FIR coefficients

Fred Marshall wrote:

> "Randy Yates" <yates@ieee.org> wrote in message
> news:THcxb.23273$Wy4.2940@newsread2.news.atl.earthlink.net...
> 
>>jack kilby wrote:
>>
>>>Hello all,
>>> Thanks for all of your responses.Kindly look in to the coeefficients
>>>and help me cross the river.a of now i work like this
>>>datain = 15 bits
>>>1 input to multiplier (from the data)= 15 bits
>>>2 input to multiplier (from coeff) = 10 bits (i multiply by 2 power
>>>10)
>>>output of multiplier = 25 bits
>>>input to accumulato =25 bits
>>>i finally take the last 16 bits out....
>>
>>Hi Jack,
>>
>>If the coefficients are only 10 bits long, then multiplying the
>>real coefficients below by 1024 (2^10) will overflow the largest
>>one:
>>
>>   round(0.538 * 1024) = 551.
>>
>>The largest value you can represent with a signed, two's complement
>>10-bit number is 511.
>>
>>Perhaps this is your problem?
> 
> 
> So, scale the coefficients by 511/0.538 = 949.8141264 or some other similar
> number that might minimize the error in the coefficients or to directly
> minimize the error in the filter response.

Ayup - that would fix it.
-- 
%  Randy Yates                  % "...the answer lies within your soul
%% Fuquay-Varina, NC            %       'cause no one knows which side
%%% 919-577-9882                %                   the coin will fall."
%%%% <yates@ieee.org>           %  'Big Wheels', *Out of the Blue*, ELO
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