Antenna Lab 22

8/11/2019 Antenna Lab 22

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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;


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


the normalized radiationintensity of the loop



plane for=1 and a=1.


the normalized radiation

intensity of the loop



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 .

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Antenna Lab 22

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