In numeric terms, the zero frequency phase slope is –149.7°/Hz for Butterworth and –183.4°/Hz for
Bessel, when normalized for a cutoff frequency of 1Hz. This will be 2p times greater in °/Hz for a cutoff of
1 radian/sec or –940.7°/Hz and –1152.4°/Hz respectively. Dividing by 360 converts °/Hz to radians/radi-
ans-per-sec yields a group delay time of 2.61s for Butterworth and 3.20s for Bessel.
Section 2 - Operation
2-8
Figure 2.3 Group Delay
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