 Let's summarize these three type of IIR filters (Butterworth, Chebychev
and Inverse Chebychev).
Butterworth IIR Filter has flat frequency response in Pass Band.
Chebychev IIR Filter has some ripple in Pass Band but its slope in Stop
Band is sharp compare to Butterworth.
Inverse Chebychev IIR Filter has ripple in Stop Band but its reduction
ratio never goes higher than the value you specified. And the slope is
relatively sharp.
That's it for this tutorial. If you want good characteristics in Pass Band, Butterworth is fine. If you want sharp cutoff characteristics, Chebychev is fine. Inverse Chebychev might be better if the system consists of quantized data (integers) because its bit length decides the level of floor noise.
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