Re: Relation between delay in FIR filter and the cutoff frequency...



brent wrote:
On Oct 7, 11:55 pm, Fully Half Baked <jfez...@xxxxxxxxxxxxxx> wrote:
On Oct 7, 5:21 pm, brent <buleg...@xxxxxxxxxxxxxxx> wrote:

I have some flash tutorials on the DFT, digital convolution and FIR
filters here:
http://www.fourier-series.com/fourierseries2/DSP.html
Perhaps this will help your understanding.
Brent
Good stuff. What's the advantage of using an inverse FFT compared to
just calculating the sinc directly?

I think there is an advantage of using the sinc function directly.
When computing the inverse FFT you need to pick a certain length IFFT
to use. The longer you pick , the more true the coefficients will be,
but the more difficult it is to compute it. Going straight to the
sinc function gives you ideal coefficients with little computational
difficulty.

The sinc you so admire is infinitely long, requiring even more coefficients than what you get from an IFFT. :-) Simply truncating the sinc results in lousy stop-band attenuation. So you window however many coefficients you decide to use and end up with "Windowed sinc" design. That is good, but there are other methods that are often more effective.

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



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