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Bessel IIR Filter (Digital Anti
-
Alias)
δs
ωp ωs
Passband Stopband
δp : Passband ripple
δs: Stopband attenuation
ωp
ωc
ωs
: Passband frequency
: Corner frequency
: Stopband frequency
Frequency [kHz]
Magnitude [dB]
ωc
1 + δp
1 - δp
-3 dB
Figure A.72: Digital Bessel IIR filter
When Bessel IIR filter is selected, this is always a combination of an analog Bessel anti
-
alias filter and a digital Bessel IIR filter
Analog anti
-
alias filter
Characteristic
7
-
pole Bessel, optimal step response
Bandwidth 185 kHz
±
20 kHz (
-
3dB) All Ranges < 200 mV
220 kHz
±
20 kHz (
-
3 dB) All Ranges ≥ 200 mV
Digital Bessel IIR filter
Characteristic 6
-
pole Bessel style IIR
User selection Auto tracking for sample rate divided by: 10, 20, 40, 100
User selects divide factor, software then adjusts filter when sample rate is changed
Bandwidth (ωc) User selectable from 0.0125 Hz to 20 kHz
0.1 dB passband flatness (ωp)
(1) DC to 2 kHz
Stopband attenuation (δs) 60 dB
Roll
-
off
36 db/Octave
Frequency [kHz]
1000 100 10 1 0.1
Frequency [kHz]
Magnitude [dB]
-150
-130
-110
-90
-70
-50
-30
-10
10
Magnitude [dB]
-0.2
-0.15
-0.1
-0.05
0
0.05
0.1
0.15
0.2
10000 1000 100 10
1
0.1
±20 mV Bessel IIR 20 kHz Overview
±20 mV Bessel IIR 20 kHz Passband flatness
0
Magnitude [%]
2.33
1.74
1.15
0.57
-0.57
-1.14
-1.71
-2.28
Frequency [kHz]
Magnitude [dB]
-150
-130
-110
-90
-70
-50
-30
-10
10
10000 1000 100 10 1 0.1
±1 V Bessel IIR 20 kHz Overview
1000 100 10 1 0.1
Frequency [kHz]
Magnitude [dB]
-0.2
-0.15
-0.1
-0.05
0
0.05
0.1
0.15
0.2
±1 V
Bessel IIR 20 kHz Passband flatness
0
Magnitude [%]
2.33
1.74
1.15
0.57
-0.57
-1.14
-1.71
-2.28
Figure A.73: Representative Bessel IIR examples
(1) Measured using a Fluke 5700 calibrator, DC normalized
GEN3i
I3763-3.1 en HBM: public 471