User Guide
Appendix A: RF Troubleshooting
Nokia Customer Care
Company Confidential
Copyright © 2005 Nokia. All rights reserved
A
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GSM1800: C7581, C7584 and L7505
GSM1900: C7523, C7525 and L7506
• Check that components are in place and solder joints are ok
• Use an ohmmeter to check that inductors are conducting DC.
• Replace matching components
3.2.2 Are RX-IQ signal waveforms and levels correct?
• Measurements can be done with an oscilloscope, a probe and signal generator.
• GSM receiver has to be active before RX IQ-signals can be measured. Procedure is explained in
section “GSM RX chain activation for manual measurements”.
• Apply –70 dBm RF signal from a signal generator to the module jig antenna connector and use
following frequencies:
- EGSM900: 942.46771 MHz (Channel 37)
- GSM1800: 1842.86771 MHz (Channel 700)
- GSM1900: 1960.06771 MHz (Channel 661)
• Remember to change correct RX channels also to Phoenix “RF controls” window!
• Check RX I and RX Q -signals in following test points:
- RX I (positive): Connect the probe to test point J7508
- RX I (negative): Connect the probe to test point J7509
- RX Q (positive): Connect the probe to test point J7510
- RX Q (negative): Connect the probe to test point J7511
• The correct RX IQ-signal is shown in figure
6.5.6 "GSM RX IQ (DC Offset 0.4 V)". Level of all four IQ-
signals should be about the same and RX IQ-signal frequency should be 67.71 kHz (lower detail
figure). The phase shift between I- and Q-signals should be 90 degrees.
3.2.2.1 RF operating voltage VBAT_ASIC ok?
• See section
“RF operating voltage VBAT_ASIC ok?”
3.2.2.2 RFBUS signals ok?
• GSM receiver has to be active before RFBUS signals can be measured. Procedure is explained in
section “GSM RX chain activation for manual measurements”. Also WCDMA/GSM transmitter and
WCDMA receiver activation can be used for the measurement but then RFBUS -signals don’t
necessarily look like in figures mentioned below.
• Measurements can be performed with an oscilloscope and a probe. Check all five RF BUS signals:
- RFBUSDAT: Connect the probe to J7504. Typical RFBUSDAT -signal is shown in figures in section
6.5.9.3 “RFBUSDAT (GSM RX)”.