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LGE Internal Use Only
Copyright © 2010 LG Electronics. Inc. All right reserved.
Only for training and service purposes
3. TECHNICAL BRIEF
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3.2 GSM MODE
3.2.1 GSM RECEIVER
The GSM-850, GSM-900, GSM-1800, and GSM-1900 receiver inputs of RTR6285 are connected to the
transceiver front-end circuits(switch module) through saw filters. 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 as shown in Figure 1-2. The balance between the complementary signals is critical
and must be maintained from the RF filter outputs all the way into the IC pins.
[Figure 1-2] GSM Receiver Inputs Topologies
Since GSM-850, GSM-900, GSM-1800, and GSM-1900 signals are time-division duplex (the handset can only
receive or transmit at one time), switches are used to separate RX and TX signals in place of frequency
duplexers – this is accomplished in the switch module. The GSM-850, GSM-900, GSM-1800, and GSM-1900
receive signals are routed to the RTR6285 through saw filters and matching networks that transform single-
ended 50-Ω
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sources to differential impedances optimized for gain and noise figure. The RTR input uses a
differential configuration to improve second-order inter-modulation and common mode rejection
performance. The RTR6285 input stages include MSM-controlled gain adjustments that maximize receiver
dynamic range.
[Figure 1-2] GSM Receiver Inputs Topologies
