I use a combination of Visual Basic Programming interfaced with FAMOS which is a DSP software like MATLAB but much easier. I am trying to separate signals from a group, which requires filtering each signal. I used FFT and then IFFT on a 600s signal but the IFFT was longer than the original. I don't understand if this changes the originality of the signal in terms of shape,which might affect the further processing of the signal. After re-sampling the original 10min signal according to Shannon-Niquist theorem and using rectangular windowing, I detect the frequency using FFT.
After I apply IFFT to the signal, does this change the phase or amplitude even slightly that might vary from the original signal?
How do I filter one particular freq before IFFT after detecting it from FFT (Maybe I use peak detection)? Is there a general method of doing it? DSP is totally new to me,and I am still attempting to learn.