CCS Technical Documentation
Troubleshooting Instructions
RH-42
Issue 2 09/2003
Nokia Corporation Confidential
Page 31
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.
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 MHz to
2125.53 MHz. The output frequency of the VCO module depends on the DC control volt-
age which is controlled by PLL circuit inside Taco.
Figure 17: Fault tree: UHF Synthesizer
START HERE
Is frequency locked to
2034.06MHz?
Change VCO
Is EVM OK?
OK
Change
Taco
Check loopfilter
components
and balun
Check VCO operating
voltage:
2.78V
Check resistor R774
Check loopfilter
components
OK
3. No
OK
2. No
1. No
OK
Yes
4. No
2. No
Yes
1. No
OK
No
OK
