No that's not what I mean

Its just what you do in Time domain reflectometery. Doing this actually you can find how impedance behaves along the line (discontinuties,or any other changes). Here is the code that I wrote (with a colleague's help) to do just that

load C:\Shaf\gen.s11; %load the file which has S11

Spar=gen(:,2:3); % All the rows but 2nd and 3rd columns

Freq=gen(:,1); % All rows but first column

fvec_sim = [0:600e6/2048:600e6-600e6/2048]; % from 0 to 600MHz, 2048 points

number_rows=size(Spar); %

number_rows=number_rows(1,1); % number of rows

for i=1:1:number_rows % turning them into proper imaginary notation

Spar_procd(i,1)=Spar(i,1)+j*Spar(i,2);

end

fdelta = fvec_sim(2)-fvec_sim(1);

fsim = max(fvec_sim)+fdelta;

tsim = 1/fsim; % tsim is step in time.

time = [0:tsim:1/fdelta-tsim];

s11 = interp1(Freq,Spar_procd,fvec_sim,'linear','extrap');

s11_windowed = s11.*(1 + cos(pi*fvec_sim/fsim))/2;

t11 = ifft(s11_windowed);

impedance = 50*(1+t11)./(1-t11); % Zo is 50

tdr = impedance;

c0 = 299792458; % speed of light in vacuum in m/s

c0_fr4 = 1/2 * c0; % speed of signal through TL

fr4_inch_per_sec = c0_fr4*100/2.54;

fr4_inchvec = time*fr4_inch_per_sec;

inchvec = fr4_inchvec/2;

figure;

plot(inchvec,abs(impedance));

grid on;

xlabel('Distance (in inches)','FontSize',12,'FontWeight','bold');

ylabel('Impedance (in Ohms)','FontSize',12,'FontWeight','bold');

title('TDR plot','FontSize',12,'FontWeight','bold');