LG C1150, 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 t switch either Tx
or Rx path on.
The logic and current is given below Table 3-1.
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 150 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).
VC1 VC2 Current
DCS Tx 0 V 2.5 ~ 3.0 V 10.0 mA max
GSM Tx 2.5 ~ 3.0 V 0 V 10.0 mA max
GSM / DCS Rx 0 V 0 V < 0.1 mA
Table 3-1 THE LOGIC TABLE