Elliptic filter

[NeedToKnow]

I am looking for MathCAD implementation for elliptic filter function.

[MichaelEarle]

Can you be more specific. Are you looking for a design method for a lumped element filter using L-C components or a distributed element filter in waveguide as for example a dual mode elliptic filter? Or are you looking to display justhe general elliptic filter response function? There is file called ELLIPTIC.MCD that was published on diskette in the1989 Electrical Engineering Applications Pack. This applied to IIR elliptic filter design.

[jeanGiraud]

From the e-book

jmG

[LouP]

Is this what you're looking for? I just did a liitle cleanup of an old sheet I of mine. It's v11.2a.

Lou

[NeedToKnow]

Hi Lou,

Your works are great. I found weird response when N = 11, rippledb = 0.0295 and attendb = 10. Please comment.

[LouP]

I 'm not sure why it starts to have problems with N=11 but works OK for some higher values of N, but if you look at the max Q of the poles, I would guess that this is already in a region where the accuracy is limited by the numerical precision of my elliptic function implementations. I suspect that the accuracy depends on the particular parameters, and I would not be surprised if the error behavior is not monotonic (as appears to be the case here). At least you see what you are getting (the response is shown for the numerically evaluated poles/zeroes, not the ideal ones).

I haven't had any accuracy issues for any practical situation. If this is a problem, you may need to edit/create elliptic functions with better accuracy. There may be built-in functions now (I use v11.2a mostly), possibly symbolic.

Lou