antenna lab 22
TRANSCRIPT
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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:
MONOPOLEAND
VVLOOP ANTENNA
Presented By:
- Gassab Oussama
- Gacem BelQassim
Supervisor:
Dr. CHALLAL 28/04/2014
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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 Monopole Antenna
The Loop Antenna
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1.1 The Monopole Antenna
The monopole antenna is a wire antenna over conducting plane, as we
know that the electromagnetic waves behaves as light because light is just
an electromagnetic wave at specific bandwidth frequency.
Image theory of electromagnetic waves:
To understand the image theory we can handle the following
concept .
The electromagnetic we can model it as a light
The conducting plane as mirror
If flashlight is put near a mirror the resulting light is equal to the
light emitted from the flashlight itself plus the reflected wave from
mirror . but if we see the mirror , we realize that it is looks like
another flashlight symmetrical to our real flashlight emitting the
same amount of light without the mirror.
So the image theory help us to determine the fields radiated by source
near conducting plane, without using the concept of reflection which
contains so many mathematical calculations and theories . we just remove
the conducting plane and we add the same source symmetrical to the
other ( under some specific opposition signs) .
To analyze monopole antenna it is better to use the concept of
image theory.
image theory conversion
fig(1.1.1) : monopole
antenna over conducting
plane .
fig(1.1.2) : image theory
conversion produces half
wave dipole.
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The parameters of monopole antenna
Since the monopole antenna is just equivalent to half-wave dipole
antenna the electric and magnetic fields are given by
E = j I02r ejkr cos 2cos ()sin
H = j I02r ejkr cos 2cos ()sin
The power density is given by
=
22
=
028
2
2
cos
2cos ()
sin
2
The power intensity , = 2So we have
, = 0282 cos2cos ()sin 2 , = 0 cos2cos ()sin 2
Where
0 =
028
2=
15
02
The radiation resistance :
Monopole antenna is radiating in the region defined by 0 < 20 <
2
But the real half- wave dipole is radiating in the region 0 < 2
0 < So we have
=
(
,
)
02
0
And we have = (,)2020 So we conclude that = 12 This implies that Zmonopole =
1
2 = 12 (73 + 42.5)
So we have Zmonopole = 36.5 +
21.25
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So we can calculate the power radiated by the monopole without using
the complicated integration by only using the circuit model relation
Prad =1
2
02 = 18.25
02
The antenna directivity :
, = 4 ( ,)Prad
=
415 02cos 2cos ( )sin 2
18.2502 = 24073 cos 2cos ()sin 2
The maximum directivity is given by D0 =240
73= 3.288
We found that D0 = 2D0(halfwave)So the monopole is more directive than half-wave dipole antennaBecause the monopole antenna is radiating only above the conducting
plane , so its energy is more concentrated in one direction.
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1.2 The Loop Antenna
The far fields of the loop antennas are
given by
= 02 1 = 02 1
Where J1is Bessel function of the firstkind with order 1 .
The power density is given by = 22 = 202282 12The power intensity , = 2So we have
,
=
20228
12
The maximum value of the Bessel function of the first kind at order one is
(1) 0.58152 if > 1.8We can use the approximation : for < 1
3 1 2
So 0 = (0.58152)2 20228 = 5.07252022 = 5.0725202The radiation resistance of the loop antenna is given by
= 202 2where = 2is the circumferenceSo the power radiated by the antenna is given by
Prad =1
202 = 404 2022
fig(1.2.1) : loop antenna
located in the x,y plane.
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The directivity of the antenna
,
= 4 ( ,)
Prad=
420228
12 40
4202
2
= 6
1
2
The maximum directivity is 0 = 60.581522 = 2.029
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2Applications of
Monopole and Loop
Antennas Monopole broadcasting antennas
the monopole antenna connected to the car or
airplane
AM broadcast receiver loop antennas
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loop antenna wound around aferrite rod to increase its inductancewithout requiring such a large size. The resulting coil is called a loopstick
antenna, a ferrite rod antenna, a ferrod antenna, or a ferrite antenna.
The term loopstick refers to the underlying loop antenna and the stickshape of the ferrite rod.
As with all small loops, loopstick antennas are most practical at lower
frequencies such as the medium-wave (AM broadcast band - 5201610 kHz) and long-wave (50500 kHz) bands, using ferrite materials
which are not too lossy at these frequencies. A multiband receiver maycontain tap points along the winding in order to tune the loopstick
antenna at widely different frequencies.
As with all small loop antennas, loopstick antennas are largely immune tolocally generated (within the near field) electrical noise, as they arecoupled directly to the magnetic field. Loopstick antennas are also used in
radio direction-finding (RDF) applications. [1]
[1] Wikipedia
http://zim//A/A/Ferrite%20%28magnet%29.htmlhttp://zim//A/A/Radio%20direction%20finder.htmlhttp://zim//A/A/Radio%20direction%20finder.htmlhttp://zim//A/A/Ferrite%20%28magnet%29.html -
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3MATLAB Program The Radiation Pattern for monopole antenna
The Radiation pattern for loop antenna
Analyzing the parameters
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3.1 the Radiation Pattern for monopole antenna
To plot the radiation pattern in y-z and x,y plane we have written the
following program.
