Gsm Mode - LG -P970 Service Manual

3.2 GSM MODE

3.2.1 GSM RECEIVER
The GSM-850/GSM-1800, receiver inputs of PMB5703 are connected directly to the transceiver front-end Module.
The GSM-900/GSM-1900 receiver inputs are using the Rx path with WCDMA1900 and WCDMA900 bands. The
GSM-850, GSM-900, GSM-1800, and GSM-1900 receiver inputs use differential configurations to improve
common-mode rejection and second-order non-linearity performance.
Figure 3-2 shows the line-up for the 2G receiver chain for bands serving only GSM. The RX digital front-end (DFE)
contains all digital signal processing. Blue arrows show gain switching inputs of the signal processing stages.
The signal path splits at the mixer input into an in-phase and an identical quadrature path. For simplicity the 2nd
path is not shown in the figure. The quadrature downconverter translates the useful signal directly to baseband
(zero-IF).
switch
LGE Internal Use Only
0 dB 17 dB
gain step gain step
RF filter
LNA mixer
[Figure 3-2] 2G Receiver Line Up-GSM Single Mode Setup
35 dB
6 dB
gain range
gain step
(1 dB step)
analog
buffer
baseband filter
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3. TECHNICAL BRIEF
Only for training and service purposes