Freq.m

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t1 = readtable("1GHZMOSNUDTIR.txt");
offset = 1500100;
step = 0.001;
periodNS = 1;
period = periodNS / step;
nPeriods = 100;
fLower = -200;
fUpper = 200;
 
%time = t1.time(end) + t1.time(2) - offset*t1.time(2);
f_s = 1/t1.time(2);
freqSequence = - f_s/2 : 1 / (nPeriods*periodNS) : f_s/2 - 1 / (nPeriods*periodNS);
f1 = abs( fftshift( fft( t1.n7((offset):(offset + nPeriods*period - 1))) ) );
f1 = abs( fftshift( sine( 2 * pi * fft( t1.time((offset):(offset + nPeriods*period - 1))) ) ) );
f1 = f1 / length( f1 );
p1 = ( 2 * abs( f1 )^2 ) / (2*50);
f1 = f1 ./ length(f1);
 
f2 = abs( fftshift( fft( t1.n16((offset):(offset + nPeriods*period - 1))) ) );
p2 = ( f2 .* conj(f2) ) / length( f2 );
f2 = f2 ./ length(f2);
 
fi = abs( fftshift( fft( t1.n9((offset):(offset + nPeriods*period - 1))) ) );
pi = ( fi .* conj(fi) ) / length( fi );
fi = fi ./ length(fi);
 
dbm1 = 10 * log10( p1 / (1E-3));
dbm2 = 10 * log10( p2 / (1E-3));
dbmi = 10 * log10( pi / (1E-3));
 
[~, idxLower] = min( abs( freqSequence - fLower ) );
[~, idxUpper] = min( abs( freqSequence - fUpper ) );
 
figure();
hold on;
stem( freqSequence, dbmi );
stem( freqSequence, dbm1 );
stem( freqSequence, dbm2 );
%set( gca, 'YScale', 'log' );
hold off;
dlmwrite("fftoutput.txt", [freqSequence( idxLower:idxUpper ).', dbm1( idxLower:idxUpper ), dbm2( idxLower:idxUpper ), dbmi( idxLower:idxUpper ) ],'delimiter',' ','precision','%20.12f');