleagues in the project room:

Mr Martin Wger, Miss Monica Alaniz, and Mr Peter Lekeaka Takunju, for their

cooperations.

Thank you all.

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BIBLIOGRAPHY

[1] ARENA 2006: Acoustic and Radio EeV Neutrino detection Activities, Jour-

nal of Physics: CONFERENCE SERIES 81 (2007) 012024.

[2] ICECUBE RESEARCH AND DEVELOPMENT:

http://www.ps.uci.edu/superk/neutrino.html,

http://www.icecube.wisc.edu/info/antarctic/,

http://hyperphysics.phy-astr.gsu.edu/hbase/particles/neutrino.html

[3] MATTHEW N.O. SADIKU: Refractive index of snow at microwave frequen-

cies, Applied Optics.,vol. 24, No.4, 15 february, 1985.

[4] LEO N COHEN: Time - Frequency Analysis, Prentice Hall Signal Processing

Series, Alvan V. Oppenheim, Series Editor.

[5] BALANIS, C.A.: Antenna Theory, analysis and design, 2nd Ed., John Wiley

and Sons, 1997.

[6] LINEAR TECHNOLOGY: Linear Technology Operational Amplifier Product

Manual

[7] POZAR, DAVID M.: Microwave Engineering, 3rd Ed., John Wiley and Sons,

2004.

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Documents

Ayobami Babatunde Iji- Vector Antenna for UltraHigh Energy Cosmic Neutrino Detection in the Antarctic Ice