plot radiation intensity of an antenna

i want to plot normalized radiation intensity U(theta,phi)in two planes phi =0 degree and phi=180 degree
for theta ranging from -180 to 180 

U(theta,phi)=eta/2((-1j*k*I*L*exp(-1j*k*r))/4*pi).^2 *(cos(theta)*cos(phi) + sin(phi)).^2

eta=377;
k=2*pi*lamda;
lamda=1;
I=2;
L=1;
r=1;

Answer 1

[Anna Case]

% Define theta and phi vectors

phi = [0 pi];

theta = linspace(-pi,pi,501).';

% Compute U

U(theta,phi)=eta/2((-1j*k*I*L*exp(-1j*k*r))/4*pi).^2 *(cos(theta)*cos(phi) + sin(phi)).^2

% Normalize U

U = U./max(U(:));

% Plot

figure;

polarplot(theta,U(:,1),'linewidth',2);

hold on;

polarplot(theta,U(:,2),'linewidth',2);

legend("\Phi = 0","\Phi = 180")

[VBBV]

@8167, define the lamda value first for calculating the antenna wave number. Then use the multplication operator in the equation for antenna

eta=377;
lamda=1; % define this variable first
k=2*pi*lamda;
I=2;
L=1;
r=1;
phi = [0 pi];
theta = linspace(-pi,pi,501).';
% Compute U
U=abs((eta/2)*((-1j*k*I*L*exp(-1j*k*r))/4*pi).^2.*(cos(theta).*cos(phi) + sin(phi)).^2);
        % ^ use the multiplication operator   
% Normalize U
U = U./max(U(:));
% Plot
figure;
polarplot(theta,U(:,1),'linewidth',2);
hold on;
polarplot(theta,U(:,2)+pi/8,'--','linewidth',2);  % 
legend("\Phi = 0","\Phi = 180")