Band-pass filters

Frequency response

Bandwidth ΔΩ=f₀ - f_u within the pass-band of the band-pass filter is defined by the cut-off frequencies f₀ and f_u. They are defined as frequencies where the amplitude has exceeded –3dB (~0.707). When a band-pass filter is configured, the bandwidth is defined by specifying the quality factor (filter[i].guete). The quality factor is the ratio of the characteristic filter frequency to bandwidth ΔΩ:

For this reason, the frequency range f₀-f_u reduces as the quality rises. The following relationship exists between the characteristic frequency of the band-pass filter and the cut-off frequencies f₀ and f_u (geometric mean):

With band-pass filters, the filter prototype has only a minor influence on filter response.