
454 Chapter 15
W-CDMA Uplink Digital Modulation for Receiver Test
W-CDMA Uplink Concepts
PRACH that will turn the ALC off. Notice that the settings may differ for the mechanical
attenuator.
When one of the conditions listed in Table 15-10 turns the ALC off, a manual power search
must be performed in order to ensure the correct output power level. Pressing the
Apply
Channel Setup
softkey executes the manual power search function. Temperature changes or
changes to certain signal generator settings may cause the output power level to change over
time. Even though the Apply Needed annunciator may be off, it is recommended that you
press
Apply Channel Setup to perform a manual power search at least every hour to maintain
the correct output power level.
W-CDMA AWGN Measurements and Bandwidths
The AWGN (additive white Gaussian noise) feature produces a noise signal across a
7.68 MHz bandwidth (2x the W-CDMA 3.84 MHz bandwidth) and lets you enter values that
adjust the noise level across this spectrum. To resolve the noise signal’s effect on the W-CDMA
signal, the ESG also displays noise values across the W-CDMA 3.84 MHz bandwidth. In
addition, the DPCH AWGN feature shows the bandwidth of the noise signal during the period
when it has a flat frequency response. This is called the flat-noise bandwidth. Figure 15-72
shows the different noise settings/values as they appear on the W-CDMA AWGN display along
with a graphical representation of the noise signal showing the different bandwidth features.
Table 15-10 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)
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