Peak Filter Ringing Near Nyquist

1

Hey – I’ve noticed that an IIR peak filter with a gain of 36db near nyquist produces a pretty undesirable ringing effect.

Is there any guidelines as to why – and if there’s any remedy? @IvanC perhaps you know?

Thanks,

J

2

Due to the bilinear transform, the actual Q factor will be exaggerated closer to nyquist (with typical cookbook filter designs). As a result you get heavy ringing.

You could use oversampling (if you can/want to afford it, 4x should be fine) as a simple way to get rid of it. Or use a different filter design method such as matched-z.

IIRC, this is probably a good starting point for the latter:

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Awesome paper thank you !