Elliptic Filters

We don't have immediate plans to include these filters. If you need to implement these, you can directly enter IIR filter coefficients in SigmaStudio's general filter block.

What is your specific need for Elliptic and Chebyshev II filters?

I need a rediculously steep brickwall filter. If the eliptical filters are staggered slightly by a few 10's of Hertz the huge ripples can be self canceling.

While researching Elliptic filters I stumbled upon what other digital filter designers would probably think is obvious: Chebyshev, Butterworth, Bessel and Elliptic filter types are all IIR filters, not FIR.

Now all of those except the Elliptic are supported by Sigma Studio and so to recreate them in Matlab or QEDesign directly is not possible via FFT. I could, of course, just just teak an FFT to fit my needs as you suggested and that is what I've been doing thus far but it just hasn't cut it. I hope this is just a software thing rather than hardware so I just wanted to wave my hands a little bigger about requesting Elliptic filters in future versions of Sigma Studio.

Matlab can certainly be used to generate elliptic filter coefficients that can be used directly in SigmaStudio. See the Matlab help file about generating the a and b coefficients here: http://www.mathworks.com/access/helpdesk/help/toolbox/signal/ellip.html

Once you've generated the a and b coefficients, you can load them directly into SigmaStudio's general filter cell (IIR coefficient selection).

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Thank you,
EZ Admin