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Chapter 15 453
W-CDMA Uplink Digital Modulation for Receiver Test
W-CDMA Uplink Concepts
The signal generator checks the timing difference between the external trigger and the
internal frame timing whenever an external trigger is received. If the single trigger mode is
selected, the signal generator checks the timing difference between the external trigger and
the internal frame timing when the first trigger is received. If continuous trigger mode is
selected, timing is checked at each trigger signal. If there is a timing difference in either
mode, then the Out Sync annunciator is displayed.
The signal generator’s behavior, when Out Sync is displayed, depends on the trigger mode
used. Table 15-9 describes the signal generator’s behavior for different trigger modes.
Special Power Control Considerations When Using DPCCH/DPDCH
in Compressed Mode or PRACH
When using either DPCCH/DPDCH in compressed mode or PRACH, more than a single
power level is required. In addition to the rapidly varying power levels for these two channels,
there are also periods of discontinuous transmission (gaps where no RF is transmitted).
Under these conditions, the automatic level control (ALC) will try to counteract the rapid
power variations. To prevent this, the signal generator employs ALC hold mode. However,
even with ALC hold active, if the RF gap is longer than five seconds, the output level may drift
significantly. Under certain conditions, such as waiting for an input trigger, the length of the
RF gap is unpredictable. Under these conditions, the signal generator turns the ALC off. Table
15-10 on page 454 shows the specific settings of the DPCCH/DPDCH in compressed mode or
Table 15-9
Trigger
Mode
ESG output signal status on Out Sync.
Single The ESG outputs frames even if Out Sync is displayed.
Continuous The ESG output is discontinued. The synchronization is corrupt and no
output is available when Out Sync is displayed. The ESG timing is
retriggered by the external trigger when this occurs.
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