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.65:
Digital Bessel IIR Filter
When Bessel IIR filter is selected, this is always a combination of the analog Bessel anti
-
alias filter and a digital Bessel IIR filter.
Analog anti
-
aliasing filter bandwidth
10 MHz
±
1 MHz (
-
3 dB)
Analog anti
-
aliasing filter characteristic
6
-
pole Bessel, optimal step response
Bessel IIR filter characteristic
8
-
pole Bessel style IIR
Bessel IIR filter user selection
User selectable fixed frequencies. If anti
-
aliasing must be prevented, care must be taken to
adapt the selected filter frequency when the sample rate is changed.
Bessel IIR filter bandwidth (ωc)
50 kHz, 100 kHz, 125 kHz, 200 kHz, 250 kHz, 400 kHz, 500 kHz, 1 MHz, 1.25 MHz, 2 MHz ,
2.5 MHz, 4 MHz, 5 MHz; fixed bandwidth selections
Bessel IIR 0.1 dB passband flatness (ωp)
(1)
DC to 250 kHz @ ωc = 5 MHz
Bessel IIR filter stop band attenuation (δs)
60 dB
Bessel IIR filter roll
-
off
48 dB/Octave
Frequency [MHz]
±
2 V Bessel IIR 200 kHz overview
±
2 V Bessel IIR 200 kHz passband flatness
M
a
g
n
it
u
d
e
[dB]
M
a
g
n
it
u
d
e
[dB]
-0.2
-0.15
-0.1
-0.05
0
0.05
0.1
0.15
0.2
0.01
0.1
1
10
100
Frequency [MHz]
0.001
0.01
0.1
1
10
100
1000
-150
-130
-110
-90
-70
-50
-30
-10
10
±
20 V Bessel IIR 200 kHz overview
±
20 V Bessel IIR 200 kHz passband flatness
M
a
g
n
it
u
d
e
[dB]
M
a
g
n
it
u
d
e
[dB]
-0.2
-0.15
-0.1
-0.05
0
0.05
0.1
0.15
0.2
Frequency [MHz]
Frequency [MHz]
0.001
0.01
0.1
1
10
100
1000
-150
-130
-110
-90
-70
-50
-30
-10
10
0.001
0.01
0.1
1
10
100
0.001
M
a
g
n
it
u
d
e
[
%
]
2.33
1.74
1.15
0.57
-0.57
0
0
-1.14
-1.71
-2.28
M
a
g
n
it
u
d
e
[
%
]
2.33
1.74
1.15
0.57
-0.57
-1.14
-1.71
-2.28
Figure A.66:
Representative Bessel IIR examples
(1)
Measured using Fluke 5700A and 5820A calibrators, DC normalized
GEN3i
I3763-3.1 en HBM: public
457
