Hi @Anant
As per my knowledge, you are trying to plot S11 of an antenna.
To find out the S11 of an antenna, you can use sparameters function from MATLAB. And, to plot it you can use rfplot function.
Here's a sample code which can give you a better understanding about the two functions.
p=patchMicrostrip;
d=design(p,4e9); %to design a patch micrsotrip antenna at 4GHz
sobj=sparameters(d,linspace(3e9,5e9,51)); %to find out the S11 of the antenna d within a range of 3GHz to 5GHz
rfplot(sobj) %to plot the S11 parameters
