User Guide

PAMS
Technical Documentation
NSE–8/9
Troubleshooting
Page 25
Issue 1 07/99
RF Troubleshooting
Measurements should be done using Spectrum Analyzer with
high–frequency 500 ohm passive probe (LO–/reference frequencies and
RF–power levels) and Oscilloscope with a 10:1 probe (DC–voltages and
low frequency signals).
RF–section is mainly build from two ASICS CRFU3 (N600) and SUMMA
(N700), external filters, MMIC PA–modules (N500, N501) and two
synthesizers. For easier troubleshooting, this RF troubleshooting
document is divided into five sections: GSM Receiver, GSM Transmitter,
PCN Receiver, PCN Transmitter and Synthesizer parts. The tolerance is
specified for critical signals/voltages.
Before changing either of the ASIC’s, please check the following things:
The soldering and connections of pins of the ASIC’s are OK, supply
voltages are OK and the signals of the synthesizers are coming to ASIC’s.
This will prevent the unnecessary changing of the ASIC’s.
Please note that the grounding of the PA–module is directly below
PA–module so it is difficult to check. The PA–module is static discharge
sensitive! So ESD protection must be used when dealing with
PA–module (ground straps and ESD soldering irons). The PA’s are class 3
moisture sensitive so parts must be dry bake.
There are still a lot of discrete components (resistors, inductors and
capacitors) which troubleshooting is done just by checking that component
is soldered or it is not missing from PCB.