Magnitude data of S-parameters

I'm analyzing data from s-parameters using the rf toolbox and I was wondering if there is a simple command for extracting the magnitude data of the parameters without having to extract it from the rfplot handle?

BR, Anna

Answer 1

[Giorgia Zucchelli]

Hi Anna,

I think I would recommend the following approach:

S = sparameters('Data.s2p'); % read the touchstone file
s_param = S.Parameters;      % extract the S-parameters from the data structure 
                             % (for convenience)
f = S.Frequencies;           % extract the frequency vector from the data structure 
                             % (for convenience)
s_param_mag = abs(s_param);  % compute the magnitude of the S-parameters 
                             % this is a standard MATLAB function
plot(f, squeeze(s_param_mag(2,1,:)));  % plot the S21 as a funtion of frequency

I hope that this helps, With best regards, Giorgia

[WIlliam Main]

I was expecting that if I convert s_param_mag to dB (i.e. log10(s_param_mag(2,1,frequency)*10 it would give the same value as I see in the plot generated by rfplot at frequency. But it does not, what am I missing? Thanks!

Answer 2

[Joe Wargo]

Hi Anna,

Just to extend the good advice Giorgia gave, if you want to look at just one of the Sij parameters (s21, for instance) you can use the rfparam() function:

    S = sparameters('Data.s2p'); % Read the touchstone file
    s21 = rfparam(S,2,1); % Extract the s21 data
    s21_mag = abs(s21);
    s21_db = 20*log10(s21_mag);

I hope that helps!

Joe