Reverse Path Troubleshooting: Evaluating TDMA Return Path Signals
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viewing TDMA signals. This will allow the capture of the TDMA events for
analysis.
Zero Span mode shows a number of parameters from a TDMA signal,
including the power of the carrier, the noise floor, and interference. Fig. 5-5
shows the Zero Span display of a TDMA signal with an ideal noise floor. The
“D” marker shows the power of the TDMA desired signal. The “U” marker
shows the power of the undesired or noise floor. Very seldom are 56 dB
desired to undesired (“D/U”) ratios achieved.
Fig. 5-5 Time Domain Signal with No Ingress in Zero Span
A more realistic case is shown in Figure 5-6. This shows that the noise floor
is much higher than in Fig. 5-5. In this case the undesired signal has
increased in power from –43 to –30dBmV. This would represent a 45 dB
“D/U”.
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