Path Of The Transmitted Gsm1800/1900 Signal - Nokia NEM-4 Series Troubleshooting Instructions

NEM-4
RF Troubleshooting

Path of the transmitted GSM1800/1900 signal

For easy error tracking it is important to know the signal path of the GSM1800/
GSM1900 transmitter. The components can be grouped into blocks and drawn as shown
below. Note that the picture shows both EGSM transmitter (bottom) and GSM1800/
GSM1900 transmitter (top).
GSM
Dir. Coupler
TX
PCN
TX
PCS
DET
The path of Mjoelner RF ASIC
The balanced TX IQ signal from base band is coming to Mjoelner RF ASIC. The GSM1900
path includes an common RF modulator for GSM1800 and GSM1900. The BB signal is
up-converted with the LO signal corresponding to the wanted TX channel. The GSM1800/
GSM1900 TX output of Mjoelner is a balanced signal.
From the output of Mjoelner the signal is fed through the Balun T701 (Balanced to single
ended) and an 3 dB pad to the PA GSM1800/1900 input.
The path of the PA
The GSM1800/GSM1900 part of the PA has a maximum output of app. 33dBm. The sup-
ply is coming directly from the Battery connectors.
The output is controlled by the power control loop. From the output of the PA the signal
Page 6(b)-84
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