Uhf Synthesizer - Nokia NKC-1X Series Troubleshooting Instructions

CCS Technical Documentation

UHF SYNTHESIZER

The UHF VCO signal is used for RF channel selection. This signal is fed as a local signal for
1st mixer of RX-path and for upconverter of TX-path. When operating on lower band the
VCO signal is divided by 2 before feeding. This synthesizer is used for channel selection in
all modes and both bands.
The UHF synthesizer consists of an external 2GHz VCO module with loop filter compo-
nents and integrated PLL parts in TACO. Integrated charge pump circuit allows analog
and digital operation modes. The VCO Oscillation frequency is from 2009.1 to 2125.53
MHz. The output frequency of the VCO module depends on the DC-control voltage which
is controlled by PLL-circuit inside TACO.
Change
VCO
2. No
OK
Check
loopfilter
components
and balun
Issue 1 02/03
Figure 18: Fault tree: UHF Synthesizer
OK
3.
No
START HERE!
Is frequency locked
Yes
to 2034,06 MHz?
1.
OK
No
Check VCO
No
operatig
voltage:
OK
2.78 V
Nokia Corporation
Troubleshooting Instructions
4. No
2.No
Is EVM OK?
YES
1.No
OK
Check loopfiler
components
Check resistor
R774
NKC-1X
Change
TACO
OK!
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