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Nokia Customer Care
7 - RF Description and Troubleshooting
Company Confidential
RH-47
Issue 1 05/04
Copyright
©
2004 Nokia Corporation
Page 23
Company Confidential
2 Check if SNR reading is OK.
Use an Oscilloscope to check levels of “RXIINN” and “RXQINN”.
If RX and TX path seem to be faulty it has to be checked if the synthesizer is working. If
yes, then check the path from the antenna test pad J800 to the antenna switch Z601
(see RX troubleshooting "Check RXTX switch").
Rx signal paths
The signal paths of the receiver are shown in following block diagram. Note that the dia-
gram shows GSM850 receiver (above) and the GSM1900 receiver (below).
Apply -80dBm signal
from Generator
to Antenna Connector
phone: local, burst mode
Rx chain
functional
RX calibration
Yes
No
GSM, PCS
RSSI reading
-80dBm
all bands
?
Yes
No
Calibration.
within
limits
?
Yes
No
SNR measurement
all bands
o.k.
?
Apply -92dBm signal
from Generator
to Antenna Connector
phone: local, burst mode
RSSI
and SNR
wrong in both
bands
?
No
Change signal level
to -60dBm
phone: local,
continous mode
SA
Z601
EGSMout
-76dBm
Yes
No
SA
Z601
Rx output
(850 &1900)
> -67dBm
?
SA
Z601
EGSMout
-76dBm
Yes
No
SA
Z604,Z603
SAWout
both lines
>-72dBm
?
Change
Z604, Z603
Check
RxTx Switch
Change
Z601
Yes
SA
Z601
EGSMout
-76dBm
No
Osci:
RF-BB
serial
Interface
o.k.
?
Yes
SA
Z601
EGSMout
-76dBm
No
Osci:
RX I/Q
level
o.k.
?
Change
Mjolner
Yes
BB Error
Check UEM
Check
SAW
SA
Z601
EGSMout
-76dBm
No
Osci:
LNA
base voltage
= 0.8V
?
Change
Mjoelner
Check
LNA
SA
Z601
EGSMout
-76dBm
Yes
No
Osci:
LNA bias
(VR4)
=2.8V
?
Check
C620, C632
and
BB (UEM)
Yes
SA
Z601
EGSMout
-76dBm
No
Osci:
RX -BB bias
(VR4)
=2.8V
?
Check
C871
and
BB (UEM)
Check
Bias
Check
Bias
= to be done in all 3 bands
= to be done in
defective band only
= to be done only once
(common for all bands)
BB Error
Check UPP
Make sure that
Synthesiser
is working
Yes
Note: RF levels given in that chart are dependent on RF probe and must be validated with a known good sample
GSM, PCS