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> Here's another one, using the same rounding principle.
> Would you care to have a look at this one too ?
>
> By the way, doesn't the rounding make this IIR filter effectively an FIR
> filter ?

No... Look at the step response. The final value in the step response of
an FIR filter depends on the number of taps whereas for an IIR filter it
depends on the poles.

Back to your filter. In addition to settling errors, the IIR quantization
errors can also produce something called 'limit cycles' which are small
output oscillations for DC inputs.

Attached is an IIR C-implementation that handles limit cycles and settling
errors. It supports poles other than 1/2^N. A simple unit-test framework
tests a few of the corner cases.

Scott=

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