LG C2100, Руководство по обслуживанию

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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 super-heterodyne architectures.
A. RF front end
RF front end consists of Antenna Switch(FL500), two SAW Filters(FL401, FL402) and dual band LNAs
integrated in transceiver (U505).
The Received RF signals(GSM 925MHz ~ 960MHz, DCS 1805MHz ~ 1880MHz) are fed into the
antenna or Mobile switch.
The Antenna Switch(FL500) is used to control the Rx and Tx paths. And, the input signals VC1 and
VC2 of a FL500 are directly connected to baseband controller to 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 (824-
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 150Ω 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 AND CURRENT