Bilinear Approximation to nth order High Pass
Frequency Response, Transfer function and pole locations are shown by
the applet below.
Fn = 0 shows the frequency response.
Fn = 1 shows the transfer function represented as a product of
Fn = 2 shows the pole and zero locations for the continuous Elliptic filter and the discrete Bilinear approximation.
To design a filter which has a gain of ~ -3dB at 0.4ws,
ws/wp = 1.25,
a minimun stop band attenuation of 80dB
and a passband ripple of 0.2dB, proceed as
Set BL = 235, WL to 300 and R = 0.2 to locate the frequency markers
and set the pass band ripple.
fc/fs until the conditions are met.
In this case N = 9,
fc/fs = 0.402.
The last entry in the first line of white text
shows the gain at 0.4ws as -2.838dB and the second line
shows the attenuation at the stop band peak is -82.46dB.
Changing Fn to 1 shows the quadratic factors needed to realize the filter and Fn = 2 show the zeros and poles.
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COPYRIGHT © 2008 Cuthbert Nyack.