LG E900 Service Manual page 26

3.2.2 GSM TRANSMITTER
The RTR6285 transmitter outputs(HB_RF_OUT1 and LB_RF_OUT1) include on-chip output matching
inductors. 50ohm output impedance is achieved by adding a series capacitor at the output pins.
The capacitor value may be optimized for specific applications and PCB characteristics based on pass-band
symmetry about the band center frequency as shown in Figure 1-3.
HB_RF_OUT1
LB_RF_OUT1
RTR6285
The RTR6285 IC is able to support GSM850/GSM 900 and GSM 1800/1900 mode transmitting. This design
guideline shows a quad-band GSM application. Both high-band and low band outputs are followed by
resistive pads to ensure that the load presented to the outputs remains close to 50ohm.
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Only for training and service purposes
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[Figure 1-4] GSM Transmitter Outputs Topologies
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3. TECHNICAL BRIEF
GSM PAM
LGE Internal Use Only