For a band-pass filter, you can calculate its Q factor as f0/BW. For a low-pass filter, its f0 is same as BW, right? But I find some low-pass filter's Q value is 0.5 or 1.5, How it can be?
Q is a parameter of an individual resonator, not a system of resonators. It is defined as the energy loss per radian of oscillation divided by the total energy stored.
The definition for a BPF will be irrelevant. The impulse response will be different for different number of resonators even if the filters have the same 3 dB bandwidth.
More resonators will have a longer ringing time. Also the type of filter shape (skirt selectivity) will have different ringing times.
This reminds me of the British tax system many years ago which taxed automobiles by the piston surface area and not the displacement or power.
if you consider half of the frequency response for LPF and BPF,
i mean frequency above Fo in LPF (and below Fo in HPF) you will find
efect of Q factor in frequency responce.
see attachment
if you consider half of the frequency response for LPF and BPF,
i mean frequency above Fo in LPF (and below Fo in HPF) you will find
efect of Q factor in frequency responce.
see attachment