Analog Prototype Filter
Since the digital cut-off frequency may be set to any value,
irrespective of the analog cut-off frequency, it is convenient to set
the analog cut-off frequency to
. In this case, the
bilinear-transform constant 
is simply set to
(I.9) to convert the analog prototype
to a digital filter with cut-off at frequency 
.
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Examples
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Frequency Warping
