Gsm Mode - LG -V909DW Service Manual

3. TECHNICAL BRIEF

3.2 GSM MODE

3.2.1 GSM RECEIVER
The GSM-900, GSM-1800, and GSM-1900 receiver inputs of MDM6200 are connected directly to the front-end
Module. The receiver inputs use differential configurations to improve common-mode rejection and second-
order non-linearity performance. The balance between the complementary signals is critical and must be
maintained from the FEM outputs all the way into the IC pins. The FEM has dual-SAW filter for GSM1800 and
GSM1900, so only one port of MDM6200 is need to support GSM high band(it means GSM1800/GSM1900).
[Figure 3-1] 2G Receiver path
[Figure 3-2] 2G/3G Receiver internal block
Since GSM-850, GSM-1800, and GSM-1900 signals are time-division duplex (the handset can only receive or
transmit at one time), switches of FEM are used to separate Rx and Tx signals in place of frequency duplexers
– this is accomplished in the switch module.
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