> > Sure! > > s^2 + s > ----------------- > s^3 + s^2 + s + 1 Ah, I see. This has 6dB/Oct slopes at both sides (like a 2pole BPF), so the 3rd pole must make a difference in the pass band only. 3 poles means one of them must be a real pole. I must check this more closely. How would it look like in a passive LC implementation ? JH.