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i need help in obtaining graphs for decoupling technique for antennas

Discussion in 'Tech, Gadgets & Science Forum' started by Charity Kasubi, May 28, 2012.

  1. C

    Charity Kasubi New Member

    #1
    May 28, 2012
    Joined: Aug 15, 2011
    Messages: 1
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    I am doing a project titled decoupling technique for antennas and high isolation my code is in matlab software i cant get correct graphs for isolation and return loss of antenna(below -10dB before and after decoupling technique) .This is an IEEE conference paper.Below is the coding i have done:
    %%%%%%%%%%%%%%%%%%%%% A Decoupling Technique for Increasing the Port Isolation Between Two Strongly Coupled Antennas %%

    %%------------------- Define Variables:----------------------%%
    % N - # of elements in array %
    % d - element spacing in wavelengths %
    % ang - theta in deg %
    % thetaS - desired user AOA (deg) %
    % thetaI - interferer AOA (deg) %
    % T - period of desired signal %
    % t - time axis for desired signal %
    % S - desired signal %
    % I - interfering signal %
    % vS,vI - steering vectors of desired user and interferers %
    % X - total array factor %
    % Rxx - total received signal correlation matrix %
    % mu - convergence parameter %
    % w - weights of ULA determined using LMS algorithm %
    % x - total received signal %
    % y - array output %
    % e - error between array output and desired signal %
    % theta - range of AOA's (rad) %
    % AF - weighted array output
    % S11,S12,S21 and S22 - scattering matrix parameters %
    % ZG and ZL - load impedances
    % Gin and Gout - input & output reflection coefficients
    %%-----------------------------------------------------------%%
    %----- -----%
    clc;clear
    all, close all;
    d = .5;
    % element spacing in terms of wavelength d = lambda/2
    gamma = 0.5;
    %S11 = 0.61<165* , S21 = 3.72<59* , S12 = 0.05<42* , S22 = 0.45<-48*;
    Sm = smat([0.61 165 3.72 59 0.05 42 0.45 -48]);
    % -- Scattering matrix
    Z0 = 50;
    ZG = 10+20j; gG = z2g(ZG,Z0);
    ZL = 30-40j; gL = z2g(ZL,Z0);


    M = 2;
    %input(' How many element do you want in uniform linear array? '); % number of elements in array
    thetaS = 0;
    %input(' Enter the desired users angle (in degrees)? ');
    thetaI= 30;
    %input ('Enter The Angle of Incidence of the Undesired Interference Source Signal : ') ; %30


    %----- Assuming the Desired Signal & Interference signal -----%

    it=1:200;
    % number of iteration
    T=3*10^8;
    %T - period of desired signal
    t=(it)*T/200;
    S=sin(2*pi*t/T);
    thetaS = thetaS*pi/180;
    % desired user AOA
    I = randn(1,200);
    thetaI = thetaI*pi/180;
    % interferer AOA

    %----- Create Array Factors for each user's signal for linear array -----%

    vS = []; vI = [];
    i=1:M;
    vS=exp(1j*(i-1)*2*pi*d*sin(thetaS)).';
    % desired signal recieved STEERING VECTOR
    vI=exp(1j*(i-1)*2*pi*d*cos(thetaI)).';
    %intereference signal recieved
    Gin = gin(Sm,gL);
    Gout = gout(Sm,gG);
    Gmag = sgain(Sm);
    % GMAG = 41.50, or, 16.18 dB

    figure(7)
    plot([Gin,Gout],
    'r--'),
    xlabel(
    'input reflection coeff')
    ylabel(
    'output reflection coeff')
    title(
    'Input & output reflection coefficient'),

    %----- Solve for Weights -----%
    w = zeros(M,1);
    for
    snr = 10; % signal to noise ratio

    X=(vS+vI);

    Rx=(X*X');
    % correlation matrix..
    end

    mu=1/(2*real(trace(Rx)))
    %mu = input('What is step size?')

    % trace(Rx) is the maximum eigen value of correlation matrix of i/p signal

    wi=zeros(M,max(it));
    for
    n = 1:length(S) % selecting the training inputs
    x = S(n)*vS + I(n)*vI;
    y=w'*x;
    %y = w*x. calulating the "------- OUTPUT BEAMFORMER-----.. where w is weight and x is the input signal'
    e = conj(S(n)) - y ;
    % calulating the --- ERROR ---- i.e " e = reference signal(desired) - output signal
    esave(n) = abs(e).^2;
    % learning curve
    w=w+mu*conj(e)*x;
    % w = w +mu*e*conj(x) calculating the ------WEIGHT----
    wi:),n)=w;
    % store weight for matrix to plot
    yy(n)=y;
    end
    w = (w./w(1));
    % normalize results to first weight % Array operations "." Element-by-element multiplicative operations are obtainedFor example,

    % C = A ./ B is the matrix with elements c(i,j) = a(i,j)/b(i,j).

    %----- Plot Results -----%

    theta = -pi/2:.02:pi/2;
    AF = zeros(1,length(theta));

    % Determine the array factor for linear array

    for
    i = 1:M
    AF = AF + w(i)'.*exp(1j*(i-1)*2*pi*d*sin(theta));
    end

    % two closely spaced printed monopole antennas %
    figure(1)
    AF = abs(AF);
    polar(theta,AF,
    '-r'), title('Measured radiation patterns of the two closely spaced printed monopole antennas'),
    grid
    on;
    xlabel(
    'Angle(Degree)')
    ylabel(
    ' Normalized gain(ratio) ')

    %**************************************************************************


    figure(2);
    plot(it,S,
    'k',it,yy,'r--')
    xlabel(
    'No. of Iterations')
    ylabel(
    'Signals')
    legend(
    'Desired signal','Array output')

    %*********MY ESTIMATE*************************************************************
    figure(3);semilogy(it,esave,
    'k')
    xlabel(
    'Iteration no.')
    ylabel(
    'error')

    figure(4);plot(it,wi)
    xlabel(
    'Iteration no.')
    ylabel(
    '|weights|')
    w=0:pi/20:pi;
    q=1:1:7;
    figure(5),

    for
    i=0:pi/20:pi
    brf_rect((i)*(20/pi)+1)=0.318+2*(0.022*cos(i)+0.265*cos(2*i)+0.045*cos(3*i));
    end
    plot(w,brf_rect,
    'r-');hold on % rectangular window
    plot(w,1.2*brf_rect,
    'k--');
    xlabel(
    'Frequency (Hz)')
    ylabel(
    'Return Loss(dB)')
    title(
    'The Return Loss of the monopole')

    figure(6),
    for
    i=0:pi/20:pi
    brf_hanning((i)*(20/pi)+1)=0.318+2*(0.0165*cos(i)+0.066*cos(2*i));
    end
    plot(w,brf_hanning,
    'g-') ;hold on % Hanning window
    plot(w,1.2*brf_hanning,
    'k--') ;
    xlabel(
    'Frequency (Hz)')
    ylabel(
    'Isolation(dB)')
    title(
    'The Isolation of the monopole')

     
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