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Elliptic IIR Band Pass Filter (Digital Anti
-
Alias)
High Pass
Stopband Band Pass
Passband
+δp
-δp
-δs
ω
ls
Low Pass
Stopband
ω
hp = hc
ω
lp
=
lc
ω
hs
ω ω
Frequency [kHz]
Magnitude [dB]
δp: Passband ripple
δs: Stopband attenuation
ωp:
ωc:
Passband frequency
Corner frequency
Stopband frequency
ωs:
Figure L.55: Digital Elliptic IIR Band Pass Filter
When Elliptic IIR filter is selected, this is always a combination of the anti
-
alias filter built
-
in the Sigma Delta ADC and a digital Elliptic IIR filter.
Analog anti
-
alias filter
Characteristic Sigma delta, optimal frequency response
-
3 dB low pass bandwidth (ωlc) 100 kHz
±
5 kHz for sample rates 250 kS/s and 125 kS/s
80 kHz
±
5 kHz for all other sample rates
Elliptic IIR band pass filter
Characteristic
14
th
order Elliptic style IIR
User selection Two fixed high pass frequencies to be combined with four fixed low pass frequencies
High pass bandwidth (ωhc) 40 Hz and 100 Hz
High pass stopband frequency (ωhs) Approximately ωhc / 2.5
Low pass bandwidth (ωlc) 2 kHz, 20 kHz, 40 kHz and 50 kHz
Low pass stopband frequency (ωs) Approximately 1.5 to 2.5 * ωc
0.1 dB passband flatness (ωp)
(1) ωhc to ωlc or maximum 10 kHz
Stopband attenuation (δs) 80 dB
Frequency [kHz]
100 10 1 0.1 0.01
100 1000 10 1 0.1 0.01
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
1000 100 10 1 0.1 0.01
1000 100 10 1 0.1 0.01
±1 V Elliptic IIR band pass 40 Hz to 50 kHz Overview ±1 V Elliptic IIR band pass 40 Hz to 50 kHz Passband flatness
±10 V
Elliptic IIR band pass 40 Hz to 50 kHz Overview ±10 V Elliptic IIR band pass 40 Hz to 50 kHz Passband flatness
0
Magnitude [%]
2.33
1.74
1.15
0.57
-0.57
-1.14
-1.71
-2.28
Frequency [kHz] Frequency [kHz]
Magn
itude [d
B]
-150
-130
-110
-90
-70
-50
-30
-10
10
Magn
itude [d
B]
-0.2
-0.15
-0.1
-0.05
0
0.05
0.1
0.15
0.2
0
Magn
itude [%
]
2.33
1.74
1.15
0.57
-0.57
-1.14
-1.71
-2.28
Figure L.56: Representative Elliptic IIR band pass examples
(1) Measured using Fluke 5700A calibrator, DC normalized
GEN3i
I3763-3.1 en HBM: public 1107