LG G7100, Service Manual

Page: 15 / 164

A. RF Front End
RF front end consists of Antenna Switch(FL405), an integrated two saw filters,(FL601),dual band
LNAs integrated in transceiver.
The Received RF signals(GSM 925MHz ~ 960MHz, DCS 1805MHz ~ 1880MHz) are fed into the
antenna or Mobile switch. An antenna matching circuit is between the antenna and the mobile
switch. The Antenna Switch(FL600) is used to control the Rx and Tx paths. And, the input signals
VC1 and VC2 of a FL600 are directly connected to baseband controller to switch either Tx or Rx
path on. Ant S/W module(FL600) is an antenna switch module for dual band phone.
The logic and current is given below table 3-1.
Table 3-1 The logic and current
<0.1 mA 0 V 0 V GSM/DCS RX
10.0 mA max 0 V 2.5 to 3 V DCS TX
10.0 mA max 2.5 to 3 V 0 V GSM TX
Current VC2 VC1
The receiver part uses a low-IF receiver architecture that allows for the on-chip integration
of the channel selection filters, eliminating the external RF image reject filters and the IF
SAW filter required in conventional super-heterodyne architecture. The Receive part of
CX74017 integrates three differential input LNAs that are matched to the 200 Ohm
balanced-output SAW filters through external LC matching networks.
3. TECHNICAL BRIEF
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