I work with Magnetic Resonance Spectroscopy data. Data (complex signals) obtained from Bruker scanners (one of the biggest manufacturers of MRS scanners) start with an important group delay - around 60-80 points (in the time domain) - probably due to the fact that they use a long FIR filter.
The effect of this group delay cumulated with some other (unfortunately unknown) problems results in a baseline distortion called Bruker smile/frown. (in the frequency domain, after FFT)
I would like to simulate this kind of distortion (smile or frown). I tried with a bandpass FIR of several taps (80- 140) and I cannot reach this effect. Could you recommend me any way of getting this distortion? Thank you in advance.