Nokia NPM-10 Series Troubleshooting Instructions page 9

CCS Technical Documentation
by a ratio based on the selected channel. The divider output is supplied to the phase
detector, which compares the frequency and phase to the 400kHz reference clock. Based
on this comparison, the phase detector controls the charge pump to either charge or dis-
charge the capacitors in the loop filter. By charging/discharging the loop filter, the con-
trol voltage to the VCO changes and the LO frequency will change. Therefore, the PLL will
make the LO frequency stay locked to the 26MHz VCXO frequency.
The loop filter consists of the following components: C639-C641 and R618-R619.
The PLL is operating at twice the channel center frequency when transmitting or receiv-
ing in the PCS band. For the GSM band, the PLL is operating at four times the channel
frequency. Therefore, divide-by-2 and divide-by-4 circuits are inserted between the PLL
output and LO inputs to the PCS and GSM mixers.
The frequency plan is shown in the table that follows:
Frequency
Channel #
Band
GSM RX 128 - 251
TX
PCS RX 512 - 810
TX
According to the previous table, the PLL must be able to cover the frequency range
3296.8 MHz to 3979.6 MHz.
Issue 1 03/2003
Table 1: PLL Frequency Plan
System Frequency Band [MHz]
869.2 - 893.8
824.2 - 848.8
1930.2 - 1989.8
1850.2 - 1909.8
Nokia Corporation
Troubleshooting Instructions RF
PLL Frequency Band [MHz]
3476.8 - 3575.2
3296.8 - 3395.2
3860.4 - 3979.6
3700.4 - 3819.6
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NPM-10
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