Elliptic IIR Band Pass Filter (Digital Anti
-
Alias)
High Pass
Stopband
Band Pass
Passband
1 + δp
1 - 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 A.247:
Digital Elliptic IIR Band Pass Filter
When Elliptic IIR filter is selected, this is always a combination of the built
-
in anti
-
alias filter of the Sigma Delta ADC and a digital Elliptic IIR
filter.
Analog anti
-
alias filter
The Sigma Delta ADC anti
-
alias filter
Elliptic IIR band pass filter
Characteristic
12
th
order Elliptic style IIR
User selection
Fixed high pass frequencies to be combined with fixed low pass frequencies
High pass bandwidth (ωhc)
tbd
High pass stopband frequency (ωhs)
Approximately ωhc / 2.5
Low pass bandwidth (ωlc)
tbd
Low pass stopband frequency (ωls)
Approximately 1.5 to 2.5 * ωc
0.1 dB passband flatness (ωp)
(1)
ωhc to ωlc, limited to 7 kHz for
±
1 mV range
High pass stopband attenuation (δhs)
-
90 dB
Low pass stopband attenuation (δls)
-
180 dB (
-
160 dB for
±
1 mV range)
Frequency [kHz]
Magnitude
[dB
]
100
Magnitude [%]
102.33
101.74
101.16
100.58
99.43
98.86
98.29
97.72
100
10
1
0.1
0.01
100
10
1
0.1
0.01
0.2
0.1
0
0.05
0.15
-0.1
-0.15
-0.05
-0.2
Frequency [kHz]
Magnitude
[dB
]
±
1 mV Elliptic band pass 50 Hz - 125 kHz Overview
±
1 mV Elliptic band pass 50 Hz - 125 kHz Passband flatness
±
10 mV Elliptic band pass 50 Hz - 125 kHz Passband flatness
100
Magnitude [%]
102.33
101.74
101.16
100.58
99.43
98.86
98.29
97.72
0.2
0.1
0
0.05
0.15
-0.1
-0.15
-0.05
-0.2
Frequency [kHz]
Magnitude
[dB
]
-160
-140
-120
-100
-80
-60
-40
-20
0.001
0.01
0.1
1
10
100
1000
0
Frequency [kHz]
Magnitude
[dB
]
±
10 mV Elliptic band pass 50 Hz - 125 kHz Overview
-160
-140
-120
-100
-80
-60
-40
-20
0.001
0.01
0.1
1
10
100
1000
0
Figure A.248:
Representative Elliptic IIR band pass examples
(1)
Measured using Fluke 5730A calibrator, DC normalized
GEN3i
I3763-3.1 en HBM: public
659
