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Altera_Forum's avatar
Altera_Forum
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15 years ago

FIR filter coefficient scaling and downscaling

I have a sensor signal which is unsigned 12 bits and i need to filter the signal using a FIR filter. The filtered output feeds into an algorithm which expects 12bit unsigned input. I have used...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
15 years ago

Your filter input range is 0 ~ 4095.

scale your coeffs so that their sum = 4096

coeff = round(4096*coeff/sum(coeff));

Then discard 12 LSBs (bit 11:0) giving you unity gain (output 0 ~ 4095);

Discard remaing 4 MSBs(bit 27:24). you may insert flag/saturate if bit 24 gets that occasional hit at extremes.