
Note, when jH(e
jvT
)j
2
¼0.5 it is 3 db below the DC value jH(e
j0T
)j
2
¼ 1.
The filtered outputs are shown in Figures 4.118 and 4.119. There is little difference in the outputs
of the two filters except for the longer transient period of the filter with Q ¼50.
4.12.1 MULTINOTCH FILTERS
When more than one notch frequency exists, a multinotch filter design is required. The previous
reference includes several methods of designing a multinotch filter. One approach is to simply use
the singlenotch design for each notch frequency and cascade the respective filters. To illustrate,
suppose the ECG signal contains a 25 Hz square wave noise signal like the one shown