If the monopole dipole is length = 4(quarter wave
monopole dipole)
We have got the following results
% This program will perform pattern for Short and monopole Antenna
% you need just to insert the the values of lambda and the length of the% monopole antenna.clc ;
L=input('enter your monopole length L= ');lambda=input('enter the value of wave length Lambda= ');
R=L/lambda;
B=2*pi/lambda ;
theta=-pi/2:pi/100:pi/2;
phi=0:pi/100:2*pi;ifR
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If the then minor lobes will occurTo see that lets take
= 8
= 2
So we got the following results
Some remarks:
We know that the general expression NRI of the dipole antenna of
length = cos 2cos 2 2for monopole antenna 2 so NRI for monopole antenna is
given by
=
cos
cos
2
.
fig(3.1.2) : the graph of
the normalized radition
intensity of the monopole
antenna when the length
of the antenna is larger
than the wave length.
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3.2 The radiation pattern for loop antenna
To plot the radiation pattern in y-z and x,y plane we have written the
following program
If we take the values = 4 = 1we have gotten thefollowing pattern
% this unfinished program will perfrom the pattern for loop antenna by% giving the radius of the loop and the wavelwngth yo work with
clc;lambda=input('enter the value of wave length lambda= ');a=input('enter the value of raduis a= ') ;
B=2*pi/lambda ;
theta=0:pi/100:pi ;phi=0:pi/100:2*pi ;
E=besselj(1,B*a.*sin(theta));subplot(1,2,1), polar(theta,E,'.r');title('the pattern for loop antenna in the y,z plane');subplot(1,2,2),polar(phi,phi./phi, '.r');title('the pattern for loop antenna in the x,y');grid;
fig(3.1.1) : the graph of
the normalized radiation
intensity of the loop
antenna in the azimuth
plane and the elevation
plane for=4 and a=1.
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If we take the values = 1 = 1we havegotten the following pattern
We see that the elevation plane pattern it has been changed to
another form where minor lopes are generated, this happen under the
property of Bessel function.
When we take the values = 1 = 3we havethe following pattern
fig(3.1.1) : the graph of
the normalized radiationintensity of the loop
antenna in the azimuth
plane and the elevation
plane for=1 and a=1.
fig(3.1.1) : the graph of
the normalized radiation
intensity of the loop
antenna in the azimuth
plane and the elevation
plane for=1 and a=3 we
remark that many minorlopes have beenoccurred.
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The side lopes are generated when the dimension of the antenna is
more larger than the wave length of the operating frequency.
3.3 Analyzing the parameters
- The monopole dipole:
Finding the azimuth and elevation plane HPBWs
The azimuth HPBW: since NRI is independent from and the monopoleantenna is radiating above the conduction plane so
HPBW = The elevation HPBW
=
1
2
cos
2cos ()
sin
2
=1
2by using the
approximation thatcos 2cos ()
sin 3()we found that3 = 12
= 0.9169 = 2.225 but the monopole antenna is radiatingonly over the conducting plane so 2.225 is replace by
2
So HPBW = 2 0.9169 = 0.6538 rad = 73.460The maximum directivity as proved before in section (1.1)
, = 4 ( ,)Prad
=
415 02cos 2cos ( )sin 2
18.2502 = 24073 cos 2cos ()sin 2
The maximum directivity is given by D0 =240
73= 3.288
- Finding the directivity by using the approximation
The beam solid angle is approximated as
A 22HPBW 2= 22x065382 = 3.42Where the directivity is given by D0 = 4A = 43.42 = 3.67
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- The loop antenna
Finding the azimuth and elevation plane HPBWs
The azimuth HPBW: since NRI is independent from HPBW
= 2
The elevation HPBW = 12 1 = 0.581522 for > 1.8By using the Bessel function table we have gotten = 0.6 = 0.6 so the beam width depend of the factor which isobvious result
HPBW = 2arcsin (0.6 )The directivity is calculated in section 1.2 and it have been found to be
, = 4 ( ,)Prad
=42022
812
4042022 = 6 12The maximum directivity is 0 = 60.581522 = 2.029- Since the number of lobes changes rapidly as the factor changes
The approximation of theHPBW
is such long and needs many
mathematical calculation and background concerning the Besselfunction
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4Observations The response of the monopole and loop antennas
in the azimuth plane
The maximum response for both antennas
The minimum response for both antennas
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4.1 The response of monopole and loop antennas in azimuth plane
Since the NRI is independent from for both antennas so thenormalized radiation intensity is always constant when we move in the
azimuth plane so the response is the same in all direction for both
antennas so they are classified as omnidirectional antennas in the
azimuth plane
4.2 The maximum response for both antennas
- The quarter wave monopole antenna
It has its maximum at = 2- The loop antenna(1) 0.58152 if > 1.8the maximum value itoccur at = 1.8 sin = 1.8 = arcsin 1.8 4.3 The minimum response for both antenna
- The quarter wave monopole antenna
It has its maximum at = 0 - The loop antenna1 = 0 = 1 = arcsin 1 for n in
integerBy using the table of Bessel function we can determine are the
position where the radiation is zero (minimum )
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Conclusion
The electromagnetic that is radiated from any source it depend on
the characteristic of that source ( dimensions ,geometry and also its
direction ). Because the electromagnetic induces under the concept of
independent superposition. And since the Radiation is related to the
wave length of the radiated wave , also the ratio of the wave length to
dimension of the source effects on the radiation pattern.
So we have studied the monopole and loop antenna and we have
found that the radiation pattern depends on the characteristic of the
antenna dimension and direction and also it depend on the wave
length of the radiating wave .