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Tutorial 9: Constructing a Low-Pass Filter from a Transfer Function
Tutorial 9: Constructing a Low-Pass Filter from a
Transfer Function
This procedure builds a fourth order Bessel-Thomson filter characterizing
SONET/SDH transmitters operating at 2.48832 Gbit/sec. The filter is loaded
into channel 1 user-correction data. The user-correction data is based on the
transfer function:
where:
Note This tutorial of manually constructing a filter is useful as an example. To aid in
the construction of 4th order Bessel Thomson filters at other frequencies, use
the MAKEFILT program located on the IBASIC UTILITIES FOR 71500 SERIES
memory card. This card is supplied with the jitter and eye-diagram analyzer.
Construct the Filter
For this example, f
0
=2.48832 Gbit/sec.
1 To construct the filter, press:
MENU, Config, TRACE POINTS and Enter 256
more 1 of 3, LINES DOTS LINES
2 Set an appropriate frequency range for the filter frequency points by setting
the span to 2/f
0
. This is 803.75514 ps for this example. Press:
Main, SEC/DIV, and enter 803.75514 ps
H
p()
105
105 105y 45y
2
10y
3
y
4
++++()
------------------------------------------------------------------------------------=
y 2.1140p=
p
jw w
r
⁄=
w
r
1.5πf
0
=
f
0
bit rate=