App-18 IM 701450-01E
Appendix 4 User-Defined Computation
Digital Filter
Type
Type Bandwidth
Gauss Low-pass
Sharp Low-pass, high-pass, and band-pass
IIR (Butterworth) Low-pass, high-pass, and band-pass
Filter Order
See the following table for the filter orders
2% 5% 10% 20% 30% (Cutoff*)
Gauss Low-pass 49 21 9 5 5
Sharp Low-pass 88 36 18 9 8
High-pass 159 65 33 17 13
IIR Low-pass 4 4432
High-pass 4 4443
* The cutoff percentage is with respect to the sample rate.
Filter Characteristics
Filter Pass-band Attenuation Slope Attenuation at Phase
Ripple the Stop-band
Gauss 0 dB * – Linear phase
Sharp ±0.3 dB –40 dB per octave (low-pass), –40 dB Linear phase
–40 dB per octave (high-pass)
IIR 0 dB –5 dB per 1/6 octave (low-pass), Not linear
–20 dB per octave (high-pass) – phase
* For Gaussian filter : –3.0 × (f/fc)
2
dB (f : frequency, fc : cutoff frequency)
Frequency Characteristics of Filters
f: Frequency (Hz)
Gauss (Cutoff 10%) Sharp (Low Pass, Cutoff 10%) IIR (Low Pass, Cutoff 10%)
Note
The higher the filter order the longer it takes for computation.
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