Tx Power Level Tuning (Gsm) - Nokia RM-42 Service Manual

RM-42
RF Troubleshooting and Manual Tuning Guide
Next action
Tuning sliders should be close to the center of the scale after the tuning and within the limits specified in the
table below. If they are not within the limits, check Tx IQ quality manually.
GSM900
I DC offset / Q DC
offset
Ampl
Phase
GSM1800/GSM1900
I/Q DC
Ampl
Phase

Tx power level tuning (GSM)

Context
Because of variations at IC process and discrete component values, actual transmitter RF gain of each phone is
different. Tx power level tuning is used to find out mapping factors called 'power coefficients'. These adjust the
GSM transmitter output power to fulfill the specifications.
For EDGE transmission the bias settings of the GSM PA are adjusted in order to improve linearity. This affects
the PA gain and hence the power levels have to be aligned separately for EDGE transmission.
Tx power level tuning has to be performed on all GSM bands.
Steps
1. Connect the phone to a spectrum analyzer.
2. From the dropdown menus, set "Operating mode" to Local, "System mode" to GSM, and Band to GSM900.
3. From the Tuning menu, choose GSM -> Tx Power Level Tuning.
4. Set Mode to Automatic and Edge to Off.
5. Set the spectrum analyzer for power level tuning:
Frequency
9241872 (Issue 1)
Min
-6 -4...+4
-1
85
-6 -0.5...+0.5
-1
95
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Copyright ©2005 Nokia. All Rights Reserved.
Typ
0
90
0
100
channel frequency (897.4MHz GSM900, 1747.8MHz
GSM1800, 1880MHz GSM1900)
Nokia Customer Care
Max
6
1
95
6
1
110
Unit
dB
dB
dB
dB
dB
dB
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