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How can I plot a sphere in 3D?

Asked by Pilar Jiménez on 5 Oct 2016
Latest activity Edited by Pilar Jiménez on 6 Oct 2016
I have to plot this equation to obtain a sphere
wave=I.*exp(j.*(((k.*x.*sin(TETA).*cos(PHI))))+((k.*y.*sin(TETA).*sin(PHI))))
but the comands mesh, surf, sphere not functioning me. I define the variables as following
puntos=200;
puntos_1=400;
teta=linspace(0,pi,puntos); %0 a 180°
phi=linspace(0,2*pi,puntos_1); %0 a 360°
[TETA,PHI]=meshgrid(teta,phi);
Could anyone help me, please?

  2 Comments

Are you trying to show the values of a plane wave on the surface of a sphere as the plane wave passes through that sphere? Or perhaps something different from that?
I trying to show the values of a plane wave (that obtain with the equation that I named "wave" in the code) like a sphere. The idea is each iteration of the values of teta and phi represent a position of the wave and the result represent the radiation of an antenna in position x=1 and y=1, then my radiation is in full range of teta and phi that's the reason for the plot a sphere. I have defined these variables:
I hope you understand my idea.

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1 Answer

Answer by Luca Fenzi on 6 Oct 2016

This code works fine:
% PARAMETERS Of the model
I=1
x=1
y=1
k=1;
j=1;
%%Grid
puntos=200; puntos_1=400;
teta=linspace(0,pi,puntos); %0 a 180°
phi=linspace(0,2*pi,puntos_1); %0 a 360°
[TETA,PHI]=meshgrid(teta,phi);
% Model
wave=I.*exp(j.*(((k.*x.*sin(TETA).*cos(PHI))))+((k.*y.*sin(TETA).*sin(PHI))))
mesh(wave)
An other option should be instead of using teta,phi, you can use
[X,Y,Z]=sphere(N)
This will permit you to obtain a three dimensional grid of (N+1)x(N+1) points, but then your model wave must be changed from polar coordinate to Cartesian coordinate.

  1 Comment

Thanks Luca, The problem is that the j is an imaginary unit not a real number, for this I can't give the value of 1. And at the end of my code I must have a sphere with the absolute results of my equation wave that is on a matrix with different dimensions matrix. I have defined these variables:
I=1; %establecida por usuario
freq=30000000; %30 Mhz - no. de ondas/seg
c=300000000000; %m/seg
wlong=c/freq; %m
k=2*pi/wlong; %no. onda

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