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 quadratic factors.

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 ~ -0.5dB at 0.12w

Set BL = 90, WL to 135 and R = 0.15 to locate the frequency markers and set the pass band ripple.

Adjust N, fc/fs until the conditions are met.

In this case N = 8, fc/fs = 0.119 and w

The last entry in the first line of white text shows the gain at 0.18w

In this case, the minimum stop band attenuation is 96.34dB.

Changing Fn to 1 shows the quadratic factors needed to realize the filter and Fn = 2 show the zeros and poles.

COPYRIGHT © 2008 Cuthbert Nyack.