Antenna Lab3

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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:

APERTURE ANTENNAS

Presented By:

-

Gassab Oussama

- Gacem BelQassim

Supervisor:

Dr. CHALLAL Mouloud

5/05/2014

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Abstract

In this small work our purpose is to analysis the aperture antenna

and its parameters under the concept of dimensions and the wavelength

ratio . and see how the radiation behave when this ratio is changed from

lower to higher values .

After that we will explain this results physically by using the

concepts of diffraction and scattering phenomena at the wall edges of the

aperture antenna.

By using MATLAB we simulate the results and we see if they

matches the theoretical concept or not .

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1

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 Rectangular aperture antennas.

The circular aperture antennas.

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1.1 The Rectangular aperture antennas.

the electric field of the rectangular aperture on

ground plane is given by ( at far field region)

= 0 = 02 = 02

And the magnetic field is given by

= 0 = =

where = 2 sin = 2

sin

The electric field of rectangular in free-space is given by

= 0 = 04 1 + = 04 (1 + ) Because the fields containing non-fundamental function which they

haven't anti-derivatives so the integrals are determined by using some

special methods sometimes numerical methods

1- the directivity is given by 0 = 42 = 42 2-half power beamwidth is given by

50.6 50.6

fig(1.1.2) : the Rectangular

aperture antenna located in the x,yplane .

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1.2 Circular apertures antenna:

A widely used microwave antenna is the

circular aperture. One of the attractive

features of this configurationis its

closed form expressions for the fields of

all the modes that can exist over the

aperture can be obtained.

To demonstrate the methods, the field

radiated by a circular aperture mounted on

an infinite ground plane will be formulated.

The electric field is given by:

r = 0 = j20 sin 1 sin sin

= j20 cos cos 1 sin sin

The directivity can be given by (the field distribution over the aperture is

constant):

D0=42 Aem= 42 Ap=42 (2) = ( 2 )2= ()2

fig(1.2.1) : the circular aperture

antenna located in the x,y plane .

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2MATLAB ProgramSimulation of antenna parameters by using MATLABsoftware is performed

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Part 1:

This Matlab code will execute 2-D radiation pattern rectangular and

circular apertures antennas.

clc ;

antennatype=input('enter the antenna type:Rectangular(1) or

Circular(2)= ');

lamda=input('enter the value of wavelength= ');

theta=pi/100:2*pi;

B=2*pi /lamda; u=B.*(sin(theta)); v=B.*(sin(theta));

%1st choice: Rectangular Aperture

ifantennatype==1

a=input('Enter the large rectangular length a= ');

b=input('Enter the small rectangular length b= ');

E1=sinc((b.*v)./2); % E-plane phi=90

E2=sinc((a.*u)./2); %H-plane phi=0

figure(1)

subplot(1,2,1)

polar(theta,E1) , title('E-plane')

subplot(1,2,2)

polar(theta,E2), title('H-plane')

%2nd choice:Circular Aperture

elseifantennatype==2

a=input('Enter raduis of circular aperture= ');

f1=B*a;

f=f1.*(sin(theta));

E=(besselj(1,f))./f; %E-plane or H-plane

figure(2)

polar(theta,E)

end

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The output :

For rectangular with the parameters = = 5we have gottenthe following graph

at the case when = = we have gotten the following graph

fig(2.1.1) : rectangular aperture

radiation pattern in the E and H

plane

=

= 5

.

fig(2.1.2) : rectangular aperatureradiation pattern in the E and H

plane = = .

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Part 2:

3-D radiation pattern of a rectangular aperture as a function of the

independent variables Vx ,Vy for aperture dimensions a = 8

and b = 4

.

clc;

b=4*lamda;

a=8*lamda;

B=2*pi /lamda; u=B.*(sin(theta)); v=B.*(sin(theta));

theta=0:0.01:pi/2;

phi=0:0.01:2*pi;

[theta,phi]=meshgrid(theta,phi);

vx=(a/lamda)*sin(theta).*cos(phi);

vy=(b/lamda)*sin(theta).*sin(phi);E1=sinc((b.*v)./2); % E-plane phi=90

E2=sinc((a.*u)./2); %H-plane phi=0

E=((1+cos(theta)./2).*abs(E1.*E2));

figure(4)

surfl(vx,vy,E);

colormap(gray);

fig(2.2.1) :

rectangular aperture

D plane =8 = 3 .

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Part 3:

3-D radiation pattern of a circular aperture as a function of the

independent variables Vx ,Vy for an aperture radius a = 3

.

clc;

a= 3;

theta=0:0.01:pi/2;

phi=0:0.01:2*pi;

[theta,phi]=meshgrid(theta,phi);

vx=(a/lamda)*sin(theta).*cos(phi);

vy=(a/lamda)*sin(theta).*sin(phi);

u=(a/lamda)*sin(theta);

E=ones(size(u));

i=find(u);

E(i)=abs(2*besselj(1,2*pi*u(i))./(2*pi*u(i)));

figure(4)

surfl(vx,vy,E);

colormap(gray);

fig(2.3.1) : circular

pattern in3-D plane

= 3

.

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3Explaining the results The concept of sinc and dirac impulse function

Simulation results

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3.2 simulation results

For a=100

we have the following result

So we have gotten a results that matches the theoretical concepts

fig(3.2.1) : circular

pattern in3-D plane = 100 all theradiation is

concentrated at the

origin and zero else

where.

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Conclusion

The radiation pattern of any antenna source it depend on the

antenna geometry and the length of the wavelength that is radiated by this

antenna, because the electromagnetic wave is always effected by the

obstacles under the concept of reflection, refraction, diffraction and

scattering phenomena. And this for main phenomena are related to the

concept of the wavelength and the dimension of the obstacles.

When the electromagnetic waves is radiated by an aperature

antenna a diffraction and scattering phenomena at the edges is occurred ,

this diffraction and scattering will be high when and in this casethe wave will spread everywhere and side lobes will be high in large

distance, at the case when the diffraction will not occur at theedges so radiation will keep traveling at straight line so it will remain

concentrated at the origin no spreading

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