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Peaking and stopband filter
In the same way, a peaking filter is obtained from a shelving filter by rotating the
pole and the zero, and by providing a conjugate pole and zero, as shown in
Figure 8.16. If the desired center frequency is , and
the radii of the pole and zero (as for the shelving filter) are
and , then we place the the upper pole and zero at
As a special case, placing the zero on the unit circle gives a stopband filter;
in this case the gain at the center frequency is zero. This is analogous
to the onepole, onezero highpass filter above.
Figure 8.16:
A peaking filter: (a) polezero diagram; (b)
frequency response. Here the filter is set to attenuate by 6 decibels at
the center frequency.

Miller Puckette
20061230