BRUEL & KJAER 1615 - Effective Bandwidth; Phase Response

EFFECTIVE BANDWIDTH
Table I gives the bandwidth at the -3.7 dB points. This bandwidth is 1/3
octave and is also the effective bandwidth of the filter. See "Definitions".
When filtering white noise, the RMS noise voltage from the filter can be in
error ± 0.4 dB when using the effective bandwidth of 1/3 octave, because of
the production tolerances on the filters.
PHASE RESPONSE
The filters, by their nature, produce considerable phase distortion in the
pass band. Figs.2.9, 2.10, show the limits within which the different filter
curves for the whole apparatus are expected to lie.
12
!
dB
10
c
0
c
::I
c
Ql
::.( 20
30
6300
540°
360°
t
1800
log
g oo
~ lead
:0 180°
Ql
Ul
c
.c
a. 360°
540°
6300
I({
A
lJ
lr
fj
w
~f
~
P'
~
\
\
~~
~
~
~
~
ll
II
I
If
iJ
% "S :Ys +'s 1fs -o + 1/s 2fs :ts "6 !j(; octave
Frequency - /6f9 :1 f
Fig.2.10 Phase response of Filter Set in 1/1 octave condition