 Save the coefficients again and see them. You may notice a0 and a2 is very
small value. These make the response worse.
That's because the resolution is not enough for this sort of IIR filter
that has low cutoff frequencies. Let's change it to quantize by 23-bits.
Then see the response again. That's in very good shape!!
That's it for this tutorial. If the cutoff frequency is very low compare to the sampling frequency, for instance 10Hz/22050Hz = 0.045%, the resolution needs 23-bits to quantize coefficients.
|