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Altera_Forum
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15 years ago

Fixed-point multiplication with "altmult_complex" megafunction

Hi, I am using the altmult_complex (complex multiplier) with inputs dataa (both real and imaginary) having 16 fractional bits, and inputs datab (both real and imaginary) having 2 decimal bits a...
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Altera_Forum
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15 years ago

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If precision is an issue, you can try using "rounding" instead of simply discarding the LSBs.

With rounding (that is adding the first bit that you discard to the result) you get a rounding error with average zero value.

Discarding the LSBs you get an error that is always positive.

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True, but as with any rounding or truncation, if you have multiple multipliers this adds a half error for each multiplier. So even though the average is the same, the error can end up being quite a bit.