LG -P500 Service Manual page 24

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.
The RTR6285 IC is able to support GSM 850/900 and GSM 1800/1900 mode transmitting. This design
guideline shows a tri-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.
Copyright © 2010 LG Electronics. Inc. All right reserved.
Only for training and service purposes
[Figure 1-3] GSM Transmitter Outputs Topologies
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3. TECHNICAL BRIEF
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