HBM Genesis GEN5i User Manual page 361

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 bandwidth
Analog anti alias filter characteristic
Bessel IIR filter characteristic
Bessel IIR filter user selection
Bessel IIR filter bandwidth (ωc)
Bessel IIR passband ripple (δp)
Bessel IIR passband (ωp)
Bessel IIR filter stopband attenuation (δs)
Bessel IIR filter roll-off
I2679-4.0 en
Figure A.24: Digital Bessel IIR Filter
400 kHz ± 25 kHz (-3 dB)
7-pole Bessel, optimal step response
8-pole Bessel style IIR
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
User selectable from 0.4 Hz to 200 kHz
(1)
0.1 dB
DC to 35 kHz @ ωc = 200 kHz
-60 dB
With Bessel IIR filter bandwidth selection ωc = 200 kHz a peak at -55 dB will occur between
1.6 MHz and 1.8 MHz due to limited analog anti alias filter amplitude reduction. At lower
bandwidth selections the digital filter will reduce this peak to -60 dB
-48 dB/octave
(1)
GEN5i
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