Re: FIR filter design question

Zeph80 wrote:
>> In windowing method for FIR design, you specify the frequency response
of
>> the desired filter at sample points fs/N, and perform an IDFT to obtain
>> h(n).
>> So doesnt this mean that you want fs to be as low as possible to
specify
>> better frequency resolution. But Fs is generally many times the cut-off
>> frequency - more than the minimum of twice the cut off needed. 
>>
>> Why is this?Isn't the frequency resolution that I specify for the
filter
>> response going to be poorer as I choose higher Fs?
>>
>>
> 
> 
> N is the size of FFT. I guess my question is, when I design this filter
> using the IDFT method, if I had a choice how would I select Fs and why?

You choose the sample rate to meet or exceed the signal's requirements. 
You choose N to provide the number of taps that you think your filter 
will need. More taps give better control of response at the cost of more 
delay and greater processing burden.

Jerry
-- 
Engineering is the art of making what you want from things you can get.
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