Creating and Using Math Waveforms
TDS5000 Series User Manual
3- 171
Tek Exponential Window: The Tek Exponential window was invented at
Tektronix. In the time domain, it is not a symmetrical bell shape as is the case
with the other windows. Instead, it is exponential with a peak at the 20%
position of the time domain gate. The frequency domain shape is triangular. Use
this window for impulse response testing where the 20% position is the zero
phase reference point. More of the acquired data record length is used to capture
the impulse response. Exact details of how to compute its values were published
in the article, Impulse-response testing lets a single test do the work of thousands
by John Pickerd in EDN magazine, April 27, 1995, page 95.
1
0
Amplitude
Time
--67 dB side lobe
0
-- 8 0
dB
Frequency bins
-- 4 0
Figure 3- 57: Tek Exponential window in the time and the frequency domains
Effects of trigger jitter. The oscilloscope acquisition system has a sample clock
that is asynchronous with respect to the input signal. This means that from one
acquisition to the next, samples may be in a different position on the waveform
with respect to the trigger. Samples may vary in position by up to one sample
interval.
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