Digital Signal Processing Reference
In-Depth Information
If the two frequency responses were carefully compared, we would see that there
is a +2.5 dB “bump” in the passband, and we lose over 2 dB in the stopband
attenuation. These changes should represent the “worst” that can happen due to
the unfortunate selection of the worst possible combination of components. (A
worst-case analysis was also run with 5% resistor values and 10% capacitor values
and the “bump” increased to 15 dB.) A Monte Carlo analysis can also be run on
the circuit to indicate the more typical extremes that might be encountered.
Depending on the nature of the application, we can live with the resulting
variations, select even more precise (expensive) components, or redesign the filter
to more stringent specifications than actually desired. This redesigned filter would
then be able to vary to some degree while still satisfying the real specifications.
However, this filter may also require a higher order, which will add cost to the
project.
Figure 4.16
Frequency responses for Example 4.5.
4.9 CONCLUSION
We have reached the end of the first part of this text. We were able to design a
variety of analog filters, view their frequency responses, and implement them in
an active filter form. Of course, we have left a good deal of material uncovered.
There are other filter types that could have been discussed. There are other
features that could have been included in the frequency response calculation and
display. Moreover, there are other implementation techniques available for analog
filters. However, it is now time to move into the realm of digital filters. We will
