Antenna Lab3

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    [P

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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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    2

    1Theoretical Concepts

    The Rectangular aperture antennas.

    The circular aperture antennas.

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    3

    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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    4

    1.2 Circular apertures antenna:

    A widely used microwave antenna is the

    circular aperture. One of the attractive

    features of this configurationis its

    simplicity in construction. In addition,

    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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    5

    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);

    shadinginterp;

    colormap(gray);

    fig(2.2.1) :

    rectangular aperture

    radiation pattern in3-

    D plane =8 = 3 .

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    10

    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);

    shading interp;

    colormap(gray);

    fig(2.3.1) : circular

    aperture radiation

    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

    aperture radiation

    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