Tx Power Level Tuning - Nokia RM-57 Service Manual

RM-57/58
RF Troubleshooting and Manual Tuning Guide

Tx power level tuning

Context
Because of variations in the IC process and discrete component values, the actual transmitter RF gain of each
phone is different. Tx power level tuning is used to find out mapping factors called 'power coefficients'. These
factors adjust the GSM transmitter output power to fulfill the required 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 "GSM850/
GSM900".
3. From the Tuning menu, choose "Tx Power Level Tuning".
4. Set Mode to Automatic and Edge to Off.
5. Adjust the spectrum analyzer for power level tuning:
Channel frequency
Span
Sweep time
Trigger
Resolution BW
Video BW
Reference level offset
Reference level
A power meter with a peak power detector can be also used. Remember to take the attenuations into
account!
Issue 1 Company Confidential
Copyright ©2005 Nokia. All Rights Reserved.
GSM850: 836.6MHz
GSM900: 897.4MHz
GSM1800: 1747.8MHz
GSM1900: 1880MHz
0 Hz
2ms
Video triggering (-10dBm)
3MHz
3MHz
sum cable attenuation with module jig
attenuation
33dBm
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