On 30-Mar-10 10:51, Dave Tweed wrote:
>
> I would also point out that in a tone-detection application, in which you only
> care about magnitude and not about phase, the low-pass filtering doesn't need
> to be a separate step. Instead of an IIR low-pass filter at the output, you
> can create an implicit FIR low-pass filter by applying a "window" function
> directly to the sine/cosine coefficients. Essentially, what you then have is
> a pair of narrow quadrature-phase bandpass filters for each frequency, and
> you're measuring the magnitude of their combined outputs (sum of squares).
>
> -- Dave Tweed
>    



     Isn't Goertzel algorithm like that?

     Mark Jordan

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