Synthesizers; 19.2 Mhz Reference Oscillator - Nokia NPM-2NX Troubleshooting Manual

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NPM-2NX

Troubleshooting

Synthesizers

There are five oscillators generating the needed frequencies for RF-section. 19.2 MHz

reference oscillator, 2GHz UHF VCO, TX VHF cascade amplifier VCO both RX VHF VCO and

BB VHF integrated in Safari. RX VHF frequency is 268.08 MHz in TDMA and 266.4 MHz in

GSM and TX VHF has three fixed frequencies, 358.08 MHz for lowband and 426.4 MHz in

GSM and 428.16 MHz in TDMA upper band. VCO's operating frequencies are controlled

by PLL-circuit of SAFARI. All locals are locked to stable 19.2 MHz reference oscillator.

The frequency range for 2GHz UHF VCO is: 2006.16 ... 2124 MHz. The output frequency

range for the lower band is from 2006.16 to 2056.02 MHz. In TDMA upper band the out-

put frequency range from the UHF VCO is from 2064.12 MHz to 2124 MHz and GSM

2063.40 ... 2123 MHz.

BB-PLL frequencies are in TDMA 77.76 MHz and in GSM 78 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.

The 19.2 MHz oscillator frequency (G801) is controlled by UEM. This 19.2 MHz signal is

connected thru SAFARI to PLL-circuits.

All synthesizers use divided VCTCXO signal as a reference signal for Phase locked loop to

provide correct LO-frequency.

BB-PLL provides to the BB needed clock signals.

Page 54

ãNokia Corporation

CCS Technical Documentation

Issue 1 07/02

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