fft phase shift: unwanted tail comes back

[Ale83]

Hi all,

I feel like my problem is a quite common one but it doesn't appear to be very much dealt with.

Briefly, I have a signal going through a system described by a transfer function (Fourier transform).

In the simplest case, my signal only experiences a phase shift in the frequency domain, that is of course a time delay in the time domain.

When I back-transform the system output, I have to face the inherent periodicity of the FFT, in the sense that the tail of the signal comes back at the very beginning of the signal: see the attached picture.

I would like the signal to be 0 in the interval 0-20 ns.

How would you solve that?

Best regards,

Ale

[Ben]

I admit this is not 100% on mark but may give you some ideas. In this thread I suggested using a zero-phase shift filter. Ignore this post if it does not help.

Ben