Creating and Using Math Waveforms
CSA7000 Series, TDS7000 Series, & TDS6000 S eries Instruments User Manual
3- 213
H Suppression Threshold. Random noise in the spectrum may have phase
values over the entire range. This could make the phase display unusable.
However, you can set the suppression threshold control to a level in dB. The
phase of any complex spectral points with a magnitude below this threshold
is set to zero.
H Phase Unwrap Algorithm. The algorithm searches for the largest magnitude
in the current span. Phase unwrap is then performed in both directions in
frequency from that point. This results in a stable phase unwrap.
H Phase Spectrum dejitter. An instrument acquisition system jitters by one
sample interval. Signals at the Nyquist frequency only have two samples per
cycle. This would cause 180_ of phase jitter if it were not corrected. The
instrument phase spectrum is dejittered so that accurate measurements of
phase are obtained from DC to the Nyquist frequency.
--35 dB
0 °
Magnitude vs. frequency
Suppression threshold
Phase vs. frequency
Figure 3- 50: Example of the effects of setting the phase suppr ession threshold
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