NEM-4
Company Confidential
RF Troubleshooting
CCS Technical Documentation
Page 6(b)-100
Copyright
2003 Nokia Corporation.
Issue 1 09/2003
Company Confidential
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
Tuning
Alt-u
RX Calibration
C
Wait until the RX Calibration window pops up.
Select
Band
GSM 900
