App-31
IM 701210-06E
Appendix
App
GAUSS Filter
Characteristics
• Pass band is flat.
• The attenuation is –3 dB at the cutoff frequency.
Attenuation is equal to –3.0×(f/
fc
)
2
.
• Has linear phase characteristics and constant group delay.
• Only low-pass filter can be specified.
-80
-60
-40
-20
0
fc
-3 dB
-3.0 (f/f
c)
2
dB
GAUSS Frequency Characteristics Example
0 f 0.1 f 0.2 f 0.3 f 0.4 f 0.5 f
dB
(f: sampling frequency [Hz])
Order Table
See below for the GAUSS filter orders.
GAUSS Filter Order
Cutoff frequency 2% 3% 4% 5% 6% 7% 8% 9%
Order 49 33 25 21 17 17 13 13
Cutoff frequency 10% 11% 12% 13% 14% 15% 16% 17%
Order 9 9 9 9 9 9 9 5
Cutoff frequency 18% 19% 20% 21% 22% 23% 24% 25%
Order 5 5 5 5 5 5 5 5
Cutoff frequency 26% 27% 28% 29% 30%
Order 5 5 5 5 5
Computation Delay
The group delay can be derived from the following equation. It is constant and depends
on the filter order.
Group delay = (Filter order – 1)/2
Unit: s/T
s
(where T
s
is the sampling frequency [s])
The computation delay can be derived from the following equation.
Computation delay = {4 + (filter order – 1)/2}×sampling period
However, if the sampling frequency exceeds 100 kHz, it is fixed to 100 kHz (10 µs).
It is also fixed to 100 kHz (10 µs) when in envelope mode.
Appendix 6 DSP Channel Computation (Optional)
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