Chapter 4
Theory of Operation
SCXI-1141/1142/1143 User Manual
4-12
ni.com
The most common effect of phase nonlinearity is ringing in response to a
step input. As Figure 4-9 shows, the SCXI-1141 elliptic filter exhibits the
most overshoot and ringing and the SCXI-1142 Bessel filter has no
overshoot or ringing. The SCXI-1143 module Butterworth filter has a step
response that is a compromise between the SCXI-1141 module and the
SCXI-1142 module. The SCXI-1143 module filter has an overshoot, but it
has less ringing than the SCXI-1141. You should consider the step response
if the intended application is sensitive to overshoot or ringing. See
Table A-1,
Settling Time with Respect to Cutoff Frequency
, for detailed
settling specifications. Additionally, use care when selecting gain settings
to assure that the input signal plus any overshoot voltage result in an output
signal within the
±
5 V range of the SCXI-1141/1142/1143 module.
Figure 4-9.
Unit Step Response of the SCXI-1141/1142/1143 Module
0
2
4
6
8
10
0
0.2
0.4
0.6
0.8
1
1.2
1.4
Time (seconds)
Bessel (1142)
Butterworth (1143)
Elliptic (1141)
Output
Voltage
(V)
