Nokia NEM-4 Series Troubleshooting Instructions page 84

NEM-4
RF Troubleshooting
GSM
Dir. Coupler
TX
PCN
TX
PCS
DET
EGSM900 TX path of Mjoelner RF ASIC
The balanced TX IQ signal is provided by the base band and is coming to the Mjoelner RF
ASIC. The TX paths of the Mjoelner RF ASIC include mainly two RF modulators for up-
conversion of the base band signals, one for EGSM900 and one common for GSM1800/
GSM1900. The base band signal is modulated with the LO signal corresponding to the
wanted TX channel. The GSM TX output of the Mjoelner RF ASIC is a balanced signal.
From the output of the Mjoelner RFASIC the signal is fed through the EGSM TX SAW fil-
ter (balanced to single-ended), a 900MHz buffer, and a 5-db pad to the PA EGSM input.
EGSM900 TX path of the Power Amplifier (PA)
The PA EGSM900 part has a maximum output power of app. 35dBm. Voltage supply is
coming directly from the Battery connectors.
The EGSM900 output is controlled by the power control loop. From the EGSM900 output
of the PA the RF signal is fed through the directional coupler (one of the power control
loop components) to the antenna switch.
Page 6(b)-80
Company Confidential
VANTL / VANTM / VANTH
3
VB_DET
VTXLOL
VTXLOH
VTXBH
VTXBL
PCN/PCS
OUTHP
Balun
OUTHM
PA
VTX
SAW
Buffer
OUTLP
OUTLM
EGSM
DET
PW-
PLFB1
loop
PLFB2
filter
VPCH/VPCL
PA_IDENT
VBATTRF
Copyright  2003 Nokia Corporation.
Company Confidential
CCS Technical Documentation
VDDDIG
RF
Controls
VDDRXBB
RF
Controls
2
Open
collector
Open
collector
PWC
2
Supply
filter
VR2
TXP TXC
1/2 1/4
2 2 2
Mjølner
2 2
Issue 1 09/2003