Re: Loading touchstone s2p file

[rbb]

Hi,

Most vendors provide s-parameters in touchstone formats as phase and
magnitude pairs, not as complex numbers. So something more like the code
below would work better...

function [sp] = read_touchstone(fname, mode);
%  [sp] = read_touchstone(fname);
%
if nargin < 2, mode = 'magph'; end

fid = fopen (fname, 'rt');
sp.freq = [];
if strcmpi(mode,'complex')
   sp.s11 = [];
   sp.s12 = [];
   sp.s21 = [];
   sp.s22 = [];
else
   sp.s11.mag = [];
   sp.s11.ph = [];
   sp.s12.mag = [];
   sp.s12.ph = [];
   sp.s21.mag = [];
   sp.s21.ph = [];
   sp.s22.mag = [];
   sp.s22.ph = [];
end
while ( ~feof(fid) )
   str = fgets (fid);
   if (str(1) == '!')
      continue;
   end
   [val, len]= sscanf (str, '%f %f %f %f %f %f %f %f %f');
   % Ignore lines with less than 9 elements
   if (len == 9)
     sp.freq = [sp.freq; val(1)];

     if strcmpi(mode,'complex')
        %sp.s11 = [sp.s11; ( complex(val(2), val(3)) ) ];
        %sp.s21 = [sp.s21; ( complex(val(4), val(5)) ) ];
        %sp.s12 = [sp.s12; ( complex(val(6), val(7)) ) ];
        %sp.s22 = [sp.s22; ( complex(val(8), val(9)) ) ];

        sp.s11 = [sp.s11; ( val(2) .* exp(i*val(3)) ) ];
        sp.s21 = [sp.s21; ( val(4) .* exp(i*val(5)) ) ];
        sp.s12 = [sp.s12; ( val(6) .* exp(i*val(7)) ) ];
        sp.s22 = [sp.s22; ( val(8) .* exp(i*val(9)) ) ];
      else % mode == 'magph'
        sp.s11.mag = [sp.s11.mag; val(2)];
        sp.s11.ph = [sp.s11.ph; val(3)];
        sp.s21.mag = [sp.s21.mag; val(4) ];
        sp.s21.ph = [sp.s21.ph; val(5) ];
        sp.s12.mag = [sp.s12.mag; val(6) ];
        sp.s12.ph = [sp.s12.ph; val(7) ];
        sp.s22.mag = [sp.s22.mag; val(8) ];
        sp.s22.ph = [sp.s22.ph; val(9) ];
      end
   end
end
fclose(fid);

Russ
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