Nokia NSB-7 Series Service Manual page 72

NSB-7
System Module
ceiver is in sleep mode and "wakes up" to a receive mode there is only ca. 5 ms for the
AFC voltage to settle. When the first burst comes in the system clock has to be settled
with +/- 0.1 ppm frequency accuracy. The VCTCXO module requires also 5 ms to settle to
the final frequency. Amplitude rises to full swing in 1... 2 ms. Because the frequency set-
tling time is higher this oscillator must be powered up early enough.
DC Compensation
DC compensation is done during DCN1 and DCN2 operations (controlled via serial bus).
DCN1 is carried out by charging large external capacitors in AGC stages to a voltage
which causes a zero dc offset. DCN2 sets the signal offset to a constant value (RXREF 1.2
V).
Page 58 ãNokia Mobile Phones Ltd.
PAMS Technical Documentation
Issue 1 06/00