antenna lab 1

8/11/2019 Antenna Lab 1

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Peoples Democratic Republic of Algeria

Ministry of Higher Education and Scientific Research

University MHamed BOUGARA Boumerdes

Institute of Electrical and Electronic Engineering

Department of Electronics

Lab Report of the Degree of

MASTER 02

InElectrical and Electronic Engineering

Telecommunication Option

Title:

DIPOLE ANTANNA

Presented By:

- Gassab Oussama

- Gacem BelQassim

Supervisor:

Dr. CHALLAL Mouloud

14/04/2014


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Abstract

Employment of a data-acquisition system for data collection and

calculations makes experiments with antennas more convenient and less

time consuming. The determined directional patterns of the dipole

antennas of different lengths are in reasonable agreement with theory.

The enhancement of the signal by using a reflector is demonstrated, and a

variant of the dipole antenna is explored. The experiments are suitable as

laboratory works and classroom demonstrations, and are attractive for

student projects.
http://iopscience.iop.org/0143-0807/30/6/017http://iopscience.iop.org/0143-0807/30/6/017


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introduction:

this world contains very amazing fundamental concepts , which

occur under highly organized manner can be formulated mathematically.

Every physical concept that happens in this world can be understand it by

using mathematical formulas . the electromagnetic theory is very

important concepts in the field of physics and it is fundamental reality in

the field of communication ( antennas transmission , radar , ) .

the electromagnetic theory describes how the electric and magnetic

fields interact with itselfs and how they interact with time and space ; the

interaction with time and space contains the concept of the wave

propagation , and the concept of the relativistic between time , space , and

energy contains the concept of relativistic theory (( Einstein's relativistic

theory )) and all concepts of electromagnetic theory are described by

Maxwell equations.

the communication antennas are devices that transmit and receive

electromagnetic waves , the purpose of building antennas is to make thetheory of electromagnetic under human control in order to enhance

science and technologies and make our life easy in all different fields. To

do all this we have to build antennas with some specified parameters and

with high performance.


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1Theoretical Concepts

The Hertizian dipole antenna

The half-wave dipole antenna


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1.1 The Hertizian dipole antenna

It is the radiation of an infinitesimal

current element .We will introduce very small method

to analyze the Hertizian dipole and

build all its parameters.

The general solution of Maxwell

equations is given by

1, = 4 (2,12 )12 2We have used the notation which is used by Fynman[1] this notation

means

1 is equivalent to (1 ,1 , 1)is the point where we observe the field2 is equivalent (

2 ,

2 ,

2)is the point where the source charge exist

Since we have only line current element so we have

2, 12 = (2, 12 ) where = where1, =

4 (2,12 )12 since the current is in one point and it isinfinitesimal we can write

= (

12

)

4 = 0lcos (

)

4 in phasor form = 0l

4 So we have in spherical coordinate = 0l4 By using the equations H s = 1 As

Es = j H2

fig(1.1.1) : the Hertizian dipole

carrying current

=

(

0

).

[1] The Feynman lectures on physics volume 2 at

chapter 21


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The far radiation fields are given by

Hs = j 0l4 sin Es =

0l

4 sin The power Radiated by the Hertizian antennaThe power density is given by the expression as

= 12 Es Hs = 22 so we get

=

202l232

2

2

sin2

so the power intensity is given by

= 2 = 202l2322 sin2 = 0sin2 where0 = 202l2322 After that we obtain the directivity of the Hertizian antenna

=

4

=

3

2sin2

The Radiation resistance can be easy found to be

= 202 = 80 2 where = 2 1.2 Half-Wave Dipole Antenna :

The half-wave dipole antenna is just a special case of the dipole antenna,

but its important enough that it will have its own section. Note that the

"half-wave" term means that the length of this dipole antenna is equal to a

half-wavelength at the frequency of operation(L=2), it consists of a thin

wire fed or excited at the mid-point by a voltage source connected to the

antenna via a transmission line, The magnetic vector potential at P due to

a differential length dl(= dz) of the dipole carrying a phasor current Is =

Io cos (z) is dAz= I0cos z dz

4

r

ejr


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If r>>L then r=r-zcosWe find Azs=

I0 cos(2 cos )2r (sin )

2

Normalized Radiation Intensity is

D(,) = U(r, ,)Umax

D(,)=(cos [2 cos ])2(sin )2

fig(1.2.2) : evaluating the

parameters at point P from half-wave dipole antenna .

fig(1.2.1) : the half-wave dipole

carrying current .


