I have equations for S11 and S21 parameters for a bandpass filter which are obviously frequency dependent. I know there are commands like sparameters() and rfplot() used specifically for plotting S parameter in Matlab. But I can't find the equations these commands use. Also I can't get the right plot from my code no matter what I try. The S parameter I get from equation are complex doubles. Using abs() command or magnitude formula sqrt(a^2+b^2) yeilds 1 for all frequency values so I assumed I should just ignore the imaginary part and plot the real part of S11. Am I correct? Should I convert just the real part of S11 to dB using 10log(S11)? I would appreciate any help you can give especially if you have made s parameter plots on Matlab using your own equation.

  • $\begingroup$ Can you please specify what these S11 and S21 parameters represent? For instance by giving the equation of the bandpass filter? $\endgroup$
    – Petrus1904
    Mar 6, 2021 at 15:09
  • $\begingroup$ These are the Scattering parameters of the filter. S11=2*iRsinv(A(1,1)); Here A(1,1) changes with frequency. $\endgroup$
    – JOHN
    Mar 6, 2021 at 15:43


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