Nokia 6150 Manuales De Servicio

PAMS

Technical Documentation

NSM–1

System Module

Original  10/98

Page 3–62

AFC is used to lock the transceivers clock to frequency of the base sta-
tion. AFC–voltage is generated in COBBA with 11 bit AD–converter.
There is a RC–filter in AFC control line to reduce the noise from the con-
verter. Settling time requirement for the RC–network comes from signal-
ling, how often PSW (pure sine wave) slots occur. They are repeated ev-
ery 10 frames, meaning that there is PSW in every 46 ms. AFC tracks
base station frequency continously, so transceiver has a stable frequency,
because there are no rapid changes in VCTCXO –output  (changes due
to temperature are relatively slow). Settling time requirement comes also
from the start up–time allowed. When transceiver is in sleep mode and
”wakes” up to receive mode, there is only  about 5 ms for the AFC–volt-
age to settle. When the first burst comes in system clock has to be settled
into +/– 0.1 ppm frequency accuracy. The VCTCXO–module requires
about 4 ms to settle into final frequency. Amplitude rises into full swing in
about 3 ms, but because frequency settling time is higher, this oscillator
must be powered up early enough.

Passband

       935 – 960

MHz

Insertion loss

3.8

dB

Maximum drive level

+10

dBm

Passband

 1805 – 1880

MHz

Insertion loss in passband

3.5

dB

Maximum drive level

+10

dBm

Input RF–frequency

925

960

MHz

Output IF–frequency

      73

MHz

Input LO–frequency

  998

 

    1033

MHz

Output  resistance
( balanced )

 

 

 

ohm

73 MHz
Open collector output