Re: Butterworth bandpass gain


polar.ninja@xxxxxxxxx skrev:
Hi, I'm working on butterworth IIR filters, I have my s-plane analogue
prototype and conversions to HP/BS/LP working fine and am able to
calculate gain and scale it correctly, do bilinear and covert to SOS,
no problem.

I'm having trouble finding references about how to calculate an overall
gain for the bandpass case. Is there any reference or paper that could
shed some light ? Apparently, I need to calculate something other than
the DC gain, the fcutoff gain ?

You have to do things in the correct order to get these things to work.
Somewhere along the line you make a LP s-domain prototype. If you
scale this LP prototype filter function such that it has unit gain at
DC,
everythings else comes out correctly once you apply the BLT or
convert to HP, BP or BS filters.

Rune

.