HDO9000 High Definition Oscilloscopes Operator's Manual
Blackman-Harris) provide maximum amplitude at the expense of frequency resolution, whereas
Hamming and Von Hann are good for general purpose use with continuous waveforms.
Window Type
Applications and Limitations
Rectangular
Normally used when the signal is transient (completely contained in the time-domain window)
or known to have a fundamental frequency component that is an integer multiple of the fun-
damental frequency of the window. Signals other than these types will show varying amounts of
spectral leakage and scallop loss, which can be corrected by selecting another type of window.
Hanning (Von Hann)
Reduces leakage and improves amplitude accuracy. However, frequency resolution is also
reduced.
Hamming
Reduces leakage and improves amplitude accuracy. However, frequency resolution is also
reduced.
Flat Top
Provides excellent amplitude accuracy with moderate reduction of leakage, but with reduced
frequency resolution.
Blackman-Harris
Reduces leakage to a minimum, but with reduced frequency resolution.
FFT Window Filter Parameters
Window Type
Highest Side Lobe
(dB)
Scallop Loss (dB)
ENBW
(bins)
Coherent Gain (dB)
Rectangular
-13
3.92
1.0
0.0
Von Hann
-32
1.42
1.5
-6.02
Hamming
-43
1.78
1.37
-5.35
Flat Top
-44
0.01
3.43
-11.05
Blackman-Harris
-67
1.13
1.71
-7.53
Interpolate Function
Linear interpolation, which inserts a straight line between sample points, is best used to reconstruct
straight-edged signals such as square waves. This is the default interpolation method used by the
oscilloscope.
(Sinx)/x interpolation, on the other hand, is suitable for reconstructing curved or irregular waveshapes,
especially when the sampling rate is 3 to 5 times the system bandwidth.
Cubic interpolation can be used to create a smooth, continuous function by applying a third-degree
polynomial.
For each method, you can select an upsample factor of 2 to 50 points to insert between samples.
1. Follow the usual steps to
, selecting
Interpolate
from the
Filter
submenu.
2. Touch
Algorithm
and select an interpolation type.
3. Enter the
Upsample
factor by which to increase sampling.
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