User Guide

CCS Technical Documentation 7 - System Module & UI
Company Confidential NMM-3
Issue 1 (11/2003) Copyright  2003 Nokia Corporation Page 7-39
Company Confidential
monitoring, long term average value is used instead.
There is 54 dB gain control in 6 dB steps and one larger step of about 30 dB in the LNA.
According to the system specification the received signal level must be measured accu-
rately in the range of -48...-110 dBm. Above -48 dBm the phone can report a constant
reading to the base station.
Production calibration is done with one RF-level.
Figure 6: RX Gain control in GSM
AFC function
The AFC is used to lock the VCTCXO frequency to the frequency of the base station. The
AFC-voltage is generated in baseband by UEME using an 11 bit DA-converter. An RC-fil-
ter on the AFC control line reduces the noise from the converter. The settling time
requirement for the RC-network comes from the start up time allowed. When the trans-
ceiver is in sleep mode and ”wakes” up to receive mode, there is only about 5 ms for the
AFC-voltage to settle. In burst reception mode the system clock has to be settled into +/
- 0.1 ppm frequency accuracy.
lna on lna off
mVpp
dB LSB
15 dB margin
Pin/dBm
6 dB
BB-amplifier
Dtos on Dtos off Dtos on Dtos off
-40 dBm
-110 -100 -90 -80 -70 -60 -50 -40 -30 -20 -10
10
20
30
40
50
60
45
51
66
+42 +36 +30 +24 +18 +12 +6 0 +12 +6 0 +6 00+6
1350
240
120