Rigol DS1102/4B User Manual page 45

Selecting an FFT Window
DS1000B series oscilloscope provides four FFT windows. Each window is a trade-off
between frequency resolution and amplitude accuracy. It depends on the desired
measurement and the source signals characteristics to determine the window to use.
Use the following guidelines to select the best window.
Table 2-9 FFT Windows
Window
Best frequency resolution
and worst amplitude
accuracy.
Rectangle
This is essentially the same
as no window.
Hanning Better frequency resolution,
poorer amplitude accuracy
than Rectangular.
Hamming Hamming has slightly better
frequency resolution than
Hanning.
Best amplitude accuracy,
Blackman
worst frequency resolution.
Key points:
FFT Resolution: The FFT resolution is the quotient between sampling rate and
the number of FFT points. With a fixed FFT points, the lower sampling rate, the
better the resolution.
Nyquist Frequency
The highest frequency that any real-time digitizing oscilloscope can acquire
without aliasing. It's normally half of the sample rate. This frequency is called
the Nyquist frequency. Frequency above the Nyquist frequency will be under
sampled, causing a situation known as aliasing.
© 2008 RIGOL Technologies, Inc.
Features
Transients or bursts, the signal
levels before and after the event
are nearly equal.
Equal-amplitude sine waves with
fixed frequencies.
Broadband random noise with a
relatively slow varying spectrum.
Sine, periodic, and narrow-band
random noise.
Transients or bursts where the
signal levels before and after the
events are significantly different.
Single frequency waveforms, to
find higher order harmonics.
User's Guide for DS1000B Series
Best for measuring
RIGOL
2-17