Uhf Synthesizer; Fig 49 Fault Finding Chart For Uhf Synthesizer - Nokia RH-13 Series Troubleshooting Manual

CCS Technical Documentation

UHF SYNTHESIZER

The UHF synthesizer consists of a external 2GHz UHF VCO, loop filter and integrated PLL
in Safari RF-IC. Safari GTE IC contains stages like counters, prescaler, divider by two,
phase and frequency comparator and a charge pump circuit which allows two opera-
tional modes analog and digital. The UHF VCO Oscillation frequency is from 2004.8 MHz
to 2124 MHz
In upper band (TDMA1900 &GSM1900) 2 GHz synthesizer frequency is fed straight to
mixers. In lower band case (AMPS, TDMA800 and GSM850) 2 GHZ UHF VCO frequency
signal is first divided by 2 inside SAFARI and then that divided signal is fed to mixers. The
output frequency of the VCO depends on the DC-control voltage which is controlled by
PLL-circuit inside SAFARI.
Change
VCO G802
2. No
OK
Check loopfilter
components and
balun T801,
C863,C862,C861,
C860,R806,
R815,R814,R813
Issue 1 11/02
Figure 49: Fault finding chart for UHF SYNTHESIZER.
OK
3.
No
START HERE!
Is frequency locked? Yes
2004.8 - 2124
MHz
1.
OK
No
Check VCO
No
operatig
voltage:
OK
2.78 V
ãNokia Corporation
Change
SAFARI N801
4. No
No
Is EVM OK?
YES
OK
No
1
Check
loopfilter
components
Check resistor
R811
RH-13
Troubleshooting
OK!
low
band
Yes
Low band:
Is divided No
signal OK?
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