Microwave and Antenna Various Matlab Codes
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Microwave and Antenna Various Matlab Codes. Some of the Projects are below.

Polar form for a Symmetrical Dipole of Finite Length: Matlab Script

The MATLAB code calculates and plots various quantities associated with a dipole antenna. Here’s a breakdown of its functionality:

  1. Variable Initialization:
    • The code prompts the user to input the length of the dipole antenna in wavelengths.
    • It sets the value of eta to 120π, representing the characteristic impedance of free space.
    • The current amplitude, I0, is set to 1.
    • The variable theta is initialized as an array ranging from 1 to 180 degrees in steps of 1, converted to radians.
    • The difference between consecutive elements in theta is stored in dth.
  2. Calculation of Radiation Pattern:
    • The code computes the radiation intensity, U, using the given dipole length (L) and theta values.
    • It determines the maximum radiation intensity, UMAX.
    • The radiated power, Prad, is calculated by summing the product of U, sin(theta), dth, and 2π.
    • The code then evaluates the directivity, D, using the formula (4π*UMAX)/Prad.
    • The directivity in decibels, D_db, is computed as 10*log10(D).
  3. Calculation and Plotting of Current Distribution:
    • The code generates an array, Z, with 1000 equally spaced points ranging from -L/2 to L/2, representing the distance along the dipole.
    • It calculates the normalized current distribution, I, based on the given Z values.
    • A plot of the absolute value of I versus Z is created to visualize the current distribution.
  4. Calculation and Plotting of Electric Field Pattern:
    • The code redefines theta as an array ranging from 1 to 360 degrees in steps of 1, converted to radians.
    • Parameters such as the distance r (set to 10) and wavelength lambda (set to 0.3) are initialized.
    • The wave number, k, is computed as 2π/lambda.
    • The dipole length, L, is adjusted to lambda/2.
    • The electric field strength, E, is calculated using the dipole antenna formula.
    • A polar plot of the absolute value of E versus theta is created to visualize the electric field pattern.
  5. Printing Results:
    • The code displays the maximum radiated power, Prad, in watts.
    • It shows the maximum directivity, D, in dimensionless units.
    • The maximum directivity, D_db, is also displayed in decibels.
    • Finally, the radiation resistance, Rr, is shown in ohms.

This MATLAB code provides insights into the characteristics of a dipole antenna, including radiated power, directivity, current distribution, and electric field pattern.

clear all; close all; clc;
L = input('\n Length of dipole in wavelength:');

eta = 120*pi;

I0 = 1;
theta = (1:1:180)*pi/180;

dth = theta(2)-theta(1);

U = eta*(abs(I0)^2/(8*pi^2))*((cos((L*pi)*cos(theta))-cos(L*pi))./sin(theta)).^2;

UMAX=max(U);

Prad = sum(U.*sin(theta)*dth*2*pi);

D = (4*pi*UMAX)/Prad;
D_db = 10*log10(D);

Rr = (2*Prad)/(abs(I0)^2);

Z=linspace(-L/2,L/2,1000);
I=sin(2*pi*(L/2-abs(Z)));
figure(1),plot(Z, abs(I));
xlabel('Z^2{\prime}/\lambda','fontsize',12);
ylabel('Normalized current distribution','fontsize',12);

theta = (1:1:360)*(pi/180);
r=10;

lambda=0.3;
k=(2*pi)/lambda;

L=lambda/2;
E=1i*eta*I0*exp(-1i*k*r)*(1/(2*pi*r))*((cos(k*L*cos(theta)/2)-cos(k*L/2))./sin(theta));
figure(2),polarplot(theta, abs(E));

fprintf('\n Maximum radiated power: %fwatts\n',Prad);
fprintf('\n Maximum directivity: %f(dimensionaless)\n',D);
fprintf('\n Maximum directivity: %f(dbi)\n',D_db);
fprintf('\n Radiation resistance: %fohms\n',Rr);

Output





Radiated Power and Maximum Directivity of any Antenna: Matlab code
% Radiated power and Directivity of an antenna:
close all;
clear all;
clc;
format long;

%Angle definition:
%Azimuth angle phi ranges between 0 to 360 degrees:
phi_degree = 0:360;
phi_rad = phi_degree * pi/180; %Converting degrees to radians

%Elevation angle theta ranges between 0 to 180 degres:
theta_degree = 0:180;
theta_rad = theta_degree* pi/180; %Converting degrees to radian

%integration step size:
dth=theta_rad (2) -theta_rad (1);
dph=phi_rad (2) -phi_rad (1) ;

[THETA, PHI] =meshgrid (theta_rad, phi_rad);
%Radiation pattern of an antenna:
U = (sin (THETA).*sin (PHI) ).^2;

