Acquisition Control 12
Agilent InfiniiVision 3000 X-Series Oscilloscopes User's Guide 189
So, in practice, an oscilloscope's sample rate should be four or more times
its bandwidth: f
S
= 4f
BW
. This way, there is less aliasing, and aliased
frequency components have a greater amount of attenuation.
See Also Evaluating Oscilloscope Sample Rates vs. Sampling Fidelity: How to
Make the Most Accurate Digital Measurements, Agilent Application Note
1587 ("http://cp.literature.agilent.com/litweb/pdf/5989- 5732EN.pdf")
Oscilloscope Rise Time
Closely related to an oscilloscope's bandwidth specification is its rise time
specification. Oscilloscopes with a Gaussian- type frequency response have
an approximate rise time of 0.35/f
BW
based on a 10% to 90% criterion.
An oscilloscope's rise time is not the fastest edge speed that the
oscilloscope can accurately measure. It is the fastest edge speed the
oscilloscope can possibly produce.
Figure 35 Sample Rate and Oscilloscope Bandwidth
Limiting oscilloscope bandwidth (f
BW
) to 1/4 the sample rate (f
S
/4)
reduces frequency components above the Nyquist frequency (f
N).
f
S
f
N
f
S
/4
-3dB
Attenuation
Aliased frequency
components
Frequency
0dB
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