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2Dipole Antenna

Characteristics

Frequency vs Length of the dipole Radiation Pattern and Gain

Feeder Line


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2.1 Frequency vs the Length of the Dipole

in fact any dipole antenna with length l radiates fields that are only the

superposition of infinitesimal Hertizian dipoles along the line l

by using the concept of superposition of Hertizian dipole we can build

general integral form for any dipole antenna with length l

the Hertizian dipole electric field is given by

Es = 0l4 sin when we perform superposition the quantity0l is generalized to integral form sin 2 l2

l

2

The electric field of any dipole antenna of length l is

Es = 04 sin sin 2 l2 l2

When we handle the integration we have gotten the following results

Es = 02 where f is given

= cos 2cos 2 we see that this function depend on 2Where we can write

2=

2 2 = so the antenna characteristicdepends on the factor

, if we want to build antennas that behaves thesame at different frequencies the factor

must be constant

= = so the relation between length and frequency can be givenas = which is the relation between frequency and length of dipoleantennas that have the same radiation pattern that depend on the function

When f is increased the length must be decreased to keep the same

radiation pattern

=

cos cos

where

=


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2.2 Radiation pattern and Gain

The radiation pattern of dipole antenna of length l depends on the

function = cos 2cos 2 The intensity and directivity can be obtained by using the same method

that we have done with Hertizian dipole ( except the radiation power

integral is performed numerically )

The intensity is in the form

=

0

cos

2cos

2

2

Where 0 = 0224 The directivity is given by 0 = 40 where is performed by usingnumerical method or math lab program

The total or absolute gain is given by 0 = 0Where is transmission losses and it equal two = 1

2

and isthe losses from the conduction and dielectric materials and it relates to theradiation resistance and loss resistance as = +To understand how the radiation pattern effected when we change the

length of the antenna we have drawn some pattern as shown below.

fig(2.2.1) , elevation plane

amplitude amplitude

patterns for dipole

anttenas with different

length .


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when the length of the dipole

antenna is increase so that > a secondary lobes appears and

the beam solid angel is increasedand that make the directivity and

the gain decreases and results

low antenna efficiency

2.3 Feeder line

To connect the antenna to the network circuit (receiver or transmitter ) we

have to use transmission lines that operates in high frequency and

perform no losses .

The concept of losses :

Because at high frequency the wave length of the wave that

propagate in the line is small or comparable to the line so the

voltage would not the same in the line and that will generate

another electromagnetic field that will propagate from the line

(small line antenna ) and that will reduce efficiency , but high

frequency transmission lines is designed under way where there is

no field outside these lines this method is performed under usingthe concept of Amper's laws (( there is no EMF field outside the

line if the line contains adjacent concentric currents moving in

opposite direction ))

There are different kinds of transmission lines the most known ones are :

fig(2.2.2) : Amplitude pattern for

dipole antenna with l=1.25.


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1- coaxial line

2- two-wireline

3- parallel-plate or planar line

4-wire above conducting plan

5-microstrip line

Each kind of line has its purpose and the most used one is the

coaxial cables with large antennas . and in small antennas like microstrip

antennas ( in cell phones ) we use microstrip line.

fig(2.3.1) : different types of Feeder lines a. coaxial cable b. two wire-line

c. parallel plate or planar line d. wire above conduction plan e.microstrip line .


