Agilent Technologies E4428C, User Manual

Page: 594 / 700

570 Chapter 16
W-CDMA Uplink Digital Modulation for Receiver Test
W-CDMA Uplink Concepts
The signal generator’s behavior, when
Out Sync
is displayed, depends on the trigger mode used. Table
16-9 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 16-10 on
page 570 shows the specific settings of the DPCCH/DPDCH in compressed mode or PRACH that will turn
the ALC off. Notice that the settings may differ for the mechanical attenuator.
Table 16-9
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.
Table 16-10 Conditions that Turn the ALC Off
Channel Type Electronic Attenuator Mechanical Attenuator
(Option UNB)
PRACH Settings
PRACH Trigger Source Immedi
Trigger
softkey set to Trigger
Message Part
data field set
to AICH
or
PRACH Mode Single Multi
softkey is set to Multi
PRACH Trigger Source Immedi
Trigger
softkey set to Trigger
or
Message Part
data field set
to AICH
or
PRACH Mode Single Multi
softkey is set to Multi
DPCCH/DPDCH Settings not applicable all compressed frames
(no normal frames)