Specifications

2.6.3 Group De lay
Group de lay
1
, shown in Fig ure 2.4, on op po site page, is de fined as the de riv a tive of ra dian phase with re spect to ra dian
fre quency, which is the slope of the phase curve. A flat group de lay is con sid ered a lin ear phase re sponse which cor re -
sponds to a con stant slope of the phase curve. With lin ear phase re sponse, the dis tor tion of com plex data sig nals will be
min i mized be cause their var i ous fre quency com po nents, due to con stant time de lay, will not shift rel a tive phase.
In nu meric terms, the zero fre quency phase slope is –293.7°/Hz for Butterworth and –351.9°/Hz for Bessel, when nor mal -
ized for a cut off fre quency of 1Hz. This will be 2π times greater in °/Hz for a cut off of 1 ra dian/sec or –1845°/Hz and
–2211°/Hz re spec tively. Di vid ing by 360 con verts °/Hz to ra di ans/ra di ans-per-sec yields a group de lay time of 5.13s for
Butterworth and 6.14s for Bessel.
Model 3380 Series Section 2 - Operation
2-7
Figure 2.3 Phase Response
[1] IEEE Standard Dictionary of Electrical and Electronic Terms, Institute of Electrical and Electronic Engineers,
IEEE-STD 100-1977, Second Edition, 1977, page 296. , shown in Figur , shown in Figur