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3Common Application ofDipole Antenna

Set top TV Antenna

Shortwave Antenna

Dipole Towers

Collinear Dipole Arrays


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3.1 Set-top TV antenna

The most common dipole antenna is the type used with telivisions, often

colloquially referred to as rabbit ears or bunny ears. While in most

applications the dipole elements are arranged along the same line, rabbitears are adjustable in length and angle. Larger dipoles are sometimeshung in a V shape with the center near the radio equipment on the ground

or the ends on the ground with the center supported. Shorter dipoles canbe hung vertically. Some have extra elements to get better reception such

as loops (especially for UHF transmissions), which can be turnablearound a vertical axis, or a dial, which modifies the electrical properties

of the antenna at each dial position.

3.2 Short wave antenna

Horizontal wire dipole antennas are popular for use on theHFshortwavebands, both for transmitting andshortwave listening.They are usually

constructed of two lengths of wire joined by astrain insulator in thecenter at which aladder line orcoaxialfeedline is attached, with the ends

supported by buildings, towers, or trees. These are simple to put up fortemporary or field use. For transmitting antennas, it is essential that the

ends of the antenna be attached to supports through strain insulators witha sufficiently highflashover voltage,since the antenna's high voltage

antinodes occur there.

Dipoles versus whip antennas

Dipoles are generally more efficient than whip antennas (quarter-wave

monopoles). The total radiated power and the radiation resistance are

twice that of a quarter-wave monopole. Thus, if a whip antenna were used

with an infinite perfectly conductingground plane,then it would be as

efficient in half-space as a dipole in free space an infinite distance fromanyconductive surfaces such as theearth's surface. However, in real life

situations, if considering the antenna height, a monopole may have anadvantage at certain radiating angles, especially at low heights.

3. 3 Dipole towers

Large constructed half-wavelength dipole towers include theWarsaw

radio mast the only half-wave dipole forlongwave ever built.

3.4 Collinear dipole arrays
http://en.wikipedia.org/wiki/High_frequencyhttp://en.wikipedia.org/wiki/Shortwave_listeninghttp://en.wikipedia.org/wiki/Strain_insulatorhttp://en.wikipedia.org/wiki/Ladder_linehttp://en.wikipedia.org/wiki/Coaxial_cablehttp://en.wikipedia.org/wiki/Electric_archttp://en.wikipedia.org/wiki/Antinodehttp://en.wikipedia.org/wiki/Ground_planehttp://en.wikipedia.org/wiki/Conductivehttp://en.wikipedia.org/wiki/Ground_%28electricity%29http://en.wikipedia.org/wiki/Warsaw_radio_masthttp://en.wikipedia.org/wiki/Warsaw_radio_masthttp://en.wikipedia.org/wiki/Longwavehttp://en.wikipedia.org/wiki/Longwavehttp://en.wikipedia.org/wiki/Warsaw_radio_masthttp://en.wikipedia.org/wiki/Warsaw_radio_masthttp://en.wikipedia.org/wiki/Warsaw_radio_masthttp://en.wikipedia.org/wiki/Ground_%28electricity%29http://en.wikipedia.org/wiki/Conductivehttp://en.wikipedia.org/wiki/Ground_planehttp://en.wikipedia.org/wiki/Antinodehttp://en.wikipedia.org/wiki/Electric_archttp://en.wikipedia.org/wiki/Coaxial_cablehttp://en.wikipedia.org/wiki/Coaxial_cablehttp://en.wikipedia.org/wiki/Ladder_linehttp://en.wikipedia.org/wiki/Strain_insulatorhttp://en.wikipedia.org/wiki/Shortwave_listeninghttp://en.wikipedia.org/wiki/High_frequencyhttp://en.wikipedia.org/wiki/High_frequencyhttp://en.wikipedia.org/wiki/High_frequencyhttp://en.wikipedia.org/wiki/High_frequency


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Vertical dipoles can be stacked end to end to makecollinear

antenna arrays,to give a higher gain than a single dipole. The radiation

pattern of the array isomnidirectional like a dipole, but the toroidal-

shaped pattern is "flattened" so more of the power is radiated in

horizontal directions and less is radiated up into the sky and down toward

the ground and wasted. Collinear arrays are a higher gain alternative to

whip antennas for fixed base station antennas for mobiletwo-way radios,

such as police, fire, or taxi dispatchers. [1]

