LG G1610, Service Manual

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3. TECHNICAL BRIEF
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(1) Receiver Part
The Aero I transceiver uses a low-IF receiver architecture which 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 superheterodyne architectures.
A. RF front end
RF front end consists of Antenna Switch(FL400), two SAW Filters(FL401, FL402)
and dual band LNAs integrated in transceiver (U401).
The Received RF signals(GSM 925MHz ~ 960MHz, DCS 1805MHz ~ 1880MHz)
are fed into the antenna or Mobile switch.
The Antenna Switch(FL400) is used to control the Rx and Tx paths. And, the input
signals VC1 and VC2 of a FL400 are directly connected to baseband controller
to switch either Tx or Rx path on.
The logic and current is given below Table 3-1.
Table 3-1 The Logic and current
VC1 VC2 Current
DCS TX
0V 2.5 ~ 3.0V 10.0 mA max
GSM TX
2.5 ~ 3.0V 0V 10.0 mA max
GSM/DCS RX
0V 0V < 0.1 mA
Three differential-input LNAs are integrated in SI4205. The GSM input
supports the GSM 850 (869-849 MHz) or E-GSM 900 (925-960MHz) bands.
The DCS input supports the DCS 1800 (1805-1880 MHz) band. The PCS
input supports the PCS 1900 (1930-1990 MHz) band.
The LNA inputs are matched to the 150ߟ balanced output SAW filters
through external LC matching networks. The LNA gain is controlled with the
LNAG[1:0] and LNAC[1:0] bits in register 05h (Figure 3-2).