App-33
IM 701210-06E
Appendix
App
IIR (Butterworth) Filter
Characteristics
• Low-pass and high-pass.
• 4th order Butterworth filter. Attenuation is approximately –24 dB/OCT.
• Pass band is flat.
• The attenuation falls to –3 dB at the cutoff frequency.
• Has non-linear phase characteristics.
• Lower frequencies can be specified as compared to other FIR filters.
-80
-60
-40
-20
0
fc
-3 dB
-24 dB
2f
c
IIR (Butterworth) Low-pass Frequency Characteristics Example
0 f 0.1 f 0.2 f 0.3 f 0.4 f 0.5 f
dB
-80
-60
-40
-20
0
f
c
1/2 f
c
-3 dB
-24 dB
IIR (Butterworth) High-pass Frequency Characteristics Example
0 f 0.1 f 0.2 f 0.3 f 0.4 f 0.5 f
dB
(f: sampling frequency [Hz])
Appendix 6 DSP Channel Computation (Optional)
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