FIR (Fc @
-
3 dB) Filter (Digital Anti
-
Alias)
Passband
Stopband
δp : Passband ripple
δs : Stopband attenuation
ωp
ωc
ωs
: Passband frequency
: Corner frequency
: Stopband frequency
-3 dB
Frequency [kHz]
Magnitude [dB]
+ δp
- δp
δs
ωp
ωs
ωc
Figure L.42:
Digital FIR (Fc @
-
3 dB) filter
When FIR (Fc @
-
3 dB) filter is selected, this is always a combination of an analog Butterworth anti
-
alias filter and a digital FIR (Fc @
-
3 dB)
filter. The FIR (Fc @
-
3 dB) is an adapted FIR filter. Its ωp is reduced by a factor of ≈1.4 compared to the FIR (Fc @
-
0.1 dB) filter. It is supported
by Perception V6.40 and higher.
Analog anti
-
aliasing filter bandwidth
370 kHz
±
20 kHz (
-
3 dB)
Analog anti
-
aliasing filter characteristic
7
-
pole Butterworth, extended passband response
FIR (Fc @
-
3 dB) filter characteristic
12
-
pole FIR; FIR is a purely digital characteristic. Its closest analog resemblance is to an
Elliptic filter. However, FIR has both overshoot and pre
-
shoot on the step response. This
means that the ringing on the signal starts before the step input is started and that the ringing
continues after the step input is complete.
FIR (Fc @
-
3 dB) filter user selection
Auto tracking for sample rate divided by: 4, 10, 20, 40
FIR (Fc @
-
3 dB) filter bandwidth (ωc)
Auto tracking the sample rate with the selected FIR (Fc @
-
3 dB) filter; user selection from
0.031 Hz to 50 kHz
FIR (Fc @
-
3 dB) filter passband flatness (ωp)
(1)
0.1 dB; DC to ≈ωc/1.4 (Adapted FIR filter behavior)
FIR (Fc @
-
3 dB) filter stopband attenuation (δs)
60 dB
FIR (Fc @
-
3 dB) filter roll
-
off
72 dB/Octave
FIR (Fc @ -3 dB) 50 kHz Overview
10
0
-10
-20
-30
-40
-50
-60
-70
-80
Frequency [kHz]
Ma
gni
tu
de
[dB
]
Passband flatness
Frequency [kHz]
Ma
gni
tu
de
[dB
]
0.2
0.1
0.05
0.15
-0.1
-0.15
-0.05
-0.2
0
10000
1000
100
10
1
0.1
1000
100
10
1
0.1
Figure L.43:
Representative FIR examples
(1)
Measured using a Fluke 5700 calibrator, DC normalized
GEN3i
I3763-3.1 en HBM: public
1089