%Performing nunerical integration to obtain
%average power radiated by the antenna:
P_avg=sum(sum (U.*sin(THETA)*dth*dph) );
%Note sum() is discrete time equivalent of integration
%use of sum() twice is to integrate w. r.t. theta and phhi

%Directivity:
%D=4*pi*P_max (theta, phi)/P_avg(theta, phi)
D=4 *pi*max(max (U) )/P_avg;
D_db = 10*log10(D);

fprintf('Average power radiated by the antenna is %f\n', P_avg);
fprintf('Directivity of the antenna is %f(dimensionless) and %f(in dB)\n',D,D_db);
surf(U);

Output



Polar form for a Loop Antenna with Uniform Current: Matlab code
clear all;close all; clc;
format long;

%-Definition of constants and initialization---%

%Free space impedance:
eta = 120*pi;
% Angle vector:
theta=(1:180)*(pi/180);
%Integration step size
dth = theta(2) - theta(1);

%Reading the radius of the loop
A = input ('\nSpecify radius of loop in wavelengths:');

%-------------------------------------------------------
%diation intensity calculation:
%A^2*omega*2 X mu^2 |I0|^2*J1^2(k*A*sin(theta))
%U
%8*eta
%Using omega = 2*pi*f and f = C/lambda,
%C 1/sqrt(mu * epsilon) and eta = sqrt{mu/epsilon) = 120*pi 
%Simplified radiation intensity is given by:
% A2*(2*pi*2*eta |I0|^2*J1^2*(k*A*sin(theta))
%----------------------------------------------------------

F = besselj(1,(2.0*pi*A*sin(theta)));
U = A^2*(2*pi)^2*F.^2*eta/8;
%Radiated power:
Prad = sum(2*pi*U.*sin (theta) *dth);
%Directivity:
D = (4.0*pi*max(U))/Prad;
D_dB = 10*log10(D);
%Padiation resistance:
Rr = 2.0*Prad;

%Calculation of eievation pattern:
% -A*k*I0*exp(-jkr)
% H_theta = ----------------------*J1*(k*A*sin(theta))
% 2*r
% Normalized Peak Current
I0 = 1;
%Distance r in neters:
r=10;

% Wavellength in meters:
lambda=1; 

%Wave nunber:
k=(2*pi)/lambda;

H_theta=-A*k*I0*exp(-1j*k*r)*besselj(1,k*A*sin(theta))/(2*r);
HdB= 20*log10(abs(H_theta)/max(abs(H_theta)));
HdB = [HdB fliplr(HdB)];
theta = [theta, theta+pi];
figure(1),polarplot(theta,HdB);
title ('Normalized far field elevation pattern for loop with constant current');
rlim([-40 01]);

%Printing the values:
fprintf('\nMaximum radiated power: %f watts\n',Prad);
fprintf(' \nMaximum directivity: %f (dimensionless) \n',D);
fprintf (' \nMaximum directivity: %f (dBi) \n' ,D_dB);
fprintf('\nRadiation resistance: %f ohms\n',Rr);

Output




Two Dimensional(2-D) Polar and Semi-Polar Patters using Matlab code
clear all;
close all;
clc;
theta = -pi:0.01:pi; % creation of a angle vector
f = 5*sin(theta).*sin(theta);% electric feild Vector
f_norm = f/max(f);% Normalization (normalized electric feild vector)
power = f_norm.^2;% Power feild
Power_in_db = 10*log10(power);%power in dB
figure(1),
subplot(221)
polarplot(theta,f);
title('Electric feild of an antena');
subplot(222)
polarplot(theta,f_norm);
title('Normalized Electric feild of an antena');
subplot(223)
polarplot(theta,power);
title('Power patern of an antena');
subplot(224)
polarplot(theta,Power_in_db);
rlim([-40,0]);
title('Power patern of antena in dB');
figure(2),polarplot(theta,f);
thetalim([0,180]);
title('semipolar plot of anormalized E-feild');

Output




Computing The Radiation Characteristics of Linear Arrays(With MATLAB code), Array factor Equation
clear all;
close all;
clc;
phi = (0:1:360).*(pi/180);
n = input('Enter the number of sources:');
d = input('Enter the spacing between the sources as fraction of wavelength:');
delta = input('Enter the phase differnce between the sources:');
psi = (2*pi*d*cos(phi))+delta;
E = (1/n)*(sin(n*psi/2)./sin(psi/2));
polarplot(phi,abs(E),'Linewidth',3);

%for to get various output plot
%For Plot1: Souces=2, spacing=0.5:0.5, Phase difference=pi/2
%For Plot2: Souces=2, spacing=0.5:0.25, Phase difference=pi/2
%For Plot1: Souces=2, spacing=0.5:0.5, Phase difference=0
%For Plot1: Souces=2, spacing=0.5:0.5, Phase difference=pi

Output


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