Z Filter 3 Poles(1R2CC) Frequency Response
Cuthbert Nyack
The Z transfer function of a 3 pole system is shown below:-
The frequency response of the 3 pole system is shown
in the applet below.
The gray curve above the magenta lines show the response between 0 and
½ ws while the
gray curve above the green lines
show the response between ½ ws
and ws. Orange lines show
the phase variation. White disc shows the unit circle, black line
is the real z axis and orange line is the imaginary z axis. Poles are
shown by the "x"s. When the "Theta" parameter is
zero the view is along the imaginary axis from the top. -90° corresponds
to a view along the real z axis from the left and +90° represents
a view along the real z axis from the right.
Note that having a pole near the unit circle produces a peak in the
response. By locating the poles at suitable locations a third order
lowpass or highpass filter can be constructed.
Parameters (0.67, 47.0, 0.48, NA, 0, 0, 10.0, 1.5, 1, 0.86) show a
low pass configuration.
Parameters (0.84, 158.0, -0.71, NA, 188, 0, 10.0, 1.5, 1, 0.12) show a
high pass configuration.
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Copyright 2000 © Cuthbert A. Nyack.