Re: pole zero stuff

richard pickworth wrote:
> Hi all.
> I am confused about pole - zero diagrams and how they relate to filter
> response.
> Also confused about unit circle and IIR filters.
> Can anyone help?

Exercise for the student:

Draw a unit circle. Label the circle from 0 to SampleRate/2 Hz.
Draw your poles and zeros. For some point on the circle,
calculate the distances to all the poles and zeros. Multiply
together the distance to all the zeros and the reciprocal of the
distance to all the poles. How does the resulting product and
the frequency of your selected point on the unit circle relate
to your expected IIR filter response?

Long ago I remember writing an Apple II program which would allow
me to use the joystick to move around a pole or zero, then (slowly)
have plotted the resulting distance product for some (not large)
number of points around a circle or vertical line. (Should run a
bit faster on a modern PC :)


IMHO. YMMV.
--
rhn A.T nicholson D.o.T c-O-m

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