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double precision filter coefficients

Question asked by rubear on Nov 4, 2016
Latest reply on Nov 4, 2016 by rubear

I am trying to implement a chebyshev filter using the values from the Chebyshev tables here: (Figure 8.27)

http://www.analog.com/media/en/training-seminars/design-handbooks/Basic-Linear-Design/Chapter8.pdf?doc=ADA4661-2.pdf 

I am using four cascaded double precision general filters.

My controller generates the coefficients and sends them to the ADAU1452 in 8.24 format.

The filter response is OK for Butterworth, but is way off for Chebyshev.  I plot the response using cascaded sections and the result looks perfect.  I am thinking that the 8.24 precision is not enough to accurately place the poles on the S-plane.  Is it possible to write 56 bit values to these filters?  

 

Thanks,

-Robert

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