5-9
C.
“ZERO SPAN” shows a number of parameters from a TDMA
signal including the power of the carrier, the noise floor, and
interference. Fig. 4-5 shows a “ZERO SPAN” 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.
Figure 5-5: Time Domain Signal with No Ingress in “ZERO
SPAN”
A more realistic case is shown in fig. 5-6. This shows that the noise
floor is much higher than in Figure 3. In this case the undesired
signal has increased in power from –43 to –30dBmV. This would
represent a 45 dB “D/U”.