Page 265 - Analog and Digital Filter Design
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262 Analog and Digital Filter Design
equalizer for this filter has a normalized capacitor value of 2.0 that must be
divided by o.R, or 314,159. The capacitor required is 6.366pF. The equalizer’s
normalized inductor value is also 2.0. This must be multiplied by R and divided
by o, which is a multiplying factor of 7.95775 x The inductor required is
15.916mH: each half winding requires a self-inductance of 3.979 mH.
*
L3=16.23mH
L1 L2
Figure 9.14 500
6.366uF 6.496uF
Equalized Third-
Order Butterworth
Filter Lowpass Section Equalizer Section
Simulation of the filter and equalizer combination was carried out using
ANALYSER III.’ The frequency response, given in Figure 9.15, shows plots for
gain and group delay. The gain is fiat until mid-band, then rolls off to give a
correct -3dB frequency of 1 kHz. The phase is not shown, but has an almost
constant rate of change with frequency, which on a linear frequency scale would
appear as a straight line.
m
Linear Circuit Sinulatar
ClNClLYSER 111 Professional
tunber One Srstens
I
Gain (dE) BUTTBDEL Delay
650 US
640 US
630 US
620 US
610 US
600 US
590 US
580 us
570 US
560 US
550 US
100 1
Figure 9.15
Simulated Frequency Response
