Re: Bessel-filter problems

[Chipmuenk]

Hello Bernd,

I'm also seeing strange kind of errors with the new besself function,
additionally I get the error message "invalid use of script in index
expression"

But are you sure that you really want to construct such a filter? Your ratio
between corner frequencies and the Nyquist frequency (2.5 GHz ???) is quite
high. Throw in a filter order of 10 and you will get a filter with
coefficients that are numerically ill-behaved.

Constructing a butterworth filter from your data shows what I mean: The
resulting coefficients range from 1 to 1e5, i.e. they differ in scale by
about 17 bits.

The other question is: Do you really need a bessel filter? If you need a
near-linear phase and a gentle roll-off, FIR filters are used in most cases.

Best regards,

Christian



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