Synthesizers; 19.44 Mhz Reference Oscillator; 58.32 Mhz Triple Multiplier - Nokia NSW-6 Series Disassembly & Troubleshooting Instructions

PAMS Technical Documentation

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 operating frequency is controlled by BAND–signal and PLL–
circuit of EROTUS. All locals are locked to the stable reference oscillator.
The frequency range for 1GHz UHF VCO is 985.23 – 1010.2 MHz and for
2Ghz UHF VCO is 2046.2 – 2107.2 Mhz.
A practical way to check out synthesizer statusis to measure the control
voltage of the VCO from the integrator capacitor C822 (LB) , C883 (HB)
or C789 (VHF). The voltage must be stable and in the correct range, and
the local oscillator is running correctly.

19.44 MHz Reference oscillator

The 19.44 MHz oscillator frequency (G850) is controlled by COBBA_D.
This 19.44 MHz signal is connected to EROTUS and TDMA1900 PLL–cir-
cuit.
All synthesizers use the 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 Triple Multiplier

The 3–multiplier is a integrated solution in EROTUS and it is used to gen-
erate second LO frequency for the receivers. The 3*multiplier output sig-
nal is multiplied by 2 and then it is fed to the 2nd downconverter.
Issue 1 12/99
E Nokia Mobile Phones Ltd.
Disassembly & Troubleshooting
NSW-6
Page 41