> Does anyone know how a high pass filter is usually implemented? The
High order elliptical filter.
> convolution approach (like the low pass filter) seems like it would be
> expensive and require a lot of extra internal buffering: a 10Hz
You could use a 'sliding fft' approach, see for example Numerical Recipes.
> signal takes 4410 samples to represent one period. To get good
> frequency resolution (so you can tell the difference between the 10Hz
> signal and a 20Hz signal, for example) I would guess your window size
> would have to be at least twice that, or 8820 samples?
A lot more than that, I'm afraid. You need more than 6 dB / octave rolloff.
Ciao,
Segher
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> Mark
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