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.73:
Digital Elliptic IIR Band Pass Filter
When Elliptic IIR filter is selected, this is always a combination of the filter built
-
in the Sigma Delta ADC and a digital Elliptic IIR filter.
Analog filter
Characteristic
Sigma delta, optimal frequency response
Low pass bandwidth (ωlc)
80 kHz
±
5 kHz (
-
3 dB)
Elliptic IIR band pass filter
Characteristic
14
th
order Elliptic style IIR
User selection
2 Fixed high pass frequencies to be combined with 4 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
Passband flatness (ωp)
(1)
0.1 dB; 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]
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
0
Magnitude [%]
2.33
1.74
1.15
0.57
-0.57
-1.14
-1.71
-2.28
Figure L.74:
Representative Elliptic IIR band pass examples
(1)
Measured using Fluke 5700A calibrator, DC normalized
GEN3t
I3995-3.1 en HBM: public
1093