HBM GEN3i, Руководство пользователя

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Elliptic IIR Filter (Digital Anti
-
Alias)
Passband Stopband
Frequency [kHz]
δp: Passband ripple
δs: Stopband attenuation
ωp:
ωc:
Passband frequency
Corner frequency
Stopband frequency ωs:
ωp=ωc ωs
Magnitude [dB]
1 + δp
1 - δp
δs
Figure A.187: Digital Elliptic IIR Filter
When Elliptic IIR filter is selected, this is always a combination of an analog Butterworth anti
-
alias filter and a digital Elliptic IIR filter.
Analog anti
-
alias filter bandwidth 460 kHz
±
25 kHz (
-
3 dB)
Analog anti
-
alias filter characteristic 7
-
pole Butterworth, extended passband response
Elliptic IIR filter characteristic 7
-
pole Elliptic style IIR
Elliptic IIR filter user selection
Auto tracking for sample rate divided by: 4
(1)
, 10, 20, 40
The user selects a division factor from the current sample rate; software then adjusts the
filter when the sample rate is changed.
Elliptic IIR filter bandwidth (ωc) User selectable from 1 Hz to 250 kHz
Elliptic IIR 0.1 dB passband (ωp)
(2)
DC to ωc
Elliptic IIR filter stopband attenuation (δs) 75 dB
With the Elliptic IIR filter bandwidth selection of ωc = 250 kHz, a peak of
-
60 dB occurs
between 1.8 MHz and 2.2 MHz due to limited analog anti
-
alias filter amplitude reduction.
At lower bandwidth selections, the digital filter reduces this peak to
-
75 dB.
Elliptic IIR filter roll
-
off
72 dB/octave
Frequency [kHz]
Magnitude
[dB
]
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
]
-130
-150
-110
-90
-70
-50
-30
-10
10
-130
-150
-110
-90
-70
-50
-30
-10
10
0.1 1 10 100 1000 10000
Frequency [kHz]
Ma
g
ni
tud
e
[
dB
]
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]
Ma
g
ni
tud
e
[
dB
]
0.1 1 10 100 1000 10000
4 V: Elliptic 200 kHz Passband flatness 4 V: Elliptic 200 kHz overview
2 V: Elliptic 200 kHz overview 2 V: Elliptic 200 kHz Passband flatness
Figure A.188: Representative Elliptic IIR examples
(1) Division by 4 not possible for the 2 MS/s sample rate
(2) Measured using a Fluke 5700A calibrator, DC normalized
GEN3i
606 I3763-3.1 en HBM: public