National Instruments USB-9233 - Alias-Free Bandwidth

© National Instruments Corporation 13 NI USB-9233 User Guide and Specifications
Figure 11. Phase Nonlinearity
Stopband
The filter significantly attenuates all signals above the stopband frequency.
The primary goal of the filter is to prevent aliasing. Therefore, the stopband
frequency scales precisely with the data rate. The stopband rejection is the
minimum amount of attenuation applied by the filter to all signals with
frequencies that would be aliased into the alias-free bandwidth.
Alias-Free Bandwidth
Any signal that appears in the alias-free bandwidth of the NI USB-9233
is not an aliased artifact of signals at a higher frequency. The alias-free
bandwidth is defined by the ability of the filter to reject frequencies above
the stopband frequency and equals the data rate minus the stopband
frequency.
0.450.15
4
2
0
–2
–4
0.100.050.00 0.400.350.300.250.20
Data Rate
Signal Frequency
Data Rate (f
s)
≤ 25 kS/s
Phase Error (degrees)
Data Rate
> 25 kS/s