MATLAB: Plotting antenna field patterns in spherical coordinates

3d plotantennaspherical coordinates

Hi, I have a 2D array which of the form A(theta, phi) and I want to plot A as a 3D surface. I have read advice which suggests to use the sph2cart function to convert to Cartesian coordinates, then use surf or mesh, but as size(A) = 46 90, i.e. it is not a square 2D array, it will not work. Any suggestions? Thanks

Best Answer

Why do you think your array needs to be square? Mesh, surf, etc. will accept any gridded data. Assuming your A values represent the radius at any given theta and phi:

 theta = linspace(0, pi, 90);
 phi = linspace(0, 2*pi, 46);
 [theta, phi] = meshgrid(theta, phi);
 A = ones(size(theta));
 [x,y,z] = sph2cart(theta, phi, A);
 mesh(x,y,z)

Is this what you're after?

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MATLAB: Smoothing contact distribution diagram in 3-D

If the smoothing is just for visualization, maybe you could use simple low-pass filtering.

E = rand(18,36)+2;
theta = linspace(0,2*pi,36);
phi = linspace(0,pi,18);
[theta, phi] = meshgrid (theta, phi);
[x,y,z]= sph2cart(theta, phi, E);
figure;surf(x,y,z);title('Rough');
%naive 'smoothening' using low-pass filtering
%using a 3 by 3 averaging filter. 1/(3*3) factor will
%normalize the results.
Es = conv2(E, ones(3,3)/9, 'same');
[x,y,z]= sph2cart(theta, phi, Es);
figure;surf(x,y,z);title('Smoothened');

MATLAB: Plotting multi-radius spherical mesh

For any one that is interested I have used the following code to anwser the question;

out=double(int32(rand(22,12)*9));
phi=linspace(0,pi,13);
theta=linspace(0,2*pi,23);
phi=[phi; phi];
theta=[theta; theta];
phi=reshape(phi,1,2*length(phi));
theta=reshape(theta,1,2*length(theta));
[phi,theta]=meshgrid(phi,theta);
r = zeros(size(phi,1),size(phi,2));
for i = 1:12
    for j=1:22
        r(j*2:j*2+1,i*2:i*2+1) = out(j,i);
    end
end
x=r.*sin(phi).*cos(theta);
y=r.*sin(phi).*sin(theta);
z=r.*cos(phi);
mesh(x,y,z)
axis square
axis off
hidden off

Best Answer

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MATLAB: Smoothing contact distribution diagram in 3-D

MATLAB: Plotting multi-radius spherical mesh

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