Bilinear Approximation to nth order Low 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 locations for the continuous Chebychev filter and the discrete Bilinear approximation.
To design a filter which has a gain of ~ -2dB at 0.1ws, ~ -80dB at
0.2ws and a passband ripple of 0.1dB, proceed as
Set BL = 75, WL to 150 and R = 0.1 to locate the frequency markers
and set the pass band ripple.
fc/fs until the conditions are met.
In this case N = 8 and
fc/fs = 0.101.
The last entry in the first line of white text
shows the gain at 0.2ws as -80.92dB and the second line
shows the attenuation at 0.1ws is -1.821dB.
Changing Fn to 1 shows the quadratic factors needed to realize the filter and Fn = 2 show the poles.
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COPYRIGHT © 2008 Cuthbert Nyack.