Nokia NEM-4 Series Troubleshooting Instructions page 104

NEM-4
RF Troubleshooting
A value (RF_TEMP), which represents the RF hardware temperature, is determined during
RX Calibration. This temperature value is used by DSP to RSSI reporting in Normal mode
of the phone. It is not visible in the calibration process.
AGC-calibration:
The AGC-calibration finds the gain values of the RX-gain system.
The AGC consists of RF LNA, which can be either on or off (gain difference between on
and off state is nominally 30dB) and BB gain which can be controlled in 6dB steps. This
gives 15 gain steps RSSI0 to RSSI14. LNA is off for steps RSSI0 to RSSI4.
AGC-calibration measures the gain at gain step RSSI4 and RSSI7. The other gain values
are calculated.
VCXO-calibration:
The VCXO-calibration ensures the function of an initial synchronization (before location
update is done) when the mobile station is in Normal mode. For an error free initial syn-
chronization, the 26MHz frequency of the VCXO must be accurate enough. Therefore, a
VCXO cal value is written into the RefOSCCAL register of the Mjoelner.
During VCXO-calibration, the VCXO cal value is changed by a DSP-algorithm until a syn-
chronization is possible. This means the VCXO oscillates at 26 MHz with a sufficient min-
imum frequency error.
To further minimize the frequency error, an initial AFC value is determined by the DSP
and written into RefOSCAFC register of the Mjoelner.
Also the DSP algorithm determines 3 AFC slope coefficients Slope C1...3 during VCXO
calibration. One AFC slope value is not sufficient for Mjoelner F3, because the AFC slope
is non-linear in this chip.
EGSM
Set operating mode to local mode
Select
Wait until the RX Calibration window pops up.
Select
Page 6(b)-100
Company Confidential
Tuning
RX Calibration
Band
Copyright  2003 Nokia Corporation.
Company Confidential
CCS Technical Documentation
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GSM 900
Issue 1 09/2003