User Guide

Issue 2 10/2004 COMPANY CONFIDENTIAL 17
Copyright © 2004 Nokia. All Rights Reserved.
NHL-12
7 - RF Description & Troubleshooting Nokia Customer Care
Troubleshooting diagram for GSM1800 receiver
Phone in “Continuous” mode, AGC setting “12”.
Yes
No
Yes
No
Yes
Yes
Yes
NoNo
Yes
Yes
NoNoYesNoYes
Apply –90dBm
1842.86771MHz signal
from generator to anten-
na connector
Oscilloscope at RX_I
Signal 140mVpp
DC offset 1.35V ***
Frequency 67.7kHz
Change ge-
nerator level
to –50dBm
Spectrum analyzer
Antenna switch out-
puts,
1800 LNA out
–61 dBm
Spectrum analyzer
Antenna switch input
-84 dBm
GSM1800 RX chain
functional
Oscilloscope
VR1 4.8V and VR3..6 2.8V
Check HELGO serial
interface
(burst mode)
Check L7102, L7103,
Z7102
C837,
V801
Oscilloscope
VANT_1...3 0V
Oscilloscope
Check HELGO se-
rial interface
(burst mode)
Check HELGO
N7300
Check Base-
band
* Spectrum analyzer
reading with 1 kohm
passive probe (right val-
ue add +26 dB)
All spectrum analyzer reading
values are measured with 1
kohm passive probe (use
tweezers to connect the
probe ground to the nearest
PWB ground). Reading value
is represented without +26
dB compensation.
Check X7100,
C7103
Check Antenna
switch Z7100
Spectrum analyzer
HELGO inputs
GSM 1800
–88 dBm
Check Base-
band
No
Synthesizer trou-
bleshooting
Spectrum analyzer
4G VCO out
3685.6MHz
∼–30 dBm (*
Yes
Check HELGO
N7300
* ** DC–level of RXI/RXQ in
continuous mode will decrease
slowly.
The original level can be resto-
red by rewriting gain set.
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