LG -A258 Service Manual page 38

3.6.2 FUNCTIONAL DESCRIPTION
3.6.2.1 Receiver
The X-GOLD™ 215 dual-band receiver is based on a Direct Conversion Receiver (DCR) architecture. Input
impedance of the LNAs is optimized to achieve a matching without (external) high quality inductors. By use of
frequency dividers (by 2/4) the LO frequency is derived from the RF frequency synthesizer. The receive path is
fully differential to suppress the on-chip interferences and reduce DC-offsets. The analog chain of the receiver
contains two LNAs (low/high band), a quadrature mixer followed by an analog baseband filter and 14-bit
continuous-time delta-sigma analog-to-digital converter. The filtered and digitized signal is fed into the digital
signal processing chain, which provides decimation, DC offset removal and programmable gain control.
RX1
GSM
850/900
RX1X
RX
GSM
1800/1900
RXX
LNA_GAIN
LGE Internal Use Only
RXBBFG[:0]
DCO
Figure. 3.6.2 RECEIVER CHAIN BLOCK DIAGRAM
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3. TECHNICAL BRIEF
RXTXDA
DigRF
RX
RXTXEN
DGAIN[5:0]
Only for training and service purposes