Synthesizer Troubleshooting; 19.44Mhz Reference Oscillator - Nokia NPC-1 Series Troubleshooting Instructions

NPC-1
Troubleshooting Instructions
2 0 0 0
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Synthesizer Troubleshooting

There are four oscillators generating the needed frequencies for RF-section. 19.44 MHz
reference oscillator, 2GHz UHF VCO, TX VHF cascade amplifier VCO and RX VHF VCO inte-
grated in Safari. RX VHF frequency is fixed 271.08 MHz and TX VHF has two fixed fre-
quencies, 361.08 MHz for lowband and 363.6 MHz for upper band. VCO's operating
frequencies are controlled by PLL-circuit of SAFARI. All locals are locked to stable

19.44MHz reference oscillator.

The frequency range for 2GHz UHF VCO is: 2009.1 - 2059.02 MHz.
It is practical way to check out synthesizer status by measuring control voltage of the
VCO from Integrator capacitor. If voltage is stable and reasonable, local oscillators are
running correctly.
19.44 MHz reference oscillator
The 19.44 MHz oscillator frequency (G790) is controlled by UEM. This 19.44 MHz signal
is connected to SAFARI and there in PLL-circuits and from SAFARI to UPP.
All synthesizers use divided VCTCXO signal as a reference signal for Phase locked loop to
provide correct LO-frequency.
Baseband also needs a reference signal where it can generate necessary the clock signals
and the VCTCXO output signal is also buffered and connected to the UPP.
Fault finding chart for 19.44 MHz oscillator
Page 30
Figure 14: Detected voltages
4 5 6
P o w e r le ve l
ãNokia Corporation
PAMS Technical Documentation
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8 0 0 A
8 0 0 D
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