NSW-5
Disassembly and Troubleshooting Instructions
PAMS Technical Documentation
Page 45
Issue 1 10/00
Nokia Mobile Phones Ltd.
Synthesizers
There are four oscillators generating the needed frequencies for RF–sec-
tion.
19.44 MHz reference oscillator:
1GHz UHF VCO,
2Ghz UHF VCO and
VHF VCO.
Only VHF VCO is discrete solution and it has two fixed frequencies,
322.38 MHz for lowband and 392.46 MHz for upper band. VHF VCOs op-
erating frequency is controlled by the PLL–circuit of EROTUS. All locals
are locked to the stable reference oscillator.
The frequency range for 1GHz UHF VCO is 985.23 – 1010.16 MHz and
for 2Ghz UHF VCO is 2046.27 – 2106.15 MHz.
A practical way to check out synthesizer status is to measure the control
voltage of the VCO from the integrator capacitor C831 (LB) , C861 (HB)
or C790 (VHF). The voltage must be stable and in the right range, and
the local oscillator must be running correctly.
19.44 MHz Reference Oscillator
The 19.44 MHz oscillator frequency (G850) is controlled by the COB-
BA_D. This 19.44 MHz signal is connected to EROTUS and TDMA1900
PLL–circuit.
All synthesizers use divided VCTCXO signal as reference signal for
Phase locked loop to provide the correct LO–frequency. The VCTCXO
output signal is also used to generate multiple LO frequency by multipli-
ers.
Baseband also needs the reference signal so it can generate necessary
clock signals, and the VCTCXO output signal is also buffered and con-
nected to MAD.
58.32 MHz 3–Multiplier
The 3–multiplier is an integrated solution in the EROTUS and it is used to
generate the second LO frequency for the receivers. The 3*multiplier out-
put signal is multiplied by 2 and then it is fed to the 2nd downconverter.
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