[1] wikipidea . dipole_antenna
http://en.wikipedia.org/wiki/Collinear_antenna_arrayhttp://en.wikipedia.org/wiki/Collinear_antenna_arrayhttp://en.wikipedia.org/wiki/Omnidirectional_antennahttp://en.wikipedia.org/wiki/Whip_antennahttp://en.wikipedia.org/wiki/Two-way_radiohttp://en.wikipedia.org/wiki/Two-way_radiohttp://en.wikipedia.org/wiki/Whip_antennahttp://en.wikipedia.org/wiki/Omnidirectional_antennahttp://en.wikipedia.org/wiki/Collinear_antenna_arrayhttp://en.wikipedia.org/wiki/Collinear_antenna_arrayhttp://en.wikipedia.org/wiki/Collinear_antenna_array


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4MATLAB ProgramSimulation of antenna parameters by using MATLABsoftware is performed


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lamda=input('enter the value of the wave length = ');

L=input('enter the dipole length L in terms of lamda = ');

ratio=L/lamda;

theta=pi/100:pi/100:2*pi;

ifratio


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The next step is to draw the Azimuth radiation pattern, we will write the

following matlab code:

The next graph is plotted:

lamda=input('enter the value of the wave length = ');

L=input('enter the dipole length L in terms of lamda = ');

ratio=L/lamda;

theta=pi/2:2*pi:130*pi;

phi=0:pi/32:2*pi;

ifratio


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2- the azimuth and elevation plane HPBWs

Hertizian dipole

Since the intensity is given by

=

0sin

2

= 02 sin2 = 12 sin = 22 4 4

= [0; 2] The bandwidth is = 4 4 = 2 = 90 The Bandwidth is = 2The maximum directivity = 324- the approximation of directivity

The approximation of A 2 = 22so the approximation of thedirectivity is given by D0 =

4A 4222 =

4 1.27 32 The half-wave dipole

We use the approximation in the case 3 cos (2) 21- the half bandwidth3 = 1

2 = 0.9169 = 2.225

The Bandwidth is given by = 1.308 = 74.95 < 90The Bandwidth is = 2The maximum directivity is given by D=

16

3 we have found that byusing some good integration by using this expression = 4 ( ,)020 The approximation value is D0 =

4

A 4

21.3082 1.83616

3


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5Observations


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Observations :

5.1 Yes, it has the same response in all directions in the azimuth plane.

Because U=W0(sin)2which is independent of U=cte when =cte because it is independent of U=Umaxat

=2and which represent a circle in the azimuth plane

[0, 2]5.2In circle path defined by

=2

[0, 2

]

5.3

=0 or =which represent a line along the axis of antenna[0, 2]


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Conclusion:

Inradio andtelecommunications a dipole antenna or doublet is the

simplest and most widely used class ofantenna.It consists of two

identical conductive elements such as metal wires or rods, which areusuallybilaterally symmetrical.The driving current from thetransmitter

is applied, or for receiving antennas the output signal to thereceiver is

taken, between the two halves of the antenna. Each side of thefeedline to

the transmitter or receiver is connected to one of the conductors. This

contrasts with amonopole antenna,which consists of a single rod or

conductor with one side of thefeedline connected to it, and the other side

connected to some type ofground.A common example of a dipole is the

"rabbit ears"television antenna found on broadcast television sets.

The most common form of dipole is two straight rods or wires

oriented end to end on the same axis, with the feedline connected to the

two adjacent ends. This is the simplest type of antenna from a theoretical

point of view. Dipoles areresonant antennas,meaning that the elements

serve asresonators,withstanding waves of radio current flowing back

and forth between their ends. So the length of the dipole elements is

determined by thewavelength of the radio waves used. The mostcommon form is the half-wave dipole, in which each of the two rod

elements is approximately 1/4 wavelength long, so the whole antenna is a

half-wavelength long.

