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Copyright © 2009 LG Electronics. Inc. All right reserved.
Only for training and service purposes
LGE Internal Use Only
3. TECHNICAL DESCRIPTION
3.7.4.1. Front End Part
SKY77521 is a transmit and receive Front End Module (FEM) designed in a very low profile (1 mm),
compact form factor for quad-band cellular handsets comprising GSM850/900, DCS1800, and PCS1900
operation — a complete transmit VCO-to-Antenna and Antenna-to receive SAW filter solution. The FEM
also supports Class 12 General Packet Radio Service (GPRS) multi-slot operation and EDGE Polar
Modulation. WCDMA switch-through support is provided by three dedicated high-linearity ports.
Figure 3-7-12. Front End part schematic
Figure 3-7-11. SKY77521Functional Block Diagram
GSM PA WITH ASM
0
R114
0
R115
0R112
33pC113
_TXEN
8
LB_RF_IN
39
MODE
PGND1
31
32
PGND2
PGND3
33
34
PGND4
RSVD
10
RX1
16
15
RX2
RX3
14
13
RX4
VAPC
4
VBATT
5
WCDMA1
18
19
WCDMA2
WCDMA3
20
BS1
7
6
BS2
GND1
2
27
GND10
GND11
28
29
GND12
GND13
30
11
GND2
GND3
12
21
GND4
GND5
22
GND6
23
GND7
24
25
GND8
GND9
26
1
HB_RF_IN
SKY77521
U101
17
ANT
C139
22p
22pC112
VBAT
C140
22p
DNI
R106
R111 0
100pL102
KMS-518
SW100
A
C
G1
G2
C132
DNI
DNI
C126
10u
C107
22pC114
47p
C109
C130
22p
DNIR108
R105 0
22p
C129
22pC125
ANT
G1
G2
0.01u
C108
SW101
UFL-R-SMT10
WRF_BAND_2
WRF_BAND_1
GRX_1800
GRX_1900
GTX_VAM
ANTSW3
ANTSW2
ANTSW0
ANTSW1
GTX_1800_1900
GTX_850_900
WRF_BAND_8_5
GRX_850
GRX_900
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