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.241:
Representative Bessel IIR examples
When Bessel IIR filter is selected, this is always a combination of the anti
-
alias filter built
-
in the Sigma Delta ADC and a digital Bessel IIR filter.
Analog anti
-
alias filter
The Sigma Delta ADC anti
-
alias filter
Bessel IIR filter
Characteristic
12
-
pole Bessel style IIR
User selection
Auto tracking to sample rate divided by: 10, 20, 40, 100
User selects divide factor from current sample rate, software then adjusts filter when sample
rate is changed
Bandwidth (ωc)
User selectable from 1 Hz to 50 kHz
0.1 dB passband flatness (ωp)
(1)
DC to 0.18 * ωc. Limited to 6 kHz for
±
1 mV range
Stopband
-
180 dB (
-
160 dB for
±
1 mV range)
Roll
-
off
-
72 dB/octave
Frequency [kHz]
Frequency [kHz]
Magnitude
[dB
]
Magnitude
[dB
]
100
Magnitude [%]
102.33
101.74
101.16
100.58
99.43
98.86
98.29
97.72
1000
100
10
1
0.1
0.2
0.1
0
0.05
0.15
-0.1
-0.15
-0.05
-0.2
Frequency [kHz]
Magnitude
[dB
]
±
1 mV Bessel 50 kHz Overview
±
1 mV Bessel 50 kHz Passband flatness
100
Magnitude [%]
102.33
101.74
101.16
100.58
99.43
98.86
98.29
97.72
1000
100
10
1
0.1
0.2
0.1
0
0.05
0.15
-0.1
-0.15
-0.05
-0.2
Frequency [kHz]
Magnitude
[dB
]
-160
-140
-120
-100
-80
-60
-40
-20
0
0.1
1
10
100
1000
±
10 V Bessel 50 kHz Overview
±
10 V Bessel 50 kHz Passband flatness
-160
-140
-120
-100
-80
-60
-40
-20
0
0.1
1
10
100
1000
Figure A.242:
Representative Bessel IIR examples
(1)
Measured using Fluke 5730A calibrator, DC normalized
GEN3i
656
I3763-3.1 en HBM: public
