Mohr CT100B Series - Cursors

5. Math Functions
5.5.4. Time-Domain Gating, or Return Loss (S
11
) Between Cursors
The CT100B is able to use time-domain gating (also called time windowing) to isolate features in
the time-domain trace for analysis in the frequency domain using the S
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Between Cursors feature.
All other time-domain features are excluded from the analysis so that only the feature of interest is
analyzed. To perform Between Cursors return loss, use the following procedure:
1. Create an S
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return loss plot using the procedure as described in Section 5.4.
2. Use the SELECT button to select a TDR trace.
3. Position the cursors around the feature of interest (e.g., a fault or connector).
4. Select the S
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Options menu, then toggle Between Cursors to On. The S
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trace may change
to reflect just the features in the highlighted time-domain cursor interval.
5. Pressing the Between Cursors On menu option again will change it to Between Cursors Hold,
which will keep the time-domain region fixed while moving the time-domain cursors.
Otherwise, you may select the S
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trace to make frequency-domain measurements using the
cursors without changing the time-domain windowing.
See Figure 5.5 through Figure 5.7 for an example of an S
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return loss plot between cursors. The
cursors bracket an SMA barrel adapter between two 3 ft. segments of coaxial cable. The S
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return
loss plot shows average 34.3 dB loss across the connector. A loosened connector shows average loss
of 26.7 dB across the connector, compatible with 7.7 dB excess return loss compared with the
tightened connector.
Figure 5.5. S
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between cursors bracketing an SMA barrel adapter on the TDR trace.
CT100B TDR Cable Analyzers Operator’s Manual 83