Rf Interface - LG 410G Service Manual

3. H/W Circuit Description

3.9 RF Interface

V_EXTH
Locosto features a fully integrated constant-gain direct conversion receiver, i.e. there is no
interstage filter needed and the baseband level at the analogue IQ- interface follows directly the RF
input level. Depending on the baseband ADC dynamic range, single- or multiple-step gain switching
schemes are possible.
An integrated, selfaligning, low-pass filter ensures the receivers to function under blocking and
reference interference conditions and avoids aliasing by baseband sampling. An automatic DC-
offset compensation is implemented and can beswitched depending on the gain setting.
LGE Internal Use Only
ANT_SW1
ANT_SW2
C433
C431 C432
1000p 1000p 1000p
Figure 3-9-1. FEM interface
-22-
FL400
GSM1900_RX1
19
VC1 GSM1900_RX2
20
VC2
GSM1800_RX1
21
VDD GSM1800_RX2
9
GND1
10
GND2
12
GND3
13
GND4
14
GND5
16
GND6
18
GND7 GSM1800_1900_TX
22
GSM850_900_TX
GND8
- 26 - Copyright © 2009 LG Electronics. Inc. All right reserved.
LMSP43QC-789TEMP
1
2
3
4
5
GSM900_RX1
6
GSM900_RX2
7
GSM850_RX1
8
GSM850_RX2
15
17
Only for training and service purposes