Biquad frequency response again
pbjrbj at viconet.com
Fri Oct 16 11:49:29 EDT 1998
>A little while ago I posted a question about how to calculate the frequency
>response of a biquad filter.
>someone pointed me to the excellent reference at
>http://www.brokersys.com/~jmac/dsp/fresp.html It provides C code for
>calculating the response curve of a given set of filter coeficients. The
>only problem is that it requires a0 to be 1.0, and I'd like to use it to
>calculate curves for Robert Bristow-Johnson's cookbook formulae, which don't
>have a0 set to 1.0.
>My question is:
>Is there a simple way to fudge the coefficients to guarantee a0 == 1.0?
YES! (and it's in the post as well as a typical system theory text.) you
do the old multiply and divide by the same quantity trick. you can
multiply the top and bottom of the transfer function by any non-zero number
you want (and it changes _nothing_). how about multiplying top and bottom
BTW, the _magnitude_ frequency response is:
pbjrbj at viconet.com a.k.a. robert at audioheads.com
a.k.a. robert at wavemechanics.com
"Don't give in to the Dark Side. Boycott intel and microsoft."
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