Several different variations of the dipole are also used, such as the

folded dipole, short dipole, cage dipole, bow-tie, andbatwing antenna.

Dipoles may be used as standalone antennas themselves, but they are also

employed asfeed antennas (driven elements)in many more complex

antenna types, such as theYagi antenna,parabolic antenna,reflective

array,turnstile antenna,log periodic antenna,andphased array.The

dipole was the earliest type of antenna; it was invented by German

physicistHeinrich Hertz around 1886 in his pioneering investigations of

radio waves.
http://en.wikipedia.org/wiki/Radiohttp://en.wikipedia.org/wiki/Telecommunicationshttp://en.wikipedia.org/wiki/Antenna_%28radio%29http://en.wikipedia.org/wiki/Bilateral_symmetryhttp://en.wikipedia.org/wiki/Transmitterhttp://en.wikipedia.org/wiki/Radio_receiverhttp://en.wikipedia.org/wiki/Feedlinehttp://en.wikipedia.org/wiki/Monopole_antennahttp://en.wikipedia.org/wiki/Feedlinehttp://en.wikipedia.org/wiki/Ground_%28electricity%29http://en.wikipedia.org/wiki/Television_antennahttp://en.wikipedia.org/wiki/Antenna_%28radio%29#Resonant_antennashttp://en.wikipedia.org/wiki/Resonatorhttp://en.wikipedia.org/wiki/Standing_wavehttp://en.wikipedia.org/wiki/Wavelengthhttp://en.wikipedia.org/wiki/Batwing_antennahttp://en.wikipedia.org/wiki/Antenna_feedhttp://en.wikipedia.org/wiki/Driven_elementhttp://en.wikipedia.org/wiki/Yagi-Uda_antennahttp://en.wikipedia.org/wiki/Parabolic_antennahttp://en.wikipedia.org/wiki/Reflective_array_antennahttp://en.wikipedia.org/wiki/Reflective_array_antennahttp://en.wikipedia.org/wiki/Turnstile_antennahttp://en.wikipedia.org/wiki/Log_periodic_antennahttp://en.wikipedia.org/wiki/Phased_array_antennahttp://en.wikipedia.org/wiki/Heinrich_Hertzhttp://en.wikipedia.org/wiki/Radio_wavehttp://en.wikipedia.org/wiki/Radio_wavehttp://en.wikipedia.org/wiki/Heinrich_Hertzhttp://en.wikipedia.org/wiki/Phased_array_antennahttp://en.wikipedia.org/wiki/Log_periodic_antennahttp://en.wikipedia.org/wiki/Turnstile_antennahttp://en.wikipedia.org/wiki/Reflective_array_antennahttp://en.wikipedia.org/wiki/Reflective_array_antennahttp://en.wikipedia.org/wiki/Reflective_array_antennahttp://en.wikipedia.org/wiki/Parabolic_antennahttp://en.wikipedia.org/wiki/Yagi-Uda_antennahttp://en.wikipedia.org/wiki/Driven_elementhttp://en.wikipedia.org/wiki/Antenna_feedhttp://en.wikipedia.org/wiki/Batwing_antennahttp://en.wikipedia.org/wiki/Wavelengthhttp://en.wikipedia.org/wiki/Standing_wavehttp://en.wikipedia.org/wiki/Resonatorhttp://en.wikipedia.org/wiki/Antenna_%28radio%29#Resonant_antennashttp://en.wikipedia.org/wiki/Television_antennahttp://en.wikipedia.org/wiki/Ground_%28electricity%29http://en.wikipedia.org/wiki/Feedlinehttp://en.wikipedia.org/wiki/Monopole_antennahttp://en.wikipedia.org/wiki/Feedlinehttp://en.wikipedia.org/wiki/Radio_receiverhttp://en.wikipedia.org/wiki/Transmitterhttp://en.wikipedia.org/wiki/Bilateral_symmetryhttp://en.wikipedia.org/wiki/Antenna_%28radio%29http://en.wikipedia.org/wiki/Telecommunicationshttp://en.wikipedia.org/wiki/Radio

antenna lab 1

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