Uhf Synthesizer - Nokia RH-42 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.
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.
Change VCO
3. No
START HERE
2. No
Is frequency locked to
2034.06MHz?
OK
Check loopfilter
components
and balun
Check VCO operating
Issue 2 09/2003
OK
Yes
1. No OK
OK
voltage:
No
2.78V
Figure 17: Fault tree: UHF Synthesizer
Nokia Corporation
Troubleshooting Instructions
4. No
Is EVM OK?
Yes
1. No OK
Check loopfilter
components
Check resistor R774
Confidential
RH-42
Change
Taco
2. No
OK
Page 31