MATLAB: FFT range for a signal

fftsignalSignal Processing Toolbox

I have a signal from which I want to find the dominant frequency.

Does fft ignore the part which is constant (like DC)? Does that part affect the fft calculations?

Thanks in Advance

fft() does not ignore the DC component. The DC component is returned as the very first vector entry of the result.

Thank you very much.

Then you just do

 t = 0:0.001:1-0.001;
 I = cos(2*pi*100*t);
 Q = sin(2*pi*100*t);
 sig1 = I+1j*Q;
 dftsig1 = fft(sig1);

Do the same for I2 and Q2, etc.