# Draw a polar plot from cartesian plot of gain function

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DM on 6 Nov 2014
Commented: DM on 6 Nov 2014

I have used MATLAB to draw the following gain function of an antenna array, the code was as follows,

```    Nt=8;
deltat=1;
Lt=8;
omegat=-2:0.01:2;
for j=1:length(omegat)
gainfunction(j)= (1/Nt) * exp(i*pi*deltat* omegat(j)* (Nt-1)) * (sin(pi*Lt*omegat(j))/sin(pi*Lt*omegat(j)*Nt^-1));
end
plot(v,abs(gainfunction))
grid on
ylabel('|f(\Omega_r)|','linewidth',25)
xlabel('\Omega_r','linewidth',15)```

The image below is a radiation pattern of an antenna, i.e it shows the gain function denoted by f(\Omega) as function of \$\Omega\$ from -2 to 2.

My question is I would like to plot the following in *polar coordinates* to see how the main lobe is in degrees.

Any thoughts on how I can continue to the polar plot using MATLAB ?

Youssef Khmou on 6 Nov 2014
In the code, v is not defined, i assume is it omegat, try :
figure;
polar(omegat,abs(gainfunction)); % 20*log10(abs(gainfunction)) doe dB DM on 6 Nov 2014
You are right about the v. Can we tell the beam width of the main lobe from this figure you provided?