Re: IIR filter problem

Hi Diego,

DX napisał(a): 
Hi


Thanks for your answers.

This is the problem...

I'm building a IIR filter using fixed point, (well the limits are -1 to
1), I've calculated the coeffs for the filter but there are values that
are out of range of -1 to 1, for instance 4.5, or 2.8 etc... and other
values that are in range  for the same filter, for example 0.5, 0.126,
etc ....

Well I can't represent this 2 kind of numbers in the same filter
because the range is -1.0 to 1.0...

What I can do to solve this...? Other suggestions...

Thank you again
Diego

the simple solution is to rescale coefficients by power of 2 before and after calculations.
In your example you divide (shift right 3 bits) all coeff. by 8 and then multiply the result by 8 (shift left 3 bits).

Better solution is to use filter design tool, like fdatool in Matlab, which gives structure and numbers normalised to -1.0 ... 1.0 range.

Regards

Roman Rumian
.

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