MATLAB: Antenna array pattern in 3D space

3d plotantenna array patternPhased Array System Toolbox

Hy guys. Can please someone help me. When I start the program I have an error: Error: Unexpected MATLAB operator.
%Tadej Trinko; three-dimensional antenna array pattern
%email:tadej.trinko@gmail.com
%Jožef Štefan International Postgraduate School (MPS IJS), Ljubljana,
%Slovenia
clear all;
% element numbers N, wavenumber B
N = input ('Enter the Number of Array Elements : ') ; 
lambda = input ('Enter the Value of Lambda (c/f) : ') ;
B =(2*pi/lambda);
j = sqrt(-1);
% Magnitude, Phase, X,Y,Z coordinate
for I = 1 : N 
    Current = I
    An(I) = input ('Enter the Magnitude of the Current : ') ;   
    Xn(I) = input ('Enter the Position of Element on X-axis : ') ;
    Yn(I) = input ('Enter the Position of Element on Y-axis : ') ;
    Zn(I) = input ('Enter the Position of Element on Z-axis : ') ;
    Jp(I) = input ('Enter the Phase of the Current : ') ;
end
Phi=(0:1:360)*pi/180;
Theta=(0:1:180)*pi/180;
[THETA,PHI]=meshgrid(Theta,Phi);
% calculate the array factor
for I=1:N
    R=An(I)*exp(1j.*(Ep+Jp(I)));
    Ep=B*((Xn(I).*cos(PHI).*sin(THETA))+(Yn(I).*sin(THETA).*sin(PHI))+(Zn(I).*cos(THETA)));
end
%plot the array factor
X=R.*sin(THETA).*cos(PHI);
Y=R.*sin(THETA).*sin(PHI);
Z=R.*cos(THETA);
figure();
mesh(X,Y,Z); %display
surf(X,Y,Z) %colored faces
Equation (1) on page 4 in article: http://www.loe.ee.upatras.gr/EM/Journals/Array%20Factor%20Measurements%20A%20Preliminary%20Stage%20in%20a%20Methodology%20for%20Smart%20Antenna%20Characterization%20Measurements.pdf
Thank you for any advice or comment.
Regards, Tadej

Best Answer

Hi Tadej, In this for loop
for I=1:N
    R=An(I)*exp(1j.*(Ep+Jp(I)));
    Ep=B*((Xn(I).*cos(PHI).*sin(THETA))+(Yn(I).*sin(THETA).*sin(PHI))+(Zn(I).*cos(THETA)));
end
You attempt to access the value of Ep the first time through the loop before it has been assigned a value. Perhaps you just need to swap the two lines and place the Ep= assignment before the R=
Also, do you know about the new Phased Array System Toolbox? That toolbox will greatly enhance your ability to design antennas and model phased array systems.
Wayne
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