Troubleshooting The Gps Rf; Limitations; Gps Receiver; General Instructions - Nokia NPD-4 Series Troubleshooting - Gps

CCS Technical Documentation

Troubleshooting the GPS RF

The purpose of this section is to define GPS test limits on the product line and to guide
the GPS RF troubleshooting.

Limitations

Measurements should be done using High-Frequency Probe with spectrum analyzer in
order to measure local and reference frequencies and RF-power levels in intermediate
stages of chain. Oscilloscope is used to measure DC-voltages and low frequency signals.
Digital multimeter is also useful measurement equipment in faultfinding. Also cellular
tester is needed in order to perform tests mentioned in this section.
External RF connector is implemented for improving reliability of the measurements and
should be used when reasonable.
GPS RF-section is mainly build around of TRF5101 PG2.1 IC (N001) ASIC. The GPS RF
block has a separate front end filter, inter stage filter, LNA, TCXO, and down converter
circuitry.
In this RF troubleshooting section, tolerances are specified for critical GPS RF signals and
voltages.
Before changing a single ASIC or component, please check the following items:
1 The soldering and alignment marks of the GPS ASICs
2 Supply voltages and control signals are OK
NOTE 1: The RF ASIC module is static discharge sensitive! It is recommended that EDS-protected
clothes and shoes are worn and that grounded soldering irons are used.
NOTE 2:The shield lid must be always replaced with new one after it is opened. Check that there are
no short circuits on PWB caused by plate ends.

GPS Receiver

General Instructions

Receiver troubleshooting is divided into four sections:
1 GPS RF general checking
2 GPS reference clock checking
3 GPS RF and GPS BB interface checking
4 GPS RX chain checking
The fastest way to troubleshoot GPS RF is to follow the GPS RF Fault-finding chart Quick
Issue 1 02/2003
Nokia Corporation
Troubleshooting — GPS
Confidential
NPD-4
Page 13