
CCS Technical Documentation
Troubleshooting Instructions RF
NPM-10
Issue 1 03/2003
Nokia Corporation Confidential
Page 15
Troubleshooting Chart for GSM850 Receiver
Figure 8: GSM850 receiver troubleshooting chart
By measuring with an oscilloscope at RXIP or RXQP on a working GSM850 receiver, the
following picture should be seen.
Signal amplitude peak-peak 704 mV
DC offset 1.38 V
Apply -55 dBm
881.6 MHz,
offset 67.71 kHz
from generator to
antenna connector
Oscilloscope at
RX I/Q signal
704 mVpp
DC offset 1.38 V
freq. 67.64 kHz
GSM chain
functional
Check Antenna
switch
at RX 850 Z700
-56 dBm
Oscilloscope
check VANT1 and
VANT2 at Z700
signal 0V
Spectrum analyzer
GSM SAW filter
Z602
output -59 dBm
Spectrum analyzer
Check signal after
inductors L603 and
L602
-59 dBm
Check SAW filter
Z602
Oscilloscope
VRX 2.7 V
check Mjoelner
serial interface
Check inductors
L603, L602
Check Base band
Check
Antenna switch
Check Mjoelner
YES
YES
YES
YES
NO
NO
NO
NO
NO
NO
YES
YES
YES
1
2
3
4
1
2
3
4
5
6